bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for arrested succession within a tropical forest fragment in Singapore
Authors: Goldsmith Gregory R. , Comita Liza S. , Chua Siew Chin
Published: March 2011

Secondary forests occupy a growing portion of the tropical landscape mosaic due to regeneration on abandoned pastures and other disturbed sites (Asneret al. 2009). Tropical secondary forests and degraded old-growth forests now account for more than half of the world's tropical forests (Chazdon 2003), and provide critical ecosystem services (Brown & Lugo 1990, Guariguata & Ostertag 2001).
Answering Queries about Access to Law Court Documents
Authors: Clinch Peter
Published: March 2011

This article by Dr Peter Clinch gives details of where to find not just law reports but also other documents relating to cases. It covers a wide range of courts, from the High Court through to Coroners Courts and Administrative tribunals
Preserving the Legal Past: the Work of the British Records Association
Authors: Smith Anthony
Published: March 2011

This article by Dr Anthony Smith describes how the British Records Association can help legal information professionals and the legal profession generally to conserve old legal records of both law firms themselves and of their clients. He also describes the activities and publications of the Association.
Everything You Always Wanted to Know About CRIV but Were Afraid to Ask
Authors: Myers Rob
Published: March 2011

The Committee on Relations with Information Vendors (CRIV) is one of thirty-seven committees organized under the American Association of Law Libraries (AALL). The purpose of CRIV is to facilitate communications between information vendors and the members of the Association by monitoring complaints and providing constructive suggestions to vendors of legal information. The Committee also serves to educate AALL member librarians on helpful ways to communicate with information vendors. This article by Rob Myers provides a brief history of CRIV, outlines the Committee's organisation and structure, discusses its activities in pursuit of its charge, and outlines its goals for the immediate future.
Working the Net
Authors: Breslin Jas
Published: March 2011

Jas Breslin gives a brief overview of how email discussion forums can be used by information professionals and information providers to enrich and enhance relationships.
The FLAG Database – 2010 Update
Authors: Clinch Peter
Published: March 2011

This report by Peter Clinch describes the procedures followed and the results obtained through updating the FLAG (Foreign Law Guide) database1, which took place during the Spring and Autumn 2010.
Cross Currents: Charting our Future … The Second Joint ALLA/NZLLA Conference, 2010
Authors: Shakespeare Rosemary
Published: March 2011

Rosemary Shakespeare attended the 2nd Joint ALLA/NZLLA Conference. Her interest was primarily in those sessions with a worldwide focus, rather than specifically the Australasia region and this article is about digitisation projects, with particular emphasis on the Law Library Microform Consortium's work.
Examples of non-commutative Hodge structures
Authors: Hertling Claus , Sabbah Claude
Published: March 2011

We show that, under a condition called minimality, if the Stokes matrix of a connection with a pole of order two and no ramification gives rise, when added to its adjoint, to a positive semidefinite Hermitian form, then the associated integrable twistor structure (or TERP structure, or noncommutative Hodge structure) is pure and polarized.
Farmer perceptions of sustainable agriculture practices and drought risk reduction in Nebraska, USA
Authors: Knutson C.L. , Haigh T. , Hayes M.J. , Widhalm M. , Nothwehr J. , Kleinschmidt M. , Graf L.
Published: March 2011

Social factors, such as farming methods, have an impact on farm vulnerability to drought, but have received little research or policy attention. Some researchers and advocates have argued that sustainable agriculture systems are less vulnerable to climate risk than conventional systems because sustainable agriculture requires producers to have skills promoting adaptability. In this paper, we investigate producers’ perceptions on the use of sustainable agriculture in reducing drought risk, and what they believe would help them better adapt to drought. We surveyed and interviewed farmer members of two sustainable agriculture organizations in Nebraska, USA, during a multi-year drought period from 1999 to 2007. Producers reported implementing a range of practices, such as organic soil building techniques, reduced tillage, targeted crop selection and diversification of crop and livestock production systems, to reduce their drought vulnerability. Although some practices were implemented specifically to reduce drought risk, producers felt that the practices they implemented as part of their normal operation were largely responsible for reducing their risk. Respondents held mixed views on the effects of insurance and farm programs on their drought management decisions. Finally, producers indicated that their ability to adapt to drought is limited by a number of barriers, especially a lack of capital and the need to respond to markets and maximize production to maintain cash flows.
International law and armed non-state actors in Afghanistan
Authors: Bellal Annyssa , Giacca Gilles , Casey-Maslen Stuart
Published: March 2011

An effective legal regime governing the actions of armed non-state actors in Afghanistan should encompass not only international humanitarian law but also international human rights law. While the applicability of Common Article 3 of the 1949 Geneva Conventions to the conflict is not controversial, how and to what extent Additional Protocol II applies is more difficult to assess, in particular in relation to the various armed actors operating in the country. The applicability of international human rights law to armed non-state actors – considered by the authors as important, particularly in Afghanistan – remains highly controversial. Nevertheless, its applicability to such actors exercising control over a population is slowly becoming more accepted. In addition, violations of peremptory norms of international law can also directly engage the legal responsibility of such groups.
A short‐duration pulse of ductile normal shear on the outer South Tibetan detachment in Bhutan: Alternating channel flow and critical taper mechanics of the eastern Himalaya
Authors: Chambers Jennifer , Parrish Randall , Argles Tom , Harris Nigel , Horstwood Matthew
Published: March 2011

