Thursday, March 19, 2020

Selectively Permeable Definition and Examples

Selectively Permeable Definition and Examples Selectively permeable means a membrane allows the passage of some molecules  or ions and inhibits the passage of others. The capacity to filter molecular transport in this manner is called selective permeability. Selective Permeability Versus Semipermeability Both semipermeable membranes and selectively permeable membranes regulate the transport of materials so that some particles pass through while others cant cross. Some texts use terns selectively permeable and semipermeable interchangeably, but they dont mean exactly the same thing. A semipermeable membrane is like a filter that allows particles to pass or not according to size, solubility, electrical charge, or other chemical or physical property. The passive transport processes of osmosis and diffusion permit transport across semipermeable membranes. A selectively permeable membrane chooses which molecules are allowed to pass based on specific criteria (e.g., molecular geometry). This facilitated or active transport  may require energy. Semipermeability can apply to both natural and synthetic materials. In addition to membranes, fibers may also be semipermeable. While selective permeability generally refers to polymers, other materials may be considered to be semipermeable. For example, a window screen is a semipermeable barrier that permits the flow of air but limits the transit of insects. Example of a Selectively Permeable Membrane The lipid bilayer of the cell membrane is an excellent example of a membrane which is both semipermeable and selectively permeable. Phospholipids in the bilayer are arranged such that the hydrophilic phosphate heads of each molecule are on the surface, exposed to the aqueous or watery environment inside and outside of cells. The hydrophobic fatty acid tails are hidden inside the membrane. The phospholipid arrangement makes the bilayer semipermeable. It allows the passage of small, uncharged solutes. Small lipid-soluble molecules can pass through the hydrophilic core of the layer, such hormones, and fat-soluble vitamins. Water passes through the semipermeable membrane via osmosis. Molecules of oxygen and carbon dioxide pass through the membrane via diffusion. However, polar molecules cannot easily pass through the lipid bilayer. They can reach the hydrophobic surface, but cant pass through the lipid layer to the other side of the membrane. Small ions face a similar problem because of their electrical charge. This is where selective permeability comes into play. Transmembrane proteins form channels that permit the passage of sodium, calcium, potassium, and chloride ions. Polar molecules can bind to surface proteins, causing a change in the configuration of the surface  and gaining them passage. Transport proteins move molecules and ions via facilitated diffusion, which does not require energy. Large molecules generally dont cross the lipid bilayer. There are special exceptions. In some cases, integral membrane proteins allow passage. In other cases, active transport is required. Here, energy is supplied in the form of adenosine triphosphate (ATP) for vesicular transport. A lipid bilayer vesicle forms around the large particle and fuses with the plasma membrane to either allow the molecule into or out of a cell. In exocytosis, the contents of the vesicle open to the outside of the cell membrane. In endocytosis, a large particle is taken into the cell. In addition to the cellular membrane, another example of a selectively permeable membrane is the inner membrane of an egg.

