bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical study of ion acceleration and plasma jet formation in the interaction of an intense laser beam normally incident on an overdense plasma
Authors: Shoucri M. , Lavocat-Dubuis X. , Matte J.-P. , Vidal F.
Published: July 2011

We present a numerical study of the acceleration of ions in the interaction of a high intensity circularly polarized laser beam normally incident on an overdense plasma target, and the subsequent formation of neutral plasma ejected toward the rear side of the target. We compare the results obtained from two different numerical codes. We use an Eulerian Vlasov code for the numerical solution of the one-dimensional relativistic Vlasov-Maxwell set of equations, for both electrons and ions, and a particle-in-cell code applied to the same problem. We consider the case when the laser free space wavelength λ0 is greater than the scale length of the jump in the plasma density at the target plasma edge Ledge (λ0 ≫ Ledge), and the ratio of the plasma density to the critical density is such that n/ncr ≫ 1. The ponderomotive pressure due to the incident high-intensity laser radiation pushes the electrons at the target plasma surface, producing a sharp density gradient at the plasma surface, which gives rise to a charge separation. The resulting electric field accelerates the ions that reach a free streaming expansion phase, where they are neutralized by the electrons. A neutral plasma jet is thus ejected toward the rear side of the target. Two cases are studied: In the first case, the laser intensity rises to a maximum and then remains constant, and in the second case, the laser intensity is a Gaussian-shaped pulse. The results show substantial differences in the phase-space structure of the ions and the electrons between these two cases. There is good agreement between the quantitative macroscopic results obtained by the two codes, and good qualitative agreement between the results showing the kinetic details of the phase-space structures. The low noise level of the Eulerian Vlasov code allows a more detailed representation of the phase-space structures associated with this system, especially in the low density regions of the phase-space where ions are accelerated.
Backlash elimination in parallel manipulators using actuation redundancy
Authors: Boudreau Roger , Mao Xu , Podhorodeski Ron
Published: July 2011

In this work, accuracy enhancement through backlash elimination is considered. When a nonredundantly actuated parallel manipulator is subjected to a wrench while following a trajectory, required actuator torque switching (going from positive to negative or vice versa) may occur. If backlash is present in the actuation hardware for a manipulator, torque switching compromises accuracy. When in-branch redundant actuation is added, a pseudoinverse torque solution requires smaller joint torques, but torque switching may still occur. A method is presented where concepts of exploiting a nullspace basis of the joint torques are used to ensure that single sense joint torques can be achieved for the actuated joints. The same sense torque solutions are obtained using nonlinear optimization. The methodology is applied to several examples simulating parallel manipulators in machining applications.
Evaluation of 3D grasps with physical interpretations using object wrench space
Authors: Jeong Hyunhwan , Cheong Joono
Published: July 2011

In this paper we propose an intuitive and practical grasp quality measure for grasping 3D objects with a multi-fingered robot hand. The proposed measure takes into account the object geometries through the concept of object wrench space. Physically, the positive measure value has a meaning of the minimum single disturbance that grasp cannot resist, while the negative measure value implies the minimum necessary helping force that restores a non-force-closure grasp into a force-closure one. We show that the measure value is invariant between similar grasps and also between different torque origins. We verify the validity of the proposed measure via simulations by using computer models of a three-fingered robot hand and polygonal objects.
ASYMPTOTIC BEHAVIOR OF THE CUSUM OF SQUARES TEST UNDER STOCHASTIC AND DETERMINISTIC TIME TRENDS
Authors: Nielsen Bent , Sohkanen Jouni S.
Published: July 2011

We generalize the cumulative sum of squares (CUSQ) test to the case of nonstationary autoregressive distributed lag models with deterministic time trends. The test may be implemented with either ordinary least squares residuals or standardized forecast errors. In explosive cases the asymptotic theory applies more generally for the least squares residuals-based test. Preliminary simulations of the tests suggest a very modest difference between the tests and a very modest variation with nuisance parameters. This supports the use of the tests in explorative analysis.
Getting the point: The role of gesture in managing intersubjectivity in a design activity
Authors: Donovan Jared , Heinemann Trine , Matthews Ben , Buur Jacob
Published: July 2011

This paper illustrates the complexity of pointing as it is employed in a design workshop. Using the method of interaction analysis, we argue that pointing is not merely employed to index, locate, or fix reference to an object. It also constitutes a practice for reestablishing intersubjectivity and solving interactional trouble such as misunderstandings or disagreements by virtue of enlisting something as part of the participants’ shared experience. We use this analysis to discuss implications for how such practices might be supported with computer mediation, arguing for a “bricolage” approach to systems development that emphasizes the provision of resources for users to collaboratively negotiate the accomplishment of intersubjectivity rather than systems that try to support pointing as a specific gestural action.
Grasping gestures: Gesturing with physical artifacts
Authors: van den Hoven Elise , Mazalek Ali
Published: July 2011

