bluuebunny/crossref_metadata_2025 huggingface dataset:
High resolution measurements of strain and tilt distributions in SiGe mesas using electron backscatter diffraction
Authors: Wilkinson Angus J.
Published: December 2006

Electron backscatter diffraction allows the elastic strain and rotation tensors to be determined at high spatial resolution and with a strain sensitivity of ∼10−4. The technique is used to investigate variations of strains and rotations near the surface of 200nm thick epitaxial layers of Si0.85Ge0.15 grown on a Si substrate patterned with mesa stripes. In wide mesa stripes the strain relaxation and lattice curvature are confined to the outer edges of the mesa. While in narrower mesas the relaxation extends across the entire mesa width. Measured stress levels confirm earlier predictions of the extent of relaxation with mesa width.
Polaritonic emission via surface plasmon cross coupling
Authors: Bonnand C. , Bellessa J. , Symonds C. , Plenet J. C.
Published: December 2006

In this letter the authors demonstrate that the emission of plasmon/exciton polaritons in an organic semiconductor can be extracted using surface plasmon cross coupling. A J-aggregated cyanine dye layer is deposited on a silver film and then the whole structure is periodically corrugated. As a result of this corrugation, the dispersion lines of the surface modes on both sides of the silver layer may cross. At this crossing point, an increase in the polaritonic emission is observed. The contributions of unpolarized incoherent states and of the TM polarized polaritons emission are separated.
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single quantum wire formation and emission at 1.5μm
Authors: Alén B. , Fuster D. , González Y. , González L. , Martínez-Pastor J.
Published: December 2006

Isolated InAs∕InP self-assembled quantum wires have been grown using in situ accumulated stress measurements to adjust the optimal InAs thickness. Atomic force microscopy imaging shows highly asymmetric nanostructures with average length exceeding more than ten times their width. High resolution optical investigation of as-grown samples reveals strong photoluminescence from individual quantum wires at 1.5μm. Additional sharp features are related to monolayer fluctuations of the two-dimensional InAs layer present during the early stages of the quantum wire self-assembling process.
Low frequency terahertz quantum cascade laser operating from 1.6to1.8THz
Authors: Walther Christoph , Scalari Giacomo , Faist Jérôme , Beere Harvey , Ritchie David
Published: December 2006

The authors report a GaAs∕Al0.1Ga0.9As quantum cascade laser based on a bound-to-continuum transition optimized for low frequency operation. High tunability of the gain curve is achieved by the Stark effect and laser emission is measured between 1.6 and 1.8THz. Pulsed mode operation up to 95K and continuous wave operation up to 80K are reported. The dynamical range in current is as high as 43%.
Linear-scaling calculation of static and dynamic polarizabilities in Hartree-Fock and density functional theory for periodic systems
Authors: Izmaylov Artur F. , Brothers Edward N. , Scuseria Gustavo E.
Published: December 2006

We present a linear-scaling method for analytically calculating static and dynamic polarizabilities with Hartree-Fock and density functional theory, using Gaussian orbitals and periodic boundary conditions. Our approach uses the direct space fast multipole method to evaluate the long-range Coulomb contributions. For exact exchange, we use efficient screening techniques developed for energy calculations. We then demonstrate the capabilities of our approach with benchmark calculations on one-, two-, and three-dimensional systems.
Field-effect transistor based on atomically flat rutile TiO2
Authors: Katayama Masao , Ikesaka Shinya , Kuwano Jun , Yamamoto Yuichi , Koinuma Hideomi , Matsumoto Yuji
Published: December 2006

The authors have fabricated a field-effect transistor (FET) based on a rutile TiO2 active channel. Top-gate transistor structure with an amorphous LaAlO3 insulator was fabricated on the ultrasmoothed rutile single crystals. Reproducible n-type FET actions were observed only by the use of ultrasmoothed TiO2 surfaces. Moreover, an anisotropy of the field-effect mobility depending on the channel direction, which reflects intrinsic nature of rutile, was definitely observed. Inserting MgO insulating buffer between TiO2 and amorphous LaAlO3 suppressed the off-state current and realized on-to-off current ratio as high as 104.
Direct measurement of carrier drift velocity and mobility in a polymer field-effect transistor
Authors: Basu Debarshi , Wang Liang , Dunn Lawrence , Yoo Byungwook , Nadkarni Suvid , Dodabalapur Ananth , Heeney Martin , McCulloch Iain
Published: December 2006

An electronic method to measure the drift velocity and mobility of charge carriers in polymer thin film transistor has been developed. The measurement is based on the movement of a packet of carriers injected into the channel. This technique can be used to explore trap states and therefore obtain a comprehensive understanding of charge transport in these materials. Drift mobility of 0.52cm2∕Vs is obtained from the transit time which is a factor of 3 higher than the field-effect transistor mobility.
Direct determination of the polarization direction of domains in BaTiO3 single crystal
Authors: Zhang Z. H. , Qi X. Y. , Duan X. F.
Published: December 2006

