bluuebunny/crossref_metadata_2025 huggingface dataset:
Common Variants of ABCB4 and ABCB11 and Plasma Lipid Levels: A Study in Sib Pairs with Gallstones, and Controls
Authors: Acalovschi Monica , Tirziu Simona , Chiorean Erica , Krawczyk Marcin , Grünhage Frank , Lammert Frank
Published: May 2009

Most epidemiological surveys have confirmed the association of low HDL‐cholesterol and high triglyceride levels with cholesterol gallstones. Our objective was to analyze the relationship between plasma lipid levels and common polymorphisms of ABCB11 (encoding the bile salt export pump, BSEP) and ABCB4 (encoding the phospholipid transporter into bile, MDR3) genes. Plasma lipids were measured in 108 index patients of sib pairs with gallstones and in 260 controls. Using PCR‐based assays with 5′‐nuclease and fluorescence detection (TaqMan), the ABCB11 coding SNP p.A444V and four haplotype‐tagging SNPs covering the ABCB4 gene (c.504C > T, c.711T > A, p.R652G, rs31653 in intron 26) were genotyped. Plasma lipids were compared in carriers of the common versus rare allele of these polymorphisms using Student's t test and Pearson's correlation. BMI and triglyceride levels were higher and HDL‐cholesterol levels were lower in affected siblings than in controls. Among cases, triglyceride and cholesterol levels were higher in carriers of the common versus rare (hetero/homozygous carriers) allele of the SNPs p.A444V of ABCB11 and C.504C > T of ABCB4. HDL‐cholesterol was lower in carriers of the common allele of rs31653. In controls, significant differences of cholesterol and HDL‐cholesterol levels were found in carriers of ABCB4 polymorphisms. Our results do not support the hypothesis of a link between ABCB4 and ABCB11 polymorphisms, lithogenic dyslipidemia, and gallstone risk.
Cloning and Molecular Characterization of the Acyl‐CoA:Diacylglycerol Acyltransferase 1 (DGAT1) Gene from Echium
Authors: Mañas‐Fernández A. , Vilches‐Ferrón M. , Garrido‐Cárdenas J. A. , Belarbi E.‐H. , Alonso D. L. , García‐Maroto F.
Published: May 2009

Boraginaceae species, such as those from the genus Echium, contain high levels of the Δ6‐desaturated γ‐linolenic (18:3n‐6) and octadecatetraenoic (18:4n‐3) acids. These are unusual fatty acids among the plant kingdom that are gaining interest due to their benefits to human health. The potential utility of acyltransferases aimed at an increase in oil yield and fatty acid profiling has been reported. In this work, a gene encoding an acyl‐CoA:diacylglycerol acyltransferase (DGAT, EC 2.3.1.20) was cloned from Echium pitardii. Genomic and cDNA sequences obtained revealed a gene structure composed of 16 exons, yielding a protein (EpDGAT) of 473 amino acids with high similarity to DGAT1 enzymes of plants. Protein features such as a predicted structure with a highly hydrophilic N‐terminus followed by 10 transmembrane domains, as well as the presence of diverse specific signatures, also indicate that EpDGAT belongs to the DGAT1 family. indeed. DGAT activity of the protein encoded by EpDGAT was confirmed by heterologous expression of the full‐length cDNA in a yeast mutant (H1246) defective in the synthesis of triacylglycerols. Fatty acid composition of the triacylglycerols synthesized by EpDGAT in H1246 yeast cultures supplemented with polyunsaturated fatty acids suggest a substrate preference for the trienoic fatty acids α‐linolenic acid (18:3n‐3) and γ‐linolenic acid over the dienoic linoleic acid (18:2n‐6). Site‐directed mutagenesis has revealed the presence of a critical residue (P178 in EpDGAT) within a reported thiolase signature for binding of acyl‐enzyme intermediates that might be involved in the active site of the enzyme. Transcript analysis for EpDGAT shows an ubiquitous expression of the gene which is increased in leaves during senescence.
Sterols and Oxidized Sterols in Feed Ingredients Obtained from Chemical and Physical Refining Processes of Fats and Oils
Authors: Ubhayasekera Sarojini J. K. A. , Dutta Paresh C.
Published: May 2009

The by‐products obtained from conventional chemical and physical refining processes for edible fats and oils are important sources of valuable fatty components such as sterols, tocopherols, fatty acids, etc., and are also used as ingredients in animal feed formulations. Reports on sterol composition and content are limited, and the levels of oxidized sterols in these valuable by‐products are unknown. This study analyzed by‐product fractions from European refineries intended for use as ingredients in animal feeds for their content and composition of sterols and sterol oxidation products. The complex mixtures of sterol oxidation products were separated and quantified by multidimensional capillary columns, a medium polar DB‐17MS and an apolar DB‐5MS, in GC and GC–MS. Sterol content ranged from 0.l to 3.4 and 0.03 to 5.0 g/100 g in the by‐product fractions collected from chemical and physical refining processes, respectively, while the corresponding ranges for sterol oxidation products were 0.02–17 and 0.02–1.5 mg/100 g.
Rapid Determination of Free Fatty Acid in Extra Virgin Olive Oil by Raman Spectroscopy and Multivariate Analysis
Authors: El‐Abassy Rasha M. , Donfack Patrice , Materny Arnulf
Published: May 2009

