bluuebunny/crossref_metadata_2025 huggingface dataset:
Cover Picture: An Organic Light‐Emitting Diode with Field‐Effect Electron Transport (Adv. Funct. Mater. 1/2008)
Authors: Schols S. , Verlaak S. , Rolin C. , Cheyns D. , Genoe J. , Heremans P.
Published: January 2008

The cover shows an organic light‐emitting diode with remote metallic cathode, reported by Sarah Schols and co‐workers on p. 136. The metallic cathode is displaced from the light‐emission zone by one to several micrometers. The injected electrons accumulate at an organic heterojunction and are transported to the light‐emission zone by field‐effect. The achieved charge‐carrier mobility and in combination with reduced optical absorption losses because of the remoteness of the cathode may lead to applications as waveguide OLEDs and possibly a laser structure. (The result was obtained in the EU‐funded project “OLAS” IST‐ FP6‐015034.)

We describe an organic light‐emitting diode (OLED) using field‐effect to transport electrons. The device is a hybrid between a diode and a field‐effect transistor. Compared to conventional OLEDs, the metallic cathode is displaced by one to several micrometers from the light‐emitting zone. This micrometer‐sized distance can be bridged by electrons with enhanced field‐effect mobility. The device is fabricated using poly(triarylamine) (PTAA) as the hole‐transport material, tris(8‐hydroxyquinoline) aluminum (Alq3) doped with 4‐(dicyanomethylene)‐2‐methyl‐6‐(julolindin‐4‐yl‐vinyl)‐4H‐pyran (DCM2) as the active light‐emitting layer, and N,N′‐ditridecylperylene‐3,4,9,10‐tetracarboxylic diimide (PTCDI‐C13H27), as the electron‐transport material. The obtained external quantum efficiencies are as high as for conventional OLEDs comprising the same materials. The quantum efficiencies of the new devices are remarkably independent of the current, up to current densities of more than 10 A cm–2. In addition, the absence of a metallic cathode covering the light‐emission zone permits top‐emission and could reduce optical absorption losses in waveguide structures. These properties may be useful in the future for the fabrication of solid‐state high‐brightness organic light sources.
Inside Front Cover: Green Synthesis and Property Characterization of Single‐Crystalline Perovskite Fluoride Nanorods (Adv. Funct. Mater. 1/2008)
Authors: Zhang F. , Mao Y. , Park T.‐J. , Wong S. S.
Published: January 2008

The synthesis of single‐crystalline, cubic perovskite KMnF3 and NH4MnF3 nanorods, and their rare‐earth‐ion‐doped analogues with reproducible shapes and sizes, has been realized using a modified template‐directed approach, report Stanislaus Wong and co‐workers on p. 103. The properties of the nanorods and their as‐doped counterparts suggest their practical incorporation into functional nanometer‐scale devices with applications in a number of fields. The cover shows the crystal structure of perovskite fluorides overlaid on a SEM image of as‐prepared KMnF3 nanorods with diameters measuring around 50 nm.

The generalized green synthesis of single‐crystalline KMnF3 and NH4MnF3 nanorods as well as of their rare‐earth ion doped analogues, possessing reproducible shape and controllable size, has been achieved using a modified template‐directed approach under ambient room‐temperature conditions, with simple inorganic salts as functional precursors. Extensive characterization of the resulting nanorods has been performed using diffraction, electron microscopy, optical spectroscopy, as well as magnetic techniques. We have studied the antiferromagnetism of as‐prepared ternary metal fluoride nanorods as well as the luminescence of their as‐doped counterparts. Our collective data suggest the possibility of the incorporation of these high‐quality, chemically pure materials into functional nanoscale devices with various potential applications that exploit the interesting optomagnetic properties of these systems.
Evaluation of Different Glutaryl Acylase Mutants to Improve the Hydolysis of Cephalosporin C in the Absence of Hydrogen Peroxide
Authors: López‐Gallego Fernando , Betancor Lorena , Sio Charles F. , Reis Carlos R. , Jimenez Pol Nadal , Guisan Jose M. , Quax Wim. J. , Fernandez‐Lafuente Roberto
Published: January 2008

2‐Oxoadipoyl‐7‐ACA is an intermediate in the conversion of cephalosporin C (CPC) to 7‐aminocephalosporanic acid (7‐ACA) when using a new route involving D‐amino acid oxidase, catalase and glutaryl acylase. A key point in the reaction design is to avoid the accumulation of hydrogen peroxide in the reaction medium as the yields of 7‐ACA decrease in the presence of this compound due to its low stability. Looking for an enzyme with improved activity towards 2‐oxoadipoyl‐7‐ACA, different mutants of glutaryl acylase from Pseudomonas SY‐77 with an improved activity towards adipoyl‐7‐ACA were evaluated. The best results on 2‐oxoadipoyl‐7‐ACA hydrolysis were found with the double mutant Y178F+F375H, which showed a Kcat increase of 6.5‐fold and a Km decrease of 3‐fold compared to the wild‐type (wt) enzyme. When this enzyme was tested in the tri‐enzymatic system to convert CPC into 7‐ACA, this mutant permitted us to reach more than an 80 % yield of 7‐ACA using a 3‐fold mass excess compared to DAAO; while the wt enzyme gave only a 40 % yield. Therefore, the application of this new mutant to the one‐pot conversion of CPC to 7‐ACA gives very good result in terms of efficiency, yield and rate of the process.
Engineering Polymer‐Enhanced Bimetallic Cooperative Interactions in the Hydrolytic Kinetic Resolution of Epoxides
Authors: Zheng Xiaolai , Jones Christopher W. , Weck Marcus
Published: January 2008

