The activation energy for GaAs/AlGaAs interdiffusion

Copyright 1997 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. This article appeared in Journal of Applied Physics 82, 4842 (1997) and may be found at

Three Dimensional Measurements of Asphaltene Deposition in a Transparent Micro-Channel

This study describes a novel experimental approach to directly measure the thicknesses of asphaltene deposits in micro-channels. The thickness of the asphaltene deposit is estimated using a visualization technique based on 3D digital microscopy. The working fluid is a mixture of n-heptane and dead oil. Induced by the addition of n-heptane, the asphaltenes present in crude oil phase separate at ambient temperature to form aggregates of asphaltene-rich phase. Part of the asphaltene aggregates deposit on the walls of the transparent micro-channel. A two-dimensional profile of the deposit across the channel at selected axial sections is measured. The influences of injection mixture volume on the growth of the thickness of deposited asphaltenes is investigated using two experimental conditions, (i) varying elapsed time at constant flow rate and (ii) increasing the flow rate at a constant elapsed time. In both cases the deposit thickness of asphaltene (δ) increases with the total injection volume (V). The experimental results obtained in this work provide new insights into the deposition process at the micro-scale level, which can be used to facilitate the development of more accurate numerical model for this applicatio

O-Glycome beam search arrays for carbohydrate ligand discovery

O-glycosylation is a post-translational modification of proteins crucial to molecular mechanisms in health and disease. O-glycans are typically highly heterogeneous. The involvement of specific O-glycan sequences in many bio-recognition systems is yet to be determined due to a lack of efficient methodologies. We describe here a targeted microarray approach: O-glycome beam search that is both robust and efficient for O-glycan ligand-discovery. Substantial simplification of the complex O-glycome profile and facile chromatographic resolution is achieved by arraying O-glycans as branches, monitoring by mass spectrometry, focusing on promising fractions, and on-array immuno-sequencing. This is orders of magnitude more sensitive than traditional methods. We have applied beam search approach to porcine stomach mucin and identified extremely minor components previously undetected within the O-glycome of this mucin that are ligands for the adhesive proteins of two rotaviruses. The approach is applicable to O-glycome recognition studies in a wide range of biological settings to give insights into glycan recognition structures in natural microenvironments

Determination of the intrinsic ferroelectric polarization in orthorhombic HoMnO3

Whether large ferroelectric polarization P exists in the orthorhombic HoMnO3 with the E-type antiferromagnetic spin ordering or not remains as one of unresolved, challenging issues in the physics of multiferroics. The issue is closely linked to an intriguing experimental difficulty for determining P of polycrystalline specimens that conventional pyroelectric current measurements performed after a poling procedure under high dc electric fields are subject to large errors due to the problems caused by leakage currents or space charges. To overcome the difficulty, we employed the PUND method, which uses successively the two positive and two negative electrical pulses, to directly measure electrical hysteresis loops in several polycrystalline HoMnO3 specimens below their N\'eel temperatures. We found that all the HoMnO3 samples had similar remnant polarization Pr values at each temperature, regardless of their variations in resistivity, dielectric constant, and pyroelectric current levels. Moreover, Pr of ~0.07 \mu\C/cm2 at 6 K is consistent with the P value obtained from the pyroelectric current measurement performed after a short pulse poling. Our findings suggest that intrinsic P of polycrystalline HoMnO3 can be determined through the PUND method and P at 0 K may reach ~0.24 \mu\C/cm2 in a single crystalline specimen.Comment: 21 pages, 6 figures, submitted to New Journal of Physic

Theory and design of Inx_{x}Ga1−x_{1-x}As1−y_{1-y}Biy_{y} mid-infrared semiconductor lasers: type-I quantum wells for emission beyond 3 μ\mum on InP substrates

We present a theoretical analysis and optimisation of the properties and performance of mid-infrared semiconductor lasers based on the dilute bismide alloy In$_{x}$Ga$_{1-x}$As$_{1-y}$Bi$_{y}$, grown on conventional (001) InP substrates. The ability to independently vary the epitaxial strain and emission wavelength in this quaternary alloy provides significant scope for band structure engineering. Our calculations demonstrate that structures based on compressively strained In$_{x}$Ga$_{1-x}$As$_{1-y}$Bi$_{y}$ quantum wells (QWs) can readily achieve emission wavelengths in the 3 -- 5 $\mu$m range, and that these QWs have large type-I band offsets. As such, these structures have the potential to overcome a number of limitations commonly associated with this application-rich but technologically challenging wavelength range. By considering structures having (i) fixed QW thickness and variable strain, and (ii) fixed strain and variable QW thickness, we quantify key trends in the properties and performance as functions of the alloy composition, structural properties, and emission wavelength, and on this basis identify routes towards the realisation of optimised devices for practical applications. Our analysis suggests that simple laser structures -- incorporating In$_{x}$Ga$_{1-x}$As$_{1-y}$Bi$_{y}$ QWs and unstrained ternary In$_{0.53}$Ga$_{0.47}$As barriers -- which are compatible with established epitaxial growth, provide a route to realising InP-based mid-infrared diode lasers.Comment: Submitted versio

