bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Site Characteristics on Nitrogen Retranslocation From Senescing Leaves
Authors: Del Arco Jose M. , Escudero Alfonso , Garrido M. Vega
Published: May 2006

The efficiency of nitrogen recovery before leaf fall in different woody species was studied with respect to the phenology of leaf abscission and to different estimates of nitrogen availability. Among the factors considered, the duration of the abscission period shows the strongest effect on the translocation efficiency. The species with gradual leaf fall exhibit lower percentages of nitrogen recovery, probably due to greater unpredictability of the exact time of abscission. Gradual leaf fall seems to be an adaptation to water stress in regions with an arid or semiarid climate. The species that occupy the more xeric sites thus show lower retranslocation rates. By contrast, the factors related to nitrogen availability show no clear effect on the reabsorption efficiency.
No Evidence for Association of OAS1 With Type 1 Diabetes in Unaffected Siblings or Type 1 Diabetic Cases
Authors: Smyth Deborah J. , Cooper Jason D. , Lowe Christopher E. , Nutland Sarah , Walker Neil M. , Clayton David G. , Todd John A.
Published: May 2006

Type 1 diabetes is a common autoimmune disorder that is strongly clustered in families. As the sharing of alleles of the HLA class II genes cannot explain all of this aggregation, alleles of multiple other loci are involved. Recently, it was reported that an A/G splice-site single nucleotide polymorphism (SNP; rs10774671) in the OAS1 gene, encoding 2′5′-oligoadenylate synthetase, was associated with a protective effect against type 1 diabetes in unaffected siblings, and yet affected siblings showed random transmission. Since this finding is difficult to explain biologically, we genotyped the OAS1 SNP in 1,552 type 1 diabetic families from the U.K., U.S., Romania, and Norway and in 4,287 type 1 diabetic cases and 4,735 control subjects from the U.K. We found no evidence of association in either unaffected (relative risk 1.00; P = 0.94) or affected (1.00; P = 0.96) siblings or in the case-control study (odds ratio 0.99; P = 0.83). These results suggest that additional evidence of association of a low penetrance effect in common disease should be sought when the primary result comes from unaffected siblings in the absence of any effect in cases.
Slow‐channel mutation in acetylcholine receptor αM4 domain and its efficient knockdown
Authors: Shen Xin‐Ming , Deymeer Feza , Sine Steven M. , Engel Andrew G.
Published: May 2006

Objective

To identify the genetic basis of a slow‐channel myasthenic syndrome, characterize functional properties of the mutant receptor, and selectively silence the mutant allele.

Methods

We performed nutation analysis, cloning, and patch‐clamp analysis of the functional properties of the mutant receptor; screening for a small interfering RNA with check plasmid; and assessed of the efficacy of small interfering RNA at the messenger RNA, protein, and functional levels.

Results

We traced the cause of a slow‐channel myasthenic syndrome to a C418W mutation in the M4 domain of the acetylcholine receptor α subunit. The mutation is the first one to occur spontaneously in an M4 domain of the receptor, and it is positioned within a stripe of hydrophobic residues facing the lipid bilayer. Kinetic analysis shows that αC418W enhances the channel opening equilibrium constant 26‐fold without altering agonist affinity. Using a check plasmid as a screening tool, we identified a small interfering RNA that markedly suppresses the mutant but not the wild‐type allele at the messenger RNA, protein, and functional levels.

Interpretation

αC418W occurring in humans causes a slow‐channel syndrome by enhancing the relative stability of the channel open state. Efficient and selective knockdown of the mutant allele holds promise of therapeutic gene silencing. Ann Neurol 2006
Evaluation of a genomics platform for cross‐species transcriptome analysis of recombinant CHO cells
Authors: Ernst Wolfgang , Trummer Evelyn , Mead Jennifer , Bessant Conrad , Strelec Harald , Katinger Hermann , Hesse Friedemann
Published: May 2006

Microarray technology for mammalian cells has been utilized mainly for humans, mouse, and rat gene expression analysis. In this approach the feasibility of cross‐species hybridization experiments using Chinese hamster ovary (CHO) cells was evaluated. Sequence alignments of available data for CHO were performed against mouse and rat transcripts to determine the homology between the investigated species. We implemented a probability model based on this homology in order to estimate the chance for successful hybridization using Agilent's 60‐mer oligonucleotide platform. Heat‐shock expression data from CHO, mouse 3T3, and rat A10 cells were generated to determine intraspecies variability, reproducibility, and specificity in order to assess the accuracy of this method. Detected signature genes, in particular from studies with the mouse arrays, showed a reliable similarity between these two rodents and were confirmed by quantitative RT‐PCR. Our findings provide evidence that cross‐species analysis can be a useful tool to study gene expression profiles of related organisms for which species‐specific microarrays are not available.
A fluid dynamics approach to bioreactor design for cell and tissue culture
Authors: Dusting Jonathan , Sheridan John , Hourigan Kerry
Published: May 2006

The problem of controlling cylindrical tank bioreactor conditions for cell and tissue culture purposes has been considered from a flow dynamics perspective. Simple laminar flows in the vortex breakdown region are proposed as being a suitable alternative to turbulent spinner flask flows and horizontally oriented rotational flows. Vortex breakdown flows have been measured using three‐dimensional Stereoscopic particle image velocimetry, and non‐dimensionalized velocity and stress distributions are presented. Regions of locally high principal stress occur in the vicinity of the impeller and the lower sidewall. Topological changes in the vortex breakdown region caused by an increase in Reynolds number are reflected in a redistribution of the peak stress regions. The inclusion of submerged scaffold models adds complexity to the flow, although vortex breakdown may still occur. Relatively large stresses occur along the edge of disks jutting into the boundary of the vortex breakdown region. © 2006 Wiley Periodicals, Inc.
Ligand binding by estrogen receptor beta attached to nanospheres measured by fluorescence correlation spectroscopy
Authors: Allen Noah W. , Thompson Nancy L.
Published: May 2006

