bluuebunny/crossref_metadata_2025 huggingface dataset:
Breast-feeding andHelicobacter pyloriinfection: systematic review and meta-analysis
Authors: Carreira Helena , Bastos Ana , Peleteiro Bárbara , Lunet Nuno
Published: May 2014

Objective

To quantify the association between breast-feeding andHelicobacter pyloriinfection, among children and adolescents.

Design

We searched MEDLINETMand ScopusTMup to January 2013. Summary relative risk estimates (RR) and 95 % confidence intervals were computed through the DerSimonian and Laird method. Heterogeneity was quantified using theI2statistic.

Setting

Twenty-seven countries/regions; four low-income, thirteen middle-income and ten high-income countries/regions.

Subjects

Studies involving samples of children and adolescents, aged 0 to 19 years.

Results

We identified thirty-eight eligible studies, which is nearly twice the number included in a previous meta-analysis on this topic. Fifteen studies compared everv. never breast-fed subjects; the summary RR was 0·87 (95 % CI 0·57, 1·32;I2=34·4 %) in middle-income and 0·85 (95 % CI 0·54, 1·34;I2=79·1 %) in high-income settings. The effect of breast-feeding for ≥4–6 months was assessed in ten studies from middle-income (summary RR=0·66; 95 % CI 0·44, 0·98;I2=65·7 %) and two from high-income countries (summary RR=1·56; 95 % CI 0·57, 4·26;I2=68·3 %). Two studies assessed the effect of exclusive breast-feeding until 6 months (OR=0·91; 95 % CI 0·61, 1·34 and OR=1·71; 95 % CI 0·66, 4·47, respectively).

Conclusions

Our results suggest a protective effect of breast-feeding in economically less developed settings. However, further research is needed, with a finer assessment of the exposure to breast-feeding and careful control for confounding, before definite conclusions can be reached.
Appetite testing in HIV-infected African adults recovering from malnutrition and given antiretroviral therapy
Authors: Rehman Andrea M , Woodd Susannah , Chisenga Molly , Siame Joshua , Sampson Gemma , PrayGod George , Koethe John R , Kelly Paul , Filteau Suzanne
Published: May 2014

Objective

The Nutritional Support for Africans Starting Antiretroviral Therapy (NUSTART) trial was designed to determine whether nutritional support for malnourished HIV-infected adults starting antiretroviral therapy (ART) can improve early survival. Appetite is related to health outcomes in this population, but the optimal appetite metric for field use is uncertain. We evaluated two measures of appetite with the goal of improving understanding and treatment of malnutrition in HIV-infected adults.

Design

Longitudinal cohort study embedded in a clinical trial of vitamin and mineral-fortified, v. unfortified, lipid-based nutritional supplements.

Setting

HIV clinics in Mwanza, Tanzania and Lusaka, Zambia.

Subjects

Malnourished (BMI<18·5 kg/m2) HIV-infected adults starting ART.

Results

Appetite measurements, by short questionnaire and by weight of maize porridge consumed in a standardized test, were compared across time and correlated with changes in weight. Appetite questionnaire scores, from polychoric correlation, and porridge test results were normally distributed for Tanzanians (n 187) but clustered and unreliable for Zambians (n 297). Among Tanzanian patients, the appetite score increased rapidly from referral for ART, plateaued at the start of ART and then increased slowly during the 12-week follow-up. Change in appetite questionnaire score, but not porridge test, correlated with weight change in the corresponding two-week intervals (P=0·002) or over the whole study (P=0·05) but a point estimate of hunger did not predict weight change (P=0·4).

Conclusions

In Tanzania change in appetite score correlated with weight change, but single point measurements did not. Appetite increases several weeks after the start of ART, which may be an appropriate time for nutritional interventions for malnourished HIV-infected adults.
Microstructural Analysis of Au/TiO2-SBA-15 Nanocomposite
Authors: Gondo Takashi , Kaneko Kenji , Nishiyama Takeshi , Yamada Kazuhiro , Saghi Zineb , Barnard Jonathan S. , Midgley Paul A.
Published: May 2014

Properties of gold nanoparticles (AuNPs) are very different from bulk gold, in particular, highly dispersed AuNPs exhibit high catalytic activities on metal oxide supports. Catalytic activities of AuNPs are strongly dependent on: (i) size and morphology; (ii) synthesis methods; (iii) nature of the support; (iv) interaction between AuNPs and the support; and (v) oxidation state of AuNPs in the synthesized catalysts. A goal is to maintain the size and to prohibit aggregation of AuNPs, since aggregations deteriorate catalytic activities. Some strong interactions are therefore required between AuNPs and their supports to prevent the movement of AuNPs. SBA-15 is a promising material for the support of AuNPs since it has ordered two-dimensional hexagonal pore channels, uniform pore size ranging from 5 to 30 nm, narrow pore size distribution, thick amorphous walls ranging from 3 to 6 nm, and high surface area. In this study, SBA-15, TiO2-SBA-15 and TiO2-SBA-15-AuNP nanocomposites were synthesized by the sol-gel method and microstructural characterizations were carried out by both X-ray diffraction analysis and electron microscopy.
Olympic citizenship and the (un)specialness of the national vest: rethinking the links between sport and citizenship law
Authors: Kostakopoulou Dora , Schrauwen Annette
Published: May 2014

