bluuebunny/crossref_metadata_2025 huggingface dataset:
HUME'S FOUR PHILOSOPHERS: RECASTING THETREATISE OF HUMAN NATURE
Authors: JOST JACOB SIDER
Published: March 2009

Disappointed by the indifferent reception of his 1739Treatise of Human Nature, particularly in view of his commitment to vividness and convincingness as epistemological criteria, Hume recast crucial arguments from hisTreatisein “The Epicurean,” “The Stoic,” “The Platonist,” and “The Sceptic,” four pieces from his 1741–2Essays Moral and Political. Locating these texts within both the dialogue and essay genres, I demonstrate how Hume continues the project of theTreatiseby showing, rather than telling, his views: he blends rhetoric and reasoned argument to show that they are in many cases indistinguishable; he depicts his speakers' conclusions as consequences of their personalities to show his skepticism about human freedom; and he concludes, in a moment strongly reminiscent of the famous end of Book I of theTreatise, by showing the limits of philosophy itself.
COMMUNITY AND THE MARKET IN MICHAEL POLANYI'S PHILOSOPHY OF SCIENCE
Authors: THORPE CHARLES
Published: March 2009

The chemist and philosopher Michael Polanyi (1891–1976) is today recognized as one of the most important twentieth-century thinkers about scientific knowledge and scientific community. Yet Polanyi's philosophy of science exhibits an unresolved tension between science as a traditional community and science as an intellectual marketplace. Binding together these different models was important for his overall intellectual and political project, which was a defense of bourgeois liberal order. His philosophy of science and his economic thought were mutually supporting elements within this political project. Polanyi's intellectual corpus formed a contradictory unity, the tensions within which were manageable only under particular historical conditions. His attempt to hold together traditional authority and the free market fit with, and derived plausibility from, the social conditions under which his philosophical work came to maturity: Keynesian class compromise and surviving habits of social deference within postwar Britain.
INQUIRING MINDS WANT TO KNOW: SOCIAL INVESTIGATION IN HISTORY AND THEORY
Authors: FURNER MARY O.
Published: March 2009

Investigating investigations, inquiring into inquiries, surveying the results of earlier surveys: for well over a century historians have been digging into the mountains of data amassed by generations of social investigators, seeking evidence to use in reconstructing past economic relations and social conditions. Like Karl Marx hunched over parliamentary Blue Books in the British Museum, we have parsed the tables and decoded the responses, searching for the stuff of social and cultural life. All this intense scrutiny suggests something of the importance of the subject. For social historians seeking nonelite sources, for policy historians studying conditions to be addressed by state or communal action, for cultural historians recovering elusive past identities, for intellectual historians listening for points of contact between action and belief, the accumulated lore deposited in past social inquiries provides indispensable concrete evidence.
SCRIPTURE AND SLAUGHTER: THE CIVIL WAR AS A THEOLOGICAL AND MORAL CRISIS
Authors: PERRY LEWIS
Published: March 2009

In a well-known 1964 essay on the “recovery” of American religious history, Henry F. May observed that some scholars had “revived” religious interpretations of the nation's greatest political crises, including the Civil War. But there was more work to be done. “A religious, or partly religious explanation of the Civil War,” May suggested, would “rest on two assertions: that serious and intractable moral conflicts were important in causing the war and that in nineteenth-century America such conflicts were particularly difficult to avoid or compromise because of the dominance of evangelical Protestantism in both sections.” In fact, both the importance of the moral conflict over slavery and the role of evangelicalism in intensifying hostilities were already attracting attention as historians reexamined previous emphases on economic factors and political bungling as explanations of a tragically unnecessary war.
Bengt Strömgren's Approach to the Galaxy
Authors: Gustafsson Bengt
Published: March 2009

The contributions of Bengt Strömgren to the exploration and understanding of the Galactic Disk are sketched. The question what we can learn from his systematic approach is discussed.
Reconciling the Metallicity Distributions of Gamma-ray Burst, Damped Lyman-α, and Lyman-break Galaxies atz≈ 3
Authors: Fynbo Johan P. U. , Prochaska J. Xavier , Sommer-Larsen Jesper , Dessauges-Zavadsky Miroslava , Møller Palle
Published: March 2009

We test the hypothesis that the host galaxies of long-duration gamma-ray bursts (GRBs) as well as quasar-selected damped Lyman-α (DLA) systems are drawn from the population of UV-selected star-forming, highzgalaxies (generally referred to as Lyman-break galaxies). Specifically, we compare the metallicity distributions of the GRB and DLA populations against simple disk models where these galaxies are drawn randomly from the distribution of star-forming galaxies according to their star-formation rate and HI cross-section respectively. We find that it is possible to match both observational distributions assuming very simple and constrained relations between luminosity, metallicity, metallicity gradients and HI sizes. The simple model can be tested by observing the luminosity distribution of GRB host galaxies and by measuring the luminosity and impact parameters of DLA selected galaxies as a function of metallicity. Our results support the expectation that GRB and DLA samples, in contrast with magnitude limited surveys, provide an almost complete census of star-forming galaxies atz≈ 3.
Stellar Populations and Dark Matter in the Milky Way Disk and in Local Group Galaxies
Authors: Grebel Eva K.
Published: March 2009

