bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the maximal value of the turbulent α ‐parameter in accretion discs
Authors: Abolmasov P. , Shakura N.I. 
Published: July 2009

AbstractIn this short paper we show that making turbulence two‐rather than three‐dimensional may increase the effective turbulent viscosity by about 40 %. Dimensionless hydrodynamical viscosity parameters up to αmax = 0.25 Mt2 may be obtained in this approach, which are in better agreement with the observational data on non‐stationary accretion than the values obtained in numerical simulations. However, the α ‐parameter values known from observations are still several times higher (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic survey of emission line B‐type stars with FORS 1 at the VLT
Authors: Hubrig S. , Schöller M. , Savanov I. , Yudin R.V. , Pogodin M.A. , Štefl St. , Rivinius Th. , Curé M. 
Published: July 2009

AbstractWe report the results of our search for magnetic fields in a sample of 16 field Be stars, the binary emission‐line B‐type star υ Sgr, and in a sample of fourteen members of the open young cluster NGC3766 in the Carina spiral arm. The sample of cluster members includes Be stars, normal B‐type stars and He‐strong/He‐weak stars. Nine Be stars have been studied with magnetic field time series obtained over ∼1 hour to get an insight into the temporal behaviour and the correlation of magnetic field properties with dynamical phenomena taking place in Be star atmospheres. The spectropolarimetric data were obtained at the European Southern Observatory with the multi‐mode instrument FORS1 installed at the 8m Kueyen telescope. We detect weak photospheric magnetic fields in four field Be stars, HD 62367, μ Cen, o Aqr, and ε Tuc. The strongest longitudinal magnetic field, 〈Bz〉 = 117 ± 38 G, was detected in the Be star HD 62367. Among the Be stars studied with time series, one Be star, λ Eri, displays cyclic variability of the magnetic field with a period of 21.12 min. The binary star υ Sgr, in the initial rapid phase of mass exchange between the two components with strong emission lines in the visible spectrum, is a magnetic variable star, probably on a timescale of a few months. The maximum longitudinal magnetic field 〈Bz〉 = –102 ± 10 G at MJD 54333.018 was measured using hydrogen lines. The cluster NGC3766 seems to be extremely interesting, where we find evidence for the presence of a magnetic field in seven early B‐type stars out of the observed fourteen cluster members (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The enigmatic primitive streak: prevailing notions and challenges concerning the body axis of mammals
Authors: Downs Karen M. 
Published: July 2009

AbstractThe primitive streak establishes the antero‐posterior body axis in all amniote species. It is thought to be the conduit through which mesoderm and endoderm progenitors ingress and migrate to their ultimate destinations. Despite its importance, the streak remains poorly defined and one of the most enigmatic structures of the animal kingdom. In particular, the posterior end of the primitive streak has not been satisfactorily identified in any species. Unexpectedly, and contrary to prevailing notions, recent evidence suggests that the murine posterior primitive streak extends beyond the embryo proper. In its extraembryonic site, the streak creates a node‐like cell reservoir from which the allantois, a universal caudal appendage of all amniotes and the future umbilical cord of placental mammals, emerges. This new insight into the fetal/umbilical relationship may explain the etiology of a large number of umbilical‐associated birth defects, many of which are correlated with abnormalities of the embryonic midline.
Gene targeting from laboratory to livestock: Current status and emerging concepts
Authors: Laible Götz , Alonso‐González Lucía 
Published: July 2009

AbstractThe development of methods for cell‐mediated transgenesis, based on somatic cell nuclear transfer, provides a tremendous opportunity to shape the genetic make‐up of livestock animals in a much more directed approach than traditional animal breeding and selection schemes. Progress in the site‐directed modulation of livestock genomes is currently limited by the low efficiencies of gene targeting imposed by the low frequency of homologous recombination and limited proliferative capacity of primary somatic cells that are used to produce transgenic animals. Here we review the current state of the art in the field, discuss the crucial aspects of the methodology and provide an overview of emerging approaches to increase the efficiency of gene targeting in somatic cells.
Catalase‐like activity of bovine met‐hemoglobin: Interaction with the pseudo‐catalytic peroxidation of anthracene traces in aqueous medium
Authors: Paco Laveille , Galarneau Anne , Drone Jullien , Fajula François , Bailly Carole , Pulvin Sylviane , Thomas Daniel 
Published: July 2009