The increasing mobility of athletes prompts a reconsideration of the presumed connection between allegiance, identity and nationality. Olympic citizenship challenges traditional understandings of community membership by calling into question the privileged status of birthright citizenship and by bringing forth a different, more fluid and changeable notion of belonging. By juxtaposing the ‘old’ world of nations competing via ‘their’ athletes, as momentary representatives of the nation, for glory, medals, dominance and prestige, to the increasing mobility of sportspersons engaging in the pursuit of athletic excellence and creative self-expression, we argue that neither the enactment of tighter rules to prevent ‘citizenship shopping’ nor the transformation of the Olympic Games into athletes' Olympics are desirable reforms. Instead, we propose a participatory growth model which would allow athletes to choose the country they intend to represent following their enmeshment into a localised web of socio-economic interactions and a flexible framework of citizenship. This cannot but have wider implications for the Olympic Charter and for politics in general.
Institutional Design and Its Constraints: Explaining ASEAN's Role in the Temple of Preah Vihear Dispute
Authors: PHAN Hao Duy
Published: May 2014

This paper focuses on the role of ASEAN in maintaining peace and security in Southeast Asia. It uses the Temple of Preah Vihear dispute as a case-study to examine both ASEAN's successes and limitations in dealing with a crisis that threatened regional peace. The paper first examines ASEAN's initial response to the conflict and highlights a period of inaction that followed. It then traces ASEAN's renewed efforts to manage the conflict and assesses ASEAN's potential to resolve the dispute. The paper concludes that ASEAN did a remarkable job in facilitating negotiations and was instrumental in preventing the conflict from further escalation. It argues, however, that ASEAN's role remains limited: in particular, problems of institutional design reduce its effectiveness in managing conflicts and settling disputes. The paper concludes by making several suggestions to increase the effectiveness of the organization in maintaining regional peace and security.
Evaluation of sex differences in health-related quality of life outcomes associated with child abuse: Results from the Ontario Child Health Study
Authors: Tanaka M. , Afifi T. O. , Wathen C. N. , Boyle M. H. , MacMillan H. L.
Published: May 2014

Aims.

Despite the advances in child maltreatment research, there is still the need for comprehensive information about how abuse affects a broad range of categories of young adult functioning, and the extent to which these vary by sex. We examined the associations between child physical abuse (PA) and sexual abuse (SA) and six areas of functioning (mental health, physical health, life satisfaction, illegal substance use, alcohol problems and daily smoking).

Methods.

Data were obtained from the 1983 Ontario Child Health Study and follow-up in 2000/2001 (n = 1893). Multilevel regression estimated the adjusted associations for PA (with severity) and SA with each of the outcomes. Estimates with an entire sample were presented with sex-by-abuse interactions to examine sex differences and then presented separately by sex.

Results.

In the adjusted model, severe PA and SA were associated with impairment in mental health, and both forms of PA (severe and non-severe) and SA were associated with low life satisfaction. In addition, severe PA was associated with illegal substance use. Child abuse variables were not associated with poor physical health, alcohol problems or smoking. Although sex-stratified analyses revealed different patterns, there was no significant sex difference in the integrated sample.

Conclusions.

This is among the first community-based studies to show a strong association between child PA and SA and low life satisfaction in young adults. The abuse effects were similar for both sexes.
Autism spectrum disorders: weighing the risk of SSRI exposure in pregnancy
Authors: Ostuzzi G. , Barbui C.
Published: May 2014

A possible link between prenatal exposure to the selective serotonin reuptake inhibitors (SSRIs) and development of autism spectrum disorders (ASDs), previously suggested by two case-control studies, was not confirmed by a recent cohort study that followed for 5–10 years more than 600,000 births. However, this study failed to demonstrate that SSRI exposure during pregnancy is safe in terms of child development outcomes, as an increased risk of ASDs cannot be completely ruled out. In the present article, the main strengths and weaknesses of this study are briefly analysed, including a possibility of confounding by indication.
Eine Skala zur Erfassung der Ekelsensitivität bei Kindern (SEEK)
Authors: Schienle Anne , Heric Alexandra
Published: May 2014

Fragestellung: Ekelsensitivität beschreibt die Neigung, Ekelerlebnisse als negativ und unkontrollierbar zu bewerten. Bisher lag noch keine Skala zur Erfassung dieser Persönlichkeitseigenschaft bei Kindern vor. Methode: Zur Entwicklung (Hauptkomponentenanalyse) und Validierung der Skala diente eine Gesamtstichprobe von 375 Kindern im Alter zwischen 8 und 12 Jahren. Außerdem wurde ein Experiment zur Ekelregulation mittels kognitiver Neubewertung mit 102 Kindern durchgeführt. Ergebnisse: Die Skala, bestehend aus 7 Items besitzt eine gute interne Konsistenz (Cronbachs α = .86). Sie korreliert positiv mit der Neigung zu einem breiten Spektrum an Angststörungen, mit Ekelempfindlichkeit und negativ mit Emotionsbewusstheit. Eine Neubewertungsinstruktion zur Ekelreduktion konnte nur von wenig ekelsensitiven Kindern genutzt werden. Schlussfolgerung: Die entwickelte Skala ist reliabel, valide und ökonomisch. Weitere Analysen in klinischen Stichproben erscheinen vielversprechend.
Selbstregulation, Lageorientierung und Aufmerksamkeit bei erwachsenen ADHS-Patienten
Authors: Elsässer Marina , Newark Patricia Elizabeth , Stieglitz Rolf-Dieter
Published: May 2014

