bluuebunny/crossref_metadata_2025 huggingface dataset:
Quadratic canonical transformation theory and higher order density matrices
Authors: Neuscamman Eric , Yanai Takeshi , Chan Garnet Kin-Lic
Published: March 2009

Canonical transformation (CT) theory provides a rigorously size-extensive description of dynamic correlation in multireference systems, with an accuracy superior to and cost scaling lower than complete active space second order perturbation theory. Here we expand our previous theory by investigating (i) a commutator approximation that is applied at quadratic, as opposed to linear, order in the effective Hamiltonian, and (ii) incorporation of the three-body reduced density matrix in the operator and density matrix decompositions. The quadratic commutator approximation improves CT’s accuracy when used with a single-determinant reference, repairing the previous formal disadvantage of the single-reference linear CT theory relative to singles and doubles coupled cluster theory. Calculations on the BH and HF binding curves confirm this improvement. In multireference systems, the three-body reduced density matrix increases the overall accuracy of the CT theory. Tests on the H2O and N2 binding curves yield results highly competitive with expensive state-of-the-art multireference methods, such as the multireference Davidson-corrected configuration interaction (MRCI+Q), averaged coupled pair functional, and averaged quadratic coupled cluster theories.
Onset of synchronization in weighted scale-free networks
Authors: Wang Wen-Xu , Huang Liang , Lai Ying-Cheng , Chen Guanrong
Published: March 2009

We investigate Kuramoto dynamics on scale-free networks to include the effect of weights, as weighted networks are conceivably more pertinent to real-world situations than unweighted networks. We consider both symmetric and asymmetric coupling schemes. Our analysis and computations indicate that more links in weighted scale-free networks can either promote or suppress synchronization. In particular, we find that as a parameter characterizing the weighting scheme is varied, there can be two distinct regimes: a normal regime where more links can enhance synchronization and an abnormal regime where the opposite occurs. A striking phenomenon is that for dense networks for which the mean-field approximation is satisfied, the point separating the two regimes does not depend on the details of the network structure such as the average degree and the degree exponent. This implies the existence of a class of weighted scale-free networks for which the synchronization dynamics are invariant with respect to the network properties. We also perform a comparison study with respect to the onset of synchronization in Kuramoto networks and the synchronization stability of networks of identical oscillators.
Simulation of switching effects in electrically dipolar manganites
Authors: Morchshakov V. , Annaorazov M. P. , Aybar H. Ş. , Yang C. P. , Troyanchuk I. O. , Bärner K.
Published: March 2009

Electrical field induced transitions between metallic and insulating magnetic states have been reported in various manganites and, in particular, in oxygen deficient Nd0.7Sr0.3MnO3−δ with 0>δ>0.2. In this series, the resistivity increases drastically with increasing δ. In polycrystals, in particular, there is mounting evidence that the oxygen deficiency and with it the resistivity is increased close to grain boundaries. Therefore, under a current load the electrical field near a grain boundary could be strong enough to induce a transition to a metallic state in a thin layer near the boundary. If, however, this sample part gets metallic, the electrical field is screened and the layer would return to its original state. As this looks like an electrical feedback mechanism, we expect that at least some manganites show electrical switching phenomena, and indeed these are observed. Numerical SPICE simulations and their comparison with the unusual experimental results, which were obtained with polycrystalline Nd0.7Sr0.3MnO3−δ and Pr0.7Ca0.3MnO3 ceramic and its Sr-substitution derivates, confirm both the existence of electrical field induced transitions and of an electrical feedback mechanism.
Simulation on the relation of distribution of overall critical transport current to that of local one in bent-damaged Bi2223 superconducting composite tape
Authors: Ochiai S. , Fujimoto M. , Okuda H. , Oh S. S. , Ha D. W.
Published: March 2009

The superconducting Bi2223/Ag/Ag alloy composite tape specimens with a length 6 cm, composed of a series circuit of six local elements with a length 1 cm, were bent by 0.37% and 1.0% for measurement of distributions of the overall (6 cm) and local (1 cm) critical transport current and n-value. When the damage amount was small (0.37% bending strain), the distributions of the measured local and overall critical currents were described by the three parameter Weibull distribution function, while when the damage amount was large (1.0% bending strain), those were described by the bimodal Weibull distribution function. The distributions of n-value in the diagram of n-value versus critical current for both local elements and overall specimens were expressed by the regression curve of n-value as a function of critical current and the normal distribution function for the deviation of the measured n-values from the regression curve. The experimentally measured critical current distribution and the diagram of the n-value versus critical current of the overall specimens were reproduced successfully in the computer by inputting the formulated distribution functions for the critical current and n-value of the local elements into the proposed simulation method, which used a Monte Carlo simulation method and a one-dimensional series circuit model for the generated voltage near the transition of superconducting to normal state.
Coverage dependent adsorption dynamics in hyperthermal organic thin film growth
Authors: Amassian A. , Desai T. V. , Kowarik S. , Hong S. , Woll A. R. , Malliaras G. G. , Schreiber F. , Engstrom J. R.
Published: March 2009

