text stringlengths 174 655k | id stringlengths 47 47 | score float64 2.52 5.25 | tokens int64 39 148k | format stringclasses 24 values | topic stringclasses 2 values | fr_ease float64 -483.68 157 | __index__ int64 0 1.48M |
|---|---|---|---|---|---|---|---|
Glucose and sucrose easily produced alcohol fermentation in yeast. Why didn't galactose and lactose?
This was the virtual experiment.
pH was set at 7
temperature 20 degrees C
20 ml of glucose was added to 1ml yeast
20ml or sucrose was added to 1ml of yeast
20ml of galactose was added to 1 ml of yeast
20ml of lactose was added to 1ml of yeast
gas was measured after 20 minutes.
Glucose and sucrose showed a reaction. Lactose and galactose didn't. Why?© BrainMass Inc. brainmass.com July 21, 2018, 9:27 pm ad1c9bdddf
Pretty well, everything that goes on in a cell happens because of enzymes. Remember, enzymes are catalytic proteins that speed up metabolic reactions and make things happen.
If yeast cells have the necessary enzymes to metabolize the sugar, then fermentation can happen. If they don't have the ... | <urn:uuid:763aab8c-5775-45a1-ba7b-1d3c316e4ee0> | 3.296875 | 209 | Q&A Forum | Science & Tech. | 67.596429 | 95,529,585 |
Hurry - Only 3 left in stock!
1. Getting Started with PHP. 2. Using Functions and Control Structures. 3. Manipulating Strings. 4. Handling User Input. 5. Working with Files and Directories. 6. Manipulating Arrays. 7. Working with Databases and MySQL. 8. Manipulating MySQL Databases with PHP. 9. Managing State Information. 10. Developing Object-Oriented PHP. Appendix A: Working with XHTML. Appendix B: Building a Web Development Environment. Appendix C: Formatting Strings. Appendix D: Secure Coding with PHP. Appendix E: Advanced Debugging Techniques. Appendix F: Connecting to SQL Server and Oracle Databases. Appendix D: Secure Coding with PHP. | <urn:uuid:f673ac53-ba0b-45ea-8648-b6c03480c4cd> | 2.765625 | 155 | Product Page | Software Dev. | 57.0675 | 95,529,588 |
NASA has just released an animation of visible and infrared satellite data from NOAA's GOES-East satellite that shows the development and movement of the weather system that spawned tornadoes affecting seven central and southern U.S. states on April 27-28, 2014. NASA's Aqua satellite captured infrared data on the system that revealed powerful storms, high into the troposphere.
This storm system generated reports of tornadoes from Nebraska, Kansas, Iowa, Oklahoma, Arkansas, Louisiana, and Mississippi.
Coupled with local weather observations, soundings, and computer models, data from satellites like NOAA's Geostationary Operational Environmental Satellite or GOES-East (also known as GOES-13) gives forecasters information about developing weather situations. In real-time, the NOAA's GOES-East satellite data in animated form showed forecasters how the area of severe weather was developing and moving.
NOAA's GOES-East satellite sits in a fixed orbit in space capturing visible and infrared imagery of weather over the eastern U.S. and Atlantic Ocean. The GOES-East satellite is operated by the National Oceanic and Atmospheric Administration. NASA/NOAA's GOES Project at the NASA Goddard Space Flight Center in Greenbelt, Md. created the animation of GOES-East satellite data that covered the period during the tornado outbreak.
The GOES-East animation of visible and infrared imagery runs 31 seconds. The animation begins on April 27 at 00:15 UTC (April 26 at 8:15 p.m. EDT) and runs through April 28 at 14:15 UTC/10:15 a.m. EDT. By 14:45 UTC/10:45 a.m. EDT on April 27 the animation shows the squall line of thunderstorms developing.
To create the video and imagery, NASA/NOAA's GOES Project takes the cloud data from NOAA's GOES-East satellite and overlays it on a true-color image of land and ocean created by data from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument that flies aboard NASA's Aqua and Terra satellites. Together, those data created the entire picture of the storm system and show its movement.
A NASA satellite also captured an image of the storm, collecting infrared data on it as it passed overhead on April 27. At NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif. a false-colored image was created of the storm system using data gathered by the Atmospheric Infrared Sounder (AIRS) instrument that flies aboard NASA's Aqua satellite on April 27 at 18:59 UTC (1:59 p.m. CDT). The AIRS image showed very cold cloud top temperatures indicating that the thunderstorms had strong uplift that pushed cloud tops to the top of the troposphere. Some of those thunderstorms had cloud tops as cold as 200 kelvin (-99.6 F/-73.1C). Temperatures drop to just under 220 degrees kelvin at the top of the troposphere (and where the tropopause begins).
"AIRS data shows spatial extent of strong convection [rapidly rising air that condenses and forms clouds] in the slow-moving severe storm system that spawned tornadoes in Arkansas, Oklahoma and Iowa," said Ed Olsen, creator of the AIRS image at NASA JPL. The AIRS image showed the thunderstorms with coldest cloud top temperatures stretched from eastern Nebraska, through western Iowa, western Missouri, northern Arkansas and southeast into northern Mississippi and Alabama.
According to the Examiner.com, the National Weather Service’s Storm Prediction Center counted 31 tornadoes on Sunday, April 27, however, that number is being refined as reports are analyzed.
CBS News reported that one tornado touched down 10 miles west of Little Rock, Arkansas around 7 p.m. CDT (at around 22:02 UTC in the GOES animation) and stayed on the ground for about 80 miles passing near several suburbs north of the city. That tornado was reported to be one-half mile wide.
The same system that spawned these tornadoes is expected to bring the possibility for severe weather further east on April 28 from Cincinnati, Ohio to New Orleans, La. For more information about current risks for severe weather, visit NOAA's Storm Prediction Center at: http://www.spc.noaa.gov.
GOES satellites provide the kind of continuous monitoring necessary for intensive data analysis. Geostationary describes an orbit in which a satellite is always in the same position with respect to the rotating Earth. This allows GOES to hover continuously over one position on Earth's surface, appearing stationary. As a result, GOES provide a constant vigil for the atmospheric "triggers" for severe weather conditions such as tornadoes, flash floods, hail storms and hurricanes.
To download the GOES animation: http://goes.gsfc.nasa.gov/pub/goes/QTmovies/140427-8_tornados.mov
For updated information about the storm system, visit NOAA's NWS website: www.weather.gov
Following is a list of (preliminary) tornado reports from NOAA's Storm Prediction Center for April 27, 2014 (1200 UTC - 1159 UTC)
Time Location County State Lat Lon Comments
1929 1 N UPLAND FRANKLIN NE 4033 9890 TORNADO ON THE GROUND FROM ABOUT 226 TO 229. (GID)
2000 1 N FLORIS DAVIS IA 4088 9233 OBSERVER SAW A BRIEF TOUCHDOWN IN A FIELD. THERE WAS NO DAMAGE. (DMX)
2000 LOVILIA MONROE IA 4114 9291 TORNADO TOUCHDOWN OBSERVED. HOUSE ROOFS TORN OFF. TREES SNAPPED OFF. (DMX)
2012 1 N FLORIS DAVIS IA 4088 9233 OBSERVER REPORTS GUSTNADO AT 312 PM JUST AHEAD OF STORM ARRIVAL. DIRT KICKED UP IN FIELD PRIOR TO HEAVY RAIN. (DMX)
2141 2 NE MOUNT VERNON LINN IA 4194 9140 SPOTTERS REPORTED TORNADO ON GROUND NEAR LINN RIDGE ROAD AND HIGHWAY 1. IT WAS LIFTING BACK UP BY 442 PM. RELAYED BY EMERGENCY MANAGEMENT. (DVN)
2142 5 N BRADSHAW YORK NE 4096 9775 BRIEF TOUCHDOWN NEAR INTERSECTION OF ROADS 18/H THAT LASTED FOR 30-45 SECONDS. WILL PROVIDE VIDEO FOR VERIFICATION. NICKLE HAIL ONGOING AT 448 PM. (GID)
2142 SPRINGVILLE LINN IA 4206 9144 TORNADO TOUCHDOWN JUST SOUTH OF SPRINGVILLE. (DVN)
2218 5 W OSCEOLA POLK NE 4118 9764 BRIEF TOUCHDOWN LASTED APPROXIMATELY 1 MINUTE. VISUAL CONFIRMATION VIA LIVE STREAM. (GID)
2218 8 WNW OSCEOLA POLK NE 4122 9769 THIS IS A CORRECTED ... APPROXIMATE TORNADO LOCATION BASED ON STORM CHASER VIDEO AND RADAR DATA THAT SHOWS TORNADO WEST OF HIGHWAY 39. BRIEF TOUCHDOWN LASTED APPROXIMATEL (GID)
2232 QUAPAW OTTAWA OK 3695 9479 FIRE STATION DESTROYED. NORTH END OF TOWN SUSTAINED HEAVY DAMAGE. (TSA)
2239 BAXTER SPRINGS CHEROKEE KS 3702 9474 *** 25 INJ *** A TORNADO DAMAGED OR DESTROYED NUMEROUS HOMES AND SEVERAL BUILDINGS IN DOWNTOWN BAXTER SPRINGS. EMERGENCY MANAGEMENT REPORTED 25 INJURIES WITH 9 OF THOSE (SGF)
2240 HAMMOND BOURBON KS 3794 9469 A TORNADO PRODUCED AN INTERMITTENT DAMAGE PATH TO THE NORTHEAST OF HAMMOND AFTER DAMAGING A GRAIN ELEVATOR AND OVERTURNING A RAIL CAR. (SGF)
2249 3 ESE PRESCOTT LINN KS 3804 9465 TORNADO SEEN FROM VIDEO SHOT BY BROADCAST MEDIA. (EAX)
2259 5 ENE MARKS QUITMAN MS 3428 9019 TORNADO REPORTED MOVING FROM QUITMAN COUNTY INTO PANOLA COUNTY NEAR HOOD ROAD. WAS MOVING INTO FORESTED AREA. (MEG)
2300 3 WNW HUME LINN KS 3811 9463 TORNADO WAS STILL ONGOING AT THIS TIME BUT BEGINNING TO ROPE OUT PER BROADCAST MEDIA VIDEO. (EAX)
0025 ROLAND PULASKI AR 3490 9250 TORNADO IS REPORTED ON THE GROUND ... AND CONFIRMED BY STATE POLICE. (LZK)
0034 1 SE MAYFLOWER FAULKNER AR 3496 9241 TORNADO HAS CROSSED INTERSTATE 40 AT MILE MARKER 140. SPOTTER ESTIMATED HALF A MILE WIDE. (LZK)
0039 SALTILLO FAULKNER AR 3503 9233 SEVERAL HOUSES DAMAGED IN SALTILLO. (LZK)
0042 2 E MAYFLOWER FAULKNER AR 3497 9238 ARKANSAS GAME AND FISH HEADQUARTERS EAST OF MAYFLOWER HAS BEEN HEAVILY DAMAGED. (LZK)
0050 VILONIA FAULKNER AR 3508 9221 NUMEROUS HOUSES AND FAST FOOD RESTAURANT DAMAGED ... ALONG WITH NUMEROUS TREES DOWN. (LZK)
0050 DENMARK WHITE AR 3548 9158 STATE POLICE ARE REPORTING A TORNADO AT DENMARK. (LZK)
0050 PLEASANT PLAINS INDEPENDENCE AR 3555 9163 THERE IS A REPORT OF A TORNADO JUST SOUTHEAST OF PLEASANT PLAINS. (LZK)
0101 1 N EL PASO WHITE AR 3513 9208 STORM SPOTTERS HAVE CONFIRMED TORNADO AT HIGHWAY 64 AND HIGHWAY 5. (LZK)
0120 6 W SEARCY WHITE AR 3524 9184 HOUSE WAS DAMAGED ON BLOODWORTH ROAD. A POWER LINE WAS DOWN ON TANNER ROAD. NUMEROUS TREES WERE UPROOTED. (LZK)
0135 STEPROCK WHITE AR 3543 9169 TIN ON THE GROUND AND POWER LINES DOWN. (LZK)
0150 DENMARK WHITE AR 3548 9158 STATE POLICE ARE REPORTING A TORNADO AT DENMARK. (LZK)
0150 PLEASANT PLAINS, INDEPENDENCE AR 3555 9163 THERE IS A REPORT OF A TORNADO JUST SOUTHEAST OF PLEASANT PLAINS. (LZK)
0205 MACKS JACKSON AR 3562 9137 A TORNADO IS REPORTED NEAR MACKS. (LZK)
0205 3 E OIL TROUGH INDEPENDENCE AR 3563 9141 POWER LINES WERE DOWNED A FEW MILES EAST OF OIL TROUGH. (LZK)
0210 JACKSONPORT JACKSON AR 3564 9131 A TORNADO WAS REPORTED AT JACKSONPORT. (LZK)
0224 3 W CAMPBELL STATION JACKSON AR 3567 9131 SHERIFF HAS THREE DEPUTIES REPORTED TORNADO ON THE GROUND ON HIGHWAY 17. (LZK)
0813 5 ENE HOSSTON BOSSIER LA 3291 9381 *** 1 INJ *** HOME DAMAGED ON BUCKSHOT RD (SHV)
Rob Gutro | Eurek Alert!
Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center
NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences | <urn:uuid:02eb09e0-71b3-4c64-a821-a89238d3fde5> | 3.171875 | 3,191 | Content Listing | Science & Tech. | 59.445154 | 95,529,589 |
Join the Conversation
To find out more about Facebook commenting please read the Conversation Guidelines and FAQs
U.S. 2nd warmest ever, 29 states break December records
New Jersey wasn't alone with its record-breaking December temperatures.
Twenty-nine other states — essentially the eastern half of the country minus Arkansas and Louisiana — had the highest-average temperatures in 121 years (since the first records), according to a report from the National Centers for Environmental Information.
The average temperature of the contiguous U.S. in 2015 was also the second-highest on record, according to the report. The first was in 2012 and the third was in 2006.
“In the past 10 years, we’ve had three record-breaking years,” said Jake Crouch, a climatologist with the National Centers for Environmental Information (NCEI). “That fits into the context of a warming world and a warming U.S.”
And this trend isn't new. For 19 consecutive years, the average temperature of the continental U.S. has gone up, according to data from the NCEI.
States that broke records last month were at least 9 degrees above what’s considered normal, which is an average of the state’s 20th century December temperatures.
New Jersey’s 14.9-degree departure from the norm was the highest of all states. Vermont was second with 14.8 degrees and New York was third with 14.6 degrees. (continued below chart)
States with a record-high December 2015
SOURCE: National Centers for Environmental Information
The two major factors responsible for the warm temperatures in December were El Niño and the pattern of the polar jet stream, Crouch said.
El Niño is a naturally occurring warming of the tropical Pacific Ocean’s temperatures that disrupts global weather patterns, generally causing a flow of warm air from the southwestern U.S. to the east, Crouch said.
On top of that, the polar jet stream that usually dips down into the northeastern part of the country in December stayed further north in December, keeping the cold air out, Crouch said.
The strength of El Niño’s influence in the northeast has a lot to do with the pressure patterns in the northern Atlantic Ocean, and usually fight for dominance, Crouch said. He said there’s an equal chance for above-average and below-average temperatures for the rest of January.
Earlier in 2015, the western part of the country saw warmer-than-normal temperatures while the east experienced extreme cold, said New Jersey state climatologist David Robinson.
The polar jet stream was further north than usual in the west, closing the door on the cold and allowing warm air to stream up from the south, Robinson said. In the East, the polar jet stream was further south than usual.
Crouch said the last time he saw so many states break temperature records was is March of 2012. Thirty-one states had record-high average temperatures, ranging from 9 to 18 degrees above normal.
“We haven’t seen much record-breaking cold that would rival the magnitude of the warmth we saw in December,” Crouch said. “Data shows that we see more frequently really warm temperature events and fewer cold ones.”
Kala Kachmar: 732-643-4061; firstname.lastname@example.org. | <urn:uuid:25776103-8164-44ba-af0b-54c409540108> | 3.046875 | 713 | News Article | Science & Tech. | 58.589998 | 95,529,596 |
Installing CodeBlocs compiler
© The scientific sentence. 1998-2016
Programming with C/C++ Language
Pointers, Arrays and Strings
Strings in C++
In C++ a string is a string of characters. represented by an array.
Then a string is an array of characters.
Strings are arrays of chars. They are words surrounded by double quotation marks.
Example: "we are coding in cpp" is a string.
To declare a string of 20 letters, we will need an array
of 21 dimension, and we write:
This would declare a string with a length of 21 characters.
Note that arrays begin at zero, not 1 for the index number.
a string ends with a null character, literally a '\0' character. However, just remember
that there will be an extra character on the end on a string.
It is like a period at the end of a sentence, it is not counted as a letter, but
it still takes up a space. Technically, in a 21 char array we could only hold 20 letters
and one null character at the end to terminate the string.
Instead of an array, we can use a pointer, and make the following
And write :
an_array = new char;
which allows us to access
an_array just as if it were an array.
To delete the string, we must put between delete and
an_array to free all the
21 bytes of memory allocated. For example:
2. Using cin.get()
Strings are useful for holding all types of long input. We use cin>> to input
a string, but it terminates the string after it reads the first space.
The best way to handle this situation is to use the function cin.getline () .
The prototype for that function is:
istream& getline(char *
feca, int length, char terminal_char);
The char *
feca is a pointer to the first element of the character array,
so that it can actually be used to access the array.
The int length is how long the string to be input can be at its maximum.
That is how big the array is.
The char terminal_char means that the string will terminate if the user
inputs whatever that character is. Note that it will discard whatever the
terminal character is.
It is possible to make a function call of cin.getline(
an_array, 21); without
the terminal character. Note that '\n' is the way of actually telling the compiler
you mean a new line, i.e. someone hitting the enter key.
Note that we are actually passing the address of the array when we pass
because arrays do not require an address operator (&) to be used to pass their address.
We can also replace by '\n' any character within the string, just we might
make sure to enclose it with single quotes to inform the compiler of its character
status, to have the getline terminate on that character.
3. String related functions
cstring is a header file that contains many functions for
1. The string comparison function: strcmp :
int strcmp ( const char *s1, const char *s2 );
const is to declare a named constant
strcmp will accept two strings. It will return an integer.
This integer will either be negative if s1 is less than s2,
zero if s1 and s2 are equal, and positive if s1 is greater than s2.
strcmp is case sensitive. It also passes the address of the character array to
the function to allow it to be accessed.
2. The string concatenate function: strcat :
char *strcat ( char *
dest, const char *
strcat is short for string concatenate, that is to add to the end,
strcat adds the second string to the first string. It returns a pointer
to the concatenated string. Beware this function, it assumes that
large enough to hold the entire contents of
src as well as its own contents.
3. The string copy function: strcpy :
char *strcpy ( char *
dest, const char *
strcpy is short for string copy, which means it copies the entire contents
dest. The contents of
dest after strcpy will be exactly
the same as
src such that strcmp (
src) will return 0.
4. The length of a string function: strlen :
size_t strlen ( const char *s );
strlen will return the length of a string, minus the
terminating character ('\0'). The size_t is an integer type
that cannot be negative.
4. Program Example
#include //for cin and cout
#include //for the string functions
using namespace std;
char fullname; // big enough to hold both firstname and lastname
cout<<"Please enter a first name: ";
cin.getline ( firstname, 50 );
if (strcmp ( firstname, "Golden mouth" ) == 0 ) // compare strings
cout<<"This first name is Golden mouth.\n";
else // if not equal
cout<<"This first name is not Golden mouth.\n";
// Find the length of your name
cout<<"This firstname is "<< strlen ( firstname ) <<" letters long. \n";
cout<<"Enter a last name: ";
cin.getline ( lastname, 50 );
fullname = '\0'; /* strcat searches for the terminating
character '\0' to cat after*/
strcat (fullname, firstname); // write firstname into fullname
strcat ( fullname, " " ); // to separate the names by a space
strcat ( fullname, lastname ); // write lastname onto the end of fullname
cout<<"The full name is "<< fullname <<"\n";
With codeBlocs, we obtain:
There are string functions that take an additional argument to indicate
the length of the destination buffer. For instance, the strcpy function has
an analogous strncpy function:
char *strncpy ( char *
dest, const char *
which will only copy
len bytes from
len should be less than the size of
the write could still go beyond the bounds of the array.
Unfortunately, strncpy can't guarantee that
dest will have a null
terminator attached to it. This might happen if the string
src is longer
dest. We might avoid this problem by using strlen to get the
src and make sure it will fit in | <urn:uuid:eac140f6-d7a7-43d4-8a6d-fe79ce5063c8> | 3.953125 | 1,446 | Documentation | Software Dev. | 66.811594 | 95,529,604 |
Behavior of Rhodopsin and Metarhodopsin in Isolated Rhabdoms of Crabs and Lobster
The photoreceptor organelles — the rhabdoms — of decapod Crustacea are elongate structures consisting of interleaved layers of microvilli from seven or eight retinular cells (1,2,3). When the eyes are broken open in an appropriate saline, the rhabdoms detach from the surrounding retinular cells, and individual rhabdoms can be identified under the microscope and studied spectrophotometrically with laterally-incident microbeams. All of the spectrophotometric measurements of rhabdoms described in this communication were performed on an instrument similar to that of Liebman and Entine (4). We have examined freshly-isolated rhabdoms as well as organelles fixed in 5% glutaraldehyde. The original reason for introducing glutaraldehyde fixation was to stabilize the structure of the isolated rhabdoms for periods commensurate with the measurements of pigment we wish to make (5). Although glutaraldehyde does not alter the absorption spectrum of either rhodopsin or metarhodopsin, it can hasten the destruction of both pigments, and therefore it is a useful tool in analyzing the pigment composition of rhabdoms by means of difference spectra.
KeywordsDifference Spectrum Blue Crab Visual Pigment Green Crab Retinular Cell
Unable to display preview. Download preview PDF.
- 2.EGUCHI, E., T.H. WATERMAN: Fine structure patterns in crustacean rhabdoms. In: The Functional Organization of the Compound Eye, C.G. Bernhard, ed., Pergamon Press, Oxford-New York, 1966.Google Scholar
- 3.RUTHERFORD, D.J., G.A. HORRIDGE: The rhabdom of the lobster eye. Quart. J. Micr. Sci. 106, 119–130 (1965).Google Scholar
- 9.BRUNO, M.S., M.I. MOTE, T.H. GOLDSMITH: Microspectrophotometry of visual pigment and spectral sensitivity of retinular cells in the crab Carcinus. Biol. Bull. 139, 416–417 (1970).Google Scholar
- 10.BRUNO, M.S., M.I. MOTE, T.H. GOLDSMITH: Spectral absorption and sensitivity measurements in single ommatidia of the green crab, Carcinus. J. Comp. Physiol. (in press).Google Scholar
- 11.FERNÁNDEZ, H.R.: A survey of the visual pigments of decapod Crustacea of South Florida. Ph.D. Thesis, University of Miami, Coral Gables, Florida, 1965.Google Scholar | <urn:uuid:95c94d57-be8d-495f-a33d-1865b30f307f> | 2.625 | 604 | Academic Writing | Science & Tech. | 49.282163 | 95,529,613 |
A solid which is bounded by six rectangular faces is known as cuboid and if the length, breadth and height of the cuboid are equal, then it is a cube.
8 vertices, 6 faces and 12 edges are there in both cube as well as cuboidcuboid. .Base of the cuboid is any face of the cuboid.
For a cuboid which has length (l), breadth (b) and height (h) has:
- Total surface area=2(lb+bh+lh)
For a cube with length x,
- Volume=x3 (because l = b = h = x)
- Total surface area=6x2
Q1.For a room of dimension 10m×8m×9m.Find out the longest pole that can be put in this room.
Solution: Longest pole is the longest diagonal of the room=
The longest pole that can be put inside the room has length=15.652m.
Q2. A cube has a volume 343cm3.Find the surface area of the cube.
Solution: The volume of the cube=a3=323
Total surface area=6a2
Total surface are of the cube=294cm2
Q3.Two cubes are joined end to end and has the volume 81cm3.Find the total surface area of the cube which is formed now.
When 2 cubes are joined end to end, it becomes a cuboid.
Volume of the cuboid=81cm3 = 2 x volume of each cube.
Let x be side of each cube.
x=9/ √2 cm
Length of the resulting cuboid=2x = 2 x 9/ √2 cm = 9√2 cm.
Breadth=9/√2 cm Height=9/√2 cm
Total surface area of the cuboid=2(lb+bh+lh)
= 2(9 √2×9/√2 + 9/√2 ×9√2 +9/√2 ×9 √2)
= 2( 81 + 81/2 + 81/2) = 2 x 162
=324 sq. cm.
Q4.A cuboidal water tank is aluminium steel sheet which is 4.5m thick. The outer dimensions are 1.5m×2.5m×3m.Find the internal dimensions and total surface area of the tank.
Solution: External dimensions of the cube are:
L=150cm, b=250cm and h=300cm.
As we know that the sheet is 4.5m thick, the internal dimensions are:
H= (300-9) =291cm
Total surface area of the tank=2(lb+bh+lh)
Q5.How many tissue boxes of size 10cm×8cm×9cm can be adjusted inside a cupboard box of size 36cm×40cm×100cm.
Solution: Volume of the tissue box = 10 x 8 x 9 cm3
Volume of the cupboard = 36 x 40 x 100 cm3.
Therefore we can say that 200 tissue boxes can be adjusted in the cupboard box. For more information contact byju’s mentors. If you have any doubts to clarify, please email to firstname.lastname@example.org
Practise This Question | <urn:uuid:5d1efa08-7da4-4b75-a826-eb0e6440dcf2> | 4 | 713 | Q&A Forum | Science & Tech. | 97.670539 | 95,529,626 |
Bohr Model: Introduction
Bohr model of atom was proposed by Neil Bohr in 1915. It came into existence with the modification of Rutherford’s model of atom. Rutherford’s model introduced nuclear model of atom, in which he explained that a nucleus (positively charged) is surrounded by negatively charged electrons. Bohr modified this atomic structure model by explaining that electrons move in fixed orbital’s (shells) and not anywhere in between and he also explained that each orbit (shell) has a fixed energy level. Rutherford basically explained nucleus of an atom and Bohr modified that model into electrons and their energy levels.
Bohr’s model consists of a small nucleus (positively charged) surrounded by negative electrons moving around the nucleus in orbits. Bohr found that an electron located away from the nucleus has more energy, and electrons close to the nucleus have less energy.
Postulates of Bohr’s Model of an Atom
- In an atom, electrons (negatively charged) revolve around the positively charged nucleus in a definite circular path called as orbits or shells.
- Each orbit or shell has a fixed energy and these circular orbits are known as orbital shells.
- The energy levels are represented by an integer (n=1, 2, 3…) known as quantum number. This range of quantum number starts from nucleus side with n=1 having the lowest energy level. The orbits n=1, 2, 3, 4… are assigned as K, L, M, N…. shells and when an electron attains the lowest energy level it is said to be in the ground state.
- The electrons in an atom move from lower energy level to higher energy level by gaining the required energy and an electron moves from higher energy level to lower energy level by losing energy.
Limitations of Bohr’s Model of an Atom
- Bohr’s model of an atom failed to explain Zeeman Effect (effect of magnetic field on the spectra of atoms).
- It also failed to explain the Stark effect (effect of electric field on the spectra of atoms).
- It violates the Heisenberg Uncertainty Principle.
- It could not explain the spectra obtained from larger atoms.
To follow more about Bohr’s model of an atom, download Byju’s-the learning app.
Practise This Question | <urn:uuid:80462c17-9608-4ca1-beff-d0084b754e0c> | 3.78125 | 494 | Knowledge Article | Science & Tech. | 43.811477 | 95,529,642 |
Scientists have identified the means by which water in our blood supply crosses over to the brain, where it becomes the cerebrospinal fluid that surrounds and protects one of our most precious organs.
Every day, about half a litre of water is transported from our blood in this way, but while researchers knew a thin tissue in the brain called the choroid plexus was involved in this process, they didn’t understand how so much cerebrospinal fluid (CSF) could be produced. Now, we may finally have the answer.
“It is brand-new knowledge on a very important physiological process involving by far the most complex organ in the human body,” says neuroscientist Nanna MacAulay from the University of Copenhagen in Denmark.
It used to be thought that osmosis and associated forces regulated how water passed into the brain to produce cerebrospinal fluid, but as MacAulay’s team explains, a number of existing studies have helped demonstrate that “osmotic water transport does not suffice to sustain the rates of CSF production consistently observed in mammals”.
To investigate what mechanism could be driving the phenomenon, MacAulay and fellow researchers studied a mouse model where the conditions required for osmotic water transport were absent.
By inhibiting osmotic water transporters in the brains of live mice, the team found a previously unknown ion transporter called the NKCC1 co-transporter; it turned out to be responsible for approximately half of CSF production.
If the same molecular channel can be manipulated in humans, it could provide a revolutionary way of accessing and controlling the water system of the brain, easing pressure without resorting to invasive surgical operations – such as drilling holes in the cranium to drain fluid, and even removing pieces of the skull.
“If we are able to target this ion and water transporter with medicine, it would affect a number of disorders involving increased intracranial pressure, including brain haemorrhage, blood clots in the brain, and hydrocephalus,” MacAulay says.
Of course, it’s always impossible to guarantee that the results seen in animal studies will be replicated in research with human patients, but here the team is hopeful, mainly because the protein structure of the choroid plexus is similar.
If they’re right, it could result in what the researchers describe as a “paradigm shift in the field”, giving us a therapeutic target to treat brain pathologies involving increased pressure in events such as strokes, along with other serious cases where patients currently have few (or zero) non-invasive options.
“Of course, it would be ground-breaking if we were able to use this mechanism as a target for medical treatment and turn down the in-flow of water to the brain to reduce intracranial pressure,” MacAulay says.
“At worst, the patient may suffer permanent damage and even die as a result of increased pressure. Therefore, this basic mechanism is an important find to us.”
Now that we know that CSF production depends on more than just osmotic gradients, the researchers say the next steps are to find how this water flow channel can be controlled in the basolateral membranes of cells, getting us another step closer to maybe one day helping patients whose brains are getting dangerously pressurised.
Watch this space.
The findings are reported in Nature Communications. | <urn:uuid:3619850f-d973-44e8-b1e9-08e6295513b9> | 4.1875 | 728 | News Article | Science & Tech. | 25.993971 | 95,529,648 |
The Great Vanishing Oil Spill
Microbes may have eaten away at BP’s oil in deep water; now the marshland needs help.
Microbes may become the heroes of the Gulf of Mexico oil spill by gobbling up oil more rapidly than anyone expected. Now some experts suggest we ought to artificially stimulate such microbes in stricken marshland areas to aid their cleanup.
Evidence published this week shows that deep-water microbes in the Gulf may be rapidly chewing up BP’s spilled crude. This could sway federal authorities to use petroleum-digesting microbes or fertilizer additives that can stimulate naturally occurring bacteria for future spills. Such measures were originally rejected for the BP spill.
Ralph Portier, a marine toxicologist at Louisiana State University, says the EPA approves of such measures in general, but they weren’t approved for the Gulf spill because it was thought they wouldn’t be necessary–a presumption that now appears to be correct.
Oil has disappeared from the Gulf’s surface waters since BP capped its blown-out well on August 15. Yet most of the estimated 4.9 million barrels of oil are unaccounted for. Some of BP’s oil, however, has reached more than 100 miles of sensitive Gulf marsh, and may remain lodged deep within sediments for years.
Portier says cleanup authorities are following a 2001 federal position paper arguing that stimulating biodegradation was unnecessary in the Gulf ecosystem. The Gulf already harbors microbes adapted to degrading the region’s naturally occurring underwater petroleum seeps, the federal paper said.
Microbial ecologist Terry Hazen, a bioremediation expert at the U.S. Department of Energy’s Lawrence Berkeley Laboratory, says that this reasoning is correct for dispersed oil. Hazen led a team that identified a strain of microbes rapidly breaking down oil at a depth of 1,100 meters and icy temperatures as low as 5 °C–conditions where biodegradation is expected to proceed slowly. The research appears this week in the journal Science.
Hazen’s team examined one of several plumes of oil droplets emanating from BP’s blowout, and observed rod-shaped bacteria feasting on the 10- to 60-micrometer droplets fast enough to halve the oil every two to six days. That rate contradicts a study of the same plume conducted by the Woods Hole Oceanographic Institution, and published in Science earlier this month, that found meager oxygen consumption (to be expected where large numbers of microbes are consuming oil) and concluded that the oil was therefore not being broken down.
The divergence, according to Hazen, is explained by the thin concentration of the oil. While immense, stretching over 35 kilometers, the oil in the studied plume maxed out at 10 parts-per-million. Oxygen depletion by microbes would thus be negligible, argues Hazen.
In recent weeks, Hazen’s group has detected no oil, although it’s possible the oil could simply have been carried out of view by Gulf currents. Federal incident commander Thad Allen told Technology Review on Wednesday that he needs a more rigorous measurement program to “get a handle on what is actually out there in the water.”
Hazen bets that the dispersed oil has indeed broken down, and says some credit for that goes to the 1.84 million gallons of dispersant sprayed on the spilling oil as part of the cleanup operation. This dispersant also likely acted as a bioremediation agent because the tiny droplets it created gave microbes more surface area to chew at.
Natural microbial activity, however, may fall short in marsh sediments where oil is concentrated and the supply of oxygen and nutrients is constrained, slowing microbial digestion to a crawl.
Artificial enhancements could speed up marsh recovery, says Portier. He says LSU scientists showed this to be true three years ago in a marsh in Lake Charles, LA, that was contaminated with heavy crude. They bolstered the marsh microbial community with an LSU-developed culture of oil-eating marsh microbes, along with diluted fertilizer. After 72 days, untreated sites still harbored more than half of their spilled oil, says Portier, whereas treated sites were clean enough to meet strict federal risk levels for residential areas.
Portier says he is working with a BP-backed research coalition of universities and state agencies that expects to have field trials underway in Gulf marshes next month.
Couldn't make it to EmTech Next to meet experts in AI, Robotics and the Economy?Go behind the scenes and check out our video | <urn:uuid:5ad61f4d-870a-470b-9fde-b4c7fdd705b1> | 3.5 | 938 | Truncated | Science & Tech. | 41.114169 | 95,529,651 |
Has Chromatography Exposed "Deceptive" Plants?
Dec 02 2016 Read 1262 Times
A researcher at the University of Bayreuth in Germany has found a fascinating example of plants being deceptive to ensure that they are pollinated — and it is thanks to the help of gas chromatography with electroantennographic (GC-EAD) and mass spectrometry (GC-MS). So, let’s look at the deceptive plants and find out how chromatography helped.
Pollination and insects
Pollination is simply the transfer of pollen from the male anther to the female stigma — an essential process in the fertilization of many plants. Some plants are self-pollinating and don’t need a bee or other insect to transfer the pollen. But many plants do need a little help from nature in the form of a pollinator. The most widely known pollinators are bees, and they are also one of the most important pollinators for plants that we use and eat — which is why the decimation of bee colonies is causing so much concern.
To ensure their survival, some plants actively attract pollinators through various methods, not just relying on their attractiveness to the pollinator. For example, some plants send out chemical signals when they need to be pollinated — attracting the right insects at the right time of year. But some plants are not content to let nature take its course and actively practice the dark art of deception to make sure of their survival.
Bees and carnivorous flies
Annemarie Heiduk, a researcher at the University of Bayreuth, has been investigating one plant — Ceropegia sandersonii, Sanderson’s parachute flower — that lures and traps carnivorous flies to make sure it gets pollinated. The flies it lures are Desmometopa — a fly that feeds on honeybees.
The flies don’t hunt the honeybees themselves, — no, they wait for spiders and other insects to kill the honeybees. The flies can detect chemical signals — alarm pheromones that the bees give off as they are attacked. They can then join in the party and feast on the honeybees along with the original predators. The flies are known as kleptoparasites — animals that steal food from the predators.
Deception and lies with Ceropegia sandersonii
To attract the flies, the parachute flowers release a fragrance that mimics the scent of dying honeybees. Irresistible to the flies, which are attracted to the flower but they find no bees — instead, the flies find themselves imprisoned in the flowers. Because the flowers have nothing to offer the flies, no food or nectar, the flowers are known as ‘deceptive flowers’ and they trap the flies for 24 hours, coating them in pollen, before releasing them. The flies, now hungry, are attracted to other parachute flowers mimicking dying honeybees transferring the pollen and completing the pollination cycle.
Heiduk used GC-MS to analyse the scent of the pollinators and GC-EAD to analyse which scents the flies were attracted to. Gas chromatography is commonly used to analyse fragrances and other aroma samples as discussed in the article, Sample Preparation Options for Aroma Analysis.
Do you like or dislike what you have read? Why not post a comment to tell others / the manufacturer and our Editor what you think. To leave comments please complete the form below. Providing the content is approved, your comment will be on screen in less than 24 hours. Leaving comments on product information and articles can assist with future editorial and article content. Post questions, thoughts or simply whether you like the content.
In This Edition Articles - Enhanced Sample Preparation - Identifying Inherent Contamination in Deep Well Microplates - How to Determine Extra Column Dispersion and Extra Column Volume - Th...
View all digital editions
Jul 29 2018 Washington DC, USA
Aug 02 2018 Barcelona, Spain
Aug 06 2018 Berlin, Germany
Aug 26 2018 Florence, Italy
Sep 05 2018 Chiba, Japan | <urn:uuid:28ab36a3-2891-4982-8882-8a2902612db5> | 3.21875 | 838 | Truncated | Science & Tech. | 41.581866 | 95,529,659 |
Hot mantle plume rising to the lithosphere induced the first large-scale sinking of lithospheric plates
Our planet Earth is the only planet in the Solar System that possesses Plate Tectonics. The Earth’s surface is in a constant state of change; the tectonic plates together with the oceans and continents continuously slide along one another, collide or sink into the Earth’s mantle.
However, it still remains unclear how Plate Tectonics started on Earth. An international research team combining modeling experts from the ETH Zürich, the GFZ German Research Centre for Geosciences, and geologists from the University of Texas and Korea University in Seoul have proposed an answer to this question in a recent publication in the journal Nature.
Based on advanced high-resolution numerical modeling and geological observations they demonstrate that a hot mantle plume rising to the lithosphere from the deep mantle might have broken the intact outer shell of the early Earth and induced the first large-scale sinking of lithospheric plates, a key process of Plate Tectonics called subduction.
The rigid outer shell of present-day Earth that includes crust and uppermost mantle, i.e. the lithosphere is divided into several plates. Lithospheric plates slide along their boundaries or colliding with each other and some of them, which are cold and heavy enough, sink into the deep mantle.
This process, called subduction is the key process of Plate Tectonics responsible for the recycling of the materials of Earth’s crust into the deep mantle and for an efficient cooling of the Earth interior. However, subduction and Plate Tectonics was not always taking place on Earth.
During the first 1 or 2 billion years of the 4.5 billion years Earth’s history, the tectonic process was very different, probably similar to present-day Venus, where the lithosphere is not broken into plates and no subduction occurs. So how did the first subduction and Plate Tectonics develop on Earth?
“Three conditions must have been met for the mantle plume to start first long-lived subduction and Plate Tectonics on Earth”, says Stephan Sobolev, Head of Geodynamic Modeling Section at GFZ and Professor of Geodynamics at University of Potsdam.
“First, the mantle plume had to be large and hot enough to produce a lot of melt. These melts intruded into the lithosphere above the plume making it mechanically weak and allowing the plume to penetrate into the crust. Second, the lithosphere had to be thick and heavy enough to sink into the mantle”.
In the beginning the broken lithosphere around the plume was probably pushed down by the load of the plume material spreading above it and then the sinking parts of the heavy lithosphere pulled down the adjacent lithosphere. “Finally there had to be liquid water in the ocean to lubricate, in a way, the surface of the sinking lithospheric plate” adds Sobolev. “This allowed it to sink deep into the Earth”.
All these conditions were fulfilled sometime in early Earth history, but were never met for other planets of the Solar System. For instance on Venus, which is most similar to the Earth, hot mantle plumes are probably quite common, but the lithosphere is too hot and light and there is no liquid water at the hot surface of Venus.
It was most likely not just an interaction of a single mantle plume with the early Earth lithosphere, but rather a number of such interactions that were responsible for the triggering of Plate Tectonics on Earth. The vigorous inner life of our unique planet created a number of “plate tectonic windows” as shown in the Figure, which joined after some time and induced global Plate Tectonics.
T.V. Gerya , R.J. Stern, M. Baes, S.V. Sobolev and S.A. Whattam, Plate tectonics on the Earth triggered by plume-induced subduction initiation, Nature, 12.11.2015, DOI: 10.1038/nature15752
Franz Ossing | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Materials Sciences
18.07.2018 | Life Sciences
18.07.2018 | Health and Medicine | <urn:uuid:cef0eaf6-8883-408c-8322-657c4afb3db4> | 4.0625 | 1,516 | Content Listing | Science & Tech. | 43.870707 | 95,529,660 |
List of extinct animals of the British Isles
This article needs additional citations for verification. (May 2013) (Learn how and when to remove this template message)
This is a list of extinct animals of the British Isles. Only a small number of these are globally extinct, most famously the Irish elk, great auk and woolly mammoth. Most of the remainder survive to some extent outside the islands. The list includes introduced species only in cases where they were able to form self-sustaining colonies for a time. Only species extinct since Great Britain was separated from mainland Europe are included. The date beside each species is the last date when a specimen was observed in the wild or, where this is not known, the approximate date of extinction. The list is complete for mammals, reptiles, freshwater fish and amphibians.
- 1 Mammals
- 2 Birds
- 3 Fish
- 4 Amphibians
- 5 Reptiles
- 6 Insects
- 7 Crustaceans
- 8 Reintroduction and re-establishment
- 9 See also
- 10 References
- 11 Further reading
- Arctic lemming – c. 8000 B.C.
- Arctic fox - c. (unknown)
- †Eurasian aurochs – c. 1000 B.C.
- Barbary macaque - c. 30,000 B.C.
- †Cave bear – c. 15,000 B.C.
- Coypu – 1978 (nonnative)
- Eurasian elk - Bronze Age
- Eurasian beaver – 1526 (reintroduced)
- Eurasian brown bear – c. A.D. 1000
- Eurasian lynx – c. A.D. 400
- Grey whale – c. 598 B.C.
- Eurasian wolf – A.D. 1680 in Great Britain, A.D. 1786 in Ireland
- †Irish elk – c. 6000 B.C.
- Narrow-headed vole – c. 8000 B.C.
- Steppe pika – c. 8000 B.C.
- Root vole – c. 1500 B.C.
- Saiga antelope – c. 10,000 B.C.
- Steppe lemming – c. 8000 B.C.
- †Tarpan – c. 7000 B.C.
- Walrus – c. 1000 B.C. (occasional visitor)
- Wild boar – c. 1400 (reintroduced)
- Wisent – c. 3000 B.C.
- Wolverine – c. 6000 B.C.
- †Woolly mammoth – c. 10,000 B.C.
- †Woolly rhinoceros – c. 10,000 B.C.
- †Cave lion – c. 10,000 B.C.
- †Scimitar-toothed cat - c. 30,000 B.C.
- †Cave hyena - c. 11,000 B.C.
- †European jaguar - c. (unknown)
- †European Ice Age leopard - c. 24,000 B.C.
- †European gazelle - c. (unknown)
- Fea's petrel – Iron Age
- Dalmatian pelican – c. 1000 B.C.
- Eurasian spoonbill – 15th century (re-established)
- Little egret – late medieval period (re-established)
- Osprey – 1916 (re-established)
- White-tailed eagle – 1916 (reintroduced)
- Western marsh harrier – late 19th century (re-established)
- Northern goshawk – late 19th century (possibly reintroduced)
- Western capercaillie – 1780s (reintroduced)
- Great bustard – 19th century (reintroduced)
- Common crane – late medieval period (re-established)
- Pied avocet – 19th century (re-established)
- Kentish plover – 20th century (last breeding record 1979)
- †Great auk – 1844
- White stork – 1416
- Red-backed shrike – 1989 (as a regular breeding bird)
- Wryneck (as a regular breeding bird)
- European pond terrapin – ≤ 3000 B.C.
- Agonum sahlbergi (ground beetle) – 1914
- Blue stag beetle – 19th century
- Graphoderus bilineatus (water beetle) – 1906
- Harpalus honestus (ground beetle) – 1905
- Horned dung beetle – 1957
- Ochthebius aeneus (water beetle) – 1913
- Platydema violaceum (tenebrionid) – 1957
- Rhantus aberratus (water beetle) – 1904
- Scybalicus oblongiusculus (ground beetle) – 1926
- Teretrius fabricii (histerid) – 1907
Bees, wasps and ants
- Andrena polita (mining bee) – 1934
- Bombus pomorum, apple bumblebee – 1864
- Bombus cullumanus, Cullum's bumblebee – 1941
- Eucera tuberculata (mining bee) – 1941
- Halictus maculatus (mining bee) – 1930
- Mellinus crabroneus (digger wasp) – c. 1950
- Odynerus reniformis (mason wasp) – 1915
- Odynerus simillimus (mason wasp) – 1905
- Short-haired bumblebee – 1989
Butterflies and moths
General reference: Waring et al., 2009.
- Aporia crataegi, black-veined white – 1925
- Borkhausenia minutella – 1950
- Conformist (moth) –
- Euclemensia woodiella (moth) – 1829
- Flame brocade (moth) – 1919
- Frosted yellow (moth) – 1914
- Gypsy moth – 1907; reappeared 1995
- Isle of Wight wave (moth) – 1931
- Large chequered skipper – c. 1989 (non-native, Channel Islands)
- Large copper – 1865
- Many-lined (moth) – 1875
- Map – c. 1914 (non-native)
- Mazarine blue – 1906
- Orache moth – 1915
- Reed tussock (moth) – 1875
- Scarce black arches (moth) – 1898 (transitory resident)
- Speckled beauty (moth) – 1898
- Union rustic (moth) – 1919
- Viper's bugloss (moth) –1969
Dragonflies and damselflies
† – Species is extinct worldwide
Reintroduction and re-establishment
The white-tailed eagle has been successfully re-established on the west coast of Scotland. Having clung on in parts of Wales, red kites have been successfully re-established in parts of England and Scotland. Ongoing projects involve both these species: the corncrake into parts of England and Scotland, and the great bustard on Salisbury Plain.
European beavers have been reintroduced to parts of Scotland, and there are plans to bring them back to other parts of Britain. A five-year trial reintroduction at Knapdale in Argyll started in 2009 and concluded in 2014. A few hundred beavers live wild in the Tay river basin, as a result of escapes from a wildlife park. A similar reintroduction trial is being undertaken on the river otter in Devon, England. In 2016, beavers were recognised as a British native species, and will be protected under law.
In 2008, moose were released into a fenced reserve on the Alladale Estate in the Highlands of Scotland. Reindeer were re-established in 1952; approximately 150–170 reindeer live around the Cairngorms region in Scotland.
In 1998, MAFF, now known as DEFRA released a report concerning the presence of two populations of wild boar living freely in the UK. These boar are thought to have escaped from wildlife parks, zoos and from farms where they are farmed for their meat, and gone on to establish breeding populations.
The northern clade pool frog was reintroduced from Swedish stock in 2005, to a single site in Norfolk, England, following detailed research to prove that it had been native prior to its extinction around 1993.
The large blue butterfly has been successfully re-established from Swedish stock at a number of sites, but few of these are open-access. There are also several successful cases of the establishment of new populations of heath fritillary.
- List of mammals of the British Isles
- Extinct animals from the Isle of Man
- List of extinct animals of Europe
- Introduced species of the British Isles
- Yalden, Derek (1999), History of British Mammals, London: T. & A.D. Poyser Ltd., ISBN 0-85661-110-7
- "The lost beasts that roamed Britain during the ice age". BBC. July 22, 2015. Retrieved 29 August 2017.
- Bill Teale (2016-09-17). "Birdwatch: Rare appearance from Kentish plover". Yorkshire Post. Retrieved 26 May 2017.
- Bumblebee superfacts, BugLife, retrieved January 23, 2013
- Waring, P.; et al. (2009), Field Guide to the Moths of Great Britain and Ireland, Hook, Hampshire: British Wildlife Publishing, ISBN 0953139999; UK Moths, Ian Kimber https://ukmoths.org.uk/, retrieved January 23, 2013 Missing or empty
- Tilbury, Christine (March 2007), Gypsy Moth Advisory Note (PDF), Forest Research: Tree Health Division, retrieved 6 February 2014
- "Viper's Bugloss Hadena irregularis – UK Moths", UK Moths, Ian Kimber, retrieved January 23, 2013
- Gilbert Van Stappen (1996), "Artemia", in Patrick Lavens & Patrick Sorgeloos, Manual on the Production and Use of Live Food for Aquaculture, FAO Fisheries Technical Paper, 361, Rome: Food and Agriculture Organization, pp. 79–106, ISBN 978-92-5-103934-2
- Geoffrey Fryer (2006), "The brine shrimp's tale: a topsy turvy evolutionary fable" (PDF), Biological Journal of the Linnean Society, 88 (3): 377–382, doi:10.1111/j.1095-8312.2006.00623.x
- George Monbiot. "15 species that should be brought back to rewild Britain". the Guardian. Retrieved 20 December 2015.
- "RSPB: Redkite Conservation".
- "The RSPB: Red kite". The RSPB. Retrieved 20 December 2015.