Monday, March 2, 2020

5 Causes of the Death of a Tree

5 Causes of the Death of a Tree Trees have an extraordinary ability to withstand many damaging agents that are ever-present in their environment. Trees have evolved over millions of years to ward off many stressors that bite and burn and starve and rot their roots, trunk, limbs, and leaves. It is amazing how a tree compartmentalizes itself to seal off dead wood and disease, defoliates to reduce the effect of drought and bleeds to extract harmful insects. We know that all trees do eventually die. There are many hundreds of seedlings and saplings that succumb for every mature tree left in the forest. All ages of trees eventually die to the same agents and only the most adaptive (and often lucky) individuals make it to old age. There are 5 factors to which a tree eventually succumbs: death from its environment, death from harmful insects and diseases, death from a catastrophic event, death from age-related collapse (starvation) and of course, death from harvest. In most cases, death is the result of several, if not all of these conditions taking place simultaneously. Lets take a look at each of these. Adverse Environment Ground and site conditions on which a tree lives ultimately determines the environmental stressors placed on that tree. If a drought-sensitive tree lives on a dry site during drought conditions, it may indeed die from lack of water. But that same tree can also be more susceptible to every other life-threatening factor placed upon it. For example, a disease that appears to be killing the tree may in effect be only a secondary issue to the initial environmental problem. Examples of adverse environments to trees are poorly draining soils, salty soils, droughty soils, air and ground pollution, extreme sun heating or cold spots and many, many others. It is particularly important to understand a tree species genetic tolerance to environmental conditions when planting. Many trees adapt very well to poor sites, but you need to understand which species fits where. Harmful Insects and Disease Virulent diseases like Dutch elm disease and the chestnut blight have caused sudden death to entire forests in North America. However, the most common diseases are more subtle in their work, killing many more trees in total than virulent types and cost forest and yard tree owners billions of dollars in forest product and specimen tree value. These common diseases include three bad ones: Armillaria root rot, oak wilt, and anthracnose. These pathogens invade the tree through leaves, roots and bark wounds and damage a trees vascular system if not prevented or treated. In natural forests, prevention is the only economic option available and is a significant part of a foresters silvicultural management plan. Harmful insects are opportunistic and often invade trees under stress from environmental problems or disease. They not only can directly cause tree death but will spread harmful disease fungi from a host tree to surrounding trees. Insects can attack a trees cambial layer by boring for food and nesting cavities, or they can defoliate a tree to the point of death. Bad insects include pine beetles, the gypsy moth, and emerald ash borers. Catastrophic Events A catastrophic event is always possible in a vast forest as well as in an urban setting. All property, including trees, are subject to being damaged or destroyed. In many cases, trees are not killed but are damaged to the point where their vigor is lost, and insects and disease take advantage of a trees loss of resistance. Significant tree losses can occur during a forest fire or when exposed to tornado-strength winds. Trees take a terrible hit when heavy ice is deposited on species sensitive to limb weight which results in breakage. Floods that do not recede quickly can cause root oxygen levels to diminish to the point where tree damage can occur. Extraordinary drought makes quick work of moisture-loving tree species and can harm all trees when extended over a long period. Old Age For trees who beat the odds and live through maturity to old age, there is a slow dying process that may take centuries to complete (in long-lived species). The modular tree compartmentalizes around damage and infected areas and continues to grow. Still, growth starts slowing after a tree matures, the ability of the plant to support itself diminishes and incurs the loss of adequate foliage for hydration and food. New immature branches, called epicormic sprouts, try to assist in maintaining an old trees vigor but are weak and are insufficient to sustain life for very long. A mature tree slowly collapses under its weight and crumbles to become the nutrients and topsoil for future trees. Timber Harvests Well remind you that trees do die to the ax. Trees via their wood have supported humankind and civilization for millennia and continue to be a necessary part of the human condition. The practice of forestry through professional foresters work continually with much success to provide a sustained flow of available wood volume and at the same time, ensure a surplus of trees. Some consider deforestation a growing global crisis.

Saturday, February 15, 2020

Contemporary film theory Essay Example | Topics and Well Written Essays - 500 words

Contemporary film theory - Essay Example lm Black Girl, which was directed by Senegalese director Ousmane Sembene is different from the typical Hollywood motion picture because the people in the movie are not stars, the story is not depicting any sort of popular or political beliefs, nor is it showing the world in a mythical fashion, where an unbelievable turn of events changes the outcome of the characters lives. This film shows what is happening in Africa with absolute realism, making Black Girl an excellent example of third cinema. An important reason why Black Girl can be considered third cinema is because it depicts the third world in a realistic manner. This is the story of a young Senegalese woman who works for a French family in Dakar. Over the course of this film, this woman is constantly mistreated by the family that she works for, making her all too aware of the racial identity that she has been labelled with. She becomes caught up in the tension between the rich French people in the area and the African people who have been oppressed since colonial times. She finds that she does not fit in with either world, leaving her alone. This film does not attempt to make any excuses for the treatment of the woman, but simply shows how large of a problem racism is within the country. In a Hollywood-style movie, there would be some sort of character growth, which would probably result in a happy ending, but this would not have been a realistic ending for this type of movie. This film is an example of â€Å"the c inema that recognises in that struggle the most gigantic cultural, scientific, and artistic manifestation of our time, the great possibility of constructing a liberated personality with each people as the starting point - in a word, the decolonisation of culture† (Solanas and Getino). Third cinema films such as Black Girl are important because of the realism that they bring to the filmmaking world. They do not offer an idealized version of events, but rather strive to tell a story in the most

