bluuebunny/crossref_metadata_2025 huggingface dataset:
Turning the Other Cheek to Terrorism: Reflections on the Contemporary Significance of Leo Tolstoy's Exegesis of the Sermon on the Mount
Authors: Christoyannopoulos Alexandre J. M. E.
Published: March 2008

The “war on terror” has brought to the fore the old debate on the role of religion in politics and international relations, a question on which Tolstoy wrote extensively during the latter part of his life. He considered Jesus to have clearly spelt out some rational moral and political rules for conduct, the most important of which was non-resistance to evil. For Tolstoy, Jesus' instructions not to resist evil, to love one's enemies and not to judge one another together imply that a sincere Christian would denounce any form of violence and warfare, and would strive to respond to (whatever gets defined as) evil with love, not force. In today's “war on terror,” therefore, Tolstoy would lament both sides' readiness to use violence to reach their aims; and he would call for Christians in particular to courageously enact the rational wisdom contained in Jesus' Sermon on the Mount. Tolstoy's exegesis of Christianity may be too literal and too rationalistic, and may lead to an exceedingly utopian political vision; but it articulates a refreshingly peaceful method for religion to shape politics, one that can moreover and paradoxically be related to by non-Christians precisely because of its alleged grounding in reason.
Questionnaire Response Latencies: Implications for Personality Assessment and Self-Schema Theory
Authors: Neubauer Aljoscha C. , Malle Bertram F.
Published: March 2008

We investigated whether the speed of responding to personality questionnaires affects the psychometric quality of the resulting questionnaire scores. Austrian adolescents (n = 106) completed Eysenck's Personality Inventory in a computerized version, which assessed single-item response latencies and the trait levels for neuroticism (N) and extraversion (E). We examined, first, the impact of questionnaire response instructions (speeded versus unspeeded) on test-retest reliability (7 weeks apart) and validity (self-peer agreement). A speeded instruction shortened response latencies, as expected, and made questionnaire scores more reliable (but not more valid). Second, we examined individual differences in habitual response speed. For N, fast responders showed greater validity (but not greater reliability) than slow responders; for E, no such effect was found. We explain these results by means of self-schemata, which appear to moderate the validity of personality assessments, but may do so differently for different traits.
Individuation and the Five Factor Model of Personality Traits1
Authors: Barbaranelli Claudio , Caprara Gian Vittorio , Maslach Christina
Published: March 2008

Two studies have been conducted respectively to examine the validity of the Italian version of the Individuation scale ( Maslach, Stapp & Santee, 1985 ), and to investigate individuation within the frame of the Five Factor Model of personality (FFM). The Italian version of the scale showed psychometric characteristics fully comparable to those of the American normative sample. Although Italians scored lower, on average, than Americans in their willingness to individuate themselves, this effect was due largely to the lower scores of Italian women, rather than men. Individuation appeared to correlate with Extraversion and Openness to Experience in both the Italian and American samples.
In‐stream geomorphic structures as drivers of hyporheic exchange
Authors: Hester Erich T. , Doyle Martin W.
Published: March 2008

Common in‐stream geomorphic structures such as debris dams and steps can drive hyporheic exchange in streams. Exchange is important for ecological stream function, and restoring function is a goal of many stream restoration projects, yet the connection between in‐stream geomorphic form, hydrogeologic setting, and hyporheic exchange remains inadequately characterized. We used the models HEC‐RAS, MODFLOW, and MODPATH to simulate coupled surface and subsurface hydraulics in a gaining stream containing a single in‐stream geomorphic structure and to systematically evaluate the impact of fundamental characteristics of the structure and its hydrogeologic setting on induced exchange. We also conducted a field study to support model results. Model results indicated that structure size, background groundwater discharge rate, and sediment hydraulic conductivity are the most important factors determining the magnitude of induced hyporheic exchange, followed by geomorphic structure type, depth to bedrock, and channel slope. Model results indicated channel‐spanning structures were more effective at driving hyporheic flow than were partially spanning structures, and weirs were more effective than were steps. Across most structure types, downwelling flux rate increased linearly with structure size, yet hyporheic residence time exhibited nonlinear behavior, increasing quickly with size at low structure sizes and declining thereafter. Important trends in model results were observed at the field site and also interpreted using simple hydraulic theory, thereby supporting the modeling approach and clarifying underlying processes.
Logarithmic bred vectors. A new ensemble method with adjustable spread and calibration time
Authors: Primo C. , Rodríguez M. A. , Gutiérrez J. M.
Published: March 2008

The breeding method is a conceptually simple and computationally cheap ensemble generation technique. Bred vectors (BV) are dynamically obtained from the nonlinear model and correspond to the spatial structures with fast‐growing fluctuations at each time. These vectors have a characteristic localized spatial structure, with only a small number of significant values corresponding to the leading fluctuation areas. The temporal and spatial growth of the BV interacts making the spatial structure a key factor of the dynamics. In this paper we introduce a new breeding technique, Logarithmic Bred Vectors (LBV), which allows growing vectors with tuneable spatial structure, more (or less) localized. This yields ensembles with different spatiotemporal dynamics (different spread, etc.). This is done by introducing a new parameter (the geometrical mean) which controls the spatial correlation of the bred vectors, from uncorrelated vectors similar to random perturbations, to fully correlated and localized vectors similar to standard bred vectors. The new method increases the diversity of the ensemble and allows the spread to grow faster preserving the model performance in terms of the root mean square error. Consequently, the ensembles can be calibrated for a desired lead time (for instance a shorter forecast range). The concepts are illustrated using a chain of diffusively coupled Lorenz systems. Preliminary evidence of the possible application in operative weather prediction models is also presented.
Vertical variation of particle speed and flux density in aeolian saltation: Measurement and modeling
Authors: Rasmussen Keld R. , Sørensen Michael
Published: March 2008

