1.
Scientific method
–
The scientific method is a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry is commonly based on empirical or measurable evidence subject to specific principles of reasoning, experiments need to be designed to test hypotheses. The most important part of the method is the experiment. The scientific method is a process, which usually begins with observations about the natural world. Human beings are naturally inquisitive, so often come up with questions about things they see or hear. The best hypotheses lead to predictions that can be tested in various ways, in general, the strongest tests of hypotheses come from carefully controlled and replicated experiments that gather empirical data. Depending on how well the tests match the predictions, the hypothesis may require refinement. If a particular hypothesis becomes very well supported a theory may be developed. Although procedures vary from one field of inquiry to another, identifiable features are shared in common between them. The overall process of the method involves making conjectures, deriving predictions from them as logical consequences. A hypothesis is a conjecture, based on knowledge obtained while formulating the question, the hypothesis might be very specific or it might be broad. Scientists then test hypotheses by conducting experiments, the purpose of an experiment is to determine whether observations agree with or conflict with the predictions derived from a hypothesis. Experiments can take anywhere from a college lab to CERNs Large Hadron Collider. There are difficulties in a statement of method, however. Though the scientific method is presented as a fixed sequence of steps. Not all steps take place in scientific inquiry, and are not always in the same order. Some philosophers and scientists have argued there is no scientific method, such as Lee Smolin. Nola and Sankey remark that For some, the idea of a theory of scientific method is yester-years debate
2.
Rat
–
Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. True rats are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, many members of other rodent genera and families are also referred to as rats, and share many characteristics with true rats. Rats are typically distinguished from mice by their size, generally, when someone discovers a large muroid rodent, its common name includes the term rat, while if it is smaller, the name includes the term mouse. The muroid family is broad and complex, and the common terms rat, scientifically, the terms are not confined to members of the Rattus and Mus genera, for example, the pack rat and cotton mouse. The best-known rat species are the black rat and the brown rat, the group is generally known as the Old World rats or true rats, and originated in Asia. Rats are bigger than most Old World mice, which are their relatives, the term rat is also used in the names of other small mammals which are not true rats. Examples include the North American pack rats, a number of species loosely called kangaroo rats, Rats such as the bandicoot rat are murine rodents related to true rats, but are not members of the genus Rattus. Male rats are called bucks, unmated females are called does, pregnant or parent females are called dams, a group of rats is referred to as a mischief. The common species are opportunistic survivors and often live with and near humans, therefore and they may cause substantial food losses, especially in developing countries. However, the distributed and problematic commensal species of rats are a minority in this diverse genus. Many species of rats are island endemics and some have become endangered due to loss or competition with the brown. Wild rodents, including rats, can carry many different zoonotic pathogens, such as Leptospira, Toxoplasma gondii, another zoonotic disease linked to the rat is the foot-and-mouth disease. The average lifespan of any given rat depends on species is being discussed. The black and brown rats diverged from other Old World rats during the beginning of the Pleistocene in the forests of Asia, specially bred rats have been kept as pets at least since the late 19th century. Pet rats are typically variants of the brown rat, but black rats. Pet rats behave differently from their wild counterparts depending on how many generations they have kept as pets. Pet rats do not pose any more of a risk than pets such as cats or dogs. Tamed rats are generally friendly and can be taught to perform selected behaviors, in 1895, Clark University in Worcester, Massachusetts established a population of domestic albino brown rats to study the effects of diet and for other physiological studies
3.
