bluuebunny/crossref_metadata_2025 huggingface dataset:
Future facilities for solar and stellar activity research
Authors: Strassmeier Klaus G.
Published: December 2007

I try to list the currently ongoing instrumental activities for solar and stellar activity research. Only projects that lead to operational ground-based facilities no later than 2013 and to operational space-based observatories no later than 2016 are considered. Any facility already in operation or any instrument under construction but with a very wide range of usage is excluded from this listing (like e.g. ALMA, Herschel or SOFIA). No details on science programs are given. The text is organized according to space, radio, and optical/IR projects.
SN 1006: a thousand-year perspective
Authors: Winkler P. Frank
Published: December 2007

We review some of the extensive historical observations of SN 1006, emphasizing estimates of its brightness at maximum. An estimate of Vmax ≈ −7.5 is consistent with what may be the most reasonable interpretation of these records and with an a posteriori calculation based on typical peak magnitudes for Type Ia supernovae together with the distance and extinction to SN 1006. We also give a brief overview of the discovery of the SN 1006 remnant in 1965, and contrast the earliest radio, optical, and X-ray observations of the remnant with recent ones, as reported in more detail by other papers in this JD09 review.
SN 1006 and other historical supernovae
Authors: Stephenson F. Richard
Published: December 2007

The supernova which appeared in AD 1006 is unique in history for its brilliance, duration of visibility, and the interest it aroused. Almost thirty separate records of the star are preserved from various parts of the world. This paper briefly summarizes historical records of SN 1006 and discusses the prospects of uncovering further historical records of supernovae.
Radio observations of SN 1006
Authors: Reynoso Estela M.
Published: December 2007

In this article I review our present knowledge of SN 1006 based on radio observations since the identification of the radio remnant four decades ago. I also report preliminary results of a new radio expansion study which combines VLA 1991/92 data with new VLA and ATCA observations performed in 2003.
On the road to consistent Type Ia supernova explosion models
Authors: Röpke Friedrich K.
Published: December 2007

Keeping up with ever more detailed observations, Type Ia supernova (SN Ia) explosion models have seen a brisk development over the past years. The aim is to construct a self-consistent picture of the physical processes in order to gain the predictive power necessary to answer questions arising from the application of SNe Ia as cosmological distance indicators. We review recent developments in modeling these objects focusing on three-dimensional simulations.
Light echoes of SNe in the LMC
Authors: Rest Armin , Suntzeff Nicholas B. , Smith R. Chris , Olsen Knut , Zenteno Alfredo , Damke Guillermo J. , Prieto Jose L. , Stubbs Christopher , Garg Arti , Challis Peter , Becker Andrew C. , Miknaitis Gajus A. , Miceli Antonino , Welch Douglss L. , Clocchiatti Alejandro , Minniti Dante , Morelli Lorenzo , Cook Kem H. , Nikolaev Sergei , Huber Mark E. , Newman Andrew
Published: December 2007

The SuperMACHO project has discovered light echoes from 3 ancient SNe in the LMC. These SNRs are three of the six youngest in the LMC, and are classified as likely SN Ia based on X-ray data.
Genesis discovery mission science results
Authors: Burnett Donald S.
Published: December 2007

Results of the Genesis mission to sample the solar wind are summarized.
Results from the SMART-1 lunar mission
Authors: Foing Bernhard H.
Published: December 2007

Results of the SMART-1 mission to Earth's Moon are summarized.
Mars Express science results and goals for the extended mission
Authors: Chicarro Agustin F.
Published: December 2007

Results of the Mars Express mission to Mars are summarized.
Hi 21-cm observations of cosmic re-ionization
Authors: Carilli Christopher L.
Published: December 2007

I review the potential for observing cosmic re-ionization using the HI 21 cm line.
The Long Wavelength Array
Authors: Taylor Gregory B.
Published: December 2007

The Long Wavelength Array (LWA) will be a new, open, user-oriented astronomical instrument operating in the relatively unexplored window from 20–80 MHz near arcsecond angular resolution and milliJansky sensitivity. Operated by the University of New Mexico on behalf of the Southwest Consortium (SWC) the LWA will provide a unique training ground for the next generation of radio astronomers. Students may also put skills learned on the LWA to work in computer science, electrical engineering, and the communications industry, among others. The development of the LWA will follow a phased build which benefits from lessons learned at each phase. Four university-based Scientific Testing and Evaluation (ST&E) teams with different areas of concentration: (i) high-resolution imaging and particle acceleration; (ii) wide-field imaging and large scale structures; (iii) ionospheric physics; and (iv) radio frequency interference (RFI) suppression and transient detection will provide the feedback needed to assure that science objectives are met as the build develops. Currently in its first year of construction funding, the LWA team is working on the design for the first station (see also Ray et al. 2006).
How to build and use special purpose PC clusters in stellar dynamics
Authors: Spurzem Rainer
Published: December 2007

Large scale, direct particle-particle, brute force N-body simulations are required to accurately resolve numerically transport processes of energy and angular momentum due to two-body relaxation, and interactions between supermassive black holes and other particles having a much smaller mass. Direct accurate N-body codes are the widely used tool for such simulations, e.g., NBODY4 or NBODY6 (Aarseth 1999, 2003), see also Harfst et al. (2007) for a less complex code variant, used for benchmarks in this paper. Makino (2002) has presented another direct N-body summation code, which is optimized for a quadratic layout of processor (p required to be a square number).
N-body codes
Authors: Aarseth Sverre J.
Published: December 2007

