Physico-Chemical Qualities Essay Example for Free

Physico-Chemical Qualities Essay a) Describe the physico-chemical qualities of water that are important to aquaculturists. Aquaculture can be defined as the high-density production of fish, shellfish and plant forms in a controlled environment. Stocking rates for high-density aquaculture are typically thousand fold greater than wild environments. Modern fish culturists employ both open and close systems to raise fish. Open systems, such as, the raceways are characterized by rapid turnover of water. Closed systems are commonplace in pond culture. Closed aquaculture systems do not have rapid turnover of water, but do not have a high surface to volume ratio facilitating exchange of gases, nutrients, energy etc. with the surroundings. Water quality for aquaculturists refers to the quality of water that enables successful propagation of the desired organisms. Physico-chemical parameters of water include: 1. Alkalinity Alkalinity relates to the capacity of the water to accept protons and is a measure of the water’s buffering capacity. There are no direct effects of alkalinity on fish and shellfish, however, it is an important parameter due to its indirect effects, including the protection of aquatic organisms from major changes in pH. In low alkalinity waters, where CO2 and dissolved carbonates are at low concentrations, photosynthesis may be inhibited, thus restricting phytoplankton growth. Levels above 175 mg CaCO3/L reduces natural food production in ponds which, in turn, leads to a decrease in optimal production. Salt water is slightly alkaline and has a strong buffering capacity so alkalinity is not usually of concern for most seawater and brackish water aquaculturists. 2. Biochemical oxygen demand ( and COD) It is a measure of the amount of oxygen required by bacteria, algae, sediments and chemicals over a set period of time. BOD is of importance in aquaculture because microbial degradation of organic matter is a major sink for dissolved oxygen, a highly important parameter for aquaculture. Aquaculture operations should not utilise waters which are polluted with chemicals and/or excessive nutrients. Increasing levels of BOD indicate organic pollution which is a cause of concern for aquaculturists. The amount of BOD needed for a particular system can be estimated by taking into  account factors such as dissolved. Oxygen requirements of the culture species, the degree of pond aeration, seasonal temperature fluctuations, expected photosynthetic activity, and oxygen solubility. 3. Carbon dioxide Their presence is important for the buffering capacity of the water. The level of carbon dioxide in the water is related to photosynthetic activity of aquatic plants and respiration of these plants and aquatic animals, as well as bio-oxidation of organic compounds. Dissolved carbon dioxide forms carbonic acid, causing a drop in pH. At equilibrium, freshwater contains about 2.0 mg/L CO2 and seldom rises above 20 to 30 mg/L. High concentrations of carbon dioxide have a narcotic effect on fish and even higher concentrations may cause death; however, such concentrations seldom occur in nature. The direct adverse effects can occur when there is an excess of free CO2, especially in waters low in dissolved oxygen. This latter situation can occur when too much free CO2 is utilized for photosynthesis of phytoplankton, or when water is vigorously aerated with CO2 free air. Free CO2 concentrations below 1 mg/L affect the acid-base balance in fish blood and tissues and cause alkalosis. Most aqua culture species will survive in waters containing up to 60 mg/L carbon dioxide provided that dissolved oxygen concentrations are high. 4. Color and appearance of water These are not highly objective measurements but many fish farmers and crustacean farmers attach a lot of significance to these two properties of pond water. Color is a result of the interaction of incident light and impurities in the water .There are three common causes of water coloration and variations in water appearance: * suspension of silt and clay particles * significant growth of plankton, particularly microalgae * suspension of humic acids and other organic acids The ‘color’ of the water, actually refers to turbidity due to significant silt and clay particle accumulation, or growth of phytoplankton and zooplankton. This type of water coloration may be beneficial in tank and  cage culture as it shades fish and prevents sunburn as well as reducing plant biofouling. It is reported that impending oxygen shortages in the water can often be detected by changes in colour. Although high colour may shade fish and impede algal growth, it is usually due to tannins. These are phenols which bind with protein and at high levels may affect fish respiration, particularly with sensitive fish species. 5. Dissolved oxygen Dissolved oxygen is the most critical water quality variable in aquaculture. Anoxia occurs when dissolved oxygen levels in the environment decrease to the point where aquatic life can no longer be supported. Some species are more resistant to low levels of oxygen than others. It was noted that the amount of oxygen required by aquatic animals is quite variable and depends on species, size, activity (levels increase with activity), water temperature (doubles with every increase of 10 °C), condition (lean fish consume less than fat fish), DO concentration, etc. The DO concentration can fluctuate in response to photosynthesis of aquatic plants and respiration of aquatic organisms. The amount of DO required also depends on partial pressure of dissolved oxygen in the water and its ability to exchange across gill membranes. DO level in water should be above 5mg/L In ponds, tanks and other enclosed culture systems, mechanical aeration can be used to lift dissolved oxygen levels, while wate r movement from currents and tides assists in open culture systems. Pure oxygen (oxygenation) may be used to supplement dissolved oxygen levels, particularly in intensive culture systems. The most common cause of low DO in an aquaculture operation is a high concentration of biodegradable organic matter in the water, resulting in a high BOD. This problem is further exacerbated at high temperatures. 