We have examined the dynamics of adsorption of diindenoperylene (DIP) on SiO2 and SiO2 modified with an interfacial organic layer using in situ real time synchrotron x-ray scattering, focusing on the effects of coverage. On both surfaces we observe a substantial increase in the probability of adsorption with increasing coverage, which is most dramatic at the highest incident kinetic energies. On the initially uncovered surfaces, we observe a smooth decrease in the probability of adsorption with increasing incident kinetic energy, indicative of trapping-mediated adsorption. Once both surfaces are covered by DIP, the effects of incident kinetic energy are greatly reduced, and trapping is very efficient over the range of kinetic energies examined. Possible reasons for efficient trapping at high coverage and at high incident kinetic energy include more efficient momentum transfer due to mass matching, and possibly direct molecular insertion. Comparison to results on another small-molecule, pentacene, suggests that this behavior should be common to hyperthermal growth of a variety of other small-molecule thin films.
Fabrication of (Fe,Mn)3O4 ferromagnetic oxide nanostructure using molybdenum nanomask atomic force microscope lithography
Authors: Goto Kazuya , Tanaka Hidekazu , Kawai Tomoji
Published: March 2009

We reported the fabrication of Fe2.5Mn0.5O4 (FMO) ferromagnetic oxide nanostructure using molybdenum (Mo) nanomask atomic force microscope (AFM) lithography technique for oxide nanospintronics applications. This technique enables us to prepare transition metal oxide nanostructures down to 200nm. The hard x-ray photoemission spectroscopy revealed that the resulting nanostructures preserve a fine electric structure as spintronics oxide same as unprocessed films. The resulting FMO nanostructure showed the magnetoresistance of about −0.11% to −0.14% at the magnetic field of 3000Oe, which value was similar to that of FMO film. These indicate that this technique can construct well defined nanoscale oxides both in structure and physical properties.
Strain relaxation of thin Si0.6Ge0.4 grown with low-temperature buffers by molecular beam epitaxy
Authors: Zhao M. , Hansson G. V. , Ni W.-X.
Published: March 2009

A double-low-temperature-buffer variable-temperature growth scheme was studied for fabrication of strain-relaxed thin Si0.6Ge0.4 layer on Si(001) by using molecular beam epitaxy (MBE), with particular focuses on the influence of growth temperature of individual low-temperature-buffer layers on the relaxation process and final structural qualities. The low-temperature buffers consisted of a 40 nm Si layer grown at an optimized temperature of ∼400 °C, followed by a 20 nm Si0.6Ge0.4 layer grown at temperatures ranging from 50 to 550 °C. A significant relaxation increase together with a surface roughness decrease both by a factor of ∼2, accompanied with the cross-hatch/cross-hatch-free surface morphology transition, took place for the sample containing a low-temperature Si0.6Ge0.4 layer that was grown at ∼200 °C. This dramatic change was explained by the association with a certain onset stage of the ordered/disordered growth transition during the low-temperature MBE, where the high density of misfit dislocation segments generated near surface cusps largely facilitated the strain relaxation of the top Si0.6Ge0.4 layer.
Thermoelectric properties of p-type LiZnSb: Assessment of ab initio calculations
Authors: Toberer Eric S. , May Andrew F. , Scanlon Cidney J. , Snyder G. Jeffery
Published: March 2009

In response to theoretical calculations on the thermoelectric performance of LiZnSb, we report the pertinent transport properties between room temperature and 523 K. Nominal LiZnSb samples are found to be p-type, with a carrier concentration in the range (4–7)×1020 cm−3. The thermoelectric figure of merit (zT) is found to be 0.02–0.08 at 523 K. Analysis of material transport parameters and previously reported ab initio calculations demonstrates that even with optimal doping, p-type LiZnSb is unlikely to achieve zT>0.2 at 523 K. The accuracy of the high zT estimate (zT>2) for n-type compositions from ab initio calculations is discussed within the current synthetic limits.
Structural and photoacoustic studies of Zn4Sb3 and ZnSb phases prepared by mechanical alloying
Authors: Trichês D. M. , Souza S. M. , de Lima J. C. , Grandi T. A. , Campos C. E. M.
Published: March 2009

The structural and photoacoustic properties of nanostructured zinc antimonides Zn4Sb3 and ZnSb prepared by mechanical alloying were studied by x-ray diffraction (XRD) and photoacoustic absorption spectroscopy (PAS). The XRD patterns revealed the existence of Zn4Sb3 and elemental Zn for 10 h of milling, Zn4Sb3 and ZnSb for 20 h of milling, and ZnSb and elemental Zn for 30 h of milling. Using the Rietveld structural refinement procedure, the experimental XRD patterns were simulated and the relative amounts of each phase for each of the milling times above were calculated. The thermal diffusivity values corresponding to each milling time were measured from the PAS signal amplitude and phase. Using the thermal diffusivity value and the relative amounts of ZnSb and elemental Zn, we estimated the thermal diffusivity for the ZnSb phase in nanometric form. The result seems to corroborate the suggestion of other researchers that the thermal conductivity tends to be smaller in materials with nanometric crystallites.
Using numerical simulations to extract parameters of toroidal electron plasmas from experimental data
Authors: Ha B. N. , Stoneking M. R. , Marler J. P.
Published: March 2009

