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Ever wondered how web maps are created? Ever wondered if you
could build something like Google Maps over a weekend? You
probably can't, but this talk will show you the basics of
what you need to know, such as importing data, rendering
maps and even building simple routes. And all of this in
* Learning how OSM data looks
* Parsing and importing the data
* Rendering maps with Mapnik
* Bits of code required to build geocoder
* Building simple router with Python and PostGIS
* And anything else I forgot to mention in this abstract but will talk about
OpenStreetMap -- the so-called "Wikipedia of maps" project, with thousands of contributors who edit the map data of the whole world. Unlike similar projects, the map data is completely free (both as in beer and as in speech) and thus anyone can make use of it.
Mapnik -- rendering framework, created specifically for OpenStreetMap, written in C++ and Python.
PostGIS -- an extension of PostgreSQL database, with support for many useful GIS features.
20th–26th June 2011 | <urn:uuid:5ccf798e-03c1-47fa-a306-35e863dfe7ed> | 2.890625 | 235 | Content Listing | Software Dev. | 45.987368 |
Find information on common issues.
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Graphene is a one-atom-thick planar sheet of sp2-bonded carbon atoms that are densely packed in a honeycomb crystal lattice. The term Graphene was coined as a combination of graphite and the suffix -ene by Hanns-Peter Boehm, who described single-layer carbon foils in 1962. Graphene is most easily visualized as an atomic-scale chicken wire made of carbon atoms and their bonds. The crystalline or "flake" form of graphite consists of many graphene sheets stacked together.
Learn more about quantum dots from the many resources on this site, listed below. More information on Graphene can be found here.
Coupled Effect of Strain and Magnetic Field on Electronic Bandstructure of Graphene
Ranking is calculated from a formula comprised of user reviews and usage data. Learn more ›
07 Dec 2010 | Publications | Contributor(s): yashudeep singh
We explore the possibility of coupling between planar strain and perpendicular magnetic field on electronic bandstructure of graphene. We study uni-axially, bi-axially and shear strained graphene …
nanoHUB.org, a resource for nanoscience and nanotechnology, is supported by the National Science Foundation and other funding agencies. | <urn:uuid:1a7625c4-4870-4e5c-ac30-bf972c9ea767> | 3.25 | 304 | Content Listing | Science & Tech. | 35.301429 |
This is the first in a series of group posts by a few of us bloggers interested in the science of climate change. For our first “mob” post, Tamino at Open Mind, Eli at Rabbet Run and yours truly here at Maribo are all writing about the carbon cycle and atmospheric carbon dioxide.
Much of the discussion on Maribo centers around the science politics of setting a short- and long-term GHG or carbon emissions target in order to stabilize atmospheric concentrations and avoid ‘dangerous’ climate change.
The emissions targets depend on how much - and for how long - the carbon dioxide we emit actually remains in the atmosphere. We need to understand the ability of the planet to take carbon out of the atmosphere, and how that itself is sensitive to climate change. The figure (IPCC WG1, Fig. 7.4) shows the annual fraction of fossil fuel emissions that remained in the atmosphere (black line is a five year mean). I'll come back to this.
The atmosphere is often compared to a bathtub. The emissions of carbon dioxide – the flow into the bathtub – are currently greater than the uptake of carbon – the flow out the drain. So carbon dioxide is accumulating in the atmospheric tub.
Personally, I like to say emissions are currently faster than the planetary uptake. Over geological time, millions of years, carbon is removed from atmosphere by weathering of rock and by burial in marine sediments. Burning fossil fuels releases this ‘fossil’ carbon to the atmosphere; deforestation and biomass burning quickly releases carbon that was stored over decades or centuries in trees. We’ve effectively sped up the flow of carbon into the atmosphere.
The increase in atmospheric CO2 since the Mauna Loa record began in the 1950s is only about half (~55%) of fossil fuel emissions. The rest has been absorbed by the oceans and terrestrial ecosystems.
The ocean ‘sink’ is best understood and easiest to measure. It can be almost entirely explained by the dissolution of CO2 in sea water, the reason the pH of the oceans is declining. Since solubility of CO2 decreases with temperature, much of this uptake has occurred in cold waters of the Southern Ocean. Other potential, but currently negligible on a global scale, ocean sinks include increases in photosynthesis by plankton [and deep-water burial of the ‘fixed carbon’] and changes in ocean circulation.
So we know with good confidence that about 30% of fossil fuel emissions have been absorbed by the oceans and the remainder by terrestrial ecosystems. The remainder must be taken up by terrestrial ecosystems.
The land sink is more challenging to quantify. We know there has been a net uptake of carbon on land. The knowledge of anthropogenic emissions and good estimate of the ocean sink allow us to infer this total land uptake or land sink. So that means carbon uptake by photosynthesis by terrestrial ecosystems is greater than carbon emissions by those ecosystems, from respiration, but also from disturbances like fires and deforestation.
Notice that I did not include deforestation as a CO2 sources above – just fossil fuel emissions. Deforestation is responsible for about 20% of total anthropogenic CO2 emissions; fossil fuels and the like for the other 80%. But since I’m talking about the net exchange of carbon between land and the atmosphere, carbon emissions from deforestation is folded into the equation.
Anyhow, field observations, including forest inventories, satellite observations of terrestrial productivity, data from ‘flux’ towers at specific locations, and modeling point to a few key players:
- Re-growth of forests on abandoned farmland in the Northern Hemisphere has led to a net uptake of carbon (at least until the trees reach maturity)
- Higher concentration of atmospheric CO2 can increase rates of photosynthesis and hence carbon uptake (“CO2 fertilization”).
- Deposition of nitrogen, emitted by burning of fossil fuels and application of fertilizer, may also be unintentionally ‘fertilizing’ forests
Knowledge of the sinks lets us calculate how anthropogenic CO2 emissions translate into increases in atmospheric concentration. Eli’s post provides a model for doing some simple experiments.
Why does this matter? Our understanding of the modern-day carbon cycle underpins to all that stuff about climate policy that you read, see, hear and smell in the news. Right now, we emit about 8 Gt of C per year, and that translates to, as Tamino points out, an increase of about 2 ppm of CO2/year in atmosphere. But what if climate change alters that way the oceans and the land take up carbon? Then the model has to change.
This is one of the great challenges in climate change science AND climate change policy. To work out what percent reduction is necessary to hit a stabilization level, we need to understand carbon cycle feedbacks: how will climate change alter the fraction of emissions that remain in the atmosphere? Here are three (of many) possible feedback effects:
ii) Drying in the tropics: Reduced rainfall in the Amazon would reduce carbon uptake and increase carbon release through fires
iii) Ocean circulation: A slowing of ocean circulation could limiting productivity in the surface ocean and sinking of carbon (via increasing stratification – topic for another day)
One way to get at these questions is to examine the year-to-year variability in CO2 growth in the atmosphere. What you see in that IPCC figure at the top of the post is that the rate of uptake by the planet varies widely year to year, from less than 20% of emissions, to over 70% of emissions.
There are a few interesting features. The year-to-year variability mostly originates from tropical forest. For example, you can see high airborne fractions or high growth rates during El Nino events (e.g., 1997-1998, 1972-3, 1982-3) due to related droughts (less C uptake) and fires (more C release). That’s not too surprising. It does serve as a warning: future drying in the tropics, due to climate and/or deforestation, could reduce the carbon sink.
In the past, most of the general circulation or climate models used in the IPCC assessments did not included a complete carbon cycle. The atmospheric CO2 concentrations were imposed based on externally generated scenarios. With a complete representation of the carbon cycle, we could instead impose emission, and allow the model to simulate the change in concentrations and uptake by land and oceans.
The latest IPCC assessment includes a comparison of some ‘coupled’ climate-carbon cycle models. All the models predict a decrease in the sink or an increase in the fraction of emissions that remain in the atmosphere. But more on that next time. | <urn:uuid:80a4bf6d-847b-4883-9429-68ab8d010523> | 3.46875 | 1,386 | Personal Blog | Science & Tech. | 39.158152 |
Helen Michel and Frank Asaro with Walter and Luis Alvarez.
The results of the iridium analysis were quite clear and completely surprising. The team (which also included chemists Helen Michel and Frank Asaro) found three parts iridium per billion more than 30 times what they had expected based on either of their hypotheses, and much, much more than contained in other stratigraphic layers! Clearly something unusual was going on at the time this clay layer was deposited but what would have caused such a spike in iridium? The team began calling their finding "the iridium anomaly," because it was so different from what had been seen anywhere else.
Now Alvarez and his team had even more questions. But first, they needed to know how widespread this iridium anomaly was. Was it a local blip the signal of a small-scale disaster restricted to a small part of the ancient seafloor or was the iridium spike found globally, indicating widespread catastrophe?
At left, a simplified graph showing iridium content across the KT boundary as measured at Gubbio, Italy. Follow up work suggested that the clay layer actually contained even more iridium than their first test had suggested 10 parts iridium per billion! At right, Gubbio, Italy and Stevns Klint, Denmark sites which confirmed the widespread presence of an iridium anomaly.
Alvarez began digging through published geological studies to identify a different site that also exposed the KT boundary. He eventually found one in Denmark and asked a colleague to perform the iridium test. The results confirmed the importance of the iridium anomaly: whatever had happened at the end of the Cretaceous had been broad in scale.
The iridium test revealed that an assumption Alvarez and his team had made about iridium deposition at the KT boundary was incorrect. To learn more, visit Making assumptions. | <urn:uuid:3cc0ccd3-5fff-458b-a508-cbafd4ca2d53> | 3.609375 | 373 | Academic Writing | Science & Tech. | 39.633239 |
The Profile class of module profile was written so that derived classes could be developed to extend the profiler. Rather than describing all the details of such an effort, I'll just present the following two examples of derived classes that can be used to do profiling. If the reader is an avid Python programmer, then it should be possible to use these as a model and create similar (and perchance better) profile classes.
If all you want to do is change how the timer is called, or which timer function is used, then the basic class has an option for that in the constructor for the class. Consider passing the name of a function to call into the constructor:
pr = profile.Profile(your_time_func)
The resulting profiler will call
your_time_func() instead of
os.times(). The function should return either a single number
or a list of numbers (like what os.times() returns). If the
function returns a single time number, or the list of returned numbers
has length 2, then you will get an especially fast version of the
Be warned that you should calibrate the profiler class for the timer function that you choose. For most machines, a timer that returns a lone integer value will provide the best results in terms of low overhead during profiling. (os.times() is pretty bad, 'cause it returns a tuple of floating point values, so all arithmetic is floating point in the profiler!). If you want to substitute a better timer in the cleanest fashion, you should derive a class, and simply put in the replacement dispatch method that better handles your timer call, along with the appropriate calibration constant :-). | <urn:uuid:221f6f52-6192-4a02-bc6a-8bcd00cad645> | 2.71875 | 342 | Documentation | Software Dev. | 52.602803 |
We experimented with wireless power transmission. Using copper coils, power can be transmitted several feet in all directions efficiently. A pair of coils will exchange energy while having little effect on other objects around them. Our project builds off the ideas of Nikola Tesla and a research team at MIT. This research may one day lead to laptops, cell phones, and other devices being powered wirelessly.
Unlike Nikola Tesla’s wireless power transmission experiment, which radiated energy into the atmosphere in all directions, like an antenna, our experiment proves to be more efficient. We take advantage of the resonant frequency of two coils of copper tubing, which we formed to specific dimensions in order to have the coils resonate at the desired frequency (between 4.8 MHz and 5.3 MHz). Our loop of 10 gauge wire that drives our primary coil has a small sinusoidal signal running through it, which it radiates. The flux from the driving loop travels through the primary coil and causes the coil to resonate. The secondary coil, which ideally is identical to the primary coil, “picks up” the vibrations from the primary coil and resonates. This interaction between the two coils, known as coupling, allows the primary coil to drive the secondary coil from a distance. Because the frequency they are vibrating at is the natural, desired frequency, it takes less energy to drive the secondary coil at the resonant "natural" frequency. The magnetic flux from the secondary coil induces a current in the receiving loop of 10 gauge wire, which drives a load.The amount of power that the coils transmit decays exponentially as they are moved further apart. As the primary coil resonates it emits evanescent waves that cause the secondary coil to resonate. As with all evanescent waves, the amplitude of the waves emitted by the primary coil diminish exponentially. This explains why the power generated by the secondary coil in the receiving loop decays exponentially as the two coils move further apart. The reason that these frequencies(4.8-5.3 Mhz) were chosen is that very few household objects interact magnetically at these frequencies. Also, organic matter, such as humans, do not interact at these frequencies. This means that there will be no detrimental effects on people or objects in the vicinity of this setup. Frequencies around 5 Mhz are also good because those frequencies, when coupled with the fact that the wave experiences exponential decay, provide us with an adequate mid-range transmitter. Short-range transmitters already exist in applications such as electronic toothbrushes which use transformers to accomplish the power transmission. This is the first mid-range efficient transmission method.
Magnetic resonance occurs when magnetic waves of certain frequencies are absorbed by an object, causing that object to resonate. The frequency absorbed by an object which causes that object to resonate is dependent on many variables, including molecular structure, shape, and size/length of the object. In our experiment we have a primary coil emitting evanescent, magnetic waves that a secondary coil absorbs. Evanescent waves are different from ordinary waves, because evanescent waves oscillate in time, but diminish over distance (This links to an example of evanescent waves) . Assuming the coils are of the same size, shape, and mass, at a certain frequency (the resonant frequency) the primary coil will resonate and cause the secondary coil to resonate as well.
Our experiment had six basic parts: the oscillator, broadcast antenna, sending coil, receiving coil, pick-up antnna,
and load. All of these except the oscillator and load are illustrated in Image 1 below. The broadcast antenna, illustrated
by object A, is a single loop of insulated copper wire. The sending coil and receiving coil are illustrated by objects
B and C respectively.These coils of copper tubing are made to be exactly the same so they resonate at the same frequency.
The pick-up antenna is object D in Image 1 and is connected in series to a load.
The resonant frequency of our coils, at which we get the most power, varies with the distance between the coils. Due to this we chose to use a frequency generator so that we could adjust the frequency as needed. Several oscillators were built to generate certain frequencies, but due to the varying nature of our resonant frequency, the frequency generator was used. A frequency generator outputs a signal of the same frequency as the resonant frequency of our copper coils, because we can output maximum power at this frequency. The signal generated is put into our driving loop of 10 gauge wire. The loop is just smaller than our primary coil (approximately 55.5 cm in diameter). The AC current in the driving loop causes the loop of wire to behave like a dipole. The driving loop is positioned parallel to the primary coil, as close as possible. The flux generated by the driving loop through the primary coil causes the coil to resonate. It is important to realize that the driving loop does not make the secondary loop resonate directly. The evanescent waves emitted by the primary coil causes the secondary coil to resonate, because the coils are of the same shape, size, and mass (or close to identical). Both the primary coil and the secondary coil are made of copper tubing that is 1/4 inch inner diameter (3/8 inch outer diameter). The coils use 60 feet of tubing each, and have about 10 turns (57.5 cm in diameter). At this point the two coils are parallel to each other and resonating, using only enough power to make the driving loop “drive” the first coil. The distance between the primary and secondary coils determines the magnitude of power that is transmitted. The power exponentially decays as the coils are moved further apart. When the secondary coil vibrates at its resonant frequency, a stronger magnetic field is generated. The receiving loop of 10 gauge wire is situated parallel to the secondary coil, as close as possible. The magnetic flux from the secondary coil induces a current in the receiving loop, which drives a resistive load.
To find the power output, we measured the voltage across a 25 ohm power resistor at varying distances and orientations. We took a measurement every 25 cm. We found that the resonant frequency changed with distance due to the imperfect match in the resonant frequencies of our coils. The frequency was then adjusted to find the maximum output voltage at every measurement.
The above graph shows the reduction in power as the distance between the coils increases. At a distance of 3.25 meters it was difficult to discern the signal from the noise.
The linearity in this logarithmic plot shows the exponential decay from our evanescent waves.
We then made the coils perpendicular to each other to reduce the coupling of the two antenna. We observed a similar reduction in power as the distance between the coils increased. The effective range of the power transmission was still 3.25 meters.
The linearity in this logarithmic plot shows the exponential decay still exists even in the perpendicular case. | <urn:uuid:00b257c2-dd2a-4f8a-b481-54fcdaf5fbd5> | 3.8125 | 1,425 | Academic Writing | Science & Tech. | 41.539015 |
This is a struct. The kind of struct is an "edge".
It has three member variables. They are integers. They are named p, q and cost.
It has one member function. A constructor. To create an object of type edge, you will have to use that constructor. The constructor provides default values, so if you don't provide any variables when you construct one, some default values will be used.
It has one overloaded operator. The operator "<". This operator is used to compare two variables of type "edge". It is used to see if the "cost" member variable of one edge is less than that of another edge.
You are reminded that in C++ the difference between a struct and a class is the default level of member visibility. In C++, a struct has member functions. It has constructors. It is just like a class. | <urn:uuid:35a83c23-ed79-4b07-a6e9-cf5ef89a8c17> | 3.53125 | 179 | Q&A Forum | Software Dev. | 65.734888 |
Public Function IsConsonant( _
ByVal vCharCode As Integer _
) As Boolean
Return True if the character with ASCII value vCharCode is a consonant. Examples:
The pre-programmed definitions for the ANSI Windows character set consider consonants to be those alphabetic characters which are not considered vowels.
IsConsonant(Asc("B")) = True
IsConsonant(Asc("A")) = FalseSee also:
IsAlpha FunctionvCharCode: ASCII value of a character which is checked to determine if it is a consonant.
Note: Function will generate a runtime error if vCharCode is < 0 (less than zero). Function will return False if vCharCode is > (greater than) 255.
Copyright 1996-1999 Entisoft
Entisoft Tools is a trademark of Entisoft. | <urn:uuid:efeff871-9064-43bb-b0ea-8aa867b74065> | 3.046875 | 181 | Documentation | Software Dev. | 32.184634 |
This section briefly introduces some concepts important to Sather that the reader may not have been exposed to in C++. It isn't meant as a complete language tutorial. More information of a tutorial nature is available from the WWW page:
S. Burson, "The Nightmare of C++", Advanced Systems November 1994, pp. 57-62. Excerpted from The UNIX-Hater's Handbook, IDG Books, San Mateo, CA, 1994.
At the time of this writing, the only compiler implementing the Sather language specification which is actively maintained is available from GNU. It is freely available, includes source for class libraries and the compiler, and compiles into ANSI C. This compiler has been ported to a wide range of UNIX and PC operating systems. | <urn:uuid:6f97a907-9701-4a6b-ae0e-dd7e0e651ab3> | 3 | 161 | Tutorial | Software Dev. | 51.955831 |
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Applying The Barometer To Weather Watching
You have a barometer. How can you use it as a weather watching aid? Here are a few tips, not an exhaustive list because I know there are others that might be interesting that I have not included.
In a previous piece, I described the types of barometers available and gave methods of setting it to sea-level pressure equivalent. Whether you have adjusted your barometer to sea-level pressure or not, the next step is sit and wait, but first you need to mark the current pressure. If you are using an aneroid barometer, record the pressure or move the marker arm over the current reading that's the "hand" you can change, usually by moving a knob at the centre of the barometer face. With an electronic barometer, hourly data are usually stored for a 12- to 24-hour period. If it doesn't, write down the pressure. If for some reason you are using a mercury barometer, they often have a sliding cursor that can be set to the current pressure level; if not, write it down. Now you wait.
While waiting and watching the skies for other weather signs, you might think about the current sea-level pressure reading. If it is lower than about 1000-1004 mb, your current weather is likely influenced by a low-pressure system. (I'll use millibars (mb) here for pressure since many barometers are so scaled. For kPa, divide by 10; hPa are also used and are equivalent to mb. For other units, see Barometers for Weather Watching.) If it is higher than say 1020 mb, high pressure is the likely local weather influence. For pressures above or below these limits, the more extreme the influence of storminess or clear skies. In between it is hard to say from the local sea-level pressure reading whether high or low pressure dominates, you may be within a transition zone.
After an hour or more, take another reading. How has the pressure changed? Consider both how many millibars it changed and the direction of change. Has it risen, fallen, or remained unchanged? By how much has it changed? Barely, some, quite a lot? This change with time is what is referred to as the pressure tendency.
If there has been no change, likely the weather you are seeing is not changing much unless there has been a significant change in temperature or solar radiation. Unfortunately, this is not a hard rule because a number of weather changes can occur with very small or no observable pressure changes an isolated shower, for example.
The following table gives terms used to describe pressure tendencies over a three-hour period. For the one-hour observation period, divide the table value by 3. You likely won't see the pressure reverse direction during the hour unless a front has passed over you.
The more rapid and extreme the pressure change over a few hours, the more extreme the weather change you can expect. This is particularly true with wind changes. If the pressure is changing by more than 1 mb/hour and if the tendency is downward, expect more stormy weather on the way. If an upward and quick change, storminess is moving out and clearing may be coming in the very near future although it may be quite windy.
The speed of the wind depends on the local pressure gradients, which is the change in pressure over a distance. The greater the gradient, the stronger the wind. The pressure tendency is not always a good predictor of the absolute wind speed, but it can tell you how the wind is likely to change over the next few hours. For example, a strong wind can blow even when the local pressure remains fairly constant. This situation suggests a strong pressure gradient that may be unchanging with time or a pressure pattern that is not moving or doing so very slowly. In such cases, the wind speed may remain high for some time. A similar minimal pressure-change situation occurs when winds are light or changing very slowly, suggesting that they will continue to remain light.
However, when winds are light (Beaufort Number 3 or less) and the pressure begins to change rapidly 1 mb or more per hour expect strong winds to develop shortly. The direction of the pressure change is not important for estimating wind speeds, only its magnitude. The direction does indicate if stormier weather is on its way (dropping pressure) or if clearing is in store (increasing pressure). As a general rule of thumb, the following table gives the likely Beaufort Scale wind speed expected for a given pressure tendency over land and over water. Such winds will likely also be gusty, so peak winds can be significantly higher.
When the pressure drop is moderate or rapid, the region will likely be coming under the influence of an approaching or deepening low pressure system, and therefore a greater likelihood for precipitation. Moderately or rapidly rising pressure usually presages fairer skies and drier weather ahead as a high pressure cell approaches or builds. Such is not always the case, because regional quirks may alter the picture. A prime example is in the snowbelt regions surrounding the Great Lakes when increasing pressure from an arctic high pressure system push strong, cold winds across the relatively warm lake waters to bury the lee shores in snow.
If you are experiencing weather conditions that indicate a cold front is approaching, look for a change in the direction of the pressure tendency. Generally, pressure will fall prior to the front and rise rapidly as the cold front passes. Warm front passages are usually marked by pressure tendencies that stop falling and level out or begin to rise slowly after the front has passed.
The more you watch how weather patterns develop in a specific region, the more you begin to see tell-tale signs in the weather patterns and their sequences. This improves your ability to forecast the coming weather and prepare you to see various weather phenomena. As Yogi Berra said, "You can see a lot by looking."
As we extend our determination of pressure tendencies over three-, six- and twelve-hour periods, the more we can deduce about the weather to come. Many electronic barometers include an encoded forecast scheme that looks at the pressure history to produce a simple forecast for either fair weather, increasing cloudiness, precipitation likely, or clearing weather. In many situations and regions, this simple forecast scheme can be reasonably accurate over a six to twenty-four hour period. Here are some simple rules.
Finally, you likely have heard media meteorologists refer to an intense storm system as a bomb or a weather bomb. The strict definition for such a phenomenon is an extra-tropical low-pressure system whose central pressure falls at an average rate of 1 mb per hour for 24-hours, or 24 mb or more over a 24-hour period. Such rapid development can lead to some wild and dangerous weather. Sometimes at a given location, the passing of a deep storm system and its replacement with a strong high pressure cell can result in a pressure increase of 24 mb or more, and while not technically a bomb, the winds can be fierce during the period.
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The BC Weather Book: | <urn:uuid:dc0103fc-1328-4387-9200-11f240e254da> | 3.078125 | 1,518 | Tutorial | Science & Tech. | 47.472685 |
Risso's Dolphins, Grampus griseus
Taxonomy Animalia Chordata Mammalia Cetacea Delphinidae Grampus griseus
Description & Behavior
Risso's dolphins, Grampus griseus (G. Cuvier, 1812), aka Grampus, are rather large cetaceans with rounded heads, similar in shape to pilot whales. They have a characteristic crease in their melons (the organ in the front of the head used for echolocation) visible from the forehead to the mouth. They have 7 or fewer pairs of teeth located in the front of their lower jaws.
Adult Risso's dolphins are a dark gray with a white underside that becomes whiter with age as the heavy criss-crossed scars that cover their bodies increase. These scars likely result from from encounters with other Risso's dolphins and their primary prey, squid. Circular white scars have also been noted resulting from bites of lampreys, cephalopods and cookiecutter sharks, and some from infestations of parasites or bacterial infections. Juveniles are light gray, which darkens as they age to a brown-gray. Like pilot whales, Risso's dolphins have a white anchor-shaped patch on the ventral side. This species has a tall, curved dorsal fin that tends to be more erect in males and long flippers. The flukes are broad and curved with a deep notch and the tailstock is slender.
Risso's dolphins are a gregarious species that form groups of between 3-30 individuals on average, however they have been known to form massive schools of thousands of dolphins. Recent studies indicate stability among groups, and it is thought that members may be genetically related. Risso's dolphins also travel with other dolphin species, and hybrids between Risso's and bottlenose dolphins have been recorded in the wild and in captivity.
They are an agile species that perform leaps and fluke and flipper slapping. The lifespan is estimated at 20-40 years.
World Range & Habitat
Risso's dolphins, Grampus griseus, are found in offshore temperate and tropical waters worldwide. The northernmost range of their habitat is Newfoundland and the Shetlands in the Atlantic, and the Gulf of Alaska in the Pacific. The southern ranges are Cape Horn, the Cape of Good Hope, Australia and New Zealand. It is not known whether this is a migratory species, however they may move to cooler waters during warmer months and travel to follow prey movement.
Feeding Behavior (Ecology)
Risso's dolphins, Grampus griseus, feed primarily on squid and are also known to feed on a variety of fish.
Risso's dolphins, Grampus griseus, are thought to reach sexual maturity when they reach between 2.6-2.8 m in length in both sexes. Little is known about the reproductive habits of this species, however Risso's dolphins in the North Atlantic have been observed calving during summer months. Calves measure about 1.2-1.5 m in length at birth.
Conservation Status & Comments
It is thought that Risso's dolphins, Grampus griseus, are abundant throughout their range, but population data are unavailable. Off the coast of California where Risso's dolphins are commonly sighted, a population of between 13,000-30,000 is estimated. These dolphins are killed for human consumption in some areas and have been sold on the open market in Taiwan. They are also caught in Japan, and in Sri Lanka where their commercial popularity increased when fisheries began selling their incidentally caught dolphins.
References & Further Research
ACS Risso's dolphin Cetacean Fact Sheet - American Cetacean Society
Photos by Marine Team - a network of professionals working in the marine environment who are dedicated to the conservation of marine species and their habitat.
Whale and Dolphin Conservation Society (WDCS)
Research Grampus griseus » Barcode of Life ~ BioOne ~ Biodiversity Heritage Library ~ CITES ~ Cornell Macaulay Library [audio / video] ~ Encyclopedia of Life (EOL) ~ ESA Online Journals ~ FishBase ~ Florida Museum of Natural History Ichthyology Department ~ GBIF ~ Google Scholar ~ ITIS ~ IUCN RedList (Threatened Status) ~ Marine Species Identification Portal ~ NCBI (PubMed, GenBank, etc.) ~ Ocean Biogeographic Information System ~ PLOS ~ SCIRIS ~ SIRIS ~ Tree of Life Web Project ~ UNEP-WCMC Species Database ~ WoRMS
Feedback & Citation
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Help us continue to share the wonders of the ocean with the world, raise awareness of marine conservation issues and their solutions, and support marine conservation scientists and students involved in the marine life sciences. Join the MarineBio Conservation Society or make a donation today. We would like to sincerely thank all of our members, donors, and sponsors, we simply could not have achieved what we have without you and we look forward to doing even more. | <urn:uuid:e93f3ad1-f1e5-4b60-ad81-243ae982b78c> | 3.5 | 1,081 | Knowledge Article | Science & Tech. | 40.008186 |
In these objects, most atoms are ionised by photons from hot stars embedded within the nebular gas, stripping away electrons. The emitted electrons, (called photoelectrons), may collide with atoms or ions within the gas, and excite them. When these excited atoms or ions revert to their ground state, they will emit a photon. The spectral lines formed by these photons are called collisionally excited lines (often abbreviated to CELs).
