bluuebunny/crossref_metadata_2025 huggingface dataset:
Taking the “Boulder” Step From Static to Dynamic Geoid: 2009 Workshop on Monitoring North American Geoid Change; Boulder, Colorado, 21–23 October 2009
Authors: Smith Dru , Edwards Karla
Published: February 2010

As coastal communities are increasingly affected by sea level rise and flooding from extreme weather events, and as less evident (yet significant) tectonic shifts reshape the North American continent, the need for elevation data that are accurate, consistent, updated, and easily accessible has become critical. Currently, however, the vertical datums in North America are defined by tide gauge and leveling observations, which inevitably become outdated and are costly to replace or repeat. Therefore, two North American governments (Canada and United States) have resolved that the next generation of their national vertical datums will be geoid‐ based and accessible through Global Navigation Satellite System (GNSS) technology.

To adequately serve as the reference surface for a future vertical datum, the geoid must be modeled accurately and its changes over time must be monitored. But what mix of tools and techniques could fulfill this requirement? To address this question and to plan for a campaign to monitor North American geoid change, experts from North America (including United States, Canada, and Mexico) and Europe specializing in satellite and terrestrial gravimetry as well as satellite positioning convened in Colorado.
Residents, Decision Makers, and Scientists Discuss Volcanic Hazard in Colombia: Knowledge Sharing and Collaboration in Volcanic Risk Mitigation at Galeras Volcano, Colombia; Pasto, Colombia, 6–11 July 2009
Authors: Sheridan Michael F. , Cordoba Gustavo
Published: February 2010

Galeras volcano, located in southwestern Colombia, imposes several hazards on the surrounding population: pyroclastic flows, lahars, ashfall, and shock waves. The current hazard map shows three zones: high, medium, and low (see A. D. Hurtado Artunduaga and G. P. Cortés Jiménez, J. Volcanol. Geotherm. Res., 77, 89–100, 1997). The pyroclastic flow hazard on this map defines the Zone of High Volcanic Hazard (ZAVA) for civil authorities.

Current activity of Galeras has provoked two contentious issues related to hazard management: (1) Decision makers announce an evacuation order of ZAVA whenever the volcanic alert reaches a high level, and (2) the Colombian government initiated a relocation program for the inhabitants within ZAVA (Colombian Decrees‐Laws 4106 and 3905). However, communities within ZAVA refuse to obey both the evacuation orders and the relocation process. To help resolve this situation, the University of Nariño (Colombia) and the State University of New York at Buffalo organized a workshop, which was sponsored by the U.S. National Science Foundation. A daily average of 92 people attended, including residents of ZAVA, decision makers, Colombian technical and scientific personnel, international scientists and researchers, students, and academics from the University of Nariño.
William E. Dietrich Receives 2009 Robert E. Horton Medal
Authors: Dunne Thomas , Dietrich William E.
Published: February 2010

William E. Dietrich was awarded the 2009 Robert E. Horton Medal at the AGU Fall Meeting Honors Ceremony, held on 16 December 2009 in San Francisco, Calif. The medal is for “outstanding contributions to hydrology.”
Blazing New Paths for Inter disciplinary Hydrology
Authors: Wilson Jennifer S. , Hermans Caroline , Sivapalan Murugesu , Vörösmarty Charles J.
Published: February 2010

As society tackles climate change adaptation and planning, community and regional managers are turning to science for answers. The role of water, and thus hydrologists, is central to many pressing questions.

Faced with concerns about water resource availability and quality degradation, society needs information on hydrologic processes at the catchment scale and smaller; although the community has significantly improved its understanding of such processes, there is a need for a new and integrative foundation of knowledge. Hydrology must not only reach beyond disciplinary boundaries but also forge broad connections with natural and social sciences to make useful water cycle predictions at regional and global scales.
Seismic Tomography of Erebus Volcano, Antarctica
Authors: Zandomeneghi Daria , Kyle Philip , Miller Pnina , Passcal Iris , Snelson Catherine , Aster Richard
Published: February 2010

Mount Erebus (77°32′S, 167°10′E; elevation 3794 meters) is the most active volcano in Antarctica and is well known for its persistent lava lake. The lake constitutes an “open window” into the conduit and underlying feeding system and offers a rare opportunity to observe a shallow convecting magmatic system.

Imaging and modeling of the internal structure of Erebus volcano are best done through compiling information from arrays of seismometers positioned strategically around the volcano. From these data, the three‐dimensional (3‐D) structure of the conduit can be pieced together. Building this 3‐D model of Erebus was a main goal of the seismic tomographic experiment Tomo Erebus (TE). During the 2007–2008 austral field season, 23 intermediate‐period seismometers were installed to contribute data, through the winter, for the passive‐source aspect of the experiment. One year later, 100 three‐component short‐period stations were deployed to record 16 chemical blasts (see Figure 1).
In the Aftermath of Haiti's Earthquake: A Discussion of Lessons Learned
Authors: Showstack Randy
Published: February 2010

The 12 January 2010 earthquake in Haiti brought massive devastation to that country (see Figure 1). In this week's issue of Eos, three noted seismologists respond to questions from Eos senior writer Randy Showstack in a news roundtable format.

