bluuebunny/crossref_metadata_2025 huggingface dataset:
Metal bead crystals for easy heating by direct current
Authors: Voigtländer Bert , Cherepanov Vasily , Elsaesser Christa , Linke Udo
Published: April 2008

The preparation of metal bead crystals with two wires attached to the crystal is described. These crystals allow for a very easy and efficient method to heat metal single crystals by direct current heating through the connecting wires of the bead crystal. This heating of the bead crystal is sufficient to clean metal surfaces such as the surfaces of Pt and Au as confirmed by Auger spectroscopy and scanning tunneling microscopy (STM). There is no need for any ion sputtering which is conventionally used to clean metal single crystal surfaces. The bead crystals with two leads fabricated from a wide range metals and metal alloys such as Cu, Mo, Ru, Rh, Pd, Ag, Ta, W, Re, Ir, Pt, Au, PtPd, PtRh, AuAg, and PtIr can be used as general purpose metal substrates for surface science studies and other applications. Additionally, these bead crystals can be used to reshape STM tips by indentation of the tip into the soft metal in order to recover atomic resolution imaging on hard substrates.
Magnetization reversal processes in epitaxial Co/Fe bi-layers grown on MgO(001)
Authors: Kohn A. , Wang C. , Petford-Long A. K. , Wang S. G. , Ward R. C. C.
Published: April 2008

We report on the mechanism of magnetization reversal in epitaxial Co/Fe bi-layers grown by molecular beam epitaxy on MgO(001) substrates. For Co films thicker than 5 nm, the crystal structure is hexagonal. The Fe layer follows an epitaxial relation relative to the MgO substrate of (001)[100]Fe//(001)[110]MgO. When deposited on a cubic Fe layer, the Co layer follows a bi-crystal epitaxial relation of (112¯0)[0001]Co//(001)⟨100⟩Fe as previously reported [Popova et al., Appl. Phys. Lett. 81, 1035 (2002); Wang et al., J. Appl. Phys. 101, 09D103 (2007)]. The magnetization reversal in-plane follows a cubic fourfold symmetry, which coincides with that of the underlying bcc Fe layer. In this study, we find that the area of each Co crystal domain spans 200−1500 nm2 and that these two domains are approximately evenly distributed. The micromagnetic reversal mechanism is a combination of coherent rotational processes and domain wall displacement. These magnetic domains are sized tens of μm and separated by predominately 90° or occasionally 180° domain walls along the Fe⟨110⟩ and Fe⟨100⟩ directions, respectively. The cubic anisotropy of the bi-crystalline Co layer is explained by exchange-coupling between hcp grains with perpendicular crystallographic orientation, each having in-plane uniaxial magnetic anisotropy along its respective [0001] direction.
Discrete state model and accurate estimation of loop entropy of RNA secondary structures
Authors: Zhang Jian , Lin Ming , Chen Rong , Wang Wei , Liang Jie
Published: April 2008

Conformational entropy makes important contribution to the stability and folding of RNA molecule, but it is challenging to either measure or compute conformational entropy associated with long loops. We develop optimized discrete k-state models of RNA backbone based on known RNA structures for computing entropy of loops, which are modeled as self-avoiding walks. To estimate entropy of hairpin, bulge, internal loop, and multibranch loop of long length (up to 50), we develop an efficient sampling method based on the sequential Monte Carlo principle. Our method considers excluded volume effect. It is general and can be applied to calculating entropy of loops with longer length and arbitrary complexity. For loops of short length, our results are in good agreement with a recent theoretical model and experimental measurement. For long loops, our estimated entropy of hairpin loops is in excellent agreement with the Jacobson–Stockmayer extrapolation model. However, for bulge loops and more complex secondary structures such as internal and multibranch loops, we find that the Jacobson–Stockmayer extrapolation model has large errors. Based on estimated entropy, we have developed empirical formulae for accurate calculation of entropy of long loops in different secondary structures. Our study on the effect of asymmetric size of loops suggest that loop entropy of internal loops is largely determined by the total loop length, and is only marginally affected by the asymmetric size of the two loops. Our finding suggests that the significant asymmetric effects of loop length in internal loops measured by experiments are likely to be partially enthalpic. Our method can be applied to develop improved energy parameters important for studying RNA stability and folding, and for predicting RNA secondary and tertiary structures. The discrete model and the program used to calculate loop entropy can be downloaded at http://gila.bioengr.uic.edu/resources/RNA.html.
Plasticity induced texture development in thick polycrystalline CdTe: Experiments and modeling
Authors: Consonni V. , Feuillet G. , Gergaud P.
Published: April 2008

The local and average texture of thick polycrystalline CdTe films is determined before, upon, and after the coalescence of the initially isolated islands, using electron backscattered diffraction and x-ray powder diffraction. The coalescence and postcoalescence processes lead to a preferential texturation, initially along the ⟨531⟩ and ⟨100⟩ crystallographic directions and then along the ⟨110⟩ preferred orientation. The selection of grain orientation during the film growth is found to be driven by strain energy minimization. A model for the microyield stress is developed when plasticity is confined to each elemental grain and accounts for the ⟨531⟩ and ⟨100⟩ preferred orientations. On the contrary, when plastic deformation can propagate from one grain to its neighbors, the Hall–Petch model applies and leads to the ⟨110⟩ preferred orientation. Furthermore, at the end of growth, the stronger ⟨111⟩ preferred orientation is observed and arises because of kinetic limitations.
Distinguishing a driver from a response system
Authors: Bu Shou L. , Jiang I-Min , Ho Ming C.
Published: April 2008