We introduce a visible Raman spectroscopic method for determining the free fatty acid (FFA) content of extra virgin olive oil with the aid of multivariate analysis. Oleic acid was used to increase the FFA content in extra virgin olive oil up to 0.80% in order to extend the calibration span. For calibration purposes, titration was carried out to determine the concentration of FFA for the investigated oil samples. As calibration model for the FFA content (FFA%), a partial least squares (PLS) regression was applied. The accuracy of the Raman calibration model was estimated using the root mean square error (RMSE) of calibration and validation and the correlation coefficient (R2) between actual and predicted values. The calibration curve of actual FFA% obtained by titration versus predicted values based on Raman spectra was established for different spectral regions. The spectral window (945–1600 cm−1), which includes carotenoid bands, was found to be a useful fingerprint region being statistically significant for the prediction of the FFA%. High R2 and small RMSE values for calibration and validation could be obtained, respectively.
Epiphyseal stapling of the proximal tibia for idiopathic genu valgum
Authors: Courvoisier Aurélien , Eid Ahmad , Merloz Philippe
Published: May 2009

Purpose

The purpose of this study is to evaluate the clinical and radiological outcomes of hemiepiphysiodesis with a single medial staple of the proximal tibia in idiopathic genu valgum angular correction.

Methods

A retrospective review was performed identifying nine adolescents (18 knees) treated for idiopathic adolescent genu valgum by means of a bilateral hemiepiphysiodesis with a single staple of the proximal tibia. The intermalleolar distance (IMD) and hip–knee–ankle angle were measured at skeletal maturity.

Results

The IMD and hip–knee–ankle angle were reduced in all patients at skeletal maturity.

Conclusion

Hemiepiphysiodesis with a single medial staple of the proximal tibia seems to be a reliable and safe alternative method to achieve correction of an idiopathic genu valgum.
Position‐based beliefs: The center‐stage effect
Authors: Valenzuela Ana , Raghubir Priya
Published: May 2009

This paper examines the existence and consequences of consumers' position‐based beliefs about product layouts. We propose that consumers believe that options placed in the center of a simultaneously presented array are the most popular. This belief translates into their choosing options placed in the center more often than those on the sides of a display: the center‐stage effect (Studies 1 and 5). Results are driven by inferences of product popularity rather than higher levels of attention to products in a given position (Studies 2 and 3). The preference for middle options is accentuated when people explicitly take into account other people's preferences, increasing the need to choose a popular option (Study 3), but attenuated when layout‐based information is not diagnostic (Study 4). Increasing the accessibility of own preferences for the intrinsic attributes about the products reduces the use of position‐based beliefs to make judgments and attenuates the center‐stage effect (Study 5). Theoretical implications for marketplace meta‐cognitions, visual information processing, position effects, and the use of overall cognitive beliefs versus perceptual attention and memory‐based individuating information to make judgments are discussed.
Transport slopes, sediment cover, and bedrock channel incision in the Henry Mountains, Utah
Authors: Johnson Joel P. L. , Whipple Kelin X. , Sklar Leonard S. , Hanks Thomas C.
Published: May 2009

Field data from channels in the Henry Mountains of Utah demonstrate that abundant coarse sediment can inhibit fluvial incision into bedrock by armoring channel beds (the cover effect). We compare several small channels that share tributary junctions and have incised into the same sedimentary bedrock unit (Navajo Sandstone) but contain differing amounts of coarse diorite clasts owing to the spatial distribution of localized sediment sources. Bedrock channels that contain abundant clasts (diorite‐rich) have steeper longitudinal slopes than tributaries of these channels with smaller drainage areas and less sediment (diorite‐poor). The diorite‐poor tributaries have incised more deeply to lower average slopes and have more reach‐scale slope variability, which may reflect bedrock properties, longitudinal sediment sorting, and incision at lower sediment supply. Diorite‐rich channels have less bedrock exposed and smoother longitudinal profiles than diorite‐poor channels. We find that (1) coarse sediment can mantle bedrock channel beds and reduce the efficiency of incision, validating the hypothesized cover effect in fluvial incision models; (2) the channel slope needed to transport the sediment load can be larger than that needed to erode bedrock, suggesting that the slope of incising bedrock channels can become adjusted to the sediment load; (3) when abundant sediment is available, transport capacity rather than thresholds of motion can be dominant in setting bedrock channel slope; and (4) cover effects can be important even when moderate amounts of bedrock are exposed in channel beds.
Bio‐optical variability of the absorption and scattering properties of the Queensland inshore and reef waters, Australia
Authors: Blondeau‐Patissier D. , Brando V. E. , Oubelkheir K. , Dekker A. G. , Clementson L. A. , Daniel P.
Published: May 2009

Inshore estuarine, lagoonal, and reef waters of the Great Barrier Reef (Australia) were sampled between 2002 and 2005 during four dry and one wet tropical seasons. Relationships among three biogeochemical concentrations and five key water optical parameters measured at 129 stations were explored to optically characterize six predefined regions. A significant spatial and seasonal variability in some of the inherent optical properties and concentrations measured was found, reaching over two orders of magnitude in the estuaries. Total suspended solids concentrations ranged from 0.5 to ∼54 mg L−1, TChl‐a ranged from 0.05 to ∼9 mg m−3, color dissolved organic matter (CDOM) ranged from 0.004 to 0.8 m−1 at 440 nm, and the backscattering coefficient ranged from 0.001 to 1.18 m−1 at 555 nm. Our data set was mainly composed of coastal stations (95%), leading to a poor correlation between the three concentrations (R2 < 0.31). The range of variation in backscattering ratios, power law exponents, and the spectral slopes of CDOM and nonalgal particulate matter is comparable with findings from other coastal and open waters around the world. The empirical relationships between TChl‐a and aph(440) were found to differ from reference models, indicating differences in phytoplankton size structure and populations. High variability in backscattering ratios and associated power law exponents as well as particulate absorption ratios indicated different trends or relationships in particle size and composition between the different regions. Stations close to the reef matrix showed specific characteristics with concentrations typical of oceanic waters but CDOM spectral slopes similar to those of coastal environments.
Size‐ and time‐resolved chemical particle characterization during CAREBeijing‐2006: Different pollution regimes and diurnal profiles
Authors: van Pinxteren D. , Brüggemann E. , Gnauk T. , Iinuma Y. , Müller K. , Nowak A. , Achtert P. , Wiedensohler A. , Herrmann H.
Published: May 2009

