bluuebunny/crossref_metadata_2025 huggingface dataset:
Risk factors for onset of persistent respiratory symptoms in children with cystic fibrosis
Authors: McColley Susanna A. , Ren Clement L. , Schechter Michael S. , Regelmann Warren E. , Pasta David J. , Konstan Michael W. ,   for the Investigators Coordinators of the Epidemiologic Study of Cystic Fibrosis
Published: February 2012

Objectives

To characterize the onset of persistent signs and symptoms of cystic fibrosis (CF) lung disease and identify characteristics that predict onset.

Study design

Patients in the Epidemiologic Study of CF who were <4 years of age at enrollment and had ≥2 years of follow‐up were included. We defined persistence as a sign or symptom that was present during two consecutive encounters separated by 60–365 days, and persistent clubbing as ≥50% of encounters with clubbing within 365 days. Predictors were assessed in a Cox proportional hazards model for age at first occurrence of each symptom.

Results

Each sign or symptom met the criterion of persistence in a substantial proportion of patients during a follow‐up period of 7 ± 3 years (mean ± SD; range 2–12). Risk factors that predicted earlier onset of signs and symptoms included pancreatic enzyme use, Pseudomonas aeruginosa infection, and prior diagnosis of asthma. Other risk factors had variable effects on signs and symptoms.

Conclusions

Signs and symptoms of lung disease begin early in CF. Risk factors previously reported for lower forced expiratory volume in 1 sec are also associated with earlier onset of persistent signs and symptoms of CF lung disease, but their impact varies. Pediatr Pulmonol. 2012. 47:966–972. © 2012 Wiley Periodicals, Inc.
An intersubunit disulfide bridge stabilizes the tetrameric nucleoside diphosphate kinase of Aquifex aeolicus
Authors: Boissier Fanny , Georgescauld Florian , Moynié Lucile , Dupuy Jean‐William , Sarger Claude , Podar Mircea , Lascu Ioan , Giraud Marie‐France , Dautant Alain
Published: February 2012

The nucleoside diphosphate kinase (Ndk) catalyzes the reversible transfer of the γ‐phosphate from nucleoside triphosphate to nucleoside diphosphate. Ndks form hexamers or two types of tetramers made of the same building block, namely, the common dimer. The secondary interfaces of the Type I tetramer found in Myxococcus xanthus Ndk and of the Type II found in Escherichia coli Ndk involve the opposite sides of subunits. Up to now, the few available structures of Ndk from thermophiles were hexameric. Here, we determined the X‐ray structures of four crystal forms of the Ndk from the hyperthermophilic bacterium Aquifex aeolicus (Aa‐Ndk). Aa‐Ndk displays numerous features of thermostable proteins and is made of the common dimer but it is a tetramer of Type I. Indeed, the insertion of three residues in a surface‐exposed spiral loop, named the Kpn‐loop, leads to the formation of a two‐turn α‐helix that prevents both hexamer and Type II tetramer assembly. Moreover, the side chain of the cysteine at position 133, which is not present in other Ndk sequences, adopts two alternate conformations. Through the secondary interface, each one forms a disulfide bridge with the equivalent Cys133 from the neighboring subunit. This disulfide bridge was progressively broken during X‐ray data collection by radiation damage. Such crosslinks counterbalance the weakness of the common‐dimer interface. A 40% decrease of the kinase activity at 60°C after reduction and alkylation of the protein corroborates the structural relevance of the disulfide bridge on the tetramer assembly and enzymatic function. Proteins 2012. © 2012 Wiley Periodicals, Inc.
In vitro inhibition of mycelial growth of Phytophthora nicotianae Breda de Haan from different hosts by Brassicaceae species. Effect of the developmental stage of the biofumigant plants
Authors: Morales‐Rodríguez Carmen , Picón‐Toro Julia , Palo Carolina , Palo Eloy J , García Ángela , Rodríguez‐Molina Carmen
Published: February 2012

BACKGROUND: The hydrolysis products of glucosinolates in Brassicaceae tissues are potentially useful for the control of fungal pathogens. The in vitro activity of these products against Phytophthora nicotianae Breda de Haan was studied, with the isolates exposed to the volatile products released from the brassica tissues.

RESULTS: The four species of Brassicaceae tested inhibited the mycelial growth of P. nicotianae isolates. The most effective developmental stage was different, depending on the species: buds yellowing in Sinapis alba L. and Brassica carinata A. Braun; seeds enlarging and all buds open in Brassica nigra (L.) W.D.J. Koch; cauliflower still covered by leaves in Brassica oleracea L. var. botrytis. At this stage, B. nigra and S. alba were the most effective (53.6 and 52.5% inhibition respectively). With all the biofumigants species tested, isolates from pepper plants were more susceptible to the brassica effect than those from tomato isolates.

CONCLUSION: The developmental stage of plants has an influence on the biofumigant potential of Brassicaceae species against P. nicotianae. The isolates differ in susceptibility to compounds released, depending on their host of origin, suggesting the differentiation of populations of P. nicotianae in relation to the host of origin. Copyright © 2012 Society of Chemical Industry
Population Health across Space and Time: the Geographical Harmonisation of the Office for National Statistics Longitudinal Study for England and Wales
Authors: Norman Paul , Riva Mylène
Published: February 2012

There is a need in health research to identify whether inequalities are increasing or improving between different geographical areas. Both cross‐sectional time‐series and longitudinal/cohort studies contribute to our knowledge, with the Office for National Statistics Longitudinal Study (LS) for England and Wales being a major resource. However, any research into geographical change over time can be hampered by boundary change or when the geographical definition for which data are available is not the geography relevant to an analysis.