Through systematic variations of the length of oligo(ethylene glycol)‐based linkers and the catalyst density of poly(styrene)‐supported cobalt‐salen catalysts, we have elucidated an optimal catalyst flexibility and density of polymeric Co‐salen catalysts for the hydrolytic kinetic resolution (HKR) of racemic terminal epoxides that follows a bimetallic cooperative pathway. The optimized polymeric catalyst brings the two cooperative Co‐salen units to a favorable proximity efficiently and hence displays significantly improved catalytic performance in the HKR compared with its monomeric small molecule analogue. Complex Co(5b), representing the most active poly(styrene)‐supported HKR catalyst known so far, can effect the resolution of a variety of epoxides to reach ≥98 % ee in 6–24 h with a low cobalt loading of 0.01–0.1 mol %.
Palladium(II)‐Catalyzed One‐Pot Enantioselective Synthesis of Arylglycine Derivatives from Ethyl Glyoxylate, p‐Toluenesulfonyl Isocyanate and Arylboronic Acids
Authors: Dai Huixiong , Yang Miao , Lu Xiyan
Published: January 2008

A palladium(II)‐catalyzed, one‐pot enantioselective synthesis of arylglycine derivatives from ethyl glyoxylate, p‐toluenesulfonyl isocyanate and arylboronic acids giving moderate to good yields and enantioselectivity has been developed. This reaction provides a convenient and efficient method for the synthesis of arylglycines.
An Unprecedented Iridium(III) Catalyst for Stereoselective Dimerisation of Terminal Alkynes
Authors: Ciclosi Marco , Estevan Francisco , Lahuerta Pascual , Passarelli Vincenzo , Pérez‐Prieto Julia , Sanaú Mercedes
Published: January 2008

A novel iridium(III) hydride complex, IrHCl(TIMP3) {HTIMP3=tris[1‐(diphenylphosphino)‐3‐methyl‐1H‐indol‐2‐yl]methane} was prepared and fully characterized in both the solid state and in solution. Chloride abstraction by silver cations provides a more reactive compound, [IrH(TIMP3)][BF4], which can react with pyridine (py) and phenylacetylene to yield the complexes [IrH(TIMP3)(py)][BF4] and [Ir(PhCHCCHCHPh)(TIMP3)][BF4], respectively. Interestingly, IrH(TIMP3)(py)][BF4] efficiently catalyses the stereoselective dimerisation of model terminal alkynes to the 1,4‐disubstituted (E)‐but‐1‐en‐3‐yne only.
Comparing ape densities and habitats in northern Congo: surveys of sympatric gorillas and chimpanzees in the Odzala and Ndoki regions
Authors: Devos Céline , Sanz Crickette , Morgan David , Onononga Jean‐Robert , Laporte Nadine , Huynen Marie‐Claude
Published: January 2008

The conservation status of western lowland gorillas and central chimpanzees in western equatorial Africa remains largely speculative because many remote areas have never been surveyed and the impact of emergent diseases in the region has not been well documented. In this study, we compared ape densities and habitats in the Lokoué study area in Odzala National Park and the Goualougo Triangle in Nouabalé‐Ndoki National Park in northern Republic of Congo. Both of these sites have long been considered strongholds for the conservation of chimpanzees and gorillas, but supposedly differ in vegetative composition and relative ape abundance. We compared habitats between these sites using conventional ground surveys and classified Landsat‐7 ETM+ satellite images. We present density estimates via both standing‐crop and marked‐nest methods for the first time for sympatric apes of the Congo Basin. The marked‐nest method was effective in depicting chimpanzee densities, but underestimated gorilla densities at both sites. Marked‐nest surveys also revealed a dramatic decline in the ape population of Lokoué which coincided with a local Ebola epidemic. Normal baseline fluctuations in ape nest encounter rates during the repeated passages of marked‐nest surveys were clearly distinguishable from a 80% decline in ape nest encounter rates at Lokoué. Our results showed that ape densities, habitat composition, and population dynamics differed between these populations in northern Congo. We emphasize the importance of intensifying monitoring efforts and further refinement of ape survey methods, as our results indicated that even the largest remaining ape populations in intact and protected forests are susceptible to sudden and dramatic declines. Am. J. Primatol. 70:439–451, 2008. © 2008 Wiley‐Liss, Inc.
Pharmacokinetics and metabolism of intravenous pirfenidone in sheep
Authors: Bruss Michael L. , Stanley Scott D. , Margolin Solomon B. , Giri Shri N.
Published: January 2008

Pirfenidone, a promising antifibrotic agent, was administered intravenously to six female sheep at 30 mg/kg. Four sheep received 14C‐pirfenidone simultaneously. Plasma and urine were obtained for assay of pirfenidone and its metabolites over two days, and tissues were obtained via necropsy. Samples were analysed for pirfenidone and metabolites using HPLC‐MS and flow scintillation spectrometry. Plasma pirfenidone disappeared with first order kinetics with a clearance of 1.2 l/kg/h, half‐life of 24 min, and distribution volume of 0.71 l/kg. After 48 h, the organs containing the largest quantity of 14C were lungs, liver and intestinal wall. Tissues with the highest concentration of 14C were lung, kidney, brain, liver, lymph node and adipose. Metabolites found in plasma and urine were hydroxypirfenidone (half‐life of 44 min) and carboxypirfenidone. Additional metabolites found in urine were hydroxypirfenidone glucuronide and acetoxypirfenidone. Approximately, 80% of the tracer eventually appeared in the urine, and approximately 50% of it was in the form of identifiable metabolites. Less than 1% of the dose appeared in the urine in the form of the parent drug. Quantitatively, most of the metabolites appeared in the urine within 2 h. Thus, the drug is rapidly and completely metabolized. Copyright © 2008 John Wiley & Sons, Ltd.
Synthesis and luminescent properties of a novel bluish‐white afterglow phosphor, b‐Zn3(PO4)2:Hf4+
Authors: Peng Zifei , Xu Zhu , Luo Caiqin , Yu Junbao , Zhang Guobin
Published: January 2008

