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‣ A Novel β-N-Acetylglucosaminidase from Streptomyces thermoviolaceus OPC-520: Gene Cloning, Expression, and Assignment to Family 3 of the Glycosyl Hydrolases

Tsujibo, Hiroshi; Hatano, Naoya; Mikami, Tadahisa; Hirasawa, Ayako; Miyamoto, Katsushiro; Inamori, Yoshihiko
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /08/1998 Português
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A β-N-acetylglucosaminidase gene (nagA) of Streptomyces thermoviolaceus OPC-520 was cloned in Streptomyces lividans 66. The nucleotide sequence of the gene, which encodes NagA, revealed an open reading frame of 1,896 bp, encoding a protein with an Mr of 66,329. The deduced primary structure of NagA was confirmed by comparison with the N-terminal amino acid sequence of the cloned β-N-acetylglucosaminidase expressed by S. lividans. The enzyme shares no sequence similarity with the classical β-N-acetylglucosaminidases belonging to family 20. However, NagA, which showed no detectable β-glucosidase activity, revealed homology with microbial β-glucosidases belonging to family 3; in particular, striking homology with the active-site regions of β-glucosidases was observed. Thus, the above-mentioned results indicate that NagA from S. thermoviolaceus OPC-520 is classified as a family 3 glycosyl hydrolase. The enzyme activity was optimal at 60°C and pH 5.0, and the apparent Km and Vmax values for p-nitrophenyl-β-N-acetylglucosamine were 425.7 μM and 24.8 μmol min−1 mg of protein−1, respectively.

‣ Cloning and sequence analysis of genes encoding xylanases and acetyl xylan esterase from Streptomyces thermoviolaceus OPC-520.

Tsujibo, H; Ohtsuki, T; Iio, T; Yamazaki, I; Miyamoto, K; Sugiyama, M; Inamori, Y
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /02/1997 Português
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Three genes encoding two types of xylanases (STX-I and STX-II) and an acetyl xylan esterase (STX-III) from Streptomyces thermoviolaceus OPC-520 were cloned, and their DNA sequences were determined. The nucleotide sequences showed that genes stx-II and stx-III were clustered on the genome. The stx-I, stx-II, and stx-III genes encoded deduced proteins of 51, 35.2, and 34.3 kDa, respectively. STX-I and STX-II bound to both insoluble xylan and crystalline cellulose (Avicel). Alignment of the deduced amino acid sequences encoded by stx-I, stx-II, and stx-III demonstrated that the three enzymes contain two functional domains, a catalytic domain and a substrate-binding domain. The catalytic domains of STX-I and STX-II showed high sequence homology to several xylanases which belong to families F and G, respectively, and that of STX-III showed striking homology with an acetyl xylan esterase from S. lividans, nodulation proteins of Rhizobium sp., and chitin deacetylase of Mucor rouxii. In the C-terminal region of STX-I, there were three reiterated amino acid sequences starting from C-L-D, and the repeats were homologous to those found in xylanase A from S. lividans, coagulation factor G subunit alpha from the horseshoe crab, Rarobacter faecitabidus protease I...

‣ Purification, properties, and partial amino acid sequences of thermostable xylanases from Streptomyces thermoviolaceus OPC-520.

Tsujibo, H; Miyamoto, K; Kuda, T; Minami, K; Sakamoto, T; Hasegawa, T; Inamori, Y
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1992 Português
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Two types of xylanases (1,4-beta-D-xylan xylanohydrolase, EC 3.2.1.8) were isolated from the culture filtrate of a thermophilic actinomycete, Streptomyces thermoviolaceus OPC-520. The enzymes (STX-I and STX-II) were purified by chromatography with DEAE-Toyopearl 650 M, CM-Toyopearl 650 M, Sephadex G-75, Phenyl-Toyopearl 650 M, and Mono Q HR. The purified enzymes showed single bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The molecular weights of STX-I and STX-II were 54,000 and 33,000, respectively. The pIs were 4.2 (STX-I) and 8.0 (STX-II). The optimum pH levels for the activity of STX-I and STX-II were pH 7.0. The optimum temperature for the activity of STX-I was 70 degrees C, and that for the activity of STX-II was 60 degrees C. The enzymes were completely inhibited by N-bromosuccinimide. The enzymes degraded xylan, producing xylose and xylobiose as the predominant products, indicating that they were endoxylanases. STX-I showed high sequence homology with the exoglucanase from Cellulomonas fimi (47% homology), and STX-II showed high sequence homology with the xylanase from Bacillus pumilus (46% homology).

