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which the stationary phase is present as or on a plane. The plane can be a paper, serving as such or impregnated by a substance as the stationary bed (paper chromatography) or a layer of solid particles spread on a |
support such as a glass plate (thin layer chromatography). Different compounds in the sample mixture travel different distances according to how strongly they interact with the stationary phase as compared to the mobile phase. The specific Retention factor (Rf) of |
each chemical can be used to aid in the identification of an unknown substance. Paper chromatography Paper chromatography is a technique that involves placing a small dot or line of sample solution onto a strip of chromatography paper. The paper |
is placed in a jar containing a shallow layer of solvent and sealed. As the solvent rises through the paper, it meets the sample mixture, which starts to travel up the paper with the solvent. This paper is made of |
cellulose, a polar substance, and the compounds within the mixture travel farther if they are non-polar. More polar substances bond with the cellulose paper more quickly, and therefore do not travel as far. Thin layer chromatography Thin layer chromatography (TLC) |
is a widely employed laboratory technique and is similar to paper chromatography. However, instead of using a stationary phase of paper, it involves a stationary phase of a thin layer of adsorbent like silica gel, alumina, or cellulose on a |
flat, inert substrate. Compared to paper, it has the advantage of faster runs, better separations, and the choice between different adsorbents. For even better resolution and to allow for quantification, high-performance TLC can be used. Displacement chromatography The basic principle |
of displacement chromatography is: A molecule with a high affinity for the chromatography matrix (the displacer) competes effectively for binding sites, and thus displace all molecules with lesser affinities. There are distinct differences between displacement and elution chromatography. In elution |
mode, substances typically emerge from a column in narrow, Gaussian peaks. Wide separation of peaks, preferably to baseline, is desired for maximum purification. The speed at which any component of a mixture travels down the column in elution mode depends |
on many factors. But for two substances to travel at different speeds, and thereby be resolved, there must be substantial differences in some interaction between the biomolecules and the chromatography matrix. Operating parameters are adjusted to maximize the effect of |
this difference. In many cases, baseline separation of the peaks can be achieved only with gradient elution and low column loadings. Thus, two drawbacks to elution mode chromatography, especially at the preparative scale, are operational complexity, due to gradient solvent |
pumping, and low throughput, due to low column loadings. Displacement chromatography has advantages over elution chromatography in that components are resolved into consecutive zones of pure substances rather than “peaks”. Because the process takes advantage of the nonlinearity of the |
isotherms, a larger column feed can be separated on a given column with the purified components recovered at significantly higher concentrations. Techniques by physical state of mobile phase Gas chromatography Gas chromatography (GC), also sometimes known as gas-liquid chromatography, (GLC), |
is a separation technique in which the mobile phase is a gas. Gas chromatography is always carried out in a column, which is typically "packed" or "capillary" (see below). Gas chromatography is based on a partition equilibrium of analyte between |
a solid stationary phase (often a liquid silicone-based material) and a mobile gas (most often helium). The stationary phase is adhered to the inside of a small-diameter glass tube (a capillary column) or a solid matrix inside a larger metal |
tube (a packed column). It is widely used in analytical chemistry; though the high temperatures used in GC make it unsuitable for high molecular weight biopolymers or proteins (heat denatures them), frequently encountered in biochemistry, it is well suited for |
use in the petrochemical, environmental monitoring and remediation, and industrial chemical fields. It is also used extensively in chemistry research. Liquid chromatography Liquid chromatography (LC) is a separation technique in which the mobile phase is a liquid. Liquid chromatography can |
be carried out either in a column or a plane. Present day liquid chromatography that generally utilizes very small packing particles and a relatively high pressure is referred to as high performance liquid chromatography (HPLC). In HPLC the sample is |
forced by a liquid at high pressure (the mobile phase) through a column that is packed with a stationary phase composed of irregularly or spherically shaped particles, a porous monolithic layer, or a porous membrane. HPLC is historically divided into |
two different sub-classes based on the polarity of the mobile and stationary phases. Methods in which the stationary phase is more polar than the mobile phase (e.g., toluene as the mobile phase, silica as the stationary phase) are termed normal |
phase liquid chromatography (NPLC) and the opposite (e.g., water-methanol mixture as the mobile phase and C18 = octadecylsilyl as the stationary phase) is termed reversed phase liquid chromatography (RPLC). Ironically the "normal phase" has fewer applications and RPLC is therefore |
