bluuebunny/crossref_metadata_2025 huggingface dataset:
The attitude of patients with mental disorders towards pharmacological and non-pharmacological treatments: emerging implications for clinical practice, service organization and research
Authors: Barbui Corrado , Tansella Michele
Published: January 2012

In recent years there has been a growing interest for exploring and describing the attitude of patients towards treatments provided by professionals working in mental health services. Not only the interest has been focused on whether patients perceive drug treatments as beneficial or harmful, but also on what patients think about non-phar-macological interventions, including psychological thera-pies and rehabilitative intervention programs provided by day-care centres, self-help groups or outpatient facilities. In the present issue ofEpidemiologia e Psichiatria Socialethree Editorials discuss the current state of the art on this topic, and highlight the profound implications that the subjective attitude of patients may have in determining the long-term success or failure of comprehensive and articulated treatment plans.
Subjective effects of antipsychotic drugs and their relevance for compliance and remission
Authors: Naber Dieter
Published: January 2012

Only recently, success criteria became more ambitious and include a more thorough consideration of negative symptoms and cognitive dysfunction. The most important change within the last decade is the long overdue consideration of the patient's perspective. His/her subjective well-being, often unchanged or even worsened by typical antipsychotics, was neglected for a long time. One reason was the prejudice that schizophrenic patients are not able to self-rate their quality of life. Another reason was the belief that such data are not necessary because the psychiatrists' perspective, “objective” psychopathology, includes these domains. Among other scales, a self-report instrument has been constructed to evaluate “subjective well-being under neuroleptics” (SWN). This scale was used in numerous open and controlled trials, indicating: a) patients, if no longer acutely psychotic or suffering from severe cognitive deficits, are able to reliably assess their subjective well-being, b) high SWN is correlated with high compliance, c) atypical antipsychotics increase SWN, and d) individual improvements of SWN and of PANSS are not strongly related. Moreover, several studies found that early improvement of subjective well-being is a major predictor for the chance of remission. All these data indicate that a better consideration of the patient's perspective is possible and necessary.
Improving the Accuracy and Precision of Cognitive Testing in Mild Dementia
Authors: Wouters Hans , Appels Bregje , van der Flier Wiesje M. , van Campen Jos , Klein Martin , Zwinderman Aeilko H. , Schmand Ben , van Gool Willem A. , Scheltens Philip , Lindeboom Robert
Published: December 2011

The CAMCOG, ADAS-cog, and MMSE, designed to grade global cognitive ability in dementia have inadequate precision and accuracy in distinguishing mild dementia from normal ageing. Adding neuropsychological tests to their scale might improve precision and accuracy in mild dementia. We, therefore, pooled neuropsychological test-batteries from two memory clinics (ns = 135 and 186) with CAMCOG data from a population study and 2 memory clinics (n = 829) and ADAS-cog data from 3 randomized controlled trials (n = 713) to estimate a common dimension of global cognitive ability using Rasch analysis. Item difficulties and individuals’ global cognitive ability levels were estimated. Difficulties of 57 items (of 64) could be validly estimated. Neuropsychological tests were more difficult than the CAMCOG, ADAS-cog, and MMSE items. Most neuropsychological tests had difficulties in the ability range of normal ageing to mild dementia. Higher than average ability levels were more precisely measured when neuropsychological tests were added to the MMSE than when these were measured with the MMSE alone. Diagnostic accuracy in mild dementia was consistently better after adding neuropsychological tests to the MMSE. We conclude that extending dementia specific instruments with neuropsychological tests improves measurement precision and accuracy of cognitive impairment in mild dementia. (JINS, 2012, 18, 314–322)
DEMOGRAPHIC CHANGE AND THE GREAT MODERATION IN AN OVERLAPPING GENERATIONS MODEL WITH MATCHING FRICTIONS
Authors: Lugauer Steven
Published: December 2011

The fraction of the labor force under 35, or youth share, has been correlated with cyclical GDP volatility over the past several decades. The youth share and business cycle fluctuations were high during the 1970s. Then, as the population aged, output volatility declined. I develop an overlapping generations model featuring search frictions and productivity shocks, in which the age distribution affects cyclical volatility through two channels. First, employment for younger workers fluctuates more, creating a composition effect. Second, inexperienced workers produce less, so firms decide how many jobs to create based on the age distribution. Both this endogenous response by firms and the composition effect increase aggregate volatility when the youth share is high. The model can replicate a large portion of the Great Moderation in GDP volatility, suggesting an important role for demographics. The model also replicates unemployment rates, separation rates, and employment volatility by age group.
ENDOGENOUS BUSINESS CYCLES IN OVERLAPPING-GENERATIONS ECONOMIES WITH MULTIPLE CONSUMPTION GOODS
Authors: Nourry Carine , Venditti Alain
Published: December 2011

We consider an overlapping-generations economy with two consumption goods. There are two sectors that produce a pure consumption good and a mixed good that can be either consumed or used as capital. We prove that the existence of Pareto-optimal expectations-driven fluctuations is compatible with standard sectoral technologies if the share of the pure consumption good is low enough. Following Reichlin's [Journal of Economic Theory40 (1986), 89–102] influential conclusion, this result suggests that some fiscal policy rules can prevent business-cycle fluctuations in the economy by driving it to the optimal steady state as soon as they are announced.
Latitudinal variation and distribution of photoperiod and temperature sensitivity for flowering in the world collection of pearl millet germplasm at ICRISAT genebank
Authors: Upadhyaya H. D. , Reddy K. N. , Irshad Ahmed Mohd , Dronavalli Naresh , Gowda C. L. L.
Published: January 2012

