bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gene expression in bovine nuclear transfer embryos in relation to donor cell efficiency in producing live offspring
Authors: Beyhan Z. , Forsberg E.J. , Eilertsen K.J. , Kent‐First M. , First N.L. 
Published: August 2006

AbstractDevelopmental abnormalities associated with the cloning process suggest that reprogramming of donor nuclei into an embryonic state may not be fully completed in most of the cloned animals. One of the areas of interest in this regard, is the analysis of gene expression patterns in nuclear transfer (NT) embryos to dissect the processes that failed and develop means to overcome the limitations imposed by these factors. In this study, we investigated expression patterns of histone deacetylase‐1, ‐2, ‐3 (HDAC‐1, ‐2, ‐3), DNA methyltransferase‐3a (DNMT3A), and octamer binding protein‐4 gene (OCT4) in donor cells with different cloning efficiencies and NT embryos derived from these cells employing a real‐time RT‐PCR assay. All genes investigated followed altered expression patterns in NT embryos when compared to IVF‐derived embryos. In general, expression of HDAC genes was elevated especially at the compact morula stage and comparable to in vitro fertilized (IVF) embryos at the hatched blastocyst stage. DNMT3A expression in NT embryos was lower than IVF embryos at all stages. Oct‐4 transcript levels were also reduced in cloned compared to IVF embryos at the compact morula and blastocyst stages. This difference disappeared at the hatched blastocyst stage. There was a donor cell effect on the expression patterns of all genes investigated. These results demonstrate altered gene expression patterns for certain genes, in cloned cattle embryos from our donor cells of different efficiency in producing live offspring. Therefore we suggest that differences in expression of developmentally important genes during early embryo development may characterize the efficiency of donor cells in producing live offspring. Mol. Reprod. Dev. 74: 18–27, 2007. © 2006 Wiley‐Liss, Inc.
Bone mineral densities in the prehistoric, Viking‐Age and medieval populations of Norway
Authors: Holck Per 
Published: August 2006

AbstractOsteoporosis is a prevalent condition in Norway, as evidenced by the fact that this country has the highest reported incidences of hip and distal forearm fractures. Because recent studies suggest a higher bone density in rural populations compared with urban ones, increased physical activity is believed to be an important factor in reducing fracture incidence. In the present investigation, 185 femoral necks from the Schreiner Collection in Oslo were measured by means of a bone‐mass scanner. The bones, anthropological specimens ranging from the Stone Age to the Middle Ages, were separated into three groups: prehistoric (n = 36), Viking Age (n = 38) and medieval (n = 111). The medieval group was further separated into urban, rural and monastic populations. The examination showed that: (a) there was no significant difference at a 5% level in average bone mineral density (BMD) between the male and female material; (b) there was no significant difference in average BMD among the prehistoric, Viking Age, and medieval periods (P = 0.151); (c) there was no significant difference in average BMD between the rural and urban medieval material; (d) there was a significant difference in average BMD only between the monastic and the rural medieval material; (e) only the medieval material showed a significantly higher average BMD than that of today (P = 0.001). These findings may indicate that factors in addition to physical activity are important for normal BMD maintenance. Copyright © 2006 John Wiley & Sons, Ltd.
Use of phenytoin, phenobarbital, or diazepam during pregnancy and risk of congenital abnormalities: a case‐time‐control study
Authors: Kjær Dorte , Horvath‐Puhó Erzsébet , Christensen Jakob , Vestergaard Mogens , Czeizel Andrew E. , Sørensen Henrik Toft , Olsen Jørn 
Published: August 2006

