bluuebunny/crossref_metadata_2025 huggingface dataset:
Stem Cell Microenvironments ‐ Unveiling the Secret of How Stem Cell Fate is Defined
Authors: Votteler Miriam , Kluger Petra J. , Walles Heike , Schenke‐Layland Katja
Published: August 2010

Stem cells are defined as unspecialized cells that are capable of long term self‐renewal and differentiation into specialized cell types. These unique properties make them an attractive cell source for regenerative medicine applications. Although the functions of various stem cells have been extensively studied in the development of organisms and in diseases, the specific factors and conditions that control stem cell fate, specifically the conditions that allow them to remain unspecialized, are not well studied. It has been suggested that adult stem cell survival and maintenance, as well as proliferation and differentiation, are controlled by the three‐dimensional (3D) microenvironment, the so‐called niche. Major functional niche components include supporting niche cells, growth‐modulating soluble factors stored within the niches, and the extracellular matrix (ECM). In this article, we review work highlighting the growing complexity of stem cell‐ECM interactions and their impact on the fields of biomaterials research and regenerative medicine.

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The Use of Fibrous, Supramolecular Membranes and Human Tubular Cells for Renal Epithelial Tissue Engineering: Towards a Suitable Membrane for a Bioartificial Kidney
Authors: Dankers Patricia Y. W. , Boomker Jasper M. , der Vlag Ali Huizinga‐van , Smedts Frank M. M. , Harmsen Martin C. , van Luyn Marja J. A.
Published: August 2010

A bioartificial kidney, which is composed of a membrane cartridge with renal epithelial cells, can substitute important kidney functions in patients with renal failure. A particular challenge is the maintenance of monolayer integrity and specialized renal epithelial cell functions ex vivo. We hypothesized that this can be improved by electro‐spun, supramolecular polymer membranes which show clear benefits in ease of processability. We found that after 7 d, in comparison to conventional microporous membranes, renal tubular cells cultured on top of our fibrous supramolecular membranes formed polarized monolayers, which is prerequisite for a well‐functioning bioartificial kidney. In future, these supramolecular membranes allow for incorporation of peptides that may increase cell function even further.

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Effects of alloying elements, microstructure, and inclusions on hydrogen induced cracking of X120 pipeline steel in wet H2S sour environment
Authors: Huang F. , Li X. G. , Liu J. , Qu Y. M. , Du C. W.
Published: August 2010

Hydrogen induced cracking (HIC) behavior of X120 pipeline steel with different amounts of Mn and Al was investigated using NACE standard TM0284‐2005 and back‐scattered electron imaging (BSE). The results demonstrated that inclusions and microstructure play significant roles in HIC susceptibility in X120 steels. The more the area and volume fraction of inclusions in the steel, the more the steel is susceptible to HIC. Three types of inclusions exist in the tested X120 steel and they play different roles in cracking. The critical size resulting in HIC cracks for pure MnS inclusions or mixed inclusions (inclusion clusters mainly composed of two or three different phases and compounds) of Mn/Al ratio >1 is smaller than that of pure Al2O3 inclusions or mixed inclusions of Mn/Al ratio <1. No HIC crack was observed at inclusions enriched in Si. The microstructure containing lath bainite and martensite/austenite (M/A) microconstituents is more susceptible to HIC than that with granular bainite and ferrite.
Preparation of Crosslinked Poly(2‐bromoethyl methacrylate) Microspheres and Decoration of Their Surfaces with Functional Polymer Brushes
Authors: Karagoz Bunyamin , Gunes Deniz , Bicak Niyazi
Published: August 2010

Synthesis and crosslinking copolymerization of 2‐bromoethylmethacrylate in aqueous suspension is described for preparing bromoalkyl‐functional microbeads (125–420 µm). Highly transparent microspheres with a density of accessible bromoethyl groups of 1.55 mmol · g−1 were prepared in the suspension, stabilized with poly(N‐vinyl pyrrolidone), by using methyl methacrylate as diluting co‐monomer and ethylene glycol dimethacrylate as crosslinker. Bromoalkyl groups on the microparticles were employed as initiation sites for either surface‐initiated ATRP of glycidyl methacrylate or ring‐opening polymerization of 2‐methyl‐2‐oxazoline to generate epoxy‐ and N‐acetylethyleneimine‐functional hairy grafts, tethered to the particle surfaces with hydrolytically stable linkages.

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Reconstruction of Achiral Polymer for Structural Chirality Using Cholesteric Liquid Crystal Medium and Light‐Driven Chiroptic Modulation
Authors: Goto Hiromasa , Ohta Reina
Published: August 2010

A series of optically inactive polythiophene derivatives bearing the azobenzene moiety are synthesized in an isotropic toluene solution. The polymers are then dissolved in a cholesteric liquid crystal (Ch*LC) medium within the liquid crystal (LC) temperature range. The dissolution process in Ch*LC produces intermolecular π‐stacking with structural chirality. Although the polymers thus prepared have no chiral center or axial chirality in the primary structure, they do exhibit consistent chiroptical activity derived from three‐dimensional chiral aggregations. Furthermore, photochemical cis–trans isomerization of the substituents allows light‐driven chiroptic modulation of the polymer.

