bluuebunny/crossref_metadata_2025 huggingface dataset:
Exact solutions of the diffusion-convection equation in cylindrical geometry
Authors: Eury S. P. , Harauchamps E. , Zou X. L. , Giruzzi G.
Published: October 2005

The analytical solution of the one-dimensional diffusion-convection equation in a cylinder has been found, for various functional forms of the diffusion coefficient, convection velocity and with an additional damping term. This is a significant generalization of a previous work [A. Clémençon, C. Guivarch, S. P. Eury, X. L. Zou, and G. Giruzzi, Phys. Plasmas 11, 4998 (2004)] on the diffusion equation, including now a convection term that can be constant, monomially increasing in the space coordinate, or have step-like variations. This type of equation has important applications in the field of magnetically confined plasmas, in which convection effects are experimentally observed in both particle and energy transports. Sharp variations of heat diffusivity, convection velocity, and damping term can result from the microturbulence which develops whenever the temperature gradient exceeds a critical value. A general scheme is developed to connect solutions in domains with different functional forms of the coefficients. The properties of the solutions are illustrated and discussed.
Differences between solid superheating and liquid supercooling
Authors: Bai Xian-Ming , Li Mo
Published: October 2005

The thermodynamic and kinetic behaviors for solid superheating and liquid supercooling were critically examined and compared via molecular-dynamics simulations. It is shown that the large elastic energy associated with internal melting and solid-liquid interface disorder play important roles in superheating. The growth rate is anisotropic for supercooling, but isotropic for superheating. Supercooling can be well described by the classical nucleation theory, whereas superheating shows many exceptions. The underlying mechanisms for these differences are discussed.
Grounded radio-frequency electrodes in contact with high density plasmas
Authors: Aanesland A. , Charles C. , Boswell R. W. , Lieberman M. A.
Published: October 2005

An analytical model is developed of an asymmetric electrode system immersed in a plasma, consisting of two dc-grounded electrodes, where the smaller one is biased at 13.56MHz. The model is compared with a set of experiments performed in a high density low pressure plasma source (an electron cyclotron resonance source) where a second electrode is immersed into the plasma and powered by radio frequency. Excellent agreement is obtained between the analytical model and the experimental results. It is found that the time average plasma potential and the direct current (dc) flowing in the system during steady state are strongly dependent on both the rf voltage (or power) and the area ratio between the larger and smaller electrodes. For area ratios larger than 80, the dc current is large and the plasma potential is constant with respect to the applied rf voltage. For area ratios smaller than 80 but larger than unity, the plasma potential increases linearly with the applied rf voltage, and the dc current is reduced compared to the large area ratio case.
Wobble motion on field-reversed configuration plasmas
Authors: Fujimoto K. , Okada M. , Gota H. , Hasegawa Y. , Fujino T. , Asai T. , Takahashi T. , Nogi Y. , Ohkuma Y.
Published: October 2005

A wobble motion on a field-reversed configuration plasma is investigated in detail. It is found from magnetic and optical measurements of the wobble motion that a few magnetic islands appear inside a separatrix at the formation phase and merge with each other at the axial contraction phase. Due to the radial and azimuthal asymmetries of the merging plasmas, the wobble motion is triggered. To assist the symmetrical formation of the plasma, conducting rings are installed near the ends of the theta-pinch coil. Using the effect of the conducting rings, the amplitude of the wobble motion is controlled to approximately one-half that without using the conducting rings and the extreme degradation of particle confinement time is not observed. An analysis of the plasma affected by a restoring force of open field lines well explains an experimental result that the period of wobble motion depends on the square root of mass density.
Charged exciton emission at 1.3μm from single InAs quantum dots grown by metalorganic chemical vapor deposition
Authors: Cade N. I. , Gotoh H. , Kamada H. , Tawara T. , Sogawa T. , Nakano H. , Okamoto H.
Published: October 2005

We have studied the emission properties of self-organized InAs quantum dots (QDs) grown in an InGaAs quantum well by metalorganic chemical vapor deposition. Low-temperature photoluminescence spectroscopy shows emission from single QDs around 1300nm; we clearly observe the formation of neutral and charged exciton and biexciton states, and we obtain a biexciton binding energy of 3.1meV. The dots exhibit an s-p shell splitting of approximately 100meV, indicating strong confinement.
Nanoparticle manipulation in the near-substrate areas of low-temperature, high-density rf plasmas
Authors: Rutkevych P. P. , Ostrikov K. , Xu S.
Published: October 2005

Manipulation of a single nanoparticle in the near-substrate areas of high-density plasmas of low-temperature glow discharges is studied. It is shown that the nanoparticles can be efficiently manipulated by the thermophoretic force controlled by external heating of the substrate stage. Particle deposition onto or repulsion from nanostructured carbon surfaces critically depends on the values of the neutral gas temperature gradient in the near-substrate areas, which is directly measured in situ in different heating regimes by originally developed temperature gradient probe. The measured values of the near-surface temperature gradient are used in the numerical model of nanoparticle dynamics in a variable-length presheath. Specific conditions enabling the nanoparticle to overcome the repulsive potential and deposit on the substrate during the discharge operation are investigated. The results are relevant to fabrication of various nanostructured films employing structural incorporation of the plasma-grown nanoparticles, in particular, to nanoparticle deposition in the plasma-enhanced chemical-vapor deposition of carbon nanostructures in hydrocarbon-based plasmas.
Steady and transient thin-jet flow
Authors: German Radoslav , Khayat Roger E.
Published: October 2005

