in character as a result. - although dieting and exercise are two different behaviors, viewing physical activity primarily as a means of losing weight or re - shaping the body is a shift in attitude that can often accompany dieting. people can respond to this by developing a driven, compulsive relationship with physical activity that pushes them to exercise when fatigued, ill, and injured, and that cuts into their ability to enjoy other things. people can also respond by developing an aversion or resistance to physical activity, because it has become associated with guilt, obligation, and anxiety for them. have breakfast within an hour of waking up. your body is craving fuel after a night ' s sleep. not only does having breakfast support an optimal metabolism, but studies have shown that having breakfast helps our bodies with appetite control. study participants were found to experience less hunger all day long when they had breakfast - - there ' s something about that meal that is uniquely satisfying to the body. ( and for those of you who are saying that you experience more hunger during the day when you eat breakfast, here ' s a news flash : the hunger you are experiencing is actually your real level of hunger. when you skip breakfast, your body sometimes begins to produce a chemical called a ketone that " covers up " your natural hunger signal. as a result, you may not notice significant hunger - - until you eat or drink something with nutrients in it that " breaks " the ketosis, causing you to feel suddenly and ravenously hungry - - a real set - up for overeating and feeling uncomfortable ). be regular with meals and snacks ; try to eat something every 3 to 4 hours. again, your metabolism is better supported when the body is fed in a regular, consistent way. erratic eating patterns with more than 4 hours between meals and snacks may cause the body to fight back against what it perceives as deprivation and uncertainty. it may cause the metabolic rate to drop, and it may signal the body to preferentially store calories as fat instead of spending them freely. think of the peace symbol when you ' re planning your plate at lunch and dinner. aim to fill 2 / 3 of your plate with carbohydrates : a fruit serving, a cooked or raw vegetable serving, and a grain. the last third of your plate is for a serving of protein ( animal or vegetable ). add a serving or 2 of fat to round things off, if your other food choices don ' t contain much fat. this meal mix : carbohy


gone for too long without eating. hunger is the physiological expression of the body ' s need for energy. there are some common symptoms of hunger that people may manifest in descending order as their blood sugar levels continue to drop. it ' s useful for you to identify your personal progression from slight hunger to over - hunger. you are more likely to begin a meal or a snack at a comfortable level of hunger if you eat within 5 - 10 minutes of your early hunger signals. - rumbling, or empty stomach - early hunger - decreased energy, particularly during physical activity - decreased ability to focus - feeling weak or shaky - nausea, cold sweats - late hunger appetite is our interest in food. it usually accompanies hunger, but it can also be stimulated by sensory triggers ( walking past a bakery ), habit ( " i always have a snack at this time " ), or emotions ( wanting food when sad or anxious ). most of us are familiar with the experience of a food " calling to us " when we are clear that we are not hungry, and eating under these circumstances once in a while is totally normal. a frequent tendency to eat from appetite rather than hunger, however, is likely to create inappropriate weight gain because it promotes consumption of calories that the body has no use for. appetite is linked to our innate need for pleasure, and can be aggravated by food deprivation, but it can also be exacerbated by a lack of fun, not enough relaxation, and insufficient outlets for soothing and comfort. our appetite for food stays more manageable when we eat enough, when we eat things we really enjoy, and when we have many other ways of relaxing and having fun. to learn more about the link between emotions, self - care needs, and eating, look at our section on emotional eating below. fullness is the physiological expression of the body having received enough energy at a meal or snack. the experience of fullness can be affected by a variety of food - related factors : - high - fiber wholegrains help to fill us up at meals and snacks, and keep us feeling full for longer. - protein is best at promoting comfortable fullness at a meal or snack, and it will continue to promote comfortable fullness for several hours afterwards. - although the presence of fat in a meal may not boost fullness in the moment because it is digested more slowly, it contributes significantly to long - lasting fullness. - fruits, vegetables, and beans provide bulk and fiber that boosts fullness. - hot foods and beverages tend


so strongly reinforced on a physiological level, we have also developed a powerful emotional relationship with food. food and eating seem to be " about " a lot of things : family, cultural values, security, fun, intimacy, personal identity, spirituality, sensuality, control, power, love … the list goes on, and on. as a result, our relationship with food can get a little distorted when we are having a hard time coping in other areas of our lives. food can be used as a way to meet other needs when we are depleted ( e. g. eating a snack, when we really need to take a nap or have a study break ). food can also be used to manage emotions ( e. g. eating to " numb - out, " or relax ). everyone eats emotionally once in a while - that ' s normal. when emotional eating becomes frequent, however, it can be really disruptive and distressing. first of all, it confuses the body, which prefers to regulate its intake according to hunger and fullness. secondly, it interferes with our ability to deal with our feelings and meet our real needs directly. it turns the language of feelings into the language of food, creating a situation in which you can begin to think that you have a " problem " with food. food isn ' t the problem - - it ' s a symptom of coping difficulties. here are some ways to manage emotional over - eating : take care of your basic needs for sleep, relaxation, social connection, and pleasure on a daily basis. there is a tendency, particularly during college, to treat these needs as optional : they are not. and ignoring the deficit doesn ' t make it go away ; it simply goes underground and pops up someplace unexpected - - like your relationship with food. create academic, athletic, social, and work schedules that don ' t require you to sacrifice the foundation of well - being. find more supportive ways to comfort or distract yourself when things are difficult. phoning a friend, taking a hot shower, going for a short walk while listening to your favorite music ; these are some ways to take a break and boost your mood without using food. get help understanding and managing feelings. the transition to college life is exciting - - and incredibly stressful. everybody struggles with this in their own way, and a little coaching can help you to understand your situation better and feel more effective. for more information about all of the above suggestions, psychological services is a fantastic resource. you can reach them at 401.


note - to date. the dome is still unfinished. as is this article. neither dome nor article will be. resumed until this autumn. so patience please... meanwhile. the information below is a step by step explanation of how to build your own geodesic dome. above, dome nearly completed, without glass and perspex windows ( its summer! ) above photo, interior of dome, nearly completed above photo, interior of dome, nearly completed. however, most governments and legislators would prefer people of low income to live here... in ' charming ' town planning projects that give the local medeival architecture a real boost to their image, eh hem... spot ales ' medieval fort and, significantly, old prison, it ' s a job to find it, but if you squint hard enough... step by step photo instructions... the first step in building a geodesic dome home is to fully understand and visualise the geometry of the structure beforehand. to do this it is essential to build a small model version that you can refer back to whenever you get confused or stuck. it ' s possible to build a dome without first doing a model, but you ' re more likely to get in a fix, which wastes time and money. to make a 50cm diameter cardboard model you ' ll need a pencil, a compass, a ruler, 15 sheets of a4 lightweight photocopy card in one colour, and 5 sheets of the same card in another colour, one large piece of thick cardboard for the base ( from a big cardboard box will do ), glue, at least twenty very small boston clips, thumbtacks and probably some other stuff too, we ' ll see as we go along. the two fluffy assistants are optional. i found a useful video on youtube showing how to ' construct a geodesic dome ' out of cardboard. the instructions are for children so even a maths moron such as myself could follow them! the dome is composed of 10 equilateral triangles that join together 6 pentagons, each pentagon being composed of 5 isosceles triangles. in all, the dome requires a total of 40 triangles, 30 of them isosceles and 10 of them equilateral. in order to attain the dome diameter of 50cm the 3 sides of the equilateral triangles must be 15cm45 long precisely ( to be called length a ). the isosceles triangles must have one side measuring, again, 15cm45 and


your base and draw an arc further along the line of your circle. then place the point where your arc crosses the line and draw another arc further along. continue all around the circle till all the points of your decagon ( ten - sided polygon ) are drawn. at this point you will discover if your compass is set precisely or not. if it isn ' t your last arc will be too far in or out. cursing loudly at this juncture may help relieve tension. if it ' s not right, rub out the marks and start again. i actually ended up having an approximate decagon and just bodged along as i do, knowing that the length a sides of the triangles would make up for any incompetent fumbling around with the compass. now use your ruler to draw straight lines from point to point, thus completing the drawing of the decagon. my assistant pointed out that my work was rather unprofessional. she explained that putting one ' s nose up against the base and scrutinising it carefully was all it took to discover my sloppy work. she even went so far as to call my other assistant over to prove her point at this moment in the proceedings my assistants became suddenly overwhelmed by a frenzy of excitement. perhaps my lack of professionalism had compromised their respect for the project. all at once my ordered workshop had degenerated into a wrestling ring! determined to get things under control, i raised my voice and commanded, ' no no, you naughty assistants! stop this monkey business at once!!! ' fearing my authority had indeed been compromised i was forced to take radical measures. reciting the affirmation ' i am strong and in control. i am respected ' i grabbed them round their fluffy bellies and firmly transported them out of the room, shutting the door behind them! they were outraged, but i felt proud to have proved to myself and to the world at large that i was an impressive figure of authority, not to be messed with. i could now get on with laying out my card dome sections, base, boston clips, thumbtacks and glue without further ado. applying glue to both sides that needed to be stuck together, i glued the pentagons and equliateral triangles alternately round the base following the decagon i ' d drawn previously, as neatly as possible. to keep everything in place it ' s essential to use the boston clips on the dome ' s edges and the thumbtacks around the base to hold everything in


