bluuebunny/crossref_metadata_2025 huggingface dataset:
From kinetic to collective behavior in thermal transport on semiconductors and semiconductor nanostructures
Authors: de Tomas C. , Cantarero A. , Lopeandia A. F. , Alvarez F. X.
Published: May 2014

We present a model which deepens into the role that normal scattering has on the thermal conductivity in semiconductor bulk, micro, and nanoscale samples. Thermal conductivity as a function of the temperature undergoes a smooth transition from a kinetic to a collective regime that depends on the importance of normal scattering events. We demonstrate that in this transition, the key point to fit experimental data is changing the way to perform the average on the scattering rates. We apply the model to bulk Si with different isotopic compositions obtaining an accurate fit. Then we calculate the thermal conductivity of Si thin films and nanowires by only introducing the effective size as additional parameter. The model provides a better prediction of the thermal conductivity behavior valid for all temperatures and sizes above 30 nm with a single expression. Avoiding the introduction of confinement or quantum effects, the model permits to establish the limit of classical theories in the study of the thermal conductivity in nanoscopic systems.
Numerical simulation of bubble dispersion in turbulent Taylor-Couette flow
Authors: Chouippe A. , Climent E. , Legendre D. , Gabillet C.
Published: May 2014

We investigate bubble dispersion in turbulent Taylor-Couette flow. The aim of this study is to describe the main mechanisms yielding preferential bubble accumulation in near-wall structures of the flow. We first proceed to direct numerical simulation of Taylor-Couette flows for three different geometrical configurations (three radius ratios η = R1/R2: η = 0.5, η = 0.72, and η = 0.91 with the outer cylinder at rest) and Reynolds numbers corresponding to turbulent regime ranging from 3000 to 8000. The statistics of the flow are discussed using two different averaging procedures that permit to characterize the mean azimuthal velocity, the Taylor vortices contribution and the small-scale turbulent fluctuations. The simulations are compared and validated with experimental and numerical data from literature. The second part of this study is devoted to bubble dispersion. Bubble accumulation is analyzed by comparing the dispersion obtained with the full turbulent flow field to bubble dispersion occurring at lower Reynolds numbers in previous works. Several patterns of preferential accumulation of bubbles have been observed depending on bubble size and the effect of gravity. For the smaller size considered, bubbles disperse homogeneously throughout the gap, while for the larger size they accumulate along the inner wall for the large gap width (η = 0.5). Varying the intensity of buoyancy yields complex evolution of the bubble spatial distribution. For low gravity effect, bubble entrapment is strong leading to accumulation along the inner wall in outflow regions (streaks of low wall shear stress). When buoyancy effect dominates on vortex trapping, bubbles rise through the vortices, while spiral patterns stretched along the inner cylinder are clearly identified. Force balance is analyzed to identify dominating forces leading to this accumulation and accumulation patterns are compared with previous experiments.
Electronic topological transition of the Lifshitz type and complex magnetic structures in heavy rare-earth metals
Authors: Andrianov A. Vl.
Published: May 2014

The determining role of the Fermi surface geometry in the formation of long-period magnetic structures in heavy rare-earth metals was considered. It was shown that all these metals are on the verge of electronic topological transition of the Lifshitz type. It was experimentally confirmed that the electronic topological transition induced by elastic deformation results in a change in the type of magnetic ordering. A universal phase diagram “magnetic ordering type—hcp lattice parameters a and c” was established for the rare-earth metals, in good agreement with the results of first-principles calculations.
The Lifshitz–Kosevich theory and Coulomb interaction in graphene
Authors: Falkovsky L. A.
Published: May 2014

The influence of Coulomb interactions on the magnetic susceptibility, chemical potential and heat capacity in graphene is considered.
Magnetization and polarization of the electron gas in multiferroics
Authors: Margulis V. A.
Published: May 2014

The microscopic mechanism of magnetization and polarization owing to the strong spin-orbital coupling of the electron gas in multiferroics is examined. Explicit analytic expressions are obtained for the magnetization and polarization of the electron gas in multiferroics.
De Haas-van Alphen effect in the band antiferromagnet FeGe2: Development of spin splitting
Authors: Grechnev G. E. , Lyogenkaya A. A. , Pluzhnikov V. B. , Svechkarev I. V. , Fedorchenko A. V. , Perz J. M.
Published: May 2014

The de Haas-van Alphen (dHvA) effect in the antiferromagnetic compound FeGe2 is studied experimentally. A sharp suppression of the amplitude of the first harmonic of the dHvA oscillations is observed for a number of orbits on the Fermi surface of FeGe2. The change in the conditions for suppression of the amplitude ("spin zeroes") when FeGe2 is doped with cobalt is determined. A method for analyzing the experimental data is proposed in which the g-factors of the conduction electrons are computed on the basis of calculations of the spin-polarized electron structure of the band antiferromagnet taking spin-orbital interactions into account. The exchange enhancement factor for spin paramagnetism in FeGe2 is also calculated.
Static correlation beyond the random phase approximation: Dissociating H2 with the Bethe-Salpeter equation and time-dependent GW
Authors: Olsen Thomas , Thygesen Kristian S.
Published: May 2014

