bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on the melt spinning process of noncircular fiber by numerical and experimental methods
Authors: Zhou Ji , Li Jian , Yu Wei , Li Xin , Zhou Chixing 
Published: March 2010

AbstractThe spinning process of noncircular fiber was investigated in this work. A combination of numerical simulations and experiments made it possible to find out the optimum processing condition for shaped fiber. First, an inverse method which combined two‐dimensional/three‐dimensional simulation with experiments was utilized to find out the temperature and draw ratio dependent surface tension in melt spinning of shaped fiber. The surface tension as a function of temperature and draw ratio was found to be decisive to the change of cross‐section. Second, an orthogonal numerical experiment and statistics analysis were carried out to determine the optimum spinning condition for the desired noncircular fiber. The optimum spinning condition was well validated by experiments. It was then proved that the integrated method in this work, including the numerical method, the inverse method to determining the surface tension, and the orthogonal analysis, can be a good solution for the design and processing of profiled fibers. POLYM. ENG. SCI., 50:1935–1944, 2010. © 2010 Society of Plastics Engineers
Identification of candidate material systems for quantum dot solar cells including the effect of strain
Authors: Dahal Som N. , Bremner Stephen P. , Honsberg Christiana B. 
Published: March 2010

AbstractHeterostructures that include self‐assembled quantum dots (SAQDs) have been suggested as model systems for the realization of novel high efficiency solar cells such as those based on intermediate bands (IBs). The lattice mismatch in the epitaxial growth of these structures, necessary for the formation of SAQDs, introduces strain throughout the structure, making the selection of materials systems with appropriate physical parameters problematic. The model solid theory is used to calculate the energy band edge alignment at Γ point of such quantum dot (QD) heterostructures including the effects of strain. With the modified band gaps due to strain, a materials search was performed for high efficiency QD solar cells among III‐V binaries and ternaries with negligible valence band offsets. This requirement of the valence band offset along with the limited band gap ranges for optimum efficiency results in only a few feasible materials systems being identified. The optimum barrier/dot material system found was Al0.57In0.43As/InP0.87Sb0.13grown on lattice matched metamorphic buffer layer, but due to miscibility gap concerns it is suggested that the Al0.50In0.50As/InAs0.41P0.59fully strained system may be preferred. Copyright © 2010 John Wiley & Sons, Ltd.
Reaction pathway of aliphatic pinacol‐type rearrangement reexamined
Authors: Itoh Shuhei , Yamataka Hiroshi 
Published: March 2010

AbstractPinacol rearrangement is often written to proceed via 1,2‐Me migration to the tertiary cationic center, followed by deprotonation to give pinacolone. Computational study was carried out for model reactions to clarify why the migration of the OH group is not involved in the mechanistic scheme despite the fact that OH is a better migrating group than Me. It was found that the migratory aptitude of X in both XCMe2‐CH2Cl and XCMe2‐CMe2Cl is in the order, NH2 > OMe > Ph > Me, indicating that a migrating group with n‐electrons has a larger aptitude than a π‐ or σ‐electron group. However, the reactivity differences became much smaller for XCMe2‐CMe2OMe, a model compound for aliphatic pinacol rearrangement. Calculations of MeOCMe2‐CMe2OMe revealed that three initial ionization steps, CO heterolysis, concerted OMe migration and concerted Me migration, compete with each other. On the other hand, the ring‐opening step of the epoxide‐type intermediate formed via OMe migration was shown to have quite a large activation barrier. It was suggested that aliphatic pinacol rearrangement proceeds via the concerted Me migration route or the CO heterolysis‐Me migration‐deprotonation route. Epoxide may form by the concerted MeO migration, but it would not be an important intermediate of pinacol rearrangement. Copyright © 2010 John Wiley & Sons, Ltd.
Photochromism of dihydroindolizines: part XIV. Synthesis and photophysical behavior of photochromic dihydroindolizine‐tripodal linkers toward anchoring sensitizers to semiconductor nanoparticles
Authors: Ahmed Saleh Abdel‐Mgeed , Al‐Raqa Shaya Y. 
Published: March 2010