Gestures play an important role in communication. They support the listener, who is trying to understand the speaker. However, they also support the speaker by facilitating the conceptualization and verbalization of messages and reducing cognitive load. Gestures thus play an important role in collaboration and also in problem-solving tasks. In human–computer interaction, gestures are also used to facilitate communication with digital applications, because their expressive nature can enable less constraining and more intuitive digital interactions than conventional user interfaces. Although gesture research in the social sciences typically considers empty-handed gestures, digital gesture interactions often make use of hand-held objects or touch surfaces to capture gestures that would be difficult to track in free space. In most cases, the physical objects used to make these gestures serve primarily as a means of sensing or input. In contrast, tangible interaction makes use of physical objects as embodiments of digital information. The physical objects in a tangible interface thus serve as representations as well as controls for the digital information they are associated with. Building on this concept, gesture interaction has the potential to make use of the physical properties of hand-held objects to enhance or change the functionality of the gestures made. In this paper, we look at the design opportunities that arise at the intersection of gesture and tangible interaction. We believe that gesturing while holding physical artifacts opens up a new interaction design space for collaborative digital applications that is largely unexplored. We provide a survey of gesture interaction work as it relates to tangible and touch interaction. Based on this survey, we define the design space of tangible gesture interaction as the use of physical devices for facilitating, supporting, enhancing, or tracking gestures people make for digital interaction purposes, and outline the design opportunities in this space.
Hepatitis B prevalence in the Turkish population of Arnhem: implications for national screening policy?
Authors: RICHTER C. , BEEST G. TER , SANCAK I. , AYDINLY R. , BULBUL K. , LAETEMIA-TOMATA F. , DE LEEUW M. , WAEGEMAEKERS T. , SWANINK C. , ROOVERS E.
Published: July 2011

Despite the increased prevalence of hepatitis B and C in most migrant groups in The Netherlands, a national screening policy for these infections is not available. In order to estimate the prevalence of hepatitis B and C in the largest group of first-generation migrants (FGM) in The Netherlands, we conducted a screening project in the Turkish community of Arnhem. In a separate project we identified patients from the target population with chronic hepatitis B and C from hospital records (1990–2008). Educational meetings concerning hepatitis were organized, with all participants being offered a blood screening test. Participants were tested for hepatitis B surface antigen (HBsAg), antibodies to hepatitis B core antigen (anti-HBc) and antibodies to hepatitis C virus (anti-HCV). In total 709 persons were tested, a complete dataset was available for 647 patients. We found that 3·0% and 0·4% of Turkish FGM aged >24 years in Arnhem had active hepatitis B, defined as HBsAg positive, and tested positive for anti-HCV, respectively. The hospital records revealed another 32 patients, 28 with hepatitis B and four with hepatitis C representing 0·7% for hepatitis B and 0·1% for hepatitis C in relation to the total number of Turkish FGM in Arnhem. We believe that active hepatitis screening of FGM from Turkey should be part of the national health policy as it will benefit the individual and public health.
Le passé composé en usage futur et la pertinence au présent
Authors: DE SAUSSURE LOUIS
Published: July 2011

Cet article étudie les effets de sens du passé composé (PC) sous la portée d'un adverbe situeur futur en français. Nous partons de l'hypothèse de Sthioul (1998) selon laquelle cet usage du PC impose une représentation conçue comme passée depuis une projection allocentrique du moment de la parole située dans le futur. Cet article considère que le PC en usage futur est un usage métalinguistique du passé composé et donc un usage métareprésentationnel (ouinterprétatif, cf. Sperber & Wilson 1995) du langage. Nous explorons les restrictions d'emploi de cet usage par des critères sémantiques (télicité, agentivité) et concluons qu'aucun d'entre eux ne forme une contrainte forte alors qu'il y a une condition pragmatique d'emploi beaucoup plus contraignante pour l'usage futur du passé composé. En particulier, nous suggérons que i) ce qui est représenté au futur n'est pas le procès mais l'état résultant (ce qui le rapproche du PC de l'accompli), ii) que l'état résultant est typiquement désirable et a déclenche une inférence à propos de l'attitude ou du comportement à tenir dans le présent dans la perspective de l'état résultant au futur. Ainsi, le passé composé en usage futur prend sa pertinence au présent et non directement au futur.
AMNIOINFUSION FOR VERY EARLY RUPTURE OF MEMBRANES
Authors: ROBERTS DEVENDER
Published: July 2011

Premature rupture of membranes (PROM) is a major cause of perinatal mortality and morbidity associated with preterm delivery in a third of cases. Fetal survival is even more compromised when the membranes rupture early in the second trimester (very early PROM). Survival is associated with problems of delivery of the very preterm fetus as well as associated risks of feto-maternal infection. In the context of studies of amnioinfusion, very early rupture of membranes is defined as rupture between 16 and 26 weeks of pregnancy.
Transcatheter closure of a large left ventricular pseudoaneurysm using an Amplatzer Vascular Plug 4 and stenting of the inferior caval vein in a child
Authors: Baspinar Osman , Mete Ahmet , Davutoglu Vedat
Published: July 2011

Left ventricular pseudoaneurysm is especially rare in childhood, and its main treatment option should be surgery. We describe the case of a 9.5-year-old boy who first underwent mitral vegetation excision and then an unsuccessful pseudoaneurysm operation. Owing to pseudoaneurysmal sac dimensions, inferior caval vein syndrome developed. We delivered the Amplatzer Vascular Plug 4 into the pseudoaneurysm and treated the inferior caval vein syndrome with a bare Cheatham–Platinum stent. The patient was asymptomatic at the last follow-up.
Use of a self-expanding custom-made stent graft to treat lateral tunnel leak, stenosis, and fenestration in the Fontan pathway
Authors: Chadalavada Sucharitha , Boolkah Soodevi , Smith Benjamin Gregory
Published: July 2011