Although many indirect methods have been chosen to study the system of estrogen receptor ligand binding, an ideal method is fluorescence correlation spectroscopy (FCS). FCS is nondestructive to the sample, uses very small sample volumes, and operates well within physiological concentration ranges. The methodology was developed to biotinylate the estrogen receptor β‐ligand binding domain (ERβ‐LBD) using biotin with a very short spacer and to then attach this protein to a 40 nm neutravidin‐coated bead (nanosphere). Diffusional FCS data were obtained for a fluorescently labeled coactivator peptide, steroid receptor coactivator peptide‐1 (A‐SRC‐1(2)), in the absence and presence of bead‐bound ERβ‐LBD. Data were also acquired in the presence of one of the endogenous ligands for ERβ, 17β‐estradiol, and with tamoxifen. The bead strategy resulted in a decreased receptor diffusion coefficient and consequent increase in the decay time of the FCS autocorrelation functions for receptor‐bound, labeled SRC‐1(2). Thus, free and bound coactivators were much more readily distinguished by FCS. Discrimination between the fluorescently labeled unbound and bound species could be determined in autocorrelation functions obtained in as few as 30 s. The advantage of using FCS with the ERβ‐LBD: bead methodology is the ability to obtain reliable and reproducible data in a short time frame. © 2006 International Society for Analytical Cytology
The “Off‐Shore” Construction of Optionally Substituted 4‐Trifluoromethyl‐2‐quinolinones
Authors: Leroux Frédéric , Lefebvre Olivier , Schlosser Manfred
Published: May 2006

Treatment of ortho‐lithiated tert‐butyl N‐arylcarbamates (i.e., BOC‐protected anilines) with N‐(trifluoroacetyl)piperidine provides 2‐(N‐BOC‐amino)aryl trifluoromethyl ketones which, upon consecutive reaction with an α‐alkoxycarbonyl‐substituted phosphorus ylide and acid (or base) yields 4‐trifluoromethyl‐2‐quinolinones which may bear additional substituents at any available position. The method is convenient and expedient. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Diversity‐Oriented Synthesis of 2,5‐Disubstituted Tetrahydrofurans Based on a “Cyclization‐Hydrogenation‐Substitution” Strategy
Authors: Freifeld Ilia , Holtz Edith , Dahmann Georg , Langer Peter
Published: May 2006

A variety of (tetrahydrofuran‐2‐yl)acetates have been prepared based on hydrogenation and subsequent nucleophilic substitutions of 2‐alkylidene‐5‐(hydroxymethyl)tetrahydrofurans. The latter are readily available by cyclization of 1,3‐dicarbonyl dianions (“free dianions”) with epibromohydrin. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Sensitive Voltammetric Sensing of the 2,3‐Dimethyl‐2,3‐dinitrobutane (Dmnb) Explosive Taggant
Authors: Wang Joseph , Thongngamdee Sompong , Lu Donglai
Published: May 2006

The highly sensitive voltammetric detection of the 2,3‐dimethyl‐2,3‐dinitrobutane (DMNB), a required additive to commercial plastic explosives, is described. The protocol relies on a fast square‐wave voltammetric measurement of the DMNB explosive taggant at an unmodified carbon fiber electrode using a phosphate buffer (pH 7.0) solution. Different solutions and working electrodes were evaluated. Under the optimal conditions, a linear response is observed over the 300–3000 μg/L DMNB concentration range examined, with a detection limit of 60 μg/L. A highly stable response, with a relative standard deviation (RSD) of 2.6%, is observed for 30 repetitive measurements. Such electrochemical approach offers great promise for a simple, rapid, sensitive and inexpensive field screening of plastic explosives. Preliminary data illustrate the utility of electrochemical detection for electrophoretic microchips for the simultaneous measurements of DMNB, cyclotrimethylenetrinitramine (RDX) and pentaerythritoltetranitrate (PETN).
Synthesis of novel thiazole and pyrrolothiadiazine derivatives from aldehyde thiosemicarbazones
Authors: Gomaa Mohsen A.‐M. , Hassan Alaa A. , Shehatta Hamdy S.
Published: May 2006

Substituted thiosemicarbazones 7a–e reacted with ethenetetracarbonitrile (TCNE) in ethyl acetate with formation of 5‐amino‐3‐(substituted ben‐zylidene‐amino)‐2‐phenylimino‐2,3‐dihydrothiazole‐4‐carbonitrile 8a–e 2‐amino‐6‐phenyl‐imino‐1,6‐ dihydropyrrolo[1,3,4]thiadiazine‐3‐carbonitrile 9, and phenyl‐(5‐{substituted phenyl}‐3H‐[1,3,4]thiadiazole‐2‐ylidene)amines 10a–e. Rationales for the observed conversations are presented. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:261–266, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20198
Synthesis and characterization of new electroluminescent materials of 1,3,4‐oxadiazole–1,2,3‐triazole hybrids and 1,3,4‐oxadiazole–1,2,3‐triazole–pyridine derivatives
Authors: Zhou Jia‐Xing , Wong Fung Fuh , Chen Chun‐Yen , Yeh Mou‐Yung
Published: May 2006

