bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental and theoretical studies on corals. I. Toward understanding the origin of color in precious red corals from Raman and IR spectroscopies and DFT calculations
Authors: Kupka Teobald , Lin Hong Ming , Stobiński Leszek , Chen Cheng‐Han , Liou Wei‐Jen , Wrzalik Roman , Flisak Zygmunt
Published: October 2009

An attempt to explain the origin of the vivid red color in precious pink and red corals was undertaken. Raman and IR spectroscopies were applied to characterize white, pink and red corals. The position of the Raman signal near 1500 cm−1 of some corals and pearls was associated by several authors with the presence of the mixture of all‐trans‐polyenic pigments, containing 6–16 conjugated CC bonds or β‐carotenoids. This hypothesis was examined theoretically by performing extensive B3LYP‐DFT calculations of vibrational spectra of the model polyenic compounds. The B3LYP/6‐311++G** predicted positions of the dominating Raman mode depend on the number of CC units (Cn parameter) and can be accurately predicted for larger systems from a simple nonlinear fit. The DFT‐predicted Raman activities of these modes are extremely sensitive to Cn, and sharply increase with the number of double bonds. This implies a presence of only—two to three polyenes differing slightly in the number of CC units as the source of color in pink and red corals. Copyright © 2009 John Wiley & Sons, Ltd.
Convenient Preparation of Biodegradable PEI‐Containing Polymers as Non‐Viral Vectors for Gene Transfection
Authors: Huang Fu‐Wei , Feng Jun , Nie Jun , Cheng Si‐Xue , Zhang Xian‐Zheng , Zhuo Ren‐Xi
Published: October 2009

Poly(L‐succinimide)‐graft‐polyethylenimines (PSPs) were prepared as non‐viral vectors for gene transfection. Branched polyethylenimine ($\overline M _{\rm w} $ = 800, PEI800) was grafted to poly(L‐succinimide) (PSI) in a one‐step reaction with no catalyst. Gel retardation assay showed that the mobility of PSP/pDNA complexes was completely retarded at the low N/P ratio of 0.42. In vitro transfection experiments showed that, at N/P ratio of 0.84, PSPs can reach the highest transfection level with ten‐fold enhancement in 293T cells and five‐fold enhancement in HeLa cells as compared with PEI25k ($\overline M _{\rm w} $ = 25 000). Fluorescent confocal microscopy showed that pGL‐3 plasmids condensed by PSPs could be effectively transported into the nuclei of HeLa cells. Significantly reduced cytotoxicity of polymers was observed towards 293T and HeLa cells, with the 50% inhibition concentration of PSPs being almost four times higher than that of PEI25k.

magnified image
Biodegradable Polymeric Microcarriers with Controllable Porous Structure for Tissue Engineering
Authors: Shi Xudong , Sun Lei , Jiang Jian , Zhang Xiaolin , Ding Wenjun , Gan Zhihua
Published: October 2009

Porous microspheres fabricated by biodegradable polymers show great potential as microcarriers for cell cultivation in tissue engineering. Herein biodegradable poly(DL‐lactide) (PLA) was used to fabricate porous microspheres through a modified double emulsion solvent evaporation method. The influence of fabrication parameters, such as the stirring speed of the primary and secondary emulsion, the polymer concentration of the oil phase, and solvent type, as well as the post‐hydrolysis treatment of the porous structure of the PLA microspheres are discussed. Good attachment and an active spread of MG‐63 cells on the microspheres is observed, which indicates that the PLA microspheres with controllable porous structure are of great potential as cell delivery carriers for tissue engineering.

magnified image
NMR and conformational studies of new 5‐phenylpyrrole‐carboxamide derivatives
Authors: López‐Cara Luisa C. , de las Infantas M. José Pineda , Carrión M. Dora , Camacho M. Encarnación , Gallo Miguel A. , Espinosa Antonio , Entrena Antonio
Published: October 2009

The 1H and 13C NMR resonances of 22 5‐(5‐substituted‐2‐nitrophenyl)‐1H‐pyrrole‐2‐carboxamides, 22 5‐(5‐substituted‐2‐aminophenyl)‐1H‐pyrrole‐2‐carboxamides, and 9 5‐phenyl‐1H‐pyrrole‐2‐carboxamides were assigned completely using the concerted application of one‐ and two‐dimensional experiments (DEPT, gs‐HMQC and gs‐HMBC). NOE studies and conformational analysis confirm the preferred conformations of such compounds. Copyright © 2009 John Wiley & Sons, Ltd.
Kidney injury molecule‐1 in renal disease
Authors: Waanders Femke , van Timmeren Mirjan M , Stegeman Coen A , Bakker Stephan JL , van Goor Harry
Published: October 2009

Kidney injury molecule‐1 (KIM‐1) is a marker for renal proximal tubular damage, the hallmark of virtually all proteinuric, toxic and ischaemic kidney diseases. KIM‐1 has gained increasing interest because of its possible pathophysiological role in modulating tubular damage and repair. In this respect, it is interesting that the best biomarkers often turn out to be important in modulation of damage and some even become therapeutic targets. The emphasis of this review is on structural and biochemical aspects of KIM‐1, its expression pattern and its pathophysiological role in renal disease. We also discuss the prognostic impact of KIM‐1 in relation to urinary protein excretion. Glomerular (proteinuria) and interstitial markers (KIM‐1) might have independent prognostic impact and so may provide independent treatment targets. Finally, the potential of KIM‐1 as biomarker of renal damage, as a predictor of renal function decline and its perspectives for monitoring therapy response, are discussed. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Gefitinib in combination with oral topotecan and cyclophosphamide in relapsed neuroblastoma: Pharmacological rationale and clinical response
Authors: Donfrancesco Alberto , De Ioris Maria Antonietta , McDowell Heather Prudence , De Pasquale Maria Debora , Ilari Ilaria , Jenkner Alessandro , Castellano Aurora , Cialfi Samantha , De Laurentis Clementina , Dominici Carlo
Published: October 2009

Aim

Activity and toxiciy of gefitinib in combination with topotecan and cyclophosphamide (CPA) were evaluated in a case‐series of relapsed neuroblastoma (NB) patients. The in vitro activity of the combination was also assessed.

