ELECTROANALYSIS, Issue 23 2009
Jiri Zeravik
Abstract This review compares various types of (bio)electronic tongues. The design and principles of potentiometric and voltammetric electronic tongues are discussed together with applications in food and environmental analysis. Different approaches towards bioelectronic tongue are presented. Several methods for evaluation and interpretation of the measured data are described. Finally, the potential of such devices for analysis of wine is discussed. [source]

Synthesis and Binding Properties of Dendritic Oxybathophenanthroline Ligands towards Copper(II)

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2005
Holger Stephan
Abstract Dendritic oxybathophenanthroline ligands (generation 0 to 3) have been synthesized by treatment of 4,7-bis(4,-hydroxyphenyl)-1,10-phenanthroline with the corresponding Fréchet-type dendrons carrying a benzylic bromide function at the focal point. The complexation of copper(II) has been studied by liquid,liquid extraction using the radioisotope 64Cu and time-resolved laser-induced fluorescence spectroscopy (TRLFS) in organic media indicating the formation of 1:3 complexes (Cu:dendritic ligand). Electronic and EPR spectroscopy were used to characterize the copper(II) chromophore, which is shown to have the expected distorted square-planar geometry with two phenanthroline donors coordinated to the copper(II) center. The third dendritic ligand therefore is proposed to be bound by secondary interactions. The stability constants of the 1:3 complexes were found to be in the order of log K , 16 in CHCl3. On the other hand, increasing generation of the dendritic Fréchet-type branches leads to enhanced shielding of the copper ion from the environment. Additional information about this behaviour was obtained by the fluorescence lifetimes, which are much less influenced upon addition of copper(II) salt to solutions of the higher generation ligands. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

Bent and Linear Forms of the (,-Oxo)bis[trichloroferrate(III)] Dianion: An Intermolecular Effect , Structural, Electronic and Magnetic Properties

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2003
Agustí Lledós
Abstract We have analyzed the great diversity of Fe,O,Fe angles, 140,180°, found in the X-ray structures of the (,-oxo)bis[trichloroferrate(III)] dianion [Cl3FeOFeCl3]2, from both experimental and theoretical points of view. Theoretical calculations show that only the linear isomer is found as a minimum on the potential energy surface. Detailed analysis of the crystal packing indicates that the angular form is due to attractive intermolecular interactions. Analysis of a selected reduced set of the 45 crystal structures retrieved from the Cambridge Structural Database allowed us to classify the bending of the [Cl3FeOFeCl3]2, dianion in three categories, depending on the balance and strength of the intermolecular O···H,X contacts. A crystal diffraction study on the bis(benzyltrimethylammonium) salt has shown both bent (144.6°) and linear (180°) forms of the (,-oxo)bis[trichloroferrate(III)] dianion. The magnetic susceptibility of this compound has been fitted by assuming two equally weighted contributions (Jang and Jlin) of the two forms, considering Jang , Jlin estimated by theoretical calculations. The obtained Jang and Jlin of ,117 and ,133 cm,1 respectively, agree well with B3LYP results. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

Intramolecular Heck Reactions for the Synthesis of the Novel Antibiotic Mensacarcin: Investigation of Catalytic, Electronic and Conjugative Effects in the Preparation of the Hexahydroanthracene Core

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 9 2005
Lutz F. Tietze
Abstract The intramolecular Heck reaction of the three complex diphenyl substrates rac - 2, 5 and rac - 6, containing substituents with different electronic and conjugative properties, were examined. The Pd compounds [Pd2(dba)3]/[(tBu)3PH]BF4, [Pd2(OAc)2{P(o -Tol)3}2] (4), [PdCl2(PPh3)2] and Pd(OAc)2 were used as catalysts. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

New Insights on Near-Infrared Emitters Based on Er-quinolinolate Complexes: Synthesis, Characterization, Structural, and Photophysical Properties,

