bluuebunny/crossref_metadata_2025_split huggingface dataset:
The reductive reaction mechanism of tobacco nitrite reductase derived from a combination of crystal structures and ultraviolet–visible microspectroscopy
Authors: Nakano Shogo , Takahashi Misa , Sakamoto Atsushi , Morikawa Hiromichi , Katayanagi Katsuo 
Published: April 2012

AbstractAssimilatory nitrite reductase (aNiR) reduces nitrite to an ammonium ion and has siroheme and a [Fe4S4] cluster as prosthetic groups. A reaction mechanism for Nii3, an aNiR from tobacco, is proposed based on high resolution X‐ray structures and UV–Vis (ultraviolet–visible) microspectroscopy of Nii3‐ligand complexes. Analysis of UV–Vis spectral changes in Nii3 crystals with increasing X‐ray exposure showed prosthetic group reductions. In Nii3‐NO structures, X‐ray irradiation enhanced the progress of the reduction reaction, and cleavage of the NO bond was observed when X‐ray doses were increased. Crystal structures of Nii3 with other bound ligands, such as Nii3‐NO and Nii3‐NH2OH, were also determined. Further, by combining information from these Nii3 ligand‐bound structures, including that of Nii3‐NO, with UV–Vis microspectral data obtained using different X‐ray doses, a reaction mechanism for aNiR was suggested. Cleavage of the two NO bonds of nitrite was envisaged as a two‐step process: first, the NO bond close to Lys224 was cleaved, followed by cleavage of the NO bond close to Arg109. X‐ray structures also indicated that aNiR‐catalyzed nitrite reduction proceeded without the need for conformation changes in active site residues. Geometrical changes in the ligand molecules and the placement of neighboring water molecules appeared to be important to the stability of the active site residue interactions (Arg109, Arg179, and Lys224) and the ligand molecule. These interactions may contribute to the efficiency of aNiR reduction reactions. Proteins 2012; © 2012 Wiley Periodicals, Inc.
Cr induced nanocrystallization of a ‐Si thin films: its mechanism
Authors: Ahamad Mohiddon Md. , Lakshun Naidu K. , Dalba G. , Rocca F. , Ghanashyam Krishna M. 
Published: April 2012

AbstractThe mechanism involved in the metal induced a ‐Si crystallization has been investigated by X‐ray absorption spectroscopy for Cr. The growth process involves the deposition on fused silica (FS) of FS/Cr(200nm)/a ‐Si(400nm) stacks (FCS) and FS/a ‐Si(400nm)/Cr(200nm) stacks (FSC) at different substrate temperatures by electron beam evaporation technique. X‐ray absorption spectra were measured at different incidence angles (total reflection, 10° and 45°) to understand the evolution of the local structure of Cr components diffusing from bottom to top or from top to bottom in FCS and FSC stacks respectively. From the qualitative and quantitative analysis, we may conclude that, in case of Cr induced MIC, at first Cr diffuses into the a ‐Si matrix, then it partially reacts with a ‐Si to form CrSi2. This will later act as crystallizing seed for a ‐Si crystallization (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nano‐droplet formation in polymer dispersed liquid crystals
Authors: Torres‐Cisneros M. , LiKamWa Patrick , May‐Arrioja D. , Ibarra‐Manzano O. G. , Plascencia‐Mora H. , Aguilera‐Gómez E. , Aviña‐Cervantes J. G. , Sanchez‐Mondragon J. J. , Song Q. , Andrade‐Lucio J. A. , Guzmán‐Cabrera R. 
Published: April 2012

AbstractIn this work we analyse the fabrication of Polymer Dispersed Liquid Crystals (PDLCs) using SU8‐2002‐2007 photoresist and 5CB and E7 Liquid Crystals. Also we report the nonlinear optical behaviour for these materials and for Polymer Dispersed Liquid Crystals with a Twisted Cell (T‐PDLC). We found that depending of several parameters, the droplets size varies from nano to micro dimensions. We report for first time, to our best knowledge, the synthesis of a SU8 Polymer Dispersed Liquid Crystal (PDLC) by using the polymer SU8 photoresist and liquid crystals (LC) and also the nonlinear behaviour of T‐PDLC. We have characterized the droplets formation from nano to micron size depending of the different variables in the synthesis. We have used this PDLC in microfabrication as planar waveguides of different thickness over Si wafers. Our results also show that PDLCs present low NL optical Kerr coefficient (n2 about 10‐9cm2/W) and that it is three orders of magnitude larger in T‐PDLC. Nevertheless, the fabrication processes of T‐PDLCs make impossible their use in microfabrication. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of oxygen on light emission from amorphous silicon nanoclusters
Authors: Yeltsina Olga S. , Andronikov Dmitrii A. , Kukin Alexei V. , Vainshtein Julia S. , Sreseli Olga M. 
Published: April 2012