- "Commissioned Report No. 685 The Scottish Beaver Trial: Ecological monitoring of the European beaver Castor fiber and other riparian mammals 2009-2014, final report" (PDF). Retrieved 18 December 2016.
- "Tay Beavers Origin". Scottish Wild Beavers. Retrieved 20 December 2015.
- "Feral wild boar in England Status, impact and management A report on behalf of Defra European Wildlife Division" (PDF). National Archives. Department for Environment, Food and Rural Affairs. Archived from the original on 1 January 2007. Retrieved 26 October 2017.
- "Feral wild boar in England Status, impact and management A report on behalf of Defra European Wildlife Division" (PDF). Archived from the original on 1 January 2007. Retrieved 26 October 2017.
- "Wild Boar". The British Association for Shooting and Conservation. BASC. Retrieved 26 October 2017.
- "Call for lynx and wolf reintroduction". BBC News. 15 July 2015. Retrieved 20 December 2015.
This article needs additional citations for verification. (August 2009) (Learn how and when to remove this template message) | <urn:uuid:e2212bad-cb89-429f-b17a-7978546aeeeb> | 3.0625 | 2,600 | Structured Data | Science & Tech. | 68.252438 | 95,529,685 |
In 2021, the Franco-German satellite MERLIN shall be launched to study methane emissions on Earth. On board is a laser system that works precisely under extreme operating conditions. The technology for this has been developed at the Fraunhofer Institute for Laser Technology ILT in Aachen and will be presented at the LASER World of Photonics 2017.
As a climate gas, methane has not yet garnered as much attention as carbon dioxide, but is – per molecule – 25 times more potent in causing global warming. However, carbon dioxide is present in the atmosphere about 200 times more frequently and is, in absolute terms, more effective. Since 2007, the methane concentration in the atmosphere has risen rapidly, although science has not yet clarified why this has occurred.
Representation of the MERLIN instrument based on the Myriade satellite platform.
CNES/illustration David DUCROS, 2016
Against this backdrop, the Franco-German MERLIN project was conceived and started in 2010. The small satellite MERLIN (Methane Remote Sensing LIDAR Mission) will be launched in 2021 and map the methane in the Earth's atmosphere. The scientists want to understand where methane is introduced into the atmosphere and where it is degraded.
The core of the satellite is a light radar (LIDAR) that sends light pulses into the atmosphere and determines the methane concentration from the backscattered light. So far, solar radiation has been required for methane measurements by means of optical spectrometers, but with MERLIN-LIDAR the values can also be measured on the dark side of the earth. In addition, measurements are also possible in small-scale cloud gaps.
How does one develop lasers for space?
The MERLIN mission places extreme operating requirements upon laser: the system must withstand shocks as well as vibrations up to 25 grms as well as varying thermal loads from -30 °C to +50 °C. In addition, organic materials such as adhesives have to be avoided as completely as possible in order not to contaminate the ambient air and, thus, the high-purity mirror surfaces. Moreover, everything has to work after the launch for the duration of the mission – three years.
For partners such as DLR (the German Aerospace Center), Airbus Defence and Space, TESAT Spacecom and ESA, Fraunhofer ILT has been developing technologies for lasers suitable for space missions for years. While individual systems have already flown, the experts have now created a new technology platform for laser systems, FULAS (Future Laser System, sponsored by the European Space Agency ESA, FKZ C0O-8/09/FF), that can be adapted to different laser beam characteristics and, thus, missions. The FULAS high power sub-assembly was completed in 2016. The system already passed the first thermal vacuum tests under realistic MERLIN conditions.
For the FULAS platform, the experts have developed not only components suitable for space travel, but also their very own construction technology. In the case of the opto-mechanical components, all essential adjustment steps are carried out with manually guided robots using the so-called Pick & Align method. As a result, the process can be automated, thus making it interesting for other industries.
MERLIN is on its way to take-off
The LIDAR laser for MERLIN is also based on the FULAS platform. Laser oscillators, amplifiers and frequency converters are attached on and under a special optical bench. The Pick & Align process is used to adjust and solder the optical components.
The parameters in detail are a challenge: for LIDAR operation, the laser system has to provide 9 mJ double pulses at two wavelengths around 1645 nm in single-frequency operation, with one of the pulses always precisely adjusted to a characteristic methane absorption line. A tailor-made design is used in this system, consisting of an oscillator with active length control, the multi-award winning InnoSlab amplifier with a wavelength of 1064 nm and an optical parametric oscillator (OPO) with two KTP crystals.
A MERLIN predecessor, the LIDAR system of the CHARM-F mission already flew in 2015 on the research aircraft HALO. At that time, the DLR Institute for Atmospheric Physics had integrated the frequency conversion for the LIDAR. For MERLIN, mounting and adjustment concepts for an optimized OPO have been developed and successfully implemented based on the FULAS technology platform. The robustness of the complete OPO structure was demonstrated in MERLIN temperature tests.
Now, since the PDR status (Preliminary Design Review) was achieved last year, the CDR (Critical Design Status) status is being developed and the construction of an EQM (Engineering Qualification Model) prepared. This model will later be subjected to extensive tests in order to prove its suitability for use in space. The findings gained from these tests will be integrated in the construction of the final flight model (FM). However, the basic laser parameters have already been demonstrated on a laboratory model based on standard components.
The MERLIN system shall go into space operation in about three years; the production technologies and the test procedures have already been established and can be used for other airworthy systems. Moreover, as is often the case in space travel, there are interesting synergies for other applications: automated adjustment of optical components, for example, is the order of the day for the production of laser sources.
The MERLIN-LIDAR model will be on display at the joint Fraunhofer stand A2.431 at the LASER World of Photonics 2017 in Munich, Germany.
The MERLIN project has been funded by the German Ministry for Economic Affairs and Energy (BMWi, grant number 50 EP 1601) and is coordinated by DLR Space Administration.
Dr. rer. nat. Jens Löhring
Head of the group Packaging
Phone +49 241 8906-673
Dipl.-Ing. Hans-Dieter Hoffmann
Head of the competence area Laser and Laser Optics
Phone +49 241 8906-206
Petra Nolis M.A. | Fraunhofer-Institut für Lasertechnik ILT
AchemAsia 2019 will take place in Shanghai
15.06.2018 | DECHEMA Gesellschaft für Chemische Technik und Biotechnologie e.V.
Insects supply chitin as a raw material for the textile industry
05.06.2018 | Fraunhofer-Institut für Grenzflächen- und Bioverfahrenstechnik IGB
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Earth Sciences
19.07.2018 | Power and Electrical Engineering
19.07.2018 | Materials Sciences | <urn:uuid:bcf38c9f-b3c7-4d7f-8e71-1d79b6a3ed8b> | 3.953125 | 1,960 | Content Listing | Science & Tech. | 40.210681 | 95,529,690 |
A sinkhole, also known as a cenote, sink, sink-hole,swallet, swallow hole, or doline (the different terms for sinkholes are often used interchangeably), is a depression or hole in the ground caused by some form of collapse of the surface layer. Most are caused by karst processes--for example, the chemical dissolution of carbonate rocks or suffosion processes. Sinkholes vary in size from 1 to 600 m (3.3 to 2,000 ft) both in diameter and depth, and vary in form from soil-lined bowls to bedrock-edged chasms. Sinkholes may form gradually or suddenly, and are found worldwide.
Sinkholes near the Dead Sea
, formed when underground salt is dissolved by freshwater intrusion, due to continuing sea-level drop.
Collapse sinkhole in gypsum
, near Madrid, central Spain.
Sinkholes may capture surface drainage from running or standing water, but may also form in high and dry places in specific locations. Sinkholes that capture drainage can hold it in large limestone caves. These caves may drain into tributaries of larger rivers.
The formation of sinkholes involves natural processes of erosion or gradual removal of slightly soluble bedrock (such as limestone) by percolating water, the collapse of a cave roof, or a lowering of the water table. Sinkholes often form through the process of suffosion. For example, groundwater may dissolve the carbonate cement holding the sandstone particles together and then carry away the lax particles, gradually forming a void.
Occasionally a sinkhole may exhibit a visible opening into a cave below. In the case of exceptionally large sinkholes, such as the Minyé sinkhole in Papua New Guinea or Cedar Sink at Mammoth Cave National Park in Kentucky, an underground stream or river may be visible across its bottom flowing from one side to the other.
Sinkholes are common where the rock below the land surface is limestone or other carbonate rock, salt beds, or in other soluble rocks, such as gypsum, that can be dissolved naturally by circulating ground water. Sinkholes also occur in sandstone and quartzite terrains.
As the rock dissolves, spaces and caverns develop underground. These sinkholes can be dramatic, because the surface land usually stays intact until there is not enough support. Then, a sudden collapse of the land surface can occur.
On 2 July 2015, scientists reported that active pits, related to sinkhole collapses and possibly associated with outbursts, were found on the comet 67P/Churyumov-Gerasimenko by the Rosetta space probe.
Collapse formed by rainwater leaking through pavement and carrying soil into a ruptured sewer pipe.
Collapses, commonly incorrectly labeled as sinkholes also occur due to human activity, such as the collapse of abandoned mines and salt cavern storage in salt domes in places like Louisiana, Mississippi and Texas. More commonly, collapses occur in urban areas due to water main breaks or sewer collapses when old pipes give way. They can also occur from the overpumping and extraction of groundwater and subsurface fluids.
Sinkholes can also form when natural water-drainage patterns are changed and new water-diversion systems are developed. Some sinkholes form when the land surface is changed, such as when industrial and runoff-storage ponds are created; the substantial weight of the new material can trigger a collapse of the roof of an existing void or cavity in the subsurface, resulting in development of a sinkhole.
Sinkholes tend to occur in karst landscapes. Karst landscapes can have up to thousands of sinkholes within a small area, giving the landscape a pock-marked appearance. These sinkholes drain all the water, so there are only subterranean rivers in these areas. Examples of karst landscapes with a plethora of massive sinkholes include Khammouan Mountains (Laos) and Mamo Plateau (Papua New Guinea). The largest known sinkholes formed in sandstone are Sima Humboldt and Sima Martel in Venezuela.
Some sinkholes form in thick layers of homogenous limestone. Their formation is facilitated by high groundwater flow, often caused by high rainfall; such rainfall causes formation of the giant sinkholes in the Nakanaï Mountains, on the New Britain island in Papua New Guinea. On the contact of limestone and insoluble rock below it, powerful underground rivers may form, creating large underground voids.
In such conditions, the largest known sinkholes of the world have formed, like the 662-metre (2,172 ft) deep Xiaozhai Tiankeng (Chongqing, China), giant sótanos in Querétaro and San Luis Potosí states in Mexico and others.
Unusual processes have formed the enormous sinkholes of Sistema Zacatón in Tamaulipas (Mexico), where more than 20 sinkholes and other karst formations have been shaped by volcanically heated, acidic groundwater. This has produced not only the formation of the deepest water-filled sinkhole in the world--Zacatón--but also unique processes of travertine sedimentation in upper parts of sinkholes, leading to sealing of these sinkholes with travertine lids.
The state of Florida in the United States is known for having frequent sinkhole collapses, especially in the central part of the state. Underlying limestone there is from 15 to 25 million years old. On the fringes of the state, sinkholes are rare or non-existent; limestone there is around 120,000 years old.
The Murge area in southern Italy also has numerous sinkholes. Sinkholes can be formed in retention ponds from large amounts of rain. An analysis of a case of sinkhole formation under a retention pond due to a large amount of rain can be seen in a sinkhole collapse study.
Sinkholes have been used for centuries as disposal sites for various forms of waste. A consequence of this is the pollution of groundwater resources, with serious health implications in such areas. The Maya civilization sometimes used sinkholes in the Yucatán Peninsula (known as cenotes) as places to deposit precious items and human sacrifices.
When sinkholes are very deep or connected to caves, they may offer challenges for experienced cavers or, when water-filled, divers. Some of the most spectacular are the Zacatón cenote in Mexico (the world's deepest water-filled sinkhole), the Boesmansgat sinkhole in South Africa, Sarisariñama tepuy in Venezuela, the Sótano del Barro in Mexico, and in the town of Mount Gambier, South Australia. Sinkholes that form in coral reefs and islands that collapse to enormous depths are known as blue holes and often become popular diving spots.
Large and visually unusual sinkholes have been well-known to local people since ancient times. Nowadays sinkholes are grouped and named in site-specific or generic names. Some examples of such names are listed below.
- Black holes - This term refers to a group of unique, round, water-filled pits in the Bahamas. These formations seem to be dissolved in carbonate mud from above, by the sea water. The dark color of the water is caused by a layer of phototropic microorganisms concentrated in a dense, purple colored layer at 15 to 20 m (49 to 66 ft) depth; this layer "swallows" the light. Metabolism in the layer of microorganisms causes heating of the water, the only known case in the natural world where microorganisms create significant thermal effects. One of them is the Black Hole of Andros.
- Blue holes - This name was initially given to the deep underwater sinkholes of the Bahamas but is often used for any deep water-filled pits formed in carbonate rocks. The name originates from the deep blue color of water in these sinkholes, which is created by the high clarity of the water and the great depth of the sinkholes; only the deep blue color of the visible spectrum can penetrate such depth and return after reflection.
- Cenotes - This refers to the characteristic water-filled sinkholes in the Yucatán Peninsula, Belize and some other regions. Many cenotes have formed in limestone deposited in shallow seas created by the Chicxulub meteorite's impact.
- Sótanos - This name is given to several giant pits in several states of Mexico.
- Tiankengs - These are extremely large sinkholes, typically deeper and wider than 250 m (820 ft), with mostly vertical walls, most often created by the collapse of underground caverns. The term means sky holes in Chinese; many of this largest type of sinkhole are located in China.
- Tomo - This term is used in New Zealand karst country to describe pot holes.
The 2010 Guatemala City sinkhole formed suddenly in May of that year; torrential rains from Tropical Storm Agatha and a bad drainage system were blamed for its creation. It swallowed a three-story building and a house; it measured approximately 20 m (66 ft) wide and 30 m (98 ft) deep. A similar hole had formed nearby in February 2007.
This large vertical hole is not a true sinkhole, as it did not form via the dissolution of limestone, dolomite, marble, or any other water-soluble rock. Guatemala City is not underlain by any carbonate rock; instead, thick deposits of volcanic ash, unwelded ash flow tuffs, and other pyroclastic debris underlie all of Guatemala City. The dissolution of rock did not form the large vertical holes that swallowed up parts of Guatemala City in 2007 and 2010.
The Guatemala City holes are instead an example of "piping pseudokarst", created by the collapse of large cavities that had developed in the weak, crumbly Quaternary volcanic deposits underlying the city. Although weak and crumbly, these volcanic deposits have enough cohesion to allow them to stand in vertical faces and to develop large subterranean voids within them. A process called "soil piping" first created large underground voids, as water from leaking water mains flowed through these volcanic deposits and mechanically washed fine volcanic materials out of them, then progressively eroded and removed coarser materials. Eventually, these underground voids became large enough that their roofs collapsed to create large holes.
Bimmah or Falling Star Sinkhole in Oman
Some of the largest sinkholes in the world are:
- Blue Hole - Dahab, Egypt. A round sinkhole or blue hole, 130 m (430 ft) deep. It includes an archway leading out to the Red Sea at 60 m (200 ft), which has been the site for many freediving and scuba attempts, the latter often fatal.
- Boesmansgat - South African freshwater sinkhole, approximately 290 m (950 ft) deep.
- Lake Kashiba - Zambia. About 3.5 hectares (8.6 acres) in area and about 100 m (330 ft) deep.
- Akhayat sinkhole is in Mersin Province, Turkey. Its dimensions are about 150 m (490 f) in diameter with a maximum depth of 70 m (230 ft).
- Bimmah Sinkhole (Hawiyat Najm, the Falling Star Sinkhole, Dibab Sinkhole) - Oman, approximately 30 m (98 ft) deep.
- The Baatara gorge sinkhole and the Baatara gorge waterfall next to Tannourine in Lebanon
- Dashiwei Tiankeng in Guangxi, China, is 613 m (2,011 ft) deep, with vertical walls. At the bottom is an isolated patch of forest with rare species.
- Dragon Hole the deepest, known, underwater ocean sinkhole in the world.
- Shaanxi tiankeng cluster, in the Daba Mountains of southern Shaanxi, China, covers an area of nearly 5019 square kilometers with the largest sinkhole being 520 meters in diameter and 320 meters deep.
- Teiq Sinkhole (Taiq, Teeq, Tayq) in Oman is one of the largest sinkholes in the world by volume: 90,000,000 m3 (3.2×109 cu ft). Several perennial wadis fall with spectacular waterfalls into this 250 m (820 ft) deep sinkhole.
- Xiaozhai Tiankeng - Chongqing Municipality, China. Double nested sinkhole with vertical walls, 662 m (2,172 ft) deep.
In the Caribbean
- Dean's Blue Hole - Bahamas. The second deepest known sinkhole under the sea, depth 203 m (666 ft). Popular location for world championships of free diving, as well as recreational diving.
In Central America
- Hranice Abyss, Moravia, Czech Republic, is the deepest known underwater cave in the world, the lowest confirmed depth (as of 27 September 2016) is 473 m (404 m below the water level).
- Pozzo del Merro, near Rome, Italy. At the bottom of an 80 m (260 ft) conical pit, and approximately 400 m (1,300 ft) deep, it is among the deepest sinkholes in the world (see Sótano del Barro below).
- Red Lake - Croatia. Approximately 530 m (1,740 ft) deep pit with nearly vertical walls, contains an approximately 280-290 m (920-950 ft) deep lake.
- Vouliagmeni - Greece. The sinkhole of Vouliagmeni is known as "The Devil Well", because it is considered extremely dangerous. Four scuba divers are known to have died in it. Maximum depth of 35.2 m (115 ft) and horizontal penetration of 150 m (490 ft).
- Water End Swallow Holes in Hertfordshire, England.
- Pouldergaderry - Ireland. This sinkhole is located in the townland of Kilderry South near Miltown, Co. Kerry at 52°7?57.5?N 9°44?45.4?W / 52.132639°N 9.745944°W. The sinkhole, which is located in an area of karst bedrock, is approximately 80 metres (260 ft) in diameter and 30 metres (98 ft) deep with many mature trees growing on the floor of the hole. At the level of the surrounding ground, the sinkhole covers an area of approximately 1.3 acres. Its presence is indicated on Ordnance Survey maps dating back to 1829.
In North America
- Cave of Swallows - San Luis Potosí. 372 m (1,220 ft) deep, round sinkhole with overhanging walls.
- Sima de las Cotorras - Chiapas. 160 m (520 ft) across, 140 m (460 ft) deep, with thousands of green parakeets and ancient rock paintings.
- Sótano de la Lucha - Chiapas. Bigger than Sima de las Cotorras and with lush vegetation on the floor. It can be reached through a cave.
- Sótano del Barro - Querétaro. 410 m (1,350 ft) deep, with nearly vertical walls.
- Zacatón - Tamaulipas. Deepest water-filled sinkhole in world, 339 m (1,112 ft) deep.
- Bayou Corne sinkhole - Assumption Parish, Louisiana. About 25 acres in area and 750 ft (230 m) deep.
- The Blue Hole - Santa Rosa, New Mexico. The surface entrance is only 80 feet (24 m) in diameter, it expands to a diameter of 130 feet (40 m) at the bottom.
- Daisetta Sinkholes - Daisetta, Texas. Several sinkholes have formed, the most recent in 2008 with a maximum diameter of 620 ft (190 m) and maximum depth of 150 ft (46 m).
- Devil's Millhopper - Gainesville, Florida. 120 ft (37 m) deep, 500 ft (150 m) wide. Twelve springs, some more visible than others, feed a pond at the bottom.
- "Golly Hole" (or "December Giant"), Calera, Alabama, appeared December 2, 1972. Approximately 300 ft (91 m) by 325 ft (99 m) and 120 ft (37 m) deep.
- Grassy Cove - Tennessee. 13.6 km2 (5.3 sq mi) in area and 42.7 m (140 ft) deep, a National Natural Landmark.
- Gypsum Sinkhole - Utah, in Capitol Reef National Park. Nearly 15 m (49 ft) in diameter and approximately 60 m (200 ft) deep.
- Kingsley Lake - Florida. 8.1 km2 (2,000 acres) in area, 27 m (89 ft) deep and almost perfectly round.
- Lake Peigneur - New Iberia, Louisiana. Original depth 11 ft (3.4 m), currently 1,300 ft (400 m) at Diamond Crystal Salt Mine collapse.
- Winter Park Sinkhole, in central Florida, appeared May 8, 1981. It was approximately 350 feet (107 m) wide and 75 feet (23 m) deep. It was notable as one of the largest recent sinkholes to form in the United States. It is now known as Lake Rose.
- Harwood Hole - Abel Tasman National Park, New Zealand, 183 m (600 ft) deep.
- Minyé sinkhole - East New Britain, Papua New Guinea. 510 m (1,670 ft) deep, with vertical walls, crossed by a powerful stream.
In South America
- Sima Humboldt - Venezuela. Largest sinkhole in sandstone, 314 m (1,030 ft) deep, with vertical walls. Unique, isolated forest on bottom.
- In the western part of Cerro Duida, Venezuela, there is a complex of canyons with sinkholes. Deepest sinkhole is 450 m (1,480 ft) deep (from lowest rim within canyon); total depth 950 m (3,120 ft).
- ^ Whittow, John (1984). Dictionary of Physical Geography. London: Penguin. p. 488. ISBN 0-14-051094-X.
- ^ Thomas, David; Goudie, Andrew, eds. (2009). The Dictionary of Physical Geography (3rd ed.). Chichester: John Wiley & Sons. p. 440. ISBN 1444313169.
- ^ Kohl, Martin (2001). "Subsidence and sinkholes in East Tennessee. A field guide to holes in the ground" (PDF). State of Tennessee. Retrieved 2014.
- ^ Lard, L., Paull, C., & Hobson, B. (1995). "Genesis of a submarine sinkhole without subaerial exposure". Geology. 23 (10): 949-951. Bibcode:1995Geo....23..949L. doi:10.1130/0091-7613(1995)023<0949:GOASSW>2.3.CO;2.
- ^ "Caves and karst - dolines and sinkholes". British Geological Survey.
- ^ Kohl, Martin (2001). "Subsidence and sinkholes in East Tennessee. A field guide to holes in the ground" (PDF). State of Tennessee. Archived from the original (PDF) on 12 October 2013. Retrieved 2014.
- ^ Breining, Greg (5 October 2007). "Getting Down and Dirty in an Underground River in Puerto Rico". The New York Times. ISSN 0362-4331. Retrieved 2016.
- ^ Palmer, Arthur N. (1 January 1991). "Origin and morphology of limestone caves". Geological Society of America Bulletin. 103 (1): 1-21. doi:10.1130/0016-7606(1991)1032.3.CO;2. ISSN 0016-7606.
- ^ Friend, Sandra (2002). Sinkholes. Pineapple Press Inc. p. 11. ISBN 1-56164-258-4. Retrieved 2010.
- ^ "Quarrying and the environment". bgs. bgs. Retrieved 2018.
- ^ "Sinkholes in Washington County". Utah gov Geological Survey. Archived from the original on 23 March 2011.
- ^ Vincent, Jean-Baptiste; et al. (2 July 2015). "Large heterogeneities in comet 67P as revealed by active pits from sinkhole collapse". Nature. 523: 63-66. Bibcode:2015Natur.523...63V. doi:10.1038/nature14564. PMID 26135448. Retrieved 2015.
- ^ Ritter, Malcolm (1 July 2015). "It's the pits: Comet appears to have sinkholes, study says". AP News. Retrieved 2015.
- ^ "What is a sinkhole?". CNC3. Retrieved 2016.
- ^ a b c d "Largest and most impressive sinkholes of the world". Wondermondo.
- ^ "Naré sinkhole". Wondermondo.
- ^ Zhu, Xuewen; Chen, Weihai (2006). "Tiankengs in the karst of China" (PDF). Speliogensis and Evolution of Karst Aquifers. 4: 1-18. ISSN 1814-294X.
- ^ "Sistema Zacatón". by Marcus Gary.
- ^ a b "Sistema Zacatón". Wondermondo.
- ^ Vazquez, Tyler (September 29, 2017). "The Hole Truth". Florida Today. Melbourne, Florida. pp. 1A,2A. Retrieved 2017.
- ^ William L. Wilson; K. Michael Garman. "IDENTIFICATION AND DELINEATION OF SINKHOLE COLLAPSE HAZARDS IN FLORIDA USING GROUND PENETRATING RADAR AND ELECTRICAL RESISTIVITY IMAGING" (PDF). Subsurface Evaluations, Inc. Case 3 - Mariner Boulevard.
- ^ Rock, Tim (2007). Diving & Snorkeling Belize (4th ed.). Footscray, Vic.: Lonely Planet. p. 65. ISBN 9781740595315.
- ^ "Sinkholes". Wondermondo.
- ^ "Black Hole of Andros". Wondermondo.
- ^ Waltham, Tony; Bell, Fred; Culshaw, Martin (2005). Sinkholes and subsidence: karst and cavernous rocks in engineering and construction (1st ed.). Berlin [u.a.]: Springer [u.a.] p. 64. ISBN 3540207252.
- ^ "Subsidence". Waikato Regional Council. Retrieved .
- ^ Fletcher, Dan (1 June 2010). "Massive Sinkhole Opens in Guatemala". Time.com. Retrieved 2013.
- ^ Vidal, Luis; Jorge Nunez (2 June 2010). "¿Que diablos provoco este escalofriante hoyo?". Las Ultimas Noticias (in Spanish). Retrieved 2013.
- ^ Than, Ker (1 June 2010). "Sinkhole in Guatemala: Giant Could Get Even Bigger". National Geographic. Retrieved 2013.
- ^ a b c Waltham, T. (2008). "Sinkhole hazard case histories in karst terrains". Quarterly Journal of Engineering Geology and Hydrogeology. 41 (3): 291-300. doi:10.1144/1470-9236/07-211.
- ^ Halliday, W.R. (2007). "Pseudokarst in the 21st Century" (PDF). Journal of Cave and Karst Studies. 69 (1): 103-113. Retrieved 2013.
- ^ Halls, Monty; Krestovnikoff, Miranda (2006). Scuba diving (1st American ed.). New York: DK Pub. p. 267. ISBN 9780756619497.
- ^ Beaumont, P.B.; Vogel, J.C. (May-June 2006). "On a timescale for the past million years of human history in central South Africa". South African Journal of Science. 102: 217-228. ISSN 0038-2353. Retrieved 2013.
- ^ Rajendran, Sankaran; Nasir, Sobhi (2014). "ASTER mapping of limestone formations and study of caves, springs and depressions in parts of Sultanate of Oman" (PDF). Environmental Earth Sciences. 71 (1): 133-146, figure 9d (page 142), page 144. doi:10.1007/s12665-013-2419-7.
- ^ "Bimmah sinkhole". Wondermondo.
- ^ Zhu, Xuewen (); et al. (2003). ? [Dashiwei Tiankeng Group, Leye, Guangxi: discoveries, exploration, definition and research]. Nanning, Guangxi, China: Guangxi Scientific and Technical Publishers. ISBN 978-7-80666-393-6.
- ^ "China Exclusive: South China Sea "blue hole" declared world's deepest". New China. Xinhua. Archived from the original on 24 July 2016.
- ^ "Researchers just discovered the world's deepest underwater sinkhole in the South China Sea". The Washington Post.
- ^ "" [Tiankeng group of geological relics with rare plants and flying cats found in Shaanxi]. Sohu.com Inc. Archived from the original on 25 November 2016.
- ^ "?--?----?""" [Deciphering the Hanzhong tiankeng group -- world-class "Nature Museum"]. Hanzhong People's Municipal Government. 25 November 2016. Archived from the original on 27 November 2016.
- ^ "Dhofar caves: A tourist's paradise". Muscat Daily. 11 January 2015. Archived from the original on 27 November 2016.
- ^ Zhu, Xuewen; Waltham, Tony (2006). "Tiankeng: definition and description" (PDF). Speleogenesis and Evolution of Karst Aquifers. 4 (1): 1-8, Fig. 4. Structural interpretation of Xiaozhai Tiankeng, page 4.
- ^ Schonauer, Scott (21 July 2007). "Missing American divers will be laid to rest after 30 years". Stars and Stripes. Retrieved 2013.
- ^ "Google Maps".
- ^ "Shop.osi.ie Mapviewer".
- ^ Wines, Michael (25 September 2013). "Ground Gives Way, and a Louisiana Town Struggles to Find Its Footing". New York Times. Retrieved 2013.
- ^ Horswell, Cindy (5 January 2009). "Daisetta sinkhole still a mystery 8 months after it formed". Houston Chronicle. Retrieved 2013.
- ^ Blumenthal, Ralph (9 May 2008). "Sinkhole and Town: Now You See It". The New York Times. Retrieved 2013.
- ^ "Devils Millhopper Geological State Park". Floridastateparks.org. Retrieved 2014.
- ^ "Nation's largest sinkhole may be near Montevallo" (March 29, 1973) The Tuscaloosa News
- ^ Dunigan, Tom. "Grassy Cove". Tennessee Landforms. Retrieved 2014.
- ^ "Cathedral Valley - Capitol Reef National Park". National Park Service, US Dept of Interior. Retrieved 2013.
- ^ "Lake Peigneur: The Swirling Vortex of Doom".
- ^ chondram (14 August 2012). "Mysterious Louisiana Sinkhole Drains Entire Lake" – via YouTube.
- ^ Huber, Red (13 November 2012). "Looking back at Winter Park's famous sinkhole". Orlando Sentinel. | <urn:uuid:93336b3c-444b-48cf-89fa-cefd61d735be> | 4.03125 | 5,902 | Knowledge Article | Science & Tech. | 64.235573 | 95,529,702 |
Dark chlorophyll synthesis may provide a potential for shade tolerance as shown by a comparative study with seedlings of European larch (Larix decidua) and Norway spruce (Picea abies)
- 117 Downloads
The ability to green in the dark represents a trait providing shade tolerance in seedlings of Norway spruce.
In contrast to angiosperm plants, gymnosperms possess two different enzymes for the reduction of protochlorophyllide to chlorophyllide: dark-operative, light-independent protochlorophyllide oxidoreductase (DPOR), consisting of three subunits: ChlL, ChlN and ChlB, and light-dependent protochlorophyllide oxidoreductase (LPOR). European larch seedlings (Larix decidua Mill.), in contrast to Norway spruce (Picea abies Karst.), accumulate only very low amounts of chlorophylls in the dark due to an inactive DPOR enzyme. In this study, we used these two species to investigate the advantage of the co-existence of two protochlorophyllide oxidoreductases on chlorophyll synthesis under different light conditions. We found that under deep shade conditions, the larch seedlings are partially etiolated with a low quantum yield of photosystem II photochemistry caused by inefficient LPOR function under that subliminal irradiance concomitant with an inactive DPOR enzyme. In contrast, spruce accumulated a significant amount of chlorophylls under deep shade conditions due to the co-existence of active DPOR and LPOR enzymes. Moreover, although PSII developed in the dark had an inactive oxygen-evolving complex, even very low irradiance is sufficient for photoactivation of PSII, as proved by the high quantum yield of photosystem II (Fv/Fm) and the disappearance of the K-step in chlorophyll a fluorescence induction under deep shade conditions in spruce. We did not find any advantage of having DPOR enzyme under high light conditions, which is consistent with the decreasing abundance of DPOR subunits with increasing light intensities. Thus, the presence of an active DPOR enzyme may represent a molecular basis for shade tolerance in coniferous seedlings.
KeywordsChlorophyll Larix decidua (European larch) Light acclimation Shade Picea abies (Norway spruce)
This work was supported by the National Program of Sustainability I (Grant LO1204) of the Ministry of Education, Youth and Sports of the Czech Republic. We are very thankful to Dr. Michal Martinka and Dr. Marek Vaculík, Department of Plant Physiology, Faculty of Natural Sciences, Comenius University in Bratislava (Slovak Republic) for invaluable material help and excellent advice during sample preparation for transmission electron microscopy and to Prof. Yuichi Fujita (Nagoya, Japan) for providing antibodies against DPOR.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
- Burke DH, Raubeson LA, Alberti M, Hearst JE, Jordan ET, Kirch SA, Valinski AEC, Conant DS, Stein DB (1993) The chlL (frx) gene: phylogenetic distribution in vascular plants and DNA sequence from Polystichum acrostichoides (Pteridophyta) and Synechococcus sp. 7200 (Cyanobacteria). Pl Syst Evol 187:89–102CrossRefGoogle Scholar
- Dawson RCM, Elliott DC, Elliott WH, Jones KM (1986) Data for biochemical research, 3rd edn. Oxford Science Publications, OxfordGoogle Scholar
- Fujita Y, Bauer CE (2003) The light-independent protochlorophyllide reductase: a nitrogenase-like enzyme catalyzing a key reaction for greening in the dark. In: Kadish K, Smith K, Guilard R (eds) Porphyrin handbook, vol 13, Chlorophylls and bilins: biosynthesis, synthesis, and degradation. Academic, San Diego, pp 109–156CrossRefGoogle Scholar
- Fujita Y, Takahashi Y, Chuganji M, Matsubara H (1992) The nifH-like (frxC) gene is involved in the biosynthesis of chlorophyll in the filamentous cyanobacterium Plectonema boryanum. Plant Cell Physiol 33:81–92Google Scholar
- Fujita Y, Takagi H, Hase T (1998) Cloning of the gene encoding a protochlorophyllide reductase: the physiological significance of the co-existence of light-dependent and -independent protochlorophyllide reduction systems in the cyanobacterium Plectonema boryanum. Plant Cell Physiol 39:177–185CrossRefPubMedGoogle Scholar
- Lichtenthaler HK, Babani F (2004) Light adaptation and senescence of the photosynthetic apparatus. Changes in pigment composition, chlorophyll fluorescence parameters and photosynthetic activity. In: Papageorgiou GC (eds) Chlorophyll a fluorescence a signature of photosynthesis—advances in photosynthesis and respiration series, vol 19. Springer, Dordrecht, pp 713–736Google Scholar
- Masuda T, Fusada N, Oosawa N, Takamatsu K, Yamamoto YY, Ohto M, Nakamura K, Goto K, Shibata D, Shirano Y, Hayashi H, Kato T, Tabata S, Shimada H, Ohta H, Takamiya K (2003) Functional analysis of isoforms of NADPH:protochlorophyllide oxidoreductase (POR), PORB and PORC, in Arabidopsis thaliana. Plant Cell Physiol 44:963–974CrossRefPubMedGoogle Scholar
- Mukai Y, Tazaki K, Fujii T, Yamamoto N (1992) Light-independent expression of three photosynthetic genes cab, rbcS and rbcL in coniferous plants. Plant Cell Physiol 33:859–866Google Scholar
- Suzuki T, Takio S, Yamamoto I, Satoh T (2001) Characterization of cDNA of the liverwort phytochrome gene, and phytochrome involvement in the light-dependent and light-independent protochlorophyllide oxidoreductase gene expression in Marchantia paleacea var. diptera. Plant Cell Physiol 42:576–852CrossRefPubMedGoogle Scholar
- Walles B, Hudák J (1975) A comparative study of chloroplast morphogenesis in seedlings of some conifers (Larix decidua, Pinus sylvestris and Picea abies). Stud Forest Suec 127:1–22Google Scholar | <urn:uuid:560790d0-0ef6-40d3-8ad6-d00ec2a42dda> | 2.890625 | 1,470 | Academic Writing | Science & Tech. | 15.147339 | 95,529,708 |
PL/SQL - FOR LOOP Statement - Tutorialspoint Summary: in this tutorial, you will learn how to use PL/SQL LOOP statement to execute a sequence of statements repeatedly. A FOR LOOP is a repetition control structure that allows you to efficiently write a loop that needs to execute a specific number of times. When the above.
ORACLE-BASE - MERGE Statement PL/SQL Loop Basic Loop, FOR Loop, WHILE Loop repeat a number of block statements in your PL/SQL program. Define label before LOOP keyword and after END LOOP keyword. The MERGE statement was introduced in Oracle 9i to conditionally insert or. Consider the following example where data from the HR_RECORDS table is.
REVERSE Reversing the loop For Loop PL SQL. - Java2s There may be a situation when you need to execute a block of code several number of times. REVERSE Reversing the loop For Loop PL SQL Oracle PL / SQL. Related examples in the same category. 1. Your first FOR loop. 2. For loop counter IN.
PLSQL Tutorial Videos and Books PL/ SQL PL SQL This appendix provides several PL/SQL programs to guide you in writing your own. How and When to Write SQL in PLSQL. How to Create a Mration Repository in Oracle SQL Developer. PL20 PLSQL Tutorial FOR LOOP in PL SQL Hands On
PLSQL 101 Working with Cursors You get a better sense of the power of the cursor in Oracle by combining it with a loop. The cursor FOR loop is an elegant and natural extension of the numeric FOR loop in PL/SQL. check out “How to Write SQL Injection Proof PL/SQL".
PL/SQL - Oracle FAQ Note: The material on trgers that was formerly in this document has been moved to A New Document on Constraints and Trgers. PL/SQL extends SQL by adding constructs found in procedural languages, resulting in a structural language that is more powerful than SQL. All PL/SQL programs are made up of blocks, which can be nested within each other. To exit a loop use the EXIT WHEN statement;. Here is an example of how to define a custom expection.
For loop counter IN 1.5 For Loop PL SQL Oracle PL / SQL Basic loop structure encloses sequence of statements in between the LOOP and END LOOP statements. PUT_LINEcounter; 6 END LOOP; 7 END; 8 / 1 2 3 4 5 PL/SQL procedure successfully. 20. Define a looping indexer as member variable in a procedure. 21.
The Oracle PL/SQL LOOP Construct - By default, iteration proceeds from the initial value to the final value, generally upward from the lower bound to the hher bound. The statement logic and value tests may be used to produce an EXIT condition. Example Syntax Oracle provides three types of loop constructs 1. The Basic.
How to write a for loop in plsql:
Rating: 92 / 100
Overall: 92 Rates | <urn:uuid:6d100229-a61b-4dfd-860f-3a4c151cbb86> | 3.5625 | 630 | Tutorial | Software Dev. | 69.235307 | 95,529,720 |
As Arctic winter sea ice hits record lows, one group of researchers is proposing that the ice be artificially restored via a multi-billion-dollar scheme akin to how ski resorts produce artificial snow.
Warm weather in the high north, caused by storms from the north Atlantic Ocean carrying warm air with them saw Arctic sea ice extent averaging just 13.4 million square kilometres in January, the lowest January extent since satellite monitoring began almost four decades ago, according to fresh analysis released this week by the US National Snow and Ice Data Center.
This is some 260,000 square kilometres fewer than last January, which was also a historic record low, and some 1.26 million square kilometres fewer than the long-term three-decade average.
NASA scientists have said that the 2015-2016 winter was the warmest ever recorded in the Arctic, but are still waiting to see whether the 2016-2017 will similarly break records.
The steady retreat of Arctic sea ice may be a boon to tourism and resource development, but the phenomenon is one of the more worrisome aspects of global warming because the phenomenon is a positive feedback loop. The more sea ice is lost, the less sunlight is reflected back into space by the white snow and ice, and water, which is much darker, absorbs more sunlight. The waters warm, leading to even more sea ice melt. Even if the nations of the world halted all greenhouse gas emissions tomorrow, this would not be enough to arrest the process. A completely ice-free summer in the Arctic is expected to arrive by 2030.
The grim news up north came as a fantastical idea seemingly out of a bad science fiction film on how to artificially re-freeze the pole was published in a journal of the American Geophysical Union.
The proposal involves the construction of wind-powered water pumps sitting on buoys and drawing water up from the ocean that would be stored in a tank. This water would then be sprayed out across the surface of the ice. Here temperatures are much colder than beneath the ice where it is insulated, and will freeze faster.
The researchers estimate that 10 million of the buoy-pump devices would be needed to improve the thickness of the ice by a metre of ice atop current levels. To put this in context, sea ice normally grows 2-3 metres in thickness each winter, so this would mark a significant reversal of current trends.
The scheme would cost a handsome $500 billion dollars per year, or more than a quarter of Canada’s GDP, putting the scheme out of reach for any one country. For comparison the US Apollo program that put humans on the moon cost $110 billion in total in today’s money.
The scientists are quite serious however, and will be testing a prototype of the buoy-pumps later this year. They do not suggest this as an alternative to limiting greenhouse gas emissions, but merely what lead researcher Steven Desch describes as a “band-aid” solution to hold on to Arctic sea ice until international climate change mitigation efforts scale up more substantially.
Such a scheme would qualify as a form of geo-engineering, defined as: “the deliberate large-scale manipulation of the planetary environment to counteract anthropogenic climate change” by Britain’s Royal Society. In 2009, the society published one of the first major investigations into the challenges of geoengineering, warning that while research on the topic should be undertaken to ensure that tools are available should it become necessary to reduce the rate of warming later this century, there are serious and complex governance issues that need to be resolved before geoengineering could be acceptable. In January, US federal scientists for the first time recommended that the country move ahead with the highly controversial research area.
The Climate Examiner speaks to BC-based Carbon Engineering about the technology, the business and the policies that could make direct air capture, synfuels and carbon sequestration work. | <urn:uuid:6520f32a-b37e-4ce1-9093-eb2b88853142> | 3.5625 | 789 | News Article | Science & Tech. | 36.174 | 95,529,740 |
The University of Arizona's Catalina Sky Survey keeps a watchful eye on asteroids that might cross the Earth's path. A byproduct of that effort is the largest database compiling the brightnesses of 200 million objects in the universe, including supernovae and stars torn up by super-massive black holes.
The night sky is filled with objects such as asteroids that dash across the sky and others such as exploding stars and variable stars that flash, dim, and brighten. Studying such phenomena can help astronomers better understand the evolution of stars, massive black holes in the centers of galaxies, and the structure of the Milky Way.
These types of objects also were essential for the recent discovery of dark energy the mysterious energy that dominates the expansion of the universe that earned last year's Nobel Prize.
Using images obtained by the UA's asteroid-hunting Catalina Sky Survey, the Catalina Real-Time Transient Survey, or CRTS, lets CalTech astronomers systematically scan the heavens for these dynamic objects, resulting in an unprecedented data set that will allow scientists worldwide to pursue new research.
"Exploring variable objects and transient phenomena like stellar explosions is one of the most vibrant and growing research areas in astrophysics," said S. George Djorgovski, professor of astronomy at Caltech and principal investigator on the CRTS. "In many cases, this yields unique information needed to understand these objects."
The new data set is based on observations taken with the 0.7-meter telescope on Mt. Bigelow in Arizona. The observations were part of the Catalina Sky Survey, a search for Near-Earth Objects, or NEOs asteroids that may pose a threat to Earth conducted by astronomers at the UA.
By repeatedly taking pictures of large swaths of the sky and comparing these images to previous ones, the CRTS is able to monitor the brightness of about half-billion objects, allowing it to search for those that dramatically brighten or dim. In this way, the CRTS team identified tens of thousands of variables, maximizing the science that can be gleaned from the original data.The new data set contains the so-called brightness histories of a total of
"This set of objects is an order of magnitude larger than the largest previously available data sets of their kind," said Andrew Drake, a staff scientist at Caltech and lead author on a poster presented at the meeting of the American Astronomical Society in Austin on Jan. 12.
"It will enable many interesting studies by the entire astronomical community."
One of the unique features of the survey, Drake said, is that it emphasizes an open-data philosophy. "We discover transient events and publish them electronically in real time, so that anyone can follow them and make additional discoveries."
"It is a good example of scientific-data sharing and reuse," Djorgovski added. "We hope to set an example of how data-intensive science should be done in the 21st century."
The data set includes more than 1,000 exploding stars called supernovae, including many unusual and novel types, as well as hundreds of so-called cataclysmic variables, pairs of stars in which one spills matter onto another, called a white dwarf; tens of thousands of other variable stars; and dwarf novae, which are binary stars that dramatically change in brightness."We take hundreds of images every night from each of our telescopes as we search for hazardous asteroids," said Edward Beshore, principal investigator of the UA's asteroid-hunting CSS. "As far back as 2005, we were asking if these data could be useful to the community of astronomers.
We are delighted that we could forge this partnership. In my estimation, it has been a great success and is a superb example of finding ways to get greater value from taxpayers' investments in basic science."
The team said it soon plans to release additional data taken with a 1.5-meter telescope on Mt. Lemmon in Arizona and a 0.5-meter telescope in Siding Spring in Australia.
In addition to Djorgovski, Drake and Beshore, the team includes staff scientist Ashish Mahabal, computational scientist Matthew Graham, postdoctoral scholar Ciro Donalek and research scientist Roy Williams from Caltech.
Researchers from other institutions include Steve Larson, Andrea Boattini, Alex Gibbs, Al Grauer, Rik Hill and Richard Kowalski from the UA; Mauricio Catelan from Universidad Catholica in Chile; Eric Christensen from the Gemini Observatory in Hawaii; and Jose Prieto from Princeton University.
The Caltech research is supported by the National Science Foundation. The work done at the UA is supported by NASA.LINKS:
Daniel Stolte | University of Arizona
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
16.07.2018 | Life Sciences
16.07.2018 | Earth Sciences | <urn:uuid:5c75f850-7d1a-4d2c-9b4a-08f8572fe481> | 3.46875 | 1,592 | Content Listing | Science & Tech. | 39.572805 | 95,529,745 |
MPQ/LMU scientists devise new interferometer to probe the geometry of band structures.
The geometry and topology of electronic states in solids plays a central role in a wide range of modern condensed-matter systems including graphene or topological insulators. However, experimentally accessing this information has proven to be challenging, especially when the bands are not well-isolated from one another. As reported in last week’s issue of Science (Science, 27 May 2016, DOI: 10.1126/science.aad5812), an international team of researchers around T. Li, Prof. I. Bloch and Dr. U. Schneider from the Ludwig-Maximilians-Universität Munich and the Max Planck Institute of Quantum Optics have devised a straightforward method to probe the band geometry using ultracold atoms in an optical lattice. Their method, which combines the controlled steering of atoms through the energy bands with atom interferometry, is an important step in the endeavor to investigate geometric and topological phenomena in synthetic band structures.
The researchers accelerated the entire lattice, which results in an inertial force in the frame of the lattice, similar to pulling on a carpet. The larger the force (2,3), the faster the atoms move in crystal momentum space, and the less important the effect of the band energies become. The effect of the band energy is negligible for the strongest forces (3). (F: force, d: distance between neighbouring lattice sites). T. Li, LMU & MPQ Munich
A wide array of fundamental phenomena in condensed matter physics, such as why some materials are insulators while others are metals, can be understood simply by examining the energies of the material’s constituent electrons. Indeed, band theory, which describes these electron energies, was one of the earliest triumphs of quantum mechanics and has driven much of the technological advances of our time, from the computer chips in our laptops to the liquid-crystal displays on our smartphones. We now know, however, that traditional band theory is incomplete.
Among the most surprising and fruitful developments in modern condensed matter physics was the realization that there is more than the energies—rather, the geometric structure of the bands also plays an important role. This geometric information is responsible for much of the exotic physics in newly discovered materials such as graphene or topological insulators and underlies an array of exciting technological possibilities from spintronics to topological quantum computing. It is, however, notoriously challenging to experimentally access.
Now, an international team of researchers, with experiments performed at the Ludwig-Maximilians-Universität Munich and the Max Planck Institute of Quantum Optics, has devised a straightforward method to probe the band geometry using ultracold atoms in an optical lattice, a synthetic crystal formed from standing waves of light. Their method relies on creating a system that can be described by a quantity known as the Wilson line.
Although originally formulated in the context of quantum chromodynamics, Wilson lines surprisingly also describe the evolution of degenerate quantum states, i.e., quantum states with the same energy. Applied to condensed matter systems, the elements of the Wilson line directly encode the geometric structure of the bands. Therefore, to access the band geometry, the researchers need only to access the Wilson line elements.
The problem, however, is that the bands of a solid are generally not degenerate. The researchers realized that there was a work-around: when moved fast enough in momentum space, the atoms no longer feel the effect of the energy bands and probe only the essential geometric information. In this regime, two bands with two different energies behave like two bands with the same energy (see Figure 1).
In their work, the researchers first cooled atoms to quantum degeneracy. The atoms were then placed into an optical lattice formed by laser beams (Figure 2) to realize a system that mimics the behavior of electrons in a solid, but without the added complexities of real materials. In addition to being exceptionally clean, optical lattices are highly tunable—different types of lattice structures can be created by changing the intensity or the polarization of the light. In their experiment, the researchers interfered three laser beams to form a graphene-like honeycomb lattice.
Although spread out over all lattice sites, the quantum degenerate atoms carry a well-defined momentum in the light crystal. The researchers then rapidly accelerated the atoms to a different momentum and measured the amount of excitations they created. When the acceleration is fast enough, such that the system is described by the Wilson line, this straightforward measurement reveals how the electronic wavefunction at the second momentum differs from the wavefunction at the first momentum. Repeating the same experiment at many different crystal momenta would yield a complete map of how the wavefunctions change over the entire momentum space of the artificial solid.
The researchers not only confirmed that it was possible to move the atoms such that the dynamics were described by two-band Wilson lines; they also revealed both the local, geometric properties and the global, topological structure of the bands. While the lowest two bands of the honeycomb lattice are known not to be topological, the results demonstrate that Wilson lines can indeed be experimentally used to probe and reveal the band geometry and topology in these novel synthetic settings.
