bluuebunny/crossref_metadata_2025 huggingface dataset:
Highly transparent and conductive double-layer oxide thin films as anodes for organic light-emitting diodes
Authors: Yang Yu , Wang Lian , Yan He , Jin Shu , Marks Tobin J. , Li Shuyou
Published: August 2006

Double-layer transparent conducting oxide thin film structures containing In-doped CdO (CIO) and Sn-doped In2O3 (ITO) layers were grown on glass by metal-organic chemical vapor deposition and ion-assisted deposition (IAD), respectively, and used as anodes for polymer light-emitting diodes (PLEDs). These films have a very low overall In content of 16at.%. For 180-nm-thick CIO/ITO films, the sheet resistance is 5.6Ω∕◻, and the average optical transmittance is 87.1% in the 400–700nm region. The overall figure of merit (Φ=T10∕Rsheet) of the double-layer CIO/ITO films is significantly greater than that of single-layer CIO, IAD-ITO, and commercial ITO films. CIO/ITO-based PLEDs exhibit comparable or superior device performance versus ITO-based control devices. CIO/ITO materials have a much lower sheet resistance than ITO, rendering them promising low In content electrode materials for large-area optoelectronic devices.
Conditions for formation of a kinetic anode layer in crossed E×B fields
Authors: Kovalenko A. Yu. , Kovalenko Yu. A. , Keidar M.
Published: August 2006

A discharge in crossed electric and magnetic fields (E×B) is considered. E×B discharge serves as a basis for Hall-effect plasma accelerators. In this letter the authors present conditions for formation of a kinetic anode layer by considering an interface between kinetic and hydrodynamic regions. It is found that the kinetic anode layer, which has a thickness of about the electron Larmor radius, is formed in the case of a high magnetic field.
Interference of charge carrier in a double-dot nanopillar transistor
Authors: Wan Yue-Min , Yang Hsien-Hsun , Sung Chin-Lung , Hu Shu-Fen
Published: August 2006

In this study, the authors investigate the mutual interaction of quantized charge carriers in a double-dot nanopillar transistor. By coupling the dots at a distance less than the Fermi wavelength λF, the authors observe full size beats in current-voltage (I-V) characteristics at 300K. Analysis based on the theory of electron charging shows that this quantum effect occurs at the state of n=1. At large bias, the excitation is found rising to a group of mixing states of n=2 and n=3. The authors propose a phonon-assisted model to explain the results and find good agreement.
Vacuum ion emission from solid electrolytes: An alternative source for focused ion beams
Authors: Escher Conrad , Thomann Sandra , Andreoli Cornel , Fink Hans-Werner , Toquant Julien , Pohl Dieter W.
Published: August 2006

A bright ion source based on the solid electrolyte (AgI)0.5(AgPO3)0.5 has been developed. The solid electrolyte source provides stable currents of Ag+ in the microampere regime that make it suitable for focused ion beam applications. Similar conditions are expected for different solid electrolyte materials and their corresponding ions. This opens a broad field of applications in structuring and modifying devices on a nanometer scale using focused ion beams.
X-ray photochemical wet etching of n-Si (100) in hydrofluoric solution
Authors: Cho I. H. , Kim D. H. , Noh D. Y.
Published: August 2006

Photochemical wet etching of n-type Si (100) was carried out in hydrofluoric acid (49wt%) solution using high-flux synchrotron x-ray radiation. Under illumination of high-flux white x-ray beam, silicon is electropolished with an etching rate of about 1.5nm∕min. When illuminated with a monochromatic x-ray beam of relatively low flux, a porous silicon layer is formed instead. The open circuit potential increases under the white x-ray beam, in contrast to the results of visible or ultraviolet photoelectrochemistry. The authors attribute the electroless electropolishing of silicon to the enhanced band bending caused by the x-ray illumination.
Structural transformation and ferroelectromagnetic behavior in single-phase Bi1−xNdxFeO3 multiferroic ceramics
Authors: Yuan G. L. , Or Siu Wing , Liu J. M. , Liu Z. G.
Published: August 2006

Single-phase Bi1−xNdxFeO3 (BNFOx) (x=0–0.2) multiferroic ceramics were prepared to study the effects of Nd substitution on their crystal structure and ferroelectromagnetic behavior. Rietveld refinement of x-ray diffraction data showed a continual transformation of crystal structure from the rhombohedral structure of BNFOx=0 (BiFeO3) to a triclinic structure in BNFOx=0.05–0.15 and a pseudotetragonal structure in BNFOx=0.175–0.2. Ferroelectromagnetic measurements revealed the existence of ferroelectricity with remnant polarization of ∼9μC∕cm2 in BNFOx=0–0.175, paraelectricity in BNFOx=0.2, and weak ferromagnetism with remnant magnetizations of 0.07–0.227emu∕g in BNFOx=0.15–0.2. Magnetoelectric coupling was obvious in BNFOx=0.15–0.175 near the Néel temperature of ∼380°C.
Polycrystalline silicon-germanium heating layer for phase-change memory applications
Authors: Lee Seung-Yun , Choi Kyu-Jeong , Ryu Sang-Ouk , Yoon Sung-Min , Lee Nam-Yeal , Park Young-Sam , Kim Sang-Hoon , Lee Sang-Heung , Yu Byoung-Gon
Published: August 2006

