bluuebunny/crossref_metadata_2025 huggingface dataset:
A maximally selected test of symmetry about zero
Authors: Laska Eugene , Meisner Morris , Wanderling Joseph
Published: June 2012

The problem of testing symmetry about zero has a long and rich history in the statistical literature. We introduce a new test that sequentially discards observations whose absolute value is below increasing thresholds defined by the data. McNemar's statistic is obtained at each threshold and the largest is used as the test statistic. We obtain the exact distribution of this maximally selected McNemar and provide tables of critical values and a program for computing p‐values. Power is compared with the t‐test, the Wilcoxon Signed Rank Test and the Sign Test. The new test, MM, is slightly less powerful than the t‐test and Wilcoxon Signed Rank Test for symmetric normal distributions with nonzero medians and substantially more powerful than all three tests for asymmetric mixtures of normal random variables with or without zero medians. The motivation for this test derives from the need to appraise the safety profile of new medications. If pre and post safety measures are obtained, then under the null hypothesis, the variables are exchangeable and the distribution of their difference is symmetric about a zero median. Large pre–post differences are the major concern of a safety assessment. The discarded small observations are not particularly relevant to safety and can reduce power to detect important asymmetry. The new test was utilized on data from an on‐road driving study performed to determine if a hypnotic, a drug used to promote sleep, has next day residual effects. Copyright © 2012 John Wiley & Sons, Ltd.
Quantitative Measurement of the Magnetic Moment of Individual Magnetic Nanoparticles by Magnetic Force Microscopy
Authors: Sievers Sibylle , Braun Kai‐Felix , Eberbeck Dietmar , Gustafsson Stefan , Olsson Eva , Schumacher Hans Werner , Siegner Uwe
Published: June 2012

The quantitative measurement of the magnetization of individual magnetic nanoparticles (MNPs) using magnetic force microscopy (MFM) is described. Quantitative measurement is realized by calibration of the MFM signal using an MNP reference sample with traceably determined magnetization. A resolution of the magnetic moment of the order of 10−18 A m2 under ambient conditions is demonstrated, which is presently limited by the tip's magnetic moment and the noise level of the instrument. The calibration scheme can be applied to practically any magnetic force microscope and tip, thus allowing a wide range of future applications, for example in nanomagnetism and biotechnology.
HEDGEHOG-GLI Signaling Drives Self-Renewal and Tumorigenicity of Human Melanoma-Initiating Cells
Authors: Santini Roberta , Vinci Maria C. , Pandolfi Silvia , Penachioni Junia Y. , Montagnani Valentina , Olivito Biagio , Gattai Riccardo , Pimpinelli Nicola , Gerlini Gianni , Borgognoni Lorenzo , Stecca Barbara
Published: June 2012

The question of whether cancer stem/tumor-initiating cells (CSC/TIC) exist in human melanomas has arisen in the last few years. Here, we have used nonadherent spheres and the aldehyde dehydrogenase (ALDH) enzymatic activity to enrich for CSC/TIC in a collection of human melanomas obtained from a broad spectrum of sites and stages. We find that melanomaspheres display extensive in vitro self-renewal ability and sustain tumor growth in vivo, generating human melanoma xenografts that recapitulate the phenotypic composition of the parental tumor. Melanomaspheres express high levels of Hedgehog (HH) pathway components and of embryonic pluripotent stem cell factors SOX2, NANOG, OCT4, and KLF4. We show that human melanomas contain a subset of cells expressing high ALDH activity (ALDHhigh), which is endowed with higher self-renewal and tumorigenic abilities than the ALDHlow population. A good correlation between the number of ALDHhigh cells and sphere formation efficiency was observed. Notably, both pharmacological inhibition of HH signaling by the SMOOTHENED (SMO) antagonist cyclopamine and GLI antagonist GANT61 and stable expression of shRNA targeting either SMO or GLI1 result in a significant decrease in melanoma stem cell self-renewal in vitro and a reduction in the number of ALDHhigh melanoma stem cells. Finally, we show that interference with the HH-GLI pathway through lentiviral-mediated silencing of SMO and GLI1 drastically diminishes tumor initiation of ALDHhigh melanoma stem cells. In conclusion, our data indicate an essential role of the HH-GLI1 signaling in controlling self-renewal and tumor initiation of melanoma CSC/TIC. Targeting HH-GLI1 is thus predicted to reduce the melanoma stem cell compartment.
FDI and economic activity in Africa: The role of local financial markets
Authors: Adjasi Charles. K. D. , Abor Joshua , Osei Kofi A. , Nyavor‐Foli Ernestine E.
Published: June 2012

This article examines the role local financial markets play in the link between foreign direct investment (FDI) and economic activity. The article uses panel data methods on 32 African countries over the period 1997 to 2008. Our results show that FDI only has a significant effect on economic activity when interacted with financial market variables, namely, private‐sector credit and savings. The results of this study imply that FDI is more productive in the presence of well‐functioning local financial markets. African governments must therefore pay particular attention to developing further local financial markets to ensure full economic benefits of FDI inflows. © 2012 Wiley Periodicals, Inc.
Foreign direct investment and technology transfer policies in Africa: A review of the Ghanaian experience
Authors: Luther Osabutey Ellis , Debrah Yaw A.
Published: June 2012

