bluuebunny/crossref_metadata_2025 huggingface dataset:
Crystallization in charged two-component suspensions
Authors: Wette Patrick , Schöpe Hans Joachim , Palberg Thomas
Published: April 2005

We report on the crystallization of colloidal crystals comprising of charged particles with different size ratio dispersed in thoroughly deionized water. Single components were characterized carefully and their nucleation behavior was investigated before the preparation of mixtures. Mixtures investigated at constant particle number densities showed body centred cubic structure, conductivity, and shear moduli comply with the assumption of a randomly substituted crystal. Most importantly, for the first time we obtain the dependence of the nucleation rate densities in dependence on the composition and (for one fixed composition) the particle number density. The process of nucleation in random substitutional crystals is found to be similar to the one-component case.
Experimental study of the NaK 3Π3 double minimum state
Authors: Morgus L. , Burns P. , Miles R. D. , Wilkins A. D. , Ogba U. , Hickman A. P. , Huennekens J.
Published: April 2005

We have used the Doppler-free, perturbation-facilitated optical-optical double-resonance technique to investigate the vibrational, rotational, and hyperfine structure of the 3Π3 double minimum state of NaK. Since this electronic state arises from an avoided crossing with the nearby 4Π3 state, we observe striking patterns in the data that provide a sensitive probe of the electronic wave function in the various regions of the double well potential. A single-mode cw dye laser excites 2(A)Σ+1(vA,J)∼1(b)ΠΩ=03(vb,J) mixed singlet-triplet “window” levels from thermally populated rovibrational ground state levels, 1(X)Σ+1(vX,J±1). Further excitation by a single-mode cw Ti:sapphire laser selects various 3Π03(vΠ,JΠ) rovibrational levels, which are detected by observing direct 3Π03→1(a)Σ+3 fluorescence in the green spectral region. Using the inverse perturbation approximation method, we have determined a 3Π03 potential curve that reproduces the measured energies to ∼0.24cm−1. In addition, the hyperfine and spin–orbit constants, bF and Av, have been determined for each region of the potential curve.
Field emission characteristics of a tungsten microelectromechanical system device
Authors: Cruz D. , Chang J. P. , Blain M. G.
Published: April 2005

We have investigated the field emission properties of free-hanging tungsten microelectromechanical system structures. These tungsten structures are designed to serve as electrodes in a Paul ion trap. Since the outer edges of the trap end cap electrodes are adjacent to the inner edges of the trap ring electrode and approximately 0.5μm apart, field emission may occur between these two edges when hundreds of volts are applied, thereby defining an edge field emitter. The arrays were tested under vacuum (10−5Torr) and at atmospheric pressure (625 Torr) to understand the field emission behavior. Vacuum tests show turn-on voltages of about 200 V for the 1 and 1.5μm radius traps and currents of ∼80nA for both sizes of trap with the largest array (106) at 6 MV/cm. The atmospheric tests showed lower turn-on voltages of approximately 150 V for both the 1 and 1.5μm radius traps. Currents up to a few μA were achieved at 6 MV/cm for smaller trap size (1μm) in the largest array indicating a gas ionization contribution. The measured current-voltage responses fitted the Fowler–Nordheim characteristics well, confirming that the current increase in vacuum was due to field emission. A stable emission current of 2.03 nA was obtained at 10 MV/cm for 11 min.
An optimal scale separation for a dynamo experiment
Authors: Plunian Franck
Published: April 2005

Scale separation between the flow and the magnetic field is a common feature of natural dynamos. It has also been used in the Karlsruhe sodium experiment in which the scale of the magnetic field is roughly seven times larger than the scale of the flow [R. Stieglitz and U. Müller, “Experimental demonstration of the homogeneous two-scale dynamo,” Phys. Fluids 13, 561 (2001)]. Recently, Fauve and Pétrélis [Peyresq Lectures on Nonlinear Phenomena, edited by J. Sepulchre (World Scientific, Singapore, 2003), p. 1] have shown that the power needed to reach the dynamo threshold in a dynamo experiment increases with the scale separation in the limit of large scale separation. With a more elaborate method based on subharmonic solutions [F. Plunian and K.-H. Rädler, “Subharmonic dynamo action in the Roberts flow,” Geophys. Astrophys. Fluid Dyn. 96, 115 (2002)], we show, for the Roberts flow, the existence of an optimal scale separation for which this power is minimum. Previous results obtained by Tilgner [“A kinematic dynamo with a small scale velocity field,” Phys. Lett. A 226, 75 (1997)] with a completely different numerical method are also reconsidered here. Again, we find an optimal scale separation in terms of minimum power for dynamo action. In addition we find that this scale separation compares very well with the one derived from the subharmonic solutions method.
Acoustoelectric current in submicron-separated quantum wires
Authors: Cunningham J. , Pepper M. , Talyanskii V. I. , Ritchie D. A.
Published: April 2005

We measure acoustoelectric current in two submicron-separated quasi-one-dimensional wires formed in an AlGaAs∕GaAs heterostructure. We show that independent control of acoustoelectric current in both wires can be achieved with a suitably chosen geometry of Schottky gates. The implications of the results on two proposed uses of single-electron acoustoelectric current flow are discussed: a single-photon source and an acoustoelectrically driven quantum computer.
Generation of wavelength-dependent, periodic line pattern in metal nanoparticle-containing polymer films by femtosecond laser irradiation
Authors: Kiesow A. , Strohkark S. , Löschner K. , Heilmann A. , Podlipensky A. , Abdolvand A. , Seifert G.
Published: April 2005