This letter reports on the performance improvement of phase-change memory (PCM) cells by applying silicon-germanium (SiGe) alloys as resistive heating layers. The in situ doped polycrystalline Si0.75Ge0.25 films, lying under holes filled with a Ge2Sb2Te5 (GST) phase-change material in a pore-style configuration, promoted the temperature rise and phase transition in the GST. The SiGe heating layer caused drastic reduction in both set and reset currents compared to a conventional TiN heater material. The threshold voltages of the PCM cells were almost uniform irrespective of the kind of heating layers. It is considered that this beneficial effect of the SiGe heating layer originates from the high electrical resistivity and low thermal conductivity of a SiGe alloy.
Voltage-controlled slow light in asymmetry double quantum dots
Authors: Yuan Chun-Hua , Zhu Ka-Di
Published: August 2006

The authors demonstrate theoretically that there exists electromagnetically induced transparency in an asymmetric double quantum dot system using tunneling instead of pump laser. The group velocity slowdown factor is theoretically analyzed as a function of electron tunneling at different broadened linewidths. With feasible parameters for applications to a 100Gbits∕s optical network, numerical calculation infers group velocity as low as 300m∕s. The scheme is expected to be useful in constructing a variable semiconductor optical buffer based on electromagnetically induced transparency in an asymmetric double quantum dot controlled by voltage.
Stable inverted bottom-emitting organic electroluminescent devices with molecular doping and morphology improvement
Authors: Chen Szu-Yi , Chu Ta-Ya , Chen Jenn-Fang , Su Chien-Ying , Chen Chin H.
Published: August 2006

Stable inverted bottom-emitting organic light-emitting diodes (IBOLEDs) have been investigated by inserting n-type Cs2O dopant between indium-tin oxide bottom cathode and Alq3, the combination of which not only improved the morphology of organic layer but enhanced the lifetime of the IBOLED. This n-type doped IBOLED achieved efficiencies of 5.2cd∕A and 2.0lm∕W at 20mA∕cm2. The 20% decay lifetime (t80) of Cs2O doped IBOLED is 270h which is about 1.7 times more stable than that of the conventional OLED (160h) and 2.5 times of Li doped IBOLED (104h).
Thermal diffusion and compositional inhomogeneity in cast Zr50Cu50 bulk metallic glass
Authors: Liu Y. , Liu C. T. , George E. P. , Wang X. Z.
Published: August 2006

Macroscale compositional inhomogeneity was found in Zr50Cu50 (at. %) bulk metallic glass castings prepared by rapid solidification. The variation of composition in the castings from surface to interior is attributed to the Soret effect induced by a large temperature gradient during cooling. Copper exhibits a positive Soret coefficient, and its concentration increases with temperature gradient. The Soret effect was detected up to a depth of 250μm and its magnitude depended on the size of the casting. The compositional inhomogeneity resulting from the Soret effect has a significant influence on the nucleation of crystallization phases in the Zr50Cu50 metallic glass.
Photocarrier injection effect and p-n junction characteristics of La0.7Sr0.3MnO3∕ZnO and Si heterostructures
Authors: Lord K. , Hunter D. , Williams T. M. , Pradhan A. K.
Published: August 2006

The authors report the fabrication of p-n junctions, consisting of p-type La0.7Sr0.3MnO3 (LSMO) and either n-type ZnO grown on sapphire or n-type Si substrates. The LSMO/ZnO junction exhibits excellent rectifying behavior over the temperature range of 77–300K with breakdown voltage less than −10V. LSMO/Si displayed p-n junction characteristics over a temperature region of 77–360K. Inserting a SrTiO3 layer between LSMO and Si remarkably improved the junction characteristics. All junctions show photocarrier injection effect, illustrating the control of transport properties of LSMO in which electron injection decreases hole concentration following the photoexcitation of both ZnO and Si.
Efficient solution of Poisson’s equation with free boundary conditions
Authors: Genovese Luigi , Deutsch Thierry , Neelov Alexey , Goedecker Stefan , Beylkin Gregory
Published: August 2006

Interpolating scaling functions give a faithful representation of a localized charge distribution by its values on a grid. For such charge distributions, using a fast Fourier method, we obtain highly accurate electrostatic potentials for free boundary conditions at the cost of O(NlogN) operations, where N is the number of grid points. Thus, with our approach, free boundary conditions are treated as efficiently as the periodic conditions via plane wave methods.
W-structured type-II superlattice long-wave infrared photodiodes with high quantum efficiency
Authors: Aifer E. H. , Tischler J. G. , Warner J. H. , Vurgaftman I. , Bewley W. W. , Meyer J. R. , Kim J. C. , Whitman L. J. , Canedy C. L. , Jackson E. M.
Published: August 2006

Results are presented for an enhanced type-II W-structured superlattice (WSL) photodiode with an 11.3μm cutoff and 34% external quantum efficiency (at 8.6μm) operating at 80K. The new WSL design employs quaternary Al0.4Ga0.49In0.11Sb barrier layers to improve collection efficiency by increasing minority-carrier mobility. By fitting the quantum efficiencies of a series of p-i-n WSL photodiodes with background-doped i-region thicknesses varying from 1to4μm, the authors determine that the minority-carrier electron diffusion length is 3.5μm. The structures were grown on semitransparent n-GaSb substrates that contributed a 35%–55% gain in quantum efficiency from multiple internal reflections.
Nanostructured-porous-silicon-based two-dimensional photonic crystals
Authors: Martín-Palma R. J. , Manso M. , Arroyo-Hernández M. , Torres-Costa V. , Martínez-Duart J. M.
Published: August 2006