This study presents an approach for distinguishing a driver from a response system. The proposed method can be applied to both unidirectional or bidirectional interactions, and to identical or structurally different systems. Compared with most previously proposed schemes, the present method is so “simple” that the driver-response relationships can generally be detected using a direct graphic way. On the other hand, quantitative estimation is also developed using the idea of the correlation dimension.
Development of a dynamic model for the subfilter scalar variance using the concept of optimal estimators
Authors: Balarac G. , Pitsch H. , Raman V.
Published: April 2008

The concept of optimal estimators, recently introduced by Moreau et al. [Phys. Fluids 18, 1 (2006)] is used as an a priori tool to discuss the accuracy of subfilter models. Placed in the framework of large-eddy simulation of combustion problems, this work focuses on the subfilter models used to evaluate the subfilter variance of a conserved scalar, the mixture fraction. The a priori tests are performed using 5123 direct numerical simulation data of forced homogeneous isotropic turbulence. First, the performance of the most commonly used models for the subfilter variance is studied. Using optimal estimators, the Smagorinsky-type model [Pierce and Moin, Phys. Fluids 10, 3041 (1998)] is shown to have the best set of parameters. However, the conventional dynamic formulation of the model leads to large errors in the variance prediction. It was found that assumptions used in the model formulation are not verified. A new dynamic procedure based on a Taylor series expansion is then proposed to improve the predictive accuracy. The a priori tests show that the new model substantially improves predictive accuracy.
Double planar wire array as a compact plasma radiation source
Authors: Kantsyrev V. L. , Rudakov L. I. , Safronova A. S. , Esaulov A. A. , Chuvatin A. S. , Coverdale C. A. , Deeney C. , Williamson K. M. , Yilmaz M. F. , Shrestha I. , Ouart N. D. , Osborne G. C.
Published: April 2008

Magnetically compressed plasmas initiated by a double planar wire array (DPWA) are efficient radiation sources. The two rows in a DPWA implode independently and then merge together at stagnation producing soft x-ray yields and powers of up to 11.5kJ∕cm and more than 0.4TW∕cm, higher than other planar arrays or low wire-number cylindrical arrays on the 1MA Zebra generator. DPWA, where precursors form in two stages, produce a shaped radiation pulse and radiate more energy in the main burst than estimates of implosion kinetic energy. High radiation efficiency, compact size (as small as 3–5mm wide), and pulse shaping show that the DPWA is a potential candidate for ICF and radiation physics research.
Strong geometric-phase effects in the hydrogen-exchange reaction at high collision energies
Authors: Bouakline Foudhil , Althorpe Stuart C. , Peláez Ruiz Daniel
Published: April 2008

We report quantum wave packet calculations of state-to-state reaction probabilities and cross sections for the reaction H+H2(v0=0,j0=0)→H2(v,j)+H, at total energies up to 4.5eV above the ground state potential minimum. The calculations are repeated using (i) the ground electronic state only, (ii) the ground state plus the diagonal non-Born–Oppenheimer correction, (iii) the ground state, diagonal non-Born–Oppenheimer correction and geometric phase (GP), and (iv) both electronic states including all nonadiabatic couplings, using the diabatic potential approach of Mahapatra et al. [J. Phys. Chem. A 105, 2321 (2001)]. The results for calculations (iii) and (iv) are in very close agreement, showing that the upper electronic state makes only a very small contribution to the state-to-state dynamics, even at energies much higher than the conical intersection minimum (at 2.74eV). At total energies above 3.5eV, many of the state-to-state reaction probabilities show strong GP effects, indicating that they are dominated by interference between one- and two-transition-state (1-TS and 2-TS) reaction paths. These effects survive the coherent sum over partial waves to produce features in the state-to-state differential cross sections which could be detected in an experiment with an angular resolution of ∼20°. Efficient dephasing of the interference between the 1-TS and 2-TS contributions causes almost complete cancellation of the GP in the integral cross sections, thus continuing a trend observed at lower energies in earlier work.
Wave-dispersive x-ray spectrometer for simultaneous acquisition of several characteristic lines based on strongly and accurately shaped Ge crystal
Authors: Hayashi Kouichi , Nakajima Kazuo , Fujiwara Kozo , Nishikata Susumu
Published: April 2008

Si and Ge are widely used as analyzing crystals for x-rays. Drastic and accurate shaping of Si or Ge gives significant advance in the x-ray field, although covalently bonded Si or Ge crystals have long been believed to be not deformable to various shapes. Recently, we developed a deformation technique for obtaining strongly and accurately shaped Si or Ge wafers of high crystal quality, and the use of the deformed wafer made it possible to produce fine-focused x-rays. In the present study, we prepared a cylindrical Ge wafer with a radius of curvature of 50mm, and acquired fluorescent x-rays simultaneously from four elements by combining the cylindrical Ge wafer with a position-sensitive detector. The energy resolution of the x-ray fluorescence spectrum was as good as that obtained using a flat single crystal, and its gain was over 100. The demonstration of the simultaneous acquisition of high-resolution x-ray fluorescence spectra indicated various possibilities of x-ray spectrometry, such as one-shot x-ray spectroscopy and highly efficient wave-dispersive x-ray spectrometers.
Hydrogen bonding in methanol clusters probed by inner-shell photoabsorption spectroscopy in the carbon and oxygen K-edge regions
Authors: Tamenori Y. , Okada K. , Takahashi O. , Arakawa S. , Tabayashi K. , Hiraya A. , Gejo T. , Honma K.
Published: April 2008