‣ Purification and properties of a thermostable chitinase from Streptomyces thermoviolaceus OPC-520.

Tsujibo, H; Minoura, K; Miyamoto, K; Endo, H; Moriwaki, M; Inamori, Y
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /02/1993 Português
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A chitinase was purified from the culture filtrate of Streptomyces thermoviolaceus OPC-520. The enzyme showed a high optimum temperature (70 to 80 degrees C), a high optimum pH level (8.0 to 10.0), and heat stability. This enzyme showed high sequence homology with chitinases from Serratia marcescens QMB1466 and Bacillus circulans WL-12.

‣ Critical Role of Ser-520 Phosphorylation for Membrane Recruitment and Activation of the ZAP-70 Tyrosine Kinase in T Cells

Yang, Yaoming; Villain, Patricia; Mustelin, Tomas; Couture, Clément
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /11/2003 Português
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Regulation of protein tyrosine kinases (PTKs) by tyrosine phosphorylation is well recognized; in fact, nearly all PTKs require phosphorylation of tyrosine residues in their “activation loop” for catalytic activity. In contrast, the phosphorylation of PTKs on serine and threonine residues has not been studied nearly as much. We report that the ZAP-70 PTK contains predominately phosphoserine in normal T lymphocytes as well as in Jurkat T leukemia cells. We have identified one site of phosphorylation as Ser-520 and find this site to be important for the recruitment and activation of ZAP-70 in T cells. Mutant ZAP-70-S520A had reduced ability to autophosphorylate and to mediate antigen receptor-induced interleukin 2 gene activation and was not enriched at the plasma membrane. These defects were rescued by addition of a myristylation signal to the N terminus of ZAP-70-S520A to force its plasma membrane and lipid raft localization. We conclude that phosphorylation of ZAP-70 at Ser-520 plays an important role in the correct localization of ZAP-70 and in priming ZAP-70 for its acute recruitment and activation upon antigen receptor ligation.

‣ Molecular Characterization of a High-Affinity Xylobiose Transporter of Streptomyces thermoviolaceus OPC-520 and Its Transcriptional Regulation

Tsujibo, Hiroshi; Kosaka, Mitsuo; Ikenishi, Sadao; Sato, Takaji; Miyamoto, Katsushiro; Inamori, Yoshihiko
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /02/2004 Português
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Streptomyces thermoviolaceus OPC-520 secretes two types of xylanases (StxI and StxII), an acetyl xylan esterase (StxIII), and an α-l-arabinofuranosidase (StxIV) in the presence of xylan. Xylan degradation products (mainly xylobiose) produced by the action of these enzymes entered the cell and were then degraded to xylose by an intracellular β-xylosidase (BxlA). A gene cluster involved in xylanolytic system of the strain was cloned and sequenced upstream of and including a BxlA-encoding gene (bxlA). The gene cluster consisted of four different open reading frames organized in the order bxlE, bxlF, bxlG, and bxlA. Reverse transcriptase PCR analysis revealed that the gene cluster is transcribed as polycistronic mRNA. The deduced gene products, comprising BxlE (a sugar-binding lipoprotein), BxlF (an integral membrane protein), and BxlG (an integral membrane protein), showed similarity to components of the bacterial ATP-binding cassette (ABC) transport system; however, the gene for the ATP binding protein was not linked to the bxl operon. The soluble recombinant BxlE protein was analyzed for its binding activity for xylooligosaccharides. The protein showed high-level affinity for xylobiose (Kd = 8.75 × 10−9 M) and for xylotriose (Kd = 8.42 × 10−8 M). Antibodies raised against the recombinant BxlE recognized the detergent-soluble BxlE isolated from S. thermoviolaceus membranes. The deduced BxlF and BxlG proteins are predicted to be integral membrane proteins. These proteins contained the conserved EAA loop (between the fourth and the fifth membrane-spanning segments) which is characteristic of membrane proteins from binding-protein-dependent ABC transporters. In addition...