A 12-year-old girl with hypoplastic right heart, double inlet left ventricle, and transposition of the great arteries had a lateral tunnel Fontan operation 8 years previously. She developed symptoms related to a combination of stenosis in the inferior caval venous pathway, a fenestration, and leak in the lateral tunnel. These were successfully treated with a custom-made stent graft.
Device closure of atrial septal defect: medium-term outcome with special reference to complications
Authors: Sadiq Masood , Kazmi Tehmina , Rehman Asif U. , Latif Farhan , Hyder Najam , Qureshi Shakeel A.
Published: July 2011

Background

There are concerns over the outcome of device closure of secundum atrial septal defect with special reference to erosions and aortic regurgitation.

Aim

To assess the medium-term outcome of device closure of atrial septal defects with special reference to complications.

Methods

A total of 205 patients with secundum atrial septal defects underwent transcatheter closure from October, 1999 to April, 2009. The median age was 18 (1.4–55) years. Amplatzer Septal Occluder was used in all the patients. Medium-term follow-up was available in 176 of 200 (88%) patients.

Results

Device closure was successful in 200 out of 205 (98%) patients. The device embolised in four patients and was associated with short inferior caval vein margin (p = 0.003). Balloon sizing in 71 patients (35%) resulted in implantation of a larger device (p = 0.002). Early complications included pericardial effusion, 2:1 heart block, and infective endocarditis (1 patient each). There were eight patients who reported migraine (3.9%). At median follow-up of 5.8 (0.6–10.3) years, complete closure occurred in 197 out of 200 patients. Short superior caval vein margin was associated with a residual shunt (p < 0.001). There were two patients who developed mild aortic regurgitation (1%), which correlated with a device-to-defect ratio of >1.3:1 (p = 0.001). There were no erosions, late embolisation, or thromboembolism. Atrial fibrillation occurred in three adults (1.5%).

Conclusions

Device closure of secundum atrial septal defects using Amplatzer Septal Occluder is safe and effective in the medium term. Short inferior caval vein margin correlates with increased risk of embolisation and short superior caval vein margin with a residual shunt. The risk of developing aortic regurgitation is low and correlates with increased device-to-defect ratio.
Persistent left superior caval vein with absent right superior caval vein: importance of awareness
Authors: Lee Sungwon , Cha Joo H. , Han Dae H.
Published: July 2011

Isolated persistent left superior caval vein is a rare anomaly of the systemic venous return. We describe an unsuccessful pacemaker implantation through the right subclavian vein, which later turned out to be due to a venous anomaly. This case and some other cases show that with the help of a multidetector computed tomography, an isolated persistent left superior caval vein is not a contraindication for subclavian approached pacemaker insertion.
Exploring patterns in dictionary definitions for synonym extraction
Authors: WANG TONG , HIRST GRAEME
Published: July 2011

Automatic determination of synonyms and/or semantically related words has various applications in Natural Language Processing. Two mainstream paradigms to date, lexicon-based and distributional approaches, both exhibit pros and cons with regard to coverage, complexity, and quality. In this paper, we propose three novel methods—two rule-based methods and one machine learning approach—to identify synonyms from definition texts in a machine-readable dictionary. Extracted synonyms are evaluated in two extrinsic experiments and one intrinsic experiment. Evaluation results show that our pattern-based approach achieves best performance in one of the experiments and satisfactory results in the other, comparable to corpus-based state-of-the-art results.
Brief Cognitive Behavioural Therapy for Hallucinations: Can it Help People Who Decide Not to Take Antipsychotic Medication? A Case Report
Authors: Hutton Paul , Morrison Anthony P. , Taylor Hannah
Published: July 2011

Background:Cognitive behavioural therapy (CBT) can be helpful for many people who experience psychosis; however most research trials have been conducted with people also taking antipsychotic medication. There is little evidence to know whether CBT can help people who choose not to take this medication, despite this being a very frequent event. Developing effective alternatives to antipsychotics would offer service users real choice.Aims:To report a case study illustrating how brief CBT may be of value to a young person experiencing psychosis and not wishing to take antipsychotic medication.Method:We describe the progress of brief CBT for a young man reporting auditory and visual hallucinations in the form of a controlling and dominating invisible companion. We describe the formulation process and discuss the impact of key interventions such as normalising and detached mindfulness.Results:Seven sessions of CBT resulted in complete disappearance of the invisible companion. The reduction in frequency and duration followed reduction in conviction in key appraisals concerning uncontrollability and unacceptability.Conclusions:This case adds to the existing evidence base by suggesting that even short-term CBT might lead to valued outcomes for service users experiencing psychosis but not wishing to take antipsychotic medication.
Stop consonant productions of Korean–English bilingual children
Authors: LEE SUE ANN S. , IVERSON GREGORY K.
Published: July 2011