AbstractPurposeCase‐control studies are often used to examine putative teratogenic drug effects during organogenesis but these studies are subject to confounding by indication, recall, and participation bias. The case‐time‐control approach is less susceptible to these sources of bias. We studied congenital abnormalities following exposure to phenytoin, phenobarbital, and diazepam in early pregnancy, i.e., second and third month, compared to mid‐pregnancy, i.e., fifth and sixth month of pregnancy.MethodsWe analyzed data from the Hungarian Case‐Control Surveillance of Congenital Abnormalities (1980–1996) in a case‐time‐control study.ResultsThe study included 22 843 children with congenital abnormalities (cases) and 38 151 children with no abnormalities (controls). Overall, odds ratio (OR) for congenital abnormalities after exposure to one of the three drugs in early pregnancy was 1.2 (95% confidence interval (CI): 1.0–1.4). Among children exposed to phenytoin OR for congenital abnormalities was 3.7 (95%CI: 0.3–49.6), for children exposed to phenobarbital the OR was 1.1 (95%CI 0.7–1.7), and for diazepam, OR for congenital abnormalities was 1.2 (95%CI: 1.0–1.4).ConclusionsThe associations we found between the drugs examined and congenital abnormalities were either only borderline significant or not statistically significant. The case‐time‐control study provides an interesting way of using existing case‐control data to study rare side effect of drugs taken during pregnancy. Copyright © 2006 John Wiley & Sons, Ltd.
Turbulenzübergang in der Rohrströmung: Die Lösung eines alten Rätsels
Authors: Eckhardt Bruno , Hof Björn , Faisst Holger 
Published: August 2006

AbstractDie Strömung von Flüssigkeiten und Gasen durch eine Röhre kann zwei Zustände annehmen. Einer ist laminar, also gleichmäßig geordnet, einer ist zeitlich‐räumlich verwirbelt und turbulent. Mit dem Übergang zur Turbulenz nimmt der Strömungswiderstand drastisch zu. Vor etwa 120 Jahren beschrieb Osborne Reynolds bereits das Verhalten der Rohrströmung sehr genau. Er beobachtete, dass der Turbulenzübergang sehr empfindlich von äußeren Störungen abhängt, was bislang rätselhaft blieb. Dieses Rätsel konnte nun mit einer Kombination aus Computerstudien, Konzepten aus der nichtlinearen Dynamik und speziell entwickelten Experimenten gelöst werden.
Ein Regenbogen ohne Regentropfen: Spielwiese
Authors: Schlichting Hans Joachim 
Published: August 2006

AbstractWenn Licht unter geeignetem Winkel auf eine quaderförmige mit Wasser gefüllte Wanne trifft, wirken die Lichtbrechungen beim Eintritt in die Wanne und beim Austritt so zusammen, dass ein bogenförmiges Band spektral zerlegten Lichts auf einer Projektionswand entsteht. Steht die Wanne mitten auf einem Overheadprojektor, so findet das Licht an allen Seitenflächen ähnliche Bedingungen vor. Unter Umständen sind dann an allen vier Wänden des Raumes “Regenbögen” zu sehen. Dieses Freihandexperiment, das ohne Aufwand realisiert werden kann, beeindruckt vor allem in großen Räumen.
Nanomagnetische Eigenschaften im Elektronenmikroskop
Authors: Schattschneider Peter 
Published: August 2006

AbstractMagnetische Festkörper besitzen die Eigenschaft des Zirkulardichroismus, das heißt ihr Absorptionsgrad für Röntgenstrahlung hängt von der zirkularen Polarisation ab. Synchrotronstrahlung eignet sich ausgezeichnet, um mit Hilfe dieses Effekts magnetische Eigenschaften zu untersuchen. Sie ist aber teuer, und die Ortsauflösung ist meist nicht besser als 50 nm. Jetzt gelang es einer internationalen Forschergruppe, Zirkulardichroismus mit einem handelsüblichen Elektronenmikroskop nachzuweisen. Damit könnte eine neue, billige Untersuchungstechnik für Nanomagnetismus begründet werden.
Speicherscheibe für 300 Gigabyte
Authors: Wengenmayr Roland 
Published: August 2006

AbstractDie optisch‐digitalen Datenspeicher CD und DVD haben unsere Lebensgewohnheiten stark verändert. Schon sind die Nachfolgesysteme Blue Ray Disk und HD‐DVD in einigen Ländern auf dem Markt. In den USA wird noch in diesem Jahr das Unternehmen InPhase Technologies in Longmond, Colorado, das erste holografische Datenspeichersystem herausbringen.
Der Lichtpfeil, der einen Tropfen durchbohrt
Authors: Schlichting Hans Joachim 
Published: August 2006

AbstractBetrachtet man Wassertropfen oder Glaskugeln in der Sonne, so kann man den Eindruck gewinnen, ein Lichtstrahl würde die Kugel geradezu durchbohren. Gleichzeitig meint man, Eintritts‐ und Austrittsöffnung zu erkennen.
Morphology and interactions of polymer brush‐coated spheres in a polymer matrix
Authors: Xu Jiajing , Qiu Feng , Zhang Hongdong , Yang Yuliang 
Published: August 2006