AbstractPhotochromic dihydroindolizines (DHIs) 4a,5‐dihydropyrrolo[1,2‐b]pyridazine based tripodal‐linker systems with adamantane core and ethyl benzoate tripods as anchoring groups have been successfully synthesized. In addition, new spirocyclopropene precursors have been prepared through both chemical and photochemical processes. The photochromic properties of the newly synthesized DHIs derivatives have been optimized and fine‐tuned by the incorporation of various substituents on the fluorene (region A) and pyridazine (region C) moieties. Several alternative routes for the synthesis of the DHIs under investigation have been established. The Sonogashira crosscoupling reaction was utilized for fragment coupling between DHIs and the phenylacetylene tether of the adamantane core. Several reaction conditions of this key reaction were surveyed to obtain optimal yields of a new series of coupling products targeted for anchoring to semiconductor nanoparticles. The chemical structures of the newly synthesized materials were elucidated by both analytical and spectroscopic tools. Irradiation of the photochromic DHIs with polychromatic light resulted in ring opened colored betaines which underwent cycloreversion reactions via thermal 1,5‐electrocyclization processes. The kinetic of the thermal 1,5‐electrocyclization was studied by using a UV/VIS/NIR spectrophotometer. The kinetic measurements showed the half‐lives of the colored betaines to be in the second domain. A pronounced increase in the half‐lives of betaines bearing dimethyl‐substituted pyridazine was noted compared with non‐substituted pyridazine betaines. A strong effect of solvent polarity on the λmax and half‐lives of the betaines was observed. The further adjustment of the absorption maxima and the kinetic properties via the manipulation of substituents on the fluorene (region A) and pyridazine moieties (region C) should yield more refined systems for application as supports onto metal‐oxide surfaces which remains an active area of our ongoing research. Copyright © 2010 John Wiley & Sons, Ltd.
On the origin of the chemical barrier and tunneling in enzymes
Authors: Machleder Sara Quaytman , Pineda J.R. Exequiel T. , Schwartz Steven D. 
Published: March 2010

AbstractThis paper presents both a review of some recent results from our group and experimental groups, and some new theoretical results all of which are helping to form a more physically rigorous picture of the process of enzymatic catalysis. A common classical picture of enzymatic catalysis is the transition state tight binding model. Schwartz and Schramm (Nat. Chem. Biol. 2009, 5, 551–558.) have recently argued from both theoretical and experimental results that this picture is incorrect. We now investigate what the nature of barriers might be in enzymatic reactions, and what this viewpoint might imply for tunneling in a hydrogen transfer enzyme. For lactate dehydrogenase we conclude that the enzymes role in catalysis is at least partially to hunt through configuration space for those configurations that minimize chemical free energy barriers. Those configurations do not seem to be stable basins on the free energy surface, and in fact the overall free energy barrier to reaction may well largely be due to this stochastic hunt—both probabilistically and energetically. We suggest further computations to test this hypothesis. Copyright © 2010 John Wiley & Sons, Ltd.
The International Linear Collider
Authors: Behnke T. 
Published: March 2010

AbstractA high energy electron positron collider is proposed to complement the large hadron collider, LHC, which has started taking data at CERN, Geneva, Switzerland. Based on superconducting acceleration technology the International Linear Collider ILC is offering a mature proposal. It will deliver high luminosity electron positron collisions at 500 GeV upgradable to 1 TeV. Experimentation at such a collider presents many unique challenges, if the huge physics potential should be harvested efficiently. In this paper after a brief review of the state of the accelerator proposal the state of the preparation of the experimental program is discussed.
Gauge anomaly‐free constraints in neutrino seesaw models
Authors: Emmanuel‐Costa D. 
Published: March 2010

AbstractThe implementation of seesaw mechanisms to give mass to neutrinos in the presence of an anomaly‐free U(1)X gauge symmetry is discussed in the context of minimal extensions of the standard model. It is shown that type‐I and type‐III seesaw mechanisms cannot be simultaneously implemented with an anomaly‐free local U(1)X, unless the symmetry is a replica of the well‐known hypercharge. For combined type‐I/II or type‐III/II seesaw models it is always possible to find nontrivial anomaly‐free charge assignments, which are however tightly constrained, if the new neutral gauge boson is kinematically accessible at LHC. The discovery of the latter and the measurement of its decays into third‐generation quarks, as well as its mixing with the standard Z boson, would allow one to discriminate among different seesaw realisations.
Phenoxodiol inhibits growth of metastatic prostate cancer cells
Authors: Aguero Martin F. , Venero Marina , Brown David M. , Smulson Mark E. , Espinoza Luis A. 
Published: March 2010

