2,148 research outputs found
Modelling Heat Transfer of Carbon Nanotubes
Modelling heat transfer of carbon nanotubes is important for the thermal
management of nanotube-based composites and nanoelectronic device. By using a
finite element method for three-dimensional anisotropic heat transfer, we have
simulated the heat conduction and temperature variations of a single nanotube,
a nanotube array and a part of nanotube-based composite surface with heat
generation. The thermal conductivity used is obtained from the upscaled value
from the molecular simulations or experiments. Simulations show that nanotube
arrays have unique cooling characteristics due to its anisotropic thermal
conductivity.Comment: 10 pages, 4 figure
Intoxicated eyewitnesses:the effect of a fully balanced placebo design on event memory and metacognitive control
Few studies have examined the impact of alcohol on metacognition for witnessed events. We used a 2x2 balanced placebo design, where mock-witnesses expected and drank alcohol, did not expect but drank alcohol, did not expect nor drank alcohol, or expected but did not drink alcohol. Participants watched a mock-crime in a bar-lab, followed by free recall and a cued-recall test with or without the option to reply âdonât knowâ (DK). Intoxicated mock-witnessesâ free recall was less complete but not less accurate. During cued-recall, alcohol led to lower accuracy, and reverse placebo participants gave more erroneous and fewer correct responses. Permitting and clarifying DK responses was associated with fewer errors and more correct responses for sober individuals; and intoxicated witnesses were less likely to opt out of erroneous responding to unanswerable questions. Our findings highlight the practical and theoretical importance of examining pharmacological effects of alcohol and expectancies in real-life settings
Supersymmetry Breaking Triggered by Monopoles
We investigate N = 1 supersymmetric gauge theories where monopole
condensation triggers supersymmetry breaking in a metastable vacuum. The
low-energy effective theory is an O'Raifeartaigh-like model of the kind
investigated recently by Shih where the R-symmetry can be spontaneously broken.
We examine several implementations with varying degrees of phenomenological
interest.Comment: 20 pages, 4 figures (v2: minor clarifications and typos fixed
Weighted-density approximation for general nonuniform fluid mixtures
In order to construct a general density-functional theory for nonuniform
fluid mixtures, we propose an extension to multicomponent systems of the
weighted-density approximation (WDA) of Curtin and Ashcroft [Phys. Rev. A 32,
2909 (1985)]. This extension corrects a deficiency in a similar extension
proposed earlier by Denton and Ashcroft [Phys. Rev. A 42, 7312 (1990)], in that
that functional cannot be applied to the multi-component nonuniform fluid
systems with spatially varying composition, such as solid-fluid interfaces. As
a test of the accuracy of our new functional, we apply it to the calculation of
the freezing phase diagram of a binary hard-sphere fluid, and compare the
results to simulation and the Denton-Ashcroft extension.Comment: 4 pages, 4 figures, to appear in Phys. Rev. E as Brief Repor
Forced Chemical Vapor Infiltration of Tubular Geometries: Modeling, Design, and Scale-Up
In advanced indirectly fired coal combustion systems and externally fired combined cycle concepts, ceramic heat exchangers are required to transfer heat from the hot combustion gases to the clean air that drives the gas turbines. For high efficiencies, the temperature of the turbine inlet needs to exceed 1,100 C and preferably be about 1,260 C. The heat exchangers will operate under pressure and experience thermal and mechanical stresses during heating and cooling, and some transients will be severe under upset conditions. Silicon carbide-matrix composites appear promising for such applications because of their high strength at elevated temperature, light weight, thermal and mechanical shock resistance, damage tolerance, and oxidation and corrosion resistance. The development of thick-walled, tubular ceramic composites has involved investigations of different fiber architectures and fixturing to obtain optimal densification and mechanical properties. The current efforts entail modeling of the densification process in order to increase densification uniformity and decrease processing time. In addition, the process is being scaled to produce components with a 10 cm outer diameter
Networks and landscapes: a framework for setting goals and evaluating performance at the large landscape scale
The objective of large landscape conservation is to mitigate complex ecological problems through interventions at multiple and overlapping scales. Implementation requires coordination among a diverse network of individuals and organizations to integrate localâscale conservation activities with broadâscale goals. This requires an understanding of the governance options and how governance regimes achieve objectives or provide performance evaluation across both space and time. However, empirical assessments measuring networkâgovernance performance in large landscape conservation are limited. We describe a wellâestablished large landscape conservation network in North America, the Roundtable on the Crown of the Continent, to explore the application of a socialâecological performance evaluation framework. Systematic approaches to setting goals, tracking progress, and collecting data for feedback can help guide adaptation. Applying the established framework to our case study provides a means of evaluating the effectiveness of network governance in large landscape conservation
The phonon theory of liquid thermodynamics
Heat capacity of matter is considered to be its most important property
because it holds information about system's degrees of freedom as well as the
regime in which the system operates, classical or quantum. Heat capacity is
well understood in gases and solids but not in the third state of matter,
liquids, and is not discussed in physics textbooks as a result. The perceived
difficulty is that interactions in a liquid are both strong and
system-specific, implying that the energy strongly depends on the liquid type
and that, therefore, liquid energy can not be calculated in general form. Here,
we develop a phonon theory of liquids where this problem is avoided. The theory
covers both classical and quantum regimes. We demonstrate good agreement of
calculated and experimental heat capacity of 21 liquids, including noble,
metallic, molecular and hydrogen-bonded network liquids in a wide range of
temperature and pressure.Comment: 7 pages, 4 figure
Soap Froths and Crystal Structures
We propose a physical mechanism to explain the crystal symmetries found in
macromolecular and supramolecular micellar materials. We argue that the packing
entropy of the hard micellar cores is frustrated by the entropic interaction of
their brush-like coronas. The latter interaction is treated as a surface effect
between neighboring Voronoi cells. The observed crystal structures correspond
to the Kelvin and Weaire-Phelan minimal foams. We show that these structures
are stable for reasonable areal entropy densities.Comment: 4 pages, RevTeX, 2 included eps figure
The in vitro effects of artificial and natural sweeteners on the immune system using whole blood culture assays
This article investigates the effects of commercially available artificial (aspartame, saccharin,
sucralose) and natural sweeteners (brown sugar, white sugar, molasses) on the immune system.
Human whole blood cultures were incubated with various sweeteners and stimulated in vitro with
either phytohemagglutinin or endotoxin. Harvested supernatants were screened for cytotoxicity and
cytokine release. Results showed that none of the artificial or natural sweeteners proved to be
cytotoxic, indicating that no cell death was induced in vitro. The natural sweetener, sugar cane
molasses (10 ug=mL), enhanced levels of the inflammatory biomarker IL-6 while all artificial
sweeteners (10 ug=mL) revealed a suppressive effect on IL-6 secretion (P<0.001). Exposure of
blood cells to sucralose-containing sweeteners under stimulatory conditions reduced levels of the
biomarker of humoral immunity, Interleukin-10 (P<0.001). The cumulative suppression of
Interleukin-6 and Interleukin-10 levels induced by sucralose may contribute to the inability in
mounting an effective humoral response when posed with an exogenous threat.Web of Scienc
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