Computer Virus Essay The emergence of technological innovations such as the advent of computer and computer programs, also paved way for the birth of certain viruses that can disrupt software programs. These viruses infect a program and allow it to spread from one computer to the others (â€œVirusesâ€). As it transfers from one computer to another, it leaves complications or ailments that like human viruses, has varying degrees of severity. Some are merely designed to annoy the computer user while others can destroy the entire computer hardware (Beal). Viruses may be categorized as a worm, Trojan or just a virus. A worm is quite similar to a virus, but unlike a virus that needs human intervention in order for it to spread, worms can spread on its own. It has the capacity to replicate itself and travel from one hardware to another through the transport features of the computerâ€™s system. Because of its replicating capacity it poses harm as it can slow down the computer the moment it becomes multitude (Beal). A Trojan on the other hand does not replicate as viruses and worms do. They appear at first as some legitimate program or file but the moment it is ran in the computer it can create various damage. Sometimes they are made to annoy while other can seriously destroy the computer by deleting files or programs. It can also create backdoors that can give other users access to the system that may give away personal or confidential information (Beal). Most of the time, these malicious programs spread with human intervention. When viruses cling onto a file and was run in the computer, it automatically spreads in the system of that computer.Trojans spread in the same way, while worms replicate itself in the system, to another system and to another. Works Cited Beal, Vangie. 2007. The Difference Between a Computer Virus, Worm and Trojan Horse. Webopedia. 11 November, 2008 http://www. webopedia. com/DidYouKnow/Internet/2004/virus. asp. Brain, Marshall. n. d. How Computer Viruses Work. HowStuffWorks. 11 November 2008 http://computer. howstuffworks. com/virus2. htm. Viruses. n. d. Kasperskylab. 11 November 2008 http://www. kaspersky. com/virusinfo.
1. In which ways does trader joeâ€™s demonstrate the importance of each responsibility in the management process- planning, organizing, leading, and controlling? Traders joeâ€™s outlet mangers are highly compensated, because they are trained on the traders joeâ€™s system inside and out. The managers are hired from within the companyâ€™s already employed employees. Trader joeâ€™s also writes job descriptions by desired soft skills. There employees are friendly and customer oriented. Trader joes have been using competitive advantages because trader joeâ€™s has been doing extremely well and have been giving some advantages over there competitors in the marketplace. 2. Traders joeâ€™s is owned by a German company operating in American. What are the biggest risks that international ownership and global events pose for trader joeâ€™s performance effectiveness and performance efficiency? Trader joeâ€™s would have to become a global management. This means that they would have to attract and hire a truly global manager who has a strong global perspective, are culturally aware, and always stay informed with the international developments. Trader joeâ€™s would have to also become more in touch with global economy in which supplies, product markets, and business competition are worldwide and not local or national. 3. Given trader joeâ€™s casual and nontraditional work environment, what should she do and what should she avoid doing in the first few days of work to establish herself as a skillful manager of this team? She should enroll in the traders joeâ€™s training program so that she could learn the ends and outs of the company and there polices. She tries to make sure that she keeps a friendly crew. She should also make sure that her employeeâ€™s under her are well trained and knows the company polices and their expectations. 4. Are there any internal weaknesses or external competitors or industry forces that might cause future problems? Trader Joe is a perfect example of a Niche market store that has a very successful product differentiation strategy by focusing on their customer needs, taking care of their employees and continuing to provide great quality products. Today world whole and organic foods are in high demand, but it can be very expensive. Trader Joe has made this possible by bringing together healthy choices that does not hurt the customerâ€™s pocket. If Trader Joe should continue to operate with this strategy they certainly have brighter horizon to see.
I am choosing this piece of art because it reminds me of the original one, the Napoleon Crossing the Alps, by the French Neoclassical painter Jacques-Louis David, and also because that I am quite like this Mario game very much. This artist had turned my childhood hero into a very good piece of art, that to me, can capture every aspect of him and his loyal pet, although Yoshi does not look that fiercely.