AbstractBACKGROUNDPhenoxodiol, a synthetic analog of Genistein, is being assessed in several clinical studies against a range of cancer types and was shown to have a good efficacy and safety profile. In this study we tested the effects of Phenoxodiol against prostate cancer cell lines.METHODSCell‐cycle analysis, plasmatic membrane damage, clonogenic assay, comet assay, and Western blot methodologies were employed to assess the effects of Phenoxodiol on prostate cancer cell lines. An in vivo model confirmed the potential therapeutic efficacy of Phenoxodiol when administered orally to tumor bearing mice.RESULTSPhenoxodiol treatment promoted a marked inhibition of proliferation and loss of colony formation in LNCaP cells in a dose‐ and time‐dependent manner. Similar effects were also observed in the metastatic prostate cell lines PC3 and DU145. Activation of poly(ADP ribose) polymerase 1 (PARP‐1) clearly indicates the induction of DNA damage by Phenoxodiol. Oral administration of Phenoxodiol induced a considerable growth inhibition of malignant tumors generated by inoculation of LNCaP cells into Balb/c nu/nu athymic mice.CONCLUSIONSThese data demonstrated that Phenoxodiol promotes apoptosis, as determined by PARP‐1 degradation, via mitochondrial depolarization and G1/S cell‐cycle arrest thereby confirming that it is active against androgen‐dependent and independent prostate cancer cells. Although a precise target for Phenoxodiol has not been identified, these data contribute to our understanding of the mechanism by which this drug promotes cell death in prostate cancer cells, and warrants the continued clinical development of Phenoxodiol as a therapeutic for the treatment of metastatic prostate cancer. Prostate 70: 1211–1221, 2010. © 2010 Wiley‐Liss, Inc.
Methoxychalcone induces cell‐cycle arrest and apoptosis in human hormone‐resistant prostate cancer cells through PI 3‐kinase‐independent inhibition of mTOR pathways
Authors: Sun Yu‐Wei , Huang Wei‐Jan , Hsiao Che‐Jen , Chen Yi‐Cheng , Lu Pin‐Hsuan , Guh Jih‐Hwa 
Published: March 2010

AbstractBACKGROUNDChalcones are contained in fruits and vegetables, and have been suggested to display anticancer activities. In this study, the anticancer mechanism of WJ9708011 (a methoxychalcone derivative) was delineated in human prostate cancer cells.METHODCell proliferation was examined by sulforhodamine B and clonogenic assays. Cell‐cycle progression and mitochondrial membrane potential (ΔΨm) were detected by flow cytometric analysis. Expressions of protein and mRNA were detected by Western blot and RT‐PCR technique, respectively. The protein synthesis was examined by [3H]leucine incorporation assay. The overexpression or knockdown techniques for specific target protein were also used in this study.RESULTSWJ9708011 induced time‐ and concentration‐dependent G1 arrest of the cell cycle and subsequent apoptosis in human prostate cancer cells. The G1‐arrest effect was confirmed by down‐regulated expressions of several G1‐phase regulators, including cyclin D1, cyclin E, cyclin‐dependent kinase (Cdk)‐4, Cdk2, phospho‐RB, E2F‐1, and Cdc25A. The mRNA expressions of cyclin D1 and cyclin E were also inhibited through the suppression of NF‐κB. WJ9708011 blocked the protein synthesis and inhibited mammalian target of rapamycin (mTOR) signaling pathways. The suppression of mTOR pathways were irrespective of Akt‐ and AMPK‐activated protein kinase (AMPK), but were attributed to mitochondrial stress, in which the down‐regulation of survivin protein level may play a crucial role.CONCLUSIONSThe data suggest that WJ9708011 induces transcriptional and translational suppression of cell‐cycle regulators that might be through Akt‐ and AMPK‐independent loss of ΔΨm and inhibition of mTOR signaling pathway, leading to G1 arrest of the cell cycle and subsequent apoptotic cell death. Prostate 70:1295–1306, 2010. © 2010 Wiley‐Liss, Inc.
On the contribution of intramolecular kinetics properties of an important rotamer of vinylpyranoanthocyanin‐phenol pigment (portisin)
Authors: Carvalho Alexandre R. F. , Oliveira Joana , de Freitas Victor , Mateus Nuno , Melo André 
Published: March 2010

