bluuebunny/crossref_metadata_2025 huggingface dataset:
AGRONOMIC AND FINANCIAL BENEFITS OF PHOSPHORUS AND NITROGEN SOURCES IN WESTERN KENYA
Authors: JAMA BASHIR , KIWIA ABEDNEGO
Published: March 2009

A better understanding of the agronomic and economic benefits of integrating organic and inorganic fertilizers is essential for their wide-scale dissemination and adoption in smallholder farming systems in developing countries. Field studies were conducted for 10 cropping seasons (1996–2000) on a Kandiudalfic Eutrudox soil to compare the effects of Minjingu phosphate rock (MPR) and triple superphosphate (TSP) on the yield of maize (Zea mays), in combination with three nitrogen (N) sources: urea, Tithonia diversifolia and Sesbania sesban leafy biomass. Urea and tithonia were applied to provide 60 kg N ha−1. Phosphorus (P) from either MPR or TSP was added either once at 250 kg P ha−1 at the beginning of the experiment or annually at 50 kg P ha−1 for five years, the two rates representing two P recapitalization strategies. From the second year, potassium (K) was added to half of each plot to correct for the deficiency that emerged. Over the 10 cropping seasons, the agronomic and economic benefits of the two P recapitalization strategies were similar and were not influenced by the P sources used. With N and K application, both P sources resulted in at least a two-fold maize grain yield increase over the control with no P application that averaged 1.1 tons ha−1. Comparing the N sources, although urea and tithonia had similar net benefits when P was applied, the total cost associated with tithonia was considerably higher. Without P application, sesbania fallow was the most financially attractive option. Sesbania fallows as an N source were also least sensitive to increases in the price of fertilizers and the cost of labour although the financial benefits of this system remained low in the absence of P and K application.
Couples' provision of informal care for parents and parents-in-law: far from sharing equally?
Authors: HENZ URSULA
Published: March 2009

This study examines whether and how couples share the provision of informal care for their parents. Four waves of the British General Household Survey contain cross-sectional information about caring for parents and parents-in-law. Descriptive and multivariate analyses were conducted on 2214 couples that provided parent care. The findings emphasise married men's contribution to informal caring for the parental generation and at the same time demonstrate the limits of their involvement. Spouses share many parts of their care-giving but this arrangement is less common with respect to personal and physical care. The more care is required the more likely are people to participate in care for their parents-in-law. More sons-in-law than daughters-in-law provide care but, once involved, daughters-in-law provide on average more hours of care than sons-in-law. Own full-time employment reduces both men's and women's caring for their parents-in-law, and men's caring drops further if their wife is not in the labour market. The findings suggest that daughters-in-law often take direct responsibility whereas sons-in-laws' care-giving depends more on their wives' involvement. Children-in-laws' informal care-giving might decrease in the future because of women's increasing involvement in the labour market and rising levels of non-marital cohabitation in mid-life.
Psychosocial wellbeing and reasons for retirement in Sweden
Authors: NORDENMARK MIKAEL , STATTIN MIKAEL
Published: March 2009

Given the increased heterogeneity of the transition from work to retirement, this study aimed to analyse the associations between different reasons for retirement and psychosocial wellbeing as a pensioner. The study used data from the SwedishPanel Survey of Ageing and the Elderly(PSAE), a nationally representative survey of the living conditions of older people in Sweden. The results show that almost one-half of all pensioners cited health problems as a contributory reason for ceasing work. Furthermore, those who retired for ‘push’ reasons, such as health problems or labour market factors, experienced lower psychosocial wellbeing than those who retired for other reasons. Moreover, the results show that those who were able to influence the time of their retirement enjoyed better psychosocial wellbeing than those who had little or no opportunity to do so. This was true when controlling for other factors relevant to the wellbeing of pensioners. The results lend support to the argument that, if a man's retirement is instigated because his skills are no longer required, there will be a decidedly negative effect on his wellbeing – and that this effect is stronger than the equivalent impact on a woman's wellbeing. In relation to previous findings in this field, the results make it clear that retirement is far from a uniform process or state.
THE AMBIVALENCE OF MODERNISM FROM THE WEIMAR REPUBLIC TO NATIONAL SOCIALISM AND RED VIENNA
Authors: MATTL SIEGFRIED
Published: March 2009

Focusing on the spectacular propaganda exhibitions “Degenerate Art” and “Degenerate Music,” critical studies of Nazism's art policy long considered the regime's public attack on modernism and the turn to pseudo-classicism as decisive proof of Nazism's reactionary character. Studies such asDie Kunst im Dritten Reich(1974), which inspired broader research on the topic in the early 1970s, subscribed to a modern conception of aesthetics in which art expresses complex systems of ideas in progress. Artistic style, from this perspective, corresponded to political tendencies and reflected the traditional divide between conservatism and progressivism. But those boundaries have become blurred in the wake of more recent research, which has demonstrated the involvement of modernist artists in Nazi art (e.g. members of the Bauhaus involved in National Socialist architecture or avant-garde filmmakers such as Walter Ruttmann in National Socialist propaganda films) and, conversely, the continual performance of popular jazz music in the Third Reich (e.g. in radio programmes). Seen against such instances of modernist collaboration and its own occasional mimicry of modernism, National Socialism acquires a more ambivalent profile, characterized by the ongoing conflict between reactionary factions and those who favoured modernization for various reasons.
Spatially resolved dynamics of high-z star forming galaxies
Authors: Genzel Reinhard
Published: March 2009

I report on two major programs to study the kinematic properties of galaxies at z ~ 1.5 − 3 with spatially resolved spectroscopy for the first time. Using the adaptive optics assisted, integral field spectrometer SINFONI on the ESO VLT, we have observed more than 70 galaxies and find compelling evidence for large, geometrically thick (turbulent), rotating disk galaxies in a majority of the objects that we can spatially resolve. It appears that these star forming disks are driven by continuous, rapid accretion of gas from their dark matter halos, and that their evolution is strongly influenced by internal, secular evolution. In contrast to the 20 submillimeter galaxies that we have investigated with the IRAM Plateau de Bure millimetre interferometer we find strong evidence for compact, major mergers. I discuss the impact of these new observations on our understanding of galaxy evolution in the early Universe.

