Effects of phase separation and decomposition on the minority carrier diffusion length in AlxGa1-xN films

Combined electron beam induced current and transmission electron microscopy (TEM) measurements have been performed on both undoped and Si-doped AlGaN epitaxial films with aluminum contents x ranging from x = 0 to x = 0.79, in order to correlate the electrical and structural properties of the films. The diffusion length of holes in the films ranges between 0.3 and 15.9 mu m, and the estimated lifetime of holes for doped samples varies between 0.2 ns and 16 mu s. Different effects contribute to the observed increase in the diffusion length with increasing aluminum content. Among others, dislocations seem to be active as nonradiative recombination sites, and phase separation and decomposition as observed by TEM in Al-rich alloys lead to the formation of a spatially indirect recombination path due to the piezoelectric field in the films. Potential fluctuations associated with these phase irregularities could also give rise to electron induced persistent conductivity contributing to the increase of the diffusion length. From our experimental observations, we conclude that the silicon dopants are partially activated in Al-rich alloys, and do not influence significantly the values of the diffusion length of holes in these samples

Time to treatment and survival in veterans with lung cancer eligible for curative intent therapy.

BackgroundThe Institute of Medicine emphasizes care timeliness as an important quality metric. We assessed treatment timeliness in stage I-IIIA lung cancer patients deemed eligible for curative intent therapy and analyzed the relationship between time to treatment (TTT) and timely treatment (TT) with survival.MethodsWe retrospectively reviewed consecutive cases of stage I-IIIA lung cancer deemed eligible for curative intent therapy at the VA San Diego Healthcare System between 10/2010-4/2017. We defined TTT as days from chest tumor board to treatment initiation and TT using guideline recommendations. We used multivariable (MVA) Cox proportional hazards regressions for survival analyses.ResultsIn 177 veterans, the median TTT was 35 days (29 days for chemoradiation, 36 for surgical resection, 42 for definitive radiation). TT occurred in 33% or 77% of patients when the most or least timely guideline recommendation was used, respectively. Patient characteristics associated with longer TTT included other cancer history, high simplified comorbidity score, stage I disease, and definitive radiation treatment. In MVA, TTT and TT [HR 0.53 (95% CI 0.27, 1.01) for least timely definition] were not associated with OS in stage I-IIIA patients, or disease-free survival in subgroup analyses of 122 stage I patients [HR 1.49 (0.62, 3.59) for least timely definition].ConclusionTreatment was timely in 33-77% of veterans with lung cancer deemed eligible for curative intent therapy. TTT and TT were not associated with survival. The time interval between diagnosis and treatment may offer an opportunity to deliver or improve other cancer care

Chemical composition and light emission properties of Si-rich-SiOx layers prepared by magnetron sputtering

The process of thermal decomposition of SiOx layers prepared by magnetron sputtering is studied with the use of photoluminescence and Auger and SIMS spectroscopies. From these measurements, we obtained the distributions of the emission properties and the chemical composition over the depth. The effect of the redistribution of silicon and oxygen over the depth is found after the high-temperature annealing which results in the formation of a Si nanocrystal. These redistributions result in the appearance of a Si-depleted region near the layer-substrate interface. The formation of a depletion layer is dependent on the excess of Si. A decrease of the silicon content over the depth of annealed layers is accompanied by a decrease of the Si nanocrystal size, as it is evidenced by the blue shift of the photoluminescence maximum. The mechanism of decomposition of SiOx and the possible reasons for the appearance of a Si-depleted region are discussed

Subthreshold and near-threshold kaon and antikaon production in proton-nucleus reactions

The differential production cross sections of K^+ and K^- mesons have been measured at the ITEP proton synchrotron in p+Be, p+Cu collisions under lab angle of 10.5^0, respectively, at 1.7 and 2.25, 2.4 GeV beam energies. A detailed comparison of these data with the results of calculations within an appropriate folding model for incoherent primary proton-nucleon, secondary pion-nucleon kaon and antikaon production processes and processes associated with the creation of antikaons via the decay of intermediate phi mesons is given. We show that the strangeness exchange process YN->NNK^- gives a small contribution to the antikaon yield in the kinematics of the performed experiment. We argue that in the case when antikaon production processes are dominated by the channels with KK^- in the final state, the cross sections of the corresponding reactions are weakly influenced by the in-medium kaon and antikaon mean fields.Comment: 24 pages. accepted for publication at J.Phys.