We investigate various approximations to the correlation energy of a H2 molecule in the dissociation limit, where the ground state is poorly described by a single Slater determinant. The correlation energies are derived from the density response function and it is shown that response functions derived from Hedin's equations (Random Phase Approximation (RPA), Time-dependent Hartree-Fock (TDHF), Bethe-Salpeter equation (BSE), and Time-Dependent GW) all reproduce the correct dissociation limit. We also show that the BSE improves the correlation energies obtained within RPA and TDHF significantly for intermediate binding distances. A Hubbard model for the dimer allows us to obtain exact analytical results for the various approximations, which is readily compared with the exact diagonalization of the model. Moreover, the model is shown to reproduce all the qualitative results from the ab initio calculations and confirms that BSE greatly improves the RPA and TDHF results despite the fact that the BSE excitation spectrum breaks down in the dissociation limit. In contrast, second order screened exchange gives a poor description of the dissociation limit, which can be attributed to the fact that it cannot be derived from an irreducible response function.
Preface: Special Topic on Advances in Density Functional Theory
Authors: Yang Weitao
Published: May 2014

This Special Topic Issue on the Advances in Density Functional Theory, published as a celebration of the fifty years of density functional theory, contains a retrospective article, a perspective article, and a collection of original research articles that showcase recent theoretical advances in the field. It provides a timely discussion reflecting a cross section of our understanding, and the theoretical and computational developments, which have significant implications in broad areas of sciences and engineering.
Modified helix-like instability structure on imploding z-pinch liners that are pre-imposed with a uniform axial magnetic field
Authors: Awe T. J. , Jennings C. A. , McBride R. D. , Cuneo M. E. , Lamppa D. C. , Martin M. R. , Rovang D. C. , Sinars D. B. , Slutz S. A. , Owen A. C. , Tomlinson K. , Gomez M. R. , Hansen S. B. , Herrmann M. C. , Jones M. C. , McKenney J. L. , Robertson G. K. , Rochau G. A. , Savage M. E. , Schroen D. G. , Stygar W. A.
Published: May 2014

Recent experiments at the Sandia National Laboratories Z Facility have, for the first time, studied the implosion dynamics of magnetized liner inertial fusion (MagLIF) style liners that were pre-imposed with a uniform axial magnetic field. As reported [T. J. Awe et al., Phys. Rev. Lett. 111, 235005 (2013)] when premagnetized with a 7 or 10 T axial field, these liners developed 3D-helix-like hydrodynamic instabilities; such instabilities starkly contrast with the azimuthally correlated magneto-Rayleigh-Taylor (MRT) instabilities that have been consistently observed in many earlier non-premagnetized experiments. The helical structure persisted throughout the implosion, even though the azimuthal drive field greatly exceeded the expected axial field at the liner's outer wall for all but the earliest stages of the experiment. Whether this modified instability structure has practical importance for magneto-inertial fusion concepts depends primarily on whether the modified instability structure is more stable than standard azimuthally correlated MRT instabilities. In this manuscript, we discuss the evolution of the helix-like instability observed on premagnetized liners. While a first principles explanation of this observation remains elusive, recent 3D simulations suggest that if a small amplitude helical perturbation can be seeded on the liner's outer surface, no further influence from the axial field is required for the instability to grow.
Nonlinear characterization of a single-axis acoustic levitator
Authors: Andrade Marco A. B. , Ramos Tiago S. , Okina Fábio T. A. , Adamowski Julio C.
Published: May 2014

The nonlinear behavior of a 20.3 kHz single-axis acoustic levitator formed by a Langevin transducer with a concave radiating surface and a concave reflector is experimentally investigated. In this study, a laser Doppler vibrometer is applied to measure the nonlinear sound field in the air gap between the transducer and the reflector. Additionally, an electronic balance is used in the measurement of the acoustic radiation force on the reflector as a function of the distance between the transducer and the reflector. The experimental results show some effects that cannot be described by the linear acoustic theory, such as the jump phenomenon, harmonic generation, and the hysteresis effect. The influence of these nonlinear effects on the acoustic levitation of small particles is discussed.
Thermal diffusivity of electrical insulators at high temperatures: Evidence for diffusion of bulk phonon-polaritons at infrared frequencies augmenting phonon heat conduction
Authors: Hofmeister Anne M. , Dong Jianjun , Branlund Joy M.
Published: May 2014

We show that laser-flash analysis measurements of the temperature (T) dependence of thermal diffusivity (D) for diverse non-metallic (e.g., silicates) single-crystals is consistently represented by D(T)  = FT−G + HT above 298 K, with G ranging from 0.3 to 2, depending on structure, and H being ∼10−4 K−1 for 51 single-crystals, 3 polycrystals, and two glasses unaffected by disorder or reconstructive phase transitions. Materials exhibiting this behavior include complex silicates with variable amounts of cation disorder, perovskite structured materials, and graphite. The high-temperature term HT becomes important by ∼1300 K, above which temperature its contribution to D(T) exceeds that of the FT−G term. The combination of the FT−G and HT terms produces the nearly temperature independent high-temperature region of D previously interpreted as the minimal phonon mean free path being limited by the finite interatomic spacing. Based on the simplicity of the fit and large number of materials it represents, this finding has repercussions for high-temperature models of heat transport. One explanation is that the two terms describing D(T) are associated with two distinct microscopic mechanisms; here, we explore the possibility that the thermal diffusivity of an electrical insulator could include both a contribution of lattice phonons (the FT−G term) and a contribution of diffusive bulk phonon-polaritons (BPP) at infrared (IR) frequencies (the HT term). The proposed BPP diffusion exists over length scales smaller than the laboratory sample sizes, and transfers mixed light and vibrational energy at a speed significantly smaller than the speed of light. Our diffusive IR-BPP hypothesis is consistent with other experimental observations such as polarization behavior, dependence of D on the number of IR peaks, and H = 0 for Ge and Si, which lack IR fundamentals. A simple quasi-particle thermal diffusion model is presented to begin understanding the contribution from bulk phonon-polaritons to overall heat conduction.
Communication: Atomic force detection of single-molecule nonlinear optical vibrational spectroscopy
Authors: Saurabh Prasoon , Mukamel Shaul
Published: May 2014