New electroluminescent materials of 1,3,4‐oxadiazole–1,2,3‐triazole and 1,3,4‐oxadiazole–1,2,3‐triazole–pyridine hybrid derivatives were synthesized and characterized. Following spectroscopic studies and characterization of their electronic properties, 1,3,4‐oxadiazole–1,2,3‐triazole hybrids and 1,3,4‐oxadiazole–1,2,3‐triazole–pyridine derivatives were found to be potentially efficient blue electroluminescent materials. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:322–328, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20210
Transacylation. Biomimetic synthesis of esters of acetic acid
Authors: Devedjiev Ivan T. , Ganev Vesselin G.
Published: May 2006

By mixing of β‐hydroxypropyl phosphate and acetic acid in ethanol solution, ethyl acetate is produced. As found, acetyl phosphate is first formed, then it reacts with the solvent to give the final ethyl acetate product. By similar procedures, acetates of methanol, n‐propanol, and n‐butanol are also produced. Propylene oxide serves as a condensing agent. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:350–352, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20216
Synthesis and structure of 1‐phospholyl‐ and di(1‐phospholyl)acetylenes and the corresponding sulfides
Authors: Sasaki Shigeru , Mori Takashi , Yoshifuji Masaaki
Published: May 2006

The acetylenes possessing one and two 1‐phospholyl groups were synthesized by reaction of the alkynyl Grignard reagents with the 1‐chlorophosphole and converted to the corresponding phosphole sulfides. Reaction of the 1‐phenylethynylphosphole sulfide with CpCo(CO)2 resulted in η4‐complexation on the phosphole moiety. The structures of the di(1‐phospholyl)acetylene disulfide and the [η4‐(1‐phenylethynylphosphole sulfide)]cobalt(I) complex were characterized by X‐ray crystallography. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:344–349, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20230
Electric field‐derived point charges to mimic the electrostatics in molecular crystals
Authors: Whitten Andrew E. , McKinnon Joshua J. , Spackman Mark A.
Published: May 2006

Because of the way the electrostatic potential is defined in a crystal, it is not possible to determine potential‐derived charges for atoms in a crystal. To overcome this limitation, we present a novel method for determining atomic charges for a molecule in a crystal based on a fit to the electric field at points on a surface around the molecule. Examples of fits to the electric field at points on a Hirshfeld surface, using crystal Hartree–Fock electron densities computed with a DZP basis set are presented for several organic molecular crystals. The field‐derived charges for common functional groups are transferable, and reflect chemical functionality as well as the subtle effects of intermolecular interactions. The charges also yield an excellent approximation to the electric field surrounding a molecule in a crystal for use in cluster calculations on molecules in solids. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 1063–1070, 2006
Dramatic performance enhancements for the FASTER optimization algorithm
Authors: Allen Benjamin D. , Mayo Stephen L.
Published: May 2006

FASTER is a combinatorial optimization algorithm useful for finding low‐energy side‐chain configurations in side‐chain placement and protein design calculations. We present two simple enhancements to FASTER that together improve the computational efficiency of these calculations by as much as two orders of magnitude with no loss of accuracy. Our results highlight the importance of choosing appropriate initial configurations, and show that efficiency can be improved by stringently limiting the number of positions that are allowed to relax in response to a perturbation. The changes we describe improve the quality of solutions found for large‐scale designs, and allow them to be found in hours rather than days. The improved FASTER algorithm finds low‐energy solutions more efficiently than common optimization schemes based on the dead‐end elimination theorem and Monte Carlo. These advances have prompted investigations into new methods for force field parameterization and multiple state design. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 1071–1075, 2006
Synergistic effect of chloride and sulfite ions on the atmospheric corrosion of bronze
Authors: Cao X. , Xu C.
Published: May 2006

The effect of chloride along with sulfite ions on the atmospheric corrosion of bronze was investigated by using periodic wet‐dry tests, surface tension tests and electrochemical impedance measurements. Scanning electron microscopy (SEM) and X‐ray diffraction (XRD) were used to characterize the corrosion products. Both the electrochemical impedance measurements and surface tension tests agreed well with the results of weight loss measurements. Synergistic effect of chloride and sulfite ions was observed during the whole process. In addition, we found that the attack of anions on the metal at the initial corrosion stage showed good agreement with their surface activity. However, as the corrosion proceeded, the interaction among the corrosion products induced by chloride and HSO3− accelerated the corrosion process. A scheme was given to explain the whole corrosion process.
Identification and formation of green rust 2 as an atmospheric corrosion product of carbon steel in marine atmospheres
Authors: Santana Rodríguez J. J. , González González J. E.
Published: May 2006

Green rust 2 (GR2(SO2−4 )) was detected amongst the products formed on a carbon steel rod exposed to atmospheric corrosion using X‐ray diffraction (XRD). The presence of green rust 2 has been related to sulphate reducing bacteria (SRB) in the sea spray. These were detected using test catch rods made out of inert material and posterior lab identification using Starkey culture. Likewise, after the exposure of said rods to sea environmental conditions, SRBs have been isolated from among the carbon steel corrosion products. The evolution of GR2(SO2−4 ) from GR1(SO2−4 ) was ruled out due to the tendency of this compund to produce GR2(SO2−4 ) in the presence of sulphate ions, as is the case here. Likewise, the evolution from GR1(Cl−) has also been ruled out since in such case as this compound should be formed (it has not been detected in any of the 39 stations studied), the enormous affinity of the GRs with divalent anions (such as is the case with SO2−4 ) as opposed to the monovalent ions (such as is the case of the Cl−) makes GR1(Cl−) transform into GR2 (SO2−4 ).
Algorithmic formulation and numerical implementation of coupled electromagnetic‐inelastic continuum models for electromagnetic metal forming
Authors: Stiemer Marcus , Unger Jaan , Svendsen Bob , Blum Heribert
Published: May 2006