AbstractHemoglobin is a member of the hemoprotein superfamily whose main role is to transport O2 in vertebrate organisms. It has two known promiscuous enzymatic activities, peroxidase and oxygenase. Here we show for the first time that bovine hemoglobin also presents a catalase‐like activity characterized by a Vmax of 344 μM/min, a KM of 24 mM and a kcat equal to 115/min. For high anthracene and hemoglobin concentrations and low hydrogen peroxide concentrations, this activity inhibits the expected oxidation of anthracene, which occurs through a peroxidase‐like mechanism. Anthracene belongs to the polycyclic aromatic hydrocarbon (PAH) family whose members are carcinogenic and persistent pollutants found in industrial waste waters. Our results show that anthracene oxidation by hemoglobin and hydrogen peroxide follows a typical bi‐bi ping‐pong mechanism with a Vmax equal to 0.250 μM/min, KM(H2O2) of 80 μM, KM(ANT) of 1.1 μM and kcat of 0.17/min. The oxidation of anthracene is shown to be pseudo‐catalytic because an excess of hemoglobin and hydrogen peroxide is required to make PAH completely disappear. Thus, bovine hemoglobin presents, in different degrees, all the catalytic activities of the hemoprotein group, which makes it a very interesting protein for biotechnological processes and one with which structure‐activity relationships can be studied.
Ferrous iron oxidation by foam immobilized Acidithiobacillus ferrooxidans: Experiments and modeling
Authors: Jaisankar S. , Modak J. M. 
Published: July 2009

AbstractFerrous iron bio‐oxidation by Acidithiobacillus ferrooxidans immobilized on polyurethane foam was investigated. Cells were immobilized on foams by placing them in a growth environment and fully bacterially activated polyurethane foams (BAPUFs) were prepared by serial subculturing in batches with partially bacterially activated foam (pBAPUFs). The dependence of foam density on cell immobilization process, the effect of pH and BAPUF loading on ferrous oxidation were studied to choose operating parameters for continuous operations. With an objective to have high cell densities both in foam and the liquid phase, pretreated foams of density 50 kg/m3 as cell support and ferrous oxidation at pH 1.5 to moderate the ferric precipitation were preferred. A novel basket‐type bioreactor for continuous ferrous iron oxidation, which features a multiple effect of stirred tank in combination with recirculation, was designed and operated. The results were compared with that of a free cell and a sheet‐type foam immobilized reactors. A fivefold increase in ferric iron productivity at 33.02 g/h/L of free volume in foam was achieved using basket‐type bioreactor when compared to a free cell continuous system. A mathematical model for ferrous iron oxidation by Acidithiobacillus ferrooxidans cells immobilized on polyurethane foam was developed with cell growth in foam accounted by an effectiveness factor. The basic parameters of simulation were estimated using the experimental data on free cell growth as well as from cell attachment to foam under nongrowing conditions. The model predicted the phase of both oxidation of ferrous in shake flasks by pBAPUFs as well as by fully activated BAPUFs for different cell loadings in foam. Model for stirred tank basket bioreactor predicted within 5% both transient and steady state of the experiments closely for the simulated dilution rates. Bio‐oxidation at high Fe2+ concentrations were simulated with experiments when substrate and product inhibition coefficients were factored into cell growth kinetics. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009
Metabolic profiling as a tool for understanding defense response of Taxus Cuspidata cells to shear stress
Authors: Han Pei‐Pei , Yuan Ying‐Jin 
Published: July 2009

AbstractTo obtain a better understanding of responsive mechanism of plant cells in response to hydrodynamic mechanical stress, a metabolic profiling approach was used to profile metabolite changes of Taxus cuspidata cells under laminar shear stress. A total of 65 intracellular metabolites were identified and quantified, using gas chromatography coupled to time‐of‐flight mass spectrometry. Potential biomarkers were found by the principal component analysis as well as partial least squares combined with variable influence in the projection. Trehalose, sorbitol, ascorbate, sucrose, and gluconic acid were mainly responsible for the discrimination between shear stress induced cells and control cells. Further analysis by mapping measured metabolite concentrations onto the metabolic network revealed that shear stress imposed restrictions on primary metabolic pathways by inhibiting tricarboxylic acid cycle, glycolysis, and N metabolism. To adapt to the shear condition, cells responded by starting defensive programs. These defensive programs included coinduction of glycolysis and sucrose metabolism, accumulation of compatible solutes, and antioxidative strategy. A strategy of defense mechanisms at the level of metabolites for T. cuspidata cells when challenged with the shear stress was proposed. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009
Microfabricated arrays of cylindrical wells facilitate single‐molecule enzymology of α‐chymotrypsin
Authors: Chen Angela Y. , Jani Ashish S. , Zheng Lifeng , Burke Peter J. , Brody James P. 
Published: July 2009