For the SINS survey we have carried out Hα integral field spectroscopy of well-resolved, UV/optically selected star-forming galaxies at z ~ 2 with SINFONI on the ESO VLT. The SINS sample is representative of the majority of massive (M* > a few 1010M⊙) star-forming galaxies at that redshift. Our data obtained with laser guide star assisted adaptive optics in good seeing show the presence of turbulent, rotating star-forming rings/disks in at least a third of the sample, plus central bulge/inner disk components in some of the best cases, whose mass fractions relative to total dynamical mass appears to scale with [NII]/Hα flux ratio and ‘star formation’ age. Another third of the SINS galaxies show clear signs of kinematic perturbations by a merger, while the last third appear to be compact, ‘dispersion’ limited systems.

Our interpretation of these data is that the buildup of the central disks and bulges of massive galaxies at z ~ 2 can be driven by the early secular evolution of gas-rich ‘proto’-disks. High-redshift disks exhibit large random motions. This turbulence may in part be stirred up by the release of gravitational energy in the rapid ‘cold’ accretion flows along the filaments of the cosmic web. As a result, dynamical friction and viscous processes proceed on a time scale of < 1 Gyr, at least an order of magnitude faster than in disk galaxies at z ~ 0. Early secular evolution thus drives gas and stars into the central regions and can build up exponential disks and massive bulges, even without major mergers. Secular evolution along with increased efficiency of star formation at high surface densities may also help to account for the short time scales of the stellar buildup observed in massive galaxies at z ~ 2.
Simulating High-Redshift Disk Galaxies: Applications to Long Duration Gamma-Ray Burst Hosts
Authors: Robertson Brant E.
Published: March 2009

The efficiency of star formation governs many observable properties of the cosmological galaxy population, yet many current models of galaxy formation largely ignore the important physics of star formation and the interstellar medium (ISM). Using hydrodynamical simulations of disk galaxies that include a treatment of the molecular ISM and star formation in molecular clouds (Robertson & Kravtsov 2008), we study the influence of star formation efficiency and molecular hydrogen abundance on the properties of high-redshift galaxy populations. In this work, we focus on a model of low-mass, star forming galaxies at 1 ≲ z ≲ 2 that may host long duration gamma-ray bursts (GRBs). Observations of GRB hosts have revealed a population of faint systems with star formation properties that often differ from Lyman-break galaxies (LBGs) and more luminous high-redshift field galaxies. Observed GRB sightlines are deficient in molecular hydrogen, but it is unclear to what degree this deficiency owes to intrinsic properties of the galaxy or the impact the GRB has on its environment. We find that hydrodynamical simulations of low-stellar mass systems at high-redshifts can reproduce the observed star formation rates and efficiencies of GRB host galaxies at redshifts 1 ≲ z ≲ 2. We show that the compact structure of low-mass high-redshift GRB hosts may lead to a molecular ISM fraction of a few tenths, well above that observed in individual GRB sightlines. However, the star formation rates of observed GRB host galaxies imply molecular gas masses of 108 – 109M⊙ similar to those produced in the simulations, and may therefore imply fairly large average H2 fractions in their ISM.
The mass content of the Sculptor dwarf spheroidal galaxy
Authors: Battaglia G. , Helmi A. , Tolstoy E. , Irwin M.
Published: March 2009

We present a new determination of the mass content of the Sculptor dwarf spheroidal galaxy, based on a novel approach which takes into account the two distinct stellar populations present in this galaxy. This method helps to partially break the well-known mass-anisotropy degeneracy present in the modelling of pressure-supported stellar systems.
An 84-μG Magnetic Field in a Galaxy at Z=0.692?
Authors: Wolfe Arthur M. , Jorgenson Regina A. , Robishaw Timothy , Heiles Carl , Prochaska Jason X.
Published: March 2009

The magnetic field pervading our Galaxy is a crucial constituent of the interstellar medium: it mediates the dynamics of interstellar clouds, the energy density of cosmic rays, and the formation of stars (Beck 2005). The field associated with ionized interstellar gas has been determined through observations of pulsars in our Galaxy. Radio-frequency measurements of pulse dispersion and the rotation of the plane of linear polarization, i.e., Faraday rotation, yield an average value B ≈ 3 μG (Han et al. 2006). The possible detection of Faraday rotation of linearly polarized photons emitted by high-redshift quasars (Kronberg et al. 2008) suggests similar magnetic fields are present in foreground galaxies with redshifts z > 1. As Faraday rotation alone, however, determines neither the magnitude nor the redshift of the magnetic field, the strength of galactic magnetic fields at redshifts z > 0 remains uncertain.