Foreign Direct Investment (FDI) into Africa has received research attention in the past two decades, and the flow of FDI into Africa has been on an upsurge. Countries such as Ghana have improved their investment climate to increase FDI attraction. Clamour for FDI has led policy focus toward attraction, with little attention to technology transfer and capacity building. FDI flow, global competitiveness index and tertiary enrollment data are adapted to evaluate technology transfer and capacity building. This article reveals that there is a policy vacuum and/or policy ineptitude: FDI policies are not integrated with education and human capital development policies, technology development policies, technology transfer policies, and private‐sector development policies. © 2012 Wiley Periodicals, Inc.
Foreign direct investment: Technology gap effects on international business capabilities of sub‐Saharan Africa
Authors: Elmawazini Khaled , Nwankwo Sonny
Published: June 2012

This article investigates the impact of foreign direct investment (FDI) on the technology gap between countries in sub‐Saharan Africa (SSA) and the Organisation for Economic Co‐operation and Development (OECD), against the backdrop of relatively weak industrial performance of SSA. OECD is used in order to measure how SSA's competitiveness compares with the more advanced economies. The article further examines how the technology gap, in turn, exacerbates international business capabilities of SSA and draws out some policy implications. Using a panel data regression model, the article finds that FDI inflows have had relatively little impact on SSA's industrial capacity development and global competitiveness, and, indeed, widened the gap between SSA and major developed economies. © 2012 Wiley Periodicals, Inc.
Challenges of microfinance accessibility by SMEs in Tanzania
Authors: Woldie Atsede , Isaac Mwita John , Saidimu Joyce
Published: June 2012

This article is based on a research exploring the challenges of microfinance accessibility by SMEs in Tanzania. A survey research methodology is adopted utilizing primary and secondary data from a purposively selected sample of SME operators. Data is collected using questionnaires and interviews which are analysed using SPSS Statistics 17.0. The evidence gathered show that the financial sector has failed to adequately extend microfinance facilities to SMEs due to high transaction costs, lack of collaterals, inadequate skills in developing and managing bankable projects. The study concludes that where default‐risk is perceived to be high, microinsurance must be taken by applicants as collateral. The article recommends initiation of intervention policies, which will uphold sustainability of SMEs and streamline accessibility to microfinance. Finally, the authors look at action‐focused solutions to support and build on the potential of public equity markets to help SMEs access microfinance as an area for further studies. © 2012 Wiley Periodicals, Inc.
Financial literacy among the educated: An exploratory study of selected university students in South Africa
Authors: Shambare Richard , Rugimbana Robert
Published: June 2012

The challenges associated with financial illiteracy are increasingly becoming a topical issue. Consequently, there is a growing body of literature explaining the antecedents and consequents of financial illiteracy. While most of these studies report on the experience from the developed world, very little is known on the subject matter in emerging economies. This study attempts to address this paucity in the body of knowledge by investigating the nature and extent of financial literacy in South Africa. Given that the literature acknowledges that financial illiteracy is a problem faced across the entire spectrum of society, including the uneducated and the educated, this study investigates financial illiteracy among university students, a section of the South African population that could be classified as being educated. A self‐administered financial literacy scale was administered to a sample of 214 students from a large South African metropolitan university. Overall, results indicate moderate levels of financial illiteracy; suggesting that even among the educated, there is a need to reinforce basic financial concepts. Some implications for financial service providers in interacting with literate consumers who may be financially illiterate are provided. © 2012 Wiley Periodicals, Inc.
Exploring children, family, and consumption behavior: Empirical evidence from Nigeria
Authors: Gbadamosi Ayantunji
Published: June 2012

Multinational enterprises, especially those in the fast‐moving consumer goods market, have long been concerned with the dynamics of family‐oriented consumption behavior. What is little known is the changing locus of power as children assume more power in family buying decisions. This paper adopts qualitative methods to address the changing role of children, strategies applied to influence family purchases, cultural shifts, and the implications for international business. Nigeria is used as a contextual base but the implications of the study could span sub‐Saharan African region. © 2012 Wiley Periodicals, Inc.
Spin‐component‐scaled electron correlation methods
Authors: Grimme Stefan , Goerigk Lars , Fink Reinhold F.
Published: June 2012

Spin‐component‐scaled (SCS) electron correlation methods for electronic structure theory are reviewed. The methods can be derived theoretically by applying special conditions to the underlying wave functions in perturbation theory. They are based on the insight that low‐order wave function expansions treat the correlation effects of electron pairs with opposite spin (OS) and same spin (SS) differently because of their different treatment at the underlying Hartree–Fock level. Physically, this is related to the different average inter‐electronic distances in the SS and OS electron pairs. The overview starts with the original SCS‐MP2 method and discusses its strengths and weaknesses and various ways to parameterize the scaling factors. Extensions to coupled‐cluster and excited state methods as well the connection to virtual‐orbital dependent density functional approaches are highlighted. The performance of various SCS methods in large thermochemical benchmarks and for excitation energies is discussed in comparison with other common electronic structure methods.

This article is categorized under:

Electronic Structure Theory > Ab Initio Electronic Structure Methods
Objective function‐based clustering
Authors: Hall Lawrence O.
Published: June 2012

Clustering is typically applied for data exploration when there are no or very few labeled data available. The goal is to find groups or clusters of like data. The clusters will be of interest to the person applying the algorithm. An objective function‐based clustering algorithm tries to minimize (or maximize) a function such that the clusters that are obtained when the minimum/maximum is reached are homogeneous. One needs to choose agoodset of features and the appropriate number of clusters to generate a good partition of the data into maximally homogeneous groups. Objective functions for clustering are introduced. Clustering algorithms generated from the given objective functions are shown, with a number of examples of widely used approaches discussed. © 2012 Wiley Periodicals, Inc.

