bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relaxations in chitin: Evidence for a glass transition
Authors: González‐campos J. Betzabe , Prokhorov Evgen , Luna‐Bárcenas Gabriel , Galván A. Mendoza , Sanchez Isaac C. , Nuño Donlucas Sergio M. , Garcia‐Gaitan B. , Kovalenko Yuriy 
Published: March 2009

AbstractRelaxations in chitin have been investigated in the temperature range 298–523 K using impedance spectroscopy in the frequency range 10−1–108 Hz. The objective was to detect a glass‐transition temperature for this naturally occurring, semicrystalline polysaccharide. The impedance study was complemented with X‐ray diffraction, thermogravimetric, and differential scanning calorimetry measurements. Preliminary impedance data treatment includes the subtraction of the dc conductivity contribution, the exclusion of contact and interfacial polarization effects, and obtaining a condition of minimum moisture content for further analysis. When all these aspects are taken into account, two relaxations are clearly revealed in the impedance data. For the first time, evidence is presented for a relaxation process, which exhibits a non‐Arrhenius temperature dependence, in dry α‐chitin (∼0.1% moisture content), and likely represents the primary α‐relaxation. This evidence suggests a glass transition temperature for chitin of 335 ± 10 K estimated on the basis of the temperature dependence of the conductivity and of the relaxation time. A second relaxation in dry α‐chitin, not previously reported in the literature, is observed from 353 K to the onset of thermal degradation (∼483 K) and is identified as the σ‐relaxation often associated with proton mobility. It exhibits a normal Arrhenius‐type temperature dependence with activation energy of 113 ± 3 kJ/mol. The latter has not been previously reported in the literature. A high frequency secondary β‐relaxation is also observed with Arrhenius activation energy of 45 ± 1 kJ/mol. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 932–943, 2009
Application of a crystallization kinetics model to simulate the effect of operation conditions on Crystaf profiles and calibration curves
Authors: Anantawaraskul Siripon , Somnukguandee Punnawit , Soares João B. P. , Limtrakul Jumras 
Published: March 2009

AbstractCrystallization analysis fractionation (Crystaf) is a polymer characterization technique used to estimate chemical composition distributions (CCDs) of semicrystalline copolymers. The Crystaf profile can be transformed into a CCD using a calibration curve that relates average comonomer content to peak crystallization temperature. The calibration curve depends on copolymer molecular properties and Crystaf operation conditions. In this investigation, we applied a crystallization kinetics model to simulate Crystaf calibration curves and to quantify how Crystaf calibration curves depend on these factors. We applied the model to estimate the CCDs of three ethylene/1‐hexene copolymers from Crystaf profiles measured at different cooling rates and showed that our predictions agree well with the CCDs described by Stockmayer's distribution. We have also used this new methodology to investigate the effects of cooling rate, molecular weight, and comonomer type on Crystaf profiles and calibration curves. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 866–876, 2009
Functionalized graphene sheet—Poly(vinylidene fluoride) conductive nanocomposites
Authors: Ansari Seema , Giannelis Emmanuel P. 
Published: March 2009

AbstractPVDF nanocomposites based on functionalized graphene sheets, FGS prepared from graphite oxide, and exfoliated graphite, EG, were prepared by solution processing and compression molding. FGS remains well dispersed in the PVDF composites as evidenced by the lack of the characteristic graphite reflection in the composites. Although the α‐phase of PVDF is seen in the EG‐based composites, a mixture of α‐ and β‐phases is present in the FGS analogs. SEM and TEM imaging show smooth fractured surfaces with oriented platelets of graphite stacks and obvious debonding from the matrix in the EG‐PVDF composites. In contrast, the FGS‐PVDF composites show a wrinkled topography of relatively thin graphene sheets bonded well to the matrix. Storage modulus of the composites was increased with FGS and EG concentration. A lower percolation threshold (2 wt %) was obtained for FGS‐PVDF composites compared to EG‐PVDF composites (above 5 wt %). Lastly, the FGS‐PVDF composites show an unusual resistance/temperature behavior. The resistance decreases with temperature, indicating an NTC behavior, whereas EG‐PVDF composites show a PTC behavior (e.g., the resistance increases with temperature). We attribute the NTC behavior of the FGS based composites to the higher aspect ratio of FGS which leads to contact resistance predominating over tunneling resistance. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 888–897, 2009
The effect of the cosolvent trifluoroethanol on a tryptophan side chain orientation in the hydrophobic core of troponin C
Authors: Julien Olivier , Mercier Pascal , Crane Melissa L. , Sykes Brian D. 
Published: March 2009