Thin polymer films containing metal nanoparticles were irradiated with ultrashort, linearly polarized laser pulses. As result of irradiation, nanostructural changes occur in a type of periodically arranged, line-like areas with modified particle size and shape distribution. The periodic formation in this nanocomposite material is observed only for a small filling factor range, which can be attributed to the percolation region or nearby. Transmission (also in cross section) and scanning electron microscopy were applied to investigate the obtained structure modifications. A linear dependency between the period Λ of the line structures and the laser wavelength λ (800, 528, 400, and 266nm) used with Λ∕λ≈0.70 is assumed. The structural changes and the physical mechanism of the periodic formation are discussed.
Exceptionally high glass-forming ability of an FeCoCrMoCBY alloy
Authors: Shen Jun , Chen Qingjun , Sun Jianfei , Fan Hongbo , Wang Gang
Published: April 2005

It has been well documented that the maximum thickness of as-cast glassy samples attainable through conventional metallurgical routes is the decisive criteria for measuring the glass-forming ability (GFA) of bulk metallic glasses (BMGs). Here we report the exceptionally high GFA of an FeCoCrMoCBY alloy which can be fabricated in the form of glassy rods with a maximum sample thickness of at least 16mm. It is demonstrated that, by substituting Fe with a proper amount of Co in a previously reported Fe-based BMG alloy, the glass formation of the resultant new alloy can be extensively favored both thermodynamically and kinetically. The new ferrous BMG alloy also exhibits a high fracture strength of 3500MPa and Vickers hardness of 1253kgmm−2.
Fast analysis of gases in the submillimeter∕terahertz with “absolute” specificity
Authors: Medvedev Ivan R. , Behnke Markus , De Lucia Frank C.
Published: April 2005

A submillimeter∕terahertz point detector for gas monitoring and quantification is described. It is based upon the fast (∼15GHz∕s) sweeping of high spectral purity (<1∕107), high brightness (∼1014K) microwave sources and a scanning electronic reference for frequency measurement. This approach can quantify the complex rotational spectrum of gases at a rate of ∼105 spectral resolution elements∕second at high signal to noise. This resolution and the uniqueness of Doppler limited rotational spectra provide “absolute” specificity and “zero” false alarm rates even in complex mixtures. Moreover, the small size, low power consumption, and the potential of very low cost make this approach attractive for a number of important applications.
High-speed 1.3μm tunnel injection quantum-dot lasers
Authors: Mi Z. , Bhattacharya P. , Fathpour S.
Published: April 2005

1.3 μ m tunnel injection quantum-dot lasers are demonstrated. The laser heterostructures are grown by molecular-beam epitaxy. The InAs self-organized quantum dots are p doped to optimize the gain. The lasers are characterized by Jth=180A∕cm2, T0=∞, dg∕dn≈1×10−14cm2, f−3dB=11GHz, chirp of 0.1Å, and zero α parameter.
Water-soluble polythiophene∕nanocrystalline TiO2 solar cells
Authors: Qiao Qiquan , McLeskey James T.
Published: April 2005

We report the characteristics of polymer∕nanocrystalline solar cells fabricated using an environmentally friendly water-soluble polythiophene and TiO2 in a bilayer configuration. The cells were made by dropping the polymer onto a TiO2 nanocrystalline film and then repeatedly sweeping a clean glass rod across the polymer as it dried. The devices showed an open circuit voltage of 0.81 V, a short circuit current density of 0.35mA∕cm2, a fill factor of 0.4, and an energy conversion efficiency of 0.13%. The water-soluble polythiophene showed significant photovoltaic behavior and the potential for use in solar cells.
Counting Individual Trapped Electrons on Liquid Helium
Authors: Papageorgiou G. , Glasson P. , Harrabi K. , Antonov V. , Collin E. , Fozooni P. , Frayne P. G. , Lea M. J. , Rees D. G. , Mukharsky Y.
Published: April 2005

We show that small numbers of electrons, including a single isolated electron, can be held in an electrostatic trap above the surface of superfluid helium. A potential well is created using microfabricated electrodes in a 5 μm diameter pool of helium. Electrons are injected into the trap from an electron reservoir on a helium microchannel. They are individually detected using a superconducting single-electron transistor as an electrometer. A Coulomb staircase is observed as electrons leave the trap one–by–one until the trap is empty. A design for a scalable quantum information processor using an array of electron traps is presented.
Misfit accommodation of compact and columnar InN epilayers grown on Ga-face GaN (0001) by molecular-beam epitaxy
Authors: Kehagias Th. , Delimitis A. , Komninou Ph. , Iliopoulos E. , Dimakis E. , Georgakilas A. , Nouet G.
Published: April 2005

