bluuebunny/crossref_metadata_2025 huggingface dataset:
Radiation-modified structure of Ge25Sb15S60 and Ge35Sb5S60 glasses
Authors: Kavetskyy T. , Shpotyuk O. , Kaban I. , Hoyer W.
Published: June 2008

Atomic structures of Ge25Sb15S60 and Ge35Sb5S60 glasses are investigated in the γ-irradiated and annealed after γ-irradiation states by means of high-energy synchrotron x-ray diffraction technique. The first sharp diffraction peak (FSDP) is detected at around 1.1Å−1 in the structure factors of both alloys studied. The FSDP position is found to be stable for radiation/annealing treatment of the samples, while the FSDP intensity shows some changes between γ-irradiated and annealed states. The peaks in the pair distribution functions observed between 2 and 4Å are related to the Ge–S, Ge–Sb, and Sb–Sb first neighbor correlations and Ge–Ge second neighbor correlations in the edge-shared GeS4∕2 tetrahedra, and S–S and/or Ge–Ge second neighbor correlations in the corner-shared GeS4∕2 tetrahedra. Three mechanisms of the radiation-/annealing-induced changes are discussed in the framework of coordination topological defect formation and bond-free solid angle concepts.
Resonant states of H3+ and D2H+
Authors: Silva Bruno C. , Barletta Paolo , Munro James J. , Tennyson Jonathan
Published: June 2008

Vibrational resonances for H3+ and D2H+, as well as H3+ at J=3, are calculated using a complex absorbing potential (CAP) method with an automated procedure to find stability points in the complex plane. Two different CAP functional forms and different CAP extents are used to analyze the consistency of the results. Calculations are performed using discrete variable representation continuum basis elements calculated to high levels of accuracy by diagonalizing large, dense, Hamiltonian matrices. For D2H+, two energy regions are analyzed: the one where D2+H+ is the only dissociation product and the one where HD+D+ can also be formed. Branching ratios are obtained in the latter case by using different CAPs. It is shown that H3+ and D2H+ support some narrow Feshbach-type resonances but that higher angular momentum states must be studied to model the pre-dissociation spectrum recorded by Carrington and co-workers [J. Chem. Phys. 98, 1073 (1993)].
Photoconductivity in organic thin films: From picoseconds to seconds after excitation
Authors: Day J. , Subramanian S. , Anthony J. E. , Lu Z. , Twieg R. J. , Ostroverkhova O.
Published: June 2008

We present a detailed study, on time scales from picoseconds to seconds, of transient and continuous wave (cw) photoconductivity in solution-grown thin films of functionalized pentacene (Pc), anthradithiophene (ADT), and dicyanomethylenedihydrofuran (DCDHF). In all films, at temperatures of 285–350 K, we observe fast carrier photogeneration and nonthermally activated charge transport on picosecond time scales. At ∼30 ps after photoexcitation at room temperature and at applied electric field of 1.2×104 V/cm, values obtained for the product of mobility and photogeneration efficiency, μη, in ADT-tri-isoproplysilylethynyl-(TIPS)-F, Pc-TIPS, and DCDHF films are ∼0.018–0.025, ∼0.01–0.022, and ∼0.002–0.004 cm2/V s, respectively, depending on the film quality, and are weakly electric field dependent. In functionalized ADT and Pc films, the power-law decay dynamics of the transient photoconductivity is observed, on time scales of up to ∼1 μs after photoexcitation, in the best samples. In contrast, in DCDHF amorphous glass, most of the photogenerated carriers are trapped within ∼200 ps. Transport of photoexcited carriers on longer time scales is probed by cw illumination through an optical chopper, with a variable chopper frequency. In contrast with what is observed on picosecond time scales, charge carriers on millisecond and longer time scales are predominantly localized, and are characterized by a broad distribution of carrier lifetimes. Such carriers make the principal contributions to dc photoconductivity.
Biosensing using split-ring resonators at microwave regime
Authors: Lee Hee-Jo , Yook Jong-Gwan
Published: June 2008

A split-ring resonator (SRR) array is experimentally demonstrated for a biosensing device at microwave frequencies. Each SRR in the array is excited by a time-varying H-field component through a microstrip transmission line in which microwaves propagate in the quasitransverse electromagnetic mode. It is found that the resonant frequency changes due to the binding of biotin and streptavidin onto the surface of the SRRs. The observed change values represent around ΔfB=120MHz and ΔfB-S=40MHz, respectively. Finally, the SRR-based biosensing device suggests a few improvements for increasing sensitivity and describes its possible application.
Nearly constant dielectric loss behavior in ionomers
Authors: Linares A. , Cánovas M. J. , Ezquerra T. A.
Published: June 2008

The electrical conductivity of a series of ionomers has been characterized by measuring the electrical conductivity in a relatively broad range of frequencies and temperatures. At low frequencies, the conductivity of the ionomers exhibits a universal Jonscher power law (JPL), and at higher frequencies a nearly constant loss (NCL) behavior. The NCL for the ionomers is qualitatively similar to that observed for other inorganic ionic conductors. However, the magnitude of NCL for ionomers is lower than that observed for inorganic ionic conductors. The analysis of the conductivity master curves suggests that the conduction mechanism, which includes both the NCL and the JPL behaviors, is governed by ion hopping of the mobile ions.
Proton conduction in thin film yttrium-doped barium zirconate
Authors: Shim Joon Hyung , Gür Turgut M. , Prinz Fritz B.
Published: June 2008