In easternmost Bhutan the South Tibetan detachment (STD) is a ductile shear zone that juxtaposes the Radi (or Sakteng) klippe of the Tethyan Sedimentary Series from underlying high‐grade Greater Himalayan rocks. In situ LA‐ICPMS U‐Th‐Pb analysis of metamorphic monazite from the immediate footwall and hanging wall of the STD within the shear zone at the base of the klippe, constrains north vergent normal shear to between 25 and 20 Ma. Coeval thrusting on the Main Central Thrust during this time supports a phase of channel flow–viscous wedge model activity, lasting only ∼3 Ma. Geochronologic data from the eastern Himalaya indicate alternating mechanisms for extrusion of the metamorphic core of the orogen from the Late Oligocene through to the Late Miocene, switching from channel flow–viscous wedge behavior to critical taper–frictional wedge behavior, each phase lasting approximately only 2 to 5 Ma. The tectonic evolution of the eastern Himalaya is comparable to central and western Himalayan tectonics during the Early Miocene, but during the Middle Miocene metamorphism and magmatism in the eastern Himalaya migrated toward the orogenic hinterland, a process not widely documented elsewhere in the Himalaya, thus highlighting the need for an orogenic model in three spatial dimensions.
Protistan microbial observatory in the Cariaco Basin, Caribbean. I. Pyrosequencing vs Sanger insights into species richness
Authors: Edgcomb Virginia , Orsi William , Bunge John , Jeon Sunok , Christen Richard , Leslin Chesley , Holder Mark , Taylor Gordon T , Suarez Paula , Varela Ramon , Epstein Slava
Published: March 2011

Microbial diversity and distribution are topics of intensive research. In two companion papers in this issue, we describe the results of the Cariaco Microbial Observatory (Caribbean Sea, Venezuela). The Basin contains the largest body of marine anoxic water, and presents an opportunity to study protistan communities across biogeochemical gradients. In the first paper, we survey 18S ribosomal RNA (rRNA) gene sequence diversity using both Sanger- and pyrosequencing-based approaches, employing multiple PCR primers, and state-of-the-art statistical analyses to estimate microbial richness missed by the survey. Sampling the Basin at three stations, in two seasons, and at four depths with distinct biogeochemical regimes, we obtained the largest, and arguably the least biased collection of over 6000 nearly full-length protistan rRNA gene sequences from a given oceanographic regime to date, and over 80 000 pyrosequencing tags. These represent all major and many minor protistan taxa, at frequencies globally similar between the two sequence collections. This large data set provided, via the recently developed parametric modeling, the first statistically sound prediction of the total size of protistan richness in a large and varied environment, such as the Cariaco Basin: over 36 000 species, defined as almost full-length 18S rRNA gene sequence clusters sharing over 99% sequence homology. This richness is a small fraction of the grand total of known protists (over 100 000–500 000 species), suggesting a degree of protistan endemism.
Differences in Cardiovascular Disease Risk Factors by Weight History: The Aerobics Center Longitudinal Study
Authors: Truesdale Kimberly P. , Stevens June , Cai Jianwen
Published: March 2011

The objective of this study was to compare cardiovascular disease (CVD) risk factor levels in adults with a history of weight loss to levels in adults who did not lose weight, after both groups subsequently experienced an approximate 1‐year interval of weight maintenance. Extant data from the Aerobics Center Longitudinal Study (ACLS) were used to identify 5,151 adults who were weight maintainers (maintained weight within ±3.0% over two consecutive periods of ∼1 year) or weight‐loss maintainers (lost >3.0– <5.0% or ≥5.0% of body weight in the first interval and maintained that loss in the second interval). Mixed models regression was used to accommodate repeated measures and adjust for gender, age, smoking, cardiorespiratory fitness, decade of clinic visit, interval length, and BMI at the time of risk factor measurement. Coefficients from the model were used to calculate the adjusted risk factor levels in the three groups. Differences in total cholesterol (−3.8 mg/dl, 95% confidence interval: −5.5, −2.0), low‐density lipoprotein (LDL) cholesterol (−3.0 mg/dl, confidence interval: −4.8, −1.1), triglycerides (−6.1 mg/dl, confidence interval: −10.6, −1.7) and diastolic blood pressure (−0.8 mg/dl, confidence interval: −1.4, −0.3) indicated that levels were slightly more favorable in the ≥5.0% weight‐loss maintenance group than weight maintenance group. Levels were similar for glucose, high‐density lipoprotein (HDL) cholesterol and systolic blood pressure. This work indicates that, when adjusted for covariates including current BMI, adults with a history of weight loss may have CVD risk factors to levels as good, or perhaps even better than, those observed in adults who maintain their weight.
Development of dual-probe atomic force microscopy system using optical beam deflection sensors with obliquely incident laser beams
Authors: Tsunemi Eika , Kobayashi Kei , Matsushige Kazumi , Yamada Hirofumi
Published: March 2011

We developed a dual-probe (DP) atomic force microscopy (AFM) system that has two independently controlled probes. The deflection of each cantilever is measured by the optical beam deflection (OBD) method. In order to keep a large space over the two probes for an objective lens with a large numerical aperture, we employed the OBD sensors with obliquely incident laser beams. In this paper, we describe the details of our developed DP-AFM system, including analysis of the sensitivity of the OBD sensor for detection of the cantilever deflection. We also describe a method to eliminate the crosstalk caused by the vertical translation of the cantilever. In addition, we demonstrate simultaneous topographic imaging of a test sample by the two probes and surface potential measurement on an α-sexithiophene (α-6T) thin film by one probe while electrical charges were injected by the other probe.
Note: He puff system for dust detector upgrade
Authors: Rais B. , Skinner C. H. , Roquemore A. L.
Published: March 2011