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Synthesis of Well‐Defined Statistical and Diblock Copolymers of Acrylamide and Acrylic Acid by Inverse Miniemulsion Raft Polymerization
Authors: Ouyang Liu , Wang Lianshi , Schork F. Joseph
Published: August 2010

Well‐defined statistical and diblock copolymers with acrylamide and acrylic acid were synthesized by inverse miniemulsion RAFT polymerization. Statistical copolymers with various composition ratios were synthesized. Compositional drift was observed during polymerization. Acrylamide was polymerized with a water‐soluble initiator (VA‐044) at 60 °C to give the RAFT‐agent‐containing acrylamide homopolymer with a narrow molecular‐weight distribution (PDI < 1.3), which was then chain‐extended with acrylic acid to obtain the diblock copolymer.

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A New Dithienylbenzotriazole‐Based Poly(2,7‐carbazole) for Efficient Photovoltaics
Authors: Peng Bo , Najari Ahmed , Liu Bo , Berrouard Philippe , Gendron David , He Yuehui , Zhou Kechao , Zou Yingping , Leclerc Mario
Published: August 2010

A new dithienyl benzotriazole‐based conjugated polymer was synthesized by Suzuki coupling reaction. The polymer was found to be soluble in common organic solvents, such as chloroform, tetrahydrofuran and chlorobenzene, with excellent film‐forming properties. The structure of the polymer was confirmed by 1H NMR, the molecular weights determined by GPC and the thermal properties investigated by TGA and DSC. The polymer films exhibited an absorption band in the wavelength range 300 to 610 nm. Preliminary photovoltaic cells based on the composite structure of indium tin oxide (ITO)/PEDOT:PSS/PCDTBTz:PC60BM (1:2 w/w)/Al showed an open‐circuit voltage of 0.92 V, a power conversion efficiency of 2.2% and a short circuit current of 5.33 mA cm−2.

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Mesophase Tractable Metallopolymers Based on a Metal Carboxylate Backbone Prepared by Drastic Solid‐to‐Solid Transformation within Solvothermal Synthesis
Authors: Choi Eun‐Young , Lee Hong‐Jun , Gao Chunji , Kwon O‐Pil , Lee Suck‐Hyun
Published: August 2010

A series of layer‐structured zinc‐containing metallopolymers were prepared through a solvothermal reaction of zinc acetate with 1,4‐benzene dicarboxylic acid derivatives bearing various nonpolar n‐alkyl groups as side chains. The resulting metallopolymers were investigated. The reaction time and the length of the alkyl substituents on the backbone have a marked effect on the mesophase structure and thermal behaviors of the metallopolymers. The metallopolymer with tetradecyloxy side chains prepared by solid‐to‐solid transformations within solvothermal synthesis exhibits a unique mesophasic behavior with melt tractability.

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Surface Modification of PVC Membranes Using Fluorothiophenol Compounds
Authors: Corrales Marta , Bierbrauer Karina , Sacristan Javier , Mijangos Carmen
Published: August 2010

The controlled chemical surface modification of PVC films by means of three fluoride aromatic compounds, 4‐fluoro thiophenol, 3,4‐difluorothiophenol and penta fluorothiophenol is reported. To obtain information about the surface selectivity of the reactions, the degree of modification of the polymer across the film was determined by depth profiling carried out using confocal Raman microscopy. It is shown that the gradient of the modification degree and the surface selectivity depend on the relationship between the rate constants of the substitution reaction and the diffusion process of the reactant. Therefore it is function of reaction time, temperature and the proportion of solvent/non‐solvent used for the reaction.

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Impact Modification of Polylactide with a Biodegradable Ethylene/Acrylate Copolymer
Authors: Afrifah Kojo A. , Matuana Laurent M.
Published: August 2010

The effectiveness and efficiency of an ethylene/acrylate copolymer in toughening semicrystalline and amorphous PLA through melt blending is studied. The mechanical properties, phase morphologies, miscibilities, and toughening mechanisms of the blends are assessed. The ethylene/acrylate impact modifier effectively improved the impact strength of the blends, regardless of the PLA type. The semicrystalline blends showed decreased tensile strength and modulus with increased impact modifier content. In contrast, the ductility, elongation at break, and energy to break increased significantly. The relatively low BDT temperature obtained for the PLA blends renders the ethylene/acrylate copolymer impact modifier a desirable additive to toughen PLA for use in cold temperatures.

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Block Copolymer Directed Nanoporous Metal Thin Films
Authors: Arora Hitesh , Li Zihui , Sai Hiroaki , Kamperman Marleen , Warren Scott C. , Wiesner Ulrich
Published: August 2010

Porous metal thin films have high potential for use in applications such as catalysis, electrical contacts, plasmonics, as well as energy storage and conversion. Structuring metal thin films on the nanoscale to generate high surface areas poses an interesting challenge as metals have high surface energy. In this communication, we demonstrate direct access to nanostructured metal nanoparticle hybrid thin films with high nanoparticle loadings through spin coating of a mixture of block copolymer and ligand stabilized platinum and palladium nanoparticles. Plasma cleaning to remove the organics results in a conductive metal thin film. We expect that the methods described here can be generalized to other metals, mixtures of metal nanoparticles, and intermetallics.

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Crystalline/Crystalline Phase Transitions in Polymer Systems Consisting of Finite‐Size Crystals in Each Crystalline Phase: Generalized Gibbs‐Thomson Equation
Authors: Hirami Matsuo
Published: August 2010

For polymer systems of two crystalline phases of one polymer component, each phase being consisted of polymer crystals of a finite size, we derive the crystalline‐crystalline phase transition relationship, i.e., generalized Gibbs‐Thomson equation. Its application combined with the crystalline‐liquid transition relationship (usual Gibbs‐Thomson equation) to the phase behavior of PT phase diagram of polyethylene (PE) is investigated, where the orthorhombic‐hexagonal phase transition of PE crystal under high pressure being involved. Comparison with experimental data leads to the estimates of the structural characteristics such as the ratios of (the end surface free energy of polymer crystal/crystal length) for the respective crystalline phases.

