|Decorative soaps, by Phanton at English Wikipedia (Transferred from en.wikipedia to Commons.) [Public domain], via Wikimedia Commons|
Tuesday, 22 August 2017
In 1865, the first U.S. patent for a liquid soap was issued to William Sheppard of New York City (No. 49,561). The patent described his "discovery that by the addition of comparatively small quantities of common soap to a large quantity of spirits of ammonia or hartshorn is thickened to the consistency of molasses, and a liquid soap is obtained of superior detergent qualities." The proportions given were to dissolve one pound of common soap in water or steam, and then add 100-lbs of ammonia such that the liquid thickens to the consistency of molasses. The product was expected to be useful for both domestic and manufacturing purposes. (Hartshorn is an ancient name for an aqueous solution of ammonia).
So, how does soap clean?
Action of soap
When used for cleaning, soap allows insoluble particles to become soluble in water, so they can then be rinsed away. For example: oil/fat is insoluble in water, but when a couple of drops of dish soap are added to the mixture, the oil/fat dissolves in the water. The insoluble oil/fat molecules become associated inside micelles, tiny spheres formed from soap molecules with polar hydrophilic (water-attracting) groups on the outside and encasing a lipophilic (fat-attracting) pocket, which shields the oil/fat molecules from the water making it soluble. Anything that is soluble will be washed away with the water.
Effect of the alkali
The type of alkali metal used determines the kind of soap product. Sodium soaps, prepared from sodium hydroxide, are firm, whereas potassium soaps, derived from potassium hydroxide, are softer or often liquid. Historically, potassium hydroxide was extracted from the ashes of bracken or other plants. Lithium soaps also tend to be hard—these are used exclusively in greases.
Effects of fats
Soaps are derivatives of fatty acids. Traditionally they have been made from triglycerides (oils and fats). Triglyceride is the chemical name for the triesters of fatty acids and glycerin. Tallow, i.e., rendered beef fat, is the most available triglyceride from animals. Its saponified product is called sodium tallowate. Typical vegetable oils used in soap making are palm oil, coconut oil, olive oil, and laurel oil. Each species offers quite different fatty acid content and hence, results in soaps of distinct feel. The seed oils give softer but milder soaps. Soap made from pure olive oil is sometimes called Castile soap or Marseille soap, and is reputed for being extra mild. The term "Castile" is also sometimes applied to soaps from a mixture of oils, but a high percentage of olive oil.
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Monday, 14 August 2017
New evidence from ancient lunar rocks suggests that an active dynamo once churned within the molten metallic core of the moon, generating a magnetic field that lasted at least 1 billion years longer than previously thought. Dynamos are natural generators of magnetic fields around terrestrial bodies, and are powered by the churning of conducting fluids within many stars and planets. In a paper published today in Science Advances, researchers from MIT and Rutgers University report that a lunar rock collected by NASA's Apollo 15 mission exhibits signs that it formed 1 to 2.5 billion years ago in the presence of a relatively weak magnetic field of about 5 microtesla. That's around 10 times weaker than Earth's current magnetic field but still 1,000 times larger than fields in interplanetary space today.
|Full moon as seen from Earth's Northern Hemisphere, by Gregory H. Revera (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons|
Several years ago, the same researchers identified 4-billion-year-old lunar rocks that formed under a much stronger field of about 100 microtesla, and they determined that the strength of this field dropped off precipitously around 3 billion years ago. At the time, the researchers were unsure whether the moon's dynamo - the related magnetic field - died out shortly thereafter or lingered in a weakened state before dissipating completely.
The results reported today support the latter scenario: After the moon's magnetic field dwindled, it nonetheless persisted for at least another billion years, existing for a total of at least 2 billion years.
Study co-author Benjamin Weiss, professor of planetary sciences in MIT's Department of Earth, Atmospheric and Planetary Sciences (EAPS), says this new extended lifetime helps to pinpoint the phenomena that powered the moon's dynamo. Specifically, the results raise the possibility of two different mechanisms - one that may have driven an earlier, much stronger dynamo, and a second that kept the moon's core simmering at a much slower boil toward the end of its lifetime.