ADVANCED FUNCTIONAL MATERIALS, Issue 14 2007
F. Artizzu
Abstract Erbium quinolinolates, commonly assumed to be mononuclear species with octahedral co-ordination geometry, have been proposed as promising materials for photonic devices but difficulties in obtaining well defined products have so far limited their use. We report here the conditions to obtain in high yields three different kinds of pure neutral erbium quinolinolates by mixing an erbium salt with 8-quinolinol (HQ) and 5,7-dihalo-8-quinolinol (H5,7XQ: X,=,Cl and Br): i),the trinuclear complex Er3Q9 (1) which is obtained with HQ deprotonated by NH3 in water or ethanol/water mixtures; ii),the already known dimeric complexes based on the unit [Er(5,7XQ)3(H2O)2] [X,=,Cl (2) and Br (3)]; iii) the mononuclear [Er(5,7XQ)2(H5,7XQ)2Cl] [X,=,Cl (4) and Br (5)] complexes, obtained in organic solvents without base addition, where the ion results coordinated to four ligands, two deprotonated chelating, and two as zwitterionic monodentate oxygen donors. These results represent a further progress with respect to a recent reinvestigation on this reaction, which has shown that obtaining pure and anhydrous octahedral ErQ3, the expected reaction product, is virtually impossible, but failed in the isolation of 1 and of the neutral tetrakis species based on H5,7XQ ligands. Structural data provide a detailed description of the molecules and of their packing which involves short contacts between quinoxaline ligands, due to ,,, interactions. Electronic and vibrational studies allow to select the fingerprints to distinguish the different products and to identify the presence of water. The structure/property relationship furnishes a satisfactory interpretation of the photo-physical properties. Experimental evidence confirms that the most important quenchers for the erbium emission are the coordinated water molecules and shows that the ligand emission is significantly affected by the ,,, interactions. [source]

Cover Picture: Fabrication of Stable Metallic Patterns Embedded in Poly(dimethylsiloxane) and Model Applications in Non-Planar Electronic and Lab-on-a-Chip Device Patterning (Adv. Funct.

ADVANCED FUNCTIONAL MATERIALS, Issue 4 2005
Mater.
Abstract A composite image is shown that highlights examples of device architectures that either incorporate or exploit polymer-embedded metallic microstructures. In work reported by Nuzzo and co-workers on p.,557, new applications of soft lithography, in conjunction with advanced forms of multilayer metallization, are used to construct these exceptionally durable structures. They are suitable for use in non-planar lithographic patterning, and as device components finding applications ranging from microelectronics to Lab-on-a-Chip analytical systems. This article describes the fabrication of durable metallic patterns that are embedded in poly(dimethylsiloxane) (PDMS) and demonstrates their use in several representative applications. The method involves the transfer and subsequent embedding of micrometer-scale gold (and other thin-film material) patterns into PDMS via adhesion chemistries mediated by silane coupling agents. We demonstrate the process as a suitable method for patterning stable functional metallization structures on PDMS, ones with limiting feature sizes less than 5,,m, and their subsequent utilization as structures suitable for use in applications ranging from soft-lithographic patterning, non-planar electronics, and microfluidic (lab-on-a-chip, LOC) analytical systems. We demonstrate specifically that metal patterns embedded in both planar and spherically curved PDMS substrates can be used as compliant contact photomasks for conventional photolithographic processes. The non-planar photomask fabricated with this technique has the same surface shape as the substrate, and thus facilitates the registration of structures in multilevel devices. This quality was specifically tested in a model demonstration in which an array of one hundred metal oxide semiconductor field-effect transistor (MOSFET) devices was fabricated on a spherically curved Si single-crystalline lens. The most significant opportunities for the processes reported here, however, appear to reside in applications in analytical chemistry that exploit devices fabricated using the methods of soft lithography. Toward this end, we demonstrate durably bonded metal patterns on PDMS that are appropriate for use in microfluidic, microanalytical, and microelectromechanical systems. We describe a multilayer metal-electrode fabrication scheme (multilaminate metal,insulator,metal (MIM) structures that substantially enhance performance and stability) and use it to enable the construction of PDMS LOC devices using electrochemical detection. A polymer-based microelectrochemical analytical system, one incorporating an electrode array for cyclic voltammetry and a microfluidic system for the electrophoretic separation of dopamine and catechol with amperometric detection, is demonstrated. [source]

Electronic and Magnetic Properties of SrTiO3/LaAlO3 Interfaces from First Principles