The polarization directions of domains in BaTiO3 single crystal are determined by convergent-beam electron diffraction directly. The intensity distributions in the (001) and (001¯) diffraction disks are different, which is due to the noncentrosymmetric unit cell of ferroelectrics. The in situ transmission electron microscopy observations on the evolution of domains under external fields indicate that the disk with a little brighter center fringes is the (001) disk and the polarization vector is toward this disk. The method provides a straightforward criterion for polarization direction determination of ferroelectric domains.
Schottky barrier formation at a carbon nanotube—metal junction
Authors: Zhu Wenguang , Kaxiras Efthimios
Published: December 2006

The issue of Schottky barrier formation at carbon nanotube (CNT) contacts with metal leads is of crucial importance for nanotube-based electronic devices. The authors examine the electronic properties of a particular structure containing a metal/CNT contact that resembles experimental setups for CNT field-effect transistors. The model consists of a single-wall (8,0) CNT with its central section fully covered by a Pd ring, representing the metal electrode. Through first-principles total energy and electronic structure calculations within density functional theory, the authors establish that the junction between the metal-covered part and the bare part of the CNT is responsible for the experimentally measured Schottky barrier of ∼0.4eV in CNT field-effect transistors.
Tunneling magnetoresistance of MnAs thin film/GaAs∕AlAs∕GaAs:MnAs nanoclusters and its AlAs barrier thickness dependence
Authors: Nam Hai Pham , Yokoyama Masafumi , Ohya Shinobu , Tanaka Masaaki
Published: December 2006

The authors have investigated tunneling magnetoresistance (TMR) of magnetic tunnel junctions (MTJs) consisting of MnAs thin film (20nm)∕GaAs(1nm)∕AlAs(d=2–5nm)∕GaAs:MnAs nanoclusters (10nm). The GaAs:MnAs material contains ferromagnetic MnAs nanoclusters in a GaAs matrix and acts as a spin injector and a spin detector. They observed an oscillatory behavior of the TMR ratio with the increasing AlAs barrier thickness, which can be explained by the quantum interference of two X-valley related wave functions in the AlAs barrier.
Femtosecond time-resolved study in InxGa1−xN (0001) ultrathin epilayers: Effects of high indium mole fraction and thickness of the films
Authors: Lioudakis Emmanouil , Othonos Andreas , Dimakis Emmanouil , Georgakilas Alexandros
Published: December 2006

In view of promising full-solar-spectrum photovoltaic systems based on InxGa1−xN ternary alloys, femtosecond time-resolved study in ultrathin epilayers was employed in order to extract the fundamental properties of material. Two different thicknesses of epilayers were employed with relative high indium mole fractions. State filling effect at various probing energy states has been observed for both epilayers. Saturation of state filling as well as enhanced photoinduced absorption occurred at higher probing wavelengths. Furthermore, coherent acoustic phonon oscillations were also observed for both ultrathin epilayers with a thickness dependent oscillation frequency. Finally, absorption band edge of these alloys has been determined.
Superconducting fault current limiter device based on (Hg,Re)-1223 superconductor
Authors: Passos C. A. C. , Orlando M. T. D. , Passamai J. L. , Medeiros E. F. , Oliveira F. D. C. , Fardin J. F. , Simonetti D. S. L.
Published: December 2006

A preliminary study of a small superconducting current limiter device based on Hg0.8Re0.2Ba2Ca2Cu3O8+δ, (Hg,Re)-1223 ceramic is described. A fault current test at 60Hz confirmed a reduction in the density of current value, from 1.55×102to0.82×102Apeak∕cm2. The prospective/limited density of current ratio observed was ∼1.9 for a 0.24cm thick sample, without any damage to the (Hg,Re)-1223 superconductor. A recovery test indicated that the polycrystalline sample kept its superconducting properties and had not shown modifications in its stoichiometry. In conclusion, (Hg,Re)-1223 can be used to build superconducting fault current limiter devices.
Mobile Voltammetric Laboratory for Ship-Board and Shore-Based Analyses of Dissolved Copper
Authors: Knight Sarah , Morley Nicholas , Leech Dónal , Cave Rachel
Published: December 2006

Environmental Context. Determining concentrations of dissolved copper in seawater is of interest, because copper (i) affects the health of aquatic biota, and (ii) has the potential to act as a water mass tracer, a marker which can be used to follow the movement of water in oceans. In situ analyses of copper and other trace metals in seawater have become increasingly popular, because they circumvent potential contamination problems associated with sample collection, storage, and transport to off-site analysis locations. This paper describes the assembly of a low-cost, mobile laboratory utilizing adsorptive cathodic stripping voltammetry (AdCSV) for the real-time determination of total dissolved copper in surface waters.
Abstract. The main advantages of using a mobile laboratory for the real-time analyses of copper in surface waters over classical discrete sampling include a reduction in the risk of sample contamination and significant savings in both time and money to the analyst. This paper outlines the development of a portable voltammetric laboratory, capable of deployment from ships or road vehicles, and an experimental method for the real time analysis of total dissolved copper in surface waters. It has been tested in estuarine and coastal waters to the west of Ireland and has proved suitable for the analysis of both fresh and marine waters. The system includes a trace metal-free sampling fish (for shipboard sampling), in-line filtration and UV-digestion units, and a voltammetric analyzer and electrode controlled by a portable PC. Analysis of samples is completed using adsorptive cathodic stripping voltammetry (AdCSV). Using this portable AdCSV laboratory, the high sample throughput – approximately three per hour with standard additions completed on every sample – means that for ship-board surveys good spatial coverage is possible without the need for time-consuming station stops. For van-based tidal surveys, the portable AdCSV laboratory is both straightforward and low in cost to deploy.
Subcellular Partitioning and the Prediction of Cadmium Toxicity to Aquatic Organisms
Authors: Wang Wen-Xiong , Rainbow Philip S.
Published: December 2006

