bluuebunny/crossref_metadata_2025 huggingface dataset:
The two‐component Camassa‐Holm system in weighted Lp spaces
Authors: Kohlmann M.
Published: June 2013

We present some new persistence results for the non‐periodic two‐component Camassa‐Holm (2CH) system in weighted Lp spaces. Working with moderate weight functions that are commonly used in time‐frequency analysis, the paper generalizes some recent persistence results for the Camassa‐Holm equation [2] to its supersymmetric extension. As an application we discuss the spatial asymptotic profile of solutions to 2CH.
Quasistatic adhesive contact of visco‐elastic bodies and its numerical treatment for very small viscosity
Authors: Roubíček T. , Panagiotopoulos C.G. , Mantič V.
Published: June 2013

An adhesive unilateral contact of elastic bodies with a small viscosity in the linear Kelvin‐Voigt rheology at small strains is scrutinized. The flow‐rule for debonding the adhesive is considered rate‐independent and unidirectional, and inertia is neglected. The asymptotics for the viscosity approaching zero towards purely elastic material involves a certain defect‐like measure recording in some sense natural additional energy dissipated in the bulk due to (vanishing) viscosity, which is demonstrated on particular 2‐dimensional computational simulations based on a semi‐implicit time discretisation and a spacial discretisation implemented by boundary‐element method.
The Y‐junction of quantum waveguides
Authors: Nazarov S.A. , Ruotsalainen K. , Uusitalo P.
Published: June 2013

A planar quantum waveguide is composed from two semi‐strips of width 1 and a semi‐strip of width H and the angle between strips is 2π/3. The spectrum of the Dirichlet problem in this waveguide is investigated. In particular, it is proved that there exists a critical width H* for which the discrete spectrum is non‐empty for any H ≤ H* and conversely is empty for any H ≥ H*. The critical width is estimated to be approximately H* ≈︁ 1.25. Furthermore, the eigenvalue in the discrete spectrum is unique for 0 ≤ H
≤ H*.
LGBT Community, Social Network Characteristics, and Smoking Behaviors in Young Sexual Minority Women
Authors: Johns Michelle Marie , Pingel Emily S. , Youatt Emily J. , Soler Jorge H. , McClelland Sara I. , Bauermeister Jose A.
Published: June 2013

Smoking rates among young sexual minority women (YSMW) are disproportionately high as compared to heterosexual populations. While this disparity has commonly been attributed to the sexual minority stress process, little empirical work has explored what may protect YSMW from high rates of smoking. Using data (N = 471) from a cross‐sectional study designed to investigate YSMW's (age 18–24) smoking behaviors and correlates; we explore the relationship of LGBT community connections, YSMW's social network characteristics, and stress to smoking behaviors (i.e., status, frequency, amount). Through this analysis, we find support for LGBT community connection as well as friendships with other sexual minorities as protective in relation to YSMW's smoking behaviors. We discuss the implications of our results, highlighting the need for future longitudinal research and interventions designed to bolster YSMW's connections to the LGBT community and their social networks.
Financial Globalization in Botswana and Nigeria: A Critique of the Thresholds Paradigm
Authors: Ahmed Abdullahi D. , van Hulten Andrew
Published: June 2013

Since the Asian financial crises, economists are more circumspect in their advocacy of financial globalization'. A new consensus emerged which contends that increased financial liberalization and capital account openness may only produce economic benefits when countries are open to trade and have good institutions and policies in place. This paper critically reviews this consensus, which we term the ‘thresholds paradigm’, through a survey of the available literature and a comparative case study of two African countries that have undertaken financial and capital account liberalization: Nigeria and Botswana. The paper argues that the thresholds paradigm leaves important theoretical and policy-related questions unresolved, in particular, the origins of good institutions and policies. Further, while at first glance the paradigm appears to capture the divergent outcomes of financial globalization policies in Nigeria and Botswana, a deeper investigation reveals important factors that are neglected and occluded. The paper concludes that economists need to be more methodologically ambidextrous and must integrate institutional factors in their theoretical frameworks in order to better understand the outcomes of ‘financial globalization’ and to provide useful policy advice to developing countries contemplating financial reforms in the future.
Intrahousehold Resource Allocation: Do Parents Reduce or Reinforce Child Ability Gaps?
Authors: Frijters Paul , Johnston David W. , Shah Manisha , Shields Michael A.
Published: June 2013

Do parents invest more or less in their high-ability children? We provide new evidence on this question by comparing observed ability differences and observed investment differences between siblings living in the United States. To overcome endogeneity issues, we use sibling differences in handedness as an instrument for cognitive ability differences. We find that parents invest more in high-ability children, with a 1 standard deviation increase in child cognitive ability increasing parental investments by approximately one-third of a standard deviation. Consequently, differences in child cognitive ability are enhanced by differential parental investments.
Next‐generation sequencing of Okazaki fragments extracted from Saccharomyces cerevisiae
Authors: Yang Wenchao , Li Xinhui
Published: June 2013