This article is categorized under:

Algorithmic Development > Scalable Statistical Methods

Algorithmic Development > Structure Discovery

Technologies > Machine Learning

Technologies > Structure Discovery and Clustering
Knowledge discovery for scheduling in computational grids
Authors: Fölling Alexander , Lepping Joachim
Published: June 2012

Scheduling in computational grids addresses the allocation of computing jobs to globally distributed compute resources. In a frequently changing resource environment, scheduling decisions have to be made rapidly. Depending on both the job properties and the current state of the resources, those decisions are different. Thus, the performance of grid scheduling systems highly depends on their adaptivity and flexibility in changing environments. Under these conditions, methods from knowledge discovery yielded significant success to augment and substitute conventional grid scheduling techniques. This paper presents a survey on approaches to extract, represent, and utilize knowledge to improve the grid scheduling performance. It aims to give researchers insight into techniques used for knowledge‐supported scheduling in large‐scale distributed computing environments. © 2012 Wiley Periodicals, Inc.

This article is categorized under:

Application Areas > Science and Technology

Technologies > Machine Learning

Technologies > Prediction
Knowledge discovery interestingness measures based on unexpectedness
Authors: Kontonasios Kleanthis‐Nikolaos , Spyropoulou Eirini , De Bie Tijl
Published: June 2012

Knowledge discovery methods often discover a large number of patterns. Although this can be considered of interest, it certainly presents considerable challenges too. Indeed, this set of patterns often contains lots of uninteresting patterns that risk overwhelming the data miner. In addition, a single interesting pattern can be discovered in a multitude of tiny variations that for all practical purposes are redundant. These issues are referred to as the pattern explosion problem. They lie at the basis of much recent research attempting to quantify interestingness and redundancy between patterns, with the purpose of filtering down a large pattern set to an interesting and compact subset. Many diverse approaches to interestingness and corresponding interestingness measures (IMs) have been proposed in the literature. Some of them, named objective IMs, define interestingness only based on objective criteria of the pattern and data at hand. Subjective IMs additionally depend on the user's prior knowledge about the dataset. Formalizing unexpectedness is probably the most common approach for defining subjective IMs, where a pattern is deemed unexpected if it contradicts the user's expectations about the dataset. Such subjective IMs based on unexpectedness form the focus of this paper. We categorize measures based on unexpectedness into two major subgroups, namely, syntactical and probabilistic approaches. Based on this distinction, we survey different methods for assessing the unexpectedness of patterns with a special focus on frequent itemsets, tiles, association rules, and classification rules. © 2012 Wiley Periodicals, Inc.

This article is categorized under:

Algorithmic Development > Association Rules

Algorithmic Development > Statistics
Phase‐shift, stimuli‐responsive perfluorocarbon nanodroplets for drug delivery to cancer
Authors: Rapoport Natalya
Published: June 2012

This review focuses on phase‐shift perfluorocarbon nanoemulsions whose action depends on an ultrasound‐triggered phase shift from a liquid to gas state. For drug‐loaded perfluorocarbon nanoemulsions, microbubbles are formed under the action of tumor‐directed ultrasound and drug is released locally into tumor volume in this process. This review covers in detail mechanisms involved in the droplet‐to‐bubble transition as well as mechanisms of ultrasound‐mediated drug delivery.WIREs Nanomed Nanobiotechnol2012, 4:492–510. doi: 10.1002/wnan.1176

This article is categorized under:

Therapeutic Approaches and Drug Discovery > Emerging Technologies

Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease
Comparison of Isoflurane and Carbon Dioxide Anesthesia in Chilean Rose Tarantulas (Grammostola rosea)
Authors: Dombrowski Daniel S. , De Voe Ryan S. , Lewbart Gregory A.
Published: June 2012

This study investigated the use of two anesthetic agents, isoflurane and carbon dioxide, in Chilean rose tarantulas (Grammostola rosea). We compared the onset, duration of anesthesia, and recovery time with both gases, and made observations regarding the effects of the anesthetic protocols. Subjectively, episodes for the isoflurane animals were uneventful. The spiders were calm throughout and did not respond adversely to gas exposure. Conversely, animals anesthetized with carbon dioxide experienced violent inductions and recoveries; the tarantulas appeared agitated when the carbon dioxide flow began. Seizure‐like activity and defecation would frequently be noted prior to induction with carbon dioxide. Neither isoflurane nor carbon dioxide seemed to have any clinically apparent short‐ or long‐term impact. The animals were all normal for at least 1‐year postexperiment. Future studies should focus on defining the impact, if any, that these anesthetic agents have on the health of invertebrate species. Zoo Biol. 32:101‐103, 2013. © 2012 Wiley Periodicals, Inc.
Primary ovarian insufficiency in classic galactosemia: role of FSH dysfunction and timing of the lesion
Authors: Gubbels Cynthia S. , Land Jolande A. , Evers Johannes L. H. , Bierau Jörgen , Menheere Paul P. C. A. , Robben Simon G. F. , Rubio‐Gozalbo M. Estela
Published: June 2012