AbstractUsing a real space implementation of the self‐consistent field theory, we calculated the morphology and interactions of spherical nanoparticles with radius Rp that are grafted by polymer chains of N monomers immersed in a chemically identical polymer melt of polymerization index P. The calculation shows that, for big particles (Rp ≫ N1/2a, with a the segment size), the interactions and density profiles of the grafted layers are that of brushes at flat interface; While for small particles (Rp ≪ N1/2a), the interactions and density profiles are characteristic of star polymers. In the case of intermediate grafted chain lengths, that is, Rp ∼ N1/2a, we found that the grafting density of the polymers and the radius of the spherical nanoparticles are both important in determining the structure and interactions of the grafted layers. Our findings suggest possible ways to tailor the structure and interactions of the nanoparticles to benefit the fabrication of polymeric nanocomposites. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2811–2820, 2006
Electrospun fiber mats of poly(3‐hydroxybutyrate), poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate), and their blends
Authors: Sombatmankhong Korakot , Suwantong Orawan , Waleetorncheepsawat Suchada , Supaphol Pitt 
Published: August 2006

AbstractElectrospinning of poly(3‐hydroxybutyrate) (PHB), poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV), and their blends was first carried out in chloroform at 50 °C on a stationary collector. The average diameter of the as‐spun fiber from PHB and PHBV solutions decreased with increasing collection distance and increased with increasing solution concentration and applied electrical potential. In all of the spinning conditions investigated, the average diameter of the as‐spun pure fibers ranged between 1.6 and 8.8 μm. Electrospinning of PHB, PHBV, and their blends was carried out further at a fixed solution concentration of 14% w/v on a homemade rotating cylindrical collector. Well‐aligned, cross‐sectionally round fibers without beads were obtained. The average diameter of the as‐spun pure and blend fibers ranged between 2.3 and 4.0 μm. The as‐spun fiber mats appeared to be more hydrophobic than the corresponding films and much improvement in the tensile strength and the elongation at break was observed for the blend fiber mats over those of the pure fiber ones. Lastly, indirect cytotoxicity evaluation of the as‐spun pure and blend fiber mats with mouse fibroblasts (L929) indicated that these mats posed no threat to the cells. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2923–2933, 2006
Conformational structures and thermodynamic properties of compact polymer chains confined between two parallel plane boundaries
Authors: Li Shi‐Ben , Zhang Lin‐Xi 
Published: August 2006

AbstractIn this paper, the authors investigated the adsorption phenomenon of compact chains confined between two parallel plane boundaries using a pruned‐enriched Rosenbluth method. The authors considered three cases with different adsorption energies of ε = 0, −1, and −3 (in units of kBT) for the confined compact chains of different chain lengths N, respectively. Several parameters were employed to describe the size and shape of compact chain, and some special behaviors in the conformational structures were investigated for the first time. For example, the size and shape of confined compact chains undergo distinct changes in the adsorption cases of ε = −1 and −3, and pass through the maximum values at the characteristic distances Dc. The authors found that this characteristic distance Dc could be scaled as Dc∼ (N + 1)ν (ν = 0.56 ± 0.01) in the case of ε = −3. In addition, the microstructures of chains were investigated, and several significant results were obtained by analyzing the segment density distribution and the mean fractions of segment in tails, trains, bridges, and loops structures. On the other hand, the thermodynamic properties were also investigated for the confined compact chains, such as average energy per bond, Helmholtz free energy per bond, and elastic force per bond. Results show that elastic forces f have different behaviors in three cases, indicating that it is not necessary to exert an external force on the boundaries in the nonadsorption case. At the same time, the average contact energy of compact chain obviously changes when the distance between the two parallel boundaries D increases, which is similar to those of the size and shape parameters. The authors also conclude that these thermodynamic properties of compact chains depend strongly on not only the adsorption energies but also the chain lengths and the confined condition. In addition, several results of the conformational and thermodynamic parameters, such as the segment density distribution and free energy, were compared with the results from the self‐consistent field theory. These investigations may help us to deepen the knowledge about the adsorption phenomenon of confined compact chains. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2888–2901, 2006
Monte Carlo simulation of diffusion effects on chain‐extension reactions
Authors: Yan Li‐Tang , Guo Bao‐Hua , Xu Jun , Xie Xu‐Ming 
Published: August 2006