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Dietary calcium decreases plasma cholesterol by down‐regulation of intestinal Niemann–Pick C1 like 1 and microsomal triacylglycerol transport protein and up‐regulation of CYP7A1 and ABCG 5/8 in hamsters
Authors: Ma Ka Ying , Yang Nan , Jiao Rui , Peng Cheng , Guan Lei , Huang Yu , Chen Zhen‐Yu
Published: August 2010

Scope: It has been shown that calcium supplementation favorably modifies plasma lipoprotein profile in postmenopausal women. The present study investigated the interaction of dietary calcium with genes of transporters, receptors and enzymes involved in cholesterol metabolism.

Methods and results: Forty‐eight ovariectomized hamsters were fed one of the four diets containing 0, 2, 6 and 8 g calcium per kg. Plasma total cholesterol (TC), triacylglycerols (TG), and non‐high density lipoprotein cholesterol were dose‐dependently decreased, whereas high‐density lipoprotein cholesterol (HDL‐C) was dose‐dependently increased with the increasing dietary calcium levels. Dietary calcium had no effect on protein mass of hepatic sterol regulatory element binding protein‐2 (SREBP), liver X receptor‐alpha (LXR), 3‐hydroxy‐3‐methylglutaryl‐CoA reductase (HMGR), LDL receptor (LDLR) and cholesterol‐7α‐hydroxylase (CYP7A1). However, dietary calcium up‐regulated the mRNA levels of hepatic CYP7A1 and intestinal ATP binding cassette transporters (ABCG5/8) whereas it down‐regulated the intestinal Niemann‐Pick C1 like 1 (NPC1L1) and microsomal triacylglycerol transport protein (MTP). In addition, dietary calcium increased the activity of intestinal acyl coenzyme A: cholesterol acyltransferase 2, while it decreased plasma cholesteryl ester transport protein (CETP).

Conclusion: Beneficial modification of lipoprotein profile by dietary calcium was mediated by sequestering bile acid absorption and enhancing excretion of fecal cholesterol, via up‐regulation of mRNA CYP7A1 and intestinal ABCG 5/8 with down‐regulation of mRNA NPC1L1 and MTP.
High‐field continuous arterial spin labeling with long labeling duration: Reduced confounds from blood transit time and postlabeling delay
Authors: Lu Hanbing , Leoni Renata , Silva Afonso C. , Stein Elliot A. , Yang Yihong
Published: August 2010

In quantitative perfusion imaging using arterial spin labeling, variable blood transit times and postlabeling delays are two confounding factors that may compromise the accuracy of perfusion quantifications. In this study, theoretical analyses and experimental data at 9.4 T demonstrate that increasing labeling duration not only enhances the contrast of the arterial spin labeling signal but also minimizes the effect of variable postlabeling delays in multislice arterial spin labeling acquisitions. With a labeling duration of 6.4 sec, arterial spin labeling signal acquired in multislice mode (11 slices) is very similar to that acquired in single‐slice mode. Previous studies have shown that inserting a delay between the spin labeling pulse and the image acquisition pulse could reduce confounds resulting from variable blood transit times at the expense of arterial spin labeling sensitivity. Our simulations suggest that enhancing the contrast of arterial spin labeling signal offers the opportunity for extending the postlabeling delay to a longer duration, minimizing systematic errors associated with a wide range of blood transit times, which could have significant implications for applying arterial spin labeling techniques to perfusion imaging of pathological conditions in animal models. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Prenatal diagnosis and follow‐up of 23 cases of cardiac tumors
Authors: Niewiadomska‐Jarosik Katarzyna , Stańczyk Jerzy , Janiak Katarzyna , Jarosik Piotr , Moll Jacek Jan , Zamojska Justyna , Respondek‐Liberska Maria
Published: August 2010

Objective

To evaluate the prenatal characteristics and postnatal outcome of cardiac tumors diagnosed at two prenatal Polish cardiology centers.

Methods

Descriptive analysis of 23 fetuses with cardiac tumors (12 multiple and 11 single) diagnosed over 16 years (from 1993 to 2009). Congestive heart failure was diagnosed when the cardiovascular profile score was seven or less.

Results

Associated structural congenital heart defects were present in three fetuses, extracardiac anomalies in three, and chromosomal anomalies in two. Congestive heart failure developed in five cases. Perinatal survival was not different between cases with and without cardiac failure (2/5 vs 12/18, p = 0.28). The main ultrasonographic signs observed prenatally in association with cardiac tumors were cardiomegaly, left ventricular outflow tract obstruction, pericardial effusion, and hypokinesis. A diagnosis of tuberous sclerosis was eventually made in all 12 fetuses with multiple tumors. Perinatal death occurred in 4/11 cases with single tumors and in 5/12 with multiple tumors (p = 0.57). Surgical resection of the tumor was performed in 3/11 neonates with single tumors (histopathologically: rhabdomyoma, teratoma, and fibroma) and in 2/12 with multiple tumors (both rhabdomyomas).