Environmental Context. There is a considerable interest in predicting cadmium (Cd) toxicity to aquatic organisms, largely stemming from environmental Cd pollution and the need to establish water quality criteria to protect aquatic ecosystems. Chemistry-orientated models have been developed over the past decades to predict Cd toxicity, focusing on identifying which Cd forms are present in the aquatic environment, and investigating their interaction with the biological site of action. Understanding the cellular fates of Cd may provide an alternative method to predict Cd toxicity, as the complex cellular interactions of Cd within the organisms can, in this way, be addressed.
Abstract. The internal metal sequestration strategies of different aquatic organisms are complex and variable; thus it is a formidable task to predict metal toxicity. Metals accumulated by aquatic organisms are associated with different subcellular compartments (i.e. heat-sensitive proteins, heat-stable proteins (metallothioneins), granules, cellular debris, and organelles). Such subcellular partitioning is dynamic in response to metal exposure and other environmental conditions, and is metal- and organism-specific. Previous models predicting metal toxicity have relied on the free ion metal activity (i.e. the free ion activity model) or more recently on the metal binding with the proposed toxicological site of action (i.e. the biotic ligand model). Neither of these models considers the complexity of internal metal subcellular fractionation, which may significantly affect metal toxicity in aquatic organisms and subsequent trophic transfer of metals to consumers. Recent studies in small aquatic organisms have revealed that the subcellular partitioning model (SPM) may provide an improved method to predict Cd toxicity, but more studies are needed in the future.
An Agar Gel Technique Demonstrates Diffusion Limitations to Cadmium Uptake by Higher Plants
Authors: Degryse Fien , Smolders Erik , Parker David R.
Published: December 2006

Environmental Context. Toxic effects of trace metals are often related to the amount of metal that is internalized by the organism. Uptake of metals by biota is usually predicted with equilibrium models, which assume that transport of the metal from the solution to the biosurface does not limit uptake. In this study, uptake of cadmium by higher plants is shown to be limited by the transport of the free ions to the root surface under a range of conditions.
Abstract. Uptake of cadmium (Cd) by spinach and wheat was higher in the presence of fast-dissociating complexes than in unbuffered solutions with the same free ion concentration. This contribution of metal complexes to metal uptake cannot be explained by equilibrium free-ion-based models, which assume that transport of the free ion to the biosurface is not limiting the uptake. To demonstrate diffusion limitations to metal uptake, we used an agar gel technique in which Cd and Zn concentrations around the roots, after 6 h of uptake, were compared with bulk concentrations. Metal depletion around the roots was clearly observed in agar where the ion activities were not buffered by complexes, whereas the depletion was less pronounced in buffered agar. Metal uptake by the plants in unbuffered media was greater as the degree of agitation increased (stirred solution > unstirred solution > agar), while no such dependence on hydrodynamic conditions was found in buffered media, which is in agreement with theoretical predictions.
Gene transfer demonstrates that muscle is not a primary target for non-cell-autonomous toxicity in familial amyotrophic lateral sclerosis
Authors: Miller Timothy M. , Kim Soo H. , Yamanaka Koji , Hester Mark , Umapathi Priya , Arnson Hannah , Rizo Liza , Mendell Jerry R. , Gage Fred H. , Cleveland Don W. , Kaspar Brian K.
Published: December 2006

Amyotrophic lateral sclerosis (ALS) is a fatal, progressive paralysis arising from the premature death of motor neurons. An inherited form is caused by a dominant mutation in the ubiquitously expressed superoxide dismutase (SOD1). SOD1 mutant expression within motor neurons is a determinant of onset and early disease, and mutant accumulation within microglia accelerates disease progression. Muscle also is a likely primary source for toxicity, because retraction of motor axons from synaptic connections to muscle is among the earliest presymptomatic events. To test involvement of muscle in ALS, viral delivery of transcription-mediated siRNA is shown to suppress mutant SOD1 accumulation within muscle alone but to be insufficient to maintain grip strength, whereas delivery to both motor neurons and muscle is sufficient. Use of a deletable mutant gene to diminish mutant SOD1 from muscle did not affect onset or survival. Finally, follistatin expression encoded by adeno-associated virus chronically inhibited myostatin and produced sustained increases in muscle mass, myofiber number, and fiber diameter, but these increases did not affect survival. Thus, SOD1-mutant-mediated damage within muscles is not a significant contributor to non-cell-autonomous pathogenesis in ALS, and enhancing muscle mass and strength provides no benefit in slowing disease onset or progression.
TRP channel activation by reversible covalent modification
Authors: Hinman Andrew , Chuang Huai-hu , Bautista Diana M. , Julius David
Published: December 2006

