bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of interaction mechanisms in nanocomposite PtCo permanent magnetic alloy
Authors: Tao Liu , Wei Li , Jiajie Li , Aru Yan , Minggang Zhu
Published: April 2011

The effect of the atomic disorder–order transformation on the interaction mechanisms in isotropic PtCo alloys has been studied by isothermal annealing at 953 K, well below the transformation temperature, for 5–30 min after quenching from 1273 K. The transmission electron microscopy (TEM) testing showed that the ordered regions grew with prolonging heat treatment time. Investigation of the interaction mechanisms in PtCo alloys has been made using analysis of the δM(H) plot. The results of the δM(H) plot and TEM indicate that the interaction mechanisms are changed by the size of the magnetically soft and hard phases. The Kneller–Hawig model was used to explain the continuously changing degree of exchange coupling between the magnetically soft and hard phases.
Nd–Fe–B thick film magnets with Nb additive prepared by vacuum arc deposition method
Authors: Nakano M. , Sahara M. , Yanai T. , Yamashita F. , Fukunaga H.
Published: April 2011

Isotropic Nd–Fe–B thick film magnets were prepared by a vacuum arc deposition method with the deposition rate of approximately 10 μm/h followed by pulse-annealing process. It was found that an optimum amount of Nb additive is effective to enhance the coercivity without the deterioration of remanence and (BH)max values of the isotropic thick films.
The microstructure and magnetization behaviors of (Pr8.2Fe86.1−xCoxB5.7)0.99Zr0.01 (x = 0–10) nanocomposite magnets
Authors: Chen Renjie , Guo Shuai , Wang Jinzhi , Lee Don , Yan Aru
Published: April 2011

Nanocomposite (Pr8.2Fe86.1−xCoxB5.7)0.99Zr0.01 (x = 0–10) ribbons consisting of Pr2(Fe,Co)14B and α-(Fe,Co) phases were prepared by a melt-spun technique. The microstructure and magnetic properties were studied. The results show that the Curie temperature increases drastically with increasing Co content. The optimal permanent magnetic properties are obtained at x = 2, and the value of Hci, Ms, Mr, and (BH)max are 6.52 kOe, 150.2 emu/g, 120.9 emu/g, and 22.34 MGOe, respectively. Typical magnetization behaviors of nanocomposite magnets are found in these ribbons. The significant remanence enhancement indicates that a strong intergrain exchange coupling exists in all ribbons studied in this work. By Co substitution, the intergrain exchange coupling is enhanced significantly. The study of microstructure shows that the larger grains of Pr2(Fe,Co)14B hard phase are surrounded by the smaller grains of α-(Fe,Co) soft phase with size about 10–20 nm in the ribbon with Co substitution. This kind of microstructure is in favor of exchange coupling between magnetically hard and soft phases and results in excellent magnetic properties.
Fluid electrons with kinetic closure for long wavelength energetic particles driven modes
Authors: Chen Yang , Parker Scott E.
Published: April 2011

A kinetic electron closure scheme is presented for the fluid electron model that has been implemented in the GEM code [J. Lang, Y. Chen, S. E. Parker, and G.-Y. Fu, Phys. Plasmas 16, 102101 (2009)]. The most important element of the closure scheme is a complete Ohm’s law for the parallel electric field E∥, derived by combining the quasineutrality condition, the Ampere’s equation and the v∥ moment of the gyrokinetic equations. A discretization method for the closure scheme is presented and studied in detail for a three-dimensional shearless slab plasma. It is found that for long wavelength shear Alfvén waves the kinetic closure scheme is both more accurate and more robust than the previous GEM algorithm [Y. Chen and S. E. Parker, J. Comput. Phys. 189, 463 (2003)], whereas for the ion-gradient-driven instability the previous algorithm is more efficient. The fluid electron model with kinetic electron closure is useful for studying energetic particles driven modes with electron kinetic damping effects.
Phase-resolved x-ray ferromagnetic resonance measurements in fluorescence yield
Authors: Marcham M. K. , Keatley P. S. , Neudert A. , Hicken R. J. , Cavill S. A. , Shelford L. R. , van der Laan G. , Telling N. D. , Childress J. R. , Katine J. A. , Shafer P. , Arenholz E.
Published: April 2011

Phase-resolved x-ray ferromagnetic resonance (XFMR) has been measured in fluorescence yield, extending the application of XFMR to opaque samples on opaque substrates. Magnetization dynamics were excited in a Co50Fe50(0.7)/Ni90Fe10(5) bilayer by means of a continuous wave microwave excitation, while x-ray magnetic circular dichroism (XMCD) spectra were measured stroboscopically at different points in the precession cycle. By tuning the x-ray energy to the L3 edges of Ni and Fe, the dependence of the real and imaginary components of the element specific magnetic susceptibility on the strength of an externally applied static bias field was determined. First results from measurements on a Co50Fe50(0.7)/Ni90Fe10(5)/Dy(1) sample confirm that enhanced damping results from the addition of the Dy cap.
Bias dependent 1/f conductivity fluctuations in low-doped La1−xCaxMnO3 manganite single crystals
Authors: Belogolovskii M. , Jung G. , Markovich V. , Dolgin B. , Wu X. D. , Yuzhelevski Y.
Published: April 2011

