bluuebunny/crossref_metadata_2025 huggingface dataset:
Clinical and adipocytokine changes after bariatric surgery in morbidly obese women
Authors: Auguet Teresa , Terra Ximena , Hernández Mercè , Sabench Fàtima , Porras Jose Antonio , Orellana‐Gavaldà Josep Maria , Llutart Jordi , Guiu‐Jurado Esther , Berlanga Alba , Martinez Salomé , Aguilar Carmen , Castillo Daniel Del , Richart Cristóbal
Published: March 2013

Objective

Recent studies report the effect of bariatric surgery on glycaemia control and prevention of type‐2‐diabetes in obese patients. This study is about the pathophysiological mechanisms associated to these changes.

Design and Methods

Circulating levels of receptors of tumor necrosis factor (TNF‐RI, TNF‐RII), visfatin, high molecular weight (HMW) adiponectin, and C reactive protein (CRP) in 30 morbidly obese women (body mass index, BMI>40 kg/m2) and 60 normal‐weight controls (BMI>25 kg/m2) were analyzed. Morbidly obese were studied at three time‐points: before surgery (baseline), and 6 and 12 months after.

Results

After surgery, the levels of TNF‐RI, TNF‐RII, visfatin, and CRP were significantly lower than its baseline levels, whereas HMW adiponectin was higher. Fasting glucose, insulin, and homeostasis model assessment of insulin resistance (HOMA2‐IR) levels were markedly lower postoperatively. High density lipoproteins (HDL) moderately increased, and triglyceride levels had sharply decreased. The study of the predictive value of variables indicated that preoperative levels of TNF‐RI and visfatin correlated positively with levels of glucose, insulin, glycosylated hemoglobin A1c, and HOMA2‐IR postoperatively, whereas adiponectin levels correlated negatively. Baseline CRP levels negatively linked to HDL and TNF‐RII positively to triglyceride.

Conclusions

The preoperative profile with high levels of proinflammatory adipocytokines is linked to smaller improvements in glucose homeostasis and lipid factors. The use of a range of biomarkers may predict the level of metabolic changes following bariatric surgery.
Body‐mass index and mortality risk in US Blacks compared to Whites
Authors: Jackson Chandra L. , Wang Nae‐Yuh , Yeh Hsin‐Chieh , Szklo Moyses , Dray‐Spira Rosemary , Brancati Frederick L.
Published: March 2013

Objective

To compare body‐mass index (BMI)‐related mortality risk in US Blacks vs. Whites as the relationship appears to differ across race/ethnicity groups.

Methods

Cross‐sectional surveys of nationally representative samples of 11,934 Blacks and 59,741 Whites aged 35‐75 in the National Health Interview Survey from 1997 to 2002 with no history of cardiovascular disease (CVD) or cancer were pooled. Mortality follow‐up was available through 2006. BMI was calculated from self‐reported height and weight. We used adjusted Cox regression analysis to adjust for potential confounders.

Results

Over 9 years of follow‐up, there were 4303 deaths (1205 among never smokers). Age‐adjusted mortality rates were higher in Blacks compared to Whites at BMI < 25 kg/m2 and showed no increase at higher levels of BMI. In men, adjusted hazard ratios for all‐cause death rose in a similar fashion across upper BMI quintiles in Blacks and Whites; in women, however, BMI was positively associated with mortality risk in Whites, but inversely associated in Blacks (P interaction = 0.01). Racial disparities were amplified in subsidiary analyses that introduced a 12‐month lag for mortality or focused on CVD mortality.

Conclusions

The relationship of elevated BMI to mortality appeared weaker in US Blacks than in Whites, especially among women.
The cost‐effectiveness of a successful community‐based obesity prevention program: The be active eat well program
Authors: Moodie Marjory L. , Herbert Jessica K. , de Silva‐Sanigorski Andrea M. , Mavoa Helen M. , Keating Catherine L. , Carter Robert C , Waters Elizabeth , Gibbs Lisa , Swinburn Boyd A.
Published: March 2013

Objective

To examine the cost‐effectiveness of Be Active Eat Well (BAEW), a large, multifaceted, community‐based capacity‐building demonstration program that promoted healthy eating and physical activity for Australian children aged 4‐12 years between 2003 and 2006.

Design and Methods

A quasi‐experimental, longitudinal design was used with anthropometric data collected at baseline (1001 children—intervention; 1183—comparator) and follow‐up. A societal perspective was employed, with intervention resource use measured retrospectively based on process evaluation reports, school newsletters, reports, and key stakeholder interviews, and valued in 2006 Australian dollars (AUD). Outcomes were measured as Body Mass Index (BMI) units saved and Disability Adjusted Life Years (DALYs) averted over the predicted cohort lifetime, and reported as incremental cost‐effectiveness ratios (with 95% uncertainty intervals).

Results

The intervention cost AUD0.34M ($0.31M; $0.38M) annually, and resulted in savings of 547 (−104; 1209) BMI units and 10.2 (−0.19; 21.6) DALYs. This translated to modest cost offsets of AUD27 311 (−$1803; $58 242) and a net cost per DALY saved of AUD29 798 (dominated; $0.26M).