The interplay between inertia and gravity is examined in this theoretical study for the steady and transient two-dimensional thin jet flow free of surface tension. The fluid emerges from a channel and is driven by both a pressure gradient maintained inside the channel and/or gravity. The flow is dictated by the thin-film equations of the boundary layer type, which are solved by expanding the flow field in terms of orthonormal modes depthwise, and using the Galerkin projection. The strength of inertia relative to gravity is found to be of crucial significance on the film flow. Transient behavior of the film is closely examined for various flow parameters, initial and exit conditions. It is shown that under a wide range of flow parameters, the steady state cannot be achieved.
A model for effective field enhancement for Fowler–Nordheim field emission
Authors: Feng Y. , Verboncoeur J. P.
Published: October 2005

The local field enhancement factor β is often introduced in the Fowler–Nordheim equation to represent the geometrical effects at the surface of the cathode, where β(s)=En(s)∕E0 for macroscopic applied field E0. Local variation of β determines the local normal surface electric field, En(s), resulting in local dependence of injection current by the Fowler–Nordheim law. In computational models, it is impractical to determine the time-dependent local surface field each time step on a microscopic space scale. Effective β is introduced in this paper which allows us to study the emission properties at a macroscopic scale. Microscopic (subgrid) local effective β is calculated only at the initial time step, and then the effective β can be recomputed for different surface electrical field through this model. The model allows reduction of dimensionality as well as the ability to include subgrid effects. The model is demonstrated on fundamental cases and compared to a calculation with a mesh fine enough to resolve the geometric features.
Semiconductor-metal hybrid structures as local magnetic-field probes: Magnetoresistance and spatial sensitivity profile
Authors: Holz Matthias , Kronenwerth Oliver , Grundler Dirk
Published: October 2005

Tailored nonmagnetic semiconductor-metal hybrid structures exhibit a large magnetoresistance effect in a homogeneous magnetic field. This is the so-called extraordinary magnetoresistance effect. Here, we study numerically the magnetoresistance of such hybrid structures in the inhomogeneous field of a magnetic dot. Surprisingly, the four-point resistance R versus magnetic field B changes its symmetry if compared to the case of a homogeneous field and is strongly dependent on the position of the local magnetic field. Interestingly, the active device area is not defined by the voltage probe separation, but by the positioning of voltage probes and current leads. We find a magnetoresistance effect as large as 18% although only 1∕60 of the device area is subject to a small magnetic field of ±50mT. These results are promising for sensing magnetic-field distributions in the nanoscale regime such as the stray fields of magnetic recording media.
Anisotropic magnetoresistance and spin polarization of La0.7Sr0.3MnO3∕SrTiO3 superlattices
Authors: Wang L. M. , Guo Chih-Chian
Published: October 2005

The crystalline structure, anisotropic magnetoresistance (AMR), and magnetization of La0.7Sr0.3MnO3∕SrTiO3 (LSMO/STO) superlattices grown by a rf sputtering system are systematically analyzed to study the spin polarization of manganite at interfaces. The presence of positive low-temperature AMR in LSMO/STO superlattices implies that two bands of majority and minority character contribute to the transport properties, leading to a reduced spin polarization. Furthermore, the magnetization of superlattices follows the T3∕2 law and decays more quickly as the thickness ratio dSTO∕dLSMO increases, corresponding to a reduced exchange coupling. The results clearly show that the spin polarization is strongly correlated with the influence of interface-induced strain on the structure.
Dependence of plasma characteristics on dc magnetron sputter parameters
Authors: Wu S. Z.
Published: October 2005

Plasma discharge characteristics of a dc magnetron system were measured by a single Langmuir probe at the center axis of the dual-side process chamber. Plasma potential, floating potential, electron and ion densities, and electron temperature were extracted with varying dc power and gas pressure during sputter deposition of a metal target; strong correlations were shown between these plasma parameters and the sputter parameters. The electron density was controlled mostly by secondary electron generation in constant power mode, while plasma potential reflects the confinement space variation due to change of discharge voltage. When discharge pressure was varied, plasma density increases with the increased amount of free stock molecules, while electron temperature inversely decreased, due to energy-loss collision events. In low-pressure discharges, the electron energy distribution function measurements show more distinctive bi-Maxwellian distribution, with the fast electron temperature gradually decreases with increased gas pressure.
Epitaxial growth and properties of Zn1−xVxO diluted magnetic semiconductor thin films
Authors: Ramachandran S. , Tiwari A. , Narayan J. , Prater J. T.
Published: October 2005