Atomic Force Microscopy (AFM) allows for a highly sensitive detection of spectroscopic signals. This has been first demonstrated for NMR of a single molecule and recently extended to stimulated Raman in the optical regime. We theoretically investigate the use of optical forces to detect time and frequency domain nonlinear optical signals. We show that, with proper phase matching, the AFM-detected signals closely resemble coherent heterodyne-detected signals. Applications are made to AFM-detected and heterodyne-detected vibrational resonances in Coherent Anti-Stokes Raman Spectroscopy (χ(3)) and sum or difference frequency generation (χ(2)).
Tensile failure of bi-materials: High strain-rate simulations of thin adhesive layers on covalent substrates
Authors: Makeev Maxim A.
Published: May 2014

In the present work, we report on results of simulation-based study of mechanical response behavior and mechanisms of failure of a nanometer-scale polyimide adherent thin-film on a silicon substrate. A transition between adhesive and cohesive modes of failure with the strain rate was shown to occur in the system, subjected to high strain-rate tensile loadings. The physical mechanisms, leading to the bi-material failure, were identified for each failure mode. The study reveals that damage development and propagation are determined by a complex interplay between coupling across the interface and relaxation processes in the adherent layer. The two act in a synergistic manner to generate an instability, leading to either cohesive or adhesive failure.
Depression of the normal-superfluid transition temperature in gated bilayer graphene
Authors: Fischetti Massimo V.
Published: May 2014

It is shown that the normal-superfluid transition in bilayer graphene predicted to occur at a high temperature is strongly affected not only by the dielectric constants of the substrate, interlayer, and gate insulators but also by the proximity of ideal metal gates. Even assuming optimistically a completely unscreened interlayer Coulomb interaction—thus bypassing the controversial problems regarding the proper way to screen the interlayer Coulomb interactions—it is shown that employing a gate-insulator thickness smaller than about 2-to-5 nm of equivalent SiO2-thickness pushes the transition temperature significantly below 300 K to the 1 K–1 mK range, depending on the dielectric constant of the gate insulator and on the dielectric mismatch of the insulators employed. These results imply that thicker and low-dielectric-constant gate insulators should be employed to observe the phase transition, but exploiting the superfluid state of gated graphene-bilayers in room-temperature device applications may be challenging.
Electrically tunable localized tunneling channels in silicene nanoribbons
Authors: Saari Timo , Huang Cheng-Yi , Nieminen Jouko , Tsai Wei-Feng , Lin Hsin , Bansil Arun
Published: May 2014

The topological phase of a silicene nanoribbon holding edge states in the bulk energy gap can be easily broken by an external electric field. Here, we show through low-energy Green's function calculations that it is possible to localize conducting channels anywhere in a silicene nanoribbon by applying an inhomogeneous electric field. The spin degeneracy of these channels can also be broken in the same manner, allowing conduction of spin as well as charge. On this basis, we suggest design of a ternary logic device, which could be used in low-power circuits. Our study demonstrates that silicene and related group IV elements with honeycomb structure could provide a platform for efficient manipulation of spin currents via external electric fields, without the need to switch magnetic fields for spintronics applications.
Ion diffusion coefficient measurements in nanochannels at various concentrations
Authors: Wang Junrong , Zhang Li , Xue Jianming , Hu Guoqing
Published: May 2014

Diffusion is one of the most fundamental properties of ionic transport in solutions. Here, we present experimental studies and theoretical analysis on the ion diffusion in nanochannels. Based on Fick's second law, we develop a current monitoring method to measure ion diffusion coefficient of high solution concentrations in nanochannels. This method is further extended to the cases at medium and low concentrations. Through monitoring ionic current during diffusion, we obtain diffusion coefficients of potassium chloride solution at different concentrations in nanochannels. These diffusion coefficients within the confined space are close to theirs bulk values. It is also found that the apparent ion diffusion equilibrium in the present experiments is very slow at low concentration, which we attribute to the slow equilibrium of the nanochannel surface charge. Finally, we get a primary acknowledge of the equilibrium rate between the nanochannel surface charge and electrolyte solution. The results in this work have improved the understanding of nanoscale diffusion and nanochannel surface charge and may be useful in nanofluidic applications such as ion-selective transport, energy conversion, and nanopore biosensors.
ZnO nanorod-smectic liquid crystal composites: Role of ZnO particle size, shape, and concentration on liquid crystal order and current–voltage properties
Authors: Branch J. , Thompson R. , Taylor J. W. , Salamanca-Riba L. , Martínez-Miranda L. J.
Published: May 2014

