2) The peeled onion bulb was chopped and measured homogenized.

2) The peeled onion bulb was chopped and measured homogenized.

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The TCP data is received by OR from port an and it is processed by TCP and TLS protocols. Then the processed data is delivered to the TLS buffer. The read event is called to read and process the data pending in the TLS buffer. This read event will pull the data from TLS buffer into the input buffer. Then the read event process cells from input buffer one by one. Each OR has routing table which maintains map from source connection and circuit ID to destination connection and circuit ID.

The transmission direction of the cell can be determined by the read event. To append the cell to the destination circuit the corresponding symmetric key is used to decrypt / encrypt the payload of the cell, replace the present circuit ID with destination circuit ID. The cell can be written directly for the destination connection if there is no data waiting in output buffer and the write event is added to the event queue. After calling the write event, the data is flushed to TLS buffer of destination. Then write event pull as many cells as possible from circuit to output buffer and add write event to event queue. The next write event carry on flushing data to output buffer and pull cells to output buffer else the cell queued in circuit queue can be delivered to network via port B by calling write event twice.

Fig. 2Processing the cells at Onion router

The IP packets in Tor network is very dynamic and based on this the cell – counting based attack implemented.

Step 1: SELECTING THE TARGET :- The attacker log the information at the exit OR, including the server host IP address and port for a circuit and circuit ID and uses CELL – RELAY-DATA to transmit the data stream.

Step 2: ENCODING THE SIGNAL :- Until the write event is called the CELL – RELAY – DATA will be waited in the circuit queue. After the write event is called then the cells are flushed into output buffer. Hence the attacker can manipulate the number of cells flushed to the output buffer all together. This way the attacker can able to embed the secret signal. To encode bit 1, the attacker can flushes three cells from circuit queue and for bit 0, flushes one cell from circuit queue.

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Step 3: RECORDING PACKETS :- After the signal is embedded in the target traffic it will be transmitted to the entry OR along with target traffic. The attacker at the entry OR will record the received cells and related information and need to determine whether the received cells are CELL – RELAY – DATA cells.

Step 4: RECOGNIZING THE EMBEDDED SIGNAL :- The attacker enters the phase of recognizing the embedded signal with the recorded cells. For this used the recovery mechanisms. Once the original signal is identified the attacker can link the communication between Alice and Bob.

There are two critical issues related to attack: (1) Encoding signals at exit OR: Two cells are not enough to encode “1” bit. Because if the attacker uses two cells to encode bit “1” then it will be easily distorted over network and also hard to recover. When the two cells arrive at the input buffer at the middle OR, the first cell will be pulled into circuit queue and then if the output buffer is empty, the first cell will be flushed into it. Then the second cell will be pulled to the circuit queue. Since the output buffer is not empty, the second cell stays in the circuit queue. When the write event is called, the first cell will be delivered to the network, while the second cell written to the output buffer and wait for the next write event.college essay for business major Consequently, two originally combined cells will be split into two separate cells at the middle router. So the attacker at the entry OR will observe two separate cells arriving at the circuit queue. This cells will be decoded as two “0” bits, leading the attacker to a wrong detection of the signal. To deal with this issue the attacker should choose at least three cells for carrying bit “1”.

For transmitting cells, proper delay interval should be selected: If the delay interval among the cells is too large, users are not able to tolerate the slow traffic and to transmit the data will choose another circuit. When this condition happens the attack will fail. And if the delay interval is too small, then it will increase the chance that cells may combined at middle OR.

(2) Decoding signals at the entry OR: Distortion of signal: Anyway the combination and division of the cells will happen due to unpredictable network delay and congestion. This will cause the embedded signal to be distorted and the probability of recognizing the embedded signal will be reduced. Because of this distortion of the signal, a recovery mechanism can be used, that recognize the embedded signal.

The combination and division of cell can be categorized into four types: (1) Two types of the cell division for the unit of the signal and (2) Two types of the cell combination for different units of signal. To deal with these types of division and combination types of the cells the recovery algorithm can be used. If the number of cells recorded in the circuit queue is smaller than how many the original signal are recovered as either two types of cell division for the unit of the signal. Suppose the number of cells recorded in the circuit queue is larger than the number of cells for carrying the signal; the recovered signal will be either two of the cell combination for different units of signal. When the signals are recovered in these types with k ≤ 2, can consider that these signals are successfully identified otherwise cannot be identified.