Tunable two-dimensional photonic band gap structures were developed, basically consisting of nanometric porous silicon (PS) rods embedded into a silicon matrix, arranged as to form a hexagonal lattice. The optical behavior of these structures was determined by calculating the band structure for the transverse magnetic and transverse electric modes, finding that the optical response can be controlled by independently varying the index of refraction of PS, the radius of the rods, and the lattice parameter. The change in the index of refraction was implemented in the range of 1.4–2.2 by controlling the PS formation parameters. Finally, it can be pointed out that the dependence of the optical behavior of the photonic crystals on polarization can lead to the development of polarization-dependent optoelectronic devices.
Dependency of organic phototransistor properties on the dielectric layers
Authors: Hu Yan , Dong Guifang , Liu Chen , Wang Liduo , Qiu Yong
Published: August 2006

Organic phototransistors with pentacene semiconductor and Ta2O5 or polymethyl methacrylate (PMMA) dielectric layer have been investigated. It was found that the phototransistor properties strongly depend on the dielectric layer. Under a broadband light with 10mW∕cm2, the sensitivity of the Ta2O5 based transistor is much higher than that of the PMMA based transistor. For Ta2O5 based transistor, the photosensitivity (the ratio of photocurrent to dark current) and the threshold voltage shift are 4000 and 13.5V, respectively. While for PMMA based transistor, the corresponding values are only 0.5 and 2.9V, respectively. That large difference is attributed to the electron trapping ability of Ta2O5.
p
-doped 1.3μm InAs∕GaAs quantum-dot laser with a low threshold current density and high differential efficiency
Authors: Liu H. Y. , Liew S. L. , Badcock T. , Mowbray D. J. , Skolnick M. S. , Ray S. K. , Choi T. L. , Groom K. M. , Stevens B. , Hasbullah F. , Jin C. Y. , Hopkinson M. , Hogg R. A.
Published: August 2006

A modification of the thickness of the low-growth-temperature component of the GaAs spacer layers in multilayer 1.3μm InAs∕GaAs quantum-dot (QD) lasers has been used to significantly improve device performance. For a p-doped seven-layer device, a reduction in the thickness of this component from 15to2nm results in a reduced reverse bias leakage current and an increase in the intensity of the spontaneous emission. In addition, a significant reduction of the threshold current density and an increase of the external differential efficiency at room temperature are obtained. These improvements indicate a reduced defect density, most probably a combination of the selective elimination of a very low density of dislocated dots and a smaller number of defects in the thinner low-growth-temperature component of the GaAs spacer layer.
A role for nest boxes in the conservation of Leadbeater's possum (Gymnobelideus leadbeateri)
Authors: Harley Dan K. P.
Published: August 2006

A combination of fires and logging mean that more than 80% of the montane ash forests inhabited by Leadbeater’s possum (Gymnobelideus leadbeateri) in the Victorian Central Highlands consist of ecologically young stands possessing few trees with hollows. As a consequence, there have been predictions of a substantial decline in Leadbeater’s possum populations over the next 40 years. If this is to be averted, or reduced in extent, then an immediate means of increasing den site availability for the species is required. The results of a recent investigation into nest-box use by the species in lowland swamp forest demonstrate that high rates of occupancy can be achieved by targeting established colonies at sites where the vegetation structure is suitable for box installation. This suggests that nest boxes can be an effective means of increasing den-site availability for the possum, and therefore have considerable potential to contribute to the species’ conservation in the short term. Such measures should be applied in conjunction with altered forestry practises that better provide for the retention and future provision of mature hollow-bearing trees.
Comparison of the healing process in hot and cold brands applied to harbour seal pups (Phoca vitulina)
Authors: Daoust Pierre-Yves , Fowler G. Mark , Stobo Wayne T.
Published: August 2006

Hot branding has been used for many years by researchers to identify seals from a long distance. In livestock, cold branding has been proposed as an alternative because it is thought to be less painful. The purpose of this study was to compare the healing process of hot and cold brands applied to harbour seal pups (Phoca vitulina). A total of 306 animals was branded with a unique set of four characters: three applied for 3–5 s with an iron heated to 500°C, and one applied for either 10 or 20 s with an iron frozen to –175°C. At three subsequent times over 10 weeks, 43, 41 and 51 animals, respectively, were recaptured, the macroscopic appearance of their brands recorded, and biopsies taken for microscopic examination. Cold brands had a faster healing rate than hot brands. However, they resulted in less destruction of hair follicles, and cold brands applied for 20 s caused more depigmentation. Regrowth of hair follicles could subsequently obscure brands, while depigmentation reduces the contrast between the brand and the surrounding fur. Cold brands applied for 20 s also caused more extensive deep vascular damage, which subsequently may have resulted in deeper wounds in some of these brands. Yet, macroscopically, other cold brands, or portions thereof, were almost invisible. On the basis of this short-term study, the technique of cold branding that we used in harbour seals does not appear to be as reliable as that of hot branding to provide permanent legible brands.
Indirect impacts of invasive cane toads (Bufo marinus) on nest predation in pig-nosed turtles (Carettochelys insculpta)
Authors: Doody J. S. , Green B. , Sims R. , Rhind D. , West P. , Steer D.
Published: August 2006