The ICRISAT genebank, Patancheru, India holds 22,211 pearl millet germplasm accessions from 50 countries, including 19,063 landraces. Among these, 15,904 landraces that were geo-referenced are either thermo-sensitive (52.5%), or photoperiod-sensitive (45.6%), or insensitive to both temperature and photoperiod (2%). Latitude ranges of 10–15°N with 39.6% and 15–20°S with 13.1% of total accessions are the important regions for pearl millet germplasm. A study on climate data of the germplasm collection sites revealed that most accessions from latitudes ranging from 10 to 20° on both sides of the equator were highly sensitive to longer photoperiod (>12.5 h) and/or lower temperature ( < 12°C). Accessions that originated in locations at higher latitudes (>20–35°) on both the hemispheres exhibited low sensitivity to both photoperiod and low temperature, as they were exposed to such climates during their evolution. The accessions that are insensitive to both photoperiod and temperature were few but they originated from locations spread across all latitudes, although the highest numbers were from mid-latitudes (15–20°) in both hemispheres. As germplasm accessions are sensitive to climatic variables such as temperature and photoperiod, recording of location-specific geo-reference data while collecting the germplasm, which can help to elucidate the sensitivity of accessions to temperature and photoperiod, is emphasized. Critical evaluation of photoperiod-sensitive accessions that are late flowering for forage production and the photoperiod-insensitive early-maturing accessions for grain production, multiple cropping and development of parental lines with synchronized flowering for the development of hybrids is suggested.
A magnetohydrodynamic simulation study of Kronian field‐aligned currents and auroras
Authors: Fukazawa Keiichiro , Ogino Tatsuki , Walker Raymond J.
Published: December 2011

Magnetohydrodynamic simulations of the interaction of Saturn's magnetosphere with the solar wind indicate that Kelvin‐Helmholtz (K‐H) waves can form on the dayside magnetopause when the interplanetary magnetic field (IMF) is northward. Dayside magnetic reconnection occurs at Saturn for northward IMF, and the combination of K‐H waves and reconnection caused enhanced vorticity in Saturn's magnetosphere. We have used a very high resolution version (Δx = 0.1 RS) of our simulation code to study the consequences of the vortices and reconnection for the generation of field‐aligned currents (FACs) and auroras in Saturn's ionosphere. We found three bands of alternating FACs toward and away from the dawn side of the ionosphere and two sets on the dusk side. The K‐H waves generated a series of toward and away currents along the dayside magnetopause. In the ionosphere they appear as a series of spots of up and down currents. The K‐H field‐aligned currents are adjacent to nearly continuous currents located from 16:00 LT, to around past midnight, and to about 07:00 LT. The largest currents densities (j∥ > 5 × 10−8 A m−2) are found at the highest latitudes. They map to the magnetopause and to the near‐Saturn tail region. We used the away current density and the Knight relationship to estimate the energy flux related to discrete auroras and obtained ∼1 mW m−2 in the region with the strongest currents. This gives approximately 7 GW for the auroral UV emitted power. We found a region of enhanced thermal energy flux in the region where cusp auroras are observed.
A revised rate‐ and state‐dependent friction law obtained by constraining constitutive and evolution laws separately with laboratory data
Authors: Nagata K. , Nakatani M. , Yoshida S.
Published: January 2012

We propose two major revisions on the rate‐ and state‐dependent friction (RSF) law on the basis of rigorous analysis of friction experiments. First, we find that the direct effect coefficient a, a parameter playing a central role in the RSF constitutive law, is much larger than the traditional, consensual estimate of less than about 0.01. We derive a lower bound of 0.035 for a directly from stress‐velocity relations measured during carefully designed step tests, without relying on any evolution laws as traditional methods do. After correcting for state changes during the steps, inferred indirectly from observed changes in acoustic transmissivities across the interface, we obtain an estimate of a as large as 0.05. Second, we calculate values of the RSF state variable Φ by feeding the measured shear stress and slip velocity values into the constitutive law. The results showed systematic deviations from predictions of the RSF evolution law of the aging type. This leads us to propose a revised evolution law, which incorporates a previously unknown weakening effect related to the shear stress. We also present additional experiment results to corroborate the presence of this new effect. Forward simulations based on our revised evolution law, combined with the larger, revised value of a, very well explain observed variations in both the shear stress and Φ throughout different phases of experiments, including quasi‐static hold, reloading after a hold, and steady state sliding at different velocities, as well as their mutual transitions, all with an identical set of parameter values.
The spatial distribution and annual cycle of upper ocean thermohaline structure
Authors: Cole Sylvia T. , Rudnick Daniel L.
Published: December 2011

