bluuebunny/crossref_metadata_2025_split huggingface dataset:
Formation and Evolution of Black Holes in Galactic Nuclei and Star Clusters
Authors: Spurzem R. , Berczik P. , Berentzen I. , Merritt D. , Preto M. , Amaro-Seoane P. 
Published: May 2008

AbstractWe study the formation, growth, and co-evolution of single and multiple supermassive black holes (SMBHs) and compact objects like neutron stars, white dwarfs, and stellar mass black holes in galactic nuclei and star clusters, focusing on the role of stellar dynamics. In this paper we focus on one exemplary topic out of a wider range of work done, the study of orbital parameters of binary black holes in galactic nuclei (binding energy, eccentricity, relativistic coalescence) as a function of initial parameters. In some cases the classical evolution of black hole binaries in dense stellar systems drives them to surprisingly high eccentricities, which is very exciting for the emission of gravitational waves and relativistic orbit shrinkage. Such results are interesting to the emerging field of gravitational wave astronomy, in relation to a number of ground and space based instruments designed to measure gravitational waves from astrophysical sources (VIRGO, Geo600, LIGO, LISA). Our models self-consistently cover the entire range from Newtonian dynamics to the relativistic coalescence of SMBH binaries.
Building Blue Stragglers with Stellar Collisions
Authors: Glebbeek Evert , Pols Onno R. 
Published: May 2008

AbstractThe evolution of stellar collision products in cluster simulations has usually been modelled using simplified prescriptions. Such prescriptions either replace the collision product with an (evolved) main sequence star, or assume that the collision product was completely mixed during the collision.It is known from hydrodynamical simulations of stellar collisions that collision products are not completely mixed, however. We have calculated the evolution of stellar collision products and find that they are brighter than normal main sequence stars of the same mass, but not as blue as models that assume that the collision product was fully mixed during the collision.
Dynamical Evolution of Globular Clusters in Hierarchical Cosmology
Authors: Gnedin Oleg Y. , Prieto José L. 
Published: May 2008

AbstractWe probe the evolution of globular clusters that could form in giant molecular clouds within high-redshift galaxies. Numerical simulations demonstrate that the large and dense enough gas clouds assemble naturally in current hierarchical models of galaxy formation. These clouds are enriched with heavy elements from earlier stars and could produce star clusters in a similar way to nearby molecular clouds. The masses and sizes of the model clusters are in excellent agreement with the observations of young massive clusters. Do these model clusters evolve into globular clusters that we see in our and external galaxies? In order to study their dynamical evolution, we calculate the orbits of model clusters using the outputs of the cosmological simulation of a Milky Way-sized galaxy. We find that at present the orbits are isotropic in the inner 50 kpc of the Galaxy and preferentially radial at larger distances. All clusters located outside 10 kpc from the center formed in the now-disrupted satellite galaxies. The spatial distribution of model clusters is spheroidal, with a power-law density profile consistent with observations. The combination of two-body scattering, tidal shocks, and stellar evolution results in the evolution of the cluster mass function from an initial power law to the observed log-normal distribution.
Sizes of Confirmed NGC 5128 Globular Clusters
Authors: Geisler Doug , Gómez M. , Woodley K. A. , Harris W. E. , Harris G. L. H. 
Published: May 2008

AbstractWe present results from a new wide-field study of the NGC 5128 globular cluster system. We have obtained new high resolution images with the Magellan 6.4m + IMACS camera. Our images cover an area of 1.2x1.2 sq. degrees and have a seeing of 0.45″. This allows us to not only resolve most of the globular clusters (GCs) but also derive their structural parameters. These are combined with existing Washington photometry in order to select by metallicity. We present here results for a subsample of 359 GCs which includes all currently confirmed GC members of the system. Our derived sizes are in very good agreement with those derived from ACS data. We find, as expected, that the metal-rich GCs in the inner regions (r < 10′) are 26% smaller than their metal-poor components, but in the outer region this normal trend is reversed. We compare our GCs to previous results for GCs, UCDs, etc. in the luminosity - size plane and find substantial overlap between different types of objects, indicating more of a continuum in these properties.
Ultra-Compact Dwarf Galaxies – More Massive than Allowed?
Authors: Hilker Michael , Mieske S. , Baumgardt H. , Dabringhausen J. 
Published: May 2008