This paper investigates how changing the ZnO nanorod size and concentration in a smectic liquid crystal affect the order of the liquid crystal and the current-voltage (I-V) curves in these ZnO nanorods - octylcyanobiphenyl (8CB) liquid crystal nanocomposites. 7 × 5 × 5 and 18 × 7 × 7 nm3 nanorods show an improvement in the alignment of the liquid crystal with increasing weight percentage of ZnO nanoparticles, up to a concentration of approximately 35% wt., similar to our previous results on ZnO nanoparticles with 8CB. The resulting I-V curves are comparable to those obtained in other organic materials used for photovoltaic applications. The I-V response of these nanorod-liquid crystal nanocomposite represents an order of magnitude improvement over what was obtained with spherical nanoparticles.
Fabrication and local laser heating of freestanding Ni80Fe20 bridges with Pt contacts displaying anisotropic magnetoresistance and anomalous Nernst effect
Authors: Brandl F. , Grundler D.
Published: May 2014

In spin caloritronics, ferromagnetic samples subject to relatively large in-plane temperature gradients ∇T have turned out to be extremely interesting. We report on a preparation technique that allows us to create freely suspended permalloy/Pt hybrid structures where a scanning laser induces ∇T on the order of a few K/μm. We observe both the anisotropic magnetoresistance at room temperature and the magnetic field dependent anomalous Nernst effect under laser heating. The technique is promising for the realization of device concepts considered in spin caloritronics based on suspended ferromagnetic nanostructures with electrical contacts.
Ptychography with broad-bandwidth radiation
Authors: Enders B. , Dierolf M. , Cloetens P. , Stockmar M. , Pfeiffer F. , Thibault P.
Published: May 2014

Ptychography, a scanning Coherent Diffractive Imaging (CDI) technique, has quickly gained momentum as a robust method to deliver quantitative images of extended specimens. A current conundrum for the development of X-ray CDI is the conflict between a need for higher flux to reach higher resolutions and the requirement to strongly filter the incident beam to satisfy the tight coherence prerequisite of the technique. Latest developments in algorithmic treatment of ptychographic data indicate that the technique is more robust than initially assumed, so that some experimental limitations can be substantially relaxed. Here, we demonstrate that ptychography can be conducted in conditions that were up to now considered insufficient, using a broad-bandwidth X-ray beam and an integrating scintillator-based detector. Our work shows the wide applicability of ptychography and paves the way to high-throughput, high-flux diffractive imaging.
Note: Error elimination for ellipsometry by laser feedback instrument
Authors: Chen Wenxue , Zhang Shulian , Long Xingwu , Ni Zhibin , Yang Biwu
Published: May 2014

Ellipsometry has in recent decades been used in measuring optical phase retardation. Known for its high resolution but uncertain accuracy, we analyze the systematic error involved with this technique and give error values regarding phase retardation measurements. We developed a laser-feedback assembly to measure phase retardation to a higher resolution and accuracy compared with that from ellipsometry. We eliminated the systematic error associated with ellipsometry using results obtained with this assembly and improved measurement accuracies for ellipsometry to about 0.2°. Such high-precision ellipsometry would greatly improve the manufacturing of wave plates.
SiN-SiC nanofilm: A nano-functional ceramic with bipolar magnetic semiconducting character
Authors: Zhang Jiahui , Li Xingxing , Yang Jinlong
Published: May 2014

Nowadays, functional ceramics have been largely explored for application in various fields. However, magnetic functional ceramics for spintronics remain little studied. Here, we propose a nano-functional ceramic of sphalerite SiN-SiC nanofilm with intrinsic ferromagnetic order. Based on first principles calculations, the SiN-SiC nanofilm is found to be a ferromagnetic semiconductor with an indirect band gap of 1.71 eV. By mean field theory, the Curie temperature is estimated to be 304 K, close to room temperature. Furthermore, the valence band and conduction band states of the nanofilm exhibit inverse spin-polarization around the Fermi level. Thus, the SiN-SiC nanofilm is a typical bipolar magnetic semiconductor in which completely spin-polarized currents with reversible spin polarization can be created and controlled by applying a gate voltage. Such a nano-functional ceramic provides a possible route for electrical manipulation of carrier's spin orientation.
Formation of nearly void-free Cu3Sn intermetallic joints using nanotwinned Cu metallization
Authors: Chiu Wei-Lan , Liu Chien-Min , Haung Yi-Sa , Chen Chih
Published: May 2014

Cu3Sn intermetallic compounds (IMCs) are more resistant to fracture than solders. In addition, the Cu3Sn IMCs are more conductive than the solders. In this study, we manufactured Cu3Sn IMCs to serve as a joint using electroplated nanotwinned Cu as a metallization layer to react with pure Sn at 260 °C and 340 °C. The results show that there were almost no Kirkendall voids generated inside the Cu3Sn layer. In addition, the kinetics of the Cu3Sn growth was analyzed to predict the time needed to form the Cu3Sn joint.
Out-of-resonance vibration modulation of ultrasound with a nonlinear oscillator for microcrack detection in a cantilever beam
Authors: He Qingbo , Xu Yanyan , Lu Siliang , Dai Daoyi
Published: May 2014

This Letter reports an out-of-resonance vibro-acoustic modulation (VAM) effect in nonlinear ultrasonic evaluation of a microcracked cantilever beam. We design a model to involve the microcracked cantilever beam in a nonlinear oscillator system whose dynamics is introduced to extend the operating vibration excitation band of the VAM out of resonance. The prototype model exhibits an effective bandwidth four times that of the traditional linear model. The reported VAM effect allows efficiently enhancing the detection, localization, and imaging of various types of microcracks in solid materials at out-of-resonance vibration excitation frequencies.
Quantum dot quantum cascade infrared photodetector
Authors: Wang Xue-Jiao , Zhai Shen-Qiang , Zhuo Ning , Liu Jun-Qi , Liu Feng-Qi , Liu Shu-Man , Wang Zhan-Guo
Published: May 2014