Genome‐wide Okazaki fragment distribution can differentiate the discontinuous from the semi‐discontinuous DNA replication model. Here, we investigated the genome‐wide Okazaki fragment distribution in Saccharomyces cerevisiae S288C. We improved the method based upon lambda exonuclease digestion to purify Okazaki fragments from S288C yeast cells, followed by Illumina sequencing. The distribution of Okazaki fragments around confirmed replication origins, including two highly efficient replication origins, supported the discontinuous DNA replication model. In S. cerevisiae mitochondria, Okazaki fragments were overrepresented in the transcribed regions, indicating the interplay between transcription and DNA replication.
HIF1 regulates WSB‐1 expression to promote hypoxia‐induced chemoresistance in hepatocellular carcinoma cells
Authors: Tong Ying , Li Qi-Gen , Xing Tian-Yu , Zhang Ming , Zhang Jian-Jun , Xia Qiang
Published: June 2013

WSB‐1 is involved in DNA damage response by targeting homeodomain‐interacting protein kinase 2 (HIPK2) for ubiquitination and degradation. Here, we report that hypoxia significantly up‐regulates the expression of WSB‐1 in human hepatocellular carcinoma (HCC) cells. We also provide evidence that WSB‐1 is a target of hypoxia‐inducible factor 1 (HIF‐1). Silencing the expression of HIF‐1α in HCC cells by RNA interference abolishes hypoxia‐induced WSB‐1 expression. Using chromatin immunoprecipitation and luciferase reporter assays, we identified a HRE of the WSB‐1 gene. Moreover, silencing the expression of WSB‐1 by RNA interference rescues HIPK2 expression in hypoxic HCC cells and promotes etoposide‐induced cell death in hypoxic HCC cells. Taken together, these data shed light on the mechanisms underlying hypoxia‐induced chemoresistance in HCC cells.
Circadian gene Clock contributes to cell proliferation and migration of glioma and is directly regulated by tumor‐suppressive miR‐124
Authors: Li Aihua , Lin Xihua , Tan Xiaochao , Yin Bin , Han Wei , Zhao Jizong , Yuan Jiangang , Qiang Boqin , Peng Xiaozhong
Published: June 2013

Although the roles of circadian Clock genes and microRNAs in tumorigenesis have been profoundly studied, mechanisms of cross‐talk between them in regulation of gliomagenesis are poorly understood. Here we show that the expression level of CLOCK is significantly increased in high‐grade human glioma tissues and glioblastoma cell lines. In contrast miR‐124 is attenuated in similar samples. Further studies show that Clock is a direct target of miR‐124, and either restoration of miR‐124 or silencing of CLOCK can reduce the activation of NF‐κB. In conclusion, we suggest that as a target of glioma suppressor miR‐124, CLOCK positively regulates glioma proliferation and migration by reinforcing NF‐κB activity.
Elevated citrate levels in non‐alcoholic fatty liver disease: The potential of citrate to promote radical production
Authors: van de Wier Bregje , Balk Jiska M. , Haenen Guido R.M.M. , Giamouridis Dimosthenis , Bakker Jaap A. , Bast Bertine C. , den Hartog Gertjan J.M. , Koek Ger H. , Bast Aalt
Published: June 2013

Plasma citrate levels were found to be elevated in non‐alcoholic fatty liver disease (NAFLD) patients. Cellular experiments indicated that increased citrate levels might originate from an excess of fatty acids. The impact of elevated citrate levels on oxidative stress was examined. It was found that citrate stimulated hydrogen peroxide induced intracellular oxidative stress in HepG2 cells. This was related to the promotion of iron mediated hydroxyl radical formation from hydrogen peroxide by citrate. The stimulating effect of citrate on the reactivity of iron promotes oxidative stress, a crucial process in the progression of NAFLD.
A randomized controlled trial on the value of misoprostol for the treatment of retained placenta in a low‐resource setting
Authors: van Beekhuizen Heleen J. , Tarimo Vincent , Pembe Andrea B. , Fauteck Heiner , Lotgering Fred K.
Published: June 2013

Objective

To evaluate the efficacy and safety of misoprostol among patients with retained placenta in a low‐resource setting.

Methods

A prospective, multicenter, randomized, double‐blind, placebo‐controlled trial was carried out in Tanzania between April 2008 and November 2011. It included patients who delivered at a gestational age of 28 weeks or more and had blood loss of 750 mL or less at 30 minutes after delivery. Sublingual misoprostol (800 μg) was compared with placebo as the primary treatment. Power analysis showed that 117 patients would be required to observe a reduction of 40% in the incidence of manual removal of the placenta (MRP; P = 0.05, 80% power), the primary outcome. The secondary outcomes were blood loss and number of blood transfusions.

Results

Interim analysis after recruitment of 95 patients showed that incidence of MRP, total blood loss, and incidence of blood transfusions were similar in the misoprostol (MRP, 40%; blood loss, 803 mL; blood transfusion, 15%) and placebo (MRP, 33%, blood loss 787 mL, blood transfusion, 23%) groups. The trial was stopped because continuation would not alter the interim conclusion that misoprostol was ineffective.

Conclusion

Treatment with misoprostol was found to have no clinically significant beneficial effect among women with retained placenta.

Clinical Trial Registration: Current Controlled Trials ISRCTN16104753
Treatment of depression in adults with cancer: a systematic review of randomized controlled trials
Authors: Walker J. , Sawhney A. , Hansen C. Holm , Ahmed S. , Martin P. , Symeonides S. , Murray G. , Sharpe M.
Published: June 2013

Background

Depression is a leading cause of disease burden worldwide and is especially problematic in people with chronic diseases, including cancer. Although depression can be effectively treated in the general population using antidepressant medication and psychological treatments, these treatments may have different benefits and harms in cancer patients. Previous reviews have not adequately addressed this topic. We therefore aimed to determine which, if any, treatments are effective for patients with diagnoses of both cancer and depression.