FSH inactivity due to secondary hypoglycosylation has been suggested as a potential mechanism for primary ovarian insufficiency in classic galactosemia. To investigate the role of FSH and to gain insight in the timing of the damage, ovarian stimulation tests were performed and data on ovarian imaging collected. Fifteen patients with primary ovarian insufficiency underwent ovarian stimulation with gonadotropins. Only one patient showed a normal increase in estradiol level, all the others had a low or no estradiol response. Anti‐Müllerian hormone measurement in all girls and women showed levels below the detection limit of 0.10 μg/l. Ovarian volumes were evaluated by MRI in 14 patients and compared to age matched controls, prepubertal controls and postmenopausal controls. The ovarian volumes of the galactosemic girls were smaller than those of the age matched controls (p = 0.001) and the prepubertal ovaries (p = 0.008), and did not differ significantly from postmenopausal ovarian volumes (p = 0.161). In conclusion we found no evidence that FSH inactivity plays a role in primary ovarian insufficiency in classic galactosemia. Moreover, ovarian imaging results point to an early onset of ovarian failure in this disease.
Uncrossing the U.S. Black-White Mortality Crossover: The Role of Cohort Forces in Life Course Mortality Risk
Authors: Masters Ryan K.
Published: June 2012

In this article, I examine the black-white crossover in U.S. adult all-cause mortality, emphasizing how cohort effects condition age-specific estimates of mortality risk. I employ hierarchical age-period-cohort methods on the National Health Interview Survey-Linked Mortality Files between 1986 and 2006 to show that the black-white mortality crossover can be uncrossed by factoring out period and cohort effects of mortality risk. That is, when controlling for variations in cohort and period patterns of U.S. adult mortality, the estimated age effects of non-Hispanic black and non-Hispanic white U.S. adult mortality risk do not cross at any age. This is the case for both men and women. Further, results show that nearly all the recent temporal change in U.S. adult mortality risk was cohort driven. The findings support the contention that the non-Hispanic black and non-Hispanic white U.S. adult populations experienced disparate cohort patterns of mortality risk and that these different experiences are driving the convergence and crossover of mortality risk at older ages.
Glycogen synthase kinase‐3β regulates leucine‐309 demethylation of protein phosphatase‐2A via PPMT1 and PME‐1
Authors: Yao Xiu-Qing , Li Xia-Chun , Zhang Xiao-Xue , Yin Yang-Yang , Liu Bin , Luo Dan-Ju , Wang Qun , Wang Jian-Zhi , Liu Gong-Ping
Published: June 2012

Protein phosphatase‐2A (PP2A) activity is significantly suppressed in Alzheimer's disease. We have reported that glycogen synthase kinase‐3β (GSK‐3β) inhibits PP2A via upregulating the phosphorylation of PP2A catalytic subunit (PP2AC). Here we studied the effects of GSK‐3β on the inhibitory demethylation of PP2A at leucine‐309 (dmL309‐PP2AC). We found that GSK‐3β regulates dmL309‐PP2AC level by regulating PME‐1 and PPMT1. Knockdown of PME‐1 or PPMT1 eliminated the effects of GSK‐3β on PP2AC. GSK‐3 could negatively regulate PP2A regulatory subunit protein level. We conclude that GSK‐3β can inhibit PP2A by increasing the inhibitory L309‐demethylation involving upregulation of PME‐1 and inhibition of PPMT1.
World Health Organization Guidelines: Use of cryotherapy for cervical intraepithelial neoplasia
Authors: Santesso Nancy , Schünemann Holger , Blumenthal Paul , De Vuyst Hugo , Gage Julia , Garcia Francisco , Jeronimo Jose , Lu Ricky , Luciani Silvana , Quek Swee C. , Awad Tahany , Broutet Nathalie
Published: June 2012

Background

In 2008, cervical cancer was responsible for 275 000 deaths, of which approximately 88% occurred in low‐ and middle‐income countries. In 2009, the World Health Organization (WHO) committed to updating recommendations for use of cryotherapy for cervical intraepithelial neoplasia (CIN).

Methods and results

We followed the WHO Handbook for Guidelines Development to develop present guidelines. An expert panel was established, which included clinicians, researchers, program directors, and methodologists. An independent group conducted systematic reviews and produced evidence summaries following the GRADE approach. GRADE evidence profiles were created for 16 key questions about the effects of cryotherapy in the presence of histologically confirmed CIN compared with no treatment and with loop electrosurgical excision procedure, as well as the use of different cryotherapy techniques. We identified a small number of randomized controlled trials or independently controlled observational studies. Surrogate outcomes were reported when evidence about outcomes critical to decision making were not available. The panel made 14 recommendations and documented factors that determined the strength and direction of the recommendations in decision tables.