Procedure

Gefitinib (250 mg/day), topotecan (0.8 mg/m2/day), and CPA (50 mg/m2/day) (GTC) were administered orally for 14 consecutive days out of 28 days. Antitumor activity of gefitinib as single agent and in combination with either topotecan or CPA was assessed in a panel of NB cell lines.

Results

Ninety‐two courses were given in 10 patients. Grade 4 neutropenia was observed in 7/92 courses (8%) and grade 4 thrombocytopenia in 8/92 (9%). Two patients had a grade 2 liver toxicity, four a grade 1/2 skin toxicity, and two a grade 1/2 diarrhea. Dose reduction of topotecan and/or CPA was required in eight patients. After four courses, three patients were in partial response (PR) and four with a stable disease (SD), while three experienced a progressive disease (PD). Time to progression (TTP) was 9 months (range, 1–27). After a median follow‐up of 16 months (range 5–54), seven patients are died of disease (DOD) and three alive with disease (AWD). All but one patient discontinued oral chemotherapy because of a PD, whilst one patient stopped chemotherapy after 27 months with a SD. In vitro, gefitinib was synergistic with topotecan and additive with CPA.

Conclusion

The GTC combination was well tolerated and the TTP was encouraging. These promising results, also supported by in vitro evidence, should be further confirmed in a phase II study. Pediatr Blood Cancer 2010; 54:55–61. © 2009 Wiley‐Liss, Inc.
Ionic equilibrium in mixtures of protophobic and protophilic polar non‐hydrogen bond donor solvents: acids, salts, and indicators in acetone containing 5 mol% DMSO
Authors: Mchedlov‐Petrossyan Nikolay O. , Filatov Dmitriy Yu. , Goga Sergey T. , Lebed Alexander V.
Published: October 2009

Properties of a protophobic polar non‐HBD solvent can be strongly modified by introduction of a small amount of a protophilic polar non‐HBD solvent. In this paper, acetone (AC) with 5 mol% additive of DMSO, a solvent with $\varepsilon _{\rm r}^{{\rm 25}} = 22$, was considered as a media for acid–base reactions. Conductance was used for determination of dissociation constants of a set of salts, hydrogen chloride, and picric acid. The last‐named was also studied by UV‐vis spectroscopy. The introduction of 5 mol% of DMSO results in suppressing, to some extent, the homoconjugation processes in AC media as well as of proton hydration by (possible) traces of water. The dissociation of salicylic acid and 2,4‐dinitrophenol was examined utilizing quinhydrone electrodes in a cell with liquid junction. The pKa values of buffer acids and ${\rm p}a_{{\rm H}^ + }^* $ values of buffer solutions were calculated by taking into account the incomplete dissociation of salts. The response of the glass electrode appeared to be satisfactory, which allowed the estimation of the pKa value of benzoic acid. The apparent ionization constants of 22 acid–base indicators in buffer mixtures and perchloric acid solutions were determined in (AC + 5 mol% DMSO) using the spectrophotometric procedure. Copyright © 2009 John Wiley & Sons, Ltd.
Aspects of Plasma in Water: Streamer Physics and Applications
Authors: Joshi Ravindra P. , Kolb Juergen F. , Xiao Shu , Schoenbach Karl H.
Published: October 2009

Physical mechanisms for streamer initiation and electrical breakdown in water are discussed. The focus is on various processes that could lead to the inception and propagation of streamers in water. Physical details associated with observed disparities in breakdown at the anode versus the cathode, differences in luminosity, and variations in streamer propagation speeds are discussed. Creation of a localized low‐density region near the site of a field enhancement is shown to be essential for streamer initiation. Finally, the use of a trigatron‐type electrically triggered switch with a triple‐point geometry is shown to be a low‐cost, compact alternative to laser (or acoustic) switching. Such controlled breakdown could be used for various applications including water purification and bio‐decontamination.

magnified image
Selective floating gate non‐volatile paper memory transistor
Authors: Martins Rodrigo , Barquinha P. , Pereira L. , Correia N. , Gonçalves G. , Ferreira I. , Fortunato E.
Published: October 2009

Here we report the performance of a selective floating gate (VGS) n‐type non‐volatile memory paper field‐effect transistor. The paper dielectric exhibits a spontaneous polarization of about 1 mCm–2 and GIZO and IZO amorphous oxides are used respectively as the channel and the gate layers. The drain and source regions are based in continuous conductive thin films that promote the integration of fibres coated with the active semiconductor. The floating memory transistor writes, reads and erases the stored information with retention times above 14500 h, and is selective (for VGS > 5 ± 0.1 V). That is, to erase stored information a symmetric pulse to the one used to write must be utilized, allowing to store in the same space different information. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multivariate process monitoring of an experimental blast furnace
Authors: Vanhatalo Erik
Published: October 2009

