bluuebunny/crossref_metadata_2025 huggingface dataset:
Fe in III–V and II–VI semiconductors
Authors: Malguth Enno , Hoffmann Axel , Phillips Matthew R.
Published: February 2008

Many theoretical and experimental studies deal with the realization of room‐temperature ferromagnetism in dilute magnetic semiconductors (DMS). However, a detailed quantitative understanding of the electronic properties of transition metal doped semiconductors has often been neglected. This article points out which issues concerning electronic states and charge transfers need to be considered using Fe as an example. Methods to address these issues are outlined, and a wealth of data on the electronic properties of Fe doped III–V and II–VI compound semiconductors that have been obtained over a few decades is reviewed thoroughly. The review is complemented by new results on the effective‐mass‐like state consisting of a hole bound to Fe2+ forming a shallow acceptor state.

The positions of established Fe3+/2+ and Fe2+/1+ charge transfer levels are summarized and predictions on the positions of further charge transfer levels are made based on the internal reference rule. The Fe3+/4+ level has not been identified unambiguously in any of the studied materials. Detailed term schemes of the observed charge states in tetrahedral and trigonal crystal field symmetry are presented including hyperfine structure, isotope effects and Jahn–Teller effect. Particularly, the radiative transitions Fe3+(4T1 → 6A1) and Fe2+(5E → 5T2) are analyzed in great detail.

An effective‐mass‐like state [Fe2+, h] consisting of a hole bound to Fe2+ is of great significance for a potential realization of spin‐coupling in a DMS. New insights on this shallow acceptor state could be obtained by means of stress dependent and temperature dependent absorption experiments in the mK range. The binding energy and effective Bohr radius were determined for GaN, GaP, InP and GaAs and a weak exchange interaction between the hole and the Fe2+ center was detected.

With regard to the Fe3+ ground state, 6A1, in GaP and InP, the hyperfine structure level Γ8 was found to be above the Γ8 level.

All results are discussed with respect to a potential realization of a ferromagnetic spin‐coupling in DMSs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Doping asymmetry in wide‐bandgap semiconductors: Origins and solutions
Authors: Yan Yanfa , Wei Su‐Huai
Published: February 2008

Wide‐bandgap (WBG) semiconductors are essential materials for making short‐wavelength and transparent optoelectronic devices. However, a serious obstacle to realizing WBG semiconductor‐based devices is their common doping asymmetry problem, i.e., a WBG semiconductor can be doped easily either p‐type or n‐type, but not both. This paper reviews the possible origins for doping asymmetry problems and updates our recent progress in searching for approaches to overcome the doping bottleneck in WBG semiconductors. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Calculating scattering matrices by wave function matching
Authors: Zwierzycki M. , Khomyakov P. A. , Starikov A. A. , Xia K. , Talanana M. , Xu P. X. , Karpan V. M. , Marushchenko I. , Turek I. , Bauer G. E. W. , Brocks G. , Kelly P. J.
Published: February 2008

The conductance of nanoscale structures can be conveniently related to their scattering properties expressed in terms of transmission and reflection coefficients. Wave function matching (WFM) is a transparent technique for calculating transmission and reflection matrices for any Hamiltonian that can be represented in tight‐binding form. A first‐principles Kohn–Sham Hamiltonian represented on a localized orbital basis or on a real space grid has such a form. WFM is based upon direct matching of the scattering‐region wave function to the Bloch modes of ideal leads used to probe the scattering region. The purpose of this paper is to give a pedagogical introduction to WFM and present some illustrative examples of its use in practice. We briefly discuss WFM for calculating the conductance of atomic wires, using a real space grid implementation. A tight‐binding muffin‐tin orbital implementation very suitable for studying spin‐dependent transport in layered magnetic materials is illustrated by looking at spin‐dependent transmission through ideal and disordered interfaces. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coarse‐grained modelling of polypyrrole morphologies
Authors: Rühle Victor , Kirkpatrick James , Kremer Kurt , Andrienko Denis
Published: February 2008

A multiscale model to simulate large scale morphologies and study charge transport in polypyrrole is developed. First, ab‐initio methods are used to derive an atomistic force field. Coarse graining of this atomistic model is then performed. At a final stage, the analysis of simulated morphologies allows to split polymer chains into conjugated segments, which can further be used to simulate both inter‐ and intrachain charge dynamics. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the application of the Edwards–Anderson order parameter to the Coulomb glass
Authors: Matulewski J. , Baranovskii S. D. , Thomas P.
Published: February 2008

It has been suggested in the literature to use a kind of a modified Edwards–Anderson (EA) order parameter borrowed from the field of spin glasses in order to characterize the correlated distribution of electrons governed by the long‐range many‐body interactions in a disordered system with localized states (the Coulomb glass). So far this idea has been applied to the lattice model of the disordered media. We show by straight‐forward Monte Carlo computer simulations that such an order parameter is of little use for interacting charge systems with spatial disorder. It turns out that the EA parameter for the spatially disordered system tends to zero at much higher temperatures than in the case of the lattice. Furthermore, the value of the modified EA parameter appears dependent on the system size, which makes this parameter rather useless. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A simple topological factor determining the allowance of pericyclic reactions
Authors: Gineityte V.
Published: February 2008