The proton conductivity of yttrium-doped barium zirconate (BYZ) films epitaxially grown on MgO(100) has been studied in the range of 140–290°C as a function of film thickness (60–670nm) in relation to their crystal and morphological structure at the nanoscale. Highly textured 60nm BYZ film epitaxially grown on MgO(100) showed high ionic conductivity, close to its bulk value. In contrast, thicker polycrystalline samples with rougher surfaces, caused by grain boundary formation, exhibited lower conductivity.
Collisionless gas flows. I. Inside arbitrary enclosures
Authors: Cai Chunpei , Liu Danny D.
Published: June 2008

This study concentrates on steady collisionless gas flows inside arbitrary enclosures, which are either convex or concave, two-dimensional or three-dimensional, formed by several plates maintained at different temperatures. If the molecular reflections on these plates are completely diffuse, then at the final steady flow stage for any point inside the enclosures, the velocity distribution function (VDF) is completely determined, and macroscopic properties such as density, velocities, temperature, and heat flux can be exactly determined by integrating the VDF with different moments. The result from this study leads to many exact solutions for internal collisionless gas flow and thermal fields, such as those inside vacuum packaged micro-/nanoelectromechanical system devices. These solutions are applicable as base solutions to solve flows with a much smaller Knudsen number.
Introduction to Focus Issue: Design and Control of Self-Organization in Distributed Active Systems
Authors: Mikhailov Alexander S. , Showalter Kenneth
Published: June 2008

Spatiotemporal self-organization is found in a wide range of distributed dynamical systems. The coupling of the active elements in these systems may be local or global or within a network, and the interactions may be diffusive or nondiffusive in nature. The articles in this focus issue describe biological and chemical systems designed to exhibit spatiotemporal dynamics and the control of such dynamics through feedback methods.
Recrystallization of ion-irradiated germanium due to intense electronic excitation
Authors: Som T. , Ghatak J. , Sinha O. P. , Sivakumar R. , Kanjilal D.
Published: June 2008

Germanium single crystals were irradiated at room temperature by 1.5MeV energy germanium ions and high energy silver ions of 100MeV. Based on the transmission and high-resolution electron microscopic investigations, we present the experimental evidence of complete recrystallization of the amorphized germanium layer, formed by the self-ion-implantation, due to intense electronic excitations generated by the swift Ag ions. This phenomenon is observed at room temperature—far below the solid phase epitaxial growth temperature and that at which low energy ion beam induced epitaxial crystallization takes place. The results are explained in the light of local transient melting due to a high rate of energy deposition by the silver ions and its subsequent cooling. Based on the calculations on thermal spike concept in combination with the nonequilibrium thermodynamics, we obtain a reasonably good estimate for the experimental observation.
Lasing from photonic structure: Cholesteric-voltage controlled nematic-cholesteric liquid crystal
Authors: Barnik Mikhail I. , Blinov Lev M. , Lazarev Vladimir V. , Palto Serguei P. , Umanskii Boris A. , Shtykov Nikolay M.
Published: June 2008

Experimental investigation and numerical simulation have been made of spectral and lasing properties of thin planar hybrid structures consisting of two layers of a cholesteric liquid crystal (ChLC) and a homogeneously aligned layer of a nematic liquid crystal between them. The light optical path in the nematic layer was controlled by an electric field. In the reference structure the ChLC layers were not doped, and the field controlled transmission spectra have been studied in detail. In the other two structures, both the ChLC layers were doped by the same laser dye (but different in the two structures) and the feedback necessary for lasing was controlled by the field induced phase retardation of the nematic layer. Therefore, the field control of the lasing spectra has been demonstrated. Numerical simulations of the transmission and lasing spectra are in good agreement with experimental data. The multilayer device described can be used as a field controllable planar microlaser.
A photoelectron-photoion coincidence imaging apparatus for femtosecond time-resolved molecular dynamics with electron time-of-flight resolution of σ=18ps and energy resolution ΔE∕E=3.5%
Authors: Vredenborg Arno , Roeterdink Wim G. , Janssen Maurice H. M.
Published: June 2008

We report on the construction and performance of a novel photoelectron-photoion coincidence machine in our laboratory in Amsterdam to measure the full three-dimensional momentum distribution of correlated electrons and ions in femtosecond time-resolved molecular beam experiments. We implemented sets of open electron and ion lenses to time stretch and velocity map the charged particles. Time switched voltages are operated on the particle lenses to enable optimal electric field strengths for velocity map focusing conditions of electrons and ions separately. The position and time sensitive detectors employ microchannel plates (MCPs) in front of delay line detectors. A special effort was made to obtain the time-of-flight (TOF) of the electrons at high temporal resolution using small pore (5μm) MCPs and implementing fast timing electronics. We measured the TOF distribution of the electrons under our typical coincidence field strengths with a temporal resolution down to σ=18ps. We observed that our electron coincidence detector has a timing resolution better than σ=16ps, which is mainly determined by the residual transit time spread of the MCPs. The typical electron energy resolution appears to be nearly laser bandwidth limited with a relative resolution of ΔEFWHM∕E=3.5% for electrons with kinetic energy near 2eV. The mass resolution of the ion detector for ions measured in coincidence with electrons is about ΔmFWHM∕m=1∕4150. The velocity map focusing of our extended source volume of particles, due to the overlap of the molecular beam with the laser beams, results in a parent ion spot on our detector focused down to σ=115μm.
Analysis of negative refraction from anomalous phase in transmission spectrum
Authors: Mandatori A. , Sibilia C. , Bertolotti M. , Haus J. W.
Published: June 2008