Process monitoring by use of multivariate projection methods has received increasing attention as it can reduce the monitoring problem for richly instrumented industrial processes with many correlated variables. This article discusses the monitoring and control of a continuously operating experimental blast furnace (EBF). A case study outlines the need for monitoring and control of the EBF and the use of principal components (PCs) to monitor the thermal state of the process. The case study addresses design, testing and online application of PC models for process monitoring. The results show how the monitoring problem can be reduced to following just a few PCs instead of many original variables. The case study highlights the problem of multivariate monitoring of a process with frequently shifting operating modes and process drifts and stresses the choice of a good reference data set of ‘normal’ process behavior. Possible solutions for adaptations of the multivariate models to process changes are also discussed. Copyright © 2009 John Wiley & Sons, Ltd.
Mitochondria and diabetes mellitus: untangling a conflictive relationship?
Authors: Schiff M. , Loublier S. , Coulibaly A. , Bénit P. , Ogier de Baulny H. , Rustin P.
Published: October 2009

Diabetes mellitus is occasionally observed in patients with skeletal muscle respiratory chain deficiency, suggesting that skeletal muscle mitochondrial dysfunction might play a pathogenic role in type 2 diabetes (T2D). In support of this hypothesis, decreased muscle mitochondrial activity has been reported in T2D patients and in mouse models of diabetes. However, recent work by several groups suggests that decreased muscle mitochondrial function may be a consequence rather than a cause of diabetes, since decreased mitochondrial function in mice affords protection from diabetes and obesity. We review the data on this controversial but important issue of potential links between mitochondrial dysfunction and diabetes.
Development and implementation of a novel assay for l‐2‐hydroxyglutarate dehydrogenase (l‐2‐HGDH) in cell lysates: l‐2‐HGDH deficiency in 15 patients with l‐2‐hydroxyglutaric aciduria
Authors: Kranendijk M. , Salomons G. S. , Gibson K. M. , Aktuglu‐Zeybek C. , Bekri S. , Christensen E. , Clarke J. , Hahn A. , Korman S. H. , Mejaski‐Bosnjak V. , Superti‐Furga A. , Vianey‐Saban C. , van der Knaap M. S. , Jakobs C. , Struys E. A.
Published: October 2009

l‐2‐hydroxyglutaric aciduria (l‐2‐HGA) is a rare inherited autosomal recessive neurometabolic disorder caused by mutations in the gene encoding l‐2‐hydroxyglutarate dehydrogenase. An assay to evaluate l‐2‐hydroxyglutarate dehydrogenase (l‐2‐HGDH) activity in fibroblast, lymphoblast and/or lymphocyte lysates has hitherto been unavailable. We developed an l‐2‐HGDH enzyme assay in cell lysates based on the conversion of stable‐isotope‐labelled l‐2‐hydroxyglutarate to 2‐ketoglutarate, which is converted into l‐glutamate in situ. The formation of stable isotope labelled l‐glutamate is therefore a direct measure of l‐2‐HGDH activity, and this product is detected by liquid chromatography‐tandem mass spectrometry. A deficiency of l‐2‐HGDH activity was detected in cell lysates from 15 out of 15 l‐2‐HGA patients. Therefore, this specific assay confirmed the diagnosis unambiguously affirming the relationship between molecular and biochemical observations. Residual activity was detected in cells derived from one l‐2‐HGA patient. The l‐2‐HGDH assay will be valuable for examining in vitro riboflavin/FAD therapy to rescue l‐2‐HGDH activity.
Simple Determination of Deoxycholic and Ursodeoxycholic Acids by Phenolphthalein‐β‐Cyclodextrin Inclusion Complex
Authors: Cadena Pabyton G. , Oliveira Eric C. , Araújo Alberto N. , Montenegro Maria C. B. S. M. , Pimentel Maria C. B. , Lima Filho José L. , Silva Valdinete L.
Published: October 2009

An expeditious colorimetric methodology for the determination of the deoxycholic acid (DCA) and of the ursodeoxycholic acid (UDCA) in pharmaceutical formulations is reported. The method is based on their competitive complexation reaction with a color indicator to form β‐cyclodextrin‐inclusion complexes. Several pH color indicators were tested, but phenolphthalein (PHP) showed the best interaction with the β‐cyclodextrin (β‐CD) with an inclusion yield higher than 95%. The best concentrations of β‐cyclodextrin to form inclusion complexes were 1.24 × 10−3 and 6.2 × 10−4 M at pH 9.5 and 10.5. Statistical analysis of the results showed that the pH had a significant effect on the DCA determination and that high β‐CD‐PHP inclusion complex concentrations had a significant negative effect on the UDCA determination (p < 0.05). The limit of detection and limit of quantification were 3.94 × 10−5 and 1.31 × 10−4 M for DCA (range: 6.1 × 10−6–3.13 × 10−3 M), 4.08 × 10−5 and 1.36 × 10−4 M for UDCA (range: 6.05 × 10−6–3.88 × 10−4 M). This simple and cheap method showed high stability and feasible instrumentation.
Impact of F-18 Fluorodeoxyglucose Positron Emission Tomography–Computed Tomography on Oncologic Patient Management: First 2 Years' Experience at a Single Canadian Cancer Center
Authors: Worsley Daniel F. , Wilson Don C. , Powe John E. , Benard Francois
Published: October 2009

Purpose

The purpose of this study was to assess the influence of positron emission tomography–computed tomography (PET-CT) results on patient management from a single Canadian oncology center during its first 2 years of operation.

Methods

A total of 3,779 consecutive patients, 18 years of age and older, who were referred for PET-CT imaging at the British Columbia Cancer Agency between July 1, 2005 and June 30, 2007, were included in this analysis. Results were tabulated from a standard questionnaire, which was given to referring physicians following completion of their patient's PET-CT study.