The purpose of this work is the algorithmic formulation and implementation of a recent coupled electromagnetic‐inelastic continuum field model (Continuum Mech. Thermodyn. 2005; 17:1–16) for a class of engineering materials, which can be dynamically formed using strong magnetic fields. Although in general relevant, temperature effects are for the applications of interest here minimal and are neglected for simplicity. In this case, the coupling is due, on the one hand, to the Lorentz force acting as an additional body force in the material. On the other hand, the spatio‐temporal development of the magnetic field is very sensitive to changes in the shape of the workpiece, resulting in additional coupling. The algorithmic formulation and numerical implementation of this coupled model is based on mixed‐element discretization of the deformation and electromagnetic fields combined with an implicit, staggered numerical solution scheme on two meshes. In particular, the mechanical degrees of freedom are solved on a Lagrangian mesh and the electromagnetic ones on an Eulerian one. The issues of the convergence behaviour of the staggered algorithm and the influence of data transfer between the meshes on the solution is discussed in detail. Finally, the numerical implementation of the model is applied to the modelling and simulation of electromagnetic sheet forming. Copyright © 2006 John Wiley & Sons, Ltd.
Expression of vascular endothelial growth factor receptor 3 and Tie1 tyrosine kinase receptor on acute leukemia cells
Authors: Kivivuori Sanna‐Maria , Siitonen Sanna , Porkka Kimmo , Vettenranta Kim , Alitalo Riitta , Saarinen‐Pihkala Ulla
Published: May 2006

Background

Recent data indicate a role for angiogenesis in hematologic malignancies. In addition to promoting new vessel growth in the bone marrow microenvironment, angiogenic factors are regulators of both hematopoietic and leukemic cells. Activation of vascular endothelial growth factor receptor 3 (VEGFR‐3) and Tie1 tyrosine kinase receptor are known to promote leukemia cell survival. The details of this complex angiogenesis‐related interaction are still uncertain.

Procedure

We studied bone marrow samples from 73 patients with acute lymphoblastic (ALL) or myelogenous (AML) leukemia by using immunological methods.

Results

Vascular endothelial growth factor receptor 3 expression was found in 15% of the samples, particularly in samples with pediatric lymphoblastic leukemias and monocytic AMLs. Tie1 protein expression was found in 11% of the samples, all of which were from adult AML patients.

Conclusions

Our findings suggest that there are angiogenesis‐related differences between pediatric and adult lymphoblastic leukemias as well as between lymphoid and myeloid leukemias. Pediatr Blood Cancer © 2006 Wiley‐Liss, Inc.
Familial Currarino syndrome presenting with peripheral primitive neuroectodermal tumour arising with a sacral teratoma
Authors: Sen G. , Sebire N.J. , Olsen O. , Kiely E. , Levitt G.A.
Published: May 2006

This report illustrates a rare genetic disorder, Currarino syndrome, in association with an unusual malignant transformation to a peripheral primitive neuroectodermal tumour within a sacral teratoma. The triad of features consists of a presacral mass, partial sacral agenesis and anorectal anomalies. The most common presentation is constipation. In this case there was a history of constipation, teratomas and spinal abnormalities in many of the family members over three generations. Detailed family history taken at time of initial presentation may have prevented delay in diagnosis and averted the need for intensive treatment, which may well cause late sequelae. Pediatr Blood Cancer 2008;50:172–175. © 2006 Wiley‐Liss, Inc.
Equilibrium heat‐induced denaturation of chitinase 40 from Streptomyces thermoviolaceus
Authors: Pyrpassopoulos Serapion , Vlassi Metaxia , Tsortos Achilleas , Papanikolau Yannis , Petratos Kyriacos , Vorgias Constantinos E. , Nounesis George
Published: May 2006

High‐precision differential scanning calorimetry (DSC) and circular dichroism (CD) have been employed to study the thermal unfolding of chitinase 40 (Chi40) from Streptomyces thermoviolaceus. Chi40 belongs to family 18 of glycosyl hydrolase superfamily bearing a catalytic domain with a “TIM barrel”‐like fold, which exhibits deviations from the (β/α)8 fold. The thermal unfolding is reversible at pH = 8.0 and 9.0. The denatured state is characterized by extensive structural changes with respect to the native. The process is characterized by slow relaxation kinetics. Even slower refolding rates are recorded upon cooling. It is shown that the denaturation calorimetric data obtained at slow heating rate (0.17 K/min) are in excellent agreement with equilibrium data obtained by extrapolation of the experimental results to zero scanning rate. Analysis of the DSC results reveals that the experimental data can be successfully fitted using either a nontwo‐state sequential model involving one equilibrium intermediate, or an independent transitions model involving the unfolding of two Chi40 energetic domains to intermediate states. The stability of the native state with respect to the final denatured state is estimated, ΔG = 24.0 kcal/mol at 25°C. The thermal results are in agreement with previous findings from chemical denaturation studies of a wide variety of (β/α)8 barrel proteins, that their unfolding is a nontwo‐state process, always involving at least one unfolding intermediate. Proteins 2006. © 2006 Wiley‐Liss, Inc.
Weak universal critical behaviour of the mixed spin‐(1/2, S ) Ising model on the Union Jack (centered square) lattice: integer versus half‐odd‐integer spin‐S case
Authors: Strečka Jozef , Čanová Lucia , Dely Ján
Published: May 2006