AbstractDynamical mass estimates of ultra-compact dwarfs galaxies and massive globular clusters in the Fornax and Virgo clusters and around the giant elliptical Cen A have revealed some surprising results: 1) above ~106M⊙ the mass-to-light (M/L) ratio increases with the objects' mass; 2) some UCDs/massive GCs show high M/L values (4 to 6) that are not compatible with standard stellar population models; and 3) in the luminosity-velocity dispersion diagram, UCDs deviate from the well-defined relation of “normal” GCs, being more in line with the Faber-Jackson relation of early-type galaxies. In this contribution, we present the observational evidences for high mass-to-light ratios of UCDs and discuss possible explanations for them.
GMOS Spectroscopy of Globular Clusters in Dwarf Elliptical Galaxies
Authors: Miller Bryan W. , Lotz Jennifer , Hilker Michael , Kissler-Patig Markus , Puzia Thomas 
Published: May 2008

AbstractWe present a Gemini/GMOS program to measure spectroscopic metallicities and ages of globular clusters (GCs) and nuclei in dwarf elliptical galaxies in the Virgo and Fornax Clusters. Preliminary results indicate that the globular clusters are old and metal-poor, very similar to the GCs in the Milky Way halo. The nuclei tend to be more metal-rich than the globular clusters but more metal-poor and older, on average, than the stars in the bodies of the galaxies. The [α/Fe] ratio appears to be solar for the GCs, nuclei, and dEs, but the uncertainties do not exclude some globular clusters from being enhanced in alpha elements.
Current Status of GRAPE Project
Authors: Makino J. 
Published: May 2008

AbstractI'll summarize the current status of GRAPE project. GRAPE-6, completed in 2002, has been used by a number of people, for a wide variety of problems such as planet formation, star cluster dynamics, galactic nuclei, and cosmology. In 2004, we started the development of the next-generation machine, GRAPE-DR. GRAPE-DR has a architecture radically different from that of previous GRAPEs. It does not have hardwired pipeline for gravitational force calculation but a large number of small and simple programmable processors. This change made it possible to apply GRAPE-DR to a wide range of problems to which GRAPE was not efficient, and at the same time it helps us to explore new algorithms for N-body simulations. The GRAPE-DR chip was completed in 2006, and second prototype board was completed in May 2007. We hope to have full production-level board commercially available by the end of year 2007. A single board will offer the theoretical peak speed of 2 Tflops, about 20 times as that of a single PCI card version of GRAPE-6.
Determining Design and Scale‐up Parameters for Degradation of Atrazine with Suspended Pseudomonas sp. ADP in Aqueous Bioreactors
Authors: Biglione Nicole , Rodgers V. G. J. , Peeples Tonya L. 
Published: May 2008

AbstractThis work investigated the kinetic parameters of atrazine mineralization by suspended cells of Pseudomonas sp. ADP in both shake flasks and spherical stirred tank batch reactors (SSTR). The degradation of atrazine and growth of Pseudomonas sp. ADP were studied. Experiments were performed at different temperatures and stirring speeds in both reactors at varying initial concentrations of atrazine. Cell growth and atrazine concentration were monitored over time, and a Monod model with one limiting substrate was used to characterize the kinetic behavior. Temperature, stirring speed, and reactor type were all found to significantly affect the regressed Monod parameters. At 27 °C and 200 rpm, for the shaker flask experiments, μmax and Ks were determined to be 0.14 (±0.01) h−1 and 1.88 (±1.80) mg/L, respectively. At 37 °C, μmax and Ks increased to 0.25 (±0.05) h−1 and 9.59 (±6.55) mg/L, respectively. As expected, stirrer speed was also found to significantly alter the kinetic parameters. At 27 °C and 125 rpm, μmax and Ks were 0.04 (±0.002) h−1 and 3.72 (±1.05) mg/L, respectively, whereas at 37 °C and 125 rpm, μmax and Ks were 0.07 (±0.008) h−1 and 1.65 (±2.06) mg/L. In the SSTR the kinetic parameters μmax and Ks at room temperature were determined to be 0.12 (±0.009) h−1 and 2.18 (±0.47) mg/L, respectively. Although the μmax values for both types of reactors were similar, the shaker flask experiments resulted in considerable error. Error analysis on calculated values of Ks were found to impact estimates in atrazine concentration by as much as two orders of magnitude, depending on the reactor design, illustrating the importance of these factors in reactor scale‐up.
mRNA‐Display‐Based Selections for Proteins with Desired Functions: A Protease‐Substrate Case Study
Authors: Valencia C. Alexander , Cotten Steven W. , Dong Biao , Liu Rihe 
Published: May 2008

