notes for selected topics

Improvement of leaching process of Geniposide with ultrasound

The effect of ultrasound on the leaching process, in which Geniposide is leached from the Gardenia fruit by deionized water at 20 degrees C, was investigated. The phase equilibrium and the dynamics were measured at static, stirring, and ultrasonically assisted conditions, respectively. The experimental results show that the extraction yield of Geniposide with ultrasound at 0.1533 W cm(-2), is increased by 16.5%, in comparison with that without ultrasound when the ratio of the solvent volume to the fruit weight is 40 ml/g. A model for mass transfer, based on the intraparticle diffusion and the external mass transfer, was developed. And the dynamic curves calculated by the model are in a good agreement with the experimental data. The external mass transfer coefficient k(f)/R and intraparticle diffusion coefficient D(e)/R2 were obtained by fitting of the experiment data. The external mass transfer coefficient with ultrasound at 0.1533 W cm(-2) is 1.63 times higher than that in static process, and the intraparticle diffusion coefficient with ultrasound at 0.1533 W cm(-2) is 3.25 times higher than that in static process.

X-ray

X-ray technology provides physicians and technicians with a noninvasive method for seeing inside objects. In the case of a patient's body, this may allow diagnosis of disease or injury without surgery. Both conventional and digital x-ray methods employ high voltage electronic tubes such as synchrotons that emit very short wavelength, high energy electromagnetic radiation in the range of 10−11–10−8 meters (3.28 × 10−10–3.94 × 10−6 feet) (a frequency of about 3 × 1019 Hz to 3 × 1016 Hz). One Hz (Hertz) is equal to 1 cps (cycle per second).

Unlike longer-wavelength, lower-frequency visible light, x-ray radiation consists of waves so small that they can pass through solid materials with little effect. As the radiation moves through materials of different densities (bone and tissue, for example), some waves are blocked and produce shadows that result in light-and-dark images. Some materials, such as bone or metal, are opaque and appear as light areas, while other materials such as air in body cavities allow most of the x-ray waves to pass through, producing dark areas in the image.

Conventional x-ray images are captured by special photographic film, sensitized with silver salts that are converted by developing processes to dark and light images. Photons striking a photographic emulsion convert some silver ions to tiny particles of silver that grow large enough during the process of developing to form tiny grains in the photographic negative. Digital x-ray processes use individual crystal photodiode assemblies (each photodiode acts as a very small light-sensitive transistor, using the light energy from individual photons to modulate an electrical current flowing through the diode) containing compounds such as cadmium tungstate or bismuth germanate to capture light energy as electrical pulses that are then converted from analog to digital signals, stored in computer memory, and processed to form visual images on computer screens. Because electronic sensors may be more sensitive than film, digital x-ray processes may use as little as 10 percent of the energy needed for conventional x rays (and may thus require less massive shielding).

Although different types of x-ray technology may be ideally suited to different applications, the use of electronic sensors and digital technology offer several advantages over conventional x rays. The capture of an image by a photosensitive electronic device is rapid and allows the image to be enlarged, colored, or adjusted in density. In addition, the use of electronically captured images may be less expensive, allowing computer-assisted data processing and storage. Conventional x-ray film must be developed, washed, fixed, and dried, requiring chemical substances that may be harmful to the environment, and the resulting images on film may require massive storage facilities.

Digital x rays can be modified electronically to increase contrast, display certain structures in color or three dimensions, or subtract areas that interfere, allowing clearer pictures of structures such as veins and arteries. Very small differences in density may be amplified for even clearer viewing. This may be important in cases in which a contrast medium is injected into veins or arteries; enhancing small differences allows the use of smaller amounts of the contrast medium, lessening the danger to patients.