The study is aimed at revealing the possible manifestation of the overlap topology of AOs at early stages of pericyclic reactions. To this end, formation of an evenmembered cycle of carbon atoms is considered as a unified model, wherein relatively strong (CC) bonds alternate with weak ones. A direct perturbative method is applied to derive algebraic expressions for energy and bond order corrections due to cyclization. To represent the overlap topology of 2pz AOs over the cycle, a new concept of the roundabout interaction is introduced. The relevant definition contains a product of resonance parameters (or overlap integrals) between orbitals of all neighboring pairs of CC bonds and a certain N‐dependent parity factor, where N coincides with the total number of these bonds. The principal result of the study consists in demonstration of proportionality of both energy and bond order corrections to the roundabout interaction of the given cycle and thereby of a direct dependence between these corrections and the overlap topology of AOs. Moreover, the sign of the roundabout interaction is shown to determine the allowance of the given way of the process, viz. cycles described by positive (negative) roundabout interactions refer to allowed (forbidden) ways. Thus, an analog of the famous Woodward‐Hoffmann rule is obtained, wherein the overlap topology of AOs stands instead of symmetry of molecular orbitals. Along with stabilization of the cycle vs. the initial open chain, the allowed processes also are necessarily characterized by growing uniformity of all bond orders over the cycle, while the forbidden ones are accompanied by both destabilization and an increasing distinction between strong and weak bonds. The results obtained also yield a new definition of the concerted nature of pericyclic processes. The general conclusions of the study are illustrated by consideration of specific examples including the electrocyclic closure of polyene chains. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Exactly solvable quantum potentials with special functions solutions
Authors: Peña J. J. , Ovando G. , Morales J. , García‐Ravelo J. , García J.
Published: February 2008

In this work, a canonical point and a gauge transformation applied to theg(x) times differential equations (DE) for special functions (SF) is used to convert it into a Schrödinger‐like equation. This method leads to exactly solvable potentials allowing special functions solutions. For specific applications, keeping in mind the general DE for SF, the choice of the coefficients that identify the SF under study allows to find the equivalent of the Witten superpotential and wavefunctions for eachg(x). That is, the choice of a particularg(x) leads straightforwardly to those exactly solvable potentials having as wavefunctions the SF under consideration. As a useful application of the proposed method, we considered explicitly the potentials associated to the standard Hermite, Laguerre, Legendre, and Bessel SF in the case of some particular forms ofg(x). However, the proposed approach can be directly applied to any other standard SF with the aim to obtain exactly solvable potentials that can be used in the modelling of quantum chemical applications. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
A classification of cranial implants based on the degree of difficulty in computer design and manufacture
Authors: Poukens Jules , Laeven Paul , Beerens Maikel , Nijenhuis Gerard , Sloten Jos Vander , Stoelinga Paul , Kessler Peter
Published: February 2008

Background

Skull defects usually create aesthetic and functional disturbances to the patient. These defects are currently reconstructed by using computer‐aided design and manufacturing processes. Classification of skull defects becomes important in discussing the complexity of reconstruction in clinical practice or comparing clinical results in scientific articles.

Methods

A more comprehensive classification, which takes into account not only the anatomical location but also the degree of difficulty in designing and manufacturing the implant, is presented here. It is not our intention to describe the different treatment modalities; therefore, only two clinical examples are presented to demonstrate the purpose of classification.

Results

The new classification enables a more detailed comparison of the clinical outcome of different modes of treatment for skull defects.

Conclusions

The proposed classification reflects the degree of difficulty in designing and manufacturing of implants and can be very useful when comparing treatment results of skull defects for clinical or scientific purposes. Copyright © 2008 John Wiley & Sons, Ltd.
Securing the next generation mobile network
Authors: Hashim Fazirulhisyam , Kibria M. Rubaiyat , Jamalipour Abbas
Published: February 2008

Despite well‐defined security models to prevent fraudulent intrusion, a number of security attacks have been reported in literature for legacy networks. While a section of these attacks are due to inherent design limitations, others stem from the pervasive introduction of Internet Protocol (IP)‐based applications and external attacks. The former can be addressed by the continual evolution of the system (as is the case with existing systems) whereas the latter requires careful designing. With the advent of all‐IP next generation mobile network (NGMN) inter‐connecting disparate access technologies, the design process assumes paramount importance in relation to detecting/preventing/eliminating migration of attacks through infected terminals. Taking into consideration the fact that standardization bodies are responsible for individual network evolution, a cooperative NGMN security architecture is proposed in this paper that identifies and isolates/eliminates security attacks. The cooperation is encased by the network elements within the NGMN hierarchy and utilizes an anomaly‐based attack detection mechanism. Several dominant security attacks are simulated to demonstrate the effectiveness of the proposed architecture. Copyright © 2008 John Wiley & Sons, Ltd.
A design of optimal key management scheme for secure and survivable wireless sensor networks
Authors: Qian Yi , Lu Kejie , Rong Bo , Tipper David
Published: February 2008