The dependence of the negative refraction of a simple Fabry–Perot system as a function of the sign of material permittivity and permeability is analyzed. It is shown that negative refraction is possible every time the transmission phase of the system shows an anomalous behavior. However if the permittivity or the permeability are complex the anomalous phase is no longer univocally related to the presence of a negative refractive index.
Experimental demonstration of phase locking of a two-dimensional fiber laser array using a self-imaging resonator
Authors: He Bing , Lou Qihong , Wang Wei , Zhou Jun , Zheng Yinghui , Dong Jingxing , Wei Yunrong , Chen Weibiao
Published: June 2008

Phase locking of a two-dimensional fiber laser array is experimentally demonstrated by using a self-imaging resonator and a spatial filter. The stable beam profiles of in-phase mode and out-of-phase mode are observed by controlling the position of spatial filter. The phase locking fiber array with in-phase mode has produced 26W coherent output. An antisymmetric eigenmode is also observed in our experiments. The phase locking is not sensitive to power variations among the pump beams and the configuration has the ability to repair a missing element.
Quantum-dot/quantum-well mixed-mode infrared photodetectors for multicolor detection
Authors: Chou Shu-Ting , Tseng Chi-Che , Chen Cheng-Nan , Lin Wei-Hsiun , Lin Shih-Yen , Wu Meng-Chyi
Published: June 2008

Quantum-dot (QD)/quantum-well (QW) mixed-mode infrared photodetectors are demonstrated in this letter for multicolor detection in both the midwavelength infrared (MWIR) and long-wavelength infrared (LWIR) ranges. Responses at 4.3, 5.6, and 10.3μm are observed for the device. The polarization-dependent response of the device has shown that the higher normal-incident absorption is observed for the MWIR peaks, which suggest that the intraband transitions in the QD structure are responsible for the MWIR peaks while the intraband transition in the QW region is responsible for the LWIR peak. A model is also established to explain the transition mechanisms of the device.
Tunneling atomic-force microscopy as a highly sensitive mapping tool for the characterization of film morphology in thin high-k dielectrics
Authors: Yanev Vasil , Rommel Mathias , Lemberger Martin , Petersen Silke , Amon Brigitte , Erlbacher Tobias , Bauer Anton J. , Ryssel Heiner , Paskaleva Albena , Weinreich Wenke , Fachmann Christian , Heitmann Johannes , Schroeder Uwe
Published: June 2008

High-k dielectric layers (HfSixOy and ZrO2) with different film morphologies were investigated by tunneling atomic-force microscopy (TUNA). Different current distributions were observed for amorphous and nanocrystalline films by analyzing TUNA current maps. This even holds for crystalline layers where highly resolved atomic-force microscopy cannot detect any crystalline structures. However, TUNA enables the determination of morphology in terms of differences in current densities between nanocrystalline grains and their boundaries. The film morphologies were proven by high-resolution transmission electron microscopy. The investigations show TUNA as powerful current mapping tool for the characterization of morphology in thin high-k films on a nanoscale.
Effects of gate dielectrics and metal electrodes on air-stable n-channel perylene tetracarboxylic dianhydride single-crystal field-effect transistors
Authors: Yamada Koichi , Takeya J. , Takenobu T. , Iwasa Y.
Published: June 2008

The effects of gate dielectric materials and metal electrodes are studied systematically for air-stable n-type single-crystal field-effect transistors based on perylene tetracarboxylic dianhydride. It is demonstrated that neither the use of high-work-function electrodes nor exposure to air is fatal to the n-type operations for the single crystals with sufficiently large electron affinity. Mobility values are ∼5×10−3cm2V−1s−1, which is one order of magnitude higher than those reported for thin-film transistors in vacuum. The most crucial among the common suspects for the generally poorer performance of n-type organic transistors was the effect of acidic hydroxyl groups in gate dielectrics.
Inversion capacitance-voltage studies on GaAs metal-oxide-semiconductor structure using transparent conducting oxide as metal gate
Authors: Yang T. , Liu Y. , Ye P. D. , Xuan Y. , Pal H. , Lundstrom M. S.
Published: June 2008

A systematic capacitance-voltage (C-V) study has been performed on GaAs metal-oxide-semiconductor (MOS) structures with atomic-layer-deposited Al2O3 as gate dielectrics and indium tin oxide (ITO) as the metal gate. The transparent conducting ITO gate allows homogeneous photoillumination on the whole MOS capacitance area, such that one can easily observe the low-frequency (LF) C-V and quasistatic C-V of GaAs at room temperature. The semiconductor capacitance effect on GaAs MOS devices has also been identified and insightfully discussed based on the obtained LF C-V curves. The semiconductor capacitance effect becomes more important for devices with high-mobility channel materials and aggressively scaled high-k gate dielectrics.
On the spectral response of quantum dot infrared photodetectors: Postgrowth annealing and polarization behaviors
Authors: Aslan B. , Song C. Y. , Liu H. C.
Published: June 2008

