bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural and ordering behavior of lamellar polystyrene‐block‐polybutadiene‐block‐polystyrene triblock copolymer containing layered silicates
Authors: Vazquez A. , López M. , Serrano E. , Valea A. , Zafeiropoulos N. E. , Mondragon I. 
Published: September 2008

AbstractNanocomposites based on organically modified montmorillonites (OMMTs) and sodium montmorillonite (CLO‐Na+) with poly(styrene‐b‐butadiene‐b‐styrene) (SBS) diblock copolymer have been investigated. Solution blending of OMMT suspension in toluene with SBS and subsequent static casting and annealing resulted in transparent films. Final samples were processed by compression molding. The intercalation spacing in the nanocomposites, microphase separation of the SBS, and the degree of dispersion of nanocomposites were investigated by X‐ray diffraction (Wide and small‐angle X‐ray scattering), transmission optical microscopy (TOM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). The increase of basal spacing of OMMT in the nanocomposites suggested the intercalation of SBS. The lamellar structure perfection was extensively affected by both OMMT. AFM images and TOM micrographs only showed well dispersed but not exfoliated nanocomposites. On the other hand, TEM showed inserted tactoids into both blocks depending on the surfactant used (stained samples) and the dispersion of those tactoids (unstained samples). Fourier transform infrared spectroscopy indicated only the presence of the OMMT into the SBS. Deviations of the decomposition pathway of pristine SBS with addition of the OMMT were found by thermogravimetric analysis. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Properties of polymer light‐emitting diodes coated on surface‐treated ITO/glass substrates
Authors: Shin Sang‐Baie , Gong Su‐Cheol , Jang Ji‐Keun , Gong Myoung‐Seon , Chang Young‐Chul , Sun Yong‐Bin , Chang Ho‐Jung 
Published: September 2008

AbstractWe fabricated blue polymer light‐emitting diodes (PLEDs) with indium tin oxide (ITO)/PEDOT : PSS/PVK/PFO‐poss/LiF/Al structures. All of the organic film layers were prepared by the spin‐coating method on plasma and heat‐treated ITO/glass substrates. The dependences of the optical and electrical properties of the PLEDs on the plasma and heat treatment of the ITO film and the introduction of poly(N‐vinylcarbazole) (PVK) layer were investigated. The AFM measurements indicated that the surface roughness of the ITO transparent film was improved by the plasma and heat treatment. In the emission spectra, the intensity of the excimer peaks of the PFO‐poss [polyhedral oligomeric silsesquioxane‐terminated poly(9,9‐dioctylfluorene)] emission layer were decreased for the PLED device with the PVK film layer compared with the one without the PVK layer. The maximum current density, luminance and current efficiency of the PLEDs were found to be about 470 mA/cm2, 486 cd/m2 at an input voltage of 12 V and 0.55 cd/A at 100 cd/m2 in luminance, respectively. The color coordinates (CIE chart) of the blue PLEDs were in the range of x = 0.17 ∼ 0.20, y = 0.13 ∼ 0.16, and the peak emission spectrum was about 430 nm, showing a good blue color. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Amine functional chloroaniline acetaldehyde condensate‐modified epoxy networks
Authors: Maity T. , Samanta B. C. , Banthia A. K. 
Published: September 2008

AbstractAn investigation was carried out to modify the fracture toughness of cured diglycidyl ether of bisphenol‐A (DGEBA) resin networks with amine functional chloroaniline acetaldehyde condensate (AFCAC) as toughening agent. The resulting networks displayed significantly improved fracture toughness. The AFCAC was synthesized by the condensation reaction of chloroaniline and acetaldehyde in the acid medium (pH‐4) and characterized by FTIR and NMR spectroscopy, elemental analysis, viscosity measurements, and mole of primary and secondary amine analysis. The DGEBA and AFCAC were molecularly miscible but developed a two‐phase microstructure upon network formation. Epoxy/AFCAC compositions were systematically varied to study the effect of concentration on the impact, adhesive, tensile, and flexural properties of modified networks. The dynamic mechanical analysis and scanning electron microscopy studies showed two‐phase morphology in the cured networks where AFCAC particles were dispersed. The AFCAC‐modified epoxy network was thermally stable up to around 338°C. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Performance in a prematriculation gross anatomy course as a predictor of performance in medical school
Authors: Tucker Richard P. 
Published: September 2008