AbstractThe unique biophysical properties of tryptophan residues have been exploited for decades to monitor protein structure and dynamics using a variety of spectroscopic techniques, such as fluorescence and nuclear magnetic resonance (NMR). We recently designed a tryptophan mutant in the regulatory N‐domain of cardiac troponin C (F77W‐cNTnC) to study the domain orientation of troponin C in muscle fibers using solid‐state NMR. In our previous study, we determined the NMR structure of calcium‐saturated mutant F77W‐V82A‐cNTnC in the presence of 19% 2,2,2‐trifluoroethanol (TFE). TFE is a widely used cosolvent in the biophysical characterization of the solution structures of peptides and proteins. It is generally assumed that the structures are unchanged in the presence of cosolvents at relatively low concentrations, and this has been verified for TFE at the level of the overall secondary and tertiary structure for several calcium regulatory proteins. Here, we present the NMR solution structure of the calcium saturated F77W‐cNTnC in presence of its biological binding partner troponin I peptide (cTnI144–163) and in the absence of TFE. We have also characterized a panel of six F77W‐cNTnC structures in the presence and absence TFE, cTnI144–163, and the extra mutation V82A, and used 19F NMR to characterize the effect of TFE on the F77(5fW) analog. Our results show that although TFE did not perturb the overall protein structure, TFE did induce a change in the orientation of the indole ring of the buried tryptophan side chain from the anticipated position based upon homology with other proteins, highlighting the potential dangers of the use of cosolvents.
High‐performance UV emitter grown on high‐crystalline‐quality AlGaN underlying layer
Authors: Tsuzuki Hirotoshi , Mori Fumiaki , Takeda Kenichiro , Ichikawa Tomoki , Iwaya Motoaki , Kamiyama Satoshi , Amano Hiroshi , Akasaki Isamu , Yoshida Harumasa , Kuwabara Masakazu , Yamashita Yoji , Kan Hirofumi 
Published: March 2009

AbstractAl0.25Ga0.75N films were grown on a grooved‐Al0.25Ga0.75N/ AlN/sapphire template by MOVPE. The dislocation density on the grooved areas was as low as 1 × 108 cm–2. We fabricated a UVA light‐emitting diode grown on such an AlGaN underlying layer exhibiting an output power of 12 mW at a DC current of 50 mA with a peak emission wavelength of 345 nm, which corresponds to an external quantum efficiency of 6.7%. This efficiency is the highest reported to date in this wavelength region. We also fabricated a 358 nm UVA laser diode (LD) using a GaN/AlGaN MQW active layer grown on an AlGaN underlying layer. This UV LD exhibits a threshold current of 73 mA and a corresponding current density of 3.8 kA/cm2 at 7 °C. The characteristic temperature T0 was 174 K in the temperature range of 7–27 °C. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrochemically induced bioactivity of porous silicon functionalized by acetylene
Authors: Pastor Ester , Salonen Jarno , Lehto Vesa‐Pekka , Matveeva Eugenia 
Published: March 2009

AbstractIn order to improve the bioactivity of porous silicon chemically functionalized by acetylene (PSi–C) and stimulate the calcium‐phosphorous (hydroxyapatite) deposition on this material from a simulated body fluid, electrochemical oxidation of the PSi–C templates has been employed. The initial functionalization by acetylene was done at 500 °C in a N2 + C2H2 gas stream of 1:1 ratio for 15 minutes; further electrochemical oxidation was performed in 80% phosphoric acid. The morphology and chemical composition of initial and oxidized porous structures were studied by the high resolution SEM technique and FTIR spectroscopy. Initial chemical functionalization leads to a very stable (practically bio‐inert) material that after electrochemical oxidation becomes bioactive. We observed that the hydroxyapatite phase has been homogeneously deposited on the electrochemically oxidized PSi–C material immersed in the SBF of Kokubo formulae at 36.5 °C just after two weeks. The layer of hydroxyapatite grown on the surface after 30 days of immersion was compact, crystalline and as thick as 5 μm. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Detection of protease activity by FRET using porous silicon as an energy acceptor
Authors: Gu Luo , Orosco Manuel , Sailor Michael J. 
Published: March 2009