Conclusions

Survival is not different between neonates with single and multiple tumors and between those with and without congestive heart failure. Copyright © 2010 John Wiley & Sons, Ltd.
Prevalence of steroid sulfatase deficiency in California according to race and ethnicity
Authors: Craig Wendy Y. , Roberson Marie , Palomaki Glenn E. , Shackleton Cedric H. L. , Marcos Josep , Haddow James E.
Published: August 2010

Objective

Estimate steroid sulfatase deficiency (STSD) prevalence among California's racial/ethnic groups using data from a previous study focused on prenatal detection of Smith‐Lemli‐Opitz syndrome (SLOS). SLOS and STSD both have low maternal serum unconjugated estriol (uE3) levels.

Methods

Prevalence was estimated using three steps: listing clinically identified cases; modeling STSD frequency at three uE3 intervals using diagnostic urine steroid measurements; applying this model to determine frequency in pregnancies not providing urine.

Results

Overall, 2151 of 777 088 pregnancies (0.28%) were screen positive; 1379 of these were explained and excluded. Fifty‐four cases were diagnosed clinically among 707 remaining pregnancies with a male fetus. Urine steroid testing identified 74 additional STSD cases: 66 (89.2%) at uE3 values < 0.15 MoM, 8 (10.8%) at 0.15–0.20 MoM, and 0 (0%) at > 0.20 MoM. Modeling estimated 107.5 STSD cases among 370 pregnancies without urine samples. In males, STSD prevalence was highest among non‐Hispanic Whites (1:1230) compared to Hispanics (1:1620) and Asians (1:1790), but differences were not significant. No STSD pregnancies were found among 65 screen positive Black women.

Conclusion

The overall prevalence estimate of 1:1500 males is consistent with published estimates and is reasonable for counseling, except among Black pregnancies where no reliable estimate could be made. Copyright © 2010 John Wiley & Sons, Ltd.
Diabetes centres: adapting to change
Authors: Shaw K , Feher M
Published: August 2010

The evolution of diabetes centres in the UK, with co‐location of clinical teams, has resulted in examples of success in improving clinical efficiency, communication and patient‐centred care.
Survey of diabetes centres 2009
Authors: Hawthorne G , Gosden C
Published: August 2010

In the 1990s the development of diabetes centres was regarded as one of the major advances in diabetes care. With today's emphasis on service redesign and reconfiguration, this survey set out to explore the role of diabetes centres in the 21st century.

The survey found that a minimum standard for the term ‘diabetes centre’ needs to be defined and that out of hours support/access for people with diabetes was limited. Diabetes centres supported high quality multidisciplinary team working and this was facilitated by the team being co‐located. Many of the medical consultants had dual roles with acute trusts that included responsibilities for acute medicine, so easy access to acute trusts facilitated effective use of medical time. The future key role for diabetes centres is to be the hub for integration of diabetes services and actively support primary and community diabetes care. Copyright © 2010 John Wiley & Sons.
Hyperglycaemia as a result of stress and possible drug interactions: a case report
Authors: Puttanna A , Cunningham AR , Scanlon JEM
Published: August 2010

We report the case of a six‐year‐old male paediatric patient diagnosed with type 1 diabetes following an emergency department admission for treatment of an asthma attack.

The patient's elevated blood glucose level of 22.9mmol/L was consistent with current guidelines for the diagnosis of diabetes. However, he remained on the same dose of insulin for three years (despite steady, normal growth). During this time he had no problems with blood glucose control and no hypoglycaemic attacks. The diagnosis of diabetes was, therefore, questioned. The values for steroid induced hyperglycaemia were markedly higher in this patient than anecdotal values. This prompted the suspicion that the steroid induced hyperglycaemia had been further exacerbated by salbutamol administration in the setting of an acute stress response.

The findings of this case illustrate the importance of understanding drug induced hyperglycaemia in the presence of intercurrent illness. Copyright © 2010 John Wiley & Sons.
From history to reality: sodium glucose co‐transporter 2 inhibitors – a novel therapy for type 2 diabetes mellitus
Authors: Nair S , Joseph F , Ewins D , Wilding J , Goenka N
Published: August 2010

The human kidney has a key role in the regulation of blood glucose predominantly by reabsorption of glucose from the glomerular filtrate via sodium glucose co‐transporter 2 (SGLT‐2) channels. These are expressed in the proximal renal tubules and are blocked by SGLT‐2 inhibitors, which are novel pharmacological agents currently in development. Specific SGLT‐2 inhibition results in significant increases in renal glucose excretion causing a net calorie loss and consequent weight loss, coupled with a lowering of blood glucose due to removal of glucose from the circulation. The main side effect of SGLT‐2 inhibitors appears to be an increase in genital infections, although concerns remain about the potential adverse effects of dehydration and electrolyte imbalance. Dapagliflozin is the SGLT‐2 inhibitor that is the furthest along in development, and is currently in phase III clinical trials.