CELs are only seen in gases at very low densities (typically less than a few thousand particles per cm³). At higher densities, the reverse process of collisional de-excitation suppresses the lines. Even the hardest vacuum produced on earth is still too dense for CELs to be observed. For this reason, when CELs were first observed by William Huggins in the spectrum of the Cat's Eye Nebula, he did not know what they were, and attributed them to a hypothetical new element called Nebulium. However, the lines he observed were later found to be emitted by extremely rarefied oxygen.
CELs are very important in the study of gaseous nebulae, because they can be used to determine the density and temperature of the gas.
Shock pattern solutions for viscous-collisional plasma ion acoustic waves in view of the linear theory of the non-equilibrium thermodynamics.(Report)
Jun 01, 2012; 1. Introduction The nonlinear propagation of electrostatic disturbances in space and laboratory plasmas has received considerable... | <urn:uuid:14a210a2-8d27-4bb0-826d-7732cd9533c8> | 4.03125 | 315 | Content Listing | Science & Tech. | 36.985615 |
New Species in Indonesia
A group of scientists, exploring the forests of Indonesia in the remote mountains of Foggia, found a wide variety of animal species, including several completely new ones.
International and Indonesian scientists have found that forest wallabies – the smallest member of the kangaroo family in the world.
These discoveries, among them also “gargulievidny” gecko with yellow eyes, were made under the research program in areas that are considered “lost world”.
Wood mouse. Most likely, a new kind of open Christopher Helgenom of the Smithsonian Institution.
They also found the imperial pigeons with gray, white and brown feathers.
Big Fat hairy rat.
Another new species – a bat, feeding on the nectar of tropical plants.
Scientists have found that black and white butterfly that is relevant to the form of an ordinary monarch. This is – one of several species of animals found in the remote mountains of Foggia in Indonesia.
Frog with a nose like Pinocchio. The male of this species nose goes up when he calls a female. When he is less active, her nose is lowered. Herpetologist Paul Oliver has found a frog on a sack of rice in the camp of their research team. | <urn:uuid:438db8ce-599b-4998-bcb9-30b8174f7f4b> | 2.828125 | 263 | Knowledge Article | Science & Tech. | 47.207273 |
Jan. 13, 2010 Forests in northern areas are stunted, verging on the edge of survival. It has been anticipated that climate change improves their growth conditions. A study published in Forest Ecology and Management journal shows that due to their genetic characteristics trees are unable to properly benefit from the lengthening growing season.
Furthermore, the researchers were surprised to find that the mortality of established trees considerably promotes the adaptation of forests to the changing environment.
In cooperation with colleagues at the Universities of Oulu and Potsdam, Anna Kuparinen, Docent at the University of Helsinki's Faculty of Biological and Environmental Sciences, simulated forest growth from southern to northern Finland. A meteorological dispersal model was applied to describe the spread of pollen and seeds in the atmosphere. Above all, the results illustrate the slowness of the adaptation process.
Generally, trees stop growing before the frosts and this cessation of growth has been programmed in their genotype. Therefore, trees are unable to effectively follow the increasing environmental growing season. Instead, they cease growth as dictated by their genotype. It is estimated that after hundred years from now northern forests will substantially lag behind the speed of growth that would be enabled by their environment.
Evolution is promoted by the mortality of established trees
The researchers assumed that demographic characteristics of the trees would have a notable impact on their adaptability. Tree species differ for example so that birch matures at a considerably younger age than pine, and birch seeds spread more effectively than pine seeds. However, the results showed that these differences had only minor impacts. Instead, the mortality of established trees played a large role in the evolutionary adaptation.
The existing trees in northern forests will survive in a warmer climate better than before but, at the same time, they prevent genetically better adapted individuals from becoming more common. In a dense stand, old trees cast a shadow and prevent new seedlings from establishing. In this way, younger seedlings, which would be more suitable to warmer conditions, cannot easily progress beyond the sapling state.
A question closely related to environmental changes is, whether humans should help the populations to adapt? For forests, possible means of human aid include thinning and planting southern seeds to more northern locations.
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Note: If no author is given, the source is cited instead. | <urn:uuid:1c255836-80cb-4dda-998b-93f6886d2949> | 3.96875 | 500 | Truncated | Science & Tech. | 27.397727 |
DEVELOPMENT AND USE OF MITE RESISTANCE TRAITS IN HONEY BEE BREEDING
Location: Honey Bee Breeding, Genetics, and Physiology Research
Title: Honey Bee (Hymenoptera: Apidae) with the Trait of Varroa Sensitive Hygiene Remove Brood with All Reproductive Stages of Varroa Mites (Mesostigmata: Varroidae)
Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 16, 2009
Publication Date: February 1, 2010
Citation: Harris, J.W., Danka, R.G., Villa, J.D. 2010. Honey Bee (Hymenoptera: Apidae) with the Trait of Varroa Sensitive Hygiene Remove Brood with All Reproductive Stages of Varroa Mites (Mesostigmata: Varroidae). Annals of the Entomological Society of America. 103(2):146-152.
Interpretive Summary: Our laboratory has produced honey bees that strongly resist varroa mites by selectively breeding for a trait called varroa-sensitive hygiene (or VSH). VSH is a form of nest cleaning behavior in which adult worker honey bees somehow smell mite-infested brood, and then they uncap and remove the infested pupae from the broodnest. Although this procedure kills and sacrifices the bee pupa, it also kills the developing offspring of the varroa mite. Over time, this behavior reduces the mite population in a colony because the older varroa mites will eventually die before being able to produce many offspring. Previous experiments with VSH bees suggested that they prefer to uncap and remove pupae that are infested with mites that produce offspring. However, there has never been direct evidence that VSH bees had this preference; there was a simple correlation between hygienic removal of brood and reduced fertility of the mites that remained in brood combs after being exposed to VSH bees for 1 week. This paper describes a couple of experiments in which the behavior of VSH bees was interpreted after mite-infested brood was exposed to the bees for only 2-3 hours. It was found that VSH bees had no preference for removing pupae that were infested by mites that produced offspring. They chewed all types of mite-infested pupae, and the level of fertility in the mites that were chewed was the same as the fertility of mites that were protected from hygiene by a screen. Thus, it appears that VSH bees can smell mite-infested pupae regardless of whether the founding mite has produced offspring. Previous work by other researchers had shown the hygienic bees do not remove mite-infested pupae because of either the smell or movement from the founding mite. Thus, because neither the adult mites nor their offspring trigger hygiene, it seems that the most likely stimulus for the hygienic removal of mite-infested pupae by VSH bees has something to do with changes in the bee pupae that are caused by mites. One author had previously suggested that the chemical profiles on the cuticle of pupae change when mites feed upon them, and this may be the source of the signal to the nest cleaning bees.
Varroa Sensitive Hygiene (VSH) is a trait of honey bees, Apis mellifera L., which supports resistance to Varroa destructor mites. VSH is the hygienic removal of mite-infested pupae from capped brood. Bees selectively bred for VSH produce colonies in which the fertility of mites decreases over time. In addition, the fertility of mites decreases after naturally infested combs are exposed to VSH bees for 1 wk. The purpose of this study was to decide if the reduction in mite fertility is caused by the initial selective removal of mites that produce offspring by VSH bees . Initially, we monitored changes in a small patch of capped brood during exposure to VSH bees at 2-h intervals through 60 h, which provided a reference for the subsequent experiment. The time series showed that hygienic manipulations of brood cells by VSH bees occur rapidly, and many pupae are uncapped, recapped and targeted for removal in about 2 h. The approach in the second experiment was to compare the percentage of fertile mites from brood exposed to VSH bees for a 3-h period to the percentage of fertile mites in brood that was protected from hygiene by a screen (on the same comb). Specifically, the fertility of mites found on pupae that were being chewed by VSH bees was measured and compared to mites from protected pupae. There were no significant differences in fertility between the two groups of mites. These results suggest that neither egg-laying by foundress mites nor mite offspring are the stimuli that trigger hygienic removal of mite-infested pupae by VSH bees. It may be that hygienic activities such as the uncapping of brood cells inhibits or disrupts reproduction by varroa mites. | <urn:uuid:8f3fa480-8b8a-4e61-842e-4fe5bd58cd1b> | 3.328125 | 1,091 | Academic Writing | Science & Tech. | 37.018889 |
The blue-eyed darner is a large darner dragonfly that is typically found in western portions of North America, Central America, and northern South America. In North America it ranges west from the Dakotas and north up in to central Canada. It appears as though this species may be extending its range east as we have found specimens of this species here in Minnesota over the past few years. It also may be the case that this species has been here in Minnesota for awhile but since the state has been so poorly surveyed until the past few years it may have been missed. It is easy to identify the species by its bright blue eyes. It also emerges much earlier then most darners. Here in Minnesota the only other darner species that we see as early in the year as the blue-eyed is the springtime darner. The springtime is much smaller so chances are if we see a big darner early in the year it is probably a blue-eyed darner. | <urn:uuid:0fb43317-77d3-41cc-a13b-02ff41a59f71> | 2.8125 | 204 | Personal Blog | Science & Tech. | 55.29603 |
Meteorites hold a record of the chemicals that existed in the early Solar System and that may have been a crucial source of the organic compounds that gave rise to life on Earth. Since the 1960s, scientists have been trying to find proof that nucleobases, the building blocks of our genetic material, came to Earth on meteorites. New research, published next week in the Proceedings of the National Academy of Sciences, indicates that certain nucleobases do reach the Earth from extraterrestrial sources, by way of certain meteorites, and in greater diversity and quantity than previously thought.
- Meteorites: Tool kits for creating life on EarthMon, 8 Aug 2011, 16:38:01 EDT
- Solar system ice: Source of Earth's waterThu, 12 Jul 2012, 16:05:50 EDT
- Earth-bound asteroids carried ever-evolving, life-starting organic compoundsThu, 9 Jun 2011, 15:36:01 EDT
- Meteorite holds clues to organic chemistry of the early EarthThu, 9 Jun 2011, 15:36:37 EDT
- NASA researchers: DNA building blocks can be made in spaceTue, 9 Aug 2011, 10:04:11 EDT | <urn:uuid:bf0765d7-d314-4cb0-a52a-0e8014842dbe> | 3.84375 | 242 | Content Listing | Science & Tech. | 22.678814 |
EARTH SCIENCE LAB
Volcanic Materials Identification
Volcanic Lava Flows and Pyroclastic Materials
Volcanic materials are divided into two main groups: Pyroclastic materials and lava flow materials. Below is a list of the various volcanic material definitions describing the general characteristics of those materials, and in some cases explanations on their formation. Read through these definitions and become familiar with them before proceeding to the online activities.
Lava Flow Materials
Aa: Aa (pronounced "ah-ah" - a Hawaiian term), is lava that has a rough, jagged, spiny, and generally clinkery surface. In thick aa flows, the rubbly surface of loose clinkers and blocks hides a massive, relatively dense interior.
Block: Fragments of lava or rock larger than 64 millimeters in size which form due to the fracturing of viscous lava flow surfaces during flow.
Lava: The term used for magma once it has erupted onto the Earth's surface. Molten rock that erupts from a vent or fissure.
Lava flow: Stream of molten rock that erupts relatively non-explosively from a volcano and moves slowly downslope. An outpouring of lava onto the land surface from a vent or fissure. Also, a solidified tongue-like or sheet-like body formed by outpouring lava.
Pahoehoe: Pahoehoe (pronounced "pah-hoy-hoy" - a Hawaiian term), is a very fluid lava flow, that in solidified form, is characterized by a smooth, billowy, or ropy surfaces.
Pillow Lava: Fluid lava erupted or flowing under water may form a special structure called pillow lava. Such structures form when molten lava breaks through the thin walls of underwater tubes, squeezes out like toothpaste, and quickly solidifies as irregular, tongue-like protrusions. This process is repeated countless times, and the resulting protrusions stack one upon another as the lava flow advances underwater. The term pillow comes from the observation that these stacked protrusions are sack- or pillow-shaped in cross section. Typically ranging from less than a foot to several feet in diameter, each pillow has a glassy outer skin formed by the rapid cooling of the lava by water. Much pillow lava is erupted under relatively high pressure created by the weight of the overlying water; there is little or no explosive interaction between hot lava and cold water. The bulk of the submarine part of a Hawaiian volcano is composed of pillow lavas.
Agglutinate: Cinders, scoria or pumice fragments that have partially welded together to form a cohesive mass. Agglutinate forms when the individual pyroclasts retain a high enough temperature after impact to partially melt together (welding). If the fragment are completely molten after impact, they may begin to flow downhill in what is known as a rootless flow.
Ash (volcanic): Fragments less than 2 millimeters in diameter of lava or rock blasted into the air by volcanic explosions.
Blocks: Fragments of lava or rock larger than 64 millimeters in size that are blasted into the air by volcanic explosions. Blocks are ejected during the eruption in a solid state, while bombs are ejected during the eruption in a semi-solid, or partial molten, condition. Generally, blocks often have an angular appearance, due to the fracturing of solid material during the eruption.
Bombs: Fragments of fluid or partially fluid lava or rock larger than 64 millimeters in size that are blasted into the air by volcanic explosions. Bombs are ejected during the eruption in a semi-solid, or partial molten, condition, while blocks are ejected during the eruption in a solid state. Volcanic bombs undergo widely varying degrees of aerodynamic and/or impact shaping, depending on their fluidity, during the flight through the atmosphere and subsequent impact with the ground. Based on their shapes after they hit the ground, bombs are variously described, in the following graphic terms:
Bread-crust Bombs - These are bombs that have had their surface fractured, without breaking the bomb apart. These fractures form in one of two ways. In both cases, the exterior shell of the bomb cools and solidifies, while the interior remains molten or partially molten. Impact with the surface can cause the bomb to flex, thus fracturing the solid surface. Once on the ground, gases in the molten interior begin to expand, causing the solid surface to fracture and expand.
Cow-Pie Bombs - Also called cow-dung bombs. These are very fluid bombs that are greatly deformed during impact. The fluid nature of the bomb causes the lava to flow outward from the center of the impact, forming a roughly circular, pancake-shaped bomb.
Fusiform bombs - Also called spindle or almond bombs. These bombs have an elongated form which tapers down at each end, with a relatively smooth surface. Many have an almond shape.
Irregular Bombs - These are bombs that have no distinguishing shape, but clearly lack the angular nature common with blocks.
Ribbon bombs - Bombs that have a long flat, ribbon-like form.
Spherical Bombs - As the name implies, these are bombs with a spherical or ball-like shape.
Cinders: Cinders are vesicular lava fragments 1 centimeter or larger in diameter. See Scoria.
Lapilli: Fragments of lava or rock between 2 and 64 millimeters in size that are blasted into the air by volcanic explosions.
Pumice: A light-colored, frothy, vesicular volcanic rock, usually of intermediate and felsic composition, formed by the expansion of gas in erupting lava. Commonly perceived as lumps or fragments of pea size and larger but can also occur abundantly as ash-size particles. Because of its numerous gas bubbles, pumice commonly floats on water.
Pyroclastic: Pertaining to fragmented (clastic) rock material formed by a volcanic explosion or ejection from a volcanic vent. See Tephra.
Reticulite: During the exceptionally high fountaining episodes of some eruptions, an extremely vesicular, feathery light pumice, called reticulite or thread-lace scoria, can form and be carried many miles downwind from the high lava fountains. Even though reticulite is the least dense kind of tephra, it does not float on water, because its vesicles are open and interconnected. Consequently, when it falls on water, it becomes easily waterlogged and sinks.
Scoria: A dark to reddish-colored, scoriaceous, vesicular volcanic rock, usually of mafic composition. Scoria forms when blobs of gas-charged lava are thrown into the air during an eruption and cool in flight, falling as dark volcanic rock containing cavities created by trapped gas bubbles.
Tephra: Solid material of all sizes explosively ejected from a volcano into the atmosphere. Tephra is the general term now used by volcanologists for airborne volcanic ejecta of any size. Historically, however, various terms have been used to describe ejecta of different sizes. Fragmental volcanic products less than 2 mm in diameter are called ash, between 2 and 64 mm in diameter are called lapilli, fragments larger than 64 mm are called blocks if they were ejected during the eruption in a solid state, while bombs are ejected during the eruption in a semi-solid, or partial molten, condition. See Pyroclastic.
All definitions have been taken and/or modified from the CVO Glossary of Volcano and Related Terminology web page. References for original sources are available on the web page.
On each of the following pages you will find an image of a sample of lava flow or pyroclastic material, and a Volcanic Materials Identification Worksheet. You may wish to review the material in the Igneous Rock Identification activity before proceeding.
Many of these samples have more than one texture. If there is more than one texture for a sample, the first texture will be that texture which appears higher on the list of texture. The second texture will be lower in the list. For example, if you determine that the sample has both glassy and vesicular textures, select glassy (higher in the list) for Texture #1, and vesicular (lower in the list) for Texture #2. If you reverse the order of the textures in the list, the textures will be marked as incorrectly identified. | <urn:uuid:304d8956-7ae8-44c6-9e98-0f904572542a> | 4.0625 | 1,776 | Tutorial | Science & Tech. | 35.56 |
Dr Kathy Townsend from Turtles in Trouble with the debris extracted from a coastal sub-adult flat back turtle in Moreton Bay, Australia. Much of this was plastic bag remnants.
To kill a whale
During the 1980s, a technique was being developed by the US navy to detect submarines - a sonar, which unlike regular sonars (which rely on sound created by other vessels) worked through emitting a high power, low frequency sound and then listening for returning echoes. The noise emitted was around 230 decibels, which is around 10,000 times louder than a passenger aeroplane taking off.
As you might imagine, this had some severe effects on marine life:
It was shown that some animals further away from the source were deaf (which is a drawback for animals which rely on being able to hear for reproduction and even feeding sometimes). Closer to the source, 13 Cuvier’s Beaked Whales were found washed up on shore with severe gas embolisms and haemorraging as a result of the pressure waves created by the sound.
180 decibels causes permanent death of hearing tissues in humans, why should the marine environment (which is even more sensitive to loud noises, due to the nature of water) be exposed to it? surely any technique which made use of such loud noises would be banned on land.
Above: How active sonar works, gas embolism in a dolphin liver and a Cuvier’s Beaked Whale. | <urn:uuid:a63a6c3d-5873-40b7-807f-b0d386a41966> | 3.65625 | 302 | Personal Blog | Science & Tech. | 42.184877 |
Prove that if , then
I know how to find , but I don't understand how to find , or that that will be less than b.
Can this even be proved? It doesn't appear to be true.
Here's a geometric proof.
If we try to construct a square equal in area to a given rectangle and the
dimensions of the rectangle are a and b, then the problem is to determine x
such that .
Look at the semi-circle in the diagram. The inscribed triangle is a right triangle, then the two smaller ones are similar. Then, we have:
Therefore, x is mean proportional between a and b, so there geometric mean is .
Since the radius of the semi-circle is , it follows that:
This holds even when a=b.
The geometric mean of two positive numbers never exceeds their arithmetic mean
Another thing to look at algebraically is since
Thanks for the proofs - they were very helpful.
Does anyone know of a good book that explains/gives practice with proofs? I don't need to for any of my courses (I'm currently in Calc II), but I think proofs are interesting, and I'd like to get better at them. Sadly I have little experience because none of the math courses I've taken required me to do proofs. Even when I took geometry in high school, they dumbed it down and barely required any proofs. It's kind of unfortunate, because I'd have more mathematical discipline if it was for a grade. Anyway, I would be interested to learn about proofs in my spare time. | <urn:uuid:29bf0108-5bb3-4b6b-a6b2-dedf46035aa8> | 3.234375 | 328 | Comment Section | Science & Tech. | 66.566875 |
Learn more physics!
why in photoelectric effect an electron absorbs only one photon.
- sachin (age 16)
In principle you can have absorption of multiple photons in the photoelectric effect. In practice the probability is very very small under ordinary circumstances. If you had a strong enough laser beam you could probably observe the effect.
Multiple (two) photon absorption to drive fluorescence is now used in some special microscopes. It does require well-focused lasers, as well as molecules which are good at absorbing those two photons. Mike W.
(published on 03/17/2009)
Follow-up on this answer. | <urn:uuid:02860aae-2f70-4148-8fa7-6f7ce6352843> | 3.171875 | 131 | Q&A Forum | Science & Tech. | 45.574615 |
My Blogs (olelog) are mainly based on my daily reading of earth science news.
Here on whatonearth.olehnielsen.dk I try to weave some of the pieces together to a greater whole with added background info.
A triple junction is the point where the boundaries between three tectonic plates, and three plate margins, meet. At the triple junction a boundary will be one of 3 types - a ridge, trench or transform fault. Of the many possible types of triple junction only a few are stable through time.
Rifting often start at a triple junction. See my log of Sunday, 9. October 2005, 09:17:01 Triple junction and rifting.
The rifting continues in the Red Sea and the African Great Rift Valley
Image from USGS
Map of East Africa showing some of the historically active volcanoes(red triangles) and the Afar Triangle (shaded, center) -- a triple junction where three plates are pulling away from one another: the Arabian Plate, and the two parts of the African Plate (the Nubian and the Somalian) splitting along the East African Rift Zone
Ridge subduction is inevitable on a world covered with plates: there are six present-day examples and probably hundreds of past instances related to former plate configurations. Ridge subduction means that an oceanic spreading center is subducted beneath a tectonic plate.
The clearest example of active spreadng ridge subduction can be observed in detail where the Chile Ridge (red line) subducts beneath South America along the Chile Trench (purple line). This ridge subduction has been going on from the Miocene to the present. The Miocene Epoch is a period of time that extends from about 23.03 to 5.332 million years before the present. At ridge subduction spreading stops beneath the overriding plate and the ridge widens into an inter-slab gap called a slab window.
This Ridge Subduction was treated in my Blog of Friday, 30 March 2007 at http://my.opera.com/nielsol/blog/2007/03/30/ridge-subduction
Prior to the ridge collision the Nazca plate was being subducted at a rapid rate (roughly 80 mm/yr for the past 3 my, and as fast as 130 mm/yr during the late Miocene) in a direction slightly north of east. Following the passage of the triple junction, the Antarctic plate is subducted at a much slower rate, roughly 20 mm/yr for the past 15 my, in a direction slightly south of east.
The 22 May 1960 Chile earthquake generated a 11 metres tsunami causing 61 deaths and $23 million in damage.
See more about this triple junction at this USGS site http://walrus.wr.usgs.gov/research/sopac.html
On the USGS earthquake map to the left I have marked the three plates involved: the Pacific Plate, the Australian Plate and the small Solomon Sea Plate. The black arrows show the movement of the Solomon Sea Plate and the Pacific Plate relative to the Australian Plate. The Red line is the ridge and the purple line the subduction zone.
This Ridge Subduction was treated in my Blog post of
Monday, 2 Apil 2007 at http://my.opera.com/nielsol/blog/2007/04/02/ solomon-earthquake
and Monday, 13 April 2009 at
Since 2007 the Solomon earthquake has been thoroughly studied, and a paper on some of the findings has been published in the journal Science.
The New Georgia Island Group of the Solomon Islands is one of four places where an active or recently active spreading ridge has subducted beneath an island arc. The spreading ridge pushing the small Solomon Sea Plate and the Australian Plate apart is being subducted beneath the Pacific Plate. The situation is rather complicated because the two plates descend beneath the overriding plate at different rates and directions.
According to the study the event began in the Australian Plate and moved across into the Solomon Sea Plate and had two centers of energy separated by lower energy areas, which is noticeable as we normally think earthquakes should stop at the plate boundaries. When the earthquake moved from one plate to the other, it quickly changed direction, mimicking the different plate motion directions of the plates involved. The authors are confident that the fault slip in the two main locations are different by 30 to 40 degrees. That behaviour during an earthquake has probably never been observed before, but it most certainly has happened here before, according to the authors.
Before about half a million years ago, the easternmost segment of the Woodlark Basin spreading ridge was subducting beneath the westernmargin of the Solomon Islands, and the ridgetrench triple junction migrated northwesterly at around 110 to 120 mm/year. The differences in plate subduction rates and directions produced a slab window, which today lies beneath the southern New Georgia Islands. (When a mid-ocean spreading ridge subducts, it typically splits apart at depth to form two tapered slab edges separated by asthenospheric mantle within an inter-slab gap called a slab window).
A cartoon in the paper shows how the Solomon Sea Plate and the Australian Plate subduct as two different layers (slabs) beneath the overriding Pacific plate, with a slab window at depth (shown as increasing empty space between the two coloured slabs). The surface subduction boundary is marked by a red line.
Map based on USGS earthquake map.
The Cocos plate is subducted beneath the Montagua transform fault between the North American plate and the Caribbean plate.
Last modified on
If you have any problems with this page or wish to comment on the site, please e-mail the webmaster | <urn:uuid:b0f42cfb-6771-4706-8a39-71fee444d9e9> | 3.703125 | 1,186 | Personal Blog | Science & Tech. | 49.935474 |
or marine power
(also sometimes referred to as ocean energy
or ocean power
) refers to the energy carried by ocean waves, tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
, and ocean temperature differences. The movement of water in the world’s oceans creates a vast store of kinetic energy
The kinetic energy of an object is the energy which it possesses due to its motion.It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes...
, or energy in motion. This energy can be harnessed to generate
Electricity generation is the process of generating electric energy from other forms of energy.The fundamental principles of electricity generation were discovered during the 1820s and early 1830s by the British scientist Michael Faraday...
electricity to power homes, transport and industries.
The term marine energy encompasses both wave power
Wave power is the transport of energy by ocean surface waves, and the capture of that energy to do useful work — for example, electricity generation, water desalination, or the pumping of water...
— power from surface waves, and tidal power
Tidal power, also called tidal energy, is a form of hydropower that converts the energy of tides into useful forms of power - mainly electricity....
— obtained from the kinetic energy of large bodies of moving water. Offshore wind power
Offshore wind power refers to the construction of wind farms in bodies of water to generate electricity from wind. Better wind speeds are available offshore compared to on land, so offshore wind power’s contribution in terms of electricity supplied is higher....
is not a form of marine energy, as wind power is derived from the wind
Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...
, even if the wind turbine
A wind turbine is a device that converts kinetic energy from the wind into mechanical energy. If the mechanical energy is used to produce electricity, the device may be called a wind generator or wind charger. If the mechanical energy is used to drive machinery, such as for grinding grain or...
s are placed over water.
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...
s have a tremendous amount of energy and are close to many if not most concentrated populations. Ocean energy has the potential of providing a substantial amount of new renewable energy
Renewable energy is energy which comes from natural resources such as sunlight, wind, rain, tides, and geothermal heat, which are renewable . About 16% of global final energy consumption comes from renewables, with 10% coming from traditional biomass, which is mainly used for heating, and 3.4% from...
around the world.
Potential of ocean energy
The theoretical potential is equivalent to 4-18 million ToE.
Theoretical global ocean energy resource
| Annual gen.|
|| Marine current power
Marine current power is a form of marine energy obtained from harnessing of the kinetic energy of marine currents, such as the Gulf stream. Although not widely used at present, marine current power has an important potential for future electricity generation...
|| Osmotic power
|| Ocean thermal energy
|| Tidal energy
|| Wave energy
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
as archipelagic country with three quarter of the area is ocean, has 49 GW recognized potential ocean energy and has 727 GW theoritical potential ocean energy.
The oceans represent a vast and largely untapped source of energy in the form of surface waves, fluid flow, salinity gradients, and thermal.
Marine current power
The energy obtained from ocean current
An ocean current is a continuous, directed movement of ocean water generated by the forces acting upon this mean flow, such as breaking waves, wind, Coriolis effect, cabbeling, temperature and salinity differences and tides caused by the gravitational pull of the Moon and the Sun...
Ocean thermal energy
The power from temperature differences at varying depths.
The energy from moving masses of water — a popular form of hydroelectric power generation. Tidal power generation comprises three main forms, namely: tidal stream power, tidal barrage power, and dynamic tidal power
Dynamic tidal power or DTP is a new and untested method of tidal power generation. It would involve creating large dam-like structure extending from the coast straight to the ocean, with a perpendicular barrier at the far end, forming a large 'T' shape....
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
and natural gas
Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...
beneath the ocean floor are also sometimes considered a form of ocean energy. An ocean engineer
Ocean engineering is an ambiguously defined term that may refer to:*Oceanographic engineering, also called marine electronics engineering, concerned with the design of electronic devices for use in the marine environment, such as the remote sensing systems used by oceanographers*Offshore...
directs all phases of discovering, extracting
The extraction of petroleum is the process by which usable petroleum is extracted and removed from the earth.-Locating the oil field:Geologists use seismic surveys to search for geological structures that may form oil reservoirs...