Hydrogen bonding in methanol clusters has been investigated by using inner-shell photoabsorption spectroscopy and density functional theory (DFT) calculations in the carbon and oxygen K-edge regions. The partial-ion-yield (PIY) curves of H(CH3OH)n+ were measured as the soft x-ray absorption spectra of methanol clusters. The first resonance peak in the PIY curves, which is assigned to the σ*(O–H) resonance transition, exhibits a 1.20eV blueshift relative to the total-ion-yield (TIY) curves of molecular methanol in the oxygen K-edge region, while it exhibits a shift of only 0.25eV in the carbon K-edge region. Decreased intensities of the transitions to higher Rydberg orbitals were observed in the PIY curves of the clusters. The drastic change in the σ*(O–H) resonance transition is interpreted by the change in the character of the σ*(O–H) molecular orbital at the H-donating OH site due to the hydrogen-bonding interaction.
A note on the fluctuation of dissipative scale in turbulence
Authors: Biferale L.
Published: April 2008

We present an application of the multifractal formalism able to predict the whole shape of the probability density function (pdf) of the dissipative scale, η. We discuss both intense velocity fluctuations, leading to dissipative scales smaller than the Kolmogorov scale, where the formalism gives a pdf decaying as a superposition of stretched exponential, and smooth velocity fluctuations, where the formalism predicts a power-law decay. Both trends are found to be in good agreement with recent direct numerical simulations [J. Schumacher, “Sub-Kolmogorov-scale fluctuations in fluid turbulence,” Europhys. Lett. 80, 54001 (2007)].
No quenching of magnetic moment for the GenCo (n=1–13) clusters: First-principles calculations
Authors: Jing Qun , Tian Fu-yang , Wang Yuan-xu
Published: April 2008

The authors predict that for the GenCo (n=1–13) clusters the magnetic moment does not quench, which is dark contrast to the previous results with transition-metal-doped Sin clusters. It may be due to the unpaired electrons of the Co atom in the clusters. For the ground state structures of the GenCo (n⩾9) clusters, the Co atom completely falls into the center of the Ge outer frame, forming metal-encapsulated Gen cages. The doping of the Co atom enhances the stability of the host Gen clusters. The Ge10Co cluster with the bicapped tetragonal antiprism structure is more stable than others, which agrees very well with the results of the experiment of the Co∕Ge binary clusters by the laser vaporization.
Critical loss radius in a Penning trap subject to multipole fields
Authors: Fajans J. , Madsen N. , Robicheaux F.
Published: April 2008

When particles in a Penning trap are subject to a magnetic multipole field, those beyond a critical radius will be lost. The critical radius depends on the history by which the field is applied, and can be much smaller if the particles are injected into a preexisting multipole than if the particles are subject to a ramped multipole. Both cases are relevant to ongoing experiments designed to trap antihydrogen.
Arbitrary amplitude quantum dust ion-acoustic solitary waves
Authors: Tribeche Mouloud , Ghebache Siham , Aoutou Kamel , Zerguini Taha Houssine
Published: April 2008

The one-dimensional quantum hydrodynamic model for a three-species quantum plasma is used to study the quantum counterpart of the well known dust ion-acoustic (DIA) wave. Two cases of physical interest are investigated, namely positive and negative dust charge. It is shown that only rarefactive solitary potentials associated with nonlinear quantum DIA (QDIA) waves involving electron density deeps can exist. The QDIA soliton experiences a spreading and the quantum effects tend to make it wider. Under certain conditions, the soliton enlarges and its pulse shape evolves into a broad central flat-bottomed (or table-bottomed) soliton as a limiting-amplitude member of the QDIA soliton family. Linear stability analysis as well as quasineutral solutions are succinctly outlined. The investigation could be of relevance to astrophysical quantum dusty plasmas.
Theory of charged particle heating by low-frequency Alfvén waves
Authors: Guo Zehua , Crabtree Chris , Chen Liu
Published: April 2008

The heating of charged particles by a linearly polarized and obliquely propagating shear Alfvén wave (SAW) at frequencies a fraction of the charged particle cyclotron frequency is demonstrated both analytically and numerically. Applying Lie perturbation theory, with the wave amplitude as the perturbation parameter, the resonance conditions in the laboratory frame are systematically derived. At the lowest order, one recovers the well-known linear cyclotron resonance condition k∥v∥−ω−nΩ=0, where v∥ is the particle velocity parallel to the background magnetic field, k∥ is the parallel wave number, ω is the wave frequency, Ω is the gyrofrequency, and n is any integer. At higher orders, however, one discovers a novel nonlinear cyclotron resonance condition given by k∥v∥−ω−nΩ∕2=0. Analytical predictions on the locations of fixed points, widths of resonances, and resonance overlapping criteria for global stochasticity are also found to agree with those given by computed Poincaré surfaces of section.
Dispersion enhancement and damping by buoyancy driven flows in two-dimensional networks of capillaries
Authors: D’Angelo Maria Veronica , Auradou Harold , Allain Catherine , Rosen Marta , Hulin Jean-Pierre
Published: April 2008