Here we report systematic studies on the epitaxial growth and properties of Zn1−xVxO[x=0.001-0.2] thin films deposited onto sapphire c-plane single crystals. The thin films were deposited using pulsed laser deposition technique and were found to be epitaxial in nature. X-ray diffraction and high resolution transmission electron microscopy were employed to study the epitaxial relations of Zn1−xVxO with the sapphire substrate and electron energy loss spectroscopy was used to establish the bonding characteristics and oxidation states of vanadium inside the ZnO host. The main emphasis is on the magnetic properties of this system taking into consideration the phase purity and microstructural characteristics of these films. Our results show that the Zn1−xVxO system, with V in zinc substitutional sites, does not exhibit any signature of ferromagnetism, both at room temperature as well as at lower temperatures down to 10 K.
Strong anisotropic spin dynamics in narrow n-InGaAs∕AlGaAs (110) quantum wells
Authors: Morita K. , Sanada H. , Matsuzaka S. , Hu C. Y. , Ohno Y. , Ohno H.
Published: October 2005

Anisotropic spin dynamics of two-dimensional electrons in strained n-InGaAs∕AlGaAs (110) quantum wells (QWs) is investigated by a time-resolved Faraday rotation technique. Strong anisotropy of the relaxation time for the electron spins in parallel (τ‖) and perpendicular (τ⊥) to the QWs is observed (τ⊥∕τ‖∼60) at 150 K as a result of the enhanced D'yakonov–Perel' (DP) spin relaxation mechanism. At 5 K, an anisotropic feature of the spin relaxation time is also observed in the presence of in-plane magnetic field, suggesting that the DP mechanism is effective for low-temperature spin relaxation.
Efficiency limits of photovoltaic fluorescent collectors
Authors: Rau Uwe , Einsele Florian , Glaeser Gerda C.
Published: October 2005

This paper examines the thermodynamic limits of photovoltaic solar energy conversion by fluorescent collectors. The maximum efficiency of a fluorescent collector corresponds to the Shockley–Queisser limit for a nonconcentrating solar cell with a single bandgap energy. To achieve this efficiency, the collector requires a photonic structure at its surface that acts as an omnidirectional spectral band stop filter. The large potential of photonic structures for the efficiency enhancement of idealized as well as real fluorescent collectors is highlighted.
Chemical passivity of III-VI bilayer terminated Si(111)
Authors: Adams Jonathan A. , Bostwick Aaron A. , Ohuchi Fumio S. , Olmstead Marjorie A.
Published: October 2005

The chemical stability of Si(111), terminated with bilayer AlSe and GaSe, upon exposure to atmosphere, N2 and O2, was investigated with core-level and valence band photoelectron spectroscopy. Si(111):GaSe and Si(111):AlSe both form stable, unreconstructed surfaces with no states in the silicon energy gap; their atomic structures are nearly identical. However, similarities in surface electronic and atomic structure do not imply similar chemical passivity. While Si(111):GaSe is largely unaffected by the exposures, Si(111):AlSe reacts irreversibly with both pure O2 and atmosphere, removing over 13 of the Se and permanently destroying long-range order.
Confirmation of information transfer using lattice images
Authors: Akashi Tetsuya , Sugawara Akira , Kasai Hiroto , Yoshida Takaho , Matsuda Tsuyoshi , Togawa Yoshihiko , Harada Ken , Tonomura Akira
Published: October 2005

A method of confirming information transfer in spatial frequency regions higher than 10nm−1 by the objective lens of an electron microscope is introduced. Two electron-diffraction waves, 000 and hkl, from a crystalline specimen are selected by an objective aperture inserted asymmetrically on the back-focal plane, and a lattice image is observed at appropriate defocus values to prove that information corresponding to the spatial frequency of hkl diffraction has been transferred. We confirmed that information for 15.6nm−1 (0.064-nm-spacing fringes in real space) and less could be transferred in a 1-million-volt field emission electron microscope.
Work function tuning of nickel silicide by co-sputtering nickel and silicon
Authors: Biswas Nivedita , Gurganus Jason , Misra Veena
Published: October 2005

Co-sputtered nickel silicide films were evaluated on thin layers of SiO2 gate dielectrics. Work function values ranging from 4.86eV for Ni rich films to 4.3eV were observed at 400°C and were found to be a strong function of the Ni and Si ratio in the films. Phase analysis indicated the presence of different phases of NixSiy for varying concentrations of Ni and Si. High-temperature characteristics, leakage, and change in equivalent oxide thickness values were also evaluated for selected conditions. Rutherford backscattering, x-ray diffraction, Auger electron spectroscopy and high-resolution transmission electron microscopy were used for material analyses.
Institutional Change through Innovation: The URBAN Community Initiative in Berlin, 1994–99
Authors: Halpern Charlotte
Published: October 2005

Reunification profoundly challenged the local government structure inherited from the Cold War period in Berlin. Yet this sudden socioeconomic and political change did not produce any immediate impact on institutional arrangements or policy instruments within the urban policy field. In this context, the implementation of the European Community Initiative URBAN, between 1994 and 1999, offered an opportunity to actors who were willing to challenge the existing balance of power to contest the legitimacy of preexisting interests and representations. The author argues that, in a context of competing interpretations of the issues raised by segregation processes which have left pockets of poverty in both parts of the city, the URBAN programme has managed to become an important driving force behind an underlying process of change. Its innovative approach to urban poverty and social exclusion exerted an impact on the parameters of this process of change, exacerbating existing political and organisational conflicts and challenging local networks, sources of legitimacy, and policy instruments.
Governance, Rurality, and Nature: Exploring Emerging Discourses of State Forestry in Britain
Authors: Stanley Kieron G , Marsden Terry K , Milbourne Paul
Published: October 2005