Particle dynamics in aeolian saltation has been studied in a boundary layer wind tunnel above beds composed of quartz grains having diameters of either 242 μm or 320 μm. The cross section of the tunnel is 600 mm × 900 mm, and its thick boundary layer allows precise estimation of the fluid friction speed. Saltation is modeled using a numerical saltation model, and predicted grain speeds agree fairly well with experimental results obtained from laser‐Doppler anemometry. The use of laser‐Doppler anemometry to study aeolian saltation is thoroughly discussed and some pitfalls are identified. At 80 mm height the ratio between air speed and grain speed is about 1.1 and from there it increases toward the bed so that at 5 mm it is about 2.0. All grain speed profiles converge toward a common value of about 1 m/s at 2−3 mm height. Moreover, the estimated launch velocity distributions depend only very weakly on the friction speed in contrast to what has often been assumed in the literature. Flux density profiles measured with a laser‐Doppler appear to be similar to most other density profiles measured with vertical array compartment traps; that is, two exponential segments will fit data between heights from a few millimeters to 100−200 mm. The experimental flux density profiles are found to agree well with model predictions. Generally, validation rates are low from 30 to 50% except at the highest level of 80 mm, where they approach 80%. When flux density profiles based on the validated data are used to estimate the total mass transport rate results are in fair agreement with measured transport rates except for conditions near threshold where as much as 50% difference is observed.
Probabilistic dynamics of soil nitrate: Coupling of ecohydrological and biogeochemical processes
Authors: Botter G. , Daly E. , Porporato A. , Rodriguez‐Iturbe I. , Rinaldo A.
Published: March 2008

In this paper we analyze the probabilistic dynamics resulting from a simplified model of soil moisture and nitrate mass in relatively arid environments, which accounts for relevant hydrologic and biogeochemical processes and for the random characters of rainfall. The soil nitrate balance includes uptake through transpiration, mineralization, nitrification, and denitrification. To allow an exact mathematical treatment, all nitrate fluxes are assumed to be linear functions of the state variables, namely, soil moisture and nitrate mass stored in soils. The range of applicability of the above simplification is investigated by means of numerical Monte Carlo simulations, showing that the linear approach is meaningful in relatively arid environments, where soil moisture contents are generally low. The moment‐generating function of the joint probability distribution (pdf) of soil nitrate and water content is derived, thereby allowing a linkage between the main features of soil nitrate statistics and the underlying soil, vegetation, rainfall, and biogeochemical parameters. Exact expressions for the moments of the nitrate pdf and for the covariance of soil moisture and nitrate mass are derived. The pdf of the nitrate mass in storage within the soil is shown to be reasonably approximated by a gamma distribution in many cases of practical interest. Interestingly, nitrogen limitation for the ecosystem is shown to be directly related to low values of the product between the rate of rainfall arrivals and the characteristic time of nitrate removal.
New properties of inclusion bodies with implications for biotechnology
Authors: Peternel Špela , Jevševar Simona , Bele Marjan , Gaberc‐Porekar Vladka , Menart Viktor
Published: March 2008

Human G‐CSF (granulocyte colony‐stimulating factor) is a well‐known biopharmaceutical drug being mostly produced by overexpression in Escherichia coli, where it appears in the form of IBs (inclusion bodies). Following our initial findings that properties of inclusion bodies strongly depend on the growth conditions used, especially growth temperature, we compared the characteristics of the G‐CSF inclusion bodies prepared at two different temperatures, namely 42 and 25 °C. IBs formed at higher growth temperatures have properties similar to the usually described IBs, containing mainly denatured recombinant protein and being almost completely insoluble in aqueous solutions containing mild detergents or low concentrations of denaturants. In contrast, when produced at lower growth temperature of 25 °C, IBs show significantly different properties. Such IBs contain a significant proportion of G‐CSF that is easily and directly extractable in the biologically active form, using non‐denaturing solutions, which can be exploited for environmentally friendly biotechnological production. Irrespective of the production temperature, a significant decrease in IB volume was observed when transferring IBs from neutral to acidic (around 4) pH. Irreversible contraction of IBs at low pH was documented at the macro‐ and micro‐scopic level using electron microscopy as a characterization tool. Together with volume decrease, a higher density, and thus decreased solubility, of IBs was observed at low pH, resulting in slower and less efficient extractability of the target protein.
First evidence of the pore-forming properties of a keratin from skin mucus of rainbow trout (Oncorhynchus mykiss, formerly Salmo gairdneri)
Authors: Molle Virginie , Campagna Sylvie , Bessin Yannick , Ebran Nathalie , Saint Nathalie , Molle Gérard
Published: March 2008