Effects of the postgrowth rapid thermal annealing on the device properties of a multilayer InAs∕GaAs quantum dot infrared photodetector are investigated. Clear shift in the spectral photoresponse toward smaller energy region with increasing annealing temperatures is shown. Polarization behaviors of the photoresponse peaks are presented.
Tunable surface plasmons for emission enhancement of silicon nanocrystals using Ag-poor cermet layer
Authors: Tang Xuan , Huang Yidong , Wang Yuxuan , Zhang Wei , Peng Jiangde
Published: June 2008

To improve the quantum efficiency from silicon nanocrystals, a structure with Ag∕Ag-poor cermet layers is proposed. Due to large permittivity of Ag-poor cermet and its dispersion characteristic, density of states can be enhanced at the energy much lower than the plasmon energy of Ag. By properly choosing the component of the Ag-poor cermet, the dispersion of surface plasmons can be engineered to increase radiative emission rate significantly at the emission energy of silicon nanocrystals. Effective enhancement is theoretically demonstrated using Ag, which was generally recognized as nonideal material for emission enhancement in silicon nanocrystals due to its high plasmon energy.
Evidence for surface dipole modifications in In2O3-based transparent conductors
Authors: Harvey S. P. , Mason T. O. , Körber C. , Gassenbauer Y. , Klein A.
Published: June 2008

Surface dipole modifications were identified for contamination-free In2O3-based transparent conducting oxides by ultraviolet photoelectron spectroscopy on both thin film and bulk ceramic specimens. In particular, heating in air was found to result in an increase in ionization potential and work function. The formation of surface dipoles may be related to the unique structure (crystal, defect) of bixbyite-based materials. These findings have important ramifications for the tuning of work functions in In2O3-based transparent conductors.
Spatial Offset of Test Field Elements from Surround Elements Affects the Strength of Motion Aftereffects
Authors: Harris John , Sullivan Daniel , Oakley Madeleine
Published: June 2008

Static movement aftereffects (MAEs) were measured after adaptation to vertical square-wave luminance gratings drifting horizontally within a central window in a surrounding stationary vertical grating. The relationship between the stationary test grating and the surround was manipulated by varying the alignment of the stationary stripes in the window and those in the surround, and the type of outline separating the window and the surround [no outline, black outline (invisible on black stripes), and red outline (visible throughout its length)]. Offsetting the stripes in the window significantly increased both the duration and ratings of the strength of MAEs. Manipulating the outline had no significant effect on either measure of MAE strength. In a second experiment, in which the stationary test fields alone were presented, participants judged how segregated the test field appeared from its surround. In contrast to the MAE measures, outline as well as offset contributed to judged segregation. In a third experiment, in which test-stripe offset was systematically manipulated, segregation ratings rose with offset. However, MAE strength was greater at medium than at either small or large (180° phase shift) offsets. The effects of these manipulations on the MAE are interpreted in terms of a spatial mechanism which integrates motion signals along collinear contours of the test field and surround, and so causes a reduction of motion contrast at the edges of the test field.
Frequency and precision of aerial surveys for kangaroo management
Authors: Pople A. R.
Published: June 2008

The appropriate frequency and precision for surveys of wildlife populations represent a trade-off between survey cost and the risk of making suboptimal management decisions because of poor survey data. The commercial harvest of kangaroos is primarily regulated through annual quotas set as proportions of absolute estimates of population size. Stochastic models were used to explore the effects of varying precision, survey frequency and harvest rate on the risk of quasiextinction for an arid-zone and a more mesic-zone kangaroo population. Quasiextinction probability increases in a sigmoidal fashion as survey frequency is reduced. The risk is greater in more arid regions and is highly sensitive to harvest rate. An appropriate management regime involves regular surveys in the major harvest areas where harvest rate can be set close to the maximum sustained yield. Outside these areas, survey frequency can be reduced in relatively mesic areas and reduced in arid regions when combined with lowered harvest rates. Relative to other factors, quasiextinction risk is only affected by survey precision (standard error/mean × 100) when it is >50%, partly reflecting the safety of the strategy of harvesting a proportion of a population estimate.
Aerial mark - recapture estimates of wild horses using natural markings
Authors: Dawson Michelle J. , Miller Cameron
Published: June 2008

Aerial mark–recapture population estimates utilising the natural markings of wild horses to identify individuals was applied in the Bogong High Plains, Alpine National Park, Victoria. A discrete population of wild horses occupying an area of 180 km2 was sampled over two days in 2005. This study explored the feasibility of a technique that aimed to enable managers to estimate the size of the horse population and monitor it over time. Four observers (including the pilot) searched for horses from a helicopter. Once horses were sighted, photographic and written observations were used to ‘mark’ each animal. The survey was repeated the following day with observations ‘recapturing’ individuals. Data were analysed using several mark–recapture estimators, and the derived population estimates ranged from 89 (±5.3, s.e.) horses to 94.7 (±7.9, s.e.) horses. We found that the method gave a level of precision relevant to management, but needs refinement. The technique and its assumptions should be tested further by increasing the number of samples and video should be used to improve identification of individuals. We believe that this is a novel application for aerial surveys, which are typically unsuitable for estimating the size of small populations. This technique was developed for horses but may be used on other conspicuous species with unique natural markings.
The influence of animal mobility on the assumption of uniform distances in aerial line-transect surveys
Authors: Fewster Rachel M. , Southwell Colin , Borchers David L. , Buckland Stephen T. , Pople Anthony R.
Published: June 2008