, and delivering offshore petroleum (via oil tanker
An oil tanker, also known as a petroleum tanker, is a merchant ship designed for the bulk transport of oil. There are two basic types of oil tankers: the crude tanker and the product tanker. Crude tankers move large quantities of unrefined crude oil from its point of extraction to refineries...
s and pipelines
Pipeline transport is the transportation of goods through a pipe. Most commonly, liquids and gases are sent, but pneumatic tubes that transport solid capsules using compressed air are also used....
,) a complex and demanding task. Also centrally important is the development of new methods to protect marine wildlife and coastal regions against the undesirable side effects of offshore oil extraction.
- Energy harvesting
Energy harvesting is the process by which energy is derived from external sources , captured, and stored for small, wireless autonomous devices, like those used in wearable electronics and wireless sensor networks.Energy harvesters...
Hydropower, hydraulic power, hydrokinetic power or water power is power that is derived from the force or energy of falling water, which may be harnessed for useful purposes. Since ancient times, hydropower has been used for irrigation and the operation of various mechanical devices, such as...
- Renewable energy commercialization
Renewable energy commercialization involves the deployment of three generations of renewable energy technologies dating back more than 100 years. First-generation technologies, which are already mature and economically competitive, include biomass, hydroelectricity, geothermal power and heat...
- SAS Ocean Energy (of Pakistan) | <urn:uuid:0d7366b5-2ed8-413b-bfe8-c53a43d51533> | 3.46875 | 1,723 | Knowledge Article | Science & Tech. | 34.745245 |
Science Fair Project Encyclopedia
In Greek mythology, Stentor was a herald on the Greek side during the Trojan War. His name has given rise to the adjective "stentorian", meaning loud-voiced, for which he was famous. See the Iliad, V, 783.
In biology, Stentor is a genus of ciliate protozoa, representative of the heterotrichs. The body is generally trumpet-shaped, hence the association with the herald, with a ring of prominent membranelles around the anterior "bell" that sweep in food and aid in swimming. Stentor are common in freshwater lakes and streams, usually attached to algae and other detritus. Some reach several millimetres in length, making them among the largest single-celled organisms.
The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details | <urn:uuid:cc925643-acf8-4e90-a945-e9a239115b5d> | 3.296875 | 196 | Knowledge Article | Science & Tech. | 42.762143 |
The autoDtd program creates a DTD file from an XML file example. The program also generates an "attributed tree" and a summary of the actual data in the file.
Listing Four (available electronically) shows the DTD autoDtd generates from the XML file in Listing One. It starts out by defining XML entities to represent numerical data. Most XML parsers will treat these entities as synonyms for strings (CDATA). However, autoDtd and xmlToSql know to map them to numerical types in C and SQL, respectively. The DTD continues with ELEMENT and ATTLIST definitions. The elements correspond to the tags in the XML file. The parenthesized lists after the element name describe the legal child tags. The child tags followed by "?" are optional. "*" indicates that any number of children of this type can follow. "+" indicates there must be at least one child of this type. The ATTLIST describes the attributes within a tag. Note that the x attribute is of type %float; and the y attribute is of type %int;. This is because of the value 3.0 for the x attribute in one of the points in the example, while there are no decimal points in the y values.
Listing Five (available electronically) shows the "attributed tree" output of autoDtd. This is a denser, more readable representation of the same data structures. There is a line for each type of tag in the XML file. Children are indented in lines following their parent. Attributes, if any, are on the same line following the tag name. The data type, if any, is indicated by a letter before the tag or attribute name, with "$" representing strings, "#" representing integers, and "%" representing floating-point numbers. Tag names may be followed by the characters ?, *, or + with the same meaning they have in DTD files.
The stats output of autoDtd (Listing Six, available electronically) summarizes the contents of the XML file. It is also used by the xmlToSql program to decide which fields to index. The stats output begins with a comment that describes the format. | <urn:uuid:4587f04a-e0af-45b3-97e8-2c580e124d7a> | 3.0625 | 452 | Documentation | Software Dev. | 51.799347 |
The In-place Hybrid MSD N-bit-Radix Sort I presented in In-place Hybrid N-bit-Radix Sort was developed as a combination of Radix Sort, Insertion Sort, and Counting Sort. This algorithm sorts arrays of integers (8, 16, 32, and 64-bit, unsigned and signed), and significantly outperforms STL sort(), which is a hybrid combination of QuickSort, Heap Sort, and Insertion Sort. In-place Hybrid MSD N-bit-Radix Sort algorithm uses a recursive Radix Sort technique based on the most-significant-digit (MSD). It sorts based on the MSD first, followed by the next digit and so on until all digits have been used for sorting. The algorithm has a nice property of being in-place (not requiring extra memory), but lacks being stable.
Stable algorithms resolve ties between array elements by placing the element that appeared first in the input array as first in the output array. Stability is not necessary when sorting only numbers, as it is impossible to differentiate the result which was sorted using a stable algorithm from one sorted using a non-stable algorithm. In this article, I develop and optimize a stable version of the MSD Radix Sort since stability is useful in cases of sorting other than only numbers.
Stable MSD Radix Sort Concept
The following discussion illustrates how an MSD Radix Sort works with decimal numbers. In this case, the radix is 10, and Decimal-Radix sorting is being performed (10-Radix Sort).
Three numbers start with a zero ( 07, 09, 01 ), four numbers start with a one (13, 15, 15, 19), three numbers start with a two (22, 28, 21 ), none start with a three, two numbers start with a four (45, 42).
Use an output array of equal size to the input array, and split it into bins that hold 3 elements, 4 elements, 3 elements, and 2 elements (as we just counted).
Place all numbers that started with zeros into the bin zero, all numbers that started with ones into the bin one, that started with twos into bin two, and so on.
Sort each of these bins based on the second digit
Create an output array of equal size for each input bin:
Place all numbers that have the second digit equal to a one in bin one, all numbers that have the second digit equal to two in bin two, and so on.
Assemble all of the bins together into a single sorted array
Note this procedure took two passes over all of the array elements: one pass for the left-most digit, and the second pass for the second digit; because each element was made of two digits in this example. The algorithm takes two passes over the entire array no matter how many elements are in the array to be sorted. Thus, run time is linear in order, times the number of digits in the elements -O( dn ), where d is the number of digits and n is the number of elements in the array. | <urn:uuid:01e14fa4-4dc4-4ad9-a2a0-5f6a9bb5848b> | 2.8125 | 634 | Documentation | Software Dev. | 49.987037 |
Vestas V164 is the world’s largest ocean wind turbine
In 1919 a German physicist Albert Betz had concluded that no wind turbine can convert more than 59.3% of the kinetic energy of the wind into mechanical energy turning a rotor. Today this is known as Betz Limit or Betz Law.
However, the same maximum result was obtained earlier by a British scientist Lanchester in 1915 and also obtained by a Russian aerodynamic scholar Zhukowsky in 1920. Al Jazari, the father of robotic engineering even a number of centuries earlier had explained about the utilization of wind energy in his book, the Book of Ingenious Devices (Arabic: Kitab al-Hiyal).
Wind Energy: Kinetic Energy of Wind Turbine
The incoming wind energy to the wind turbine is at 100%, say Einput = 100. Wind energy is a kinetic energy and is given by equation ½ mv2. The equation describe that the kinetic energy is relatively dependent on the speed (or velocity) of the wind, v.
For example, if the wind turbine could collect or gain wind’s kinetic energy 100% from the incoming wind Einput. The wind energy at the exit of the wind turbine would be zero. The velocity or speed of the wind also would be zero.
If the wind stops moving at the exit of the wind turbine, then no more fresh or new wind could get in, because it’s being blocked. This explains why that the wind turbine could not gain 100% of kinetic energy from wind rather than maximum of 59.3% from the total wind’s kinetic energy.
For a wind turbine to rotate and collect wind’s kinetic energy there has to be some wind movement to the turbine, some of the wind energy collected and some is left and flow out.
Wind Energy: Turbine Efficiency
Based on the first article that we have discussed previously about wind power and wind energy, all those numbers could be multiply with 0.593. This is the theoretical maximum power of any design of wind turbines.
Equation from the previous article for power of wind hitting the turbine:
Powerwind = 1/2 x Swept Area x Air Density x Velocity3
Theoretical maximum power of wind turbine:
Powermax-turbine = 0.593 x (1/2 x Swept Area x Air Density x Velocity3)
In real world limit below “Betz limit” such as 0.35 to 0.45 is a common even among the world’s best designed wind turbines. So if somebody comes to convince you saying that their product could collect 80% from wind energy you already know the answer. On the other hand if somebody comes and telling you the truth that their design could collect only 25% of wind energy, you have to shake his hand immediately for his honesty.
This is the link for some models of smaller wind turbines for home usage if readers might be interested to see, Wind Energy for Home. In their website you could find as well some DIY models which are easy for installation. Hopefully, we are going to discuss more on other topics of wind energy in the next coming articles. Thanks for reading.
Next & Previous articles in series: | <urn:uuid:768d7a1e-96c2-4ef9-8bf7-335d45098711> | 3.625 | 670 | Knowledge Article | Science & Tech. | 55.18964 |
ANSI Common Lisp 7 Objects 7.1 Object Creation and Initialization
The generic function shared-initialize is used to fill the
of an instance
using initialization arguments and :initform
forms when an instance is created, when an
instance is re-initialized,
when an instance
is updated to conform to a redefined class, and when
an instance is updated to conform to a different class.
standard method combination. It takes the following arguments: the
instance to be initialized, a
specification of a set of names of slots
accessible in that instance, and any number of initialization
arguments. The arguments after the first two must form an
initialization argument list.
The second argument to shared-initialize may be one of the following:
- It can be a (possibly empty) list of slot names,
which specifies the set of those slot names.
- It can be the symbol t, which specifies the set of all of the slots.
There is a system-supplied primary method for shared-initialize
whose first parameter specializer is the class standard-object.
This method behaves as follows on each slot,
whether shared or local:
- If an initialization argument in the
initialization argument list specifies a value for that slot,
that value is stored
into the slot, even if a value has already been stored in the slot
before the method is run.
The affected slots are independent of which
slots are indicated by the second argument to shared-initialize.
- Any slots
indicated by the second argument that are still
unbound at this point are initialized according to their
:initform forms. For any such slot
that has an :initform form,
that form is evaluated in the
lexical environment of its defining
defclass form and the result is stored into the slot.
if a before method stores a value in the
slot, the :initform form will not be used to supply a value
for the slot. If
the second argument specifies a name that does not correspond to any
in the instance, the results are unspecified.
- The rules mentioned in Section 7.1.4 Rules for Initialization Arguments are obeyed.
The generic function shared-initialize is called by the
system-supplied primary methods
initialize-instance. Thus, methods can be written for
shared-initialize to specify actions that should be taken in all of | <urn:uuid:f8b38d3c-c52b-44a8-9f0c-095969854ca9> | 2.78125 | 514 | Documentation | Software Dev. | 35.468944 |
BLACK SMOKER CHIMNEY ROCKS
Some of the most inaccessible rocks on Planet Earth are on the seafloor, at mid-ocean ridges (spreading centers, where two tectonic plates are separating). Seafloor hydrothermal vents at mid-ocean ridges were first discovered back in the 1970s, but they still demand much awe and wonder.
Near spreading centers, cold ocean water that has percolated downward into oceanic crust gets heated up and rises through fracture systems to emerge as seafloor hydrothermal springs. While in the subsurface, the superheated waters leach out metals and other materials from the rocks. As the waters emerge from the seafloor, the surrounding cold bottom waters induce precipitation of dissolved minerals. The result is small to large chimneys that appear to be smoking (see example; another example). It’s not really smoke. The chimneys are emitting clouds of finely-crystalline precipitates. The chimneys themselves are composed of several different minerals, and are gradually built up by consolidation of precipitates. The rocks making up these black smokers are dominated by sulfide minerals.
Here’s a partial cross-section slice from two amalgamated seafloor chimneys. The golden-brown, metallic-lustered, sparkly material along the upper left margin is principally chalcopyrite (CuFeS2 - copper iron sulfide). The dark material in the rest of the specimen is mostly a mix of chalcopyrite and sphalerite (ZnS - zinc sulfide). The whitish material is principally anhydrite (CaSO4 - calcium sulfate).
Black smoker chimney rock (above & below; 8.8 cm across) - partial cross-section slice of two amalgamated chimneys.
Below: labels indicate chimney interiors and white line shows approximate boundary between the two fused chimneys.
Black smoker chimneys vary in size from quite small to well over 100' tall. They are moderately unstable on short geologic time scales. An abundance of odd life forms occupy the environs of these seafloor hydrothermal vents. Unlike ecosystems anywhere else, the base of the food chain for these vent biotas is not photosynthetic organisms, but chemosynthetic organisms. It's been hypothesized that life on Earth originated in seafloor hydrothermal vent areas.
Collected 19 November 1981 by the deep-sea submersible Alvin (Alvin dive # 1156).
Locality: seafloor hydrothermal vent at 2597 meters depth, northern East Pacific Rise, near-easternmost Pacific Basin. Coordinates: 20° 51.00’ North, 109° 04.00’ West. | <urn:uuid:564bbe0e-de9c-4570-83c0-c34a1431ebd1> | 3.703125 | 576 | Knowledge Article | Science & Tech. | 36.171378 |
IT'S dog eat dogor more properly jelly eat jellyin the Black Sea. The latest comb jelly to arrive is gobbling up an earlier invader that ran riot when it reached the sea in the 1980s, wrecking its ecology.
The seeds of disaster were sown in the 1970s as increasing salinity, pollution and overfishing began to bite. "The Black Sea ecosystem was about as screwed up as something could get," says Monty Graham, a biologist at the Dauphin Island Sea Lab in Alabama. Then the comb jelly
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content. | <urn:uuid:15fe9892-23c0-4848-9f35-2f86f02148dd> | 2.703125 | 140 | Truncated | Science & Tech. | 53.532298 |
Malagopsis doggeri has no common name, which is true of more than 90% of insect species.
Malagopsis doggeri is just one of hundreds of thousands of parasitic wasps, and despite its bright coloration and relatively large size, it was only discovered in 2003. The species was named after the senior authors pet dog.
The image above is of the only known specimen, the holotype, which was collected in Kibale Forest National Park in Western Uganda in August 2003.
Learn about the distinctive facial protuberance of Malagopsis doggeri and the Afrotropical genera it is believed to be related to.
Read about the biology of parasitoids and find information regarding the size of Malagopsis doggeri.
Discover the areas of the world that Malagopsis doggeri has been found and the type of habitat it has been collected from.
Find out why it is hard to assess the conservation status of Malagopsis doggeri.
Get reference material for Malagopsis doggeri.
Despite its bright coloration and relatively large size, Malagopsis doggeri was only discovered in 2003.
The adult female uses her ovipositor to reach, paralyse and lay an egg on the concealed host.
A typical environment for the habitat of Malagopsis doggeri. | <urn:uuid:ce27f5a8-c78c-491f-b97b-83595e327880> | 3.21875 | 280 | Knowledge Article | Science & Tech. | 29.257687 |
Nitrogen becomes artificial fertilizer
In the Haber-Bosch process nitrogen is extracted from the air to form ammonia. This is an important stage in the production of artificial fertilizers and the process won Fritz Haber the 1918 Nobel Prize in Chemistry. Even though the chemical process has been known for a long time, thanks to Ertl’s work we now understand how it functions. The reaction can only take place on a catalytic surface of iron. The surface provides support to enable the atoms in the nitrogen molecules to release their bonds so that they can bind to hydrogen and form ammonia. Ertl has studied the reaction with the help of several different spectroscopic methods and put the different results together to form the complete picture. | <urn:uuid:4cff28c1-c990-43bf-98f1-5364ecbdb6cb> | 3.421875 | 148 | Knowledge Article | Science & Tech. | 41.162857 |
That's the sound of steam bursting from the Earth at Nevada Geothermal's Blue Mountain project. Harnessing the earth's heat to generate electricity has long been an overlooked renewable resource, despite having produced power reliably in Italy since 1904.
You see, the Earth's heat never stops—meaning a geothermal power plant can produce electricity as regularly as a nuclear power plant can. And it also has nearly no emissions of the greenhouse gases causing climate change.
The U.S. produces more than 100,000 gigawatt-hours per year of geothermal electricity already, but it could produce as much as 3.2 trillion gigawatt-hours. So why isn't there more? Well, it comes down to economics. Unlike drilling to reach oil and natural gas fields, drilling for geothermal power doesn’t produce immediate dividends.
The U.S. Department of Energy aims to help with that by funding research into subsurface exploration. And right now near Reno, Nevada, U.S. government scientists and partners are testing an advanced geothermal technology that could make it available across the country. Here's hoping they make steam.
[The above text is an exact transcript of this podcast.] | <urn:uuid:5f317f2e-7283-400c-b9e5-15e26605ec24> | 3.53125 | 246 | Truncated | Science & Tech. | 55.652229 |
In an electrolytic cell electrical energyA system's capacity to do work. is consumed and an otherwise spontaneous redox reaction is reversed. A galvanic cellAn electrochemical cell in which a spontaneous reaction occurs. Such a cell can be used to generate electricity. Also called voltaic cell., on the other hand, produces electrical energy as a result of a spontaneous redox process. The electronA negatively charged, sub-atomic particle with charge of 1.602 x 10-19 coulombs and mass of9.109 x 1023 kilograms; electrons have both wave and particle properties; electrons occupy most of the volume of an atom but represent only a tiny fraction of an atom's mass. transfer characteristic of such a process is made to occur in two separate half-cells. Electrons released during an oxidationThat part of a chemical reaction in which a reactant loses electrons; simultaneous reduction of a reactant must occur. half-equation must flow through a wire or other external circuit before they can be accepted in a reductionThat part of a chemical reaction in which a reactant gains electrons; simultaneous oxidation of a reactant must occur. half-equation. Consequently an electrical current is made to flow.
A typical galvanic cell, the Daniell cell, was used to power telegraphs 100 years ago. This cell is based on the spontaneous redox reaction
Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s) (1)
(You can verify that this reaction is spontaneous by dipping a piece of zinc metalAn element characterized by a glossy surface, high thermal and electrical conductivity, malleability, and ductility. in a copper sulfate solutionA mixture of one or more substances dissolved in a solvent to give a homogeneous mixture.. In a short time the surface of the zinc will become plated with red-brown copper metal.) The half-equations
Zn(s) → Zn2+(aq) + 2e– (1a)
Cu2+(aq) + 2e– → Cu(s) (1b)
indicate that for each mole of zinc which is oxidized and goes into solution as zinc ions, 2 mol electrons are transferred to copper ions, converting them to copper atomsThe smallest particle of an element that can be involved in chemical combination with another element; an atom consists of protons and neutrons in a tiny, very dense nucleus, surrounded by electrons, which occupy most of its volume..
To produce electrical current we must prevent the Zn(s) from contacting the Cu2+(aq) ions and transferring the electrons directly. This is done in the Daniell cell by pouring a concentratedIncreased the concentration of a mixture or solution (verb). Having a large concentration (adjective). copper sulfate solution into the bottom of a glassA solid material that does not have the long-range order of a crystal lattice; an amorphous solid. A glass melts over a range of temperatures instead of having the definite melting temperature characteristic of crystalline solids. jar and then carefully pouring a layer of less concentrated zinc sulfate solution above it. Because it contains less soluteThe substance added to a solvent to make a solution. per unitA particular measure of a physical quantity that is used to express the magnitude of the physical quantity; for example, the meter is the unit of the physical quantity, length. volume, the zinc sulfate solution is less dense. It floats on the copper sulfate and does not mix with it. Therefore a copper electrodeIn an electrochemical cell, a surface on which oxidation or reduction occurs; an electrode conducts electric current into or out of a cell. placed in the bottom of the jar contacts only Cu2+(aq) ions, and a zinc electrode suspended in the zinc sulfate solution contacts only Zn2+(aq) ions.salt bridgeA connection that permits ions to pass but that restricts the flow of solution between the anode half cell and the cathode half cell in an electrochemical cell.. This contains an electrolyteA substance that dissolves to produce a solution containing ions, which cause the solution to conduct electricity., KCl, so that current can flow from one half-cell to the other, but the contents of the two half-cells cannot mix. The left-hand electrode in Fig. 1 is a Zn rod dipping in a solution of ZnSO4. Thus both components of the Zn2+/Zn redox couple are present, and the metal electrode can conduct electrons produced by Eq. (1a) to the wire in the external circuit. Since oxidation of Zn to Zn2+ occurs at the left-hand electrode, this electrode is the anodeThe electrode in an electrochemical cell where oxidation occurs. The positively charged electrode in a vacuum tube..
The right-hand electrode is a strip of Cu dipping in a solution of CuSO4. Here both components of the Cu2+/Cu redox couple are present, and Eq. (1b) can occur. Electrons supplied by the external circuit are conducted through Cu to the electrode surface, where they combine with Cu2+ ions to produce more Cu. Since reduction occurs at this right-hand electrode, this electrode is the cathodeThe electrode in an electrochemical cell where reduction occurs; the negatively charged electrode in a vacuum tube.. The net effect of the two half-cells is that electrons are forced into the external circuit at the anode and withdrawn from it at the cathode. This will cause current to flow, or, if current is prevented from flowing by a device such as the voltmeter in Fig. 1, it will cause an electrical potential difference (voltage) to build up.
The components of the redox couples at the electrodes in a galvanic cell need not always be a solidA state of matter having a specific shape and volume and in which the particles do not readily change their relative positions. and a species in solution. This is evident from Fig. 2. In this case the spontaneous redox reaction
2Fe2+(aq) + Cl2(g) → 2Fe3+(aq) + 2Cl–(aq) (2)
is involved. The oxidation half-equation at the anode is
Fe3+(aq) → Fe2+(aq) + e– (2a)
Thus at the right-hand electrode in Fig. 2 both components of the redox couple are in aqueousDescribing a solution in which the solvent is water. solution. Reaction (2a) occurs at the surface of the platinum wire, which conducts the released electrons to the external circuit.
The left-hand electrode in Fig. 2 is a gasA state of matter in which a substance occupies the full volume of its container and changes shape to match the shape of the container. In a gas the distance between particles is much greater than the diameters of the particles themselves; hence the distances between particles can change as necessary so that the matter uniformly occupies its container. electrode. It consists of a platinum strip dipping in a solution which contains chloride ions. The electrode is surrounded by a glass tube through which chlorine gas can be pumped. At this electrode the reaction is a reduction:
Cl2(g) + 2e–→ 2Cl–(aq) (2b)
Therefore the left-hand electrode is the cathode. Since electrons are forced into the external circuit at the anode and withdrawn at the cathode, electrons flow from right to left in this cell. | <urn:uuid:01800929-e7e1-424b-ad40-59c91660faa7> | 2.984375 | 1,552 | Tutorial | Science & Tech. | 44.531538 |
|A water beetle Rhantus suturalis on bare new pond-liner - its breathing air-bubble is visible at its rear.|
|Beetle larva in side view|
|Beetle larva in dorsal view|
Again, I haven't identified this larva (yet) though it does look like Rhantus, maybe a smallish early stage - time will tell, but there are several which can be seen swimming actively to and from the surface. Meanwhile, up on the surface, taking advantage of surface tension to allow propulsion, pondskaters of the genus Gerris, probably the common pondskater G. lacustris, hunt for prey items that fall into (or rather, onto) the water. This species is well known as an early coloniser of new ponds (Denton 2007) and can be seen skating rapidly towards potential prey which is then pierced with the tubular mouthparts.
|A pondskater Gerris lacustris, an early coloniser of new ponds|
So, although the pond is unlikely to mature that much more before next spring when the first full plant-growing season starts, an aquatic community is beginning to develop and will undoubtedly feature here from time to time as interesting species and behaviour catch my eye.
'Til then, if you'd like more info about creating a wildlife-friendly garden pond, why not download an advice booklet here (from the excellent Pond Conservation).
Denton, J. (2007). Water Bugs and Water Beetles of Surrey. Surrey Wildlife Trust, Woking.
Foster, G.N. & Friday, L.E. (2012). Keys to the adults of water beetles of Britain and Ireland (Part 1) (2nd ed.). Handbooks for the Identification of British Insects 4(5): i-iv, 1-144.
Savage, A.A. (1989). Adults of the British Aquatic Hemiptera Heteroptera. A Key with Ecological Notes. FBA, Ambleside. | <urn:uuid:a88502c2-0f32-4d62-a24f-4565b1df232d> | 2.8125 | 422 | Personal Blog | Science & Tech. | 57.533893 |
A generator expression is a compact generator notation in parentheses:
A generator expression yields a new generator object. It consists of a single expression followed by at least one for clause and zero or more for or if clauses. The iterating values of the new generator are those that would be produced by considering each of the for or if clauses a block, nesting from left to right, and evaluating the expression to yield a value that is reached the innermost block for each iteration.
Variables used in the generator expression are evaluated lazily when the next() method is called for generator object (in the same fashion as normal generators). However, the leftmost for clause is immediately evaluated so that error produced by it can be seen before any other possible error in the code that handles the generator expression. Subsequent for clauses cannot be evaluated immediately since they may depend on the previous for loop. For example: "(x*y for x in range(10) for y in bar(x))".
The parentheses can be omitted on calls with only one argument. See section 5.3.4 for the detail.
See About this document... for information on suggesting changes. | <urn:uuid:c3cdc251-b76c-497e-9453-50a1a028e86d> | 3.609375 | 234 | Documentation | Software Dev. | 46.455182 |
Energy in 3 consecutive forms: potential, kinetic, internal (Photo credit: Wikipedia)
A rock has potential energy (PE) localized in it when you lift it up above the ground. The rock is the system; everything else it encounters is the surroundings. Drop the rock and its PE changes to kinetic energy (energy of movement, KE), pushing air aside as it falls (therefore spreading out the rock’s KE a bit) before it hits the ground, dispersing a tiny bit of sound energy (compressed air) and causing a little heating (molecular motion energy) of the ground it hits and in the rock itself. The rock is unchanged (after a minute when it disperses to the air the small amount of heat it got from hitting the ground). But the potential energy that your muscles localized in by lifting it up is now totally spread out and dispersed all over in a little air movement and a little heating of the air and ground.
A hot frying pan? The iron atoms in a hot frying pan (system) in a room (surroundings) are vibrating very rapidly, like fast "dancing in place". Therefore, considering both the pan and the room, the motion energy in the hot pan is localized. That motion energy will disperse—if it is not hindered, according to the second law. Whenever the less rapidly moving molecules in the cooler air of the room hit the hot pan, the fast-vibrating iron atoms transfer some of their energy to the air molecules. The pan’s localized energy thus becomes dispersed, spread out more widely to molecules in the room air.
Some Rusting Iron
In a chemical reaction such as iron rusting, i.e., iron plus oxygen to form iron oxide (rust), the reactants of iron and oxygen don't have to be at a high temperature to have energy localized within them. Iron atoms (as -Fe-Fe-Fe-) plus oxygen molecules of the air (O-O) have more energy localized within their bonds than does the product of their reaction, iron rust (iron oxide).
That’s why iron reacts with oxygen—to release energy from their combined total of higher energy bonds and form the lower energy bonds in iron oxide. Then, all that difference in energy becomes dispersed to the surroundings as heat i.e., the reaction is exothermic and makes molecules in the surroundings move faster. But remember how chemical reactions occur! Remember that it requires energy to break bonds and therefore to start any reaction there must be some extra energy, an activation energy supplied somehow to break a bond or many bonds in the reacting substances. Then, if the bonds that are being formed in the product are much stronger than those being broken in the reactants, that difference in energy (which usually causes greater motion energy of all the molecules) can feed back to break more bonds in the reactants.
However, in the case of iron reacting with oxygen at normal room temperature around 298 K, the process is very slow because only a few oxygen atoms are moving exceptionally fast and hit the iron just right so an Fe-Fe bond and an O-O bond are broken and an Fe-O bond can form. There isn't enough heat (motion energy) localized in nearby iron atoms, and there are no other unusually fast-moving oxygen molecules. It's a slow process depending on collision of the small amount of fast moving oxygen atoms in the surroundings to make it happen.
Therefore, even in moist air (that speeds up another process yielding iron oxide), iron doesn't react very rapidly with oxygen but it steadily does so and in time, both the iron atoms and the oxygen molecule spread out to the surroundings the portion of their bond energy that iron oxide doesn't need for its existence at that temperature.