The influence of a small relative density difference (Δρ∕ρ≃3×10−4) on the displacement of two miscible Newtonian liquids is studied experimentally in transparent two-dimensional square networks of microchannels held vertically; the channel width distribution is log normal with a mean value of a=0.33mm. Maps of the local relative concentration are obtained by an optical light absorption technique. Both stable displacements in which the denser fluid enters at the bottom of the cell and displaces the lighter one and unstable displacements in which the lighter fluid is injected at the bottom and displaces the denser one are realized. Except at the lowest mean flow velocity U, the average C(x,t) of the relative concentration satisfies a convection-dispersion equation. The relative magnitude of ∣U∣ and of the velocity Ug of buoyancy driven fluid motions is characterized by the gravity number Ng=Ug∕∣U∣. At low gravity numbers ∣Ng∣<0.01 (or equivalently high Péclet numbers Pe=Ua∕Dm>500), the dispersivities ld in the stable and unstable configurations are similar to ld∝Pe0.5. At low velocities such that ∣Ng∣>0.01, ld increases like 1/Pe in the unstable configuration (Ng<0), while it becomes constant and close to the length of individual channels in the stable case (Ng>0). Isoconcentration lines c(x,y,t)=0.5 are globally flat in the stable configuration, while in the unstable case, they display spikes and troughs with a rms amplitude σf parallel to the flow. For Ng>−0.2, σf increases initially with the distance and reaches a constant limit, while it keeps increasing for Ng<−0.2. A model taking into account buoyancy forces driving the instability and the transverse exchange of tracer between rising fingers and the surrounding fluid is suggested and its applicability to previous results obtained in three-dimensional media is discussed.
Charge patching method for electronic structure of organic systems
Authors: Vukmirović Nenad , Wang Lin-Wang
Published: April 2008

The development of the charge patching method for the calculation of the electronic structure of organic systems containing a large number of atoms was presented. The method was tested on a range of systems including alkane and alkene chains, polyacenes, polythiophenes, polypyrroles, polyfuranes, polyphenylene vinylene, and poly(amidoamine) dendrimers. The results obtained by the method are in very good agreement with direct calculations based on density functional theory, since the eigenstate errors are typically of the order of a few tens of meV.
Piezoelectric and ferroelectric properties of Bi-compensated (Bi1/2Na1/2)TiO3–(Bi1/2K1/2)TiO3 lead-free piezoelectric ceramics
Authors: Zhang Ya-Ru , Li Jing-Feng , Zhang Bo-Ping , Peng Chun-E
Published: April 2008

( Bi 1 / 2 Na 1 / 2 ) TiO 3 – ( Bi 1 / 2 K 1 / 2 ) TiO 3 (BNT-BKT) ceramics as a promising candidate for lead-free piezoelectric ceramics were studied with a special emphasis on the compositional dependence of piezoelectric and ferroelectric properties. One mole percent excess Bi was added to compensate for the volatilization of Bi3+ ions during sintering, which was found to be effective in improving the piezoelectric properties of the resultant BNT-BKT ceramics. The piezoelectric, ferroelectric, and dielectric properties of the Bi-compensated BNT-BKT ceramics were investigated and discussed in relation to the morphotropic phase boundary that is close to the composition range of 20–24 mol % BKT. The maximum piezoelectric constant d33 (207 pC/N) and electromechanical coupling factor kp (35%) were obtained at the compositions of 23% and 20%, respectively.
Investigation of microflow reversal by ac electrokinetics in orthogonal electrodes for micropump design
Authors: Yang Kai , Wu Jie
Published: April 2008

Orthogonal electrodes have been reported to produce high velocity microflows when excited by ac signals, showing potential for micropumping applications. This paper investigates the microflow reversal phenomena in such orthogonal electrode micropumps. Three types of microflow fields were observed by changing the applied electric signals. Three ac electrokinetic processes, capacitive electrode polarization, Faradaic polarization, and the ac electrothermal effect, are proposed to explain the different flow patterns, respectively. The hypotheses were corroborated by impedance analysis, numerical simulations, and velocity measurements. The investigation of microflow reversal can improve the understanding of ac electrokinetics and hence effectively manipulate fluids.
DairyMod and EcoMod: biophysical pasture-simulation models for Australia and New Zealand
Authors: Johnson I. R. , Chapman D. F. , Snow V. O. , Eckard R. J. , Parsons A. J. , Lambert M. G. , Cullen B. R.
Published: April 2008

DairyMod and EcoMod, which are biophysical pasture-simulation models for Australian and New Zealand grazing systems, are described. Each model has a common underlying biophysical structure, with the main differences being in their available management options. The third model in this group is the SGS Pasture Model, which has been previously described, and these models are referred to collectively as ‘the model’. The model includes modules for pasture growth and utilisation by grazing animals, water and nutrient dynamics, animal physiology and production and a range of options for pasture management, irrigation and fertiliser application. Up to 100 independent paddocks can be defined to represent spatial variation within a notional farm. Paddocks can have different soil types, nutrient status, pasture species, fertiliser and irrigation management, but are subject to the same weather. Management options include commonly used rotational grazing management strategies and continuous grazing with fixed or variable stock numbers. A cutting regime simulates calculation of seasonal pasture growth rates. The focus of the present paper is on recent developments to the management routines and nutrient dynamics, including organic matter, inorganic nutrients, leaching and gaseous nitrogen losses, and greenhouse gases. Some model applications are presented and the role of the model in research projects is discussed.
Social networks in arid Australia: a review of concepts and evidence
Authors: McAllister R. R. J. , Cheers B. , Darbas T. , Davies J. , Richards C. , Robinson C. J. , Ashley M. , Fernando D. , Maru Y. T.
Published: April 2008