The health benefits of tea

Recent research findings about the health benefits of tea shouldn't be surprising. A single tea leaf contains a wide variety of substances. The two substances receiving the most attention in tea, however, are antioxidants and caffeine.
Antioxidants
We learned about oxidation a few sections ago. Just like tea leaves, apples and car hoods, humans are susceptible to oxidation. Oxygen molecules create stress on our tissues and organs by introducing harmful free radicals that lead to complications such as cancer and heart disease. Free radicals are charged atoms or molecules. They have to steal an electron from the molecules.
Antioxidants are substances that slow down the damaging effects of oxidation, and they are found naturally in fruits and vegetables. Once they are introduced into the body, antioxidants neutralize free radicals by giving up an electron. The antioxidant is harmless, because it is stable with or without its extra electron. Examples of powerful antioxidants are vitamin C, vitamin E and beta-carotene.
Tea contains a wide range of antioxidants. Scientists haven't agreed yet on the effectiveness of these substances, but the general consensus points toward polyphenolic compounds as the most abundant and helpful source of antioxidants in tea. Several kinds of polyphenols known as catechins, are common in green tea and considered to provide the best protection from oxidation. Black tea offers strong antioxidants, too, but the polyphenols have different structures and are not quite as effective. The reason for this goes back once again to the different ways to process tea -- the catechins that stay in green tea transform into theaflavin and thearubigin in black teas.
Caffeine
Like coffee, tea contains caffeine, the stimulant that wakes us up and increases concentration. The amount of caffeine in a cup of tea varies greatly -- everything from location to processing decisions affects the outcome -- but most agree that there's more caffeine in coffee than in tea. A standard cup of coffee contains anywhere from 80 to 120 milligrams (mg) of caffeine, while a cup of tea can have between 20 and 60 mg of caffeine. Most reports note that black tea is the strongest, containing about 30 to 40 mg. Green tea and oolong tea contain less, somewhere between 10 and 20 mg. White tea is thought to contain almost a negligible amount of caffeine, about 1 percent of the caffeine in a cup of coffee.

A look toward the future of Industrial organic chemistry

Industrial organic chemistry was once based on coal oil. Today it is based mainly on petroleum and natural gas. However, both of these resources are limited in supply and may not last through the twenty-first century.
Because coal reserves are much greater than those of oil and natural gas, perhaps syn gas from coal will become a major source of organic chemicals. However, coal is also a finite raw material, and therefore there is much interest in developing methods for converting renewable resources, such as plants, into industrial organic chemicals. Recently a major chemical company nnounced its plan to build a small plant for the production of 1,3-propanediol from sugar. This same company has set a goal of producing 25 percent of its feedstocks from renewable resources by 2010.
Although this might seem an unrealistic goal, it does indicate current thinking within the chemical industry.

WATER CHEMISTRY

Tropical freshwater aquarium fish reside in a wide range of water habitats– from fast-flowing mountain streams, to great lakes, to slow-moving rainforest rivers. Each of these biotopes, besides having unique fish species, has unique water properties due to environmental factors. Because fish do come from unique natural water sources, their water in captivity should have similar characteristics. To recreate natural settings, the aquariast should have some knowledge of basic water chemistry, specifically pH, water hardness, and the nitrogen cycle.

PH
The pH scale is a scale which is used to measure the acidity or alkalinity of a substance. The scale ranges from 0-14, with 0 being the most acidic, and 14 being the most alkaline. Water with a neutral pH of 7.0 has an equal ratio of H+ ions to OH- ions. Water with a pH below 7.0, is considered acidic (having a more H+ ions than OH- ions), while water with a pH above 7.0 is considered alkaline or basic (having a more OH- ions than H+ ions). Almost all freshwater fish inhabit waters with a pH from 5.0-9.0, with the majority of these inhabiting water with a slightly acidic to neutral pH (6-7.5).
In aquaria, the pH of tap water can be manipulated though the use of phosphate, bicarbonate, and other buffers. However the pH may change despite these buffers. The development of a low pH can usually be attributed to decaying material such as plant and animal wastes. When the pH drops below 5.5, bacteria (Nitrosomonas) that break down ammonium are reduced, and the ammonium level rises.
Lowering the pH: The pH can be lowered by using a pH-lowering chemical (available at pet shops). Be aware that many pH-lowering products use phosphate-based chemicals. Phosphate is a nutrient that encourages algae growth. The pH can also be lowered by plants and fish during respiration, when CO2 is exhaled into the water. In hard water, the pH may be difficult to lower. First, soften the water by peat filtration or reverse osmosis, and then try lowering the pH.
Raising the pH: The pH can be raised in an aquarium by adding baking soda (bicarbonate) or *** a water change (thus removing some organic buildup which reduces pH).