The authors position social forestry within the emergent research agenda studies of rural governance. They argue that scant attention has been paid to the theoretical concerns arising in studies of governance—either in rural networks, or in forestry more particularly. Issues arising from the governmentality approaches, alongside the metagovernance concerns of regulation and neo-liberal theories more broadly, direct a call for research to address the complexities of social interaction with cultures of nature; problematising institutions, and the complexities of placing communities in governance. The authors suggest that these changing modes of governance configure communities, places, and institutions in the wake of such interrelationships.
Sex steroid levels and Leydig cell ultrastructure of the male common sheath-tail bat, Taphozous georgianus
Authors: Jolly SE , Blackshaw AW
Published: October 2005

Male sheath-tail bats were collected from central Queensland over a 12-month period. Plasma testosterone levels peaked in August, coincident with an increase in the volume of the accessory glands and ampulla/seminal vesicle secretion. Peak spermatogenesis occurred in summer and autumn and declined in the face of maximal testosterone levels in winter. Levels of androstenedione and 5 alpha-dihydrotestosterone were high compared with testosterone levels and showed no significant seasonal changes. Ultrastructural examination of Leydig cell cytoplasm revealed numerous lipid droplets and mitochondria, and an abundant smooth endoplasmic reticulum. There were no seasonal changes in Leydig cell ultrastructure. The anomalous reproductive pattern in this species is consistent with the imposition of a cold-induced winter spermatogenic shutdown, on a framework of continuous spermatogenesis, with spring peaks in testosterone and accessory gland activity.
Characterization of epitopes of seminal plasma antigen stimulating human monoclonal sperm-immobilizing antibodies: a personal review
Authors: Isojima S
Published: October 2005

In observations made between 1974 and 1984, 40 of 303 women with unexplained sterility (13.2%) showed positive sperm-immobilizing antibodies. Among many kinds of antibodies to human sperm including sperm coating antigens, the biologically active antibodies, such as sperm-immobilizing agglutinating antibodies and blocking antibodies for fertilization, could be relevant to infertility. Harmless sperm-binding antibodies are present even in the sera and cervical mucus of fertile women. Antigens corresponding to monoclonal antibodies (1C4, 2C6, 2E5), which were generated to human sperm coating antigens and indicated strong sperm-immobilizing activities, seemed to have carbohydrate epitopes. The majority of women with sterility of unknown cause appeared to raise sperm-immobilizing antibodies to carbohydrate epitopes of sperm. The stable human-mouse heterohybridoma H6-3C4 secreting monoclonal antibody (IgM, lambda) with extremely high titres of sperm-immobilizing (SI50, 5000 units) and agglutinating (1:1600) activities was successfully established from peripheral lymphocytes of a sterile woman. The chemical structure of an antigen epitope corresponding to human monoclonal antibody H6-3C4 was found to consist of internally repetitive, unbranched N-acetyllactosamine (blood type i antigen). Ejaculated human sperm appeared to be densely covered with sialyl blood type i antigen and sialyl branched internally repetitive N-acetyllactosamine (sialyl blood type I antigen). The antibody-producing V-H and V-L genes of the human hybridoma H6-3C1 were cloned and preserved to stabilize antibody production. Class-switch variants of heavy chain from mu to gamma (IgG1, lambda) in human Mab H6-3C4 were produced by recombinant DNA technology.
Mammary glands in male marsupials. 2. Development of teat primordia in Didelphis virginiana and Monodelphis domestica
Authors: Robinson ES , Renfree MB , Short RV , VandeBerg JL
Published: October 2005

Young and adults of both sexes of two didelphid marsupials, Didelphis virginiana and Monodelphis domestica, were examined externally for evidence of mammary gland development. Female young possessed teat numbers typical of adult females (13-15 in D. virginiana; 11-13 in M. domestica). Male young showed variable teat numbers which were always low compared with females, with the majority possessing 2-4 in anterior positions. Teats were also present in adult males of both species, in similar numbers and locations to those of young males. There are no previous reports of the presence of teats in any adult male marsupials. No mammary primordia in males have been recorded at any stage of development in the most thoroughly studied Australian marsupials. Our findings strengthen the view that there is a dichotomy between the two marsupial lineages in the regulation of male mammary gland expression.
Acute effects of ethane dimethane sulfonate (EDS) on the structure of the cauda epididymidis in the rat: selective destruction of clear cells in the proximal cauda region
Authors: Liu X , Temple-Smith PD , Risbridger GP
Published: October 2005