Tracy Li, Lucia Duca, Martin Reitter, Fabian Grusdt, Eugene Demler, Manuel Endres, Monika Schleier-Smith, Immanuel Bloch, Ulrich Schneider
Bloch state tomography using Wilson lines
Science 352, 1094 (2016), 27 May 2016, DOI: 10.1126/science.aad5812
Image description: Figure 1:
The researchers accelerated the entire lattice, which results in an inertial force in the frame of the lattice, similar to pulling on a carpet. The larger the force (2,3), the faster the atoms move in crystal momentum space, and the less important the effect of the band energies become. The effect of the band energy is negligible for the strongest forces (3). (F: force, d: distance between neighbouring lattice sites).
Image description: Figure 2:
The researchers interfered three laser beams at 120-degree angles to form a graphene-like honeycomb lattice. The atoms are trapped in the honeycomb structure formed from by the valleys (dark blue) of the potential.
Dr. Ulrich Schneider
LMU Munich, Faculty of Physics
Schellingstr. 4, 80799 Munich, Germany
University of Cambridge, Cambridge, UK
Phone: +49 (0)122 333 7239
Prof. Dr. Immanuel Bloch
Chair of Quantum Optics, LMU Munich
Schellingstr. 4, 80799 Munich
Director at Max Planck Institute of Quantum Optics
85748 Garching, Germany
Phone: +49 (0)89 / 32 905 -138
Dr. Olivia Meyer-Streng
Press & Public Relations
Max Planck Institute of Quantum Optics, Garching, Germany
Phone: +49 (0)89 / 32 905 -213
Dr. Olivia Meyer-Streng | Max-Planck-Institut für Quantenoptik
First evidence on the source of extragalactic particles
13.07.2018 | Technische Universität München
Simpler interferometer can fine tune even the quickest pulses of light
12.07.2018 | University of Rochester
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
13.07.2018 | Event News
13.07.2018 | Materials Sciences
13.07.2018 | Life Sciences | <urn:uuid:4396c8dc-63ac-45cb-a578-e99a10861ec8> | 3.09375 | 2,122 | Content Listing | Science & Tech. | 37.147862 | 95,529,746 |
The Structure of Tropical Rain Forest: Synusiae and Stratification
A complex plant community is analogous (though admittedly only superficially) to a human society. The members of a human community form social classes, all the members of a given class standing in a similar relationship to the members of other classes and having a similar function in the society as a whole. Each human community thus has a characteristic social structure determined by the nature and the relative importance of the classes which compose it. In a like fashion the species in the more complex plant communities form ecological classes or groups. In the community as a whole the species are of varied stature and varied life-form, but the members of the same ecological group are similar in life-form and in their relation to the environment. These ecological groups, the analogues of the human social classes, will here be called synusiae, a term originally introduced by Gams . A synusia is thus a group of plants of similar life-form, filling the same niche and playing a similar role, in the community of which it forms a part. In the words of Saxton , who used the term in a slightly broader sense than Gams, it is an aggregation of species (or individuals) making similar demands on a similar habitat. The species of the same synusia, though often widely different taxonomically, are to a large extent ecologically equivalent.
KeywordsRain Forest Tree Seedling Tropical Rain Forest Tall Tree Tree Stratum
Unable to display preview. Download preview PDF.
- Gams, H. (1918) ‘Prinzipienfragen der Vegetationsforschung’, Vjschr. naturf. Ges. Zürich, lxiii 293–493.Google Scholar
- Brown, W. H. (1919) Vegetation of Philippine Mountains (Manila).Google Scholar
- Mildbraed, J. (1922) Wissenschaftliche Ergebnisse der zweiten deutschen Zentral-Afrika-Expedition 1910–1911 unter Führung Adolf Friedrichs, Herzog zu Mecklenburg (Leipzig).Google Scholar
- Chevalier, A. (1917) ‘La forêt et les bois du Gabon’, Les Végétaux utiles d’Afrique tropicale française, fasc. 9 (Paris).Google Scholar
- Booberg, G. (1932) ‘Grondvormen, étages, en phytocoenosen van Java’s vegetatie’, Hand. 6 de ned.-ind. natuurw. Congr., 1931, 329–46.Google Scholar
- Davis, T. A. Vi., and Richards, P. W. (1933–4) ‘The vegetation of Moraballi Creek, British Guiana: an ecological study of a limited area of Tropical Rain Forest. Parts I and II’, J. Ecol. xxi 350–84; xxn 106–55.Google Scholar
- Aubréville, A. (1933) ‘La forêt de la Côte d’Ivoire’, Bull. Corn. Aft. occid. franc., xv 205–61.Google Scholar
- Beard, J. S. (1946) ‘The natural vegetation of Trinidad’, Oxf. For. Mem., no. 20.Google Scholar | <urn:uuid:8df9a55f-f2d4-40d0-9c34-6cfb1cc5451e> | 3.453125 | 741 | Academic Writing | Science & Tech. | 57.14856 | 95,529,775 |
NCERT Computer: Chapter 7 – Introduction to C + + Part 8
2 Explicit Conversion
It is also called type casting. It temporarily changes a variable data type from its declared data type to a new one. It may be noted here that type casting can only be done on the right hand side of the assignment statement.
Initially variable salary is defined as float but for the above calculation it is first converted to double data type and then added to the variable bonus.
A number which does not charge its value during execution of a program is known as a constant.
Floating Point Numerals
Character and string literals
Any attempt to change the value of a constant will result in an error message. A constant in C++ can be of any of the basic data types.
const qualifier can be used to declare constant as shown below:
The above declaration means that Pi is a constant of float types having a value 3.1415.
Examples of valid constant declarations are:
A variable is the most fundamental aspect of any computer language.
Variable are used in C++, where we need storage for any value, which will change in program.
It is a location in the computer memory which can store data and is given a symbolic name for easy reference.
The variables can be used to hold different values at different values at different times during the execution of a program.
To understand more clearly we should study the following statements:
For example, a variable Total of type float can be declared as shown below:
Similarly the variable Net can also be defined as shown below:
Examples of valid variable declarations are:
(i) int count;
(ii) int i, j, k;
(iii) char ch, first;
(iv) float total, Net;
(v) long int sal; | <urn:uuid:22bfe343-c5ce-4838-a9e7-c1df93d0ec79> | 3.890625 | 376 | Tutorial | Software Dev. | 43.539923 | 95,529,789 |
At the Apollo 17 site, the tracks laid down by the lunar rover are clearly visible, along with the last foot trails left on the moon. The images also show where the astronauts placed some of the scientific instruments that provided the first insight into the moon's environment and interior.
The paths left by astronauts Alan Shepard and Edgar Mitchell on both Apollo 14 moon walks are visible in this image. (At the end of the second moon walk, Shepard famously hit two golf balls.) The descent stage of the lunar module Antares is also visible. Credit: (Credit: NASA's Goddard Space Flight Center/ASU)
"We can retrace the astronauts' steps with greater clarity to see where they took lunar samples," said Noah Petro, a lunar geologist at NASA's Goddard Space Flight Center in Greenbelt, Md., who is a member of the LRO project science team.
All three images show distinct trails left in the moon's thin soil when the astronauts exited the lunar modules and explored on foot. In the Apollo 17 image, the foot trails, including the last path made on the moon by humans, are easily distinguished from the dual tracks left by the lunar rover, which remains parked east of the lander.
"The new low-altitude Narrow Angle Camera images sharpen our view of the moon's surface," said Arizona State University researcher Mark Robinson, principal investigator for the Lunar Reconnaissance Orbiter Camera (LROC). "A great example is the sharpness of the rover tracks at the Apollo 17 site. In previous images the rover tracks were visible, but now they are sharp parallel lines on the surface."
At each site, trails also run to the west of the landers, where the astronauts placed the Apollo Lunar Surface Experiments Package (ALSEP) to monitor the moon's environment and interior.
This equipment was a key part of every Apollo mission. It provided the first insights into the moon's internal structure, measurements of the lunar surface pressure and the composition of its atmosphere. Apollo 11 carried a simpler version of the science package.
One of the details that shows up is a bright L-shape in the Apollo 12 image. It marks the locations of cables running from ALSEP's central station to two of its instruments. Although the cables are much too small for direct viewing, they show up because they reflect light very well.
The higher resolution of these images is possible because of adjustments made to LRO's orbit, which is slightly oval-shaped or elliptical "Without changing the average altitude, we made the orbit more elliptical, so the lowest part of the orbit is on the sunlit side of the moon," said Goddard's John Keller, deputy LRO project scientist. "This put LRO in a perfect position to take these new pictures of the surface."
. The maneuver lowered LRO from its usual altitude of approximately 31 miles (50 kilometers) to an altitude that dipped as low as nearly 13 miles (21 kilometers) as it passed over the moon's surface. The spacecraft has remained in this orbit for 28 days, long enough for the moon to completely rotate. This allows full coverage of the surface by LROC's Wide Angle Camera. The cycle ends today when the spacecraft will be returned to its 31-mile orbit.
"These images remind us of our fantastic Apollo history and beckon us to continue to move forward in exploration of our solar system.," said Jim Green, Director of the Planetary Science Division at NASA Headquarters in Washington.
LRO was built and managed by Goddard. Initial research was funded by the Exploration Systems Mission Directorate at NASA Headquarters. In September 2010, after a one-year successful exploration mission, the mission turned its attention from exploration objectives to scientific research in NASA's Science Mission Directorate.To learn more about LRO, visit:
Nancy Neal-Jones | EurekAlert!
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Earth Sciences
19.07.2018 | Power and Electrical Engineering
19.07.2018 | Materials Sciences | <urn:uuid:29398d66-59a0-4079-8f12-3f82e638d056> | 3.765625 | 1,419 | Content Listing | Science & Tech. | 44.599361 | 95,529,790 |
+44 1803 865913
Covers Protura, Collembola, Diplura, Thysanura, Odonata, Ephemeroptera, Blattaria, Mantodea, Isoptera, Zoraptera, Plecoptera, Phasmatodea, Grylloblattodea, Orthoptera, Embiidina, Dermaptera, Homoptera, Hemiptera, Psocoptera, Mallophaga, Anoplura, and Thysanoptera.
There are 22 Orders, 293 Families, 3745 Genera, 14372 Species (subspecies), 7190 synonyms and 972 references included in this volume. The Latin names of species are arranged into alphabetical order under every family. Each species of insect includes their Latin name, synonyms, hosts, and distribution. Attached to the end of the volume are selected references; Index to Genera, Families, Superfamilies, Sections, Suborders and Orders of insects and Index to Species and Subspecies of insects.
There are currently no reviews for this book. Be the first to review this book!
Your orders support book donation projects
They [the books] arrived in wonderful condition and it was a joy to see how well they were protected.
Search and browse over 110,000 wildlife and science products
Multi-currency. Secure worldwide shipping
Wildlife, science and conservation since 1985 | <urn:uuid:ca5b272f-f14f-407d-bc37-b8795399097c> | 2.828125 | 296 | Content Listing | Science & Tech. | 14.142778 | 95,529,791 |
Northern Rocky Mountain Science Center (NOROCK)
USGS scientist Todd Preston using an Unmanned Aerial Vehicle (UAV). USGS is actively exploring the use of small unmanned aerial system (aka drones) for scientific data collection and testing whether or not they are useful in monitoring wildlife. These systems have proven their utility in military reconnaissance missions and are now finding a second life in scientific...
Title: Snow and Avalanche Science - Highlights of applied avalanche research and forecasting
- Avalanches impact transportation corridors, with subsequent economic ramifications, including the Going-to-the-Sun Road in Glacier National Park.
- Large magnitude avalanches affect the landscape creating new habitat for flora and fauna.
The responses of pikas and marmots to weather and snowpack dynamics have been species-specific.
In 2018, USGS and partners completed an incredible feat against a harmful aquatic invasive species when over 240,000 pounds of invasive Silver Carp and Bighead Carp were removed from Creve Coeur Lake in Maryland Heights, Missouri.
This image shows the perimeter of Rainbow Glacier in Glacier National Park: 1966, 1998, 2005, 2015.
Siyeh Glacier (upper – 2015 satellite photo, lower - 2005 aerial photo). The glacier margin is more clearly identified in the 2015 image because seasonal snow is persisting on the ice and rock debris atop the ice can be more clearly seen than in the heavily shaded 2005 image.
USGS scientist Sarah Fitzgerald holds a surf scoter that has been fitted with a satellite tag that works by transmitting the location of the birds to satellites that are orbiting the Earth. (Jonathan Fiely, USGS)
Image from a remote camera placed in a golden eagle nest in the Mojave Desert. The parent is feed the chick a snake.
Scientist participating in snowmobile training in Montana. | <urn:uuid:2045034d-8daf-4444-982b-080ee46bb681> | 3.484375 | 373 | Content Listing | Science & Tech. | 34.461887 | 95,529,795 |
Astronomy, Missions, sun
25 May , 2018 by Matt Williams
Two upcoming missions – NASA’s Parker Solar Probe and the ESA’s Solar Orbiter – will get closer to the Sun than ever before in the hopes of unlocking its secrets.
Astronomy, Observing, Skywatching, sun
22 May , 2018 by David Dickinson
Have you been keeping an eye on Sol lately? One of the top astronomy stories for 2018 may be what’s not happening, and how inactive our host star has become.
Aurora, Solar Astronomy, sun
28 Mar , 2018 by Evan Gough
Scientists are getting better at predicting colorful auroras here on Earth by closely watching the behavior of the Sun.
Astronomy, Aurora, Missions, NASA, News, Solar Astronomy, sun
25 Mar , 2018 by Bob King
Join NASA’s most daring mission to the Sun by sending your name along for the ride on the Parker Solar Probe that’s set to launch this summer.
Astronomy, Solar Astronomy, sun
26 Feb , 2018 by Evan Gough
SOHO is celebrating a huge milestone, and one it was never intended to meet: it has now observed one complete, 22-year cycle in the life of the Sun.
5 Oct , 2017 by Matt Williams
A team of scientists from the Harvard Smithsonian Center for Astrophysics have proposed a bold idea for protecting Earth against solar flare activity – placing a giant magnetic shield in orbit!
Astronomy, Aurora, Hubble, NASA, Solar System, sun, Uranus
11 Apr , 2017 by Bob King
French astronomers discover the brightest auroras on Uranus ever seen, and they look … weird.
News, Solar Astronomy, sun
30 Mar , 2017 by Matt Williams
The Smithsonian Astrophysical Observatory and Draper are helping NASA to develop the Solar Probe Plus, the first spacecraft that will “touch”the face of the Sun.
Astronomy, Eclipses, Infographics, Moon, News, Science, Skywatching, Solar System, sun
5 Feb , 2017 by Bob King
This Friday evening watch the Moon tippy-toe right up to Earth’s inner shadow for a sweet penumbral eclipse.
Astronomy, Climate, Curiosity, Mars, Mars Science Laboratory, NASA, sun
27 Jan , 2017 by Bob King
Carl Sagan hit on the idea 40 years ago. Now, a team of scientists have discovered that a trifecta of gases may have warmed Mars enough for liquid water to gush.
Space stories from across the internet, sent to you by email. | <urn:uuid:85fa41d2-4634-4d1e-a57c-d8d1234e3f1a> | 2.84375 | 549 | Content Listing | Science & Tech. | 42.683149 | 95,529,857 |
In February’s Physics World: Mining the Moon becomes a serious prospect
With an estimated 1.6 billion tonnes of water ice at its poles and an abundance of rare-earth elements hidden below its surface, the Moon is rich ground for mining.
In this month’s issue of Physics World, science writer Richard Corfield explains how private firms and space agencies are dreaming of tapping into these lucrative resources and turning the Moon's grey, barren landscape into a money-making conveyer belt.
Since NASA disbanded its manned Apollo missions to the Moon over 40 years ago, unmanned spaceflight has made giant strides and has identified a bountiful supply of water ice at the north and south poles of the Moon.
“It is this, more than anything else,” Corfield writes, “that has kindled interest in mining the Moon, for where there is ice, there is fuel.”
Texas-based Shackleton Energy Company (SEC) plans to mine the vast reserves of water ice and convert it into rocket propellant in the form of hydrogen and oxygen, which would then be sold to space partners in low Earth orbit.
As the company’s chief executive officer, Dale Tietz, explains, the plan is to build a “gas station in space” in which rocket propellant will be sold at prices significantly lower than the cost of sending fuel from Earth.
SEC plans to extract the water ice by sending humans and robots to mine the lunar poles, and then use some of the converted products to power mining hoppers, lunar rovers and life support for its own activities.
Moon Express, another privately funded lunar-resources company, is also interested in using water ice as fuel – but in a different form. It plans to fuel its operations and spacecraft using “high-test peroxide” (HTP), which has a long and illustrious history as a propellant.
As for mining the rare-earth elements on the Moon, China is making the most noticeable headway. The Jade Rabbit lander successfully touched down on the Moon in December 2013 and the Chinese space agency has publicly suggested establishing a “base on the Moon as we did in the South Pole and the North Pole”.
With a near-monopoly on the dwindling terrestrial rare-earth elements, which are vital for everything from mobile phones to computers and car batteries, it is no surprise that China may want to cast its net wider.
“All interested parties agree that the Moon – one step from Earth – is the essential first toehold for humankind’s diaspora to the stars,” Corfield concludes. | <urn:uuid:e166ff55-880b-45d0-a059-58e0ef50aa98> | 2.984375 | 543 | Truncated | Science & Tech. | 38.127465 | 95,529,858 |
In a new study appearing in the June edition of the journal Icarus, scientists used images collected over several years by NASA's Cassini spacecraft to discover that the heat from within the planet powers the jet streams.
A particularly strong jet stream churns through Saturn's northern hemisphere in this false-color view from NASA's Cassini spacecraft. Image credit: NASA/JPL-Caltech/SSI
Condensation of water from Saturn's internal heating led to temperature differences in the atmosphere. The temperature differences created eddies, or disturbances that move air back and forth at the same latitude, and those eddies, in turn, accelerated the jet streams like rotating gears driving a conveyor belt.
A competing theory had assumed that the energy for the temperature differences came from the sun. That is how it works in the Earth's atmosphere.
"We know the atmospheres of planets such as Saturn and Jupiter can get their energy from only two places: the sun or the internal heating. The challenge has been coming up with ways to use the data so that we can tell the difference," said Tony Del Genio of NASA's Goddard Institute for Space Studies, N.Y., the lead author of the paper and a member of the Cassini imaging team.
The new study was possible in part because Cassini has been in orbit around Saturn long enough to obtain the large number of observations required to see subtle patterns emerge from the day-to-day variations in weather. "Understanding what drives the meteorology on Saturn, and in general on gaseous planets, has been one of our cardinal goals since the inception of the Cassini mission," said Carolyn Porco, imaging team lead, based at the Space Science Institute, Boulder, Colo. "It is very gratifying to see that we're finally coming to understand those atmospheric processes that make Earth similar to, and also different from, other planets."
Rather than having a thin atmosphere and solid-and-liquid surface like Earth, Saturn is a gas giant whose deep atmosphere is layered with multiple cloud decks at high altitudes. A series of jet streams slice across the face of Saturn visible to the human eye and also at altitudes detectable to the near-infrared filters of Cassini's cameras. While most blow eastward, some blow westward. Jet streams occur on Saturn in places where the temperature varies significantly from one latitude to another.
Thanks to the filters on Cassini's cameras, which can see near-infrared light reflected to space, scientists now have observed the Saturn jet stream process for the first time at two different, low altitudes. One filtered view shows the upper part of the troposphere, a high layer of the atmosphere where Cassini sees thick, high-altitude hazes and where heating by the sun is strong. Views through another filter capture images deeper down, at the tops of ammonia ice clouds, where solar heating is weak but closer to where weather originates. This is where water condenses and makes clouds and rain.
In the new study, which is a follow-up to results published in 2007, the authors used automated cloud tracking software to analyze the movements and speeds of clouds seen in hundreds of Cassini images from 2005 through 2012.
"With our improved tracking algorithm, we've been able to extract nearly 120,000 wind vectors from 560 images, giving us an unprecedented picture of Saturn's wind flow at two independent altitudes on a global scale," said co-author and imaging team associate John Barbara, also at the Goddard Institute for Space Studies. The team's findings provide an observational test for existing models that scientists use to study the mechanisms that power the jet streams.
By seeing for the first time how these eddies accelerate the jet streams at two different altitudes, scientists found the eddies were weak at the higher altitudes where previous researchers had found that most of the sun's heating occurs. The eddies were stronger deeper in the atmosphere. Thus, the authors could discount heating from the sun and infer instead that the internal heat of the planet is ultimately driving the acceleration of the jet streams, not the sun. The mechanism that best matched the observations would involve internal heat from the planet stirring up water vapor from Saturn's interior. That water vapor condenses in some places as air rises and releases heat as it makes clouds and rain. This heat provides the energy to create the eddies that drive the jet streams.
The condensation of water was not actually observed; most of that process occurs at lower altitudes not visible to Cassini. But the condensation in mid-latitude storms does happen on both Saturn and Earth. Storms on Earth – the low- and high-pressure centers on weather maps – are driven mainly by the sun's heating and do not mainly occur because of the condensation of water, Del Genio said. On Saturn, the condensation heating is the main driver of the storms, and the sun's heating is not important.
Images of one of the strongest jet streams and a figure from the paper can be found at http://www.nasa.gov/cassini , http://saturn.jpl.nasa.gov and http://ciclops.org .
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute in Boulder, Colo.Jia-Rui C. Cook 818-354-0850
Bill Steigerwald | EurekAlert!
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Life Sciences
18.07.2018 | Life Sciences
18.07.2018 | Information Technology | <urn:uuid:3ccc8a21-dcc8-4cdd-a071-db901e4e2c56> | 4.1875 | 1,816 | Content Listing | Science & Tech. | 44.831752 | 95,529,866 |
The world could be at a turning point in the battle against climate change – as a study showed that emissions of greenhouse gas CO2 have ‘flattened out’ in the past three years.Cannibal, 21, said 'I liked the taste of her brain' after eating lover, 45
The researchers said that it’s unclear whether the slowdown – mainly caused by declining coal use in China – is permanent or just a blip.
The news also comes amid concern that Donald Trump could back out of climate deals.
‘It is far too early to proclaim we have reached a peak,’ said co-author Glen Peters, a senior researcher at the Center for International Climate and Environmental Research in Oslo.
‘Nevertheless, the unexpected reductions in Chinese emissions give hope that the world’s biggest emitter can deliver much more ambitious emission reductions.’
‘This could be the turning point we have hoped for,’ said David Ray, a professor of carbon management at the University of Edinburgh, who was not involved with the study.
‘To tackle climate change those bonds must be broken and here we have the first signs that they are at least starting to loosen.”
The study, published in the journal Earth System Science Data, says global CO2 emissions from fossil fuels and industry is projected to grow by just 0.2 percent this year.
That would mean emissions have leveled off at about 36 billion metric tons in the past three years even though the world economy has expanded, suggesting the historical bonds between economic gains and emissions growth may have been severed.
Peters said it remains unclear whether the Chinese slowdown was due to a restructuring of the Chinese economy or a sign of economic instability. | <urn:uuid:1236b62a-bf06-4e2c-857b-53f65e4fc4cc> | 2.703125 | 356 | Truncated | Science & Tech. | 42.802536 | 95,529,896 |
Many warm-blooded animals slip into an inert sleep-like state as part of a unique strategy to get past harsh winters when food supplies are low and the need for energy to stay warm is high. The immune system is in sleep mode as well.
"The production of antibodies, and white blood cells is stopped. Basically all cell reproduction shuts off," says Angela Luis, a doctoral candidate in ecology at Penn State's Center for Infectious Disease Dynamics.
However, animals regularly snap out of their torpor, and become fully active. But such sudden breaks from slumber eat into much of the animal's stored energy reserves, and it is not fully clear why the animals need to wake up, and how often
Some scientists think the answer lies in bacterial infections that could run rampant in the face of an immune system that is essentially asleep.
"Animals cannot tell when they need to wake up, or if they are infected," says Luis. If the animals hibernate for long they risk serious infection, she says, while waking up frequently wastes precious energy, and could prove fatal as well.
In other words, animals with an optimal time of torpor will win out over others, says Luis, who presented her findings at the 91st annual meeting of the Ecological Society of America.
Luis and her colleagues used a simple mathematical model that mimicked the growth of bacteria such as E. coli and Salmonella in European ground squirrels, and how it affected their torpor patterns in relation to temperature.
Microbial growth depends on temperature. Most bacteria grow faster when it is warm and much slower when it is cold. For animals exposed to Salmonella, which multiplies rapidly in warm temperature, a regular break in hibernation would be an important adaptation to combat the germs, when experiencing a warmer winter. However, Salmonella doesn't thrive at very low temperatures, so when animals experience a particularly cold winter, these breaks wouldn't be crucial.
But if the animals were exposed to certain pathogens that thrive at low temperatures, like some E. coli, the animals would still have to regularly break their hibernation to ensure protection at all temperatures, Luis explains.
"Our model, which is confirmed by field data, shows that torpor patterns generally seen in some hibernating animals may be an evolutionary adaptation to help protect them from bacteria that grow well in low temperatures," says Luis.
The researchers suggest that an understanding of how pathogens interact with their hibernating hosts could provide valuable insight into the spread and emergence of zoonotic diseases.
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Materials Sciences
20.07.2018 | Physics and Astronomy
20.07.2018 | Materials Sciences | <urn:uuid:aecf01d9-ce0c-4776-a522-e6c8871cfec6> | 4 | 1,117 | Content Listing | Science & Tech. | 39.426639 | 95,529,898 |
Dawn captured the most detailed pictures of Ceres as it orbits from a proximity of 22 miles above the surface. The new orbit allowed the spacecraft to get a sharper image of Ceres's weird bright spots at the Occator crater.
Space July 4, 2018
A new theory suggests gravity of smaller space debris could explain the strange orbits of Sedna and other trans-Neptunian objects. Here's why it failed to debunk the existence of Planet Nine.
Space June 7, 2018
Building on data from New Horizons and Rosetta mission on comet 67P, scientists presented ‘the giant comet cosmochemical model of Pluto formation.’ The team floated the idea that Pluto could actually be a giant comet after all.
Space May 24, 2018
Data from NASA's Dawn spacecraft suggest that dwarf planet Ceres has a cycle of condensation and sublimation. Scientists said that this process was previously seen only on comets.
Space March 15, 2018
A six-year-old girl from Ireland wrote to NASA, asking the space agency to 'make Pluto a planet again.' The little astronaut wannabe is now the most adorable member of the contingent pushing to give Pluto back its planetary status.
Space February 19, 2018
Astronomers have discovered the first-ever dwarf planet in the Solar System to be surrounded by a ring. But the question is, how did it even form one of its own?
Space October 12, 2017
Astronomers first spotted the distant celestial object UZ224 in 2014. After years of observation, they reveal that 'DeeDee' meets all the new requirements to be considered a dwarf planet.
Space April 16, 2017
A group of scientists is proposing a new definition that would classify celestial objects as planets. If the new criteria get adopted, the Solar System could be home of more than 100 planets, which would include the Earth's moon.
Space March 19, 2017
A team of scientists at NASA published a new proposal that aims to change the way planetary scientists define and classify planets. If approved, it means Pluto may be deemed a planet again.
Space February 21, 2017
NASA's Dawn spacecraft detected carbon-containing materials on Ceres similar to what may have been the building blocks for life on Earth. The organic molecules also appear to be native to this dwarf planet.
Space February 17, 2017
Particles from asteroid impacts that occurred millions of years ago cloak the surface of Ceres. The particles may hide the dwarf planet's true makeup.
Space January 26, 2017
A new study proposes that Planet Nine could previously be a 'rogue planet,' a free-moving body not bound to any host star, which eventually got snatched into the solar system through the sun’s gravitational pull.
Space January 13, 2017
Those icy ridges found on the Tartarus Dorsa region of Pluto are similar to the so-called penitentes on Earth, making it possible for the same features to exist elsewhere in the solar system, a new study has found.
Space January 6, 2017
Water on dwarf planet Ceres is frozen as ice, but the biggest asteroid in the solar system was once an ocean world. Early in its history, Ceres had water that churned and flowed, helping separate it into layers of rocks and ice.
Space December 16, 2016
Pluto is the smallest planet in our solar system, and the coldest as well. With that being the truth, researchers are attempting to find out if life could be sustained on the planet, especially in its oceans under the ice.
Space December 5, 2016
Observations made through NASA's Chandra X-ray Observatory revealed Pluto emits X-rays. Why are astronomers puzzled by the radiation from the dwarf planet?
Space September 18, 2016
The red spot at the north pole of Charon, the largest moon of Pluto, may have been produced by methane from the dwarf planet's atmosphere. How did this reddish region form?
Space September 15, 2016
During its 4.5 billion-year history, Ceres is not immune to violent asteroid collisions. A new study suggests a strange anomaly on the dwarf planet: researchers say Ceres is missing a few large impact craters.
Space July 26, 2016
Permanently shadowed regions on dwarf planet Ceres may be frigid enough to hold debris of water ice, a new study suggests. NASA's Dawn mission has helped locate these "cold traps."
Space July 8, 2016
A present-day liquid ocean could be hiding beneath the icy crust of Pluto. The dwarf planet would have shrunk if its ocean has completely frozen millions of years ago.
Space June 22, 2016
A new study found that the dwarf planet 2007 OR10, nicknamed 'Snow White,' is much bigger and darker than previously believed. This makes Snow White the third biggest dwarf planet in our solar system.
Space May 13, 2016
The second brightest icy dwarf planet in the Kuiper belt is not alone. NASA's Hubble Space telescope has detected a small, dark moon around Makemake, revealing insight about dwarf planet systems.
Space April 27, 2016
NASA scientists unveiled images showing a detailed look of the mysterious black spots on the surface of Ceres. The images gave scientists better understanding of the evolution of the dwarf planet.
Space March 23, 2016
Pluto has a geographically diverse surface. Researchers said this is influenced by the dwarf planet's water ice and volatile ices.
Space March 20, 2016
NASA released a new color animation of dwarf planet Ceres. The high-resolution images from the Dawn mission were enhanced to give people a vivid experience as they fly over the crater-filled planet.
Space January 30, 2016
The newest images from the Dawn spacecraft orbiting the tiny world are revealing new insights into intriguing 'bright spots.' Photos were snapped at the closest distance yet, researchers say.
Space January 14, 2016
NASA released new high-resolution images of Pluto that show what appears to be icebergs that float on the surface.
Space January 8, 2016
Observations made by Dawn's Framing Camera suggest that the mysterious Ceres bright spots are primarily composed of hydrated magnesium sulfates. Also known as Epsom salt, this substance is used on Earth for treating a range of ailments.
Space December 10, 2015
Astronomers spy an icy body that looks to be the most distant thing in the solar system. So now researchers will have to wait about a year to determine just how big of a deal this thing is.
Space November 12, 2015
The New Horizons spacecraft sends back images of mountains on Pluto that may be ice volcanoes, NASA says. Circular mountains near the dwarf planet's south pole show crater-like central depressions, scientists say.
Space November 10, 2015
The New Horizons spacecraft approaching Pluto for a July rendezvous has snapped a 360-degree panorama of the dward planet. Scientists say the images show a much more complex surface than expected.
Space June 15, 2015
As it prepares to fly by Pluto, NASA's New Horizons spacecraft has snapped the best photos of Pluto ever taken. The probe will reach its destination on July 14.
Space April 30, 2015
Tiny world orbiting in solar system's asteroid belt captured in dramatic new phographs from space probe Dawn. NASA predicts even better images in coming weeks as spacecraft moves into closer orbits around Ceres.
Geek April 19, 2015
In 1930, astronomer Clyde Tombaugh discovered Pluto from an observatory in Flagstaff, Arizona. Though demoted to a dwarf planet in 2006, Pluto is now the star of a year-long celebration.
Internet Culture April 7, 2015
Astronomers get first good look at two of Pluto's five known moons, courtesy of images from the NASA spacecraft. The dwarf planet's moons Nix and Hydra are both less than 100 miles wide.
Space February 22, 2015
New, sharper images of dwarf planet raise more questions than answers, astronomers say. Scientists eagerly await the arrival of the Dawn spacecraft at Ceres in March.
Space February 18, 2015
Dwarf planet or asteroid? Call it what you will, the giant space rock is slowly revealing its secrets as a NASA spacecraft approaches for a rendezvous in March.
Space February 6, 2015
NASA spacecraft starts a photographic record of its approach to the dwarf planet at the edge of the solar system. New Horizons spacecraft will make its closest approach to Pluto in July.
Space January 25, 2015
New Horizons is approaching Pluto, marking a historic moment in the exploration of space.
Space January 5, 2015
The Dawn spacecraft visited the asteroid Vesta, now it is closing in on the dwarf planet Ceres. What will it find when it gets there?
Space January 2, 2015
Astronomers studying "adolescent" version of our own sun say it may be surrounded with Pluto-like dwarf planets. Observations provide insights into how solar systems form, from birth to maturity, researchers say.
Space December 12, 2014
Ceres, the only dwarf planet in the inner solar system, has been imaged by the Dawn spacecraft as it speeds toward an encounter with the icy body.
Space December 8, 2014
The New Horizons spacecraft has been travelling toward Pluto since 2006. On Dec. 6, it will wake up from hibernation to prepare for its long-awaited encounter with the dwarf planet in January 2015.
Space December 2, 2014
The team behind the New Horizons mission, which was launched to study Pluto in 2006, is eyeing to explore three Kuiper Belt objects located a billion miles beyond the dwarf planet.
Space October 22, 2014
The public speaks: give Pluto back it status as a planet. Debate rages over Pluto's second-class "dwarf planet" classification.
Space October 3, 2014
Feature | Health | <urn:uuid:8bf08ef1-d1de-4923-b062-9b8619d6e44b> | 3.609375 | 2,012 | Content Listing | Science & Tech. | 53.352331 | 95,529,912 |
You’ve made it to the end of the sixth part of this series, so let’s summarize:
- You can assign closures to variables, then call them later on.
- Closures can accept parameters and return values, like regular functions.
- You can pass closures into functions as parameters, and those closures can have parameters of their own and a return value.
- If the last parameter to your function is a closure, you can use trailing closure syntax.
- Swift automatically provides shorthand parameter names like
$1, but not everyone uses them.
- If you use external values inside your closures, they will be captured so the closure can refer to them later.
Master iOS 11 now!
My book Practical iOS 11 gives you seven complete coding projects that teach all the major new features in iOS 11 in a smart, practical way. | <urn:uuid:8099a4d8-2e89-4883-b27e-ba08164d9531> | 3.03125 | 178 | Tutorial | Software Dev. | 49.822397 | 95,529,948 |
Enjoy some of the extensive magazine, newspaper and web-based coverage of our work through the years.
Enjoy a sampling of print media featuring Dr. Nichols' efforts collected on ISSU.
Loggerhead sea turtles captured the imagination of marine enthusiasts everywhere long before Crush made his big screen debut in Finding Nemo. They’re among the oldest creatures on earth and have remained essentially unchanged for 110 million years. That’s a pretty long time considering we boring ‘anatomically modern’ homo sapiens have only been wandering around for about 200,000 years. No contest. Loggerheads are endangered and the North Pacific population has been decimated by hunting, bycatch, and loss of nesting beaches. And yet, a chance to do something that might make a difference by giving them a shot at recovery…
Baja California hosts a longline shark fishery that incidentally kills hundreds of loggerheads every year. (Longlines are miles-long lengths of gear set on the ocean floor with baited hooks). When turtles move through the area to feed and rest, they often swallow the hooks or become entangled in gear. This means lots of dead loggerheads.
There’s a little place called Lopez Mateos in Central Baja where outreach and conservation efforts have resulted in social pressure to stop destructive longline practices. And get this, fishermen are now actually willing to stop if we buy their gear. Translation: Sans longlines, as many as 600 loggerheads would be spared annually. In my opinion, it could be the most cost effective turtle restoration and conservation effort in history. The Ocean Conservancy (TOC) agrees and they’re hoping to raise $10,000 to support a local buyout. Sure, it’s one project in a single community, but would also serve as a low cost case study which if successful will be replicated Baja and beyond.
Okay to be honest, I admit I was more than a little skeptical of yet another buyout, so asked TOC how this would actually keep anyone from coming back into the area. Wouldn’t fishermen just start longlining again in a few years? The satisfying response from the folks on the ground after the jump…
And for anyone interested in making a contribution, email me at email@example.com and I’ll provide more detail.
While they won’t long-line, they will remain fishing (with far less destructive gear),in the region. They will be one form of enforcement. Community pressure and supervision will be another enforcement tool…since the community has adopted the goal of turtle conservation and building a conservation-tourism industry. When there is an economic incentive for community members to run businesses based on taking tourists to see the turtles, that creates significant community pressure and supervision to ensure that ‘turtle wasteful’ fishing practices are not re-introduced.
I’m not saying this is perfect and foolproof, it is frankly an experiment to see if it can be implemented and replicated. And, it’s only part of the package. We also have to implement other parts of the program, such as technical assistance to help this community and others build a viable conservation tourism economic base (around seeing turtles, whales and other wildlife), along the lines of the success and San Ignacio.
But, after having visited Lopez Mateo, and seeing the work and leaders of Pro-Peninsula and Groupo Tortugaro over the past decade (who are the real hero’s in this story), I have great confidence in the commitment, ethics, and value of local leaders who are making this policy happen. And if we can save 3-600 turtles every year for one time investment of $10k, it’s a bargain. We expend hundreds of thousands of dollars in the U.S. to protect a fraction of that number.
Recent research has confirmed what many boaters already know – you experience emotional, behavioral... continue
TORONTO, July 9, 2018 /CNW/ - According to the National Marine Manufacturers... continue | <urn:uuid:2e851883-cd08-446b-98f4-e8959fe4b59d> | 2.609375 | 842 | Personal Blog | Science & Tech. | 45.229658 | 95,529,956 |
The Arctic has heated twice as much as the rest of the world with large consequences for example for the wildlife, the pollutants and the cryosphere and with possible large positive feedback effects on climate. Although the knowledge about the Arctic has increased over the last years, Arctic is still one of the regions of which we know least. This is especially true for the high Arctic. One of the main reasons for this is the lack of infrastructure.
The infrastructure ICOS RI, is a European infrastructure consisting of measurement sites where concentrations of atmospheric carbon climate gases and/or ecosystem fluxes are measured. ICOS/DK is a network of measurement sites in Denmark and Greenland, which will contribute to the European ICOS RI.
Marin Basis Monitoring Program is a part of the GEM program, and take place in Young Sund every year in late July until middle of August. The program follows the levels and changes in
The objective of the project is to strengthen the understanding of the regional and local processes controlling the arctic climate changes. It is our intension to observe the development of CO2 in the arctic atmosphere at Zackenberg Marine Station by an artic fjord sampling and analyzing concentrations as well as the fluxes. | <urn:uuid:ff773033-6006-41af-acd2-d60d3ac6528c> | 2.921875 | 245 | About (Org.) | Science & Tech. | 34.900238 | 95,529,986 |
The event system¶
The event module provides a system for properties and events, to let different components of an application react to each-other and to user input.
Componentclass provides a base class which can be subclassed to create the different components of an app.
- Each component has
propertiesto reflect the state of the component.
- Properties can only be mutated by
actions. Calling (i.e. invoking) an action will not apply the action at once; actions are processed in batches.
- When properties are modified (i.e. the state is changed),
reactionswill be invoked. The reactions are processed when all pending actions are done. This means that during processing reactions, the state never changes, which is a great thing to rely on!
- Reactions can also react to events generated by
emitters, such as mouse events.
event loopobject is responsible for scheduling actions and reactions and can be used by the user to e.g. make a function be called later. It intergrates with Python’s own asyncio loop.
The asynchronous nature of actions combined with the fact that the state does not change during processing reactions, makes it easy to reason about cause and effect. The information flows in one direction. This concept was gratefully taken from modern frameworks such as React/Flux and Veux.
One might suggest that the information flow is still circular, because there is an arrow going from reactions to actions. This is true, but note that actions invoked from reactions are not directly executed; they are pended and will be executed only after all reactions are done.
Relation to other parts of Flexx¶
This event system and its
form the basis for
app.JsComponent and the UI system
the same in both languages.
Other than that, this is a generic event system that could drive any system that is based on asyncio.
An event is something that has occurred at a certain moment in time,
such as the mouse being pressed down or a property changing its value.
In Flexx, events are represented with dictionary objects that
provide information about the event (such as what button was pressed,
or the old and new value of a property). A custom
class is used that inherits from
dict but allows attribute access,
ev.button as an alternative to
Each event object has at least two attributes:
a reference to the Component object emitting the event, and
type, a string
indicating the type of the event.
The Component class¶
Component class provides a base
class for objects that have properties, actions, reactions and emitters.
flexx.ui.Widget inherits from
which inherits from
class MyObject(event.Component): ... # attributes/properties/actions/reactions/emitters go here def init(self): super().init() ...
It is common to implement the
init() method of the component class. It gets
automatically called by the component, at a moment when all properties have
been initialized, but no events have been emitted yet. This is a good time
to further initialize the component, and/or to instantiate sub components.
One rarely needs to implement the
init() is called, the component is the currently “active”
component, which can be used to e.g. descrive a hierarchy of objects, as is
done with widgets. It also implies that mutations are allowed and that actions
on the component itself have a direct effect (invoking actions of other
components is still asynchronous though).
Properties represent state¶
Properties can be defined using one of
the several property classes. For example:
class MyObject(event.Component): foo = event.AnyProp(8, settable=True, doc='can have any value') bar = event.IntProp()
Properties accept one positional arguments to set the default value. If not
given, a sensible default value is used that depends on the type of property.
foo property above is marked as settable, so that the class will have
set_foo() action. Docs can be added too. Note that properties
are readonly: they can can only be mutated by actions.
Property values can be initialized when a component is created (also non-settable properties):
c = MyComponent(foo=42)
One can also set the initial value of a property to a function object. This creates an auto-reaction that sets the property, and makes it possible to hook things up in a very concise manner. In the example below, the label text will be automatically updated when the username property changes:
c = UiLabel(text=lambda: self.username)
An event is emitted every time that a property changes. This event has attributes
new_value (except for in-place array mutations, as
explained below). At initialization, a component sends out an event for each property,
which has the same value for
Component classes can also have
which are read-only (usually static) non-observable values (e.g.
Actions can mutate properties¶
Actions can be defined to mutate properties:
class MyObject(event.Component): foo = event.AnyProp(8, settable=True, doc='can have any value') bar = event.IntProp() @event.action def increase_bar(self): self._mutate_bar(self.bar + 1) # shorthand for self._mutate('bar', self.bar + 1)
Actions can have any number of (positional) arguments. Note that actions are asynchronous, i.e. calling an action will not apply it immediately, unless it is called from another action.
Since actions are asynchronous, their inner function should not return a value.
Invoking (i.e. calling) an action always returns the component itself, which
allows chainging action invokations, e.g.
Mutations are done via the
or by the auto-generated
Mutations can only be done from an action. Trying
to do so otherwise will result in an error. This may seem limiting at first,
but it greatly helps keeping it easy to reason about information flowing
through your application, even as it scales.
Mutations to array-like properties¶
The above shows the simple and most common use of mutations. For list properties, mutations can also be done in-place:
class MyObject(event.Component): items = event.ListProp() def add_item(self, item): self._mutate_items([item], 'insert', len(self.items))
This allows more fine-grained control over state updates, which can also be handled by reactions in much more efficient ways. The types of mutations are ‘set’ (the default), ‘insert’, ‘replace’, and ‘remove’. In the latter, the provided value is the number of elements to remove. For the others it must be a list of elements to set/insert/replace at the specified index.
Emitters create events¶
Emitters make it easy to generate events.
Similar to actions, they are created with a decorator.
class MyObject(event.Component): @event.emitter def pointer_down(self, js_event): ''' Event emitted when the mouse/touchpad/screen is pressed. ''' return dict(button=js_event.button)
Emitters can have any number of arguments and should return a dictionary, which will get emitted as an event, with the event type matching the name of the emitter.
Note that stricly speaking emitters are not necessary as
can be used to generate an event. However, they provide a mechanism to
generate an event based on certain input data, and also document the
events that a component may emit.
Reactions are used to react to events and
changes in properties, using an underlying handler function:
class MyObject(event.Component): first_name = event.StringProp(settable=True) last_name = event.StringProp(settable=True) @event.reaction('first_name', 'last_name') def greet(self, *events): print('hi', self.first_name, self.last_name) @event.reaction('!foo') def handle_foo(self, *events): for ev in events: print(ev)
This example demonstrates multiple concepts. Firstly, the reactions are
connected via connection-strings that specify the types of the
event; in this case the
greeter reaction is connected to “first_name” and
handle_foo is connected to the event-type “foo” of the
object. This connection-string can also be a path, e.g.
“sub.subsub.event_type”. This allows for some powerful mechanics, as
discussed in the section on dynamism.
One can also see that the reaction-function accepts
This is because reactions can be passed zero or more events. If a reaction
is called manually (e.g.
ob.handle_foo()) it will have zero events.
When called by the event system, it will have at least 1 event. When
e.g. a property is set twice, the function will be called
just once, but with multiple events. If all events need to be processed
for ev in events: ....
In most cases, you will connect to events that are known beforehand,
like those corresponding to properties and emitters.
If you connect to an event that is not known (like “foo” in the example
above) Flexx will display a warning. Use
'!foo' as a connection string
(i.e. prepend an exclamation mark) to suppress such warnings.
Another useful feature of the event system is that a reaction can connect to
multiple events at once, as the
greet reaction does.
The following is less common, but it is possible to create a reaction from a
normal function, by using the
c = MyComponent() # Using a decorator @c.reaction('foo', 'bar') def handle_func1(self, *events): print(events) # Explicit notation def handle_func2(self, *events): print(events) c.reaction(handle_func2, 'foo', 'bar') # this is fine too: c.reaction('foo', 'bar', handle_func2)
Greedy and automatic reactions¶
Each reaction operates in a certain “mode”. In mode “normal”, the event system ensures that all events are handled in the order that they were emitted. This is often the most useful approach, but this implies that a reaction can be called multiple times during a single event loop iteration, with other reactions called in between to ensure the consisten event order.
If it is preferred that all events targeted at a reaction are handled with a single call to that reaction, it can be set to mode “greedy”. Cases where this makes sense is when all related events must be processed simultenously, or simply when performance matters a lot and order matters less.
Reactions with mode “auto” are automatically triggered when any of the
properties that the reaction uses is changed. Such reactions can be
created by specifying the
mode argument, or simply by creating a
reaction with zero connections strings. We refer to such reactions as
“auto reactions” or “implicit reactions”. This is a convenient feature,
but should probably be avoided when a lot (say hundreds) of properties
class MyObject(event.Component): first_name = event.StringProp(settable=True) last_name = event.StringProp(settable=True) @event.reaction def greet(self): print('hi', self.first_name, self.last_name)
A similar useful feature is to assign a property (at initialization) using a function. In such a case, the function is turned into an implicit reaction. This can be convenient to easily connect different parts of an app.
class MyObject(event.Component): first_name = event.StringProp(settable=True) last_name = event.StringProp(settable=True) person = MyObject() label = UiLabel(text=lambda: person.first_name)
Reacting to in-place mutations¶
In-place mutations to lists or arrays can be reacted to by processing the events one by one:
class MyComponent(event.Component): @event.reaction('other.items') def track_array(self, *events): for ev in events: if ev.mutation == 'set': self.items[:] = ev.objects elif ev.mutation == 'insert': self.items[ev.index:ev.index] = ev.objects elif ev.mutation == 'remove': self.items[ev.index:ev.index+ev.objects] = # objects is int here elif ev.mutation == 'replace': self.items[ev.index:ev.index+len(ev.objects)] = ev.objects else: assert False, 'we cover all mutations'
For convenience, the mutation can also be “replicated” using the
Connection string syntax¶
The strings used to connect events follow a few simple syntax rules:
- Connection strings consist of parts separated by dots, thus forming a path. If an element on the path is a property, the connection will automatically reset when that property changes (a.k.a. dynamism, more on this below).
- Each part can end with one star (‘*’), indicating that the part is a list and that a connection should be made for each item in the list.
- With two stars, the connection is made recursively, e.g. “children**” connects to “children” and the children’s children, etc.
- Stripped of ‘*’, each part must be a valid identifier (ASCII).
- The total string optionally has a label suffix separated by a colon. The label itself may consist of any characters.
- The string can have a “!” at the very start to suppress warnings for connections to event types that Flexx is not aware of at initialization time (i.e. not corresponding to a property or emitter).
An extreme example could be
"!foo.children**.text:mylabel", which connects
to the “text” event of the children (and their children, and their children’s
children etc.) of the
foo attribute. The “!” is common in cases like
this to suppress warnings if not all children have a
Labels are a feature that makes it possible to infuence the order by which reactions are called, and provide a means to disconnect specific (groups of) handlers.
class MyObject(event.Component): @event.reaction('foo') def given_foo_handler(*events): ... @event.reaction('foo:aa') def my_foo_handler(*events): # This one is called first: 'aa' < 'given_f...' ...
When an event is emitted, any connected reactions are scheduled in the order of a key, which is the label if present, and otherwise the name of the name of the reaction.
The label can also be used in the
@h.reaction('foo:mylabel') def handle_foo(*events): ... ... h.disconnect('foo:mylabel') # don't need reference to handle_foo
Dynamism is a concept that allows one to connect to events for which
the source can change. For the following example, assume that
Component subclass that has properties
main = Node() main.parent = Node() main.children = Node(), Node() @main.reaction('parent.foo') def parent_foo_handler(*events): ... @main.reaction('children*.foo') def children_foo_handler(*events): ...
parent_foo_handler gets invoked when the “foo” event gets
emitted on the parent of main. Similarly, the
gets invoked when any of the children emits its “foo” event. Note that
in some cases you might also want to connect to changes of the
children property itself.
