bluuebunny/crossref_metadata_2025 huggingface dataset:
Electricity supply, irregularities, and the prospect for solar energy and energy sustainability in Sub-Saharan Africa
Authors: Nkwetta Dan Nchelatebe , Smyth Mervyn , Van Thong Vu , Driesen Johan , Belmans Ronnie
Published: March 2010

Countries in Sub-Saharan Africa (SSA) are faced with the problem of expanding urban growth and demographic shift, necessitating the need to achieve a sustainable rate of positive economic growth. To move toward a sustainable future, many reforms have been implemented, including in the energy sector. Reforms in the energy sector will lead to a secure future energy supply, open globalised energy market, as well as providing basic energy needs. Unfortunately electrical energy production within SSA countries is primarily by wood fueled power stations and large hydroschemes (with oil and gas to a lesser extent). Large hydropower systems are environmentally destructive, and the combustion of wood generates millions of tons of carbon dioxide and green house gas emissions. The recent price fluctuations of crude oil and natural gas and the inconsistent and insufficient power supply have further increased public dissatisfaction. This paper demonstrates how the SSA region with its natural resources is capable of producing a stable electrical energy supply sector through renewable energy technologies (RETs), extending electricity supply to off-grid areas via photovoltaics (PV) and maintaining a continuous energy supply, with no significant impact on the environment and detriment to health of the local population. The most common characteristics of weak and unstable grids in SSA countries and their energy generation are investigated. Distributed generation technologies for rural electrifications (PV off-grid systems) as well as the grid-connected PVs are evaluated. This paper also demonstrates the possibility and merits of promoting specific RETs such as combined solar thermal energy systems for hospital equipment sterilization and powering solar air-conditioning systems in SSA countries, thus offsetting dependence on current power supply networks.
Scattering theory for two-body quantum systems with singular potentials in a time-periodic electric field
Authors: Adachi Tadayoshi , Kimura Toshiyuki , Shimizu Yoshimasa
Published: March 2010

Recently, the first author [Adachi, “Asymptotic completeness for N-body quantum systems with long-range interactions in a time-periodic electric field,” Commun. Math. Phys. 275, 443 (2007)] proved the asymptotic completeness for N-body quantum systems with long-range interactions in a time-periodic electric field whose mean in time is nonzero by obtaining propagation estimates for the physical propagator. However, in his work, it is needed that potentials under consideration are sufficiently smooth. In this paper, when N=2, we prove the asymptotic completeness of (modified) wave operators under the assumption that the potential has the local singularity of type |x|−1+ϵ when d≥3 and 0<ϵ<1, where d is the space dimension. We also discuss the modifiers in the position representation, which are used in the definition of the modified wave operators in the long-range case.
Transport of momentum in full f gyrokinetics
Authors: Parra Felix I. , Catto Peter J.
Published: March 2010

Full f electrostatic gyrokinetic formulations employ two gyrokinetic equations, one for ions and the other for electrons, and quasineutrality to obtain the ion and electron distribution functions and the electrostatic potential. We demonstrate with several examples that the long wavelength radial electric field obtained with full f approaches is extremely sensitive to errors in the ion and electron density since small deviations in density give rise to large, nonphysical deviations in the conservation of toroidal angular momentum. For typical tokamak values, a relative error of 10−7 in the ion or electron densities is enough to obtain the incorrect toroidal rotation. Based on the insights gained with the examples considered, three simple tests to check transport of toroidal angular momentum in full f simulations are proposed.
Physics of neutralization of intense high-energy ion beam pulses by electrons
Authors: Kaganovich I. D. , Davidson R. C. , Dorf M. A. , Startsev E. A. , Sefkow A. B. , Lee E. P. , Friedman A.
Published: March 2010

Neutralization and focusing of intense charged particle beam pulses by electrons form the basis for a wide range of applications to high energy accelerators and colliders, heavy ion fusion, and astrophysics. For example, for ballistic propagation of intense ion beam pulses, background plasma can be used to effectively neutralize the beam charge and current, so that the self-electric and self-magnetic fields do not affect the ballistic propagation of the beam. From the practical perspective of designing advanced plasma sources for beam neutralization, a robust theory should be able to predict the self-electric and self-magnetic fields during beam propagation through the background plasma. The major scaling relations for the self-electric and self-magnetic fields of intense ion charge bunches propagating through background plasma have been determined taking into account the effects of transients during beam entry into the plasma, the excitation of collective plasma waves, the effects of gas ionization, finite electron temperature, and applied solenoidal and dipole magnetic fields. Accounting for plasma production by gas ionization yields a larger self-magnetic field of the ion beam compared to the case without ionization, and a wake of current density and self-magnetic field perturbations is generated behind the beam pulse. A solenoidal magnetic field can be applied for controlling the beam propagation. Making use of theoretical models and advanced numerical simulations, it is shown that even a small applied magnetic field of about 100 G can strongly affect the beam neutralization. It has also been demonstrated that in the presence of an applied magnetic field the ion beam pulse can excite large-amplitude whistler waves, thereby producing a complex structure of self-electric and self-magnetic fields. The presence of an applied solenoidal magnetic field may also cause a strong enhancement of the radial self-electric field of the beam pulse propagating through the background plasma. If controlled, this physical effect can be used for optimized beam transport over long distances.
Existence of homoclinic connections in continuous piecewise linear systems
Authors: Carmona Victoriano , Fernández-Sánchez Fernando , García-Medina Elisabeth , Teruel Antonio E.
Published: March 2010