Results

From July 1, 2005 to June 30, 2007, 3,779 consecutive fluoro-2-deoxyglucose PET-CT examinations were performed in patients aged 18 years or older. A total of 3,429 referring-physician surveys (90.7%) were returned. The results of the PET-CT study resulted in a change in treatment decision in 49.8% of the studies and resulted in improved decision making in 83.2% of the studies.

Conclusion

This series demonstrated that the results from PET-CT studies performed at a single Canadian oncology center during the first 2 years of its operation altered patient management in 50% of cases and resulted in improved decision making in the majority of cases.
Topoisomerase IIα‐dependent induction of a persistent DNA damage response in response to transient etoposide exposure
Authors: Soubeyrand Sébastien , Pope Louise , Haché Robert J.G.
Published: October 2009

Cytotoxicity of the topoisomerase II (topoII) poison etoposide has been ascribed to the persistent covalent trapping of topoII in DNA cleavage complexes that become lethal as cells replicate their DNA. However, short term etoposide treatment also leads to subsequent cell death, suggesting that the lesions that lead to cytotoxicity arise rapidly and prior to the onset DNA replication. In the present study 1h treatment with 25μM etoposide was highly toxic and initiated a double‐stranded DNA damage response as reflected by the recruitment of ATM, MDC1 and DNA‐PKcs to γH2AX foci. While most DNA breaks were rapidly repaired upon withdrawal of the etoposide treatment, the repair machinery remained engaged in foci for at least 24h following withdrawal. TopoII siRNA ablation showed the etoposide toxicity and γH2AX response to correlate with the inability of the cell to correct topoIIα‐initiated DNA damage. γH2AX induction was resistant to the inhibition of DNA replication and transcription, but was increased by pre‐treatment with the histone deacetylase inhibitor trichostatin A. These results link the lethality of etoposide to the generation of persistent topoIIα‐dependent DNA defects within topologically open chromatin domains.
Unbewusste Wahrnehmung
Authors: Kiesel Andrea
Published: October 2009

Zusammenfassung. Die Wirkungsweise unbewusster Reize wird unter anderem mit der Methode des subliminalen Primings untersucht. Subliminal präsentierte Prime-Reize beeinflussen die Verarbeitung eines Targets, wenn ihre Verarbeitung intendiert ist und diese Reize im Experimentalkontext erwartet werden können. Zur Erklärung dieser Befunde haben wir existierende Konzepte zur Handlungsvorbereitung weiterentwickelt. Das Erklärungskonzept der handlungsdeterminierenden Reizerwartungen postuliert einen zweistufigen Prozess für Vorbereitung und Ausführung intendierter Handlungen. Zunächst werden handlungsdeterminierende Reizerwartungen spezifiziert entsprechend der aktuell instruierten Aufgabe bzw. des erlebten Aufgabenkontextes. Als zweiter Prozess findet ein Abgleich des tatsächlichen Reizes mit den Reizerwartungen statt. Stimmt der Reiz mit den handlungsdeterminierenden Reizerwartungen überein, wird die entsprechende Reaktion automatisch aktiviert. Dieser Ansatz kann viele Befunde zum subliminalem Priming erklären, die bisher widersprüchlich erschienen. Er ist nicht nur auf übliche Experimentalkontexte mit Zweifachwahlreaktionen anwendbar, sondern gilt auch für Aufgabenkontexte mit mehrfachen Handlungsbereitschaften und für die freie Wahl zwischen zwei Handlungsalternativen. Ob das Erklärungskonzept der handlungsdeterminierenden Reizerwartungen ausreicht, um alle Arten des subliminalen Primings zu erklären ist unklar. Hier ist weitere Forschung notwendig um zu klären ob und gegebenenfalls unter welchen Bedingungen unbewusste Reize komplexere Verarbeitungsprozesse, wie semantische Verarbeitung oder exekutive Kontrollprozesse beeinflussen.
Tuning the emission profiles of various self-assembled InxGa1−xAs nanostructures by rapid thermal annealing
Authors: Lee Jihoon H. , Wang Zhiming M. , Dorogan Vitaliy G. , Mazur Yuiry I. , Ware Morgan E. , Salamo Gregory J.
Published: October 2009

Tuning the emission profiles of various novel InxGa1−xAs nanostructures, such as quantum rods, quantum dot pairs (QDPs), bridged QDPs, dimpled quantum dots (QDs), and low-temperature-capped QDs, is demonstrated by postgrowth rapid thermal annealing. Specifically, improved optical properties, such as a much narrower full width at half maximum of 16 meV and a continuous blueshift, are demonstrated. The enhanced optical properties are attributed to the interchange of In and Ga atoms induced by both defect-assisted intermixing and strain-assisted intermixing. These results can find applications as an optical enhancement in nanostructures is critical for the improvements on device functionality.
Magnetic resonance in FexMn1−xS single crystals
Authors: Vorotynov A. M. , Abramova G. M. , Popov M. A. , Petrakovskii G. A. , Bovina A. F. , Sokolov V. V. , Mita E.
Published: October 2009

The results of the experimental study and computer simulation of the resonance spectra of a single crystal of the iron-manganese sulfide FexMn1−xS (0≤x≤0.29) are presented. The resonance properties of the concentrated solid solutions are explained by the formation of a homogeneous FexMn1−xS matrix with randomly distributed superparamagnetic iron nanoparticles. The mean diameter (⟨D⟩=6.19 nm at T=250 K) and the axial first-order anisotropy constant (К1=4.08 erg/cm3 at T=250 K) of the ferromagnetic particles are determined. The volume fraction of the iron phase is estimated.
Electron drift velocity in lattice-matched AlInN/AlN/GaN channel at high electric fields
Authors: Ardaravičius L. , Ramonas M. , Liberis J. , Kiprijanovič O. , Matulionis A. , Xie J. , Wu M. , Leach J. H. , Morkoç H.
Published: October 2009

