6,123 research outputs found
Diisopropylamide and TMP turbo-grignard reagents : a structural rationale for their contrasting reactivities
A neutral dimeric molecule in crystal form, the diisopropylamido turbo-Grignard reagent "(iPr2N)MgClâ
LiCl" (see structure; blue N, red O, green Mg, yellow Cl, black C) separates into several charged ate species in dynamic exchange with each other in THF solution as determined by a combination of EXSY and DOSY NMR studies
Patients presenting with miliaria while wearing flame resistant clothing in high ambient temperatures: a case series
<p>Abstract</p> <p>Introduction</p> <p>Clothing can be a cause of occupational dermatitis. Frequent causes of clothing-related dermatological problems can be the fabric itself and/or chemical additives used in the laundering process, friction from certain fabrics excessively rubbing the skin, or heat retention from perspiration-soaked clothing in hot working environments. To the best of our knowledge, these are the first reported cases of miliaria rubra associated with prolonged use of flame resistant clothing in the medical literature.</p> <p>Case presentation</p> <p>We report 18 cases (14 men and 4 women, with an age range of 19 to 37 years) of moderate to severe skin irritation associated with wearing flame resistant clothing in hot arid environments (temperature range: 39 to 50°C, 5% to 25% relative humidity). We describe the medical history in detail of a 23-year-old Caucasian woman and a 31-year-old African-American man. A summary of the other 16 patients is also provided.</p> <p>Conclusions</p> <p>These cases illustrate the potential serious nature of miliaria with superimposed <it>Staphylococcus </it>infections. All 18 patients fully recovered with topical skin treatment and modifications to their dress ensemble. Clothing, in particular blend fabrics, must be thoroughly laundered to adequately remove detergent residue. While in hot environments, individuals with sensitive skin should take the necessary precautions such as regular changing of clothing and good personal hygiene to ensure that their skin remains as dry and clean as possible. It is also important that they report to their health care provider as soon as skin irritation or rash appears to initiate any necessary medical procedures. Miliaria rubra can take a week or longer to clear, so removal of exposure to certain fabric types may be necessary.</p
The halo white dwarf population
Halo white dwarfs can provide important information about the properties and
evolution of the galactic halo. In this paper we compute, assuming a standard
IMF and updated models of white dwarf cooling, the expected luminosity
function, both in luminosity and in visual magnitude, for different star
formation rates. We show that a deep enough survey (limiting magnitude > 20)
could provide important information about the halo age and the duration of the
formation stage. We also show that the number of white dwarfs produced using
the recently proposed biased IMFs cannot represent a large fraction of the halo
dark matter if they are constrained by the presently observed luminosity
function. Furthermore, we show that a robust determination of the bright
portion of the luminosity function can provide strong constraints on the
allowable IMF shapes.Comment: 29 pages (AASTeX), 7 eps figures included, accepted for publication
in Ap
Probing Unstable Massive Neutrinos with Current Cosmic Microwave Background Observations
The pattern of anisotropies in the Cosmic Microwave Background depends upon
the masses and lifetimes of the three neutrino species. A neutrino species of
mass greater than 10 eV with lifetime between 10^{13} sec and 10^{17} sec
leaves a very distinct signature (due to the integrated Sachs-Wolfe effect):
the anisotropies at large angles are predicted to be comparable to those on
degree scales. Present data exclude such a possibility and hence this region of
parameter space. For eV, sec, we find
an interesting possibility: the Integrated Sachs Wolfe peak produced by the
decaying neutrino in low- models mimics the acoustic peak expected in
an model.Comment: 5 pages, 4 figure
Modeling the Low State Spectrum of the X-Ray Nova XTE J1118+480
Based on recent multiwavelength observations of the new X-ray nova XTE
J1118+480, we can place strong constraints on the geometry of the accretion
flow in which a low/hard state spectrum, characteristic of an accreting black
hole binary, is produced. We argue that the absence of any soft blackbody-like
component in the X-ray band implies the existence of an extended hot
optically-thin region, with the optically-thick cool disk truncated at some
radius R_{tr} > 55 R_{Schw}. We show that such a model can indeed reproduce the
main features of the observed spectrum: the relatively high optical to X-ray
ratio, the sharp downturn in the far UV band and the hard X-ray spectrum. The
absence of the disk blackbody component also underscores the requirement that
the seed photons for thermal Comptonization be produced locally in the hot
flow, e.g. via synchrotron radiation. We attribute the observed spectral break
at 2 keV to absorption in a warm, partially ionized gas.Comment: 6 pages, including 1 figure; LaTeX (emulateapj5.sty), to appear in
Ap
Hubble Space Telescope WFPC-2 Imaging of Cassiopeia A
The young SNR Cassiopeia A was imaged with WFPC-2 through four filters
selected to capture the complete velocity range of the remnant's main shell in
several important emission lines. Primary lines detected were [O III]
4959,5007, [N II] 6583, [S II] 6716,6731 + [O II] 7319,7330 + [O I] 6300,6364,
and [S III] 9069,9532. About 3/4th of the remnant's main shell was imaged in
all four filters. Considerable detail is observed in the reverse-shocked ejecta
with typical knot scale lengths of 0.2"-0.4" (1 - 2 x 10^16 cm). Both bright
and faint emission features appear highly clumped. Large differences in [S III]
and [O III] line intensities indicating chemical abundance differences are also
seen, particularly in knots located along the bright northern limb and near the
base of the northeast jet. A line of curved overlapping filament in the
remnant's northwestern rim appears to mark the location of the remnant's
reverse shock front in this region. Finger-like ejecta structures elsewhere
suggest cases where the reverse shock front is encountering the remnant's
clumped ejecta. Narrow-band [N II] images of the remnant's circumstellar knots
("QSFs") reveal them to be 0.1"-0.6" thick knots and filaments, often with
diffuse edges facing away from the center of expansion. Three color composite
images of the whole remnant and certain sections along with individual filter
enlargements of selected regions of the bright optical shell are presented and
discussed.Comment: 26 pages, 12 figures Accepted to the Astronomical Journa
Excited states of linear polyenes
We present density matrix renormalisation group calculations of the Pariser-
Parr-Pople-Peierls model of linear polyenes within the adiabatic approximation.