ADVANCED MATERIALS, Issue 26-27 2010
Hanghui Chen
Abstract A number of intriguing properties emerge upon the formation of the epitaxial interface between the insulating oxides LaAlO3 and SrTiO3. These properties, which include a quasi two-dimensional conducting electron gas, low temperature superconductivity, and magnetism, are not present in the bulk materials, generating a great deal of interest in the fundamental physics of their origins. While it is generally accepted that the novel behavior arises as a result of a combination of electronic and atomic reconstructions and growth-induced defects, the complex interplay between these effects remains unclear. In this report, we review the progress that has been made towards unraveling the complete picture of the SrTiO3/LaAlO3 interface, focusing primarily on present ab initio theoretical work and its relation to the experimental data. In the process, we highlight some key unresolved issues and discuss how they might be addressed by future experimental and theoretical studies. [source]

Postoperative adjuvant transarterial chemoembolization for participants with hepatocellular carcinoma: A meta-analysis

HEPATOLOGY RESEARCH, Issue 10 2010
Jian-Hong Zhong
Aim:, The efficacy of transarterial chemoembolization (TACE) for inoperable hepatocellular carcinoma (HCC) is positive, but for postoperative HCC, many studies have reported controversial results. The present study aimed to evaluate the efficacy of postoperative adjuvant TACE for participants with HCC. Methods:, Electronic and manual searches were conducted to identify randomized controlled trials (RCT) evaluating postoperative adjuvant TACE for participants with HCC. Results:, Six RCT totaling 659 participants, of whom almost all were of stage IIIA HCC, were included. For the 1-year tumor recurrence rate, hepatectomy plus TACE showed statistically significant less incidence of recurrence, with a pooled risk ratio (RR) of 0.68 (95% confidence interval [CI] = 0.55,0.84, P = 0.0003). For 1-year mortality, the trials were favorable for TACE with a pooled risk ratio of 0.48 (95% CI = 0.35,0.65, P < 0.00001). For 3-year mortality, the trials also revealed statistically significant less incidence, with a pooled risk ratio of 0.76 (95% CI = 0.64,0.90, P = 0.002). However, for 5-year mortality, TACE did not demonstrate statistically significant less incidence (RR = 0.94, 95% CI = 0.81,1.08, P = 0.36). Transient fever and nausea/vomiting were reported as side-effects of TACE but were well tolerated by most participants. Conclusion:, Postoperative adjuvant TACE seems promising for participants with HCC with risk factors (multiple nodules of >5 cm or vascular invasion) but requires further trial. [source]

Electronic and Mechanical Coupling in Bent ZnO Nanowires

ADVANCED MATERIALS, Issue 48 2009
Xiaobing Han
A red shift of the exciton of ZnO nanowires is efficiently produced by bending strain, as demonstrated by a low-temperature (81,K) cathodoluminescence (CL) study of ZnO nanowires bent into L- or S-shapes. The figure shows a nanowire (Fig. a) with the positions of CL measurements marked. The corresponding CL spectra,revealing a peak shift and broadening in the region of the bend,are shown in Figure b. [source]

A simple mounting model for consistent determination of the accuracy and repeatability of apex locators

INTERNATIONAL ENDODONTIC JOURNAL, Issue 2 2006
A. ElAyouti
Abstract Aim, To develop a precise and simple mounting model (MM) for evaluating apex locators and to compare the repeatability of the MM with a conventional visual method (VM). Methodology, Electronic working length determination was performed in 32 maxillary central incisors using two methods: (i) the MM method and (ii) a conventional VM. The MM utilizes a micrometer to determine the distance travelled by the measuring file during working length determination. In the VM, the length of the measuring file (representing the working length) is determined visually using a caliper and a microscope at 6× magnification. Each measurement was repeated once. The repeatability of each method was evaluated by calculating the coefficient of repeatability. Results, The coefficient of repeatability, which includes 95% of the differences between repeated measurements, was 0.04 mm for MM compared with 0.9 mm for VM. The measurement error of MM was significantly lower than VM (0.02 and 0.4 mm respectively). There was a statistically significant difference between the means of absolute difference in repeated measurements: MM 0.01 mm (95% confidence interval (CI): 0.01; 0.02 mm) compared with VM 0.4 mm (95% CI: 0.3; 0.5 mm). Conclusion, The new MM had superior repeatability in comparison with the conventional method where visual interpretation is a source of inaccurate measurement. [source]

Comment on "Memory Effect and Negative Differential Resistance by Electrode-Induced Two-Dimensional Single-Electron Tunneling in Molecular and Organic Electronic Devices"