Local detection of surface dust is needed for the safe operation of next-step magnetic fusion devices such as ITER. An electrostatic dust detector, based on a grid of interlocking circuit traces biased to 50 V, has been developed to detect dust on remote surfaces and was successfully tested for the first time on the National Spherical Torus Experiment. In this note, we report a helium puff system that clears residual dust from this detector and any incident debris or fibers that might cause a permanent short circuit. Two consecutive helium puffs delivered by three 0.45 mm nozzles at an angle of 30º cleared the entire 5 cm × 5 cm surface of the detector.
Optical transition, electron-phonon coupling and fluorescent quenching of La2(MoO4)3:Eu3+ phosphor
Authors: Tian Yue , Chen Baojiu , Hua Ruinian , Sun Jiashi , Cheng Lihong , Zhong Haiyang , Li Xiangping , Zhang Jinsu , Zheng Yanfeng , Yu Tingting , Huang Libo , Yu Hongquan
Published: March 2011

La2(MoO4)3 phosphors with various Eu3+ concentrations were prepared via a facile co-precipitation process. The crystal structure and morphology of the phosphors were characterized by means of XRD and field emission scanning electron microscope. The crystal unit cell parameters a, b, and c for the monoclinic phase La2(MoO4)3 were calculated to be 16.989, 11.927, and 16.086 Å, respectively. The average size of the phosphor particles was estimated to be around 88.5 nm. The Huang–Rhys factor was derived from the phonon sideband spectra to be 0.073. The self-generated quenching process of Eu3+ was explained based on Auzel’s model, and the intrinsic radiative transition lifetime for 5D0 level was confirmed to be 0.99 ms. A new approach for calculating the Judd–Ofelt parameters was developed, meanwhile the Judd–Ofelt parameters Ωλ (λ = 2, 4, 6) of Eu3+ in La2(MoO4)3 phosphors were confirmed to be 10.70 × 10−20, 1.07 × 10−20, and 0.56 × 10−20 cm2, respectively. Finally, the optimal doping concentration for achieving maximum emission intensity was confirmed to be 17 mol. % by analyzing the concentration quenching.
First-principles study of the critical thickness in asymmetric ferroelectric tunnel junctions
Authors: Cai Meng-Qiu , Du Yong , Huang Bo-Yun
Published: March 2011

The absent critical thickness of fully relaxed asymmetric ferroelectric tunnel junctions is investigated by first-principles calculations. The results show that PbTiO3 thin film between Pt and SrRuO3 electrodes can still retain a significant and stable polarization down to thicknesses as small as 0.8 nm, quite unlike the case of symmetric ferroelectric tunnel junctions. We trace this surprising result to the generation of a large electric field by the charge transfer between the electrodes caused by their different electronic environments, which acts against the depolarization field and enhances the ferroelectricity, leading to the reduction, or even complete elimination, for the critical thickness.
A dual analyzer for real-time impedance and noise spectroscopy of nanoscale devices
Authors: Joo Min-Kyu , Kang Pilsoo , Kim Yongha , Kim Gyu-Tae , Kim Sangtae
Published: March 2011

This paper introduces a simple portable dual analyzer which allows real-time ac-impedance measurements and noise spectroscopic analysis simultaneously, employing one or two data acquisition systems together with a low noise current-to-voltage preamplifier. The input signal composed of numerous selected frequencies of sinusoidal voltages with a dc bias was applied to a device under the test (DUT): single walled carbon nanotube field effect transistors (SWCNT-FETs). Each frequency component, ranging from 1 to 46.4 kHz, was successfully mapped to a Nyquist plot using the background of the electrical noise power spectrum. It is, thus, clearly demonstrated that this dual analyzer enables the real-time ac-impedance analysis and the frequency response of the carrier transport in the SWCNT-FETs as a DUT.
Energy enhancement for deuteron beam fast ignition of a precompressed inertial confinement fusion target
Authors: Yang Xiaoling , Miley George H. , Flippo Kirk A. , Hora Heinrich
Published: March 2011

Fast Ignition (FI) is recognized as a potentially promising approach to achieve the high-energy-gain target performance needed for commercial inertial confinement fusion. Here we consider deuteron beam driven FI which provides not only the “hot spot” ignition spark, but also extra “bonus” fusion energy through reactions in the target. In this study, we estimate the impact of the added deposition energy due to the fusion reactions occurring, based on calculations using a modified energy multiplication factor Fc. The deuteron beam energy deposition range and time are also evaluated in order to estimate the desired deuteron initial energy. It is shown that an average of 30% extra energy can be gained from deuterons with 1 MeV initial energy and 12% from deuterons with 3 MeV initial energy. These results indicate that the energy benefit of this approach could be significant, but a much more comprehensive calculation is needed to realize a full 3D design for realistic experimental studies.
Studies on structures of lipid A-monophosphate clusters
Authors: Faunce Chester A. , Reichelt Hendrik , Paradies Henrich H.
Published: March 2011