Water Hardness
The degree of water hardness relates to the amount of dissolved minerals, especially calcium and magnesium, in the water. Water hardness is generally expressed in the amount of calcium carbonate (CaCO3). Water hardness is measured in ppm (part per million), kH (carbonate hardness), and dH (degrees of hardness) or gH (general hardness). Water is expressed as soft (having few dissolved minerals) or “hard” (having many dissolved minerals. General levels of water hardness are expressed in the table below (1 dH is equivalent to about 17 ppm).
very soft 0 to 70 ppm 0 to 4 GH (dH)
soft 70 to 135 ppm 4 to 8 GH (dH)
medium hard 135 to 200 ppm 8 to 12 GH(dH)
hard 200 to 350 ppm 12 to 20 GH (dH)
very hard over 350 ppm over 20 GH (dH)
For most aquariasts water hardness is not particularly important. However, excessively soft water can cause problems. Because softer water has less buffering capacity due to a lack of CaCO3 (a natural buffer), and is subject to pH crashes, where the pH falls dramatically causing harm to aquarium inhabitants.
Carbonate Hardness: Carbonate hardness (kH) is not used as a measurement of hardness as often. KH includes the presence of minerals and charged ions, other than Ca and Mg, dissolved in water.
Changing the Water Hardness: Water hardness can be manipulated in several ways. To make the water softer, the water can be filtered through peat moss or filtered through a reverse osmosis system. Ion exchange resins also can be used to lower the water hardness. Boiling water for a period of time can also reduce its hardness. To harden the water, filter the water through dolomite or crushed coral until the desired hardness is reached.
Electrical Conductivity: By running an htmlelectrical current through the water, the level of conductivity can be found. Conductivity indicates the amount of ions (electrically charged particles) are in the water. The higher the water hardness, the greater the conductivity. Testing the conductivity of the water only finds the total amount of ions present in the water, and does not give the origin of the ions, whether they are Mg, Ca, or Fe.

Oxygen
Aquatic plants, animals, and bacteria depend on oxygen dissolved in water for respiration. Oxygen can be added to the aquarium through an air pump attached to some sort of air stone, by utilizing a filter that creates much su***ce disturbance, or by using a wet-dry filter system. Plants also add oxygen during the day with photosynthesis, although use oxygen at night during respiration. Thus, in a planted tank, the oxygen levels fall at night. At a higher temperature, less oxygen is dissolved in water and more aeration is required.

Carbon Dioxide
Carbon dioxide is another gas present in water as a byproduct of the respiration of organisms in the aquarium. During photosynthesis, plants require carbon dioxide. When there is a lack of carbon dioxide, the leaves of plants begin to yellow, and growth slows. Some of the carbon dioxide dissolved in water forms carbonic acid, which lowers the pH. If there is too much carbon dioxide in the tank, the fish will suffer.
Adding Carbon Dioxide: Carbon dioxide can be added by lower the water hardness to free CO2 from calcium bicarbonate. CO2 can also be added by the use of a CO2 system.

