The relationship between epitaxial growth, defect microstructure and luminescence in GaN

ABSTRACT Production of the siderophore 2,3-dihyroxybenzoic acid (2,3-DHBA) is required for the wild-type virulence of Brucella abortus in cattle. A possible explanation for this requirement was uncovered when it was determined that a B. abortus dhbC mutant (BHB1) defective in 2,3-DHBA production displays marked growth restriction in comparison to its parent strain, B. abortus 2308, when cultured in the presence of erythritol under low-iron conditions. This phenotype is not displayed when these strains are cultured under low-iron conditions in the presence of other readily utilizable carbon and energy sources. The addition of either exogenous 2,3-DHBA or FeCl3 relieves this growth defect, suggesting that the inability of the B. abortus dhbC mutant to display wild-type growth in the presence of erythritol under iron-limiting conditions is due to a defect in iron acquisition. Restoring 2,3-DHBA production to the B. abortus dhbC mutant by genetic complementation abolished the erythritol-specific growth defect exhibited by this strain in low-iron medium, verifying the relationship between 2,3-DHBA production and efficient growth in the presence of erythritol under low-iron conditions. The positive correlation between 2,3-DHBA production and growth in the presence of erythritol was further substantiated by the observation that the addition of erythritol to low-iron cultures of B. abortus 2308 stimulated the production of 2,3-DHBA by increasing the transcription of the dhbCEBA operon. Correspondingly, the level of exogenous iron needed to repress dhbCEBA expression in B. abortus 2308 was also greater when this strain was cultured in the presence of erythritol than that required when it was cultured in the presence of any of the other readily utilizable carbon and energy sources tested. The tissues of the bovine reproductive tract are rich in erythritol during the latter stages of pregnancy, and the ability to metabolize erythritol is thought to be important to the virulence of B. abortus in pregnant ruminants. Consequently, the experimental findings presented here offer a plausible explanation for the attenuation of the B. abortus 2,3-DHBA-deficient mutant BHB1 in pregnant ruminants.

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Some observations on the relationship between etch-pit form and structure in biotite

Clay Minerals ◽

10.1180/claymin.1985.020.2.10 ◽

1985 ◽

Vol 20 (2) ◽

pp. 263-271 ◽

Cited By ~ 2

Author(s):

J. A. Medina ◽

M. Morante ◽

S. Leguey ◽

J. Tornero

Keyword(s):

Epitaxial Growth ◽

Iron Content ◽

Chemical Compositions ◽

Previous Knowledge ◽

Structural Explanation ◽

High Iron Content ◽

High Iron ◽

Etch Pit ◽

The Relationship

The object of this study was to find a structural explanation for the corrosion figures produced in biotites having different chemical compositions and to apply this information to other di- or trioctahedral micas. The biotites investigated were used in earlier studies of epitaxial growth, so that previous knowledge of their surface behaviour was available. The biotites studied were from Evje, Norway (number 1), Guomum, Czechoslovakia (number 2), and Tanokami Yama, Japan (number 3). All were very dark in colour due to their high iron content.

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Epitaxial Gold in Au/Si Eutectic Reaction and Epitaxial Aluminum Spikes in Al-1%Si/Ti-W/Si System

MRS Proceedings ◽

10.1557/proc-116-471 ◽

1988 ◽

Vol 116 ◽

Cited By ~ 1

Author(s):

Peng-Heng Chang

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Epitaxial Growth ◽

Orientation Relationship ◽

Gold Film ◽

Eutectic Reaction ◽

Orientation Relationships ◽

Transmission Electron ◽

Relationship Of ◽

The Relationship

AbstractEpitaxial regrowth of gold film on Si as a result of Au/Si eutectic reaction and epitaxial aluminum spikes forming at IC contacts during sintering have been investigated by transmission electron microscopy (TEM). For gold film on Si, three types of epitaxy were observed: (1) the crystal structures of the two lattices are exactly the same, (2) the two structures have the orientation relationship of Au(111)//Si(111) and Au[132]//Si[231] and (3) 20° misorientation from the relationship in (2). Two orientation relationships were observed in the case of Al spike in Si: (1) Al[011]//Si[123] and Al(200)//Si(11), (2) Al[001]//Si[112] and 2° misorientation between Al(200) and Si(111). Possible mechanisms are proposed to explained the observed epitaxial growth.