The epidermis of fish is covered with a layer of mucus, which contributes to the defence of the species against parasites, bacteria and fungi. We have previously extracted glycoproteins from various mucus samples from fish and have shown that they present pore-forming activities well correlated with strong antibacterial properties [Ebran, Julien, Orange, Saglio, Lemaitre and Molle (2000) Biochim. Biophys. Acta 1467, 271–280]. The present study focuses on the 65 kDa glycoprotein, Tr65, from the rainbow trout (Oncorhynchus mykiss, formerly Salmo gairdneri). Enzymatic digestion of Tr65 yielded a fragment pattern with strong homology with that of trout type II cytokeratin. Sequence analysis of the cDNA clone obtained by PCR confirmed this homology. We thus constructed a plasmid to overproduce the recombinant Tr65. We extracted and purified this recombinant Tr65, using it for multichannel and single-channel experiments in azolectin bilayers. Our results with recombinant Tr65 confirmed the pore-forming properties already shown with native antibacterial Tr65. These findings offer new insights into the function of keratin proteins present in various mucosal surfaces of animals and human beings.
A xyloglucan-specific family 12 glycosyl hydrolase from Aspergillus niger: recombinant expression, purification and characterization
Authors: Master Emma R. , Zheng Yun , Storms Reginald , Tsang Adrian , Powlowski Justin
Published: March 2008

A new GH12 (glycosyl hydrolase 12) family XEG [xyloglucan-specific endo-β-1,4-glucanase (EC 3.2.1.151)] from Aspergillus niger, AnXEG12A, was overexpressed, purified and characterized. Whereas seven xyloglucanases from GH74 and two xyloglucanases from GH5 have been characterized previously, this is only the third characterized example of a GH12 family xyloglucanase. GH12 enzymes are structurally and mechanistically distinct from GH74 enzymes. Although over 100 GH12 sequences are now available, little is known about the structural and biochemical bases of xyloglucan binding and hydrolysis by GH12 enzymes. Comparison of the AnXEG12A cDNA sequence with the genome sequence of A. niger showed the presence of two introns, one in the coding region and the second one in the 333-nt-long 3′-untranslated region of the transcript. The enzyme was expressed recombinantly in A. niger and was readily purified from the culture supernatant. The isolated enzyme appeared to have been processed by a kexin-type protease, which removed a short prosequence. The substrate specificity was restricted to xyloglucan, with cleavage at unbranched glucose in the backbone. The apparent kinetic parameters were similar to those reported for other xyloglucan-degrading endoglucanases. The pH optimum (5.0) and temperature resulting in highest enzyme activity (50–60 °C) were higher than those reported for a GH12 family xyloglucanase from Aspergillus aculeatus, but similar to those of cellulose-specific endoglucanases from the GH12 family. Phylogenetic, sequence and structural comparisons of GH12 family endoglucanases helped to delineate features that appear to be correlated to xyloglucan specificity.
A conserved hydrogen-bond network in the catalytic centre of animal glutaminyl cyclases is critical for catalysis
Authors: Huang Kai-Fa , Wang Yu-Ruei , Chang En-Cheng , Chou Tsung-Lin , Wang Andrew H.-J.
Published: March 2008

QCs (glutaminyl cyclases; glutaminyl-peptide cyclotransferases, EC 2.3.2.5) catalyse N-terminal pyroglutamate formation in numerous bioactive peptides and proteins. The enzymes were reported to be involved in several pathological conditions such as amyloidotic disease, osteoporosis, rheumatoid arthritis and melanoma. The crystal structure of human QC revealed an unusual H-bond (hydrogen-bond) network in the active site, formed by several highly conserved residues (Ser160, Glu201, Asp248, Asp305 and His319), within which Glu201 and Asp248 were found to bind to substrate. In the present study we combined steady-state enzyme kinetic and X-ray structural analyses of 11 single-mutation human QCs to investigate the roles of the H-bond network in catalysis. Our results showed that disrupting one or both of the central H-bonds, i.e., Glu201···Asp305 and Asp248···Asp305, reduced the steady-state catalysis dramatically. The roles of these two COOH···COOH bonds on catalysis could be partly replaced by COOH···water bonds, but not by COOH···CONH2 bonds, reminiscent of the low-barrier Asp···Asp H-bond in the active site of pepsin-like aspartic peptidases. Mutations on Asp305, a residue located at the centre of the H-bond network, raised the Km value of the enzyme by 4.4–19-fold, but decreased the kcat value by 79–2842-fold, indicating that Asp305 primarily plays a catalytic role. In addition, results from mutational studies on Ser160 and His319 suggest that these two residues might help to stabilize the conformations of Asp248 and Asp305 respectively. These data allow us to propose an essential proton transfer between Glu201, Asp305 and Asp248 during the catalysis by animal QCs.
Sperm express a Ca2+-regulated NAADP synthase
Authors: Vasudevan Sridhar R. , Galione Antony , Churchill Grant C.
Published: March 2008

NAADP (nicotinic acid–adenine dinucleotide phosphate), the most potent Ca2+-mobilizing second messenger, is active in a wide range of organisms and cell types. Until now, all NAADP-producing enzymes have been thought to be members of the ADP-ribosyl cyclase family. ADP-ribosyl cyclases exhibit promiscuous substrate selectivity, synthesize a variety of products and are regulated in a limited manner, which may be non-physiological. In the present paper, we report the presence of an enzyme on the surface of sea urchin sperm that exhibits bell-shaped regulation by Ca2+ over a range (EC50 of 10 nM and IC50 of 50 μM) that is physiologically relevant. Uniquely, this surface enzyme possesses complete selectivity for nucleotides with a 2′-phosphate group and exhibits only base-exchange activity without any detectable cyclase activity. Taken together, these findings indicate that this novel enzyme should be considered as the first true NAADP synthase.
A study of electrostatic force nonlinearities in resonant microstructures
Authors: Agarwal Manu , Chandorkar Saurabh A. , Mehta Harsh , Candler Robert N. , Kim Bongsang , Hopcroft Matthew A. , Melamud Renata , Jha Chandra M. , Bahl Gaurav , Yama Gary , Kenny Thomas W. , Murmann Boris
Published: March 2008

