bluuebunny/crossref_metadata_2025 huggingface dataset:
On the arc and curve complex of a surface
Authors: KORKMAZ MUSTAFA , PAPADOPOULOS ATHANASE
Published: December 2009

We study the arc and curve complex AC(S) of an oriented connected surface S of finite type with punctures. We show that if the surface is not a sphere with one, two or three punctures nor a torus with one puncture, then the simplicial automorphism group of AC(S) coincides with the natural image of the extended mapping class group of S in that group. We also show that for any vertex of AC(S), the combinatorial structure of the link of that vertex characterizes the type of a curve or of an arc in S that represents that vertex. We also give a proof of the fact if S is not a sphere with at most three punctures, then the natural embedding of the curve complex of S in AC(S) is a quasi-isometry. The last result, at least under some slightly more restrictive conditions on S, was already known. As a corollary, AC(S) is Gromov-hyperbolic.
Looking back and looking ahead: local empowerment and governance in the Annapurna Conservation Area, Nepal
Authors: BARAL NABIN , STERN MARC J.
Published: December 2009

Diversifying governance models for protected areas serves as one strategy to address some of the challenges they are facing. This paper explores the potential of local communities to be the primary actor in the governance of the Annapurna Conservation Area (ACA) following its planned handover to them in 2012. In doing so, the paper serves as an important baseline from which to monitor a new experiment in protected area governance. During the summer of 2007, the executive members and implementing staff of the Conservation Area Management Committees (CAMCs) were interviewed and local villagers surveyed. Both quantitative and qualitative data were collected to assess the CAMCs’ capacities to manage ACA without outside support. All CAMCs had more than a decade of managerial experience and considerable local support. Villagers largely considered the CAMCs as legitimate institutions, and their executive members as trustworthy. CAMC members were confident about assuming management responsibility of the area. The devolution of power to an overarching local council to govern ACA will present some challenges, especially with regard to lower-performing CAMCs. However, key factors identified in the literature as critical to good governance portend positive prospects for the transition.
Zirkonium: Non-invasive software for sound spatialisation
Authors: Ramakrishnan Chandrasekhar
Published: December 2009

Zirkonium is a flexible, non-invasive, open-source program for sound spatialisation over spherical (dome-shaped) loudspeaker setups. By non-invasive, we mean that Zirkonium offers the artist spatialisation capabilities without forcing her to change her usual way of working. This is achieved by supporting a variety of means of designing and controlling spatialisations. Zikonium accommodates user-defined speaker distributions and offers HRTF-based headphone simulation for situations when the actual speaker setup is not available. It can acquire sound sources from files, live input, or via the so-called device mode, which allows Zirkonium to appear to other programs as an audio interface. Control data may be predefined and stored in a file or generated elsewhere and sent over OSC. This paper details Zirkonium, its design philosophy and implementation, and how we have been using it since 2005.
Interactive Interfaces: Installations produced at the ZKM | IMA
Authors: Dipper Götz
Published: December 2009

This article discusses the installations that have been produced at the ZKM | Institute for Music and Acoustics since 1997. The first part of the article will present common characteristics of these installations. The primary quality the installations share is their orientation towards interactivity. Some installations additionally distinguish themselves through their relationship to (computer) games, for example, while others are characterised by their suitability for use as didactic tools. The second part of the article will describe the installations individually and highlight their unique features.
Music, Machines, Media and the Museum
Authors: Weibel Peter
Published: December 2009

The ZKM|Center for Art and Media in Karlsruhe is called Center because it is a museum and more than a museum. As a museum it has a classical museological function as a support and distribution system: Collection and archive, exhibitions and events. But in addition to it, the ZKM has two institutes for research, development and production (Institute for Music and Acoustics and Institute for Visual Media). The ZKM is a center for all media and for all art forms created in the 20th century. The machine based moving image has shifted the image from the classical position as space based art to time based art. Therefore the ZKM is the only museum of the world that integrated the mother of time based art, namely music, in his permanent collection and in its temporary exhibitions. This article describes the logic in the evolution of modern art, which is followed by the mission statement of the ZKM.
Effects of kinetic mass transfer and transient flow conditions on widening mixing zones in coastal aquifers
Authors: Lu Chunhui , Kitanidis Peter K. , Luo Jian
Published: December 2009