Measurements of the image charge induced on electrodes provide the primary means of diagnosing plasmas in the Lawrence Non-neutral Torus II (LNT II) [Phys. Rev. Lett. 100, 155001 (2008)]. Therefore, it is necessary to develop techniques that determine characteristics of the electron plasma from features of the induced image charge signal. This paper presents a numerical study which finds that the frequency of the image charge signal due to the toroidal version of the m=1 diocotron mode is proportional to the total trapped charge and inversely proportional to magnetic field strength, as in the cylindrical case. In the toroidal case, additional information about the m=1 motion of the plasma can be obtained by analysis of the image charge signal amplitude and shape. Finally, results from the numerical simulations are compared to experimental data from the LNT II and plasma characteristics are reported.
Magnetic spin states and vortex stability control in elongated Ni80Fe20 nanorings
Authors: Ren Y. , Adeyeye A. O.
Published: March 2009

We present the results of a systematic characterization of the magnetization reversal mechanism of arrays of elongated Ni80Fe20 nanorings using focused magneto-optical Kerr effect measurements. The long axis of the rings was varied from 850 nm to 1.60 μm while the aspect ratio, ring width, and thickness were fixed at 2, 150 nm, and 25 nm, respectively. We observed an increase in the range of stability of the intermediate vortex state with both increasing length (l) of the ring and varying field orientations. Interestingly, for l>lcrit, the reversal process drastically changes from a two-step switching to a single step switching without the formation of a vortex state and from a one-step switching to a double step switching with the formation of a vortex state when the applied field is (±5°) away from the easy and hard axes of the ring, respectively. There is a good agreement between the experimental results and micromagnetic simulations.
A dielectrophoresis-based microchannel system
Authors: Zhao X. X. , Gao Y. , Huang J. P.
Published: March 2009

In this paper, we will propose a dielectrophoresis-based microchannel system. Based on numerical calculations and theoretical analysis, we investigate the dynamic behaviors of a microparticle in this system, in the presence of nonuniform electric fields generated by point microelectrodes. Good agreement is shown between them. It is found that the microelectrodes enable the system equilibrium to shift between monostable and bistable states. Further, we reveal that the microparticle can oscillate along the microchannel with a fixed period for the ideal case without a drag force, and that it can be located in either monostable or bistable states for the cases with drag forces. In view of these findings, we carefully address the possibility to design several microfluidic devices, namely, a microparticulate clock for timing, a binary random number generator for conducting stochastic calculations, and a flip-flop device for system memory.
Structures and harmonic vibrational frequencies for excited states of diatomic molecules with CCSD(R12) and CCSD(F12) models
Authors: Yang Jun , Hättig Christof
Published: March 2009

The equation-of-motion coupled-cluster method for excited states with the singles-and-doubles model (CCSD) has been implemented for ansatz 2 of the explicitly correlated CCSD(R12) and CCSD(F12) methods as part of the program package Dalton. In this model, an orthonormal complementary auxiliary basis set is used for the resolution-of-identity approximation in order to calculate the three-electron integrals needed for CCSD(R12) and CCSD(F12). The additional CCSD(R12) or CCSD(F12) terms introduced within ansatz 2, which are not present in ansatz 1, are derived and discussed with regard to the extra costs needed for their computation. As a first application the basis set convergence of equilibrium bond lengths and harmonic vibrational frequencies has been investigated for some singlet excited states of the diatomic molecules N2, CO, BF, and BH. The calculated CCSD(F12) results show that the average absolute deviations of the bond lengths and frequencies from the basis set limits are below 0.1 pm and 5 cm−1 as well as 0.05 pm and 1 cm−1 for the triple- and quadruple-ζ basis sets, respectively. These deviations are shown to largely arise from the SCF basis set incompleteness errors.
Thermal grafting of fluorinated molecular monolayers on doped amorphous silicon surfaces
Authors: Sabbah H. , Conde J. P. , Chu V. , Zebda A. , Ababou-Girard S. , Solal F. , Godet C.
Published: March 2009

Thermally induced (160–300 °C) gas phase grafting of linear alkene molecules (perfluorodecene) was performed on hydrogenated amorphous silicon (a-Si:H) films, either nominally undoped or doped with different boron and phosphorus concentrations. Dense and smooth a-Si:H films were grown using plasma decomposition of silane. Quantitative analysis of in situ x-ray photoelectron spectroscopy indicates the grafting of a single layer of organic molecules. The hydrophobic properties of perfluorodecene-modified surfaces were studied as a function of surface coverage. Annealing experiments in ultrahigh vacuum show the covalent binding and the thermal stability of these immobilized layers up to 370 °C; this temperature corresponds to the Si–C bond cleavage temperature. In contrast with hydrogenated crystalline Si(111):H, no heavy wet chemistry surface preparation is required for thermal grafting of alkene molecules on a-Si:H films. A threshold grafting temperature is observed, with a strong dependence on the doping level which produces a large contrast in the molecular coverage for grafting performed at 230 °C.
Instrument response standard in time-resolved fluorescence
Authors: Luchowski Rafal , Gryczynski Zygmunt , Sarkar Pabak , Borejdo Julian , Szabelski Mariusz , Kapusta Peter , Gryczynski Ignacy
Published: March 2009

The fluorescence of LDS 798 dye in aqueous solution has a very short lifetime of 24ps, independent of excitation wavelength. The time response of common photon counting detectors depends on the wavelength of the registered photon. In lifetime measurements, the instrument response function (IRF) is usually approximated by the temporal profile of the scattered excitation light. Because λExc is typically much shorter than λEm, a systematic error may be present in these measurements. We demonstrate that the fluorescence decay of LDS 798 is a better approximation of IRF, in particular, for avalanche photodiodes used in the near infrared spectral region.
In situ investigation of the stability field and relaxation behavior of nanodomain structures in morphotropic Pb[Zr1−xTix]O3 under variations in electric field and temperature
Authors: Schönau Kristin A. , Knapp Michael , Maglione Mario , Fuess Hartmut
Published: March 2009