This letter investigates the nature of amplitude frequency (A-f) dependence caused by nonlinearities in the parallel plate electrostatic transduced in resonant microstructures. We present analytical and experimental evidences that the A-f nonlinearities are practically always dominated by third order nonlinear terms. For an electrostatically unbalanced system, we show that the bias voltage at which second and third order nonlinearities have equal impact on A-f dependence corresponds to ∼90% of the dc pull-in voltage.
On chip sorting of bacterial cells using sugar-encapsulated magnetic nanoparticles
Authors: Shih Po-Hung , Shiu Jau-Ye , Lin Po-Chiao , Lin Chun-Cheng , Veres Teodor , Chen Peilin
Published: March 2008

Here we describe an integrated microfluidic sorting device, which utilized sugar-encapsulated magnetic nanoparticles to separate a specific strain of bacteria from a mixture solution. In our system, microfluidic devices consisting of two inlets and an electromagnet or a permanent magnet have been constructed by a soft lithography process. The magnetic field generated by either the electromagnet or the permanent magnet was strong enough to attract the bacteria bound to magnetic nanoparticles to cross the stream boundary of the laminar flow. The sorting efficiency was found to depend on both the flow rate and the strength of the magnetic field. The maximum sorting efficiency was measured to be higher than 90% and the selectivity was almost 100%. Since this microfluidic sorting device was able to separate 103 bacterial cells within 1min, it could be used for pathogenic diagnose applications.
Intelligent actuation strategy via image feedbacks for a magnetically actuated autofocusing module in mobile phones
Authors: Chao Paul C.-P. , Chiu Chi-Wei , Liang He-Kai , Kao Nicholas Y.-Y.
Published: March 2008

This study proposes a new miniaturized autofocusing mechanism and an intelligent autofocusing algorithm with digital images as feedbacks. An actuation scheme for autofocusing is fostered via (1) capturing image by a complementary metal-oxide semiconductor sensor array, (2) evaluating the clearness of images by the well-known method of discrete cosine transformation (DCT), and (3) actuating the lens in the designed mechanism to the best-focusing position estimated by a neural network (NN), assisted by a genetic algorithm (GA).
Biomedical applications of small silver clusters
Authors: Pereiro M. , Baldomir D. , Botana J. , Arias J. E. , Warda K. , Wojtczak L.
Published: March 2008

The ground-state properties of small silver clusters Agn (2⩽n⩽24) have been studied using a linear combination of atomic Gaussian-type orbitals within the density functional theory. The results show that the Ag13 clusters, due to their noticeable magnetic moment and their considerable highest occupied-lowest unoccupied molecular orbital gap, are promising candidates for the magnetic applications of nanoparticles. In particular, our study suggests that the silver nanoclusters made out of Ag13 clusters, as building blocks, are suitable for possible future applications in biomedicine, since they could improve some present-day difficulties of magnetic nanoparticles such as toxicity and opsonization.
The Kohn-Sham kinetic energy density as indicator of the electron localization: Atomic shell structure
Authors: Navarrete-López Alejandra M. , Garza Jorge , Vargas Rubicelia
Published: March 2008

In this report, it is shown that the Kohn-Sham (KS) kinetic energy density (KED) contains the average local electrostatic potential (ALEP) and the average local ionization energy (ALIE); the shell structure in atomic systems is presented as one application of the KS-KED. By writing the KS-KED from the KS equations, this quantity was divided in three contributions: orbital, Coulomb, and exchange correlation. By studying several closed and open shell atoms, the shell structure was established by the maxima presented by the Coulomb contribution and the minima in the orbital contribution of the KS-KED. The exchange-correlation contribution to the KS-KED does not show maxima or minima, but this quantity shows bumps where the division between shells is expected. The results obtained in this work were compared with other shell structure indicators such as the electron localization function, the ALEP, the ALIE, and the radial distribution function. The most important result in this work is related to the fact that even when the ALEP and the ALIE functions were built with different arguments to each other, they are contained in the KS-KED. In this way, the KS-KED shows its importance to reveal the electron localization in atomic systems.
Excited states of the water molecule: Analysis of the valence and Rydberg character
Authors: Rubio Mercedes , Serrano-Andrés Luis , Merchán Manuela
Published: March 2008

The excited states of the water molecule have been analyzed by using the extended quantum-chemical multistate CASPT2 method, namely, MS-CASPT2, in conjunction with large one-electron basis sets of atomic natural orbital type. The study includes 13 singlet and triplet excited states, both valence and 3s-, 3p-, and 3d-members of the Rydberg series converging to the lowest ionization potential and the 3s- and 3p-Rydberg members converging to the second low-lying state of the cation, 1A12. The research has been focused on the analysis of the valence or Rydberg character of the low-lying states. The computation of the 1B11 state of water at different geometries indicates that it has a predominant 3s-Rydberg character at the equilibrium geometry of the molecule but it becomes progressively a valence state described mainly by the one-electron 1b1→4a1 promotion, as expected from a textbook of general chemistry, upon elongation of the O–H bonds. The described valence-Rydberg mixing is established to be originated by a molecular orbital (MO) Rydbergization process, as suggested earlier by R. S. Mulliken [Acc. Chem. Res. 9, 7 (1976)]. The same phenomenon occurs also for the 1A21 state whereas a more complex behavior has been determined for the 2A11 state, where both MO Rydbergization and configurational mixing take place. Similar conclusions have been obtained for the triplet states of the molecule.
Resilience of tunneling magnetoresistive heads against electrical overstress
Authors: Guarisco Davide
Published: March 2008

