bluuebunny/crossref_metadata_2025 huggingface dataset:
Sheet carrier density enhancement by Si3N4 passivation on nonpolar a-plane (112¯) sapphire grown AlGaN∕GaN heterostructures
Authors: Arulkumaran S. , Selvaraj S. Lawrence , Egawa T. , Ng G. I.
Published: March 2008

The AlGaN∕GaN heterostructures (HSs) with high two dimensional electron gas mobility (1070cm2∕Vs) were grown on nonpolar a-plane (112¯0) sapphire substrate by metal organic chemical vapor deposition. High crystalline quality (reduced screw, edge, and mixed dislocations) with small root mean square surface roughness and small peak-valley distance values were observed in a-plane sapphire grown AlGaN∕GaN HSs. Hexagonal-GaN phase was also observed on a-plane sapphire grown AlGaN∕GaN HSs. An average increase of ns up to 22% for a plane and 26% for c plane were found after Si3N4 passivation. The product of ns and μH also increases for both a-plane (19%) and c-plane (28%) sapphire grown AlGaN∕GaN HSs in a wide range of measurement temperature (87–400K). The enhancement of sheet carrier density by Si3N4 passivation for nonpolar (112¯0) sapphire grown AlGaN∕GaN HSs is a useful result for the design of future GaN high-electron-mobility transistors.
Ion-modulated electrical conduction in polyaniline-based field-effect transistors
Authors: Li Yu-Chang , Lin Yu-Ju , Yeh Hong-Jian , Wen Ten-Chin , Huang Li-Ming , Chen Ying-Kuo , Wang Yeong-Her
Published: March 2008

The electrical characteristics of a field-effect transistor (FET) using bilayer water-soluble polymer electrolytes/conjugated polymer, that is, poly(ethyleneimine) (PEI)/polyaniline (PANI) doped with camphor sulfonic acid (CSA) structure, are discussed. The NH3+ cations from PEI were stuffed into the PANI-CSA to dedope nitrogen (imine) by applying gate voltage, and this results in the achievement of transistor behavior in drain current modulation. The PANI-CSA/PEI-based organic FETs working in depletion mode with a high field-effect mobility of ∼2.48cm2∕Vs at atmosphere conditions are demonstrated.
Loss budget of a setup for measuring mechanical dissipations of silicon wafers between 300 and 4K
Authors: Zendri J. P. , Bignotto M. , Bonaldi M. , Cerdonio M. , Conti L. , Ferrario L. , Liguori N. , Maraner A. , Serra E. , Taffarello L.
Published: March 2008

A setup for measuring mechanical losses of silicon wafers has been fully characterized from room temperature to 4K in the frequency range between 300Hz and 4kHz: it consists of silicon wafers with nodal suspension and capacitive and optical vibration sensors. Major contributions to mechanical losses are investigated and compared with experimental data scanning the full temperature range; in particular, losses due to the thermoelastic effect and to the wafer clamp are modeled via finite element method analysis; surface losses and gas damping are also estimated. The reproducibility of the measurements of total losses is also discussed and the setup capabilities for measuring additive losses contributed by thin films deposited on the wafers or bonding layers. For instance, assuming that additive losses are due to an 80-nm-thick wafer bond layer with Young modulus about ten times smaller than that of silicon, we achieve a sensitivity to bond losses at the level of 5×10−3 at 4K and at about 2kHz.
Double scaling limit for matrix models with nonanalytic potentials
Authors: Shcherbina Mariya
Published: March 2008

We study the double scaling limit for unitary invariant ensembles of random matrices with nonanalytic potentials and find the asymptotic expansion for the entries of the corresponding Jacobi matrix. Our approach is based on the perturbation expansion for the string equations. The first order perturbation terms of the Jacobi matrix coefficients are expressed through the Hastings–McLeod solution of the Painleve II equation. The limiting reproducing kernel is expressed in terms of solutions of the Dirac system of differential equations with a potential defined by the first order terms of the expansion.
The structure of classical extensions of quantum probability theory
Authors: Stulpe Werner , Busch Paul
Published: March 2008

On the basis of a suggestive definition of a classical extension of quantum mechanics in terms of statistical models, we prove that every such classical extension is essentially given by the so-called Misra–Bugajski reduction map. We consider how this map enables one to understand quantum mechanics as a reduced classical statistical theory on the projective Hilbert space as phase space and discuss features of the induced hidden-variable model. Moreover, some relevant technical results on the topology and Borel structure of the projective Hilbert space are reviewed.
Rotations of occupied invariant subspaces in self-consistent field calculations
Authors: Rubensson Emanuel H. , Rudberg Elias , Sałek Paweł
Published: March 2008

In this article, the self-consistent field (SCF) procedure as used in Hartree–Fock and Kohn–Sham calculations is viewed as a sequence of rotations of the so-called occupied invariant subspace of the potential and density matrices. Computational approximations are characterized as erroneous rotations of this subspace. Differences between subspaces are measured and controlled by the canonical angles between them. With this approach, a first step is taken toward a method where errors from computational approximations are rigorously controlled and threshold values are directly related to the accuracy of the current trial density, thus eliminating the use of ad hoc threshold values. Then, the use of computational resources can be kept down as much as possible without impairment of the SCF convergence.
High-resolution observations of an amorphous layer and subsurface damage formed by femtosecond laser irradiation of silicon
Authors: Crawford T. H. R. , Yamanaka J. , Botton G. A. , Haugen H. K.
Published: March 2008