Single crystalline clusters of lipid A-monophosphate were grown from organic dispersions containing 5–15% (v/v) water at various volume fractions, ϕ, and temperatures. The morphology of the single lipid A-monophosphate crystals was either rhombohedral or hexagonal. The hexagonal crystals were needlelike or cylindrical in shape, with the long dimension parallel to the c axis of the unit cell. The crystalline clusters were studied using electron microscopy and x-ray powder diffraction. Employing molecular location methods following a Rietveld refinement and whole-pattern refinement revealed two monoclinic crystal structures in the space groups P21 and C2, both converged with RF = 0.179. The two monoclinic crystal structures were packing (hydrocarbon chains) and conformational (sugar) polymorphs. Neither of these two structures had been encountered previously. Only intramolecular hydrogen bonding was observed for the polymorphs, which were located between the amide and the carboxyl groups. Another crystalline structure was found in the volume-fraction range 2.00 × 10−3 ≤ ϕ ≤ 2.50 × 10−3, which displayed hexagonal symmetry. The hexagonal symmetry of the self-assembled lipid A-monophosphate crystalline phase might be reconciled with the monoclinic symmetry found at low-volume-fractions. Therefore, lowering the symmetry from cubic, i.e., Ia $\overline 3$3¯d, to rhombohedral R $\overline 3$3¯ m, and finally to the monoclinic space group C2 was acceptable if the lipid A-monophosphate anion was completely orientationally ordered.
Effects of volatile additives in solutions used to prepare polythiophene-based thin-film transistors
Authors: Ichikawa Musubu , Yamamura Kenta , Jeon Hyeon-Gu , Nakajima Miyako , Taniguchi Yoshio
Published: March 2011

We investigate the effects of volatile additives in solutions used to prepare thin-film transistors (TFTs) of regioregular poly(3-hexylthiophene) (P3HT). We use the additives trifluoromethylbenzene (TFMB) and methylcyclohexane (MCH) because they are poor solvents for P3HT. The additives improve the performance of the resulting TFTs when the boiling point (Tb) of the major solvent, carbon tetrachloride, is lower than that of the additive. The maximum mobility is (4.0 ± 0.9) × 10–2 cm2V–1s–1, which is 6.1 times larger than that of TFTs prepared without TFMB or MCH added to the solution; the on/off ratio and the subthreshold slope were also improved. The relative Tb of the solvent and the additive affected the film formation with the amount of TFMB or MCH remaining at the final stage of thin film deposition influencing the precipitation of P3HT aggregates.
Characterizations of Seebeck coefficients and thermoelectric figures of merit for AlInN alloys with various In-contents
Authors: Zhang Jing , Tong Hua , Liu Guangyu , Herbsommer Juan A. , Huang G. S. , Tansu Nelson
Published: March 2011

Thermoelectric properties of AlInN alloys, grown by metalorganic vapor phase epitaxy (MOVPE), with In-contents (x) from 11% up to 21.34% were characterized and analyzed at room temperature. The thermoelectric figure of merit (Z*T) values of the n-Al1−xInxN alloys were measured as high as 0.391 up to 0.532 at T = 300 K. The use of high In-content (x = 21.34%) AlInN alloys leads to significant reduction in thermal conductivity [κ = 1.62 W/(mK)] due to the increased alloy scattering, however, the optimized thermoelectric material was obtained for AlInN alloy with In-content of 17% attributed to its large power factor.
New measurement system for on line in core high-energy neutron flux monitoring in materials testing reactor conditions
Authors: Geslot B. , Vermeeren L. , Filliatre P. , Lopez A. Legrand , Barbot L. , Jammes C. , Bréaud S. , Oriol L. , Villard J.-F.
Published: March 2011

Flux monitoring is of great interest for experimental studies in material testing reactors. Nowadays, only the thermal neutron flux can be monitored on line, e.g., using fission chambers or self-powered neutron detectors. In the framework of the Joint Instrumentation Laboratory between SCK-CEN and CEA, we have developed a fast neutron detector system (FNDS) capable of measuring on line the local high-energy neutron flux in fission reactor core and reflector locations. FNDS is based on fission chambers measurements in Campbelling mode. The system consists of two detectors, one detector being mainly sensitive to fast neutrons and the other one to thermal neutrons. On line data processing uses the CEA depletion code DARWIN in order to disentangle fast and thermal neutrons components, taking into account the isotopic evolution of the fissile deposit. The first results of FNDS experimental test in the BR2 reactor are presented in this paper. Several fission chambers have been irradiated up to a fluence of about 7 × 1020 n/cm2. A good agreement (less than 10% discrepancy) was observed between FNDS fast flux estimation and reference flux measurement.
Evaluation of Turner relaxed state as a model of long-lived ion-trapping structures in plasma focus and Z-pinches
Authors: Auluck S. K. H.
Published: March 2011

Relatively long-lived spheroidal structures coincident with the neutron emission phase have been observed in frozen deuterium fiber Z-pinch and some plasma focus devices. Existence of energetic ion-trapping mechanism in plasma focus has also been inferred from experimental data. It has been conjectured that these are related phenomena. This paper applies Turner’s theory [L. Turner, IEEE Trans. Plasma Sci. 14, 849 (1986)] of relaxation of a Hall magnetofluid to construct a model of these structures and ion-trapping mechanism. Turner's solution modified for a finite-length plasma is used to obtain expressions for the magnetic field, velocity, and equilibrium pressure fields and is shown to represent an entity which is simultaneously a fluid vortex, a force-free magnetic field, a confined finite-pressure plasma, a charged object, and a trapped energetic ion beam. Characteristic features expected from diagnostic experiments are evaluated and shown to resemble experimental observations.
Photodissociation dynamics of D2O via the $\tilde B({}^1A_1)$B̃(A11) electronic state
Authors: Cheng Yuan , Cheng Lina , Guo Qing , Yuan Kaijun , Dai Dongxu , Yang Xueming
Published: March 2011