Conclusion

The present document summarizes new evidence‐based WHO recommendations about the use of cryotherapy in women with histologically confirmed CIN for low‐, middle‐, and high‐income countries.
Heritage Politics in Adelaide
Authors: Mosler Sharon
Published: June 2012

In this study, Sharon Mosler examines heritage issues and conflicts in Adelaide from enactment of the first South Australian Heritage Act in 1978 to its successor in 1993, and also analyses issues leading from that period into the twenty-first century.
The Financial Inclusion Imperative and Sustainable Approaches
Authors: Joshi Deepali Pant
Published: June 2012

The need for Financial Inclusion is fast emerging as an international policy issue at the macro level. The Financial Inclusion Imperative and Sustainable Approaches is a comprehensive account of various components of the Financial Inclusion. It presents a blueprint to combat poverty and highlights the critical role of banks and the microfinance sector. This book is comprehensive and gives a contemporary treatment of major issues facing the Indian Economy today. It combines academic rigor and objectivity with clear presentation. In this incisive book, the author asks searching questions and offers carefully thought-out answers. This book will be a valuable source of reference on the subject for bankers, policy-makers, teachers and students of economics.
Influence of porous media heterogeneity on nonaqueous phase liquid dissolution fingering and upscaled mass transfer
Authors: Farthing M. W. , Seyedabbasi M. A. , Imhoff P. T. , Miller C. T.
Published: June 2012

The utility of existing models for describing upscaled mass transfer from nonaqueous phase liquid (NAPL) were examined when preferential dissolution pathways form in NAPL‐contaminated zones that extend over the scale of decimeters. Laboratory experiments were conducted in two well‐characterized, heterogeneous packings. Using data from these experiments and simulations, existing methods for upscaling the mass transfer rate coefficient for NAPL dissolution based on dissolution front length growth (LDF), aquifer heterogeneity and spatial moments of NAPL distribution, and the ganglia‐to‐pool ratio (GTP) were evaluated along with an equilibrium stream tube (EST) model for predicting contaminant flux. When the correlation length of permeability perpendicular to the mean water flow direction was 6.0 cm, greater than the scale of dissolution fingers, only 4.8% of the NAPL resided in pools. Dissolution fingers formed in this experiment, and the LDF, GTP, and EST models resulted in similar predictions of effluent concentrations, with root‐mean‐square errors (RMSEs) between 0.035 and 0.079 and the LDF‐heterogeneous model best. When the correlation scale was smaller (1.0 cm), 66.7% of the NAPL was in pools, and preferential dissolution pathways were dominated by channeling, preferential dissolution caused by spatial variations in aqueous phase permeability, and NAPL saturation. For this experiment the EST and GTP models performed well, with RMSEs of 0.055 and 0.103, respectively. Dissolution fingering was important when the permeability correlation length was sufficiently large that dissolution finger formation was not disrupted and NAPL pools were not dominant.
Elucidating the temporal order of silencing
Authors: Izaurralde Elisa
Published: June 2012

Three recent studies, one published in this issue of EMBO reports, show that miRNA‐mediated translational inhibition of mRNA targets precedes mRNA deadenylation and decay.
Osteoporotische Frakturen des Beckenrings
Authors: Rommens P. , Wagner D. , Hofmann A.
Published: June 2012

Durch die Alterung der Bevölkerung sind wir mit einer Zunahme an osteoporotischen und Ermüdungsfrakturen des Beckenrings konfrontiert. Sie werden durch niedrigenergetische Traumen verursacht. Die konventionelle Diagnostik ist weniger aufschlussreich als bei Jugendlichen und Erwachsenen, eine CT- oder MRT-Diagnostik ist erforderlich. Die Erscheinungsformen sind multipel und bieten ein ganzes Spektrum von Instabilitäten. Die konventionelle Klassifikation trifft nicht auf alle Erscheinungsformen dieser Frakturen zu. Die Behandlung umfasst sowohl konservative als auch operative Verfahren. Entscheidend dabei sind der Grad und die Lokalisation der Instabilität. Die Osteosyntheseformen unterscheiden sich von denen der Beckenringfrakturen bei Erwachsenen. Der transsakrale Positionsstab, die iliolumbale Fixation und die winkelstabile Plattenosteosynthese kommen zunehmend zum Einsatz.
Effect of noise in open chaotic billiards
Authors: Altmann Eduardo G. , Leitão Jorge C. , Viana Lopes João
Published: June 2012

We investigate the effect of white-noise perturbations on chaotic trajectories in open billiards. We focus on the temporal decay of the survival probability for generic mixed-phase-space billiards. The survival probability has a total of five different decay regimes that prevail for different intermediate times. We combine new calculations and recent results on noise perturbed Hamiltonian systems to characterize the origin of these regimes and to compute how the parameters scale with noise intensity and billiard openness. Numerical simulations in the annular billiard support and illustrate our results.
Billiards with a given number of (k,n)-orbits
Authors: Pinto-de-Carvalho Sônia , Ramírez-Ros Rafael
Published: June 2012

We consider billiard dynamics inside a smooth strictly convex curve. For each pair of integers (k,n), we focus our attention on the billiard trajectory that traces a closed polygon with n sides and makes k turns inside the billiard table, called a (k,n)-orbit. Birkhoff proved that a strictly convex billiard always has at least two (k,n)-orbits for any relatively prime integers k and n such that 1≤k<n. In this paper, we show that Birkhoff’s lower bound is optimal by presenting examples of strictly convex billiards with exactly two (k,n)-orbits. We generalize the result to billiards with given even numbers of orbits for a finite number of periods.
Study of dynamics and crystallization kinetics of 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile at ambient and elevated pressure
Authors: Adrjanowicz K. , Kaminski K. , Paluch M. , Ngai K. L. , Yu Lian
Published: June 2012