We review some advances relating to direct N-body codes. In particular, there has been significant progress in dealing with large-N systems containing a few dominant members. The simulation of massive black holes also requires treatment of relativistic effects for strongly bound two-body orbits. Although somewhat costly, the addition of post-Newtonian terms is still straightforward when used in connection with regularization methods. Several versions of multiple regularization are especially well suited to studying black hole problems. We also report on a new stability criterion for the general three-body problem which will provide a robust test in systems where hierarchies are a troublesome feature, as in the case of star cluster simulations with primordial binaries.
Pulsar as barycenter coordinate clock
Authors: Ilyasov Yuri P. , Kopeikin S. M. , Sazhin Mikhail V. , Zharov Vladimir E.
Published: December 2007

Pulsars can be considered as very precise clocks if they are observed from the barycenter of the Solar system. Pulsar Timing Array (PTA) can be used to establish new astronomical reference frame which describes both space and time properties. Among these arrays most remarkable are the Parks Pulsar Timing Array (PPTA) and Kalyazin Pulsar Timing Array (KPTA).
The small telescopes still useful for astrometry
Authors: Stavinschi Magda G.
Published: December 2007

We make a case for the usefulness of small telescopes astrometry.
Status of the European Extremely Large Telescope (E-ELT)
Authors: Monnet Guy J.
Published: December 2007

The European initiative for an Extremely Large Telescope is presented. During the past year the transition from the 100 m OWL concept to a 30 m to 42 m diameter telescope has been made. The history and the current status of this development is described.
Current and future status of gravitational wave astronomy - gravitational wave facilities
Authors: Rowan Sheila
Published: December 2007

Currently a network of interferometric gravitational wave detectors is in operation around the globe, in parallel with existing acoustic bar-type detectors. Searches are underway aimed at the first direct detection of gravitational radiation from astrophysical sources. This paper briefly summarizes the current status of operating gravitational wave facilities, plans for future detector upgrades, and the status of the planned space-based gravitational wave detectorLISA.
International Virtual Observatory Alliance
Authors: Ohishi Masatoshi
Published: December 2007

The International Virtual Observatory Alliance is briefly introduced as a concensus-based group to construct International Virtual Observatory – a new, planet-wide research infrastructure for the 21st century astronomy. Standardized protocols by the IVOA were used to interconnect more than 10 astronomical obsrvatories and data centers to provide astronomers with multiwavelength astronomical data. The priority areas for technical development and planned developments are described.
The Square Kilometre Array
Authors: Schilizzi Richard T.
Published: December 2007

The Square Kilometre Array (SKA) is a global project to design and build a new generation radio telescope at metre to centimetre wavelengths.
Study on the environment around QSOs with redshift of 1–3 using the JVO System
Authors: Shirasaki Yuji , Tanaka Masahiro , Honda Satoshi , Kawanomoto Satoshi , Mizumoto Yoshihiko , Ohishi Masatoshi , Yasuda Naoki , Masunaga Yoshifumi , Ishihara Yasuhide , Tsutsumi Jumpei , Nakamoto Hiroyuki , Kobayashi Yuusuke , Sakamoto Michito
Published: December 2007

Virtual Observatory (VO) is an emerging astronomical infrastructure for sharing the astronomical data set in the world. National Astronomical Observatory of Japan (NAOJ) started its VO project (Japanese Virtual Observatory – JVO) in 2002, and developed JVO portal prototypes. We have carried out several science use cases, such as cosmic string searches and QSO environment studies, by using the prototype system to examine the functionality of the system. This paper describes a preliminary result of the latter science use case.
New generation wide-fast-deep optical surveys: petabytes from the sky
Authors: Tyson J. Anthony
Published: December 2007

Many fundamental problems in optical astronomy – from planetary science, galactic structure, optical transients, to large-scale structure and cosmology – could be addressed though the same data set with millions of exposures in superb seeing, in multiple passbands, to very faint magnitudes over a large area of sky. This capability is largely driven by technology. In a logical progression towards this scientific capability, several increasingly ambitious wide-field optical surveys are planned in the next few years. A uniform high quality database covering all these science areas would be an ideal match to the VO. The above utopian goal of simultaneous pursuit of parallel surveys is achievable, but it relies on the ability to image a wide field quickly and deeply, and it is a non-linear function of the camera+telescope étendue.
Virtual Observatory as a tool for stellar spectroscopy
Authors: Škoda Petr
Published: December 2007

The Virtual Observatory (VO) is often presented as an all-purpose tool for the astronomer to do all his current work in a single web browser, from which he can control all data searches, reductions and mainly the full data analysis. This idea seems to be already fulfilling in certain fields of astronomy like is the search of unknown correlations between various parameters in large scale surveys, galaxy statistics or cross-identification of objects. The current VO tools are, however, lacking support for important capabilities needed in stellar spectroscopy. Especially the high-resolution spectroscopy of stars with rapid line profile variations or of those with complicated emission profiles (like Be or symbiotic stars) benefits from a number of specific methods implemented today only in stand-alone legacy packages working with local data.
Interconnecting the Virtual Observatory with computational grid infrastructures
Authors: Pasian Fabio , Taffoni Giuliano , Vuerli Claudio
Published: December 2007

