bluuebunny/crossref_metadata_2025 huggingface dataset:
A frequency-adjustable electromagnet for hyperthermia measurements on magnetic nanoparticles
Authors: Lacroix L.-M. , Carrey J. , Respaud M.
Published: September 2008

We describe a low-cost and simple setup for hyperthermia measurements on colloidal solutions of magnetic nanoparticles (ferrofluids) with a frequency-adjustable magnetic field in the range of 5–500kHz produced by an electromagnet. By optimizing the general conception and each component (nature of the wires, design of the electromagnet, etc.), a highly efficient setup is obtained. For instance, in a useful gap of 1.1cm, a magnetic field of 4.8mT is generated at 100 and 500kHz with output powers of 3.4 and 75W, respectively. A maximum magnetic field of 30mT is obtained at 100kHz. The temperature of the colloidal solution is measured using optical fiber sensors. To remove contributions due to heating of the electromagnet, a differential measurement is used. In this configuration the sensitivity is better than 1.5mW at 100kHz and 19.3mT. This setup allows one to measure weak heating powers on highly diluted colloidal solutions. The hyperthermia characteristics of a solution of Fe nanoparticles are described, where both the magnetic field and the frequency dependence of heating power have been measured.
Probing protein environment in an enzymatic process: All-electron quantum chemical analysis combined with ab initio quantum mechanical/molecular mechanical modeling of chorismate mutase
Authors: Ishida Toyokazu
Published: September 2008

In this study, we investigated the electronic character of protein environment in enzymatic processes by performing all-electron QM calculations based on the fragment molecular orbital (FMO) method. By introducing a new computational strategy combining all-electron QM analysis with ab initio QM/MM modeling, we investigated the details of molecular interaction energy between a reactive substrate and amino acid residues at a catalytic site. For a practical application, we selected the chorismate mutase catalyzed reaction as an example. Because the computational time required to perform all-electron QM reaction path searches was very large, we employed the ab initio QM/MM modeling technique to construct reliable reaction profiles and performed all-electron FMO calculations for the selected geometries. The main focus of the paper is to analyze the details of electrostatic stabilization, which is considered to be the major feature of enzymatic catalyses, and to clarify how the electronic structure of proteins is polarized in response to the change in electron distribution of the substrate. By performing interaction energy decomposition analysis from a quantum chemical viewpoint, we clarified the relationship between the location of amino acid residues on the protein domain and the degree of electronic polarization of each residue. In particular, in the enzymatic transition state, Arg7, Glu78, and Arg90 are highly polarized in response to the delocalized electronic character of the substrate, and as a result, a large amount of electrostatic stabilization energy is stored in the molecular interaction between the enzyme and the substrate and supplied for transition state stabilization.
Photoelectron spectroscopic study of the anionic transition metalorganic complexes [Fe1,2(COT)]− and [Co(COT)]−
Authors: Li Xiang , Eustis Soren N. , Bowen Kit H. , Kandalam Anil
Published: September 2008

The gas-phase, iron and cobalt cyclooctatetraene cluster anions, [Fe1,2(COT)]− and [Co(COT)]−, were generated using a laser vaporization source and studied using mass spectrometry and anion photoelectron spectroscopy. Density functional theory was employed to compute the structures and spin multiplicities of these cluster anions as well as those of their corresponding neutrals. Both experimental and theoretically predicted electron affinities and photodetachment transition energies are in good agreement, authenticating the structures and spin multiplicities predicted by theory. The implied spin magnetic moments of these systems suggest that [Fe(COT)], [Fe2(COT)], and [Co(COT)] retain the magnetic moments of the Fe atom, the Fe2 dimer, and the Co atom, respectively. Thus, the interaction of these transition metal, atomic and dimeric moieties with a COT molecule does not quench their magnetic moments, leading to the possibility that these combinations may be useful in forming novel magnetic materials.
Rydberg energies using excited state density functional theory
Authors: Cheng Chiao-Lun , Wu Qin , Van Voorhis Troy
Published: September 2008

We utilize excited state density functional theory (eDFT) to study Rydberg states in atoms. We show both analytically and numerically that semilocal functionals can give quite reasonable Rydberg energies from eDFT, even in cases where time dependent density functional theory (TDDFT) fails catastrophically. We trace these findings to the fact that in eDFT the Kohn–Sham potential for each state is computed using the appropriate excited state density. Unlike the ground state potential, which typically falls off exponentially, the sequence of excited state potentials has a component that falls off polynomially with distance, leading to a Rydberg-type series. We also address the rigorous basis of eDFT for these systems. Perdew and Levy have shown using the constrained search formalism that every stationary density corresponds, in principle, to an exact stationary state of the full many-body Hamiltonian. In the present context, this means that the excited state DFT solutions are rigorous as long as they deliver the minimum noninteracting kinetic energy for the given density. We use optimized effective potential techniques to show that, in some cases, the eDFT Rydberg solutions appear to deliver the minimum kinetic energy because the associated density is not pure state v-representable. We thus find that eDFT plays a complementary role to constrained DFT: The former works only if the excited state density is not the ground state of some potential while the latter applies only when the density is a ground state density.
On the Kirkwood–Buff inversion procedure
Authors: Smith Paul E.
Published: September 2008