The width of a mixing zone between freshwater and seawater is important primarily because it directly reflects the extent of mixing and the growth and decay of the mixing zone indicates changes of the flow regime and water exchange between freshwater and coastal seawater. Wide mixing zones have been found in many coastal aquifers all over the world. However, the mechanisms responsible for wide mixing zones are not well understood. This work examines the hypothesis that kinetic mass transfer coupled with transient conditions, which create the movement of the mixing zone, may widen mixing zones in coastal aquifers. The hypothesis is tested by conducting two‐dimensional numerical simulations based on a variable‐density groundwater model for a scaled‐tank model and a field‐scale model. Periodic water levels, representing periodic tidal motion and freshwater table fluctuations, are imposed at the seaward and landward boundary, respectively, which cause the movement of the mixing zone. Both the scaled‐tank model and the field model show that the combination of the moving mixing zone and kinetic mass transfer may significantly enhance the extent of mixing and create a wider mixing zone than the models without kinetic mass transfer. In addition, sensitivity analyses indicate that a larger capacity ratio (immobile porosity/mobile porosity) of mass transfer leads to a wider mixing zone, and the maximum width of the mixing zone may be reached for a given capacity ratio when the mean retention time scale in the immobile domain (the reciprocal of mass transfer rate) and the period of water level fluctuations are comparable.
Distribution of recycled crust within the upper mantle: Insights from the oxygen isotope composition of MORB from the Australian‐Antarctic Discordance
Authors: Cooper Kari M. , Eiler John M. , Sims Kenneth W. W. , Langmuir Charles H.
Published: December 2009

Geochemical heterogeneity within the mantle has long been recognized through the diversity of trace element and radiogenic isotopic compositions of mantle‐derived rocks, yet the specific origin, abundance, and distribution of enriched material within the mantle have been difficult to quantify. In particular, the origin of the distinctive geochemical characteristics of Indian mantle has been debated for decades. We present new laser fluorination oxygen isotope measurements of mid‐ocean ridge basalt from the Australian‐Antarctic Discordance (AAD), an area where a particularly abrupt transition occurs between Pacific‐type mid‐ocean ridge basalts (MORB) and Atlantic‐type MORB. These data show no distinction in average δ18O between Pacific‐ and Atlantic‐type MORB, indicating that the origin of Indian‐type mantle cannot be attributed to the presence of pelagic sediment. The combined radiogenic isotope, δ18O, and trace element characteristics of Indian‐type MORB at the AAD are consistent with contamination of the Indian upper mantle by lower crustal material. We also present a compilation of available laser fluorination δ18O data for MORB and use these data to evaluate the nature and percentage of enriched material within the upper mantle globally. Data for each ocean basin fit a normal distribution, with indistinguishable means and standard deviations, implying that the variation in δ18O of MORB reflects a stochastic process that operates similarly across all ocean basins. Monte Carlo simulations show that the mean and standard deviation of the MORB data are robust indicators of the mean and standard deviation of the parent distribution of data. Further, although some skewness in the data cannot be ruled out, Monte Carlo results are most consistent with a normal parent distribution. This similarity in characteristics of the δ18O data between ocean basins, together with correlations of δ18O with radiogenic isotope and trace element characteristics of subsets of the data, suggest that the upper mantle globally contains an average of ∼5–10% recycled crustal material and that the depleted mantle in the absence of this component would have δ18O of ∼5.25‰. The Monte Carlo simulations also suggest that additional oxygen isotope data may be used in the future to test the ability of geodynamical models to predict the physical distribution of enriched domains within the upper mantle.
Climate change contributes to more frequent consecutive positive Indian Ocean Dipole events
Authors: Cai W. , Sullivan A. , Cowan T.
Published: December 2009

Are the 2006–2008 three‐consecutive positive Indian Ocean Dipole (pIOD) events linked to climate change? Using 20th century experiments submitted for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4), we show that a 19‐model average IOD index over the 1950–1999 period yields an upward trend. The associated circulation trends provide a favourable environment for pIOD development, leading to a 17% increase in pIOD frequency compared with the case in which trends are removed. The majority of the increase manifests as a frequency increase in the two‐ and three‐consecutive events. The circulation trends are in turn consistent with wind changes associated with a weaker Walker circulation in the Pacific and an enhanced land‐sea temperature contrast in the Indian Ocean (IO) sector. Our results suggest that although it is difficult to attribute the trigger of the recent consecutive pIODs, climate change is increasing the occurrences of such events.
Multifluid Block‐Adaptive‐Tree Solar wind Roe‐type Upwind Scheme: Magnetospheric composition and dynamics during geomagnetic storms—Initial results
Authors: Glocer A. , Tóth G. , Ma Y. , Gombosi T. , Zhang J.‐C. , Kistler L. M.
Published: December 2009