AbstractSurface effects, in particular oxygen passivation, are known to have drastic influence on emission spectra of semiconductor nanoclusters. The goal of this work was to obtain light emission from amorphous silicon nanoclusters by means of oxygen passivation. Granulated films of amorphous silicon nanoclusters were fabricated by the laser electrodispersion technique, which allows obtaining nanoclusters of uniform sizes. Two methods were applied in order to incorporate oxygen into the films, and both result in improvement of the luminescent properties of the films. The role of oxygen passivation as well as the effect of thermal annealing is considered. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ab‐initio study of silicon nanowires
Authors: Karazhanov Smagul , Marstein Erik , Holt Arve 
Published: April 2012

AbstractFour different size nanowires of Si have been studied by the density functional theory. We have shown that distinct from the bulk silicon with indirect band structure the one of the silicon nanowires is direct. Both valence band maximum and conduction band minimum are located at the Γ point. Optical properties of the nanowires have been studied. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Separation of energies of the direct (through‐space) and indirect (through‐bridge) interactions in SCF LCAO MO theory*
Authors: Nalewajski Roman F. 
Published: April 2012

AbstractWithin the standard SCF LCAO MO theory the electronic energy is partitioned into components associated with pairs of atomic orbitals and contributions due to the direct (through‐space) and indirect (through‐bridge) chemical bonds in molecules are identified. Conditions for the overall bonding effect of the implicit bridge interactions are qualitatively examined using the simplest case of the three‐orbital model and possible extensions including electron correlation are briefly commented upon. © 2012 Wiley Periodicals, Inc.
Divide‐and‐conquer‐based symmetry adapted cluster method: Synergistic effect of subsystem fragmentation and configuration selection
Authors: Yoshikawa Takeshi , Kobayashi Masato , Nakai Hiromi 
Published: April 2012

AbstractIn this article, we develop the symmetry adopted cluster (SAC) theory based on the divide‐and‐conquer (DC) method, which accomplishes the linear‐scaling computational time with respect to the system size, as well as the DC‐based coupled cluster (CC) method does. Although the perturbative configuration selection adopted in the SAC program significantly reduces its computational cost compared with the CC calculations, the reduction of the configurations leads to less inclusion of the total correlation energy. However, the numerical assessments confirmed that the use of the local orbitals constructed in each subsystem in DC‐SAC calculations reduces the loss in total correlation energy, which provides more reliable total and relative energies than the standard SAC method. © 2012 Wiley Periodicals, Inc.
The role of aromaticity on the building of nanohybrid materials functionalized with metalated (Au(III), Ag(III), Cu(III)) extended porphyrins and single‐walled carbon nanohorns: A theoretical study
Authors: Muñiz Jesús , Sansores Enrique , Olea Alfredo , Valenzuela Edgar 
Published: April 2012

AbstractAn ab initio, systematic study on the aromaticity involving the group of metalated extended porphyrins, termed meso‐hexakis(pentafluorophenyl)‐substituted[26]hexaphyrin(1.1.1.1.1.1) (HP), was performed for the first time. The aromatic behavior of the system shifted to antiaromatic in the [28]HP analogue, due to the presence of hydrogen atoms that break the orbital symmetry. The absorption bands observed in the experiment were assigned to an intraligand charge transfer, where the intrametallic character is also important. The excited states reveal the absorption of visible light and the possibility of electronic transfer to different systems. We propose a system such as single‐walled carbon nanohorns (SWCNHs), due to their special electronic properties, and predict a novel nanohybrid material. The evidence of electronic communication between both species is presented in this work. The HP aromaticity and the spatial configuration of the interaction with SWCNHs are also related to the strength of electronic transfer among the systems, making the HP metalated antiaromatic species and their corresponding nanohybrids potential candidates to be used as building blocks in photovoltaic cell materials. © 2012 Wiley Periodicals, Inc.
Mechanistic models for the intramolecular hydroxycarbene–formaldehyde conversion and their intermolecular interactions: Theory and chemistry of radicals, mono‐, and dications of hydroxycarbene and related configurations
Authors: Buck Henk M. 
Published: April 2012