Beijing, the capital of China, faces severe air pollution problems, resulting from a steep economic growth during the past decades. To better characterize the processes leading to the frequently observed high concentrations of air pollutants on a regional scale, the international field campaign “Campaigns of Air Quality Research in Beijing and Surrounding Region 2006” (CAREBeijing‐2006) was conducted in summer 2006. In this contribution, we present chemical data of size‐resolved particles, obtained by a five‐stage Berner impactor during 3 weeks at both an urban and suburban site in the area of Beijing, China. The samples were analyzed for inorganic ions (Cl−, SO42−, NO3−, NH4+, K+, Ca2+, Na+, and Mg2+), carbon sum parameters (OC, EC, and WSOC), and a variety of organic compounds such as dicarboxylic acids, alkanes, PAHs, and, for the first time in China, nitrooxy‐organosulfates. On average, the observed PM10 (where PM is particulate matter) mass concentrations were 133 μg m−3 and 112 μg m−3 at the urban and suburban site, respectively. A high influence of meteorology on the PM pollution was observed and is discussed. The highest concentrations of both PM mass and particle constituents were observed when sampled air masses originated south of Beijing and moved over the area with low wind speeds. During such periods, a strong increase of daytime concentrations of the secondary ions sulfate, nitrate, ammonium, and also some dicarboxylic acids could be observed. A strong diurnal variation of particle sulfate concentration with increasing values from morning to afternoon was observed during an intensive period, which could be attributed to regional production. Similar observations were made for oxalic acid. Generally, water‐soluble organic carbon concentrations were enhanced by a factor of 2 in fine particles during the studied period of intense photochemistry. Elemental carbon, alkanes, and PAHs showed clear nighttime concentration maxima obviously due to enhanced emissions and a relatively low mixing volume during night. For the newly studied compound group of nitrooxy‐organosulfates, qualitative data can be presented indicating an influence of nighttime chemistry and/or anthropogenic activities on their concentrations. The investigation of an intense nucleation and particle growth event revealed that the youngest particles largely consist of ammonium sulfate and primary carbonaceous material, with a possible contribution of secondary organic compounds.
Simulating the evolution of soot mixing state with a particle‐resolved aerosol model
Authors: Riemer N. , West M. , Zaveri R. A. , Easter R. C.
Published: May 2009

The mixing state of soot particles in the atmosphere is of crucial importance for assessing their climatic impact, since it governs their chemical reactivity, cloud condensation nuclei activity, and radiative properties. To improve the mixing state representation in models, we present a new approach, the stochastic particle‐resolved model PartMC‐MOSAIC, which explicitly resolves the composition of individual particles in a given population of different types of aerosol particles. This approach tracks the evolution of the mixing state of particles due to emission, dilution, condensation, and coagulation. To make this direct stochastic particle‐based method practical, we implemented a new multiscale stochastic coagulation method. With this method we achieved high computational efficiency for situations when the coagulation kernel is highly nonuniform, as is the case for many realistic applications. PartMC‐MOSAIC was applied to an idealized urban plume case representative of a large urban area to simulate the evolution of carbonaceous aerosols of different types due to coagulation and condensation. For this urban plume scenario we quantified the individual processes that contributed to the aging of the aerosol distribution, illustrating the capabilities of our modeling approach. The results showed for the first time the multidimensional structure of particle composition, which is usually lost in sectional or modal aerosol models.
On the association between spring Arctic sea ice concentration and Chinese summer rainfall
Authors: Wu Bingyi , Zhang Renhe , Wang Bin , D'Arrigo Rosanne
Published: May 2009

A statistical relationship between spring Arctic sea ice concentration (SIC) and Chinese summer rainfall is identified using singular value decomposition (SVD). Results show that decreased (increased) spring SIC in the Arctic Ocean and the Greenland Sea corresponds to increased (decreased) summer rainfall in northeast China and central China between the Yangtze River and the Yellow River (28°–36°N); and decreased (increased) rainfall in south China. Corresponding summer 500 hPa height anomalies show a Eurasian wave train structure, which originates in northern Europe and extends southeastwards to northeast China, and a south‐north dipole structure over East Asia south to Lake Baikal. Such a spatial distribution of 500 hPa height anomalies and corresponding summer rainfall anomalies cannot be entirely attributed to the impact of East Asian summer monsoon (EASM) variability. The spring Arctic SIC provides a complementary precursor for Chinese summer rainfall variability. The combined impacts of both spring Arctic SIC and Eurasian snow cover on the Eurasian wave train may explain their statistical linkage.
Multi-instantons and multicuts
Authors: Mariño Marcos , Schiappa Ricardo , Weiss Marlene
Published: May 2009