Einleitung: Es wurden Selbststeuerungskompetenzen und der Einfluss der Unaufmerksamkeit auf die Selbststeuerung bei Erwachsenen mit einer Aufmerksamkeits-Defizit/Hyperaktivitätsstörung (ADHS) untersucht. Methode: Erwachsene mit ADHS und gesunde Kontrollen füllten die Kurzversion des Selbststeuerungs-Inventars (SSI-K) und den Fragebogen zur Messung der Handlungskontrolle (HAKEMP 90) aus. Die Beeinträchtigungen der Aufmerksamkeit wurden bei den ADHS-Patienten mittels entsprechenden Subskalen aus dem ADHS-Selbstbeurteilungsbogen (ADHS-SB) und den Conners Adult ADHD Rating Scales (CAARS-R) erfasst. Mittels Kovarianzanalyse wurden Gruppenunterschiede in der Selbststeuerung zwischen ADHS-Patienten und Kontrollpersonen untersucht. Als nächster Schritt wurde der Zusammenhang zwischen Selbststeuerung und Unaufmerksamkeit bei ADHS-Patienten anhand einer einfachen linearen Regression überprüft. Ergebnisse und Schlussfolgerung: Erwachsene mit ADHS zeichnen sich durch eine geringe Selbstmotivation, eine stärkere Hemmung der willentlichen Prozesse in Form von Willenshemmung und Selbsthemmung, sowie einer Disposition zur Lageorientierung aus. Die Beeinträchtigung der Aufmerksamkeit bei der ADHS-Gruppe scheint die Willenshemmung zu begünstigen.
Oral pathobiont induces systemic inflammation and metabolic changes associated with alteration of gut microbiota
Authors: Arimatsu Kei , Yamada Hitomi , Miyazawa Haruna , Minagawa Takayoshi , Nakajima Mayuka , Ryder Mark I. , Gotoh Kazuyoshi , Motooka Daisuke , Nakamura Shota , Iida Tetsuya , Yamazaki Kazuhisa
Published: May 2014

Periodontitis has been implicated as a risk factor for metabolic disorders such as type 2 diabetes, atherosclerotic vascular diseases and non-alcoholic fatty liver disease. Although bacteremias from dental plaque and/or elevated circulating inflammatory cytokines emanating from the inflamed gingiva are suspected mechanisms linking periodontitis and these diseases, direct evidence is lacking. We hypothesize that disturbances of the gut microbiota by swallowed bacteria induce a metabolic endotoxemia leading metabolic disorders. To investigate this hypothesis, changes in the gut microbiota, insulin and glucose intolerance and levels of tissue inflammation were analysed in mice after oral administration of Porphyromonas gingivalis, a representative periodontopathogens. Pyrosequencing revealed that the population belonging to Bacteroidales was significantly elevated in P. gingivalis-administered mice which coincided with increases in insulin resistance and systemic inflammation. In P. gingivalis-administered mice blood endotoxin levels tended to be higher, whereas gene expression of tight junction proteins in the ileum was significantly decreased. These results provide a new paradigm for the interrelationship between periodontitis and systemic diseases.
Combined use of quantitative ED-EPMA, Raman microspectrometry, and ATR-FTIR imaging techniques for the analysis of individual particles
Authors: Jung Hae-Jin , Eom Hyo-Jin , Kang Hyun-Woo , Moreau Myriam , Sobanska Sophie , Ro Chul-Un
Published: May 2014

Quantitative ED-EPMA, RMS, and ATR-FTIR imaging techniques were used in combination for the analysis of the same individual particles for the first time.
Adhesion of lactoferrin and bone morphogenetic protein-2 to a rutile surface: dependence on the surface hydrophobicity
Authors: Sun Tianyang , Han Guang , Lindgren Matteus , Shen Zhijian , Laaksonen Aatto
Published: May 2014

Binding of the proteins human lactoferrin (LF) and human bone morphogenetic protein-2 (BMP2) to a hydroxylated TiO2 rutile (110) surface has been modeled using molecular dynamics (MD) simulations.
Iridium-catalysed borylation of sterically hindered C(sp3)–H bonds: remarkable rate acceleration by a catalytic amount of potassium tert-butoxide
Authors: Ohmura Toshimichi , Torigoe Takeru , Suginome Michinori
Published: May 2014

The C(sp3)–H bonds located at the methyl groups of an isopropyl group efficiently participate in iridium-catalysed C–H borylation.
Pd-catalyzed highly regio-, diastereo-, and enantioselective allylic alkylation of α-fluorophosphonates
Authors: Huang Ying , Zhang Qing-Song , Fang Ping , Chen Tie-Gen , Zhu Jun , Hou Xue-Long
Published: May 2014

α-Fluorophosphonates with two chiral centers have been synthesised in high diastereo- and enatioselectivites via Pd-catalyzed AAA of 2-fluoro-2-(diethoxyphosphoryl)acetate with monosubstituted allylic substrates. Their transformations were also demonstrated.
Directed functionalization of 1,2-dihydropyridines: stereoselective synthesis of 2,6-disubstituted piperidines
Authors: Pelletier Guillaume , Constantineau-Forget Léa , Charette André B.
Published: May 2014

A practical and highly stereoselective approach to access 2,6-disubstituted piperidines using an amidine auxiliary is reported. These were reduced to the saturated piperidine rings with high diastereoselectivity.
(2S,5R)-2-Methylaminomethyl-1-methyl-5-phenylpyrrolidine, a chiral diamine ligand for copper(ii)-catalysed Henry reactions with superb enantiocontrol
Authors: Scharnagel Dagmar , Prause Felix , Kaldun Johannes , Haase Robert G. , Breuning Matthias
Published: May 2014

Copper(ii)-complexes of a cis-2-aminomethyl-5-phenylpyrrolidine catalyse enantioselective Henry reactions with extraordinarily high stereocontrol.
Double axial chirality promoted asymmetric [2,3] Stevens rearrangement of N-cinnamyl l-alanine amide-derived ammonium ylides
Authors: Tayama Eiji , Naganuma Noriko , Iwamoto Hajime , Hasegawa Eietsu
Published: May 2014