Photodissociation dynamics of D2O in the $\tilde B({}^1A_1)$B̃(A11) state at different photolysis wavelengths have been investigated using the D-atom Rydberg “tagging” time-of-flight (TOF) technique, in combination with a tunable vacuum ultraviolet photolysis light source. TOF spectra of the D-atom product from the D2O photodissociation in both parallel and perpendicular polarizations have been measured. Product kinetic energy distributions and angular distributions have been derived from these TOF spectra. From these distributions, internal state distributions of the OD product as well as the OD quantum state specific angular anisotropy parameters have been derived. Two product channels governed by distinct dissociation dynamics have been clearly observed in the $\tilde B({}^1A_1)$B̃(A11) state photodissociation: ground electronic state radical product OD(X 2Π) + D and excited electronic state OD(A 2Σ+) + D. The OD(A) + D channel proceeds via adiabatic pathway on the $\tilde B({}^1A_1)$B̃(A11) state surface, producing rovibrational excitation in the OD(A) product, while the OD(X) + D channel is generated through nonadiabatic pathway mainly via conical intersections between the $\tilde B({}^1A_1)$B̃(A11) and the $\tilde X({}^1A_1)$X̃(A11) state surfaces. Due to strong angular force induced by the conical intersections, the OD(X) product is extremely hot in the rotational excitation close to the energy limit (N ∼ 50 for v = 0). However, the vibrational excitation is cold in the OD(X) product with dominant population in the ground vibrational state v = 0. Detailed experimental results at different photolysis wavelengths show that at higher energy the unstable periodic orbit, from which dissociation starts, on the $\tilde B$B̃ state has stronger excitation degree of the OD internal state. The negative angular anisotropy parameters of the OD(A) products suggest that the angular forces in this adiabatic dissociation pathway from these periodic orbits have changed the original angular distribution of the D2O molecule excited by the $\tilde B({}^1A_1)\break \leftarrow \tilde X({}^1A_1)$B̃(A11)←X̃(A11) parallel transition.
Frustrated metastable behavior of magnetic and transport properties in charge ordered La1−xCaxMnO3+δ manganites
Authors: Hussain Shah Wiqar , Mumtaz A.
Published: March 2011

We have studied the effect of metastable, irreversibility induced by repeated thermal cycles on the electric transport and magnetization of polycrystalline samples of La1-xCaxMnO3 (0.48 ≤ x ≤ 0.55) close to charge ordering. With time and thermal cycling (T < 300 K) there is an irreversible transformation of the low-temperature phase from a partially ferromagnetic and metallic to one that is less ferromagnetic and highly resistive for the composition close to charge ordering (x = 0.50 and 0.52). Irrespective of the actual ground state of the compound, the effect of thermal cycling is toward an increase of the amount of the insulating phase. We have observed the magnetic relaxation in the metastable state and also the revival of the metastable state (in a relaxed sample) due to high temperature thermal treatment. We observed changes in the resistivity and magnetization as the revived metastable state is cycled. The time changes in the magnetization are logarithmic in general and activation energies are consistent with those expected for electron transfer between Mn ions. Changes induced by thermal cycling can be inhibited by applying magnetic field. These results suggest that oxygen nonstoichiometry results in mechanical strains in this two-phase system, leading to the development of frustrated metastable states which relax toward the more stable charge-ordered and antiferromagnetic microdomains. Our results also suggest that the growth and coexistence of phases gives rise to microstructural tracks and strain accommodation, producing the observed irreversibility.
Actuators for the generation of highly nonlinear solitary waves
Authors: Ni Xianglei , Rizzo Piervincenzo , Daraio Chiara
Published: March 2011

In this paper we present the design of two actuators for the generation of highly nonlinear solitary waves (HNSWs), which are mechanical waves that can form and travel in highly nonlinear systems. These waves are characterized by a constant spatial wavelength and by a tunable propagation speed, dependent on the wave amplitude. To date, the simplest and widely adopted method to generate HNSWs is by impacting a striker onto a chain of beads of equal size and mass. This operation is conducted manually and it might be impracticable if repetition rates higher than 0.1 Hz are necessary. It is known that the HNSWs’ properties, such as amplitude, duration, and speed can be modified by changing the size or the material of the particles, the velocity of the striker, and/or the precompression on the chain. To address the limitations associated with the manual generation of HNSWs we designed, built, and tested two actuators. The first actuator consists of a chain of particles wrapped by an electromagnet that induces static precompression on the chain. This design allows for the generation of solitary waves with controlled properties. The second actuator consists of a chain surmounted by an electromagnet that lifts and releases a striker. This actuator permits the remote and noncontact generation of solitary waves. The performance of both actuators is evaluated by comparing the experimental HNSWs to theoretical predictions, based on the long wavelength approximation.
Diffusion and drift of graphene flake on graphite surface
Authors: Lebedeva Irina V. , Knizhnik Andrey A. , Popov Andrey M. , Ershova Olga V. , Lozovik Yurii E. , Potapkin Boris V.
Published: March 2011