In this paper, we investigate optimal key management design for secure and survivable heterogeneous wireless sensor networks (HWSNs). In particular, we formulate the key management problem as a multi‐objective optimization problem, in which the cost of the sensor network, and the security and survivability metrics of the sensor network are taken into account. To solve the multi‐objective optimization model, we develop a genetic algorithm (GA)‐based approach that can efficiently obtain near‐optimal solutions. We show the performance of our scheme through extensive numerical results. With a small amount of powerful sensor nodes in HWSN, we can balance the cost of the sensor network and the resilience of the sensor network with the required security constraint in different hostile environment. Copyright © 2008 John Wiley & Sons, Ltd.
Interactions at the interface between thermoplastic rubber and polychloroprene adhesive
Authors: Navarro‐Bañón M. Virtudes , Pastor‐Blas M. Mercedes , Martín‐Martínez José Miguel
Published: February 2008

The interface produced between a chlorinated thermoplastic styrene‐butadiene‐styrene rubber and a polychloroprene (PCP) adhesive has been studied and compared to the interface produced using a polyurethane (PU) adhesive. Chlorination of the rubber was produced by spin coating solutions of trichloroisocyanuric acid in methyl ethyl ketone. The adhesive solution was spin coated on to the chlorinated rubber and the interface between the chlorinated rubber and the adhesive was analyzed by infrared spectroscopy.

Chlorination of the rubber produces cross‐linking of the outermost chlorinated and oxidized rubber surface, which becomes insoluble in toluene. The chlorinated rubber chains are able to migrate through the chlorinated rubber/adhesive interface and produce a cross‐linked interface. Similar interfaces are obtained with PU or PCP adhesive. However it is the addition of a thermoreactive phenolic tackifier resin to the PCP adhesive, which imparts appropriate rheological properties to the PCP adhesive, responsible for the increased adhesion properties. Copyright © 2008 John Wiley & Sons, Ltd.
Effect of Sodium Dodecyl Sulphate on the Physicochemical, Thermal and Pasting Properties of Cassava Starch
Authors: Radhika Gopinathan S. , Moorthy Subramoney N.
Published: February 2008

The effect of different concentrations of sodium dodecyl sulphate (SDS) on cassava starch properties after complexation and in situ addition were studied. The swelling volume of the starch‐SDS complexes increased to a maximum of 100 mL/g with increase in concentration of SDS (even at 0.004 mol SDS) with a corresponding decrease in solubility. During in situ addition also, a similar but gradual behaviour was observed for swelling volume and solubility. The apparent and total amylose contents showed an irregular trend. The soluble amylose content decreased with increase in concentration of SDS. In vitro enzyme digestibility of starch‐SDS complexes was significantly lowered compared to that of native starch. The water‐binding capacity showed an initial decrease followed by a significant increase at higher concentrations of SDS. DSC studies showed that in addition to the gelatinisation endotherm, a peak corresponding to the melting of the starch‐SDS complex was obtained in the case of in situ addition of the surfactant. The peak viscosity of starch during in situ addition of SDS exhibited a rapid increase except at the highest concentration. The peak viscosity of starch‐SDS complexes underwent an initial reduction followed by a gradual increase at higher concentrations. The breakdown, setback and pasting temperature were also affected.
Differential effects of D‐amphetamine on red and blue light‐induced photic activation: A novel BOLD fMRI assay of human dopamine function
Authors: Cowan Ronald L. , Wood Julia , Dietrich Mary S. , de.B. Frederick Blaise , Lukas Scott E. , Renshaw Perry F.
Published: February 2008

The neurotransmitter dopamine (DA) is implicated in the pathophysiology of central nervous system (CNS) illnesses including Parkinson's disease, attention deficit disorder, schizophrenia, and substance abuse. A better understanding of CNS DA function would be of importance in improving our understanding of these conditions. Several lines of evidence suggest that exploring visual system function may be a useful paradigm for examining DA function. Clinical and basic science findings suggest that the visual response to blue light might prove a useful assay of CNS DA tone. To test this hypothesis, we used the functional magnetic resonance imaging (fMRI) BOLD method to measure visual cortical activation in human subjects (N = 6) in response to 8 Hz flashing red and blue light stimuli during placebo conditions and during the oral administration of 2.5 mg of D‐amphetamine, a drug known to increase synaptic concentrations of DA and other monoamine neurotransmitters. There was no effect of D‐amphetamine administration on the percent BOLD signal change to red or blue light. However, there was a specific augmentation of the spatial extent of activation (as measured by the number of activated pixels; P = 0.018) to blue, but not red light following D‐amphetamine administration. This finding is consistent with our hypothesis that blue light function may have utility as an assay of CNS DA tone. However, several limitations to the study, including the small sample size, low dosage of D‐amphetamine, and the fact that D‐amphetamine increases synaptic concentrations of DA and other monoamine neurotransmitters do not permit a conclusion regarding a specific role for DA in the observed increase in spatial activation to blue light in the amphetamine condition. Synapse 62:268–272, 2008. © 2008 Wiley‐Liss, Inc.
Regulation of complexin 1 and complexin 2 in the developing human prefrontal cortex
Authors: Salimi Kayvon , Glantz Leisa A. , Hamer Robert M. , German Thomas T. , Gilmore John H. , Jarskog L. Fredrik
Published: February 2008

