bluuebunny/crossref_metadata_2025 huggingface dataset:
Deep ocean heat content is key to estimating Earth's radiation balance
Authors: Kumar Mohi
Published: October 2011

Despite the fact that average temperatures on land have been increasing from year to year, globally averaged surface temperatures from 2000 to 2010 have shown only moderate warming. This is because sea surface temperatures over the past decade have been flat, if not slightly decreasing. In light of this, scientists are curious about whether this reduced rate of surface warming indicates a reduction of the accumulation of heat in the Earth system over the same period. Palmer et al. used multicentury climate model simulations to study the relationships among decadal trends in top‐of‐atmosphere radiation balance (which controls the heat content of the Earth system), ocean heat content, and surface temperature. Consistent with previous studies, they found that all models show large variability in sea surface temperature (SST). This large internal variability in SST could easily “mask the anthropogenic warming signal for a decade or more,” the authors note. By contrast, ocean heat content more closely tracks the radiation budget at the top of the atmosphere, suggesting that measurements of ocean heat to deeper levels would help us monitor climate change more accurately. (Geophysical Research Letters, doi:10.1029/2011GL047835, 2011)
Seasonal variation in the oxygen isotopic composition of different‐sized planktonic foraminifer Neogloboquadrina pachyderma (sinistral) in the northwestern North Pacific and implications for reconstruction of the paleoenvironment
Authors: Kuroyanagi Azumi , Kawahata Hodaka , Nishi Hiroshi
Published: October 2011

The oxygen isotope value (δ18O) of planktonic foraminifer shells is one of the most commonly used proxies to reconstruct the paleoenvironment. Neogloboquadrina pachyderma (sinistral) (N. pachyderma (sin.)) is a dominant foraminifer in subpolar and polar region that is used extensively for high‐latitude paleoreconstruction. The present study examined seasonal variation in δ18O of N. pachyderma (sin.) using sediment trap samples collected over 3.5 years in the northwestern North Pacific Ocean. The vital offset value was about −1‰, which agrees with previous plankton tow studies. Large shell individuals (180–250 μm) secrete their shells in a shallower and warmer environment than small ones (125–180 μm), and the difference in δ18O between shell size showed seasonal variation. Although large individuals calcify at a slower rate with slightly heavier δ18O than small individuals, differences between size classes mainly reflect different habitation in the water column and are related to seasonal changes in stratification. During summer, large individuals would calcify mainly at 25–35 m depth, while small individuals calcify near the pycnocline at ∼45 m. During winter, both size classes calcify at or slightly above the weak pycnocline at 45–65 m. Thus, the shell δ18O could record the oceanographic environment around pycnocline depth, and size‐specific differences in δ18O reflect water column stratification. The annual flux‐weighted δ18O corresponded to non‐flux‐weighted mean δ18O value due to the equal contribution of two flux peaks and differences between size classes also related to the stratification. It suggests that fossil δ18O data could represent the annual mean environment around pycnocline and past stratification.
Cationic State Distributions over Chlorophyll Pairs in Photosystem I and II
Authors: Saito Keisuke , Ishikita Hiroshi
Published: October 2011

Photosystem I (PSI) and II (PSII) possess chlorophyll pairs P~A~/P~B~ and P~D1~/P~D2~, respectively. These chlorophylls are the primary electron donors in the light-induced electron transfer. After the electron transfer, the radical cation remains on these chlorophyll pairs, forming [P~A~/P~B~]^·+^ and [P~D1~/P~D2~]^·+^. The positive charge distributions over the two chlorophylls were reported to be 10/90-50/50 for P~A~^·+^/P~B~^·+^ [1,2] and 70/30-80/20 for P~D1~^·+^/P~D2~^·+^ [3,4]. To clarify the origin of the distributions, we calculated ratios of P~A~^·+^/P~B~^·+^ and P~D1~^·+^/P~D2~^·+^ with a quantum mechanical/molecular mechanical (QM/MM) approach and the redox potentials (E~m~) of monomeric chlorophylls P~A~, P~B~, P~D1~, and P~D2~ with an electrostatic continuum-model approach, using the crystal structures of PSI [5] and PSII [6].1) Our QM/MM calculation reproduced the experimentally measured ratios of P~A~^·+^/P~B~^·+^ [1,2] and P~D1~^·+^/P~D2~^·+^ [3,4]. The calculated ratios were strongly correlated with the calculated E~m~ values. 2) We analyzed residues on puseudo-symmetrical subunit pairs PsaA/PasB and D1/D2 that shifted E~m~ of P~A~, P~B~, P~D1~, and P~D2~ and identified the residue pairs responsible for the P~A~^·+^/P~B~^·+^ and the P~D1~^·+^/P~D2~^·+^ ratios. In PSII, the difference in the electrostatic protein environments between D1 and D2 was significant in determining the P~D1~^·+^/P~D2~^·+^ ratio, whereas geometric differences between P~A~ and P~B~ (P~A~ as the C13^2^ epimer of chlorophyll a and the H-bond pattern) played a role in determining the P~A~^·+^/P~B~^·+^ ratio in PSI.References:[1] A. N. Webber, W. Lupitz, Biochim. Biophys. Acta. 1507 (2001) 61.[2] M. Pantelidou, P. R. Chitnis et al., Biochemistry 43 (2004) 8380.[3] I. H. Davis, P. Heathcote et al., Biochim. Biophys. Acta. 1143 (1993) 183.[4] T. Okubo, T. Tomo et al., Biochemistry 46 (2007) 4390.[5] P. Jordan, P. Fromme et al., Nature 411 (2001) 909.[6] Y. Umena, K. Kawakami et al., Nature 473 (2011) 55.
The Integration of Lexical, Syntactic, and Discourse Features in Bilingual Adolescents' Writing: An Exploratory Approach
Authors: Danzak Robin L.
Published: October 2011