Method

We conducted a systematic review of relevant randomized controlled trials identified through searches of Medline, EMBASE, PsycINFO and The Cochrane Central Register of Controlled Trials (CENTRAL).

Results

Seven relatively small trials met the selection criteria. These provided some evidence that antidepressant medication, given alone or in combination with a psychological treatment, may be effective. We found no good evidence for psychological treatments given alone or for any other forms of treatment.

Conclusions

There is very limited evidence from clinical trials to guide the treatment of cancer patients with a diagnosis of depression, especially for psychological treatments. High quality trials of treatments for depression in patients with cancer are urgently needed.
COST-EFFECTIVENESS OF AN ADVANCE NOTIFICATION LETTER TO INCREASE COLORECTAL CANCER SCREENING
Authors: Cronin Paula , Goodall Stephen , Lockett Trevor , O'Keefe Christine M. , Norman Richard , Church Jody
Published: June 2013

Objectives:The aim of this study is to evaluate the cost-effectiveness of a patient-direct mailed advance notification letter on participants of a National Bowel Cancer Screening Program (NBCSP) in Australia, which was launched in August 2006 and offers free fecal occult blood testing to all Australians turning 50, 55, or 65 years of age in any given year.

Methods:This study followed a hypothetical cohort of 50-year-old, 55-year-old, and 65-year-old patients undergoing fecal occult blood test (FOBT) screening through a decision analytic Markov model. The intervention compared two strategies: (i) advance letter, NBCSP, and FOBT compared with (ii) NBCSP and FOBT. The main outcome measures were life-years gained (LYG), quality-adjusted life-years (QALYs) gained and incremental cost-effectiveness ratio.

Results:An advance notification screening letter would yield an additional 54 per 100,000 colorectal cancer deaths avoided compared with no letter. The estimated cost-effectiveness was $3,976 per LYG and $6,976 per QALY gained.

Conclusions:An advance notification letter in the NBCSP may have a significant impact on LYG and cancer deaths avoided. It is cost-effective and offers a feasible strategy that could be rolled out across other screening program at an acceptable cost.
Three-dimensional labels: A unified approach to labels for a general spatial grammar interpreter
Authors: Hoisl Frank , Shea Kristina
Published: June 2013

Spatial grammars are rule-based, generative systems for the specification of formal languages. Set and shape grammar formulations of spatial grammars enable the definition of spatial design languages and the creation of alternative designs. The original formalism includes labels that provide the possibility to restrict the application of rules or to incorporate additional, nongeometric information in grammar rules. Labels have been used in various ways. This paper investigates the different uses of labels in existing spatial grammars, both paper based and computational, and introduces a new concept of three-dimensional (3-D) labels for spatial grammars. The approach consolidates the different label types in one integrated concept. The main use of 3-D labels is that they can simplify the matching of the left-hand side of rules in parametric grammars. A prototype implementation is used to illustrate the approach through a mechanical engineering example of generating robot arm concepts. This approach more readily enables the use of complex solid geometry in the definition and application of parametric rules. Thus, the flexible generation of complex, meaningful design solutions for mechanical engineering applications can be achieved using parametric spatial grammars combined with 3-D labels.
Reevaluating Art Crime's Famous Figures
Authors: Durney Mark
Published: June 2013

This article seeks to demonstrate that the figures used to describe the size and scope of cultural property crimes—that it is a $6 billion illicit industry and that it ranks among the third or fourth largest criminal enterprise annually—are without statistical merit. It underscores the ambiguities inherent in the figures and uses the 2003 theft of the Duke of Buccleuch's painting by Leonardo da Vinci,Madonna of the Yarnwinder, to illustrate the difficulties related to establishing monetary estimates for cultural property crimes. It calls for a more empirical approach to measuring the magnitude of the problem on the part of cultural property crime experts. Finally, it examines the reporting methods of the world's largest cultural property crimes law enforcement agency, theComando Carabinieri per la Tutela del Patrimonio Culturale, in order to provide a model for others to follow in the effort to communicate the severity of the problem and to increase its financial, social, and political support.
Survival, Revival and Continuance: The Menglian Weaving Revival Project
Authors: Shuzhong He , Prott Lyndel
Published: June 2013

Recent efforts to ensure the survival of cultural diversity in a globalized world have led to efforts to preserve, revitalize, and continue craft traditions in marginal communities. This article records an effort to support the distinctive Dai culture in the province of Yunnan, China, by first establishing an archive of documents, photographs, and oral records of the traditions of a Dai community in the county of Menglian and following that by reviving and expanding the traditional weaving carried out by Dai women. It shows the complexity of this kind of activity, the need to encourage younger members of the community to learn the distinctive techniques of weaving and to develop a niche market for its products. Group crafts and traditions have often developed and varied over centuries; further adaptations may be needed to restore viability. Reinstatement of quality improved its value by adopting wider looms, better dyeing techniques, higher quality thread, and by encouraging new creative efforts in the development of the final product, thus providing better economic returns to the weavers and the community in general. In providing an exemplary process for isolated and dispirited communities to improve their economic circumstances and reinvigorate their ethnic traditions, it demonstrates the significant contribution that nongovernmental organizations can make to this kind of work.
Time-on-Task in Children with ADHD: An ex-Gaussian Analysis
Authors: Tarantino Vincenza , Cutini Simone , Mogentale Carla , Bisiacchi Patrizia Silvia
Published: June 2013