Using transmission electron microscopy (TEM), we observed the micro- and nanostructures of silicon after irradiation by ∼150fs duration pulses centered at 800nm wavelength. Specimens irradiated with a single pulse of 11J∕cm2 fluence and with five pulses, each with a fluence of 1.3J∕cm2, exhibited various structures which included amorphous phases. The amorphous phases were pure silicon, as was revealed by high-resolution TEM imaging, nanobeam diffraction patterns, high-angle annular dark-field images, conventional diffraction images, and energy-dispersive x-ray spectra. Irradiation with a single pulse of 1.5J∕cm2 produced neither amorphous material nor lattice defects. Single-pulse irradiation at a fluence of 33J∕cm2 and irradiation by four pulses at 11J∕cm2 led to substantial subsurface damage around the center of the laser spot. It is concluded that multiple-pulse irradiation produces crystallographic damage more readily than a single pulse.
Investigation of metal nanoparticles on a Si surface using an x-ray standing wave field
Authors: Tiwari M. K. , Bhalerao G. M. , Babu M. , Sinha A. K. , Mukherjee C.
Published: March 2008

An x-ray standing wave field generated under total external reflection condition is used to characterize the average vertical dimension of metal nanoparticles as well as their nature of dispersion on a flat surface. This approach is applied to characterize the distribution of Fe nanoparticles deposited on a silicon surface using a solution dip method. The atomic force microscopy results on these nanoparticles reinforce our interpretation. The authors believe that the present method has a strong utility in characterizing, over a large area, the morphology of the surfaces coated with nanoparticles. The method also provides element specific analysis for the nanoparticulate matter.
High speed laser tomography system
Authors: Samsonov D. , Elsaesser A. , Edwards A. , Thomas H. M. , Morfill G. E.
Published: March 2008

A high speed laser tomography system was developed capable of acquiring three-dimensional (3D) images of optically thin clouds of moving micron-sized particles. It operates by parallel-shifting an illuminating laser sheet with a pair of galvanometer-driven mirrors and synchronously recording two-dimensional (2D) images of thin slices of the imaged volume. The maximum scanning speed achieved was 120000slices∕s, sequences of 24 volume scans (up to 256 slices each) have been obtained. The 2D slices were stacked to form 3D images of the volume, then the positions of the particles were identified and followed in the consecutive scans. The system was used to image a complex plasma with particles moving at speeds up to cm/s.
Photostability of electronically excited polyacenes: A case study of vibronic coupling in the naphthalene radical cation
Authors: Sivaranjana Reddy V. , Mahapatra S.
Published: March 2008

Novel issues of electronic nonadiabatic coupling in the excited state dynamics of prototypical naphthalene radical cation of polycyclic aromatic hydrocarbon of the polyacene family are theoretically investigated. A benchmark ab initio quantum dynamical study is performed and its complex vibronic spectra and nonradiative decay are examined. The findings are in very good accord with the experiment, unambiguously establishing the crucial role of intricate electron-nuclear coupling in the photoinduced dynamical processes of this system.
Hydrostatic compression and high-pressure elastic constants of coesite silica
Authors: Kimizuka Hajime , Ogata Shigenobu , Li Ju
Published: March 2008

Using density-functional theory, we computed all the independent elastic constants of coesite, a high-pressure polymorph of silica, as functions of pressure up to 15 GPa. The results are in good agreement with experimental measurements under ambient conditions. Also, the predicted pressure-dependent elastic properties are consistent with x-ray data in the literature concerning lattice strains at high pressures. We find that coesite, like quartz, exhibits a gradual softening of a shear modulus B44 with increasing pressure, in contrast to the rising bulk modulus.
Near-field second-harmonic generation in single gold nanoparticles
Authors: Zavelani-Rossi M. , Celebrano M. , Biagioni P. , Polli D. , Finazzi M. , Duò L. , Cerullo G. , Labardi M. , Allegrini M. , Grand J. , Adam P.-M.
Published: March 2008

Second-harmonic generation from single gold elliptical nanoparticles is experimentally investigated by a nonlinear scanning near-field optical microscope (SNOM). The near-field nonlinear response is found to be directly related to local surface plasmon resonances and to particle morphology. The combined analysis of linear and second-harmonic SNOM images provides discrimination among different light extinction particle behaviors, not achievable just with linear techniques. The polarization state of the emitted second harmonic is also investigated, providing experimental evidence of second-harmonic particle emission modes peculiar to near-field excitation.
Growth of In2O3(100) on Y-stabilized ZrO2(100) by O-plasma assisted molecular beam epitaxy
Authors: Bourlange A. , Payne D. J. , Egdell R. G. , Foord J. S. , Edwards P. P. , Jones M. O. , Schertel A. , Dobson P. J. , Hutchison J. L.
Published: March 2008

Thin films of In2O3 have been grown on Y-stabilized ZrO2(100) by oxygen plasma assisted molecular beam epitaxy with a substrate temperature of 650°C. Ordered epitaxial growth was confirmed by high resolution transmission electron microscopy. The position of the valence band onset in the x-ray photoemission spectra of the epitaxial films is found to be inconsistent with the widely quoted value of 3.75eV for the fundamental bandgap of In2O3 and suggests a revised value of 2.67eV.
Thermal chemical vapor deposition growth of zinc oxide nanostructures for dye-sensitized solar cell fabrication
Authors: Cheng An-Jen , Tzeng Yonhua , Zhou Yi , Park Minseo , Wu Tsung-hsueh , Shannon Curtis , Wang Dake , Lee Wonwoo
Published: March 2008

