conditioning, but that depends on the efficiency of your air conditioning unit and the temperature of the outside air and all that. a reasonable estimate is that you ' ll have to buy a watt of air conditioning power for every three to five watts of power consumed in your beowulf. ahhh, physics. a wonderful thing. let me remind you one last time that if there is any chance at all that your air conditioning can shut down while your computers are still operating and they are not in a large room with plenty of circulation, you should think seriously about some sort of thermal kill switch. computer hardware breaks or even catches on fire if it gets hot enough, and i can tell you from bitter experience that the temperature in a smallish closed room ( in an otherwise cool building ) will go up to well over 100 farenheit in a remarkably short time if there is more than a kilowatt being released inside with no ventilation or air conditioning. the temperature inside the cases will be considerably higher, and the temperature of the cpu and memory chips and hard drives higher still. we ' re now done with the serious stuff. i ' ll wrap up this section by reminding you to think about other kinds of infrastructure that you might want to provide for your beowulf room if it is in some sort of organization ; fiber or copper lines to your organization lan switch or router, for example, or connections to printing facilities. a phone ( or two ) is often nice, possibly equipped with a modem and terminal or network server if you plan on managing remotely ( as in from someplace network - inaccessible ). finally, you may want to think about physically securing the location. you ' ve just built a pile of pc ' s that ( however cheap the nodes ) is worth thousands, possibly hundreds of thousands of dollars. it would be a shame if you came in after a weekend to discover that an entrepreneur with a pickup truck had disassembled and made off with a large chunk of them. i wish that i could say that this is very unlikely, but we ' ve had computers stolen ( including one high end beowulf node ) from just outside our beowulf room, which is itself located on a low - traffic hall inside a generally locked building with a carded lot. we ' re likely going to move our beowulf room to new digs on a no traffic corridor that you have to have a building map to find. so think about locks, traffic patterns, access both day and night, and don ' t make it too


likely going to move our beowulf room to new digs on a no traffic corridor that you have to have a building map to find. so think about locks, traffic patterns, access both day and night, and don ' t make it too easy for an ` ` entrepreneur ' ' to make off with your hard - earned nodes and support hardware. the answer, fortunately, is that it is not difficult at all to build, and once built and configured, it is extremely easy ( and cheap! ) to maintain. linux ( or at least some sort of unix ) expertise is obviously very useful, but most linux distributions fully support generic cluster computing ` ` out of the box ' '. the most difficult single things to master are how to implement a scalable installation mechanism for your cluster ( or lan ), and how to largely automate software maintenance for your cluster ( or lan ) so that you do work once, and it is automatically applied to all the nodes ( or workstations ) you manage. why do i keep putting down nodes ( or workstations )? hmmm, good question! i suppose the answer is that from one point of view a generic compute cluster can be thought of as a lan consisting of specialized workstations. in particular, workstations with no x or gui installed, that indeed might not even have video and a keyboard installed at all, that are missing sound and games and office tools and a whole lot of user applications, but that do have compilers and other development tools, a wide range of application and development libraries, specialized libraries and toolsets for supporting e. g. pvm or mpi computations, and perhaps some specialized node monitoring daemons or batch job management tools installed. nearly all of this could equally be installed on a workstation, and if you run cluster nodes in your workstation lan, you are very likely ( and wise ) to go ahead and install all the cluster tools but perhaps the batch schedulers on your workstations as well, so that the only difference between a workstation and a cluster node is that most ` ` desktop user ' ' interactive / user interface components are missing on the latter. note that this is not the strategy adopted by the ` ` true beowulf ' ' package builders11. 10, who install custom kernels and tools to make cluster nodes look like ` ` cpus ' ' in a big multiprocessor system with a unified pid space and transparent job distribution and management. in this latter approach, nodes are not works


, who install custom kernels and tools to make cluster nodes look like ` ` cpus ' ' in a big multiprocessor system with a unified pid space and transparent job distribution and management. in this latter approach, nodes are not workstations, and you can ' t ` ` log into a node ' ' any more than one can ` ` log into a cpu ' ' on a mp system. this suggests that it is time for a pretty fundamental split in the discussion. all those who want to build a beowulfish cluster on top of their existing lan, integrated with and possibly even transparently including their desktop workstations, creating nodes that are basically specialized, particularly simple workstations ( that one can log into to run jobs or do whatever you like, just as one could a workstation ) please move one full pace to the left. unless, of course, you happen to be sitting down, or moving to the left would cause you to fall off of a tall building and die, can ' t have that. all the rest of you, who want none of this ` ` workstation cluster ' ' crap and want to build a beowulf, pure and simple, similarly step to the right, if only metaphorically. wishy washy ones can stay where they are and read both of the following sections to figure out which one they might be, or might become, and how.


download cbse physics solved board question papers 2008, 2009, 2010 & 2011 – all versions ( delhi, outside delhi & foreign ) the question papers are in pdf format, all question papers with solution in a single file. so, it may take some time for the download to finish. categories : cbse physics, downloads, model question papers, physics links, question bank, sample papers, solved problems tags : central board of secondary education, delhi, education, equations of motion, kendriya vidyalaya, ohm ' s law, physics, tests is all physics which we had studied in class 11 and 12 are correct or …? i would like to quote just one thing, “ science tells the first word of everything and the last word of nothing ” what we learnt yesterday might have changed today and may change in future. we have to adapt ourselves to the new findings, discoveries and inventions. further, what we learn in class xi and xii is up to that level and we when we go to higher levels, we learn things more deeply and many things will be dealt differently. a rock is thrown vertically upward from the ground with an initial speed 15m / s. a. how high does it go b. how much time is required for the rock to reach its maximum height? c. what is the rock ’ s height at t = 2. 00s? ( posted by merhawi ) v = 0 m / s ( at the max height ) ( b ) from the above case ( c ) use s = ut + 1 / 2 at2 put t = 2s, u = 15m / s, a = - 10m / s2 s = 30 – 20 = 10 m ( if you use g = 9. 8 m / s2 the answers will be slightly different ) q. a weather balloon is floating at a constant height above earth when it releases a pack of instruments. a. if the pack hits the ground with a velocity of - 73. 5 m / s, how far did the pack fall? b. how long did it take for the pack to fall? v = - 73. 5 m / s ( - since downwards ) a = - g = - 9. 8 m / s 2 from the equation of motion v = u + at - 73. 5 = - 9. 8 x t from the equation of motion s = ut + 1 / 2 a t2 u = 0 m / s s = 0. 5 x ( - 9. 8 ) x 7. 5 x 7


diamond anvil cells can apply millions of atmospheres of pressure to a solid or liquid, while allowing it to be observed through the diamond “ windows. ” for the first time, researchers have introduced optical tweezers into one of these cells in order to trap sample particles. the experiment, described in physical review letters, directly measured the viscosity of the water surrounding the particles. further development of this technique could permit investigations of the mechanical changes in biological cells and other soft materials placed under high pressure. a diamond anvil cell ( dac ) is a sealed volume sandwiched between the flat, millimeter - wide tips of two diamonds. when squeezed, the pressure in the cell can reach levels found in the core of the earth. diamonds are not only strong enough to handle these pressures, but they are also transparent to optical and x - ray probes. however, studying certain mechanical properties requires the controlled application of localized forces, which has been difficult to realize in a dac. for their force “ handle, ” richard bowman of the university of glasgow, in the uk, and his colleagues chose optical tweezers, which are highly focused lasers that trap particles. to overcome the spatial constraints of a dac, the team used part of their laser to create a second beam that reflected back on the cell. the combined beams trapped micron - sized silica beads suspended in a water sample. because the optical forces were known, the random vibrations of trapped beads provided a direct measure of the water viscosity. the team recorded a threefold increase in viscosity for a pressure rise of atmospheres — a result that agrees well with previous measurements and builds confidence in the new technique. – michael schirber


quantum system can emit only photons with energy equal ( within the uncertainty ) to the difference between two energy states. even if the atom is in a superposition of energy states \ left | \ psi \ right > = c _ 0 \ left | 0 \ right > + c _ 1 \ left | 1 \ right > + c _ 2 \ left | 2 \ right > + \ ldots \ qquad ( 1 ) with average energy somewhere between the levels, it can emit only certain set of photons : $ e _ 1 - e _ 0 $, $ e _ 2 - e _ 0 $, $ e _ 2 - e _ 1 $ etc. emission of a photon is an act of measurement since the energy of the emitted particle contains information about the atom. if the energy of the photon is $ e _ 2 - e _ 1 $ then the energy of the electron in the atom is $ e _ 1 $ - the energy of the final state of the transition. the next photon emitted by this atom will have energy equal to $ e _ 1 - e _ 0 $ for sure. if one observe photons emitted by an ensemble of atoms in state ( 1 ) he will see $ e _ 1 - e _ 0 $ photons with probability $ \ left | c _ 1 \ right | ^ 2 $, any of $ e _ 2 - e _ 0 $ and $ e _ 2 - e _ 1 $ with probability $ \ left | c _ 2 \ right | ^ 2 $ and so on. the total energy emitted by the system while it is coming to ground state is equal to average energy of state ( 1 ) multiplied by the number of atoms in the ensemble. energy conservation is not violated. the same is true for mixed states for which the probability of certain photon is determined by the density matrix of the system.


