bluuebunny/crossref_metadata_2025 huggingface dataset:
Migrating to Riches? Evidence from the California Gold Rush
Authors: CLAY KAREN , JONES RANDALL
Published: December 2008

Gold discoveries in 1848 set off a large and extremely rapid migration to California. This article uses newly collected data from the 1850 and 1852 Censuses of Population together with the public use sample of the 1850 Census of Population to examine who went to California and how they did economically. We find that the propensity to migrate was affected by the individual's age and literacy, distance of the state from California, and average state latitude. Consistent with the historical literature, we find that economic outcomes were generally small or even zero for miners but were positive and large for nonminers.
Evidence of a microbial community associated with rock varnish at Yungay, Atacama Desert, Chile
Authors: Kuhlman Kimberly R. , Venkat Parth , La Duc Myron T. , Kuhlman Gregory M. , McKay Christopher P.
Published: December 2008

Rock varnish is a very slow‐growing nanostratigraphic coating consisting of approximately 70% fine‐grained clay and 30% iron and manganese oxides that forms on the surfaces of rocks in arid and semiarid climates. The microbial diversity associated with rock varnish collected from the hyperarid Yungay region of the Atacama Desert was investigated using culture‐independent biomolecular methods and an adenosine triphosphate (ATP) assay. The extraction of DNA from rock varnish collected at Yungay, a region in which little to no DNA has been extracted from the surface soil (<1 cm) to date, indicates that rock varnish may provide a niche habitat for microbial life where water is essentially absent. The clone library constructed suggests the presence of numerous phylogenetically distinct microorganisms, ranging in diversity from Cyanobacterial to á‐proteobacteria lineages. The findings also show that only a few micrometers of varnish material are enough to shelter microbes like Chroococcidiopsis spp. from the intense ultraviolet radiation present in the Atacama Desert. Whether or not microorganisms are involved in its nucleation and/or growth, rock varnish appears to provide a microhabitat resembling cryptoendolithic communities seen on a larger scale.
Recent Extreme Avalanches: Triggered by Climate Change?
Authors: Huggel Christian , Caplan‐Auerbach Jacqueline , Wessels Rick
Published: December 2008

On 25 September 2008, seismo meters operated by the Alaska Volcano Observatory (AVO) registered strong ground shaking. On the basis of previous experience with such large seismic signals, AVO personnel were able to rapidly identify the seismic event as an avalanche. Two days later, an AVO overflight of Iliamna volcano, near Alaska's Cook Inlet, confirmed that a massive chunk of glacial ice and rock had broken free from its position on the upper flanks of the volcano, generating a massive avalanche that could have buried an entire town had it occurred in a more populated area.

Rapidly moving rock, ice, or debris avalanches, such as the one that occurred on Iliamna, can be highly destructive and deadly. Similar events have caused the deaths of hundreds to thousands of people [Keefer and Larsen, 2007]. In general, avalanches that move more than 1 million cubic meters of material are rare. However, a remarkable series of large avalanches recently occurred in Alaska and the Caucasus, providing a new opportunity to better understand this type of hazard. All events initiated in steep mountain slopes, involved rock and significant amounts of ice, and traveled for 10–35 kilometers.
Climate Change and Agriculture in Africa: Impact Assessment and Adaptation Strategies
Authors: Brown Molly E. , McCusker Brent
Published: December 2008

As climate change has emerged as a significant threat, there is much concern about how vulnerable agricultural communities will adapt, particularly as global population continues to rise. Much of the current lack of productivity and economic marginalization of African agriculture arises from global trade regimes that give a competitive advantage to Western farmers, from low use of agricultural inputs, and from a dearth of infrastructure and services for the agriculture sector. For centuries, African farmers have used a wide variety of risk‐reducing livelihood strategies, including diversifying income sources, switching crops, and investing in marketing. However, improving their productivity to “modern” levels has remained a distant dream, resulting in a continual reduction in investment in the sector over the past five decades.
Seismic detection of a subglacial lake near the South Pole, Antarctica
Authors: Peters L. E. , Anandakrishnan S. , Holland C. W. , Horgan H. J. , Blankenship D. D. , Voigt D. E.
Published: December 2008

Seismic reflection data are analyzed to verify radar identification of a subglaical lake near the geographic South Pole. The seismic amplitude variation with offset (AVO) technique is applied to confirm the presence of extensive free water, and seismic imaging of the subsurface constrains lake depth and deeper subglacial structure in the region. This lake is at least 4.2 km wide (and likely as much as 10 km in diameter), is up to 32 ± 10 m deep, and occupies a basin of thick sedimentary strata. These results imply that extensive water storage is occurring in the South Pole region. The proximity of this lake to the Amundsen ‐ Scott South Pole Station makes research drilling to sample the lake and underlying sediments feasible and supportable.
On the influence of sea‐ice inhomogeneities onto roll convection in cold‐air outbreaks
Authors: Gryschka M. , Drüe C. , Etling D. , Raasch S.
Published: December 2008