Complexin 1 (CX1) and complexin 2 (CX2) are presynaptic proteins that modulate neurotransmitter release and are used as markers of inhibitory and excitatory synapses, respectively. The aim of this study was to gain insight into the development of inhibitory and excitatory synapses in human prefrontal cortex (PFC) by examining the expression of CX1 and CX2 in postmortem tissues. Relative complexin protein levels were measured by Western blotting in postmortem dorsolateral prefrontal cortex (DLPFC) of 42 subjects without neurological or psychiatric disease ranging in age from 18 gestational weeks to 25 years. Samples were batched a priori into fetal, 0–12 month, 1–5 years, 6–10 years, 11–15 years, 16–20 years, and 21–25 years age groups. CX1 and CX2 expression and CX2/CX1 demonstrated a significant effect of age group by ANOVA. Group CX1 level increased progressively across development and was lowest in the fetal group and highest in the young adult group, whereas group CX2 level increased between the fetal and the 6–10 years groups and then plateaued. Consistent with these divergent patterns, there was a significant effect of age group on CX2/CX1, which was higher in fetal and infant groups than in the young adult group. Furthermore, regression analysis demonstrated linear relationships of CX1 and CX2/CX1 with age, whereas CX2 was better described as having a curvilinear relationship with age. These data indicate that complexin expression increases during synaptic maturation in human DLPFC and that an increase in the influence of inhibitory synapses relative to that of excitatory synapses occurs during development in this cortical region. Synapse 62:273–282, 2008. © 2008 Wiley‐Liss, Inc.
Reference genes for normalization: A study of rat brain tissue
Authors: Bonefeld Birgit Egeskov , Elfving Betina , Wegener Gregers
Published: February 2008

Quantitative real‐time polymerase chain reaction (qPCR) has become a widely used tool in the search for disease genes. When examining gene expression with qPCR in psychiatric diseases, endogenous reference gene(s) must be used for normalization. Traditionally, genes such as β‐actin (ActB), Gapd, and 18s rRNA, assumed to be stably expressed, have been used for normalization. However, it has become clear that expression of these genes is influenced by different experimental paradigms. Since stable gene expression of houskeeping genes (HKGs), therefore, cannot be expected, alternative strategies are warranted. With the overall aim to inspect the gene expression of three target genes, NMDAR1, SORT, and CREB, in rat hippocampus, we tested a panel of eight HKGs, 18s rRNA, ActB, CycA, Gapd, Hmbs, Hprt1, Rpl13A, and Ywhaz in order to select the most stably expressed gene, using the NormFinder and geNorm software applets. Additionally, we have applied four different normalization approaches for normalization of the three target genes. We found using the NormFinder software that Ywhaz is the most stably expressed gene among the eight tested HKGs. However, the results of the analysis of the target genes are highly dependent on the choice of normalization approach. Moreover, the number of HKGs, used for selection of the most stable HKG, also influences on the result of the gene expression analysis of target genes. These results underline the importance of choosing a proper normalization strategy when analyzing gene expression with qPCR. The strategy should be unbiased and carried out in every specific experimental setting. Synapse 62:302–309, 2008. © 2008 Wiley‐Liss, Inc.
Dopamine D2High receptors on intact cells
Authors: Seeman Philip
Published: February 2008

In humans, behavioral dopamine supersensitivity occurs in schizophrenia and in Parkinson's disease. In animals, behavioral dopamine supersensitivity is consistently associated with increased dopamine D2High receptors in homogenized striata in vitro. Because D2High receptors have not yet been detected in intact cells, we used [3H]domperidone to detect D2High sites in intact rat anterior pituitary adenoma culture cells. Although [3H]raclopride and [3H]spiperone did not detect D2High receptors in intact cells or in rat fresh striatal slices, [3H]domperidone readily detected D2High receptors, warranting an in vivo search for D2High variations in human diseases. Synapse 62:314–318, 2008. © 2008 Wiley‐Liss, Inc.
Cross‐Magnetron‐Effekt und ITO‐Schichtabscheidung
Authors: Kupfer Hartmut , Richter Frank , Kleinhempel Ronny , Blüthner Ralf , Raubold Thomas
Published: February 2008

Eine Großflächenbeschichtung mit leitfähigen transparenten Schichten erfordert eine homogene Verteilung der Prozessparameter am Substrat. Nachteilig wirken sich hierbei der Cross‐Corner‐Effekt bei der Einzel‐Magnetronquelle sowie der Cross‐Magnetron‐Effekt beim Dualmagnetron aus. Messungen belegen einen erheblichen Einfluss dieser Effekte auf die laterale Verteilung der Plasmaeigenschaften am Substrat. Es werden die gemessenen funktionellen Eigenschaften von Indium‐Zinn‐Oxydschichten im Zusammenhang mit der Konzentration des dissoziierten Sauerstoffs im Prozessgas diskutiert, die von den Plasmaeigenschaften und dem Sauerstoffpartialdruck bestimmt wird.
Novel stress responses facilitate Saccharomyces cerevisiae growth in the presence of the monocarboxylate preservatives
Authors: Mollapour Mehdi , Shepherd Andy , Piper Peter W.
Published: February 2008

