631 research outputs found
Coexistence of Superconductivity and Spin Density Wave orderings in the organic superconductor (TMTSF)_2PF_6
The phase diagram of the organic superconductor (TMTSF)_2PF_6 has been
revisited using transport measurements with an improved control of the applied
pressure. We have found a 0.8 kbar wide pressure domain below the critical
point (9.43 kbar, 1.2 K) for the stabilisation of the superconducting ground
state featuring a coexistence regime between spin density wave (SDW) and
superconductivity (SC). The inhomogeneous character of the said pressure domain
is supported by the analysis of the resistivity between T_SDW and T_SC and the
superconducting critical current. The onset temperature T_SC is practically
constant (1.20+-0.01 K) in this region where only the SC/SDW domain proportion
below T_SC is increasing under pressure. An homogeneous superconducting state
is recovered above the critical pressure with T_SC falling at increasing
pressure. We propose a model comparing the free energy of a phase exhibiting a
segregation between SDW and SC domains and the free energy of homogeneous
phases which explains fairly well our experimental findings.Comment: 13 pages, 10 figures, revised v: fig.9 added, section 4.2 rewritten,
accepted v: sections 4&5 improve
Influence of Quantum Hall Effect on Linear and Nonlinear Conductivity in the FISDW States of the Organic Conductor (TMTSF)_2PF_6
We report a detailed characterization of quantum Hall effect (QHE) influence
on the linear and non-linear resistivity tensor in FISDW phases of the organic
conductor (TMTSF)2PF6. We show that the behavior at low electric fields,
observed for nominally pure single crystals with different values of the
resistivity ratio, is fully consistent with a theoretical model, which takes
QHE nature of FISDW and residual quasi-particle density associated with
different crystal imperfection levels into account. The non-linearity in
longitudinal and diagonal resistivity tensor components observed at large
electric fields reconciles preceding contradictory results. Our theoretical
model offers a qualitatively good explanation of the observed features if a
sliding of the density wave with the concomitant destruction of QHE, switched
on above a finite electric field, is taken into account.Comment: 8 pages, 6 figures, submitted to EPJ
4-Lump kinetic model for hydrotreated gas oil catalytic cracking
This study has monitored the influence of one of the hydrodesulphurisation process parameters - H2/CH ratio on the properties of three catalytic cracking products (gas, petrol, light cyclic oil, and heavy cyclic oil ).
The microactivity test (MAT) was applied to all kinetic measurements. A 4-lump, non-isothermal and non-stationary kinetic model for the fixed, plug-flow MAT reactor was developed to model catalytic cracking of hydrotreated gas oil. Kinetic constants were estimated by the Nelder Mead method. The product yields predicted by the model showed good confirmity with experimental data
Electronic states of elongated PbSe/PbS Core/shell quantum dots
The optical characteristics of colloidal quantum dots (QDs) are highly dependent on the physical geometry of the QD (size, shape) as well as composition. These dependencies make such systems attractive for application in novel optical devices, notably for solar cell technology. Empirical electronic structure methods, such as kcenterdotp theory, or empirical pseudopotential theories have successfully reproduced experimentally observed transitions in CdSe and PbSe colloidal QDs. Our approach uses the kcenterdotp method to predict such properties as the electronic structure and dipole transitions of ellipsoidal PbSe/PbS core/shell structure colloidal QDs, as a function of eccentricity. Due to the anisotropy between the longitudinal (z) and transverse (x and y) directions, we present results from elongation along both the x and z directions
Anisotropic charge dynamics in the quantum spin-liquid candidate -(BEDT-TTF)Cu(CN)
We have in detail characterized the anisotropic charge response of the dimer
Mott insulator -(BEDT-TTF)\-Cu(CN) by dc conductivity, Hall
effect and dielectric spectroscopy. At room temperature the Hall coefficient is
positive and close to the value expected from stoichiometry; the temperature
behavior follows the dc resistivity . Within the planes the dc
conductivity is well described by variable-range hopping in two dimensions;
this model, however, fails for the out-of-plane direction. An unusually broad
in-plane dielectric relaxation is detected below about 60 K; it slows down much
faster than the dc conductivity following an Arrhenius law. At around 17 K we