The mixed spin‐(1/2, S ) Ising model on the Union Jack (centered square) lattice is investigated by establishing the mapping relationship with its corresponding eight‐vertex model. An interplay between the nearest‐neighbour interaction, the competing next‐nearest‐neighbour interaction and the single‐ion anisotropy gives rise to a rather complex critical behaviour displayed in the reentrant phase transitions, the weak universal critical behaviour, as well as, a presence of first‐ and second‐order phase transitions. The most interesting finding to emerge from the present study relates to a variation of the weak‐universal critical exponents along the line of bicritical points, which is being twice as large for the mixed spin‐(1/2, S ) systems with the integer spin‐S atoms as for the ones with the half‐odd‐integer spin‐S atoms. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of carrier diffusion length in MOCVD‐grown GaN epilayers on sapphire by optical techniques
Authors: Lutsenko E. V. , Gurskii A. L. , Pavlovskii V. N. , Yablonskii G. P. , Malinauskas T. , Jarašiūnas K. , Schineller B. , Heuken M.
Published: May 2006

Two optical techniques for the determination of a bipolar diffusion length LD of optically excited carriers in GaN epitaxial layers, namely a time‐resolved picosecond four‐wave mixing (FWM) on free carrier grating and time‐integrated photoluminescence (PL) are presented and examined. The PL technique is based on time‐integrated photoluminescence (PL) spectra measurements from the front and back sides of the sample under cw and nanosecond pulsed laser excitation. The another method utilizes time‐resolved picosecond four‐wave mixing (FWM) at various light‐induced grating periods to extract diffusion coefficient and carrier recombination lifetime. The value of the diffusion length derived by means of FWM decreases with GaN layer thickness from LD = 260 nm (for 1.7 μm‐thick layer) to LD = 100 nm (for 0.3 μm‐thick layer). The integral PL measurements give the value of LD = 120‐130 nm for the 620 nm layer under pulsed excitation intensities up to 200 kW/cm2. It increases to 150‐170 nm at the excitation intensity enhancement to 1 MW/cm2. These values are close to the value of the diffusion length equal to 160 nm obtained using FWM for this layer thickness evidencing the compatibility of both methods. The changes in the value of LD are discussed in terms of the defect distribution in the epitaxial GaN layer. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microscopic theory of carrier‐carrier scattering in nitride based quantum‐dot systems
Authors: Nielsen T. R. , Seebeck J. , Lorke M. , Gartner P. , Jahnke F.
Published: May 2006

A microscopic theory is applied to study carrier‐carrier Coulomb scattering in nitride‐based quantum dots. Kinetic equations for the carrier population are used to define capture and relaxation rates. For the states involved in the scattering processes, the combined influence of the quantum‐confined Stark effect and manybody renormalizations is taken into account. It is shown that the charge separation due to the built‐in field is accompanied with strong Hartree energy shifts, which can increase the scattering efficiency. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
AlGaN metal‐semiconductor‐metal structure for pressure sensing applications
Authors: Hassan Z. , Lee Y. C. , Ng S. S. , Yam F. K. , Liu Y. , Rang Z. , Kauser M. Z. , Ruden P. P. , Nathan M. I.
Published: May 2006

We report on the effects of hydrostatic pressure on an Alx Ga1–x N metal‐semiconductor‐metal (MSM) structure with Ni Schottky contacts. Structural, optical, and electrical analysis of the Alx Ga1–x N film were carried out using atomic force microscopy (AFM), high resolution X‐ray diffraction (HRXRD), Raman, UV‐visible spectroscopy, and Hall effect measurements. The AlN mole fraction in this film was determined to be about 24%. Current‐voltage (I‐V) measurements of the MSM structure under hydrostatic pressure indicated a linear decrease of current with pressure. The decrease of the current under pressure was attributed to an increase in barrier height, tentatively attributed to a combination of piezoelectric and band structure effects. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
HVPE growth of high quality GaN layers
Authors: Brückner Peter , Habel Frank , Scholz Ferdinand
Published: May 2006

The surface morphology of HVPE layers typically shows a high density of pyramidal structures which makes some polishing step necessary before their subsequent use in the next epitaxial growth. We found that a slight misorientation of the substrate totally suppresses the development of these pyramidal structures. The misorientation angle was varied between 0° and 0.6°. We did not observe any influence of the direction of miscut. Surface roughness measurements exhibited, that these HVPE grown layers on miscut templates had a comparably flat surface to MOVPE grown samples. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Degradation of blue LEDs related to structural disorder
Authors: Kamanin A. V. , Kolmakov A. G. , Kop'ev P. S. , Onushkin G. A. , Sakharov A. V. , Shmidt N. M. , Sizov D. S. , Sitnikova A. A. , Zakgeim A. L. , Zolotareva R. V. , Usikov A. S.
Published: May 2006

The degradation of blue light emitting diodes (LEDs) with different structural disorder based on MQW InGaN/GaN grown by MOCVD on sapphire has been investigated. New approach to analyze the degradation has been used. It takes into account the structural disorder determined by the extended defect system relaxation and related with poor coalescence of the mosaic structure domains. The results obtained leads to assumption that the migration and segregations of Ga on domain dislocation boundaries of the mosaic structure and the change of energy activation of Mg related centers are important reasons of degradation for all types of LEDs The fastest degradation for poor ordered LEDs was observed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Three methods for the growth of InGaN nanostructures by MOVPE
Authors: Oliver R. A. , Kappers M. J. , van der Laak N. K. , Humphreys C. J.
Published: May 2006