A new bluish‐white long‐lasting phosphorescent material, Hf4+‐doped b‐Zn3(PO4)2, was prepared by the conventional high‐temperature solid‐state method. The photoluminescence (PL) spectrum reveals that it exhibits a strong blue emission band centred at 470 nm, with asymmetry on the long wavelength side; this material emits bluish‐white light and shows strong afterglow phosphorescence after it is excited with a 254 nm UV lamp. The phosphorescence lasts nearly 40 min in the light perception of the dark‐adapted human eye (0.32 mcd/m2). The possible phosphorescence mechanism is also analysed. Copyright © 2008 John Wiley & Sons, Ltd.
Redirection of flux through the FPP branch‐point in Saccharomyces cerevisiae by down‐regulating squalene synthase
Authors: Paradise Eric M. , Kirby James , Chan Rossana , Keasling Jay D.
Published: January 2008

Saccharomyces cerevisiae utilizes several regulatory mechanisms to maintain tight control over the intracellular level of farnesyl diphosphate (FPP), the central precursor to nearly all yeast isoprenoid products. High‐level production of non‐native isoprenoid products requires that FPP flux be diverted from production of sterols to the heterologous metabolic reactions. To do so, expression of the gene encoding squalene synthase (ERG9), the first committed step in sterol biosynthesis, was down‐regulated by replacing its native promoter with the methionine‐repressible MET3 promoter. The intracellular levels of FPP were then assayed by expressing the gene encoding amorphadiene synthase (ADS) and converting the FPP to amorphadiene. Under certain culture conditions amorphadiene production increased fivefold upon ERG9 repression. With increasing flux to amorphadiene, squalene and ergosterol production each decreased. The levels of these three metabolites were dependent not only upon the level of ERG9 repression, but also the timing of its repression relative to the induction of ADS and genes responsible for enhancing flux to FPP. Biotechnol. Bioeng. 2008;99: 371–378. © 2007 Wiley Periodicals, Inc.
Carbon‐Centered Radical Addition and β‐Scission Reactions: Modeling of Activation Energies and Pre‐exponential Factors
Authors: Sabbe Maarten K. , Reyniers Marie‐Françoise , Van Speybroeck Veronique , Waroquier Michel , Marin Guy B.
Published: January 2008

A consistent set of group additive values ΔGAV° for 46 groups is derived, allowing the calculation of rate coefficients for hydrocarbon radical additions and β‐scission reactions. A database of 51 rate coefficients based on CBS‐QB3 calculations with corrections for hindered internal rotation was used as training set. The results of this computational method agree well with experimentally observed rate coefficients with a mean factor of deviation of 3, as benchmarked on a set of nine reactions. The temperature dependence on the resulting ΔGAV°s in the broad range of 300–1300 K is limited to ±4.5 kJ mol−1 on activation energies and to ±0.4 on logA (A: pre‐exponential factor) for 90 % of the groups. Validation of the ΔGAV°s was performed for a test set of 13 reactions. In the absence of severe steric hindrance and resonance effects in the transition state, the rate coefficients predicted by group additivity are within a factor of 3 of the CBS‐QB3 ab initio rate coefficients for more than 90 % of the reactions in the test set. It can thus be expected that in most cases the GA method performs even better than standard DFT calculations for which a deviation factor of 10 is generally considered to be acceptable.
A Pragmatic Recipe for the Treatment of Hindered Rotations in the Vibrational Averaging of Molecular Properties
Authors: Mort Brendan C. , Autschbach Jochen
Published: January 2008

A computational protocol for the treatment of hindered rotations in the vibrational averaging of molecular properties is described. As examples, the specific rotations ${[\alpha ]_{\rm{D}} }$ of (R)‐methyloxirane, (1S)‐methylnorbornanone, and (S)‐epichlorohydrin and the spin‐spin coupling constant ${J_{{\rm{HD}}} }$ for ${[Ir(Cp)(PMe_3 )H_2 ]^ + }$ are investigated. For each of the four molecules, the relaxed and unrelaxed potential energy surfaces along the rotational coordinate of interest are used to solve the nuclear Schrödinger equation using a pseudospectral method. Analysis of the results demonstrate that the vibrational averaging for low‐frequency modes that represent hindered rotations can lead to unphysical behavior at high temperatures while simply neglecting the rotational contributions is also not desirable. The method described in this work connects the (an)harmonic oscillator behavior at low temperatures with the free rotor‐like behavior at high temperatures.
Relationship of serum fibrosis markers with liver fibrosis stage and collagen content in patients with advanced chronic hepatitis C
Authors: Fontana Robert J. , Goodman Zachary D. , Dienstag Jules L. , Bonkovsky Herbert L. , Naishadham Deepa , Sterling Richard K. , Su Grace L. , Ghosh Mita , Wright Elizabeth C.
Published: January 2008