The Magnetic Field Structure of Mercury’s Magnetotail

In this study, we use the magnetic field data measured by MErcury Surface, Space ENvironment, GEochemistry, and Ranging from 2011 to 2015 to investigate the average magnetic field morphology of Mercury’s magnetotail in the down tail 0–3 RM (RM = 2,440 km, Mercury’s radius). It is found that Mercury has a terrestrial‐like magnetotail; the magnetic field structure beyond 1.5 RM down tail is stretched significantly with typical lobe field 50 nT. A cross‐tail current sheet separating the antiparallel field lines of lobes is present in the equatorial plane. The magnetotail width in north‐south direction is about 5 RM, while the transverse width is about 4 RM. Thus, the magnetotail shows elongation along the north‐south direction. At the cross‐tail current sheet center, the normal component of magnetic field (10–20 nT) is much larger than the cross‐tail component. The lobe‐field‐aligned component of magnetic field over current sheet can be well fitted by Harris sheet model. The curvature radius of field lines at sheet center usually reaches a minimum around midnight (100–200 km) with stronger current density (40–50 nA/m2), while the curvature radius increases toward both flanks (400–600 km) with the decreased current density (about 20 nA/m2). The half‐thickness of current sheet around midnight is about 0.25 RM or 600 km, and the inner edge of current sheet is located at the down tail about 1.5 RM. Our results about the field structure in the near Mercury’s tail show an evident dawn‐dusk asymmetry as that found in the Earth’s magnetotail, but reasons should be different. Possible reasons are discussed.Key PointsThe magnetic field distribution, configuration, and current density in Mercury’s magnetotail are quantitatively addressedMercury’s magnetotail is elongated along the south‐north direction, which is probably due to the effect of the dipole offset or the induction effect of coreThe magnetic structure of tail current sheet shows a clear dawn‐dusk asymmetry with smaller Bz and less flaring field on the dusksidePeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142544/1/jgra54041.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142544/2/jgra54041_am.pd

Mercury's three‐dimensional asymmetric magnetopause

Mercury's magnetopause is unique in the solar system due to its relatively small size and its close proximity to the Sun. Based on 3 years of MErcury Surface, Space ENvironment, GEochemistry, and Ranging orbital Magnetometer and the Fast Imaging Plasma Spectrometer data, the mean magnetopause location was determined for a total of 5694 passes. We fit these magnetopause locations to a three‐dimensional nonaxially symmetric magnetopause which includes an indentation for the cusp region that has been successfully applied to the Earth. Our model predicts that Mercury's magnetopause is highly indented surrounding the cusp with central depth ~0.64 RM and large dayside extension. The dayside polar magnetopause dimension is, thus, smaller than the equatorial magnetopause dimension. Cross sections of the dayside magnetopause in planes perpendicular to the Mercury‐Sun line are prolate and elongated along the dawn‐dusk direction. In contrast, the magnetopause downstream of the terminator plane is larger in the north‐south than the east‐west directions by a ratio of 2.6 RM to 2.2 RM at a distance of 1.5 RM downstream of Mercury. Due to the northward offset of the internal dipole, the model predicts that solar wind has direct access to the surface of Mercury at middle magnetic latitudes in the southern hemisphere. During extremely high solar wind pressure conditions, the northern hemisphere middle magnetic latitudes may also be subject to direct solar wind impact.Key PointsMercury's magnetopause near‐cusp indentationMagnetotail cross sections elongated in north‐south directionExtreme solar wind pressure events were analyzedPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/115924/1/jgra52083_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/115924/2/jgra52083.pd

Measurement of proton electromagnetic form factors in e+e−→ppˉe^+e^- \to p\bar{p} in the energy region 2.00-3.08 GeV

The process of $e^+e^- \rightarrow p\bar{p}$ is studied at 22 center-of-mass energy points ($\sqrt{s}$) from 2.00 to 3.08 GeV, exploiting 688.5~pb$^{-1}$ of data collected with the BESIII detector operating at the BEPCII collider. The Born cross section~($\sigma_{p\bar{p}}$) of $e^+e^- \rightarrow p\bar{p}$ is measured with the energy-scan technique and it is found to be consistent with previously published data, but with much improved accuracy. In addition, the electromagnetic form-factor ratio ($|G_{E}/G_{M}|$) and the value of the effective ($|G_{\rm{eff}}|$), electric ($|G_E|$) and magnetic ($|G_M|$) form factors are measured by studying the helicity angle of the proton at 16 center-of-mass energy points. $|G_{E}/G_{M}|$ and $|G_M|$ are determined with high accuracy, providing uncertainties comparable to data in the space-like region, and $|G_E|$ is measured for the first time. We reach unprecedented accuracy, and precision results in the time-like region provide information to improve our understanding of the proton inner structure and to test theoretical models which depend on non-perturbative Quantum Chromodynamics

Observation of ηc→ωω\eta_c\to\omega\omega in J/ψ→γωωJ/\psi\to\gamma\omega\omega

Using a sample of $(1310.6\pm7.0)\times10^6$ $J/\psi$ events recorded with the BESIII detector at the symmetric electron positron collider BEPCII, we report the observation of the decay of the $(1^1 S_0)$ charmonium state $\eta_c$ into a pair of $\omega$ mesons in the process $J/\psi\to\gamma\omega\omega$. The branching fraction is measured for the first time to be $\mathcal{B}(\eta_c\to\omega\omega)= (2.88\pm0.10\pm0.46\pm0.68)\times10^{-3}$, where the first uncertainty is statistical, the second systematic and the third is from the uncertainty of $\mathcal{B}(J/\psi\to\gamma\eta_c)$. The mass and width of the $\eta_c$ are determined as $M=(2985.9\pm0.7\pm2.1)\,$MeV/$c^2$ and $\Gamma=(33.8\pm1.6\pm4.1)\,$MeV.Comment: 13 pages, 6 figure