bluuebunny/crossref_metadata_2025 huggingface dataset:
The “natural history” of health technology assessment
Authors: Battista Renaldo N. , Hodge Matthew J.
Published: June 2009

The collective experience of health technology assessment (HTA) in different countries delineates a pattern of development, a “natural history,” of HTA in three phases: emergence, consolidation, and expansion. This study examines the rationale for HTA, definitions of its scope and breadth, its methods and organizational models, and its knowledge translation strategies, as HTA moves from one phase to the next. The study then identifies factors that facilitate or delay the transitions.
ESTIMATION FOR A NONSTATIONARY SEMI-STRONG GARCH(1,1) MODEL WITH HEAVY-TAILED ERRORS
Authors: Linton Oliver , Pan Jiazhu , Wang Hui
Published: June 2009

This paper studies the estimation of a semi-strong GARCH(1,1) model when it does not have a stationary solution, where semi-strong means that we do not require the errors to be independent over time. We establish necessary and sufficient conditions for a semi-strong GARCH(1,1) process to have a unique stationary solution. For the nonstationary semi-strong GARCH(1,1) model, we prove that a local minimizer of the least absolute deviations (LAD) criterion converges at the rate$\root \of n $to a normal distribution under very mild moment conditions for the errors. Furthermore, when the distributions of the errors are in the domain of attraction of a stable law with the exponentκ∈ (1, 2), it is shown that the asymptotic distribution of the Gaussian quasi-maximum likelihood estimator (QMLE) is non-Gaussian but is some stable law with the exponentκ∈ (0, 2). The asymptotic distribution is difficult to estimate using standard parametric methods. Therefore, we propose a percentile-t subsampling bootstrap method to do inference when the errors are independent and identically distributed, as in Hall and Yao (2003). Our result implies that the least absolute deviations estimator (LADE) is always asymptotically normal regardless of whether there exists a stationary solution or not, even when the errors are heavy-tailed. So the LADE is more appealing when the errors are heavy-tailed. Numerical results lend further support to our theoretical results.
GMM ESTIMATION FOR DYNAMIC PANELS WITH FIXED EFFECTS AND STRONG INSTRUMENTS AT UNITY
Authors: Han Chirok , Phillips Peter C. B.
Published: June 2009

This paper develops new estimation and inference procedures for dynamic panel data models with fixed effects and incidental trends. A simple consistent GMM estimation method is proposed that avoids the weak moment condition problem that is known to affect conventional GMM estimation when the autoregressive coefficient (ρ) is near unity. In both panel and time series cases, the estimator has standard Gaussian asymptotics for all values of ρ ∈ (−1, 1] irrespective of how the composite cross-section and time series sample sizes pass to infinity. Simulations reveal that the estimator has little bias even in very small samples. The approach is applied to panel unit root testing.
POOLING ESTIMATES WITH DIFFERENT RATES OF CONVERGENCE: A MINIMUMχ2APPROACH WITH EMPHASIS ON A SOCIAL INTERACTIONS MODEL
Authors: Lee Lung-fei
Published: June 2009

This paper considers the extension of the classical minimum distance approach for the pooling of estimates with various rates of convergence. Under a setting where relatively high rates of convergence can be attained, the minimum distance estimators are shown to be consistent and asymptotically normally distributed. The constrained estimates can be efficient relative to the unconstrained ones. The minimized distance function is shown to be asymptoticallyχ2-distributed, and can be used as a goodness-of-fit test for the constraints. As the extension is motivated by some social interactions models, which are of interest in their own right, we discuss this approach for the estimation and testing of a social interactions model.
SPECIFICATION OF VARIANCE MATRICES FOR PANEL DATA MODELS
Authors: Magnus Jan R. , Muris Chris
Published: June 2009

Many regression models have two dimensions, say time (t = 1,…,T) and households (i = 1,…,N), as in panel data, error components, or spatial econometrics. In estimating such models we need to specify the structure of the error variance matrix Ω, which is of dimension T N × T N. If T N is large, then direct computation of the determinant and inverse of Ω is not practical. In this note we define structures of Ω that allow the computation of its determinant and inverse, only using matrices of orders T and N, and at the same time allowing for heteroskedasticity, for household- or station-specific autocorrelation, and for time-specific spatial correlation.
Episodic outbreaks bias estimates of age-specific force of infection: a corrected method using measles as an example
Authors: FERRARI M. J. , DJIBO A. , GRAIS R. F. , GRENFELL B. T. , BJØRNSTAD O. N.
Published: June 2009

Understanding age-specific differences in infection rates can be important in predicting the magnitude of and mortality in outbreaks and targeting age groups for vaccination programmes. Standard methods to estimate age-specific rates assume that the age-specific force of infection is constant in time. However, this assumption may easily be violated in the face of a highly variable outbreak history, as recently observed for acute immunizing infections like measles, in strongly seasonal settings. Here we investigate the biases that result from ignoring such fluctuations in incidence and present a correction based on the epidemic history. We apply the method to data from a measles outbreak in Niamey, Niger and show that, despite a bimodal age distribution of cases, the estimated age-specific force of infection is unimodal and concentrated in young children (<5 years) consistent with previous analyses of age-specific rates in the region.
Relationship of cholera incidence to El Niño and solar activity elucidated by time-series analysis
Authors: OHTOMO K. , KOBAYASHI N. , SUMI A. , OHTOMO N.
Published: June 2009