The stability field of nanodomain structures recently discovered at the morphotropic phase boundary of undoped lead zirconate titanate [Schönau et al., Phys. Rev. B 75, 184117 (2007)] has been investigated with respect to temperature and electric field. Under electric field for distinct compositions, such as PbZr0.535Ti0.465O3, the starting domain structure of tetragonal microdomains and nanodomains is reversibly alternated into rhombohedral microdomains at high voltage. We now show that this material exhibits a dielectric relaxation directly below the formation temperature of nanodomain structures, correlated either to a high domain wall density or to polar nanoregions with activation energies in the range observed for relaxor ferroelectrics.
Magnetization and magnetic anisotropy of metallophthalocyanine molecules from the first principles calculations
Authors: Wang Junhua , Shi Yisheng , Cao Juexian , Wu Ruqian
Published: March 2009

Using the full potential linearized augmented plane wave method, we explored the magnetic anisotropy energies of metallophthalocyanine molecules with Mn, Fe, Co, and Ni. Their spin magnetic moments can be expressed as 8−nμB (n=5,6,7,8 for Mn, Fe, Co, and Ni). Interestingly, Mn-phthalocyanine has a large orbital magnetic moment of 0.19μB and a sizable magnetic anisotropy energy of 2.72 meV useable for applications.
Room temperature spontaneous emission enhancement from quantum dots in photonic crystal slab cavities in the telecommunications C band
Authors: Hostein R. , Braive R. , Larqué M. , Lee K.-H. , Talneau A. , Le Gratiet L. , Robert-Philip I. , Sagnes I. , Beveratos A.
Published: March 2009

We report on the control of the spontaneous emission dynamics from InAsP self-assembled quantum dots emitting in the telecommunications C band and weakly coupled to the mode of a double heterostructure cavity etched on a suspended InP membrane at room temperature. The quality factor of the cavity mode is 44×103 with an ultralow modal volume of the order of 1.2(λ/n)3, inducing an enhancement in the spontaneous emission rate of up a factor of 2.8 at 300 K.
Pulsed metal-organic chemical vapor deposition of high-quality AlN/GaN superlattices for near-infrared intersubband transitions
Authors: Bayram C. , Péré-laperne N. , McClintock R. , Fain B. , Razeghi M.
Published: March 2009

A pulsed metal-organic chemical vapor deposition technique is developed for the growth of high-quality AlN/GaN superlattices (SLs) with intersubband (ISB) transitions at optical communications wavelengths. Tunability of the AlN and GaN layers is demonstrated. Indium is shown to improve SL surface and structural quality. Capping thickness is shown to be crucial for ISB transition characteristics. Effects of barrier- and well-doping on the ISB absorption are reported.
Fabrication and characterization of low temperature polycrystalline silicon thin film transistors by ink-jet printed nickel-mediated lateral crystallization
Authors: Lee Jang-Sik , Kim Min-Sun , Kim Dongjo , Kim Yong-Mu , Moon Jooho , Joo Seung-Ki
Published: March 2009

High-performance polycrystalline silicon thin film transistors (poly-Si TFTs) were fabricated by using ink-jet printed nickel on large area glass substrates. Direct-printed Ni dots were used as a catalyst to crystallize the amorphous silicon into poly-Si for use in the channel region of TFT devices by metal-induced lateral crystallization. The fabricated poly-Si TFTs showed high field-effect mobility and on-off ratio that are comparable to the TFTs prepared using conventional semiconductor processes. The method presented here is a combination of bottom-up and top-down approaches and has a potential to be used in next generation high-performance poly-Si TFT fabrication.
On the anisotropic shear resistance of hard transition metal nitrides TMN (TM=Ti, Zr, Hf)
Authors: Zhang R. F. , Sheng S. H. , Veprek S.
Published: March 2009

The anisotropic shear moduli and strengths of hard fcc-TMN (TM=Ti, Zr, Hf) have been calculated by ab initio density functional theory in order to better understand their shear resistance. TiN shows the largest shear strength among the three nitrides, being consistent with the known facts that TiN is harder than HfN which is harder than ZrN. The electronic origin is further addressed. Based on the smooth shapes of the stress-strain curves and on the variation of electronic structure during shear deformations, the abrupt lattice instability mode reported previously for TiN (110)⟨11¯0⟩ shear deformation is not supported by our data.
Colossal dielectric constant up to gigahertz at room temperature
Authors: Krohns S. , Lunkenheimer P. , Kant Ch. , Pronin A. V. , Brom H. B. , Nugroho A. A. , Diantoro M. , Loidl A.
Published: March 2009

The applicability of recently discovered materials with extremely high (“colossal”) dielectric constants, required for future electronics, suffers from the fact that their dielectric constant ε′ only is huge in a limited frequency range below about 1 MHz. In the present report, we show that the dielectric properties of a charge-ordered nickelate, La15/8Sr1/8NiO4, surpass those of other materials. Especially, ε′ retains its colossal magnitude of >10 000 well into the gigahertz range.
Acoustoelectric luminescence from a field-effect n-i-p lateral junction
Authors: De Simoni Giorgio , Piazza Vincenzo , Sorba Lucia , Biasiol Giorgio , Beltram Fabio
Published: March 2009