AbstractWe have studied with theoretical and mechanistic models the intramolecular 1,2‐hydrogen shift in trans‐hydroxycarbene‐formaldehyde and trans‐methylhydroxycarbene‐acetaldehyde/vinyl alcohol, and the corresponding intermolecular complexation between hydroxycarbene (cis and trans) with formaldehyde. The purpose of our work is making an analysis of the proposed intramolecular hydrogen shifts mainly based on thermodynamic principles and the product selectivity on monochromatic irradiation of trans‐hydroxycarbene in carbon monoxide and molecular hydrogen, and formaldehyde. A geometric visualization of the various intermolecular complexes between hydroxycarbene and formaldehyde, based on ab initio results, is demonstrated and discussed with a concept abstracted from the van't Hoff dynamics for a regular tetrahedron in which the interstitial carbon changes its position from tetrahedral into a trigonal‐bipyramidal configuration. This concept has been also used for interactions via proton transfer, concretized as hydrogen‐bonded complexation in hydroxycarbene‐formaldehyde. With the introduced definitions for various van't Hoff ratio numbers, it was possible to judge the ab initio results of the intermolecular complexes between the hydroxycarbenes and formaldehyde. To make an eye‐opener, we discuss the role of the carbene lone pair in hydroxycarbene extended to the formation of mono‐ and dications demonstrating intermediates or transition states with an exclusive mechanistic behavior. Especially, substituted diaryl methylene dications are of interest for nucleophilic substitution reactions, which occur via an in‐plane tetracoordinate carbon intermediate, showing coherence with the orbital organization of methylene dications. A reaction of this type differs fundamentally from the classical S reaction. © 2012 Wiley Periodicals, Inc.
Traveling‐wave ion mobility mass spectrometry of protein complexes: accurate calibrated collision cross‐sections of human insulin oligomers
Authors: Salbo Rune , Bush Matthew F. , Naver Helle , Campuzano Iain , Robinson Carol V. , Pettersson Ingrid , Jørgensen Thomas J. D. , Haselmann Kim F. 
Published: April 2012

RATIONALEThe collision cross‐section (Ω) of a protein or protein complex ion can be measured using traveling‐wave (T‐wave) ion mobility (IM) mass spectrometry (MS) via calibration with compounds of known Ω. The T‐wave Ω‐values depend strongly on instrument parameters and calibrant selection. Optimization of instrument parameters and calibration standards are crucial for obtaining accurate T‐wave Ω‐values.METHODSHuman insulin and the fast‐acting insulin aspart under native‐like conditions (ammonium acetate, physiological pH) were analyzed on Waters SYNAPT G1 and G2 HDMS instruments. The calibrated T‐wave Ω‐values of insulin monomer, dimer, and hexamer ions were measured using many different combinations of denatured and native‐like calibrants (masses between 2.85 and 256 kDa) and T‐wave conditions. Drift‐tube Ω‐values were obtained on a modified SYNAPT G1.RESULTSInsulin T‐wave Ω‐values were measured at 26 combinations of T‐wave velocity and amplitude. Optimal sets of calibrants were identified that yield Ω‐values with minimal dependence on T‐wave conditions and calibration plots with high R2‐values. The T‐wave Ω‐values determined under conditions satisfying these criteria had absolute errors <2%. Structural differences between human insulin and fast‐acting insulin aspart were probed with IM‐MS. Insulin aspart monomers have increased flexibility, while hexamers are more compact than human insulin.CONCLUSIONSAccurate T‐wave Ω‐values that are indistinguishable from drift‐tube values are obtained when using (1) native‐like calibrants with masses that closely bracket that of the analyte, (2) T‐wave velocities that maximize the R2 of the calibration plot for those calibrants, and (3) at least three replicates at T‐wave velocities that yield calibration plots with high R2. Copyright © 2012 John Wiley & Sons, Ltd.
Determination of low‐level (sub‐microgram) sulfur concentrations by isotope dilution multi‐collector inductively couple plasma mass spectrometry using a 33S spike and internal normalization for mass bias correction
Authors: Mann Jacqueline L. , Vocke Robert D. , Kelly W. Robert 
Published: April 2012

