Eritrea is a small country in Africa that is located on the shore of the red sea. Eritrea borders three countries by land, which include Sudan, Djibouti, and Ethiopia. Eritrea was a part of Ethiopia until 1993 when it won its independence following a 30-year war (BBC, 2020). At the moment, the country is characterized by its tense political environment and poor socioeconomic development. The dictatorship of Isaias Afwerki brought by the militarization of society and a highly constricted political climate (BBC, 2020). Still, the countrys favorable location on the seacoast and its rich history could attract visitors. The present paper will seek to outlinet he travel and visa requirements for Eritrea.
The conditions of entrance into Eritrea vary greatly depending on the citizenship status of the traveler. People who hold an Eritrea National Identification card do not need a visa to enter the country. Additionally, people who are citizens of Uganda and Sudan have simplified procedures with regards to entry. Ugandan citizens do not need to hold a visa to travel into Eritrea. The citizens of Sudan can obtain their Eritrean visa on arrival once they land in the country ( Eritrea visa information , 2020). Citizens of all other countries need to apply for a visa at their local Eritrean embassy. There are various kinds of visas that grant entry into Eritrea, including official, employment, business, student, tourist, transit, and other visas. The requirements for Eritrean visa vary by country, with some states having specific documentation requirements. It is recommended that people contact their local diplomatic mission to receive information about visa requirements for their country.
The requirements for U.S. citizens are published on the official website of the Embassy of Eritrea along with the application form. According to the instructions, the application form should be filled out in full by every visa applicant, except for dependants included in their parents passports (Embassy of Eritrea, 2016). There are no specific requirements for photographs other than that they should be passport-sized. Proof of USA residency permit is essential for an application unless the person is traveling with a USA passport (Embassy of Eritrea, 2016). Any passport used for a visa application must be valid for at least six months after the end date of the trip (Embassy of Eritrea, 2016). People who travel to Eritrea with Diplomatic or Official missions are required to provide a diplomatic note or a note verbal to receive their visa.
In addition, to obtain a business visa, a person must submit a letter from a sponsoring company. This letter should include the purpose of the trip and should be enclosed with the application form (Embassy of Eritrea, 2016). All travelers are required to submit a document proving that they have sufficient funds to cover their expenses. This can include a bank statement or any other document showing an individuals current financial status. Lastly, USA citizens and residents are required to submit an entry fee. For employment and one-time business visas, the fee is $70, whereas students and tourists need to pay $50 (Embassy of Eritrea, 2016). A multiple-trip business visa fee depends on the length of the visa and varies from $110 (3 months) to $300 (12 months).
Overall, although Eritrea is not a popular tourist destination, it can attract people due to its rich history and an excellent geographic position. For those who wish to travel to Eritrea, it is crucial to learn more about entry requirements. The citizens of most countries need a visa to enter Eritrea, which can be received at a local embassy. For citizens and residents of the United States, visa requirements include submitting an application with proof of funds, a passport-sized photograph, and a processing fee. Information about other requirements for application in other countries can be found by contacting a local embassy.
References
BCC. (2020). Eritrea country profile. Web.
Embassy of Eritrea. (2016). Application for entry visa. Web.
The process of choosing an instrument to conduct an investigation may be based on two principal indicators, that is to say on validity and reliability. The two notions are applied to the evaluation of scientific research, as they show the quality of information extracted from a specific finding. The issue of trustworthiness that can be attributed to particular empirical data and results is poignant in any research field. Validity and reliability may serve as a basis for building a scientific study and distinguishing a reputable hypothesis from those that are not supported factually.
Figure 9.2 shows three potential combinations that validity and reliability form jointly their ratio may be used in this way to indicate the value of a measurement instrument. The target, in this case, is a metaphorical representation of the correlation between the notions in question, its center is the concept that a researcher aims to measure, and the shots are the quality with which the goal is reached. Figure 9.2a shows an instrument that is neither valid nor reliable the quality of measurement in this scenario is the lowest. The second figure demonstrates sufficient reliability; still, validity is not attained. It could imply that incorrect values for a large number of interviewees, for instance, are being evaluated. Figure 9.2c shows an image, where the heart of a target is hit, demonstrating the highest validity and reliability. Therefore, the figure constitutes one of the ways to see the relationships between validity and reliability.
To consider the research conducted in the domain of social work objective, it needs to be based on proper methodology. For instance, if a researcher wants to establish whether assembly-line workers at a factory are content with their labor conditions, the notion of satisfaction would be the center of the metaphorical target. When the right values are evaluated for all the respondents, and the consistent group estimate is reached, the research corresponds to figure 9.2c and may be declared valid and reliable.
The term validity is used to indicate the degree to which measurements correspond to the concepts that these measurements should reflect. Face validity answers the question to what degree an instrument, such as a test or an assessment, reaches its specified goal. Construct subtype of validity appears to determine the degree of interpretation adequacy that was constructed with a method applied to empirical data of theory. Content validity shows whether an instrument is appropriate to evaluate the principal aspects of a concept. Additionally, it is usually used to measure attributes of the present. Criterion validity may be viewed as an evaluation of the level to which a measurement corresponds to an outer standard about the notion under consideration. An example of this criterion implementation is a language test that is supposed to determine the level of learners knowledge and divide them into corresponding groups. If the test predicts the learners language competence adequately, then it passed the criteria.