Purpose

The purpose of this study was to assess the bilingual writing of adolescent English language learners (ELLs) using quantitative tools. Linguistic measures were applied to the participants' writing at the lexical, syntactic, and discourse levels, with the goal of comparing outcomes at each of these levels across languages (Spanish/English) and genres (expository/narrative).

Method

Twenty Spanish-speaking ELLs, ages 11–14 years, each produced 8 expository and narrative autobiographical texts. Texts were coded and scored for lexical sophistication, syntactic complexity, and overall text quality. Scores were analyzed using Friedman’s 2-way analysis of variance by ranks (Siegel & Castellan, 1988); resulting ranks were compared across languages and genre topics.

Results

The text topic impacted rank differences at all levels. Performance at the three levels was similar across languages, indicating that participants were emerging writers in both Spanish and English. The impact of genre was generally inconsequential at all levels.

Conclusion

Similar results across languages implied the potential transfer of writing skills. Overall, students appeared to apply a knowledge-telling strategy to writing rather than strategically planning, composing, and revising their writing. Finally, outcomes highlighted the synergistic relationships among linguistic levels in text composition, indicating a need to address the interaction of vocabulary, morphosyntax, and text-level structures in the instruction and assessment of ELL writing.
Do Developmental Communication Disorders Exist in the Signed Modality? Perspectives From Professionals
Authors: Quinto-Pozos David , Forber-Pratt Anjali J. , Singleton Jenny L.
Published: October 2011

Purpose

This study focused on whether developmental communication disorders exist in American Sign Language (ASL) and how they might be characterized. ASL studies is an emerging field; educators and clinicians have minimal access to descriptions of communication disorders of the signed modality. Additionally, there are limited resources for assessing ASL acquisition. This article is designed to raise clinicians' awareness about developmental communication disorders in ASL and categorize types of atypicality that have been witnessed.

Method

We conducted 4 focus groups and one 1-on-1 interview with a total of 22 adults (7 Deaf, 15 hearing) who work at bilingual–bicultural (ASL–English) schools for the Deaf. Experiences of these educators and language professionals were analyzed qualitatively using a combination of grounded theory (Charmaz, 2001; Strauss & Corbin, 1998) and a modified van Kaam approach (Moustakas, 1994).

Results

Participants confirmed observations of children with suspected communication disorders and considered the prevalence, possible etiologies, and psychosocial aspects of such disorders in ASL. They reported frustration at the lack of diagnostic tools for reliable identification and intervention strategies to be used in educational settings.

Conclusion

This work provides us with practitioner accounts proving that developmental communication disorders do exist in ASL. Future reports will describe primary data from signers with atypical language attributes.
Addressing Clinician–Client Mismatch: A Preliminary Intervention Study With a Bilingual Vietnamese–English Preschooler
Authors: Pham Giang , Kohnert Kathryn , Mann Deanine
Published: October 2011

Purpose

This project examined receptive vocabulary treatment outcomes in the two languages of a bilingual preschooler with moderate to severe language impairment.

Method

A series of single-subject experimental designs was used to compare English-only (EO) and bilingual (BI) approaches to receptive vocabulary treatment. The participant, Nam, was a boy age 3;11 (years;months) who was learning Vietnamese as a first language at home and English in his early childhood education program. Treatment was implemented by an EO interventionist using a computer interface and prerecorded audio files in Vietnamese and English. The dependent measure was the percentage of items that were correctly identified in each language.

Results

Combined studies revealed that the BI approach increased Nam’s attention to task and was as effective as the EO approach for increasing his receptive vocabulary in English. Nam made vocabulary gains in both treatment conditions; receptive vocabulary gains were evident in both Vietnamese and English.

Conclusion

This project showed that it is feasible for an EO clinician to promote gains in both the home and school languages of a BI child through creative collaborations with BI colleagues and the use of technology. Replication with additional participants and treatment activities is needed to make further generalizations.
Anomalous resonant frequency changes in piezoelectric microcantilevers by monolayer formation of Au films
Authors: Hoon Lee Jeong , Seon Hwang Kyo , Sung Yoon Dae , Kim Hyungsuk , Song Seung-Ho , Yoon Kang Ji , Song Kim Tae
Published: October 2011

Although the resonant frequency of a microcantilever has been reported to be changed by surface stress and/or flexural rigidity, the reasons still remained unclear. Here, we present an observation of anomalous resonant frequency change with positive values at 3.25 Å thickness of Au, where it represents the monolayer formation of Au films. This result illustrates the surface stress-dependence of the resonant frequency. The thickness at where the resonant frequency shift would become zero through the compensation of the mass, and the surface stress is expected to be approximately three monolayers (9.7 Å).
Harmonic sums and polylogarithms generated by cyclotomic polynomials
Authors: Ablinger Jakob , Blümlein Johannes , Schneider Carsten
Published: October 2011