Diffusion and drift of a graphene flake on a graphite surface are analyzed. A potential energy relief of the graphene flake is computed using ab initio and empirical calculations. Based on the analysis of this relief, different mechanisms of diffusion and drift of the graphene flake on the graphite surface are considered. A new mechanism of diffusion and drift of the flake is proposed. According to the proposed mechanism, rotational transition of the flake from commensurate to incommensurate state takes place with subsequent simultaneous rotation and translational motion until a commensurate state is reached again, and so on. Analytic expressions for the diffusion coefficient and mobility of the flake corresponding to different mechanisms are derived in wide ranges of temperatures and sizes of the flake. The molecular dynamics simulations and estimates based on ab initio and empirical calculations demonstrate that the proposed mechanism can be dominant under certain conditions. The influence of structural defects on the diffusion of the flake is examined on the basis of calculations of the potential energy relief and molecular dynamics simulations. The methods of control over the diffusion and drift of graphene components in nanoelectromechanical systems are discussed. The possibility to experimentally determine the barriers to relative motion of graphene layers based on the study of diffusion of a graphene flake is considered. The results obtained can also be applied to polycyclic aromatic molecules on graphene and should be qualitatively valid for a set of commensurate adsorbate–adsorbent systems.
Detection of a ZnSe secondary phase in coevaporated Cu2ZnSnSe4 thin films
Authors: Redinger Alex , Hönes Katja , Fontané Xavier , Izquierdo-Roca Victor , Saucedo Edgardo , Valle Nathalie , Pérez-Rodríguez Alejandro , Siebentritt Susanne
Published: March 2011

Cu 2 ZnSnSe 4 (CZTSe) thin films are grown by coevaporation. Composition depth profiles reveal that a Zn rich phase is present at the CZTSe/Mo interface. Raman measurements on the as grown films are used to study the near surface region and the CZTSe/Mo interface, after mechanically removing the thin film from the Mo coated glass. These measurements provide direct experimental evidence of the formation of a ZnSe phase at the CZTSe/Mo interface. While the Raman spectra at the surface region are dominated by CZTSe modes, those measured at the CZTSe/Mo interface are dominated by ZnSe and MoSe2 modes.
Envelope molecular-orbital theory of extended systems. I. Electronic states of organic quasilinear nanoheterostructures
Authors: Arce J. C. , Perdomo-Ortiz A. , Zambrano M. L. , Mujica-Martínez C.
Published: March 2011

A conceptually appealing and computationally economical course-grained molecular-orbital (MO) theory for extended quasilinear molecular heterostructures is presented. The formalism, which is based on a straightforward adaptation, by including explicitly the vacuum, of the envelope-function approximation widely employed in solid-state physics leads to a mapping of the three-dimensional single-particle eigenvalue equations into simple one-dimensional hole and electron Schrödinger-like equations with piecewise-constant effective potentials and masses. The eigenfunctions of these equations are envelope MO’s in which the short-wavelength oscillations present in the full MO’s, associated with the atomistic details of the molecular potential, are smoothed out automatically. The approach is illustrated by calculating the envelope MO’s of high-lying occupied and low-lying virtual π states in prototypical nanometric heterostructures constituted by oligomers of polyacetylene and polydiacetylene. Comparison with atomistic electronic-structure calculations reveals that the envelope-MO energies agree very well with the energies of the π MO’s and that the envelope MO’s describe precisely the long-wavelength variations of the π MO’s. This envelope MO theory, which is generalizable to extended systems of any dimensionality, is seen to provide a useful tool for the qualitative interpretation and quantitative prediction of the single-particle quantum states in mesoscopic molecular structures and the design of nanometric molecular devices with tailored energy levels and wavefunctions.
Phase-controlling phononic crystal
Authors: Swinteck N. , Robillard J. -F. , Bringuier S. , Bucay J. , Muralidharan K. , Vasseur J. O. , Runge K. , Deymier P. A.
Published: March 2011

We report on a phononic crystal (PC) consisting of a square array of cylindrical polyvinylchloride inclusions in air that can be used to control the relative phase of two incident acoustic waves with different incident angles. The phase shift between waves propagating through the crystal depends on the angle of incidence of the incoming waves and the PC length. The behavior of the PC is analyzed using the finite-difference-time-domain method. The band structure and equifrequency contours calculated via the plane wave expansion method show that the distinctive phase controlling properties are attributed to noncollinear wave and group velocity vectors in the PC as well as the degree of refraction.
Unzipping and folding of graphene by swift heavy ions
Authors: Akcöltekin S. , Bukowska H. , Peters T. , Osmani O. , Monnet I. , Alzaher I. , d’Etat B. Ban , Lebius H. , Schleberger M.
Published: March 2011

We show that graphene on a dielectric substrate sustains major modifications if irradiated with swift heavy ions under oblique angles. Due to a combination of defect creation in the graphene layer and hillock creation in the substrate, graphene is split and folded along the ion track yielding double layer nanoribbons. The folded parts are up to several 100 nm in length. Our results indicate that the radiation hardness of graphene devices is questionable but also open up a new way of introducing extended low-dimensional defects in a controlled way.
Continuous modulation of signal polarization in an exciton polariton amplifier
Authors: Zhang Chuanyi , Zhang Yongyou , Jin Guojun
Published: March 2011

