bluuebunny/crossref_metadata_2025_split huggingface dataset:
Finite‐difference time‐domain simulation of acoustic propagation in heterogeneous dispersive medium
Authors: Norton Guy V. 
Published: March 2007

AbstractAccurate modeling of pulse propagation and scattering is a problem in many disciplines (i.e., electromagnetics and acoustics). It is even more tenuous when the medium is dispersive. Blackstock [D. T. Blackstock, J Acoust Soc Am 77 (1985) 2050] first proposed a theory that resulted in adding an additional term (the derivative of the convolution between the causal time‐domain propagation factor and the acoustic pressure) that takes into account the dispersive nature of the medium. Thus deriving a modified wave equation applicable to either linear or nonlinear propagation. For the case of an acoustic wave propagating in a two‐dimensional heterogeneous dispersive medium, a finite‐difference time‐domain representation of the modified linear wave equation can been used to solve for the acoustic pressure. The method is applied to the case of scattering from and propagating through a 2‐D infinitely long cylinder with the properties of fat tissue encapsulating a cyst. It is found that ignoring the heterogeneity in the medium can lead to significant error in the propagated/scattered field. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007
Spondylolysis in the lower thoracic–upper lumbar spine in a British medieval population
Authors: Mays S. 
Published: March 2007

AbstractSpondylolysis is generally a condition of the lower lumbar spine, but occasionally it is observed at cranial to L4. It is generally agreed that spondylolysis in the lower lumbar spine represents fatigue failure of the neural arch. However, whether a biomechanical explanation is adequate to explain lesions cranial to L4 is disputed. Morphological aspects of spondylolysis at T12–L3 (five cases) are compared with those of lesions at L4–L6 (24 cases) in a mediaeval English skeletal series with the aim of shedding light upon any differences in aetiology of lesions at the two sites. It was found that spondylolysis at T12–L3 was more often unilateral than in L4–L6. In T12–L3, clefts more often took an angulated, dog‐leg course across the pars interarticularis, whereas most in L4–L6 were fairly straight and had an oblique orientation. In T12–L3, clefts often had facetted opposing surfaces suggestive of a diarthrodial joint, but this was only seen once in L4–L6. It is suggested on morphological grounds that facetted defects are more likely congenital than acquired. The need for consideration of factors in addition to activity regimes when interpreting spondylolysis in earlier populations is emphasised. Copyright © 2007 John Wiley & Sons, Ltd.
A two‐station embossing process for rapid fabrication of surface microstructures on thermoplastic polymers
Authors: Yao Donggang , Nagarajan Pratapkumar , Li Lei , Yi Allen Y. 
Published: March 2007

AbstractAn embossing strategy involving a hot station and a cold station for sequentially heating and cooling the embossing tool was investigated to reduce cycle times in hot embossing polymer microstructures. Experimental studies showed that aluminum stamps with a thickness of 1.4 mm can be rapidly heated from room temperature to 200°C in 3 s using contact heating against a hot station at 250°C. Microchannels and microlenses were successfully embossed onto high‐density polyethylene and acrylonitrile–butadiene–styrene substrates using a heating time less than 3 s and a total cycle time around 10 s. The two‐station embossing process for the microlens was also numerically studied. The simulated filling behavior agreed with the experimental observation and the predicted thermal and deformation history of the polymer offered a good explanation on the experimentally observed process characteristics. POLYM. ENG. SCI., 47:530–539, 2007. © 2007 Society of Plastics Engineers.
Crystallization of poly(vinyl alcohol) during solvent removal: Infrared characterization and mathematical modeling
Authors: Wong Sim‐Siong , Altinkaya Sacide Alsoy , Mallapragada Surya K. 
Published: March 2007

