2,422 research outputs found
Steps towards the development of an experimentally verified simulation of pool nucleate boiling on a silicon wafer with artificial sites
Nucleate boiling is a very effective heat transfer cooling process, used in numerous industrial applications. Despite intensive research over decades, a reliable model of nucleate pool boiling is still not available. This paper presents a numerical and experimental investigation of nucleate boiling from artificial nucleation sites.
The numerical investigation described in the first section of the paper is carried out by a hybrid mechanistic numerical code first developed at the University of Ljubljana to simulate the temperature field in a heated stainless steel plate with a large number of nucleation sites during pool boiling of water at atmospheric pressure. It is now being redeveloped to interpret experiments on pool boiling at artificial sites on a silicon plate and as a design tool to investigate different arrangements of sites to achieve high heat fluxes. The code combines full simulation of the temperature field in the solid wall with simplified models or correlations for processes in the liquid-vapour region. The current capabilities and limitations of the code are reviewed and improvements are discussed. Examples are given of the removal of computational constraints on the activation of sites in close proximity and improvements to the bubble growth model. Preliminary simulations are presented to compare the wall conditions to be used in the experiments on silicon at Edinburgh University with the conditions in current experiments on thin metal foils at Ljubljana.
An experimental rig for boiling experiments with artificial cavities on a 0.38 mm thick silicon wafer immersed in FC-72, developed at Edinburgh University, is described in the second part of the paper
Regulation of peripheral inflammation by spinal p38 MAP kinase in rats.
BackgroundSomatic afferent input to the spinal cord from a peripheral inflammatory site can modulate the peripheral response. However, the intracellular signaling mechanisms in the spinal cord that regulate this linkage have not been defined. Previous studies suggest spinal cord p38 mitogen-activated protein (MAP) kinase and cytokines participate in nociceptive behavior. We therefore determined whether these pathways also regulate peripheral inflammation in rat adjuvant arthritis, which is a model of rheumatoid arthritis.Methods and findingsSelective blockade of spinal cord p38 MAP kinase by administering the p38 inhibitor SB203580 via intrathecal (IT) catheters in rats with adjuvant arthritis markedly suppressed paw swelling, inhibited synovial inflammation, and decreased radiographic evidence of joint destruction. The same dose of SB203580 delivered systemically had no effect, indicating that the effect was mediated by local concentrations in the neural compartment. Evaluation of articular gene expression by quantitative real-time PCR showed that spinal p38 inhibition markedly decreased synovial interleukin-1 and -6 and matrix metalloproteinase (MMP3) gene expression. Activation of p38 required tumor necrosis factor alpha (TNFalpha) in the nervous system because IT etanercept (a TNF inhibitor) given during adjuvant arthritis blocked spinal p38 phosphorylation and reduced clinical signs of adjuvant arthritis.ConclusionsThese data suggest that peripheral inflammation is sensed by the central nervous system (CNS), which subsequently activates stress-induced kinases in the spinal cord via a TNFalpha-dependent mechanism. Intracellular p38 MAP kinase signaling processes this information and profoundly modulates somatic inflammatory responses. Characterization of this mechanism could have clinical and basic research implications by supporting development of new treatments for arthritis and clarifying how the CNS regulates peripheral immune responses
Recommended from our members
Simulation and experimental investigation of pool boiling on a silicon wafer with artificial nucleation sites
This paper reports progress on a project to develop a design tool for large arrays of nucleation sites at specified locations to achieve high rates of cooling by pool boiling. The tool will be based on an improved version of a hybrid simulation, in which the 3-D temperature field in the wall is solved numerically, along with simple sub-models for bubble-driven heat transfer that require experimental calibration. Improvements to the computer code and progress with the experiments are reported briefly. The paper focuses on the development of a sub-model for the lateral coalescence of bubbles, which is shown to cause irregularity in the bubble production by a regular array of nucleation sites
High precision radial velocities with GIANO spectra
Radial velocities (RV) measured from near-infrared (NIR) spectra are a
potentially excellent tool to search for extrasolar planets around cool or
active stars. High resolution infrared (IR) spectrographs now available are
reaching the high precision of visible instruments, with a constant improvement
over time. GIANO is an infrared echelle spectrograph at the Telescopio
Nazionale Galileo (TNG) and it is a powerful tool to provide high resolution