The cane toad (Bufo marinus) was introduced into Australia in 1935. Because this toxic frog is novel to the Australian fauna, its introduction has impacted native fauna in a variety of ways. We anticipated a severe decline in the yellow-spotted monitor lizard (Varanus panoptes) associated with the arrival of cane toads along the Daly River, Northern Territory, and predicted a simultaneous impact on nest predation in the pig-nosed turtle (Carettochelys insculpta) because the lizard is the chief predator of C. insculpta eggs at the site. We surveyed for monitors and cane toads for five years at two sites before and after the arrival of cane toads, and surveyed for turtle nest predation for three years before, and one year after, the arrival of the toads. Collectively, our data and observations, combined with unpublished reports, indicate that: (1) cane toads arrived at our study sites during the wet seasons of 2003–04 and 2004–05; (2) the lizard V. panoptes readily succumbs to cane toad toxins; (3) . panoptes has experienced a marked decline in relative population numbers coincident with the arrival of the toads at the site; and (4) V. panoptes has been reduced to such low numbers that it is currently no longer a significant predator of pig-nosed turtle eggs.
Home range and den characteristics of the brush-tailed rabbit-rat (Conilurus penicillatus) in the monsoonal tropics of the Northern Territory, Australia
Authors: Firth Ronald S. C. , Woinarski John C. Z. , Noske Richard A.
Published: August 2006

Radio-telemetry was used to investigate the home range and den characteristics of the brush-tailed rabbit-rat (Conilurus penicillatus) from three sites in the monsoonal tropics of the Northern Territory, Australia. Radio-tracking was conducted in a series of discontinuous 4–17-day sessions, over a 2-year period. The home ranges of 61 C. penicillatus were estimated using the minimum convex polygon (MCP) and fixed kernel (K95% and K50%) methods. There were no significant differences in home-range size among the three sites or between wet and dry seasons, which suggests that vegetation structure, floristics and season play relatively little role in movements of C. penicillatus. The mean home-range size was 0.79 ± 0.09 ha (MCP estimate) to 0.97 ± 0.12 ha (K95% estimate). The home ranges of males were larger than those of females (mean MCP estimates of 1.07 ± 0.15 and 0.45 ± 0.06 ha respectively). C. penicillatus denned primarily in fallen logs and in hollows of eucalypts and bloodwoods (Corymbia spp.). Rough-barked trees appeared to be preferred. The diameter at breast height (DBH) of den trees varied significantly between the three sites, being greatest at site C1 (34.5 ± 2.4 cm) and least at site C2 (26.1 ± 1.0 cm). Den trees had larger DBH than randomly selected trees at each site. The diameter at the mid-point (DMP) of both den and randomly selected logs were not significantly different between sites. Many individuals used more than one den site per tracking session. The small home ranges of C. penicillatus and its reliance on hollows in trees and logs suggest that this species is very vulnerable to local extinction following long-term annual and destructive fire regimes and land clearing, even in comparatively small patches.
Efficacy of manufactured PIGOUT® baits for localised control of feral pigs in the semi-arid Queensland rangelands
Authors: Cowled Brendan D. , Gifford Eddie , Smith Michelle , Staples Linton , Lapidge Steven J.
Published: August 2006

Conservative population declines of 73% were recorded in three independent feral pig populations in Welford National Park, Queensland, when PIGOUT® baits containing 72 mg of sodium fluoroacetate were used in a baiting program following prefeeding. Declines were measured using a prebaiting population census with remote cameras, followed by carcass recovery. The knockdown of susceptible feral pigs may have been higher than this, since any carcasses not recovered reduced the recorded efficacy. In addition, feral pigs know to have left the baiting area after trapping and telemetry-tagging, and subsequently not exposed to toxic baits, were included in the analysis. The use of remote cameras and carcass recovery appears to be a relatively accurate means of recording localised declines in feral pig populations. This method is applicable only when carcass recovery is possible, such as in open areas in the semi-arid rangelands. A decline of 86% of radio-tagged feral pigs attending bait stations was also recorded. Camera observations revealed no non-target consumption of baits. Measurement of sodium fluoroacetate–contaminated tissues from feral pigs showed that residues were too low to present a significant risk to recorded scavenging animals in the area. Some feral pigs vomited before death, with vomitus containing sodium fluoroacetate poison at high concentrations. No vomitus was consumed by non-target species. Almost all feral pigs were killed relatively rapidly after ingestion of sodium fluoroacetate and the signs observed in a small number of poisoned feral pigs did not indicate a significant welfare concern.
Freshwater turtles of the TransFly region of Papua New Guinea - notes on diversity, distribution, reproduction, harvest and trade
Authors: Georges Arthur , Guarino Fiorenzo , Bito Biatus
Published: August 2006