AbstractThe University of California at Davis School of Medicine offers a prematriculation program to nontraditional students. As part of the program, students take a 7‐day course on the gross anatomy of the upper limb that concludes with a written examination and a practical examination based on prosections. Here, the performance of students who took the course from 2002 to 2004 (n = 48) is compared with their performance in the medical gross anatomy course as well as their performance on Step 1 of the United States Medical Licensing Examination (USMLE). Both rank in the prematriculation program's anatomy course and the score on the examination were correlated (significant at the 0.01 level) with performance on the medical gross anatomy midterm and final examinations, the overall final grade, and class rank. Performance in the prematriculation anatomy course was also correlated with the score on Step 1 of the USMLE (rank significant at the 0.02 level; examination score, significant at the 0.05 level). Students who took the prematriculation course who eventually withdrew, were dismissed for academic reasons, or who failed the first attempt at the Step 1 of the licensing exam (n = 5) had a significantly lower score (77.6 ± 11.1; P < 0.05) on the prematriculation examination than did successful prematriculation students (86.2 ± 7.9). Thus, a gross anatomy examination following a short prematriculation course can be a predictor not only of medical student performance in anatomy, but also of performance on a standardized licensing examination. Anat Sci Ed 1:224–227, 2008. © 2008 American Association of Anatomists.
The controversial 30 nm chromatin fibre
Authors: Staynov Dontcho Z. 
Published: September 2008

AbstractDNA is packed as chromatin on several levels in the eukaryotic nucleus. Dissection of chromatin with nucleases produces three stable substructures: the nucleosome core particle, the chromatosome and the 30 nm fibre. Whilst the first two allow transcription, the 30 nm fibre is taken to be the first level of transcriptionally dormant chromatin and it has an important functional role in cell differentiation and epigenetic regulation. Its structure has been a subject of continuing discussion since native fibres cannot readily be crystallized. This problem has recently been addressed by reconstitution of fibres on repeats of DNA sequences having nucleosome‐positioning properties and two different structures were reported.1,2The reconstitution results and their interpretations are compared in this review with experimental data from native chromatin and it is shown that the results of Robinson et al.2 conform well with the known structural features of native fibres and are a good first step towards understanding the structure of the fibre. BioEssays 30:1003–1009, 2008. © 2008 Wiley Periodicals, Inc.
The art of community detection
Authors: Gulbahce Natali , Lehmann Sune 
Published: September 2008

AbstractNetworks in nature possess a remarkable amount of structure. Via a series of data‐driven discoveries, the cutting edge of network science has recently progressed from positing that the random graphs of mathematical graph theory might accurately describe real networks to the current viewpoint that networks in nature are highly complex and structured entities. The identification of high order structures in networks unveils insights into their functional organization. Recently, Clauset, Moore, and Newman,1 introduced a new algorithm that identifies such heterogeneities in complex networks by utilizing the hierarchy that necessarily organizes the many levels of structure. Here, we anchor their algorithm in a general community detection framework and discuss the future of community detection. BioEssays 30:934–938, 2008. © 2008 Wiley Periodicals, Inc.
Of tacit knowledge, texts and thing‐based learning (TBL)
Authors: Rangachari P. K. 
Published: September 2008

AbstractPractical knowledge has two dimensions‐ a visible, codified component that resembles the tip of an iceberg. The larger but crucial tacit component which lies submerged consists of values, procedures and tricks of the trade and cannot be easily documented or codified. Undergraduate science students were given an opportunity to explore this component through an inquiry‐based course.
A portable bioinformatics course for upper‐division undergraduate curriculum in sciences
Authors: Floriano Wely B. 
Published: September 2008