This study determined the utility of a panel of serum fibrosis markers along with routine laboratory tests in estimating the likelihood of histological cirrhosis in a cohort of prior nonresponders with chronic hepatitis C. The relationship between serum markers and quantitative hepatic collagen content was also determined. Liver biopsy samples from 513 subjects enrolled in the HALT-C trial were assigned Ishak fibrosis scores. The collagen content of 386 sirius-red stained, nonfragmented biopsy samples was quantified using computerized morphometry. Serum tissue inhibitor of matrix metalloproteinase-1 (TIMP-1), amino-terminal peptide of type III procollagen (PIIINP), hyaluronic acid (HA), and YKL-40 levels were determined using commercially available assays.Sixty-two percent of patients had noncirrhotic fibrosis (Ishak stage 2-4) whereas 38% had cirrhosis (Ishak stage 5,6). Multivariate analysis identified a 3-variable model (HA, TIMP-1, and platelet count) that had an area under the receiver operating curve (AUROC) of 0.81 for estimating the presence of cirrhosis. This model was significantly better than that derived from the cirrhosis discriminant score (AUROC 0.70), the AST-to-platelet ratio (AUROC 0.73), and a prior model developed in HALT-C patients (AUROC 0.79). Multivariate analysis demonstrated that the serum fibrosis markers correlated substantially better with Ishak fibrosis scores than with the log hepatic collagen content (AUROC 0.84 versus 0.72).

Conclusion:

A 3-variable model consisting of serum HA, TIMP-1, and platelet count was better than other published models in identifying cirrhosis in HALT-C Trial subjects. The stronger correlation of the serum markers with Ishak scores suggests that serum fibrosis markers reflect the pattern of fibrosis more closely than the quantity of hepatic collagen.
Coupled choosability of plane graphs
Authors: Wang Weifan , Lih Ko‐Wei
Published: January 2008

A plane graph G is coupled k‐choosable if, for any list assignment L satisfying $|{{L}}({{x}})|= {{k}}$ for every ${{x}}\in {{V}}({{G}})\cup {{F}}({{G}})$, there is a coloring that assigns to each vertex and each face a color from its list such that any two adjacent or incident elements receive distinct colors. We prove that every plane graph is coupled 7‐choosable. We further show that maximal plane graphs, ${{K}}_{{4}}$‐minor free graphs, and plane graphs with maximum degree at most three are coupled 6‐choosable. © 2008 Wiley Periodicals, Inc. J Graph Theory 58: 27–44, 2008
Expression of CXCL12 and its receptor CXCR4 correlates with lymph node metastasis in submucosal esophageal cancer
Authors: Sasaki Ken , Natsugoe Shoji , Ishigami Sumiya , Matsumoto Masataka , Okumura Hiroshi , Setoyama Tetsuro , Uchikado Yasuto , Kita Yoshiaki , Tamotsu Kiyokazu , Sakurai Toshihide , Owaki Tetsuhiro , Aikou Takashi
Published: January 2008

Background and Objectives

The chemokine CXCL12 and its receptor CXCR4 are involved in cell migration, proliferation, and angiogenesis, and promote organ‐specific localization of distant metastases in various carcinomas. We examined their expression and microvessel density (MVD) in submucosal esophageal squamous cell carcinoma (ESCC) and analyzed their connection to clinicopathological findings including lymph node micrometastasis (LMM).

Methods

Eighty‐six patients with submucosal ESCC underwent curative resection from 1985 to 2002. Immunohistochemical staining of CXCL12, CXCR4, and CD34 was performed with primary tumors, and staining of cytokeratin was performed with dissected lymph nodes. MVD was calculated from CD34 expression, and LMM detected by cytokeratin staining.

Results

Expression of CXCL12, but not CXCR4, correlated with lymph node metastasis. There was no significant correlation between the expression of CXCL12 and/or CXCR4 and MVD. LMM was detected in 8 cases and 14 lymph nodes. CXCL12 expression and high MVD were found in tumors with lymph node metastasis including LMM. Furthermore, in the CXCR4‐positive tumors, positive CXCL12 expression was more significantly correlated with lymph node metastasis and/or LMM than negative CXCL12 expression.

Conclusions

Evaluation of CXCL12 and CXCR4 expression should assist detection of lymph node metastasis including LMM in submucosal ESCC. J. Surg. Oncol. 2008;97:433–438. © 2008 Wiley‐Liss, Inc.
Preparation and characterization of cellulose acetate‐coated compound fertilizer with controlled‐release and water‐retention
Authors: Wu Lan , Liu Mingzhu
Published: January 2008

A novel cellulose acetate‐coated compound fertilizer with controlled‐release and water‐retention (CAFCW) was prepared, which possessed the three‐layer structure. Its core was water‐soluble compound fertilizer granular, the inner coating was cellulose acetate (CA), and the outer coating was poly(acrylic acid‐co‐acrylamide)/unexpanded vermiculite (P(AA‐co‐AM)/UVMT) superabsorbent composite. The effects of the amount of acrylamide, crosslinker, initiator, degree of neutralization of acrylic acid (AA), and unexpanded vermiculite concentration on water absorbency were investigated and optimized. The water absorbency of CAFCW was 72 times its own weight if it was allowed to swell in tap water at room temperature for 90 min. Element analysis and atomic absorption spectrophotometer results showed that the product contained 11% nitrogen, 6% phosphorus (shown by P2O5), 9% potassium (shown by K2O), 1% calcium (shown by CaO), and 0.4% magnesium (shown by MgO). Swelling rate, slow‐release, and water‐retention properties of CAFCW were also investigated. This product with good controlled‐release and water‐retention capacity, being degradable in soil and environmentally friendly, could be especially useful in agricultural and horticultural applications. Copyright © 2008 John Wiley & Sons, Ltd.
The Mycobacterium tuberculosis serine/threonine kinase PknL phosphorylates Rv2175c: Mass spectrometric profiling of the activation loop phosphorylation sites and their role in the recruitment of Rv2175c
Authors: Canova Marc J. , Veyron‐Churlet Romain , Zanella‐Cleon Isabelle , Cohen‐Gonsaud Martin , Cozzone Alain J. , Becchi Michel , Kremer Laurent , Molle Virginie
Published: January 2008