In this study we use large‐eddy simulations (LES) to model roll convection within the convective atmospheric boundary‐layer (CBL) during strong cold‐air outbreaks (CAO). Previous LES were mostly unsuccessful in reproducing clear signals of roll convection, especially in case of strong surface heating and weak vertical wind shear in the CBL. In nature however, this phenomenon is very robust and roll convection can be observed as cloud streets in satellite pictures of almost any CAO. Previous LES studies assumed homogeneous sea‐ice, unlike the current study, where under strong surface heating clear signals of rolls appear only when introducing sea‐ice inhomogeneities in the marginal ice zone. For weaker surface heating, rolls also appear without sea‐ice inhomogeneities. The results of this study suggest that in case of strong surface heating and weak vertical wind shear surface inhomogeneities increase the chance of roll formation.
Effects of vertically propagating thermal tides on the mean structure and dynamics of Mars' lower thermosphere
Authors: Moudden Y. , Forbes J. M.
Published: December 2008

A general circulation model of Mars' atmosphere is used to elucidate the effects of vertically propagating thermal tides excited near the surface on the zonal mean density, temperature and wind structure of Mars' atmosphere between 90 and 160 km. The effects are substantial, and amount to order 10–40%, 10–50 K and 50–160 m s−1, respectively, at these altitudes under low dust conditions (dust visible optical depth = 0.3). These induced changes in the zonal mean structure are dominated by the non‐migrating tides. Of particular note are the mean density perturbations, which represent an important consideration for modeling of the aerobraking region (100–170 km).
A revised kinematic model for the relative motion between Pacific oceanic plates and North America since the Late Cretaceous
Authors: Doubrovine Pavel V. , Tarduno John A.
Published: December 2008

The convergence between the Pacific, Farallon, and Kula oceanic plates and the North American plate has provided a driving force for tectonic processes that have shaped the western margin of North America. Yet reconstructions of plate motion in the Pacific basin have traditionally relied on the assumption of fixed hot spots. In the last decade, substantial Cretaceous to Paleogene motion between the Pacific and Atlantic hot spots has been recognized, providing motivation to reevaluate the history of relative motion between Pacific oceanic plates and North America by means of plate circuit reconstructions. This paper presents new kinematic models based on two alternative plate circuits linking the Pacific plate to North America since Late Cretaceous time. When compared to models relying on fixity of Pacific and Indo‐Atlantic hot spots, our reconstructions suggest that the Pacific‐Kula and Pacific‐Farallon ridges were ∼600–1000 km closer to the western margin of North America and hence that the Farallon and Kula plates were smaller in Late Cretaceous to middle Eocene time. These findings cast significant doubt on the viability of a configuration of the Farallon‐Kula ridge that juxtaposes the Kula plate with the southern part of the paleo‐North American margin during this time interval. The results of our new reconstructions also suggest more oblique convergence between the Farallon (or Kula) plate and North America from the Late Cretaceous to the middle Eocene related to the combination of dominantly northwest motion of the Pacific plate and steady southwest motion of North America. This provides an efficient mechanism for the coast‐parallel translation of some accreted terranes of North America. It may also explain the structure of geological units in western North America, such as the Central Belt of the Franciscan Complex, which show a dominant coast‐parallel fabric formed during an interval coeval with the episode of oblique convergence.
Major solar energetic particle events of solar cycles 22 and 23: Intensities above the streaming limit
Authors: Lario D. , Aran A. , Decker R. B.
Published: December 2008

Large solar energetic particle (SEP) events constitute a serious radiation hazard to astronauts and spacecraft systems. It is essential to determine the highest particle intensities reached in SEP events, especially at the energies that pose serious risks to human health and spacecraft performance. It has been argued that the highest particle intensities measured during large SEP events occur in association with the passage of shocks driven by coronal mass ejections known as the energetic storm particle (ESP) component. Furthermore, it has been argued that the intensities measured early in the SEP events (known as the prompt component) are bounded by a maximum intensity plateau that results from wave‐particle interactions that restrict the free streaming of particles (also called the “streaming limit”). We analyze proton intensities measured by the GOES spacecraft at the energy channels P5 (∼39–82 MeV) and P7 (∼110–500 MeV) during solar cycles 22 and 23 and examine whether the highest intensities were measured during the prompt or the ESP components of the SEP events. We find three (one) SEP events in which the highest proton intensities measured during the prompt component at the energy channel P5 (P7) exceeded by a factor of 4 or more the previously determined “streaming limit”. Arguments to explain intensities during the prompt components exceeding this limit invoke interplanetary conditions that inhibit the amplification of waves resonating with the streaming particles and/or the presence of interplanetary structures able to confine and/or mirror energetic particles. We analyze these possibilities for each one of these events.
Recent Use of Behavioral Genetics in Criminal Cases
Authors: Farahany Nita
Published: December 2008

Human behavioral genetics research has been introduced in the U.S. criminal justice system, and its use will likely become more prevalent in the near future. This presentation will discusses the recent attempts by criminal defendants to introduce genetic predisposition testimony to negate the voluntariness of their conduct, to negate mens rea, to bolster an insanity defense or as mitigating evidence during sentencing. Although courts have thus far limited such testimony, the opinions in these cases demonstrate a likelihood that such evidence will play a larger role in future cases.To watch Professor Farahany's presentation, please see the "Google Video posting": http://video.google.com/videoplay?docid=585209098810298267&hl=en.
Challenging or Reinforcing Social Prejudice?
Authors: Longino Helen
Published: December 2008