used considerably more. Specific techniques under this broad heading are listed below. Affinity chromatography Affinity chromatography is based on selective non-covalent interaction between an analyte and specific molecules. It is very specific, but not very robust. It is often used |
in biochemistry in the purification of proteins bound to tags. These fusion proteins are labeled with compounds such as His-tags, biotin or antigens, which bind to the stationary phase specifically. After purification, some of these tags are usually removed and |
the pure protein is obtained. Affinity chromatography often utilizes a biomolecule's affinity for a metal (Zn, Cu, Fe, etc.). Columns are often manually prepared. Traditional affinity columns are used as a preparative step to flush out unwanted biomolecules. However, HPLC |
techniques exist that do utilize affinity chromatogaphy properties. Immobilized Metal Affinity Chromatography (IMAC) is useful to separate aforementioned molecules based on the relative affinity for the metal (I.e. Dionex IMAC). Often these columns can be loaded with different metals to |
create a column with a targeted affinity. Supercritical fluid chromatography Supercritical fluid chromatography is a separation technique in which the mobile phase is a fluid above and relatively close to its critical temperature and pressure. Techniques by separation mechanism Ion |
exchange chromatography Ion exchange chromatography (usually referred to as ion chromatography) uses an ion exchange mechanism to separate analytes based on their respective charges. It is usually performed in columns but can also be useful in planar mode. Ion exchange |
chromatography uses a charged stationary phase to separate charged compounds including anions, cations, amino acids, peptides, and proteins. In conventional methods the stationary phase is an ion exchange resin that carries charged functional groups that interact with oppositely charged groups |
of the compound to retain. Ion exchange chromatography is commonly used to purify proteins using FPLC. Size-exclusion chromatography Size-exclusion chromatography (SEC) is also known as gel permeation chromatography (GPC) or gel filtration chromatography and separates molecules according to their size |
(or more accurately according to their hydrodynamic diameter or hydrodynamic volume). Smaller molecules are able to enter the pores of the media and, therefore, molecules are trapped and removed from the flow of the mobile phase. The average residence time |
in the pores depends upon the effective size of the analyte molecules. However, molecules that are larger than the average pore size of the packing are excluded and thus suffer essentially no retention; such species are the first to be |
eluted. It is generally a low-resolution chromatography technique and thus it is often reserved for the final, "polishing" step of a purification. It is also useful for determining the tertiary structure and quaternary structure of purified proteins, especially since it |
can be carried out under native solution conditions. Expanded Bed Adsorption (EBA) Chromatographic Separation Expanded Bed Adsorption (EBA) Chromatographic Separation captures a target protein from a crude feed stream when it passes through a chromatography column system containing adsorbent beads. |
With this technique the crude feedstock can be treated directly in the chromatographic column, avoiding the traditional clarification and pre-treatment steps. EBA Chromatographic Separation is highly scalable, from laboratory-based 1 cm diameter columns to large production columns up to 2 |
meter in diameter. These columns can typically handle feed stock throughput of more than 1,000,000 liter per day with a production capacity of 1000 MT protein per year. Special techniques Reversed-phase chromatography Reversed-phase chromatography (RPC) is any liquid chromatography procedure |
in which the mobile phase is significantly more polar than the stationary phase. It is so named because in normal-phase liquid chromatography, the mobile phase is significantly less polar than the stationary phase. Hydrophobic molecules in the mobile phase tend |
to adsorb to the relatively hydrophobic stationary phase. Hydrophilic molecules in the mobile phase will tend to elute first. Two-dimensional chromatography In some cases, the chemistry within a given column can be insufficient to separate some analytes. It is possible |
to direct a series of unresolved peaks onto a second column with different physico-chemical (Chemical classification) properties. Since the mechanism of retention on this new solid support is different from the first dimensional separation, it can be possible to separate |
compounds that are indistinguishable by one-dimensional chromatography. The sample is spotted at one corner of a square plate,developed, air-dried, then rotated by 90° and usually redeveloped in a second solvent system. Simulated moving-bed chromatography Pyrolysis gas chromatography Pyrolysis gas chromatography |
mass spectrometry is a method of chemical analysis in which the sample is heated to decomposition to produce smaller molecules that are separated by gas chromatography and detected using mass spectrometry. Pyrolysis is the thermal decomposition of materials in an |
