790 research outputs found
On Heat-Treatable Copper-Chromium Alloy, 1
A mother alloy of 10% Cr and 90% Cu was prepared by sintering. This was alloyed with the Cu melt and Cu-Cr alloys containing about 0.5% Cr was obtained. These alloys could be deformed easily in both the hot and cold states. By measuring the hardness change, age-hardening properties of cast alloys were studied, which were quenched from 950 deg and aged at 300 to 700 deg for 1 hour. The maximum hardness was obtained with the tempering temperature of 500 deg. For the temperature of solution-treatment, 950 deg was insufficient and that above 1000 deg necessary. For the tempering time, a treatment at 500 deg for 1 hr. or at 450 deg for 3 hrs. yielded the maximum hardness. As for the properties for electrical conductors, 3 kinds of wires (diam. 2 mm.) were made: (1) after cold-drawn to 2 mm., solution-treated, quenched, and then tempered (500 deg, 1 hr.); (2) after quenching, cold-drawn (75% reduction) to 2 mm. and tempered (500 deg, 1 hr.); and (3) after quenching, cold-drawn (81%) to intermediate diameter, tempered (500 deg, 1 hr.) and then cold-drawn (88%) again. Properties obtained for the 3 kinds, respectively, were as follows: conductivity 91, 90, and 86%. Tensile strength and strength for electrical conductivity are given
Histamine N-methyltransferase Modulates Human Bronchial Smooth Muscle Contraction
To elucidate the modulatory role of histamine-degrading enzymes in
airway constrictor responses, human bronchial strips were studied
under isometric conditions in vitro. Pretreatment of tissues with
the histamine N-methyltransferase (HMT) inhibitor SKF 91488
specifically potentiated the contractile responses to histamine,
causing a leftward displacement of the concentration response curves,
whereas the diamine oxidase inhibitor aminoguanidine had no effect.
This potentiation was attenuated by mechanical removal of the
epithelium. The HMT activity was detected in the human bronchi,
which was less in the epithelium-denuded tissues than the
epithelium-intact tissues. These results suggest that HMT localized
to the airway epithelium may play a protective role against
histamine-mediated bronchoconstriction in humans
Kerr/CFT Correspondence in the Low Energy Limit of Heterotic String Theory
We investigate the recently proposed Kerr/CFT correspondence in the context
of heterotic string theory. The Kerr/CFT correspondence states that the
near-horizon states of an extremal four (or higher) dimensional black hole
could be identified with a certain chiral conformal field theory under the
conjecture that the central charges from the non-gravitational fields vanish.
The corresponding Virasoro algebra is generated by a class of diffeomorphisms
which preserves the appropriate boundary conditions on the near-horizon
geometry. To understand the chiral conformal field theory, we consider the
class of extremal Kerr-Sen black hole (that contains three non-gravitational
fields) as a class of solutions in the low energy limit (effective field
theory) of heterotic string theory. We derive the expression of the conserved
charges for the extremal Kerr-Sen solutions that contain dilaton, abelian gauge
filed and antisymmetric tensor filed. We confirm and extend the validity of the
conjecture (that the central charges from the non-gravitational fields vanish)
for theories including antisymmetric tensor fields. We combine the calculated
central charges with the expected form of the temperature using the Cardy
formula to obtain the entropy of the extremal black hole microscopically; in
agreement with the macroscopic Bekenstein-Hawking entropy of the extremal black
hole.Comment: 14 pages, a few sentences added to the introduction, version to
appear in JHE
Upper airway dynamics during negative expiratory pressure in apneic and non-apneic awake snorers
BACKGROUND: The ability of negative expiratory pressure (NEP) technique to differentiate between awake snorers with and without obstructive sleep apnea-hypopnea (OSAH) was investigated. METHODS: Forty-eight subjects with sleep disordered breathing (SDB) and 7 healthy subjects, as non-snorer controls, underwent the NEP application of -5 and -7 cmH(2)O in the seated and supine position during wakefulness, after performing a sleep study. The upper airway collapsibility was assessed by computing the volume exhaled during the first 0.5 sec. (V,NEP(0.5)) and 1 sec. (V,NEP(1)) following the NEP start. RESULTS: Patients with severe (AHI ≥ 30) (n = 19) and mild-to-moderate (AHI <30 and >5) (n = 15) OSAH had lower V,NEP(0.5 )(340 ± 88 ml) as compared to snorers (AHI ≤ 5) (n = 14) (427 ± 101 ml; p < 0.01) and controls (n = 7) (492 ± 69 ml; p < 0.001) in the supine position with NEP -5 cmH(2)O. Less significant differences among the different groups were observed for V,NEP(0.5 )in the seated position with NEP -5 cmH(2)O and in both positions with NEP -7 cmH(2)O (only OSAH patients vs controls, p < 0.001). Similar results were obtained for V,NEP(1 )in either position by using both NEP -5 cmH(2)O and -7 cmH(2)O. In spite of this, a substantial overlapping of V,NEP(0.5 )and V,NEP(1 )between snorers and OSAH patients did not allow to identify a reliable diagnostic cut-off level. An inverse correlation with AHI was found for V,NEP(0.5 )in the supine position with NEP -5 cmH(2)O (r(s )= -0.46, p < 0.05) in severe OSAH patients. CONCLUSION: The awake OSAH patients exhibit values of V,NEP(0.5 )and V,NEP(1 )lesser than those of awake snorers. The NEP technique, however, appears to have a limited usefulness as clinical tool for routine screening of the OSAH patients during wakefulness