ADVANCED MATERIALS, Issue 21 2006
S. Majumdar
No abstract is available for this article. [source]

Update on course and outcome in eating disorders

INTERNATIONAL JOURNAL OF EATING DISORDERS, Issue 3 2010
Pamela K. Keel PhD
Abstract Objective: To review recent studies describing eating disorder course and outcome. Method: Electronic and manual searches were conducted to identify relevant articles published since 2004. Results: Twenty-six articles were identified. For anorexia nervosa (AN), most patients ascertained through outpatient settings achieved remission by 5-year follow-up. Inpatient treatment predicted poor prognosis as inpatient samples demonstrated lower remission rates. Outcome differed between bulimia nervosa (BN) and eating disorders not otherwise specified (EDNOS), including binge eating disorder (BED), for shorter follow-up durations; however, outcomes appeared similar between BN and related EDNOS by 5-year follow-up. Greater psychiatric comorbidity emerged as a significant predictor of poor prognosis in BN, whereas few prognostic indicators were identified for BED or other EDNOS. Discussion: Results support optimism for most patients with eating disorders. However, more effective treatments are needed for adult AN inpatients and approximately 30% of patients with BN and related EDNOS who remain ill 10,20 years following presentation. © 2010 by Wiley Periodicals, Inc. Int J Eat Disord 2010 [source]

Electronic and Magnetic Properties of Ligand-Free FePt Nanoparticles,

ADVANCED MATERIALS, Issue 5 2005
H.-G. Boyen
Ligand-free FePt nanoparticles are prepared in densely packed arrays (see Figure) under ultrahigh vacuum conditions, in which oxygen and hydrogen plasmas are used to remove the organic shells that are present after particle synthesis. The electronic structure and magnetic properties of the "bare", face-centered-cubic FePt particles are presented. Applications in high-density magnetic data recording are foreseen. [source]

Electronic and charge aspects of potential endocrine disruptors: Applications to pharmacological clustering

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 4-5 2003
James W. King
Abstract Quantitative structure,activity relationships in a series of 37 substituted indoles with endocrine disruptor potential were performed using the structural indices FTe (electronic) and FTc (charge), in conjunction with a clustering technique, to relate substitution patterns to reported relative binding affinities for the calf estrogen receptor. Data clusters were generated by a primary numerically descending sort of the structure indices with a concurrent secondary numerically descending sort of the binding data. Reversal of the numerical descent of the latter served to delineate cluster boundaries. Analysis within the clusters defined the effect of substituents and their molecular positions on the pharmacological data. These results confirmed in detail a similar previous study in the same series using the more general FTm index and again suggested the same structure of a molecule with greater receptor binding ability than any in the database. The methodology used in these studies permits a rational presentation and subsequent interpretation of data that initially appear to be totally random and devoid of recoverable information content. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003 [source]

The effect of periodontal therapy on the survival rate and incidence of complications of multirooted teeth with furcation involvement after an observation period of at least 5 years: a systematic review

JOURNAL OF CLINICAL PERIODONTOLOGY, Issue 2 2009
Guy Huynh-Ba
Abstract Objective: To systematically review the survival rate and incidence of complications of furcation-involved multirooted teeth following periodontal therapy after at least 5 years. Material and methods: Electronic and manual searches were performed up to and including January 2008. Publication selection, data extraction and validity assessment were performed independently by three reviewers. Results: Twenty-two publications met the inclusion criteria. Because of the heterogeneity of the data, a meta-analysis could not be performed. The survival rate of molars treated non-surgically was >90% after 5,9 years. The corresponding values for the different surgical procedures were: Surgical therapy: 43.1% to 96%, observation period: 5,53 years. Tunnelling procedures: 42.9% to 92.9%, observation period: 5,8 years. Surgical resective procedures including amputation(s) and hemisections: 62% to 100%, observation period: 5,13 years. Guided tissue regeneration (GTR): 83.3% to 100%, observation period: 5,12 years. The most frequent complications included caries in the furcation area after tunnelling procedures and root fractures after root-resective procedures. Conclusions: Good long-term survival rates (up to 100%) of multirooted teeth with furcation involvement were obtained following various therapeutic approaches. Initial furcation involvement (Degree I) could be successfully managed by non-surgical mechanical debridement. Vertical root fractures and endodontic failures were the most frequent complications observed following resective procedures. [source]