what is a story walk? it ’ s an exciting initiative that combines a children ’ s story with a walking route while connecting families with their library and community. a way to inspire parents, teachers, and caregivers to take young children on a short stroll that is fun for all. we have these story walks that you can borrow : ayres, katherine – up down and around brown, margaret wise – big red barn bruchac, joseph – many nations cauley, lorinda bryan – clap your hands buehner, caralyn – snowmen at night crews, donald – ten black dots dodd, emma – what pet to get dorros, arthur – animal tracks ehlert, lois – growing vegetable soup ( english / espanol ) katz, karen – the colors of us martin, bill – chicka chicka boom boom marzollo, jean – how kids grow mcgrath, barbara barbieri — the baseball counting book moore, clement c. – the night before christmas penn, audrey – the kissing hand raschka, chris – charlie parker played be bop sendak, maurice – where the wild things are senisi, ellen b. – kindergarten kids shannon, david – duck on a bike silverstein, shel — the giving tree tillman, nancy – wherever you are my love will find you winthrop, elizabeth – shoes ( 2 copies ) behrens, janice – let ’ s vote on it! brett, jan – the mitten each story walk portfolio contains : - laminated posters ( number varies with length of book ) and “ story walk start ” + “ the end ” - inventory page - what is a story walk™ - about wee read - samples of flyers for times we have used this - guidelines for making / using this story walk™ - guide sheet for the story to be used / given as you see fit - survey for families - sample of child sign in sheet — we made them to match each story. these were given to children at the start of the walk and collected at the end where children could choose a free book. we use them to know how many children and what ages read the story. please feel free to add your own flyers, survey results, summary of the event, etc. while pages of the book may not be altered in any way ; flyers, surveys, guides, and vism sheet may be reproduced. the first story walk™ project was created by anne ferguson of montpelier, vermont and developed in collaboration with the vermont bicycle & pedestrian coalition and the kellogg


please update your flash player to view content. since the late 1800s, artificial methods to increase the fish population in california have been employed in order to fill a void between nature ’ s ability to produce fish and anglers ’ demands for them. to keep up with the demand, the california state legislature passed “ an act to provide for the restoration and preservation of fish in the waters of this state ” april 2, 1870. under this act, the three newly appointed commissioners of fisheries were given the duty to establish “ fish breederies ” and stock streams, lakes and bays with both foreign and domestic fish. for areas such as lake almanor, having a healthy fish population is key to a thriving community. the beautiful 28, 257 - acre reservoir is home to a variety of fish, which help attract anglers from all over. this manmade lake has reaped the benefits of the restoration act through the almanor fishing association ’ s cage - rearing project. for the last 25 years, fish have been artificially planted and reared in the waters, making up more than half of lake almanor ’ s fish population. “ the whole community relies on the quality of fishing here. lake almanor is the key and we want to keep it as healthy as possible, ” said rich dangler, afa board president. cage rearing history community members rhonda dakota, ruben chavez and jim pleau started the lake almanor fish pen project in 1979 with the assistance of the california department of fish and game. in the beginning, only two netted squares framed in 2 - by - 4 - inch lumber were used to rear the fish. after a couple successful years, dfg donated four aluminum cages to the program. not long after, lake oroville ’ s cage rearing program ended and their cages were sent to lake almanor. by 1982, the program had 10 cages, which helped expand the fish rearing efforts. today, it is the largest and most successful cage program in california. eventually, the dfg ran out of money to feed the fish and instead of canceling the project, afa took over. every year, for more than 18 years, dfg has supported the cage - rearing project by donating 50, 000 rainbow trout fingerlings for planting. when the fish arrive on the dfg truck, they are hosed into a large cage in groups of 5, 000. the cage is then secured to a pontoon boat that has a special crank built just for use in this project.


. when the fish arrive on the dfg truck, they are hosed into a large cage in groups of 5, 000. the cage is then secured to a pontoon boat that has a special crank built just for use in this project. volunteers navigate the loaded pontoon to the hamilton branch side of lake almanor and then manually net the fish into 10 separate cages, with 5, 000 in each cage. the fingerlings are planted when they are about 4 to 6 inches in size and by the time they are released, they have grown to 10 to 14 inches. throughout the winter, normally between november and april, volunteers feed the fish on a day - to - day basis, counting and removing any that didn ’ t survive through the night. over the years, native bird life and previously reared and released fish have adapted to the feeding schedule and will often be seen hanging around the cages, waiting for their next meal. kokanee power donates 15, 000 pounds of fish food to last through the winter. according to dangler, if they run out of food, the fish are released early. if any food is left over, it is donated to the chester high school hatchery. usually, the fish remain in the cages until late april or early may. throughout the years, more than 1 million fish have been reared in the hamilton branch cages. aside from afa ’ s fish - rearing program, dfg plants fish throughout plumas county at different times throughout the year. a monthly fish - planting schedule can be found by visiting nrm. dfg. ca. gov / fishplants. the dfg currently stocks approximately 1, 000 bodies of water within california and operates 21 public hatcheries. continuing its successful cage - rearing project for another year, afa members and volunteers worked together to transfer 50, 000 fingerlings to the hamilton branch cages nov. 6 and 7. “ this year ’ s fingerlings were rather large and should be 10 – 12 inches by the time they are released in late may, ” reported afa ’ s website. starting this year, dfg is requiring a mixture of both diploids ( fertile fish ) and triploids ( sterile fish ) be planted in the lake. up until now, all fish delivered have been eagle lake diploids ; however, with the new requirement in place, both types of fish were planted. eagle lake diploids dominated the mixture with 30, 000 delivered, while only 20, 000 shasta triploids


fish delivered have been eagle lake diploids ; however, with the new requirement in place, both types of fish were planted. eagle lake diploids dominated the mixture with 30, 000 delivered, while only 20, 000 shasta triploids were delivered. “ we are researching how well the triploids will survive in the cages, ” said dangler. “ they are more susceptible to stress, which means we will have to work a lot harder to rear them. ” this year is also the first year the newly restored cages will be used. for the last three years, the 10 cages have been undergoing restoration after being in the water for nearly 25 years. the restoration cost $ 37, 000, which was donated by california inland fisheries foundation inc., kokanee power, plumas county fish and game commission and afa. the future of afa as the economy plummets, fewer and fewer people are able to contribute to memberships in groups such as almanor fishing association. over the last year, membership has declined by almost one - quarter. although much of the cost associated with the cage - rearing project is covered by generous donations, if membership continues to fall, the association may have to close its doors. according to dangler, if this were to happen, it is likely the cage program would also be forced to shut down. with the majority of lake almanor ’ s fish being reared through afa ’ s project, the fish population could be faced with a decline in numbers, and anglers would be diverted out of the area. volunteers to help feed the fish have also seen a decline ; there are several feeding slots available for this year ’ s batch of fingerlings. to volunteer for a feeding slot call 259 - 5899. afa membership is not limited to the almanor area, and many of its members live throughout plumas county. membership levels start as low as $ 25. to become a member visit almanorfishingassociation. com. 15th annual century rides scheduled for june 22 little league nears regional tourneys greenville ’ s catcher, brent washoe, is a second too late as chester ’ s jason schlueter slides into home plate for a run during a chester home game in late may.... read more... fishing report for the week of 6 / 13 / 2013 hunter hedman displays a beautiful brown trout he caught at bucks lake. it took him only five minutes of fishing to hook the biggest fish of his life, he said.


the story of the minotaur mazes are very ancient and appear many times in history. according to ancient legend, daedalus constructed the so called " cretan labyrinth " in knossos, to house the legendary minotaur. the minotaur was a fearsome creature, half man and half bull killed by theseus in the famous legend in which he escapes using a ball of string provided by ariadne. although we don ' t have direct evidence in the form of buried walls for the shape of the cretan labyrinth, there is a traditional idea about its shape, and a very nice geometrical construction for drawing one. this gives us our first link between mathematics and mazes. you can draw this on paper, or if you are on a beach it looks very good drawn into the sand with the help of a stick. to draw a traditional cretan labyrinth, start with the cross and dots on the right. the picture below shows you how to complete the cretan labyrinth. notice that the when you connect the lines you alternate left and right round the square. now you can complete the picture. building the cretan labyrinth here is a java applet showing how to complete the cretan labyrinth. notice how you connect the lines. try following the route from the entrance to the centre. this path is surprisingly long and in a full size labyrinth it would have taken some time to get to the centre. however, there is a further surprise in store. although the path to the centre is very long there is only one way in and one way out! theseus had to make no difficult decisions at all on his way to kill the minotaur. indeed, it was easy with this design to get to the centre and just as easy to get out again. in short there was no need for threads, ariadne, broken hearts, suicide or any of the other features of the story. exactly the same geometric pattern as the cretan labyrinth appears in many different cultures and it is quite a common artistic image. examples of similar mazes have been found scratched into caves in cornwall ( possibly by visiting phonecian sea farers or by visiting mathematicians in a moment of boredom ), on roman coins and in pictures drawn by native american indians. the pattern is of interest to mathematicians because it packs a very long path into a small space. using other seeds an alternative seed using different seeds ( or starting shapes ) when drawing the maze leads to different labyrinths. an important feature of the creta


