1,118 research outputs found
A novel gnd mutation leading to increased L-lysine production in Corynebacterium glutamicum
ArticleFems Microbiology Letters. 242(2): 265-274 (2005)journal articl
Hubbard band or oxygen vacancy states in the correlated electron metal SrVO?
We study the effect of oxygen vacancies on the electronic structure of the
model strongly correlated metal SrVO. By means of angle-resolved
photoemission (ARPES) synchrotron experiments, we investigate the systematic
effect of the UV dose on the measured spectra. We observe the onset of a
spurious dose-dependent prominent peak at an energy range were the lower
Hubbard band has been previously reported in this compound, raising questions
on its previous interpretation. By a careful analysis of the dose dependent
effects we succeed in disentangling the contributions coming from the oxygen
vacancy states and from the lower Hubbard band. We obtain the intrinsic ARPES
spectrum for the zero-vacancy limit, where a clear signal of a lower Hubbard
band remains. We support our study by means of state-of-the-art ab initio
calculations that include correlation effects and the presence of oxygen
vacancies. Our results underscore the relevance of potential spurious states
affecting ARPES experiments in correlated metals, which are associated to the
ubiquitous oxygen vacancies as extensively reported in the context of a
two-dimensional electron gas (2DEG) at the surface of insulating
transition metal oxides.Comment: Manuscript + Supplemental Material, 12 pages, 9 figure
Beam Halo Imaging with a Digital Optical Mask
Beam halo is an important factor in any high intensity accelerator. It can
cause difficulties in the control of the beam, emittance growth, particle loss
and even damage to the accelerator. It is therefore essential to understand the
mechanisms of halo formation and its dynamics in order to control and minimize
its effects. Experimental measurement of the halo distribution is an important
tool for such studies. In this paper, we present a new adaptive masking method
that we have developed to image beam halo, which uses a digital
micro-mirror-array device (DMD). This method has been thoroughly investigated
in the laboratory using laser and white light sources, and with real beams
produced by the University of Maryland Electron Ring (UMER). A high dynamic
range ~10(5) has been demonstrated with this new method and recent studies
indicate that this number can be exceeded for more intense beams by at least an
order of magnitude. The method is flexible, easy to setup and can be used at
any accelerator or light source. We present the results of our measurements of
the performance of the method and images of beam halos produced under various
experimental conditions.Comment: 44 pgs.; submitted to Phys. Rev. ST Accel. and Beams, 3/9/201
Evidence for phase formation in potassium intercalated 1,2;8,9-dibenzopentacene
We have prepared potassium intercalated 1,2;8,9-dibenzopentacene films under
vacuum conditions. The evolution of the electronic excitation spectra upon
potassium addition as measured using electron energy-loss spectroscopy clearly
indicate the formation of particular doped phases with compositions
Kdibenzopentacene ( = 1,2,3). Moreover, the stability of these phases as
a function of temperature has been explored. Finally, the electronic excitation
spectra also give insight into the electronic ground state of the potassium
doped 1,2;8,9-dibenzopentacene films.Comment: 6 pages, 5 figures. arXiv admin note: text overlap with
arXiv:1201.200
Absorption of Scintillation Light in a 100 Liquid Xenon Ray Detector and Expected Detector Performance
An 800L liquid xenon scintillation ray detector is being developed
for the MEG experiment which will search for decay
at the Paul Scherrer Institut. Absorption of scintillation light of xenon by
impurities might possibly limit the performance of such a detector. We used a
100L prototype with an active volume of 372x372x496 mm to study the
scintillation light absorption. We have developed a method to evaluate the
light absorption, separately from elastic scattering of light, by measuring
cosmic rays and sources. By using a suitable purification technique,
an absorption length longer than 100 cm has been achieved. The effects of the
light absorption on the energy resolution are estimated by Monte Carlo
simulation.Comment: 18 pages, 10 figures (eps). Submitted to Nucl. Instr. and Meth.