In this paper, we presented a cell-counting based attack against Tor network. This can confirm the anonymous communication among the user quickly and accurately and it is very difficult to detect. The attacker at the exit OR manipulates the transmission of cells from the target TCP stream and embeds a secret signal into the cell counter variation of the TCP stream. Then the attacker at the entry OR recognizes the embedded signal using developed recovery algorithms and links the communication relationship among the users. In this attack the detection rate is monotonously increasing function with the delay interval and decreasing function of the variance of one way transmission delay along a circuit. This attack could drastically and quickly degrade the anonymity service that Tor provides. Due to the fundamental design of the Tor network, defending against this attack remains a very challenging task that we will investigate in future work.

REFERENCES

[1] W. Yu, X. Fu, S. Graham, D. Xuan, and W. Zhao, “DSSS-based flow marking technique for invisible traceback,” in Proc. IEEE S&P,May 2007, pp. 18–32.

[2] N. B. Amir Houmansadr and N. Kiyavash, “RAINBOW: A robust and invisible non-blind watermark for network flows,” in Proc.16thNDSS, Feb. 2009, pp. 1–13.

[3] V. Shmatikov and M.-H. Wang, “Timing analysis in low-latency MIX networks: Attacks and defenses,” in Proc. ESORICS, 2006, pp. 18–31.

[4] V. Fusenig, E. Staab, U. Sorger, and T. Engel, “Slotted packet counting attacks on anonymity protocols,” in Proc. AISC, 2009, pp. 53–60.

[5] X. Wang, S. Chen, and S. Jajodia, “Tracking anonymous peer-to-peer VoIP calls on the internet,” in Proc. 12th ACM CCS, Nov. 2005, pp.81–91.

[6] K. Bauer, D. McCoy, D. Grunwald, T. Kohno, and D. Sicker, “Lowresource routing attacks against anonymous systems,” Univ. Colorado Boulder, Boulder, CO, Tech. Rep., Aug. 2007.

[7] X. Fu, Z. Ling, J. Luo, W. Yu, W. Jia, and W. Zhao, “One cell is enough to break Tor’s anonymity,” in Proc. Black Hat DC,Feb.2009[Online]. Available: http://www.blackhat.com/presentations/bh-dc-09/Fu/

BlackHat-DC-09-Fu-Break-Tors-Anonymity.pdf

[8] R. Dingledine, N. Mathewson, and P. Syverson, “Tor: Anonymity online,” 2008 [Online]. Available: http://tor.eff.org/index.html.en

[9] R. Dingledine and N. Mathewson, “Tor protocol specification,”2008 [Online]. Available: https://gitweb.torproject.org/torspec.git?a=blob_plain;hb=HEAD;f=tor-spec.txt

[10] J. Reardon, “Improving Tor using a TCP-over-DTLS tunnel,” Master’s thesis, University of Waterloo, Waterloo, ON, Canada, Sep. 2008.

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1052 words (4 pages) Essay

7th Aug 2018 Biology Reference this

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The experiment was about the isolation and characterization of DNA. The DNA was isolated from the onion. The mass of the isolated DNA was 15.11 g. The purity of isolated DNA was estimated by calculating the ratio based from the absorbance at 260nm and 280nm resulted to 0.671 meaning more protein was absorbed. Meanwhile in denaturation of DNA, the initial absorbance at 260 nm was 1.304 higher than the absorbance at 260 nm after heating which was 1.095.

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Deoxyribonucleic acid (DNA) is the genetic material in humans and all other organisms. DNA isolation is the removal of DNA from the cell which it normally resides. Isolation is the removal of DNA from the cell in which it normally inhabits. (1)

Onions are used since it contains little amount of starch which allows the DNA to be more visible. The filtrate is made up of onions treated with salt, distilled water and detergent collectively called as lysis solution. DNA purification is done by enzymatic degradation of contaminating proteins with ethanol. A spectrophotometer is used in determining the concentration and purity of the proteins. (2)

The peeled onion bulb was chopped and measured homogenized. The sample was placed in a blender added with an ice-cold lysis solution then for 45 seconds at low speed. Meanwhile, the lysis solution used was prepared beforehand by mixing 5.00 ml of liquid detergent, 5.00 ml of 0.500M EDTA, 10.0 ml of 50% Na Cl solution, and 80 ml of distilled water and placed in an ice bath. After homogenizing, the sample was filtered through the cheesecloth and the collected filtrate was placed in a 250-ml beaker. A 10.0 ml of 5% pepsin solution was added to the filtrate and placed on an ice bath for 10 minutes with occasional stirring. Ice cold 30.0 ml of 95% ethanol was pipette to the side of the beaker containing the sample and stand for 10 minutes on ice bath. Once the DNA precipitates appeared at the interface of the solution, the DNA was already ready for isolation. The spooled DNA was transferred immediately to a pre-weighed 100-ml beaker to determine the mass and percent yield of the sample. The isolated DNA was added with 10.0 ml of 95% ethanol then covered with aluminum foil and refrigerated in preparation for the next laboratory procedure.