The Nitrogen Cycle
When fishes excrete waste, plants deteriorate, and food rots, the resulting waste does not just disappear. The waste, in the form of nitrogen compounds, is broken down into other compounds by bacteria, until the final product, nitrate NO3 is absorbed by plants or removed through gravel siphoning. This process of converting NH3/NH4 (of fish, plant, and other waste) into NO3 is known as nitrification. The steps of this process are most evident when the tank is first established or when the tank is out of balance.
When the tank is first set up, there are not nitrifying bacteria present (unless gravel or filters from an already established tank are used). A few hardy fish are added to the tank. By the first day, trace amounts of ammonia/ammonium (more toxic ammonia if the pH is above 7.0, less toxic ammonium when the pH is below 7.0) have built up. Within a few days, the ammonia level rises to a toxic level. By this time Nitrosomonas bacteria have begun to develop. These bacteria begin to break down the ammonia into nitrite (NO2), which is less toxic than ammonia/ammonium. Another type of bacteria, Nitrobacters, break down the nitrite (NO2) into less toxic nitrate (NO3). The nitrate is absorbed by plants or algae, or is removed when a water change is carried out. Although nitrate is less toxic than other nitrogen compounds, in high levels, it can be toxic.
This cycle also occurs when the tank becomes out of balance. If waste levels become too high, because of over-feeding, overstocking, and/or lack of water changes, ammonia levels will rise again. In this case, water changes should be performed until normal levels are restored.
This cycle can occur when the bacteria that breakdown organic wastes die. This can occur when the tank or filter is washed with soap or some disinfectant. If this occurs, the tank will have to be cycled again. Be aware that too acidic (below 5.5 pH) water or some medications can also deplete the bacteria population.

Nitrosomonas Nitrobacters
NH3 -----------------> NO2 -----------------> NO3
excess food absorbed by plants
fish waste removed during water changes plant matter
death

The Computational Chemistry

In 1929, shortly after the emergence of quantum mechanics, Paul Dirac made his

famous statement that in principle the physical laws necessary to understand all of

chemistry were at that point known—the only difficulty was that their application

to chemical systems generally led to equations that were too difficult to solve.

Consequently, at that time quantum principles could be rigorously applied only to

simple atoms and molecules, such as H, He, H2+, and H2.

During the 1930s the first approximate quantum mechanical methods for molecules were

developed, leading to some success in modeling electronic behavior in many-electron

molecules. For example, Eric Hückel developed a rudimentary molecular orbital model

for the behavior of electrons in organic polyenes. During the late 1930s and early

1940s the first electronic digital computers were developed, and after World War II

their use significantly expanded the application of classical and quantum mechanical

principles to chemical problems.

A measure of the progress that computer technology spawned was the awarding of the

Nobel Prize in chemistry in 1966 to Robert Mulliken for his creation of molecular

orbital theory and its use in the calculation of the electronic structure of

molecules. In his acceptance speech Mulliken announced the emergence of

computational chemistry as a recognized specialty within the field of chemistry: "In

conclusion, I would like to emphasize strongly my belief that the era of computing

chemists, when hundreds if not thousands of chemists will go to the computing

machine instead of the laboratory for increasingly many facets of chemical

information, is already at hand."

The 1998 Nobel Prize in chemistry, awarded to Walter Kohn (who developed the

density-functional theory) and John Pople (who developed the use of computational

methods in quantum chemistry) for their contributions to the advancement of

computational chemistry, provided further evidence that the field had become a

mature, reliable, and essential method of scientific inquiry. Today a vast

literature exists, and computational chemistry has become an essential subject in

the education of chemists at both the graduate and undergraduate levels.

The technical breadth of computational chemistry and the interdisciplinary character

of its applications make the formulation of a concise definition challenging.

Computational chemistry might be broadly defined as the attempt to model chemical

and biochemical phenomena (structure, properties, reactivity, etc.) via computer-

implementation of the theoretical principles of classical and quantum mechanical

physics. Chemists and biochemists are interested in a wide array of molecules,

including simple inorganic molecules, organic species of intermediate complexity,

transition metal complexes with htmlheavy metal ions, polymers, and biological macro-

molecules, such as proteins and nucleic acids. In their studies of these diverse

species they have a wide range of computational tools at their command. Therefore,

assessing the strengths and weaknesses of these tools, and choosing the most

appropriate method for the task at hand is a serious challenge for the computational

chemist.

