2,618 research outputs found
Rotational Cooling of Polar Molecules by Stark-tuned Cavity Resonance
A general scheme for rotational cooling of diatomic heteronuclear molecules
is proposed. It uses a superconducting microwave cavity to enhance the
spontaneous decay via Purcell effect. Rotational cooling can be induced by
sequentially tuning each rotational transition to cavity resonance, starting
from the highest transition level to the lowest using an electric field.
Electrostatic multipoles can be used to provide large confinement volume with
essentially homogeneous background electric field.Comment: 10 pages, 6 figure
Correlation Between Polymer Packing And Gas Transport Properties For Co2/N2 Separation In Glassy Fluorinated Polyimide Membrane
Gas separation performance of a membrane highly hinges on its physical properties. In this study, the interplay between polymer packing of a membrane and its gas transport behaviours (permeability and selectivity) was investigated through a series of 6FDA-DAM:DABA (3:2) polyimide membranes with different polymer compactness. The chemical structure and the polymer packing of the resulting membrane were characterized using attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and packing density measurement, respectively. CO2/N2 separation efficiency of the membrane was evaluated at 25oC with feed pressure up to 6 bar. N2 permeability was found to rely on the membrane’s packing density, which signified its greater dependence on molecular sieving. In contrast, sorption showed a more vital role in determining the CO2 permeability. In this work, the membrane with a final thickness of 97±2 μm had successfully surpassed the Robeson’s 2008 upper bound plot with a CO2 permeability of 83 Barrer and CO2/N2 selectivity of 97 at 3 bar permeation
XAX: a multi-ton, multi-target detection system for dark matter, double beta decay and pp solar neutrinos
A multi-target detection system XAX, comprising concentric 10 ton targets of
136Xe and 129/131Xe, together with a geometrically similar or larger target of
liquid Ar, is described. Each is configured as a two-phase
scintillation/ionization TPC detector, enhanced by a full 4pi array of
ultra-low radioactivity Quartz Photon Intensifying Detectors (QUPIDs) replacing
the conventional photomultipliers for detection of scintillation light. It is
shown that background levels in XAX can be reduced to the level required for
dark matter particle (WIMP) mass measurement at a 10^-10 pb WIMP-nucleon cross
section, with single-event sensitivity below 10^-11 pb. The use of multiple
target elements allows for confirmation of the A^2 dependence of a coherent
cross section, and the different Xe isotopes provide information on the
spin-dependence of the dark matter interaction. The event rates observed by Xe
and Ar would modulate annually with opposite phases from each other for WIMP
mass >~100 GeV/c^2. The large target mass of 136Xe and high degree of
background reduction allow neutrinoless double beta decay to be observed with
lifetimes of 10^27-10^28 years, corresponding to the Majorana neutrino mass
range 0.01-0.1 eV, the most likely range from observed neutrino mass
differences. The use of a 136Xe-depleted 129/131Xe target will also allow
measurement of the pp solar neutrino spectrum to a precision of 1-2%.Comment: 16 pages with 17 figure
Modelling cohesive-frictional particulate solids for bulk handling applications
Many powders and particulate solids are cohesive in nature and the strength often exhibits dependence on the consolidation stress. As a result, the stress history in the material leading up to a handling scenario needs to be considered when evaluating its handleability. This paper outlines the development of a DEM contact model accounting for plasticity and adhesion force, which is shown to be suitable for modelling the stress history dependent cohesive strength. The model was used to simulate the confined consolidation and the subsequent unconfined loading of iron ore fines with particle sizes up to 1.18mm. The predicted flow function was found to be comparable to the experimental results
Transcriptional profiles of Burkholderia pseudomallei reveal the direct and indirect roles of Sigma E under oxidative stress conditions
This is the final version of the article. Available from BioMed Central via the DOI in this record.BACKGROUND: Burkholderia pseudomallei, the causative agent of melioidosis, is a Gram-negative bacterium widely distributed in soil and water in endemic areas. This soil saprophyte can survive harsh environmental conditions, even in soils where herbicides (containing superoxide generators) are abundant. Sigma factor E (σE) is a key regulator of extra-cytoplasmic stress response in Gram-negative bacteria. In this study, we identified the B. pseudomallei σE regulon and characterized the indirect role that σE plays in the regulation of spermidine, contributing to the successful survival of B. pseudomallei in stressful environments. RESULTS: Changes in the global transcriptional profiles of B. pseudomallei wild type and σE mutant under physiological and oxidative stress (hydrogen peroxide) conditions were determined. We identified 307 up-regulated genes under oxidative stress condition. Comparison of the transcriptional profiles of B. pseudomallei wild type and σE mutant under control or oxidative stress conditions identified 85 oxidative-responsive genes regulated by σE, including genes involved in cell membrane repair, maintenance of protein folding and oxidative stress response and potential virulence factors such as a type VI secretion system (T6SS). Importantly, we identified that the speG gene, encoding spermidine-acetyltransferase, is a novel member of the B. pseudomallei σE regulon. The expression of speG was regulated by σE, implying that σE plays an indirect role in the regulation of physiological level of spermidine to protect the bacteria during oxidative stress. CONCLUSION: This study identified B. pseudomallei genes directly regulated by σE in response to oxidative stress and revealed the indirect role of σE in the regulation of the polyamine spermidine (via regulation of speG) for bacterial cell protection during oxidative stress. This study provides new insights into the regulatory mechanisms by which σE contributes to the survival of B. pseudomallei under stressful conditions.This work was supported by the National Science and Technology Development Agency and Siriraj Grant for Research and Development. S. Jitprasutwit was supported by the Royal Golden Jubilee Ph. D. Program (PHD0270/2551)
Evidence for field-induced excitations in low-temperature thermal conductivity of Bi_2Sr_2CaCu_2O_8
The thermal conductivity ,, of Bi_2Sr_2CaCu_2O_8 was studied as a
function of magnetic field. Above 5 K, after an initial decrease,
presents a kink followed by a plateau, as recently reported by Krishana et al..