AbstractThis article discusses the challenges that bioinformatics education is facing and describes a bioinformatics course that is successfully taught at the California State Polytechnic University, Pomona, to the fourth year undergraduate students in biological sciences, chemistry, and computer science. Information on lecture and computer practice topics, free for academic use software and web links required for the laboratory exercises and student surveys for two instances of the course, is presented. This course emphasizes hands‐on experience and focuses on developing practical skills while providing a solid knowledge base for critically applying these skills. It is designed in blocks of 1‐hour lecture followed by 2 hours of computer laboratory exercises, both covering the same general topic, for a total of 30 hours of lecture and 60 hours of computer practice. The heavy computational aspect of this course was designed to use a single multiprocessor computer server running Linux, accessible from laptops through Virtual Network Computing sessions. The laptops can be either provided by the institution or owned by the individual students. This configuration avoids the need to install and maintain bioinformatics software on each laptop. Only a single installation is required for most bioinformatics software on the Linux server. The content of this course and its software/hardware configuration are well suited for institutions with no dedicated computer laboratory. This author believes that the same model can be successfully implemented in other institutions, especially those who do not have a strong instructional computer technology support such as community colleges and small universities.
Biochemistry and molecular biology techniques for person characterization
Authors: Herrero Salvador , Ivorra Jose Luis , García‐Sogo Magdalena , Martínez‐Cortina Carmen 
Published: September 2008

AbstractUsing the traditional serological tests and the most novel techniques for DNA fingerprinting, forensic scientists scan different traits that vary from person to person and use the data to include or exclude suspects based on matching with the evidence obtained in a criminal case. Although the forensic application of these methods is well known, the procedures and techniques used to obtain these results are not so well studied. Here, we report a laboratory exercise aimed to familiarize the students in several of the methods and markers employed for people individualization. With this exercise, students have to characterize themselves and an unknown sample according to the following characteristics: ABO blood group, presence or absence of Y chromosome, and their polymorphism for a variable number of tandem repeats (VNTR). This exercise has been originally developed for students of the course “Techniques in Criminology” within the Bachelor of Criminology. Although the schedule and procedures have been addressed to students who are faced for their first time with a laboratory of molecular biology, the exercise can also be adapted to students in more specialized courses and studies.
Theoretical Study of the Human Bradykinin–Bradykinin B2 Receptor Complex
Authors: Gieldon Artur , Lopez Jakob J. , Glaubitz Clemens , Schwalbe Harald 
Published: September 2008

AbstractThe interaction of bradykinin (BK) with the bradykinin B2 receptor (B2R) was analyzed by using molecular modeling (MM) and molecular dynamics (MD) simulations. A homology model for B2R has been generated and the recently determined receptor‐bound solid‐state NMR spectroscopic structure of BK (Lopez et al.,Angew. Chem.2008,120, 1692–1695;Angew. Chem. Int. Ed.2008,47, 1668–1671) has been modeled into the binding pocket of the receptor to probe the putative ligand–receptor interface. The experimental hormone structure fitted well into the binding pocket of the receptor model and remained stable during the MD simulation. We propose a parallel orientation of the side chains for Arg1 and Arg9 in BK that is bound to B2R. The MD simulation study also allows the conformational changes that lead to the activated form of B2R to be analyzed. The hydrogen bond between N140 (3.35) and W283 (6.48) is the key interaction that keeps the receptor in its inactive form. This hydrogen bond is broken during the MD simulation due to rotation of transmembrane helix 3 (TM3) and is replaced by a new hydrogen bond between W283 (6.48) and N324 (7.45). We propose that this interaction is specific for the activated form of the bradykinin B2 receptor. Additionally, we compared and discussed our putative model in the context of the structural model of the partially activated rhodopsin (Rh*) and with the known biochemical and structural data.
Understanding the Two‐Step Spin‐Transition Phenomenon in Iron(II) 1D Chain Materials
Authors: Neville Suzanne M. , Leita Benjamin A. , Halder Gregory J. , Kepert Cameron J. , Moubaraki Boujemaa , Létard Jean‐François , Murray Keith S. 
Published: September 2008