We discuss various aspects of multi-instanton configurations in generic multicut matrix models. Explicit formulas are presented in the two-cut case and, in particular, we obtain general formulas for multi-instanton amplitudes in the one-cut matrix model case as a degeneration of the two-cut case. These formulas show that the instanton gas is ultradilute due to the repulsion among the matrix model eigenvalues. We exemplify and test our general results in the cubic matrix model, where multi-instanton amplitudes can be also computed with orthogonal polynomials. As an application, we derive general expressions for multi-instanton contributions in two-dimensional quantum gravity, verifying them by computing the instanton corrections to the string equation. The resulting amplitudes can be interpreted as regularized partition functions for multiple ZZ-branes, which take into full account their backreaction on the target geometry. Finally, we also derive structural properties of the trans-series solution to the Painlevé I equation.
Effects of boron and phosphorus doping on the photoluminescence of self-assembled germanium quantum dots
Authors: Sustersic N. , Nataraj L. , Weiland C. , Coppinger M. , Shaleev M. V. , Novikov A. V. , Opila R. , Cloutier S. G. , Kolodzey J.
Published: May 2009

The doping of Ge quantum dots grown on Si (100) was investigated using atomic force microscopy and photoluminescence spectroscopy. The dots produced photoluminescence in the energy range from 0.75 to 0.95 eV. Compared to the undoped dots, the boron and phosphorus doped dots demonstrated a shift in peak emission toward lower energy by 60–80 meV, which is attributed to the decrease in density of the smaller sized dots. Increased photoluminescence intensity with temperature indicated higher activation energy with doping, suggesting a higher probability of radiative transitions at elevated temperatures, potentially important for various applications.
Novel characteristics of valveless pumping
Authors: Timmermann S. , Ottesen J. T.
Published: May 2009

This study investigates the occurrence of valveless pumping in a fluid-filled system consisting of two open tanks connected by an elastic tube. We show that directional flow can be achieved by introducing a periodic pinching applied at an asymmetrical location along the tube, and that the flow direction depends on the pumping frequency. We propose a relation between wave propagation velocity, tube length, and resonance frequencies associated with shifts in the pumping direction using numerical simulations. The eigenfrequencies of the system are estimated from the linearized system, and we show that these eigenfrequencies constitute the resonance frequencies and the horizontal slope frequencies of the system; “horizontal slope frequency” being a new concept. A simple model is suggested, explaining the effect of the gravity driven part of the oscillation observed in response to the tank and tube diameter changes. Results are partly compared with experimental findings.
Optimal photonic-crystal parameters assuring single-mode operation of 1300 nm AlInGaAs vertical-cavity surface-emitting laser
Authors: Czyszanowski Tomasz , Sarzała Robert P. , Dems Maciej , Nakwaski Włodzimierz , Thienpont Hugo , Panajotov Krassimir
Published: May 2009

We present a self-consistent analysis of InP-based 1300 nm AlInGaAs photonic-crystal vertical-cavity surface-emitting lasers (PhC VCSELs) and tunnel-junction PhC VCSELs, and analyze the influence of the electrical confinement, the PhC hole diameter and etching depth, and the size of the single defect optical aperture on the threshold current and the transverse mode discrimination. We also investigate the thermal performance of the two VCSEL configurations. As a result we determine the optimal PhC parameters assuring stable, single-mode operation in a broad range of driving currents.
Orientation dependence of nickel silicide formation in contacts to silicon nanowires
Authors: Dellas N. S. , Liu B. Z. , Eichfeld S. M. , Eichfeld C. M. , Mayer T. S. , Mohney S. E.
Published: May 2009

The orientation dependence of Ni silicide phase formation in the silicidation of silicon nanowires (SiNWs) by Ni has been studied. SiNWs with a [112] growth direction contacted by Ni pads form θ-Ni2Si for annealing conditions from 350 to 700 °C for 2 min. The θ-Ni2Si has an epitaxial orientation of θ-Ni2Si[001]∥Si[111¯] and θ-Ni2Si(100)∥Si(112) with the SiNW. On the other hand, SiNWs with a [111] growth direction react with Ni pads to form NiSi2 with an epitaxial orientation of NiSi2[11¯0]∥Si[11¯0] and NiSi2(111)∥Si(111) after annealing at 450 °C for 2 min. The [111] SiNWs were also silicided at 700 °C for 2 min, forming the low-resistivity NiSi phase. The epitaxial phases identified in the reactions of Ni films with SiNWs suggest that lattice matching at both the silicide/Si growth front and the surface of the original SiNW may play a significant role in determining the first silicide segment to grow.
Recurrences determine the dynamics
Authors: Robinson Geoffrey , Thiel Marco
Published: May 2009

We show that under suitable assumptions, Poincaré recurrences of a dynamical system determine its topology in phase space. Therefore, dynamical systems with the same recurrences are dynamically equivalent. This conclusion can be drawn from a theorem proved in this paper which states that the recurrence matrix determines the topology of closed sets. The theorem states that if a set of points M is mapped onto another set N, such that two points in N are closer than some prescribed fixed distance if and only if the corresponding points in M are closer than some, in general different, prescribed fixed distance, then both sets are homeomorphic, i.e., identical up to a continuous change in the coordinate system. The theorem justifies a range of methods in nonlinear dynamics which are based on recurrence properties.
Trapping characteristics of Al2O3/HfO2/SiO2 stack structure prepared by low temperature in situ oxidation in dc sputtering
Authors: Chang Chia-Hua , Hwu Jenn-Gwo
Published: May 2009