Arid systems are markedly different from non-arid systems. This distinctiveness extends to arid-social networks, by which we mean social networks which are influenced by the suite of factors driving arid and semi-arid regions. Neither the process of how aridity interacts with social structure, nor what happens as a result of this interaction, is adequately understood. This paper postulates three relative characteristics which make arid-social networks distinct: that they are tightly bound, are hierarchical in structure and, hence, prone to power abuses, and contain a relatively higher proportion of weak links, making them reactive to crisis. These ideas were modified from workshop discussions during 2006. Although they are neither tested nor presented as strong beliefs, they are based on the anecdotal observations of arid-system scientists with many years of experience. This paper does not test the ideas, but rather examines them in the context of five arid-social network case studies with the aim of hypotheses building. Our cases are networks related to pastoralism, Aboriginal outstations, the ‘Far West Coast Aboriginal Enterprise Network’ and natural resources in both the Lake-Eyre basin and the Murray–Darling catchment. Our cases highlight that (1) social networks do not have clear boundaries, and that how participants perceive their network boundaries may differ from what network data imply, (2) although network structures are important determinants of system behaviour, the role of participants as individuals is still pivotal, (3) and while in certain arid cases weak links are engaged in crisis, the exact structure of all weak links in terms of how they place participants in relation to other communities is what matters.
How can we identify socio-regions in the rangelands of Australia?
Authors: Maru Y. T. , Chewings V. H.
Published: April 2008

The Australian rangelands are divided into regions for statistical reporting, cultural identification or administrative and bioregional management purposes. However, many of these divisions do not reflect the characteristics of inland towns. In this study we used the Urban Centre/Locality (UCL) structure (for settlements with at least 200 people) as the smallest unit of analysis to build preliminary socio-regions based on demographic (e.g. Median Age and percentage of Indigenous people in UCL), socio-economic (dependency ratio and unemployment rate) and a few environmental indicators (e.g. Normalised Difference Vegetation Index (NDVI) and Rainfall variability). A key finding of the study is that there are strong differences among UCLs in the rangelands. A threshold of around 5000 people is apparent with some indicators across all UCLs around which variability changes. There is much greater variability in the indicators among UCLs with fewer than 5000 people than there is among UCLs with over 5000 people. This confirms the need to consider statistical units smaller than those commonly used such as Statistical Local Areas (SLAs) as these and other regionalisation techniques mask the detail within areas that contain socio-economically and culturally different settlements. The high variability of indicator values observed for UCLs with smaller populations suggests that they have more diverse research, policy and investment needs than larger urban centres. We used a non-traditional approach and grouped UCLs into socio-regions based on their social characteristics instead of their geographic location. This created clusters of similar UCLs rather than contiguous regions. Some of these socio-regions cross administrative and statistical borders. The regionalisation presented in this study is likely to be valuable when selecting case-study areas for research projects and, in the long-term, when developing policy and investment initiatives.
The 'desert syndrome' - causally-linked factors that characterise outback Australia
Authors: Stafford Smith Mark
Published: April 2008

The desert knowledge community has been motivated by the assertion that outback Australia is characterised by a set of features that are not individually unique, but which together cause it to function in ways that are fundamentally different to other physical and social environments. This paper sets out to appraise this assertion. It documents the evidence for the individual features – (i) climate variability at various scales in space and time (climate variability), (ii) widespread low and patchy primary productivity (scarce resources), (iii) sparse, mobile and patchy human population (sparse population), (iv) distant markets and decision-making (remoteness), (v) further perceived unpredictability in markets, labour and policy (social variability), (vi) limited research knowledge and persistent traditional and local knowledge (local knowledge), and (vii) particular types of people, culture and institutions (cultural differences). It then assesses whether there is evidence for the hypothesis that these features are causally linked to act as a consistent syndrome. This can only be partially confirmed as yet, but, if true, implies that management and policy for the region must recognise that the causal links are unlikely to be easily broken. The key consequence for desert people is that they should put more time into planning and managing for their apparently careless treatment by the environment and bureaucracy, and less time railing against it, because it will not go away. The key consequence for sympathetic outsiders is that there are great opportunities to create a policy context in which desert innovation can thrive in response to the ‘desert syndrome’.
Intuitive statistics by 8-month-old infants
Authors: Xu Fei , Garcia Vashti
Published: April 2008

Human learners make inductive inferences based on small amounts of data: we generalize from samples to populations and vice versa. The academic discipline of statistics formalizes these intuitive statistical inferences. What is the origin of this ability? We report six experiments investigating whether 8-month-old infants are “intuitive statisticians.” Our results showed that, given a sample, the infants were able to make inferences about the population from which the sample had been drawn. Conversely, given information about the entire population of relatively small size, the infants were able to make predictions about the sample. Our findings provide evidence that infants possess a powerful mechanism for inductive learning, either using heuristics or basic principles of probability. This ability to make inferences based on samples or information about the population develops early and in the absence of schooling or explicit teaching. Human infants may be rational learners from very early in development.
Blue light-induced autophosphorylation of phototropin is a primary step for signaling
Authors: Inoue Shin-ichiro , Kinoshita Toshinori , Matsumoto Masaki , Nakayama Keiichi I. , Doi Michio , Shimazaki Ken-ichiro
Published: April 2008