A general approach is presented to express the Kirkwood–Buff integrals, the central component of the Kirkwood–Buff theory of solutions, in terms of thermodynamic properties of solution mixtures. A general expression valid for any number of components is provided in terms of matrix cofactors, while explicit expressions are given for three and four component mixtures. The corresponding symmetric ideal solution values are also presented for four and higher component mixtures.
Poisson sigma model with branes and hyperelliptic Riemann surfaces
Authors: Ferrario Andrea
Published: September 2008

We derive the explicit form of the superpropagators in the presence of general boundary conditions (coisotropic branes) for the Poisson sigma model. This generalizes the results presented by Cattaneo and Felder [“A path integral approach to the Kontsevich quantization formula,” Commun. Math. Phys. 212, 591 (2000)] and Cattaneo and Felder [“Coisotropic submanifolds in Poisson geometry and branes in the Poisson sigma model,” Lett. Math. Phys. 69, 157 (2004)] for Kontsevich’s angle function [Kontsevich, M., “Deformation quantization of Poisson manifolds I,” e-print arXiv:hep.th/0101170] used in the deformation quantization program of Poisson manifolds. The relevant superpropagators for n branes are defined as gauge fixed homotopy operators of a complex of differential forms on n sided polygons Pn with particular “alternating” boundary conditions. In the presence of more than three branes we use first order Riemann theta functions with odd singular characteristics on the Jacobian variety of a hyperelliptic Riemann surface (canonical setting). In genus g the superpropagators present g zero mode contributions.
Weakly nonlinear stability analysis of a flow past a neo-Hookean solid at arbitrary Reynolds numbers
Authors: Chokshi Paresh , Kumaran V.
Published: September 2008

The finite amplitude stability of a plane Couette flow over a deformable solid medium is analyzed with emphasis on the class of high Reynolds number (Re) modes, referred to as the wall modes, for which the viscous stresses are confined to a thin layer adjacent to the fluid-solid interface with thickness O(Re−1/3) times the channel width in the limit Re⪢1. Here, the Reynolds number is defined in terms of the top plate velocity V and the channel width R. Previous linear stability analyses have shown that the wall modes are unstable for Newtonian flow past a linear viscoelastic solid. In the present study, the analysis is extended to examine the weakly nonlinear stability of these unstable wall modes in order to determine the nature of bifurcation of the transition point to finite amplitude states. To account for the finite strain deformations, the flexible solid medium is described by a neo-Hookean elastic model which is a generalization of the commonly used linear constitutive model. The linear stability analysis provides the critical shear rate Γc and the critical wavenumber in the axial direction αc, where the dimensionless shear rate is defined as Γ=ρV2/G, where ρ is the fluid density and G is the shear modulus of the elastic solid. The critical parameter Γc for the neo-Hookean solid is found to be close to Γc for the linear elastic solid analyzed in the previous studies. The first Landau constant s(1), which is the finite amplitude correction to the linear growth rate, is evaluated in the weakly nonlinear stability analysis using both the numerical technique and the high Re asymptotic analysis. The real part of the Landau constant, sr(1), is negative for the wall mode instability in the limit Re⪢1 for a wide range of dimensionless solid thickness H, indicating that there is a supercritical bifurcation of the wall mode instability. The amplitude of the supercritically bifurcated equilibrium state is derived in the vicinity of the critical point. The equilibrium amplitude, in the form A1e2/(Γ−Γc), is found to scale as Re−1/3 in the limit Re⪢1 and is proportional to H2.3 for H⪢1 in the same limit.
Fluoropolymer indium-tin-oxide buffer layers for improved power conversion in organic photovoltaics
Authors: Kang Bonan , Tan L. W. , Silva S. R. P.
Published: September 2008

We investigate the effects of polytetrafluoroethylene (PTFE) on poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM) based organic photovoltaic (OPV) devices by inserting thermally evaporated PTFE films between indium-tin-oxide (ITO) and P3HT:PCBM layers. Significant improvement in terms of open-circuit voltage, short-circuit current, and thereby in its commensurate power conversion efficiency is achieved compared to devices with poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) layers. The OPVs performance enhancement is attributed to the formation of an artificial dipole layer resulting from the rich, negatively charged fluorine that facilitates the hole extraction process. This result shows the high potential of PTFE as a low cost and stable ITO buffer layer for OPV devices.
Boundaries of Siegel disks: Numerical studies of their dynamics and regularity
Authors: de la Llave Rafael , Petrov Nikola P.
Published: September 2008