Behavior genetics holds out the hope of unbiased study of the biological bases of human behavior. Without more rigorous reflection on behavioral concepts, however, behavior genetics will succeed only in reinforcing social biases. This point is illustrated with reference to studies on aggression, sexual orientation, and gender differences.To watch Professor Longino's presentation, please see the "Google Video posting":http://video.google.com/videoplay?docid=-3926548921438712173&hl=en.
Mitochondrial calcium overload triggers complement-dependent superoxide-mediated programmed cell death inTrypanosoma cruzi
Authors: Irigoín Florencia , Inada Natalia M. , Fernandes Mariana P. , Piacenza Lucía , Gadelha Fernanda R. , Vercesi Anibal E. , Radi Rafael
Published: December 2008

The epimastigote stage of Trypanosoma cruzi undergoes PCD (programmed cell death) when exposed to FHS (fresh human serum). Although it has been known for over 30 years that complement is responsible for FHS-induced death, the link between complement activation and triggering of PCD has not been established. We have previously shown that the mitochondrion participates in the orchestration of PCD in this model. Several changes in mitochondrial function were described, and in particular it was shown that mitochondrion-derived O2•− (superoxide radical) is necessary for PCD. In the present study, we establish mitochondrial Ca2+ overload as the link between complement deposition and the observed changes in mitochondrial physiology and the triggering of PCD. We show that complement activation ends with the assembly of the MAC (membrane attack complex), which allows influx of Ca2+ and release of respiratory substrates to the medium. Direct consequences of these events are accumulation of Ca2+ in the mitochondrion and decrease in cell respiration. Mitochondrial Ca2+ causes partial dissipation of the inner membrane potential and consequent mitochondrial uncoupling. Moreover, we provide evidence that mitochondrial Ca2+ overload is responsible for the increased O2•− production, and that if cytosolic Ca2+ rise is not accompanied by the accumulation of the cation in the mitochondrion and consequent production of O2•−, epimastigotes die by necrosis instead of PCD. Thus our results suggest a model in which MAC assembly on the parasite surface allows Ca2+ entry and its accumulation in the mitochondrion, leading to O2•− production, which in turn constitutes a PCD signal.
Brain Tumors Frequently Encountered by Speech-Language Pathologists: A Review and Tutorial
Authors: Mayer Jamie F.
Published: December 2008

Purpose
: As diagnostic and treatment techniques for brain tumors improve, the prevalence of patients diagnosed and living with the neurologic consequences of brain tumors is increasing. The purpose of this paper is to outline pertinent information regarding brain tumors to facilitate rehabilitation efforts by speech-language pathologists (SLPs).

Method
: The current empirical literature was critically reviewed to provide a synopsis of brain tumor occurrence rates, tumor classification methods, pediatric and geriatric issues, and basic medical and rehabilitative treatment information. Due to the large literature base pertaining to many very rare brain tumors, only those tumors likely to be encountered most frequently by SLPs are highlighted.

Results and Conclusions
: Speech, language, cognitive, and swallowing problems are common brain tumor sequelae. Patients diagnosed with brain tumors can and do benefit from rehabilitative services addressing these deficits. SLPs should have a working knowledge of brain tumors to facilitate and maximize rehabilitation-related diagnostic and treatment decisions for this patient population.
Potential energy curves and electronic structure of 3d transition metal hydrides and their cations
Authors: Goel Satyender , Masunov Artëm E.
Published: December 2008

We investigate gas-phase neutral and cationic hydrides formed by 3d transition metals from Sc to Cu with density functional theory (DFT) methods. The performance of two exchange-correlation functionals, Boese–Martin for kinetics (BMK) and Tao–Perdew–Staroverov-Scuseria (TPSS), in predicting bond lengths and energetics, electronic structures, dipole moments, and ionization potentials is evaluated in comparison with available experimental data. To ensure a unique self-consistent field (SCF) solution, we use stability analysis, Fermi smearing, and continuity analysis of the potential energy curves. Broken-symmetry approach was adapted in order to get the qualitatively correct description of the bond dissociation. We found that on average BMK predicted values of dissociation energies and ionization potentials are closer to experiment than those obtained with high level wave function theory methods. This agreement deteriorates quickly when the fraction of the Hartree–Fock exchange in DFT functional is decreased. Natural bond orbital (NBO) population analysis was used to describe the details of chemical bonding in the systems studied. The multireference character in the wave function description of the hydrides is reproduced in broken-symmetry DFT description, as evidenced by NBO analysis. We also propose a new scheme to correct for spin contamination arising in broken-symmetry DFT approach. Unlike conventional schemes, our spin correction is introduced for each spin-polarized electron pair individually and therefore is expected to yield more accurate energy values. We derive an expression to extract the energy of the pure singlet state from the energy of the broken-symmetry DFT description of the low spin state and the energies of the high spin states (pentuplet and two spin-contaminated triplets in the case of two spin-polarized electron pairs). The high spin states are build with canonical natural orbitals and do not require SCF convergence.
Tunable VUV photochemistry using Rydberg H-atom time-of-flight spectroscopy
Authors: Yuan Kaijun , Cheng Lina , Cheng Yuan , Guo Qing , Dai Dongxu , Yang Xueming
Published: December 2008