Sunday, February 2, 2020

Cultural Impacts of Sino-Japanese War Essay Example | Topics and Well Written Essays - 2250 words

Cultural Impacts of Sino-Japanese War - Essay Example At the same time as both - China and Japan - had benefited from a mostly symbiotic, i"big brother-little brother" rapport in prehistoric times, and the twist of the 20th century marked the commencement of their disturbed rapport up to now. Japan's imperialist triumph over China in the earliest Sino-Japanese War (1894-1985) upturned China's preceding supremacy within the bond and lay down the tenor for Japan's domination over China for the century ahead. China's consequential bearing of Achilles' heel and persecution was worsened by enforced lenience to Japan at the "Versailles Peace Conference post-World War I"ii, which sparkled crowded anti-Japanese lobbies terminating in the 'May Fourth Movement of 1919' and a countrywide imposed sanctions of Japanese merchandise that pursued (Shih 1986). Later on, Japanese carnage in the following Sino-Japanese War (1937-1945) also seeded crowded anti-Japanese movements and cemented China's hatred of Japan, eventually fueling the anti-Japanese con stituents of Chinese jingoism. Till 2005, 'the Rape of Nanjing of December 1937'iii - the most horrible single event of Japanese bloodbath in China, where 300,000 Chinese nationals were cruelly assassinated throughout six weeks - persisted to exist on in Chinese reminiscences as a mark of Japanese brutality and a stimulation for continuous anti-Japanese ways of thinking in China these days (Backman 2005). The intensifying Sino-Japanese conflict is driven both by larger historical factors and by East Asia's changing strategic balance. World War II and the Cold War left the Sino-Japanese rivalry unresolved (Backman 2005). Japan's surrender in 1945 did not result in regional reconciliation or integration in East Asia, or a common acceptance within Japan of the ravages perpetrated by the imperialistic regime. Although most Japanese supported the U.S.-created peace establishment and vowed never again to engage in warfare, the values, perceptions, and leaders of the period of imperial expansion were not categorically washed their hands of, as their fascist equivalents had been in Europe. This was partly the result of U.S. decisions to retain the emperor and permit politicians and bureaucrats associated with the imperial wartime regime to regain positions and organize political parties in the "new" postwar Japan (McCluskey 1999). More broadly, postwar Japanese society did not entirely jettis on its distorted self-image of Japan as a struggling Asian nation beset by Western imperialists and eventually forced into a defensive war. Many Japanese also prefer to see themselves as victims of the war and not as aggressors, largely as a result of the nuclear bombing of Hiroshima and Nagasaki. Moreover, the Communist victory in China in 1949iv created lasting geopolitical divisions between the two Asian powers that made reconciliation even more difficult. In order to strengthen their own nationalist credentials, the leaders of the Chinese Communist Party (CCP) deliberately sought to sustain and strengthen a public image of Japan as a potentially aggressive, militaristic nation. During the Cold War, the U.S.-Soviet strategic conflict in East Asia not only overshadowed but effectively