Dye-sensitized solar cells (DSSCs) were fabricated using a quasialigned one-dimensional zinc oxide (ZnO) nanostructure. The ZnO nanostructures were grown on indium tin oxide (ITO) coated glass substrate via a thermal chemical vapor deposition (CVD). It has been considered that thermal CVD is not suitable for the growth of ZnO nanostructure on ITO/glass due to the high processing temperature. However, we have demonstrated that a densely populated ZnO nanostructure can be prepared on ITO/glass substrate by a double-source double-tube CVD process. The power conversion efficiency of our device is 0.6%.
Impact of aluminum nitride as an insulator on the performance of zinc oxide thin film transistors
Authors: De Souza M. M. , Jejurikar S. , Adhi K. P.
Published: March 2008

The performance of zinc oxide thin film transistors with aluminium nitride (AlN) as insulator is presented. AlN reduces surface roughness of the interface by nearly thirty times in comparison to silicon dioxide and six times in comparison with silicon nitride. This results in an enhancement of mobility by nearly an order of magnitude. The interface states are correspondingly reduced, resulting in enhanced properties of subthreshold slope and on/off ratio.
Electro-optical properties of an orthoconic liquid crystal mixture (W-182) and its molecular dynamics
Authors: Nayek P. , Kundu S. , Roy S. K. , Pal Majumder T. , Bennis N. , Oton J. M. , Dabrowski R.
Published: March 2008

We observed that the perfect dark state problem could be solved by using orthoconic antiferroelectric liquid crystal (OAFLC) instead of normal AFLC by comparing the properties of isocontrast and dispersion chromaticity of W-182 OAFLC and normal AFLC CS-4001. We electro-optically observed that several subphases such as SmCγ*, SmC*β, SmC*α and antiferroelectric SmI*A phases exist in W-182 OAFLC. We dielectrically observed in 4μm thin cell that during heating, several new phases appeared. In the high temperature antiferroelectric region, a higher order than SmC* phase could be detected dielectrically, in the temperature range of 91–98°C, behaving similar to SmCγ* and also, another phase below SmC* region could be dielectrically detected in the temperature range of 103–1100°C, behaving similar to SmCα*, and an antiferroelectric, similar to SmIA* phase, was observed in the lower temperature region of the antiferroelectric phase; those are definitely arising due to surface force and interfacial charges interactions. We observed both PH and PL relaxation modes in both cells, although they differed in their strength and relaxation frequency. We studied extensively our observations of PH and PL modes in the antiferroelectric region, a Goldstone mode in the ferroelectric region and a soft mode in the ferroelectric region and SmA* phases.
Measurement of the specific heat capacity of water-based Al2O3 nanofluid
Authors: Zhou Sheng-Qi , Ni Rui
Published: March 2008

In this letter, we have presented an experimental investigation of the specific heat cp of water-based Al2O3 nanofluid with a differential scanning calorimeter. The result indicates that the specific heat cp of nanofluid decreases gradually as the nanoparticle volume fraction ϕ increases from 0.0% to 21.7%. The relationship between them exhibits good agreement with the prediction from the thermal equilibrium model [Eq. (2)]. The other simple mixing model [Eq. (1)] fails to predict the specific heat cp of nanofluid.
Tough Fe-based bulk metallic glasses
Authors: Lewandowski J. J. , Gu X. J. , Shamimi Nouri A. , Poon S. J. , Shiflet G. J.
Published: March 2008

The toughness of Fe-based bulk metallic glasses (BMGs) has been significantly improved via systematic changes in chemistry. Chemistry changes were selected based on their likely effects on critical elastic constants shown to affect plasticity/toughness in various BMGs, in addition to their recently discovered effects on chemical bonding in these Fe-based systems. The fracture energy obtained on notched toughness samples tested in mode I was correlated with chemistry-induced changes to Poisson’s ratio ν and the ratio of the elastic shear modulus μ to the bulk modulus B, as was the strain energy at fracture for smooth cylindrical compression samples that failed under mode II conditions. Fractographic observations correlate well with the observed increases in toughness.
Origin of green emission from ZnS nanobelts as revealed by scanning near-field optical microscopy
Authors: Tsuruoka T. , Liang C. H. , Terabe K. , Hasegawa T.
Published: March 2008

The emission properties of ZnS nanobelts synthesized through thermal evaporation were investigated by means of scanning near-field optical microscopy. The photoluminescence (PL) images of single nanobelts exhibited a bright line along their length. The local light emission spectra measured over the bright lines showed a green emission peak around 535nm, which was in good agreement with a PL peak obtained for an ensemble of the nanobelts. From careful scanning-electron-microscopy observations of identical nanobelts, we found that the observed green emission is related to line or planar defects of the ZnS nanobelts.
Influence of H2O and O2 on threshold voltage shift in organic thin-film transistors: Deprotonation of SiOH on SiO2 gate-insulator surface
Authors: Kumaki Daisuke , Umeda Tokiyoshi , Tokito Shizuo
Published: March 2008