We demonstrate an InAs quantum dot quantum cascade infrared photodetector operating at room temperature with a peak detection wavelength of 4.3 μm. The detector shows sensitive photoresponse for normal-incidence light, which is attributed to an intraband transition of the quantum dots and the following transfer of excited electrons on a cascade of quantum levels. The InAs quantum dots for the infrared absorption were formed by making use of self-assembled quantum dots in the Stranski–Krastanov growth mode and two-step strain-compensation design based on InAs/GaAs/InGaAs/InAlAs heterostructure, while the following extraction quantum stairs formed by LO-phonon energy are based on a strain-compensated InGaAs/InAlAs chirped superlattice. Johnson noise limited detectivities of 3.64 × 1011 and 4.83 × 106 Jones at zero bias were obtained at 80 K and room temperature, respectively. Due to the low dark current and distinct photoresponse up to room temperature, this device can form high temperature imaging.
Indirect precise angular control using four-wave mixing
Authors: Zhang Wei , Ding Dong-Sheng , Jiang Yun-Kun , Shi Bao-Sen , Guo Guang-Can
Published: May 2014

Here, we show indirect precise angular control using a four-wave mixing (FWM) process. This was performed with a superposition of light with orbital angular momentum in an M-Type configuration of a hot 85Rb atomic ensemble. A gear-shaped interference pattern is observed at FWM light with a donut-shaped input signal. The gear could be rotated and is controlled through the change of the polarization of the pump laser. Our experimental results that are based on nonlinear coherent interactions have applications in image processing and precise angular control.
At DOE, nonproliferation sinks despite its success
Authors: Kramer David
Published: May 2014

Milestones are slipping for US efforts to round up vulnerable fissile materials and convert research reactors to low-enriched uranium.
The tidal disruption of stars by supermassive black holes
Authors: Gezari Suvi
Published: May 2014

Catching the black hole in the act of ingesting a star can reveal a lot about the normally quiet heart of a distant galaxy.
Psychological insights for improved physics teaching
Authors: Aguilar Lauren , Walton Greg , Wieman Carl
Published: May 2014

If classroom practices designed to increase diversity in physics are to succeed, physics teachers need to understand students’ perspectives.
Characterisation of Nanostructured Co3O4 Synthesised by the Thermal Decomposition of an Inorganic Precursor
Authors: Kalpanadevi K. , Sinduja C. R. , Manimekalai R.
Published: May 2014

Nanocrystalline Co3O4 has been synthesised using an inorganic precursor via thermal decomposition. The prepared inorganic precursor Co(cinnamate)2(N2H4)2 was characterised by hydrazine and metal analyses, infrared spectral analysis, and thermogravimetric analysis. Using appropriate annealing conditions, cobalt oxide nanoparticles of average size ~11 nm were synthesised by thermal treatment of the precursor. The nanoparticles’ size and structure were characterised using X-ray diffraction, high-resolution transmission electron microscopy, selected-area electron diffraction, and scanning electron microscopy techniques.
Impact of rain-fed cropping on the hydrology and fertility of alluvial clays in the more arid areas of the upper Darling Basin, eastern Australia
Authors: Young Rick , Huth Neil , Harden Steven , McLeod Ross
Published: May 2014

The impact of cropping on the hydrology and fertility of Vertosols in the northern Darling Basin (average annual rainfall >550 mm) has received much attention, together with the constraints placed on crop growth by naturally occurring subsoil salt stocks. These factors have not been quantified in the drier (450–550 mm), marginal cropping areas to the west. With widespread adoption of zero tillage technology and the potential for large increases in the capture and storage of rainfall in good seasons, mobilisation of salt could be exacerbated should crop water use be constrained by salt toxicity and/or nutrient deficiency. We investigated the size of salt stocks, historic deep drainage, and nutrient depletion under continuous cropping in the Grey and Brown Vertosols of the Walgett and Coonamble districts of north-western NSW. Soils collected from seven paired sites (cropped v. control native vegetation) showed chloride concentrations >500 mg/kg within 0–1.2 m, high exchangeable sodium percentage (~30%) at depth and deficiency in phosphorus, manganese and zinc. Soil total nitrogen decreased from an average stock of 4.9 t/ha at a rate of 0.008 t/ha.year under cropping within 0–0.1 m and soil carbon stocks decreased from 39 t/ha by 0.20 t/ha.year within 0–0.5 m.. Despite low rainfall, high evaporation and the large water-holding capacity of the cracking clays, there were significant downward shifts in chloride concentrations under cropping. Estimates of deep drainage under continuous cropping using chloride mass balance, chloride-front displacement and crop water-balance modelling with the Agricultural Production Systems Simulator (APSIM) generally agreed (range 0.1–2% of average annual rainfall). Simulations suggested that deep drainage may be increased 5–10-fold under zero-tillage winter cropping due to enhanced capture of rainfall by zero tillage compared with traditional practices. The associated flushing of salt from the root-zone together with correction of nutrient deficiency would enhance crop water use and productivity. Current methods indicate little storage in the subsoil for future deep drainage and that hydraulic conductivity is very low. Hence, the long-term effects of any increase in drainage rates, due to changes in cropping practices and/or climate, on the potential for salinisation of groundwater or transient water logging of the surface, are equivocal.
Identification of Hipk2 as an essential regulator of white fat development
Authors: Sjölund Jonas , Pelorosso Facundo G. , Quigley David A. , DelRosario Reyno , Balmain Allan
Published: May 2014