Our knowledge on the age structure, the chemical evolution, and the kinematics of the Galactic disk has grown substantially during the last years. Recent results on the properties of the stellar populations in the Galactic disk are summarized, and ongoing and future surveys and facilities are discussed. A short overview of recent mass estimates for the Milky Way is presented, and a brief summary of some of the key properties of the Galactic companions is given. The coming decade promises major breakthroughs in understanding our Milky Way, its disk, and the role of its satellites.
Galaxy Interactions, Star Formation History, and Bulgeless Galaxies
Authors: Jogee Shardha
Published: March 2009

Hierarchical ΛCDM models provide a successful paradigm for the growth of dark matter on large scales, but they face important challenges in predicting how the baryonic components of galaxies evolve. I present constraints on two aspects of this evolution: (1) The interaction history of galaxies over the last 7 Gyr and the impact of interactions on their star formation properties, based on Jogeeet al. (2008a, b); (2) Constraints on the origin of bulges in hierarchical models and the challenge posed in accounting for galaxies with low bulge-to-total ratios, based on Weinzirl, Jogee, Khochar, Burkert, & Kormendy (2008, hereafter WJKBK08).
Mergers and Disk Survival in ΛCDM
Authors: Bullock James S. , Stewart Kyle R. , Purcell Chris W.
Published: March 2009

Disk galaxies are common in our universe and this is a source of concern for hierarchical formation models like ΛCDM. Here we investigate this issue as motivated by raw merger statistics derived for galaxy-size dark matter halos from ΛCDM simulations. Our analysis shows that a majority (~ 70%) of galaxy halos with M0 = 1012M⊙ at z = 0 should have accreted at least one object with mass m > 1011M⊙ ≃ 3 Mdisk over the last 10 Gyr. Mergers involving larger objects m ≳ 3 × 1011M⊙ should have been very rare for Milky-Way size halos today, and this pinpoints m/M ~ 0.1 mass-ratio mergers as the most worrying ones for the survival of thin galactic disks. Motivated by these results, we use use high-resolution, dissipationless N-body simulations to study the response of stellar Milky-Way type disks to these common mergers and show that thin disks do not survive the bombardment. The remnant galaxies are roughly three times as thick and twice as kinematically hot as the observed thin disk of the Milky Way. Finally, we evaluate the suggestion that disks may be preserved if the mergers involve gas-rich progenitors. Using empirical measures to assign stellar masses and gas masses to dark matter halos as a function of redshift, we show that the vast majority of large mergers experienced by 1012M⊙ halos should be gas-rich (fgas > 0.5), suggesting that this is a potentially viable solution to the disk formation conundrum. Moreover, gas-rich mergers should become increasingly rare in more massive halos > 1012.5M⊙, and this suggest that merger gas fractions may play an important role in establishing morphological trends with galaxy luminosity.
Abundance Gradient in the Disk of NGC 300
Authors: Vlajić Marija , Bland-Hawthorn Joss , Freeman Ken C.
Published: March 2009

The structure of the outer parts of galactic disks and the nature of their stellar populations are fundamental to our understanding of the formation and evolution of spiral galaxies. Ages and metallicity distributions of stars in the outermost regions of spiral disks provide important clues on how and when the disks are assembled. In our earlier work we trace the extended stellar disk of NGC 300 out to a radius of at least 10 disk scale lengths, with no sign of truncation. We now revisit the outer disk of NGC 300 in order to derive the metallicity distribution of the faint stellar population in its outskirts. We find that predominantly old stellar population in the outer disk exhibits a negative abundance gradient – as predicted by the chemical evolution models – out to about 10 kpc, followed by the metallicity plateau in the outermost disk.
Chemically tagging the Galactic disk: abundance patterns of old open clusters
Authors: De Silva G. M. , Freeman K. C. , Bland-Hawthorn J.
Published: March 2009

The long term goal of large-scale chemical tagging is to use stellar elemental abundances as a tracer of dispersed substructures of the Galactic disk. The identification of such lost stellar aggregates and exploring their chemical properties will be key in understanding the formation and evolution of the disk. Present day stellar structures such as open clusters and moving groups are the ideal testing grounds for the viability of chemical tagging, as they are believed to be the remnants of the original larger star-forming aggregates. We examine recent high resolution abundance studies of open clusters to explore the various abundance trends and reassess the prospects of large-scale chemical tagging.
Bars in Cuspy Dark Halos
Authors: Dubinski John , Berentzen Ingo , Shlosman Isaac
Published: March 2009

We examine the bar instability in models with an exponential disk and a cuspy NFW-like dark matter (DM) halo inspired by cosmological simulations. Bar evolution is studied as a function of numerical resolution in a sequence of models spanning 104 – 108 DM particles - including a multi-mass model with an effective resolution of 1010. The goal is to find convergence in dynamical behaviour. We characterize the bar growth, the buckling instability, pattern speed decay through resonant transfer of angular momentum, and possible destruction of the DM halo cusp. Overall, most characteristics converge in behaviour for halos containing more than 107 particles in detail. Notably, the formation of the bar does not destroy the density cusp in this case. These higher resolution simulations clearly illustrate the importance of discrete resonances in transporting angular momentum from the bar to the halo.
Kinematical & Chemical Characteristics of the Thin and Thick Disks
Authors: Wyse Rosemary F. G.
Published: March 2009

