The postorbital bar is a bone which, with the exception of Tarsiers runs around the eyesocket of most Prosimians. This is in contrast to the higher primates, Anthropoids, who have evolved fully enclosed sockets to protect their eyes.
One theory for this evolutionary difference is the relative importance of vision to both orders. As anthropoids tend to be diurnal, and rely heavily on visual input, prosimians are mainly nocturnal and have a decreased reliance on visual input.
References
Campbell, Bernard G.; & Loy, James D.; (2000). Humankind Emerging (8th ed.). Allyn & Bacon. p 85.
George Jessen was an optometrist who was an early pioneer of the contact lens. He is credited with being on of the first to employ the concept of orthokeratology, a direct attempt to reduce refractive error with the use of a contact lens, under the term orthofocus.
Jessen received his training at the Chicago College of Optometry, now called the Illinois College of Optometry. In 1976, the Contact Lens Manufacturing Association awarded him the The Dr. Joseph Dallos Award for “outstanding contribution to the development and advancement of the contact lens industry and for service to humanity”.[1]
Jessen worked closely with his mentor, Newton K. Wesley and in 1978 the two won Food and Drug Administration approval of their hyrdogel soft contact lenses. Together they founded the Wesley-Jessen Corporation as well as the National Eye Research Foundation, which presents the Dr. George N. Jessen Award for Clinical Excellence each year at its annual meeting.
Reference
McQueen, Adrienn Orthokertaology Eyewitness No. 4 2003
The Blessing Way is a 1970 novel by Tony Hillerman, his first. It introduces Navajo Tribal Police Lt. Joe Leaphorn, who works with anthropologist Bergen McKee to investigate a series of murders, possibly involving the supernatural, in the Four Corners area.
In his autobiography, Hillerman explained that McKee was the main character, and initially Leaphorn had a minor role. However, at the advice of his editors, he expanded Leaphorn’s role, and in later books Leaphorn would become a main character.
The book has references to the Anasazi and the Hopi, though it is mainly about the Navajo (see: The Blessingway).
In the tight binding model, it is assumed
that the full Hamiltonian <math>H</math> of the system may be approximated by the
Hamiltonian of an isolated atom centred at each lattice point. The
atomic orbitals <math>\psi_n</math>, which are eigenfunctions of the single atom
Hamiltonian <math>H_{at}</math>, are assumed to be very small at distances exceeding the
lattice constant. This is what is meant by tight-binding. It is
further assumed that any corrections to the atomic potential <math>\Delta U</math>, which are
required to obtain the full Hamiltonian <math>H</math> of the system, are appreciable
only when the atomic orbitals are small. The solution to the
time-independent single electron Schrödinger equation <math>\phi</math> is then
assumed to be a linear combination of atomic orbitals
- <math>\phi(\vec{r}) = \sum_n b_n \psi_n(\vec{r})</math>.
This leads to a matrix equation for the coefficients <math>b_n</math> and Bloch energies <math>\varepsilon</math> of the form
- <math>\varepsilon(\vec{k}) = E_m - {\beta_m + \sum_{\vec{R}\neq 0} \gamma_m(\vec{R}) e^{i \vec{k} \cdot \vec{R}}\over b_m + \sum_{\vec{R}\neq 0} \alpha_m(\vec{R}) e^{i \vec{k} \cdot \vec{R}}}</math>,
where <math>E_m</math> is the energy of the <math>m</math>th atomic level,
- <math> \beta_m = -\int \psi_m^*(\vec{r})\Delta U(\vec{r}) \phi(\vec{r}) d\vec{r}</math>,
- <math> \alpha_m(\vec{R}) = \int \psi_m^*(\vec{r}) \phi(\vec{r}-\vec{R}) d\vec{r}</math>,
and
- <math> \gamma_m(\vec{R}) = -\int \psi_m^*(\vec{r}) \Delta U(\vec{r}) \phi(\vec{r}-\vec{R}) d\vec{r}</math>
are the overlap integrals.
The tight binding model is typically used for calculations of electronic band structure and energy gaps in the static regime. However, in combination with other methods such as the random phase approximation (RPA) model, the dynamic response of systems may also be studied.