Conclusions

BAEW was affordable and cost‐effective, and generated substantial spin‐offs in terms of activity beyond funding levels. Elements fundamental to its success and any potential cost efficiencies associated with scaling‐up now require identification.
Influence of morphology on positive temperature coefficient effect for conductive polymer composites with carbon black dispersed at interface
Authors: Lu Chang , Cao Qing‐Qing , Huang Xin‐Hui , Hu Xiao‐Ning , He Yu‐Xin , Liu Cui‐Yun , Zhang Yu‐Qing
Published: March 2013

Selective localization of carbon black (CB) at the interface of polymer blends was achieved by the method that EBA‐g‐MAH was first reacted with CB, and then blended with poly(ethylene‐co‐butyl acrylate)/nylon6 (EBA/PA6). In CB‐filled EBA/PA6 blends, EBA and PA6 phases formed cocontinuous morphology and CB was localized in PA6 phase. The percolation threshold was 5 wt%. A single PTC (positive temperature coefficient) effect was observed in this composite. The appearance of PTC effect was originated from the thermal expansion of EBA phase. In the EBA‐g‐MAH filled EBA/PA6 blends, TEM results showed that CB particles were induced by EBA‐g‐MAH to localize at the interface, resulting that the percolation threshold was much lower than that of EBA/PA6/CB. Influence of morphology on PTC effect of EBA/PA6/EBA‐g‐MAH/CB composites was studied. In the composites with sea‐island morphology, the conductive network was fabricated by dispersed phase and CB at the interface. Thermal expansion of matrix interrupted the contact of dispersed phases and conductive network formed by CB particles at the interface, resulting in the double PTC effect. The composites with co‐continuous morphology exhibited single PTC effect due to the fact that conductive network was only fabricated by CB localized at the interface. POLYM. ENG. SCI., 53:2640–2649, 2013. © 2013 Society of Plastics Engineers
Preparation and dynamic properties of an anisotropic natural rubber film as viewed by electron spin resonance–spin probe method
Authors: Valić Srećko , Bonato Jasminka , Andreis Mladen , Klepac Damir , Didović Mirna Petković
Published: March 2013

Natural rubber (NR) films with the thickness of about 1 mm were prepared by removing the liquid phase from NR latex, which was previously irradiated. The primary radiation dose varied from 0 kGy (for unirradiated NR) to 200 kGy. Dry NR films were uniaxially stretched, and the degree of deformation, defined as λ = l/l0 (l0 and l being the lengths of relaxed and uniaxially deformed sample, respectively), was varied from λ = 1.0 (relaxed state) to λ = 2.7. Samples were then irradiated with secondary dose, which was chosen to be 100 or 200 kGy. NR films were characterized by differential scanning calorimetry and electron spin resonance–spin probe method. In addition, samples were exposed to accelerated thermal aging, and changes in molecular dynamics and structure were obtained. It has been shown that the application of deformation during the cross‐linking leads to the restriction in segmental mobility for the lower secondary dose, whereas for the higher secondary dose, larger values of λ induce an opposite effect originating from the structural changes. Thermally aged samples show higher amount of the gel phase and consequently higher fraction of slow motional chain segments. POLYM. ENG. SCI., 53:2284–2291, 2013. © 2013 Society of Plastics Engineers
In situ emulsion polymerization and characterization of poly(butyl acrylate‐co‐methyl methacrylate)/silica nanosystems
Authors: Buhin Zrinka , Blagojević Sanja Lučić , Leskovac Mirela
Published: March 2013

In this study influence of monomer ratio, butyl acrylate (BA), and methyl methacrylate (MMA) as well as silica nanofiller morphology (pyrogenic and colloidal) and concentration on the emulsion particle size distribution and properties of polyacrylate film (PA) synthesized by in situ emulsion polymerization were investigated. The ratios of the monomers BA/MMA were 100/0, 70/30, 50/50, 30/70, 0/100 and the filler concentration 0–10.0 mass%. PA nanocomposite films were characterized by using thermogravimetric analysis, differential scanning calorimetry, and tensile test. Research has shown that monomer ratio has significant influence on glass transition temperature (Tg). The addition of both types of silica filler, pyrogenic and colloidal, has no effect on Tg. Thermogravimetric analysis showed that systems with higher BA fraction have better thermal stability than systems with higher MMA fraction. Addition of the both type of silica nanofiller enhanced thermal stability of PAs, however, systems with colloidal silica are more stable. Pyrogenic silica and higher amounts of colloidal silica nanofiller increased PA emulsion particle size up to several micrometers. Addition of higher amounts of colloidal silica improved mechanical properties compared to the neat PA matrix. POLYM. ENG. SCI., 53:2292–2298, 2013. © 2013 Society of Plastics Engineers
Membrane phospholipid bilayer as a determinant of monoacylglycerol lipase kinetic profile and conformational repertoire
Authors: Nasr Mahmoud L. , Shi Xiaomeng , Bowman Anna L. , Johnson Michael , Zvonok Nikolai , Janero David R. , Vemuri V. Kiran , Wales Thomas E. , Engen John R. , Makriyannis Alexandros
Published: March 2013

The membrane‐associated serine hydrolase, monoacylglycerol lipase (MGL), is a well‐recognized therapeutic target that regulates endocannabinoid signaling. Crystallographic studies, while providing structural information about static MGL states, offer no direct experimental insight into the impact of MGL's membrane association upon its structure–function landscape. We report application of phospholipid bilayer nanodiscs as biomembrane models with which to evaluate the effect of a membrane system on the catalytic properties and conformational dynamics of human MGL (hMGL). Anionic and charge‐neutral phospholipid bilayer nanodiscs enhanced hMGL's kinetic properties [apparent maximum velocity (Vmax) and substrate affinity (Km)]. Hydrogen exchange mass spectrometry (HX MS) was used as a conformational analysis method to profile experimentally the extent of hMGL–nanodisc interaction and its impact upon hMGL structure. We provide evidence that significant regions of hMGL lid‐domain helix α4 and neighboring helix α6 interact with the nanodisc phospholipid bilayer, anchoring hMGL in a more open conformation to facilitate ligand access to the enzyme's substrate‐binding channel. Covalent modification of membrane‐associated hMGL by the irreversible carbamate inhibitor, AM6580, shielded the active site region, but did not increase solvent exposure of the lid domain, suggesting that the inactive, carbamylated enzyme remains intact and membrane associated. Molecular dynamics simulations generated conformational models congruent with the open, membrane‐associated topology of active and inhibited, covalently‐modified hMGL. Our data indicate that hMGL interaction with a phospholipid membrane bilayer induces regional changes in the enzyme's conformation that favor its recruiting lipophilic substrate/inhibitor from membrane stores to the active site via the lid, resulting in enhanced hMGL catalytic activity and substrate affinity.
Structure‐based network analysis of an evolved G protein‐coupled receptor homodimer interface
Authors: Nichols Sara E. , Hernández Carlos X. , Wang Yi , McCammon James Andrew
Published: March 2013