##time sound files found on the art and life in africa project site to get a sense of how the instruments might sound. another suggestion, given in one of the site ’ s own teaching modules, is to do a search for “ jewelry ” ( also under “ function ” ). students should consider materials, functions, and styles ( as described in the captions ) in order to gain a better understanding of african motifs and the purpose of bodily decoration. students are better able to understand artifacts when they are placed in the context of important facets of people ’ s lives, such as childhood, puberty, religious belief, marriage, and death. students could look for art or objects in western culture ( in the present or historically ) that compare to african art and artifacts in similar categories. challenging examples might be the nkisi, or power figures of the kongo people from congo, or the mbari houses of the igbo people from nigeria, used to represent and to try to harness spiritual forces. these items might be compared in a variety of ways with sculptures of saints or carved altars in christian churches. the point here is not to change students ’ own beliefs, but to discuss uses of art, as well as a deeper point : what strategies do human beings in all cultures use to deal with the unpredictability of life? in short, this is a wonderful site that not only offers an abundance of images from africa and information about africa, but also many creative ways to understand and use the material in classroom settings.


today, i spoke with krista wilkinson, ph. d., who is an expert in the field of augmentative communication, particularly for people with cognitive disabilities. her interests include vocabulary learning and the use of visual supports in communication and education. i approached dr. wilkinson with my struggle to create, for the future clear helper web site, a set of navigation icons that would enable people with cognitive disabilities to find the information they want quickly and easily. i said i would like to use icons shown by research to be effective communicators. she confirmed for me that little research has been performed in this area. after more discussion, we agreed that icons we have seen in use on web sites seem arbitrary, or bereft of context. she explained that even the common use of left - and right arrows on web sites to indicate previous - and next pages is not contextually accurate in practice. she said that people with cognitive disabilities can find it confusing that a click to a right arrow does not actually present the next page from the right. instead, a new page just appears. dr. wilkinson showed me an augmentative communication device, called the tango, that uses arrow buttons in a contextually appropriate manner. below is a picture of it. note the green arrow buttons on both sides of the middle set of icon buttons. when a user presses a green, up - arrow button, the middle set of icon buttons revolve upward like a slot machine acts, and presents a new set. when a user presses a green, right - or left arrow button, the middle set of icon buttons scrolls in the relevant direction, and presents a new set. dr. wilkinson suggested i might make web pages act similarly when left - and right arrow buttons are clicked. i can ’ t think of an accessible way to do that, but i will consider it. another suggestion she made would be much easier to implement ; left - and right arrow buttons could be paired with a contextually - appropriate sound. an example of this would be a recording of a page turning. again, little research has been performed to demonstrate that the context of icons can be understood, or that the pairing of icons with sound is more effective than not. i ’ ll do what i can to experiment with these ideas on the future clear helper web site. perhaps, through evaluations by users, and via automated web - site evaluation tools, the effectiveness of the navigation icons i plan to use could be measured. note : no endorsement is intended or implied for the tango.


what is mediation? mediation is a confidential and “ out - of - court ” procedure which gives parties involved in a dispute a chance to meet and negotiate a resolution to their conflict with the assistance of a trained mediator. agreements that are reached during the course of a mediation session could include : repair, return or replacement of property, acceptance of social service referrals, payment of medical expenses, or arrangements to modify or cease specific behavior. in most cases, the mediation process can be very healing as it allows participants to address the underlying issues that gave rise to the dispute, without the formalities or restrictions of the courtroom. mediation is where two or more people, who are in conflict, get together to discuss their problems, trying to resolve them with the help of a neutral person - the mediator. the mediation session provides a structured, confidential setting designed to assist persons in working out their own problems. the purpose of mediation is not to judge guilt or innocence, but to help parties get at the root of their problems and devise their own resolution to them. the difference between mediation and court processing are significant. in a court case, guilt or innocence must be proven. in mediation, however, proof is not required ; the objective instead is to resolve a dispute by reaching a settlement that is agreeable to both parties. mediation allows participants to address the underlying issues that caused the dispute without the formality or restrictions of the courtroom. therefore, mediation can be very healing. mediation is not bound to the rules of a formal system and disputants retain the responsibility to make the final decision regarding the outcome of their mediation has proven effective when : - situations or issues are so great parties are unable to organize or focus on proper - a dispute involves such a great number of parties that a moderator is required. - parties involved in the conflict are not familiar with problem - solving procedures. - there are no laws, rules, or regulations to explain how the situation should be - false perceptions, poor communication, or intense feelings are involved. - parties do not want to use the legal system due to cost, time, publicity, or uncertain filing your complaint you may file your complaint by telephoning the restorative justice center at ( 515 ) 286 - 3057. the intake worker will record all of the information you provide such as dates, times, names and addresses.


of electrical energy, that of heating and cooking with electricity. " it was a message that inspired j. d. ross, seattle city light ’ s superintendent of lighting, to promote the installation of electric ranges in seattle homes and apartments. to implement his plan, ross recalled in a 1937 seattle star article, he told his staff to " order a carload of those ranges and advertise that we ’ ll wire them in free.... those early ranges had to be installed and wired correctly to give any service at all, and our boys knew how to do it. " still, even with ross ’ s interest and drive, customers did not rush out to purchase electric ranges. furthermore, seattle city light had a difficult time acquiring parts and key materials during world war i. the big boom for electric cooking came after the war when an improved range came on the market and appliance companies collaborated with city light to promote electric appliances. for example, the hughes company, a division of edison electric appliance company, suggested in a letter to the seattle municipal light and power plant, city of seattle engineering department, that they join together to promote the sale of electric ranges. " do you realize that in the very near future your greatest means of revenue is going to come from the electric range and other electrical cooking devices.... we are in a position to answer any questions pertaining to this subject [ cooking with electricity ], and to give you assistance in building up this load. " eight years later edison electric appliance company allocated money for advertising electric ranges and provided lecturers for a cooking school. between 1924 and 1927 the number of ranges in seattle homes jumped from under 3, 000 to over 11, 000. during the 1920s various business and civic groups vigorously promoted the sale of electric appliances. in 1923 the seattle electric club, which had as its members businesses concerned with any and every aspect of electricity, celebrated an electric week. the exhibit, held in a large tent in bothell, a suburb of seattle, showcased cooking demonstrations and promoted the idea that " the work is done by the most willing of servants, electricity harnessed to push buttons.... let electric mary do your work.... [ she ] will take a big load off the shoulders of any housewife ". two years later the seattle times backed the progressive seattle exhibition. though it did not focus exclusively on electricity, the exhibition ’ s spotlight shone on electric appliances, including radios. to entice customers, merchants showcased electric appliances during daily demonstrations.


". two years later the seattle times backed the progressive seattle exhibition. though it did not focus exclusively on electricity, the exhibition ’ s spotlight shone on electric appliances, including radios. to entice customers, merchants showcased electric appliances during daily demonstrations. at the puget sound power and light booth, company representatives told visitors they would receive assistance in selecting the appropriate range as well as prompt service after the installation. " our facilities and success in equipping thousands of seattle homes and apartment houses with electric ranges and service enable us to demonstrate the best in electrical cookery, " said a spokesman for the company. between january and september of 1927, puget power announced, " more electric ranges have been installed on our lines than there were in the entire state of washington only six years ago! " the utility company sold westinghouse, hotpoint, and crawford electric ranges and offered very low time payments. before refrigerators became popular and necessary kitchen equipment, apartment houses installed coolers as a way to extend the life of perishables. the cooler, sometimes referred to as a cooling closet, can best be described as a cupboard, often made of wood, with one to three shelves. the back side, set against an outside kitchen or dining area wall, had a three - to five - inch opening covered with perforated tin or wire screen. this allowed air to flow in while keeping insects out. standing in mute testimony to the past, these small openings, usually located below or at the side of a window, are still visible on many early seattle apartments. coolers sufficed in seattle ’ s moderate climate. though not cold enough to keep perishable food such as meat from spoiling, they worked well for the short - term storage of fruits and vegetables, jars of jam and preserves, and cheeses. a cooler was comparable to having a small cellar in the kitchen. owners and tenants considered them an important apartment amenity. real estate promotional material for apartments indicates that in addition to, or in place of coolers, buildings furnished refrigerators. until the 1920s, these were actually iceboxes. the icebox usually had a finished ash, pine, or oak shell that was lined with zinc, slate, porcelain, or galvanized metal. iceboxes came in a variety of sizes and shapes and had doors that opened to reveal adjustable shelves, with a separate compartment for ice. a pan set in the bottom held melting ice water, which had to be emptied frequently. tenants eagerly awaited the weekly delivery of ice. " the ‘


sizes and shapes and had doors that opened to reveal adjustable shelves, with a separate compartment for ice. a pan set in the bottom held melting ice water, which had to be emptied frequently. tenants eagerly awaited the weekly delivery of ice. " the ‘ ice man ’ would break up the large blocks into sections for ease in carrying up the stairs to the waiting iceboxes. the neighborhood kids would gather around the wagon to get an ice sliver to suck on, " recalled al wilding who lived in several seattle apartments during the 1930s. because the ice melted and iceboxes leaked, these " refrigerators " could be exceedingly messy. whenever possible, they were placed on a back porch. this was a most convenient place for the apartment that had back steps - the renter did not have to be home when the ice man delivered. he could just bring the ice to the porch, open the icebox door, and insert the block of ice. as late as 1924 the roy vue apartments, in seattle ’ s capitol hill district, bragged that each apartment would have outside porches, " containing a large refrigerator. " in apartments without porches the icebox would frequently be housed on a wall with an opening onto the apartment corridor or in the entrance hall of individual apartments. bernice ovadia, who lived in the monmouth apartments, recalled that their icebox was in the front hall. " sometimes we had to get up at night to empty the water from the melting ice. that was a very unpleasant task. " once manufacturers figured out the mechanism for electric refrigerators to make ice cubes and freeze food, that technological wonder became one of the new appliance ’ s most important selling points. apartments promising true refrigerators reminded prospective tenants that each apartment had its own, enabling tenants to make " their own ice and frozen dainties. " the ice cube trays of the 1920s and 1930s were made of tin or nickel - plated copper with plated brass dividers, and required a dunking under warm water to remove the ice. many an anxious homemaker ruined her elegant frozen dessert by dousing the tray with very hot water in order to speed the process. in the mid 1930s, when engineers finally solved the choice of coolants and other design dilemmas, the refrigerator was well on its way to becoming an indispensable machine. along the way, companies tested many improvements. one, the electro - kold, employed a single machine, located in a basement or other out - of - the -