The term ‘grid’, in the Virtual Observatory (VO) context, has mainly been used to indicate a set of interoperable services, allowing transparent access to a set of geographically distributed and heterogeneous archives and catalogues, data exchange and analysis, etc. The design of the VO has been however mainly geared at allowing users to access registered services.
The Astro-Wise system: a federated information accumulator for astronomy
Authors: Valentijn Edwin A. , Keijn Gijs Verdoes
Published: December 2007

The Astro-Wise consortium has designed a new paradigm, ‘Awe‘, and implemented a fully scalable and distributed information system to overcome the huge information avalanche in wide-field astronomical imaging Surveys.
Image processing and scientific workflows in the Virtual Observatory context
Authors: Slezak Eric , Schaaff André , Claudon Jean-Julien
Published: December 2007

Since 2005, the workflow working group of OV-France gathers astronomers from five french institutes with common objectives: (i) defining use cases of general interest; (ii) identifying the simplest workflow structure allowing portability; and (iii) suggesting solutions for designing and exploiting easily such workflows (cf. Astrogrid developments). Our workflow definition is the following: a sequence of tasks executed within a controlled context by an architecture taking into account VO standards.
Special Session 7 Astronomy in Antartica
Authors: Burton Michael G.
Published: December 2007

The high, dry and stable climatic conditions on top of the Antarctic plateau offer exceptional conditions for a wide range of observational astronomy, from optical to millimetre wavelengths. This is principally on account of the greatly reduced thermal backgrounds, the improved atmospheric transmission and the supurb seeing, in comparison with conditions at temperate latitude sites. The polar plateaus in the Arctic may also offer excellent conditions for astronomy, though these have yet to be quantified. We briefly review the history of astronomy in Antarctica and outline some of the activities now taking place on the polar plateaus, and plans for the future.
Design and construction of the moving optical systems of IRAIT
Authors: Colomé Josep , Abia Carlos , Domínguez Inma , Isern Jordi , Tosti Gino , Busso Maurizio , Nucciarelli Giuliano , Roncella Fabio , Straniero Oscar , Dolci Mauro
Published: December 2007

The IRAIT (International Robotic Antarctic Infrared Telescope) project (Tosti et al. 2006) is based on a 80 cm aperture telescope to observe in the infrared range. It is due to start operations in spring 2008, several months after installation in Dome C (Antarctica). We describe the contributions made to such project by the Institute for Space Studies of Catalonia (IEEC) and the University of Granada, whose participation has been mainly focused in developing the moving optical system for the secondary (M2) and tertiary (M3) mirrors of the telescope. Moving parts of the optical system provide focusing and chopping capabilities, implemented in M2, and a rotation mechanism, implemented in M3, allow observation in either Nasmyth foci. The work package includes the design and construction of both mirrors, the mechanical supports, the electronics and the control software, all prepared to work at the low temperatures at Antarctica. A Spanish company, NTE, was contracted to carry out the design and manufacture. Tests at low temperature and integration in the telescope were finished during summer 2006, before sending the telescope to Antarctica, scheduled by the end of the same year.
Cosmic microwave background: probing the universe from z = 6 to 1100
Authors: Spergel David N.
Published: December 2007

Observations of cosmic microwave background temperature and polarization fluctuations are sensitive to both physical conditions at recombination (z = 1100) and physical process along the line of sight. I will discuss recent results from the Wilkinson Microwave Anisotropy Probe and planned ground and space-based observations. The talk will emphasize the role of CMB observations in determining the initial conditions for the growth of structure and as a probe of the physics of re-ionization.
End-to-end science from major facilities: does the VO have a role?
Authors: Gilmore Gerard F.
Published: December 2007

The Virtual Observatory provides a natural solution to the existence problem in communications: how can one ask a question of another unless you know the other exists? Many think e-mail from apparent strangers, e-blogs, etc., suggest there is no shortage of possible such solutions. In that context, is the Virtual Observatory in fact the necessary and desirable part of the solution? Specifically, does the VO necessarily play a critical role in delivering end-to-end facility science, from ideas, through proposals, resources/facilities, to distributed, reviewed, knowledge? If not, what else needs to be added?
Dissolved aluminum, indium, and cerium in the Sea of Japan and the Sea of Okhotsk: Comparison to the marginal seas of the western North Pacific
Authors: Obata Hajime , Alibo Dia Sotto , Nozaki Yoshiyuki
Published: December 2007