Hot-electron transport was probed by nanosecond-pulsed measurements for a nominally undoped two-dimensional channel confined in a nearly lattice-matched Al0.82In0.18N/AlN/GaN structure at room temperature. The electric field was applied parallel to the interface, the pulsed technique enabled minimization of Joule heating. No current saturation was reached at fields up to 180 kV/cm. The effect of the channel length on the current is considered. The electron drift velocity is deduced under the assumption of uniform electric field and field-independent electron density. The highest estimated drift velocity reaches ∼3.2×107 cm/s when the AlN spacer thickness is 1 nm. At high fields, a weak (if any) dependence of the drift velocity on the spacer thickness is found in the range from 1 to 2 nm. The measured drift velocity is low for heterostructures with thinner spacers (0.3 nm).
Ablation and structural changes induced in InP surfaces by single 10 fs laser pulses in air
Authors: Bonse J. , Rosenfeld A. , Grebing C. , Steinmeyer G. , Mailman N. , Botton G. A. , Haugen H. K.
Published: October 2009

Ablation of single-crystalline (100) indium phosphide wafer surfaces with single 10 fs Ti:sapphire laser pulses in air has been studied by means of complementary cross-sectional transmission electron microscopy, scanning force microscopy, and optical microscopy. A local protrusion of ∼70 nm height is generated within the ablation craters for fluences exceeding 0.78 J/cm2. This morphological feature has been studied in detail, revealing the material structure of the laser-affected zone and its spatial extent. The resolidified layer (60–200 nm thick) consists of polycrystalline grains (5–15 nm diameter) and is covered by an ∼10 nm thick amorphous top layer. Interestingly, the sharp boundary of the solidified layer to the unaffected crystal underneath exhibits a Gaussian-like shape and does not follow the shape of the surface topography. Evidence is presented that the central crater protrusion is formed by near-surface optical breakdown, and that the absorption in the material transiently changes during the femtosecond-laser pulse.
Effects of pressure on the electronic and structural properties of LaOFeAs
Authors: Yang Yong , Hu Xiao
Published: October 2009

We studied the pressure effects on the electronic and structural properties of LaOFeAs by first-principles calculations. For the antiferromagnetic (AFM) phase with stripelike aligned Fe spins, the electronic density of states at the Fermi level [N(EF)] slightly descends first with increasing applied pressure, then bounces up with further increasing pressure (or decreasing volume), and reaches its maximum at ∼29.2 GPa with the volume ∼80% of the ambient pressure value (V0). Similar behavior is expected in the physical quantities that are proportional to N(EF), such as the electronic specific heat and the Pauli paramagnetic susceptibility. At this volume (V=0.8V0), the LaOFeAs crystal undergoes a structural phase transition from the orthorhombic structure to the tetragonal one, which is accompanied by the disappearance of the long-ranged AFM order.
Betatron x-ray generation from electrons accelerated in a plasma cavity in the presence of laser fields
Authors: Thomas A. G. R. , Krushelnick K.
Published: October 2009

X-ray generation by many charged particles experiencing accelerations similar to those in laser wakefield accelerator experiments, including the effects of the interaction of the laser pulse with trapped electrons, as well as betatron oscillations in an electron cavity, is directly evaluated. Semianalytic calculations of high energy photons are performed by solving classical spectral integrals for x rays produced by the combined action of a laser pulse and the fields of an electron cavity in an underdense plasma. Angularly resolved power spectra for electron bunches accelerated in the combined electromagnetic fields due to a Gaussian laser field and a paraboloid potential due to an electron cavity are calculated using a semianalytic numerical algorithm to explicitly calculate the well known spectral integrals. The laser polarizes the resulting x-ray radiation. In addition to the high energy photons due to the betatron oscillations, lower energy radiation is emitted in a conical emission pattern due to the coherent addition of radiation from the linear acceleration of the electrons in the wakefield.
The fractional Schrödinger operator and Toeplitz matrices
Authors: Hatzinikitas Agapitos
Published: October 2009

Confining a quantum particle in a compact subinterval of the real line with Dirichlet boundary conditions, we identify the connection of the one-dimensional fractional Schödinger operator with the truncated Toeplitz matrices. We determine the asymptotic behavior of the product of eigenvalues for the α-stable symmetric laws by employing the Szegö’s strong limit theorem. The results of the present work can be applied to a recently proposed model for a particle hopping on a bounded interval in one dimension whose hopping probability is given a discrete representation of the fractional Laplacian.
Low-temperature magnetic property of polymer encapsulated gold nanoparticles
Authors: Mallick Kaushik , Witcomb Michael , Erasmus Rudolph , Strydom André
Published: October 2009

Gold-polyaniline composite is reported by the polymerization of aniline hydrochloride monomer using HAuCl4 as the oxidant. HAuCl4 was dissolved in toluene using a phase-transfer catalyst, Aliquat 336. The oxidative polymerization of aniline hydrochloride leads to the formation of polyaniline with a diameter of <50 nm, while the reduction in auric acid results in the formation of gold nanoparticles with an average diameter ∼4 nm. The resultant composite material was characterized by means of different techniques, such as UV-vis, IR, and Raman spectroscopies, which offered the information about the chemical structure of polymer, whereas electron microscopy images provided information regarding the morphology of the composite material and the distribution of the metal particles in the polymer matrix. dc-magnetization measurements down to low temperatures (2 K) enabled the identification of a small, but field-independent paramagnetic behavior of the composite, and this is argued to originate from the charge transfer between the gold 5d-electron shell and the organic matrix. We believe that this material holds promise for both electronic and magnetic applications through suitable concentration levels of the metallic dopant.
Metal-induced dopant (boron and phosphorus) activation process in amorphous germanium for monolithic three-dimensional integration
Authors: Park Jin-Hong , Tada Munehiro , Jung Woo-Shik , Wong H.-S. Philip , Saraswat Krishna C.
Published: October 2009