Line-transect distance sampling is a widely used method for estimating animal density from aerial surveys. Analysis of line-transect distance data usually relies on a requirement that the statistical distribution of distances of animal groups from the transect line is uniform. We show that this requirement is satisfied by the survey design if all other assumptions of distance sampling hold, but it can be violated by consistent survey problems such as responsive movement of the animals towards or away from the observer. We hypothesise that problems with the uniform requirement are unlikely to be encountered for immobile taxa, but might become substantial for species of high mobility. We test evidence for non-uniformity using double-observer distance data from two aerial surveys of five species with a spectrum of mobility capabilities and tendencies. No clear evidence against uniformity was found for crabeater seals or emperor penguins on the pack-ice in East Antarctica, while minor non-uniformity consistent with responsive movement up to 30 m was found for Adelie penguins. Strong evidence of either non-uniformity or a failure of the capture–recapture validating method was found for eastern grey kangaroos and red kangaroos in Queensland.
Design of aerial surveys for population estimation and the management of macropods in the Northern Tablelands of New South Wales, Australia
Authors: Cairns S. C. , Lollback G. W. , Payne N.
Published: June 2008

As part of a kangaroo management program, eastern grey kangaroos (Macropus giganteus) and common wallaroos (M. robustus robustus) are harvested from three kangaroo management zones in north-eastern New South Wales, Australia. To set sustainable harvest quotas, it is necessary to obtain reasonably accurate estimates of the sizes of the populations of these two species of macropod. Recently, this has been done on two occasions using helicopter line-transect surveys. For the most recent of these surveys, conducted in 2004, each management zone was subdivided into three strata of increasing kangaroo density and the surveys were designed in relation to this stratification using an automated survey design algorithm. The results of the surveys were that eastern grey kangaroo densities were estimated as 8.11 ± 1.81 km–2 in the Glen Innes zone, 10.23 ± 2.41 km–2 in the Armidale zone and 4.82 ± 0.87 km–2 in the Upper Hunter zone. Wallaroo densities for these three zones were 3.06 ± 0.73 km–2, 5.68 ± 3.45 km–2 and 4.40 ± 1.01 km–2 respectively. The wallaroo densities were determined by multiplying the initial estimated densities by a correction factor of 1.85. Across the three kangaroo management zones, eastern grey kangaroo densities did not change in any significant way between the two surveys. This was also the case for wallaroos in the Glen Innes and Armidale zones. Wallaroo density in the Upper Hunter zone, however, increased significantly between the two surveys. Over a decade before these surveys were conducted, a series of ground surveys using walked line-transect sampling were undertaken. The density estimates derived from the helicopter surveys proved to be broadly comparable to those derived from the ground surveys, suggesting that conducting helicopter line-transect surveys designed using the method deployed here is effective in producing population estimates for the purpose of kangaroo management.
Application of distance sampling to estimate population densities of large herbivores in Kruger National Park
Authors: Kruger J. M. , Reilly B. K. , Whyte I. J.
Published: June 2008

Aerial surveys have been used in the Kruger National Park, South Africa, to count large ungulates since the late 1970s. After 1998, aerial line-transect sampling using fixed-wing aircraft and Distance analyses replaced the ‘total’ counting method. This paper investigates these methods and three sampling intensities for estimating the densities of nine large ungulate species in Kruger National Park. Estimates suitable for the detection of population trends and making management decisions were decided by examination of coefficients of variation (set <20%, a priori). Despite the likely violation of some key assumptions of Distance sampling methods, analyses gave population estimates with adequate coefficients of variation for monitoring trends in impala, giraffe, zebra, kudu, white rhinoceros, and elephant bull populations. Significant improvements in precision were obtained at higher sampling intensities for kudu, giraffe, bull elephants and white rhinoceros, but these species already had sufficiently precise population estimates for the detection of trends at the lowest sampling intensity (15%). The estimates for warthog, wildebeest and waterbuck populations were, however, insufficiently precise for assessing population trends. Increasing sampling intensity to 22% and higher did not significantly increase the precision of the Distance estimates for these species. Shortcomings in interpretation of the data caused by violations of critical assumptions of analyses are identified and discussed.
Theory and application of mark - recapture and related techniques to aerial surveys of wildlife
Authors: Barker Richard
Published: June 2008

The key difficulty in assessing animal numbers from the air is that not all animals are seen by the observers. Methods for estimating detection probabilities, or accounting for imperfect detection, are reviewed including double surveys, use of sightability models, mark–resight, and mark–recapture. The assumptions needed for each method are considered as well as issues concerning survey design. For closed-population mark–recapture modelling particular attention is given to multiple observer studies. An emphasis is that an assumption of complete independence in double-observer studies is rarely justifiable and that independent observers will generally only satisfy an assumption of conditional independence and not complete independence.
Detectability of penguins in aerial surveys over the pack-ice off Antarctica
Authors: Southwell Colin , Paxton Charles G. M. , Borchers David L.
Published: June 2008