We develop a method using population‐weighted centroids of estimating an LS member's location at a previous time point and then link this to a small‐area geography, the 2001 Census Output Areas. This is not so that analyses can be carried out at this scale but so that records can be linked to larger geographies or area classifications. A time‐series or longitudinal analysis can then be carried out and geographical trends observed. In terms of reliability, we find that accuracy improves with increasing size of geographical units and when area typologies are used.

In example analyses using a geodemographic classification attached to LS members' records, we find that in a time series of cross‐sections, mortality improves across all area types but not to the same extent. A longitudinal analysis indicates that changes in the area types in which people were living lead to steeper health gradients than if people had stayed living in the same type of area. Differences, though, are small, suggesting that, in the main, there is little mobility between area types.

We recommend that longitudinal and cohort studies retain the postcode of each member's address so that ongoing linkages can be made when administrative boundary changes occur and for relevance to application relevant geographies. Our method can be used to enhance previous records and thereby maximise previous investment in the collection of data. Copyright © 2012 John Wiley & Sons, Ltd.
Nonlinear vertex discriminant analysis with reproducing kernels
Authors: Wu Tong Tong , Wu Yichao
Published: February 2012

The novel supervised learning method of vertex discriminant analysis (VDA) has been demonstrated for its good performance in multicategory classification. The current paper explores an elaboration of VDA for nonlinear discrimination. By incorporating reproducing kernels, VDA can be generalized from linear discrimination to nonlinear discrimination. Our numerical experiments show that the new reproducing kernel‐based method leads to accurate classification for both linear and nonlinear cases. © 2012 Wiley Periodicals, Inc. Statistical Analysis and Data Mining, 2012
The role of noncoding RNAs in chromatin regulation during differentiation
Authors: Nahkuri Satu , Paro Renato
Published: February 2012

A myriad of nuclear noncoding RNAs (ncRNAs) have been discovered since the paradigm of RNAs as plain conveyors of protein translation was discarded. There is increasing evidence that at vital intersections of developmental pathways, ncRNAs target the chromatin modulating machinery to its site of action. However, the mechanistic details of processes involved are still largely unclear, and well‐characterized metazoan ncRNA species implicated in chromatin regulation during differentiation remain few. Nevertheless, four major categories are slowly emerging: cis‐acting antisense ncRNAs that flag the neighboring genes for the propagation of chromatin marks; allele‐specific ncRNAs that perform similar tasks, but target larger loci that typically vary in size from hundreds of thousands of base pairs to a whole chromosome; structural ncRNAs proposed to act as scaffolds that couple chromatin shaping complexes of distinct functionalities; and cofactor ncRNAs with a capacity to inhibit or activate essential components of the intertwined chromatin and transcription apparatuses. WIREs Dev Biol 2012. doi: 10.1002/wdev.41

For further resources related to this article, please visit the WIREs website.
Bird and bat mortality at short, monopole cell towers in Rock Creek Park, Washington, D.C., USA
Authors: Dickey Stephanie D. , Gates J. Edward , Dickey Bradley , Ferebee Ken
Published: February 2012

Bird and bat mortality resulting from collisions with manmade towers is well‐documented, and our understanding of this phenomenon is increasing, particularly for taller structures (≥61 m) with guy wires and the obstruction lighting required by the U.S. Federal Aviation Administration. However, shorter, monopole tower designs remain underinvestigated. We report the results of a 3‐year study (2006–2008) on the effects of 2 existing telecommunication (“cell phone”) towers on migratory bird and bat mortality in Rock Creek Park (ROCR), Washington, D.C., USA. The towers in ROCR are the shorter (30.9 m and 39.6 m in ht), monopole design and lack obstruction lighting and guy wires. We conducted mortality surveys on a daily basis during spring and autumn migrations, and conducted weekly surveys during the summer. Bird carcasses were collected, but we were unable to attribute any avian or bat mortality to the towers at these sites. © 2012 The Wildlife Society.
Magnesium(II), Calcium(II), and Barium(II) Coordination Compounds Constructed by 1H‐Tetrazolate‐5‐acetic Acid Ligand
Authors: Li Qiao‐Yun , Yang Gao‐Wen , Shen Lei , He Ming‐Hua , Shen Wei , Gu Kun , Jin Jian‐Ning
Published: February 2012

Reactions of H2tza (H2tza = 1H‐tetrazolate‐5‐acetic acid) with Mg(NO3)2·6H2O, Ca(NO3)2·4H2O, or Ba(NO3)2 with the presence of KOH under hydrothermal conditions, produced three new coordination compounds, [M(tza)(H2O)2] (M = Mg (1), Ca (2), Ba (3)). These compounds were structurally characterized by elemental analysis, IR spectroscopy, and single‐crystal X‐ray diffraction. Compounds 1 and 3 display 2D structures, whereas 2 reveals a 1D structure with bridging tza ligand molecules as linkers. Furthermore, the luminescence properties of 1–3 at room temperature in the solid state were also investigated. The results show that the nature of metal ions play an important role in governing the molecular frameworks of 1–3, and the strong coordinate abilities of carboxylate and tetrazolate group, endow tza with abundant coordination modes.
Cultural aspects in the management of inborn errors of metabolism
Authors: Stockler Sylvia , Moeslinger Dorothea , Herle Marion , Wimmer Banu , Ipsiroglu Osman S.
Published: February 2012