AbstractCrystallization of semicrystalline polymer films during drying has a significant effect on the rate of solvent removal. Understanding and controlling the crystallization kinetics is important in controlling residual solvent levels and drying kinetics. The degree of crystallinity of the poly(vinyl alcohol) films during multicomponent drying was investigated using Fourier transform infrared spectroscopy (FTIR). The 1141 cm−1 band is sensitive to the degree of crystallinity of the polymer and the growth of intensity of this band was monitored as drying progressed. The results from the FTIR studies were comparable to the results obtained from differential scanning calorimetry. Studies were conducted to test the effect of initial solvent composition (water–methanol mixture), drying temperature, and polymer molecular weight on the rate of crystallization and the final crystallinity of the films. An increase in initial methanol composition increased the crystallization rate but did not affect the final degree of crystallinity. An increase in drying temperature and decrease in polymer molecular weight increased the rate of crystallization as well as the final degree of crystallinity. Based on the experimental data, rate constants for crystallization kinetics were extracted from our previously developed model based on free volume theory. The experimental data and the simulation results showed good agreement. The ability of the free volume theory to illustrate the crystallization behavior validated the model and improved its capability. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 930–935, 2007
Molecular dynamics simulation of water diffusion inside an amorphous polyacrylate latex film
Authors: Chen Zhengxia , Gu Qiang , Zou Haifeng , Zhao Tianqi , Wang Hongyan 
Published: March 2007

AbstractMolecular dynamics simulations were applied to investigate the diffusion behaviors of water molecules at temperatures ranging from 323 to 443 K inside amorphous polyacrylate. The results showed that the simulated diffusion coefficients and activation energies were similar to those of experiments. Moreover, the activation energy of water molecules at high temperatures was higher than that at low temperatures by 3.16 kcal mol−1, which was close to the hydrogen‐bonding energy between water and polyacrylate. An analysis of the experimental desorption curves of water molecules and their activation energies has confirmed that there are two forms of water molecules inside rubbery polyacrylate, namely, free water and bound water. In addition, it has been concluded that bound water molecules move from one polar group of polyacrylate to another, and this is followed by occasional jumps. Simulated information is very helpful in designing new polyacrylate latex systems and optimizing existent polyacrylate systems. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 884–891, 2007
Structure and mechanical properties of poly(L‐lactic acid) crystals and fibers
Authors: de Oca H. Montes , Ward I. M. 
Published: March 2007

AbstractThe elastic constants of poly(L‐lactic acid) (PLLA) crystals are reported on the basis of a commercial software package and the published crystal structure of the α form. A chain modulus of 36 GPa and a shear modulus of 3 GPa have been obtained for cylindrically symmetric aggregates of perfectly oriented crystals. The helical conformation of the PLLA molecule reduces the stiffness in the chain axis direction because bond rotation plays a significant role in the deformation. X‐ray crystal strain measurements suggest that shear of the α crystal parallel to the helix axis is the easiest mode of deformation, in agreement with the expectations obtained from the low shear modulus of 3 GPa obtained from the theoretical calculations. A combination of small‐ and wide‐angle X‐ray scattering, differential scanning calorimetry, dynamic mechanical thermal analysis, and shrinkage measurements has been used to characterize the structure that develops and the crystal transformation that occurs during fiber processing. The structure that develops during processing very much depends on the crystal transformation, and a structural model is proposed for fibers at different degrees of plastic deformation. The transformation of the α crystal into the β form and vice versa is governed primarily by shear along the helix axis because the chains must shear past each other during the crystal transformation, disrupting the lamellar packing. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 892–902, 2007
Optical transitions in pairs of trivalent ion–interstitial fluorine in alkaline‐earth fluorides
Authors: Radzhabov E. , Nepomnyashchikh A. , Kirm M. 
Published: March 2007

AbstractAbsorption, excitation in vacuum ultraviolet region, emission and decay of emission of alkaline‐earth crystals (CaF2, SrF2, BaF2) doped by different concentrations of YF3 or LaF3 were studied. New emission bands in the region 3–6 eV and excitation bands just below exciton edges were observed. Unempirical Hartree–Fock and density functional calculations of alkaline‐earth crystal clusters containing Y or La impurity were performed. We concluded that observed optical bands belong to transitions between interstitial fluorine and trivalent metal parts of pairs Me3+–F–i. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic structure and spectroscopic properties of interstitial anions in the nanoporous complex oxide 12CaO·7Al2O3
Authors: Sushko P. V. , Muñoz Ramo D. , Shluger A. L. 
Published: March 2007