Crystallographic structures and experimental assays of human CXC chemokine receptor type 4 (CXCR4) provide strong evidence for the capacity to homodimerize, potentially as a means of allosteric regulation. Even so, how this homodimer forms and its biological significance has yet to be fully characterized. By applying principles from network analysis, sequence‐based approaches such as statistical coupling analysis to determine coevolutionary residues, can be used in conjunction with molecular dynamics simulations to identify residues relevant to dimerization. Here, the predominant coevolution sector lies along the observed dimer interface, suggesting functional relevance. Furthermore, coevolution scoring provides a basis for determining significant nodes, termed hubs, in the network formed by residues found along the interface of the homodimer. These node residues coincide with hotspots indicating potential druggability. Drug design efforts targeting such key residues could potentially result in modulation of binding and therapeutic benefits for disease states, such as lung cancers, lymphomas and latent HIV‐1 infection. Furthermore, this method may be applied to any protein–protein interaction.
Crystallographic analysis of the ENTH domain from yeast epsin Ent2 that induces a cell division phenotype
Authors: Costakes Gregory T. , Sen Arpita , Aguilar R. Claudio. , Stauffacher Cynthia V.
Published: March 2013

Epsins are eukaryotic, endocytic adaptor proteins primarily involved in the early steps of clathrin mediated endocytosis. Two epsins exist inSaccharomyces cerevisiae, Ent1 and Ent2, with single epsin knockouts being viable, while the double knockout is not. These proteins contain a highly conserved Epsin N‐terminal homology (ENTH) domain that is essential for cell viability. In addition, overexpression of the ENTH domain of Ent2 (ENTH2) was shown to play a role in cell division by interacting with the septin organizing, Cdc42 GTPase activating protein, Bem3, leading to increased cytokinesis failure. In contrast, overexpression of the ENTH domain of Ent1 (ENTH1) does not affect cytokinesis, despite being 75% identical to ENTH2. An ENTH2N112D, S114E, E118Qmutant that switches residues in loop 7 to those found correspondingly in ENTH1 was incapable of inducing the cytokinesis phenotype. In order to better understand the role of loop 7 in the ENTH2‐induced phenotype at a molecular level, X‐ray crystallography was used to elucidate the structures of yeast ENTH2WTand ENTH2DEQ. Our results indicate that mutations did not affect the conformation of loop 7, but rather introduce an increased negative charge on a potential interaction interface. Morphological analysis of cells overexpressing ENTH2 loop 7 mutants showed that the cytokinesis failure phenotype was abolished by the single mutants N112D, E118Q, and to a lesser extent by S114E. Taken together, our results indicate that the interaction surface that contains loop 7 and the specific nature of these residues are crucial for ENTH2 involvement in cytokinesis. This research provides insight into a molecular mechanism by which ENTH2, but not ENTH1, overexpression in yeast leads to cell division defects. Structural data of WT and mutant ENTH2 domains along within vivophenotypic analysis of ENTH2 overexpressing cells indicate that the biochemical nature of three loop 7 residues is crucial for its role in cytokinesis.
Peptidyl cyclopropenones: Reversible inhibitors, irreversible inhibitors, or substrates of cysteine proteases?
Authors: Cohen Meital , Bretler Uriel , Albeck Amnon
Published: March 2013

Peptidyl cyclopropenones were previously introduced as selective cysteine protease reversible inhibitors. In the present study we synthesized one such peptidyl cyclopropenone and investigated its interaction with papain, a prototype cysteine protease. A set of kinetics, biochemical, HPLC, MS, and 13C‐NMR experiments revealed that the peptidyl cyclopropenone was an irreversible inhibitor of the enzyme, alkylating the catalytic cysteine. In parallel, this cyclopropenone also behaved as an alternative substrate of the enzyme, providing a product that was tentatively suggested to be either a spiroepoxy cyclopropanone or a gamma‐lactone. Thus, a single family of compounds exhibits an unusual variety of activities, being reversible inhibitors, irreversible inhibitors and alternative substrates towards enzymes of the same family.
Copper‐chaperones with dicoordinated Cu(I)—Unique protection mechanism
Authors: Ansbacher Tamar , Chourasia Mukesh , Shurki Avital
Published: March 2013