Knowledge of penguin abundance at regional and circumpolar scales across the Southern Ocean is important for the development of ecosystem models and to estimate prey consumption by penguins to assess potential competition with fisheries’ operations. One means of estimating penguin abundance is to undertake aerial surveys across the pack-ice surrounding Antarctica where penguins forage. However, it has long been recognised that aerial counts and resultant abundance estimates are likely to be negatively biased unless detectability is estimated and taken into account. Mark–recapture line-transect methods were used to estimate the detectability of penguin groups resting on ice floes during helicopter surveys over the pack-ice off Antarctica. Group size had the greatest effect of several measured covariates on detectability. Despite a concerted effort to meet the central assumption of conventional line-transect sampling (all objects on the transect line are detected), this was close to being achieved by single observers only in the case of the occasional very large group of >20 penguins. Emperor penguins were more detectable than Adélie penguins. Although observers undertook an extensive simulation training program before the survey, overall they improved in their ability to detect penguin groups throughout the survey. Mark–recapture line-transect methods can provide less biased estimation than conventional line-transect methods in aerial survey applications. This improvement comes with some costs, including the need for more demanding data-recording procedures and the need to use larger, more expensive aircraft. These additional costs will often be small compared with the basic cost, but the gain in terms of improved estimation may be substantial.
On bias, precision and accuracy in wildlife aerial surveys
Authors: Hone Jim
Published: June 2008

Bias, precision and accuracy have been studied extensively in wildlife population estimation including aerial surveys. A review of the literature shows that the concepts of bias and precision are used broadly consistently. Aerial survey data from known populations of feral pig carcases and white-tailed deer show that few density estimates are unbiased and precise. Research is needed, however, to clarify how much bias and how much precision are enough for the various types of wildlife management activities. Accuracy is used in two closely related but different ways. One set of definitions of accuracy relates to deviations from the true value (bias) and the second set relates to squared deviations from the true value (bias and precision). The implications are that authors are encouraged to clearly state which definition of accuracy they use, or focus solely on bias and precision.
Drosophila melanogaster
as a model host to dissect the immunopathogenesis of zygomycosis
Authors: Chamilos Georgios , Lewis Russell E. , Hu Jianhua , Xiao Lianchun , Zal Tomasz , Gilliet Michel , Halder Georg , Kontoyiannis Dimitrios P.
Published: June 2008

Zygomycosis is an emerging frequently fatal opportunistic mycosis whose immunopathogenesis is poorly understood. We developed a zygomycosis model by injecting
Drosophila melanogaster
flies with a standardized amount of fungal spores from clinical Zygomycetes isolates to study virulence and host defense mechanisms. We found that, as opposed to most other fungi, which are nonpathogenic in
D. melanogaster
(e.g.,
Aspergillus fumigatus
), Zygomycetes rapidly infect and kill wild-type flies
. Toll
-deficient flies exhibited increased susceptibility to Zygomycetes, whereas constitutive overexpression of the antifungal peptide
Drosomycin
in transgenic flies partially restored resistance to zygomycosis.
D. melanogaster
Schneider 2 phagocytic cells displayed decreased phagocytosis and caused less hyphal damage to Zygomycetes compared with that to
A. fumigatus
. Furthermore, phagocytosis-defective
eater
mutant flies displayed increased susceptibility to Zygomycetes infection. Classic enhancers of Zygomycetes virulence in humans, such as corticosteroids, increased iron supply, and iron availability through treatment with deferoxamine dramatically increased Zygomycetes pathogenicity in our model. In contrast, iron starvation induced by treatment with the iron chelator deferasirox significantly protected flies infected with Zygomycetes. Whole-genome expression profiling in wild-type flies after infection with Zygomycetes vs.
A. fumigatus
identified genes selectively down-regulated by Zygomycetes, which act in pathogen recognition, immune defense, stress response, detoxification, steroid metabolism, or tissue repair or have unknown functions. Our results provide insights into the factors that mediate host–pathogen interactions in zygomycosis and establish
D. melanogaster
as a promising model to study this important mycosis.
A genome-wide view of the spectrum of spontaneous mutations in yeast
Authors: Lynch Michael , Sung Way , Morris Krystalynne , Coffey Nicole , Landry Christian R. , Dopman Erik B. , Dickinson W. Joseph , Okamoto Kazufusa , Kulkarni Shilpa , Hartl Daniel L. , Thomas W. Kelley
Published: June 2008

The mutation process ultimately defines the genetic features of all populations and, hence, has a bearing on a wide range of issues involving evolutionary genetics, inheritance, and genetic disorders, including the predisposition to cancer. Nevertheless, formidable technical barriers have constrained our understanding of the rate at which mutations arise and the molecular spectrum of their effects. Here, we report on the use of complete-genome sequencing in the characterization of spontaneously arising mutations in the yeast
Saccharomyces cerevisiae
. Our results confirm some findings previously obtained by indirect methods but also yield numerous unexpected findings, in particular a very high rate of point mutation and skewed distribution of base-substitution types in the mitochondrion, a very high rate of segmental duplication and deletion in the nuclear genome, and substantial deviations in the mutational profile among various model organisms.
Direct maternal deaths in Norway 1976–1995
Authors: BEATHE ANDERSGAARD ALICE , LANGHOFF‐ROOS JENS , ØIAN PÅL
Published: June 2008