I discuss how the chemical abundance distributions, kinematics and age distributions of stars in the thin and thick disks of the Galaxy can be used to decipher the merger history of the Milky Way, a typical large galaxy. The observational evidence points to a rather quiescent past merging history, unusual in the context of the ‘consensus’ cold-dark-matter cosmology favoured from observations of structure on scales larger than individual galaxies.
The chemical fingerprints of the thin and the thick disk
Authors: Feltzing Sofia , Oey Sally , Bensby Thomas
Published: March 2009

The past history and origin of the different Galactic stellar populations are manifested in their different chemical abundance patterns. We obtained new elemental abundances for 553 F and G dwarf stars, to more accurately quantify these patterns for the thin and thick disks. However, the exact definition of disk membership is not straightforward. Stars that have a high likelihood of belonging to the thin disk show different abundance patterns from those for the thick disk. In contrast, we show that stars for the Hercules Stream do not show unique abundance patterns, but rather follow those of the thin and thick disks. This strongly suggests that the Hercules Stream is a feature induced by internal dynamics within the Galaxy rather than the remnant of an accreted satellite.
Beryllium and the formation of the Thick Disk and of the Halo
Authors: Pasquini Luca , Smiljanic R. , Bonifacio P. , Gratton R. , Galli D. , Randich S.
Published: March 2009

We use Beryllium to investigate star formation in the early Galaxy. Be has been demonstrated to be a good indicator of time in these early epochs. By analyzing the so-far largest sample of halo and thick disk metal poor stars, we find a clear scatter in Be for a given value of [Fe/H] and [O/H]. The scatter is very pronounced for Halo stars, while it is marginal for thick disk stars. Our halo stars separate in the [α/Fe] - Be diagram, showing two main branches: one indistinguishable from the thick disk stars, and one with lower [α/Fe] ratio. The stars belonging to this branch are characterized by highly eccentric orbits and small perigalactic radius (Rmin). Their kinematics are consistent with an accreted component.
The initial luminosity and mass functions of Galactic open clusters
Authors: Zinnecker Hans , Piskunov Anatoly E. , Kharchenko Nina V. , Röser Siegfried , Schilbach Elena , Scholz Ralf-Dieter
Published: March 2009

We have derived a complete magnitude-limited sample of 440 Galactic open clusters in the solar neighborhood, with integrated V-magnitude brighter than 8 mag. This sample can be used to infer the present-day luminosity and mass functions of open clusters up to a given age; it can even be used to construct the initial mass and luminosity function (IMF, ILF) of clusters (defined as visible clusters with age 4 – 8 Myr). The high-mass end of the cluster IMF is a power-law with a slope of −2 or slightly shallower (−1.7) while the luminous cluster ILF has a power-slope of −1, in agreement with what is found for extragalactic clusters. Both distribution functions show a turnover, starting at 300 M⊙ and integrated magnitude −3 mag, respectively. The overall birthrate of clusters is 0.4 clusters per kpc2 and per Myr. The average present-day cluster mass is 700 M⊙, while the average initial cluster mass is 4500 M⊙. The difference of these two average masses indicates the high infant mortality and/or weight loss of Galactic open clusters (due to dynamical evolution).
Star Formation in Disks: Spiral Arms, Turbulence, and Triggering Mechanisms
Authors: Elmegreen Bruce G.
Published: March 2009

Star formation is enhanced in spiral arms because of a combination of orbit crowding, cloud collisions, and gravitational instabilities. The characteristic mass for the instability is 107M⊙in gas and 105M⊙in stars, and the morphology is the familiar beads on a string with 1-2 kpc separation. Similar instabilities occur in resonance rings and tidal tails. Sequential triggering from stellar pressure occurs in two ways. For short times and near distances, it occurs in the bright rims and dense knots that lag behind during cloud dispersal. For long times, it occurs in swept-up shells and along the periphery of cleared regions. The first case should be common but difficult to disentangle from independent star formation in the same cloud. The second case has a causality condition and a collapse condition and is often easy to recognize. Turbulent triggering produces a hierarchy of dense cloudy structure and an associated hierarchy of young star positions. There should also be a correlation between the duration of star formation and the size of the region that is analogous to the size-linewidth relation in the gas. The cosmological context is provided by observations of star formation in high redshift galaxies. Sequential and turbulent triggering is not yet observable, but gravitational instabilities are, and they show a scale up from local instabilities by a factor of ~3 in size and ~100 in mass. This is most easily explained as the result of an increase in the ISM turbulent speed by a factor of ~5. In the clumpiest galaxies at high redshift, the clumps are so large that they should interact with each other and merge in the center, where they form or contribute to the bulge.
Evolution and chemical and dynamical effects of high-mass stars
Authors: Meynet Georges , Chiappini Cristina , Georgy Cyril , Pignatari Marco , Hirschi Raphael , Ekström Sylvia , Maeder André
Published: March 2009

We review general characteristics of massive stars, present the main observable constraints that stellar models should reproduce. We discuss the impact of massive star nucleosynthesis on the early phases of the chemical evolution of the Milky Way (MW). We show that rotating models can account for the important primary nitrogen production needed at low metallicity. Interestingly such rotating models can also better account for other features as the variation with the metallicity of the C/O ratio. Damped Lyman Alpha (DLA) systems present similar characteristics as the halo of the MW for what concern the N/O and C/O ratios. Although in DLAs, the star formation history might be quite different from that of the halo, in these systems also, rotating stars (both massive and intermediate) probably play an important role for explaining these features. The production of primary nitrogen is accompanied by an overproduction of other elements as13C,22Ne and s-process elements. We show also how the observed variation with the metallicity of the number ratio of type Ibc to type II supernovae may be a consequence of the metallicity dependence of the line-driven stellar winds.
Chemical Yields from Supernovae and Hypernovae
Authors: Nomoto Ken'ichi , Wanajo Shinya , Kamiya Yasuomi , Tominaga Nozomu , Umeda Hideyuki
Published: March 2009

