420 research outputs found
A Cross-Whiskers Junction as a Novel Fabrication Process for Intrinsic Josephson Junction
A Bi2Sr2CaCu2O8+d cross-whiskers junction has been successfully discovered as
a novel intrinsic Josephson junction without using any technique for
micro-fabrication. Two Bi2Sr2CaCu2O8+d whisker crystals were placed crosswise
on a MgO substrate and heated at 850C for 30 min. They were electrically
connected at their c-planes. The measurement terminals were made at the four
ends of the whiskers. The I-V characteristics of the cross-whiskers junction at
5K were found to show a clear multiple-branch structure with a spacing of
approximately 15 mV that is a feature of the intrinsic Josephson junction. The
critical current density Jc was estimated to be 1170 A/cm2. The
branch-structure was strongly suppressed by the magnetic field above 1kOe.Comment: 4 pages, PDF fil
Use of the λ Red-recombineering method for genetic engineering of Pantoea ananatis
<p>Abstract</p> <p>Background</p> <p><it>Pantoea ananatis</it>, a member of the <it>Enterobacteriacea </it>family, is a new and promising subject for biotechnological research. Over recent years, impressive progress in its application to L-glutamate production has been achieved. Nevertheless, genetic and biotechnological studies of <it>Pantoea ananatis </it>have been impeded because of the absence of genetic tools for rapid construction of direct mutations in this bacterium. The λ Red-recombineering technique previously developed in <it>E. coli </it>and used for gene inactivation in several other bacteria is a high-performance tool for rapid construction of precise genome modifications.</p> <p>Results</p> <p>In this study, the expression of λ Red genes in <it>P. ananatis </it>was found to be highly toxic. A screening was performed to select mutants of <it>P. ananatis </it>that were resistant to the toxic affects of λ Red. A mutant strain, SC17(0) was identified that grew well under conditions of simultaneous expression of λ <it>gam</it>, <it>bet</it>, and <it>exo </it>genes. Using this strain, procedures for fast introduction of multiple rearrangements to the <it>Pantoea ananatis </it>genome based on the λ Red-dependent integration of the PCR-generated DNA fragments with as short as 40 bp flanking homologies have been demonstrated.</p> <p>Conclusion</p> <p>The λ Red-recombineering technology was successfully used for rapid generation of chromosomal modifications in the specially selected <it>P. ananatis </it>recipient strain. The procedure of electro-transformation with chromosomal DNA has been developed for transfer of the marked mutation between different <it>P. ananatis </it>strains. Combination of these techniques with λ Int/Xis-dependent excision of selective markers significantly accelerates basic research and construction of producing strains.</p
Point-contact spectroscopy of the antiferromagnetic superconductor HoNi2B2C in the normal and superconducting state
Point-contact (PC) spectroscopy measurements on antiferromagnetic (AF)
(T_N=5.2K) HoNi2B2C single crystals in the normal and two different
superconducting (SC) states (T_c=8.5K and T_c^*=5.6K<T_c, with 2\Delta/kT_c^*=3.9. The strong coupling
Eliashberg analysis of the low-temperature SC phase with T_c^*=5.6K =T_N,
coexisting with the commensurate AF structure, suggests a sizable value of the
EPI constant \lambda_s=0.93. We also provide strong support for the recently
proposed by us ''Fermi surface (FS) separation'' scenario for the coexistence
of magnetism and superconductivity in magnetic borocarbides, namely, that the
superconductivity in the commensurate AF phase survives at a special (nearly
isotropic) FS sheet without an admixture of Ho 5d states. Above T_c^* the SC
features in the PC characteristics are strongly suppressed pointing to a
specific weakened SC state between T_c* and T_c.Comment: 11 pages, 8 figs, to be published in PRB, Vol.75, Iss.2
d-like Symmetry of the Order Parameter and Intrinsic Josephson Effects in Bi2212 Cross-Whisker Junctions
An intrinsic tunnel junction was made using two Bi-2212 single crystal
whiskers. The two whiskers with a cross-angle were overlaid at their c-planes
and connected by annealing. The angular dependence of the critical current
density along the c-axis is of the d-wave symmetry. However, the angular
dependence is much stronger than that of the conventional d-wave. Furthermore,
the current vs. voltage characteristics of the cross-whiskers junctions show a
multiple-branch structure at any cross-angle, indicating the formation of the
intrinsic Josephson junction array.Comment: 4 pages PDF fil
The complete genome sequence of Pantoea ananatis AJ13355, an organism with great biotechnological potential
Pantoea ananatis AJ13355 is a newly identified member of the Enterobacteriaceae family with promising biotechnological applications. This bacterium is able to grow at an acidic pH and is resistant to saturating concentrations of L-glutamic acid, making this organism a suitable host for the production of L-glutamate. In the current study, the complete genomic sequence of P. ananatis AJ13355 was determined. The genome was found to consist of a single circular chromosome consisting of 4,555,536 bp [DDBJ: AP012032] and a circular plasmid, pEA320, of 321,744 bp [DDBJ: AP012033]. After automated annotation, 4,071 protein-coding sequences were identified in the P. ananatis AJ13355 genome. For 4,025 of these genes, functions were assigned based on homologies to known proteins. A high level of nucleotide sequence identity (99%) was revealed between the genome of P. ananatis AJ13355 and the previously published genome of P. ananatis LMG 20103. Short colinear regions, which are identical to DNA sequences in the Escherichia coli MG1655 chromosome, were found to be widely dispersed along the P. ananatis AJ13355 genome. Conjugal gene transfer from E. coli to P. ananatis, mediated by homologous recombination between short identical sequences, was also experimentally demonstrated. The determination of the genome sequence has paved the way for the directed metabolic engineering of P. ananatis to produce biotechnologically relevant compounds