A surface-acoustic-wave (SAW) driven light-emitting-diode structure that can implement a single-photon source for quantum-cryptography applications is demonstrated. Our lateral n-i-p junction is realized starting from an undoped GaAs/AlGaAs quantum well by gating. It incorporates interdigitated transducers for SAW generation and lateral gates for current control. We demonstrate acoustoelectric transport and SAW-driven electroluminescence. The acoustoelectric current can be controlled down to complete pinch-off by means of the lateral gates.
Correlations between elastic moduli and molar volume in metallic glasses
Authors: Wang J. Q. , Wang W. H. , Yu H. B. , Bai H. Y.
Published: March 2009

We report clear correlations between bulk modulus (K) and average molar volume Vm, and between Poisson’s ratio ν and Vm for various bulk metallic glasses. The origin for the correlations between elastic moduli and Vm are discussed. The established correlation, associated with Poisson’s ratio ν, and since the ν correlates with plasticity of metallic glasses, indicates that the average molar volume is important factor to be considered for plastic metallic glasses searching. The found correlations also suggest a close relation between the mechanical properties and the short-range atomic bonding, and assist in understanding deformation behavior in metallic glasses.
Transmission electron microscopy study on the crystallization and boron distribution of CoFeB/MgO/CoFeB magnetic tunnel junctions with various capping layers
Authors: Miyajima Toyoo , Ibusuki Takahiro , Umehara Shinjiro , Sato Masashige , Eguchi Shin , Tsukada Mineharu , Kataoka Yuji
Published: March 2009

High-resolution transmission electron microscopy and electron energy-loss spectroscopy (EELS) were used to study the microstructural properties of CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) with various capping layers. Crystallization of CoFeB layers was strongly dependent on the capping materials, and was affected by B diffusion. With NiFe-cap MTJs, CoFeB crystallized from the cap interface and formed a fcc structure; on the other hand, with Ta- and Ti-cap MTJs, CoFeB crystallized from the MgO interface and formed a bcc structure. EELS analysis showed that B mainly diffused to the capping layers and rarely to the MgO layers with increasing temperature. With Ti-cap MTJs, B diffusion caused hcp-Ti crystals to form an amorphous structure and CoFeB crystallized at lower temperature.
Charge-transition levels of oxygen vacancy as the origin of device instability in HfO2 gate stacks through quasiparticle energy calculations
Authors: Choi Eun-Ae , Chang K. J.
Published: March 2009

We perform quasiparticle energy calculations to study the charge-transition levels of oxygen vacancy (VO) in HfO2. The negative-U property of VO can explain flat band voltage shifts and threshold voltage (Vth) instability in hafnium based devices. In p+ Si gate electrode, the Fermi level pinning varies by up to 0.55 eV, in good agreement with the measured values. Depending on gate bias, VO traps electrons or holes from the Si channel, causing the Vth instability. It is suggested that short time-scale charge trapping/detrapping is due to metastable VO−1 centers, whereas stable VO−2 centers dominate long time-scale instability.
Root length density and soil water distribution in drip-irrigated olive orchards in Argentina under arid conditions
Authors: Searles Peter S. , Saravia Diego A. , Rousseaux M. Cecilia
Published: March 2009

Several studies have evaluated many above-ground aspects of olive production, but essential root system characteristics have been little examined. The objective of our study was to evaluate root length density (RLD) and root distribution relative to soil water content in three commercial orchards (north-west Argentina). Depending on the orchard, the different drip emitter arrangements included either: (1) emitters spaced continuously at 1-m intervals along the drip line (CE-4; 4 emitters per tree); (2) 4 emitters per tree spaced at 1-m intervals, but with a space of 2 m between emitters of neighbouring trees (E-4); or (3) 2 emitters per tree with 4 m between emitters of neighbouring trees (E-2). All of the orchards included either var. Manzanilla fina or Manzanilla reina trees (5–8 years old) growing in sandy soils, although the specific characteristics of each orchard differed. Root length density values (2.5–3.5 cm/cm3) in the upper soil depth (0–0.5 m) were fairly uniform along the drip line in the continuous emitter (CE-4) orchard. In contrast, roots were more concentrated in the E-4 and E-2 orchards, in some cases with maximum RLD values of up to 7 cm/cm3. Approximately 70% of the root system was located in the upper 0.5 m of soil depth, and most of the roots were within 0.5 m of the drip line. For each of the three orchards, significant linear relationships between soil water content and RLD were detected based on 42 sampling positions that included various distances from the trunk and soil depths. Values of RLD averaged over the entire rooting zone and total tree root length per leaf area for the three orchards were estimated to range from 0.19 to 0.48 cm/cm3 and from 1.8 to 3.5 km/m2, respectively. These results should reduce the uncertainty associated with the magnitude of RLD values under drip irrigation as intensively managed olive orchards continue to expand in established and new growing regions.
Role of root exudates and root turnover in the below-ground N transfer from Canavalia ensiformis (jackbean) to the associated Musa acuminata (banana)
Authors: Sierra Jorge , Desfontaines Lucienne
Published: March 2009