The organic liquid ROY, i.e., 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile, has been a subject of detailed study in the last few years. One interest in ROY lies in its polymorph-dependent fast crystal growth mode below and above the glass transition temperature. This growth mode is not diffusion controlled, and the possibility that it is enabled by secondary relaxation had been suggested. However, a previous study by dielectric relaxation spectroscopy had not been able to find any resolved secondary relaxation. The present paper reports new dielectric measurements of ROY in the liquid and glassy states at ambient pressure and elevated pressure, which were performed to provide more insight into the molecular dynamics as well as the crystallization tendency of ROY. In the search of secondary relaxation, a special glassy state of ROY was prepared by applying high pressure to the liquid state, from which secondary relaxation was possibly resolved. Thus, the role of secondary relaxation in crystallization of ROY remains to be clarified. Notwithstanding, the secondary relaxation present is not necessarily the sole enabler of crystallization. In an effort to search for possible cause of crystallization other than secondary relaxation, we also performed crystallization kinetics studies of ROY at different T and P combinations while keeping the structural relaxation time constant. The results show that crystallization of ROY speeds up with pressure, opposite to the trend found in the crystallization of ibuprofen studied up to 1 GPa. The dielectric relaxation and thermodynamic properties of ROY with phenolphthalein dimethylether (PDE) are similar in many respects, but PDE does not crystallize. Taking all the above into account, besides the secondary relaxation, the specific chemical structure, molecular interactions and packing of the molecules are additional factors that could affect the kinetics of crystallization found in ROY.
Molecular dynamics with quantum transitions study of the vibrational relaxation of the HOD bend fundamental in liquid D2O
Authors: Bastida Adolfo , Zúñiga José , Requena Alberto , Miguel Beatriz
Published: June 2012

The molecular dynamics with quantum transitions method is used to study the vibrational relaxation of the HOD bend fundamental in liquid D2O. All of the vibrational bending degrees of freedom of the HOD and D2O molecules are described by quantum mechanics, while the remaining translational and rotational degrees of freedom are described classically. The effect of the coupling between the rotational and vibrational degrees of freedom of the deuterated water molecules is analyzed. A kinetic mechanism based on three steps is proposed in order to interpret the dynamics of the system. It is shown that intermolecular vibrational energy transfer plays an important role in the relaxation process and also that the transfer of energy into the rotational degrees of freedom is favored over the transfer of energy into the translational motions. The thermalization of the system after the relaxation is reached in a shorter time scale than that of the recovery of the hydrogen bond network. The relaxation and equilibration times obtained compare well with experimental and previous theoretical results.
In-plane steering of nematicon waveguides across an electrically tuned interface
Authors: Piccardi Armando , Alberucci Alessandro , Barboza Raouf , Buchnev Oleksandr , Kaczmarek Malgosia , Assanto Gaetano
Published: June 2012

We study the interaction of a spatial soliton waveguide with a voltage defined and electrically tuned interface in nematic liquid crystals, whereby the optic axis is reoriented through the use of patterned electrodes. We investigate refraction and total internal reflection of nematicon wavepackets, disclosing the role of anisotropy and obtaining a remarkable in-plane steering as large as 55°.
Equation-of-motion coupled-cluster method for the study of shape resonance
Authors: Ghosh Aryya , Vaval Nayana , Pal Sourav
Published: June 2012

The equation-of-motion coupled-cluster method (EOM-CC) is applied for the first time to calculate the energy and width of a shape resonance in an electron-molecule scattering. The procedure is based on inclusion of complex absorbing potential with EOM-CC theory. We have applied this method to investigate the shape resonance in e−N2, e−CO, and e−C2H2.
Thermoelectric properties of Zn5Sb4In2-δ (δ = 0.15)
Authors: Wu Y. , Litvinchuk A. P. , Toberer E. S. , Snyder G. J. , Newman N. , Fischer A. , Scheidt E.-W. , Scherer W. , Häussermann U.
Published: June 2012

The polymorphic intermetallic compound Zn5Sb4In2−δ (δ = 0.15(3)) shows promising thermoelectric properties at low temperatures, approaching a figure of merit ZT of 0.3 at 300 K. However, thermopower and electrical resistivity changes discontinuously at around 220 K. Measurement of the specific heat locates the previously unknown temperature of the order-disorder phase transition at around 180 K. Investigation of the charge carrier concentration and mobility by Hall measurements and infrared reflection spectroscopy indicate a mixed conduction behavior and the activation of charge carriers at temperatures above 220 K. Zn5Sb4In2−δ has a low thermal stability, and at temperatures above 470 K samples decompose into a mixture of Zn, InSb, and Zn4Sb3.
Laser-pumped paraffin-coated cell rubidium frequency standard
Authors: Bandi Thejesh , Affolderbach Christoph , Mileti Gaetano
Published: June 2012

We have realized and studied a rubidium atomic frequency standard based on a paraffin-coated cell, exhibiting a short-term frequency stability <3 × 10−12 τ−1/2 between τ = 1 and 100 s. Characterization of the wall-coating is performed by measuring the T1 and T2 relaxation times. Perturbations of the medium- to long-term clock stability, due to variations in the laser-intensity, laser frequency, the microwave power shift, and the shifts due to temperature variations are measured and analyzed. A method for reducing the intensity light-shift by detuning the laser frequency and the resulting improvement in clock stability is demonstrated. This work is of relevance for further improvements on Rb cell standards using anti-relaxation wall-coating technology.
Transport formulation of the gyrokinetic turbulence
Authors: Wang Shaojie
Published: June 2012