Using time-series analysis, we investigated the monthly cholera incidence in Dhaka, Bangladesh during an 18-year period for its relationship to the sea surface temperature (SST) linked to El Niño, and to the sunspot number. Dominant periodic modes identified for cholera incidence were 11·0, 4·8, 3·5, 2·9, 1·6, 1·0 and 0·5 years. The majority of these modes, e.g. the 11·0-, 4·8-, 3·5-, 1·6- and 1·0-year modes, were essentially consistent with those obtained for the SST data (dominant modes: 5·1, 3·7, 2·5, 2·1, 1·5, 1·0 years) and the sunspot number data (dominant modes: 22·1, 11·1, 7·3, 4·8, 3·1 years). We confirmed that the variations of cholera incidence were synchronous with SSTs, and were inversely correlated to the sunspot numbers. These results suggest that the cholera incidence in Bangladesh may have been influenced by the occurrence of El Niño and also by the periodic change of solar activity.
Assessing the risk from emerging infections
Authors: MORGAN D. , KIRKBRIDE H. , HEWITT K. , SAID B. , WALSH A. L.
Published: June 2009

Emerging infections pose a constant threat to society and can require a substantial response, thus systems to assess the threat level and inform prioritization of resources are essential. A systematic approach to assessing the risk from emerging infections to public health in the UK has been developed. This qualitative assessment of risk is performed using algorithms to consider the probability of an infection entering the UK population, and its potential impact, and to identify knowledge gaps. The risk assessments are carried out by a multidisciplinary, cross-governmental group of experts working in human and animal health. This approach has been piloted on a range of infectious threats identified by horizon scanning activities. A formal risk assessment of this nature should be considered for any new or emerging infection in humans or animals, unless there is good evidence that the infection is neither a recognized human disease nor a potential zoonosis.
Serotype and antibiotic resistance of isolates from patients with invasive pneumococcal disease in Japan
Authors: CHIBA N. , MOROZUMI M. , SUNAOSHI K. , TAKAHASHI S. , TAKANO M. , KOMORI T. , SUNAKAWA K. , UBUKATA K.
Published: June 2009

Invasive pneumococcal disease (IPD) is of concern in Japan, where the heptavalent pneumococcal conjugate vaccine (PCV7) is unavailable. We determined serotypes, genotypes indicating β-lactam resistance, and antibiotic susceptibilities of 496 isolates from normally sterile sites in patients (193 children, 303 adults) from 186 institutions between August 2006 and July 2007. Disease presentations included sepsis (46·2%), pneumonia (31·5%), and meningitis (17·5%). Mortality was 1·4% in children and 22·1% in adults, many of whom had underlying diseases. In children, serotype 6B (22·5%) was followed by 19F (14·1%), and 14 (13·1%); potential coverages of PCV7 and PCV13 were 75·4% and 93·7%, respectively. In adults, serotype 12F (14·3%) was followed by 3 (11·3%), and 6B (10·3%); 23-valent polysaccharide vaccine (PPV23) coverage was 85·4%. Most serotype 12F strains were gPISP, withpbp2bgene alteration; carbapenem had an excellent MIC90.PCV7 is recommended for children and PPV23 for adults to increase prevention against IPD.
Common signatures for gene expression in postnatal patients with patent arterial ducts and stented arteries
Authors: Mueller Peter P. , Drynda Andreas , Goltz Diane , Hoehn René , Hauser Hansjörg , Peuster Matthias
Published: June 2009

The detailed molecular processes associated with postnatal remodelling of blood vessels are presently not understood. To characterize the response of the patients undergoing stenting of the patent arterial duct, we harvested samples of vascular tissue during surgical repair. Histological analysis of explanted ducts confirmed the patency of the ducts immediately after birth. As expected, a previously unstented duct that was examined 7 months after birth had become closed and ligamentous. Whole genome expression profiling of these samples showed that a large fraction, over 10%, of the gene sequences examined were expressed differentially between the samples taken from patients with open as opposed to the ligamentous duct. Interestingly, in 2 patients in whom closure was prevented by insertion of stents, one showed an expression profile that was similar to that of the patient initially having an unstented open duct, whereas the other was more closely related to the profile of the patient with a duct that had become ligamentous. Moreover, in 2 specimens obtained from patients with stented pulmonary arteries, a large fraction of the genes that were differentially expressed were identical to the pattern seen in the samples from the patients with open ducts. The gene regulation appeared to be independent of the nature of the respective malformations, and the site of implantation of the stents. These findings suggest that a set of differentially expressed genes are indicative for a transcriptional programme in neonatal remodelling of the arterial duct, which may also take place in patients in whom ductal closure is prevented by stents, or in those with stented pulmonary arteries. The differentially expressed genes included a significant number of extracellular matrix synthetic genes, and could therefore be predictive for vascular remodelling and neointimal formation.
Theory and experimental validation of a Class E PA above theoretical maximum frequency
Authors: Cipriani Elisa , Colantonio Paolo , Giannini Franco , Giofré Rocco
Published: June 2009