Little amount of DNA sample was placed in a test tube added with 1.00 ml of 20% TCA followed by heating the sample for 10 minutes in water bath with 1.00 ml distilled water. A 2.00 ml of diphenylamine solution was added then heat again in a water bath for 10 minutes. The color change was observed and the absorbance of the sample from 400 nm to 700 nm was scanned to determine the wavelength of maximum absorption. Mean while, little amount of the DNA sample was placed in a separate test tube filled with 5.00 ml distilled water and scanned to read the absorbance at 260 nm then at 280 nm. After determining the A260/A280 value, the sample was heated to boil for 5 minutes and read the absorbance adain at 260 nm.

The mass of the raw sample gathered from onion is 30.4 g. After homogenization and adding of pepsin solution and ethanol, DNA precipitates were became visible and transferred to another beaker. The isolated DNA measures 23 g.

The calculated percentage yield was quite high. However, still some sources of error was done while conducting the experiment, the sample with DNA precipitates was disturbed while transferring the DNA. The accumulated DNA precipitates is enough for the next procedure which is characterization.

Heat denaturation of DNA, causes the double helix structure to unwind and form single stranded DNA. Thus, the bases unstacked and can absorb more light causing an increase after denaturation. But based on the results gathered, the initial absorbance at 260 nm was 1.304 then was decreased after heating which was 1.095. The calculated percent increase in absorbance was 8%. This error is maybe, due to the heating process. The DNA acquired was quite greater and was not totally heated afterwards causing double helix structure not to unwind and form a single stranded DNA.

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The filtrate gathered from this experiment was made of onions and lysis solution. Onion was used in this study due to low starch content, allowing the DNA to be more visible considering the onion as one of the best source of DNA. (4)

The used of lysis solution was to separate the DNA from extra cell components and to keep the location in which the DNA will not be tainted. The NaCL provides NA+ ions that will obstruct the negative charge as of phosphate ends of DNA. Permitting these ends to come nearer so they can precipitate out of a cold solution. The detergent causes the breaking down of the cell membrane by emulsifying the cell proteins and lipids. Also, disrupting the polar connections that collectively holds the cell membrane. The complexes formed with these lipids and proteins causes the precipitate out of solution. Meanwhile, the purpose of EDTA is to chelates metal ions. (5) A Pepsin solution was used for purification via enzymatic degradation.

DNA is polar due to its extremely charged phosphate backbone which makes it soluble in water. Thus DNA is insoluble in ice cold ethanol, as a result when the cold ethanol was added, it causes stable ionic bonds to form and precipitate the DNA.

Heating the sample is the one responsible for the observed color of DNA with diphenylamine. When the DNA is heated with acid, the 2-deoxyribose is converted to w-hydroxylaevulinic aldehyde, which reacts with the compound diphenylamine. Through this, a blue-colored compound supposed to produce. In our sample the color observed was green possibly because of the DNA concentration.

The ratio of absorptions at 260 nm vs 280 nm is frequently used to evaluate DNA contamination of protein solutions. The nucleic acids, DNA and RNA, absorbs at 260 nm and proteins absorb at 280 nm. Based on the results, the rate ratio of absorptions at 260 nm vs 280 nm is 0.671. Since proteins absorb light at 280 nm, the ratio is low meaning there is a lot of protein absorbed at 280nm.

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2769 words (11 pages) Essay

1st Jan 1970 Psychology Reference this

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Research methodology refers to the various sequential steps adopted by a researcher in studying the problem with certain objectives in mind. It is an explanation of the method of systematic and critical investigation into an identified subject of study. With an explanation of the elements in the concept of Research Onion (Saunders, Lewis, & Thomhil, 2007) the researcher will describe the steps adopted to do this research. In short we can say that a research methodology is the description, explanation and justification of various methods of conducting research (Sharavanavel, 2006).