Siegel disks are domains around fixed points of holomorphic maps in which the maps are locally linearizable (i.e., become a rotation under an appropriate change of coordinates which is analytic in a neighborhood of the origin). The dynamical behavior of the iterates of the map on the boundary of the Siegel disk exhibits strong scaling properties which have been intensively studied in the physical and mathematical literature. In the cases we study, the boundary of the Siegel disk is a Jordan curve containing a critical point of the map (we consider critical maps of different orders), and there exists a natural parametrization which transforms the dynamics on the boundary into a rotation. We compute numerically this parameterization and use methods of harmonic analysis to compute the global Hölder regularity of the parametrization for different maps and rotation numbers. We obtain that the regularity of the boundaries and the scaling exponents are universal numbers in the sense of renormalization theory (i.e., they do not depend on the map when the map ranges in an open set), and only depend on the order of the critical point of the map in the boundary of the Siegel disk and the tail of the continued function expansion of the rotation number. We also discuss some possible relations between the regularity of the parametrization of the boundaries and the corresponding scaling exponents.
Germanium nanocrystal density and size effects on carrier storage and emission
Authors: El Hdiy A. , Gacem K. , Troyon M. , Ronda A. , Bassani F. , Berbezier I.
Published: September 2008

We are interested in germanium nanocrystal density and size effects on the carrier storage and emission processes. For this purpose, high frequency capacitance-voltage and current-voltage characteristics were performed for temperatures varying from 300 to 77 K. Ge nanocrystals were deposited on a silicon dioxide/p-doped silicon structure and capped with a thin amorphous silicon layer. Results evidenced an electron storage phenomenon in nanocrystals that presented two different behaviors depending on the temperature. For temperatures higher than ∼140 K, the storage was mainly controlled by the nanocrystal density. At low temperatures the storage was reduced due to lowering of the tunneling barrier that resulted from a carrier quantum confinement process. Thermal activation energy of the carrier emission process was revealed as varying linearly with nanocrystal energy band gap. Activation energy was identified as a barrier height to be overcome by the emitted electrons.
Two-layer Hall-effect model with arbitrary surface-donor profiles: application to ZnO
Authors: Look D. C.
Published: September 2008

A complete two-layer Hall-effect model, allowing arbitrary donor and acceptor profiles, is presented and applied to the problem of conductive surface layers in ZnO. Temperature-dependent mobility and carrier concentration data in the temperature range of 20–320 K are fitted with an efficient algorithm easily implemented in commercial mathematics programs such as MATHCAD. The model is applied to two ZnO samples, grown by the melt (MLT) and hydrothermal (HYD) processes, respectively. Under the assumption of a “square” surface-donor profile, the fitted surface-layer thicknesses are 48 and 2.5 nm, respectively, for the MLT and HYD samples. The surface-donor concentrations are 7.6×1017 and 8.3×1018 cm−3, and the integrated surface-donor concentrations are 2.1×1012 and 3.6×1012 cm−2. For an assumed Gaussian [NDs(0)exp(−z2/ds2)] donor profile, the fitted values of ds are nearly the same as those for the square profile. The values of ND,s(0) are about 50% larger and the integrated donor-concentration values are about 15% larger, for both samples. As a surface-analysis tool, the Hall effect is extremely sensitive and applicable over a wide range of surface-layer conditions.
Enhancement of the thermoelectric performances of In2O3 by the coupled substitution of M2+/Sn4+ for In3+
Authors: Bérardan David , Guilmeau Emmanuel , Maignan Antoine , Raveau Bernard
Published: September 2008

The thermoelectric properties of air-prepared cosubstituted indium oxide based compounds belonging to the series In2−2xMxSnxO3 (M=Zn, Cu, or Ni) have been studied. X-ray diffraction studies show that the solubility limit xmax increases from xmax=0.35 for M=Cu to xmax=0.45 for M=Zn and xmax=0.55 for M=Ni. The lattice parameters, following the Vegard law with increasing substitution rates are in good agreement with the divalent oxidation state for the M cations. Compared to the undoped In2O3 prepared in air, the electrical resistivity of the cosubstituted phases (M=Zn,Cu) is strongly decreased and exhibits a metallic behavior. A more complex behavior is observed for the Ni/Sn cosubstituted samples whose resistivity first decreases and then increases with x. The lowest resistivity values do not exceed 0.5 mΩ cm at room temperature. Despite the lower values of the thermopower in cosubstituted samples, the thermoelectric power factor is significantly higher than that of the undoped In2O3, leading to values exceeding 5.10−4 W m−1 K−2. Furthermore, as the lattice thermal conductivity is strongly reduced by the cosubstitution due to mass fluctuation scattering of the phonons, promising thermoelectric figure of merit ZT is observed, close to 0.3 at 1273 K in In1.6Zn0.2Sn0.2O3. Thus, this study emphasizes the important role of cosubstitution to improve the thermoelectric properties of these n-type oxides.
Defect-induced states in the electronic structure of a Cu(100)-benzenethiolate-pentacene heterostructure
Authors: Kanjilal Aloke , Betti Maria Grazia , Mariani Carlo
Published: September 2008

We report on the influence of defects in the electronic properties of a pentacene single-layer grown on a benzenethiolate self-assembled-monolayer (Bt-SAM) adsorbed on Cu(100) at 300 K, using high-resolution ultraviolet photoelectron spectroscopy. The weak interaction between pentacene and the underlying Bt-SAM is deduced by the lineshape and evolution of the highest-occupied molecular orbital (HOMO). Closer inspection of the pentacene HOMO band reveals a skewed feature, where the contribution in the low binding energy side is found originating from states associated to structural defects that can be reduced by controlled mild-temperature annealing (355 K). Presence of such defects influences also the pentacene HOMO onset energy and hole-injection barrier that can be reduced to typical value of this organic heterostructure after the annealing.
Rayleigh surface acoustic wave modes of interdigital transducer/(100) AlN/(111) diamond
Authors: Wu Sean , Ro Ruyen , Lin Zhi-Xun , Lee Maw-Shung
Published: September 2008