Low frequency noise in current biased La0.82Ca0.18MnO3 single crystals has been investigated in a wide temperature range from 79 to 290 K. Despite pronounced changes in the magnetic properties and dissipation mechanisms of the sample with changing temperature, the noise spectra were found to be always of the 1/f type, and their intensity (except for the lowest temperature studied) scaled as the square of the bias. At liquid nitrogen temperatures and under a bias exceeding some threshold value, the behavior of the noise deviates from the quasiequilibrium modulation noise and starts to depend in a nonmonotonic way on the bias. It has been verified that the observed noise obeys the Dutta and Horn model of 1/f noise in solids. The appearance of nonequilibrium 1/f noise and its dependence on bias have been associated with changes in the distribution of activation energies in the underlying energy landscape. These changes have been correlated with bias induced changes in the intrinsic tunneling mechanism dominating dissipation in La0.82Ca0.18MnO3 at low temperatures.
Correlation and size dependence of the lattice strain, binding energy, elastic modulus, and thermal stability for Au and Ag nanostructures
Authors: Liu X. J. , Zhou Z. F. , Yang L. W. , Li J. W. , Xie G. F. , Fu S. Y. , Sun C. Q.
Published: April 2011

As a group of wonder materials, gold and silver at the nanoscale demonstrate many intriguing properties that cannot be seen from their bulk counterparts. However, consistent insight into the mechanism behind the fascinations and their interdependence given by one integrated model is highly desirable. Based on Goldschmidt-Pauling’s rule of bond contraction and its extension to the local bond energy, binding energy density, and atomic cohesive energy, we have developed such a model that is able to reconcile the observed size dependence of the lattice strain, core level shift, elastic modulus, and thermal stability of Au and Ag nanostructures from the perspective of skin-depth bond order loss. Theoretical reproduction of the measured size trends confirms that the undercoordination-induced local bond contraction, bond strength gain, and the associated binding energy density gain, the cohesive energy loss and the tunable fraction of such undercoordinated atoms dictate the observed fascinations, which should shed light on the understanding of the unusual behavior of other nanostructured materials as well.
Size effect on magnetoelectric coupling in multiferroic heterostructures
Authors: Lu XiaoYan , Li Hui
Published: April 2011

Based on thermodynamic theory, size-dependent magnetoelectric coupling effect in layered multiferroic heterostructures was investigated with the consideration of surface effect and size effect. Critical size of the BaTiO3 thin film epitaxially grown between SrRuO3 electrodes on a thick CoFe2O4 substrate was probed numerically by finding the point where paraferroelectric phase transition occurs. The critical size of the BaTiO3 film in the considered system is about 37–56 nm, which is dependent on the applied magnetostriction because of the strong magnetoelectric coupling effect. The magnetoelectric coupling effect is unstable in the vicinity of the critical size and disappears below the critical size.
Electric-field-induced monoclinic phase in (Ba,Sr)TiO3 thin film
Authors: Anokhin A. S. , Yuzyuk Yu. I. , Golovko Yu. I. , Mukhortov V. M. , El Marssi M.
Published: April 2011

We have studied electric-field-induced symmetry lowering in the tetragonal (001)-oriented heteroepitaxial (Ba0.8Sr0.2)TiO3 thin film deposited on (001)MgO substrate. Polarized micro-Raman spectra were recorded from the film area in between two planar electrodes deposited on the film surface. Presence of c domains with polarization normal to the substrate was confirmed from polarized Raman study under zero field, while splitting and hardening of the E(TO) soft mode and polarization changes in the Raman spectra suggest monoclinic symmetry under external electric field.
Formation of structured nanophases in halide crystals
Authors: Kulveit J. , Demo P. , Polák K. , Sveshnikov A. M. , Kožíšek Z.
Published: April 2011

When halide crystals KCl and NaCl are slightly doped by \documentclass[12pt]{minimal}\begin{document}$\rm PbCl_2$\end{document} PbCl 2, (in orders of \documentclass[12pt]{minimal}\begin{document}$10^{-4} \; \rm mol/mol$\end{document}10−4 mol / mol ) the structurally stable nanophases (“quantum dots”) are formed via nucleation within the bulks of their matrices. Using lattice modeling we have found in KCl–Pb system natural nucleation pathway from single impurity–vacancy complex to Suzuki phase, not demonstrated in previous analyses; further transition to \documentclass[12pt]{minimal}\begin{document}$\rm PbCl_2$\end{document} PbCl 2 is difficult due to high stability of this phase. In the case of NaCl–Pb, no stable “end point” of aggregation was observed and our calculations suggest nucleation may readily proceed to large \documentclass[12pt]{minimal}\begin{document}$\rm PbCl_2$\end{document} PbCl 2 clusters when initially formed platelike cluster reaches a certain critical thickness. These results coincide with our experimental data.
Intersatellite laser ranging with homodyne optical phase locking for Space Advanced Gravity Measurements mission
Authors: Yeh Hsien-Chi , Yan Qi-Zhong , Liang Yu-Rong , Wang Ying , Luo Jun
Published: April 2011

In this paper, we present the scheme and the preliminary results of an intersatellite laser ranging system that is designed for the Earth's gravity recovery mission proposed in China, called Space Advanced Gravity Measurements (SAGM). The proposed intersatellite distance is about 100 km and the precision of inter-satellite range monitoring is 10 nm/Hz1/2 at 0.1 Hz. To meet the needs, we designed a transponder-type intersatellite laser ranging system by using a homodyne optical phase locking technique, which is different from the heterodyne optical phase-locked loop used in GRACE follow-on mission. Since an ultrastable oscillator is unnecessary in the homodyne phase-locked loop, the measurement error caused by the frequency instability of the ultrastable oscillator need not be taken into account. In the preliminary study, a heterodyne interferometer with 10-m baseline (measurement arm-length) was built up to demonstrate the validity of the measurement scheme. The measurement results show that a resolution of displacement measurement of about 3.2 nm had been achieved.
A high frequency sensor for optical beam deflection atomic force microscopy
Authors: Enning Raoul , Ziegler Dominik , Nievergelt Adrian , Friedlos Ralph , Venkataramani Krithika , Stemmer Andreas
Published: April 2011