"The concept of a planetary magnetic field produced by moving liquid metal is an idea that is really only a few decades old," Weiss says. "What powers this motion on Earth and other bodies, particularly on the moon, is not well-understood. We can figure this out by knowing the lifetime of the lunar dynamo."
Weiss' co-authors are lead author Sonia Tikoo, a former MIT graduate student who is now an assistant professor at Rutgers; David Shuster of the University of California at Berkeley; Clément Suavet and Huapei Wang of EAPS; and Timothy Grove, the R.R. Schrock Professor of Geology and associate head of EAPS.
Since NASA's Apollo astronauts brought back samples from the lunar surface, scientists have found some of these rocks to be accurate "recorders" of the moon's ancient magnetic field. Such rocks contain thousands of tiny grains that, like compass needles, aligned in the direction of ancient fields when the rocks crystallized eons ago. Such grains can give scientists a measure of the moon's ancient field strength.
Until recently, Weiss and others had been unable to find samples much younger than 3.2 billion years old that could accurately record magnetic fields. As a result, they had only been able to gauge the strength of the moon's magnetic field between 3.2 and 4.2 billion years ago.
"The problem is, there are very few lunar rocks that are younger than about 3 billion years old, because right around then, the moon cooled off, volcanism largely ceased and, along with it, formation of new igneous rocks on the lunar surface," Weiss explains. "So there were no young samples we could measure to see if there was a field after 3 billion years."
There is, however, a small class of rocks brought back from the Apollo missions that formed not from ancient lunar eruptions but from asteroid impacts later in the moon's history. These rocks melted from the heat of such impacts and recrystallized in orientations determined by the moon's magnetic field.
Weiss and his colleagues analyzed one such rock, known as Apollo 15 sample 15498, which was originally collected on Aug. 1, 1971, from the southern rim of the moon's Dune Crater. The sample is a mix of minerals and rock fragments, welded together by a glassy matrix, the grains of which preserve records of the moon's magnetic field at the time the rock was assembled.
"We found that this glassy material that welds things together has excellent magnetic recording properties," Weiss says.
The team determined that the rock sample was about 1 to 2.5 billion years old - much younger than the samples they previously analyzed. They developed a technique to decipher the ancient magnetic field recorded in the rock's glassy matrix by first measuring the rock's natural magnetic properties using a very sensitive magnetometer.
They then exposed the rock to a known magnetic field in the lab, and heated the rock to close to the extreme temperatures in which it originally formed. They measured how the rock's magnetization changed as they increased the surrounding temperature.
"You see how magnetized it gets from getting heated in that known magnetic field, then you compare that field to the natural magnetic field you measured beforehand, and from that you can figure out what the ancient field strength was," Weiss explains.
The researchers did have to make one significant adjustment to the experiment to better simulate the original lunar environment, and in particular, its atmosphere. While the Earth's atmosphere contains around 20 percent oxygen, the moon has only imperceptible traces of the gas. In collaboration with Grove, Suavet built a customized, oxygen-deprived oven in which to heat the rocks, preventing them from rusting while at the same time simulating the oxygen-free environment in which the rocks were originally magnetized.
"In this way, we finally have gotten an accurate measurement of the lunar field," Weiss says.
From their experiments, the researchers determined that, around 1 to 2.5 billion years ago, the moon harbored a relatively weak magnetic field, with a strength of about 5 microtesla - two orders of magnitude weaker than the moon's field around 3 to 4 billion years ago. Such a dramatic dip suggests to Weiss and his colleagues that the moon's dynamo may have been driven by two distinct mechanisms.
Scientists have proposed that the moon's dynamo may have been powered by the Earth's gravitational pull. Early in its history, the moon orbited much closer to the Earth, and the Earth's gravity, in such close proximity, may have been strong enough to pull on and rotate the rocky exterior of the moon. The moon's liquid center may have been dragged along with the moon's outer shell, generating a very strong magnetic field in the process.
It's thought that the moon may have moved sufficiently far away from the Earth by about 3 billion years ago, such that the power available for the dynamo by this mechanism became insufficient. This happens to be right around the time the moon's magnetic field strength dropped. A different mechanism may have then kicked in to sustain this weakened field. As the moon moved away from the Earth, its core likely sustained a low boil via a slow process of cooling over at least 1 billion years.