The effectiveness of antipsychotic medication in the management of behaviour problems in adults with intellectual disabilities

JOURNAL OF INTELLECTUAL DISABILITY RESEARCH, Issue 10 2007
S. Deb
Abstract Background Psychopharmacological intervention in the management of behaviour problems in adults with intellectual disabilities (ID) has become a common treatment strategy. This has become a cause for concern, given that the evidence for its effectiveness is uncertain and most drugs are not licensed for this use. Methods A comprehensive systematic review of empirical research on the effectiveness of antipsychotic medication was conducted. Electronic and manual searches of literature were conducted. Stringent scientific methodology determined those primary trials that were worthy of inclusion. Results This review revealed one randomized controlled trial (RCT), one controlled, four uncontrolled prospective and three retrospective case series studies in adults. Additionally, two studies in both adults and children , one crossover RCT and one prospective controlled trial , were found. Conclusion Presently, there is RCT-based evidence for risperidone to be effective in both adults and children; however, this treatment carries a certain amount of risk associated with adverse effects. There is also evidence to support the use of other antipsychotics, primarily atypicals, but the evidence is based on noncontrolled case studies. There is currently not enough evidence available to recommend specific medication for specific behaviour problems. Before prescribing medication, clinicians should carry out a thorough assessment of behaviour, including its causes and consequences, and draw up a formulation providing the rationale for the prescribed intervention after considering all medication- and nonmedication-based management options. [source]

Meta-analysis: isosorbide-mononitrate alone or with either beta-blockers or endoscopic therapy for the management of oesophageal varices

ALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 7 2010
L. L. Gluud
Aliment Pharmacol Ther 2010; 32: 859,871 Summary Background, The evidence concerning the use of isosorbide-mononitrate (IsMn) for oesophageal varices is equivocal. Aim, To assess the effects of IsMn for patients with oesophageal varices and no previous bleeding (primary prevention) or previous variceal bleeding (secondary prevention). Methods, Systematic review with meta-analyses of randomized trials on IsMn alone or with beta-blockers or endoscopic therapy for oesophageal varices. Electronic and manual searches were combined. Randomized trials on primary and secondary prevention were included. The primary outcome measure was mortality. Intention-to-treat random effects meta-analyses were performed. The robustness of the results was assessed in trial sequential analyses. Results, Ten randomized trials on primary and 17 on secondary prevention were included. Evidence of bias was identified. No apparent effect of IsMn on mortality compared with placebo or beta-blockers or IsMn plus beta-blockers vs. beta-blockers was identified. Compared with endoscopic therapy, IsMn plus beta-blockers had no apparent effect on bleeding, but did seem to reduce mortality in secondary prevention (RR 0.73, 95% CI 0.59,0.89), but not in primary prevention. The effect of IsMn plus beta-blockers on mortality in secondary prevention was not confirmed in trial sequential analysis. Conclusions, Isosorbide-mononitrate used alone or in combination with beta blockers does not seem to offer any reduction in bleeding in the primary or secondary prevention of oesophageal varices. Compared with endoscopic therapy, there may be a survival advantage in using IsMn and beta-blockers, but additional large multicentre trials are needed to verify this finding. [source]

Systematic review: the short-term and long-term efficacy of adalimumab following discontinuation of infliximab

ALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 10 2009
C. MA
Summary Background, Therapy with adalimumab has been shown to be effective in Crohn's disease (CD) patients who have lost response or are intolerant to infliximab. Aim, To determine the efficacy of adalimumab in CD patients who discontinued infliximab through a systematic review. Methods, Electronic searches of EMBASE and MEDLINE databases up to May 1, 2009, as well as abstracts from the AGA (2006,2008), ACG (2006,2007), UEGW (2006,2008) and CDDW (2006,2009) identified randomized-controlled trials (RCT) or open-labelled cohorts (OLC) evaluating the short-term and/or long-term efficacy of adalimumab in infliximab failures. The response rates for short-term (clinical response and remission at 4 weeks) and long-term (remission at 6 and 12 months) efficacy were considered. Results, A total of 1810 CD patients were identified among the 15 studies (2 RCT and 13 OLC). The majority of studies evaluated CD patients who either lost response or were intolerable to infliximab, although five OLCs permitted patients refractory to infliximab. Short-term clinical response (n = 9 articles) ranged from 41% to 83%. Long-term clinical remission at 12 months (n = 8 articles) ranged from 19% to 68%. The occurrence of severe adverse events ranged from 0% to 19% and four patients died. Conclusions, Current RCT and OLC evidence suggest that adalimumab is an efficacious therapy for CD patients who discontinue infliximab. [source]

Systematic review and meta-analysis: is 1-week proton pump inhibitor-based triple therapy sufficient to heal peptic ulcer?

ALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 7 2005
J. P. Gisbert
Summary Aims :,To systematically review the efficacy on ulcer healing of 1-week combination of a proton pump inhibitor plus two antibiotics and to perform a meta-analysis of randomized clinical trials to evaluate whether 7 days of proton pump inhibitor-based triple therapy is sufficient to heal peptic ulcer. Methods :,Studies where 1-week proton pump inhibitor-based triple therapy was administered to heal peptic ulcer were included. Randomized clinical trials comparing the efficacy on ulcer healing of 7-day proton pump inhibitor-based triple therapy versus this same regimen but prolonging the proton pump inhibitor for several more weeks were included in the meta-analysis. Electronic and manual bibliographical searches were conducted. Meta-analysis was performed combining the odds ratios of the individual studies. Results :,Twenty-four studies (2342 patients) assessed ulcer healing with 1-week proton pump inhibitor-based triple therapy. Mean healing rate was 86%, and 95% in Helicobacter pylori -eradicated patients. Six studies (862 patients), were included in the meta-analysis. Mean ulcer healing rate with a 7-day treatment was 91% versus 92% when proton pump inhibitor was prolonged for 2,4 more weeks (odds ratio = 1.11; 95% confidence interval = 0.71,1.74). Conclusion :,In patients with peptic ulcer and H. pylori infection, prolonging therapy with proton pump inhibitor after a triple therapy for 7 days with a proton pump inhibitor and two antibiotics is not necessary to induce ulcer healing. [source]

Electronic and atomic relaxation processes in irradiated cryocrystals

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 2 2005
E. V. Savchenko
Abstract Relaxation processes and stability of charge centers in preirradiated cryocrystals doped with atomic and molecular species are discussed. The study was performed combining techniques of spectrally resolved thermally stimulated luminescence (TSL), thermally stimulated exoelectron emission (TSEE) and photon-stimulated exoelectron emission (PSEE). Comparison of the yields of electrons and photons in VUV and visible ranges made it possible to discriminate between reactions of charge carriers and neutral reactive species and find interconnection between atomic and electronic processes of relaxation. The radiative mechanism of electronic relaxation stimulation via an atomic subsystem is verified. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Electronic and transport properties of Dy2Co7B3 compound

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2003
A. Kowalczyk
Abstract New results of the electronic and transport properties (electrical resistivity) of Dy2Co7B3 compound are reported. This alloy crystallizes in the hexagonal Ce2Co7B3 type of structure. The electronic structure has been studied by the X-ray photoemission spectroscopy (XPS). The valence band of the XPS spectra is determined mainly by the Co(3d) and Dy(4f) bands. The peaks positions are in good agreement with binding energies of a metallic dysprosium and cobalt. The resistivity at low temperatures shows a T2 dependence. At higher temperatures the resistivity is no linear function of temperature, which indicates an electron-phonon interaction in the presence of a small s-d scattering. [source]

Electronic and structural properties of strontium chalcogenides SrS, SrSe and SrTe

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 11 2004
D. Rached
Abstract We present the results of a first-principles study of the electronic and structural properties of strontium chalcogenides, SrS, SrSe and SrTe. The computational method is based on the full-potential linear muffin-tin orbitals method (FP-LMTO) augmented by a plane-wave basis (PLW). The exchange and correlation energy is described in the local density approximation (LDA) using the Perdew,Wang parameterization including a generalized gradient approximation (GGA). The calculated results of the structural properties are given for the NaCl (B1) and CsCl (B2) structures. We have also carried out band-structure calculations for the three considered compound, but only for the NaCl (B1) structure. A reasonable agreement is found from the comparison of our results with other theoretical calculations and experimental data. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Financial Market Design and the Equity Premium: Electronic versus Floor Trading