The magnetosphere contains a significant amount of ionospheric O+, particularly during geomagnetically active times. The presence of ionospheric plasma in the magnetosphere has a notable impact on magnetospheric composition and processes. We present a new multifluid MHD version of the Block‐Adaptive‐Tree Solar wind Roe‐type Upwind Scheme model of the magnetosphere to track the fate and consequences of ionospheric outflow. The multifluid MHD equations are presented as are the novel techniques for overcoming the formidable challenges associated with solving them. Our new model is then applied to the May 4, 1998 and March 31, 2001 geomagnetic storms. The results are juxtaposed with traditional single‐fluid MHD and multispecies MHD simulations from a previous study, thereby allowing us to assess the benefits of using a more complex model with additional physics. We find that our multifluid MHD model (with outflow) gives comparable results to the multispecies MHD model (with outflow), including a more strongly negative Dst, reduced CPCP, and a drastically improved magnetic field at geosynchronous orbit, as compared to single‐fluid MHD with no outflow. Significant differences in composition and magnetic field are found between the multispecies and multifluid approach further away from the Earth. We further demonstrate the ability to explore pressure and bulk velocity differences between H+ and O+, which is not possible when utilizing the other techniques considered.
Hydro‐ecological linkages in urbanizing watersheds: An empirical assessment of in‐stream nitrate loss and evidence of saturation kinetics
Authors: Claessens Luc , Tague Christina L. , Band Lawrence E. , Groffman Peter M. , Kenworthy Stephen T.
Published: December 2009

We examined the effect of discharge on in‐stream NO3− loss for a suburban stream in Maryland and addressed two questions: (1) How important is in‐stream nitrogen removal in this biogeoclimatic setting? (2) Is there evidence of saturation kinetics? We conducted the study in a 2.4 km forested stream section, over a period of drought and wet conditions (2001–2004). We calculated NO3− loss from monthly and seasonal mass balances and constructed NO3− loss duration curves. NO3− loss was fairly constant across flow regimes, averaging 0.8 g N ha−1 d−1 per unit watershed area. Proportional NO3− loss (relative to transport) reached 96% at low flows and converged to 0% at high flows. Duration curve analysis showed that proportional NO3− loss was generally low, averaging 6% loss, and only 5% of the time exceeded 22% loss. We extrapolated NO3− removal to the 3.8 km2 watershed. In‐stream NO3− removal corresponded to only 2% of watershed nitrogen inputs and 3% of total losses. Our results suggest that for urbanizing watersheds subject to high nitrogen inputs, in‐stream processing has only a limited potential for reducing watershed nitrogen export. We examined whether NO3− loss patterns showed evidence of saturation kinetics. Estimates of water travel time were used to calculate first‐order NO3− loss metrics. NO3− loss first‐order rate constant (Kc) was negatively related with NO3− concentration. This evidence of saturation kinetics suggests that the common use of first‐order process models is not valid in streams subject to high nitrogen inputs, requiring the need for higher‐order process models.
Managing population and drought risks using many‐objective water portfolio planning under uncertainty
Authors: Kasprzyk J. R. , Reed P. M. , Kirsch B. R. , Characklis G. W.
Published: December 2009

This study contributes a many‐objective analysis of the tradeoffs associated with using the portfolio planning approach for managing the urban water supply risks posed by growing population demands and droughts. The analysis focuses on four supply portfolio strategies: (1) portfolios with permanent rights to reservoir inflows, (2) adaptive options contracts added to the permanent rights, (3) rights, options, and leases, and (4) rights, options, and leases subject to a critical reliability constraint used to represent a maximally risk averse case. The portfolio planning strategies were evaluated using a 10 year Monte Carlo simulation of a city in the Lower Rio Grande Valley (LRGV) within Texas. Our solution sets provide the tradeoff surfaces between portfolios' expected values for cost, cost variability, reliability, surplus water, frequency of using leases, and dropped (or unused) transfers of water. Using an additional severe drought scenario, this work shows that leases and options can reduce the potential for critical supply failures when urban supply systems must contend with unexpected and severe extremes in both demand and water scarcity. In summary, this paper contributes a framework that couples interactive visualization and many‐objective optimization to innovate urban water portfolio planning under uncertainty. The many‐objective analysis of the LRGV case study shows that effective water portfolio planning can simultaneously improve the costs, efficiency, and reliability of urban water supply while ensuring adaptability and resiliency to future changes.
Hypertension-Induced Vascular Remodeling Contributes to Reduced Cerebral Perfusion and the Development of Spontaneous Stroke in Aged SHRSP Rats
Authors: Henning Erica C , Warach Steven , Spatz Maria
Published: December 2009