Observations of the spatial distribution and persistence of thermohaline structure are presented, and show how advection and diffusion affect a passive tracer. More than two years of underwater glider observations in the central subtropical North Pacific showed thermohaline variability over horizontal scales from 5 to 1300 km. Thermohaline fluctuations along isopycnals (spice fluctuations) were elevated in layers throughout the water column with the largest fluctuations near the surface and subtropical frontal regions. Fluctuations were uncorrelated between the layers but stirred by the same velocity field. Spice variance had local extrema in the vertical because of differences in source water properties and the influence of neighboring water masses. Spice variance spanned about three orders of magnitude along deeper isopycnals with larger variance where different water masses met and where velocity and vorticity variance were elevated. Horizontal wave number spectra of spice had slopes of −2 everywhere in the upper 1000 m. Submesoscale spice fluctuations had slopes in physical space near the ratio of the Coriolis parameter to the buoyancy frequency (f/N), consistent with predictions of quasi‐geostrophic theory. In the mixed layer, thermohaline structure had a significant annual cycle with smaller interannual differences. Thermohaline fluctuations left behind during restratification and isolated from the mixed layer decayed with time because of diffusion along isopycnals. Horizontal diffusivity estimates in the remnant mixed layer were 0.4 m2 s−1 at 15–28 km wavelengths and 0.9 m2 s−1 at 35–45 km wavelengths.
The relative importance of chlorine and bromine radicals in the oxidation of atmospheric mercury at Barrow, Alaska
Authors: Stephens Chelsea R. , Shepson Paul B. , Steffen Alexandra , Bottenheim Jan W. , Liao Jin , Huey L. Greg , Apel Eric , Weinheimer Andy , Hall Samuel R. , Cantrell Christopher , Sive Barkley C. , Knapp D. J. , Montzka D. D. , Hornbrook Rebecca S.
Published: December 2011

Mercury is a toxic environmental contaminant originating from both natural and anthropogenic sources. Gaseous elemental mercury (GEM) is relatively long lived in the midlatitudes and can be transported long distances in the atmosphere. In the Polar Regions, mercury can have a much shorter lifetime and is known to experience episodic depletions following polar sunrise in concert with ozone depletion events. A series of photochemically initiated reactions involving halogen radicals is believed to be the primary pathway responsible for converting elemental mercury to oxidized forms of reactive gaseous mercury (RGM) that are subsequently deposited to snow and ice surfaces. Using field measurements from the Ocean‐Atmosphere‐Sea Ice‐Snowpack (OASIS) 2009 field campaign of GEM, RGM, ozone, and a large suite of both inorganic halogen and volatile organic compounds, we calculated steady state Br and Cl atom concentrations and investigated the contribution of Br, BrO, Cl, ClO, O3, and OH to the observed decay of GEM for five cases of apparent first‐order decay. The results of this study indicate that Br and BrO are the dominant oxidizers for Arctic mercury depletion events, with Br having the greatest overall contribution to GEM decay. Ozone is likely the primary factor controlling the relative contribution of Br and BrO, as BrO is a product of the reaction of Br with ozone, and reaction with O3 can be the largest Br atom sink. Cl was not found to be significant in any of the studied events; however, this result is highly dependent on the rate constant, for which there is a large range in the literature. Modeled 48 h back trajectories of the mercury depletion events studied here indicate significant time spent over sea ice–covered regions, where the concentration of halogen radicals is likely higher than those estimated using local‐scale chemical mole fractions.
A pure marine aerosol model, for use in remote sensing applications
Authors: Sayer A. M. , Smirnov A. , Hsu N. C. , Holben B. N.
Published: January 2012

Retrievals of aerosol optical depth (AOD) and related parameters from satellite measurements typically involve prescribed models of aerosol size and composition, and are therefore dependent on how well these models are able to represent the radiative behavior of real aerosols. This study uses aerosol volume size distributions retrieved from Sun‐photometer measurements at 11 Aerosol Robotic Network (AERONET) island sites, spread throughout the world's oceans, as a basis to define such a model for pure (unpolluted) maritime aerosol. Volume size distributions are observed to be bimodal and approximately lognormal, although the coarse mode is skewed with a long tail on the low‐radius end. The relationship of AOD and size distribution parameters to meteorological conditions is also examined. As wind speed increases, so do coarse‐mode volume and radius. The AOD and Ångström exponent show linear relationships with wind speed, although with considerable scatter. Links between aerosol properties and near‐surface relative humidity, columnar water vapor, and sea surface temperature are also explored. A recommended bimodal maritime model, which is able to reconstruct the AERONET AOD with accuracy of order 0.01–0.02, is presented for use in aerosol remote sensing applications. This accuracy holds at most sites and for wavelengths between 340 nm and 1020 nm. Calculated lidar ratios are also provided, and are in the range of other studies, although differ more strongly from those currently used in Cloud‐Aerosol Lidar with Orthogonal Polarization (CALIOP) processing.
A single-cell view of ammonium assimilation in coral–dinoflagellate symbiosis
Authors: Pernice Mathieu , Meibom Anders , Van Den Heuvel Annamieke , Kopp Christophe , Domart-Coulon Isabelle , Hoegh-Guldberg Ove , Dove Sophie
Published: January 2012