In this research, Rayleigh surface acoustic wave (SAW) modes of interdigital transducer (IDT)/(100) AlN/(111) diamond were theoretically analyzed and exhibited some excellent acoustic properties. Those Rayleigh SAW modes have smaller film thickness ratios (h/λ), higher phase velocities, and larger electromechanical coupling coefficients (K2) than the ones of IDT/(002) AlN/(111) diamond. Especially for mode 1, the phase velocity is 10 474 m/s, the K2 is 2.31%, and the film thickness ratio (h/λ) is 0.3. The research results exhibit that IDT/(100) AlN/(111) diamond has some excellent properties and provides a predictable and theoretical basis for further application in high velocity SAW devices.
Studies on dielectric and magnetic properties of (x) Ni0.2Co0.8Fe2O4+(1−x) barium lead zirconate titanate magnetoelectric composites
Authors: Bammannavar B. K. , Naik L. R. , Chougule B. K.
Published: September 2008

The piezomagnetic (ferrite)–piezoelectric (ferroelectric) composites with compositions (x) Ni0.2Co0.8Fe2O4+(1−x) Ba0.8Pb0.2Zr0.8Ti0.2O3 [barium lead zirconate titanate (BPZT)] in which x varies as 0.0, 0.15, 0.30, 0.45, and 1.0 mol % were prepared by conventional ceramic double-sintering method. The presence of constituent phases in the composites was confirmed by x-ray diffraction studies and the average grain size was calculated by using scanning electron microscopy. The dielectric constant (ε′) and loss tangent (tan δ) were measured as a function of frequency in the frequency range 20 Hz–1 MHz. Variation of the dielectric constant and loss tangent with temperature at four fixed frequencies (1, 10, and 100 KHz and 1 MHz) was studied. The ac conductivity was studied to understand the conduction mechanism in terms of small polarons. The hysteresis behavior was studied to understand the magnetic properties such as saturation magnetization (Ms) and magnetic moment (μB). The static magnetoelectric (ME) voltage coefficient was measured as function of applied dc magnetic field and variation in ME response has been explained in terms of the content of piezomagnetic phase and the intensity of applied magnetic field. The maximum ME conversion factor of 536 μV/cm Oe was observed for 15% Ni0.2Co0.8Fe2O4+85% BPZT composite.
One- and two-photon absorption properties of diamond nitrogen-vacancy defect centers: A theoretical study
Authors: Lin Chih-Kai , Wang Yi-Hsieh , Chang Huan-Cheng , Hayashi M. , Lin S. H.
Published: September 2008

The negatively charged nitrogen-vacancy defect center, (NV)–, in diamond has been investigated theoretically for its one- and two-photon absorption properties involving the first excited state with the A32→E3 transition. Time-dependent density functional theory (TD-DFT), configuration interaction with single excitation (CIS), and complete active space self-consistent field (CASSCF) were employed in this investigation along with the 6-31G(d) basis set. Diamond lattice models containing 24–104 carbon atoms were constructed to imitate the local environment of the defect center. TD-DFT calculations in large molecular cluster models (with 85 or more carbon atoms) predicted the vertical excitation energy quite consistent with the experimental absorption maximum. CASSCF calculations were feasible only for small cluster models (less than 50 carbon atoms) but yielded one-photon absorption (OPA) and two-photon absorption (TPA) cross sections somewhat larger than the experimental values obtained with linearly polarized incident light [T.-L. Wee et al., J. Phys. Chem. A 111, 9379 (2007)]. CIS calculations in larger cluster models showed a systematic overestimation of the excitation energy while just slightly underestimated the OPA cross section and overestimated the TPA cross section. The agreements between calculations and measurements suggest that the computational approaches established in this work are applicable to explore the optical properties of related defect centers in diamond as well.
Proposal for observation of retardation effect between two quantum dots via current noise
Authors: Chen Yueh-Nan , Gilz Lukas
Published: September 2008

We propose to observe the retardation effect between two quantum dots in a one-dimensional waveguide. The effect of retardation is more pronounced comparing to that in free space. If the photons are to be reflected by a mirror at one of the ends, the interference role played by the reflecting photon is found to be destructive. With the combination of p-i-n junction, the retardation effect can be read out via current-noise spectrums.
Nonlinear Poisson–Boltzmann model of charged lipid membranes: Accounting for the presence of zwitterionic lipids
Authors: Mengistu Demmelash H. , May Sylvio
Published: September 2008