In this article, we report an experimental method for studying tunable vacuum ultraviolet (VUV) photochemistry using the H-atom Rydberg tagging technique. In this method, two VUV laser light beams were generated using nonlinear four-wave mixing scheme in a single Kr gas cell: one VUV beam is fixed at the 121.6 nm wavelength to probe the H-atom product through the Lyman α transition, the other beam can be tunable for photodissociating molecules in the wavelength range λVUV=121–190 nm. Preliminary results on the H2O photodissociation in the B̃ state are reported here. These results suggest that the experimental method is a powerful tool for investigating photodissociation dynamics in the VUV region for molecules involving H-atom processes.
4
d
transition-metal impurity rhodium in GaAs grown by metal-organic chemical vapor deposition
Authors: Iqbal M. Zafar , Majid A. , Naz Nazir A. , Qurashi Umar S.
Published: December 2008

Deep levels associated with 4d transition-metal impurity rhodium have been investigated in GaAs epitaxial layers grown by metal-organic chemical vapor deposition, using deep level transient spectroscopy (DLTS) technique. A comprehensive study of deep levels in the entire bandgap of GaAs has been carried out using both n- and p-type GaAs crystals over a wide temperature scan range, 12–470 K. In the n-type, Rh-doped material, two prominent broadbands of deep levels are found to be associated with Rh impurity; one in the upper-half and the other in the lower-half bandgap. In addition, one relatively small peak at the high temperature end of the majority-carrier emission spectra, corresponds to a deep level at Ec−0.92 eV, is also detected in the n-type Rh-doped samples. The minority carrier (hole) emission band in n-type material is found to consist of a doublet of hole emitting deep levels, labeled RhA and RhB, in the lower-half bandgap. This doublet is clearly observed to correspond to two Rh-related deep levels, labeled RhA and RhB, in the majority-carrier emission spectrum of p-type GaAs. In addition, a small hole emission peak, RhC, at the high-temperature end of the spectrum of p-type material corresponds to a deep level at Ev+0.87 eV. Data on directly measured carrier capture cross sections of deep levels are reported, wherever experimentally possible. Detailed double-correlation DLTS measurements are performed to investigate the characteristics of the observed Rh-related deep levels. The broad deep-level band in the upper-half bandgap, as well as the lower-half bandgap levels, RhA and RhB, are found to exhibit pronounced dependence of the thermal emission rates on electric field. While the former band cannot be resolved into component peaks, detailed data on the electric field dependence of hole emission rates are reported for the levels RhA and RhB over a range of measurement temperatures and analyzed in the light of the available theories. This analysis suggests the deep level RhB to be associated with a charged center while the deep level RhA is probably associated with an autolocalized self-trapping center.
Turbulent flow in pipes and channels as cross-stream “inverse cascades” of vorticity
Authors: Eyink Gregory L.
Published: December 2008

A commonplace view of pressure-driven turbulence in pipes and channels is as “cascades” of streamwise momentum toward the viscous layer at the wall. We present in this paper an alternative picture of these flows as “inverse cascades” of spanwise vorticity in the cross-stream direction but away from the viscous sublayer. We show that there is a constant spatial flux of spanwise vorticity due to vorticity conservation and that this flux is necessary to produce pressure drop and energy dissipation. The vorticity transport is shown to be dominated by viscous diffusion at distances closer to the wall than the peak Reynolds stress, well into the classical log layer. The Perry–Chong model based on “representative” hairpin/horseshoe vortices predicts a single sign of the turbulent vorticity flux over the whole log layer, whereas the actual flux must change sign at the location of the Reynolds-stress maximum. Sign reversal may be achieved by assuming a slow power-law decay of the Townsend “eddy-intensity function” for wall-normal distances greater than the hairpin length scale. The vortex-cascade picture presented here has a close analog in the theory of quantum superfluids and superconductors, the “phase slippage” of quantized vortex lines. Most of our results should therefore apply as well to superfluid turbulence in pipes and channels. We also discuss issues about drag reduction from this perspective.
Nonlinear optical susceptibility of multicomponent tellurite thin film glasses
Authors: Munoz-Martin D. , Fernandez H. , Fernandez-Navarro J. M. , Gonzalo J. , Solis J. , Fierro J. L. G. , Domingo C. , Garcia-Ramos J. V.
Published: December 2008

Tellurite (TeO2–TiO2–Nb2O5) thin film glasses have been produced by pulsed laser deposition. The dispersion of the real and imaginary parts of the linear refractive index has been measured in the range from 300 to 1700 nm. Films present high refractive index (n=2.01) and reduced absorption (k<10−4) at λ=1500 nm. The nonlinear third order optical susceptibility (|χ(3)|) has been determined at four different wavelengths (600, 800, 1200, and 1500 nm). The out-of-resonance |χ(3)| values (∼10−12 esu) are found to be ten times higher than those of the bulk glass and 102 times higher than that of silica. Compositional and structural analysis reveals an increase of both the Ti atomic content and the fraction of nonbridging oxygen bonds in the deposited films. Both factors lead to a higher hyperpolarizability of the film constituents that is proposed to be responsible for the high |χ(3)| value of the films.
Anion photoelectron spectroscopy of transition metal- and lanthanide metal-silicon clusters: MSin− (n=6–20)
Authors: Koyasu Kiichirou , Atobe Junko , Furuse Shunsuke , Nakajima Atsushi
Published: December 2008