RATIONALEThe certification of sulfur (S) in Standard Reference Materials™ by the National Institute of Standards and Technology (NIST) has been exclusively performed using isotope dilution thermal ionization mass spectrometry (ID‐TIMS). The ID‐TIMS measurement method is limited in its capability for low concentration measurements (<1 µg/g) due to the blank associated with the chemical reduction procedure (≈0.2 S µg). Newly developed materials and applications, such as biofuels made from soy and nanomedicine, pose a challenge to the ID‐TIMS technique because of their very low concentrations (<<1 µg/g) of S. As described here, a measurement technique with low S blanks is essential for low‐level S measurements.METHODSAn isotope dilution (ID) multi‐collector inductively coupled plasma mass spectrometry (MC‐ICP‐MS) method combined with an internal normalization approach for mass bias correction has been used to determine low‐level S concentrations in synthetically prepared mixtures using a 33S‐enriched spike material. Dilute sulfur solutions (1 µg S/g) were prepared from NIST SRM 3154 (Sulfate Spectrometric Solution) to test the capability of this technique for measuring very low‐level S concentrations.RESULTSThe concentration results for each solution were 0.983 ± 0.004 µg/g (95% CI, n = 2, k = 2), 1.006 ± 0.005 µg/g (95% CI, n = 2, k = 2), and 0.999 ± 0.003 µg/g (95% CI, n = 2, k = 2), in excellent agreement with the gravimetric determination, deviating less than 0.35% and suggesting the technique can yield unbiased and accurate results. The blanks averaged 13 ± 0.0017 ng S (1s).CONCLUSIONSThe data results provide a clear indication that the ID‐MC‐ICP‐MS method for the determination of low‐level S concentrations is feasible. The more than one order of magnitude reduction of the blanks suggests that it is a better alternative to the ID‐TIMS method for very low S materials such as are encountered in biofuels and some biochemical species. Published 2012. This article is a US Government work and is in the public domain in the USA.
Bullying in schools: What is the problem, and how can educators solve it?
Authors: Strohmeier Dagmar , Noam Gil G. 
Published: April 2012

AbstractThis chapter reviews recent research on bullying from an educator's perspective. It is well known that bullying, a serious issue in schools, can be prevented when educators intervene. But research has shown that it is difficult for educators to detect bullying situations in their school and intervene competently and effectively. This chapter examines how educators can detect bullying, how they can best tackle serious cases of bullying, and how they can best prevent bullying in the long run.
Making bullying prevention a priority in Finnish schools: The KiVa antibullying program
Authors: Salmivalli Christina , Poskiparta Elisa 
Published: April 2012

AbstractThe KiVa antibullying program has been widely implemented in Finnish comprehensive schools since 2009. The program is predicated on the idea that a positive change in the behaviors of classmates can reduce the rewards gained by the perpetrators of bullying and consequently their motivation to bully in the first place. KiVa involves both universal and bullying specific actions to prevent the emergence of new cases of bullying, stop ongoing bullying, and reduce the negative consequences of victimization. The program has been evaluated in a randomized controlled trial involving 234 Finnish schools and during broad dissemination across Finnish schools (the evaluation involving almost one thousand schools) with positive findings. The program content and the implementation model are presented in this article, and the findings from the evaluation studies are summarized.
Human Stromal (Mesenchymal) Stem Cells from Bone Marrow, Adipose Tissue and Skin Exhibit Differences in Molecular Phenotype and Differentiation Potential
Authors: Al-Nbaheen May , vishnubalaji Radhakrishnan , Ali Dalia , Bouslimi Amel , Al-Jassir Fawzi , Megges Matthias , Prigione Alessandro , Adjaye James , Kassem Moustapha , Aldahmash Abdullah 
Published: April 2012

AbstractHuman stromal (mesenchymal) stem cells (hMSCs) are multipotent stem cells with ability to differentiate into mesoderm-type cells e.g. osteoblasts and adipocytes and thus they are being introduced into clinical trials for tissue regeneration. Traditionally, hMSCs have been isolated from bone marrow, but the number of cells obtained is limited. Here, we compared the MSC-like cell populations, obtained from alternative sources for MSC: adipose tissue and skin, with the standard phenotype of human bone marrow MSC (BM-MSCs). MSC from human adipose tissue (human adipose stromal cells (hATSCs)) and human skin (human adult skin stromal cells, (hASSCs) and human new-born skin stromal cells (hNSSCs)) grew readily in culture and the growth rate was highest in hNSSCs and lowest in hATSCs. Compared with phenotype of hBM-MSC, all cell populations were CD34−, CD45−, CD14−, CD31−, HLA-DR−, CD13+, CD29+, CD44+, CD73+, CD90+,and CD105+. When exposed to in vitro differentiation, hATSCs, hASSCs and hNSSCs exhibited quantitative differences in their ability to differentiate into adipocytes and to osteoblastic cells. Using a microarray-based approach we have unveiled a common MSC molecular signature composed of 33 CD markers including known MSC markers and several novel markers e.g. CD165, CD276, and CD82. However, significant differences in the molecular phenotype between these different stromal cell populations were observed suggesting ontological and functional differences. In conclusion, MSC populations obtained from different tissues exhibit significant differences in their proliferation, differentiation and molecular phenotype, which should be taken into consideration when planning their use in clinical protocols.
Adolescent leisure dimensions, psychosocial adjustment, and gender effects
Authors: Bradley Graham L. , Inglis Brad C. 
Published: April 2012