The nonlinear Poisson–Boltzmann model is used to derive analytical expressions for the free energies of both mixed anionic-zwitterionic and mixed cationic-zwitterionic lipid membranes as function of the mole fraction of charged lipids. Accounting explicitly for the electrostatic properties of the zwitterionic lipid species affects the free energy of anionic and cationic membranes in a qualitatively different way: That of an anionic membrane changes monotonously as a function of the mole fraction of charged lipids, whereas it passes through a pronounced minimum for a cationic membrane.
Submicrometer periodic patterns fixed by photopolymerization of dissipative structures
Authors: Hoischen A. , Benning S. A. , Kitzerow H.-S.
Published: September 2008

In photoreactive liquid crystals, spontaneous pattern formation can be used to fabricate phase gratings or polymer films with a periodic surface modulation. Typically, the periodicity of such structures is comparable to the sample thickness, and thus in the range between several micrometers and about 100 μm. Here, attempts to create and to investigate smaller structures are presented. For a chevron pattern, periodicities as small as 800 nm could be detected.
Microvortices and recirculating flow generated by an oscillatory microplate for microfluidic applications
Authors: Lin Cheng Ming , Lai Yu Shang , Liu Hsin Ping , Wo Andrew M.
Published: September 2008

Circulatory flow structures can be useful in a microfluidic device but often are difficult to generate mechanically in microscale. This paper presents generation of such flow via an in-plane resonating microplate (100×100×1.2μm3) actuated by Lorentz law. Results show either one of two nonlinear time-mean flow structures is feasible for the finite plate: (1) two-dimensional (2D) small-scale, counter-rotating microvortices or (2) three-dimensional, large-scale, recirculating flow. Sharpness of microplate’s edge is found to be the decisive factor for 2D microvortices to form. Both flow structures are robust and controllable. Potential applications include trapping and mixing of bioparticles in microfluidic devices.
Modified electron-beam-induced deposition of metal nanostructure arrays using a parallel electron beam
Authors: Basu Joysurya , Barry Carter C. , Divakar R. , Shenoy Vijay B. , Ravishankar N.
Published: September 2008

A modified electron-beam-induced deposition method using a parallel beam of electrons is developed. The method relies on the buildup of surface potential on an insulating surface exposed to an electron beam. Presence of sharp edges on the insulating surface implies presence of large electric fields that lead to site-specific nucleation of metal vapor on those regions. Feature sizes as small as 20nm can be deposited without the need to use fine probes, and thus the limitation of probe size imposed on the resolution is overcome. The use of pure metal vapor also renders the process inherently clean.
Carrier transport mechanisms of nonvolatile memory devices based on nanocomposites consisting of ZnO nanoparticles with polymethylmethacrylate nanocomposites sandwiched between two C60 layers
Authors: Park Kyu Ha , Jung Jae Hun , Li Fushan , Son Dong Ick , Kim Tae Whan
Published: September 2008

Transmission electron microscope images showed that ZnO nanoparticles were formed in a polymethylmethacrylate (PMMA) layer. Current-voltage (I-V) curves for the Al∕C60∕ZnO nanoparticles embedded in the PMMA layer/C60/indium tin oxide (ITO) device at 300K showed a current bistability with a large on/off ratio of 104, which was much larger than the on/off ratio of the device without C60 layers, indicative of significant enhancement of memory storage. Carrier transport mechanisms of the memory effects for the Al∕C60∕ZnO nanoparticles embedded in the PMMA layer/C60/ITO device are described on the basis of the I-V results.
Toward the existence of ultrafast diffusion paths in Cu with a gradient microstructure: Room temperature diffusion of Ni
Authors: Wang Z. B. , Lu K. , Wilde G. , Divinski S.
Published: September 2008

Room temperature diffusion of Ni63 in Cu with a gradient microstructure prepared by surface mechanical attrition treatment (SMAT) was investigated by applying the radiotracer technique. The results reveal significant penetration of Ni into the nanostructured layer. The relevant diffusivity is higher than that along the conventional high-angle grain boundaries by about six orders of magnitude. This behavior is associated with a higher energy state of internal interfaces produced via plastic deformation. The diffusivity in the top surface layer is somewhat smaller than that in the subsurface layer. This fact is related to nanotwin formation in the former during SMAT.
Closed Spaces: Can't Live with Them, Can't Live without Them
Authors: Schlottmann Antje
Published: September 2008

Spatial assumptions, mostly taken for granted in mediated and face-to-face language use, both represent and constitute social reality. How, though, do their hidden logics work in detail? What are their respective imaginative effects and functions? And, in view of their involvement in discourses of discrimination, are they dispensable? By using the press coverage of the German reunification as a case study, I discuss the social embeddedness and maintenance of fairly traditional spatial concepts in general, and the Euclidean ‘container concept’ in particular on a theoretical level. In everyday social practice, it is argued, these concepts have both constraining and enabling implications. Their constitutive dimension, however, is often neglected in recent critical discourse animated by ‘new’ spatial imaginations such as flows, networks, folds, or rhizomes. In this respect, I argue that everyday ‘containerization’ surely (over)simplifies contingency and complexity. Yet, the ‘closed spaces’ still remain reasonable and to a certain extent, indispensable tools for making the world intelligible by identifying, organizing, and structuring complex phenomena. Hence, instead of only searching for new and ‘more adequate’ spatial representations, the everyday use of the ‘old’ ones should also remain a subject of thorough sociogeographic inquiry.
The Formation of Constellation III in the Large Magellanic Cloud
Authors: Harris Jason , Zaritsky Dennis
Published: September 2008