The influence of H2O and O2 on the transistor characteristics in p- and n-type organic thin-film transistors (OTFTs) fabricated on the SiO2 gate insulator was investigated. In both p- and n-type OTFTs, the threshold voltage (Vth) shifted drastically to positive direction after exposure to ambient air and dry air, although the field-effect mobilities in saturation regime were almost unchanged before and after the Vth shift. The Vth shifts to the positive direction indicate that negative charges are generated on the SiO2 gate-insulator surface by exposure to ambient air and dry air. The influence of SiO− on the gate-insulator surface and deprotonation processes of SiOH caused by H2O and O2 were discussed as the origin of the significantly positive Vth shift.
Optical second harmonic generation from the twin boundary of ZnO thin films grown on silicon
Authors: Lo Kuang-Yao , Lo Shih-Chieh , Yu Chang-Feng , Tite Teddy , Huang Jung-Y. , Huang Yi-Jen , Chang Ren-Chuan , Chu Sheng-Yuan
Published: March 2008

The symmetry of the twin boundaries of ZnO epitaxial film was detected with reflective second harmonic generation (RSHG). The twin boundaries exhibit mirror symmetry with a polar configuration across the boundary plane and yield a nonvanishing polar contribution to RSHG. The nonvanishing second-order susceptibility supports the notion that the measured RSHG originates from the planar defect, which depends on the residual stress in the thin film. We analyzed our RSHG result by correlating the macroscopic data from optic probe with the microscopic data from tunneling electron microscope.
Mitigating Climate Change through Green Buildings and Smart Growth
Authors: Brown Marilyn A , Southworth Frank
Published: March 2008

Energy-efficient buildings are seen by climate change experts as one of the least-cost approaches to mitigating greenhouse gas emissions. This paper summarizes a study carried out for the Pew Center on Global Climate Change that takes a broader look at the potential role of a climate-friendly built environment including not only considerations of how buildings are constructed and used, but also how they interface with the electric grid and where they are located in terms of urban densities and access to employment and services. In addition to summarizing mechanisms of change (barriers and drivers) the paper reviews a set of policies that could bring carbon emissions in the building sector in 2025 almost back to 2004 levels. By the middle of the century the combination of green buildings and smart growth could deliver the deeper reductions that many believe are needed to mitigate climate change.
Aboriginal Settlement Patterns in Canadian Cities: Does the Classic Index-Based Approach Apply?
Authors: Starchenko Oksana , Peters Evelyn J
Published: March 2008

Based on the evidence obtained in qualitative studies, Massey and Denton argued in their 1988 paper (“The dimensions of residential segregation” Social Forces67 281–315) that the residential segregation of ethnic or racialized groups is a complex and multidimensional phenomenon and, therefore, should be measured along several dimensions simultaneously. In a systematic review and analysis of all segregation measures proposed to that date, they identified five conceptually distinct dimensions of ethnic segregation—evenness, exposure, concentration, centralization, and clustering—and ‘best indices’ to measure them. This index-based approach has achieved a ‘canonical’ status and has been employed in numerous studies of segregation patterns. However, it is often overlooked that the structure of ethnic residential segregation uncovered by Massey and Denton is specific to the context in which segregation takes place—that is, the residential segregation of ethnic and racialized groups in US cities. This paper attempts to assess the utility of Massey and Denton's five-dimensional structure of segregation for the study of settlement patterns of Aboriginal people in Canadian metropolitan areas. We find that the application of the Massey and Denton model to the urban Aboriginal population in Canadian cities produces a significantly different structure of segregation.
Accommodating Open Plan: Children, Clutter, and Containment in Suburban Houses in Sydney, Australia
Authors: Dowling Robyn
Published: March 2008

Open-plan living areas are one of the defining features of contemporary suburban architecture in spatially expansive nations like Australia, the United States, and Canada. In these contexts, the European and modernist meanings of ‘open plan’ are joined by relations between parents and children and identities associated with motherhood and homemaking. Using a feminist and material-culture analysis of the practices of living open plan in this distinctive historical and geographical context, this paper offers a different interpretation of the social significance of the open-planned domestic interior. Drawing on research conducted with residents of new, open-planned houses on the outskirts of Sydney and, in particular, mothers' narratives of the materialities of their home and the place of children and open plan within it, I show how open plan is held together, as a material and imaginative space, by a balancing of aesthetic considerations and the materiality and anxieties produced by children. The processes of living open plan entailed accommodating family ideals and practices to suit the house and/or altering the house to suit the family: banishing children from open-plan areas to maintain their simplicity; embracing children's presence; placing furniture to enclose it; knocking out walls to open it.
A Neural Turn? On the Ontology of the Geographical Subject
Authors: Korf Benedikt
Published: March 2008

The modernist conception of the autonomous ‘subject’ as centred, sovereign, and coherently rational, acting intentionally, knowledgeably, and volitionally, has been challenged from a variety of sources, including poststructuralism, feminism, and posthumanism. A different kind of attack on the modernist subject has recently been staged by neurobiologists who have started to decentre the subject from within—to ‘naturalise’ (and materialise) the subject. This biological naturalism—the new ‘life sciences’—claims to challenge our conceptions of self, the ethical subject, and what we conceive of as ‘life’. But what conceptions we have of the configurations of the self is fundamental to our understandings and conceptions of ethics. This paper traces a debate between German neurobiologists and (post)humanist philosophers on the ontology of such things as ‘free will’, ‘ethical agency’, and the ‘self’ as an example of how the dispute between naturalists and nonnaturalist or postnaturalists is instrumental in sharpening our understanding of the self and of ethical agency. The paper argues that naturalism is bound to fail due to its inability to grasp the intersubjectivist nature of ethical agency, a theme which links up with recent geographical writing on ethics. I suggest, building on a recent contribution of Huib Ernste in this journal, that we should consider Helmuth Plessner's concept of eccentric positionality and ontology of the possible as a postmetaphysical kind of ethical humanism.
The ‘Skyscraper Settlement’: Home and Residence at Christodora House
Authors: Blunt Alison
Published: March 2008