Stroke in spontaneously-hypertensive, stroke-prone (SHRSP) rats is of particular interest because the pathogenesis is believed to be similar to that in the clinical setting. In this study, we employed multi-modal MRI—ASL, DWI, T2, GRE, T1 (pre/post contrast)—to investigate the natural history of spontaneous cerebral infarction and the specific role of cerebral perfusion in disease development. Twelve female SHRSP rats (age: ∼1 year) were imaged within 1 to 3 days of symptom onset. The distribution of ischemic lesions was the following: 28.1% visual, 21.9% striatal, 18.8% motorsensory, 12.5% thalamic, 12.5% auditory, 3.1% frontal/prelimbic, and 3.1% multiple areas. Ischemic lesions had significantly reduced blood flow in comparison with healthy tissue. Ischemic lesions were characterized by hyperplastic, thrombosed, and compressed vessels. These findings suggest that ischemic lesion development is related to hypertension-induced vascular remodeling and persistent hypoperfusion. This model should be useful for studying the relationship between chronic hypertension and subsequent stroke, both in terms of primary and secondary prevention.
Interleukin-6 Release after Carotid Artery Stenting and Periprocedural New Ischemic Lesions
Authors: Abe Yuko , Sakaguchi Manabu , Furukado Shigetaka , Fujinaka Toshiyuki , Sakoda Saburo , Yoshimine Toshiki , Kitagawa Kazuo
Published: December 2009

Carotid artery stenting (CAS) is currently a standard procedure to treat severe carotid artery stenosis. This procedure causes mechanical plaque rupture, potentially releasing soluble factors into the circulating blood. The purpose of this study is to clarify whether inflammation factors are released from an atherosclerotic plaque after CAS and whether local release of inflammation factors is associated with periprocedural new ischemic lesions. The study consisted of 35 patients with 40 severely stenotic carotid arteries who underwent CAS. Blood samples were obtained from the aorta before the procedure and from the carotid plaque site just after the procedure. Blood levels of interleukin-6 (IL-6), interleukin-18, matrix metalloproteinase (MMP)-2, and tissue inhibitor of MMP-1 were determined. Diffusion-weighted magnetic resonance imaging was performed before and after the procedure. Among inflammatory markers, IL-6 levels markedly increased at the plaque site in comparison to those at the aorta ( P<0.001). The IL-6 levels in the local samples were significantly higher in symptomatic lesions than those in asymptomatic lesions. More importantly, higher local IL-6 levels were associated with the appearance of new ischemic lesions ( P=0.003). The association remained significant ( P=0.030) after controlling for potential risk factors for CAS. Association of local IL-6 levels and periprocedural new ischemic lesions suggests that massive release from the plaque and entry into the cerebral circulation of IL-6 might be one of important factors on periprocedural complications related to CAS.
3 Ounces Is All You Need
Authors: Suiter Debra M. , Leder Steven B.
Published: December 2009

Accurate screening of individuals who are at risk for oropharyngeal dysphagia is critically important because of the negative outcomes associated with the disorder. This article provides a review of a recently published study in which results of the 3-ounce water swallow test were compared with results of instrumental dysphagia testing. Clinical implications are discussed.
The Modified Barium Swallow Impairment Profile (MBSImP): A New Standard Physiologic Approach to Swallowing Assessment and Targeted Treatment
Authors: Sandidge John
Published: December 2009