The computation of Feynman integrals in massive higher order perturbative calculations in renormalizable quantum field theories requires extensions of multiply nested harmonic sums, which can be generated as real representations by Mellin transforms of Poincaré–iterated integrals, including denominators of higher cyclotomic polynomials. We derive the cyclotomic harmonic polylogarithms and harmonic sums and study their algebraic and structural relations. The analytic continuation of cyclotomic harmonic sums to complex values of N is performed using analytic representations. We also consider special values of the cyclotomic harmonic polylogarithms at argument x = 1, respectively, for the cyclotomic harmonic sums at N → ∞, which are related to colored multiple zeta values, deriving various of their relations, based on the stuffle and shuffle algebras and three multiple argument relations. We also consider infinite generalized nested harmonic sums at roots of unity which are related to the infinite cyclotomic harmonic sums. Basis representations are derived for weight \documentclass[12pt]{minimal}\begin{document}$\sf{w=1,2}$\end{document}w=1,2 sums up to cyclotomy \documentclass[12pt]{minimal}\begin{document}$\sf{l=20}$\end{document}l=20. This paper is dedicated to Martinus Veltman on the occasion of his 80th birthday.
Excess entropy in natural language: Present state and perspectives
Authors: Dębowski Łukasz
Published: October 2011

We review recent progress in understanding the meaning of mutual information in natural language. Let us define words in a text as strings that occur sufficiently often. In a few previous papers, we have shown that a power-law distribution for so defined words (a.k.a. Herdan’s law) is obeyed if there is a similar power-law growth of (algorithmic) mutual information between adjacent portions of texts of increasing length. Moreover, the power-law growth of information holds if texts describe a complicated infinite (algorithmically) random object in a highly repetitive way, according to an analogous power-law distribution. The described object may be immutable (like a mathematical or physical constant) or may evolve slowly in time (like cultural heritage). Here, we reflect on the respective mathematical results in a less technical way. We also discuss feasibility of deciding to what extent these results apply to the actual human communication.
Comprehensive control of optical polarization anisotropy in semiconducting nanowires
Authors: Fang Lei , Zhao Xianwei , Chiu Yi-Hsin , Ko Dongkyun , Reddy Kongara M. , Lemberger Thomas R. , Padture Nitin P. , Yang Fengyuan , Johnston-Halperin Ezekiel
Published: October 2011

The demonstration of strong photoluminescence polarization anisotropy in semiconducting nanowires embodies both technological promise and scientific challenge. Here, we present progress on both fronts through the study of the photoluminescence polarization anisotropy of randomly oriented nanowire ensembles in materials without/with crystalline anisotropy, small/wide bandgap, and both III-V/II-VI chemistry (InP/ZnO nanowires, respectively). Comprehensive control of the polarization anisotropy is realized by dielectric matching with conformally deposited Ta2O5 (dielectric ratios of 9.6:4.41 and 4.0:4.41 for InP and ZnO, respectively). After dielectric matching, the polarization anisotropy of the nanowire ensembles is reduced by 86% for InP:Ta2O5 and 84% for ZnO:Ta2O5.
Re-examining the properties of the aqueous vapor–liquid interface using dispersion corrected density functional theory
Authors: Baer Marcel D. , Mundy Christopher J. , McGrath Matthew J. , Kuo I.-F. Will , Siepmann J. Ilja , Tobias Douglas J.
Published: October 2011

First-principles molecular dynamics simulations, in which the forces are computed from electronic structure calculations, have great potential to provide unique insight into structure, dynamics, electronic properties, and chemistry of interfacial systems that is not available from empirical force fields. The majority of current first-principles simulations are driven by forces derived from density functional theory with generalized gradient approximations to the exchange-correlation energy, which do not capture dispersion interactions. We have carried out first-principles molecular dynamics simulations of air-water interfaces employing a particular generalized gradient approximation to the exchange-correlation functional (BLYP), with and without empirical dispersion corrections. We assess the utility of the dispersion corrections by comparison of a variety of structural, dynamic, and thermodynamic properties of bulk and interfacial water with experimental data, as well as other first-principles and force field-based simulations.
Metallic-nanoparticle assisted enhanced band-to-band tunneling current
Authors: Sarkar Deblina , Banerjee Kaustav
Published: October 2011

Metallic nanoparticle assisted band-to-band tunneling is proposed, and the impact of such nanoparticle induced states on the tunneling probability and current is modeled and analyzed. An analytical formula for tunneling probability is derived for the case of constant force, and it is shown that the incorporation of these particles in the forbidden gap can lead to a substantial increase in the tunneling current. The effect of the Fermi-level pinning position on the tunneling current is studied, and the pinning value for obtaining maximum improvement in current is discussed depending on the force conditions. It is also shown that an asymmetric pinning is required to leverage maximum benefits from the insertion of metallic nanoparticles.
Ergodic parameters and dynamical complexity
Authors: Mendes Rui Vilela
Published: October 2011

Using a cocycle formulation, old and new ergodic parameters beyond the Lyapunov exponent are rigorously characterized. Dynamical Renyi entropies and fluctuations of the local expansion rate are related by a generalization of the Pesin formula. How the ergodic parameters may be used to characterize the complexity of dynamical systems is illustrated by some examples: clustering and synchronization, self-organized criticality and the topological structure of networks.
Natural complexity, computational complexity and depth
Authors: Machta J.
Published: October 2011

