SUMMARY / RELATED TOPICS

Cellulose

Cellulose is an organic compound with the formula n, a polysaccharide consisting of a linear chain of several hundred to many thousands of β linked D-glucose units. Cellulose is an important structural component of the primary cell wall of green plants, many forms of algae and the oomycetes; some species of bacteria secrete it to form biofilms. Cellulose is the most abundant organic polymer on Earth; the cellulose content of cotton fiber is 90%, that of wood is 40–50%, that of dried hemp is 57%. Cellulose is used to produce paperboard and paper. Smaller quantities are converted into a wide variety of derivative products such as cellophane and rayon. Conversion of cellulose from energy crops into biofuels such as cellulosic ethanol is under development as a renewable fuel source. Cellulose for industrial use is obtained from wood pulp and cotton; some animals ruminants and termites, can digest cellulose with the help of symbiotic micro-organisms that live in their guts, such as Trichonympha. In human nutrition, cellulose is a non-digestible constituent of insoluble dietary fiber, acting as a hydrophilic bulking agent for feces and aiding in defecation.

Cellulose was discovered in 1838 by the French chemist Anselme Payen, who isolated it from plant matter and determined its chemical formula. Cellulose was used to produce the first successful thermoplastic polymer, celluloid, by Hyatt Manufacturing Company in 1870. Production of rayon from cellulose began in the 1890s and cellophane was invented in 1912. Hermann Staudinger determined the polymer structure of cellulose in 1920; the compound was first chemically synthesized by Kobayashi and Shoda. Cellulose has no taste, is odorless, is hydrophilic with the contact angle of 20–30 degrees, is insoluble in water and most organic solvents, is chiral and is biodegradable, it was shown to melt at 467 °C in pulse tests made by Dauenhauer et al.. It can be broken down chemically into its glucose units by treating it with concentrated mineral acids at high temperature. Cellulose is derived from D-glucose units; this linkage motif contrasts with that for α-glycosidic bonds present in glycogen. Cellulose is a straight chain polymer.

Unlike starch, no coiling or branching occurs and the molecule adopts an extended and rather stiff rod-like conformation, aided by the equatorial conformation of the glucose residues. The multiple hydroxyl groups on the glucose from one chain form hydrogen bonds with oxygen atoms on the same or on a neighbor chain, holding the chains together side-by-side and forming microfibrils with high tensile strength; this confers tensile strength in cell walls where cellulose microfibrils are meshed into a polysaccharide matrix. The high tensile strength of plant stems and of the tree wood arises from the arrangement of cellulose fibers intimately distributed into the lignin matrix; the mechanical role of cellulose fibers in the wood matrix responsible for its strong structural resistance, can somewhat be compared to that of the reinforcement bars in concrete, lignin playing here the role of the hardened cement paste acting as the "glue" in between the cellulose fibers. Compared to starch, cellulose is much more crystalline.

Whereas starch undergoes a crystalline to amorphous transition when heated beyond 60–70 °C in water, cellulose requires a temperature of 320 °C and pressure of 25 MPa to become amorphous in water. Several different crystalline structures of cellulose are known, corresponding to the location of hydrogen bonds between and within strands. Natural cellulose is cellulose I, with structures Iα and Iβ. Cellulose produced by bacteria and algae is enriched in Iα while cellulose of higher plants consists of Iβ. Cellulose in regenerated cellulose fibers is cellulose II; the conversion of cellulose I to cellulose II is irreversible, suggesting that cellulose I is metastable and cellulose II is stable. With various chemical treatments it is possible to produce the structures cellulose III and cellulose IV. Many properties of cellulose depend on its chain length or degree of polymerization, the number of glucose units that make up one polymer molecule. Cellulose from wood pulp has typical chain lengths between 1700 units.

Molecules with small chain length resulting from the breakdown of cellulose are known as cellodextrins. Cellulose contains 44.44% carbon, 6.17% hydrogen, 49.39% oxygen. The chemical formula of cellulose is n where n is the degree of polymerization and represents the number of glucose groups. Plant-derived cellulose is found in a mixture with hemicellulose, lignin and other substances, while bacterial cellulose is quite pure, has a much higher water content and higher tensile strength due to higher chain lengths. Cellulose is soluble in Schweizer's reagent, cupriethylenediamine, cadmiumethylenediamine, N-methylmorpholine N-oxide, lithium chloride / dimethylacetamide; this is used in the production of regenerated celluloses from dissolving pulp. Cellulose is soluble in many kinds of ionic liquids. Cellulose consists of amorphous regions. By treating it with strong acid, the amorphous regions can be broken up, thereby producing nanocrystalline cellulose, a novel material with many desirable properties.