AbstractThe kinetics of an important rotamerization occurring in vinylpyranoanthocyanin‐phenol pigment (Portisin) was analyzed according to the transition state (TS) formalism. The relevant stationary states, the TS and the equivalent minima, were fully characterized. This included the optimization of the respective geometries and the analytical calculation of all vibrational frequencies. The reaction coordinate was identified, as associated with a single imaginary frequency in TS, and an appropriate intrinsic coordinate analysis (IRC) ensured that this state was connected with the correspondent equivalent minima. For the minimum, the harmonic and one‐dimensional hindered rotor models were used to describe the reaction coordinate. The activation thermodynamics properties were then evaluated. The results obtained were interpreted according to the theoretical models assumed. The results are important for a prompt result for this group of portisins. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Assessing the performances of some recently proposed density functionals for the description of bond dissociations involving organic radicals
Authors: Tognetti Vincent , Cortona Pietro , Adamo Carlo 
Published: March 2010

AbstractIn this article, we have assessed the performances of some recently proposed density functionals for the prediction of reaction energies involving radicals, notably bond dissociations of small organic molecules or of TEMPO‐based ones, and β‐scissions, focusing on our TCA family and on range‐separated hybrids. It is found that no functional belonging to these two families is able to compete with the M0x one. We have tried to improve the performances of the range‐separated hybrids by the optimization of the attenuation parameter, but the improvements for one dataset lead to an unavoidable deterioration for the others. Furthermore, the differences between two different approaches to the long‐range/short‐range separation are discussed in terms of average enhancement factors, emphasizing the crucial choice of the approximate scheme used for the short‐range part. Finally, the influence of the geometries has been considered and found to be negligible for this kind of molecular sets, validating the usual single point energies strategies developed in such benchmarking assessments. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Thermal effects on small para‐hydrogen clusters
Authors: Navarro Jesús , Guardiola Rafael 
Published: March 2010

AbstractA brief review of different quantum Monte Carlo simulations of small (p‐H2)N clusters is presented. The clusters are viewed as a set of N structureless p‐H2 molecules, interacting via an isotropic pairwise potential. Properties as superfluidity, magic numbers, radial structure, excitation spectra, and abundance production of (p‐H2)N clusters are discussed and, whenever possible, a comparison with 4HeN droplets is presented. All together, the simulations indicate that temperature has a paradoxical effect of the properties of (p‐H2)N clusters, as they are solid‐like at high T and liquid‐like at low T, due to quantum delocalization at the lowest temperature. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
DFT study of vanadyl (IV) complexes with low molecular mass ligands: Picolinate, oxalate, malonate, and maltolate
Authors: Rodrigues Guilherme Dos Santos , da Silva Cunha Ivan , Silva Guilherme Gomes , de Noronha Antonio Luiz Oliveira , de Abreu Heitor Avelino , Duarte Hélio Anderson 
Published: March 2010

AbstractThe insulin‐mimetic activity of the VO2+ complexes are much related to its chemical speciation in the blood serum. Low molecular mass ligands must have an important role in the mechanism of the VO2+ biological activity affecting directly its absorption efficacy. In the present work, the chemical speciation of vanadyl (VO2+) with malonate, maltolate, oxalate and picolinate ligands has been investigated by means of DFT/PCM calculations. Metal/Ligand 1:1 and 1:2 complexes have been calculated. All tautomers, conformations and the presence of water molecules acting as ligand fulfilling the coordination sphere of the metal center have been studied. The results showed that the 1:1 species prefer to have square pyramidal structure with two water molecules in the equatorial axis. The 1:2 species prefer the hexacoordinated structure with one water molecule in the available coordination site in the cis position with respect to the oxo group. The 6‐membered ring malonate complex prefers to keep the square pyramidal structure without water molecule in the coordination sphere. The Gibbs free reaction energy for the formation of the 1:2 complexes from the interaction of the 1:1 complexes and the ligand was estimated. The error of the estimated values compared to the experimental data is not larger than 5 kcal mol−1 at the PBE/TZVP level of theory using the UAHF‐PCM for estimating the solvation free energy. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Domain‐averaged Fermi hole and domain‐restricted reduced density matrices: A critical comparison
Authors: Alcoba Diego R. , Bochicchio Roberto C. , Lain Luis , Torre Alicia 
Published: March 2010