Dissolved aluminum, indium, and cerium were measured in seawater from the Sea of Japan and the Sea of Okhotsk. Surface maxima of Al in the eastern Japan Basin indicate a signature of atmospheric mineral dust deposition resembling that of In. Data from all stations in this study show that Ce was markedly high in well‐oxygenated bottom waters. The Ce:Al ratios of settling particles and surface sediments implicate the benthic flux of Ce as its cause. The In:Al ratios found in this study are not as high as those of the South China Sea and Sulu Sea, suggesting the minor influence of atmospheric deposition on the In:Al ratios in seawater. Fractionation between In and Al during scavenging processes, in addition to input from the bottom sediment, might contribute to the In enrichment of seawater. Apparent differences between In and Ce distributions in the marginal seas show that the benthic supply mechanism of In is not merely a simple redox‐related process.
Stratospheric transport using 6‐h‐averaged winds from a data assimilation system
Authors: Pawson Steven , Stajner Ivanka , Kawa S. Randolph , Hayashi Hiroo , Tan Wei‐Wu , Nielsen J. Eric , Zhu Zhengxin , Chang Lang‐Ping , Livesey Nathaniel J.
Published: December 2007

Stratospheric transport calculated using assimilated winds has been shown to be too fast in many cases, because of excessive mixing and an overstrong residual circulation. It is shown that the use of 6‐h‐averaged wind fields instead of instantaneous analyses can substantially reduce this problem for NASA's Goddard Earth Observing System version 4 (GEOS‐4) sequential data assimilation system. Two examples are used to illustrate impacts in an off‐line chemistry transport model. An age‐of‐air computation shows that the stratosphere becomes substantially older when time‐averaged winds are used, yet still not as old as that determined from observations. An ozone assimilation experiment reveals improvements in the spatial structure of assimilated ozone, better agreement with independent observations, and a 40–60% reduction in observation‐minus‐forecast residuals. The averaged meteorological fields have also been incorporated in the on‐line transport computations: This is equivalent to using a 6‐h square‐wave filter at the analysis times. Sub‐6‐h noise in the system is substantially reduced with this approach. Two additional examples of transport are shown. A simulation of 2004–2005 shows that the descent of N2O in the Arctic polar vortex is represented more accurately than in previous studies. A tape recorder signal is evident in the tropical moisture; it ascends about 30% faster than that in the real atmosphere. In summary, the use of 6‐h‐averaged winds substantially improves the transport characteristics of the assimilated data, although the circulation remains too fast.
Power‐law distribution of fault slip‐rates in southern California
Authors: Meade Brendan J.
Published: December 2007

The spatial partitioning of deformation in the continental crust and, in particular, at plate boundary zones is determined by the distribution of fault slip‐rates. Analytic and numerical models of strain accumulation in the elastic upper crust have been divided into those that parameterize faulting as localized on a finite length fault system comprised of relatively few fast slip‐rate faults, or as distributed throughout a continuum of relatively slow slip‐rate faults. We demonstrate that in the southern California fault system, between the Pacific and North American plates, both geologically and geodetically constrained fault slip‐rate catalogs obey a power‐law frequency distribution. Using this empirically constrained scaling relationship we derive an analytic expression for the partitioning of potency accumulation rate, which determines the distribution and magnitude of slip localization. This model describes the kinematics of both micro‐plate and continuum deformation models, and predicts that ∼97% of the deformation in southern California is accommodated on faults slipping at >1 mm/yr which is consistent with models of continental deformation which explicitly represent a large though finite number of deforming structures.
Microearthquake streaks and seismicity triggered by slow earthquakes on the mobile south flank of Kilauea Volcano, Hawai'i
Authors: Wolfe Cecily J. , Brooks Benjamin A. , Foster James H. , Okubo Paul G.
Published: December 2007

We perform waveform cross correlation and high precision relocation of both background seismicity and seismicity triggered by periodic slow earthquakes at Kilauea Volcano's mobile south flank. We demonstrate that the triggered seismicity dominantly occurs on several preexisting fault zones at the Hilina region. Regardless of the velocity model employed, the relocated earthquake epicenters and triggered seismicity localize onto distinct fault zones that form streaks aligned with the slow earthquake surface displacements determined from GPS. Due to the unknown effects of velocity heterogeneity and nonideal station coverage, our relocation analyses cannot distinguish whether some of these fault zones occur within the volcanic crust at shallow depths or whether all occur on the decollement between the volcano and preexisting oceanic crust at depths of ∼8 km. Nonetheless, these Hilina fault zones consistently respond to stress perturbations from nearby slow earthquakes.
Selection Strategies for Binaural and Monaural Cochlear Implantation
Authors: Perreau Ann E. , Tyler Richard S. , Witt Shelley , Dunn Camille
Published: December 2007

Purpose

We propose theoretical guidelines for cochlear implant selection criteria in adults and children that emphasize the contribution of each ear to the binaural advantage. The guidelines outline options for implanting one ear only, implanting one ear plus use of a contralateral hearing aid, and implanting both ears.

Method

Our method for selecting the best cochlear implant or hearing aid outcome is derived from the amount of usable hearing of the patient. This approach requires the measurement of aided speech perception with each ear separately and then bilaterally. Guidelines are based on the following: (a) overall level of performance with hearing aids relative to what is expected from a cochlear implant, (b) the contributions from each ear, and (c) whether there is a binaural advantage.

Conclusions

Our general recommendation is to provide the patient with the best opportunity for binaural hearing. Since the guidelines put forth in this article are theoretically based, future efforts should be aimed at examining the validity of these guidelines.
Stimulus Repetition Rate and the Reference Levels for Clicks and Short Tone Bursts: A Warning to Audiologists, Researchers, Calibration Laboratories, and Equipment Manufacturers
Authors: Lightfoot Guy , Sininger Yvonne , Burkard Robert , Lodwig Andre
Published: December 2007

Purpose

To make the audiologic community aware of a technical issue with potential for misunderstanding that could affect the design, calibration, and use of auditory brainstem response (ABR) systems.