We review the final stages of stellar evolution, supernova properties, and chemical yields as a function of the progenitor's mass. (1) 8 - 10M⊙stars are super-AGB stars when the O+Ne+Mg core collapses due to electron capture. These AGB-supernovae may constitute an SN 2008S-like sub-class of Type IIn supernovae. These stars produce little α-elements and Fe-peak elements, but are important sources of Zn and light p-nuclei. (2) 10 - 90M⊙stars undergo Fe-core collapse. Nucleosynthesis in aspherical explosions is important, as it can well reproduce the abundance patterns observed in extremely metal-poor stars. (3) 90 - 140M⊙stars undergo pulsational nuclear instabilities at various nuclear burning stages, including O and Si-burning. (4) Very massive stars withM≳ 140M⊙either become pair-instability SNe, or undergo core-collapse to form intermediate mass black holes if the mass loss is small enough.
Effects of Supernova Feedback on the Formation of Galaxies
Authors: Scannapieco Cecilia , Tissera Patricia B. , White Simon D. M. , Springel Volker
Published: March 2009

We study the effects of Supernova (SN) feedback on the formation of galaxies using hydrodynamical simulations in a ΛCDM cosmology. We use an extended version of the code GADGET-2 which includes chemical enrichment and energy feedback by Type II and Type Ia SN, metal-dependent cooling and a multiphase model for the gas component. We focus on the effects of SN feedback on the star formation process, galaxy morphology, evolution of the specific angular momentum and chemical properties. We find that SN feedback plays a fundamental role in galaxy evolution, producing a self-regulated cycle for star formation, preventing the early consumption of gas and allowing disks to form at late times. The SN feedback model is able to reproduce the expected dependence on virial mass, with less massive systems being more strongly affected.
Chemodynamical simulations of the Milky Way Galaxy
Authors: Kobayashi Chiaki
Published: March 2009

We simulate the chemodynamical evolution of the Milky Way Galaxy, including the nucleosynthesis yields of hypernovae and a new progenitor model for Type Ia Supernovae (SNe Ia). In our nucleosynthesis yields of core-collapse supernovae, we use light curve and spectral fitting to individual supernovae to estimate the mass of the progenitor, the explosion energy, and the iron mass produced. A large contribution of hypernovae is required from the observed abundance of Zn ([Zn/Fe] ~0). In our progenitor model of SNe Ia, based on the single degenerate scenario, the SN Ia lifetime distribution spans a range of 0.1–20 Gyr with peaks at both ~ 0.1 and 1 Gyr. A metallicity effect from white dwarf winds is required from the observed trends of elemental abundance ratios (i.e., [(α,Mn,Zn)/Fe]-[Fe/H] relations). In our simulated Milky Way-type galaxy, the kinematical and chemical properties of the bulge, disk, and halo are broadly consistent with observations. 80% of the thick disk stars are older than ~8 Gyr and tend to have larger [α/Fe] than in the thin disk.
Chemical evolution of the Galaxy disk in connection with large-scale winds
Authors: Tsujimoto Takuji , Bland-Hawthorn Joss , Freeman Kenneth C.
Published: March 2009

Comparison of elemental abundance features between old and young thin disk stars may reveal the action of ravaging winds from the Galactic bulge, which once enriched the whole disk, and set up the steep abundance gradient in the inner disk (RGC ≲ 10–;12 kpc) and simultaneously the metallicity floor ([Fe/H]~ −0.5) in the outer disk. After the end of a crucial influence by winds, chemical enrichment through accretion of a metal-poor material from the halo onto the disk gradually reduced the metallicity of the inner region, whereas an increase in the metallicity proceeded beyond a solar circle. This results in a flattening of abundance gradient in the inner disk, and our chemical evolution models confirm this mechanism for a flattening, which is in good agreement with the observations. Our scenario also naturally explains an observed break in the metallicity floor of the outer disk by young stars since the limit of self-enrichment in the outer disk is supposed to be [Fe/H]≲ −1 and inevitably incurs a direct influence of the dilution by a low-metal infall whose metallicity is [Fe/H]~ −1. Accordingly, we propose that the enrichment by large-scale winds is a crucial factor for chemical evolution of the disk, and claim to reconsider the models thus far for the disk including the solar neighborhood, in which the metallicity is predicted to monotonously increase with time. Furthermore, we anticipate that a flattening of abundance gradient together with a metal-rich floor in the outer disk are the hallmark of disk galaxies with significant central bulges.
Cold Dark Matter Substructure and Galactic Disks
Authors: Kazantzidis Stelios , Zentner Andrew R. , Bullock James S.
Published: March 2009