Allyl isothiocyanate, the pungent principle of wasabi and other mustard oils, produces pain by activating TRPA1, an excitatory ion channel on sensory nerve endings. Isothiocyanates are membrane-permeable electrophiles that form adducts with thiols and primary amines, suggesting that covalent modification, rather than classical lock-and-key binding, accounts for their agonist properties. Indeed, we show that thiol reactive compounds of diverse structure activate TRPA1 in a manner that relies on covalent modification of cysteine residues within the cytoplasmic N terminus of the channel. These findings suggest an unusual paradigm whereby natural products activate a receptor through direct, reversible, and covalent protein modification.
An Accidental Sect: How War Made Belief in Sierra Leone
Authors: Richards Paul
Published: December 2006

Idealists consider beliefs cause wars. Realists consider wars cause beliefs. The war in Sierra Leone offers some scope to test between these two views. The main rebel faction, the Revolutionary United Front (RUF) was, sociologically speaking, an accidental sect. It lost its original ideologues at an early stage, and absorbed others with a different orientation as a result of military misfortunes. Bombing reinforced the sectarian tendencies of an enclaved movement, and belief proliferated. This confounded military assessments that the movement could be rapidly brought to heel by a private military intervention sponsored by British and South African mineral interests. The movement became an uncontrollable juggernaut, driven by strange sacrificial notions directed against rural populations it had once set out to liberate. The war in Sierra Leone is consistent with the Durkheimian argument that performance forges collective representations. Dealing with armed insurgency in Africa requires appreciation of the artefactual and circumstantial character of social and religious beliefs.
Pupils' enjoyment of history: what lessons can teachers learn from their pupils?
Authors: Harris Richard , Haydn Terry
Published: December 2006

This article explores pupil attitudes towards history as a school subject in England, with a view to developing a better understanding of the factors which influence disaffection or engagement with the subject. The study attempts to identify what pupils like and dislike about how they are taught and what they are taught in history lessons. The study was carried out in 12 secondary schools with pupils aged 11–14. Questionnaires were returned from 1740 pupils and 160 of these were involved in focus group interviews. The findings show that how pupils are taught appears to matter more than what they are taught and identifies teaching approaches that pupils considered to be particularly effective, and teaching approaches that appear to contribute to pupil disaffection and disengagement from the subject. The study also provides insights into the extent to which pupils find history enjoyable compared to other school subjects. Although the study is primarily of interest to history teachers, it may also be of interest to teachers of other subjects who have a concern for the degree of pupil engagement with their subject.
Illusions of consensus: New South Wales stakeholders' constructions of the identity of history
Authors: Simpson Ian , Halse Christine
Published: December 2006

This article analyses the relationships between the perspectives of stakeholders involved in the development of the 1998 New South Wales Stages 4–5 history syllabus. It examined four key issues that emerged in the debates about history education during the review and found that stakeholders' views diverged significantly on three of these issues. While loose coalitions formed around particular issues, stakeholders provided different rationales for their positions, and coalitions re‐formed on other debates. The analysis highlights the divergence between stakeholders and between the Commonwealth and state governments and stakeholders on the desirable content and goals of history education. The findings indicate that consultation might not produce consensus, and that even the appearance of consensus can be grounded in substantively and philosophically different premises. In practical terms, the findings suggest that if the purpose of consultation as a method of curriculum development is to produce a syllabus that reflects the diverse perspectives held by stakeholders, then the syllabus structure needs to make provision for content options as well as common core areas of study.
The evolution of Education Studies in higher education in England
Authors: Burton Diana , Bartlett Steve
Published: December 2006

In this article we examine the recent development of Education Studies as an undergraduate subject of study in England. The evolution of Education Studies is inextricably linked to the political context which it exists to critique. Changes within teacher education have spawned education studies in a number of guises. It is only latterly that policy changes have created the conditions for Education Studies to thrive as a subject in its own right. The genesis of the subject is traced through a brief historical analysis and its current various manifestations are outlined. The nature of Education Studies is discussed. Fundamentally, the authors contend that Education Studies provides a set of analytical discourses that facilitate critique of shifting knowledge bases, policy contexts and socio‐economic developments as they impact upon education.
Functional genomics via multiscale analysis: application to gene expression and ChIP-on-chip data
Authors: Lerman Gilad , McQuown Joseph , Blais Alexandre , Dynlacht Brian D. , Chen Guangliang , Mishra Bud
Published: December 2006

We present a fast, versatile and adaptive-multiscale algorithm for analyzing a wide-variety of DNA microarray data. Its primary application is in normalization of array data as well as subsequent identification of ‘enriched targets’, e.g. differentially expressed genes in expression profiling arrays and enriched sites in ChIP-on-chip experimental data.

We show how to accommodate the unique characteristics of ChIP-on-chip data, where the set of ‘enriched targets’ is large, asymmetric and whose proportion to the whole data varies locally.