The concepts used in social work theories, such as democracy, public, and representation, are not as easy to quantify. Hence, indicators that only indirectly correspond to the concepts that they represent are used. And in this case, there is a danger that the selected indicators will inadequately reflect the concepts that are measured. To be valid, researches should be comprehensive and complete. Nonetheless, ensuring validity is often considered a significant issue related to measurement in social sciences.
The measures for this study are divided into two categories. The first category describes the attributes of the former female prisoners who are reasserted within the first three years after being released from state prison. The second category studies the factors that influence recidivism among female prisoners. In the first category, four standard measures of recidivism were used: rearrest, reconviction, resentence to prison and return to prison with or without a new sentence (Deschenes, Owen, and Crow, 2006, p.19). The method of coding used in this study is the case-by-variable matrix. The major presentation of data consists of the profile of the female and all prisoners that were released in 1994 from prisons in the 15 states used in the study. The data is presented in three columns: characteristic (variable), females, and all. The variables used include: race (White, Black and Other), ethnicity (Hispanic and Non-Hispanic), age at release (14-17, 18-24, 25-29, 30-34, 35-39, 40-44, and 45 or older), an offense for which inmate was serving a sentence (violent, property, drugs, public-order and other), sentence length in months (mean and median), time served before release in months (mean and median), percent of sentence served before release, prior arrest (mean and median), prior conviction (mean and median) and prior prison sentence.
Measurement of variables and choice of measurement scales used in the study
The main variables used in the study are: race, ethnicity, age at release, an offense for which inmate was serving a sentence, sentence length in months, time served before release, percent of sentence served before release, a prior arrest, prior conviction, and prior prison sentence. Both the ordinal and nominal measurement scales were used in the study. The variables race, ethnicity, age at release, and offense for which inmate was serving a sentence, were measured using the nominal scale of measurement. This scale of measurement groups the data into various categories. The data for each case can only belong to one category and not more. The variable race in this study consists of three categories: white, black, and other. The variable ethnicity consists of two categories: Hispanic and non-Hispanic. The variable age at release consists of seven categories: 14-17, 18-24, 25-29, 30-34, 35-39, 40-44 and 45 or older. The variable offense for which inmate was serving a sentence consists of five categories: violent, property, drugs, public order, and others. The other variables sentence length in months, time served before release, percent of sentence served before release, a prior arrest, prior conviction, and prior prison sentence were measured using the ordinal scale of measurement (Deschenes, Owen, and Crow, 2006, p.21). The researchers only had to assign the appropriate number to each participant. For the nominal level data, the responses given by the participants were coded as numbers to facilitate the statistical analysis. For instance, for the race, white was assigned the number 1, black the number 2, and other the number 3. For the ordinal level data, the values associated with the numbers are specified for analysis.
Graphic presentations used in the study
Several graphic presentations have been used throughout the study and include tables, line graphs, bar graphs, pie charts, and column graphs. Tables are the most commonly used graphic presentations and total 21 in number. Table 1 shows the profile of females and all prisoners released in 1994 from prisons in 15 states as described above (Deschenes, Owen, and Crow, 2006, p.21). Table 2 shows the recidivism rates for female offenders. The female offenders are categorized into four groups: rearrested, reconvicted, returned to prison with a new prison sentence, and returned to prison with or without a new prison sentence. Table 3 indicates the length of the period (in months) from release in 1994 to the first incarceration for female inmates. Table 6 shows the recidivism rate of all prisoners by type of incarceration offense (Deschenes, Owen, and Crow, 2006, p.31). The majority of these tables are derived from table 1, which is the main table. Tables are derived commonly by separating the variables used in the study. Three line graphs have been used to present data. Figure 1 is a line graph that indicates the time to recidivism for female prisoners for specified time intervals. The Y-axis shows the percent of released prisoners (ranging from 0 to 100%). The X-axis shows the time after the release and ranges from 0 months to 3 years. Bar graphs have also been used, for instance, in figure 2 and figure 5. Figure 2 shows the percent of prisoners rearrested by incarceration type. On the Y-axis is the type of offense committed while on the X-axis is the percentage of those rearrested. Each bar is divided into two; the black bar representing the female prisoners and the white bar representing all prisoners. Figure 5 shows the offense category and yearly mean arrest rates before and after incarceration. The Y-axis shows the type of incarceration offense committed before and after incarceration. The X-axis shows the yearly arrest rates (Deschenes, Owen, and Crow, 2006, p.41). Each bar is divided into two; the blue bar represents before incarceration and the red bar represents after incarceration. Figure 3 is a pie chart that shows the rearrest categories for female offenders for the first new arrest following release. The categories include violence, property, drug, public order, other, and none. Each category is differentiated from the others using a distinct color and the percentage for each category is also indicated. Figure 4 is a column graph that shows the percentage of prisoners with any rearrest by type of offense (Deschenes, Owen, and Crow, 2006, p.39). The Y-axis shows the percentages which range from 0% to 50%. The X-axis shows the types of offense which include: violent, property, drug, public order, other and unknown. Each of the offense types is shaded differently and the data labels are indicated above each column.