Phototropins are autophosphorylating protein kinases of plant-specific blue light receptors. They regulate various blue light responses, including phototropism, chloroplast movements, hypocotyl growth inhibition, leaf flattening, and stomatal opening. However, the physiological role of autophosphorylation remains unknown. Here, we identified phosphorylation sites of Ser or Thr in the N terminus, Hinge1 region, kinase domain, and C terminus in
Arabidopsis
phototropin1 (phot1) by liquid chromatography–tandem mass spectrometry
in vivo
. We substituted these Ser or Thr residues with Ala in phot1 and analyzed their functions by inspecting the phot1-mediated responses of stomatal opening, phototropism, chloroplast accumulation, and leaf flattening after the transformation of the
phot1 phot2
double mutant. Among these sites, we found that autophosphorylation of Ser-851 in the activation loop of the kinase domain was required for the responses mentioned above, whereas the phosphorylation of the other Ser and Thr, except those in the activation loop, was not. Ser-849 in the loop may have an additional role in the responses. Immunological analysis revealed that Ser-851 was phosphorylated rapidly by blue light in a fluence-dependent manner and dephosphorylated gradually upon darkness. We conclude that autophosphorylation of Ser-851 is a primary step that mediates signaling between photochemical reaction and physiological events.
Photodynamic therapy plus low-dose cyclophosphamide generates antitumor immunity in a mouse model
Authors: Castano Ana P. , Mroz Pawel , Wu Mei X. , Hamblin Michael R.
Published: April 2008

Photodynamic therapy (PDT) is a modality for the treatment of cancer involving excitation of nontoxic photosensitizers with harmless visible light-producing cytotoxic reactive oxygen species. PDT causes apoptosis and necrosis of tumor cells, destruction of the tumor blood supply, and activation of the immune system. The objective of this study was to compare in an animal model of metastatic cancer PDT alone and PDT combined with low-dose cyclophosphamide (CY) a treatment that has been proposed to deplete regulatory T cells (T-regs) and increase the immune response to some tumors. We used J774 tumors (a highly metastatic reticulum cell sarcoma line) and PDT with benzoporphyrin derivative monoacid ring A, verteporfin for injection (BPD; 1-mg/kg injected i.v. followed after 15 min by 150 J/cm2of 690-nm light). CY (50 or 150 mg/kg i.p.) was injected 48 h before light delivery. PDT alone led to tumor regressions and a survival advantage but no permanent cures were obtained. BPD–PDT in combination with low-dose CY (but not high-dose CY) led to 70% permanent cures. Low-dose CY alone gave no permanent cures but did provide a survival advantage and was shown to reduce CD4+FoxP3+ T-regs in lymph nodes, whereas high-dose CY reduced other lymphocyte classes as well. Cured animals were rechallenged with J774 cells, and the tumors were rejected in 71% of mice. Cured mice had tumor-specific T cells in spleens as determined by a51Cr release assay. We conclude that low-dose CY depletes T-regs and potentiates BPD–PDT, leading to tumor cures and memory immunity.
A fungal-responsive MAPK cascade regulates phytoalexin biosynthesis in
Arabidopsis
Authors: Ren Dongtao , Liu Yidong , Yang Kwang-Yeol , Han Ling , Mao Guohong , Glazebrook Jane , Zhang Shuqun
Published: April 2008

Plant recognition of pathogens leads to rapid activation of MPK3 and MPK6, two
Arabidopsis
mitogen-activated protein kinases (MAPKs), and their orthologs in other species. Here, we report that synthesis of camalexin, the major phytoalexin in
Arabidopsis
, is regulated by the MPK3/MPK6 cascade. Activation of MPK3/MPK6 by expression of active upstream MAPK kinase (MAPKK) or MAPKK kinase (MAPKKK) was sufficient to induce camalexin synthesis in the absence of pathogen attack. Induction of camalexin by
Botrytis cinerea
was preceded by MPK3/MPK6 activation, and compromised in
mpk3
and
mpk6
mutants. Genetic analysis placed the MPK3/MPK6 cascade upstream of PHYTOALEXIN DEFICIENT 2 (PAD2) and PAD3, but independent or downstream of PAD1 and PAD4. Camalexin induction after MPK3/MPK6 activation was preceded by rapid and coordinated up-regulation of multiple genes encoding enzymes in the tryptophan (Trp) biosynthetic pathway, in the conversion of Trp to indole-3-acetaldoxime (IAOx, a branch point between primary and secondary metabolism), and in the camalexin biosynthetic pathway downstream of IAOx. These results indicate that the MPK3/MPK6 cascade regulates camalexin synthesis through transcriptional regulation of the biosynthetic genes after pathogen infection.
Hepatitis C virus NS5A anchor peptide disrupts human immunodeficiency virus
Authors: Bobardt Michael D. , Cheng Guofeng , de Witte Lot , Selvarajah Suganya , Chatterji Udayan , Sanders-Beer Brigitte E. , Geijtenbeek Teunis B. H. , Chisari Francis V. , Gallay Philippe A.
Published: April 2008