‣ The Photosynthetic Electron Transport Chain of Chlamydomonas reinhardi: VIII. The 520 nm Light-induced Absorbance Change in the Wild-type and Mutant Strains 1

Chua, Nam-Hai; Levine, R. P.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1969 Português
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The 520 nm light-induced absorbance change in wild-type and 4 mutant strains of Chlamydomonas reinhardi was investigated. In the wild-type strain the absorbance change is composed of at least 2 components, P520 I and P520 II, sensitized by Systems I and II respectively. Some of the properties of these components can be studied by using the appropriate photosynthetic mutant strain. A group of mutant strains modified in the photochemical complex of System II shows only the P520 I absorbance change, whereas a mutant strain deficient in active P700 exhibits only the P520 II absorbance change. The possible relationship between these absorbance changes and the photosynthetic electron transport pathway is discussed.

‣ Hepatic cirrhosis: A clinico-pathological review of 520 cases

MacSween, R. N. M.; Scott, A. R.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /12/1973 Português
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A clinico-pathological review of 520 patients with hepatic cirrhosis coming to necropsy at the Western Infirmary, Glasgow over the period 1900-69 is reported. There has been an overall increase in incidence of cirrhosis since the 1940s, and this has been largely due to a rise in female incidence. A similar trend in the period 1940-71 has been confirmed at a national level in data abstracted from the Annual Reports of the Registrar General for Scotland.

‣ Action Spectrum for the Appearance of the 520 mμ Difference Band in Illuminated Chlorella Cells

Rubinstein, D.; Rabinowitch, E.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /03/1964 Português
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An action spectrum of the 520 mμ difference band in Chlorella is determined using dim illumination. Pigment (or pigments) absorbing most strongly at and above 680 mμ, probably the so-called “long-wave forms” of chlorophyll a appear to be the primary sensitizer of the 520 mμ effect.

‣ Rapid Simultaneous Detection by Real-Time PCR of Cytomegalovirus UL97 Mutations in Codons 460 and 520 Conferring Ganciclovir Resistance▿

Göhring, Katharina; Mikeler, Elfriede; Jahn, Gerhard; Hamprecht, Klaus
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Português
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Ganciclovir (GCV) resistance is an emerging problem for transplant recipients. A sensitive and rapid real-time PCR approach for simultaneous and semiquantitative detection of human cytomegalovirus (HCMV) UL97 mutations in codons 460/520 was established by LightCycler and confirmed by restriction fragment length polymorphism and sequencing. Results from HCMV laboratory strains were compared with results from 11 GCV-resistant clinical isolates.

‣ DYRK1A Autophosphorylation on Serine Residue 520 Modulates Its Kinase Activity via 14-3-3 Binding

Alvarez, Mónica; Altafaj, Xavier; Aranda, Sergi; de la Luna, Susana
Fonte: The American Society for Cell Biology Publicador: The American Society for Cell Biology
Tipo: Artigo de Revista Científica
Publicado em /04/2007 Português
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Dual-specificity tyrosine-phosphorylated and regulated kinase (DYRK) proteins are an evolutionarily conserved family of protein kinases, with members identified from yeast to humans, that participate in a variety of cellular processes. DYRKs are serine/threonine protein kinases that are activated by autophosphorylation on a tyrosine residue in the activation loop. The family member DYRK1A has been shown to phosphorylate several cytosolic proteins and a number of splicing and transcription factors, including members of the nuclear factor of activated T cells family. In the present study, we show that DYRK1A autophosphorylates, via an intramolecular mechanism, on Ser-520, in the PEST domain of the protein. We also show that phosphorylation of this residue, which we show is subjected to dynamic changes in vivo, mediates the interaction of DYRK1A with 14-3-3β. A second 14-3-3 binding site is present within the N-terminal of the protein. In the context of the DYRK1A molecule, neither site can act independently of the other. Bacterially produced DYRK1A and the mutant DYRK1A/S520A have similar kinase activities, suggesting that Ser-520 phosphorylation does not affect the intrinsic kinase activity on its own. Instead, we demonstrate that this phosphorylation allows the binding of 14-3-3β...