InGaN nanostructures have been grown (i) by a droplet epitaxy route, (ii) by pre‐treatment of the GaN pseudo‐substrate with SiH4 and NH3, and (iii) by annealing an InGaN epilayer under a H2 flux. The various methodologies are discussed in the context of possible device applications and of studies of the physics of single nitride quantum dots. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
AlGaN/GaN/InGaN/GaN HEMTs with an InGaN‐notch
Authors: Liu J. , Zhou Y. G. , Zhu J. , Lau K. M. , Chen K. J.
Published: May 2006

We report an AlGaN/GaN/InGaN/GaN double heterojunction HEMT (DH‐HEMT) with reduced buffer leakage and high‐mobility two‐dimensional‐electron‐gas (2DEG). A 3‐nm thin InxGa1–xN (x = 0.1) layer was inserted into the conventional AlGaN/GaN HEMT structure. A 2DEG mobility of around 1300 cm2/Vs and a sheet resistance of 480 Ω/sq were obtained at room temperature on this new DH‐HEMT structure grown on sapphire substrate with MOCVD‐grown GaN buffer. A peak transconductance of 230 mS/mm, a peak current gain cutoff frequency (fT ) of 14.5 GHz, and a peak power gain cutoff frequency (fmax ) of 45.4 GHz were achieved on a 1×100 μm device. The off‐state source‐drain leakage current is as low as ∼5 μA/mm at VDS = 10 V and the gate leakage current is about 10 μA/mm at a reverse bias of 20 V. For the devices on sapphire substrate, maximum power density of 3.4 W/mm and PAE of 41% were obtained at 2 GHz. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Imaging of inhomogeneous magnetization and currents coupled with anomalous transport properties in manganites
Authors: Tokunaga M. , Song H. , Tokunaga Y. , Tamegai T.
Published: May 2006

The cover picture of this issue of physica status solidi (c) has been taken from the article [1].
A CUSUM scheme with variable sample sizes and sampling intervals for monitoring the process mean and variance
Authors: Wu Zhang , Zhang Sheng , Wang Penghui
Published: May 2006

The adaptive control feature and CUSUM chart are two monitoring schemes that are much more effective than the traditional static Shewhart chart in detecting process shifts in mean and variance. However, the designs and analyses of the adaptive CUSUM chart are mathematically intractable and the operation is very laborious. This article proposes a VSSI WLC scheme, which is a weighted‐loss‐function‐based CUSUM (WLC) scheme using variable sample sizes and sampling intervals (VSSI). This scheme detects the two‐sided mean shift $\delta_{\mu}$ and increasing standard deviation shift $\delta_{\sigma}$ based on a single statistic WL (the weighted loss function). Most importantly, the VSSI WLC scheme is much easier to operate and design than a VSSI CCC scheme which comprises three individual CUSUM charts (two of them monitoring the increasing and decreasing mean shifts and one monitoring the increasing variance shift). Overall, the VSSI WLC scheme is much more effective than the static $\bar{X}$&S charts (by 72.36%), the VSSI $\bar {X}$&S charts (by 30.97%) and the static WLC scheme (by 50.94%) for detection. It is even more effective than the complicated VSSI CCC scheme for most cases. Copyright © 2006 John Wiley & Sons, Ltd.
Statistical methods for determining the accuracy of quantitative polymerase chain reaction‐based tests
Authors: Richardson Barbra A. , Hughes James P. , Benki Sarah
Published: May 2006

Quantitative polymerase chain reaction (PCR)‐based tests are used in several different scientific fields to determine levels of a target DNA sequence of interest (the target molecule). The accuracy of quantitative PCR‐based tests can be assessed by using the assay to determine the number of copies of the target molecule in a sample with a known concentration of the target molecule. For example, a sample with a known concentration of a target DNA sequence is serially diluted into replicate aliquots and these are tested to determine if the observed quantity of the target is close to the expected quantity (given the concentration in the original sample and the dilution). Statistical methods that are conventionally used to assess the accuracy of these assays do not take into account the variability in the number of target molecules in each aliquot from the original sample. We develop methods that take into account this extra variation and which determine the accuracy of quantitative PCR‐based tests in estimating the number of target molecules based on a set of assays of serial dilutions from an original sample with a known concentration of target molecules. These methods are applied to data from an experiment to test the accuracy of a real‐time PCR assay at low HIV‐1 DNA copy levels. Copyright © 2006 John Wiley & Sons, Ltd.
Relations among three aspects of first‐year college students' epistemologies of science
Authors: Smith Carol L. , Wenk Laura
Published: May 2006

At the start of their first semester, 35 college freshmen were given an interview probing (a) their differentiation of scientists' ideas from evidence, and hypotheses from theories; (b) their understanding of the inherent uncertainty of scientific knowledge; and (c) their reasoning about scientific controversies. The most common responses were in terms of an epistemology in which scientists' ideas and evidence are differentiated, and theories are understood as tested hypotheses (Level 2 in our system based on Carey, Evans, Honda, Jay, & Unger, 1989), although students varied in how consistently they differentiated theories and evidence across all questions. Responses in which theories are understood as broader explanatory frameworks guiding hypothesis testing (Level 3) were virtually nonexistent, but some students gave responses that showed awareness of processes of interpreting and reinterpreting patterns of results (Level 2.5). Responses across the three parts of the interview were significantly related. Consistently differentiating scientists' ideas from evidence was strongly related to appreciating the inherent uncertainty of scientific knowledge and with having a deeper understanding of the reasons for scientific controversies and how to resolve them. © 2006 Wiley Periodicals, Inc. J Res Sci Teach 43: 747–785, 2006
Analysis of leptin signalling in hematopoietic cells using an adapted MAPPIT strategy
Authors: Montoye T. , Piessevaux J. , Lavens D. , Wauman J. , Catteeuw D. , Vandekerckhove J. , Lemmens I. , Tavernier J.
Published: May 2006