AbstractThree analogous one dimensional (1D) polymeric iron(II) spin crossover (SCO) materials containing the new ligand 4,6‐bis(2′,2′′‐pyridyl)pyrazine (bdpp) have been comprehensively characterised magnetically (thermal and light‐induced) and structurally. Within this series are two polymorphs of the formula [Fe(NCS)2(bdpp)], 1 and 2 a, which differ magnetically in that phase 1 undergoes a full two‐step SCO (T1/2(1)=135 K and T1/2(2)=90 K) whereas phase 2 a remains high spin (HS) over all temperatures. The central distinction between these two materials lies in the presence of intermolecular π–π interactions generated by the crystal packing in 1, which are absent in 2 a. The isostructural selenocyanate analogue of 2 a, [Fe(NCSe)2(bdpp)], 2 b, undergoes a full two‐step SCO (T1/2(1)=200 K and T1/2(2)=125 K). Structural analyses of 1 and 2 b at a range of temperatures provide deep insight into their two‐step SCO nature. Structural analysis of 1 at 25 K (1LS–LS), 123 K (1LS–HS) and 250 K (1HS–HS) reveals two distinct iron(II) centres at each temperature, with ordered, alternating HS and LS (low spin) sites at the intermediate plateau (IP) temperatures. In contrast, structural analysis of 2 b at 90 K (2 bLS), 150 K (2 bLS/HS) and 250 K (2 bHS) reveals one unique iron(II) centre at each temperature with an “averaged” LS/HS character at the IP temperature. Weak planes of diffuse scattering in the single‐crystal X‐ray diffraction patterns were observed for this phase at 90 and 150 K, indicating that 1D long range ordering of alternating HS/LS iron(II) centres occurs along the 1D coordination chains, but that there is no correlation between chains. The lack of observable diffuse scattering at 250 K suggests that the onset of the 1D structural ordering in the chain direction corresponds to the first step of the SCO and that this structural transition is electronically driven. The photomagnetic properties of both 1 and 2 b have been investigated and show ≈62 and 53 % photo‐excitation of a HS metastable state at low temperatures and T(LIESST) values of 55 and 49 K, respectively. Relaxation studies on the HS fraction in 2 b fitted well to a stretched exponential model with kinetic parameters indicative of weak cooperativity.
Phosphorescent Thymidine Triphosphate Sensor Based on a Donor–Acceptor Ensemble System using Intermolecular Energy Transfer
Authors: Kwon Tae‐Hyuk , Kim Hee Jin , Hong Jong‐In 
Published: September 2008

AbstractAn ensemble sensor system that exhibited selective luminescence enhancement upon binding to thymidine 5′‐triphosphate (TTP) in HEPES buffer over other nucleotides was developed. The ensemble system consisted of an energy acceptor (FIrpic–bis(Zn2+–dipicolylamine conjugate, FIrpic=bis[(4,6‐difluorophenyl)‐pyridinato‐N,C2+]picolinate) derivative) and an energy donor (mCP–Zn2+–cyclen, mCP=N,N′‐dicarbazolyl‐3,5‐benzene). Among the nucleotides, the selective recognition and luminescence enhancement for TTP was achieved by the strong binding of the thymine unit to Zn2+–cyclen (cyclen=1,4,7,10‐tetraazacyclododecane) and intermolecular energy transfer between the mCP and FIrpic moieties.
Cooperativity between the β‐tubulin carboxy tail and the body of the molecule is required for microtubule function
Authors: Popodi Ellen M. , Hoyle Henry D. , Turner F. Rudolf , Raff Elizabeth C. 
Published: September 2008

AbstractUsing Drosophila spermatogenesis as a model, we show that function of the β‐tubulin C‐terminal tail (CTT) is not independent of the body of the molecule. For optimal microtubule function, the β‐tubulin CTT and body must match. β2 is the only β‐tubulin used in meiosis and spermatid differentiation. β1‐tubulin is used in basal bodies, but β1 cannot replace β2. However, when β1 is co‐expressed with β2, both β‐tubulins are equally incorporated into all microtubules, and males exhibit near wild type fertility. In contrast, co‐expression of β2β1C and β1β2C, two reciprocal chimeric molecules with bodies and tails swapped, results in defects in meiosis, cytoskeletal microtubules, and axonemes; males produce few functional sperm and few or no progeny. In these experiments, all the same β‐tubulin parts are present, but unlike the co‐assembled native β‐tubulins, the “trans” configuration of the co‐assembled chimeras is poorly functional. Our data thus reveal essential intra‐molecular interactions between the CTT and other parts of the β‐tubulin molecule, even though the CTT is a flexible surface feature of tubulin heterodimers and microtubules. In addition, we show that Drosophila sperm tail length depends on the total tubulin pool available for axoneme assembly and spermatid elongation. D. melanogaster and other Drosophila species have extraordinarily long sperm tails, the length of which is remarkably constant in wild type flies. We show that in males of experimental genotypes that express wild type tubulins but have half the amount of the normal tubulin pool size, sperm tails are substantially shorter than wild type. Cell Motil. Cytoskeleton 2008. © 2008 Wiley‐Liss, Inc.
Development of spray‐ and freeze‐dried high‐concentration sesamol emulsions and antioxidant evaluation in fibroblasts and UV‐exposed rat skin slices
Authors: Alencar Juliana , Gosset Gaëlle , Rahmouni Hidayat , Culcasi Marcel , Robin Maxime , Reynier Jean‐Pierre , Piccerelle Philippe , Pietri Sylvia 
Published: September 2008