The performance of tunneling magnetoresistive (TuMR) heads under electrical overstress and electrostatic discharge is investigated. Alumina-based TuMR longitudinal heads of the 3.5in. 160Gbytes∕platter class are subjected to controlled stress until a predefined level of relative resistance drop (5%–60%) is achieved. The bias current is then readjusted to achieve a constant bias voltage and dynamic-electric test is performed. It is found that the stressed heads still perform similarly to the unstressed ones up to a resistance drop of ∼30%. Accelerated lifetime test did not detect statistically significant differences in reliability between the stressed and unstressed parts.
New topic of supercritical fluids: Local activity coefficients of supercritical solvent and cosolvent around solute
Authors: Hou Minqiang , Zhang Xiaogang , Han Buxing , Song Jiyuan , Liu Gang , Zhang Zhaofu , Zhang Jianling
Published: March 2008

The study of inhomogeneity in supercritical fluids (SCFs) is of great importance. In this work, we propose the concept of local activity coefficients in supercritical (SC) solutions, which link thermodynamics and inhomogeneity in SC systems. The local activity coefficients of CO2+acetonitrile+phenol blue and CO2+aceticacid+phenol blue systems are investigated at 308.15K in critical region and outside critical region. To do this, the local compositions of CO2+acetonitrile and CO2+acetic acid mixed solvents around phenol blue are first estimated using UV-visible spectroscopy. Then it is considered that there exist bulk phase and local phase around phenol blue in the systems. The activity coefficients of CO2 and the cosolvents (acetonitrile or acetic acid) in bulk phase are calculated using Peng-Robinson equation of state. The local activity coefficients of CO2 and the cosolvents are then calculated on the basis of thermodynamic principles. It is demonstrated that in the critical region the local activity coefficients differ from bulk activity coefficients significantly and are sensitive to pressure. This can explain many unusual phenomena in SC systems in critical region thermodynamically.
Magnetoresistive-based static tester for actuators
Authors: Borme J. , Freitas A. S. , Cardoso S. , Almeida J. M. , Chaves R. C. , Freitas P. P.
Published: March 2008

A static tester for precision actuators is proposed. It is intended to test the functioning of future actuators to be used in hard drive read heads. The design allows a simple fabrication of a nanometer-scale position measurement system that can measure lateral, vertical, and angular displacements. The tester consists of (a) a reference magnetic layer of CoCrPt, (150×100μm2, 600nm thick) and (b) a sequence of four spin-valve sensors. The tested sensors have crossed anisotropies, 6.9% magnetoresistance with a linear response, 0.5%∕mT sensitivity, coercive field less than 0.1mT and resistance of 1680Ω in the parallel state. A noise level of 6nV∕√Hz was measured at thermal background for 0.2mA of applied current. The lateral displacement is measured by the two spin valves in the center. While the magnetic element is passing over these sensors, the measured signal on each of them varies in opposite directions, allowing a precise measurement of the center position. The two outer spin valves are sensitive to the angular orientation of the magnetic element. The relative movements of the spin valves and magnetic element are controlled by computer using piezoelectric crystals and step motors. Since the sensors are measuring the in-plane component of the field, the signal measured decreases rapidly with sensor-to-plane distance. An appropriate range for flight height is about 30μm. Simulations of the signal are in agreement with measurements.
Hyperfine interaction analysis on the multiferroic properties of Fe doped MnWO4 using Mössbauer spectroscopy
Authors: Choi Dong Hyeok , Kim Chul Sung
Published: March 2008

We have investigated the hyperfine interaction and multiferroic properties of Fe doped Mn0.98Fe0.02WO4 polycrystalline powders using Mössbauer spectroscopy. The crystal structures are determined to be monoclinic, space group P2∕c, with the lattice constants a=4.827Å, b=5.756Å, c=4.994Å, and β=88.86°. The Mössbauer spectra below Néel temperature (15K) show the eight-absorbed spectrum lines. It suggests that the electric quadrupole interaction is as large as the magnetic dipole interaction. From the Mössbauer spectra of 4.2K, we have obtained hyperfine field (Hhf) to be 72.1kOe, quadrupole splitting (ΔEQ) to be 2.0mm∕s, and the asymmetry parameter (η) of an electric field gradient (EFG) to be 0. However, η at 9K is 0.30. Also, the observed EFG is asymmetric in the noncollinear spin spiral configuration ranging from 9to13K, indicating that EFG shows the indirect evidence of a spontaneous polarization.
Numerical investigation of domain walls in constrained geometries
Authors: Fangohr Hans , Zimmermann Jürgen P. , Boardman Richard P. , Gonzalez David C. , de Groot Cornelis H.
Published: March 2008