In this review article we consider the role of the kidney in glucose homeostasis in normal and diabetic subjects. We also review the history and concept of SGLT‐2 inhibition, and discuss the future potential clinical utility of this promising new class of drugs. Copyright © 2010 John Wiley & Sons.
Thermal Sensitivity of HMX Crystals and HMX‐Based Explosives Treated under Various Conditions
Authors: Zhang Chaoyang , Peng Qiang , Wang Liyan , Wang Xiaochuan
Published: August 2010

The Five‐Second Explosion Point (5‐SEP) tests and the SEM detections in this research showed that the HMX crystals and the HMX‐based explosives treated under different conditions can possess different thermal sensitivities. That is to say, higher impurity, smaller granularity, and worse integrity of HMX crystals can make them more thermally sensitive. The addition of metal or metal oxide particles, especially nanoparticles to HMX can also enhance its thermal sensitivity. Meanwhile, coating of HMX crystals with polymers to form perfect PBX and to keep them undamaged are helpful to decrease their thermal sensitivity. Furthermore, the thermal sensitivity of temperature‐aged HMX changes differently in terms of the integrity of its particles. Therefore, it can be concluded that conditions which increase the surface energy of HMX crystals or which make the HMX molecules more active to decompose at lower temperature will increase the thermal sensitivity of HMX. Additionally, the variation in the thermal sensitivity of HMX treated under different conditions is generally more temperate than that of its mechanical sensitivity.
Characterization of the horseweed (Conyza canadensis) transcriptome using GS‐FLX 454 pyrosequencing and its application for expression analysis of candidate non‐target herbicide resistance genes
Authors: Peng Yanhui , Abercrombie Laura LG , Yuan Joshua S , Riggins Chance W , Sammons R Douglas , Tranel Patrick J , Stewart C Neal
Published: August 2010

BACKGROUND: The de novo transcriptome sequencing of a weedy plant using GS‐FLX 454 technologies is reported. Horseweed (Conyza canadensis L.) was the first broadleaf weed to evolve glyphosate resistance in agriculture, and also is the most widely distributed glyphosate‐resistant weed in the United States and the world. However, available sequence data for this species are scant. The transcriptomic sequence should be useful for gene discovery, and to help elucidate the non‐target‐based glyphosate resistance mechanism and the genomic basis of weediness.

RESULTS: Sequencing experiments yielded 411 962 raw reads, an average read length of 233 bp and a total dataset of 95.8 Mb (NCBI accession number SRA010952). After trimming and quality control, 379 152 high‐quality sequences were retained and assembled into contigs. The assembly resulted in 31 783 unique transcripts, including 16 102 contigs and 15 681 singletons. The average coverage depth for each contig and each nucleotide position was 22‐fold and 12‐fold respectively. A total of 16 306 unique sequences were annotated by searching a custom plant protein database. The utility of the transcriptome data was demonstrated by further exploration of ABC transporters, which were previously hypothesized to play a role in non‐target glyphosate resistance. Real‐time RT‐PCR primers were designed from the transcriptome data, which made it possible to assess expression patterns of 17 ABC transporters from resistant and susceptible horseweed accessions from Tennessee, with and without glyphosate treatment.

CONCLUSION: These results show that GS‐FLX 454 sequencing is a powerful and cost‐effective platform for the development of functional genomic tools for a weed species. Copyright © 2010 Society of Chemical Industry
Formation of {100} facet‐terminated nanocrystalline diamond by microwave plasma chemical vapor deposition: Edge effect
Authors: Tang C. J. , Fernandes A. J. S. , Buijnsters J. G. , Abe I. , Domingues M. F. F. , Pinto J. L.
Published: August 2010

{100} Facet‐terminated nanocrystalline and {100} textured large‐grained polycrystalline diamond (PCD) have been grown simultaneously not only on different substrates but also on the same substrate from a single deposition run using high‐power microwave plasma chemical vapor deposition (MPCVD). The synthesis of diamond with varying morphologies in the same deposition run was achieved by combining the effect of nitrogen addition on diamond growth and the influence of substrate size and geometry on the distribution of the plasma power density and temperature along the substrate. We have modeled the temperature distribution on the substrates by computer simulations using the finite element method. The formation mechanism of several morphologies including both {100} facet‐terminated nanocrystalline and {100} textured large‐grained PCD on one substrate is discussed based on this temperature analysis and other simulation results described in the literature.
Detailed study of superconductivity in nanostructured nanocrystalline boron doped diamond thin films
Authors: Mandal Soumen , Naud Cécile , Williams Oliver A. , Bustarret Étienne , Omnès Franck , Rodière Pierre , Meunier Tristan , Saminadayar Laurent , Bäuerle Christopher
Published: August 2010

In this paper, we report on the transport properties of nanostructured boron doped diamond thin films. The nanostructures made from polycrystalline boron doped diamond show clear evidence of superconductivity with critical temperatures in the Kelvin range and critical field in the Tesla range. Such robust superconducting properties in these superhard materials make them promising candidates for superconducting nanoelectromechanical systems.
Passivation of H‐terminated diamond with MOCVD‐aluminium nitride – a key to understand and stabilize its surface conductivity
Authors: Kueck Daniel , Scharpf Jochen , Ebert Wolfgang , Fikry Mohamed , Scholz Ferdinand , Kohn Erhard
Published: August 2010

The surface conductivity of hydrogen (H)‐terminated diamond still suffers from instabilities at high temperature especially in O‐containing atmosphere and/or under high power FET device operation. For devices based on this H‐induced surface conductivity concept, stabilization is thus essential. In this investigation AlN, deposited by MOCVD at 800 °C, has been used as passivation and gate dielectric in Surface Channel MESFET and MISFET structures. Despite the high deposition temperature, the H‐induced channel is still present in the case of both structures and can be fully modulated. Surface Channel MESFETs yield a maximum output current density of 200 mA/mm (at pS = 9.5 × 1012 cm−2) in enhancement mode of operation. MISFETs display 20 mA/mm current density (at pS = 2.1 × 1012 cm−2) in semi‐enhancement mode of operation, the maximum current being limited by AlN dielectric breakdown. The film shows strong adhesion. To explain all features consistently, it is proposed that the interfacial bonding is provided by a H‐double bond.
Diamond nanotextured surfaces for enhanced protein redox activity
Authors: Yang Nianjun , Smirnov Waldemar , Kriele Armin , Hoffmann Rene , Nebel Christoph E.
Published: August 2010