Contact:  lerman@umn.edu

Supplementary information: Supplementary figures, related preprint, free software as well as our raw DNA microarray data with PCR validations are available at as well as Bioinformatics online.
Hydrodynamics of prey capture in sharks: effects of substrate
Authors: Nauwelaerts Sandra , Wilga Cheryl , Sanford Christopher , Lauder George
Published: December 2006

In suction feeding, a volume of water is drawn into the mouth of a predator. Previous studies of suction feeding in fishes have shown that significant fluid velocities are confined to a region within one mouth width from the mouth. Therefore, the predator must be relatively close to the prey to ensure capture success. Here, theoretical modelling is combined with empirical data to unravel the mechanism behind feeding on a substrate. First, we approached the problem theoretically by combining the stream functions of two sinks. Computational fluid dynamics modelling is then applied to make quantitative predictions regarding the effects of substrate proximity on the feeding hydrodynamics of a benthic shark. An oblique circular cylinder and a shark head model were used. To test the models, we used digital particle image velocimetry to record fluid flow around the mouth of white-spotted bamboo sharks,Chiloscyllium plagiosum, during suction feeding on the substrate and in the water column. Empirical results confirmed the modelling predictions: the length of the flow field can be doubled due to passive substrate effects during prey capture. Feeding near a substrate extends the distance over which suction is effective and a predator strike can be effective further from the prey.
Individual and gender fingerprints in human body odour
Authors: Penn Dustin J , Oberzaucher Elisabeth , Grammer Karl , Fischer Gottfried , Soini Helena A , Wiesler Donald , Novotny Milos V , Dixon Sarah J , Xu Yun , Brereton Richard G
Published: December 2006

Individuals are thought to have their own distinctive scent, analogous to a signature or fingerprint. To test this idea, we collected axillary sweat, urine and saliva from 197 adults from a village in the Austrian Alps, taking five sweat samples per subject over 10 weeks using a novel skin sampling device. We analysed samples using stir bar sorptive extraction in connection with thermal desorption gas chromatograph–mass spectrometry (GC–MS), and then we statistically analysed the chromatographic profiles using pattern recognition techniques. We found more volatile compounds in axillary sweat than in urine or saliva, and among these we found 373 peaks that were consistent over time (detected in four out of five samples per individual). Among these candidate compounds, we found individually distinct and reproducible GC–MS fingerprints, a reproducible difference between the sexes, and we identified the chemical structures of 44 individual and 12 gender-specific volatile compounds. These individual compounds provide candidates for major histocompatibility complex and other genetically determined odours. This is the first study on human axillary odour to sample a large number of subjects, and our findings are relevant to understanding the chemical nature of human odour, and efforts to design electronic sensors (e-nose) for biometric fingerprinting and disease diagnoses.
A hybrid polymer gel with controlled rates of cross-link rupture and self-repair
Authors: Kersey Farrell R , Loveless David M , Craig Stephen L
Published: December 2006

A family of hybrid polymer gels is described, in which covalent cross-links create a permanent, stiff scaffold onto which reversible metal–ligand coordinative cross-links are added. The reversible metal–ligand interactions are shown to bear mechanical stress within the hybrid gel, and relaxations in response to that applied stress are consistent with the stress-free kinetics of ligand exchange in systems that model the reversible cross-links. The stress-induced dissociation of a model metal–ligand complex is examined by a single-molecule force spectroscopy, and its mechanical response is compared with a previously studied complex. The mechanical response of the individual interactions is relevant to those found in the family of hybrid gels, and the modular platform is therefore suitable for the study of stress-induced molecular dissociations, and their subsequent repair, within a macroscopic material of fixed structure.
The evolution of piston-driven pipe flow: thermal transpiration
Authors: Davis A.M.J
Published: December 2006

The steady-state transition from and to the uniform entry and exit flow profiles is well described, at large aspect ratio, in terms of the stream function by the pipe eigenfunctions. But these latter are unsuited to oscillatory motion or the time evolution of the symmetric piston-driven pipe flow, for which an appropriate solution has a combination of a Fourier series along the finite pipe and a Fourier–Bessel series in the transverse direction. A non-uniqueness requires the identification of a solvability condition and care is needed in demonstrating its satisfaction. An additional result is that the solution must be constructed to satisfy the normal flow conditions identically. Application is made to thermal transpiration, recently explained by the revised Navier–Stokes equations and boundary conditions.
The Cape element in the Afrotemperate flora: from Cape to Cairo?
Authors: Galley Chloé , Bytebier Benny , Bellstedt Dirk U , Peter Linder H
Published: December 2006

The build-up of biodiversity is the result of immigration andin situspeciation. We investigate these two processes for four lineages (Disa, Irideae p.p., thePentaschistisclade and Restionaceae) that are widespread in the Afrotemperate flora. These four lineages may be representative of the numerous clades which are species rich in the Cape and also occur in the highlands of tropical Africa. It is as yet unclear in which direction the lineages spread. Three hypotheses have been proposed: (i) a tropical origin with a southward migration towards the Cape, (ii) a Cape origin with a northward migration into tropical Africa, and (iii) vicariance. None of these hypotheses has been thoroughly tested. We reconstruct the historical biogeography of the four lineages using likelihood optimization onto molecular phylogenies. We find that tropical taxa are nested within a predominantly Cape clade. There is unidirectional migration from the Cape into the Drakensberg and from there northwards into tropical Africa. The amount ofin situdiversification differs between areas and clades. Dating estimates show that the migration into tropical East Africa has occurred in the last 17 Myr, consistent with the Mio-Pliocene formation of the mountains in this area.
Pterin pigment granules are responsible for both broadband light scattering and wavelength selective absorption in the wing scales of pierid butterflies
Authors: Morehouse Nathan I , Vukusic Peter , Rutowski Ron
Published: December 2006

