by dr. aleksandra drizo dr. aleksandra drizo, phosphoreduc llc. ceo, 70 south winooski avenue ; burlington, vt, usa 05405. corresponding author : firstname. lastname @ example. org phosphorus pollution problem water eutrophication caused by excess nutrient loading from human activities has been recognized as one of the major water quality issues for several decades ( 1, 2 ). the world resources institute has identified 415 hypoxic coastal zones in the world. the situation is even more alarming for freshwater resources with 54 % of lakes in asia, 53 % in europe, 48 % in north america, 41 % in south america and 30 % in africa being identified as eutrophic ( 3 ). although some environments are more greatly influenced by changing levels of nitrogen, addition of just 1 g of phosphorus promotes the growth of up to 100 g algae, and as such, represents the principal trigger of eutrophication and toxic blue - green algae blooms. the effect of algae blooms these blooms can decrease the oxygen levels in the waters, resulting in fish kills and reduced biodiversity. they can also cause foul odors and tastes, diminishing the recreational appeal of the waters or their potential for use as a water supply source. some species have even been found to release chemicals that are toxic to animals and humans. sources of phosphorus pollution given the magnitude of eutrophication worldwide, solutions for reducing phosphorus loading from municipal, agricultural, industrial, urban and rural point and nonpoint sources have been sought worldwide. while point source pollution is definable and thus controllable, nonpoint ( diffuse ) pollution originates from a variety of run - off sources, and consequently, controlling this type of contamination is even more complex, requiring an integration of technological, socio - economical and educational factors. methods of phosphorus removal methods for phosphorus removal from wastewaters and storm water runoff have emerged over the past few years. however, the current absence of the governmental regulations for phosphorus discharge limits, coupled with the extremely high costs of environmental technologies verification ( etv ) programs impose insurmountable obstacles in phosphorus removal technologies applications. current regulatory framework despite the recognized need for phosphorus reduction worldwide ( 2 - 5 ), the current regulatory framework for attenuation of this type of contamination has been extremely limited. phosphorus discharge criteria have been developed only for municipal wastewater treatment facilities ( mwtf ) and, in a very few developed countries. moreover, the current phosphorus removal methods ( either chemical or biological ) used in mw


was awarded the seed start - up funding that enabled me to establish my business phosphoreduc llc ( www. phosphoreduc. com ). the seed funding also provided necessary funding for patent applications. we currently have patents pending for the two of our technologies, one for phosphorus removal from point pollution sources and the other for phosphorus removal from agricultural and urban drain outflows. our filtration systems are passive systems consisting of one or more filter units filled with iron ( fe ) and / or calcium ( ca ) based filtration material, modified steel slag, a recyclable by - product from the steel industry. the filtration media is packed, arranged and engaged with one another in specially - designed modules so as to form a modular composite filter, according to the method developed by phopshoreduc llc. to date, we have demonstrated that phosphoreduc filter systems reduce phosphorous, suspended solids and pathogens ( e. coli ) loads from sewage, agricultural and urban point and nonpoint pollution sources by 70 – 100 percent by systems implemented in a variety of climatic regions, on 4 continents. the examples of phosphoreduc applications include : 1. agricultural runoff treatment : a simple cartridge system installed to reduce phosphorus and solids from agricultural tile drains collecting water from 30 acres in vermont achieved reductions averaging 72 % and 75 %, respectively ( figure 1 ). currently, there is no agricultural practice designed to reduce phosphorus loading from agricultural tile drains. we have showed that phosphorus concentrations measured in 6 different agricultural drains over 10 spring storm events exceeded critical 0. 1 - 0. 2 mg / l p concentrations for incipient eutrophication in each rain event. feed bunks ( silage leachate ) runoff treatment, known as one of the most toxic waste streams on farms. currently, the vegetative treatment area ( practice code 635 ) is the major “ best management practice ” recommended by the us natural resources conservation service ( nrcs ) and widely implemented to treat silage leachate runoff on farms in the us ( 7 ). while it cannot achieve more than 20 % phosphorus reduction efficiency, the current cost of this practice implementation is in order of $ 15, 220 per acre. the results from a 2 year investigation by our research team has shown that the implementation of an innovative “ treatment train ” consisting of a phosphoreduc filter, and a vegetative trench could achieve up to 90 % phosphorus reduction at half the cost of the currently recommended 635


by our research team has shown that the implementation of an innovative “ treatment train ” consisting of a phosphoreduc filter, and a vegetative trench could achieve up to 90 % phosphorus reduction at half the cost of the currently recommended 635 practice ( 8 ). 2. urban stormwater treatment phosphoreduc filter installed in columbus, oh to treat a golf - course stormwater pond achieved an average of 85 % reduction efficiency. several follow up installations are planned in 2012. 3. sewage treatment phosphoreduc filter has been implemented in southern taiwan to test system efficacy in sewage wastewater treatment originating from the university student residences. this system showed nearly 100 % reductions in dissolved and total phosphorus and suspended solids over 10 months of investigation ( 9 ). following successful treatment in taiwan, two filter installations are currently planned to reduce phosphorus loading originating from a mixed sewage and urban runoff effluent and causing eutrophication of tubarao lagoons in vitoria state, brazil. the future of innovative phosphorus removal technologies despite all of the above obstacles, during the past two years phosphoreduc technologies started to gain interest among governmental agencies in the us and internationally. we have contributed to eutrophication prevention and water quality improvements in over 40 laboratory, pilot, demonstration and full scale projects across 5 continents ( europe, north america, south america, asia, new zealand ). in sweden, professor gunno renman developed polonite based systems for phosphorus removal from residential septic systems. however, polonite filtration material is made from the natural calcium rich material found only in poland, which restricts systems applications beyond these two countries. in any future research and development of phosphorus removal technologies we ought to keep in mind the fact that as a key component of fertilizers, phosphorus is fundamental for the world ’ s food supplies, and an irreplaceable and essential element of life with its sole source as phosphate - bearing rocks ( 10 - 11 ). phosphorus resources are non - renewable with global reserves estimated to reach their peak in the next 50 - 100 years ( 10 ). the current rate of phosphate extraction is reported at 167 million tonnes per year with a growing demand that accounts for a 2 % annual increase. with continuing decline of global phosphate reserves, the impacts are likely be immense, particularly in terms of rising food prices, growing food insecurity and widening inequalities between developed and developing countries ( 10 - 11 ). thus, not only should we continue research, development and implementation


renman, g. ( 2011 ). the use of blast furnace and electric arc furnace steel slag in water pollution control. ferrous slag - resource development for an environmentally sustainable world. euroslag publication no. 5. pp 103 - 11. url : http : / / www. euroslag. org / about - us / history / conferencesdetail /? tx _ ttnews [ tt _ news ] = 19 & chash = ae437d3893598f2b5faf16f5edf6a16c. ( 7 ) usda nrcs ( 2008 ). vegetative treatment area practice 635. usda, natural resources conservation service ― practice code 635. url : http : / / www. nrcs. usda. gov / internet / fse _ documents / nrcs143 _ 026548. pdf ( 8 ) drizo, a., liang, k. and gorres, j. ( 2011 ). phosphorus and e. coli reduction from silage leachate via innovative phosphoreduc filtration. final report to the conservation innovations grants program, submitted december 2011. university of vermont grant agreement number : 69 - 3a75 - 9 - 121. ( 9 ) autm, the association of university technology managers ( 2011 ). academic filtration innovations aim to solve what ails a perishable resource : water. published in the 2011 edition of a better world report. respond, recover, restructure : technologies helping the world in the face of adversity, pp 78 - 83. www. betterworldrpoject. net ( 10 ) the broker ( 2009 ). peak phosphorus - the next inconvenient truth. the broker online 15, august 2009. url : http : / / globalpnetwork. net / resource / peak - phosphorus - next - inconvenient - truth ( 11 ) yoshida, h., van dijk, k., drizo, a., vanginkel, s., matsubae, k. and buehrer, m. ( 2011 ). chapter 6 : phosphorus recovery and reuse. in : dijk, k. and yoshida, h. ( ed. ). phosphorus, food and our future. frontiers in life sciences. in review.


what is iron deficiency? if you feel like your energy levels are low, you ’ re lacking motivation and you could fall asleep at your desk everyday, don ’ t blame your job right away. instead, take a close look at the signs and symptoms of iron deficiency. iron deficiency is the most prevalent nutrition deficiency in the world. it occurs when the body ’ s stores of iron are low ( the stage prior to anemia ), and, it may or may not cause any symptoms. iron deficiency disproportionately affects those in developing countries but it is also prevalent in industrialized countries. iron deficiency anemia develops when low iron stores persist for a period of time and the body cannot make enough healthy red blood cells to deliver oxygen throughout the body. in the united states, the largest nationwide survey, the national nutrition and health examination surveys ( nhanes ) found that approximately 16 % of teenage girls aged 16 - 19 and 12 % of women aged 20 - 49 are deficient in iron. these numbers are staggering in a country with an abundant food supply and an array of multivitamin and iron supplements. - stoltzfus rj. defining iron - deficiency anemia in public health terms : reexamining the nature and magnitude of the public health problem. j nutr 2001 ; 131 : 565s - 7s. - micronutrient deficiencies. iron deficiency anaemia. world health organization. http : / / www. who. int / nutrition / topics / ida / en / index. html - iron deficiency anemia. national anemia action council. http : / / www. anemia. org / patients / faq / # ida - iron deficiency. mmwr weekly. cdc. 2002 ; 51 ( 40 ) : 897 - 899. http : / / www. cdc. gov / mmwr / preview / mmwrhtml / mm5140a1. htm # tab1 - institute of medicine. food and nutrition board. dietary reference intakes for vitamin a, vitamin k, arsenic, boron, chromium, copper, iodine, iron, manganese, molybdenum, nickel, silicon, vanadium and zinc. washington, dc : national academy press, 2001. - monson er. iron and absorption : dietary factors which impact iron bioavailability. j am dietet assoc. 1988 ; 88 : 786 - 90. - tapiero h, gate l, tew kd. iron : deficiencies