Holographic Wilsonian flows and emergent fermions in extremal charged black holes
We study holographic Wilsonian RG in a general class of asymptotically AdS
backgrounds with a U(1) gauge field. We consider free charged Dirac fermions in
such a background, and integrate them up to an intermediate radial distance,
yielding an equivalent low energy dual field theory. The new ingredient,
compared to scalars, involves a `generalized' basis of coherent states which
labels a particular half of the fermion components as coordinates or momenta,
depending on the choice of quantization (standard or alternative). We apply
this technology to explicitly compute RG flows of charged fermionic operators
and their composites (double trace operators) in field theories dual to (a)
pure AdS and (b) extremal charged black hole geometries. The flow diagrams and
fixed points are determined explicitly. In the case of the extremal black hole,
the RG flows connect two fixed points at the UV AdS boundary to two fixed
points at the IR AdS_2 region. The double trace flow is shown, both numerically
and analytically, to develop a pole singularity in the AdS_2 region at low
frequency and near the Fermi momentum, which can be traced to the appearance of
massless fermion modes on the low energy cut-off surface. The low energy field
theory action we derive exactly agrees with the semi-holographic action
proposed by Faulkner and Polchinski in arXiv:1001.5049 [hep-th]. In terms of
field theory, the holographic version of Wilsonian RG leads to a quantum theory
with random sources. In the extremal black hole background the random sources
become `light' in the AdS_2 region near the Fermi surface and emerge as new
dynamical degrees of freedom.Comment: 37 pages (including 8 pages of appendix), 10 figures and 2 table
On Holographic description of the Kerr-Newman-AdS-dS black holes
In this paper, we study the holographic description of the generic
four-dimensional non-extremal Kerr-Newman-AdS-dS black holes. We find that if
focusing on the near-horizon region, for the massless scalar scattering in the
low-frequency limit, there exists hidden conformal symmetry on the solution
space. Similar to the Kerr case, this suggests that the Kerr-Newman-AdS-dS
black hole is dual to a two-dimensional CFT with central charges
and temperatures
. The macroscopic Bekenstein-Hawking
entropy could be recovered from the microscopic counting in dual CFT via the
Cardy formula. Using the Minkowski prescription, we compute the real-time
correlators of the scalar, photon and graviton in near horizon geometry of near
extremal Kerr-AdS-dS black hole. In all these cases, the retarded Green's
function and the corresponding absorption cross section are in perfect match
with CFT prediction. We further discuss the low-frequency scattering of a
charged scalar by a Kerr-Newman-AdS-dS black hole and find the dual CFT
description.Comment: 22 pages; minor corrections, conlusion unchanged, references
added;published versio
Hidden Conformal Symmetry of the Reissner-Nordstr{\o}m Black Holes
Motivated by recent progresses in the holographic descriptions of the Kerr
and Reissner-Nordstr{\o}m (RN) black holes, we explore the hidden conformal
symmetry of nonextremal uplifted 5D RN black hole by studying the near horizon
wave equation of a massless scalar field propagating in this background.
Similar to the Kerr black hole case, this hidden symmetry is broken by the
periodicity of the associated angle coordinate in the background geometry, but
the results somehow testify the dual CFT description of the nonextremal RN
black holes. The duality is further supported by matching of the entropies and
absorption cross sections calculated from both CFT and gravity sides.Comment: 14 pages, no figur
Holographic Dual of Linear Dilaton Black Hole in Einstein-Maxwell-Dilaton-Axion Gravity
Motivated by the recently proposed Kerr/CFT correspondence, we investigate
the holographic dual of the extremal and non-extremal rotating linear dilaton
black hole in Einstein-Maxwell-Dilaton-Axion Gravity. For the case of extremal
black hole, by imposing the appropriate boundary condition at spatial infinity
of the near horizon extremal geometry, the Virasoro algebra of conserved
charges associated with the asymptotic symmetry group is obtained. It is shown
that the microscopic entropy of the dual conformal field given by Cardy formula
exactly agrees with Bekenstein-Hawking entropy of extremal black hole. Then, by
rewriting the wave equation of massless scalar field with sufficient low energy
as the SL(2, R)SL(2, R) Casimir operator, we find the hidden
conformal symmetry of the non-extremal linear dilaton black hole, which implies
that the non-extremal rotating linear dilaton black hole is holographically
dual to a two dimensional conformal field theory with the non-zero left and
right temperatures. Furthermore, it is shown that the entropy of non-extremal
black hole can be reproduced by using Cardy formula.Comment: 15 pages, no figure, published versio
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