The event system automatically reconnects reactions when necessary. This concept makes it very easy to connect to the right events without the need for a lot of boilerplate code.
Note that the above example would also work if
parent would be a
regular attribute instead of a property, but the reaction would not be
automatically reconnected when it changed.
Implicit reactions are also dynamic, maybe even more so! In the example below,
the reaction accesses the
children property, thus it will be called whenever
that property changes. It also connects to the
visible event of
all children, and to the
foo event of all children that are visible.
@main.reaction def _implicit_reacion(): for child in main.children: if child.visible: do_something_with(child.foo)
This mechanism is powerful, but one can see how it can potentially access (and thus connect to) many properties, especially if the reaction calls other functions that access more properties. Also keep in mind that implicit reactions have more overhead (because they fully reconnect every time after they are called). One should probably avoid them for properties that change 100 times per second.
The event system presented here is quite flexible and designed to cover the needs of a variety of event/messaging mechanisms. This section discusses how this system relates to some common patterns, and how these can be implemented.
The idea of the observer pattern is that observers keep track (the state of) of an object, and that an object is agnostic about what it’s tracked by. For example, in a music player, instead of writing code to update the window-title inside the function that starts a song, there would be a concept of a “current song”, and the window would listen for changes to the current song to update the title when it changes.
Component object keeps track of its observers
(reactions) and notifies them when there are changes. In our music player
example, there would be a property “current_song”, and a reaction to
take action when it changes.
As is common in the observer pattern, the reactions keep track of the
objects that they observe. Therefore both
objects have a
dispose() method for cleaning up.
Signals and slots¶
The Qt GUI toolkit makes use of a mechanism called “signals and slots” as
an easy way to connect different components of an application. In
flexx.event signals translate to properties and assoctated setter actions,
and slots to the reactions that connect to them.
Although signals and slots provide a convenient mechanism, they make it easy to create “spaghetti apps” where the information flows all over the place, which is exactly what frameworks like Flux, Veux and Flexx try to overcome.
Overloadable event handlers¶
In Qt, the “event system” consists of methods that handles an event, which
can be overloaded in subclasses to handle an event differently. In
flexx.event, actions and reactions can similarly be re-implemented in
subclasses, and these can call the original handler using
super() if needed.
In pub-sub, publishers generate messages identified by a ‘topic’, and subscribers can subscribe to such topics. There can be zero or more publishers and zero or more subscribers to any topic.
flexx.event a Component object can play the role of a broker.
Publishers can simply emit events. The event type represents the message
topic. Subscribers are represented by handlers. | <urn:uuid:f92e922c-7b67-4c60-9a56-764a2f84f4ce> | 2.640625 | 4,270 | Documentation | Software Dev. | 51.497434 | 95,529,988 |
Stanford scientists develop ultrafast nickel-iron battery
BY MARK SHWARTZ
Stanford University scientists have breathed new life into the nickel-iron battery, a rechargeable technology developed by Thomas Edison more than a century ago.
Designed in the early 1900s to power electric vehicles, the Edison battery largely went out of favor in the mid-1970s. Today only a handful of companies manufacture nickel-iron batteries, primarily to store surplus electricity from solar panels and wind turbines.
"The Edison battery is very durable, but it has a number of drawbacks," said Hongjie Dai, professor of chemistry. "A typical battery can take hours to charge, and the rate of discharge is also very slow."
Now, Dai and his colleagues have dramatically improved the performance of this century-old technology. The Stanford team has created an ultrafast nickel-iron battery that can be fully charged in about 2 minutes and discharged in less than 30 seconds. The results are published in the June 26 issue of the journal Nature Communications.
Graduate student Hailiang Wang, lead author of the study, said the team managed to increase the charging and discharging rate by nearly 1,000 times.
"We've made it really fast," Wang said.
The high-performance, low-cost battery could someday be used to help power electric vehicles, much as Edison originally intended, Dai said.
"Hopefully we can give the nickel-iron battery a new life," he added.
Edison, an early advocate of all-electric vehicles, began marketing the nickel-iron battery around 1900. It was used in electric cars until about 1920. The battery's long life and reliability made it a popular backup power source for railroads, mines and other industries until the mid-20th century.
Edison created the nickel-iron battery as an inexpensive alternative to corrosive lead-acid batteries. Its basic design consists of two electrodes – a cathode made of nickel and an anode made of iron – bathed in an alkaline solution.
"Importantly, both nickel and iron are abundant elements on Earth and relatively nontoxic," Dai noted.
Carbon has long been used to enhance electrical conductivity in electrodes. To improve the Edison battery's performance, the Stanford team used graphene – nanosized sheets of carbon that are only 1-atom thick – and multi-walled carbon nanotubes, each consisting of about 10 concentric graphene sheets rolled together.
"In conventional electrodes, people randomly mix iron and nickel materials with conductive carbon," Wang explained. "Instead, we grew nanocrystals of iron oxide onto graphene, and nanocrystals of nickel hydroxide onto carbon nanotubes."
This technique produced strong chemical bonding between the metal particles and the carbon nanomaterials, which had a dramatic effect on performance.
"Coupling the nickel and iron particles to the carbon substrate allows electrical charges to move quickly between the electrodes and the outside circuit," Dai said. "The result is an ultrafast version of the nickel-iron battery that's capable of charging and discharging in seconds."
The 1-volt prototype battery developed in Dai's lab has just enough power to operate a flashlight. The researchers' goal is to make a bigger battery that could be used for the electrical grid or transportation.
Most electric cars, such as the Nissan Leaf and the Chevy Volt, run on lithium-ion batteries, which can store a lot of energy but typically take hours to charge.
"Our battery probably won't be able to power an electric car by itself because the energy density is not ideal," Wang said. "But it could assist lithium-ion batteries by giving them a real power boost for faster acceleration and regenerative braking."
The enhanced Edison battery might be especially useful in emergency situations, Dai added. "There may be applications for the military, for example, where you have to charge something very quickly," he said.
"It's definitely scalable," Wang said. "Nickel, iron and carbon are relatively inexpensive. And the electrolyte is just water with potassium hydroxide, which is also very cheap and safe. It won't blow up in a car."
The prototype battery has one key drawback – the ability to hold a charge over time. "It doesn't have the charge-discharge cycling stability that we would like," Dai said. "Right now it decays by about 20 percent over 800 cycles. That's about the same as a lithium-ion battery. But our battery is really fast, so we'd be using it more often. Ideally, we don't want it to decay at all."
Dai said the use of strongly coupled nanomaterials represents a very exciting approach to making electrodes.
"It's different from traditional methods, where you simply mix materials together. I think Thomas Edison would be happy to see this progress," he said.
Other co-authors of the study are postdoctoral scholars Yongye Liang and Yanguang Li, graduate student Ming Gong and undergraduates Wesley Chang and Tyler Mefford of Stanford; Jigang Zhou, Jian Wang and Tom Regier of Canadian Light Source Inc.; and Fei Wei of Tsinghua University.
This work was supported by Intel, a Stinehart/Reed Award from the Precourt Institute for Energy at Stanford and a Stanford Graduate Fellowship.
Mark Shwartz writes about energy technology for the Precourt Institute for Energy at Stanford University.
Have a Nice Day,
FYI: Adding pictures
Bored?... take a crack at the unanswered posts
Please post your Watts-at-speed in the survey | <urn:uuid:fa21870e-0117-4950-abba-6f7f59356084> | 3.421875 | 1,151 | Comment Section | Science & Tech. | 36.708799 | 95,530,007 |
January 4, 2016 at 8:31 AM
Researchers believe they've come up with a new, more accurate method for determining the strength of surface gravity on distant, faint stars. And painting more accurate pictures of stars is vital to studying the alien worlds that orbit them.
"If you don't know the star, you don't know the planet," University of British Columbia's Jaymie Matthews, a co-author on the research published Friday in Science Advances, said in a statement. You have to determine the strength of gravity on a star's surface before you can calculate its size and mass, assuming the star isn't close enough to measure directly.
When scientists go looking for alien exoplanets — ones that sit far outside our solar system — they rely entirely on those planets' host stars. Measuring the way a star's light appears to flicker and dim from Earth's perspective allows scientists to calculate an astonishing number of things about the planets transiting around that star, including whether it's the right size and distance from its star to hold liquid water. But to make those calculations, you need accurate stellar measurements. Otherwise, you might misjudge the size of a planet. That's a problem when you're looking for worlds that could host life as we know it, since you want to track down planets that are small and rocky like Earth.
Lots of the stars imaged by the Kepler space telescope are too far away or dim for scientists to study the planets around them effectively. That's where the new technique, called the autocorrelation function timescale technique (timescale technique for short) comes in. Led by University of Vienna's Thomas Kallinger, researchers from Europe, Canada and Australia determined that using the timescale of variations in a star's brightness might be more accurate for determining gravity than the degree of brightness itself.
When they tested the timescale method on stars that are close enough to be studied with standard techniques, they found it to be about six times more accurate than the flicker method, which was developed in 2013 to study distant, dim stars by measuring the brightness of short variations caused by the bubbling of the star's gas.
As techniques like these continue to improve, scientists will be able to confidently study increasingly distant worlds, widening our net in the search for life. | <urn:uuid:daa3efff-2a7c-4174-8baf-46cca3a52be6> | 4.1875 | 469 | News Article | Science & Tech. | 38.8795 | 95,530,014 |
7°C / 44°F
The measurements for the water temperature in Kareela, New South Wales are provided by the daily satellite readings provided by the NOAA. The temperatures given are the sea surface temperature (SST) which is most relevant to recreational users.
The graph below shows the range of monthly Kareela water temperature derived from many years of historical sea surface temperature data.
These average ocean temperatures for Kareela are calculated from several years of archived data.
Whilst sea temperatures for Kareela are as accurate as current data allows, there may be slight local and regional variations depending on conditions. Time of day and wind direction may have a temporary local effect as can water flows from neraby rivers. | <urn:uuid:963ecedf-cc98-460c-8e2d-3dd3e0760e58> | 2.5625 | 143 | Knowledge Article | Science & Tech. | 21.769713 | 95,530,027 |
Frequency is the number of occurrences of a repeating event per unit of time. It is also referred to as temporal frequency, which emphasizes the contrast to spatial frequency and angular frequency. The period is the duration of time of one cycle in a repeating event, so the period is the reciprocal of the frequency. For example, if a newborn baby's heart beats at a frequency of 120 times a minute, its period—the time interval between beats—is half a second (that is, 60 seconds divided by 120 beats). Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio signals (sound), radio waves, and light.
|In SI base units||s−1|
For cyclical processes, such as rotation, oscillations, or waves, frequency is defined as a number of cycles per unit time. In physics and engineering disciplines, such as optics, acoustics, and radio, frequency is usually denoted by a Latin letter f or by the Greek letter or ν (nu) (see e.g. Planck's formula).
The relation between the frequency and the period of a repeating event or oscillation is given by
The SI derived unit of frequency is the hertz (Hz), named after the German physicist Heinrich Hertz. One hertz means that an event repeats once per second. A previous name for this unit was cycles per second (cps). The SI unit for period is the second.
Period versus frequencyEdit
As a matter of convenience, longer and slower waves, such as ocean surface waves, tend to be described by wave period rather than frequency. Short and fast waves, like audio and radio, are usually described by their frequency instead of period. These commonly used conversions are listed below:
|Frequency||1 mHz (10−3 Hz)||1 Hz (100 Hz)||1 kHz (103 Hz)||1 MHz (106 Hz)||1 GHz (109 Hz)||1 THz (1012 Hz)|
|Period||1 ks (103 s)||1 s (100 s)||1 ms (10−3 s)||1 µs (10−6 s)||1 ns (10−9 s)||1 ps (10−12 s)|
Related types of frequencyEdit
- Angular frequency, usually denoted by the Greek letter ω (omega), is defined as the rate of change of angular displacement, θ, (during rotation), or the rate of change of the phase of a sinusoidal waveform (notably in oscillations and waves), or as the rate of change of the argument to the sine function:
- Angular frequency is commonly measured in radians per second (rad/s) but, for discrete-time signals, can also be expressed as radians per sampling interval, which is a dimensionless quantity. Angular frequency (in radians) is larger than regular frequency (in Hz) by a factor of 2π.
- Spatial frequency is analogous to temporal frequency, but the time axis is replaced by one or more spatial displacement axes. E.g.:
In wave propagation Edit
For periodic waves in nondispersive media (that is, media in which the wave speed is independent of frequency), frequency has an inverse relationship to the wavelength, λ (lambda). Even in dispersive media, the frequency f of a sinusoidal wave is equal to the phase velocity v of the wave divided by the wavelength λ of the wave:
Measurement of frequency can done in the following ways,
Calculating the frequency of a repeating event is accomplished by counting the number of times that event occurs within a specific time period, then dividing the count by the length of the time period. For example, if 71 events occur within 15 seconds the frequency is:
If the number of counts is not very large, it is more accurate to measure the time interval for a predetermined number of occurrences, rather than the number of occurrences within a specified time. The latter method introduces a random error into the count of between zero and one count, so on average half a count. This is called gating error and causes an average error in the calculated frequency of , or a fractional error of where is the timing interval and is the measured frequency. This error decreases with frequency, so it is generally a problem at low frequencies where the number of counts N is small.
An older method of measuring the frequency of rotating or vibrating objects is to use a stroboscope. This is an intense repetitively flashing light (strobe light) whose frequency can be adjusted with a calibrated timing circuit. The strobe light is pointed at the rotating object and the frequency adjusted up and down. When the frequency of the strobe equals the frequency of the rotating or vibrating object, the object completes one cycle of oscillation and returns to its original position between the flashes of light, so when illuminated by the strobe the object appears stationary. Then the frequency can be read from the calibrated readout on the stroboscope. A downside of this method is that an object rotating at an integral multiple of the strobing frequency will also appear stationary.
Higher frequencies are usually measured with a frequency counter. This is an electronic instrument which measures the frequency of an applied repetitive electronic signal and displays the result in hertz on a digital display. It uses digital logic to count the number of cycles during a time interval established by a precision quartz time base. Cyclic processes that are not electrical in nature, such as the rotation rate of a shaft, mechanical vibrations, or sound waves, can be converted to a repetitive electronic signal by transducers and the signal applied to a frequency counter. Frequency counters can currently cover the range up to about 100 GHz. This represents the limit of direct counting methods; frequencies above this must be measured by indirect methods.
Above the range of frequency counters, frequencies of electromagnetic signals are often measured indirectly by means of heterodyning (frequency conversion). A reference signal of a known frequency near the unknown frequency is mixed with the unknown frequency in a nonlinear mixing device such as a diode. This creates a heterodyne or "beat" signal at the difference between the two frequencies. If the two signals are close together in frequency the heterodyne is low enough to be measured by a frequency counter. This process only measures the difference between the unknown frequency and the reference frequency. To reach higher frequencies, several stages of heterodyning can be used. Current research is extending this method to infrared and light frequencies (optical heterodyne detection).
Visible light is an electromagnetic wave, consisting of oscillating electric and magnetic fields traveling through space. The frequency of the wave determines its color: ×1014 Hz is red light, 4×1014 Hz is violet light, and between these (in the range 4- 8×1014 Hz) are all the other colors of the 8visible spectrum. An electromagnetic wave can have a frequency less than ×1014 Hz, but it will be invisible to the human eye; such waves are called 4infrared (IR) radiation. At even lower frequency, the wave is called a microwave, and at still lower frequencies it is called a radio wave. Likewise, an electromagnetic wave can have a frequency higher than ×1014 Hz, but it will be invisible to the human eye; such waves are called 8ultraviolet (UV) radiation. Even higher-frequency waves are called X-rays, and higher still are gamma rays.
All of these waves, from the lowest-frequency radio waves to the highest-frequency gamma rays, are fundamentally the same, and they are all called electromagnetic radiation. They all travel through a vacuum at the same speed (the speed of light), giving them wavelengths inversely proportional to their frequencies.
where c is the speed of light (c in a vacuum, or less in other media), f is the frequency and λ is the wavelength.
In dispersive media, such as glass, the speed depends somewhat on frequency, so the wavelength is not quite inversely proportional to frequency.
Sound propagates as mechanical vibration waves of pressure and displacement, in air or other substances.. In general, frequency components of a sound determine its "color", its timbre. When speaking about the frequency (in singular) of a sound, it means the property that most determines pitch.
The frequencies an ear can hear are limited to a specific range of frequencies. The audible frequency range for humans is typically given as being between about 20 Hz and 20,000 Hz (20 kHz), though the high frequency limit usually reduces with age. Other species have different hearing ranges. For example, some dog breeds can perceive vibrations up to 60,000 Hz.
In many media, such as air, the speed of sound is approximately independent of frequency, so the wavelength of the sound waves (distance between repetitions) is approximately inversely proportional to frequency.
In Europe, Africa, Australia, Southern South America, most of Asia, and Russia, the frequency of the alternating current in household electrical outlets is 50 Hz (close to the tone G), whereas in North America and Northern South America, the frequency of the alternating current in household electrical outlets is 60 Hz (between the tones B♭ and B; that is, a minor third above the European frequency). The frequency of the 'hum' in an audio recording can show where the recording was made, in countries using a European, or an American, grid frequency.
- Audio frequency
- Bandwidth (signal processing)
- Cutoff frequency
- Electronic filter
- Frequency band
- Frequency converter
- Frequency domain
- Frequency distribution
- Frequency extender
- Frequency grid
- Frequency modulation
- Frequency spectrum
- Interaction frequency
- Natural frequency
- Negative frequency
- Periodicity (disambiguation)
- Pink noise
- Radar signal characteristics
- Signaling (telecommunications)
- Spread spectrum
- Spectral component
Notes and referencesEdit
- "Definition of FREQUENCY". Retrieved 3 October 2016.
- "Definition of PERIOD". Retrieved 3 October 2016.
- Davies, A. (1997). Handbook of Condition Monitoring: Techniques and Methodology. New York: Springer. ISBN 978-0-412-61320-3.
- Bakshi, K.A.; A.V. Bakshi; U.A. Bakshi (2008). Electronic Measurement Systems. US: Technical Publications. pp. 4–14. ISBN 978-81-8431-206-5.
- "Definition of SOUND". Retrieved 3 October 2016.
- Pilhofer, Michael (2007). Music Theory for Dummies. For Dummies. p. 97. ISBN 9780470167946.
- Elert, Glenn; Timothy Condon (2003). "Frequency Range of Dog Hearing". The Physics Factbook. Retrieved 2008-10-22.
|Look up frequency or often in Wiktionary, the free dictionary.|
- Conversion: frequency to wavelength and back
- Conversion: period, cycle duration, periodic time to frequency
- Keyboard frequencies = naming of notes - The English and American system versus the German system
- Teaching resource for 14-16yrs on sound including frequency
- A simple tutorial on how to build a frequency meter
- A frequency generator with sound, useful for hearing tests | <urn:uuid:b5411fb5-178c-4c3f-ab55-20de994ef539> | 4.3125 | 2,349 | Knowledge Article | Science & Tech. | 42.667147 | 95,530,037 |
TeachMeFinance.com - explain Positive Area
Positive Area --
The area on a sounding representing the layer in which a lifted parcel would be warmer than the environment; thus, the area between the environmental temperature profile and the path of the lifted parcel. Positive area is a measure of the energy available for convection; see CAPE.
About the author
Copyright © 2005 by Mark McCracken, All Rights Reserved. TeachMeFinance.com is an informational website, and should not be used as a substitute for professional medical, legal or financial advice. Information presented at TeachMeFinance.com is provided on an "AS-IS" basis. Please read the disclaimer for details. | <urn:uuid:bcaa1dc8-852f-4b87-8455-434a37db6bdd> | 3.03125 | 144 | Knowledge Article | Science & Tech. | 30.78688 | 95,530,046 |
Proposed redefinition of SI base units(Redirected from New SI definitions)
The International Committee for Weights and Measures (CIPM) has proposed:23 revised definitions of the SI base units, for consideration at the 26th General Conference on Weights and Measures (CGPM). It is expected that the formal vote, scheduled for 16 November 2018, will be approved and that the new definitions will to come into force on 20 May 2019. The metric system was originally conceived as a system of measurement that was derivable from unchanging phenomena. However, when the metric system was first introduced in France in 1799, technical limitations necessitated the use of artefacts (the prototype metre and prototype kilogram) instead. In 1960 the metre was redefined in terms of the wavelength of light from a specified source, making it derivable from natural phenomena, leaving the prototype kilogram as the only artefact upon which the SI unit definitions depend. If the proposed redefinition is accepted, the metric system (SI) will, for the first time, be wholly derivable from natural phenomena.
The proposal can be summarised as follows:
There will still be the same seven base units (second, metre, kilogram, ampere, kelvin, mole, and candela). Of these, the kilogram, ampere, kelvin and mole will be redefined by choosing exact numerical values for the Planck constant, the elementary electric charge, the Boltzmann constant, and the Avogadro constant, respectively. The second, metre and candela are already defined by physical constants and it is only necessary to edit their present definitions. The new definitions will improve the SI without changing the size of any units, thus ensuring continuity with present measurements.
Further details are found in the draft chapter of the Ninth SI Brochure.
The last major overhaul of the metric system was in 1960 when the International System of Units (SI) was formally published as a coherent set of units of measure. SI is structured around seven base units whose definition are unconstrained by that of any other unit and another twenty-two named units derived from these base units. Although the set of units form a coherent system, the definitions do not. The proposal before the CIPM seeks to remedy this by using the fundamental quantities of nature as the basis for deriving the base units. This will mean, amongst other things, that the prototype kilogram will cease to be used as the definitive replica of the kilogram. The second and the metre are already defined in such a manner.
A number of authors have published criticisms of the revised definitions—including that the proposal had failed to address the impact of breaking the link between the definition of the dalton and the definitions of the kilogram, the mole and the Avogadro constant.
The basic structure of SI was developed over a period of about 170 years (1791 to 1960). Since 1960, technological advances have made it possible to address various weaknesses in SI, such as the dependence on an artefact to define the kilogram.
Development of SIEdit
During the early years of the French Revolution, the leaders of the French National Constituent Assembly decided to introduce a completely new system of measurement based on the principles of logic and natural phenomena. Specifically, the metre was defined as one ten-millionth of the distance from the North Pole to the Equator, and the kilogram as the mass of one thousandth of a cubic metre of pure water. Although these definitions were chosen so that nobody would "own" the units, they could not be measured with sufficient convenience or precision for practical use. Instead, realizations were created in the form of the mètre des Archives and kilogramme des Archives which were a "best attempt" at fulfilling these principles.
In 1875, by which time the use of the metric system had become widespread in Europe and in Latin America, twenty industrially developed nations met for the Convention of the Metre. The result was the signing of the Treaty of the Metre under which three bodies were set up to take custody of the international prototype kilogram and metre and to regulate comparisons with national prototypes. They were:
- CGPM (General Conference on Weights and Measures / Conférence générale des poids et mesures)—The Conference meets every four to six years and consists of delegates of the nations who had signed the convention. It discusses and examines the arrangements required to ensure the propagation and improvement of the International System of Units and it endorses the results of new fundamental metrological determinations.
- CIPM (International Committee for Weights and Measures / Comité international des poids et mesures)—The Committee consists of eighteen eminent scientists, each from a different country, nominated by the CGPM. The CIPM meets annually and is tasked to advise the CGPM. The CIPM has set up a number of sub-committees, each charged with a particular area of interest. One of these, the Consultative Committee for Units (CCU), amongst other things, advises the CIPM on matters concerning units of measurement.
- BIPM (International Bureau for Weights and Measures / Bureau international des poids et mesures)—The Bureau provides safe keeping of the international prototype kilogram and metre, provides laboratory facilities for regular comparisons of the national prototypes with the international prototype and is the secretariat for the CIPM and the CGPM.
The first CGPM (1889) formally approved the use of 40 prototype metres and 40 prototype kilograms from the British firm Johnson Matthey as the standards mandated by the Convention of the Metre. One of each of these was nominated by lot as the international prototypes, other copies were retained by the CGPM as working copies and the rest were distributed to member nations for use as their national prototypes. At regular intervals the national prototypes were compared with and recalibrated against the international prototype. In 1921 the Convention of the Metre was revised and the mandate of the CGPM was extended to provide standards for all units of measure, not just mass and length. In the ensuing years the CGPM took on responsibility for providing standards of electric current (1946), luminosity (1946), temperature (1948), time (1956) and molar mass (1971).
The 9th CGPM (1948) instructed the CIPM "to make recommendations for a single practical system of units of measurement, suitable for adoption by all countries adhering to the Metre Convention". The recommendations based on this mandate were presented to the 11th CGPM (1960) where they were formally accepted and given the name "Système International d'Unités" and its abbreviation "SI".
Impetus for changeEdit
Changing the underlying principles behind the definition of the SI base units is not without precedent. The 11th CGPM (1960) defined the SI metre in terms of the wavelength of krypton-86 radiation, replacing the pre-SI metre bar. The 13th CGPM (1967) replaced the original definition of the second (which was based on a back-calculation of the Earth's rotation in the year 1900) with a definition based on the frequency of the radiation emitted between two hyperfine levels of the ground state of the caesium 133 atom. And the 17th CGPM (1983) replaced the 1960 definition of the metre with one based on the second, by giving an exact definition of the speed of light in units of metres per second.
Over the years, drifts of up to ×10−8 kilograms per annum in the national prototype kilograms relative to the international prototype kilogram have been detected. There was no way of determining whether the national prototypes were gaining mass or whether the IPK was losing mass. 2 At the 21st meeting of the CGPM (1999), national laboratories were urged to investigate ways of breaking the link between the kilogram and a specific artefact. Newcastle University metrologist Peter Cumpson has since identified mercury vapour absorption or carbonaceous contamination as possible causes of this drift.
Independently of this drift having been identified, the Avogadro project and development of the Kibble balance (known as a "watt balance" before 2016) promised methods of indirectly measuring mass with a very high precision. These projects provided tools that would enable alternative means of redefining the kilogram.
A report published in 2007 by the Consultative Committee for Thermometry (CCT) to the CIPM noted that their current definition of temperature has proved to be unsatisfactory for temperatures below 20 kelvins and for temperatures above 1300 kelvins. The committee was of the view that the Boltzmann constant provided a better basis for temperature measurement than did the triple point of water, as it overcame these difficulties.
At its 23rd meeting (2007), the CGPM mandated the CIPM to investigate the use of natural constants as the basis for all units of measure rather than the artefacts that were then in use. The following year this was endorsed by the International Union of Pure and Applied Physics (IUPAP). At a meeting of the CCU held in Reading, United Kingdom, in September 2010, a resolution and draft changes to the SI brochure that were to be presented to the next meeting of the CIPM in October 2010 were agreed to in principle. The CIPM meeting of October 2010 found that "the conditions set by the General Conference at its 23rd meeting have not yet been fully met.[Note 2] For this reason the CIPM does not propose a revision of the SI at the present time"; however, the CIPM presented a resolution for consideration at the 24th CGPM (17–21 October 2011) to agree to the new definitions in principle, but not to implement them until the details have been finalised. This resolution was accepted by the conference, and in addition the CGPM moved the date of the 25th meeting forward from 2015 to 2014. At the 25th meeting (18–20 November 2014), it was found that "despite [the progress in the necessary requirements] the data do not yet appear to be sufficiently robust for the CGPM to adopt the revised SI at its 25th meeting", thus postponing the revision to the next meeting in 2018. A revised Draft Resolution A for consideration at the 26th meeting of the CGPM is available.
Following a recommendation from its Consultative Committee for Units (CCU), the BIPM has proposed that, in addition to the speed of light, four further constants of nature should be defined to have exact values. Using the values recommended for standardization in the CODATA 2017 adjustment, these would be:
These constants were described in the 2006 version of the SI manual, but in that version the latter three were defined as "constants to be obtained by experiment" rather than as "defining constants".
The CCU also proposed that the numerical values associated with the following constants of nature be retained unchanged:
- The speed of light c is exactly 792458 metres per second (m⋅s−1). 299
- The ground state hyperfine splitting frequency of the caesium-133 atom Δν(133Cs)hfs is exactly 192631770 hertz (Hz). 9
- The luminous efficacy Kcd of monochromatic radiation of frequency ×1012 Hz is exactly 540. 683 lumen per watt (lm⋅W−1)
The seven definitions above are rewritten below after converting the derived units (joule, coulomb, hertz, lumen and watt) into the seven base units (second, metre, kilogram, ampere, kelvin, mole and candela), according to the updated draft of the 9th edition of the SI Brochure (2016). In the list that follows, the symbol sr stands for the dimensionless unit steradian.
In addition the CIPM proposes that
These changes will have the effect of redefining the SI base units, though the definitions of the derived SI units in terms of the base units will remain the same.
Impact on base unit definitionsEdit
The CCU proposal recommended that the text of the definitions of all the base units be either refined or rewritten changing the emphasis from explicit-unit to explicit-constant type definitions. Explicit-unit type definitions define a unit in terms of a specific example of that unit—for example in 1324 Edward II defined the inch as being the length of three barleycorns and since 1889 the kilogram has been defined as being the mass of the International Prototype Kilogram. In explicit-constant definitions, a constant of nature is given a specified value and the definition of the unit emerges as a consequence. For example, in 1983, the speed of light was defined to be exactly 792458 metres per second and, since the second had been independently defined, the length of the metre could thus be derived. 299
The proposed definition of the second is effectively the same as the current definition, the only difference being that the conditions under which the measurements are made are more rigorously defined.
- Current definition: The second is the duration of 192631770 periods of the radiation corresponding to the transition between the two 9hyperfine levels of the ground state of the caesium-133 atom.
- Proposed definition: The second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical value of the caesium frequency ΔνCs, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 192631770 when expressed in the unit 9Hz, which is equal to s−1.
The proposed definition of the metre is effectively the same as the current definition, the only difference being that the additional rigour in the definition of the second will propagate to the metre.
- Current definition: The metre is the length of the path travelled by light in vacuum during a time interval of 1/ of a second.
- Proposed definition: The metre, symbol m, is the SI unit of length. It is defined by taking the fixed numerical value of the speed of light in vacuum c to be 792458 when expressed in the unit m⋅s−1, where the second is defined in terms of the caesium frequency ΔνCs. 299
The definition of the kilogram is due to change fundamentally—the current definition defines the kilogram as being the mass of the international prototype kilogram, which is an artefact and not a constant of nature, whereas the new definition relates it to the equivalent energy of a photon given its frequency via the Planck constant.
- Current definition: The kilogram is the unit of mass; it is equal to the mass of the international prototype of the kilogram.
- Proposed definition: The kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant h to be 07015×10−34 when expressed in the unit J⋅s, which is equal to kg⋅m2⋅s−1, where the metre and the second are defined in terms of c and ΔνCs. 6.626
A consequence of this change is that the new definition of the kilogram is dependent on the definitions of the second and the metre.
The definition of the ampere is undergoing a major revision—the current definition, which is difficult to realise with high precision in practice, is being replaced by a definition that is more intuitive and that is easier to realise.
- Current definition: The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 m apart in vacuum, would produce between these conductors a force equal to ×10−7 newton per metre of length. 2
- Proposed definition: The ampere, symbol A, is the SI unit of electric current. It is defined by taking the fixed numerical value of the elementary charge e to be 176634×10−19 when expressed in the unit 1.602C, which is equal to A⋅s, where the second is defined in terms of ΔνCs.
Since the current definition contains a reference to force, which has the dimensions MLT−2, it follows that in SI the kilogram, metre and second, the base units representing these dimensions, must be defined before the ampere can be defined. Other consequences of the current definition are that in SI the value of vacuum permeability (μ0) is fixed at exactly ×10−7 H⋅m−1. 4π Since the speed of light in vacuum (c) is also fixed, it follows from the relationship
that the vacuum permittivity (ε0) has a fixed value, and from
A consequence of the proposed changes to the definition of the ampere is that the definition will no longer depend on the definitions of the kilogram and the metre, but will still depend on the definition of the second. In addition, the numerical values of the vacuum permeability, vacuum permittivity and impedance of free space, which, in the current definition are exact, will be subject to experimental error.
The definition of the kelvin will undergo a fundamental change if the proposal is accepted. Rather than using the triple point of water to fix the temperature scale, the proposal recommends that the energy equivalent as given by Boltzmann's equation be used.
- Current definition: The kelvin, unit of thermodynamic temperature, is 1/ of the thermodynamic temperature of the triple point of water.
- Proposed definition: The kelvin, symbol K, is the SI unit of thermodynamic temperature. It is defined by taking the fixed numerical value of the Boltzmann constant k to be 649×10−23 when expressed in the unit J⋅K−1, which is equal to kg⋅m2⋅s−2⋅K−1, where the kilogram, metre and second are defined in terms of h, c and ΔνCs. 1.380
One consequence of this change is that the new definition makes the definition of the kelvin depend on the definitions of the second, the metre, and the kilogram.
The current definition of the mole links it to the kilogram. The proposed definition will break that link by making a mole a specific number of entities of the substance in question.
- Current definition: The mole is the amount of substance of a system that contains as many elementary entities as there are atoms in 0.012 kilogram of carbon-12. When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles.
- Proposed definition::22 The mole, symbol mol, is the SI unit of amount of substance. One mole contains exactly 14076×1023 elementary entities. This number is the fixed numerical value of the 6.022Avogadro constant, NA, when expressed in the unit mol−1 and is called the Avogadro number.
- The amount of substance, symbol n, of a system is a measure of the number of specified elementary entities. An elementary entity may be an atom, a molecule, an ion, an electron, any other particle or specified group of particles.
One consequence of this change is that the current defined relationship between the mass of the 12C atom, the dalton, the kilogram, and the Avogadro number will no longer be valid. One of the following must change:
- The mass of a 12C atom is exactly 12 dalton.
- The number of dalton in a gram is exactly the numerical value of the Avogadro number.
The wording of the Draft of the ninth SI Brochure implies the first, which would mean that the second will no longer be true. The molar mass constant, while still with great accuracy remaining equal to 1 g/mol, will no longer be exactly equal to that.
The proposed definition of the candela is effectively the same as the current definition, but has been rephrased with the only difference being the additional rigour in the definition of the second and metre will propagate to the candela.
- Current definition: The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency ×1012 Hz and that has a radiant intensity in that direction of 5401/ watt per steradian.
- Proposed definition: The candela, symbol cd, is the SI unit of luminous intensity in a given direction. It is defined by taking the fixed numerical value of the luminous efficacy of monochromatic radiation of frequency ×1012 Hz, Kcd, to be 683 when expressed in the unit lm⋅W−1, which is equal to cd⋅sr⋅W−1, or cd⋅sr⋅kg−1⋅m−2⋅s3, where the kilogram, metre and second are defined in terms of h, c and ΔνCs. 540
Impact on reproducibilityEdit
Apart from the candela,[Note 4] all the base units will be defined in terms of universal physical constants, but without a direct one-to-one correspondence between the constants and the base units. Thus six physical constants will be needed to define the six base units.
When the New SI was first designed, there were more than six suitable physical constants from which the designers could choose. For example, once length and time had been established, the universal gravitational constant G could, from a dimensional point of view, be used to define mass.[Note 5] It should be noted that in practice G can only be measured with a relative uncertainty of the order of 10−5[Note 6] which would have resulted in upper limit of the kilogram's reproducibility being around 10−5 whereas the current international prototype kilogram can be measured with a reproducibility of 1.2 × 10−8. The choice of physical constants was made on the basis of minimal uncertainty associated with measuring the constant and the degree of independence of the constant in respect of other constants that were being used. Although the BIPM has developed a standard mise en pratique (practical technique) for each type of measurement, the mise en pratique used to make the measurement is not part of the measurement's definition—it is merely an assurance that the measurement can be done without exceeding the specified maximum uncertainty.
Uncertainty of fundamental physical constantsEdit
Fundamental physical constants are often highly dependent upon each other. This implies that the best value of a fundamental physical constant, one with the least uncertainty, often can be determined by directly measuring other fundamental physical constants, from which the value can be calculated. The uncertainty in these constants is then determined from the uncertainty of the others by the propagation of uncertainty. Constants whose value is fixed, for determining the units in which they are expressed, don't have an uncertainty associated with them, so they do not account for any extra uncertainty in the value of the calculated constant. One of the reasons the SI unit system will be changed is that determination of values can often be greatly improved if expressed in these new units. This is due to the dependence of these values on physical constants.
The following table catalogues the notable changes in determination of fundamental physical constants. The constants are expressed in direct measurements and fixed constants to minimize and determine the uncertainty. Some constants in that expression do not contribute significantly to the uncertainty; only the significant factors are noted. The value of the relative uncertainty by the data of CODATA of 2014 is given, and is expressed in the relative uncertainty of the significant factors, noted with ur(constant). An approximately equals sign (≈) is used if an uncertainty is only approximated by the expression. This is due to unsignificant factors or rounding errors.
|Constant||Symbol||Current definition||Proposed definition|
|Relation to directly measured and fixed constants||Significant factor(s) in uncertainty||Relative uncertainty||Relation to directly measured and fixed constants||Significant factor(s) in uncertainty||Relative uncertainty|
|Mass of IPK[Note 7]||1 kg||none||exact|
|Von Klitzing constant||none||exact|
|Magnetic constant||×10−7 m⋅kg⋅s−2⋅A−2 4π||none||exact|
|Impedance of free space||none||exact|
|Electron molar mass|
|Unified atomic mass unit or dalton|
|Molar mass constant||0.001 kg⋅mol−1||none||exact|
|Atomic mass of carbon-12|
|Molar mass of carbon-12||0.012 kg⋅mol−1||none||exact|
|Faraday constant||[Note 8]||none||exact|
|Temperature of triple point of water||273.16 K||none||exact|
|Molar gas constant||none||exact|
It should be noted that the relative atomic mass of the electron Ar(e) is measured relative to the mass of a carbon-12 atom (divided by 12). When the Avogadro constant is set in the new SI, atomic masses might be measured in dalton (by fixing the Avogadro constant), instead of atomic mass units (by fixing the mass of carbon-12), thus resulting in a difference between the values of the relative atomic mass and the atomic mass in units of dalton.
In 1993, the International Union of Pure and Applied Chemistry (IUPAC) approved the use of the dalton as an alternative to the unified atomic mass unit with the qualification that the CGPM had not given its approval. This approval has since been given. Following the proposal to redefine the mole by fixing the value of the Avogadro constant, Brian Leonard of the University of Akron, writing in Metrologia proposed that the dalton (Da) be redefined such that NA = (g/Da) mol−1, but that the unified atomic mass unit (mu) retain its current definition based on the mass of 12C, ceasing to exactly equal to the dalton. This would result in the dalton and the atomic mass unit potentially differing from each other with a relative uncertainty of the order of 10−10.
Much of the work done by the CIPM is delegated to consultative committees. The CIPM Consultative Committee for Units (CCU) has made the proposed changes while other committees have examined the proposal in detail and have made recommendations regarding their acceptance by the CGPM in 2014. The various consultative committees have laid down a number of criteria that must be met before they will support the CCU's proposal, including:
- For the redefinition of the kilogram, at least three separate experiments be carried out yielding values for the Planck constant having a relative expanded (95%) uncertainty of no more than ×10−8 and at least one of these values should be better than 5×10−8. Both the 2Kibble balance and the Avogadro project should be included in the experiments and any differences between these be reconciled.
- For the redefinition of the kelvin, the relative uncertainty of Boltzmann constant derived from two fundamentally different methods such as acoustic gas thermometry and dielectric constant gas thermometry be better than one part in 10−6 and that these values be corroborated by other measurements.
On 1 September 2012 the European Association of National Metrology Institutes (EURAMET) launched a formal project to reduce the relative difference between the Kibble balance and the silicon sphere approach to measuring the kilogram from ±5)×10−8 to within (17×10−8. 2
As of March 2013[update] the proposed redefinition is known as the "New SI", but Mohr, in a paper following the CGPM proposal but predating the formal CCU proposal, suggested that since the proposed system makes use of atomic scale phenomena rather than macroscopic phenomena, it should be called the "Quantum SI System".
As of the 2014 CODATA recommended values of the fundamental physical constants (published in 2016, using data collected through the end of 2014), all measurements meet the CGPM's requirements and the way is clear to proceed with the redefinition and the next CGPM quadrennial meeting in late 2018.
On 20 October 2017, the 106th meeting of the International Committee for Weights and Measures (CIPM) formally accepted a revised Draft Resolution A calling for the redefinition of the SI, to be voted on at the 26th CGPM,:17–23 The same day, in response to the CIPM's endorsement of the final values:22, the CODATA Task Group on Fundamental Constants published its 2017 recommended values for the four constants (with uncertainties) and proposed numerical values for the redefinition (without uncertainty).
In 2010 Marcus Foster of the Commonwealth Scientific and Industrial Research Organisation published a wide-ranging critique of SI in which he raised numerous issues ranging from basic issues such as the absence of the symbol "Ω" from most Western keyboards to the abstract issues such as inadequate formalism in the metrological concepts on which SI is based. The changes proposed in the New SI only addressed issues regarding the definition of the base units including new definitions of the candela and the mole—units that Foster argued were not true base units. Other issues raised by Foster fell outside the scope of the proposal.
Explicit-unit and explicit-constant definitionsEdit
Concerns have been expressed that the use of explicit-constant definitions of the unit being defined that are not related to an example of its quantity will have many adverse effects. Although this criticism applies to the proposed linking of the kilogram to the Planck constant via a route that requires a knowledge of both special relativity and quantum mechanics, it does not apply to the proposed definition of the ampere, which is closer to an example of its quantity than is the current definition. Some observers have welcomed the proposal to base the definition of electric current on the charge of the electron rather than the current definition of a force between two parallel current-carrying wires – since the nature of the electromagnetic interaction between two bodies at the quantum electrodynamics level is somewhat different from the nature at classical electrodynamic levels, it is considered inappropriate to use classical electrodynamics to define quantities that exist at quantum electrodynamic levels.
Mass and the Avogadro constantEdit
When the scale of the divergence between the IPK and national kilogram prototypes was reported in 2005, a debate arose on how best to redefine the kilogram – should the kilogram be defined in terms of the mass of the silicon-28 atom or should it be determined using the Kibble balance? The mass of a silicon atom could be determined using the Avogadro project and using the Avogadro number be linked directly to the kilogram.
Concern has also been expressed that the authors of the proposal had failed to address the impact of breaking the link between the mole, kilogram, the dalton (Da) and the Avogadro constant (NA).[Note 9] This direct link has caused many to argue that the mole is not a true physical unit, but, in the words of the Swedish philosopher Johansson, the mole is a "scaling factor".
The SI Brochure (8th edition) defines the dalton in terms of the mass of an atom of 12C. It defines the Avogadro constant in terms of this mass and the kilogram, making it determined by experiment. The proposal fixes the Avogadro constant, and the draft of the Ninth SI Brochure retains the definition of dalton in terms of 12C, with the effect that the link between the dalton and the kilogram will be broken.
Temperature is somewhat of an enigma – room temperature can be measured by means of expansion and contraction of a liquid in a thermometer, but high temperatures are often associated with a colour. Wojciech T. Chyla, approaching the structure of SI from a philosophical point of view in the Journal of the Polish Physical Society, argued that temperature is not a real base unit but is rather an average of the thermal energies of the individual particles that make up the body concerned. He noted that in many theoretical papers, temperature is represented by the quantities Θ or β where
and k is the Boltzmann constant.
Chyla acknowledged however that in the macroscopic world temperature plays the role of a base unit as much of the theory of thermodynamics is based on temperature.
The Consultative Committee for Thermometry, part of the International Committee for Weights and Measures publishes a mise en pratique (practical technique), last updated in 1990, for measuring temperature which, at very low and at very high temperatures, makes great use of linking energy to temperature via the Boltzmann constant.
Foster argued that "luminous intensity [the candela] is not a physical quantity, but a photobiological quantity that exists in human perception", thereby questioning whether the candela should be a base unit.
- Prototype No. 8(41) was accidentally stamped with the number 41, but its accessories carry the proper number 8. Since there is no prototype marked 8, this prototype is referred to as 8(41).
- In particular the CIPM was to prepare a detailed mise en pratique for each the new definitions of the kilogram, ampere, kelvin and mole set by the 23rd CGPM
- These are the final values proposed for standardization, but have not been formally accepted yet.
- Measurement of the candela also requires a knowledge of the response of the human eye to different wavelengths of light known as the (luminosity function) and denoted by V(λ), a function computed by the International Commission on Illumination (CIE) to different wavelengths of light.
- The dimensions of G are L3M−1T−2, so once standards have been established for length and for time, mass can in theory be deduced from G. Also, when fundamental constants as relations between these three units are set, the units can be deduced by a combination of these constants, for example as a linear combination of Planck units.
- The following terms are defined in International vocabulary of metrology – Basic and general concepts and associated terms:
- measurement reproducibility – definition 2.25
- standard measurement uncertainty – definition 2.30
- relative standard measurement uncertainty – definition 2.32
- Technically, the mass of International Prototype Kilogram would no longer be a "fundamental physical constant" when the artefact is abandoned in the new SI.
- Although the calculation of the uncertainty implies that the fine structure constant isn't a significant factor, because of rounding errors, the uncertainty in fine structure constant does have an effect on the determined value.
- The two quantities of the Avogadro constant NA and the Avogadro number NN are numerically the same, but while NA has the unit mol−1, NN is a pure number.
- Proceedings of the 106th meeting (PDF). International Committee for Weights and Measures. Sèvres. 16–20 October 2017.
- Milton, Martin (14 November 2016). Highlights in the work of the BIPM in 2016 (PDF). SIM XXII General Assembly. Montevideo, Uruguay. p. 10. The conference runs from 13–16 November; the redefinition is scheduled for the morning of the last day.
- Mohr, Peter J.; Newell, David B.; Taylor, Barry N. (26 September 2016). "CODATA recommended values of the fundamental physical constants: 2014". Reviews of Modern Physics. 88 (3): 035009-1–73. arXiv: . Bibcode:2016RvMP...88c5009M. doi:10.1103/RevModPhys.88.035009.
This is a truly major development, because these uncertainties are now sufficiently small that the adoption of the new SI by the 26th CGPM is expected.
- "Universe's Constants Now Known with Sufficient Certainty to Completely Redefine the International System of Units" (Press release). NIST. 22 November 2016. Retrieved 31 December 2016.
- Wood, B. (3–4 November 2014). "Report on the Meeting of the CODATA Task Group on Fundamental Constants" (PDF). BIPM. p. 7.
[BIPM director Martin] Milton responded to a question about what would happen if ... the CIPM or the CGPM voted not to move forward with the redefinition of the SI. He responded that he felt that by that time the decision to move forward should be seen as a foregone conclusion.
- BIPM statement: Information for users about the proposed revision of the SI (PDF)
- Decision CIPM/105-13 (October 2016). The day is the 144th anniversary of the Metre Convention.
- Crease, Robert P. (2011). "France: "Realities of Life and Labor"". World in the Balance. New York: W. W. Norton & Company, Inc. pp. 83–84. ISBN 978-0-393-07298-3.
- Kühne, Michael (22 March 2012). "Redefinition of the SI". Keynote address, ITS9 (Ninth International Temperature Symposium). Los Angeles: NIST. Archived from the original on 2013-06-18. Retrieved 2012-03-01.
- "Draft of the ninth SI Brochure" (PDF). BIPM. 10 November 2016. pp. 2–9. Retrieved 2017-01-12.
- The dalton is not defined in the formal proposal to be voted upon by the CGPM, only in the (draft) Ninth SI Brochure.
- Alder, Ken (2002). The Measure of all Things – The Seven-Year-Odyssey that Transformed the World. London: Abacus. p. 1. ISBN 0-349-11507-9.
- "Metric Convention of 1875 [English translation]". Washington, D.C.: Office of the President of the United States. 1876. Archived from the original on 2005-03-01.
- "The Metre Convention". Sèvres, France: International Bureau of Weights and Measures. Retrieved 2013-06-21.
- "CIPM: International Committee for Weights and Measures". Sèvres, France: BIPM. Retrieved 2010-10-03.
- "Resolution of the 1st meeting of the CGPM (1889)". Sèvres, France: International Bureau of Weights and Measures. Retrieved 2013-06-21.
- Jabbour, Z.J.; Yaniv, S.L. (2001). "The Kilogram and Measurements of Mass and Force" (PDF). Journal of Research of the National Institute of Standards and Technology. National Institute of Standards and Technology (NIST). 106 (1): 25–46. doi:10.6028/jres.106.003. Archived from the original (PDF) on 2011-06-04. Retrieved 2011-03-28.
- International Bureau of Weights and Measures (2006), The International System of Units (SI) (PDF) (8th ed.), pp. 95, 97, 138–140, ISBN 92-822-2213-6, archived (PDF) from the original on 2017-08-14
- Girard, G. (1994). "The Third Periodic Verification of National Prototypes of the Kilogram (1988–1992)". Metrologia. 31 (4): 317–336. Bibcode:1994Metro..31..317G. doi:10.1088/0026-1394/31/4/007.
- "Resolution 6 of the 9th meeting of the CGPM (1948): Proposal for establishing a practical system of units of measurement". Retrieved 2011-03-23.
