Van Der Waals Forces Definition

Van Der Waals Forces Definition Van der Waals Forces are the weak forces which contribute to intermolecular bonding  between molecules. Molecules inherently possess energy and their electrons are always in motion, so transient concentrations of electrons in one region or another lead electrically positive regions of a molecule to be attracted to the electrons of another molecule. Similarly, negatively-charged regions of one molecule are repulsed by negatively-charged regions of another molecule. Van der Waals forces are the sum of the attractive and repulsive electrical forces between atoms and molecules. These forces differ from covalent and ionic chemical bonding because they result from fluctuations in charge density of particles. Examples of van der Waals forces include hydrogen bonding, dispersion forces, and dipole-dipole interactions. Key Takeaways: Van der Waals Forces Van der Waals forces are distance-dependent forces between atoms and molecule not associated with covalent or ionic chemical bonds.Sometimes the term is used to encompass all intermolecular forces, although some scientists only include London dispersion force, Debye force, and Keeson force.Van der Waals forces are the weakest of the chemical forces, but they still play an important role in the properties of molecules and in surface science. Properties of Van der Waals Forces Certain characteristics are displayed by van der Waals forces: The forces are additive.The forces are weaker than either ionic or covalent chemical bonds.They are not directional.The forces act only over a very short range. The interaction is greater when molecules draw closer.Van der Waals forces are independent of temperature, with the exception of dipole-dipole interactions. Components of Van der Waals Forces Van der Waals forces are the weakest intermolecular forces. Their strength typically ranges from 0.4 to 4 kJ/mol and act over distances less than 0.6 nm. When the distance is less than 0.4 nm, the net effect of the forces is repulsive as electron clouds repel each other. There are four major contributions to van der Waals forces: There is a negative component that prevents molecules from collapsing. This is due to the Pauli exclusion principle.Either an attractive or repulsive electrostatic interaction occurs between permanent charges, dipoles, quadrupoles, and multipoles. This interaction is called Keesom interaction or Keesom force, named for Willem Hendrik Keesom.Induction or polarization occurs. This is an attractive force between a permanent polarity on one molecule and an induced polarity on another. This interaction is called the Debye force for Peter J.W. Debye.London dispersion force is the attraction between any pair of molecules due to instantaneous polarization. The force is named after Fritz London. Note even nonpolar molecules experience London dispersion. Van der Waals Forces, Geckos, and Arthropods Geckos, insects, and some spiders have setae on their foot pads that allow them to climb extremely smooth surfaces, such as glass. In fact, a gecko can even hang from a single toe! Scientists have proposed numerous explanations for the phenomena, but it turns out the primary cause of the adhesion is the electrostatic force more than van der Waals forces or capillary action. Researchers have produced dry glue and adhesive tape based on analysis of gecko and spider feet. The stickiness results both from tiny velcro-like hair and also the addition of lipids, which are found on gecko feet. Gecko feet are sticky because of van der Waals forces, electrostatic forces, and lipids found on their skin. StephanHoerold / Getty Images Real-Life Spiderman In 2014, DARPA tested its Geckskin, a material based on the setae of gecko footpads. A 100-kg researcher, carrying an additional 20 kg of gear, scaled an 8 m (26 ft) glass wall using two climbing paddles. The goal is to give military personnel Spiderman-like abilities. Scientists have found a way to use van der Waals forces to help people cling to smooth surfaces, such as glass and walls. OrangeDukeProductions / Getty Images Sources Autumn, Kellar; Sitti, Metin; Liang, Yiching A.; Peattie, Anne M.; Hansen, Wendy R.; Sponberg, Simon; Kenny, Thomas W.; Fearing, Ronald; Israelachvili, Jacob N.; Full, Robert J. (2002). Evidence for van der Waals adhesion in gecko setae. Proceedings of the National Academy of Sciences. 99 (19): 12252–6. doi:10.1073/pnas.192252799Dzyaloshinskii, I. D.; Lifshitz, E. M.; Pitaevskii, L. P. (1961). General theory of van der Waals forces. Soviet Physics Uspekhi. 4 (2): 153. doi:10.1070/PU1961v004n02ABEH003330Israelachvili, J. (1985–2004). Intermolecular and Surface Forces. Academic Press. ISBN 978-0-12-375181-2.Parsegian, V. A. (2006). van der Waals Forces: A Handbook for Biologists, Chemists, Engineers, and Physicists. Cambridge University Press. ISBN 978-0-521-83906-8.Wolff, J. O.; Gorb, S. N. (18 May 2011). The influence of humidity on the attachment ability of the spider Philodromus dispar (Araneae, Philodromidae). Proceedings of the Royal Society B: Biological Sciences. 279 (1726): 139–143. doi:10.1098/rspb.2011.0505