Certain yeasts are relatively resistant to the small number of monocarboxylic acids allowed in food preservation, with the result that these preservatives often have to be used in high concentrations in order to prevent spoilage. When grown at slightly acid pH, Saccharomyces cerevisiae acquires elevated resistance to these acids by means of discrete stress responses. Acquisition of resistance to acetic acid involves loss of Fps1p, the aquaglyceroporin of the plasma membrane that facilitates the passive diffusional entry of this acid into cells. Acetic acid stress transiently activates Hog1p mitogen‐activated protein kinase, which then directly phosphorylates Fps1p in order to target this channel for endocytosis and degradation in the vacuole. Other carboxylate preservatives (propionate, sorbate or benzoate) are too large to traverse the Fps1p pore. Instead, being more lipophilic than acetic acid, they enter cells mainly by a process of non‐facilitated diffusion across the plasma membrane. Once inside the cell, these acids activate War1p, a transcription factor that induces the gene for the Pdr12p plasma membrane ATP‐binding cassette transporter. Pdr12p lowers the intracellular levels of propionate, sorbate or benzoate by catalysing the active efflux of the preservative anion from the cell. Still other mechanisms of weak acid resistance are found in Zygosaccharomyces, including a capacity for the oxidative degradation of sorbic and benzoic acids conferred by a mitochondrial monooxygenase, a system absent in S. cerevisiae. Copyright © 2008 John Wiley & Sons, Ltd.
Implementation of an Ultra‐short‐stay Program After Breast Cancer Surgery in Four Hospitals: Perceived Barriers and Facilitators
Authors: de Kok Mascha , van der Weijden Trudy , Kessels Alfons , Dirksen Carmen , van de Velde Cornelis , Roukema Jan , van der Ent Fred , Bell Antoine , von Meyenfeldt Maarten
Published: February 2008

Background

The objective of this study was to identify barriers and facilitators that professionals see when implementing a program incorporating ultra‐short hospital admission in the treatment of breast cancer. Such an intervention is an essential step when designing a strategy for implementation of a care program that is different from established daily routines.

Methods

In a prospective quasi‐experimental study qualitative data were collected from four hospitals in the Netherlands between January 2005 and July 2006. Potential barriers and facilitators for successful implementation were extracted from detailed notes of all contacts between the researchers and each participating hospital. Subsequently, these items were categorized according to themes.

Results

Over 40 items were identified. Most barriers concerned organizational and program‐related aspects, whereas the most common facilitators addressed organizational issues. Six of the 29 study recommendations were perceived as impeding or facilitating. Thirty of the 40 barriers were mentioned in one hospital only. Several key factors were found that determine the success of implementation of an ultrashort‐stay program. Provision of care in the home setting should be assured. Policy makers and insurance companies should acknowledge that multidisciplinary care teams and teams integrating primary and secondary care fulfill important roles in delivering continuity of care. Specific strategies should be set out to convince everybody in the organization about the new ideas, particularly the minority of people who do not agree with the plans.

Conclusions

A set of barriers and facilitators for implementation of the program was described that may be used by any professional preparing to perform breast cancer surgery in an ultrashort–stay facility. The systematic approach that led to this set may be used by any healthcare professional concerned with implementation and consolidation of innovative programs in healthcare in order to enhance the effectiveness of the chosen strategy.
A New Technique for Presentation of Scientific Works: Video in Poster
Authors: Bozdag Ali Dogan
Published: February 2008

Background

Presentations at scientific congresses and symposiums can be in two different forms: poster or oral presentation. Each method has some advantages and disadvantages. To combine the advantages of oral and poster presentations, a new presentation type was conceived: “video in poster.”

Methods

The top of the portable digital video display (DVD) player is opened 180° to keep the screen and the body of the DVD player in the same plane. The poster is attached to the DVD player and a window is made in the poster to expose the screen of the DVD player so the screen appears as a picture on the poster. Then this video in poster is fixed to the panel. When the DVD player is turned on, the video presentation of the surgical procedure starts.

Results

Several posters were presented at different medical congresses in 2007 using the “video in poster” technique, and they received poster awards.

Conclusions

The video in poster combines the advantages of both oral and poster presentations.
Differential control of isocitrate lyase gene transcription by non‐fermentable carbon sources in the milk yeast Kluyveromyces lactis
Authors: Rodicio Rosaura , López Maria Luz , Cuadrado Sara , Cid Alejandra F. , Redruello Begoña , Moreno Fernando , Heinisch Jürgen J. , Hegewald Anne-Kathrin , Breunig Karin D.
Published: February 2008

The KlICL1 gene, encoding isocitrate lyase in Kluyveromyces lactis, is essential for ethanol utilization. Deletion analyses identified two functional promoter elements, CSRE‐A and CSRE‐B. Transcription is activated on ethanol, but not on glucose, glycerol or lactate. Expression depends on the KlCat8p transcription factor and KlSip4p binds to the promoter elements. Glycerol diminishes KlICL1 expression and a single carbon source responsive element (CSRE) sequence is both necessary and sufficient to mediate this regulation. The glycerol effect is less pronounced in Saccharomyces cerevisiae than in K. lactis. Mutants lacking KlGUT2 (which encodes the glycerol 3‐phosphate dehydrogenase) still show reduced expression in glycerol, whereas mutants deficient in glycerol kinase (Klgut1) do not. We conclude that a metabolite of glycerol is required for this regulation.
Isolation and functional characterization of a β‐eudesmol synthase, a new sesquiterpene synthase from Zingiber zerumbet Smith
Authors: Yu Fengnian , Harada Hisashi , Yamasaki Kazuhisa , Okamoto Sho , Hirase Souta , Tanaka Yasuo , Misawa Norihiko , Utsumi Ryutaro
Published: February 2008