Paul Mann, senior research scientist with the Institute for Geophysics at the University of Texas at Austin, has just returned from Haiti, where he and a colleague worked on a fault rupture survey; they plan to conduct an offshore fault survey soon. Glen Mattioli, professor of geosciences at the University of Arkansas, Fayetteville, has been part of a team conducting a Global Positioning System (GPS) survey of Haiti to measure ground deformation following the earthquake and to install a number of continuous GPS sites to examine after slip, viscoelastic relaxation, and the time return to interseismic deformation (see Figure 2). Work by Mann, Mattioli, and their colleagues has been supported through a U.S. National Science Foundation Rapid Response Research ( RAPID) proposal grant provided to Purdue University, with Eric Calais serving as principal investigator. Carol Prentice, a seismologist with the U.S. Geological Survey's Earthquake Hazards Team, has been conducting paleoseismic research on the active faults in the Caribbean region since 1991, including projects on Hispaniola, Puerto Rico, Trinidad, and Jamaica.
In Memoriam
Authors: Anonymous
Published: February 2010

Lew Allen, 84, 4 January 2010, Planetary Sciences, 1960

Richard C. Anderson, 78, 8 January 2009, Volcanology, 1965
Bridging Geodynamics, Hazards, and Capacity Building in East Africa: Advanced Workshop on Evaluating, Monitoring, and Communicating Volcanic and Seismic Hazards in East Africa; Trieste, Italy, 17–28 August 2009
Authors: Fischer Tobias P.
Published: February 2010

Africa exhibits some of the most spectacular volcanic and tectonic features on Earth. Hazards associated with these features include volcanic eruptions, earthquakes, and carbon dioxide (CO2) degassing. For example, in 2002 an eruption destroyed 25% of the city of Goma, Congo, and forced 500,000 people to evacuate. In 1986, hundreds died as a result of the CO2 degassing at Lake Nyos, Cameroon. In Tanzania in 2007, explosive activity of the carbonatite volcano Ol Doinyo Lengai forced the evacuation of the region. From the 1980s to the present, Nyamuragira (Congo) had numerous eruptions, each with sulfur dioxide (SO2) emissions exceeding 1 million tons. Large rift‐related fault systems that cross national boundaries challenge efforts for integrated seismic hazard evaluations. These observations highlight the need for basic and hazards‐related research in East Africa.
Workshop Targets Development of Geodetic Transient Detection Methods: 2009 SCEC Annual Meeting: Workshop on Transient Anomalous Strain Detection; Palm Springs, California, 12–13 September 2009
Authors: Murray‐Moraleda Jessica R. , Lohman Rowena
Published: February 2010

The Southern California Earthquake Center (SCEC) is a community of researchers at institutions worldwide working to improve understanding of earthquakes and mitigate earthquake risk. One of SCEC's priority objectives is to “develop a geodetic network processing system that will detect anomalous strain transients.” Given the growing number of continuously recording geodetic networks consisting of hundreds of stations, an automated means for systematically searching data for transient signals, especially in near real time, is critical for network operations, hazard monitoring, and event response. The SCEC Transient Detection Test Exercise began in 2008 to foster an active community of researchers working on this problem, explore promising methods, and combine effective approaches in novel ways. A workshop was held in California to assess what has been learned thus far and discuss areas of focus as the project moves forward.
H. Thomas Rossby Receives 2009 Maurice Ewing Medal
Authors: Rhines Peter B. , Rossby H. Thomas
Published: February 2010

H. Thomas Rossby was awarded the 2009 Maurice Ewing Medal at the AGU Fall Meeting Honors Ceremony, held on 16 December 2009 in San Francisco, Calif. The medal is for “significant original contributions to the scientific understanding of the processes in the ocean; for the advancement of oceanographic engineering, technology, and instrumentation; or outstanding service to marine science.”
AGU Fellows Elected for 2010
Authors: Anonymous
Published: February 2010

AGU Fellows are members who have made exceptional contributions to Earth and space sciences as valued by their peer groups and vetted by a committee of Fellows.
Comparative metaproteomics reveals ocean-scale shifts in microbial nutrient utilization and energy transduction
Authors: Morris Robert M , Nunn Brook L , Frazar Christian , Goodlett David R , Ting Ying S , Rocap Gabrielle
Published: February 2010

Bacteria and Archaea play critical roles in marine energy fluxes and nutrient cycles by incorporating and redistributing dissolved organic matter and inorganic nutrients in the oceans. How these microorganisms do this work at the level of the expressed protein is known only from a few studies of targeted lineages. We used comparative membrane metaproteomics to identify functional responses of communities to different nutrient concentrations on an oceanic scale. Comparative analyses of microbial membrane fractions revealed shifts in nutrient utilization and energy transduction along an environmental gradient in South Atlantic surface waters, from a low-nutrient gyre to a highly productive coastal upwelling region. The dominant membrane proteins identified (19%) were TonB-dependent transporters (TBDTs), which are known to utilize a proton motive force to transport nutrients across the outer membrane of Gram-negative bacteria. The ocean-wide importance of TonB-dependent nutrient acquisition in marine bacteria was unsuspected. Diverse light-harvesting rhodopsins were detected in membrane proteomes from every sample. Proteomic evidence of both TBDTs and rhodopsins in the same lineages suggest that phototrophic bacterioplankton have the potential to use energy from light to fuel transport activities. We also identified viral proteins in every sample and archaeal ammonia monooxygenase proteins in the upwelling region, suggesting that Archaea are important nitrifiers in nutrient-rich surface waters.
Removal of Melatonin Receptor Type 1 Induces Insulin Resistance in the Mouse
Authors: Contreras‐Alcantara Susana , Baba Kenkichi , Tosini Gianluca
Published: February 2010