Method

Two international standards published in 2007 relating to the stimuli commonly used in ABR tests were studied and the behavior of a commercially available ABR system examined with regard to the relationship between stimulus level and repetition rate.

Results

There is potential for misunderstanding of the need to compensate for the effect of stimulus rate on stimulus level. Although rapidly presented stimuli appear louder as the rate is increased, it is inappropriate to compensate for this when calibrating the stimulus level of ABR systems.

Conclusions

Users of ABR systems should, if possible, use the stimulus reference levels now available in an international standard rather than establish local values. No adjustment of level should be made to account for different stimulus repetition rates. Users of ABR systems should check their systems to ensure that no automatic level adjustment is made; if necessary, equipment manufacturers should be consulted.
Dynamics of nanoscale jet formation and impingement on flat surfaces
Authors: Murad Sohail , Puri Ishwar K.
Published: December 2007

Molecular-dynamics simulations are used to investigate the formation of water nanojets. The fluid is forced through a nano-orifice to establish a nanojet, which then impinges on a flat surface. The simulations show that to produce jets in the 1nm diameter range, the orifice surface must be hydrophobic, otherwise the nanojet kinetic energy/inertia may never be able to overcome the attractive forces of the surface to form a jet. In addition, for the nanojet to form a stable liquid film on the surface of impingement, the surface cannot be either hydrophobic or too hydrophilic. Finally the stability/formation of the nanojet is not sensitive to the orifice surface temperature. The same physical laws that govern flows at the micro- and macroscales adequately describe nanojet flows in the absence of strong interfacial forces.
Inelastic neutron scattering study of methyl groups rotation in some methylxanthines
Authors: Prager M. , Pawlukojc A. , Wischnewski A. , Wuttke J.
Published: December 2007

The three isomeric dimethylxanthines and trimethylxanthine are studied by neutron spectroscopy up to energy transfers of 100meV at energy resolutions ranging from 0.7μeV to some meV. The loss of elastic intensity with increasing temperature can be modeled by quasielastic methyl rotation. The number of inequivalent methyl groups is in agreement with those of the room temperature crystal structures. Activation energies are obtained. In the case of theophylline, a doublet tunneling band is observed at 15.1 and 17.5μeV. In theobromine, a single tunneling band at 0.3μeV is found. Orientational disorder in caffeine leads to a 2.7μeV broad distribution of tunneling bands around the elastic line. At the same time, broad low energy phonon spectra characterize an orientational glassy state with weak methyl rotational potentials. Librational energies of the dimethylxanthines are clearly seen in the phonon densities of states. Rotational potentials can be derived which explain consistently all observables. While their symmetry in general is threefold, theophylline shows a close to sixfold potential reflecting a mirror symmetry.
Cherenkov radiation of a fast electron in ultrashort intense laser plasmas
Authors: Hu Qiang-Lin , Liu Shi-Bing , Li Wei
Published: December 2007

The Cherenkov radiation resulting from a fast electron in ultrashort intense laser plasma is explored theoretically based on the density perturbation theory. The radiation emitting conditions and characteristics of the corresponding Cherenkov geometry are discussed in detail. By numerical computation, a significant conclusion is revealed that the THz radiation of Cherenkov-type can be excited by the coupling of a fast electron produced by an intense ultrashort pulse laser and plasma medium in specifically parameter conditions. The results show that the radiation intensity is strongly dependent on the pulse duration of incident laser and the velocity of a fast electron, the emission spectrum width is dependent on the plasma density and the ratio of a fast electron and laser group velocities, and the emission angle distribution is dependent on the effective radius of laser beam.
Evidence of rf-driven dendritic vortex avalanches in MgB2 microwave resonators
Authors: Ghigo G. , Laviano F. , Gozzelino L. , Gerbaldo R. , Mezzetti E. , Monticone E. , Portesi C.
Published: December 2007

The influence of dendritic magnetic-flux penetration on the microwave response of superconducting magnesium diboride (MgB2) films is investigated by a coplanar resonator technique. The characteristic feature consists of abrupt jumps in the resonance curves, which are shown to be induced by vortex avalanches freezing magnetic flux inside the resonator. Flux shaking provided by radio frequency currents is the origin of such avalanches, since a mechanism for magnetic instability of the dendrite type is local heating produced from flux motion. Once the external magnetic field has been changed, the interaction between microwave currents and flux lines influences the vortex-relaxation process. As a consequence, the vortex system is maintained close to a nonequilibrium state during the whole frequency sweep (few seconds), resulting in the observation of several events of dendrite nucleation and branching. From the analysis of a robust statistics, it results that avalanche-size distributions before and after flux-pinning tailoring by heavy-ion irradiation are fully consistent with a thermomagnetic model and with molecular dynamics simulations reported in literature.
Realization of p-type conduction in undoped MgxZn1−xO thin films by controlling Mg content
Authors: Li Y. F. , Yao B. , Lu Y. M. , Wei Z. P. , Gai Y. Q. , Zheng C. J. , Zhang Z. Z. , Li B. H. , Shen D. Z. , Fan X. W. , Tang Z. K.
Published: December 2007