Numerical methods are often used to put in evidence the existence of global connections in differential systems. The principal reason is that the corresponding analytical proofs are usually very complicated. In this work we give an analytical proof of the existence of a pair of homoclinic connections in a continuous piecewise linear system, which can be considered to be a version of the widely studied Michelson system. Although the computations developed in this proof are specific to the system, the techniques can be extended to other piecewise linear systems.
Observation of runaway electron beams by visible color camera in the Experimental Advanced Superconducting Tokamak
Authors: Shi Yuejiang , Fu Jia , Li Jiahong , Yang Yu , Wang Fudi , Li Yingying , Zhang Wei , Wan Baonian , Chen Zhongyong
Published: March 2010

The synchrotron radiation originated from the energetic runaway electrons has been measured by a visible complementary metal oxide semiconductor camera working in the wavelength ranges of 380–750 nm in the Experimental Advanced Superconducting Tokamak [H. Q. Liu et al., Plasma Phys. Contr. Fusion 49, 995 (2007)]. With a tangential viewing into the plasma in the direction of electron approach on the equatorial plane, the synchrotron radiation from the energetic runaway electrons was measured in full poloidal cross section. The synchrotron radiation diagnostics provides a direct pattern of the runaway beam inside the plasma. The energy and pitch angle of runaway electrons have been obtained according to the synchrotron radiation pattern. A stable shell shape of synchrotron radiation has been observed in a few runaway discharges.
Stress-relaxation behavior in gels with ionic and covalent crosslinks
Authors: Zhao Xuanhe , Huebsch Nathaniel , Mooney David J. , Suo Zhigang
Published: March 2010

Long-chained polymers in alginate hydrogels can form networks by either ionic or covalent crosslinks. This paper shows that the type of crosslinks can markedly affect the stress-relaxation behavior of the gels. In gels with only ionic crosslinks, stress relaxes mainly through breaking and subsequent reforming of the ionic crosslinks, and the time scale of the relaxation is independent of the size of the sample. By contrast, in gels with only covalent crosslinks, stress relaxes mainly through migration of water, and the relaxation slows down as the size of the sample increases. Implications of these observations are discussed.
Trace correcting density matrix extrapolation in self-consistent geometry optimization
Authors: Niklasson Anders M. N. , Challacombe Matt , Tymczak C. J. , Németh Károly
Published: March 2010

A linear scaling trace correcting density matrix extrapolation method is proposed for accelerated self-consistency convergence in geometry optimization. The technique is based on nonorthogonal trace correcting purification and perturbation theory. Compared with alternative schemes, extrapolated total energies are often an order of magnitude closer to the self-consistent solution. For insulators, the computational cost is low and it scales linearly with the size of the perturbed region affected by the modified geometry, O(Npert). For local perturbations, the computational cost is therefore independent of the total size of the system and scales as O(1).
Effect of counterion valence on the pH responsiveness of polyamidoamine dendrimer structure
Authors: Liu Yun , Porcar Lionel , Hong Kunlun , Shew Chwen-Yang , Li Xin , Liu Emily , Butler Paul D. , Herwig Kenneth W. , Smith Gregory S. , Chen Wei-Ren
Published: March 2010

An accurate determination of the structure characteristics of protonated generation 5 polyamidoamine dendrimers in aqueous solution has been conducted by analyzing the small angle neutron scattering databased on a statistical mechanics model. In our investigation, the primary focus is to elucidate the effect of counterion valence on the counterion association and its impact on the intramolecular density profile within a dendrimer. In the range of our study for molecular protonation, a strong dependence of the structural properties of charged dendrimers on counterion valence is revealed. Our findings indicate that the association of a large amount of divalent counterions significantly reduces the effective charge of a dendrimer molecule. Surprisingly, no discernible transition of the density distribution profile is observed for the dendrimer charged by D2SO4, as opposed to our previous observation of a pronounced transition in intramolecular density profile for the dendrimer charged by DCl. These findings may be understood from the thermodynamic processes of counterions.
Irreversible altering of crystalline phase of phase-change Ge–Sb thin films
Authors: Krusin-Elbaum L. , Shakhvorostov D. , Cabral C. , Raoux S. , Jordan-Sweet J. L.
Published: March 2010

The stability of the crystalline phase of binary phase-change GexSb1−x films is investigated over a wide range of Ge content. From Raman spectroscopy we find the Ge–Sb crystalline structure irreversibly altered after exposure to a laser beam. We show that with increasing beam intensity/temperature Ge agglomerates and precipitates out in the amount growing with x. A simple empirical relation links Ge precipitation temperature TGep to the rate of change dTcryst/dx of crystallization, with the precipitation easiest on the mid-range x plateau, where Tcryst is nearly constant. Our findings point to a preferable 15%≲x≲50% window, that may achieve the desired cycling/archival properties of a phase-change cell.
Intrinsic limits of subthreshold slope in biased bilayer graphene transistor
Authors: Majumdar Kausik , Murali Kota V. R. M. , Bhat Navakanta , Lin Yu-Ming
Published: March 2010