In this paper, we have identified a new sesquiterpene synthase gene (ZSS2) from Zingiber zerumbet Smith. Functional expression of ZSS2 in Escherichia coli and in vitro enzyme assay showed that the encoded enzyme catalyzed the formation of β‐eudesmol and five additional by‐products. Quantitative RT‐PCR analysis revealed that ZSS2 transcript accumulation in rhizomes has strong seasonal variations. To further confirm the enzyme activity of ZSS2 and to assess the potential for metabolic engineering of β‐eudesmol production, we introduced a gene cluster encoding six enzymes of the mevalonate pathway into E. coli and coexpressed it with ZSS2. When supplemented with mevalonate, the engineered E. coli produced a similar sesquiterpene profile to that produced in the in vitro enzyme assay, and the yield of β‐eudesmol reached 100 mg/L.
Crystal structure of the ternary FimC–FimFt–FimDN complex indicates conserved pilus chaperone–subunit complex recognition by the usher FimD
Authors: Eidam Oliv , Dworkowski Florian S.N. , Glockshuber Rudi , Grütter Markus G. , Capitani Guido
Published: February 2008

Type 1 pili, anchored to the outer membrane protein FimD, enable uropathogenic Escherichia coli to attach to host cells. During pilus biogenesis, the N‐terminal periplasmic domain of FimD (FimDN) binds complexes between the chaperone FimC and pilus subunits via its partly disordered N‐terminal segment, as recently shown for the FimC–FimHP–FimDN ternary complex. We report the structure of a new ternary complex (FimC–FimFt–FimDN) with the subunit FimFt instead of FimHp. FimDN recognizes FimC–FimFt and FimC–FimHP very similarly, predominantly through hydrophobic interactions. The conserved binding mode at a “hot spot” on the chaperone surface could guide the design of pilus assembly inhibitors.
R‐spondin1 synergizes with Wnt3A in inducing osteoblast differentiation and osteoprotegerin expression
Authors: Lu Wenyan , Kim Kyung-Ah , Liu Jianzhong , Abo Arie , Feng Xu , Cao Xu , Li Yonghe
Published: February 2008

R‐spondins are a new group of Wnt/β‐catenin signaling agonists, however, the role of these proteins in bone remains unclear. We reported herein that R‐sponin1 (Rspo1) acted synergistically with Wnt3A to activate Wnt/β‐catenin signaling in the uncommitted mesenchymal C2C12 cells. Furthermore, we found that Rspo1 at concentrations as low as 10 ng/ml synergized strongly with Wnt3A to induce C2C12 osteoblastic differentiation and osteoprotegerin expression. These events were blocked by Wnt/β‐catenin signaling antagonist Dickkopf‐1. Finally, we demonstrated that Rspo1 synergized with Wnt3A to induce primary mouse osteoblast differentiation. Together, these findings suggest that Rpos1 may play an important role in bone remodeling.
The second transmembrane domain of the large conductance, voltage‐ and calcium‐gated potassium channelβ1subunit is a lithocholate sensor
Authors: Bukiya Anna N. , Vaithianathan Thirumalini , Toro Ligia , Dopico Alejandro M.
Published: February 2008

Bile acids and other steroids modify large conductance, calcium‐ and voltage‐gated potassium (BK) channel activity contributing to non‐genomic modulation of myogenic tone. Accessory BKβ1subunits are necessary for lithocholate (LC) to activate BK channels and vasodilate. The protein regions that sense steroid action, however, remain unknown. Using recombinant channels in 1‐palmitoyl‐2‐oleoyl‐phosphatidylethanolamine/1‐palmitoyl‐2‐oleoyl‐phosphatidylserine bilayers we now demonstrate that complex proteolipid domains and cytoarchitecture are unnecessary forβ1to mediate LC action;β1and a simple phospholipid microenvironment suffice. Sinceβ1senses LC butβ4does not, we made chimeras swapping regions between these subunits and, following channel heterologous expression, demonstrate thatβ1TM2 is a bile acid‐recognizing sensor.
Phosphate availability affects the tonoplast localization of PLDζ2, an Arabidopsis thaliana phospholipase D
Authors: Yamaryo Yoshiki , Dubots Emmanuelle , Albrieux Catherine , Baldan Barbara , Block Maryse A.
Published: February 2008

Under phosphate deprivation, higher plants change their lipid composition and recycle phosphate from phospholipids. A phospholipase D, PLDζ2, is involved in this recycling and in other cellular functions related to plant development. We investigated the localization of Arabidopsis PLDζ2 by cell fractionation and in vivo GFP confocal imaging. AtPLDζ2 localizes to the tonoplast and the Nter regulatory domain is sufficient for its sorting. Under phosphate deprivation, AtPLDζ2 remains located in the tonoplast but its distribution is uneven. We observed PLDζ2‐enriched tonoplast domains preferentially positioned close to mitochondria and beside chloroplasts. In absence of PLDζ2, membrane developments were visualized inside vacuoles.
Proteasome inhibitor MG132 blocks viral DNA replication and assembly of human cytomegalovirus
Authors: Kaspari Marion , Tavalai Nina , Stamminger Thomas , Zimmermann Albert , Schilf Rita , Bogner Elke
Published: February 2008