The electronic properties of silicon clusters containing a transition or lanthanide metal atom from group 3, 4, or 5, MSin, (M=Sc, Ti, V, Y, Zr, Nb, Lu, Tb, Ho, Hf, and Ta) were investigated by anion photoelectron spectroscopy at 213nm. In the case of the group 3 elements Sc, Y, Lu, Tb, and Ho, the threshold energy of electron detachment exhibits local maxima at n=10 and 16, while in case of the group 4 elements Ti, Zr, and Hf, the threshold energy exhibits a local minimum at n=16, associated with the presence of a small bump in the spectrum. These electronic characteristics of MSin are closely related to a cooperative effect between their geometric and electronic structures, which is discussed, together with the results of experiments that probe their geometric stability via their reactivity to H2O adsorption, and with theoretical calculations.
Three-dimensional direct numerical simulation of electromagnetically driven multiscale shallow layer flows: Numerical modeling and physical properties
Authors: Lardeau Sylvain , Ferrari Simone , Rossi Lionel
Published: December 2008

Three-dimensional (3D) direct numerical simulations of a flow driven by multiscale electromagnetic forcing are performed in order to reproduce with maximum accuracy the quasi-two-dimensional (2D) flow generated by the same multiscale forcing in the laboratory. The method presented is based on a 3D description of the flow and the electromagnetic forcing. Very good agreements between our simulations and the experiments are found both on velocity and acceleration field, this last comparison being, to our knowledge, done for the first time. Such agreement requires that both experiments and simulations are carefully performed and, more importantly, that the underlying simplification to model the experiments and the multiscale electromagnetic forcing do not introduce significant errors. The results presented in this paper differ significantly from previous 2D direct numerical simulation in which a classical linear Rayleigh friction modeling term was used to mimic the effect of the wall-normal friction. Indeed, purely 2D simulations are found to underestimate the Reynolds number and, due to the dominance of nonhomogeneous bottom friction, lead to the wrong physical mechanism. For the range of conditions presented in this paper, the Reynolds number, defined by the ratio between acceleration and viscous terms, remains the order of unity, and the Hartmann number, defined by the ratio between electromagnetic force terms and viscous terms, is about 2. The main conclusion is that 3D simulations are required to model the (3D) electromagnetic forces and the wall-normal shear. Indeed, even if the flow is quasi-2D in terms of energy, a full 3D approach is required to simulate these shallow layer flows driven by multiscale electromagnetic forcing. In the range of forcing intensity investigated in this paper, these multiscale flows remain quasi-2D, with negligible energy in the wall-normal velocity component. It is also shown that the driving terms are the electromagnetic forcing and the pressure gradient which are mostly antialigned but not strictly opposite, and their intensity differs locally. Indeed, no term in the Navier–Stokes equation can be neglected.
Photon-exposure-dependent photon-stimulated desorption for obtaining photolysis cross section of molecules adsorbed on surface by monochromatic soft x-ray photons
Authors: Chou L.-C. , Jang C.-Y. , Wu Y.-H. , Tsai W.-C. , Wang S.-K. , Chen J. , Chang S.-C. , Liu C.-C. , Shai Y. , Wen C.-R.
Published: December 2008

Photon-exposure-dependent positive- and negative-ion photon-stimulated desorption (PSD) was proposed to study the photoreactions and obtain the photolysis cross sections of molecules adsorbed on a single-crystal surface by monochromatic soft x-ray photons with energy near the core level of adsorbate. The changes in the F+ and F− PSD ion yields were measured from CF3Cl molecules adsorbed on Si(111)-7×7 at 30K (CF3Cl dose=0.3×1015molecules∕cm2, ∼0.75 monolayer) during irradiation of monochromatic soft x-ray photons near the F(1s) edge. The PSD ion yield data show the following characteristics: (a) The dissociation of adsorbed CF3Cl molecules is due to a combination of direct photodissociation via excitation of F(1s) core level and substrate-mediated dissociation [dissociative attachment and dipolar dissociation induced by the photoelectrons emitting from the silicon substrate]. (b) the F+ ion desorption is associated with the bond breaking of the surface CF3Cl, CF2Cl, CFCl, and SiF species. (c) the F− yield is mainly due to DA and DD of the adsorbed CF3Cl molecules. (d) The surface SiF is formed by reaction of the surface Si atom with the neutral fluorine atom, F+, or F− ion produced by scission of C–F bond of CF3Cl, CF2Cl, or CFCl species. A kinetic model was proposed for the explanation of the photolysis of this submonolayer CF3Cl-covered surface. Based on this model and the variation rates of the F+∕F− signals during fixed-energy monochromatic photon bombardment at 690.2 and 692.6eV [near the F(1s) edge], the photolysis cross section was deduced as a function of energy.
Spherical cap bubbles with a toroidal bubbly wake
Authors: Landel J. R. , Cossu C. , Caulfield C. P.
Published: December 2008