Although it is widely known that high intra-individual variability (IIV) is a key characteristic of attention deficit/hyperactivity disorder (ADHD), a detailed exploration of the IIV pattern during the time course of a cognitive task has never been carried out. In this study, 30 children with ADHD and 30 controls, were administered the Conners’ Continuous Performance Task (CPT-II). The across-block individual performance of the groups was analyzed using an ex-Gaussian approach, which enabled a clearer understanding of how individual response times (RTs) fluctuate during a task in comparison with conventional measures of central tendency. While the conventional measures showed a significant group effect on mean RTs but similar RT trends across blocks between the two groups, the ex-Gaussian results revealed no actual differences between the two groups in the normally distributed component of mean RTs (mu). In contrast to the control group, the children with ADHD showed a steep increase in the exponentially distributed component of RTs (tau) across blocks, thereby indicating that extremely long RTs progressively increased soon after the beginning of the task. Taken together, the results demonstrated that sustained attention deficit in ADHD can be detected by analyzing the IIV in the first few task blocks. (JINS, 2013,19, 1–9)
Entwicklung eines Fragebogens zur Erhebung von negativem Spillover zwischen Arbeit und Privatleben (B-AOF)
Authors: Schuller Katja , Rau Renate
Published: June 2013

Seit einigen Jahren wird vermehrt über gesundheitliche Beeinträchtigungen aufgrund einer fehlenden Balance zwischen dem Arbeits- und dem Privatleben berichtet. Für die Erfassung der Beziehungen zwischen dem Arbeits- und Privatleben fehlte im deutschsprachigen Raum bisher ein geeignetes Verfahren. Daher wurde ein Fragebogen zur Erhebung negativen Spillovers, also der Übertragung negativer Effekte von der Arbeit auf das Privatleben und umgekehrt entwickelt und validiert. In vier Studien mit insgesamt 880 Teilnehmern wurden die Konstrukt- und Kriterienvalidität sowie die Reliabilität des Verfahrens geprüft. Dabei erwies sich die Skala „Negatives Spillover von der Arbeit auf das Privatleben” mit ihren Unterskalen zeitbasiertes und beanspruchungsbasiertes Spillover als hinreichend konstrukt- und kriterienvalide sowie reliabel und ökonomisch. Für die Skala, die die entgegengesetzte Wirkrichtung (vom Privatleben zur Arbeit) erfasst, wurde weiterer Entwicklungsbedarf aufgezeigt.
Understanding Children’s Choices and Cognition in Video Game Play
Authors: Hamlen Karla R.
Published: June 2013

This article provides a synthesis of a group of research studies conducted to better understand in what ways children’s entertainment video game play choices relate to their creativity, motivations, problem-solving strategies, learning preferences, and beliefs about how to play games. Three studies were conducted among American students: (1) a survey and creativity assessment with students aged 9–11, (2) an in-depth qualitative study with three adolescent boys, and (3) an online survey. Key findings from this research relate to both psychological factors motivating video game play, and cognition and choices children make while playing video games. Results from these studies demonstrate that, despite assumptions that children play video games to avoid mental stimulation, children are actually motivated by the challenge and thinking required by video games. The reward system used in video games is a strong continuing motivator for boys in particular. Among both genders, playing certain genres of video games is related to utilizing particular learning strategies. Additionally, though creativity does not appear to be hindered by video game play, the most creative children are generally not choosing to spend their time on video games. Finally, children create their own code of conduct and ethics within video game play, although an individual’s work ethic within video games tends to reflect patterns in other areas of life. Collectively, these studies provide a rich picture of children’s video game play and show consistency, both between game contexts and real life choices, and with other literature related to children’s motivations and strategies for learning.
Model for determination of mid-gap states in amorphous metal oxides from thin film transistors
Authors: Bubel S. , Chabinyc M. L.
Published: June 2013

The electronic density of states in metal oxide semiconductors like amorphous zinc oxide (a-ZnO) and its ternary and quaternary oxide alloys with indium, gallium, tin, or aluminum are different from amorphous silicon, or disordered materials such as pentacene, or P3HT. Many ZnO based semiconductors exhibit a steep decaying density of acceptor tail states (trap DOS) and a Fermi level (EF) close to the conduction band energy (EC). Considering thin film transistor (TFT) operation in accumulation mode, the quasi Fermi level for electrons (Eq) moves even closer to EC. Classic analytic TFT simulations use the simplification EC−EF>  ‘several’kT and cannot reproduce exponential tail states with a characteristic energy smaller than 1/2 kT. We demonstrate an analytic model for tail and deep acceptor states, valid for all amorphous metal oxides and include the effect of trap assisted hopping instead of simpler percolation or mobility edge models, to account for the observed field dependent mobility.
X-ray radiographic expansion measurements of isochorically heated thin wire targets
Authors: Hochhaus D. C. , Aurand B. , Basko M. , Ecker B. , Kühl T. , Ma T. , Rosmej F. , Zielbauer B. , Neumayer P.
Published: June 2013