THE JOURNAL OF FINANCE, Issue 6 2005
PANKAJ K. JAIN
ABSTRACT We assemble the announcement and actual introduction dates of electronic trading by the leading exchanges of 120 countries to examine the impact of automation, controlling for risk factors and economic conditions. Dividend growth models and international CAPM suggest a significant decline in the equity premium, especially in emerging markets. Consistent with this reduction in the equity premium in the long run, there is a positive short-term price reaction to the switch. Further analysis of trading turnover supports the notion that electronic trading enhances the liquidity and informativeness of stock markets, leading to a reduction in the cost of capital. [source]

R&D Intensity and Acquisitions in High-Technology Industries: Evidence from the US Electronic and Electrical Equipment Industries

THE JOURNAL OF INDUSTRIAL ECONOMICS, Issue 1 2000
Bruce A. Blonigen
Theory suggests R&D intensity and acquisition activity may be either directly or inversely related. However, we know relatively little about which firms are responsible for acquisition activity in high-technology industries, which are not only R&D-intensive, but also have substantial acquisition activity in the United States. Using a panel of 217 US electronic and electrical equipment firms from 1985,93 and limited dependent variable estimation techniques, we find a substantial negative correlation between R&D-intensity and a firm's propensity to acquire. This result is surprisingly robust to numerous sensitivity tests and is significant in both the ,within' and ,between' dimensions of our data. [source]

Tuning Electronic and Steric Effects: Highly Enantioselective [4+1] Pyrroline Annulation of Sulfur Ylides with ,,,-Unsaturated Imines,

ANGEWANDTE CHEMIE, Issue 26 2010
Liang-Qiu Lu
Sterische und elektronische Effekte: Mithilfe einer neuartigen [4+1]-Cycloaddition von atropisomeren Schwefel-Yliden 1 und ungesättigten Iminen 2 gelingt die Synthese enantiomerenangereicherter Pyrroline 3 in hohen Ausbeuten. Die beobachteten hohen Stereoselektivitäten wurden anhand einer Konformationsanalyse der Ylide erklärt. [source]

Electronic structure calculations for inhomogeneous systems: Interfaces, surfaces, and nanocontacts

ANNALEN DER PHYSIK, Issue 8 2008
U. Schwingenschlögl
Abstract The article gives an introduction into the application of density functional theory (DFT) to inhomogeneous systems. To begin with, we describe the interplay of specific materials at interfaces, resulting in structure relaxation and modifications of the chemical bonding. We address interfaces between YBa2Cu3O7 and a normal metal, in order to quantify the intrinsic interface charge transfer into the superconductor. Moreover, we study the internal interfaces in a V6O13 battery cathode and the effects of ion incorporation during the charging and discharging process. The second part of the article deals with the influence of surfaces on the nearby electronic states. Here, we investigate a LaAlO3/SrTiO3 heterostructure in a thin film geometry. We particularly explain the experimental dependence of the electronic states at the heterointerface on the surface layer thickness. Afterwards, surface relaxations are studied for both the clean Ge(001) surface and for self-assembled Pt nanowires on Ge(001). In the third part, we turn to atomic and molecular contacts. We compare the properties of prototypical Al nanocontact geometries, aiming at insight into the chemical bonding and the occupation of the atomic orbitals. Finally, the local electronic structure of a benzene-1,4-dithiol molecule between two Au electrodes is discussed as an example for a molecular bridge. [source]

