Many-body And Hot-phonon Effects In The Radiative Emission Spectrum Of Cds Under High Excitation Intensities

We present here experimental results concerning the photoluminescence spectrum of CdS under high excitation intensities. With increasing excitation intensity the single emission band observed at 77 °K shows a peak displacement towards lower energies, and enhancement of its low-energy side as well as of its high-energy side. These effects increase with excitation intensity. We develop a complete model that can account for the above behavior and the emission band shape. The broadening is mainly due to nonequilibrium distribution of LO phonons, though contributions to the high-energy side from hot electrons is quite significant. Self-energy corrections account for the band reduction and consequently to the shift of the luminescence band peak towards lower energies. © 1975 The American Physical Society.1162213222

Optical Control Of The Two-dimensional Electron-gas Density In Modulation-doped Quantum Wells Studied By Magnetophotoluminescence

We show by magnetoluminescence and photoluminescence excitation spectroscopy that the density of the two-dimensional electron gas in a GaAs/AlxGa1-xAs asymmetric modulation-doped multiple quantum-well structure is changed when the sample is excited with photons having an energy lower than the alloy band gap. © 1993 The American Physical Society.4831967196

Effect of cattle trampling and farm machinery traffic on soil compaction of an Entic Haplustoll in a semiarid region of Argentina

Soil compaction has detrimental effects on the physical, mechanical and hydraulic properties of soils, and affects important soil processes and function, and crop productivity. This work was conducted to investigate soil compaction impacts in integrated arable croppinglivestock systems managed under conventional tillage (CT) and no-tillage (NT). The work examined the combined effects of cattle trampling and farm machinery traffic on: soil strength, soil deformation, and water infiltration into soil. The following treatments were applied to soil (Entic Haplustoll, 60% sand) managed under CT and NT: three traffic intensities (1, 5, 7 passes) performed with light (2WD, 53 kN) and heavy (4WD, 100.4 kN) tractors, and two stocking densities (400 and 700 kg ha-1 ), respectively. Controls were also used to represent the condition of the soil without any effect of livestock or field traffic. In both tillage systems, soil penetration resistance (strength) increased and water infiltration into soil decreased as traffic intensities or stocking rates applied increased. There was a significant traffic intensity × stocking rate interaction, which influenced the depth and extent of soil compaction at depth. Despite these results, stubble grazing during fallow should not be discouraged as this practice offers mixed farming systems several agronomic and financial benefits. If stubble was to be grazed, the system would need to be carefully managed: (1) avoid ‘random’ traffic using permanent or semipermanent traffic paths to minimise the field wheeled area, (2) vacate livestock from the field, or confine it to a sacrificial area, when the soil water content exceeds a critical level above which soil damage is likely, and (3) maintain more than 60%–70% ground cover. Tillage repair treatments can be targeted to those sacrificial or ‘hot-spots’ areas so that localised, as supposed to widespread, compaction problems are rectified before the next crop is established

Evidence Of A Two-dimensional To Three-dimensional Transition In Si -doped Gaas Structures

We report on the change of character, from an isolated well to a superlattice, of multiple -doped structures as a function of the doping period ds. This effect is evidenced by the drastic change in the photoluminescence excitation spectra and the deviation on the total electron density extracted from Shubnikovde Haas oscillation measurements as ds decreases. Self-consistent-calculation results performed for these systems are used for comparison. © 1993 The American Physical Society.4816123161231

Photoluminescence Study Of Interfaces Between Heavily Doped Al 0.48in 0.52as:si Layers And Inp (fe) Substrates