- "Resolution 12 of the 11th meeting of the CGPM (1960): Système International d'Unités". Sèvres, France. Retrieved 2011-03-23.
- International Bureau of Weights and Measures (2006), The International System of Units (SI) (PDF) (8th ed.), pp. 112–116, ISBN 92-822-2213-6, archived (PDF) from the original on 2017-08-14
- Mohr, Peter (6 December 2010). "Recent progress in fundamental constants and the International System of Units" (PDF). Third Workshop on Precision Physics and Fundamental Physical Constants. Retrieved 2011-01-02.
- Whipple, Tom (7 January 2013). "The dirty secret of why you are not quite as heavy as you think". The Times. London. p. 15. Retrieved 2011-03-23.
- Ghose, Tia (6 January 2013). "The Kilogram Has Gained Weight". LiveScience. Retrieved 2011-03-23.
- Crease, Robert P. (22 March 2011). "Metrology in the balance". Physics World. Institute of Physics. Retrieved 2012-06-28.
- Fischer, J.; et al. (2 May 2007). "Report to the CIPM on the implications of changing the definition of the base unit kelvin" (PDF). Retrieved 2011-01-02.
- "Resolution proposal submitted to the IUPAP Assembly by Commission C2 (SUNAMCO)" (PDF). International Union of Pure and Applied Physics. 2008. Retrieved 2015-09-06.
- Mills, Ian (29 September 2010). "On the possible future revision of the International System of Units, the SI" (PDF). CCU. Retrieved 2011-01-01.
- Mills, Ian (29 September 2010). "Draft Chapter 2 for SI Brochure, following redefinitions of the base units" (PDF). CCU. Retrieved 2011-01-01.
- "Resolution 12 of the 23rd meeting of the CGPM (2007)". Sèvres, France: General Conference on Weights and Measures. Retrieved 2013-06-21.
- "Towards the "new SI"". International Bureau of Weights and Measures (BIPM). Retrieved 2011-02-20.
- "On the possible future revision of the International System of Units, the SI – Draft Resolution A" (PDF). International Committee for Weights and Measures (CIPM). Retrieved 2011-07-14.
- "Resolution 1: On the possible future revision of the International System of Units, the SI" (PDF). 24th meeting of the General Conference on Weights and Measures. Sèvres, France: International Bureau for Weights and Measures. 21 Oct 2011. It is not expected to be adopted until some prerequisite conditions are met, and in any case not before 2014. See "Possible changes to the international system of units". IUPAC Wire. International Union of Pure and Applied Chemistry. 34 (1). January–February 2012.
- "General Conference on Weights and Measures approves possible changes to the International System of Units, including redefinition of the kilogram" (PDF) (Press release). Sèvres, France: General Conference on Weights and Measures. 23 October 2011. Retrieved 2011-10-25.
- Mohr, Peter (2 November 2011). "Redefining the SI base units". NIST Newsletter. NIST. Retrieved 2012-03-01.
- "Resolutions adopted by the CGPM at its 25th meeting (18–20 November 2014)" (PDF). Sèvres, France: International Bureau for Weights and Measures. 21 November 2014.
- Draft Resolution A "On the revision of the International System of units (SI)" to be submitted to the CGPM at its 26th meeting (2018) (PDF)
- Newell, David B.; Cabiati, F.; Fischer, J.; Fujii, K.; Karshenboim, S. G.; Margolis, H. S.; de Mirandés, E.; Mohr, P. J.; Nez, F.; Pachucki, K.; Quinn, T. J.; Taylor, B. N.; Wang, M.; Wood, B. M.; Zhang, Z.; et al. (Committee on Data for Science and Technology (CODATA) Task Group on Fundamental Constants (TGFC)) (20 October 2017). "The CODATA 2017 Values of h, e, k, and NA for the Revision of the SI". Metrologia (in press). Institute of Physics. Bibcode:2018Metro..55L..13N. doi: .
- Mills, Ian (September–October 2011). "Part II—Explicit-Constant Definitions for the Kilogram and for the Mole". Chemistry International. 33 (5): 12–15. ISSN 0193-6484.
- Travenor, Robert (2007). Smoot's Ear – The Measure of Humanity. Yale University Press. pp. 35–36. ISBN 978-0-300-14334-8.
- "The BIPM watt balance". International Bureau of Weights and Measures. 2012. Retrieved 2013-03-28.
- Taylor, Barry N (November–December 2011). "The Current SI Seen From the Perspective of the Proposed New SI". Journal of Research of the National Institute of Standards and Technology. National Institute of Standards and Technology (NIST). 116 (6): 797–80. doi:10.6028/jres.116.022.
- "Unit of electric current (ampere)". Historical context of the SI. NIST. Retrieved 2015-09-07.
- Orfanidis, Sophocles J. (31 August 2010). Electromagnetic Waves and Antennas (PDF). ECE Department, Rutgers University. 1.3 Constitutive Relations. Retrieved 2013-06-24.
- Chyla, W.T. (December 2011). "Evolution of the International Metric System of Units SI" (PDF). Acta Physica Polonica A. 120 (6): 998–1011. Retrieved 2013-06-22.
- Wyszecki, G; Blevin, WR; Kessler, KG; Mielenz, KD (1983). Principles covering Photometry (PDF). Sevres: Conférence général des poids et mesures (CGPM).
- "What is a mise en pratique?". BIPM. 2011. Retrieved 2015-09-06.
is a set of instructions that allows the definition to be realized in practice at the highest level.
- Mills, Ian; Cvitaš, Tomislav; Homann, Klaus; Kallay, Nikola; Kuchitsu, Kozo (1993). Quantities, Units and Symbols in Physical Chemistry International Union of Pure and Applied Chemistry; Physical Chemistry Division (2nd ed.). International Union of Pure and Applied Chemistry, Blackwell Science Ltd. ISBN 0-632-03583-8.
- International Bureau of Weights and Measures (2006), The International System of Units (SI) (PDF) (8th ed.), pp. 114, 115, ISBN 92-822-2213-6, archived (PDF) from the original on 2017-08-14
- Leonard, Brian Phillip (May 2012). "Why the dalton should be redefined exactly in terms of the kilogram" (PDF). Metrologia. 49 (4): 487–491. Bibcode:2012Metro..49..487L. doi:10.1088/0026-1394/49/4/487.
- "Recommendations of the Consultative Committee for Mass and Related Quantities to the International Committee for Weights and Measures" (PDF). 12th Meeting of the CCM. Sèvres: Bureau International des Poids et Mesures. 26 March 2010. Retrieved 2012-06-27.
- "Recommendations of the Consultative Committee for Amount of Substance: Metrology in Chemistry to the International Committee for Weights and Measures" (PDF). 16th Meeting of the CCQM. Sèvres: Bureau International des Poids et Mesures. 15–16 April 2010. Retrieved 2012-06-27.
- "Recommendations of the Consultative Committee for Thermometry to the International Committee for Weights and Measures" (PDF). 25th Meeting of the Consultative Committee for Thermometry. Sèvres: Bureau International des Poids et Mesures. 6–7 May 2010. Retrieved 2012-06-27.
- "kilogram NOW – Realization of the awaited definition of the kilogram". European Association of National Metrology Institutes. Retrieved 2012-10-08.
- Mohr, Peter J. (2008). "The Quantum SI: A Possible New International System of Units". Advances in Quantum Chemistry. Academic Press. 53: 34. Bibcode:2008AdQC...53...27M. doi:10.1016/s0065-3276(07)53003-0. ISBN 978-0-12-373925-4. Retrieved 2012-04-02.
- Foster, Marcus P (5 October 2010). "The next 50 years of the SI: a review of the opportunities for the e-Science age". Metrologia. 47 (6). Bibcode:2010Metro..47R..41F. doi:10.1088/0026-1394/47/6/R01. Retrieved 2013-06-24.
- Price, Gary (2011). "A sceptic's review of the New SI". Accreditation and Quality Assurance. 16 (3): 121–132. doi:10.1007/s00769-010-0738-x.
- Censullo, Albert C (September–October 2011). "Part I—From the Current "Kilogram Problem" to a Proposed Definition". Chemistry International. 33 (5): 9–12. ISSN 0193-6484.
- Burns, D Thorburn; Korte, EH (2013). "The Background and Implications of the "New SI" for Analytical Chemists" (PDF). Journal of the Association of Public Analysts (Online). London: Association of Public Analysts (41 2): 28–44. Retrieved 2013-06-25.
- Davis, Richard (October 2011). "Proposed change to the definition of the kilogram: Consequences for legal metrology" (PDF). OIML Bulletin. LII (4).
- Johansson, Ingvar (2011). "The Mole is Not an Ordinary Measurement Unit". Accreditation and Quality Assurance (16): 467–470. doi:10.1007/s00769-011-0804-z.
- Leonard, B.P. (2010). "Comments on recent proposals for redefining the mole and kilogram". Metrologia. 47 (3): L5–L8. Bibcode:2010Metro..47L...5L. doi:10.1088/0026-1394/47/3/L01. Retrieved 2013-09-15.
- Pavese, Franco (2011). "Some reflections on the proposed redefinition of the unit for the amount of substance and of other SI units". Accreditation and Quality Assurance. 16 (3): 161–165. doi:10.1007/s00769-010-0700-y.
- "Mise en pratique for the definition of the kelvin" (PDF). Sèvres, France: Consultative Committee for Thermometry (CCT), International Committee for Weights and Measures (CIPM). 2011. Retrieved 2013-06-25.
- Consultative Committee for Thermometry (CCT) (1989). "The International Temperature Scale of 1990 (ITS-90)" (PDF). Procès-verbaux du Comité International des Poids et Mesures, 78th meeting. Sèvres, France: International Committee for Weights and Measures (CIPM). Retrieved 2013-06-25.
- International Bureau of Weights and Measures (2016-11-10), SI Brochure: The International System of Units (SI) (PDF) (Draft to be finalized in 2018) (Preliminary 9th ed.), archived (PDF) from the original on 2017-01-13
- International Bureau of Weights and Measures (BIPM) (2017-08-10). "Input data for the special CODATA-2017 adjustment". Metrologia (Updated ed.). Retrieved 2017-08-14. | <urn:uuid:d1c89ec9-2c1e-4d3d-8be5-cdcb1a6ced0a> | 3.25 | 11,143 | Knowledge Article | Science & Tech. | 53.422476 | 95,530,049 |
Graphic courtesy of Hong Mu, New York University.Every day our bodies come under a barrage of toxic agents—cigarette smoke, the sun, free radicals, and other carcinogenic substances—that create damaging lesions in our DNA that can initiate cancer and other human diseases.
Fortunately, nature has provided living organisms with repair processes to seek out and remove such dangerous lesions; repair allows the DNA to be restored to its original base sequence so it can carry out its fundamental jobs: to be replicated and to be copied into a sister molecule, RNA, for the manufacture of proteins and other tasks.
The 2015 Nobel Prize in Chemistry was awarded to three scientists for their work on the mechanisms of DNA repair. Nonetheless, much remains to be understood about these intricate molecular processes.
Now, a team led by professor Suse Broyde and postdoctoral researcher Hong Mu—both in the Department of Biology at New York University (NYU)—has identified and described how a major player in the repair process, called nucleotide excision repair or NER, works to recognize certain lesions for subsequent removal by the NER machinery. Included among the lesions are bulky chemicals that link tightly to the DNA bases; these are called polycyclic aromatic hydrocarbons (PAH), or carcinogenic precursors inhaled through automobile exhaust or cigarette smoke, that ultimately can attach to our DNA.
The findings, published as an “Editor’s Choice” article in a recent issue of Chemical Research in Toxicology, a journal of the American Chemical Society, are helping researchers to better understand why certain lesions triggered by environmental and other agents are more likely to be repaired while others persist to cause mutations and cancer.
Image courtesy of the San Diego Supercomputer Center
DNA repair begins with a protein called XPC (xeroderma pigmentosum C protein complex), whose job is to patrol the genome for certain types of lesion-induced DNA disturbances. Once it encounters a damaged DNA, it inserts a beta-hairpin (a simple protein structural motif involving two beta strands that look like a hairpin) between the two DNA strands, which serves to recognize the lesion so that NER can ultimately remove it.
“It has been shown that NER recognizes a wide range of DNA lesions, whose NER susceptibilities vary for reasons that are not well understood,” said Broyde. “Understanding differences in the XPC recognition mechanism for lesions with different sizes and shapes may help us understand this variability.”
In the current study, the researchers sought to identify and describe the molecular pathway that Rad4, a yeast version of XPC, takes when it binds to a bulky DNA lesion derived from the PAH benzo[a]pyrene. For this DNA lesion, a large multi-ringed structure is bound to the DNA base guanine (G); the rings are inserted into the DNA helix, rupturing the DNA base pairs. The partner base cytosine (C) is extruded from the double helix.
Atomic-level Simulations Using Gordon
To learn more about the binding process of the yeast-XPC, called Rad4, the researchers turned to the Gordon supercomputer at the San Diego Supercomputer Center (SDSC) at UC San Diego to simulate at an atomic level the lesion recognition pathway. As described in the paper, the simulations showed a pathway in which the yeast-XPC/Rad4 initially captures the extruded/pre-flipped base C, the base partner to the damaged G.
Subsequently, as the DNA bends and unwinds, a second base is flipped into the protein, the beta-hairpin is inserted into the double helix, while the multi-ringed part of the lesion is pushed to the helix exterior. The lesion is eventually excised by the NER machinery.
The mechanism differed significantly from that of a prior study with a UV-light-induced lesion, CPD, which can cause skin cancer. This lesion-containing DNA duplex does not contain an extruded/pre-flipped base that can be captured initially. In this case, the simulations showed that two bases opposite the lesion flipped in correlated motion to open the lesion site for subsequent beta-hairpin insertion, while the small CPD lesion is easily extruded before the hairpin inserted.
“Combined, our research shows that the structure of the lesion-containing DNA impacts the binding pathway of yeast-XPC/Rad4 to the lesions,” said Mu, the study’s first author, “and that the pathway may be tailored to the particular disturbance to DNA caused by lesions of various sizes and shapes. This capability may play an important role in the ability of XPC to recognize a wide variety of lesion types. In the case of repair resistant lesions it is hypothesized that productive binding that leads to subsequent excision is obstructed.”
Added Broyde: “Individuals who harbor repair-resistant lesions could potentially be identified through highly sensitive measuring techniques (“adductomics”) that can utilize, for example, hair or urine samples. Such individuals could then be counseled to alter their lifestyles, to cease smoking for example, and be vigilant about monitoring early cancers.”
The work also has application to drug design. In the case of chemotherapeutic drugs, such as cis-platinum, the efficacy of the drug is diminished by its repair through NER; a goal in the design of more advanced agents of this family is to develop ones that are less repair-susceptible. Understanding the essential mechanism that initiates NER through lesion recognition could aid in the design of more potent drugs that are NER resistant.
The simulations were based on molecular dynamics calculations designed to find the most efficient pathway used by XPC/Rad4 to move from a state where its lesion-recognition domain was unbound to where it is correctly bound to the DNA lesion. Since the pathway was totally unknown, the researchers said it was essential to explore many possibilities to locate the best path, with the lowest and hence most favorable energy barrier for binding.
“These extremely compute-intensive calculations required the resources of Gordon in order to permit the computations to be carried out in parallel and hence be achieved in a reasonable amount of time,” said Mu.
As a next step, the researchers are preparing to investigate a library of DNA lesions characterized by Nicholas Geacintov, professor of chemistry at NYU and co-author of the paper. Geacintov, in collaboration with professor Dinshaw Patel of Memorial Sloan Kettering Cancer Center, and Broyde, has determined the NMR structures, NER efficiencies, and other biochemical and biophysical properties of the damaged DNA duplexes in the library. This work will seek to evaluate how pathways differ among a variety of lesions and evaluate whether the pathways correlate with repair susceptibility.
Also participating in the study were Jung-Hyun Min, associate professor of chemistry, University of Illinois at Chicago; and Yingkai Zhang, professor of chemistry at NYU.
Support for the study came from the National Institute for Environmental Health Sciences (NIEHS), National Institute of General Medical Sciences (NIGMS), and the National Science Foundation (NSF), grant # MCB060037 for the computing resources at XSEDE.
Like this article? Click here to subscribe to free newsletters from Lab Manager | <urn:uuid:5dd052ae-c677-4d2e-9c38-cb451c3c264e> | 3.65625 | 1,540 | News Article | Science & Tech. | 21.471817 | 95,530,066 |
Talk: C++: No more nulls! (Fixing the billion dollar mistake)
I recently worked for several years in a large C# code base where null was banned. It was beautiful! In C++ it can be even better.
Null is a traditional way of indicating "no value", but the approach has several problems:
- All pointers can be null, there's nothing explicit about which ones are actually allowed be so
- Interfaces get harder to understand
- You risk ending up with a lot of pointless null checks
- You risk dereferencing a null pointer
Disallowing null eliminates null pointer dereferencing, makes it explicit which variables might not contain a value, removes unnecessary null checks, and makes the code safer and much easier to reason about.
We'll start with going through the common uses of null (as arguments, return values and members). We'll then look at ways to improve our code by:
- For non-optional values, using non-nullable types (value semantics, references, move semantics)
- For optional values, using C++17's std::optional. (We'll go into detail here, also discussing performance)
Tony Hoare, the inventor of null, calls it his "billion-dollar mistake". Let's see if we can fix it. | <urn:uuid:d2a6216d-5a8e-4240-9a1c-c818ab50137a> | 3.015625 | 273 | News (Org.) | Software Dev. | 47.227444 | 95,530,069 |
Some anticipated the collision of the century: the vast, drifting B15-A iceberg was apparently on collision course with the floating pier of ice known as the Drygalski ice tongue. Whatever actually happens from here, Envisats radar vision will pierce through Antarctic clouds to give researchers a ringside seat.
A collision was predicted to have already occurred by now by some authorities, but B-15As drift appears to have slowed markedly in recent days, explains Mark Drinkwater of ESAs Ice/Oceans Unit: "The iceberg may have run aground just before colliding. This supports the hypothesis that the seabed around the Drygalski ice tongue is shallow, and surrounded by deposits of glacial material that may have helped preserve it from past collisions, despite its apparent fragility. "What may be needed to release it from its present stalled location is for the surface currents to turn it into the wind, combined with help from a mixture of wind, tides and bottom melting to float it off its perch."
To follow events for yourself, visit ESAs Earthwatching site, where the latest images from Envisats Advanced Synthetic Aperture Radar (ASAR) instrument are being posted online daily.
Mariangela D’Acunto | alfa
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Life Sciences
18.07.2018 | Materials Sciences
18.07.2018 | Health and Medicine | <urn:uuid:91e733c1-f2f8-46f5-bcc3-6c2bcfb01786> | 3.625 | 888 | Content Listing | Science & Tech. | 38.022633 | 95,530,086 |
Space telescope discovers five exoplanets orbiting a star in the constellation of Cygnus
A group of scientists led by the University of Birmingham has discovered the oldest known solar system containing Earth-sized planets. Five of these comparatively small planets orbit the star Kepler-444, whose birth dates back about 11.2 billion years.
The new findings are based on data from NASA’s Kepler Space Observatory. They suggest that habitable worlds might have existed earlier in the Universe than previously thought. Researchers from the Max Planck Institute for Solar System Research and the University of Göttingen in Germany contributed to this groundbreaking study.
The planetary system around the star Kepler-444 appears like a distant version of our own inner solar system: Even though not four, but five small planets orbit the host star, their sizes all lie between those of Mercury and Venus.
The exoplanets orbit Kepler-444 in less than ten days or, equivalently, at less than one-tenth Earth’s distance from the Sun. The age of the system is a surprise: with 11.2 billion years, it is almost two and a half times as old as our solar system. So far, no other system of comparable age is known to host Earth-sized planets.
The team carried out the research using asteroseismology: with the help of the Kepler Space Observatory the researchers listened to the natural resonances of the host star which are caused by sound waves trapped within it. “These oscillations lead to miniscule variations in its brightness which allow us to measure its diameter, mass, and age”, says Saskia Hekker from the Max Planck Institute for Solar System Research.
The planets were detected from the dimming that occurs when they passed in front of the star. This fractional fading in the intensity of the light received from the star enables scientists to accurately measure the sizes of the planets relative to the size of the star.
The Kepler Space Observatory has been searching for exoplanets since 2009. Over a period of four years it repeatedly turned its gaze to star Kepler-444. “Long, uninterrupted observations are necessary to observe the weak pulsations. Only with the exquisite, high quality data from the Kepler mission has this been possible”, explains Dr. Timothy White from the University of Göttingen.
"There are far-reaching implications from this discovery”, says Tiago Campante from the University of Birmingham, who led the research. It proves that Earth-sized planets have formed throughout most of the Universe’s 13.8-billion-year history. Hekker clarifies that “We therefore think it is possible that worlds which could support life may have existed even in this early phase of the Universe’s evolution.
Since the beginning of this year, Saskia Hekker heads the new Max Planck Research Group “Stellar Ages and Galactic Evolution” at the MPS. After receiving her doctorate in 2007 at the University of Leiden in the Netherlands, she did research at the Royal Observatory of Belgium and at the University of Birmingham in England. In 2011 she received the prestigious Veni Fellowship of the Netherlands Organization for Scientific Research to continue her work at the Astronomical Institute "Anton Pannenkoek" of the University of Amsterdam. Since 2013 Hekker’s scientific home is the MPS in Göttingen where she was awarded a Starting Grant of the European Research Council.
Dr. Birgit Krummheuer
Max Planck Institute for Solar System Research, Göttingen
Phone: +49 551 384979-462
Fax: +49 551 384979-240
Dr. Saskia Hekker
Max Planck Institute for Solar System Research, Göttingen
Phone: +49 551 384979-257
Dr. Timothy White
Institut für Astrophysik, Universität Göttingen
Phone: +49 551 3913-811
T.L. Campante et al.
An ancient extrasolar system with five sub-Earth-size planets
Astrophysical Journal, 27 January 2015
Dr. Birgit Krummheuer | Max Planck Institute for Solar System Research, Göttingen
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Materials Sciences
19.07.2018 | Earth Sciences
19.07.2018 | Life Sciences | <urn:uuid:2e106cf5-21c2-4024-935f-27cc721666be> | 3.5625 | 1,522 | Content Listing | Science & Tech. | 45.396667 | 95,530,101 |
Metal-catalyzed cross-couplings of carbon bonds could enable creation of libraries of drug candidates to accelerate drug discovery
James Bond had his reasons for ordering his martinis “shaken, not stirred.” Similarly, drug manufacturers need to make sure the molecules in a new drug are arranged in an exact manner, lest there be dire consequences. Specifically, they need to be wary of enantiomers, mirror-image molecules composed of the same atoms, but arranged differently.
“One mirror image could be therapeutic while another could be poisonous,” said Dr. Mark R. Biscoe, assistant professor of chemistry at The City College of New York. The classic case is thalidomide, a drug marketed in the 1950s and 1960s to treat morning sickness, which resulted in serious birth defects.
Professor Biscoe led a team of researchers at CCNY that developed a new method for preparing libraries of single-enantiomer molecules for therapeutic and toxicity studies that is faster and potentially less costly than methods now used in the pharmaceutical industry. Their findings were reported in Nature Chemistry.
Currently, drug developers typically rely on a chiral resolution process whereby compounds with roughly equal parts of the two enantiomers are separated into the individual enantiomers. Bioenzymatic processes can also be employed to generate single-enantiomer molecules. These strategies are wasteful and costly, Professor Biscoe explained.
He and colleagues found that a metal such as palladium could be employed to achieve a cross-coupling reaction with a single-enantiomer molecule without impacting the integrity of the mirror image formed in the product. By doing so, they could isolate one mirror image for evaluation as a drug candidate.
“By using a single-enantiomer partner in a cross-coupling reaction, we can rapidly generate a diverse library of biologically active molecules for use in drug screening,” he said.
The research was funded by the National Institutes of Health, City College, the Alfred P. Sloan Foundation and PSC-CUNY, with additional support from the National Science Foundation and the American Chemical Society Petroleum Research Fund.
Ling Li,Chao-Yuan Wang,Rongcai Huang& Mark R. Biscoe;Nature Chemistry5,607–612(2013)doi:10.1038/nchem.1652 | <urn:uuid:96ae8fe9-994d-4c2f-985c-a8b9d83e0fb7> | 3.015625 | 489 | Truncated | Science & Tech. | 28.989839 | 95,530,108 |
The challenges of combating terrorism, both domestically and abroad.
UA Study: Mexican Wolves Did Not Interbreed With Dogs
The endangered Mexican gray wolf (Canis lupus baileyi) has weathered challenges from near extinction to political wrangling. Now, a genetic study settles whether the wolves might have interbred with dogs.
The Journal of Heredity study could affect future conservation and management of the wolves.
Once distributed across the southwestern U.S. and northern Mexico, Mexican wolves were hunted, trapped and poisoned to the brink of extinction by 1976, when the federal government listed them as a protected species under the U.S. Endangered Species Act.
Since then, captive breeding programs have taken Mexican wolves from three captive groups totaling seven genetic "founders" to a population of around 100, reintroduced into Arizona and New Mexico recovery zones.
But reestablishment and protection have faced opposition from ranchers and their political allies, who view the wolves as a danger to livestock.
Following attempts to lump Mexican wolves in with their more populous cousin, the gray wolf (which is itself listed as endangered and threatened in certain areas), researchers established that the Mexican wolf is its own subspecies, eligible for protection.
More recently, jurisdictions like Apache County have justified removing some of those protections by arguing the wolves have interbred with dogs, producing a "wolf-dog hybrid."
"There were some anecdotal reports about, they may be mixed with domestic dogs, and they had certain traits that looked like they may be domestic dogs. So that was kind of always in the back of everyone's mind," said Bob Fitak, now a postdoctoral researcher at Duke University, who performed the research as part of his dissertation at University of Arizona.
Mexican wolves are smaller than other North American wolves. Their skulls are different, and their coats are distinctive. Earlier studies examining these factors, combined with smaller-scale genetic testing, already suggested that no interbreeding had occurred.
Now, by analyzing 172,000 single nucleotide polymorphisms — simple, one-letter changes in DNA bases that scientists use as biomarkers and for establishing heredity — Fitak and his colleagues believe they have settled the question.
"It's not that we don't find any genetic variation that looks like it could be from dog. The question is, what we do find that looks like dog is probably just due to sharing a dog ancestor, you know, several thousand years ago." | <urn:uuid:64eccce5-3903-4dd9-b494-dab41d37f473> | 3.4375 | 501 | Truncated | Science & Tech. | 32.640042 | 95,530,123 |
Floods, hurricanes and unusually cold weather can be linked to man-made climate change, scientists have said.
Humans are causing the jet-streams which circle the Earth to change.Shocking footage shows massive wildfire raging near Yosemite National Park
In turn it changes our weather systems, a new study has shown.
Giant airstreams, which move in wave patterns between the Arctic circle and the tropics, transport heat and moisture and are largely responsible for which weather we get.
But when the pattern is disturbed, the airstreams stall which can cause droughts or floods.
Warming caused by greenhouse gases from fossil fuels creates favourable conditions for such events to happen, an international team of scientists has concluded.
Heartwarming pictures show Eve the bald black bear's tale of survivalMichael Mann from the Pennsylvania State University in the US, lead author of the study published in Scientific Reports, said: ‘In data from computer simulations as well as observations, we identify changes that favour unusually persistent, extreme meanders of the jet stream that support such extreme weather events.
‘Human activity has been suspected of contributing to this pattern before, but now we uncover a clear fingerprint of human activity.’
Air movements are largely driven by temperature differences between the equator and the poles.
Since the Arctic is more rapidly warming than other regions, this temperature difference is decreasing and land masses are warming more rapidly than the oceans, especially in summer.
Both changes have an impact on those global air movements and this includes the giant air-streams that are called planetary waves because they circle Earth’s northern hemisphere in huge turns between the tropics and the Arctic.France accuses US of starting trade war and applying 'law of the jungle'
Stefan Rahmstorf from the Potsdam Institute for Climate Impact Research (PIK) in Germany, added: ‘If the same weather persists for weeks on end in one region, then sunny days can turn into a serious heat wave and drought, or lasting rains can lead to flooding’.
He added: ‘Identifying the human fingerprint on this process is advanced forensics.’
Scientists found most of the extreme weather effects occurred in the past four decades.
Dim Coumou from the Department of Water and Climate Risk at VU University in Amsterdam, said: ‘The more frequent persistent and meandering jet-stream states seems to be a relatively recent phenomenon, which makes it even more relevant.
‘We certainly need to further investigate this – there is some good evidence, but also many open questions.’ | <urn:uuid:5339adb5-eebc-4b3c-89b2-afa303cd124a> | 3.390625 | 534 | News Article | Science & Tech. | 30.470847 | 95,530,131 |
Enzymes are proteins that speed along the chemical reactions necessary for all life on Earth -- plants as well as animals -- and many of the enzymes are the same. One of the jobs of enzymes is to process food and convert it into a form that can provide energy for the organism. Animals get their food from what they eat, but plants get their food in a process called photosynthesis -- a process in which enzymes play key roles.
How Enzymes Work
Every chemical reaction requires a little kick of energy to get started. That energy is called the activation energy. Enzymes bring together molecules -- called substrates -- and lower the activation energy of chemical reactions, creating chemical products. Enzymes increase the rate of chemical reactions by as much as many millions of times. Enzymes catalyze, or promote, chemical reactions, and they are not used up in the chemical reaction. That is, once the products have been released from the enzyme, it's ready to accept new substrates and start again.
Photosynthesis is a series of chemical and physical interactions that uses energy from light to convert six carbon dioxide molecules and 12 water molecules into one molecule of glucose, six water molecules and six oxygen molecules. The energy harvesting steps are light-dependent, while the steps that build the glucose molecule are light-independent -- that is, they can even happen in the dark. The entire process involves several enzymes, but two are especially important: ATPase and Rubisco.
The first stage of the light-dependent reaction occurs when a photon -- a tiny packet of light energy -- is absorbed by chlorophyll. The energy is transferred along a chain of neighboring molecules until it jumps to another molecule. Along the way, the electron energy moves some protons from one side of a membrane to another.
As the captured light energy is used to transfer protons to one side of a membrane within the plant cell, the extra protons create an electric field across the membrane. The force of the electric field pushes the protons back to the other side of the membrane, but there's only one way across: through an enzyme called ATPase. ATPase is built right into the membrane, like a turnstyle that lets one proton through at a time as it rotates. The rotation adds energy to a molecule of adenosine diphosphate, by converting the adenosine diphosphate, ADP, to adenosine triphosphate, ATP. ATP is like a battery for the cell. It contains energy that the cell can use to do other things.
The "synthesis" of "photosynthesis" is the building of a sugar molecule from carbon dioxide, and that part of the process is done by another enzyme: ribulose bisphosphate carboxylase, often abbreviated as rubisco. Rubisco combines three five-carbon sugar molecules with three carbon dioxide molecules -- which the plant extracts from the air -- to make three six-carbon molecules. Several molecules of ATP give their energy to the next steps, which convert the rubisco products to glucose and other molecules and another set of five-carbon sugars to start all over again. This process is called the Calvin cycle. Rubisco works slowly, as enzymes go, creating only about three glucose molecules a second, so plants need a lot of rubisco. Some scientists believe rubisco is the most abundant protein on Earth. | <urn:uuid:21a7627b-a88a-4ce1-b3b8-4fc0b6330eb2> | 4.15625 | 692 | Knowledge Article | Science & Tech. | 32.714699 | 95,530,133 |
Returns the horizontal offset from the selected drawing location to
the left edge of the first character drawn. If this is positive, the
first glyph is to the right of the drawing location.
The alias neg_width() is present to match the bounding_box() documentation for list context.
The alias left_bearing() is present to match font terminology.
|advance_width()||The advance width of the string, if the driver supports that, otherwise the same as end_offset.|
The distance from the right of the last glyph to the end of the advance
If the glyph overflows the right side of the advance width this value is negative.
The distance from the left-most pixel of the left-most glyph to the
right-most pixel of the right-most glyph.
Equals advance_width - left_bearing - right_bearing (and implemented that way.)
The lowest position relative to the font baseline that any character
in the font reaches in the character cell. Normally negative.
At least one font weve seen has reported a positive number for this.
|global_ascent()||The highest position relative to the font baseline that any character in the font reaches in the character cell. Normally positive.|
|descent()||The lowest position relative to the font baseline that any character in the supplied string reaches. Negative when any characters glyph reaches below the baseline.|
|ascent()||The highest position relative to the font baseline that any character in the supplied string reaches. Positive if any characters glyph reaches above the baseline.|
|font_height()||The maximum displayed height of any string using this font.|
|text_height()||The displayed height of the supplied string.|
These methods include bugs kept for backwards compatibility and shouldnt be used in new code.
total_width() The total displayed width of the string.
New code should use display_width().
This depends on end_offset(), and is limited by its backward compatibility.
end_offset pos_width The offset from the selected drawing location to the right edge of the last character drawn. Should always be positive.
You can use the alias pos_width() if you are used to the bounding_box() documentation for list context.
For backwards compatibility this method returns the maximum of the advance width and the offset of the right edge of the last glyph.
new(...) Called by Imager::Font->bounding_box() to create the object.
Doesnt reproduce the functionality that you get using the x and y parameters to Imager::Font->bounding_box(). I considered:
my ($left, $top, $right, $bottom) = $box->offset(x=>$x, y=>$y)
but this is about as clumsy as the original.
Tony Cook <firstname.lastname@example.org>
|perl v5.20.3||IMAGER::FONT::BBOX (3)||2012-09-28| | <urn:uuid:27650217-2351-4875-8a09-37d64210b042> | 2.515625 | 633 | Documentation | Software Dev. | 51.964277 | 95,530,166 |
Long ago humans and Neanderthals Interbred: What happened to Neanderthal genes?
The Neanderthals disappeared about 30,000 years ago, but little pieces of them live on in the form of DNA sequences scattered through the modern human genome. A new study by geneticists at the University of California, Davis, shows why these traces of our closest relatives are slowly being removed by natural selection.
"On average, there has been weak but widespread selection against Neanderthal genes," said Graham Coop, professor in the UC Davis Department of Evolution and Ecology and Center for Population Biology, and senior author on a paper describing the work published Nov. 8 in the journal PLOS Genetics. That selection seems to be a consequence of a small population of Neanderthals mixing with a much larger population of modern humans.
Neanderthals split from our African ancestors over half a million years ago, and lived in Europe and Central Asia until a few tens of thousands of years ago. Archaeological discoveries have shown that they had quite a sophisticated culture, Coop said. Thanks to DNA samples retrieved from a number of fossils, we have enough data on the Neanderthal genome to identify their genes among ours.
When modern humans left Africa about 50,000 to 80,000 years ago and spread through Europe and Asia, they interbred with Neanderthals. The first hybrid offspring would have been, on average, a 50-50 mix of modern human and Neanderthal genes, and could then have themselves bred with modern humans, Neanderthals or other hybrids.
So what happened to the Neanderthal DNA? Today, Neanderthal genes are a few percent of the genome of people of European ancestry, a little more common in people of East Asian descent, and almost absent in people of African ancestry.
Coop and postdoctoral researchers Ivan Juric and Simon Aeschbacher devised methods to measure the degree of natural selection acting on Neanderthal DNA in the human genome.
One hypothesis has been that Neanderthals quickly became genetically incompatible with modern humans, so their hybrid offspring were not "fit" in evolutionary terms - they either failed to thrive or were not fertile.
Weak but Widespread Selection Against Neanderthal Genes
The researchers found something different. Rather than showing strong selection against a few Neanderthal genes, they found weak, but widespread selection against many Neanderthal DNA sequences that is slowly removing it from our genome.
Coop said that's consistent with a small, isolated population of Neanderthals mixing with a much larger population of modern humans. Inbreeding in small populations means that genetic variants can remain common even if they're harmful to some degree. But when they mix into a larger population, natural selection starts to act against those variants and weed them out.
"The human population size has historically been much larger, and this is important since selection is more efficient at removing deleterious variants in large populations," Juric said. "Weakly deleterious variants that could persist in Neanderthals could not persist in humans. We think that this simple explanation can account for the pattern of Neanderthal ancestry that we see today along the genome of modern humans."
The findings are consistent with other recently published work. If Neanderthals had been more numerous when modern humans encountered them, we might have a different mix of Neanderthal and human genes, Juric said.
More information: Juric I, Aeschbacher S, Coop G (2016) The Strength of Selection against Neanderthal Introgression. PLoS Genet 12(11): e1006340. DOI: 10.1371/journal.pgen.1006340
Provided by: UC Davis | <urn:uuid:f039333a-119e-4af1-8086-ac11b223aaaf> | 3.578125 | 748 | News Article | Science & Tech. | 37.411322 | 95,530,171 |
Upper littoral zones of 13 lakes with fish and 10 lakes without fish were sampled to compare macroinvertebrate communities. Lakes with fish had lower macroinvertebrate species richness, diversity, and smaller-sized individuals than lakes without fish. Larger invertebrates, including most large invertebrate predators, such as dytiscids, corixids, odonates, Gammarus, and Chaoborus, were generally not found in lakes with fish. To determine the feeding behavior of a conspicuous invertebrate predator found in fishless lakes, the predaceous diving beetle ( Coleoptera: Dytiscidae), we used microcosm feeding experiments and a molecular technique for gut content analysis. Dytiscids were sit-and-wait predators in the laboratory, feeding on large, mobile species and avoiding smaller, benthic species. Gut content analyses of field-caught dytiscids, as assessed by native polyacrylamide gel electrophoresis, were not entirely consistent with laboratory selectivity studies, but the field results did confirm that dytiscids fed on large mobile species. However, we cannot rule out the possibility that small prey might also have been ingested. We conclude that fish impact macroinvertebrate diversity in the upper littoral zones of these arctic lakes by excluding large invertebrates and decreasing species richness, diversity, and size-distribution of individuals. Dytiscids in fishless lakes feed on large species as well, but clearly do not eliminate them from lakes as do fish.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below | <urn:uuid:e4278579-bf62-4cbf-92da-aa4e00d841ff> | 3.125 | 341 | Academic Writing | Science & Tech. | 4.871667 | 95,530,187 |
There are more templating systems written in Perl than you could possibly keep in your head all at once. To help you make sense of Mason’s place in the world, this section presents Mason’s most important and distinctive features. By the end of this section, you should see that Mason pushes the boundaries of the term "templating system,” with lots of features aimed at helping you manage the larger tasks of site design and maintenance.
As we mentioned before, the basic unit of Mason code is called a component. It is a chunk of Mason code that can accept input parameters and generate output text. An important feature of Mason is that any component may call any other component at any point during its execution, much like a Perl subroutine calling another Perl subroutine. Because of this feature, a component may represent a single web page, a part of a web page (like a side navigation bar), or even a shared utility function that generates no output of its own. This separation of design elements allows you to use Mason as a sort of glorified server-side include (SSI) mechanism, as in Example 1-1, Example 1-2, and Example 1-3. Executing mainpage.mas will produce a full page of HTML with the header and footer inserted in place.
Example 1-1. header.mas
<html> <head><title>Welcome to Wally World!</title></head> <body bgcolor="#CCFFCC">
Example 1-3 introduces the
call tag syntax,
<& &>, which is used to call another
component and insert its output into the surrounding text. The
component tag can also accept arguments, which in this case can help
unify site design by moving the page header text into the
Example 1-3. mainpage.mas
<& header.mas &> <center><h1>Wally World Home</h1></center> Here at Wally World you'll find all the finest accoutrements. <& footer.mas &>
The header.mas component in Example 1-4 now accepts an argument called
$head that contains the text that should get
inserted into the
<h1> tags. A
component’s arguments are declared by using an
<%args> block, which you’ll
see in more detail later in the book. The
argument becomes an honest-to-goodness Perl variable that can be used
throughout the rest of the component. It’s lexically
scoped in the header.mas component using
Example 1-4. header.mas
<%args> $head </%args> <html> <head><title>Welcome to Wally World!</title></head> <body bgcolor="#CCFFCC"> <center><h1><% $head %></h1></center>
The footer.mas component in Example 1-5 is fairly straightforward. It just provides a link to the document root.
component in Example 1-6, the arguments are passed to the
header.mas component by using standard Perl
syntax (i.e., commas, quotes, and the
operator). In fact, any Perl syntax for passing a list can be used,
because the argument list is specified in real Perl syntax.
Example 1-6. mainpage.mas
<& header.mas, head => "Wally World Home" &> Here at Wally World you'll find all the latest accoutrements. <& footer.mas &>
Aside from the fact that there’s a little bit of Perl thrown into the mix for passing parameters, the examples we’ve seen don’t really show anything that you couldn’t do using standard server-side include (SSI) techniques. In fact, the usage demonstrated in these examples is relatively uncommon in building Mason sites, because there are better ways to get the job done. One of the greatest features of Mason is that components can inherit behavior from other components, much like classes and objects in an object-oriented hierarchy. Typically, each component will inherit from a single component called the autohandler . The autohandler implements general behavior for all components, such as the content of headers and footers. Individual components implement specific behavior, such as the body text of the individual pages.
Example 1-7. autohandler
<html> <head><title>Welcome to Wally World!</title></head> <body bgcolor="#CCFFCC"> <center><h1><% $m->base_comp->attr('head') %></h1></center> % $m->call_next; <center><a href="/">Home</a></center> </body></html>
Example 1-8. mainpage.mas
<%attr> head => "Wally World Home" </%attr> Here at Wally World you'll find all the finest accoutrements.
Notice that the header and footer are now both all in one file, the
autohandler. Visually, this helps unify the page content, because
that are opened in the
header are closed in the same file. The other important difference
here is that mainpage.mas no longer has to call
the header and footer components explicitly, but rather Mason calls
the parent component automatically and it wraps its header and footer
around the main content. The page header is now specified by an
attributes block, one of Mason’s object-oriented
mechanisms. An attribute is a component property that inherits via
Mason’s component inheritance chain.
There are zillions of other uses for Mason’s inheritance mechanism, which will be further explored in Chapter 5.
Anyone who has built any dynamically generated web sites knows that sometimes certain portions of a site can take longer to generate and serve than you want to make your users wait. Furthermore, portions of a site might be only “semidynamic,” meaning that their content changes periodically but stays static for a long time between changes. Alternatively, as might happen on a news site or for an online poll, content may change continually, but a lag time of a few minutes in updating the content would be acceptable if it improves site performance. For cases like these, Mason provides a very sophisticated caching mechanism that you can use to control how often the output of a component is rebuilt. You can base the expiration decision on time, on certain key parameters like username or content ID, or on an explicit agent that decides when specific data has expired.
The caching mechanism can be used for the output of a component, for an arbitrary block of text, or for any Perl data structure you might want to cache. The first-class support for caching is one of Mason’s most endearing qualities, and you’ll learn to appreciate it the first time it saves you from spending hours optimizing sluggish code.
To aid overall performance, Mason also has an intelligent internal caching mechanism. During execution, Mason turns each component into Perl source code on disk, then compiles the Perl code into bytecode, then executes the bytecode to produce the component’s output. It would be a waste of computing resources to repeat this cycle every time a component needs to be executed, so Mason caches at each stage. As an aid to rapid development, Mason will check your components’ modification times and invalidate its cache when you make changes to your components, ensuring that any changes you make to your site take effect immediately. When your site moves from development to production, you probably won’t be making frequent changes to your site, so you can disable the freshness checks in order to improve your site’s responsiveness.
As mentioned before, the most common use of
Mason is in building large, dynamic,
data-driven web sites. The most popular
web server around is
Apache, and one of
Apache’s most powerful features is
mod_perl, which lets you use the full power of
Perl within the Apache server process. Therefore, it should come as
no surprise that Mason is designed to cooperate fully
mod_perl. Mason comes with drop-in
mod_perl handlers that let Apache serve your Mason
components directly. It lets you take advantage of the sophisticated
decision-making mechanisms that Apache has evolved to support, such
as custom authentication methods, content negotiation, and dynamic
URL rewriting. Mason’s caching mechanism and other
performance considerations are designed specifically for the task of
serving dynamic content efficiently and with enough flexibility to
let you design creative solutions to your specific problems. Although
Mason lets you build a site without relying very much on assumptions
about the server environment, learning about
mod_perl and Apache’s request
cycle can help you use Mason to create slick and powerful
A caveat is necessary when using the term “object-oriented” to describe Mason’s content-wrapping and inheritance schemes, because Mason merely borrows some ideas from the object-oriented world rather than employing Perl’s (or any other language’s) built-in object-oriented inheritance. | <urn:uuid:32e3693e-fa18-4d14-a8eb-2e3cb1870763> | 2.875 | 1,936 | Documentation | Software Dev. | 44.541005 | 95,530,203 |
Single Neurons Can Silence the Crowd
Sensory stimuli are processed in the somatosensory cortex in the brain. In the current study, the Poulet lab shows that pyramidal cells generate single signals that activate PV interneurons. These cells, in turn, stimulate other nerves but inhibit their firing, including the pyramidal cells that activated them in the first place. Credit: Jean-Sebastian Jouhanneau, MDC
James Poulet's lab at the MDC uses advanced techniques to monitor the activity of networks of single sensory neurons in the brain. By listening in on hundreds of conversations, the scientists have discovered how a single signal from one cell manages to attract attention.
When we are awake, an incredible amount of sensory information flows into the brain, where it is filtered to distinguish important signals from all the noise. Crucial steps in this processing take place in the neocortex, which has a layered structure like six computer servers stacked on top of each other. Sensory nerves throughout the body collect information and transmit it along their wire-like axons into specific layers of this structure. Inside the neocortex it jumps to other neurons, and if the signal is strong enough, they generate an action potential and transmit a signal of their own. This electrochemical charge races up their axons into other layers of the cortex and is ultimately transmitted to other regions of the brain.
Along the way the signal can be amplified by excitatory neurons such as pyramidal cells (PYRs) or dampened by inhibitory neurons such as SST and PV cells. Inhibition keeps a signal from spreading until it overloads the system – as seen in conditions like epilepsy. Strangely, many excitatory PYR cells fire infrequently, in single bursts of activity. Now James Poulet's lab at the MDC has discovered how these quiet neurons manage to make themselves heard. Their work appears in the current issue of Nature Communications.
Whole-cell measurements of input and outputStudying the effects of single "spikes" from PYR cells required listening in on their activity, as well as that of neighboring PV and SST neurons. The types can be distinguished by the molecules they produce, but scientists haven't had a full picture of how they interact with each other as signals move through the sensory cortex.
"Whole-cell recordings are an advanced method that can be performed in living mice that have been genetically modified," says Jean-Sebastian Jouanneau, a postdoc in Poulet's lab and a lead author on the paper. "We can now apply it to specific neurons that we have identified visually. It's a unique approach that allows us to stimulate single neurons and monitor the tiny fluctuations in their electrical activity that generate action potentials. By stimulating the nerves one after another, and listening in on the network, we can check whether the cells are connected to each other and determine the effects a signal has."
The scientists carried out this procedure hundreds of times, breaking a record by monitoring four neurons simultaneously in each experiment. Putting all the data together required large-scale analysis by Jens Kremkow, a former lab member and also lead author on the paper.
A quiet voice that makes everything even quieterThe analysis produced some surprising results. A single spike from a PYR cell didn't provoke any activity in the other PYR cells or SST neurons it was attached to. But the PV neurons told a different story. The one-off signal from the PYR cell caused the PV neuron to fire – an amazingly efficient response.
The effects of this transmission were equally surprising. "The signal produced by the PV cell – after stimulation by the PYR cell – was passed on to target nerve cells and prevented them from generating action potentials of their own," Poulet says. "Those targets included PYR cells – the types of cells that had stimulated it in the first place! The result is a situation where one signal manages to silence all the neighbors."
The situation is a bit like a professor who comes into a classroom where people are chatting and shuffling papers around. If he starts speaking loudly, students often raise their own voices so that they can still hear themselves as well. But if he speaks very softly, they usually quickly quiet down – and may shush their neighbors – to hear what he is saying.
"We've seen this type of signal dampening before, but not in response to a single spike," Poulet says. "Observing this effect required studying the signal in an intact and active network. This could be an important mechanism that helps the brain filter subtle but important stimuli so that they will be heard despite the noise."
This article has been republished from materials provided by The Max-Delbrück-Centrum für Molekulare Medizin. Note: material may have been edited for length and content. For further information, please contact the cited source.
Jouhanneau, J., Kremkow, J., & Poulet, J. F. (2018). Single synaptic inputs drive high-precision action potentials in parvalbumin expressing GABA-ergic cortical neurons in vivo. Nature Communications, 9(1). doi:10.1038/s41467-018-03995-2
NeuroTrauma Sciences and Henry Ford Health System Announce Agreements for Neurological Injury ResearchNews
Research indicates exosomes have therapeutic potential for improving recovery after stroke, traumatic brain injury.READ MORE
Processed Meats Associated with Manic EpisodesNews
Analysis of over 1,000 people with and without psychiatric disorders has shown that nitrates—chemicals used to cure meats such as beef jerky, salami, hot dogs and other processed meat snacks—may contribute to mania, an abnormal mood state.READ MORE
Orexin Neurons are Promising Target for Medications to Treat Binge EatingNews
The researchers studied female rats fed a control diet or a sugary, high-fat diet that causes weight gain and binge eating patterns.READ MORE | <urn:uuid:99b83519-cd56-4696-be83-c152d0528061> | 3.6875 | 1,251 | Truncated | Science & Tech. | 40.693607 | 95,530,205 |
NASA's Curiosity Rover Sharpens Paradox of Ancient Mars
Mars scientists are wrestling with a problem. Ample evidence says ancient Mars was sometimes wet, with water flowing and pooling on the planet’s surface. Yet, the ancient sun was about one-third less warm and climate modelers struggle to produce scenarios that get the surface of Mars warm enough for keeping water unfrozen.