Improvement of the coding and measurement scales used in the study
The measurement and coding scales used in the study could have been improved in different ways. First, the variable race could have included other significant categories such as Hispanic, Asian Americans, and Native Americans in place of the other category. This would make it easier for readers to know how other significant minority races are affected by recidivism. Second, the variable age at release could have been measured using the ratio scale of measurement instead of the nominal scale. The researchers should have let the participants indicate their exact age rather than categorizing them. This would have provided the researchers with exact information about the ages at which the highest and lowest rates of recidivism occur. Lastly, the variable offense for which inmate was serving a sentence should have been left as an open-ended question. There are many offenses that can be committed and therefore the researchers in this study limited the responses of the participants by listing the categories. The responses to the open-ended question could have been coded once all the responses had been identified after the data collection. This would have enabled the researchers to identify the perspectives of the participants without limiting them.
References
Deschenes, E.P., Owen, B., and Crow, J. (2006). Recidivism among female prisoners: Secondary analysis of the 1994 BJS recidivism data set, 2004-IJ-CX-0038.
China is a country in East Asia whose key industries include manufacturing, agriculture, and mining. With a 68.8% contribution to the countrys Gross Domestic Product (GDP), manufacturing is, by far, the biggest of the productions (Sawe, 2017). In the past decade, the country has surpassed the global leaders in this industry. Currently, China accounts for up to 19.8% of global production total (Richter, 2020). The nations mining sector boasts a 9.2% share of the worlds total mining market in such minerals as gold, copper, coal, and tin (Sawe, 2017). Lastly, although only about 15% of Chinas land is arable, the countrys agriculture industry is strong enough to feed its enormous population (Richter, 2020). All these sectors are mainly capital intensive because they require a large amount of investment in their production. They also have a high percentage of fixed assets, including equipment, plant, and property.
China is at the risk of the middle-income trap (MIT) for a number of reasons. First, the country is experiencing a massive macroeconomic imbalance, especially after leaving the East Asian development model and allowing a rise in inequality (Islam, 2015). The situation has led to social tensions and declining capital efficiency, which may lead to the middle-income trap. Second, China has recently had a few financial crises due to unsound trade liberalization (Holland, 2017). For this reason, the country is expected to experience a growth lower than that of high-income economies or stagnation in the middle-income category, which may cause the MIT. Lastly, Yao (2015) notes that any economy which plucks the low-hanging fruit of industrialization and urbanization is likely to be trapped in the middle-income trap (para. 9). In recent times, China has enjoyed a sharp rise in its key industries: mining, agriculture, and manufacturing. Thus, this situation is likely to ensnare this East Asian country in the MIT.
Sociological studies of the impact of society on individual experiences require a consistent theory with particular explanatory potential. These theories are generally based on many empirical observations and are intended to explain them. Sanford (2017) distinguishes between personality theories, which examine how social variables affect different parts of the individual, and social theories, which explore how institutional settings should be arranged for beneficial impact. Based on these theories, sociologists can propose specific hypotheses and test them through research. For instance, a particular sociological theory argues that human personality is conditioned by the social environment and nurture entirely. In this case, the researchers can propose a hypothesis that the two identical twins placed in unequal conditions will become completely different people.
The verification of this particular hypothesis involves considerable ethical constraints, similar to other people-related studies. Therefore, sociologists use special research methods and tools that help them collect data. Generally, social scientists use tests, questionnaires, observation, interviews, documents, and digital data analysis, and, more rarely, experiments. Researchers also develop theoretical concepts that explain the mechanisms of the influence of social attitudes on the individual, such as conventional wisdom (Sanford, 2017, p. 19). This term refers to routine rigid ideas that often pass from generation to generation without critical analysis. These concepts are used by sociologists to explain the impact of society on peoples thoughts, feelings, and behavior, while the research methodology allows them to verify it.
From my perspective, society has a significant influence on my personality and many aspects of my inner and social life. This impact primarily concerns the information and messages that I perceive. Based on them, I construct my thoughts, and therefore my ideas about the world. The society in which I live has shaped my speech, my appearance, and my social environment. Thus, it can be stated that social influence covers all spheres of human life.
Reference
Sanford, N. (2017). Self and society: Social change and individual development. Piscataway, NJ: Transaction Publishers.
The impact of genetics and the environment has been a topic of lasting research that has not been finished so far. Psychologists still have no definite answer to the question regarding the role of nature and nurture. Some researchers stress that people inherit a set of specific traits that define their development and shape their behavior (Coon, Mitterer, & Martini, 2018). Others emphasize that the environment has a substantial effect on people, determining their choices. Notably, the two opposing views both have empirical evidence, which may seem the question to be rhetoric. However, it is still possible to assume that although hereditary features and the environment are both important, the latter is a defining factor in human development. In order to support this idea, it is necessary to have a closer look at such aspects as lifespan development, emotion, and motivation since they are central to making a human being.
Lifespan Development
All people go through several developmental stages that are characterized by certain peculiarities. Humans do not live in isolation, which is common for any species in the world. People live in certain groups that expand exponentially when an individual passes the corresponding developmental stage. Infants world is confined to their caregivers and close family (Coon et al., 2018). Toddlers and older children have friends and interact with different people outside their families. Adults create their own families, work on their professional growth, and have diverse social links.