European Health Care Systems have not yet accommodated both previous and current migration waves. Children from immigrant families, especially children with chronic conditions, are particularly affected from the shortcomings in medical care. One condition, phenylketonuria (PKU), is an inborn error of metabolism (IEM) which results in intellectual disability unless treated with a lifelong phenylalanine (Phe) restricted diet. In our PKU clinic, patients from families who previously had emmigrated from the geographic area of Turkey to Austria, exhibited worse blood Phe control and cognitive development than comparable patients from native Austrian families. Using structured and semi‐structured interviews, questionnaires, and illness narratives, we identified language, psychosocial, economic, educational and cultural barriers as factors influencing adherence to treatment. Our findings led us to conclude that access to interpreter services, exploration of the socio‐cultural background and of family ecology, as well as bi‐directional communication and medical decision making according to the “best interest of the child” principle, may improve outcomes in patients requiring complex treatment and care.
Reliability and validity of the Turkish version of the Performance-Oriented Mobility Assessment I
Authors: Yücel Serap D. , Şahin Füsun , Doğu Beril , Şahin Tülay , Kuran Banu , Gürsakal Sevda
Published: February 2012

The Performance-Oriented Mobility Assessment (POMA)-I is widely used assessment tool for evaluation of balance and gait properties. The aim of this study was to translate POMA-I to Turkish and to assess its reliability and validity. People with amputated lower extremities using prosthetics, those who underwent orthopedic surgery within the last 6 months, those dependent on wheel chairs and also bed-ridden patients, subjects with dementia and Alzheimer’s disease, and illiterate people were excluded. After translation into Turkish, the Turkish version of the scale was applied on the participants at 2-week intervals. Volunteers ≥65 years of age were enrolled in the study. Internal consistencies of POMA subscale scores of postural balance and gait, and total score were calculated using Cronbach’s α coefficient. The Turkish version was evaluated with respect to inter- and intrarater reliability and test–retest reliability intraclass correlation coefficient (ICC). For validation, Pearson’s correlation coefficient between POMA and Berg Balance Scale (BBS) and Timed Up and Go Test (TUGT) was estimated. Eighty participants enrolled in the study with a mean age of 76.5 ± 6.75 years. In the reliability evaluation of the scale, considering postural balance, gait, and total score, Cronbach’s α coefficients were found to be 0.72, 0.83, and 0.88, respectively. ICCs were detected above 0.70 for test–retest reliability and also for interrater and intrarater reliability. In validation study POMA total score had a strong positive correlation with BBS total score (r = 0.86, p < 0.0001), and also a negative correlation with TUGT (r = −0.75, p < 0.0001). According to the results of this study, the Turkish version of the POMA-I scale has been found to be a reliable and a valid scale for elderly Turkish people.
Results of a survey by the European Society of Radiology (ESR): undergraduate radiology education in Europe—influences of a modern teaching approach
Authors: Oris Elena , Verstraete Koenraad , Valcke Martin ,   on behalf of the ESR Working Group on Undergraduate Education
Published: February 2012

Objectives

The purpose of the present study is to determine in what way a conventional versus a modern medical curriculum influences teaching delivery in formal radiology education.

Methods

A web-based questionnaire was distributed by the ESR to radiology teaching staff from 93 European teaching institutions.

Results

Early exposure to radiology in pre-clinical years is typically reported in institutions with a modern curriculum. The average number of teaching hours related to radiology is similar in both curriculum types (60 h). Radiology in modern curricula is mainly taught by radiologists, radiology trainees (50%), radiographers (20%) or clinicians (17%). Mandatory clerkships are pertinent to modern curricula (55% vs. 41% conventional curriculum), which start in the first (13% vs. 4% conventional curriculum) or second year of the training (9% vs. 2% conventional curriculum). The common core in both curricula consists of radiology examinations, to work with radiology teaching files, to attend radiology conferences, and to participate in multidisciplinary meetings.

Conclusion

The influence of a modern curriculum on the formal radiology teaching is visible in terms of earlier exposure to radiology, involvement of a wider range of staff grades and range of profession involved in teaching, and radiology clerkships with more active and integrated tasks.

Main Message

• This study looks at differences in the nature of formal radiology teaching.
miR‐20a promotes migration and invasion by regulating TNKS2 in human cervical cancer cells
Authors: Kang Hong-Wei , Wang Fang , Wei Qian , Zhao Yi-Fan , Liu Min , Li Xin , Tang Hua
Published: February 2012

miR‐20a is an important member of the miR‐17–92 cluster, and its real function in cervical cancer cells is unknown. Our study demonstrated that miR‐20a was upregulated in cervical cancer tissues. Overexpression of miR‐20a in cervical cancer‐derived cell lines, HeLa and C‐33A, enhanced long‐term cellular proliferation, migration and invasion, whereas inhibition of miR‐20a suppressed those functions. We also confirmed that oncogenic TNKS2 is directly upregulated by miR‐20a. Furthermore, suppression of TNKS2 expression could inhibit colony formation, migration and invasion of cervical cancer cells. Therefore, we concluded that miR‐20a can promote migration and invasion of cervical cancer cells through the upregulation of TNKS2.
More on puzzling words and spellings in Aramaic incantation bowls and related texts
Authors: Müller-Kessler Christa
Published: February 2012

