bluuebunny/crossref_metadata_2025 huggingface dataset:
Biology of eggs, embryos and larvae ofRhinelepis aspera(Spix & Agassiz, 1829) (Pisces: Siluriformes)
Authors: da Rocha Perini Violeta , Sato Yoshimi , Rizzo Elizete , Bazzoli Nilo
Published: October 2009

The black armoured catfishRhinelepis asperais an important commercial species found in the São Francisco River (Brazil) that has great potential for pisciculture. This paper presents, for the first time, information on the embryogenesis and larval development of this species. The breeder fish were subjected to spawning induction with crude carp pituitary extract. Eggs were kept in incubators at 24°C and embryogenesis was observed with a stereomicroscope until hatching. Ovary fragments, samples of recently extruded oocytes and larvae were fixed in Bouin's solution and subjected to routine histology techniques. Recently extruded oocytes were also analyzed with a scanning electron microscope (SEM). Females (80%) had a positive response to hypophysation. Oocyte extrusion was performed at 8 h and 30 min after the second hormone injection and the fertilization rate achieved 72.4 ± 8.8%. Recently extruded oocytes had a mean diameter of 1360.80 ± 40.87 μm and presented a conspicuous jelly coat covering the zona pellucida. Histochemical reactions indicated the presence of neutral glycoproteins in the yolk globules and in the zona pellucida. These reactions also indicated the presence of neutral glycoproteins and carboxylated acid glycoconjugates in the follicular cells and the jelly coat. These compounds form mucosubstances that can be related to the adhesiveness of the eggs. Under the SEM the oocytes presented a micropyle disc and a thick jelly coat over their surface. The closure of the blastopore occurred 9 h and 40 min after fertilization and embryogenesis was completed at 45 h and 50 min after fertilization, when the embryos were incubated at 24°C. The total absorption of the yolk sac occurred during the fifth day indicating the need for an exogenous food supply. These results provide essential information for the successful breeding and management of the promisingR. aspera.
Browsing for conservation: Springtime forage value of midstory shrubs of degraded oak savannas in southern Wisconsin
Authors: Hedtcke Janet , Posner Joshua , Rosemeyer Martha , Albrecht Ken
Published: October 2009

Oak (Quercusspp.) savanna is a rare and dwindling ecosystem primarily due to the clearing of vast areas for agriculture and encroachment of woody midstory shrubs in the remnant areas. There is interest in introducing controlled grazing to re-open these ecologically sensitive semi-wooded areas. We report the forage quality and diet selection by Scottish Highland cattle (Bos taurusspp.), a breed recognized for their browsing behavior, of the most common shrubs in this ecosystem. Shrub species sampled included prickly ash (Xanthoxylem americanaMill), gooseberry (Ribes missourienseNutt.), gray dogwood (Cornus racemesaL.), multiflora rose (Rosa multifloraThunb. ex Murr.), black or red raspberry (Rubusspp.) and wild parsnip (Pastinaca sativaL). Leaf biomass was collected in June 2001 and 2002 and analyzed for forage quality. Animal observations showed that diet included a fairly even mixture of shrub leaves, grass and herbaceous forbs. Prickly ash and raspberry were most frequently browsed and had the highest crude protein (CP; 190 g kg−1), while multiflora rose and gray dogwood, neither highly browsed upon, had the lowest levels of CP (120 g kg−1). All shrubs had highin-vitrotrue digestibility, with prickly ash approaching 850 g kg−1(as compared to 688 g kg−1for mature alfalfa). The quality of the shrub layer in late spring is adequate to provide nutritional support for beef cattle as long as dry matter intake is not limited. Integrating shrubs into the rotation could expand the pasture base by providing feed at a time when cool-season pastures are typically quasi-dormant.
North Atlantic Current variability through marine isotope stage M2 (circa 3.3 Ma) during the mid‐Pliocene
Authors: De Schepper Stijn , Head Martin J. , Groeneveld Jeroen
Published: October 2009

The mid‐Pliocene was an episode of prolonged global warmth and strong North Atlantic thermohaline circulation, interrupted briefly at circa 3.30 Ma by a global cooling event corresponding to marine isotope stage (MIS) M2. Paleoceanographic changes in the eastern North Atlantic have been reconstructed between circa 3.35 and 3.24 Ma at Deep Sea Drilling Project Site 610 and Integrated Ocean Drilling Program Site 1308. Mg/Ca ratios andδ18O fromGlobigerina bulloidesare used to reconstruct the temperature and relative salinity of surface waters, and dinoflagellate cyst assemblages are used to assess variability in the North Atlantic Current (NAC). Our sea surface temperature data indicate warm waters at both sites before and after MIS M2 but a cooling of ∼2–3°C during MIS M2. A dinoflagellate cyst assemblage overturn marked by a decline inOperculodinium centrocarpumreflects a southward shift or slowdown of the NAC between circa 3.330 and 3.283 Ma, reducing northward heat transport 23–35 ka before the global ice volume maximum of MIS M2. This will have established conditions that ultimately allowed the Greenland ice sheet to expand, leading to the global cooling event at MIS M2. Comparison with an ice‐rafted debris record excludes fresh water input via icebergs in the northeast Atlantic as a cause of NAC decline. The mechanism causing the temporary disruption of the NAC may be related to a brief reopening of the Panamanian Gateway at about this time.
Stochastic soil water dynamics of phreatophyte vegetation with dimorphic root systems
Authors: Vervoort R. Willem , van der Zee Sjoerd E. A. T. M.
Published: October 2009