Aims. To report direct maternal mortality ratio (MMR) in Norway between 1976 and 1995 including a description of the underlying complications in pregnancy, the causes of death and assessment of standard of care. Methods. The maternal deaths were identified through the Cause of Death Registry, Statistics Norway, and Medical Birth Registry of Norway. We requested copies of the hospital case records and the maternal death autopsies. The direct maternal deaths were classified on the basis underlying causes and assessed for substandard care according to the guidelines at the time of death and preventability provided optimal conditions and up to date guidelines. Results. In the period 1976–1995 we identified 61 direct maternal deaths in Norway. The direct MMR was 5.5/100,000 births. Sufficient information was available for analysis in 51 of these cases. Six deaths occurred in early pregnancy. Among the 45 women who gave birth, 32 had a cesarean section, and the death was judged to be related to a complication of the operation in more than half of these cases. The standard of care and the possibility of preventing death were evaluated in 49 cases. Substandard care was observed in 21 of them and 27 were considered avoidable or potentially avoidable. Conclusion. The direct MMR in Norway was 5.5/100,000 births. The main causes were complications of hypertensive disease of pregnancy and thromboembolism. The majority of maternal deaths were associated with cesarean delivery and considered potentially avoidable.
Endoglin, PlGF and sFlt‐1 as markers for predicting pre‐eclampsia
Authors: DE VIVO ANTONIO , BAVIERA GIOVANNI , GIORDANO DOMENICO , TODARELLO GIOVANNA , CORRADO FRANCESCO , D'ANNA ROSARIO
Published: June 2008

Objective. To evaluate the ability of endoglin, placental growth factor (PlGF) and the soluble form of vascular endothelial growth factor receptor (sFlt‐1) measurements in gestational weeks 24–28 were used to predict pre‐eclampsia. Design. Observational, prospective study. Setting. Department of Gynecological, Obstetrical Sciences and Reproductive Medicine, University of Messina. Sample. Fifty‐two pre‐eclamptic and 52 healthy pregnant women. Methods. A maternal serum sample was frozen and stored at 1‐h 50‐g glucose challenge test between 24 and 28 weeks’ gestation. A second maternal serum sample was collected at admission for the onset of the disease in the pre‐eclamptic group and at admission for delivery in the control group. Levels of endoglin, sFlt‐1 and the PlGF were measured in the stored serum. Pre‐eclamptic subjects were also divided into women with early‐onset (<37 weeks) and women with late‐onset pre‐eclampsia (≥37 weeks). Results. Levels of endoglin, sFlt‐1, and sFlt‐1: PlGF ratio were found to be higher in the pre‐eclamptic group in both trimesters. No differences were found between early‐ and late‐onset pre‐eclamptic. The Receiver Operating Characteristics curve, applied to the second trimester marker values, showed the best diagnostic profile for sFlt‐1: PlGF (area under the curve, AUC =0.92) followed by endoglin (AUC =0.88), sFlt‐1 (AUC =0.87) and PlGF (AUC = 0.83). This finding was confirmed by Bayesian analysis which highlighted a specificity, a sensitivity, a diagnostic accuracy, a positive predictive value and a negative predictive value of 88.5% for sFlt‐1: PlGF using a cut‐off of 38.47. Conclusions. Endoglin, PlGF and sFlt‐1 might be used as markers for predicting pre‐eclampsia, but sFlt‐1: PlGF seems to be more accurate.
The Nottingham Apprenticeship Model: Schools in partnership with artists and creative practitioners
Authors: Griffiths Morwenna , Woolf Felicity
Published: June 2008

This article documents the collaborative research and development of an apprenticeship model of learning for the arts. It focuses on teachers working in partnership with artists and other creative practitioners. The model is rooted in theories of social learning and cognitive apprenticeship. It was developed and tested through collaborative research, some of it action research. The aim was to explore and test the model for appropriateness and for its impact on the learning of all participants (children, teachers, creative practitioners). The model was found to be useful as a guide to the organisation of children's learning in the arts. Moreover, using the model had a positive effect on the inclusion of children on the margins into wider school learning. The model was also useful in facilitating the professional development of the adults concerned: teachers, artists and others.
‘Straitjacket’ or ‘springboard for sustainable learning’? The implications of formative assessment practices in vocational learning cultures
Authors: Davies Jenifer , Ecclestone Kathryn
Published: June 2008

In contrast to theoretical and empirical insights from research into formative assessment in compulsory schooling, understanding the relationship between formative assessment, motivation and learning in vocational education has been a topic neglected by researchers. The Improving Formative Assessment project (IFA) addresses this gap, using a sociocultural approach to explore the relationship between formative assessment practices and ‘learning cultures’ in vocational education. This article explores the influence of learning cultures in vocational education on the practice of formative assessment and evaluates critically two closely related questions. Why do some learning cultures foster formative assessment that leads to instrumental learning while others develop deeper forms of learning? When is formative assessment a springboard for sustainable learning, and when does it remain an instrumental straitjacket?
Teachers' work in reading literacy across the curriculum in the senior phase of learning
Authors: Harreveld Bobby , Baker Kathy , Isdale Lindy
Published: June 2008