This paper reports an investigation and a proposed solution to design Class E power amplifiers above the theoretical maximum frequency allowed by the adopted active device. Starting from the traditional time domain analysis, a numerical algorithm has been developed and presented in order to extend Class E feasibility through the optimization of the output voltage waveform. A hybrid Class E amplifier in laterally diffused metal oxide semiconductor (LDMOS) technology has been designed and measured. The final amplifier shows an output power of more than 10 W with an associated efficiency of 49% (power added efficiency (PAE) = 45%) over a 100-MHz bandwidth around 2.14 GHz.
Design considerations for the hot embossing of microstrip antennas on plastic foils
Authors: Kilian Andreas , Fuchs Michael , Schmidt Lorenz-Peter
Published: June 2009

In this contribution, fundamental design considerations for a novel metallization technique to realize millimeter-wave microstrip structures are presented. This hot embossing technology is a fast and economic process originating from the production of three-dimensional molded interconnect devices. Conductive structures are coated onto plastic parts or plastic foils using a heated stamp. This approach shows high potential and therefore will be investigated for the fabrication of low-cost printed antennas at millimeter-wave frequencies. The focus of this contribution is on design guidelines considering process parameters and interactions with substrate and copper foil characteristics derived from the fabrication and measurement of single microstrip patch antenna prototypes for radar applications in the industrial, scientific and medical (ISM) band at 24 GHz. Far-reaching potential lies in the utilization of the three-dimensional manufacturing technology for the construction of conformal integrated antenna systems based on the thermoforming capabilities of polymer substrates.
Theoretical performance of reiterated LMMSE filtering and coded radar waveforms
Authors: Ruggiano Mayazzurra , Stolp Emiel , van Genderen Piet
Published: June 2009

Orthogonal frequency division multiplexing (OFDM) waveforms offer strong advantages for integrated communication and radar systems. However, they exhibit inherent high-range sidelobes after matched filtering when standard communication constellation symbols are used for the coding of the carriers. Consequently, they require filtering at the receiver that can serve for sidelobe suppression in order to avoid target masking. However, unmasking is not the only concern; it is crucial to evaluate the filtering scheme both in terms of sidelobe suppression capability and in terms of output signal-to-noise ratio. This last criterion is essential when aiming at also detecting weaker reflections. In this paper the theoretical performance of the reiterated filtering technique based on linear minimum mean square error (LMMSE) is derived and compared to the matched filter. The unmasking capabilities are relevant, but also output power figures. Complex-valued filter output peaks are also evaluated and compared to the matched filter output peaks. Moreover, the performance of reiterated LMMSE is evaluated for OFDM communication-encoded radar waveforms.
A rugged 100 W high-voltage vertical MOSFET L-band radar device
Authors: Battaglia Brian , Rice Dave , Le Phuong , Gogoi Bishnu , Purchine Mike , Davies Robert , Wright Walt , Lutz Dave , Elliott Alex , Tran Son , Neeley Robert , Cai Will
Published: June 2009

The silicon vertical MOSFET RF power amplifier described in this paper is the industry’s first to utilize high-voltage vertical technology. Operating under pulse conditions of 200 µs pulse width and 10% duty cycle, it delivers more than 100 W of peak power. Operating in Class AB with only 50 mA of bias current the device achieves more than 20 dB of gain and 47% power added efficiency at P1dB compression across 200 MHz of bandwidth at L-band from 1.2 to 1.4 GHz. The DC characteristics include a BVdss of 95 V enabling high-voltage operation with a 48 V power supply. The device is inherently rugged and withstands mismatch tolerances of 20:1 voltage standing wave ratio over all phase angles at full rated power and with 3 dB of input power over-drive and 10% greater than nominal voltage.
Design and evaluation of 20-GHz power amplifiers in 130-nm CMOS
Authors: Ferndahl Mattias , Johansson Ted , Zirath Herbert
Published: June 2009

The use of 130-nm CMOS for power amplifiers at 20 GHz is explored through a set of power amplifiers as well as transistor level measurements. The power amplifiers explore single versus cascode configuration, smaller versus larger transistor sizes, and the combination of two amplifiers using power splitters/combiners. A maximum output power of 63 mW at 20 GHz was achieved. Transistor-level characterization using load pull measurements on 1-mm gate width transistors yielded 148-mW/mm output power. Transistor modeling and layout for power amplifiers are also discussed. An estimate on the maximum achievable output at 20 GHz from 130-nm CMOS power amplifiers, based on findings in this paper and the literature, is finally presented.
Space-FFT-accelerated marching-on-in-degree methods for finite periodic structures
Authors: Geranmayeh Amir , Ackermann Wolfgang , Weiland Thomas
Published: June 2009