The base-induced asymmetric [2,3] Stevens rearrangement of N-cinnamyl tetraalkylammonium ylides derived from l-alanine amides proceeds via a double axially chiral intermediate to afford the corresponding α-substituted alanine derivatives with high enantio- and diastereoselectivities.
Copper–organic frameworks assembled from in situ generated 5-(4-pyridyl)tetrazole building blocks: synthesis, structural features, topological analysis and catalytic oxidation of alcohols
Authors: Nasani Rajendar , Saha Manideepa , Mobin Shaikh M. , Martins Luísa M. D. R. S. , Pombeiro Armando J. L. , Kirillov Alexander M. , Mukhopadhyay Suman
Published: May 2014

Two copper based MOFs generated by cycloaddition of nitrile and azide show high activity towards oxidation of secondary alcohol.
Structural studies of copper(ii) complexes with 2-(2-aminoethyl)pyridine derived Schiff bases and application as precursors of thin organic–inorganic layers
Authors: Barwiolek Magdalena , Szlyk Edward , Berg Andrzej , Wojtczak Andrzej , Muziol Tadeusz , Jezierska Julia
Published: May 2014

Cu(ii) complexes with Schiff bases derived from 2-pyridin-2-ylethanamine were obtained and characterized by UV-Vis, fluorescence, and IR spectra.
Compact microfluidic device for rapid concentration of PET tracers
Authors: Tseng Wei-Yu , van Dam R. Michael
Published: May 2014

Convenient, rapid, and repeatable concentration of positron emission tomography (PET) tracers is achieved by microfluidic membrane distillation.
Antifungal amphiphilic aminoglycosides
Authors: Chang C.-W. T. , Takemoto J. Y.
Published: May 2014

A C8 alkyl chain at the O-4′′ position of kanamycin B transforms this aminoglycoside into an amphiphilic broad spectrum antifungal compound.
An ESIPT fluorescent probe sensitive to protein α-helix structures
Authors: Jiang Nan , Yang Chanli , Dong Xiongwei , Sun Xianglang , Zhang Dan , Liu Changlin
Published: May 2014

A benzazole derivative,1, was observed to undergo the excited-state intramolecular proton transfer (ESIPT) process with α-helical proteins. The cell images showed a difference in the staining of normal and cancerous prostate cells by1, which might be due to the different membrane protein levels.
Thiol–ene “click” reactions and recent applications in polymer and materials synthesis: a first update
Authors: Lowe Andrew B.
Published: May 2014

This contribution serves as an update to a previous review (Polym. Chem.2010,1, 17–36) and highlights recent applications of thiol–ene ‘click’ chemistry as an efficient tool for both polymer/materials synthesis as well as modification.
1,6-Naphthodione-based monomers and polymers
Authors: Zhang Haichang , Neudörfl Jörg-Martin , Tieke Bernd
Published: May 2014

Deeply coloured 1,6-naphthodifuranone-/1,6-naphthodipyrrolidone-based monomers and polymers are reported. The polymers exhibit broad and strong absorption in the visible region from 400 to 1000 nm, and low band gaps of 1.20–1.41 eV.
Probing structural and catalytic characteristics of galactose oxidase confined in nanoscale chemical environments
Authors: Ikemoto Hideki , Mossin Susanne L. , Ulstrup Jens , Chi Qijin
Published: May 2014

Synopsis: structural and catalytic features of a complex enzyme galactose oxidase confined in nanoscale chemical environments wereinvestigatedto show the catalytic efficiency of the enzyme depending on both the degree of space confinement and immobilization method.
Pyrolysis of azetidinone derivatives: a versatile route towards electron-rich alkenes, C-1 allylation and/or homologation of aldehydes
Authors: Al-Hamdan Nouf S. , Habib Osama M. , Ibrahim Yehia A. , Al-Awadi Nouria A. , El-Dusouqui Osman M. E.
Published: May 2014

Pyrolysis of β-lactams and β-thiolactams led essentially to stereoselective synthesis of the high energy electron-rich Z-alkenes.
NXO beta structure mimicry: an ultrashort turn/hairpin mimic that folds in water
Authors: Rabong Constantin , Schuster Christoph , Liptaj Tibor , Prónayová Nadežda , Delchev Vassil B. , Jordis Ulrich , Phopase Jaywant
Published: May 2014

An NXO building block derived tetrapeptide mimic emulates a natural proline-glycine β-turn/hairpin in polar media, including water at room temperature.
Fabrication of tunable Au SERS nanostructures by a versatile technique and application in detecting sodium cyclamate
Authors: Chen Jing , Shen Wen , Das Biswajit , Li Yiyan , Qin Gaowu
Published: May 2014

Three tunable Au SERS nanostructures (nanoparticles, nanowire–nanoparticle conjugations, nanofilms) were fabricated and used for sodium cyclamate detection.
In situ assessment of the contact angles of nanoparticles adsorbed at fluid interfaces by multiple angle of incidence ellipsometry
Authors: Stocco Antonio , Su Ge , Nobili Maurizio , In Martin , Wang Dayang
Published: May 2014

Contact angles and surface coverage of nanoparticles adsorbing at the fluid interface are assessed by ellipsometry. Results reveal the competition between wetting and colloidal interactions.
Self-assembly of an azobenzene-containing polymer prepared by a multi-component reaction: supramolecular nanospheres with photo-induced deformation properties
Authors: Wang Shuai , Zhang Ning , Ge Xiaopeng , Wan Yingbo , Li Xiaohong , Yan Li , Xia Yijun , Song Bo
Published: May 2014