The author develops a house biography of Christodora House, New York City, to investigate the relationships between the built form of a settlement house and new forms of residence within it. Settlement houses were founded from the 1880s as centres of neighbourhood welfare and social work, and housed resident workers in the poorest parts of cities. Founded in 1897, Christodora House occupied a purpose-built ‘skyscraper’ on Tompkins Square from 1928 to 1948. This building not only provided new and modern accommodation for settlement work, but also incorporated new forms of housing. The author considers the ways in which the building itself—both as ‘house’ and as ‘skyscraper’—was not only shaped by, but also recast, embodied practices of settlement, inhabitation, and domestic life. As a skyscraper built for settlement work, Christodora House represented a new, but ultimately unsuccessful, form of dwelling in the city.
Novel Festuca arundinacea Shreb. and Dactylis glomerata L. germplasm to improve adaptation for marginal environments
Authors: Harris C. A. , Clark S. G. , Reed K. F. M. , Nie Z. N. , Smith K. F.
Published: March 2008

Tall fescue (Festuca arundinacea Schreb., Lolium arundinceum Schreb., S.J. Darbyshire) and cocksfoot (Dactylis glomerata L.) were identified for improvement for low to medium rainfall (400–700 mm) environments where persistence of common cultivars has been unreliable. Over 200 accessions and experimental varieties of tall fescue and cocksfoot sourced from the Mediterranean basin were screened over 2 years at sites on the North-West Slopes of NSW and on the Central Highlands of Victoria, respectively. These were compared with some locally naturalised plants and most of the cultivars available in Australasia as well as cultivars developed for warm temperate and Mediterranean climates in Italy, France, Uruguay and the USA. To date, the screened accessions and experimental varieties have exhibited varying degrees of summer activity and other attributes of commercial value.
Six tall fescue accessions were selected for development of synthetic varieties. These included three Sardinian accessions that after 2 years had superior persistence to cv. Demeter and recorded the highest yield scores, the mean of which exceeded that of the best performing cultivars by 34% and that of Demeter by 64%. A further three select North African accessions of tall fescue had similar yield ratings to Demeter and that of the best performing winter-active, summer-dormant cultivars.
After 2 years, four Mediterranean accessions of cocksfoot were selected. These had recorded the highest yield scores, the mean of which was 34% greater than that recorded for the highest yielding cultivars and 40% greater than cv. Currie, compared with which these accessions were densely tillered and fine-leafed. The four select Mediterranean cocksfoot accessions exhibited 100% persistence; the persistence of the cultivars ranged from 31–97%.
Select plants of the best performing accessions were subsequently removed from the field sites and transferred to pollen-proof glasshouse chambers for synthesis of experimental varieties. The endophyte-free tall fescue synthetics were based on Sardinian accessions selected for year round production and persistence or North African accessions that had similar yield to Demeter but with improved winter production and some summer activity. The cocksfoot synthetics were based on select plants of accessions from North Africa and included both D. glomerata and D. glomerata ssp. glomerata × spp. hispanica hybrids exhibiting persistence, dense tillering and seasonal productivity.
Herbage mass and persistence of pasture legumes and grasses at two potentially different saline and waterlogging sites in northern New South Wales
Authors: Boschma S. P. , Lodge G. M. , Harden S.
Published: March 2008

Two adjacent sites (a naturalised pasture and a previously cropped area) with differing potentials for salinity/sodicity and waterlogging near Tamworth, New South Wales were sown with temperate perennial grasses and legumes, temperate annual legumes and tropical perennial grasses to assess their herbage mass and persistence from 2003 to 2006. Plots were either grazed or mown seasonally. Days to flower in the establishment year and seedling regeneration were assessed each year for the annual legumes. In May 2003, salinity levels at soil depths >0.6 m were as high as 8 and 12 dS/m at the naturalised pasture and previously cropped sites, respectively, but generally were >5 and >3 dS/m at a soil depth of 0–0.10 m for these sites in 2004–05. With below average rainfall, no waterlogging was observed at the previously cropped site and only short-term waterlogging of a few days duration occurred at the naturalised pasture site. Under these conditions Puccinellia ciliata cv. Menemen did not establish or perform well, but Thinopyrum ponticum (cvv. Dundas and Tyrrell) was productive and persistent compared with Phalaris aquatica. At both sites, Digitaria eriantha cv. Premier and Chloris gayana cv. Katambora were the best tropical grasses, while the performance of Bothriochloa bladhii subsp. glabra cv. Swann was good at the previously cropped site and Panicum coloratum subsp. makarikariense cv. Bambatsi was best at the naturalised pasture site. At both sites, Medicago sativa had the highest herbage mass and persistence, with cv. Aquarius being superior to cv. Salado after 3 years. Compared with M. sativa, the herbage mass and persistence of Trifolium fragiferum was low. Of the annual legumes, M. polymorpha cv. Scimitar and Melilotus sulcatus had the highest herbage mass.
An environmental weed risk assessment model for Australian forage improvement programs
Authors: Stone Lynley M. , Byrne Margaret , Virtue John G.
Published: March 2008