Placebo
–
A placebo is a substance or treatment with no active therapeutic effect. A placebo may be given to a person in order to deceive the recipient into thinking that it is an active treatment. This phenomenon, in which the recipient perceives an improvement in condition due to personal expectations, research about the effect is ongoing. Placebos are an important methodological tool in medical research, common placebos include inert tablets, vehicle infusions, sham surgery, and other procedures based on false information. Placebo effects are the subject of research aiming to understand underlying neurobiological mechanisms of action in pain relief, immunosuppression, Parkinsons disease. Brain imaging techniques done by Emeran Mayer, Johanna Jarco and Matt Lieberman showed that placebo can have real, in other cases, like asthma, the effect is purely subjective, when the patient reports improvement despite no objective change in the underlying condition. The placebo effect is a phenomenon, in fact, it is part of the response to any active medical intervention. The placebo effect points to the importance of perception and the role in physical health. The use of placebos as treatment in clinical medicine is ethically problematic as it introduces deception, the United Kingdom Parliamentary Committee on Science and Technology has stated that. prescribing placebos. Usually relies on some degree of patient deception and prescribing pure placebos is bad medicine and their effect is unreliable and unpredictable and cannot form the sole basis of any treatment on the NHS. In 1955, Henry K. Beecher proposed that placebos could have important effects. The article received a flurry of criticism, but the later published a Cochrane review with similar conclusions. A placebo has been defined as a substance or procedure and that is objectively without specific activity for the condition being treated. Under this definition, a variety of things can be placebos. Likewise, the effects of stimulation from implanted electrodes in the brains of those with advanced Parkinsons disease are greater when they are aware they are receiving this stimulation, sometimes administering or prescribing a placebo merges into fake medicine. Common placebos include pills or saline injections, fake surgeries have also seen some use. An example is the Finish Meniscal Legion Study Group’s trial published in The New England Journal of Medicine, while examples of placebo treatments can be found, defining the placebo concept remains elusive. A placebo electronic cigarette contains 0 mg of nicotine, instead they introduced the term meaning response for the meaning that the brain associates with the placebo, which causes a physiological placebo effect
4.
Enzyme assay
–
Enzyme assays are laboratory methods for measuring enzymatic activity. They are vital for the study of enzyme kinetics and enzyme inhibition, the quantity or concentration of an enzyme can be expressed in molar amounts, as with any other chemical, or in terms of activity in enzyme units. Enzyme activity = moles of substrate converted per unit time = rate × reaction volume, Enzyme activity is a measure of the quantity of active enzyme present and is thus dependent on conditions, which should be specified. The SI unit is the katal,1 katal =1 mol s−1, a more practical and commonly used value is enzyme unit =1 μmol min−1. 1 U corresponds to 16.67 nanokatals, Enzyme activity as given in katal generally refers to that of the assumed natural target substrate of the enzyme. Enzyme activity can also be given as that of certain standardized substrates, such as gelatin, then measured in gelatin digesting units, or milk proteins, the units GDU and MCU are based on how fast one gram of the enzyme will digest gelatin or milk proteins, respectively. 1 GDU equals approximately 1.5 MCU, the specific activity of an enzyme is another common unit. This is the activity of an enzyme per milligram of total protein, specific activity gives a measurement of enzyme purity in the mixture. It is the moles of product formed by an enzyme in an amount of time under given conditions per milligram of total proteins. Specific activity is equal to the rate of reaction multiplied by the volume of reaction divided by the mass of total protein, the SI unit is katal kg−1, but a more practical unit is μmol mg−1 min−1. Specific activity is a measure of enzyme processivity, at a specific substrate concentration, for elimination of errors arising from differences in cultivation batches and/or misfolded enzyme etc. an active site titration needs to be done. This is a measure of the amount of enzyme, calculated by e. g. titrating the amount of active sites present by employing an irreversible inhibitor. The specific activity should then be expressed as μmol min−1 mg−1 active enzyme, if the molecular weight of the enzyme is known, the turnover number, or μmol product per second per μmol of active enzyme, can be calculated from the specific activity. The turnover number can be visualized as the number of each enzyme molecule carries out its catalytic cycle per second. The rate of a reaction is the concentration of substrate disappearing per unit time, the impure sample has lower specific activity because some of the mass is not actually enzyme. If the specific activity of 100% pure enzyme is known, then a sample will have a lower specific activity. All enzyme assays measure either the consumption of substrate or production of product over time, a large number of different methods of measuring the concentrations of substrates and products exist and many enzymes can be assayed in several different ways. Biochemists usually study enzyme-catalysed reactions using four types of experiments, Initial rate experiments, when an enzyme is mixed with a large excess of the substrate, the enzyme-substrate intermediate builds up in a fast initial transient
5.