Assimilation of inorganic nitrogen from nutrient-poor tropical seas is an essential challenge for the endosymbiosis between reef-building corals and dinoflagellates. Despite the clear evidence that reef-building corals can use ammonium as inorganic nitrogen source, the dynamics and precise roles of host and symbionts in this fundamental process remain unclear. Here, we combine high spatial resolution ion microprobe imaging (NanoSIMS) and pulse-chase isotopic labeling in order to track the dynamics of ammonium incorporation within the intact symbiosis between the reef-building coral Acropora aspera and its dinoflagellate symbionts. We demonstrate that both dinoflagellate and animal cells have the capacity to rapidly fix nitrogen from seawater enriched in ammonium (in less than one hour). Further, by establishing the relative strengths of the capability to assimilate nitrogen for each cell compartment, we infer that dinoflagellate symbionts can fix 14 to 23 times more nitrogen than their coral host cells in response to a sudden pulse of ammonium-enriched seawater. Given the importance of nitrogen in cell maintenance, growth and functioning, the capability to fix ammonium from seawater into the symbiotic system may be a key component of coral nutrition. Interestingly, this metabolic response appears to be triggered rapidly by episodic nitrogen availability. The methods and results presented in this study open up for the exploration of dynamics and spatial patterns associated with metabolic activities and nutritional interactions in a multitude of organisms that live in symbiotic relationships.
Activated plasma coagulation β-Factor XII-induced vasoconstriction in rats
Authors: Papageorgiou Peter C. , Yeo Erik L. , Backx Peter H. , Floras John S.
Published: January 2012

By inducing BK (bradykinin)-stimulated adrenomedullary catecholamine release, bolus injection of the β-fragment of activated plasma coagulation Factor XII (β-FXIIa) transiently elevates BP (blood pressure) and HR (heart rate) of anaesthetized, vagotomized, ganglion-blocked, captopril-treated bioassay rats. We hypothesized that intravenous infusion of β-FXIIa into intact untreated rats would elicit a qualitatively similar vasoconstrictor response. BN (Brown Norway) rats received for 60 min either: (i) saline (control; n=10); (ii) β-FXIIa (85 ng/min per kg of body weight; n=9); or (iii) β-FXIIa after 2ADX (bilateral adrenalectomy; n=9). LV (left ventricular) volume and aortic BP were recorded before (30 min baseline), during (60 min) and after (30 min recovery) the infusion. TPR (total peripheral resistance) was derived from MAP (mean arterial pressure), SV (stroke volume) and HR. Saline had no haemodynamic effects. β-FXIIa infusion increased its plasma concentration 3-fold in both groups. In adrenally intact rats, β-FXIIa infusion increased MAP by 6% (5±2 mmHg) and TPR by 45% (0.50±0.12 mmHg/ml per min), despite falls in SV (−38±8 μl) and HR [−18±5 b.p.m. (beats/min)] (all P<0.05). In 2ADX rats, β-FXIIa had no HR effect, but decreased SV (−89±9 μl) and MAP (−4±1 mmHg), and increased TPR by 66% (0.59±0.15 mmHg/ml per min) (all P<0.05). After infusion, adrenally intact rats exhibited persistent vasoconstriction (MAP, 10±1 mmHg; TPR, 0.55±0.07 mmHg/ml per min; both P<0.05), whereas in 2ADX rats, MAP remained 5±1 mmHg below baseline (P<0.05) and TPR returned to baseline. End-study arterial adrenaline (epinephrine) concentrations in the three groups were 1.9±0.6, 9.8±4.1 and 0.6±0.2 nmol/l respectively. Thus, in neurally intact lightly anaesthetized untreated rats, β-FXIIa infusion induces both adrenal catecholamine-mediated and adrenally independent increases in peripheral resistance.
Energetics of stochastic resonance
Authors: Jung Peter , Marchesoni Fabio
Published: December 2011

In this paper, we discuss the motion of a Brownian particle in a double-well potential driven by a periodic force in terms of energies delivered by the periodic and the noise forces and energy dissipated into the viscous environment. It is shown that, while the power delivered by the periodic force to the Brownian particle is controlled by the strength of the noise, the power delivered by the noise itself is independent of the amplitude and frequency of the periodic force. The implications of this result for the mechanism of stochastic resonance in an equilibrium system is that it is not energy from the noise force which enhances a small periodic force, but rather an increase of energy delivered by the periodic force, regulated by the strength of the noise. We further re-evaluate the frequency dependence of stochastic resonance in terms of energetic terms including efficiency.
Huygens (and others) revisited
Authors: Wiesenfeld Kurt , Borrero-Echeverry Daniel
Published: December 2011

We develop a generic iterative map model of coupled oscillators based on simple physical processes common to many such systems. The model allows us to understand, from a unified perspective, the range of different outcomes reported for experiments by Huygens and modern realizations of his two coupled clocks.
The role of the isothermal bulk modulus in the molecular dynamics of super-cooled liquids
Authors: Papathanassiou Anthony N. , Sakellis Ilias , Grammatikakis John , Roland C. Michael
Published: December 2011

Elastic models imply that the energy expended for a flow event in ultra-viscous matter coincides with the elastic work required for deforming and re-arranging the environment of the moving entity. This is quite promising for explaining the strong non-Arrhenius behavior of dynamic quantities of fragile super-cooled liquids. We argue that the activation volume obtained from dielectric relaxation and light-scattering experiments for super-cooled liquids should scale with the Gibbs free energy of activation, with a proportionality constant determined by the isothermal bulk modulus and its pressure derivative, as described by an earlier thermodynamic elastic model. For certain super-cooled liquids the bulk compression transpiring in the local environment, as governed by the isothermal bulk modulus, play a significant role in the reorientational dynamics, with far-field density fluctuations and volume changes avoided by shear deformation.
A method for fine positioning of diagnostic packages in inertial confinement fusion experiments
Authors: Wang Wei , Shi Tielin , Lee Kok-Meng
Published: December 2011