Here we report a measurement of a magnetic field of B ≈ 84 μG in a galaxy at z =0.692, using the same Zeeman-splitting technique that revealed an average value of B = 6 μG in the neutral interstellar gas of our Galaxy (Heiles et al. 2004). This is unexpected, as the leading theory of magnetic field generation, the mean-field dynamo model, predicts large-scale magnetic fields to be weaker in the past, rather than stronger (Parker 1970).

The full text of this paper was published in Nature (Wolfe et al. 2008).
The Galactic Disk-Halo Transition – Evidence from Stellar Abundances
Authors: Nissen Poul Erik , Schuster William J.
Published: March 2009

New information on the relations between the Galactic disks, the halo, and satellite galaxies is being obtained from elemental abundances of stars having metallicities in the range −1.5 < [Fe/H] < −0.5. The first results for a sample of 26 halo stars and 13 thick-disk stars observed with the ESO VLT/UVES spectrograph are presented. The halo stars fall in two distinct groups: one group (9 stars) has [α/Fe] = 0.30 ± 0.03 like the thick-disk stars. The other group (17 stars) shows a clearly deviating trend ranging from [α/Fe] = 0.20 at [Fe/H] = −1.3 to [α/Fe] = 0.08 at [Fe/H] = −0.8. The kinematics of the stars are discussed and the abundance ratios Na/Fe, Ni/Fe, Cu/Fe and Ba/Y are applied to see if the “low-alpha” stars are connected to the thin disk or to Milky Way satellite galaxies. Furthermore, we compare our data with simulations of chemical abundance distributions in hierarchically formed stellar halos in a ΛCDM Universe.
Abundance Gradients and Substructures in Disks
Authors: Freeman K. C.
Published: March 2009

I will first discuss abundance gradients in the Milky Way and nearby disk galaxies, then the problem of substructures in the Galactic Disk, and finally some new opportunities for investigating substructure in disks.
Mapping low-latitude stellar substructure with SEGUE photometry
Authors: de Jong Jelte T. A. , Yanny Brian , Rix Hans-Walter , Bell Eric F. , Dolphin Andrew E.
Published: March 2009

Encircling the Milky Way at low latitudes, the Low Latitude Stream is a large stellar structure, the origin of which is as yet unknown. As part of the SEGUE survey, several photometric scans have been obtained that cross the Galactic plane, spread over a longitude range of 50° to 203°. These data allow a systematic study of the structure of the Galaxy at low latitudes, where the Low Latitude Stream resides. We apply colour-magnitude diagram fitting techniques to map the stellar (sub)structure in these regions, enabling the detection of overdensities with respect to smooth models. These detections can be used to distinguish between different models of the Low Latitude Stream, and help to shed light on the nature of the system.
The Bulge-disc connection in the Milky Way
Authors: Binney James
Published: March 2009

Bulges come in two flavours – classical and pseudo. The principal characteristics of each flavour are summarised and their impact on discs is considered. Classical bulges probably inhibit the formation of stellar discs. Pseudobulges exchange angular momentum with stars and gas in their companion discs, and also with its embedding dark halo. Since the structure of a pseudobulge depends critically on its angular momentum, these exchanges are expected to modify the bulge. The consequences of this modification are not yet satisfactorily understood. The Galaxy has a pseudobulge. I review the manifestations of its interaction with the disc. More work is needed on the dynamics of gas near the bulge's corotation radius, and on tracing the stellar population in the inner few hundred parsecs of the Galaxy.
Stellar abundances tracing the formation of the Galactic Bulge
Authors: Barbuy Beatriz , Zoccali Manuela , Ortolani Sergio , Hill Vanessa , Renzini Alvio , Meléndez Jorge , Gómez Anita , Asplund Martin , Minniti Dante , Bica Eduardo , Alves-Brito Alan
Published: March 2009

The metallicity distribution and abundance ratios of the Galactic bulge are reviewed. Issues raised by different groups in recent work, in particular the high metallicity end, a comparison between the oxygen abundances derived from different indicators, the [OI] 630nm and IR OH lines, and the issue of measuring giants vs. dwarfs, are discussed. Finally, abundances in bulge globular clusters are briefly described.
The influence of star clusters on galactic disks: new insights in star-formation in galaxies
Authors: Kroupa Pavel
Published: March 2009

Stars form in embedded star clusters which play a key role in determining the properties of a galaxy's stellar population. A large fraction of newly born massive stars are shot out from dynamically unstable embedded-cluster cores spreading them to large distances before they explode. Embedded clusters blow out their gas once the feedback energy from the new stellar population overcomes its binding energy, leading to cluster expansion and in many cases dissolution into the galaxy. Galactic disks may be thickened by such processes, and some thick disks may be the result of an early epoch of vigorous star-formation. Binary stellar systems are disrupted in clusters leading to a lower fraction of binaries in the field, while long-lived clusters harden degenerate-stellar binaries such that the SNIa rate may increase by orders of magnitude in those galaxies that were able to form long-lived clusters. The stellar initial mass function of the whole galaxy must be computed by adding the IMFs in the individual clusters. The resulting integrated galactic initial mass function (IGIMF) is top-light for SFRs < 10M⊙/yr, and its slope and, more importantly, its upper stellar mass limit depend on the star-formation rate (SFR), explaining naturally the mass–metallicity relation of galaxies. Based on the IGIMF theory, the re-calibrated Hα-luminosity–SFR relation implies dwarf irregular galaxies to have the same gas-depletion time-scale as major disk galaxies, implying a major change of our concept of dwarf-galaxy evolution. A galaxy transforms about 0.3 per cent of its neutral gas mass every 10 Myr into stars. The IGIMF-theory also naturally leads to the observed radial Hα cutoff in disk galaxies without a radial star-formation cutoff. It emerges that the thorough understanding of the physics and distribution of star clusters may be leading to a major paradigm shift in our understanding of galaxy evolution.
Measuring Outer Disk Warps with Optical Spectroscopy
Authors: Christlein Daniel , Bland-Hawthorn Joss
Published: March 2009