‣ Inhibition of KSP by ARRY-520 Induces Cell Cycle Block and Cell Death via the Mitochondrial Pathway in AML Cells

Carter, Bing Z.; Mak, Duncan H.; Woessner, Richard; Gross, Stefan; Schober, Wendy D.; Estrov, Zeev; Kantarjian, Hagop; Andreeff, Michael
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
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Kinesin spindle protein (KSP), a microtubule-associated motor protein essential for cell cycle progression, is overexpressed in many cancers and a potential anti-tumor target. We found that inhibition of KSP by a selective inhibitor, ARRY-520, blocked cell cycle progression, leading to apoptosis in acute myeloid leukemia cell lines which express high levels of KSP. Knockdown of p53, overexpression of XIAP, and mutation in caspase-8 did not significantly affect sensitivity to ARRY-520, suggesting that the response is independent of p53, XIAP, and the extrinsic apoptotic pathway. Although ARRY-520 induced mitotic arrest in both HL-60 and Bcl-2-overexpressing HL-60Bcl-2 cells, cell death was blunted in HL-60Bcl-2 cells, suggesting that the apoptotic program is executed through the mitochondrial pathway. Accordingly, inhibition of Bcl-2 by ABT-737 was synergistic with ARRY-520 in HL-60Bcl-2 cells. Furthermore, ARRY-520 increased Bim protein levels prior to caspase activation in HL-60 cells. ARRY-520 significantly inhibited tumor growth of xenografts in SCID mice and inhibited AML blast but not normal colony formation, supporting a critical role for KSP in proliferation of leukemic progenitor cells. These results demonstrate that ARRY-520 potently induces cell cycle block and subsequent death in leukemic cells via the mitochondrial pathway and has potential to eradicate AML progenitor cells.

‣ TARDBP regulates glycolysis in hepatocellular carcinoma by regulating PFKP through miR-520

Park, Yun-Yong; Kim, Sang Bae; Han, Hee Dong; Sohn, Bo-Hwa; Kim, Ji-Hoon; Liang, Jiyong; Lu, Yiling; Mills, Gordon B.; Sood, Anil K.; Lee, Ju-Seog
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
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Metabolic changes are common features of many cancer cells and are frequently associated with the clinical outcome of patients with various cancers including hepatocellular carcinoma (HCC). Thus, aberrant metabolic pathways in cancer cells are attractive targets for cancer therapy. However, our understanding of cancer-specific regulatory mechanisms of cell metabolism is still very limited. We found that Tat activating regulatory DNA-binding protein (TARDBP) is a novel regulator of glycolysis in HCC cells. TARDBP regulates expression of the platelet isoform of phosphofructokinase (PFKP), the rate-limiting enzyme of glycolysis that catalyzes the irreversible conversion of fructose-6-phosphate to fructose-1,6-bisphosphate. Silencing of TARDBP expression in multiple HCC cell lines leads to impaired glucose metabolism and inhibition of in vitro and in vivo growth of HCC cells. Notably, the miR-520 family is an intermediate regulator of TARDBP-mediated regulation of glycolysis. Mechanistically, TARDBP suppressed expression of the miR-520 family, which in turn inhibited expression of PFKP. We further showed that expression of TARDBP is significantly associated with the overall survival of patients with HCC.

‣ Implicações fático-jurídicas da MP 520 : a precariedade dos vínculos empregatícios nos Hospitais Universitários e o comprometimento de suas funções = Fatic Legal Implications of MP 520: The precariousness of employment contracts in University Hospitals and the commitment of its functions

Silva, Aimeé Mastella Sampaio da; Lucca, Maicon Scariotti; Bellinaso, Pedro Augusto François
Fonte: Superior Tribunal de Justiça do Brasil Publicador: Superior Tribunal de Justiça do Brasil
Tipo: Artigo de Revista Científica
Português
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Discorre sobre as implicações da Medida Provisória 520, editada com o objetivo de criar uma empresa pública que gerisse a prestação de serviços médico-hospitalares, bem como a contratação de mão de obra por hospitais universitários.