6. Gas super saturation (total gas pressure) Super saturation of dissolved gas occurs when the pressure of the dissolved gas (total gas pressure; TGP) exceeds the atmospheric pressure. TGP refers to the sum of the partial pressures of dissolved gases in the water (i.e. oxygen, nitrogen and carbon dioxide). | Oxygen supersaturation| Nitrogen supersaturation| Carbon dioxide supersaturation| Definition| Total gas pressure is not above saturation level.| Total gas pressure is above saturation level| Condition of higher levels of dissolved gases in water due to entrainment, pressure increases, or heating.| Mechanism| Oxygen displaces nitrogen in liquid| | diffusion| Reason why| Pure oxygen is used to oxygenate| -Situation develops when water and air is mixed under pressure.-Situation develops when water is heated| When there is high phytoplankton activity though respiration at night.| Results| up to 200–300% can be tolerated if oxygen is used directly or duringphotosynthesis (when air is used, nitrogen becomes the main component and problems can occur). It can cause massive distension of the swim bladder of salmonids, although the mortality is usually low. | gas bubble trauma which may cause acute or chronic problems,especially in eggs, larvae and juveniles.| levels above 20 ppm can lead to stress. mortalitymay not occur, even at levels of 30-40 ppm , High carbon dioxide levels in fish transport systems (where ventilation is absent) can inhibitoxygen uptake.| 7. Hardness Total hardness primarily measures the concentration of all metal cations (usually dominated by calcium and magnesium in freshwater) in the water. Soft water is usually acidic while hard water is generally alkaline. In soft waters, carbonate and bicarbonate salts are in short supply. Hard water has been found to reduce the toxicity of several heavy metals (calcium and magnesium) as well as ammonia and the hydrogen ion. Some aquacultural species have a specific requirement for calcium, for bone formation in fish and exoskeleton formation in crustaceans. Calcium is also necessary for proper osmoregulation, and the calcium ion generally reduces the toxicity of hydrogen ions, ammonia and metal ions. High calcium levels in freshwater can inhibit phytoplankton growth; however, blue-green algae are known to thrive in harder water (high Ca2+) which can influence productivity of the pond water. Meade (1989) recommended a range between 10 and 400 mg/L for aquaculture. 8. pH The term pH refers to the hydrogen ion (H+) concentration in water; more  generally, pH refers to how acidic or basic water is. In aquaculture, low pH is often a consequence of sulfuric acid formation by the oxidation of sulphide-containing sediments. Note that acidification of highly alkaline water can increase the free carbon dioxide concentration, resulting in CO2 toxicity rather than pH imbalance. In addition, acid water tends to dissolve metals more readily. High pH in aquaculture is commonly a result of excess photosynthesis in waters with high alkalinity and low calcium hardness. pH can indirectly affect aquaculture species through its effect on other chemical parameters. Low pH; * reduces the amount of dissolved inorganic phosphorus and CO2 available for phytoplankton photosynthesis. * results in the solubilisation of potentially toxic metals from the sediments Hugh pH makes the toxic form of ammonia more prevalent. Meade (1989) recommended that pH be maintained at between 6.5 and 8.0 for all aquaculture species. In freshwater, pH can change quickly due to the amount of carbon dioxide added or removed during plant growth. In culture systems, particularly recirculation systems, the pH may be reduced (more acidic) by the production of metabolites. Buffering is, therefore, important in such systems. Seawater, in general, resists changes in the pH values. NOTE: pH can change by the hour as a function of photosynthesis which removes carbon dioxide. This is particularly the case in pond-based culture systems. 9. Salinity (total dissolved solids) Salinity is the main measure used in aquaculture, as it influences the water and salt balance (osmoregulation) of aquatic animals. Estuarine waters may range from 0.5 to more than 30 ppt often depending on the depth of the sample; marine waters range between 30.0 to 40.0 ppt. Salinity directly affects the levels of dissolved oxygen: the higher the salinity, the lower the dissolved oxygen levels at given water temperature. Like temperature, salinity is an important limiting factor in the distribution of many aquatic animals. Salinity requirements can vary for particular species depending on  their life cycle stage. Salinity also affects the temperature requirements of some species. Freshwater organisms have body fluids more concentrated in ions than the surrounding water, meaning that they are hypersaline or hypertonic to the environment. These animals tend to accumulate water which they must excrete while retaining ions. Saltwater species have body fluids more dilute in ions than t he surrounding water; they are hyposaline or hypotonic to their environment. They must excrete ions and uptake water continually. Salinity tolerance varies significantly between species and some species have wider tolerances than others. 