The interfacial structural properties of compact InN films and of noncoalesced three-dimensional InN islands, grown by molecular-beam epitaxy on Ga-face GaN/Al2O3 (0001) substrates, were investigated by transmission electron microscopy. Compact film growth was accomplished employing an InN nucleation layer, grown at low substrate temperatures. A 60° misfit dislocation network effectively accommodated the lattice mismatch in the InN/GaN interface in both cases of epilayers. The lattice constants of InN were determined by electron diffraction analysis, revealing a 0.28% larger in-plane parameter of the compact InN film relative to the corresponding lattice parameter of the InN islands. This is attributed to thermal tensile strain developed during post-growth cooling down of the epilayers, which also compensated the remaining compressive strain originating from the in-plane lattice mismatch of InN and GaN.
Discrimination between normal and cancer cells by using spectral analysis of delayed luminescence.
Authors: Musumeci Francesco , Privitera Giuseppe , Scordino Agata , Tudisco Salvatore , Lo Presti Carmine , Applegate Lee Ann , Niggli Hugo J.
Published: April 2005

In our present studies, the time-resolved emission spectrum of delayed luminescence of cell cultures of human fibroblast and human melanoma have been measured using a sophisticated single photon device. Noticeable differences have been found both in the emission spectra, which are time dependent, and in the timing aspects of the different spectral components. This powerful and noninvasive technique can be applied in all fields of skin research, such as the investigation of skin abnormalities and to test the effect of products involved in regeneration, antiaging, and UV-light protection in order to prevent skin cancer.
Ultrafast magnetization dynamics of epitaxial Fe films on AlGaAs (001)
Authors: Zhao H. B. , Talbayev D. , Yang Q. G. , Lüpke G. , Hanbicki A. T. , Li C. H. , van ’t Erve O. M. J. , Kioseoglou G. , Jonker B. T.
Published: April 2005

Uniform magnetization precessions are generated by ultrafast optical excitation along the in-plane easy axis [100], as well as along the hard axis [1-10], in epitaxial Fe films grown on AlGaAs (001) over a wide range of applied magnetic fields. From the temporal evolution of the coherent magnetization precession, we determine the magnetic anisotropy constants and damping parameters which are crucial in designing fast magnetic switching devices and spintronics devices.
Effects of thermal annealing on the band gap of GaInAsSb
Authors: Dier Oliver , Dachs Susanne , Grau Markus , Lin Chun , Lauer Christian , Amann Markus-Christian
Published: April 2005

In this Letter, the thermal stability of GaInAsSb grown by molecular-beam epitaxy was investigated. We found a strong blueshift for both bulk material and multiple-quantum-well (MQW) structures caused by thermal annealing. The shift is almost independent of design parameters such as indium concentration, strain, and growth parameters such as temperature. For a 500-nm-thick GaInAsSb bulk layer, a blueshift of 83meV was found after annealing for 2h at 520°C, whereas for MQW structures the maximum shift was 61meV.
Highly sensitive fiber Bragg grating refractive index sensors
Authors: Liang Wei , Huang Yanyi , Xu Yong , Lee Reginald K. , Yariv Amnon
Published: April 2005

We combine fiber Bragg grating (FBG) technology with a wet chemical etch-erosion procedure and demonstrate two types of refractive index sensors using single-mode optical fibers. The first index sensor device is an etch-eroded single FBG with a radius of 3μm, which is used to measure the indices of four different liquids. The second index sensor device is an etch-eroded fiber Fabry-Pérot interferometer (FFPI) with a radius of ∼1.5μm and is used to measure the refractive indices of isopropyl alcohol solutions of different concentrations. Due to its narrower resonance spectral feature, the FFPI sensor has a higher sensitivity than the FBG sensor and can detect an index variation of 1.4×10−5. Since we can measure the reflection signal, these two types of sensors can be fabricated at the end of a fiber and used as point sensors.
Cross-gain modulation in broad-area vertical-cavity semiconductor optical amplifier
Authors: Marino Francesco , Furfaro Luca , Balle Salvador
Published: April 2005

We demonstrate that broad-area vertical-cavity semiconductor optical amplifiers allow for wavelength conversion at 2.5Gb∕s via cross-gain modulation (XGM). XGM is reached with a saturation beam of only 1.5mW over an optical bandwidth of 0.7nm (215GHz). Depending on the wavelengths of the injected fields, inverted or noninverted output can be obtained.
Preferential outcrossing in Banksia ilicifolia (Proteaceae)
Authors: Heliyanto Bambang , Veneklaas Erik J. , Lambers Hans , Krauss Siegfried L.
Published: April 2005

The breeding system of Banksia ilicifolia was assessed by performing controlled hand-pollination manipulations on flowers in a natural population in Perth, Western Australia. The percentage of 2000 flowers per treatment converted to fruits and seeds was assessed across 24 recipient plants following (1) self-pollination, (2) local outcross pollination (same population), (3) non-local outcross pollination (pollen sourced from another population 30 km away), (4) unpollinated but bagged flowers and (5) unpollinated, unbagged flowers (natural pollination). The relative performance of the resulting seeds was assessed by seed weight, germination rates and, in an unplanned component of the study, resistance to a fungal pathogen. The percentage of flowers converted to fruits following self-pollination was low (0.9%), but demonstrated self-compatibility. Fruit set following cross-pollinations (3.6 and 3.3% for non-local and local crosses, respectively) was significantly greater than that following self-pollination, open-pollination (0.4%) and autogamous (0.04%) treatments. Low fruit set for open-pollinated flowers, compared with self- and outcross-pollination treatments, suggests pollen limitation. Pollen tubes were observed in 15 and 20% of upper styles of flowers hand-pollinated with self and local outcross pollen, respectively. Seed germination was dependent on the source of pollen, where fewer selfed seeds germinated (37%) than did both non-local and local outcrossed seeds (83 and 91%, respectively). Selfed seedlings showed poorer survival (33.3%) following fungal attack than both non-local and local outcrossed seeds (69.2 and 68.5%, respectively). Only 13% of selfed seeds survived to be 2-month-old seedlings, compared with 63% for non-local and 57% for local outcrossed seeds. Ultimately, for 2000 flowers hand-pollinated with self pollen, only three seedlings survived to an age of 16 weeks, compared with 37 and 45 seedlings for local-cross and non-local cross treatments on 2000 hand-pollinated flowers, respectively. These results indicate that in this population, B. ilicifolia is self-compatible, but preferentially outcrossing, with strong early acting inbreeding depression. Consequently, the breeding system of B. ilicifolia promotes the maintenance of genetic variation and a high genetic load.
Leaf gigantism in coastal areas: morphological and physiological variation in four species on the Tasman Peninsula, Tasmania
Authors: Blackman Christopher J. , Jordan Gregory J. , Wiltshire Robert J. E.
Published: April 2005

