Electronic properties of deep levels in p‐type CdTe

DLTS and associated electrical measurements were made on unintentionally doped CdTe crystals obtained from several vendors, on Cu‐doped CdTe, and on Te‐annealed CdTe. All of the crystals were p‐type. Four majority carrier deep levels were observed in the temperature range from 100–300 K with activation energies relative to the valence band of 0.2, 0.41, 0.45, and 0.65 eV. Two of these levels were specific to certain crystals while the other two were seen in every sample and are attributed to common impurities or native defects. Fluctuations in the concentrations of levels across samples and as a result of modest sample heating (400 K) were also observed

Elastic and inelastic tunneling characteristics of AIAs/GaAs heterojunctions

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Inelastic tunneling characteristics of AIAs/GaAs heterojunction barriers

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X-ray photoelectron spectroscopy investigation of the mixed anion GaSb/InAs heterointerface

X-ray photoelectron spectroscopy has been used to measure levels of anion cross-incorporation and to study interface formation for the mixed anion GaSb/lnAs heterojunction. Anion cross-incorporation was measured in 20 Å thick GaSb layers grown on lnAs, and 20 Å thick InAs layers grown on GaSb for cracked and uncracked sources. It was found that significantly less anion cross-incorporation occurs in structures grown with cracked sources. Interface formation was investigated by studying Sb soaks of InAs surfaces and As soaks of GaSb surfaces as a function of cracker power and soak time. Exchange of the group V surface atoms was found to be an increasing function of both cracker power and soak time. We find that further optimization of current growth parameters may be possible by modifying the soak time used at interfaces

Study of interface asymmetry in InAs–GaSb heterojunctions

We present reflection high energy electron diffraction, secondary ion mass spectroscopy, scanning tunneling microscopy and x‐ray photoelectron spectroscopy studies of the abruptness of InAs–GaSb interfaces. We find that the interface abruptness depends on growth order: InAs grown on GaSb is extended, while GaSb grown on InAs is more abrupt. We first present observations of the interfacial asymmetry, including measurements of band alignments as a function of growth order. We then examine more detailed studies of the InAs–GaSb interface to determine the mechanisms causing the extended interface. Our results show that Sb incorporation into the InAs overlayer and As exchange for Sb in the GaSb underlayer are the most likely causes of the interfacial asymmetry

McCune-Albright syndrome and the extraskeletal manifestations of fibrous dysplasia

Fibrous dysplasia (FD) is sometimes accompanied by extraskeletal manifestations that can include any combination of café-au-lait macules, hyperfunctioning endocrinopathies, such as gonadotropin-independent precocious puberty, hyperthyroidism, growth hormone excess, FGF23-mediated renal phosphate wasting, and/or Cushing syndrome, as well as other less common features. The combination of any of these findings, with or without FD, is known as McCune-Albright syndrome (MAS). The broad spectrum of involved tissues and the unpredictable combination of findings owe to the fact that molecular defect is due to dominant activating mutations in the widely expressed signaling protein, Gsα, and the fact these mutations arises sporadically, often times early in development, prior to gastrulation, and can distribute across many or few tissues

Structural model optimization using statistical evaluation

The results of research in applying statistical methods to the problem of structural dynamic system identification are presented. The study is in three parts: a review of previous approaches by other researchers, a development of various linear estimators which might find application, and the design and development of a computer program which uses a Bayesian estimator. The method is tried on two models and is successful where the predicted stiffness matrix is a proper model, e.g., a bending beam is represented by a bending model. Difficulties are encountered when the model concept varies. There is also evidence that nonlinearity must be handled properly to speed the convergence

Fully Unintegrated Parton Correlation Functions and Factorization in Lowest Order Hard Scattering

Motivated by the need to correct the potentially large kinematic errors in approximations used in the standard formulation of perturbative QCD, we reformulate deeply inelastic lepton-proton scattering in terms of gauge invariant, universal parton correlation functions which depend on all components of parton four-momentum. Currently, different hard QCD processes are described by very different perturbative formalisms, each relying on its own set of kinematical approximations. In this paper we show how to set up formalism that avoids approximations on final-state momenta, and thus has a very general domain of applicability. The use of exact kinematics introduces a number of significant conceptual shifts already at leading order, and tightly constrains the formalism. We show how to define parton correlation functions that generalize the concepts of parton density, fragmentation function, and soft factor. After setting up a general subtraction formalism, we obtain a factorization theorem. To avoid complications with Ward identities the full derivation is restricted to abelian gauge theories; even so the resulting structure is highly suggestive of a similar treatment for non-abelian gauge theories.Comment: 44 pages, 69 figures typos fixed, clarifications and second appendix adde

QCD Factorization for Semi-Inclusive Deep-Inelastic Scattering at Low Transverse Momentum

We demonstrate a factorization formula for semi-inclusive deep-inelastic scattering with hadrons in the current fragmentation region detected at low transverse momentum. To facilitate the factorization, we introduce the transverse-momentum dependent parton distributions and fragmentation functions with gauge links slightly off the light-cone, and with soft-gluon radiations subtracted. We verify the factorization to one-loop order in perturbative quantum chromodynamics and argue that it is valid to all orders in perturbation theory.Comment: 28 pages, figures include

Radar signal categorization using a neural network

Neural networks were used to analyze a complex simulated radar environment which contains noisy radar pulses generated by many different emitters. The neural network used is an energy minimizing network (the BSB model) which forms energy minima - attractors in the network dynamical system - based on learned input data. The system first determines how many emitters are present (the deinterleaving problem). Pulses from individual simulated emitters give rise to separate stable attractors in the network. Once individual emitters are characterized, it is possible to make tentative identifications of them based on their observed parameters. As a test of this idea, a neural network was used to form a small data base that potentially could make emitter identifications