Electronic structure and transport properties of quantum dots

ANNALEN DER PHYSIK, Issue 5 2004
M. Tews
Abstract The subject of this paper are electronic properties of isolated quantum dots as well as transport properties of quantum dots coupled to two electronic reservoirs. Thereby special focus is put on the effects of Coulomb interaction and possible correlations in the quantum dot states. First, the regime of sequential tunneling to the reservoirs is investigated. It is shown that in case degenerate states participate in transport, the resonance positions in the differential conductance generally depend on temperature and the degree of degeneracy. This effect can be used to directly probe degeneracies in a quantum dot spectrum. A further effect, characteristic for sequential tunneling events, is the complete blocking of individual channels for transport. A generalisation of the well known spin blockade is found for correlated dot states transitions through which are not directly spin-forbidden. In the second part, the electronic structure of spherical quantum dots is calculated. In order to account for correlation effects, the few-particle Schrödinger equation is solved by an exact diagonalization procedure. The calculated electronic structure compares to experimental findings obtained on colloidal semiconductor nanocrystals by Scanning Tunneling Spectroscopy. It is found that the electric field induced by the tunneling tip is gives rise to a Stark effect which can break the spherical symmetry of the electronic ground state density which is in agreement with wave-function mapping experiments. The symmetry breaking depends on the competition between exchange energy and the Stark energy. Moreover, a systematic dependence on particle number is found for the excitation energies of optical transitions which explains recent experimental findings on self-organized quantum dots. In the last part, co-tunneling in the Coulomb blockade regime is studied. For this end the tunneling current is calculated up to the forth order perturbation theory in the tunnel coupling by a real-time Green's function approach for the non-equilibrium case. The differential conductance calculated for a quantum dot containing up to two interacting electrons shows complex signatures of the excitation spectrum which are explained by a combination of co-tunneling and sequential tunneling processes. Thereby the calculations show a peak structure within the Coulomb blockade regime which has also been observed in experiment. [source]

Review of singleton fetal and neonatal deaths associated with cranial trauma and cephalic delivery during a national intrapartum-related confidential enquiry

BJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 5 2005
Fidelma O'Mahony
Objective To review delivery details of intrapartum-related fetal and neonatal deaths with singleton cephalic presentation and birthweight of 2500 g or more in which traumatic cranial or cervical spine injury or substantial difficulty at delivery of the head was a dominant feature. Design Review of freestyle summary reports and standard questionnaire responses submitted to the national secretariat for the Confidential Enquiry into Stillbirths and Death in Infancy (CESDI) during the 1994/1995 intrapartum-related mortality enquiry following regional multidisciplinary panel review. Setting United Kingdom. Sample Of the 873 cases of intrapartum-related deaths reported in the 1994,1995 national enquiry, 709 weighed more than 2499 g. Reports from 181 (89 from 1994 and 92 from 1995) with a chance of meeting criteria for cranial or cervical trauma as significant contributors to death were examined in detail. Thirty-seven were judged to meet the criteria stated in the objectives (23 from 1994 and 14 from 1995) and form the basis for this review. Methods Electronic and hand search of CESDI records relating to intrapartum-related deaths. Main outcome measures Intrapartum events and features of care. Results There was evidence of fetal compromise present before birth in 33 of the 37 (89%) study group cases reviewed. One delivery was performed vaginally without instrumentation, and in one there was no attempt at vaginal delivery before caesarean section (CS) in the second stage of labour. Twenty-four cases (65%) were delivered vaginally and 11 (30%) by CS after failure to deliver vaginally with instruments. A single instrument was used in six cases of vaginal delivery (four ventouse and two Kjelland's forceps). At least two separate attempts with different instruments were made in 24 cases. Overall, the ventouse was used in 27 cases and forceps in 29 cases. In six cases, three separate attempts were made with at least two different instruments, all of which included use of ventouse. The grade of operator was recorded in 27 cases. Of these, a consultant obstetrician was present at only one delivery and no consultant was recorded to have made the first attempt to deliver a baby. In six cases, shoulder dystocia was also reported. Conclusions This study suggests a lower incidence of death from difficult cephalic delivery and cranial trauma than previously reported. The CESDI studies were believed to have achieved high levels of ascertainment for all intrapartum-related deaths from which the cases reported here were selected. Strictly applied entry criteria used in this study could have restricted the number of cases considered as could limited in vivo or postmortem investigations and lack of detailed autopsy. When cranial traumatic injury was observed, it was almost always associated with physical difficulty at delivery and the use of instruments. The use of ventouse as the primary or only instrument did not prevent this outcome. Some injuries occurred apparently without evidence of unreasonable force, but poorly judged persistence with attempts at vaginal delivery in the presence of failure to progress or signs of fetal compromise were the main contributory factor regardless of which instruments were used. [source]

ChemInform Abstract: Probing the Electronic and Structural Properties of the Niobium Trimer Cluster and Its Mono- and Dioxides: Nb3On - and Nb3On (n = 0,2)

CHEMINFORM, Issue 29 2009
Hua-Jin Zhai
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: Chemical Bonding and Electronic and Magnetic Structure in LaOFeAs.

CHEMINFORM, Issue 15 2009
Jacek C. Wojdel
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]