Quantum Mechanics of Atoms

An exact solution for Schrödinger's wave equation can be obtained for the hydrogen atom; however, for larger atoms and molecules (which contain more than one electron), Schrödinger's equation can be solved only approximately. Although this may sound so restrictive as to make the equation useless, there are well-established approaches that allow for practical and accurate calculations on atoms and molecules. This is done by *** some assumptions about larger systems based upon the hydrogen atom, as explained below.

When the Schrödinger equation is solved for the hydrogen atom, the resulting wavefunctions for the various possible energies that the atom can have are used to determine atomic orbitals. An orbital is a region in space where an electron is most likely to be found. For example, the lowest-energy wavefunction for a hydrogen atom is the so-called 1s orbital (see Figure 1), which is a spherical region in space surrounding the nucleus. For some higher-energy states, the orbitals are not necessarily spherical in shape (e.g., the 2p orbital pictured in Figure 1).



Figure 1.

For atoms larger than htmlhydrogen, one assumes that the orbitals occupied by the electrons have the same shape as the hydrogen orbitals but are differing in size and energy. The energies corresponding to these orbitals may be found by solving an approximate version of Schrödinger's equation. These atomic orbitals, in turn, may be used as the building blocks to the electronic behavior in molecules, as we shall see below. As it happens, two electrons may share an atomic orbital; we say that these electrons are paired. Chemists have developed a system of rules for determining which orbitals are occupied in which atoms; calculations can then be done to determine the energies of the electrons in the atoms.

For atoms larger than hydrogen, one assumes that the orbitals occupied by the electrons have the same shape as the hydrogen orbitals but are differing in size and energy. The energies corresponding to these orbitals may be found by solving an approximate version of Schrödinger's equation. These atomic orbitals, in turn, may be used as the building blocks to the electronic behavior in molecules, as we shall see below. As it happens, two electrons may share an atomic orbital; we say that these electrons are paired. Chemists have developed a system of rules for determining which orbitals are occupied in which atoms; calculations can then be done to determine the energies of the electrons in the atoms.

Chemical explosive reaction

A chemical explosive is a compound or mixture which, upon the application of heat or shock, decomposes or rearranges with extreme rapidity, yielding much gas and heat. Many substances not ordinarily classed as explosives may do one, or even two, of these things. For example, at high temperatures (> 2000°C) a mixture of nitrogen and oxygen can be made to react with great rapidity and yield the gaseous product nitric oxide; yet the mixture is not an explosive since it does not evolve heat, but rather absorbs heat.

N2 + O2 → 2NO - 43,200 calories (or 180 kJ) per mole of N2

For a chemical to be an explosive, it must exhibit all of the following:

*Rapid expansion (i.e.,. rapid production of gases or rapid heating of surroundings)
*Evolution of heat
*Rapidity of reaction
*Initiation of reaction

Applications of solar energy technology

Solar energy technologies use solar radiation for practical ends. Technologies that use secondary solar resources such as biomass, wind, waves and ocean thermal gradients can be included in a broader description of solar energy but only primary resource applications are discussed here. Because the performance of solar technologies varies widely between regions, they should be deployed in a way that carefully considers these variations.

Solar technologies are broadly characterized as either passive or active depending on the way they capture, convert and distribute sunlight. Active solar techniques use photovoltaic panels, pumps, fans and to convert sunlight into useful outputs. Passive solar techniques include selecting materials with favorable thermal properties, designing spaces that naturally circulate air, and referencing the position of a building to the Sun. Several common materials are titanium dioxide,stannic oxide and so on.Active solar technologies increase the supply of energy and are considered supply side technologies, while passive solar technologies reduce the need for alternate resources and are generally considered demand side technologies.

Moisturisers linked to skin cancer

Over-the-counter skin creams could increase the likelihood of skin cancer. A study has found that commonly used moisturising creams significantly increase the development rate of non-melanoma skin cancer in UVB pre-treated mice - but not humans, yet!