A method based on binocular vision servoing for positioning of a diagnostic package in inertial confinement fusion (ICF) experiments is presented. The general diagnostic instrument manipulator will provide precision three dimension positioning and alignment-to-target capability in ICF experiments. In this work, we focus on the final precise automatic positioning with a binocular vision system. A three dimension image projection vector (IPV), which has an almost linear relationship with the target position in 3D space under the condition of weak perspective, is introduced to extract target position information from binocular image. The difference of the IPV between the current image and the desired image will be used as the input of servo controller. A differential motion model was found for the hybrid manipulator with three degrees of freedom. With this model and the said IPV, the servo strategy will be dramatically simplified compare with general image based visual servo in which the image Jacobian matrix needs estimated online. The experiment result implies that the locating accuracy of the manipulator is less than two pixels. This method can also be used in micromanipulation visual servo field.
Introduction to Focus Issue: Nonlinear and Stochastic Physics in Biology
Authors: Bahar Sonya , Neiman Alexander B. , Jung Peter , Kurths Jürgen , Schimansky-Geier Lutz , Showalter Kenneth
Published: December 2011

Frank Moss was a leading figure in the study of nonlinear and stochastic processes in biological systems. His work, particularly in the area of stochastic resonance, has been highly influential to the interdisciplinary scientific community. This Focus Issue pays tribute to Moss with articles that describe the most recent advances in the field he helped to create. In this Introduction, we review Moss’s seminal scientific contributions and introduce the articles that make up this Focus Issue.
Griffiths phase-like behavior and spin-phonon coupling in double perovskite Tb2NiMnO6
Authors: Nair Harikrishnan S. , Swain Diptikanta , N. Hariharan , Adiga Shilpa , Narayana Chandrabhas , Elzabeth Suja
Published: December 2011

The Griffiths phase-like features and the spin-phonon coupling effects observed in Tb2NiMnO6 are reported. The double perovskite compound crystallizes in monoclinic P21/n space group and exhibits a magnetic phase transition at Tc ∼ 111 K as an abrupt change in magnetization. A negative deviation from ideal Curie--Weiss law exhibited by 1/χ(T) curves and less-than-unity susceptibility exponents from the power-law analysis of inverse susceptibility are reminiscent of Griffiths phase-like features. Arrott plots derived from magnetization isotherms support the inhomogeneous nature of magnetism in this material. The observed effects originate from antiferromagnetic interactions that arise from inherent disorder in the system. Raman scattering experiments display no magnetic-order-induced phonon renormalization below Tc in Tb2NiMnO6, which is different from the results observed in other double perovskites and is correlated to the smaller size of the rare earth. The temperature evolution of full-width-at-half-maximum for the stretching mode at 645 cm−1 presents an anomaly that coincides with the magnetic transition temperature and signals a close connection between magnetism and lattice in this material.
Eigenmodes of quasi-static magnetic islands in current sheet
Authors: Li Yi , Cai Xiaohui , Chai Lihui , Zheng Huinan , Shen Chao , Wang Shui
Published: December 2011

As observation have shown, magnetic islands often appear before and/or after the onset of magnetic reconnections in the current sheets, and they also appear in the current sheets in the solar corona, Earth’s magnetotail, and Earth’s magnetopause. Thus, the existence of magnetic islands can affect the initial conditions in magnetic reconnection. In this paper, we propose a model of quasi-static magnetic island eigenmodes in the current sheet. This model analytically describes the magnetic field structures in the quasi-static case, which will provide a possible approach to reconstructing the magnetic structures in the current sheet via observation data. This model is self-consistent in the kinetic theory. Also, the distribution function of charged particles in the magnetic island can be calculated.
A molecular dynamics study of water nucleation using the TIP4P/2005 model
Authors: Pérez Alejandro , Rubio Angel
Published: December 2011

Extensive molecular dynamics simulations were conducted using the TIP4P/2005 water model of Abascal and Vega [J. Chem. Phys. 123, 234505 (2005)] to investigate its condensation from supersaturated vapor to liquid at 330 K. The mean first passage time method [J. Wedekind, R. Strey, and D. Reguera, J. Chem. Phys. 126, 134103 (2007); L. S. Bartell and D. T. Wu, 125, 194503 (2006)] was used to analyze the influence of finite size effects, thermostats, and charged species on the nucleation dynamics. We find that the Nosé–Hoover thermostat and the one proposed by Bussi et al. [J. Chem. Phys. 126, 014101 (2007)] give essentially the same averages. We identify the maximum thermostat coupling time to guarantee proper thermostating for these simulations. The presence of charged species has a dramatic impact on the dynamics, inducing a marked change towards a pure growth regime, which highlights the importance of ions in the formation of liquid droplets in the atmosphere. It was found a small but noticeable sign preference at intermediate cluster sizes (between 5 and 30 water molecules) corresponding mostly to the formation of the second solvation shell around the ion. The TIP4P/2005 water model predicts that anions induce faster formation of water clusters than cations of the same magnitude of charge.
Performance of large-area few-layer graphene saturable absorber in femtosecond bulk laser
Authors: Xu Jin-Long , Li Xian-Lei , He Jing-Liang , Hao Xiao-Peng , Wu Yong-Zhong , Yang Ying , Yang Ke-Jian
Published: December 2011