AbstractSingle‐molecule enzymology allows scientists to examine the distributions of kinetic rates among members of a population. We describe a simple method for the analysis of single‐molecule enzymatic kinetics and provide comparisons to ensemble‐averaged kinetics. To isolate our model enzyme, α‐chymotrypsin, into single molecules, we use an array of cylindrical poly(dimethylsiloxane) wells 2 μm in diameter and 1.35 μm in height. Inside the wells, a protease assay with a profluorescent substrate detects α‐chymotrypsin activity. We hold the concentration of α‐chymotrypsin at 0.39 nM in a given well with an enzyme‐to‐substrate ratio of 1:6,666 molecules. Fluorescence emitted by the substrate is proportional to enzyme activity and detectable by a charge‐coupled device. This method allows for the simultaneous real‐time characterization of hundreds of individual enzymes. We analyze single‐molecule kinetics by recording and observing their intensity trajectories over time. By testing our method with our current instruments, we confirm that our methodology is useful for the analysis of single enzymes for extracting static inhomogeneity. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009
Human insulin A‐chain peptide analog(s) with in vitro biological activity
Authors: Le Flem Guillaume , Pecher Julien , Le Flem‐Bonhomme Valerie , Withdrawn Author , Rochette Jacques , Pujol Jean‐Pierre , Bogdanowicz Patrick 
Published: July 2009

AbstractIn a previous study, we showed that a synthetic human insulin 1‐chain analog, named analog (3) was capable of mimicking in vitro effects of native insulin, including stimulation of cell proliferation, glucose uptake and glycogen synthesis. Here, we have synthesized three new analogs (6, 9, 12) of the human A‐chain, bearing or not their N‐ or C‐terminal residue, to determine the structural features which are responsible for their biological properties. In vitro experiments clearly demonstrated that the N‐terminal part of the peptides is required for the biological activity of the molecules, suggesting its crucial role in the mechanism underlying the cellular effect. Our findings may help to better understand the mechanism of interaction between insulin and its receptor. In addition, the present data demonstrate that some mini‐insulin derived from the A‐chain can exert similar effects as native insulin. These small peptides may offer specific advantages over insulin in the definition of new strategies for diabetes treatment. Copyright © 2009 John Wiley & Sons, Ltd.This article was published online on 17 July 2009. An error was subsequently identified. This notice is included in the online and print versions to indicate that both have been corrected 4 August 2009.
Synthesis and EPR Studies of 2′‐Deoxyuridines with Alkynyl, Rodlike Linkages
Authors: Sniady Adam , Sevilla Michael D. , Meneni Srinivasarao , Lis Tadeusz , Szafert Slawomir , Khanduri Deepthi , Finke John M. , Dembinski Roman 
Published: July 2009

AbstractSonogashira coupling of diacetyl 5‐ethynyl‐2′‐deoxyuridine with diacetyl 5‐iodo‐2′‐deoxyuridine gave the acylated ethynediyl‐linked 2′‐deoxyuridine dimer (3 b; 63 %), which was deprotected with ammonia/methanol to give ethynediyl‐linked 2′‐deoxyuridines (3 a; 79 %). Treatment of 5‐ethynyl‐2′‐deoxyuridine (1 a) with 5‐iodo‐2′‐deoxyuridine gave the furopyrimidine linked to 2′‐deoxyuridine (78 %). Catalytic oxidative coupling of 1 a (O2, CuI, Pd/C, N,N‐dimethylformamide) gave butadiynediyl‐linked 2′‐deoxyuridines (4; 84 %). Double Sonogashira coupling of 5‐iodo‐2′‐deoxyuridine with 1,4‐diethynylbenzene gave 1,4‐phenylenediethynediyl‐bridged 2′‐deoxyuridines (5; 83 %). Cu‐catalyzed cycloisomerization of dimers 4 and 5 gave their furopyrimidine derivatives. One‐electron addition to 1 a, 3 a, and 4 gave the anion radical, the EPR spectra of which showed that the unpaired electron is largely localized at C6 of one uracil ring (17 G doublet) at 77 K. The EPR spectra of the one‐electron‐oxidized derivatives of ethynediyl‐ and butadiynediyl‐linked uridines 3 a and 4 at 77 K showed that the unpaired electron is delocalized over both rings. Therefore, structures 3 a and 4 provide an efficient electronic link for hole conduction between the uracil rings. However, for the excess electron, an activation barrier prevents coupling to both rings. These dimeric structures could provide a gate that would separate hole transfer from electron transport between strands in DNA systems. In the crystal structure of acylated dimer 3 b, the bases were found in the anti position relative to each other across the ethynyl link, and similar anti conformation was preserved in the derived furopyrimidine–deoxyuridine dinucleoside.
Catalytic Asymmetric Synthesis of β‐Sultams as Precursors for Taurine Derivatives
Authors: Zajac Marian , Peters René 
Published: July 2009