3.2. UNDERSTANDING RESEARCH PROCESS

The concept of research onion (Saunders, Lewis, & Thomhil, 2007) will be used to understand the research process used by the researcher.

The main layers in the research onion are research philosophy, research approaches, strategy, choices, time horizon, and techniques and methods of data collection. An explanation of some these elements of research onion will provide the researcher with required knowledge to conduct this study (Saunders, Lewis, & Thomhil, 2007).

Figure : 3.1

Source: Saunders, Lewis, & Thomhil (2007)

3.2.1. RESEARCH PHILOSOPHY

A research philosophy is a belief or idea regarding the collection, interpretation, and analysis of data collected. There are various philosophies are explained in Saunder’s research onion. The most significant among them are Positivism, Realism, interpretative, Objectivism, Subjectivism, Pragmatism, Functionalist, Interpretative, Radical humanist, Humanist and structuralist (Saunders, Lewis, & Thomhil, 2007).

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Positivism holds reality as stable. an objective view point can be described by this. This philosophy further says that knowledge that are not based on positivism is invalid and blurred (Miller Strang & Miller, 2010). Realism is a philosophy that holds scientific approach to development and knowledge . The basic assumption of this philosophy is that which is actually is. It is independent from the belief of the people. There are two types of realism. The one is direct and the other critical realism. From the point of view of a direct realist the world is static and having no change. Critical realism holds change as constant (Buchanam & Bryman,2009). In Pragmatism problems are dealt with directly. This philosophy is more interested in results or truth rather than the principles associated with it. (William James, 2009) This philosophy holds that a concept or theoretical principle should be set on the basis of how it works (Saunders, Lewis, & Thomhil, 2007).

The philosophy adopted by the researcher in this study realism

3.2.2. RESEARCH APPROACHES

The second last layer of the research onion of Saunders (Saunders, Lewis, & Thomhil, 2007) is research approaches.

Figure:3.2

Source: Created by the author (2010)

There are two types of approaches the Deductive and Inductive (Jonker & Pennink, 2009).

3.2.2.1 Deductive Approach

It is a journey from general to particular. Here the hypothesis and the theory are checked first and then move to results that are more specific. Here conclusion follows logically from the available facts (Jonker & Pennink, 2009).

3.2.2.2 Inductive Approach

In this approach an empirical observation takes the researcher to a result. Here specific observations will reach to more generalizations and forming up of theories. It is from specific to general. This method is mainly used in the qualitative research (Myers, 2009).

3.2.2.3 Quantitative Approach

Quantitative methods always focus on the numbers and its frequencies. It does not emphasize on the experience and meanings but quantify the data collected. In quantitative approach the data will be subject to rigorous and strict analysis (Kothari, 2008).

3.2.2.4. Qualitative Approach

In qualitative Approach the data is collected mainly to describe factors rather than reaching to a statistical inference. It is an unstructured exploratory research method. Here the important factors of character, behavior, attitude, opinion etc are subjectively assessed. (Myers, 2009) Usually qualitative studies are used for explanatory purposes (Kothari, 2008).

This research study is a qualitative research with an inductive approach. Here the researcher will look into the specific situation of the nurses in the selected hospital and attempt to move to the generalization of the findings.

3.2.3. RESEARCH STRATEGY

The next important layer in the research onion is research strategy. There are various strategies that researchers adopt for a particular research study. In Saunders’ research onion various research strategies are explained. Some of the strategies are experiment, survey, action research, case study, grounded theory, ethnography and archival research (Saunders, Lewis, & Thomhil, 2007).

Experimental research is mainly used for the research in physical sciences. It is used to identify the cause effect relationships and verifying inferences. The main features of this technique are isolation of factors, replication of experiment, and quantitative measurement of results (Sharavanavel, 2006).

Survey research studies large and small populations by selecting and studying samples chosen from the populations to discover the relative incidence, distribution and interrelations of sociological and psychological variables. This research is mainly used to investigate social and psychological factors (Saunders, Lewis, & Thomhil, 2007).

Case study is a comprehensive study of a social unit. Here the subject of the study is a person, group, or a social institution. In this research the context is analysed in detail. Real life situations in real life context is analysed and studied (Sharavanavel, 2006).

Action research is a study associated with a particular project and problem (Coghlan & Brannick, 2009). The objective of this research can be finding immediate solution for a problem faced in a society. Therefore we can say that action research is concerned with actual life. It studies the ‘what’, ‘how’, and ‘why’ of actual life. In short it is an attempt to understand the present issues and a help to predict the future changes (Jonker & Pennink, 2009).