AbstractThis work demonstrates a method for detection of protease activity using porous Si as the energy acceptor in a Fluorescence Resonance Energy Transfer (FRET) assay. A fluorescent dye (fluorescein) is trapped in a porous Si matrix, where its fluorescence is quenched. The dye is trapped using a protein (zein), and the action of proteases (Pronase E) release the dye from the quenching matrix. A strong fluorescence signal appears within 30 min of Pronase E addition. A control with no Pronase E shows little fluorescence, and a control using heat‐denatured Pronase E shows approximately 50% of the fluorescence of the active protease. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
In‐situ investigation of the structural phase transition in kesterite
Authors: Schorr Susan , Gonzalez‐Aviles Gabriela 
Published: March 2009

AbstractA polycrystalline Cu2ZnSnS4 sample (kesterite) was investigated by in‐situ high temperature diffraction using synchrotron X‐rays, revealing for the first time a structural phase transition from the tetragonal kesterite type structure (space group I$ \bar 4 $2m) to the cubic sphalerite type structure (space group F$ \bar 4 $3m). Within 866–883 °C a phase transition region occurs, were a tetragonal phase and a cubic phase coexists. Outside the phase transition region, the lattice parameter of the tetragonal phase increase nearly linearly with increasing temperature, whereas the lattice parameter of the cubic phase show first a negative thermal expansion changing at ∼930 °C to a further linear increase of acub. A cation anti‐site occupancy can only be observed within the phase transition region. On the other hand, the anion position parameters x and z change, which starts at ∼150 °C and lasts up to the phase transition region. Both atomic position parameters reach nearly the ideal value of 1/4, indicating the anion in the middle of the cation tetrahedra. Thus the structural phase transition in Cu2ZnSnS4 from the tetragonal kesterite type to the cubic sphalerite type structure is characterized much more by a displacive behaviour of the anion substructure then by an anti‐site occupancy of the cation substructure. Because the space group I$ \bar 4 $2m) is not a subgroup of I$ \bar 4 $2d) and a group‐subgroup relation is mandatory for displacive phase transitions, the non‐existence of a I$ \bar 4 $2m) → I$ \bar 4 $2d) transition seems plausible. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
UV photoreflectance spectroscopy in strained silicon on insulator structures
Authors: Munguía Jacobo , Bluet Jean‐Marie , Chouaib Houssam , Bremond Georges , Bru‐Chevallier Catherine 
Published: March 2009

AbstractThe optical modulation technique of photoreflectance (PR) is applied on tensely‐strained silicon on insulator (sSOI) substrates in order to determine the deformation potential in the strained silicon direct band gap. Raman spectroscopy is used for strain determination. A redshift of the Si direct band gap transition is observed as the strain induced in the layer is increased. We report a band gap shrinkage at Γ‐point down to 60 ± 6 meV, 120 ± 15 meV and 127 ± 13 meV for 0.77 ± 0.02%, 1.22 ± 0.02% and 1.40 ± 0.03% of strain, respectively. The obtained deformation potential in the direct band gap (a = –0.55 eV and b = –2.45 eV) are in good agreement with previously reported results for bulk material. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Critical diameters and temperature domains for MBE growth of III–V nanowires on lattice mismatched substrates
Authors: Cirlin G. E. , Dubrovskii V. G. , Soshnikov I. P. , Sibirev N. V. , Samsonenko Yu. B. , Bouravleuv A. D. , Harmand J. C. , Glas F. 
Published: March 2009

AbstractWe report on the growth properties of InAs, InP and GaAs nanowires (NWs) on different lattice mismatched substrates, in particular, on Si(111), during Au‐assisted molecular beam epitaxy (MBE). We show that the critical diameter for the epitaxial growth of dislocation‐free III–V NWs decreases as the lattice mismatch increases and equals 24 nm for InAs NWs on Si(111), 39 nm for InP NWs on Si(111), 44 nm for InAs NWs on GaAs(111)B, and 110 nm for GaAs NWs on Si(111). When the diameters exceed these critical values, the NWs are dislocated or do not grow at all. The corresponding temperature domains for NW growth extend from 320 °C to 340 °C for InAs NWs on Si(111), 330 °C to 360 °C for InP NWs on Si(111), 370 °C to 420 °C for InAs NWs on GaAs(111)B and 380 °C to 540 °C for GaAs NWs on Si(111). Experimental values for critical diameters are compared to the previous findings and are discussed within the frame of a theoretical model. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Toward a More Realistic QSAR Approach to Predicting Metal Toxicity
Authors: Lepădatu Costinel , Enache Monica , Walker John D. 
Published: March 2009