"As the moon cools, its core acts like a lava lamp - low-density stuff rises because it's hot or because its composition is different from that of the surrounding fluid," Weiss says. "That's how we think the Earth's dynamo works, and that's what we suggest the late lunar dynamo was doing as well."
The researchers are planning to analyze even younger lunar rocks to determine when the dynamo died off completely.
"Today the moon's field is essentially zero," Weiss says. "And we now know it turned off somewhere between the formation of this rock and today."
This research was supported, in part, by NASA.
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Monday, 7 August 2017
Immune cells patrol the gut to ensure that harmful microbes hidden in the food we eat don't sneak into the body. Cells that are capable of triggering inflammation are balanced by cells that promote tolerance, protecting the body without damaging sensitive tissues. When the balance tilts too far toward inflammation, inflammatory bowel disease can result.
Now, researchers at Washington University School of Medicine in St. Louis have found that a kind of tolerance-promoting immune cell appears in mice that carry a specific bacterium in their guts. Further, the bacterium needs tryptophan - one of the building blocks of proteins - to trigger the cells' appearance.
"We established a link between one bacterial species - Lactobacillus reuteri - that is a normal part of the gut microbiome, and the development of a population of cells that promote tolerance," said Marco Colonna, MD, the Robert Rock Belliveau MD Professor of Pathology and the study's senior author. "The more tryptophan the mice had in their diet, the more of these immune cells they had."
If such findings hold true for people, it would suggest that the combination of L. reuteri and a tryptophan-rich diet may foster a more tolerant, less inflammatory gut environment, which could mean relief for the million or more Americans living with the abdominal pain and diarrhea of inflammatory bowel disease.
|A representation of the 3D structure of the protein myoglobin showing turquoise α-helices. By AzaToth (self made based on PDB entry) [Public domain], via Wikimedia Commons|
Postdoctoral researcher Luisa Cervantes-Barragan, PhD, was studying a kind of immune cell that promotes tolerance when she discovered that one group of study mice had such cells, while a second group of study mice that were the same strain of mice but were housed far apart from the first group did not have such cells.
The mice were genetically identical but had been born and raised separately, indicating that an environmental factor influenced whether the immune cells developed.
She suspected the difference had to do with the mice's gut microbiomes - the community of bacteria, viruses and fungi that normally live within the gastrointestinal tract.
Cervantes-Barragan collaborated with Chyi-Song Hsieh, MD, PhD, the Alan A. and Edith L. Wolff Distinguished Professor of Medicine, to sequence DNA from the intestines of the two groups of mice. They found six bacterial species present in the mice with the immune cells but absent from the mice without them.
With the help of Jeffrey I. Gordon, MD, the Dr. Robert J. Glaser Distinguished University Professor, the researchers turned to mice that had lived under sterile conditions since birth to identify which of the six species was involved in inducing the immune cells. Such mice lack a gut microbiome and do not develop this kind of immune cell. When L. reuteri was introduced to the germ-free mice, the immune cells arose.
To understand how the bacteria affected the immune system, the researchers grew L. reuteri in liquid and then transferred small amounts of the liquid - without bacteria - to immature immune cells isolated from mice. The immune cells developed into the tolerance-promoting cells. When the active component was purified from the liquid, it turned out to be a byproduct of tryptophan metabolism known as indole-3-lactic acid.
Tryptophan - commonly associated with turkey - is a normal part of the mouse and the human diet. Protein-rich foods contain appreciable amounts: nuts, eggs, seeds, beans, poultry, yogurt, cheese, even chocolate.
When the researchers doubled the amount of tryptophan in the mice's feed, the number of such cells rose by about 50 percent. When tryptophan levels were halved, the number of cells dropped by half.
People have the same tolerance-promoting cells as mice, and most of us shelter L. reuteri in our gastrointestinal tracts. It is not known whether tryptophan byproducts from L. reuteri induce the cells to develop in people as they do in mice, but defects in genes related to tryptophan have been found in people with inflammatory bowel disease.
"The development of these cells is probably something we want to encourage since these cells control inflammation on the inner surface of the intestines," Cervantes-Barragan said. "Potentially, high levels of tryptophan in the presence of L. reuteri may induce expansion of this population."