Confirmation bias
–
Confirmation bias, also called confirmatory bias or myside bias, is the tendency to search for, interpret, favor, and recall information in a way that confirms ones preexisting beliefs or hypotheses. It is a type of bias and a systematic error of inductive reasoning. People display this bias when they gather or remember information selectively, the effect is stronger for emotionally charged issues and for deeply entrenched beliefs. People also tend to interpret ambiguous evidence as supporting their existing position, biased search, interpretation and memory have been invoked to explain attitude polarization, belief perseverance, the irrational primacy effect and illusory correlation. A series of experiments in the 1960s suggested that people are biased toward confirming their existing beliefs, later work re-interpreted these results as a tendency to test ideas in a one-sided way, focusing on one possibility and ignoring alternatives. In certain situations, this tendency can bias peoples conclusions, explanations for the observed biases include wishful thinking and the limited human capacity to process information. Another explanation is that people show confirmation bias because they are weighing up the costs of being wrong, rather than investigating in a neutral, confirmation biases contribute to overconfidence in personal beliefs and can maintain or strengthen beliefs in the face of contrary evidence. Poor decisions due to these biases have been found in political and organizational contexts, confirmation biases are effects in information processing. Others apply the more broadly to the tendency to preserve ones existing beliefs when searching for evidence, interpreting it. Experiments have found repeatedly that people tend to test hypotheses in a one-sided way, rather than searching through all the relevant evidence, they phrase questions to receive an affirmative answer that supports their theory. They look for the consequences that they would expect if their hypothesis were true, for example, someone using yes/no questions to find a number he or she suspects to be the number 3 might ask, Is it an odd number. People prefer this type of question, called a positive test, would yield exactly the same information. However, this does not mean that people seek tests that guarantee a positive answer, in studies where subjects could select either such pseudo-tests or genuinely diagnostic ones, they favored the genuinely diagnostic. The preference for positive tests in itself is not a bias, however, in combination with other effects, this strategy can confirm existing beliefs or assumptions, independently of whether they are true. In real-world situations, evidence is often complex and mixed, for example, various contradictory ideas about someone could each be supported by concentrating on one aspect of his or her behavior. Thus any search for evidence in favor of a hypothesis is likely to succeed, one illustration of this is the way the phrasing of a question can significantly change the answer. For example, people who are asked, Are you happy with your social life, report greater satisfaction than those asked, Are you unhappy with your social life. Even a small change in a questions wording can affect how people search through available information and this was shown using a fictional child custody case
6.
Clinical trial
–
Clinical trials are experiments or observations done in clinical research. Clinical trials generate data on safety and efficacy and they are conducted only after they have received health authority/ethics committee approval in the country where approval of the therapy is sought. These authorities are responsible for vetting the risk/benefit ratio of the trial – their approval does not mean that the therapy is safe or effective, only that the trial may be conducted. Clinical trials can vary in size and cost, and they can involve a research center or multiple centers. Clinical study design aims to ensure the validity and reproducibility of the results. Trials can be costly, depending on a number of factors. The sponsor may be an organization or a pharmaceutical, biotechnology or medical device company. Certain functions necessary to the trial, such as monitoring and lab work, may be managed by an outsourced partner, only 10 percent of all drugs started in human clinical trials become an approved drug. Some clinical trials involve healthy subjects with no pre-existing medical conditions, other clinical trials pertain to patients with specific health conditions who are willing to try an experimental treatment. When participants are healthy volunteers who receive financial incentives, the goals are different than when the participants are sick, during dosing periods, study subjects typically remain under supervision for one to 40 nights. Usually pilot experiments are conducted to gain insights for design of the trial to follow. There are two goals to testing medical treatments, to whether they work well enough, called efficacy or effectiveness. The benefits must outweigh the risks, in the US, the elderly constitute only 14 percent of the population, while they consume over one-third of drugs. Women, children and people with unrelated medical conditions are frequently excluded. For women, a reason for exclusion is the possibility of pregnancy. If the sponsor cannot obtain enough test subjects at one location investigators at other locations are recruited to join the study, during the trial, investigators recruit subjects with the predetermined characteristics, administer the treatment and collect data on the subjects health for a defined time period. The researchers send the data to the sponsor, who then analyzes the pooled data using statistical tests. Except for small, single-location trials, the design and objectives are specified in a document called a clinical trial protocol
7.