A nanotextured diamond electrode was utilized to achieve optimized electrochemical redox‐interactions of cytochrome c (cyt c) with the diamond transducer. The nanotextured surface was realized using a top–down technology where diamond nanoparticles are used as etching masks. Macroscopic characterizations of the OH‐terminated surface using cyclic voltammetry reveal adsorption‐controlled cyt c/electrode interaction. The adsorption is assigned to the electrostatic attraction force of positively charged cyt c parts with the slightly negatively charged diamond surface in pH 7 buffer. Atomic force microscopy experiments in physiologic buffer solutions on flat diamond surface confirms the adsorption of cyt c on OH‐terminated diamond surfaces without structural changes of cyt c.
Diamond Schottky‐pn diode without trade‐off relationship between on‐resistance and blocking voltage
Authors: Makino Toshiharu , Kato Hiromitsu , Tokuda Norio , Ogura Masahiko , Takeuchi Daisuke , Oyama Kazuhiro , Tanimoto Satoshi , Okushi Hideyo , Yamasaki Satoshi
Published: August 2010

We successfully improved a merged diamond diode, namely a Schottky‐pn diode (SPND), which is composed of a fully depleted n‐type active layer sandwiched between a highly doped p+‐type layer and a Schottky metal. According to the analysis of operation mechanisms based on band diagrams, we increased the acceptor concentration in the p+‐type layer in order to decrease the on‐resistance (RonS), and increased the n‐type layer width to reach higher blocking voltage (Vblock). Consequently, much lower RonS of 0.03 mΩ cm2 and higher Vblock than those of the previously reported diamond SPND were achieved simultaneously. Thus, we elucidated experimentally that the diamond SPND has no trade‐off relationship between RonS and Vblock, and is suitable for low‐loss high‐power switching devices.
Effects of post‐growth annealing on physical properties of SrRuO3 thin film grown by MOCVD
Authors: Anooz S. Bin , Schwarzkopf J. , Dirsyte R. , Wagner G. , Fornari R.
Published: August 2010

We report on the annealing effects on strontium ruthenate thin films deposited on SrTiO3 using liquid‐delivery metalorganic chemical vapor deposition (MOCVD). The results of high resolution X‐ray diffraction (HR‐XRD), Raman spectroscopy, atomic force microscopy (AFM), and electrical resistivity, before and after a post‐growth annealing process were analyzed and compared. XRD and Raman spectroscopy for the as‐deposited film revealed that the film had c‐axis orientation and contained RuO2 as secondary phase. Single phase SrRuO3 could be obtained by annealing the film at 700 °C. Annealing at higher temperatures up to 850 °C leads to ruthenium deficiency, which is revealed by an increase in the out‐of‐plane lattice parameter, while at even higher annealing temperatures a decrease in the out‐of‐plane lattice parameter was detected might be due to diffusion of Ti from the substrate. The electrical resistivity increased with increasing annealing temperature up to 950 °C and showed typical metallic temperature dependence, while for the film annealed at 1000 °C a semiconductor‐like behavior was observed.
Integrated impedance based hydrocarbon gas sensors with Na‐zeolite/Cr2O3 thin film interfaces: Electrochemical mechanism of the impedance changes
Authors: Dubbe Andreas
Published: August 2010

This study aims to clarify the mechanism of a hydrocarbon gas sensor effect, which involves impedance changes of a Na+ ion conducting Pt‐doped zeolite layer in contact with chromia (Cr2O3) films as electrodes. Based on our previous studies on sensing characteristics and model experiments with asymmetrical cells, a coherent picture of the sensing mechanism is derived: The impedance change is attributed to the process of Na+ ion insertion from the zeolite into the chromia film. The impedance of this interface process is a function of the electrical potential at the interface. Combined with the observation that gas sorption in the zeolite micropores causes changes of the electrochemical potential at the zeolite surface, these two effects explain the observed sensor effect. The sensor response as predicted from this theory agrees well with the experimental data of the original sensor. Implications for the development of integrated devices are discussed.
Structural, electronic, linear, and nonlinear optical properties of ZnCdTe2 chalcopyrite
Authors: Ouahrani Tarik , Reshak Ali H. , Khenata R. , Baltache H. , Amrani B. , Bouhemadou A.
Published: August 2010

We report results of first‐principles density functional calculations using the full‐potential linearized augmented plane wave method. The generalized gradient approximation (GGA) and the Engel–Vosko‐GGA (EV‐GGA) formalism were used for the exchange–correlation energy to calculate the structural, electronic, linear, and nonlinear optical properties of the chalcopyrite ZnCdTe2 compound. The valence band maximum and the conduction band minimum are located at the Γ‐point, resulting in a direct band gap of about 0.71 eV for GGA and 1.29 eV for EV‐GGA. The results of bulk properties, such as lattice parameters (a, c, and u), bulk modulus B, and its pressure derivative B′ are evaluated. The optical properties of this compound, namely the real and the imaginary parts of the dielectric function, reflectivity, and refractive index, show a considerable anisotropy as a consequence ZnCdTe2 posseses a strong birefringence. In addition, the extinction coefficient, the electron energy loss function, and the nonlinear susceptibility are calculated and their spectra are analyzed.
Coefficient of thermal expansion of stacked auxetic and negative thermal expansion laminates
Authors: Lim Teik‐Cheng
Published: August 2010