Causes of crime in Trinidad

There are several causes of crime in Trinidad and Tobago but this essay will analyse four of these causes of crime in Trinidad and Tobago.Firstly I will analyse the laxity with which the government has been dealing with the crime situation; It will also be discussed that a nation that forgets God will sin in this way; The eroding morals of society is another ;and the impact of the media on people’s lives. Ð ¡auses of crime And the raison detre successive governments have been unable and unsuccessful in dealing with this problem is primarily because they have all adopted a Euro-centric approach instead of an Afri-centric approach. The Euro-centric approach focuses on the results/effects of a problem while the Afri-centric deals with the causes. This writer strongly contends that the endemic causes of crime in Trinidad and Tobago are three-fold, viz, the 18th century imposed Euro-centric British education system, the abolition of corporal punishment in schools in February 2001 and the subliminal Americanisation of all aspects of life in Trinidad and Tobago, 24/7 365 days a year. The fact of the matter is that the current Euro-centric education system produces young people who are unemployable, devoid of the vital life-survival- empowerment skills and any sense of direction plus low esteem. As a result of all this societal baggage on their shoulders, these young people have no other choice but to resort to a life of crime to survive, And this mind-set makes sense to them, period. The Euro-centric education system continues to imbue in these young people a sense of worthlessness, nothingness and unpreparedness. At the end of their matriculation, these young people seriously and disgracefully lack the 3Rs— Reading, Writing and Arithmetic. They are doomed, period. They are totally convinced (rightly or wrongly) that society, as in the System, has failed them. They feel betrayed by society. Ipso facto, they not only internalise their accepted truism that they are failures but more self-destructively, they also publicly act out Bob Marleys lyrical dictum that the Babylon system is a vampire. Ergo, they are now totally convinced that they have the right to turn on society—crime, therefore, becomes their magnetic force just to survive. On the thorny issue of corporal punishment, this writer vociferously rejects the Euro-centric notion that the decision to abolish was based on research carried out in North America and Europe. Thats the problem. Again, this is exactly what the renowned Euro-centric psychologist Sigmund Freud did centuries ago, namely, using the European behaviour/experience as the norm, standard and model for all people ( including governments) to accept and follow—total, unabashed rejection by this Afri-centric scholar/professor, period. This decision not only represents a direct correlation with but also a very dangerous embrace of the Euro-centric world view and policy-making modus operandi. And thats the problem with solving crime in Trinidad and Tobago. The stark reality is that the historical experience/behaviour of the European coloniser is totally different from that of the colonised. Ergo, what is good and works for the European coloniser is not necessarily good and works for the colonised. That must be clearly understood by public policy-makers in Trinidad and Tobago. The truth be told: As a direct result of the Euro-centric decision made in 2001, today (2012) the chickens (have finally) come home to roost in Trinidad and Tobago, period. The subliminal Americanisation of life in Trinidad and Tobago is overtly reflected in the proclivity for crass materialism, instant gratification, 50 Cent philosophy, disgusting ghetto attire, slangs, body antics and mannerisms of young people, gang turf warfare, just to cite a few. Indeed, judging the daily attire of young, mature and older Trinbagonians one can correctly conclude that just maybe Trinidad and Tobago has been re-assigned. albeit re-located, from the tropical (hot) zone to the temperate (cold) zone. The truth be told: The failed Euro-centric education system in Trinidad and Tobago compels young people to gravitate and mimic only the most self-destructive aspects of American ghetto life styles. In the final analysis, this writer offers the following Afri-centric solutions to deal with crime — (i) radical surgery on the current dependency Euro-centric education system (ii) re-introduction of corporal punishment in schools so that young people will respect/obey adult authority/discipline and (iii) immediate deletion of the BET and BET J channels on Trinidad and Tobagos daily television schedule.