In recent years, magnetic domain wall structures in ferromagnetic nanowires have attracted growing attention, opening paths to develop novel devices which exploit magnetoresistive effects. A reduction of the domain wall length in geometrically constrained areas has been predicted and observed. In this article, we consider a rectangular constriction (width s0, length 2d0) in form of a thin film, attached to a rectangular pad (width s1) on either side. The material considered is Ni (Ms=490kA∕m) with a weak in-plane anisotropy (K1=2000J∕m3). We investigate the dependence of the domain wall length as a function of the constriction geometry. Micromagnetic simulations are used to systematically study the head-to-head domain walls between head-to-head domains (case A) and Néel walls between sidewise domain orientations (case B). We present the resulting domain wall length w as a function of 2d0 and s0 and analyze the magnetization patterns. A reduction of the domain wall length to below 11nm is found (where the corresponding unconstrained domain wall length is 69nm). For constriction lengths above a critical value (case B only), the single 180° domain wall splits into two 90° domain walls.
Magnetic ordering in (Th,U)Co2X2(X=Ge,Si) solid solutions
Authors: Yamamura T. , Li D. X. , Kuznietz M. , Shiokawa Y.
Published: March 2008

Our recent study on ThCo2Ge2 and ThCo2Si2 confirmed that ferromagnetic ordering of Co moments exists in both compounds below Curie temperature TC. This is clearly different from corresponding uranium compounds UCo2Si2 and UCo2Ge2 that show antiferromagnetic transition and no magnetic ordering of Co moments can be detected. In this work, we investigate the magnetic properties of (Th1−xUx)Co2Si2 and (Th1−xUx)Co2Ge2 solid solutions. The experimental results reveal complex magnetism, i.e., mixing of ferromagnetism and antiferromagnetism, in the compounds with middle compositions. For (Th1−xUx)Co2Si2, it is observed that TC is larger than TN, while increasing the uranium content enlarges the paramagnetic Curie temperature from θ<−3000K (x=0.17) to θ>−280K (x>0.69). In contrast, for (Th1−xUx)Co2Ge2, TC is smaller than TN and the paramagnetic Curie temperature reduces with increasing x from θ>0K (x=0) to θ<−400K (x>0.86).
High-field and low-field magnetoresistances of CoFe nanoparticles elaborated by organometallic chemistry
Authors: Tan Reasmey P. , Carrey Julian , Respaud Marc , Desvaux Céline , Renaud Philippe , Chaudret Bruno
Published: March 2008

We report on magnetotransport measurements on CoFe nanoparticles surrounded by an insulating organic layer. Samples were obtained by evaporating a solution of nanoparticles on a patterned substrate. Typical behavior of Coulomb blockade in array of nanoparticles is observed. High- and low-field magnetoresistances have been evidenced. Below 10K, a large high-field magnetoresistance is measured, reaching up to 500%. Its amplitude decreases strongly with increasing voltage. At 1.6K, this high-field magnetoresistance vanishes and an inverse low-field tunneling magnetoresistance is observed.
Epitaxial growth of hcp/fcc Co bilayer films on Al2O3(0001) substrates
Authors: Ohtake Mitsuru , Futamoto Masaaki , Kirino Fumiyoshi , Fujita Norihito , Inaba Nobuyuki
Published: March 2008

Co magnetic bilayer films with different stacking structures of fcc/hcp and hcp/fcc were successfully prepared on Al2O3(0001) substrates employing Au and Cu underlayers. The structure and the magnetic properties of these bilayer films were investigated. The crystal structure and the strain of Co layers are influenced by the underlayer. Q-band ferromagnetic resonance analysis has shown that the Co bilayer films consist magnetically of fcc and hcp phases. It has been shown possible to prepare hcp/fcc Co epitaxial magnetic bilayer films that can be used for patterned media applications.
Factors influencing deformation stability of binary glasses
Authors: Murali P. , Ramamurty U. , Shenoy Vijay B.
Published: March 2008

A possible mechanism of strain accommodation in large deformation of glasses is crystallization; deformation stability is a measure of the resistance of glasses to crystallization. We study the effect of atomic size ratio and atomic stiffness parameter (related to the curvature of the interatomic potential) on deformation stability of binary glasses using molecular static simulations. The deformation stability of a glass is found to increase with increasing atomic size ratio and magnitude of the atomic stiffness, which is proportional to the bulk modulus of the pure crystalline system, as well as the ratio of atomic stiffnesses of constituent atoms. To understand the role of the above parameters on deformation stability, misfit energies of randomly substituted solid solution fcc crystals and glasses are compared for various atomic size ratios and atomic stiffness values. Unlike in fcc solid solution, the misfit energy of binary glasses is found to be insensitive to the atomic size ratio. It is also found that the packing fraction of glasses is insensitive to the atomic size ratio, consistent with the above result. Beyond a critical atomic size ratio, the misfit energy of fcc solid solution exceeds the energy of the glass, thus making the amorphous state completely stable to deformation induced crystallization. Our analysis shows that critical atomic size ratio decreases with increasing atomic stiffness which leads to an increase in the deformation stability of glasses.
Spectral formation in x-ray pulsars and associated identities involving the Laguerre polynomials
Authors: Becker Peter A.
Published: March 2008

The partial differential equation governing the formation of the radiation spectrum in the shocked plasma accreting onto an x-ray pulsar is solved to obtain the associated Green’s function describing the scattering of monochromatic radiation injected into the plasma at a fixed altitude above the star. Collisions between the photons and the infalling electrons cause both the ordered and random components of the plasma energy to be transferred to the radiation, which escapes by diffusing through the walls of the accretion column. The analytical solution for the Green’s function provides important physical insight into the formation of the observed spectra in x-ray pulsars. Interesting mathematical aspects of the problem include the establishment of a new summation formula involving the Laguerre polynomials, based on the calculation of the photon number density via integration of Green’s function.
High-harmonic generation in cavitated plasmas
Authors: Schroeder C. B. , Esarey E. , Comier-Michel E. , Leemans W. P.
Published: March 2008