One of the most critical roles of a speech-language pathologist (SLP) is making decisions from a swallowing assessment about life sustaining and life quality issues such as the ability to continue to eat and drink. The optimal swallowing assessment requires recognizing subtle variations in the physiologic components and events that comprise an intact, healthy swallowing mechanism. No voluntary standard currently exists for swallowing evaluation terminology, measurement, or reporting. Bonnie Martin-Harris, a practicing clinician and researcher, sought to evaluate if a protocol that standardized language, administration/measurement of contrast viscosities, and reporting method could be validly and reliably executed for the modified barium swallow study (MBSS). A five-year study supported by the National Institute on Deafness and Other Communication Disorders (NIDCD) rigorously tested the content and external validity and reliability of a method that resulted in developing a standardized tool, the Modified Barium Swallow Impairment Profile (MBSImP) (Martin-Harris et al., 2008). A web-based learning environment is under construction and will be available for any clinician who desires training and competence in using the MBSImP. This article provides background on development of the MBSImP, the importance and benefit of standardized, objective assessment, and detail on features and status of the MBSImP web site.
Creating a Swallow Screening Program at Mass General Hospital: A Model for Development and Implementation
Authors: Cohen Audrey K.
Published: December 2009

The Massachusetts General Hospital-Swallow Screening Tool (MGH-SST) is a two-part dysphagia screening tool for use by trained staff working with acute neuroscience patients. It was developed in 2004 for use on our neuroscience inpatient units using factors sensitive to aspiration risk. The MGH-SST provides early detection of those at risk for aspiration, guides the decision whether a patient can safely eat or drink, and acts as a trigger for appropriate speech--language pathology (SLP) consult for a comprehensive swallow evaluation. A staff education module was developed including a training video with clinical examples to simulate disordered clinical features, as well as a competency assessment. The MGH-SST was validated using trained nurses with patients with a broad range of neurological and neurosurgical injuries, comparing the MGH-SST results to an instrumental dysphagia assessment, fiberoptic endoscopic evaluation of swallowing (FEES). It was found to be a valid and effective screening to identify patients at risk for dysphagia. Elements critical to the success of a dysphagia screening program include multi-disciplinary collaboration, administrative support, comprehensive training to ensure reliable and consistent administration, and continuous performance measurements.
High-temperature alkali vapor cells with antirelaxation surface coatings
Authors: Seltzer S. J. , Romalis M. V.
Published: December 2009

Antirelaxation surface coatings allow long spin relaxation times in alkali-metal cells without buffer gas, enabling faster diffusion of the alkali atoms throughout the cell and giving larger signals due to narrower optical linewidths. Effective coatings were previously unavailable for operation at temperatures above 80 °C. We demonstrate that octadecyltrichlorosilane (OTS) can allow potassium or rubidium atoms to experience hundreds of collisions with the cell surface before depolarizing, and that an OTS coating remains effective up to about 170 °C for both potassium and rubidium. We consider the experimental concerns of operating without buffer gas and with minimal quenching gas at high vapor density, studying the stricter need for effective quenching of excited atoms and deriving the optical rotation signal shape for atoms with resolved hyperfine structure in the spin-temperature regime. As an example of a high-temperature application of antirelaxation coated alkali vapor cells, we operate a spin-exchange relaxation-free atomic magnetometer with sensitivity of 6 fT/Hz and magnetic linewidth as narrow as 2 Hz.
On the possible surface nature of the electrical activity in He II
Authors: Gutliansky E. D.
Published: December 2009

A simple phenomenological model is proposed which can explain qualitatively the generation of electric fields in He II by second sound and vibrations of the capacitor walls. The model is based on the assumption that a bound state of He atoms exists on a helium-wetted surface, forming a dipole moment (dipole layer). Furthermore, it is assumed that the the character of the wetting changes upon the transition of the helium in the bulk to the superfluid state, and the change of the wetting is a second-order phase transition due to the onset of additional condensation of atoms from the bulk into the dipole layer and the transition of that layer to the superfluid state. This transition is described using Landau theory with an order parameter Ψ=nsexpiφ. It follows from the theory that the value of the ratio of the oscillations of the potential difference to the temperature difference on the capacitor plates generating the second sound is independent of temperature and that the potential difference generated by vibrations of the wall of a torsion pendulum is proportional to the square of its velocity.
Nonlinear surface electron transport over liquid helium
Authors: Nasyedkin K. A. , Sivokon V. E. , Monarkha Yu. P. , Sokolov S. S.
Published: December 2009