the pattern is of interest to mathematicians because it packs a very long path into a small space. using other seeds an alternative seed using different seeds ( or starting shapes ) when drawing the maze leads to different labyrinths. an important feature of the cretan labyrinth is that there is only one entrance and only one route toward the centre. we can ask the ( mathematical ) question of whether all seeds lead to labyrinths with one entrance and route. although the cretan maze is the most common, and probably the oldest, there are lots of others that we can draw. let ' s try a different seed such as the one above on the right. the alternative labyrinth to draw the complete picture remember to alternate drawing the lines from left to right. the resulting maze in this case is shown on the left. the rise of the maze the term " labyrinth " is now generally means a construction that leads you from a starting point to a goal by taking you on a tortuous path, but requires no actual decisions. your whole path is predetermined by the builder of the labyrinth. sacred sites were sometimes constructed as labyrinths by people who believed in the action of fate giving you an ultimate destiny which was entirely beyond control. however, following the christianisation of the roman empire, and the belief in the action of free will, a different form of construction came into being. this was the maze. in a maze intrepid travellers had to make a series of decisions, and their ultimate fates ( in particular whether they reached the centre ) relied upon the results of those decisions. mazes were often built into the floors of churches and you were supposed to pray as you found your way towards the centre. the idea of the puzzle maze was developed during the middle ages and later into the celebrated hedge maze, often found in the grounds of stately homes. the modern use of the hedge maze is now purely recreational. the puzzle is usually to find your way to the centre ( and out again ) starting from the entrance. many mazes around the world are open to the public and make a great day out. examples include the jubilee maze centre at symonds yat ( which has a fine museum of mazes at its centre ), and the maze at longleat, which has bridges and changes its pathways during the day. if you get lost in this maze then clues are available. perhaps the most famous public maze in england is the hedge maze at hampton court near london, which was constructed in 1690 ad and is still open to the public


changes its pathways during the day. if you get lost in this maze then clues are available. perhaps the most famous public maze in england is the hedge maze at hampton court near london, which was constructed in 1690 ad and is still open to the public. if you get the chance, visit the maze at hampton court and indeed hampton court itself. we hope that you are convinced that mazes are both fun and important. now let ' s think how, as mathematicians, we could try to solve the puzzle of how to get to the centre of a maze ( and out again ) quickly and reliably. mazes and networks next we will explain the link between mazes and networks. in fact we will transform a maze into a network. the result will look very different but the transformation will help us solve the problem of getting to the centre of a maze and then back out again. by doing this we will employ a very useful technique in mathematics : transform a hard problem into a simpler one which we can solve more easily. how to walk round mazes and networks the point we are trying to reach in a maze is called the centre of the maze. some mazes can be solved by putting one hand on the hedge and following it round. unfortunately this doesn ' t always work. in this section we will show how to transform a maze into a network and give a method for walking round networks which is guaranteed to find the centre. if we ' ve transformed a maze into a network this then solves our problem of finding the way to the centre of the maze. we have chosen the point " m " in our maze. this is where network topology comes in and we will use these ideas to simplify the maze to its essential components. a sample maze when you go round a maze it doesn ' t matter how much you twist and turn, all that does matter are points where you have to make decisions. in a cretan labyrinth you don ' t have to decide anything at all, as once you enter the labyrinth you simply keep walking until you reach the centre. the centre point, the place we are trying to get to, is labeled m. we ' ve put a decision point at the start as you can always decide not to enter the maze. to simplify the maze we draw a network. in this network we write down all of the decision points as points on a piece of paper. we now draw paths from each of these points to the others, but only if you can go from one to another in the maze without having


a network. in this network we write down all of the decision points as points on a piece of paper. we now draw paths from each of these points to the others, but only if you can go from one to another in the maze without having to make a decision in between. this gives you a network. here is the maze with all the decision points marked. a sample maze - with decision points here is the completed network for the maze : a sample maze - as a network in contrast, here is the network of the cretan labyrinth. the only decision points are at the beginning and the end : the cretan labyrinth - as a network using the network it is much easier to see how to solve the maze. indeed, we can label the solution just in terms of the decision points that you go through. for the cretan labyrinth this gives a - > b. for the more complicated maze one route to the centre is a - > b - > d - > k - > i - > m. you should be able to find many more routes to the centre using this diagram. how many do you think there are? the trick of reducing the maze to its bare essentials by finding a diagram which contains all of the information in the maze, is widely used in mathematics. a good example of this is the map of an underground railway system or metro. often these maps only show the railway lines, stations and interconnections. distances between stations on the ground do not always correspond to distances on a map. but do travellers on the train care? perhaps not, as they often only need to know how to get between stations. in fact, stripping away the unnecessary information might actually help then navigate successfully. when we think in terms of networks, the problem of solving a maze becomes the following : can you find a route in the network which takes you from the beginning to the centre and then back again? it is worth saying that there are really two different problems here. one is to find the route when you don ' t have a map of the maze to hand. this is the case in most recreational mazes. the second is to find the route when you do have a map. this case would arise if you were ( for example ) trying to find your way around a road network or a telephone exchange ( or indeed the underground ). we will consider the case when we don ' t have a map available. in a network the decision points are called nodes and the lines connecting nodes are called edges or paths.


around a road network or a telephone exchange ( or indeed the underground ). we will consider the case when we don ' t have a map available. in a network the decision points are called nodes and the lines connecting nodes are called edges or paths. given a map of a network, the spaces left between the edges and the space outside are called the faces. if an odd number of paths meet at a node then it is called an odd node and if an even number of paths meet then it is called an even node. a dead end ( such as the decision point at c ) is an odd node as only one path leads into it. the parts of a network networks were first studied by the great swiss mathematician leonard euler. euler was one of the most productive mathematicians who ever lived and he created a lot of modern mathematics. in 1736 euler became interested in networks through trying to solve the problem of the bridges of konigsberg. konigsberg, now called kaliningrad, is a town in russia on the baltic sea which has the river pregel running through it with the island of kneiphof in the middle of the river. the mainland and the island were connected by bridges in the arrangement shown below : the bridges of konigsberg the citizens of konigsberg had noticed that there seemed to be no way of going for a walk in which each bridge was crossed once and once only, but wondered whether they were being stupid and that there might be a route if only they looked hard enough. euler took up this challenge and started by reducing the problem to a network. in this network, the nodes were the four land masses a, b, c, d and the edges were the bridges. here is the resulting network : the network of the bridges of konigsberg the problem of the bridges of konigsberg can now be stated as follows : can you start from any node and construct a route around the network which will bring you back to the node and go down each path once and only once? it is possible to ask this question for any network, not just for the one above and euler came up with a brilliant solution to the general problem. here it is : - if you have any network which has only even nodes then you can start at any node and find a route which returns you to that node which goes down each path once and once only. - if the network has exactly two odd nodes then you can construct a route which starts at one odd node and ends up at the other and goes through


and find a route which returns you to that node which goes down each path once and once only. - if the network has exactly two odd nodes then you can construct a route which starts at one odd node and ends up at the other and goes through every path once and once only. - if the network has more than two odd nodes then there is no route that goes through every path once and once only. it is worth pointing out that no network can have only one ( or indeed any odd number ) of odd nodes. the network for the bridges of konigsberg has four odd nodes so no route is possible which crosses over every bridge once and once only. to make this possible the simplest solution is to demolish the bridge between a and c, then at least you can walk from b to d going over each bridge once and only once ( although you can ' t do this if you want to start and finish in the same place ). this is a neat solution mathematically, not a great idea if you happen to live in konigsberg. we seem to have come a long way from solving a maze, but in fact we have nearly finished. the proof of euler ' s theorem actually gives us a way of solving the maze. what we do is use the methods described in the proof to construct a route into the centre of the maze and back out again which goes down each path at most twice. to start we first take the network for the maze. now, these networks have a collection of odd and even nodes and this makes it awkward to use any of the results of the above theorem. our first step is to convert the maze into one with only even nodes. this we do by the simple process of drawing each path between two nodes twice. what this means on the ground is that in following our way around the maze we are allowed to take each path twice but no more. think about this - this is very necessary. if we could only go down each path once then there would be no way out of a dead end! for our example maze this gives the following network : the network of our maze doubling up the number of paths in the network corresponding to our maze has converted it into a network with only even nodes. euler ' s first result states that in such a network we can construct a path from any node which will return us to that node and which goes down each path once and once only. now, suppose that we start at the entrance to the maze at point a and find this route. as it goes


network we can construct a path from any node which will return us to that node and which goes down each path once and once only. now, suppose that we start at the entrance to the maze at point a and find this route. as it goes down every path, sooner or later it will go down a path which leads to the centre of the maze. this is a splendid start. now continuing along our route we will eventually get back to the start of the maze again. it looks as though we have found a foolproof way of cracking the maze. what is the catch? well there isn ' t one really, except that the route we construct may not be optimal ( ie. it may be much longer than the shortest route into the centre and back ). this makes the method inefficient for solving problems concerned with traffic flow ( for which there are much better methods around ) but it doesn ' t matter too much for the networks corresponding to mazes. as we have not given the proof of euler ' s theorem, we can ' t immediately jump to the solution. fortunately this has already been done for us and we will describe the method of m. tremaux, which is described in the book ` ` mathematical recreations and essays ' ' by rouse ball. what is nice about the method we are going to describe is that you don ' t need to use a map of the maze, but you do need to use a packet of peanuts and a bag of crisps. how to solve a maze using a packet of peanuts and a bag of crisps you enter the maze, which we will assume has high hedges which you can ' t see over, and that all paths and nodes ( where you make decisions ) look very much the same. the peanuts and crisps are used as markers in the maze. trail the peanuts ( here and there ) as you go and leave a peanut at all decision points. this will tell you whether you have been to a decision point before or whether you have gone down a path before ( without being too ecologically unfriendly ). if you go down a path a second time, then trail a path of crisps. if you have a rule that you never go down a path with crisps this will stop you going down that path again. if you reach a decision point which does not have a peanut there we call this a new node. leave a peanut there, it now becomes an old node. similarly, a path without peanuts or a path in which you are