A polymer with regulated azobenzene groups was synthesized by one-pot multi-component polymerization, and its self-assembly and photo induced-deformation properties are investigated.
Expansion planning for smart transmission grids using AC model and shunt compensation
Authors: Torres Santiago P. , Castro Carlos A.
Published: May 2014

It is widely recognised that large amounts of limited controlled renewable generation in smart grids bring major challenges. The increasing complexity to solve the transmission expansion planning (TEP) problem emphasises the need to face it with new models and more efficient optimisation techniques. In this research work, a load shedding formulation is proposed, extended for the AC model that takes into account shunt compensation additions to solve the TEP problem. This allows an integrated transmission line and shunt compensation planning that can be solved more efficiently. To solve the TEP problem, an improved version of local particle swarm optimisation is used. Solutions obtained in very well‐known test and realistic networks demonstrate that this implementation can be very interesting for practical use.
Magnetic-field-induced phase transitions in the quasi-one-dimensional organic conductor HMTSF–TCNQ
Authors: Murata K. , Fukumoto Y. , Yokogawa K. , Takaoka R. , Kang W. , Brooks J. S. , Graf D. , Yoshino H. , Sasaki T. , Kato R.
Published: May 2014

Motivated by an interest to see if the field-induced (FI) phase in the charge-density wave (CDW) system is similar to the field-induced-SDW (FISDW) in (TMTSF)2X, (TMTSF: tetramethyltetraselenafulvalene), we examined the magnetic-field-induced phases in a quasi-one-dimensional (Q1D) organic conductor HMTSF–TCNQ (hexamethylene- tetraselenafulvalene- tetracyanoquinodimethane) under a pressure of 1.1 GPa, where the CDW occurring at 30 K is suppressed. The work was carried out by measurements of angular-dependent magnetoresistance oscillations and exploratory work on the Hall effect. It turned out that the FI-phase, most likely a FICDW for B > 0.1 T, accompany a quantum Hall effect, and the FI-phase transitions are controlled by the field component along the least conducting axis. Above 10 T, the lowest Landau level of the small 2D Fermi pocket (due to incomplete nesting of Fermi surface) exceeds the Fermi level, reaching the quantum limit. Although there are many differences between the CDW (HMTSF–TCNQ) and SDW ((TMTSF)2X) systems, a similar scenario for field-induced phases seems to hold.
Magnetic quantum oscillations in the charge-density-wave state of the organic metals α-(BEDT-TTF)2MHg(SCN)4 with M = K and Tl
Authors: Kartsovnik M. V. , Zverev V. N. , Andres D. , Biberacher W. , Helm T. , Grigoriev P. D. , Ramazashvili R. , Kushch N. D. , Müller H.
Published: May 2014

The low-temperature charge-density-wave (CDW) state in the layered organic metals α-(BEDT-TTF)2MHg(SCN)4 has been studied by means of the Shubnikov–de Haas and de Haas–van Alphen effects. In addition to the dominant α-frequency, which is also observed in the normal state, both the magnetoresistance and magnetic torque possess a slowly oscillating component. These slow oscillations provide a firm evidence for the CDW-induced reconstruction of the original cylindrical Fermi surface. The α-oscillations of the interlayer magnetoresistance exhibit an anomalous phase inversion in the CDW state, whereas the de Haas–van Alphen signal maintains the normal phase. We argue that the anomaly may be attributed to the magnetic-breakdown origin of the α-oscillations in the CDW state. A theoretical model illustrating the possibility of a phase inversion in the oscillating interlayer conductivity in the presence of a spatially fluctuating magnetic breakdown gap is proposed.
Theoretical calculations and vibrational potential energy surface of 4-silaspiro(3,3)heptane
Authors: Ocola Esther J. , Medders Cross , Meinander Niklas , Laane Jaan
Published: May 2014

Theoretical computations have been carried out on 4-silaspiro(3,3)heptane (SSH) in order to calculate its molecular structure and conformational energies. The molecule has two puckered four-membered rings with dihedral angles of 34.2° and a tilt angle of 9.4° between the two rings. Energy calculations were carried out for different conformations of SSH. These results allowed the generation of a two-dimensional ring-puckering potential energy surface (PES) of the form V = a(x14 + x24) – b(x12 + x22) + cx12x22, where x1 and x2 are the ring-puckering coordinates for the two rings. The presence of sufficiently high potential energy barriers prevents the molecule from undergoing pseudorotation. The quantum states, wave functions, and predicted spectra resulting from the PESs were calculated.
The cavity electromagnetic field within the polarizable continuum model of solvation
Authors: Pipolo Silvio , Corni Stefano , Cammi Roberto
Published: May 2014

Cavity field effects can be defined as the consequences of the solvent polarization induced by the probing electromagnetic field upon spectroscopies of molecules in solution, and enter in the definitions of solute response properties. The polarizable continuum model of solvation (PCM) has been extended in the past years to address the cavity-field issue through the definition of an effective dipole moment that couples to the external electromagnetic field. We present here a rigorous derivation of such cavity-field treatment within the PCM starting from the general radiation-matter Hamiltonian within inhomogeneous dielectrics and recasting the interaction term to a dipolar form within the long wavelength approximation. To this aim we generalize the Göppert-Mayer and Power-Zienau-Woolley gauge transformations, usually applied in vacuo, to the case of a cavity vector potential. Our derivation also allows extending the cavity-field correction in the long-wavelength limit to the velocity gauge through the definition of an effective linear momentum operator. Furthermore, this work sets the basis for the general PCM treatment of the electromagnetic cavity field, capable to describe the radiation-matter interaction in dielectric media beyond the long-wavelength limit, providing also a tool to investigate spectroscopic properties of more complex systems such as molecules close to large nanoparticles.
Compact cold stage for micro-computerized tomography imaging of chilled or frozen samples
Authors: Hullar Ted , Paige David F. , Rowland Douglas J. , Anastasio Cort
Published: May 2014