Many plant species with agronomic potential have been introduced for livestock forage and have subsequently become weeds of natural ecosystems, or ‘environmental weeds’. Stringent border quarantine procedures introduced by Australia in 1997 ensure few high weed risk species are now imported into the country; however, there are no protocols for assessing and managing weed risk in use on a national scale ‘post-border’ (i.e. once a plant species is in the country). Environmental weed risk management in forage improvement programs aims to minimise the risk that new species and cultivar introductions will be invasive in natural ecosystems. We describe an environmental weed risk assessment (EWRA) model specifically aimed at assessing the weed potential of exotic and native forage species. The EWRA model predicts and ranks species for weed risk by assessing invasiveness, impacts and potential distribution. Assessments are based on published evidence, experimental observations and intuitive responses from experienced pasture researchers, in collaboration with weed experts. This model specifically addresses the need for environmental weed risk management in forage improvement programs.
Field evaluation of perennial grasses and herbs in southern Australia. 2. Persistence, root characteristics and summer activity
Authors: Nie Z. N. , Miller S. , Moore G. A. , Hackney B. F. , Boschma S. P. , Reed K. F. M. , Mitchell M. , Albertsen T. O. , Clark S. , Craig A. D. , Kearney G. , Li G. D. , Dear B. S.
Published: March 2008

Field experiments were carried out at seven sites in southern Australia from 2002 to 2006 to measure changes in plant frequency, root characteristics and summer activity for a range of grass and herb species or cultivars. Annual rainfall during the experimental period was on average 75 mm lower than the long-term average. Plant frequency differed significantly between species and between sites. Temperate grasses generally had higher frequencies than subtropical grasses, native grasses and herbs. Cocksfoot (Dactylis glomerata cvv. Currie, Porto), tall wheat grass (Thinopyrum ponticum cv. Dundas), winter-active tall fescue (Festuca arundinacea cvv. Fraydo, Resolute MaxP) and phalaris (Phalaris aquatica cvv. Atlas PG, Australian) were the most persistent of the temperate perennial species over the experimental period. The frequency of most cultivars declined from year 2 to year 4 after establishment, but the frequency of kikuyu (Pennisetum clandestinum cv.Whittet) and wallaby grass (Austrodanthonia richardsonii cv. Taranna) increased by over 5% from year 2 to year 3, and cocksfoot (cv. Currie) increased from year 3 to year 4. At two sites where measurements were made, there were significant differences in rooting depth between species. Whittet kikuyu was the deepest among all species with a rooting depth of up to 2 m, followed by phalaris, tall fescue, grazing brome (Bromus stamineus) and tall wheat grass. Root density was affected by plant genotype and soil structure. Root density of the species varied significantly in the subsoil (0.1–1.1 m) and deeper subsoil (1.1–2 m) but not in the topsoil (0–0.1 m). Green-leafiness over summer was generally higher for subtropical grasses, native grasses, herbs and some summer-active temperate grasses, than most temperate grasses with high summer dormancy.
Tolerance of aluminium toxicity in annual Medicago species and lucerne
Authors: Scott B. J. , Ewing M. A. , Williams R. , Humphries A. W. , Coombes N. E.
Published: March 2008

A rapid (7 day) solution-based screening test was developed using 15 annual Medicago cultivars and one M. sativa. Based on a relative root regrowth after exposures to aluminium (Al), Zodiac (M. murex), Orion (M. sphaerocarpos) and the M. polymorha cultivars Santiago, Cavalier and Serena had the greatest Al tolerance. Herald (M. littoralis) and Rivoli (M. tornata) were most sensitive. Ranking for Al tolerance from the solution culture correlated well (r = 0.80) with ranking for tolerance of the 16 genotypes grown in an acidic soil (unlimed pHCa 4.1). We screened 17 Australian populations of lucerne (M. sativa) using a 24 h ‘pulse’ of 75 µmol/L Al, and a three day ‘recovery’ of 10 µmol/L Al. We identified and recovered plants with a root regrowth of ≥5 mm in all 17 populations with selection intensities of 2 to 4%.
Four of these selected populations (Aurora, UQL-1, A513 and TO2-011) were polycrossed within each population to produce four populations of seed from the cycle 1 selections. The length of root regrowth under Al stress was improved for all four populations of cycle 1 selection (P ≤ 0.001; from 2.6 mm for the original populations to 6.3 mm for the cycle 1 selections). In a subsequent experiment the cycle 2 selections from Aurora, UQL-1 and TO2-011 had significantly greater root regrowth than both the cycle 1 selections (P ≤ 0.001; 8.3 cf. 6.6 mm) and the unselected populations (3.0 mm). The selections from TO2-011 appeared to have greater improvement in the average length of root regrowth after 2 cycles of selection. Selected germplasm was more tolerant than GAAT in our evaluation. Based on estimation of realised heritability, it seemed likely that higher selection intensities would give more rapid improvements in tolerance. Our studies have not investigated the physiological basis of any tolerance of Al which we observed.
Improving lucerne nodulation at low pH: contribution of rhizobial and plant genotype to the nodulation of lucerne seedlings growing in solution culture at pH 5
Authors: Charman N. , Ballard R. A. , Humphries A. W. , Auricht G. C.
Published: March 2008