Some believe that hereditary traits make people go through their developmental stages in a particular way due to a set of physical features and psychological peculiarities. However, hereditary characteristics may be developed or unnoticed, which leads to their decline. The story of triplets who were placed in three different families is illustrative in terms of the role of nurture in lifespan development ([email protected], 2019). The three boys were raised in different socioeconomic environments that defined the activities their families chose for their children. Parents also chose different parenting styles, which proved to shape behavioral models the triplets exhibited in their adulthood. The boys had different approaches in their professional lives, they also developed different coping strategies.
Emotion
Emotions play an important role in peoples lives, making humans human. The mechanics of emotions have been studied in detail, and peoples emotional reactions are associated with specific neurological and psychological peculiarities (Coon et al., 2018). People are frightened when they face a hazardous situation, and they feel happy when their needs are satisfied. However, it is impossible to deny that human emotions are often socially determined. For instance, in western cultures, males are expected to be reserved while females are allowed to display emotions freely (Coon et al., 2018). In their childhood, people adopt the corresponding roles and emotional patterns.
The role of emotions is exemplified by David Reimers story. The life of the boy who was raised as a girl but chose to be a man in his adulthood may seem an illustration of the role of nature (Asociacion de Bioetica de el Salvador, 2015). However, the environment played a crucial role in Davids life. After the surgical incident, the family raised their son as a girl, but he was not physically a girl. The child received mixed data about genders, as, on the one hand, the society with its divided roles shaped the way the child behaved. On the other hand, a psychologist tried to form (rather ineffectively) certain gender-related views. Negative emotions and social exclusion made the boy choose his gender eventually.
Motivation
Finally, motivation is another important driver of peoples development that shows the pivotal role of nurture. Peoples actions are guided by intrinsic and extrinsic motivations (Coon et al., 2018). Again, people have different physical, mental, and creative potential based on genetic aspects. Nevertheless, their motivations are also shaped by the environment, which can be traced in both stories mentioned above. David wanted to fit in, which was essential for meeting his higher-level needs. He understood that he was not actually a girl based on the existing norms, so he chose to be a boy. The triplets had different motivations (regarding their business, their families, and other spheres) that were shaped by their relationships with their parents. While two of the brothers found their place in the world, one of them could not cope with depressive symptoms and committed suicide.
Conclusion
In conclusion, it is necessary to state that the environment is dominant, although genetic features are also important. Hereditary traits are the basis, but nurture shapes the way different features evolve or disappear. Humans live in groups that create norms and attitudes that affect such areas as lifespan development, emotions, and motivation. In their turn, these three concepts are the pillars of an individuals character and behavior. A human being comes to this world with a set of features, but people also need to adjust to the environment, so they tend to use their hereditary scope to fit in rather than develop to their full potential.
References
Asociacion de Bioetica de el Salvador. (2015). Documental David Reimer [Video file]. Web.
Coon, D., Mitterer, J. O., & Martini, T. S. (2018). Introduction to psychology: gateways to mind and behavior (15th ed.). Boston, MA: Cengage.
Symbiosis between marine Cnidarians (coral reefs; Order Scleractinia) and unicellular photosynthetic dinoflagellates (algae; genus Symbiodinium) is a common feature of marine biota. While Cnidarians feed on zooplankton and supply the dinoflagellates with assimilable nitrogen, phosphorus and carbon, in turn the dinoflagellates, commonly known as zooxanthellae, derive photosynthates notably glycerol, glucose and some amino acids for the animal partner (Clayton & Laskerh, 1984). Cnidarians bleaching is a deterrent phenomenon that severely disturbs the coral reef ecosystems, caused by various stressors like heavy metal and other pollutants, high irradiance, ultraviolet exposure, low salinity and high temperature. A temperature barely 1-2oC above the summer tropical water surface temperatures is sufficient to induce Cnidarian bleaching. According to Ralph, Gademann & Larkum (2001) the optimal surface water temperature of coral reef stays around 28.5oC, and incidences when temperature was risen to ca. 32oC about 80% of reef were destructed by bleaching. Contrary to this most of the marine organisms are rarely affected to temperature rises even up to 40-45oC. Temperature-induced Cnidarian bleaching is either a collapse of symbiotic interaction or is a loss of photosynthetic pigments- chlorophyll and carotenoids of the dinoflagellates. Evidence suggest that several host factors viz. protein hyperphosphorylation, calcium deposition, reactive oxygen (nitrous oxide) production etc. are accountable for this phenomenon (Sawyer & Muscatine, 2001; Weis, 2008).
We tested a hypothesis that more than actual pigment loss it is the detachment and population reduction of zooxanthellae that contributes to Cnidarian bleaching. Since zooxanthellae are also associate with sea anemone Aiptasia pulchella, we selected it as test model and monitored change in zooxanthellae counts and chlorophyll content as a function of time in two higher than optimal temperature regimes.