the usa. japanese theorist sato tetsutaro developed the concept of a fleet at a minimum 70 % of the u. s. ' s. this would enable the japanese navy to win two decisive battles, the first early in a war, against the us pacific fleet, and the second against the us atlantic fleet which would inevitably be despatched as reinforcements. evans and peattie, kaigunjapan ' s first priority was to refit the pre - dreadnoughts she had captured from russia, and to complete satsuma and aki. like the south carolinas, the satsumas were designed before dreadnought, but gun shortages in britain ( which supplied them ) delayed her completion and resulted in her carrying a mixed armament, so she was known as a semi - dreadnought. these were followed by a modified aki - type : kawachi and settsu, which were laid down in 1909 and complete in 1912, and were armed with four 12 - inch / 50, eight 12 - inch / 45, ten 6 - inch / 45, and eight 4. 7 - inch / 40. " although nominally dreadnoughts, these ships did not have a really uniform main battery, since the guns differed in length, and therefore in performance, particularly at very long range. " page 229, gardiner, robert and gray, randal ( ed ) conway ' s all the world ' s fighting ships 1906 - 1921, conway maritime press, london, 1982. isbn 0 - 85177 - 245 - 5. this would have made fire control very difficult. dreadnoughts in other countries, a bretagne - class battleship. ] ] compared to the other major naval powers, france was slow to start building dreadnoughts, instead finishing the planned danton - class of pre - dreadnoughts, laying down five in 1907 and 1908. it was not until september 1910 the first of the courbet - class was laid down, making france the eleventh nation to enter the dreadnought race. the dreadnought race saw france drop from second to fifth in terms of naval power ; however, the closer alliance with britain made these reduced forces more than adequate for french needs. even though cuniberti had promoted the idea of an all - big - gun battleship in italy well before dreadnought, it took until 1909 for italy to lay down one of her own. the construction of dante alighieri was prompted by rumours of austro - hungarian dreadnought building. a further five dread


how machine learning can help to understand brain signals if a neurotechnological prosthesis should act upon commands from the brain, these have to be interpreted correctly. it is a challenging task because the amount of data is huge and the signals that the brain emits also change over time. computer scientists therefore want to leave it to learning machines to solve this ever - changing puzzle. | gunnar grah talked to martin riedmiller, machine learning lab | the usual way to make a computer do something goes like this : you decide what problem the machine is supposed to solve for you, then you write a programme that does exactly this. modern washing machines work that way. they have been told exactly what to do at what moment. this approach works very well for clearly defined problems, like getting dirt out of laundry. but there are many problems where solutions are not obvious, and the point of departure might always be a little bit different and require different solutions. in this case, computer scientists opt for letting the computer figure out the optimal solution for itself, an approach that is called “ machine learning ”. the human as trainer, not programmer machine learning resembles somewhat how humans acquire new skills, i. e. through examples, the structuring of a problem, and gaining experience. if, for instance, a computer is supposed to learn the different appearances of a broad - leaved tree and a conifer, a human “ trainer ” would provide the learning machine with examples of both classes, telling it in each case which class the tree on the picture belongs to. after some time, the computer will be able to correctly classify the presented trees, even though no human ever provided it with an actual list of things to look out for in order to master the task. if a problem requires not only a classification, but learning a complex procedure, like a robot walking on two legs without falling over, a trainer will at first be required to tell the machine whether an approach was “ good ” or “ bad ”. after sufficient training, the machine will master the problem and show some robustness in its solution, even if the situation varies slightly. also, a trained machine will be able to solve a new situation – e. g. the robot carrying something and therefore changing its weight distribution – faster than if it was starting from scratch. learning from the brain the secret of machine learning lies in the nature of the software that is at work at its base. a solution to a problem does not exist as specific lines of code that govern how the input from the


it was starting from scratch. learning from the brain the secret of machine learning lies in the nature of the software that is at work at its base. a solution to a problem does not exist as specific lines of code that govern how the input from the environment is dealt with in order to reach a desired outcome. instead, it employs an “ artificial neural network ”. this is a kind of programme that took its inspiration from the structure of the brain, where many individual items ( the nerve cells ) solve relatively simple problems ( like adding or multiplying values ), but are able to tackle much more complex tasks by being connected and existing in large numbers. an artificial neural network takes this concept into the realm of bits and bytes, but plays by the same rules. learning, just as in the real brain, manifests itself in the change of connections between individual neurons. these connectivity patterns between a multitude of mathematically represented nerve cells are where the solution to a given problem is stored. in consequence, there exists no neat equation that provides the solution, even though the final answer that the machine provides to a given problem is simple. the biological brain has acted as an inspiration, but computer scientists take this metaphor only as far as it is useful to them. to date, making the individual artificial neuron more and more complex, and thus ever more life - like, has not provided any real advantages, and software engineers therefore tend to go for what works best, not necessarily what comes closest to a real nerve cell. in terms of the general architecture however, natural evolution has led to time - tested concepts that are being exploited. machine learning programmes that analyse images, for instance, draw upon the structure of the visual cortex and the way how it breaks down the task into extracting individual features from a scene. using artificial networks to understand real ones within brainlinks - braintools, the task is a formidable one : machine learning is destined to help analysing signals recorded from brain activity. there is no intrinsic connection though that makes this link between a real and an artificial neural network something special : neither is machine learning the only approach to make sense of the activity of billions of nerve cells, nor is it less suitable to analyse completely different sets of data, like stock market developments. ultimately, machine learning should make it possible to read out movement commands from the brain ’ s surface. these could then be sent to a prosthesis or an assistive device like a robot – the use - case which the strategy “ linc ” within the cluster


learning should make it possible to read out movement commands from the brain ’ s surface. these could then be sent to a prosthesis or an assistive device like a robot – the use - case which the strategy “ linc ” within the cluster aims for. so far, it is an open question what kind of commands could actually be discriminated within the patterns of signals that electrodes can read out from the brain ’ s surface. could machine learning reliably identify the difference between different grasp movements, for instance as they are necessary to grab either a pen or a bottle? will the computer look for individual movements, or will it be able to extract whole intentions like “ i want to put the bottle back into the fridge ”? such higher concepts would be an elegant way to steer a prosthetic arm. the user would not have to think all commands in the right order and with the right extent, but could leave it to the autonomously planning prosthesis to figure out the best way after sending a general command. however, there is a pitfall : in abstract concepts, it might become even more difficult to know what the activity pattern actually stands for. we might find an activity pattern that appears every time that the person thinks “ fridge ”, but it might actually stand for an association that the person makes, like “ cold ”. between the infinite number of possible thoughts and possible connections, this will be an ambitious challenge for data analysis by machine learning. furthermore, it remains to be seen how many activity patterns are identical between individuals. ideally, a patient should not have to go through lengthy training sessions to teach the system all manners of different movements from scratch, but the device should arrive with some pre - installed knowledge of the most basic patterns. even then, there would be enough that the system would have to learn in order to adapt to the individual patient. after all, no two brains – not even those of twins – are identical. and it is very likely that the same holds true for the brain ’ s activity patterns. but computer scientists are optimistic that these training sessions would not take too long – rather minutes or hours than days and weeks. but machine learning is not only a useful tool on the user ’ s end. likewise, artificial neural networks could come in handy to help a robotic arm or other assistive device to execute movements and find the ideal action to reach a certain goal. what makes machine learning an attractive candidate for this task it that its artificial neural network learned the solution to a problem and wasn ’ t spoon -


stressarticle free pass stress, in physical sciences and engineering, force per unit area within materials that arises from externally applied forces, uneven heating, or permanent deformation and that permits an accurate description and prediction of elastic, plastic, and fluid behaviour. a stress is expressed as a quotient of a force divided by an area. there are many kinds of stress. normal stress arises from forces that are perpendicular to a cross - sectional area of the material, whereas shear stress arises from forces that are parallel to, and lie in, the plane of the cross - sectional area. if a bar having a cross - sectional area of 4 square inches ( 26 square cm ) is pulled lengthwise by a force of 40, 000 pounds ( 180, 000 newtons ) at each end, the normal stress within the bar is equal to 40, 000 pounds divided by 4 square inches, or 10, 000 pounds per square inch ( psi ; 7, 000 newtons per square cm ). this specific normal stress that results from tension is called tensile stress. if the two forces are reversed, so as to compress the bar along its length, the normal stress is called compressive stress. if the forces are everywhere perpendicular to all surfaces of a material, as in the case of an object immersed in a fluid that may be compressed itself, the normal stress is called hydrostatic pressure, or simply pressure. the stress beneath the earth ’ s surface that compresses rock bodies to great densities is called lithostatic pressure. shear stress in solids results from actions such as twisting a metal bar about a longitudinal axis as in tightening a screw. shear stress in fluids results from actions such as the flow of liquids and gases through pipes, the sliding of a metal surface over a liquid lubricant, and the passage of an airplane through air. shear stresses, however small, applied to true fluids produce continuous deformation or flow as layers of the fluid move over each other at different velocities like individual cards in a deck of cards that is spread. for shear stress, see also shear modulus. reaction to stresses within elastic solids causes them to return to their original shape when the applied forces are removed. yield stress, marking the transition from elastic to plastic behaviour, is the minimum stress at which a solid will undergo permanent deformation or plastic flow without a significant increase in the load or external force. the earth shows an elastic response to the stresses caused by earthquakes in the way it propagates seismic waves, whereas it undergoes plastic deformation beneath the surface under