Sugar substitute
–
A sugar substitute is a food additive that provides a sweet taste like that of sugar while containing significantly less food energy. Some sugar substitutes are produced by nature, and others produced synthetically and those that are not produced by nature are, in general, called artificial sweeteners. An important class of sugar substitutes is known as high-intensity sweeteners and these are compounds with many times the sweetness of sucrose, common table sugar. As a result, much less sweetener is required and energy contribution is often negligible, the sensation of sweetness caused by these compounds is sometimes notably different from sucrose, so they are often used in complex mixtures that achieve the most natural sweet sensation. If the sucrose that is replaced has contributed to the texture of the product, in the United States, seven intensely sweet sugar substitutes have been approved for use. They are stevia, aspartame, sucralose, neotame, acesulfame potassium, saccharin, cyclamates are used outside the U. S. but have been prohibited in the U. S. since 1969. Others, which may or may not be approved depending on jurisdiction, include allulose, the U. S. Food and Drug Administration regulates artificial sweeteners as food additives. Food additives must be approved by the FDA, which publishes a generally recognized as safe list of additives, stevia is exempt under the FDAs GRAS policy due to its being a natural substance in wide use well before 1958, and the FDA has approved it on these grounds. The conclusions about safety are based on a review of a large body of information. The majority of sugar substitutes approved for use are artificially synthesized compounds. However, some bulk natural sugar substitutes are known, including sorbitol and xylitol, which are found in berries, fruit, vegetables and it is not commercially viable to extract these products from fruits and vegetables, so they are produced by catalytic hydrogenation of the appropriate reducing sugar. For example, xylose is converted to xylitol, lactose to lactitol, other natural substitutes are known, but these have yet to gain official approval for food use. Sorbitol and xylitol are examples of sugar alcohols and these are, in general, less sweet than sucrose but have similar bulk properties and can be used in a wide range of food products. Sometimes the sweetness profile is fine-tuned by mixing these with high-intensity sweeteners, as with all food products, the development of a formulation to replace sucrose is a complex proprietary process. This allows them to eat the foods they normally would while allowing them to lose weight. Dental care – Carbohydrates and sugars usually adhere to the tooth enamel, the bacteria convert the sugar to acids that decay the teeth. Sugar substitutes, unlike sugar, do not erode teeth as they are not fermented by the microflora of the dental plaque. A sweetener that can actually benefit dental health is xylitol, which tends to prevent bacteria from adhering to the surface, thus preventing plaque formation
8.
Polyacrylamide gel electrophoresis
–
Mobility is a function of the length, conformation and charge of the molecule. For nucleic acids, urea is the most commonly used denaturant, for proteins, sodium dodecyl sulfate is an anionic detergent applied to protein samples to linearize proteins and to impart a negative charge to linearized proteins. In most proteins, the binding of SDS to the polypeptide chain imparts an even distribution of charge per unit mass, samples may be any material containing proteins or nucleic acids. These may be derived, for example from prokaryotic or eukaryotic cells, tissues, viruses, environmental samples. Synthetic biomolecules such as oligonucleotides may also be used as analytes, the sample to analyze is optionally mixed with a chemical denaturant if so desired, usually SDS for proteins or urea for nucleic acids. SDS is a detergent that denatures secondary and non–disulfide–linked tertiary structures. Urea breaks the bonds between the base pairs of the nucleic acid, causing the constituent strands to separate. Heating the samples to at least 60 °C further promotes denaturation and this is known as reducing SDS-PAGE. A tracking dye may be added to the solution and this typically has a higher electrophoretic mobility than the analytes to allow the experimenter to track the progress of the solution through the gel during the electrophoretic run. The gels typically consist of acrylamide, bisacrylamide, the optional denaturant, the solution may be degassed under a vacuum to prevent the formation of air bubbles during polymerization. Alternatively, butanol may be added to the gel after it is poured. A source of radicals and a stabilizer, such as ammonium persulfate. The polymerization reaction creates a gel because of the added bisacrylamide, the ratio of bisacrylamide to acrylamide can be varied for special purposes, but is generally about 1 part in 35. The acrylamide concentration of the gel can also be varied, generally in the range from 5% to 25%, lower percentage gels are better for resolving very high molecular weight molecules, while much higher percentages are needed to resolve smaller proteins. Gels are usually polymerized between two plates in a gel caster, with a comb inserted at the top to create the sample wells. After the gel is polymerized the comb can be removed and the gel is ready for electrophoresis, various buffer systems are used in PAGE depending on the nature of the sample and the experimental objective. The buffers used at the anode and cathode may be the same or different, an electric field is applied across the gel, causing the negatively charged proteins or nucleic acids to migrate across the gel away from the negative electrode and towards the positive electrode. Depending on their size, each biomolecule moves differently through the gel matrix, small molecules more easily fit through the pores in the gel, after the set amount of time, the biomolecules have migrated different distances based on their size
9.