inert atmosphere or a vacuum. The sample is put into direct contact with a platinum wire, or placed in a quartz sample tube, and rapidly heated to 600–1000 °C. Depending on the application even higher temperatures are used. Three different |
heating techniques are used in actual pyrolyzers: Isothermal furnace, inductive heating (Curie Point filament), and resistive heating using platinum filaments. Large molecules cleave at their weakest points and produce smaller, more volatile fragments. These fragments can be separated by gas |
chromatography. Pyrolysis GC chromatograms are typically complex because a wide range of different decomposition products is formed. The data can either be used as fingerprint to prove material identity or the GC/MS data is used to identify individual fragments to |
obtain structural information. To increase the volatility of polar fragments, various methylating reagents can be added to a sample before pyrolysis. Besides the usage of dedicated pyrolyzers, pyrolysis GC of solid and liquid samples can be performed directly inside Programmable |
Temperature Vaporizer (PTV) injectors that provide quick heating (up to 30 °C/s) and high maximum temperatures of 600–650 °C. This is sufficient for some pyrolysis applications. The main advantage is that no dedicated instrument has to be purchased and pyrolysis |
can be performed as part of routine GC analysis. In this case quartz GC inlet liners have to be used. Quantitative data can be acquired, and good results of derivatization inside the PTV injector are published as well. Fast protein |
liquid chromatography Fast protein liquid chromatography (FPLC) is a term applied to several chromatography techniques which are used to purify proteins. Many of these techniques are identical to those carried out under high performance liquid chromatography, however use of FPLC |
techniques are typically for preparing large scale batches of a purified product. Countercurrent chromatography Countercurrent chromatography (CCC) is a type of liquid-liquid chromatography, where both the stationary and mobile phases are liquids. The operating principle of CCC equipment requires a |
column consisting of an open tube coiled around a bobbin. The bobbin is rotated in a double-axis gyratory motion (a cardioid), which causes a variable gravity (G) field to act on the column during each rotation. This motion causes the |
column to see one partitioning step per revolution and components of the sample separate in the column due to their partitioning coefficient between the two immiscible liquid phases used. There are many types of CCC available today. These include HSCCC |
(High Speed CCC) and HPCCC (High Performance CCC). HPCCC is the latest and best performing version of the instrumentation available currently. Chiral chromatography Chiral chromatography involves the separation of stereoisomers. In the case of enantiomers, these have no chemical or |
physical differences apart from being three-dimensional mirror images. Conventional chromatography or other separation processes are incapable of separating them. To enable chiral separations to take place, either the mobile phase or the stationary phase must themselves be made chiral, giving |
differing affinities between the analytes. Chiral chromatography HPLC columns (with a chiral stationary phase) in both normal and reversed phase are commercially available. See also - IUPAC Nomenclature for Chromatography IUPAC Recommendations 1993, Pure & Appl. Chem., Vol. 65, No. |
4, pp.819–872, 1993. - Still, W. C.; Kahn, M.; Mitra, A. J. Org. Chem. 1978, 43(14), 2923–2925. doi:10.1021/jo00408a041 - Laurence M. Harwood, Christopher J. Moody (13 June 1989). Experimental organic chemistry: Principles and Practice (Illustrated ed.). WileyBlackwell. pp. 180–185. ISBN |
978-0-632-02017-1 [Amazon-US | Amazon-UK]. - Christian B. Anfinsen, John Tileston Edsall, Frederic Middlebrook Richards Advances in Protein Chemistry. Science 1976, 6-7. - Displacement Chromatography 101. Sachem, Inc. Austin, TX 78737 - Pascal Bailon, George K. Ehrlich, Wen-Jian Fung and Wolfgang |
Science: Chrom-Ed Series - Overlapping Peaks Program – Learning by Simulations - Chromatography Videos – MIT OCW – Digital Lab Techniques Manual - Chromatography Equations Calculators – MicroSolv Technology Corporation |
Other Proposed Treatments It is one of the cardinal principles of natural medicine that treatment should aim not only to treat illness but also to enhance wellness. According to this ideal, a proper course of treatment should improve your sense of general well-being, enhance your immunity to illness, raise your physical stamina, and increase mental alertness, as well as resolve |
the specific condition you took it for. Unfortunately, while there can be little doubt that this is a laudable goal, it is easier to laud it than to achieve it. Conventional medicine tends to focus on treating diseases rather than increasing wellness, not as a matter of philosophical principle, but because it is easier to accomplish. Probably the strongest force |
affecting wellness is genetics. Beyond that, common sense steps endorsed by all physicians include increasing exercise, reducing stress, improving diet, getting enough sleep, and living a life of moderation without bad habits, such as smoking or overeating. Beyond this, however, it is difficult to make strong affirmations, and the optimum forms of diet and exercise and other aspects of lifestyle |