High resolution X-ray microCT (computerized tomography) can be used to image a variety of objects, including temperature-sensitive materials. In cases where the sample must be chilled or frozen to maintain sample integrity, either the microCT machine itself must be placed in a refrigerated chamber, or a relatively expensive commercial cold stage must be purchased. We describe here the design and construction of a low-cost custom cold stage suitable for use in a microCT imaging system. Our device uses a boron nitride sample holder, two-stage Peltier cooler, fan-cooled heat sink, and electronic controller to maintain sample temperatures as low as −25 °C ± 0.2 °C for the duration of a tomography acquisition. The design does not require modification to the microCT machine, and is easily installed and removed. Our custom cold stage represents a cost-effective solution for refrigerating CT samples for imaging, and is especially useful for shared equipment or machines unsuitable for cold room use.
ARPES experiment in fermiology of quasi-2D metals (Review Article)
Authors: Kordyuk A. A.
Published: May 2014

Angle-resolved photoemission spectroscopy (ARPES) enables direct observation of the Fermi surface and underlying electronic structure of crystals, which are the basic concepts necessary to describe all the electronic properties of solids and to reveal the nature of key electronic interactions involved. ARPES proved to be the most efficient for studies of quasi-2D metals, to which the most challenging and hence exciting compounds belong. This stimulated tremendously the development of ARPES in the recent years. The aim of this paper is to introduce the reader to the state-of-the-art ARPES experiment and to review the results of its application to such highly topical problems in solid state physics as high temperature superconductivity in cuprates and iron-based superconductors and electronic ordering in the transition metal dichalcogenides and manganites.
Features of the electronic structure of the layered superconductors RNi2B2C, RFe4Al8, and FeSe
Authors: Logosha A. V. , Grechnev G. E. , Lyogenkaya A. A. , Panfilov A. S.
Published: May 2014

The electronic structure and a number of thermodynamic characteristics of layered magnetic superconductors in the systems RNi2B2C, RFe4Al8, and FeSe in the normal state are calculated from first principles. The electronic states and the interactions responsible for the electronic, structural, and magnetic properties of these systems are analyzed.
Band gap narrowing in BaTiO3 nanoparticles facilitated by multiple mechanisms
Authors: Ramakanth S. , James Raju K. C.
Published: May 2014

In the present work, BaTiO3 nanoparticles of four different size ranges were prepared by sol-gel method. The optical band gap of these particles at some size ranges has come down to 2.53 eV from 3.2 eV, resulting in substantial increase in optical absorption by these ferroelectric nanoparticles making them potential candidates for light energy harvesting. XRD results show the presence of higher compressive strain in 23 nm and 54 nm size particles, they exhibit a higher band gap narrowing, whereas tensile strain is observed in 31 nm and 34 nm particles, and they do not show the marginal band gap narrowing. The 23 nm and 54 nm particles also show a coupling of free carriers to phonons by increasing the intensity of LO phonon mode at 715 cm−1. The higher surface charge density is expected in case of enhanced surface optical Raman modes (638 cm−1) contained in 31 and 34 nm size particles. In addition to this, the red shift in an LO mode Raman spectral line at 305 cm−1 with decrease in particle size depicts the presence of phonon confinement in it. The enhanced optical absorption in 23 nm and 54 nm size particles with a narrowed band gap of 3 eV and 2.53 eV is due to exchange correlation interactions between the carriers present in these particles. In 31 nm and 34 nm range particles, the absorption got bleached exhibiting increased band gaps of 3.08 eV and 3.2 eV, respectively. It is due to filling up of conduction band resulting from weakening of exchange correlation interactions between the charge carriers. Hence, it is concluded that the band gap narrowing in the nanoparticles of average size 23 nm/54 nm is a consequence of multiple effects like strain, electron-phonon interaction, and exchange correlation interactions between the carriers which is subdued in some other size ranges like 31 nm/34 nm.
Photoelectron spectroscopy of boron aluminum hydride cluster anions
Authors: Wang Haopeng , Zhang Xinxing , Ko Yeon Jae , Gantefoer Gerd , Bowen Kit H. , Li Xiang , Kiran Boggavarapu , Kandalam Anil K.
Published: May 2014

Boron aluminum hydride clusters are studied through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations. Boron aluminum hydride cluster anions, BxAlyHz−, were generated in a pulsed arc cluster ionization source and identified by time-of-flight mass spectrometry. After mass selection, their photoelectron spectra were measured by a magnetic bottle-type electron energy analyzer. The resultant photoelectron spectra as well as calculations on a selected series of stoichiometries reveal significant geometrical changes upon substitution of aluminum atoms by boron atoms.
Electrostatic interaction between colloidal particles trapped at an electrolyte interface
Authors: Majee Arghya , Bier Markus , Dietrich S.
Published: May 2014

The electrostatic interaction between colloidal particles trapped at the interface between two immiscible electrolyte solutions is studied in the limit of small inter-particle distances. Within an appropriate model analytic expressions for the electrostatic potential as well as for the surface and line interaction energies are obtained. They demonstrate that the widely used superposition approximation, which is commonly applied to large distances between the colloidal particles, fails qualitatively at small distances, and is quantitatively unreliable even at large distances. Our results contribute to an improved description of the interaction between colloidal particles trapped at fluid interfaces.
Excitations and benchmark ensemble density functional theory for two electrons
Authors: Pribram-Jones Aurora , Yang Zeng-hui , Trail John R. , Burke Kieron , Needs Richard J. , Ullrich Carsten A.
Published: May 2014