START as the detector of choice for large-scale muon triggering systems

Further progress in building high-granular large-scale systems based on Scintillation Tiles with MRS APD light readout (START) became possible thanks to the creation of an improved version of MRS APD. The cost of the system may now be significantly reduced by using inexpensive extruded scintillator. More than 160 START samples were assembled based on this design modification and proved to possess 100% MIP detection efficiency and the intrinsic noise rate of less than 0.08 Hz. Long-term stability of START characteristics was confirmed after 3.5 months of operation

Оледенение севера Западной Сибири – спорные вопросы и пути их решения

Different approaches to the problem of Quaternary glaciation of the North-West Siberia have been considered in the present paper, in which also analysis of glaciological situation has been done for the region. New obtained materials are given to show evidence of ancient glaciation in the Near-Ural region. As well the middle reach of the Ob’ River along its right-hand bank has been elucidated. The stated data have clearly demonstrated that diverse geological processes occurred to form the Quaternary deposits in the North-West Siberia. Partly it was an activity of glaciers advanced to the lowland from the centers of glaciation in the surrounding mountains. A role of not small importance belonged also to tectonic processes, which Ob’ erosion-accumulative influence and sea transgressions from the Arctic Ocean were connected with. At that all these occurred at the background of deep rock freezing. Study of moraines along the whole length of valleys from the ends of the modern glaciers until the formations of the maximal advance of ancient glaciers confirm our previous conclusion that glaciation also in this part of Siberia could be morphologically of a mountain-valley form only. Developing under conditions of strong permafrost and cryoaridization, the Pleistocene glaciers in the North-West Siberia concentrated in its mountains and did not advance farther than to the foothills. The upland of Siberian Uval, which sometimes has been considered as a moraine relic, presents another formation. It is a completely built system of Ob’ terraces representing the blocks of uplift deposits elevated by tectonics along the renewed ancient faults. The conclusion demonstrates that the subsequent spread of the stone moraine material happened as a result of movement of icebergs which broke of the glaciers with the trapped rock debris during sea transgressions from the Arctic Ocean. It has been established that, according to the results of absolute dating of the studied sediments, the Sartan advance of the glaciers, at any rate, concurred with the sea transgression conditioned by tectonic processes in Arctic.Рассмотрены различные подходы к проблеме четвертичного оледенения севера Западной Сибири и анализируется гляциологическая ситуация этого региона. Приведены новые материалы по изучению следов древних ледников в Приуралье и на правобережье Средней Оби. Сделан вывод, что в плейстоцене ледники на севере Западной Сибири концентрировались в её горном обрамлении и не продвигались дальше предгорий. Последующий разнос каменного материала морен происходил при перемещении айсбергов, оторвавшихся от ледников с вмороженными в них обломками горных пород, по водной акватории во время трансгрессий моря со стороны Северного Ледовитого океана. Установлено, что, согласно результатам датирования изученных отложений, по крайней мере, сартанское наступание ледников совпадало с трансгрессией моря, которая была обусловлена тектоническими процессами в Арктике.

New method of studying slow strange meson properties in nuclear matter

We suggest the new experimental method to explore the properties of slow strange mesons at normal nuclear matter density. We show that the $K^{+}$ and $K^{-}$ mesons with extremely small momenta relative to the surrounding medium rest frame can be produced in nucleus-nucleon collisions and their production cross sections are experimentally measurable. The experiments on study of the momentum dependence of meson-nuclear potentials are discussed.Comment: 4 pages, 2 figure

Electron-enhanced reactions responsible for photoluminescence spectrum change in II-VI compounds

Electron-enhanced reactions in II-VI compounds are shown to be caused by the presence of some mobile defects which diffusion is not enhanced under excitation. At the same time, electron-enhanced diffusion can be imitated in these reactions due to carrier trapping by deep centers that do or even do not take part in the reaction. To elucidate the real defect reaction mechanism a detailed study is required in every case. For this purpose, a method of mobile defect detection and their diffusion characteristic direct investigation has been elaborated