Significance

We have used a bioinformatics approach to discover a role for the
homeodomain-interacting protein kinase 2
(
Hipk2
) gene in adipogenesis. Using gene correlation networks from skin and mammary gland from genetically heterogeneous mice, we predicted a function for the
Hipk2
gene in fat development. In support of this hypothesis, silencing of
Hipk2
potently suppressed adipocyte differentiation in vitro, and deletion of
Hipk2
in mice led to reduced adiposity, increased insulin sensitivity, and partial resistance to high-fat diet–induced obesity. These data demonstrate the value of gene network approaches for analysis of gene function in vivo, and provide a biological framework for discovery of potential target genes, such as
Hipk2
, in metabolic and other diseases.
Indian Diaspora as a factor in India–Malaysia relations
Authors: Singh Amit
Published: May 2014

The paper studies the presence of Indian Diaspora in Malaysia in transforming the India– Malaysia bilateral relations. At present, both these countries treat the Indian Diaspora as a liability. However, if India and Malaysia consider ethnic Indians as an asset, the ties between New Delhi and Kuala Lumpur will improve significantly.
Artin-Whaples approximations of bounded degree in algebraic varieties
Authors: Mantova Vincenzo , Zannier Umberto
Published: May 2014

The celebrated Artin-Whaples approximation theorem (which is a generalization of the Chinese remainder theorem) asserts that, given a field

K
K

, distinct places

v

1

,
…
,

v

n

v_{1},\dots ,v_{n}

of

K
K

, and points

x

1

,
…
,

x

n

∈

P

1

(
K
)

x_{1},\dots ,x_{n}\in \mathbb {P}_{1}(K)

, it is possible to find an

x
∈

P

1

(
K
)

x\in \mathbb {P}_{1}(K)

simultaneously near

x

i

x_{i}

w.r.t.

v

i

v_{i}

with any prescribed accuracy. If we replace

P

1

\mathbb {P}_{1}

with other algebraic varieties

V
V

, the analogous conclusion does not generally hold, e.g., because

V
V

may contain too few points over

K
K

. However, it has been proved by a number of authors that, at least in the case of global fields, it holds if we allow

x
x

to be algebraic over

K
K

. These results do not directly contain either the case of

P

1

\mathbb {P}_{1}

or the case of general fields, and above all they do not control the degree of

x
x

.

In this paper we offer different arguments leading to a general approximation theorem properly generalizing that of Artin-Whaples. This works for every

V
V

,

K
K

as above, and not only asserts the existence of a suitable

x
∈
V
(

K
¯

)

x\in V(\overline {K})

, but bounds explicitly the degree

[
K
(
x
)
:
K
]

[K(x):K]

in terms only of geometric invariants of

V
V

. It shall also be seen that such a bound is in a sense close to being best-possible.
A dimeric equilibrium intermediate nucleates Drp1 reassembly on mitochondrial membranes for fission
Authors: Macdonald Patrick J. , Stepanyants Natalia , Mehrotra Niharika , Mears Jason A. , Qi Xin , Sesaki Hiromi , Ramachandran Rajesh
Published: May 2014

The GTPase dynamin-related protein 1 (Drp1) catalyzes mitochondrial division, but the mechanisms remain poorly understood. Much of what is attributed to Drp1’s mechanism of action in mitochondrial membrane fission parallels that of prototypical dynamin in endocytic vesicle scission. Unlike the case for dynamin, however, no lipid target for Drp1 activation at the mitochondria has been identified. In addition, the oligomerization properties of Drp1 have not been well established. We show that the mitochondria-specific lipid cardiolipin is a potent stimulator of Drp1 GTPase activity, as well as of membrane tubulation. We establish further that under physiological conditions, Drp1 coexists as two morphologically distinct polymeric species, one nucleotide bound in solution and the other membrane associated, which equilibrate via a dimeric assembly intermediate. With two mutations, C300A and C505A, that shift Drp1 polymerization equilibria in opposite directions, we demonstrate that dimers, and not multimers, potentiate the reassembly and reorganization of Drp1 for mitochondrial membrane remodeling both in vitro and in vivo.
Lipid domain–dependent regulation of single-cell wound repair
Authors: Vaughan Emily M. , You Jae-Sung , Elsie Yu Hoi-Ying , Lasek Amber , Vitale Nicolas , Hornberger Troy A. , Bement William M.
Published: May 2014

After damage, cells reseal their plasma membrane and repair the underlying cortical cytoskeleton. Although many different proteins have been implicated in cell repair, the potential role of specific lipids has not been explored. Here we report that cell damage elicits rapid formation of spatially organized lipid domains around the damage site, with different lipids concentrated in different domains as a result of both de novo synthesis and transport. One of these lipids—diacylglycerol (DAG)—rapidly accumulates in a broad domain that overlaps the zones of active Rho and Cdc42, GTPases that regulate repair of the cortical cytoskeleton. Formation of the DAG domain is required for Cdc42 and Rho activation and healing. Two DAG targets, protein kinase C (PKC) β and η, are recruited to cell wounds and play mutually antagonistic roles in the healing process: PKCβ participates in Rho and Cdc42 activation, whereas PKCη inhibits Rho and Cdc42 activation. The results reveal an unexpected diversity in subcellular lipid domains and the importance of such domains for a basic cellular process.
Perioperative care
Authors: David Cain , Mark Edwards , Hamilton Mark , Freeman Nikki , Myles Paul , Tolchard Steve , Older Paul
Published: May 2014