Undoped MgxZn1−xO thin films with Mg content of 0⩽x⩽0.20 were grown on c-sapphire substrate by plasma-assisted molecular beam epitaxy. The MgxZn1−xO shows n-type conduction in Mg content of x⩽0.05, and the carrier concentration decreases slowly from 1018to1017cm−3 with increasing Mg content. However, as x⩾0.10, the MgxZn1−xO begins to show p-type conduction, and the carrier concentration goes down sharply to 1015cm−3 firstly and then increases slowly with increasing Mg content from 1015to1016cm−3. The mechanism of transformation from n to p type and change of the carrier concentrations with Mg content were investigated by photoluminescence and absorption measurements as well as first-principle calculation.
Numerical analysis of optothermionic refrigeration in semiconductor triple-well structure
Authors: Han Peng , Jin Kui-juan , Ren Shang-Fen , Zhou Yue-liang , Lu Hui-bin
Published: December 2007

The refrigeration processes in the InP/AlInAs triple-well semiconductor system with various structures are analyzed theoretically based on the model of optothermionic refrigeration. Thermal energy extraction in the triple-well system is calculated to be as much as 26 W/cm2 theoretically with properly designed well widths and doping densities. Furthermore, the temperature drop distributions for hot semiconductor devices are obtained self-consistently with various parameters including cross-sectional area, generation heat, environment temperature, and refrigeration heat.
Correlation between cation disorder and flux pinning in the YBa2Cu3O7 coated conductor
Authors: Maroni V. A. , Li Y. , Feldmann D. M. , Jia Q. X.
Published: December 2007

A correlation has been observed between the through-thickness cation disorder level in YBa2Cu3O7 (YBCO) coated conductor films and the commonly observed falloff in layer-by-layer through-thickness critical current density (Jc) of YBCO films produced by pulsed laser deposition (PLD) on single crystal substrates. The amount of cation disorder with respect to the aggregate, c-axis-textured YBCO content was measured by Raman spectroscopy methods combined with step milling of 1.5–1.7μm thick YBCO films. For PLD YBCO films on single crystal strontium titanate, the Raman results indicate a sharp drop off in cation disorder from the substrate surface outward toward the top of the YBCO film. This drop off appears to level out in the 0.4–0.6μm range, after which the cation disorder level remains relatively constant. This trend appears to be very much like the one reported by others for the through-thickness Jc dependence of PLD YBCO on single crystal specimens. Conversely, metal-organic-deposition-produced YBCO films on rolling assisted biaxially textured substrates do not exhibit a strong through-thickness Jc dependence or a measurable change in the relative amount of cation disorder, again through thickness. The results of this study suggest that cation disorder in the YBCO lattice leads to increased flux pinning strength and that the cation disorder domains most probably occur on a size scale in the range from one to perhaps a few YBCO unit cell dimensions.
A Cu-based alloyed Ohmic contact system on n-type GaAs
Authors: Chen Ke-Shian , Chang Edward Yi , Lin Chia-Ching , Lee Cheng-Shih , Huang Wei-Ching , Lee Ching-Ting
Published: December 2007

An alloyed Pd∕Ge∕Cu Ohmic contact to n-type GaAs is reported for the first time. The Pd∕Ge∕Cu Ohmic contact exhibited a very low specific contact resistance of 5.73×10−7Ωcm2 at a low annealing temperature of 250°C. This result is comparable to the reported Pd∕Ge and Au∕Ge∕Ni Ohmic contact systems to n-type GaAs with doping concentrations about 1×1018cm−3. The Ohmic contact formation mechanisms and microstructure evolution were investigated using secondary ion mass spectrometry, x-ray diffraction, transmission electron microscopy, and energy dispersive spectrometer. The Ohmic contact behavior was related to the formation of Cu3Ge and PdGaxAsy compounds after annealing.
Microstructure of NbN epitaxial ultrathin films grown on A-, M-, and R-plane sapphire
Authors: Espiau de Lamaëstre R. , Odier Ph. , Villégier J.-C.
Published: December 2007

We compared ultrathin NbN films (2.5–10nm) simultaneously grown by dc reactive sputtering at 600°C on A, M, and R orientations of sapphire substrates. Film structures and superconducting properties were characterized. We show that actual NbN device films on R-Al2O3 are (135) oriented and suffer from detrimental disoriented twin domains. On the contrary, NbN on M-Al2O3 is shown to be untwined, leading to a lower resistivity, an increased critical current density Jc (>4MAcm−2 at 4.2K), and a higher critical temperature Tc (11.3K for 4.4nm). These results offer promising alternative for better performances of superconducting detectors and mixers.
Etching of lithium niobate using standard Ti indiffusion technique
Authors: Sivan Vijay , Mitchell Arnan , Bui Lam , Holland Anthony , Bhargava Suresh , Priest Timothy
Published: December 2007