The original work of Jacques-Louis is about a mighty general, who is bravely charges in the front of the army toward the enemy. Napoleon proportion show that he is the real commander, not just any soldier or any captain, but the great Napoleon Bonaparte himself. Calmly sitting on his fiery horse, finger points toward the Alps, Napoleon leading his people to victories. To sum up, this painting express Napoleon as the hero of the peoples of France, the one who freed them from the hands of Louis the sixteenth.
The Mario Crossing the Mushroom Kingdom shows a quite similar meaning. Instead of crossing the dangerous Alps, Mario just crossing the Mushroom Kingdom. Now, what we all know what Mario do in the Mushroom Kingdom: fighting evils, rescue the princess, and freed the kingdom from the tyrant's hands, so that makes Mario a hero too, right? Yes! Yes, it is! Mario is the hero of the Mushroom Kingdom.
Although Mario just a plumber, he has fought for the Kingdom with all he has, his running skill as you can see in the games, and he freed them from the tyrant.The painting is very accurate in some ways, the costume, Mario's beer belly, his clothes, and all, Mario did not really wear gloves until recently, but that can be pretermit. What is different from the original painting is that, instead of pointing his finger toward the Kingdom, Mario holds a mushroom.
Funny, I would say, because in the game, Mario power up by eating special mushrooms from the mystery boxes scattered around the kingdom, they can make him bigger, and stronger depends on what mushroom he eats, and that is very interesting to see the mushroom in the painting.
The Mario Crossing the Mushroom Kingdom resembles most detail from the original one: Mario's proportion, Yoshi front legs, and back legs positions, the harness, and the cape. There is one interesting thing is that Yoshi left eye is glancing backward just like Napoleon's horse eye position, glancing backward. His attention to the small details like that amuse me a lot, it makes me to look for other version of Napoleon Crossing the Alps, just to look at their eyes, although I don't see the name carved in the rock anywhere in the picture, but that is not important.
There is something about Naburanja version of the dinosaur Yoshi that keeps me wonder. You see, normally, Yoshi's appearance is a cute little green dinosaur, with a frog like tongue that can swallow enemies. But here, all I see is probably the grow up version of Yoshi. He is bigger, looks more muscular, his green skin looks fade a bit, perhaps to shows old age. Yoshi normally is seen wearing brown boots, but now the boots were completely torn by his claws, like Yoshi had grown up suddenly, so suddenly that he could not take off his boots, so he had to let them be torn.
Naburanja usage of colors to describe the gloomy, sad atmosphere of the scenario, where the Kingdom is invaded, and overran by monster, the princess being kidnapped with no hope to rescue her, and so on, is incredible. Naburanja use the dark, gray color to describe it. What more, is that when Mario and Yoshi showed up, light breaks through the darkness, to shine upon our heroes, where ever they go.
The colors where Mario stands, are bright colors, red, blue, light dirt yellow, green, and white. It shows that Mario is going to be the savior of the Mushroom KingdomOverall, the painting is magnificent to me, its capture the picture of the hero of my childhood quite correctly, using the Napoleon Crossing the Alps style of drawing. Naburanja colors usage is wonderful, it described the scenario of Mushroom Kingdom correctly, and he depicted Mario like a saint, light shine bright where ever he goes. This painting of Naburanja has many interesting aspect that I love very much, and this is the way I mostly see it, also it makes me chuckle every times I come across it.
Assessment of Plant Tissue Culture
Plant tissue culture, the growth of plant cells outside an intact plant, is a technique essential in many areas of the plant sciences. Cultures of individual or groups of plant cells, and whole organs, contribute to understanding both fundamental and applied science.
It relies on maintaining plant cells in aseptic conditions on a suitable nutrient medium. The culture can be sustained as a mass of undifferentiated cells for an extended period of time, or regenerated into whole plants.Â
Designing a strategy to culture cells from a plant for the first time can still seem like a matter of trial and error, and luck. However, the commercial production of valuable horticulture crops by micropropagation, which relies on tissue culture, shows that it exists in the routine, as well as experimental, world.