the refrigerator was well on its way to becoming an indispensable machine. along the way, companies tested many improvements. one, the electro - kold, employed a single machine, located in a basement or other out - of - the - way place, to operate 20 kitchen refrigerators in individual apartments. another system converted the older iceboxes into refrigerators operated by electricity. the president of modern appliances for frigidaire distributors explained how it worked, but because the process was rather complicated, he reminded people that the company would happily sell them a new electrical refrigerator, " complete, with the mechanism in its own cabinet. " most apartments chose that option. although modern amenities were most evident in the kitchen, the entire apartment benefited from technological advancements. bathrooms acquired built - in tubs with showers, telephones became common, rooms were wired for radio aerials, and garages became a necessity. aware of the importance of appealing to the middle class, apartment owners hired decorators to choose specially designed wallpaper and select fabric for lobby furniture. clearly, owners paid attention to the wants and needs of prospective tenants. that so many seattle apartments, built so long ago, are still fronting seattle streets is testimony to their role in the urban landscape. jacqueline b. williams is author of wagon wheel kitchens : food on the oregon trail ( university press of kansas ) and the way we ate : pacific northwest cooking, 1843 - 1900 ( washington state university press ). diana james is at heart, and by training, a preservationist. she and williams are currently researching early ( 1900 - 1939 ) seattle apartments. research for this article was partially funded by a grant from 4culture.


problems with prepositions prepositions are words that often show direction ; for example, below, above, over, under, around, through, in, out, between, among, to, toward ( s ). other common prepositions include of, for ( also sometimes a conjunction ), from, with, like ( also sometimes a verb ). rule : you shouldn ’ t use or end a sentence with an unnecessary preposition, i. e., when the meaning is clear without the preposition. sentences may end with necessary prepositions. correct : that is something i cannot agree with. with is a necessary preposition. incorrect : where did he go to? correct : where did he go? to is unnecessary because the meaning is clear without it. rule : don ’ t follow like with a subject and verb because prepositions are followed only by nouns that act as the object of the preposition. use as or as if or as though instead of like when a subject and verb follow. correct : i wish i could be more like her. incorrect : it doesn ’ t look like she will show up for dinner. correct : it doesn ’ t look as if ( or as though ) she will show up for dinner. which sentence is correct? 1. a. where did you get this at? b. where did you get this? 2. a. i will go later on. b. i will go later. 3. a. take your shoes off the bed. b. take your shoes off of the bed. 4. a. cut it up into small pieces. b. cut it into small pieces. 5. a. i look like my sister. b. i look as my sister. pop quiz answers posted on saturday, july 19th, 2008, at 12 : 31 am


| a fool or simpleton ; ninny. | | an extraordinary or unusual thing, person, or event ; an exceptional example or instance. | | — the chemical symbol for | the symbol for the element rubidium. the symbol for rubidium. | rubidium ( r - bid ' e - əm ) pronunciation key a soft, silvery - white metallic element of the alkali group. it ignites spontaneously in air and reacts violently with water. rubidium is used in photoelectric cells, in making vacuum tubes, and in radiometric dating. atomic number 37 ; atomic weight 85. 47 ; melting point 38. 89°c ; boiling point 688°c ; specific gravity ( solid ) 1. 532 ; valence 1, 2, 3, 4. see periodic table. rb / r - b - l / abbreviation : " realtime blackhole list ". a service that allows people to blacklist sites for emitting spam, and makes the blacklist available in real time to electronic - mail transport programs that know how to use rbl so they can filter out mail from those sites. drastic ( and controversial ) but effective. there is an rbl home page ( http : / / maps. vix. com / rbl / usage. html ). chemical element of group 1 ( also called group ia ) in the periodic table, the alkali metal group. rubidium is the second most reactive metal and is very soft, with a silvery - white lustre. a brief treatment of rubidium follows. for full treatment, see alkali metal. learn more about rb with a free trial on britannica. com.


develop your pln ( personal learning network ) below, you ' ll find several approaches to plns. there ' s no right or wrong way to get started, so take what you like and leave the rest. excerpt from the wiki by australian educator, sue waters the aim of sue ' s site is to help you gain the skills to build your own personal learning network ( pln )! personal learning networks ( plns ) are all about using web tools such as blogs, wiki, twitter, facebook to create connects with others which extend our learning, increases our reflection while enabling us to learn together as part of a global community. plns increase our opportunities to ask questions and receive help compared to our normal daily face - to - face interactions. best of a pln is it ' s personal! you make all the choices : - what tools you use! - who you connect with! - how you want to learn! - when you want to learn! personal learning networks : the power of the human network what is a personal learning network ( pln )? definition one : personal learning networks are : - a concept based on web 2. 0 and social software - learner - driven, problem - based, or motivated by interested - based on the idea that learning will take place in different contexts, and not come from one place or person - set their own learning goals - manage their learning ; managing both content and process - communicate with others in the process of learning - and thereby achieve learning goals this information is from a wiki by judith epcke ( @ jepcke ) and scott meech ( @ smeech ). continue reading at the wiki. judy & scott ' s work is licensed under a creative commons attribution - noncommercial - share alike 3. 0 united states license. - free tech for teachers a blog by richard byrne about, well, free tech for teachers. reviews, advice, descriptions of how teachers use the tech. - what should i read? - a few suggestions. - social media reading list - the idea for this page is to build a ' best of the web ' reading / watching list for school leadership regarding using social media for school advancement. rather than talk about how great social media is we ' re using social media to build this reading list. - a 21st century professional development proposal : a personal learning network + specific web tools = a true 21st century teacher.


even if brain size accounts for just 10 to 20 percent of an iq test score, it is possible to conjecture what kind of average scores would be made by a group of people with 30 percent larger brains. we can readily calculate that a population with a mean brain size of 1, 750 cc would be expected to have an average iq of 149. this is a score that would be labeled at the genius level. and if there was normal variability among boskops, as among the rest of us, then perhaps 15 to 20 percent of them would be expected to score over 180. in a classroom with 35 big - headed, baby - faced boskop kids, you would likely encounter five or six with iq scores at the upper range of what has ever been recorded in human history. the boskops coexisted with our homo sapiens forebears. just as we see the ancient homo erectus as a savage primitive, boskop may have viewed us in somewhat the same way. they died and we lived, and we can ’ t answer the question why. why didn ’ t they outthink the smaller - brained hominids like ourselves and spread across the planet? perhaps they didn ’ t want to. longer brain pathways lead to larger and deeper memory hierarchies. these confer a greater ability to examine and discard more blind alleys, to see more consequences of a plan before enacting it. in general this enables us to think things through. if boskops had longer chains of cortical networks — longer mental assembly lines — they would have created longer and more complex classification chains. when they looked down a road as far as they could, before choosing a path, they would have seen farther than we can : more potential outcomes, more possible downstream costs and benefits. as more possible outcomes of a plan become visible, the variance among judgments between individuals will likely lessen. there are far fewer correct paths — intelligent paths — than there are paths. it is sometimes argued that the illusion of free will arises from the fact that we can ’ t adequately judge all p ossible moves, with the result that our choices are based on imperfect, sometimes impoverished, information. perhaps the boskops were trapped by their ability to see clearly where things would head. perhaps they were prisoners of those majestic brains. there is another, again poignant, possible explanation for the disappearance of the big - brained people. maybe all that thoughtfulness was of no particular survival value in 10, 000 b. c


head. perhaps they were prisoners of those majestic brains. there is another, again poignant, possible explanation for the disappearance of the big - brained people. maybe all that thoughtfulness was of no particular survival value in 10, 000 b. c. the great genius of civilization is that it allows individuals to store memory and operating rules outside of their brains, in the world that surrounds them. the human brain is a sort of central processing unit operating on multiple memory disks, some stored in the head, some in the culture. lacking the external hard drive of a literate society, the boskops were unable to exploit the vast potential locked up in their expanded cortex. they were born just a few millennia too soon. in any event, boskops are gone, and the more we learn about them, the more we miss them. their demise is likely to have been gradual. a big skull was not conducive to easy births, and thus a within - group pressure toward smaller heads was probably always present, as it still is in present - day humans, who have an unusually high infant mortality rate due to big - headed babies. this pressure, together with possible interbreeding with migrating groups of smaller - brained peoples, may have led to a gradual decrease in the frequency of the boskop genes in the growing population of what is now south africa. then again, as is all too evident, human history has often been a history of savagery. genocide and oppression seem primitive, whereas modern institutions from schools to hospices seem enlightened. surely, we like to think, our future portends more of the latter than the former. if learning and gentility are signs of civilization, perhaps our almost - big brains are straining against their residual atavism, struggling to expand. perhaps the preternaturally civilized boskops had no chance against our barbarous ancestors, but could be leaders of society if they were among us today. maybe traces of boskops, and their unusual nature, linger on in isolated corners of the world. physical anthropologists report that boskop features still occasionally pop up in living populations of bushmen, raising the possibility that the last of the race may have walked the dusty transvaal in the not - too - distant past. some genes stay around in a population, or mix themselves into surrounding populations via interbreeding. the genes may remain on the periphery, neither becoming widely fixed in the population at large nor being entirely eliminated from the gene pool. just about 100 miles


recursion is a programming paradigm as well as a problem solving strategy thought to be very challenging to grasp for university students. this article outlines a pilot study, which expands the age range of students exposed to the concept of recursion in computer science through instruction in a series of interesting and engaging activities. in this study, a small number of students ( n = 9 ) aged 11 to 13 years, were presented with a new and unique recursion curriculum involving hands - on experiences over a seven - week period at the university of victoria, canada. the curriculum was comprised of a series of progressively challenging recursion activities — roughly based upon the ideas of ‘ computer science unplugged ’ ( bell, witten, & fellows, 2009 ) — and included programming applications with microworlds ex, a programming language based on logo. through this engagement, an increased number of students recognized and understood the concepts covered. we hypothesize that through experiences for youth with activities such as those outlined here, the number of students who understand fundamental computer science applications and who might potentially pursue computer science in post - secondary education will increase. we hypothesis further that through an earlier encounter of “ challenging ” concepts the learning and understanding of those will become easier at the university level. in this paper, the curriculum, classroom experiences, preliminary, largely descriptive and qualitative results and next steps in the research are discussed. gunion, katherine ; milford, todd ; and stege, ulrike " the paradigm recursion : is it more accessible when introduced in middle school?, " the journal of problem solving : 2, article 8.