We present experimental data and a theoretical analysis of the nonequilibrium mobility of surface electrons in liquid helium. The experiments are carried out in the temperature range where electron mobility is limited by electron scattering on surface excitations of the liquid helium (ripplons). Holding and driving electric fields of wide ranges are used in the measurements. Special attention is paid to the condition of strong holding fields, under which hot electrons are confined to the ground surface level. Depending on the relation between the momentum relaxation rate and electron-electron collision frequency, different theoretical approaches are used to describe the nonlinear mobility of surface electrons. The results obtained allow one to estimate the range of physical parameters in which experimental data can be described by the theory of nonlinear electron transport within the ground surface level.
Monte-Carlo investigation of an anisotropic Ising model
Authors: Murtazaev A. K. , Ibaev Zh. G.
Published: December 2009

The Monte Carlo method is used to study long-period modulated structures in an anisotropic Ising model with competing interactions (ANNNI model). The character, particularities, and dependence of the modulated structures on the temperature and ratio of the exchange interaction constants between the nearest and next-to-nearest neighbors are determined. The phase diagram is constructed.
Heat capacity studies of the magnetic phase transition in sodium-rich NaxCoO2 (0.73⩽x⩽0.87)
Authors: Baran A. , Botko M. , Zorkovská A. , Kajňaková M. , Feher A. , Śebek J. , Šantavá E. , Peng J. P. , Lin C. T.
Published: December 2009

Specific heat measurements in the temperature region from 2to50K in magnetic field up to 10T, oriented parallel and perpendicular to the CoO2 layers, are carried out on a series of high-quality single crystals of NaxCoO2 (x=0.73, 0.76, 0.77, 0.78 and 0.87). Surprisingly, a sharp lambda-type anomaly was observed only for the concentration x=0.76 at temperature 21.80±0.02K, while for all the remaining doping levels a rounded anomaly in the experimental data was visible at a temperature of ∼20K, indicating a smeared magnetic phase transition. While a magnetic field oriented perpendicular to the CoO2 layers shifts the temperature of this anomaly to lower values, a parallel magnetic field has no influence on it; this indirectly supports the idea of A-type antiferromagnetic ordering in the systems studied.
Thermoelectric effect in layered conductors at low temperatures
Authors: Galbova O. , Kirichenko O. V. , Peschanskiĭ V. G.
Published: December 2009

The linear response of the electronic system of a layered conductor to the presence of a temperature gradient is investigated theoretically. The dependence of the thermoelectric power on the temperature and external magnetic field is found at temperatures below the Debye temperature. Experimental investigation of this dependence will make it possible to study different relaxation mechanisms in a system of conduction electrons and to determine the structure of the electronic energy spectrum.
Enhancement in ultraviolet optoelectronic performance of photoconductive semiconductor switch based on ZnO nanobelts film
Authors: Zheng X. J. , Yang B. , Zhang T. , Jiang C. B. , Mao S. X. , Chen Y. Q. , Yuan B.
Published: December 2009

Photoconductive semiconductor switches (PCSSs) based on ZnO nanobelts film and ZnO thin film were fabricated and applied into a test circuit to control the circuit state. The photosensitivity, leakage current from I-V characteristics, and the “on-off” voltage ratio from voltage spectrums of the former are 102 times higher, ten times lower, and two times higher than that of the latter, respectively. It indicates that PCSS based on ZnO nanobelts film has larger photoresponse, better “off state,” and more effective switching function, and they are regarded as consequences of longer transport path and higher surface to volume ratio according to oxygen chemisorption mechanism.
Multipurpose furnace for in situ studies of polycrystalline materials using synchrotron radiation
Authors: Sharma Hemant , Wattjes Alix C. , Amirthalingam Murugaiyan , Zuidwijk Thim , Geerlofs Nico , Offerman S. Erik
Published: December 2009