AbstractThe knowledge of the properties and the applicability of domain‐restricted matrices has provided important advances in the description of molecular electronic distributions. In this work, we perform a critical comparison between two different methods: the domain‐averaged Fermi hole (DAFH) approach and the domain‐restricted first‐order reduced density matrix (DRRDM) one, focusing our study on both physical and mathematical points of view. Our results permit to show that both methods have a markedly different behavior at correlated wave function level: the DAFH approach provides information related with electron cloud localization and populations while the DRRDM is a true density matrix. To exemplify the theoretical discussion, we present a numerical test example and a simple analytical model that show such features. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
The CCSD(T) model with Cholesky decomposition of orbital energy denominators
Authors: Cacheiro Javier López , Pedersen Thomas Bondo , Fernández Berta , De Merás Alfredo Sánchez , Koch Henrik 
Published: March 2010

AbstractA new implementation of the coupled cluster singles and doubles with approximate triples correction method [CCSD(T)] using Cholesky decomposition of the orbital energy denominators is described. The new algorithm reduces the scaling of CCSD(T) from N7 to N6, where N is the number of orbitals. The Cholesky decomposition is carried out using simple analytical expressions that allow us to evaluate a priori the order in which the decomposition should be carried out and to obtain the relevant parts of the vectors whenever needed in the calculation. Several benchmarks have been carried out comparing the performance of the conventional and Cholesky CCSD(T) implementations. The Cholesky implementation shows a speed‐up factor larger than O2/V, where O is the number of occupied and V the number of virtual orbitals, and in general at most 5 vectors are needed to get a precision of μEh. We demonstrate that the Cholesky algorithm is better suited for studying large systems. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
Characterizing protein glycosylation sites through higher‐energy C‐trap dissociation
Authors: Segu Zaneer M. , Mechref Yehia 
Published: March 2010

AbstractAssigning glycosylation sites of glycoproteins and their microheterogeneity is still a very challenging analytical task despite the rapid advancements in mass spectrometry. It is shown here that glycopeptide ions can be fragmented efficiently using the higher‐energy C‐trap dissociation (HCD) feature of a linear ion trap orbitrap hybrid mass spectrometer (LTQ Orbitrap). An attractive aspect of this dissociation option is the generation of distinct Y1 ions (peptide+GlcNAc), thus allowing unequivocal assignment of N‐glycosylation sites of glycoproteins. The combination of the very informative collision‐induced dissociation spectra acquired in the linear ion trap with the distinct features of HCD offers very useful information aiding in the characterization of the glycosylation sites of glycoproteins. The HCD activation energy needed to obtain optimum Y1 ions was studied in terms of glycan structure and charge state, and size and structure of the peptide backbone. The latter appeared to be primarily dictating the needed HCD energy. The distinct Y1 ion formation in HCD facilitated an easy assignment of such an ion and its subsequent isolation and dissociation through multiple‐stage tandem mass spectrometry. The resulting MS3 spectrum of the Y1 ion facilitates database searching and de novo sequencing thus prompting the subsequent identification of the peptide backbone and associated glycosylation sites. Moreover, fragment ions formed by HCD are detected in the Orbitrap, thus overcoming the 1/3 cut‐off limitation that is commonly associated with ion trap mass spectrometers. As a result, in addition to the Y1 ion, the common glycan oxonium ions are also detected. The high mass accuracy offered by the LTQ Orbitrap mass spectrometer is also an attractive feature that allows a confident assignment of protein glycosylation sites and the microheterogeneity of such sites. Copyright © 2010 John Wiley & Sons, Ltd.