In the absence of an effective vaccine, there is an urgent need for safe and effective antiviral agents to prevent transmission of HIV. Here, we report that an amphipathic α-helical peptide derived from the hepatitis C virus NS5A anchor domain (designated C5A in this article) that has been shown to be virocidal for the hepatitis C virus (HCV) also has potent antiviral activity against HIV. C5A exhibits a broad range of antiviral activity against HIV isolates, and it prevents infection of the three
in vivo
targets of HIV: CD4
+
T lymphocytes, macrophages, and dendritic cells by disrupting the integrity of the viral membrane and capsid core while preserving the integrity of host membranes. C5A can interrupt an ongoing T cell infection, and it can prevent transmigration of HIV through primary genital epithelial cells, infection of mucosal target cells and transfer from dendritic cells to T cells
ex vivo
, justifying future experiments to determine whether C5A can prevent HIV transmission
in vivo
.
Tbx5-dependent pathway regulating diastolic function in congenital heart disease
Authors: Zhu Yonghong , Gramolini Anthony O. , Walsh Mark A. , Zhou Yu-Qing , Slorach Cameron , Friedberg Mark K. , Takeuchi Jun K. , Sun Hui , Henkelman R. Mark , Backx Peter H. , Redington Andrew N. , MacLennan David H. , Bruneau Benoit G.
Published: April 2008

At the end of every heartbeat, cardiac myocytes must relax to allow filling of the heart. Impaired relaxation is a significant factor in heart failure, but all pathways regulating the cardiac relaxation apparatus are not known. Haploinsufficiency of the T-box transcription factor
Tbx5
in mouse and man causes congenital heart defects (CHDs) as part of Holt–Oram syndrome (HOS). Here, we show that haploinsufficiency of
Tbx5
in mouse results in cell-autonomous defects in ventricular relaxation.
Tbx5
dosage modulates expression of the sarco(endo)plasmic reticulum Ca
2+
-ATPase isoform 2a encoded by
Atp2a2
and
Tbx5
haploinsufficiency in ventricular myocytes results in impaired Ca
2+
uptake dynamics and Ca
2+
transient prolongation. We also demonstrate that Tbx5 can activate the
Atp2a2
promoter. Furthermore, we find that patients with HOS have significant diastolic filling abnormalities. These results reveal a direct genetic pathway that regulates cardiac diastolic function, implying that patients with structural CHDs may have clinically important underlying anomalies in heart function that merit treatment.
Pelvic floor muscle training in the prevention and treatment of urinary incontinence in women – what is the evidence?
Authors: BROSTRØM SØREN , LOSE GUNNAR
Published: April 2008

Many women suffer from urinary incontinence (UI). During and after pregnancy, women are advised to perform pelvic floor muscle training (PFMT) to prevent the development of UI. In established UI, PFMT is prescribed routinely as first‐line treatment. Published studies are small, underpowered and of uneven methodological quality. Variations in study populations, intervention types and outcome measures make comparisons difficult. While further studies are needed, the available evidence suggests a lack of long‐term efficacy of peripartum PFMT. In established UI, there seems to be a modest immediate response to PFMT. Based on the available evidence, we believe that a critical reappraisal of PFMT is needed, and judgments on the place of PFMT in current clinical practice should be reserved until further evidence, including cost‐benefit analyses, has unequivocally demonstrated a clinically relevant efficacy.
Transrectal ultrasound and the diagnosis of rectovaginal endometriosis: a prospective observational study
Authors: GRIFFITHS ANTHONY , KOUTSOURIDOU ROXANI , VAUGHAN SUE , PENKETH RICHARD , ASHLEY ROBERTS S. , TORKINGTON JARED
Published: April 2008

Background. Rectovaginal endometriosis is a severe form of pelvic endometriosis in which pharmacological treatment is relatively ineffective (Vercellini et al., Fertil Steril. 2005;84:1375–87). Laparoscopic surgical treatment is effective, but has the potential risks of bowel perforation and colostomy formation (Darai et al., Am J Obstet Gynecol. 2005;192:394–400). Transrectal ultrasound scanning can be applied as a preoperative tool to predict the presence of rectovaginal endometriosis and bowel wall involvement (Abrao et al., J Am Assoc Gynecol Laparosc. 2004;11:50–4). Methods. Thirty‐two women underwent transrectal ultrasound followed by therapeutic laparoscopy. Likelihood ratios and post‐test prevalences were calculated with Fagan's normogram. This was then extrapolated with the aid of a mathematical model to a low‐risk population. Results. A positive likelihood ratio was found to be 10.89 (95% confidence ratio (CI): 1.62–73.15) and a negative likelihood ratio was found to be 0.24 (95% CI: 0.1–0.57). The pre‐test prevalence of rectovaginal endometriosis was 56%. The positive post‐test prevalence probability was 93%, and the negative post‐test prevalence probability was 23%. Conclusion. Preoperative transrectal ultrasound scanning for rectovaginal endometriosis is an extremely accurate predictive test, and strongly predicts the need for extensive laparoscopic dissection and potential bowel resection.
Long‐term consequences of gynecological cancer treatment on urinary incontinence: a population‐based cross‐sectional study
Authors: EGIL SKJELDESTAD FINN , HAGEN BJØRN
Published: April 2008