By contrast, below 1K, the thermal conductivity was found to \emph{increase}
with increasing field. This behavior is indicative of a finite density of
states and is not compatible with the existence of a field-induced fully gapped
state which was recently proposed to describe the
plateau regime. Our low-temperature results are in agreement with recent works
predicting a field-induced enhancement of thermal conductivity by Doppler shift
of quasi-particle spectrum.Comment: 4 pages including 4 eps figures, submitted to Phys. Rev. Let
Vortex Matter Transition in BiSrCaCuO under Tilted Fields
Vortex phase diagram under tilted fields from the axis in
BiSrCaCuO is studied by local magnetization
hysteresis measurements using Hall probes. When the field is applied at large
angles from the axis, an anomaly () other than the well-known
peak effect () are found at fields below . The angular dependence of
the field is nonmonotonic and clearly different from that of
and depends on the oxygen content of the crystal. The results suggest existence
of a vortex matter transition under tilted fields. Possible mechanisms of the
transition are discussed.Comment: Revtex, 4 pages, some corrections are adde
High Aspect Pattern Formation by Integration of Micro Inkjetting and Electroless Plating
This paper reports on formation of high aspect micro patterns on low
temperature co-fired ceramic (LTCC) substrates by integrating micro inkjetting
with electroless plating. Micro inkjetting was realized by using an inkjetting
printer that ejects ink droplets from a printhead. This printhead consists of a
glass nozzle with a diameter of 50 micrometers and a piezoelectric transducer
that is coated on the nozzle. The silver colloidal solution was inkjetted on a
sintered CT800 ceramic substrate, followed by curing at 200 degrees C for 60
minutes. As a result, the silver trace with a thickness of 200 nm was obtained.
The substrate, with the ejected silver thin film as the seed layer, was then
immersed into a preinitiator solution to coat a layer of palladium for
enhancing the deposition of nickel. Electroless nickel plating was successfully
conducted at a rate of 0.39 micrometers /min, and the thickness of traces was
plated up to 84 micrometers. This study demonstrates that the integration of
inkjetting with plating is an effective method to form high aspect patterns at
the demand location.Comment: Submitted on behalf of EDA Publishing Association
(http://irevues.inist.fr/handle/2042/16838
Site controlled red-yellow-green light emitting InGaN quantum discs on nano-tipped GaN rods
We report a method of growing site controlled InGaN multiple quantum discs (QDs) at uniform wafer scale on coalescence free ultra-high density (>80%) nanorod templates by metal organic chemical vapour deposition (MOCVD). The dislocation and coalescence free nature of the GaN space filling nanorod arrays eliminates the well-known emission problems seen in InGaN based visible light sources that these types of crystallographic defects cause. Correlative scanning transmission electron microscopy (STEM), energy-dispersive X-ray (EDX) mapping and cathodoluminescence (CL) hyperspectral imaging illustrates the controlled site selection of the red, yellow and green (RYG) emission at these nano tips. This article reveals that the nanorod tips’ broad emission in the RYG visible range is in fact achieved by manipulating the InGaN QD’s confinement dimensions, rather than significantly increasing the In%. This article details the easily controlled method of manipulating the QDs dimensions producing high crystal quality InGaN without complicated growth conditions needed for strain relaxation and alloy compositional changes seen for bulk planar GaN templates
Correction: Site controlled red-yellow-green light emitting InGaN quantum discs on nano-tipped GaN rods
Correction for 'Site controlled red-yellow-green light emitting InGaN quantum discs on nano-tipped GaN rods' by M. Conroy et al., Nanoscale, 2016, 8 , 11019-11026
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