We present a detailed reconstruction of the star-formation history of the Constellation III region in the Large Magellanic Cloud, to constrain the formation mechanism of this enigmatic feature. Star formation in Constellation III seems to have taken place during two distinct epochs: there is the 8–15 Myr epoch that had previously been recognized, but we also see strong evidence for a separate ‘burst’ of star formation 25–30 Myr ago. The ‘super-supernova' or GRB blast wave model for the formation of Constellation III is difficult to reconcile with such an extended, two-epoch star formation history, because the shock wave should have induced star formation throughout the structure simultaneously, and any unconsumed gas would quickly be dissipated, leaving nothing from which to form a subsequent burst of activity. We propose a ‘truly stochastic’ self-propagating star formation model, distinct from the canonical model in which star formation proceeds in a radially directed wave from the center of Constellation III to its perimeter. As others have noted, and we now confirm, the bulk age gradients demanded by such a model are simply not present in Constellation III. In our scenario, the prestellar gas is somehow pushed into these large-scale arc structures, without simultaneously triggering immediate and violent star formation throughout the structure. Rather, star formation proceeds in the arc according to the local physical conditions of the gas. Self-propagating star formation is certainly possible, but in a truly stochastic manner, without a directed, large scale pattern.
The Spitzer Survey of the Large Magellanic Cloud: SAGE, A Review of Initial Results
Authors: Meixner M.
Published: September 2008

We have performed a uniform and unbiased imaging survey of the Large Magellanic Cloud, using the IRAC and MIPS instruments on board the Spitzer Space Telescope. This Spitzer survey of the Large Magellanic Cloud is surveying the agents of a galaxy's evolution (SAGE), the interstellar medium and stars. The SAGE data are nonproprietary and the team has been creating catalogs and improved images for use by the astronomical community. This paper highlights some of the initial results being published by the SAGE team covering the topics of evolved stars and their mass-loss return to the ISM, young stellar objects and the properties of the ISM dust.
The regulation of body weight: lessons from the seasonal animal
Authors: Morgan Peter J. , Mercer Julian G.
Published: September 2008

The hypothalamus is a major regulatory centre involved in the control of many important physiological axes. One of these axes is the regulation of ingestive behaviour. Recent work using a combination of genetic-mutant mouse models together with targeted gene deletions has contributed much to our understanding of how neural pathways of the hypothalamus are involved in the regulation of energy balance in animals. These pathways are also relevant to human energy homeostasis, as mutations in key genes are correlated with obesity. Many of the genes identified mediate the effects of leptin, and are therefore primarily involved in sensing and responding to peripheral signals. In seasonal animals, such as the Siberian hamster (Phodopus sungorus), there is evidence for a higher level of regulation. The systems involved regulate body weight around an apparent 'set-point' through the action of photoperiod via the neurohormone, melatonin. The ability to manipulate energy balance through photoperiod (and melatonin) in the seasonal-animal model offers novel opportunities to identify further fundamental aspects of the control mechanisms involved in the central control of energy homeostasis and body weight.
A healthy body, a healthy mind: long-term impact of diet on mood and cognitive function
Authors: Rogers Peter J.
Published: September 2008

Certain dietary risk factors for physical ill health are also risk factors for depression and cognitive impairment. Although cholesterol lowering has been suggested to increase vulnerability to depression, there is better support for an alternative hypothesis that intake ofn-3 long-chain polyunsaturated fatty acids can affect mood (and aggression). Possible mechanisms for such effects include modification of neuronal cell membrane fluidity and consequent impact on neurotransmitter function. Stronger evidence exists concerning a role for diet in influencing cognitive impairment and cognitive decline in older age, in particular through its impact on vascular disease. For example, cognitive impairment is associated with atherosclerosis, type 2 diabetes and hypertension, and findings from a broad range of studies show significant relationships between cognitive function and intakes of various nutrients, including long-chain polyunsaturated fatty acids, antioxidant vitamins, and folate and vitamin B12. Further support is provided by data on nutrient status and cognitive function. Almost all this evidence, however, comes from epidemiological and correlational studies. Given the problem of separating cause and effect from such evidence, and the fact that cognitive impairment and cognitive decline (and depression) are very likely to be significant factors contributing to the consumption of a poor diet, greater emphasis should now be placed on conducting intervention studies. An efficient approach to this problem could be to include assessments of mood and cognitive function as outcome measures in studies designed primarily to investigate the impact of dietary interventions on markers of physical health.
Theoretical developments in the study and prediction of food intake
Authors: Yearsley Jonathan , Tolkamp Bert J. , Illius Andrew W.
Published: September 2008