AbstractThe subject of this paper is to present molecular descriptors representing the electronegativity of OMO (occupied molecular orbital) and UMO (unoccupied molecular orbital) quantum molecular states that could be used to obtain information on the mechanism of electron transfer between metal compound and biological receptor. The molecular descriptors that were used suggested that the (s,p) and (dN) metal ions have different mechanisms of interaction with the receptor. This result explains why the correlation activity–descriptor is rather poor or practically does not exist when all metal ions are analyzed together (irrespective of their valence shell). Since this interaction is the last event of the long chain of processes of the metal ion up to the biological target, such molecular descriptors could be used together with other descriptors in QSAR models for prediction of biological activity.
Composite beam composed of steel and precast concrete (modularized hybrid system). Part IV: Application for multi‐residential housing
Authors: Hong Won‐Kee , Kim Seung‐Il , Park Seon‐Chee , Kim Jin‐Min , Lee Seung‐Geun , Yoon Ki‐Joon , Kim Sun‐Kuk 
Published: March 2009

AbstractMulti‐residential bearing wall apartments have been constructed to meet the needs of the population growth in metropolitan Korea since 1980. It is extremely difficult to remodel wall‐type multi‐residential apartments due to the nature of the bearing walls. Residents also experience noise and vibrations generated between floors. It is necessary to introduce a frame structure that enables easy remodelling for the realization of long life of apartment. This paper introduces an efficient, multi‐residential modularized hybrid system (MHS). The material quantities, material cost and amount of CO2 emission for the MHS are compared to that of bearing wall structures (linear rectangular shape and tower shape) and flat slab structures. A multi‐residential apartment with an MHS composite girder ensures architectural plan flexibility and easy remodelling, while the floor heights are maintained at the same floor height as in bearing wall structures. The material cost of MHS multi‐residential housing can be reduced by reducing the amount of concrete and reinforcement steels required for the slabs and walls. The MHS also reduces CO2 emission in accordance with the reduction of construction materials. Dry‐type construction can be environment friendly by reducing human resources, temporary materials and waste. Copyright © 2009 John Wiley & Sons, Ltd.
Practical modelling of high‐rise dual systems with reinforced concrete slab‐column frames
Authors: Shin Myoungsu , Kang Thomas H.‐K. , Grossman Jacob S. 
Published: March 2009

AbstractThis paper discusses practical modelling issues pertinent to the design of an irregularly shaped reinforced concrete (RC) high‐rise building currently under development in New York City. The structure analysed consists of a 60‐storey residential tower and a 25‐storey hotel building structurally connected to each other. For the seismic force resistance, a dual system combining ordinary RC shear walls and intermediate slab–column moment frames was used at the upper portion, while a building frame system of ordinary RC shear walls was used at the lower portion of the structure. A variety of models were used to simulate the behaviour of various elements of the structure, with special attention given to overall systemic effects of different member stiffnesses considered to account for distinct stress levels under service and ultimate loads. The models used for slab–column frames and shear walls were verified by comparing with other available models or laboratory tests. The in‐plane flexibility of floor diaphragms at the interface between the two substructures with different geometries was simulated to identify the most critical wind conditions for each structural member. Finally, building dynamic analyses were performed to demonstrate the modelling issues to be considered for the lateral force design of irregular high‐rise buildings. Copyright © 2009 John Wiley & Sons, Ltd.
Progressive collapse resisting capacity of tube‐type structures
Authors: Kim Jinkoo , Lee Young‐Ho 
Published: March 2009

AbstractIn this study, the progressive collapse potential of tube‐type buildings, such as diagrid and tubular structures, composed of lateral load‐resisting perimeter frames and internal pin‐connected gravity frames, was evaluated by nonlinear static and dynamic analyses. To this end, 36‐ and 54‐storey structures were designed as analysis models and progressive collapse analyses were carried out by removing first‐storey columns. According to the analysis results, the progressive collapse of tube‐type analysis model buildings occurred when perimeter columns corresponding to more than 11% of all member cross‐sectional areas were removed from one side of the structures. When the diagonals located around a corner were removed, the ratio was reduced to 8%. It was observed that the corner columns in the diagrid system helped prevent the propagation of member failure all around the perimeter. Copyright © 2009 John Wiley & Sons, Ltd.
Simply too complicated
Authors: Tedeschi Riccardo 
Published: March 2009