A Leaky Tire
Air in a tire is at a higher pressure than the atmosphere around it, so it shoots out even from a small hole. (Every spontaneous physical or chemical process involves the second law!) Those nitrogen and oxygen molecules in the tire each have motion energy but it is far more localized, compressed in the small volume of the tire, than it would be in the huge volume of the atmosphere. Thus, the second law explains why punctures or blowouts occur: the motion energy of those localized molecules will become dispersed and spread out to the lower-pressure, larger-volume atmosphere if it is no longer hindered by the tire walls from becoming so.
A Melting Ice Cube
An ice cube melts in a big warm room. How can the melting of a little ice cube in a warm room maybe 200,000 times bigger than it is be an example of the second law? How could that possibly be a spreading out of energy? But the second law has to do with energy dispersal and there's a little spreading out in that 200,001st part of that total of system plus surroundings!
Lots of things are happening when molecules of the warm air disperse some of their energy to the molecules that are vibrating (like dancing rapidly in one place) in the ice cube. Right at the surface many hydrogen bonds between the water molecules of the ice are broken by the motion energy of the air molecules being transferred to the those surface molecules. (This doesn't change the amount of motion energy of those molecules and therefore their temperature doesn't change. They increase in potential energy due to the hydrogen-bond breaking.) Now, because the water molecules whose hydrogen bonds to other molecules in the rigid ice structure are broken, they are free to form hydrogen bonds to other water molecules that are liquid—they can exchange partners and move from one to another. The vibrational energy that allowed them to dance in place in the crystal is changed to translational energy in the liquid and the molecules can move just a bit.
Thus, although the true picture is just a bit more complex (i.e., it is the closer energy levels in translation than in solid vibration that make the energy far more dispersed in liquid than solid), we can sense that the movement of molecules in liquid water allows the energy to be more spread out than in crystalline ice, even at melting temperature. It is not a matter of order and "disorder"!
Order to Disorder
The second law tells us about energy dispersal, and entropy is the word for how that energy dispersal is measured—how spread out the energy becomes in a system, how much more dispersed it has become compared to how localized it was. Such energy changes and consequent entropy changes are the focus for understanding how and why spontaneous events occur in nature. Only sometimes do the structures or arrangements of molecules in an object help us to see greater or lesser localization of energy (that used to be called "order to disorder").
Now we can understand what scientists have been talking about the last century and a half when they spoke in apparently mysterious sentences like "The entropy of the universe increases toward a maximum." All they meant was simply that energy, everywhere, spreads out as much as it can (and that spreading out of energy is measured by entropy).Second,Thermodynamics,life,Energy,Photo,Wikipedia,Rock,system,surroundings,Drop,movement,muscles,room,Some,Iron,chemical,reaction,temperature,product,difference,Remember,activation,collision,molecule,portion,existence,Leaky,Tire,atmosphere,Thus,walls,Cube,times,example,dispersal,Lots,crystal,translation,vibration,disorder,Order,events,nature,arrangements,universe,ScienceShot,Smallest,Possible,news,Largest,beginnings,Chemistry,Mind,Science,drug,children,Technologue,Oceans,Four,Covalent,Bond,Split,atoms,reactions,substances,blowouts,articles,kinetic,molecules,oxygen,oxide,reactants,doesn,hydrogen,entropy
Blogger Labels: Second,Thermodynamics,life,Energy,Photo,Wikipedia,Rock,system,surroundings,Drop,movement,muscles,room,Some,Iron,chemical,reaction,temperature,product,difference,Remember,activation,collision,molecule,portion,existence,Leaky,Tire,atmosphere,Thus,walls,Cube,times,example,dispersal,Lots,crystal,translation,vibration,disorder,Order,events,nature,arrangements,universe,ScienceShot,Smallest,Possible,news,Largest,beginnings,Chemistry,Mind,Science,drug,children,Technologue,Oceans,Four,Covalent,Bond,Split,atoms,reactions,substances,blowouts,articles,kinetic,molecules,oxygen,oxide,reactants,doesn,hydrogen,entropy | <urn:uuid:90ba1e84-3a57-4c53-b92c-00216417fef1> | 3.890625 | 1,837 | Personal Blog | Science & Tech. | 28.841721 |
Our first step was to come up with questions to answer. Then we used the State Climate Office (SCO) database to find information about tornadoes.
After we found out about the locations, dates, and magnitude of the tornadoes, we used a software find the locations of hurricane tracks.
Using this information, we matched the hurricanes to the tornadoes, and made maps using G.I.S. (Geographic Information System) software. | <urn:uuid:ff8af28d-b7c5-40fa-81c7-e4da94cc0d2c> | 2.765625 | 92 | Audio Transcript | Science & Tech. | 46.021304 |
In the diagram the point P' can move to different places along the
dotted line. Each position P' takes will fix a corresponding
position for P. If P' moves along a straight line what does P do ?
In the diagram the point P can move to different places around the
dotted circle. Each position P takes will fix a corresponding
position for P'. As P moves around on that circle what will P' do?
A cheap and simple toy with lots of mathematics. Can you interpret
the images that are produced? Can you predict the pattern that will
be produced using different wheels?
A pattern continues forever in both directions.
Imagine it's on a roll of paper and two strips are torn off, one
of which is turned upside-down and placed underneath the other.
It is not possible to shift the lower strip horizontally so that
it lines up and matches the upper strip.
This problem is about that kind of symmetry.
The pattern is a trace from a point on a rolling wheel.
Before starting, you may find it useful to explore How far does it move? .
Point 1 is on the circumference of the wheel and its trace looks
Forget the wheel for a moment and just concentrate on the trace
If this trace was turned upside-down you would certainly not be
able to line it up with itself.
Would "Trace Two" line up with itself upside-down?
Justify your answer, if you can.
The third trace is made where a horizontal line from Point 1
intersects with a vertical line through the centre of the wheel. It
looks like this :
Can "Trace Three" line up with itself upside-down? | <urn:uuid:b67eb3e8-9290-46af-b938-723034ed3b43> | 4.0625 | 357 | Q&A Forum | Science & Tech. | 68.386316 |
A personal investigation of Conway's Rational Tangles. What were
the interesting questions that needed to be asked, and where did
Label the joints and legs of these graph theory caterpillars so that the vertex sums are all equal.
Find all the ways of placing the numbers 1 to 9 on a W shape, with
3 numbers on each leg, so that each set of 3 numbers has the same
in how many ways can you place the numbers 1, 2, 3 … 9 in the
nine regions of the Olympic Emblem (5 overlapping circles) so that
the amount in each ring is the same?
Label this plum tree graph to make it totally magic!
Think about the mathematics of round robin scheduling.
The Four Colour Conjecture was first stated just over 150 years ago, and finally proved conclusively in 1976. It is an outstanding example of how old ideas can be combined with new discoveries. . . .
This article explains the use of the idea of connectedness in networks, in two different ways, to bring into focus the basics of the game of Go, namely capture and territory.
Find the point whose sum of distances from the vertices (corners)
of a given triangle is a minimum.
The game of go has a simple mechanism. This discussion of the principle of two eyes in go has shown that the game does not depend on equally clear-cut concepts.
Explore creating 'factors and multiples' graphs such that no lines joining the numbers cross
A Hamiltonian circuit is a continuous path in a graph that passes through each of the vertices exactly once and returns to the start.
How many Hamiltonian circuits can you find in these graphs?
Can you cross each of the seven bridges that join the north and south of the river to the two islands, once and once only, without retracing your steps?
If you can copy a network without lifting your pen off the paper and without drawing any line twice, then it is traversable.
Decide which of these diagrams are traversable.
The reader is invited to investigate changes (or permutations) in the ringing of church bells, illustrated by braid diagrams showing the order in which the bells are rung.
The tangles created by the twists and turns of the Conway rope
trick are surprisingly symmetrical. Here's why!
Imagine you had to plan the tour for the Olympic Torch. Is there an efficient way of choosing the shortest possible route?
The knight's move on a chess board is 2 steps in one direction and one step in the other direction. Prove that a knight cannot visit every square on the board once and only (a tour) on a 2 by n board. . . .
The graph represents a salesman’s area of activity with the
shops that the salesman must visit each day. What route around the
shops has the minimum total distance?
This article looks at the importance in mathematics of representing places and spaces mathematics. Many famous mathematicians have spent time working on problems that involve moving and mapping. . . .
This is the second of two articles and discusses problems relating
to the curvature of space, shortest distances on surfaces,
triangulations of surfaces and representation by graphs.
In how many distinct ways can six islands be joined by bridges so that each island can be reached from every other island...
A connected graph is a graph in which we can get from any vertex to
any other by travelling along the edges. A tree is a connected
graph with no closed circuits (or loops. Prove that every tree. . . .
Euler discussed whether or not it was possible to stroll around Koenigsberg crossing each of its seven bridges exactly once. Experiment with different numbers of islands and bridges.
This article for teachers discusses examples of problems in which
there is no obvious method but in which children can be encouraged
to think deeply about the context and extend their ability to. . . .
Toni Beardon has chosen this article introducing a rich area for
practical exploration and discovery in 3D geometry
This article invites you to get familiar with a strategic game called "sprouts". The game is simple enough for younger children to understand, and has also provided experienced mathematicians with. . . .
Eulerian and Hamiltonian circuits are defined with some simple examples and a couple of puzzles to illustrate Hamiltonian circuits. | <urn:uuid:b810c489-44a1-4352-9650-a1b1d72aae6c> | 3.09375 | 906 | Content Listing | Science & Tech. | 58.077562 |
October 2, 2009
A red-black tree is a data structure, similar to a binary tree, which is always approximately balanced, so that individual insert and lookup operations take only O(log n) time. Red-black trees are popular because of their good performance and the relative simplicity of their balancing operations. Our discussion of red-black trees is drawn from Section 3.3 of Chris Okasaki’s book Purely Functional Data Structures.
A red-black tree is a binary search tree in which each node is colored either red or black. A red-black tree maintains two invariants that ensure its balance:
- No red node ever has a red child.
- Every path from the root to an empty node has the same number of black nodes.
Thus, the shortest possible path has only black nodes, and the longest possible path has alternating red and black nodes, so the longest path is never more than twice as long as the shortest path, and the tree is approximately balanced.
Lookup in red-black trees is identical to its binary-tree counterpart; the colors make no difference. The balance condition is maintained by the insert operation. Each new node is initially colored red. If its parent is black, the tree remains balanced, and nothing need be done. However, if its parent is red, the first invariant is violated, and a balancing function is called to repair the violation by rewriting the black-red-red path as a red node with two black children. This may propagate the invariant up the tree, so the balancing function is called recursively until it reaches the root of the tree, which is always recolored black.
Your task is to write functions to maintain red-black trees; you should provide an insert function, a lookup function, and an enlist function that returns a list with the nodes of the tree in order. Each node should contain a key and a value, so the red-black tree can be used as a dictionary, in the manner of the treaps and ternary search tries that we have written in previous exercises. When you are finished, you are welcome to read or run a suggested solution, or to post your own solution or discuss the exercise in the comments below.
Pages: 1 2 | <urn:uuid:d3da7cd3-bde7-405b-b23f-6619758340bc> | 3.609375 | 463 | Tutorial | Software Dev. | 50.993235 |
NEWS > SCIENCE > SCIENTISTS FINALLY MAKE A SMART MOVE BY GIVING ROBOTS BEE BRAINS RATHER THAN HUMAN ONES
SCIENTISTS FINALLY MAKE A SMART MOVE BY GIVING ROBOTS BEE BRAINS RATHER THAN HUMAN ONES
October 3 2012
Sheffield, U.K. – Throughout the years there have been many nightmare scenarios depicted in fiction that show the world being dominated and controlled by evil, malevolent, and very self-aware robots, the types of things that inspire a very keen awareness of the dangers of technology.
We are not, at least yet, anywhere near such advances. In fact the smartest robots in the world right now are barely able to toast bread with explicit instructions so the idea that they will someday soon plot against us and destroy all life on the planet is, at best, a far-fetched concept.
However researchers are working on that very thing, hoping to make robots much smarter and eventually embed them with some of the same traits that human beings have, albeit it with indestructible bodies and incredible strength, a mix that could well lead to the apocalypse we have all been dreading and the eventual end of humanity, Luckily some scientists are no so eager to send humanity into that long goodnight and have instead decided to make robots with the intelligence of bees, something that will most certainly make the robots jerks but not bent on world destruction, we hope at least.
“Because the honey bee brain is smaller and more accessible than any vertebrate brain, we hope to eventually be able to produce an accurate and complete model that we can test within a flying robot,” said lead researcher Dr. James Marshall.
The tests will presumably force the flying killer robots to huddle around a Queen robot and make oil.
It’s not clear if such a brain would be able to be transplanted into larger flying robots, say the size of drones, or actual drones, which of course would end up being a serious problem.
“On the surface this is a great advance because it will allow us to push the technology forward without risking, at least immediately, the end of all humanity but like all technology as it improves it will become more pervasive and ultimately much deadlier and that is a bad thing. It’s good that they will have bug brains for now but what if those bugs grow up?” said Scrape TV Science analyst Dr. Howard Poe. “That is a serious concern. After all bees are jerks and killer robots are jerks and when you fuse those two things you could very well have a recipe for disaster on scale that we could not have possibly imagined. Perhaps we should just get rid of robots entirely.”
It’s not clear how large a Queen killer robot would be, but large and likely nasty.
“I personally do not want to meet my end at the hands of a killer robot. The last thing I want is to have the life choked out of me by some pneumatically controlled grip of steel, well at least that is one of the last things I want. These bee robots would preclude that but I don’t know that what we would be getting would be much better,” continued Poe. “I think that all of this is just dangerous technology and we should really start reconsidering what we are doing with it and why we are doing it. Bees are jerks, robots are jerks, and humans are jerks so all of this is just a disaster waiting to happen really.”
It’s believed likely that the researchers will be the first to die because monsters always turn on their creators first.
Anna Phillips, Science Correspondent | <urn:uuid:2d609341-aea4-4d20-95e1-ff699bea6074> | 2.953125 | 771 | Truncated | Science & Tech. | 50.029973 |
Confuciusornis, from the early Cretaceous of China,
is the oldest known beaked bird, and one of the oldest known
birds -- only Archaeopteryx, from the late Jurassic of
Germany, is older. Confuciusornis is a member of the Confuciusornithidae, the sister-group to the clade composed of Enantiornithes + Ornithurae (includes modern birds).
About the Species
This specimen is preserved in lithographic stone. This is the case for most fossil birds, because their very delicate bones, many of which are hollow, can only survive the fossilization process in environments producing particularly fine-grained stone. Unfortunately, preservation in slabs such as this obscures the entire ventral side of the specimen. However, CT scanning enables us to digitally erase the lithographic stone, revealing the underside of these specimens with unprecedented detail. Examples are shown below.
This specimen was collected from Lower Cretaceous sediments of the Liao Ning Province in northeastern China. It was made available to the University of Texas High-Resolution X-ray CT Facility for scanning by Dr. Jian Guan of the Beijing Natural History Museum and Dr. Oscar Alcober of the Museo de Ciencias Naturales, San Juan, Argentina. Scanning was funded by Dr. Timothy Rowe of The University of Texas at Austin.
About this Specimen
The specimen was scanned by Richard Ketcham and Timothy Rowe on 16-17 July 1998 along the long axis of the slab encasing it for a total of 618 slices, each slice 0.5 mm thick, with an interslice spacing of 0.45 mm (for a slice overlap of 0.05 mm).
Chiappe, L. M., J. Shu-an, J. Qiang, and M. A. Norell. 1999. Anatomy and systematics of the Confuciusornithidae (Theropoda: Aves) from the late Mesozoic of northeastern China. Bulletin of the American Museum of Natural History 242:3-89.
Hou, L.-H., Z. Zhou, L. D. Martin, and A. Feduccia. 1995. A beaked bird from the Jurassic of China. Nature 337:616-618. | <urn:uuid:b6fbd010-9a09-4cc7-a474-58845b5af472> | 3.4375 | 478 | Knowledge Article | Science & Tech. | 53.386958 |
Facts about the Definition of the Element Boron The Element Boron is defined as... A soft, brown, amorphous or crystalline nonmetallic element, extracted chiefly from kernite and borax and used in flares, propellant mixtures, nuclear reactor control elements, abrasives, and hard metallic alloys. The most common uses of Boron are in heat resistant alloys.
Interesting Facts about the Origin and Meaning of the element name Boron What are the origins of the word Boron ? The name originates from a combination of words taken from borax and carbon
Facts about the Classification of the Element Boron Boron is classified as a "Metalloid" element and is located in Groups 13, 14,15, 16 and 17 of the Periodic Table. An element classified as a Metalloid has properties of both metals and non-metals. Some are semi-conductors and can carry an electrical charge making them useful in calculators and computers.
Brief Facts about the Discovery and History of the Element Boron Jons Jacob Berzelius identified boron as an element in 1824. It was isolated by Sir Humphrey Davy, Gay-Lussac and L. J. Thenard in 1808. Pure boron was produced by the American chemist W. Weintraub in 1909.
Occurrence of the element Boron in the Atmosphere Obtained from kernite, boric acid, colemanite, ulexite and borates and produced in USA and Turkey. Boric acid is sometimes found in volcanic spring waters.
Common Uses of Boron Heat resistant alloys
The Properties of the Element Boron
Name of Element : Boron Symbol of Element : B Atomic Number of Boron : 5 Atomic Mass: 10.811 amu Melting Point: 2300.0 °C - 2573.15 °K Boiling Point: 2550.0 °C - 2823.15 °K Number of Protons/Electrons in Boron : 5 Number of Neutrons in Boron : 6 Crystal Structure: Rhombohedral Density @ 293 K: 2.34 g/cm3 Color of Boron : brown
The element Boron and the Periodic Table Find out more facts about Boron on the Periodic Table which arranges every chemical element according to its atomic number, as based on the periodic law, so that chemical elements with similar properties are in the same column. Our Periodic Table is simple to use - just click on the symbol for Boron for additional facts and info and for an instant comparison of the Atomic Weight, Melting Point, Boiling Point and Mass - G/cc of Boron with any other element. An invaluable source for more interesting facts and information about the Boron element and as a Chemistry reference guide.
Facts and Info about the element Boron - IUPAC and the Modern Standardised Periodic Table The Standardised Periodic Table in use today was agreed by the International Union of Pure Applied Chemistry, IUPAC, in 1985 which includes the Boron element. The famous Russian Scientist, Dimitri Mendeleev, perceived the correct classification method of "the periodic table" for the 65 elements which were known in his time. Jons Jacob Berzelius identified boron as an element in 1824. It was isolated by Sir Humphrey Davy, Gay-Lussac and L. J. Thenard in 1808. Pure boron was produced by the American chemist W. Weintraub in 1909. The Standardised Periodic Table now recognises more periods and elements than Dimitri Mendeleev knew in his day but still all fitting into his concept of the "Periodic Table" in which Boron is just one element that can be found. | <urn:uuid:513bf739-f958-4b03-9710-d5a524400e8d> | 3.71875 | 790 | Knowledge Article | Science & Tech. | 45.980591 |
It isn't easy to predict exactly when a satellite like UARS will re-enter Earth's atmosphere, since the space it travels through changes density over time due to incoming particles and radiation energy from activity on the sun. Credit: NASA
Solar Activity Can Affect Re-Entry of UARS Satellite
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The world's eyes are on the Upper Atmosphere Research Satellite (UARS) headed toward re-entry into Earth's atmosphere. The satellite is currently predicted to re-enter sometime on the afternoon of Friday, September 23, 2011, but it hasn't been easy to precisely determine the path and pace of UARS despite the fact that scientists well understand how satellites move through space. The problem lies in the fact that space itself changes over time -- the upper layers of Earth's atmosphere can warm up and, more importantly, puff up in response to incoming energy and particles from the sun.
Satellites experience drag as they move through the outer reaches of Earth's atmosphere, a large region of hot gas known as the thermosphere. Like a marshmallow held over a campfire, the thermosphere puffs up when heated by solar ultraviolet and x-radiation. The more the thermosphere swells, the more drag satellite experience. For satellites at lower inclinations and at low latitudes near the equator, this increase in energy mostly comes from the bright area surrounding sunspots and solar flares. The number of photons at the higher energies can increase by up to 100 times or more within a few minutes due to a single flare, and can then last up to a day before returning to pre-flare levels.
Over the last few weeks a variety of solar events have affected the density of the thermosphere. With an increase in solar activity, there's been a sharp uptick in extreme ultraviolet photons being deposited into Earth's upper atmosphere. In addition, a large flare, categorized as an X1.4 class flare, peaked on September 22 at 7:01 AM ET. The output of this particular flare could increase the drag on satellites at heights of 300 miles by up to about 50%, but at UARS' current altitude of about 110 miles, it will only experience a change in drag of under 1%, but it nevertheless represents the varying solar activities that make for an environment that is difficult to categorize one moment to the next. And that environment has everything to do with the amount of atmospheric drag on UARS and, consequently, its re-entry time. New events occurring on the currently very active Sun might affect the re-entry of UARS even more.
Solar activity driving premature reentry of satellites is not new. Strong solar activity caused the early reentry of the Skylab orbiting observatory, and the famous “Halloween Storms” of Oct-Nov 2003 caused the Student Nitric Oxide Explorer (SNOE) satellite to reenter earlier than expected before these storms occurred.
Measurements by Solar Dynamics Observatory and other spacecraft in NASA's Heliophysics System Observatory are currently helping to refine how scientists and spacecraft operators can predict drag on all satellites.
› UARS website
› Heliophysics, Studing the Sun-Earth Connection website
Phil Chamberlin/Karen C. Fox/Tony Phillips
NASA's Goddard Space Flight Center | <urn:uuid:c03aa946-2ab5-462a-a2f0-2d1d0a6cba8e> | 3.890625 | 675 | Knowledge Article | Science & Tech. | 31.783904 |
Look up monthly U.S., Statewide, Divisional, and Regional Temperature, Precipitation, Degree Days, and Palmer (Drought) rankings for 1-12, 18, 24, 36, 48, 60-month, and Year-to-Date time periods. Data and statistics are as of January 1895.
Please note, Degree Days are not available for Agricultural Belts
Wyoming Temperature Rankings, October 1963
More information on Climatological Rankings
(out of 119 years)
|Aug - Oct 1963
|118th Coldest||1912||Coldest since: 1962|
|1st Warmest||1963||Warmest to Date| | <urn:uuid:54fed444-ba36-49fb-9d8a-232dbbf732b6> | 2.796875 | 140 | Structured Data | Science & Tech. | 51.857104 |
Energy: The Story of the Integral Fast Reactor” by Charles E. Till and Yoon
Chang gives the history of the IFR at
Argonne. The book is now available on Amazon.com…
More about the book
About the authors:
Dr. Charles E. Till, Emeritus Member — National Academy of Engineering (NAE) website
Dr. Yoon Il Chang, Argonne Distinguished Fellow
Reactors Designed by Argonne National Laboratory
Integral Fast Reactor
The Integral Fast Reactor (IFR) is a revolutionary reactor design concept developed at Argonne
National Laboratory. The IFR is a
reactor fueled by metal alloy and cooled by liquid sodium. On
April 3, 1986, two tests demonstrated the inherent safety of the IFR concept. These tests
simulated accidents involving loss of coolant flow. Even with its normal shutdown devices disabled,
the reactor shut itself down safely without overheating anywhere in the system.
The information about the IFR included in this page is reprinted with permission from the book “Plentiful Energy: The Story of the Integral Fast Reactor” by Charles E. Till and Yoon Chang, CreateSpace, ISBN 1-4663-8460-3 (2011).
Integral Fast Reactor
The Integral Fast Reactor (IFR) is a fast reactor system developed at Argonne National Laboratory
in the decade 1984 to 1994. The IFR
project developed the technology for a complete system; the reactor, the entire fuel cycle,
and the waste management technologies were all included in the development program. The reactor
concept had important features and characteristics that were completely new and fuel cycle and
waste management technologies that were entirely new developments. The reactor is a “fast” reactor – that
is, the chain reaction is maintained by “fast” neutrons with high energy – which
produces its own fuel. The IFR reactor
and associated fuel cycle is a closed system. Electrical power is generated, new fissile fuel
is produced to replace the fuel burned, its used fuel is processed for recycling by pyroprocessing – a
new development – and waste is put
in its final form for disposal. All this is done on one self-sufficient site.
The IFR’s history is embedded in the history of nuclear power in the United States – in its ups and downs, and in the plusses and minuses of nuclear technology itself. Its story starts sixty years ago with the first reactor that ever produced useful electrical power. IFR development began in 1984 with the “advanced reactor development program” that was carried out for a decade at Argonne. Although the program was nearly complete in 1994, US President Bill Clinton announced in his State of the Union address that year that, ‘We are eliminating programs that are no longer needed, such as nuclear power research and development’, and the IFR, as the nation’s principal such program, was cancelled. But it continues at a low level in studies and programs of the US Department of Energy and in programs around the world today, due to its ability to provide a truly inexhaustible energy technology for entire nations.
Learn more about the Integral Fast Reactor (IFR)
More information on the Integral
Fast Reactor (IFR) can
be found in the compiled list of links and multimedia features below. If you still have
unanswered questions about the IFR,
send them to
. We’ll be sure to pose them to our researchers, and we’ll respond to you personally.
For more information on the IFR:
- New book tells history of Integral Fast Reactor — NE Highlights (Jan. 13, 2012)
- Passively safe reactors rely on nature to keep them cool — Reprinted from Argonne Logos - (Winter 2002 -- vol. 20, no. 1)
What is the IFR?, by George S. Stanford, Ph.D. (May 2013) [210KB]
- Science Council for Global Initiatives — An international nonprofit organization dedicated to informing the public and policymakers about technologies and strategies that can lead to an energy-rich world.
Papers on the IFR available at the DOE Energy Citations Database:
- The Integral Fast Reactor — by Y.I. Chang, CONF-8810155-28, (1988)
- Integral fast reactor concept: Physics of operation and safety — by D.C. Wade and Y.I. Chang, 6151427, (1988)
- For a more extensive list of papers on the IFR go to DOE Energy Citations Database Search and search for 'integral fast reactor' (using brackets)
For more information on pyroprocessing:
- Argonne’s pyroprocessing and advanced reactor research featured on WGN radio —NE Highlights (Jul. 23, 2012)
The IFR in the Popular Media:
- PBS Interview with Charles E. Till — transcript of an interview done for the show "Why do Americans Fear Nuclear Power?" from PBS Frontline
History of the Integral Fast Reactor (IFR) — A one-hour TV show on the history of nuclear energy in the US, Argonne's role, and the IFR. Re-posted on Vimeo with permission by Steve Kirsch
History of the Integral Fast Reactor
— A 10 minutes version of the TV show on the history of nuclear energy in the US, Argonne's role, and the IFR.
“Pandora’s Promise” the Movie
Watch the official trailer of the documentary by Robert Stone that premiered at Sundance Film Festival 2013 and will open in U.S. movie theaters June 2013 (Screenings list — from “Pandora’s Promise” website).
Last Modified: Tue, May 28, 2013 8:24 PM | <urn:uuid:60382e9a-4830-4434-8e3b-9afed0ac0c5a> | 3.1875 | 1,240 | Knowledge Article | Science & Tech. | 47.977223 |
Scientists have revealed for the first time the genetic information, or genome, of the platypus in the journal Nature today.
This enigmatic and unique animal has a fascinating mix of mammal and reptile characteristics and this research reveals the individual gene groups for these traits.
The results give clues to how the different genes may function in other mammals and further help to understand how these genes evolved.
An international team analysed the DNA from a female platypus and then produced a sequence of the whole genome, the first time this has been done. They compared the genetic information with other mammals and a chicken.
The team identified the genetic areas that correspond to many of the platypus' unusual characteristics.
The platypus, Ornithorhynchus anatinus, also known as duck-billed platypus, is a type of mammal called a monotreme - they lay eggs instead of live young. They also produce milk that the youngsters suckle through the mother's abdominal skin as she lacks nipples. The team found that the genes responsible for lactating were preserved since the last common ancestor of monotremes and ancient mammals branched away from each other about 166 million years ago.
Additionally to laying eggs, platypuses share other characteristics with reptiles, such as the production of venom. However, they are the only mammal to deliver their poison using spurs in their hind legs. The team found the corresponding venom genes to be similar to those in reptiles but they had evolved independently of each other in a process known as convergent evolution.
The team also found a high number of genes associated with immune responses in the platypus. These may give the youngsters an especially good response to fighting off infections and diseases.