Leaf gigantism is an example of marked morphological variation associated with abrupt environmental gradients of increasing coastal exposure. This study characterises the morphology and anatomy of leaf gigantism in four species across two habitats on the coastal headlands of the Tasman Peninsula, Tasmania, Australia. In addition, the genetic basis and adaptive significance of leaf gigantism are examined. Leaf gigantism was characterised in Leptospermum scoparium, Acacia verticillata and Allocasuarina monilifera by greater thickness and succulence, and by greater thickness and increased support tissue in Allocasuarina crassa. Glasshouse-grown seedlings of each species derived from exposed and inland field sites showed that leaf gigantism has both genetic and environmental components. Leaf succulence and a slower growth rate were shown to be heritable in seedlings from the exposed site of L. scoparium and A. verticillata, indicating genetic differentiation. In the reciprocal translocation trial, the higher degree of stress tolerance (as measured by chlorophyll florescence) exhibited by seedlings of L. scoparium and A. verticillata from the exposed site demonstrated the adaptive significance of leaf gigantism in these species. The ecological and evolutionary implications of leaf gigantism on the Tasman Peninsula are discussed.
Use of growth characteristics for predicting plant age of three obligate-seeder Proteaceae species
Authors: Jenkins Meaghan E. , Morrison David A. , Auld Tony D.
Published: April 2005

We tested the ability to predict plant (and hence population) age for three fire-sensitive obligate-seeder Proteaceae species (Banksia ericifolia, Banksia marginata and Petrophile pulchella) in the heath and woodland vegetation of the Sydney region. To do this we sampled the number of growth whorls, as well as other growth characteristics (stem girth and height measurements, and canopy area and volume estimates), in areas of known time since last fire (TSLF). The average number of growth whorls was a very good predictor of plant age for both Banksia species (R2 = 98%, 99%), but this needed to be corrected for linear underestimation in P. pulchella (R2 = 92%). This technique could successfully be applied to these species in similar habitats across a large spatial scale, and so this information can be used to determine the age of a population in areas of unknown TSLF. A sample size of 15 plants was sufficient for accurate age estimates of all species; however, better estimates of TSLF for a particular plant community were obtained when estimates from two or more of the species were combined. We thus provide empirical evidence for the validity and accuracy of the growth-whorl technique for predicting plant age and hence TSLF. This information will assist in informing the development of appropriate management strategies for plants in relation to fire. Of the other growth characteristics studied, stem girth was the most reliable predictor; however, in general these other characteristics had wide confidence intervals on the predictions for sites greater than 10 years TSLF, owing to a non-linear relationship with age.
Consequences of soil map unit uncertainty on environmental risk assessment
Authors: Webb T. H. , Lilburne L. R.
Published: April 2005

Soil maps are being applied in modelling of environmental risk at a regional scale. Analysis of soil maps shows that there can be considerable uncertainty in map unit composition with consequent spatial variability in soil properties within map units. Uncertainty of map unit composition arises from a number of factors including map labels that do not reflect the mix of soil types present and imprecise location of map unit boundaries. Usually little, if any, information is supplied as to the extent and magnitude of these uncertainties. In this paper we develop datasets to quantify soil property variability for map units on the Canterbury Plains and use expert knowledge to quantify uncertainty in map unit composition for a small case-study area. We then apply Monte Carlo sampling to the estimated range of soil properties to input soil data into the GLEAMS simulation model to assess the effect of soil variability on nitrate leaching.
The simulation results show that there is considerable uncertainty in leaching from data derived from current soil map units. Even simple map units (map units characterised by a single soil type) have a wide range of potential leaching related to variation in soil profiles within the soil type. When map-unit inclusions were accounted for, variation in leaching risk can increase by 10–30%. Compound map units encompass the range of variability of the named component soils and there is a smaller increase in leaching variability in these units (compared with simple map units) when inclusions are added to the analysis. We discuss the implications of this study to the use of current soil survey data and make recommendations for future soil survey practice. In particular, greater effort is needed on description of the composition and reliability of soil map units.
Responsiveness of wheat (Triticum aestivum) to liquid and granular phosphorus fertilisers in southern Australian soils
Authors: McBeath T. M. , Armstrong R. D. , Lombi E. , McLaughlin M. J. , Holloway R. E.
Published: April 2005