The adipocyte‐secreted hormone leptin participates in the regulation of hematopoiesis and enhances proliferation of hematopoietic cells. We used an adaptation of the MAPPIT mammalian two‐hybrid method to study leptin signalling in a hematopoietic setting. We confirmed the known interactions of suppressor of cytokine signalling 3 (SOCS3) and STAT5 with the Y985 and Y1077 motifs of the leptin receptor, respectively. We also provide evidence for novel interactions at the Y1077 motif, including phospholipase C gamma and several members of the SOCS protein family, further underscoring the important role of the Y1077 motif in leptin signalling.
Differentiation of monocyte‐derived dendritic cells is associated with upregulation and activation of Rac‐1 small GTPase
Authors: Giammarioli Anna Maria , Gambardella Lucrezia , Quaranta Maria Giovanna , Lapenta Caterina , Santini Stefano Maria , Belardelli Filippo , Viora Marina , Malorni Walter
Published: May 2006

Critical changes occurring in Rac‐1 molecule, a cytoskeleton organizing small GTPase associated with cell ruffling, have been analyzed in dendritic cells (DCs) derived from monocytes cultured with granulocyte‐macrophage colony‐stimulating factor and IFN‐α or IL‐4. Although with different kinetics, both agents induced activation of Rac‐1 molecule and, more importantly, an upregulation of both protein expression and mRNA transcription. These findings strengthen the role of Rac‐1 molecule in the induction of DC differentiation and suggest that, besides its activation, the upregulation of Rac‐1 molecule might also play a role in the acquisition of DC mature phenotype.
Kind of Blue and the economy of modal jazz
Authors: BARRETT SAMUEL
Published: May 2006

Kind of Blue has been misrepresented by its promoters. The roots in the blues of the best-selling jazz album have repeatedly been obscured in favour of modal features whose associations are less problematic for those coping with the realities of racial injustice. The case that the blues underpins the modal language of the album is made through reconsideration of the claims made for compositional features of individual tracks. Recognition of the transformed blues language that lies at the heart of the album places questions of its significance on a new footing, opening up the mix of musical languages on the album to interpretation within the context of integrationist ideals of the late 1950s. A critical reading of the album against this backdrop leads to the suggestion that the ongoing commercial success of the album can be partly attributed to a retention of integrationist ideals that masks the reality of persistent inequalities in race relations.
The rough guide to critics: musicians discuss the role of the music press
Authors: BRENNAN MATT
Published: May 2006

This article explores the relationship between musicians and the music press from the musicians' point of view, based on a collection of recent interviews with musicians working in the pop and jazz fields. It will expose some of the concrete effects of the music press using examples from the everyday experiences of musicians, which include the influence of the press in record retail, genre labelling, and creating industry buzz. But while musicians may have a pragmatic understanding of the role of music criticism, their perspectives are emotionally heated in direct proportion to the influence the press holds over their own livelihoods. The interests of the working music critic often conflict with the interests of the working musician, and this article will conclude with a discussion of how the practical conflict of interests between musicians and critics is reflected in ideological differences between the two groups.
Die affektive Bewertung von imaginierten Gerüchen mit dem semantischen Differential
Authors: Reik Petra , Skrandies Wolfgang
Published: May 2006

Zusammenfassung. Mit dem semantischen Differential lässt sich die konnotative Bedeutung von Worten in unabhängigen Dimensionen beschreiben und auf den Skalen “Evaluation“, “Stärke“ und “Aktivität“ lokalisieren. Unser Experiment geht der Frage nach, ob imaginierte Gerüche sich mit dem semantischen Differential konsistent beurteilen lassen. Da Geruchswahrnehmung eng mit emotionalem Erleben verbunden ist, nehmen wir an, dass auch imaginierte Gerüche stärker durch die Dimension “Evaluation“ erklärt werden. Einunddreißig Substantive, die mit Gerüchen assoziiert sind, wurden von 138 erwachsenen Versuchspersonen beurteilt. Mit einer Faktorenanalyse konnten die drei erwarteten Faktoren gefunden werden. Der Faktor “Evaluation“ erklärt mit 32.75% die meiste Varianz. Die Gewichtung des Faktors ist ähnlich wie die, die durch die Beurteilung von eher emotionslosen Worten erreicht wird. Die Berechnung einer Clusteranalyse führte zu einer deutlichen Zuordnung von angenehmen und unangenehmen Gerüchen in verschiedene Cluster. Es zeigt sich, dass Gerüche signifikant geringere Distanzen im semantischen Raum aufweisen, wenn sie sich hinsichtlich Herkunft oder Verwendung ähneln.
Orthografie oder Orthographie?
Authors: Engl Verena , Hutzler Florian , Jacobs Arthur M. , Võ Melissa L.-H. , Braun Mario
Published: May 2006