Jackbean is an annual legume frequently used as green manure in tropical intercropping systems with bananas. Although the beneficial effect of nitrogen (N) release from above-ground residues on banana nutrition is well known, little information is available on the N transfer from jackbean roots before and after the above-ground harvest. The aim of this study was to assess the relative contribution of exudates and root turnover in the N transfer from jackbean to banana in a greenhouse experiment. Nitrogen transfer was studied in a 6-month trial using the 15N leaf feeding method, and estimated with a box model of 15N dilution based on the observed data of 15N content in exudates and decomposing roots. For the sowing–harvest period, the amount of N transferred from jackbean exudates represented 16% of banana N uptake and 0.7% of jackbean N uptake. Therefore, the N transfer flux via exudates was 23 times higher in terms of N input for the recipient plant than in terms of N output for the donor plant. This value, which is an index of the effectiveness of N transfer, was lower than those reported previously for other soil–plant systems in greenhouse conditions. This would be due to differences in root traits of the recipient plants. The amount of transferred N from root turnover after jackbean harvest represented 52% of banana N uptake in that period. The box model described N transfer from both legume N sources adequately (r2 = 0.92). For the whole experiment, 38% of banana N uptake was derived from jackbean (6% from exudates and 32% from root turnover), and 62% from soil N. The results indicated that N transfer from root exudates of jackbean would be a useful but minor process compared with N release from root turnover in soil. The experimental and theoretical approach proposed in this study may be useful in screening studies to assess the capability of herbaceous legumes to transfer N.
Differential sulfur efficiency in canola genotypes at vegetative and grain maturity stage
Authors: Balint Tatjana , Rengel Zdenko
Published: March 2009

The breeding process can be facilitated if sulfur efficiency in canola at maturity can be reliably determined by screening germplasm in the vegetative stage. Twelve canola genotypes chosen from a preliminary screening study with either high or low S efficiency indices were tested for consistency in S efficiency between vegetative stage and maturity. Plants were grown under glasshouse conditions using low or adequate S supply. The criteria for efficiency assessment at the vegetative stage were: shoot biomass at deficient S supply, relative biomass production, and S utilisation efficiency. Considering these three criteria of S efficiency, only one canola genotype was classified as efficient (Surpass 402 CL). Three genotypes were classified as inefficient under two criteria: genotypes IB 1337 and Surpass 300 TT for relative biomass production at low S supply and S-utilisation efficiency, and IB 1368 for biomass production and relative biomass production.
In addition to seed yield, relative seed yield, and S utilisation, four additional efficiency criteria were used for the maturity stage: harvest index, S harvest index, and oil and protein concentrations in the seed. For all efficiency criteria used, highly significant genotypic differences existed. IB 1368 was ranked efficient under all criteria. Genotypes Surpass 402 CL and 46C74 were ranked inefficient at maturity but efficient at the vegetative stage. In conclusion, screening canola germplasm for S efficiency requires an assessment of the efficiency at maturity rather than during vegetative growth.
Fertiliser N and P applications on two Vertosols in north-eastern Australia. 2. Grain P concentration and P removal in grain from two long-term experiments
Authors: Lester David W. , Birch Colin J. , Dowling Chris W.
Published: March 2009

Within north-eastern Australia’s grain-production region there are few reports outlining nitrogen (N) and phosphorus (P) fertiliser effects on grain P concentration and P removal in grain. Two long-term N × P fertiliser experiments with different cultivation durations were conducted, one at ‘Colonsay’ on the Darling Downs in southern Queensland (commencing 1985 after 40 years of cultivation), and the other at ‘Myling’ on the north-west plains of New South Wales (commencing 1996 after 9 years of cultivation). Applications of N and P fertiliser independently influenced both grain P concentration and P removal for a range of summer and winter cereal and legume crops. Generally, if N fertiliser application increased grain yield, the grain P concentration decreased as grain yield increased; however, if grain yield did not respond to N fertiliser, grain P concentration was unaffected. P fertiliser applications typically increased grain P concentration. Wheat and barley grain P concentrations were generally higher in this subtropical region than reported values from temperate regions in Australia. Grain sorghum values were similar to those from subtropical areas overseas, but were greater than reported values from more tropical production zones. Mungbean and chickpea grain P concentrations were consistent with other reported values. Experimental results indicated grain P concentrations for estimating grain P removal in the northern grains region of 3400 mg/kg for sorghum, 3500 mg/kg for wheat and barley, and 4000–4500 mg/kg for mungbean.
At both sites, grain P removal was greater with summer and winter cereals than with legume crops. Larger grain yields with N fertiliser application had the largest influence on grain P removal at the Colonsay site, with an additional 23.3 kg P/ha removed from plots with 80 kg N/ha applied compared with nil N over 5 analysed crops from 1998 to 2003. Grain P removal was 20.9, 17.1, and 19.7 kg P/ha in the 3 sorghum crops at this site in this period. Thus, application of P at 10 kg P/ha.crop for this 5-crop study period did not replace P removed. In the predominantly winter-cropped Myling experiment with a shorter duration of cultivation and smaller N fertiliser response, cumulative removal was more influenced by P fertiliser, with 10 kg fertiliser P/ha.crop generally sufficient to provide replacement P. These results support findings of negative P balances recently reported for grain production in this region and suggest a need for further investigation into the implications of a continuing negative P balance on the sustainability of grain production.
Identification of endosperm and maternal plant QTLs for protein and lysine contents of rice across different environments
Authors: Shi C. H. , Shi Y. , Lou X. Y. , Xu H. M. , Zheng X. , Wu J. G.
Published: March 2009