Solid density matter at temperatures ranging from 150 eV to <5 eV has been created by irradiating thin wire targets with high-energy laser pulses at intensities ≈1018W/cm2. Energy deposition and transport of the laser-produced fast electrons are inferred from spatially resolved Kα-spectroscopy. Time resolved x-ray radiography is employed to image the target mass density up to solid density and proves isochoric heating. The subsequent hydrodynamic evolution of the target is observed for up to 3 ns and is compared to radiation-hydrodynamic simulations. At distances of several hundred micrometers from the laser interaction region, where temperatures of 5–20 eV and small temperature gradients are found, the hydrodynamic evolution of the wire is a near axially symmetric isentropic expansion, and good agreement between simulations and radiography data confirms heating of the wire over hundreds of micrometers.
Direct measurements of forces between different charged colloidal particles and their prediction by the theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO)
Authors: Ruiz-Cabello F. Javier Montes , Maroni Plinio , Borkovec Michal
Published: June 2013

Force measurements between three types of latex particles of diameters down to 1 μm with sulfate and carboxyl surface functionalities were carried out with the multi-particle colloidal probe technique. The experiments were performed in monovalent electrolyte up to concentrations of about 5 mM. The force profiles could be quantified with the theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO) by invoking non-retarded van der Waals forces and the Poisson-Boltzmann description of double layer forces within the constant regulation approximation. The forces measured in the symmetric systems were used to extract particle and surface properties, namely, the Hamaker constant, surface potentials, and regulation parameters. The regulation parameter is found to be independent of solution composition. With these values at hand, the DLVO theory is capable to accurately predict the measured forces in the asymmetric systems down to distances of 2–3 nm without adjustable parameters. This success indicates that DLVO theory is highly reliable to quantify interaction forces in such systems. However, charge regulation effects are found to be important, and they must be considered to obtain correct description of the forces. The use of the classical constant charge or constant potential boundary conditions may lead to erroneous results. To make reliable predictions of the force profiles, the surface potentials must be extracted from direct force measurements too. For highly charged surfaces, the commonly used electrophoresis techniques are found to yield incorrect estimates of this quantity.
Elemental content of enamel and dentin after bleaching of teeth (a comparative study between laser-induced breakdown spectroscopy and x-ray photoelectron spectroscopy)
Authors: Imam H. , Ahmed Doaa , Eldakrouri Ashraf
Published: June 2013

The elemental content of the superficial and inner enamel as well as that of dentin was analyzed using laser-induced breakdown spectroscopy (LIBS) and x-ray photoelectron spectroscopy (XPS) of bleached and unbleached tooth specimens. It is thus clear from the spectral analysis using both the LIBS and XPS technique that elemental changes (though insignificant within the scopes of this study) of variable intensities do occur on the surface of the enamel and extend deeper to reach dentin. The results of the LIBS revealed a slight reduction in the calcium levels in the bleached compared to the control specimens in all the different bleaching groups and in both enamel and dentin. The good correlation found between the LIBS and XPS results demonstrates the possibility of LIBS technique for detection of minor loss in calcium and phosphorus in enamel and dentin.
Microwave sidebands for laser cooling by direct modulation of a tapered amplifier
Authors: Mahnke J. , Kulas S. , Geisel I. , Jöllenbeck S. , Ertmer W. , Klempt C.
Published: June 2013

Laser cooling of atoms usually necessitates several laser frequencies. Alkaline atoms, for example, are cooled by two lasers with a frequency difference in the gigahertz range. This gap cannot be closed with simple shifting techniques. Here, we present a method of generating sidebands at 6.6 GHz by modulating the current of a tapered amplifier, which is seeded by an unmodulated master laser. The sidebands enable trapping of 1.1 × 109 87Rb atoms in a chip-based magneto-optical trap. Compared to the direct modulation of the master laser, this method allows for an easy implementation, a fast adjustment over a wide frequency range, and the simultaneous extraction of unmodulated light for manipulation and detection. The low power consumption, small size, and applicability for multiple frequencies benefit a wide range of applications reaching from atom-based mobile sensors to the laser cooling of molecules.
Interactions of defect complexes and domain walls in CuO-doped ferroelectric (K,Na)NbO3
Authors: Eichel Rüdiger-A. , Erünal Ebru , Jakes Peter , Körbel Sabine , Elsässer Christian , Kungl Hans , Acker Jérôme , Hoffmann Michael J.
Published: June 2013

“Lead-free” piezoelectric sodium potassium niobate has been studied with respect to its defect structure when doping with CuO. The results indicate that two kinds of mutually compensating charged defect complexes are formed, (Cu′′′Nb−VO••)′ and (VO••−Cu′′′Nb−VO••)•. Concerning the interplay of these defect complexes with the piezoelectric materials properties, the trimeric (VO••−Cu′′′Nb−VO••)• defect complex primarily has an elastic dipole moment and thus is proposed to impact the electromechanical properties, whereas the dimeric (Cu′′′Nb−VO••)′ defect possesses an electric dipole moment in addition to an elastic distortion. Both types of defect complexes can impede domain-wall motion and may contribute to ferroelectric “hardening.”
Extreme charge density SrTiO3/GdTiO3 heterostructure field effect transistors
Authors: Boucherit M. , Shoron O. F. , Cain T. A. , Jackson C. A. , Stemmer S. , Rajan S.
Published: June 2013