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Continuum Limit of a Step Flow Model of Epitaxial Growth

MRS Proceedings ◽

10.1557/proc-701-t1.7.1 ◽

2001 ◽

Vol 701 ◽

Cited By ~ 1

Author(s):

R.V. Kohn ◽

T.S. Lo ◽

N.K. Yip

Keyword(s):

Epitaxial Growth ◽

Jacobi Equation ◽

Flow Model ◽

Space Dimension ◽

Film Surface ◽

Local Behavior ◽

Free Boundaries ◽

Step Flow ◽

The Relationship ◽

Hamilton Jacobi Equation

ABSTRACTWe examine a class of step ow models of epitaxial growth obtained from a Burton-Cabrera-Frank (BCF) type approach in one space dimension. Our goal is to derive a consistent contin uummodel for the evolutionof the film surface. Away from peaks and valleys, the surface height solves a Hamilton-Jacobi equation (HJE). The peaks are free boundaries for this HJE. Their evolution must be specified by boundary conditions reecting the micro- scopic physics of nucleation. We inv estigate this boundary condition by numerical simulation of the step ow dynamics using a simple nucleation law. Our results rev ealthe presence of special structures in the profile near a peak; we discuss the relationship between these structures and the contin uumequation. We further address the importance of evaporation for matching the local behavior near the peak to the solution of the contin uum equation.

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Erf2, a Novel Gene Product That Affects the Localization and Palmitoylation of Ras2 in Saccharomyces cerevisiae

Molecular and Cellular Biology ◽

10.1128/mcb.19.10.6775 ◽

1999 ◽

Vol 19 (10) ◽

pp. 6775-6787 ◽

Cited By ~ 126

Author(s):

Doug J. Bartels ◽

David A. Mitchell ◽

Xiangwen Dong ◽

Robert J. Deschenes

Keyword(s):

Subcellular Localization ◽

Integral Membrane Protein ◽

Subcellular Fractionation ◽

Growth Defect ◽

Loss Of Function ◽

Reading Frame ◽

Rich Domain ◽

Carboxy Terminal ◽

The Relationship ◽

Yeast Genetic

ABSTRACT Plasma membrane localization of Ras requires posttranslational addition of farnesyl and palmitoyl lipid moieties to a C-terminal CaaX motif (C is cysteine, a is any aliphatic residue, X is the carboxy terminal residue). To better understand the relationship between posttranslational processing and the subcellular localization of Ras, a yeast genetic screen was undertaken based on the loss of function of a palmitoylation-dependentRAS2 allele. Mutations were identified in an uncharacterized open reading frame (YLR246w) that we have designated ERF2 and a previously described suppressor of hyperactive Ras, SHR5. ERF2 encodes a 41-kDa protein with four predicted transmembrane (TM) segments and a motif consisting of the amino acids Asp-His-His-Cys (DHHC) within a cysteine-rich domain (CRD), called DHHC-CRD. Mutations within the DHHC-CRD abolish Erf2 function. Subcellular fractionation and immunolocalization experiments reveal that Erf2 tagged with a triply iterated hemagglutinin epitope is an integral membrane protein that colocalizes with the yeast endoplasmic reticulum marker Kar2. Strains lacking ERF2 are viable, but they have a synthetic growth defect in the absence of RAS2 and partially suppress the heat shock sensitivity resulting from expression of the hyperactiveRAS2(V19) allele. Ras2 proteins expressed in anerf2Δ strain have a reduced level of palmitoylation and are partially mislocalized to the vacuole. Based on these observations, we propose that Erf2 is a component of a previously uncharacterized Ras subcellular localization pathway. Putative members of an Erf2 family of proteins have been uncovered in yeast, plant, worm, insect, and mammalian genome databases, suggesting that Erf2 plays a role in Ras localization in all eucaryotes.