We calculate the vertical and relaxed transition energies, and relaxed
geometries for various excitations on long chains. The triplet (3Bu+) and even-
parity singlet (2Ag+) states have a 2-soliton and 4-soliton form, respectively,
both with large relaxation energies. The dipole-allowed (1Bu-) state forms an
exciton-polaron and has a very small relaxation energy. The relaxed energy of
the 2Ag+ state lies below that of the 1Bu- state. We observe an attraction
between the soliton-antisoliton pairs in the 2Ag+ state. The calculated
excitation energies agree well with the observed values for polyene oligomers;
the agreement with polyacetylene thin films is less good, and we comment on the
possible sources of the discrepencies. The photoinduced absorption is
interpreted. The spin-spin correlation function shows that the unpaired spins
coincide with the geometrical soliton positions. We study the roles of
electron-electron interactions and electron-lattice coupling in determining the
excitation energies and soliton structures. The electronic interactions play
the key role in determining the ground state dimerisation and the excited state
transition energies.Comment: LaTeX, 15 pages, 9 figure
Recommended from our members
Pyrochemical Glovebox Line Replacement and Modernization Effort at Los Alamos National Laboratory Plutonium Facility.
Los Alamos National Laboratory (LANL), as part of the stockpile stewardship mission, is developing the capability to manufacture replacement pits for the United States nuclear weapon stockpile. Part of this effort requires that the various manufacturing activities formerly performed at the Rocky Flats be reconstructed at LANL, modernized to improve operation, and re-certified for pit production. Part of this effort requires that new pyrochemical metal production facilities be installed in TA-55 to replace existing outdated equipment. The purpose of this effort is design, build/procure, assemble, cold test, and support installation activities for ten pyrochemical processing gloveboxes and processing support equipment for insertion into a selected PF-4 laboratory. Eight of the gloveboxes will be connected to a common trolley tunnel with a state-of-the-art automated transport system that can access each glovebox. Five of those gloveboxes will be designed to accommodate standard water-cooled pyrochemical processing furnaces with appropriate lift mechanisms for handling the furnace products and processing hardware. Another glovebox will be designed to accommodate an improved breaking press that will be designed/procured to break alpha metal up to a thickness of l-inch, eliminate introduction of hydraulic oil to the glovebox environment, provide appropriate shielding for prevention of glovebox damage due to shrapnel projectiles, and use interchangeable impact tools in order to be able to process both contaminated and clean metals with the same machine. In addition, a storage glovebox and a distillation glovebox (already developed) will be attached to the transport system. Two other gloveboxes, one accommodating two casting furnaces and another storage glovebox, will be installed in the laboratory independent of the transport system. A transfer system (trolley) will be incorporated to handle material flow between the pyrochemical furnace gloveboxes, the press glovebox, the storage glovebox, and the distillation glovebox. The trolley will be very simple to operate, able to accommodate at least 50 pounds, require minimal maintenance, and be able to be requested and operated fiom any of the glovebox locations on the line. The transfer system will be capable of discharging its load in some manner through the open door to the entrance of each of the gloveboxes on the line. This may be an automatic function with manual selection for unusual loads or a completely manual operation. An existing commercial or otherwise proven system will be used if possible to minimize the design and test time needed for the system. Two commercial systems examined so far are the Montrac monorail type system available from Montech Incorporated and the Linear Synchronous Motor system available from MagneMotion Inc. Work to be completed during FY02 includes glovebox design, transport system industry research, demonstration of selected commercial transport systems, transport system conceptual design, metal breaking press conceptual design, and glovebox furnace lift mechanism design. Glovebox fabrication/procurement, material transport system procurement, press procurement, lift mechanism procurement, system assembly and staging, system testing, assistance in installing the system into TA-55, assistance with NMT configuration management approvals, and shakeout testing of the system is scheduled for FY03 and FY04. The goal is to have a fully functioning and modernized pyrochemical processing line in PF-4 ready for processing sometime in the first or second quarter of FY04
Lithium and aluminium carbamato derivatives of the utility amide 2, 2, 6, 6- tetramethylpiperidide
Insertion of CO2 into the metal-N bond of a series of synthetically-important alkali-metal TMP (2,2,6,6-tetramethylpiperidide) complexes has been studied. Determined by X-ray crystallography, the molecular structure of the TMEDA-solvated Li derivative shows a central 8-membered (LiOCO)2 ring lying in a chair conformation with distorted tetrahedral lithium centres. While trying to obtain crystals of a THF solvated derivative, a mixed carbonato/carbamato dodecanuclear lithium cluster was formed containing two central (CO3)2- fragments and eight O2CTMP ligands with four distinct bonding modes. A bisalkylaluminium carbamato complex has also been prepared via two different methods (CO2 insertion into a pre-formed Al-N bond and ligand transfer from the corresponding lithium reagent) which adopts a dimeric structure in the solid state
The Somatosensory Link in Fibromyalgia: Functional Connectivity of the Primary Somatosensory Cortex Is Altered by Sustained Pain and Is Associated With Clinical/Autonomic Dysfunction
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111091/1/art39043.pd
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