Depth is a complexity measure for natural systems of the kind studied in statistical physics and is defined in terms of computational complexity. Depth quantifies the length of the shortest parallel computation required to construct a typical system state or history starting from simple initial conditions. The properties of depth are discussed and it is compared with other complexity measures. Depth can only be large for systems with embedded computation.
Interface crack between superconducting film and substrate
Authors: Yong Huadong , Zhou Youhe
Published: October 2011

The interface crack problem in the superconducting film-substrate structure under the magnetic field is investigated. A solution of the two-dimensional magnetoelastic problem is found. It is assumed that the plane stress state of deformation prevails in the structure. We take into consideration both cases of interface crack in the film-substrate structure and the superconductor slab. The fracture behaviors are considered for the non-superconducting substrate and superconducting substrate. Based on the simple geometrical and material assumptions, we express the explicit analytical description of the stress intensity factor and energy release rate. An increase of the stress intensity factor and energy release rate with the applied field has been observed. During the field reduction, the variations of the fracture behavior exhibit a complex characteristic. In addition, the effect of the deformation of the substrate is significant. This work may provide a tool for the analysis of the mechanical instability in the film-substrate structure.
Influence of mobile DNA-protein-DNA bridges on DNA configurations: Coarse-grained Monte-Carlo simulations
Authors: de Vries Renko
Published: October 2011

A large literature exists on modeling the influence of sequence-specific DNA-binding proteins on the shape of the DNA double helix in terms of one or a few fixed constraints. This approach is inadequate for the many proteins that bind DNA sequence independently, and that are present in very large quantities rather than as a few copies, such as the nucleoid proteins in bacterial cells. The influence of such proteins on DNA configurations is better modeled in terms of a great number of mobile constraints on the DNA. Types of constraints that mimic the influence of various known non-specifically DNA binding proteins include DNA bending, wrapping, and bridging. Using Monte-Carlo simulations, we here investigate the influence of (non-interacting) mobile DNA-protein-DNA bridges on the configurations of a 1000 bp piece of linear DNA, for both homogeneous DNA and DNA with an intrinsic planar bend. Results are compared to experimental data on the bacterial nucleoid protein H-NS that forms DNA-protein-DNA bridges. In agreement with data on H-NS, we find very strong positioning of DNA-protein-DNA bridges in the vicinity of planar bends. H-NS binds to DNA very cooperatively, but for non-interacting bridges we only find a moderate DNA-induced clustering. Finally, it has been suggested that H-NS is an important contributor to the extreme condensation of bacterial DNA into a nucleoid structure, but we find only a moderate compaction of DNA coils with increasing numbers of non-interacting bridges. Our results illustrate the importance of quantifying the various effects on DNA configurations that have been proposed for proteins that bind DNA sequence independently.
Quantitative measurement of scattering and extinction spectra of nanoparticles by darkfield microscopy
Authors: Mercatelli Raffaella , Romano Giovanni , Ratto Fulvio , Matteini Paolo , Centi Sonia , Cialdai Francesca , Monici Monica , Pini Roberto , Fusi Franco
Published: October 2011

We demonstrate a versatile concept for the quasi simultaneous and quantitative measurement of light extinction and scattering cross section spectra of nanoparticles in a darkfield microscope. We validate this method by the analysis of an aqueous suspension of gold nanorods and comparison with both numerical simulations and standard spectrophotometry measurements. Our approach holds the promise to allow one to map the principal optical properties of nanoparticles in a biological sample with μm spatial resolution, which is an issue of particular relevance for applications in biomedical optics such as photothermolysis and laser hyperthermia.
Information symmetries in irreversible processes
Authors: Ellison Christopher J. , Mahoney John R. , James Ryan G. , Crutchfield James P. , Reichardt Jörg
Published: October 2011

We study dynamical reversibility in stationary stochastic processes from an information-theoretic perspective. Extending earlier work on the reversibility of Markov chains, we focus on finitary processes with arbitrarily long conditional correlations. In particular, we examine stationary processes represented or generated by edge-emitting, finite-state hidden Markov models. Surprisingly, we find pervasive temporal asymmetries in the statistics of such stationary processes. As a consequence, the computational resources necessary to generate a process in the forward and reverse temporal directions are generally not the same. In fact, an exhaustive survey indicates that most stationary processes are irreversible. We study the ensuing relations between model topology in different representations, the process’s statistical properties, and its reversibility in detail. A process’s temporal asymmetry is efficiently captured using two canonical unifilar representations of the generating model, the forward-time and reverse-time ε-machines. We analyze example irreversible processes whose ε-machine representations change size under time reversal, including one which has a finite number of recurrent causal states in one direction, but an infinite number in the opposite. From the forward-time and reverse-time ε-machines, we are able to construct a symmetrized, but nonunifilar, generator of a process—the bidirectional machine. Using the bidirectional machine, we show how to directly calculate a process’s fundamental information properties, many of which are otherwise only poorly approximated via process samples. The tools we introduce and the insights we offer provide a better understanding of the many facets of reversibility and irreversibility in stochastic processes.
How hidden are hidden processes? A primer on crypticity and entropy convergence
Authors: Mahoney John R. , Ellison Christopher J. , James Ryan G. , Crutchfield James P.
Published: October 2011