This study provides evidence that proteasomal activity is required at multiple steps in human cytomegalovirus replication. Electron microscopy revealed that no viral particles were assembled in the presence of proteasome inhibitor MG132. Immunofluorescence and Western blot analyses using MG132 demonstrated that immediate early gene expression was suppressed at low but not high MOI. In contrast, expression of late proteins was completely blocked independent of MOI. Additionally, pulsed‐field gel electrophoresis demonstrated that MG132 interferes with cleavage of HCMV DNA. Bromodeoxyuridine incorporation studies showed that de novo viral DNA synthesis is reduced in the presence of MG132. Furthermore, in contrast to previous hypotheses we demonstrated that neither the ND10 components PML and hDaxx nor NFκB activation represent the target for MG132.
Wake transition in the flow around two circular cylinders in staggered arrangements
Authors: CARMO BRUNO S. , SHERWIN SPENCER J. , BEARMAN PETER W. , WILLDEN RICHARD H. J.
Published: February 2008

The wake transition of the flow around two circular cylinders placed in staggered arrangements with fixed streamwise separation of 5Dand cross-stream separation varying from 0 to 3Dhas been studied. The wake transition is compared to that of a single isolated cylinder. Linear stability analysis utilizing Floquet theory and direct numerical simulations using a spectral/hp element spatial discretization were carried out. The unstable modes that first appear in the wake transition of the flow around a single cylinder, which are the long-spanwise-wavelength mode A and the short-spanwise-wavelength mode B, are also found in the flow around the staggered arrangements. However, a third mode, referred to as mode C, is also present in the wake transition of the flow around staggered arrangements, depending on the relative positioning of the cylinders. This mode has an intermediate spanwise wavelength and period-doubling character. The structure and onset characteristics of mode C are analysed and the nonlinear character of the bifurcation for this mode is investigated.
Feasibility, efficiency and transportability of short-horizon optimal mixing protocols
Authors: CORTELEZZI LUCA , ADROVER ALESSANDRA , GIONA MASSIMILIANO
Published: February 2008

We consider, as a case study, the optimization of mixing protocols for a two-dimensional, piecewise steady, nonlinear flow, the sine flow, for both the advective–diffusive and purely advective cases. We use the mix-norm as the cost function to be minimized by the optimization procedure. We show that the cost function possesses a complex structure of local minima of nearly the same values and, consequently, that the problem possesses a large number of sub-optimal protocols with nearly the same mixing efficiency as the optimal protocol. We present a computationally efficient optimization procedure able to find a sub-optimal protocol through a sequence of short-time-horizon optimizations. We show that short-time-horizon optimal mixing protocols, although sub-optimal, are both feasible and efficient at mixing flows with and without diffusion. We also show that these optimized protocols can be derived, at lower computational cost, for purely advective flows and successfully transported to advective–diffusive flows with small molecular diffusivity. We characterize our results by discussing the asymptotic properties of the optimized protocols both in the pure advection and in the advection–diffusion cases. In particular, we quantify the mixing efficiency of the optimized protocols using the Lyapunov exponents and Poincaré sections for the pure advection case, and the eigenvalue–eigenfunction spectrum for the advection–diffusion case. Our results indicate that the optimization over very short-time horizons could in principle be used as an on-line procedure for enhancing mixing in laboratory experiments, and in future engineering applications.
On beach cusp formation
Authors: DODD NICHOLAS , STOKER ADAM M. , CALVETE DANIEL , SRIARIYAWAT ANURAK
Published: February 2008

A system of shallow water equations and a bed evolution equation are used to examine the evolution of perturbations on an erodible, initially plane beach subject to normal wave incidence. Both a permeable (under Darcy's law) and an impermeable beach are considered. It is found that alongshore-periodic morphological features reminiscent of swash beach cusps form after a number of incident wave periods on both beaches. On the permeable (impermeable) beach these patterns are accretional (erosional). In both cases flow is ‘horn divergent’. Spacings of the cusps are consistent with observations, and are close to those provided by a standing synchronous linear edge wave. An analysis of the processes leading to bed change is presented. Two physical mechanisms are identified: concentration gradient and flow divergence, which are dominant in the lower and upper swash respectively, and their difference over a wave cycle leads to erosion or deposition on an impermeable beach. Infiltration enters this balance in the upper swash. A bed wave of elevation is shown to advance up the beach at the tip of the uprush, with a smaller wave of depression on the backwash. It is found that cusp horns can grow by a positive feedback mechanism stemming from decreased (increased) backwash on positive (negative) bed perturbations.
On the calculation of the available potential energy of an isolated perturbation in a density-stratified fluid
Authors: LAMB KEVIN G.
Published: February 2008