A fast, yet unconditionally stable, solution of time-domain electric field integral equations (TD EFIE) pertinent to the scattering analysis of uniformly meshed and/or periodic conducting structures is introduced. A one-dimensional discrete fast Fourier transform (FFT)-based algorithm is proffered to expedite the calculation of the recursive spatial convolution products of the Toeplitz–block–Toeplitz retarded interaction matrices in a new marching-without-time-variable scheme. Additional saving owing to the system periodicity is concatenated with the Toeplitz properties due to the uniform discretization in multi-level sense. The total computational cost and storage requirements of the proposed method scale as O(Nt2Nslog Ns) and O(Nt Ns), respectively, as opposed to O(Nt2Ns2) and O(NtNs2) for classical marching-on-in-order methods, where Nt and Ns are the number of temporal and spatial unknowns, respectively. Simulation results for arrays of plate-like and cylindrical scatterers demonstrate the accuracy and efficiency of the technique.
The equal application of the laws of war: a principle under pressure
Authors: Roberts Adam
Published: June 2009

The ‘equal application’ principle is that in international armed conflicts, the laws of war apply equally to all who are entitled to participate directly in hostilities, irrespective of the justice of their causes. The principle, which depends on maintaining separation betweenjus ad bellumandjus in bello, faces serious challenges in contemporary armed conflicts and discourses. Some variations of the principle may be inevitable. However, it has a firm basis in treaties and in historical experience. It is the strongest practical basis that exists, or is likely to exist, for maintaining certain elements of moderation in war. The rival proposition – that the rights and obligations of combatants under the laws of war should apply in a fundamentally unequal manner, depending on which side is deemed to be the more justified – is unsound in conception, impossible to implement effectively and dangerous in its effects.
Physical forcing of nitrogen fixation and diazotroph community structure in the North Pacific subtropical gyre
Authors: Church Matthew J. , Mahaffey Claire , Letelier Ricardo M. , Lukas Roger , Zehr Jonathan P. , Karl David M.
Published: June 2009

Dinitrogen (N2) fixing microorganisms (termed diazotrophs) exert important control on the ocean carbon cycle. However, despite increased awareness on the roles of these microorganisms in ocean biogeochemistry and ecology, the processes controlling variability in diazotroph distributions, abundances, and activities remain largely unknown. In this study, we examine 3 years (2004–2007) of approximately monthly measurements of upper ocean diazotroph community structure and rates of N2 fixation at Station ALOHA (22°45′N, 158°W), the field site for the Hawaii Ocean Time‐series program in the central North Pacific subtropical gyre (NPSG). The structure of the N2‐fixing microorganism assemblage varied widely in time with unicellular N2‐fixing microorganisms frequently dominating diazotroph abundances in the late winter and early spring, while filamentous microorganisms (specifically various heterocyst‐forming cyanobacteria and Trichodesmium spp.) fluctuated episodically during the summer. On average, a large fraction (∼80%) of the daily N2 fixation was partitioned into the biomass of <10 μm microorganisms. Rates of N2 fixation were variable in time, with peak N2 fixation frequently coinciding with periods when heterocystous N2‐fixing cyanobacteria were abundant. During the summer months when sea surface temperatures exceeded 25.2°C and concentrations of nitrate plus nitrite were at their annual minimum, rates of N2 fixation often increased during periods of positive sea surface height anomalies, as reflected in satellite altimetry. Our results suggest mesoscale physical forcing may comprise an important control on variability in N2 fixation and diazotroph community structure in the NPSG.
Spatial changes in soil organic carbon density and storage of cultivated soils in China from 1980 to 2000
Authors: Yu Yanyan , Guo Zhengtang , Wu Haibin , Kahmann Julia A. , Oldfield Frank
Published: June 2009

We address the spatial changes in organic carbon density and storage in cultivated soils in China from 1980 to 2000 on the basis of measured data from individual studies and those acquired during the second national soil survey in China. The results show a carbon gain in ∼66% of the cultivated area of China as a whole with the increase in soil organic carbon (SOC) density mostly ranging from 10% to 30%. Soil organic carbon density increased in fluvi‐aquic soils (fluvisols, Food and Agriculture Organization (FAO) of the United Nations) in north China, irrigated silting soils (calcaric fluvisols) in northwest China, latosolic red earths (haplic acrisols/alisols), and paddy soils (fluvisols/cambisols) in south China. In contrast, significant decreases are observed in black soils (phaeozems) in northeast China and latosols (haplic acrisols) in southwest China. No significant changes are detected in loessial soils (calcaric regosols) and dark loessial soils (calcisols) in the loess plateau region. The total SOC storage and average density in the upper 20 cm in the late 1990s are estimated to be ∼5.37 Pg C and 2.77 kg/m2, respectively, compared with the values of ∼5.11 Pg C and 2.63 kg/m2 in the early 1980s. This reveals an increase of SOC storage of 0.26 Pg C and suggests an overall carbon sink for cultivated soils in China, which has contributed 2–3% to the global terrestrial ecosystem carbon absorption from 1980 to 2000. Statistical analyses suggest an insignificant contribution to the observed SOC increase from climate change, and we infer that it is mostly attributable to improved agricultural practices. Despite the SOC density increases over 20 years, the SOC density of the cultivated soils in China in the late 1990s is still ∼30% lower compared to their uncultivated counterparts in comparable soil types, suggesting a considerable potential for SOC restoration through improving management practices. Assuming a restoration of ∼50% of the lost SOC in the next 30–50 years, these soils could potentially absorb ∼1.03 Pg C from the atmosphere.
Model investigation of the influence of the crustal magnetic field on the oxygen ion distribution in the near Martian tail
Authors: Li Lei , Zhang Yiteng
Published: June 2009