The Chelidae is a family of side-necked turtles restricted in distribution to South America and Australasia. While their biology in Australia is reasonably well known, species in New Guinea are very poorly known despite high diversity, especially in the southern lowlands. In this paper, we report on the diversity, distribution, habitat and reproductive biology of the freshwater turtles of the TransFly region of the Western Province of Papua New Guinea, with special emphasis on reproduction of Emydura subglobosa, Elseya branderhorsti and Elseya novaeguineae. Seven species were captured, with reliable records of an eighth. A key to the freshwater turtles of the TransFly region is provided. Harvest methods, consumption, and trade in turtles by the TransFly communities are documented. There is mounting pressure to take advantage of revenue opportunities afforded by the Asian turtle trade, but this is impeded by lack of transport infrastructure. There is also insufficient demographic information on any New Guinean turtle species to make a reasoned judgment on the level of harvest that would be sustainable. Nor is there sufficient information on captive rearing for most species, and where it is available it is not accessible by local villagers. These knowledge gaps need to be addressed and factored into a management plan that is implemented before local communities can capitalise on the commercial opportunities provided by the turtle fauna without risking collapse of the resource and the implications for their concurrent subsistence economy that would follow.
Importance of diurnal refugia to a hare-wallaby reintroduction in Western Australia
Authors: Hardman Blair , Moro Dorian
Published: August 2006

In an effort to learn more about the potential for reintroduction of hare-wallabies to sites in Australia, 34 captive-bred hare-wallabies were released onto Peron Peninsula within the Shark Bay World Heritage Property in 2001 as part of an experimental reintroduction program. One objective of this experiment was to characterise their behaviour and daytime refugia to identify suitable habitat for future releases. The mala (Lagorchestes hirsutus) and merrnine (Lagostrophus fasciatus) were fitted with radio-transmitters and tracked daily. Merrnine were more faithful to a previously occupied shelter than mala. Mala maintained a solitary daytime habit at all times. Within the study area, mala preferentially sought low-lying vegetation primarily comprising the species Lamarchea hakeifolia, which provided dense cover up to 1 m in height, under which they constructed scrapes. L. hakeifolia was preferred as shelter vegetation instead of Triodia (spinifex) hummocks, despite Triodia hummock habitat being preferred by mala in central Australia. Merrnine occupied taller vegetation with an open understorey to 1.5 m, although the extremity of the understorey remained dense at this height. Individual merrnine sometimes sheltered with conspecifics of the opposite sex. Since both species utilised floristically and structurally variable vegetation, we suggest that they have the ability to cope with vegetation that has been altered by changes in fire regimes and introduced herbivores. This is particularly important for future reintroduction exercises as the results suggest that vegetation characteristics required to support these species, particularly mala, may be variable rather than limited to perceived necessary habitat types in central Australia or on islands. These results should allow future reintroduction projects to consider a wider range of release-site options during their planning phase.
Feral pigs in north-western Australia: population recovery after 1080 baiting and further control
Authors: Twigg Laurie E. , Lowe Tim , Everett Michael , Martin Gary
Published: August 2006

The recovery rate of a population of feral pigs (Sus scrofa) in the west Kimberley in north-western Australia was determined 12 months after a 1080 (sodium fluoroacetate)-baiting program. An estimated 56 pigs were present in the 15 000-ha study area in August 2005 compared with the prebaiting levels of 250–275 pigs in 2004 (11 pigs were known to be alive on site after the 2004 baiting). This represents a population recovery of 20–23% of the 2004 prebaiting levels. Although most pigs were in good body condition, environmental conditions were quite different between the two years. In 2005, some waterholes were dry or comprised mainly muddy water with little associated shelter for feral pigs. Consequently, and in contrast to 2004, no pigs were seen, and no bait take could be attributed to feral pigs, at the four resurveyed waterholes. Most pig sightings, and activity, were close to the Fitzroy River. Fermented wheat, with blood and bone, was used to determine areas of pig activity, and also used as prefeed before 1080-baiting commenced in 2005. Using the same bait stations as for 2004, plus additional stations established in new areas of pig activity, 1080-treated wheat and malted barley again proved highly effective in reducing pig numbers. The daily sighting index before and after 1080-baiting indicated that pig numbers had been reduced by ~90% within four days. Estimated pre- and postpoisoning density, with and without an edge effect, was 0.12–1.7 pigs km–2 and 0.05–0.67 pigs km–2. Pig tracks decreased to zero on the six track plots within two days of baiting, but the number of macropod tracks remained constant over the four-day baiting period. Thirty-eight poisoned pigs were found after 1080-baiting, and these were generally in clustered groups within 200 m of an active bait station. Poisoned juvenile pigs were again found closer to the active bait stations than were adult or subadult pigs (P < 0.05).
Genetic structure infers generally high philopatry and male-biased dispersal of brushtail possums (Trichosurus vulpecula) in urban Australia
Authors: Stow A. J. , Minarovic N. , Eymann J. , Cooper D. W. , Webley L. S.
Published: August 2006