The incidence of obesity, insulin resistance, and type 2 diabetes (T2D) is increasing at an alarming rate worldwide. Emerging experimental evidence suggests that the hormone melatonin plays an important role in the regulation of glucose metabolisms. In this study, we report that removal of melatonin receptor type 1 (MT1) significantly impairs the ability of mice to metabolize glucose and such inability is probably due to an increased insulin resistance in these mice. Our data suggest that MT1 receptors are implicated in the pathogenesis of T2D and open the door for a detailed exploration on the mechanisms by which MT1 receptors signaling may affect glucose metabolism.
The Impact of Exposure Misclassification on Associations Between Prepregnancy BMI and Adverse Pregnancy Outcomes
Authors: Bodnar Lisa M. , Siega‐Riz Anna Maria , Simhan Hyagriv N. , Diesel Jill C. , Abrams Barbara
Published: February 2010

Prepregnancy BMI is a widely used marker of maternal nutritional status that relies on maternal self‐report of prepregnancy weight and height. Pregravid BMI has been associated with adverse health outcomes for the mother and infant, but the impact of BMI misclassification on measures of effect has not been quantified. The authors applied published probabilistic bias analysis methods to quantify the impact of exposure misclassification bias on well‐established associations between self‐reported prepregnancy BMI category and five pregnancy outcomes (small for gestational age (SGA) and large for gestational age (LGA) birth, spontaneous preterm birth (sPTB), gestational diabetes mellitus (GDM), and preeclampsia) derived from a hospital‐based delivery database in Pittsburgh, PA (2003–2005; n = 18,362). The bias analysis method recreates the data that would have been observed had BMI been correctly classified, assuming given classification parameters. The point estimates derived from the bias analysis account for random error as well as systematic error caused by exposure misclassification bias and additional uncertainty contributed by classification errors. In conventional multivariable logistic regression models, underweight women were at increased risk of SGA and sPTB, and reduced risk of LGA, whereas overweight, obese, and severely obese women had elevated risks of LGA, GDM, and preeclampsia compared with normal‐weight women. After applying the probabilistic bias analysis method, adjusted point estimates were attenuated, indicating the conventional estimates were biased away from the null. However, the majority of relations remained readily apparent. This analysis suggests that in this population, associations between self‐reported prepregnancy BMI and pregnancy outcomes are slightly overestimated.
Maladaptive Eating Patterns, Quality of Life, and Weight Outcomes Following Gastric Bypass: Results of an Internet Survey
Authors: Kofman Michele D. , Lent Michelle R. , Swencionis Charles
Published: February 2010

Bariatric surgery is the most effective treatment for severe obesity. However, evidence suggests that maladaptive eating behaviors such as binge eating, grazing, and a loss of control when eating may impact postsurgical weight outcomes. The current study sought to characterize the weight outcomes, eating patterns, and perceived health‐related quality of life of individuals 3–10 years following gastric bypass (GBP) surgery and to assess the relationships between eating behaviors, weight outcomes, and quality of life. Eligible participants (N = 497) completed an Internet survey of their eating behaviors, health‐related quality of life, and weight history. Participants self‐reported a mean maximum postsurgical loss of 81% of their excess weight and maintained a mean weight loss of 70% 3–10 years following surgery (mean 4.2 years). Eighty‐seven percent reported weight regain ranging from 1 to 124 lb (mean 22.6 lb). Frequency of binge eating, a loss of control when eating, and grazing were all significantly correlated with greater weight regain (binge eating r = 0.24, P = 0.006; loss of control r = 0.36, P < 0.01; grazing r = 0.39, P < 0.001) and lesser excess weight loss (EWL) (binge eating r = −0.21, P = 0.013; loss of control r = −0.41, P < 0.001; grazing r = −0.27, P < 0.001). Poorer health‐related quality of life was associated with binge eating disorder (BED) (t[463] = 9.7, P < 0.001) and grazing two or more times per week (t[361] = 9.0, P < 0.001). These findings suggest that eating disturbances and a loss of control when eating are significant following GBP and are risk factors for diminished weight outcomes.
Microporous Framework Solids
Authors: Wright Paul A
Published: February 2010

The field of microporous solids in solid state chemistry has seen a huge expansion over the last decades with new developments in a diverse range of directions and applications. Drawing upon nature as an inspiration, scientists are continually extending known families and preparing porous solids with novel structures. In turn, the novel properties that these possess stimulate further research and applications. Microporous Framework Solids describes fundamental principles and experimental practices of the synthetic chemistry and physical characterisation of crystalline microporous solids. It also provides a clear and up to date discussion of different types of microporous materials, their applications and emerging areas of current interest, written from a personal research perspective. Topics include the different types of solids and their properties with key emphasis placed on the relationship between properties and structure. Structural methods are also discussed including the role of diffraction, NMR and computational studies. Finally, applications for catalysis are reviewed. This book is ideal for new researchers in the field of microporous solids both in academia and industry who require a detailed and informative overview of the subject. It provides a comprehensive review of microporous materials in an easily accessible style offering a valuable source of references over a wide range of topics.
Controlled room temperature ROP of L-lactide by ICl3: a simple halogen-bonding catalyst
Authors: Coulembier Olivier , Meyer Franck , Dubois Philippe
Published: February 2010