In this work, we investigate the intrinsic limits of subthreshold slope in a dual gated bilayer graphene transistor using a coupled self-consistent Poisson-bandstructure solver. We benchmark the solver by matching the bias dependent band gap results obtained from the solver against published experimental data. We show that the intrinsic bias dependence of the electronic structure and the self-consistent electrostatics limit the subthreshold slope obtained in such a transistor well above the Boltzmann limit of 60 mV/decade at room temperature, but much below the results experimentally shown till date, indicating room for technological improvement of bilayer graphene.
Synthesis and photovoltaic effect of vertically aligned ZnO/ZnS core/shell nanowire arrays
Authors: Wang K. , Chen J. J. , Zeng Z. M. , Tarr J. , Zhou W. L. , Zhang Y. , Yan Y. F. , Jiang C. S. , Pern J. , Mascarenhas A.
Published: March 2010

A vertically aligned ZnO/ZnS core/shell nanowire array with type II band alignment was directly synthesized on an indium-tin-oxide glass substrate and the photovoltaic effect of the nanowire array was investigated. The epitaxial relationship, wurtzite (0001) matching zinc-blende (111), was observed in the ZnO/ZnS nano-heterostructure. ZnS coating is found to quench the photoluminescence of ZnO nanowires but enhance the photocurrent with faster response in the photovoltaic device, indicating improvement in charge separation and collection in the type II core/shell nanowire.
Origin of weak-link behavior of grain boundaries in superconducting cuprates and pnictides
Authors: Deutscher Guy
Published: March 2010

Superconducting cuprates and pnictides composed of CuO2 or AsFe planes, respectively, with intercalated insulating layers, are at the crossroads of three families of crystalline solids: Metals, doped Mott insulators, and ferroelectrics. The metallic and doped insulator approaches to high temperature superconductivity are essentially electronic ones, while in ferroelectrics atomic displacements play a key role. We show that pairing by contraction of in-plane Cu–O (or As–Fe) bonds, as proposed by the bond contraction pairing model, is prevented by the tensile strain generated by dislocations at grain boundaries. This explains why weak link behavior already sets in at low angle boundaries.
Tunnel field effect transistor with increased ON current, low-k spacer and high-k dielectric
Authors: Anghel Costin , Chilagani Prathyusha , Amara Amara , Vladimirescu Andrei
Published: March 2010

An improved double-gate tunnel field-effect transistor structure with superior performance is proposed. The originality consists in the introduction of a low-k spacer that is combined with a high-k gate dielectric. Numerical simulations demonstrate that the use of the low-k spacer and high-k gate dielectric leads to a high on-current, ION, and reduced subthreshold slope. The proposed structure increases ION by a factor of 3.8 and reduces the subthreshold slope by a factor of 2 compared to other structures described in literature.
Excitonic effects in the optical properties of CdSe nanowires
Authors: Vilhena José G. , Botti Silvana , Marques Miguel A. L.
Published: March 2010

Using a first-principle approach beyond density functional theory we calculate the electronic and optical properties of small diameter CdSe nanowires. Our results demonstrate how some approximations commonly used in bulk systems fail at this nanoscale level and how indispensable it is to include crystal local fields and excitonic effects to predict the unique optical properties of nanowires. From our results, we then construct a simple model to describe the optical gap as a function of the diameter of the wire, that turns out to be in excellent agreement with experiments for intermediate and large diameters.
Tailoring of magnetic properties of patterned cobalt antidots by simple manipulation of lattice symmetry
Authors: Deshpande N. G. , Seo M. S. , Jin X. R. , Lee S. J. , Lee Y. P. , Rhee J. Y. , Kim K. W.
Published: March 2010

Cobalt (Co) antidot arrays with different lattice geometries, square and rhomboid structures were fabricated and their magnetic reversal properties were studied by scanning-electron microscopy (SEM), magneto-optic Kerr effect, and magnetic force microscopy (MFM). Different lattice symmetries induced the corresponding anisotropies with changing easy and hard axes. The nearest-neighbor rule is not applicable in case of the rhomboid antidot lattice, while the inclusion theory is. These results are different from those of the previous investigations. The differences are due to different sizes and spacing’s between the antidots. The MFM images in the remanent state showed well-defined domain structures, periodic in nature according to the lattice geometry.
Wavelike rippling in multiwalled carbon nanotubes under pure bending
Authors: Nikiforov I. , Zhang D.-B. , James R. D. , Dumitrică T.
Published: March 2010

Objective molecular dynamics is used to systematically investigate elastic bending in carbon nanotubes up to 4.2 nm in diameter. A contrasting behavior is revealed: While single-wall tubes buckle in a gradual way, with a clear intermediate regime before they fully buckle, multiwalled tubes with closed cores exhibit a rate- and size-independent direct transition to an unusual wavelike mode with a 1 nm characteristic length. This rippling mode has a nearly-linear bending response and causes a ∼35% reduction in the stiffness of the thickest multiwalled tubes.
Valence states of nanocrystalline Ceria under combined effects of hydrogen reduction and particle size
Authors: Wan Xuefei , Goberman Daniel , Shaw Leon L. , Yi Guangshun , Chow Gan-Moog
Published: March 2010