To investigate the influence of the Martian crustal magnetic field on the acceleration and escape of the planetary ions in the near tail region, the distributions of planetary oxygen ions are studied by means of test particle simulation in an electromagnetic environment created by a recent multispecies Magnetohydrodynamics (MHD) simulation of the solar wind interaction with Mars, with crustal field included or excluded. Results under different crustal field conditions are compared to determine the effects of crustal field. It is found that when crustal field is present, draped magnetic field lines are replaced by closed field lines in the near tail region and the electric field is also intensified because of the Hall effect. As a result, the oxygen ion distribution reveals distinct stream structures in the tail region when crustal field is included, with one hot stream at the central tail and two cold streams at the flank of the tail. Some energetic ions inside the hot stream are accelerated toward the planet, instead of escaping downstream.
Solar flares and solar subphotospheric vorticity
Authors: Komm R. , Hill F.
Published: June 2009

We explore the relation between surface magnetic flux of the sun and subsurface flow vorticity for flaring and nonflaring solar active regions. For this purpose, we use a data set consisting of 1009 active regions, including the vorticity measurements of their subsurface flows derived from high‐resolution global oscillation network group (GONG) helioseismology data and the corresponding X‐ray flare data from the geostationary operation environmental satellite (GOES). Using quantities averaged over the disk passage of active regions, we find that, while there is a considerable spread of the flux and vorticity values, they are more or less linearly related. We distinguish the level of flare activity by X‐ray flare class and find that large flux or large vorticity values are sufficient for an active region to produce low‐intensity C‐class flares. Active regions that produce high‐intensity X‐class flares are characterized by large values of both flux and vorticity. Active regions that produce M‐class flares of intermediate intensity are characterized by large vorticity values. The inclusion of solar subsurface vorticity thus helps to distinguish between flaring and nonflaring active regions.
Three‐dimensional model of Hellenic Arc deformation and origin of the Cretan uplift
Authors: Ganas Athanassios , Parsons Tom
Published: June 2009

The Hellenic Arc of Greece is the most seismically active part of Europe, but little is know about its mechanics. We modeled deformation along the arc using a finite element model. The model was intended to capture large‐scale 3‐D structure of Nubian plate subduction beneath the Aegean block and its deformational consequences. The shape of the interface was developed using mapped traces at the surface and earthquake hypocenters at depth. Model block motions were constrained by recent compilations of GPS velocity vectors. We simulated a 10 ka period of convergence between Nubia and the Aegean and calculated the strain field in the overriding plate as well as the spatial distribution and orientation of differential stress (∣σ1 − σ3∣). From these calculations we derived testable quantities such as the expected seismic moment rate on the interplate contact, uplift pattern, and distribution of strain modes. Our relatively simple model broadly reproduced observed uplift patterns, earthquake activity, and loci of extension and contraction. The model showed a localization of uplift near the island of Crete, where the fastest Aegean uplift rates are well documented. Comparison of calculated expected seismic moment and observed earthquake catalogs implies a nearly fully coupled interplate contact. On the basis of our modeling results, we suggest that south Aegean deformation is driven primarily by the fast moving (∼33 mm a−1) Aegean upper plate overriding a nearly stalled (∼5 mm a−1) Nubian lower plate. This tectonic setting thus more closely resembles a continental thrust than it does a typical oceanic subduction zone.
Spatial variations of P wave attenuation in the mantle beneath North America
Authors: Hwang Yong Keun , Ritsema Jeroen , Goes Saskia
Published: June 2009

We estimate the spatial variation of the seismic parameter t* using teleseismic (epicentral distance = 30°–85°) P wave spectra of about 200 deep (focal depths > 200 km) earthquakes recorded by 378 broadband seismometers in the United States and Canada. Relative P wave spectral ratios up to 1 Hz for about 63,000 station pairs with high signal‐to‐noise ratio and impulsive P waveforms are inverted for t*P by least squares inversion. The continental‐scale t*P pattern correlates to the age of geological terrains and the seismic, heat flow, gravity, and magnetic variations across North America. Predominantly low values of t*P are obtained in stable central North America (SNA), and high t*P values are obtained for stations in the tectonically active western part of the continent (TNA). This variation is similar to that observed previously in short‐period amplitude anomalies, spectral ratio variations, and ScS reverberations. On average, we resolve a contrast in t*P between SNA and TNA of about 0.2 s. We resolve regional variations in t*P, which correlate with tectonics. Relatively low t*P is associated with currently active subduction below Alaska. Relatively high t*P is found in SNA below the Appalachians and the Gulf Coast. The consistency between t*P and tectonics suggests that the observed variations in t*P are, on the scale of around 200–500 km, predominantly due to intrinsic attenuation. The similar patterns in t*P and predicted values for a recent global attenuation model confirm this further. The compatibility with the t*P computed for attenuation estimated via a thermal interpretation of shear wave velocity anomalies illustrates that variations in seismic velocity are predominantly due to physical effects with a strong attenuation signature, most likely temperature or a combination of temperature and water content.
Representing eddy stress in an Arctic Ocean model
Authors: Holloway Greg , Wang Zeliang
Published: June 2009