In the School of Biological Sciences at the University of Liverpool, we have experience over many years with the techniques and applications of plant cell culture.
What is Plant Tissue Culture?
Plant cells can be grown in isolation from intact plants in tissue culture systems. The cells have the characteristics of callus cells, rather than other plant cell types. These are the cells that appear on cut surfaces when a plant is wounded and which gradually cover and seal the damaged area.
Pieces of plant tissue will slowly divide and grow into a colourless mass of cells if they are kept in special conditions. These are:
initiated from the most appropriate plant tissue for the particular plant variety
presence of a high concentration of auxin and cytokinin growth regulators in the growth media
a growth medium containing organic and inorganic compounds to sustain the cells
aseptic conditions during culture to exclude competition from microorganisms
The plant cells can grow on a solid surface as friable, pale-brown lumps (called callus), or as individual or small clusters of cells in a liquid medium called a suspension culture. These cells can beÂ maintained indefinitely provided they are sub-cultured regularly into fresh growth medium.
Tissue culture cells generally lack the distinctive features of most plant cells. They have a small vacuole, lack chloroplasts and photosynthetic pathways and the structural or chemical features that distinguish so many cell types within the intact plant are absent. They are most similar to the undifferentiated cells found in meristematic regions which become fated to develop into each cell type as the plant grows. Tissue cultured cells can also be induced to re-differentiate into whole plants by alterations to the growth media.
Plant tissue cultures can be initiated from almost any part of a plant. The physiological state of the plant does have an influence on its response to attempts to initiate tissue culture. The parent plant must be healthy and free from obvious signs of disease or decay. The source, termed explant, may be dictated by the reason for carrying out the tissue culture. Younger tissue contains a higher proportion of actively dividing cells and is more responsive to a callus initiation programme. The plants themselves must be actively growing, and not about to enter a period of dormancy.Â
The exact conditions required to initiate and sustain plant cells in culture, or to regenerate intact plants from cultured cells, are different for each plant species. Each variety of a species will often have a particular set of cultural requirements. Despite all the knowledge that has been obtained about plant tissue culture during the twentieth century, these conditions have to be identified for each variety through experimentation.
Utilising anther culture to select for cold hardiness
Crosses between distantly related species can bring together novel gene combinations. However, the hybrid offspring can be few in number, genetically unstable and require years of further selection andÂ screening before any advantageous characteristics can be brought near to commercial use.
Anther culture (androgenesis), to generate haploid plants from pollen microspores, is one way to shorten this process. It allows novel allele combinations, particularly ones involving recessive characters, to be assessed in intact plants. Useful individuals can then be developed into homozygous and fertile plants through chromosome doubling techniques, and brought into a breeding programme.
We have recently been involved in a collaborative project with the Institute of Grassland and Environmental Research (IGER) to use this approach to improve cold-tolerance and fodder quality in grazing grasses. Crosses betweenÂ Lolium multiflorumÂ ( Italian ryegrass) andFestuca arundinaceaÂ (tall fescue) should offer valuable combinations of characteristics. TheLoliumÂ species should provide good growth characteristics, while theÂ FestucaÂ provides stress-tolerance. One hybrid individual (Festulolium) resulting from such a cross had already shown drought-tolerance characteristics.Â However, the out-breeding nature of these grass species, along with the hexaploid genome ofÂ F. arundinaceaÂ and autotetraploidÂ L. multiflorumindicated that a lengthy breeding programme might be necessary.
The research project therefore aimed to produce androgenic plants from the existing pentaploidFestuloliumÂ plant and assess them for cold tolerance. This exploited the expertise in tissue culture at the University of Liverpool together with experience in breeding for stress-tolerance at IGER.