Whilst investigating the potential of caffeine as an agent for the inhibition of skin cancer, US researchers innocently selected four commercially available skin creams to act as potential caffeine vehicles: Dermabase, Dermovan, Eucerin and Vanicream.

As a precaution, they chose to first assess the possible carcinogenic properties of one of the creams, Dermabase. To their suprise, the analysis revealed significant increases in both number and volume of tumours in mice.

The research took a consequent U-turn with individual tests then carried out on each of the four creams. All showed significant tumourigenic effects after a 17 week trial period. The worst offender, Dermovan, demonstrated a 95% increase in the number of developed tumours compared with the control mice.

Good diet may reduce risk of cancer

Men who eat more fruit and vegetables have less risk of developing a type of cancer

of the oesophagus, a study by a Japanese medical team said on Thursday.

The study, spearheaded by Japan's health ministry, monitored 39 000 men aged 45 to

74 over about eight years, during which time 116 developed the type of cancer called

oesophageal squamous cell carcinoma (SCC).

Esophageal SCC is a common type of cancer among Japanese men, strongly linked to

smoking and drinking alcohol, according to the study led by Shoichiro Tsugane, chief

of the Epidemiology and Prevention Division at Japan's National Cancer Centre.

The study divided men into three groups and found that those who ate the most fruit

and vegetables had nearly half the risk of developing oesophageal SCC compared with

the group with the least vegetable-based diet.

"An increase in consumption of total fruit and vegetables by 100 grams per day was

associated with an 11-percent decrease in the incidence of esophageal SCC," the

researchers said in a statement.

The study concluded that vegetables, especially the so-called cruciferous family of

vegetables that includes radishes and cabbages, may help prevent oesophageal SCC.

A diet rich in fruit and vegetables would lower the risk of developing this type of

cancer to nearly one-third, even among men who smoke and drink, it said.

But the study warned that fruits and veggies were no substitute for the health

benefits of quitting smoking or drinking.

A scientific study at Britain's Institute of Food Research showed last month that

men who ate more broccoli, one of the cruciferous vegetables, reduced their risk of

prostate cancer and other chronic diseases.