A small but growing literature indicates that many animal colours are produced by combinations of structural and pigmentary mechanisms. We investigated one such complex colour phenotype: the highly chromatic wing colours of pierid butterflies including oranges, yellows and patterns which appear white to the human eye, but strongly absorb the ultraviolet (UV) wavelengths visible to butterflies. Pierids produce these bright colours using wing scales that contain collections of minute granules. However, to date, no work has directly characterized the molecular composition or optical properties of these granules. We present results that indicate these granules contain pterin pigments. We also find that pterin granules increase light reflection from single wing scales, such that wing scales containing denser granule arrays reflect more light than those with less dense granule collections. As male wing scales contain more pterin granules than those of females, the sexual dichromatism found in many pierid species can be explained by differences in wing scale pterin deposition. Additionally, the colour pattern elements produced by these pterins are known to be important during mating interactions in a number of pierid species. Therefore, we discuss the potential relevance of our results within the framework of sexual selection and colour signal evolution.
Plasticity in animal personality traits: does prior experience alter the degree of boldness?
Authors: Frost Ashley J , Winrow-Giffen Alexandria , Ashley Paul J , Sneddon Lynne U
Published: December 2006

Theoreticians predict that animal ‘personality’ traits may be maladaptive if fixed throughout different contexts, so the present study aimed to test whether these traits are fixed or plastic. Rainbow trout (Onchorhyncus mykiss) were given emboldening or negative experiences in the forms of watching bold or shy individuals responding to novelty or winning or losing fights to examine whether prior experience affected boldness. Bold individuals that lost fights or watched shy demonstrators became more shy by increasing their latency to approach a novel object, whereas shy observers that watched bold demonstrators remained cautious and did not modify their responses to novelty. Shy winners became bolder and decreased their latency to approach a novel object, but shy losers also displayed this shift. In comparison, control groups showed no change in behaviour. Bold fishes given negative experiences reduced their boldness which may be an adaptive response; however, shy fishes may base their strategic decisions upon self-assessment of their relative competitive ability and increase their boldness in situations where getting to resources more quickly ensures they outcompete better competitors.
Sperm competition and sperm midpiece size: no consistent pattern in passerine birds
Authors: Immler Simone , Birkhead Tim R
Published: December 2006

Sperm competition is thought to be a major force driving the evolution of sperm shape and function. However, previous studies investigating the relationship between the risk of sperm competition and sperm morphometry revealed inconclusive results and marked differences between taxonomic groups. In a comparative study of two families of passerines (Fringillidae and Sylviidae) and also across species belonging to different passerine families, we investigated the relative importance of the phylogenetic background on the relationship between sperm morphometry and the risk of sperm competition. The risk of sperm competition was inferred from relative testis mass as an indicator of investment in sperm production. We found: (i) a significant positive association between both midpiece length and flagellum length and relative testis mass in the Fringillidae, (ii) a significant negative association between sperm trait dimensions and relative testis mass in the Sylviidae, and (iii) no association across all species. Despite the striking difference in the patterns shown by the Sylviidae and the Fringillidae, the relationship between midpiece length and flagellum length was positive in both families and across all species with positive allometry. Reasons for the differences and similarities between passerine families are discussed.
Is correction for protein concentration appropriate for protein adduct dosimetry? Hypothesis and clues from an aflatoxin B1‐exposed population
Authors: Peng Tao , Li Le‐Qun , Peng Min‐Hao , Liu Zhi‐Ming , Liu Tang‐Wei , Yan Lu‐Nan , Shen Han‐Ming , Wang LianWen , Wang Qiao , Wang Kai‐bo , Liang Ren‐xiang , Wei Zong‐liang , Ong Choon Nam , Santella Regina M.
Published: December 2006

Protein adducts are useful biomarkers for assessing exposure, metabolism and risk of carcinogens. Aflatoxin B1–albumin adducts (AAA) and protein carbonyl content (PCC) have long been used for assessing aflatoxin exposure and oxidative stress to proteins, and the quantitative data are almost exclusively expressed per mg protein. Given the large variation in protein concentrations in plasma among populations, this may not be the most appropriate method. The objective was to test the hypothesis that AAA and PCC should be expressed per mL plasma in population studies. AAA and PCC were analyzed among 402 subjects from three regions of China with a gradient in hepatocellular carcinoma (HCC) mortality ranging from 21 to 97 per 100 000. When biomarker values were expressed per mL plasma, the AAA level was significantly associated with plasma PCC (r = 0.262, P < 0.001), and adjusted levels of AAA and PCC paralleled HCC mortalities in the three regions, suggesting a role for aflatoxin‐related oxidative stress in hepatocarcinogenesis in this population. In addition, there were statistically significant associations between both protein biomarkers, expressed per mL plasma, and the levels of alanine aminotransferase and aspartate aminotransferase in hepatitis B virus‐infected subjects, suggesting roles for aflatoxin exposure, oxidative stress and hepatitis B virus infection in the development of HCC. The present data suggest that interindividual variation in plasma protein concentration may influence the dosimetry and relevant interpretation of protein biomarkers. (Cancer Sci 2007; 98: 140–146)
Role of habitat in determining macroinvertebrate production in an intermittent‐stream system
Authors: CHADWICK MICHAEL A. , HURYN ALEXANDER D.
Published: December 2006