Experiences with a number of ocean models have shown Arctic Ocean circulation to be quite dependent upon assumptions about eddy stresses. A key difference is between assuming that subgrid eddies act as friction and assuming that eddies act to generate entropy, propelling mean flows (sometimes called “neptune”). Fisheries and Oceans Canada is developing global ocean and sea ice modeling after Nucleus for European Modeling of the Ocean (NEMO). We have modified NEMO to include neptune as an alternative to friction. Consistent with previous modeling studies, our results show marked impacts. Neptune supports narrow cyclonic midwater and deepwater currents around the peripheries of Arctic basins. Neptune also induces two‐way flows through channels in the Canadian Archipelago and limits the width of the ice tongue exiting at Fram Strait.
Effects of ejecta accumulation on the crater population of asteroid 433 Eros
Authors: Blitz C. , Lognonné P. , Komatitsch D. , Baratoux D.
Published: June 2009

The crater population of asteroid 433 Eros exhibits a deficit in small crater diameters that has been suggested to result from impact‐induced seismic shaking initiating downslope movements of regolith material, covering these small craters. As in lunar maria, saturation equilibrium was expected to characterize the crater population of Eros, but was surprisingly not shown by the data set. The surface of Eros displays evidence of burial by regolith especially for boulders, suggesting that ejecta coverage erases the craters in addition to seismic shaking erasure. In this work we investigate the production and erasure of craters by impact ejecta and compare derived crater size distributions with those measured for Eros. We simulate a bombardment of Eros by an impactor population derived from the Main Asteroid Belt and estimate the crater and ejecta characteristics with a scaling law, allowing ejecta to progressively create a regolith blanket. Assuming the contribution of the ejecta blanketing process only, we find a good agreement between the simulated and the observed population of 250 m to 4 km diameter craters for exposure times of 600 Ma and 400 Ma. This suggests a major impact or breakup that occurred about 500 Ma ago, inducing a surface reset. A mismatch for craters with a diameter smaller than ∼100 m remains, indicating that seismic shaking (or another erasure process) is still necessary to explain their low number. Our simulations emphasize the importance of an accurate modeling of both processes to fully understand and interpret the small body size‐frequency crater curves.
Improving simulated soil temperatures and soil freeze/thaw at high‐latitude regions in the Simple Biosphere/Carnegie‐Ames‐Stanford Approach model
Authors: Schaefer Kevin , Zhang Tingjun , Slater Andrew G. , Lu Lixin , Etringer Andrew , Baker Ian
Published: June 2009

Proper simulation of soil temperature and permafrost at high latitudes in land surface models requires proper simulation of the processes that control snowpack development. The Simple Biosphere/Carnegie‐Ames‐Stanford Approach (SiBCASA) did not account for depth hoar development and wind compaction, which dominate snow processes at high latitudes. Consequently, SiBCASA had difficulty properly simulating seasonal soil freeze/thaw and permafrost. We improved simulated soil temperatures at high latitudes by (1) incorporating a snow classification scheme that includes depth hoar development and wind compaction, (2) including the effects of organic matter on soil physical properties, and (3) increasing the soil column depth. We ran test simulations at eddy covariance flux tower sites using the North American Regional Reanalysis (NARR) as input meteorology. The NARR captured the observed variability in air temperature, but tended to overestimate precipitation. These changes produced modest improvements in simulated soil temperature at the midlatitude sites because the original snow model already included the weight compaction, thermal aging, and melting processes that dominate snowpack evolution at these locations. We saw significant improvement in simulated soil temperatures and active layer depth at the high‐latitude tundra and boreal forest sites. Adding snow classifications had the biggest effect on simulated soil temperatures at the tundra site while the organic soil properties had the biggest effect at the boreal forest site. Implementing snow classes, a deeper soil column, or organic soil properties separately was not sufficient to produce realistic soil temperatures and freeze/thaw processes at high latitudes. Only the combined effects of simultaneously implementing all three changes significantly improved the simulated soil temperatures and active layer depth at the tundra and boreal sites.
How old is the Baikal Rift Zone? Insight from apatite fission track thermochronology
Authors: Jolivet M. , De Boisgrollier T. , Petit C. , Fournier M. , Sankov V. A. , Ringenbach J.‐C. , Byzov L. , Miroshnichenko A. I. , Kovalenko S. N. , Anisimova S. V.
Published: June 2009