We present evidence of etching LiNbO3 when annealing two wafers in contact with an intermediate Ti strip. Etched features are characterized qualitatively using atomic force microscopy. The impact of the Ti strip thickness on the depth and roughness of the etched surface is quantified. Etched trenches of similar depths to the original Ti film are achieved with very smooth etched surface.
Effect of nonstoichiometric defects on antiparallel domain formation in LiNbO3
Authors: Liu Xiaoyan , Kitamura Kenji , Terabe Kazuya , Zeng Huarong , Yin Qingrui
Published: December 2007

The structures of inverted nanodomains in LiNbO3 crystals were investigated using atomic force microscopy (AFM) combined with piezoresponse force microscopy and atomic force acoustic microscopy. The acoustic and AFM topographic images reflected in domain structures with polarization orientation revealed that unexpected antiparallel domains randomly exist in inverted nanodomains in congruent LiNbO3 but not in near-stoichiometric one. The Gibbs free energy change ΔG associating with the internal field Eint in congruent LiNbO3 was discussed. We propose that nonstoichiometric defects, which caused Eint during polarization reversal, play a key role in formation of antiparallel domains in congruent LiNbO3 crystals.
Effects of fire retardant on heathland soils in south-eastern Australia
Authors: Hopmans P. , Collett N. , Bickford R.
Published: December 2007

A study was undertaken to assess the effects of fire retardant application, unmodified by heat of fire, on soil properties in 2 fire-prone heathland communities at Marlo and the Grampians in south-eastern Australia. Fire retardant (Phos-Chek D75-R at 0.144 g/L) was applied at rates of 0.5, 1.0, and 1.5 L/m2 and compared with control treatments of nil and 1.0 L/m2 of water. Monitoring of surface soils showed that pH at both sites decreased while soil salinity increased immediately after application followed by a rapid decline to pre-treatment values within 12 months. The impact of retardant on total carbon and nitrogen was minor and within the range of natural variation of C and N in surface soils at both sites. Levels of readily available or labile forms of N increased at both sites but declined rapidly to background values after 12 months. Applications of retardant progressively increased extractable P in the surface soil at Marlo, in contrast to the Grampians where a rapid increase was observed after two months followed by a decline after 12 months. These results showed a significant increase in labile P in the surface soil after 12 months and also indicated that a large proportion of the phosphate applied had leached into the subsoil. Likewise, fire retardant applied at the highest rate caused increases in labile sulfate after 2 months at both sites, followed by a rapid decline to background levels. It is expected that the elevated levels of soil phosphate in particular could have a long-term impacts on growth and composition of heathland vegetation known to be sensitive to elevated levels of phosphate in soil.
Variation in soil strength, bulk density and gravel concentration along a toposequence in Abeokuta, south-western Nigeria
Authors: Salako F. K. , Dada P. O. , Adesodun J. K. , Olowokere F. A. , Adekunle I. O.
Published: December 2007

This study was carried out at Abeokuta, south-western Nigeria, to understand the variation in soil strength, gravel distribution, and bulk density along a toposequence. In 2003, a 120-m transect on a fallowed land was sampled at every 1 m for topsoil bulk density measurement by excavation (3278 cm3 pits), while soil strength was measured at every soil depth increment of 25 mm to 0.50 m depth. Total dry (ρt) and fine earth (<2 mm) (ρf) bulk densities were determined. Soil water content was also determined. Gravel was divided into classes of 2–4, 4–8, 8–16, and >16 mm. In 2006, four 100-m transects were considered; two each on adjacent fallowed and cultivated lands. Soil strength and water content were measured. The fine earth fraction of topsoil ranged from 62 to 90.6%. Gravel in the 2–4 mm class was dominant with a range of 0.8–35.7%. Thus, cores ≥50 mm could be used in the topsoil to obtain reliable estimates of bulk density.
Total bulk density (ρt) was reduced by 4–19% when corrected for gravel to obtain ρf. Soil strength of the lower slope was highest in 2003 (1981–4482 kPa) and lowest in 2006 (1546 kPa). In spite of the apparent significant influence of water content on soil strength, the relationship was weakly expressed by regression analysis, as only 35% of variation in soil strength was explained by water content at 0.10–0.15 m soil depth in 2003. No relationship was found in 2006; the cultivated segment had higher soil strength (2045 kPa) than the fallowed segment (1970 kPa) even though the water contents were similar. Also, only the 2–4 mm gravel significantly influenced ρt. Land use, soil depth, and slope position significantly affected soil strength. Root-limiting soil strength (>2000 kPa) would certainly be encountered below 0.20 m soil depth in the wet season irrespective of land use. Management of this gravelly landscape must be based on the heterogeneous nature of soil physical properties along the toposequence, and this could be made effective by grouping the soils according to slope position and taking interest in the few portions of the landscape with extreme values of gravel distribution and high soil strength.
Adapting agriculture to climate change
Authors: Howden S. Mark , Soussana Jean-François , Tubiello Francesco N. , Chhetri Netra , Dunlop Michael , Meinke Holger
Published: December 2007