Worldview as it Relates to Philosophy Research Paper

Worldview as it Relates to Philosophy - Research Paper Example Through experience and education individuals develop these perspectives and implement them as a means of living their daily existence. When considering myself I recognize that my worldview has changed drastically over the course of my life and has been greatly influenced by experience and philosophy. This essay considers my current worldview and the way my past worldview has been influenced and changed through philosophy. Before taking this course my worldview was strongly rooted in religious doctrines. Throughout the formative periods of my life I grew up in an environment that was strictly Christian. Within this environment my parents and most of my peers believed in the major tenants of the Christian religion. Growing up in this environment I learned to adopt most of the religious principles that are espoused by the Christian religion. In terms of the creation of the world I believed that Earth and the universe had been created by God. I believed in morals as they related to the c oncept of good and evil as established by the Bible. In these regards, morality was presented as an easily understandable concept – if an individual adhered to the law and the tenants of the Bible then they were a moral and good person. I also embraced a concept of the afterlife. If individuals adhered to the Biblical principles and allowed God into their life then I believed they would go to heaven. Conversely, if they disregarded these aspects, they would go to Hell. My relation to science and logic were complex. While I embraced the principle of science in an overarching sense, I came to believe that oftentimes science could be wrong or mistaken. Specifically, in terms of evolution and cosmology I believed that while scientists had approached the concepts of existence and biology with their greatest ability, they were ultimately flawed in their findings. I understood that that ultimately their current scientific investigations would be proven wrong and they would ultimatel y discover that God and Biblical principles were the true reality of existence. When I look back on my worldview during this period of my life I recognize that I was greatly influenced by my personal surroundings and parents’ influence. As I gradually became more exposed to new ideas and new people my worldview drastically changed. In large part, the philosophical ideas I was exposed to in this course shaped and sharpened my worldview in a variety of ways. One of the major notions that I came to recognize through my research in philosophy emerged in terms of Christian morality. While Christianity noted that there were easily understood concepts of good and evil, my exposure to philosophers such as Friedrich Nietzsche in Beyond Good and Evil led me to understand that moral actions couldn’t easily be broken down into concepts of ‘good’ and ‘evil’ but often involve a complex number of philosophical implications (Nietzsche 1993). Another profound such changes that I experienced occurred in my understanding and eventual embracement of scientific principles. As I previously indicated that I had believed science did not properly understand Christian understandings of the world, as I became exposed to more scientific thought I came to understand that in large part the principles behind such concepts as evolution are supported by substantial scientific research. In these regards, I learned to increasingly embrace the notion that many of the claims made in the Bible may be wrong. As I became exposed to earlier notions of mythology, such as the Epic of Gilgamesh, which contains a flood story, I further came to recognize

Can Genetically Modified Organisms Save the World Essay

Can Genetically Modified Organisms Save the World - Essay Example Today, the process of genetic modification is rapidly advancing throughout the planet. In 2004, 8.25 million farmers in 17 nations (Ahmed, 30) grew the crops. The production and marketing of GM foods are due to the superficial benefits they hold either to the producer or to consumption of these genetic foods. In the beginning, GM seeds developers needed their products to be accepted by producers and focus on innovations that have direct benefit to the farmers and the food industry at large. For example, the International Rice Research Institute located in the Philippines manufactured the GM golden rice to help people in the South East Asia that were lacking food. GMO foods are unavoidable and we cannot live without them. The WHO, the Food, Drug Administration, and other scientific bodies in the world have strongly advocated for the use of GM foods, since they do not have any harm to the human health. Additionally, research shows that the risks to human health that may be brought about by the consumption of GM foods are the same as those that are brought about by the consumption of non-GM foods. Moreover, the GM foods are safe to use as they tested for food safety and passed the safety assessment. Some people believe that GM foods should be eliminated due to the risks they have like the health issues. It is a fact that people have eaten some of the GM foods unknowingly, but no complains of serious concerns (Ahmed, 18). By 2040, the world’s population is predicted to increase significantly and this therefore means that there are more resources to use and more people to feed. This growing human population entails to being open to new ideas and the use of new technology to curb food insecurity. Moreover, with this new technology, there are many benefits that the genetic modification has in terms of dealing with malnutrition, food security, and agricultural