The purpose of this study was to conduct an acoustic examination of the obstruent stops produced by Korean–English bilingual children in connection with the question of whether bilinguals establish distinct categories of speech sounds across languages. Stop productions were obtained from ninety children in two age ranges, five and ten years: thirty Korean–English bilinguals, thirty monolingual Koreans and thirty monolingual English speakers. Voice-Onset-Time (VOT) lag at word-initial stop and fundamental frequency (f0) in the following vowel (hereafter vowel-onset f0) were measured. The bilingual children showed different patterns of VOT in comparison to both English and Korean monolinguals, with longer VOT in their production of Korean stop consonants and shorter VOT for English. Moreover, the ten-year-old bilinguals distinguished all stop categories using both VOT and vowel-onset f0,whereas the five-year-olds tended to make stop distinctions based on VOT but not vowel-onset f0. The results of this study suggest that bilingual children at around five years of age do not yet have fully separate stop systems, and that the systems continue to evolve during the developmental period.
High rates of serum selenium deficiency among HIV- and HCV-infected and uninfected drug users in Buenos Aires, Argentina
Authors: Sheehan Heidi B , Benetucci Jorge , Muzzio Estela , Redini Liliana , Naveira Jorge , Segura Marcela , Weissenbacher Mercedes , Tang Alice M
Published: July 2011

Objective

To describe the prevalence of low serum Se and determine whether HIV, hepatitis C virus (HCV) and/or the types of drugs used are associated with serum Se in a cohort of infected and uninfected drug users.

Design

Independent correlates of low serum Se levels based on data collected from food recalls, physical examinations and clinical questionnaires were identified using multivariate regression analysis.

Setting

Buenos Aires, Argentina

Subjects

A total of 205 (twenty-five female and 180 male) former and current drug users.

Results

Drug users had an average serum Se level of 69·8 (sd32·8) μg/dl, and 82 % were considered deficient (<85 μg/dl). Multivariate analyses found that HIV- and/or HCV-infected individuals had lower mean Se compared with healthy, uninfected drug users (HIV/HCV co-infection: −25·3 μg/l (se7·6),P= 0·001; HIV alone: −28·9 μg/l (se6·9),P< 0·001; HCV alone: −19·4 μg/l (se7·1),P= 0·006). Current and previous drug use was associated with higher serum Se. Cigarette smoking and heavy alcohol consumption were not found to be associated with Se status.

Conclusions

Low serum Se levels are highly prevalent among drug users in Buenos Aires, Argentina. Se supplementation and/or dietary interventions may be warranted in drug users who are at high risk for HIV and/or HCV infection.
Socio-economic differences in takeaway food consumption among adults
Authors: Miura Kyoko , Giskes Katrina , Turrell Gavin
Published: July 2011

Objective

To examine socio-economic differences in the frequency and types of takeaway foods consumed.

Design

A cross-sectional postal survey.

Setting

Participants were asked about their usual consumption of overall takeaway food (<4 times/month or ≥4 times/month) and of twenty-two specific takeaway food items (<1 time/month or ≥1 time/month); these latter foods were grouped into ‘healthy’ and ‘less healthy’ choices. Socio-economic position was measured on the basis of educational level and equivalised household income, and differences in takeaway food consumption were assessed by calculating prevalence ratios using log binomial regression.

Subjects

Adults aged 25–64 years from Brisbane, Australia, were randomly selected from the electoral roll (n903; 63·7 % response rate).

Results

Compared with their more educated counterparts, the least educated were more regular consumers of overall takeaway food and fruit or vegetable juice and less regular consumers of sushi. For the ‘less healthy’ items, the least educated more regularly consumed potato chips, savoury pies, fried chicken and non-diet soft drinks; however, the least educated were less likely to consume curry. Household income was not associated with overall takeaway consumption. The lowest-income group was a more regular consumer of fruit or vegetable juice compared with the highest-income group. Among the ‘less healthy’ items, the lowest-income group was a more regular consumer of fried fish, ice cream and milk shakes, whereas curry was consumed less regularly.

Conclusions

The frequency and types of takeaway foods consumed by socio-economically disadvantaged groups may contribute to inequalities in overweight or obesity and to chronic disease.
The Significant Role of Centrosomes in Stem Cell Division and Differentiation
Authors: Schatten Heide , Sun Qing-Yuan
Published: July 2011

The role of centrosomes in stem cell division has recently been highlighted and further ascribes important functions to centrosomes in stem cell maintenance, cellular differentiation, and development. Advanced cell and molecular studies coupled with immunofluorescence, electron microscopy, and live cell imaging of specific centrosome proteins have contributed greatly to our knowledge of centrosome composition, structure, and dynamics and have uncovered new insights into mechanisms of centrosome functions in asymmetric cell division. The establishment of asymmetry and differential positioning of mother and daughter centrosomes during stem cell mitosis is important for allowing one cell to maintain stem cell characteristics while the sibling cell undergoes differentiation. Another key role for centrosomes has been revealed in primary cilia of embryonic stem cells that play significant roles in cellular signaling and are therefore critically important for stem cell decisions. Studies of signaling through primary cilia may contribute important information that may aid in the production of specific cells that are suitable for tissue repair and regeneration in the field of regenerative medicine.
Social information and political participation on the internet: an experiment
Authors: Margetts Helen , John Peter , Escher Tobias , Reissfelder Stéphane
Published: July 2011