10. Suspended solids and turbidity There are three basic types of suspended solids: ï€ ­Ã¯â‚¬  phytoplankton, zooplankton and bacterial blooms ï€ ­Ã¯â‚¬  suspended organic and humic acids ï€ ­Ã¯â‚¬  suspension of silt and clay particles All influence the level of turbidity (turbidity increases with suspended solids) and scatter light, restricting penetration into water. In aquaculture ponds, less light penetrating to the bottom inhibits growth of troublesome filamentous algae and aquatic weeds. This turbidity is often measured in centimetres using a secchi disc. Typically, if the secchi disk reading is below 10 cm water turbidity is excessive. If turbidity is due to the presence of phytoplankton, there is likely to be a problem with dissolved oxygen concentrations when the light level decreases below the photosynthetic compensation level. Conversely, if turbidity is due to silt/clay or organic matter, planktonic productivity will be low. Suspended solids can cause gill irritations and tissue damage, which increases the stress levels of aquatic animals. Turbid waters can also shield food organisms and clog filters. The practice of mechanical aeration tends to create water currents which maintain soil particles in suspension and perpetuates the turbidity of the pond. Problems of off-flavors in fish and crayfish are less common in turbid ponds. (except where algae cause the turbidity). The effect of this criteria varies considerably between species. Meade (1989) recommended a level below 80 mg/L for aquaculture species. Marine species (e.g. snapper) are generally less tolerant, so the recommended guideline is

Ancient Advances In Mathematics :: essays research papers fc

Ancient Advances in Mathematics   Ã‚  Ã‚  Ã‚  Ã‚  Ancient knowledge of the sciences was often wrong and wholly unsatisfactory by modern standards. However not all of the knowledge of the more learned peoples of the past was false. In fact without people like Euclid or Plato we may not have been as advanced in this age as we are. Mathematics is an adventure in ideas. Within the history of mathematics, one finds the ideas and lives of some of the most brilliant people in the history of mankind's' populace upon Earth.   Ã‚  Ã‚  Ã‚  Ã‚  First man created a number system of base 10. Certainly, it is not just coincidence that man just so happens to have ten fingers or ten toes, for when our primitive ancestors first discovered the need to count they definitely would have used their fingers to help them along just like a child today. When primitive man learned to count up to ten he somehow differentiated himself from other animals. As an object of a higher thinking, man invented ten number- sounds. The needs and possessions of primitive man were not many. When the need to count over ten aroused, he simply combined the number-sounds related with his fingers. So, if he wished to define one more than ten, he simply said one-ten. Thus our word eleven is simply a modern form of the Teutonic ein-lifon. Since those first sounds were created, man has only added five new basic number-sounds to the ten primary ones. They are â€Å"hundred,† â€Å"thousand,† â€Å" million,† â€Å"billion† (a thousand millions in America, a million millions in England), â€Å"trillion† (a million millions in America, a million-million millions in England). Because primitive man invented the same number of number-sounds as he had fingers, our number system is a decimal one, or a scale based on ten, consisting of limitless repetitions of the first ten number sounds.   Ã‚  Ã‚  Ã‚  Ã‚  Undoubtedly, if nature had given man thirteen fingers instead of ten, our number system would be much changed. For instance, with a base thirteen number system we would call fifteen, two-thirteen's. While some intelligent and well-schooled scholars might argue whether or not base ten is the most adequate number system, base ten is the irreversible favorite among all the nations.   Ã‚  Ã‚  Ã‚  Ã‚  Of course, primitive man most certainly did not realize the concept of the number system he had just created. Man simply used the number-sounds loosely as adjectives. So an amount of ten fish was ten fish, whereas ten is an adjective describing the noun fish.   Ã‚  Ã‚  Ã‚  Ã‚  Soon the need to keep tally on one's counting raised. The simple solution was to make a vertical mark. Thus, on many caves we see a number of Ancient Advances In Mathematics :: essays research papers fc Ancient Advances in Mathematics   Ã‚  Ã‚  Ã‚  Ã‚  Ancient knowledge of the sciences was often wrong and wholly unsatisfactory by modern standards. However not all of the knowledge of the more learned peoples of the past was false. In fact without people like Euclid or Plato we may not have been as advanced in this age as we are. Mathematics is an adventure in ideas. Within the history of mathematics, one finds the ideas and lives of some of the most brilliant people in the history of mankind's' populace upon Earth.   Ã‚  Ã‚  Ã‚  Ã‚  First man created a number system of base 10. Certainly, it is not just coincidence that man just so happens to have ten fingers or ten toes, for when our primitive ancestors first discovered the need to count they definitely would have used their fingers to help them along just like a child today. When primitive man learned to count up to ten he somehow differentiated himself from other animals. As an object of a higher thinking, man invented ten number- sounds. The needs and possessions of primitive man were not many. When the need to count over ten aroused, he simply combined the number-sounds related with his fingers. So, if he wished to define one more than ten, he simply said one-ten. Thus our word eleven is simply a modern form of the Teutonic ein-lifon. Since those first sounds were created, man has only added five new basic number-sounds to the ten primary ones. They are â€Å"hundred,† â€Å"thousand,† â€Å" million,† â€Å"billion† (a thousand millions in America, a million millions in England), â€Å"trillion† (a million millions in America, a million-million millions in England). Because primitive man invented the same number of number-sounds as he had fingers, our number system is a decimal one, or a scale based on ten, consisting of limitless repetitions of the first ten number sounds.   