The ability of ICl3 to activate electrophilic substrates through halogen bonding and its catalytic activity towards the ring-opening polymerization of L-lactide is demonstrated in this communication. Association of techniques highlights the production of narrowly dispersed PLA of predictable molecular weights from this commercially available molecule.
Development of a pepper-pot device to determine the emittance of an ion beam generated by electron cyclotron resonance ion sources
Authors: Strohmeier M. , Benitez J. Y. , Leitner D. , Lyneis C. M. , Todd D. S. , Bantel M.
Published: February 2010

This paper describes the recent development and commissioning of a pepper-pot emittance meter at the Lawrence Berkeley National Laboratory (LBNL). It is based on a potassium bromide (KBr) scintillator screen in combination with a charged coupled device camera. Pepper-pot scanners record the full four-dimensional transverse phase space emittances which are particularly interesting for electron cyclotron resonance ion sources. The strengths and limitations of evaluating emittances using optical pepper-pot scanners are described and systematic errors induced by the optical data acquisition system will be presented. Light yield tests of KBr exposed to different ion species and first emittance measurement data using ion beams extracted from the 6.4 GHz LBNL electron cyclotron resonance ion source are presented and discussed.
Cesium control and diagnostics in surface plasma negative ion sources
Authors: Dudnikov Vadim , Chapovsky Pavel , Dudnikov Andrei
Published: February 2010

For efficient and reliable negative ion generation it is very important to improve a cesium control and diagnostics. Laser beam attenuation and resonance fluorescence can be used for measurement of cesium distribution and cesium control. Resonant laser excitation and two-photon excitation can be used for improved cesium ionization and cesium trapping in the discharge chamber. Simple and inexpensive diode lasers can be used for cesium diagnostics and control. Cesium migration along the surface is an important mechanism of cesium escaping. It is important to develop a suppression of cesium migration and cesium accumulation on the extraction system.
Thermal expansion of skutterudites
Authors: Rogl G. , Zhang L. , Rogl P. , Grytsiv A. , Falmbigl M. , Rajs D. , Kriegisch M. , Müller H. , Bauer E. , Koppensteiner J. , Schranz W. , Zehetbauer M. , Henkie Z. , Maple M. B.
Published: February 2010

The current paper gives an overview of the newly obtained thermal expansion coefficients of skutterudites as well as those so far available in literature. Thermal expansion was determined for CoSb3, Pt4Sn4.4Sb7.6, for As- and Ge-based skutterudites as well as for various high-ZT skutterudites (micro- and nanostructured) with didymium (DD) and mischmetal (Mm) as filler atoms in frameworks of (Fe1−xCox)4Sb12 and (Fe1−xNix)4Sb12, and for double and triple-filled skutterudites such as Ca0.07Ba0.23Co3.95Ni0.05Sb12 and Sr0.025Ba0.075Yb0.1Co4Sb12. For low temperatures, a capacitance dilatometer was used (4–300 K), whereas for temperatures 300<T<750 K, a dynamic mechanical analyzer was employed. For a set of Ge-, P-, and Sb-based skutterudites, lattice parameters of single crystals, measured at three different temperatures, were used to derive the thermal expansion coefficient. The semiclassical model of Mukherjee [Phys. Rev. Lett. 76, 1876 (1996)] has been successfully used to quantitatively describe the thermal expansion coefficient in terms of Einstein and Debye temperatures, which compare well with the corresponding results from specific heat, electrical resistivity, or temperature dependent x-ray measurements.
Quantitative assessment of sample stiffness and sliding friction from force curves in atomic force microscopy
Authors: Pratt Jon R. , Shaw Gordon A. , Kumanchik Lee , Burnham Nancy A.
Published: February 2010

It has long been recognized that the angular deflection of an atomic force microscope (AFM) cantilever under “normal” loading conditions can be profoundly influenced by the friction between the tip and the surface. It is shown here that a remarkably quantifiable hysteresis occurs in the slope of loading curves whenever the normal flexural stiffness of the AFM cantilever is greater than that of the sample. This situation arises naturally in cantilever-on-cantilever calibration, but also when trying to measure the stiffness of nanomechanical devices or test structures, or when probing any type of surface or structure that is much more compliant along the surface normal than in transverse directions. Expressions and techniques for evaluating the coefficient of sliding friction between the cantilever tip and sample from normal force curves, as well as relations for determining the stiffness of a mechanically compliant specimen are presented. The model is experimentally supported by the results of cantilever-on-cantilever spring constant calibrations. The cantilever spring constants determined here agree with the values determined using the NIST electrostatic force balance within the limits of the largest uncertainty component, which had a relative value of less than 2.5%. This points the way for quantitative testing of micromechanical and nanomechanical components, more accurate calibration of AFM force, and provides nanotribologists access to information about contact friction from normal force curves.
Determination of the intrinsic temperature dependent thermal conductivity from analysis of surface temperature of laser irradiated materials
Authors: Elhadj Selim , Matthews Manyalibo J. , Yang Steven T. , Cooke Diane J. , Stolken James S. , Vignes Ryan M. , Draggoo Vaughn G. , Bisson Scott E.
Published: February 2010