This paper tests whether the social information provided by the internet affects the decision to participate in politics. In a field experiment, subjects could choose to sign petitions and donate money to support causes. Participants were randomized into treatment groups that received varying information about how many other people had participated and a control group receiving no social information. Results show that social information has a varying effect according to the numbers provided, which is strongest when there are more than a million other participants, supporting claims about critical mass, and tipping points in political participation.
Electoral incentives, party discipline, and legislative organization: manipulating legislative committees to win elections and maintain party unity
Authors: Fujimura Naofumi
Published: July 2011

Political parties are often faced with seemingly opposing goals when trying to secure members’ reelection and maintain party unity. On one hand, a party needs to fulfill members’ diverse electoral needs for their reelection, and on the other hand, the party must force members to vote in unison according to party lines for collective decisions. How does a party influence its members to take unified action while meeting their individual electoral needs? Through an analysis of the Japanese Diet, this study argues that parties attempt to achieve the reelection of their members and maintain party unity by manipulating legislative committee assignments and deliberations. In particular, the study demonstrates that a party shapes committees in a different way according to policy areas over which committees have jurisdiction. A party tends to accept its members’ requests for affiliation and allow their self-management in committees concerned with particularistic benefits so that they can deliver specific benefits to each electoral district. In addition, a party tends to assign members who have average policy positions in the party to committees concerned with general benefits to make policies that satisfy many constituencies.
The universal "shape" of human languages: spectral analysis beyond speech
Authors: Moscoso del Prado Fermin
Published: July 2011

A common recommendation for linguists is that, when analyzing language, they should take a "man-from-mars", know-nothing, perspective to describe the structures that they observe, if possible limiting themselves to the mechanical application of a set of well-defined techniques and criteria. Unfortunately, the complex nature of linguistic structures makes it difficult to adopt such a detached perspective. A language, as represented by a corpus of text, can be described macroscopically by the symbolic periodogram of the corpus, analogous to the spectrograms commonly used for describing speech. Here, I show that the periodogram exhibits a universal "shape" from human languages, and this shape originates in known properties of the human mind. Despite the universality of the overall pattern, subtle differences also reveal particularities of individual languages. These differences demonstrate the long-held --but unproven-- hypothesis that human languages balance the amount of structure contained in different levels of description so that the total amount of linguistic structure remains fairly constant across languages. The universal pattern found in the periodograms illustrates how the biological properties of the mind constrain the structure of human languages.
SED-ML Script Language
Authors: Bergmann Frank
Published: July 2011

The Simulation Experiment Description Markup Language (SED-ML) is a XML format describing simulation experiments, so that they can be easily exchanged independent of software tools that created them. This document describes the SED-ML Script, a Python based shorthand that makes it easy to create / edit SED-ML documents.
Mono-carboxylated diaminedichloridoplatinum(iv) complexes – selective synthesis, characterization, and cytotoxicity
Authors: Pichler Verena , Valiahdi Seied M. , Jakupec Michael A. , Arion Vladimir B. , Galanski Mathea S. , Keppler Bernhard K.
Published: July 2011

Selective mono-carboxylation of (OC-6-43)-dichlorido(N,N-dimethyl-ethane-1,2-diamine)dihydroxido platinum(iv) with succinic anhydride and subsequent esterification afforded novel cytotoxic platinum complexes with IC50 values down to the low nanomolar range.
Advanced core/multishell germanium/silicon nanowire heterostructures: The Au-diffusion bottleneck
Authors: Dayeh Shadi A. , Mack Nathan H. , Huang Jian Yu , Picraux S. T.
Published: July 2011

Synthesis of germanium/silicon (Ge/Si) core/shell nanowire heterostructures is typically accompanied by unwanted gold (Au) diffusion on the Ge nanowire sidewalls, resulting in rough surface morphology, undesired whisker growth, and detrimental performance of electronic devices. Here, we advance understanding of this Au diffusion on nanowires, its diameter dependence and its kinetic origin. We devise a growth procedure to form a blocking layer between the Au seed and Ge nanowire sidewalls leading to elimination the Au diffusion for in situ synthesis of high quality Ge/Si core/shell heterostructures.
Design and evaluation of a pulsed-jet chirped-pulse millimeter-wave spectrometer for the 70–102 GHz region
Authors: Park G. Barratt , Steeves Adam H. , Kuyanov-Prozument Kirill , Neill Justin L. , Field Robert W.
Published: July 2011