AbstractDry sesamol emulsions were synthesized from several combinations of saccharose with hydroxypropylmethylcellulose (HPMC) or sodium caseinate (SC) using spray‐drying techniques at 120° to 180°C, or freeze‐drying. On the basis of physical characteristics such as droplet size distribution, residual moisture, and microscopic structure, the best material was obtained when spray‐drying was applied at either 150° or 180°C with SC or HPMC as excipients, respectively. The extent to which the antioxidant properties of free sesamol towards a set of free radicals (galvinoxyl, diphenylpicrylhydrazyl, superoxide, and hydroxyl) were altered in the starting and reconstituted liquid emulsions submitted to normal storage or pre‐exposed to a flux hydroxyl radicals was investigated. Emulsions were further evaluated for their antioxidant properties in cultured 3T3 murine fibroblasts and in an ex vivo model of ultraviolet irradiated rat skin. It was found that, in the material having the best physical properties, encapsulation was decisive in: (1) improving the overall antioxidant behavior of reconstituted versus starting liquid emulsions: (2) sparing sesamol consumption due to free radical attack; and (3) significantly protecting cells and skin against free radical‐ or irradiation‐induced enzymatic release and/or lipid peroxidation. Demonstrating a high activity at high dilutions where interactions of excipient become negligible, the new emulsions could be of great interest in sesamol‐based pharmacology or topical applications. Drug Dev Res 69:251–266, 2008. © 2008 Wiley‐Liss, Inc.
Effect of clomiphene on [Ca2+]i rises and cell viability in rabbit corneal epithelial cells
Authors: Huang Chorng‐Chih , Huang Chun‐Jen , Cheng Jin‐Shiung , Liu Shiuh‐In , Chen I‐Shu , Tsai Jeng‐Yu , Chou Chiang‐Ting , Lin Muh‐Chiou , Jan Chung‐Ren 
Published: September 2008

AbstractThe effect of clomiphene a first‐line therapy for WHO group II (eu‐estrogenic) infertility on cytosolic free Ca2+ concentrations ([Ca2+]i) and viability has not been explored in rabbit corneal epithelial cells (SIRC). This study examined whether clomiphene altered [Ca2+]i levels and caused cell death in SIRC cells. [Ca2+]i and cell viability were measured using the fluorescent dyes fura‐2 and WST‐1, respectively. Clomiphene at concentrations ≥5 µM increased [Ca2+]i in a concentration‐dependent manner. The Ca2+ signal was reduced partly by removing extracellular Ca2+. The clomiphene‐induced Ca2+ influx was insensitive to blockade of L‐type Ca2+ channel blockers. In Ca2+‐free medium, after pretreatment with 1 µM thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor), clomiphene failed to increase [Ca2+]i. Inhibition of phospholipase C with 2 µM U73122 did not change clomiphene‐induced [Ca2+]i rises. At concentrations of 0.5–20 µM, clomiphene killed cells in a concentration‐dependent manner. The cytotoxic effect of 15 µM clomiphene was not reversed by prechelating cytosolic Ca2+ with BAPTA/AM. Collectively, in SIRC cells, clomiphene‐induced [Ca2+]i rises by causing Ca2+ release from the endoplasmic reticulum and Ca2+ influx from non‐L‐type Ca2+ channels. Clomiphene‐caused cytotoxicity was not mediated by a preceding [Ca2+]i rise. Drug Dev Res 69:272–278, 2008 ©2008 Wiley‐Liss, Inc.