As the direct uptake of deep groundwater by vegetation may be essential in semiarid regions, we incorporated this process in stochastic root zone water balance models. The direct water uptake by vegetation via deep tap roots is simulated using one additional empirical parameter. This is considered for the case of feedback with root zone saturation and without such feedback. The model that accounts for feedback between shallow root zone saturation and groundwater uptake by deep roots takes up less water if the shallow root zone is wet. The behavior of the models demonstrates that for certain combinations of climate and groundwater depths this feedback becomes important in determining differences in total evapotranspiration (ET). This feedback mechanism also captures hydraulic redistribution processes. The range of relative contributions of groundwater to ET predicted by the models was similar to values derived in isotope studies.
Modeling soil depth from topographic and land cover attributes
Authors: Tesfa Teklu K. , Tarboton David G. , Chandler David G. , McNamara James P.
Published: October 2009

Soil depth is an important input parameter in hydrological and ecological modeling. Presently, the soil depth data available in national soil databases (STATSGO and SSURGO) from the Natural Resources Conservation Service are provided as averages within generalized land units (map units). Spatial uncertainty within these units limits their applicability for distributed modeling in complex terrain. This work reports statistical models for prediction of soil depth in a semiarid mountainous watershed that are based upon the relationship between soil depth and topographic and land cover attributes. Soil depth was surveyed by driving a rod into the ground until refusal at locations selected to represent the topographic and land cover variation in the Dry Creek Experimental Watershed near Boise, Idaho. The soil depth survey consisted of a model calibration set, measured at 819 locations over 8 subwatersheds representing topographic and land cover variability and a model testing set, measured at 130 more broadly distributed locations in the watershed. Many model input variables were developed for regression to the field data. Topographic attributes were derived from a digital elevation model. Land cover attributes were derived from Landsat remote sensing images and high‐resolution aerial photographs. Generalized additive and random forests models were developed to predict soil depth over the watershed. They were able to explain about 50% of the soil depth spatial variation, which is an important improvement over the soil depth extracted from the SSURGO national soil database.
A new perspective on warming of the global oceans
Authors: Palmer M. D. , Good S. A. , Haines K. , Rayner N. A. , Stott P. A.
Published: October 2009

Changes in ocean circulation associated with internal climate variability have a major influence on upper ocean temperatures, particularly in regions such as the North Atlantic, which are relatively well‐observed and therefore over‐represented in the observational record. As a result, global estimates of upper ocean heat content can give misleading estimates of the roles of natural and anthropogenic factors in causing oceanic warming. We present a method to quantify ocean warming that filters out the natural internal variability from both observations and climate simulations and better isolates externally forced air‐sea heat flux changes. We obtain a much clearer picture of the drivers of oceanic temperature changes, being able to detect the effects of both anthropogenic and volcanic influences simultaneously in the observed record. Our results show that climate models are capable of capturing in remarkable detail the externally forced component of ocean temperature evolution over the last five decades.
A statistical rainfall‐runoff mixture model with heavy‐tailed components
Authors: Carreau J. , Naveau P. , Sauquet E.
Published: October 2009

We present a conditional density model of river runoff given covariate information which includes precipitation at four surrounding stations. The proposed model is nonparametric in the central part of the distribution and relies on extreme value theory parametric assumptions for the upper tail of the distribution. From the trained conditional density model, we can compute quantiles of various levels. The median can serve to simulate river runoff, quantiles of level 5% and 95% can be used to form a 90% confidence interval, and, finally, extreme quantiles can estimate the probability of large runoff. The conditional density model is based on a mixture of hybrid Paretos. The hybrid Pareto is built by stitching a truncated Gaussian with a generalized Pareto distribution. The mixture is made conditional by considering its parameters as functions of covariates. A neural network is used to implement those functions. A penalty term on the tail indexes is added to the conditional log likelihood to guide the maximum likelihood estimator toward solutions that are preferred. This alleviates the difficulties encountered with the maximum likelihood estimator of the tail index on small training sets. We evaluate the proposed model on rainfall‐runoff data from the Orgeval basin in France. The effect of the tail penalty is further illustrated on synthetic data.
Fiber bundle model for multiscale modeling of hydromechanical triggering of shallow landslides
Authors: Cohen D. , Lehmann P. , Or D.
Published: October 2009

Sudden and rapid mass movements associated with landslides and snow avalanches present a hazard to life and infrastructure, yet their predictions and triggering mechanisms remain poorly understood. Statistical methods and correlative studies have been used to produce landslide or avalanche susceptibility maps, often with limited physical basis. Mechanistic approaches based on factor‐of‐safety computation seldom represent the progressive transition from local failure events to a landslide and, in general, do not include heterogeneities associated with land cover or with subsurface material properties and hydrologic pathways. Focusing on rainfall‐induced shallow landslides, we propose the use of the fiber bundle model (FBM), a generic yet powerful and adaptable model used in modeling fatigue and fracture of complex and disordered materials. The primary strength of the FBM is its ability to represent the progressive failure of cracks and shear zones and the ruptures of highly heterogeneous bonding elements that are present in soils at all scales. The model also provides a natural framework for interpretation of acoustic emission signatures from failing slopes, which may form the basis of a monitoring and warning system.
Estrogen-Receptor-Mediated Protection of Cerebral Endothelial Cell Viability and Mitochondrial Function after Ischemic Insult in vitro
Authors: Guo Jiabin , Krause Diana N , Horne James , Weiss John H , Li Xuejun , Duckles Sue P
Published: October 2009