garden of eden to the building of the first city to the tower of babel. humorous it is that so much space is devoted to depictions of the first chapters of genesis. it is as if the maker of the protestant ladder realized after he had drawn about six scenes from genesis that he was running out of space, and so he quickly leaped over lots of history to get to the crucifixion of christ, the really big historical event. around the time of christ we have the interesting scene of john the baptist ' s head being presented by salome ( never know if the protestants were caravaggio - lovers, you know.. ). a second difference between the two ladders is that the protestant portrays two separate channels or tubes of history, the catholic and the protestant, rather than one. the catholics had looked at the protestants as a withered branch ; the protestants recognized the " parallel track " of the roman catholic church with the pope in charge. finally, however, the protestant ladder shows that the catholic " track " of history will end in an unceremonious way when the road turns back on itself and the pope is overturned. the last picture on the " catholic side " shows an upside - down pope being lowered into a fire - - perhaps he will fall victim to the same fires with which he has burned the protestant martyrs. what lies at the end of the protestant road, in contrast? a straight road to heaven. the protestant road is narrower than the catholic one ( " narrow is the way that leads to salvation " ) but it, after all, is the " true " one. by looking at the competing catholic and protestant ladders, then, the student can see how artistic representation can be used in the service of religious propaganda. spalding and whitman and the protestant ladder jette further informs us, however, that spalding seemed to make very little use of the ladder in teaching. why? because protestants, as " people of the book " and " transformers of culture " ( no, george bush isn ' t the first " transformer " ), were more interested in cultivating literacy and the land for the indians. by 1839 spalding had published the first printed book in the nez perce language ( jette doesn ' t tell us if this was a bible, but the eager student would, no doubt, follow up this lead ), and the protestant ladder just seemed to be a kind of afterthought so as not to let the catholics have all the good ideas. let ' s pause


chemical principles / will it react? an introduction to chemical equilibrium and so, nothing that to our world appears, perishes completely, for nature ever upbuilds one thing from another ' s ruin ; suffering nothing yet to come to birth but by another ' s death. lucretius ( 95 - 55 b. c. ) the main question asked in chapter 2 was " if a given set of substances will react to give a desired product, how much of each substance is needed? " our basic assumptions were that matter cannot be arbitrarily created or destroyed, and that atoms going into a reaction must come out again as products. in this chapter we ask a second question : " will a reaction occur, eventually? " is there a tendency or a drive for a given reaction to take place, and if we wait long enough will we find that reactants have been converted spontaneously into products? this question leads to the ideas of spontaneity and of chemical equilibrium. a third question, " will a reaction occur in a reasonably short time? " involves chemical kinetics, which will be discussed in chapter 22. for the moment, we will be satisfied if we can predict which way a chemical reaction will go by itself, ignoring the time factor. spontaneous reactions a chemical reaction that will occur on its own, given enough time, is said to be spontaneous. in the open air, and under the conditions inside an automobile engine, the combustion of gasoline is spontaneous : c7h16 + 11 o2 → 7co2 + 8 h2o ( the reaction is exothermic, or heat emitting. the enthalpy change, which was defined in chapter 2, is large and negative : = - 4812 kj mole - 1 of heptane at 298 k. the heat emitted causes the product gases to expand, and it is the pressure from these expanding gases that drives the car. ) in contrast, the reverse reaction under the same conditions is not spontaneous : 7co2 + 8h2o c7h16 + 11 o2 no one seriously proposes that gasoline can be obtained spontaneously from a mixture of water vapor and carbon dioxide. explosions are examples of rapid, spontaneous reactions, but a reaction need not be as rapid as an explosion to be spontaneous. it is important to understand clearly the difference between rapidity and spontaneity. if you mix oxygen and hydrogen gases at room temperature, they will remain together without appreciable reaction for years. yet the reaction to produce water is genuinely spontaneous


it is important to understand clearly the difference between rapidity and spontaneity. if you mix oxygen and hydrogen gases at room temperature, they will remain together without appreciable reaction for years. yet the reaction to produce water is genuinely spontaneous : 2h2 + o2 → 2h2o we know that this is true because we can trigger the reaction with a match, or catalyst of finely divided platinum metal. the preceding sentence suggests why a chemist is interested in whether a reaction is spontaneous, that is, whether it has a natural tendency to occur. if a desirable chemical reaction is spontaneous but slow, it may be possible to speed up the process. increasing the temperature will often do the trick, or a catalyst may work. we will discuss the functions of a catalyst in detail in chapter 22. but in brief, we can say now that a catalyst is a substance that helps a naturally spontaneous reaction to go faster by providing an easier pathway for it. gasoline will burn rapidly in air at a high enough temperature. the role of a spark plug in an automobile engine is to provide this initial temperature. the heat produced by the reaction maintains the high temperature needed to keep it going thereafter. gasoline will combine with oxygen at room temperature if the proper catalyst is used, because the reaction is naturally spontaneous but slow. but no catalyst will ever make carbon dioxide and water recombine to produce gasoline and oxygen at room temperature and moderate pressures, and it would be a foolish chemist who spent time trying to find such a catalyst. in short, an understanding of spontaneous and nonspontaneous reactions helps a chemist to see the limits of what is possible. if a reaction is possible but not currently realizable, it may be worthwhile to look for ways to carry it out. if the process is inherently impossible, then it is time to study something else. equilibrium and the equilibrium constant the speed with which a reaction takes a place ordinarily depends on the most concentrations of the reacting substances. this is common sense, since most reactions take place when molecules collide, and the more molecules there are per unit of volume, the more often collisions will occur. the industrial fixation of atmospheric nitrogen is very important in the manufacture of agricultural fertilizers ( and explosives ). one of the steps in nitrogen fixation, in the presence of a catalyst, is n2 + o2 → 2no ( 4 - 1 ) if this reaction took place by simple collision of one molecule of n2 and one molecule of o2, then we would expect


nitrogen fixation, in the presence of a catalyst, is n2 + o2 → 2no ( 4 - 1 ) if this reaction took place by simple collision of one molecule of n2 and one molecule of o2, then we would expect the rate of collision ( and hence the rate of reaction ) to be proportional to the concentrations of n2 and o2 : rate of no production r1 = k1 [ n2 ] [ o2 ] ( 4 - 2 ) the proportionality constant k1 is called the forward - reaction rate constant, and the bracketed terms [ n2 ] [ o2 ] represent concentrations in moles per liter. this rate constant, which we will discuss in more detail in chapter 22, usually varies with temperature. most reactions go faster at higher temperatures, so k1 is larger at higher temperatures. but k1 does not depend on the concentrations of nitrogen and oxygen gases present. all of the concentration dependence of the overall forward reaction rate, r1, is contained in the terms [ n2 ] and [ o2 ]. if this reaction began rapidly in a sealed tank with high starting concentrations of both gases, then as more n2 and o2 were consumed, the forward reaction would become progressively slower. the rate of reaction would decrease because the frequency of collision of molecules would diminish as fewer n2 and o2 molecules were left in the tank. the reverse reaction can also occur. if this reaction took place by the collision of two molecules of no to make one molecule of each starting gas, 2no → n2 + o2 ( 4 - 3 ) then the rate of reaction again would be proportional to the concentration of each of the colliding molecules. since these molecules are of the same compound, no, the rate would be proportional to the square of the no concentration : rate of no removal [ no ] [ no ] r2 = k2 [ no ] 2 ( 4 - 4 ) where r2 is the overall reverse reaction rate and k2 is the rev ~ rse - reaction rate constant. if little no is present when the experiment begins, this reaction will occur at a negligible rate. but as more no accumulates by the forward reaction, the faster it will be broken down by the reverse reaction. thus as the forward rate, r1, decreases, the reverse rate, r2, increases. eventually the point will be reached at which the forward and reverse reactions exactly balance ( 4 - 5 ) : r1 = r2 [ n2 ] [