We demonstrate a novel electronic readout for quadrant photodiode based optical beam deflection setups. In our readout, the signals used to calculate the deflections remain as currents, instead of undergoing an immediate conversion to voltages. Bipolar current mirrors are used to perform all mathematical operations at the transistor level, including the signal normalizing division. This method has numerous advantages, leading to significantly simpler designs that avoid large voltage swings and parasitic capacitances. The bandwidth of our readout is solely limited by the capacitance of the quadrant photodiode junctions, making the effective bandwidth a function of the intensity of photocurrents and thus the applied power of the beam deflection laser. Using commercially available components and laser intensities of 1–4 mW we achieved a 3 dB bandwidth of 20 MHz with deflection sensitivities of up to 0.5–1 ${\text{V}}/\text{{nm}}$V/nm and deflection noise levels below 4.5 ${\text{fm}}/{\sqrt{\text{Hz}}}$fm/Hz. Atomic resolution imaging of muscovite mica using FM–AFM in water demonstrates the sensitivity of this novel readout.
Resonant inelastic x-ray scattering at the limit of subfemtosecond natural lifetime
Authors: Marchenko T. , Journel L. , Marin T. , Guillemin R. , Carniato S. , Žitnik M. , Kavčič M. , Bučar K. , Mihelič A. , Hoszowska J. , Cao W. , Simon M.
Published: April 2011

We present measurements of the resonant inelastic x-ray scattering (RIXS) spectra of the CH3I molecule in the hard-x-ray region near the iodine L2 and L3 absorption edges. We show that dispersive RIXS spectral features that were recognized as a fingerprint of dissociative molecular states can be interpreted in terms of ultrashort natural lifetime of ∼200 attoseconds in the case of the iodine L-shell core-hole. Our results demonstrate the capacity of the RIXS technique to reveal subtle dynamical effects in molecules with sensitivity to nuclear rearrangement on a subfemtosecond time scale.
Turbulent boundary layers over smooth and rough forward-facing steps
Authors: Ren Huiying , Wu Yanhua
Published: April 2011

The present work explores the impact of the roughness on the turbulent boundary layers over forward-facing steps. The roughness topography on the top surface of the rough step is replicated from a realistic turbine blade and embodies three-dimensional and highly irregular topographical features. High spatial resolution particle image velocimetry measurements are performed in the x−y planes at two different spanwise positions in turbulent boundary layers over both smooth and rough steps of the same mean heights at Reh=3450 and δ/h=8. Comparison of mean flow structures, Reynolds normal and shear stresses, quadrant analysis of instantaneous shear stress contributing events, and average spanwise vorticity reveals that the separated flow after the step is weakened by the surface roughness on top of the step while the flow ahead of the step is invariant to the surface conditions. The characteristics of the coherent spanwise vortices such as the numbers, size, and circulation distributions are also found to be significantly modified by the roughness topography.
Decrimping: The first stage of collagen thermal denaturation unraveled by in situ second-harmonic-generation imaging
Authors: Liao Chien-Sheng , Zhuo Zong-Yan , Yu Jiun-Yann , Tzeng Yu-Yi , Chu Shi-Wei , Yu Shih-Fan , Chao Pen-Hsiu Grace
Published: April 2011

With polarized and time-lapsed second-harmonic-generation (SHG) imaging, three distinct thermodynamic stages are revealed during heating of collagenous tissue. In the first “decrimping” stage, SHG intensity remains unchanged while the characteristic crimp pattern of collagen fiber disappears. The intactness of underlying fibrils is confirmed by unaffected second-order susceptibility, suggesting decrimping is related to the breakage of cross-linking between collagen fibrils. In the latter stages, significant SHG decrease is observed, providing quantification to collagen thermal denaturation. This study manifests the benefits of adopting SHG for understanding the thermal response of collagen, and will be useful toward better thermal therapy design.
Inkjet-printed stretchable silver electrode on wave structured elastomeric substrate
Authors: Chung Seungjun , Lee Jaemyon , Song Hyunsoo , Kim Sangwoo , Jeong Jaewook , Hong Yongtaek
Published: April 2011

We report high performance and stable inkjet-printed stretchable silver electrodes on wave structured elastomeric substrates. Highly conductive silver electrodes were deposited directly on a ultraviolet ozone treated polydimethylsiloxane (PDMS) substrates having vertical wavy structures. Adhesion between printed silver lines and PDMS surface has been enhanced by intentionally roughened PDMS surface with wire-electro discharge machined aluminum mold. During slow (16.7 μm/s) stretching test, resistance of the printed silver electrode was increased only by three times at 30% tensile strain. Inkjet-printed silver electrodes also showed good mechanical stability during 1000-time fast (1 mm/s) cycling test with 10% tensile strain, showing maximum resistance change of less than three times.
Convergent flow in a two-layer system and plateau development
Authors: Gratton Julio , Perazzo Carlos Alberto
Published: April 2011