down that path again. if you reach a decision point which does not have a peanut there we call this a new node. leave a peanut there, it now becomes an old node. similarly, a path without peanuts or a path in which you are currently on and dropping peanuts for the first time is a new path. a path with peanuts already on it and on which you are now dropping crisps is called an old path. here is now how to solve any maze. - start at the entrance and take any path. - if at any point you come to a new node then take any new path. - if you come to an old node, or the end of a blind alley, and you are on a new path then turn back along this path. - if you come to an old node and you are on an old path then take a new path ( if such exists ) or an old path otherwise. - never go down a path more than twice. if you follow this procedure then you will eventually reach the centre and then get back out again. this of course only happens if no one eats the peanuts, and here we have to hope for the best! try it out on the examples in the exercises, for which a pencil mark will substitute for the peanuts. for an example, on the network of our maze the method gives as one possible route, the route : interestingly enough, if you read the account of harris ' adventures in the hampton court maze from the book three men in a boat, you will find that he also used a marker. instead of a peanut, they used a baby ' s bun which showed them when they had come back to the same point. unfortunately as there was only one bun available it didn ' t help much with solving the maze itself and left the baby hungry. try this method out and see if you can discover why and how it works. we have seen how to transform a maze into a network. as we mentioned before, you can think of an underground rail system as a network of connected stations. the internet is a network of computers. in fact, there are many other examples of real systems that we can think of as networks. the amazing thing about mathematics is its power to connect them all! more information on mazes, networks and many other areas of mathematics can be found in our forthcoming book, mathematics galore!, masterclasses, discovery workshops, and team projects in mathematics and its applications by c j budd and c j sangwin, to be published soon by oup.


areas of mathematics can be found in our forthcoming book, mathematics galore!, masterclasses, discovery workshops, and team projects in mathematics and its applications by c j budd and c j sangwin, to be published soon by oup. this article is adapted from one originally published on the website of the newton institute, as part of the posters in the london underground series. - radio controlled? by robert leese ( plus, issue 8 ). - robert leese explains how the mathematics of colouring graphs ( networks ) can help avoid interference on your mobile phone. - call routing in telephone networks by richard gibbens and stephen turner ( plus, issue 2 ). - find out how modern telephone networks use mathematics to make it possible for a person to dial a friend in another country just as easily as if they were in the same street, or to read web pages that are on a computer in another continent. - theseus and the minotaur - try your hand at these fantastic web - based maze puzzles. about the authors chris sangwin is a research fellow at the school of mathematics and statistics, university of birmingham. chris budd is professor of applied mathematics at the university of bath, and professor of mathematics for the royal institution. he is particularly interested in applying mathematics to the real world and promoting the public understanding of mathematics.


what is cope? it is a call to universities and research funding agencies to " recognise the crucial value of the services provided by scholarly publishers, the desirability of open access [ oa ] to the scholarly literature, and the need for a stable source of funding for publishers who choose to provide open access to their journals ' contents. " signatories to cope are asked to commit to, " the timely establishment of durable mechanisms for underwriting reasonable publication charges for articles written by its faculty and published in fee - based open - access journals and for which other institutions would not be expected to provide funds. " specifically, signatories are invited to create gold oa funds to assist researchers to pay to publish their papers in oa journals — which instead of charging readers to read ( via a subscription ), impose an author - side article processing fee ( apc ). the deal is that by paying a fee an author can ensure that the publisher will make his or her paper freely available on the web for anyone to read, and thereby increase its impact. cope is the brain child of harvard ' s stuart shieber, a professor of computer science, and director of the university ' s office for scholarly communication. shieber outlined the thinking behind cope in an article published in august in plos biology. cope is necessary, he explained, because oa journal publishing is currently " at a systematic disadvantage relative to the traditional [ subscription, or toll access ( ta ) ] model ". the implication is that authors would be willing to publish their papers in an oa journal, if someone else was prepared to pay the associated publishing fee. universities need to support oa publishing, concluded shieber, in order for it to become " a sustainable, efficient system ". only then, he added, can the two journal publishing systems ( oa and ta ) " compete on a more level playing field. " what ' s the bigger picture here? for the past several decades scholarly journal publishing has been in the grips of the so - called serials crisis. this has made it increasingly difficult for research institutions to fund subscriptions to all the journals that their researchers need to do their work properly. this is both an affordability problem ( since it means that each year universities have to reduce the number of journals they subscribe to due to a shortage of funds ) and an access problem ( since researchers cannot read papers published in journals for which their institution has no subscription ). open access publishing ( gold oa ) was devised as a way of overcoming these problems — by shifting


to due to a shortage of funds ) and an access problem ( since researchers cannot read papers published in journals for which their institution has no subscription ). open access publishing ( gold oa ) was devised as a way of overcoming these problems — by shifting costs from the reader side of the publication process to the author side by charging a one - off publication fee. although the access and affordability problems are part and parcel of the larger serials crisis if we want to understand the current situation more clearly, and assess the likelihood of cope resolving matters, it may help to view them as two separate problems. there are two reasons for doing this. first, as a result of pressure brought to bear on publishers by oa advocates the majority of ta journals now permit authors to self - archive copies of their papers in their institutional repository. known as green oa, this practice ensures that copies of papers published in ta journals can nevertheless be made freely available on the web. however, since universities still need to pay subscriptions to access all the papers that have not been self - archived, green oa is unlikely to have any substantial impact on the affordability problem, at least in the short term. it does, however, hold out the promise of solving the access problem. indeed, so far as access is concerned green oa has a significant advantage over gold oa, because if all researchers began self - archiving their papers it would be possible to make 100 % of the global research output freely available on the web practically overnight. by contrast, it would take a considerable amount of time and effort to convert all journals to gold oa — even assuming that publishers agreed to the conversion. however, in practice today only around 15 % of research is being self - archived by authors. and while research institutions can require self - archiving, very few have yet introduced self - archiving mandates, and it is not at all clear yet whether the growth in mandates will accelerate in the near future. what are the origins of the serials crisis? it is partly a consequence of a continuous growth in the number of journals, but mainly a result of price inflation, which appears to be endemic to the scholarly journal market. hyperinflation, argues shieber is the result of " systemic dysfunctionalities " inherent to a subscription business model when applied to scholarly journals. as in insurance - based health markets, he says, it leads to moral hazard — " the phenomenon of overconsumption of a good by a consumer who is insulated from the good ' s cost ".


model when applied to scholarly journals. as in insurance - based health markets, he says, it leads to moral hazard — " the phenomenon of overconsumption of a good by a consumer who is insulated from the good ' s cost ". in other words, he explains in plos biology, " the ' consumers ' of scholarly articles ( the readers, typically faculty, students, and researchers at universities and other research institutions ) are insulated from the cost of reading, that is, from the subscription fees paid by the institutions ' research libraries. " this is a problem that anti - trust economist mark mccabe outlined to me seven years ago. as he put in 2002, " one distinctive aspect of this market is that end users do not pay for the material they use since the actual purchases are mediated by the libraries. this means that the principals ( the professors, the scientists, the researchers of a particular institution ) ask their agent ( the library ) to buy whatever they need, and the agent has no way of enforcing price discipline on the users. so there is a disconnect. " the second reason for treating access separately from affordability is that while gold oa could in theory eventually produce 100 % oa ( and so solve the access problem ) it is not at all clear that it can solve the affordability problem. since cope proposes gold oa as a solution to the predicament that the research community finds itself in, a key question, therefore, is whether gold oa can avoid the systemic dysfunctionalities characteristic of ta publishing. currently the signs are not good. when pioneer oa publisher biomed central ( bmc ) launched, for instance, it charged $ 525 to publish an article. today its standard apc is nearly three times higher, at $ 1, 535 ; and authors can pay anything up to $ 2, 365 to publish an article in a bmc journal like the journal of biology. similar increases have been evident with other oa publishers. when public library of science ( plos ) launched its first journal, for instance, it charged an apc of $ 1, 500 ; today it charges nearly twice as much, with costs ranging from $ 2, 250 to $ 2, 900. ( plos one charges $ 1, 350, but is not a traditional journal ). moreover with most researchers unable to fund the cost of paying apcs themselves a number of alternative payment options have been devised. this has led to the creation of gold oa funds like those envisaged by cope


but is not a traditional journal ). moreover with most researchers unable to fund the cost of paying apcs themselves a number of alternative payment options have been devised. this has led to the creation of gold oa funds like those envisaged by cope ( there are currently 21 gold oa funds, plus an ambitious project called scoap3 that hopes to convert the entire particle physics literature from a subscription model to gold oa ), and to the so - called " institutional membership scheme ". inevitably such schemes involve paying apcs from centralised funds. institutional membership, for instance, involves a research institution bulk - buying the right for all its researchers to publish their papers in any of a specific gold oa publisher ' s portfolio of journals — with the costs generally charged to the library budget. essentially, it is a quasi - subscription. as a quasi - subscription institutional membership creates a similar " disconnect " between user and purchaser as occurs with ta publishing. gold oa funds will inevitably have the same effect. as shieber points out, the danger is that " since authors would not now have to pay the processing fee, they would over - consume in a price - blind fashion, and processing fees would hyperinflate just as the subscription fees. " it seems that this is not just a theoretical danger. in august 2007 unrest erupted over the institutional membership scheme operated by bmc, leading to the science and medical libraries at yale university publicly announcing that they were discontinuing membership. explaining their decision yale librarians pointed out that the university had been asked to pay biomed central less than $ 4, 700 to publish articles in bmc journals in 2005, but that the figure had grown to $ 31, 625 in 2006. " this experiment in open - access publishing has proved unsustainable, " the librarians concluded. a further fifteen universities also cancelled their bmc membership scheme. bmc responded by saying that the price hike was a consequence of a rapid rise in the number of papers published in its journals. this is no doubt fair comment, but appears to confirm that oa publishing suffers from the same disconnect between principal and agent as is evident with ta publishing, and that this results in the same inflationary spiral. in discussing this issue earlier this year i concluded that oa publishing funded with gold oa funds, or institutional memberships, is likely to produce the same hyperinflationary effect that shieber worries about. in other words, while gold oa funds could eventually solve the access


