433 research outputs found
Effect of disorder on the thermal transport and elastic properties in thermoelectric Zn4Sb3
Zn4Sb3 undergoes a phase transition from alpha to beta phase at T1[approximate]250 K. The high temperature beta-Zn4Sb3 phase has been widely investigated as a potential state-of-the-art thermoelectric (TE) material, due to its remarkably low thermal conductivity. We have performed electronic and thermal transport measurements exploring the structural phase transition at 250 K. The alpha to beta phase transition manifests itself by anomalies in the resistivity, thermopower, and specific heat at 250 K as well as by a reduction in the thermal conductivity as Zn4Sb3 changes phase from the ordered alpha to the disordered beta-phase. Moreover, measurements of the elastic constants using resonant ultrasound spectroscopy (RUS) reveal a dramatic softening at the order-disorder transition upon warming. These measurements provide further evidence that the remarkable thermoelectric properties of beta-Zn4Sb3 are tied to the disorder in the crystal structure
Thermoelectric and Seebeck coefficients of granular metals
In this work we present a detailed study and derivation of the thermopower
and thermoelectric coefficient of nano-granular metals at large tunneling
conductance between the grains, g_T>> 1. An important criterion for the
performance of a thermoelectric device is the thermodynamic figure of merit
which is derived using the kinetic coefficients of granular metals. All results
are valid at intermediate temperatures, E_c>>T/g_T>\delta, where \delta is the
mean energy level spacing for a single grain and E_c its charging energy. We
show that the electron-electron interaction leads to an increase of the
thermopower with decreasing grain size and discuss our results in the light of
future generation thermoelectric materials for low temperature applications.
The behavior of the figure of merit depending on system parameters like grain
size, tunneling conductance, and temperature is presented.Comment: 27 pages, 10 figures, revtex
Functional Relaxation and Guided Imagery as Complementary Therapy in Asthma: A Randomized Controlled Clinical Trial
Background: Asthma is a frequently disabling and almost invariably distressing disease that has a high overall prevalence. Although relaxation techniques and hypnotherapeutic interventions have proven their effectiveness in numerous trials, relaxation therapies are still not recommended in treatment guidelines due to a lack of methodological quality in many of the trials. Therefore, this study aims to investigate the efficacy of the brief relaxation technique of functional relaxation (FR) and guided imagery (GI) in adult asthmatics in a randomized controlled trial. Methods: 64 patients with extrinsic bronchial asthma were treated over a 4-week period and assessed at baseline, after treatment and after 4 months, for follow-up. 16 patients completed FR, 14 GI, 15 both FR and GI (FR/GI) and 13 received a placebo relaxation technique as the control intervention (CI). The forced expiratory volume in the first second (FEV 1) as well as the specific airway resistance (sR(aw)) were employed as primary outcome measures. Results: Participation in FR, GI and FR/GI led to increases in FEV 1 (% predicted) of 7.6 +/- 13.2, 3.3 +/- 9.8, and 8.3 +/- 21.0, respectively, as compared to -1.8 +/- 11.1 in the CI group at the end of the therapy. After follow-up, the increases in FEV 1 were 6.9 +/- 10.3 in the FR group, 4.4 +/- 7.3 in the GI and 4.5 +/- 8.1 in the FR/GI, compared to -2.8 +/- 9.2 in the CI. Improvements in sR(aw) (% predicted) were in keeping with the changes in FEV 1 in all groups. Conclusions: Our study confirms a positive effect of FR on respiratory parameters and suggests a clinically relevant long-term benefit from FR as a nonpharmacological and complementary therapy treatment option. Copyright (C) 2009 S. Karger AG, Base
Effect of disorder on the thermal transport and elastic properties in thermoelectric Zn\u3csub\u3e4\u3c/sub\u3eSb\u3csub\u3e3\u3c/sub\u3e
Zn4Sb3 undergoes a phase transition from α to ÎČ phase at T1â250 K. The high temperature ÎČ-Zn4Sb3 phase has been widely investigated as a potential state-of-the-art thermoelectric (TE) material, due to its remarkably low thermal conductivity. We have performed electronic and thermal transport measurements exploring the structural phase transition at 250 K. The α to ÎČ phase transition manifests itself by anomalies in the resistivity, thermopower, and specific heat at 250 K as well as by a reduction in the thermal conductivity as Zn4Sb3 changes phase from the ordered α to the disordered ÎČ-phase. Moreover, measurements of the elastic constants using resonant ultrasound spectroscopy (RUS) reveal a dramatic softening at the order-disorder transition upon warming. These measurements provide further evidence that the remarkable thermoelectric properties of ÎČ-Zn4Sb3 are tied to the disorder in the crystal structure
Mauve Assembly Metrics
Summary: High-throughput DNA sequencing technologies have spurred the development of numerous novel methods for genome assembly. With few exceptions, these algorithms are heuristic and require one or more parameters to be manually set by the user. One approach to parameter tuning involves assembling data from an organism with an available high-quality reference genome, and measuring assembly accuracy using some metrics
Solvent contribution to the stability of a physical gel characterized by quasi-elastic neutron scattering
The dynamics of a physical gel, namely the Low Molecular Mass Organic Gelator
{\textit Methyl-4,6-O-benzylidene- -D-mannopyranoside (-manno)}
in water and toluene are probed by neutron scattering. Using high gelator
concentrations, we were able to determine, on a timescale from a few ps to 1
ns, the number of solvent molecules that are immobilised by the rigid network
formed by the gelators. We found that only few toluene molecules per gelator
participate to the network which is formed by hydrogen bonding between the
gelators' sugar moieties. In water, however, the interactions leading to the
gel formations are weaker, involving dipolar, hydrophobic or
interactions and hydrogen bonds are formed between the gelators and the
surrounding water. Therefore, around 10 to 14 water molecules per gelator are
immobilised by the presence of the network. This study shows that neutron
scattering can give valuable information about the behaviour of solvent
confined in a molecular gel.Comment: Langmuir (2015
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