Modern anaesthesia requires an appreciation of the potential to reduce perioperative complications through improved pre-assessment, risk stratification, individualised anaesthetic techniques and appropriate interpretation and response to intraoperative clinical signs and advanced monitoring. This chapter contains detailed discussion of cases relating to cardiopulmonary exercise testing (CPET) (case 2.3), intraoperative fluid management (case 2.1) and the prevention of accidental awareness under general anaesthesia (AAGA) (case 2.2). CPET allows objective testing of cardiopulmonary reserve prior to the stress of major surgery; the data produced enables patients and anaesthetists to make informed choices about perioperative management. This case describes the physiological principles and growing evidence base supporting its use. Intraoperative fluid management, and advanced monitors to direct it are the subject of increasing focus in modern anaesthesia. This case highlights the importance of understanding the strengths and limitations of the technology now available. AAGA (accidental awareness during general anaesthesia) is a highly feared complication of anaesthesia, both by patients and anaesthetists. This case discusses identifying those at risk, techniques to prevent AAGA and principles of managing cases when they arise.
Laparoscopic and bariatric surgery
Authors: Middleditch Alex , Athanassoglou Vassilis , Miller Timothy E. , Savic Louise , Bellamy Mark C.
Published: May 2014

Anaesthetic practice must evolve in response to developments in surgical techniques; the expansions in use of laparoscopic approaches and bariatric surgery are two such areas explored by the cases in this chapter. Laparoscopic surgical techniques may reduce the stress response to surgery and as part of an enhanced recovery program may reduce hospital stays and the morbidity associated with surgery. Anaesthetic techniques must be adapted to accommodate the physiological consequences of the pneumoperitoneum, and anaesthetists must be aware of and confident to manage the potential intraoperative complications. Case 3.1 discusses anaesthesia for a laparoscopic colectomy. Anaesthesia for bariatric surgery (such as gastroplasty or gastric banding), as described in case 3.2, provides multiple challenges arising from the physiological changes found in the morbidly obese, potentially difficult airway management and drug dosing, and management of associated comorbidities.
Obstetric anaesthesia
Authors: Syme Phoebe , Bogod David , Hurford Dom , Howell Paul
Published: May 2014

Obstetric anaesthesia provides unique challenges to the anaesthetist, especially those relating to the sometimes conflicting needs of the mother and fetus. This chapter discusses in depth the management of obstetric haemorrhage (case 5.1), and the Category 1 emergency caesarean section (CS) (case 5.2). Antepartum obstetric haemorrhage (due to placenta praevia or placental abruption) requires carefully planned and coordinated team management. The anaesthetist has a key role in ensuring maternal safety through appropriate selection of anaesthetic technique, and planning the response to ongoing haemorrhage. Bleeding during caesarean section may be rapid and life-threatening, management requires knowledge of strategic blood product administration, blood conservation techniques, pharmacological treatment for uterine atony and the surgical techniques which may be deployed. The category 1 CS places the anaesthetist under considerable pressure, and requires anaesthesia in a potentially challenging situation of a complex patient whom the anaesthetist has only just met. Anticipation of complications is key to ensure good outcome for mother and baby.
Multiple trauma
Authors: Sampson Caroline , Parr Michael
Published: May 2014

Case 8.1 describes in detail the assessment and management of a multiply injured patient from their arrival in the emergency department through to their intraoperative period and postoperative care. Challenges encountered at every stage are discussed and key learning points explored. The primary survey is a structured assessment of the trauma patient which identifies immediately life-threatening injuries, and expedites their management. Intraosseous cannulation has emerged as a useful strategy for vascular access in trauma. Careful fluid resuscitation, airway management and induction of anaesthesia are essential to prevent avoidable complications of trauma. FAST scanning and/or early CT imaging are key investigations to plan management. Anticipation of physiological responses to trauma, application of lessons learnt from the battlefield and close cooperation with surgeons to help stage definitive repair are part of a team approach to the trauma patient.
Cardiac disease and anaesthesia
Authors: DeVile Michael , Foex Pierre , Jackson Robert , Nolan Jerry
Published: May 2014

Anaesthetists have a key role in preventing cardiac complications during the perioperative period, but now are also increasingly involved in supporting patients who have suffered spontaneous acute cardiac events. Case 9.1 discusses the increasingly common situation of a patient with coronary stents in situ presenting for unrelated surgery. It is essential for anaesthetists to understand the implications of the presence of these devices and how this may impact on their anaesthetic techniques. A key issue is appropriate management of antiplatelet medication; this case describes the issues in depth and demonstrates the potential consequences of poor management. Patients suffering out of hospital arrest, as described in case 9.2, are increasingly seen as treatable – such aggressive management requires familiarity and quick decision making by the anaesthetic team. Expeditious stabilisation in the emergency department and transfer to the coronary catheter laboratory whilst implementing a neuroprotective strategy may significantly impact on neurological recovery.
A tight scaling relation of dark matter in galaxy clusters
Authors: Chan Man Ho
Published: May 2014