‣ Technical and operational analysis of the fortress secure wireless access bridge (ES-520) in support of tactical military coalition operations

Geathers, Sandy.
Fonte: Monterey California. Naval Postgraduate School Publicador: Monterey California. Naval Postgraduate School
Tipo: Tese de Doutorado
Português
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Technology Studies (COASTS) field experimentation program, utilize an access point, wireless bridge, switch, and security gateway. Reducing equipment requirements in the field is most desirable to minimize the equipment footprint, cost, and power required. The COASTS research group, involved in developing a scalable, multi-mission, system of systems for coalition environments, relies heavily on Commercial-Off-The-Shelf (COTS) network technology. Evaluating the performance of COTS technology such as the Fortress Secure Wireless Access Bridge (ES-520) directly supports the programs objectives. This thesis will analyze the performance of the Fortress Secure Wireless Access Bridge (ES-520) vs. traditional 802.11a/b/g wireless access points. Additionally, radio frequency (RF) propagation performance will be analyzed for distance, mobility, sustainability, and technical advantages/disadvantages with respect to varying antenna configurations and physical parameters such as climate and terrain. Testing and evaluation will be accomplished under the COASTS field experimentation program.

‣ Laparoscopic Cholecystectomy and Open Cholecystectomy in Acute Cholecystitis: Critical Analysis of 520 Cases; Colecistectomia por Laparoscopia e por Laparotomia na Colecistite Aguda: Análise Crítica de 520 Casos

Teixeira, João Araújo; Serviço de Cirurgia. Faculdade de Medicina. Universidade do Porto/Hospital de S. João. Porto. Portugal.; Ribeiro, Carlos; Serviço de Cirurgia. Faculdade de Medicina. Universidade do Porto/Hospital de S. João. Porto. Portugal.;
Fonte: Ordem dos Médicos Publicador: Ordem dos Médicos
Tipo: info:eu-repo/semantics/article; article; info:eu-repo/semantics/publishedVersion Formato: application/pdf; application/pdf
Publicado em 30/12/2014 Português
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Introduction: Despite the skepticism with which it was initially seen, laparoscopic cholecystectomy is now the technique of choice for acute cholecystitis. It is, however, important to evaluate the results in comparison with classic cholecystectomy, since the latter is still used by some surgeons in certain situations.Material and Methods: Our research corresponds to the analysis of 520 patients operated on for acute cholecystitis performed in the department of surgery at the São João Hospital in Oporto - 412 (79.2%) laparoscopic cholecystectomies and 108 (20.8%) open cholecystectomies - from 2007 to 2013. We evaluated comorbidities, leukocytosis, time between diagnosis and surgery, ASA, per and postoperative complications, mortality, reoperations, lesion of main bile duct, conversion rate and hospital stay, in order to compare these two techniques. The conversion group was included in laparoscopic cholecystectomy. Statistical analysis was based on descriptive statistic procedures and the evaluation of contrast between groups was based on Fishers’ exact test. Significant values were considered for p < 0.05.Results: Laparoscopic Cholecystectomy versus Open Cholecystectomy: Mortality: 0.7% vs 3,7% (p = 0.0369); Peroperative complications: 3.6% vs 12.9% (p = 0.0006); Surgical postoperative complications: 7.7% vs 17.5% (p = 0.0055); Medical postoperative complications: 4.3% vs 5.5% (p = 0.6077); Lesion of the main bile duct: 0.9% vs 1.8% (p = 0.6091); Reoperation: 2.9% vs 5.5% (p = 0.2315); Hospital stay up to 4 days after surgery: 64.8% vs 18.5% (p < 0.001). The convertion rate was of 10.7%: 8.8% in early surgery (before 4 days after de diagnosis) and 13.7% in the late surgery (after this time but in the same stay) (p = 0.1425). Multiple causes led to convertion: surgical complications (biliary lesions...