Cu(I) dicoordination with thiolate ligands is not common. Yet, different from its homologue proteins, human copper chaperone is known to bind Cu(I) using this low coordination number while binding Cu(I) only via the two conserved Cysteine residues, Cys12 and Cys15. Based on structural analysis, this work determines that the protein possesses two distinct conformations referred to as “in” and “out” due to the relative positioning of Cys12 (one of Cu(I) binding residues). The “out” conformation, with Cys12 pointing out, imposes a buried Cu(I) position, whereas the “in” conformation with Cys12 pointing inwards results in a more exposed Cu(I) thus, available for transfer. Using QM/MM methods along with thermodynamic cycles these two conformations are shown to exhibit different coordination preference, suggesting that the protein has evolved to have a unique Cu(I) protection mechanism. It is proposed that the “out” conformation with a preference to dicoordination prevents Cu(I) interaction with external ligands and/or Cu(I) release to the solvent, whereas the “in” conformation with preference to tricoordinated Cu(I), facilitates Cu(I) transfer to target proteins, where additional ligands are involved. Proteins 2013; 81:1411–1419. © 2013 Wiley Periodicals, Inc.
Why is Svalbard an island? Evidence for two‐stage uplift, magmatic underplating, and mantle thermal anomalies
Authors: Dörr N. , Clift P. D. , Lisker F. , Spiegel C.
Published: March 2013

Svalbard is an anomalous, subaerial part of the Barents Shelf, Northeast Atlantic Ocean. In this study, we performed both, one‐ and two‐dimensional subsidence analyses based on basin structure, water depth, and thermochronology, to quantify and date the phases of uplift affecting Svalbard during the Cenozoic. Svalbard has experienced two phases of uplift, from >36 to ~10 Ma, and since ~10 Ma, similar in timing to uplift phases identified in Greenland, Scandinavia, and the Barents Shelf. Total uplift across much of the Central Tertiary Basin of Svalbard is >1.5 km and exceeds 2.5 km in parts of the West Spitsbergen Foldbelt (WSFB). Uplift from >36 to ~10 Ma accounts for the greatest part of the vertical motion and like the younger phase reduces in magnitude towards the east. Flexural rigidity of the lithosphere is estimated to be low (Te ≈ 5 km), so that post‐36 Ma erosion of the WSFB contributes little to the uplift, whose permanent nature and proximity to the synchronous Yermak Plateau favors a link to regional magmatic underplating. Plume dynamic support and flexural unloading along the western transform plate margin can be ruled out as influences on vertical motions. Since ~10 Ma renewed uplift, generating the modern topography may be linked to thermal erosion of the mantle lithosphere under Svalbard. We suggest that a likely cause of much of the surface uplift is the northward propagation of the Knipovich Ridge to establish continuous seafloor spreading through the Fram Strait after ~10 Ma.
Good Customers: The Value of Customers by Mode of Acquisition
Authors: Uncles Mark D. , East Robert , Lomax Wendy
Published: March 2013

Are referred customers more valuable than customers recruited through advertising/promotion? This question is answered using data accumulated from surveys covering the satisfaction, recommendation, retention, spending and mode of acquisition of customers. The database comprises 6578 records and covers 15 product/service category groupings.

Overall, referral customers are somewhat more satisfied, recommend their brand more, and have superior retention when compared to customers recruited through advertising/promotion. These findings suggest that referral customers are more profitable than advertising customers but, unexpectedly, their superiority over advertising customers rests mainly on their greater retention rather than their higher level of recommendation.

On this evidence, referral customers bring somewhat more benefit to a firm than those recruited through advertising/promotion. Projections for a 7-year period illustrate the magnitude of these benefits. Also discussed and illustrated is a possible secondary outcome – social amplification.
IUPAC-NIST Solubility Data Series. 94. Rare Earth Metal Iodides and Bromides in Water and Aqueous Systems. Part 2. Bromides
Authors: Mioduski Tomasz , Gumiński Cezary , Zeng Dewen , Voigt Heidelore
Published: March 2013

This work presents solubility data for rare earth metal bromides in water and in aqueous ternary systems. Compilations of all available experimental data are introduced for each rare earth metal bromide with a corresponding critical evaluation. Every such evaluation contains a collection of all solubility results in water, a selection of suggested solubility data and a brief discussion of the multicomponent systems. Because the ternary systems were almost never studied more than once, no critical evaluations of such data were possible. Only simple bromides (no complexes) are treated as the input substances in this work. The literature has been covered through the end of 2011.
IUPAC-NIST Solubility Data Series. 97. Solubility of Higher Acetylenes and Triple Bonded Derivatives
Authors: Skrzecz Adam
Published: March 2013

Solubility of Ethyne in Liquids was published in 2001 as Vol. 76 of the IUPAC-NIST Solubility Data Series. The current work extends the coverage to the solubility in liquids of higher gaseous and liquid acetylenes and to derivatives that contain a triple carbon-carbon bond. Predictive methods for estimating solubilities in water are summarised and usually give values to within an order of magnitude. The literature has been surveyed to the end of 2010.
IUPAC-NIST Solubility Data Series. 98. Solubility of Polycyclic Aromatic Hydrocarbons in Pure and Organic Solvent Mixtures: Revised and Updated. Part 2. Ternary Solvent Mixtures
Authors: Acree William E.
Published: March 2013

This work updates Vols. 54, 58, and 59 in the IUPAC Solubility Data Series and presents solubility data for polycyclic aromatic hydrocarbon solutes dissolved in ternary organic solvent mixtures. Published solubility data for anthracene, phenanthrene, and pyrene that appeared in the primary literature between 1995 to the end of 2011 are compiled and critically evaluated. Experimental solubility data for 119 different solute-ternary solvent systems are included in the volume. Solubility data published prior to 1995 were contained in three earlier volumes (Vols. 54, 58, and 59) and are not repeated here.
IUPAC-NIST Solubility Data Series. 98. Solubility of Polycyclic Aromatic Hydrocarbons in Pure and Organic Solvent Mixtures—Revised and Updated. Part 3. Neat Organic Solvents
Authors: Acree William E.
Published: March 2013