Of eight groups of five adult male Sprague-Dawley rats, three groups received an intraperitoneal dose of EDS (75 mg kg-1) in DMSO (dimethylsulfoxide in water; 1:3) and three control groups received DMSO only. One EDS and one control group were killed 1, 2 and 3 days after treatment. One EDS+T group, given a 5-cm implant of T sufficient to maintain normal serum T concentrations, and one untreated control group were killed on Day 3. Epididymides were fixed by vascular perfusion and embedded in Epon/Araldite for light and electron microscopic studies. Epididymal duct diameters and epithelial heights were measured from 1-micron sections and structural changes were assessed from thin sections using a Jeol 100B electron microscope. Morphological studies showed a reduction in duct diameter and an associated increase in epithelial height in the proximal cauda epididymidis of the experimental groups. In the EDS+T implant group, epithelial heights were significantly greater than in controls but duct diameters remained unchanged. The most obvious structural change in the proximal cauda epididymidis was the selective destruction of clear cells in the epithelium. Initially, vacuoles were observed in the lateral intercellular spaces of the epithelium; large autophagic vacuoles then appeared in the clear cells, which had degenerated and disappeared from the epithelium by Day 3. Progressive infiltration of leucocytes into the intertubular interstitium, the epithelium and lumen of the proximal cauda was also observed. Loss of clear cells in the proximal cauda epididymidis was also seen in the EDS+T group, suggesting that clear-cell degeneration was not associated with reduced concentrations of circulating androgen. In all EDS-treated groups, however, clear cells and duct profiles in the distal cauda epididymidis remained unaffected. The reason for their protection from the effects of EDS has not yet been determined. These results suggest that, in addition to other specific lesions described in previous studies, EDS also has a direct effect on the rat epididymis that appears to be specifically targeted to the clear cells in the proximal caudal region.
Human testis cDNAs identified by sera from infertile patients: a molecular biological approach to immunocontraceptive development
Authors: Liang ZG , O'Hern PA , Yavetz B , Yavetz H , Goldberg E
Published: October 2005

Sera from patients with known or suspected immunological infertility were used to screen a human testis cDNA library. A total of 59 sera detected 38 unique cDNA inserts of which four were testis specific by Northern blot analyses. One of these is a testis-specific isoform of calpastatin. Five additional clones, although not testis specific, were found to be testis abundant. The number and type of clones identified by these human sera suggests a possible aetiology for immunologic infertility. The testis-specific clones will be further characterized to establish their usefulness as contraceptive vaccine candidates.
The mammalian zona pellucida: its biochemistry, immunochemistry, molecular biology, and developmental expression
Authors: Dunbar BS , Avery S , Lee V , Prasad S , Schwahn D , Schwoebel E , Skinner S , Wilkins B
Published: October 2005

Many studies of the molecular and biochemical aspects of mammalian fertilization have focused on the interaction of the spermatozoa with the zona pellucida (ZP). The zona pellucida, a unique extracellular matrix surrounding the mammalian oocyte, is formed during ovarian follicular development. Following ovulation of the mature ovum, the spermatozoa must bind to and penetrate this matrix before the fertilization process is completed and the male and female genetic information combine. Although numerous models for this interaction have been proposed, the complete process has yet to be elucidated. The precise mechanisms by which these interactions occur also vary markedly among different mammalian species, making it more difficult to establish a unified model. To a great extent, the study of the molecules involved in these interactions have been limited because small numbers of female gametes are available for these studies. The recent development of techniques to isolate large numbers of zonae pellucidae as well as advances in immunological and molecular biology techniques have permitted the detailed characterization of ZP proteins. Although there is a paucity of information on the post-translational modification and extracellular processing of these molecules which result in matrix formation, a number of properties have been elucidated allowing better correlation between the structure and function of different ZP proteins among species. This review reflects these studies in relation to protein nomenclature and the molecular complexity of ZP antigens.
Transgenic sheep and wool growth: possibilities and current status
Authors: Powell BC , Walker SK , Bawden CS , Sivaprasad AV , Rogers GE
Published: October 2005

Merino wool is the result of generations of selection, yet improvements in wool quality and performance are still being sought. Through gene manipulation, sheep transgenesis offers possibilities of understanding the relationship between wool keratin protein composition and fibre structure and properties and of introducing novel changes to fibre properties and growth rates. We have established an efficient sheep transgenesis programme with an overall transgenic rate of 2.1% of zygotes injected. However, by incorporating in vitro culture and assessment of injected zygotes, this equates to a transgenic rate of 13% from 516 lambs born. With the first keratin gene construct, a wool keratin type II intermediate filament gene, four live F0 transgenic sheep have been produced and all express the transgene. In one of them, the highest expressor, phenotypic and ultrastructural changes were evident in the fleece. To improve wool growth rate by increasing the supply of cysteine to the follicle, transgenic sheep are being produced carrying the two genes necessary for endogenous cysteine synthesis. Three promoters have been tested driving the cysteine synthesis genes: two general promoters, the Rous sarcoma virus long terminal repeat and mouse phosphoglycerate kinase promoter, and a rumen-specific promoter from the sheep small proline-rich protein gene. To date, one transgenic sheep (bearing the small proline-rich protein promoter constructs) has produced cysteine in the rumen, although the amount was low at 3 months of age and not detectable at 6 months.
Sperm competition: evolutionary causes and consequences
Authors: Birkhead TR
Published: October 2005