as the forward rate, r1, decreases, the reverse rate, r2, increases. eventually the point will be reached at which the forward and reverse reactions exactly balance ( 4 - 5 ) : r1 = r2 [ n2 ] [ o2 ] k1 = k2 [ no ] 2 this is the condition of equilibrium. had you been monitoring the concentrations of the three gases, n2 o2, and no, you would have found that the composition of the reacting mixture had reached an equilibrium state and thereafter ceased to change with time. this does not mean that the individual reactions had stopped, only that they were proceeding at equal rates ; that is, they had arrived at, and thereafter maintained, a condition of balance or equilibrium. the condition of equilibrium can be illustrated by imagining two large fish tanks, connected by a channel ( figure 4 - 1 ). one tank initially contains 10 goldfish, and the other contains 10 guppies. if you watch the fish swimming aimlessly long enough, you will eventually find that approximately 5 of each type of fish are present in each tank. each fish has the same chance of blundering through the channel into the other tank. but as long as there are more goldfish in the left tank ( figure 4 - la ), there is a greater probability that a goldfish will swim from left to right than the reverse. similarly, as long as the number of guppies in the right tank exceeds that in the left, there will be a net flow of guppies to the left, even though there is nothing in the left tank to make the guppies prefer it. thus the rate of flow of guppies is proportional to the concentration of guppies present. a similar statement can be made for the goldfish. at equilibrium ( figure 4 - 1b ), on an average there will be 5 guppies and 5 goldfish in each tank. but they will not always be the same 5 of each fish. if 1 guppy wanders from the left tank into the right, then it or a different guppy may wander back a little later. thus at equilibrium we find that the fish have not stopped swimming, only that over a period of time the total number of guppies and goldfish in each tank remains constant. if we were to fill each tank with 9 goldfish and then throw in 1 guppy, we would see that, in its aimless swimming, it would spend half its time in one tank and half in the other (


each tank remains constant. if we were to fill each tank with 9 goldfish and then throw in 1 guppy, we would see that, in its aimless swimming, it would spend half its time in one tank and half in the other ( figure 4 - 1 c ). in the no reaction we considered, there will be a constant concentration of no molecules at equilibrium, but they will not always be the same no molecules. individual no molecules will react to re - form n2 and o2, and other reactant molecules will make more no. as with the goldfish, only on a head - count or concentration basis have changes ceased at equilibrium. the equilibrium condition for the no - producing reaction, equation 4 - 1, can be rewritten in a more useful form : in which the ratio of forward and reverse rate constants is expressed as a simple constant, the equilibrium constant, keq. this equilibrium constant will vary as the temperature varies, but it is independent of the concentrations of the reactants and products. it tells us the ratio of products to reactants at equilibrium, and is an extremely useful quantity for determining whether a desired reaction will take place spontaneously. general form of the equilibrium constant we derived the equilibrium - constant expression for the no reaction by assuming that we knew the way that the forward and reverse steps occurred at the molecular level. if the no reaction proceeded by simple collision of two molecules, the derivation would be perfectly correct. the actual mechanism of this reaction is more complicated. but it is important, and fortunate for chemists, that we do not have to know the reaction mechanism to write the proper equilibrium constant. the equilibrium - constant expression can always be written from the balanced chemical equation, with no other information, even when the forward and reverse rate expressions are more complicated than the balanced equation would suggest. ( we shall prove this in chapter 16. ) in our no example, the forward reaction actually takes place by a series of complicated chain steps. the reverse reaction takes place by a complementary set of reactions, so that these complications cancel one another in the final ratio of concentrations that gives us the equilibrium constant. the details of the mechanism are " invisible " to the equilibrium - constant expression, and irrelevant to equilibrium calculations. a general chemical reaction can be written as in this expression, a and b represent the reactants ; c and d, the products. the letters a, b, c, and d represent the number of moles of each substance involved in the balanced reaction, and the double arrows indicate a state of equilibrium


, a and b represent the reactants ; c and d, the products. the letters a, b, c, and d represent the number of moles of each substance involved in the balanced reaction, and the double arrows indicate a state of equilibrium. although only two reactants and two products are shown in the general reaction, the principle is extendable to any number. the correct equilibrium - constant expression for this reaction is it is the ratio of product concentrations to reactant concentrations, with each concentration term raised to a power given by the number of moles of that substance appearing in the balanced chemical equation. because it is based on the quantities of reactants and products present at equilibrium, equation 4 - 8 is called the law of mass action. | give the equilibrium - constant expression for the reaction | the equilibrium constant is given by since all four substances have a coefficient of 1 in the balanced equation, their concentrations are all raised to the first power in the equilibrium - constant expression. | what is the equilibrium - constant expression for the formation of water from hydrogen and oxygen gases? the reaction is | since two moles of hydrogen and water are involved in the chemical equation, their concentrations are squared in the keq expression. | give the equilibrium - constant expression for the dissociation ( breaking up ) of water into hydrogen and oxygen. the reaction is | an important general point emerges here. this reaction is the reverse of that of example 2, and the equilibrium - constant expression is the inverse, or reciprocal, of the earlier one. if a balanced chemical reaction is reversed, then the equilibrium - constant expression must be inverted, since what once were reactants now are products, and vice versa. | the dissociation of water can just as properly be written as what then is the equilibrium - constant expression? notice that when the reaction from example 3 is divided by 2, resulting in the example 4 reaction, the equilibrium constant is the square root of the old value, or the old keq to the one - half power. similarly, if the reaction is doubled, the keq must be squared. in general, it is perfectly proper to multiply all the coefficients of a balanced chemical reaction by any positive or negative number, n, and the equation will remain balanced. ( multiplying all the coefficients of an equation by - 1 is formally the same as writing the equation in reverse. write out a simple equation and prove to yourself that this is so. ) but if all the co1ficients of an equation are multiplied by n,


coefficients of an equation by - 1 is formally the same as writing the equation in reverse. write out a simple equation and prove to yourself that this is so. ) but if all the co1ficients of an equation are multiplied by n, then the new equilibrium - constant expression is the old one raised to the nth power. hence, when working with equilibrium constants, one must keep the corresponding chemical reactions clearly in mind. | the reaction for the formation or the breakdown of ammonia can be written in a number of ways : ( each of these expressions might be appropriate, depending on whether you were focusing on nitrogen, ammonia, hydrogen, or the dissociation of ammonia. ) what are the equilibrium - constant expressions for each formulation, and how are the equilibrium constants related? notice that there is nothing wrong with fractional powers in the equilibrium - constant expression. using equilibrium constants equilibrium constants have two main purposes : - 1. to help us tell whether a reaction will be spontaneous under specified conditions. - 2. to enable us to calculate the concentration of reactants and products that will be present once equilibrium has been reached. we can illustrate how equilibrium constants can be used to achieve these ends, and also the fact that an equilibrium constant is indeed constant, with real data from one of the most intensively studied of all reactions, that between hydrogen and iodine to yield hydrogen iodide : if we mix hydrogen and iodine in a sealed flask and observe the reaction, the gradual fading of the purple color of the iodine vapor tells us that iodine is being consumed. this reaction was studied first by the german chemist max bodenstein in 1893. table 4 - 1 contains the data from bodenstein ' s experiments. the experimental data are in the first three columns. in the fourth column, we have calculated the simple ratio of product and reactant concentrations, [ hi ] / [ h2 ] [ i2 ], to see if it is constant. it clearly is not, for as the hydrogen concentration is decreased and the iodine concentration is increased, this ratio varies from 2. 60 to less than 1. the law of mass action ( section 4 - 3 ) dictates that the equilibrium - constant expression should contain the square of the hi concentration, since the reaction involves 2 moles of hi for every mole of h2 and i2, the fifth column shows that the ratio [ hi ] 2 / [ h2 ] [ i2 ] is constant within a mean deviation of approximately 3 %


, since the reaction involves 2 moles of hi for every mole of h2 and i2, the fifth column shows that the ratio [ hi ] 2 / [ h2 ] [ i2 ] is constant within a mean deviation of approximately 3 %. * therefore, this ratio is the proper equilibrium - constant expression, and the average value of keq for these six runs is 50. 53. the equilibrium constant can be used to determine whether a reaction under specified conditions will go spontaneously in the forward or in the reverse direction. the ratio of product concentration to reactant concentration, identical to the equilibrium constant in form but not necessarily at equilibrium conditions, is called the reaction quotient, q : q = ( not necessarily at equilibrium ) ( 4 - 10 ) if there are too many reactant molecules present for equilibrium to exist, then the concentration terms in the denominator will make the reaction quotient, q, smaller than keq. the reaction will go forward spontaneously to make more product. however, if an experiment is set up so that the reaction quotient is greater than keq, then too many product molecules are present for equilibrium and the reverse reaction will proceed spontaneously. therefore, a comparison of the actual concentration ratio or reaction quotient with the equilibrium constant allows us to predict in which direction a reaction will go spontaneously under the given set of circumstances : q < keq ( forward reaction spontaneous ) q > keq ( reverse reaction spontaneous ) ( 4 - 11 ) q = keq ( reactants and products at equilibrium ) - these are bodenstein ' s original numbers. modern data can be much more accurate, with less deviation in keq. the mean deviation is the average of the deviations of individual calculated keq from the average keq. | if 1. 0 x 10 - 2 mole each of hydrogen and iodine gases are placed in a i - liter flask at 448°c with 2. 0 x 10 - 3 mole of hi, will more hi be produced? | the reaction quotient under these conditions is this is smaller than the equilibrium value of 50. 53 in table 4 - 1, which tells us that excess reactants are present. hence, equilibrium will not be reached until more hi has been formed. | if only 1. 0 x 10 - 3 mole each of h2 and i2 had been used, together with 2. 0 x 10 - 3 mole of hi, would more hi have been produced spontaneously? | you can verify that the reaction quotient