In order to describe the development of plateaus such as the Tibet and the Altiplano we extend the two-layer model used in a previous paper [C. A. Perazzo and J. Gratton, Phys. Fluids 22, 056603 (2010)] to reproduce the evolution of mountain ranges. As before, we consider the convergent motion of a system of two liquid layers to simulate the crust and the upper mantle that form a lithospheric plate, but now we assume that the viscosity of the crust falls off abruptly at a specified depth. We derive a nonlinear differential equation for the evolution of the thickness of the crust. The solution of this equation shows that the process consists of a first stage in which a peaked range is formed and grows until its root reaches the depth where its viscosity drops. After that the range ceases to grow in height and a flat plateau appears at its top. In this second stage the plateau width increases linearly with time as its sides move outward as traveling waves. We derive simple approximate formulas for various properties of the plateau and its evolution.
Inequivalent solutions for Dirac spin-$\bf \frac{1}{2}\;$12 particles under conservation of parity II
Authors: Liu C. J.
Published: April 2011

By law of conservation of parity we show that Dirac equation in an electromagnetic field can be split up into two uncoupled two-component equations. As a result, we shall find twice as many as the conventional solutions. For free particles four linearly independent plane wave solutions which hold for E > 0 and also for E < 0 can be established. In a Coulomb field we shall easily find the stationary solutions.
Hot wire chemical vapor deposition of germanium selenide thin films for nonvolatile random access memory applications
Authors: Reso D. , Silinskas M. , Lisker M. , Schubert A. , Burte E. P.
Published: April 2011

Thin films of germanium selenide (GexSe100−x with 0<x<57) were deposited on different substrates by hot wire metalorganic chemical vapor deposition using tetraallylgermanium and di-tert-butylselenide. The growth kinetics of the deposition process as well as the properties of the films were investigated. The growth rate was found to decrease with increasing temperature and decreasing pressure. The conformal step coverage was demonstrated. Germanium selenide films covered and subsequently diffused by silver were used as programmable metallization cells for a verification of the electrical switching properties.
A transparent ultraviolet triggered amorphous selenium p-n junction
Authors: Saito Ichitaro , Miyazaki Wataru , Onishi Masanori , Kudo Yuki , Masuzawa Tomoaki , Yamada Takatoshi , Koh Angel , Chua Daniel , Soga Kenichi , Overend Mauro , Aono Masami , Amaratunga Gehan A. J. , Okano Ken
Published: April 2011

This paper will introduce a semitransparent amorphous selenium (a-Se) film exhibiting photovoltaic effects under ultraviolet light created through a simple and inexpensive method. We found that chlorine can be doped into a-Se through electrolysis of saturated salt water, and converts the weak p-type material into an n-type material. Furthermore, we found that a p-n diode fabricated through this process has shown an open circuit voltage of 0.35 V toward ultraviolet illumination. Our results suggest the possibility of doping control depending on the electric current during electrolysis and the possibility of developing a simple doping method for amorphous photoconductors.
Square optical vortices generated by binary spiral zone plates
Authors: Gao Nan , Xie Changqing , Li Chun , Jin Chunshui , Liu Ming
Published: April 2011

Binary phase square spiral zone plates (BPSSZPs), a special type of binary phase vortex lenses, are introduced to generate focused optical vortices showing square symmetry. The numerical solution and fabrication method, as well as the experimental results are given. Different from conventional vortex lenses, these BPSSZPs produce focused vortices with small topological charge following a modulo-4 transmutation rule. In addition, the central diffracted image rotates in the vicinity of the focal plane. These interesting properties suggest that BPSSZPs might become key components for many potential applications such as optical image processing and quantum computation.
The Validity of Composite Photographs for Assessing Masculinity Preferences
Authors: Scott Isabel M , Penton-Voak Ian S
Published: April 2011

Among non-human animals, exaggerated male traits may signal immunocompetence and are often attractive to females. This finding has not been reliably replicated in human populations, however, where preferences for feminised male faces are often observed in experiments. Some authors have suggested that certain experimental approaches, and in particular the use of ‘composite’, or averaged, photographs, may lack ecological validity and elicit misleading responses. This may account for reports of preferences for femininity.

To date, however, experiments have varied on numerous, often confounded, methodological dimensions, making the contribution of different factors difficult to assess. To address this, we conducted an experiment to examine the influence of stimulus type on participant responses. Masculinity preferences were measured using both composite photographs and the photographs from which they were composed, while all other methodological variables were held constant. In contrast to predictions by previous authors, composites elicited significantly stronger overall preferences for masculinity, especially when textural information was reduced during the averaging process. The existence of preferences for feminised male faces is unlikely to be explained by the use of composite photographs alone.
Case study on effects of water management and rice straw incorporation in rice fields on production, oxidation, and emission of methane during fallow and following rice seasons
Authors: Zhang G. B. , Ji Y. , Ma J. , Xu H. , Cai Z. C.
Published: April 2011

To investigate production, oxidation, and emission of methane (CH4) in rice fields during the fallow and following rice seasons as affected by water management and rice straw incorporation in the fallow season, field and incubation experiments were carried out from November 2007 to November 2008. Four treatments, i.e. two water managements (flooded and drained) and two rates of rice straw application (0 and 4.8 t/ha), were laid out in a randomised block design. Results show that obvious CH4 production occurred in flooded fields in the late fallow season; consequently, fallow CH4 emission contributed 9.6–33.1% to the annual total emission. However, emission mainly occurred during the rice season. During the rice season, the mean CH4 production potential in flooded fields was 2.6–3.8 times that in drained fields, making the total CH4 emission 2.1–2.5 times that in drained fields. Rice straw incorporated in flooded fields significantly increased production and emission of CH4 during both the fallow and the following rice seasons (P < 0.05), but in drained fields, no significant effect was observed (P > 0.05). There was no significant difference in mean CH4 oxidation potential between the treatments (P > 0.05), indicating that water management and rice straw incorporation in the fallow season have little influence on CH4 oxidation during the fallow and following rice seasons. Based on the findings, water management and rice straw incorporation in the fallow season significantly affected CH4 emission during the fallow and the following rice seasons by influencing CH4 production rather than CH4 oxidation in fields.
Soil type influences the leaching of microbial indicators under natural rainfall following application of dairy shed effluent
Authors: Aislabie Jackie , McLeod Malcolm , Ryburn Janine , McGill Alexandra , Thornburrow Daniel
Published: April 2011