AbstractA novel nano‐porous oxide 12CaO·7Al2O3 (C12A7) can host a large concentration of interstitial ions, which are present in high concentrations of the order of 1021 cm–3. We use ab initio calculations and an embedded cluster approach to investigate the effect of the interstitial ions on the optical absorption of C12A7. It is demonstrated that the position of the absorption edge can shift in the range of at least 1.5 eV depending on the chemical composition of different interstitial ions. This property of C12A7 can be used for fabrication of materials with tuneable band gaps on the basis of the same lattice host. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Localization and movement of native interstitials in chlorinated SrCl2:Fe crystals
Authors: Ghica D. , Nistor S. V. , Goovaerts E. 
Published: March 2007

AbstractThe formation of the electron trapped Fe+(IV) centre, produced by X‐ray irradiation at 80 K and further annealing at temperatures of up to 700 K in chlorinated SrCl2:Fe crystals, has been investigated by Electron Paramagnetic Resonance. Our studies report the transformation of the monoclinic Fe+(III) centre into the axial Fe+(IV) centre above 450 K. The formation of the Fe+(IV) centre is attributed to the presence and thermally activated movement of neighbouring interstitial chlorine and alkali impurity Na+ ions. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quantum fluctuation and the magnetically structural symmetry in ferrimagnetic superlattices
Authors: Qiu Rong‐ke , Zhang Zhi‐dong 
Published: March 2007

AbstractThe magnetization and the quantum fluctuations in several ferrimagnetic superlattices consisting of 2–6 different magnetic sublayers are studied by employing Holstein–Primakoff transformations and Green's functions technique only for zero temperature. Investigating ferrimagnetic superlattices with different magnetic sublayers and different spin configurations, we find that when some of spin quantum numbers are adjusted, some sublayer magnetizations at zero‐temperature exhibit a minimum, correspondingly, the quantum fluctuation of the system exhibits a maximum point. Different spin configurations have different quantum fluctuations of the system. The maximum point of the quantum fluctuation of the system is related with higher symmetry of the system. It differs from the symmetry of crystallographic point‐groups or space‐groups, but belongs to the type III Shubnikou group of magnetic group, which describes antiferromagnetic or ferrimagnetic state. We define it as the magnetically structural symmetry. The higher the magnetically structural symmetry of the system is, the stronger the quantum fluctuation of the system is, for varying spin quantum numbers and different spin configurations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Elastic and piezoelectric fields in quantum wire semiconductor structures – A boundary integral equation analysis
Authors: Pan E. , Albrecht J. D. , Zhang Y. 
Published: March 2007

AbstractThis paper presents a rigorous analysis on the elastic and piezoelectric fields in quantum wire (QWR) semiconductor structures using the accurate boundary integral equation method. The materials modelled include both zincblende and wurtzite III–V semiconductors, and both the well‐accepted inclusion and structural inhomogeneity models are discussed. While the difference in the strain field between the inclusion and inhomogeneity models is consistent with previously published results, within about 10%, the difference in the induced piezoelectric fields between these two models can be very large, sometimes even with different signs (for zincblende semiconductors). The electric field distribution in polygonal QWRs with different sides is also studied and it is found that the electric field in triangular and square QWRs can be very different from the fields in polygonal QWRs with more than four sides. These findings should provide important considerations and trend analyses for both growth and modelling associated with QWR semiconductor structures. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Specification and patterning of the animal‐vegetal axis in sea urchins by the canonical Wnt signaling pathway
Authors: Kumburegama Shalika , Wikramanayake Athula H. 
Published: March 2007