We report on the fabrication and electrical characteristics of the first SrTiO3/GdTiO3 (STO/GTO) heterostructure field-effect transistors (HFETs). The high two-dimensional electron gas (2DEG) density of 3 × 1014 cm−2 formed due to the polar discontinuity at the STO/GTO interface was used as a channel to create inverted HFETs. Plasma O2 treatment was found to reduce current leakage by 3 orders of magnitude at reverse bias, leading to rectifying Schottky behavior. A charge modulation of 0.6 × 1014 cm−2 is reported here, which represents the highest sheet charge modulated in any planar field effect transistor to date.
Estimation of sunshine duration in Saudi Arabia
Authors: Mohandes Mohamed A. , Rehman Shafiqur
Published: June 2013

In this paper we propose machine learning algorithms to estimate the sunshine duration at any region in Saudi Arabia using easily obtained parameters that include: maximum possible day length (So), extraterrestrial solar radiation at that particular location (Ho), latitude, longitude, altitude, and month number. Two neural network algorithms, namely, Particle Swarm Optimization (PSO) algorithm and Support Vector Machine (SVM), are used to estimate the sunshine duration (S). Due to the limited number of measurement stations, we use the leave-one-out strategy, where data from 40 measurement stations are used to build the model and data from the remaining 41st station are utilized to assess accuracy of the modeled system. This process is repeated for each of the 41 stations. Minimum mean absolute percent errors (MAPE) of 2.3% and 2.7% were obtained at Al-Madina station using PSO and SVM methods while the respective maximum values of 22.9% and 16.7% were observed at Al-Numas station. In general, higher MAPE values were found during summer time (June-August) and lower in winter time (January-February and November-December). Results indicate the viability of the proposed methods for estimating sunshine duration in Saudi Arabia, and the system is expected to perform similarly in other countries with similar environment.
Persistent coexistence of cyclically competing species in spatially extended ecosystems
Authors: Park Junpyo , Do Younghae , Huang Zi-Gang , Lai Ying-Cheng
Published: June 2013

A fundamental result in the evolutionary-game paradigm of cyclic competition in spatially extended ecological systems, as represented by the classic Reichenbach-Mobilia-Frey (RMF) model, is that high mobility tends to hamper or even exclude species coexistence. This result was obtained under the hypothesis that individuals move randomly without taking into account the suitability of their local environment. We incorporate local habitat suitability into the RMF model and investigate its effect on coexistence. In particular, we hypothesize the use of “basic instinct” of an individual to determine its movement at any time step. That is, an individual is more likely to move when the local habitat becomes hostile and is no longer favorable for survival and growth. We show that, when such local habitat suitability is taken into account, robust coexistence can emerge even in the high-mobility regime where extinction is certain in the RMF model. A surprising finding is that coexistence is accompanied by the occurrence of substantial empty space in the system. Reexamination of the RMF model confirms the necessity and the important role of empty space in coexistence. Our study implies that adaptation/movements according to local habitat suitability are a fundamental factor to promote species coexistence and, consequently, biodiversity.
Ion-beam driven lower hybrid waves in a magnetized dusty plasma
Authors: Prakash Ved , Vijayshri  , Sharma Suresh C. , Gupta Ruby
Published: June 2013

An ion beam drives lower hybrid waves to instability in a magnetized dusty plasma via Cerenkov interaction. A dispersion relation and the growth rate of the lower hybrid waves have been derived taking into account the dust charge fluctuations. The frequency and the growth rate of the unstable wave instability increase with relative density of negatively charged dust grains. The lower hybrid modes with phase velocity comparable to the beam velocity possess a large growth rate. Moreover, the growth rate of the instability increases with beam density and scales as the one-third power of the beam density.
Kinetics of hydrogen adsorption and desorption on Si(100) surfaces
Authors: Narita Yuzuru , Inanaga Shoji , Namiki Akira
Published: June 2013

The kinetics of molecular hydrogen reactions at the Si (100) surface has been studied by simulation to extract the physics underlying two unexpected experimental observations: apparently first-order desorption kinetics and an increase in sticking probability with hydrogen coverage. At a partially H-terminated Si(100) surface, each Si dimer assumes an unoccupied dimer (UOD), singly occupied dimer (SOD), or doubly occupied dimer (DOD) structure. In our hydrogen reaction model based on an inter-dimer mechanism, a site consisting of an adjacent pair of a DOD and a UOD (DOD/UOD) is a key component for the desorption and adsorption kinetics of hydrogen at the Si(100) surface. To simulate reaction kinetics of both reactions, DU (D: DOD, U: UOD) and SS (S: SOD) pathways are proposed: DU pathway claims that the adsorption as well as desorption of hydrogen takes place at common sites having a cis-configured SOD/SOD pair that is transformed transiently from a DOD/UOD pair by H(D) diffusion. Thus the adsorption obeys the so-called 4H mechanism, but the desorption obeys the 2H mechanism. SS pathway claims that the adsorption occurs at sites having a UOD/UOD pair, and the desorption occurs at sites having a cis-configured SOD/SOD pair that is generated by diffusion of isolated SODs. To simulate temperature-programmed-desorption spectra and sticking probability vs coverage curves, thermo-statistics for a lattice-gas system characterized with parameters for hydrogen pairing and dimer clustering is used to evaluate equilibrium populations of DOD/UOD pairs and isolated SODs. The model simulation based on the above reaction model successfully reproduces all of the complicated, coverage dependent adsorption and desorption reactions of hydrogen at Si(100) surfaces. Specifically, at high coverage above 0.1 ML majority of the adsorption and desorption proceed along the DU pathway. Hence, it is suggested that the adsorption and desorption in the high coverage regime are not microscopically reversible. On the other hand, at low coverages below 0.1 ML, the simulation shows up that the majority of adsorption proceeds along the SS pathway, and the desorption by the DU pathway. Since both reactions obey the 2H mechanism, it is suggested that the desorption and adsorption in the low coverage regime are microscopically reversible.
On-chip Brownian relaxation measurements of magnetic nanobeads in the time domain
Authors: Østerberg Frederik Westergaard , Rizzi Giovanni , Hansen Mikkel Fougt
Published: June 2013