Anthers containing immature pollen (microspores) are the starting material for androgenesis. Flowers have to be selected at the correct developmental stage, which varies from species to species. In addition, some individual genotypes may not be amenable to anther culture, or require specific pretreatments. Careful microscopy and testing of successful pre-treatments of related species are therefore necessary when dealing with a new species. For the Graminae, microspores must be at the mononucleate stage and no pre-treatment is necessary.Â
The cut flowers were surface sterilised and opened in sterile conditions under a binocular microscope. The anthers were dissected and transferred to a solid nutrient medium. Large numbers could be placed on each petri dish. Callus developed, which was transferred to a different medium to initiate embryos and so generate haploid plants.Â
Over 200 androgenic plants were produced at Liverpool, each originating from a different microspore. Each therefore represented a genetically different individual. Testing for phosphoglucosisomerase, where a different isozyme was contributed by each of the five chromosome groups within theÂ FestuloliumÂ plant, indicated that the pollen-derived plants had a wide variety of chromosome combinations from each of the parents of the hybrid. The freezing-tolerance of these plants varied considerably, with three individuals able to survive the extreme cold of -14 degrees Celsius. When the chromosome complement of two of these plants was examined using genomicÂ in situÂ hybridisation (GISH), they carried virtually the whole genome ofÂ F.Â pratensis, a parent ofÂ F. arundinaceaÂ noted for its freezing-tolerance.
Unfortunately, the fertility of these two plants was not restored by chromosome doubling, so that they could not be used for further breeding. However, they demonstrated the potential of androgenesis for rapid assessment of the genetic potential available from a difficult breeding combination, indicating that this type of wide cross revealed characters of cold and drought tolerance that were worth pursuing
CASE STUDYÂ 2
Using somaclonal variation to select for disease resistance plant tissue cultures isolated from even a single cell can show variation after repeated subculture. Distinct lines can be selected with their own particular morphology and physiology. It suggests that the tissue culture contains a population of genotypes whose proportion can be altered by imposing an appropriate selection pressure. This variation can be transmitted to plants regenerated from the tissue cultures, and is called somaclonal variation. It provides an additional source of novel variation for exploitation by plant breeders.Â
The carrot cultivar Fancy was used in our laboratory to generate a series of 197 regenerant progeny lines. These plants showed considerable morphological variation. They were tested for resistance to the leaf spot pathogenÂ Alternaria dauci, which can cause total necrosis of mature leaves. They had a greater degree of variation in response than the parental cultivar, including some more resistant lines.Â
Scanning electron micrographs of surface of carrot leaf 3 days after inoculation with A. dauci. (LHS) germination from multiseptate conidiospore (RHS) penetration of hyphae through epidermal surface rather than through stomata. Scale bar = 10 micrometres.
One symptom of the disease is loss of chlorophyll and total soluble polyphenol compounds. These reduce to a low level 6 days after inoculation of excised leaves withÂ A. dauciÂ spores when compared with uninoculated leaves. Regenerant progeny with high chlorophyll levels maintained higher chlorophyll levels after challenge withÂ A. dauci.Â After self-pollinating selected high- and low-chlorophyll regenerant plants, this characteristic was inherited by their progeny, suggesting that the capacity to resist this infection is inherited.
CASE STUDYÂ 3
Demonstration of tissue culture for teaching
Regenerated African violets (Saintpaulia ionantha)
The starting point for all tissue cultures is plant tissue, called an explant. It can be initiated from any part of a plant root, stem, petiole, leaf or flower although the success of any one of these varies between species. It is essential that the surface of the explant is sterilised to remove all microbial contamination. Plant cell division is slow compared to the growth of bacteria and fungi, and even minor contaminants will easily over-grow the plant tissue culture. The explant is then incubated on a sterile nutrient medium to initiate the tissue culture. The composition of the growth medium is designed to both sustain the plant cells, encourage cell division, and control development of either an undifferentiated cell mass, or particular plant organs.Â
The concentration of the growth regulators in the medium, namely auxin and cytokinin, seems to be the critical factor for determining whether a tissue culture is initiated, and how it subsequently develops.Â The explant should initially form a callus, from which it is possible to generate multiple embryos and then shoots, forming the basis for plant regeneration and thus the technology of micropropagation. The first stage of tissue culture initiation is vital for information on what combination of media components will give a friable, fast-growing callus, or a green chlorophyllous callus, or embryo, root or shoot formation.Â
There is at present no way to predict the exact growth medium, and growth protocol, to generate a particular type of callus. These characteristics have to be determined through a carefully designed and observed experiment for each new plant species, and frequently also for each new variety of the species which is taken into tissue culture. The basis of the experiment will be media and protocols that give the desired effect in other plant species, and experience.