Nonlinear gyrokinetic equation is formulated in the Fokker-Planck form that puts the effects of the turbulent wave scattering into the divergence of a diffusive-convective flux in the phase space, unified with the binary collision operator. The macroscopic transport fluxes of the particle and heat transport due to the gyrokinetic turbulence are systematically derived, with the diffusive and convective fluxes and the nonlinear turbulence heating rate identified. The proposed theory includes the ponderomotive effects on the turbulent convection and heating, which were not included in the previous quasilinear theory.
Simultaneous high-resolution two-dimensional spatial and one-dimensional picosecond streaked x-ray pinhole imaging
Authors: Steel A. B. , Nagel S. R. , Dunn J. , Baldis H. A.
Published: June 2012

A Kentech x-ray streak camera was run at the LLNL compact multipulse terawatt (COMET) laser to record simultaneous space- and time-resolved measurements of picosecond laser-produced plasmas. Four different x-ray energy channels were monitored using broadband filters to record the time history of Cu targets heated at irradiances of 1016–1019 W/cm2. Through the Cu filter channel, a time-resolution below 3 ps was obtained. Additionally, an array of 10 μm diameter pinholes was placed in front of the camera to produce multiple time-resolved x-ray images on the photocathode and time-integrated images on the phosphor with 10 and 15 times magnification, respectively, with spatial resolution of < 13 μm.
Secondary electron emissions and dust charging currents in the nonequilibrium dusty plasma with power-law distributions
Authors: Gong Jingyu , Du Jiulin
Published: June 2012

We study the secondary electron emissions induced by the impact of electrons on dust grains and the resulting dust charging processes in the nonequilibrium dusty plasma with power-law distributions. We derive new expressions of the secondary emitted electron flux and the dust charging currents that are generalized by the power-law q-distributions, where the nonlinear core functions are numerically studied for the nonextensive parameter q. Our numerical analyses show that the power-law q-distribution of the primary electrons has a significant effect on both the secondary emitted electron flux and the dust charging currents, and this effect depends strongly on the ratio of the electrostatic potential energy of the primary electrons at the dust grain’s surface to the thermodynamic energy, implying that a competition in the dusty plasma between these two energies plays a crucial role in this novel effect.
Frequency stabilization of an external-cavity diode laser to metastable argon atoms in a discharge
Authors: Douglas P. , Maher-McWilliams C. , Barker P. F.
Published: June 2012

A laser stabilization scheme using magnetic dichroism in a RF plasma discharge is presented. This method has been used to provide a frequency stable external-cavity diode laser that is locked to the 4s[\documentclass[12pt]{minimal}\begin{document}$\frac{3}{2}$\end{document}32]2 → 4p[\documentclass[12pt]{minimal}\begin{document}$\frac{5}{2}$\end{document}52]3 argon laser cooling transition at 811.53 nm. Using saturated absorption spectroscopy, we lock the laser to a Doppler free peak which gave a locking range of 20 MHz when the slope of the error signal was maximized. The stability of the laser was characterized by determining the square root Allan variance of laser frequency fluctuations when the laser was locked. A stability of 129 kHz was measured at 1 s averaging time for data acquired over 6000 s.
Intrinsic and extrinsic defect relaxation behavior of ZnO ceramics
Authors: Zhao Xuetong , Li Jianying , Li Huan , Li Shengtao
Published: June 2012

The behavior of intrinsic and extrinsic defect relaxations in ZnO ceramics has been systematically investigated. The defect relaxations are characterized by various parameters, and electric modulus is proposed to be more sensitive to the defect relaxations. Four defect relaxations with various energy levels are found at different temperatures. Two defect relaxations appearing below 243 K with energy levels (L1, L2) about 0.24 eV and 0.35 eV are suggested to be intrinsic defects relating to interstitial Zn and vacancy oxygen, which are not affected by additives and impulse current degradation. Another two defect relaxations appearing above 353 K are proposed to be extrinsic defects associated with energy level (L3) at intergranular phase and energy level (L4) at grain-boundary interfaces, respectively. The extrinsic defect relaxations are closely related with additives and electrical performance. Only L4 was reduced from 0.84 eV to 0.76 eV by impulse current degradation while other defect energy levels keep unchanged. It is further proposed that L4 is mainly responsible for the electrical properties and stability of ZnO ceramics, and it mainly contributes to the grain boundary resistance of ZnO ceramics. A schematic energy band diagram is demonstrated for interpreting the intrinsic and extrinsic defect relaxations in ZnO ceramics.
A study on exchange coupled structures of Fe/NiO and NiO/Fe interfaced with n- and p-silicon substrates
Authors: Srivastava Neelabh , Srivastava P. C.
Published: June 2012