Using a newly developed mapping model with endosperm and maternal main effects and QTL × environment interaction effects on quantitative quality traits of seed in cereal crops, the investigation of quantitative trait loci (QTLs) located on triploid endosperm and diploid maternal plant genomes for protein content and lysine content of rice grain under different environments was carried out with two backcross (BC1F1 and BC2F1) populations from a set of 241 recombinant inbred lines derived from an elite hybrid cross of Shanyou 63. The results showed a total of 18 QTLs to be associated with these two quality traits of rice, which were subsequently mapped on chromosomes 2, 3, 5, 6, 7, 10, 11 and 12. Three of these QTLs were also found having QTL × environment interaction effects. Therefore, the genetic main effects from QTLs located on chromosomes in endosperm and maternal plant genomes and their QTL × environment interaction effects in different environments were all important for protein and lysine contents in rice. The influence of environmental factors on the expression of some QTLs located in different genetic systems could not be ignored for both nutrient quality traits.
Grain number determination in an old and a modern Mediterranean wheat as affected by pre-anthesis shading
Authors: Acreche Martín M. , Briceño-Félix Guillermo , Sánchez Juan A. Martín , Slafer Gustavo A.
Published: March 2009

As the number of grains per unit area has been the main bread wheat (Triticum aestivum) yield determinant affected by breeding, and this variable is highly responsive to pre-anthesis shading, the analysis of the effects of shading on old and modern wheats appears to be a good method to explore how breeding has improved yield. Two field experiments were carried out in a region of Mediterranean Spain with an old cultivar (Aragon 03) and a modern line (advanced line ID-2151) and with 4 shading treatments that reduced by c. 75% the daily incoming solar radiation: unshaded control, shading from jointing to anthesis, shading from jointing to the beginning of booting, and shading from the beginning of booting to anthesis. Grain number per m2 differed between cultivars and was affected by shading. The old cultivar had much fewer grains per spikelet (c. 45%) and slightly fewer spikelets per spike (c. 15%) than the modern line and shading decreased only the number of grains per spikelet in direct proportion to the reduction of the incoming solar radiation, leaving the number of spikes per m2 unaffected by either of the 2 factors. Shading the crop during the entire spike growing period also decreased harvest index (c. 17%), although the reduction in partitioning was not evident at anthesis. As the biomass and spike dry weight at anthesis were similarly and consistently reduced by shading, it seemed that pre-anthesis shading reduced the number of developing florets, with its effects on the number of grains per m2, without major changes in resource allocation among structural components of the spike (rachis, glumes, and awns).
Lessons from nearly 20 years of Precision Agriculture research, development, and adoption as a guide to its appropriate application
Authors: Bramley R. G. V.
Published: March 2009

Precision Agriculture (PA) is an all-encompassing term given to the use of a suite of technologies that promote improved management of agricultural production through recognition that the potential productivity of agricultural land can vary considerably, even over very short distances (a few m). It can be regarded as a means of increasing the chance that the right crop management strategies are implemented in the right place at the right time.
Numerous examples exist of the successful application of PA to various cropping systems around the world, in many cases supported by a burgeoning PA literature. However, the rate of adoption by growers of many crops remains low and, in some industries, is negligible. One such example is the Australian sugar industry, in spite of its relatively high rate of adoption of controlled traffic and the ready access that growers have to supporting infrastructure such as local GPS base stations. However, the Australian sugar industry is now seeking an informed basis from which to make decisions as to appropriate investment in PA, whether these be in terms of pragmatic application by growers, the level of involvement (if any) by millers, or with respect to research to facilitate such adoption. A part of acquiring this informed view of PA is to look at its application in other cropping systems. This review therefore examines PA research and application in a range of cropping systems from around the world and considers the key drivers of variability in these production systems. Constraints to the adoption of PA and its likely economic benefits are also considered in light of experiences from around the world.
It is concluded that sugarcane production is ideally suited to the adoption of PA. Like other broadacre systems, such as cereal production, the opportunity exists to target the management of inputs to production. However, the vertically integrated nature of the sugar industry and existence of a potentially significant crop quality imperative also present opportunities for targeted strategies such as selective harvesting, as used in the wine industry. Thus, to get the best result from adoption of PA, the sugar industry will need to consider it as a tool for optimising management of the production of sugar, as opposed to solely an avenue for improving the agronomic management of sugarcane. Several recommendations are made as to how this adoption might be supported.
Contaminated Goods
Authors: Bennett Tony
Published: March 2009

Who says comics are just for kids? Publisher Tony Bennett looks back on a series of landmark legal battles
Terrorised Media
Authors: Hattotuwa Sanjana
Published: March 2009

The prosecution of a journalist under Sri Lankan terrorism laws exposes a blatant disregard for free speech, says Sanjana Hattotuwa
Not in My Backyard
Authors: Heins Marjorie
Published: March 2009

The Internet threatens to make US obscenity law unworkable, says Marjorie Heins
Crimes of Transgression
Authors: Julius Anthony , Petley Julian
Published: March 2009