A new method for extracting ensemble Kohn-Sham potentials from accurate excited state densities is applied to a variety of two-electron systems, exploring the behavior of exact ensemble density functional theory. The issue of separating the Hartree energy and the choice of degenerate eigenstates is explored. A new approximation, spin eigenstate Hartree-exchange, is derived. Exact conditions that are proven include the signs of the correlation energy components and the asymptotic behavior of the potential for small weights of the excited states. Many energy components are given as a function of the weights for two electrons in a one-dimensional flat box, in a box with a large barrier to create charge transfer excitations, in a three-dimensional harmonic well (Hooke's atom), and for the He atom singlet-triplet ensemble, singlet-triplet-singlet ensemble, and triplet bi-ensemble.
Impact of cation-based localized electronic states on the conduction and valence band structure of Al1−xInxN alloys
Authors: Schulz S. , Caro M. A. , O'Reilly E. P.
Published: May 2014

We demonstrate that cation-related localized states strongly perturb the band structure of Al1−xInxN leading to a strong band gap bowing at low In content. Our first-principles calculations show that In-related localized states are formed both in the conduction and the valence band in Al1−xInxN for low In composition, x, and that these localized states dominate the evolution of the band structure with increasing x. Therefore, the commonly used assumption of a single composition-independent bowing parameter breaks down when describing the evolution both of the conduction and of the valence band edge in Al1−xInxN.
Comment on “Laser ablation of Cu and plume expansion into 1 atm ambient gas” [J. Appl. Phys. 97, 063305 (2005)]
Authors: Autrique D. , Alexiades V.
Published: May 2014

A hydrodynamic model used for the study of ns-laser ablation in an ambient environment [Z. Chen and A. Bogaerts, J. Appl. Phys. 97, 063305 (2005)] was investigated and compared with an in-house developed code. After a detailed analysis of the source code and the underlying theoretical framework, significant flaws were detected in the model. It was found that the respective model as well as the ones presented in some earlier and later manuscripts is not able to simulate the ablation process, i.e., target heating, material removal, breakdown, plasma formation, and plume expansion, self-consistently. The present findings indicate that their use should be discontinued when modeling the overall ablation process. Based on existing models in the literature, alternative theoretical pathways are proposed to facilitate future computational studies of ns-laser ablation.
The PtAl− and PtAl2− anions: Theoretical and photoelectron spectroscopic characterization
Authors: Zhang Xinxing , Ganteför Gerd , Bowen Kit H. , Alexandrova Anastassia N.
Published: May 2014

We report a joint photoelectron spectroscopic and theoretical study of the PtAl− and PtAl2− anions. The ground state structures and electronic configurations of these species were identified to be C∞v, 1Σ+ for PtAl−, and C2v, 2B1 for PtAl2−. Structured anion photoelectron spectra of these clusters were recorded and interpreted using ab initio calculations. Good agreement between theory and experiment was found. All experimental features were successfully assigned to one-electron transitions from the ground state of the anions to the ground or excited states of the corresponding neutral species.
Effect of growth temperature on ballistic electron transport through the Au/Si(001) interface
Authors: Eckes M. W. , Friend B. E. , Stollenwerk A. J.
Published: May 2014

Ballistic electron emission spectroscopy was used to investigate electron transport through Au/Si(001) Schottky diodes grown at 35 °C and 22 °C. Aside from a decreased Schottky height, this small increase in temperature introduced an energy dependent scattering component, which was absent in the samples grown at 22 °C. These differences may be attributed to the increased amount of Au-Si intermixing at the interface. Despite the non-epitaxial nature of the growth technique, strong evidence was found in both sets of samples that indicated the presence of a forward-focused current subject to some degree of parallel momentum conservation at the interface. This evidence was present in all samples grown at 35 °C, but was only observed in those samples grown at 22 °C when the Au films were 10 nm or thicker. This sensitivity to growth temperature could account for discrepancies in previous studies on Au/Si(001).
Note: A novel method to measure the deformation of diamond anvils under high pressure
Authors: Liu Shenggang , Li Zeren , Jing Qiuming , Zhang Yi , Ma Heli , Tao Tianjiong , Wang Xiang , Bi Yan , Weng Jidong , Xu Ji-an
Published: May 2014

A novel and simple method based on optical-fiber frequency domain interferometer to measure the deformation of diamond anvils under high pressure is presented. The working principle and application examples are given in this paper. The deformation of diamond anvils is obtained up to 37.7 GPa, our results verify that the deformation has an obvious difference between uploading and downloading at a given pressure, the maximum difference is up to 4.5 μm at 18.8 GPa, and the cupping effect is observed directly.
Predicting the influence of long-range molecular interactions on macroscopic-scale diffusion by homogenization of the Smoluchowski equation
Authors: Kekenes-Huskey P. M. , Gillette A. K. , McCammon J. A.
Published: May 2014