This study reveals that the Ce4+ to Ce3+ ratio in CeO2 nanoparticles (<20 nm) increases with increasing temperature under a hydrogen atmosphere. Such anomalous behavior is due to the physical effect of nanoparticle sizes on increasing the oxidation state of Ce ions in CeO2, which is stronger than the chemical effect of hydrogen reduction. This discovery offers an effective way to independently control the specific surface area and Ce3+ concentration of CeO2 nanoparticles.
Enhanced magnetic response of fluids using self-assembled petal-like iron oxide particles
Authors: Son You-Hwan , Lee Jung-Kun , Soong Yee , Martello Donald , Chyu Minking
Published: March 2010

Using self-assembled iron oxide (SAIO) particles with petal-like morphology, aqueous fluids containing magnetic particles were prepared and the effect of hierarchical particle surface on the viscoelasticity under magnetic was investigated. The fluids consisting of self-assembled iron oxide particles exhibit highly tunable viscoelasticity which is controlled by applying external magnetic field. A difference between SAIO particles and spherical particles is explained by the fact that surface features of the self-assembled particles increased the network strength between particles in the fluids.
Aging-stabilization of ferroelectric domains and internal electric field due to short-range ordering of charged point defects: Phase field modeling
Authors: Rao Wei-Feng , Cheng Tian-Le , Wang Yu U.
Published: March 2010

Computer modeling and simulation is performed to study the domain stabilization effect due to short-range ordering of charged point defects in aged ferroelectrics. Phase field model takes into account various energetic contributions involved in domain aging phenomenon, including chemical, domain wall, electrostatic and elastostatic energies, as well as domain-dependent internal electric field associated with the short-range ordering of charged point defects. The internal electric field strength is estimated by the computer simulation. Clausius–Clapeyron-type thermodynamic analysis of field-induced ferroelectric phase transition is used to evaluate aging-produced internal field strength from relevant experimental data, which is in agreement with the computer simulation.
Gap-crossing in fragmented habitats by mahogany gliders (Petaurus gracilis). Do they cross roads and powerline corridors?
Authors: Asari Yumiko , Johnson Christopher N. , Parsons Mark , Larson Johan
Published: March 2010

The mahogany glider (Petaurus gracilis) is one of the most threatened arboreal mammals in Australia. Although its habitat is affected by fragmentation, gap-crossing behaviour of the species has not been studied. A radio-tracking survey was undertaken on six individuals (three males, three females) in a woodland patch bisected by a 35.8-m-wide highway and a 31.5-m-wide powerline corridor, in north-east Queensland. The mean home ranges of males were 20.1 ± 3.3 ha, 21.3 ± 7.9 ha and 20.9 ± 8.2 ha, as measured by the Minimum Convex Polygon, Kernel and Harmonic Mean methods respectively. The mean home ranges of females were 8.9 ± 0.5 ha, 9.0 ± 4.2 ha and 8.8 ± 2.3 ha, as measured by the Minimum Convex Polygon, Kernel and Harmonic Mean methods respectively. Two males and one female were observed crossing linear gaps. However, there was less crossing than expected, and females were less likely to cross than males. One male used a narrow strip of woodland at the opposite side of the highway as supplemental habitat for foraging. This individual also used scattered trees in a grassland matrix for foraging or denning. Another male used a wooden power pole as a launching site to cross the highway. This study emphasises the importance of protecting large trees along linear barriers in open habitat, and suggests that gliding poles may be used to facilitate gap-crossing by mahogany gliders.
Forelimb musculature of kangaroos with particular emphasis on the tammar wallaby Macropus eugenii (Desmarest, 1817)
Authors: Harvey Kathryn J. , Warburton Natalie
Published: March 2010

Comparative morphological studies can provide insights into an animal’s ecology and evolutionary history. Functional morphological studies of the kangaroo forelimb are few in number and new work could provide novel tools to aid in the interpretation of fossil taxa and the understanding of the evolutionary history of kangaroos and marsupials as a whole. A description of the shoulder and forelimb musculature of the tammar wallaby (Macropus eugenii) with comparisons to the red kangaroo (Macropus rufus Desmarest, 1842), the western grey kangaroo (Macropus fuliginosus Desmarest, 1817) and the quokka (Setonix brachyurus Quoy & Gaimard, 1830) is presented. The species chosen were readily available and represent a range in size of the archetypal kangaroo form. Muscle maps of forelimb and shoulder muscles were constructed as an aid to comparing the spatial arrangement of muscle origins and insertions. The anatomical pattern of forelimb musculature in terrestrial macropodine kangaroos and wallabies is highly conservative. Functionally, the musculature of the forelimb corresponds to a supporting role of the limb during slow pentapedal locomotion. The illustrations of muscle insertions provided in this work will be a useful reference for future work in comparative marsupial anatomy and palaeobiology.
Hybridisation between dingoes and domestic dogs: a comment on Jones (2009)
Authors: Glen A. S.
Published: March 2010