The strong trends in climate change already evident, the likelihood of further changes occurring, and the increasing scale of potential climate impacts give urgency to addressing agricultural adaptation more coherently. There are many potential adaptation options available for marginal change of existing agricultural systems, often variations of existing climate risk management. We show that implementation of these options is likely to have substantial benefits under moderate climate change for some cropping systems. However, there are limits to their effectiveness under more severe climate changes. Hence, more systemic changes in resource allocation need to be considered, such as targeted diversification of production systems and livelihoods. We argue that achieving increased adaptation action will necessitate integration of climate change-related issues with other risk factors, such as climate variability and market risk, and with other policy domains, such as sustainable development. Dealing with the many barriers to effective adaptation will require a comprehensive and dynamic policy approach covering a range of scales and issues, for example, from the understanding by farmers of change in risk profiles to the establishment of efficient markets that facilitate response strategies. Science, too, has to adapt. Multidisciplinary problems require multidisciplinary solutions, i.e., a focus on integrated rather than disciplinary science and a strengthening of the interface with decision makers. A crucial component of this approach is the implementation of adaptation assessment frameworks that are relevant, robust, and easily operated by all stakeholders, practitioners, policymakers, and scientists.
Global fish production and climate change
Authors: Brander K. M.
Published: December 2007

Current global fisheries production of ≈160 million tons is rising as a result of increases in aquaculture production. A number of climate-related threats to both capture fisheries and aquaculture are identified, but we have low confidence in predictions of future fisheries production because of uncertainty over future global aquatic net primary production and the transfer of this production through the food chain to human consumption. Recent changes in the distribution and productivity of a number of fish species can be ascribed with high confidence to regional climate variability, such as the El Niño–Southern Oscillation. Future production may increase in some high-latitude regions because of warming and decreased ice cover, but the dynamics in low-latitude regions are governed by different processes, and production may decline as a result of reduced vertical mixing of the water column and, hence, reduced recycling of nutrients. There are strong interactions between the effects of fishing and the effects of climate because fishing reduces the age, size, and geographic diversity of populations and the biodiversity of marine ecosystems, making both more sensitive to additional stresses such as climate change. Inland fisheries are additionally threatened by changes in precipitation and water management. The frequency and intensity of extreme climate events is likely to have a major impact on future fisheries production in both inland and marine systems. Reducing fishing mortality in the majority of fisheries, which are currently fully exploited or overexploited, is the principal feasible means of reducing the impacts of climate change.
The interplay between the master transcription factor PU.1 and miR-424 regulates human monocyte/macrophage differentiation
Authors: Rosa A. , Ballarino M. , Sorrentino A. , Sthandier O. , De Angelis F. G. , Marchioni M. , Masella B. , Guarini A. , Fatica A. , Peschle C. , Bozzoni I.
Published: December 2007

We describe a pathway by which the master transcription factor PU.1 regulates human monocyte/macrophage differentiation. This includes miR-424 and the transcriptional factor NFI-A. We show that PU.1 and these two components are interlinked in a finely tuned temporal and regulatory circuitry: PU.1 activates the transcription of miR-424, and this up-regulation is involved in stimulating monocyte differentiation through miR-424-dependent translational repression of NFI-A. In turn, the decrease in NFI-A levels is important for the activation of differentiation-specific genes such as
M-CSFr
. In line with these data, both RNAi against NFI-A and ectopic expression of miR-424 in precursor cells enhance monocytic differentiation, whereas the ectopic expression of NFI-A has an opposite effect. The interplay among these three components was demonstrated in myeloid cell lines as well as in human CD34+ differentiation. These data point to the important role of miR-424 and NFI-A in controlling the monocyte/macrophage differentiation program.
Insulin stimulates the cleavage and release of the extracellular domain of Klotho by ADAM10 and ADAM17
Authors: Chen Ci-Di , Podvin Sonia , Gillespie Earl , Leeman Susan E. , Abraham Carmela R.
Published: December 2007

Cleavage and release (shedding) of membrane proteins is a critical regulatory step in many normal and pathological processes. Evidence suggests that the antiaging transmembrane protein Klotho (KL) is shed from the cell surface by proteolytic cleavage. In this study, we attempted to identify the enzymes responsible for the shedding of KL by treating KL-transfected COS-7 cells with a panel of proteinase inhibitors and measuring cleavage products by Western blot. We report that metalloproteinase inhibitors, including EDTA, EGTA, and TAPI-1, inhibit the shedding of KL, whereas insulin increases shedding. The effects of the inhibitors in KL-transfected COS-7 cells were repeated in studies on rat kidney slices
ex vivo
, which validates the use of COS-7 cells as our model system. Tissue inhibitor of metalloproteinase (Timp)-3 effectively inhibits KL cleavage, whereas Timp-1 and Timp-2 do not, a profile that indicates the involvement of members of the A Desintegrin and Metalloproteinase (ADAM) family. Cotransfection of KL with either ADAM10 or ADAM17 enhances KL cleavage, whereas cotransfection of KL with small interference RNAs specific to ADAM10 and ADAM17 inhibits KL secretion. These results indicate that KL shedding is mediated mainly by ADAM10 and ADAM17 in KL-transfected COS-7 cells. The effect of insulin is abolished when ADAM10 or ADAM17 are silenced. Furthermore, we demonstrate that the effect of insulin on KL shedding is inhibited by wortmannin, showing that insulin acts through a PI3K-dependent pathway. Insulin enhances KL shedding without increasing ADAM10 and ADAM17 mRNA and protein levels, suggesting that it acts by stimulating their proteolytic activities.