The effect of rhizobial strain and lucerne genotype on the nodulation of lucerne seedlings growing in solution cultures maintained at pH 5 was measured in two greenhouse experiments. Sinorhizobium strain SRDI291 increased the percentage of plants nodulated when compared with the commercial inoculant strain RRI128 (89% cf. 45% and 86% cf. 23% in the two experiments, respectively). Similarly, the mean number of nodules per nodulated plant (NNP) was greatest in the SRDI291 treatments (3.5 cf. 1.7 and 3.1 cf. 1.8). Plant genotype had fewer, but still significant effects on nodulation. Overall, lucerne genotype CRCSA29 had the highest percentage of plants forming nodules and most NNP (63% and 2.9); genotype L97a had the lowest (46% and 1.9). Greater variation in NNP occurred when the lucerne genotypes were inoculated with RRI128. Most notable was the better nodulation of CRCSA29 with 2.8 NNP compared with only 1.2 NNP for the two unselected genotypes (SARDI Ten and L97a). The lucerne genotypes typically had variable NNP, as exemplified in CRCSA29 inoculated with RRI128 where it ranged from 0–14, providing the opportunity for further plant selection. The work demonstrates that there remains substantial opportunity to increase the potential of lucerne to nodulate at low pH. Gains would appear to be most easily made by changing the strain of rhizobia that is used for inoculation.
Production and persistence of temperate perennial grasses and legumes at five saline sites in southern Australia
Authors: Nichols P. G. H. , Rogers M. E. , Craig A. D. , Albertsen T. O. , Miller S. M. , McClements D. R. , Hughes S. J. , D'Antuono M. F. , Dear B. S.
Published: March 2008

Herbage production and persistence of 24 perennial legumes from 20 species and 19 perennial grasses from 10 species were measured at five sites across southern Australia that differed in annual rainfall and extent of salinity and waterlogging. At Cranbrook, Western Australia, a site with occasional waterlogging and a summer salinity [estimated by electrical conductivity (ECe)] of 6.9 dS/m in the surface 10 cm of soil, strawberry clover (Trifolium fragiferum L.) and Lotus uligonosis Schkuhr produced 2.7 t/ha in the second year and had the highest legume plant frequencies in year 3, while herbage production of L. tenuis Waldst. & Kit. ex Willd. and L. corniculatus L. was not significantly lower. No grasses produced more than 0.3 t/ha in the second year, but tall wheatgrass (Thinopyrum ponticum (Podp.) Z.-W. Liu & R.-C. Wang) was the most persistent. At Girgarre, Victoria, another site with occasional waterlogging and a summer ECe of 8.0 dS/m, phalaris (Phalaris aquatica L.) produced 8.5 t/ha in the second year, while production of tall wheatgrass and perennial ryegrass (Lolium perenne L.) was not significantly lower. Sulla (Hedysarum coronarium L.) was the only legume that produced more than 1 t/ha. Phalaris, tall wheatgrass and sulla had the highest densities in the third year. At Duranillin (Western Australia) and Keith (South Australia), which both experienced extensive winter waterlogging and had summer ECe >30 dS/m, puccinellia (Puccinellia ciliata Bor) and tall wheatgrass were the only grass or legume species that persisted beyond the first summer. Puccinellia was the only species to produce useful quantities of herbage (1.0 t/ha) in year 3 at Duranillin. No perennial grasses or legumes produced more than 0.35 t/ha in either year 2 or year 3 at Tammin, Western Australia, the lowest rainfall site (330 mm mean annual rainfall) with summer ECe of 10.9 dS/m. Genotypic differences within sites were indicated for several species, suggesting opportunities to develop cultivars better adapted to saline soils
Evidence for olfactory search in wandering albatross,
Diomedea exulans
Authors: Nevitt Gabrielle A. , Losekoot Marcel , Weimerskirch Henri
Published: March 2008

Wandering albatrosses (
Diomedea exulans
) forage over thousands of square kilometers of open ocean for patchily distributed live prey and carrion. These birds have large olfactory bulbs and respond to fishy-scented odors in at-sea trials, suggesting that olfaction plays a role in natural foraging behavior. With the advent of new, fine-scale tracking technologies, we are beginning to explore how birds track prey in the pelagic environment, and we relate these observations to models of odor transport in natural situations. These models suggest that odors emanating from prey will tend to disperse laterally and downwind of the odor source and acquire an irregular and patchy concentration distribution due to turbulent transport. For a seabird foraging over the ocean, this scenario suggests that olfactory search would be facilitated by crosswind flight to optimize the probability of encountering a plume emanating from a prey item, followed by upwind, zigzag flight to localize the prey. By contrast, birds approaching prey by sight would be expected to fly directly to a prey item, irrespective of wind direction. Using high-precision global positioning system (GPS) loggers in conjunction with stomach temperature recorders to simultaneously monitor feeding events, we confirm these predictions in freely ranging wandering albatrosses. We found that initial olfactory detection was implicated in nearly half (46.8%) of all flown approaches preceding prey-capture events, accounting for 45.5% of total prey mass captured by in-flight foraging. These results offer insights into the sensory basis for area-restricted search at the large spatial scales of the open ocean.
Merging two gene-expression studies via cross-platform normalization
Authors: Shabalin Andrey A. , Tjelmeland Håkon , Fan Cheng , Perou Charles M. , Nobel Andrew B.
Published: March 2008

Motivation: Gene-expression microarrays are currently being applied in a variety of biomedical applications. This article considers the problem of how to merge datasets arising from different gene-expression studies of a common organism and phenotype. Of particular interest is how to merge data from different technological platforms.