Grounded theory is a qualitative research study. It is mainly used in the social sciences. When the traditional scientific method looks to start the research with a hypothesis this method is adopts the system of going directly into the data collection first. All the data collected are placed in different codes to identify common factors. From the group of these codes then a theory is formed (Charmaz, 2006).

Ethnography is a unique qualitative research method. In this study the researcher will stay in the research location. The researcher stays with the population and get a first hand information from the particular culture or group (Murchison, 2009).

The final element in the Research strategy is Archival research strategy. It means the entire study will be based on the materials of the study kept in some archives by some other researchers. In this strategy a huge quantity of data is available and so often the data remain uncontrollable. Therefore it is not possible to make casual conclusions on the basis of such types of data (Graham, Towl &. Crihton, 2010).

In this research the researcher has adopted the strategy of a case study to obtain data from the samples selected. The study will be conducted among the nurses in a single hospital.

3.2.4. CHOICES

The next layer in the research onion is Choice. These choices can be divided into Mono method, Mixed method and Multi method. In this researcher adopts one method for his study from various methods of research. In Mixed method the researcher adopts generally two methods such as qualitative or quantitative research methods. In Multi method a number of research methods are brought together to investigate or to make a study (Saunders, Lewis, & Thomhil, 2007).

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In this study of the occupational stress of the nurses the researcher has adopted mixed method and multi method of choice. Yet only the qualitative research method is used here by the researcher to do the studies on the occupational stress among the nurses.

3.2.5. TIME HORIZONES

Time Horizons can be indicated as a time target fixed. A time limit is usually fixed for the completion of a task or activity. It refers to a planning or a preparation. Here the time limit for the completion of a research study is explained. There are two types of time horizons. The first one is Cross Sectional and the second is Longitudinal. In Cross sectional study the time is prefixed for the completion a study. In longitudinal no time is limit for the data collection, data analysis, and other completion of the research. Behavioral studies usually conducted in longitudinal methods as it needs a long time for observation (Saunders, Lewis, & Thomhil, 2009).

In this study of the occupational stress of the nurses the time horizon was cross sectional method that was adopted by the researcher. The time horizon for conducting the research was prefixed and planned. a limited period of time was allotted to the researcher to conduct the data collection for the samples selected.

The most important elements in a research study are data collection and data analysis. a systematically collected data and its proper analysis will answer a research question. It is a technique with a procedure (Bryman & Bell, 2007). The reliability and validity of a research is directly applied to the measurement of data (Wood & Ross-Kerr, 2010). There are two types of data collected for a systematic analysis for any research. They are Primary Data and Secondary Data (Kumar, 2008).

Primary Data refers to that information that are generated first time or that are generated to meet the specific requirements of the investigation at hand. Primary data is collected directly from the respondents or the subjects of experiment (Yin, 2010). Here there is a proper control over the information gathered (Bhattacharyya, 2006). The major disadvantage here is that it is more time consuming. Some times the primary data collection becomes more difficult as the suitable persons or samples are not at hand (Reason & Bradbury, 2006).

There are various sources of primary data. They are, Questionnaire, Interview Schedules and interviews, Focus groups, Case Studies, Experiments, Observations, Surveys and Discussions (Collrel & McKenzie, 2010).

The researcher, in this study, has collected the primary source of data by employing interview schedule, and structured questionnaire. The Questionnaire enlists questions, which translate the research objectives into specific questions. The question must also encourage the respondent so that the necessary data is obtained. In this study the researcher has employed both factual as well as opinion and attitude questions.

3.2.6.2. Secondary Data

Secondary data is not collected directly from the respondents. Here the data has been collected by some others (Bhattacharyya, 2006). It can be collection of the review of the primary data. The collection of secondary data is cheap in terms of time and economy. For a comparison of two types of statistics and reaching to an inference secondary data can be very effective. Yet the secondary data can be outdated and can be subjective as it has already evolved in the mind of somebody else. Secondary data can be uncontrollable and vast making it to be inappropriate for a particular purpose (Saunders, Lewis, & Thomhil, 2007).

There are various sources of secondary data. Books, Journals, News Papers, Reports and publications, Articles in magazines and websites, government statistics, company or organization statistics (Bryman & Bell, 2007).

In this study to collect the secondary data the researcher will be using various materials pertaining to the topic of the research. A number of books, health related articles, health journals, web pages, hospital statistics and news papers will be used for the collection of secondary data.