On the density-potential mapping in time-dependent density functional theory

The key questions of uniqueness and existence in time-dependent density functional theory are usually formulated only for potentials and densities that are analytic in time. Simple examples, standard in quantum mechanics, lead however to non-analyticities. We reformulate these questions in terms of a non-linear Schr\"odinger equation with a potential that depends non-locally on the wavefunction.Comment: 8 pages, 2 figure

Electrical behavior of GaAs–AlAs heterostructures

We report an experimental study of the electrical behavior of GaAs–AlAs–GaAs heterostructures grown by metal–organic chemical vapor deposition. The structures consisted of a layer of AlAs several thousand angstroms thick sandwiched between layers of GaAs which were a few microns thick. The top layer of GaAs was doped degenerately n-type with Se, while the bottom layer was nondegenerately doped. Capacitance–voltage (C–V) and curent–voltage (I–V) curves were obtained as a function of temperature, illumination, and rate of data acquisition. Deep-level transient spectroscopy (DLTS) measurements were also made. The C–V showed hysteresis near zero bias with the capacitance being larger when the voltage was swept from reverse to forward bias in the dark. The C–V displayed a light sensitive peak near zero bias. With illumination, the capacitance was greater, and no hysteresis was observed. We explain these phenomena as being due to deep levels near the AlAs–GaAs interface; DLTS has confirmed this. I–V curves taken in darkness also showed hysteresis. We take this as further evidence of deep levels. Additionally, capacitance failed to level off in reverse bias, indicating a lack of inversion in the samples

The NASA Ames Research Center one- and two-dimensional stratospheric models. Part 2: The two-dimensional model

The two-dimensional model of stratospheric constituents is presented in detail. The derivation of pertinent transport parameters and the numerical solution of the species continuity equations, including a technique for treating the stiff differential equations that represent the chemical kinetic terms, and appropriate methods for simulating the diurnal variations of the solar zenith angle and species concentrations are discussed. Predicted distributions of tracer constituents (ozone, carbon 14, nitric acid) are compared with observed distributions

Environmental effects of SPS: The middle atmosphere

The heavy lift launch vehicle associated with the solar power satellite (SPS) would deposit in the upper atmosphere exhaust and reentry products which could modify the composition of the stratosphere, mesosphere, and lower ionosphere. In order to assess such effects, atmospheric model simulations were performed, especially considering a geographic zone centered at the launch and reentry latitudes

Surfactant-aided exfoliation of molydenum disulphide for ultrafast pulse generation through edge-state saturable absorption

We use liquid phase exfoliation to produce dispersions of molybdenum disulphide (MoS2) nanoflakes in aqueous surfactant solutions. The chemical structures of the bile salt surfactants play a crucial role in the exfoliation and stabilization of MoS2. The resultant MoS2 dispersions are heavily enriched in single and few (<6) layer flakes with large edge to surface area ratio. We use the dispersions to fabricate free-standing polymer composite wide-band saturable absorbers to develop mode-locked and Q- switched fibre lasers, tunable from 1535-1565 and 1030-1070 nm, respectively. We attribute this sub-bandgap optical absorption and its nonlinear saturation behaviour to edge-mediated states introduced within the material band-gap of the exfoliated MoS2 nanoflakes.Comment: 6 pages, 5 figure

Prior events predict cerebrovascular and coronary outcomes in the PROGRESS trial

&lt;p&gt;&lt;b&gt;Background and Purpose:&lt;/b&gt; The relationship between baseline and recurrent vascular events may be important in the targeting of secondary prevention strategies. We examined the relationship between initial event and various types of further vascular outcomes and associated effects of blood pressure (BP)–lowering.&lt;/p&gt; &lt;p&gt;&lt;b&gt;Methods:&lt;/b&gt; Subsidiary analyses of the Perindopril Protection Against Recurrent Stroke Study (PROGRESS) trial, a randomized, placebo-controlled trial that established the benefits of BP–lowering in 6105 patients (mean age 64 years, 30% female) with cerebrovascular disease, randomly assigned to either active treatment (perindopril for all, plus indapamide in those with neither an indication for, nor a contraindication to, a diuretic) or placebo(s).&lt;/p&gt; &lt;p&gt;&lt;b&gt;Results:&lt;/b&gt; Stroke subtypes and coronary events were associated with 1.5- to 6.6-fold greater risk of recurrence of the same event (hazard ratios, 1.51 to 6.64; P=0.1 for large artery infarction, P&#60;0.0001 for other events). However, 46% to 92% of further vascular outcomes were not of the same type. Active treatment produced comparable reductions in the risk of vascular outcomes among patients with a broad range of vascular events at entry (relative risk reduction, 25%; P&#60;0.0001 for ischemic stroke; 42%, P=0.0006 for hemorrhagic stroke; 17%, P=0.3 for coronary events; P homogeneity=0.4).&lt;/p&gt; &lt;p&gt;&lt;b&gt;Conclusions:&lt;/b&gt; Patients with previous vascular events are at high risk of recurrences of the same event. However, because they are also at risk of other vascular outcomes, a broad range of secondary prevention strategies is necessary for their treatment. BP–lowering is likely to be one of the most effective and generalizable strategies across a variety of major vascular events including stroke and myocardial infarction.&lt;/p&gt