We perform a set of high-resolution, fully self-consistent dissipationless N-body simulations to investigate the influence of cold dark matter (CDM) substructure on the dynamical evolution of thin galactic disks. Our method combines cosmological simulations of galaxy-sized CDM halos to derive the properties of substructure populations and controlled numerical experiments of consecutive subhalo impacts onto initially-thin, fully-formed disk galaxies. We demonstrate that close encounters between massive subhalos and galactic disks since z ~ 1 should be common occurrences in ΛCDM models. In contrast, extremely few satellites in present-day CDM halos are likely to have a significant impact on the disk structure. One typical host halo merger history is used to seed controlled N-body experiments of subhalo-disk encounters. As a result of these accretion events, the disk thickens considerably at all radii with the disk scale height increasing in excess of a factor of 2 in the solar neighborhood. We show that interactions with the subhalo population produce a wealth of distinctive morphological signatures in the disk stars, many of which resemble those being discovered in the Milky Way (MW), M31, and in other disk galaxies, including: conspicuous flares; bars; low-lived, ring-like features in the outskirts; and low-density, filamentary structures above the disk plane. These findings highlight the significant role of CDM substructure in setting the structure of disk galaxies and driving galaxy evolution.
Hydrodynamical Adaptive Mesh Refinement Simulations of Disk Galaxies
Authors: Gibson Brad K. , Courty Stéphanie , Sánchez-Blázquez Patricia , Teyssier Romain , House Elisa L. , Brook Chris B. , Kawata Daisuke
Published: March 2009

To date, fully cosmological hydrodynamic disk simulations to redshift zero have only been undertaken with particle-based codes, such as GADGET, Gasoline, or GCD+. In light of the (supposed) limitations of traditional implementations of smoothed particle hydrodynamics (SPH), or at the very least, their respective idiosyncrasies, it is important to explore complementary approaches to the SPH paradigm to galaxy formation. We present the first high-resolution cosmological disk simulations to redshift zero using an adaptive mesh refinement (AMR)-based hydrodynamical code, in this case, RAMSES. We analyse the temporal and spatial evolution of the simulated stellar disks' vertical heating, velocity ellipsoids, stellar populations, vertical and radial abundance gradients (gas and stars), assembly/infall histories, warps/lopsideness, disk edges/truncations (gas and stars), ISM physics implementations, and compare and contrast these properties with our sample of cosmological SPH disks, generated with GCD+. These preliminary results are the first in our long-term Galactic Archaeology Simulation program.
Spin-Hall effect in a finite two-dimensional electron gas sample with a central defect
Authors: Chen Son-Hsien , Klik Ivo , Chang Ching-Ray
Published: March 2009

We study spin and charge accumulation in two-dimensional electron gas (2DEG) with spin-orbit Rashba interactions. The Landauer–Keldysh formalism is employed to numerically compute accumulations in a 2DEG finite square sample with and without an embedded spin-independent hard-wall impurity. Cases with two and four attached ideal leads are considered. We find that in the two directions perpendicular to the Rashba field the impurity induces, respectively, a dipole and a quadrupole. In the direction parallel to the Rashba field the spin accumulation is determined purely by the imposed boundary conditions.
Effect of interface spin-flip scattering on the spin polarized transport through a quantum dot: Master equation approach
Authors: Ma M. J. , Jalil M. B. A. , Tan S. G.
Published: March 2009

We investigate the spin-flip scattering effects on the tunnel magnetoresistance (TMR) through the double barrier magnetic tunnel junction, where a two-energy level quantum dot is sandwiched by two ferromagnetic leads. The spin-flip scattering, which occurs at the interface between the lead and the dot, suppresses the TMR in the bias voltage regions corresponding to the singly occupied (SO) and freely occupied (FO) quantum dot state, respectively. In the FO state, the dot can be occupied by up to two electrons or holes. The suppression of the TMR in the SO region is more significant than that in the FO region in the weak spin-flip regime, i.e., when spin-flip probability η<0.5. When η=0.5, the TMR vanishes for both bias regions. Under strong spin-flip condition, i.e., η>0.5, negative TMR is observed in both occupied regions, with the magnitude occurring in the FO region greater. High asymmetry between the spin-flip strengths of spin-up and spin-down electrons can result in an enhancement in the TMR.
Impedance spectroscopy studies on polycrystalline BiFeO3 thin films on Pt/Si substrates
Authors: Srivastava Amar , Garg Ashish , Morrison Finlay D.
Published: March 2009

In this paper, we report on the results of temperature dependent impedance measurements on chemical solution deposited BiFeO3 thin films on Pt/Si substrates. X-ray diffraction analysis showed the presence of predominately single phase BiFeO3. The measurements were made in the frequency range of 100–107 Hz and between 27 and 250 °C. Plots between real and imaginary parts of impedance (Z′ and Z″) and electrical modulus (M′ and M″) in the above frequency and temperature domain suggest the presence of two relaxation regimes which are attributed to bulk and grain boundary responses. Below 150 °C, both conductivity and real dielectric constant show a steplike behavior. The frequency independent regions in 10–100 kHz indicate relaxation of the bulk conduction, while at lower frequency there is a strong frequency dependence associated with the dispersion toward relaxation of the grain boundary. In contrast, at and above 150 °C, frequency independent behavior of dc conduction becomes dominant. The bulk dielectric constant was estimated as ∼225, which is close to the values reported in the literature. Estimated grain and grain boundary conductivity activation energies are 0.28 and 0.81 eV, respectively.
Gold surface with gold nitride–a surface enhanced Raman scattering active substrate
Authors: Brieva A. C. , Alves L. , Krishnamurthy S. , Šiller L.
Published: March 2009