The Natural History Museum looks after the first platypus specimen brought to the UK from Australia more than 200 years ago. It is called the holotype, or type specimen, and is the specimen upon which the description is based. It is often referred to when other similar animals need to be identified.
The Museum has more than 850,000 type specimens and scientists from around the world refer to them whenever a species needs to be researched.
Platypuses live in the waterways of southern and eastern Australia and Tasmania. They are very secretive and rarely breed in captivity so very little is known about their lifestyle and habits.
Their aquatic habitats face more and more threats from pollution, habitat destruction and climate change, so makes this research and future conservation and understanding of the species all the more important. | <urn:uuid:5b06bce7-9acb-4c7d-8361-e74586f1aa2f> | 3.921875 | 515 | Knowledge Article | Science & Tech. | 34.212392 |
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A brief description of how Voice over Internet Protocol enables you to make phone calls using your internet connection. From HowStuffWorks.com.
A brief description of how Internet Radio works broadcasts music online including a description of how you can set up an internet radio. From HowStuffWorks.com.
The Internet was the result of some visionary thinking by people in the early 1960s who saw great potential value in allowing computers to share information on research and development in scientific ...
A brief fascinating description of how Internet Odors might create smells from your computer; virtual reality at work. From HowStuffWorks.com.
A comprehensive page on the history of the internet, from its beginnings to the world wide web, the dotcom bubble and more.
Glowcaps is a pill bottle with a difference. Equipped with an internet enabled chip, you tell it when you are supposed to take your medication and it keeps track of whether you have unscrewed its top ...
By 2020, 50 billion 'things' will be online. An infographic from Cisco packed with information about the internet of things.
A brief description of how Internet Infrastructure works, covering domain name servers, network access points and backbones. From HowStuffWorks.com.
An introduction to the internet of things, RFID technology and more.
These pages takes a fascinating look inside the world of computers and the internet. There is good use of colour and the site makes good use of flash to explain computers, microprocessors, the ...
Showing 1 - 10 of 45 | <urn:uuid:b8e8ae25-fa53-4e7f-a818-7a30147a3863> | 2.703125 | 412 | Content Listing | Science & Tech. | 56.462909 |
The concept of water column is quite important, since many aquatic phenomena are explained by the incomplete vertical mixing of chemical, physical or biological parameters. For example, when studying the metabolism of benthic organisms, it is the specific bottom layer concentration of available chemicals in the water column that is meaningful, rather than the average value of those chemicals throughout the water column.
Hydrostatic pressure can be analyzed by the height of a water column, which effectively yields the pressure at a given depth of the column.
Vertical distribution of fish larvae and its relation to water column structure in the southwestern Gulf of California (1).
Oct 01, 2007; Abstract: The seasonal evolution of vertical distribution of fish larvae and its relationship with seasonal stratification, as... | <urn:uuid:397eaed8-df5b-4383-8701-b8c8b10b5677> | 3.109375 | 151 | Knowledge Article | Science & Tech. | 23.393571 |
even lend a hand in the synthesis of drugs
and supplements such as vitamin E.
But enzyme-driven processes these
days can get much more involved than
just throwing starting materials into
an animal gut. Often materials need to
undergo additional reactions, treatment
with a solvent or dyeing with a chemical, before or after an enzyme can do its
job. For many of these reactions, heat is
required as a catalyst.
The problem: Most known enzymes
work only at conditions matching those
of the organism from which they came.
So temperatures have to be repeatedly
ramped up and lowered at various stages
of a multistep process. “You have to cool
it down for the biological part and heat
it back up for the next step,” says Vicki
Thompson of Idaho National Labora-
tory in Idaho Falls. “That makes the
process more expensive, and it’s waste-
ful of energy.”
During low-temperature stages, mate-
rials can also be vulnerable to attack
from a plethora of microbes.
The breakdown of long chains of glucose molecules from plants, or cellulose,
faces such troubles. Cellulose stored in
corn stover — the grassy part of corn that
people don’t eat and a potential biofuel
source — is tied up in complex chemical arrangements, making it hard for
enzymes working alone to get access.
So the biomass has to be mashed up
a bit first. It’s heated and treated with
corrosive chemicals like acids or salty
solutions, which expose the cellulose.
But the plant products have to be neutralized and cooled before a collection of
room-temperature enzymes can digest
the material into usable sugars.
Cellulose-breaking enzymes, called
cellulases, made by organisms that normally thrive under extreme conditions,
in places like hot springs or hydrothermal vents, could offer a solution.
“You can take those enzymes and use
them under the industrial conditions
that you are interested in,” explains
Thompson, who has been studying
organisms that live in extreme environments and the proteins they make for
more than a decade.
Biologist Thomas Brock unearthed one
of the first known extremophiles from
hot pools in Yellowstone National Park
in Wyoming in the 1960s. Later named
Thermus aquaticus, the bacterium
thrived best at temperatures around
70° C. This finding suggested life could
exist in all kinds of places that were previously thought of as dead zones.
Explorations in volcanic soil, hot
vents, deep seas and salt deserts have
turned up thousands of extremophiles
since, says Thompson. A sizable portion
love the heat. Notably, a heat-loving,
DNA-building enzyme from T. aquaticus
has been a major boon for genetic engineering and forensics. To analyze DNA
from collected samples, scientists need
large amounts of uncontaminated copies. By simply adding the enzyme, Taq
polymerase, to a starting strand of DNA
and other genetic ingredients, scientists
can make lots of DNA copies with no
contamination to worry about.
Over the last two decades, Frank Robb
of the University of Maryland, Baltimore
has scoured some of the hottest corners
of the Earth — from the hot springs at
Yellowstone to the deep-sea vents of the
Okinawa Trough — in search of interesting heat-loving enzymes. An ability
to break down cellulose is one sought-after skill in the “help wanted” ads.
Robb and Graham want cellulases
that can do their thing at temperatures
of 100° C or even higher. The more
types the better, since some enzymes
specialize in cutting the cellulose into
chunks and some break it down even
further into glucose.
Fueled by heat From a
hot pool in Nevada (above),
researchers pulled a cellulose-busting enzyme called EBI-244.
The enzyme shows its maximum
breakdown activity above 100°
Celsius (right), making it a good
candidate for use in biofuel
EBI-244 activity vs. temperature
Activity (micromole glucose/min/mg)
60 70 95 100
120 115 110 105 90 85 80 75 65 | <urn:uuid:c3959ada-bab7-47d5-b9f3-5991b3e574ce> | 3.796875 | 924 | Knowledge Article | Science & Tech. | 41.317239 |
IPCC AR4 Ensemble Statistics
The 20c3m experiments are forced with historical green house gas forcing as well as the time varying ozone, sulfate, volcanic aerosols, and solar output for the 1900-2000 period. This analysis uses 20th century experiments from 10 models. The B1, A1B and A2 experiments are forced with a predicted green house gas forcing scenario for the 2000-2100 period. There are 10 models for the A1B scenario, 9 for the B1 scenario and 8 for the A2 scenario. Click here for details on what models are included in each scenario.
For models with multiple realizations of the same experiment (ensembles), these ensemble members are first averaged together to get a mean for that model before computing the multi-model (ensemble) mean. It is desirable to perform multiple realizations because small differences in the climate system, for example slight displacements in high and/or low pressure systems, grow with time so that after a few weeks the atmospheric state will differ considerably between simulations. (This is sometimes referred to as the butterfly effect and why one can't make specific weather forecasts beyond about 10 days.) By performing a number of ensembles runs and then averaging across them suppresses the internal variability to highlight the change in climate due to greenhouse gases or other forcings.
The observations are constructed in the manner described by Fritch et al. (2002) using daily station data from the Global Historical Climate Network and interpolating the resulting extremes' indices to a T42 grid using inverse distance weighting.
The variables are based on daily values over the course of the annual cycle; they are not broken out by season.
Output from each model is either on or interpolated to a common T42 grid (~2.8 x 2.8 degrees) to facilitate the model inter-comparison. More details on the IPCC scenarios can be found here. | <urn:uuid:646c2f2d-bca3-4d70-a51d-c2f802ce0c49> | 3.25 | 392 | Knowledge Article | Science & Tech. | 40.348269 |
Naturally, everybody’s talking about the weather. It been hot and dry and lots of people wonder why.
“Climate change” is the pat answer.
However, one of the meteorologists I follow -- John Wheeler, with WDAY-TV in Fargo, N.D., where I live -- says the summer's heat isn’t the direct result of a warming globe.
“Actually, the frequency of 100 degree F days in Fargo has been in decline in recent years,” he wrote in a recent column that appears in the Fargo Forum. “During the drier 1970s and 1980s, 100 degree F days occurred at an average of 1 or 2 a year [in Fargo]. However, since 1989 during a mostly wet period, there have only been four 100 degree F days. There was only one in July 19995, two in July 2006 and one in July 2012. All four occurred during dry intervals of the overall wet period of the past 20 years.”
Wheeler concludes, “There are numerous indications of a warming around the world, but 100-degrees F in Fargo is more of a representation of the dryness of the soils than a changing climate.” | <urn:uuid:c30a6aea-c4b9-4334-995f-e6e674c82eb3> | 2.765625 | 252 | Personal Blog | Science & Tech. | 70.097851 |
19 year old Aisha Mustafa has invented a propulsion device which could very well result in a cheaper means of energy consumption for spacecrafts. What have you done today?
She's a student at Sohag University, and she invented the propulsion device that eschews radioactive based jet and rocket engine set up for quantum physics and chemical reactions. It generates energy from electric energy using the Casimir polder force, which occurs between separate surfaces and objects in a vacuum.
Sounds like she could be the mother of future Star Trek like space travel here! This is also a huge improvement over rocket fuel based models that rely on solid and liquid fuels.
Mustafa said the next step is testing it at with a major scientific research organization and one day hopefully bringing it practically into space missions | <urn:uuid:7739ea6a-7cad-4cdf-92e5-225647bdf9e9> | 3.40625 | 157 | Listicle | Science & Tech. | 31.749678 |
Uljamin, 1884 : Doliolid|
Phylum Chordata / Subphylum Urochordata / Class Thaliacea / Order Doliolida / Family Doliolidae
Using a mucous net, Dolioletta is a very adept filter feeder on particles ranging up to 100 micrometers in size. Gill slits are located within the relatively large pharynx, which also holds the mucus secreting endostyle. Water is pumped through the mucous net by the action of gill cilia. With their efficient filtering mechanism, dense aggregations of this species can quickly deplete phytoplankton within a wide area. When food is plentiful, Dolioletta is amazingly prolific, with a single oozooid capable of producing thousands of gonozooids in a matter of days. This species can form dense swarms of up to an average of 500 per cubic meter, and may be the most abundant pelagic tunicate off the California coast. It is the most cold tolerant of all the doliolids, ranging farther north than any other species. Although usually oceanic, occasionally dense swarms may inundate nearshore waters. On close approach, their presence is usually revealed when the doliolid attempts to dart away using rapid contractions of the body muscles.
All photographs © David Wrobel and may not be used or copied without permission! | <urn:uuid:274239fb-9e66-4cb3-9622-f301f9ab0d94> | 3.125 | 290 | Knowledge Article | Science & Tech. | 29.004049 |
Given a rhombus, as shown on the right, with diagonals of length 2a and 2b, express the area and the side s in terms of a and b.
The area is made up of four right triangles with total area of 2ab.
To find an expression for s consider this figure where the four right triangles from the rhombus are assembled at the vertices of an auxiliary square of side length a + b.
The area of the auxiliary square is equal to the sum of the area of the rhombus (the four triangles) and the area of a square of side length s formed on the side of the rhombus.
CHECK? Click HERE. (Use the "Back" key to return)
For GSP files to explore alternatives, click HERE. | <urn:uuid:34ce27d5-81be-4717-a500-2392a76b1a3d> | 3.8125 | 165 | Tutorial | Science & Tech. | 70.512913 |
Informational Brochures for Parents
Grade level: K 1 2 3 4 5
Introducing Investigations to Families
Investigations Resources for Families
Resources that are components of Investigations that are designed to support families at home. All of these should be coming home with your child at different times throughout the year.
Once a class is registered on SuccessNet, students and parents can have online access from home to:
* Student Resources (Shapes, GeoLogo, and e-tools)
* Investigations Student Math Handbook (SMH) in English and/or Spanish
* Notices the teacher has posted for the class or for particular students
Please contact your child's school for user names and password information needed for accessing these resources online.
Help for Parents
Resources for helping your child learn math
Questions to Ask When Helping Your Child at Home with Math
This is nice as a bookmark or a refrigerator reference. Copy double-sided and cut in half. This will make two bookmarks - one for yourself and one for a friend.
Helping Your Child Learn Math
A free publication (pdf. file) from the U.S. Department of Education
Helping Your Child Learn Math (Spanish version)
Math at Home
Math Dictionary for Kids
A free English/Spanish Web resource offers ten activities that help parents of elementary-aged children do math with their children as a part of everyday routines
Early Childhood: Activities for Your Day
Frequently Asked Questions - Some of these questions are in response to concerns that were brought up during Citizens' Time at School Board Meetings. Some have come up through discussions with parents and teachers in PWCS.
||The National Council of Teachers of Mathematics (NCTM) is pleased to provide a selection of resources for parents and families to help students learn math http://www.nctm.org/resources/families.aspx including a book titled
A Family's Guide: Fostering Your Child's Success in School Mathematics
||Dedicated to Helping families enjoy mathematics outside school through a series of fun and engaging, high-quality challenges. Most of these challenges are at the middle school level, but several would be accessible to high-ability elementary math students as well. The "Family Corner" provides additional support for all parents working to support their children's mathematics education at home
|This Web site is designed for K-5 students. It presents math challenges to help learners become better problem solvers.
|The Other Resources link on the PWCS Math Web site includes links to online games and applets that allow students of all ages opportunities to practice or enhance what they know about mathematics. This link includes additional research for parents as well. | <urn:uuid:ba52a67c-1f03-49b2-895c-9c951d42bfdb> | 3.6875 | 555 | Content Listing | Science & Tech. | 40.365721 |
On the 40th anniversary of the famous ‘Blue Marble’ photograph taken of Earth from space, Planetary Collective presents a short film documenting astronauts’ life-changing stories of seeing the Earth from the outside – a perspective-altering experience often described as the Overview Effect.
One of the most stunning ISS timelapses yet.
Breathtaking composite series of images photographed from the Earth-orbiting International Space Station, approximately 240 miles above home.
Is Earth really a sort of giant living organism as the Gaia hypothesis predicts? A new discovery made at the University of Maryland may provide a key to answering this question. This key of sulfur could allow scientists to unlock heretofore hidden interactions between ocean organisms, atmosphere, and land — interactions that might provide evidence supporting this famous theory.
The Gaia hypothesis — first articulated by James Lovelock and Lynn Margulis in the 1970s — holds that Earth’s physical and biological processes are inextricably connected to form a self-regulating, essentially sentient, system.
One of the early predictions of this hypothesis was that there should be a sulfur compound made by organisms in the oceans that was stable enough against oxidation in water to allow its transfer to the air. Either the sulfur compound itself, or its atmospheric oxidation product, would have to return sulfur from the sea to the land surfaces. The most likely candidate for this role was deemed to be dimethylsulfide.
Newly published work done at the University of Maryland by first author Harry Oduro, together with UMD geochemist James Farquhar and marine biologist Kathryn Van Alstyne of Western Washington University, provides a tool for tracing and measuring the movement of sulfur through ocean organisms, the atmosphere and the land in ways that may help prove or disprove the controversial Gaia theory. Their study appears in this week’s Online Early Edition of the Proceedings of the National Academy of Sciences (PNAS).
According to Oduro and his colleagues, this work presents the first direct measurements of the isotopic composition of dimethylsulfide and of its precursor dimethylsulfoniopropionate. These measurements reveal differences in the isotope ratios of these two sulfur compounds that are produced by macroalga and phytoplankton. These measurements (1) are linked to the compounds’ metabolism by these ocean organisms and (2) carry implications for tracking dimethylsulfide emissions from the ocean to the atmosphere.
Sulfur, the tenth most abundant element in the universe, is part of many inorganic and organic compounds. Sulfur cycles sulfur through the land, atmosphere and living things and plays critical roles in both climate and in the health of organisms and ecosystems.
“Dimethylsulfide emissions play a role in climate regulation through transformation to aerosols that are thought to influence the Earth’s radiation balance,” says Oduro, who conducted the research while completing a Ph.D. in geology & earth system sciences at Maryland and now is a postdoctoral fellow at the Massachusetts Institute of Technology. “We show that differences in isotopic composition of dimethylsulfide may vary in ways that will help us to refine estimates of its emission into the atmosphere and of its cycling in the oceans.”
As with many other chemical elements, sulfur consists of different isotopes. All isotopes of an element are characterized by having the same number of electrons and protons but different numbers of neutrons. Therefore, isotopes of an element are characterized by identical chemical properties, but different mass and nuclear properties. As a result, it can be possible for scientists to use unique combinations of an element’s radioactive isotopes as isotopic signatures through which compounds with that element can be traced.
“What Harry did in this research was to devise a way to isolate and measure the sulfur isotopic composition of these two sulfur compounds,” says Farquhar, a professor in the University of Maryland’s department of geology. “This was a very difficult measurement to do right, and his measurements revealed an unexpected variability in an isotopic signal that appears to be related to the way the sulfur is metabolized.
“Harry’s work establishes that we should expect to see variability in the sulfur isotope signatures of these compounds in the oceans under different environmental conditions and for different organisms. I think this will ultimately be very important for using isotopes to trace the cycling of these compounds in the surface oceans as well as the flux of dimethylsulfide to the atmosphere. The ability to do this could help us answer important climate questions, and ultimately better predict climate changes. And it may even help us to better trace connections between dimethylsulfide emissions and sulfate aerosols, ultimately testing a coupling in the Gaia hypothesis,” Farquhar says.
(via Science Daily)
Envisat ASAR image of the McClure Strait in the Canadian Arctic Archipelago, acquired on Aug. 31, 2007. The McClure Strait is the most direct route of the Northwest Passage and has been fully open since early August 2007.
At about 100 meters from the cargo bay of the space shuttle Challenger, Bruce McCandless II was farther out than anyone had ever been before. Guided by a Manned Maneuvering Unit (MMU), astronaut McCandless, pictured above, was floating free in space. McCandless and fellow NASA astronaut Robert Stewart were the first to experience such an “untethered space walk” during Space Shuttle mission 41-B in 1984.
ISS Cometrise Time Lapse
A retinal flash of beauty seen aboard the ISS unlike any other from the newly discovered Comet Lovejoy.
Ocean Sand, Bahamas – Image taken by the Enhanced Thematic Mapper plus (ETM+) instrument aboard the Landsat 7 satellite. Tides and ocean currents in the Bahamas sculpted the sand and seaweed beds into these multicolored, fluted patterns in much the same way that winds sculpted the vast sand dunes in the Sahara Desert. Gorgeous!
Hang on tight while we grab the next page | <urn:uuid:f172a3d3-0c65-480e-afd0-b8f58a58c6ff> | 3.3125 | 1,260 | Content Listing | Science & Tech. | 23.083024 |
Acids, Bases, and Indicators
Return to Chemistry Index
Edwin A. Metzl Lincoln Park High School
2001 North Orchard Street Mall
Chicago IL 60614
This is a multileveled approach to learning some of the common
characteristics of acidic and basic solutions and use of some of the
Apron Distilled water
Safety goggles 200 mL 0.1 M HCl
13 small or medium sized test tubes 200 mL 0.01 M NaOH
Test tube racks to hold 12 test tubes a few leaves from
1 glass stirring rod Red Cabbage
12 250mm beakers Heat source such as
1 glass marking pencil a hot plate
1 10 ml graduate cylinder Pot or 1 L beaker
1 100 ml graduate cylinder Various solutions of
At least 6 acid-base indicators which unknown pH
should include: Blue & Red Litmus Paper 13 Eye Droppers
Universal indicator paper
Phenol Red + others
The teaching strategy is both multifacetted and multileveled. At the
lowest level, litmus paper testing of different household products might be an
effective means of introducing the student to acid and bases. However, for
purposes of this discussion, it will be presumed that the class is very advanced
and the teacher may decide how far and how fast to proceed.
Acid-base indicators are substances that change color as a function of pH,
usually over a range of 1 to 2 pH units. These indicators are weak acids or
weak bases which disassociate and change colors when equilibrium shifts per
Le Chatelier's principle. Indicators are available that shift color for every
value of the pH scale. The earliest indicators were extracted from plants. In
this lab, we will compare indicator colors to known pH's; use the juice from red
cabbage as an indicator; use red cabbage indicator to find the pH of unknowns;
and lastly, do an acid-base titration.
Preparation of standard solutions
-Obtain 12 250 mL beakers and label them 1 through 12. To beaker 1,
add 100 mL of 0.1 M HCl. This solution has a pH of 1. Measure 10 mL
of this solution and add it to beaker 2 with 90 mL distilled water.
The resulting solution has a pH of 2. Follow this procedure for
beakers 3, 4, 5, and 6. Of course, beaker 7 will have only distilled
water with a pH of 7.
-To beaker 12, add 100 mL of 0.01 M NaOH solution. This has a pH of 12.
Successive dilutions by factors of ten will produce pH values of 11,
10, 9, and 8.
Comparing indicators with known pH's
-Label 12 test tubes and take samples of each known pH solution. Use
whichever indicators are available to compare indicators with these
knowns. Note which indicators appear to be best for given ranges
Extraction of an indicator from red cabbage
-Cut leaves from the red cabbage into small pieces and place them into
a clean large beaker with enough distilled water to cover the pieces.
Boil the cabbage and water until the solution is a deep purple. Use
the stirring rod to keep all leaf pieces in the boiling water. Permit
the solution to cool.
Using red cabbage as an indicator
-Place 5 mL of known pH solutions in each of your labelled test tubes.
To these, add 5 drops of red cabbage indicator. You are now ready to
compare your unknowns with your knowns by placing 5 mL of an unknown
into a clean test tube, adding 5 drops of red cabbage juice and
comparing the unknown with your knowns.
Using red cabbage for titration
-Only a few words on this subject ... As all titrations that this
writer is familiar with use phenolphthalein as an indicator, there
is no reason for not using red cabbage instead. For those not
familiar with titrations, it is a method of determining quantities
necessary to change a solution of one pH into a solution of a
A comparison should be made by the students of the cabbage indicator with
the "store bought" varieties plus a comparison between the various indicators.
Questions, such as, "Which is the best indicator?" should be more specific with
questions such as, "Which has the most discernible color change?" and "Which
might be used for a specific range?"
Of course, with teacher approval only, students could try extracting other
colored substances from leaves and flower petals to test as indicators...try tea
and beet juice as examples.
Cabbage juice appears to be a useful indicator, as do other some
naturally colored materials. Materials serve best within specific pH ranges. | <urn:uuid:17bb61d7-330e-4687-b62a-f5f72c23c3d9> | 3.203125 | 1,000 | Tutorial | Science & Tech. | 60.642547 |
My question is very simple. If frequency is defined as the cylces per unit time, Then what is meant by "Frequency of an Electron" ? If the rotation of electron around a nucleus is considered then, ...
What do we actually mean when we say that matter is a wave? What does the wavelength of this matter wave indicate? The idea of a particle behaving like a wave is kinda incomprehensible to me. ... | <urn:uuid:82024c57-db8c-43fa-9c9b-3cfff1744c2b> | 2.90625 | 86 | Q&A Forum | Science & Tech. | 59.680819 |
This section illustrates you how to escape all special characters from the given string or text. Here, you can learn the way of detecting all special characters present in the given string.
This section provides an example for the best illustration about the way of matching special characters in the given string or text. This program finds special characters and replaces all the detected special characters by "F" character and display whole string with the "F" character place of any special characters in the given string or text.
This method compiles a regular expression "[^a-zA-Z0-9 ]" which does not detects a to z, A to Z and 0 to 9 characters, means it detects all special symbols or characters.
Here is the code of the program:
If you are facing any programming issue, such as compilation errors or not able to find the code you are looking for.
Ask your questions, our development team will try to give answers to your questions. | <urn:uuid:0881bbdf-9a66-4fa2-8b38-84083d1bac52> | 3.390625 | 196 | Documentation | Software Dev. | 54.091585 |
AOH :: SOIL.TXT|
Borderland: Remineralizing the Soil
REMINERALIZING THE SOIL
Most of us are aware that the greenhouse effect is rapidly
becoming a serious threat to our climate. There is widespread
agreement that it is the reason we lost almost one-third of all
our grains in 1988, and were not able to produce enough wheat,
corn, etc. to feed ourselves.
The greenhouse effect is caused partly by human activities --
burning fossil fuels, cutting down the rainforests, etc., which
put into the atmosphere carbon dioxide and other gases that trap
additional heat from the sun, creating a kind of greenhouse. It
is also happening because many of the earth's forests are dying
from both man-made (pollution, acid rain) and natural causes. It
is well known that much of the minerals in the earth's soil have
been gradually eroded away since the last ice age. Since
minerals (iron, calcium, etc.) are essential nutrients for every
form of life, the world's forests have been weakening and dying
for hundreds of years.
When the glaciers build up during each ice age, they grind up the
rocks in their path into a fine dust, called "loess." This rock
dust is then carried by water and wind to many parts of the
earth. Since rocks are made of minerals, this is how the
essential minerals are returned to the soil, and the forests
become revitalized once again.
THE KEY TO OUR SURVIVAL
Experimental studies have shown that remineralizing the soil with
finely ground gravel dust triples or quadruples the growth rate
By grinding up mixed gravels (which contain the full spectrum of
minerals) into a dust as fine as talcum powder so they can be
made use of quickly by the plants, and by spreading this dust by
airplane, blower-truck and every conceivable means over most of
the world's remaining forests, the forests will become
rejuvenated. We also need to plant vast quantities of new, fast-
growing species of trees on remineralized soil.
As the revitalized forests thrive and spread, they will consume
much of the excess carbon dioxide in the atmosphere, reducing the
greenhouse effect substantially. This will decrease the threat
of a global food emergency which is now threatening us, and give
us time to develop ways of conserving energy, much more efficient
machines, and nonpolluting energy sources.
Remineralizing agricultural soils will enable us to grow much
more food, enough to stockpile to get us through the coming
climate crisis. It will also replace all the chemical
fertilizers and pesticides which are poisoning the earth, the
rivers, the farmers and ourselves. Remineralizing the soil
produces plants so well nourished and hardy they can resist most
insects all by themselves. They are also better able to
withstand climatic extremes, including heat, cold and drought,
all the things which now threaten our ability to grow enough
Remineralizing most of the forests of the world and planting
billions of new trees is obviously a major project, but it is
well within our industrial capabilities. It will cost about what
the world spends on weapons and military activities every two
years. There is evidence that it must be done quickly if we want
to maximize our chances of stabilizing the climate before
millions more of us starve to death, this time in every region of
We know what to do, and we can afford it. Have we got the will
The scientific evidence for remineralizing the soil can be found
in The End: The Imminent Ice Age and How We Can Stop It
(Celestial Arts), $8.95. Some visual evidence of the dramatic
effects of remineralization and the experiences of some of the
people working in this area can be found in the video Stopping
the Coming Ice Age ($19.95).
Both are available from the Institute For A Future, 2000 Center
Street, Berkeley, CA 94704. Credit card orders can be made toll-
free by calling 1-800-441-7701. In California (415) 524-2700.
This perspective has been endorsed by several prominent
scientists, including the following:
"I consider this completely valid. It requires immediate
-- Victor Kovda, former President, Scientific Committee for
Environmental Problems, International Council of Scientific
"An astonishing service for humanity. A complete world view
which has been sitting under the noses of many scientists, and
which all of them seem to have overlooked."
--Kenneth E. F. Watt, Professor of Environmental Studies,
University of California, and author of the "Annual Review of the
Environment" for the Encyclopedia Brittanica
"This is very important."
--Wibjorn Karlen, climatologist, University of Stockholm
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(Science: physics) a lens built up, progressively, in zones or steps, each zone with its own individual radius. Considerable spherical correction is attained, and the weight of the lens is greatly reduced.
Fresnel lenses were originally designed for lighthouses but they are now attainable for small spotlights, automobile headlights, and similar uses.
Please contribute to this project, if you have more information about this term feel free to edit this page
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Scientists working in Haiti have obtained the first-ever photos of an endangered Black-capped Petrel chick—a little ball of gray fluff that was discovered at its nest inside a mountaintop cave. The finding helps answer questions about this secretive species’ life cycle.