Nanocrystalline cellulose was used as the filler phase in bio-based polymer matrices to produce nanocomposites with su

Haymarket (Boston)

Haymarket in Boston is an open-air market on Blackstone and North Streets, next to the Rose Fitzgerald Kennedy Greenway between the North End and Government Center. The market is operated by the Haymarket Pushcart Association, founded in 1974 to negotiate with the city on issues such as waste removal and traffic; the 50 Haymarket vendors sell fruit and seafood at low prices. The market offers "produce its vendors obtain from wholesale distribution terminals north of Boston," the New England Produce Center in Chelsea. Prices are low because the wholesale markets need to make room for new shipments arriving over the weekend; the market is open "from dawn to dusk" every Saturday. The market's location and days of operation were established by a 1952 state law and by a 1978 city ordinance. Vendors are licensed by the City of Boston Inspectional Services Department; the market is adjacent to the Haymarket MBTA station, served by two subway lines and many bus routes. Inexpensive validated parking for Haymarket shoppers is available at the Parcel 7 Garage.

The discount was created as a "mitigation" measure for the impact of the Big Dig highway project on Haymarket. A study conducted for the Boston Redevelopment Authority in 2009 by the Project for Public Spaces found that "Haymarket attracts one of the most diverse populations of any market we have worked on.... Customers include every imaginable ethnic group and income level. Haymarket is the primary place where most of its shoppers buy produce and it serves a vital role in the Boston food distribution system." In 2015, two Johns Hopkins University graduate students proposed the creation in Baltimore of a market modeled after Haymarket, to address the problems of food going to waste and the lack of access to fresh produce in low-income communities. Markets have operated in this part of Boston since the 1600s; the first market buildings were constructed in 1734. The indoor market at Faneuil Hall opened in 1742. Open-air markets have been in continuous existence in the vicinity since early in the 19th century, with many transformations over the years.

The Haymarket Pushcart Association traces its roots to 1820. In the early 20th century, hundreds of street vendors did business on 24 city blocks. Laws passed beginning in 1908 limited the locations; the predecessor of today's market was relocated from Haymarket Square in 1952 to make way for construction of the elevated Central Artery. A state law passed in that year designates the current location of Haymarket for use by "hawkers and peddlers" on Fridays and Saturdays. Through much of the 20th century, most Haymarket vendors were of Italian ancestry. Today the mix of vendors is more diverse. According to Haymarket Pushcart Association President Otto Gallotto, "This place has always been an immigrants’ market with affordable prices. From when the Irish and Italians came to Boston and now, we have every ethnicity both buying and selling at Haymarket.”The market takes its name from Haymarket Square, a former town square, located a block to the north, where some vendors operated during the 19th century and the first half of the 20th century.

The market is located on the Freedom Trail, adjacent to the Blackstone Block Historic District, "the oldest extant city block in the country." This part of Boston has been called the "Market District" since at least 1910. The name was in use through at least the 1950s fell out of use, has been revived; the Market District includes the indoor Boston Public Market, Quincy Market, a market in the proposed Haymarket Square Hotel. Haymarket inspires strong feelings, both pro and con, among Boston visitors. Conflicts between Haymarket vendors and the City of Boston have arisen at times over issues including trash and truck parking. A 2005 Boston Globe article quoted then-Mayor Thomas Menino: "Haymarket is part of the uniqueness of Boston. My parents took me there. I wouldn't want the vendors to not be part of the Boston landscape. We want people to be able to buy affordable fruit and vegetables, but have to meet us halfway. They can't continue to live outside the rules. We have to have constructive dialogue with them."

Concerns about odor and litter led the City of Boston to install several large trash compactors on the site in 2009. In 1976, the Massachusetts Bicentennial Commission and the City of Boston commissioned a public art installation in the streets and sidewalks used for the market; the installation, called "Asaroton, 1976", by Mags Harries and Lajos Heder, was described by the artists as follows: "The embedded bronze pieces replicate the trash and debris that might cover the street. When the stalls and real debris of the farmer’s market cover the art, it becomes part of a living experience. On the other days of the week it is a memory of the market." The installation was removed prior to the Big Dig construction, stored at the Museum of Science. An updated version was reinstalled at Haymarket in 2006. Scenes in the 1968 movie The Thomas Crown Affair, the 1972 movie Fuzz, the 1982 movie Hanky Panky were filmed at Haymarket. Haymarket is a frequent subject for local photographers. Today the Market is in full operation.