Warps in the outer gaseous disks of galaxies are a ubiquitous phenomenon, but it is still unclear what generates them. One theory is that warps are generated internally through spontaneous bending instabilities. Other theories suggest that they result from the interaction of the outer disk with accreting extragalactic material. In this case, we expect to find cases where the circular velocity of the warp gas is poorly correlated with the rotational velocity of the galaxy disk at the same radius. Optical spectroscopy presents itself as an interesting alternative to 21-cm observations for testing this prediction, because (i) separating the kinematics of the warp from those of the disk requires a spatial resolution that is higher than what is achieved at 21 cm at low HI column density; (ii) optical spectroscopy also provides important information on star formation rates, gas excitation, and chemical abundances, which provide clues to the origin of the gas in warps. We present here preliminary results of a study of the kinematics of gas in the outer-disk warps of seven edge-on galaxies, using multi-hour VLT/FORS2 spectroscopy.
HI in Galactic Disks
Authors: Brinks Elias , Bigiel Frank , Leroy Adam , Walter Fabian , de Blok W. J. G. , Bagetakos Ioannis , Usero Antonio , Kennicutt Robert C.
Published: March 2009

Studies of the atomic phase of the interstellar medium, via the 21–cm spectral line of neutral hydrogen (H I), play a key rôle in our attempts to understand the structure and evolution of disk galaxies. We present here results from The H I Nearby Galaxy Survey (THINGS) and focus on the mass distribution as derived from the observed kinematics, and on the link between gas and star formation rate surface density, i.e., the Schmidt–Kennicutt law. Also, we briefly dwell on the wealth and wide variety of structures, often outlining what seem to be expanding shells surrounding sites of recent, massive star formation.
Disk Stability and Turbulence Generation: Effects of the Stellar Component
Authors: Kim Woong-Tae
Published: March 2009

Galactic disks consist of both stars and gas. The stars gravitationally influence the gas either in disks at large or within spiral arms, leading to the formation of giant clouds and turbulence driving in the gas. In featureless disks as in flocculent galaxies, swing amplification operating in a combined star-gas disk is efficient to form bound condensations and feed a significant level of random gas motions. This occurs when the gaseous Toomre parameter is less than 1.4 for the stellar parameters similar to the solar neighbourhood conditions. In disks with spiral features, on the other hand, spiral-arm spurs and associated giant clouds develop as a consequence of magneto-Jeans instability in which magnetic tension counterbalances the stabilizing Coriolis force. Spiral shocks are inherently unstable when the vertical dimension is taken into account, exhibiting flapping motions of the shock front. This naturally converts the kinetic energy in galaxy rotation into random kinetic energy of the gas. The resulting turbulent motions are supersonic and persist despite strong shock dissipation. Thermal instability occurring in gas flows across spiral arms prompts phases transitions that produce a significant fraction of thermally-unstable, intermediate-temperature gas in the postshock expansion zones.
Halo chemistry and first stars. The chemical composition of the matter in the early Galaxy, from C to Mg
Authors: Spite M. , Bonifacio P. , Cayrel R. , Spite F. , Francois P. , Ludwig H. G. , Caffau E. , Andrievsky S. , Barbuy B. , Plez B. , Molaro P. , Andersen J. , Beers T. , Depagne E. , Nordström B. , Primas F.
Published: March 2009

From NLTE computations of the magnesium abundance in a sample of extremely metal-poor giants we derive [Mg/Fe]=+0.7, leading to [Al/Mg]=−0.80 and [Na/Mg]=−0.85 in the early Galaxy. The ratio [O/Mg] should be near to the solar value. Measurements of nitrogen abundances derived from the analysis of the NH band in eight more stars confirm the large scatter of the ratios [N/Fe] and [N/O] in the early Galaxy.
Numerical simulations of galaxy evolution in cosmological context
Authors: Martig Marie , Bournaud Frédéric , Teyssier Romain
Published: March 2009

Large volume cosmological simulations succeed in reproducing the large-scale structure of the Universe. However, they lack resolution and may not take into account all relevant physical processes to test if the detail properties of galaxies can be explained by the CDM paradigm. On the other hand, galaxy-scale simulations could resolve this in a robust way but do not usually include a realistic cosmological context.

To study galaxy evolution in cosmological context, we use a new method that consists in coupling cosmological simulations and galactic scale simulations. For this, we record merger and gas accretion histories from cosmological simulations and re-simulate at very high resolution the evolution of baryons and dark matter within the virial radius of a target galaxy. This allows us for example to better take into account gas evolution and associated star formation, to finely study the internal evolution of galaxies and their disks in a realistic cosmological context.