A method is proposed for producing coherent x-rays via high-harmonic generation using ultraintense lasers interacting with highly stripped ions in cavitated plasmas. This method relies on plasma cavitation by the wake of an intense drive beam (laser or electron beam) to produce an ion cavity. An ultrashort pulse laser propagating in the plasma-electron-free ion cavity generates laser harmonics. The longitudinal electron motion, which inhibits high-harmonic generation at high laser intensities, can be suppressed by the space-charge field in the ion cavity or by using a counterpropagating laser pulse. Periodic suppression of the longitudinal electron motion may also be used to quasi-phase-match. This method enables harmonic generation to be extended to the sub-Å regime.
Evidence of turbulence in laser-induced plasmas
Authors: Roberson S. D. , Akpovo C. , Mezonlin E.-D. , Johnson J. A.
Published: March 2008

By focusing a pulsed single mode Nd:YAG laser, we created low temperature plasmas at various pressures with various target gases and collected spectral light emissions to investigate the possibility of turbulent behavior in these types of plasmas. Characteristic fluctuation frequencies, chaotic dimensions, spectral indices, and turbulent fluctuation energies are determined from fluctuations in these spectral light emissions. Values calculated for the spectral index and the chaotic index for each plasma event are found to be within the known values for other turbulent plasma systems. Thus, turbulent fluctuations on a nanosecond time scale are confirmed in the time evolutions of various singly ionized and neutral spectral lines of various gases.
Correlation of structural and magnetic properties of ferromagnetic Mn-implanted Si1−xGex films
Authors: Ko V. , Teo K. L. , Liew T. , Chong T. C. , Liu T. , Wee A. T. S. , Du A. Y. , Stoffel M. , Schmidt O. G.
Published: March 2008

We present a comprehensive study relating the magnetic properties to structural properties of Mn+-implanted Si1−xGex films as a function of Ge content (x=0–0.5). Ferromagnetic ordering with three critical temperatures, TB∼10–16K, TC1∼650–780K, and TC2∼825–860K, are reported in this material system. Element specific x-ray absorption fine structure results show that the majority of the Mn ions are nonsubstitutional in all samples. The transmission-electron microscopy coupled with z contrast and chemical analysis reveals the presence of Mn-rich nanosized clusters including Mn4Si7 in Si-rich samples and Mn7Ge3 phases in Ge-rich samples. A composition transition occurred at x∼0.2–0.3, where we observe a change in bond lengths and defect structures. Additionally, an enhancement in magnetizations with an increase in both TB and TC1 as well as a conversion from n-type to p-type conduction are also detected.
Hard-x-ray microscopy with Fresnel zone plates reaches 40nm Rayleigh resolution
Authors: Chu Y. S. , Yi J. M. , De Carlo F. , Shen Q. , Lee Wah-Keat , Wu H. J. , Wang C. L. , Wang J. Y. , Liu C. J. , Wang C. H. , Wu S. R. , Chien C. C. , Hwu Y. , Tkachuk A. , Yun W. , Feser M. , Liang K. S. , Yang C. S. , Je J. H. , Margaritondo G.
Published: March 2008

Substantial improvements in the nanofabrication and characteristics of gold Fresnel zone plates yielded unprecedented resolution levels in hard-x-ray microscopy. Tests performed on a variety of specimens with 8–10keV photons demonstrated a first-order lateral resolution below 40nm based on the Rayleigh criterion. Combined with the use of a phase contrast technique, this makes it possible to view features in the 30nm range; good-quality images can be obtained at video rate, down to 50ms∕frame. The important repercussions on materials science, nanotechnology, and the life sciences are discussed.
Thermoelectric and transport properties of n-type Bi2Te3 nanocomposites
Authors: Gothard N. , Ji X. , He J. , Tritt Terry M.
Published: March 2008

A series of Bi2Te3 nanocomposite samples have been prepared by incorporating nanoparticle concentrations of 5–50mol% into a bulk matrix via a mixing process and subsequently hot pressing into highly densified pellets. The electrical resistivity, thermopower, total thermal conductivity, carrier concentration, and Hall mobility have been measured for these composites, and the power factor, lattice thermal conductivity, and figure of merit (ZT) have been calculated. The results are discussed in light of the underlying electrical and thermal transport mechanisms.
Electrode-dependent electrical properties of metal/Nb-doped SrTiO3 junctions
Authors: Park C. , Seo Y. , Jung J. , Kim D.-W.
Published: March 2008

In this study, we discuss the electrical properties of junctions consisting of metal electrodes and Nb-doped SrTiO3(001) single crystals. The junctions formed with large work function metals (Ni, Au, Pd, and Pt) resulted in rectifying transport. A hysteretic feature was observed in the current (I)-voltage (V) and capacitance (C)-V characteristics of these junctions upon polarity reversal. The ideal Schottky–Mott rule could not explain the barrier height obtained from the I-V data, indicating the existence of interface states. Analyses of the C-V data revealed that a low dielectric constant layer existed at the interface. The interface states and layers affected the transport and the related resistance switching characteristics of the junctions.
Excitonic band edges and optical anisotropy of InAs∕InP quantum dot structures
Authors: Mazur Yu. I. , Noda S. , Tarasov G. G. , Dorogan V. G. , Salamo G. J. , Bierwagen O. , Masselink W. T. , Decuir E. A. , Manasreh M. O.
Published: March 2008