References
- J.C. Slater and G.F. Koster, Phys. Rev. 94, 1498 (1954).
- C.M. Goringe, D.R. Bowler and E. Hernández, Rep. Prog. Phys. 60, 1447 (1997).
- N. W. Ashcroft and N. D. Mermin, Solid State Physics (Thomson Learning, Toronto, 1976).
Transmission Electron Aberration-corrected Microscope or TEAM is a $100 million U.S. Department of Energy research project being conducted at five US laboratories.
The intention of the project is to develop a transmission electron microscope capable of 0.05 nanometres (0.5 x 10−10m) resolution, about half the size of a hydrogen atom. As electron microscope lenses normally produce a significant amount of aberration, a complex system of lenses to correct the aberrated images is required.
The first TEAM microscope will be based at the Lawrence Berkeley National Laboratory in Berkeley, California and is intended to become operational around 2007/2008. The other laboratories involved are
- Argonne National Laboratory
- Brookhaven National Laboratory
- Oak Ridge National Laboratory
- Frederick Seitz Materials Research Laboratory at the University of Illinois at Urbana-Champaign.
In chemistry, radical initiators are substances that can produce radical species under mild conditions and promote radical polymerization reactions. These substances generally possess weak bonds—bonds that have small bond dissociation energies. Radical initiators are utilized in industrial processes such as polymer synthesis. Typical examples are halogen molecules, azo compounds, and organic peroxides.
- Like all diatomic molecules, halogens can generate two free radicals resulting from the homolysis of the bond, but halogens undergo the homolytic fission relatively easily. Chlorine, for example, gives two chlorine radicals (Cl•) by irradiation with ultraviolet light. This process is used for chlorination of alkanes.
- Azo compounds (R-N=N-R’) can be the precursor of two carbon-centered radicals (R• and R’•) and nitrogen gas upon heating and/or by irradiation. For example, AIBN and ABCN yield isobutyronitrile and cyclohexanecarbonitrile radicals, respectively.
- Organic peroxides each have a peroxide bond (-O-O-), which is readily cleaved to give two oxygen-centered radicals. The oxyl radicals are rather unstable and believed to be transformed into relatively stable carbon-centered radicals. For example, di-t(tertiary)-butylperoxide (tBuOOtBu) gives two t-butanoyl radicals (tBuO•) and the radicals become methyl radicals (CH3•) with the loss of acetone. Benzoyl peroxide ((PhCOO)2) generates benzoyloxyl radicals (PhCOO•), each of which loses carbon dioxide to be converted into a phenyl radical (Ph•). Methyl ethyl ketone peroxide is also common, and acetone peroxide is on rare occasions used as a radical initiator, too.
Radical initiators, especially azo compounds and organic peroxides, are inherently unstable. They must be kept in a cool place or refrigerated. Care should be taken with the handling of the compounds or an explosion may occur.
See also: Initiator
Trifocals are eyeglasses where the lenses have 3 regions to correct for distance, intermediate (arm’s length), and near vision. They are mostly used by people with advanced presbyopia who have been prescribed 2 diopters or more of reading addition. The intermediate addition is normally half the reading addition. So, for someone with a distance prescription of -4 diopters and a reading addition of +3, the reading portion of their trifocals would have a net power of -1, and the intermediate segment would be -2.5 diopters.
Trifocal lenses are made in similar styles to bifocals, but with an additional segment for intermediate vision above the reading section. A common style is the 7×28 flat-top or D-shaped segment, 28 mm wide, with a 7 mm high intermediate segment. Larger intermediate segments are available, and are particularly useful for people who spend a lot of time using computers.
Trifocals are becoming rarer as more people choose to wear progressive lenses.
Donald Rumsfeld is a trifocal-wearer.
Rapid manufacturing is an additive fabrication technique for manufacturing solid objects by the sequential delivery of energy and/or material to specified points in space to produce that part. Current practice is to control the manufacturing process by computer using a mathematical model created with the aid of a computer. Rapid manufacturing done in parallel batch production can provide a large advantage in speed and cost compared to alternative manufacturing techniques such as plastic injection molding or die casting. Rapid manufacturing may involve custom parts, replacement parts, short run production, or series production. (When the part is used in the development process only, the appropriate term is rapid prototyping.)