The recent review by Jones (2009) presents a strong argument that Victoria’s wild dog population cannot reliably be categorised into dingoes (Canis lupus dingo), feral dogs (C. l. familiaris) and hybrids. This presents a problem in the light of the dingo’s recent listing as a threatened species in that state. Wildlife managers must come to grips with questions regarding the relative conservation value of ‘dingoes’ with varying degrees of domestic dog ancestry. This will require improved knowledge of the ecological function of wild dogs, as well as extensive research into public attitudes towards the animals.
A review of chemical, biological and fertility control options for the camel in Australia
Authors: Lapidge Steven J. , Eason Charlie T. , Humphrys Simon T.
Published: March 2010

Since their introduction to Australia in 1840 the one-humped camel, Camelus dromedarius, has gone from the colonist’s companion to a conservationist’s conundrum in the fragile arid ecosystems of Australia. Current management techniques are failing to curb present population growth and alternatives must be sought. This review assess the applicability of currently registered and developmental vertebrate pesticides and fertility control agents for camel control, as well as examining the potential usefulness of known C. dromedarius diseases for biological control. Not surprisingly, little is known about the lethality of most vertebrate pesticides used in Australia to camels. More has been published on adverse reactions to pharmaceuticals used in agriculture and the racing industry. An examination of the literature on C. dromedarius diseases, such as camel pox virus, contagious ecthyma and papillomatosis, indicates that the infections generally result in high morbidity but not necessarily mortality and this alone may not justify their consideration for use in Australia. The possibility exists that other undiscovered or unstudied biological control agents from other camilid species may offer greater potential for population control. As a long-lived species the camel is also not ideally suited to fertility control. Notwithstanding, anti-fertility agents may have their place in preventing the re-establishment of camel populations once they have been reduced through mechanical, biological or chemical means. Delivery of any generic chemical or fertility control agent will, however, require a species-tailored pathway and an appropriate large-scale deployment method. Accordingly, we put forward avenues of investigation to yield improved tools for camel control.
Perceptions of pastoralists and conservation reserve managers on managing feral camels and their impacts
Authors: Zeng B. , Edwards G. P.
Published: March 2010

The perceptions of people living within the current range of feral camels and involved in the pastoral industry and conservation reserve management were assessed through a questionnaire survey. The survey was designed to gauge understanding about the distribution and abundance of feral camels, perspective on camel impacts, and attitudes towards different camel management options. Camels occurred on 74.2% of pastoral properties and 51.4% of reserves that were surveyed. Camels were reported to be increasing on more than 50% of pastoral properties and 88% of reserves and were reported to cause damage on most properties where they occurred. The total monetary value of this damage (including management to mitigate it) was estimated to be $7.15 million per annum on the pastoral estate and $0.37 million per annum across the conservation estate within or on the margins of the camel range. On the pastoral estate, ~$2.40 million of the damage per annum was to infrastructure whereas production losses amounted to $3.42 million per annum. A minority of pastoral properties and reserves reported tangible benefits that accrued from selling camels, eating camels and using camels for natural resource management activities including weed control. The monetary value of the benefit was estimated to be about $0.58 million per annum across the pastoral estate, compared with ~$34 379 per annum across the conservation estate. Pastoralists and reserve managers generally saw a need to control camels and their impacts and currently play an active role in this regard. Both landholder groups favoured culling and commercial use to manage camel impacts but were comfortable using all of the available approaches and willing to consider new ones.
Evaluation of the impacts of feral camels
Authors: Edwards G. P. , Zeng B. , Saalfeld W. K. , Vaarzon-Morel P.
Published: March 2010

Feral camels have significant negative impacts on the environment and the social/cultural values of Aboriginal people. These impacts include damage to vegetation through feeding behaviour and trampling; suppression of recruitment in some plant species; damage to wetlands through fouling, trampling, and sedimentation; competition with native animals for food, water and shelter; damage to sites such as waterholes, that have cultural significance to Aboriginal people; destruction of bushfood resources; reduction in Aboriginal people’s enjoyment of natural areas; creation of dangerous driving conditions; damage to people and vehicles due to collisions, and being a general nuisance in remote settlements. Negative economic impacts of feral camels mainly include direct control and management costs, impacts on livestock production through camels competing with stock for food and other resources and damage to production-related infrastructure. The annual net impact cost of feral camels was estimated to be –$10.67 million for those elements that could be evaluated according to market values. We established a positive density/damage relationship for camels and infrastructure on pastoral properties, which is likely to hold true for environmental variables and cultural/social variables as well. Therefore, irrespective of climate change, the magnitude of the negative impacts of feral camels will undoubtedly increase if the population is allowed to continue to increase. Furthermore, the likelihood that camels would be epidemiologically involved in the spread of exotic diseases like bluetongue and surra (were there to be outbreaks of these diseases in Australia) is also very likely to increase with population density. On the basis of our present understanding, we recommend that feral camels be managed to a long-term target density of 0.1–0.2 camels/km2 at property to regional scales (areas in the order of 10 000–100 000 km2) in order to mitigate broad-scale negative impacts on the environmental, social/cultural and production assets of the Australian rangelands.
Distribution and abundance of the feral camel (Camelus dromedarius) in Australia
Authors: Saalfeld W. K. , Edwards G. P.
Published: March 2010