The corpus of Aramaic incantation bowls and their related texts opens a new approach to the lexicographical study of the Aramaic dialects in Babylonia of late antiquity. Some of these texts were copies of “Vorlagen” that the scribes no longer understood. Nevertheless, they are more reliable text sources than one supposes. Errors, garbled spellings, miscomprehensions and misreadings are always feasible, and are typical phenomena of copied texts. In the case of new text variants one can approach the puzzling words and text passages anew. This study deals first and foremost with words that are obvious corrupted spellings or scribal errors caused by text transmissions. There are also cases of the breakdown of standard spellings and orthographic conventions from the dialect of “Vorlage” that hide the lexical assignment of a word. Since one is dealing here with the earliest text material of the late Aramaic period, they can be taken as a significant contribution to the placing of many lexemes in existing dictionaries.
Japanese exploration of Central Asia: The Ōtani expeditions and their British connections
Authors: Galambos Imre , Kōichi Kitsudō
Published: February 2012

The Archives of the Royal Geographical Society (RGS) include a small lot of material relating to the three expeditions to western China organized and financed by Count Ōtani Kozui (1902–14), with the aim of exploring Buddhist sites. Ōtani also recognized the significance of promoting their results outside of Japan and integrating them into the international academic community, primarily Britain. Since his collection was later dispersed, the material in the RGS Archives provides valuable information on the expeditions and clarifies the context for some of the discoveries. In addition, it evidences traces of the interaction between Japanese and British scholarly circles, as an example of the complex international network of scholarship on Central Asia in the early part of the twentieth century. It also shows the efforts invested by the Japanese side in trying to have their results acknowledged as being equal to those of Western explorers.
Cyclic loss of open solar flux since 1868: The link to heliospheric current sheet tilt and implications for the Maunder Minimum
Authors: Owens M. J. , Lockwood M.
Published: February 2012

Open solar flux (OSF) variations can be described by the imbalance between source and loss terms. We use spacecraft and geomagnetic observations of OSF from 1868 to present and assume the OSF source, S, varies with the observed sunspot number, R. Computing the required fractional OSF loss, χ, reveals a clear solar cycle variation, in approximate phase with R. While peak R varies significantly from cycle to cycle, χ is surprisingly constant in both amplitude and waveform. Comparisons of χ with measures of heliospheric current sheet (HCS) orientation reveal a strong correlation. The cyclic nature of χ is exploited to reconstruct OSF back to the start of sunspot records in 1610. This agrees well with the available spacecraft, geomagnetic, and cosmogenic isotope observations. Assuming S is proportional to R yields near‐zero OSF throughout the Maunder Minimum. However, χ becomes negative during periods of low R, particularly the most recent solar minimum, meaning OSF production is underestimated. This is related to continued coronal mass ejection (CME) activity, and therefore OSF production, throughout solar minimum, despite R falling to zero. Correcting S for this produces a better match to the recent solar minimum OSF observations. It also results in a cycling, nonzero OSF during the Maunder Minimum, in agreement with cosmogenic isotope observations. These results suggest that during the Maunder Minimum, HCS tilt cycled as over recent solar cycles, and the CME rate was roughly constant at the levels measured during the most recent two solar minima.
Observations and effects of artificial density layers on oblique high‐frequency backscatter
Authors: Theurer T. E. , Bristow W. A.
Published: February 2012

An improved method of estimating ground‐scattered power using high‐frequency (HF) ray tracing techniques that overcomes the limitations of the derivation presented by Bristow and Greenwald (1995) is presented. The improved method is applied toward identifying the effects of an artificial ionospheric density layer on measured ground scatter power. The presence of artificial density layers induced at the High Frequency Active Auroral Research Program (HAARP) station in Gakona, Alaska, are observed through the ground‐scattered power received by the Kodiak Super Dual Auroral Radar Network (SuperDARN) HF radar. The location and physical dimensions of the artificial layers are estimated by simulating radar returns using HF ray tracing through a model ionosphere that includes a model artificial density layer. Simulation results of ground‐scattered power as a function of range are compared to the measured ground‐scattered power as a function of range during a time period when artificial layers were evident in ionogram data. It is shown that a model artificial density layer based on research by Pedersen et al. (2009) produces simulation results that approximate the mean of the measured results.
A network theory for resource exchange between rivers and their watersheds
Authors: Sabo John L. , Hagen Elizabeth M.
Published: February 2012

Watersheds are drained by river networks, which route materials and energy from headwaters to terminal water bodies. River networks likewise perfuse the terrestrial portion of watershed ecosystems and reroute some of these materials upslope via material exchange between rivers and land. Here we develop a model of resource exchange between rivers and watersheds to predict the spatial extent of material and nutrient fluxes from aquatic portions of watershed ecosystems. The model is based on a geomorphic template that includes river network structure, topography, and channel sinuosity as well as important biological attributes (productivity and dispersal ability). Analysis of this model suggests that the geomorphic template strongly influences the spatial extent of resource flows in watershed ecosystems. The geomorphic template also predicts the location of areas of concentrated resource exchange, typically at ridge crests, in meander bends, and tributary junctions. We contend that these areas represent hotspots of foraging activity for terrestrial consumers, especially those at the reach scale (meander bends). More generally, our model suggests that the spatial extent of aquatic resource flow equal in magnitude to 20% or greater of terrestrial production may encompass as much as 20%–50% of terrestrial portions of watersheds. Resource flow from rivers to terrestrial ecosystems is not merely an edge effect. Instead, the river network may reroute a substantial flux of materials into watershed ecosystems.
Weight matrix based identification of terpene synthases conserved motifs in Arabidopsis thaliana proteome
Authors: Srivastava Suchita , Luqman Suaib , Khan Feroz
Published: February 2012