Rapid manufacturing for large products with layer-based manufacturing from metals, plastics, or composite materials is well known for several industrial applications in the military (MPH-Optomec) and aerospace (Boeing) sectors. Small products and microsystem applications are known in medical (Siemens)as well as diagnostics and sensor technologies. Batch production of very small parts by rapid manufacturing techniques may offer cost and time advantages. Increasingly, rapid manufacturing is being applied to automotive, motor sports, jewelry, dentistry, orthodontics, medicine, consumer products, and collectibles.
References
- Hopkinson, N. , Hague, R. , Dickens, P. (2005). Rapid Manufacturing (Abstract). Germany: Wiley-VCH.
- Wright, Paul K. (2001). 21st Century manufacturing. New Jersey: Prentice-Hall.
- Wohlers, T. (2007). Wohlers Report 2007. Wohlers Associates, Inc.
See also
- Solid freeform fabrication
- The TCT Magazine - Bi monthly magazine focusing on rapid product development
- Additive manufacturing
External links
- The Rapid Prototyping Home Page
- RM-Platform.com The European collaboration on Rapid Manufactoring.
- microTEC RM for MEMS since 1996
- MINAM
- DIPI New Technologies for RM like Cold Gas Spray
- Rapid Manufacturing Research Group at the Wolfson School of Mechanical and Manufacturing Engineering at Loughborough University
- Rapid manufacturing supplier ProtoCAM provides info on resins, characteristics, benefits, examples, and materials
- Manufacturing Engineering Centre (MEC), Cardiff University, UK. Rapid Manufacturing Research and Services.
- Technical Articles - Articles on rapid manufacturing from Wohlers Associates
- Econolyst RM - Rapid Manufacturing consultancy & training services
- [1] - Rapid Manufacturing Software research and services
The Glock 31 is a pistol manufactured by Glock. It is a Glock 22 modified to fire the .357 SIG ammunition. It uses a modified slide, frame, .357 SIG barrel and magazine but is otherwise near identical in looks to the Glock 22. It has a 15-round magazine capacity. (A Glock 31 can be converted to .40 S&W with no further modification than a new barrel.)
The Glock 31 has become a popular law enforcement, sports and hunting pistol, but is less pleasant to shoot than the Glock 17 because of its sharp recoil.
The difference between the Glock 31 and the Glock 31C is that the barrel and slide are ported on the C model to reduce muzzle climb while shooting the pistol.
References
External links
A leaflet in botany is a part of a compound leaf. A leaflet may resemble an entire leaf, but it is not borne on a stem as a leaf is, but rather on a vein of the whole leaf. Compound leaves are common in many plant families.
Leaflets borne on the central vein of a leaf are referred to as pinnae; the compound leaves themselves are described as pinnate. A plant may be further subdivided in that the pinnae are themselves split into leaflets, or pinnules; these leaves are now twice pinnate, or bipinnate. A few plant species even have tripinnate leaves.
A kit lens is a “starter” lens sold bundled with an interchangeable-lens camera such as an SLR. It is generally a cheap lens priced at the lowest end of the manufacturer’s range, so as to not add much to a camera’s price. Originally, kit lenses were generally of normal focal length; more recently, kit lenses tend to be cheap zoom lenses that range from medium wide angle to mild telephoto. While prime standard lenses bundled with SLR cameras were generally sharp and fast enough for most kinds of photography, most kit zooms are deliberately limited in abilities, so that the camera purchaser will have an incentive to purchase additional lenses in the future.
Porter Michael “Mike” Peterson (born June 17, 1976 in Gainesville, Florida) is an American football Middle linebacker for the Jacksonville Jaguars of the National Football League. Also played for the Indianapolis Colts from 1999-2002.
College
He played collegiately at the University of Florida starting 24 of 42 games posted up 249 tackles, 3 force fumbles, 13 tackles for a loss and 8.5 sacks and was named to Associated Press All-SEC first-team.