The purpose of the present paper is to review recent theoretical developments in food intake modelling applied to animal science and ecology. The models are divided into those that have been developed for intensive agricultural systems, and those which consider more extensive systems and natural systems. For the most part the present paper discusses models that predict the food intake of herbivores. The mechanisms of each model are discussed, along with a brief mention of the experimental support for the most popular models. We include a discussion of models that approach the study of food intake behaviour from an evolutionary perspective, and suggest that lifetime models are especially useful when food intake carries an intrinsic cost. These long timescale evolutionary models contrast with the more common food intake models, whose timescale is usually much shorter. We conclude that the ‘eating to requirements’ model highlights an important food intake mechanism that provides an accurate predictive tool for intensive agricultural systems. The mechanisms of food intake regulation in extensive systems are less certain, and closer links between the ideas of animal science and ecology will be helpful for improving our understanding of food intake regulation.
Energy balance and cancer: the role of insulin and insulin-like growth factor-I
Authors: Kaaks R. , Lukanova A.
Published: September 2008

Recent theories propose that a Western lifestyle may increase cancer risk through alterations in the metabolism of insulin and insulin-like growth factors (IGF; McKeown-Eyssen, 1994; Giovannucci, 1995; Kaaks, 1996; Werner & LeRoith, 1996). Insulin regulates energy metabolism, and increases the bioactivity of IGF-I, by enhancing its synthesis, and by decreasing several of its binding proteins (IGFBP; IGFBP-1 and -2). Insulin and IGF-I both stimulate anabolic processes as a function of available energy and elementary substrates (e.g. amino acids). The anabolic signals by insulin or IGF-I can promote tumour development by inhibiting apoptosis, and by stimulating cell proliferation. Furthermore, both insulin and IGF-I stimulate the synthesis of sex steroids, and inhibit the synthesis of sex hormone-binding globulin (SHBG), a binding protein that regulates the bioavailability of circulating sex steroids to tissues. The present paper reviews epidemiological findings relating the risk of cancers of the colo-rectum, pancreas, breast, endometrium and prostate to body size (obesity, height) and physical activity, and discusses the relationships between obesity and physical activity and plasma levels of insulin, IGF-I and IGFBP. Subsequent sections review epidemiological findings relating cancer risk to indices of chronic hyperinsulinaemia, and to plasma levels of IGF-I and IGFBP. Conclusions are that chronic hyperinsulinaemia may be a cause of cancers of the colon, pancreas and endometrium, and also possibly of the breast. On the other hand, elevated plasma IGF-I, as total concentrations or relative to levels of IGFBP-3, appears to be related to an increased risk of prostate cancer, breast cancer in young women, and possibly colo-rectal cancer. For cancers of the endometrium, breast and prostate, these findings are discussed in the context of relationships between insulin and IGF-I and levels of bioavailable sex steroids.
Nutrition–hormone receptor–gene interactions: implications for development and disease
Authors: Dauncey M. J. , White P. , Burton K. A. , Katsumata M.
Published: September 2008

Nutrition profoundly alters the phenotypic expression of a given genotype, particularly during fetal and postnatal development. Many hormones act as nutritional signals and their receptors play a key role in mediating the effects of nutrition on numerous genes involved in differentiation, growth and metabolism. Polypeptide hormones act on membrane-bound receptors to trigger gene transcription via complex intracellular signalling pathways. By contrast, nuclear receptors for lipid-soluble molecules such as glucocorticoids (GC) and thyroid hormones (TH) directly regulate transcription via DNA binding and chromatin remodelling. Nuclear hormone receptors are members of a large superfamily of transcriptional regulators with the ability to activate or repress many genes involved in development and disease. Nutrition influences not only hormone synthesis and metabolism but also hormone receptors, and regulation is mediated either by specific nutrients or by energy status. Recent studies on the role of early environment on development have implicated GC and their receptors in the programming of adult disease. Intrauterine growth restriction and postnatal undernutrition also induce striking differences in TH-receptor isoforms in functionally-distinct muscles, with critical implications for gene transcription of myosin isoforms, glucose transporters, uncoupling proteins and cation pumps. Such findings highlight a mechanism by which nutritional status can influence normal development, and modify nutrient utilization, thermogenesis, peripheral sensitivity to insulin and optimal cardiac function. Diet and stage of development will also influence the transcriptional activity of drugs acting as ligands for nuclear receptors. Potential interactions between nuclear receptors, including those for retinoic acid and vitamin D, should not be overlooked in intervention programmes using I or vitamin A supplementation of young and adult human populations.
Producing tender and flavoursome beef with enhanced nutritional characteristics
Authors: Moloney A. P. , Mooney M. T. , Kerry J. P. , Troy D. J.
Published: September 2008