Analytical expressions for the in‐plane and out‐of‐plane coefficients of thermal expansion for laminates with isotropic laminas are presented herein based on (i) zero net force on the laminate edges, (ii) equal displacement of the lamina edges, and (iii) Hooke's law in three dimensions. Results show that a laminate consisting of alternating auxetic (with positive coefficient of thermal expansion, CTE) and negative thermal expansion (NTE) (with positive Poisson's ratio) laminas exhibit a more negative effective CTE than a laminate of alternating conventional laminas (positive Poisson's ratio and positive CTE) with unconventional laminas (auxetic and NTE). Finally, temperature‐dependent CTE for such laminates are developed and plotted for special cases. It is herein shown that under certain circumstances, the magnitude of temperature‐dependent effective CTE tends to infinity.
Counterintuitive modulus from semi‐auxetic laminates
Authors: Lim T.‐C. , Rajendra Acharya U.
Published: August 2010

Semi‐auxetic laminates consist of conventional and auxetic laminas such that the interlacing effect results in overall properties that are absent in both conventional and purely auxetic materials. Of late it has been shown that the in‐plane Young's modulus of a semi‐auxetic laminate always exceeds the rule of mixtures. In this paper, the conditions by which the in‐plane modulus exceeds the stiffness of the phase with higher modulus is established. In addition, an example is demonstrated whereby the maximum point of the in‐plane modulus occurs where the volume fraction of the stiffer phase is lower than that of the more compliant phase.
A simple theoretical approach to designing nanotube‐based sensors
Authors: Rocha C. G. , Ferreira M. S.
Published: August 2010

Nanotube‐based sensors are high‐sensitivity devices that can probe a number of nano‐sized impurities through doping‐induced variations in their conductivity. One key question for designing efficient sensors is to establish which impurity/nanotube combination will generate maximum sensitivity. Standard ways for selecting a good nanotube/impurity combination consists of an ad hoc approach that involves sifting through an immense universe of possibilities. This trial‐and‐error approach, despite being time‐consuming and computationally demanding, does not necessarily result in sensitivity optimization. A mathematically transparent theoretical formalism was adopted to introduce an inverse way of thinking about the nanotube/impurity combination by establishing a set of characteristics these components must have to generate high sensitivity devices. In this way guidelines were generated that can narrow the search for the ideal components of nanotube‐based sensors. We illustrate this method with a few examples of nanotubes doped with a different single‐atom impurities.
Role of non‐collinear magnetization: From ferromagnetic nanowires to quantum rings
Authors: Sedlmayr Nicholas , Dugaev Vitalii , Berakdar Jamal
Published: August 2010

We consider interaction effects related to a non‐uniform magnetization in ferromagnetic nanowires and their possible generalization to nanorings. First we show that the electric current in a ferromagnetic nanowire with more than one domain wall induces an exchange coupling between the walls mediated by the spin‐dependent interference of scattered carriers. This interaction reveals a complex behavior as a function of mutual orientations and separation of the domain walls, thus affecting the domain wall dynamics. Then we consider how the theory should be modified in the case of a magnetized quantum ring. In this case the situation is more complicated because the vortex and onion magnetization states in the ring are not truly ferromagnetic.
Electronic structure and magnetism of monatomic one‐dimensional metal nanostructures on metal surfaces
Authors: Ignatiev P. A. , Negulyaev N. N. , Niebergall L. , Hashemi H. , Hergert W. , Stepanyuk V. S.
Published: August 2010

We report on theoretical studies of one‐dimensional (1D) monatomic metal nanostructures coupled to metal substrates, which support surface states. The aim of the work is to demonstrate general features of electronic structure, magnetic properties, and interactions in such systems. We start from simple finite monatomic chains. It is shown that electronic confinement in 1D metallic chains can be observed at energies of projected band gaps of a metallic substrate. At other energies the confinement is significantly suppressed by scattering of chain states into the metallic substrate. Although this scattering decreases the exchange interaction between magnetic atoms incorporated into the chain, we show that it is still possible to get a significant enhancement of the exchange interaction in short chains. The next problem addressed in the paper is related to the interaction of the surface state with ad‐chains and 1D resonators. Special attention is paid to a possible impact of confinement in 1D resonators on atomic diffusion and self‐organization inside them. Finally, we illustrate the theoretical approach for the treatment of magnetization dynamics in 1D nanostructures.
Spin selective transport through Aharonov–Bohm and Aharonov–Casher triple quantum dot systems
Authors: Tosi Leandro , Aligia A. A.
Published: August 2010

We calculate the conductance through a system of three quantum dots (QDs) under two different sets of conditions that lead to spin filtering effects under an applied magnetic field. In one of them, a spin is localized in one QD, as proposed by Delgado et al. [Phys. Rev. Lett. 101, 226810 (2008)]. In the other one, all dots are equivalent by symmetry and the system is subject to a Rashba spin–orbit coupling. We solve the problem using a simple effective Hamiltonian for the low‐energy subspace, improving the accuracy of previous results. We obtain that correlation effects related to the Kondo physics play a minor role for parameters estimated previously and high enough magnetic field. Both systems lead to a magnetic field tunable “spin valve”.
Novel polyanion conduction in Sc2(WO4)3 type negative thermal expansion oxides
Authors: Zhou Yongkai , Neiman Arkady , Adams Stefan
Published: August 2010