1. 0 x 10 - 3 mole each of h2 and i2 had been used, together with 2. 0 x 10 - 3 mole of hi, would more hi have been produced spontaneously? | you can verify that the reaction quotient is q = 4. 0. because this is less than keq, the forward reaction is still spontaneous. | if the conditions of example 7 are changed so that the hi concentration is increased to 2. 0 x 10 - 2 mole liter - 1, what happens to the reaction? | the reaction quotient now is q = 400. this is greater than keq - there are now too many product molecules and too few reactant molecules for equilibrium to exist. thus the reverse reaction occurs more rapidly than the forward reaction. equilibrium is reached only by converting some of the hi to h2 and 12, so the reverse reaction is spontaneous. | if the conditions of example 7 are changed so that the hi concentration is 7. 1 x 10 - 3 mole liter - 1, in which direction is the reaction spontaneous? | under these conditions, since q equals keq within the limits of accuracy of the data, the system as described is at equilibrium, and neither the forward nor the backward reaction is spontaneous. ( both reactions are still taking place at the molecular level, of course, but they are balanced so their net effects cancel. ) the second use for equilibrium constants is to calculate the concentrations of reactants and products that will be present at equilibrium. | if a 1 - liter flask contains 1. 0 x 10 - 3 mole each of h2 and i2 at 448°c, what amount of hi is present when the gas mixture is at equilibrium? | the keq expression is treated as an ordinary algebraic equation, and solved for the hi concentration : you can verify that in example 7 the hi concentration was less than this equilibrium value ; in example 8 it was more ; and in example 9 it was just this value. | one - tenth of a mole, 0. 10 mole, of hydrogen iodide is placed in an otherwise empty 5. 0 liter flask at 448°c. when the contents have come to equilibrium, how much hydrogen and iodine will be in the flask? | from the stoichiometry of the reaction, the concentrations of h2 and i2 must be the same. for every mole of h2 and i2 formed, 2 moles of hi must decompose. let y equal the number of moles of


0 can be solved by the quadratic formula, thus for this problem the first solution is physically impossible since it shows more h2 reacting than was originally present. the second solution is the correct answer : y = 0. 935 10 - 3 mole liter - 1. therefore, the equilibrium concentrations are units and equilibrium constants as we have seen, the square brackets around a chemical symbol, as in [ n2 ], represent concentrations, usually but not exclusively in units of moles liter - 1. concentrations expressed as moles liter - 1 are often given the special symbol c, as in cn2, the concentrations measured in these units is denoted by kc. an equilibrium constant as we have defined it thus far may itself have units. in example 1, keq is unitless since the moles2 1iter - 2 of the numerator and denominator cancel. in example 2, the units of keq are moles - 1 liter since concentration occurs to the second power in the numerator and to the third power in the denominator. in example 3 the units of keq are the inverse : moles liter - 1. the units demanded by example 4, moles1 / 2 liter - 1 / 2, may seem strange but they are perfectly respectable. | what are the units for the equilibrium constants in the four reactions of example 5? | the keq expression is treated as an ordinary algebraic equation, and solved for the hi concentration : the question of units for keq becomes important as soon as we realize that we can measure concentration in units other than moles liter - 1. the partial pressure in atmospheres is a convenient unit when dealing with gas mixtures, and the equilibrium constant then is identified by kp. since the numerical values of kp and kc in general will be different, one must be sure what the units are when using a numerical constant. | one step in the commercial synthesis of sulfuric acid is the reaction of sulfur dioxide and oxygen to make sulfur trioxide : at 1000 k, the equilibrium constant for this reaction is kp = 3. 50 atm - 1. if the total pressure in the reaction chamber is 1. 00 atm and the partial pressure of unused 02 at equilibrium is 0. 10 atm, what is the ratio of concentrations of product ( s03 ) to reactant ( s02 )? the equilibrium mixture has 0. 59 mole of s03 for every 1 mole of s02. the ideal gas law permits us to convert between atmospheres


of concentrations of product ( s03 ) to reactant ( s02 )? the equilibrium mixture has 0. 59 mole of s03 for every 1 mole of s02. the ideal gas law permits us to convert between atmospheres and moles liter - 1, and between kp and kc : pv = nrt ( 3 - 8 ) ( 4 - 12 ) in the general chemical reaction written earlier, δn ( read " delta n " ), the increase in number of moles of gas during the reaction, is n = c + d - a - b ( 4 - 13 ) the equilibrium - constant expression in terms of partial pressures is with the ideal gas law applied to each gas component, we can convert this expression to kc : ( rt ) δn = kc ( rt ) δn ( 4 - 15 ) ( do not confuse the two uses of the symbol c in equation 4 - 15 : one is for concentration in moles liter - 1 and the other for the number of moles of substance c. ) | what is the numerical value of kc for the reaction of example 14? | three moles of reactant gases are converted into only 2 moles of product, so δn = - 1. hence at 1000 k, although the numerical answers that result when different units are used may differ, the physical reality must be the same. | what is the concentration of oxygen in example 14, in moles liter - 1? solve example 14 again using kc from example 15. | three moles of reactant gases are converted into only 2 moles of product, so δn = - 1. hence at 1000 k, this is the same ration of so _ 3 to so _ 4 as was obtained when atmospheres were used. the choice is one of convenience. equilibrium involving gases with liquids or solids all the examples considered so far have involved only one physical state, a gas, and are examples of homogeneous equilibria. equilibria that involve two or more physical states ( such as a gas with a liquid or a solid ) are called hetergenous equilibria. if one or more of the reactants or products are solids or liquids, how does this affect the form of the equilibrium constant? the answer, in short, is that any pure solids or liquids that may be present at equilibrium have the same effect on the equilibrium no matter how much solid or liquid is present. the concentration of a pure solid or liquid can be considered constant, and for convenience


, in short, is that any pure solids or liquids that may be present at equilibrium have the same effect on the equilibrium no matter how much solid or liquid is present. the concentration of a pure solid or liquid can be considered constant, and for convenience all such constant terms are brought to the left side of the equation and incorporated into the equilibrium constant itself. as an example, limestone ( calcium carbonate, caco3 ), breaks down into quicklime ( calcium oxide, cao ) and carbon dioxide, co2 : the simple equilibrium - constant expression is - k ' eq = as long as any solid limestone and quicklime are in contact with the gas, their effect on the equilibrium is unchanging. hence the terms [ caco3 ] and [ cao ] remain constant and can be merged with k ' eq : - keq = k ' eq [ co2 ( g ) ] this form of the equilibrium - constant expression tells us that, at a given temperature, the concentration of carbon - dioxide gas above limestone and calcium oxide is a fixed quantity. ( this is true only as long as both solid forms are present. ) measuring concentration in units of atmospheres, we get - kp = pco2 with the experimental value 0. 236 atm at 800°c. we can see what this means experimentally by considering a cylinder to which caco, and cao have been added. the cylinder has a movable piston, as shown in figure 4 - 2. if the piston is fixed at one position, then caco3 will decompose until the pressure of co2 above the solids is 0. 236 atm ( if the temperature is 800°c ). if you try to decrease the pressure by raising the piston, then more caco3 will decompose until the pressure again rises to 0. 236 atm. conversely, if you try to increase the pressure by lowering the piston, some of the co2 gas will react with cao and become caco3 decreasing the amount of co2 gas present until the pressure once more is 0. 236 atm. the only way to increase pco2, is to raise the temperature, which increases the value of kp itself to 1 atm at 894°c and to 1. 04 atm at 900°c. an even simpler example is the vaporization of a liquid such as water : this process can be treated as a chemical reaction in a formal sense even though bonds within molecules are not made or broken. imagine that the cylinder shown in figure 4 -


room temperature, then iodine is present as deep purple crystals rather than as vapor. what then is the form of the equilibrium - constant expression, and does the equilibrium depend on the amount of iodine crystals present? | the reaction is and the equilibrium - constant expression is : as long as some i2 ( s ) crystals are present, the quantity is immaterial as far as equilibrium is concerned. | tin ( iv ) oxide reacts with carbon monoxide to form metallic tin and co2 by the reaction what is the equilibrium - constant expression? | what is the equilibrium - constant expression for the following reaction leading to liquid water? what would the expression be if the product were water vapor? if the product is h2o ( l ), the equilibrium - constant expression is if the product is h2o ( g ), the equilibrium - constant expression is the preceding example shows that as long as liquid water is present the gas - phase concentration is fixed at the vapor pressure of water at that temperature. hence the water contribution, being constant, can be lumped into keq. factors affecting equilibrium : le chatelier ' s principle equilibrium represents a balance between two opposing reactions. how sensitive is this balance to changes in the conditions of a reaction? what can be done to change the equilibrium state? these are very practical questions if, for example, one is trying to increase the yield of a useful product in a reaction. under specified conditions, the equilibrium - constant expression tells us the ratio of product to reactants when the forward and backward reactions are in balance. this equilibrium constant is not affected by changes in concentration of reactants or products. however, if products can be withdrawn continuously, then the reacting system can be kept constantly off - balance, or short of equilibrium. more reactants will be used and a continuous stream of new products will be formed. this method is useful when one product of the reaction can escape as a gas, be condensed or frozen out of a gas phase as a liquid or solid, be washed out of the gas mixture by a spray of a liquid in which it is especially soluble, or be precipitated from a gas or solution. for example, when solid lime ( cao ) and coke ( c ) are heated in an electric furnace to make calcium carbide ( cac2 ), the reaction, which at 2000 - 3000°c has an equilibrium constant of close to 1. 00, is tipped toward calcium carbide formation by the continuous removal of carbon monoxide gas. in the industrial manufacture