We present and demonstrate a new method for on-chip Brownian relaxation measurements on magnetic nanobeads in the time domain using magnetoresistive sensors. The beads are being magnetized by the sensor self-field arising from the bias current passed through the sensors and thus no external magnetic fields are needed. First, the method is demonstrated on Brownian relaxation measurements of beads with nominal sizes of 40, 80, 130, and 250 nm. The results are found to compare well to those obtained by an already established measurement technique in the frequency domain. Next, we demonstrate the time and frequency domain methods on Brownian relaxation detection of clustering of streptavidin coated magnetic beads in the presence of different concentrations of biotin-conjugated bovine serum albumin and obtain comparable results. In the time domain, a measurement is carried out in less than 30 s, which is about six times faster than in the frequency domain. This substantial reduction of the measurement time allows for continuous monitoring of the bead dynamics vs. time and opens for time-resolved studies, e.g., of binding kinetics.
Effect of two-temperature electrons distribution on an electrostatic plasma sheath
Authors: Ou Jing , Xiang Nong , Gan Chunyun , Yang Jinhong
Published: June 2013

A magnetized collisionless plasma sheath containing two-temperature electrons is studied using a one-dimensional model in which the low-temperature electrons are described by Maxwellian distribution (MD) and high-temperature electrons are described by truncated Maxwellian distribution (TMD). Based on the ion wave approach, a modified sheath criterion including effect of TMD caused by high-temperature electrons energy above the sheath potential energy is established theoretically. The model is also used to investigate numerically the sheath structure and energy flux to the wall for plasmas parameters of an open divertor tokamak-like. Our results show that the profiles of the sheath potential, two-temperature electrons and ions densities, high-temperature electrons and ions velocities as well as the energy flux to the wall depend on the high-temperature electrons concentration, temperature, and velocity distribution function associated with sheath potential. In addition, the results obtained in the high-temperature electrons with TMD as well as with MD sheaths are compared for the different sheath potential.
O2 rotational temperature measurements in an atmospheric air microdischarge by radar resonance-enhanced multiphoton ionization
Authors: Sawyer Jordan , Wu Yue , Zhang Zhili , Adams Steven F.
Published: June 2013

Nonintrusive spatially resolved rotational temperature measurements in an atmospheric air microdischarge are presented. The measurements were based on coherent microwave Rayleigh scattering (Radar) from resonance-enhanced multiphoton ionization of molecular oxygen. The open air DC microdischarge source operated in a stable “normal-glow” mode and pin-to-pin electrodes spaced 1.3 mm apart. The second harmonic of a tunable dye laser beam was focused between the two electrodes and scanned between 286 and 288 nm. Coherent microwave Rayleigh scattering was used to collect the two-photon rotational spectra of O2 at C3Π(v = 2)←X3Σ(v′ = 0) transitions. The Boltzmann plots from analyses of the O2 rotational lines determined local rotational temperatures at various axial locations between the electrodes. The molecular oxygen rotational temperature varied from ∼1150 K to ∼1350 K within the discharge area. The measurements had an accuracy of ∼±50 K.
Magnetic properties and magnetic relaxation in a suspension of CoFe2O4 nanoparticles
Authors: Babić-Stojić B. , Jokanović V. , Milivojević D. , Jagličić Z. , Makovec D. , Jović N. , Marinović-Cincović M.
Published: June 2013

We present a study of dynamic magnetic properties of superparamagnetic CoFe2O4 nanoparticles of average size 5.9 nm suspended in an organic liquid. The relaxation times of the particle magnetic moments are found to be strongly dependent on the size of the particles, and also considerably dependent on interparticle interactions. Besides the lower frequency peak, an additional much faster relaxation is observed in the frequency dependence of the imaginary part of the ac magnetic susceptibility below the freezing point of the liquid. It is found that a large contribution to the magnetic relaxation of the lower frequency peak originates from the particles of dimensions 6.3–5.1 nm with interparticle interactions in the range 25-82 K, which correspond to nearer-neighbor particles. Much faster relaxation indicates that its significant part arises from the particles of dimensions 5.8–5.0 nm with interactions in the range 1–52 K which include also more distant neighbors.
Dynamic boundary crisis in the Lorenz-type map
Authors: Maslennikov Oleg V. , Nekorkin Vladimir I.
Published: June 2013

Effects of the slowly varying control parameters on bifurcations of the equilibria and limit cycles have been previously studied in detail. In this paper, the concept of dynamic bifurcations is extended to chaotic phenomena. We consider this problem for a Lorenz-type map. As the control parameter passes through a critical value, the dynamic boundary crisis of a chaotic attractor takes place. We discover and analyze the effects of delayed exit from the chaotic region and non-exponential decay of the number of surviving trajectory points. The property of the delay increase with increasing rate of the control parameter change has also been demonstrated and explained.
Temperature dependent electric field control of the electron spin relaxation in (111)A GaAs quantum wells
Authors: Wang G. , Balocchi A. , Lagarde D. , Zhu C. R. , Amand T. , Renucci P. , Shi Z. W. , Wang W. X. , Liu B. L. , Marie X.
Published: June 2013