Material and Methods
We have collected Aiptasia pulchella individuals from their natural habitat and set up growth conditions in two tanks (capacity?). We placed about 10 animals in distilled water, to which Instant ocean salt mix equivalent to 35 g L-1 was added (35 ppt salinity). The temperature was set at 28oC and 32oC. One additional tank kept at 25oC was used as control. The water was periodically circulated for aeration and as feed small particle fish food from local market was given two/ three times a week (check?). We have sampled three animals at zero time from the control tank and data was used for all the other sets. Further, we have sampled 5 animals from the treated sets (higher temperatures) on first and third week from the respective tanks. The polyps were weight (in mg) after being dried with paper towel. We then homogenized in 5 ml of seawater using a hand homogenizer. Large polyps we cut in two halves before homogenizing. We then separated zooxanthellae by vortexing the samples for 1 min and divided the suspension in two parts. Using 1 ml sample we proceeded for chlorophyll estimation by vortexing with 9 ml of acetone. After settling the coarse precipitates the samples were centrifuged at 1000×g for 5 min and the supernatant was decant off. The absorbance was recorded at 665, 647, and 630 nm against acetone blank. We calculated chlorophyll concentration using the formula (A);
Thereafter, we applied a drop of the polyp homogenate to the hemocytometer chamber for counting under high power (450 X). Each counting chamber was square of area of 3 mm enclosing 3 mm × 3 mm = 9 sq. mm area, which was divided in to nine squares each having 1 sq. mm area. The central square was divided in 25 small squares so each of these small squares had 1/25 sq. mm area, which was further divided in 16 small squares each of which now had 1/25 × 1/16 = 1/400 sq. mm area. We counted zooxanthellae in 5 of the 25 small squares. This means, counting of the cells was done in 5 × 16 = 80 small squares having a volume of 1/400 × 1/10 = 1/40003 mm of the sample per sq. Hence, no. of cells (B) = [(Total no. of cells counted × dilution × 4000)/ no. of small squares] × 5 (ml homogenate). We also calculated chlorophyll/ zooxanthellae ratio as (A) ÷ (B).
Figure 1. Zoox cell density against growth periodFigure 2. Zoox chl against growth period
Results
The average values of zooxanthellae cell number per mg animal and chlorophyll per liter in the control (n=3) and two high temperature sets (28, 32oC; n=7-10) of homogenized sea anemone is shown respectively in Fig. 1 and 2. In control the initial number declined and thereafter increased, but chlorophyll was high during first week and then it kept decreasing. The zooxanthellae counts and chlorophyll in animals kept at 28oC steadily increased though this increase was much lower than the controls in prolong incubation. Somewhat same increase in zooxanthellae number was recorded even at 32oC but here chlorophyll content did not change until 1 week and thereafter it shot up to a level even higher than control. Hence overall growth related changes in cell number and chlorophyll content did not match each other which indicate that the parameters responded differently to growth period and to the tested temperatures.
Discussion
There was a completely opposite trend in number and chlorophyll content in the controls during the given growth period. This suggests that zooxanthellae was still in the acclimatization phase when lower numbers of cells had excess chlorophyll in the beginning and later when cells were acclimatized the cell density sharply increased though there was not much increase in chlorophyll content. The hypothesis that zooxanthellae dislodged at high temperatures can be justified if during growth at 28/32oC both zooxanthellae count and chlorophyll content would have concomitantly decreased compared to the control. If we consider the week 3 chl data of 32oC as experimental artifact, then we indeed found lower chlorophyll and cell number in heat treated samples than the controls during the growth phase. Hence the results support the working hypothesis that the dinoflagellates tend to escape the hosts when exposed to stressor-like high temperatures. If the effects were bleaching of the dinoflagellates then we would have seen lower chlorophyll in higher number of zooxanthellae at higher temperature regimes compared to control as growth advanced. Further, there should have been a temperature-dependent decrease in chlorophyll content in the dinoflagellates, which is clearly not the case.
Conclusion
Notwithstanding, it would be desirable to repeat the experiments with more animals to get statistically relevant results. Moreover, the animals from fields should be first acclimatized to the lab conditions for at least two generations under control conditions before the experiment on high temperature regime is conducted. With these precautions the hypothesis is expected to be more rigorously tested. To conclude, within the experimental limitations, a reduction in zooxanthellae population seems to be the primary cause of Cnidarian bleaching.
References
Clayton, W.S. & Laskerh, H.R.(1984). Host Feeding Regime and Zooxanthellal Photosynthesis in the Anemone, Aiptasia Pallida (Verrill). Biological Bulletin, 167, 590-600.
Ralph, P.J., Gademann, R. & Larkum, A.W.D.(2001). Zooxanthellae expelled from bleached corals at 33oC are photosynthetically competent. Marine Ecology Progress Series, 220, 163-168.
Sawyer, S.J. & Muscatine, L.(2001). Cellular mechanisms underlying temperature- induced bleaching in the tropical sea anemone Aiptasia pulchella. The Journal of Experimental Biology, 204, 3443-3456.
Weis, V.M.(2008). Cellular mechanisms of Cnidarian bleaching: stress causes the collapse of symbiosis. The Journal of Experimental Biology, 211, 3059-3066.