The perception of healthiness and/or safety, tenderness, juiciness and aroma or flavour are important quality criteria that influence the decision of a consumer to purchase beef. Beef production systems represent the combined and interacting effects of genotype, gender, age at slaughter and nutrition before slaughter. The present paper highlights recent information on how beef production systems can be modified to enhance the tenderness, flavour and healthiness of beef. Carcass management post-slaughter has a larger effect on meat tenderness than gender, genotype or feeding systems. Optimum ‘pasture to plate’ management systems are being established to ensure beef tenderness. The chemistry underlying beef flavour is complex, with in excess of 140 components identified in cooked beef volatiles. Flavour of beef is influenced by cattle diet, but assessment of flavour by a taste panel is subject to the previous experiences and preferences of the panellists. Modern lean beef can have an intramuscular fat concentration of 25–50 g/kg and can be considered a low-fat food. As the quantity of grass in the diet of cattle is increased, there is a decrease in saturated fatty acid concentration, and an increase in then-3 polyunsaturated fatty acid and conjugated linoleic acid concentrations. It is concluded that there is opportunity to exploit the diet of cattle to produce tender flavoursome beef that has an increased conjugated linoleic acid concentration, a lower fat concentration and a fatty acid profile more compatible with current human dietary recommendations.
Dietary monounsaturated fatty acids and haemostasis
Authors: Kelly Colette N. M. , Smith Ruth D. , Williams Christine M.
Published: September 2008

Diets high in monounsaturated fatty acids (MUFA) are increasingly being recommended as a highly-effective cholesterol-lowering strategy in populations at risk of CHD. However, the need for a re-appraisal of the benefits of diets rich in MUFA became apparent as a result of recent studies showing that meals high in olive oil cause greater postprandial activation of blood coagulation factor VII than meals rich in saturated fatty acids. The present review evaluates the evidence for the effects of MUFA-rich diets on fasting and postprandial measurements of haemostasis, and describes data from a recently-completed long-term controlled dietary intervention study. The data show that a background diet high in MUFA has no adverse effect on fasting haemostatic variables and decreases the postprandial activation of factor VII in response to a standard fat-containing meal. Since the same study also showed a significant reduction in theex vivoactivation of platelets in subjects on the high-MUFA diet, the overall findings suggest that there is no reason for concern regarding adverse haemostatic consequences of high-MUFA diets.
The impact of globalisation, free trade and technology on food and nutrition in the new millennium
Authors: McMichael Philip
Published: September 2008

The millennium promises a dramatic politicisation of the food question. In addition to the prominent issues of food security, hunger and nutrition, bioengineering, food safety and quality, there are related issues of environmental sustainability, power, sovereignty and rights. All these issues are deeply implicated in the current corporate form of globalisation, which is transforming historic global arrangements by subordinating public institutions and the question of food security to private solutions. The present paper questions the self-evident association between globalisation and nutritional improvement.
Nutritional factors and visual function in premature infants
Authors: Jewell Victoria C. , Northrop-Clewes Christine A. , Tubman Richard , Thurnham David I.
Published: September 2008

Approximately 5–7 % of all infants are born prematurely, and birth before 37 weeks is the most common cause of neonatal mortality, morbidity and long-term disability. Premature infants are poorly equipped for life outside the womb, and oxidant stress has been implicated in the aetiology of visual impairment in these infants, who are often exposed to increased O2concentrations and high light intensity in neonatal units. The carotenoids lutein and zeaxanthin, which give the macular area of the eye its yellow colour, are located in the retinal pigment epithelium of the eye, and are believed to play a role in protecting it against oxidative and light damage. The macular pigments are of dietary origin, and green leafy vegetables are the primary source of lutein and zeaxanthin. Lutein is one of the five most common carotenoids found in the diet. There is current interest in the macular pigment in relation to age-related macular degeneration, but these pigments may also have a protective role in the retinal pigment epithelium of the newborn infant. Little information is available on blood lutein and zeaxanthin levels in neonates. Levels of lutein in human milk are two to three times higher than those of β-carotene, whereas their concentrations in the mothers’ blood are approximately the same. Human milk is the main dietary source of lutein and zeaxanthin for infants until weaning occurs. The biochemical mechanisms which mediate the transport of the macular carotenoids into the eye are not known, but tubulin has been identified as the major carotenoid-binding protein, and may play a role in the physiology of the macula.
Impact of climatic and other environmental changes on food production and population health in the coming decades
Authors: McMichael A. J.
Published: September 2008

World population will reach an estimated nine billion by 2050. Given this factor and continued economic development in today's low-income countries, the total global demand for food will increase approximately threefold over the coming half-century. Meanwhile, against this background, newly-occurring global environmental changes such as climate change are anticipated to affect food production. Other incipient large-scale environmental changes likely to affect food production include stratospheric O3depletion, the accelerating loss of biodiversity (with knock-on effects on crop and livestock pest species) and the perturbation of several of the great elemental cycles of N and S. The ways in which these various environmental influences affect the production of food (crops and livestock on land, and wild and cultivated fisheries) are complex and interactive. Uncertainties therefore persist about how global climate change is likely to affect world and regional food production. On balance, recent modelling-based estimates indicate that, in the medium to longer term, if not over the next several decades, climate change is likely to affect crop yields adversely, especially in food-insecure regions. The prospect of increased climatic variability further increases the risks to future food production. Given these possible though uncertain adverse impacts of climatic and other environmental changes on world food production, there is a need to apply the Precautionary Principle. There are finite, and increasingly evident, limits to agro-ecosystems and to wild fisheries. Our capacity to maintain food supplies for an increasingly large and increasingly expectant world population will depend on maximising the efficiency and sustainability of production methods, incorporating socially-beneficial genetic biotechnologies, and taking pre-emptive action to minimise detrimental ecologically-damaging global environmental changes.