We study the behavior of polarizations and phases in an exciton polariton amplifier based on a semiconductor microcavity. The parametric amplification is strongly influenced by combining the polarizations and relative phase of the lasers exciting the signal, pump, and idler states. In this way, significantly, the light emitting from the signal state can be manipulated continuously from the left to the right circular polarization or vice versa. This manipulation of the signal polarization can be used to encode information and provide stable source of polarized light in the spin-dependent optoelectronic devices.
Characteristics of the dual-bridge giant magnetoresistance magnetometer
Authors: Jeng Jen-Tzong , Hsu Ting-Yu
Published: March 2011

The responsivity and the field noise characteristics of the giant magnetoresistance (GMR) magnetometer driven by an alternating magnetic field are investigated. The harmonic spectrum of the sensor voltage shows that only the odd harmonics of excitation frequency are sensitive to the external dc field. To cancel out the even harmonics, the dual-bridge GMR magnetometer with the balanced output is proposed. With the dual-bridge configuration, the field-to-voltage transfer coefficient is doubled and the field noise is reduced by a factor of 1.4. The minimum field noise is 7 nT/√Hz at 1 Hz with the ac excitation power of 5.5 mW. The proposed sensor is suitable for the electronic compass application.
Long range energy transfer in conjugated polymer sequential bilayers
Authors: Cury L. A. , Bourdakos K. N. , Dai DeChang , Dias F. B. , Monkman A. P.
Published: March 2011

Steady-state and time-resolved photoluminescence have been used to investigate the optical properties of bilayer and blend films made from poly(9,9-dioctyl-fluorene-2,7-diyl) (PFO) and poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH PPV). Energy transfer has been observed in both systems. From steady-state photoluminescence measurements, the energy transfer was characterized by the effective enhancement of the MEH PPV emission intensity after exciting the donor states. Relatively faster decays for the PFO donor emission have been observed in the blends as well as in the bilayer structures, confirming effective energy transfer in both structures. In contrast to the bilayers, the time decay of the acceptor emission in the blends presents a long decay component, which was assigned to the exciplex formation in these samples. For the blends the acceptor emission is in fact a composition of exciplex and MEH PPV emissions, the later being due to Förster energy transfer from PFO. In the bilayers, the exciplex is not observed and temperature dependence photoluminescence measurements show that exciton migration has no significant contribution to the energy transfer. The efficiency and very long range of the energy transfer in the bilayers is explained assuming a surface–surface interaction geometry where the donor/acceptor distances involved are much longer than the common Förster radius.
Interaction of a Taylor blast wave with isotropic turbulence
Authors: Bhagatwala Ankit , Lele Sanjiva K.
Published: March 2011

Simulations of the Taylor blast wave through a region of compressible isotropic turbulence are carried out. The turbulent fluctuations are either significantly attenuated or unchanged depending on the initial strength of the shock wave. It is shown through Eulerian simulations and Lagrangian tracking of particles that both these effects are primarily related to the vorticity-dilatation term in the vorticity transport equation. The turbulence length scales associated with this problem are defined and the effect on them quantified. Turbulence also distorts the shock, which can lead to substantial local variations in shock strength and asphericity. Transverse vorticity amplification is compared with linear planar shock-turbulence theory. Aspects that distinguish spherical shock-turbulence interaction from the planar case are stressed.
Molecular control of pentacene/ZnO photoinduced charge transfer
Authors: Spalenka Josef W. , Paoprasert Peerasak , Franking Ryan , Hamers Robert J. , Gopalan Padma , Evans Paul G.
Published: March 2011

Photoinduced charge transfer modifies the device properties of illuminated pentacene field effect transistors (FETs) incorporating ZnO quantum dots at the gate insulator/pentacene interface. The transferred charge is trapped on electronic states associated with the ZnO quantum dots, with a steady state population approximately proportional to the rate of organic-inorganic charge transfer. Trapped charge shifts the threshold voltage of the FETs, providing the means to evaluate the rate of organic/inorganic charge transfer and the effects of interface modification. Monolayers of the wide-gap alkane stearic acid and the conjugated oligomer terthiophene attached to the ZnO suppress or permit charge transfer, respectively.
Observation and numerical analysis of plasma parameters in a capillary discharge-produced plasma channel waveguide
Authors: Terauchi Hiromitsu , Bobrova Nadezhda , Sasorov Pavel , Kikuchi Takashi , Sasaki Toru , Higashiguchi Takeshi , Yugami Noboru , Kodama Ryosuke
Published: March 2011

We observed the parameters of the discharge-produced plasma in cylindrical capillary. Plasma parameters of the waveguide were investigated by use of both a Normarski laser interferometer and a hydrogen plasma line spectrum. A space-averaged maximum temperature of 3.3 eV with electron densities of the order of 1017 cm−3 was observed at a discharge time of 150 ns and a maximum discharge current of 200 A. One-dimensional dissipative magnetohydrodynamic (MHD) code was used to analyze the discharge dynamics in the gas-filled capillary discharge waveguide for high-intensity laser pulses. Simulations were performed for the conditions of the experiment. We compared the temporal behavior of the electron temperature and the radial electron density profiles, measured in the experiment with the results of the numerical simulations. They occurred to be in a good agreement. An ultrashort, intense laser pulse was guided by use of this plasma channel.
Initial stages of graphitization on SiC(000-1), as studied by phase atomic force microscopy
Authors: Ferrer F. J. , Moreau E. , Vignaud D. , Deresmes D. , Godey S. , Wallart X.
Published: March 2011