Recent field trials on alkaline soils in southern Australia showed significant grain yield responses to liquid compared with traditional granular forms of P fertiliser. However the advantages of liquid over granular P forms of fertiliser has not been consistent on all soil types. In order to better predict the soil types on which liquid P fertilisers are likely to have potential, a glasshouse trial was conducted to compare the responsiveness of wheat to both liquid and granular forms of P on a wide range of Australian soils. A granular P fertiliser (triple superphosphate) and 2 liquid fertilisers (phosphoric acid and ammonium polyphosphate) were compared at a rate equivalent to 12 kg P/ha in 29 soils representing many of the soil types used for grain production in Victoria and South Australia. Wheat biomass was enhanced by P application in 86% of the soils tested. In 62% of the P-responsive soils, wheat dry matter was significantly greater when liquid P fertilisers were used compared with the granular form. Chemical analysis of the soils tested showed that the better performance of liquid P forms was not correlated to total P concentration in soil, P buffer capacity, or P availability as measured by Colwell-P. However, there was a significant positive relationship between calcium carbonate (CaCO3) content of soil and wheat responsiveness to liquid P fertiliser.
Leaching of macronutrients and metals from undisturbed soils treated with metal-spiked sewage sludge. 3. Distribution of residual metals
Authors: McLaren R. G. , Clucas L. M. , Taylor M. D.
Published: April 2005

Sewage sludge is increasingly been applied to land in New Zealand in an attempt to recycle the valuable plant nutrients such material contains. However, there are concerns regarding the environmental fate of heavy metals contained in the sludge. This study examines the soil profile distributions of metals (Cd, Cr, Cu, Ni, Pb, Zn) in large undisturbed soil lysimeters treated with metal-spiked sewage sludge, following 3 years of drainage leachate monitoring. For 3 forest soils that had all received surface applications of sludge, analytical results demonstrated considerable transport of metals from the sludge into the underlying litter and mineral soil layers. Determination of individual metal/Cr ratios revealed considerable differential mobility between metals, with Cd, Ni, and Zn being most mobile, and Cu and Pb being only slightly more mobile than Cr. Total metal analysis was relatively insensitive in detecting metal movement down the soil profile compared with determination of extractable metals (EDTA or Ca(NO3)2 extraction). Maximum depths of metal penetration varied between metals, but were similar for all 3 forest soils, averaging 0.15, 0.20, 0.25, 0.35, and 0.45 m for Pb, Cu, Cd, Ni, and Zn, respectively. In contrast to the forest soils, when sludge was incorporated into the top 0.10 m of 2 pasture soils, little movement of metals could be detected below the layer of incorporation. However, even in these soils, the determination of metal/Cr ratios indicated that some differential movement of metals had taken place. For the forest soils, the results indicate considerable potential for the long-term and sustained leaching of metals by normal convective and diffusive transport processes. This would appear to be of less concern where sludge has been incorporated into the pasture soils. These results clearly have implications for selection of the most appropriate soils and conditions for sludge application to the land.
IL-1 receptor–associated kinase M is a central regulator of osteoclast differentiation and activation
Authors: Li Hongmei , Cuartas Esteban , Cui Weiguo , Choi Yongwon , Crawford Todd D. , Ke Hua Zhu , Kobayashi Koichi S. , Flavell Richard A. , Vignery Agnès
Published: April 2005

Osteoporosis is a serious problem worldwide; it is characterized by bone fractures in response to relatively mild trauma. Osteoclasts originate from the fusion of macrophages and they play a central role in bone development and remodeling via the resorption of bone. Therefore, osteoclasts are important mediators of bone loss that leads, for example, to osteoporosis. Interleukin (IL)-1 receptor (IL-1R)–associated kinase M (IRAK-M) is only expressed in cells of the myeloid lineage and it inhibits signaling downstream of IL-1R and Toll-like receptors (TLRs). However, it lacks a functional catalytic site and, thus, cannot function as a kinase. IRAK-M associates with, and prevents the dissociation of, IRAK–IRAK-4–TNF receptor–associated factor 6 from the TLR signaling complex, with resultant disruption of downstream signaling. Thus, IRAK-M acts as a dominant negative IRAK. We show here that mice that lack IRAK-M develop severe osteoporosis, which is associated with the accelerated differentiation of osteoclasts, an increase in the half-life of osteoclasts, and their activation. Ligation of IL-1R or TLRs results in hyperactivation of NF-κB and mitogen-activated protein kinase signaling pathways, which are essential for osteoclast differentiation. Thus, IRAK-M is a key regulator of the bone loss that is due to osteoclastic resorption of bone.
Hierarchy of resistance to cervical neoplasia mediated by combinations of killer immunoglobulin-like receptor and human leukocyte antigen loci
Authors: Carrington Mary , Wang Sophia , Martin Maureen P. , Gao Xiaojiang , Schiffman Mark , Cheng Jie , Herrero Rolando , Rodriguez Ana Cecilia , Kurman Robert , Mortel Rodrigue , Schwartz Peter , Glass Andrew , Hildesheim Allan
Published: April 2005