Lacking Nutrients? The Health Risks You Face

You hear a lot about vitamins and supplements and their great health benefits. But do you know the scary things that can happen when your body is lacking one of more of these key nutrients?
Check out our list of the top 11 vitamins and supplements to see what ailments await you if you’re lacking a key nutrient like calcium or vitamin C.
It may not paint a pretty picture, but it is information that you and your family need to take preventative action now.
Already ailing from one or more of the following afflictions? You can start reversing your ailments by starting a vitamin and supplement program now.
B-Vitamins (B Complex)
Without adequate vitamin B complex, you can experience one or more of any one of these symptoms:
• mental problems
• heart palpitations
• heart arrhythmias
• fibrillation
• indigestion
• chronic fatigue
• chronic exhaustion
• paranoia, vague fears, fear that something dreadful is about to happen
• nervousness
• ADD (attention deficiency), inability to concentrate, irritability
• feeling of uneasiness
• thoughts of dying
• easy agitation, frustration
• inability to sleep (insomnia)
• restlessness
• tingling in hands
• tingling fingers and toes
• rashes
• crying spells, inability to cope
• soreness all over
Calcium
Without an adequate, constant supply of calcium your bones become weaker and develop tiny holes. These “porous bones” lead to osteoporosis. A Surgeon General report warns that by 2020 half of all Americans older than 50 will be at risk for fractures from osteoporosis and low bone mass. Populations most at risk of a calcium deficiency are post-menopausal women.
[urlhttp://www.lookchem.com/cas-558/55870-43-4.html]Coenzyme Q10[/url]
CoQ10 levels decrease with age and are low in patients with chronic diseases such as:
• heart conditions
• muscular dystrophies
• Parkinson's disease
• Cancer
• Diabetes
• HIV/AIDS
Fish Oil (essential fatty acids)
• hardening of the arteries (buildup of atherosclerotic plaque)
• breast cancer
• diabetes
• heart disease
• depression
• memory loss
• acne
• aging
• allergies
• arthritis
• asthma
• high blood pressure
• obesity
• stroke
Folic Acid
Folic acid is a B vitamin that helps the body make healthy new cells. A lack of folic acid can lead to:
• major birth defects of baby’s brain or spine
• heart disease
• stroke
• cancer
• Alzheimer’s disease
• anemia
• weakness
Glucosamine
When you have a glucosamine deficiency, cartilage hardens and bone spurs develop which leads to deformities in the joints. Your mobility becomes limited and osteoarthritis develops.
Iron
A deficiency of iron limits oxygen delivery to cells, resulting in fatigue, poor work performance, and decreased immunity. Having iron deficiency anemia may cause you to feel tired and often look pale. Iron deficiency anemia is common, especially in women. One in five women and half of all pregnant women are iron deficient. You can usually correct iron deficiency anemia with iron supplementation.
Magnesium
Magnesium is needed for more than 300 body reactions. Even a mild deficiency causes:
• sensitiveness to noise
• nervousness
• irritability
• mental depression
• confusion
• twitching
• trembling
• apprehension
• insomnia
• muscle weakness
• cramps in the toes, feet, legs or fingers.
Vitamin C
• tiredness
• weakness
• sore muscles
• bleeding gums
• wounds that don’t heal quickly, if at all
Vitamin D
• bones become thin, brittle or misshapen
• rickets for children
• osteomalacia in adults
• osteoporis (vitamin D works with C to strengthen bones)
• inflammation
Vitamin E
• destruction of vital red blood cells
• weakened immune system
In extreme cases vitamin deficiencies can even lead to death.
If you're concerned you may be lacking some essential vitamins thanks to bad eating habits, then a vitamin supplement can be a good way to fill the gaps. Try a daily multivitamin supplement and you might just be surprised at how much better you feel overall.
Order from the Diet.com Store and we’ll send you a copy of the informative Vitamin and Supplement Guide – this insightful guide is our FREE GIFT to you!

Drug and Chemical-Related Gastroenteritis

Many drugs cause nausea, vomiting, and diarrhea as adverse effects. A detailed drug history must be obtained. In mild cases, cessation followed by reuse of the drug may establish a causal relationship. Commonly responsible drugs include antacids containing Mg, antibiotics, antihelminthics, cytotoxics (used in cancer therapy), digitek, lanoxin, heavy metals, laxatives, and radiation therapy. Use of antibiotics may lead to Clostridium difficile-induced diarrhea.

Iatrogenic, accidental, or intentional heavy-metal poisoning frequently produces nausea, vomiting, abdominal pain, and diarrhea.

Laxative abuse, sometimes denied by patients, may lead to weakness, vomiting, diarrhea, electrolyte depletion, and metabolic disturbances.

Various plants and mushrooms cause a syndrome of gastroenteritis.

Chemistry of Soap


The basic structure of all soaps is essentially the same, consisting of a long hydrophobic (water-fearing) hydrocarbon "tail" and a hydrophilic (waterloving) anionic "head":

CH3CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2CH2COO− or CH3(CH2)nCOO−

The length of the hydrocarbon chain ("n") varies with the type of fat or oil but is usually quite long. The anionic charge on the carboxylate head is usually balanced by either a positively charged potassium (K+) or sodium (Na+) cation. In *** soap, triglycerides in fat or oils are heated in the presence of a strong alkali base such as sodium hydroxide, producing three molecules of soap for every molecule of glycerol. This process is called saponification and is illustrated in Figure 1.

Like synthetic detergents, soaps are "su***ce active" substances (su***ctants) and as such make water better at cleaning su***ces. Water, although a good general solvent, is unfortunately also a substance with a very high su***ce tension. Because of this, water molecules generally prefer to stay together rather than to wet other su***ces. Su***ctants work by reducing the su***ce tension of water, allowing the water molecules to better wet the su***ce and thus increase water's ability to dissolve dirty, oily stains.