The interaction between functional and mechanistic approaches to sperm competition and between male and female perspectives are described and illustrated by a study of the zebra finch, Taeniopygia guttata. Sperm competition experiments in the laboratory show that last male sperm precedence occurs (as it does in many other taxa) although the mechanism is unknown (as in most other taxa). Empirically-derived values were used to construct a mathematical model of sperm competition in the zebra finch. The model indicates that precedence occurs as a consequence of: (i) the temporal pattern of pair copulations; (ii) the rate at which sperm are lost from the female tract; and (iii) more sperm being transferred during extra-pair copulations than during pair copulations. The latter effect is a consequence of males seeking extra-pair copulations after their own pair copulation period has ended. The effect of sperm numbers on the pattern of sperm precedence may be further increased by: (i) extra-pair males increasing ejaculate size (sperm numbers) (for which there is no evidence); (ii) extra-pair males being of a better quality and transferring more sperm or better quality sperm (for which there is some evidence); and (iii) cryptic female choice. Females eject over 99% of sperm following insemination; if they eject fewer sperm from males chosen as extra-pair copulation partners, the potential for cryptic female choice is considerable. However, this is still being investigated. The model also predicts the optimal time for an extra-pair copulation to occur (from either a male or female perspective). A comparison between the predicted and observed pattern suggests that the optimal timing of extra-pair copulations is constrained in both sexes.
The distribution of microvilli over the villous surface of the normal human term placenta is homogenous
Authors: Karimu AL , Burton GJ
Published: October 2005

The study was carried out to estimate stereologically whether regional differences exist in the distribution of microvilli between vasculo-syncytial (VSM) and non-vasculo-syncytial (non-VSM) areas of the villous surface in normal term placenta. In ten placentae a normal lobe was perfusion-fixed at a pressure of 60 mm Hg, and the intervillous space was perfused at 10 mm Hg. The tissue was routinely processed for ultrastructural examination. Stereological estimates relating to the length and diameter of microvilli, and to the villous surface amplification factor in adjacent but contrasting (VSM and non-VSM) regions, were obtained. A paired 't' test showed no significant difference in the villous surface amplification factor between the two regions (5.18 +/- 0.54 and 5.22 +/- 0.54 respectively, mean +/- s.e.m. P > 0.05). In addition, there were no significant differences between the length and diameter of microvilli in both regions (P > 0.05 in both). The results confirm that the normal term placenta has a continuous and even covering of microvilli over the syncytium.
Patch-Burning Desert Nature Reserves in Western Australia Using Aircraft
Authors: Burrows ND
Published: October 2005

Fire management in desert nature reserves in Western Australia aims to restrict the spread of wildfires and to re-introduce a spatial and temporal mosaic of firecreated patches. Aerial ignition is well suited to patchburning the large, remote and poorly accessible desert reserves. The Weather Factor, a function incorporating wind speed, temperature and relative humidity, dxectly
influenced the ignition rate, the range of sizes of burnt patches and the area burnt. During the trials described here, some 140,000 ha of spinifex fuels in the Gibson Desert Nature Reserve were patch-burnt using aircraft at a total cost of A$O.32 ha-1.
Heat Evolved From Smoldering Peat
Authors: Frandsen WH
Published: October 2005

Smoldering ground fires can raise mineral soil
temperatures above 300�C for several hours with peak
temperatures near 600�C. Such temperatures can result in
the decomposition of organic material and kill important
soil organisms. The heat evolved per unit organic mass
was investigated by monitoring the mass of oxygen
consumed during smoldering. Organic bulk densities of
laboratory samples were comparable to field observa
tions and ranged from 90 to 180 kg m-3. Moisture and
inorganic contents were expressed as mass ratios relative
to the organic mass. Moisture ratios ranged from zero to
0.8 and inorganic ratios from near zero (natural peat
inorganic ratio) to 4.0. Heat evolved per unit organic
mass was independent of organic bulk density and inor
ganic ratio, and changed little with moisture ratio within
the limits of combustion. The average value for all
observations (N= 190) was 14.2 MJ kg-1with an error less
than 4.5%.
Fire in Semiarid, Mallee Shrublands - Size of Flames From Discrete Fuel Arrays and Their Role in the Spread of Fire
Authors: Bradstock RA , Gill AM
Published: October 2005

Aspects of flammability of the major fuel arrays in a mallee shrubland community, and the basis for fire-spread in these discrete fuels, are examined and discussed. Relationships between plant size and weight of litter (shrubs and mallee eucalypts) or grass hummocks (Triodia irritans) were studied. Hummock mass was a function of hummock diameter and height. On ignition, maximum flame length was related to hummock height and diameter. For mallee eucalypts the mass of litter beneath individual plants was related to the diameter of the litter bed. Flame length was also related to litter bed diameter. In other species of shrubs, fires were not sustained independently. We hypothesize that T. irritans will play a major role in fire spread in communities because flames from hummocks will have the greatest ability to bridge gaps between fuel arrays (flames longer than in eucalypts). Size of hummocks will have an important bearing on propagation of fire across fuel-gaps. By contrast, the main role of eucalypts in fire-spread may be as a source of burning brands which initiate spot fires. There is scope to understand fire-spread in these communities on the basis of flame lengths (in conjunction with plant size) in relation to wind.
The Influence of Fuel, Weather and Fire Shape Variables on Fire-Spread in Grasslands
Authors: Cheney NP , Gould JS , Catchpole WR
Published: October 2005