Using large-area graphene sheets of 1-10 layers prepared by the improved liquid phase exfoliation technique, the mode locking operation of a diode-pumped Yb:KGW laser was demonstrated. Near-transform-limited 428 fs pulses were yielded at 1031.1 nm with an output power of 504 mW, corresponding to the slope efficiency of 27% and peak power of 13.8 kW. The output power ratio and the slope efficiency ratio of mode locking to free running were as high as 93% and 100%, respectively. This demonstration may open a proper way to achieve low-cost and efficient femtosecond bulk laser.
Energetics and energy scaling of quasi-monoenergetic protons in laser radiation pressure acceleration
Authors: Liu Tung-Chang , Shao Xi , Liu Chuan-Sheng , Su Jao-Jang , Eliasson Bengt , Tripathi Vipin , Dudnikova Galina , Sagdeev Roald Z.
Published: December 2011

Theoretical and computational studies of the ion energy scaling of the radiation pressure acceleration of an ultra-thin foil by short pulse intense laser irradiation are presented. To obtain a quasi-monoenergetic ion beam with an energy spread of less than 20%, two-dimensional particle-in-cell simulations show that the maximum energy of the quasi-monoenergetic ion beam is limited by self-induced transparency at the density minima caused by the Rayleigh-Taylor instability. For foils of optimal thickness, the time over which Rayleigh-Taylor instability fully develops and transparency occurs is almost independent of the laser amplitude. With a laser power of about one petawatt, quasi-monogenetic protons with 200 MeV and carbon ions with 100 MeV per nucleon can be obtained, suitable for particle therapy applications.
Development of a new dynamic gas flow-control system in the pressure range of 1 Pa–133 Pa
Authors: Hong S. S. , Khan Wakil , Chung J. W.
Published: December 2011

A new flow-control system (FCS-705) has been developed at Korea Research Institute of Standards and Science. The system is intended for calibration of vacuum gauges in the pressure range of 1 Pa–133 Pa by comparison method. This paper describes some basic characteristics of the system including; (1) the design and construction of the system, (2) the generation of stable pressures in the chamber, (3) achieving high upstream pressure limit by installing a short duct in the by-pass pumping line, and (4) investigation of the gas flow regimes within the short duct.
Optical properties of a-plane (Al, Ga)N/GaN multiple quantum wells grown on strain engineered Zn1−xMgxO layers by molecular beam epitaxy
Authors: Xia Y. , Brault J. , Nemoz M. , Teisseire M. , Vinter B. , Leroux M. , Chauveau J.-M.
Published: December 2011

Nonpolar (112¯0) Al0.2Ga0.8N/GaN multiple quantum wells (MQWs) have been grown by molecular beam epitaxy on (112¯0) Zn0.74Mg0.26O templates on r-plane sapphire substrates. The quantum wells exhibit well-resolved photoluminescence peaks in the ultra-violet region, and no sign of quantum confined Stark effect is observed in the complete multiple quantum well series. The results agree well with flat band quantum well calculations. Furthermore, we show that the MQW structures are strongly polarized along the [0001] direction. The origin of the polarization is discussed in terms of the strain anisotropy dependence of the exciton optical oscillator strengths.
Growth temperature dependence of exciton lifetime in wurtzite InP nanowires grown on silicon substrates
Authors: Chauvin N. , Hadj Alouane M. H. , Anufriev R. , Khmissi H. , Naji K. , Patriarche G. , Bru-Chevallier C. , Gendry M.
Published: January 2012

InP nanowires grown on silicon substrate are investigated using time-resolved spectroscopy. A strong modification of the exciton lifetime is observed (from 0.11 to 1.2 ns) when the growth temperature is increased from 340 °C to 460 °C. This strong dependence is not related to the density of zinc-blende insertions in the wurtzite nanowires or to the wurtzite exciton linewidth. The excitation power dependence of the lifetime and linewidth is investigated, and these results allow us to interpret the growth temperature dependence on the lifetime as a consequence of the reduction of the surface recombination velocity with the growth temperature.
Communication: Spectroscopic phase and lineshapes in high-resolution broadband sum frequency vibrational spectroscopy: Resolving interfacial inhomogeneities of “identical” molecular groups
Authors: Velarde Luis , Zhang Xian-yi , Lu Zhou , Joly Alan G. , Wang Zheming , Wang Hong-fei
Published: December 2011

The ability to achieve sub-wavenumber resolution (0.6 cm−1) and a large signal-to-noise ratio in high-resolution broadband sum-frequency generation vibrational spectroscopy (HR-BB-SFG-VS) allows for the detailed SFG spectral lineshapes to be used in the unambiguous determination of fine spectral features. Changes in the structural spectroscopic phase in SFG-VS as a function of beam polarization and experimental geometry proved to be instrumental in the identification of an unexpected 2.78 ± 0.07 cm−1 spectral splitting for the two methyl groups at the vapor/dimethyl sulfoxide (DMSO, (CH3)2SO) liquid interface as well as in the determination of their orientational angles.
Calculation of phonon dispersion in carbon nanotubes using a continuum-atomistic finite element approach
Authors: Leamy Michael J.
Published: December 2011