The relationship between the polyatomic anion conduction and negative thermal expansion (NTE) in Sc2(WO4)3 type structure has been investigated by a combination of computational, electrochemical and X‐ray diffraction approaches. The motion of the effective charge carriers in solid‐state ionics can be visualised by molecular dynamics (MD) simulations if proper initial structure and force‐field are known. By successfully reproducing the NTE for a large temperature range, we have designed and verified a valid force‐field to predict the mobile species in Sc2(WO4)3. Using the same force‐field a series of correlated WO migrations are observed in extended isothermal–isobaric MD simulations. Tubandt‐type electrolysis experiments confirmed that the mobile species in Sc2(WO4)3 is anionic. Scandium tungstate is thus the prototype of novel class of ionic conductors, a WO anion conductors. The relationship of the ion transport in this unique ion conductors with polyatomic mobile charge carriers to the NTE is discussed.
In situ 3D X‐ray microtomography study comparing auxetic and non‐auxetic polymeric foams under tension
Authors: McDonald Samuel A. , Dedreuil‐Monet Ghislain , Yao Yong Tao , Alderson Andrew , Withers Philip J.
Published: August 2010

X‐ray microtomography has been used to study in situ the uniaxial tensile response of low‐density polyurethane foam. Two variants have been examined, one before and one after treatment to generate auxetic behaviour. For both variants, microstructurally faithful finite element (FE) models have been constructed from the initial tomographs. For each variant a series of tomographs have been collected during progressive straining. Poisson's ratios of 0.30 (conventional, non‐auxetic) and −0.22 (auxetic) have been measured for the two variants by digital image correlation (DIC) between successive images. By comparison, the FE models exhibited Poisson's ratio's of 0.5 and −0.3, respectively. Key micromechanical mechanisms responsible for the auxetic effect have been observed during straining, such as the straightening of bent ribs and rotation of nodes (joints), compared to changes in the angles between essentially straight struts for the non‐auxetic variant. The microstructurally faithful FE models confirm the mechanisms observed in the experiments and enable characteristic rib and node behaviour to be followed in greater detail.
Anisotropy energy, spin‐atomic vibration interaction, and spin‐flip Hamiltonian of a single atomic spin system: application to iron ion
Authors: Kokado Satoshi , Harigaya Kikuo , Sakuma Akimasa
Published: August 2010

We derive an anisotropy energy VA, a spin‐atomic vibration interaction VSA, and a spin‐flip Hamiltonian VSF of a single atomic spin system, “Fe2+ (3d6) in a crystal field of tetragonal symmetry”. The perturbation theory is here applied to the system with the spin‐orbit interaction and the kinetic and potential energies, in which difference of vibration displacement between a nucleus and electrons is taken into account. We first find conditions to enhance a coefficient |D | of VA = – |D |S2Z, with SZ being the Z component of a spin operator. Second, the presence or absence of VSA and VSF is shown for any parameter sets. Also, some coefficients of VSA are proportional to 1/√f, with f being a vibration frequency, although a coefficient of the conventional spin‐phonon interaction has √f (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Highly luminescent nanostructures of CdS and ZnS prepared by microwaves heating: effect of sulphide concentration
Authors: Ortíz Samuel , Gómez Idalia , Elizondo Perla , Cavazos José
Published: August 2010

Nearly monodisperse and highly luminescent ZnS and CdS NPs were obtained by microwave irradiation. The ZnS and CdS NPs solutions were prepared by adding freshly prepared ZnSO4 or CdSO4 solution to a thioacetamide solution at pH 8 in the presence of sodium citrate in solution used as stabilizer. The precursors concentration were such that the sulphide ion concentrations were 3 × 10–2 M, 6 × 10–2 M and 8 × 10–2 M, for each of these [S] concentrations the [Zn] or [Cd] content were fixed at 3 × 10–2 M. NPs were prepared under microwave irradiation for 1 min at 905 W of power. The NPs samples were taken when the temperature descended to ambient temperature for further analysis. Effect of concentration of Cd and Zn ions were studied in the luminescence property. RXD, AFM, TEM and UV‐Vis were used too as analytical equipment for characterization. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evaluation of oscillator strength in colloidal CdSe/CdS dots‐in‐rods
Authors: Pisanello Ferruccio , Leménager Godefroy , Martiradonna Luigi , Spinicelli Piernicola , Fiore Angela , Amo Alberto , Giacobino Elisabeth , Cingolani Roberto , De Vittorio Massimo , Bramati Alberto
Published: August 2010

The oscillator strength in CdSe/CdS colloidal dot‐in‐rods is evaluated and assessed to be of ∼1.5. On the basis of this finding, the possibility to reach the strong coupling regime with photonic crystals nanocavities is discussed. In spite that carefully choosing the cavity parameters the strong coupling regime could be analytically achieved at room temperature, theoretical considerations show that the typical Rabi doublet cannot be resolved. The work draws also a viable strategy toward the observation of the strong coupling at cryogenic temperatures. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Collective electronic excitations in a potassium‐covered Be surface
Authors: Echeverry J. P. , Chulkov E. V. , Silkin V. M.
Published: August 2010

We investigate within a two‐component jellium model the collective electronic excitations in a one‐monolayer (1ML) potassium covered beryllium surface. The calculations of the surface dynamical response properties have been performed with one‐particle energies and wave functions derived from the Kohn‐Sham density‐functional theory. The dispersion relation for the surface plasmon modes as well as the real and imaginary parts of the induced dynamical charge density oscillations are presented. Comparison of the collective modes in the 1ML K/Be system with that of a clean Be surface is made. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)