In this paper we utilised a range of data sources to estimate the extent, density distribution and population size of the feral camel in Australia in 2008. Camels currently occupy 3.3 million km2 and are spread across much of arid Western Australia, South Australia, the Northern Territory and far western Queensland. Up to 50% of Australia’s rangelands are reported as having camels present. The research reported here supports a current minimum population estimate for the feral camel in Australia of ~1 million animals at an overall density of 0.29 camels/km2. Densities vary, and the modelling of available data indicates that two substantial areas of high density are present, one centred on the Simpson Desert and the other on the Great Sandy Desert. The high density area covering the eastern part of the Great Sandy Desert has predicted densities in the range of 0.5 to >2 animals/km2 whereas that on the Simpson Desert is in the range 0.5–1.0 animals/km2.
Targeting the protein prenyltransferases efficiently reduces tumor development in mice with K-RAS-induced lung cancer
Authors: Liu Meng , Sjogren Anna-Karin M. , Karlsson Christin , Ibrahim Mohamed X. , Andersson Karin M. E. , Olofsson Frida J. , Wahlstrom Annika M. , Dalin Martin , Yu Huiming , Chen Zhenggang , Yang Shao H. , Young Stephen G. , Bergo Martin O.
Published: March 2010

RAS and RHO proteins, which contribute to tumorigenesis and metastasis, undergo posttranslational modification with an isoprenyl lipid by protein farnesyltransferase (FTase) or protein geranylgeranyltransferase-I (GGTase-I). Inhibitors of FTase and GGTase-I were developed to block RAS-induced malignancies, but their utility has been difficult to evaluate because of off-target effects, drug resistance, and toxicity. Moreover, the impact of FTase deficiency and combined FTase/GGTase-I deficiency has not been evaluated with genetic approaches. We found that inactivation of FTase eliminated farnesylation of HDJ2 and H-RAS, prevented H-RAS targeting to the plasma membrane, and blocked proliferation of primary and K-RAS
G12D
-expressing fibroblasts. FTase inactivation in mice with K-RAS-induced lung cancer reduced tumor growth and improved survival, similar to results obtained previously with inactivation of GGTase-I. Simultaneous inactivation of FTase and GGTase-I markedly reduced lung tumors and improved survival without apparent pulmonary toxicity. These data shed light on the biochemical and therapeutic importance of FTase and suggest that simultaneous inhibition of FTase and GGTase-I could be useful in cancer therapeutics.
Systematic discovery of nonobvious human disease models through orthologous phenotypes
Authors: McGary Kriston L. , Park Tae Joo , Woods John O. , Cha Hye Ji , Wallingford John B. , Marcotte Edward M.
Published: March 2010

Biologists have long used model organisms to study human diseases, particularly when the model bears a close resemblance to the disease. We present a method that quantitatively and systematically identifies nonobvious equivalences between mutant phenotypes in different species, based on overlapping sets of orthologous genes from human, mouse, yeast, worm, and plant (212,542 gene-phenotype associations). These orthologous phenotypes, or phenologs, predict unique genes associated with diseases. Our method suggests a yeast model for angiogenesis defects, a worm model for breast cancer, mouse models of autism, and a plant model for the neural crest defects associated with Waardenburg syndrome, among others. Using these models, we show thatSOX13regulates angiogenesis, and thatSEC23IPis a likely Waardenburg gene. Phenologs reveal functionally coherent, evolutionarily conserved gene networks—many predating the plant-animal divergence—capable of identifying candidate disease genes.
Out-of-equilibrium conformational cycling of GroEL under saturating ATP concentrations
Authors: Frank Gabriel A. , Goomanovsky Mila , Davidi Amit , Ziv Guy , Horovitz Amnon , Haran Gilad
Published: March 2010

The molecular chaperone GroEL exists in at least two allosteric states, T and R, that interconvert in an ATP-controlled manner. Thermodynamic analysis suggests that the T-state population becomes negligible with increasing ATP concentrations, in conflict with the requirement for conformational cycling, which is essential for the operation of molecular machines. To solve this conundrum, we performed fluorescence correlation spectroscopy on the single-ring version of GroEL, using a fluorescent switch recently built into its structure, which turns “on,” i.e., increases its fluorescence dramatically, when ATP is added. A series of correlation functions was measured as a function of ATP concentration and analyzed using singular-value decomposition. The analysis assigned the signal to two states whose dynamics clearly differ. Surprisingly, even at ATP saturation, ∼50% of the molecules still populate the T state at any instance of time, indicating constant out-of-equilibrium cycling between T and R. Only upon addition of the cochaperonin GroES does the T-state population vanish. Our results suggest a model in which the T/R ratio is controlled by the rate of ADP release after hydrolysis, which can be determined accordingly.
The phosphatase and tensin homolog regulates epidermal growth factor receptor (EGFR) inhibitor response by targeting EGFR for degradation
Authors: Vivanco Igor , Rohle Daniel , Versele Matthias , Iwanami Akio , Kuga Daisuke , Oldrini Barbara , Tanaka Kazuhiro , Dang Julie , Kubek Sara , Palaskas Nicolaos , Hsueh Teli , Evans Michael , Mulholland David , Wolle Daniel , Rajasekaran Sigrid , Rajasekaran Ayyappan , Liau Linda M. , Cloughesy Timothy F. , Dikic Ivan , Brennan Cameron , Wu Hong , Mischel Paul S. , Perera Timothy , Mellinghoff Ingo K.
Published: March 2010