AbstractStarting from the late 1990s and in the first years of the new century, the business of credit securitization has known incredible development, but the credit crunch triggered in August 2007 by American sub‐prime residential mortgages has probably cut to the heart of the so‐called “warehouse and sell” model of business. As a contribution to a higher level of transparency in the business of securitization, this paper tries to give an answer to the question “why is it so difficult to evaluate ABSs and CDOs?” In brief, one might say that “it is not a matter of financial models”. The problem is that ABS and CDO contracts are often too complicated, and there is a significant level of uncertainty concerning the key parameters that characterize the credit portfolios sold by securitization (default probabilities, recovery rates, default correlation), coupled with a strong sensitivity of the CDO prices to the variations of these parameters. At the moment we do not know if ABSs and CDOs will ever have a future, but we know for sure that, to survive, the securitization business will have to change. Hopefully, this crisis will probably bring some benefit in the coming years, probably because it will force big international banks to move toward simpler structures, more secure standards in the selection of borrowers, and a higher level of openness about economic information. If this does happen, we will hopefully remember the events of September and October 2008 as a kind of “adolescent crisis” that led to a more mature market. But for this to happen it is essential that investors learn to apply a few “commonsense” rules in the asset selection process and do not forget to estimate their own fair values and perform their own stress tests when they decide to put their money into these kind of products. Copyright © 2009 Wilmott Magazine Ltd
To the Knowledge of Interpseudohalogens: A Contribution to Cyanogen Isocyanate (NC–NCO)
Authors: Schmidt Carsten L. , Fischer Dieter , Himmel Hans‐Jörg , Köppe Ralf , Schnöckel Hansgeorg , Jansen Martin 
Published: March 2009

AbstractCyanogen isocyanate (NC–NCO) has been prepared and studied using a combined experimental and theoretical approach. A crystalline film of the interpseudohalogen species was stabilized by vapor deposition on a cold substrate (T = –100 °C). From IR spectroscopy on the “free” molecule, trapped in a matrix of solid argon, the connectivity and geometry of this unstable interpseudohalogen was deduced and substantiated by theoretical calculations. With this information, the crystal structure of NCNCO in the solid state could be analysed using powder X‐ray diffraction [Pbca (No. 61), a = 7.63(1) Å, b = 6.50(2) Å, c = 6.03(6) Å; V = 299.5(1) Å3]. The compound transforms into amorphous polymeric C2N2O at T > –68 °C. The results obtained were compared with recent findings and further discussed in the general context of C–N–(O) chemistry.
Reversal of glycogen storage disease type IIIa‐related cardiomyopathy with modification of diet
Authors: Dagli A. I. , Zori R. T. , McCune H. , Ivsic T. , Maisenbacher M. K. , Weinstein D. A. 
Published: March 2009

SummaryGlycogen storage disease type III (GSD III) is caused by a deficiency in debranching enzyme, which leads to an accumulation of abnormal glycogen called limit dextrin in affected tissues. Muscle and liver involvement is present in GSD type IIIa, while the defect is limited to the liver only in GSD type IIIb. Besides skeletal muscle involvement, a cardiomyopathy resembling idiopathic hypertrophic cardiomyopathy is seen. Management consists of maintaining normoglycaemia by supplementation with cornstarch therapy and/or protein. While studies are lacking regarding the best treatment for skeletal muscle disease, a high‐protein diet was previously reported to be beneficial. No cases of improvement in cardiomyopathy have been reported. Our patient presented in infancy with hypoglycaemia and hepatomegaly. His prescribed management consisted of cornstarch supplementation and a high‐protein diet providing 20% of his total energy needs. At 16 years of age, he developed a severe cardiomyopathy with a left ventricular mass index of 209 g/m2. The cardiomyopathy remained stable on a protein intake of 20–25% of total energy. At age 22 years, the diet was changed to increase his protein intake to 30% of total energy and minimize his cornstarch therapy to only what was required to maintain normoglycaemia. Dramatic improvement in the cardiomyopathy occurred. Over one year, his left ventricular mass index decreased from 159.7 g/m2 to 78 g/m2 (normal 50–86 g/m2) and the creatine kinase levels decreased from 455 U/L to 282 U/L. Avoidance of overtreatment with carbohydrate and a high‐protein diet can reverse and may prevent cardiomyopathy.