A leading theory is to have a thicker carbon-dioxide atmosphere forming a greenhouse-gas blanket, helping to warm the surface of ancient Mars. However, according to a new analysis of data from NASA's Mars rover Curiosity, Mars had far too little carbon dioxide about 3.5 billion years ago to provide enough greenhouse-effect warming to thaw water ice.
The same Martian bedrock in which Curiosity found sediments from an ancient lake where microbes could have thrived is the source of the evidence adding to the quandary about how such a lake could have existed. Curiosity detected no carbonate minerals in the samples of the bedrock it analyzed. The new analysis concludes that the dearth of carbonates in that bedrock means Mars' atmosphere when the lake existed -- about 3.5 billion years ago -- could not have held much carbon dioxide.
"We've been particularly struck with the absence of carbonate minerals in sedimentary rock the rover has examined," said Thomas Bristow of NASA's Ames Research Center, Moffett Field, California. "It would be really hard to get liquid water even if there were a hundred times more carbon dioxide in the atmosphere than what the mineral evidence in the rock tells us." Bristow is the principal investigator for the Chemistry and Mineralogy (CheMin) instrument on Curiosity and lead author of the study being published this week in the Proceedings of the National Academy of Science.
Curiosity has made no definitive detection of carbonates in any lakebed rocks sampled since it landed in Gale Crater in 2011. CheMin can identify carbonate if it makes up just a few percent of the rock. The new analysis by Bristow and 13 co-authors calculates the maximum amount of carbon dioxide that could have been present, consistent with that dearth of carbonate.
In water, carbon dioxide combines with positively charged ions such as magnesium and ferrous iron to form carbonate minerals. Other minerals in the same rocks indicate those ions were readily available. The other minerals, such as magnetite and clay minerals, also provide evidence that subsequent conditions never became so acidic that carbonates would have dissolved away, as they can in acidic groundwater.
The dilemma has been building for years: Evidence about factors that affect surface temperatures -- mainly the energy received from the young sun and the blanketing provided by the planet's atmosphere -- adds up to a mismatch with widespread evidence for river networks and lakes on ancient Mars. Clues such as isotope ratios in today's Martian atmosphere indicate the planet once held a much denser atmosphere than it does now. Yet theoretical models of the ancient Martian climate struggle to produce conditions that would allow liquid water on the Martian surface for many millions of years. One successful model proposes a thick carbon-dioxide atmosphere that also contains molecular hydrogen. How such an atmosphere would be generated and sustained, however, is controversial.
The new study pins the puzzle to a particular place and time, with an on-the-ground check for carbonates in exactly the same sediments that hold the record of a lake about a billion years after the planet formed.
For the past two decades, researchers have used spectrometers on Mars orbiters to search for carbonate that could have resulted from an early era of more abundant carbon dioxide. They have found far less than anticipated.
"It's been a mystery why there hasn't been much carbonate seen from orbit," Bristow said. "You could get out of the quandary by saying the carbonates may still be there, but we just can't see them from orbit because they're covered by dust, or buried, or we're not looking in the right place. The Curiosity results bring the paradox to a focus. This is the first time we've checked for carbonates on the ground in a rock we know formed from sediments deposited under water."
The new analysis concludes that no more than a few tens of millibars of carbon dioxide could have been present when the lake existed, or it would have produced enough carbonate for Curiosity's CheMin to detect it. A millibar is one one-thousandth of sea-level air pressure on Earth. The current atmosphere of Mars is less than 10 millibars and about 95 percent carbon dioxide.
"This analysis fits with many theoretical studies that the surface of Mars, even that long ago, was not warm enough for water to be liquid," said Robert Haberle, a Mars-climate scientist at NASA Ames and a co-author of the paper. "It's really a puzzle to me."
Researchers are evaluating multiple ideas for how to reconcile the dilemma.
"Some think perhaps the lake wasn't an open body of liquid water. Maybe it was liquid covered with ice," Haberle said. "You could still get some sediments through to accumulate in the lakebed if the ice weren't too thick."
A drawback to that explanation is that the rover team has sought and not found in Gale Crater evidence that would be expected from ice-covered lakes, such as large and deep cracks called ice wedges, or "dropstones," which become embedded in soft lakebed sediments when they penetrate thinning ice.
If the lakes were not frozen, the puzzle is made more challenging by the new analysis of what the lack of a carbonate detection by Curiosity implies about the ancient Martian atmosphere.
"Curiosity's traverse through streambeds, deltas, and hundreds of vertical feet of mud deposited in ancient lakes calls out for a vigorous hydrological system supplying the water and sediment to create the rocks we're finding," said Curiosity Project Scientist Ashwin Vasavada of NASA's Jet Propulsion Laboratory, Pasadena, California. "Carbon dioxide, mixed with other gases like hydrogen, has been the leading candidate for the warming influence needed for such a system. This surprising result would seem to take it out of the running."
When two lines of scientific evidence appear irreconcilable, the scene may be set for an advance in understanding why they are not. The Curiosity mission is continuing to investigate ancient environmental conditions on Mars. It is managed by JPL, a division of Caltech in Pasadena, for NASA's Science Mission Directorate, Washington. Curiosity and other Mars science missions are a key part of NASA's Journey to Mars, building on decades of robotic exploration to send humans to the Red Planet in the 2030s.
Contrasting Colors of Crater Dunes and Gullies
Gullies are relatively common features in the steep slopes of crater walls, possibly formed by dry debris flows, movement of carbon dioxide frost, or perhaps the melting of ground ice.
This example shows a section of crater wall from the rocky crater rim at the far left of the image, down to the dark dusty dunes on the crater floor in the bottom right. (North is to the left.) The rock of the crater walls shows up deep orange, and the sandy deposits on the crater floor and the base of the crater walls appear blue. The sand isn't really blue; the different colors in this image represent different material compositions.
The gullies in this image have two main sections: a scalloped alcove at the top of the gully (left/center), and defined channel sections further down the crater wall (right/center). Material from the alcove will have traveled down the channel to the crater floor. This normally forms a third section to a typical gully, a debris fan. Fans commonly visible at the base of gullies are not obvious in this example however, as the wind blown sediments (blue) have covered the crater floor after gully formation.
The University of Arizona, Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp., Boulder, Colo. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate, Washington. | <urn:uuid:690b4a26-3423-4115-86f2-cc58201cbe2c> | 4.3125 | 1,687 | News Article | Science & Tech. | 36.435748 | 95,530,219 |
Bob Rawlings was at the helm of the Pueblo Chieftain for more than 37 years and was a powerful force in protecting Southeastern Colorado's water resources. Rawlings died earlier this year at age 92.
CDPHE recently upped its enforcement on groundwater monitoring with smaller landfills that accept up to 20 tons of waste per day.
Manure runs downhill. It’s just a matter of where it ends up.
A short stretch of the river drops into a narrow channel that allows to run deeper, faster and colder.
The US and Mexico signed a new agreement to share water from the Colorado River, and improve conservation in Mexico, particularly on farms.
The agreement includes spending millions of dollars on conservation projects and drawing up plans to deal with drought and climate change.
The EPA is installing a barrier at the mine outside Silverton to prevent another spill like the one in 2015 that sent 3 million gallons of toxic water into rivers.
Millions of people rely on crops and cattle that feed off the aquifer. As streams dry up, conservation becomes key.
Overall, the river serves more than 40 million people in cities, farms and tribes in Arizona, California, Colorado, Nevada, New Mexico, Utah and Wyoming. Mexico also gets a share.
Utah wants cleanup compensation and unspecified damages in the 3-million-gallon Gold King Mine spill that was accidently triggered by EPA contractors. | <urn:uuid:5ff10363-2dc6-4f87-b3f3-0ec06d274d7c> | 2.84375 | 290 | Content Listing | Science & Tech. | 48.87 | 95,530,231 |
A new $15 million gift by Lynda and Stewart Resnick in support of the Resnick Sustainability Institute at Caltech will help scientists and engineers advance research aimed at helping humanity sustainably meet its needs.
The AAAS has elected three Caltech faculty members—John Brady, Kenneth Farley, and Fiona Harrison—as fellows. Also named to the academy was Katherine T. Faber, who will be joining the Caltech faculty in July.
Today's Earth Week feature highlights three cross-disciplinary research centers where Caltech scientists and engineers collaborate on projects that will have a positive impact on energy, the environment, and Earth's sustainable future.
As the final element of Evolution, Caltech's new Bi/Ge 105 course, a dozen students spent their spring break snorkeling with penguins and sharks, hiking a volcano, and otherwise taking in the natural laboratory for evolution that is the Galápagos Islands.
Caltech joins the world in celebrating Earth Week, April 21–25, 2014, with events, news, and features highlighting our past, present, and future contributions to a healthier, cleaner, and greener planet.
A lot can happen to a rock over the course of two and a half billion years. It can get buried and heated; fluids remove some of its minerals and precipitate others; its chemistry changes. So if you want to use that rock to learn about the conditions on the early Earth, you have to do some geologic sleuthing: You have to figure out which parts of the rock are original and which came later. That is a tricky task, but now a team of Caltech researchers has developed and applied a unique technique that removes much of the guesswork.
Using gravity measurements collected by NASA's Cassini spacecraft, scientists have confirmed that Saturn's moon Enceladus harbors a large subsurface ocean near its south pole, fueling plumes first seen in 2005.
Mark Simons, professor of geophysics at Caltech, along with graduate student Brent Minchew, recently logged over 40 hours of flight time mapping the surface of Iceland's glaciers. Flying over two comparatively small ice caps, Hofsjökull and Langjökull, they traveled with NASA pilots and engineers in a retrofitted Gulfstream III business jet, crisscrossing the glaciers numerous times. | <urn:uuid:e519f547-499f-4b53-be7a-399a496d0a77> | 2.5625 | 480 | News (Org.) | Science & Tech. | 35.277705 | 95,530,232 |
Being one of the least recycled plastics, polystyrene is a notorious plastic pollutant with less than 2% of its produced volume recycled. While it is also a surprisingly inert polymer, with a degradation lifespan of up to a million years, its bad recycling reputation mainly comes from the fact that the recycling of its most commonly produced form seems to be economically inefficient.
The expanded form of polystyrene (commonly referred to as styrofoam) unlike other plastics easily erodes down in landfills due to its lightweight properties, making it easily air-transferrable and able to reach kilometric distances, mostly ending up in the ocean.
Figure 1: Eroded styrofoam contaminates areas to a much larger extent than other plastics do, making it more recognizable as a food to fish, while being difficult to clean out.
We aim to degrade polystyrene in two stages; the first one being a chemical dissolving process of polystyrene to its styrene monomers and the second one being the feeding of the styrene to our genetically engineered bacterial cultures.
The main degradation of styrene will be achieved by using an aromatic compound degradation pathway found in Pseudomonas putida F1 strain. This pathway is effective in providing the organism P. putida to degrade and incorporate aromatic hydrocarbons such as toluene and benzene as nutritious sources of carbon to the cell. Because styrene seems structurally similar to the hydrocarbons of the tod pathway, our research is focusing on modifying the enzymes of the pathway to metabolise styrene in almost the same manner as it would for toluene and others. Some studies have in fact already proved that the enzymes in the degradation of toluene are able to recognise styrene as a substrate.
Figure 2: Proposed tod operon pathway on styrene.
TodE and its action on styrene have been investigated before, yielding results that show that an intermediate of styrene breakdown called 3-vinylcatechol is capable of inactivating TodE. We will analyse the TodE gene more closely using bioinformatics with the hopes of altering the active site to better fit the intermediate 3-vinylcatechol, along with overexpression of TodE to speed up the catalysis. Although TodF has already been registered as a BioBrick by Leicester 2013, this year we will attempt to modify their BioBrick to suit the intermediates of styrene, as TodF is an important stage in the tod pathway.
Another focus part of human practices we plan to educate local schools and their pupils on the issue of plastic waste and the use of synthetic biology as a universal problem solver. We also aim to spread awareness through social media and collaborating with other scientists in order to responsibly use plastics in laboratories. | <urn:uuid:a19e09e8-da38-4050-9bd6-8a7ef4c1fe6e> | 3.46875 | 583 | Academic Writing | Science & Tech. | 18.233615 | 95,530,239 |
The Celsius scale, previously known as the centigrade scale, is a temperature scale used by the International System of Units (SI). As an SI derived unit, it is used by all countries except the United States and Liberia. It is named after the Swedish astronomer Anders Celsius (1701–1744), who developed a similar temperature scale. The degree Celsius (symbol: °C) can refer to a specific temperature on the Celsius scale or a unit to indicate a difference between two temperatures or an uncertainty. Before being renamed to honor Anders Celsius in 1948, the unit was called centigrade, from the Latin centum, which means 100, and gradus, which means steps.
Before 1954, the Celsius scale was based on 0 °C for the freezing point of water and 100 °C for the boiling point of water at 1 atm pressure following a change introduced in 1743 by Jean-Pierre Christin to reverse the Celsius thermometer scale (from water boiling at 0 degrees and ice melting at 100 degrees). This scale is widely taught in schools today.
By international agreement, since 1954 the unit "degree Celsius" and the Celsius scale are defined by absolute zero and the triple point of Vienna Standard Mean Ocean Water (VSMOW), a specially purified water. This definition also precisely relates the Celsius scale to the Kelvin scale, which defines the SI base unit of thermodynamic temperature with symbol K. Absolute zero, the lowest temperature possible, is defined as being exactly 0 K and −273.15 °C. The temperature of the triple point of water is defined as exactly 273.16 K (0.01 °C; 32.02 °F). This means that a temperature difference of one degree Celsius and that of one kelvin are exactly the same.
In 1742, Swedish astronomer Anders Celsius (1701–1744) created a temperature scale that reversed the scale now known as "Celsius": 0 represented the boiling point of water, while 100 represented the freezing point of water. In his paper Observations of two persistent degrees on a thermometer, he recounted his experiments showing that the melting point of ice is essentially unaffected by pressure. He also determined with remarkable precision how the boiling point of water varied as a function of atmospheric pressure. He proposed that the zero point of his temperature scale, being the boiling point, would be calibrated at the mean barometric pressure at mean sea level. This pressure is known as one standard atmosphere. The BIPM's 10th General Conference on Weights and Measures (CGPM) later defined one standard atmosphere to equal precisely 1,013,250 dynes per square centimetre (101.325 kPa).
In 1743, the Lyonnais physicist Jean-Pierre Christin, permanent secretary of the Académie des sciences, belles-lettres et arts de LyonFR, working independently of Celsius, developed a scale where zero represented the freezing point of water and 100 represented the boiling point of water. On 19 May 1743 he published the design of a mercury thermometer, the "Thermometer of Lyon" built by the craftsman Pierre Casati that used this scale.
In 1744, coincident with the death of Anders Celsius, the Swedish botanist Carl Linnaeus (1707–1778) reversed Celsius's scale. His custom-made "linnaeus-thermometer", for use in his greenhouses, was made by Daniel Ekström, Sweden's leading maker of scientific instruments at the time, whose workshop was located in the basement of the Stockholm observatory. As often happened in this age before modern communications, numerous physicists, scientists, and instrument makers are credited with having independently developed this same scale; among them were Pehr Elvius, the secretary of the Royal Swedish Academy of Sciences (which had an instrument workshop) and with whom Linnaeus had been corresponding; Daniel Ekström[SV], the instrument maker; and Mårten Strömer (1707–1770) who had studied astronomy under Anders Celsius.
The first known Swedish document reporting temperatures in this modern "forward" Celsius scale is the paper Hortus Upsaliensis dated 16 December 1745 that Linnaeus wrote to a student of his, Samuel Nauclér. In it, Linnaeus recounted the temperatures inside the orangery at the University of Uppsala Botanical Garden:
...since the caldarium (the hot part of the greenhouse) by the angle of the windows, merely from the rays of the sun, obtains such heat that the thermometer often reaches 30 degrees, although the keen gardener usually takes care not to let it rise to more than 20 to 25 degrees, and in winter not under 15 degrees...
Centigrade, hectograde and Celsius
Since the 19th century, the scientific and thermometry communities worldwide have used the phrase "centigrade scale". Temperatures on the centigrade scale were often reported simply as degrees or, when greater specificity was desired, as degrees centigrade (symbol: °C). Because the term centigrade was also the Spanish and French language name for a unit of angular measurement (1/10000 of a right angle) and had a similar connotation in other languages, the term centesimal degree (known as the gradian, "grad" or "gon": 1ᵍ = 0.9°, 100ᵍ = 90°) was used when very precise, unambiguous language was required by international standards bodies such as the BIPM. More properly, what was defined as "centigrade" then would now be "hectograde".
To eliminate any confusion, the 9th CGPM and the CIPM (Comité international des poids et mesures) formally adopted "degree Celsius" in 1948,[a] formally keeping the recognized degree symbol, rather than adopting the gradian/centesimal degree symbol.
For scientific use, "Celsius" is the term usually used, with "centigrade" remaining in common but decreasing use, especially in informal contexts in English-speaking countries. It was not until February 1985 that the forecasts issued by the BBC switched from "centigrade" to "Celsius".
Some key temperatures relating the Celsius scale to other temperature scales are shown in the table below.
|Absolute zero (exactly)||0 K||−273.15 °C||−459.67 °F|
|Boiling point of liquid nitrogen||77.4 K||−195.8 °C||−320.4 °F|
|Sublimation point of dry ice||195.1 K||−78 °C||−108.4 °F|
|Intersection of Celsius and Fahrenheit scales||233.15 K||−40 °C||−40 °F|
|Melting point of H2O (purified ice)||273.1499 K||−0.0001 °C||31.9998 °F|
|Water's triple point (exactly)||273.16 K||0.01 °C||32.018 °F|
|Normal human body temperature (average)||310.15 K||37.0 °C||98.6 °F|
|Water's boiling point at 1 atm (101.325 kPa)
(approximate: see Boiling point)[b]
|373.1339 K||99.9839 °C||211.971 °F|
Name and symbol typesetting
The "degree Celsius" has been the only SI unit whose full unit name contains an uppercase letter since the SI base unit for temperature, the kelvin, became the proper name in 1967 replacing the term degrees Kelvin. The plural form is degrees Celsius.
The general rule of the International Bureau of Weights and Measures (BIPM) is that the numerical value always precedes the unit, and a space is always used to separate the unit from the number, e.g. "30.2 °C" (not "30.2°C" or "30.2° C"). Thus the value of the quantity is the product of the number and the unit, the space being regarded as a multiplication sign (just as a space between units implies multiplication). The only exceptions to this rule are for the unit symbols for degree, minute, and second for plane angle (°, ′, and ″, respectively), for which no space is left between the numerical value and the unit symbol. Other languages, and various publishing houses, may follow different typographical rules.
Unicode provides the Celsius symbol at code point U+2103 ℃ degree celsius. However, this is a compatibility character provided for roundtrip compatibility with legacy encodings. It easily allows correct rendering for vertically written East Asian scripts, such as Chinese. The Unicode standard explicitly discourages the use of this character: "In normal use, it is better to represent degrees Celsius "°C" with a sequence of U+00B0 ° degree sign + U+0043 C latin capital letter c, rather than U+2103 ℃ degree celsius. For searching, treat these two sequences as identical."
Shown below is the degree Celsius character followed immediately by the two-component version:
- ℃ °C
When viewed on computers that properly support Unicode, the above line may be similar to the image in the line below (enlarged for clarity):
Temperatures and intervals
The degree Celsius is subject to the same rules as the kelvin with regard to the use of its unit name and symbol. Thus, besides expressing specific temperatures along its scale (e.g. "Gallium melts at 29.7646 °C" and "The temperature outside is 23 degrees Celsius"), the degree Celsius is also suitable for expressing temperature intervals: differences between temperatures or their uncertainties (e.g. "The output of the heat exchanger is hotter by 40 degrees Celsius", and "Our standard uncertainty is ±3 °C"). Because of this dual usage, one must not rely upon the unit name or its symbol to denote that a quantity is a temperature interval; it must be unambiguous through context or explicit statement that the quantity is an interval.[c] This is sometimes solved by using the symbol °C (pronounced "degrees Celsius") for a temperature, and C° (pronounced "Celsius degrees") for a temperature interval, although this usage is non-standard.
Celsius measurement follows an interval system but not a ratio system; and it follows a relative scale not an absolute scale. For example, 20 °C is not twice the heat energy of 10 °C; and 0 °C is not the lowest Celsius value. Thus, degrees Celsius is a useful interval measurement but does not possess the characteristics of ratio measures like weight or distance.
Coexistence of Kelvin and Celsius scales
In science and in engineering, the Celsius scale and the Kelvin scale are often used in combination in close contexts, e.g. "a measured value was 0.01023 °C with an uncertainty of 70 µK". This practice is permissible because the magnitude of the degree Celsius is equal to that of the kelvin. Notwithstanding the official endorsement provided by decision #3 of Resolution 3 of the 13th CGPM, which stated "a temperature interval may also be expressed in degrees Celsius", the practice of simultaneously using both °C and K remains widespread throughout the scientific world as the use of SI-prefixed forms of the degree Celsius (such as "µ°C" or "microdegrees Celsius") to express a temperature interval has not been well-adopted.
Melting and boiling points of water
One effect of defining the Celsius scale at the triple point of Vienna Standard Mean Ocean Water (VSMOW, 273.16 K and 0.01 °C), and at absolute zero (0 K and −273.15 °C), is that neither the melting nor boiling point of water under one standard atmosphere (101.325 kPa) remains a defining point for the Celsius scale. In 1948 when the 9th General Conference on Weights and Measures (CGPM) in Resolution 3 first considered using the triple point of water as a defining point, the triple point was so close to being 0.01 °C greater than water's known melting point, it was simply defined as precisely 0.01 °C. However, current measurements show that the difference between the triple and melting points of VSMOW is actually very slightly (<0.001 °C) greater than 0.01 °C. Thus, the actual melting point of ice is very slightly (less than a thousandth of a degree) below 0 °C. Also, defining water's triple point at 273.16 K precisely defined the magnitude of each 1 °C increment in terms of the absolute thermodynamic temperature scale (referencing absolute zero). Now decoupled from the actual boiling point of water, the value "100 °C" is hotter than 0 °C – in absolute terms – by a factor of precisely 373.15/ (approximately 36.61% thermodynamically hotter). When adhering strictly to the two-point definition for calibration, the boiling point of VSMOW under one standard atmosphere of pressure is actually 373.1339 K (99.9839 °C). When calibrated to ITS-90 (a calibration standard comprising many definition points and commonly used for high-precision instrumentation), the boiling point of VSMOW is slightly less, about 99.974 °C.
This boiling-point difference of 16.1 millikelvin between the Celsius scale's original definition and the current one (based on absolute zero and the triple point) has little practical meaning in common daily applications because water's boiling point is very sensitive to variations in barometric pressure. For example, an altitude change of only 28 cm (11 in) causes the boiling point to change by one millikelvin.
|from Celsius||to Celsius|
|Fahrenheit||[°F] = [°C] × 9⁄5 + 32||[°C] = ([°F] − 32) × 5⁄9|
|Kelvin||[K] = [°C] + 273.15||[°C] = [K] − 273.15|
|Rankine||[°R] = ([°C] + 273.15) × 9⁄5||[°C] = ([°R] − 491.67) × 5⁄9|
|For temperature intervals rather than specific temperatures,|
1 °C = 1 K = 9⁄5 °F = 9⁄5 °R
Comparisons among various temperature scales
- According to The Oxford English Dictionary (OED), the term "Celsius' thermometer" had been used at least as early as 1797. Further, the term "The Celsius or Centigrade thermometer" was again used in reference to a particular type of thermometer at least as early as 1850. The OED also cites this 1928 reporting of a temperature: "My altitude was about 5,800 metres, the temperature was 28° Celsius." However, dictionaries seek to find the earliest use of a word or term and are not a useful resource as regards to the terminology used throughout the history of science. According to several writings of Dr. Terry Quinn CBE FRS, Director of the BIPM (1988–2004), including "Temperature Scales from the early days of thermometry to the 21st century" (PDF). (146 KiB) as well as Temperature (2nd Edition/1990/Academic Press/0125696817), the term Celsius in connection with the centigrade scale was not used whatsoever by the scientific or thermometry communities until after the CIPM and CGPM adopted the term in 1948. The BIPM was not even aware that "degree Celsius" was in sporadic, non-scientific use before that time. It is also noteworthy that the twelve-volume, 1933 edition of OED didn't even have a listing for the word Celsius (but did have listings for both centigrade and centesimal in the context of temperature measurement). The 1948 adoption of Celsius accomplished three objectives:
- 1. All common temperature scales would have their units named after someone closely associated with them; namely, Kelvin, Celsius, Fahrenheit, Réaumur and Rankine.
- 2. Notwithstanding the important contribution of Linnaeus who gave the Celsius scale its modern form, Celsius' name was the obvious choice because it began with the letter C. Thus, the symbol °C that for centuries had been used in association with the name centigrade could remain in use and would simultaneously inherit an intuitive association with the new name.
- 3. The new name eliminated the ambiguity of the term "centigrade", freeing it to refer exclusively to the French-language name for the unit of angular measurement.
- For Vienna Standard Mean Ocean Water at one standard atmosphere (101.325 kPa) when calibrated solely per the two-point definition of thermodynamic temperature. Older definitions of the Celsius scale once defined the boiling point of water under one standard atmosphere as being precisely 100 °C. However, the current definition results in a boiling point that is actually 16.1 mK less. For more about the actual boiling point of water, see VSMOW in temperature measurement. A different approximation uses ITS-90, which approximates the temperature to 99.974 °C
- In 1948, Resolution 7 of the 9th CGPM stated, "To indicate a temperature interval or difference, rather than a temperature, the word 'degree' in full, or the abbreviation 'deg' must be used." This resolution was abrogated in 1967/1968 by Resolution 3 of the 13th CGPM, which stated that ["The names "degree Kelvin" and "degree", the symbols "°K" and "deg" and the rules for their use given in Resolution 7 of the 9th CGPM (1948),] ...and the designation of the unit to express an interval or a difference of temperatures are abrogated, but the usages which derive from these decisions remain permissible for the time being." Consequently, there is now wide freedom in usage regarding how to indicate a temperature interval. The most important thing is that one's intention must be clear and the basic rule of the SI must be followed; namely that the unit name or its symbol must not be relied upon to indicate the nature of the quantity. Thus, if a temperature interval is, say, 10 K or 10 °C (which may be written 10 kelvin or 10 degrees Celsius), it must be unambiguous through obvious context or explicit statement that the quantity is an interval. Rules governing the expressing of temperatures and intervals are covered in the BIPM's "SI Brochure, 8th edition" (PDF). (1.39 MiB).
- "Celsius temperature scale". Encyclopædia Britannica. Retrieved 19 February 2012.
Celsius temperature scale, also called centigrade temperature scale, scale based on 0 ° for the freezing point of water and 100 ° for the boiling point of water at 1 atm pressure.
- Helmenstine, Anne Marie (December 15, 2014). "What Is the Difference Between Celsius and Centigrade?". Chemistry.about.com. About.com. Retrieved March 16, 2015.
- "SI brochure, section 126.96.36.199". International Bureau of Weights and Measures. Archived from the original on 26 September 2007. Retrieved 9 May 2008.
- "Essentials of the SI: Base & derived units". Retrieved 9 May 2008.
- Celsius, Anders (1742) "Observationer om twänne beständiga grader på en thermometer" (Observations about two stable degrees on a thermometer), Kungliga Svenska Vetenskapsakademiens Handlingar (Proceedings of the Royal Swedish Academy of Sciences), 3 : 171–180 and Fig. 1.
- "Resolution 4 of the 10th meeting of the CGPM (1954)".
- Don Rittner; Ronald A. Bailey (2005): Encyclopedia of Chemistry. Facts On File, Manhattan, New York City. pp. 43.
- Smith, Jacqueline (2009). "Appendix I: Chronology". The Facts on File Dictionary of Weather and Climate. Infobase Publishing. p. 246. ISBN 978-1-4381-0951-0.
1743 Jean-Pierre Christin inverts the fixed points on Celsius' scale, to produce the scale used today.
- Mercure de France (1743): MEMOIRE sur la dilatation du Mercure dans le Thermométre. Chaubert; Jean de Nully, Pissot, Duchesne, Paris. pp. 1609–1610.
- Journal helvétique (1743): LION. Imprimerie des Journalistes, Neuchâtel. pp. 308–310.
- Memoires pour L'Histoire des Sciences et des Beaux Arts (1743): DE LYON. Chaubert, París. pp. 2125–2128.
- Citation: Uppsala University (Sweden), Linnaeus' thermometer
- Citation for Daniel Ekström, Mårten Strömer, Christin of Lyons: The Physics Hypertextbook, Temperature; citation for Christin of Lyons: Le Moyne College, Glossary, (Celsius scale); citation for Linnaeus' connection with Pehr Elvius and Daniel Ekström: Uppsala University (Sweden), Linnaeus' thermometer; general citation: The Uppsala Astronomical Observatory, History of the Celsius temperature scale
- Citations: University of Wisconsin–Madison, Linnæus & his Garden and; Uppsala University, Linnaeus' thermometer
- "CIPM, 1948 and 9th CGPM, 1948". International Bureau of Weights and Measures. Retrieved 9 May 2008.
- "centigrade, adj. and n". Oxford English Dictionary. Oxford University Press. Retrieved 20 November 2011.
- on YouTube
- Lide, D.R., ed. (1990–1991). Handbook of Chemistry and Physics. 71st ed. CRC Press. p. 4–22.
- The ice point of purified water has been measured at 089(10) degrees Celsius – see Magnum, B.W. (June 1995). 0.000"Reproducibility of the Temperature of the Ice Point in Routine Measurements" (PDF). Nist Technical Note. 1411. Archived from the original (PDF) on July 14, 2007. Retrieved 11 February 2007.
- Elert, Glenn (2005). "Temperature of a Healthy Human (Body Temperature)". The Physics Factbook. Retrieved 22 August 2007.
- "Unit of thermodynamic temperature (kelvin)". The NIST Reference on Constants, Units, and Uncertainty: Historical context of the SI. National Institute of Standards and Technology (NIST). 2000. Retrieved 16 November 2011.
- BIPM, SI Brochure, Section 5.3.3.
- For more information on conventions used in technical writing, see the informative SI Unit rules and style conventions by the NIST as well as the BIPM's SI brochure: Subsection 5.3.3, Formatting the value of a quantity.
- "22.2". The Unicode Standard, Version 9.0 (PDF). Mountain View, CA, USA: The Unicode Consortium. July 2016. ISBN 978-1-936213-13-9. Retrieved 20 April 2017.
- Decision #3 of Resolution 3 of the 13th CGPM
- H.D. Young, R.A. Freedman (2008). University Physics with Modern Physics (12th ed.). Addison Wesley. p. 573
- This fact is demonstrated in the book Biostatistics: A Guide to Design, Analysis, and Discovery By Ronald N. Forthofer, Eun Sul Lee and Mike Hernandez
- "Resolution 3 of the 9th CGPM (1948)". International Bureau of Weights and Measures. Retrieved 9 May 2008.
- Citation: London South Bank University, Water Structure and Behavior, notes c1 and c2
|Look up Celsius in Wiktionary, the free dictionary.|
- NIST, Basic unit definitions: Kelvin
- The Uppsala Astronomical Observatory, History of the Celsius temperature scale
- London South Bank University, Water, scientific data
- BIPM, SI brochure, section 188.8.131.52, Unit of thermodynamic temperature
- TAMPILE, Comparison of temperature scales
- C to F converter, Celsius to Fahrenheit Converter | <urn:uuid:1d8bdd72-4668-4162-a825-5732647b8590> | 4.0625 | 5,178 | Knowledge Article | Science & Tech. | 54.819357 | 95,530,249 |
The same researchers already broke the first part of the codes last autumn, and have now put together a comprehensive picture of how the immune system checks for dangers both in and outside our cells.
According to the researchers this new information, produced with the aid of artificial neural networks, means that it should be possible to predict all the immune system’s known, and also as yet unknown codes. This should in turn lead to the development of new targeted treatments, for e.g. cancer and infectious diseases.
Professor Søren Buus from the Faculty of Health Sciences at the University of Copenhagen has been at the forefront of this research project.
The body’s natural defences uses these codes in such a way that microorganisms cannot detect and discover its functions. It this unique protection that has so far made it difficult for scientists to decode the entire human immune system and thus develop precise immunological tools and carry out organ transplants.
Sandra Szivos | alfa
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences | <urn:uuid:7502966e-c0db-49f6-b77a-1e29b41f2f8c> | 3.09375 | 778 | Content Listing | Science & Tech. | 39.622535 | 95,530,254 |
Consider first a linear equation of the form 2x - 5y = 8.
Now choose a linear inequality of the form 5y < 2x - 8 or 5y > 2x - 8.
What are the major differences between the linear equation graph and the linear inequality graph?© BrainMass Inc. brainmass.com July 17, 2018, 7:27 pm ad1c9bdddf
Consider first a linear equation of the form 2x - 5y = 8
The equation 2x - 5y = 8 is the equation of a line. You can rearrange it so that it's in slope-intercept form:
2x - 5y = 8
-5y = -2x + 8
y = (2/5)x - (8/5)
This line has a y-intercept of -8/5 and a slope of 2/5. The graph is below. It is made up of all the points (x, y) for which the equation holds. For example, the point (1, -6/5) is a point on the line because 2(1) - 5(-6/5) = 8 is true. The point (0, 8) is not on the line because 2(0) - 7(8) = 8 is not true.
Now choose a linear inequality of the form 5 < 2x - 8 or 5 > 2x - 8
Let's look at the first one. You can write this as y < ...
The solution uses an example of a linear equation and an example of a linear inequality to demonstrate how to graph each kind of relation and the differences between the graphs. | <urn:uuid:a98a7d4f-7561-48c7-bf6a-9086ec5e7f59> | 3.921875 | 347 | Tutorial | Science & Tech. | 93.664054 | 95,530,308 |
A new Duke theory identifies the height-to-base ratio that helped humanity master fire and migrate across the globe
From ancient Egyptians roasting a dripping cut of beef next to the Great Pyramid of Giza to a Boy Scout learning to build a log cabin fire in his backyard, everyone builds fires with the same general shape.
Today in Nature Scientific Reports, engineering professor Adrian Bejan shows that the best campfires are roughly as tall as they are wide. The shape is the most efficient for the flow of air and heat.
"Our bonfires are shaped as cones and pyramids, as tall as they are wide at the base. They look the same in all sizes, from the firewood in the chimney, to the tree logs and wooden benches in the center of the university campus after the big game," Bejan said.
Courtesy of Duke University
And now we know why.
In a study published in Nature Scientific Reports on June 8, Adrian Bejan, the J.A. Jones professor of mechanical engineering at Duke University, shows that, all other variables being equal, the best fires are roughly as tall as they are wide. This is why, he argues, everyone has built fires that basically look the same since the dawn of time.
'Humans from all eras have been relying on this design,' said Bejan. 'The reason is that this shape is the most efficient for air and heat flow. Our success in building fires in turn made it possible for humans to migrate and spread across the globe heat flow from fire facilitates the movement and spreading of human mass on the globe, which is a direct prediction of the Constructal Law.'
In 1996, Bejan penned the Constructal Law that postulates that movement -- or 'flow' -- systems such as trees, rivers or air currents evolve into configurations that provide easier and easier access to flows. Now internationally recognized, the law is increasingly finding applications in improving design and maximizing efficiency of manmade systems.
Bejan continued, 'Our bonfires are shaped as cones and pyramids, as tall as they are wide at the base. They look the same in all sizes, from the firewood in the chimney, to the tree logs and wooden benches in the center of the university campus after the big game. They look the same as the pile of charcoal we make to grill meat. And now we know why.'
So the next time you're out camping and want to build the perfect fire, now you know what general shape it should take.
But you already knew that, didn't you?
'Why humans build fires shaped the same way.' Adrian Bejan. Nature Scientific Reports, 2015; 5:11270. DOI: 10.1038/srep11270
Ken Kingery | EurekAlert!
In borophene, boundaries are no barrier
17.07.2018 | Rice University
Research finds new molecular structures in boron-based nanoclusters
13.07.2018 | Brown University
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
17.07.2018 | Power and Electrical Engineering | <urn:uuid:b794feb2-2dc0-4202-9a6b-00409c5644bc> | 3.609375 | 1,191 | Content Listing | Science & Tech. | 47.182367 | 95,530,315 |
Neutronium (sometimes shortened to neutrium, also referred to as neutrite) is a hypothetical substance composed purely of neutrons. The word was coined by scientist Andreas von Antropoff in 1926 (before the discovery of the neutron) for the conjectured "element of atomic number zero" that he placed at the head of the periodic table. However, the meaning of the term has changed over time, and from the last half of the 20th century onward it has been also used to refer to extremely dense substances resembling the neutron-degenerate matter theorized to exist in the cores of neutron stars; hereinafter "degenerate neutronium" will refer to this. Science fiction and popular literature frequently use the term "neutronium" to refer to a highly dense phase of matter composed primarily of neutrons.
Neutronium and neutron stars
Neutronium is used in popular literature to refer to the material present in the cores of neutron stars (stars which are too massive to be supported by electron degeneracy pressure and which collapse into a denser phase of matter). This term is very rarely used in scientific literature, for three reasons: there are multiple definitions for the term "neutronium"; there is considerable uncertainty over the composition of the material in the cores of neutron stars (it could be neutron-degenerate matter, strange matter, quark matter, or a variant or combination of the above); the properties of neutron star material should depend on depth due to changing pressure (see below), and no sharp boundary between the crust (consisting primarily of atomic nuclei) and almost protonless inner layer is expected to exist.
When neutron star core material is presumed to consist mostly of free neutrons, it is typically referred to as neutron-degenerate matter in scientific literature.
Neutronium and the periodic table
The term "neutronium" was coined in 1926 by Andreas von Antropoff for a conjectured form of matter made up of neutrons with no protons or electrons, which he placed as the chemical element of atomic number zero at the head of his new version of the periodic table. It was subsequently placed in the middle of several spiral representations of the periodic system for classifying the chemical elements, such as those of Charles Janet (1928), E. I. Emerson (1944), John D. Clark (1950) and in Philip Stewart's Chemical Galaxy (2005).
Although the term is not used in the scientific literature either for a condensed form of matter, or as an element, there have been reports that, besides the free neutron, there may exist two bound forms of neutrons without protons. If neutronium were considered to be an element, then these neutron clusters could be considered to be the isotopes of that element. However, these reports have not been further substantiated.
- Mononeutron: An isolated neutron undergoes beta decay with a mean lifetime of approximately 15 minutes (half-life of approximately 10 minutes), becoming a proton (the nucleus of hydrogen), an electron and an antineutrino.
- Dineutron: The dineutron, containing two neutrons, was unambiguously observed in 2012 in the decay of beryllium-16. It is not a bound particle, but had been proposed as an extremely short-lived state produced by nuclear reactions involving tritium. It has been suggested to have a transitory existence in nuclear reactions produced by helions (helium 3 nuclei, completely ionised) that result in the formation of a proton and a nucleus having the same atomic number as the target nucleus but a mass number two units greater. The dineutron hypothesis had been used in nuclear reactions with exotic nuclei for a long time. Several applications of the dineutron in nuclear reactions can be found in review papers. Its existence has been proven to be relevant for nuclear structure of exotic nuclei. A system made up of only two neutrons is not bound, though the attraction between them is very nearly enough to make them so. This has some consequences on nucleosynthesis and the abundance of the chemical elements.
- Trineutron: A trineutron state consisting of three bound neutrons has not been detected, and is not expected to exist even for a short time.
- Tetraneutron: A tetraneutron is a hypothetical particle consisting of four bound neutrons. Reports of its existence have not been replicated.
- Pentaneutron: Calculations indicate that the hypothetical pentaneutron state, consisting of a cluster of five neutrons, would not be bound.
Although not called "neutronium", the National Nuclear Data Center's Nuclear Wallet Cards lists as its first "isotope" an "element" with the symbol n and atomic number Z = 0 and mass number A = 1. This isotope is described as decaying to element H with a half life of ±0.02 min. 10.24
Free neutrons decay with a half-life of 10 minutes and 11 seconds. While this lifetime is long enough to permit the study of neutronium's chemical properties, there are serious practical problems. Having no charge or electrons, neutronium would not interact with ordinary low-energy photons (light) and would feel no electrostatic forces, so it would diffuse into the walls of most containers made of ordinary matter. Certain materials are able to resist diffusion or absorption of ultracold neutrons due to nuclear-quantum effects, specifically reflection caused by the strong interaction. In the presence of other elements, low energy (thermal) neutrons readily undergo neutron capture to form heavier (and often radioactive) isotope of the element. Neutronium is left off most periodic tables.
Neutron matter at standard pressure and temperature is predicted by the ideal gas law to be less dense than even hydrogen, with a density of only kg/m3 (roughly 27 times less 0.045 dense than air). Similar to helium, neutron matter is predicted to remain gaseous down to absolute zero at normal pressures, as the zero-point energy of the system is too high to allow condensation. However, neutron matter should in theory, form a degenerate gaseous Bose–Einstein condensate at these temperatures, composed of neutron pairs called dineutrons. At higher temperatures, neutron matter will condense with sufficient pressure, and solidify with even greater pressure. Such pressures exist in neutron stars, where the extreme pressure causes the neutron matter to become degenerate. However, in the presence of atomic matter compressed to the state of electron degeneracy, the β− decay may be inhibited due to the Pauli exclusion principle, thus making free neutrons stable. Also, elevated pressures should make neutrons degenerate themselves. Compared to ordinary elements, neutronium should be more compressible due to the absence of electrically charged protons and electrons. This makes neutronium more energetically favorable than (positive-Z) atomic nuclei and leads to their conversion to (degenerate) neutronium through electron capture, a process which is believed to occur in stellar cores in the final seconds of the lifetime of massive stars, where it is facilitated by cooling via
e emission. As a result, degenerate neutronium can have a density of ×1017 kg/m3, roughly 13 4magnitudes denser than the densest known ordinary substances. It was theorized that extreme pressures of order MeV/fm3 may deform the neutrons into a 100 cubic symmetry, allowing tighter packing of neutrons, or cause a strange matter formation.
The term neutronium has been popular in science fiction since at least the middle of the 20th century. It typically refers to an extremely dense, incredibly strong form of matter. While presumably inspired by the concept of neutron-degenerate matter in the cores of neutron stars, the material used in fiction bears at most only a superficial resemblance, usually depicted as an extremely strong solid under Earth-like conditions, or possessing exotic properties such as the ability to manipulate time and space. In contrast, all proposed forms of neutron star core material are fluids and are extremely unstable at pressures lower than that found in stellar cores. According to one analysis, a neutron star with a mass below about 0.2 solar masses would explode.
- Inglis-Arkell, Esther (2012-04-14). "Neutrium: The Most Neutral Hypothetical State of Matter Ever". io9.com. Retrieved 2013-02-11.
- Zhuravleva, Valentina (2005). Ballad of the Stars: Stories of Science Fiction, Ultraimagination, and TRIZ. Technical Innovation Center, Inc. ISBN 9780964074064.
- von Antropoff, A. (1926). "Eine neue Form des periodischen Systems der Elementen". Zeitschrift für Angewandte Chemie. 39 (23): 722–725. doi:10.1002/ange.19260392303.
- Stewart, P. J. (2007). "A century on from Dmitrii Mendeleev: Tables and spirals, noble gases and Nobel prizes". Foundations of Chemistry. 9 (3): 235–245. doi:10.1007/s10698-007-9038-x.
- Angelo, J. A. (2006). Encyclopedia of Space and Astronomy. Infobase Publishing. p. 178. ISBN 978-0-8160-5330-8.
- Timofeyuk, N. K. (2003). "Do multineutrons exist?". Journal of Physics G. 29 (2): L9. arXiv: . Bibcode:2003JPhG...29L...9T. doi:10.1088/0954-3899/29/2/102.
- Schirber, M. (2012). "Nuclei Emit Paired-up Neutrons". Physics. 5: 30. Bibcode:2012PhyOJ...5...30S. doi:10.1103/Physics.5.30.
- Spyrou, A.; Kohley, Z.; Baumann, T.; Bazin, D.; et al. (2012). "First Observation of Ground State Dineutron Decay: 16Be". Physical Review Letters. 108 (10): 102501. Bibcode:2012PhRvL.108j2501S. doi:10.1103/PhysRevLett.108.102501. PMID 22463404.
- Bertulani, C. A.; Baur, G. (1986). "Coincidence Cross-sections for the Dissociation of Light Ions in High-energy Collisions" (PDF). Nuclear Physics A. 480 (3–4): 615–628. Bibcode:1988NuPhA.480..615B. doi:10.1016/0375-9474(88)90467-8. Archived from the original (PDF) on 2011-07-20.
- Bertulani, C. A.; Canto, L. F.; Hussein, M. S. (1993). "The Structure And Reactions Of Neutron-Rich Nuclei" (PDF). Physics Reports. 226 (6): 281–376. Bibcode:1993PhR...226..281B. doi:10.1016/0370-1573(93)90128-Z. Archived from the original (PDF) on 2011-09-28.
- Hagino, K.; Sagawa, H.; Nakamura, T.; Shimoura, S. (2009). "Two-particle correlations in continuum dipole transitions in Borromean nuclei". Physical Review C. 80 (3): 1301. arXiv: . Bibcode:2009PhRvC..80c1301H. doi:10.1103/PhysRevC.80.031301.
- MacDonald, J.; Mullan, D. J. (2009). "Big Bang Nucleosynthesis: The Strong Nuclear Force meets the Weak Anthropic Principle". Physical Review D. 80 (4): 3507. arXiv: . Bibcode:2009PhRvD..80d3507M. doi:10.1103/PhysRevD.80.043507.
- Kneller, J. P.; McLaughlin, G. C. (2004). "The Effect of Bound Dineutrons upon BBN". Physical Review D. 70 (4): 3512. arXiv: . Bibcode:2004PhRvD..70d3512K. doi:10.1103/PhysRevD.70.043512.
- Bertulani, C. A.; Zelevinsky, V. (2002). "Is the tetraneutron a bound dineutron-dineutron molecule?". Journal of Physics G. 29 (10): 2431. arXiv: . Bibcode:2003JPhG...29.2431B. doi:10.1088/0954-3899/29/10/309.
- Bevelacqua, J. J. (1981). "Particle stability of the pentaneutron". Physics Letters B. 102 (2–3): 79–80. Bibcode:1981PhLB..102...79B. doi:10.1016/0370-2693(81)91033-9.
- Felipe J. Llanes-Estrada; Gaspar Moreno Navarro (2011). "Cubic neutrons". Modern Physics Letters A. 27 (6): 1250033. arXiv: . Bibcode:2012MPLA...2750033L. doi:10.1142/S0217732312500332.
- K. Sumiyoshi; S. Yamada; H. Suzuki; W. Hillebrandt (1998). "The fate of a neutron star just below the minimum mass: does it explode?". Astronomy and Astrophysics. 334: 159–168. arXiv: . Bibcode:1998A&A...334..159S.
Given this assumption... the minimum possible mass of a neutron star is 0.189 (solar masses) | <urn:uuid:dcd0bf3f-da72-46a1-bed8-615fd42b6347> | 3.9375 | 2,989 | Knowledge Article | Science & Tech. | 61.944206 | 95,530,325 |
Entanglement: Einstein's gift to quantum mechanics
published: March 30, 2018, recorded: March 2018, views: 37
Report a problem or upload filesIf you have found a problem with this lecture or would like to send us extra material, articles, exercises, etc., please use our ticket system to describe your request and upload the data.
Enter your e-mail into the 'Cc' field, and we will keep you updated with your request's status.
One of the surprising features predicted by quantum mechanics is what is called "entanglement" between objects in different places, which Albert Einstein famously called "spooky action at a distance", and felt was so contrary to common-sense (and incompatible with his theory of gravity) that an attempt to demonstrate it experimentally would surely show that quantum theory was not correct. But when it eventually become possible to test it experimentally, quantum mechanics passed the test. In recent years it has become apparent that while Einstein's opposition to quantum theory was wrong, the property of "entanglement" that he identified as a prediction of quantum theory is not just a curiosity that philosophers can debate, but perhaps its central ingredient. It lies at the heart of the recent discoveries of "topological quantum matter" (the work for which Haldane shared the 2016 Nobel Prize for Physics), and is now viewed as a "resource" or fuel that could drive future powerful "quantum computers". Einstein felt the introduction of the "cosmological constant" in his theory of gravity was his "biggest mistake", but today it seems likely that it is related to the recently discovered "dark energy". If his disbelief in entanglement was his "second biggest mistake", it, like the first, has been a very fruitful one indeed.
Link this pageWould you like to put a link to this lecture on your homepage?
Go ahead! Copy the HTML snippet ! | <urn:uuid:0cab032f-b57f-4f19-a01c-f05b4678890d> | 3.046875 | 389 | Truncated | Science & Tech. | 36.19365 | 95,530,354 |
Bernard Deacon @bernarddeacon
Global heatwave in a La Nina year? Don’t worry though. The UK has a ‘clean growth’ strategy. Or should that be a ‘complacency growth’ strategy?