This assignment focuses on the Camelopardalis species a type of giraffe. One of the noticeable characteristics of this species is its elongated neck that enables it to reach the topmost part of the trees to be able to get foliage for sustainability. This essay looks into the long-necked trait and what has led to its development. Amongst the synergistic population, this is a species that had taken its line of life which had been influenced by the rule of natural selection and survival for the fittest. Due to the variations in the amount of rainfall the vegetation dries up and the remains are usually at the treetops hence they are forced to adapt through this trait. Camelopardalis (camelopard) is the species that originated from the Romans; the species are depicted to contain a blend of characteristics of both the leopard and the camel. The giraffe (Giraffa camelopardalis) and the okapi are the two remaining populations of the family Giraffidae in this species. There exists several subspecies which were classified by the color of their skin and pattern variations. Giraffes are long-necked, even-toed land-living mammals. They are the largest ruminant animals existing. Their body is covered with uneven patches of fur whose color range from black to yellow. These patches are separated by white color, manila backgrounds (David& Bruce 1996).
Due to their selective nature of feeding, the giraffes are known to be well associated with acacia trees although their existence can be found in open woodlands, savannas, and the grasslands. Formally, their existence occurred in sub-Saharan Africa (Chad to South Africa) in the dry and bare savanna zones wherever trees existed. Nowadays, their range has greatly contradicted due to human influence and climatic changes, especially in the West African countries. (David & Bruce 1996).
Giraffes are known to have evolved from antelope-like mammals that used to exist in Asia and Europe 40-50 million years ago. The earliest was one that looked like a deer that appeared in the early Miocene. Later, the genera Palaeotragus and Samotherium were seen in the mid-Miocene. They all had taller and slender shoulders although they had shorter necks. In the late Pliocene, the subspecies of the girrafids had reduced drastically leaving only the Okapi and the modern Giraffe with the latter approximated to have had appeared about a million years ago. The okapi which resembles the giraffe has far shorter neck as compared to the modern giraffes. An adult giraffe is approximately 15-17ft tall with the length of the neck said to be 2.4m although male giraffes are said to be taller than the female ones (David& Bruce 1996).
Giraffes long neck showed welcoming gesturers for Scientists quest to explain the theory of evolution among the animals. As per Lamarcks argument, we imagine a scenario in the long past when there was stiff competition for food by the browsing animals on the ground (David& Bruce 1996). The alternative way was the foliage which was on top of the trees. Think of a time in life where the ancestors of the giraffe were the deer or the antelope. The changes in the environment obliged the animals to look for food up the trees which led to changes of organ development structure of the animal such as prolonged neck and tall hind legged giraffes. This theory was supported by the Darwin theory of survival for the fittest which supports the idea that the animal had a lot of competition from the browsers forcing them to search for food from the top of the trees which made the species with short necks to die off leaving the ones with long powerful necks to survive. These changes affected their next generations due to DNA modification (David& Bruce 1996).
The other theory that supports the evolution of the long neck is sexual selection. This sexual selection theory was proposed by Simons and Scheepers (David& Bruce 1996). During mating, these animals especially the males use their long necks to attack each other. This is the way they compete for the female. The one that is defeated runs away or gets killed through continuous kicking. The stronger male that remains, is the one that mates with the female. These genes being powerful and strong are expressed physically through the actions of the giraffe hence the eventual selection of the longer and stronger necks over the shorter ones.
Necking also has another function which is sexual relations between the males. Males neck each other till they mount and achieve a sexual climax. The male encounters occur severally as compared to necking between the male and the female during sexual production male and female neck for the real sexual production. Animals that were able to stretch above the other animals survived. They rather mated and left young ones which had either inherited some abnormal necks that will be different in one way or the other. This practice continued for a long because there are no longer giraffes with shorter or normal necks. The evolution of the giraffe shows that through sexual reproduction, hereditary genes are passed on to future generations through dictating the conformation of the DNA which carries these genes. According to David and Bruce, inheritance of favorable characteristics can only occur if there is an alteration in the gene carrier or DNA of an animal (1996).
Due to climatic changes and human interference into Giraffes ecosystems, the giraffes will be forced into smaller ecosystems where they will compete for food and mating partners. We expect them to develop very tall, powerful, and muscular necks to help them stand the competition for mating and foliage.
Reference
David, J. D., & BDruce H. W. (1996). Darwinism Evolving: Systems Dynamics and the Genealogy of Natural Selection. Massachusetts: MIT Press.
Bis(imino)pyridine (BIP) with imino-C (SC) and imino-N (SN) substituents.
Bis(imino)pyridine ligands are an important class of ligands that are currently being investigated around the globe for their properties in numerous fields of industry. Their tridentate nitrogen donor complexes, with different transition metals, give these ligands unique electronic and redox properties.
The unique catalytic properties and the flexibility of these substances are not limited to the catalysis of ethylene, on which they were initially discovered, but they have within a decade expanded to embrace many other chemical mediated processes, such as the reduction of ketones via hydrogenation, metathesis etc.
However, their properties are yet not fully known and there is still some optimization to be done for every potential application, while still, an integrated cost-efficient and productive catalyst remains to be found
Preparation (Synthesis) of BIPs
BIP synthesis from the condensation of diacetylpyridine (Sc=CH3) or 2,6-pyridine carboxaldehyde (Sc=H), or 2,6-dibenzoyl-pyridine (Sc=phenyl), with an aniline (SN= aryl) or generally another amine (SNNH2).
Generally, synthesis of BIPs proceeds with condensation of an amine with for example 2,6-diacetylpyridine, which is the most popular method for synthesis of BIPs.
Different amines and ligand modifications have been utilised for this purpose giving a variety of products with different properties and conformations.