Protective effects of estrogen against experimental stroke and neuronal ischemic insult are well-documented, but it is not known whether estrogen prevents ischemic injury to brain endothelium, a key component of the neurovascular unit. Increasing evidence indicates that estrogen exerts protective effects through mitochondrial mechanisms. We previously found 17β-estradiol (E2) to improve mitochondrial efficiency and reduce mitochondrial superoxide in brain blood vessels and endothelial cells. Thus we hypothesized E2 will preserve mitochondrial function and protect brain endothelial cells against ischemic damage. To test this, an in vitro ischemic model, oxygen-glucose deprivation (OGD)/reperfusion, was applied to immortalized mouse brain endothelial cells (bEnd.3). OGD/reperfusion-induced cell death was prevented by long-term (24, 48 h), but not short-term (0.5, 12 h), pretreatment with 10 nmol/L E2. Protective effects of E2 on endothelial cell viability were mimicked by an estrogen-receptor (ER) agonist selective for ERα (PPT), but not by one selective for ERβ (DPN). In addition, E2 significantly decreased mitochondrial superoxide and preserved mitochondrial membrane potential and ATP levels in early stages of OGD/reperfusion. All of the E2 effects were blocked by the ER antagonist, ICI-182,780. These findings indicate that E2 can preserve endothelial mitochondrial function and provide protection against ischemic injury through ER-mediated mechanisms.
Iba1+/NG2+ Macrophage-Like Cells Expressing a Variety of Neuroprotective Factors Ameliorate Ischemic Damage of the Brain
Authors: Smirkin Anna , Matsumoto Hiroaki , Takahashi Hisaaki , Inoue Akihiro , Tagawa Masahiko , Ohue Shiro , Watanabe Hideaki , Yano Hajime , Kumon Yoshiaki , Ohnishi Takanori , Tanaka Junya
Published: October 2009

In a transient 90-min middle cerebral artery occlusion (MCAO) model of rats, a large ischemic lesion is formed where macrophage-like cells massively accumulate, many of which express a macrophage marker, Iba1, and an oligodendrocyte progenitor cell marker, NG2 chondroitin sulfate proteoglycan (NG2); therefore, the cells were termed BINCs (Brain Iba1+/NG2+Cells). A bone marrow transplantation experiment using green-fluorescent protein-transgenic rats showed that BINCs were derived from bone marrow. 5-Fluorouracil (5FU) injection at 2 days post reperfusion (2 dpr) markedly reduced the number of BINCs at 7 dpr, causing enlargement of necrotic volumes and frequent death of the rats. When isolated BINCs were transplanted into 5FU-aggravated ischemic lesion, the volume of the lesion was much reduced. Quantitative real-time RT-PCR showed that BINCs expressed mRNAs encoding bFGF, BMP2, BMP4, BMP7, GDNF, HGF, IGF-1, PDGF-A, and VEGF. In particular, BINCs expressed IGF-1 mRNA at a very high level. Immunohistochemical staining showed that IGF-1-expressing BINCs were found not only in rat but also human ischemic brain lesions. These results suggest that bone marrow-derived BINCs play a beneficial role in ischemic brain lesions, at least in part, through secretion of neuroprotective factors.
Analysis of feral pig (Sus scrofa) movement in a Hawaiian forest ecosystem using GPS satellite collars
Authors: Salbosa Lasha-Lynn , Lepczyk Dr. Christopher
Published: October 2009

The ecosystem altering impacts of feral pigs have been widely documented around the world. However, a general framework for their control and management has been lacking, especially in island ecosystems. One reason for this lack of management is that we have little knowledge of how pigs move through different island ecosystems, especially ones that are topographically challenging such as Hawai‛i. With recent advances in telemetry and movement modeling, it is now becoming practical to understand where these large introduced animals are moving and how they are using habitat. Hence, the primary goal of this study is to understand feral pig movement in terms of terrain, slope restrictions, and distance traveled beyond a natal site, within an island forested landscape. Based upon this goal, the objectives were to (1) assess different methods of time-series analysis in terms of animal movement and home range, and (2) use the information to inform wildlife management and policy. In 2008, a total of 36 feral pigs were collared with Global Positioning System (GPS) units across four different field sites on three Hawaiian Islands (Maui, Molokai, and Kauai) and tracked for an average of 60 +/- 10 days. Of the 36 collared animals, only four could be used for analysis due to various technological failures. Using three different movement modeling approaches (Brownian Bridge, minimum convex polygon, and the kernel density estimator), we found that feral pigs, within the heterogeneous landscape of Hawaiian watersheds have a spatial recognition limit or ecological neighborhood of between 1.65 and 2 km. All three methods indicated a slight variation of individual home range estimates. These results demonstrated that pigs move less in heterogeneous and heavily vegetated ecosystems. Even under the most conservative estimate, pigs moved 0.2 km/day. Considering that feral pigs disperse exotic plants and increase nutrient loading of streams, our results indicate that even a small abundance of pigs have a very large impact on the native ecosystems of Hawaii, due to their concentration around a natal site or resource center. Based upon this work, we suggest that managers must increase measures to limit habitat connectivity, such as perimeter fences and trapping along remote roadways that are used as feral pig dispersal mechanisms.
SSR - Identification from EST
Authors: Riju Aikkal
Published: October 2009