The strategy for designing a medium to initiate tissue culture, showing how growth regulators and other factors modulate development, can be demonstrated using the African Violet, a popular house plant. Leaf sections are the source of explants.Â This demonstration is regularly carried out by a student class, and gives reliable results. Sterile supplies are provided from central facilities, and provision of sterile working areas (for example, in laminar flow hoods) is an advantage, although cultures can be initiated in an open laboratory with careful aseptic technique. The standard precautions used during any laboratory work involving chemicals or microbes should be adopted. If you are in any doubt about safety hazards associated with this demonstration, you should consult your local safety adviser.Â Â
Step 1 selection of the leaves
Leaves are cut from healthy plants, leaving a short length of petiole attached. They should be selected to each yield several explants of leaf squares with approximately 1 cm sides. The youngest and oldest leaves should be avoided.Â
Wash the dust off the leaves in a beaker of distilled water, holding the leaf stalk with forceps.
Step 2 surface sterilisation and preparation of the explants
This part of the procedure should be carried out in a sterile working area, or with meticulous aseptic technique.Â
The leaf, with the petiole still attached, should be immersed in 70% ethanol for 30 seconds, then transferred to a sterile petri dish. Sterile scissors and forceps are then used to cut squares from the leaf as explants, each with approximately 1 cm sides.
The explants are transferred into a 10% hypochlorite bleach solution for 5 minutes, gently agitating once or twice during this time. They are then washed free of bleach by immersing in four successive beakers of sterile distilled water, leaving them for 2-3 minutes in each.
Three explants are placed on each petri dish of growth medium (seeÂ tableÂ andÂ below), with the upper epidermis pressed gently against the surface of the agar to make good contact.Â
The petri dishes are sealed with plastic film to prevent moisture loss, and incubated at 25oC in 16h light/8h dark.
Step 3 assessment of tissue culture development
The explants are incubated for 4 6 weeks, and inspected at weekly or fortnightly intervals. The growth of obvious bacterial or fungal colonies indicates contamination, and data from such cultures is obviously suspect. The development of dark brown tissue cultures can also be a consequence of contamination.Â
The media used in the demonstration are designed to show the effects of auxin, cytokinin, sucrose and mineral salts on development. The media were based on the well-known Murashige and Skoog inorganic medium, with additions as shown in thisÂ table.Â
TheseÂ picturesÂ show typical results, after about 8 weeks on each medium. To summarise, multiple adventitious buds form on theÂ controlÂ medium,Â leading to many small shoots on the upper surface where the leaf is not in contact with the medium.
Absence ofÂ sucroseÂ inhibits this production. Shoot production is also limited on the low sucrose concentration, but comparable with the control at high sucrose.
At zero and low levels ofÂ cytokinin, callus forms where the leaf surface is in contact with the medium, while at high levels, shoot formation is stimulated.
At zero and low levels ofÂ auxinsÂ there is a stimulus to shoot formation,Â but at high concentrations, large numbers of roots are formed.
At low and zero levels ofÂ MSÂ salts, there is no growth at all.
These very obvious variations demonstrate the importance of a carbon and inorganic salt source for plant growth, as well as the effect of the auxin:cytokinin ration on the control of plant development.
ForÂ publicationsÂ describing this work, follow this link
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Write something about yourself. No need to be fancy, just an overview.