The phosphatase and tensin homolog (PTEN) is a tumor suppressor that is inactivated in many human cancers. PTEN loss has been associated with resistance to inhibitors of the epidermal growth factor receptor (EGFR), but the molecular basis of this resistance is unclear. It is believed that unopposed phosphatidylinositol-3-kinase (PI3K) activation through multiple receptor tyrosine kinases (RTKs) can relieve PTEN-deficient cancers from their “dependence” on EGFR or any other single RTK for survival. Here we report a distinct resistance mechanism whereby PTEN inactivation specifically raises EGFR activity by impairing the ligand-induced ubiquitylation and degradation of the activated receptor through destabilization of newly formed ubiquitin ligase Cbl complexes. PTEN-associated resistance to EGFR kinase inhibitors is phenocopied by expression of dominant negative Cbl and can be overcome by more complete EGFR kinase inhibition. PTEN inactivation does not confer resistance to inhibitors of the MET or PDGFRA kinase. Our study identifies a critical role for PTEN in EGFR signal termination and suggests that more potent EGFR inhibition should overcome resistance caused by PI3K pathway activation.
Primary State Formation in the Virú Valley, North Coast of Peru
Authors: Millaire Jean-François
Published: March 2010

The origins of urban life and functioning states are two of the most fascinating research problems in anthropological archeology and a topic that has intrigued generations of scholars working on the Peruvian north coast. In this region, Andeanists have documented the rise of Moche as a dominant culture during the first millennium A.D., and the emergence of urban life and stately institutions at this society’s principal center. Although there is a broad consensus that Moche represents an archaic state, it is still unclear whether it is an example of primary state formation or a case of a second-generation state. To document this question, archaeological excavations were recently carried out at the Gallinazo Group site in the Virú Valley. Results from a radiocarbon dating program indicate that a functioning state probably emerged in this valley during the second century B.C., possibly preceding Moche by a few centuries. These results necessarily raise question regarding the nature of state development on the north coast of Peru and, in particular, whether there was a single center of state development in this region or multiple sites where similar conditions and processes led to the parallel emergence of functioning states.
Genomic arrangement of bacterial operons is constrained by biological pathways encoded in the genome
Authors: Yin Yanbin , Zhang Han , Olman Victor , Xu Ying
Published: March 2010

It is generally known that bacterial genes working in the same biological pathways tend to group into operons, possibly to facilitate cotranscription and to provide stoichiometry. However, very little is understood about what may determine the global arrangement of bacterial genes in a genome beyond the operon level. Here we present evidence that the global arrangement of operons in a bacterial genome is largely influenced by the tendency that a bacterium keeps its operons encoding the same biological pathway in nearby genomic locations, and by the tendency to keep operons involved in multiple pathways in locations close to the other members of their participating pathways. We also observed that the activation frequencies of pathways also influence the genomic locations of their encoding operons, tending to have operons of the more frequently activated pathways more tightly clustered together. We have quantitatively assessed the influences on the global genomic arrangement of operons by different factors. We found that the current arrangements of operons in most of the bacterial genomes we studied tend to minimize the overall distance between consecutive operons of a same pathway across all pathways encoded in the genome.
Revealing strengths and weaknesses of methods for gene network inference
Authors: Marbach Daniel , Prill Robert J. , Schaffter Thomas , Mattiussi Claudio , Floreano Dario , Stolovitzky Gustavo
Published: March 2010

Numerous methods have been developed for inferring gene regulatory networks from expression data, however, both their absolute and comparative performance remain poorly understood. In this paper, we introduce a framework for critical performance assessment of methods for gene network inference. We present an
in silico
benchmark suite that we provided as a blinded, community-wide challenge within the context of the DREAM (Dialogue on Reverse Engineering Assessment and Methods) project. We assess the performance of 29 gene-network-inference methods, which have been applied independently by participating teams. Performance profiling reveals that current inference methods are affected, to various degrees, by different types of systematic prediction errors. In particular, all but the best-performing method failed to accurately infer multiple regulatory inputs (combinatorial regulation) of genes. The results of this community-wide experiment show that reliable network inference from gene expression data remains an unsolved problem, and they indicate potential ways of network reconstruction improvements.
Annexin A1 regulates TGF-β signaling and promotes metastasis formation of basal-like breast cancer cells
Authors: de Graauw Marjo , van Miltenburg Martine H. , Schmidt Marjanka K. , Pont Chantal , Lalai Reshma , Kartopawiro Joelle , Pardali Evangelia , Le Dévédec Sylvia E. , Smit Vincent T. , van der Wal Annemieke , Van't Veer Laura J. , Cleton-Jansen Anne-Marie , ten Dijke Peter , van de Water Bob
Published: March 2010