Tutorial of Identification of SSR from EST resources using online Tools
Near-field investigations of nanoshell cylinder dimers
Authors: Höflich Katja , Gösele Ulrich , Christiansen Silke
Published: October 2009

Metallic nanoparticles are known to exhibit strong particle size dependent localized surface plasmon resonances due to their specific optical response described via the complex dielectric function. Using the two-dimensional finite element method, the near-field behavior of core-shell nanocylinder dimers with either a dielectric or a gold core and a silver shell was investigated. With a detailed analysis the positions of maximum field enhancement usable for highly sensitive spectroscopy were unveiled and the surface charge distributions of the different kinds of resonances were visualized. It is shown that the usual far-field spectra do not give reliable estimates of local electric field peaks. Furthermore one observes a distinct mode at the natural plasma frequency of the silver shell which is independent of the core material. This mode is identified as a volume plasmon mode.
Analytic second derivatives in closed-shell coupled-cluster theory with spin-orbit coupling
Authors: Wang Fan , Gauss Jürgen
Published: October 2009

The theory for geometrical second derivatives of the energy is outlined for the recently suggested two-component coupled-cluster approach using relativistic effective core potentials with spin-orbit coupling included in the post-Hartree–Fock treatment [F. Wang, J. Gauss, and C. van Wüllen, J. Chem. Phys. 129, 064113 (2008)], and an implementation is reported at the coupled-cluster singles and doubles (CCSD) level as well as at the CCSD level augmented by a perturbative treatment of triple excitations [CCSD(T)]. The applicability of the developed analytic second-derivative techniques is demonstrated by computing harmonic and fundamental frequencies for PtH2, PbH2, and HgH2 with the required cubic and semidiagonal quartic force fields obtained by numerical differentiation of the analytically evaluated quadratic force constants. Spin-orbit coupling effects are shown to be non-negligible for the three considered molecules and thus need to be considered in the case of high-accuracy predictions.
Characterization of a CO2/N2/Ar supersonic flowing discharge
Authors: Drake D. J. , Popović S. , Vušković L.
Published: October 2009

In this paper we are presenting the full characterization of a supersonic flowing CO2/N2/Ar discharge at static pressures of 1–20 Torr and Mach number 2.15. In all aspects besides the flow speed and gas temperature, these conditions correspond to Martian entry plasma. Plasma parameters were determined by optical emission spectroscopy techniques. The gas and vibrational temperature were found from analysis of the rotational and vibrational spectra of the CO B Σ1+−A Π1 Ångstrom system, respectively. The electron density was determined from the absolute intensity of the N2 C Π3u−B Π3g second positive system. A kinetic model for the discharge was developed to calculate the electron density and compared with experimental data.
Optical nonlinear absorption characteristics of AgInSbTe phase change thin films
Authors: Liu Jing , Wei Jingsong
Published: October 2009

The AgInSbTe phase change thin films are very important as optical recording and the super-resolution mask materials in high density optical information storage. In this work, the effective nonlinear absorption coefficients of amorphous and crystalline AgInSbTe thin films were measured by the open-mode Z-scan method and no evidence of nonlinear refraction was found in the closed-mode Z-scan measurement. The effective nonlinear absorption coefficient βeff of amorphous AgInSbTe thin films is 7.53×10−3 m/W and the effective photon-absorption number n is 1.722; βeff of crystalline AgInSbTe thin films is 3.5×10−2 m/W, which is of an order lager than that of amorphous state, and the n value is 1.7011. The giant nonlinearity of AgInSbTe results from the free carrier absorption in the nanosecond time scale and this characteristic should be responsible for the mechanism of optical recording as well as the readout of super-resolution disk.
Tuning birefringence by using two-dimensional photonic band structure
Authors: Xiao Xiao , Hou Bo , Wen Weijia , Sheng Ping
Published: October 2009

Birefringence is an optical characteristic intrinsic to anisotropic materials. In the paper, we show the microwave birefringence can be tuned as a function of frequency by utilizing the band structures of a two-dimensional photonic crystal consisting of metallic cylinders arranged in a two-dimensional square lattice. By measuring the transmission and mapping the field inside of the sample, the birefringence was directly determined. An agreement between band structure calculations and experiment measurements was achieved, with the frequency at the center of transmission band showing the least birefringence and the frequency at the band edge exhibiting the most.
Effect of nucleated Cu phase on magnetic properties and electronic structures in bcc Fe: Ab initio study
Authors: Choi Heechae , Kim Chiho , Chung Yong-Chae
Published: October 2009