AbstractPattern formation along the sea urchin A‐V axis is initiated by the selective activation of the canonical Wnt signaling pathway in vegetal blastomeres. Activation of this pathway is essential for deployment of the endomesoderm gene regulatory network (EGRN), and for pattern formation along the entire A‐V axis. During early embryogenesis the canonical Wnt signaling pathway is selectively activated by Dishevelled (Dsh), a critical activator of the Wnt pathway. Dsh is highly enriched in vesicular structures at the vegetal pole in eggs and early embryos, and selective activation of this protein leads to the nuclearization of β‐catenin in the endomesoderm. Following activation of canonical Wnt signaling by Dsh, signaling by β‐catenin and the Lef/Tcf transcription factors regulates endomesoderm specification by activating the EGRN. One critical early target of nuclear β‐catenin is Wnt8, which is selectively expressed in the micromeres at the 16‐cell stage and in the macromeres one cleavage division later. Wnt8 signaling is not required for the endomesoderm‐inducing activity of the micromeres, but this protein regulates primary mesenchyme cell differentiation. Within the endomesodermal domain Wnt8 regulates the later specification of endoderm and mesoderm. These results have highlighted the important role of the canonical Wnt signaling pathway in patterning the A‐V axis in the sea urchin embryo, and have strongly suggested that this axis is initially specified by a cytoplasmic/cytoarchitectural mechanism to activate Dsh in vegetal blastomeres. Additionally, this work along with work in vertebrates and cnidarians has shown that the canonical Wnt pathway plays a conserved role in early pattern formation in metazoan embryos.
Reference ranges for tissue Doppler measures of maternal systolic and diastolic left ventricular function
Authors: Bamfo J. E. A. K. , Kametas N. A. , Nicolaides K. H. , Chambers J. B. 
Published: March 2007

AbstractObjectivesTissue Doppler imaging (TDI) is an echocardiographic technique that evaluates longitudinal myocardial tissue velocities during left ventricular systolic and diastolic function, relatively independently of loading conditions. Limited data are available regarding maternal cardiac function using TDI. The aim of this study was to construct reference charts for TDI indices in normal pregnancy.MethodsThis was a cross‐sectional study on 104 pregnant women at 11–38 weeks of gestation and 19 non‐pregnant controls. Doppler echocardiography was used to assess transmitral inflow velocities during diastole (peak velocity of early (E) and late (A) atrial filling), whilst TDI at the septal and lateral margins of the mitral annulus measured diastolic velocities (peak velocity of early (E′) and late (A′) diastolic filling) and peak systolic velocity (S′). The left ventricular filling index (E : E′ ratio) was derived. The Tei index (ratio of isovolumetric time to ejection time) was measured.ResultsSystolic function assessed by TDI S′ velocity was unaltered at the septal and lateral margins, although S′ velocity at the lateral margin was higher (12%, P = 0.028) in the first two trimesters, compared to non‐pregnant controls. Diastolic function was modified as demonstrated by an increase in A velocity (P P = 0.024). Similarly, A′ increased at the septal and lateral margins ( P < 0.001 and P = 0.02, respectively), resulting in a decrease in E′ : A′ ratios at the septal and lateral mitral margins ( P = 0.001 and P = 0.001, respectively). E : E′ at both mitral margins and Tei index were unaltered.ConclusionThis study gives normal ranges for TDI indices in pregnancy. TDI demonstrated modified longitudinal systolic and diastolic function. Future studies will evaluate the potential of this technique in pregnancies complicated by hypertension and cardiac disease. Copyright © 2007 ISUOG. Published by John Wiley & Sons, Ltd.
Beta‐diversity of lepidopteran larval communities in a Japanese temperate forest: effects of phenology and tree species
Authors: Murakami Masashi , Ichie Tomoaki , Hirao Toshihide 
Published: March 2007

AbstractThe specialization of herbivores among tree species is poorly understood despite its fundamental importance as a factor regulating diversity. To examine the effect of tree species on larval community structure, the larval communities in 10 temperate deciduous tree species that differed in leaf emergence pattern (flush‐ vs. intermediate‐type) were seasonally surveyed. The newly developed soft, nitrogen‐rich leaves of all species became tough and nitrogen‐poor as the season progressed. Following the changes in leaf quality, two distinct seasonal lepidopteran larval communities emerged, with a marked turnover in early July. The beta diversity, or dissimilarity, of species composition in the larval communities among tree species was higher in summer than in spring. These results imply that the lepidopteran larval communities as a whole were supported by alpha diversity in spring and by beta diversity in summer, demonstrating that the plant diversity of this forest could support a caterpillar community. We examined the importance of spatio‐temporal variations in leaf quality within and among tree species in promoting herbivore diversity, although other factors, such as tree species phylogeny and predators, may also have a large effect on lepidopteran larval communities.
Iron supplement use among Danish pregnant women
Authors: Knudsen Vibeke K , Hansen Harald S , Ovesen Lars , Mikkelsen Tina B , Olsen Sjurður F 
Published: March 2007