i concluded that oa publishing funded with gold oa funds, or institutional memberships, is likely to produce the same hyperinflationary effect that shieber worries about. in other words, while gold oa funds could eventually solve the access problem, it is far from clear that they can resolve the affordability problem. oa advocate peter suber challenged my conclusion. " as soon as we shift costs from the reader side to the author side, then, we create market pressure to keep them low enough to attract rather than deter authors... [ and ]... precisely because high prices in an oa world would exclude authors, and not merely readers, there is a natural, market - based check on excessive prices. " besides, he added, the majority of oa journals do not currently charge an apc. as he put it : " it ' s relevant to point out here that most oa journals charge no publication fees or institutional memberships at all. i ' ve argued that even fee - based gold oa is not the threat that richard seems to think. but even if i ' m entirely wrong about that : fee - based gold oa is a minority of gold oa, and no - fee gold oa doesn ' t pose any of the threats that richard describes. " shieber likewise cites evidence showing that the number of oa journals currently charging apcs is low. writing in plos biology he reported that fewer than 25 % of the open - access journals in the directory of open access journals ( doaj ) are listed as charging a publication fee, " the remainder relying on other sources of direct or in - kind support. " can we assume that this will continue to be the case? shieber thinks not. for this reason he reaches a slightly different conclusion to suber : " [ p ] rocessing fees are likely to be an important revenue model for open - access journals, as they scale beyond the tiny fraction of overall journals that they currently constitute ; processing fees are the only revenue source that inherently scales directly with the publishing services provided by a journal. the importance of the processing - fee model can be seen in the fact that of the open - access journals of sufficient standing to have an institute for scientific information ( isi ) impact factor, the proportion charging processing fees rises above 50 %. " putting a cap on it shieber nonetheless suggests that gold oa can avoid the hyperinflation that has plagued ta publishing — if research institutions impose a cap on the money made available


factor, the proportion charging processing fees rises above 50 %. " putting a cap on it shieber nonetheless suggests that gold oa can avoid the hyperinflation that has plagued ta publishing — if research institutions impose a cap on the money made available to authors when reimbursing their publishing fees. with a cap, he explains, authors " would have to trade off whether using a certain amount of their limited allocation of funds for a given journal was appropriate in relation to the services and imprimatur that the journal provides, thereby reintroducing exactly the economic trade off that is missing from the current system. " he concludes, " in essence, the caps would act as inverse deductibles still allowing the economic signal to pass through to authors. in this approach, decisions about what is a reasonable fee are delegated to authors who choose on the basis of a market mechanism ; the institution needn ' t stipulate reasonableness a priori. " this invites us to wonder what constitutes a reasonable fee, and whether a researcher would know a reasonable fee when presented with the bill. but would a cap work? " on the plus side, " says suber, " a cap will give authors a reason to husband their resources, or their allocation, introducing a note of price competition into their decision about where to submit a new work. " on the other side, he adds, " [ a ] fter an author spends her allocation, she might just submit subsequent work from the same fiscal year to a no - fee journal ( oa or ta ). that ' s compatible with price competition for the first article ; but it ' s also compatible with disregarding price competition even for the first article. it ' s compatible with oa for the subsequent articles ; but it ' s also compatible with ta for the subsequent articles. " however, the more important point, perhaps, is that universities will inevitably struggle to provide sufficient money to allow a gold oa fund to ameliorate the predicament the research community currently finds itself in. this point was graphically demonstrated by cornell doctoral student phil davis in may, when reporting on the plan of cope signatory cornell to make $ 50, 000 available for a gold fund. " considering that the cornell university library spends nearly $ 18 million dollars on collections, $ 50k seems like pocket change, " he said. " from an management standpoint, it may take much more than $ 50k in staff and faculty time to administrate and process author charges


nearly $ 18 million dollars on collections, $ 50k seems like pocket change, " he said. " from an management standpoint, it may take much more than $ 50k in staff and faculty time to administrate and process author charges one article at a time. " with apcs costing up to $ 3, 000 per article ( and some, like cell press, charging as much as $ 5, 000 ), pocket change like this can hardly be expected to make much impression on the serials crisis. and since most of a library ' s budget will inevitably remain locked up in traditional journal subscriptions — which can be expected to continue to increase in price each year — it is hard to see how cope - like initiatives will have much impact on either the affordability or the access problem. " the notion of a cope cap on the amount that funders and / or universities commit to subsidising authors for gold oa fees is predicated on the enthymeme ( i. e. the unstated or unrealised premise ) that publishers abandon subscriptions and convert to gold oa publishing, " says harnad. in a post on liblicense harnad adds : " there are 25, 000 journals, most of them not gold oa, let alone equitably priced gold oa, publishing 2. 5 million articles a year from 10, 000 universities worldwide. the tacit hope of cope is to persuade all journals to abandon subscriptions and convert to equitably priced gold oa by offering to pay for equitably priced publication today. " in short, cope could only prove efficacious if universities cancelled all or most of their journal subscriptions and reallocated the money to pay for gold oa ( which they cannot risk doing ), or of publishers voluntarily converting their journals to gold oa. but as harnad points out, " publishers have no reason to stop charging successful subscriptions just because some universities and / or funders commit to offering authors a capped gold - oa subsidy. " in response to a claim on the liblicense mailing list that cope is a key oa initiative, and will allow " a smooth and successful transition to open access, harnad responded : " it is just a very expensive way of generating some oa for a small fraction of a university ' s research output. " like harnad, executive editor for social sciences at penn university press sandy thatcher is doubtful that gold oa


responded : " it is just a very expensive way of generating some oa for a small fraction of a university ' s research output. " like harnad, executive editor for social sciences at penn university press sandy thatcher is doubtful that gold oa funds will achieve very much. commenting on a press release that the scholarly publishing and academic resources coalition ( sparc ) posted on liblicense extolling the creation of gold oa funds at the university of calgary and the university of california at berkeley, thatcher said : " i wonder how such initiatives really will change the economics of the system overall, especially in the short term. universities will still be paying for subscriptions for many journals and [ are ] now adding fees in addition. " in short, for so long as universities have to continue paying constantly increasing subscription fees to traditional publishers they cannot hope to buy oa for more than a handful of their researcher ' s ' papers. this, of course, is the crux of the systemic disadvantage that shieber bemoans : research institutions cannot force a transition to gold oa if their library budgets are already committed to traditional journal subscriptions. but it is far from clear that cope can do anything to resolve it. once again, we have to conclude that not only will cope fail to resolve the affordability problem, but it will have little impact on the access problem. indeed, not only are budgets already seriously over - stretched, they face further cuts as a result of the current financial crisis. at least two of the cope signatories — cornell and mit — are in the process of reducing their library budgets. there must therefore be doubts as to how long gold oa funds can be supported. one of the first gold oa funds to be created was introduced at the university of amsterdam in 2007. earlier this year, however, it was closed — " due to a precarious financial situation. " asks harnad : " would it not be more timely and useful ( for oa ) to encourage every university to provide oa for its own research output, by mandating green oa self - archiving, rather than making formal or financial commitments before or instead of doing so? green oa, after all, is easy to implement, incurs no additional costs, and offers a much quicker route to oa. as it is, he says, only two of the five signatories to cope ( harvard and mit ) have introduced mandates, suggesting that cope signatories may have lost sight of the primary objective —


offers a much quicker route to oa. as it is, he says, only two of the five signatories to cope ( harvard and mit ) have introduced mandates, suggesting that cope signatories may have lost sight of the primary objective — to make as much research oa, as quickly as possible. cope, says harnad, is, " in effect simply encouraging universities to put up the cash today and then just sit and wait to see whether offering the capped subsidy will take the bait. meanwhile, access continues to be lost, year after year. " let a thousand flowers bloom? one can of course argue that cope does have the virtue of drawing attention to oa and the way in which the research community is being held hostage by scholarly publishers. is that not a valuable thing to do? in any case, what ' s wrong with experimentation? should we not let a thousand flowers bloom? sure, says harnad, people are free to experiment, and they are free to speculate ; but the first step of any institution serious about oa should be to do the most obvious and rational thing : introduce a self - archiving mandate. " with green oa mandates safely seeing to access, we have nothing to lose in getting into speculative economics. but without green oa mandates we lose our very raison d ' etre, oa, in favour of speculative economics. " besides, he adds, taking a scattergun approach simply disperses the energies of the research community, and distracts them from the goal — to achieve oa as quickly as possible. and that, he says, is precisely what green oa can do. " this is definitely not a case for ' let a thousand flowers bloom, ' in parallel. it is much too late in the day for that, especially with the green oa mandate option fully within every university ' s reach. " for harnad, therefore, achieving oa should be treated as a serial process, with green oa taking priority over gold oa. suber disagrees, arguing that there is no reason why gold and green oa initiatives should not be pursued simultaneously. " i do think the two can and should run in parallel. " suber adds however : " [ a ] ny university willing to launch a fund to support gold oa should also be willing to adopt a green oa mandate. more : one of the primary arguments for a gold oa fund ( namely, to provide oa to a larger fraction of the university ' s