Objective. To study urinary incontinence among long‐term survivors of gynecological cancer. Study design. In a population‐based, cross‐sectional design, we identified 319 recurrence‐free survivors of gynecological cancer, and 1,276 controls without a history of gynecological cancer. All participants were addressed with a 16‐pages questionnaire covering issues of quality of life, general health, daily living conditions, natural functions and co‐morbidities. Following 1 reminder, the response rates were 55 and 41% for cases and controls, respectively. Urinary incontinence (total, stress, urge and mixed) was in agreement with definitions of the International Continence Society. Results. Mean relapse‐free follow‐up time after treatment was 12 years (range: 8–17 years) for cases. The prevalence of total, stress, urge and mixed urinary incontinence were 34.3, 24, 0.8 and 9.5%, respectively. Previous gynecological cancer treatment was not associated with any outcomes of urinary incontinence. Obesity, previous and current use of HRT were associated with total, stress and mixed urinary incontinence, whereas increasing parity order was associated with total and stress urinary incontinence. In comparison with single factor analyses, the combination of obesity and parity 2+ had a multiplicative effect on total, stress and mixed incontinence. Conclusion. Recurrence‐free long‐term survivors of gynecological cancer are not at increased risk for urinary incontinence.
MRI anatomical study of the outside‐in transobturator suburethral tape procedure
Authors: FERNANDEZ PEDRO , RAIFFORT CYRIL , DELANEY SARAH , SALOMON LAURENCE , CARBONNE BRUNO , DELMAS VINCENT , ANSQUER YAN
Published: April 2008

Background. This study aims to clarify the relationship between the outside‐in transobturator suburethral tape and the anatomical structures at the blind passage of the obturator foramen, and to detail the tape position, shape, and the factors on which they are dependent. Methods. MRI scans were performed on 30 patients operated on with a dermal porcine collagen suburethral tape, indicated for urodynamically proven stress incontinence. Results. The lateral bladder wall was the closest structure to the tape at the passage of the obturator foramen, whereas vascular injuries appeared to be minimal using the outside‐in technique. The distance from tape to bladder neck was correlated with the distance from tape to pubococcygeal line (PCL) (p = 0.001), and with urethral length (p = 0.049). From the obturator foramen to its passage under the urethra, the tape was U‐shaped with a cranio‐caudal and antero‐posterior orientation. The cranio‐caudal tape shape was correlated with the distance between the tape and the PCL (p = 0.002), and to the patient's anatomical characteristics: distance between the bladder neck and the pubis (p = 0.01), and the urethral length (p = 0.01). The antero‐posterior shape was correlated with the urethral length (p = 0.02). Conclusion. The lateral bladder wall is the structure most at risk during the outside‐in transobturator suburethral tape procedure. The distance from tape to bladder neck is dependent on the vertical position of the tape. The tape shape is dependent on both tape position under the urethra and the patient's anatomical characteristics.
Pregnancy outcomes of women with pruritus, normal bile salts and liver enzymes: a case control study
Authors: YOONG WAI , MEMTSA M. , PUN S. , WEST P. , LOO C. , OKOLO S.
Published: April 2008

Background. Obstetric cholestasis (OC) is associated with increased maternal and perinatal complications. Nevertheless, data on pregnancy outcomes of women who experience pruritus on a transient basis, but have normal bile salts and liver function tests (LFT) is scarce. Methods. The maternal and fetal outcomes of 144 women with pruritus but normal bile salts and LFTs were compared with the next delivered patient without itch who matched for age, ethnicity and parity. Results. The study and control groups had similar mean gestational ages at delivery and birth weights (p>0.05, t test). However, women with pruritus were more likely to have meconium‐stained liqor, abnormal intrapartum cardiotocography and postpartum hemorrhage (PPH) (p<0.05, Fisher's exact test). There appears to be a trend towards a higher rate of instrumental delivery (p = 0.07) in the study compared to the control group, although this did not reach statistical significance. Conclusion. This study suggests that women who have transient pruritus with normal bile salts and liver biochemistry appear to have higher intrapartum and postpartum complications and require increased vigilance. In order to evaluate this finding, further prospective studies will be required.
Modifiable determinants of fetal macrosomia: role of lifestyle‐related factors
Authors: VOLDNER NANNA , FRØSLIE KATHRINE F. , BO KARI , HAAKSTAD LENE , HOFF CAMILLA , GODANG KRISTIN , BOLLERSLEV JENS , HENRIKSEN TORE
Published: April 2008

Background. Newborn macrosomia is associated with both short‐ and long‐term health risks for the infant, and increases the prevalence of birth complications. Parity, maternal age and gender of the child are known variables that influence fetal growth. The purpose of the present investigation was to evaluate prospectively the contributions of modifiable maternal predictors of fetal macrosomia (≥4,200 g), which included lifestyle‐related factors, such as nutritional intake, physical activity, and plasma glucose values, in addition to overweight and pregnancy weight gain. Methods. Some 553 women were followed through pregnancy. Predictive variables were subjected to univariate and multiple logistic regression analysis. Among these were: body mass index (BMI), weight gain, maternal subcutaneous fat (mm), fasting and 2‐h plasma glucose, self‐reported physical activity before and during pregnancy, and nutritional intake of macronutrients. Gestational age, parity and gender were also included in the model. All continuous variables were dichotomized using the upper quartile as the cut‐off point in most cases. Results. If physical activity was left out of the analyses, BMI, weight gain, plasma glucose and gestational age were independent determinants of macrosomia. After including low level pre‐gestational physical activity in the model, we found that this was now a significant determinant of delivering a macrosomic infant with an OR = 2.9 (95% CI: 1.9, 7.3). Conclusion. The present study indicates that a low level of pre‐gestational physical activity adds to the modifiable determinants of newborn macrosomia.