In this work, a dielectric stack with Al2O3/HfO2/SiO2 (1.8 nm/1.6 nm/2.5 nm) trilayer structure prepared by low temperature in situ natural oxidation during dc sputtering is investigated. We study the electrical characteristics, including the dielectric leakage of 10−8 A/cm2 at Vg=−2 V, the current transport mechanism and trap distributions through the trilayer dielectric stack. The Fowler–Nordheim barrier height of the prepared Al2O3 (ϕFN,Al2O3) was extracted as 3.06±0.15 eV. The current variation ratios [ΔJg/Jg(0)] during constant voltage stressing were found to decrease with raising gate stress voltages for the trilayer stack in comparison with that [ΔJg/Jg(0)] increase with raising gate stress voltages for the two-layer HfO2/SiO2 stack. Shallow traps located in HfO2 were supposed to be major trapping centers within the trilayer stack. The proposed method of in situ oxidation during dc sputtering is of merit and low in process temperature. The trilayer dielectric stacks are an alternative option for nonvolatile memory application, especially under the consideration of low temperature limitation.
Domain structure and dielectric properties in nanocomposite ferroelectric thin layers with spherical dielectric inclusions
Authors: Geddes B. , Artemev A.
Published: May 2009

The phase field model was used to simulate the domain structure and polarization versus applied field hysteresis curves of a composite layer consisting of a ferroelectric matrix and spherical dielectric inclusions. Simulation results demonstrate that the introduction of dielectric inclusions into the ferroelectric matrix can lead to the stabilization of the polydomain structure in a wide range of applied fields. As a result a significant increase in susceptibility can be obtained due to the composite structure formation, which causes the addition of an extrinsic contribution into susceptibility. The composite structure can produce a number of different partially switched (partially poled) states with different values of the remnant polarization that are stable in wide ranges of the applied field producing a close to linear dielectric response with high susceptibility.
Scintillator based detector for fast-ion losses induced by magnetohydrodynamic instabilities in the ASDEX upgrade tokamak
Authors: García-Muñoz M. , Fahrbach H.-U. , Zohm H. ,   the ASDEX Upgrade Team
Published: May 2009

A scintillator based detector for fast-ion losses has been designed and installed on the ASDEX upgrade (AUG) tokamak [A. Herrmann and O. Gruber, Fusion Sci. Technol. 44, 569 (2003)]. The detector resolves in time the energy and pitch angle of fast-ion losses induced by magnetohydrodynamics (MHD) fluctuations. The use of a novel scintillator material with a very short decay time and high quantum efficiency allows to identify the MHD fluctuations responsible for the ion losses through Fourier analysis. A Faraday cup (secondary scintillator plate) has been embedded behind the scintillator plate for an absolute calibration of the detector. The detector is mounted on a manipulator to vary its radial position with respect to the plasma. A thermocouple on the inner side of the graphite protection enables the safety search for the most adequate radial position. To align the scintillator light pattern with the light detectors a system composed by a lens and a vacuum-compatible halogen lamp has been allocated within the detector head. In this paper, the design of the scintillator probe, as well as the new technique used to analyze the data through spectrograms will be described. A last section is devoted to discuss the diagnosis prospects of this method for ITER [M. Shimada et al., Nucl. Fusion 47, S1 (2007)].
Magnetic phases and structural properties in Co/Ru superlattices
Authors: Alayo W. , Tafur Miguel , Baggio-Saitovitch E. , Pelegrini F. , Nascimento V. P.
Published: May 2009

We report studies by x-ray diffraction, ferromagnetic resonance (FMR), and x-ray magnetic circular dichroism (XMCD) in Co/Ru superlattices grown by magnetron sputtering. We studied the [Co(50 Å)/Ru(tRu)]20 samples, which were deposited at room temperature on Si substrates with the Ru thicknesses, tRu, varying between 9 and 33 Å. The main and secondary uniform absorption modes, observed in the FMR spectra, are associated with the Co/Ru interfaces and the bulk Co regions, respectively. The main mode becomes more intense than the secondary one for increasing tRu. This is attributed to the roughness and/or atomic interdiffusion, which leads, with increasing tRu, to an increasing volume of Co/Ru interfacial regions and a decreasing volume of pure Co regions. The XMCD measurements provide Co spin magnetic moments lower than the bulk Co value, confirming the presence of a Co magnetic region with a lower local effective magnetization attributed to the Co/Ru interfaces.
In situ strain profiling of elastoplastic bending in Ti–6Al–4V alloy by synchrotron energy dispersive x-ray diffraction
Authors: Croft M. , Shukla V. , Akdoğan E. K. , Jisrawi N. , Zhong Z. , Sadangi R. , Ignatov A. , Balarinni L. , Horvath K. , Tsakalakos T.
Published: May 2009

Elastic and plastic strain evolution under four-point bending has been studied by synchrotron energy dispersive x-ray diffraction. Measured strain profiles across the specimen thickness showed an increasing linear elastic strain gradient under increasing four-point bending load up to ∼2 kN. The bulk elastic modulus of Ti–6Al–4V was determined as 118 GPa. The onset of plastic deformation was found to set in at a total in-plane strain of ∼0.008, both under tension and compression. Plastic deformation under bending is initiated in the vicinity of the surface and at a stress of 1100 MPa, and propagates inward, while a finite core region remains elastically deformed up to 3.67 kN loading. The onset of the plastic regime and the plastic regime itself has been verified by monitoring the line broadening of the (100) peak of α-Ti. The effective compression/tension stress-strain curve has been obtained from the scaling collapse of strain profile data taken at seven external load levels. A similar multiple load scaling collapse of the plastic strain variation has also been obtained. The level of precision in strain measurement reported herein was evaluated and found to be 1.5×10−5 or better.
Observation of surface enhanced IR absorption coefficient in alkanethiol based self-assembled monolayers on GaAs(001)
Authors: Marshall Gregory M. , Bensebaa Farid , Dubowski Jan J.
Published: May 2009