Abstractβ‐Sultams, biologically interesting sulfonyl analogues of β‐lactams, have been prepared by an organocatalytic asymmetric formal [2+2]‐cycloaddition approach of non‐nucleophilic imines with alkyl sulfonyl chlorides. In the case of very electron poor N‐tosyl imines derived from chloral or ethylglyoxylate, this reaction type was catalyzed by cinchona alkaloids providing the heterocycles in high yield, with good diastereoselectivity and up to 94 % ee. Mechanistic investigations suggested that the product formation proceeded via a zwitterionic imine–catalyst adduct. The scope was significantly extended by 2‐pyridylsulfonyl imines derived from non‐activated aromatic aldehydes employing Yb(OTf)3 as Lewis acid cocatalyst. The synthetic value of the strained enantioenriched β‐sultams was demonstrated by smooth nucleophilic ring opening reactions with O‐, N‐ and C‐nucleophiles yielding a variety of acyclic β‐aminosulfonyl (taurine) derivatives (sulfonates, sulfonamides, sulfones) without racemization or epimerization.
Synthesis, Spectroscopy, Nonlinear Optics, and Theoretical Investigations of Thienylethynyl Octopoles with a Tunable Core
Authors: Oliva María Moreno , Casado Juan , López Navarrete Juan T. , Hennrich Gunther , van Cleuvenbergen Stijn , Asselberghs Inge , Clays Koen , Ruiz Delgado M. Carmen , Brédas Jean‐Luc , Seixas de Melo J. Sérgio , De Cola Luisa 
Published: July 2009

AbstractWe have synthesized three new molecules that have three thienylethynyl arms substituting a central benzene core and different electron donor/acceptor groups in the three remaining phenyl positions. The absorption, fluorescence, phosphorescence, and transient triplet–triplet spectra are analyzed in the light of the electronic structure of the ground and excited states obtained from quantum‐chemical calculations. From the above, the relevant photophysical data (including quantum yields, lifetimes, and rate constants) could be derived. It was found that the major deactivation pathway is internal conversion, which competes with the fluorescence and intersystem crossing processes. For the three investigated compounds, we provide convincing theoretical support corroborating these findings and further conclusions based on the theoretical information obtained. These molecules are one of the very few cases in which the depolarization ratios, obtained from the NLO optical measurements, clearly reflect the octopolar configuration. Molecular hyperpolarizabilities have been measured and display a typical dependence on the donor–acceptor substitution pattern.
Chemoselective Synthesis of Substituted Imines, Secondary Amines, and β‐Amino Carbonyl Compounds from Nitroaromatics through Cascade Reactions on Gold Catalysts
Authors: Santos Laura L. , Serna Pedro , Corma Avelino 
Published: July 2009