Dispersion calculations are presented for cylindrical carbon nanotubes using a manifold-based continuum-atomistic finite element formulation combined with Bloch analysis. The formulated finite elements allow any (n,m) chiral nanotube, or mixed tubes formed by periodically-repeating heterojunctions, to be examined quickly and accurately using only three input parameters (radius, chiral angle, and unit cell length) and a trivial structured mesh, thus avoiding the tedious geometry generation and energy minimization tasks associated with ab initio and lattice dynamics-based techniques. A critical assessment of the technique is pursued to determine the validity range of the resulting dispersion calculations, and to identify any dispersion anomalies. Two small anomalies in the dispersion curves are documented, which can be easily identified and therefore rectified. They include difficulty in achieving a zero energy point for the acoustic twisting phonon, and a branch veering in nanotubes with nonzero chiral angle. The twisting mode quickly restores its correct group velocity as wavenumber increases, while the branch veering is associated with a rapid exchange of eigenvectors at the veering point, which also lessens its impact. By taking into account the two noted anomalies, accurate predictions of acoustic and low-frequency optical branches can be achieved out to the midpoint of the first Brillouin zone.
Thermal conductivity prediction of nanoscale phononic crystal slabs using a hybrid lattice dynamics-continuum mechanics technique
Authors: Reinke Charles M. , Su Mehmet F. , Davis Bruce L. , Kim Bongsang , Hussein Mahmoud I. , Leseman Zayd C. , Olsson-III Roy H. , El-Kady Ihab
Published: December 2011

Recent work has demonstrated that nanostructuring of a semiconductor material to form a phononic crystal (PnC) can significantly reduce its thermal conductivity. In this paper, we present a classical method that combines atomic-level information with the application of Bloch theory at the continuum level for the prediction of the thermal conductivity of finite-thickness PnCs with unit cells sized in the micron scale. Lattice dynamics calculations are done at the bulk material level, and the plane-wave expansion method is implemented at the macrosale PnC unit cell level. The combination of the lattice dynamics-based and continuum mechanics-based dispersion information is then used in the Callaway-Holland model to calculate the thermal transport properties of the PnC. We demonstrate that this hybrid approach provides both accurate and efficient predictions of the thermal conductivity.
In-plane confinement and waveguiding of surface acoustic waves through line defects in pillars-based phononic crystal
Authors: Khelif Abdelkrim , Achaoui Younes , Aoubiza Boujemaa
Published: December 2011

We present a theoretical analysis of an in-plane confinement and a waveguiding of surface acoustic waves in pillars-based phononic crystal. The artificial crystal is made up of cylindrical pillars placed on a semi-infinite medium and arranged in a square array. With a well-chosen of the geometrical parameters, this pillars-based system can display two kinds of complete band gaps for guided waves propagating near the surface, a low frequency gap based on locally resonant mode of pillars as well as a higher frequency gap appearing at Bragg scattering regime. In addition, we demonstrate a waveguiding of surface acoustic wave inside an extended linear defect created by removing rows of pillars in the perfect crystal. We discuss the transmission and the polarization of such confined mode appearing in the higher frequency band gap. We highlight the strong similarity of such defect mode and the Rayleigh wave of free surface medium. An efficient finite element analysis is used to simulate the propagation of guided waves through silicon pillars on a silicon substrate.
Asymmetric energy transport in defected boron nitride nanoribbons: Implications for thermal rectification
Authors: Muralidharan Krishna , Erdmann R. G. , Runge K. , Deymier P. A.
Published: December 2011

Using molecular dynamics simulations, the thermal transport properties of boron nitride nanoribbons (BNNR) containing geometrically-asymmetric triangular nano-vacancies were investigated. By suitably interpreting the time-evolution of spatially decomposed heat-current autocorrelation function in terms of phonon propagation characteristics, we have demonstrated the possibility of observing defect induced direction-dependent thermal transport in BNNR. This was further confirmed by appropriate analysis of direction dependent thermal diffusivity estimations in BNNR.
Two-dimensional phononic thermal conductance in thin membranes in the Casimir limit
Authors: Maasilta I. J.
Published: December 2011

We discuss computational analysis of phononic thermal conduction in the suspended membrane geometry, in the case where heat can flow out radially in two dimensions from a central source. As we are mostly interested in the low-temperature behavior where bulk scattering of phonons becomes irrelevant, we study the limit where all phonon scattering takes place at the membrane surfaces. Moreover, we limit the discussion here to the case where this surface scattering is fully diffusive, the so called Casimir limit. Our analysis shows that in the two-dimensional case, no analytic results are available, in contrast to the well known 1D Casimir limit. Numerical solutions are presented for the temperature profiles in the membrane radial direction, for several different membrane thicknesses and heater diameters. Our results can be applied, for example, in the design of membrane-supported bolometric radiation detectors.
Realization of a 33 GHz phononic crystal fabricated in a freestanding membrane
Authors: Goettler Drew F. , Su Mehmet F. , Reinke Charles M. , Alaie Seyedhamidreza , Hopkins Patrick E. , Olsson Roy H. , El-Kady Ihab , Leseman Zayd C.
Published: December 2011