This work updates Vols. 54, 58, and 59 in the IUPAC Solubility Data Series and presents solubility data for polycyclic aromatic hydrocarbon solutes dissolved in neat organic solvents. Published solubility data for acenaphthene, anthracene, biphenyl, carbazole, dibenzofuran, dibenzothiophene, fluoranthene, fluorene, naphthalene, phenanthrene, phenothiazine, pyrene, thianthrene, and xanthene that appeared in the primary literature from 1995 to the end of 2011 are compiled and critically evaluated. Experimental solubility data for more than 550 different solute-organic solvent systems are included. Solubility data published prior to 1995 were contained in three earlier volumes (Vols. 54, 58, and 59) and are not repeated in this volume.
Reference Correlation of the Thermal Conductivity of n-Hexane from the Triple Point to 600 K and up to 500 MPa
Authors: Assael M. J. , Mylona S. K. , Tsiglifisi Ch. A. , Huber M. L. , Perkins R. A.
Published: March 2013

This paper contains new, representative reference equations for the thermal conductivity of n-hexane. The equations are based in part upon a body of experimental data that has been critically assessed for internal consistency and for agreement with theory whenever possible. In the case of the dilute-gas thermal conductivity, a theoretically based correlation was adopted in order to extend the temperature range of the experimental data. Moreover, in the critical region, the experimentally observed enhancement of the thermal conductivity is well represented by theoretically based equations containing just one adjustable parameter. The correlations are applicable for the temperature range from the triple point to 600 K and pressures up to 500 MPa. The overall uncertainty (considered to be estimates of a combined expanded uncertainty with a coverage factor of 2) of the proposed correlation is estimated, for pressures less than 500 MPa and temperatures less than 600 K, to be less than 6%.
Deposition of model chains on surfaces: Anomalous relation between flux and stability
Authors: Jana Pritam Kumar , Heuer Andreas
Published: March 2013

Model chains are studied via Monte Carlo simulations which are deposited with a fixed flux on a substrate. They may represent, e.g., stiff lipophilic chains with an head group and tail groups mimicking the alkyl chain. After some subsequent fixed simulation time we determine the final energy as a function of flux and temperature. Surprisingly, in some range of temperature and flux the final energy increases with decreasing flux. The physical origin of this counterintuitive observation is elucidated. In contrast, when performing equivalent cooling experiments no such anomaly is observed. Furthermore, it is elaborated whether flux experiments give rise to configurations with lower energies as compared to cooling experiments. These results are related to recent experiments by the Ediger group where very stable configurations of glass-forming systems have been generated via flux experiments.
Fast and efficient single electron transfer between distant quantum dots
Authors: Hermelin S. , Takada S. , Yamamoto M. , Tarucha S. , Wieck A. D. , Saminadayar L. , Bäuerle C. , Meunier T.
Published: March 2013

Lateral quantum dots are a promising system for quantum information processing devices. The required basic manipulations of a single electron spin have indeed been demonstrated. However, a stringent requirement is the ability to transfer quantum information from place to place within one sample. In this work, we explore and demonstrate the possibility to transfer a single electron between two distant quantum dots in a fast and reliable manner.
Light-matter coupling in ZnTe-based micropillar cavities containing CdTe quantum dots
Authors: Jakubczyk T. , Pacuski W. , Smoleński T. , Golnik A. , Florian M. , Jahnke F. , Kruse C. , Hommel D. , Kossacki P.
Published: March 2013

We study the coupling of CdTe quantum dots emission with ZnTe-based micropillar cavity modes. Nonresonant cavity mode feeding is reported together with an enhancement of the emission of a quantum dot thanks to resonant coupling with the cavity mode. The coupling is evidenced both in experiments with continuous and pulsed excitation. A theoretical Purcell factor is calculated and an experimental Purcell factor 5.7 is determined confirming the theoretical predictions. Additionally, we discuss the influence of the cascaded emission occurring under increased excitation power on the observed decay time of the excitonic transition.
Test of the fluctuation theorem for single-electron transport
Authors: Küng B. , Rössler C. , Beck M. , Marthaler M. , Golubev D. S. , Utsumi Y. , Ihn T. , Ensslin K.
Published: March 2013

Using time-resolved charge detection in a double quantum dot, we present an experimental test of the fluctuation theorem. The fluctuation theorem, a result from nonequilibrium statistical mechanics, quantifies the ratio of occurrence of fluctuations that drive a small system against the direction favored by the second law of thermodynamics. Here, these fluctuations take the form of single electrons flowing against the source–drain bias voltage across the double quantum dot. Our results, covering configurations close to as well as far from equilibrium, agree with the theoretical predictions, when the finite bandwidth of the charge detection is taken into account. In further measurements, we study a fluctuation relation that is a generalization of the Johnson–Nyquist formula and relates the second-order conductance to the voltage dependence of the noise. Current and noise can be determined with the time-resolved charge detection method. Our measurements confirm the fluctuation relation in the nonlinear transport regime of the double quantum dot.
Field-effect control of tunneling barrier height by exploiting graphene's low density of states
Authors: Ponomarenko L. A. , Belle B. D. , Jalil R. , Britnell L. , Gorbachev R. V. , Geim A. K. , Novoselov K. S. , Castro Neto A. H. , Eaves L. , Katsnelson M. I.
Published: March 2013

We exploit the low density of electronic states of graphene to modulate the tunnel current flowing perpendicular to the atomic layers of a multi-layer graphene-boron nitride device. This is achieved by using the electric field effect to raise the Fermi energy of the graphene emitter layer and thereby reduce the effective barrier height for tunneling electrons. We discuss how the electron charge density in the graphene layers and the properties of the boron nitride tunnel barrier determine the device characteristics under operating conditions and derive expressions for carrier tunneling in these highly anisotropic layered heterostructures.
Ultrastrong light-matter coupling at terahertz frequencies with split ring resonators and inter-Landau level transitions
Authors: Scalari G. , Maissen C. , Hagenmüller D. , De Liberato S. , Ciuti C. , Reichl C. , Wegscheider W. , Schuh D. , Beck M. , Faist J.
Published: March 2013