Interfacial structures of ferromagnetic (FM)/antiferromagnetic (AF) (Fe/NiO) and AF/FM (NiO/Fe) on n- and p-Si substrates have been realized by sequential deposition of FM and AF layers on the silicon substrates by electron beam evaporation technique. The structures have been characterized from x-ray diffraction (XRD), atomic force microscopy (AFM), magnetic force microscopy (MFM), and M-H characteristics. It has been found that there is a strong interfacial intermixing to form the various oxide and silicide phases of Fe2O3, β-Fe2O3, β″-Fe2O3, NiSi, Ni3Si, and Fe5Si3. AFM micrographs show the granular morphology of the top layer of the structure, with a large grain size of ∼400 nm, however, the XRD data show the crystallite size of ∼20 to 70 nm. It seems that the crystallites are clustered to form larger grains. MFM features show a large domain size corresponding to AFM grain size for Fe/NiO/Si structure and very small domain of nanometer size for NiO/Fe/Si structure (having NiO as a top layer). M-H characteristics show that the magnetic behavior is only significant for Fe/NiO/nSi structure with a significant coercivity and exchange bias than for all other interfacial structures of Fe/NiO/pSi, NiO/Fe/pSi, and NiO/Fe/nSi. Thus, it has been found that Fe/NiO/nSi structure can be used in magneto-electronic device applications. It seems that the observed result of significant exchange bias and coercivity is due to the microstructural and chemical structure changes in the antiferromagnetic layer along with the roughness (data as obtained from AFM).
Treatment with orthophosphoric acid enhances the thermal stability of the piezoelectricity in low-density polyethylene ferroelectrets
Authors: Rychkov Dmitry , Alberto Pisani Altafim Ruy , Qiu Xunlin , Gerhard Reimund
Published: June 2012

Ferroelectrets have been fabricated from low-density polyethylene (LDPE) films by means of a template-based lamination. The temperature dependence of the piezoelectric d33 coefficient has been investigated. It was found that low-density polyethylene ferroelectrets have rather low thermal stability with the piezoelectric coefficient decaying almost to zero already at 100 °C. This behavior is attributed to the poor electret properties of the polyethylene films used for the fabrication of the ferroelectrets. In order to improve the charge trapping and the thermal stability of electret charge and piezoelectricity, LDPE ferroelectrets were treated with orthophosphoric acid. The treatment resulted in considerable improvements of the charge stability in LDPE films and in ferroelectret systems made from them. For example, the charge and piezoelectric-coefficient decay curves shifted to higher temperatures by 60 K and 40 K, respectively. It is shown that the decay of the piezoelectric coefficient in LDPE ferroelectrets is governed by the relaxation of less stable positive charges. The treatment also leads to noticeable changes in the chemical composition of the LDPE surface. Infrared spectroscopy reveals absorption bands attributed to phosphorus-containing structures, while scanning electron microscopy shows new island-like structures, 50–200 nm in diameter, on the modified surface.
Domain epitaxy in TiO2/α-Al2O3 thin film heterostructures with Ti2O3 transient layer
Authors: Bayati M. R. , Molaei R. , Narayan R. J. , Narayan J. , Zhou H. , Pennycook S. J.
Published: June 2012

Rutile TiO2 films were grown epitaxially on α-alumina (sapphire(0001)) substrates and characterized by x-ray diffraction and scanning transmission electron microscopy. It was revealed that the rutile film initially grows pseudomorphically on sapphire as Ti2O3 and, after a few monolayers, it grows tetragonally on the Ti2O3/sapphire platform. Formation of the Ti2O3 transient layer was attributed to the symmetry mismatch between tetragonal structure of TiO2 and hexagonal structure of alumina. The separation between the ½[101¯](101) misfit dislocations was dictated by Ti2O3 and was determined to be 9.7 Å which is consistent with 4/3 and 3/2 alternating domains across the film/substrate interface.
Efficient optical gain media comprising binary blends of poly(3-hexylthiophene) and poly(9,9-dioctylfluorene-co-benzothiadiazole)
Authors: Xia R. , Stavrinou P. N. , Bradley D. D. C. , Kim Y.
Published: June 2012

We report the results of a study of the optical gain properties of binary blend films of regioregular poly(3-hexylthiophene) (RR-P3HT) and poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT). Efficient optical gain is observed in the 10–20 wt. % RR-P3HT composition range and can be tuned to the ∼650 nm window utilised for polymer optical fibre data-communications, with maximum gain ∼50 cm−1. At higher P3HT fractions, gain thresholds increase substantially, consistent with the observed concomitant improvement in photocharge generation. Distributed feed back lasers with one-dimensional gratings exhibit pump pulse thresholds as low as 8 nJ (26 μJ cm−2, 2.17 kW cm−2), lower than many other polymer-based gain media in this wavelength range. They also provide relatively high slope efficiencies >2%. The confluence of efficient optical gain with electronic properties that are conducive to charge carrier injection and transport is relatively novel and is expected to be a necessary requirement for the achievement of electrically pumped lasing.
Increased electrical conductivity in fine-grained (Zr,Hf)NiSn based thermoelectric materials with nanoscale precipitates
Authors: Xie Han-Hui , Yu Cui , Zhu Tie-Jun , Fu Chen-Guang , Jeffrey Snyder G. , Zhao Xin-Bing
Published: June 2012

Grain refinement has been conducted to reduce the thermal conductivity and improve the thermoelectric performance of the (Zr,Hf)NiSn based half-Heusler alloys. Nanoscale in situ precipitates were found embedded in the matrix with submicron grains. The lattice thermal conductivity was decreased due to the enhanced boundary scattering of phonons. The increased carrier concentration and electrical conductivity were observed compared to the coarse-grained alloys, which is discussed in relation to the existence of nanoscale precipitates, the effect of antisite defects, and composition change. It is suggested that the nanoscale precipitates play a significant role in the observed electrical conductivity increase.