High-density two-dimensional electron system induced by oxygen vacancies in ZnO
We realize a two-dimensional electron system (2DES) in ZnO by simply
depositing pure aluminum on its surface in ultra-high vacuum, and characterize
its electronic structure using angle-resolved photoemission spectroscopy. The
aluminum oxidizes into alumina by creating oxygen vacancies that dope the bulk
conduction band of ZnO and confine the electrons near its surface. The electron
density of the 2DES is up to two orders of magnitude higher than those obtained
in ZnO heterostructures. The 2DES shows two -type subbands, that we compare
to the -like 2DESs in titanates, with clear signatures of many-body
interactions that we analyze through a self-consistent extraction of the system
self-energy and a modeling as a coupling of a 2D Fermi liquid with a Debye
distribution of phonons.Comment: Article + Supplementary Material, 12 pages, 3 main figures, 6
supplementary figure
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Mutations in the Satellite Cell Gene MEGF10 Cause a Recessive Congenital Myopathy with Minicores
We ascertained a nuclear family in which three of four siblings were affected with an unclassified autosomal recessive myopathy characterized by severe weakness, respiratory impairment, scoliosis, joint contractures, and an unusual combination of dystrophic and myopathic features on muscle biopsy. Whole genome sequence from one affected subject was filtered using linkage data and variant databases. A single gene, MEGF10, contained nonsynonymous mutations that co-segregated with the phenotype. Affected subjects were compound heterozygous for missense mutations c.976T > C (p.C326R) and c.2320T > C (p.C774R). Screening the MEGF10 open reading frame in 190 patients with genetically unexplained myopathies revealed a heterozygous mutation, c.211C > T (p.R71W), in one additional subject with a similar clinical and histological presentation as the discovery family. All three mutations were absent from at least 645 genotyped unaffected control subjects. MEGF10 contains 17 atypical epidermal growth factor-like domains, each of which contains eight cysteine residues that likely form disulfide bonds. Both the p.C326R and p.C774R mutations alter one of these residues, which are completely conserved in vertebrates. Previous work showed that murine Megf10 is required for preserving the undifferentiated, proliferative potential of satellite cells, myogenic precursors that regenerate skeletal muscle in response to injury or disease. Here, knockdown of megf10 in zebrafish by four different morpholinos resulted in abnormal phenotypes including unhatched eggs, curved tails, impaired motility, and disorganized muscle tissue, corroborating the pathogenicity of the human mutations. Our data establish the importance of MEGF10 in human skeletal muscle and suggest satellite cell dysfunction as a novel myopathic mechanism
Fibroblast growth factor 19 expression correlates with tumor progression and poorer prognosis of hepatocellular carcinoma
<p>Abstract</p> <p>Background</p> <p>Although fibroblast growth factor 19 (FGF19) can promote liver carcinogenesis in mice, its involvement in human hepatocellular carcinoma (HCC) has not been well investigated. FGF19, a member of the FGF family, has unique specificity for its receptor FGFR4. This study aimed to clarify the involvement of FGF19 in the development of HCC.</p> <p>Methods</p> <p>We investigated human FGF19 and FGFR4 expression in 40 hepatocellular carcinoma specimens using quantitative real-time reverse transcription polymerase chain reaction (RT-PCR) analysis and immunohistochemistry. Moreover, we examined the expression and the distribution of FGF19 and FGFR4 in 5 hepatocellular carcinoma cell lines (HepG2, HuH7, HLE, HLF, and JHH7) using RT-PCR and immunohistochemistry. To test the role of the FGF19/FGFR4 system in tumor progression, we used recombinant FGF19 protein and small interfering RNA (siRNA) of <it>FGF19 </it>and <it>FGFR4 </it>to regulate their concentrations.</p> <p>Results</p> <p>We found that FGF19 was significantly overexpressed in HCCs as compared with corresponding noncancerous liver tissue (<it>P </it>< 0.05). Univariate and multivariate analyses revealed that the tumor <it>FGF19 </it>mRNA expression was an independent prognostic factor for overall and disease-free survival. Moreover, we found that the FGF19 recombinant protein could increase the proliferation (<it>P </it>< 0.01, <it>n </it>= 12) and invasion (<it>P </it>< 0.01, <it>n </it>= 6) capabilities of human hepatocellular carcinoma cell lines and inhibited their apoptosis (<it>P </it>< 0.01, <it>n </it>= 12). Inversely, decreasing <it>FGF19 </it>and <it>FGFR4 </it>expression by siRNA significantly inhibited proliferation and increased apoptosis in JHH7 cells (<it>P </it>< 0.01, <it>n </it>= 12). The postoperative serum FGF19 levels in HCC patients was significantly lower than the preoperative levels (<it>P </it>< 0.01, <it>n </it>= 29).</p> <p>Conclusions</p> <p>FGF19 is critically involved in the development of HCCs. Targeting FGF19 inhibition is an attractive potential therapeutic strategy for HCC.</p
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