Apatite fission track analysis (AFTA) data are used to bring new light on the long‐term and recent history of the Baikal rift region (Siberia). We describe the evolution of the topography along a NW–SE profile from the Siberian platform to the Barguzin range across the Baikal–southern Patom range and the northern termination of Lake Baikal. Our results show that the Baikal‐Patom range started to form in the Early Carboniferous and was reactivated in Middle Jurassic–Lower Cretaceous times during the orogenic collapse of the Mongol‐Okhotsk belt. Samples located in the Siberian platform recorded a continuous sedimentation up to the early Carboniferous but remain unaffected by later tectonic episodes. The Barguzin basin probably started to form as early as Late Cretaceous, suggesting a continuum of deformation between the postorogenic collapse and the opening of the Baikal Rift System (BRS). The initial driving mechanism for the opening of the BRS is thus independent from the India‐Asia collision. AFTA show a late Miocene–early Pliocene increase in tectonic extension in the BRS that confirms previous thoughts and might reflect the first significant effect of the stress field generated by the India‐Asia collision.
Stratospheric ozone depletion reduces ocean carbon uptake and enhances ocean acidification
Authors: Lenton Andrew , Codron Francis , Bopp Laurent , Metzl Nicolas , Cadule Patricia , Tagliabue Alessandro , Le Sommer Julien
Published: June 2009

Observational and atmospheric inversion studies find that the strength of the Southern Ocean carbon dioxide (CO2) sink is not increasing, despite rising atmospheric CO2. However, this is yet to be captured by contemporary coupled‐climate‐carbon‐models used to predict future climate. We show that by accounting for stratospheric ozone depletion in a coupled‐climate‐carbon‐model, the ventilation of carbon rich deep water is enhanced through stronger winds, increasing surface water CO2 at a rate in good agreement with observed trends. We find that Southern Ocean uptake is reduced by 2.47 PgC (1987–2004) and is consistent with atmospheric inversion studies. The enhanced ventilation also accelerates ocean acidification, despite lesser Southern Ocean CO2 uptake. Our results link two important anthropogenic changes: stratospheric ozone depletion and greenhouse gas increases; and suggest that studies of future climate that neglect stratospheric ozone depletion likely overestimate regional and global oceanic CO2 uptake and underestimate the impact of ocean acidification.
Potential waves for pitch‐angle scattering of near‐equatorially mirroring energetic electrons due to the violation of the second adiabatic invariant
Authors: Shprits Yuri Y.
Published: June 2009

Bounce and MLT averaged diffusion rates due to gyroresonance scattering by plasmaspheric hiss, lightning generated whistlers, and whistlers due to VLF transmitters inside the plasmasphere; and chorus waves outside the plasmasphere; are computed in high resolution in pitch‐angle. The computed rates show that another scattering mechanism is required to provide pitch‐angle scatting for nearly equatorially mirroring particles at low energies outside the plasmasphere and at a wide range of energies in the slot region. We show that magnetosonic waves and ElectroMagnetic Ion Cyclotron (EMIC) waves can be in bounce resonance with electrons for a wide range of energies and pitch‐angles, and may be responsible for the scattering of electrons with equatorial pitch‐angels close to 90°. Bounce resonance may also result in an in‐situ acceleration of equatorially mirroring particles.
Effects of spatio‐temporal variability of precipitation on contaminant migration in the vadose zone
Authors: Wang Peng , Quinlan Peter , Tartakovsky Daniel M.
Published: June 2009

Annual meteorological data are routinely used in models of contaminant migration through the vadose zone. In arid and semi‐arid regions, models based on such data yield negligibly small net infiltration rates that are insufficient to cause groundwater contamination. We conduct a series of flow and transport simulations, in which daily data from a weather station serve as input, to demonstrate that precipitation patterns typical of (semi‐)arid regions make the reliance on annual data questionable. We demonstrate that the accuracy of temporally averaged predictions is influenced by the degree of nonlinearity of the Richards equation describing flow in partially saturated porous media. Additional errors are introduced when one ignores topographical and/or urban features that tend to focus and increase local infiltration rates.
Drought return times in the Sahel: A question of attribution
Authors: Greene Arthur M. , Giannini Alessandra , Zebiak Stephen E.
Published: June 2009

Recurrence times for extreme drought events in the African Sahel are estimated using a classical peaks‐over‐threshold model. Results, which are computed for both mean seasonal rainfall and fractional area in drought, suggest that the distribution of dry extremes after about 1970 is statistically distinct from that of preceding years. This finding throws into relief the critical role played by attribution of causes, and the necessity of improving our understanding of the physical processes driving precipitation variability in the Sahel.
Wavelength dependence of dust aerosol single scattering albedo as observed by the Compact Reconnaissance Imaging Spectrometer
Authors: Wolff M. J. , Smith M. D. , Clancy R. T. , Arvidson R. , Kahre M. , Seelos F. , Murchie S. , Savijärvi H.
Published: June 2009