Using the first-principles calculations, the change in magnetism and electronic structures during Cu nucleation in bcc Fe system was investigated. For modeling the Fe-rich bcc FeCu alloy, FexCu1−x (x≥0.75) were employed in the supercell system. Nonmagnetic Cu atoms were precipitated on the (100) plane of bcc Fe crystal, whereas the magnetized Cu atoms preferred to be precipitated on the (110) plane. Magnetization energies showed a linear decrease as the Cu concentration increased in bcc Fe. The magnetic moments of Fe atoms increased for larger concentration of Cu atoms. Electron density of states showed that the enhanced magnetic moment of Fe atoms resulted from the shift of minority spin states toward higher levels, which was associated with the bond formation between Cu and Fe atoms.
Dual Lindstedt series and Kolmogorov–Arnol’d–Moser theorem
Authors: Frasca Marco
Published: October 2009

We prove that there exists a Lindstedt series that holds when a Hamiltonian is driven by a perturbation going to infinity. This series appears to be dual to a standard Lindstedt series as it can be obtained by interchanging the role of the perturbation and the unperturbed system. The existence of this dual series implies that a dual Kolmogorov–Arnol'd–Moser (KAM) theorem holds, and when a leading order Hamiltonian exists, which is nondegenerate, the effect of tori reforming can be observed with a system passing from regular motion to fully developed chaos and back to regular motion with the reappearance of invariant tori. We apply these results to a perturbed harmonic oscillator, proving numerically the appearance of tori reforming. Tori reforming appears as an effect that limits chaotic behavior to a finite range of parameter space of some Hamiltonian systems. Dual KAM theorem, as proved here, applies when the perturbation, combined with a kinetic term, provides again an integrable system.
Spectroscopic study of the B Π1 state of K39H
Authors: Lee Ang-Yu , Luh Wei-Tzou
Published: October 2009

The B Π1 excited electronic state of K39H has been observed for the first time by a pulsed fluorescence excitation spectroscopic technique. We have found only one vibrational level, in which seven e-parity and seven f-parity sublevels are identified. The Dunham-type coefficients A00, A01, and A02 and the mean internuclear separation for the B Π1 state have been derived. Their numeric values are separately 27 682.64(1) cm−1, 1.533(1) cm−1, −0.001 25(2) cm−1, and 3.345(1) Å for the B Π1+ state; 27 682.66(2) cm−1, 1.532(2) cm−1, −0.001 20(3) cm−1, and 3.347(2) Å for the B Π1− state. The dissociation energy D0 is determined to be 131.4(7) cm−1. The vibrational frequency and the dissociation energy for the B 1Π state have also been estimated and the results are compared with recent ab initio calculations.
The “hot spots” conjecture for a certain class of planar convex domains
Authors: Miyamoto Yasuhito
Published: October 2009

We prove the “hot spots” conjecture of Rauch [“Five problems: An introduction to the qualitative theory of partial differential equations,” Partial Differential Equations and Related Topics (Program, Tulane Univ., New Orleans, La., 1974), Lecture Notes in Mathematics (Springer, Berlin, 1975), Vol. 446, pp. 355–369] for a certain class of planar convex domains. Specifically, we show that an eigenfunction corresponding to the lowest nonzero eigenvalue of the Neumann Laplacian on Ω attains its maximum (minimum) at points in ∂Ω. One class of domains is the planar convex domain Ω satisfying diam(Ω)2/|Ω|<1.378. When Ω is a disk, diam(Ω)2/|Ω|≈1.273. Hence, this condition indicates that Ω is a nearly circular planar convex domain. However, symmetries of the domain are not assumed. We give other sufficient conditions for domains for which the conjecture holds. We also give a new isoperimetric inequality.
Advantages of admittance spectroscopy over time-of-flight technique for studying dispersive charge transport in an organic semiconductor
Authors: Tsung K. K. , So S. K.
Published: October 2009

We show that admittance spectroscopy (AS) is a better technique than time of flight (TOF) to study the charge transport properties in dispersive materials. The hole transport properties of N,N′-diphenyl-N,N′-bis(1-naphthyl)(1,1′-biphenyl)-4,4′-diamine (NPB) doped with different traps were evaluated by AS and TOF techniques. It was found that both techniques can show clear signals for measuring the mobility of NPB doped with shallow traps. When NPB was doped with deep traps, the AS signals were still clear for mobility extraction. In sharp contrast, the TOF transients become featureless and the carrier transit time cannot be determined. The validity of AS in mobility determination was demonstrated by comparing the extracted AS to TOF mobilities. Generally, the hole mobilities extracted by these two techniques were in excellent agreement. In addition, we will demonstrate that AS can be employed to measure carrier dispersion.
Dynamic characterizations of high diffraction efficiency in volume Bragg grating formed by holographic photopolymerization
Authors: Pu Haihui , Yin Dejin , Gao Bin , Gao Hongyue , Dai Haitao , Liu Jianhua
Published: October 2009

Volume Bragg grating with 96% diffraction efficiency (DE) was efficiently formed by holographic photopolymerization in blend syrup of photocurable trimethylolpropane triacrylate monomer and nematic liquid crystal. The formation dynamics of the composite gratings was quantitatively characterized under the frame of one-dimensional reaction-diffusion model with a revision of individual decay constants for monomer diffusion and reaction. Initial parameters of diffusion and reaction were analytically determined from the measured first order DE at the beginning stage. Evolutions of the DE, both in curing and postcuring periods, were excellently simulated, especially with postcuring reaction been taken into account.
Size, shape, and flexibility of proteins and DNA
Authors: Rawat Nidhi , Biswas Parbati
Published: October 2009