AbstractSubstituted imines, α,β‐unsaturated imines, substituted secondary amines, and β‐amino carbonyl compounds have been synthesized by means of new cascade reactions with mono‐ or bifunctional gold‐based solid catalysts under mild reaction conditions. The related synthetic route involves the hydrogenation of a nitroaromatic compound in the presence of a second reactant such as an aldehyde, α,β‐unsaturated carbonyl compound, or alkyne, which circumvents an ex situ reduction process for producing the aromatic amine. The process is shown to be highly selective towards other competing groups, such as double bonds, carbonyls, halogens, nitriles, or cinnamates, and thereby allows the synthesis of different substituted nitrogenated compounds. For the preparation of imines, substituted anilines are formed and condensed in situ with aldehydes to provide the final product through two tandem reactions. High chemoselectivity is observed, for instance, when double bonds or halides are present within the reactants. In addition, we show that the Au/TiO2system is also able to catalyze the chemoselective hydrogenation of imines, so that secondary amines can be prepared directly through a three‐step cascade reaction by starting from nitroaromatic compounds and aldehydes. On the other hand, Au/TiO2can also be used as a bifunctional catalyst to obtain substituted β‐amino carbonyl compounds from nitroaromatics and α,β‐unsaturated carbonyl compounds. Whereas gold sites promote the in situ formation of anilines, the intrinsic acidity of Ti species on the support surface accelerates the subsequent Michael addition. Finally, two gold‐catalyzed reactions, that is, the hydrogenation of nitro groups and a hydroamination, have been coupled to synthesize additional substituted imines from nitroaromatic compounds and alkynes.
Counterions Control the Self‐Assembly of Structurally Persistent Micelles: Theoretical Prediction and Experimental Observation of Stabilization by Sodium Ions
Authors: Jäger Christof M. , Hirsch Andreas , Schade Boris , Böttcher Christoph , Clark Timothy 
Published: July 2009

AbstractWe show by molecular‐dynamics (MD) simulations and cryo‐transmission electron microscopy (cryo‐TEM) experiments that the size and form of structurally persistent micelles formed by the T‐shaped amphiphile 1 are controlled by the counterions. The two techniques reveal that the micelles are specifically stabilized by sodium counterions relative to potassium ions. Both the simulations and the cryo‐TEM experiments suggest that the micelles are stabilized by strongly conserved hydrated contact ion pairs with sodium counterions but not with potassium ions. We suggest that the TEM is observing local high density due to hydrated carboxylate/sodium ion pairs at the surface of the micelle. A high concentration of such structures is found in MD simulations with sodium counterions, but not with potassium.
PCNCP Ligands in the Chromium‐Catalyzed Oligomerization of Ethylene: Tri‐ versus Tetramerization
Authors: Klemps Christian , Payet Elina , Magna Lionel , Saussine Lucien , Le Goff Xavier F. , Le Floch Pascal 
Published: July 2009

AbstractChromium(III) complexes bearing R′N(CH2PR2)2 (PCNCP) ligands have been prepared. Upon activation with methylaluminoxane, these complexes proved to be effective in the selective tri‐ and tetramerization of ethylene. The formation of either 1‐hexene or 1‐octene was found to be highly dependent on the steric bulk of the substituents R on the phosphine moieties. This observation was rationalized by using density functional theory calculations on selected steps of the metallacyclic mechanism of the ethylene oligomerization reaction.
Cyclopropenylcarbinol Derivatives as New Versatile Intermediates in Organic Synthesis: Application to the Formation of Enantiomerically Pure Alkylidenecyclopropane Derivatives
Authors: Simaan Samah , Masarwa Ahmad , Zohar Elinor , Stanger Amnon , Bertus Philippe , Marek Ilan 
Published: July 2009

AbstractThe copper‐catalyzed carbomagnesiation (or hydrometalation) reaction of chiral cyclopropenylcarbinol derivatives, obtained by means of a kinetic resolution of secondary allylic alcohols, leads to an easy and straightforward preparation of enantiomerically pure alkylidenecyclopropane derivatives. The reaction mechanism is composed of a syn‐carbometalation followed by a syn‐elimination reaction. To gain further insight into the reaction mechanism of the carbometalation, the diastereoselective formation of cyclopropylcarbinol was also achieved and was found to be very sensitive to the nature of the organometallic species used for the addition reaction. Cyclopropylcarbinol could also be prepared through a diastereoselective reduction of cyclopropenylcarbinol derivatives. Finally, functionalization of enantiomerically enriched cyclopropenylcarbinols into the corresponding acetate or phosphinite derivatives leads, under mild conditions, to various enantiomerically pure heterosubstituted alkylidenecyclopropanes.
ChemInform Abstract: Dynamic Disorder of Bi2+8 Clusters in the Plastic Phase (Bi8)3Bi[InI4]9.
Authors: Wosylus Aron , Dubenskyy Vitaly , Schwarz Ulrich , Ruck Michael 
Published: July 2009

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Facile Chemical Insertion of Lithium in Eu0.33Zr2(PO4)3 — An Elegant Approach for Tuning the Photoluminescence Properties.
Authors: Saradhi M. P. , Pralong V. , Varadaraju U. V. , Raveau B. 
Published: July 2009

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.