Terpenes comprise the most diverse collection of natural products. Out of more than 30,000 individual terpenoids identified, at least half are synthesized by plants. A relatively small, but quantitatively significant, number of terpenoids are involved in primary plant metabolism. However, the vast majorities are classified as secondary metabolites; compounds not required for plant growth and development but presumed to have an ecological function in communication or defense and are widely used in industrial applications. Terpene hydrocarbon scaffolds are generated by the action of the mechanistically intriguing family of mono-, sesqui-, and diterpene synthases collectively termed as terpene synthases, that catalyze multistep reactions with diphosphorylated substrates of 10 (geranyl diphosphate), 15 (farnesyl diphosphate) or 20 (geranylgeranyl diphosphate) carbons. In the studied work, we performed a computational study on proteome wide identification of terpene synthase motifs in Arabidopsis thaliana proteome on the basis of weight matrix approach. We have developed an optimal weight matrix for the identification of terpene synthase motifs in the plant’s proteome. Weight matrix was constructed by aligning orthologous sequences of known terpene synthases originated from diverse plant species viz., Abies grandis, Nicotiana tobaccum etc. Sequences of detected domains & motifs were retrieved through SwissProtKB/NCBI on the basis of specific conservation IDs of Prosite, Pfam, Interpro, Prodom, COG, TIGR databases, while position specific scoring matrices were made through MEME, MotifSampler, PossuMsearch tools. Weight matrix based search of conserved motifs in the proteome of A. thaliana was done through ESA, Lahead and Simple algorithm based search tools of PossuMsearch biosuite in Linux system. Prediction was first validated by using positive control data set and optimized the method to reach prediction accuracy upto >90%. After tool performance evaluation, prediction was made on whole proteome at specific threshold/score value. Significant results were found in A. thaliana with motif similarity ranges from 80% to 100%. This proteome wide search model paves the path to identify more terpene synthases genes in A. thaliana, as well as in other plant systems.
Inhibiton of NFκB activation and aromatase activity by vanilloids: An in vitro and in silico study
Authors: Luqman Suaib , Meena Abha , Marler Laura , Kondratyuk Tamara , Pezzuto John
Published: February 2012

Target-specific drugs, including natural products, offer promise for the amelioration of cancer and other human ailments with reduced side-effects. Capsaicin, the pungent ingredient present in chillies (Capsicum annuum L.), and capsazepine, a synthetic analogue of capsaicin (collectively referred to as vanilloids), are known to possess a variety of pharmacological and physiological properties. In our continuous effort to discover cancer chemopreventive agents from natural products, we investigated the effect of vanilloids on NFκB activation with stably transfected 293/NFκB-Luc human embryonic kidney cells induced by treatment with tumor necrosis factor (TNFα), and aromatase activity. Capsaicin and capsazepine blocked TNFα-induced NFκB activation in a dose-dependent manner with IC50 values of 13.5 and 8.5 μM, respectively. No cytotoxicity was observed at higher test concentration (20 μg/mL). In addition, these vanilloids inhibited aromatase activity with IC50 values of 0.68 and 4.21 μM, respectively. Computer aided molecular docking studies showed acceptable docking scores indicating good binding affinity of vanilloids with aromatase and NFκB. Based on these findings, aromatase and NFκB are suggested as valid targets for these compounds; additional investigation of chemopreventive or chemotherapeutic potential is required.
Evidence for intrinsic superconductivity at Tc1 in PrOs4Sb12
Authors: Andraka B. , Pocsy K.
Published: February 2012

Superconductivity in PrOs4Sb12 shows unusual sample size dependence. Large good quality crystals exhibit two superconducting transitions at Tc1 (∼1.85 K) and Tc2 (∼1.74 K). The upper temperature transition is manifested by the change of slope in C/T. It is shown that this transition is suppressed when the crystal is polished to a thickness smaller than 50 μm. At the same time the polishing enhances the transition at Tc2. This behavior is independent on whether material studied is removed from the interior or contains the original surface of the as-cast crystal. The effect of sample polishing is similar to that of powdering, which clearly induces a large number of defects.
Magnetophotonic crystal comprising electro-optical layer for controlling helicity of light
Authors: Goto Taichi , Inoue Mitsuteru
Published: February 2012

We present a magnetophotonic crystal (MPC) comprising an electro-optical (EO) layer which can control the helicity of the light by low voltage at high speed at room temperature. Within the photonic bandgap of the MPC the localized spectral position of eigen circularly polarized modes are separated. The change of refractive index of EO layer in MPC allows us to choose which eigen mode works at the wavelength of the light source. This medium does not require the high voltage to change the phase of light because of thin thickness of EO layer. In this paper, the calculated results showed that the helicity of light can be controlled by low voltage (<0.5 V) in MPC comprising EO layer. Such a behavior is fascinating for the micro switching device which modulates the rotation direction of circularly polarized light in the optical-magnetic recording system.
Design of a spoke-type permanent-magnet motor with optimal winding configuration for electric vehicle applications
Authors: Chen Qian , Liu Guohai , Gong Wensheng , Qu Li , Zhao Wenxiang , Shen Yue
Published: February 2012