Recent studies in different types of galaxies reveal that the product of the central density and the core radius (ρcrc) is a constant. However, some empirical studies involving galaxy clusters suggest that the product ρcrc depends weakly on the total dark halo mass. In this Letter, we re-analyse the hot gas data from 106 clusters and obtain a surprisingly tight scaling relation: $\rho _{\rm c} \propto r_{\rm c}^{-1.46 \pm 0.16}$. This result generally agrees with the claims that ρcrc is not a constant for all scales of structure. Moreover, this relation does not support the velocity-dependent cross-section of dark matter if the core formation is due to the self-interaction of dark matter.
Spectroscopy of the enigmatic short-period cataclysmic variable IR Com in an extended low state
Authors: Manser C. J. , Gänsicke B. T.
Published: May 2014

We report the occurrence of a deep low state in the eclipsing short-period cataclysmic variable (CV) IR Com, lasting more than two years. Spectroscopy obtained in this state shows the system as a detached white dwarf plus low-mass companion, indicating that accretion has practically ceased. The spectral type of the companion derived from the SDSS spectrum is M6–7, somewhat later than expected for the orbital period of IR Com. Its radial velocity amplitude, K2 = 419.6 ± 3.4 km s−1, together with the inclination of 75°–90° implies 0.8 < Mwd <1.0 M⊙. We estimate the white dwarf temperature to be ≃15 000 K, and the absence of Zeeman splitting in the Balmer lines rules out magnetic fields in excess of ≃5 MG. IR Com still defies an unambiguous classification, in particular the occurrence of a deep, long low state is so far unique among short-period CVs that are not strongly magnetic.
Eic1 links Mis18 with the CCAN/Mis6/Ctf19 complex to promote CENP-A assembly
Authors: Subramanian Lakxmi , Toda Nicholas R. T. , Rappsilber Juri , Allshire Robin C.
Published: May 2014

CENP-A chromatin forms the foundation for kinetochore assembly. Replication-independent incorporation of CENP-A at centromeres depends on its chaperone HJURP
Scm3
, and Mis18 in vertebrates and fission yeast. The recruitment of Mis18 and HJURP
Scm3
to centromeres is cell cycle regulated. Vertebrate Mis18 associates with Mis18BP1
KNL2
, which is critical for the recruitment of Mis18 and HJURP
Scm3
. We identify two novel fission yeast Mis18-interacting proteins (Eic1 and Eic2), components of the Mis18 complex. Eic1 is essential to maintain Cnp1
CENP-A
at centromeres and is crucial for kinetochore integrity; Eic2 is dispensable. Eic1 also associates with Fta7
CENP-Q/Okp1
, Cnl2
Nkp2
and Mal2
CENP-O/Mcm21
, components of the constitutive CCAN/Mis6/Ctf19 complex. No Mis18BP1
KNL2
orthologue has been identified in fission yeast, consequently it remains unknown how the key Cnp1
CENP-A
loading factor Mis18 is recruited. Our findings suggest that Eic1 serves a function analogous to that of Mis18BP1
KNL2
, thus representing the functional counterpart of Mis18BP1
KNL2
in fission yeast that connects with a module within the CCAN/Mis6/Ctf19 complex to allow the temporally regulated recruitment of the Mis18/Scm3
HJURP
Cnp1
CENP-A
loading factors. The novel interactions identified between CENP-A loading factors and the CCAN/Mis6/Ctf19 complex are likely to also contribute to CENP-A maintenance in other organisms.
Rhizobium lemnae sp. nov., a bacterial endophyte of Lemna aequinoctialis
Authors: Kittiwongwattana Chokchai , Thawai Chitti
Published: May 2014

Bacterial strain L6-16Twas isolated fromLemna aequinoctialis. Cells were Gram-stain-negative, rod-shaped and motile with monopolar flagella. The phylogenetic analysis of its nearly complete 16S rRNA gene sequence revealed that strain L6-16Twas a member of the genusRhizobium. Its closest relative wasRhizobium tarimensePL-41Twith a 16S rRNA gene sequence similarity value of 98.3 %. Sequence similarity analysis of the housekeepingrecAandatpDgenes showed low levels of sequence similarity (<93.9 %) between strain L6-16Tand other species of the genusRhizobium. Strain L6-16Twas able to grow between pH 5 and 11 (optimum 7.0) and at temperatures ranging from 20 to 41 °C (optimum 30 °C). It tolerated NaCl up to 1 % (w/v) (optimum 0.5 %). C18 : 1ω7cand/or C18 : 1ω6c(summed feature 8; 79.5 %) were found as predominant cellular fatty acids. The DNA G+C content of strain L6-16Twas 58.1 mol% (Tm). Based on low levels of DNA–DNA relatedness, strain L6-16Twas distinct from members of phylogenetically related species includingR. tarimensePL-41T(38.3±0.8 %),Rhizobium rosettiformansW3T(6.9±0.4 %) andRhizobium pseudoryzaeJ3-A127T(12.3±0.6 %). Strain L6-16Twas unable to nodulate the roots ofPhaseolus vulgaris, andnodCandnifHgenes were not detected. The results obtained from phylogenetic analyses, phenotypic characterization and DNA–DNA hybridization indicated that strain L6-16Trepresents a novel species of the genusRhizobium, for which the nameRhizobium lemnaesp. nov. is proposed. The type strain is L6-16T( = NBRC 109339T = BCC 55143T).