In this work, we investigate a low temperature boron (B) and phosphorus (P) activation in amorphous (α)-Ge using metal-induced crystallization technique. Eight candidates of metals (Pd, Cu, Ni, Au, Co, Al, Pt, and Ti) are used to crystallize the α-Ge at a low temperature. Resistivity measurement, transmission electron microscopy, and x-ray diffraction analyses reveal behaviors of the metal-induced dopant activation process using the metals reacting with α-Ge. It is revealed that Co achieves the highest B and P activation ratio in Ge below 360 °C with a slow diffusion rate. This method can be utilized to activate gate, source, and drain of transistors on upper layers in three-dimensional integrated circuits, where low temperature processing is critical.
Thermal cycling induced reversibility/irreversibility in the ac electrical properties of La0.50Ca0.50MnO3+δ by impedance spectroscopy
Authors: Nadeem M. , Mushtaq A.
Published: October 2009

In this work, we address the issue of microstructural changes in the electrical properties of charge ordered polycrystalline La0.50Ca0.50MnO3+δ sample during thermal cycling through impedance spectroscopy. The modulations of relaxation time with temperatures and different thermal cycling shows different magnitudes of impedance plane plots. Thermal cycling induces varying mechanical and electrical stresses in the grains and in the grain boundaries, changing the resistance of the grains (R1) and the grain boundaries (R2) by changing the boundary potentials and trap state scattering cross sections. At metal-insulator transition temperature (MIT), R1 increases with polynomial first order and R2 increases with polynomial second order. The values of R1 and R2 show different orders of variations along with reversible and irreversible behaviors around and below MIT. We report a method by virtue of which charge ordering temperature TCO has been determined with the change in the magnitude of grain boundary resistance by thermal cycling. Localization of charge carriers in the traps with thermal cycling around MIT and delocalization of charge carriers with different frequencies have been discussed.
Unusual two-dimensional electrical charge transport at the surface of polycrystalline perovskite ultrathin films
Authors: Ngamou Patrick Herve Tchoua , Kohse-Höinghaus Katharina , Bahlawane Naoufal
Published: October 2009

The discontinuity of the lattice at the surface leads to an inherent presence of dangling bonds and atomic coordinations that differ from that of the bulk. As a consequence of this effect, we report on a two-dimensional confinement of the charge transport at the surface of polycrystalline perovskite oxide. Studying the surface transport separately from the bulk effect was approached by the investigation of ultrathin and stress-free LaCoO3 films that are grown on amorphous and nonconducting substrates using pulsed-spray evaporation chemical vapor deposition. The electrical characterization demonstrates an intriguing surface localization of the charge carriers. This surface trapping, which is observed above room temperature, dominates the electrical transport up to a temperature that depends on the film thickness, e.g., up to 440 K for 8-nm-thick films. This high-temperature effect, which is attributed to the surface adsorption of oxygen, points at a largely ignored surface effect in the study of thin and ultrathin films of transition metal oxides. Desorbing surface oxygen was experimentally shown to disrupt the two-dimensional confinement of the charge transport.
Ferroelectric properties of ruthenium-doped lead zinc niobate-lead titanate single crystal
Authors: Scholz T. , Mihailova B. , Schneider G. A. , Pagels N. , Heck J. , Malcherek T. , Fernandes R. P. , Marinova V. , Gospodinov M. , Bismayer U.
Published: October 2009

Using atomic force microscopy and piezoresponse force microscopy (PFM), as well as complementary dielectric measurements, the ferroelectric domain structure of single crystals of pure and ruthenium (Ru)-doped 0.9Pb(Zn1/3Nb2/3)O3 (PZN)-0.1PbTiO3 (PT), and Ru/(Zn+Nb+Ti)∼0.002 was analyzed. The coexistence of tetragonal and nontetragonal ferroelectric domains in PZN-PT near the morphotropic phase boundary (MPB) was directly observed via PFM imaging. The incorporation of Ru in the perovskite structure substantially decreases the ferroelectric domain size, thus reducing the polar fraction distributed in the pseudocubic matrix. The polarization and strain hysteresis loops show that Ru doping leads to significant ferroelectric hardening, which is attractive for high-power applications. The local structure and valent state of the incorporated Ru cations were additionally analyzed by electron paramagnetic resonance spectroscopy. Our results demonstrate that doping of tetragonal PZN-PT near MPB is a promising route to design advanced multifunctional single-crystal materials.
Complete sets of elastic constants and photoelastic coefficients of pure and MgO-doped lithium niobate crystals at room temperature
Authors: Andrushchak A. S. , Mytsyk B. G. , Laba H. P. , Yurkevych O. V. , Solskii I. M. , Kityk A. V. , Sahraoui B.
Published: October 2009

This paper presents the results of ultrasonic measurements of LiNbO3 and LiNbO3:MgO crystals. The tensors of piezoelectric coefficients, elastic stiffness constants, and elastic compliances are determined for both crystals at room temperature. Combining these data with the results of piezo-optical measurements, a complete set of photoelastic tensor coefficients is also calculated. Doping of LiNbO3 crystals by MgO does not lead to a considerable modification of their elastic and photoelastic properties. However, LiNbO3:MgO is characterized by a considerably higher resistance with respect to powerful light radiation, making it promising for future application in acousto-optic devices that deal with superpowerful laser radiation. Presented here are the complete tensor sets of elastic constants and photoelastic coefficients of LiNbO3 and LiNbO3:MgO crystals that may be used for a geometry optimization of acousto-optical interaction providing the best diffraction efficiency of acousto-optical cells made of these materials.
Obtaining the dielectric constant of solids from capacitance measurements with a pointer electrode
Authors: Guadarrama-Santana A. , García-Valenzuela A.
Published: October 2009