Experiment
–
An experiment is a procedure carried out to support, refute, or validate a hypothesis. Experiments provide insight into cause-and-effect by demonstrating what outcome occurs when a particular factor is manipulated, experiments vary greatly in goal and scale, but always rely on repeatable procedure and logical analysis of the results. There also exists natural experimental studies, a child may carry out basic experiments to understand gravity, while teams of scientists may take years of systematic investigation to advance their understanding of a phenomenon. Experiments and other types of activities are very important to student learning in the science classroom. Experiments can raise test scores and help a student become more engaged and interested in the material they are learning, experiments can vary from personal and informal natural comparisons, to highly controlled. Uses of experiments vary considerably between the natural and human sciences, experiments typically include controls, which are designed to minimize the effects of variables other than the single independent variable. This increases the reliability of the results, often through a comparison between control measurements and the other measurements, scientific controls are a part of the scientific method. Ideally, all variables in an experiment are controlled and none are uncontrolled, in such an experiment, if all controls work as expected, it is possible to conclude that the experiment works as intended, and that results are due to the effect of the tested variable. In the scientific method, an experiment is a procedure that arbitrates between competing models or hypotheses. Researchers also use experimentation to test existing theories or new hypotheses to support or disprove them, an experiment usually tests a hypothesis, which is an expectation about how a particular process or phenomenon works. However, an experiment may also aim to answer a question, without a specific expectation about what the experiment reveals. If an experiment is conducted, the results usually either support or disprove the hypothesis. According to some philosophies of science, an experiment can never prove a hypothesis, on the other hand, an experiment that provides a counterexample can disprove a theory or hypothesis. An experiment must also control the possible confounding factors—any factors that would mar the accuracy or repeatability of the experiment or the ability to interpret the results, confounding is commonly eliminated through scientific controls and/or, in randomized experiments, through random assignment. In engineering and the sciences, experiments are a primary component of the scientific method. They are used to test theories and hypotheses about how physical processes work under particular conditions, typically, experiments in these fields focus on replication of identical procedures in hopes of producing identical results in each replication. In medicine and the sciences, the prevalence of experimental research varies widely across disciplines. In contrast to norms in the sciences, the focus is typically on the average treatment effect or another test statistic produced by the experiment
10.
Design of experiments
–
The design of experiments is the design of any task that aims to describe or explain the variation of information under conditions that are hypothesized to reflect the variation. In its simplest form, an experiment aims at predicting the outcome by introducing a change of the preconditions, the change in the predictor is generally hypothesized to result in a change in the second variable, hence called the outcome variable. Main concerns in design include the establishment of validity, reliability. Related concerns include achieving appropriate levels of power and sensitivity. Correctly designed experiments advance knowledge in the natural and social sciences, other applications include marketing and policy making. In 1747, while serving as surgeon on HMS Salisbury, James Lind carried out a clinical trial to compare remedies for scurvy. This systematic clinical trial constitutes a type of DOE, Lind selected 12 men from the ship, all suffering from scurvy. Lind limited his subjects to men who were as similar as I could have them and he divided them into six pairs, giving each pair different supplements to their basic diet for two weeks. The treatments were all remedies that had proposed, A quart of cider every day. Twenty five gutts of vitriol three times a day upon an empty stomach, one half-pint of seawater every day. A mixture of garlic, mustard, and horseradish in a lump the size of a nutmeg, two spoonfuls of vinegar three times a day. Two oranges and one every day. The citrus treatment stopped after six days when they ran out of fruit, apart from that, only group one showed some effect of its treatment. The remainder of the crew served as a control. Charles S. Peirce randomly assigned volunteers to a blinded, repeated-measures design to evaluate their ability to discriminate weights, peirces experiment inspired other researchers in psychology and education, which developed a research tradition of randomized experiments in laboratories and specialized textbooks in the 1800s. Charles S. Peirce also contributed the first English-language publication on a design for regression models in 1876. A pioneering optimal design for regression was suggested by Gergonne in 1815. In 1918 Kirstine Smith published optimal designs for polynomials of degree six, herman Chernoff wrote an overview of optimal sequential designs, while adaptive designs have been surveyed by S. Zacks
"Control". Encyclopædia Britannica. 7 (11th ed.). 1911.
"