We study strong light-matter coupling at terahertz frequencies employing a system based on an array of deeply subwavelength split ring resonators deposited on top of an ensemble of modulation-doped quantum wells. By applying a magnetic field parallel to the epitaxial growth axis, at low temperatures, Landau Levels are formed. We probe the interaction of the inter-Landau level transitions with the resonators modes, measuring a normalized coupling ratio Ωωc=0.58 between the inter-Landau level frequency ωc and the Rabi frequency Ω of the system. The physics of the system is studied as a function of the metasurface composition and of the number of quantum wells. We demonstrate that the light-matter coupling strength is basically independent from the metamaterial lattice spacing.
Synchrotron nanoimaging of single In-rich InGaN nanowires
Authors: Segura-Ruiz J. , Martínez-Criado G. , Chu M. H. , Denker C. , Malindretos J. , Rizzi A.
Published: March 2013

This work reports on the elemental distribution and local structure of single InxGa1–xN nanowires (NWs) grown by molecular beam epitaxy on Si (111) substrates using X-ray fluorescence nanoprobe. Ga and In maps reveal an inhomogeneous elemental distribution along the NWs, with a higher Ga concentration at the bottom of the NW. Scanning electron microscopy images show that the inhomogeneous axial distribution is not correlated with a X-ray beam induced damage, and therefore, should be an intrinsic characteristic of the NWs arising from the growth process. Spatially resolved X-ray absorption near edge structure spectroscopy data acquired around the In K-edge show that the tetrahedral structure is preserved around the absorbing In-atoms all along the NW, and suggests that the compositional modulation could be affecting its long-range order.
Magnetic hyperfine field in antiferromagnetic RGa2 (R = Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er) studied by perturbed angular correlation spectroscopy using Cd111
Authors: Cavalcante F. H. M. , Pereira L. F. D. , Cavalcante J. T. , Saitovitch H. , Carbonari A. W. , Saxena R. N. , Forker M.
Published: March 2013

The magnetic and electric hyperfine interactions of the nuclear probe Cd111 in the hexagonal antiferromagnetic rare earth-gallium RGa2 (R = Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Er) intermetallic compounds have been investigated by perturbed angular correlation (PAC) spectroscopy as a function of temperature. With the exception of R = Nd and Ho, the magnetic hyperfine field Bhf is roughly proportional to the spin projection (g − 1)J of the R constituent. However, in the group of the light rare earths, the variation of Bhf with (g − 1)J is much weaker than that for the heavy R constituents, in contrast to the trend reported for all rare earth intermetallics investigated up to now as well as to the trend of the magnetic ordering temperatures of RGa2. The orientation of the 4f spins relative to the c axis of RGa2 deduced from the angle between Bhf and the symmetry axis of the electric field gradient was found to be temperature independent and in agreement with the results of previous magnetization measurements. Except for SmGa2 where the hyperfine field shows an abrupt decrease near TN, the temperature dependence of Bhf(T) is consistent with second order phase transitions. The magnetic ordering temperatures deduced from Bhf(T) agree with magnetization and neutron diffraction results.
Crystallographically textured self-biased W-type hexaferrites for X-band microwave applications
Authors: Su Zhijuan , Chen Yajie , Hu Bolin , Sokolov Alexander S. , Bennett Steven , Burns Lee , Xing Xing , Harris Vincent G.
Published: March 2013

We report the magnetic and structural properties of a series of W-type barium hexaferrites of composition BaZn2−xCoxFe16O27, where x = 0.15, 0.20, and 0.25. The anisotropy field of these barium ferrites (BaW) decreased with the substitution of divalent Co ions, while they maintained crystallographic c-axis texture. The measured anisotropy field was ∼10 kOe, and a hysteresis loop squareness Mr/Ms = 79% was obtained due to well-controlled grain size within the range of single domain scale. These two properties make the BaW suitable for applications in microwave devices at lower frequencies, such as self-biased circulators operated at X-band frequencies.
Stress effects on complex permeability spectra of Mn-substituted cobalt ferrite
Authors: Lo C. C. H. , Fan B.
Published: March 2013

The effects of axial applied stresses on the magnetization processes in Mn-substituted cobalt ferrite (CoMnxFe2-xO4 with x = 0 to 0.4) toroids have been studied by measuring the circumferential complex permeability spectra μ* = μ′ − iμ″ from 1 kHz to 15 MHz. The μ* spectra were described using a dispersion equation to determine the relative susceptibilities due to domain wall motion (χD0) and magnetization rotation (χS0). Mn-substitution into cobalt ferrite was found to reduce the magnetocrystalline anisotropy and hence the susceptibility is increased. Under axial compressive stresses, χD0 and χS0 of all samples decrease. The Mn-substituted samples with x = 0.2 and 0.3 show larger reductions in χD0 and χS0 than the pure cobalt ferrite. The stress effects on χS0 and the dependence of the magnetomechanical effect on Mn content were reproduced in model calculations by taking into account the combined effects of stress-induced and magnetocrystalline anisotropies on magnetization rotation.
Group action in topos quantum physics
Authors: Flori C.
Published: March 2013