Ã‚  Ã‚  Ã‚  Ã‚  Undoubtedly, if nature had given man thirteen fingers instead of ten, our number system would be much changed. For instance, with a base thirteen number system we would call fifteen, two-thirteen's. While some intelligent and well-schooled scholars might argue whether or not base ten is the most adequate number system, base ten is the irreversible favorite among all the nations.   Ã‚  Ã‚  Ã‚  Ã‚  Of course, primitive man most certainly did not realize the concept of the number system he had just created. Man simply used the number-sounds loosely as adjectives. So an amount of ten fish was ten fish, whereas ten is an adjective describing the noun fish.   Ã‚  Ã‚  Ã‚  Ã‚  Soon the need to keep tally on one's counting raised. The simple solution was to make a vertical mark. Thus, on many caves we see a number of

Conflict on a Trading Floor

Conflict on a Trading Floor The case describes the ethical dilemma occurred in FirstAmerica Bank. The sales department of the bank was preparing a 700 mln. USD loan contract for one of the bank’s former client: Poseidon Cruise Lines. Poseidon intended to order a large cruise ship for their fleet to a French shipyard, which required a contract to be signed for five years and in French francs. This in turn raised concerns in Poseidon management, related to the possible economic costs/losses related to dollar-franc exchange transaction risks, since the cash flow of Poseidon was in dollars. The contract elaboration was assigned to Linda, one of the top salespersons of the FirstAmerica bank and the author of article, as an assistant to her. Linda had a reputation of being volatile and hot tempered person, with aggrieve business style. She was particularly known for her prudence in receiving full credit for the good results of closed deals by her. Since Linda had personal relationships with the CFO and treasurer of Poseidon, she proposed to elaborate a structure, which will minimize the Poseidon costs and risks for those transactions. The elaborated scheme suggested that FirstAmerica provides francs to Poseidon in several tranches and receives the interest rates and loan principal in dollars, thus eliminating Poseidon’s franc obligations. In reality the scheme developed by Linda was offering much more profit for the bank and cost for Poseidon, than it was observed in terms of other usual transactions. This resulted in dilemma for the author, since a definite mismatch between his personal values, ethics and his expected behavior occurred. He knew that this transaction is not the best option for the client and the agreement was obtained in the result of deception from Linda’s side. The dilemma has different dimensions, such as prudential, economic and ethical. The prudential dimension exists, since (1) the author feels him owing to Linda, as she has played a great role in hiring the author by the bank, (2) he has a fear of losing a promising job and (3) he wants to show up as a good employee. The economic dimension of the dilemma was that he feels responsible for his job duties and wants to ensure good economic indicators for the bank, as well as they both will receive significant bonuses based on the volume of contract. The ethical aspect of the dilemma was that the author didn’t like lying and values honesty and has a fear of negative consequences. The alternatives that the author has are as follows: a) follow Linda and keep silence, b) speak with Linda, but state the problem in terms of consequences, c) refuse to collaborate with Linda, d) inform Poseidon on the problems, and e) inform higher level of management. By following Linda and keeping silence the author can satisfy his prudential and economic concerns but feel remorse and personal discrepancies in terms of personal ethics. Talking to Linda and stating the problem in terms of consequences can produce positive impact for all dimensions of the problem if she agrees and negative impact for all dimensions if she disagrees. By refusing to collaborate with Linda, the author will satisfy his ethical concerns, but is risking losing his job and sacrificing prudential and economic concerns. By informing Poseidon on deception the outcomes could be the same as with previous alternative, as well as can face legal concerns in terms of information secrecy. Informing higher level of management will produce a positive impact if the management agrees with the arguments, or will produce negative impact, if the management disagrees. The most important issue to consider, is that if the client learns about deception, then there will be no any positive outcomes from the alternatives, which consider continuation of deception. The probability of that to happen is very high, since the client was not yet fully convinced and probably will try its investigation further. Taking into consideration all above mentioned, the best solution appears to be speaking to Linda and if necessary to higher level management, but clearly state the possible consequences of the action and not just higher than usual profit of the bank. If the possible consequences are stated properly, there is higher probability of stakeholders to agree with arguments and arrive at the most desired outcome in this situation. If this doesn’t happen, than this bank is not the place to work.