Alkanethiol self-assembled monolayers (SAMs) of various methylene group chain lengths [HS–(CH2)n–CH3] (n=9,11,13,15,17) were fabricated on the GaAs(001) surface followed by characterization using Fourier transform infrared spectroscopy. Modal analysis of the CH2 stretching mode region (2800–3000 cm−1) showed that linear scaling of the n-dependent factors accurately reproduced the spectral data, supporting a chain-length consistent physical model upon which a measurement of the absorption coefficient was based. Evaluated from the linearity of the absorbance data, a peak coefficient of 3.5×104 cm−1 was obtained and a domain for ordered self-assembly was assigned for values n>9. Compared with measurements of the absorption coefficient made in the liquid phase, the SAM phase coefficient was determined to be about six times greater. This enhancement effect is discussed in terms of contributions relating to the locally ordered environment and is largely attributed to the chemical properties of the interface. We believe this to be the first demonstration of IR spectral enhancement of a molecular species chemisorbed on the semiconductor surface.
Parameter extraction of solar cells using particle swarm optimization
Authors: Ye Meiying , Wang Xiaodong , Xu Yousheng
Published: May 2009

In this article, particle swarm optimization (PSO) was applied to extract the solar cell parameters from illuminated current-voltage characteristics. The performance of the PSO was compared with the genetic algorithms (GAs) for the single and double diode models. Based on synthetic and experimental current-voltage data, it has been confirmed that the proposed method can obtain higher parameter precision with better computational efficiency than the GA method. Compared with conventional gradient-based methods, even without a good initial guess, the PSO method can obtain the parameters of solar cells as close as possible to the practical parameters only based on a broad range specified for each of the parameters.
Low temperature formation and evolution of a 10 nm amorphous Ni–Si layer on [001] silicon studied by in situ transmission electron microscopy
Authors: Alberti Alessandra , Bongiorno Corrado , Mocuta Cristian , Metzger Till , Spinella Corrado , Rimini Emanuele
Published: May 2009

We investigated low temperature formation of a 10 nm thick amorphous Ni–Si layer after room temperature deposition of a 7 nm Ni layer on [001] Si, by in situ transmission electron microscopy analyses. Instead of a conventional time sequence of phases or an immediate formation of NiSi2 domains, annealing at 220 °C promotes Ni diffusion through a thin interfacial amorphous layer, formed during deposition, into the Si lattice until the entire supply of pure Ni atoms is consumed. High concentration nickel diffusion induces a crystalline-to-amorphous transformation of the original silicon lattice. Further increasing the temperature, in the range between 300 and 350 °C, causes crystalline NiSi2 domains to nucleate and grow within the amorphous matrix.
Infrared absorption of gaseous c-ClCOOH and t-ClCOOH recorded with a step-scan Fourier-transform spectrometer
Authors: Chu Li-Kang , Lee Yuan-Pern
Published: May 2009

Two conformers of ClCOOH were produced upon irradiation at 355 nm of a gaseous flowing mixture of Cl2, HCOOH, and N2. A step-scan Fourier-transform infrared spectrometer coupled with a multipass absorption cell was utilized to monitor the transient spectra of ClCOOH. Absorption bands with origins at 1808.0 and 1328.5 cm−1 are attributed to the C=O stretching and COH bending modes of t-ClCOOH, respectively; those at 1883.0 and 1284.9 cm−1 are assigned as the C=O stretching and COH bending modes of c-ClCOOH, respectively. These observed vibrational wavenumbers agree with corresponding values for t-ClCOOH and c-ClCOOH predicted with B3LYP/aug-cc-pVTZ density-functional theory and the observed rotational contours agree satisfactorily with simulated bands based on predicted rotational parameters. The observed relative intensities indicate that t-ClCOOH is more stable than c-ClCOOH by ∼3 kJ mol−1. A simple kinetic model is employed to account for the production and decay of ClCOOH.
Importance of plasma response to nonaxisymmetric perturbations in tokamaks
Authors: Park Jong-kyu , Boozer Allen H. , Menard Jonathan E. , Garofalo Andrea M. , Schaffer Michael J. , Hawryluk Richard J. , Kaye Stanley M. , Gerhardt Stefan P. , Sabbagh Steve A. ,   NSTX Team
Published: May 2009