Annexin A1 (AnxA1) is a candidate regulator of the epithelial- to mesenchymal (EMT)-like phenotypic switch, a pivotal event in breast cancer progression. We show here that AnxA1 expression is associated with a highly invasive basal-like breast cancer subtype both in a panel of human breast cancer cell lines as in breast cancer patients and that AnxA1 is functionally related to breast cancer progression. AnxA1 knockdown in invasive basal-like breast cancer cells reduced the number of spontaneous lung metastasis, whereas additional expression of AnxA1 enhanced metastatic spread. AnxA1 promotes metastasis formation by enhancing TGFβ/Smad signaling and actin reorganization, which facilitates an EMT-like switch, thereby allowing efficient cell migration and invasion of metastatic breast cancer cells.
In colorectal cancer mast cells contribute to systemic regulatory T-cell dysfunction
Authors: Blatner Nichole R. , Bonertz Andreas , Beckhove Philipp , Cheon Eric C. , Krantz Seth B. , Strouch Matthew , Weitz Juergen , Koch Moritz , Halverson Amy L. , Bentrem David J. , Khazaie Khashayarsha
Published: March 2010

T-regulatory cells (Treg) and mast cells (MC) are abundant in colorectal cancer (CRC) tumors. Interaction between the two is known to promote immune suppression or loss of Treg functions and autoimmunity. Here, we demonstrate that in both human CRC and murine polyposis the outcome of this interaction is the generation of potently immune suppressive but proinflammatory Treg (ΔTreg). These Treg shut down IL10, gain potential to express IL17, and switch from suppressing to promoting MC expansion and degranulation. This change is also brought about by direct coculture of MC and Treg, or culture of Treg in medium containing IL6 and IL2. IL6 deficiency in the bone marrow of mice susceptible to polyposis eliminated IL17 production by the polyp infiltrating Treg, but did not significantly affect the growth of polyps or the generation of proinflammatory Treg. IL6-deficient MC could generate proinflammatory Treg. Thus, MC induce Treg to switch function and escalate inflammation in CRC without losing T-cell–suppressive properties. IL6 and IL17 are not needed in this process.
High-
κ
oxide nanoribbons as gate dielectrics for high mobility top-gated graphene transistors
Authors: Liao Lei , Bai Jingwei , Qu Yongquan , Lin Yung-chen , Li Yujing , Huang Yu , Duan Xiangfeng
Published: March 2010

Deposition of high-
κ
dielectrics onto graphene is of significant challenge due to the difficulties of nucleating high quality oxide on pristine graphene without introducing defects into the monolayer of carbon lattice. Previous efforts to deposit high-
κ
dielectrics on graphene often resulted in significant degradation in carrier mobility. Here we report an entirely new strategy to integrate high quality high-
κ
dielectrics with graphene by first synthesizing freestanding high-
κ
oxide nanoribbons at high temperature and then transferring them onto graphene at room temperature. We show that single crystalline Al
2
O
3
nanoribbons can be synthesized with excellent dielectric properties. Using such nanoribbons as the gate dielectrics, we have demonstrated top-gated graphene transistors with the highest carrier mobility (up to 23,600 cm
2
/V·s) reported to date, and a more than 10-fold increase in transconductance compared to the back-gated devices. This method opens a new avenue to integrate high-
κ
dielectrics on graphene with the preservation of the pristine nature of graphene and high carrier mobility, representing an important step forward to high-performance graphene electronics.
Uncoupling of the transactivation and transrepression functions of PARP1 protein
Authors: Kotova Elena , Jarnik Michael , Tulin Alexei V.
Published: March 2010

Poly(ADP ribose) polymerase 1 (PARP1) is a nuclear protein that regulates chromatin remodeling and transcription as well as DNA repair and genome stability pathways. Recent studies have revealed a paradoxical dual role of PARP1 protein in transcription. Specifically, although PARP1 controls transcriptional activation of a subset of genes that are heat shock- or hormone-dependent, it also directly inactivates transcription, establishes heterochromatin domains, and silences retrotransposable elements. However, the domains required for these disparate functions are currently unknown. In this paper, we report the discovery of a previously undescribed mutation in the
Drosophila Parp
locus. We show that the mutants express a deletion mutant of PARP1 protein with an altered DNA binding domain that carries only the second Zn-finger. We demonstrate that this alteration specifically excludes PARP1 protein from heterochromatin and makes PARP1 unable to maintain repression of retrotransposable elements. By characterizing the biological activity of this unique PARP1 mutant protein isoform, we have uncoupled the transactivation and transrepression functions of this protein.
Mapping amorphous calcium phosphate transformation into crystalline mineral from the cell to the bone in zebrafish fin rays
Authors: Mahamid Julia , Aichmayer Barbara , Shimoni Eyal , Ziblat Roy , Li Chenghao , Siegel Stefan , Paris Oskar , Fratzl Peter , Weiner Steve , Addadi Lia
Published: March 2010

The continuously forming fin bony rays of zebrafish represent a simple bone model system in which mineralization is temporally and spatially resolved. The mineralized collagen fibrils of the fin bones are identical in structure to those found in all known bone materials. We study the continuous mineralization process within the tissue by using synchrotron microbeam x-ray diffraction and small-angle scattering, combined with cryo-scanning electron microscopy. The former provides information on the mineral phase and the mineral particles size and shape, whereas the latter allows high-resolution imaging of native hydrated tissues. The integration of the two techniques demonstrates that new mineral is delivered and deposited as packages of amorphous calcium phosphate nanospheres, which transform into platelets of crystalline apatite within the collagen matrix.