The macroscopic diffusion constant for a charged diffuser is in part dependent on (1) the volume excluded by solute “obstacles” and (2) long-range interactions between those obstacles and the diffuser. Increasing excluded volume reduces transport of the diffuser, while long-range interactions can either increase or decrease diffusivity, depending on the nature of the potential. We previously demonstrated [P. M. Kekenes-Huskey et al., Biophys. J. 105, 2130 (2013)] using homogenization theory that the configuration of molecular-scale obstacles can both hinder diffusion and induce diffusional anisotropy for small ions. As the density of molecular obstacles increases, van der Waals (vdW) and electrostatic interactions between obstacle and a diffuser become significant and can strongly influence the latter's diffusivity, which was neglected in our original model. Here, we extend this methodology to include a fixed (time-independent) potential of mean force, through homogenization of the Smoluchowski equation. We consider the diffusion of ions in crowded, hydrophilic environments at physiological ionic strengths and find that electrostatic and vdW interactions can enhance or depress effective diffusion rates for attractive or repulsive forces, respectively. Additionally, we show that the observed diffusion rate may be reduced independent of non-specific electrostatic and vdW interactions by treating obstacles that exhibit specific binding interactions as “buffers” that absorb free diffusers. Finally, we demonstrate that effective diffusion rates are sensitive to distribution of surface charge on a globular protein, Troponin C, suggesting that the use of molecular structures with atomistic-scale resolution can account for electrostatic influences on substrate transport. This approach offers new insight into the influence of molecular-scale, long-range interactions on transport of charged species, particularly for diffusion-influenced signaling events occurring in crowded cellular environments.
Physical origins of weak H2 binding on carbon nanostructures: Insight from ab initio studies of chemically functionalized graphene nanoribbons
Authors: Ulman Kanchan , Bhaumik Debarati , Wood Brandon C. , Narasimhan Shobhana
Published: May 2014

We have performed ab initio density functional theory calculations, incorporating London dispersion corrections, to study the absorption of molecular hydrogen on zigzag graphene nanoribbons whose edges have been functionalized by OH, NH2, COOH, NO2, or H2PO3. We find that hydrogen molecules always preferentially bind at or near the functionalized edge, and display induced dipole moments. Binding is generally enhanced by the presence of polar functional groups. The largest gains are observed for groups with oxygen lone pairs that can facilitate local charge reorganization, with the biggest single enhancement in adsorption energy found for “strong functionalization” by H2PO3 (115 meV/H2 versus 52 meV/H2 on bare graphene). We show that for binding on the “outer edge” near the functional group, the presence of the group can introduce appreciable contributions from Debye interactions and higher-order multipole electrostatic terms, in addition to the dominant London dispersion interactions. For those functional groups that contain the OH moiety, the adsorption energy is linearly proportional to the number of lone pairs on oxygen atoms. Mixed functionalization with two different functional groups on a graphene edge can also have a synergistic effect, particularly when electron-donating and electron-withdrawing groups are combined. For binding on the “inner edge” somewhat farther from the functional group, most of the binding again arises from London interactions; however, there is also significant charge redistribution in the π manifold, which directly reflects the electron donating or withdrawing capacity of the functional group. Our results offer insight into the specific origins of weak binding of gas molecules on graphene, and suggest that edge functionalization could perhaps be used in combination with other strategies to increase the uptake of hydrogen in graphene. They also have relevance for the storage of hydrogen in porous carbon materials, such as activated carbons.
Mode conversion and absorption of fast waves at high ion cyclotron harmonics in inhomogeneous magnetic fields
Authors: Cho Suwon , Kwak Jong-Gu
Published: May 2014

The propagation and absorption of high harmonic fast waves is of interest for non-inductive current drives in fusion experiments. The fast wave can be coupled with the ion Bernstein wave that propagates in the high magnetic field side of an ion cyclotron harmonic resonance layer. This coupling and the absorption are analyzed using the hot plasma dispersion relation and a wave equation that was converted from an approximate dispersion relation for the case where λi=k⊥2ρi2/2≳1 (where k⊥ is the perpendicular wave number and ρi is the ion Larmor radius). It is found that both reflection and conversion may occur near the harmonic resonance layer but that they decrease rapidly, giving rise to a sharp increase in the absorption as the parallel wave number increases.
Band alignments of different buffer layers (CdS, Zn(O,S), and In2S3) on Cu2ZnSnS4
Authors: Yan Chang , Liu Fangyang , Song Ning , Ng Boon K. , Stride John A. , Tadich Anton , Hao Xiaojing
Published: May 2014

The heterojunctions of different n-type buffers, i.e., CdS, Zn(O,S), and In2S3 on p-type Cu2ZnSnS4 (CZTS) were investigated using X-ray Photoelectron Spectroscopy (XPS) and Near Edge X-ray Absorption Fine Structure (NEXAFS) Measurements. The band alignment of the heterojunctions formed between CZTS and the buffer materials was carefully measured. The XPS data were used to determine the Valence Band Offsets (VBO) of different buffer/CZTS heterojunctions. The Conduction Band Offset (CBO) was calculated indirectly by XPS data and directly measured by NEXAFS characterization. The CBO of the CdS/CZTS heterojunction was found to be cliff-like with CBOXPS = −0.24 ± 0.10 eV and CBONEXAFS = −0.18 ± 0.10 eV, whereas those of Zn(O,S) and In2S3 were found to be spike-like with CBOXPS = 0.92 ± 0.10 eV and CBONEXAFS = 0.87 ± 0.10 eV for Zn(O,S)/CZTS and CBOXPS = 0.41 ± 0.10 eV for In2S3/CZTS, respectively. The CZTS photovoltaic device using the spike-like In2S3 buffer was found to yield a higher open circuit voltage (Voc) than that using the cliff-like CdS buffer. However, the CBO of In2S3/CZTS is slightly higher than the optimum level and thus acts to block the flow of light-generated electrons, significantly reducing the short circuit current (Jsc) and Fill Factor (FF) and thereby limiting the efficiency. Instead, the use of a hybrid buffer for optimization of band alignment is proposed.