‣ Stopping effects in U+U collisions with a beam energy of 520 MeV/nucleon

Luo, Xiao-Feng; Dong, Xin; Shao, Ming; Wu, Ke-Jun; Li, Cheng; Chen, Hong-Fang; Xu, Hu-Shan
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
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A Relativistic Transport Model (ART1.0) is applied to simulate the stopping effects in tip-tip and body-body U+U collisions, at a beam kinetic energy of 520 MeV/nucleon. Our simulation results have demonstrated that both central collisions of the two extreme orientations can achieve full stopping, and also form a bulk of hot, dense nuclear matter with a sufficiently large volume and long duration, due to the largely deformed uranium nuclei. The nucleon sideward flow in the tip-tip collisions is nearly 3 times larger than that in body-body ones at normalized impact parameter $b/b_{max}<0.5$, and that the body-body central collisions have a largest negative nucleon elliptic flow $v_{2}=-12%$ in contrast to zero in tip-tip ones. Thus the extreme circumstance and the novel experimental observables in tip-tip and body-body collisions can provide a good condition and sensitive probe to study the nuclear EoS, respectively. The Cooling Storage Ring (CSR) External Target Facility (ETF) to be built at Lanzhou, China, delivering the uranium beam up to 520 MeV/nucleon is expected to make significant contribution to explore the nuclear equation of state (EoS).; Comment: 7 pages, 9 figures. Phys. Rev. C 76, 044902 (2007)

‣ Near-infrared line imaging of the starburst galaxies NGC 520, NGC 1614 and NGC 7714

Kotilainen, J. K.; Reunanen, J.; Laine, S.; Ryder, S. D.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 23/11/2000 Português
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We present high spatial resolution (0.6 arcsec) near-infrared broad-band JHK images and Br_gamma 2.1661 micron and H_2 1-0 S(1) 2.122 micron emission line images of the nuclear regions in the interacting starburst galaxies NGC 520, NGC 1614 and NGC 7714. The near-infrared emission line and radio morphologies are in general agreement, although there are differences in details. In NGC 1614, we detect a nuclear double structure in Br_gamma, in agreement with the radio double structure. We derive average extinctions of A(K) = 0.41 and A(K) = 0.18 toward the nuclear regions of NGC 1614 and NGC 7714, respectively. For NGC 520, the extinction is much higher, A(K) = 1.2 - 1.6. The observed H_2/Br_gamma ratios indicate that the main excitation mechanism of the molecular gas is fluorescence by intense UV radiation from clusters of hot young stars, while shock excitation can be ruled out. The starburst regions in all galaxies exhibit small Br_gamma equivalent widths. Assuming a constant star formation model, even with a lowered upper mass cutoff of M_u = 30 M_o, results in rather old ages (10 - 40 Myr), in disagreement with the clumpy near-infrared morphologies. We prefer a model of an instantaneous burst of star formation with M_u = 100 M_o...

‣ A solution of Sun's $520 challenge concerning 520/pi

Rogers, Mathew; Straub, Armin
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 08/10/2012 Português
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We prove a Ramanujan-type formula for $520/\pi$ conjectured by Sun. Our proof begins with a hypergeometric representation of the relevant double series, which relies on a recent generating function for Legendre polynomials by Wan and Zudilin. After showing that appropriate modular parameters can be introduced, we then apply standard techniques, going back to Ramanujan, for establishing series for $1/\pi$.; Comment: 17 pages

‣ Cluster Abell 520: a perspective based on member galaxies. A cluster forming at the crossing of three filaments?

Girardi, M.; Barrena, R.; Boschin, W.; Ellingson, E.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 18/09/2008 Português
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The connection of cluster mergers with the presence of extended, diffuse radio sources in galaxy clusters is still debated. An interesting case is the rich, merging cluster Abell 520, containing a radio halo. A recent gravitational analysis has shown in this cluster the presence of a massive dark core suggested to be a possible problem for the current cold dark matter paradigm. We aim to obtain new insights into the internal dynamics of Abell 520 analyzing velocities and positions of member galaxies. Our analysis is based on redshift data for 293 galaxies in the cluster field obtained combining new redshift data for 86 galaxies acquired at the TNG with data obtained by CNOC team and other few data from the literature. We also use new photometric data obtained at the INT telescope. We combine galaxy velocities and positions to select 167 cluster members around z~0.201. We analyze the cluster structure using the weighted gap analysis, the KMM method, the Dressler-Shectman statistics and the analysis of the velocity dispersion profiles. We compare our results with those from X-ray, radio and gravitational lensing analyses. We find that Abell 520 is definitely a very complex system. Our results suggest that we are looking at a cluster forming at the crossing of three filaments of the large scale structure. In particular...