The initial stages of graphitization on 4H- and 6H-SiC (000-1) under ultrahigh vacuum at temperatures of 1125–1175°C have been studied by atomic force microscopy (AFM), X-ray photoemission spectroscopy and reflected high energy electron diffraction. A progressive coverage of the surface by graphene has been observed depending on the time and temperature of annealing. Graphene growth mainly starts from the step edges, although it sometimes nucleates in the middle of a SiC terrace. Comparison of the topographic and phase AFM images shows that the latter are the most efficient for identifying graphene before complete coverage of the surface.
Photochemical reaction of sulfur hexafluoride with water in low-temperature xenon matrices
Authors: Yamada Yasuhiro , Tamura Hiroyuki , Takeda Daisuke
Published: March 2011

Sulfur hexafluoride SF6 is a very stable molecule with which very few reactions with other molecules have been reported. Here, we report a photochemical reaction of SF6 with water molecules using a matrix-isolation technique, where SF6 and H2O were co-condensed in Xe matrices, and the products were observed using infrared spectroscopy. Irradiation at 193 nm from an ArF excimer laser caused the simultaneous decomposition of SF6 and H2O, which resulted in the production of novel species. Infrared spectra and molecular orbital calculations of the species showed that the product was a SF4⋯HF⋯HOF complex, which consists of hydrogen bonds and charge transfer interaction between S and F atoms. The assignment of the species was confirmed by isotope shifts using D and 18O isotope substitutions.
Thin-film transistors based on poly(3,3‴-dialkyl-quarterthiophene) and zinc oxide nanowires with improved ambient stability
Authors: Vieira Sara M. C. , Hsieh Gen-Wen , Unalan Husnu E. , Dag Sefa , Amaratunga Gehan A. J. , Milne William I.
Published: March 2011

The ambient stability of thin-film transistors (TFTs) based on zinc oxide (ZnO) nanowires embedded in poly(3,3‴-dialkyl-quarterthiophene) was monitored through time dependence of electrical characteristics over a period of 16 months. The hybrid-based TFT showed an initial hole mobility in the linear regime of 4.2×10−4 cm2/V s. After 16 months storage in ambient conditions (exposed to air, moisture, and light) the mobility decreased to 2.3×10−5 cm2/V s. Comparatively the organic-based TFT lost total carrier mobility after one month storage making the hybrid-based TFTs more suitable for transistor applications when improved stability combined with structural flexibility are required.
CO2 adsorption on TiO2(110) rutile: Insight from dispersion-corrected density functional theory calculations and scanning tunneling microscopy experiments
Authors: Sorescu Dan C. , Lee Junseok , Al-Saidi Wissam A. , Jordan Kenneth D.
Published: March 2011

Adsorption of CO2 on the rutile(110) surface was investigated using dispersion-corrected density functional theory and scanning tunneling microscopy (STM). On the oxidized surface the CO2 molecules are found to bind most strongly at the five-fold coordinated Ti sites adopting tilted or flat configurations. The presence of bridging oxygen defects introduces two new adsorption structures, the most stable of which involves CO2 molecules bound in tilted configurations at the defect sites. Inclusion of dispersion corrections in the density functional theory calculations leads to large increases in the calculated adsorption energies bringing these quantities into good agreement with experimental data. The STM measurements confirm two of the calculated adsorption configurations.
Communication: Turnover behavior of effective mobility in a tube with periodic entropy potential
Authors: Dagdug Leonardo , Berezhkovskii Alexander M. , Makhnovskii Yurii A. , Zitserman Vladimir Yu. , Bezrukov Sergey M.
Published: March 2011

Using Brownian dynamics simulations, we study the effective mobility and diffusion coefficient of a point particle in a tube formed from identical compartments of varying diameter, as functions of the driving force applied along the tube axis. Our primary focus is on how the driving force dependences of these transport coefficients are modified by the changes in the compartment shape. In addition to monotonically increasing or decreasing behavior of the effective mobility in periodic entropy potentials reported earlier, we now show that the effective mobility can even be nonmonotonic in the driving force.
Communication: Combining non-Boltzmann sampling with free energy perturbation to calculate free energies of hydration of quantum models from a simulation of an approximate model
Authors: Wood Robert H. , Dong Haitao
Published: March 2011

This paper proposes combining non-Boltzmann sampling with free energy perturbation to allow calculations of the free energy of hydration of a solute with both solute–water and water–water interactions with the nearest waters calculated by high-level quantum models. The method involves simulation of an approximate model of all interactions and uses both free energy perturbation and non-Boltzmann sampling to calculate the difference in energy between the approximate and quantum models.
Patterned magnetic traps for magnetophoretic assembly and actuation of microrotor pumps
Authors: Henighan T. , Giglio D. , Chen A. , Vieira G. , Sooryakumar R.
Published: March 2011

We demonstrate a microscopic magnetic rotor pump for fluidic channels whose components are assembled in situ and powered by weak external magnetic fields (<150 Oe). A platform of patterned Permalloy microdisks and microcavities provided for the transport, trapping, and rotation of the superparamagnetic spherical microrotors. Parallel actuation of several rotors without direct physical link to external energy sources, tunable rotation speeds, and reversible drive torques offers significant advantages over macroscopic techniques to control flow within microfluidic devices. The effectiveness of trapping and transporting magnetic nanoparticles by the disks illustrate scalability to smaller, submicrometer sized devices.