11 Matching Results

Search Results

Advanced search parameters have been applied.

Laser excitation

Description: Topics covered include: effects of parity non-conserving weak neutral interactions in atoms; spectroscopy of exotic atoms; and relativistic many-body dynamic theories. (GHT)
Date: January 1, 1982
Creator: Huang, K.N.
Partner: UNT Libraries Government Documents Department

Theoretical triply differential cross section of electron-impact ionization of atoms

Description: The triply differential cross section of electron-impact ionization of atoms is given in a parameterized form, suitable for theoretical computations or for semi-empirical fittings. Application of the present formulation is demonstrated. Merits of coplanar measurements are discussed. It is also shown that the coplanar up-down asymmetry of the ejected electron is linear in the scattering angle, or the momentum transfer, of the incident electron for small momentum transfers.
Date: January 1, 1983
Creator: Huang, K.N.
Partner: UNT Libraries Government Documents Department

Off-specular reflectivity study of sputter-deposition of platinum during growth

Description: A series of off-specular diffuse scattering measurements were performed by scanning the detector arm parallel to the sample surface during growth of platinum films on polished silicon substrates. During early stage of growth, we observe a halo of diffuse scattering around the specular reflection which is similar to Henzler`s ring. A model of random islands was developed to explain the halo of diffuse scattering. During late growth, the film surface was consistent with partially self-affine surface.
Date: August 1, 1995
Creator: You, H.; Huang, K.G. & Kampwirth, R.T.
Partner: UNT Libraries Government Documents Department

The ANL X6B beamline at NSLS: A versatile facility

Description: We have described the x-ray optics and beamline performance of the ANL X6B beam line at the NSLS. Considerable flexibility has been built into the beam line to accommodate a wide range of x-ray diffraction, scattering, and spectroscopy experiments with various requirements. We presented selected examples of experimental results and showed that with the high intensity, high energy resolution, high-q resolution, and energy tunability, the X6B beam line has become a versatile facility.
Date: July 1, 1994
Creator: Huang, K. G.; Ramanathan, M. & Montano, P. A.
Partner: UNT Libraries Government Documents Department

Concentration of synchrotron beams by means of monolithic polycapillary x-ray optics

Description: Capillary Optics have proven to be a valuable tool for concentrating synchrotron radiation. Single tapered capillaries are used at several facilities. However, most of these optics collect only over a small area. this can be overcome by using larger capillary structures. Polycapillary optics can deflect x-rays by larger angles than other x-ray optics that use only one or two reflections. Conventional x-ray optics that achieve similar deflections, are much more energy selective than capillaries. Therefore, capillaries achieve very short focal distances for a wide range of energies. The measurements shown here represent first tests performed with polycapillaries of large input diameter. The performance with respect to transmission efficiency and spot size was evaluated for a set of four very different prototypes. It is shown that a significant gain may be achieved if a spot size of the order of 0.1 mm is required. Further, some characteristics of the different optics are discussed.
Date: August 1, 1995
Creator: Ullrich, J.B.; Klotzko, I.L.; Huang, K.G.; Owens, S.M.; Aloisi, D.C.; Hofmann, F.A. et al.
Partner: UNT Libraries Government Documents Department

Global Analysis of Heat Shock Response in Desulfovibrio vulgaris Hildenborough.

Description: Desulfovibrio vulgaris Hildenborough belongs to a class ofsulfate-reducing bacteria (SRB) and is found ubiquitously in nature.Given the importance of SRB-mediated reduction for bioremediation ofmetal ion contaminants, ongoing research on D. vulgaris has been in thedirection of elucidating regulatory mechanisms for this organism under avariety of stress conditions. This work presents a global view of thisorganism's response to elevated growth temperature using whole-celltranscriptomics and proteomics tools. Transcriptional response (1.7-foldchange or greater; Z>1.5) ranged from 1,135 genes at 15 min to 1,463genes at 120 min for a temperature up-shift of 13oC from a growthtemperature of 37oC for this organism and suggested both direct andindirect modes of heat sensing. Clusters of orthologous group categoriesthat were significantly affected included posttranslationalmodifications; protein turnover and chaperones (up-regulated); energyproduction and conversion (down-regulated), nucleotide transport,metabolism (down-regulated), and translation; ribosomal structure; andbiogenesis (down-regulated). Analysis of the genome sequence revealed thepresence of features of both negative and positive regulation whichincluded the CIRCE element and promoter sequences corresponding to thealternate sigma factors ?32 and ?54. While mechanisms of heat shockcontrol for some genes appeared to coincide with those established forEscherichia coli and Bacillus subtilis, the presence of unique controlschemes for several other genes was also evident. Analysis of proteinexpression levels using differential in-gel electrophoresis suggestedgood agreement with transcriptional profiles of several heat shockproteins, including DnaK (DVU0811), HtpG (DVU2643), HtrA (DVU1468), andAhpC (DVU2247). The proteomics study also suggested the possibility ofposttranslational modifications in the chaperones DnaK, AhpC, GroES(DVU1977), and GroEL (DVU1976) and also several periplasmic ABCtransporters.
Date: September 16, 2005
Creator: Chhabra, S.R.; He, Q.; Huang, K.H.; Gaucher, S.P.; Alm, E.J.; He,Z. et al.
Partner: UNT Libraries Government Documents Department