to launch a fund to support gold oa should also be willing to adopt a green oa mandate. more : one of the primary arguments for a gold oa fund ( namely, to provide oa to a larger fraction of the university ' s research output ) applies even more strongly to a green oa mandate. " consequently, he concludes, " i ' d like to see universities support both green and gold oa with strong, effective policies. if they do, i don ' t care whether they adopt the green policy first and then the gold, or vice versa. but i do worry [ that ] when a university adopts a gold oa policy without seeing that its reasons for doing so are even stronger reasons to adopt a green policy as well. " all in all there are good reasons to be highly sceptical about the likely efficacy of cope. for as long as library budgets are tied up with subscriptions it is hard to see how gold oa funds can break the logjam, unless they are accompanied by green self - archiving mandates. the cope signatories have perhaps mistaken intent for action. the good news is that it would take very little to turn cope from a well - meaning but probably ineffectual initiative into one with real teeth. all that is needed is to require that, in addition to creating a gold oa fund, cope signatories commit to introduce a green oa mandate. not only would this have the merit of pleasing both harnad and suber, but it would be far more likely to help the research community achieve oa ( as in access ). as it is, cope gives the impression of being a step back from the historic moment last year when harvard ' s faculty of arts and sciences became the first university department in the us to adopt a green mandate — an initiative that was also masterminded by shieber. that said, although adding teeth to cope could help solve the access problem it is not certain that it would do much to address the affordability problem — since there is no evidence that either green or gold oa are capable of reducing the costs of scholarly communication ( as currently conceived ). consequently affordability will doubtless remain a continuing concern for the research community, and for taxpayers — the people who ultimately fund scholarly communication. it may be that if green mandates multiplied they would eventually generate enough oa to induce subscription cancellations, releasing the subscription funds to pay for — and hence encouraging publishers to convert to — gold oa. but that is speculation.


chicago – a system that allows surgeons to perform laparoscopic gastric bypass surgery from a remote console, controlling up to three robotic arms and a binocular camera, was successfully tested in 10 patients, according to a study in the august issue of archives of surgery, one of the jama / archives journals. the laparoscopic gastric bypass surgery ( a roux - en - y procedure ) is often considered the most challenging minimally invasive procedure in general surgery, requiring a learning curve of 75 to100 cases for even experienced surgeons to achieve the highest level of proficiency, according to background information in the article. although robotic surgical techniques have been developed to assist laparoscopic gastric bypass surgery, the complex geometry of the surgery has required repositioning of the robot, complicating its use. catherine j. mohr, m. s. m. e., of the stanford school of medicine, calif., and colleagues report the first 10 patients to undergo a totally robotic laparoscopic roux - en - y gastric bypass surgery ( during march and april 2004 ) using a technique developed to minimize robot repositioning. the results were compared with a sample of 10 patients who had undergone standard laparoscopic roux - en - y gastric bypass surgery during july to september 2002. there were no significant differences in the general health, age or body mass index ( bmi, calculated as weight in kilograms divided by the square of height in meters ) of the two sets of patients. all patients were women. the researchers compared surgical times as well as the ratio of the procedure time to the patient ' s bmi. the number and severity of complication were comparable, the researchers found. " the median length of time to complete the procedure was significantly shorter with the robot ( 169 vs. 208 minutes ), " the authors report. " in addition, the ratio of procedure time to bmi was considerably lower with the robot ( median, 3. 8 vs. 5. 0 minutes per bmi for the laparoscopic cases ). moreover, the rate at which the operative times improved indicate that the learning curve for the robotic procedure is considerably shorter. we found that the mean minutes per bmi of our second five robotic procedures was 3. 45 minutes, whereas the laparoscopic data for our senior attending surgeon did not attain a comparable five - case mean of the metric until case 42. in addition, when the data from a bariatric fellow from the same institution [ stanford medical school ] were compared, that


dartmouth medical school investigators are learning more about how low doses of arsenic, such as the levels found in drinking water in many areas of the united states, affect human physiology. in a paper published online on dec. 2 in the journal chemical research in toxicology, the researchers report that three different steroid hormones all show similar responses to arsenic, suggesting a broader effect and a common mechanism of arsenic on how these hormones function. " since most of the health consequences of exposure to arsenic - various cancers, diabetes, heart and vascular disease, reproductive and developmental effects, etc. - involve these same steroid receptors, we think that disruption of their normal function could explain, in large part, how arsenic can influence so many disease risks, " says joshua hamilton, one of the authors on this study and the director of the center for environmental health sciences at dartmouth and dartmouth ' s superfund basic research program on toxic metals. hamilton ' s laboratory had earlier found that arsenic disrupts the activity of the glucocorticoid receptor, and this follow up study considered the progesterone and mineralocorticoid receptors, which regulate a wide range of biological processes. this current work was done in collaboration with jack bodwell, the lead author on this paper and a research associate professor of physiology at dartmouth medical school. hamilton, bodwell, and their team found that arsenic appears to suppress the ability of all three of these critical receptors to respond to their normal hormone signals. chemicals that disrupt steroid hormone receptor signaling are called endocrine disruptors, and this study provides further evidence that arsenic, a metal, does not behave like other endocrine disruptors such as pesticides. " arsenic does not activate these receptors, as some endocrine disruptors do, by mimicking the natural hormone, nor does it block the ability of the normal hormones to activate their specific receptor, as most other endocrine disruptors do, " says hamilton, who is also a professor of pharmacology and toxicology at dartmouth medical school. " nor does it affect the ability of the hormone - activated receptor to move to the nucleus of the cell or to bind to dna to initiate gene expression. yet, somehow arsenic still strongly affects the ability of these hormone - activated receptors to regulate gene expression. there ' s still a lot more to learn. " the study also looked into the effects of different levels of arsenic on these receptors. at very low doses ( comparable to what is found in drinking water at the current and previous u. s.


. there ' s still a lot more to learn. " the study also looked into the effects of different levels of arsenic on these receptors. at very low doses ( comparable to what is found in drinking water at the current and previous u. s. regulatory limits, in the range of 5 - 50 ppb ) arsenic enhances hormone - stimulated gene expression, by two - to three - fold. at slightly higher doses ( in the range of 50 - 200 ppb, commonly found in drinking water from contaminated wells in new hampshire and elsewhere in the u. s. ) arsenic has the exact opposite effect, strongly and almost completely inhibiting hormone - stimulated gene expression by these receptors. this non - conventional dose - response suggests that arsenic might have very different biological effects at the lower and higher doses. " elucidating these complex biological effects of arsenic on hormone signaling at different doses will be critical to our overall understanding of how arsenic influences human health, and should be considered as an important component of determining the overall disease risk of people who are exposed to arsenic in their drinking water, " says hamilton. the work is funded by grants to dartmouth collaborators hamilton and bodwell from the national institute of environmental health sciences, a component of the national institutes of health. both researchers are members of the niehs - funded superfund basic research program at dartmouth and dartmouth ' s center for environmental health sciences. co - authors on the study include julie a. gosse, and athena p. nomikos, both of dartmouth and both recipients of training fellowships from dartmouth ' s superfund basic research program. last reviewed : by john m. grohol, psy. d. on 21 feb 2009 published on psychcentral. com. all rights reserved.


individual differences | methods | statistics | clinical | educational | industrial | professional items | world psychology | | formosan subterranean termite soldiers ( red colored heads ) and workers ( pale colored heads ). | formosan subterranean termite soldiers ( red colored heads ) and workers ( pale colored heads ). termites are a group of eusocial insects that, until recently, were classified at the taxonomic rank of order isoptera ( see taxonomy below ), but are now accepted as the epifamily termitoidae, of the cockroach order blattodea. while termites are commonly known, especially in australia, as " white ants, " they are only distantly related to the ants. as eusocial insects, termites live in colonies that, at maturity, number from several hundred to several million individuals. colonies use decentralised, self - organised systems of activity guided by swarm intelligence which exploit food sources and environments unavailable to any single insect acting alone. a typical colony contains nymphs ( semi - mature young ), workers, soldiers, and reproductive individuals of both genders, sometimes containing several egg - laying queens. a female that has flown, mated, and is producing eggs is called a " queen. " similarly, a male that has flown, mated, and is in proximity to a queen is termed a " king. " research using genetic techniques to determine relatedness of colony members has shown that the original idea that colonies are only ever headed by a monogamous royal pair is wrong. multiple pairs of reproductives within a colony are commonly encountered. in the families rhinotermitidae and termitidae, and possibly others, sperm competition does not seem to occur ( male genitalia are very simple and the sperm are anucleate ), suggesting that only one male ( king ) generally mates within the colony. at maturity, a primary queen has a great capacity to lay eggs. in physogastric species, the queen adds an extra set of ovaries with each molt, resulting in a greatly distended abdomen and increased fecundity, often reported to reach a production of more than 2, 000 eggs a day. the distended abdomen increases the queen ' s body length to several times more than before mating and reduces her ability to move freely, though attendant workers provide assistance. the queen is widely believed to be a primary source of pheromones useful in colony integration, and these are thought to be spread through shared feeding ( trop