We investigate a stationary process’s crypticity—a measure of the difference between its hidden state information and its observed information—using the causal states of computational mechanics. Here, we motivate crypticity and cryptic order as physically meaningful quantities that monitor how hidden a hidden process is. This is done by recasting previous results on the convergence of block entropy and block-state entropy in a geometric setting, one that is more intuitive and that leads to a number of new results. For example, we connect crypticity to how an observer synchronizes to a process. We show that the block-causal-state entropy is a convex function of block length. We give a complete analysis of spin chains. We present a classification scheme that surveys stationary processes in terms of their possible cryptic and Markov orders. We illustrate related entropy convergence behaviors using a new form of foliated information diagram. Finally, along the way, we provide a variety of interpretations of crypticity and cryptic order to establish their naturalness and pervasiveness. This is also a first step in developing applications in spatially extended and network dynamical systems.
Fabrication of multi-layer polymeric micro-sieve having narrow slot pores with conventional ultraviolet-lithography and micro-fabrication techniques
Authors: Ebrahimi Warkiani Majid , Lou Chao-Ping , Gong Hai-Qing
Published: October 2011

Fast detection of waterborne pathogens is important for securing the hygiene of drinking water. Detection of pathogens in water at low concentrations and minute quantities demands rapid and efficient enrichment methods in order to improve the signal-to-noise ratio of bio-sensors. We propose and demonstrate a low cost and rapid method to fabricate a multi-layer polymeric micro-sieve using conventional lithography techniques. The micro-fabricated micro-sieves are made of several layers of SU-8 photoresist using multiple coating and exposure steps and a single developing process. The obtained micro-sieves have good mechanical properties, smooth surfaces, high porosity (≈40%), and narrow pore size distribution (coefficient of variation < 3.33%). Sample loading and back-flushing using the multi-layer micro-sieve resulted in more than 90% recovery of pathogens, which showed improved performance than current commercial filters.
Effect of Zn incorporation into CuInS2 solar cell absorbers on microstructural and electrical properties
Authors: Schmidt S. S. , Abou-Ras D. , Unold T. , Eisenbarth T. , Wilhelm H. , Grimm A. , Klaer J. , Schock H.-W.
Published: October 2011

Zn incorporation into CuInS2 absorbers is found to increase the open-circuit voltage but decrease the short-circuit current of the corresponding thin-film solar cells. In this article, we study the effect of Zn incorporation into CuInS2 absorbers with a focus on the mechanisms leading to the measured changes in the electrical properties of the solar cells. Solar cells with varying Zn concentrations in their absorbers are characterized via the application of transmission electron microscopy, quantum efficiency, and current-voltage measurements, as well as admittance, x-ray photoelectron and photoluminescence spectroscopy. A Zn accumulation on the absorber side of the CuInS2–CdS interface and a higher structural defect density within the absorber are found after Zn incorporation. Capacitance, quantum efficiency, and current-voltage measurements in combination with device simulations suggest that Zn incorporation induces or enhances a shallow donor at the CuInS2–CdS interface. The interface defect pins the Fermi level close to the CdS conduction band, leading to an inversion at the heterointerface and thus reducing the recombination at interface defects and increasing the open-circuit voltage. A shallow bulk acceptor about 0.15 eV above the valence band edge is observed to increase with increasing Zn concentration in the CuInS2 absorbers and is responsible for a gradual decrease in the short-circuit current and the gain in the open-circuit voltage as the Zn concentration increases.
Concentration fluctuations in non-isothermal reaction-diffusion systems. II. The nonlinear case
Authors: Bedeaux D. , Ortiz de Zárate J. M. , Pagonabarraga I. , Sengers J. V. , Kjelstrup S.
Published: October 2011

In this paper, we consider a simple reaction-diffusion system, namely, a binary fluid mixture with an association-dissociation reaction between two species. We study fluctuations at hydrodynamic spatiotemporal scales when this mixture is driven out of equilibrium by the presence of a temperature gradient, while still being far away from any chemical instability. This study extends the analysis in our first paper on the subject [J. M. Ortiz de Zárate, J. V. Sengers, D. Bedeaux, and S. Kjelstrup, J. Chem. Phys. 127, 034501 (2007)10.1063/1.2746326], where we considered fluctuations in a non-isothermal reaction-diffusion system but still close to equilibrium. The present extension is based on mesoscopic non-equilibrium thermodynamics that we recently developed [D. Bedeaux, I. Pagonabarraga, J. M. Ortiz de Zárate, J. V. Sengers, and S. Kjelstrup, Phys. Chem. Chem. Phys. 12, 12780 (2010)10.1039/c0cp00289e] to derive the law of mass action and fluctuation-dissipation theorems for the random contributions to the dissipative fluxes in the nonlinear macroscopic description. Just as for non-equilibrium fluctuations close to equilibrium, we again find an enhancement of the intensity of the concentration fluctuations in the presence of a temperature gradient. The non-equilibrium concentration fluctuations are in both cases spatially long ranged, with an intensity depending on the wave number q. The intensity exhibits a crossover from a ∝q−4 to a ∝q−2 behavior depending on whether the corresponding wavelength is smaller or larger than the penetration depth of the reacting mixture. This opens a possibility to distinguish between diffusion- or activation-controlled regimes of the reaction experimentally. The important conclusion overall is that non-equilibrium fluctuations in non-isothermal reaction-diffusion systems are always long ranged.
Instanton calculations of tunneling splittings for water dimer and trimer
Authors: Richardson Jeremy O. , Althorpe Stuart C. , Wales David J.
Published: October 2011