Zusammenfassung. Vor zehn Jahren wurde eine Reform der deutschen Orthografie beschlossen. Anhand einer Blickbewegungsstudie, an der sowohl erwachsene Leser als auch Kinder teilnahmen, sollte untersucht werden, welche Auswirkungen die Rechtschreibreform auf das Lesen hatte. Die Ergebnisse liefern erste Hinweise dafür, dass die Rechtschreibreform die Worterkennung insgesamt nicht beeinträchtigt hat. Lediglich die Wörter zum Erhalt der Stammschreibung in Zusammensetzungen (Balletttänzerin vs. Ballettänzerin) konnten sowohl von Kindern als auch von Erwachsenen in alter Rechtschreibung schneller gelesen werden. Ein gemischtes Bild ergab sich außerdem bei der Getrenntschreibung (kennen lernen vs. kennenlernen): Hier können zwar Erwachsene die zusammengeschriebenen alten Wörter besser verarbeiten, Kinder hingegen die neu auseinander geschriebenen. Einerseits wird für die konsequente Umsetzung einer einheitlichen Schreibweise vor allem im Sinne der Kinder plädiert, andererseits auf die Notwendigkeit empirischer Studien zur Absicherung theoretischer Vorüberlegungen hingewiesen.
Quasi‐decadal variability of fall extreme wave heights in the western North Pacific
Authors: Sasaki W. , Iwasaki S. I. , Matsuura T. , Iizuka S.
Published: May 2006

We present a prominent quasi–decadal variability of fall extreme wave heights (H90, September–November mean of the monthly 90th percentile of significant wave heights) in the western North Pacific (WNP), based on wave reanalysis of the ERA40. It is found by applying an Empirical Orthogonal Function (EOF) analysis to H90 for 1957–2001 that the first EOF mode captures a monopole structure with maximum amplitude in the south of Japan with quasi–decadal variability of approximately 15–year. The quasi–decadal variability is also found partially in H90 observed around southern coast of Japan. By comparing intense tropical cyclone (ITC, with central pressure below 980 hPa) tracks for the decennial periods, we may be able to attribute the quasi–decadal variability of H90 in the WNP to the changes in the ITC tracks around the south of Japan.
Transmission electron microscopy investigation of self-assembly ZnO twinning nanostructures
Authors: Zhang Z. H. , Liu H. H. , Jian J. K. , Zou K. , Duan X. F.
Published: May 2006

Self-assembly ZnO twinning nanostructures are studied by transmission electron microscopy systematically. Selected area electron diffraction and high-resolution transmission electron microscopy observations indicate two types of twin boundaries (011¯1¯) and (011¯3) appeared in the same nanostructure and the twinning relationships are well defined. Convergent-beam electron diffraction techniques determine the polarities of the building blocks are all Zn terminated with the help of theoretical simulations, which is further confirmed by electron energy loss spectroscopy under (0002) and (0002¯) Bragg conditions.
Very low threshold, carrier-confined diode lasers by a single selective area growth
Authors: Cai Jianxin , Choa Fow-Sen , Gu Yonglin , Ji Xiaoming , Yan Jingzhou , Ru Guoyun , Cheng Liwei , Fan Jenyu
Published: May 2006

Very low threshold, carrier-confined semiconductor lasers made of a single selective area growth by metal organic chemical vapor deposition without using any regrowth are reported. Room-temperature continuous wave threshold of 2.7mA emitting around 1.54μm was achieved from as-cleaved facet. The fabricated lasers have good uniformity across the wafer and initial aging test shows that the laser is reliable.
Observation of one-electron charge in an enhancement-mode InAs single-electron transistor at 4.2K
Authors: Jones G. M. , Hu B. H. , Yang C. H. , Yang M. J. , Lyanda-Geller Y. B.
Published: May 2006

We demonstrate experimentally single-electron quantum dots using a single-top-gate transistor configuration on a composite quantum well. The data indicate a 15meV Coulomb charging energy and a 20meV orbital energy spacing, which imply a quantum dot of 20nm in diameter. Combining with the inherent advantage of a large electron g* factor in InAs, our demonstration is significant for a solid state implementation of a scalable quantum computing.
Controlled single electron transfer between Si:P dots
Authors: Buehler T. M. , Chan V. , Ferguson A. J. , Dzurak A. S. , Hudson F. E. , Reilly D. J. , Hamilton A. R. , Clark R. G. , Jamieson D. N. , Yang C. , Pakes C. I. , Prawer S.
Published: May 2006

We demonstrate electrical control of Si:P double dots in which the potential is defined by nanoscale phosphorus-doped regions. Each dot contains approximately 600 phosphorus atoms and has a diameter close to 30nm. On application of a differential bias across the dots, electron transfer is observed, using single electron transistors in both dc and rf modes as charge detectors. With the possibility to scale the dots down to a few and even single atoms these results open the way to a new class of precision-doped quantum dots in silicon.
A common allosteric site and mechanism in caspases
Authors: Scheer Justin M. , Romanowski Michael J. , Wells James A.
Published: May 2006

We present a common allosteric mechanism for control of inflammatory and apoptotic caspases. Highly specific thiol-containing inhibitors of the human inflammatory caspase-1 were identified by using disulfide trapping, a method for site-directed small-molecule discovery. These compounds became trapped by forming a disulfide bond with a cysteine residue in the cavity at the dimer interface ≈15 Å away from the active site. Mutational and structural analysis uncovered a linear circuit of functional residues that runs from one active site through the allosteric cavity and into the second active site. Kinetic analysis revealed robust positive cooperativity not seen in other endopeptidases. Recently, disulfide trapping identified a similar small-molecule site and allosteric transition in the apoptotic caspase-7 that shares only a 23% sequence identity with caspase-1. Together, these studies show a general small-molecule-binding site for functionally reversing the zymogen activation of caspases and suggest a common regulatory site for the allosteric control of inflammation and apoptosis.