Teaching students to read is one of the main aims of education systems around the world. For a significant number of adolescents, however, formal schooling has failed to deliver adequate reading proficiency. This article reports on a study of teachers' responses to a reading intervention programme for adolescents implemented in a senior secondary college in Australia in 2006. It engages with the question: in what ways does the reading intervention affect senior secondary teachers' knowledge of reading literacy and their motivation to provide reading literacy support to students in content area subjects? Data were collected from 20 semi‐structured interviews with 15 teachers over a six‐month period. The findings suggest that, despite the success of the intervention for the students, in this particular senior school context the teachers were largely resistant to expectations that they engage with the process of teaching reading in all senior phases of learning curriculum areas.
Developing a characterisation of citizenship education: issues arising from work undertaken in a higher education network
Authors: Davies Ian , Arthur James , Harrison Tom , Watson Helen
Published: June 2008

In order to understand better the way in which the emerging field of citizenship education is being characterised we reflect on work emerging from a higher education network (citizED) for citizenship education. Three of the four authors of this article are closely involved in that network. CitizED was established with funding from the Teacher Training Agency (TTA) (now the Training and Development Agency for Schools, TDA) in order to establish a network and provide resources to support the initial training of citizenship teachers. We analysed download data from the network's website, a sample of the resources produced by the network, and interviewed a sample of users and developers. In this article we identify who is using the resources, how they are using them and what form of citizenship education is developing as a result. We argue that there is now a clear citizenship teacher education community that uses common resources for a variety of purposes. We suggest that there is some consensus in relation to the official characterisation of citizenship, but that ‘turf wars’ still exist in this contested field.
Promising performance of a juvenile justice diversion programme in remote Aboriginal communities, Northern Territory, Australia
Authors: CLOUGH ALAN R. , LEE KYLIE KIM SAN , CONIGRAVE KATHERINE M.
Published: June 2008

Introduction and Aims. Diversion from court and prison has been recommended for Indigenous Australian youth who commit offences. As no evaluations of such programmes have been published, we describe processes and early outcomes of a diversion programme in the Northern Territory. Design and Methods. From 2003 to 2006, among 1700 remote Indigenous community residents, 35 young people (aged 11–18 years, median 15 years) committed offences. They were diverted from criminal justice and referred to a community‐based diversion initiative. Client assessment records and staff interviews furnished data to examine clients' diversion pathways and early programme results. Results. Eighteen clients were reportedly using a substance at the time of their offence; cannabis (n = 9), petrol (n = 5), alcohol (n = 4). The remaining 17 had histories of using one or more of these. Two clients could not complete local diversion programs because they moved to other regions; one case was not pursued for legal reasons, leaving 32 clients exposed to the local programme. By July 2006, four clients were continuing in their programmes, three had breached them, but 25 had completed them in periods ranging from 2 to 60 weeks (median = 26 weeks), a completion rate of 89% (25/28). Just one client re‐offended after completing diversion. Discussion and Conclusions. A high completion rate was achieved despite: a dearth of locally available drug and alcohol treatment services and diversion options; shifts in police approaches; heavy administrative burdens to meet legal requirements; and difficulties communicating across cultural barriers.
Spontaneous spinal subarachnoid haemorrhage—a complication of alcohol withdrawal therapy
Authors: YALDIZLI ÖZGÜR , EULER SEBASTIAN , WILLI BERENIKA , WIESBECK GERHARD A. , WURST FRIEDRICH M.
Published: June 2008

Background. Non‐traumatic spontaneous idiopathic spinal subarachnoid haemorrhage (SSH) is extremely rare. So far, only 12 cases have been described in the literature and there are no data regarding the association between alcohol dependence and SSH. Case Summary. We report the first case of an alcohol‐dependent patient with an idiopathic non‐traumatic cervical subarachnoid haemorrhage after alcohol withdrawal therapy. Conclusions. Clinicians should be aware of alcohol dependence as an independent risk factor for not only intracranial, but subarachnoid haemorrhage. We recommend performing spinal imaging in alcoholics with sudden onset of severe neck or back pain, even if neurological deficits are absent or coagulation parameters are normal.
Wernicke‐Korsakoff syndrome (WKS) in Australia: no room for complacency
Authors: FEENEY GERALD F. X. , CONNOR JASON P.
Published: June 2008

Australia has made a substantial contribution to the recognition and treatment of the Wernicke‐Korsakoff syndrome (WKS). Much of this occurred over a generation ago, and vigilance in identifying this condition needs to be sustained. More recently, treatment protocols have been developed by the Royal College of Physicians (London). These provide guidelines on when and how to treat both patients at risk and those with acute Wernicke's encephalopathy (WE). It is not known how widespread these recommendations have been applied in Australia. We highlight these current treatment guidelines and illustrate management issues with two case reports. A decline in treatment practices in the United Kingdom prompted the development of these guidelines. Current treatment practices in Australia have not been reported. All alcohol and drug workers need to be reminded regularly of this condition and the need for prompt recognition and treatment.