We aim at obtaining a statistical view on galaxy evolution from z ≃ 2 to 0, and we present here the first results of the study: we mainly stress the importance of taking into account gas accretion along filaments to understand galaxy evolution.
A Roadmap for Delivering the Promise of Gaia
Authors: Prusti T. , Aerts C. , Grebel E. K. , Jordi C. , Klioner S. A. , Lindegren L. , Mignard F. , Randich S. , Walton N. A.
Published: March 2009

Gaia development is in full speed aiming to the launch in December 2011. While the entities formally responsible to make Gaia happen are very focused to be ready in time, it is necessary to explore the readiness of the wider scientific community to exploit Gaia data in the future. The GST sees a role for itself in building and enabling the community to use the Gaia catalogues when they become available. This paper gives the background for the current activities the GST is taking to promote the community to start preparations for the exploitation of Gaia data.
Measurement of Mass
Authors: Lawn Richard , Prichard Elizabeth
Published: March 2009

This guide explains the best methods for undertaking the measurement of mass, one of the most frequent operations in the analytical laboratory. It is a technique required when obtaining a known quantity of a sample for analysis; for preparation of analytical reagents; and for preparation of calibration standards etc. After an initial discussion of the units of mass and other terminology, the guide goes on to look at the types of balance and their features, followed by coverage of location, calibration, accuracy and use of the balance. Practical exercises are then provided. Measurement of Mass is one of the Practical Laboratory Skills Training Guides, a series that aims to make achieving best practice easy. These invaluable manuals will enable both experienced and inexperienced staff to get the essential basics of any experiment right simply by following the clear and easy to use instructions provided. The guides are written by experienced scientists and include minimal theory, plenty of practical exercises in order to assess competence, and trouble shooting information. The other titles are: Measurement of Volume; Measurement of pH; High Performance Liquid Chromatography; and Gas Chromatography.
Measurement of Volume
Authors: Lawn Richard , Prichard Elizabeth
Published: March 2009

This guide explains the best methods for undertaking the measurement of volume, one of the most frequent operations in the laboratory. It is required when obtaining a known quantity of a sample for analysis; for preparation of analytical reagents; and for preparation of calibration standards and quantitative analysis by titrimetry. After an initial section covering the units of volume and other terminology, the various types of volume measuring apparatus are then described. Later sections cover the importance of temperature, calibration, accuracy and use of the different types of apparatus, and the uncertainty of volume measurements. A series of practical exercises are also provided. Measurement of Volume is one of the Practical Laboratory Skills Training Guides, a series that aims to make achieving best practice easy. These invaluable manuals will enable both experienced and inexperienced staff to get the essential basics of any experiment right simply by following the clear and easy to use instructions provided. The guides are written by experienced scientists and include minimal theory, plenty of practical exercises in order to assess competence, and trouble shooting information. Other titles are: Measurement of Mass; Measurement of pH; High Performance Liquid Chromatography; and Gas Chromatography.
Optical and microstructural study of a single layer of InGaN quantum dots
Authors: Bai J. , Wang Q. , Wang T. , Cullis A. G. , Parbrook P. J.
Published: March 2009

Two typical kinds of InGaN quantum dots (QDs) have been grown on sapphires under different conditions through modifying the NH3 flow rate using metal-organic chemical vapor deposition: small spherical dots with a high dot density and large truncated pyramidal dots with a low dot density. The small dots have been found typically coherent and defect-free, while a strain relaxation has often been observed in the large dots. Consequently, this leads to a massive difference in optical properties between them. The optical properties have been investigated by means of temperature-dependent and excitation power-dependent microphotoluminescence measurements. It has been found that the small spherical QDs show higher optical quantum efficiency and much weaker piezoelectric field induced quantum-confined Stark effect than the large truncated QDs. Based on the energy balance between the strain and surface energy, the influence of V/III ratio on the transition from two-dimensional to three-dimensional growth mode during the QD growth has been discussed.
Gain characteristics of the InGaAs strained quantum wells with GaAs, AlGaAs, and GaAsP barriers in vertical-external-cavity surface-emitting lasers
Authors: Zhang Peng , Song Yanrong , Tian Jinrong , Zhang Xinping , Zhang Zhigang
Published: March 2009

InGaAs strained quantum wells (QWs) with GaAs, AlGaAs, and GaAsP barriers are widely used in optically pumped vertical-external-cavity surface-emitting lasers operating at 1 μm wavelength band. Compared with the reported data, the model-solid theory, which is more suitable for the studied materials, is selected to calculate the band offset. The band structures and the gain characteristics of the three different QWs are computed and compared, and the theoretical results are in good agreement with the recent experimental reports. The numerical simulation shows that the QW with the GaAs barrier has the highest absorption but the lowest peak gain, while for the AlGaAs barrier, it has the lowest absorption but the highest peak gain, and for the GaAsP barrier, it has a moderate absorption and peak gain. GaAsP is the most appropriate candidate for the barrier of InGaAs strained QW when the low-threshold, large-gain, and high-temperature characteristics are demanded simultaneously.
Polarization-independent intersubband based GaInAsN quantum-well photodetector with dominant detection at 1.42 μm
Authors: Albo Asaf , Vardi Alon , Fekete Dan , Bahir Gad
Published: March 2009

We report on a room temperature polarization-independent intersubband photocurrent (PC) in quantum-well infrared photodetector based on a GaInAsN/GaAs standard multiple-quantum-well structure. The dominant room temperature PC is peaked at 1.42 μm with peak responsivity of 2 A/W and exhibits similar intensities in TM and TE polarizations. The structure’s energy levels were analyzed using a ten band k⋅p model. As a result of this analysis the 1.42 μm dominant PC transition is attributed to a transition from the fundamental E1− electron level into the localized quasicontinuum state formed by the unconfined E2+ electron energy level.
Thermomigration in Pb-free SnAg solder joint under alternating current stressing
Authors: Hsiao Hsiang-Yao , Chen Chih
Published: March 2009