Absence of Tc-Pinning Phenomenon Under High Pressure in High-Entropy REO0.5F0.5BiS2 Layered Superconductor
Recently, robustness of superconductivity (transition temperature, Tc) under
high pressures has been observed in high-entropy alloy (HEA), bcc-type
Ti-Zr-Hf-Nb-Ta, and HEA-type compounds (Ag,In,Sn,Pb,Bi)Te with a NaCl-type
structure. Since those materials have three-dimensional crystal structure,
investigation on the pressure dependence of Tc of low-dimensional materials is
needed to understand the phenomena. Here, we investigated the superconducting
properties and the crystal structure of BiS2-based layered system
REO0.5F0.5BiS2. Although the robustness of Tc was induced in MTe with
increasing M-site configurational entropy, the increase in RE-site
configurational entropy does not induce robustness of Tc under high pressures
in REO0.5F0.5BiS2. The crystal structure of HEA-type REO0.5F0.5BiS2 was
confirmed as monoclinic P21/m, which is the same space group as the
zero-entropy counterpart LaO0.5F0.5BiS2. The results suggest that an increase
in configurational entropy at blocking layers do not affect crystal structure
and superconducting properties under high pressures in the BiS2-based layered
system.Comment: 9 pages, 4 figure
Full-Fledged Dwarf Irregular Galaxy Leo A
We have studied Leo A - the isolated and extremely gas rich dwarf irregular
galaxy of very low stellar mass and metallicity. Ages of the stellar
populations in Leo A are ranging from ~10 Myr to ~10 Gyr. Here we report the
discovery of an old stellar halo and a sharp stellar edge. Also we find the
distribution of stars extending beyond the gaseous envelope of the galaxy.
Therefore, Leo A by its structure as well as stellar and gaseous content is
found to resemble massive disk galaxies. This implies that galaxies of very low
stellar mass are also able to develop complex structures, challenging
contemporary understanding of galaxy evolution.Comment: 9 pages, 3 figures, submitted to ApJ
Minichromosome Maintenance Protein 7 is a potential therapeutic target in human cancer and a novel prognostic marker of non-small cell lung cancer.
BACKGROUND: The research emphasis in anti-cancer drug discovery has always been to search for a drug with the greatest antitumor potential but fewest side effects. This can only be achieved if the drug used is against a specific target located in the tumor cells. In this study, we evaluated Minichromosome Maintenance Protein 7 (MCM7) as a novel therapeutic target in cancer. RESULTS: Immunohistochemical analysis showed that MCM7 was positively stained in 196 of 331 non-small cell lung cancer (NSCLC), 21 of 29 bladder tumor and 25 of 70 liver tumor cases whereas no significant staining was observed in various normal tissues. We also found an elevated expression of MCM7 to be associated with poor prognosis for patients with NSCLC (P = 0.0055). qRT-PCR revealed a higher expression of MCM7 in clinical bladder cancer tissues than in corresponding non-neoplastic tissues (P < 0.0001), and we confirmed that a wide range of cancers also overexpressed MCM7 by cDNA microarray analysis. Suppression of MCM7 using specific siRNAs inhibited incorporation of BrdU in lung and bladder cancer cells overexpressing MCM7, and suppressed the growth of those cells more efficiently than that of normal cell strains expressing lower levels of MCM7. CONCLUSIONS: Since MCM7 expression was generally low in a number of normal tissues we examined, MCM7 has the characteristics of an ideal candidate for molecular targeted cancer therapy in various tumors and also as a good prognostic biomarker for NSCLC patients.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are
Alpha-fetoprotein-producing primary lung carcinoma: A case report
Alpha-fetoprotein (AFP)-producing lung adenocarcinoma is a rare type of lung cancer, with its characteristics not yet fully clarified. We recently encountered a case of this type of lung cancer. The patient was a 69-year-old man who consulted an internist with the chief complaint of epigastric pain. Chest X-ray and CT revealed a lobulated mass measuring 70 mm in diameter in the right lower lung field and a metastasis in the right hilar lymph nodes. Of the tumor markers, the serum AFP was elevated (4620 ng/ml), and the serum carcinoembryonic antigen and carbohydrate antigen 19-9 were also slightly elevated. Transbronchial lung biopsy revealed the diagnosis of lung cancer. Under thoracoscopic assistance, right lower lobectomy + mediastinal lymph node dissection was carried out. Immunostaining showed the tumor cells to be AFP-positive. The tumor was thus diagnosed as an AFP-producing lung adenocarcinoma. The patient followed an uneventful clinical course after the surgery, with serum AFP decreasing to the normal range by about 2 weeks after the surgery. As of this writing, no sign of tumor recurrence has been noted. This case is presented here with a review of the literature
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