The spoke-type motor has higher torque density than the conventional one resulting from its structure for concentrating flux from permanent magnets (PMs). However, this motor suffers from the serious distortion of back electromotive force (EMF). This paper proposes a cost-effective approach to design a spoke-type motor with lower harmonics of back-EMF for electric vehicle. The key is to superimpose the coil-EMF of one phase in such a way that the harmonics of the phase-EMF can be canceled, resulting in essentially sinusoidal waveforms. By using finite element method (FEM), an optimal coil-EMF vectors distribution for minimum harmonics of the phase-EMF is obtained and verified. In addition, the co-simulation technology is adopted to verify that the torque ripple under the optimal winding configuration can be significantly suppressed.
A neutron diagnostic for high current deuterium beams
Authors: Rebai M. , Cavenago M. , Croci G. , Dalla Palma M. , Gervasini G. , Ghezzi F. , Grosso G. , Murtas F. , Pasqualotto R. , Perelli Cippo E. , Tardocchi M. , Tollin M. , Gorini G.
Published: February 2012

A neutron diagnostic for high current deuterium beams is proposed for installation on the spectral shear interferometry for direct electric field reconstruction (SPIDER, Source for Production of Ion of Deuterium Extracted from RF plasma) test beam facility. The proposed detection system is called Close-contact Neutron Emission Surface Mapping (CNESM). The diagnostic aims at providing the map of the neutron emission on the beam dump surface by placing a detector in close contact, right behind the dump. CNESM uses gas electron multiplier detectors equipped with a cathode that also serves as neutron-proton converter foil. The cathode is made of a thin polythene film and an aluminium film; it is designed for detection of neutrons of energy >2.2 MeV with an incidence angle < 45°. CNESM was designed on the basis of simulations of the different steps from the deuteron beam interaction with the beam dump to the neutron detection in the nGEM. Neutron scattering was simulated with the MCNPX code. CNESM on SPIDER is a first step towards the application of this diagnostic technique to the MITICA beam test facility, where it will be used to resolve the horizontal profile of the beam intensity.
Liquid metal alloy ion source based metal ion injection into a room-temperature electron beam ion source
Authors: Thorn A. , Ritter E. , Ullmann F. , Pilz W. , Bischoff L. , Zschornack G.
Published: February 2012

We have carried out a series of measurements demonstrating the feasibility of using the Dresden electron beam ion source (EBIS)-A, a table-top sized, permanent magnet technology based electron beam ion source, as a charge breeder. Low charged gold ions from an AuGe liquid metal alloy ion source were injected into the EBIS and re-extracted as highly charged ions, thereby producing charge states as high as Au60 +. The setup, the charge breeding technique, breeding efficiencies as well as acceptance and emittance studies are presented.
Effects of adsorption and roughness upon the collision processes at the convertor surface of a plasma sputter negative ion source
Authors: Kenmotsu T. , Wada M.
Published: February 2012

Atomic collision processes associated with surface production of negative hydrogen ions (H−) by particle reflection at molybdenum surface immersed in hydrogen plasma have been investigated. To calculate sputtering yields of Cs, as well as energy spectra and angular distributions of reflected hydrogen atoms from molybdenum surface by H+ ion and Cs+ ion bombardments, a Monte Carlo simulation code ACAT (Atomic Collision in Amorphous Target) was run with the corresponding surface conditions. A fractal surface model has been developed and adopted to ACAT for evaluating the effect due to roughness of target material. The results obtained with ACAT have indicated that the retention of hydrogen atoms leads to the reduction in sputtering yields of Cs, and the surface roughness does largely affect the sputtering yields of Cs.
Beam current enhancement of microwave plasma ion source utilizing double-port rectangular cavity resonator
Authors: Lee Yuna , Park Yeong-Shin , Jo Jong-Gab , Yang J. J. , Hwang Y. S.
Published: February 2012

Microwave plasma ion source with rectangular cavity resonator has been examined to improve ion beam current by changing wave launcher type from single-port to double-port. The cavity resonators with double-port and single-port wave launchers are designed to get resonance effect at TE-103 mode and TE-102 mode, respectively. In order to confirm that the cavities are acting as resonator, the microwave power for breakdown is measured and compared with the E-field strength estimated from the HFSS (High Frequency Structure Simulator) simulation. Langmuir probe measurements show that double-port cavity enhances central density of plasma ion source by modifying non-uniform plasma density profile of the single-port cavity. Correspondingly, beam current from the plasma ion source utilizing the double-port resonator is measured to be higher than that utilizing single-port resonator. Moreover, the enhancement in plasma density and ion beam current utilizing the double-port resonator is more pronounced as higher microwave power applied to the plasma ion source. Therefore, the rectangular cavity resonator utilizing the double-port is expected to enhance the performance of plasma ion source in terms of ion beam extraction.
Studies for aluminum photoionization in hot cavity for the selective production of exotic species project
Authors: Scarpa D. , Vasquez J. , Tomaselli A. , Grassi D. , Biasetto L. , Cavazza A. , Corradetti S. , Manzolaro M. , Montano J. , Andrighetto A. , Prete G.
Published: February 2012