Anthony Julius and Julian Petley discuss obscenity and the limits of liberal tolerance
Prime Cuts
Authors: Perkins Murray
Published: March 2009

Murray Perkins is a film examiner who classifies hard-core porn. He talks to Index about what it takes to make the grade
Web Control
Authors: Petley Julian
Published: March 2009

Attempts to rid the Internet of pornographic material are beginning to have a wider impact on freedom of expression online, says Julian Petley
Dark Magic
Authors: Rowson Martin
Published: March 2009

Breaking cultural taboos is a sure way of causing offence. It’s also the impetus for the best political satire, says author and cartoonist Martin Rowson
Pretty Babies
Authors: Higonnet Anne
Published: March 2009

When it comes to representing children, art and law are on a collision course, writes Anne Higonnet, and photographers are in the dock
Democracy Surge
Authors: Jayasekera Rohan
Published: March 2009

As Iraq begins an unprecedented year of voting, Rohan Jayasekera assesses the prospects for success in elections across the country
Wall of Silence
Authors: Martínez Sanjuana , MacSweeney Christina
Published: March 2009

Sanjuana Martínez analyses the culture of intimidation facing investigative journalists in Mexico — from attacks on reporters to criminal activity
Are You Sure You’Re Not Scared?
Authors: Portela Ena Lucia , Caistor Nick , Hopkinson Amanda
Published: March 2009

The Newman family’s feud with their neighbour takes an unexpected turn after state security comes calling. An extract from Ena Lucia Portela’s novel in progress
Cycle of Abuse
Authors: Martellozzo Elena , Taylor Helen
Published: March 2009

Downloading child pornography perpetuates the original act of assault, say Elena Martellozzo and Helen Taylor
SOCIAL SELECTIVITY OF TRACK MOBILITY IN SECONDARY SCHOOLS
Authors: Jacob Marita , Tieben Nicole
Published: March 2009

Previous research has shown that track mobility during secondary education is influenced by parental background. However, family background effects might vary due to institutional variations in the educational structure. Therefore, in our paper we compare social selectivity of track mobility in two countries, Germany and The Netherlands. Both countries offer a hierarchically tracked educational system, but differ in details. Further, both countries established educational reforms in the late sixties, changing the conditions for track mobility differently. In our empirical analyses using data from the Family Survey Dutch Population and the German Life History Study we find that changing to a higher track is more likely for students who face the threat of status demotion, whereas changing to a lower track is independent of status maintenance motives. Intra-secondary transitions occur less often in The Netherlands than in Germany and are less motivated by status maintenance. Educational legislation reduces the effects of relative education of the parents only on upward mobility in Germany and only on downward mobility in The Netherlands.
Time (and PPARβ/δ) heals all wounds
Authors: Short Ben
Published: March 2009

Organotypic cultures help to unravel how a transcription factor modulates crosstalk between different layers of the skin.
Gα12/13 regulate epiboly by inhibiting E-cadherin activity and modulating the actin cytoskeleton
Authors: Lin Fang , Chen Songhai , Sepich Diane S. , Panizzi Jennifer Ray , Clendenon Sherry G. , Marrs James A. , Hamm Heidi E. , Solnica-Krezel Lilianna
Published: March 2009

Epiboly spreads and thins the blastoderm over the yolk cell during zebrafish gastrulation, and involves coordinated movements of several cell layers. Although recent studies have begun to elucidate the processes that underlie these epibolic movements, the cellular and molecular mechanisms involved remain to be fully defined. Here, we show that gastrulae with altered Gα12/13 signaling display delayed epibolic movement of the deep cells, abnormal movement of dorsal forerunner cells, and dissociation of cells from the blastoderm, phenocopying e-cadherin mutants. Biochemical and genetic studies indicate that Gα12/13 regulate epiboly, in part by associating with the cytoplasmic terminus of E-cadherin, and thereby inhibiting E-cadherin activity and cell adhesion. Furthermore, we demonstrate that Gα12/13 modulate epibolic movements of the enveloping layer by regulating actin cytoskeleton organization through a RhoGEF/Rho-dependent pathway. These results provide the first in vivo evidence that Gα12/13 regulate epiboly through two distinct mechanisms: limiting E-cadherin activity and modulating the organization of the actin cytoskeleton.
NF-κB and Snail1a coordinate the cell cycle with gastrulation
Authors: Liu Xiaolin , Huang Sizhou , Ma Jun , Li Chun , Zhang Yaoguang , Luo Lingfei
Published: March 2009

The cell cycle needs to strictly coordinate with developmental processes to ensure correct generation of the body plan and different tissues. However, the molecular mechanism underlying the coordination remains largely unknown. In this study, we investigate how the cell cycle coordinates gastrulation cell movements in zebrafish. We present a system to modulate the cell cycle in early zebrafish embryos by manipulating the geminin-Cdt1 balance. Alterations of the cell cycle change the apoptotic level during gastrulation, which correlates with the nuclear level of antiapoptotic nuclear factor κB (NF-κB). NF-κB associates with the Snail1a promoter region on the chromatin and directly activates Snail1a, an important factor controlling cell delamination, which is the initial step of mesendodermal cell movements during gastrulation. In effect, the cell cycle coordinates the delamination of mesendodermal cells through the transcription of Snail1a. Our results suggest a molecular mechanism by which NF-κB and Snail1a coordinate the cell cycle through gastrulation.