spectra for accurate RV measurements of exoplanets and for chemical and
dynamical studies of stellar or extragalactic objects. No other high spectral
resolution IR instrument has GIANO's capability to cover the entire NIR
wavelength range (0.95-2.45 micron) in a single exposure. In this paper we
describe the ensemble of procedures that we have developed to measure high
precision RVs on GIANO spectra acquired during the Science Verification (SV)
run, using the telluric lines as wavelength reference. We used the Cross
Correlation Function (CCF) method to determine the velocity for both the star
and the telluric lines. For this purpose, we constructed two suitable digital
masks that include about 2000 stellar lines, and a similar number of telluric
lines. The method is applied to various targets with different spectral type,
from K2V to M8 stars. We reached different precisions mainly depending on the H
-magnitudes: for H ~ 5 we obtain an rms scatter of ~ 10 m s-1, while for H ~ 9
the standard deviation increases to ~ 50 - 80 m s-1. The corresponding
theoretical error expectations are ~4 m s-1 and 30 m s-1, respectively. Finally
we provide the RVs measured with our procedure for the targets observed during
GIANO Science Verification.Comment: 26 pages, 15 figures, 6 table
Mutual independence of critical temperature and superfluid density under pressure in optimally electron-doped superconducting LaFeAsOF
The superconducting properties of LaFeAsOF in conditions of
optimal electron-doping are investigated upon the application of external
pressure up to kbar. Measurements of muon-spin spectroscopy and dc
magnetometry evidence a clear mutual independence between the critical
temperature and the low-temperature saturation value for the ratio
(superfluid density over effective band mass of Cooper pairs).
Remarkably, a dramatic increase of % is reported for at
the maximum pressure value while is substantially unaffected in the
whole accessed experimental window. We argue and demonstrate that the
explanation for the observed results must take the effect of non-magnetic
impurities on multi-band superconductivity into account. In particular, the
unique possibility to modify the ratio between intra-band and inter-bands
scattering rates by acting on structural parameters while keeping the amount of
chemical disorder constant is a striking result of our proposed model.Comment: 8 pages (Main text: 5 pages. Paper merged with supplemental
information), 5 figure
Sound mining in the North : a guide to environmental regulation and best practices supporting social sustainability
Julkaistu versi
Intrinsic electronic superconducting phases at 60 K and 90 K in double-layer YBaCuO
We study superconducting transition temperature () of oxygen-doped
double-layer high-temperature superconductors YBaCuO (0
1) as a function of the oxygen dopant concentration
() and planar hole-doping concentration (). We find that ,
while clearly influenced by the development of the chain ordering as seen in
the plot, lies on a universal curve originating at the
critical hole concentration () = 1/16 in the plot.
Our analysis suggests that the universal behavior of () can be
understood in terms of the competition and collaboration of chemical-phases and
electronic-phases that exist in the system. We conclude that the global
superconductivity behavior of YBaCuO as a function of
doping is electronically driven and dictated by pristine electronic phases at
magic doping numbers that follow the hierarchical order based on , such as
2 , 3 and 4 . We find that there are
at least two intrinsic electronic superconducting phases of = 60 K at 2
= 1/8 and = 90 K at 3 = 3/16.Comment: 4 pages, 2 figure
Anisotropic in-plane optical conductivity in detwinned Ba(Fe1-xCox)2As2
We study the anisotropic in-plane optical conductivity of detwinned
Ba(Fe1-xCox)2As2 single crystals for x=0, 2.5% and 4.5% in a broad energy range
(3 meV-5 eV) across their structural and magnetic transitions. For temperatures
below the Neel transition, the topology of the reconstructed Fermi surface,
combined with the distinct behavior of the scattering rates, determines the
anisotropy of the low frequency optical response. For the itinerant charge
carriers, we are able to disentangle the evolution of the Drude weights and
scattering rates and to observe their enhancement along the orthorhombic
antiferromagnetic a-axis with respect to the ferromagnetic b-axis. For
temperatures above Ts, uniaxial stress leads to a finite in-plane anisotropy.
The anisotropy of the optical conductivity, leading to a significant dichroism,
extends to high frequencies in the mid- and near-infrared regions. The
temperature dependence of the dichroism at all dopings scales with the
anisotropy ratio of the dc conductivity, suggesting the electronic nature of
the structural transition. Our findings bear testimony to a large nematic
susceptibility that couples very effectively to the uniaxial lattice strain. In
order to clarify the subtle interplay of magnetism and Fermi surface topology
we compare our results with theoretical calculations obtained from density
functional theory within the full-potential linear augmented plane-wave method.Comment: 17 pages, 9 figure
- …