Personal
Peterson is the older brother of Chicago Bears Running back Adrian Peterson. He currently resides in Gainesville, Florida with his wife Chantal and his son Mike Jr.
External links
Boehm Syndrome is a symptom-specific map-dot-fingerprint dystrophy of the cornea.
The epithelium is separated from the stroma by a membrane. In map-dot-fingerprint dystrophy, this membrane develops abnormally exhibiting a map-like appearance or perhaps opaque dots. Sometimes lines are formed that resemble small fingerprints. In some cases, this irregular structure can lead to painful epithelial erosions.
Symptoms
In Boehm Syndrome, recurrent epithelial erosions occur only when the eyelids are opened after some period of sleep. Recurrent corneal erosions may happen at any time of night or day. Boehm Syndrome does not. It occurs only when the inside of the eyelid tears away epithelial cells after minutes or hours of sleep. This may expose nerve endings, causing moderate to severe pain for hours or days. Once the erosions begin, even periods of brief sleep can exacerbate the problem.
Patients may describe the sensation as “my eyelids stick to my eyes when I try to open them, which is immediately followed by intense pain“. In some cases, this syndrome may disappear after one or more episodes. For others, it may be a lifelong disease.
Treatment
Treatment may include some of the standard procedures used on corneal erosions, like corneal abrasion.
There has been some success with the use of highly permeable extended-wear contact lenses worn only during sleep. These lenses, often referred to as “bandage lenses”, or “contact bandages” are prescribed with the lowest available prescription, as they simply act as a buffer between the surface of the cornea and the eyelids.
External links
- Facts About the Cornea and Corneal Disease The National Eye Institute (NEI)
In mathematics, the Weinstein conjecture refers to a general existence problem for periodic orbits of Hamiltonian or Reeb vector flows. More specifically, the current understanding is that a regular compact contact type level set of a Hamiltonian on a symplectic manifold should carry at least one periodic orbit of the Hamiltonian flow. The conjecture is stated for any Hamiltonian on any 2n-dimensional symplectic manifold.
By definition, a level set of contact type admits a contact form obtained by contracting the Hamiltonian vector field into the symplectic form. In this case, the Hamiltonian flow is a Reeb vector field on that level set. It is a fact that any contact manifold (M,α) can be embedded into a canonical symplectic manifold, called the symplectization of M, such that M is a contact type level set (of a canonically defined Hamiltonian) and the Reeb vector field is a Hamiltonian flow. That is, any contact manifold can be made to satisfy the requirements of the Weinstein conjecture. Since it is known that any orbit of a Hamiltonian flow is contained in a level set, the Weinstein conjecture is a statement about contact manifolds.
It has been known that any contact form is isotopic to a form that admits a closed Reeb orbit; for example, for any contact manifold there is a compatible open book decomposition, whose binding is a closed Reeb orbit. This is not enough to prove the Weinstein conjecture, though, because the Weinstein conjecture states that every contact form admits a closed Reeb orbit, while an open book determines a closed Reeb orbit for a form which is only isotopic to the given form.
The conjecture was formulated in 1978 by Alan Weinstein. In several cases, the existence of a periodic orbit was known. For instance, Rabinowitz showed that on star-shaped level sets of a Hamiltonian function on a symplectic manifold, there were always periodic orbits (Weinstein independently proved the special case of convex level sets). Weinstein observed that the hypotheses of several such existence theorems could be subsumed in the condition that the level set be of contact type. (Weinstein’s original conjecture included the condition that the first de Rham cohomology group of the level set is trivial; this hypothesis turned out to be unnecessary).
In October 2006, Clifford Taubes posted an article to the mathematics arXivThe Seiberg-Witten equations and the Weinstein conjecture, Clifford Taubes which contains a proposed proof of the conjecture for 3-dimensional manifolds. His proof uses a variant of Seiberg-Witten Floer homology and pursues a strategy analogous to his proof that the Seiberg-Witten and Gromov invariants are equivalent on a symplectic four-manifold. Taubes’s proof provides a shortcut to a the closely related program of proving the Weinstein conjecture by showing that the Embedded contact homology of any contact three-manifold is nontrivial.