Two methods for calculating the available potential energy (APE) of an isolated feature in a density-stratified fluid, such as an internal solitary wave or an eddy, are compared. The first formulation calculates the APE by integrating the perturbation potential energy density Ew. The second uses an available potential energy density Ea. Both formulations are based on the reference density obtained by adiabatically rearranging the density field to a state of minimum energy. It is shown, under more general conditions than used previously, that (i) the integrals of Ew and Ea over a finite domain are identical; and (ii) that for an isolated feature in an unbounded domain, the far-field density $\bar\rho(z)$ can be used as the reference density if Ea is used to find the APE. This is not the case when Ew is used, hence use of the available potential energy density formulation is simpler in this situation.
Measured scaling properties of the transition boundaries in a rotating suspension of non-Brownian settling particles
Authors: MATSON W. R. , ACKERSON B. J. , TONG P.
Published: February 2008

Series of concentration and velocity patterns are found for the rotating suspension of non-Brownian settling particles in a completely filled horizontal cylinder. Individual flow states, or phases, are studied using both side and cross-sectional imaging to examine the detailed flow structures. The overall steady-state phase diagram of the system is mapped over a wide range of the rotation rate and fluid viscosity. Effects of the particle radius a, volume fraction φ, and cylinder radius R on the transition boundaries are examined. It is found that the phase diagram of the rotating suspensions can be divided into three regions, in which the transition boundaries obey different scaling laws. A theoretical attempt is made to understand the scaling behaviour of the transition boundaries. The theoretical understanding is achieved at three different levels: a general dimensional consideration, a scaling analysis on the continuum equations of motion, and a specific instability calculation for the transition boundary at the centrifugal limit.
A higher-order boundary layer analysis for lipid vesicles with two fluid domains
Authors: DAS SOVAN L. , JENKINS JAMES T.
Published: February 2008

We obtain approximate solutions to the equations that govern the shape of giant unilamellar vesicles (GUVs) with two fluid phases. The equations involve a dimensionless small parameter related to the resistance to changes in its local mean curvature. Asymptotic solutions for the shape are obtained up to and including terms of first order in the small parameter. At this order, we determine a relationship between the tangent angle at the interface and the difference in the Gaussian curvature stiffnesses of the co-existing phases. This relationship demonstrates that a difference in the Gaussian curvature stiffnesses moves the phase boundary away from the neck, as determined in previous numerical studies. The analytical expression for the tangent angle obtained here can be used to determine elastic parameters for the membranes from experimental data. Use of the analytical expression will eliminate the need for the repeated generation of numerical solutions in the estimation of the material parameters. Our analytical solution also reduces the number of measurements needed as inputs for an existing boundary layer analysis.
Pension Reform in Latin America: Distributional Principles, Inequalities and Alternative Policy Options
Authors: ARZA CAMILA
Published: February 2008

During the 1990s a wave of major structural reforms that changed the distributional principles underpinning pension policies spread across Latin America. Outcomes were not always as expected. The implementation of new pension rules in the socio-economic, political and institutional context of Latin America has resulted in a number of inequalities which affect pension system performance and the gains that different income groups and generations may obtain. In order to overcome the distributional drawbacks of reform, Latin American governments may need to afford a new role to non-contributive pensions, as well as consider the application of specific regulatory adjustments to reduce the risks and inequalities involved in the private pillar. Cross-border policy learning may provide useful tools to achieve these aims.
The President's ‘New’ Constituency: Lula and the Pragmatic Vote in Brazil's 2006 Presidential Elections
Authors: ZUCCO CESAR
Published: February 2008

The 2006 presidential elections in Brazil witnessed a dramatic shift of Lula's voting base away from the more developed regions of the country and towards the poorest areas. This paper uses municipal-level data to argue that while this shift represents an important change for the support base of Lula himself, it can mostly be explained by the government's massive cash transfer programme, the Bolsa Familia, and by the empirical regularity with which presidential candidates from the incumbent party in Brazil always perform better in the less developed regions of the country.
The Resistance of the Marginalised: Catholics in Eastern Michoacán and the Mexican State, 1920–40
Authors: MANZO ENRIQUE GUERRA
Published: February 2008

This article analyses Catholic resistance to the anti-clerical laws of the 1920–1940 period in various municipalities in eastern Michoacán. It argues that the diverse strategies adopted by Catholics in each region was more a response to the variety of local power dynamics at play, than an expression of different religious expressions (sacramental versus ‘popular’ Catholicism). It concludes that the predominance of pacific forms of resistance was the result both of efforts on the part of the ecclesiastical hierarchy to reach a modus vivendi with the Mexican state, and of social expressions of Catholicism ‘from below’.
A first checklist of parmelioid and similar lichens in Europe and some adjacent territories, adopting revised generic circumscriptions and with indications of species distributions
Authors: HAWKSWORTH David L. , BLANCO Oscar , DIVAKAR Pradeep K. , AHTI Teuvo , CRESPO Ana
Published: February 2008

After a discussion of changing generic concepts in the parmelioid lichens, a checklist with the current species placements is presented. Twenty-five genera and 143 species are accepted for Europe, of which 17 genera and 112 species belong to the monophyletic parmelioid clade. The individual countries from which species are reported are provided, along with references to key publications. Synonyms used at species rank in Europe are cross-referenced, and the dates of publication of all names are provided. One new combination is made: Xanthoparmelia pulvinaris (syn. Parmelia pulvinaris, X. pseudohungarica).