Fire-spread was measured on 121 grass fires in a 2500 ha experimental site in the Northern Territory, Australia. Selected plots were harvested to alter the height, load and bulk density of the fuel-bed. Fires were lit from a line and allowed to travel up to 400 m down-wind. Fire-spread was correlated with fuel, weather and fireshape variables using multiple regression techniques. Wind speed had most effect on fire-spread. The influence of the other variables was examined after a model for wind speed and moisture content had been fitted. Fuel load did not influence fire-spread. Fires in natural swards burnt 18% faster than fires in cut grass, but this increase could not be fully explained by changes in the height or bulk density of the fuel bed. Grass type characterised either by species group or by surface-area-to-volume ratio of the fuel particle, did not appear to significantly influence fire-spread. Differences in spread rates between the two grasses were attributed to differences in grass curing. The influence of grass curing appeared to be less than indicated by published models. Models of fire-spread in grasslands currently in use need to be revised. Ignition line length was a significant variable influencing fire-spread and this must be taken into consideration when using experimental fires to validate theoretical models or develop empirical models from field observations.
Stages of Bryophyte Succession After Fire in Mediterranean Forests (SE Spain)
Authors: Delasheras J , Guerra J , Herranz JM
Published: October 2005

The dynamics of bryophyte vegetation of burnt Mediterranean forests was studied over a period of 3 years, using permanent square plots of 1 M2 set in 9 sites burnt in different years (1989-1970). One site unaffected by fire was used as a control. The sites were located in the Tus and Mundo valleys (Province of Albacete, SE Spain). Floristic richness, bryophyte turf cover and fugacity of the bryophyte species were calculated for each plot. With the data obtained, four bryophyte communities were characterized: colonizing, competing, seasonal and perennial species. A temporal scheme describing three stages of bryophyte succession after fire was constructed: colonizing stage, competing stage (with two phases) and stabilization stage.
Plumes Above Line Fires in a Cross-Wind
Authors: Mercer GN , Weber RO
Published: October 2005

A model for the plume above a line fire in a cross wind is constructed. This problem is shown to reduce to numerically solving a system of 6 coupled ordinary differential equations for given initial conditions that depend upon the fire characteristics. The model is valid above the flaming zone and takes inputs such as the width, velocity and temperature of the plume at a given height above the flaming zone, Different horizontal ambient wind velocities are allowed for and a comparison is made between some of these representative wind profiles. The plume trajectory, width, velocity and temperature are calculated for these different representative velocity profiles. This model has application to the calculation of temperature-time exposures of vegetation above line fires and hence can be used in models that predict effects such as leaf scorch and canopy stored seed death. On a larger scale it has application to the problem of tracking burning brands which can cause spotting ahead of the fire.
Structural-Properties and Dimensional Relations of Some Mediterranean Shrub Fuels
Authors: Pereira JMC , Sequeira NMS , Carreiras JMB
Published: October 2005

Structural properties of fuelbeds and particles of 60 plants of four shrub species (Ulex parviflorus,Lygos monosperma, Erica arborea, and Erica scoparia) common in the undergrowth of maritime pine forests were inventoried, namely total biomass, biomass distribution by diameter class, dead-to-live biomass ratios, bulk density, and surface-to-volume ratios. Porosity and packing ratios were calculated from the inventoried data. Results are compared with those reported for other shrub fuels of mediterranean and other plant communities. We developed dimensional relations to simplify prediction of total plant biomass, as well as biomass in the 1-hour, 10-hour, and 100-hour timelag size classes. Dimension analysis results are considered quite satisfactory for L. monosperma and Erica sp., while there seems to be some room for improvement regarding our ability to predict biomass of U. parviflorus, based on simple measurements of plant dimensions.
Assessing Grassland Moisture and Biomass in Tasmania - the Application of Remote-Sensing and Empirical-Models for a Cloudy Environment
Authors: Chladil MA , Nunez M
Published: October 2005

The operational feasibility of NOAA/AVHRR data and two semi-empirical moisture models were evaluated in the grasslands of southeastern Tasmania (Australia) during the 1988/89 fire season. A limited ground-truthing experiment compared the grassland dry biomass, soil moisture and fuel moisture with the satellite derived NDVI and the Soil Dryness Index (SDI) and the Grassland Curing Index (GCI). The NDVI gave good results for fuel moisture content (FMC) and soil moisture content (SMC) but unreliable image availability precludes the use of NDVI as a stand alone system for fire managers. The SDI and GCI also performed well in predicting SMC and FMC. Very good results were obtained when the NDVI and the GCI were combined. These results suggest the combination of data will provide both the accuracy and the continuity of information needed for operational use by fire managers. The methods used here could be cheaply and quickly repeated for use in other similar fire prone and cloudy environments.
Demographic Patterns and Productivity of Post-Fire Regeneration in Portuguese Mediterranean Maquis
Authors: Clemente AS , Rego FC , Correia OA
Published: October 2005