Selective production of exotic species (SPES) is an ISOL-based accelerator facility that will be built in the Legnaro INFN Laboratory (Italy), intended to provide an intense neutron-rich radioactive ion beams obtained by proton induced fission of an uranium carbide target. Beside this main target, a silicon carbide (SiC) target will the first to be used to deliver some p-rich beams. This target will validate also the functionality of the SPES facility with aluminum beam as result of hitting SiC target with protons. In the past off-line studies on laser photoionization of aluminum have performed in Pavia Spectroscopy Laboratory and in Laboratori Nazionali di Legnaro where, recently, a XeCl excimer laser was installed in order to test the laser ionization in the SPES hot cavity. Results are promising to justify further studies with this technique, aiming a better characterization of the SPES ion extraction capability under laser photoionization.
Magnetic properties of isotropic Sm–Fe–N magnets produced by compression shearing method
Authors: Saito Tetsuji , Kitazima Hiroshi
Published: February 2012

TbCu7-type Sm–Fe–N powder was consolidated into bulk materials at room temperature by the compression shearing method. The resultant Sm–Fe–N bulk magnets retained the original TbCu7-type structure without any appreciable decomposition. It was found that the TbCu7-type Sm–Fe–N bulk magnet is magnetically isotropic. The isotropic Sm–Fe–N bulk magnets exhibited a maximum energy product of 20 MGOe with a coercivity of 9.5 kOe.
Experimental evidence on the Altshuler-Aronov-Spivak interference of the topological surface states in the exfoliated Bi2Te3 nanoflakes
Authors: Li Zhaoguo , Qin Yuyuan , Song Fengqi , Wang Qiang-Hua , Wang Xuefeng , Wang Baigeng , Ding Haifeng , Van Haesondonck Chris , Wan Jianguo , Zhang Yuheng , Wang Guanghou
Published: February 2012

Here, we demonstrate the Altshuler-Aronov-Spivak (AAS) interference of the topological surface states on the exfoliated Bi2Te3 microflakes by a flux period of h/2e in their magnetoresistance oscillations and its weak field character. Both the oscillations with the period of h/e and h/2e are observed. The h/2e-period AAS oscillation gradually dominates with increasing the sample widths and the temperatures. This reveals the transition of the Dirac Fermions’ transport to the diffusive regime.
Coupling resistance between n-type surface accumulation layer and p-type bulk in InN:Mg thin films
Authors: Hurni Christophe A. , Choi Soojeong , Bierwagen Oliver , Speck James S.
Published: February 2012

Indium nitride is the least studied of the III-nitride though it has great potential due to its small bandgap of 0.65 eV and a small effective electron mass. InN:Mg was recently confirmed to be p-type. However, Hall measurements on InN:Mg still show n-type conductivity, even when InN:Mg is very thick. Some studies have suggested the possibility of a high coupling resistance between the surface electron accumulation and the bulk p-InN. In this study, we show through vertical and transmission-line model measurement that this coupling resistance is small and should not affect conductivity and Hall measurements.
In situ study of the growth properties of Ni-rare earth silicides for interlayer and alloy systems on Si(100)
Authors: Demeulemeester J. , Knaepen W. , Smeets D. , Schrauwen A. , Comrie C. M. , Barradas N. P. , Vieira A. , Detavernier C. , Temst K. , Vantomme A.
Published: February 2012

We report on the solid-phase reaction of thin Ni-rare earth films on a Si(100) substrate, for a variety of rare earth (RE) elements (Y, Gd, Dy, and Er). Both interlayer (Ni/RE/〈Si〉) and alloy (Ni-RE/〈Si〉) configurations were studied. The phase sequence during reaction was revealed using real-time x-ray diffraction whereas the elemental diffusion and growth kinetics were examined by real-time Rutherford backscattering spectrometry. All RE elements studied exert a similar influence on the solid phase reaction. Independent of the RE element or its initial distribution a ternary Ni2Si2RE phase forms, which ends up at the surface after NiSi growth. With respect to growth kinetics, the RE metal addition hampers the Ni diffusion process even for low concentrations of 2.5 at. %, resulting in the simultaneous growth of Ni-rich silicide and NiSi. Moreover, the formation of Ni2Si2RE during NiSi growth alters the Ni diffusion mechanism in the interlayer causing a sudden acceleration of the Ni silicide growth. Besides a significant effect on the silicide growth, we have found that adding 5 at. % Er (relative to Ni) lowers the NiSi Schottky barrier height on n-type Si(100) by approximately 0.1 eV for the interlayer and alloy configuration.
High density InAlAs/GaAlAs quantum dots for non-linear optics in microcavities
Authors: Kuszelewicz R. , Benoit J.-M. , Barbay S. , Lemaître A. , Patriarche G. , Meunier K. , Tierno A. , Ackemann T.
Published: February 2012

Structural and optical properties of InAlAs/GaAlAs quantum dots grown by molecular beam epitaxy are studied using transmission electron microscopy and temperature- and time-resolved photoluminescence. The control of the recombination lifetime (50 ps-1.25 ns) and of the dot density (5.10–8-2.1011 cm–3) strongly suggest that these material systems can find wide applications in opto-electronic devices as focusing non-linear dispersive materials as well as fast saturable absorbers.
Ground-state power quenching in two-state lasing quantum dot lasers
Authors: Gioannini Mariangela
Published: February 2012