Topos theory has been suggested first by Isham and Butterfield, and then by Isham and Döring, as an alternative mathematical structure within which to formulate physical theories. In particular, it has been used to reformulate standard quantum mechanics in such a way that a novel type of logic is used to represent propositions. In this paper, we extend this formulation to include the notion of a group and group transformation in such a way that we overcome the problem of twisted presheaves. In order to implement this we need to change the type of topos involved, so as to render the notion of continuity of the group action meaningful.
Carbon X-ray absorption spectra of fluoroethenes and acetone: A study at the coupled cluster, density functional, and static-exchange levels of theory
Authors: Fransson Thomas , Coriani Sonia , Christiansen Ove , Norman Patrick
Published: March 2013

Near carbon K-edge X-ray absorption fine structure spectra of a series of fluorine-substituted ethenes and acetone have been studied using coupled cluster and density functional theory (DFT) polarization propagator methods, as well as the static-exchange (STEX) approach. With the complex polarization propagator (CPP) implemented in coupled cluster theory, relaxation effects following the excitation of core electrons are accounted for in terms of electron correlation, enabling a systematic convergence of these effects with respect to electron excitations in the cluster operator. Coupled cluster results have been used as benchmarks for the assessment of propagator methods in DFT as well as the state-specific static-exchange approach. Calculations on ethene and 1,1-difluoroethene illustrate the possibility of using nonrelativistic coupled cluster singles and doubles (CCSD) with additional effects of electron correlation and relativity added as scalar shifts in energetics. It has been demonstrated that CPP spectra obtained with coupled cluster singles and approximate doubles (CC2), CCSD, and DFT (with a Coulomb attenuated exchange-correlation functional) yield excellent predictions of chemical shifts for vinylfluoride, 1,1-difluoroethene, trifluoroethene, as well as good spectral features for acetone in the case of CCSD and DFT. Following this, CPP-DFT is considered to be a viable option for the calculation of X-ray absorption spectra of larger π-conjugated systems, and CC2 is deemed applicable for chemical shifts but not for studies of fine structure features. The CCSD method as well as the more approximate CC2 method are shown to yield spectral features relating to π*-resonances in good agreement with experiment, not only for the aforementioned molecules but also for ethene, cis-1,2-difluoroethene, and tetrafluoroethene. The STEX approach is shown to underestimate π*-peak separations due to spectral compressions, a characteristic which is inherent to this method.
Magnetotransport properties in epitaxial Fe3O4(001) thin films with current perpendicular to the plane geometry
Authors: Yanagihara H. , Shimada K. , Niizeki T. , Kita E. , Inoue J. , Fukushima A. , Yuasa S.
Published: March 2013

We investigated the fundamental transport properties of epitaxial magnetite (Fe3O4) films with applied current perpendicular to the plane geometry. The devices with a junction area of 36 μm2 were fabricated with TiN/Fe3O4/ TM (TM: Ti and Fe) stacking. Both the temperature dependence and the magnetic field dependence of the junction resistance were measured. Most of the resistance properties were independent of whether the electrode was magnetic (Fe) or nonmagnetic (Ti). Below the Verwey point, the junction resistance abruptly increased with decreasing temperature, and the resistance reached maximum at approximately 30 K. The magnetoresistance showed a peak of ∼27% at T≈55 K. The observed resistance behavior was consistent with a hopping conduction mechanism with a Coulomb interaction.
First-principles analyses of unusual ferromagnetism observed in CrSi2(core)/SiO2(shell) nanocables
Authors: Lee Cheng-Tse , Li Tzu-Yuan , Chiou Shian-Haw , Lo Shen-Chuan , Han You-Hong , Ouyang Hao
Published: March 2013

One-dimensional nanostructures such as nanowires (NWs), nanotubes, and nanocables can sometimes show unique physical properties compared to their bulk counterparts owing to their reduced diameter and high aspect ratio. The first-principles density functional-theory based on spin polarized calculations was used to investigate CrSi2/SiO2 nanowires. The CrSi2 and SiO2 in bulk are diamagnetic, but the ferromagnetism in CrSi2/SiO2 nanowire has been found. Results showed that the ferromagnetism was from Cr atoms around the interface between SiO2 and CrSi2. As the lattice constants were fixed and unfixed during calculations, the average magnetizations per Cr atom around the interface became 1.02μB/atom and 1.06μB/atom, respectively. The asymmetrical bonding-surroundings, causing the exchange interaction, can be the major ferromagnetic source. The effect of roughness and oxygen distribution to magnetization is also considered.
Narrow-bandwidth solar upconversion: Case studies of existing systems and generalized fundamental limits
Authors: Briggs Justin A. , Atre Ashwin C. , Dionne Jennifer A.
Published: March 2013

Upconversion of sub-bandgap photons is a promising approach to exceed the Shockley-Queisser limit in solar technologies. Calculations have indicated that ideal, upconverter-enhanced cell efficiencies can exceed 44% for non-concentrated sunlight, but such improvements have yet to be observed experimentally. To explain this discrepancy, we develop a thermodynamic model of an upconverter-cell considering a highly realistic narrow-band, non-unity-quantum-yield upconverter. As expected, solar cell efficiencies increase with increasing upconverter bandwidth and quantum yield, with maximum efficiency enhancements found for near-infrared upconverter absorption bands. Our model indicates that existing bimolecular and lanthanide-based upconverters will not improve cell efficiencies more than 1%, consistent with recent experiments. However, our calculations show that these upconverters can significantly increase cell efficiencies from 28% to over 34% with improved quantum yield, despite their narrow bandwidths. Our results highlight the interplay of absorption and quantum yield in upconversion, and provide a platform for optimizing future solar upconverter designs.
A tool for measuring the bending length in thin wires
Authors: Lorenzini M. , Cagnoli G. , Cesarini E. , Losurdo G. , Martelli F. , Piergiovanni F. , Vetrano F. , Viceré A.
Published: March 2013