Chirped-pulse millimeter-wave (CPmmW) spectroscopy is the first broadband (multi-GHz in each shot) Fourier-transform technique for high-resolution survey spectroscopy in the millimeter-wave region. The design is based on chirped-pulse Fourier-transform microwave (CP-FTMW) spectroscopy [G. G. Brown, B. C. Dian, K. O. Douglass, S. M. Geyer, S. T. Shipman, and B. H. Pate, Rev. Sci. Instrum. 79, 053103 (2008)]10.1063/1.2919120, which is described for frequencies up to 20 GHz. We have built an instrument that covers the 70–102 GHz frequency region and can acquire up to 12 GHz of spectrum in a single shot. Challenges to using chirped-pulse Fourier-transform spectroscopy in the millimeter-wave region include lower achievable sample polarization, shorter Doppler dephasing times, and problems with signal phase stability. However, these challenges have been partially overcome and preliminary tests indicate a significant advantage over existing millimeter-wave spectrometers in the time required to record survey spectra. Further improvement to the sensitivity is expected as more powerful broadband millimeter-wave amplifiers become affordable. The ability to acquire broadband Fourier-transform millimeter-wave spectra enables rapid measurement of survey spectra at sufficiently high resolution to measure diagnostically important electronic properties such as electric and magnetic dipole moments and hyperfine coupling constants. It should also yield accurate relative line strengths across a broadband region. Several example spectra are presented to demonstrate initial applications of the spectrometer.
InGaAs surface preparation for atomic layer deposition by hydrogen cleaning and improvement with high temperature anneal
Authors: Melitz Wilhelm , Shen Jian , Kent Tyler , Kummel Andrew C. , Droopad Ravi
Published: July 2011

Using in situ atomic scale imaging with scanning tunneling microscopy/spectroscopy, a combination of atomic hydrogen dosing, annealing, and trimethyl aluminum dosing is observed to produce an ordered unpinned passivation layer on an air exposed InGaAs(001)-(4 × 2) surface with only monatomic steps. This shows that conventional gate-last semiconductor processing can be employed to fabricate a variety of electronic devices, even on air exposed compound semiconductors.
Dissipative quantum coherent dynamics probed in phase-space: Electronically resonant 5-color 4-wave mixing on I2(B) in solid Kr
Authors: Segale D. , Apkarian V. A.
Published: July 2011

Spectrally resolved, 4-wave mixing measurements in five resonant colors are used to interrogate vibronic quantum coherences in phase-space. We highlight the principles through measurements on the B-state of I2 in solid Kr – a prototype of a system strongly coupled to its environment. The measurements consist of preparing a superposition of wavepackets on the B-state and interrogating their cross-coherence as they get entangled with the environment. The study provides direct realizations of fundamental quantum principles in the mechanics of molecular matter, among them: the distinction between quantum and classical coherent dynamics of a system entangled with the environment, coherent dissipation, event-driven decoherence, environment selected coherent states, and non-local mechanics.
Spectroscopic study of (two-dimensional) molecule-based magnets: [MII(TCNE)(NCMe)2][SbF6] (M = Fe, Mn, Ni)
Authors: Olson Christopher , Heth Christopher L. , Lapidus Saul H. , Stephens Peter W. , Halder Gregory J. , Pokhodnya Konstantin
Published: July 2011

The M-[TCNE] (M = 3d metal; TCNE = tetracyanoethylene) system is one of the most interesting classes of molecule-based magnets, exhibiting a plethora of compositions and structures (inorganic polymer chains, 2D layers, 3D networks, and amorphous solids) with a wide range of magnetic ordering temperatures (up to 400 K). A systematic study of vibrational (both infrared and, for the first time, Raman) properties of the family of new TCNE-based magnets of MII(TCNE) (NCMe)2[SbF6] [M = Mn, Fe, Ni] composition is discussed in conjunction with their magnetic behavior and newly reso-lved crystal structures. The vibrational properties of the isolated TCNE•− anion in the paramagnetic Bu4N [TCNE•−] salt and recently characterized 2D layered magnet FeII(TCNE)(NCMe)2[FeCl4] are also reported for comparison. Additionally, a linear correlation between νC=C (ag) frequency of the TCNE ligand and its formal charge Z (the spin density on the π* orbital), Z = [1571 − νC=C (ag)]/154.5 [e], is presented. It is shown that monitoring Z by Raman spectroscopy is of great use in providing information that allows understanding the peculiarity of the superexchange interaction in M-[TCNE] magnets and establishing the structure-magnetic properties correlations in this class of magnetic material.
Relaxation of energetic S(1D) atoms in Xe gas: Comparison of ab initio calculations with experimental data
Authors: Bovino S. , Zhang P. , Kharchenko V. , Dalgarno A.
Published: July 2011

In this paper, we report our investigation of the translational energy relaxation of fast S(1D) atoms in a Xe thermal bath. The interaction potential of Xe-S was constructed using ab initio methods. Total and differential cross sections were then calculated. The latter have been incorporated into the construction of the kernel of the Boltzmann equation describing the energy relaxation process. The solution of the Boltzmann equation was obtained and results were compared with those reported in experiments [G. Nan, and P. L. Houston, J. Chem. Phys. 97, 7865 (1992)]10.1063/1.463461. Good agreement with the measured time-dependent relative velocity of fast S(1D) atoms was obtained except at long relaxation times. The discrepancy may be due to the error accumulation caused by the use of hard sphere approximation and the Monte Carlo analysis of the experimental data. Our accurate description of the energy relaxation process led to an increase in the number of collisions required to achieve equilibrium by an order of magnitude compared to the number given by the hard-sphere approximation.
Time-dependent importance sampling in semiclassical initial value representation calculations for time correlation functions
Authors: Tao Guohua , Miller William H.
Published: July 2011