Lead-free solders have been adopted by the microelectronics industry. However, their thermomigration behaviors are unclear. Thermomigration in eutectic SnAg3.5 solder joints was investigated using an alternating current (ac) of 0.57 A at 100 °C. The ac eliminates the electromigration effect and creates a thermal gradient of 2829 °C/cm, facilitating the study of thermomigration. Arrays of tiny markers fabricated by a focused ion beam are employed to measure the thermomigration rate. It is found that Sn atoms migrated toward the hot end. The thermomigration flux and molar heat of transport are measured to be 5.0×1012 atoms/cm2 and 1.36 kJ/mole, respectively.
Nematicons in chiral nematic liquid crystals
Authors: Laudyn Urszula A. , Kwasny Michal , Karpierz Miroslaw A.
Published: March 2009

We report on the experimental studies of the existence of spatial solitons called nematicons in chiral nematic liquid crystal cells. The low absorption allows us to observe soliton propagation at a distance of over a few millimeters in range. The results of our experiment also show that it is possible to create independent nematicons in different layers formed by a helical structure of the liquid crystals.
A lighting mechanism for flat electron emission lamp
Authors: Li Jung-Yu , Chen Shih-Pu , Li Chia-Hung , Lin Yi-Ping , Chou Yen-I , Liu Ming-Chung , Wang Po-Hung , Zeng Hui-Kai , Hsieh Tai-Chiung , Juang Jenh-Yih
Published: March 2009

We propose a lighting mechanism for generating uniform planar light. The device integrates electron beams induced by gas discharge with cathodoluminescence at the anode, where the spectra of the emitted light depend entirely on the phosphor materials coated on the anode. Consequently, ultraviolet is not required and the usage of mercury can be avoided. In addition, the features of double-side lighting, transparency, and gray-scale images indicate that the flat electron emission lamp might become potential candidate for the next generation green lighting source.
Fourier-transform photoabsorption spectroscopy of quantum-confinement effects in individual GeSn nanodots
Authors: Naruse Nobuyasu , Mera Yutaka , Nakamura Yoshiaki , Ichikawa Masakazu , Maeda Koji
Published: March 2009

Spatially resolved Fourier-transform photoabsorption spectra of individual Ge1−xSnx nanodots, obtained by a technique based on scanning tunneling microscopy, exhibited a distinct peak far below the absorption edge of the Si substrate, which showed a clear blue shift with decreasing dot size. The energy position of the peak measured in high accuracy was in good agreement with the optical transition energy between discrete levels theoretically predicted by the size dependence due to a quantum-confinement effect, which was previously observed in scanning tunneling spectroscopic measurements.
Integrated genomic profiling of endometrial carcinoma associates aggressive tumors with indicators of PI3 kinase activation
Authors: Salvesen H. B. , Carter S. L. , Mannelqvist M. , Dutt A. , Getz G. , Stefansson I. M. , Raeder M. B. , Sos M. L. , Engelsen I. B. , Trovik J. , Wik E. , Greulich H. , Bø T. H. , Jonassen I. , Thomas R. K. , Zander T. , Garraway L. A. , Øyan A. M. , Sellers W. R. , Kalland K. H. , Meyerson M. , Akslen L. A. , Beroukhim R.
Published: March 2009

Although 75% of endometrial cancers are treated at an early stage, 15% to 20% of these recur. We performed an integrated analysis of genome-wide expression and copy-number data for primary endometrial carcinomas with extensive clinical and histopathological data to detect features predictive of recurrent disease. Unsupervised analysis of the expression data distinguished 2 major clusters with strikingly different phenotypes, including significant differences in disease-free survival. To identify possible mechanisms for these differences, we performed a global genomic survey of amplifications, deletions, and loss of heterozygosity, which identified 11 significantly amplified and 13 significantly deleted regions. Amplifications of 3q26.32 harboring the oncogenePIK3CAwere associated with poor prognosis and segregated with the aggressive transcriptional cluster. Moreover, samples withPIK3CAamplification carried signatures associated with in vitro activation of PI3 kinase (PI3K), a signature that was shared by aggressive tumors withoutPIK3CAamplification. Tumors with loss ofPTENexpression orPIK3CAoverexpression that did not havePIK3CAamplification also shared the PI3K activation signature, high protein expression of the PI3K pathway member STMN1, and an aggressive phenotype in test and validation datasets. However, mutations ofPTENorPIK3CAwere not associated with the same expression profile or aggressive phenotype. STMN1 expression had independent prognostic value. The results affirm the utility of systematic characterization of the cancer genome in clinically annotated specimens and suggest the particular importance of the PI3K pathway in patients who have aggressive endometrial cancer.
Self-assembly of dimeric tetraurea calix[4]pyrrole capsules
Authors: Ballester Pablo , Gil-Ramírez Guzmán
Published: March 2009