We investigate the ability of the recently developed ring-polymer instanton (RPI) method [J. O. Richardson and S. C. Althorpe, J. Chem. Phys. 134, 054109 (2011)]10.1063/1.3530589 to treat tunneling in water clusters. We show that the RPI method is easy to extend to treat tunneling between more than two minima, using elementary graph theory. Tests of the method on water dimer and trimer yield a set of instanton periodic orbits which correspond to all known tunneling pathways in these systems. Splitting patterns obtained from the orbits are in good overall agreement with experiment. The agreement is closer for the deuterated than for the protonated clusters, almost certainly because the main approximation in the calculations is neglect of anharmonicity perpendicular to the tunneling path. All the calculations were performed on a desktop computer, which suggests that similar calculations will be possible on much larger clusters.
Time-fractional KdV equation for plasma of two different temperature electrons and stationary ion
Authors: El-Wakil S. A. , Abulwafa Essam M. , El-Shewy E. K. , Mahmoud Abeer A.
Published: October 2011

Using the time-fractional KdV equation, the nonlinear properties of small but finite amplitude electron-acoustic solitary waves are studied in a homogeneous system of unmagnetized collisionless plasma. This plasma consists of cold electrons fluid, non-thermal hot electrons, and stationary ions. Employing the reductive perturbation technique and the Euler-Lagrange equation, the time-fractional KdV equation is derived and it is solved using variational method. It is found that the time-fractional parameter significantly changes the soliton amplitude of the electron-acoustic solitary waves. The results are compared with the structures of the broadband electrostatic noise observed in the dayside auroral zone.
A self-consistent three-wave coupling model with complex linear frequencies
Authors: Kim J.-H. , Terry P. W.
Published: October 2011

A three-wave coupling model with complex linear frequencies is investigated for the nonlinear interaction in a triad that has linearly unstable and stable modes. Time scales associated with linear and nonlinear physics are identified and compared with features of the frequency spectrum. From appropriate time scales, the frequency spectra are well characterized even in the transition to the steady state. The nonlinear time scales that best match spectral features are the nonlinear frequency of the fixed point and a frequency that depends on the amplitude displacement from the fixed point through the large-amplitude Jacobian elliptic solution. Two limited efforts to model the effect of other triads suggest robustness in the single triad results.
Investigation on the limit of weak infrared photodetection
Authors: Yang Y. , Liu H. C. , Hao M. R. , Shen W. Z.
Published: October 2011

We investigate the limit of weak infrared photodetection based on a systematic analysis of three main noise mechanisms, and point out the principles to achieve the ultimate performance. Two key issues should be addressed to realize ultra-sensitive infrared photodetection: suppression of background radiation, selection and optimization of photodetectors. We quantitatively studied the dependence of ultimate performance on the background temperature and emissivity. It is revealed that the background limited infrared performance detectivity for mid-infrared photodetection can be increased from the range of 1010 to 1011 cmHz1/2/W to 1015 cmHz1/2/W or even higher values, when the background radiation temperature decreases from the ambient to liquid nitrogen temperature. Furthermore, we investigate the feasibility of photoconductive infrared photodetectors for ultra-sensitive photodetection. Our simulations shows that ideal quantum well infrared photodetectors (QWIPs) can reach background limited infrared performance at feasible operation temperatures facing even very weak background radiation. For specific and quantitative analyses, QWIPs are used as the examples. However, the conclusions apply to a broader range of cases.
Efficiency droop behaviors of the blue LEDs on patterned sapphire substrate
Authors: Yan J. , Yu T. J. , Li X. B. , Tao Y. B. , Xu C. L. , Long H. , Yang Z. Y. , Zhang G. Y.
Published: October 2011

In this paper, different efficiency behaviors of blue LEDs fabricated on the conventional sapphire substrate (C-LEDs) and patterned sapphire substrate (PSSLEDs) by metal organic chemical vapor deposition are investigated. Maximum external quantum efficiency (EQE) of PSSLEDs shows about 23.5 % improvement compared with that of C-LEDs. However, PSSLEDs have lower peak-efficiency-current at which the EQE reaches maximum, and suffer more serious efficiency droop. Besides, slight changes of efficiency droop for these two type LEDs in aging experiments indicate that structure defects do not play major roles for efficiency droop, and faster broadenings of the full width at half maximum of the electro-luminescence (EL) spectrum when injection current increases suggest stronger band filling effects in PSSLEDs. From the rate equation analyses, the value of coefficient C' is found to be two orders larger than Auger coefficient, and PSSLEDs have a greater coefficient C', which implies more carriers overflow from QWs in PSSLEDs. Therefore, it is suggested that, compared to Auger recombination, carrier overflow from QWs would play a more important part in the efficiency droop of blue LEDs.
Origin of predominantly a type dislocations in InGaN layers and wells grown on (0001) GaN
Authors: Meng F. Y. , McFelea H. , Datta R. , Chowdhury U. , Werkhoven C. , Arena C. , Mahajan S.
Published: October 2011