the influence of alcohol or drugs. - wearing a helmet and making sure your children wear helmets when : - riding a bike, motorcycle, snowmobile, scooter, or all - terrain vehicle ; - playing a contact sport, such as football, ice hockey, or boxing ; - using in - line skates or riding a skateboard ; - batting and running bases in baseball or softball ; - riding a horse ; or - skiing or snowboarding. - making living areas safer for seniors, by : - removing tripping hazards such as throw rugs and clutter in walkways ; - using nonslip mats in the bathtub and on shower floors ; installing grab bars next to the toilet and in the tub or shower ; - installing handrails on both sides of stairways ; - improving lighting throughout the home ; and - maintaining a regular physical activity program, if your doctor agrees, to improve lower body strength and balance. 1, 2, 3 - making living areas safer for children, by : - installing window guards to keep young children from falling out of open windows ; and - using safety gates at the top and bottom of stairs when young children are around. - making sure the surface on your child ' s playground is made of shock - absorbing material, such as hardwood mulch or sand. 4 - judge jo, lindsey c, underwood m, winsemius d. balance improvements in older women : effects of exercise training. physical therapy 1993 ; 73 ( 4 ) : 254 – 265. - lord sr, caplan ga, ward ja. balance, reaction time, and muscle strength in exercising older women : a pilot study. archives of physical and medical rehabilitation 1993 ; 74 ( 8 ) : 837 – 839. - campbell aj, robertson mc, gardner mm, norton rn, buchner dm. falls prevention over 2 years : a randomized controlled trial in women 80 years and older. age and aging 1999 ; 28 : 513 – 518. - mack mg, sacks jj, thompson d. testing the impact attenuation of loose fill playground surfaces. injury prevention 2000 ; 6 : 141 – 144.


evidence suggests that life originated in extreme environments, for example, at high temperatures. the national science foundation ( nsf ) has initiated a program called life in the extreme environment ( lexen ) that is dedicated to finding new and exciting organisms that live in harsh environments. the extreme 2000 research expedition, at hydrothermal vent sites in the sea of cortes, is led by marine scientists george luther and craig cary from the university of delaware and anna - louise reysenbach from portland state university. their chief objective is to make real - time chemical measurements at the vents using microsensors developed by dr. luthers group, which will guide the microbiologists and molecular biologists in dr. carys and dr. reysenbachs groups in finding organisms that are descendants of early chemical detective work at the bottom of the sea hydrothermal vents home to the closest relatives of the oldest life on earth? using special tools housed in a wand on the sub alvin, researchers will be testing the chemistry of vent water in search of microscopic organisms. the wand houses a thermometer, an apparatus called the sipper to collect small water samples, and a super - sensitive the analyzer is like a sophisticated underwater snooper. it can be used near the vents and, from its chemical readings, tell scientists what kind of microbes might live there. while our food chain is based on energy from the sun, the suns rays never reach the deep sea. there, organisms must rely on a different energy source : the chemicals that rocket out of the vents. during a previous expedition, the extreme 2000 scientific team found that the presence of two compounds hydrogen sulfide ( h2s ) and iron monosulfide ( fes ) may be an important indicator of the oldest microscopic vent life. these compounds react to form the mineral pyrite ( fools gold ) and hydrogen gas. the hydrogen provides the energy that these microbes need to grow. with the analyzers help, marine scientists may be able to track down the nearest descendants of the first life on earth, and perhaps on other planets. europa, one of the moons of jupiter, is covered in ice. however, recent findings suggest that portions of the ice move, which is strong evidence that liquid water lies beneath the ice. the water may be maintained in its liquid state by hydrothermal vents. if hydrothermal vents exist on europa, theres a possibility that ancient microbes could live


in march 2011, the u. s. computer security company rsa announced that hackers had gained access to security tokens it produces that let millions of government and private - sector employees, including those of defense contractors such as lockheed martin, connect remotely to their office computers. most critical information systems in the united states are operated by the private sector and remain vulnerable to cyber attacks. newly proposed legislation would require businesses to meet minimum standards of protection, but has raised concerns about regulatory overreach. grounded in a realistic assessment of technology, matthew c. waxman and kenneth anderson outline a practical alternative with which to evaluate the use of autonomous weaponry that incorporates codes of conduct based on traditional legal and ethical principles governing weapons and warfare. adam segal says the recent chinese cyberattacks on bloomberg and the new york timeshighlights both the willingness of beijing to shape the narrative about china, as well as the vulnerability the top leadership feels about how they are portrayed. cyber weapons are different from conventional weapons in that their effects do not directly manifest themselves in the " real world. " there are three broad categories of potential effects of cyberattacks : personal, economic, and physical. adam segal, cfr ' s maurice r. greenberg senior fellow for china studies, leads a conversation on u. s. - china relations through the lens of cybersecurity issues, as part of cfr ' s academic conference call series. linda robinson discusses her recently released council special report, the future of u. s. special operations forces, which calls for conceptual, institutional, and operational changes to reorient u. s. special operations forces to ensure that they are employed to best effect. foreign governments, non - state actors, and criminal networks are targeting the digital networks of the united states with increasing frequency and sophistication. u. s. cybersecurity has made progress, but relies heavily on the private sector to secure infrastructure critical to national security. cybersecurity expert knake recommends the united states use international forums to promote mechanisms that address security concerns in cyberspace while ensuring the internet remains open for the free exchange of ideas across national boundaries. the council on foreign relations ' david rockefeller studies program — cfr ' s " think tank " — is home to more than seventy full - time, adjunct, and visiting scholars and practitioners ( called " fellows " ). their expertise covers the world ' s major regions as well as the critical issues shaping today ' s global agenda. download the printable cfr experts guide.


an ambulatory electrocardiogram ( ekg or ecg ) records the electrical activity of your heart while you do your usual activities. ( ambulatory means that you are able to walk. ) ambulatory monitors are referred to by several names, including ambulatory electrocardiogram, ambulatory ekg, holter monitoring, 24 - hour ekg, or cardiac event monitoring. many heart problems become noticeable only during activity, such as exercise, eating, sex, stress, bowel movements, or even sleeping. a continuous 24 - hour recording is more likely to detect any abnormal heartbeats that occur during these activities. many people have irregular heartbeats ( arrhythmias ) from time to time. the importance of irregular heartbeats depends on the type of pattern they produce, how often they occur, how long they last, and whether they occur at the same time you have symptoms. because arrhythmias can occur off and on, it may be hard to record an arrhythmia while you are in the doctor ' s office. there are several different types of ambulatory monitors. your doctor will choose the type that is most appropriate for you and is most likely to help diagnose your heart problem. why it is done ambulatory ekg monitoring is done to : - look for and record irregular heartbeats that occur intermittently or during certain activities. - find out what is causing chest pain, dizziness, or fainting. these are symptoms of possible heart problems. - look for poor blood flow to your heart muscle ( ischemia ). - check to see if treatment for an irregular heartbeat is working. how to prepare many medicines may change the results of this test. be sure to tell your doctor about all the nonprescription and prescription medicines you take. since an ekg is often used to monitor a preexisting heart condition, such as an irregular heartbeat ( arrhythmia ), make sure that your doctor has copies of any previous ekg results. take a shower or bath before the discs are put on. you will not be able to get the discs wet during the test. wear a loose blouse or shirt. do not wear jewelry or clothes with metal buttons or buckles, because these can interfere with the recording. women should not wear an underwire bra for the same reason. if your doctor asks you to keep a symptom and activity diary, be sure you have a method. in this diary, you will record


| tests and services inhalation therapy instruction what is a peak flow meter? a peak flow meter ( pfm ) is a device used to measure how well your child ' s asthma is under control. the device measures air flowing out of the lungs, called peak expiratory flow rate ( pefr ), as a child with asthma forcefully blows into the device. a peak flow meter, when used properly, can reveal narrowing of the airways well in advance of an asthma attack. used mainly by children with moderate to severe and persistent asthma, peak flow meters can help determine : why should a peak flow meter be used? - when to seek emergency medical care. - the effectiveness of your child ' s asthma management and treatment plan. - when to stop or add medication, as directed by your child ' s physician. - what triggers the asthma attack ( such as exercise - induced asthma ). the pfm removes a lot of guesswork out of managing your child ' s asthma. it can provide you, your child ' s physician, or even the school teachers with information about how open the airways are in your child ' s lungs. the pfm can detect small changes in the large airways before your child starts to wheeze. using a pfm every day will let you know when your child ' s peak flows are starting to drop. this allows you to make early changes in your child ' s medication or routine to help prevent your child ' s asthma symptoms from getting worse. the pfm can also identify the value at which you will need to call your child ' s physician or go to the emergency room. how to use a peak flow meter : what are peak flow zones? - use the pfm once daily and whenever your child is experiencing early warning signs. always use the pfm before taking reliever medication. - hold the pfm by the handle. - before each use, make sure the pointer is reset to zero. - have your child stand up straight. remove chewing gum or any food from your child ' s mouth. - have your child take a deep breath and put the mouthpiece in his / her mouth. seal his / her lips and teeth tightly around the mouthpiece. - let your child blow out as hard and as fast as he / she can. remember a fast blast is better than a slow blow. - note the number where the pointer has stopped on the scale. - reset the pointer to zero. - repeat this routine three times. you will know your child has done the technique correctly when the numbers