1. The effect of channel drying on macroinvertebrate production was studied at the habitat and reach scale in a catchment drained by intermittent streams in Maine, U.S.A. The catchment includes two first‐order streams and their second‐order confluence. Six reaches were selected for study based on differences in channel slope and habitat cover (bedrock, riffle/run, debris dam and pool). Stream water in each reach was acidic and oligotrophic.

2. The study reaches had different degrees of channel drying. In the first‐order reaches, surface flow ceased earlier in the season and for longer periods than second‐order reaches. Regardless of reach, pool and debris dam habitats retained water longer than riffle/runs and bedrock. Unlike other habitats, debris dams retained moisture for relatively long periods following cessation of surface flow.

3. Reach‐specific macroinvertebrate production ranged from approximately 1.7 to 2.9 g AFDM m−2 year−1 which are among the lowest values ever reported. Habitat‐specific production ranged from approximately 0.5 to 5.0 g AFDM m−2 year−1 (bedrock and debris dams, respectively).

4. At the reach scale, quantities of stored benthic organic matter (range approximately 200–600 g AFDM−2) decreased in a downstream direction.

5. A combination of differences in the timing and duration of channel drying, habitat structure and detritus standing stocks appeared to influence levels of invertebrate production among the study reaches.

6. Our interpretation of a canonical correspondence analysis indicates that drying is more important than habitat in affecting macroinvertebrate production in this intermittent stream system.
Should research ethics triumph over clinical ethics?
Authors: Kottow Michael H.
Published: December 2006

Evidence‐based medicine (EBM) and its main strategy, randomized clinical trials, have had less impact on medical practice than might be expected. Of the various reasons that make practitioners wary of applying research results, this paper explores some consequences of scientists’ and research sponsors’ adamant insistence that reliable science can only be achieved if protocols adhere exclusively to the ethics of investigation basically reduced to obtaining informed consent and avoiding risks as far as possible. This means, and has been explicitly contended, that neither patients nor doctors should fall prey to the therapeutic fallacy which leads them to expect that research will also take care of patient‐subjects’ medical welfare. Doctors would betray their profession if they allowed clinical research to disregard their therapeutic obligations in favour of strict scientific methodology, as is bound to happen when using placebos in spite of existing therapy, disregarding equipoise, disallowing benefit claims, emphasizing the distinction between research ethics and clinical ethics but denying any difference between therapeutic and non‐therapeutic trials. That scientists and practitioners should not agree on needs and priorities in the medical context, constitutes an additional factor in the less than optimal reception of EBM by the health care professions.
Pressure ulcer prevalence in Europe: a pilot study
Authors: Vanderwee Katrien , Clark Michael , Dealey Carol , Gunningberg Lena , Defloor Tom
Published: December 2006

Rationale and aims  Numerous prevalence studies have been conducted. The problem with these studies is that prevalence proportions cannot be compared with each other, because of differences in performance of each survey. There is no agreed standardized method for determining prevalence proportions. This study aimed to develop and pilot a uniform data collection instrument and methodology to measure the pressure ulcer prevalence and to get some insight into pressure ulcer prevalence across different patient groups in Europe.

Methods  Pressure ulcer experts from different European countries developed a data collection instrument, which included five categories of data: general data, patient data, risk assessment, skin observation and prevention. A convenience sample of university and general hospitals of Belgium, Italy, Portugal, UK and Sweden participated in the study. In each participating hospital, teams of two trained nurses who collected the data on the wards were established. All patients admitted before midnight on the day of the survey and older than 18 years were included.

Results  The data collection instrument and study procedure of the survey were found to be effective by all participants. 5947 patients were surveyed in 25 hospitals in five European countries. The pressure ulcer prevalence (grade 1–4) was 18.1% and if grade 1 ulcers were excluded, it was 10.5%. The sacrum and heels were the most affected locations. Only 9.7% of the patients in need of prevention received fully adequate preventive care.

Conclusion  The methodology is sufficiently robust to measure and compare pressure ulcer prevalence in different countries. The pressure ulcer prevalence was higher than expected and relatively few patients received adequate prevention. This indicates that more attention to prevention is needed in Europe.
Pre-main-sequence stars in the Lagoon Nebula (M8)
Authors: Arias J. I. , Barbá R. H. , Morrell N. I.
Published: December 2006