The brushtail possum (Trichosurus vulpecula) is in decline throughout much of its natural range with the notable exception of urban areas and a few islands. In some urban areas, its density can be high enough to cause conflict with householders. We provide the first genetic-based study of dispersal for T. vulpecula in the urban environment. Seven microsatellite markers were used to investigate genetic structure of adult male (n = 53) and female (n = 39) possums sampled from mainland suburbs of Sydney, and on nearby Scotland Island. Samples from Scotland Island also provide an opportunity to assess the effect of isolation on genetic variability, which, as theory would predict, was significantly lower than observed in mainland samples. Male-biased dispersal was inferred from patterns of relatedness between individuals of each sex. Average relatedness was significantly higher between adult female possums than between adult male possums sampled within the same garden area. In addition, males were genotypically more similar to one another at substantially greater geographic distances than females. Along with male-biased dispersal, strong localised genetic structure for both sexes infers generally high philopatry. Dispersal distances were greatest for adult male possums sampled from mainland locations. However, even for these males, genotypic similarity between possums separated by distances further than ~900 m was lower than the sample average, suggesting infrequent dispersal beyond this distance. Knowledge of dispersal patterns is important to managing the density levels of overabundant T. vulpecula in urban areas.
Migratory shearwaters integrate oceanic resources across the Pacific Ocean in an endless summer
Authors: Shaffer Scott A. , Tremblay Yann , Weimerskirch Henri , Scott Darren , Thompson David R. , Sagar Paul M. , Moller Henrik , Taylor Graeme A. , Foley David G. , Block Barbara A. , Costa Daniel P.
Published: August 2006

Electronic tracking tags have revolutionized our understanding of broad-scale movements and habitat use of highly mobile marine animals, but a large gap in our knowledge still remains for a wide range of small species. Here, we report the extraordinary transequatorial postbreeding migrations of a small seabird, the sooty shearwater, obtained with miniature archival tags that log data for estimating position, dive depth, and ambient temperature. Tracks (262 ± 23 days) reveal that shearwaters fly across the entire Pacific Ocean in a figure-eight pattern while traveling 64,037 ± 9,779 km roundtrip, the longest animal migration ever recorded electronically. Each shearwater made a prolonged stopover in one of three discrete regions off Japan, Alaska, or California before returning to New Zealand through a relatively narrow corridor in the central Pacific Ocean. Transit rates as high as 910 ± 186 km·day−1were recorded, and shearwaters accessed prey resources in both the Northern and Southern Hemisphere’s most productive waters from the surface to 68.2 m depth. Our results indicate that sooty shearwaters integrate oceanic resources throughout the Pacific Basin on a yearly scale. Sooty shearwater populations today are declining, and because they operate on a global scale, they may serve as an important indicator of climate change and ocean health.
Effective countermeasure against poisoning by organophosphorus insecticides and nerve agents
Authors: Albuquerque Edson X. , Pereira Edna F. R. , Aracava Yasco , Fawcett William P. , Oliveira Maristela , Randall William R. , Hamilton Tracey A. , Kan Robert K. , Romano James A. , Adler Michael
Published: August 2006

The nerve agents soman, sarin, VX, and tabun are deadly organophosphorus (OP) compounds chemically related to OP insecticides. Most of their acute toxicity results from the irreversible inhibition of acetylcholinesterase (AChE), the enzyme that inactivates the neurotransmitter acetylcholine. The limitations of available therapies against OP poisoning are well recognized, and more effective antidotes are needed. Here, we demonstrate that galantamine, a reversible and centrally acting AChE inhibitor approved for treatment of mild to moderate Alzheimer’s disease, protects guinea pigs from the acute toxicity of lethal doses of the nerve agents soman and sarin, and of paraoxon, the active metabolite of the insecticide parathion. In combination with atropine, a single dose of galantamine administered before or soon after acute exposure to lethal doses of soman, sarin, or paraoxon effectively and safely counteracted their toxicity. Doses of galantamine needed to protect guinea pigs fully against the lethality of OPs were well tolerated. In preventing the lethality of nerve agents, galantamine was far more effective than pyridostigmine, a peripherally acting AChE inhibitor, and it was less toxic than huperzine, a centrally acting AChE inhibitor. Thus, a galantamine-based therapy emerges as an effective and safe countermeasure against OP poisoning.
Fatness at birth predicts adult susceptibility to ovarian suppression: An empirical test of the Predictive Adaptive Response hypothesis
Authors: Jasienska Grazyna , Thune Inger , Ellison Peter T.
Published: August 2006

Poor fetal environments are thought to produce adaptive changes in human developmental trajectories according to the Predictive Adaptive Response hypothesis. Although many studies have demonstrated correlations between indicators of fetal environment and negative adult health outcomes, the adaptive significance of these outcomes is unclear. Our study explicitly tests the adaptive nature of fetal programming in humans. We show that differences in nutritional status at birth are associated with adaptive differences in the sensitivity of adult ovarian function to energetic stress. Women who were born as relatively fat babies do not exhibit ovarian suppression in response to moderate levels of physical activity at adulthood, in contrast to women who were born as skinnier babies. The levels of estradiol in women born in the highest tertile of ponderal index (an indicator of neonatal nutritional status) were 37% and 46% higher, respectively, than levels of estradiol in women born in the low and middle ponderal index tertiles. These findings suggest that fetal programming of reproductive function results in developmentally plastic, but essentially adaptive, shifts in set points of ovarian response to energetic stress, such that women who were gestated under conditions of energetic constraint show greater sensitivity to energetic stress in adulthood. Our results have practical implications in terms of behavioral strategies for reducing the risk of breast cancer. We suggest that the amount of activity necessary to reduce levels of estrogen, which may in turn reduce cancer risk, can depend on a woman's nutritional status at birth.
Online counselling: The motives and experiences of young people who choose the Internet instead of face to face or telephone counselling
Authors: King Robert , Bambling Matthew , Lloyd Chris , Gomurra Rio , Smith Stacy , Reid Wendy , Wegner Karly
Published: August 2006