, and the effectiveness of your child ' s medications ) to your child ' s physician. - every morning, before taking asthma medications - during asthma symptoms or an asthma attack - after taking medication for an asthma attack - other times as recommended by your child ' s physician how can i obtain a peak flow meter? consult your child ' s physician about obtaining a peak flow meter and for step - by - step instructions on how to use the device. if you are using more than one peak flow meter, be sure they are the same brand. what are oximeters? an oximeter is a small machine that measures oxygen saturation ( the amount of oxygen ) in your child ' s blood. to get this measurement, a small sensor ( similar to an adhesive bandage ) is taped onto your child ' s finger or toe. when the oximeter is on, a small red light can be seen in the sensor. the sensor is painless and the red light does not get hot. what is a spirometer? a spirometer is a device used by your child ' s physician that assesses lung function. spirometry, the evaluation of lung function with a spirometer, is one of the simplest, most common pulmonary function tests and may be necessary for any of the following reasons : after taking a deep breath, your child forcefully breathes out into the spirometer as completely and forcefully as possible. the spirometer measures both the amount of air expelled and how quickly the air was expelled from the lungs. the measurements are recorded by the spirometer. - to determine how well the lungs receive, hold, and utilize air - to monitor a lung disease - to monitor the effectiveness of treatment - to determine the severity of a lung disease - to determine whether the lung disease is restrictive ( decreased airflow ) or obstructive ( disruption of airflow ) the normal, healthy values measured by the spirometer for the amount of air exhaled vary from child to child. your results are compared to the average expected in someone of the same age, height, sex, and race, according to the national heart, lung, and blood institute ( nhlbi ). however, if the values fall below 85 percent of the average, it may indicate a lung disease or other airflow obstruction. if a child has abnormal spirometer measurements, he / she may be referred for other lung tests to establish a diagnosis. hand - held nebulizer treatments a nebulizer is a type of inhaler that sprays a fine


obstruction. if a child has abnormal spirometer measurements, he / she may be referred for other lung tests to establish a diagnosis. hand - held nebulizer treatments a nebulizer is a type of inhaler that sprays a fine, liquid mist of medication. this is done through a mask, using oxygen or air under pressure, or an ultrasonic machine ( often used by persons who cannot use a metered - dose inhaler, such as infants and young children, and persons with severe asthma ). a mouthpiece is connected to a machine via plastic tubing to deliver the medication. the medications used in nebulizers help your child by loosening the mucus in the lungs so it can be coughed out more easily, and by relaxing the airway muscles so that more air can move in and out of the lungs. breathing the medication straight into the lungs works better and faster than taking the medication by mouth. nebulizer treatments take about 15 to 20 minutes to give the medication. giving a treatment : the following steps are recommended when giving a treatment to your child. however, always consult your child ' s physician for specific instructions. after each treatment : gather supplies needed, including : - medication to be nebulized - nebulizer set ( nebulizer cup, mouthpiece or mask, tubing to connect to nebulizer machine ) - find a quiet activity to do while your child sits up for the treatment ( i. e., reading a book or playing a quiet game ). - place the nebulizer on a flat surface ( i. e., table or the floor ). - plug the unit into a wall outlet. - connect the air tubing to the nebulizer machine. - put the medication into the nebulizer cup and screw the cap on securely. - connect the other end of the air tubing to the nebulizer cup. - connect the mouthpiece or face mask to the nebulizer cup. - turn the machine on. - check to make sure a fine mist of medication is coming through the face mask or mouthpiece. - place the mouthpiece in the child ' s mouth with the lips sealed around the mouthpiece. - encourage your child to take slow deep breaths in and out of their mouth. the mist should disappear with each breath. - place the mask over your child ' s mouth and nose. the adjustable elastic band may be used to hold the mask in place. - encourage your child to take deep breaths in and out for the


adolescent medicine : : orthopaedic problems what is scoliosis? a normal spine, when viewed from behind, appears straight. however, a spine affected by scoliosis shows evidence of a lateral, or sideways, curvature, and a rotation of the back bones ( vertebrae ), giving the appearance that the person is leaning to one side. the scoliosis research society defines scoliosis as a curvature of the spine measuring 10 degrees or greater on x - ray. scoliosis is a type of spinal deformity and should not be confused with poor posture. four common types of curve patterns seen in scoliosis are : what causes scoliosis? in most ( 80 to 85 percent ) cases, the cause of scoliosis is unknown - a condition called idiopathic scoliosis. scoliosis is more common in females than males. according to the national institute of arthritis and musculoskeletal and skin diseases, three to five out of every 1, 000 children develop spinal curves that are considered large enough to require treatment. the american academy of orthopaedic surgeons, in cooperation with the scoliosis research society, describe three different types of scoliosis that can occur in children - congenital ( present at birth ), neuromuscular, or idiopathic. other causes of scoliosis may include : what are the symptoms of scoliosis? the following are the most common symptoms of scoliosis. however, each adolescent may experience symptoms differently. symptoms may include : back pain, leg pain, and changes in bowel and bladder habits are not commonly associated with idiopathic scoliosis. a adolescent experiencing these types of symptoms requires further medical evaluation by a physician. the symptoms of scoliosis may resemble other spinal conditions or deformities, or may be a result of an injury or infection. always consult your adolescent ' s physician for a diagnosis. how is scoliosis diagnosed? the physician makes the diagnosis of scoliosis with a complete medical history of the adolescent, physical examination, and diagnostic tests. the physician obtains a complete prenatal and birth history of the adolescent and asks if other family members are known to have scoliosis. the physician will also ask about developmental milestones since some types of scoliosis can be associated with other neuromuscular disorders. developmental delays may require further medical evaluation. in addition to a complete medical history and physical examination, x - rays ( a diagnostic test which uses invisible electromagnetic energy beams to


the success of a concurrent system depends on well designed hardware, flexible software that controls the hardware, and clear marketing vision. to adapt the changing marketing requirement, hardware and software need to have flexible architectures. this article is focused on software development issues, and discusses concurrency design at application layer as opposed to concurrency inside the operating system. any multi - threaded system can be considered a concurrent system ; for example, a lengthy task can be implemented as a background thread so that it will not block the graphical user interface. here, we are discussing concurrent systems which can be characterized by the following traits : - system input and output can be clearly identified. - system internal consists of system resources, such as hardware modules, which are used to process system input and generates system output. - one or more execution steps are needed for a system input to be processed by system resources and to become a system output. - the system resources and their relationship are identified by system analysis. the concurrency properties of system resources determine the constraints between execution steps, which ultimately define the system concurrency behavior. the above description can be illustrated in figure 1. the system consists of three resources : 2 inputs and 2 outputs. each input needs to go through two steps to become output. resources 1 and 2 are independent and can be parallel. the output of resources 1 and 2 are the input of resource 3, which is independent of 1 and 2. figure 1. a sample concurrent system most concurrent systems have these design goals : - have an easy to understand software architecture so that the desired concurrency can be implemented and verified quickly. - have a solid system concurrency kernel to adapt system environmental changes such as inconsistent hardware responses, and still achieve high system reliability. - have a good scalable architecture to adapt new requirement changes. - system concurrency and throughput are well understood by all teams involved in the system specification and design, not just by a few key software engineers. therefore, the concurrent software should expose how the current system internally works with minimum cost, so that the team communications can be conducted effectively. - different system concurrencies can be achieved with different execution configurations without major interruption to the system reliability. for a complex concurrent system, the design cost to achieve such goals could be very high for inexperienced engineers. most systems end up with only a few engineers who can understand and maintain the fragile concurrent kernels. what is needed to meet the concurrent system design goal from a management perspective? - to have the capability to quickly understand the marketing or hardware concurrency requirement, and to provide a clear road map on how to


can understand and maintain the fragile concurrent kernels. what is needed to meet the concurrent system design goal from a management perspective? - to have the capability to quickly understand the marketing or hardware concurrency requirement, and to provide a clear road map on how to achieve the desired software system concurrency at an early stage of development, not when delivering the alpha or beta product. this requires the software engineer to have a clear understanding of the system resource concurrency at the very beginning. - to shorten the cycle of turning the desired concurrency into a real functioning software system. - to communicate the achievable concurrency goal to other teams frequently, and to adjust the concurrency accordingly based on new marketing input, or new resource constraints improvements or limitations, such as hardware. the followings are common issues found in a concurrent software design : - the software team member is not very experienced in concurrency design. most teams have engineers knowing threads, critical sections, semaphores, and events. but, this usually does not guarantee achieving the design goals listed above. - the understanding of system concurrency is very slow. the software engineer could not present a full picture of how the system concurrency design is going to be working until the alpha or beta stage. therefore, nobody will question how the system concurrency is designed since there is no good method to communicate the software design. the engineer usually gives you his / her understanding of the system concurrency on small pieces, which is hard to convince the software team manager or other teams that the software team has fully understood the system and will be able to deliver on schedule. - the marketing group has a wrong system throughput assumption and commitment at the beginning of a project, with false understanding of the system resource constraints, or the complexity for available engineers to achieve the desired high throughput without sacrificing software system reliability. the marketing group might assume that software engineers could just achieve it, but have no way to verify it during the process until it is too late. - almost all designs do not have a clear distinction between the code controlling the system resource operation and the code performing the system resource concurrency. this architecture makes it very hard to enhance upon new concurrency requirements. by simply using a synchronization object, such as a critical section, event, or semaphore from the operating system, it ' s almost impossible to perform such a partition without a major investment on the system architecture design. unfortunately, most applications do not separate the two domains and let one engineer handle all of them, who is already overwhelmed by the concurrency choreography. the software