An experimental and analytical approach is described to determine the temperature dependent intrinsic lattice thermal conductivity, k(T), for a broad range of materials. k(T) of silica, sapphire, spinel, and lithium fluoride were derived from surface temperature measurements. Surfaces were heated from room temperature up to 3000 K using a CO2-laser irradiance ≤5 kW/cm2. The solution of the nonlinear heat flow equation was used to extract parameters of k(T)=A×Tε, where −1.13≤ε≤0 depending on the material. Results generally show good agreement with reported k(T). Below evaporation, the phonon-only k remains the dominant heat transport mechanism during laser heating.
Tunneling between carbon nanofiber and gold electrodes
Authors: Yamada Toshishige , Saito Tsutomu , Suzuki Makoto , Wilhite Patrick , Sun Xuhui , Akhavantafti Navid , Fabris Drazen , Yang Cary Y.
Published: February 2010

In a carbon nanofiber (CNF)-metal system such as a bridge between two gold electrodes, passing high current (current stressing) reduces the total resistance of the system (CNF resistance RCNF plus contact resistance Rc) by orders of magnitude. The role of current stressing is modeled as a reduction in the interfacial tunneling gap with transport characteristics attributed to tunneling between Au and CNF. The model predicts a reduction in Rc and gradual disappearance of the nonlinearity in the current-voltage (I-V) characteristics as Rc decreases. These results are consistent with measured I-V behavior.
Generation of a dynamic polarized laser beam for applications in laser welding
Authors: Gräf Stephan , Staupendahl Gisbert , Seiser Carlo , Meyer Bernd-Jürgen , Müller Frank A.
Published: February 2010

The temporal control and optimization of laser beam parameters, e.g., the beam power, can be employed to enhance the quality and reliability of the welding process. Until now, the influence of a time-dependent beam polarization has been less investigated in welding. The publication describes a new experimental arrangement allowing the fast variation of the polarization of CO2 laser radiation [“dynamic polarization” (DP)]. The key element of the setup is a high power interference laser beam modulator for cw laser power rating of up to 4 kW. Weld seams were produced with different process parameters in the technically relevant steels St37 and Ck45 and in the precoated steel 22MnB5 (USIBOR 1500P). The welds were subsequently characterized by roughness measurements of the top bead surfaces and by the preparation of cross sections and their macroscopic analysis. The experiments on welding with DP showed a significant influence on the keyhole and melt pool dynamics, especially a reduction in the top bead roughness at certain DP frequencies up to a factor of about 3. In addition, a threshold behavior for this effect was observed. It was shown that the cross sectional shape and thus the degree of energy coupling to the material was unaffected by the DP. Finally, during welding USIBOR 1500P with DP an enhanced melt pool stirring was achieved. The results show that the temporal modulation of energy coupling to the material caused by DP is suitable to enhance the quality and reliability of the welding process.
Angular and energy distribution of fast electrons emitted from a solid surface irradiated by femtosecond laser pulses in various conditions
Authors: Wang Wentao , Liu Jiansheng , Cai Yi , Wang Cheng , Liu Li , Xia Changquan , Deng Aihua , Xu Yi , Leng Yuxin , Li Ruxin , Xu Zhizhan
Published: February 2010

Angular and energy distributions of fast electrons generated from the interaction of 60 fs, 795 nm laser pulses with aluminum targets have been experimentally investigated in various conditions. Increasing laser intensities from the nonrelativistic to the relativistic, a transition of the angular distribution of outgoing fast electrons from the specular reflection direction to the target normal has been observed for p-polarized laser irradiation. The fast electrons’ energy spectrum at high laser intensity, e.g., ∼2.6×1018 W/cm2, consists of two peaks, which are found to originate from the target normal with low energy and specular reflection direction with high energy, respectively. By adding a prepulse to generate preplasma, the electron yields at the direction of the reflected laser can be greatly enhanced, and a double-peak angular distribution is observed. Besides, a more collimated electron emission peak in the specular reflection direction can be obtained by employing a larger f-number focusing system.
Perturbative triples corrections in state-specific multireference coupled cluster theory
Authors: Evangelista Francesco A. , Prochnow Eric , Gauss Jürgen , Schaefer Henry F.
Published: February 2010