can identify a pronounced dielectric anomaly concomitantly with anomalous
features in the mean relaxation time and spectral broadening. The out-of-plane
relaxation, on the other hand, shows a much weaker dielectric anomaly; it
closely follows the temperature behavior of the respective dc resistivity. At
lower temperatures, the dielectric constant becomes smaller both within and
perpendicular to the planes; also the relaxation levels off. The observed
behavior bears features of relaxor-like ferroelectricity. Because
heterogeneities impede its long-range development, only a weak tunneling-like
dynamics persists at low temperatures. We suggest that the random potential and
domain structure gradually emerge due to the coupling to the anion network.Comment: 14 pages, 13 figure
Theoretical analysis of GaAs/AlGaAs quantum dots in quantum wire array for intermediate band solar cell
A GaAs quantum dot (QD) array embedded in a AlGaAs host material was
fabricated using a strain-free approach, through combination of neutral beam etching
and atomic hydrogen-assisted molecular beam epitaxy regrowth. In this work, we
performed theoretical simulations on a GaAs/AlGaAs quantum well, GaAs QD and
QD array based intermediated band solar cell (IBSC) using a combined multiband
k·p and drift-diffusion transportation method. The electronic structure, IB band
dispersion, and optical transitions, including absorption and spontaneous emission
among the valence band, intermediate band, and conduction band, were calculated.
Based on these results, maximum conversion efficiency of GaAs/AlGaAs QD
array based IBSC devices were calculated by a drift-diffusion model adapted to
IBSC under the radiative recombination limit
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Safety and Pharmacokinetics of a Four Monoclonal Antibody Combination Against Botulinum C and D Neurotoxins.
Botulism is caused by botulinum neurotoxin (BoNT), the most poisonous substance known. BoNTs are also classified as Tier 1 biothreat agents due to their high potency and lethality. The existence of seven BoNT serotypes (A-G), which differ between 35% to 68% in amino acid sequence, necessitates the development of serotype specific countermeasures. We present results of a Phase 1 clinical study of an anti-toxin to BoNT serotypes C and D, NTM-1634, which consists of an equimolar mixture of four fully human IgG1 monoclonal antibodies (mAbs), each binding to non-overlapping epitopes on BoNT serotypes C and D resulting in potent toxin neutralization in rodents. This first-in-human study evaluated the safety and pharmacokinetics of escalating doses of NTM-1634 administered intravenously to healthy adults (NCT03046550). Three cohorts of eight healthy subjects received a single intravenous dose of NTM-1634 or placebo at 0.33 mg/kg, 0.66 mg/kg or 1 mg/kg. Follow-up examinations and pharmacokinetic evaluations were continued up to 121 days post-infusion. Subjects were monitored using physical examinations, hematology and chemistry blood tests, and electrocardiograms. Pharmacokinetic parameters were estimated using noncompartmental methods. The results demonstrated that the materials were safe and well-tolerated with the expected half-lives for human mAbs and with minimal anti-drug antibodies detected over the dose ranges and duration of the study
Cultural relativism and the discourse of intercultural communication: aporias of praxis in the intercultural public sphere
The premise of much intercultural communication pedagogy and research is to educate people from different cultures towards open and transformative positions of mutual understanding and respect. This discourse in the instance of its articulation realises and sustains Intercultural Communication epistemologically â as an academic field of social enquiry, and judgementally â as one which locates itself on a moral terrain. By adopting an ethical stance towards difference, the discourse of intercultural communication finds itself caught in a series of aporias, or performative contradictions, where interculturalists are projected simultaneously into positions of cultural relativism on the one hand and ideological totalism on the other. Such aporias arise because the theoretical premises upon which the discourse relies are problematic. We trace these thematics to a politics of presence operating within the discourse of intercultural communication and links this to questions of judgement and truth in the intercultural public sphere. We propose that the politics of presence be set aside in favour of an intercultural praxis which is oriented to responsibility rather than to truth
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