These crow-sized seabirds nest only in the Caribbean and feed as far away as Gulf Stream waters off the Mid-Atlantic United States. Best estimates suggest that fewer than 2,000 breeding pairs remain, and the data collected at this nest have already been incorporated into a new conservation plan for the species (available as a PDF).
“Finding this nest shows both that gems of biodiversity are yet to be found in Haiti, despite its environmental and economic troubles, and that there’s still time to save rare species if we act swiftly,” said James Goetz, a Cornell Lab of Ornithology graduate student who helped lead the project. The nest was found on March 3, 2011, by a team from Grupo Jaragua, a nonprofit from the Dominican Republic.
Upon finding the nest, the researchers set up a motion-activated camera at the entrance to the cave. Over the next four months, the camera caught dozens of images of the parents arriving to feed the chick, as well as visits by rats and a dog, which fortunately did not disturb the growing chick.
In early July the camera photographed the chick waddling to the edge of the cave in preparation for its first flight, four months after the nest was found. The bird presumably departed safely in mid-July (the camera’s batteries ran out before then) and is now probably winging over the open ocean hundreds or thousands of miles away (the adult in the photo at left is not the same bird). Out of only a handful of nests found in the last decade, this is the only one that scientists have been able to monitor.
Black-capped Petrels are an enduring mystery among Caribbean birds. Once abundant, they fell victim to overharvest, habitat loss, and introduced predators such as rats, cats, dogs, and mongooses. By about 1850 they were thought extinct—until scattered at-sea sightings and the discovery, in 1963, of a few nesting sites in Haiti rekindled hopes for the species.
The ensuing five decades have turned up few clues about a bird that spends most of its life at sea, returning to land only a few dozen nights per year to visit nests in treacherously steep cloud forests. Only three remaining nesting areas—all on the island of Hispaniola—are known, although sightings along Cuba’s eastern coast in 2004 indicate the birds probably nest there as well.
In Haiti, poverty creates intense pressure on natural resources. Agricultural clearings reach to the tops of most mountains, no matter how steep. Loss of habitat threatens more than a dozen endemic Hispaniolan species, as well as wintering North American birds such as the American Redstart and Bicknell’s Thrush, a vulnerable species.
Lessons learned from studying this nest and the chick’s progress will help inform new efforts to discover nesting areas on Hispaniola and other islands. Until now, researchers have had to draw on details of better-known relatives such as Bermuda and Hawaiian petrels. “For such a poorly known species, every new scrap of information helps us gain ground in learning how to make conservation work for it,” Goetz said.
(Our work on the Black-capped Petrel has been funded by the U.S. Fish and Wildlife Service and the John D. and Catherine T. MacArthur Foundation. Our partners in this important work include American Bird Conservancy, BirdLife International, and Grupo Jaragua, Images: Black-capped Petrel chick on its nest in a Haitian cave, photographed by J. Volquez of Grupo Jaragua; an adult photographed over the Gulf Stream off Cape Hatteras, North Carolina, by Patrick Coin via a Creative Commons license.) | <urn:uuid:eddc00e8-233d-4052-b0ed-4ee8ea31ab45> | 3.109375 | 824 | Knowledge Article | Science & Tech. | 46.558756 |
In order to properly identify and catalog the biodiversity of a site, researchers often have to physically collect specimens by hand for more thorough study in a laboratory. Examples of species are collected by SCUBA divers using nets and collection bottles, and by using devices called suction samplers that act like vacuum cleaners to collect small organisms. More quantitative methods include more systematic approaches such as quadrat sampling along the intertidal zone.
Much like observation by passive quadrat sampling, active collection using quadrat sampling involves using a series of squares (quadrats) of a set size placed across a habitat of interest. Species found within quadrats are collected for later identification. As with passive quadrat sampling, abundances of organisms found at the study site can be calculated using the number found per quadrat and the size of the quadrat area. Example specimens are often kept in long-term research collections for historical record. This is a time-tested sampling technique that is, as with all hand collecting, best suited for coastal areas where access to a habitat is relatively easy.
|Scientists and assistants quadrat sampling along a transect line on the
coast of Hokkaido, Japan. (Natural Geography in Shore Areas - NaGISA)|
|Scientists sort specimens taken in quadrat sampling along the coast of
Kodiak Island, Alaska. (Natural Geography in Shore Areas - NaGISA. Gayle Neufeld)|
Click on the links below to see what Census projects use this technology: | <urn:uuid:15ae49c7-9bdd-4c15-9541-e904f69de9af> | 3.96875 | 309 | Knowledge Article | Science & Tech. | 23.510909 |
Mud wasps are large, solitary Australian wasps.
Mud wasps: solitary and harmless
Mud wasps are large, solitary Australian insects that build nests of mud and provide live, paralysed prey for their larvae to feed on.
1 October 2008 | Updated 14 October 2011
There are many different species of Australian mud wasps in the Families Vespidae and Sphecidae. They vary in size and colour but are often all black or black with orange or yellow bands or markings. They build nests of mud or 'clay'.
Mud wasps are found all over Australia and in all terrestrial habitats.
They are solitary insects and the nest is constructed by a single female wasp. Some species attach nests to rock faces, tree trunks or buildings.
Others build inside cavities, such as holes in tree trunks or machinery and in infrequently used taps and pipes or the handles of tools left outside.
They are part of Australia’s native fauna and should be left alone if possible.
Typically, the female wasp catches a particular an insect or spider (what depends on the species of wasp) then stings and paralyses it. She then carries it back to the nest, lays an egg on it and seals the nest. The wasp grub hatches, consumes the food provided and pupates in the cell. When the adult emerges it chews its way out of the cell.
Adults feed on nectar and drink water. Sometimes the wasps can be seen gathering mud at the edges of streams, dams or puddles.
Mud wasps are not pests. The females are not aggressive and rarely sting.
They are part of Australia’s native fauna and should be left alone if possible. If a mud nest is considered unsightly it can be knocked off, which is probably best done when the owner of the nest is not around.
CSIRO Entomology is not currently researching mud wasps. This fact sheet is provided for information only.
Find out about more Australian insects. | <urn:uuid:909314c8-344c-4f73-9f18-d8dc3dce6b65> | 3.59375 | 428 | Knowledge Article | Science & Tech. | 59.579767 |
Fusion reactors are being studied as an alternative to fission reactors. The design of nuclear fusion reactors, which are still in the experimental stage, differs considerably from that of fission reactors. In a fusion reactor, the principal problem is the containment of the plasma fuel, which must be at a temperature of millions of degrees in order to initiate the reaction. Magnetic fields have been used in several ways to hold the plasmas in a "magnetic bottle." If development should reach a practical stage of application, it is expected that fusion reactors would have many advantages over fission reactors. Fusion reactors, for instance, would produce less hazardous radioactive waste. Because their fuel, deuterium (an isotope of hydrogen readily separated from water), is far less expensive to obtain than enriched uranium, fusion reactors also would be far more economical to operate.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved. | <urn:uuid:da19a19b-e75e-4024-aa50-d5fe48735f7a> | 4.1875 | 191 | Knowledge Article | Science & Tech. | 29.694909 |
Unicode and Internationalization
The effect of Unicode on Tcl scripts is actually very limited. There is a new backslash sequence, \uXXXX, that specifies a 16-bit Unicode character. There are also facilities to work with character set encodings and message catalogs.
The Tcl I/O system supports character set translations. It automatically converts files to Unicode when it reads them in, and it converts them to the native system encoding during output. The fconfigure -encoding option can be used to specify alternate encodings for files. This option is described on page 209.
The encoding Command
The encoding command provides access to the basic encoding mechanism used in Tcl. The encoding convertfrom and convertto operations convert strings between different encodings. The encoding system operation queries and sets the encoding used by the operating system. The encoding command is described on page 212.
The msgcat Package
Message catalogs are implemented by the msgcat package, which is described on page 216. A message catalog stores translations of user messages into other languages. Tcl makes message catalogs easy to use.
UTF-8 and Unicode C API
The effects of Unicode on the Tcl C API is more fundamental. Tcl uses UTF-8 to represent Unicode internally. This encoding is compatible with ASCII, so Tcl extentions that only pass ASCII strings to Tcl continue to work normally. However, to take advantage of Unicode, Tcl extensions need to translate strings into UTF-8 or Unicode before calling the Tcl C library. There is a C API for this. An example of its use is shown on page 629. | <urn:uuid:110b4896-7f2f-4c9e-b3c0-096dda58e8cd> | 2.703125 | 338 | Documentation | Software Dev. | 39.514836 |
Webb Research Corporation, based out of Falmouth, Massachusetts, has invented what it is calling a “Slocum glider.”
The name Slocum comes from Canadian-American seaman and adventurer Joshua Slocum (1844-1909), the first person to make a solo circumnavigation of the world—sail around the world alone (between 1895 and 1898).
The Webb vessel is also called a “thermal glider” because it uses thermal energy, temperature differences in the ocean, to move in the water. So far, a two-month test has been conducted with the vehicle, which does not use a propeller to move along.
The six-foot (1.5-meter) long, 132-pound (60-kilogram) vehicle changes its height under the water by pumping fluid back and forth between bladders that are located on the interior and exterior of the hull. The hull’s diameter is about 8.4 inches (21.3 centimeters).
In relatively warm water, wax positioned inside a chamber melts and expands. Such action makes a pumping action that pushes the water from the interior to the exterior bladder.
The Slocum glider can descend to 6,500 feet (2,000 meters) for a time period of about five years. It has a maximum range of 24,800 miles (40,000 kilometers).
To move up, fluid is pumped from the interior bladder to the exterior one. Thus, its volume increases as the exterior bladder expands in size. Such an arrangement increases the buoyancy of the vehicle, and it rises in the water.
When the vessel reaches the ocean’s surface, the pumps are recharged as wax melts and again expands. Fluid is drawn back into the interior bladder from the exterior one, and the vessel submerges back down into the water.
Fins on the vessel give forward momentum as it rises and falls in the water. It can move at a horizontal speed of about one mile (1.4 kilometer) per hour, as it moves up and down about 4,000 feet in a cycle all with a temperature difference of about 43 degrees (Fahrenheit).
Long-duration batteries transmit data from the vessel through a RF (radio-frequency) modem, ARGOS satellite-based ground system, and Iridium satellite system.
The Slocum glider is expected to help measure ocean currents, sea surface heights, temperatures, and various other properties of ocean waters. Because of its small cost to operate, Webb Research foresees that many such vehicles could be used in the future in order to study and map the dynamic features of subsurface coastal waters.
Please turn the page to learn more about Webb Research Corporation and its founder Douglas Webb, along with additional information about Joshua Slocum. | <urn:uuid:0ab7afe7-1d72-4418-9ff7-f3aefab375c1> | 3.984375 | 585 | Knowledge Article | Science & Tech. | 51.801577 |
We've heard it called many things, a sign of the end of times or as "Armageddon" at the cinema. However asteroids have become a much more publicly aware reality than a scientific phenomenon. Just after sunrise today, an estimated 10 ton meteor flew through the earth's atmosphere at hypersonic speed around 33,000 mph! To put that into perspective, the Blue Angles reach speeds of 700 mph and the record fastest pitch was set by Aroldis Chapman at 105 mph, so 33,000 mph is hard to wrap your mind around! It shattered about 18 to 32 miles above ground raining its debris over a large area over the Ural Mountains of Russia. Many people who saw the event in the Chelyabinsk region said it looked like an incredibly bright fireball. There are reports of over 750 people injured, mostly from shattered windows & glass from the sonic boom. The "explosion" heard was from the shock wave of the meteoroid.
"I would think that this is likely an exploding fireball (or bolide) event caused by the atmospheric impact of a small asteroid," Don Yeomans, head of NASA's Near-Earth Object Program. "If the reports of ground damage can be verified, it might suggest an object whose original size was several meters in extent before entering the atmosphere, fragmenting and exploding due to the unequal pressure on the leading side vs. the trailing side." Yeomans added, the meteor "pancaked and exploded."
So we could be talking about an object around 10 to 20 ft. before entering the earth's atmosphere, fragmenting, and then exploding. The raining chunks that exploded (the meteorites) found downrange will give scientists a better idea of its size and what it was made of (rock, metal, or both). Scientist Phillip Plait explained that looking at a number of the incredible videos of the event, the train (term for meteor trail) was shown for some time before you hear the explosion which would explain the sound coming from the shock wave from the meteoroid going through our atmosphere high above the ground. That "boom" happens when a large mass is moving at multiple times the speed of sound through the air. The train also seems to split, so that could be where the main mass split leading to debris falling in multiple locations.
All this seems to be a HUGE coincidence that it comes on the same day that asteroid 2012 DA14 will come 17,200 miles close to the Earth. The two events have been deemed unrelated by NASA, as they are on two completely different paths. DA14 poses no threat to us, but is a great opportunity for scientists to observe & get a better understanding of orbit characteristics. These events tend to be random and some are difficult to track, especially smaller NEO's (near-Earth objects) like the one that moved over Russia today. There have been many agencies put into place to research & track NEO's which are comets & asteroids that are pushed by gravitational attraction of nearby planets into orbits that move them into Earth's neighborhood. I don't know about you, but I hope we aren't that attractive because that is not the type of neighbor I want moving in!
Picture courtesy of Dave Herald on 2/12/13 when 2012 DA14 was still 770,000 miles from Earth.
So why is it so hard to predict when pieces of these asteroids are going to cause major problems like what we saw today? NEO discovery teams use CCD cameras (charged couple devices) similar to those in camcorders that record images digitally in many electronic pixels. When looking at how close a NEO is to Earth, the teams need to look at the objects location through multiple images, the direction its going, & its brightness to get a glimpse at its path & general orbit characteristics. With this morning's meteor possibly being 10 to 20 feet, that is very small compared to DA14 which looks to be about 164 feet and grazing the earth within 17, 200 miles. DA14 is the largest object of its kind to be seen coming this close to Earth.
You can watch all the action at www.nasa.gov at around 1:25pm Central when it is closest to the Earth, visible only by telescope to Europe, Australia, & Asia at that point. But we will get some action too around 8pm Central when larger telescopes catch a glimpse of it passing our neck of the woods. Nasa will be doing a live stream of the entire event for your viewing pleasure!
In the end, it's is a scary thing to think about. For most of us who spend a lot of our time looking down, I know I will spend more time looking up from now on! Our solar system is full of mysteries just waiting to be unlocked, and I am sure scientists will continue to look for those keys to help us understand what the heavens have in store for us. Or we could just take R.E.M.'s approach and sing, "It's the end of the world as we know it, and I feel fine". | <urn:uuid:a9a72aa1-7516-4638-a388-bcf0bdbf22a7> | 3.015625 | 1,024 | Personal Blog | Science & Tech. | 60.276644 |
Eight Weeks of Prototype: Week 4, Event Handling in Prototype
I will now show you how to write event handlers when observing events with Prototype. I showed you some basic examples in the previous section of handling some events, but there is more to it than that!
When you define an event handler, the event object is passed as the first argument to the handler. This allows you to find out more information about the event, such as which specific element the event occurred on or to determine which key was pressed (for a key-related event).
Listing 5 shows a basic example of how to access this object. My own personal preference for the name of the event object is to use
e, since if you use
Typically this variable will be used in conjunction with the
Event variable. That is, rather than methods being available to call directly on
e, they are passed to the relevant
Event method (such as | <urn:uuid:9aca3518-7fb9-4d37-9871-4e6017252cf1> | 2.9375 | 188 | Personal Blog | Software Dev. | 43.13 |
Unit tangent vectors, Normal vectors, and Gradients
So I'm kinda new to Physics Forums but I've been using threads as guides for about a year now.
Basically, I'm hardcore studying for my Calc III exam (the final is in a few weeks) and I came across an interesting lapse in my understanding (well many in fact, but one in particular).
First of all I can assume that a tangent and a normal/perpendicular vector are NOT the same thing, yet for some reason they both have pretty much the same characteristics.
I know that finding at least one of them involves finding the partial derivatives of a given function, which then are used as the components of the gradient function (the upside down triangle thing) Right?
And a gradient gives you... the normal vector right? or something regarding the tangent plane at a point, whose normal vector is that of the surface of the function? I could be mistaken but my major malfunction seems to be that I can't differentiate (no math puns please- I'm doing more studying than sleeping) between finding the normal vector and the unit tangent vector, which in practice seem to be the same thing (at least for me.)
(It is at this point where I actually noticed the warning at the top of the page regarding the template I am supposed to use. I apologize, and if a problem arises I'll be glad to repost using the template, which at this point seems pointless...) | <urn:uuid:74c1e02c-f9dd-4e1a-b28b-19a9d078fbd4> | 2.890625 | 302 | Comment Section | Science & Tech. | 58.959265 |
Text starting in column 1 or more is formatted using fixed font.
Text placed between <pre></pre> tags is treated as "verbatim" and left unformatted.
A URL coded "bare" becomes a link based on its own text:
A bare URL for an image of type gif, png or jpg becomes an inline image:
A URL like:
[http://www.transcoding.org Transcode Wiki]
Comes out as:
And without the text it becomes a reference:
[http://www.transcoding.org] turns into:
URL's placed inside of [] (double square brackets) become references to internal Wiki pages that look like Foo?. Clicking on the ? after saving will present you with a virgin Edit page, so that is how you create new Wiki pages!
Do not use spaces in internal Wiki links, use underscores instead, or the search mechanism might not work on your pages!
If something in your text is treated as a link and you don't want it to be treated as a link, put it between <nowiki></nowiki> tags!
So, '''foo''' or <b>foo</b>will show as foo.
Italic text is created using the HTML <i> tag OR by using the wiki '' delimiters.
So, ''foo'' or <i>foo</i>will show as foo.
And '''''foo''''' or <b><i>foo</i></b>will show as foo.
This particular wiki also supports the <tt></tt> <u></u> and <strike></strike> tags for monospaced, underline, and
:foo ::foo :::foobecomes
*one **two **three ***four
#one ##two ##three ###four
;<i><b>Sections</b>: are defined ...</i> -Phil
Colors are defined by matching <color></color> tags. Supported colors are red blue green purple brown orange and yellow.
Since I needed them, <br> and <center></center> are also supported...
as is the color <white></white> for doing visual layout.
||Aaaa Bbbb Cccc||Dddd Eeee||Fffff Ggg|| ||A || B || C|| ||||Iiiii Jjjjjjj Kkkkk|| C|| ||||||Lllllll Mmmmmmm Nnnnnn Ooooo Ppp||
|Aaaa Bbbb Cccc||Dddd Eeee||Fffff Ggg|
|Iiiii Jjjjjjj Kkkkk||C|
|Lllllll Mmmmmmm Nnnnnn Ooooo Ppp| | <urn:uuid:219a9847-406c-4a36-85e2-863963501b72> | 2.6875 | 587 | Structured Data | Software Dev. | 81.017516 |
Country of Origin: United States of America
Approximate: 198.12 x 271.78 x 210.82cm (6ft 6in. x 8ft 11in. x 6ft 11in.)
Wood, mylar, and plastics
New Horizons will be the first spacecraft to visit Pluto and the Kuiper Belt in the outer solar system. It was launched aboard an Atlas V rocket from Cape Canaveral Air Force Base, Florida, on January 19, 2006, and conducted a Jupiter flyby 13 months later to gain further acceleration. New Horizons will make its closest approach to Pluto on July 14, 2015.
The half-ton spacecraft contains scientific instruments to map the surface geology and composition of Pluto and its three moons, investigate Pluto's atmosphere, measure the solar wind, and assess interplanetary dust and other particles. After it passes Pluto, controllers plan to fly the spacecraft by one or two Kuiper Belt objects. New Horizons carries several souvenirs from Earth, including some of the remains of Clyde Tombaugh (1906-1997), discoverer of Pluto, and a piece of SpaceShipOne.
The Johns Hopkins University Applied Physics Laboratory donated this to the Museum in 2008.
Gift of John Hopkins University, Applied Physics Labaratory. | <urn:uuid:afb979b4-2779-4a45-9b88-abb032b00fb1> | 2.6875 | 259 | Knowledge Article | Science & Tech. | 52.356842 |
The cell is a fundamental component of our modern definition of life and living things. Cells are regarded as the basic building blocks of life and are used in the elusive definition of what it means to be 'alive'.
Let's take a look at one definition of life:
"Living things are chemical organizations composed of cells and capable of reproducing themselves. (Keeton 1986, 85)"
This definition is rooted in two theories, cell theory and biogenesis theory. Cell theory, first proposed in the late 1830s by two German scientists Matthias Jakob Schleiden and Theodor Schwann, states that all living things are composed of cells. Biogenesis theory, proposed in 1858 by Rudolf Virchow states that all living cells arise from existing (living) cells and no cells are created spontaneously from non-living matter (Keeton 1986, 84).
Cells organize things. They keep chemical processes tidy and compartmentalized so individual cell processes do not interfere with others and the cell can go about its business of metabolizing, reproducing, etc. To organize things, cell components are enclosed in a membrane which serves as a barrier between the outside world and the cell's internal chemistry. The cell membrane is a selective barrier, meaning that it lets some chemicals in and others out and in doing so maintains the balance necessary for the cell to live.
Two Fundamental Cell Types
All living organisms can be sorted into one of two groups depending on the fundamental structure of their cells. These two groups are the prokaryotes and the eukaryotes. Prokaryotes are organisms made up of cells that lack a cell nucleus or any membrane-encased organelles. Eukaryotes are organisms made up of cells that possess a membrane-bound nucleus (that holds genetic material) as well as membrane-bound organelles.
Anatomy of a Prokaryotic Cell
A typical prokaryotic cell might contain the following parts:
- cell wall
- plasma membrane
- flagella and pili
Anatomy of a Eukaryotic Cell
A typical eukaryotic cell might contain the following parts:
- plasma membrane
- endoplasmic reticulum
- Golgi apparatus
The Cell Membrane
The cell membrane regulates the crossing of chemicals in and out of the cell in several ways: by diffusion (the tendency of solute molecules to minimize concentration and thus move from an area of higher concentration towards an area of lower concentration until concentrations equalize), osmosis (the movement of solvent across a selective boundary in order to equalize the concentration of a solute that is unable to move across the boundary), and selective transport (via membrane channels and membrane pumps). | <urn:uuid:b3da68dd-ba02-408b-b00a-2e22f5213114> | 3.828125 | 560 | Knowledge Article | Science & Tech. | 23.213683 |
Settling first in New York City and then in Leonia, N.J., Fermi began his new life at Columbia University, in New York City. Within weeks of his arrival, news that uranium could fission astounded the physics community. Scientists had known for many years that nuclei could disgorge small chunks, such as alpha particles, beta particles, protons, and neutrons, either in natural radioactivity or upon bombardment by a projectile. However, they had never seen a nucleus split almost in two. The implications were both exciting and ominous, and they were recognized widely. When uranium fissioned, some mass was converted to energy, according to Albert Einstein's famous formula E = mc2. Uranium also emitted a few neutrons in addition to the larger fragments. If these neutrons could be slowed to maximize their efficiency, they could participate in a controlled chain reaction to produce energy; that is, a nuclear reactor could be built. The same neutrons traveling at their initial high speed could also participate in an uncontrolled chain reaction, liberating an enormous amount of energy through many generations of fission events, all within a fraction of a second; that is, an atomic bomb could be built.
Working primarily with the Hungarian-born physicist Leo Szilard, Fermi constructed experimental arrangements of neutron sources and pieces of uranium. They sought to determine the necessary size of a structure, the best material to use as a moderator to slow neutrons, the necessary purity of all components (so neutrons would not be lost), and the best substance for forming control rods that could absorb neutrons to slow or stop the reaction. Fermi visited Washington, D.C., to alert the U.S. Navy about their research, but his guarded enthusiasm led only to a tiny grant. It was left to Einstein's letter to U.S. Pres. Franklin D. Roosevelt about the potential of an atomic bomb, in the summer of 1939, to initiate continuing government interest, and even that grew slowly.
When the United States entered World War II in December 1941, nuclear research was consolidated to some degree. Fermi had built a series of piles, as he called them, at Columbia. Now he moved to the University of Chicago, where he continued to construct piles in a space under the stands of the football field. The final structure, a flattened sphere about 7.5 metres (25 feet) in diameter, contained 380 tons of graphite blocks as the moderator and 6 tons of uranium metal and 40 tons of uranium oxide as the fuel, distributed in a careful pattern. The pile went critical on Dec. 2, 1942, proving that a nuclear reaction could be initiated, controlled, and stopped. Chicago Pile-1, as it was called, was the first prototype for several large nuclear reactors constructed at Hanford, Wash., where plutonium, a man-made element heavier than uranium, was produced. Plutonium also could fission and thus was another route to the atomic bomb.
In 1944 Fermi became an American citizen and moved to Los Alamos, N.M., where physicist J. Robert Oppenheimerled the Manhattan Project's laboratory, whose mission was to fashion weapons out of the rare uranium-235 isotope and plutonium. Fermi was an associate director of the lab and headed one of its divisions. When the first plutonium bomb was tested on July 16, 1945, near Alamogordo, N.M., Fermi ingeniously made a rough calculation of its explosive energy by noting how far slips of paper were blown from the vertical.
After the war ended, Fermi accepted a permanent position at the University of Chicago, where he influenced another distinguished group of physicists, including Harold Agnew, Owen Chamberlin, Geoffrey Chew, James Cronin, Jerome Friedman, Richard Garwin, Murray Gell-Mann, Marvin Goldberger, Tsung-Dao Lee, Jack Steinberger, and Chen Ning Yang. As in Rome, Fermi recognized that his current pursuits, now in nuclear physics, were approaching a condition of maturity. He thus redirected his sights on reactions at higher energies, a field called elementary particle physics, or high-energy physics.
Since the war, science had been recognized in the United States as highly important to national security. Fermi largely avoided politics, but he did agree to serve on the General Advisory Committee (GAC), which counseled the five commissioners of the Atomic Energy Commission. In response to the revelation in September 1949 that the Soviet Union had detonated an atomic bomb, many Americans urged the government to try to construct a thermonuclear bomb, which can be orders of magnitude more powerful. GAC was publicly unanimous in opposing this step, mostly on technical grounds, with Fermi and Isidor Rabi going further by introducing an ethical question into so-called objective advice. Such a bomb, they wrote, becomes a weapon which in practical effect is almost one of genocide . It is necessarily an evil thing considered in any light. U.S. Pres. Harry S. Truman decided otherwise, and a loyal Fermi went for a time back to Los Alamos to assist in the development of fusion weapons, however with the hope that they might prove impossible to construct.
Fermi primarily investigated subatomic particles, particularly pi mesons and muons, after returning to Chicago. He was also known as a superb teacher, and many of his lectures are still in print. During his later years he raised a question now known as the Fermi paradox: Where is everybody? He was asking why no extraterrestrial civilizations seemed to be around to be detected, despite the great size and age of the universe. He pessimistically thought that the answer might involve nuclear annihilation. | <urn:uuid:5548aed9-feca-4e08-a7f2-31a364268088> | 3.84375 | 1,173 | Knowledge Article | Science & Tech. | 42.171362 |
This true-color satellite image shows a large phytoplankton bloom, several hundred square kilometers in size, in the Indian Ocean off the west coast of Tasmania. In this scene, the rich concentration of microscopic marine plants gives the water a lighter, more turquoise appearance which helps to highlight the current patterns there. Notice the eddies, or vortices in the water, that can be seen in several places. It is possible that these eddies were formed by converging ocean currents flowing around Tasmania, or by fresh river runoff from the island, or both.
Often, eddies in the sea serve as a means for stirring the water, thus providing nutrients that help support phytoplankton blooms, which in turn provide nutrition for other organisms. Effectively, these eddies help feed the sea (click to read an article on this topic).
This image was acquired November 7, 2000, by the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) flying aboard the Orbview-2 satellite. Tasmania is located off Australia's southeastern coast.
Image courtesy SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE | <urn:uuid:92c48474-1b8b-49a9-a067-2409bc5025d9> | 4.0625 | 246 | Knowledge Article | Science & Tech. | 37.864733 |
The ECL implementation of strings is ANSI Common-Lisp compliant. There are basically four string types as shown in Table 14.1. As explained in Chapter 11, when Unicode support is disabled, character and base-character are the same type and the last two string types are equivalent to the first two.