Calix[4]pyrroles having extended aromatic cavities have been functionalized with 4 ureas in theparaposition of theirmesophenyl substituents. This elaboration of the upper rim was completed in 2 synthetic steps starting from the α,α,α,α-tetranitro isomer of the calix[4]pyrrole obtained in the acid catalyzed condensation ofp-nitrophenyl methyl ketone and pyrrole. In dichloromethane solution and in the presence of 4,4′-bipyridineN-N′-dioxide the tetraurea calix[4]pyrrole dimerizes reversibly forming a cyclic array of 16 hydrogen bonds and encapsulating 1 molecule of bis-N-oxide. The encapsulated guest is bound in the cavity by hydrogen bonding to the 2 endohedral calix[4]pyrrole centers. Further evidence for dimerization of the tetraurea calix[4]pyrroles is provided by1H-NMR experiments and by the formation of mixed capsules.
The role of the dioxin-responsive element cluster between theCyp1a1andCyp1a2loci in aryl hydrocarbon receptor biology
Authors: Nukaya Manabu , Moran Susan , Bradfield Christopher A.
Published: March 2009

The aryl hydrocarbon receptor (AHR) plays a central role in 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin) hepatotoxicity, regulation of xenobiotic metabolism, and hepatovascular development. Each of these processes appears to be dependent on binding of the AHR to dioxin- responsive elements (DREs) within the genome. TheCyp1a1andCyp1a2loci represent linked genes thought to play important roles in AHR biology. In the mouse, 8 DREs are located in the 14-kb intergenic region between theCyp1a1andCyp1a2genes. Seven of these DREs, collectively known as the DRE cluster (DREC), are located 1.4 kb upstream of theCyp1a1transcriptional start site and 12.6 kb upstream of theCyp1a2start site. To investigate the role of the DREC in each aspect of AHR biology, we generated a DREC-deficient mouse model through homologous recombination. Using this mouse model, we demonstrate that the DREC controls the adaptive up-regulation of bothCyp1a1andCyp1a2genes in vivo. Using selected aspects of acute hepatic injury as endpoints, we also demonstrate that DREC null mice are more sensitive to dioxin-induced hepatotoxicity than WT mice. The results of parallel toxicologic studies using individualCyp1a1andCyp1a2null mice support the observation that up-regulation of these P450s is not the cause of many aspects of dioxin hepatotoxicity. Finally, we observed normal closure of the ductus venosus (DV) in DREC null mice. Given the 100% penetrance of patent DV inAhrnull mice, these results indicate thatCyp1a1andCyp1a2do not play a dominant role in AHR-mediated vascular development.
Inferring clonal expansion and cancer stem cell dynamics from DNA methylation patterns in colorectal cancers
Authors: Siegmund Kimberly D. , Marjoram Paul , Woo Yen-Jung , Tavaré Simon , Shibata Darryl
Published: March 2009

Cancers are clonal expansions, but how a single, transformed human cell grows into a billion-cell tumor is uncertain because serial observations are impractical. Potentially, this history is surreptitiously recorded within genomes that become increasingly numerous, polymorphic, and physically separated after transformation. To correlate physical with epigenetic pairwise distances, small 2,000- to 10,000-cell gland fragments were sampled from left and right sides of 12 primary colorectal cancers, and passenger methylation at 2 CpG-rich regions was measured by bisulfite sequencing. Methylation patterns were polymorphic but differences were similar between different parts of the same tumor, consistent with relatively isotropic or “flat” clonal expansions that could be simulated by rapid initial population expansions. Methylation patterns were too diverse to be consistent with very rare cancer stem cells but were more consistent with multiple (≈4 to 1,000) long-lived cancer stem cell lineages per cancer gland. Our study illustrates the potential to reconstruct the unperturbed biology of human cancers from epigenetic passenger variations in their present-day genomes.
Treatment of Iron Deficiency Anemia in Orthopedic Surgery with Intravenous Iron: Efficacy and Limits
Authors: Theusinger Oliver M. , Leyvraz Pierre-François , Schanz Urs , Seifert Burkhardt , Spahn Donat R.
Published: March 2009

Background

Preoperative anemia is frequent in patients undergoing orthopedic surgery. The purpose of this study was to assess the preoperative increase of hemoglobin in iron deficiency anemia patients treated with intravenous iron.

Methods

After obtaining written informed consent, 20 patients with iron deficiency anemia received 900 mg intravenous iron sucrose over 10 days starting 4 weeks before surgery. Changes of hemoglobin and iron status were measured over 4 weeks and at discharge. In the last 11 patients, endogenous erythropoietin was also measured. Data were analyzed using the Friedman test followed by pairwise Wilcoxon signed rank tests with Bonferroni correction.

Results

Hemoglobin increased significantly (P < 0.0001) after intravenous iron treatment. Overall, the mean maximum increase was 1.0 +/- 0.6 g/dl (range, 0.2-2.2 g/dl). Ferritin increased from 78 +/- 70 to 428 +/- 191 microg/l (P = 0.0001), ferritin index decreased from 2.7 +/- 2.4 to 1.5 +/- 1.0 (P = 0.0001), and soluble transferrin receptor decreased from 4.1 +/- 2.3 mg/l to 3.7 +/- 2.3 mg/l (P = 0.049), whereas transferrin saturation (20.5 +/- 9.0 to 22.9 +/- 9.0%) and serum iron (13.3 +/- 4.6 to 13.1 +/- 4.5 microm) did not change significantly after intravenous iron treatment. Endogenous erythropoietin decreased from 261 +/- 130 pg/ml to 190 +/- 49 pg/ml 2 weeks after intravenous iron treatment (P = 0.050, not significant after Bonferroni correction). No adverse events related to intravenous iron were observed. The maximum increase of hemoglobin was observed 2 weeks after the start of intravenous iron treatment, indicating that administration of intravenous iron 2-3 weeks before surgery may be optimal.