AbstractmRNA‐display is an amplification‐based, iterative rounds of in vitro protein selection technique that circumvents a number of difficulties associated with yeast two‐hybrid and phage display. Because of the covalent linkage between the genotype and the phenotype, mRNA‐display provides a powerful means for reading and amplifying a peptide or protein sequence after it has been selected from a library with a diversity in the range of 1012–1013. In this paper, we briefly review the recent progress in using mRNA‐display to identify affinity reagents, binding partners, and enzyme substrates from synthetic peptide or natural proteome libraries. To facilitate the use of mRNA‐display in research laboratories without previous experience, we provide a detailed analysis of the critical steps of an mRNA‐display‐based selection in a case study for the identification of the natural substrates of caspases, including the generation of an mRNA‐displayed proteome library, removal of abundant sequences, and selection of proteins with desired functions. The advantages and technical limitations of mRNA‐display as a general peptide or protein selection tool are also addressed.
Proximal mutations at the type 1 copper site of CotA laccase: spectroscopic, redox, kinetic and structural characterization of I494A and L386A mutants
Authors: Durão Paulo , Chen Zhenjia , Silva Catarina S. , Soares Cláudio M. , Pereira Manuela M. , Todorovic Smilja , Hildebrandt Peter , Bento Isabel , Lindley Peter F. , Martins Lígia O. 
Published: May 2008

In the present study the CotA laccase from Bacillus subtilis has been mutated at two hydrophobic residues in the vicinity of the type 1 copper site. The mutation of Leu386 to an alanine residue appears to cause only very subtle alterations in the properties of the enzyme indicating minimal changes in the structure of the copper centres. However, the replacement of Ile494 by an alanine residue leads to significant changes in the enzyme. Thus the major visible absorption band is upshifted by 16 nm to 625 nm and exhibits an increased intensity, whereas the intensity of the shoulder at approx. 330 nm is decreased by a factor of two. Simulation of the EPR spectrum of the I494A mutant reveals differences in the type 1 as well as in the type 2 copper centre reflecting modifications of the geometry of these centres. The intensity weighted frequencies &lt;νCu-S&gt;, calculated from resonance Raman spectra are 410 cm−1 for the wild-type enzyme and 396 cm−1 for the I494A mutant, indicating an increase of the Cu–S bond length in the type 1 copper site of the mutant. Overall the data clearly indicate that the Ile494 mutation causes a major alteration of the structure near the type 1 copper site and this has been confirmed by X-ray crystallography. The crystal structure shows the presence of a fifth ligand, a solvent molecule, at the type 1 copper site leading to an approximate trigonal bipyramidal geometry. The redox potentials of the L386A and I494A mutants are shifted downwards by approx. 60 and 100 mV respectively. These changes correlate well with decreased catalytic efficiency of both mutants compared with the wild-type.
High Cu(I) and low proton affinities of the CXXC motif of Bacillus subtilis CopZ
Authors: Zhou Liang , Singleton Chloe , Le Brun Nick E. 
Published: May 2008

CopZ, an Atx1-like copper chaperone from the bacterium Bacillus subtilis, functions as part of a complex cellular machinery for Cu(I) trafficking and detoxification, in which it interacts specifically with the transmembrane Cu(I)-transporter CopA. Here we demonstrate that the cysteine residues of the MXCXXC Cu(I)-binding motif of CopZ have low proton affinities, with both exhibiting pKa values of 6 or below. Chelator competition experiments demonstrated that the protein binds Cu(I) with extremely high affinity, with a small but significant pH-dependence over the range pH 6.5–8.0. From these data, a pH-corrected formation constant, β2=∼6×1022 M−2, was determined. Rapid exchange of Cu(I) between CopZ and the Cu(I)-chelator BCS (bathocuproine disulfonate) indicated that the mechanism of exchange does not involve simple dissociation of Cu(I) from CopZ (or BCS), but instead proceeds via the formation of a transient Cu(I)-mediated protein–chelator complex. Such a mechanism has similarities to the Cu(I)-exchange pathway that occurs between components of copper-trafficking pathways.
Relationship between age and measures of balance, strength and gait: linear and non-linear analyses
Authors: El Haber Natalie , Erbas Bircan , Hill Keith D. , Wark John D. 
Published: May 2008