We analyze the determination of the dielectric constant of macroscopic solid samples in a nondestructive way from measurements of the capacitance between a pointer electrode and the sample’s surface. We assembled an experimental device and found that an accuracy of 1% or better can be attained with common laboratory instrumentation.
Atomically flat SrO-terminated SrTiO3(001) substrate
Authors: Bachelet R. , Sánchez F. , Palomares F. J. , Ocal C. , Fontcuberta J.
Published: October 2009

We show that atomically flat single SrO-terminated SrTiO3(001) substrates can be obtained through simple high-temperature treatment. Amplitude-modulation atomic force microscopy with phase-lag analysis and x-ray photoelectron spectroscopy, have been used to demonstrate that the ratio between the two chemical terminations can be tailored by choosing the annealing time. Moreover, the progressive SrO surface enrichment (up to 100%) is accompanied by a self-assembly process which results in the spatial separation at the nanoscale of both chemical terminations. We further demonstrate that this opens a interesting avenue for selective chemical reaction and growth of oxide nanostructures.
The effect of temperature on resonator characteristics of a Si nanocrystal planar microcavity
Authors: Seo Se-Young , Kim Kyung Joong
Published: October 2009

The effect of temperature on the resonator characteristics of a Si nanocrystal (Si-nc) planar microcavity was investigated. A microcavity comprises of an active Si-nc layer sandwiched between Si∕SiO2 distributed Bragg reflectors (DBRs). Typical microcavity results such as spectral narrowing and a luminescence decay rate enhancement of Si-nc luminescence can be observed. Temperature-dependent photoluminescence (PL) and the time-resolved PL of the microcavity were measured and analyzed with the model, while taking the thermal effect on the DBRs into account. We found that the thermo-optic effect of the Si layer on the DBRs plays a predominant role in determining temperature-dependent cavity performances such as resonance wavelengths, Q factors, and spontaneous emission times.
Quasi-thermal noise in space plasma: “kappa” distributions
Authors: Le Chat G. , Issautier K. , Meyer-Vernet N. , Zouganelis I. , Maksimovic M. , Moncuquet M.
Published: October 2009

The transport of energy in collisionless plasmas, especially in space plasmas, is far from being understood. Measuring the temperature of the electrons and their nonthermal properties can give important clues to understand the transport properties. Quasi-thermal noise (QTN) spectroscopy is a reliable tool for measuring accurately the electron density and temperature since it is less sensitive to the spacecraft perturbations than particle detectors. This work models the plasma QTN using a generalized Lorentzian (“kappa”) distribution function for the electrons. This noise is produced by the quasi-thermal fluctuations of the electrons and by the Doppler-shifted thermal fluctuations of the ions. A sum of two Maxwellian functions has mainly been used for modeling the QTN of the electrons, but the observations have shown that the electrons are better fitted by a kappa distribution function. Pioneer work on QTN calculation only considered integer values of κ. This paper extends these calculations to real values of κ and gives the analytic expressions and numerical calculations of the QTN with a kappa distribution function. This paper shows some generic properties and gives some practical consequences for plasma wave measurements in space.
Modulation of propagation characteristics of spin waves induced by perpendicular electric currents
Authors: Xing X. J. , Yu Y. P. , Li S. W.
Published: October 2009

We have theoretically and numerically investigated the effect of perpendicular currents on the propagation characteristics of spin waves on a wire composing the free layer of a spin valve. Our theory shows that the single Slonczewski’s spin-transfer torque can cause the spin-wave Doppler effect and modify the spin-wave attenuation and that the fieldlike torque makes negligible contribution due to its relatively small magnitude. Micromagnetic simulations confirm these theoretical predictions and further reveal that spin waves at suprathreshold currents are instable and become chaotic with increased time. Finally, selective tuning of the spin-wave attenuation is demonstrated by using local, individual currents.
Highly efficient tris(8-hydroxyquinoline) aluminum-based organic light-emitting diodes utilized by balanced energy transfer with cosensitizing fluorescent dyes
Authors: Park Young Wook , Kim Young Min , Choi Jin Hwan , Park Tae Hyun , Huh Jin Woo , Kim Hong Suk , Cho Min Ju , Choi Dong Hoon , Ju Byeong-Kwon
Published: October 2009

We report on the development of highly efficient organic light-emitting diodes (OLEDs) utilized by balancing the energy transfer between multiple dopants, that is, multiple emissions from the multiple dopants were realized by balanced distributed energy transfer. From the cosensitizing fluorescent OLEDs, the peak external quantum efficiency (EQE) of 4.8% at 130 cd/m2 is demonstrated, which realized theoretical limits of ∼5.0% and means that nearly 100% of the singlet excitons are radiative. Also, the optimized device accompanying thickness-modulated electron transport layer for the enhanced light outcoupling demonstrated the highly improved peak EQE and current efficiency of 6.7%, and 23.4 cd/A.
Electronic structure at the perylene-tetracarboxylic acid dianhydride/Ag(111) interface studied with two-photon photoelectron spectroscopy
Authors: Sachs Sönke , Schwalb Christian H. , Marks Manuel , Schöll Achim , Reinert Friedrich , Umbach Eberhard , Höfer Ulrich
Published: October 2009