We formulated and implemented a perturbative triples correction for the state-specific multireference coupled cluster approach with singles and doubles suggested by Mukherjee and co-workers, Mk-MRCCSD [Mol. Phys. 94, 157 (1998)]. Our derivation of the energy correction [Mk-MRCCSD(T)] is based on a constrained search for stationary points of the Mk-MRCC energy functional together with a perturbative expansion with respect to the appearing triples cluster operator. The Λ-Mk-MRCCSD(T) approach derived in this way consists in (1) a correction to the off-diagonal matrix elements of the effective Hamiltonian which is unique to coupled cluster methods based on the Jeziorski–Monkhorst ansatz, and (2) an asymmetric energy correction to the diagonal elements of the effective Hamiltonian. The Mk-MRCCSD(T) correction is obtained from the Λ-Mk-MRCCSD(T) method by approximating the singles and doubles Lagrange multipliers with the corresponding cluster amplitudes. We investigate the performance of the Mk-MRCCSD(T) method by applying it to the potential energy curve of the BeH2 model and F2 and the geometry and harmonic vibrational frequencies of ozone. Computation of the energy difference between the mono- and bicyclic forms of the 2,6-pyridyne diradical illustrates the potential of Mk-MRCCSD(T) as a tool for the study of realistic chemical problems requiring multireference zeroth-order wave functions.
A new analytical potential energy surface for the adsorption system CO/Cu(100)
Authors: Marquardt Roberto , Cuvelier Frédéric , Olsen Roar A. , Baerends Evert Jan , Tremblay Jean Christophe , Saalfrank Peter
Published: February 2010

Electronic structure data and analytical representations of the potential energy surface for the adsorption of carbon monoxide on a crystalline copper Cu(100) substrate are reviewed. It is found that a previously published and widely used analytical hypersurface for this process [J. C. Tully, M. Gomez, and M. Head-Gordon, J. Vac. Sci. Technol. A 11, 1914 (1993)] represents rather poorly the data obtained from a slab type calculation of the electronic structure. A new, global analytical representation of the potential energy surface for this process is derived via a nonlinear adjustment of parameters. It is more general and fits qualitatively better the electronic structure data. Key characteristic elements of the new surface are the “top” equilibrium adsorption site in the perpendicular arrangement Cu–C–O with Cu–C and C–O distances of 184 and 115 pm, the desorption energy of 0.76 eV and the barrier for lateral diffusion of 33 meV, including approximative corrections for the variation of zero point energy. Anharmonic vibrational fundamentals and overtones are also calculated from six dimensional variational calculations. All these values agree equally well or better with experimental data than previous published theoretical data within estimated uncertainties. The analytical representation is compact and robust, and may be used to describe other adsorption processes of diatomic molecules, including dissociative chemisorption.
Network analysis of human heartbeat dynamics
Authors: Shao Zhi-Gang
Published: February 2010

We construct the complex networks of human heartbeat dynamics and investigate their statistical properties, using the visibility algorithm proposed by Lacasa and co-workers [Proc. Natl. Acad. Sci. U.S.A. 105, 4972 (2008)]. Our results show that the associated networks for the time series of heartbeat interval are always scale-free, high clustering, hierarchy, and assortative mixing. In particular, the assortative coefficient of associated networks could distinguish between healthy subjects and patients with congestive heart failure.
Effect of rotation on the electrohydrodynamic instability of a fluid layer with an electrical conductivity gradient
Authors: Ruo An-Cheng , Chang Min-Hsing , Chen Falin
Published: February 2010

The electrohydrodynamic instability of a horizontal rotating fluid layer with a vertical electrical conductivity gradient is considered. An external electric field is applied across the fluid layer to induce an unstably stratified electrical body force. A linear stability analysis has been performed to study the effect of rotation on the onset of electrohydrodynamic instability in the fluid layer. Results show that the instability behaviors depend heavily on the boundary condition of bottom surface. In the case of stress-free condition, rotation enhances the stability and the onset of instability will be dominated by the oscillatory mode once the speed of rotation (or Taylor number) exceeds a critical value. In contrast, in the case of rigid bottom surface, rotation also tends to stabilize the fluid layer and the stationary mode will prevail eventually with increasing Taylor number. However rotation becomes destabilizing as the critical mode shifts from oscillatory to stationary. Moreover, under the same electrical conductivity gradient, the case with stress-free bottom surface is always more unstable than that with rigid bottom surface in the small Taylor number domain. However this situation is reversed at high Taylor number region since the stability of the stress-free case will be enhanced more rapidly than the rigid case.
Accurate measurements of the thermal diffusivity of thin filaments by lock-in thermography
Authors: Salazar Agustín , Mendioroz Arantza , Fuente Raquel , Celorrio Ricardo
Published: February 2010

In lock-in (modulated) thermography the lateral thermal diffusivity can be obtained from the slope of the linear relation between the phase of the surface temperature and the distance to the heating spot. However, this slope is greatly affected by heat losses, leading to an overestimation of the thermal diffusivity, especially for thin samples of poor thermal conducting materials. In this paper, we present a complete theoretical model to calculate the surface temperature of filaments heated by a focused and modulated laser beam. All heat losses have been included: conduction to the gas, convection, and radiation. Monofilaments and coated wires have been studied. Conduction to the gas has been identified as the most disturbing effect preventing from the direct use of the slope method to measure the thermal diffusivity. As a result, by keeping the sample in vacuum a slope method combining amplitude and phase can be used to obtain the accurate diffusivity value. Measurements performed in a wide variety of filaments confirm the validity of the conclusion. On the other hand, in the case of coated wires, the slope method gives an effective thermal diffusivity, which verifies the in-parallel thermal resistor model. As an application, the slope method has been used to retrieve the thermal conductivity of thin tubes by filling them with a liquid of known thermal properties.
Stress- and magnetic field-induced entropy changes in Fe-doped Ni–Mn–Ga shape-memory alloys
Authors: Soto-Parra D. E. , Vives Eduard , González-Alonso David , Mañosa Lluís , Planes Antoni , Romero Ricardo , Matutes-Aquino J. A. , Ochoa-Gamboa R. A. , Flores-Zúñiga H.
Published: February 2010