The ability of soil to function as a barrier between microbial pathogens in wastes and groundwater following application of animal wastes is dependent on soil structure. We irrigated soil lysimeters with dairy shed effluent at intervals of 3–4 months and monitored microbial indicators (somatic coliphage, faecal enterococci, Escherichia coli) in soil core leachates for 1 year. The lysimeters were maintained in a lysimeter facility under natural soil temperature and moisture regimes. Microbial indicators were rapidly transported to depth in well-structured Netherton clay loam soil. Peak concentrations of E. coli and somatic coliphage were detected immediately following dairy shed effluent application to Netherton clay loam soil, and E. coli continued to leach from the soil following rainfall. In contrast, microbial indicators were rarely detected in leachates from fine-structured Manawatu sandy loam soil. Potential for leaching was dependent on soil moisture conditions in Manawatu soil but not Netherton soil, where leaching occurred regardless. Dye studies confirmed that E. coli can be transported to depth by flow through continuous macropores in Netherton soils. However, in the main E. coli was retained in topsoil of Netherton and Manawatu soil.
Microbial community and ecotoxicity analysis of bioremediated, weathered hydrocarbon-contaminated soil
Authors: Sheppard Petra J. , Adetutu Eric M. , Makadia Tanvi H. , Ball Andrew S.
Published: April 2011

Bioremediated soils are usually disposed of after meeting legislated guidelines defined by chemical and ecotoxicity tests. In many countries including Australia, ecotoxicity tests are not yet mandatory safety requirements. This study investigated the biotreatment of weathered hydrocarbon-contaminated soils in 12-week laboratory-based microcosms. Monitored natural attenuation resulted in ~43% reduction of total petroleum hydrocarbon contaminant to 5503 mg/kg (C16–C35), making the soil suitable for disposal as waste under current guidelines (pesticide and metal contents within safe limits). 16S rDNA (universal and AlkB) and ITS-based DGGE fingerprints showed stable and adapted microbial communities throughout the experimental period. However, ecotoxicology assays showed 100% mortality of earthworms (Eisena fetida) in potting soils containing ≥50% (≥2751 mg/kg, legally safe in situ concentrations) contaminated soil over 14 days. Up to 70% reduction in radish (Raphanus sativus) seed germination was observed in potting soils containing ≥10% contaminated soil (≥550 mg/kg, legally safe ex situ concentrations for soil disposal into residential areas). The results indicate the toxicity of these soils to soil biota despite meeting legislated Australian safe levels and guidelines for disposal or use in residential areas.
Ginninderra revisited: the contribution of B. E. Butler to statistical pedology
Authors: Webster R.
Published: April 2011

The 1960s were a decade of controversy like no other in soil systematics. Bruce E. Butler had recently moved to Canberra and was perplexed by the apparent lack of ‘orderliness’ in the soil patterns on the Tablelands there. He sought elucidation by the then newly developing methods in multivariate and spatial statistics.
Two surveys of soil on the Ginninderra Experiment Station, 12 km north of Canberra, were planned to provide data for analysis. The first was made on a grid at ~180-m intervals, at the nodes of which the soil profiles were described and samples taken for chemical analysis. Correlations between variables were weak, a principal coordinate analysis showed the scatter of sampling points as a single cloud, and classification proved to be of little value in predicting individual variables. The second survey had a spatially nested design with distances 5, 18, 56, and 180 m, leading to the estimation of the components of variance of several topsoil properties at those distances. The accumulated components provided rough variograms with contrasting patterns; there was little coherence. Almost all the variance in soil potassium (K), for example, occurs within 180 m, whereas some 35% of the variance in phosphorus (P) occurs over longer distances.
This paper revisits that research, emphasising its innovation and adding a modern geostatistical analysis from the original grid data. The conventional variogram of P has an estimated correlation range of 728 m, and a map made by kriging shows a coarse pattern of variation. In contrast, the variogram of K appears as all nugget at the working scale, and so kriging or any form of interpolation from 180-m grids is not sensible. Denser sampling is needed, and proximal sensing by gamma-ray spectrometry seems a promising approach.
Population biology of the long-nosed potoroo (Potorous tridactylus) in the Southern Highlands of New South Wales
Authors: Norton Melinda A. , Claridge Andrew W. , French Kris , Prentice Alison
Published: April 2011