Tokamaks are sensitive to deviations from axisymmetry as small as δB/B0∼10−4. These nonaxisymmetric perturbations greatly modify plasma confinement and performance by either destroying magnetic surfaces with subsequent locking or deforming magnetic surfaces with associated nonambipolar transport. The Ideal Perturbed Equilibrium Code (IPEC) calculates ideal perturbed equilibria and provides important basis for understanding the sensitivity of tokamak plasmas to perturbations. IPEC calculations indicate that the ideal plasma response, or equivalently the effect by ideally perturbed plasma currents, is essential to explain locking experiments on National Spherical Torus eXperiment (NSTX) and DIII-D. The ideal plasma response is also important for neoclassical toroidal viscosity (NTV) in nonambipolar transport. The consistency between NTV theory and magnetic braking experiments on NSTX and DIII-D can be improved when the variation in the field strength in IPEC is coupled with generalized NTV theory. These plasma response effects will be compared with the previous vacuum superpositions to illustrate the importance. However, plasma response based on ideal perturbed equilibria is still not sufficiently accurate to predict the details of NTV transport and can be inconsistent when currents associated with a toroidal torque become comparable to ideal perturbed currents.
Effect of ion and ion-beam mass ratio on the formation of ion-acoustic solitons in magnetized plasma in the presence of electron inertia
Authors: Kalita B. C. , Barman S. N.
Published: May 2009

The propagation of ion-acoustic solitary waves in magnetized plasma with cold ions and ion-beams together with electron inertia has been investigated theoretically through the Korteweg–de Vries equation. Subject to the drift velocity of the ion beam, the existence of compressive solitons is found to become extinct as α (=cold ion mass/ion-beam mass) tends to 0.01 when γ=0.985 (γ is the beam velocity/phase velocity). Interestingly, a transitional direction of propagation of solitary waves has been unearthed for change over, from compressive solitons to rarefactive solitons based on α and συ(=cosine of the angle θ made by the wave propagation direction ξ with the direction of the magnetic field) for fixed Q(=electron mass/ion mass). Further, the direction of propagation of ion-acoustic waves is found to be the deterministic factor to admit compressive or rarefactive solitons subject to beam outsource.
Point defects in CaF2 and CeO2 investigated by the periodic electrostatic embedded cluster method
Authors: Burow Asbjörn M. , Sierka Marek , Döbler Jens , Sauer Joachim
Published: May 2009

A periodic electrostatic embedding scheme is presented that uses the periodic fast multipole method. The convergence of properties with increasing cluster size is examined for cluster models of calcium fluoride. Properties investigated are the electron density, the density of states, the electronic excitation of color centers, and energies of defect formation. The embedded cluster method is applied to CeO2 and oxygen vacancies in bulk CeO2 as well as on its (111) surface. Employing the PBE0 functional, vacancy formation energies of 3.0 and 3.3 eV have been obtained for the bulk and the (111) surface, respectively. Formation of subsurface defects requires 3.33 eV (singlet open shell). The localization of the electrons left behind on defect formation in Ce 4f states is discussed. Occupied Ce 4f states are well localized on nearest Ce atoms for surface and subsurface vacancies. Localization apart from the vacancy was obtained for bulk. The total CPU time spent on the embedding part did not exceed 30 s on a single CPU even if 8000 basis functions of the cluster are involved.
Fragment analysis of single-molecule conduction
Authors: Fowler P. W. , Pickup B. T. , Todorova T. Z. , Pisanski T.
Published: May 2009

In the tight-binding source and sink potential model of transmission in single-molecule π-conjugated conductors, vanishing of the opacity polynomial defines a necessary condition for zero conductance at a given energy. Theorems are given for calculating opacity polynomials of composite devices in terms of opacity and characteristic polynomials of the subunits. These relations rationalize the positions and shapes of zeros in transmission curves for devices consisting of molecules with side chains or of units assembled in series and take an especially simple form for polymeric molecules with identical repeat units.
A versatile apparatus for time-resolved photoemission spectroscopy via femtosecond pump-probe experiments
Authors: Carpene E. , Mancini E. , Dallera C. , Ghiringhelli G. , Manzoni C. , Cerullo G. , De Silvestri S.
Published: May 2009

A laser-based system for time-resolved photoemission spectroscopy using up to 6.2 eV photons is presented. The versatility of the laser source permits several combinations of pump and probe photon energies with pulse durations of 50–100 fs. The ultrahigh vacuum system, equipped with evaporators, a low energy electron diffraction system and an Auger spectrometer, grants the possibility to grow and characterize thin films in situ. The electron energy analyzer is a time-of-flight spectrometer with a multianode detector allowing high count rates. The performance of the whole experimental setup is investigated on Cu(100), Cu(111), and Ag(111) single crystals.
Analysis and calibration of absorptive images of Bose–Einstein condensate at nonzero temperatures
Authors: Szczepkowski J. , Gartman R. , Witkowski M. , Tracewski L. , Zawada M. , Gawlik W.
Published: May 2009

We describe the method allowing quantitative interpretation of absorptive images of mixtures of Bose–Einstein condensate and thermal atoms which reduces possible systematic errors associated with evaluation of the contribution of each fraction and eliminates arbitrariness of most of the previous approaches. By using known temperature dependence of the BEC fraction, the analysis allows precise calibration of the fitting results. The developed method is verified in two different measurements and compares well with theoretical calculations and with measurements performed by another group.
Transient absorption and higher-order nonlinearities in silver nanoplatelets
Authors: Jayabalan J. , Singh Asha , Chari Rama , Khan Salahuddin , Srivastava Himanshu , Oak S. M.
Published: May 2009

We show that the imaginary parts of higher-order optical nonlinearities and their decay times can be determined by a time-intensity domain analysis of the conventional transient absorption data. Using this method we have measured the values and decay times of third, fifth and seventh-order nonlinear susceptibilities of silver nanoplatelets in water. The origin of these higher-order nonlinearities is explained using a two-temperature model.
Strongly driven crystallization processes in a metallic glass
Authors: LaGrange Thomas , Grummon David S. , Reed Bryan W. , Browning Nigel D. , King Wayne E. , Campbell Geoffrey H.
Published: May 2009