Although Mycobacterium tuberculosis (M. tb) comprises 11 serine/threonine protein kinases, the mechanisms of regulation of these kinases and the nature of their endogenous substrates remain largely unknown. Herein, we characterized the M. tb kinase PknL by demonstrating that it expresses autophosphorylation activity and phosphorylates Rv2175c. On‐target dephosphorylation/MALDI‐TOF for identification of phosphorylated peptides was used in combination with LC‐ESI/MS/MS for localization of phosphorylation sites. By doing so, five phosphorylated threonine residues were identified in PknL. Among them, we showed that the activation loop phosphorylated residues Thr173 and Thr175 were essential for the autophosphorylation activity of PknL. Phosphorylation of the activation loop Thr173 residue is also required for optimal PknL‐mediated phosphorylation of Rv2175c. Together, our results indicate that phosphorylation of the PknL activation loop Thr residues not only controls PknL kinase activity but is also required for recruitment and phosphorylation of its substrate. Rv2175c was found to be phosphorylated when overexpressed and purified from Mycobacterium smegmatis as 2‐DE indicated the presence of different phosphorylated isoforms. Given the presence of the dcw gene cluster in the close vicinity of the pknL/Rv2175c locus, and its conservation in all mycobacterial species, we propose that PknL/Rv2175c may represent a functional pair in the regulation of mycobacterial cell division and cell envelope biosynthesis.
Proteomic analysis for inhibitory effect of chitosan oligosaccharides on 3T3‐L1 adipocyte differentiation
Authors: Rahman Md. Atiar , Kumar Suresh G. , Kim Sang Woo , Hwang Hye Jin , Baek Yu Mi , Lee Sung Hak , Hwang Hee Sun , Shon Yun Hee , Nam Kyung Soo , Yun Jong Won
Published: January 2008

In the present study, we performed a differential proteomic analysis using 2‐DE combined with MS to clarify the molecular mechanism for the suppressive effect of chitosan oligosaccharides (CO) during differentiation of adipocyte 3T3‐L1. Cell differentiation was significantly inhibited by CO at the concentration of 4 mg/mL. Protein mapping of adipocyte homogenates by 2‐DE revealed that numerous protein spots were differentially altered in response to CO treatment. Out of 50 identified proteins showing significant alterations, six were up‐regulated and 44 were down‐regulated by CO treatment in comparison to control mature adipocytes. Among them, most of the proteins are associated with lipid metabolism, cytoskeleton, and redox regulation, in which the levels of farnesyl diphosphate synthetase (FDS), dedicator of cytokinesis 9 (DOCK9), and chloride intracellular channel 1 (CLIC1) were significantly reduced (>two‐fold) with CO treatment. These results have not previously been examined in the context of adipogenesis, and thus can be used as novel biomarkers. Taken together with immunoblot analysis, it was concluded that the inhibitory effect of CO on adipocyte differentiation was mediated by C/EBPα and PPARγ pathway through significant downregulations of important adipogenic molecules such as fatty acid binding protein and glucose transporter 4.
The effect of etching on Ge(111) surfaces and Pd Schottky contacts
Authors: Nel J. M. , Griffiths T. C. , van Schalkwyk L. , Auret F. D. , Hayes M. , van den Berg N.
Published: January 2008

The etch rates of various etches and the resulting morphology of the Ge (111) surface have been investigated using atomic force microscopy (AFM) techniques and the oxidation rate of the germanium after etching was monitored by ellipsometry. The effect of the etch on the stability of Pd Schottky barrier diodes (SBDs) was monitored over a period of time using current voltage measurements. It was found that those etches with high etch rates produced much rougher surfaces which in turn showed significant variation in the leakage currents of SBDs deposited on these surfaces. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Piezospectroscopic analysis of mobile defects in semiconducting materials
Authors: Dobaczewski L. , Peaker A. R. , Markevich V. P. , Hawkins I. D. , Nielsen K. Bonde
Published: January 2008

The piezospectroscopic analysis of point defects allows to describe fixed defects embedded in a crystal environment of immobile atoms. This description works well when all atoms vibrate around fixed equilibrium positions and these vibrations are much faster than the time scale of the experiment while the equilibrium positions do not evolve within this time scale. For some defects this condition is not fulfilled at temperatures of the DLTS experiment, which somehow is reflected in a departure from what the theory predicts. On the other hand, systematic discrepancies between results of theoretical piezospectroscopic analysis and experiment can be a valuable source of information about a defect. We discuss how these re‐orientation processes can be identified from the observed piezospectroscopic parameters for a number of defect complexes observed in silicon and germanium with the use of the high‐resolution Laplace Deep Level Transient Spectroscopy. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of band anticrossing in InGaPN alloys grown on GaAs substrates
Authors: Lin K. I. , Lin H. C. , Wang T. S. , Lee M. H. , Hwang J. S.
Published: January 2008