ABSTRACTLeisure provides the context for much of adolescent behaviour and development. While both theory and research point to the benefits of participation in leisure activities that are highly structured, the association between structured leisure and psychosocial adjustment is not uniformly high. This paper presents a model of adolescent leisure comprising three dimensions: structure, effort, and social contact. Adolescent adjustment is hypothesized to increase with participation in activities characterized by each of these attributes. Adjustment is also predicted to vary with gender, and with the interaction of gender and leisure participation. These propositions were tested in a questionnaire‐based study of 433 Australian adolescents. Results revealed majority support for hypotheses pertaining to the positive effects of the leisure dimensions, and for gender differences in leisure participation and adjustment. Evidence was also obtained of gender‐differentiated effects of leisure on adjustment, with social leisure predicting adjustment more strongly in females than males.
Perinatal outcome in cases of latent syphilis during pregnancy
Authors: Krakauer Yonit , Pariente Gali , Sergienko Ruslan , Wiznitzer Arnon , Sheiner Eyal 
Published: April 2012

AbstractObjectiveTo investigate factors associated with latent syphilis and pregnancy outcome among women with latent syphilis.MethodsA retrospective population‐based study was conducted to compare all pregnancies among women with and without latent syphilis at Soroka University Medical Center, Be'er‐Sheva, Israel, between 1988 and 2010. Stratified analysis using a multiple logistic regression model was performed to control for confounders.ResultsOf the 219 656 deliveries during the study period, 159 (0.1%) involved women with latent syphilis. Multivariate analysis with backward elimination revealed the following conditions to be significantly associated with latent syphilis: fetal growth restriction (odds ratio [OR] 2.20; 95% confidence interval [CI], 1.07–4.49; P = 0.03); drug abuse (OR 9.95; 95% CI, 1.31–75.46; P = 0.02); tobacco use (OR 3.35; 95% CI, 1.74–6.45; P < 0.05); and Jewish (vs Bedouin) ethnicity (OR 4.05; 95% CI, 2.65–6.20; P < 0.05).ConclusionWomen with latent syphilis are at risk for adverse maternal and perinatal outcomes, including fetal growth restriction. Careful surveillance of these high‐risk pregnancies should be considered.
Vertical dispersion of model microorganisms in horizontal shear flow
Authors: Ishikawa Takuji 
Published: April 2012

AbstractMicroorganisms often swim upwards due to the cell’s phototaxis, chemotaxis or geotaxis, in flow fields with vertical velocity gradients. In this study, the vertical dispersion of model microorganisms was investigated under horizontal shear conditions. A microorganism was modelled as a spherical squirmer with or without bottom-heaviness. First, the three-dimensional movement of 100 identical squirmers in a homogeneous suspension was computed by the Stokesian dynamics method. The results show that the dispersion of squirmers is strongly affected by the swimming velocity and bottom-heaviness of the cells and the shear rate of the background flow. The vertical diffusion is considerably smaller than the horizontal diffusion. Interestingly, the vertical diffusion decreases as the volume fraction and the stresslet of squirmers decrease, which is opposite of the tendency in diffusion with no background flow. Next, a continuum model of a suspension of squirmers was developed using the diffusion tensor and the drift velocity to simulate the spatial distribution of squirmers in macroscopic flow fields. The results of the continuum model illustrate that the gyrotactic trapping found by Durham, Kessler & Stocker (Science, vol. 323, 2009, pp. 1067–1070) also appears in the present model considering cell–cell hydrodynamic interactions. In the case of horizontal Poiseuille flow, the volume fraction of bottom-heavy cells in the channel becomes considerably larger than that at the inlet. These fundamental findings are helpful for understanding the distribution of microorganisms in various water regimes in nature and industry.