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Continuum imit of a tep Flow odel of Epitaxial Growth

MRS Proceedings ◽

10.1557/proc-696-t1.7 ◽

2001 ◽

Vol 696 ◽

Cited By ~ 2

Author(s):

R.V. Kohn ◽

T.S. Lo ◽

N.K. Yip

Keyword(s):

Numerical Simulation ◽

Boundary Condition ◽

Boundary Conditions ◽

Epitaxial Growth ◽

Space Dimension ◽

Local Behavior ◽

Free Boundaries ◽

The Relationship ◽

One Space Dimension

AbstractWe examine a class of step ow models of epitaxial growth obtained from a Burton-Cabrera-Frank (BCF) type approach in one space dimension. ur goal is to derive a consistent contin uummodel for the ev olutionof the lm surface. Away from peaks and valleys, the surface height solves a Hamilton- acobi equation (H E). he peaks are free boundaries for this H E. heir evolution must be speci ed by boundary conditions re ecting the microscopic physics of nucleation. e investigate this boundary condition by numerical simulation of the step ow dynamics using a simple n ucleationlaw. ur results rev ealthe presence of sp ecial structures in the pro le near a peak; we discuss the relationship between these structures and the contin uumequation. e further address the importance of ev aporationfor matching the local behavior near the peak to the solution of the contin uum equation.

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Atomic interface structure-property investigations

Canadian Journal of Physics ◽

10.1139/p99-075 ◽

2000 ◽

Vol 77 (12) ◽

pp. 985-994

Author(s):

K L Kavanagh

Keyword(s):

Thin Films ◽

Epitaxial Growth ◽

Interface Structure ◽

Magnetic Multilayers ◽

Ferroelectric Thin Films ◽

Structure Property ◽

Interface Formation ◽

Semiconductor Contacts ◽

The Relationship ◽

Impurities And Defects

Our current understanding of the relationship between interfacialstructure and the resulting properties remains very rudimentary.This is a concern for many fields and applications, includingmetal/semiconductor contacts, insulator/semiconductor field effectjunctions, magnetic multilayers, ferroelectric thin films, andsemiconductor heterostructures. The situation is slightly improvedin the case of epitaxial growth where a deposited layer followsthe structure of the underlying substrate. However, even withthese systems the interfacial properties are difficult to predictaccurately, even when impurities and defects can be ignored. Thispaper highlights a number of recent examples of interfacestructure-property investigations that have attempted tounderstand how the interface formation determines the relevantfilm or interface property. PACS Nos.: 68.55.Jk, 68.55.Ln, 68.65.+g

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The Relationship between Surface Pits Density and Growth Parameters during the Epitaxial Growth of 4H-SiC

Materials Science Forum ◽

10.4028/www.scientific.net/msf.858.229 ◽

2016 ◽

Vol 858 ◽

pp. 229-232 ◽

Cited By ~ 1

Author(s):

Wei Yu Chen ◽

Han Chieh Ho ◽

Po Fei Yang ◽

Liang Choo Hsia

Keyword(s):

Growth Rate ◽

Epitaxial Growth ◽

Growth Temperature ◽

Growth Parameters ◽

Lower Surface ◽

Ratio Condition ◽

Background Doping ◽

Good Uniformity ◽

Temperature And Growth ◽

The Relationship

In this study, different parameters of 4H-SiC epitaxial growth were used to investigate the influence on surface pits density. It was found that the density of surface pits can be reduced significantly at lower C/Si ratio condition but doping uniformity became worse simultaneously. The background doping was higher than 2E15 cm-3 when C/Si ratio was lower than 1.0. Influences of growth temperature and growth rate are also discussed. The lower surface pits density 4H-SiC epilayer with good uniformity (s/mean below 2%) can be realized during optimal condition.

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