than before mating and reduces her ability to move freely, though attendant workers provide assistance. the queen is widely believed to be a primary source of pheromones useful in colony integration, and these are thought to be spread through shared feeding ( trophallaxis ). the king grows only slightly larger after initial mating and continues to mate with the queen for life ( a termite queen can live for forty - five years ). this is very different from ant colonies, in which a queen mates once with the male ( s ) and stores the gametes for life, as the male ants die shortly after mating. the winged ( or " alate ' " ) caste, also referred to as the reproductive caste, are generally the only termites with well - developed eyes, although workers of some harvesting species do have well - developed compound eyes, and, in other species, soldiers with eyes occasionally appear. termites on the path to becoming alates ( going through incomplete metamorphosis ) form a subcaste in certain species of termites, functioning as workers ( " pseudergates " ) and also as potential supplementary reproductives. supplementaries have the ability to replace a dead primary reproductive and, at least in some species, several are recruited once a primary queen is lost. in areas with a distinct dry season, the alates leave the nest in large swarms after the first good soaking rain of the rainy season. in other regions, flights may occur throughout the year, or more commonly, in the spring and autumn. termites are relatively poor fliers and are readily blown downwind in wind speeds of less than 2 km / h, shedding their wings soon after landing at an acceptable site, where they mate and attempt to form a nest in damp timber or earth. worker termites undertake the labors of foraging, food storage, brood and nest maintenance, and some defense duties in certain species. workers are the main caste in the colony for the digestion of cellulose in food and are the most likely to be found in infested wood. this is achieved in one of two ways. in all termite families except the termitidae, there are flagellate protists in the gut that assist in cellulose digestion. however, in the termitidae, which account for approximately 60 percent of all termite species, the flagellates have been lost and this digestive role is taken up, in part, by a consortium of prokaryotic organisms. this simple story


in the termitidae, which account for approximately 60 percent of all termite species, the flagellates have been lost and this digestive role is taken up, in part, by a consortium of prokaryotic organisms. this simple story, which has been in entomology textbooks for decades, is complicated by the finding that all studied termites can produce their own cellulase enzymes, and therefore might digest wood in the absence of their symbiotic microbes although there is now evidence suggesting that these gut microbes make use of termite - produced cellulase enzymes. our knowledge of the relationships between the microbial and termite parts of their digestion is still rudimentary. what is true in all termite species, however, is that the workers feed the other members of the colony with substances derived from the digestion of plant material, either from the mouth or anus. this process of feeding of one colony member by another is known as trophallaxis and is one of the keys to the success of the group. it frees the parents from feeding all but the first generation of offspring, allowing for the group to grow much larger and ensuring that the necessary gut symbionts are transferred from one generation to another. some termite species do not have a true worker caste, instead relying on nymphs that perform the same work without differentiating as a separate caste. the soldier caste has anatomical and behavioural specializations, providing strength and armour which are primarily useful against ant attack. the proportion of soldiers within a colony varies both within and among species. many soldiers have jaws so enlarged that they cannot feed themselves, but instead, like juveniles, are fed by workers. the pantropical subfamily nasutitermitinae have soldiers with the ability to exude noxious liquids through either a horn - like nozzle ( nasus ). simple holes in the forehead called " fontanelles " and which exude defensive secretions are a feature of the family rhinotermitidae. many species are readily identified using the characteristics of the soldiers ' heads, mandibles, or nasus. among the drywood termites, a soldier ' s globular ( " phragmotic " ) head can be used to block their narrow tunnels. termite soldiers are usually blind, but in some families, particularly among the dampwood termites, soldiers developing from the reproductive line may have at least partly functional eyes. the specialization of the soldier caste is principally a defence against predation by ants


. termite soldiers are usually blind, but in some families, particularly among the dampwood termites, soldiers developing from the reproductive line may have at least partly functional eyes. the specialization of the soldier caste is principally a defence against predation by ants. the wide range of jaw types and phragmotic heads provides methods that effectively block narrow termite tunnels against ant entry. a tunnel - blocking soldier can rebuff attacks from many ants. usually more soldiers stand by behind the initial soldier so once the first one falls another soldier will take the place. in cases where the intrusion is coming from a breach that is larger than the soldier ' s head, defense requires special formations where soldiers form a phalanx - like formation around the breach and bite at intruders or exude toxins from the nasus or fontanelle. this formation involves self - sacrifice because once the workers have repaired the breach during fighting, no return is provided, thus leading to the death of all defenders. another form of self - sacrifice is performed by southeast asian tar - baby termites ( globitermes sulphureus ). the soldiers of this species commit suicide by autothysis — rupturing a large gland just beneath the surface of their cuticle. the thick yellow fluid in the gland becomes very sticky on contact with the air, entangling ants or other insects who are trying to invade the nest. termites undergo incomplete metamorphosis. freshly hatched young appear as tiny termites that grow without significant morphological changes ( other than wings and soldier specializations ). some species of termite have dimorphic soldiers ( up to three times the size of smaller soldiers ). though their value is unknown, speculation is that they may function as an elite class that defends only the inner tunnels of the mound. evidence for this is that, even when provoked, these large soldiers do not defend themselves but retreat deeper into the mound. on the other hand, dimorphic soldiers are common in some australian species of schedorhinotermes that neither build mounds nor appear to maintain complex nest structures. some termite taxa are without soldiers ; perhaps the best known of these are in the apicotermitinae. termites are generally grouped according to their feeding behaviour. thus, the commonly used general groupings are subterranean, soil - feeding, drywood, dampwood, and grass - eating. of these, subterraneans and drywoods are primarily responsible for damage to human - made structures. all termites eat cellulo


, the commonly used general groupings are subterranean, soil - feeding, drywood, dampwood, and grass - eating. of these, subterraneans and drywoods are primarily responsible for damage to human - made structures. all termites eat cellulose in its various forms as plant fibre. cellulose is a rich energy source ( as demonstrated by the amount of energy released when wood is burned ), but remains difficult to digest. termites rely primarily upon symbiotic protozoa ( metamonads ) such as trichonympha, and other microbes in their gut to digest the cellulose for them and absorb the end products for their own use. gut protozoa, such as trichonympha, in turn rely on symbiotic bacteria embedded on their surfaces to produce some of the necessary digestive enzymes. this relationship is one of the finest examples of mutualism among animals. most so - called higher termites, especially in the family termitidae, can produce their own cellulase enzymes. however, they still retain a rich gut fauna and primarily rely upon the bacteria. owing to closely related bacterial species, it is strongly presumed that the termites ' gut flora are descended from the gut flora of the ancestral wood - eating cockroaches, like those of the genus cryptocercus. some species of termite practice fungiculture. they maintain a “ garden ” of specialized fungi of genus termitomyces, which are nourished by the excrement of the insects. when the fungi are eaten, their spores pass undamaged through the intestines of the termites to complete the cycle by germinating in the fresh faecal pellets. they are also well known for eating smaller insects in a last resort environment. in captivity edit few zoos hold termites, due to the difficulty in keeping them captive and the reluctance of authorities to permit potential pests. one of them is zoo basel in switzerland. at zoo basel, two african termite ( macrotermes bellicosus ) populations exist and thrive - resulting in very rare ( in captivity ) mass migrations of young flying termites. this happened last in september 2008, when thousands of male termites left their mound each night, died, and covered the floors and water pits of the house their exhibit is in. ecologically, termites are important in nutrient recycling, habitat creation, soil formation and quality and, particularly the winged reproductives, as food for countless predators. the role of term


covered the floors and water pits of the house their exhibit is in. ecologically, termites are important in nutrient recycling, habitat creation, soil formation and quality and, particularly the winged reproductives, as food for countless predators. the role of termites in hollowing timbers and thus providing shelter and increased wood surface areas for other creatures is critical for the survival of a large number of timber - inhabiting species. larger termite mounds play a role in providing a habitat for plants and animals, especially on plains in africa that are seasonally inundated by a rainy season, providing a retreat above the water for smaller animals and birds, and a growing medium for woody shrubs with root systems that cannot withstand inundation for several weeks. in addition, scorpions, lizards, snakes, small mammals, and birds live in abandoned or weathered mounds, and aardvarks dig substantial caves and burrows in them, which then become homes for larger animals such as hyenas and mongooses. as detrivores, termites clear away leaf and woody litter and so reduce the severity of the annual bush fires in african savannas, which are not as destructive as those in australia and the u. s. a. their role in bioturbation on the khorat plateau is under investigation. globally, termites are found roughly between 50 degrees north & south, with the greatest biomass in the tropics and the greatest diversity in tropical forests and mediterranean shrublands. termites are also considered to be a major source of atmospheric methane, one of the prime greenhouse gases. termites have been common since at least the cretaceous period. termites also eat bone and other parts of carcasses, and their traces have been found on dinosaur bones from the middle jurassic in china. termites divide labour among castes, produce overlapping generations and take care of young collectively. - main article : termites - nestbuilding - main article : termites - animal human interaction other behavior of note edit taxonomy, evolution and systematicsedit recent dna evidence has supported the hypothesis, originally based on morphology, that termites are most closely related to the wood - eating cockroaches ( genus cryptocercus ), to which the singular and very primitive mastotermes darwiniensis shows some telltale similarities. most recently, this has led some authors to propose that termites be reclassified as a single family, termitidae, within the order blattodea, which contains cockroaches. however, most researchers advocate the less drastic