An efficient time-dependent importance sampling method is developed for the Monte Carlo calculation of time correlation functions via the initial value representation (IVR) of semiclassical (SC) theory. A prefactor-free time-dependent sampling function weights the importance of a trajectory based on the magnitude of its contribution to the time correlation function, and global trial moves are used to facilitate the efficient sampling the phase space of initial conditions. The method can be generally applied to sampling rare events efficiently while avoiding being trapped in a local region of the phase space. Results presented in the paper for two system-bath models demonstrate the efficiency of this new importance sampling method for full SC-IVR calculations.
Transitional types of electron conductivity in cryogenic media
Authors: Nazin S. , Shikin V.
Published: July 2011

Possible descriptions of electron conductivity in the transitional density region between free and localized electronic states in cryogenic media are discussed.
Extraordinary acoustic shielding by a monolayer of periodical polymethyl methacrylate cylinders immersed in water
Authors: Peng Shasha , Qiu Chunyin , He Zhaojian , Ye Yangtao , Xu Shengjun , Tang Kun , Ke Manzhu , Liu Zhengyou
Published: July 2011

We study, both experimentally and numerically, the acoustic transmission through a monolayer of periodical polymethyl methacrylate cylinders immersed in water. Beyond our expectation, nearly-total reflection is observed for the system, consisting of two ingredients with low impedance contrast. Our investigation manifests that this extraordinary acoustic shielding mostly stems from the resonant excitation of the localized Stoneley surface waves in individual cylinders. Such local modes are rooted in the complicated coupling between the longitudinal and transverse waves and are unique in acoustic systems.
Classification of integrable two-component Hamiltonian systems of hydrodynamic type in 2 + 1 dimensions
Authors: Ferapontov E. V. , Odesskii A. V. , Stoilov N. M.
Published: July 2011

Hamiltonian systems of hydrodynamic type occur in a wide range of applications including fluid dynamics, the Whitham averaging procedure, and the theory of Frobenius manifolds. In 1 + 1 dimensions, the requirement of the integrability of such systems by the generalised hodograph transform implies that integrable Hamiltonians depend on a certain number of arbitrary functions of two variables. On the contrary, in 2 + 1 dimensions the requirement of the integrability by the method of hydrodynamic reductions, which is a natural analogue of the generalised hodograph transform in higher dimensions, leads to finite-dimensional moduli spaces of integrable Hamiltonians. In this paper we classify integrable two-component Hamiltonian systems of hydrodynamic type for all existing classes of differential-geometric Poisson brackets in 2D, establishing a parametrisation of integrable Hamiltonians via elliptic/hypergeometric functions. Our approach is based on the Godunov-type representation of Hamiltonian systems, and utilises a novel construction of Godunov's systems in terms of generalised hypergeometric functions.
Shubnikov-de Haas-like oscillatory pattern of dc conductivity in a 2-dimensional indium gallium arsenide
Authors: Lyong Kang Nam , Chil Lee Sang , Don Choi Sang
Published: July 2011

The conductivity formula derived by using the KC reduction identity and a state-dependent projection technique is applied to a two-dimensional system of electrons interacting with deformation potential acoustic phonons. The system is in the presence of a perpendicular magnetic field and of the Rashba spin-orbit interaction (RSOI). The dc conductivity is shown to oscillate with the magnetic field above 0.6T near the Zeeman factor g=-0.8 and the RSOI strength α0=0.5×10-11eV·m. The pattern of oscillations is shown to be susceptible to change even by small change in g and α0, while the deformation potential constant, which characterizes the electron-phonon interaction, plays no role in changing the pattern at the temperature T=70 K.
Structural effects on Stokes and anti-Stokes luminescence of double-perovskite (Ba,Sr)2CaMoO6: Yb3+,Eu3+
Authors: Ye Shi , Li Yajie , Yu Dechao , Yang Zhongmin , Zhang Qinyuan
Published: July 2011

This paper deals with the investigation of structural effects on Stokes and anti-Stokes luminescence properties of double-perovskite (Ba,Sr)2CaMoO6: Eu3+,Yb3+. It is found that the tilting of the (Ca/Mo)O6 octahedra framework favors energy transfer from the MoO6 group to Eu3+/Yb3+ at the B site for Stokes luminescence processes, in which the structural connectivity angle ∠Mo–O–Eu/Yb is slightly smaller than 180°. While Eu3+/Yb3+ at the A site with a structural connectivity angle ∠Mo–O–Eu/Yb of around 90° least benefits the energy transfer. The linear connectivity of Yb–O–Mo–O–Eu with or without tilting of the (Ca/Mo)O6 framework for Eu3+ and Yb3+ at the B site strongly restrains the anti-Stokes luminescence. Whereas, it shows normal anti-Stokes luminescence for Eu3+ or Yb3+ at the A site and Yb3+ or Eu3+ at the B site with ∠Yb–O–Eu of around 90°. This research may open up promising new perspectives for designing novel luminescent materials with high efficiency.
Epitaxial growth and characterization of graphene on free-standing polycrystalline 3C-SiC
Authors: Huang Han , Liang Wong Swee , Tin Chin-Che , Qiang Luo Zhi , Xiang Shen Ze , Chen Wei , Shen Wee Andrew Thye
Published: July 2011