Size, shape, and flexibility are the important topological parameters which characterize the functional specificity and different types of interactions in proteins and DNA. The size of proteins and DNA, often measured by the radius of gyration (RG), are determined from the coordinates of their respective structures available in Protein Data Bank and Nucleic Acid Data Bank. The mean square radius of gyration obeys Flory’s scaling law given by ⟨RG2⟩∼N2ν where N is the number of amino acid residues/nucleotides. The scaling exponent ν reflects the different characteristic features of nonglobular proteins, natively unstructured proteins, and DNA. The asymmetry in the shapes of proteins and DNA are investigated using the asphericity (Δ) parameter and the shape parameter (S), calculated from the eigenvalues of the moment of inertia tensor. The distributions of Δ and S show that most nonglobular proteins and DNA are aspherical and prolate (S>0). Natively unstructured proteins are comparatively spherically symmetrical having both prolate and oblate shapes. The flexibility of these molecules is characterized by the persistence length (lp). Persistence length for natively unstructured proteins is determined by fitting the distance distribution function P(r) to the wormlike chain (WLC) model in the limit of r⪢RG. For nonglobular proteins and DNA, lp may be computed from the Benoit–Doty approximation for unperturbed radius of gyration of the WLC. The flexibilities of the proteins and DNA increases with the chain length. This is due to an increase in the nonlocal interactions with the increase in N, needed to minimize the conformational fluctuations in the native state. The persistence length of these proteins has not yet been measured directly. Analysis of the two-body contacts for the proteins reveals that the nonglobular proteins are less densely packed compared to the natively unstructured proteins with least side-chain side chain contacts even though side-chain backbone contacts predominate in the two types of proteins.
Gaseous Diffusion Coefficients
Authors: Marrero T. R. , Mason E. A.
Published: October 2009

Diffusion coefficients of binary mixtures of dilute gases are comprehensively compiled, critically evaluated, and correlated by new semi-empirical expressions. There are seventy-four systems for which the data are sufficiently extensive, consistent and accurate to allow diffusion coefficients to be recommended with confidence. Deviation plots are given for most of these systems. Almost every gaseous diffusion coefficient which was experimentally determined and reported prior to 1970 can be obtained from the annotated bibliography and table of gas pairs.

A detailed analysis of experimental methods is given, and intercomparison of their results helps establish reliability limits for the data, which depend strongly on temperature. Direct measurements are supplemented by calculations based on knowledge of intermolecular forces derived from independent sources—molecular beam scattering for high temperatures, and London dispersion constants for low temperatures. In addition, diffusion coefficients for several mixtures are obtained from experimental data on mixture viscosities and thermal diffusion factors. Combination of all these results gives diffusion coefficients over a very extensive temperature range, from very low temperatures to 10 000 K.

All data are corrected for composition dependence and for quantum effects. New semi-empirical equations are derived for making such corrections easily.
Selected Values of Evaporation and Condensation Coefficients for Simple Substances
Authors: Pound G. M.
Published: October 2009

Tables of selected data on the coefficients of evaporation and condensation far from equilibrium for simple substances are presented, together with a rationale for the exclusion or choice of data and an estimate of the precision measure.
Atlas of the Observed Absorption Spectrum of Carbon Monoxide Between 1060 and 1900 Å
Authors: Tilford S. G. , Simmons J. D.
Published: October 2009

This atlas summarizes the results of a recent investigation of the carbon monoxide absorption spectrum between 1060 and 1900 Å. Twelve electronic transitions are observed in this region; four electric dipole allowed electric transitions from the ground state X 1Σ+ to the A 1Π, B 1Σ+, C 1Σ+, and E 1Π states, and eight forbidden transitions to the a′ 3Σ+, e 3Σ-, a 3Π, D 1Δ, d 3Δi, I 1Σ-, j 3Σ+, and c 3Π states. The following items are presented in the atlas:

(1) A photograph of the spectrum with band assignments;

(2) a table of band head measurements and assignments arranged by wavelength;

(3) a summary of the spectroscopic constants and potential curve for each electronic state;

(4) a line list, arranged by wavelength, of the observed rotational lines of the allowed transitions.
Effective interaction between large colloidal particles immersed in a bidisperse suspension of short-ranged attractive colloids
Authors: Jamnik A.
Published: October 2009

The effective force between two large hard spheres mimicking lyophobic colloids (solute) immersed in an asymmetric two-component mixture of smaller particles (solvents), interacting via Baxter’s sticky hard sphere (SHS) potential, was studied using integral equation theory and Monte Carlo simulation. The theoretical predictions were calculated from the analytic solution of the Percus–Yevick/Ornstein–Zernike integral equation for spatial correlations in a three-component mixture at vanishing solute concentration, while the simulation results were obtained by applying a special simulation technique developed for sampling the hard-sphere collision force. Due to layering of the solvent molecules, the effective force between the particles of the solute oscillates with periods equal to the molecular diameters of both solvent components. The attractive force between the solute particles in the SHS mixture comprising strongly attractive molecules of either component decays slower than that in the mixture with weaker interparticle attraction. Similar features are also observed when inspecting the separate contributions of individual components to the total solute-solute force. At sufficient strength of the interparticle stickiness, these oscillations disappear, the force becoming long ranged and attractive at all separations.
Colloidal permeability of liquid membranes consisting of hard particles by nonequilibrium simulations
Authors: Ariza María J. , Puertas Antonio M.
Published: October 2009