Isothermal stress- and magnetic field-induced entropy changes in a Fe-doped Ni–Mn–Ga alloy have been measured in the limits of low applied stress and magnetic field. We have obtained that in this limit while elastocaloric is conventional, giving rise to an increase of entropy when a stress is applied, magnetocaloric effect is inverse, which means that entropy decreases by application of an applied magnetic field. This inverse effect is a consequence of the magnetostructural coupling driven by the martensitic transition.
Calibration of low-temperature ac susceptometers with a copper cylinder standard
Authors: Chen D.-X. , Skumryev V.
Published: February 2010

A high-quality low-temperature ac susceptometer is calibrated by comparing the measured ac susceptibility of a copper cylinder with its eddy-current ac susceptibility accurately calculated. Different from conventional calibration techniques that compare the measured results with the known property of a standard sample at certain fixed temperature T, field amplitude Hm, and frequency f, to get a magnitude correction factor, here, the electromagnetic properties of the copper cylinder are unknown and are determined during the calibration of the ac susceptometer in the entire T, Hm, and f range. It is shown that the maximum magnitude error and the maximum phase error of the susceptometer are less than 0.7% and 0.3°, respectively, in the region T=5–300 K and f=111–1111 Hz at Hm=800 A/m, after a magnitude correction by a constant factor as done in a conventional calibration. However, the magnitude and phase errors can reach 2% and 4.3° at 10 000 and 11 Hz, respectively. Since the errors are reproducible, a large portion of them may be further corrected after a calibration, the procedure for which is given. Conceptual discussions concerning the error sources, comparison with other calibration methods, and applications of ac susceptibility techniques are presented.
Development and operation of research-scale III–V nanowire growth reactors
Authors: Schroer M. D. , Xu S. Y. , Bergman A. M. , Petta J. R.
Published: February 2010

III–V nanowires are useful platforms for studying the electronic and mechanical properties of materials at the nanometer scale. However, the costs associated with commercial nanowire growth reactors are prohibitive for most research groups. We developed hot-wall and cold-wall metal organic vapor phase epitaxy reactors for the growth of InAs nanowires, which both use the same gas handling system. The hot-wall reactor is based on an inexpensive quartz tube furnace and yields InAs nanowires for a narrow range of operating conditions. Improvement of crystal quality and an increase in growth run to growth run reproducibility are obtained using a homebuilt UHV cold-wall reactor with a base pressure of 2×10−9 Torr. A load lock on the UHV reactor prevents the growth chamber from being exposed to atmospheric conditions during sample transfers. Nanowires grown in the cold-wall system have a low defect density, as determined using transmission electron microscopy, and exhibit field effect gating with mobilities approaching 16 000 cm2/(V s).
Parameter space region in the collisional magnetized electronegative plasma
Authors: Yasserian Kiomars , Aslaninejad Morteza
Published: February 2010

The influence of the elastic collisions on the structure of a magnetized electronegative discharge is investigated. For a constant magnetic field, the profiles of the velocities of positive ions, the density of species, and electric potential are obtained. Furthermore, the positive ion flux is obtained as a function of magnetic field strength for different values of the collision frequency. The results show that in the absence of collision in a constant magnetic field, the discharge structure is uniform while by taking the collision into account, the structure becomes multilayer stratified. By increasing the collision frequency the discharge leaves the multilayer structure, and related oscillations in the plasma potential and space charge vanish. The parameter space region is obtained for collisionless and collisional cases. In this paper it is shown that a combined effect of collision and magnetic field determines the presheath-sheath structure.
Self-fields in thin superconducting tapes: Implications for the thickness effect in coated conductors
Authors: Sanchez Alvaro , Navau Carles , Del-Valle Nuria , Chen Du-Xing , Clem John R.
Published: February 2010

A large decrease in transport current density has been observed in high-temperature superconducting films for increasing film thickness. In this work we theoretically explain the nature and the ubiquitous presence of this so-called thickness effect by analyzing the self-field created by the transport currents in the superconductor, assuming a realistic field-dependent critical-current density Jc. This knowledge can help in finding ways to improve transport current in superconducting films.
Misfit strain relaxation in m-plane epitaxy of InGaN on ZnO
Authors: Wu Z. H. , Sun K. W. , Wei Q. Y. , Fischer A. M. , Ponce F. A. , Kawai Y. , Iwaya M. , Kamiyama S. , Amano H. , Akasaki I.
Published: February 2010