The band anticrossing (BAC) model is introduced to describe the influence of the incorporated nitrogen on the band structure of dilute nitrides. An isolated N introduces highly localized states in these nitrides, which interact with the extended conduction‐band states of the host semiconductor. The interaction splits the conduction band into an upper and a lower subband. There are reports of the band‐gap reduction in InGaPN, but no experimental observations of the upper subband have been reported. In this work, temperature‐dependent photoreflectance (PR) and photoluminescence (PL) spectra are employed to examine the band structure of InGaPN/GaAs heterostructures. Besides the band gap, the upper subband predicted by the BAC model is observed in the PR spectra. By eliminating the contributions of the strain and ordering effects in InGaPN, and assigning the localized state energy EN introduced by an isolated N to be 2.04 eV at 293 K, the interaction potential is determined as 1.449±0.170 eV. With N incorporation, the PL peak energy exhibits a particular behavior with temperature, which is not observed in the PR spectra. This is attributed to carrier localization at low temperatures occurring in N‐diluted semiconductors. Additionally, the temperature dependence of the band gap is described by the BAC model incorporating two different EN levels, either constant or temperature‐dependent. In our hands, the assumption of the temperature‐dependent EN level results in a better fit with the experimental data. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An investigation of thermal boundary resistance in 1.3 µm edge‐emitting dilute nitride quantum well laser diodes
Authors: MacKenzie R. , Lim J. J. , Bull S. , Sujecki S. , Larkins E. C.
Published: January 2008

A theoretical investigation into the impact of the thermal boundary resistance on the performance of uncooled edge‐emitting 1.3μm InGaAsN/GaAs quantum well lasers has been performed. A state‐of‐the‐art 2D laser diode simulation tool has been extended to accurately model the thermal resistance due to the acoustic material mismatch and defect scattering at epitaxial interfaces. A small, but noticeable, increase in quantum well temperature is observed. The results clearly highlight the need for the inclusion of thermal boundary resistance in device simulation tools. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermally dependent gain of 1.3 µm dilute nitride double quantum well lasers
Authors: MacKenzie R. , Bull S. , Lim J. J. , Chao S. , Sujecki S. , Sadeghi M. , Wang S. M. , Larsson A. , Melanen P. , Sipilä P. , Uusimaa P. , Larkins E. C.
Published: January 2008

A systematic study of the dependence of the optical gain on the injection current and temperature in InGaAsN/GaAs lasers has been performed. The amplified spontaneous emission has been measured from a series of both facet‐coated and uncoated 1.3 μm edge‐emitting double quantum well lasers. The net gain, modal gain, cavity loss, quasi‐Fermi level separation and width of the gain spectra have been extracted using Cassidy's method. The peak gain was found to shift 0.41 nm/K between 300 K and 340 K and 0.60 nm/K between 340 K and 380 K. The value of the peak gain was found to decrease with temperature at a rate of 0.26 cm−1/K. The increase in the full at width half maxima of the gain spectra was determined to be 0.35 nm/K. These values are all comparable to those found for the more traditional 1.3 μm InP‐based devices, suggesting that InGaAsN/GaAs lasers are a viable alternative to replace such InP‐based devices, in particular for uncooled access network applications. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoluminescence microscopy investigation of lattice relaxation and defect formation processes in pseudomorphically strained InGaAsN multiple quantum wells
Authors: Lu W. , Chao S. , Bull S. , Andrianov A. V. , Grant V. A. , Campion R. P. , Foxon C. T. , Sadeghi M. , Wang S. M. , Larsson A. , Larkins E. C.
Published: January 2008

Photoluminescence microscopy (PLM) and photoluminescence (PL) spectroscopy have been used to investigate the influences of the number of quantum wells (QWs) and nitrogen concentration [N] on the quality of InGaAsN multiple QWs (MQWs). No misfit dislocations and/or carrier localization were observed in as‐grown InGaAsN MQWs. PL measurement results suggest that the PL efficiency and interfaces in the InGaAsN/GaAs QWs do not deteriorate with increasing number of QWs. In an InGaAsN 7 QW structure, even after annealing at temperatures as high as 850 °C, misfit dislocations were still not observed. This is contrary to the lattice relaxation behaviour of annealed InGaAs MQWs and is attributed to the impurity pinning of dislocations by nitrogen. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Fermi level position in as‐grown GaInNAs(Sb) quantum wells and layers studied by contactless electroreflectance
Authors: Kudrawiec R. , Yuen H. B. , Bank S. R. , Bae H. P. , Wistey M. A. , Harris J. S. , Motyka M. , Gladysiewicz M. , Misiewicz J.
Published: January 2008

It is shown that the Fermi level in as‐grown GaInNAs(Sb) material wants to be pinned at an energy which is located very close to the Fermi level‐stabilization energy (EFS). For 7.5‐nm‐thick GaInNAs(Sb) layers (quantum wells in fact) this energy lies ∼0.9 eV above the GaAs valence band whereas the EFS is known to be located ∼4.9±0.2 eV below the vacuum level (∼0.6 eV above the GaAs valence band). Increased the GaInNAs(Sb) layer thickness to 100 nm the Fermi level pinning shifts closer to the Fermi level‐stabilization energy and is located ∼0.8 eV above the GaAs valence band. This observation is associated with this fact that the ability to pin the Fermi level close to the EFS enhances when the total number of N‐related native point defects increased. In this case, the total number of point defects increases because of the increase in GaInNAs(Sb) thickness. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mg doping of InN and the use of yttrium‐stabilised zirconia substrates
Authors: Swartz C. H. , Durbin S. M. , Anderson P. A. , Carder D. , Reeves R. J. , Chandril S. , Myers T. H. , Kennedy V. J. , Ahrenkiel S. P.
Published: January 2008