The prediction of the rise speed of large buoyant bubbles is a fundamental fluid mechanics problem relevant to a number of applications ranging from carbon sequestration technology to chemical engineering or astrophysics. Single large bubbles typically have a spherical cap shape with bubbles of larger volume rising faster than the ones of smaller volume. However, except in well-controlled experiments, the released gas splits into a leading cap bubble, followed by a crown of satellite bubbles that can contain up to 50% of the total volume of gas. We find that in this case the satellite bubbles rearrange in a characteristic toroidal crown and the leading bubble takes a lenticular shape. The rise speeds of these multipart bubble systems and the ratios of the torus radii to the leading cap curvature radii are quite constant and predictable in the mean and are furthermore independent of the gas partitioning between the leading lenticular bubble and the crown of satellite bubbles. We also find that this multipart bubble system rises slightly faster than a single cap bubble with the same total injected volume of gas.
Symplectic approach to calculation of magnetic field line trajectories in physical space with realistic magnetic geometry in divertor tokamaks
Authors: Punjabi Alkesh , Ali Halima
Published: December 2008

A new approach to integration of magnetic field lines in divertor tokamaks is proposed. In this approach, an analytic equilibrium generating function (EGF) is constructed in natural canonical coordinates (ψ,θ) from experimental data from a Grad–Shafranov equilibrium solver for a tokamak. ψ is the toroidal magnetic flux and θ is the poloidal angle. Natural canonical coordinates (ψ,θ,φ) can be transformed to physical position (R,Z,φ) using a canonical transformation. (R,Z,φ) are cylindrical coordinates. Another canonical transformation is used to construct a symplectic map for integration of magnetic field lines. Trajectories of field lines calculated from this symplectic map in natural canonical coordinates can be transformed to trajectories in real physical space. Unlike in magnetic coordinates [O. Kerwin, A. Punjabi, and H. Ali, Phys. Plasmas 15, 072504 (2008)], the symplectic map in natural canonical coordinates can integrate trajectories across the separatrix surface, and at the same time, give trajectories in physical space. Unlike symplectic maps in physical coordinates (x,y) or (R,Z), the continuous analog of a symplectic map in natural canonical coordinates does not distort trajectories in toroidal planes intervening the discrete map. This approach is applied to the DIII-D tokamak [J. L. Luxon and L. E. Davis, Fusion Technol. 8, 441 (1985)]. The EGF for the DIII-D gives quite an accurate representation of equilibrium magnetic surfaces close to the separatrix surface. This new approach is applied to demonstrate the sensitivity of stochastic broadening using a set of perturbations that generically approximate the size of the field errors and statistical topological noise expected in a poloidally diverted tokamak. Plans for future application of this approach are discussed.
Scanning near-field optical microscopy study of metallic square hole array nanostructures
Authors: Li Jiang-Yan , Li Zhi-Yuan , Yang Hai-Fang , Jin Ai-Zi
Published: December 2008

We fabricate periodic arrays of simple-square and composite-square air hole nanostructures on a 120 nm thick Au film deposited on glass substrate by focused ion beam technology and study their optical properties by examining the optical near-field distribution via scanning near-field optical microscopy in the near-infrared region. The simple-square nanostructure only contains one square air hole in each unit cell, while the composite-square one contains the same size square air hole in the center and eight smaller square air holes in the periphery. The measured optical near-field patterns for the two nanostructures show very different distribution features. High intensity light spots locate within the central square air hole in the simple-square structure, while they sit at the peripheral smaller square air holes in the composite-square structure. Numerical simulations based on the plane-wave transfer-matrix method have been carried out to analyze the optical near-field patterns for the two metallic nanostructures and agree well with the experimental data. The results indicate that light interaction with metallic nanostructures is very sensitive to even a small change in the subtle geometrical feature. Meanwhile, by comparing near-field patterns with dielectric nanostructures theoretically, we also find that optical confinement is better for gold nanostructures than for dielectric nanostructures.
The accuracy of acoustic birefringence shear wave measurements in sheet metal
Authors: Dixon S. , Fletcher M. P. , Rowlands G.
Published: December 2008

In rolled metal sheet the through thickness shear wave energy is steered into two orthogonal polarizations, parallel and perpendicular to the sheet’s rolling direction. Ultrasonic velocity measurements used to determine the orientation distribution coefficients in thin sheets can be obtained from the fast Fourier transform of the time domain signal. It is observed that the data obtained using a linearly polarized electromagnetic acoustic transducer (EMAT) do not correspond with that obtained using a radially polarized EMAT. An analytical model has been developed, which explains the source of this effect from the using the fast Fourier transform.
Trapping centers engineering by including of nanoparticles into organic semiconductors
Authors: Weis Martin , Lin Jack , Manaka Takaaki , Iwamoto Mitsumasa
Published: December 2008

This paper reports the characteristics of an organic field-effect transistor (OFET) with silicon nanoparticles (NPs) on a semiconductor-gate insulator interface, which work as trapping centers of charge carriers. Charge transport and injection phenomenon were studied by electrical measurements and optical time-resolved microscopy second harmonic generation (TRM-SHG) technique sensitive to injected carrier distribution and internal electric fields. We found that OFETs with low concentration of intrinsic carriers and operating in terms of injection type OFET are extremely sensitive to the internal electric field. An enormous threshold voltage shift due to trapped charge was observed, and the possibility to adjust it by controlling the NP density was found. We demonstrate that the NP film can serve to design the accumulated charge in OFET and thus change in charge injection time and transport properties. The detailed analysis of pentacene OFET based on dielectric properties and the Maxwell–Wagner model reveals internal electric field created by NPs. Additionally, the effect of NPs is discussed with respect to mobility estimated by electrical and TRM-SHG experiment; its decrease is related to deceleration of carrier propagation by trapping effect.
High-density, high-temperature alkali vapor cell
Authors: Lorenz V. O. , Dai X. , Green H. , Asnicar T. R. , Cundiff S. T.
Published: December 2008