Bis(aryl-imino) pyridine ligands can be synthesized from the condensation reaction of 2,6-pyridinedicarboxaldehyde or 2,6-diacetylpyridine or 2,6-dibenzoylpyridine with anilines in alcohol or CH2Cl231 solution, at elevated temperatures.
It is possible to condensate amino-heterocycles such as amino-pyrrolyl, triazolyl, carbazoles and indolyls as N-substituents with the condensation reaction with 2,6-diacetylpyridine to form N-azolyl BIP structures with N-N bonding.
Liu et al. have condensed 2,6-diacetylpyridine with the hydrazine of oxamic acid to obtain bis (semioxamazide-imino) pyridine at 55oC in a methanol solution.
Other Syntheses: Synthesis of 2-(chloro-substituted-1H-benzoimidazol-2-yl)-6- (1-aryl-iminoethyl) pyridines (L1-L6) (Reaction 7).
Complexes of BIP with Fe and Co
These complexes can be prepared in numerous ways and with a varying number of metal substituents. Typically, the synthesis of the iron and cobalt halide systems proceeds by treatment of BIP with the respective metal halide (e.g. FeCl2, CoCl2, FeCl3) salts in THF, or n-butanol (boiling at 80oC for about 10min. or CH2Cl231,40 for about 2hrs,25 or at 40oC for about 1hrs). The complex formed is paramagnetic, coloured, high-spin species, pentacoordinate in most cases, with pseudo-square-pyramidal geometry, with a nearly perpendicular arrangement of the aryl, rings relative to the square plane.
Preparation of dimeric bis(aryl-imino) pyridine iron dinitrogen compounds with aryl substituents smaller than isopropyl from a related precursor. FeBr2 may be achieved by stirring the THF solutions of these precursors in the presence of naphthalene resulting in the iron dinitrogen compounds.
A straightforward method for the synthesis of bis(imino)pyridine iron dialkyl compounds is by substitution of the pyridine ligands in (py)2Fe(CH2SiMe3)2 with the appropriate chelate
Applications of BIP Fe and Co complexes
Polymerization of ethylene to polyethene
Polymerization of ethylene to polyethene proceeds via a Cossee-type propagation mechanism, involving the migratory insertion of ethylene into a metal alkyl bond and in the case of FeII, iron(II) alkyl cations act as propagating species.
It is terminated through:
A bimolecular ²-H transfer to metal (BHT), or monomer
A less common chain transfer to aluminium
Fe and Co halide complexes of BIP with aryl groups with substituents in the ortho position upon activation with MAO, give an active ethylene polymerization catalyst converting ethylene to highly linear polyethene. The reaction is affected by the type of metal-ligand, metal substituent, structure, reaction conditions, branching, and molecular weight distribution.
Oligomerization of ethylene to ±-olefins
±-olefins in the range C6-C20 are used as comonomers in the polymerization of ethylene to give linear low-density polyethene or for the preparation of detergents and synthetic lubricants.
They are also used to prepare detergents and synthetic lubricants. The reaction mechanism is not well understood. The reaction is affected by steric effects and the electronic factor of ligands.
Other factors influencing the reaction include metal activities, reaction conditions, molecular weight distribution, and cocatalysts.
Polymerization of Butadiene to polybutadiene
Polybutadiene is a material that finds extensive and diverse applications in the tire industry but studies on butadiene polymerization, remain scarce. In butadiene polymerization, selective cis-1,4 polymerization of butadiene is of prime importance since the elastomeric rubbery product, cis-1,4-polybutadiene, constitutes one of the major ingredients in the tire industry. The structure of the active centre is the determining factor for the activity, molecular weight, and stereochemistry of polymerization.
FeII pyridinediimine systems were first reported by the tire and rubber company Goodyear for the co-dimerization of butadiene and ethylene.
Hydrosilylation of aldehydes and ketones
Reduction of C=O bonds to alcohols is an important reaction in organic synthesis with hydrosilylation being among the most useful reduction methods. Due to chemoselectivity issues and severe reaction conditions with other reaction routes (metal hydrides), there is a serious demand for new, mild, and chemoselective reducing methods.
Due to chemoselectivity issues and severe reaction conditions with other reaction routes (metal hydrides`), there is a serious demand for new, mild, and chemoselective reducing methods.
Iron dialkyl ligands are used in the hydrosilylation process because:
BIPs are tolerant in many functional groups
BIPs are some of the most active iron-based reduction catalysts
Acetylene polymerization
Polyacetylene gives rise to metallic conductivity after suitable doping and is one of the most important conjugated polymers. The macroscopic morphology of the polymer produced in that way is dependent on the reaction conditions.
Stirring has been found important for film formation as it increases the yield. The rate of polymerization has been found to decrease with time due to the slow diffusion of acetylene through the gel. With time, the insoluble polymer rapidly encapsulates the catalyst, preventing further polymerization.
Copolymerization with Hexene
Late transition metal catalysts tolerate heteroatomic functionalities, opening up the possibility for copolymerization of olefins with other monomers to produce linear or branched systems. The copolymerization of ethylene with other ±-olefins comonomers is an important industrial process for the control of the densities of the produced polymers.
BIP with Ni
Synthesis of Ni complexes with BArIP is generally similar to Fe and Co complexes. That is the reaction of the relevant ligand with the respective nickel salt (NiCl2) in boiling THF.