This study used a Consensual Qualitative Research methodology to explore the motivations and experiences of young people who utilize the Internet for counselling over other counselling media. Semi‐structured online group interviews (focus groups) were conducted with 39 participants from the Kids Help Line, a 24‐hour national telephone and counselling service located in Australia. Analysis revealed five domains relevant to the adolescents’ motives and experiences and the frequency of categories within and across cases were analyzed to generate and understand themes and patterns. Specific motivators and barriers are identified and discussed, as are implications for practice and continued research.
Attitudes to counselling via the Internet: A comparison between in‐person counselling clients and Internet support group users
Authors: Skinner Adrian E. G. , Latchford Gary
Published: August 2006

E‐therapy has emerged as an apparently popular alternative to face‐to‐face (f2f) therapy, with some evidence of effectiveness and of the ability of therapist and client to develop a good therapeutic relationship. As yet, however, little is known about those choosing this form of therapy. The present study investigated self disclosure style and attitudes towards e‐therapy in three groups: current e‐therapy clients, current users of Internet mental health support groups, and current f2f counselling clients. Participants completed a measure of self disclosure (the SD‐40) and answered questions asking about the influence of factors thought to be potentially important in influencing a decision to undertake e‐therapy, adapted by the authors. Two versions were used, pencil and paper and web‐based. Unfortunately, too few e‐therapy clients were recruited for the data to be analysed. There was no significant difference in self disclosure style between Internet support group users and f2f therapy users, though the latter had a higher tendency to self disclose. Attitudes were generally not extreme, but Internet support group users were significantly more positive about the influence of using computers to communicate with a therapist. In summary, the study found that Internet support group users had broadly positive views of the advantages of e‐therapy, particularly if they had had some personal experience of therapy. Experience of both using the Internet and therapy appear to be important in determining attitudes towards e‐therapy. Self disclosure was also found to be related to some attitudes to e‐therapy. The difficulties recruiting e‐therapy participants was a surprise given the efforts to do this, and may reflect the fact that e‐therapy is not widely used. This raises the question of why those who appear to have positive attitudes to e‐therapy are not, in fact, engaging in it.
Telephone and online counselling for young people: A naturalistic comparison of session outcome, session impact and therapeutic alliance
Authors: King Robert , Bambling Matthew , Reid Wendy , Thomas Ian
Published: August 2006

Kids Help Line is a national service providing free telephone counselling and online counselling to young people in Australia. This study used a naturalistic design and standardized measures to compare outcomes, session impact and therapeutic alliance for samples of 100 young people receiving a single session of telephone counselling and 86 young people receiving a single session of online counselling, provided by Kids Help Line. Results suggested that telephone counselling is associated with better counselling outcomes, higher session impact and stronger counselling alliance when compared with online counselling. The limitations imposed by a naturalistic design require caution in interpretation of the results. However, the pattern of results suggests that there are differences in effectiveness between telephone and online counselling. The most likely explanation is the greater communication efficiency of telephone counselling, which enables more counselling work to be undertaken in the time available. Implications for further development of online counselling are discussed.
ATP-binding cassette transporter A7 enhances phagocytosis of apoptotic cells and associated ERK signaling in macrophages
Authors: Jehle Andreas W. , Gardai Shyra J. , Li Suzhao , Linsel-Nitschke Patrick , Morimoto Konosuke , Janssen William J. , Vandivier R. William , Wang Nan , Greenberg Steven , Dale Benjamin M. , Qin Chunbo , Henson Peter M. , Tall Alan R.
Published: August 2006

The mammalian ATP-binding cassette transporters A1 and A7 (ABCA1 and -A7) show sequence similarity to CED-7, a Caenorhabditis elegans gene that mediates the clearance of apoptotic cells. Using RNA interference or gene targeting, we show that knock down of macrophage ABCA7 but not -A1 results in defective engulfment of apoptotic cells. In response to apoptotic cells, ABCA7 moves to the macrophage cell surface and colocalizes with the low-density lipoprotein receptor–related protein 1 (LRP1) in phagocytic cups. The cell surface localization of ABCA7 and LRP1 is defective in ABCA7-deficient cells. C1q is an opsonin of apoptotic cells that acts via phagocyte LRP1 to induce extracellular signal–regulated kinase (ERK) signaling. We show that ERK signaling is required for phagocytosis of apoptotic cells and that ERK phosphorylation in response to apoptotic cells or C1q is defective in ABCA7-deficient cells. These studies reveal a major role of ABCA7 and not -A1 in the clearance of apoptotic cells and therefore suggest that ABCA7 is an authentic orthologue of CED-7.
Functional implications of calcium permeability of the channel formed by pannexin 1
Authors: Vanden Abeele Fabien , Bidaux Gabriel , Gordienko Dmitri , Beck Benjamin , Panchin Yuri V. , Baranova Ancha V. , Ivanov Dmitry V. , Skryma Roman , Prevarskaya Natalia
Published: August 2006