We present a vapor cell design that enables resonant optical spectroscopy in high-density, high-temperature alkali metal vapors. Optical access is provided via reflection from the interface between the vapor and a sapphire window. The cell resists corrosion from the highly reactive alkali vapors, in our case, potassium, up to 800 °C (number densities up to 1019 cm−3). The cells maintain their integrity for an average of 100 h above 500 °C with about 10 heating/cooling cycles.
Power generation and shunt damping performance of a single crystal lead magnesium niobate-lead zirconate titanate unimorph: Analysis and experiment
Authors: Erturk A. , Bilgen O. , Inman D. J.
Published: December 2008

This letter investigates the power generation and shunt damping performance of the single crystal piezoelectric ceramic lead magnesium niobate–lead zirconate titanate (PMN-PZT) analytically and experimentally. PMN-PZT is a recently developed interface for energy harvesting and shunt damping with its large piezoelectric constant (−2252 pm/V) and coupling coefficient (0.95) for the transverse piezoelectric mode. A unimorph PMN-PZT cantilever with an aluminum substrate is tested under base excitation and its electromechanical response is predicted with a coupled distributed parameter model. The power generation performance of the device is 138 μW/(g2 cm3) at 1744 Hz, causing 84% tip vibration attenuation due to the resistive shunt damping effect.
Reduction in charged defects associated with oxygen vacancies in hafnia by magnesium incorporation: First-principles study
Authors: Umezawa Naoto , Sato Motoyuki , Shiraishi Kenji
Published: December 2008

Charged defects in a gate insulating oxide significantly degrade electric properties of the field-effect transistors. We report on our analysis of the effects of Mg incorporation into HfO2 upon reduction in the positive charges associated with oxygen vacancies VO+2. Our comprehensive study using first-principles calculations revealed that a Mg atom substituted for Hf is stable in charge negative MgHf−2 and strongly binds with VO+2, neutralizing the defect. This contributes to the suppressing of the electron traps at the defect site, improving the reliability of Hf-based gate oxides.
Carbon nanotubes filled with ferromagnetic alloy nanowires: Lightweight and wide-band microwave absorber
Authors: Lv Ruitao , Kang Feiyu , Gu Jialin , Gui Xuchun , Wei Jinquan , Wang Kunlin , Wu Dehai
Published: December 2008

Thin-walled carbon nanotubes (CNTs) filled with different ferromagnetic alloy (FeCo, FeNi, and FeCoNi) nanowires were prepared by using trichlorobenzene as carbon precursor. They were dispersed into epoxy resin and then coated onto 180×180 mm2 aluminum substrates to form microwave-absorption coatings with 2.0 mm thickness. Reﬂection loss exceeding −5 dB was obtained between 5 and 18 GHz for coating containing 1.3 wt % FeCo-filled CNTs. A minimum reﬂection loss value of −28.2 dB was achieved at 15.2 GHz in FeCoNi-filled CNTs/epoxy coating. The areal densities of coatings are only 2.35 kg/m2, which is favorable for the applications requiring low density.
Soft Spaces, Fuzzy Boundaries, and Metagovernance: The New Spatial Planning in the Thames Gateway
Authors: Allmendinger Phil , Haughton Graham
Published: December 2008

This paper examines the changing practices of spatial planning, critically engaging with state theory to argue that a new generation of ‘soft spaces’ and ‘fuzzy boundaries' occupies a key position in the emergent planning system. In the process we question whether privileged scales and sectors can meaningfully be identified in current state-restructuring processes. We use interviews with key national policy makers and a case study of the Thames Gateway to test our ideas.
The Financial Centres of Shanghai and Hong Kong: Competition or Complementarity?
Authors: Karreman Bas , van der Knaap Bert
Published: December 2008

The contemporary rise of China in the new geo-economy is increasingly pressurising the spatial distribution of financial activity in mainland China and Hong Kong. With the reemergence of Shanghai, many people foresee the future demise of Hong Kong as the most important financial centre for the Chinese mainland. This paper shows that this conviction seems rather premature. From an examination of the regional distribution pattern of the mainland-China-based companies listed on the stock exchanges of Shanghai and Hong Kong it appears that both financial centres have relatively distinct hinterlands. Furthermore, it is shown that the exchanges of Shanghai and Hong Kong differ strongly in terms of sectoral specialisation. These results indicate that both centres reveal a considerable amount of complementarity.
Simultaneous Coefficient Penalization and Model Selection in Geographically Weighted Regression: The Geographically Weighted Lasso
Authors: Wheeler David C
Published: December 2008