Response of Desulfovibrio vulgaris to Alkaline Stress

Description: The response of exponentially growing Desulfovibrio vulgarisHildenborough to pH 10 stress was studied using oligonucleotidemicroarrays and a study set of mutants with genes suggested by microarraydata to be involved in the alkaline stress response deleted. The datashowed that the response of D. vulgaris to increased pH is generallysimilar to that of Escherichia coli but is apparently controlled byunique regulatory circuits since the alternative sigma factors (sigma Sand sigma E) contributing to this stress response in E. coli appear to beabsent in D. vulgaris. Genes previously reported to be up-regulated in E.coli were up-regulated in D. vulgaris; these genes included three ATPasegenes and a tryptophan synthase gene. Transcription of chaperone andprotease genes (encoding ATP-dependent Clp and La proteases and DnaK) wasalso elevated in D. vulgaris. As in E. coli, genes involved in flagellumsynthesis were down-regulated. The transcriptional data also identifiedregulators, distinct from sigma S and sigma E, that are likely part of aD. vulgaris Hildenborough-specific stress response system.Characterization of a study set of mutants with genes implicated inalkaline stress response deleted confirmed that there was protectiveinvolvement of the sodium/proton antiporter NhaC-2, tryptophanase A, andtwo putative regulators/histidine kinases (DVU0331 andDVU2580).
Date: November 30, 2007
Creator: Stolyar, S.; He, Q.; He, Z.; Yang, Z.; Borglin, S.E.; Joyner, D. et al.
Partner: UNT Libraries Government Documents Department

Temporal transcriptomic analysis of Desulfovibrio vulgaris Hildenborough transition into stationary phase growth during electrondonor depletion

Description: Desulfovibrio vulgaris was cultivated in a defined medium, and biomass was sampled for approximately 70 h to characterize the shifts in gene expression as cells transitioned from the exponential to the stationary phase during electron donor depletion. In addition to temporal transcriptomics, total protein, carbohydrate, lactate, acetate, and sulfate levels were measured. The microarray data were examined for statistically significant expression changes, hierarchical cluster analysis, and promoter element prediction and were validated by quantitative PCR. As the cells transitioned from the exponential phase to the stationary phase, a majority of the down-expressed genes were involved in translation and transcription, and this trend continued at the remaining times. There were general increases in relative expression for intracellular trafficking and secretion, ion transport, and coenzyme metabolism as the cells entered the stationary phase. As expected, the DNA replication machinery was down-expressed, and the expression of genes involved in DNA repair increased during the stationary phase. Genes involved in amino acid acquisition, carbohydrate metabolism, energy production, and cell envelope biogenesis did not exhibit uniform transcriptional responses. Interestingly, most phage-related genes were up-expressed at the onset of the stationary phase. This result suggested that nutrient depletion may affect community dynamics and DNA transfer mechanisms of sulfate-reducing bacteria via the phage cycle. The putative feoAB system (in addition to other presumptive iron metabolism genes) was significantly up-expressed, and this suggested the possible importance of Fe{sup 2+} acquisition under metal-reducing conditions. The expression of a large subset of carbohydrate-related genes was altered, and the total cellular carbohydrate levels declined during the growth phase transition. Interestingly, the D. vulgaris genome does not contain a putative rpoS gene, a common attribute of the {delta}-Proteobacteria genomes sequenced to date, and the transcription profiles of other putative rpo genes were not significantly altered. Our results indicated that in addition to ...
Date: August 1, 2006
Creator: Clark, M.E.; He, Q.; He, Z.; Huang, K.H.; Alm, E.J.; Wan, X.-F. et al.
Partner: UNT Libraries Government Documents Department

Global transcriptional, physiological and metabolite analyses of Desulfovibrio vulgaris Hildenborough responses to salt adaptation

Description: The response of Desulfovibrio vulgaris Hildenborough to salt adaptation (long-term NaCl exposure) was examined by physiological, global transcriptional, and metabolite analyses. The growth of D. vulgaris was inhibited by high levels of NaCl, and the growth inhibition could be relieved by the addition of exogenous amino acids (e.g., glutamate, alanine, tryptophan) or yeast extract. Salt adaptation induced the expression of genes involved in amino acid biosynthesis and transport, electron transfer, hydrogen oxidation, and general stress responses (e.g., heat shock proteins, phage shock proteins, and oxidative stress response proteins). Genes involved in carbon metabolism, cell motility, and phage structures were repressed. Comparison of transcriptomic profiles of D. vulgaris responses to salt adaptation with those of salt shock (short-term NaCl exposure) showed some similarity as well as a significant difference. Metabolite assays showed that glutamate and alanine were accumulated under salt adaptation, suggesting that they may be used as osmoprotectants in D. vulgaris. A conceptual model is proposed to link the observed results to currently available knowledge for further understanding the mechanisms of D. vulgaris adaptation to elevated NaCl.
Date: December 1, 2009
Creator: He, Z.; Zhou, A.; Baidoo, E.; He, Q.; Joachimiak, M. P.; Benke, P. et al.
Partner: UNT Libraries Government Documents Department

The Early Optical Brightening in the GRB 071010B

Description: We report the detection of early (60-230 s) optical emission of the gamma-ray burst afterglow of GRB071010B. No significant correlation with the prompt {gamma}-ray emission was found. Our high time-resolution data combining with other measurements within 2 days after the burst indicate that GRB071010B is composed of a weak early brightening ({alpha} {approx} 0.6), probably caused by the peak frequency passing through the optical wavelengths, followed by a decay ({alpha} {approx} -0.51), attributed to continuous energy injection by patchy jets.
Date: April 8, 2008
Creator: Wang, J H; Schwamb, M E; Huang, K Y; Wen, C Y; Zhang, Z W; Wang, S Y et al.
Partner: UNT Libraries Government Documents Department