AbstractThe diffusion effects on chain‐extension reactions using carboxyl‐terminated polyamide‐12 as a model reactant with bisoxazolines were investigated by the stochastic Monte Carlo method. Thus, complicated direct modeling and numerical calculations were avoided. The chain‐length dependence and detailed diffusive behavior were discussed in depth. The diffusion effects retarded the progress of chain‐extension reactions and led to lower coupling efficiency. The simulated results indicated that the diffusion effects could make the final molecular weight distributions wider. In the presence of diffusion and with the progress of the coupling efficiency, peaks in the evolution curves of the weight‐average molecular weight and valleys in the evolution curves of the polydispersity index were observed, respectively, when the coupling efficiency was low enough. These phenomena were different from those without diffusion effects and were analyzed in detail. The critical entanglement chain length had strong effects on the simulated results of the diffusion effects, especially when its value was near the average chain length. The results also showed that the effects of the reactant degradation made the molecular weight distribution of the reaction system wider and weakened the diffusion effects on the coupling reaction. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2902–2911, 2006
How inaccuracies in protein structure models affect estimates of protein–ligand interactions: Computational analysis of HIV‐I protease inhibitor binding
Authors: Thorsteinsdottir Holmfridur B. , Schwede Torsten , Zoete Vincent , Meuwly Markus 
Published: August 2006

AbstractThe influence of possible inaccuracies that can arise during homology modeling of protein structures used for ligand binding studies were investigated with the molecular mechanics generalized Born surface area (MM‐GBSA) method. For this, a family of well‐characterized HIV‐I protease–inhibitor complexes was used. Validation of MM‐GBSA led to a correlation coefficient ranging from 0.72 to 0.93 between calculated and experimental binding free energies ΔG. All calculated ΔG values were based on molecular dynamics simulations with explicit solvent. Errors introduced into the protein structure through misplacement of side‐chains during rotamer modeling led to a correlation coefficient between ΔGcalc and ΔGexp of 0.75 compared with 0.90 for the correctly placed side chains. This is in contrast to homology models for members of the retroviral protease family with template structures ranging in sequence identity between 32% and 51%. For these protein models, the correlation coefficients vary between 0.84 and 0.87, which is considerably closer to the original protein (0.90). It is concluded that HIV‐I low sequence identity with the template structure still allows creating sufficiently reliable homology models to be used for ligand‐binding studies, although placement of the rotamers is a critical step during the modeling. Proteins 2006. © 2006 Wiley‐Liss, Inc.
Describing and projecting the age and spatial structures of interregional migration in Italy
Authors: Raymer James , Bonaguidi Alberto , Valentini Alessandro 
Published: August 2006

AbstractA multiplicative component model is applied in this paper to present a simple, yet powerful, framework for analysing and projecting internal migration flows. The multiplicative components are useful for identifying important underlying structures in the migration patterns. To demonstrate, seven periods of age‐specific interregional migration in Italy (1970–1971 to 2000–2001) are analysed. This information is then used to project the age and spatial structures forward to the 2010–2011 period. The projection model focuses on the underlying structures, which allows both the stable and changing aspects of the migration patterns to be included. Copyright © 2006 John Wiley & Sons, Ltd.
Blacks and Hispanics in urban America: similar patterns of residential segregation?
Authors: Johnston Ron , Poulsen Michael , Forrest James 
Published: August 2006

AbstractStudies of residential segregation of Blacks and Hispanics in United States' metropolitan areas over recent decades have suggested a convergence between the two groups, as Black segregation levels declined somewhat, whilst those for Hispanics have increased substantially. The latter has been associated with the rapid and very substantial growth in the Hispanic population. To some considerable extent, those changes have been taking place in different parts of the US. Many of the metropolitan areas experiencing major increases in their Hispanic populations contain relatively few Blacks; and the changes have varied considerably across the country. So are similar processes in operation? Are the same characteristics associated with high levels of segregation for each ethnic group? Regression analyses of data for 1980 and 2000, and for changes between those two dates, suggest that they are: that the size of a minority group – both absolute and as a percentage of the metropolitan population – is significantly linked to segregation levels and changes in them. There is clear convergence taking place, reflecting increasing segregation among recently‐arrived Hispanics and some desegregation among Blacks. This is consistent with general models of residential segregation, even if they are occurring in different parts of the country. Copyright © 2006 John Wiley & Sons, Ltd.
Prediction of ITQ‐21 Zeolite Phase Crystallinity: ParametricVersusNon‐parametric Strategies
Authors: Baumes Laurent A. , Moliner Manuel , Corma Avelino 
Published: August 2006