Table 14.1. Common Lisp string types
|string||(array character (*))||8 or 32 bits per character, adjustable.|
|simple-string||(simple-array character (*))||8 or 32 bits per character, not adjustable nor displaced.|
|base-string||(array base-char (*))||8 bits per character, adjustable.|
|simple-base-string||(simple-array base-char (*))||8 bits per character, not adjustable nor displaced.|
It is important to remember that strings with unicode characters can only be printed readably when the external format supports those characters. If this is not the case, ECL will signal a serious-condition. This condition will abort your program if not properly handled. | <urn:uuid:e3c47ff5-d5f8-4768-b8e0-9613819f943a> | 2.921875 | 224 | Documentation | Software Dev. | 54.995113 |
In some respects, science is so far advanced that something the experts consider trivial is astonishing to the public. For a long time, many decades, we've routinely monitored the Earth's daily rotation to within tiny fractions of a second. But nobody notices until the planet gets a little off, and the clocks need to be adjusted. The first "leap second" was inserted into the record 40 years ago, in 1972. Now the telecom gurus who run the world's central communication systems are getting tired of dealing with leap seconds and want to call them off. Who cares about the planet any more, they argue. Scientists care, of course, and other extreme precisionists. But the dispute, which came up at a Geneva meeting of the International Telecommunication Union when a recommendation to drop leap seconds could not be agreed upon, is considered headline news today because it just seems so bizarre to everyday people.
I've written an explainer about the larger field of length-of-day studies. This line of research has been going on for centuries and is unexpectedly fruitful. | <urn:uuid:48e3ae89-5e98-44ec-9715-3068479df075> | 2.90625 | 214 | Personal Blog | Science & Tech. | 46.086174 |
C. Kinematics And Dynamics
C3. First Law Of Motion
Inertia - Masses Hanging In Series
To demonstrate inertia of rest in a counterintuitive way.
Stand with two weights, three strings, and a pulling bar (hanging from the lowest string), as photographed.
Ask your students to vote before doing the experiment; then break the string with the fewest votes.
Description of Demo:
: Two masses are hung in series from a fixed point alternating with three strings as photographed. When you pull downward on the third (bottom) string, which of the strings will break: the top, the middle, or the bottom string? A: It depends on how you pull. If you pull very quickly, the bottom string will break, due to the inertia of the bottom mass. If you pull slowly, the top string will break, because the weights increase the tension in the top string.
Sutton, Demonstration Experiments in Physics, Demonstrations M-100. Inertial Reaction and M-101. Breaking a Rope by Sutton, Demonstration Experiments in Physics, Demonstrations M-100. Inertial Reaction and M-101. Breaking a Rope by Inertia. ◙P. LeCorbeiller, A Classical Experiment Illustrating the Notion of "Jerk," AJP 14, 64-65 (1946). ◙Frank G. Karioris, Inertia demonstration revisited, AJP 46, 710-713 (1978). ◙Steven H. Schot, Jerk: The time rate of change of acceleration, AJP 46, 1090-1094 (1978). ◙Stephen Luzader, Letter: What a Jerk!, TPT 26, 423 (1988). ◙T. R. Sandin, The Jerk, TPT 28,
Created & Modified by
April 21, 2000 | <urn:uuid:a0e9fb82-ea5e-4003-9a11-ee3cdbc59736> | 3.984375 | 395 | Tutorial | Science & Tech. | 76.161793 |
Herman Melville’s Moby Dick may paint a picture of the sperm whale as a terrifying, ferocious creature that destroys ships and attacks the sailors on them, but modern research shows that sperm whales are compassionate and social creatures, dangerous only to the fish and squid that the giant whale feasts on for dinner, or to the orca whales that prey on sperm whale calves. A heartwarming and unusual recent discovery does even more to distinguish the sperm whale from its deadly reputation, as a group of sperm whales were observed “adopting” a bottlenose dolphin with a spinal malformation.
Behavioral ecologists Alexander Wilson and Jens Krause discovered this unique phenomenon when they set out to observe sperm whales off the island of Pico in the Azores in 2011. Upon arriving there, they discovered a whale group of adult sperm whales, several whale calves, and an adult male bottlenose dolphin. Over the next eight days, the pair observed the dolphin with the whales six more times, socializing and even nuzzling and rubbing members of the group. At times, the sperm whales seemed merely to tolerate the dolphin’s affection, while at others, they reciprocated. "It really looked like they had accepted the dolphin for whatever reason," Wilson reports to ScienceNOW. "They were being very sociable."
Did you know there are about 40 species of dolphin? When you think of dolphins, you might just be picturing the bottlenose dolphin or the common dolphin, but what about the long-snouted spinner dolphin? (And did you know that the killer whale is actually a kind of dolphin too?)
Long-snouted spinner dolphins are relatively small for oceanic dolphins, growing only about 7 feet long (the bottlenose dolphin is about 10 feet long). Spinner dolphins are highly social and are often seen in pods of hundreds of dolphins. Like all dolphins, spinners communicate by echolocation, which is an elaborate series of clicks and whistles. Spinner dolphins also slap the surface of the water with their fins to communicate. | <urn:uuid:7016fb8b-cdbf-4a1d-a51e-3b4be2542cf8> | 3.453125 | 434 | Personal Blog | Science & Tech. | 41.230547 |
This is an important question, because it is thought to be due to temperature, convection and radiative physics. But what about other possible factors? I’ve started gathering a list and some notes for discussion on the excellent and still very active Clive Best lapse rate thread. Regulars know that when a post title contain a question mark, there are going to be demands for help… TB
Dr Tim Ball has a good recent article here, which contains some useful diagrams, such as this one:
Tropopause height at the Poles varies between 7 km in winter and 10 km in summer, at the Equator the range is 17 to 18 km. The difference in seasonal range is because of the difference in seasonal temperature range. How do you build even those simple dynamics into a computer model?
Answer: the best way to make a start is to quantify the various effects which contribute to the height difference in the polar and equatorial tropopause, using the clues offered by seasonal variation as a guide.
So, what else apart from temperature, convection and radiation might affect the height of the tropopause?
Here’s my probably list, I’ll update it with suggestions made in comments.
The Earth is 43.5km bigger in diameter at the equator than it is at the poles. Wikipedia says this is due to rotation; i.e. the centrifugal effect of the spinning mass.
“Without any idea of the Earth’s interior, we can state a “constant density” of 5.515 g/cm³ and, according to theoretical arguments (seeLeonhard Euler, Albert Wangerin, etc.), such a body rotating like the Earth would have a flattening of 1:230.
In fact the measured flattening is 1:298.25, which is more similar to a sphere and a strong argument that the Earth’s core is very compact.”
Of course, for a centrifugal force to be effective, there must be a coupling between the atmosphere and Earth. There clearly is some, because at the surface, the atmosphere goes round at the same speed the Earth does, give or take local variation. If it didn’t, our brollys would be blown inside out by 1000mph winds. However, there is shear as we go up from the surface, and jet streams, geostrophic winds, meridional circulation etc. So how do we quantify the effect?
If the Earth was on it’s own in space, then notwithstanding other effects the atmosphere would be pulled towards sphericity. However, Earth lies in a planetary plane orbiting the Sun, with a close by moon 1/6th its mass. About.com has this to say:
“The gravitational pull of the moon and the sun creates tides on the earth. While tides are most commonly associated with oceans and large bodies of water, gravity creates tides in the atmosphere and even the lithosphere (the surface of the earth). The atmospheric tidal bulge extends far into space but the tidal bulge of the lithosphere is limited to approximately 12 inches (30 cm) twice a day.
The moon, which is approximately 240,000 miles (386,240 km) from the earth, exerts a greater influence on the tides then does the sun, which sits 93 million miles (150 million km) from the earth. The strength of the sun’s gravity is 179 times that of the moon’s but the moon is responsible for 56% of the earth’s tidal energy while the sun claims responsibility for a mere 44% (due to the moon’s proximity but the sun’s much larger size).”
But we would expect the atmosphere to relax back towards sphericity (notwithstanding other factors) where it is not in line with these heavenly bodies. So how fast does it relax? How far is “far out into space”?
Clearly the Earth’s topography has a hand in keeping the near surface atmosphere moving round with the surface, indeed there are clear inverse relationships between changes in atmospheric angular momentum (AAM), zonal Atmospheric Circulation Index ACI and the Earth’s length of day (LOD). So large amounts of coupled energy are evidence of the coupling between the atmosphere and solid Earth. What effect does this have on the difference in height of the troposphere between equator and poles? The north pole is pretty flat, the northern hemisphere is pretty mountainous and forested in places. The southern hemisphere is mostly ocean, but big waves will also couple the air and sea. Is there a difference in tropopause profile between the hemispheres which offers any clues here? Or would its signal be lost in profile differences due to larger effects such as general circulation?
Over to you. | <urn:uuid:6bb15839-2f18-46f4-82ca-8e1aa1c24f22> | 3.53125 | 995 | Comment Section | Science & Tech. | 54.738928 |
|This is a stub or unfinished. Contribute by editing me.|
A hash table is a dictionary-like data structure that provides O(1) lookup time. You associate keys with values (e.g. a dictionary associates words with definitions). Often a hash table is implemented using a hash function and an ordinary array. Collisions (when multiple keys map to the same array index) must be dealt with somehow or the hash table is severely crippled.
Typically a standard hash table library (see UsingHashMap for details) will be adequate.
There are two completely separate algorithms involved in a hash table -- the "hash function" and the "collision resolution algorithm". Any hash function can be mix-and-matched with any collision resolution algorithm.
Hash Functions
Most hash functions attempt to minimize the number of collisions, by attempting to spread all the expected keys uniformly over the array. In a few rare cases where all possible values are known ahead of time, it is possible to design a "perfect hash function" that maps each value to a different key, which eliminates all collisions.
Key Length
An incredibly simple hash function could be the length of the key. This is a terrible hash function for (hopefully) obvious reasons.
Key Value
If the key is given as a C-like string of length L, we can define the key value as such:
key + key + ... + key[L-2] + key[L-1]
This is a common but poor hash function. For example, "foo", "oof", and "fnp" all hash to the same index.
Good hash functions
- Julienne Walker has a list of good hash functions.
non-uniform hash functions
Has anyone done research on non-uniform hash functions? Non-uniform hash functions that deliberately make several related values hash to the same key?
- In a spelling checker using a Bloom filter, it's OK if a hash function allows thousands of non-words (such as strings that begin with "qqtt") to "collide" to a single key, as long as no correctly-spelled word collides with that same key.
- When searching a table of information using a person's name as the "value", it may be useful to have common mis-spellings of that name all hash to the same key.
- Since certain patterns in Hashlife occur overwhelmingly more often than other patterns, it may be useful to have a hash function that makes each of the most-frequent patterns hash to a key with no collisions, even if it causes less-frequent patterns to hash to a key with an average of 2 or 3 collisions, and some extremely rare patterns to a key with dozens of collisions.
- Most "hash functions" attempt to simulate a "random oracle", to have "well-mixed ... avalanche". However, the hash function used in Python dictionaries has horrible avalanche behavior, but it gives better results on typical hash tables than a perfect random oracle (and therefore better than even cryptographically secure hashes)..
Collision Resolution
Separate Chaining
Linear Probing
Linear probing means that if collision occurs, the next probe will be at a[index + k], where k is the constant.
Quadratic Probing
Common Operations
If we follow the wiki: RulesOfOptimization, we will need to do some testing before and after we implement some new "improved" hash table. Perhaps you will find the test data collected by Peter Kankowski to be useful as "fair and unbiased" test data to use to compare your spiffy new hash table with the default hash table built into your language. | <urn:uuid:be8a389e-19b6-4d70-8ae2-7271c0b92a2f> | 3.765625 | 764 | Knowledge Article | Software Dev. | 50.146356 |
C# is an object-oriented programming language developed by Microsoft Corporation . C# source code as well as those of other .NET languages is compiled into an intermediate byte code called Microsoft Intermediate Langauge. C# is primarily derived from the C, C++, and Java programming languages with some features of Microsoft's Visual Basic in the mix. C# is used to develop applications for the Microsoft .NET environment. .NET offers an alternative to Java development. Microsoft's Visual Studio .NET development environment incorporates several different languages including ASP.NET, C#, C++, and J# (Microsoft Java for .NET), all of which compile to the Common Language Runtime.
A new form of iterator employs co-routines via a functional-style yield keyword similar to the one found in the Python language.
1. Anonymous methods provide closure functionality.C# version 3.0 introduces several language extensions to support higher order, functional style class libraries. The extensions enable the construction of compositional APIs with the expressive power of query languages in areas such as relational databases and XML. C# 3.0 will include the following new features:
2. Generics or parameterized types support some features not supported by C++ templates such as type constraints on generic parameters. However, expressions cannot be used as generic parameters as in C++ templates. In contrast to the Java implementation, parameterized types are first class objects in the virtual machine, allowing for optimizations and preservation of type information.
3. Nullable value types facilitate interaction with SQL databases. Sample nullable type declaration:
int? variableName = null;
4. Partial types allow the separation of a class implementation into more than one source file. This feature was implemented primarily so Visual Studio generated code can be kept seperate from developer code.
1. Anonymous types: tuple types automatically inferred and created from object initializers.Microsoft C# developers note that C# 3.0 is bytecode compatible with C# version 2.0. For the most part, enhancements comprise purely syntactic or compile-time improvements.
2. Object initializers ease construction and initialization of objects.
3. Implicitly typed local variables permit the type of local variables to be inferred from the expressions used to initialize them.
4. Implicitly typed arrays: a form of array creation and initialization that infers the element type of the array from an array initializer.
5. Extension methods make it possible to extend existing types and constructed types with additional methods.
6. Lambda expressions: an evolution of anonymous methods providing improved type inference and conversions to both delegate types and expression trees.
7. Expression trees permit lambda expressions to be represented as data (expression trees) instead of as code (delegates).
8. Query expressions provide a language integrated syntax for queries that is similar to relational and hierarchical query languages such as SQL and XQuery.
C# was designed for developing components in a fully object-oriented manner as part of the Microsoft .NET initiative. C# debuted in the year 2000 at the Professional Developers Conference (PDC) where Microsoft founder Bill Gates was the keynote speaker. At the same time, Visual Studio .NET was announced.
The primary architects of C# were Peter Golde, Eric Gunnerson, Anders Hejlsberg, Peter Sollichy, and Scott Wiltamuth. Of these, the principal designer of the the C# language was Anders Hejlsberg, a lead architect at Microsoft. Previously, he was a framework designer with experience with Visual J++ (Microsoft's old version of the Java language), Delphi, and Turbo Pascal.
Both C# and the Common Language Infrastructure (CLI) have been submitted to international standards organizations European Computer Manufacturers Association (ECMA) and International Organization for Standardization (ISO) / International Electrotechnical Commission (IEC). | <urn:uuid:49069a38-0a2c-4113-a354-c3e03c9de2fb> | 3.40625 | 789 | Knowledge Article | Software Dev. | 27.063054 |
Inspired by my visit to the Kennedy Space Center and the large amount of information NASA gave me on the new Constellation Space Program. We are going to do a series of articles on the new space problem as it progresses.
These articles will delve into what the Constellation Program will consist of in terms of technology, vehicles and goals. We will be posting NASA Press Releases as they come in and also hope to get interviews with program designers, engineers and Constellation Astronauts.
So let’s get started.
First off, what is the Constellation Space Program?
Before the end of the next decade, NASA astronauts will again explore the surface of the moon. And this time, we're going to stay, building outposts and paving the way for eventual journeys beyond.
This journey begins soon, with development of a new spaceship. Building on the best of Apollo and shuttle technology, NASA's creating a 21st century exploration system that will be affordable, reliable, versatile, and safe.
The centerpiece of this system is a new spacecraft designed to carry four astronauts to and from the moon, support up to six crewmembers on future missions to Mars, and deliver crew and supplies to the International Space Station.
The new crew vehicle will be shaped like an Apollo capsule, but it will be three times larger, allowing four astronauts to travel to the moon at a time.
The new ship can be reused up to 10 times. After the craft parachutes to dry land (with a splashdown as a backup option), NASA can easily recover it, replace the heat shield and launch it again.
Coupled with the new lunar lander, the system sends twice as many astronauts to the surface as Apollo, and they can stay longer, with the initial missions lasting four to seven days. And while Apollo was limited to landings along the moon's equator, the new ship carries enough propellant to land anywhere on the moon's surface.
Once a lunar outpost is established, crews could remain on the lunar surface for up to six months. The spacecraft can also operate without a crew in lunar orbit, eliminating the need for one astronaut to stay behind while others explore the surface.Safe and reliable
The launch system that will get the crew off the ground builds on powerful, reliable shuttle propulsion elements. Astronauts will launch on a rocket called Ares I, which uses a single five-segment solid rocket booster, a derivative of the space shuttle's solid rocket booster, for the first stage. A liquid oxygen/liquid hydrogen J-2X engine derived from the J-2 engine used on Apollo's second stage will power the crew exploration vehicle's second stage. The Ares I can lift more than 55,000 pounds to low Earth orbit
Ares V, a heavy lift launch vehicle, will use five RS-68 liquid oxygen/liquid hydrogen engines mounted below a larger version of the space shuttle's external tank, and two five-segment solid propellant rocket boosters for the first stage. The upper stage will use the same J-2X engine as the Ares I. The Ares V can lift more than 286,000 pounds to low Earth orbit and stands approximately 360 feet tall. This versatile system will be used to carry cargo and the components into orbit needed to go to the moon and later to Mars. It can be modified to carry crew as well. Ares V and Ares I
Best of all, these launch systems are 10 times safer than the shuttle because of an escape rocket on top of the capsule that can quickly blast the crew away if launch problems develop. There's also little chance of damage from launch vehicle debris, since the capsule sits on top of the rocket.The Flight Plan
In just five years, the new ship will begin to ferry crew and supplies to the International Space Station. Plans call for as many as six trips to the outpost a year. In the meantime, robotic missions will lay the groundwork for lunar exploration. In 2018, humans will return to the moon.
Here's how a mission would unfold:
A heavy-lift rocket blasts off, carrying a lunar lander and a "departure stage" needed to leave Earth's orbit (below left). The crew launches separately (below, center), then docks their capsule with the lander and departure stage and heads for the moon (below, right).
Three days later, the crew goes into lunar orbit (below, left). The four astronauts climb into the lander, leaving the capsule to wait for them in orbit. After landing and exploring the surface for seven days, the crew blasts off in a portion of the lander (below, center), docks with the capsule and travels back to Earth. After a de-orbit burn, the service module is jettisoned, exposing the heat shield for the first time in the mission. The parachutes deploy, the heat shield is dropped and the capsule sets down on dry land (below, right).'Into the Cosmos'
with a minimum of two lunar missions per year, momentum will build quickly toward a permanent outpost. Crews will stay longer and learn to exploit the moon's resources, while landers make one way trips to deliver cargo. Eventually, the new system could rotate crews to and from a lunar outpost every six months.
Planners are already looking at the lunar south pole as a candidate for an outpost because of concentrations of hydrogen thought to be in the form of water ice, and an abundance of sunlight to provide power.
These plans give NASA a huge head start in getting to Mars. We will already have the heavy-lift system needed to get there, as well as a versatile crew capsule. A lunar outpost just three days away from Earth will give us needed practice of "living off the land" away from our home planet, before making the longer trek to Mars.
This is not some far off pipe dream plan either; the Constellation Program is already under way. Prototype vehicles have been built and are being tested. New Space Suits are being designed and Lunar habitats are being tested in Antarctica for Human inhabitation on the Moon. The Engines for the Launch vehicles are built and are being testing as we speak.
This will all lead to the first Manned mission to Mars. Everything about Constellation is being designed to lead us to Mars and right now NASA estimates that the very first Commander that will lead Humans to Mars is between the ages of 6 and 16 years old.
This fact given to me by NASA while on tour of the Kennedy Space Center gave me goose bumps. A Crew of people from my Daughters generation will be the first ever Humans in the history of Mankind to step foot on another planet.
These are indeed exciting times, however, given the fickle nature of Congress funding will always be something to be worried about and that’s why right now every American Citizen needs to email or call their Congressional Representatives and tell them that you expect them to support NASA’s funding needs for the foreseeable future and I mean right now!!! Don’t hesitate, be a factor in moving Mankind forward into the future.
Now that you have an overview of what Constellation is, our next article will dive into the details of the vehicles themselves. So stay tuned.
Please feel free to discuss this article and ask questions.All Information, Material and Pictures are provided courtesy of NASA | <urn:uuid:96fa045e-ae1a-442a-84a8-76cd88e2f072> | 3.234375 | 1,494 | Comment Section | Science & Tech. | 52.120301 |
Joined: 16 Mar 2004
|Posted: Mon Jul 14, 2008 11:11 am Post subject: Superbugs, shapes and nanotechnology
|September 2007 - Society for General Microbiology
Superbugs, shapes and nanotechnology
A common hospital superbug called Clostridium has a protective coat of armour that can self assemble when put into a test tube on its own, which may have important commercial uses in nanotechnology, according to scientists speaking today at the Society for General Microbiology's 161st Meeting at the University of Edinburgh, UK.
Like many other micro-organisms, Clostridium difficile produces a lattice coat made of proteins to surround its cell wall and protect it like a suit of armour. The complete protein coat is then attached to the underlying cell wall with chemical bonds. "We have discovered that these protein coats have a remarkable ability to self-assemble when they are taken off the bacteria and put into a test tube. Normally, on the bacteria, the proteins are not randomly arranged, they form regularly spaced geometrically arranged shapes, a bit like the rings in chain mail", says Dr Neil Fairweather of Imperial College London, UK. "We discovered that the proteins can do the same thing, and form the same distinct layers and shape, on their own in a test tube".
This finding opens up two areas of research for the science teams. It may lead to new ways of fighting hospital superbugs like Clostridium difficile by exposing weaknesses in the coats, or by identifying new target molecules. And in the new field of nanotechnology, where tiny particles are currently used in sunscreens and other products, finding ways to make molecules self assemble themselves into regular shapes could have important commercial applications.
"The field of nanotechnology is opening up to many new areas, and our research points to applications for this exciting technology in fighting superbugs like C. difficile" says Dr Fairweather. | <urn:uuid:15a2edaf-2dcd-4791-a912-2fb04312010f> | 3.109375 | 397 | Comment Section | Science & Tech. | 27.042067 |
Hydrology - Groundwater
Become more familiar with groundwater and some of the issues that influence it. You will start to think beyond the water that you can see and move into more complex ideas such as pollution and caves. You will use the internet to help you gain knowledge as well as doing hands-on activities.
Did You Know?
Winds caused by changes in barometric pressure are what give Wind Cave its name. These winds have been measured at the cave's walk-in entrance at over 70 mph. The winds at the natural entrance of the cave attracted the attention of Native Americans and early settlers. | <urn:uuid:cd81489a-4c38-46cc-8bfe-04080181486f> | 3.015625 | 124 | Knowledge Article | Science & Tech. | 54.987642 |
One Day's Temperature Map
October 20, 2009
The Thermal Emission Spectrometer on NASA's Mars Global Surveyor provided the first systematic study of Martian weather. For three Mars years, TES operated much like a terrestrial weather satellite, making daily weather maps to track changes in atmospheric temperature, water-ice clouds, water vapor, and dust. This map shows temperatures on Mars on Sept. 10, 2006.
Topics: Environment, Water vapor, Spectrometers, Mars, Weather, Thermal Emission Spectrometer, Thermal infrared spectroscopy, Mini-TES, Climate of Mars | <urn:uuid:31ef9da5-5f03-425d-97f2-0228ae60a141> | 3.0625 | 121 | Truncated | Science & Tech. | 27.785798 |
John Dreher wrote:However I fear that the mechanics of the collision between two rolling spheres, with allowance for the assumed interaction at the contact point of the impact with regards to friction, puts the theoretical basis well beyond grade 6-8 level
With an appropriate choice of hypothesis and initial test conditions, one can usually ignore the small amount of friction between a sphere and a flat level surface and the small amount of elastic behavior at contact and air fluid flow and all the other complicating factors. Engineers make these simplifying assumptions all the time, they just have to go to the trouble of calculating the maximum error that could be caused by the simplification if they don't want to end up with a nasty surprise of being VERY WRONG in their predictions. For a science project, your hypothesis doesn't have to be correct! It has to be testable. A lot of great scientific discoveries have occured when somebody's hypothesis was WRONG! Many times actually proving that you have actually proved a hypotheisis is correct is EXTREMELY DIFFICULT. A good example of this is amount of effort that Michelson-Morley in their famous experiment.
If you start out with one stationary and one is moving object, that is a lot simpler than if both are moving. If you choose spheres as your objects, you eliminate a lot of geometry and effects of geometry. If you restrict your observations to the first few inches of travel before and after a collision, the effects of friction are less likely to accumulate and become significant. If you ignore the behavior 1 usec before and 1 usec after a collision, you won't have to try and deal with the precise contact behaviors and will only be left with the outcome of the collision.
The analysis of "dry-ice-sliders" can also get very complicated. Sublimation is occurring which is changing the mass so it is extremely difficult to know what the mass the slider is at all points in time. Yes there are again a set of simplifying assumptions that can be made, but again if you try and build a set of equations that fully includes everything, it can get far more complicated than interactions that don't involve state changes in matter. BEWARE: There is also a frost-bite safety hazard handling dry ice. Collisions of dry ice can send fragments in unexpected directions which means everone has to be fully protected head to toe, face shields, gloves, etc. so that dry ice fragments don't come in contact with any skin. Protective clothing needs to be simliar to the choice welder's make so that there aren't any pockets, cuffs, exposed sock/shoe openings where very hot (or in this case very cold) things can find their way into. Ava and Mom,
don't get discouraged by a couple of engineers/scientists discussing the complicating factors.
The fundamental baisis for Physics is simply coming up with an explaination for things that are observed.
If you get out your magnifying glass and look at every minute and complicating detail, you can make Physics really really hard.
If you stand back and look at things in less detail, it is far easier to come up with a testable hypothesis and experiment to test it.
At the 6-8 grade level, the first order effects are the important ones to be concerned with and not all of the minutia. | <urn:uuid:53a5382f-13f1-4455-a9e7-21cf83925459> | 2.984375 | 691 | Comment Section | Science & Tech. | 43.349025 |
Why is southern sea ice increasing?
What the science says...
|Select a level...||Basic||Intermediate|
|Antarctic sea ice has grown in recent decades despite the Southern Ocean warming at the same time.|
First of all, it’s worth remembering that sea ice is not to be confused with land ice. This distinction might seem obvious, but the two are often confused in media reports. Sea ice is frozen seawater floating on the surface, whereas land ice is a layer of snow that has accumulated over time on a landmass. Antarctica is losing land ice at an accelerating rate.
However, it is clear that the extent of sea ice around the coast of the continent is growing. Why? The first explanation which comes to mind is that the Southern Ocean must be cooling. But on the contrary, the Southern Ocean has warmed by around 0.5°C in the three decades since satellites began measuring sea ice trends.
The true reasons for the increasing ice are a complex set of factors. One factor is an increase in precipitation over the Southern Ocean, which means more snowfall. However, this trend is expected to reverse in coming decades as the Antarctic continues to warm.
Finally, southern sea ice is not particularly important to the climate. Unlike land ice, sea ice doesn’t affect sea levels because it’s already displacing water. And unlike the situation in the Arctic, where disappearing sea ice is making the Arctic Ocean less reflective and amplifying Arctic warming, a decline in southern sea ice would not warm the Antarctic climate. For as long as climatologists have studied it, the Southern Ocean has been almost ice-free in summer, the time of year when it would receive enough heat from the Sun to have a large effect. The issue of southern sea ice is really just a distraction which diverts our attention from the more important issue of sea ice melt in the Arctic.
In conclusion, the increase of southern sea ice does not contradict global warming. The Southern Ocean is in fact warming, the increase of sea ice is due to a variety of factors, and sea ice is not as important to the Antarctic climate as it is to the Arctic.
Last updated on 20 October 2010 by James Wight. | <urn:uuid:c12198e2-ccf6-4461-a3a0-75364abfa644> | 3.46875 | 458 | Knowledge Article | Science & Tech. | 55.117307 |
7. Linked tables and relationships
The previous page has a picture showing two tables with related fields. These are depicted graphically as a line between them.
The line between the fields has a '1' on one side and the infinity sign on the other. In Access this indicates a 'one-to-many' relationship. This is described in more detail on the Entity Relationship Diagram mini-web.
A small relational database may only contain two tables whilst a large corporate database could contain hundreds of tables.
Challenge see if you can find out one extra fact on this topic that we haven't already told you
Click on this link: database diagrams
Copyright © www.teach-ict.com | <urn:uuid:fd4d3433-2b30-435e-93ac-4d53a1ca3a5d> | 3.25 | 146 | Tutorial | Software Dev. | 51.537261 |
It's often said -- occasionally even by us -- that we currently know of but a single ecosystem, our own, with no other data points for reference. That's not precisely true. Although we know of no other naturally-occuring ecosystem (yet), it is possible to construct self-contained ecologies, receiving no input other than sunlight -- just like the Earth. The "Biosphere II" project, despite its many failings, stands as one of the biggest experiments in such construction. But it turns out that you don't have to buy up land in the Arizona desert to give the biosphere experiment a try. You can do it on your desk.