Killer immunoglobulin-like receptor (KIR) recognition of specific human histocompatibility leukocyte antigen (HLA) class I allotypes contributes to the array of receptor–ligand interactions that determine natural killer (NK) cell response to its target. Contrasting genetic effects of KIR/HLA combinations have been observed in infectious and autoimmune diseases, where genotypes associated with NK cell activation seem to be protective or to confer susceptibility, respectively. We show here that combinations of KIR and HLA loci also affect the risk of developing cervical neoplasia. Specific inhibitory KIR/HLA ligand pairs decrease the risk of developing neoplasia, whereas the presence of the activating receptor KIR3DS1 results in increased risk of disease, particularly when the protective inhibitory combinations are missing. These data suggest a continuum of resistance conferred by NK cell inhibition to susceptibility involving NK cell activation in the development of cervical neoplasia and underscore the pervasive influence of KIR/HLA genetic variation in human disease pathogenesis.
Understanding how combinations of HLA and KIR genes influence disease
Authors: Rajagopalan Sumati , Long Eric O.
Published: April 2005

Combinations of HLA and killer cell immunoglobulin–like receptor (KIR) genes have been associated with diseases as diverse as autoimmunity, viral infections, reproductive failure, and now cancer. Much as early observations of disease associations with HLA polymorphism preceded a detailed knowledge of HLA recognition by T cell receptors, the recently reported disease associations with HLA–KIR gene combinations beg for a better understanding of the underlying mechanisms.
Mature DIABLO/Smac Is Produced by the IMP Protease Complex on the Mitochondrial Inner Membrane
Authors: Burri Lena , Strahm Yvan , Hawkins Christine J. , Gentle Ian E. , Puryer Michelle A. , Verhagen Anne , Callus Bernard , Vaux David , Lithgow Trevor
Published: April 2005

DIABLO/Smac is a mitochondrial protein that can promote apoptosis by promoting the release and activation of caspases. To do so, DIABLO/Smac must first be processed by a mitochondrial protease and then released into the cytosol, and we show this in an intact cellular system. We propose that the precursor form of DIABLO/Smac enters the mitochondria through a stop-transfer pathway and is processed to its active form by the inner membrane peptidase (IMP) complex. Catalytic subunits of the mammalian IMP complex were identified based on sequence conservation and functional complementation, and the novel sequence motif RX5P in Imp1 and NX5S in Imp2 distinguish the two catalytic subunits. DIABLO/Smac is one of only a few specific proteins identified as substrates for the IMP complex in the mitochondrial intermembrane space.
Global Roles of Ssn6 in Tup1- and Nrg1-dependent Gene Regulation in the Fungal Pathogen,Candida albicans
Authors: García-Sánchez Susana , Mavor Abigail L. , Russell Claire L. , Argimon Silvia , Dennison Paul , Enjalbert Brice , Brown Alistair J.P.
Published: April 2005

In budding yeast, Tup1 and Ssn6/Cyc8 form a corepressor that regulates a large number of genes. This Tup1-Ssn6 corepressor appears to be conserved from yeast to man. In the pathogenic fungus Candida albicans, Tup1 regulates cellular morphogenesis, phenotypic switching, and metabolism, but the role of Ssn6 remains unclear. We show that there are clear differences in the morphological and invasive phenotypes of C. albicans ssn6 and tup1 mutants. Unlike Tup1, Ssn6 depletion promoted morphological events reminiscent of phenotypic switching rather than filamentous growth. Transcript profiling revealed minimal overlap between the Ssn6 and Tup1 regulons. Hypha-specific genes, which are repressed by Tup1 and Nrg1, were not derepressed in ssn6 cells under the conditions studied. In contrast, the phase specific gene WH11 was derepressed in ssn6 cells, but not in tup1 or nrg1 cells. Hence Ssn6 and Tup1 play distinct roles in C. albicans. Nevertheless, both Ssn6 and Tup1 were required for the Nrg1-mediated repression of an artificial NRE promoter, and lexA-Nrg1 mediated repression in the C. albicans one-hybrid system. These observations are explained in models that are generally consistent with the Tup1-Ssn6 paradigm in budding yeast.
Induction of theCandida albicansFilamentous Growth Program by Relief of Transcriptional Repression: A Genome-wide Analysis
Authors: Kadosh David , Johnson Alexander D.
Published: April 2005

Candida albicans, the major human fungal pathogen, undergoes a reversible morphological transition from blastospores (round budding cells) to filaments (elongated cells attached end-to-end). This transition, which is induced upon exposure of C. albicans cells to a number of host conditions, including serum and body temperature (37°C), is required for virulence. Using whole-genome DNA microarray analysis, we describe 61 genes that are significantly induced (≥2-fold) during the blastospore to filament transition that takes place in response to exposure to serum and 37°C. We next show that approximately half of these genes are transcriptionally repressed in the blastospore state by three transcriptional repressors, Rfg1, Nrg1, and Tup1. We conclude that the relief of this transcriptional repression plays a key role in bringing the C. albicans filamentous growth program into play, and we describe the framework of this transcriptional circuit.
Nuclear Targeting of Adenovirus Type 2 Requires CRM1-mediated Nuclear Export
Authors: Strunze Sten , Trotman Lloyd C. , Boucke Karin , Greber Urs F.
Published: April 2005