Threading dislocations that are of a type were observed to form locally in InGaN layers and wells containing 7%–15% indium. Direct correlations between a type dislocations and stacking faults in InGaN layers and wells were observed. The formation of these dislocations is attributed to the dissociation of Shockley partials bounding the stacking faults.
Soft x-ray emission spectroscopy studies of the electronic structure of silicon supersaturated with sulfur
Authors: Sullivan J. T. , Wilks R. G. , Winkler M. T. , Weinhardt L. , Recht D. , Said A. J. , Newman B. K. , Zhang Y. , Blum M. , Krause S. , Yang W. L. , Heske C. , Aziz M. J. , Bär M. , Buonassisi T.
Published: October 2011

We apply soft x-ray emission spectroscopy (XES) to measure the electronic structure of crystalline silicon supersaturated with sulfur (up to 0.7 at. %), a candidate intermediate-band solar cell material. Si L2,3 emission features are observed above the conventional Si valence band maximum, with intensity scaling linearly with S concentration. The lineshape of the S-induced features change across the insulator-to-metal transition, indicating a significant modification of the local electronic structure concurrent with the change in macroscopic electronic behavior. The relationship between the Si L2,3 XES spectral features and the anomalously high sub-band gap infrared absorption is discussed.
High-Q aluminum nitride Lamb wave resonators with biconvex edges
Authors: Lin Chih-Ming , Lai Yun-Ju , Hsu Jin-Chen , Chen Yung-Yu , Senesky Debbie G. , Pisano Albert P.
Published: October 2011

A Lamb wave resonator utilizing an aluminum nitride (AlN) plate with biconvex edges to enhance the quality factor (Q) is demonstrated. The simulation results based on finite element analysis verify that the use of the biconvex edges, instead of the conventional flat edges, can efficiently confine mechanical energy in the AlN Lamb wave resonator. Specifically, the measured frequency response of a 491.8-MHz AlN Lamb wave resonator with biconvex edges yields a Q of 3280 which represents a 2.6× enhancement in Q over a 517.9-MHz Lamb wave resonator on the same AlN plate but with the suspended flat edges.
The electronic structure of Ti2 and Ti2+
Authors: Kalemos Apostolos , Mavridis Aristides
Published: October 2011

The Ti2 and Ti2+ molecular systems have been studied through multireference variational and single reference coupled-cluster methods coupled with large basis sets. Potential energy curves have been constructed for 30 (Ti2) and 2 (Ti2+) states and the usual spectroscopic parameters have been extracted. The main feature of the potential curves is the existence of van der Waals minima (Ti2) around 7 bohr irrespective of the molecular symmetry, and 4s2–4s1 interactions (Ti2+) around 6 bohr. Numerous avoided crossings lead to stronger covalent bonds emanating from 4s1–4s1 atomic distributions. The X-state of the neutral species is formally a 3Δg state with the first excited state lying within 1 kcal/mol. The removal of the symmetry defining e− leads to the X2Σg+ state of Ti2+.
Increased efficiency of low band gap polymer solar cells at elevated temperature and its origins
Authors: Yang Bin , Cox James , Yuan Yongbo , Guo Fawen , Huang Jinsong
Published: October 2011

Photovoltaic characteristics of a low bandgap polymer, poly[(4,4′-bis(2-lethylhexyl)dithieno-[3,2-b:2′,3′-d]silole)-2,6-diyl-alt-(2,1,3-benzothiadiazole)-4,7-diyl], based bulk hetero-junction organic photovoltaic were investigated from room temperature (RT) to 145 °C to evaluate its applications in harsh environments. The power conversion efficiency was found to increase from 4.1% at RT to 4.5% at 105 °C with increased short circuit current density (Jsc) and fill factor (FF) despite the decreased open circuit voltage (Voc). Detailed investigation revealed that Jsc and FF improvements were caused by the increased and balanced carrier mobilities at higher temperatures. The Voc of the low bandgap polymer solar cell is determined not only by the energy levels and dark currents, but also by the binding energy of charge transfer excitons (CTEs). A slower reduction of Voc is observed at high temperatures due to the decreased binding energy of CTEs.
Vibrational and orientational dynamics of water in aqueous hydroxide solutions
Authors: Hunger Johannes , Liu Liyuan , Tielrooij Klaas-Jan , Bonn Mischa , Bakker Huib
Published: October 2011

We report the vibrational and orientational dynamics of water molecules in isotopically diluted NaOH and NaOD solutions using polarization-resolved femtosecond vibrational spectroscopy and terahertz time-domain dielectric relaxation measurements. We observe a speed-up of the vibrational relaxation of the O–D stretching vibration of HDO molecules outside the first hydration shell of OH− from 1.7 ± 0.2 ps for neat water to 1.0 ± 0.2 ps for a solution of 5 M NaOH in HDO:H2O. For the O–H vibration of HDO molecules outside the first hydration shell of OD−, we observe a similar speed-up from 750 ± 50 fs to 600 ± 50 fs for a solution of 6 M NaOD in HDO:D2O. The acceleration of the decay is assigned to fluctuations in the energy levels of the HDO molecules due to charge transfer events and charge fluctuations. The reorientation dynamics of water molecules outside the first hydration shell are observed to show the same time constant of 2.5 ± 0.2 ps as in bulk liquid water, indicating that there is no long range effect of the hydroxide ion on the hydrogen-bond structure of liquid water. The terahertz dielectric relaxation experiments show that the transfer of the hydroxide ion through liquid water involves the simultaneous motion of ∼7 surrounding water molecules, considerably less than previously reported for the proton.
Implementation of a portable electronic system for providing pain relief to patellofemoral pain syndrome patients
Authors: Chang Chien Jia-Ren , Lin Guo-Hong , Hsu Ar-Tyan
Published: October 2011