Properties of the interface between the epitaxial layer of heavily doped Al 0.48In 0.52As:Si and the InP(Fe) substrate are investigated by photoluminescence in AlInAs:Si/InP(Fe) heteroestructures grown by molecular beam epitaxy. The effect on heterostructure optical properties of including a thin Al 0.22Ga 0.26In 0.52As:Si layer at the interface is investigated as well. To explain the different interface emission energies observed, the results are analyzed by using the mixed-type I-II interface model, which considers in the type II interface a narrow InAs well, with variable width, between AlInAs and InP. The observation of the interface emission at energies as high as 1.36 eV, at low excitation intensity, is explained taking into account the high doping level of the samples. The observed interface transition luminescence thermal quenching is tentatively explained by analyzing the spatial distribution of electrons in the triangular quantum well formed at the type II interface (or at the mixed I-II interface) as a function of the temperature. © 2002 American Institute of Physics.911189999004Sacilotti, M., Motisuke, F., Monteil, Y., Abraham, P., Iikawa, F., Montes, C., Furtado, M., Waldman, B., (1992) J. Cryst. Growth, 124, p. 589. , jcr JCRGAE 0022-0248Quillec, M., (1991) Proc. SPIE, 1361, p. 34. , spi PSISDG 0277-786XLaureto, E., Dias, I.F.L., Duarte, J.L., Di Mauro, E., Iwamoto, H., Freitas, M.T.P., Lourenço, S.A., Harmand, J.C., (1999) J. Appl. Phys., 85, p. 1. , jaJAPIAU 0021-8979Mondry, M.J., Babic, D.I., Bowers, J.E., Coldren, L.A., (1992) IEEE Photonics Technol. Lett., 4, p. 627. , ptl IPTLEL 1041-1135Bhat, R., Koza, M., Kash, K., Allen, S., Hong, W., Schwartz, S., Chang, G., Lin, P., (1991) J. Cryst. 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SALO, a novel classical pathway complement inhibitor from saliva of the sand fly Lutzomyia longipalpis.

Blood-feeding insects inject potent salivary components including complement inhibitors into their host's skin to acquire a blood meal. Sand fly saliva was shown to inhibit the classical pathway of complement; however, the molecular identity of the inhibitor remains unknown. Here, we identified SALO as the classical pathway complement inhibitor. SALO, an 11 kDa protein, has no homology to proteins of any other organism apart from New World sand flies. rSALO anti-complement activity has the same chromatographic properties as the Lu. longipalpis salivary gland homogenate (SGH)counterparts and anti-rSALO antibodies blocked the classical pathway complement activity of rSALO and SGH. Both rSALO and SGH inhibited C4b deposition and cleavage of C4. rSALO, however, did not inhibit the protease activity of C1s nor the enzymatic activity of factor Xa, uPA, thrombin, kallikrein, trypsin and plasmin. Importantly, rSALO did not inhibit the alternative or the lectin pathway of complement. In conclusion our data shows that SALO is a specific classical pathway complement inhibitor present in the saliva of Lu. longipalpis. Importantly, due to its small size and specificity, SALO may offer a therapeutic alternative for complement classical pathway-mediated pathogenic effects in human diseases

Non-linear QCD dynamics and exclusive production in epep collisions

The exclusive processes in electron-proton ($ep$) interactions are an important tool to investigate the QCD dynamics at high energies as they are in general driven by the gluon content of proton which is strongly subject to parton saturation effects. In this paper we compute the cross sections for the exclusive vector meson production as well as the deeply virtual Compton scattering (DVCS) relying on the color dipole approach and considering the numerical solution of the Balitsky-Kovchegov equation including running coupling corrections. We show that the small-$x$ evolution given by this evolution equation is able to describe the DESY-HERA data and is relevant for the physics of the exclusive observables in future electron-proton colliders and in photoproduction processes to be measured in coherent interactions at the LHC.Comment: 6 pages, 4 figure

Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR

Relationship of edge localized mode burst times with divertor flux loop signal phase in JET

A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM

Phylogenomics and the rise of the angiosperms

Angiosperms are the cornerstone of most terrestrial ecosystems and human livelihoods1,2. A robust understanding of angiosperm evolution is required to explain their rise to ecological dominance. So far, the angiosperm tree of life has been determined primarily by means of analyses of the plastid genome3,4. Many studies have drawn on this foundational work, such as classification and first insights into angiosperm diversification since their Mesozoic origins5,6,7. However, the limited and biased sampling of both taxa and genomes undermines confidence in the tree and its implications. Here, we build the tree of life for almost 8,000 (about 60%) angiosperm genera using a standardized set of 353 nuclear genes8. This 15-fold increase in genus-level sampling relative to comparable nuclear studies9 provides a critical test of earlier results and brings notable change to key groups, especially in rosids, while substantiating many previously predicted relationships. Scaling this tree to time using 200 fossils, we discovered that early angiosperm evolution was characterized by high gene tree conflict and explosive diversification, giving rise to more than 80% of extant angiosperm orders. Steady diversification ensued through the remaining Mesozoic Era until rates resurged in the Cenozoic Era, concurrent with decreasing global temperatures and tightly linked with gene tree conflict. Taken together, our extensive sampling combined with advanced phylogenomic methods shows the deep history and full complexity in the evolution of a megadiverse clade