2,262 research outputs found
Optimization Schemes for Efficient Multiple Exciton Generation and Extraction in Colloidal Quantum Dots
Multiple exciton generation is a process in which more than one electron hole
pair is generated per absorbed photon. It allows us to increase the efficiency
of solar energy harvesting. Experimental studies have shown the multiple
exciton generation yield of 1.2 in isolated colloidal quantum dots. However
real photoelectric devices require the extraction of electron hole pairs to
electric contacts. We provide a systematic study of the corresponding quantum
coherent processes including extraction and injection and show that a proper
design of extraction and injection rates enhances the yield significantly up to
values around 1.6.Comment: 5 pages, accepted by The Journal of Chemical Physic
Improved numerical methods for turbulent viscous flows aerothermal modeling program, phase 2
The details of a study to develop accurate and efficient numerical schemes to predict complex flows are described. In this program, several discretization schemes were evaluated using simple test cases. This assessment led to the selection of three schemes for an in-depth evaluation based on two-dimensional flows. The scheme with the superior overall performance was incorporated in a computer program for three-dimensional flows. To improve the computational efficiency, the selected discretization scheme was combined with a direct solution approach in which the fluid flow equations are solved simultaneously rather than sequentially
Tunneling between two systems of interacting chiral fermions
We develop a theory of tunneling between two systems of spinless chiral
fermions. This setup can be realized at the edge of a quantum Hall bilayer
structure. We find that the differential conductance of such a device in the
absence of interactions has an infinitely sharp peak as a function of applied
voltage. Interaction between fermions results in broadening of the conductance
peak. We focus on the regime of strong interactions, in which the shape of the
peak manifests well defined features associated with the elementary excitations
of the system.Comment: 12 page
Role of the Calcium Plateau in the Neuronal Injury and Behavioral Morbidities Following Organophosphate Intoxication
Organophosphate (OP) chemicals include nerve agents and pesticides, and there is a growing concern of OP based chemical attacks against civilians. Current antidotes are essential in limiting immediate mortality associated with OP exposure. However, further research is needed to identify molecular mechanisms underlying long-term neurological deficits following survival of OP toxicity in order to develop effective therapeutics. We have developed rat survival models of OP induced status epilepticus (SE) that mimic chronic mortality and morbidity following OP intoxication. We have observed significant elevations in hippocampal calcium levels after OP SE that persisted for weeks following initial survival. Drugs inhibiting intracellular calcium-induced calcium release such as dantrolene, levetiracetam, and carisbamate lowered OP-SE mediated protracted calcium elevations. Given the critical role of calcium signaling in modulating behavior and cell-death mechanisms, drugs targeted at preventing the development of the calcium plateau could enhance neuroprotection, help reduce morbidity and improve outcome following survival of OP SE
Structural and Physical Properties of CaFe4As3 Single Crystals
We report the synthesis, and structural and physical properties of CaFe4As3
single crystals. Needle-like single crystals of CaFe4As3 were grown out of Sn
flux and the compound adopts an orthorhombic structure as determined by X-ray
diffraction measurements. Electrical, magnetic, and thermal properties indicate
that the system undergoes two successive phase transitions occurring at TN1 ~
90 K and TN2 ~ 26 K. At TN1, electrical resistivities (\rho(b) and \rho(ac))
are enhanced while magnetic susceptibilities (\chi(b) and \chi(ac)) are reduced
in both directions parallel and perpendicular to the b-axis, consistent with
the scenario of antiferromagnetic spin-density-wave formation. At TN2, specific
heat reveals a slope change, and \chi(ac) decreases sharply but \chi(b) has a
clear jump before it decreases again with decreasing temperature. Remarkably,
both \rho(b) and \rho(ac) decrease sharply with thermal hysteresis, indicating
the first-order nature of the phase transition at TN2. At low temperatures,
\rho(b) and \rho(ac) can be described by {\rho} = {\rho}0 + AT^\alpha ({\rho}0,
A, and {\alpha} are constants). Interestingly, these constants vary with
applied magnetic field. The ground state of CaFe4As3 is discussed.Comment: 15 pages, 8 figures, Submitted to Physical Review
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