In this study, a portable electromyogram (EMG) system and a stimulator are developed for patellofemoral pain syndrome patients, with the objective of reducing the pain experienced by these patients; the patellar pain is caused by an imbalance between the vastus medialis obliquus (VMO) and the vastus lateralis (VL). The EMG measurement circuit and the electrical stimulation device proposed in this study are specifically designed for the VMO and the VL; they are capable of real-time waveform recording, possess analyzing functions, and can upload their measurement data to a computer for storage and analysis. The system can calculate and record the time difference between the EMGs of the VMO and the VL, as well as the signal strengths of both the EMGs. As soon as the system detects the generation of the EMG of the VL, it quickly calculates and processes the event and stimulates the VMO as feedback through electrical stimulation units, in order to induce its contraction. The system can adjust the signal strength, time length, and the sequence of the electrical stimulation, both manually and automatically. The output waveform of the electrical stimulation circuit is a dual-phase asymmetrical pulse waveform. The primary function of the electrical simulation circuit is to ensure that the muscles contract effectively. The performance of the device can be seen that the width of each pulse is 20–1000 μs, the frequency of each pulse is 10–100 Hz, and current strength is 10–60 mA.
Insight into unusual impurity absorbability of GeO2 in GeO2/Ge stacks
Authors: Ogawa Shingo , Suda Taichi , Yamamoto Takashi , Kutsuki Katsuhiro , Hideshima Iori , Hosoi Takuji , Shimura Takayoshi , Watanabe Heiji
Published: October 2011

Adsorbed species and its diffusion behaviors in GeO2/Ge stacks, which are future alternative metal-oxide-semiconductor (MOS) materials, have been investigated using various physical analyses. We clarified that GeO2 rapidly absorbs moisture in air just after its exposure. After the absorbed moisture in GeO2 reaches a certain limit, the GeO2 starts to absorb some organic molecules, which is accompanied by a structural change in GeO2 to form a partial carbonate or hydroxide. We also found that the hydrogen distribution in GeO2 shows intrinsic characteristics, indicative of different diffusion behaviors at the surface and at the GeO2/Ge interface. Because the impurity absorbability of GeO2 has a great influence on the electrical properties in Ge-MOS devices, these results provide valuable information in realizing high quality GeO2/Ge stacks for the actual use of Ge-MOS technologies.
Picosecond carrier lifetimes in dilute GaInNAs grown on InP substrate
Authors: Mangeney J. , Laurent T. , Martin M. , Harmand J. C. , Travers L. , Mauguin O.
Published: October 2011

We study the carrier relaxation dynamics in Ga1−yIny N0.03As0.97 layers grown on InP substrate by molecular beam epitaxy. This dilute nitride semiconductor is a potential candidate for ultrafast components such as photoconductive terahertz devices driven at 1.55 μm wavelength. Carrier lifetimes are measured by pump-probe experiments at 1550 nm wavelength and the shortest carrier lifetime is 2.6 ps under photoexcitation with ∼4.2 μJ/cm2. We observe two contributions in the differential transmittance decay. These contributions are discussed in terms of photocarrier recombination processes.
Wrinkles formation and evolution of nanoribbons with finite length on elastomeric substrate
Authors: Feng Xue , Qu Binrui , Lu Bingwei , Zhao Zhihua , Fang Xufei
Published: October 2011

We report in situ observation of wrinkles formation and evolution of Si nanoribbons with finite length on elastomeric substrate via white light interferometer. The wrinkle originates from the middle of the nanoribbon, propagates symmetrically to the two ends, and finally reaches the stable configuration. The wavelength and amplitude will increase abruptly when the released strain exceeds the critical value. The interface interaction between Si nanoribbons and elastomeric substrate plays the key role for wrinkles formation.
Dynamic mechanical behavior of magnetorheological nanocomposites filled with carbon nanotubes
Authors: Li R. , Sun L. Z.
Published: October 2011

Magnetorheological (MR) elastomer composites with the addition of multi-walled carbon nanotubes are developed. The dynamic mechanical responses of the MR nanocomposites to applied magnetic fields are investigated through dynamic mechanical analysis. It is found that a small amount of carbon nanotubes can effectively improve the mechanical performance of conventional MR elastomers. The MR nanocomposites have shown not only large jumps in zero-field dynamic stiffness and damping, but also higher magnetic-field-induced improvement in these dynamic mechanical properties.
Multi-beam generations at pre-designed directions based on anisotropic zero-index metamaterials
Authors: Cheng Qiang , Xiang Jiang Wei , Jun Cui Tie
Published: October 2011

We show that anisotropic zero-index metamaterials (AZIMs) can be utilized to realize single- and multiple-beam generations in the pre-designed directions. It has been shown that a high-gain beam will be generated when a line source is located in an AZIM, directing to the AZIM principle-axis direction. By rotating the principle axis to an arbitrary angle, the beam direction is adjusted correspondingly to that angle. Therefore, multi-beams are generated at the desired directions by designing differently oriented AZIMs. An experiment is carried out to validate this property, which shows good agreement to the theoretical analysis.