Conclusion

Treatment with intravenous iron allows correcting iron deficiency anemia before elective surgery.
Burst Activation of the Cerebral Cortex by Flash Stimuli during Isoflurane Anesthesia in Rats
Authors: Hudetz Anthony G. , Imas Olga A.
Published: March 2009

Background

The degree of suppression of sensory functions during general anesthesia is controversial. Here, the authors investigated whether discrete flash stimuli induced cortical field potential responses at an isoflurane concentration producing burst suppression and compared the spatiotemporal properties and frequency spectra of flash-induced burst responses with those occurring spontaneously.

Methods

Rats were equipped with multiple epidural and intracortical electrodes to record cortical field potentials in the right hemisphere at several locations along the anterior-posterior axis. At isoflurane concentrations of 1.1, 1.4, and 1.8%, discrete light flashes were delivered to the left eye while cortical field potentials were continuously recorded.

Results

Isoflurane at 1.4-1.8% produced burst suppression. Each flash produced a visual evoked potential in the primary visual cortex followed by secondary bursting activity in more anterior regions. The average latency and duration of these bursts were 220 and 810 ms, respectively. The spontaneous and flash-induced bursts were similar in frequency, duration, and spatial distribution. They had maximum power in the frontal (primary motor) cortex with a dominant frequency of 10 Hz.

Conclusions

The results suggest that discrete flash stimuli activate the motor regions of the cerebral cortex during isoflurane anesthesia and that these activations are analogous with those that occur spontaneously during burst suppression. Electrocortical suppression of the cortex during anesthesia does not prevent its response to visual stimuli.
Midazolam Potentiates Nociceptive Behavior, Sensitizes Cutaneous Reflexes, and Is Devoid of Sedative Action in Neonatal Rats
Authors: Koch Stephanie C. , Fitzgerald Maria , Hathway Gareth J.
Published: March 2009

Background

The significant postnatal maturation of gamma-aminobutyric acid signaling in the developing brain is likely to have important implications for infant pain processing. Gamma-aminobutyric acid receptor activation evokes analgesia and sedation in the adult, but the impact of immature gamma-aminobutyric acid signaling on modulators of the gamma-aminobutyric acid type A receptor, such as the benzodiazepines, is not known in infants.

Methods

Nociceptive processing was measured using behavioral and electrophysiological recordings of hind limb flexor withdrawal threshold and magnitude to mechanical and thermal stimulation of the hind paw. The effects of midazolam (0.1-10 mg/kg subcutaneously, 0.1 mg/kg intrathecally) or saline treatment were compared in rats aged 3, 10, 21, and 40 days (adult). The sedative action of midazolam was assessed at each age using righting reflex latencies.

Results

Midazolam dose-dependently decreased mechanical reflex thresholds and increased mechanical and thermal reflex magnitudes in neonates. In older rat pups and adults, midazolam had the reverse effect, increasing thresholds and decreasing reflex magnitude. These differences were mediated supraspinally; intrathecal administration of midazolam did not affect flexion reflexes at any age. Midazolam had no sedative action in the youngest rats; sedation increased gradually through postnatal development.

Conclusions

The results show a striking reversal in the effects of midazolam on nociception and sedation in rats between postnatal days 3 and 10. Midazolam fails to sedate young rats and sensitizes their flexor reflex activity. The sedative and desensitizing effects of midazolam are not observed until later in life after maturation in supraspinal centers. The results indicate a need to better understand the pharmacology of drugs used routinely in neonatal intensive care.
Intrathecal Magnesium Sulfate Administration at the Time of Experimental Ischemia Improves Neurological Functioning by Reducing Acute and Delayed Loss of Motor Neurons in the Spinal Cord
Authors: Jellish Walter S. , Zhang Xin , Langen Kenneth E. , Spector Matthew S. , Scalfani Michael T. , White Fletcher A.
Published: March 2009

Background

In this study, the authors determined the effect of magnesium sulfate on intrathecal glutamate concentrations, hindlimb motor function, and histopathology after a transient episode of spinal cord ischemia.

Methods

Fifty-two New Zealand White rabbits underwent spinal cord ischemia for 30 min. Fifteen minutes before ischemia, animals received intrathecal magnesium sulfate (MgSO4) (3 mg/kg) or placebo (artificial cerebrospinal fluid). Intrathecal microdialysis samples were measured for glutamate using high-performance liquid chromatography. Neurologic function and spinal cord histopathology were assessed throughout the recovery period.

Results

Intrathecal glutamate levels in placebo-treated animals were higher after spinal cord ischemia compared with sham- and MgSO4-treated animals. MgSO4-treated animals had increased lower extremity motor function compared with the placebo group (64.7% vs 14.3%, P < 0.01). Histologic examination of placebo-treated animals revealed significant motor neuron cell loss at thoracolumbar levels by Day 7 (P < 0.05), whereas lower lumbar regions displayed significant neuron loss on Day 1. Spinal cords from MgSO4-treated animals exhibited less neuronal loss in lumbar regions. Similar effects were present in the thoracolumbar segments on Day 7. A significant correlation existed between diminished neuronal loss and hind leg movement (Tarlov score) and demonstrates that the neurologic outcome after MgSO4 treatment was related to lower lumbar ventral horn cell survival (r2 = 0.812, P < 0.001).

Conclusions

These results demonstrate that MgSO4 affords significant spinal cord motor neuron protection by diminishing acute neuronal loss at the foci of the ischemic injury (L3-L6) with delayed neuronal degeneration in adjacent spinal cord regions (T7-L2).