The microstructure of m-plane InGaN epilayers grown on m-plane ZnO has been found to depend significantly on indium composition for the range from 0.07 to 0.17, where anisotropic lattice mismatch between InGaN and ZnO results in decreasingly tensile and increasingly compressive stress along the a and c lattice axes, respectively. For indium compositions below ∼0.10, periodic arrays of misfit dislocations with a Burgers vector of 1/3[112¯0] are observed parallel to the [0001] direction. For indium compositions above ∼0.12, generation of basal-plane stacking faults relieve the compressive stress along the [0001] direction. These characteristic mechanisms of strain relaxation should provide new approaches to engineer thick InGaN layers with reduced lattice misfit strain.
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production in flowing Ar–O2 surface-wave microwave discharges: Possible use for oxygen-iodine laser excitation
Authors: Guerra Vasco , Kutasi Kinga , Sá Paulo A.
Published: February 2010

Herein we present the calculations conducted on an Ar–O2 surface-wave microwave discharge and its afterglow, and show that this system can be effectively used for the oxygen-iodine laser excitation. It is demonstrated that at pressures higher than 10 mbar O2(a) yields higher than the threshold yield required for positive gain can be achieved along the afterglow. Additionally, the density of O(P3) atoms, which can quench the I(P21/2) excited state, can be tuned to the desired level.
Simultaneous measurement of core electron temperature and density fluctuations during electron cyclotron heating on DIII-D
Authors: White A. E. , Schmitz L. , Peebles W. A. , Rhodes T. L. , Carter T. A. , McKee G. R. , Shafer M. W. , Staebler G. M. , Burrell K. H. , DeBoo J. C. , Prater R.
Published: February 2010

New measurements show that long-wavelength (kθρs<0.5) electron temperature fluctuations can play an important role in determining electron thermal transport in low-confinement mode (L-mode) tokamak plasmas. In neutral beam-heated L-mode tokamak plasmas, electron thermal transport and the amplitude of long-wavelength electron temperature fluctuations both increase in cases where local electron cyclotron heating (ECH) is used to modify the plasma profiles. In contrast, the amplitude of simultaneously measured long-wavelength density fluctuations does not significantly increase. Linear stability analysis indicates that the ratio of the trapped electron mode (TEM) to ion temperature gradient (ITG) mode growth rates increases in the cases with ECH. The increased importance of the TEM drive relative to the ITG mode drive in the cases with ECH may be associated with the increases in electron thermal transport and electron temperature fluctuations.
Modeling disequilibrium in gas ensembles: How quantum state populations evolve under multicollision conditions; CO∗+Ar, CO, O2, and N2
Authors: McCaffery Anthony J. , Marsh Richard J.
Published: February 2010

The method of Marsh and McCaffery [J. Chem. Phys. 117, 503 (2002)] is used to quantify how rovibrational populations and mode temperatures change as an ensemble of CO molecules, initially excited to (v;j)=(8;12), evolves to thermal equilibrium in a bath gas. The bath gases considered are Ar, N2, O2, and CO all at 300 K with the diatomics in their (0;8) rovibrational states. Ensembles generally contain 1000 molecules, 10% of which are excited CO (CO∗) molecules. State (v;j) populations and mode temperatures of CO∗ and bath molecules are calculated for successive collisions to 1000 or more. We find that relaxation to local thermodynamic equilibrium occurs in distinct phases that vary widely in rate of cooling. There is especially fast vibration-vibration (VV) exchange in CO∗–CO mixtures that is largely decoupled from rotation and translation. Several aspects of ensemble behavior may be rationalized using concepts established in quantum state resolved single collision studies. We demonstrate the existence of a simultaneous energy quasiresonant, angular momentum conserving, low Δj VV process that can cause either ultrafast relaxation or up pumping of the kind seen in a number of experiments.
Electron scattering at high momentum transfer from methane: Analysis of line shapes
Authors: Vos Maarten
Published: February 2010

The measurement of the energy distribution of keV electrons backscattered elastically from molecules reveals one or more peaks. These peaks are at nonzero energy loss and have an intrinsic width. The usual interpretation of these measurements is attractively simple and assumes billiard-ball-type collisions between the electron and a specific atom in the molecule, and the scattering atom is assumed to behave as a free particle. The peak position is then related to the mass of the scattering atom, and its width is a Compton profile of the momentum distribution of this atom in the molecule. Here we explore the limits of the validity of this picture for the case of electrons scattering from methane. The biggest discrepancy is found for electrons scattering from carbon. For electrons scattering from hydrogen the effects are substantial at relatively low incoming energies and appear to decrease with increasing momentum transfer. The discrepancy is analyzed in terms of the force the atom experiences near the equilibrium position.
Current deep level transient spectroscopy analysis of AlInN/GaN high electron mobility transistors: Mechanism of gate leakage
Authors: Chikhaoui W. , Bluet J.-M. , Poisson M.-A. , Sarazin N. , Dua C. , Bru-Chevallier C.
Published: February 2010

In order to assess possible mechanisms of gate reverse-bias leakage current in AlInN/GaN high electron mobility transistors (HEMTs) grown by metalorganic chemical-vapor deposition on SiC substrates, temperature-dependent current-voltage measurements combined with Fourier transform current deep level transient spectroscopy (FT-CDLTS) are performed in the temperature range of 200–400 K. In this range of temperature reverse-bias leakage current flow is found to be dominated by Poole–Frenkel emission. Based on CDLTS measurements, a model of leakage current transport via a trap state located at the AlInN/metal interface with an activation energy of 0.37 eV is suggested. The trap nature is shown to be an extended trap, most probably associated with dislocations in the AlInN barrier layer.