Determining fundamental properties of InN is beset with difficulties. Since a conducting surface accumulation layer creates difficulties when assessing the impact of dopants, variable magnetic field Hall effect measurements were performed to separate various conducting layers. In addition to verifying p‐type doping with Mg, variable magnetic field Hall effect was used to show that growth of InN on YSZ will greatly reduce the background n‐type concentration for thinner layers, (with n ∼ 2×1017 cm−3, the lowest achieved on half micron thick material), making microns‐thick growth less important than the typical method of growth on sapphire with GaN buffer layers. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Carrier‐induced refractive index change in InN
Authors: Bulutay C. , Zakhleniuk N. A.
Published: January 2008

Rapid development of InN technology demands comprehensive assessment of the electronic and optoelectronic potential of this material. In this theoretical work the effect of free electrons on the optical properties of the wurtzite phase of InN is investigated. The blue shift of the optical absorption edge by the free‐carrier band filling is known as the Burstein‐Moss effect for which InN offers to be a very suitable candidate as has been recently demonstrated experimentally. Due to well known Kramers‐Kronig relations, a change in absorption is accompanied by a change in the index of refraction. Considering n‐type InN samples with free electron concentrations ranging from 5×1017 to 5×1020 cm−3, and employing a nonlocal empirical pseudopotential band structure, it is shown that this leads to a few percent change of the index of refraction. These carrier‐induced refractive index changes can be utilized in optical switches, futhermore it needs to be taken into account in the design of InN‐based optical devices such as lasers and optical modulators. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structure of cubic polytype indium nitride layers on top of modified sapphire substrates
Authors: Morales F. M. , Lozano J. G. , García R. , Lebedev V. , Wang Ch. Y. , Cimalla V. , Ambacher O. , González D.
Published: January 2008

The occurrence of cubic indium nitride thin layers grown by molecular beam epitaxy on top of c‐plane sapphire substrates modified by an intermediate layer of cubic indium oxide is reported. An orientation relationship between the (0001) plane of Al2O3and both (001) surfaces of body‐centered cubic In2O3and zinc‐blende InN is demonstrated by means of electron and X‐ray diffraction and by transmission electron microscopy. We propose that the demonstrated approach is able to stabilize the non equilibrium phase of InN (i. e., the cubic polytype) due to a low lattice mismatch together with a four fold surface atomic arrangement of the indium oxide‐indium nitride interface. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Study of SiNx:Hy passivant layers for AlGaN/GaN high electron mobility transistors
Authors: Redondo‐Cubero A. , Gago R. , Romero M. F. , Jiménez A. , González‐Posada F. , Braña A. F. , Muñoz E.
Published: January 2008

In this work, hydrogenated silicon nitride (SiNx:Hy) grown by chemical vapour deposition as passivant layers for high electron mobility transistors (HEMT) have been studied. The film composition and bonding structure were determined by ion beam analysis and x‐ray absorption spectroscopy techniques, respectively. The effects of gas precursors (SiH4/N2 and SiH4/NH3) and film/substrate interface on the film growth have been addressed. The growth on different substrates (Si, GaN, AlGaN), and the effects of plasma pre‐treatments have been studied before the growth and the film growth evolution. Results yield no significant differences in all the analysed samples. This points out the relevant role of SiHn radicals as growth precursor species and that intrinsic characteristics of the SiNx:Hy layers are not affected by the film/substrate interface. Hence, improved performance of HEMT with surface plasma pre‐treatments before passivation should be related to extrinsic mechanisms (such as creation of defects in AlGaN surface, removal of the surface contamination or ion‐induced roughness). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High temperature instabilities of ohmic contacts on p‐GaN
Authors: Trevisanello Lorenzo , Meneghini Matteo , Zehnder Ulrich , Hahn Berthold , Meneghesso Gaudenzio , Zanoni Enrico
Published: January 2008

This paper describes an investigation of the instabilities of ohmic contacts on p‐type GaN submitted to long term high temperature stress. Transfer Length Method (TLM) was used to separately analyze the contribution of contact resistivity and sheet resistance on contact degradation. Before treatment, contacts showed linear behaviour, indicating good ohmic properties. On the other hand, thermal ageing at 250 °C induced the degradation of electrical characteristics: in particular, (i) an increase of the contact resistivity was detected after stress, as well as (ii) a rectifying behaviour in current‐voltage (IV) characteristics of contact appeared. The degradation process has been ascribed to the diffusion of an atomics species from PECVD‐deposited passivation layer to p‐type ohmic contact: the interaction of this species with acceptor dopant can lower acceptor concentration, thus broadening the Schottky barrier at the interface and inducing the observed non‐linearity of the contacts. The square root time dependence of degradation of the electrical characteristics agreed with the hypothesis of diffusion. After 160 hours of aging, the passivation layer was removed and the structures were submitted to a new thermal treatment. This further treatment was found to induce the recovery of the electrical characteristics of the contacts, due to the fact that passivation acts like (i) a source of atomic species responsible of diffusion and/or (ii) a blocking layer for these species: the removal of passivation stopped the diffusion process and make outgassing process possible. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microstructured horizontal alumina pore arrays as growth templates for large area few and single nanowire devices
Authors: Xiang Ying , Lee Woo , Nielsch Kornelius , Abstreiter Gerhard , Fontcuberta i Morral Anna
Published: January 2008