Heatwave sees record high temperatures around world this week
From Europe to Africa, extreme and widespread heat raises climate concerns in hottest La Niña year to date on record
Record high temperatures have been set across much of the world this week as an unusually prolonged and broad heatwave intensifies concerns about climate change.
The past month has seen power shortages in California as record heat forced a surge of demand for air conditioners. Algeria has experienced the hottest temperature ever reliably registered in Africa. Britain, meanwhile, has experienced its third longest heatwave, melting the roof of a science building in Glasgow and exposing ancient hill forts in Wales.
The World Meteorological Organization (WMO) said the rising temperatures were at odds with a global cyclical climate phenomena known as La Niña, which is usually associated with cooling.
Paolo Ruti of the WMO said it was difficult to ascribe any one weather event to climate change, but that recent high temperatures, intense rains and slow-moving fronts were in line with forecasts of how rising emissions will affect the climate.
“Recent analysis suggests that anthropogenic forcing might indeed affect the characteristics of summer blocking events in the Euro-Asia sector, in particular leading to longer blocking episodes,” he said.
Extreme weather events have buffeted much of the world over the past 12months, from the “Day Zero” drought in Cape Town to the abnormally powerful hurricanes Harvey and Irma that buffeted the east coast of the US and Caribbean.
Underscoring the link, a new report from scientists at the World Weather Attribution group indicates that manmade climate change and its effect on rainfall made the recent Cape Town drought three times more likely. | <urn:uuid:e3ac2444-ab62-47fc-b455-777ba24bc7ba> | 2.8125 | 399 | News Article | Science & Tech. | 29.259541 | 95,530,360 |
Definition of geothermal
- geothermal steam
- geothermal regions
These example sentences are selected automatically from various online news sources to reflect current usage of the word 'geothermal.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.
Geothermal comes partly from the Greek thermos, "hot". Most geothermal electricity is provided by power plants situated in areas where there is significant activity of the Earth's great tectonic plates—often the same areas where volcanoes are found. But hot water from deep underground may be used by cities far from volcanoes to heat buildings or sidewalks. And a newer source of geothermal energy relies on a less dramatic kind of heat: Individual homeowners can now install heat pumps that take advantage of the 50°-60° temperature of the soil near the surface to provide heating in cold weather (and air-conditioning in the warm months). These very small-scale geothermal systems may eventually supply more useful energy than the large power plants.
: of, relating to, or using the natural heat produced inside the Earth; also : produced by such heat
What made you want to look up geothermal? Please tell us where you read or heard it (including the quote, if possible).
Test Your Emoji Exceptionalism | <urn:uuid:947a4dec-8ce9-4138-a6c2-a89b7161e4cc> | 3.59375 | 271 | Structured Data | Science & Tech. | 34.87266 | 95,530,366 |
A View from Emerging Technology from the arXiv
Brinicles and the Origin of Life
Extraordinary tubes of ice that grow down into the ocean from ice sheets could be as significant for the origin of life as hydrothermal vents, say chemists
One of the more curious processes that occur beneath the Antarctic sea ice in winter is the formation of brinicles. These are hollow tubes of ice that project down from the ice pack into the sea below, like icicles.
However, brinicles form in a very different way from icicles but are poorly understood, partly because of the difficulty in observing them. Indeed, they were only filmed forming in situ for the first time for the BBC documentary frozen planet which aired in 2011.
Today, Julyan Cartwright at the University of Granada in Spain and a few pals hope to change that by examining the formation, chemistry and structure of brinicles in more detail. They say the structures are a special form of chemical system known as a chemical garden that depends crucially on the interplay between highly concentrated brine, water close to its freezing point and the formation of ice.
But more interestingly, they say that brinicles may have played an important role in the origin of life on Earth and that similar structures elsewhere in the solar system could be equally important.
Conventional chemical gardens are tubular structures that form when metal salt crystals are immersed in certain solutions.
They occur in a number of natural situations such as in some geological formations and around hydrothermal vents.
Usually, the tubular structures grow upwards. But in brinicles, the tubes grow downwards, so what gives?
The effect occurs in the ice below the sea surface because brine has a lower freezing point then water. When trapped seawater freezes, it excludes salt increasing the salinity the brine nearby and lowering its freezing point even further.
If the ice cracks, the trapped brine can leak into the sea below and flows downwards, because it is denser than water.
What’s more, because it is so cold, the brine turns any seawater it meets into ice. That’s how the tubular structure forms and continues to grow as long as the brine flows.
This process raises interesting questions for physicists. For example, the process by which ice rejects salt to increase the salinity of brine has interesting similarities to the process of osmosis in reverse.
That’s important because reverse osmosis is the key process at work in the desalination plants that turn seawater into drinking water.
It’s just possible that a better understanding of how brinicles perform the same process to produce pure ice could lead to better ways of doing this.
But Cartwright and co’s most interesting observation is that brinicles also create chemical gradients, electric potentials and membranes–all the conditions necessary for the formation of life.
Exactly the same conditions occur at hydrothermal vents which have been the focus of attention for many biologists wanting to better understand how life might have formed.
The point that Cartwright and co-make is that brinicles can be just as interesting. “As brinicles play an important role in the dynamics of brine transport through sea ice, they might also play a role in this scenario of a cold origin of life, just as hydrothermal vents do in the hot environment theories,” they say.
What’s more, brinicles could well be ubiquitous on ocean bearing planets and moons such as Europa, where they might play equally interesting roles.
Clearly, a fascinating area where further work could be highly fruitful.
Ref: arxiv.org/abs/1304.1774: Brinicles as a Case of Inverse Chemical Gardens
Couldn't make it to EmTech Next to meet experts in AI, Robotics and the Economy?Go behind the scenes and check out our video | <urn:uuid:db205c4c-1f9f-4413-a0d4-1ad3918a4c21> | 3.875 | 814 | Truncated | Science & Tech. | 39.378619 | 95,530,368 |
Given a doubling time growth scenario, write an equation for exponential growth. Find the population at a specific time. Also, solve for the percent growth rate.
From Margaret Claypool
This algebra & precalculus video tutorial explains how to use the compound interest formula to solve investment word problems. This video contains plenty of ...
From The Organic Chemistry Tutor
Introduction to Exponential Decay. Using the exponential decay formula to calculate k, calculating the mass of carbon-14 remaining after a given time, and ...
From Khan Academy
In this video, I work through an example problem in which a population doubles every twelve hours. We come up with an exponential growth formula that can be ...
From Kisker Educational Videos
In this video I demonstrate how to calculate the growth factor, number of bacteria, rate of growth, and time to reach a population due to exponential growth. | <urn:uuid:2b0eeaf5-2eae-4774-ade4-8c9f84954d22> | 2.71875 | 178 | Content Listing | Science & Tech. | 42.170431 | 95,530,371 |
A team of researchers that included Johns Hopkins University geologist Naomi Levin has announced the discovery of a partial foot skeleton with characteristics (such as an opposable big toe bone) that don’t match those of Lucy, the human ancestor (or hominin) known to inhabit that region and considered by many to be the ancestor of all modern humans.
The discovery is important because it provides first-ever evidence that at least two pre-human ancestors lived between 3 million and 4 million years ago in the Afar region of Ethiopia, and that they had different ways of moving around the landscape.
“The foot belonged to a hominin species -- not yet named -- that overlaps in age with Lucy (Australopithecus afarensis). Although it was found in a neighboring project area that is relatively close to the Lucy fossil site, it does not look like an A. afarensis foot,” explains Levin, an assistant professor in the Morton K. Blaustein Department of Earth and Planetary Sciences in the Krieger School of Arts and Sciences.
A paper in the March 29 issue of Nature describes this foot, which is similar in some ways to the remains of another hominin fossil, called Ardipithecus ramidus, but which has different features.Its discovery could shed light on how our ancestors learned to walk upright, according to Levin.
The finding is important, Levin says, because it shows that there is much more to learn about the role of locomotion in human evolution.
“This fossil makes the story of locomotion more complex, and it shows that we have a lot more to learn about how humans transitioned from moving around in trees to moving around on the ground -- on two legs.This fossil shows that some hominins may have been capable of doing both,” she says.
The fossil, dated to approximately 3.4 million years ago, was discovered in 2009 in sediments along the Burtele drainage in the Afar region of Ethiopia that is now very hot and dry. The researchers believe the area was wetter and more wooded when the Burtele hominin lived, based on its deltaic sedimentary context, results from isotopic studies and the range of fossil animals found near the site.
“We’re just at the beginning of understanding the environmental context for this important fossil. It will be a critical part of understanding this hominin, its habitat and the role that the environment played in its evolution,” she says.
Lisa De Nike | Newswise Science News
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
16.07.2018 | Life Sciences
16.07.2018 | Earth Sciences | <urn:uuid:0c326f11-bef2-4334-8b3f-a40f6b4fa908> | 3.703125 | 1,154 | Content Listing | Science & Tech. | 41.632564 | 95,530,430 |
Large Enhancements in Dissociative Electron Attachment to Chlorine Containing Molecules Adsorbed on H2O Ice
The study of chlorine-containing molecules, especially chlorofluoro-carbons (CFCs), has received continued interest mainly because of their well-known association with the ozone depletion in the Earth’s stratosphere. It was first proposed1 that chlorine atoms are produced by photolysis of such species as CF2C12 (CFC-12) and CFCl3 (CFC-11). For the former species, the reaction is: CF2Cl2 + hv→Cl + CF2Cl. The resultant Cl atom destroys ozone via a (Cl, C1O) reaction chain. The significance of CFCs to the ozone depletion has been well recognized since the discovery of the Antarctic ozone hole.2 Nevertheless, the above photodissociation model predicts a maximum rate of Cl atom production in the upper stratosphere at altitudes of 30∼40 km and a negligible rate below 20 km.1 However, the ozone hole is found at the lower polar stratosphere at an altitude of ∼15 km. It is known that the creation of the ozone hole is closely related to the existence of polar stratospheric clouds (PSCs) that form in the Antarctic stratosphere due to the extreme cold temperature; these PSCs consist mainly of condensed-phase water ice and nitric acid/ice.3,4 The formation of the ozone hole has been attributed to heterogeneous reactions occurring on surfaces of PSC ice particles, which convert chlorine from the inactive compounds (HCl and ClONO2) into reactive Cl2: HCl + ClONO2 → Cl2 + HNO3.3,4 Upon photolysis, Cl2 releases chlorine to destroy O3.
KeywordsOzone Depletion Ozone Hole Incident Electron Energy Dissociative Electron Attachment Polar Stratospheric Cloud
Unable to display preview. Download preview PDF.
- 9.N. V. Klassen, in Radiation Chemistry: Principles and Applications, ed. by Farhataziz and M. A. Rodgers, (VCH, New Year, 1987), chap.2.Google Scholar | <urn:uuid:199e591a-4f42-4538-92a2-f974577f7391> | 3.046875 | 462 | Truncated | Science & Tech. | 43.641038 | 95,530,453 |
Main Article Content
Ecological mathematical models are useful tools to define geographic distribution and ecological features of species, playing a fundamental role in defining conservation policies. Through the various methods we can use, recently, those which work with only-presence-data are growing in popularity and particularly MaxEnt. The recent colonization of Foreste Casentinesi National Park by Black Woodpecker represent a very interesting study-case to show how this method work, analysing possible evolution of an expansion process that is still evolving.
Downloads month by month
Download data is not yet available. | <urn:uuid:5ddd617c-1c7b-4567-91d2-4eee8f62505a> | 2.734375 | 117 | Truncated | Science & Tech. | 3.255217 | 95,530,455 |
Scientists at JILA have found one possible way to solve the blinking problem and have induced quantum dots to emit photons (the smallest particles of light) faster and more consistently.
The advance could make quantum dots more sensitive as fluorescent tags in biomedical tests and single-molecule studies and steadier sources of single photons for “unbreakable” quantum encryption. JILA is a joint venture of the National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder.
By bathing the dots in a watery solution of an antioxidant chemical used as a food additive, the JILA team increased photon emission rate four- to fivefold, a “shocking” result because the rate at which light radiates is generally considered an immutable property of the dot, JILA/NIST Fellow David Nesbitt says. The JILA scientists dramatically reduced the average time delay between excitation of a quantum dot and resulting photon emission from 21 nanoseconds to 4 nanoseconds while reducing the probability of blinking up to 100 fold.
Nesbitt calls blinking the “hidden dirty secret” of quantum dots. (Nesbitt notes that blinking is not always an annoyance. For example, it can serve as a measurement probe of very slow rates of electron flow through nanoscale materials).
The quantum dots used in the JILA experiments were made of cadmium-selenide cores just 4 nanometers wide coated with zinc sulfide. When a dot is excited by a brief laser pulse, one electron is separated from the “hole” it normally occupies. A few nanoseconds later, the electron typically falls back into the hole, sometimes producing a single photon—always in a color that depends on dot size, greenish-yellow in this case.
But every so often the electron fails to make it back to its hole and instead is ejected to imperfections on the dot’s surface. The chemical added at JILA apparently attaches to these imperfections, blocking the electron from being trapped and thereby preventing the dot from blinking off.
Laura Ost | EurekAlert!
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Materials Sciences
18.07.2018 | Life Sciences
18.07.2018 | Health and Medicine | <urn:uuid:305ac8a5-f29c-42e4-b1ed-fdc6657705b4> | 3.515625 | 1,075 | Content Listing | Science & Tech. | 37.679869 | 95,530,456 |
We live in a galaxy known as the Milky Way – a vast conglomeration of 300 billion stars, planets whizzing around them, and clouds of gas and dust floating in between.
Though it has long been known that the Milky Way and its orbiting companion Andromeda are the dominant members of a small group of galaxies, the Local Group, which is about 3 million light years across, much less was known about our immediate neighbourhood in the universe.
Now, a new paper by York University Physics & Astronomy Professor Marshall McCall, published today in the Monthly Notices of the Royal Astronomical Society, maps out bright galaxies within 35-million light years of the Earth, offering up an expanded picture of what lies beyond our doorstep.
"All bright galaxies within 20 million light years, including us, are organized in a 'Local Sheet' 34-million light years across and only 1.5-million light years thick," says McCall. "The Milky Way and Andromeda are encircled by twelve large galaxies arranged in a ring about 24-million light years across – this 'Council of Giants' stands in gravitational judgment of the Local Group by restricting its range of influence."
McCall says twelve of the fourteen giants in the Local Sheet, including the Milky Way and Andromeda, are "spiral galaxies" which have highly flattened disks in which stars are forming. The remaining two are more puffy "elliptical galaxies", whose stellar bulks were laid down long ago. Intriguingly, the two ellipticals sit on opposite sides of the Council. Winds expelled in the earliest phases of their development might have shepherded gas towards the Local Group, thereby helping to build the disks of the Milky Way and Andromeda.
McCall also examined how galaxies in the Council are spinning. He comments: "Thinking of a galaxy as a screw in a piece of wood, the direction of spin can be described as the direction the screw would move (in or out) if it were turned the same way as the galaxy rotates. Unexpectedly, the spin directions of Council giants are arranged around a small circle on the sky. This unusual alignment might have been set up by gravitational torques imposed by the Milky Way and Andromeda when the universe was smaller."
The boundary defined by the Council has led to insights about the conditions which led to the formation of the Milky Way. Most important, only a very small enhancement in the density of matter in the universe appears to have been required to produce the Local Group. To arrive at such an orderly arrangement as the Local Sheet and its Council, it seems that nearby galaxies must have developed within a pre-existing sheet-like foundation comprised primarily of dark matter.
"Recent surveys of the more distant universe have revealed that galaxies lie in sheets and filaments with large regions of empty space called voids in between," says McCall. "The geometry is like that of a sponge. What the new map reveals is that structure akin to that seen on large scales extends down to the smallest."
York University is helping to shape the global thinkers and thinking that will define tomorrow. York U's unwavering commitment to excellence reflects a rich diversity of perspectives and a strong sense of social responsibility that sets us apart. A York U degree empowers graduates to thrive in the world and achieve their life goals through a rigorous academic foundation balanced by real-world experiential education. As a globally recognized research centre, York U is fully engaged in the critical discussions that lead to innovative solutions to the most pressing local and global social challenges. York U's 11 faculties and 27 research centres are thinking bigger, broader and more globally, partnering with 288 leading universities worldwide. York U's community is strong − 55,000 students, 7,000 faculty and staff, and more than 250,000 alumni.
Media Contact: Robin Heron, Media Relations, York University, 416 736 2100 x22097/ email@example.com
Robin Heron | EurekAlert!
What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
18.07.2018 | Materials Sciences
18.07.2018 | Life Sciences
18.07.2018 | Health and Medicine | <urn:uuid:dd860b63-bea4-4599-99f7-01c0f00cb970> | 4.21875 | 1,446 | Content Listing | Science & Tech. | 44.236857 | 95,530,457 |
NASA's Mars Atmosphere and Volatile Evolution (MAVEN) mission has identified the process that appears to have played a key role in the transition of the Martian climate from an early, warm and wet environment that might have supported surface life to the cold, arid planet Mars is today.
MAVEN data have enabled researchers to determine the rate at which the Martian atmosphere currently is losing gas to space via stripping by the solar wind. The findings reveal that the erosion of Mars' atmosphere increases significantly during solar storms. The scientific results from the mission appear in the Nov. 5 issues of the journals Science and Geophysical Research Letters.
"Mars appears to have had a thick atmosphere warm enough to support liquid water which is a key ingredient and medium for life as we currently know it," said John Grunsfeld, astronaut and associate administrator for the NASA Science Mission Directorate in Washington. "Understanding what happened to the Mars atmosphere will inform our knowledge of the dynamics and evolution of any planetary atmosphere. Learning what can cause changes to a planet's environment from one that could host microbes at the surface to one that doesn't is important to know, and is a key question that is being addressed in NASA's journey to Mars."
MAVEN measurements indicate that the solar wind strips away gas at a rate of about 100 grams (equivalent to roughly 1/4 pound) every second. "Like the theft of a few coins from a cash register every day, the loss becomes significant over time," said Bruce Jakosky, MAVEN principal investigator at the University of Colorado, Boulder. "We've seen that the atmospheric erosion increases significantly during solar storms, so we think the loss rate was much higher billions of years ago when the sun was young and more active."
In addition, a series of dramatic solar storms hit Mars' atmosphere in March 2015, and MAVEN found that the loss was accelerated. The combination of greater loss rates and increased solar storms in the past suggests that loss of atmosphere to space was likely a major process in changing the Martian climate.
The solar wind is a stream of particles, mainly protons and electrons, flowing from the sun's atmosphere at a speed of about one million miles per hour. The magnetic field carried by the solar wind as it flows past Mars can generate an electric field, much as a turbine on Earth can be used to generate electricity. This electric field accelerates electrically charged gas atoms, called ions, in Mars' upper atmosphere and shoots them into space.
MAVEN has been examining how solar wind and ultraviolet light strip gas from of the top of the planet's atmosphere. New results indicate that the loss is experienced in three different regions of the Red Planet: down the "tail," where the solar wind flows behind Mars, above the Martian poles in a "polar plume," and from an extended cloud of gas surrounding Mars. The science team determined that almost 75 percent of the escaping ions come from the tail region, and nearly 25 percent are from the plume region, with just a minor contribution from the extended cloud.
Ancient regions on Mars bear signs of abundant water – such as features resembling valleys carved by rivers and mineral deposits that only form in the presence of liquid water. These features have led scientists to think that billions of years ago, the atmosphere of Mars was much denser and warm enough to form rivers, lakes and perhaps even oceans of liquid water.
Recently, researchers using NASA's Mars Reconnaissance Orbiter observed the seasonal appearance of hydrated salts indicating briny liquid water on Mars. However, the current Martian atmosphere is far too cold and thin to support long-lived or extensive amounts of liquid water on the planet's surface.
"Solar-wind erosion is an important mechanism for atmospheric loss, and was important enough to account for significant change in the Martian climate," said Joe Grebowsky, MAVEN project scientist from NASA's Goddard Space Flight Center in Greenbelt, Maryland. "MAVEN also is studying other loss processes—such as loss due to impact of ions or escape of hydrogen atoms—and these will only increase the importance of atmospheric escape."
The goal of NASA's MAVEN mission, launched to Mars in November 2013, is to determine how much of the planet's atmosphere and water have been lost to space. It is the first such mission devoted to understanding how the sun might have influenced atmospheric changes on the Red Planet. MAVEN has been operating at Mars for just over a year and will complete its primary science mission on Nov. 16.
Explore further: Sputtering: How mars may have lost its atmosphere
More information: "MAVEN observations of the response of Mars to an interplanetary coronal mass ejection," by B.M. Jakosky et al. www.sciencemag.org/lookup/doi/ … 1126/science.aad0210
"Early MAVEN Deep Dip campaign reveals thermosphere and ionosphere variability," by S. Bougher et al. www.sciencemag.org/lookup/doi/ … 1126/science.aad0459
"Discovery of diffuse auroras on Mars," by N.M. Schneider et al. www.sciencemag.org/lookup/doi/ … 1126/science.aad0313
"Dust observations at orbital altitudes surrounding Mars," by L. Andersson et al. www.sciencemag.org/lookup/doi/ … 1126/science.aad0398 | <urn:uuid:6f54ceff-ec27-4fa5-a649-40d56a9793a5> | 3.671875 | 1,110 | Knowledge Article | Science & Tech. | 46.646644 | 95,530,466 |
What is shell scripting?
What is shell scripting?
When talking about "programming" people tend to think that all code is a "program", but this just isn't true. Languages like VB, and C/C++, require that you first take the code that you write, and convert it to machine code (compile). After that (often done in the same step) you then "link" your code together into a Program. Linking has to do with putting together required external code (libraries) that are required by your program. Anyway, getting off topic, "Programming" is compiled into machine code.
Scripting is a different animal. Scripting doesn't require (from a top level view, anyways) that the code you write be compiled. Now, obviously before any code can run on a system, it must first be converted, but the compilation and linking isn't done by the programmer in a script. You have a program (typically called an Interpreter) that runs the lines of the script, and essentially compiles them on the fly. So, as the script writer, all you have to do is make changes to your script, and run it. The only drawbacks to this, is that your code is always available for view by anyone (that's actually a plus if you ask me), and it's slower when running. Compiled programs are typically fast, and scripts are usually slow. I wouldn't write something like a video game (even if there are libraries for it) in a scripting language. I might do something not time critical in one though. That's the general difference between programming and scripting, and I guess helps to answer what a "script" is.
In *nix, you have a wide variety of interfaces, because the idea is that the user is in control of their environment, unlike an OS such as windows, where you pretty much have to deal with the same interfaces. The command line in windows/DOS will never change...the syntax, etc. In *nix you can choose your own interface for the command line...this interface is called a shell. The most popular (by far) interface is Bash (The Bourne Again Shell). Most (if not all) operating systems provide a way to "batch commands" into a single file. So that when you run this simple script, it does a sequence of command line commands, that are typically repetitious and a pain to type over and over. Don't underestimate its power however, thinking that it is stuck just with batched command line commands.... it has the power of if statements, and loops, for conditional branching and recursive behavior. Shell scripts are a very powerful tool, that are often overlooked.
thanks for the quick and in-depth reply, What kind of things have people have managed to do with shell scripting?
also, i know this might not be the right place to ask, but how do people become a moderator of the forums?
That's a list there. People will be able to post answers to that question for ages..... a couple common uses of Shell Scripts have been things such as log file rotations (programs can generate files that detail what it did, or what occured, called a log, they get too big, and a company wants them archived, so they build a shell script to automatically copy the log, (or group of logs) compress them, and back them up, then clear/remove the originals). There have been shell scripts to download youtube video's to your hard-drive... heck, a lot of startup scripts (startx... a big one) is a shell script. Shell scripts that monitor zombie processes...etc, etc. It's a big list.
So I have a JTextfield in the cells of 1 of the columns in my JTable
I want to allow only numbers and up to one dot/period. Doesant ...
vb.Net - Regular Expression Tester
Every now and then I find another use for a regular expression. For those not familiar with regular expressions, they can be as cryptic to ...
I'm trying to build a client and a server in the same program. For example, user 1 sends a packet of data to user 2, user 2 after receiving the ... | <urn:uuid:848c2679-6f89-42b6-86c1-f62b07bdd32d> | 3.234375 | 876 | Comment Section | Software Dev. | 68.162324 | 95,530,467 |
Behavior-Driven Development is a software development process that puts feature behaviors first. A behavior is how a feature operates within a well-defined scenario of inputs, actions, and outcomes. Behaviors are identified using specification by example. Behavior specs become the requirements, the acceptance criteria, and the acceptance tests. Test frameworks can directly automate specs as well – declarative specs for unique product behaviors should be the units of coverage. The most prevalent BDD test frameworks are Cucumber derivatives that write specs in the “Given-When-Then” Gherkin language.
- The Big BDD Picture is better collaboration and automation.
- The Cardinal Rule of BDD is one scenario, one behavior.
- The Golden Gherkin Rule is to treat other readers as you would want to be treated.
- Write Gherkin so that people who don’t know the feature will understand it.
BDD 101 is the go-to resource for learning BDD (and the most popular series on the blog).
- Introducing BDD
- The Gherkin Language
- Gherkin By Example
- Writing Good Gherkin
- Behavior-Driven Agile
- Unit, Integration, and End-to-End Tests
- Test Data
- Manual Testing
- 12 Awesome Benefits of BDD
- BDD Example Mapping
- ‑‑BDD; Automation without Collaboration
- BDD‑‑; Collaboration without Automation
- The Airing of Grievances: BDD
- The Behavior-Driven Three Amigos
- Who Should Lead BDD?
- Winning Support for BDD
- Are Gherkin Scenarios with Multiple When-Then Pairs Okay?
- Are Multiple Scenario Outlines in a Feature File Okay?
- Good Gherkin Scenario Titles
- In BDD, What Should Be A Feature?
- Should Gherkin Steps Use First-Person or Third-Person?
- 10 Things You Lose Without Automation
- 5 Things I Love About SpecFlow
- Cucumber-JVM for Java
- Cucumber-JVM Global Hook Workarounds
- Gherkin Syntax Highlighting in Atom
- Gherkin Syntax Highlighting in Chrome
- Gherkin Syntax Highlighting in Notepad++
- Pipe Character Escape for Gherkin Tables
- YAML Comments in Gherkin Feature Files
- Gherkin language reference
- Introducing BDD by Dan North
- Introducing Example Mapping, a recorded webinar from Cucumber
Like to cook? Try my cucumber recipe! | <urn:uuid:44a5f477-50ca-4fd7-867c-fb49b879d16c> | 2.921875 | 557 | Listicle | Software Dev. | 34.088881 | 95,530,478 |
Based on his successful work Special Relativity and Motions Faster than Light , Moses Fayngold has written a thorough presentation of the special theory of relativity. The unique feature of the textbook is its two-leveled structure helping students to master the material more effectively: the first level presents a qualitative discussion of a problem, while the second one contains its rigorous treatment. Fayngold points out the connection between fundamental principles and known phenomena. In three new chapters on 'Relativity at Work' (Electromagnetism, Optics, Quantum Mechanics), he not only shows what relativity is, but also how it works. The scope of new material extends to include a chapter on Causality and on Applied Relativity, including astrophysical and accelerator topics. Backed throughout by numerous examples and exercises. | <urn:uuid:221429d1-8f1d-4018-bba3-89a09fcf128a> | 3.40625 | 161 | Product Page | Science & Tech. | 16.489167 | 95,530,481 |
Type Function Object File Library io.* Return value Number Revision 2018.3332 Keywords seek, files See also io.open()
Sets and gets the file position, measured from the beginning of the file, to the position given by offset plus a base.
The function can be used to get the current file position (
"set" the file position to the beginning, end, or any position between.
File:seek( [mode] [, offset] )
String. Can be one of the following values:
"set"— base is position 0 (beginning of the file)
"cur"— base is current position (default)
"end"— base is end of file
The default value for mode is
"cur", and for offset is
0. Therefore, the call
File:seek() returns the current file position without changing it. The call
File:seek("set") sets the position to the beginning of the file and returns
0. The call
File:seek("end") sets the position to the end of the file, and returns its size.
Number. Specifies the position for the
"set" mode. The number is
0 based (which is the beginning of the file).
local fh = io.tmpfile() fh:write( "My temporary file data" ) fh:flush() -- Ensure data written to file print( "file position: ", fh:seek() ) -- Show current position fh:seek( "set", 0 ) -- Reset file position to beginning local content = fh:read( "*a" ) -- Read all the file print( "File content: " .. content ) print( "file position: ", fh:seek("end") ) -- Show the end position of file | <urn:uuid:a3b3ce5f-a1f7-4793-8608-8bd1d6c51858> | 4.09375 | 372 | Documentation | Software Dev. | 62.454428 | 95,530,486 |
Photon-Counting Monolithic Avalanche Photodiode Arrays for the Super Collider
In fiber tracking, calorimetry, and other high energy and nuclear physics experiments, the need arises to detect an optical signal consisting of a few photons (in some cases a single photoelectron) with a detector insensitive to magnetic fields. Previous attempts to detect a single photoelectron have involved avalanche photodiodes (APDs) operated in the Geiger mode , the visible light photon counter , and a photomultiplier tube with an APD as the anode . In this paper it is demonstrated that silicon APDs, biased below the breakdown voltage, can be used to detect a signal of a few photons with conventional pulse counting circuitry at room temperature. Moderate cooling, it is further argued, could make it possible to detect a single photoelectron.
KeywordsBreakdown Voltage Ionization Rate Avalanche Photodiode Fiber Tracking Shaping Time
Unable to display preview. Download preview PDF.
- 3.P. Cushman and R. Rusack, “A PMT Using Avalanche Photodiodes,” Conference Record of the 1992 IEEE Nuclear Science Symposium, Vol.1, p.278, 1992Google Scholar
- 4.A. N. Ishaque, “Noise Modeling of Deep-Diffused Avalanche Photodiodes,” GE-CRD Internal Report, 1992Google Scholar
- 5.A. N. Ishaque, “Electric Field Profile and Potential Distribution in a Deep-Diffused Avalanche Photodiode,” GE-CRD Internal Report, 1992Google Scholar
- 7.J. M. Pimbley, “Avalanche Ionization in the Presence of a Bandgap Discontinuity,” GE-CRD Internal Report, 1991.Google Scholar
- 8.A. N. Ishaque, “Analytical Approximation of the Ionization Rate in Semiconductors,” GE-CRD Internal Report, 1991.Google Scholar | <urn:uuid:88c14cfc-887d-4979-ab8a-b4b1f50ef1b1> | 2.8125 | 425 | Truncated | Science & Tech. | 34.66054 | 95,530,515 |
A chemistry question asks which of the following has three lone pairs of electrons around the central atom and the possible multiple choice answers include BF2 -
(2 flourines and a negative charge) and CIF2 - ? I thought only a metal and non metal could form an ionic bond? do I not know this because I've just started year 12 and I haven't learnt of this yet?
Turn on thread page Beta
How can two non metals bond and form an ion? watch
- Thread Starter
- 29-10-2017 16:19
- 29-10-2017 16:28
It’s not ionic bonding that the question is about, the answer is ClF2 - because the Cl is in group 7 so naturally has 7 outer electrons, when bonded to two other atoms it would have 2 lone pairs and a free radical (don’t worry if you haven’t learnt this yet because you will) adding another electron causes the free radical to just become another line pair whilst giving an overall charge or -1 because of the extra electron
- 29-10-2017 16:36
ClF2- will have 3 lone pairs of electrons around the central atom (Cl). This is because chlorine has 7 valence electrons (it's in group 7), and flourine has 7 valence electrons, and there's two of them. There's also a negative charge, meaning there's one extra electron.
Add the number of electrons up, you get 22 electrons. A full outer shell will have 8 electrons, so if you take away the highest multiple of 8 under the number of electrons (22), you get 16. 22-16=6. So there are 6 electrons unpaired around the central atom, but they exist in pairs, so 6/2=3. There are 3 lone pairs.
If you draw the dot and cross structure of ClF2- you will see this shown more clearly. Also, these compounds do not have ionic bonding, they show covalent bonding, they share electron pairs. | <urn:uuid:ee36a056-04b6-4579-98cb-e4c20a2fb05c> | 3.921875 | 421 | Comment Section | Science & Tech. | 69.567195 | 95,530,532 |
IceCube spots a neutrino source: A black hole jet pointed at Earth
For most of astronomy’s history, understanding the heavens was limited to what we could see: the narrow band of the electromagnetic spectrum that constitutes visible light. Only over the last century or so have we expanded beyond that, into the infrared and microwaves and up into the higher energies of X-rays and gamma-rays. The past few years have brought an even more fundamental change: we’ve started detecting astronomical events without photons at all. This was done most famously by LIGO, the hardware that detected gravitational waves. But LIGO was actually late to the game, as the South Pole’s IceCube detector had started listening in on cosmic neutrinos a few years earlier.
But in one critical aspect, LIGO beat IceCube to the punch: it spotted an event where the gravitational wave signal was paired with an optical signal, a burst of gamma rays. This marked the first instance of what’s being termed “multimessenger” astronomy, where a single event is observed using physically distinct signals.
While IceCube has spotted some phenomenally energetic neutrinos, we’ve not been able to match those with a specific photon source. As of today, that has changed with the announcement that an energetic neutrino was likely to have been sent our way by a blazar, a supermassive black hole with a jet pointed in Earth’s direction. | <urn:uuid:2b76e51d-732e-4f6c-bf4d-942f8acd2d52> | 3.4375 | 307 | News Article | Science & Tech. | 31.766158 | 95,530,537 |
An effective mechanism for rapid and efficient microfluidic particle trapping and concentration is proposed without requiring any mechanically moving parts. When a voltage beyond the threshold atmospheric ionization value is applied on a sharp electrode tip mounted at an angle above a microfluidic liquid chamber, the bulk electrohydrodynamic air thrust that is generated results in interfacial shear and, hence, primary azimuthal liquid surface recirculation. This discharge driven vortex mechanism, in turn, causes a secondary bulk meridional liquid recirculation, which produces an inward radial force near the bottom of the chamber. Particles suspended in the liquid are then rapidly convected by the bulk recirculation toward the bottom, where the inward radial force causes them to spiral in a helical swirl-like fashion toward a stagnation point. In particular, we show that these flows, similar to Batchelor flows occurring in a cylindrical liquid column between a stationary and rotating disk, can be used for the separation of red blood cells from blood plasma in a miniaturized device.
Mendeley saves you time finding and organizing research
Choose a citation style from the tabs below | <urn:uuid:622442c7-4246-42b5-8908-1a86786ffc90> | 2.640625 | 234 | Academic Writing | Science & Tech. | 2.29421 | 95,530,544 |
Jimmy Westlake: A great year for Orionid Meteors
October 13, 2009
Did you get to see Halley’s Comet when it sailed past Earth in 1985 and ’86? If not, you’ll have to wait until the year 2061 for another chance, because Halley’s Comet requires 76 years to orbit the sun. In the meantime, you can watch tiny pieces of Halley’s Comet rain down into the Earth’s atmosphere every May and October during our annual Aquarid and Orionid meteor showers.
Comets are like big, dirty snowballs that hover near the outer edges of the solar system in perpetual cold and dark. But every so often, the gravity of the sun tugs a comet into the warm inner regions of the solar system. As the snowball approaches the sun, the solar heat vaporizes the top layers of ice, releasing clouds of steam and millions of tiny dust grains trapped in the ice. The combined forces of sunlight and solar wind blow the gaseous vapors away from the snowball, forming the comet’s graceful, flowing tail and filling the comet’s path with dusty debris. After a comet has made many passes around the sun, its orbit may fill with dusty debris, like a river of dust in space.
The Earth crosses Halley’s dust river twice each year, once on May 5 and again on Oct. 21. When one of these dust particles plows into the Earth’s upper atmosphere at nearly 150,000 mph, it incinerates in a brief but brilliant flash of light called a meteor. Cometary dust grains are so small that you could easily hold 1,000 of them in the cupped palm of your hand.
This October’s Orionid meteor shower will peak between the hours of midnight and dawn on the morning of Oct. 21. A single observer with the benefit of dark, clear skies might see between one and two dozen meteors, or “shooting stars,” each hour. The slender crescent moon will set early in the evening this year, leaving the sky nice and dark for meteor watching.
The October meteors that Halley’s Comet sends our way are called Orionid meteors because they seem to fan out from a point in the sky near the familiar star pattern of Orion the Hunter. Orion doesn’t rise above our eastern horizon until about 11 p.m. in late October, so don’t expect to see many meteors before midnight. You’ll see Orionid meteors in every part of the sky, but they will all point back to a common origin near Orion’s bright star Betelgeuse, high in the southeastern sky at about 4 a.m. The closer to dawn you watch, the more meteors you will likely see, as the Earth rotates us more in the direction of Orion. And, although the peak of the meteor activity occurs on the morning of Oct. 21, you can still see a few Orionid meteors on the mornings of Oct. 20 and 22, as well.
Consider the Orionid meteor shower a warm-up for 2061, when Halley’s Comet itself returns.
Recommended Stories For You
Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. He is an avid astronomer whose photographs and articles have been published all around the world. Check out Jimmy’s Web site at http://www.jwestlake.com.
Trending In: Explore Steamboat
- Man self-splints broken arm after being thrown from horse in Zirkels
- City to consider vacating easements near RiverView development on Yampa River
- Steamboat dog makes miraculous recovery
- Routt County real estate transactions for July 6 to 12, 2018
- Drinking in the library: The Record for Saturday, July 14, 2018 | <urn:uuid:06f3e5d4-f19d-4b0d-a01d-07a7f928733a> | 3.40625 | 808 | Personal Blog | Science & Tech. | 63.692354 | 95,530,547 |
Experimental Methods and Procedures in Monolayers
When a very small amount of a virtually insoluble and nonvolatile organic substance is carefully placed on the surface of water, which has a relatively high surface tension, either of the following results may be observed: (1) The substance may remain as a compact drop (or as a solid mass), leaving the rest of the liquid surface clean, or (2) it may spread out over the entire available surface of the water. The formation of a stable monolayer by any substance is determined by the interactive forces between that substance and the subphase, water.
KeywordsSurface Viscosity Monomolecular Film Ethyl Laurate Torsion Wire Spread Monolayer
Unable to display preview. Download preview PDF. | <urn:uuid:944d393b-42a5-46bf-883d-d7cd4123d307> | 2.578125 | 159 | Truncated | Science & Tech. | 15.177019 | 95,530,568 |
Characteristics and failure mechanism of an ancient earthquake-induced landslide with an extremely wide distribution area
- 63 Downloads
The Lamuajue landslide is located in Lamuajue village on the right bank of the Meigu River, Sichuan Province, China. This landslide is an ancient landslide with an extremely wide distribution area, covering an area of 19 km2 with a maximum width of 5.5 km and an estimated residual volume of 3×108 m3. The objectives of this study were to identify the characteristics and failure mechanism of this landslide. In this study, based on field investigations, aerial photography, and profile surveys, the boundary, lithology, structure of the strata, and characteristics of the landslide deposits were determined. A gently angled weak interlayer consisting of shale was the main factor contributing to the occurrence of the Lamuajue landslide. The deposition area can be divided into three zones: zone A is an avalanche deposition area mainly composed of blocks, fragments, and debris with diameters ranging from 0.1 m to 3 m; zone B is a residual integrated rock mass deposition area with large blocks, boulders and “fake bedrock”; and zone C is a deposition zone of limestone blocks and fragments. Three types of failure mechanism were analyzed and combined to explain the Lamuajue landslide based on the features of the accumulation area. First, a shattering–sliding mechanism caused by earthquakes in zone A. Second, a sliding mechanism along the weak intercalation caused by gravity and water in zone B. Third, a shattering–ejection mechanism generated by earthquakes in zone C. The results provide a distinctive case for the study of gigantic landslides induced by earthquakes, which is very important for understanding and assessing ancient earthquakeinduced landslides.
KeywordsEarthquake-induced landslide Lamuajue landslide Ancient landslide Geological feature Failure mechanism
Unable to display preview. Download preview PDF.
This research is financially supported by the Open Research Fund from the Key Laboratory of Mountain Hazards and Earth Surface Process (Chinese Academy of Sciences) (Grant No. KLMHESP-17-06), the Independent Research Fund from the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection (Chengdu University of Technology) (Grant No. 40100-00002219). We thank Prof. LU Guo-ping and reviewers for their constructive comments which helped in improving our paper.
- Cheng J, Liu J, Xu XW, Gan WJ (2014) Tectonic characteristics of strong earthquakes in Daliangshan sub-block and impact of the Ms6.5 Ludian earthquake in 2014 on the surrounding faults. Seismology and Geology 36(4): 1229–1241. https://doi. org/10.3969/j.issn.0253-4967.2014.04.023 (In Chinese)Google Scholar
- Cui YL, Deng JH, Dai FC, et al. (2015) Causes Analysis of Ancient Landslides Based on the Landscape and Kinematical Characteristics. Journal of Sichuan University (Engineering Science Edition) 47(1): 69–73. https://doi.org/10.15961/j.jsuese.2015.01.010 (In Chinese)Google Scholar
- Dong JJ, Yang CM, Yu WL, et al. (2013) Velocity-displacement dependent friction coefficient and the kinematics of giant landslide. In: Ugai K, Yagi H, Wakai A (eds) Earthquake-Induced Landslides. Springer, Berlin, Heidelberg. pp 395–401. https://doi.org/10.1007/978-3-642-32238-9_41Google Scholar
- Guerricchio A, Doglioni A, Galeandro A, et al. (2010) Deep seated gravitational slope deformation and hydraulic vulnerability of the low Biferno valley (southern Italy). Proceedings 11th IAEG, Auckland, New Zealand. pp 683–689.Google Scholar
- Huang RQ (2009) Mechanism and geomechanical modes of landslide hazards triggered by Wenchuan 8.0 earthquake. Chinese Journal of Rock Mechanics and Engineering 28(6): 1239–1249. (In Chinese)Google Scholar
- Huang RQ (2015) Understanding the Mechanism of Large-Scale Landslides. In: Lollino G, et al. (eds.), Engineering Geology for Society and Territory-Volume 2, Springer. pp 13–32. https://doi.org/10.1007/978-3-319-09057-3_2Google Scholar
- Sepúlveda SA, Murphy W, Jibson RW, et al. (2005) Seismically induced rock slope failures resulting from topographic amplification of strong ground motions: the case of Pacoima Canyon, California. Engineering Geology 80(3–4): 336–348. https://doi.org/10.1016/j.enggeo.2005.07.004CrossRefGoogle Scholar
- Togo T, Shimamoto T, Dong JJ, et al. (2014) Triggering and runaway processes of catastrophic Tsaoling landslide induced by the 1999 Taiwan Chi-Chi earthquake, as revealed by highvelocity friction experiments. Geophysical Research Letters 41(6): 1907–1915. https://doi.org/10.1002/2013GL059169CrossRefGoogle Scholar
- Xu Q, Pei XJ, Huang RQ (2009) Large-scale landslides induced by the Wenchuan earthquake. Science Press, Beijing. pp 22–28. (In Chinese)Google Scholar
- Xu Q, Liu HX, Zou W, et al. (2010) Large-scale shaking table test study of acceleration dynamic responses characteristics of slopes. Chinese Journal of Rock Mechanics and Engineering 29(12): 2421–2428. (In Chinese)Google Scholar
- Yang CM, Yu WL, Dong JJ, et al. (2014), Initiation, movement, and run-out of the giant Tsaoling landslide — What can we learn from a simple rigid block model and a velocitydisplacement dependent friction law? Engineering Geology 182: 158–181. https://doi.org/10.1016/j.enggeo.2014. 08.008CrossRefGoogle Scholar
- Zhang ZY, Wang ST, Wang LS (1981) Principles of Engineering Geological Analysis. Geological Publishing House. Beijing, China. pp 245–246. (In Chinese)Google Scholar
- Zhang ZY, Wang ST, Wang LS, et al. (2009) Principles of Engineering Geological Analysis. Geological Publishing House. Beijing, China. p 287. (In Chinese)Google Scholar | <urn:uuid:86b09473-7432-47bd-aaa1-62f3de24a218> | 2.859375 | 1,406 | Academic Writing | Science & Tech. | 57.982266 | 95,530,571 |
Bioremediation of Tannery Effluents by Filamentous Cyanobacteria Anabaena Flos-Aquae West
Received Date: Aug 09, 2011 / Accepted Date: Oct 19, 2011 / Published Date: Oct 29, 2011
Heavy metal pollution of ground and surface waters by industrial effluents has become a serious threat to the environment especially in developing countries. Though many conventional physicochemical methods are currently being practiced, biotechnological methods are becoming attractive alternatives, as they are economical and eco-friendly. In this study, the search for innovative and eco-friendly biotechnologies to remove toxicants from effluents has focused attention on the detoxification capacity of a variety of microbe\'s especially cyanobacteria. The treated effluents from tannery industry were collected and added to the cyanobacterial growth medium in various proportions. The photosynthetic pigments and nitrogen status of Anabaena flos-aquae were analysed before and after the treatment with effluent. The present investigations showed that Anabaena flos-aquae can serve as the potential bioremedial organism for industrial pollution.
Citation: Kannan V, Vijayasanthi M, Rajmohan N (2011) Bioremediation of Tannery Effluents by Filamentous Cyanobacteria Anabaena Flos-Aquae West. Hydrol Current Res 2: 122. Doi: 10.4172/2157-7587.1000122
Copyright: © 2011 Kannan V, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Select your language of interest to view the total content in your interested language
Share This Article
4th World Congress on Climate Change and Global Warming
August 06-07, 2018 Osaka, Japan
International Conference on Environment and Climate Change
September 13-14,2018 Bucharest, Romania
- Total views: 11747
- [From(publication date): 12-2011 - Jul 22, 2018]
- Breakdown by view type
- HTML page views: 7943
- PDF downloads: 3804 | <urn:uuid:7413f78e-1dde-4386-98cf-c197810310ef> | 2.546875 | 471 | Truncated | Science & Tech. | 18.234847 | 95,530,606 |
|کد مقاله||کد نشریه||سال انتشار||مقاله انگلیسی||ترجمه فارسی||نسخه تمام متن|
|5744804||1412370||2017||5 صفحه PDF||سفارش دهید||دانلود کنید|
The use of artificial light at night and its ecological consequences are increasing around the world. Light pollution can lead to massive mortality episodes for nocturnally active petrels, one of the most threatened avian groups. Some fledglings can be attracted or disoriented by artificial light on their first flights. Studies testing the effect of artificial light characteristics on attractiveness to seabirds have not provided conclusive results and there is some urgency as some endangered petrel species experience high light-induced mortality. We designed a field experiment to test the effect of three common outdoor lighting systems with different light spectra (high pressure sodium, metal halide and light emitting diode) on the number and the body condition of grounded fledglings of the short-tailed shearwater Ardenna tenuirostris. A total of 235 birds was grounded during 99 experimental hours (33Â h for each treatment). 47% of birds was grounded when metal halide lights were on, while light emitting diode and high pressure sodium lights showed lower percentages of attraction (29% and 24%). Metal halide multiplied the mortality risk by a factor of 1.6 and 1.9 respectively in comparison with light emitting diode and high pressure sodium lights. No differences in body condition were detected among the birds grounded by the different lighting systems. We recommend the adoption of high pressure sodium lights (or with similar spectra) into petrel-friendly lighting designs together with other light mitigation measures such as light attenuation, lateral shielding to reduce spill and appropriate orientation.
Journal: Journal for Nature Conservation - Volume 39, September 2017, Pages 68-72 | <urn:uuid:ebeecc63-fffe-4ede-88de-c30da87a361f> | 2.78125 | 455 | Truncated | Science & Tech. | 39.827418 | 95,530,607 |
Now, evolutionary and developmental biologists at the University of Georgia and the Hebrew University of Jerusalem have uncovered evidence that after fruit flies mate, the presence of sperm and male proteins in the female's reproductive tract sets off an amazing cascade of heretofore undescribed gene activity. Understanding how this works will give scientists new insights into reproduction, but it could also provide methods to safely control the spread of insect pests by interfering with their reproduction.
"We have been able to define a large number of mating-responsive genes that are activated in Drosophila," said Michael Bender, a developmental biologist in the department of genetics at UGA. "There is a lot of potential in this work for uncovering basic aspects of reproductive biology that will be useful in pest-control approaches."
The research was just published in the online edition of the Proceedings of the National Academy of Sciences. The work resulted from a collaboration between Bender, Paul Mack, a postdoctoral fellow in the Bender lab at UGA, Yael Heifetz of Hebrew University and Anat Kapelnikov, a graduate student in the Heifetz lab. A number of undergraduates at UGA also worked on the research.
Drosophila has been used as a model animal for nearly a century. It is easy to manipulate in a lab, lives only a few weeks and begins mating soon after hatching. Its entire genetic map or genome has also been sequenced, giving researchers a powerful tool in understanding intricate biological processes and the genes that direct them.
Bender's team, using both the established genomic background of Drosophila and studies of mating insects, showed that the sperm and proteins transferred from males to females during mating have "profound effects" on female gene expression. Most surprising is that gene activity rapidly escalates about six hours after mating--something previously unknown.
"We looked at the reproductive tracts of females at three, six and 24 hours post-mating," said Mack. "Just getting enough material through dissection is extremely difficult and time-consuming, but this kind of time-based evaluation of post-mating gene expression in Drosophila had never been done."
Perhaps surprisingly, very little is known about how gene expression in female reproductive tissues changes in response to the presence of sperm and male molecules. The study compared 3-day-old mated and unmated females and discovered the presence in mated females of a startling 539 genes whose activity changes after mating.