A Theory About Witches Living In Salem - Free Essay Example

Sample details Pages: 2 Words: 642 Downloads: 10 Date added: 2019/05/28 Category History Essay Level High school Tags: Salem Witch Trials Essay Did you like this example? Youre a wizard, Harry! This famous quote from J. K. Rowlingrs Harry Potter and the Sorcerers Stone, gives Harry Potter a new, positive look on life. The women accused of being witches also heard this and had a new look on life, but not in a positive way. Those words meant the end of their life. In 1692, more than 200 people were accused of practicing witchcraft in a seven month period full of fear and worry, now infamously known as the Salem Witch Trials. Life was quite different in colonial New England than today. Arianne Pinchukrs article Religion in New England Colonies tells how religion was a major part of everyday life. According to her article, the Puritans felt they were superior to anyone who was not a Puritan, and many non-Puritans were often mistreated and killed. This relates to the trials because the witches that were convicted were considered followers of the devil, not of God. Another source for this question is an article from the September 7, 2015 edition of the New Yorker. According to Schiffrs article The Witches of Salem, in 1692, a series of mysterious events were blamed on witches living in Salem. Witchcraft was the second capital crime established only after idolatry when the colonists formed a legal code in 1641. Martha Goodwin, one of the defendants, was unable to sufficiently recite the Lordrs Prayer, leading her to be hanged in November of 1688. In conclusion, the article summarizes that the witches were see n as criminals.A third source, an article about Bridget Bishop by Kiera Stevenson, says Bridget Bishop was the first woman to be hanged starting what is now infamously known as the Salem Witch Trials. Don’t waste time! Our writers will create an original "A Theory About Witches Living In Salem" essay for you Create order In early June of 1692, Bishop was accused of witchcraft and was hanged. She died due to peoplers fear of the unknown. Her trial lasted only eight days, after she was accused of every mysterious happenings in Salem, including an illness spreading. When the villagers ministerrs daughter became ill, Bishop was the one blamed. After more and more girls were found sick, the doctor announced the cause to be witchcraft. The village girls were all accusing Bishop of glancing at them and them falling, with her being the only one to revive them. The entire town seemed to have something against Bridget and her case; they watched as she was led up to Gallows Hill to be hanged on June 10, 1692, starting a seven month era of fear and panic.Loiselle Brett wrote an article about the trials. Her article says it all started when three girls went to an Indian slave woman to tell them their fortunes. What started out as a fun time, tuned dreadful when the three girls started having uncontrollable scream ing fits and temporary blindness and deafness. The village doctor was at a loss for the cause and blamed it on witchcraft. By May of 1692, the prisons were overflowing with witches; the townrs legal system was stressed because they could not hold any trials. The colony did not have a charter and the town magistrates felt they did not have the power to hold capital trials. It was not until the new governor Sir William Phips, arrived on May 14, 1692 that the trials could begin. It was when the governorrs own wife was accused that he disbanded the court and the trials were ended on October 29, 1692.The answer is no one really knows. It has been shown that true magic is impossible. The closest answer that has been found is that the people were scared and science was not advanced enough to find a true answer, so everyone blamed it on what they knew, which at the time was religion. In conclusion, the Salem Witch Trials was simply a sickness that swept over the village of Salem could have been something as simple as an ear infection or a panic attack, not witchcraft.