An age-related decline in balance, gait and lower-extremity muscle strength measures may lead to increased risk of falls and fractures. Previous studies have reported a possible non-linear age-related decline in these measures, but the choice of methodological approach has limited its interpretation. Healthy community-dwelling women (n=212) 21–82 years of age were evaluated for strength [Nicholas MMT (manual muscle tester)], gait [CSA (clinical stride analyser)], activity [HAP (human activity profile)] and static and dynamic balance [CBS (Chattecx balance system), LBT (Lord's balance test) and the ST (step test)]. A GAM (generalized additive model) was developed for each outcome variable to estimate the functional relationship, with age as a continuous variable. Performance was maintained until 45–55 years of age, depending on the outcome measure. Thereafter a decline in performance was evident with increasing age in all measures. Overall, a significant non-linear relationship with age was demonstrated for lower-extremity strength measures (MMT), velocity and double support duration of gait (CSA) and some clinical and laboratory balance tests [ST, LBT (eyes open) and the CBS]. Linear relationships were demonstrated by the LBT with eyes closed and activity measures. Balance, lower-extremity muscle strength and gait may decline non-linearly with age. Our study suggests possible threshold effects between age and balance, muscle strength and gait measures in women. Further research into these threshold effects may have implications for the optimal timing of exercise and other interventions to reduce the risk of falls and fractures.
HIV-positive patients treated with protease inhibitors have vascular changes resembling those observed in atherosclerotic cardiovascular disease
Authors: Lekakis John , Tsiodras Sotirios , Ikonomidis Ignatios , Palios John , Poulakou Garyfalia , Rallidis Loukianos , Antoniadou Anastasia , Panagopoulos Periklis , Papadopoulos Antonios , Giamarellou Helen , Kremastinos Dimitrios T. 
Published: May 2008

A metabolic syndrome associated with atherosclerosis and cardiovascular disease has been described in HIV-positive individuals. In the present study we investigated whether HIV-positive individuals and CAD (coronary artery disease) patients have similarities in their vascular function and structure. In a case-control study, we compared measurements of carotid artery IMT (intima-media thickness) and brachial artery FMD (flow-mediated vasodilation) in HIV-positive individuals with age- and sex-matched controls with similar risk factors and patients with established CAD. Seventy-one HIV patients, age 42±13.9 years (91% male), were compared with 29 CAD patients and 25 controls. HIV patients had higher IMT than controls and similar IMT to CAD patients (0.64±0.2 compared with 0.55±0.05 and 0.66±0.08 mm respectively; F=4.2, P=0.01). Patients taking protease inhibitors had higher IMT (0.69±0.2 compared with 0.57±0.15 mm; P=0.01), blood pressure, cholesterol and triacylglycerols than those not taking protease inhibtors (P&lt;0.05). In multiple regression analyses, increasing blood pressure (β: 0.37, P=0.001), glucose (β: 0.26, P=0.016), cholesterol (β: 0.24, P=0.033), duration of HIV disease (β: 0.33, P=0.008) and use of protease inhibitors (β: 0.27, P=0.04) were the most important determinants of IMT respectively. FMD was associated only with triacylglycerol measurements. Patients with HIV present arterial changes resembling those found in patients with atherosclerotic cardiovascular disease. These vascular changes are closely related to protease-inhibitor-induced changes of metabolic parameters. Thus intensive treatment of these metabolic parameters might retard atherosclerosis in HIV patients.
Haem oxygenase-1 gene transfer protects retinal ganglion cells from ischaemia/reperfusion injury
Authors: Peng Pai-Huei , Ko Mei-Lan , Chen Chau-Fong , Juan Shu-Hui 
Published: May 2008

RGC (retinal ganglion cell) death following ischaemic insult is the major cause of a number of vision-threatening diseases, including glaucoma. The aim of the present study was to evaluate the role of HO-1 (haem oxygenase-1) in the retina against IR (ischaemia/reperfusion) injury. Adenovirus-mediated HO-1 gene transfer (Adv-HO-1) was carried out by injection into the vitreous body to induce HO-1 overexpression. At 3 weeks after transfection, levels of HO-1 expression, as measured by Western blot analysis, immunohistochemical staining and activity assay, were drastically up-regulated. Transient retinal ischaemia was induced by raising the intraocular pressure to 150 mmHg for 60 min. Untreated IR caused a significant decrease in RGC numbers at 3 and 7 days after reperfusion (76.1 and 67.2% of control eyes with sham IR respectively; P&lt;0.001). Eyes pretreated with Adv-HO-1 had less RGC loss on day 3 and 7 following reperfusion compared with control eyes injected with Adv-GFP (adenovirus containing a gene for green fluorescent protein; 94.3 and 88.2% respectively; P=0.007 and 0.001). SnP (tin protoporphyrin), an HO-1 inhibitor, counteracted the effects of Adv-HO-1. In conclusion, these findings provide evidence that augmentation of HO-1 enzyme overexpression by intravitreal injection is able to protect RGCs against IR-induced damage.
Increased plasma urotensin-II levels are associated with diabetic retinopathy and carotid atherosclerosis in Type 2 diabetes
Authors: Suguro Toshiaki , Watanabe Takuya , Kodate Syuusuke , Xu Gang , Hirano Tsutomu , Adachi Mitsuru , Miyazaki Akira 
Published: May 2008