Although human pannexins (PanX) are homologous to gap junction molecules, their physiological function in vertebrates remains poorly understood. Our results demonstrate that overexpression of PanX1 results in the formation of Ca2+-permeable gap junction channels between adjacent cells, thus, allowing direct intercellular Ca2+ diffusion and facilitating intercellular Ca2+ wave propagation. More intriguingly, our results strongly suggest that PanX1 may also form Ca2+-permeable channels in the endoplasmic reticulum (ER). These channels contribute to the ER Ca2+ leak and thereby affect the ER Ca2+ load. Because leakage remains the most enigmatic of those processes involved in intracellular calcium homeostasis, and the molecular nature of the leak channels is as yet unknown, the results of this work provide new insight into calcium signaling mechanisms. These results imply that for vertebrates, a new protein family, referred to as pannexins, may not simply duplicate the connexin function but may also provide additional pathways for intra- and intercellular calcium signaling and homeostasis.
N-syndecan deficiency impairs neural migration in brain
Authors: Hienola Anni , Tumova Sarka , Kulesskiy Evgeny , Rauvala Heikki
Published: August 2006

N-syndecan (syndecan-3) is a transmembrane proteoglycan that is abundantly expressed in the major axonal pathways and in the migratory routes of the developing brain. When ligated by heparin-binding (HB) growth-associated molecule (GAM; pleiotrophin), N-syndecan mediates cortactin–Src kinase-dependent neurite outgrowth. However, the functional role of N-syndecan in brain development remains unexplored. In this study, we show that N-syndecan deficiency perturbs the laminar structure of the cerebral cortex as a result of impaired radial migration. In addition, neural migration in the rostral migratory stream is impaired in the N-syndecan–null mice. We suggest that the migration defect depends on impaired HB-GAM–induced Src kinase activation and haptotactic migration. Furthermore, we show that N-syndecan interacts with EGF receptor (EGFR) at the plasma membrane and is required in EGFR-induced neuronal migration.
Perturbing integrin function inhibits microtubule growth from centrosomes, spindle assembly, and cytokinesis
Authors: Reverte Carlos G. , Benware Angela , Jones Christopher W. , LaFlamme Susan E.
Published: August 2006

In many mammalian cell types, integrin-mediated cell-matrix adhesion is required for the G1–S transition of the cell cycle. As cells approach mitosis, a dramatic remodeling of their cytoskeleton accompanies dynamic changes in matrix adhesion, suggesting a mechanistic link. However, the role of integrins in cell division remains mostly unexplored. Using two cellular systems, we demonstrate that a point mutation in the β1 cytoplasmic domain (β1 tail) known to decrease integrin activity supports entry into mitosis but inhibits the assembly of a radial microtubule array focused at the centrosome during interphase, the formation of a bipolar spindle at mitosis and cytokinesis. These events are restored by externally activating the mutant integrin with specific antibodies. This is the first demonstration that the integrin β1 tail can regulate centrosome function, the assembly of the mitotic spindle, and cytokinesis.
Phosphoinositide signaling plays a key role in cytokinesis
Authors: Janetopoulos Chris , Devreotes Peter
Published: August 2006

To perform the vital functions of motility and division, cells must undergo dramatic shifts in cell polarity. Recent evidence suggests that polarized distributions of phosphatidylinositol 4,5-bisphosphate and phosphatidylinositol 3,4,5-trisphosphate, which are clearly important for regulating cell morphology during migration, also play an important role during the final event in cell division, which is cytokinesis. Thus, there is a critical interplay between the membrane phosphoinositides and the cytoskeletal cortex that regulates the complex series of cell shape changes that accompany these two processes.
Plectin-controlled keratin cytoarchitecture affects MAP kinases involved in cellular stress response and migration
Authors: Osmanagic-Myers Selma , Gregor Martin , Walko Gernot , Burgstaller Gerald , Reipert Siegfried , Wiche Gerhard
Published: August 2006

Plectin is a major intermediate filament (IF)–based cytolinker protein that stabilizes cells and tissues mechanically, regulates actin filament dynamics, and serves as a scaffolding platform for signaling molecules. In this study, we show that plectin deficiency is a cause of aberrant keratin cytoskeleton organization caused by a lack of orthogonal IF cross-linking. Keratin networks in plectin-deficient cells were more susceptible to osmotic shock–induced retraction from peripheral areas, and their okadaic acid–induced disruption (paralleled by stress-activated MAP kinase p38 activation) proceeded faster. Basal activities of the MAP kinase Erk1/2 and of the membrane-associated upstream protein kinases c-Src and PKCδ were significantly elevated, and increased migration rates, as assessed by in vitro wound-closure assays and time-lapse microscopy, were observed. Forced expression of RACK1, which is the plectin-binding receptor protein for activated PKCδ, in wild-type keratinocytes elevated their migration potential close to that of plectin-null cells. These data establish a link between cytolinker-controlled cytoarchitecture/scaffolding functions of keratin IFs and specific MAP kinase cascades mediating distinct cellular responses.
From imaging to understanding: Frontiers in Live Cell Imaging, Bethesda, MD, April 19–21, 2006
Authors: Wang Yu-li , Hahn Klaus M. , Murphy Robert F. , Horwitz Alan F.
Published: August 2006

A recent meeting entitled Frontiers in Live Cell Imaging was attended by more than 400 cell biologists, physicists, chemists, mathematicians, and engineers. Unlike typical special topics meetings, which bring together investigators in a defined field primarily to review recent progress, the purpose of this meeting was to promote cross-disciplinary interactions by introducing emerging methods on the one hand and important biological applications on the other. The goal was to turn live cell imaging from a “technique” used in cell biology into a new exploratory science that combines a number of research fields.