The paper analyses theoretically the quenching of the ground state (GS) power observed in InAs/GaAs quantum dot lasers when emitting simultaneously from both ground state and excited state. The model, based on a set of rate equations for the electrons, holes, and photons, shows that the power quenching is caused by the different time scales of the electron and hole intra-level dynamic, as well as by the long transport time of the holes in the GaAs barrier. The results presented also evidence how the very different dynamics of electrons and holes have other important consequences on the laser behavior; we show for example that the electron and hole carrier densities of the states resonant with lasing modes are never clamped at the threshold value, and that the damping of relaxation oscillations is strongly influenced by the hole dynamics.
Simulation of the flow around an upstream transversely oscillating cylinder and a stationary cylinder in tandem
Authors: Bao Sheng , Chen Sheng , Liu Zhaohui , Li Jing , Wang Hanfeng , Zheng Chuguang
Published: February 2012

The flow around a transversely oscillating cylinder in tandem with a stationary cylinder was studied using the lattice Boltzmann method at Re = 100. The influences of spacing, oscillation frequency, and amplitude on the flow field were investigated in detail. It was found that, when the upstream cylinder oscillates with small amplitude, the flow pattern can be changed significantly from that of its fixed counterpart. First, the stagnation region ceases to exist. Second, the transition from the vortex suppression (VS) regime to the vortex formation (VF) regime appears earlier than when both cylinders are fixed. Moreover, the system has a wider frequency range of lock-in for both tandem cylinders in the VS regime, while the locked frequency range is slightly increased in the VF regime. The locked region of the tandem-paired cylinders is only slightly wider than that of a single oscillating cylinder. When the system is unlocked, different responses occur in the wakes of the two cylinders. Analysis of the power spectral of lift forces, lift phase portraits, and vorticity contours shows that the wake is regular under conditions of small spacing and small oscillating amplitude. However, with larger spacing, higher oscillating frequency or larger amplitude, the oscillation is powerful enough to dominate the flow field, inducing chaotic flow. The drag and lift forces of both oscillating and stationary cylinders are also discussed. The results reveal large differences between the case of one oscillating cylinder and that of two stationary tandem cylinders.
Efficient simultaneous reverse Monte Carlo modeling of pair-distribution functions and extended x-ray-absorption fine structure spectra of crystalline disordered materials
Authors: Németh Károly , Chapman Karena W. , Balasubramanian Mahalingam , Shyam Badri , Chupas Peter J. , Heald Steve M. , Newville Matt , Klingler Robert J. , Winans Randall E. , Almer Jonathan D. , Sandi Giselle , Srajer George
Published: February 2012

An efficient implementation of simultaneous reverse Monte Carlo (RMC) modeling of pair distribution function (PDF) and EXAFS spectra is reported. This implementation is an extension of the technique established by Krayzman et al. [J. Appl. Cryst. 42, 867 (2009)] in the sense that it enables simultaneous real-space fitting of x-ray PDF with accurate treatment of Q-dependence of the scattering cross-sections and EXAFS with multiple photoelectron scattering included. The extension also allows for atom swaps during EXAFS fits thereby enabling modeling the effects of chemical disorder, such as migrating atoms and vacancies. Significant acceleration of EXAFS computation is achieved via discretization of effective path lengths and subsequent reduction of operation counts. The validity and accuracy of the approach is illustrated on small atomic clusters and on 5500–9000 atom models of bcc-Fe and α-Fe2O3. The accuracy gains of combined simultaneous EXAFS and PDF fits are pointed out against PDF-only and EXAFS-only RMC fits. Our modeling approach may be widely used in PDF and EXAFS based investigations of disordered materials.
Measurement of semiconductor surface potential using the scanning electron microscope
Authors: Heath Jennifer T. , Jiang Chun-Sheng , Al-Jassim Mowafak M.
Published: February 2012

We calibrate the secondary electron signal from a standard scanning electron microscope to voltage, yielding an image of the surface or near-surface potential. Data on both atomically abrupt heterojunction GaInP/GaAs and diffused homojunction Si solar cell devices clearly show the expected variation in potential with position and applied bias, giving depletion widths and locating metallurgical junctions to an accuracy better than 10 nm. In some images, distortion near the p-n junction is observed, seemingly consistent with the effects of lateral electric fields (patch fields). Reducing the tube bias removes this distortion. This approach results in rapid and straightforward collection of near-surface potential data using a standard scanning electron microscope.
Structural and optical evaluation of InGaN/GaN multi-quantum wells on template consisting of in-plane alternately arranged relaxed InGaN and GaN
Authors: Okada Narihito , Yamada Yoichi , Tadatomo Kazuyuki
Published: February 2012

Templates consisting of in-plane alternately arranged relaxed InGaN and GaN were obtained by (11–22) facet growth and mass transport via metal-organic vapor phase epitaxy. InGaN/GaN multi-quantum wells (MQWs) were grown on the novel templates, and their optical and structural properties were investigated. From photoluminescence measurement, longer and shorter peak emission wavelengths were observed from the MQWs on the InGaN and GaN regions, respectively. The discrepancy of the peak emission wavelength for the MQWs on the alternately arranged relaxed InGaN and GaN was caused by the compositional-pulling effect, which contributed to the InN molar fraction and the thickness of the InGaN quantum well. The reduction of the quantum-confined Stark effect on the InGaN region of the template was confirmed by revealing the structural and optical properties of the MQWs.