Applications of BIP-Ni
Oligomerization of ethylene
The reaction is increased by ethylene pressure, temperature and cocatalyst to metal ratio.
Butadiene polymerization
Occurs similarly to that of Fe and Co BIP complexes.
Norbornene polymerization
Several parameters, including the nature of catalytic precursors, the concentration of MAO, reaction temperature and reaction time have some effect on the activities of the complexes and the molecular weight of the PNB.
The bicyclo[2,2,1]hept-2-ene, known as norbornene, polymerizes to give products that exhibit strong thermal stability, have excellent dielectric properties (low dielectric constant, excellent transparency, small optical dielectric loss), optical transparency, large refractive index, and unusual transport properties, mechanical properties, high chemical resistance, high glass transition and decomposition temperatures, good UV resistance, and low water uptake, which can be of use in microelectronics applications
BIP complexed to Mn
Similar to Fe, Co and Ni, halide complexes, adding an Mn metal centre in BIP is accomplished with the addition of the Mn halide in the respective BIP ligand in refluxing acetonitrile in yields ranging 40-77% or THF in higher yields (80-95%). Toluene solution can also be used, same as reaction with manganese perchlorate.
Applications BIP-Mn
Superoxide-Dismutase
The superoxide anion is formed during respiration.
Dismutase enzymes catalyze excess superoxide as it is harmful at high levels.
Electrochemical applications
Electronically conducting polymers are used in various devices.
Polymerization of ethylene
The Mn ligand redox properties are widely used industrially.
All mammalian life consumes oxygen as the ultimate oxidant supporting cellular respiration with a considerable portion of the oxygen metabolized through its superoxide anion. The superoxide anion is the one-electron reduction product of molecular oxygen formed as a byproduct of normal cellular respiration.
In organisms, superoxide dismutase enzymes (SOD-oxidoreductase enzymes Mn, Fe, Cu, Zn, Ni-based) present in cell mitochondria, plasma, and the extracellular spaces in eukaryotic and some prokaryotic cells, catalyze the disproportionation of superoxide to dioxygen and hydrogen peroxide, which then is decomposed via catalase to water and dioxygen. The inability of the human body to adequately control and limit the overproduction of superoxide anion.
Electronically conducting polymers have been studied extensively owing to their potential applications in energy conversion devices, sensors, electrochromic displays, microelectronic devices, electrocatalysis, military etc.
Fe(II)- and Co(II) complexes bearing bis(imino)-pyridine and related ligands are famous for their efficient ligand framework in the polymerization of ethene at high activities and adjustable product properties. On the other hand, despite all BIPs being redox-active, it is the Mn ligand redox properties, which enable its application on different industrial aspects.
Conclusion
In this paper, bis(imino)pyridine and methods for its synthesis, syntheses of its complexes with Fe, Co, Ni and Mn and the applications of these complexes in different chemical processes have been covered.
The success with BIPs in the polymerization of ethylene is due mostly to the ease of structural modification (steric control) of these compounds which allows for greater control in the MW distributions and properties of final product and optimization possibilities (via cocatalysts temperature, metal centre etc.) in the production line.
Despite the much-sought high productivities of BIP for ethylene polymerization and oligomerization and its cost-effectiveness for this application, the BIP as a catalyst for that industry still needs to be tested/ studied or modified.
Owing to their tridentate system their unique properties, structural flexibility and previous (even if recent`) experience of BIPs in the PE industry, it was possible to use the BIP ligands in a range of applications.
Research bias are nearly impossible to eliminate completely, yet their excessive presence implies that the veracity and accuracy of research results reduces extensively. Therefore, addressing the issue of research bias is essential. In qualitative research, bias may occur due to the imperfections in data collection tools. Namely, the interview and survey models allow participants to respond in the manner that they deem as necessary as opposed to voicing their actual opinions or stating the facts. In addition, there is a possibility of an interviewer misinterpreting the collected information in the way that supports the research hypothesis, thus skewing the outcomes and contributing to further confusion.
Bias in Quantitative Research
Quantitative research is not devoid of bias, either, mostly due to the errors made at the stage fo sampling. By using an unnecessarily homogenous research population, one can receive the research results that do not represent the actual situation. In addition, quantitative research bias may occur in the scenarios that involve any systematic error leading to the mismanagement of quantitative information. For instance, if a researcher does not standardize their interactions with a patient, misinterpretation of data and the further introduction of bias into the quantitative analysis will ensue (Krehenwinkel et al. 8). Therefore, using a homogenous approach toward the collection of data is essential in quantitative studies.
Considerations before Creating the Research Protocol
When creating a research protocol, one must ensure that possible bias is addressed accordingly, which can be achieved by considering the weaknesses of the chosen type of research. In addition, before compiling a research protocol, one must set specific research goals and define the milestones for their completion. Additionally, the key characteristics of the target population have to be identified to ensure that the necessary information is gathered properly. Thus, one will ensure that the collected data is accurate and research results are representative of the studied problem.
Work Cited
Krehenwinkel, Henrik, et al. Estimating and Mitigating Amplification Bias in Qualitative and Quantitative Arthropod Metabarcoding. Scientific Reports, vol. 7. no. 1, 2017, pp. 1-12.