Saturday, January 25, 2020

The Abnormal Aspect of Othello :: Othello essays

The Abnormal Aspect of Othello  Ã‚        Ã‚   Let us in this essay discuss the abnormal outlook on life found in Shakespeare’s tragedy Othello. Is a distorted view on life expressed only by the villain?    Iago is generally recognized as the one character possessing and operating by abnormal psychology. But Lily B. Campbell in Shakespeare’s Tragic Heroes tells of the time when the hero himself approached â€Å"madness†:    Othello himself cries:    thou hast set me on the rack. I swear ‘t is better to be much abus’d Than but to know a little.    And then we find him torturing himself with the thoughts of Cassio’s kisses on Desdemona’s lips, and he reiterates the property idea in his talk of being robbed. From this time on, Othello has become the slave of passion. As he cries farewell to the tranquil mind, to content, to war and his occupation, as he demands that Iago prove his love a whore, as he threatens Iago and begs for proof at the same time, he is finally led almost to the verge of madness [. . .] . (165)    Fortunately the protagonist regains his equilibrium, and when he does kill, it is for the noble reason of cleansing the world of a â€Å"strumpet.† On the other hand, the baseness of the villain Iago never alters. David Bevington in William Shakespeare: Four Tragedies describes the irrationality and self-destructiveness of the ancient’s behavior:    Emilia understands that jealousy is not a rational affliction but a self-induced disease of the mind. Jealous persons, she tells Desdemona, â€Å"are not ever jealous for the cause, / But jealous for they’re jealous. It is a monster / Begot upon itself, born on itself† (3.4.161 – 163). Iago’s own testimonial bears this out, for his jealousy is at once wholly irrational and agonizingly self-destructive. â€Å"I do suspect the lusty Moor / Hath leaped into my seat, the thought thereof / Doth , like a poisonous mineral, gnaw my innards† (2.1.296 – 298). (223)    Blanche Coles in Shakespeare’s Four Giants affirms the Bard’s commitment to abnormal psychology, and his employment of same in this play:    That Shakespeare was keenly interested in the study of the abnormal mind is commonly accepted among students. [. . .] The suggestion that Iago may have been intentionally drawn as a psychopathic personality is not new. [. . .] Even a casual scrutiny of a book on case histories of psychopathic patients will find Iago peeping out from many of its pages.