Human U-II (urotensin-II), the most potent vasoconstrictor peptide identified to date, is associated with cardiovascular disease. A single nucleotide polymorphism (S89N) in the gene encoding U-II (UTS2) is associated with the onset of Type 2 diabetes and insulin resistance in the Japanese population. In the present study, we have demonstrated a relationship between plasma U-II levels and the progression of diabetic retinopathy and vascular complications in patients with Type 2 diabetes. Eye fundus, IMT (intima-media thickness) and plaque score in the carotid artery, BP (blood pressure), FPG (fasting plasma glucose), HbA1c (glycated haemoglobin), U-II, angiogenesis-stimulating factors, such as VEGF (vascular endothelial growth factor) and heregulin-β1, and lipid profiles were determined in 64 patients with Type 2 diabetes and 24 non-diabetic controls. FPG, HbA1c and VEGF levels were significantly higher in patients with Type 2 diabetes than in non-diabetic controls. Diabetes duration, insufficient glycaemic and BP control, plasma U-II levels, IMT, plaque score and nephropathy grade increased significantly across the subjects as follows: non-diabetic controls, patients with Type 2 diabetes without retinopathy (group N), patients with Type 2 diabetes with simple (background) retinopathy (group A) and patients with Type 2 diabetes with pre-proliferative and proliferative retinopathy (group B). The prevalence of obesity and smoking, age, low-density lipoprotein, triacylglycerols (triglycerides) and heregulin-β1 were not significantly different among the four groups. In all subjects, U-II levels were significantly positively correlated with IMT, FPG, and systolic and diastolic BP. Multiple logistic regression analysis revealed that, of the above parameters, U-II levels alone had a significantly independent association with diabetic retinopathy. In conclusion, the results of the present study provide the first evidence that increased plasma U-II levels may be associated with the progression of diabetic retinopathy and carotid atherosclerosis in patients with Type 2 diabetes.
The β-Glucosidases Responsible for Bioactivation of Hydroxynitrile Glucosides in Lotus japonicus
Authors: Morant Anne Vinther , Bjarnholt Nanna , Kragh Mads Emil , Kjærgaard Christian Hauge , Jørgensen Kirsten , Paquette Suzanne Michelle , Piotrowski Markus , Imberty Anne , Olsen Carl Erik , Møller Birger Lindberg , Bak Søren 
Published: May 2008

Abstract
Lotus japonicus accumulates the hydroxynitrile glucosides lotaustralin, linamarin, and rhodiocyanosides A and D. Upon tissue disruption, the hydroxynitrile glucosides are bioactivated by hydrolysis by specific β-glucosidases. A mixture of two hydroxynitrile glucoside-cleaving β-glucosidases was isolated from L. japonicus leaves and identified by protein sequencing as LjBGD2 and LjBGD4. The isolated hydroxynitrile glucoside-cleaving β-glucosidases preferentially hydrolyzed rhodiocyanoside A and lotaustralin, whereas linamarin was only slowly hydrolyzed, in agreement with measurements of their rate of degradation upon tissue disruption in L. japonicus leaves. Comparative homology modeling predicted that LjBGD2 and LjBGD4 had nearly identical overall topologies and substrate-binding pockets. Heterologous expression of LjBGD2 and LjBGD4 in Arabidopsis (Arabidopsis thaliana) enabled analysis of their individual substrate specificity profiles and confirmed that both LjBGD2 and LjBGD4 preferentially hydrolyze the hydroxynitrile glucosides present in L. japonicus. Phylogenetic analyses revealed a third L. japonicus putative hydroxynitrile glucoside-cleaving β-glucosidase, LjBGD7. Reverse transcription-polymerase chain reaction analysis showed that LjBGD2 and LjBGD4 are expressed in aerial parts of young L. japonicus plants, while LjBGD7 is expressed exclusively in roots. The differential expression pattern of LjBGD2, LjBGD4, and LjBGD7 corresponds to the previously observed expression profile for CYP79D3 and CYP79D4, encoding the two cytochromes P450 that catalyze the first committed step in the biosyntheis of hydroxynitrile glucosides in L. japonicus, with CYP79D3 expression in aerial tissues and CYP79D4 expression in roots.