Incoming adenovirus type 2 (Ad2) and Ad5 shuttle bidirectionally along microtubules, biased to the microtubule-organizing center by the dynein/dynactin motor complex. It is unknown how the particles reach the nuclear pore complex, where capsids disassemble and viral DNA enters the nucleus. Here, we identified a novel link between nuclear export and microtubule-mediated transport. Two distinct inhibitors of the nuclear export factor CRM1, leptomycin B (LMB) and ratjadone A (RJA) or CRM1-siRNAs blocked adenovirus infection, arrested cytoplasmic transport of viral particles at the microtubule-organizing center or in the cytoplasm and prevented capsid disassembly and nuclear import of the viral genome. In mitotic cells where CRM1 is in the cytoplasm, adenovirus particles were not associated with microtubules but upon LMB treatment, they enriched at the spindle poles implying that CRM1 inhibited microtubule association of adenovirus. We propose that CRM1, a nuclear factor exported by CRM1 or a protein complex containing CRM1 is part of a sensor mechanism triggering the unloading of the incoming adenovirus particles from microtubules proximal to the nucleus of interphase cells.
Mobile assemblies based on the Bennett linkage
Authors: Chen Y , You Z
Published: April 2005

This paper presents a method of building large mobile assemblies using the Bennett linkage. The method is based on a basic single-layer layout consisting of overlapping 4
R
loops, each of which is a Bennett linkage. The assemblies created have a single degree of freedom, and are overconstrained and scaleable, allowing unlimited extension by repetition. In general, they deploy into a circular or non-circular cylindrical profile. The joints of the assemblies move spirally on the surface during deployment. Under some particular geometrical conditions, the profiles of the assemblies can become arch-like or flat. Moreover, the single-layer assemblies can be extended to form multi-layer mechanisms, even mobile masts. The paper shows the great versatility of the Bennett linkage and demonstrates that the century-old invention can play an important role in the construction of deployable structures.
Flexibility of spatial averaging in visual perception
Authors: Lombrozo Tania , Judson Jeff , MacLeod Donald I.A
Published: April 2005

The classical receptive field (RF) concept—the idea that a visual neuron responds to fixed parts and properties of a stimulus—has been challenged by a series of recent physiological results. Here, we extend these findings to human vision, demonstrating that the extent of spatial averaging in contrast perception is also flexible, depending strongly on stimulus contrast and uniformity. At low contrast, spatial averaging is greatest (about 11 min of arc) within uniform regions such as edges, as expected if the relevant neurons have orientation-selective RFs. At high contrast, spatial averaging is minimal. These results can be understood if the visual system is balancing a trade-off between noise reduction, which favours large areas of averaging, and detail preservation, which favours minimal averaging. Two distinct populations of neurons with hard-wired RFs could account for our results, as could the more intriguing possibility of dynamic, contrast-dependent RFs.
Evidence for recombination in scorpion mitochondrial DNA (Scorpiones: Buthidae)
Authors: Gantenbein Benjamin , Fet Victor , Gantenbein-Ritter Iris A , Balloux François
Published: April 2005

There has been very little undisputed evidence for recombination in animal mitochondrial DNA (mtDNA) provided so far. Previous unpublished results suggestive of mtDNA recombination in the scorpion family Buthidae, together with cytological evidence for a unique mechanism of mitochondrial fusion in that family, prompted us to investigate this group in more details. First, we sequenced the complete mtDNA genome ofMesobuthus gibbosus, and chose two genes opposing each other (16S andcoxI). We then sequenced 150 individuals from the natural populations of four species of Buthidae (Old World generaButhusandMesobuthus). We observed strong evidence for widespread recombination through highly significant negative correlations between linkage disequilibrium and physical distance in three out of four species. The evidence is further confirmed when using five other tests for recombination and by the presence of a high amount of homoplasy in phylogenetic trees.
Oxidation by 2-oxoglutarate oxygenases: non-haem iron systems in catalysis and signalling
Authors: Hewitson K.S , Granatino N , Welford R.W.D , McDonough M.A , Schofield C.J
Published: April 2005

The 2-oxoglutarate (2OG) and ferrous iron dependent oxygenases are a superfamily of enzymes that catalyse a wide range of reactions including hydroxylations, desaturations and oxidative ring closures. Recently, it has been discovered that they act as sensors in the hypoxic response in humans and other animals. Substrate oxidation is coupled to conversion of 2OG to succinate and carbon dioxide. Kinetic, spectroscopic and structural studies are consistent with a consensus mechanism in which ordered binding of (co)substrates enables control of reactive intermediates. Binding of the substrate to the active site triggers the enzyme for ligation of dioxygen to the metal. Oxidative decarboxylation of 2OG then generates the ferryl species thought to mediate substrate oxidation. Structural studies reveal a conserved double-stranded β-helix core responsible for binding the iron, via a 2His-1carboxylate motif and the 2OG side chain. The rigidity of this core contrasts with the conformational flexibility of surrounding regions that are involved in binding the substrate. Here we discuss the roles of 2OG oxygenases in terms of the generic structural and mechanistic features that render the 2OG oxygenases suited for their functions.
The Living Planet Index: using species population time series to track trends in biodiversity
Authors: Loh Jonathan , Green Rhys E , Ricketts Taylor , Lamoreux John , Jenkins Martin , Kapos Valerie , Randers Jorgen
Published: April 2005

The Living Planet Index was developed to measure the changing state of the world's biodiversity over time. It uses time-series data to calculate average rates of change in a large number of populations of terrestrial, freshwater and marine vertebrate species. The dataset contains about 3000 population time series for over 1100 species. Two methods of calculating the index are outlined: the chain method and a method based on linear modelling of log-transformed data. The dataset is analysed to compare the relative representation of biogeographic realms, ecoregional biomes, threat status and taxonomic groups among species contributing to the index.