Phononic crystals (PnCs) are man-made structures with periodically varying material properties such as density, ρ, and elastic modulus, E. Periodic variations of the material properties with nanoscale characteristic dimensions yield PnCs that operate at frequencies above 10 GHz, allowing for the manipulation of thermal properties. In this article, a 2D simple cubic lattice PnC operating at 33 GHz is reported. The PnC is created by nanofabrication with a focused ion beam. A freestanding membrane of silicon is ion milled to create a simple cubic array of 32 nm diameter holes that are subsequently backfilled with tungsten to create inclusions at a spacing of 100 nm. Simulations are used to predict the operating frequency of the PnC. Additional modeling shows that milling a freestanding membrane has a unique characteristic; the exit via has a conical shape, or trumpet-like appearance.
Solid-State Methylamine VUV Irradiation Study Using Carbon Monoxide as an H Radical Scavenger
Authors: Bossa Jean-Baptiste , Borget Fabien , Duvernay Fabrice , Danger Grégoire , Theulé Patrice , Chiavassa Thierry
Published: January 2012

Solid-phase methylamine (CH3NH2) was vacuum ultraviolet (VUV) photoprocessed at low temperature (20 K) using a hydrogen flow discharge lamp, which allows irradiation down to 120 nm. Methanimine (CH2=NH), the methylammonium cation (CH3NH3+) and the counterion CN–, as well as the amino radical (NH2), methane (CH4) and ammonia (NH3), were identified as the photoproducts by using FTIR spectroscopy. So far, the branching ratios of the photodissociation pathways of methylamine in the solid phase remain unknown. The methylamine molecule holds two non-equivalent hydrogen atoms on the methyl and the amino group, so we can expect the formation of two distinct radicals via a carbon–hydrogen or a nitrogen–hydrogen bond cleavage, namely CH2NH2 and CH3NH. These radicals are highly reactive and may reform methylamine with hydrogen atom recombination. Their direct infrared spectroscopic detection is therefore tricky. To solve that problem, we use carbon monoxide (CO) as an H radical scavenger, forming the intermediate species HCO. After the irradiation of a CH3NH2 : CO binary ice mixture, formamide (NH2CHO) and N-methylformamide (CH3NHCHO) were identified as the main photoproducts using both infrared and mass spectrometry. We give a rough approximation of the branching ratios, which are in agreement with previous studies in the gas phase.
Structure and function of the small terminase component of the DNA packaging machine in T4-like bacteriophages
Authors: Sun Siyang , Gao Song , Kondabagil Kiran , Xiang Ye , Rossmann Michael G. , Rao Venigalla B.
Published: December 2011

Tailed DNA bacteriophages assemble empty procapsids that are subsequently filled with the viral genome by means of a DNA packaging machine situated at a special fivefold vertex. The packaging machine consists of a “small terminase” and a “large terminase” component. One of the functions of the small terminase is to initiate packaging of the viral genome, whereas the large terminase is responsible for the ATP-powered translocation of DNA. The small terminase subunit has three domains, an N-terminal DNA-binding domain, a central oligomerization domain, and a C-terminal domain for interacting with the large terminase. Here we report structures of the central domain in two different oligomerization states for a small terminase from the T4 family of phages. In addition, we report biochemical studies that establish the function for each of the small terminase domains. On the basis of the structural and biochemical information, we propose a model for DNA packaging initiation.
Crystal structures of (Mg

1-
x

,Fe

x

)SiO
3
postperovskite at high pressures
Authors: Yamanaka Takamitsu , Hirose Kei , Mao Wendy L. , Meng Yue , Ganesh P. , Shulenburger Luke , Shen Guoyin , Hemley Russell J.
Published: January 2012

X-ray diffraction experiments on postperovskite (ppv) with compositions (Mg
0.9
Fe
0.1
)SiO
3
and (Mg
0.6
Fe
0.4
)SiO
3
at Earth core-mantle boundary pressures reveal different crystal structures. The former adopts the CaIrO
3
-type structure with space group
Cmcm
, whereas the latter crystallizes in a structure with the
Pmcm
(
Pmma
) space group. The latter has a significantly higher density (
ρ
 = 6.119(1) g/cm
3
) than the former (
ρ
 = 5.694(8) g/cm
3
) due to both the larger amount of iron and the smaller ionic radius of Fe
2+
as a result of an electronic spin transition observed by X-ray emission spectroscopy (XES). The smaller ionic radius for low-spin compared to high-spin Fe
2+
also leads to an ordered cation distribution in the M1 and M2 crystallographic sites of the higher density ppv structure. Rietveld structure refinement indicates that approximately 70% of the total Fe
2+
in that phase occupies the M2 site. XES results indicate a loss of 70% of the unpaired electronic spins consistent with a low spin M2 site and high spin M1 site. First-principles calculations of the magnetic ordering confirm that
Pmcm
with a two-site model is energetically more favorable at high pressure, and predict that the ordered structure is anisotropic in its electrical and elastic properties. These results suggest that interpretations of seismic structure in the deep mantle need to treat a broader range of mineral structures than previously considered.