749 research outputs found
Endothermic salts integrated in impermeable suits do not reduce heat strain during exercise
Wearing impermeable garments during work inherently leads to heat strain, even in cold
environments [1]. Phase change materials (mainly paraffin’s or salt [4]) may be used as a thermal
buffer (e.g. [2]) to reduce initial heat stress. Salts can also be used to absorb sweat, which may
enhance the cooling power from the skin.
Recently, specific encapsulated salts utilising KSCN (potassium thiocyanate) have been developed
that consume energy when the KSCN dissolves in water. The heat consumed when the KSCN
(present inside 150 g of capsules containing 60% KSCN salt) dissolves in water is 22410 J (249 J/g *
60% * 150 g). When this solving takes place over a period of 30 minutes, the average power
transfer is 12 W. One (1) g of KSCN-containing capsules absorbs close to 1 g of moisture. If we
assume that 150 g sweat extra can be evaporated from the skin, this yields an extra cooling power
of 182 W for 30 minutes. However this evaporated water from the skin is subsequently absorbed
by the KSCN in the capsules. During this absorption from the gas phase, the condensation heat is
released to the KSCN salt: about 182 W for 30 minutes. However, we hypothesise that this
condensation heat will be partly transferred to the body and partly to the environment [3],
providing a net benefit to the body.
Thus, the total cooling effect due to the salt capsules is composed of two parts:
• The cooling effect of about 12 W due to the heat consumption by the dissolving of the salts in
water;
• The cooling effect of maximal 182 W, which equals the difference between the evaporative
heat and the condensation heat. The latter is generated in the salt capsules that transfer part
of the heat to the environment.
The overall cooling effect should therefore be in between 12 W and 194 W.
The purpose of our study was to test the efficacy of a KSCN-based absorbing salt as a PCM for use
within impermeable protective clothing. We tested the PCM during 20 min of moderate exercise
in a hot (35°C, 40% relative humidity) environment, and hypothesized that thermal strain would be
lower in the PCM compared to the non-PCM condition
An unusual cause of acute cardiogenic shock in the operating room
A 51-year-old man with a renal carcinoma with inferior vena cava (IVC) invasion was referred to our hospital for the performance of a radical nephrectomy with IVC thrombus excision. To prevent embolism, an IVC filter was implanted the day before surgery below the suprahepatic veins. On nephrectomy completion, the clinical status of the patient started to deteriorate and an unsuccessful attempt was made to excise the IVC thrombus. The patient developed profound refractory hypotension without significant bleeding and worsening splanchnic stasis was noted. A transesophageal echocardiogram was immediately performed in the operating room, revealing a hemispheric mass protruding from the IVC ostium to the right atrium, completely blocking all venous return. Volume depletion was evident by low left and right atrial volumes and increased septum mobility. No other abnormalities were found that could explain the shock, namely ventricular dysfunction or valvular disease. Cardiac surgery consultation was immediately obtained, ultimately deciding to perform a median sternotomy with direct exploration of right atrium. Under cardiopulmonary bypass, a 6-cm long thrombotic mass was identified, involving the IVC filter, blocking all lower body venous return; the removal of the mass reversed the shock. The patient had an uneventful recovery. Adverse outcomes associated with IVC filters are common. Our case highlights the importance of a team approach to rapid changes in hemodynamic status in the operating room, including the surgeon, the anesthesiologist, and the cardiologist. It also emphasizes the pivotal role of transesophageal echocardiogram in the clinical evaluation of severely unstable patien
Perturbative QCD Fragmentation Functions for and Production
The dominant production mechanism for bound states in high
energy processes is the production of a high energy or quark,
followed by its fragmentation into the state. We calculate the
fragmentation functions for the production of the S-wave states and
to leading order in the QCD coupling constant. The fragmentation
probabilities for and
are approximately and , while those
for and are smaller by almost two
orders of magnitude.Comment: Latex, 12 pages, 3 figures available upon request, NUHEP-TH-93-
QCD sum rules analysis of the rare B_c \rar X\nu\bar{\nu} decays
Taking into account the gluon correction contributions to the correlation
function, the form factors relevant to the rare B_c \rar X \nu\bar{\nu}
decays are calculated in the framework of the three point QCD sum rules, where
stands for axial vector particle, , and vector particles,
. The total decay width as well as the branching ratio of these
decays are evaluated using the dependent expressions of the form factors.