remain unclear. In fact, they may always remain unclear, as it is impossible to perform double-blind, placebo-controlled studies on most lifestyle habits. (For information on why such studies are irreplaceable see "Why Does This Database Depend on Double-blind Studies?" ) Principal Proposed Natural Treatments In order to function at our best, we need good nutrition. However, the modern diet often |
fails to provide people with sufficient amounts of all the necessary nutrients. For this reason, use of a multivitamin/multimineral supplement might be expected to enhance overall health and well-being, and preliminary double-blind trials generally support this view. For more information, see the article on General Nutritional Support . The herb Panax ginseng has an ancient reputation as a healthful “tonic.” |
According to a more modern concept developed in the former USSR, ginseng functions as an “adaptogen.” This term is defined as follows: An adaptogen helps the body adapt to stresses of various kinds, whether heat, cold, exertion, trauma, sleep deprivation, toxic exposure, radiation, infection, or psychologic stress. In addition, an adaptogen causes no side effects, is effective in treating a |
wide variety of illnesses, and helps return an organism toward balance no matter what may have gone wrong. From a modern scientific perspective, it is not truly clear that such things as adaptogens actually exist. However, there is some evidence that ginseng may satisfy some of the definition’s requirements. In addition, ginseng has also shown some potential for enhancing immunity |
, mental function , and sports performance , all effects consistent with the adaptogen concept. For more information on these possibilities, as well as dosage and safety issues, see the full Ginseng article . Other Proposed Natural Treatments Numerous other alternative therapies are claimed by their proponents to improve overall wellness, including acupuncture , Ayurveda , chiropractic , detoxification , |
homeopathy , massage , naturopathy , osteopathic manipulation , Reiki , Tai Chi , Therapeutic Touch , traditional Chinese herbal medicine , and yoga . However, there is as yet little meaningful evidence to support these claims. For a discussion of homeopathic approaches to general wellness, see the Homeopathy database . - Reviewer: EBSCO CAM Review Board - Review Date: |
Assistant Secretary of State for Inter-American Affairs Edwin Martin seeks a resolution of support from the Organization of American States. Ambassador to the United Nations Adlai Stevenson lays the matter |
before the U.N. Security Council. The ships of the naval quarantine fleet move into place around Cuba. Soviet submarines threaten the quarantine by moving into the Caribbean area. Soviet freighters |
bound for Cuba with military supplies stop dead in the water, but the oil tanker Bucharest continues towards Cuba. In the evening Robert Kennedy meets with Ambassador Dobrynin at the |
Soviet Embassy. After the Organization of American States endorsed the quarantine, President Kennedy asks Khrushchev to halt any Russian ships heading toward Cuba. The president's greatest concern is that a |
BINGE EATING DISORDER "Signs and Symptoms" To date, there has been some degree of confusion as to what exactly the term "binge eating" really means. Although the professional community still has yet to define [or quantify] what constitutes a binge-eating |
episode, it's reasonable to assume the signs and symptoms listed below are a good barometer of what is characteristic binge eating. In many respects, Binge Eating Disorder [BED] is similar to Bulimia without the compensatory behaviors. In addition, the term |
compulsive overeating may be "interchangeable" with BED - although some compulsive overeaters have a pattern of eating constantly ["grazing"] rather than experiencing episodes of binge eating per se. Signs and symptoms Binge Eating / Compulsive Overeating [COE] - Preoccupation with |
food. - Rapid consumption of food in significant excess of nutritional need - Sneaking or hoarding food - even immediately after meals. - Feeling ashamed or fearful when confronted about the problem. - Excessive concern about weight and body shape. |
- Sense of "losing control" during binge episode. - Feeling lonely, depressed, worried, self preoccupied - Spending a great deal of time alone / social isolation - Alternating between binge eating and "dieting" Treating BED at Milestones As with many |
other eating disorders, the characteristics of a binge eating disorder appear to mimic [inherent among] other dependencies or addictions - whether to a substance or set of behaviors. In fact, the most recent committee of the American Psychiatric Association "officially" |
included BED as a bona fide disorder [disease]. The link below lists the criteria for "dependency" and requires only three of the several criteria "fit" for a diagnosis of dependency [aka addiction] to be considered. The program offered at Milestones |
is comprised of two primary components, making the treatment experience unique in comparison to other programs. The first is the setting - utilizing apartment-style residences affording residential participants an opportunity to experience treatment in a "real world" environment. Participants grocery |
shop with our dietitian within the community, learn to prepare their own meals per the prescribed [meal] food / meal plan they have formulated with the dietitian, attend a full schedule of groups and individual therapies at our clinical campus |