The nitration of gold surfaces is a nonpolluting method, which can lead to large scale production of substrates with remarkable properties and applications. We present a topographical study of the nanoscale structure of the gold nitride surfaces produced by radio frequency (rf) nitrogen plasma etching of thin gold films. Atomic force microscopy images taken after rf etching reveal the striking appearance of the cluster assembly with large clusters surrounded by small clusters (7.9±1.4 and 2.3±0.9 nm, respectively) appearing to exhibit an attractive interaction. We discuss the possible mechanism for this attraction based on a colloid model by Messina et al. [Phys. Rev. Lett. 85, 872 (2000)]. This surface exhibits a notable surface enhanced Raman scattering effect demonstrated with L-alanine and rhodamine-6G. The significance of this work is that we found that this SERS active gold nitride surface can be prepared in just one step: by nitrogen plasma etching a thin gold film. Until now most SERS active gold cluster covered surfaces have been prepared in several steps very often requiring complex lithography.
Fourier-transform microwave spectroscopy of the CCCCl radical
Authors: Yoshikawa Takashi , Sumiyoshi Yoshihiro , Endo Yasuki
Published: March 2009

Pure rotational spectra of the CCCCl radical in a supersonic jet have been observed for the first time by Fourier-transform microwave spectroscopy. The radical was produced by a pulsed electric discharge in a C2H2 and CCl4 mixture diluted to 0.3% and 0.2% with Ne, respectively. Transitions with spin and hyperfine splittings were observed for two isotopologs, CCC35Cl and CCC37Cl, in the region from 11.4 GHz for N=2-1 to 34.2 GHz for N=6-5. The molecular constants including the hyperfine coupling constants due to the Cl nucleus have been determined precisely. From the rotational analyses and high-level ab initio calculations, the molecular structure of the CCCCl radical is concluded to be bent in the ground electronic state.
Experimental demonstration of phase resonances in metallic compound gratings with subwavelength slits in the millimeter wave regime
Authors: Navarro-Cía Miguel , Skigin Diana C. , Beruete Miguel , Sorolla Mario
Published: March 2009

We provide experimental evidence of phase resonances in metallic periodic structures in which each period comprises several subwavelength slits of the same width. We have analyzed and measured the response of these structures in the millimeter wave regime and show that phase resonances are characterized by a remarkable minimum in the transmission response, as predicted by numerical calculations. We compare experimental with numerical results, obtaining a very good agreement between them. This experimental confirmation encourages research in compound structures and their multiple potential applications, such as frequency selective surfaces.
Near-infrared photon upconversion devices based on GaNAsSb active layer lattice matched to GaAs
Authors: Yang Y. , Shen W. Z. , Liu H. C. , Laframboise S. R. , Wicaksono S. , Yoon S. F. , Tan K. H.
Published: March 2009

Room-temperature full GaAs-based near-infrared (NIR) upconversion has been demonstrated by connecting lattice-matched GaNAsSb/GaAs p-i-n photodetectors in series with commercial GaAs/AlGaAs light-emitting diodes (LEDs). Due to the avalanche gain in GaNAsSb/GaAs photodetectors and high internal efficiency in GaAs/AlGaAs LEDs, the upconversion efficiency of the integrated system reaches 0.048 W/W under −7 V bias, much higher than any existing NIR upconverters without amplifying structures. We have further investigated the dependence of the upconversion efficiency on applied bias and incident light intensity. The present work establishes an experimental base for direct epitaxial growth of full GaAs-based NIR upconverters with high upconversion efficiencies.
High velocity shear horizontal surface acoustic wave modes of interdigital transducer/(100) AlN/(111) diamond
Authors: Wu Sean , Ro Ruyen , Lin Zhi-Xun , Lee Maw-Shung
Published: March 2009

In this research, shear horizontal (SH) surface acoustic wave (SAW) modes of interdigital transducer (IDT)/(100) AlN/(111) diamond propagated along the y-axis were theoretically analyzed and they exhibited excellent SH SAW properties. This is special for mode 0 where the K2 curve shows a maximum value (1.27%) at h/λ=0.28 and the velocity is 7496 m/s. The research results provide a predictable and theoretical basis for further application on high velocity SH SAW devices.
Effect of crossing geometry on the plasmonic behavior of dielectric core/metal sheath nanowires
Authors: Prokes S. M. , Alexson D. A. , Glembocki O. J. , Park H. D. , Rendell R. W.
Published: March 2009

We have shown that dielectric/metal composite nanowires exhibit very strong surface enhanced Raman spectroscopy (SERS) signals when arranged in a random three-dimensional geometry. Since the intersections of the nanowires are critical in generating the high electric fields necessary for this enhancement, we are investigating this effect under more controlled conditions. We examined nanowire arrays formed by e-beam lithography and we have examined the plasmonic effects, both longitudinal and transverse, due to changes in crossing geometry by specific placements of dielectric/metal nanowires on these arrays. Results indicate significant angular effects on the SERS enhancement supported by electric field calculations.
Photoluminescence studies of impurity transitions in Mg-doped AlGaN alloys
Authors: Nakarmi M. L. , Nepal N. , Lin J. Y. , Jiang H. X.
Published: March 2009