Friday, January 17, 2020

Hitler’s Anti-Semitic Ideas and Medical Experiments

In the 1930’s, during the Great Depression, Hitler was presented with an opportunity to persuade the German public of his anti-Semitic ideas through the use of propaganda. This was an easy task for Hitler to accomplish with the morale of the country already low after their defeat in World War I, 15 years prior. Germany was reeling from the effects of the New York stock market crash and the German people were seeking a leader who inspired confidence and would return hope for a better future. All of these factors gave Hitler’s ideas the perfect opportunity to germinate and take root in the minds of the citizenry. Hitler’s hatred was not limited to the Jewish community. Jews were only but one of the racially targeted groups that the Nazi Party sought to exterminate. Gypsies, the handicapped, homosexuals, Jehovah Witnesses, and the Poles were also considered to be threats to Hitler’s cause. Additionally, the Nazi’s persecution extended to political opponents such as the Communists, Socialists, Social Democrats, and trade union leaders. Preceding Hitler’s rise to power in 1933, German anthropologists, psychiatrists, and geneticists were already researching and studying racial hygiene and eugenics. These medical professionals embraced the Nazi regime who supported their study of eugenics. Scientists were attempting to prove that there was a genetic link within the superior race that would have justified Hitler’s purging of the inferior being from the nation. German scientists needed political backing for government funding and the Nazi regime needed the scientists to legitimatize their policies of anti-Semitism. It was the perfect marriage that resulted in the prefect storm. As World War II began and the Third Reich’s anti-Semitic views continued to infect the country, the German scientists worked diligently to prefect the Master Race through experimentation of those deemed degenerate by the Nazi Regime. In October of 1939, the Nazi’s initiated Action T4 (short for Tiergartenstra? e 4), or more commonly known as the Euthanasia Program. This program was the result of a petition received by the parents of a German child born with severe disabilities requesting Hitler’s permission to have the child put to death. Hitler approved the deliberate murder of the child and authorized the creation of the Reich Committee for the Scientific Registering of Serious Hereditary and Congenital Illnesses which would oversee the approval of future applications to put children in similar circumstances to death. Soon the Euthanasia Program was extended to adults with physical and mental disabilities as well. Anyone deemed unworthy of life was murdered as part of the T4 Program as the Nazi’s attempted to cleanse the German people of racially unsound elements. In addition to the T4 Program, many painful and inhumane of experiments were performed on the gypsies, the handicapped, homosexuals, Jehovah Witnesses, and the Poles. Experiments were done by physicians from the German air force and from the German Experimental Institution for Aviation in hopes of prolonging the survival of Axis military personnel. These experiments consisted of the use of a low-pressure chamber to determine the maximum altitude from which crews of damaged aircraft could parachute to safety. Freezing experiments were also done on concentration camp prisoners in hopes of finding an effective treatment for hypothermia. One experiment at Dachau was conducted to study various methods of making sea water drinkable. Many Roma gypsies were deprived food and given nothing but sea water to drink and died from dehydration as a result of this experiment. Experiments were also done to determine ways to effectively treat injured German military and occupation personnel with pharmaceuticals. Scientists used concentration camp prisoners as guinea pigs to test immunization compounds comprised of sera for the prevention and treatment of infectious diseases such as malaria, typhus, tuberculosis, typhoid fever, yellow fever, and infectious hepatitis. Bone grafting experiments were also done to test a new drug called sulfanilamide. Phosgene and mustard gas were tested on some prisoners as possible antidotes. Josef Mengele performed infamous experiments used in perfecting the Nazi’s idea of the â€Å"Master Race. Mengele conducted medical experiments on twins at the concentration camp of Auschwitz. The twins would be thoroughly measured, shaved, and photographed. They were forced to sit in vats of hot water until they passed out and would be photographed again. The twins also received hot water enemas and would be forced to suffer through painful and humiliating urological examinations. After all of these examinations were complete, the twins would be put to death by an injection in the heart and dissected for further research. In addition to these heinous experiments he also directed serological experiments on Roma gypsies, as did Werner Fischer at Sachsenhausen, in order to determine how different â€Å"races† withstood various contagious diseases. Further experiments were done in the study of sterilization to determine a cost effective way to easily sterilize those that the Nazi’s determined were racially inferior. Between the Nazi’s rise to power and their strong anti-Semitic teachings coupled with the studies already in progress by German geneticists, psychiatrists, and anthropologists the medical experiments performed during World War II were inevitable. The experiments that took place on prisoners of the concentration camps were clearly not limited to the Jews. In order for the scientists to prove their theories on racial hygiene the experiments had to be conducted on each of the races and groups that were regarded as inferior. This resulted in the gypsies, the handicapped, homosexuals, Jehovah Witnesses, and the Poles falling victim to the same experiments that were conducted on the Jews in hopes of creating the â€Å"Master Race. †

Wednesday, January 8, 2020

Annotated Bibliography On Online Banking Deception

Abstract The thesis is about online banking deception. â€Å"Online banking fraud† is about committing theft or fraud by means of the features of Internet to illegitimately confiscate cash from, or move it to, some other bank account. During the past decades, most of the problems in the field of cyber-security and more specifically online banking fraud have been investigated from technological perspective. That is, these problems were considered solely as technical problems which required technical security solutions. However, most of the problems in the field of cyber-security are more economic than technical. Based on their explanation, economics introduces breakthroughs in understanding problems of security, based on explaining the actors involved and their socio-economic incentives. Accordingly, in this research we have reviewed Economics of Information Security literature to study the possible explanatory factors that may explain why certain targets are by cybercriminals. Around m id-1990’s, banks started to offer Internet banking mainly to increase cost-effectiveness and customer reach (Jaleshgari, 1999). Electronic banking platforms act as efficient channels throughout which transactions could be carried out with little effort (Popa Vrancianu, 2010). Though, as these web-centred, platforms of â€Å"online banking† have turn out to be widespread amongst e-businesses and citizens that employ them increasingly in their day-to-day actions; â€Å"Online Banking Fraud† augmented as