"EcoSpheres" are sealed globes containing filtered water, a variety of microorganisms and shrimp, able to live and reproduce for years, even a decade or more, with only sunlight as input. They come in a variety of sizes; the larger ones tend to last longer. They require no maintenance other than keeping them at a comfortable temperature.
I don't have one of these, and the various typos and clumsy constructions on the website give me some caution. The UK website is much better, however, and there are equivalent sites for a handful of other countries. Nonetheless, I'd have just checked the site and gone about my business had I not seen an essay by one EcoSphere owner -- Carl Sagan.
Sagan, an astronomer, was perhaps best known for trying to get non-scientists to think about the bigger picture of how humans affected their environment, and the potential for other environments on other planets. He wrote this about the globes:
Unlike an aquarium, this little world is a closed ecological system. Light gets in, but nothing else - no food, no water, no nutrients. Everything must be recycled. Just like the Earth. In our larger world, we also - plants and animals and microorganisms - live off each other, breathe and eat each other's wastes, depend on one another. Life on our world, too, is powered by light. Light from the Sun, which passes through the clear air, is harvested by plants and powers them to combine carbon dioxide and water into carbohydrates and other foodstuffs, which in turn provide the staple diet of the animals.Our big world is very like this little one, and we are very like the shrimp. But there is at least one major difference: Unlike the shrimp, we are able to change our environment. We can do to ourselves what a careless owner of such a crystal sphere can do to the shrimp.
I honestly don't know if EcoSpheres would have a particular pedagogical or philosophical value for most people. I have some doubts. Ecological simulations allow one to explore new parameters and learn from mistakes, for example, and one could argue that the EcoSphere is little more than an ant farm for the lazy.
But the underlying concept of an ecology one can observe over the months and years, one where a mistake -- leaving it in the dark for too long, or in the heat -- can lead to an unrecoverable catastrophe, has a certain metaphorical value. Watching the growth and decline cycles of shrimp and bacteria won't lead to any great insights into how best to manage environmental changes on Earth, but it may provide an ongoing reminder of the fragility and finality of the great wager we have made.
Sagan saw in the EcoSpheres a metaphor, as well, one not just of caution, but of hope. If we can figure out how to maintain our own planet, he believed, we could one day have the ability to shape other planets as well, responsibly, with foresight and wisdom. The Earth won't be our only example of a complex ecosystem forever.
You probably have seen these, but they’re still worth linking, I think: Kevin Kelly in Out of Control and in Cool Tools. I wonder whether owning one of these EcoSpheres would affect my thinking about systems generally, and suspect that it would, in fact. Maybe getting a world that’s self-contained and looking at it can make us think about worlds as they are, and as they might be.
I've just realized this blog looks quite a bit different in IE than it does in Firefox. I've always been viewing it in IE and there was never any content off to the right. Now I just viewed it in Firefox and there's content /info there (like the Utne thing).
It looks really good in Firefox but in IE all the stuff that is supposed to be to the right is all smushed to the bottom.
Just an FYI!
This reminded me of an old International Wildlife magazine article of a man who just went to a scummy ditch and scooped out some algae and water with an old big jar used for preserves. He just sealed it with a normal canning lid. He did different experimints to test the hardiness of the enclosed ecosystem like leaving it in the sun or a closet for extended periods of time. One jar grew a slime that had unusual colours.
These ecosystems thrived and probably still do years after he started.
I think I'm going to the ditch in the back 40 right now!
This comment applies to most of worldchanging's postings-- they are all so darn innovative in terms of topic, content, angle, etc., but you wouldn't necessarily know it just by scanning through the list. I think that the "section" headings (i.e. in this piece The Means of Expression - Media, Creativity and Experience) are displayed too prominently. Visually, it almost looks like the newer postings are follow-ups on previous postings, when actually each of these postings is completely original. Having a completely original heading each time (including the subtitle), would highlight the diversity of topics better. Could you note the "section" or the "type of posting" in some other way, that's less prominent?
Had a scary thought about these ecosystems in a jar. Suppose someone uses them as an excuse to avoid protecting biological diversity? They could say, "See? Why worry about protecting the thousands of insect species in rainforests, if all it takes to keep the air/solid cycle going is some algae and some shrimp?"
Also I wonder if any researchers (perhaps NASA, ESA, RSA and others interested in long human spaceflight) have thought about trying to scale these things up by putting more critters in them. Seems like it would be very hard to test. You'd have to be very patient to see if any unstable feedback arose in the system.
Oh--and for Jason--what you're seeing in IE is a bug involving the CSS float property. Snap your screen resolution 1024 by 768 or greater, maximize IE and the right hand column will snap back into it's proper place.
I owned one for years, and would take it along to client meetings and lectures [local ones; these are a bit much for air travel]. It's a terrific teacher of the inescapable and profoundly significant fact that we live our lives in a system closed to matter and open to energy -- from which most other environmental lessons directly follow. | <urn:uuid:5e37f153-825b-4cd4-8b52-35cf5d58b595> | 2.90625 | 1,464 | Comment Section | Science & Tech. | 52.153885 |
Scientists will grapple ‘for years’ to best understand the whys and wherefores of a four-day rapid melting affecting 97 percent of Greenland’s enormous ice sheet. ‘Weird’ in a number of ways … but precise role of global warming remains to be determined.
That startlingly rapid four-day widespread melt of Greenland’s massive ice sheet between July 8 and July 12?
It was “global weirding” for sure. And “weird weather” by any stretch. Just what it has to do with global warming remains to be best answered by the relevant scientists, whose reasoned assessments we’ll have to eagerly await.
But don’t worry. They’re on it.
The before-and-after images of Greenland’s ice sheet instantly attracted widespread media attention, and deservedly so given the speed and scope of the melt. Which is not to suggest that it was necessarily unprecedented or even unforeseen.
Image courtesy of NASA/JPL.
Much of the initial media coverage reflected the cautionary approach taken by NASA’s Jet Propulsion Laboratory in announcing the melt. The best reports on the melt noted that such events have occurred previously, most recently in 1889. But they noted too that this melt event is the first noted in the observational record now at the start of its 90th decade.
Some others, however, rushed to mistakenly headline the event as if the entire ice sheet had melted — WRONG. Oy Vey.
Far better to report, as Associated Press science writer Seth Borenstein did, that Greenland’s ice sheet — even its “coldest and highest place, Summit Station,” “suddenly started melting a bit this month … showed melting.”
(Had the whole ice sheet melted away over just four days, some have observed, we hardly would have had to wait long to learn about it in headlines, no matter how 24/7 they might be.)
So what gives? AP’s Borenstein, The New York Times’ Kelly Slivka, and others noted that such melting is not unprecedented … only highly unusual. Both reported the JPL points that the ice melt area had increased from about 40 percent of the ice sheet to about 97 percent in just four days. (The most extensive seen by satellites over the past 30 years was about 55 percent, Borenstein reported.)
Both Borenstein and Slivka picked up too on another point made by NASA/JPL:
Summer in Greenland has been freakishly warm so far. That’s because of frequent high pressure systems that have parked over the island, bringing warm clear weather that melts ice and snow, explained University of Georgia climatologist Thomas Mote.
Every 150 Years over the past 10,000
Slivka reported NASA Goddard Space Flight Center glaciologist Lora Koenig as saying the July 8-12 melt, while an extreme event, needs to be seen in a historical context: over the past 10,000 years of its history, large-scale melting events have occurred roughly every 150 years or so. With the previous huge melt in 1889, this latest extreme melt appears to be running pretty much on schedule.
Koenig pointed out too that surface ice on the sheet’s summit appeared to be within one degree Celsius — about 1.8 degrees Fahrenheit — of refreezing, which may have gotten under way around the July 14 end of the melt.
In his syndicated report, AP’s Borenstein quoted NASA chief scientist Waleed Abdalati as saying “It’s a big signal, the meaning of which we’re going to sort out for years to come.”
In a next-day analysis after his site initially had to rely on a reposting from The Huffington Post, Climate Central science writer Andrew Freedman took a look at “The Story Behind Record Ice Loss in Greenland.”
No More ‘Steady-State’ Arctic Climate
While “dramatic and worrisome to many climate scientists,” Freedman reported, the sudden melt “does not necessarily mean that Greenland is headed for a far faster and more significant melt than scientists already anticipate.” He reported on an e-mail exchange with University of Colorado research associate William Colgan: “Since we are looking at a record event, rather than a trend,” Colgan had written to him, “it is not really possible to directly translate this into a projection of future ice sheet behavior.”
Freedman also reported Colgan’s comment that “Perhaps all we can say is that the frequency with which Greenland melt years are being established is exceptional. It clearly demonstrates that the Arctic climate is no longer in steady-state … but rather that Arctic climate is in a highly transient state, whereby progressively more extreme events are exceeded as climate trends in a given direction.”
“I think it is clear that entire ice sheet melt events are now increasing in frequency as a result of anthropogenic [manmade] climate change, rather than natural variability in solar isolation,” Colgan wrote.
Freedman concluded that this particular melt “was set off by unusually mild weather conditions that have occurred more frequently in that region during recent summers.” He pointed to NASA/JPL’s finding of a number of upper-atmosphere high pressure centers, or “ridges,” over Greenland since May, leading to mild air temperatures and reduced cloud coverage … “similar to the weather patterns that have caused record heat in much of the U.S. this summer.”
Freedman reported also that Greenland’s west coast sea surface temperatures also have run warmer than average, likely contributing to a recent calving of a massive iceberg from the Petermann Glacier in mid-July.
So. Is it global warming? Maybe, and maybe not. But probably related in at least some ways, it would seem. Details and critical fine points, nuances, and uncertainties still to be determined.
Is it “global weirding”? You be the judge.
Is it weird weather? And not only in Greenland in mid-July but across much of North America throughout the spring and now well into the sultry and drought-stricken summer months?
That much seems a gimme. Bingo. For the precise climate connection, let’s wait for involved scientists to study, assess … and put forth some evidence-based findings. | <urn:uuid:0193864d-7787-4d4a-a663-3841123a56cf> | 3.578125 | 1,363 | Comment Section | Science & Tech. | 48.391448 |
Biology of Australia
Scorpions are the oldest known land animal, and were possibly the first to invade the land. In Australia the arid zone has more species of scorpion than any other subregion.
Urodocua is the endemic genus of Australian scorpion, with 11 species. Unlike other scorpions, the members of this genus digs a deep spiral burrow, not living under bark and rocks as other scorpions. This burrowing habit has allowed it to colonise the vast arid areas of Australia.
Isometroides vescus has a variant of the burrowing habit, it occupies burrows of burrowing spiders after eating the owner, appearing to prey exclusively on burrowing spiders.
Penny Van Oosterzee, 1993, The Centre - The Natural history of Australia's Desert Regions, Reed Australia.
|Author: M.H.Monroe firstname.lastname@example.org Sources & Further reading| | <urn:uuid:6e1b8b53-0e32-4d67-b78d-05ce8ef3c69c> | 3.625 | 195 | Knowledge Article | Science & Tech. | 42.537163 |
event library provides functions for understanding an event and the environment in which it was raised as well as actions for sending events.
There are three categories of event functions.
For historical reasons, some of these are Web-centric. The following functions are available:
event:env()- returns information about the event's environment. The function takes an argument that determines what will be returned:
caller -return the URL of the Web page on which the event is firing (assumes an event in the
ip -return the IP number of the endpoint (client).
referer -return the URL of the referring page to the caller (assumes a web event).
title -return the page title of the calling page.
- txn_id - return the transaction ID of this ruleset evaluation.
event:attr() -returns a specific event attribute. The function takes the name of the attribute to be returned as its sole argument.
event:attrs() -returns all the event attributes as a map.
event:channel()- returns information about the event channel. The function takes an argument that determines what is returned:
id- returns the event channel identifier.
The event library supports sending events to event channels.
event:send(<subscription_map>, <domain>, <type>)
<type> are expressions that evaluate to strings. These arguments are optional. If they are not present, the values with keys
_type from the subscription map will be used.
A subscription map is any map that contains an event channel identifier (identified by the key
cid) or an event signal URL (identified by the key
esl). The other key-value pairs in the map are optional. The following code sample shows a subscription map:
Given the preceding subscription map declaration, we could send a
notification:status event to the event channel identified by the CID in the map as follows:
If the subscription map contains both a CID and an ESL, the ESL is used to send the event.
Event attributes can be specified in the optional action parameter
attrs. To send a
notification:status event with the attributes priority and subject, we would modify the preceding example as follows:
Of course, the arguments and parameters of an action can be calculated.
If the ESL or CID have non-standard keys in the subscription map, you can use the parameters
esl_key to give the key name:
The default behavior of send() is to use the Sky event protocol in asynchronous mode. To force synchronous event processing, add the attribute
_async with value 0 to the attributes.
Results are only available for synchronous mode events. In general, you shouldn't be relying on results from sending an event. Rather, the recommended pattern is to have the receiving event network communicate by sending an event to the original sender. However, it is often useful to know whether or not the
send() succeeded. To support this, the system will raise a
system:send_complete event when all threads have completed. The event has a single attribute called
send_results that contains an array of the results of the individual sends. Each member of the array has the following structure:
You can use a rule like the following listen for the system event and loop over the results:
Obviously, you probably don't want to merely print the status out, but rather check it and do something if it is not 200.
A common pattern when sending events is to loop over the subscribers and then raise an explicit event when done. The on final guard condition is used to ensure the explicit event is only raised once.
The difference between raising an explicit event
on final and using the system generated
system:send_complete event shown above might not be obvious.
The primary difference is that the explicit event does have access to result information, including status. But, both the explicit event shown in the preceding code and the
system:send_complete event will cause any rules that are selected based on the respective events to be scheduled. Similarly neither will cause rules to be run before
send() is complete since parallel
send() actions must all complete before the rule they are in can complete.
The blog post Federating Personal Clouds shows an example using | <urn:uuid:ee88fbd6-a27d-4b7c-8914-e76a70525620> | 2.828125 | 885 | Documentation | Software Dev. | 40.535283 |
You can use the Refactoring feature to create variables and fields. This feature allows you to create and declare variables and fields while coding without planning ahead. This topic includes information about:
You can create a variable when you have an undeclared identifier that exists within a procedure block scope. This feature gives you the capability to select an undeclared identifier and create a new variable declaration with a simple menu selection or keyboard shortcut. When you invoke the Declare Variable dialog, the dialog contains a suggested name for the variable, based on the selection itself. If you choose to name the variable something else, the operation succeeds in creating the variable, however, the undeclared identifier symbol (Error Insight underlining) remains.
Variable names must conform to the language rules for an identifier. In Delphi, the variable name:
The refactoring engine attempts to suggest a type for the variable that it is to create. The engine evaluates binary operations of the selected statement and uses the type of the sum of the child operands as the type for the new variable. For example, consider the following statement:
myVar := x + 1;
The refactoring engine automatically assumes the new variable myVar should be set to type Integer, provided x is an Integer.
Often, the refactoring engine can infer the type by evaluating a statement. For instance, the statement If foo Then... implies that foo is a Boolean. In the example If (foo = 5) Then... the expression result is a Boolean. Nonetheless, the expression is a comparison of an ordinal (5) and an unknown type (foo). The binary operation indicates that foo must be an ordinal.
You can declare a field when you have an undeclared identifier that exists within a class scope. Like the Declare Variable feature, you can refactor a field you create in code and the refactoring engine will create the field declaration for you in the correct location. To perform this operation successfully, the field must exist within the scope of its parent class. This can be accomplished either by coding the field within the class itself, or by prefixing the field name with the object name, which provides the context for the field.
The rules for declaring a field are the same as those for declaring a variable:
The following examples show what will happen when declaring variables and fields using the refactoring feature.
Consider the following code:
TFoo = class private procedure Foo1; end; ... implementation procedure TFoo.Foo1; begin FTestString := 'test'; // refactor TestString, assign field end;
Assume you apply a Declare Field refactoring. This would be the result:
TFoo = class private FTestString: string; procedure Foo1; end;
If you apply a Declare Variable refactoring instead, the result is:
procedure TFoo.Foo1; var // added by refactor TestString: string; // added by refactor begin TestString := 'test'; // added by refactor TestString := 'whatever'; end;
Copyright(C) 2008 CodeGear(TM). All Rights Reserved.
What do you think about this topic? Send feedback! | <urn:uuid:28fabace-4568-4fa0-93d7-8d8d052aad78> | 3.03125 | 661 | Documentation | Software Dev. | 39.773241 |
While it is true that modern multi-stage nuclear weapons utilize tritium as a D-T fusion fuel, it is only half true that we are limited to one half-life cycle and untrue that you can only 'make' tritium in Fast Breeder Reactors.
The United States has a large stock of decommissioned nuclear weapons. These have been removed from service both due to age and to the requirements of past arms control accords. The tritium (it is a gas, being an isotope of hydrogen, at room and operating temperature) from these weapons has been reclaimed. Although the amount of usable tritium in the resultant store does drop by arund 5.5% per year, that still leaves a sizable amount which can be used for the remaining weapons in commission, enough to take us through probably at least another few years of weapons maintenance.
Finally, the U.S. Department of Energy, in association with the Tennessee Valley Authority, the operators of the Watts Bar reactor near Spring City, Tennessee, has designed, tested and implemented a new method of tritium production. Normal operation of the Watts Bar reactor, which is a commercial Pressurized Light Water Reactor, involves the placement of 'burnable absorber rods' inside the reactor vessel. These rods, containing boron carbide, serve to absorb some of the neutron flux from the normal reactor operation before it reaches the shielding of the containment vessel, and to regulate the 'rate' of the nuclear reaction inside. Special versions of these rods, called 'burnable absorber rods', are laced with lithium-6 aluminate. When this material is struck by neutrons, it produces tritium. Zirconium placed inside the rods along with the lithium aluminate captures the resulting tritium in a chemical reaction and sequesters it. When the rods are removed during the course of the normal 18-month fueling cycle of the reactor, the tritium-producing burnable absorber rods (TPBARs, in govspeak) are removed and sent to a DOE faciilty, where the zirconium is processed to recover the bonded tritium. In 2003, both the Watts Bar and Sequoyah reactors were certified and began planning to include TPBARs in their next cycle.
Dates and facility names from: http://www.tva.gov/news/tritium.htm | <urn:uuid:e5f9e9ec-52e6-47e1-a0fb-f07c687129b2> | 3.0625 | 496 | Knowledge Article | Science & Tech. | 43.61694 |
Chapter 5: Natural selection
"Nothing in biology makes sense except in light of evolution" - Theodosius Dobzhansky (1973)
Understanding natural selection is crucial to understanding wildlife ecology and practically any other topic in biology. This chapter gives you the basic concepts of natural selection so that you will be able to apply this important principle throughout this course, as well as in your day-to-day life.
WHAT IS NATURAL SELECTION?
Natural selection is the process by which the organisms in a population that are best adapted to the environment increase in frequency relative to less well-adapted forms, over a number of generations. The consequence of natural selection is that through time species (generally) develop characteristics that make them increasingly well-adapted to their environments, ultimately resulting in a world filled with a fascinating diversity of life forms. Natural selection is a simple but immensely powerful concept, and is a pillar of our understanding of biology at all organizational scales. This process commonly is summed up as "the survival of the fittest" in popular culture, although this simplification leaves out some of the important subtleties of natural selection, as described below.
WHAT ARE THE CONDITIONS NECESSARY FOR NATURAL SELECTION TO OCCUR?
Four general conditions necessary for natural selection to occur are:
A. More organisms are born than can survive.
B. Organisms vary in their characteristics, even within a species.
C. Variation is inherited.
D. Differences in reproduction and survival are due to variation among organisms.
If all four of these conditions occur, which they commonly do in both natural and human-influenced ecological systems, then natural selection will occur. If any of these is not true, then natural selection cannot occur. Let's consider each of these in a bit more detail.
A. MORE ORGANISMS ARE BORN THAN CAN SURVIVE
If every individual organism born were to survive and reproduce to its maximum ability, we would expect explosive exponential growth in populations to occur regularly. The fact that this rarely happens (and never continues for long) indicates that there are many individuals born into the world with low probabilities of survival and reproduction. Let's illustrate this concept with rabbits and assume they have an average litter size of 10 offspring (5 males, 5 females) and a generation time of approximately 4 months. Starting with a single female rabbit, and keeping track of just female organisms for the sake of simplicity, we will have 5 new female rabbits in 4 months. In four more months those new female rabbits will be reproducing, and we will have approximately 5×5=25 new female offspring. Those 25 rabbits will in turn produce 25×5=625 offspring in 4 months, and the process will continue so that after 10 generations, a mere 40 months, the number of new female rabbits born would be 50 billion! There is of course not enough space or food for this many rabbits in the real world and in a natural ecosystem forces such as competition, disease, predators, and harsh abiotic (physical) conditions prevent such exponential growth from occurring for long. Competition, disease, predation, and abiotic conditions are among the most important limiting factors in ecological systems, and they quite often shape the path of natural selection.
B. ORGANISMS VARY, EVEN WITHIN A SPECIES
Variation among individual organisms of the same species has been well documented, and you can illustrate this to yourself by thinking of the range of differences in physical appearance and aptitudes that exists among people you know. Of course, variation among individuals occurs in other species as well and this variation fuels the process of natural selection because it gives natural selection something to "act on." That is, if a faster gazelle were better able to elude the claws of a cheetah, then this gazelle would be more likely to survive. If all of the organisms within a population were completely identical, it would not be possible for natural selection to occur; if all gazelles ran the same speed, then there would be no "faster" individuals to avoid the clutches of predators. There are biomechanical limits, of course, to just how fast a gazelle can run and eventually all healthy adult gazelles will be able to run at the same maximum speed. However, natural selection also acts on other factors, such as the ability to dodge back and forth or to detect the predator from further away. Meanwhile, natural selection also favors cheetahs that can overcome the speed and agility of gazelles. When you start to realize that each species varies in hundreds of different ways and has to constantly adapt to changing conditions (including behavior of its predators or of its prey), you begin to understand how the complex and often bizarre life on this planet has developed through time.
C. VARIATION IS INHERITED
In general the causes behind variation in organisms can be divided into two categories, environmental and heritable. Environmental variation is that which has no genetic basis, but is the result of the conditions under which an individual lives. For example, our generation tends to have a diet higher in protein than that of our grandparents and in general we grow taller than our grandparents did. This is due to the food we consume, not to any underlying genetic superiority. If you prefer a more "natural" example, imagine predators existing in sites rich vs. poor in prey species. If a predator is raised in a site rich in prey, it likely will eat more and grow larger. On the other hand, if raised in a place where prey are limiting, they would be more likely to remain smaller when fully mature, simply because they could not acquire sufficient food. Only when variation among organisms is inherited from the previous generation, i.e. it has a genetic basis, will natural selection be able to occur. Natural selection cannot act on variation that is due purely to environmental conditions. In reality, variation among organisms often is the result of a combination of environmental and heritable causes, as illustrated by the variation in height among humans. People may be short because they have short parents who possess genes for short stature that they have passed down to their offspring. However, people may also be short if they did not receive proper nutrition when they were in their growing years, even if they do possess genes for a tall stature. The first cause for shortness is heritable, whereas the second is environmental, but natural selection would only be able to act on height to the degree that it is in fact heritable.
D. DIFFERENCES IN REPRODUCTION AND SURVIVAL ARE DUE TO VARIATION AMONG ORGANISMS
It is widely observed that the probability of survival and reproduction often varies tremendously among organisms. Furthermore, differences in the traits of organisms will often be the cause of their differences in survival and reproduction. It is readily apparent that the organisms with the highest rates of survival and reproduction will be those that have their genes best represented in the next generation, and hence natural selection occurs whenever variation in survival and reproduction is at least partially caused by a heritable trait that varies among organisms.
Let's look at the example of tule perch to demonstrate this. Tule perch are small (4-6 inch long) fish that occur only in the fresh waters of Central California. Each female tule perch gives birth to 15-40 young, which are essentially miniature adults (which swim away after being born). It turns out that the number and size of young produced by a female is an inherited trait and is an adaptation to the environment in which the perch live. Thus female tule perch that live in the Russian River produce 25-35 small young and typically become pregnant in their first year of life. In contrast, tule perch in Clear Lake typically produce 15-20 large young and wait until their second year to become pregnant. The reason for the striking difference in life histories of the two populations is the nature of the environments. The Russian River is a large, isolated coastal stream that fluctuates enormously in flow from year to year; in this harsh system each adult female has a relatively low probability of survival from year to year so natural selection has favored females that produce a lot of young quickly. Clear Lake, in contrast, is a relatively benign environment where each adult female has a fairly high probability of survival from year to year, provided they are large enough to escape predators. Thus natural selection favors females that produce large young and that devote all their energy in the first year to becoming even larger. If both forms were brought into laboratory aquaria and raised under identical conditions, the Russian River fish would still produce lots of small young and Clear Lake fish would still produce comparatively small numbers of large young.
Table of Contents
1. Roots of the modern environmental dilemma: A brief history of the relationship between humans and wildlife
2. A history of wildlife in North America
3. Climatic determinants of global patterns of biodiversity
5. Natural selection
6. Principles of ecology
7. Niche and habitat
8. Conservation biology
9. Conservation in the USA: legislative milestones
10. Alien invaders
11. Wildlife and Pollution
12. What you can do to save wildlife
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Help us continue to share the wonders of the ocean with the world, raise awareness of marine conservation issues and their solutions, and support marine conservation scientists and students involved in the marine life sciences. Join the MarineBio Conservation Society or make a donation today. We would like to sincerely thank all of our members, donors, and sponsors, we simply could not have achieved what we have without you and we look forward to doing even more. | <urn:uuid:50fb9d80-95f6-481d-979e-1b9b42d42ca0> | 4.25 | 2,004 | Knowledge Article | Science & Tech. | 35.632904 |
Advanced Nuclear Power Reactors
(Updated October 2011)
- The next two generations of nuclear reactors are currently being developed in several countries.
- The first (3rd generation) advanced reactors have been operating in Japan since 1996. Late 3rd generation designs are now being built.
- Newer advanced reactors have simpler designs which reduce capital cost. They are more fuel efficient and are inherently safer.
Several generations of reactors are commonly distinguished. Generation I reactors were developed in 1950-60s, and outside the UK none are still running today. Generation II reactors are typified by the present US and French fleets and most in operation elsewhere. Generation III (and 3+) are the Advanced Reactors discussed in this paper. The first are in operation in Japan and others are under construction or ready to be ordered. Generation IV designs are still on the drawing board and will not be operational before 2020 at the earliest.
About 85% of the world's nuclear electricity is generated by reactors derived from designs originally developed for naval use. These and other second-generation nuclear power units have been found to be safe and reliable, but they are being superseded by better designs.
Reactor suppliers in North America, Japan, Europe, Russia and elsewhere have a dozen new nuclear reactor designs at advanced stages of planning, while others are at a research and development stage. Fourth-generation reactors are at concept stage.
Third-generation reactors have: | <urn:uuid:4ecff0f5-3983-4316-bddd-48de140cf166> | 3.171875 | 289 | Knowledge Article | Science & Tech. | 31.34448 |
"Prospero was the first UK satellite to be launched on a UK launch vehicle; it would also be the last. Ministers had cancelled the rocket project in the run up to the flight. However, as the Black Arrow was ready, the programme team decided to go-ahead anyway. Prospero was blasted into orbit from the remote Woomera base in the Australian desert. It turns out, the satellite is still up there. Carrying a series of experiments to investigate the effects of the space environment, the satellite operated successfully until 1973 and was contacted annually until 1996. Now, a team led by PhD student Roger Duthie from University College London's Mullard Space Science Laboratory in Surrey is hoping to re-establish communications in time for the satellite's 40th anniversary. "First, we have to re-engineer the ground segment from knowledge lost, then test the communications to see if it's still alive," Duthie told the Space Boffins podcast." More at the BBC
According to Wikipedia "As of 2006, radio transmissions from Prospero could still be heard on 137.560 MHz, although it had officially been deactivated in 1996, when the UK's Defence Research Establishment decommissioned their satellite tracking station at Lasham, Hampshire. It is in a low Earth orbit, and is not expected to decay for about 100 years." | <urn:uuid:8ee09799-9b9d-46b9-b199-8ac2288b7416> | 3.046875 | 273 | Truncated | Science & Tech. | 45.570329 |