Observations by the Compact Reconnaissance Imaging Spectrometer (CRISM) onboard the Mars Reconnaissance Orbiter (MRO) over the range 440–2920 nm of the very dusty Martian atmosphere of the 2007 planet‐encircling dust event are combined with those made by both Mars Exploration Rovers (MERs) to better characterize the single scattering albedo (ω0) of Martian dust aerosols. Using the diagnostic geometry of the CRISM emission phase function (EPF) sequences and the “ground truth” connection provided at both MER locations allows one to more effectively isolate the single scattering albedo (ω0). This approach eliminates a significant portion of the type of uncertainty involved in many of the earlier radiative transfer analyses. Furthermore, the use of a “first principles” or microphysical representation of the aerosol scattering properties offers a direct path to produce a set of complex refractive indices (m = n + ik) that are consistent with the retrieved ω0 values. We consider a family of effective particle radii: 1.2, 1.4, 1.6, and 1.8 μm. The resulting set of model data comparisons, ω0, and m are presented along with an assessment of potential sources of error and uncertainty. We discuss our results within the context of previous work, including the apparent dichotomy of the literature values: “dark” (solar band ω0 = 0.89–0.90) and “bright” (solar band ω0 = 0.92–0.94). Previous work suggests that a mean radius of 1.8 μm is representative for the conditions sampled by the CRISM observations. Using the m for this case and a smaller effective particle radius more appropriate for diffuse dust conditions (1.4 μm), we examine EPF‐derived optical depths relative to the MER 880 nm optical depths. Finally, we explore the potential impact of the resulting brighter solar band ω0 of 0.94 to atmospheric temperatures in the planetary boundary layer.
Induced pluripotent stem cells and the stability of the differentiated state
Authors: Colman Alan , Dreesen Oliver
Published: June 2009

For much of the last century, the differentiated state that characterizes the many cell types of an adult organism was thought to be stable and abrogated only in rare instances by transdifferentiation, metaplasia or cancer. This stability was thought to reside in the autoregulatory molecular circuitry that exists between the cytoplasm and the nucleus, a status quo that could be disrupted during somatic cell nuclear transfer, to reprogramme cells to a pluripotent state. Pioneering work in the 1980s showed that transdifferentiation of cell lineages could be induced by the addition of transcription factors. However, these conversions were usually confined to cell types from the same germ layer, and proof of conversion was difficult to obtain. This deficiency has now been overturned by demonstrations that exogenously added transcription factors can convert differentiated cell types into embryonic‐like induced pluripotent stem cells. Here, we highlight the recent progress, and the implications of this work for our understanding of the relationship between the pluripotent and more differentiated cell states.
TIP150 interacts with and targets MCAK at the microtubule plus ends
Authors: Jiang Kai , Wang Jianyu , Liu Jing , Ward Tarsha , Wordeman Linda , Davidson Alec , Wang Fengsong , Yao Xuebiao
Published: June 2009

The microtubule (MT) cytoskeleton orchestrates the cellular plasticity and dynamics that underlie morphogenesis and cell division. Growing MT plus ends have emerged as dynamic regulatory machineries in which specialized proteins—called plus‐end tracking proteins (+TIPs)—bind to and control the plus‐end dynamics that are essential for cell division and migration. However, the molecular mechanisms underlying the plus‐end regulation by +TIPs at spindle and astral MTs have remained elusive. Here, we show that TIP150 is a new +TIP that binds to end‐binding protein 1 (EB1) in vitro and co‐localizes with EB1 at the MT plus ends in vivo. Suppression of EB1 eliminates the plus‐end localization of TIP150. Interestingly, TIP150 also binds to mitotic centromere‐associated kinesin (MCAK), an MT depolymerase that localizes to the plus end of MTs. Suppression of TIP150 diminishes the plus‐end localization of MCAK. Importantly, aurora B‐mediated phosphorylation disrupts the TIP150–MCAK association in vitro. We reason that TIP150 facilitates the EB1‐dependent loading of MCAK onto MT plus ends and orchestrates the dynamics at the plus end of MTs.
Understanding How Students Learn: Preparing Students to Become Professionals
Authors: Stevens Lizbeth Curme
Published: June 2009

The intent of this article is to share my research endeavors in order to raise awareness of issues relative to what and how we teach as a means to spark interest in applying the scholarship of teaching and learning to what we do as faculty in communication sciences and disorders (CSD). My own interest in teaching and learning emerged rather abruptly after I introduced academic service-learning (AS-L) into one of my graduate courses (Stevens, 2002). To better prepare students to enter our profession, I have provided them with unique learning opportunities working with various community partners including both speech-language pathologists (SLPs) and teachers who supported persons with severe communication disorders.
Evaluation of Evidence in Evidence-Based Practice and How Library Science Can Help
Authors: Epstein Laura , Nazario Athena , Yu Betty
Published: June 2009

In this article, we describe how collaboration with our university librarian at San Francisco State University led to the integration of information literacy competency standards within our curriculum, as outlined by the American Library Association (ALA). The ALA standards are related to the evaluation of evidence, a key component of evidence-based practice and these were infused across four courses in the communicative disorders program focused on language development and disorders. In particular, ALA Standard 3 stipulates that the student who is information literate evaluates information and its sources critically and incorporates selected information into his or her knowledge base and value system. The integration of Standard 3 within language disorders courses is described in detail. We anticipate that the infusion of information literacy skills related to the evaluation of evidence during academic training will make such skills an integral part of the clinical process for future clinicians.
Reaching Millennials Through Innovations in Teaching
Authors: Shaughnessy Paige
Published: June 2009

On any given day, on college and university campuses across the United States, four generations bump up against each other. Some are shocked and outraged by the attitudes and demands of the newest generation; others are dazed, stunned, and even offended by the conventions and expectations of an earlier generation. Three generations of college professors are facing perceived irrelevance by the newest generation to hit the scene. This article addresses generational differences between today’s students and those who teach them. Research and recommended practice to build on the strengths and learning needs for students and future professionals in communication sciences and disorders are discussed.