A comparison of our results with the predictions of the relativistic
constituent quark model is presented.Comment: 21 Pages, 2 Figures and 5 Table
Analysis of the vector and axialvector mesons with QCD sum rules
In this article, we study the vector and axialvector mesons with the
QCD sum rules, and make reasonable predictions for the masses and decay
constants, then calculate the leptonic decay widths. The present predictions
for the masses and decay constants can be confronted with the experimental data
in the future. We can also take the masses and decay constants as basic input
parameters and study other phenomenological quantities with the three-point
vacuum correlation functions via the QCD sum rules.Comment: 14 pages, 16 figure
Using Heavy Quark Spin Symmetry in Semileptonic Decays
The form factors parameterizing the B_c semileptonic matrix elements can be
related to a few invariant functions if the decoupling of the spin of the heavy
quarks in B_c and in the mesons produced in the semileptonic decays is
exploited. We compute the form factors as overlap integral of the meson
wave-functions obtained using a QCD relativistic potential model, and give
predictions for semileptonic and non-leptonic B_c decay modes. We also discuss
possible experimental tests of the heavy quark spin symmetry in B_c decays.Comment: RevTex, 22 pages, 2 figure
Top A_FB at the Tevatron vs. charge asymmetry at the LHC in chiral U(1) flavor models with flavored Higgs doublets
We consider the top forward-backward (FB) asymmetry at the Tevatron and top
charge asymmetry at the LHC within chiral U(1)^\prime models with
flavor-dependent U(1)^\prime charges and flavored Higgs fields, which were
introduced in the ref. [65]. The models could enhance not only the top
forward-backward asymmetry at Tevatron, but also the top charge asymmetry at
LHC, without too large same-sign top pair production rates. We identify
parameter spaces for the U(1)^\prime gauge boson and (pseudo)scalar Higgs
bosons where all the experimental data could be accommodated, including the
case with about 125 GeV Higgs boson, as suggested recently by ATLAS and CMS.Comment: 11 pages, 6 figures, figures and discussion adde
Hierarchies from Fluxes in String Compactifications
Warped compactifications with significant warping provide one of the few
known mechanisms for naturally generating large hierarchies of physical scales.
We demonstrate that this mechanism is realizable in string theory, and give
examples involving orientifold compactifications of IIB string theory and
F-theory compactifications on Calabi-Yau four-folds. In each case, the
hierarchy of scales is fixed by a choice of RR and NS fluxes in the compact
manifold. Our solutions involve compactifications of the Klebanov-Strassler
gravity dual to a confining N=1 supersymmetric gauge theory,and the hierarchy
reflects the small scale of chiral symmetry breaking in the dual gauge theory.Comment: 35 pages. v2: minor eqn. and reference change
The Effective Lagrangian in the Randall-Sundrum Model and Electroweak Physics
We consider the two-brane Randall-Sundrum (RS) model with bulk gauge fields.
We carefully match the bulk theory to a 4D low-energy effective Lagrangian. In
addition to the four-fermion operators induced by KK exchange we find that
large negative S and T parameters are induced in the effective theory. This is
a tree-level effect and is a consequence of the shapes of the W and Z wave
functions in the bulk. Such effects are generic in extra dimensional theories
where the standard model (SM) gauge bosons have non-uniform wave functions
along the extra dimension. The corrections to precision electroweak observables
in the RS model are mostly dominated by S. We fit the parameters of the RS
model to the experimental data and find somewhat stronger bounds than
previously obtained; however, the standard model bound on the Higgs mass from
precision measurements can only be slightly relaxed in this theory.Comment: 16 pages, LaTeX, 1 figure included, uses JHEP.cls, extended
introduction, added reference
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