The electronic structure of the prototype metal/organic contact 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) on a Ag(111)-surface has been investigated using time- and angle-resolved two-photon photoelectron spectroscopy (2PPE). Our analysis addresses particularly the nature of the interface state (IS) emerging at the interface due to the substrate-adsorbate interaction [C. H. Schwalb, S. Sachs, M. Marks et al., Phys. Rev. Lett. 101, 146801 (2008)]. Its free-electron-like dispersion and a possible backfolding at the surface Brillouin zone boundaries are discussed. Time-resolved pump-probe experiments reveal the inelastic electron lifetime along the dispersion parabola and show its decrease for increasing parallel momentum. The temperature dependence of the peak linewidth indicates a coupling of the IS to molecular vibrations. Moreover, additional aspects are addressed, such as the determination of the electron attenuation length of photoelectrons for low kinetic energy originating from the IS and the work function change of the sample upon PTCDA adsorption with very high energy resolution.
Phase separation of two-component Bose–Einstein condensates
Authors: Liu Zuhan
Published: October 2009

Recently, coupled systems of nonlinear Schrödinger equations have been used extensively to describe mixtures Bose–Einstein condensates. In this paper, we study the distribution of two different hyperfine spin states of a binary mixture of three dimensional Bose–Einstein condensates. In a double condensate, an interface may occur due to large intraspecies and interspecies scattering lengths. We prove that there is an asymptotic separation of different phases in the strong coupling (Thomas–Fermi) limit.
Remote plasma treatment of Si surfaces: Enhanced nucleation in low-temperature chemical vapor deposition
Authors: Kumar Navneet , Yanguas-Gil Angel , Daly Scott R. , Girolami Gregory S. , Abelson John R.
Published: October 2009

The nucleation density on Si(100):H is increased by two orders of magnitude after exposing the surface to a remote argon plasma. We study HfB2 growth from Hf(BH4)4 and MgO growth from Mg(DMDBA)2 plus H2O. In the latter case, pretreatment allows the growth of MgO films with an rms roughness below 0.5 nm, whereas in absence of plasma treatment no nucleation is observed. The plasma does not damage the substrate and is compatible with microelectronics technology. We propose that H desorption is the key mechanism leading to nucleation enhancement, and that remote plasma activation is likely to be generally applicable.
Unusual transport behavior of the SrTiO3-based homojunctions
Authors: Lü W. M. , Sun J. R. , Wang J. , Shen B. G.
Published: October 2009

Two homojunctions composed of La0.15Sr0.85TiO3 films and SrTiO3:Nb substrates have been fabricated in the oxygen atmospheres of 10 and 20 Pa, respectively, and their transport behaviors are studied in the temperature range from 10 to 350 K. The most remarkable observations are the temperature independence of the current-voltage relations as well as the temperature/bias independence of the capacitance in the low temperature region in the junction obtained in an oxygen pressure of 10 Pa, and the exponential growth of current with reverse voltage. The rectifying behaviors can be well described by the Shockley equation at high temperatures, and the interfacial barrier, deduced from the current-voltage characteristics, are ∼1.35 and ∼0.73 eV, decreasing with oxygen pressure. The experiment results can be understood by assuming the formation of an insulating interfacial layer in the junctions.
The quantum normal form approach to reactive scattering: The cumulative reaction probability for collinear exchange reactions
Authors: Goussev Arseni , Schubert Roman , Waalkens Holger , Wiggins Stephen
Published: October 2009

The quantum normal form approach to quantum transition state theory is used to compute the cumulative reaction probability for collinear exchange reactions. It is shown that for heavy-atom systems such as the nitrogen-exchange reaction, the quantum normal form approach gives excellent results and has major computational benefits over full reactive scattering approaches. For light atom systems such as the hydrogen-exchange reaction however, the quantum normal approach is shown to give only poor results. This failure is attributed to the importance of tunneling trajectories in light atom reactions that are not captured by the quantum normal form as indicated by the only very slow convergence of the quantum normal form for such systems.
Physical and chemical transformations of sodium cyanide at high pressures
Authors: Chen Jing-Yin , Yoo Choong-Shik
Published: October 2009

Pressure-induced physical and chemical transformations of sodium cyanide (NaCN) have been studied up to 50 GPa in diamond-anvil cells, using micro-Raman spectroscopy and angle-resolved synchrotron x-ray diffraction. We observe three phase transitions in this pressure range: NaCN-IIA (orthorhombic, Immm), to NaCN-IIB (orthorhombic, Pmmn) at 4 GPa, to NaCN-III (monoclinic, Cm) at 8 GPa, and to NaCN-IV (tetragonal, P4mm) at 15 GPa, which is stable to 25 GPa. At higher pressures, NaCN-IV undergoes an irreversible chemical change, which occurs over a large pressure range between 25 and 34 GPa. The new material exhibits a broad yet strong Raman band at around 1550 cm−1, indicating the formation of C=N bonds in a similar configuration of carbon graphite. The absence of sharp diffraction lines in this material suggests an amorphous nature of CN polymer products.
Ab initio molecular dynamics study of supercritical carbon dioxide including dispersion corrections
Authors: Balasubramanian Sundaram , Kohlmeyer Axel , Klein Michael L.
Published: October 2009

Density functional theory based ab initio molecular dynamics simulations with explicit inclusion of empirical van der Waals (vdW) corrections of supercritical carbon dioxide have been performed. Significant changes in the intermolecular pair correlation functions of the fluid modeled with the added vdW interactions are observed, particularly at lower densities. The closest neighbor to a molecule is seen to be oriented in a distorted T-shaped geometry, consistent with earlier experiments and simulations.