it ' s almost impossible to perform such a partition without a major investment on the system architecture design. unfortunately, most applications do not separate the two domains and let one engineer handle all of them, who is already overwhelmed by the concurrency choreography. the software manager usually does not understand the importance of such a design, or they don ' t have the time to spend on infrastructure building, and just want to see something is beginning to work. the result is that more time will be wasted during debugging and the feature enhancement period. - the fragile concurrency architecture is hard to understand. it is almost impossible for new engineers to take over the design, except to abandon the old one, and then propose a " better architecture " which usually goes through the same design cycle and delays the schedule. the software manager usually is not aware of the engineer ' s redesign approach except to accept it, since both the engineer and manager have no choice to improve the old architecture. - the manager and software engineer mistakenly think that object oriented analysis of the concurrent hardware modules will guarantee a good concurrent software design which delivers a flexible concurrent software architecture. most ooa just help engineers to identify objects in a system without concurrency analysis, and engineers have to use a synchronization object in the operating system to address concurrency. if this approach is used, it will not help achieve the concurrent system design goals listed above. unfortunately, most systems are designed with such approach. - engineers begin to experience an unexplained hang, and begin to put a sleep function somewhere to solve weird timing problems, simply because the understanding of system resource concurrency is not complete at the beginning, and the design can not adapt to a different running environment. when switching to different platforms, such as a faster machine, software needs major retest, or a possible overhaul. and the engineer and the manager begin to hide facts from the upper manager. the development cost goes up, and the software always needs major " improvements " to adapt to a new hardware with a newly tuned concurrency, which should not happen if it is well designed at the beginning. - typically, the design of a system concurrency is architected by a senior person in a team, and it is very hard for other people to challenge the delicate design. system maintenance and enhancement for the concurrency part is a major issue with such a design approach. how to address those issues the cost of making a complex concurrent system flexible and reliable is extremely high for average engineers who simply use the operating system ' s critical section, semaphore, event, and


a major issue with such a design approach. how to address those issues the cost of making a complex concurrent system flexible and reliable is extremely high for average engineers who simply use the operating system ' s critical section, semaphore, event, and thread. to address the above problems, we need to develop a platform to help engineers in modeling a concurrent system with an easily understood object model, communicating the design by a user friendly graphical user interface, and verifying the internal concurrency of the design quickly by simulation. - a simple concurrent object model is needed. an object oriented analysis method based on the model should be easy to perform. - an inter - task communication mechanism is provided based on the object model to allow task synchronization. - a design development toolkit is needed to support the object oriented analysis, and helps software engineers to spend more time on understanding the system concurrency, and system resource controlling during implementation, instead of struggling with multithreaded code that is implemented with operating system synchronization objects such as critical sections, semaphores, and events. - the design platform provides a graphic presentation of the system concurrent execution status that helps software engineers to present and to validate a design effectively. eventually, it will help the whole team, even different groups, to understand the system concurrency internals. - the object model and its development toolkit allow separation of the code performing system resource concurrency and the code performing system resource control. in figure 1, the code controlling resource 1 is a resource control domain. the code controlling independent resources 1 and 2 to operate in parallel is a system resource concurrency domain. this architecture helps the manager to partition the concurrent system design work into two domains so that it can be assigned to different engineers to improve team productivity and product reliability. usually, a manager will not offer a resource to implement above the environment to help the design long term, since it is very time consuming and no immediate results can be seen. jek platform is designed to address these issues with the above concurrent system design goals, and makes concurrent problems easier to model for software engineers. jek sdk automatically turns a modeled application job into a concurrent execution engine. the object model also separates the resource synchronization code and the resource control code, so that the engineer can spend more time understanding system concurrency, instead of dealing with operating system synchronization objects, which is used by most software engineers. it will also help the engineer to spend more time communicating their understanding of the system concurrency within a team, or with other


more time understanding system concurrency, instead of dealing with operating system synchronization objects, which is used by most software engineers. it will also help the engineer to spend more time communicating their understanding of the system concurrency within a team, or with other teams. here, two samples are presented ( please go to www. jekplatform. com / codeprojectsamples. htm to get the source code ) to demonstrate how the jek platform works : - sample 1 : philosophers dining problem. - sample 2 : automated coffee machine. sample 1. philosophers dining problem the philosophers dining problem is five philosophers sitting around a table doing what they do best : thinking and eating. in the middle of the table is a plate of food, and in between each philosopher is a fork. the philosophers spend most of their time thinking, but when they get hungry, they reach for the two forks next to them and start eating. a philosopher cannot begin eating until he has both forks. when he is done eating, he puts the sticks down and continues thinking. to solve the problem with jek platform, five routes are defined to represent the actions of five philosophers. each route has two tasks : eat and think. obviously, eat task of each philosopher ' s route can not be active at the same time because of resource constraints. a mutex synchronization resource is used to restrict the eat task of each philosopher. the resource allocation scheduling algorithm in the jek kernel has an important feature to avoid a deadlock in this sample : if one philosopher gets a fork and finds another is already taken, it will release the one and notify other tasks in other routes so that other philosopher can continue to eat. the following diagram, figure 2, illustrates the philosopher dining job execution engine ' s timing diagram. the application code is pretty simply since it does not need to handle threads and thread synchronization that is handled in the jek sdk, but simply describes the resources ( forks ) and tasks ( philosophers ' actions ). figure 2. jek studio monitors the philosophers dining job execution in figure 2, jek studio gui has four components illustrated by four yellow bubbles : - the task matrix presents the application engine internal structure and the real - time execution activity status. - the task timing diagram presents a more detailed real - time execution status for tasks, which helps developers to understand and to validate concurrent system behavior quickly. - the activity resource matrix presents real - time task activity resource status. - the synchronization resource matrix presents real


presents a more detailed real - time execution status for tasks, which helps developers to understand and to validate concurrent system behavior quickly. - the activity resource matrix presents real - time task activity resource status. - the synchronization resource matrix presents real - time task occupy status. - the task trace window displays log status, which is also saved in a log file. in jek studio, five routes are shown in the task matrix. its execution is shown in the task execution timing diagram. the four blue bubbles are explained as follows : - blue bubble 1. job execution engine starts to execute job. philosophers 1 and 4 start to eat. - blue bubble 2. philosophers 3 and 5 start to eat at the same time. philosophers 1 and 4 start to rest at the same time. the reason that philosopher 3 and 5 can start to eat at the same time is because the application code is configured so that the eat time for all philosophers are the same. the rest times are also the same for all philosophers. - blue bubble 3. it ' s interesting to observe the job execution status after a few loops. philosophers 1, 2, 4 are resting. philosophers 3 and 5 are eating. if observed carefully, philosophers 3 and 5 are not starting to eat at the exact same time. philosophers 1, 2, 4 do not rest at the same time. - blue bubble 4. this is another interesting job execution status. only one philosopher, # 2, is eating at this moment. philosophers 1, 3, 4, 5 are all resting. the reason, the resting times of all philosophers are longer than eating times. - another observation is that fairness is not guaranteed for each route. it ' s unpredictable which philosopher will get a chance to eat next time based on the scheduler used. - route starvation is possible. in other words, some philosophers might never get a chance to eat. this is not demonstrated in the graph since the result is random. you can try to start the engine a few times and the results could be different each time. if not using simulation, it is very hard for a software engineer to answer : if scenarios marked by the blue bubbles 3 and 4 are possible. sample 2. automated coffee machine an automated coffee machine mixes milk, sugar, and coffee into a cup, and serves the cup to customer when it is done. figure 3. coffee machine model analysis the coffee machine has five robots : - platform robot. it holds the coffee cup, so that milk, sugar, and coffee can be poured into it and gets mixed


displayed with different y axis values. multiple bars in the same y axis represent the same task executed at different times. route 1 controlling milk, sugar, and coffee robot ( orange color ) has three tasks from bottom to top : - task1 _ 1 : control milk robot to pour milk. - task1 _ 2 : control sugar robot to pour sugar. - task1 _ 3 : control coffee robot to pour coffee. route 2 controlling cup robot ( blue ) has two tasks from bottom to top : - task2 _ 1 : control cup robot to put cup onto platform robot. - task2 _ 2 : control platform robot to serve mixed coffee to customer. the six blue bubbles in figure 4 are explained as follows : - blue bubble 1. task2 _ 1 puts a cup onto the platform robot. - blue bubble 2. task1 _ 1 and task1 _ 2 pour milk and sugar into an empty cup at the same time. - blue bubble 3. task1 _ 2 finishes pouring sugar and task1 _ 1 is still pouring milk. - blue bubble 4. task1 _ 3 starts pouring coffee. - blue bubble 5. task2 _ 2 controls the platform robot to serve mixed coffee. - blue bubble 6. repeat the same process. figure 4. coffee machine execution status of solution 1 this robot is not very efficient. route 1 is idle after blue bubble 5. to increase the throughput, another independent platform robot is added to make route 1 as busy as possible. the position of platform robot 1 is different from that of platform robot 2. therefore, the control code for pouring milk, sugar, and coffee is different in context, but have the same structure. figure 5 is a new robot diagram. figure 5. platform 2 robot is added route 3 ( burgundy red color ) is added to serve second cup, which is presented as red in figure 6. it has identical tasks as defined in route 2. since a new platform robot is added, route 2 and 3 are redefined as follows : route 2 controlling cup robot ( blue ) has two tasks : - task2 _ 1 : control cup robot to put cup onto platform robot 1. - task2 _ 2 : control platform robot 1 to serve mixed coffee to customer 1. route 3 controlling cup robot ( burgundy red ) has two tasks : - task3 _ 1 : control cup robot to put cup onto platform robot 2. - task3 _ 2 : control platform robot 2 to serve mixed coffee to customer 2. figure 6. solution 2 coffee machine has two platform robots the five