We demonstrate the electrical control of the electron spin relaxation in GaAs/AlGaAs multiple quantum wells grown on (111)A substrate. By embedding the wells in a NIP structure, the application of an external bias yields a large increase of the electron spin relaxation time due to the compensation of the Dresselhaus spin-splitting by the Rashba one. Depending on the direction of the applied electric field, the electron spin relaxation can be slowed-down or sped-up. It can be tuned by a factor 50 at 75 K and still by a factor 2 at 250 K.
Time-domain study of spin-wave dynamics in two-dimensional arrays of bi-component magnetic structures
Authors: Saha Susmita , Barman Saswati , Ding Junjia , Adeyeye Adekunle O. , Barman Anjan
Published: June 2013

Spin-waves in single Ni80Fe20 (Py) and Co bi-component units embedded in two-dimensional arrays thereof are investigated by all-optical time-resolved magneto-optical Kerr effect microscope. Two bands of modes observed for the bias field applied along the long-axis of the bi-component unit convert into four distinct bands, and the mode frequencies change significantly as the field is rotated to the short-axis. Micromagnetic simulations reproduce the experimental results, and comparison with single Py and Co elements and single bi-component unit reveals significant variations of mode frequencies and mode profiles, indicating opportunities for magnonic band engineering in this type of bi-component arrays.
Plasma focus ion beam fluence and flux—For various gases
Authors: Lee S. , Saw S. H.
Published: June 2013

A recent paper derived benchmarks for deuteron beam fluence and flux in a plasma focus (PF) [S. Lee and S. H. Saw, Phys. Plasmas 19, 112703 (2012)]. In the present work we start from first principles, derive the flux equation of the ion beam of any gas; link to the Lee Model code and hence compute the ion beam properties of the PF. The results show that, for a given PF, the fluence, flux, ion number and ion current decrease from the lightest to the heaviest gas except for trend-breaking higher values for Ar fluence and flux. The energy fluence, energy flux, power flow, and damage factors are relatively constant from H2 to N2 but increase for Ne, Ar, Kr and Xe due to radiative cooling and collapse effects. This paper provides much needed benchmark reference values and scaling trends for ion beams of a PF operated in any gas.
Metal oxide semiconductor structure using oxygen-terminated diamond
Authors: Chicot G. , Maréchal A. , Motte R. , Muret P. , Gheeraert E. , Pernot J.
Published: June 2013

Metal-oxide-semiconductor structures with aluminum oxide as insulator and p-type (100) mono-crystalline diamond as semiconductor have been fabricated and investigated by capacitance versus voltage and current versus voltage measurements. The aluminum oxide dielectric was deposited using low temperature atomic layer deposition on an oxygenated diamond surface. The capacitance voltage measurements demonstrate that accumulation, depletion, and deep depletion regimes can be controlled by the bias voltage, opening the route for diamond metal-oxide-semiconductor field effect transistor. A band diagram is proposed and discussed.
Ferromagnetic antiphase domain boundary in Mn-doped hexagonal BaTiO3 multiferroics
Authors: Wei Xian-Kui , Su Yantao , Sui Yu , Zhou Zhongxiang , Yao Yuan , Jin Changqing , Yu Richeng
Published: June 2013

The magnetic properties of hexagonal Ba(Ti1−xMnx)O3 (x = 1/9, 1/6) samples specifically treated under different thermal conditions are investigated. A magnetic transformation from paramagnetism of as-grown samples to weak ferromagnetism of post-annealed samples is observed at room temperature. Associated with the structural modulation characteristics and dielectric behaviors, our experimental results reveal that the high-temperature ferromagnetism in Mn-doped hexagonal BaTiO3 derives from RIII types of antiphase domain boundaries. Spin glass transitions are observed at Tsg = 48 K and 44 K in the densely doped as-grown and post-annealed samples, respectively, but the transitions are not intrinsic properties of the hexagonal phases.
Integration of large-area metallic nanohole arrays with multimode optical fibers for surface plasmon resonance sensing
Authors: Jia Peipei , Yang Jun
Published: June 2013

Here, we report an implementation of enhanced surface plasmon resonance sensing on optical fibers through integration of large-area metallic nanohole arrays on the endfaces of multimode optical fibers by a template transfer method. The Au nanohole array integrated optical fiber sensors show a high refractive index sensitivity 559 nm per refractive index unit, narrow resonant peak width less than 10 nm in aqueous solution, and consistent optical responses with peak position variation less than 0.5 nm for various core diameters of optical fibers at same dielectric conditions. These specifications demonstrates that the nanohole array based optical fibers can serve as a high-performance, portable and lensless plasmonic platform with superior robustness and accessibility for surface plasmon resonance sensing.
Nanotube array controlled carbon plasma deposition
Authors: Qian Shi , Cao Huiliang , Liu Xuanyong , Ding Chuanxian
Published: June 2013

Finding approaches to control the elementary processes of plasma-solid interactions and direct the fluxes of matter at nano-scales becomes an important aspect in science. This letter reports that, by taking advantages of the spacing characteristics of discrete TiO2 nanotube arrays, the flying trajectories and the subsequent implantation and deposition manner of energetic carbon ions can be directed and controlled to fabricate hollow conical arrays. The study provides an alternative method for plasma nano-manufacturing.