Deep ultraviolet photoluminescence spectroscopy was employed to study the impurity transitions in Mg-doped AlGaN alloys. A group of deep level impurity transitions was observed in Mg-doped AlxGa1−xN alloys, which was identified to have the same origin as the previously reported blue line at 2.8eV in Mg-doped GaN and was assigned to the recombination of electrons bound to the nitrogen vacancy with three positive charges (VN3+) and neutral Mg acceptors. Based on the measured activation energies of the Mg acceptors in AlGaN and the observed impurity emission peaks, the VN3+ energy levels in AlxGa1−xN have been deduced for the entire alloy range. It is demonstrated that the presence of high density of VN3+ deep donors translates to the reduced p-type conductivity in AlGaN alloys due to their ability for capturing free holes.
Plasma carotenoids, retinol and tocopherol levels and the risk of ovarian cancer
Authors: JEONG NAN‐HEE , SONG EUN‐SEOP , LEE JONG‐MIN , LEE KWANG‐BEOM , KIM MI‐KYUNG , CHEON JI‐EUN , LEE JAE‐KWAN , SON SUNG‐KYONG , LEE JUNG‐PIL , KIM JAE‐HOON , HUR SOO‐YOUNG , KWON YONG‐IL
Published: March 2009

Objective. We investigated the relation between plasma carotenoids, retinol and tocopherol levels and ovarian cancer risk in Korean women. Design. Hospital‐based case–control study. Setting. Six tertiary medical institutes in Korea. Population. Forty‐five epithelial ovarian cancers and 135 age‐matched controls. Methods. Preoperative plasma concentrations of β‐carotene, lycopene, zeaxanthin plus lutein, retinol, α‐tocopherol, and γ‐tocopherol were measured by reverse‐phase, gradient high‐pressure liquid chromatography. Main outcome measures. Odds ratios (OR) and 95% confidence intervals (95%CI) were estimated by tertiles to evaluate the effect of micronutrients on endometrial cancer risk after adjustment for body mass (BMI) index, menopause, parity, oral contraceptive use, smoking status, and alcohol consumption status. Results. Women in the highest tertile for β‐carotene had 0.12‐times the risk of ovarian cancer of in the lowest tertile (OR 0.12; 95%CI 0.04–0.36). Women with the highest tertiles of lycopene (OR 0.09; 95%CI 0.03–0.32), zeaxanthin/lutein (OR 0.21; 95%CI 0.09–0.52), retinol (OR 0.45; 95%CI 0.21–0.98), α‐tocopherol (OR 0.23; 95%CI 0.10–0.53) and γ‐tocopherol (OR 0.28; 95%CI 0.11–0.70) had lower risk of ovarian cancer than women in the lowest tertiles. Results were consistent across strata of socio‐epidemiologic factors. Conclusions. Micronutrients, specifically ß‐carotene, lycopene, zeaxanthin, lutein, retinol, α‐tocopherol, and γ‐tocopherol, may play a role in reducing the risk of ovarian cancer.
Invariant deformations of orbit closures in 𝔰𝔩(𝔫)
Authors: Jansou Sébastien , Ressayre Nicolas
Published: March 2009

We study deformations of orbit closures for the action of a connected semisimple group

G
G

on its Lie algebra

g

\mathfrak {g}

, especially when

G
G

is the special linear group.

The tools we use are the invariant Hilbert scheme and the sheets of

g

\mathfrak {g}

. We show that when

G
G

is the special linear group, the connected components of the invariant Hilbert schemes we get are the geometric quotients of the sheets of

g

\mathfrak {g}

. These quotients were constructed by Katsylo for a general semisimple Lie algebra

g

\mathfrak {g}

; in our case, they happen to be affine spaces.
Oncogenic Adenomatous Polyposis Coli Mutants Impair the Mitotic Checkpoint through Direct Interaction with Mad2
Authors: Zhang Jiayin , Neisa Roberto , Mao Yinghui
Published: March 2009

The majority of colorectal tumors are aneuploid because of the underlying chromosome instability (CIN) phenotype, in which a defective mitotic checkpoint is implicated. Adenomatous polyposis coli (APC), a tumor suppressor gene that is commonly mutated in colon cancers, has been suggested in causing CIN; however, the molecular mechanism remains unresolved. In this study, we report an interaction of tumor-associated N-terminal APC fragments (N-APC) with Mad2, an essential mitotic checkpoint protein, providing a direct molecular support for linking APC mutations to the generation of CIN. N-APC interacts with Mad2 in Xenopus egg extracts, colon cancer cells, and in vitro with purified components. The interaction between N-APC and Mad2 decreases the soluble pool of Mad2, which is essential for Mad2 cycling and releasing from unattached kinetochores to produce a diffusible |P`wait anaphase|P' signal. Addition of such an N-APC mutant of egg extracts inactivates the mitotic checkpoint. Expressing a tumor-associated N-APC mutant in mammalian cells with an intact mitotic checkpoint produces premature anaphase onset with missegregated chromosomes.
Evaluation of Postnatal Weight Growth in Very Low Birth Weight Infants
Authors: Bertino Enrico , Milani Silvano , Boni Luisa , Coscia Alessandra , Rossetti Gessica , Testa Tiziana , Giuliani Francesca , Appino Irene , Spada Elena , Fabris Claudio
Published: March 2009