dissociation to hydrogen and iodine is favored much more. the hydrogen iodide - producing reaction is exothermic or heat emitting : ( if you check this figure against appendix 3, remember that this reaction involves gaseous iodine, not solid. ) if the external temperature of this reaction is lowered, the equilibrium is shifted in favor of the heat - emitting or forward reaction ; conversely, if the temperature is increased, the reverse reaction, producing h2 and i2 is favored. the equilibrium shifts so as to counteract to some extent the effect of adding heat externally ( raising the temperature ) or removing it ( lowering the temperature ). the temperature dependence of the equilibrium point is one example of a more general principle, known as le chatelier ' s principle : if an external stress is applied to a system at chemical equilibrium, then the equilibrium point will change in such a way as to counteract the effects of that stress. if the forward half of an equilibrium reaction is exothermic, then keq will decrease as the temperature increases ; if it is endothermic, keq will increase. only for a heat - absorbing reaction can the equilibrium yield of products be improved by increasing the temperature. a good way to remember this is to write the reaction explicitly with a heat term : then it is clear that adding heat, just like adding hi, shifts the reaction to the left. ( see figure 4 - 3. ) le chatelier ' s principle is true for other kinds of stress, such as pressure changes. the equilibrium constant, keq, is not altered by a pressure change at constant temperature. however, the relative amounts of reactants and products will change in a way that can be predicted from le chatelier ' s principle. the hydrogen - iodine reaction involves an equal number ( 2 ) of moles of reactants and product. therefore, if we double the pressure at constant temperature, the volume of the mixture of gases will be halved. all concentrations in moles liter - 1 will be doubled, but their ratio will be the same. in example 12, doubling the concentrations of the reactants and product does not change the equilibrium constant : - keq = - = 50. 51 thus the hydrogen - iodine equilibrium is not sensitive to pressure changes. notice that in this case keq does not have units, since the concentration units in the numerator and denominator cancel. in contrast, the dissociation of ammonia is affected by changes in pressure because the


not sensitive to pressure changes. notice that in this case keq does not have units, since the concentration units in the numerator and denominator cancel. in contrast, the dissociation of ammonia is affected by changes in pressure because the number of moles ( 2 ) of reactant does not equal the total number of moles ( 4 ) of products : the equilibrium constant for this reaction at 25°c is - keq = 2. 5 10 - 9 mole2 liter - 2 one set of equilibrium conditions is - n2 = 3. 28 10 - 3 mole liter - 1 - h2 = 2. 05 10 - 3 mole liter - 1 - nh3 = 0. 106 mole liter - 1 ( can you verify that these concentrations satisfy the equilibrium condition? ) if we now double the pressure at constant temperature, thereby halving the volume and doubling each concentration, - n2 = 6. 56 10 - 3 mole liter - 1 - h2 = 4. 10 10 - 3 mole liter - 1 - nh3 = 0. 212 mole liter - 1 the ratio of products to reactants, the reaction quotient, is no longer equal to keq : - q = 1. 0 10 - 8 mole2 liter - 2 since q is greater than keq, too many product molecules are present for equilibrium. the reverse reaction will run spontaneously, thereby forming more nh3 and decreasing the amounts of h2 and n2. consequently, part of the increased pressure is offset when the reaction shifts in the direction that lowers the total number of moles of gas present. in general, a reaction that reduces the number of moles of gas will be favored by an increase in pressure, and one that produces more gas will be disfavored. ( see figure 4 - 4. ) | if the hydrogen iodide reaction were run at a temperature at which the iodine was a solid, would an increase in pressure shift the equilibrium reaction toward more hi, or less? what would be the effect of pressure on keq? | since the reaction of 2 moles of gaseous hi now yields 1 mole of gaseous h2 and 1 mole of solid i2 the stress of increased pressure is relieved by dissociating hi to h2 and i2. however, keq will be unchanged by the pressure increase. what effect does a catalyst have on a reaction at equilibrium? none. a catalyst cannot change the value of keq, but it can increase the speed with which equilibrium is reached. this


. however, keq will be unchanged by the pressure increase. what effect does a catalyst have on a reaction at equilibrium? none. a catalyst cannot change the value of keq, but it can increase the speed with which equilibrium is reached. this is the main function of a catalyst. it can take the reaction only to the same equilibrium state that would be reached eventually without the catalyst. catalysts are useful, nevertheless. many desirable reactions, although spontaneous, occur at extremely slow rates under ordinary conditions. in automobile engines, the main smog - producing reaction involving oxides of nitrogen is ( once no is present, it reacts readily with more oxygen to make brown n02. ) at the high temperature of an automobile engine, keq for this reaction is so large that appreciable amounts of no are formed. however, at 25°c, keq = 10 - 30. ( using only the previous two bits of information and le chatelier ' s principle, predict whether the reaction as written is endothermic or exothermic. check your answer using data from appendix 3. ) the amount of no present in the atmosphere at equilibrium at 25°c should be negligible. no should decompose spontaneously to n2 and o2 as the exhaust gases cool. but any southern californian can verify that this is not what happens. both no and n02 are indeed present, because the gases of the atmosphere are not at equilibrium. the rate of decomposition of no is extremely slow, although the reaction is spontaneous. one approach to the smog problem has been to search for a catalyst for the reaction that could be housed in an exhaust system and could break down no in the exhaust gases as they cool. finding a catalyst is possible ; a practical problem arises from the gradual poisoning of the catalyst by gasoline additives, such as lead compounds. this is the reason why new cars with catalytic converters only use lead - free gasoline. a proof of the assertion that a catalyst cannot change the equilibrium constant is illustrated in figure 4 - 5. if a catalyst could shift the equilibrium point of a reacting gas mixture and produce a volume change, then this expansion and contraction could be harnessed by mechanical means and made to do work. we would have a true perpetual - motion machine that would deliver power without an energy source. from common sense and experience we know this to be impossible. this " common sense " is stated scientifically as the first law of thermodynamics, which will be discussed in chapter 15


motion machine that would deliver power without an energy source. from common sense and experience we know this to be impossible. this " common sense " is stated scientifically as the first law of thermodynamics, which will be discussed in chapter 15. a mathematician would call this a proof by contradiction : if we assume that a catalyst can alter keq, then we must assume the existence of a perpetual - motion machine. however, a perpetual - motion machine cannot exist ; therefore our initial assumption was wrong, and we must conclude that a catalyst cannot alter keq. in summary, keq is a function of temperature, but it is not a function of reactant or product concentrations, total pressure, or the presence or absence of catalysts. the relative amounts of substances at equilibrium can be changed by applying an external stress to the equilibrium mixture of reactants and products, and the change is one that will relieve this stress. this last statement, le chatelier ' s principle, enables us to predict what will happen to a reaction when external factors are changed, without having to make exact calculations. a spontaneous reaction is one that will take place, given enough time, without outside assistance. some spontaneous reactions are rapid, but time is not an element in the definition of spontaneity. a reaction can be almost infinitely slow and still be spontaneous. the net reaction that we observe is the result of competition between forward and reverse steps. if the forward process is faster, then products accumulate, and we say that the reaction is spontaneous in the forward direction. if the reverse process is faster, then reactants accumulate, and we say that the reverse reaction is the spontaneous one. if both forward and reverse processes take place at the same rate, then no net change is observed in any of the reaction components. this is the condition of chemical equilibrium. the ratio of products to reactants, each concentration term being raised to a power corresponding to the coefficient of that substance in the balanced chemical equation, is called the equilibrium constant, keq. ( see equation 4 - 8. ) it can be used to predict whether a given reaction under specified conditions will be spontaneous, and to calculate the concentrations of reactants and products at equilibrium. the reaction quotient, q, has a form that is identical with that of the equilibrium constant, keq, but q applies under nonequilibrium conditions as well. for a given set of conditions, if q is smaller than keq, the forward reaction is spontaneous ; if q is greater than keq,


that of the equilibrium constant, keq, but q applies under nonequilibrium conditions as well. for a given set of conditions, if q is smaller than keq, the forward reaction is spontaneous ; if q is greater than keq, the reverse reaction is spontaneous ; and if q = keq, the system is at equilibrium. the equilibrium constant can be used with any convenient set of concentration units : moles liter - 1, pressure in atmospheres, or others. its numerical value will depend on the units of concentration, so one must be careful to match the proper values of keq and units when solving problems. if gas concentrations are expressed in moles liter - 1, the equilibrium constant is designated by kc ; if in atmospheres, by kp. just as partial pressure of the jth component of a gas mixture is related to moles per liter by pj = cjrt, so kp and kc are related by kp = kc ( rt ) δn, in which δn is the net change in number of moles of gas during the reaction. when some of the reactants or products are pure solids or liquids, they act as infinite reservoirs of material as long as some solid or liquid is left. their effect on equilibrium depends only on their presence, not on how much of the solid or liquid is present. their effective concentrations are constant, and can be incorporated into keq. in practice, this simply means omitting concentration terms for pure solids and liquids from the equilibrium - constant expression. evaporation of a liquid can be treated formally as a chemical reaction with the liquid as reactant and vapor as product. these conventions for writing concentration terms for a liquid permit us to write the equilibrium constant for evaporation as kp = pj where pj is the equilibrium vapor pressure of substance j. le chatelier ' s principle states that if stress is applied to a system at equilibrium the amounts of reactants and products will shift in such a manner as to minimize the stress. this means that for a heat - absorbing, or endothermic, reaction, keq increases as the temperature is increased, since carrying out more of the reaction is a way of absorbing some of the added heat. similarly, cooling increases keq for a heat - emitting or exothermic reaction. although the equilibrium constant keq is independent of pressure, and changing the total pressure on a reacting system does not alter keq directly, an increase in pressure does cause the reaction to shift in