Anorexia and Bulimia Essay -- Causes of Bulimia, Eating Disorders

Anorexia and Bulimia: A Concise Overview As many as 20% of females in their teenage and young adult years suffer from anorexia nervosa or bulimia nervosa (Alexander-Mott, 4). Males are also afflicted by these eating disorders, but at a much lower rate, with a female to male ratio of six to one. Those with anorexia nervosa refuse to maintain a normal body weight by not eating and have an intense fear of gaining weight. People with bulimia nervosa go through periods of binge eating and then purging (vomiting), or sometimes not purging but instead refraining from eating at all for days. Both of these disorders wreak havoc on a person's body and mental state, forcing them to become emaciated and often depressed. There is no known exact cause of either anorexia nervosa or bulimia nervosa, but many factors play a role in the initial onset, such as: personality traits, low self-esteem, and social and cultural influences (Costin, 21). Many anorexics have specific personality traits that urge them to refrain from eating. Many are perfectionists that will diet and exercise and not eat until their bodies are perfect. Unfortunately, however, he or she never thinks their body is perfect, and continues their destructive cycle. Anorexics that are perfectionists also tend to want to be in control at all times. Often , they feel as though others are trying to force them to do Breaux 2 things, and so, take complete control of their bodies. Marcia, an anorexic, wrote in her diary "I am in control; people are just jealous because I have will power" (D., 6). Another factor is low self-esteem. One anorexic said of her low self-esteem, "My goal in life was to please; like a chameleon, I'd change to suit whomever I was with. I always felt I was in the way†¦" (D., 1). Anorexics with low self-esteem often feel they are worthless and do not deserve to eat. Not only do they not eat, but they constantly berate themselves with insults. They hate their bodies, and cannot realize their true appearance, instead seeing a distorted image. When she weighed a mere 98 pounds, Marcia told herself, "You are a pig. You are disgusting. You must suffer" (D., 5). Bulimics also suffer from low self-esteem and feel ashamed of their behavior. Feeling guilty after eating is a co... ...orted self-image, low self-esteem, and a need for control. "Eating disorders are not about food or weight but about a disordered 'sense of self' looking for approval and finding it, however Breaux 5 temporarily, in the pursuit of thinness or the comfort of food" (Costin, 48). Treatment is an option for anorexics and bulimics, though it can take years, and sometimes it never succeeds. Hopefully, though, friends and loved ones of anorexics and bulimics will see the warning signs and seek help for them. Bibliography Alexander-Mott, LeeAnn. Understanding Eating Disorders. Washington, D.C.: Taylor & Francis Ltd., 1994. Costin, Carolyn. The Eating Disorder Sourcebook. Los Angeles, CA: Lowell House, 1996. K.D.K. "My Story." Online. March 3, 2000 <http://www.dana.ucc.nau.edu/ ~kdk2/mystory.html> D., Marcia. "My Story." Online. March 3, 2000 <http://www.members. Tripod.com/~MarciaD/index.html> Thayne, Becky. Hope and Recovery. New York, New York: Emma Lou Thayne, 1992.