The population biology of the long-nosed potoroo (Potorous tridactylus) was investigated at Barren Grounds Nature Reserve and Budderoo National Park in the Southern Highlands of New South Wales (NSW). Both study areas are important conservation reserves for this threatened species, with a large gap north (~300 km) to the next known viable population on the mid-north coast of NSW at Mount Royal. Potoroos were live-trapped using bandicoot-sized cage traps, each set ~100 m apart along walking tracks and fire trails. Trapping was conducted each autumn and spring over five years to enumerate the local population of potoroos and to describe their morphometrics. The local long-nosed potoroos were larger in size than those recorded to the south on mainland Australia, but smaller than those in north-eastern NSW, supporting the concept of a latitudinal cline in body size. Sexual dimorphism was observed, with adult males having larger body weights, head lengths and pes lengths. Between one-third and two-thirds of all males and females were captured in only a single trapping session, indicative of low levels of survivorship and/or high levels of dispersal or transience. Males regularly overlapped at trap sites with females, more so than with other males, while females rarely overlapped at trap sites. Barren Grounds Nature Reserve supported a larger number of potoroos and a greater degree of home range overlap between individuals.
Sulfiredoxin–Peroxiredoxin IV axis promotes human lung cancer progression through modulation of specific phosphokinase signaling
Authors: Wei Qiou , Jiang Hong , Xiao Zhen , Baker Alyson , Young Matthew R. , Veenstra Timothy D. , Colburn Nancy H.
Published: April 2011

Oxidative stress is known to cause tumorigenesis through induction of DNA and lipid damage. It also promotes cancer progression through a largely unknown mechanism. Sulfiredoxin (Srx) is a novel oxidative stress-induced antioxidant protein whose function in tumorigenesis and cancer progression has not been well studied. We report that Srx is highly expressed in human lung cancer. Knockdown of Srx reduces anchorage-independent colony formation, cell migration, and invasion of human lung cancer cells. Srx preferentially interacts with Peroxiredoxin (Prx) IV relative to other Prxs due to its intrinsic higher binding affinity. Knockdown of Prx IV recapitulates the phenotypic changes of depleting Srx. Disruption or enhancement of the Srx–Prx IV axis leads respectively to reduction or acceleration of tumor growth and metastasis formation in vivo. Through identification and validation of the downstream mediators we unraveled the Srx-mediated signaling network that traverses AP-1–activating and other phosphokinase signaling cascades. Our work reveals that the Srx–Prx IV axis is critical for lung cancer maintenance and metastasis, suggesting that targeting the Srx–Prx IV axis may provide unique effective strategies for cancer prevention and treatment.
Genome sequencing of environmental
Escherichia coli
expands understanding of the ecology and speciation of the model bacterial species
Authors: Luo Chengwei , Walk Seth T. , Gordon David M. , Feldgarden Michael , Tiedje James M. , Konstantinidis Konstantinos T.
Published: April 2011

Defining bacterial species remains a challenging problem even for the model bacterium
Escherichia coli
and has major practical consequences for reliable diagnosis of infectious disease agents and regulations for transport and possession of organisms of economic importance.
E. coli
traditionally is thought to live within the gastrointestinal tract of humans and other warm-blooded animals and not to survive for extended periods outside its host; this understanding is the basis for its widespread use as a fecal contamination indicator. Here, we report the genome sequences of nine environmentally adapted strains that are phenotypically and taxonomically indistinguishable from typical
E. coli
(commensal or pathogenic). We find, however, that the commensal genomes encode for more functions that are important for fitness in the human gut, do not exchange genetic material with their environmental counterparts, and hence do not evolve according to the recently proposed fragmented speciation model. These findings are consistent with a more stringent and ecologic definition for bacterial species than the current definition and provide means to start replacing traditional approaches of defining distinctive phenotypes for new species with omics-based procedures. They also have important implications for reliable diagnosis and regulation of pathogenic
E. coli
and for the coliform cell-counting test.
Cysteine-rich secretory protein 4 is an inhibitor of transient receptor potential M8 with a role in establishing sperm function
Authors: Gibbs Gerard M. , Orta Gerardo , Reddy Thulasimala , Koppers Adam J. , Martínez-López Pablo , Luis de la Vega-Beltràn José , Lo Jennifer C. Y. , Veldhuis Nicholas , Jamsai Duangporn , McIntyre Peter , Darszon Alberto , O'Bryan Moira K.
Published: April 2011

The cysteine-rich secretory proteins (CRISPs) are a group of four proteins in the mouse that are expressed abundantly in the male reproductive tract, and to a lesser extent in other tissues. Analysis of reptile CRISPs and mouse CRISP2 has shown that CRISPs can regulate cellular homeostasis via ion channels. With the exception of the ability of CRISP2 to regulate ryanodine receptors, the in vivo targets of mammalian CRISPs function are unknown. In this study, we have characterized the ion channel regulatory activity of epididymal CRISP4 using electrophysiology, cell assays, and mouse models. Through patch-clamping of testicular sperm, the CRISP4 CRISP domain was shown to inhibit the transient receptor potential (TRP) ion channel TRPM8. These data were confirmed using a stably transfected CHO cell line. TRPM8 is a major cold receptor in the body, but is found in other tissues, including the testis and on the tail and head of mouse and human sperm. Functional assays using sperm from wild-type mice showed that TRPM8 activation significantly reduced the number of sperm undergoing the progesterone-induced acrosome reaction following capacitation, and that this response was reversed by the coaddition of CRISP4. In accordance, sperm from
Crisp4
null mice had a compromised ability to undergo to the progesterone-induced acrosome reaction. Collectively, these data identify CRISP4 as an endogenous regulator of TRPM8 with a role in normal sperm function.
Tonic inhibition of chronic pain by neuropeptide Y
Authors: Solway Brian , Bose Soma C. , Corder Gregory , Donahue Renee R. , Taylor Bradley K.
Published: April 2011