AbstractObjectivesTo evaluate compliance with the national recommendation on supplemental iron to all pregnant women in Denmark and to explore differences between compliers and non-compliers with respect to dietary habits and other lifestyle factors.DesignIntake of supplemental iron from pure iron supplements and from multivitamin and mineral preparations was estimated in mid-pregnancy.SettingNationwide cohort study, the Danish National Birth Cohort (DNBC), comprising more than 100 000 women recruited in early pregnancy.SubjectsInformation on diet and dietary supplements was available for 54 371 women. Of these, information on lifestyle factors was available for 50 902 women.ResultsA high compliance with the recommendation was found, as approximately 77% of the women reported use of iron supplements during pregnancy. However, many of the compliers did not obtain the recommended doses of iron, which can partly be explained by the lack of iron preparations of appropriate doses available on the Danish market. Compliance with the recommendation was associated with age above 20 years, primiparity, body mass index < 30 kg m− 2, non-smoking and long education. No major differences were seen in dietary intake between compliers and non-compliers.ConclusionOverall, a high compliance rate was found among participants of the DNBC but a clarification on daily dose is needed, and more concern should be paid to vulnerable groups such as young, smoking women and women with no or short education.
Optimization of Bioreactor Using Metabolic Control Analysis Approach
Authors: Konde Kakasaheb S. , Modak Jayant M. 
Published: March 2007

AbstractA new methodology based on a metabolic control analysis (MCA) approach is developed for the optimization of continuous cascade bioreactor system. A general framework for representation of a cascade bioreactor system consisting of a large number of reactors as a single network is proposed. The kinetic and transport processes occurring in the system are represented as a reaction network with appropriate stoichiometry. Such representation of the bioreactor systems makes it amenable to the direct application of the MCA approach. The process sensitivity information is extracted using MCA methodology in the form of flux and concentration control coefficients. The process sensitivity information is shown to be a useful guide for determining the choice of decision variables for the purpose of optimization. A generalized problem of optimization of the bioreactor is formulated in which the decision variables are the operating conditions and kinetic parameters. The gradient of the objective function to be maximized with respect to all decision variables is obtained in the form of response coefficients. This gradient information can be used in any gradient‐based optimization algorithm. The efficiency of the proposed technique is demonstrated with two examples taken from literature: biotransformation of crotonobetaine and alcohol fermentation in cascade bioreactor system.
Protein Arrays: Labeling the Protein and Probing the Array for Protein-Protein Interactions
Authors: MacBeath Gavin 
Published: March 2007

INTRODUCTIONTo detect protein-protein interactions, a protein microarray can be incubated with a fluorescently labeled protein. After the array is washed, stable interactions can be identified by scanning the slide for fluorescent spots. This protocol uses cyanine-3 (Cy3) or cyanine-5 (Cy5) monofunctionally activated dyes to label the probe proteins.
Protein Arrays: Labeling the Compounds and Probing the Array for Protein-Small Molecule Interactions
Authors: MacBeath Gavin 
Published: March 2007

INTRODUCTIONTo detect protein interactions with small molecules, a protein microarray is incubated with a fluorescently labeled compound, the array is washed, and stable interactions are identified by scanning the slide for fluorescence. It is often advantageous to label the small molecules indirectly, by covalently linking them to a previously labeled carrier molecule such as BSA. This protocol describes the labeling of BSA with Cy3 or Cy5, the linkage of the small molecule to the labeled BSA, and the probing of protein microarrays with the fluorescently labeled conjugate.
Protein Arrays: Probing the Array and Detecting Radioactive Spots for Kinase-Substrate Interactions
Authors: MacBeath Gavin 
Published: March 2007

INTRODUCTIONProtein arrays can be probed for potential substrates of protein kinases. To identify substrates of a kinase of interest, a protein microarray is incubated with that kinase and [γ-33P]ATP. Following an appropriate incubation, the array is washed, coated with a photographic emulsion, and incubated further; the emulsion is developed and then imaged with a scanning light microscope.