[near the residential complex], attend local community support groups in the evenings, and visit with our physicians and clinical staff regularly throughout their stay. In effect, the experience is one of providing a supportive and structured setting without the restrictive |
elements of a "hospital" or institutional facility. A key element in providing the support necessary to begin recovery is remaining in the company of other participants during the initial phase of the treatment. This provides both a form of supervision |
and a deterrent from the behavior often associated with binge eating: namely eating in isolation or alone. Secondly, Milestones approaches treatment from a more "holistic" perspective. Doing so is best described by the acronym "SERF" - Spirituality, Exercise, Rest, and |
Food Plan. Spirituality need not equate with any religious or spiritual beliefs imposed on or by anyone. In fact, Spirituality at Milestones simply is left up to the individual to cultivate with his or her own working definition. For most, |
it is a belief in a "higher power" and still for others it may be a return to some of their original religious beliefs. For everyone, it is an individual journey. Exercise is individualized and represents collaboration between the resident |
and clinical team. It is meant to be in the service of restoring and maintaining a healthy body rather than an "intensive" means of controlling body weight. Rest is simply about finding the correct balance in recovery between work and |
play and narrowing the gap between an "all or none", "feast or famine" approach to daily living. The food plan suggested by Milestones is a blend of structured eating and a combination of healthy, whole foods that are bought and |
prepared by PARTICIPANTS with the guidance and supervision of our dietitian and ancillary staff. In brief participants select their own preferences within the guidelines of their individual food plans. The guidelines require participants to abstain from "junk foods" and eliminate |
most highly processed [sugar and flour laden] food products as well as weigh and measure portions per their food plan while in residence. It is important to mention most participants who seek treatment for most eating disorders may have a |
tendency to focus on "trading in the binging and/or "purging" to become better at restricting or "losing weight" and as such, it is important to understand the predisposition to replace one form of an eating disorder for another. Acknowledging this |
is helpful to maintaining the prescribed treatment plan both during and after the residential treatment experience. Body mass and subsequent weight loss will likely change as a result of abstaining from overeating and move in the direction [towards] of a |
healthy "set point" as an outcome of the recovery process. Each participant is assigned an individual therapist whom they meet with on a regular basis during their stay as well as attend groups and experiential therapies per the schedule In |
A Reference Resource Life Before the Presidency Herbert Clark Hoover was born on August 10, 1874. For the first nine years of his life, he lived in the small town of West Branch, Iowa, the place of his birth. His |
Quaker father, Jessie Clark Hoover, a blacksmith and farm equipment salesman, suffered a heart attack and died when Herbert was six years old. Three years later, the boy's mother, Huldah Minthorn Hoover, developed pneumonia and also passed away, orphaning Herbert, |
his older brother Theodore, and little sister Mary. Passed around among relatives for a few years, Hoover ended up with his uncle, Dr. John Minthorn, who lived in Oregon. The young Hoover was shy, sensitive, introverted, and somewhat suspicious, characteristics |
that developed, at least in part, in reaction to the loss of his parents at such a young age. He attended Friends Pacific Academy in Newberg, Oregon, earning average to failing grades in all subjects except math. Determined, nevertheless, to |
go to the newly established Stanford University in Palo Alto, California, Hoover studied hard and barely passed the university's entrance exam. He went on to major in geology and participated in a host of extracurricular activities, serving as class treasurer |
of the junior and senior student bodies and managing the school baseball and football teams. To pay his tuition, Hoover worked as a clerk in the registration office and showed considerable entrepreneurial skill by starting a student laundry service. Career |
and Monetary Success During the summers, Hoover worked as a student assistant on geological survey teams in Arkansas, California, and Nevada. After his graduation in 1895, he looked hard to find work as a surveyor but ended up laboring seventy |
hours a week at a gold mine near Nevada City, California, pushing ore carts. Luck came his way with an office job in San Francisco, putting him in touch with a firm in need of an engineer to inspect and |
evaluate mines for potential purchase. Hoover then moved to Australia in 1897 and China in 1899, where he worked as a mining engineer until 1902. A string of similar jobs took him all over the world and helped Hoover become |
a giant in his field. He opened his own mining consulting business in 1908; by 1914, Hoover was financially secure, earning his wealth from high-salaried positions, his ownership of profitable Burmese silver mines, and royalties from writing the leading textbook |
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