Dramatically up-regulated in the dorsal horn of the mammalian spinal cord following inflammation or nerve injury, neuropeptide Y (NPY) is poised to regulate the transmission of sensory signals. We found that doxycycline-induced conditional in vivo (
Npy
tet/tet
) knockdown of NPY produced rapid, reversible, and repeatable increases in the intensity and duration of tactile and thermal hypersensitivity. Remarkably, when allowed to resolve for several weeks, behavioral hypersensitivity could be dramatically reinstated with NPY knockdown or intrathecal administration of Y1 or Y2 receptor antagonists. In addition, Y2 antagonism increased dorsal horn expression of Fos and phosphorylated form of extracellular signal-related kinase. Taken together, these data establish spinal NPY receptor systems as an endogenous braking mechanism that exerts a tonic, long-lasting, broad-spectrum inhibitory control of spinal nociceptive transmission, thus impeding the transition from acute to chronic pain. NPY and its receptors appear to be part of a mechanism whereby mammals naturally recover from the hyperalgesia associated with inflammation or nerve injury.
Design of a switchable eliminase
Authors: Korendovych Ivan V. , Kulp Daniel W. , Wu Yibing , Cheng Hong , Roder Heinrich , DeGrado William F.
Published: April 2011

The active sites of enzymes are lined with side chains whose dynamic, geometric, and chemical properties have been finely tuned relative to the corresponding residues in water. For example, the carboxylates of glutamate and aspartate are weakly basic in water but become strongly basic when dehydrated in enzymatic sites. The dehydration of the carboxylate, although intrinsically thermodynamically unfavorable, is achieved by harnessing the free energy of folding and substrate binding to reach the required basicity. Allosterically regulated enzymes additionally rely on the free energy of ligand binding to stabilize the protein in a catalytically competent state. We demonstrate the interplay of protein folding energetics and functional group tuning to convert calmodulin (CaM), a regulatory binding protein, into AlleyCat, an allosterically controlled eliminase. Upon binding Ca(II), native CaM opens a hydrophobic pocket on each of its domains. We computationally identified a mutant that (
i
) accommodates carboxylate as a general base within these pockets, (
ii
) interacts productively in the Michaelis complex with the substrate, and (
iii
) stabilizes the transition state for the reaction. Remarkably, a single mutation of an apolar residue at the bottom of an otherwise hydrophobic cavity confers catalytic activity on calmodulin. AlleyCat showed the expected pH-rate profile, and it was inactivated by mutation of its active site Glu to Gln. A variety of control mutants demonstrated the specificity of the design. The activity of this minimal 75-residue allosterically regulated catalyst is similar to that obtained using more elaborate computational approaches to redesign complex enzymes to catalyze the Kemp elimination reaction.
Biosynthesis of hemiketal eicosanoids by cross-over of the 5-lipoxygenase and cyclooxygenase-2 pathways
Authors: Griesser Markus , Suzuki Takashi , Tejera Noemi , Mont Stacey , Boeglin William E. , Pozzi Ambra , Schneider Claus
Published: April 2011

The prostaglandin and leukotriene families of lipid mediators are formed via two distinct biosynthetic pathways that are initiated by the oxygenation of arachidonic acid by either cyclooxygenase-2 (COX-2) or 5-lipoxygenase (5-LOX), respectively. The 5-LOX product 5
S
-hydroxyeicosatetraenoic acid, however, can also serve as an efficient substrate for COX-2, forming a bicyclic diendoperoxide with structural similarities to the arachidonic acid-derived prostaglandin endoperoxide PGH
2
[Schneider C, et al. (2006)
J Am Chem Soc
128:720–721]. Here we identify two cyclic hemiketal (HK) eicosanoids, HKD
2
and HKE
2
, as the major nonenzymatic rearrangement products of the diendoperoxide using liquid chromatography–mass spectrometry analyses as well as UV and NMR spectroscopy. HKD
2
and HKE
2
are furoketals formed by spontaneous cyclization of their respective 8,9-dioxo-5
S
,11
R
,12
S
,15
S
-tetrahydroxy- or 11,12-dioxo-5
S
,8
S
,9
S
,15
S
-tetrahydroxy-eicosadi-6
E
,13
E
-enoic acid precursors, resulting from opening of the 9
S
,11
R
- and 8
S
,12
S
-peroxide rings of the diendoperoxide. Furthermore, the diendoperoxide is an efficient substrate for the hematopoietic type of prostaglandin D synthase resulting in formation of HKD
2
, equivalent to the enzymatic transformation of PGH
2
to PGD
2
. HKD
2
and HKE
2
were formed in human blood leukocytes activated with bacterial lipopolysaccharide and calcium ionophore A23187, and biosynthesis was blocked by inhibitors of 5-LOX or COX-2. HKD
2
and HKE
2
stimulated migration and tubulogenesis of microvascular endothelial cells, implicating a proangiogenic role of the hemiketals in inflammatory sites that involve expression of 5-LOX and COX-2. Identification of the highly oxygenated hemiketal eicosanoids provides evidence for a previously unrecognized biosynthetic cross-over of the 5-LOX and COX-2 pathways.
Evolutionary history predicts plant defense against an invasive pest
Authors: Desurmont Gaylord A. , Donoghue Michael J. , Clement Wendy L. , Agrawal Anurag A.
Published: April 2011