. most recently, this has led some authors to propose that termites be reclassified as a single family, termitidae, within the order blattodea, which contains cockroaches. however, most researchers advocate the less drastic measure of retaining the termites as termitoidae, an epifamily of the cockroach order, which preserves the classification of termites at family level and below. evolutionary history edit the oldest unambiguous termite fossils date to the early cretaceous, although structures from the late triassic have been interpreted as fossilized termite nests. given the diversity of cretaceous termites, it is likely that they had their origin at least sometime in the jurassic. weesner believes that mastotermitidae termites may go back to the permian and fossil wings have been discovered in the permian of kansas which have a close resemblance to wings of mastotermes of the mastotermitidae, which is the most primitive living termite. it is thought to be the descendant of cryptocercus genus, the wood roach. this fossil is called pycnoblattina. it folded its wings in a convex pattern between segments 1a and 2a. mastotermes is the only living insect that does the same, it has long been accepted that termites are closely related to cockroaches and mantids, and they are classified in the same superorder ( dictyoptera ), but new research has shed light on the details of termite evolution. there is now strong evidence suggesting that termites are really highly modified, social, wood - eating cockroaches. a study conducted by scientists has found that endosymbiotic bacteria from termites and a genus of cockroaches, cryptocercus, share the strongest phylogenetical similarities out of all other cockroaches. both termites and cryptocercus also share similar morphological and social features — most cockroaches do not show social characteristics, but cryptocercus takes care of its young and exhibits other social behaviour. as mentioned above, the primitive giant northern termite ( mastotermes darwiniensis ) exhibits numerous cockroach - like characteristics, such as laying its eggs in rafts and having anal lobes on the wings that are not shared with other termites. - kalotermitidae ( 22 genera, 419 species ) - rhinotermitidae ( 14 genera, 343 species ) - termitidae ( 236 genera, 1958 species ) the most


the wings that are not shared with other termites. - kalotermitidae ( 22 genera, 419 species ) - rhinotermitidae ( 14 genera, 343 species ) - termitidae ( 236 genera, 1958 species ) the most current classification of termites is summarized by engel & krishna ( 2004 ). - ↑ ( 22 june 2007 ) hidden cellulases in termites : revision of an old hypothesis. biology letters 3 ( 3 ) : 336 – 339. - ↑ piper, ross ( 2007 ), extraordinary animals : an encyclopedia of curious and unusual animals, greenwood press. - ↑ c. bordereau, a. robert, v. van tuyen & a. peppuy ( 1997 ). suicidal defensive behavior by frontal gland dehiscence in globitermes sulphureus haviland soldiers ( isoptera ). insectes sociaux 44 ( 3 ) : 289 – 297. - ↑ the evolution of fungus - growing termites and their mutualistic fungal symbionts by duur k. aanen, paul eggleton, corinne rouland - lefevre, tobias guldberg - frøslev, søren rosendahl & jacobus j. boomsma - ↑ fungus - farming insects : multiple origins and diverse evolutionary histories by ulrich g. mueller & nicole gerardo - ↑ [ http : / / www. nzz. ch / nachrichten / panorama / im _ zoo _ basel _ fliegen _ die _ termiten _ aus _ _ 1. 848530. html ( german ) im zoo basel fliegen die termiten aus ]. neue zurcher zeitung, retrieved 2011 - 05 - 21 - ↑ lofjle & kubiniok, landform development and bioturbation on the khorat plateau, northeast thailand, nat. hist. bull. siam soc. ( 56 ), 1996 - ↑ 403 forbidden - ↑ lo, n. et al. evidence for cocladogenesis between diverse dictyopteran lineages and their intracellular endosymbionts. molecular biology and evolution, 20, 907 – 913 ( 2003 ) - ↑ ware, j. l. et al. relationships among the major lineages of dictyoptera : the effect of outgroup selection on dictyopteran tree topology. systematic entomology, 33, 429 – 450 ( 2008 ) - ↑ inward, d., g. beccaloni


lineages of dictyoptera : the effect of outgroup selection on dictyopteran tree topology. systematic entomology, 33, 429 – 450 ( 2008 ) - ↑ inward, d., g. beccaloni, and p. eggleton. 2007. death of an order : a comprehensive molecular phylogenetic study confirms that termites are eusocial cockroaches. biology letters 3 : 331 - 335. - ↑ includeonly > " termites are ' social cockroaches ' ", bbc news, 13 april 2007. - ↑ eggleton, p. & al. ( 2007 ), biological letters, june 7, cited in science news vol. 171, p. 318 - ↑ lo, n. & al. ( 2007 ), biology letters, 14 august 2007, doi 10. 1098 / rsbl. 2007. 0264 - ↑ gay and calaby 1970 termites of the australian region. in ; krishna k weesner fm eds. biology of termites, vol. ii academic press ny p401 - ↑ weesner fm ( 1960 ) evolution biology of termites. annual review of entomology. 5 ; 153 - 170. - ↑ tilyard rj ( 1937 ) kansas permian insects.. part xx the cockroaches, or order blattariai, ii am. journal of science 34 ; 169 - 202, 249 - 276. - ↑ evidence for cocladogenesis between diverse dictyopteran lineages and their intracellular endosymbionts - ↑ engel, m. s. and k. krishna ( 2004 ). family - group names for termites ( isoptera ). american museum novitates 3432 ( 1 ) : 1 – 9. - grimaldi, d. and engel, m. s. ( 2005 ). evolution of the insects, cambridge university press. - termite terms - cretaceous termites david attenborough, life in the undergrowth, episode 5 supersocieties, 37 mins and 15 secs ff. abe t., bignell d. e., higashi m. ( eds. ) ( 2000 ). termites : evolution, sociality, symbioses, ecology, ecolab, kluwer academic publishers. - university of nebraska page on termites - termite hub from national pest management association - includes faqs, types of termites, etc. - a summary of termite control methods - university


, ecolab, kluwer academic publishers. - university of nebraska page on termites - termite hub from national pest management association - includes faqs, types of termites, etc. - a summary of termite control methods - university of california advice on drywood termites - termite pest control information - usa national pesticide information center - catalogue of the termites of the world - pictures of termites - transitional species in insect evolution - cretaceous termites and soil phosphorus - beneficial uses of termites - texas a & m university department of entomology - center for urban & structural entomology - the soul of the white ant - eugene n. marais - termite terminology - a glossary of terms - urban entomology program university of toronto - list of termite types - isoptera : termites ( csiro australia entomology ). - ' termite guts can save the planet ', says nobel laureate - amitermes floridensis, florida darkwinged subterranean termite - coptotermes formosanus, formosan subterranean termite - coptotermes gestroi, asian subterranean termite - cryptotermes brevis, west indian drywood termite - heterotermes sp., west indian subterranean termite - cryptotermes cavifrons, a drywood termite - incisitermes minor, western drywood termite - neotermes spp., florida dampwood termites - prorhinotermes simplex, cuban subterranean termite - reticulitermes spp., native u. s. a. subterranean termites | this page uses creative commons licensed content from wikipedia ( view authors ). |


50 simple tools used to rebuild haiti parts of this article were adapted from an article at popular mechanics rebuilding is an inevitable part of putting our lives back together after a disaster. when an emergency occurs, we need tools to build, repair and maintain our homes¬ † to make them livable once more. those who survived the¬ † haitian earthquake¬ † know this all too well. we are all¬ † familiar with the devastation that occurred with the haitian earthquake, the lives lost and the reconstruction still taking place. according to an article in popular mechanics, relief workers who responded to the disaster were asked to bring their own tools in order to rebuild parts of haiti and they did so using 50 tools. ¬ † it is ironic that these tools played such a large role in the reconstruction of¬ † this broken island. the tools used for reconstruction¬ † not only created shelters for families, and areas for sanitation, but they gave the haitians hope that one day their island would be restored. in the backbreaking early stages of rubble removal, simple hand tools played a vital role in transporting and removing debris. acquiring basic hand tools ‚ aeshovels, axes and hammers ‚ aemeet immediate demolition needs and then take on a long - term role once construction resumes. the tools used in the first phase of reconstruction were : 1. round point and square nose shovels, preferably heavy - duty variety with extra long blade socket. 2. pick axe 3. pulaski axe 4. rig builder ’ s hatchet 6. bow saw 7. 24 - oz. framing hammer 8. sledge hammer 9. digging bars, preferably both pointed and chisel tip varieties ; crow bars. 10. leather or synthetic work gloves 11. protective eye wear 12. hard hats 13. dust masks 14. contractor - grade wheel barrows 15. bolt cutters 16. large - diameter heavy - duty weatherproof rope ; small - diameter light - duty line 17. rope hoist / pulley, minimum 250 - lb. capacity 18. folding knife shelter construction was the next step in rebuilding haiti. simple sheds made of little more than lumber and nails can provide families secure shelter, a measure of sanitation and the stability to endure harsh weather. in the absence of fuel or electricity, fairly sophistication construction can begin with such basic hand tools as saws, braces and squares. the tools and materials used in the second phase of reconstruction were : 1. 8 - point crosscut saw 2. carpenter ’ s pencil 3. carpenter ’


##owels, plumb bob, brick set, mason ’ s level, jointer, stone tracer, stone chisel. 9. simple optical level, such as a builder ’ s level or transit. 10. basic electrician ’ s tool kit ( haiti uses 110 - volt power, the same as north america ) : side - cutting pliers, diagonal pliers, needle - nose pliers, electrician ’ s multi - tool wire stripper / screw cutter, solenoid voltage tester, fork meter and spare aa batteries. 11. metric / sae tap and die set 12. kerosene and kerosene lanterns, waterproof matches 13. charcoal and charcoal grills 14. chlorine bleach for water disinfection, lifestraws or similar filtration tools, and refillable water bottles 15. anti - bacterial soap, shop towels, and toilet paper. quite simply, ¬ † having these¬ † tools and¬ † equipment on hand¬ † will help you operate in a non - technological environment. investing in¬ † quality tools could assist in rebuilding your home and lives more quickly and efficiently. ¬ † a special thanks to all the relief workers who participated in rebuilding this island¬ † and¬ † giving¬ † hope back to the haitians. your volunteerism¬ † is a true act of kindness and a great example of the human spirit. this information has been made available by ready nutrition author : tess pennington author ' s web site : made available by : ready nutrition date : september 29th, 2011 related categories : preparedness, reserve supplies, world news