AbstractThis work deals with data analysis techniques and high‐throughput tools for synthesis and characterization of solid materials. In previous studies, it was found that the final properties of materials could be successfully modeled using learning systems. Machine learning algorithms such as neural networks, support vector machines, and regression trees are non‐parametric strategies. They are compared to traditional parametric statistical approaches. We review a wide range of statistical methodologies, and all the methods are evaluated using experimental data derived from an exploration‐optimization of the material ITQ‐21. The results are judged on the numerical prediction of phase's crystallinity. We discuss the theoretical aspects of such statistical techniques, which make them an attractive method when compared to other learning strategies for modeling the properties of the solids. Advantages and drawbacks are highlighted. We show that such approaches, by offering broad solutions, can reach high‐level performances while offering ease of use, comprehensibility, and control. Finally, we shed light on both the interpretation and stability of results, which remain the main drawbacks of the majority of machine learning methodologies when trying to retrieve knowledge from the data treatment.
Using QSPR Models to Predict the Enthalpy of Vaporization of 209 Polychlorinated Biphenyl Congeners
Authors: Padmanabhan Jaganathan , Parthasarathi Ramakrishnan , Subramanian Venkatesan , Chattaraj Pratim K. 
Published: August 2006

AbstractQuantitative Structure–Property Relationship (QSPR) models to correlate the vaporization enthalpies (ΔvapHm) of a set containing biphenyl and 16/26 Polychlorinated Biphenyls (PCBs) with their conceptual Density Functional Theory (DFT)‐based global reactivity parameter such as electrophilicity index (ω) along with the energy of lowest unoccupied molecular orbital (ELUMO) and the number of chlorine substituents (NCl) as descriptors are presented. A good coefficient of determination (r2=0.976/0.858) and internal predictive ability ($\rm{ r_{{\rm{cv}}}^2 }$=0.948/0.758) values are obtained indicating the significance of the considered descriptors in the property analysis. The developed model is used to predict ΔvapHm of the remaining 193/183 PCB congeners.
Peptide derivatization as a strategy to form fixed‐charge peptide radicals
Authors: Karnezis Asimo , Barlow Christopher K. , O'Hair Richard A. J. , McFadyen W. David 
Published: August 2006

AbstractAs a means of generating fixed‐charge peptide radicals in the gas phase we have examined the collision‐induced dissociation (CID) chemistry of ternary [CuII(terpy)(TMPP‐M)]2+ complexes, where terpy = 2,2′:6′2″‐terpyridine and TMPP‐M represents a peptide (M) modified by conversion of the N‐terminal amine to a [tris(2,4,6‐trimethoxyphenyl)phosphonium]acetamide (TMPP‐) fixed‐charge derivative. The following modified peptides were examined: oligoglycines, (Gly)n (n = 1–5), alanylglycine, glycylalanine, dialanine, trialanine and leucine‐enkephaline (YGGFL). The [CuII(terpy)(TMPP‐M)]2+ complexes are readily formed upon electrospray ionization (ESI) of a mixture of derivatized peptide and [CuII(terpy)(NO3)2] and generally fragment to form transient peptide radical cations, TMPP‐M+., which undergo rapid decarboxylation for the simple aliphatic peptides. This is contrasted with the complexes containing the unmodified peptides, which predominantly undergo fragmentation of the coordinated peptide. These differences demonstrate the importance of proton mobility in directing fragmentation of ternary copper(II) peptide complexes. In the case of leucine‐enkephaline, a sufficient yield of the radical cation was obtained to allow further CID. The TMPP‐YGGFL+. ion showed a rich fragmentation chemistry, including CO2 loss, side‐chain losses of an isopropyl radical, 2‐methylpropene and p‐quinomethide, and *a1 and *a4 sequence ion formation. In contrast, the even‐electron TMPP‐YGGFL+ ion fragments to form *an and *bn sequence ions as well as the [*b4 + H2O]+ rearrangement ion. Copyright © 2006 John Wiley & Sons, Ltd.