After a wildfire in September, 1991, post-fire regeneration of Serra da Arrábida maquis was studied and compared to an adjacent 30-yr-old unburned site. Two years after fire, cover and aboveground biomass was half of the amount found in unburned stands. This rapid recovery was mainly due to resprouting species: Q. coccifera was dominant during all stages of regeneration. Herbaceous species were abundant during the first two years after fire but became scarce in the older communities. Obligate seeders showed different patterns of recovery: Cistus species established many seedlings immediately after fire, but were less abundant in older stands; Rosmarinus officinalis attained high dominance in unburned sites but seedling recruitment was delayed, yet continuous during post-fire succession. This difference between two genera with the same obligate seeding strategy suggests that life history responses to environmental factors may affect or shape species distribution during post-fire regeneration.
The use of nest boxes in urban natural vegetation remnants by vertebrate fauna
Authors: Harper Michael J. , McCarthy Michael A. , van der Ree Rodney
Published: October 2005

Nest boxes are routinely installed as a substitute for natural tree hollows to provide den and nest sites for a range of hollow-utilising fauna. We installed 120 nest boxes in 20 patches of indigenous vegetation (remnants) across the urban/suburban landscape of Melbourne, south-eastern Australia, and investigated their use by indigenous and exotic vertebrate species over a period of 12 months. Nest-box use was dominated by the common brushtail possum (Trichosurus vulpecula), the common ringtail possum (Pseudocheirus peregrinus) and the common myna (Acridotheres tristis), an aggressive introduced bird. We found that brushtail and ringtail possums utilised nest boxes all year round but more frequently in cooler months (May–August). Common mynas dominated nest-box use during spring/summer, potentially reducing the availability of this resource to indigenous species. We found evidence that the probability of a nest box being occupied by either species of possum was greater in remnants with abundant possum populations. Brushtail possums preferred thick-walled pine nest boxes over thin-walled plywood nest boxes, most likely owing to differences in their thermal insulation properties. Although considerable economic costs would be involved in using nest boxes as a long-term substitute for hollow-bearing trees, nest boxes may provide a temporary hollow resource until hollow-bearing trees are recruited in urban remnants.
H-ras, K-ras, and inner plasma membrane raft proteins operate in nanoclusters with differential dependence on the actin cytoskeleton
Authors: Plowman Sarah J. , Muncke Cornelia , Parton Robert G. , Hancock John F.
Published: October 2005

Plasma membrane compartmentalization imposes lateral segregation on membrane proteins that is important for regulating signal transduction. We use computational modeling of immunogold spatial point patterns on intact plasma membrane sheets to test different models of inner plasma membrane organization. We find compartmentalization at the nanoscale level but show that a classical raft model of preexisting stable domains into which lipid raft proteins partition is incompatible with the spatial point patterns generated by the immunogold labeling of a palmitoylated raft marker protein. Rather, ≈30% of the raft protein exists in cholesterol-dependent nanoclusters, with ≈70% distributed as monomers. The cluster/monomer ratio (number of proteins in clusters/number of proteins outside clusters) is independent of expression level. H-rasG12V and K-rasG12V proteins also operate in nanoclusters with fixed cluster/monomer ratios that are independent of expression level. Detailed calibration of the immunogold imaging protocol suggests that radii of raft and RasG12V protein nanoclusters may be as small as 11 and 6 nm, respectively, and shows that the nanoclusters contain small numbers (6.0-7.7) of proteins. Raft nanoclusters do not form if the actin cytoskeleton is disassembled. The formation of K-rasG12V but not H-rasG12V nanoclusters also is actin-dependent. K-rasG12V but not H-rasG12V signaling is abrogated by actin cytoskeleton disassembly, which shows that nanoclustering is critical for Ras function. These findings argue against stable preexisting domains on the inner plasma membrane in favor of dynamic actively regulated nanoclusters similar to those proposed for the outer plasma membrane. RasG12V nanoclusters may facilitate the assembly of essential signal transduction complexes.
WWOX
gene restoration prevents lung cancer growth
in vitro
and
in vivo
Authors: Fabbri Muller , Iliopoulos Dimitrios , Trapasso Francesco , Aqeilan Rami I. , Cimmino Amelia , Zanesi Nicola , Yendamuri Sai , Han Shuang-Yin , Amadori Dino , Huebner Kay , Croce Carlo M.
Published: October 2005

The
WWOX
(WW domain containing oxidoreductase) gene at the common fragile site, FRA16D, is altered in many types of cancer, including lung cancer. We have examined the tumor suppressor function of
WWOX
in preclinical lung cancer models. The
WWOX
gene was expressed in lung cancer cell lines through recombinant adenovirus (Ad) infection (Ad-
WWOX
), and through a drug [ponasterone A, (ponA)]-inducible system. After
WWOX
restoration
in vitro
, endogenous Wwox protein-negative cell lines (A549, H460, and H1299) underwent apoptosis through activation of the intrinsic apoptotic caspase cascade in A549 and H460 cells. Ectopic expression of Wwox caused dramatic suppression of tumorigenicity of A549, H460, and H1299 cells in nude mice after Ad-
WWOX
infection and after ponA induction of Wwox expression in H1299 lung cancer cells. Tumorigenicity and
in vitro
growth of U2020 (Wwox-positive) lung cancer cells was unaffected by Wwox overexpression. This study confirms that
WWOX
is a tumor suppressor gene and is highly effective in preventing growth of lung cancer xenografts, whether introduced through viral infection or by induction of a silent
WWOX
transgene.