In the field of spatial analysis, the interest of some researchers in modeling relationships between variables locally has led to the development of regression models with spatially varying coefficients. One such model that has been widely applied is geographically weighted regression (GWR). In the application of GWR, marginal inference on the spatial pattern of regression coefficients is often of interest, as is, less typically, prediction and estimation of the response variable. Empirical research and simulation studies have demonstrated that local correlation in explanatory variables can lead to estimated regression coefficients in GWR that are strongly correlated and, hence, problematic for inference on relationships between variables. The author introduces a penalized form of GWR, called the ‘geographically weighted lasso’ (GWL) which adds a constraint on the magnitude of the estimated regression coefficients to limit the effects of explanatory-variable correlation. The GWL also performs local model selection by potentially shrinking some of the estimated regression coefficients to zero in some locations of the study area. Two versions of the GWL are introduced: one designed to improve prediction of the response variable, and one more oriented toward constraining regression coefficients for inference. The results of applying the GWL to simulated and real datasets show that this method stabilizes regression coefficients in the presence of collinearity and produces lower prediction and estimation error of the response variable than does GWR and another constrained version of GWR—geographically weighted ridge regression.
Migration, Urbanization, and Drug Use and Casual Sex in China: A Multilevel Analysis
Authors: Yang Xiushi , Luo Huasong
Published: December 2008

Using data from a survey conducted in 2003 and employing multilevel modeling, this paper examines the impact of migration and urbanization on drug abuse and casual sex in China. The results suggest that being a migrant predicts significantly higher odds of having casual sex but lower odds of drug abuse. Living in an urban place is a significant risk factor for both illicit drug use and casual sex. There are significant cross-community (primary sampling unit) variances in the random intercept component, suggesting that the likelihood of drug abuse and casual sex is influenced by where one lives. After controlling for differences in individual demographic and psychosocial characteristics, social influences, and community factors, the intracommunity correlation is higher for drug use (0.32) than for casual sex (0.11). The results of random coefficient models further suggest that the impact of migration on drug use and casual sex also varies across communities.
A P
IIB
-type Ca
2+
-ATPase is essential for stress adaptation in
Physcomitrella patens
Authors: Qudeimat Enas , Faltusz Alexander M. C. , Wheeler Glen , Lang Daniel , Holtorf Hauke , Brownlee Colin , Reski Ralf , Frank Wolfgang
Published: December 2008

Transient cytosolic Ca
2+
([Ca
2+
]
cyt
) elevations are early events in plant signaling pathways including those related to abiotic stress. The restoration of [Ca
2+
]
cyt
to prestimulus levels involves ATP-driven Ca
2+
pumps, but direct evidence for an essential role of a plant Ca
2+
-ATPase in abiotic stress adaptation is missing. Here, we report on a stress-responsive Ca
2+
-ATPase gene (
PCA1
) from the moss
Physcomitrella patens.
Functional analysis of
PCA1
in a Ca
2+
transport-deficient yeast mutant suggests that
PCA1
encodes a P
IIB
-type Ca
2+
-ATPase harboring an N-terminal autoinhibitory domain. In vivo localizations identified membranes of small vacuoles as the integration site for a PCA1:GFP fusion protein.
PCA1
mRNA levels are up-regulated by dehydration, NaCl, and abscisic acid, and
PCA1
loss-of-function mutants (Δ
PCA1
) exhibit an enhanced susceptibility to salt stress. The Δ
PCA1
lines show sustained elevated [Ca
2+
]
cyt
in response to salt treatment in contrast to WT that shows transient Ca
2+
elevations, indicating a direct role for PCA1 in the restoration of prestimulus [Ca
2+
]
cyt
. The altered Ca
2+
response of the Δ
PCA1
mutant lines correlates with altered expression levels of stress-induced genes, suggesting disturbance of a stress-associated signaling pathway. We propose that PCA1 is an essential component for abiotic stress adaptation in
Physcomitrella
involved in the generation of a specific salt-induced Ca
2+
signature.
RETRACTED: A genomic approach to colon cancer risk stratification yields biologic insights into therapeutic opportunities
Authors: Garman Katherine S. , Acharya Chaitanya R. , Edelman Elena , Grade Marian , Gaedcke Jochen , Sud Shivani , Barry William , Diehl Anna Mae , Provenzale Dawn , Ginsburg Geoffrey S. , Ghadimi B. Michael , Ried Thomas , Nevins Joseph R. , Mukherjee Sayan , Hsu David , Potti Anil
Published: December 2008

Gene expression profiles provide an opportunity to dissect the heterogeneity of solid tumors, including colon cancer, to improve prognosis and predict response to therapies. Bayesian binary regression methods were used to generate a signature of disease recurrence in patients with resected early stage colon cancer validated in an independent cohort. A 50-gene signature was developed that effectively distinguished early stage colon cancer patients with a low or high risk of disease recurrence. RT-PCR analysis of the 50-gene signature validated 9 of the top 10 differentially expressed genes. When applied to two independent validation cohorts of 55 and 73 patients, the 50-gene model accurately predicted recurrence. Standard Kaplan–Meier survival analysis confirmed the prognostic accuracy (
P
< 0.01, log rank), as did multivariate Cox proportional hazard models. We tested potential targeted therapeutic options for patients at high risk for disease recurrence and found a clinically important relationship between sensitivity to celecoxib, LY-294002 (PI3kinase inhibitor), retinol, and sulindac in colon cancer cell lines expressing the poor prognostic phenotype (
P
< 0.01,
t
test), which performed better than standard chemotherapy (5-FU and oxaliplatin). We present a genomic strategy in early stage colon cancer to identify patients at highest risk of recurrence. An ability to move beyond current staging by refining the estimation of prognosis in early stage colon cancer also has implications for individualized therapy.