We demonstrate the fabrication of horizontally aligned and well‐defined nanopore structures by anodic oxidation of aluminum thin films and micro stripes on a Si substrate. We are able to control both, the pore diameters and interpore distances from 10 nm to 130 nm and from 30 nm to 275 nm, respectively. The anisotropy of the system induces some deviations in the pore configuration from the typical honeycomb structure. By decreasing the dimensions of the Al structures, the final pore diameter and interpore distance remains constant, enabling the transition from multiple to a few nanowire porous structures. Finally, we successfully filled the nanopores by pulsed electroplating, as demonstrated both by Scanning Electron Microscopy and by current–voltage measurements. Having full control over the size, the density, the position and the orientation of the porous structure, our approach is promising for many exciting applications, including nanoelectronics and sensing. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Surface chemical and nanomechanical alterations in plasma immersion ion implanted PET
Authors: Kereszturi Klára , Tóth András , Mohai Miklós , Bertóti Imre
Published: January 2008

Poly(ethylene terephthalate) (PET) surface was treated by plasma immersion ion implantation (PIII or PI3) in nitrogen. The treatment conditions like acceleration voltage, ion fluence and fluence rate were varied systematically. The PIII‐induced alterations in the surface chemical composition and bonding of the constituent elements were studied by XPS. Nanoindentation and nanoscratch measurements were applied to investigate the related changes in the hardness, elastic modulus and wear resistance. Nitrogen PIII treatment of PET led to incorporation of nitrogen and decrease of surface O/C ratio. The bulk plasmon loss energy of the C 1s peak increased, implying compaction of the surface layer. PIII treatment increased the mean surface roughness and hardness (H), and decreased the elastic modulus (E). Process conditions were found, under which a four‐fold increase was obtained in the wear resistance. Improvement in wear resistance was accompanied by increase in the H/E ratio. Copyright © 2008 John Wiley & Sons, Ltd.
Surface modification, characterization and biofunctionality of pegylated titanate films obtained by the sol‐gel method
Authors: Pérez Mercedes Hernando , Noval Alvaro Muñoz , Navas Carmen Rodríguez , Silvan Miguel Manso , Torres‐Costa Vicente , Ceccone Giacomo , Ruiz Josefa P. García , Rossi Francois
Published: January 2008

Pegylated titanates have been prepared as biomedical supports in the form of thin films. The independent preparation of a polyethylene glycol (PEG) and a titanium isopropoxide (TIPT) precursor was followed by mixing at different molar ratios and spin casting onto Si (100) substrates to form the films. Activation of the hybrid structure was induced by annealing at temperatures right below the PEG melting point. Structural and compositional changes during these steps were followed by Fourier transformed infrared (FTIR) spectroscopy, XPS and water contact angle (CA) measurements. Biofunctionality of the pegylated titanates as antifouling ophthalmic films was tested on the one hand by determination of optical constants using genetic algorithms. On the other hand, indication of surface biocompatibility was provided by seeding mesenchymal stem cells. The results show that PEG‐rich surfaces are less biocompatible than mild inorganic surfaces as derived from the inhibition of cytoskeleton polarization. Copyright © 2008 John Wiley & Sons, Ltd.
Survismeter for simultaneous viscosity and surface tension study for molecular interactions
Authors: Singh Man
Published: January 2008

Survismeter simultaneously measures viscosities and surface tensions of several standard solvents (AR, methanol, ethanol, glycerol, ethyl acetate, n‐hexane, diethyl ether, chloroform, benzene, CCl4 and formic acid) and freshly prepared solutions of urea (U), 1‐methylurea (MU), 1,3‐dimethylurea (DMU) at several temperatures. Analysis for accuracies and hydrophobic interactions were made with data of solvents and solutions respectively. It replaces the use of viscometers and stalagmometer for viscosity and surface tensions individually. A decrease with one CH3 of MU and an increase with two CH3 of DMU in viscosities for 288.15–298.15 K with reverse trend for 303.15–308.15 K are noticed. Surface tension decreases from U to MU and increases with DMU at a slightly higher rate, but decreases with temperature. The CH3 is noticed to weaken hydrophilic interactions and strengthening hydrophobic interactions with stronger structure effecting changes in MU and DMU. Copyright © 2008 John Wiley & Sons, Ltd.
Physicochemical Characteristics of Starches of Two Sets of Near‐isogenic Wheat Lines with Different Amylose Content
Authors: Hung Pham Van , Yasui Takeshi , Maeda Tomoko , Morita Naofumi
Published: January 2008

Wheat lines with modified amylose content were produced by controlling the null alleles of three homoeologous Wx loci, Wx‐A1, Wx‐B1 and Wx‐D1 and those with triple‐null Wx alleles were found to yield waxy, amylose‐free starch. In this study, the new near‐isogenic lines developed by the recurrent backcross method between cv. Kanto 107 and the waxy mutant lines, K107Wx1 or K107Wx2, were cultivated and the physicochemical characteristics of their starches were investigated. The apparent amylose contents of the waxy near‐isogenic lines were 1.6 – 3.8%, whereas those of the non‐waxy near‐isogenic lines were 23.2 – 25.4%. The waxy lines had higher gelatinization temperature and enthalpy than the non‐waxy lines and no peak of amylose‐lipid complex as determined by DSC. The X‐ray diffraction patterns from both waxy and non‐waxy near‐isogenic lines corresponded to A‐type crystallization, like their parent lines. The starches isolated from the waxy lines had lower pasting onset and peak temperatures, higher peak viscosities and breakdown and lower final viscosity than those of the non‐waxy lines in the Viscoamylograph. The starch of non‐waxy near‐isogenic lines had lower peak and final viscosities and higher breakdown than did the recurrent parent line, cv. Kanto 107. The characteristics of the new wheat starches were well understood and classified, which will contribute to the wide application of these starches in food processing.