There is general agreement about the need for longitudinal studies of very low birth weight infants (VLBWI) to evaluate their postnatal growth and to generate distance and velocity charts that allow neonatologists and pediatricians to detect earlier whether a child is not growing adequately. There are no satisfactory growth charts for VLBWI. We analyzed the weight growth of 262 VLBWIs from birth to 2 years of corrected age. Individual growth profiles were fitted with a 7‐constant exponential‐logistic function suitable for modelling weight growth pattern. After a postnatal weight loss, all VLBWIs showed a late neonatal peak of velocity between the seventh and 21st weeks; the large majority of them also experienced an early neonatal peak between the second and the sixth weeks. Small‐for‐gestational‐age VLBWIs with major morbidities grew less than reference appropriate‐for‐gestational‐age VLBWIs without major morbidities: at 2 years, the difference in weight was about 860 g. The more severe growth impairment in VLBWIs with major morbidities was almost entirely due to the reduced height of the late neonatal peak of velocity. The mathematical function used in this study is expected to be a useful tool to trace model‐based longitudinal distance and velocity charts specific for VLBWIs. Moreover, this function also could be used to evaluate to what extent different pathological conditions or nutritional and medical care protocols affect growth kinetics.
Probiotics in Preterm Infants: A Controversial Issue
Authors: Isolauri Erika
Published: March 2009

Current research is directed toward innovative dietary compositions that exert specific effects on health promotion and reducing the risk of diseases. For example, the demonstration that the gut microbiota is an important constituent in the intestine's mucosal barrier has led to new therapeutic strategies for infections as well as allergic and inflammatory conditions. Specific probiotic bacteria have been shown to stabilize the gut microbial environment and the intestine's permeability barrier, and to enhance systemic and mucosal IgA responses. These comprise important targets in the preterm infant, who is particularly susceptible to infection and inflammation and in whom the immature enterocyte responds to intraluminal antigens with proinflammatory cytokines. Recent data point to differences in immunomodulatory effects between candidate probiotic bacteria. Each probiotic strain is a unique component itself, and each strain has specific properties that cannot be extrapolated from other, even closely related, strains. Therefore, these properties of probiotic bacteria should be characterized during preclinical and clinical evaluations. Furthermore, because probiotics are a tool with which to modify the gut barrier and microbiota, the strains used must be obtained from acceptable sources with a proven safety record and efficacy to guarantee their future clinical applications. The approach of supplementation with single components, however, overlooks the role of dietary composition, with its range of nutrients and other potentially active components, and also the conceivable combined effects. Consequently, research now focuses both on characterizing specific probiotic strains and on how the food matrix and the dietary content interact with the most efficient probiotic strains.
Nutrition of Preterm Infants After Hospital Discharge
Authors: Griffin Ian J , Cooke Richard J
Published: March 2009

Growth failure in preterm infants remains extremely common despite advances in neonatal care. Many, or even a majority, leave the hospital with weights below the 10th centile for age. Because of this, the possibility of nutritional interventions to improve postdischarge growth has been considered. A variety of interventions have been tested in randomized controlled trials in formula‐fed infants. Although the studies vary in design and in the intervention used, on balance the evidence supports the use of fortified formulas in formula‐fed preterm infants after hospital discharge. Specially designed postdischarge formulas and preterm infant formulas seem equally efficacious. The situation for infants fed human milk is much less clear. Although the postdischarge growth in human milk–fed infants is not as good as in formula‐fed infants, no interventions have been examined in human milk–fed infants in a randomized study, to our knowledge. We are unaware of any evidence that any of the commonly proposed nutritional interventions in human milk–fed infants after hospital discharge are either safe or efficacious. In the absence of such evidence, it seems prudent to avoid untested interventions in this population and to concentrate our efforts on the encouragement of breast‐feeding after hospital discharge.
Complementary Feeding Practices in Preterm Infants: An Observational Study in a Cohort of Italian Infants
Authors: Fanaro Silvia , Borsari Gloria , Vigi Vittorio
Published: March 2009

Background:

There are no evidence‐based guidelines for weaning preterm infants, and the timing of weaning and the diet offered tend to reflect tradition and marketing rather than medical advice.

Procedures:

In a survey of complementary feeding practices in preterm infants conducted at the University Hospital of Ferrara, Italy, we evaluated the effect of sex, gestational age (GA), birth weight (BW), and milk feeding, and of the mother's age, education, and professional status, on weaning.

Results:

Complete data were available for 156 infants. Solid food was introduced, on average, 22.2 weeks after birth and 15.1 weeks after term; 6.5% of infants (considering chronological age) and 60.9% (considering corrected age) were weaned before 4 months; 18% of infants weighed <5 kg at weaning (most had low GA and BW). Among maternal factors, only age significantly influenced the weaning schedule. Milk feeding did not affect initiation of weaning; however, formula‐fed infants, most of whom had lower GA and BW, were lighter and younger (from term) than were their counterparts. The first solid food was mashed fruit in 46.8% of cases. Meat and gluten were offered 5 and 7 weeks (average) after the initiation of weaning.

Conclusions:

A matter of concern emerging from our study is that in almost 50% of cases, the first solid food offered to infants is low in energy density, and its protein, iron, and zinc content is negligible. It is evident that despite the lack of a general consensus, mothers of preterm babies should receive customized instructions from family pediatricians and health caregivers about weaning.