the actions of serving sugar, milk, and coffee to platform robot 2. the design of route 3 and 4 are the same as before. figure 7 is the timing diagram of a new coffee machine. figure 7. new concurrency of higher system throughput for the coffee machine with 2 platform robots the five blue bubbles in figure 7 are explained as follows : - blue bubble 1. task4 _ 1 puts cup onto platform robot 1. - blue bubble 2. task1 _ 1 and task1 _ 2 pour milk and sugar into empty cup at the same time to the cup platform robot 1. the cut robot starts to put a cup on platform 2 since it is free at this time. - blue bubble 3. task2 _ 2 starts to add sugar into cup 2 on platform robot 2. the reason that this action can happen is that the sugar robot just finishes adding sugar for cup 1 on platform robot 1. it is also clear that the milk robot is still busy pouring milk into cup 1. therefore, cup 2 only has sugar for now. - blue bubble 4. task2 _ 1 starts to pour milk into cup 2 since it just finishes pouring milk for cup 1 on platform robot 1. coffee robot begins to add coffee into cup 1 on platform robot 1. - blue bubble 5. cup robot begins to serve cup 1 to customer since coffee is done for cup 1. it is obvious that the choreography of this new coffee machine is different from that of the previous coffee machine. it appears to a user that its robots are smarter and works more intelligently since it starts to do the next job more promptly. the above three samples demonstrate the following : - it is easy to model and to analyze the concurrency of machine control with the jek platform. - to adapt to a new hardware configuration, the jek sdk helps achieve new system concurrency with minimum code changes. - jek studio can visually identify system throughput potential quickly so that better throughput can be achieved. - the samples demonstrated in these solutions have a pretty simple architecture ( see downloaded code ). if not using the jek platform, can we solve the problem quickly? a few questions are raised here. - if several teams, such as marketing, hardware, and software, are working on the product, they might stop when solution 2 is working. do they know that solution 3 is the best solution? can they figure it out quickly? - team members might be satisfied when they see that robots are working in parallel. if it is found that improvements can be made, how much code change


this multimedia lesson for grades 7 - 10 explores the physical forces that act in concert to create snowflakes. students build an apparatus that creates conditions similar to a winter cloud and produce their own snow crystals indoors. by watching the snow crystals grow, they learn about how snowflake size and shape is determined by the forces that act on water molecules at the atomic and molecular levels. digital models and snowflake photo galleries bring together a cohesive package to help kids visualize what ' s happening at the molecular scale. editor ' s note : this lab activity calls for dry ice. see related materials for a link to the noaa ' s " dry ice safety " guidelines, and for a link to snow crystal images produced by an electron microscope. lewis structures, vsepr, condensation, covalent bond, crystals, electron sharing, ice, physics of snowflakes, snow formation, valence electrons, valence shell metadata instance created january 2, 2013 by caroline hall january 2, 2013 by caroline hall aaas benchmark alignments ( 2008 version ) 4. the physical setting 4b. the earth 6 - 8 : 4b / m15. the atmosphere is a mixture of nitrogen, oxygen, and trace amounts of water vapor, carbon dioxide, and other gases. 4d. the structure of matter 6 - 8 : 4d / m1a. all matter is made up of atoms, which are far too small to see directly through a microscope. 6 - 8 : 4d / m1cd. atoms may link together in well - defined molecules, or may be packed together in crystal patterns. different arrangements of atoms into groups compose all substances and determine the characteristic properties of substances. 6 - 8 : 4d / m3cd. in solids, the atoms or molecules are closely locked in position and can only vibrate. in liquids, they have higher energy, are more loosely connected, and can slide past one another ; some molecules may get enough energy to escape into a gas. in gases, the atoms or molecules have still more energy and are free of one another except during occasional collisions. 9 - 12 : 4d / h2. the number of protons in the nucleus determines what an atom ' s electron configuration can be and so defines the element. an atom ' s electron configuration, particularly the outermost electrons, determines how the atom can interact with other atoms. atoms form bonds to other atoms by transferring or sharing electrons. 9 - 12 : 4d / h7a. atoms often join with one another in various


electron configuration, particularly the outermost electrons, determines how the atom can interact with other atoms. atoms form bonds to other atoms by transferring or sharing electrons. 9 - 12 : 4d / h7a. atoms often join with one another in various combinations in distinct molecules or in repeating three - dimensional crystal patterns. 12. habits of mind 12c. manipulation and observation 6 - 8 : 12c / m3. make accurate measurements of length, volume, weight, elapsed time, rates, and temperature by using appropriate devices. < a href = " http : / / www. compadre. org / precollege / items / detail. cfm? id = 12568 " > wgbh educational foundation. teachers ' domain : why do snowflakes come in so many shapes and sizes?. boston : wgbh educational foundation, 2010. < / a > teachers ' domain : why do snowflakes come in so many shapes and sizes? ( wgbh educational foundation, boston, 2010 ), www document, ( http : / / www. teachersdomain. org / resource / lsps07. sci. phys. matter. lpsnowflakes / ). teachers ' domain : why do snowflakes come in so many shapes and sizes?. ( 2010 ). retrieved may 21, 2013, from wgbh educational foundation : http : / / www. teachersdomain. org / resource / lsps07. sci. phys. matter. lpsnowflakes / wgbh educational foundation. teachers ' domain : why do snowflakes come in so many shapes and sizes?. boston : wgbh educational foundation, 2010. http : / / www. teachersdomain. org / resource / lsps07. sci. phys. matter. lpsnowflakes / ( accessed 21 may 2013 ). teachers ' domain : why do snowflakes come in so many shapes and sizes?. boston : wgbh educational foundation, 2010. 21 may 2013 < http : / / www. teachersdomain. org / resource / lsps07. sci. phys. matter. lpsnowflakes / >. % t teachers ' domain : why do snowflakes come in so many shapes and sizes? % d 2010 % i wgbh educational foundation % c boston % u http : / / www. teachersdomain. org / resource / lsps07.


modern programming languages have little support for writing secure software, making it all too easy to write programs with exploitable vulnerabilities. in these lectures, we explore a general technique based on type qualifiers that allows programmers to write down, in their souce code, their intentions with respect to security. we will describe how to mechanically verify that annotated code adheres to the policy. we will discuss the theoretical foundations and practical implementation issues. as a particular example, we show how to use type qualifiers to find format - string vulnerabilities in widely - deployed c programs and to find other security vulnerabilites in the linux kernel. we will also look at alias analysis, another important program analysis problem, and show how a must - alias analysis system corresponds to a system for statically checking access control. this series of lectures will discuss the requirements, protocols, and components of network security software on the internet. topics will include secure tunnels, security for web services, privacy constraints, design features that create or address dos threats, and the use of programmable security tokens in network protocols. the primary emphasis will be the relationship between models and design, including topics like the quantification of dos threats, models for code security in programmable tokens, strategies for composition and interoperation, and practical strategies for formal analysis of network protocol designs and software. in these lectures, we will analyze the security infrastructure in current, main - stream programming systems and platforms such as the java virtual machine and common language runtime. we will explain how byte code verification collaborates with the class loader and security manager to provide a secure run - time environment. we will also use theoretical tools to determine what properties current security systems based on stack inspection have and provide concrete proposals for improving the infrastructure for next - generation programming languages and systems.


microsoft windows 8 and windows server 2012, the latest operating system and windows makeover, were released in fall 2012. for programmers, many new apis were included in the features added. several of the new features focus on the venerable sockets interface, the basic network paradigm first introduced in berkeley software distribution ( bsd ) unix in the early 1980s. sockets still form the basis for networking on all of the major platforms including windows, mac os, linux, ios, and android. you might want to consider these new windows socket apis for your next project when writing new apps or refactoring older applications for windows. new windows 8 features for sockets programming are found at both ends of the network spectrum : - window runtime ( winrt ) sockets : used for low - level networking in windows store apps. - high - performance sockets : used in writing network servers for desktop apps that need low network latency and the highest performance. - websockets : the other new networking apis are socket - related, at least in name ; these are extensions to the http protocols for the creation of a special web socket that is fully bidirectional once the connection is established, either endpoint can initiate or send packets. herein i provide a brief introduction to these new networking socket features available on windows 8 and windows server 2012. the focus will be more on winrt sockets, since these will appeal to a larger set of developers. sockets and windows the original berkeley socket implementation developed in 1983 was very simple, based on the design of unix file i / o. a network socket became a special type of file handle. bsd networking functions were basic : socket ( open or create ), connect ( for tcp ), close. several types of sockets were supported including tcp ( stream ), udp ( datagram ), and later unix domain sockets. for tcp servers and applications receiving udp packets, the listen functions would bind to a network address and listen for incoming packets. for use with udp, there were the recvfrom functions. a few other functions were provided for getting and setting socket options, getting a host by name or address ; and there were the poll functions to check on the state of a socket. with the adoption of windows sockets ( winsock ) in 1993, microsoft added support for sockets to windows. the initial winsock 1. 1 api was relatively modest with calls similar to bsd unix plus a number of windows - specific extension functions. over time, the winsock api has grown larger and