A novel particulate membrane, comprised of a confined fluid of colloidal hard spheres, is presented and studied by means of simulations. Using a fluid of smaller hard spheres as feed, the transport properties of the membrane are studied as a function of the volume fractions of both the feed solution and membrane and the size ratio between both types of particles. Our simulations show that the fluid in the membrane is compressed to the permeate side due to the pressure of the feed. This effect controls the permeability behavior of the membrane: impermeable when the feed pressure is too low, or when the pressure is high enough to induce crystallization of the membrane fluid. Thus, the permeability first increases and then decreases, upon increasing the feed concentration. Finally we focus in systems with high concentrations of the feed and membrane fluids, where completely impermeable membranes are obtained only when the feed spheres are big enough (σf>0.38σm).
Density-based energy decomposition analysis for intermolecular interactions with variationally determined intermediate state energies
Authors: Wu Qin , Ayers Paul W. , Zhang Yingkai
Published: October 2009

The first purely density-based energy decomposition analysis (EDA) for intermolecular binding is developed within the density functional theory. The most important feature of this scheme is to variationally determine the frozen density energy, based on a constrained search formalism and implemented with the Wu–Yang algorithm [Q. Wu and W. Yang, J. Chem. Phys. 118, 2498 (2003)]. This variational process dispenses with the Heitler–London antisymmetrization of wave functions used in most previous methods and calculates the electrostatic and Pauli repulsion energies together without any distortion of the frozen density, an important fact that enables a clean separation of these two terms from the relaxation (i.e., polarization and charge transfer) terms. The new EDA also employs the constrained density functional theory approach [Q. Wu and T. Van Voorhis, Phys. Rev. A 72, 24502 (2005)] to separate out charge transfer effects. Because the charge transfer energy is based on the density flow in real space, it has a small basis set dependence. Applications of this decomposition to hydrogen bonding in the water dimer and the formamide dimer show that the frozen density energy dominates the binding in these systems, consistent with the noncovalent nature of the interactions. A more detailed examination reveals how the interplay of electrostatics and the Pauli repulsion determines the distance and angular dependence of these hydrogen bonds.
Room temperature ferromagnetism in nanostructured ZnO–Al system
Authors: Chen S. J. , Suzuki K. , Garitaonandia J. S.
Published: October 2009

The origin of the room-temperature ferromagnetism (RTF) in ZnO-based dilute magnetic semiconductors remains controversial. We experimentally demonstrate here that it is possible to induce RTF in ball milled (ZnO)1−x/Alx without any ferromagnetic dopant. Our work shows that RTF in (ZnO)1−x/Alx (x=0–0.5) can be realized simply by milling a mixture of high purity ZnO and Al fine powders for 8 h. The spontaneous magnetization of the milled powders is found to increase by annealing under a reduced pressure. The magnetization value depends highly on both the ratio of Al to ZnO and the annealing temperature. X-ray photoelectron spectroscopy results have revealed that the Zn2+ ions in (ZnO)1−x/Alx are partially reduced into a lower ionic state. As there are no magnetic impurities present in our samples, the origin of ferromagnetism is most likely to be due to the charge transfer between Zn and Al at the interfaces of the ball milled nanograins. Our results reinforce the significant role played by the alterations of the electronic structures in the RTF of ZnO.
Observation of quantum-Hall effect in gated epitaxial graphene grown on SiC (0001)
Authors: Shen T. , Gu J. J. , Xu M. , Wu Y. Q. , Bolen M. L. , Capano M. A. , Engel L. W. , Ye P. D.
Published: October 2009

Epitaxial graphene films examined were formed on the Si-face of semi-insulating 4H-SiC substrates by a high temperature sublimation process. A high-k gate stack on the epitaxial graphene was realized by inserting a fully oxidized nanometer thin aluminum film as a seeding layer, followed by an atomic-layer deposition process. The electrical properties of epitaxial graphene films are retained after gate stack formation without significant degradation. At low temperatures, the quantum-Hall effect in Hall resistance is observed along with pronounced Shubnikov–de Haas oscillations in diagonal magnetoresistance of gated epitaxial graphene on SiC (0001).
Quantum dynamical effects in liquid water: A semiclassical study on the diffusion and the infrared absorption spectrum
Authors: Liu Jian , Miller William H. , Paesani Francesco , Zhang Wei , Case David A.
Published: October 2009