We report the discovery of new pre-main-sequence (PMS) stars in the Lagoon Nebula (M8) at a distance of 1.25 kpc, based on intermediate-resolution spectra obtained with the Boller & Chivens spectrograph at the 6.5-m Magellan I Telescope (Las Campanas Observatory, Chile). According to the spectral types, the presence of emission lines and the lithium λ 6708 absorption line, we are able to identify 27 classical T Tauri stars, seven weak-lined T Tauri stars and three PMS emission objects with spectral type G, which we include in a separate stellar class denominated ‘PMS Fe/Ge class’. Using near-infrared photometry either from the Two-Micron All-Sky Survey or from our own previous work, we derive effective temperatures and luminosities for these stars and locate them in the Hertzsprung–Russell diagram, in order to estimate their masses and ages. We find that almost all of our sample stars are younger than 3 × 106 yr and span over a range of masses between 0.8 and 2.5 M⊙. A cross-correlation between our spectroscopic data and the X-ray sources detected with the Chandra ACIS instrument is also presented.
A SNARE‐protein has opposing functions in penetration resistance and defence signalling pathways
Authors: Zhang Ziguo , Feechan Angela , Pedersen Carsten , Newman Mari‐Anne , Qiu Jin‐long , Olesen Karen L. , Thordal‐Christensen Hans
Published: December 2006

Penetration resistance is often the first line of defence against fungal pathogens. Subsequently induced defences are mediated by the programmed cell death (PCD) reaction pathway and the salicylic acid (SA), jasmonic acid (JA) and ethylene (ET) signalling pathways. We previously demonstrated that full penetration resistance in Arabidopsis against the non‐host barley powdery mildew fungus (Blumeria graminis f.sp. hordei) requires the syntaxin SYP121 (PEN1). Here we report that SYP121, together with SYP122, functions as a negative regulator of subsequently induced defence pathways. The SA level in the syntaxin double mutant syp121–1 syp122–1 is dramatically elevated, resulting in necrosis and dwarfism. This phenotype is partially rescued by introducing the SA‐signalling mutations eds1–2, eds5–3, sid2–1 and npr1–1 as well as the NahG transgene. These partially rescued triple mutants have an unknown defence to Pseudomonas syringae pv. tomato, and have increased HR‐like responses to non‐host and host powdery mildew fungi. The HR‐like responses cause efficient resistance to the latter. These defence pathways are SA‐independent. Furthermore, the JA/ET signalling marker, PDF1.2, is highly upregulated in the triple mutants. Thus SYP121 and SYP122 are negative regulators of PCD, SA, JA and ET pathways through a molecular function distinct from that of SYP121 in penetration resistance. Our data suggest that individual cells preferentially express either penetration resistance or the subsequently induced defences.
Rapid differentiation of Candida albicans from non‐albicans species by germ tube test directly from BacTAlert blood culture bottles
Authors: Terlecka Jolanta A. , Du Cros Philipp A. , Orla Morrissey C. , Spelman Denis
Published: December 2006

Bloodstream infections (BSIs) caused by Candida species are increasing in incidence, and are associated with high mortality rates, which are due in part to a delay in the administration of appropriate antifungal therapy. Earlier identification of yeast isolates from blood cultures may improve clinical outcomes. Identification of a Candida as albicans or non‐albicans species depends on the presence or absence of germ tubes. Conventionally, germ tube test (GTT) is performed on colonies grown on agar plate after 24–48 h of incubation. In the present study, the GTT was performed earlier on an aliquot taken from blood culture bottle, after yeast cells were seen in Gram stain and the results were compared with the GTT using the conventional method. Thirty‐one consecutive bloodstream isolates of yeast were included in this prospective study over 10 months. There was 100% concordance between the two GTT methods. Final identification was confirmed by standard laboratory procedures. The performance of GTT directly from blood culture bottles has important implications for early, appropriate therapy in patients with candidaemia.
High‐risk febrile neutropenia in Auckland 2003–2004: the influence of the microbiology laboratory on patient treatment and the use of pathogen‐specific therapy
Authors: Ritchie S. , Palmer S. , Ellis‐Pegler R.
Published: December 2006

Background: International guidelines recommend routine microbiological assessment of patients with febrile neutropenia, but do not recommend a change from broad‐spectrum antibiotic therapy to pathogen‐specific therapy when a clinically relevant organism has been isolated. The aim of the study was to determine the aetiology of febrile neutropenia in adult haematology patients at Auckland City Hospital, to document the changes in treatment made following isolation of a clinically relevant organism and to assess adverse outcomes in any patient who received pathogen‐specific therapy after a positive culture result.

Methods: The results of all microbiological tests together with antibiotic therapy were recorded from consecutive patients with fever and a neutrophil count <0.5 × 109/L over 1 year beginning in May 2003.

Results: One thousand one hundred and ninety‐six specimens were collected from 81 patients during 116 episodes of febrile neutropenia. A pathogen was isolated from blood cultures in 40 episodes: Gram‐positive cocci accounted for 46% of isolates and Gram‐negative bacilli for 35%. Isolation of a pathogen from blood cultures resulted in a change of treatment in 25 of 40 (62.5%, 95%CI 46–77%) episodes. In 12 of these episodes, antibiotic therapy was optimized to a single pathogen‐specific agent. No adverse events or subsequent changes in antibiotic therapy occurred in any of these 12 patients. Isolation of a pathogen from specimens other than blood seldom led to a change in therapy.

Conclusion: Isolation of a pathogen from blood cultures often allows antibiotic therapy to be simplified to a pathogen‐specific regimen. Further study of this approach is warranted.