technological development in teaching and learning 23 feb 2012 10 : 49 the second day of the ngl conference opened with a presentation by charles crook, professor at the university of nottingham, and docent in information and communications technology. professor charles crook, university of nottingham. he spoke about how the latest technology creates new situations, which in turn lead to new experiences in terms of student learning. the interpersonal dynamic in teaching and learning has changed. in his presentations, charles crook talked about his work examining what actually happens with learning when people use technology and learn alongside others instead of individually. he makes comparisons with earlier ideas within pedagogy, referring to piaget and vygotsky. " there exists an undeniable tension between teaching and learning and technology, " he states. charles crook mentions two symptoms of e - learning at institutes of education. one is the many students per teacher and the other is a changed pedagogy. what does it mean to be educated? he has looked at quality in communication and interaction between students in their work. he has also examined the significance of place and students ' study environment. the presentation provided an interesting insight into the research that requires a position alongside the technological developments within the world of teaching. it is important to establish in what ways social situations create new grounds for teaching and learning. translation based on the original text by annette skogsjo. photo by annette skogsjo. ngl pa hogskolan dalarna next generation learning conference


we consider a simple pure substance under hydrostatic conditions described by the following fundamental equation : where the extensive variables u, v and n are the internal energy, the volume, and the number of particles respectively, and the intensive variables t, p and are the temperature, the pressure and the chemical potential respectively. equation ( ) corresponds to the choice of the variables u, v and n as independent variables of the entropy s ( u, v, n ). these variables are precisely those which are fixed and determine the macrostate of the members of the microcanonical ensemble and consequently s is the relevant potential in this statistical ensemble. it is useful to define the following quantities :, and so that eq. ( ) can then be written in the dimensionless form : in general, for other thermodynamic systems with degrees of freedom, one will have : where are extensive variables, and the corresponding entropic conjugate variables. massieu - planck functions are entropic thermodynamic potentials defined as legendre transformations of the entropy. in the case of a pure substance, the following ( dimensionless ) potentials can be formally defined : the function was first introduced by massieu, and it is called massieu ' s potential. the function was introduced by planck and is called planck ' s. potential. given the extensivity of, and using euler ' s theorem for homogeneous functions, it is easy to see that. therefore the legendre transformation of all variables redefines the entropy, substituting eq. ( ) into the differentials of the potentials defined above one gets : from eq. ( ) one obtains : the above equations allow a re - derivation of all the standard thermodynamic equations in terms of, and. for instance, maxwell relations can be deduced, by imposing that the equations ( ) - ( ) are exact differentials ( equality of crossed derivatives ). moreover, eq. ( ) is the gibbs - duhem equation which states that the complete set of intensive variables of the system are not all independent. on the other hand, the extremal condition of leads us to deduce that, and are homogeneous at equilibrium.


with solar and wind energies maturing as recognized alternative - power sources, there are other alternatives providing clean power on scales both large and small. these power generators are distinctive in how they create electricity and are a growing business for electrical contractors ( ecs ) that take note of them. biomass is the most commercially established “ other ” alternative energy. popularly used to create biofuels, such energy sources are being used for on - site power cogeneration or distributed generation. biofuel is sustainable, offering carbon - neutral emissions output. a nonfossil - fuel source, its most popular “ feedstocks, ” as they are called, include wood waste, agricultural residues ( straw, manure, grasses ) and municipal solid waste. when used to create energy, feedstocks become the fuel for biopower. biofuel is certainly not a new idea. wood was north america ’ s primary heating source until coal. by the 1950s, electricity and natural gas displaced wood heat. the energy crisis of the 1970s brought new attention, research and new ideas to biomass as an alternative - energy source. by the 1980s, biomass power plants were being built in north america. today, the biomass power association ( bpa ) in portland, maine, represents 80 biomass power plants in 20 states across the country. biopower systems are typically direct - fired, co - fired, gasification or modular ( transportable ). a growing sector industrial info resources ( iir ) in texas, a provider of global market intelligence for industrial, heavy manufacturing and energy markets, reports more than $ 3 billion in u. s. biomass power - generation projects are scheduled to begin construction this year. research by biomass power and thermal magazine reveals a 20 percent increase in proposed biomass projects going into this year. the top 10 states with the most operating plants and proposed projects are california ( 22 ), florida ( 16 ), new york ( 14 ), new hampshire ( 14 ), maine ( 11 ), michigan ( 11 ), massachusetts ( 10 ), minnesota ( 9 ), pennsylvania ( 9 ) and connecticut ( 8 ). in addition, the california energy commission has set an ambitious goal to add as much as 2, 200 megawatts ( mw ) of biomass power by 2020, part of that state ’ s goal to achieve 33 percent of its electricity from renewable sources by that year. though biomass currently plays a relatively small role in the u. s. electric power - generation market - — it represents about 10 gigawatts ( gw ) of electricity generation


[ this section may require several minutes to download ] please click on underlined categories to view : [ to search for subject matter, depress ctrl / f ] : plants yielding fibers have been second only to food plants in their usefulness to humans and their influence on the furthering of civilization. primitive humans in their attempts to obtain the three most important necessities for life : food, shelter & clothing, focused on plants. even though animal products were available, some form of clothing was needed that was lighter and cooler than skins and hides. it was easier to obtain from plants such items as bowstrings, nets, snares, etc. also plant products were available from the leaves, stems and roots of many plants to construct shelter. very early on plant fibers have had a more extensive use than silk, wool and other animal fibers. gradually as humans ’ needs multiplied, the use of vegetable fibers increased greatly until presently they continue to be of great importance even after the onset of plastics. it is impossible to estimate the number of species of fiber plants, but over a thousand species of plants have yielded fibers in america alone, and over 800 occur in the philippines. however, plant fibers of commercial importance ore relatively few, the greater number being native species used locally by primitive peoples in all parts of the world. their durability often exceeds those of synthetic manufacture, one example being sisal & manila hemps. the most prominent fibers of the present are of great antiquity. the cultivation of flax, for example, dates back to the stone age of europe, as discovered in the remains of the swiss lake dwellers. linen was used in ancient egypt and cotton was the ancient national textile of india, being used by all the aboriginal peop0les of the new world as well. ramie or china grass has been grown in the orient many thousands of years. plastic materials are often used instead of natural products because they cost less and sometimes tend to be more durable. however, natural plant products continue to have some superior attributes and are used when materials are readily available. there are six principal groups of fibers distinguished according to the way in which they are used. textile fibers are the most important in that they are used for fabrics, cordage and netting. to make fabrics and netting flexible fibers are twisted together into thread or yarn and then either spun, knitted, woven or in some other way utilized. fabrics include cloth for wearing apparel, domestic use, awnings, sails, etc., and also coarser materials such as gunn


are twisted together into thread or yarn and then either spun, knitted, woven or in some other way utilized. fabrics include cloth for wearing apparel, domestic use, awnings, sails, etc., and also coarser materials such as gunny and burlap. fabric fibers are all of some commercial value. netting fibers that are used for hammocks, lace and all forms of nets include many of the commercial fabric fibers and a number of native fibers as well. both commercial and native fibers are used for cordage. for this the individual fibers are twisted together instead of being woven. binder twine, fish lines, hawsers, rope and cables are among the many types. brush fibers are stiff tough fibers including small stems and twigs that are utilized for making brooms and brushes. rough weaving & plaitling fibers. plaits are fibrous, flat and pliable strands that are interlaced to make straw hats, baskets, sandals, chair seats, etc. the most elastic strands are woven together for mattings and the thatched roofs of houses. the supple twigs or woody fibers are for making chairs, baskets and other wickerwork. filling fibers are used for stuffing mattresses, cushions and in upholstery ; for caulking seams in boats and in casks and barrels ; as stiffening in plaster and as packing material. natural fabrics are usually obtained from tree basts that are extracted from bark in layers or sheets and pounded into rough substitutes for lace or cloth. fibers for paper manufacture includes textile fibers and wood fibers that are used in either the raw or manufactured state. a plant cannot be restricted absolutely to any single group because the same fiber may be used for different purposes. also, a plant may yield more than one kind of fiber. thus the following discussion includes species that are considered in the group in which they are of the greatest importance. all fibers are similar in that they are sclerenchyma cells that serve as part of the plant skeleton. they are predominantly long cells with thick walls and small cavities and usually pointed ends. the walls often contain lignin as well as cellulose. fibers occur singly or in small groups, but they are more apt to form sheets of tissue with the individual cells overlapping and interlocking. fibers may occur in almost any part of a plant : stems, leaves, fruits, seeds, etc. the four main types grouped according to their origin include bast fibers, wood fibers, scleren


the individual cells overlapping and interlocking. fibers may occur in almost any part of a plant : stems, leaves, fruits, seeds, etc. the four main types grouped according to their origin include bast fibers, wood fibers, sclerenchyma cells associated with the vascular bundle strands in leaves, and surface fibers that are hair like outgrowths on the seeds of the plants. the term “ bast fiber ” is subject to criticism, as it gives no indication as to the particular tissue or region in which the fibers occur. it might be preferable to designate those fibers that occur in the outer parts of the stem as cortical fibers, pericyclic fibers or phloem fibers. but “ bast ” is a term that has been in use for a long time and is so established in commerce that it will be used in this discussion. fibers of economic importance occur in many different plant families, especially those from the tropics. some of the more important families are the palmaceae, gramineae, liliaceae, musaceae, amaryllidaceae, malvaceae, urticaceae, linaceae, moraceae, tiliaceae, bromeliaceae, bombacaceae, and luguminosae. these fibers must be long and possess a high tensile strength and cohesiveness with pliability. they must have a fine, uniform, lustrous staple and must be durable and abundantly available. only a small number of the different kinds of fibers possess these traits and are thus of commercial importance. the principal textile fibers are grouped into three classes : surface fibers, soft fibers and hard fibers, with the last two often referred to as long fibers. surface or short fibers include the so - called cottons. the soft fibers are the bast fibers that are found mainly in the pericycle or secondary phloem of dicotyledon stems. bast fibers are capable of subdivision into very fine flexible strands and are used for the best grades of cordage and fabrics. included are hemp, jute, flax and ramie. hard or mixed fibers are structural elements found mainly in the leaves of many tropical monocots, although they may be found in fruits and stems. they are used for the more coarse textiles. sisal, abaca, henequen, agaves, coconut and pineapple are examples of plants with hard fibers. cotton is one of the greatest of all industrial crops. it is the principal fiber plant as well as one