"One novel feature of this research was Paul's decision to look at what happens over time," said Bender. "That's how we found out that the activity hits a peak six hours after mating. This indicates quite a large genetic response in the female tract to male-derived molecules and sperm."
Though considerable research has been done on male Drosophila over the years, relatively little had focused on females. Just why the array of gene expression peaks at 6 hours is not yet clear, but revealing this timing could help in controlling insect pests. That is one reason the research was funded by the Binational Agricultural Research and Development (BARD) Fund, a joint program between the United States and Israel. Since 1979, BARD has funded nearly 900 research projects in almost all 50 states. Support for the research also came from The National Institutes of Health.
The Bender and Heifetz teams weren't operating in the dark, since earlier studies had examined some post-mating gene expression in Drosophila, but that earlier work did not examine expression over a set time period and involved examining the whole bodies of mated insects, not just their reproductive tracts.
The researchers' double approach using genomics and proteomics--the study of proteins and the products they turn on--was especially productive because it allowed them to identify genes they would not have found using a single approach.
"The next step will be to choose a few of the most promising genes and to explore their function in females," said Bender.
Once the gene functions are known, then scientists can begin to examine how to manipulate them--both to study the biology involved and to find potential targets for pest control.
Kim Carlyle | EurekAlert!
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
20.07.2018 | Power and Electrical Engineering
20.07.2018 | Information Technology
20.07.2018 | Materials Sciences | <urn:uuid:5b4da1b2-455a-457c-a626-011a48febb4f> | 3.484375 | 1,430 | Content Listing | Science & Tech. | 35.26372 | 95,530,616 |
A research team led by Wayne State University, in collaboration with Michigan State University, has identified a single gene in honeybees that separates the queens from the workers.
The scientists unraveled the gene's inner workings and published the results in the current issue of Biology Letters. The gene, which is responsible for leg and wing development, plays a crucial role in the evolution of bees' ability to carry pollen.
"The gene — Ultrabithorax, or Ubx — is responsible for making hind legs different from fore legs so they can carry pollen" said Aleksandar Popadic, associate professor of biological sciences in Wayne State University's College of Liberal Arts and Science and principal investigator of the study. "In some groups, like crickets, Ubx is responsible for creating a 'jumping' hind leg. In others, such as bees, it makes a pollen basket — a 'naked,' bristle-free leg region that creates a space for packing pollen."
"Other studies have shed some light on this gene's role in this realm, but our team examined in great detail how the modifications take place," added Zachary Huang, MSU entomologist.
Ubx represses the development of bristles on bees' hind legs, creating a smooth surface that can be used for packing pollen. This important discovery can be used as a foray into more commercial studies focused on providing means to enhance a bee's pollination ability – the bigger the pollen basket, the more pollen that can be packed in it and transported back to the hive.
While workers have these distinct features, queens do not. The team confirmed this by isolating and silencing Ubx. This made the pollen baskets completely disappear, altered the growth of the pollen comb and reduced the size of the pollen press. Interestingly, Ubx is also expressed in the same region of the hind legs in bumble bees, which are in the same family as honey bees. This finding suggests that the evolution of the pollen-gathering apparatus in all corbiculate bees may have a shared origin and could be traced to the acquisition of novel functions by Ubx.
In another interesting finding, researchers identified that bees living in more complex social structures have an advantage over isolated populations in developing these important functions.
"The pollen baskets are much less elaborate or completely absent in bees that are less socially complex," Huang said. "We conclude that the evolution of pollen baskets is a major innovation among social insects and is tied directly to more complex social behaviors."
The value of agricultural crops dependent on honey bee pollination was estimated to be $14.6 billion per year in the U.S. in 2013.
"In Michigan alone, the fruit and vegetable industries produce over $2 billion per year, and nearly 50 percent of that value is due entirely to honey bee pollination," said Huang. "This shows that bees are contributing significantly to the state and national economy."
This study, along with future research by Popadic and Huang, may provide an option for improving the shrinking population of bees' pollen-collecting capacity, leading to increased pollination and hopeful increases in fruit and vegetable production.
This research was funded to Popadic by the National Institute of General Medical Sciences of the National Institutes of Health, number GM071927.
Wayne State University is one of the nation's pre-eminent public research universities in an urban setting. Through its multidisciplinary approach to research and education, and its ongoing collaboration with government, industry and other institutions, the university seeks to enhance economic growth and improve the quality of life in the city of Detroit, state of Michigan and throughout the world.
Colorectal cancer risk factors decrypted
13.07.2018 | Max-Planck-Institut für Stoffwechselforschung
Algae Have Land Genes
13.07.2018 | Julius-Maximilians-Universität Würzburg
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
13.07.2018 | Event News
13.07.2018 | Materials Sciences
13.07.2018 | Life Sciences | <urn:uuid:af8b556f-a684-407f-ad0b-a060860f3741> | 3.5625 | 1,383 | Content Listing | Science & Tech. | 37.310319 | 95,530,632 |
Calculus for Beginners and Artists
by Daniel Kleitman
Publisher: MIT 2009
Calculus is the study of how things change. It provides a framework for modeling systems in which there is change, and a way to deduce the predictions of such models. This online textbook provides an overview of Calculus in clear, easy to understand language designed for the non-mathematician.
Home page url
Download or read it online for free here:
by Matt Boelkins - Grand Valley State University
Where many texts present a general theory of calculus followed by substantial collections of worked examples, we instead pose problems or situations, consider possibilities, and then ask students to investigate and explore.
by Russell A. Gordon - Whitman College
The text represents one person's attempt to put the essential ideas of calculus into a short and concise format. It may not appeal to a wide range of mathematicians, but it should provide most students with a good foundation in calculus.
by Leif Mejlbro - BookBoon
Guidelines for solutions of problems concerning sequences and power series. It is not an alternative textbook, but it can be a useful supplement to the ordinary textbooks. The text presupposes some knowledge of calculus of functions in one variable.
by Raymond Benedict McClenon - Ginn and company
The book covers some parts of plane trigonometry and analytic geometry, followed by an introduction to the differential calculus, including differentiation of simpler algebraic functions and applications to problems of rates and maxima and minima. | <urn:uuid:df8eac2f-8eaf-419e-954c-8a8213097dd2> | 2.703125 | 310 | Content Listing | Science & Tech. | 26.00532 | 95,530,641 |
The Complete Reference of Geometry Formulas covering the following topics
- Basic Properties
- Line Properties
- Angle Properties
- Triangle Properties
- Circle Properties
- Property of Sides
- Property of Angles
- Property of Exterior Angles
- Areas of Triangle
- More Rules
- Medians of a Triangle(Centroid)
- Apollonius Theorem
- Altitudes of Triangle(Orthocenter)
- Internal Bisectors of Triangle(Incenter)
- Perpendicular Bisectors of Triangle(CircumCenter)
- MidPoint Theorem
- Types of Triangles
and many more with regular updates .
This geometry formulae collection is useful for MBA exams , competitive and even curriculum exam .
It lists out all the important maths formulas/topics in Geometry. Regular review of these formulas/concepts will definitely help improve your grades.
Write us at [email protected]
for suggestions and feedback for improvements.
Follow us on twitter @gamesnapps4u
Ad Labels Added | <urn:uuid:fe691f7b-08d3-4b08-86a5-93d0d892e6f6> | 2.859375 | 221 | Product Page | Science & Tech. | 0.285512 | 95,530,648 |
In the desert of northwest Australia, about 10 miles east of the small mining town of Newman, lies a natural wonder. If you fly overhead, you’ll see vast carpets of green spinifex grass, pockmarked by barren red circles, as if some deity had repeatedly stubbed out a cosmic cigar on the parched landscape.
These disks of bare soil are called “fairy circles,” and they’re not unique to Australia—they also exist 6,000 miles away in Namibia. There, the circles number in the millions, and extend over some 1,500 miles of desert. They comprise different grasses but their patterns are the same: low-lying vegetation freckled by circles of empty soil. They almost seem alive, growing and shrinking with a lifespan of 30 to 60 years.
Local people believe them to be the work (or footprints) of deities and spirits. Scientists have tried to come up with more grounded explanations since they first started writing about the circles in the 1920s. Some suggested that they’re the work of grazing ants, or radioactive gases leaking from underground, or poisonous plants that kill off their competitors.
Over the last century, two main hypotheses for the cause of these circles have fought their way to the top of the scrum. The first is from Norbert Juergens of the University of Hamburg, who says that the circles are the work of sand termites. To store water, he argues, these insects eat the roots of grasses within a circular patch, allowing the underlying grains of sand to catch and absorb the falling rain. The result is Namibia’s version of a beaver dam—an engineered reservoir. And according to Juergens, the fierce competition between neighboring termite colonies causes the regular spacing of the circles.
Many other researchers, including entomologists and botanists, aren’t convinced. They think the circles occur because plants engage in a tug-of-war for water and other scarce nutrients. Due to their battles, the landscape “self-organizes” into rings of deep-rooted grasses, draining water from a central reservoir where no other plants can thrive. This explains why, as the researchers Michael Cramer and Nichole Barger found in 2013, the fairy circles are restricted to places with low rainfall, and why they grow after dry years and shrink after wet ones.
Stephan Getzin from the University of Goettingen started off as a fan of the termite hypothesis when he began studying the fairy circles in 1999. But he defected to the self-organization camp after studying aerial images of the fairy circles, and seeing just how regular they are. “They have an extremely regular hexagonal spacing, like a honeycomb,” he says. “That pattern persists throughout the landscape for hundreds of thousands of meters. Termites and ants are not known to cause such strictly ordered patterns.” In May 2014, he published a paper outlining his evidence for the self-organization hypothesis.
Three days later, he got an email from Bronwyn Bell, an environmental manager at an iron-ore mine in Newman. We have something similar here, she said. To prove her point, she attached an aerial photo. “When I saw it, it looked really convincing,” says Getzin. Seven months later, he was on a plane bound for Newman.
Getzin and his colleagues found that the Australian circles exist in the same orderly honeycomb as their Namibian counterparts, with almost exactly the same spatial traits. And by measuring temperature and analyzing soil samples, they worked out how the circles might form.
The critical point is that the area around Newman doesn’t get enough rain to sustain an even carpet of plants, so there’s competition for water. Plants that grow a little bit bigger than their neighbors draw in more water: Their deeper roots loosen the soil around them, allowing more water to seep in. Nearby plants benefit, while those further away die of drought. They leave patches of bare earth that are too hard, compact, and hot for seeds to germinate. These empty circles act as rain collectors: any water that falls on them runs off to the side, where it nourishes the encircling plants.
When Getzin simulated all of this on a computer, he produced virtual patterns that are almost indistinguishable from the actual fairy circles.
He thinks that the Namibian circles form in a slightly different way. There, the fight for water mostly occurs underground; in Australia, it happens on the surface. But the basic idea is the same: Water conflicts that play out over meters create patterns that pockmark the land for kilometers. “The new paper moves us closer toward a unifying theory of fairy-circle formation,” says Barger.
It also weakens the termite hypothesis. Getzin found that most Australian fairy circles show no signs of these insects. He also mapped the locations of termite nests in one particular site and found that they’re randomly distributed, clustered in some areas and absent from others. That’s very different to the even hexagonal spacing of the fairy circles themselves.
There’s something compelling about the termite hypothesis, which involves creatures actively shaping their world. It plays to our appreciation of agency, and perhaps our love for underdogs (or under-insects, as it were). By contrast, the self-organization concept is less intuitive. It’s much harder to imagine how thirsty plants, just by sitting there, could produce these beautiful, kilometer-wide patterns. Indeed, Juergens once described the idea to me as “just a synonym for fairies.”
And yet, the natural world is full of examples of beautiful patterns that have deceptively simple origins.
In 1952, Alan Turing, the English mathematician and code-breaker, suggested that the stripes and spots of many animals are produced by two molecules: an activator that produces the pattern, and an inhibitor that blocks it. These diffuse through the skin and interact with each other. Depending on how strongly they interact and how fast they spread, Turing predicted that they’d result in everything from zebra-like stripes to cheetah-esque spots. (Try it out for yourself.)
Many studies have since found many examples of these “Turing patterns.” They’re evident in the pigments of animal skins and seashells, and even the cells of your fingers—examples of local interactions between spreading entities that create complicated, repeating patterns over vast scales. Scientists have seen such patterns in the distributions of parasites and hosts, and the location of plants in deserts. Getzin sees them in the fairy circles.
“Fairy circles have certainly jumped from an obscure phenomenon known to only a few, to a celebrated but mysterious landform,” says Walter Tschinkel, an entomologist from Florida State University. But “correlation between a computed model and nature is still not proof of causation, no matter how nicely the output mimics nature.”
It will take an experiment to truly solve the fairy-circle mystery. Scientists will need to show that they can artificially create or close up the circles by manipulating water levels, soil quality, or termite numbers. That’s a tall order for a phenomenon that exists across miles and decades.
Absent such experiments, it would certainly help to find more fairy circles. Barger thinks the odds are good. “With the increasing availability of satellite images globally it’s likely that we will continue to discover more instances of these circular gap patterns in arid environments in the future.”
We want to hear what you think. Submit a letter to the editor or write to firstname.lastname@example.org. | <urn:uuid:088a5a6e-40c8-4a56-8afd-f1ea46bf3c0a> | 3.703125 | 1,617 | News Article | Science & Tech. | 46.57399 | 95,530,650 |
You are currently converting Force units from Newton to Joule/Centimeter
3601 Newton (N)
360100 Joule/Centimeter (J/cm)
Newton : Newton is the International System of Units (SI) derived unit of force. It is the force required to accelerate a mass of one kilogram by one metre per second squared. Its symbol is N. The unit of Newton is equivalent to the units kilogram-meter per squared second (kg•m•s⁻²).
Joule/Centimeter : Joule per centimeter is a unit of force with official symbol “J/cm”. It is equal to 0.01 newtons, or 10 millinewtons.
Force Conversion Calculator
Most popular convertion pairs of force
- Frequency Wavelength | <urn:uuid:78eb8ab6-a85b-4219-a62b-7e329468351f> | 3.078125 | 167 | Tutorial | Science & Tech. | 49.391667 | 95,530,651 |
Methane Sinks Distribution
At present the amount of methane removed from the atmosphere each year is about 500 Tg/yr or more than 90% of that released into the atmosphere each year. Most of the methane is removed by reacting with tropospheric OH radicals; lesser amounts are removed by soils and stratospheric oxidation by OH, O(1D), and minor reactions. This chapter is on the removal rate of CH4 and its variability in space and time.
KeywordsRemoval Rate Middle Atmosphere Destruction Rate Atmospheric Methane Methane Uptake
Unable to display preview. Download preview PDF.
- DeMore, W.B., S.P. Sander, C.J. Howard, A.R. Ravishankara, D.M. Golden, C.E. Kolb, R.F. Hampson, M.J. Kurylo, M.J. Molina. 1992. Chemical Kinetics and Photochemical Data for Use in Stratospheric Modeling. NASA Evaluation No. 10.Google Scholar
- Ehhalt, D.H., L.E. Heidt, E.A. Martell. 1972. The concentrations of atmospheric methane between 44 and 62 kilometers altitude. J. Geophys. Res., 77: 2, 1932, 196.Google Scholar
- Gunson, M.R., C.B. Farmer, R.H. Norton, R. Zander, C.P. Rinsland, J.H. Shaw, B.-C. Gao. 1990. Measurements of CH4, N2O, CO, H2O, and 03 in the middle atmosphere by the Atmospheric Trace Molecule SpectroscopyGoogle Scholar
- Experiment on Spacelab 3. J. Geophys. Res., 95 (D9):13,867–13,882.Google Scholar
- Hahn, C.J., S.G. Warren, J. London, R.L. Jenne, R.M. Chervin. 1987. Climatological Data for Clouds over the Globe from Surface Observations. Report NDP-026, Carbon Dioxide Information Center, Oak Ridge, TN.Google Scholar
- Khalil, M.A.K., R.A. Rasmussen. 1992. Forest hydrocarbon emissions: relationships between fluxes and ambient concentrations. J. Air & Waste Manage. Assoc., 42: 810–813.Google Scholar
- Lu, Y. 1993. Model calculations of radiative transfer and tropospheric chemistry. Ph.D. dissertation, Oregon Graduate Institute, Beaverton, OR.Google Scholar
- Matthews, E. 1984. Vegetation, land-use and seasonal albedo data sets: documentation of archived data tape. NASA Technical Memorandum 86107, Goddard Space Flight Center, New York, U.S.A.Google Scholar
- NOAA/CMDL (National Oceanic and Atmospheric Administration, Climate Monitoring and Diagnostics Laboratory Flask Sampling Program). 1990. In: Trends ‘80, A Compendium of Data on Global Change (T.A. Boden, P. Kanciruk, and M.P. Farrell, eds.), 148–189. Carbon Dioxide Information Analysis Center, Oak Ridge, TN, USA, ORNLJCDIAC-36.Google Scholar
- Taylor, F.W. A. Dudhia, C.D. Rodgers. 1989. Proposed reference models for nitrous oxide and methane in the middle atmosphere. In: Handbook for MAP, Vol. 31. (G.M. Keating, ed.), 67–79.Google Scholar
- Thompson, A.M. 1992. The oxidizing capacity of the Earth’s atmosphere: probable past and future changes. Science, 256:1, 157–1, 165.Google Scholar
- Weisenstein, D.K., M.K.W. Ko, N.-D. Sze. 1992. The chlorine budget of the present-day atmosphere: a modeling study. J. Geophys. Res., 97 (D2):2, 547–2, 559.Google Scholar | <urn:uuid:4681ed46-26e8-4f00-9277-be75336ba97e> | 3.5 | 863 | Academic Writing | Science & Tech. | 74.710097 | 95,530,674 |
Beef Peptides Block Bitter Tastes
News May 17, 2018 | Original Story from the American Chemical Society.
From burgers to steaks, beef has a long history of being a delicious part of dinner. But what if that pleasant experience of eating beef could extend beyond the dinner plate? Now, one group reports in ACS’ Journal of Agricultural and Food Chemistry that beef protein, when broken down into peptides, can block bitter taste receptors on the tongue. Such peptides could someday be used to make other foods and even medicines taste better.
Most people try to avoid bitter flavors because they find them to be unpleasant. But some healthful foods are bitter, as are some medications. So, the food and pharmaceutical industries have been looking at ways to reduce or eliminate bitter sensations, which are detected in humans by 25 receptors known as T2Rs. Only a few inhibitors of T2R activity have been identified so far. In recent years, bioactive peptides created from breaking down food proteins, through a process known as enzymatic hydrolysis, have gained attention for reducing bitterness and inflammation. Because beef proteins have been shown to generate desirable flavor-promoting peptides, Prashen Chelikani, Rotimi E. Aluko and colleagues wanted to see if these peptides could block bitter tastes.
The researchers hydrolyzed beef protein with six different enzymes: alcalase, chymotrypsin, trypsin, pepsin, flavourzyme and thermoase. Peptides produced from trypsin and pepsin digestion were the most effective in reducing the intensity of the bitterness of quinine in a test with an electronic tongue. These peptides were also the longest, which suggests that peptide size might play an important role. The group notes this could impact not only the food industry but the pharmaceutical industry as well.
This article has been republished from materials provided by the American Chemical Society. Note: material may have been edited for length and content. For further information, please contact the cited source.
Beef Protein-Derived Peptides as Bitter Taste Receptor T2R4 Blockers. Chunlei Zhang, Adeola M. Alashi, Nisha Singh, Kun Liu, Prashen Chelikani, and Rotimi E. Aluko. J. Agric. Food Chem., 2018, 66 (19), pp 4902–4912, DOI: 10.1021/acs.jafc.8b00830.
Synthetic Material That Detects Enzymatic ActivityNews
Scientists integrate protein and polymer building blocks to create stimulus-responsive systemsREAD MORE
Rapid and Cost-Effective Instrument that Measures Molecular DynamicsNews
By combining mass spectrometry and thermal desorption, researchers honed a new method to measure excitation and relaxation rates of uracil, the building block of RNA.READ MORE | <urn:uuid:b3842527-50b5-431b-a461-4ce3aa6e849a> | 2.984375 | 599 | Truncated | Science & Tech. | 37.28707 | 95,530,678 |
Rocks become weathered in several ways.
Over the course of time, rocks naturally disintegrate and decompose through a process known as weathering. Weathering is the breakdown of exposed rock and soil on the earth’s surface through various means. There are two different types of weathering—chemical and physical. Physical weathering, also known as mechanical weathering, occurs in three different ways.
Frost Wedging and Thermal Expansion
Every day, rock on the earth’s surface expands and contracts due to heating and cooling. When rock is heated, it expands; upon cooling, it contracts. This constant expansion and contraction can cause the rock to break up and become weathered. Different types of minerals have different rates of expansion and contraction; where there are different minerals in the rock, there is likely to see more weathering.
Water from precipitation, such as rain or melting snow, can seep into cracks and chips in the rock. The water can freeze if the temperature is cold enough; once it freezes, it expands and causes rock to break apart. This expansion pushes the rock out of place, which can wear away and chip the rock. This stage of mechanical weathering occurs most often in areas where there are a large number of freeze-thaw cycles throughout the year. Mountainous areas and areas closer to the North and South Poles experience frost wedging, also known as ice wedging, more often than other areas. In areas with cliffs that experience frost wedging, the chips of rock break off and collect at the base, forming what is known as a talus slope.
Unloading, also known as exfoliation, is the second stage of mechanical weathering. Exfoliation is the process of rock breaking off into sheets or leaves parallel with the ground surface. The rocks can become cracked; when soil beneath the rock begins to erode or expand, it pushes the rock upwards. The rock then becomes stressed and can crack into large sheets known as exfoliation sheets.
Plants and animals can cause rock to crack and break into sheets. Plant roots can cause the rock to form cracks, known as joints, and the roots pushing up soil contribute to the rocks breaking up. Some plants can also produce chemical components that lead to the breakdown of rock. Animals contribute to the weathering of rock when they burrow into the soil. This burrowing helps push soil upward, which can damage the rock above. Animals also contribute to weathering by exposing covered rock. | <urn:uuid:4b245e3c-e0e6-4c94-8b13-41a116edea2b> | 4.3125 | 507 | Knowledge Article | Science & Tech. | 51.527537 | 95,530,682 |
Spallation Neutron Source
The Spallation Neutron Source (SNS) is an accelerator-based neutron source facility that provides the most intense pulsed neutron beams in the world for scientific research and industrial development. Each year, this facility hosts hundreds of researchers from universities, national laboratories, and industry, who conduct basic and applied research and technology development using neutrons. SNS is part of Oak Ridge National Laboratory, which is managed by UT-Battelle for the United States Department of Energy (DOE). SNS is a DOE Office of Science user facility, and it is open to scientists and researchers from all over the world.
|A DOE Office of Science User Facility|
|Location:||Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States|
|Scientific Purpose:||Provide unique information about the structure and properties of materials across the spectrum of biology, chemistry, physics, and engineering.|
|Organization:||SNS is part of the ORNL Neutron Sciences Directorate, which also includes the High Flux Isotope Reactor, a steady-state neutron source.|
Neutron scattering researchEdit
Neutron scattering allows scientists to count scattered neutrons, measure their energies and the angles at which they scatter, and map their final positions. This information can reveal the molecular and magnetic structure and behavior of materials, such as high-temperature superconductors, polymers, metals, and biological samples. In addition to studies focused on fundamental physics, neutron scattering research has applications in structural biology and biotechnology, magnetism and superconductivity, chemical and engineering materials, nanotechnology, complex fluids, and others.
How SNS worksEdit
The spallation process at SNS begins with negatively charged hydrogen ions that are produced by an ion source. Each ion consists of a proton orbited by two electrons. The ions are injected into a linear particle accelerator, or linac, which accelerates them to an energy of about one GeV (or to about 90% the speed of light). The ions pass through a foil, which strips off each ion's two electrons, converting it to a proton. The protons pass into a ring-shaped structure, a proton accumulator ring, where they spin around at very high speeds and accumulate in “bunches.” Each bunch of protons is released from the ring as a pulse, at a rate of 60 times per second (60 hertz). The high-energy proton pulses strike a target of liquid mercury, where spallation occurs. The spalled neutrons are then slowed down in a moderator and guided through beam lines to areas containing special instruments where they are used in a wide variety of experiments.
Most of the world's neutron sources were built decades ago, and although the uses and demand for neutrons have increased throughout the years, few new sources have been built. To fill that need for a new, improved neutron source, the DOE Office of Basic Energy Sciences funded the construction of SNS, which would provide the most intense pulsed neutron beams in the world for scientific research and industrial development.
The construction of SNS was a partnership of six DOE national laboratories: Argonne, Brookhaven, Lawrence Berkeley, Los Alamos, Oak Ridge, and Jefferson. This collaboration was one of the largest of its kind in U.S. scientific history and was used to bring together the best minds and experience from many different fields.
After more than five years of construction and a cost of $1.4 billion, SNS was completed in April 2006. The first three instruments began commissioning and were available to the scientific community in August 2007.
As of 2017, a total of 20 instruments have been completed, and SNS is hosting about 1,400 researchers per year.
- Official website
- T. E. Mason et al., "The Spallation Neutron Source: A Powerful Tool for Materials Research," arXiv:physics/0007068v1.
- "SNS: Neutrons for 'molecular movies,'" Symmetry, vol. 03(05), Jun/Jul, 2006. | <urn:uuid:50c86b62-da9b-4cc2-8639-eb55831a2f85> | 3.59375 | 861 | Knowledge Article | Science & Tech. | 36.92585 | 95,530,689 |
A complete account of the fundamental techniques of general relativity and their application to cosmology. The book includes reviews of the different cosmological models and their classification, including such topics as causality and horizons, the cosmological parameters, observational tests and constraints of cosmology, symmetries and the large scale topology of space and space-time, and the use of supernovas as cosmological indicators.
The perturbations to the cosmological models are discussed throughout the volume. The cosmic microwave background is presented, with an emphasis in secondary distortions in relation to cosmological models and large scale structures. Recent results on dark matter are summarised. A general review of primordial nucleosynthesis is given. Gravitational lensing is discussed in great detail. Most contributions show a balance between theory and observation.
Readership: A solid background for students and researchers intending to work in the field of theoretical and observational cosmology.
Series: NATO Science Series U
Number Of Pages: 396
Published: 30th September 1999
Country of Publication: NL
Dimensions (cm): 23.39 x 15.6 x 2.18
Weight (kg): 0.59 | <urn:uuid:9b651c7a-0e85-40f9-8f66-985cf0a488a0> | 2.609375 | 243 | Product Page | Science & Tech. | 25.905253 | 95,530,693 |
Investigating dye-sensitised solar cells
Files in This Item:
|RevisedManuscript SPIE PhotonicsEurope 10 DSSC.pdf||200.06 kB||Adobe PDF||Download|
|Title:||Investigating dye-sensitised solar cells||Authors:||Tobin, Laura L.
Sheridan, John T.
|Permanent link:||http://hdl.handle.net/10197/2741||Date:||13-Apr-2010||Abstract:||At present there is a global concern of environmental issues and future energy supplies, for instance global warming and the rapid depletion of fossil fuels. This trepidation has initiated a more critical investigation into alternative and renewable sources of power such as geothermal, biomass, hydropower, wind and solar energy. The immense dependence on electrical power in today’s society has prompted the manufacturing of devices such as photovoltaic (PV) cells to help alleviate and replace current electrical demands of the power grid. The most popular and commercially available PV cells are silicon solar cells which have to date the greatest efficiencies for PV cells. The drawback however is that the manufacturing of these cells is complex and costly due to the expense and difficulty of producing and processing pure silicon. One relatively inexpensive alternative to silicon PV cells that we are currently studying are dye-sensitised solar cells (DSSCs or Grätzel Cells). DSSCs are biomimetic solar cells which are based on the process of photosynthesis. The SFI Strategic Research Centre for Solar Energy Conversion is a research cluster based in Ireland formed with the express intention of bringing together industry and academia to produce renewable energy solutions. Our specific research area is in DSSC and their opto-electrical properties. We are currently developing testing equipment for multiple DSSC and optoelectronic models which will describe the performance and behaviour of DSSCs.||Funding Details:||Science Foundation Ireland||Type of material:||Conference Publication||Publisher:||SPIE||Copyright (published version):||2010 Society of Photo-Optical Instrumentation Engineers.||Keywords:||Dye sensitised solar cells;Photovoltaic;Optoelectronic||Subject LCSH:||Dye-sensitized solar cells
|DOI:||10.1117/12.854591||Language:||en||Status of Item:||Peer reviewed||Is part of:||Wehrspohn, R.B. and Gombert, A. (eds.). Proceedings of SPIE : Volume 7725 : Proceedings of SPIE, 0277-786X, v. 7725 SPIE is an international society advancing an interdisciplinary approach to the science and application of light. Photonics for Solar Energy Systems III||Conference Details:||SPIE Photonics Europe: Photonics for Solar Energy Systems III, 12th- 16th April, Brussels, 2010.|
|Appears in Collections:||Solar Energy Conversion (SEC) Cluster Research Collection|
Physics Research Collection
Electrical and Electronic Engineering Research Collection
Show full item record
Page view(s) 20171
This item is available under the Attribution-NonCommercial-NoDerivs 3.0 Ireland. No item may be reproduced for commercial purposes. For other possible restrictions on use please refer to the publisher's URL where this is made available, or to notes contained in the item itself. Other terms may apply. | <urn:uuid:547f1a38-2108-4998-9e9b-dba6e3e1042b> | 2.59375 | 720 | Academic Writing | Science & Tech. | 32.555389 | 95,530,708 |
Artist impression of a Viking orbiter releasing a lander descent capsule
|Manufacturer||Jet Propulsion Laboratory / Martin Marietta|
|Country of origin||United States|
|Operator||NASA / JPL|
Orbiters: 4 years at Mars|
Landers: 4–6 years at Mars
|Launch mass||3,527 kilograms (7,776 lb)|
Orbiters: 620 watts (solar array)|
Lander: 70 watts (two RTG units)
Viking 1 orbiter|
August 17, 1980
Viking 1 lander
July 20, 1976 (landing) to November 13, 1982
Viking 2 orbiter
July 25, 1978
Viking 2 lander
September 3, 1976 (landing) to April 11, 1980
August 20, 1975
September 9, 1975
The Viking program consisted of a pair of American space probes sent to Mars, Viking 1 and Viking 2. Each spacecraft was composed of two main parts: an orbiter designed to photograph the surface of Mars from orbit, and a lander designed to study the planet from the surface. The orbiters also served as communication relays for the landers once they touched down.
The Viking program grew from NASA's earlier, even more ambitious, Voyager Mars program, which was not related to the successful Voyager deep space probes of the late 1970s. Viking 1 was launched on August 20, 1975, and the second craft, Viking 2, was launched on September 9, 1975, both riding atop Titan III-E rockets with Centaur upper stages. Viking 1 entered Mars orbit on June 19, 1976, with Viking 2 following suit on August 7.
After orbiting Mars for more than a month and returning images used for landing site selection, the orbiters and landers detached; the landers then entered the Martian atmosphere and soft-landed at the sites that had been chosen. The Viking 1 lander touched down on the surface of Mars on July 20, 1976, and was joined by the Viking 2 lander on September 3. The orbiters continued imaging and performing other scientific operations from orbit while the landers deployed instruments on the surface.
The project cost roughly 1 billion USD in 1970s dollars, equivalent to about 5 billion USD in 2016 dollars. The mission was considered successful and is credited with helping to form most of the body of knowledge about Mars through the late 1990s and early 2000s.
- 1 Science objectives
- 2 Viking orbiters
- 3 Viking landers
- 4 Control systems
- 5 Financial cost of the Viking program
- 6 Mission end
- 7 Viking lander locations
- 8 See also
- 9 References
- 10 Further reading
- 11 External links
- Obtain high-resolution images of the Martian surface
- Characterize the structure and composition of the atmosphere and surface
- Search for evidence of life on Mars
The primary objectives of the two Viking orbiters were to transport the landers to Mars, perform reconnaissance to locate and certify landing sites, act as communications relays for the landers, and to perform their own scientific investigations. Each orbiter, based on the earlier Mariner 9 spacecraft, was an octagon approximately 2.5 m across. The fully fueled orbiter-lander pair had a mass of 3527 kg. After separation and landing, the lander had a mass of about 600 kg and the orbiter 900 kg. The total launch mass was 2328 kg, of which 1445 kg were propellant and attitude control gas. The eight faces of the ring-like structure were 0.4572 m high and were alternately 1.397 and 0.508 m wide. The overall height was 3.29 m from the lander attachment points on the bottom to the launch vehicle attachment points on top. There were 16 modular compartments, 3 on each of the 4 long faces and one on each short face. Four solar panel wings extended from the axis of the orbiter, the distance from tip to tip of two oppositely extended solar panels was 9.75 m.
The main propulsion unit was mounted above the orbiter bus. Propulsion was furnished by a bipropellant (monomethylhydrazine and nitrogen tetroxide) liquid-fueled rocket engine which could be gimballed up to 9 degrees. The engine was capable of 1,323 N (297 lbf) thrust, translating to a change in velocity of 1480 m/s. Attitude control was achieved by 12 small compressed-nitrogen jets.
An acquisition Sun sensor, a cruise Sun sensor, a Canopus star tracker and an inertial reference unit consisting of six gyroscopes allowed three-axis stabilization. Two accelerometers were also on board. Communications were accomplished through a 20 W S-band (2.3 GHz) transmitter and two 20 W TWTAs. An X band (8.4 GHz) downlink was also added specifically for radio science and to conduct communications experiments. Uplink was via S band (2.1 GHz). A two-axis steerable parabolic dish antenna with a diameter of approximately 1.5 m was attached at one edge of the orbiter base, and a fixed low-gain antenna extended from the top of the bus. Two tape recorders were each capable of storing 1280 megabits. A 381-MHz relay radio was also available.
The power to the two orbiter craft was provided by eight 1.57 × 1.23 m solar panels, two on each wing. The solar panels comprised a total of 34,800 solar cells and produced 620 W of power at Mars. Power was also stored in two nickel-cadmium 30-A·h batteries.
The combined area of the four panels was 15 square meters (160 square feet), and they provided both regulated and unregulated direct current power; unregulated power was provided to the radio transmitter and the lander.
Two 30-amp-hour, nickel-cadmium, rechargeable batteries provided power when the spacecraft was not facing the Sun, and during launch, correction maneuvers and Mars occultation.
By discovering many geological forms that are typically formed from large amounts of water, the images from the orbiters caused a revolution in our ideas about water on Mars. Huge river valleys were found in many areas. They showed that floods of water broke through dams, carved deep valleys, eroded grooves into bedrock, and travelled thousands of kilometers. Large areas in the southern hemisphere contained branched stream networks, suggesting that rain once fell. The flanks of some volcanoes are believed to have been exposed to rainfall because they resemble those caused on Hawaiian volcanoes. Many craters look as if the impactor fell into mud. When they were formed, ice in the soil may have melted, turned the ground into mud, then flowed across the surface. Normally, material from an impact goes up, then down. It does not flow across the surface, going around obstacles, as it does on some Martian craters. Regions, called "Chaotic Terrain," seemed to have quickly lost great volumes of water, causing large channels to be formed. The amount of water involved was estimated to ten thousand times the flow of the Mississippi River. Underground volcanism may have melted frozen ice; the water then flowed away and the ground collapsed to leave chaotic terrain.
Each lander comprised a six-sided aluminium base with alternate 1.09 and 0.56 m (3 ft 7 in and 1 ft 10 in) long sides, supported on three extended legs attached to the shorter sides. The leg footpads formed the vertices of an equilateral triangle with 2.21 m (7 ft 3 in) sides when viewed from above, with the long sides of the base forming a straight line with the two adjoining footpads. Instrumentation was attached inside and on top of the base, elevated above the surface by the extended legs.
Each lander was enclosed in an aeroshell heat shield designed to slow the lander down during the entry phase. To prevent contamination of Mars by Earth organisms, each lander, upon assembly and enclosure within the aeroshell, was enclosed in a pressurized "bioshield" and then sterilized at a temperature of 111 °C (232 °F) for 40 hours. For thermal reasons, the cap of the bioshield was jettisoned after the Centaur upper stage powered the Viking orbiter/lander combination out of Earth orbit.
Descent and landing
Each lander arrived at Mars attached to the orbiter. The assembly orbited Mars many times before the lander was released and separated from the orbiter for descent to the surface. Descent comprised four distinct phases, starting with a deorbit burn. The lander then experienced atmospheric entry with peak heating occurring after a few seconds after the start of frictional heating with the Martian atmosphere. At an altitude of about 6 kilometers (3.7 miles) and traveling at a velocity of 900 kilometers per hour (600 mph), the parachute deployed, the aeroshell released and the lander's legs unfolded. At an altitude of about 1.5 kilometers (5,000 feet), the lander activated its three retro-engines and was released from the parachute. The lander then immediately used retrorockets to slow and control its descent, with a soft landing on the surface of Mars.
Propulsion for deorbit was provided by the monopropellant hydrazine (N2H4), through a rocket with 12 nozzles arranged in four clusters of three that provided 32 newtons (7.2 lbf) thrust, translating to a change in velocity of 180 m/s (590 ft/s). These nozzles also acted as the control thrusters for translation and rotation of the lander.
Terminal descent (after use of a parachute) and landing utilized three (one affixed on each long side of the base, separated by 120 degrees) monopropellant hydrazine engines. The engines had 18 nozzles to disperse the exhaust and minimize effects on the ground, and were throttleable from 276 to 2,667 newtons (62 to 600 lbf). The hydrazine was purified in order to prevent contamination of the Martian surface with Earth microbes. The lander carried 85 kg (187 lb) of propellant at launch, contained in two spherical titanium tanks mounted on opposite sides of the lander beneath the RTG windscreens, giving a total launch mass of 657 kg (1,448 lb). Control was achieved through the use of an inertial reference unit, four gyros, a radar altimeter, a terminal descent and landing radar, and the control thrusters.
Power was provided by two radioisotope thermoelectric generator (RTG) units containing plutonium-238 affixed to opposite sides of the lander base and covered by wind screens. Each generator was 28 cm (11 in) tall, 58 cm (23 in) in diameter, had a mass of 13.6 kg (30 lb) and provided 30 watts continuous power at 4.4 volts. Four wet cell sealed nickel-cadmium 8 ampere-hours (28,800 coulombs), 28 volts rechargeable batteries were also on board to handle peak power loads.
Communications were accomplished through a 20-watt S-band transmitter using two traveling-wave tubes. A two-axis steerable high-gain parabolic antenna was mounted on a boom near one edge of the lander base. An omnidirectional low-gain S-band antenna also extended from the base. Both these antennae allowed for communication directly with the Earth, permitting Viking 1 to continue to work long after both orbiters had failed. A UHF (381 MHz) antenna provided a one-way relay to the orbiter using a 30 watt relay radio. Data storage was on a 40-Mbit tape recorder, and the lander computer had a 6000-word memory for command instructions.
The lander carried instruments to achieve the primary scientific objectives of the lander mission: to study the biology, chemical composition (organic and inorganic), meteorology, seismology, magnetic properties, appearance, and physical properties of the Martian surface and atmosphere. Two 360-degree cylindrical scan cameras were mounted near one long side of the base. From the center of this side extended the sampler arm, with a collector head, temperature sensor, and magnet on the end. A meteorology boom, holding temperature, wind direction, and wind velocity sensors extended out and up from the top of one of the lander legs. A seismometer, magnet and camera test targets, and magnifying mirror are mounted opposite the cameras, near the high-gain antenna. An interior environmentally controlled compartment held the biology experiment and the gas chromatograph mass spectrometer. The X-ray fluorescence spectrometer was also mounted within the structure. A pressure sensor was attached under the lander body. The scientific payload had a total mass of approximately 91 kg (201 lb).
The Viking landers conducted biological experiments designed to detect life in the Martian soil (if it existed) with experiments designed by three separate teams, under the direction of chief scientist Gerald Soffen of NASA. One experiment turned positive for the detection of metabolism (current life), but based on the results of the other two experiments that failed to reveal any organic molecules in the soil, most scientists became convinced that the positive results were likely caused by non-biological chemical reactions from highly oxidizing soil conditions.
Although there is consensus that the Viking lander results demonstrated a lack of biosignatures in soils at the two landing sites, the test results and their limitations are still under assessment. The validity of the positive 'Labeled Release' (LR) results hinged entirely on the absence of an oxidative agent in the Martian soil, but one was later discovered by the Phoenix lander in the form of perchlorate salts. It has been proposed that organic compounds could have been present in the soil analyzed by both Viking 1 and Viking 2, but remained unnoticed due to the presence of perchlorate, as detected by Phoenix in 2008. Researchers found that perchlorate will destroy organics when heated and will produce chloromethane and dichloromethane, the identical chlorine compounds discovered by both Viking landers when they performed the same tests on Mars.
The question of microbial life on Mars remains unresolved. Nonetheless, on April 12, 2012, an international team of scientists reported studies, based on mathematical speculation through complexity analysis of the Labeled Release experiments of the 1976 Viking Mission, that may suggest the detection of "extant microbial life on Mars."
The leader of the imaging team was Thomas Mutch, a geologist at Brown University in Providence, Rhode Island. The camera uses a movable mirror to illumate 12 photo diodes. Each of the 12 silicon diodes are designed to be sensitive to different frequences of light. Several diodes are placed to focus accurately at distances between six and 43 feet away from the lander.
The cameras scanned at a rate of five vertical scan lines per second, each composed of 512 pixels. The 300 degree panorama images were composed of 9150 lines. The cameras scan was slow enough that in a crew shot several members show up several times in the shot as they moved themselves as the camera scanned.
The Viking landers used a Guidance, Control and Sequencing Computer (GCSC) consisting of two Honeywell HDC 402 24-bit computers with 18K of plated-wire memory, while the Viking orbiters used a Command Computer Subsystem (CCS) using two custom-designed 18-bit serial processors.
Financial cost of the Viking program
The two orbiters cost 217 million USD (at the time), which is about 1 billion USD in 2016 year-dollars. The most expensive single part of the program was the lander's life-detection unit, which cost about 60 million then or 300 million USD in 2016 year-dollars. Development of the Viking lander design cost 357 million USD. This was decades before "faster, better, cheaper", Viking needed to pioneer never before imagined technologies under the pressure of national prestige pulled by the Global Cold War conflict and a Space race, not to mention a possibility they might discover extraterrestrial life for the first time (it would only be after the mission, with results created by Viking that such an idea rang less plausible). The experiments had to adhere to a special 1971 directive that mandated that no single failure shall stop the return of more than one experiment—a difficult and expensive task for a device with over 40,000 parts.
The Viking camera system cost 27.3 million USD to develop, or about 100 million in 2016 year-dollars. When the Imaging system design was completed, it was difficult to find anyone who could manufacture it so advanced. The program managers were later praised for fending off pressure to go with a simpler, less advanced imaging system, especially when the views rolled in. The program did save some money by cutting out a third lander and reducing the number of experiments on the lander.
The craft eventually failed, one by one, as follows:
|Craft||Arrival date||Shut-off date||Operational lifetime||Cause of failure|
|Viking 2 orbiter||August 7, 1976||July 25, 1978||1 year, 11 months, 18 days||Shut down after fuel leak in propulsion system.|
|Viking 2 lander||September 3, 1976||April 11, 1980||3 years, 7 months, 8 days||Shut down after battery failure.|
|Viking 1 orbiter||June 19, 1976||August 17, 1980||4 years, 1-month, 19 days||Shut down after depletion of attitude control fuel.|
|Viking 1 lander||July 20, 1976||November 13, 1982||6 years, 3 months, 22 days||Shut down after human error during software update caused the lander's antenna to go down, terminating power and communication.|
The Viking program ended on May 21, 1983. To prevent an imminent impact with Mars the orbit of Viking 1 orbiter was raised on August 7, 1980 before it was shut down 10 days later. Impact and potential contamination on the planet's surface is possible from 2019 onwards. It's unknown if the Viking 2 orbiter's orbit was also raised to prevent an impact.
The Viking 1 lander was found to be about 6 kilometers from its planned landing site by the Mars Reconnaissance Orbiter in December 2006.
Viking lander locations
|Wikimedia Commons has media related to Viking mission.|
- Composition of Mars
- Curiosity rover
- Exploration of Mars
- Life on Mars
- List of missions to Mars
- List of rocks on Mars
- Mariner 9 (important orbiter that preceded Viking)
- Mars Science Laboratory
- Mars Pathfinder
- Norman L. Crabill
- Opportunity rover
- Space exploration
- Spirit rover
- Unmanned space mission
- U.S. Space Exploration History on U.S. Stamps
- Williams, David R. Dr. (December 18, 2006). "Viking Mission to Mars". NASA. Retrieved February 2, 2014.
- Nelson, Jon. "Viking 1". NASA. Retrieved February 2, 2014.
- Nelson, Jon. "Viking 2". NASA. Retrieved February 2, 2014.
- "NASA – NSSDCA – Spacecraft – Details – Viking 1 Orbiter". nssdc.gsfc.nasa.gov. Retrieved 2016-12-13.
- "Viking 1: First U.S. Lander on Mars". Space.com. Retrieved 2016-12-13.
- Thomas, Ryland; Williamson, Samuel H. (2018). "What Was the U.S. GDP Then?". MeasuringWorth. Retrieved January 5, 2018. United States Gross Domestic Product deflator figures follow the Measuring Worth series.
- "The Viking Program". The Center for Planetary Science. Retrieved April 13, 2018.
- "Viking Lander". California Science Center. Retrieved April 13, 2018.
- "Sitemap – NASA Jet Propulsion Laboratory". Retrieved March 27, 2012.
- Hugh H. Kieffer (1992). Mars. University of Arizona Press. ISBN 978-0-8165-1257-7. Retrieved March 7, 2011.
- Raeburn, P. 1998. Uncovering the Secrets of the Red Planet Mars. National Geographic Society. Washington D.C.
- Moore, P. et al. 1990. The Atlas of the Solar System. Mitchell Beazley Publishers NY, NY.
- Morton, O. 2002. Mapping Mars. Picador, NY, NY
- "Amazing Search for Life On Mars." Popular Mechanics, June 1976, pp. 61–63.
- Soffen, G. A., and C. W. Snyder, First Viking mission to Mars, Science, 193, 759–766, August 1976.
- BEEGLE, LUTHER W.; et al. (August 2007). "A Concept for NASA's Mars 2016 Astrobiology Field Laboratory". Astrobiology. 7 (4): 545–577. Bibcode:2007AsBio...7..545B. doi:10.1089/ast.2007.0153. PMID 17723090. Retrieved July 20, 2009.
- Johnson, John (August 6, 2008). "Perchlorate found in Martian soil". Los Angeles Times.
- "Martian Life Or Not? NASA's Phoenix Team Analyzes Results". Science Daily. August 6, 2008.
- Navarro–Gonzáles, Rafael; Edgar Vargas; José de la Rosa; Alejandro C. Raga; Christopher P. McKay (December 15, 2010). "Reanalysis of the Viking results suggests perchlorate and organics at midlatitudes on Mars". Journal of Geophysical Research: Planets. 115 (E12010). Retrieved January 7, 2011.
- Than, Ker (April 15, 2012). "Life on Mars Found by NASA's Viking Mission". National Geographic. Retrieved April 13, 2018.
- Bianciardi, Giorgio; Miller, Joseph D.; Straat, Patricia Ann; Levin, Gilbert V. (March 2012). "Complexity Analysis of the Viking Labeled Release Experiments". IJASS. 13 (1): 14–26. Bibcode:2012IJASS..13...14B. doi:10.5139/IJASS.2012.13.1.14. Archived from the original on April 15, 2012. Retrieved April 15, 2012.
- Klotz, Irene (April 12, 2012). "Mars Viking Robots 'Found Life'". DiscoveryNews. Retrieved April 16, 2012.
- The Viking Lander Imaging Team (1978). "Chapter 8: Cameras Without Pictures". The Martian Landscape. NASA. p. 22.
- McElheny, Victor K. (July 21, 1976). "Viking Cameras Light in Weight, Use Little Power, Work Slowly". The New York Times. Retrieved September 28, 2013.
- Tomayko, James (April 1987). "Computers in Spaceflight: The NASA Experience". NASA. Retrieved February 6, 2010.
- Holmberg, Neil A.; Robert P. Faust; H. Milton Holt (November 1980). "NASA Reference Publication 1027: Viking '75 spacecraft design and test summary. Volume 1 – Lander design" (PDF). NASA. Retrieved February 6, 2010.
- Holmberg, Neil A.; Robert P. Faust; H. Milton Holt (November 1980). "NASA Reference Publication 1027: Viking '75 spacecraft design and test summary. Volume 2 – Orbiter design" (PDF). NASA. Retrieved February 6, 2010.
- McCurdy, Howard E. (2001-11-14). Faster, Better, Cheaper: Low-Cost Innovation in the U.S. Space Program. JHU Press. ISBN 9780801867200.
- As the Viking program was a government expense, the inflation index of the United States Nominal Gross Domestic Product per capita is used for the inflation-adjusting calculation.
- "Viking 1 Orbiter spacecraft details". National Space Science Date Center. NASA. May 14, 2012. Retrieved July 23, 2012.
- Chandler, David (December 5, 2006). "Probe's powerful camera spots Vikings on Mars". New Scientist. Retrieved October 8, 2013. | <urn:uuid:f8701a99-f798-4bbd-a523-e1d085bf7d83> | 3.078125 | 5,089 | Knowledge Article | Science & Tech. | 59.403315 | 95,530,724 |