automatic number plate recognition automatic number plate recognition ( anpr ; see also other names below ) is a mass surveillance method that uses optical character recognition on images to read vehicle registration plates. they can use existing closed - circuit television or road - rule enforcement cameras, or ones specifically designed for the task. they are used by various police forces and as a method of electronic toll collection on pay - per - use roads and cataloging the movements of traffic or individuals. anpr can be used to store the images captured by the cameras as well as the text from the license plate, with some configurable to store a photograph of the driver. systems commonly use infrared lighting to allow the camera to take the picture at any time of the day. anpr technology tends to be region - specific, owing to plate variation from place to place. concerns about these systems have centered on privacy fears of government tracking citizens ' movements, misidentification, high error rates, and increased government spending. other names anpr is sometimes known by various other terms : - automatic license - plate recognition ( alpr ) - automatic vehicle identification ( avi ) - car plate recognition ( cpr ) - license - plate recognition ( lpr ) - lecture automatique de plaques d ' immatriculation ( lapi ) development history anpr was invented in 1976 at the police scientific development branch in the uk. prototype systems were working by 1979, and contracts were let to produce industrial systems, first at emi electronics, and then at computer recognition systems ( crs ) in wokingham, uk. early trial systems were deployed on the a1 road and at the dartford tunnel. the first arrest through detection of a stolen car was made in 1981. the software aspect of the system runs on standard home computer hardware and can be linked to other applications or databases. it first uses a series of image manipulation techniques to detect, normalize and enhance the image of the number plate, and then optical character recognition ( ocr ) to extract the alphanumerics of the license plate. anpr systems are generally deployed in one of two basic approaches : one allows for the entire process to be performed at the lane location in real - time, and the other transmits all the images from many lanes to a remote computer location and performs the ocr process there at some later point in time. when done at the lane site, the information captured of the plate alphanumeric, date - time, lane identification, and any other information required is completed in approximately 250 milliseconds


image. there are a number of possible difficulties that the software must be able to cope with. these include : - poor image resolution, usually because the plate is too far away but sometimes resulting from the use of a low - quality camera. - blurry images, particularly motion blur. - poor lighting and low contrast due to overexposure, reflection or shadows. - an object obscuring ( part of ) the plate, quite often a tow bar, or dirt on the plate. - a different font, popular for vanity plates ( some countries do not allow such plates, eliminating the problem ). - circumvention techniques. - lack of coordination between countries or states. two cars from different countries or states can have the same number but different design of the plate. while some of these problems can be corrected within the software, it is primarily left to the hardware side of the system to work out solutions to these difficulties. increasing the height of the camera may avoid problems with objects ( such as other vehicles ) obscuring the plate but introduces and increases other problems, such as the adjusting for the increased skew of the plate. on some cars, tow bars may obscure one or two characters of the license plate. bikes on bike racks can also obscure the number plate, though in some countries and jurisdictions, such as victoria, australia, " bike plates " are supposed to be fitted. some small - scale systems allow for some errors in the license plate. when used for giving specific vehicles access to a barricaded area, the decision may be made to have an acceptable error rate of one character. this is because the likelihood of an unauthorized car having such a similar license plate is seen as quite small. however, this level of inaccuracy would not be acceptable in most applications of an anpr system. imaging hardware at the front end of any anpr system is the imaging hardware which captures the image of the license plates. the initial image capture forms a critically important part of the anpr system which, in accordance to the garbage in, garbage out principle of computing, will often determine the overall performance. license plate capture is typically performed by specialized cameras designed specifically for the task. factors which pose difficulty for license plate imaging cameras include speed of the vehicles being recorded, varying ambient lighting conditions, headlight glare and harsh environmental conditions. most dedicated license plate capture cameras will incorporate infrared illumination in order to solve the problems of lighting and plate reflectivity. many countries now use license plates that are retroreflective. this returns the


lighting conditions, headlight glare and harsh environmental conditions. most dedicated license plate capture cameras will incorporate infrared illumination in order to solve the problems of lighting and plate reflectivity. many countries now use license plates that are retroreflective. this returns the light back to the source and thus improves the contrast of the image. in some countries, the characters on the plate are not reflective, giving a high level of contrast with the reflective background in any lighting conditions. a camera that makes use of active infrared imaging ( with a normal colour filter over the lens and an infrared illuminator next to it ) benefits greatly from this as the infrared waves are reflected back from the plate. this is only possible on dedicated anpr cameras, however, and so cameras used for other purposes must rely more heavily on the software capabilities. further, when a full - colour image is required as well as use of the anpr - retrieved details it is necessary to have one infrared - enabled camera and one normal ( colour ) camera working together. to avoid blurring it is ideal to have the shutter speed of a dedicated camera set to 1 / 1000 of a second. because the car is moving, slower shutter speeds could result in an image which is too blurred to read using the ocr software, especially if the camera is much higher up than the vehicle. in slow - moving traffic, or when the camera is at a lower level and the vehicle is at an angle approaching the camera, the shutter speed does not need to be so fast. shutter speeds of 1 / 500 of a second can cope with traffic moving up to 40 mph ( 64 km / h ) and 1 / 250 of a second up to 5 mph ( 8 km / h ). license plate capture cameras can now produce usable images from vehicles traveling at 120 mph ( 190 km / h ). to maximize the chances of effective license plate capture, installers should carefully consider the positioning of the camera relative to the target capture area. exceeding threshold angles of incidence between camera lens and license plate will greatly reduce the probability of obtaining usable images due to distortion. manufacturers have developed tools to help eliminate errors from the physical installation of license plate capture cameras circumvention techniques vehicle owners have used a variety of techniques in an attempt to evade anpr systems and road - rule enforcement cameras in general. one method increases the reflective properties of the lettering and makes it more likely that the system will be unable to locate the plate or produce a high enough level of contrast to be able to read it. this is typically done by using


enforcement cameras in general. one method increases the reflective properties of the lettering and makes it more likely that the system will be unable to locate the plate or produce a high enough level of contrast to be able to read it. this is typically done by using a plate cover or a spray, though claims regarding the effectiveness of the latter are disputed. in most jurisdictions, the covers are illegal and covered under existing laws, while in most countries there is no law to disallow the use of the sprays. other users have attempted to smear their license plate with dirt or utilize covers to mask the plate. novelty frames around texas license plates were made illegal in texas on 1 september 2003 by texas senate bill 439 because they caused problems with anpr devices. that law made it a class c misdemeanor ( punishable by a fine of up to us $ 200 ), or class b ( punishable by a fine of up to us $ 2, 000 and 180 days in jail ) if it can be proven that the owner did it to deliberately obscure their plates. the law was later clarified in 2007 to allow novelty frames. if an anpr system cannot read the plate it can flag the image for attention, with the human operators looking to see if they are able to identify the alphanumerics. in order to avoid surveillance or penalty charges, there has been an upsurge in car cloning. this is usually achieved by copying registration plates from another car of a similar model and age. this can be difficult to detect, especially as cloners may change the registration plates and travel behavior to hinder investigations. other possible options include ir emitting leds around the license plate which would serve to " blind " cameras. police enforcement several state police forces, and the department of justice ( victoria ) utilise both fixed and mobile anpr systems. the new south wales police force highway patrol were the first to trial and use a fixed anpr camera system in australia in 2005. in 2009 they began a roll - out of a mobile anpr system ( known officially as manpr ) with three infrared cameras fitted to its highway patrol fleet. the system identifies unregistered and stolen vehicles as well as disqulified or suspended drivers as well as other ' persons of interest ' such as persons having outstanding warrants. on 11 march 2008, the federal constitutional court of germany ruled that some areas of the laws permitting the use of automated number plate recognition systems in germany violated the right to privacy. more specifically, the court found that


such as persons having outstanding warrants. on 11 march 2008, the federal constitutional court of germany ruled that some areas of the laws permitting the use of automated number plate recognition systems in germany violated the right to privacy. more specifically, the court found that the retention of any sort of information ( i. e. number plate data ) which wasn ' t for any pre - destined use ( e. g. for use tracking suspected terrorists or for enforcement of speeding laws ) was in violation of german law. these systems were provided by jenoptik robot gmbh, and called trafficapture. the project of system integration « olli technology » and the ministry of internal affairs of ukraine department of state traffic inspection ( sti ) experiments on the introduction of a modern technical complex which is capable to locate stolen cars, drivers deprived of driving licenses and other problem cars in real time. the ukrainian complex " video control " working by a principle of video fixing of the car with recognition of license plates with check under data base. the city of mechelen uses an anpr system since september 2011 to scan all cars crossing the city limits ( inbound and outbound ). cars listed on ' black lists ' ( no insurance, stolen, etc. ) generate an alarm in the dispatching room, so they can be intercepted by a patrol. as of early 2012, 1 million cars per week are automatically checked in this way. several hungarian auxiliary police units use a system called matrix police in cooperation with the police. it consists of a portable computer equipped with a webcam that scans the stolen car database using automatic number plate recognition. the system is installed on the dashboard of selected patrol vehicles ( pda based handheld versions also exist ) and is mainly used to control the license plate of parking cars. as the auxiliary police doesn ' t have the authority to order moving vehicles to stop, if a stolen car is found, the formal police is informed. several cities have tested and some have put into service the " city security administration system " i. e. capital ankara has debuted kgys - " kent guvenlik yonetim sistemi " which consists of a registration plate number recognition system on the main arteries and city exits. the system has been used with two cameras per lane, one for plate recognition, one for speed detection. now the system has been widened to network all the registration number cameras together, and enforcing average speed over preset distances. some arteries have 70kmh limit, and some 50 kmh, and photo evidence with date - time details are