Atticus Finch †To Kill a Mockingbird Essay

Throughout chapters 1-17 in To Kill A Mockingbird, Atticus Finch is shown as a very courageous and non-judgemental person. At times in the book he is also a very caring father but he can be strict at times. His name, Atticus is also a very polite man and always shows courtesy to the people he meets. Many people that live in Maycomb know Atticus is a gentleman and is very polite. He also has a conscience when he says that if he didn’t defend a Negro then he would be ashamed and wouldn’t be able to hold his head up in town. Harper Lee portrayed Atticus as a very courageous man. Atticus is courageous because he takes up a case no one else dares to take, the Tom Robinson case. He was willing to risk his honour and dignity to help the poorly accused black man. Although he gets a lot of abuse from various people, for example Mrs Dubose when she says, â€Å"Atticus is a nigger-lover†, he still doesn’t step down from the case and ignores people. He even put his Children in the way when Scout nearly gets in to a fight against Cecil Jacobs when Cecil Jacobs says that â€Å"Scout Finch’s daddy defends niggers†. Scout even takes abuse from her own family when her cousin, Francis, says that Atticus is a â€Å"nigger-lover† which really puts Scout on edge and she starts a fight with Francis. Atticus is also a very non-judgemental person and will always look at things from both sides of the story. In chapter 3 Atticus says, â€Å"You never really understand a person until you consider things from his point of view until you climb into his skin and walk around in it†. Here, Atticus is saying that you can’t judge something until you see things from their point of view, until you see what they’re experiencing. Atticus is a very caring father but a strict one too. He is very caring when Scout comes home from her first day in school and complains that Miss Caroline (the teacher) doesn’t want Atticus and Scout reading together any more. Atticus decides to make a deal with Scout, â€Å"If you’ll concede the necessity of going to school, we’ll go on reading every night just as we always have†. This shows that he cares about Scout concerns and decides to make a deal to make her happy. Although caring he is also a strict father and when Jem loses her cool and destroys Mrs Dubose’s flowers he makes Jem go back and apologies. To do something like this to a sick lady is inexcusable. I strongly advise you to go down and have a talk with Mrs Dubose†. As well as a good father he is also a very polite and well-mannered man. For example, in the court trial with Mayella, Atticus wouldn’t call her Mayella but Miss Mayella but Mayella took it like Atticus was mocking her. Judge Taylor had to calm her down by saying, â€Å"Mr Finch is always courteous to everybody†. This is saying that Atticus is always polite and courteous to everyone he meets. He is also very polite to Mrs Dubose even though Mrs Dubose shout insults to him every time he walks by. Atticus would sweep off his hat, wave gallantly to her and say, ‘Good evening, Mrs Dubose! You look like a picture this evening. ’† This shows that even though Mrs Dubose is horrid to him, he still says hello and is polite to her. Atticus is also very aware of his own reputation and tries to be morally good as much as he can be. He does this by helping Tom Robinson in a case they would probably lose. Scout asks him why he is defending Tom Robinson and Atticus replies, â€Å"The main one is that if I didn’t, I couldn’t hold my head up in town†. This shows he has morals that he follows so that he can have respect not for others but himself as well. Throughout chapters 1-17 Atticus is shown as a courageous person. As well as being courageous he is non-judgemental especially when he says, â€Å"You never really understand a person until you consider things from his point of view until you climb into his skin and walk around in it†. Atticus is also portrayed as a caring father when Scout is having trouble at school; Atticus is there to support her. Harper Lee has overall made Atticus a very polite, wise and respected man in To Kill A Mockingbird.

Irlen Syndrome Symptoms, Description, and How to Help

Irlen  Syndrome  was initially called Scotopic Sensitivity Syndrome. It was first identified by an Educational Psychologist named Helen Irlen in the 1980s. She wrote a book called Reading by the Colors (Avery Press, 1991), to support individuals with Irlen Syndrome. The exact cause of Irlen remains unknown. However, it is believed to originate in the retina of the eye or in the visual cortex of the brain. Individuals with Irlen Syndrome seem to see words that are blurry, have patterns or appear to move on the page. As the individual continues to read, the problem seems to worsen. Colored overlays and filters are used to help individuals with Irlen Syndrome because they sometimes appear to reduce the perceptual distortions and visual stress experienced by some children during reading. Research in this area, however, is quite limited. Most people are unaware that they have Irlen Syndrome. Irlen syndrome is often confused with an optical problem; however, it is a problem with processing, the inability or weakness in processing visual information. It often runs in families and typically goes misdiagnosed as a learning disability or dyslexia. Symptoms of Irlen Syndrome Trouble reading wordsHeadache while readingWeaker academic performanceWeak concentrationComplaints of eye strain while readingTires while readingDepth perception is much weakerWill also affect math performanceOften exhibits sensitivity to lights (especially fluorescent types)Trouble focusingWeak/poor comprehensionDifficulty tracking words on a line and will often skip wordsReads in a strained word by word fashion and with great hesitancyAvoids readingWeaker written workTrouble copyingRandom spacingRandom letter sizesWriting up or downhillInconsistent spelling The reason for all of these symptoms is largely due to the fact that print looks different to individuals with Irlens Syndrome. How Can You Help? Dimmer lightsNatural lighting appears to helpIrlen lenses (colored lenses, colored overlays)Colored paper for reading materials and worksheetsAdditional time for reading assignmentsIf lights cant be dimmed, individuals should be allowed to wear a visor.Shorten time spent on readingProvide more frequent breaksAllow the child to use a ruler to ease the tracking of words while reading. It is important to note that Irlen syndrome and visual treatments are unproven and not recognized by the major academic Pediatric Organizations in the US(AAP, AOA, and AAO.). To learn more about Irlens, you can take a self-test.