coarse textiles. sisal, abaca, henequen, agaves, coconut and pineapple are examples of plants with hard fibers. cotton is one of the greatest of all industrial crops. it is the principal fiber plant as well as one of the oldest and most economical. it was known since ancient times and well before written records. there are references to cotton by the ancient greeks and romans. cotton was found in india before 1, 800 b. c. the hindus were believed to be one of the first people to weave cloth in the eastern hemisphere, although reference to nordic traders of woven goods in north america during the bronze age has been made by fell 1982 ( http : / / faculty. ucr. edu / ~ legneref / bronze / fell2. htm ). cotton was introduced to europe by the arabs who called the plant “ qutn. ” the plant had several origins because columbus found it in cultivation in the west indies, and it was known to the amerindians of neotropical america in pre - columbian times. cotton became a commercial crop in the united states after 1787.. several species of the genus gossypium provide what we call cotton. the fine fibrous hairs that occur on the seeds constitute the raw material. these hairs are flattened, twisted and tubular. they compose the lint, floss or staple. their length and other qualities vary with the different varieties. the plant is a perennial shrub or small tree naturally, but under cultivation it is treated as an annual. it branches freely and grows to a height of 4 - 8 ft. cotton thrives in sandy soil in humid regions that are near water. this environment is typified in the southern united states and in the river valleys of india and egypt. cotton matures in 5 - 6 months and is ready to harvest soon after. hundreds of varieties have been developed from wild ancestors or produced by breeding during the long period of cultivation. varieties differ in fiber character as well as other morphological features. cotton is a difficult group to classify and the exact number of species is subject to argument. cultivated cottons of commercial importance are usually referred to one or another of four species : gossypium barbadense and g. hirsutum in the western hemisphere and g. arboreum and g. herbaceum in the eastern hemisphere. 1. - - gossypium barbadense probably originated in tropical south america. the flowers are bright yellow with purple spots. the fruit, or boll, has


at various points along the path toward productive nanosystems for molecular manufacturing it would be useful to be able to calculate the properties and reactions of assemblies of atoms of various sizes. within the domain of non - relativistic quantum mechanics, such information is supplied by the schrodinger equation, but this can only be solved analytically for the hydrogen atom and ions with only one electron. for larger atoms and molecules, numerical solutions require compromises between computational feasibility and accuracy. recent work from researchers at argonne national laboratory suggests that machine learning can be an efficient alternative to numerical computations. a hat tip to kurzweilai. net for pointing to this new scientist article by lisa grossman “ molecules from scratch without the fiendish physics “ : a suite of artificial intelligence algorithms may become the ultimate chemistry set. software can now quickly predict a property of molecules from their theoretical structure. similar advances should allow chemists to design new molecules on computers instead of by lengthy trial - and - error. our physical understanding of the macroscopic world is so good that everything from bridges to aircraft can be designed and tested on a computer. there ’ s no need to make every possible design to figure out which ones work. microscopic molecules are a different story. “ basically, we are still doing chemistry like thomas edison, ” says anatole von lilienfeld of argonne national laboratory in lemont, illinois. the chief enemy of computer - aided chemical design is the schrodinger equation. in theory, this mathematical beast can be solved to give the probability that electrons in an atom or molecule will be in certain positions, giving rise to chemical and physical properties. but because the equation increases in complexity as more electrons and protons are introduced, exact solutions only exist for the simplest systems : the hydrogen atom, composed of one electron and one proton, and the hydrogen molecule, which has two electrons and two protons. … the researchers developed a machine learning model to calculate the atomisation energy — the energy of all the bonds holding a molecule together and applied it to a database of 7165 small organic molecules of known structure and atomization energy and containing up to seven atoms of carbon, nitrogen, oxygen, or sulfur, plus the number of hydrogen atoms necessary to saturate the bonds. these molecules had atomization energies ranging from 800 to 2000 kcal / mol. the model was trained on a subset of 1000 compounds and then used to calculate the energies of the remaining molecules in the database. the results showed a mean error of only 9.


august 5, 2008 taking play seriously by robin marantz henig part viiii koach karl continues this great article on " play " … bateson, a prominent play scholar who recognizes the quandary posed by equifinality, suggested that play is the best way to reach certain goals. through play, an individual avoids what he called the lure of ‘ ‘ false endpoints, ’ ’ a problem - solving style more typical of harried adults than of playful youngsters. false endpoints are avoided through play, bateson wrote, because players are having so much fun that they keep noodling away at a problem and might well arrive at something better than the first, good - enough solution. but maybe the flexibility hypothesis is itself a false endpoint. maybe the idea that play is the best route to a whole host of good results — creativity, social agility, overall mental suppleness — is just the first idea scientists landed on, and they were inclined to accept it because it fit so well with their innate ideas about the nature of childhood. this is the view of a small group of play scholars we ’ ll call the play skeptics. what worries the play skeptics is that most people in the industrialized west — scientists in the field, play advocates and all the rest of us, parents, teachers, doctors, scholars, all the children and all the aging children — have been ensnared by what skeptics call the ‘ ‘ play ethos. ’ ’ by this they mean the reflexive, unexamined belief that play is an unmitigated good with a crucial, though vaguely defined, evolutionary function. ‘ ‘ play ethos ’ ’ comes from peter smith, a psychology professor at the university of london and a leading authority on play ’ s effect on children ’ s emotional development. he uses it as a cautionary term, a reminder that most conclusions about play ’ s adaptive function have so far been based not on scientific evidence but on wishful thinking. in one of his early experiments, smith and his colleagues put 3 - and 4 - year - olds in two different play settings. in one group the children were allowed to play, in whatever way they felt like, with several wooden sticks. in the other group they were shown by an adult ‘ ‘ play tutor ’ ’ how to fit two sticks together to make a longer one. then the children were given two tasks. first they had to retrieve a marble by connecting two sticks. both groups performed this task,


throughout life there are many times when outside influences change or influence decision - making. the young child has inner motivation to learn and explore, but as he matures, finds outside sources to be a motivating force for development, as well. along with being a beneficial influence, there are moments when peer pressure can overwhelm a child and lead him down a challenging path. and, peer pressure is a real thing – it is not only observable, but changes the way the brain behaves. as a young adult, observational learning plays a part in development through observing and then doing. a child sees another child playing a game in a certain way and having success, so the observing child tries the same behavior. albert bandura was a leading researcher in this area. his famous bobo doll studies found that the young child is greatly influenced by observing other ’ s actions. when a child sees something that catches his attention, he retains the information, attempts to reproduce it, and then feels motivated to continue the behavior if it is met with success. observational learning and peer pressure are two different things – one being the observing of behaviors and then the child attempting to reproduce them based on a child ’ s own free will. peer pressure is the act of one child coercing another to follow suit. often the behavior being pressured is questionable or taboo, such as smoking cigarettes or drinking alcohol. peer pressure and the brain recent studies find that peer pressure influences the way our brains behave, which leads to better understanding about the impact of peer pressure and the developing child. according to studies from temple university, peer pressure has an effect on brain signals involved in risk and reward department, especially when the teen ’ s friends are around. compared to adults in the study, teenagers were much more likely to take risks they would not normally take on their own when with friends. brain signals were more activated in the reward center of the brain, firing greatest during at risk behaviors. peer pressure can be difficult for young adults to deal with, and learning ways to say “ no ” or avoid pressure - filled situations can become overwhelming. resisting peer pressure is not just about saying “ no, ” but how the brain functions. children that have stronger connections among regions in their frontal lobes, along with other areas of the brain, are better equipped to resist peer pressure. during adolescence, the frontal lobes of the brain develop rapidly, causing axioms in the region to have a coating of fatty myelin, which insulates them and causes the frontal lobes to more effectively communicate with other


register new player welcome to our world of fun trivia quizzes and quiz games : hard drive basics " the hard drive is a critical component in a computer system. this is a quiz on some hard drive trivia. good luck and enjoy! " 15 points per correct answer - no time limit the first hard disks, created in the 1950s, could be up to 20 inches in diameter. which company invented the hard disk? when purchasing a hard disk which of these is generally not a specification that would be of concern? inside the hard disk drive, where is the data actually stored? when a user formats a disk, they are generally performing a high - level format which prepares the drive to hold data. when a low - level format is performed, how does it divide the platter? read and write bits and bytes sectors and tracks kilobytes and megabytes which of these is disk interfaces was the precursor to scsi ( small computer system interface )? hard drive failure rates are measured with mtbf ( mean time between failures ). which of these failures would be reason to replace your current hard disk? can ' t read cds an external hard disk is often purchased by the home computer user for backups of the main hard disk ( generally installed internally to the computer case ). which of these interfaces is commonly used for this purpose? which of these refers to the hard drive circuit board? during the life of a disk, is it true that defragmentation of the file system can significantly improve performance? which of these is not known as one of the world ' s hard disk manufacturers? copyright, funtrivia. com. all rights reserved. legal / conditions of use compiled nov 03 12