Licensed Vendors are not allowed to sell anything to the public after 7 pm or risk a $1,000 fine issued by the city if caught. On Saturday nights nearing the 7 pm market-shut-down deadline, vendors liquidate any remaining inventory selling whatever they have left for pennies on the dollar. What is not sold is thrown out by the pallet full into the onsite trash compactors. Worthy of note, the Hay Market Garage offers $1.00 parking up to two hours or $3.00 parking

Trojan wave packet

A trojan wave packet is a wave packet, nonstationary and nonspreading. It is part of an artificially created system that consists of a nucleus and one or more electron wave packets, and, excited under a continuous electromagnetic field; the strong, polarized electromagnetic field, holds or "traps" each electron wave packet in an intentionally selected orbit. They derive their names from the trojan asteroids in the Sun–Jupiter system. Trojan asteroids orbit around the Sun in Jupiter's orbit at its Lagrangian equilibrium points L4 and L5, where they are phase-locked and protected from collision with each other, this phenomenon is analogous to the way the wave packet is held together; the concept of the Trojan wave packet is derived from a flourishing area of physics which manipulates atoms and ions at the atomic level creating ion traps. Ion traps allow the manipulation of atoms and are used to create new states of matter including ionic liquids, Wigner crystals and Bose–Einstein condensates; this ability to manipulate the quantum properties directly is key to the real life development of applicable nanodevices such as quantum dots and microchip traps.

In 2004 it was shown that it is possible to create a trap, a single atom. Within the atom, the behavior of an electron can be manipulated. During experiments in 2004 using lithium atoms in an excited state, researchers were able to localize an electron in a classical orbit for 15,000 orbits, it was neither dispersing. This "classical atom" was synthesized by "tethering" the electron using a microwave field to which its motion is phase locked; the phase lock of the electrons in this unique atomic system is, as mentioned above, analogous to the phase locked asteroids of Jupiter's orbit. The techniques explored in this experiment are a solution to a problem that dates back to 1926. Physicists at that time realized that any localized wave packet will spread around the orbit of the electrons. Physicist noticed that "the wave equation is dispersive for the atomic Coulomb potential." In the 1980s several groups of researchers proved this to be true. The wave packets coherently interfered with themselves.

The real world innovation realized with experiments such as Trojan wave packets, is localizing the wave packets, i.e. with no dispersion. Applying a polarized circular EM field, at microwave frequencies, synchronized with an electron wave packet, intentionally keeps the electron wave packets in a Lagrange type orbit; the Trojan wave packet experiments built on previous work with lithium atoms in an excited state. These are atoms, which respond sensitively to electric and magnetic fields, have decay periods that are prolonged, electrons, which for all intents and purposes operate in classical orbits; the sensitivity to electric and magnetic fields is important because this allows control and response by the polarized microwave field. The next logical step is to attempt to move from single electron wave packets to more than one electron wave packet; this had been accomplished in barium atoms, with two electron wave packets. These two were localized; however these created dispersion after colliding near the nucleus.

Another technique employed a nondispersive pair of electrons, but one of these had to have a localized orbit close to the nucleus. The nondispersive two-electron Trojan wave packets demonstration changes all that; these are the next step analogue of the one electron Trojan wave packets – and designed for excited helium atoms. As of July 2005, atoms with coherent, stable two-electron, nondispersing wave packets had been created; these are excited helium-like atoms, or quantum dot helium, are atomic analogues to the three body problem of Newton's classical physics, which includes today's astrophysics. In tandem, circularly polarized electromagnetic and magnetic fields stabilize the two electron configuration in the helium atom or the quantum dot helium; the stability is maintained over a broad spectrum, because of this, the configuration of two electron wave packets is considered to be nondispersive. For example, with the quantum dot helium, configured for confining electrons in two spatial dimensions, there now exists a variety of trojan wave packet configurations with two electrons, as of 2005, only one in three dimensions.

In 2012 an essential experimental step was undertaken not only generating but locking the Trojan wavepackets on adiabatically changed frequency and expanding the atoms as once predicted by Kalinski and Eberly. It will allow to create two electron Langmuir Trojan wave packets in Helium by the sequential excitation in adiabatic Stark field able to produce the circular one-electron aureola over He+ first and put the second electron in similar state. Atomic orbital Rydberg state Soliton wave Quantum scar March, Raymond E.. Practical Aspects of Ion Trap Mass Spectrometry: Volume I: Fundamentals of Ion Trap Mass Spectrometry. USA: CRC Press. ISBN 978-0-8493-4452-7. March, Raymond E.. Quadrupole Ion Trap Mass Spectrometry. Wiley, John & Sons, Incorporated. ISBN 978-0-471-48888-0. Sirko, L.. M.. "The pendulum approximation for the main quantal resonance in periodically driven Hydrogen atoms". Applied Physics B: Lasers and Optics. 60: S195–S202. Klar, H.. "Periodic orbits in atomic hydrogen exposed to circularly polarised laser light".

Zeitschrift für Physik D. 11: 45–52. Bibcode:1989ZPhyD..11...45K. Doi:10.1007/BF01436583. Maeda, H.. F.. "Nondispersing Bohr Wave Packets". Physical Review Letters. 102: 103001–103004. Bibcod