It has long been hypothesized that invasive pests may be facilitated by the evolutionary naïveté of their new hosts, but this prediction has never been examined in a phylogenetic framework. To address the hypothesis, we have been studying the invasive viburnum leaf beetle (
Pyrrhalta viburni
), which is decimating North American native species of
Viburnum
, a clade of worldwide importance as understory shrubs and ornamentals. In a phylogenetic field experiment using 16 species of
Viburnum
, we show that old-world
Viburnum
species that evolved in the presence of
Pyrrhalta
beetles mount a massive defensive wound response that crushes eggs of the pest insect; in contrast, naïve North American species that share no evolutionary history with
Pyrrhalta
beetles show a markedly lower response. This convergent continental difference in the defensive response of
Viburnum
spp. against insect oviposition contrasts with little difference in the quality of leaves for beetle larvae. Females show strong oviposition preferences that correspond with larval performance regardless of continental origin, which has facilitated colonization of susceptible North American species. Thus, although much attention has been paid to escape from enemies as a factor in the establishment and spread of nonnative organisms, the colonization of undefended resources seems to play a major role in the success of invasive species such as the viburnum leaf beetle.
Multiple mating and its relationship to brood size in pregnant fishes versus pregnant mammals and other viviparous vertebrates
Authors: Avise John C. , Liu Jin-Xian
Published: April 2011

We summarize the literature on rates of multiple paternity and sire numbers per clutch in viviparous fishes vs. mammals, two vertebrate groups in which pregnancy is common but entails very different numbers of embryos (for species surveyed, piscine broods averaged >10-fold larger than mammalian litters). As deduced from genetic parentage analyses, multiple mating by the pregnant sex proved to be common in assayed species but averaged significantly higher in fish than mammals. However, within either of these groups we found no significant correlations between brood size and genetically deduced incidence of multiple mating by females. Overall, these findings offer little support for the hypothesis that clutch size in pregnant species predicts the outcome of selection for multiple mating by brooders. Instead, whatever factors promote multiple mating by members of the gestating sex seem to do so in surprisingly similar ways in live-bearing vertebrates otherwise as different as fish and mammals. Similar conclusions emerged when we extended the survey to viviparous amphibians and reptiles. One notion consistent with these empirical observations is that although several fitness benefits probably accrue from multiple mating, logistical constraints on mate-encounter rates routinely truncate multiple mating far below levels that otherwise could be accommodated, especially in species with larger broods. We develop this concept into a “logistical constraint hypothesis” that may help to explain these mating outcomes in viviparous vertebrates. Under the logistical constraint hypothesis, propensities for multiple mating in each species register a balance between near-universal fitness benefits from multiple mating and species-idiosyncratic logistical limits on polygamy.
Reversible suppression of an essential gene in adult mice using transgenic RNA interference
Authors: McJunkin Katherine , Mazurek Anthony , Premsrirut Prem K. , Zuber Johannes , Dow Lukas E. , Simon Janelle , Stillman Bruce , Lowe Scott W.
Published: April 2011

RNAi has revolutionized loss-of-function genetics by enabling sequence-specific suppression of virtually any gene. Furthermore, tetracycline response elements (TRE) can drive expression of short hairpin RNAs (shRNAs) for inducible and reversible target gene suppression. Here, we demonstrate the feasibility of transgenic inducible RNAi for suppression of essential genes. We set out to directly target cell proliferation by screening an RNAi library against DNA replication factors and identified multiple shRNAs against Replication Protein A, subunit 3 (RPA3). We generated transgenic mice with TRE-driven Rpa3 shRNAs whose expression enforced a reversible cell cycle arrest. In adult mice, the block in cell proliferation caused rapid atrophy of the intestinal epithelium which led to weight loss and lethality within 8–11 d of shRNA induction. Upon shRNA withdrawal, villus atrophy and weight loss were fully reversible. Thus, shRpa3 transgenic mice provide an interesting tool to study tissue maintenance and regeneration. Overall, we have established a robust system that serves the purpose of temperature-sensitive alleles in other model organisms, enabling inducible and reversible suppression of essential genes in a mammalian system.
Congenital bone marrow failure in DNA-PKcs mutant mice associated with deficiencies in DNA repair
Authors: Zhang Shichuan , Yajima Hirohiko , Huynh HoangDinh , Zheng Junke , Callen Elsa , Chen Hua-Tang , Wong Nancy , Bunting Samuel , Lin Yu-Fen , Li Mengxia , Lee Kyung-Jone , Story Michael , Gapud Eric , Sleckman Barry P. , Nussenzweig André , Zhang Cheng Cheng , Chen David J. , Chen Benjamin P.C.
Published: April 2011

The nonhomologous end-joining (NHEJ) pathway is essential for radioresistance and lymphocyte-specific V(D)J (variable [diversity] joining) recombination. Defects in NHEJ also impair hematopoietic stem cell (HSC) activity with age but do not affect the initial establishment of HSC reserves. In this paper, we report that, in contrast to deoxyribonucleic acid (DNA)–dependent protein kinase catalytic subunit (DNA-PKcs)–null mice, knockin mice with the DNA-PKcs3A/3A allele, which codes for three alanine substitutions at the mouse Thr2605 phosphorylation cluster, die prematurely because of congenital bone marrow failure. Impaired proliferation of DNA-PKcs3A/3A HSCs is caused by excessive DNA damage and p53-dependent apoptosis. In addition, increased apoptosis in the intestinal crypt and epidermal hyperpigmentation indicate the presence of elevated genotoxic stress and p53 activation. Analysis of embryonic fibroblasts further reveals that DNA-PKcs3A/3A cells are hypersensitive to DNA cross-linking agents and are defective in both homologous recombination and the Fanconi anemia DNA damage response pathways. We conclude that phosphorylation of DNA-PKcs is essential for the normal activation of multiple DNA repair pathways, which in turn is critical for the maintenance of diverse populations of tissue stem cells in mice.