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Tuesday, 1 August 2017
In 1774, Joseph Priestley, British Presbyterian minister and chemist, identified a gas which he called "dephlogisticated air" - later known as oxygen. Priestley found that mercury heated in air became coated with "red rust of mercury," which, when heated separately, was converted back to mercury with "air" given off. Studying this "air" given off, he observed that candles burned very brightly in it. Also, a mouse in a sealed vessel with it could breathe it much longer than ordinary air. A strong believer in the phlogiston theory, Priestley considered it to be "air from which the phlogiston had been removed." Further experiments convinced him that ordinary air is one fifth dephlogisticated air, the rest considered by him to be phlogiston.
|Joseph Priestley, by Charles Turner [Public domain], via Wikimedia Commons|
However, oxygen was in fact first discovered earlier, by Swedish pharmacist Carl Wilhelm Scheele. He had produced oxygen gas by heating mercuric oxide and various nitrates in 1771–2. Scheele called the gas "fire air" because it was the only known supporter of combustion, and wrote an account of this discovery in a manuscript he titled Treatise on Air and Fire, which he sent to his publisher in 1775. That document was published in 1777.
Because Priestly published his findings first, he is usually given priority in the discovery.
The French chemist Antoine Laurent Lavoisier later claimed to have discovered the new substance independently. Priestley visited Lavoisier in October 1774 and told him about his experiment and how he liberated the new gas. Scheele also posted a letter to Lavoisier on September 30, 1774 that described his discovery of the previously unknown substance, but Lavoisier never acknowledged receiving it (a copy of the letter was found in Scheele's belongings after his death). Long before this, one of the first known experiments on the relationship between combustion and air was conducted by the 2nd century BCE Greek writer on mechanics, Philo of Byzantium. In his work Pneumatica, Philo observed that inverting a vessel over a burning candle and surrounding the vessel's neck with water resulted in some water rising into the neck. Philo incorrectly surmised that parts of the air in the vessel were converted into the classical element fire and thus were able to escape through pores in the glass. Many centuries later Leonardo da Vinci built on Philo's work by observing that a portion of air is consumed during combustion and respiration.
In the late 17th century, Robert Boyle proved that air is necessary for combustion. English chemist John Mayow (1641–1679) refined this work by showing that fire requires only a part of air that he called spiritus nitroaereus. In one experiment, he found that placing either a mouse or a lit candle in a closed container over water caused the water to rise and replace one-fourteenth of the air's volume before extinguishing the subjects. From this he surmised that nitroaereus is consumed in both respiration and combustion.
Mayow observed that antimony increased in weight when heated, and inferred that the nitroaereus must have combined with it. He also thought that the lungs separate nitroaereus from air and pass it into the blood and that animal heat and muscle movement result from the reaction of nitroaereus with certain substances in the body. Accounts of these and other experiments and ideas were published in 1668 in his work Tractatus duo in the tract "De respiratione".
Robert Hooke, Ole Borch, Mikhail Lomonosov, and Pierre Bayen all produced oxygen in experiments in the 17th and the 18th century but none of them recognized it as a chemical element. This may have been in part due to the prevalence of the philosophy of combustion and corrosion called the phlogiston theory, which was then the favored explanation of those processes.
Established in 1667 by the German alchemist J. J. Becher, and modified by the chemist Georg Ernst Stahl by 1731, phlogiston theory stated that all combustible materials were made of two parts. One part, called phlogiston, was given off when the substance containing it was burned, while the dephlogisticated part was thought to be its true form, or calx.
Highly combustible materials that leave little residue, such as wood or coal, were thought to be made mostly of phlogiston; non-combustible substances that corrode, such as iron, contained very little. Air did not play a role in phlogiston theory, nor were any initial quantitative experiments conducted to test the idea; instead, it was based on observations of what happens when something burns, that most common objects appear to become lighter and seem to lose something in the process. The fact that a substance like wood gains overall weight in burning was hidden by the buoyancy of the gaseous combustion products.
This theory, while it was on the right track, was unfortunately set up backwards. Rather than combustion or corrosion occurring as a result of the decomposition of phlogiston compounds into their base elements with the phlogiston being lost to the air, it is in fact the result of oxygen from the air combining with the base elements to produce oxides. Indeed, one of the first clues that the phlogiston theory was incorrect was that metals gain weight in rusting (when they were supposedly losing phlogiston).
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