Great effort is currently being put into the development and construction of the second generation, advanced gravitational wave detectors, Advanced Virgo and Advanced LIGO. The development of new low thermal noise suspensions of mirrors, based on the experience gained in the previous experiments, is part of this task. Quasi-monolithic suspensions with fused silica wires avoid the problem of rubbing friction introduced by steel cradle arrangements by directly welding the wires to silica blocks bonded to the mirror. Moreover, the mechanical loss level introduced by silica (ϕfs ∼ 10−7 in thin fused silica wires) is by far less than the one associated with steel. The low frequency dynamical behaviour of the suspension can be computed and optimized, provided that the wire bending shape under pendulum motion is known. Due to the production process, fused silica wires are thicker near the two ends (necks), so that analytical bending computations are very complicated. We developed a tool to directly measure the low frequency bending parameters of fused silica wires, and we tested it on the wires produced for the Virgo+ monolithic suspensions. The working principle and a set of test measurements are presented and explained.
Spontaneous exchange bias in a nanocomposite of BiFeO3-Bi2Fe4O9
Authors: Maity Tuhin , Goswami Sudipta , Bhattacharya Dipten , Das Gopes C. , Roy Saibal
Published: March 2013

We have observed a large as well as path-dependent spontaneous exchange bias (HSEB) (∼30–60 mT) in a nanocomposite of BiFeO3-Bi2Fe4O9 across 5–300 K when it is measured in an unmagnetized state following zero-field cooling and appropriate demagnetization. The path dependency yields a variation in the exchange bias depending on the sign of the starting field and the path followed in tracing the hysteresis loop. The asymmetry thus observed—ΔHSEB—is found to be decreasing nonmonotonically across 5–300 K with a peak around 200 K. The ΔHSEB together with large HSEB could have significant ramification in tuning the exchange bias driven effects and consequent applications.
High quality multiferroic BiFeO3 films prepared by pulsed laser deposition on glass substrates at reduced temperatures
Authors: Chang H. W. , Yuan F. T. , Tien S. H. , Li P. Y. , Wang C. R. , Tu C. S. , Jen S. U.
Published: March 2013

Phase structure and ferroelectric properties of BiFeO3 (BFO) films grown on Pt(111) buffered glass substrates at various growth temperatures and oxygen pressures have been studied. The optimization of the 20-nm-thick Pt(111) bottom electrode enables BFO films to form perovskite single phase structure at reduced temperatures between 400–500 °C. Microstructure of fine grains and smooth surface is obtained, which is favorable for applications. Multiferroic properties including 2Pr of 15.1–124 μC/cm2, Ec of 351–680 kV/cm, and Ms of 5–8 emu/cm3 are achieved within the oxygen pressure range of 10–75 mTorr. The optimized ferroelectric properties are comparable to the reported values of BFO samples using Si and MgO single crystal substrates. The results of this study may broaden the possibility of the use of BFO films.
Accurate prediction of nuclear magnetic resonance shielding constants: Towards the accuracy of CCSD(T) complete basis set limit
Authors: Sun Meng , Zhang Igor Ying , Wu Anan , Xu Xin
Published: March 2013

In this work, we have calculated the nuclear magnetic resonance (NMR) shielding constants for 42 molecules at the levels of second order Møller-Plesset perturbation (MP2) and coupled-cluster singles and doubles model augmented by perturbative corrections for triple excitations CCSD(T). Basis set extrapolations to the complete basis set (CBS) limit have been performed. A focal-point analysis method for magnetic parameters was proposed here, which adds the [σe(CCSD(T)) − σe(MP2)] difference to the MP2/CBS number to approximate the corresponding CCSD(T)/CBS value. Systematical comparison has demonstrated the usefulness of this FPA-M/CBS scheme.
Internal solitary wave transformation over a bottom step: Loss of energy
Authors: Talipova Tatiana , Terletska Katherina , Maderich Vladimir , Brovchenko Igor , Jung Kyung Tae , Pelinovsky Efim , Grimshaw Roger
Published: March 2013

In this paper, we extend the numerical study of Maderich et al. [“Interaction of a large amplitude interfacial solitary wave of depression with a bottom step,” Phys. Fluids 22, 076602 (2010)10.1063/1.3455984] on the interaction of an interfacial solitary wave with a bottom step, considering (i) the energy loss of solitary waves of both polarities interacting with a bottom step and (ii) features of the transformation of a large-amplitude internal solitary waves at the step. We show that the dependence of energy loss on the step height is not monotonic, but has different maximum positions for different incident wave polarities. The energy loss does not exceed 50% of the energy of an incident wave. The results of our numerical modeling are compared with some recent results from laboratory tank modeling.
Effect of the Pt buffer layer on perpendicular exchange bias based on collinear/non-collinear coupling in a Cr2O3/Co3Pt interface
Authors: Ashida T. , Sato Y. , Nozaki T. , Sahashi M.
Published: March 2013

In this study, we fabricated a Cr2O3 (0001) film without and with a Pt buffer layer and investigated its effect on perpendicular exchange coupling in a Cr2O3/Co3Pt interface. The results showed that the exchange bias field (μ0Hex) and blocking temperature (TB) of a Cr2O3 film without and with Pt were very different. The Cr2O3 film without Pt had a lower μ0Hex of 176 Oe and a lower TB of 75 K, whereas that with Pt had a higher μ0Hex of 436 Oe and a higher TB of 150 K. We discussed this difference in μ0Hex and TB values based on collinear/non-collinear coupling in a ferromagnetic and antiferromagnetic interface using Meiklejohn and Bean's exchange anisotropy model.