The crystallization of amorphous NiTi thin films was studied in situ using pulsed laser heating in a dynamic transmission electron microscope. A single pulse can crystallize small areas of the film within 2 μs. The crystallized volume fraction and morphology depend strongly on the laser energy, the laser spatial profile, and the heat transport in the film. As compared to slower furnace and continuous wave laser annealing, pulsed laser heating produces a dramatically different microstructure. Higher than expected crystallization rates were observed under pulsed irradiation that do not correlate with kinetic data obtained from the slow-heating crystallization experiments.
General trend for adsorbate-induced segregation of subsurface metal atoms in bimetallic surfaces
Authors: Menning Carl A. , Chen Jingguang G.
Published: May 2009

It is well known that the unique chemical properties of transition metal alloys depend on the configuration of metal atoms of the bimetallic surfaces. Using density functional theory calculations, the thermodynamic potential for segregation of an admetal from the subsurface to surface configuration is shown to correlate linearly with the difference in occupied d-band center, Δεd, between these two configurations for a wide range of bimetallic systems. The thermodynamic potential for segregation is also shown to increase with the Pauling electronegativity for several adsorbates, including atomic H, O, C, N, S, and Se. A generalized equation is provided to predict the stable surface configuration for the bimetallic systems with different adsorbates.
Toward real-time charged-particle image reconstruction using polar onion-peeling
Authors: Roberts G. M. , Nixon J. L. , Lecointre J. , Wrede E. , Verlet J. R. R.
Published: May 2009

A method to reconstruct full three-dimensional photofragment distributions from their two-dimensional (2D) projection onto a detection plane is presented, for processes in which the expanding Newton sphere has cylindrical symmetry around an axis parallel to the projection plane. The method is based on: (1) onion-peeling in polar coordinates [Zhao et al., Rev. Sci. Instrum. 73, 3044 (2002)] in which the contribution to the 2D projection from events outside the plane bisecting the Newton sphere are subtracted in polar coordinates at incrementally decreasing radii; and (2) ideas borrowed from the basis set expansion (pBASEX) method in polar coordinates [Garcia et al., Rev. Sci. Instrum. 75, 4989 (2004)], which we use to generate 2D projections at each incremental radius for the subtraction. Our method is as good as the pBASEX method in terms of accuracy, is devoid of centerline noise common to reconstruction methods employing Cartesian coordinates; and it is computationally cheap allowing images to be reconstructed as they are being acquired in a typical imaging experiment.
Continuum description of the interfacial layer of nematic liquid crystals in contact with solid surfaces
Authors: Barbero Giovanni , Dahl Ingolf , Komitov Lachezar
Published: May 2009

We investigate when it is possible to introduce surface physical parameters characterizing the nematic/substrate interface. The analysis is performed by solving the problem assuming that the presence of the surface introduces a spatial variation, mainly localized close to the limiting surfaces, of the bulk properties of the nematic (delocalized model). The results of the calculation are compared to the prediction of a model in which the presence of the surface is taken into account by means of new physical parameters, localized to the surface (localized model). We show that if the viscous dissipative effects or the surface alignment effects are considered, the two models predict the same relaxation times and the same threshold for the Freedericksz transition is obtained. From these results we deduce that the localized models are equivalent to the delocalized ones. A continuum description of the interfacial layer of nematic liquid crystals in contact with solid surface in terms of surface properties is then correct, which makes the solution of this kind of problems simpler. Also a softening of the elastic constants near the surfaces can be represented by a localized surface energy term.
Rapid on-chip genetic detection microfluidic platform for real world applications
Authors: Senapati Satyajyoti , Mahon Andrew R. , Gordon Jason , Nowak Carsten , Sengupta Shramik , Powell Thomas H. Q. , Feder Jeffrey , Lodge David M. , Chang Hsueh-Chia
Published: May 2009

The development of genetic detection protocols for field applications is an important aspect of modern medical diagnostic technology and environmental monitoring. In this paper, we report a rapid, portable, and inexpensive DNA hybridization technique using a bead-based microfluidic platform that functions by passing fluorescently labeled target DNA through a chamber packed with functionalized beads within a microfluidic channel. DNA hybridization is then assessed using a digital camera attached to a Clare Chemical DR-45M dark reader non-UV transilluminator that uses visible light as an excitation source and a blue and amber filter to reveal fluorescence. This microfluidic approach significantly enhances hybridization by reducing the diffusion time between target DNA and the silica surface. The use of probe-functionalized beads as solid support also enhances the sensitivity and limit of detection due to a larger surface area per unit volume. This platform could be adapted for use in medical applications and environmental monitoring, including the detection of harmful organisms in the ballast water of ships.
Band structure for a bend-core liquid crystal fiber
Authors: Palomares Laura O. , Castro-Garay P. , Reyes J. Adrian
Published: May 2009

We study the propagation of optical fields in a cylindrical fiber of a banana bend-core liquid crystal formed by uniformly tilted coaxial cylindrical smectic layers, surrounded by vacuum. By solving numerically Maxwell’s equations, we find the band structure in both uniaxial and biaxial limits. For the biaxial case, we show that the backward propagation is restricted to certain narrow frequency band gaps, whereas for the forward one the fiber behaves similarly to a standard waveguide. We also find that the fiber modes are elliptically polarized slowly leaky modes whose attenuation coefficients are damped oscillating functions of frequency.