The epitaxial growth of graphene on inexpensive, commercially available, free-standing polycrystalline 3 C-SiC has been achieved by solid state graphitization in ultrahigh vacuum. The structural and electronic properties of such epitaxial graphene (EG) have been explored by Raman spectroscopy, scanning tunneling microscopy (STM), and scanning tunneling spectroscopy (STS). The Raman results show that the grown EG is compressively stressed. The quality of such EG is similar to that on single-crystalline hexagonal SiC substrates. The STM measurements show that the EG grown on polycrystalline SiC presents atomically smooth surfaces across large regions of the underlying SiC substrate with some nanometer-scale features, such as one-dimensional (1-D) ridges, 1-D grain boundaries, and graphene in different stacking sequences. The STS measurements reveal the electronic properties of such EG at an atomic scale. Our approach suggests a more inexpensive way to grow high quality and large scale graphene and represents a promising step toward commercialization of graphene-based electronics.
Spatially resolved inhomogeneous depressions of the excitons Zeeman splitting in an integrated magnetic-multiple quantum wells system
Authors: Abdelrahman A. , Kang H. , Yim S. Y. , Vasiliev M. , Alameh K. , Lee Y. T.
Published: July 2011

We report on the generation of a nonuniform spatial distribution of the heavy and light-hole excitons in a multiple quantum wells system integrated with a localized inhomogeneous weak magnetic field. An inhomogeneous spatially resolved depression of the Zeeman splittings of the heavy-hole excitons and the light-hole excitons with respect to their translational wave vectors is observed. A localized inverted concentration of the two types of the excitons due to the inhomogeneity of the magnetic field is also measured. A simple method to integrate permanent magnetic materials with the multiple quantum wells system is used to create an accessible degree of control for magnetically manipulating the excitonic distributions.
Surface polaronic effect on donor-impurity states of a wurtzite nitride nanowire: Two-parameter variational approach
Authors: Zhang Li , Shi J. J. , Shao P. M.
Published: July 2011

By employing the two-parameter variational approach, the donor-impurity states with surface optical (SO) phonons, also called SO phonon bound polarons in a quasi-one-dimensional (Q1D) wurtzite nanowire (NW) are investigated. Numerical calculations on a GaN NW are performed. The results reveal that the SO phonon contribution to the binding energy of the SO phonon bound polaron in GaN NWs reaches 200 meV, which is one order of magnitude larger than that of GaAs NWs with the same radius. The large contribution of SO phonons to the total binding energy is mainly ascribed to the stronger electron-phonon coupling constant in GaN materials. The calculated results of impurity binding energy are consistent with the recent experimental measurement of the active energy in GaN NW systems. The numerical results also shows that the two-parameter variational approach is necessary and suitable for the description of donor-impurity states in Q1D wurtzite GaN NW structures, especial for the NWs with a relatively small radius (such as R < 10 nm).
Helicoidal surfaces with constant anisotropic mean curvature
Authors: Kuhns Chad , Palmer Bennett
Published: July 2011

We study surfaces which are in equilibrium for an anisotropic surface energy and which are invariant under a helicoidal motion. For anisotropic functionals with axially symmetric Wulff shapes, we generalize the recently developed twizzler representation [Perdomo, O., A dynamical interpretation of the profile curve of CMC twizzlers surfaces, e-print arXiv:1001.5198v1] to the anisotropic case and show how all helicoidal constant anisotropic mean curvature surfaces can be obtained by quadratures. When the functional is not axially symmetric, we produce a canonical critical point which is analogous to the classical helicoid.
Existence of modulated structure and negative magnetoresistance in Ga excess Ni-Mn-Ga
Authors: Singh Sanjay , Rawat R. , Barman S. R.
Published: July 2011

Ni2−xMnGa1+x (0.4 ≤ x ≤ 0.9) show the existence of modulated crystal structure at room temperature (RT) in the martensite phase, exhibit ferromagnetic behavior and have high martensitic transition temperature. The saturation magnetic moment decreases as Ga content increases, and this is related to antisite defects between Mn and Ga atoms leading to Mn-Mn nearest neighbor antiferromagnetic interaction. Negative magnetoresistance is observed at RT that increases linearly with magnetic field. These properties of Ga excess Ni-Mn-Ga show that it is a potential candidate for technological applications.
Classical capillary turbulence on the surface of quantum liquid He-II
Authors: Abdurakhimov L. V. , Brazhnikov M. Yu. , Remizov I. A. , Levchenko A. A.
Published: July 2011

Superfluid helium-4 is a unique liquid for the experimental study of capillary wave turbulence because of its very low viscosity. We have studied the influence of the amplitude and spectral characteristics of an excitation force on the behavior of the turbulence cascade of capillary waves in a 30-cm-diam cylindrical cell. The experimental results can be explained in terms of wave turbulence theory (WTT) when the pump amplitude is relatively high. However, a very interesting phenomenon is observed at moderate harmonic surface excitation amplitudes. The turbulence spectrum deviates from the power law form predicted by WTT at high frequencies; a local maximum develops, which can be interpreted as wave energy accumulation. Our estimates show that a special case of wave turbulence was realized in our experiments, namely, a discrete turbulence in which the discreteness of the cell resonant frequencies has a strong effect on the mechanism of the nonlinear interaction.