Optical transitions in InAs∕InP quantum dot structures are studied and interpreted in terms of heavy- (hh) and light-hole (lh) excitons originating in InAs valence band. Appearance of a step-like absorption and two activation energies in photoluminescence spectra of quantum dots under temperature elevation is described as a transition from the excitonic states to the two-dimensional-like states realized in the InAs∕InP quantum dots. A mixture of hh and lh states determines the anisotropy of the transmission spectra and may result in rotation of the polarization plane for light transmitted through the InAs∕InP quantum dot system.
Differential effects of oligosaccharides on the hydration of simple cations
Authors: Eriksson Mats , Lindhorst Thisbe K. , Hartke Bernd
Published: March 2008

Changed ion hydration properties near surfaces, proteins, and deoxyribose nucleic acid have been reported before in the literature. In the present work, we extend this work to carbohydrates: We have performed classical-mechanical molecular dynamics simulations to study solvation properties of simple cations of biological relevance (Na+,K+,Mg2+,Ca2+) in explicit water, near single and multiple oligosaccharides as glycocalyx models. We find that our oligosaccharides prefer direct contact with K+ over Na+, but that the Na+ contacts are longer lived. These interactions also lead to strong but short-lived changes in oligosaccharide conformations, with oligosaccharides wrapping around K+ with multiple contacts. These findings may have implications for current hypotheses on glycocalyx functions.
Experimental study on quantum confinement effects in silicon nanowire metal-oxide-semiconductor field-effect transistors and single-electron transistors
Authors: Kobayashi Masaharu , Hiramoto Toshiro
Published: March 2008

The effects of quantum confinement on transport properties of silicon nanowire metal-oxide-semiconductor field-effect transistors (FETs) and single-electron transistors are experimentally investigated. By carefully designing the channel width, the nanowire transistors operate as silicon nanowire FETs (SNWFETs) or single-charge transistors. Large quantum confinement in ultranarrow silicon nanowires plays a key role in these devices. We also adopt a special device configuration in which both n-type and p-type operations can be attained in an identical device, and the dependence on the channel direction and charge polarity is intensively investigated. Statistical measurements and band structure calculation reveal that [110] p-channel SNWFETs show smaller threshold voltage variations and [100] single-hole transistors show the largest Coulomb blockade oscillations at room temperature.
The effect of line-tying on tearing modes
Authors: Delzanno Gian Luca , Finn John M.
Published: March 2008

Cylindrical magnetohydrodynamic (MHD) constant-ψ or nonconstant-ψ tearing modes that are linearly unstable with periodic axial boundary conditions are studied in a line-tied cylinder. Examples of these two respective classes of modes, with m=1 and m=2 (m being the azimuthal mode number), are studied. With a suitable MHD equilibrium, the former modes are marginally stable in ideal MHD for periodic axial boundary conditions, and occur as fast tearing modes (resistive kinks) in the presence of resistivity η. The latter modes are stable in ideal MHD for periodic axial boundary conditions, and with resistivity occur as constant-ψ tearing modes, unstable in a range of parameters. In both cases, the results for the line-tied modes show the expected tearing scaling with η for very long plasmas, but the scaling becomes γ∝η for smaller cylinder lengths L. These results are consistent with the following interpretation: For L→∞, the modes have a tearing width characteristic of tearing, leading to characteristic tearing mode growth. As L decreases, the modes develop a geometric width, which increases as L decreases; the γ∝η scaling occurs when L is small enough that the geometric width exceeds the tearing width.
Three-point frequency fluctuation correlation functions of the OH stretch in liquid water
Authors: Garrett-Roe Sean , Hamm Peter
Published: March 2008

Characterizing the dynamics of the OH stretch in isotopically substituted liquid water (HOD in D2O) in terms of three-point frequency fluctuation correlation functions and joint probability densities shows that dynamics during hydrogen bond rearrangements occur primarily along a coordinate which is perpendicular to the spectroscopic coordinate. Molecular dynamics simulations show that three-point correlation functions are sensitive to this motion, unlike two-point correlation functions, and can select sets of trajectories which linger in the area of the transition state. Three-dimensional-infrared correlation spectroscopy could potentially measure these dynamics, though motional narrowing significantly changes the shape of the resulting spectra.
Density functional theory studies of inorganic metallocene multidecker Vn(P6)n+1 (n=1–4) sandwich clusters
Authors: Wang Jinlan , Zhang Xiuyun , Schleyer Paul von Ragué , Chen Zhongfang
Published: March 2008

Motivated by the synthesis of the first entirely inorganic metallocene sandwich ion [η5–Ti–(P5)2]2− [E. Urnezius et al. Science 295, 832 (2002)], we have designed a new inorganic metallocene sandwich [η6-V-(P6)2] and multidecker sandwich clusters up to V4(P6)5 by employing an all electron gradient-corrected density functional theory. The binding energies of the Vn(P6)n+1 complexes increase rapidly from half sandwich to the smallest full sandwich and become gradually afterwards. The highest occupied and lowest unoccupied molecular orbital gap and the vertical ionization energy decrease with increasing cluster size. The Vn(P6)n+1 clusters are nonferromagnetic and prefer the lowest available spin states. The smallest sandwich cluster, V(P6)2, has the high stability and might serve as a building block for one-dimensional inorganic polymers with high stabilities.