References
- Ginzburg, Viktor. The Weinstein conjecture and the theorems of nearby and almost existence
- Taubes, C. H., The Seiberg-Witten equations and the Weinstein conjecture.
- Weinstein Alan, On the hypotheses of Rabinowitz’ periodic orbit theorem. Journal of Diff. Eq., Vol. 33 , 1979 , pp. 353 - 358.
A rotary compression pump works in cycles. Over each cycle a volume is created in contact with the cavity where pressure is to be lowered. By random motion, molecules from the vacuum pass into the volume created by the pump. This volume is then cut off from the cavity and compressed in contact with a one way valve. If the volume is compressed enough some of the molecules will pass through the valve.
The maximum efficiency of a rotary compression pump is the ratio between the volume in contact with the vacuum and the smallest contracted volume in contact with the valve. If the ratio is 1:1000 and the pump is exhausting to atmospheric pressure, the highest achievable vacuum is 1/1000 of atmospheric pressure. This corresponds to 0.76 Torr or 101.3 Pa. This limitation makes rotary compression pumps very hard to construct if lower pressures than about 1 Torr is to be achieved. The simplicity of the process makes the rotary compression pump cheap and it is widely used as a low vacuum pump or a fore pump to a diffusion pump.
See also rotary vane pump
Lukas Meindl GmbH & Co.KG, most commonly known as Meindl, is a German footwear manufacturer located in Kirchanschöring, Bavaria, known for its high-quality products, including popular boots for hiking.
- Meindl’s Official Web Site
- For the scientific field the same name see Plant physiology.
Plant Physiology is a peer-reviewed scientific journal that publishes articles on the physiology, biochemistry, cellular and molecular biology, genetics, biophysics, and environmental biology of plants. The journal is published by American Society of Plant Biologists on a monthly basis and has been published since 1926. It is a highly cited journal in the field with an impact factor over 5 in 2004.
The current editor in chief is American biologist Donald R. Ort.
A PV mount is a lens mount developed by Panavision for use with both 16 mm and 35 mm movie cameras. It is the only mount offered with Panavision cameras and Panavision-designed lenses, and since the company only rents its equipment, this is likely to remain an exclusive arrangement for the time being. However, Panavision also modifies (”Panavises”) its third party camera and lens equipment in the interest of allowing clients to retain their personal preferences regarding equipment. As they are the only company who can offer this, customers wanting to use Panavision lenses on non-Panavision cameras or vice versa must rent this equipment directly through Panavision. The mount itself contains four pronged flanges, one of which contains a locating pin in the center. This pin must be seated at the bottom of the camera lens mount, the only place in the seating where a complementary hole exists. This means that the lens can only be oriented in one position, which may be perceived as a disadvantage in certain shooting conditions. (Although this was originally likely by design to prevent mis-orienting anamorphic optics, it remains an issue for spherical lenses.) The mount is locked into place using a friction locking ring which, in conjunction with the four prongs of the flange, creates a very strong lens seating. This has become a crucial factor in recent years, as bigger lenses with zoom capabilities, longer focal lengths, or larger lens elements have raised the bar on requirements for mount stability. Furthermore, the tendency is for flange focal distance to become a more critical factor as sharper lenses, film stock with higher resolving power, and post-production workflows which preserve more of the original camera negative’s information continue to make technological progress and advancement. Flange focal distance is also more likely to be rigorously checked as tastes for wider angle lenses continue to push the envelope, as wider lenses have a much narrower tolerance for lens displacement. Because of all of these reasons, along with the exclusivity of the mount for virtually all shoots renting from Panavision, the PV mount has become a massive success since it was first released in conjunction with the Panaflex in 1972. Because of the strength of the mount, it remains, along with the Arri PL, one of only two lens mounts still in major usage by a large number of professional productions.
Technical specifications
- Flange focal distance: 57.15 mm
- Diameter: 49.50 mm
- Cameras:
- 35 mm all Panavision models and several Arri and Moviecam models (as available)
- 16 mm Panavision “Elaine”, several Arri and Aaton models (as available)