The important role of liquid water in many areas of science from chemistry, physics, biology, geology to climate research, etc., has motivated numerous theoretical studies of its structure and dynamics. The significance of quantum effects on the properties of water, however, has not yet been fully resolved. In this paper we focus on quantum dynamical effects in liquid water based on the linearized semiclassical initial value representation (LSC-IVR) with a quantum version of the simple point charge/flexible (q-SPC/fw) model [Paesani et al., J. Chem. Phys. 125, 184507 (2006)] for the potential energy function. The infrared (IR) absorption spectrum and the translational diffusion constants have been obtained from the corresponding thermal correlation functions, and the effects of intermolecular and intramolecular correlations have been studied. The LSC-IVR simulation results are compared with those predicted by the centroid molecular dynamics (CMD) approach. Although the LSC-IVR and CMD results agree well for the broadband for hindered motions in liquid water, the intramolecular bending and O–H stretching peaks predicted by the LSC-IVR are blueshifted from those given by CMD; reasons for this are discussed. We also suggest that the broadband in the IR spectrum corresponding to restricted translation and libration gives more information than the diffusion constant on the nature of quantum effects on translational and rotational motions and should thus receive more attention in this regard.
1 mm ultrafast superconducting stripline molecule detector
Authors: Zen N. , Casaburi A. , Shiki S. , Suzuki K. , Ejrnaes M. , Cristiano R. , Ohkubo M.
Published: October 2009

Superconducting stripline detectors (SSLDs) are promising for detecting keV molecules at nanosecond response times and with mass-independent detection efficiency. However, a fast response time is incompatible with practical centimeter detector size. A parallel configuration of striplines provides a means to address this problem. Experimental results and simulation for promisingly large 1-mm-square parallel niobium SSLDs show that nanosecond pulses are produced by superconducting-normal transition within only one of the parallel striplines instead of cascade switching of all the parallel striplines. Successful detection of a series of multimers of immunoglobulin G up to 584 kDa supports the mass-independent efficiency for mass spectrometry.
Microphotoluminescence study of exciton polaritons guided in ZnO nanorods
Authors: Li Wenliang , Gao Min , Zhang Xiaoxian , Liu Dongfang , Peng Lian-Mao , Xie Sishen
Published: October 2009

By confocal microphotoluminescence spectroscopy, we study the influence of the localized excitation position on the guided near band edge emission from the end facets of ZnO nanorods. An increased propagation distance of the guided emission causes dramatically depressed excitonic emission and pronounced blueshifts of the Fabry–Pérot cavity modes. The blueshifts can be understood on the basis of enhanced inelastic processes of the exciton polaritons guided in the nanorod cavities and reduced oscillator strength. The blueshifts exhibit local maxima at LO phonon-related emissions, emphasizing the role of the LO phonons in the relaxation and inelastic scattering of the exciton polaritons.
Virtual circular array using material-embedded linear source distributions
Authors: Kwon Do-Hoon
Published: October 2009

Linear arrays of sources embedded inside a thin material slab are designed such that they radiate the same fields as a circular array of radiators in free space in a two-dimensional configuration. The design is based on the coordinate transformation approach, where a circular domain containing a distribution of line sources is transformed into a rectangular slab. The source distribution in the transformed space forms two closely-spaced linear arrays and the resulting material slab is matched along the boundary with free space. Full-wave simulations are performed for verification.
Influence of GeSi interfacial layer on Ge–Ge optical phonon mode in SiO2 films embedded with Ge nanocrystals
Authors: Liu L. Z. , Gao F. , Wu X. L. , Li T. H. , Chu Paul K.
Published: October 2009

The Ge–Ge optical phonon peak at 300 cm−1 acquired from amorphous SiO2 films embedded with Ge nanocrystals by Raman scattering is sensitive to the Si content. When the Si concentration is high, a thin GeSi interfacial layer forms around the Ge nanocrystals. A tensile stress is produced to partially offset the compressive stress imposed by the SiO2 matrix on the Ge nanocrystals, consequently downshifting the frequency of the optical phonon and increasing its linewidth. Theoretical calculation based on phonon confinement and compressive effects discloses that the interfacial layer plays a crucial role in the optical phonon behavior.
Magnetostructural coupling and magnetocaloric effect in Ni–Mn–In
Authors: Li B. , Ren W. J. , Zhang Q. , Lv X. K. , Liu X. G. , Meng H. , Li J. , Li D. , Zhang Z. D.
Published: October 2009

Magnetic-field-induced martensitic phase transition and the concomitant change of volume are investigated in Ni–Mn–In alloy. A well-defined linear relationship is found between the quantity characterizing magnetic degree of freedom and the thermal expansion on behalf of structural degree of freedom, which demonstrates the magnetostructural coupling. Within the exchange-inversion model, such a linear relationship is theoretically derived and the magnetostructural correlation is elucidated. The lattice-entropy change contributes about one half of the total entropy change, suggesting that the magnetostructural coupling plays an important role in the magnetocaloric effect of Ni–Mn–In alloy.
Pointing in Stereoscopic Space
Authors: Heuer Herbert , Rapp Katrin
Published: October 2009

Movements in virtual stereoscopic space tend to be difficult and slow. To shed some light on the origins of these difficulties, we studied open-loop pointing with targets presented in a mirror stereoscope. Whilst targets were placed in a virtual horizontal plane, movement end-points were located in an inclined plane. The inclination of this plane was a stable individual characteristic. Amplitude errors gave no evidence of a contraction bias. Open-loop movements had fairly straight trajectories, but closed-loop movements were strongly curved so that they ended in a horizontal plane rather than in an inclined one. Effects of closed-loop movements on subsequent open-loop movements (calibration effects) were only small. These findings reveal that movements in a virtual environment exhibit a number of characteristics also seen in real environments, but in addition they reflect specific visual illusions. Extensive calibration procedures are needed to overcome such errors for the reliance on closed-loop control of pointing to be relaxed.