The two methods show very similar results: terrestrial species declined on average by 25% from 1970 to 2000. Birds and mammals are over-represented in comparison with other vertebrate classes, and temperate species are over-represented compared with tropical species, but there is little difference in representation between threatened and non-threatened species. Some of the problems arising from over-representation are reduced by the way in which the index is calculated. It may be possible to reduce this further by post-stratification and weighting, but new information would first need to be collected for data-poor classes, realms and biomes.
Measuring biodiversity and sustainable management in forests and agricultural landscapes
Authors: Dudley Nigel , Baldock David , Nasi Robert , Stolton Sue
Published: April 2005

Most of the world's biodiversity will continue to exist outside protected areas and there are also managed lands within many protected areas. In the assessment of millennium targets, there is therefore a need for indicators to measure biodiversity and suitability of habitats for biodiversity both across the whole landscape/seascape and in specific managed habitats. The two predominant land uses in many inhabited areas are forestry and agriculture and these are examined. Many national-level criteria and indicator systems already exist that attempt to assess biodiversity in forests and the impacts of forest management, but there is generally less experience in measuring these values in agricultural landscapes. Existing systems are reviewed, both for their usefulness in providing indicators and to assess the extent to which they have been applied. This preliminary gap analysis is used in the development of a set of indicators suitable for measuring progress towards the conservation of biodiversity in managed forests and agriculture. The paper concludes with a draft set of indicators for discussion, with suggestions including proportion of land under sustainable management, amount of produce from such land, area of natural or high quality semi-natural land within landscapes under sustainable management and key indicator species.
Prospects for monitoring freshwater ecosystems towards the 2010 targets
Authors: Revenga C , Campbell I , Abell R , de Villiers P , Bryer M
Published: April 2005

Human activities have severely affected the condition of freshwater ecosystems worldwide. Physical alteration, habitat loss, water withdrawal, pollution, overexploitation and the introduction of non-native species all contribute to the decline in freshwater species. Today, freshwater species are, in general, at higher risk of extinction than those in forests, grasslands and coastal ecosystems. For North America alone, the projected extinction rate for freshwater fauna is five times greater than that for terrestrial fauna—a rate comparable to the species loss in tropical rainforest. Because many of these extinctions go unseen, the level of assessment and knowledge of the status and trends of freshwater species are still very poor, with species going extinct before they are even taxonomically classified.

Increasing human population growth and achieving the sustainable development targets set forth in 2002 will place even higher demands on the already stressed freshwater ecosystems, unless an integrated approach to managing water for people and ecosystems is implemented by a broad constituency. To inform and implement policies that support an integrated approach to water management, as well as to measure progress in halting the rapid decline in freshwater species, basin-level indicators describing the condition and threats to freshwater ecosystems and species are required. This paper discusses the extent and quality of data available on the number and size of populations of freshwater species, as well as the change in the extent and condition of natural freshwater habitats. The paper presents indicators that can be applied at multiple scales, highlighting the usefulness of using remote sensing and geographical information systems technologies to fill some of the existing information gaps. Finally, the paper includes an analysis of major data gaps and information needs with respect to freshwater species to measure progress towards the 2010 biodiversity targets.
Who enjoys ‘TRIPs’ abroad? An empirical analysis of intellectual property rights in the Uruguay Round
Authors: McCalman Phillip
Published: April 2005

Abstract.  Analysis of the Uruguay Round is extended by quantifying the impact of the TRIPs agreement. The static costs of raising the standards of patent protection are captured by the transfers of income between countries, with the majority of countries estimated to make net payments abroad, the United States being a major beneficiary. To offset these transfers the model provides estimates of the dynamic benefits from the greater incentive to innovate, revealing that there is potential for all countries to benefit from the TRIPs agreement in the long run. However, the distribution of these benefits is highly skewed towards developed countries. JEL classification: O34, F43
The comparative advantage of public ownership: evidence from U.S. electric utilities
Authors: Kwoka John E.
Published: April 2005

Abstract.  Studies of the performance effects of public vs private ownership have found mixed evidence. This paper draws on theory suggesting that public enterprise may have an advantage in producing goods and services whose quality attributes are difficult to specify a priori. Using a comprehensive data set of U.S. electric utilities to estimate cost functions, we find that while privately owned systems achieve lower costs in generation, public systems generally have an advantage in the end‐user‐oriented distribution function with its more non‐contractible quality attributes. Other evidence on quality differences by ownership type and by enterprise size supports this distinction. JEL classification: L33, L94
Explaining the deteriorating entry earnings of Canada's immigrant cohorts, 1966 – 2000
Authors: Aydemir Abdurrahman , Skuterud Mikal
Published: April 2005

Abstract.  Using the 1981, 1986, 1991, 1996, and 2001 Canadian Censuses, we explore causes of the deterioration in entry earnings of successive cohorts of immigrant men and women. Roughly one‐third of the deterioration is explained by compositional shifts in language ability and region of birth. We find no evidence of a decline in the returns to foreign education for either immigrant men or immigrant women but a definite deterioration in the returns to foreign labour market experience, most strongly among men from non‐traditional source countries. We can explain roughly two‐thirds of the male and one‐half of the female deterioration without any reference to entry labour market conditions. When we also account for entry conditions, our results suggest Canada's immigrants of the late 1990s would otherwise have enjoyed entry earnings equal to or higher than their counterparts of the 1960s.