Growth and Characterization of ZnMgS and ZnMgS/ZnSe Quantum Wells grown on GaAs (100) by Using MBE

C. Bradford,R. T. Moug,A. Curran,D. Thuau,R. J. Warburton,K. A. Prior 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5

Structures containing Zn1-xMgxS have been grown lattice matched to GaAs by using molecular beam epitaxy (MBE) with ZnS as the source of S. The composition of the alloy produced has been determined using double-crystal X-ray spectroscopy and X-ray interference measurements. Both techniques indicate that 0.88 ≤ x ≤ 0.93. This result is conrmed by both secondary ion mass spectroscopy and an Auger analysis carried out on the material. These results show that the crystalline quality of the material produced is excellent and that it has been grown coherently to the GaAs substrate. Photoluminescence spectroscopy shows a high intensity emission with a narrow full width half maximum, confirming the suitability of this alloy as a high-bandgap barrier material. Structures containing Zn1-xMgxS have been grown lattice matched to GaAs by using molecular beam epitaxy (MBE) with ZnS as the source of S. The composition of the alloy produced has been determined using double-crystal X-ray spectroscopy and X-ray interference measurements. Both techniques indicate that 0.88 ≤ x ≤ 0.93. This result is conrmed by both secondary ion mass spectroscopy and an Auger analysis carried out on the material. These results show that the crystalline quality of the material produced is excellent and that it has been grown coherently to the GaAs substrate. Photoluminescence spectroscopy shows a high intensity emission with a narrow full width half maximum, confirming the suitability of this alloy as a high-bandgap barrier material.

A Dynamic General Equilibrium Model of Phased Korean Reunification

Scott C. Bradford,Kerk L. Phillips 한국경제연구학회 2005 Korea and the World Economy Vol.6 No.1

Micro-Raman Studies of Zincblende MgS

D Wolverson,L. C. Smith,C. Bradford,B. C. Cavenett,K. A. Prior 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5

Recent improvements in UV Raman spectrometer capability have resulted from the availability of much improved dielectric filters, and we can now observe directly both the longitudinal and the transverse optic phonon modes of the wide-bandgap zincblende semiconductor MgS. We are, thus, able to confirm the earlier measured and calculated phonon frequencies with improved accuracy. The strong sequence of overtone modes that we observe is interpreted in terms of the resonance behavior of the Raman scattering process at this excitation energy. The spectra also show features which, by comparison to ab-initio calculations of the phonon dispersion and density of states, can be identified as arising from multiple Raman scattering processes involving longitudinal acoustic phonons near the Brillouin zone boundary.

Time-dependent analysis of reinforced concrete structures using the layered finite element method

Bradford, M.A.,Gilbert, R.I.,Sun, S.C.H. Techno-Press 1999 Structural Engineering and Mechanics, An Int'l Jou Vol.8 No.6

The response of a reinforced concrete structure to loading is both immediate and time-dependent. Under a sustained load, the deflections caused by creep and shrinkage may be several times their instantaneous values. The paper describes a general finite element procedure, based on the so-called layered model, to analyse reinforced concrete members, and shows in particular how the simple Step by Step Method may be incorporated into this procedure. By invoking the Modified Newton Raphson Method as a solution procedure, the accuracy of the finite element method is verified against independent test results, and then applied to a variety of problems in order to demonstrate its efficacy. The method forms a general method for analysing highly indeterminate concrete structures in the time domain.

Cyclophilin A: A Mediator of Cardiovascular Pathology

Nwe Nwe Soe, MD,Bradford C. Berk, MD 대한고혈압학회 2011 Clinical Hypertension Vol.17 No.4

Cyclophilin A (CyPA) is a 17 kDa, ubiquitously expressed multifunctional protein that possesses peptidylprolyl cis-trans isomerase activity and scaffold function. Its expression is increased in inflammatory conditions including rheumatoid arthritis, autoimmune disease and cancer. Intracellular CyPA regulates protein trafficking, signal transduction, transcription regulation and the activity of certain other proteins. Secreted CyPA activates cardiovascular cells resulting in a variety of cardiovascular diseases; including vascular remodeling, abdominal aortic aneurysms formation, atherosclerosis, cardiac hypertrophy and myocardial ischemic reperfusion injury.

Disturbed Flow-Induced Endothelial Proatherogenic Signaling <i>Via</i> Regulating Post-Translational Modifications and Epigenetic Events

Heo, Kyung-Sun,Berk, Bradford C.,Abe, Jun-ichi Mary Ann Liebert 2016 ANTIOXIDANTS AND REDOX SIGNALING Vol.25 No.7

Dynamic interaction analysis of a LIM train and elevated bridge system

H. Xia,W. W. Guo,C. Y. Xia,Y.-L. Pi,M. A. Bradford 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.12

A three-dimensional dynamic interaction model is developed for a LIM (linear induction motor) train and elevated bridge system, which is composed of a LIM-driven vehicle submodel and a finite element bridge submodel. Each LIM vehicle is modeled by a 27 degrees-of-freedom dynamic system. The expressions for the electromagnetic force between the linear motor and the reaction plate are derived, and the force model is established. By applying a modal superposition technique to the bridge submodel and using the measured track irregularities as the self-excitations of the train-bridge system, the equations of motion are established for analyzing the dynamic responses of the LIM vehicle and the elevated bridge. The proposed framework is applied to a 3-span elevated bridge with 29.9 m simply-supported girders. The full histories of the LIM train traversing the bridge are simulated, from which the dynamic responses of the LIM vehicle and elevated bridge system are obtained. The proposed method may help to find a way to assess the dynamic properties of elevated bridges and the running safety of a LIM train with reasonable computational effort.

THE EVOLUTION OF STAR FORMATION HISTORIES OF QUIESCENT GALAXIES

Pacifici, Camilla,Kassin, Susan A.,Weiner, Benjamin J.,Holden, Bradford,Gardner, Jonathan P.,Faber, Sandra M.,Ferguson, Henry C.,Koo, David C.,Primack, Joel R.,Bell, Eric F.,Dekel, Avishai,Gawiser, Er American Astronomical Society 2016 The Astrophysical Journal Vol.832 No.1

<P>Although there has been much progress in understanding how galaxies evolve, we still do not understand how and when they stop forming stars and become quiescent. We address this by applying our galaxy spectral energy distribution models, which incorporate physically motivated star formation histories (SFHs) from cosmological simulations, to a sample of quiescent galaxies at 0.2 < z < 2.1. A total of 845 quiescent galaxies with multi-band photometry spanning rest-frame ultraviolet through near-infrared wavelengths are selected from the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS) data set. We compute median SFHs of these galaxies in bins of stellar mass and redshift. At all redshifts and stellar masses, the median SFHs rise, reach a peak, and then decline to reach quiescence. At high redshift, we find that the rise and decline are fast, as expected, because the universe is young. At low redshift, the duration of these phases depends strongly on stellar mass. Low-mass galaxies (log(M*/M-circle dot) similar to 9.5) grow on average slowly, take a long time to reach their peak of star formation (greater than or similar to 4 Gyr), and then the declining phase is fast (less than or similar to 2 Gyr). Conversely, high-mass galaxies (log(M*/M-circle dot) similar to 11) grow on average fast (less than or similar to 2 Gyr), and, after reaching their peak, decrease the star formation slowly (greater than or similar to 3). These findings are consistent with galaxy stellar mass being a driving factor in determining how evolved galaxies are, with high-mass galaxies being the most evolved at any time (i.e., downsizing). The different durations we observe in the declining phases also suggest that low- and high-mass galaxies experience different quenching mechanisms, which operate on different timescales.</P>