Results: The article makes two contributions to the problem. The first is a simple cross-study normalization method, which is based on linked gene/sample clustering of the given datasets. The second is the introduction and description of several general validation measures that can be used to assess and compare cross-study normalization methods. The proposed normalization method is applied to three existing breast cancer datasets, and is compared to several competing normalization methods using the proposed validation measures.

Availability: The supplementary materials and XPN Matlab code are publicly available at website: https://genome.unc.edu/xpn

Contact:  shabalin@email.unc.edu

Supplementary information: Supplementary data are available at Bioinformatics online.
Carolina Foxtail (Alopecurus carolinianus): Susceptibility and Suitability as an Alternative Host to Rice Blast Disease (Magnaporthe oryzae [formerly M. grisea])
Authors: Jia Y. , Gealy D. , Lin M. J. , Wu L. , Black H.
Published: March 2008

Carolina foxtail (Alopecurus carolinianus) has not been reported to host Magnaporthe oryzae. A collection of Carolina foxtail obtained from several Arkansas locations over a 4-year period was inoculated with four races of the fungus under greenhouse conditions and, in all cases, inoculation resulted in the formation of irregular, yellow and brown lesions without obvious gray centers that are characteristic for blast on rice. Differences in these lesions were not observed among our collection. These lesions appeared to differ from typical blast lesions on inoculated rice leaves but were evident following artificial inoculation of Carolina foxtail in the greenhouse. M. oryzae races that differed in pathogenicity toward rice cultivars also displayed differences in lesion development on Carolina foxtail. The most virulent race on rice cultivars also produced lesions most rapidly on Carolina foxtail. These lesions developed more quickly on Carolina foxtail than on the most susceptible rice cultivars tested, including a susceptible California cultivar, M202. M. oryzae isolates cultured from these lesions in the infected Carolina foxtail caused typical disease symptoms of blast on inoculated rice cultivars. We suggest that Carolina foxtail is a new and previously unrecognized host for the blast pathogen.
Visual Rating and the Use of Image Analysis for Assessing Different Symptoms of Citrus Canker on Grapefruit Leaves
Authors: Bock C. H. , Parker P. E. , Cook A. Z. , Gottwald T. R.
Published: March 2008

Citrus canker is caused by the bacterial pathogen Xanthomonas axonopodis pv. citri and infects several citrus species in wet tropical and subtropical citrus growing regions. Accurate, precise, and reproducible disease assessment is needed for monitoring epidemics and disease response in breeding material. The objective of this study was to assess reproducibility of image analysis (IA) for measuring severity of canker symptoms and to compare this to visual assessments made by three visual raters (VR1-3) for various symptom types (lesion numbers, % area necrotic, and % area necrotic+chlorotic), and to assess inter- and intra-VR reproducibility. Digital images of 210 citrus leaves with a range of symptom severity were assessed on two separate occasions. IA was more precise than VRs for all symptom types (inter-assessment correlation coefficients, r, for lesion numbers by IA = 0.99, by VRs = 0.89 to 0.94; for %, r for % area necrotic+chlorotic for IA = 0.97 and for VRs = 0.86 to 0.89; and r for % area necrotic for IA = 0.96 and for VRs = 0.74 to 0.85). Accuracy based on Lin's concordance coefficient also followed a similar pattern, with IA being most consistently accurate for all symptom types (bias correction factor, Cb = 0.99 to 1.00) compared to visual raters (Cb = 0.85 to 1.00). Lesion number was the most reproducible symptom assessment (Lin's concordance correlation coefficient, ρc, = 0.76 to 0.99), followed by % area necrotic+chlorotic (ρc = 0.85 to 0.97), and finally % area necrotic (ρc = 0.72 to 0.96). Based on the “true” value provided by IA, precision among VRs was reasonable for number of lesions per leaf (r = 0.88 to 0.94), slightly less precision for % area necrotic+chlorotic (r = 0.87 to 0.92), and poorest precision for % area necrotic (r = 0.77 to 0.83). Loss in accuracy was less, but showed a similar trend with counts of lesion numbers (Cb = 0.93 to 0.99) which was more consistently accurately reproduced by VRs than either % area necrotic (Cb = 0.85 to 0.99) or % area necrotic+chlorotic (Cb = 0.91 to 1.00). Thus, visual raters suffered losses in both precision and accuracy, with loss in precision estimating % area necrotic being the greatest. Indeed, only for % area necrotic was there a significant effect of rater (a two-way random effects model ANOVA returned a P < 0.001 and 0.016 for rater in assessments 1 and 2, respectively). VRs showed a marked preference for clustering of % area severity estimates, especially at severity >20% area (e.g., 25, 30, 35, 40, etc.), yet VRs were prepared to estimate disease of <1% area, and at 1% increments up to 20%. There was a linear relationship between actual disease (IA assessments) and VRs. IA appears to provide a highly reproducible way to assess canker-infected leaves for disease, but symptom characters (symptom heterogeneity, coalescence of lesions) could lead to discrepancies in results, and full automation of the system remains to be tested.