We report a multipurpose furnace designed for studies using synchrotron radiation on polycrystalline materials, namely, metals, ceramics, and (semi)crystalline polymers. The furnace has been designed to carry out three-dimensional (3D) x-ray diffraction measurements but can also be used for other types of synchrotron radiation research. The furnace has a very low thermal gradient across the specimen (<0.2 °C/mm). Accurate determination of the temperature can be carried out by welding a thermocouple to the specimen. The furnace can be rotated over an angle of 90° in order to determine the crystallographic orientation of each individual grain. It is possible to follow growth kinetics of all grains in the illuminated volume of the specimen. The specimen environment can be controlled varying from vacuum (up to 10−5 mbar) to gas or air filled. The maximum temperature of operation is 1500 °C, with the possibility of achieving high heating (up to 20 °C/s) and cooling rates (up to 30 °C/s without quenching gas). 3D maps of the microstructure of the specimen can be generated at elevated temperatures by bringing the high-resolution detector close to the specimen. We show an example of a simulation of the heat affected zone during the thermal cycle of a weld in a transformation-induced plasticity steel carried out using the furnace. The unique characteristics of the furnace open possibility of new fields in materials research using synchrotron radiation.
On the dynamic roughening transition in nanocomposite film growth
Authors: Shaha K. P. , Pei Y. T. , Chen C. Q. , Turkin A. A. , Vainshtein D. I. , De Hosson J. Th. M.
Published: December 2009

Surface roughness and dynamic growth behavior of TiC/a-C nanocomposite films deposited by nonreactive pulsed-dc (p-dc) magnetron sputtering were studied using atomic force microscopy, cross-sectional scanning, and transmission electron microscopy. From detailed analyses of surface morphology and growth conditions, it is concluded that a transition in growth mechanisms occurs, i.e., a mechanism dominated by geometric shadowing at a p-dc frequency of 100 kHz evolving to a surface diffusion mechanism driven by impact-induced atomistic downhill flow process by Ar+ ions at a p-dc frequency of 350 kHz. It is shown that rapid smoothening of initially rough surfaces with rms roughness from ∼6 to <1 nm can be effectively achieved with p-dc sputtering at 350 kHz pulse frequency, leading to a transition from a strong columnar to a columnar-free microstructure.
Accurate dipole polarizabilities for water clusters n=2–12 at the coupled-cluster level of theory and benchmarking of various density functionals
Authors: Hammond Jeff R. , Govind Niranjan , Kowalski Karol , Autschbach Jochen , Xantheas Sotiris S.
Published: December 2009

The static dipole polarizabilities of water clusters (2≤N≤12) are determined at the coupled-cluster level of theory (CCSD). For the dipole polarizability of the water monomer it was determined that the role of the basis set is more important than that of electron correlation and that the basis set augmentation converges with two sets of diffuse functions. The CCSD results are used to benchmark a variety of density functionals while the performance of several families of basis sets (Dunning, Pople, and Sadlej) in producing accurate values for the polarizabilities was also examined. The Sadlej family of basis sets was found to produce accurate results when compared to the ones obtained with the much larger Dunning basis sets. It was furthermore determined that the PBE0 density functional with the aug-cc-pVDZ basis set produces overall remarkably accurate polarizabilities at a moderate computational cost.
Electroluminescence from n-ZnO nanowires/p-GaN heterostructure light-emitting diodes
Authors: Chen Chih-Han , Chang Shoou-Jinn , Chang Sheng-Po , Li Meng-Ju , Chen I-Cherng , Hsueh Ting-Jen , Hsu Cheng-Liang
Published: December 2009

The investigation explores the fabrication and characteristics of ZnO nanowire (NW)/p-GaN/ZnO NW heterojunction light-emitting diodes (LEDs). Vertically aligned ZnO NWs arrays were grown on the p-GaN substrate. The n-p-n heterojunction LED was fabricated by combining indium tin oxide/glass substrate with the prepared ZnO NWs/p-GaN substrate. The symmetrical rectifying behavior demonstrates that the heterostructure herein was formed with two p-n junction diodes and connected back to back. The room-temperature electroluminescent emission peak at 415 nm was attributed to the band offset at the interface between n-ZnO and p-GaN and defect-related emission from ZnO and GaN. Finally, the photograph indicated the LED clearly emitted blue light.
An analytical method to study the effects of a substrate in surface-enhanced Raman scattering
Authors: Huang Shao Ying , Wu Bae-Ian , Zhang Baile , Lee Yee Hui , Liberman Vladimir , Rothschild Mordechai
Published: December 2009

In studies of surface-enhanced Raman scattering (SERS), individual metal nanoparticle and particle assemblies introduce enhancement of electromagnetic fields. However, the contributions to enhancement due to the substrate supporting the particles are yet to be studied analytically. In this communication, we present an analytical method to investigate the effect of a substrate with realistic layers in SERS. The proposed method quantifies the effect of a substrate on the electric field on the nanoparticles surface in SERS experiments. By applying the proposed method, optimal constructions of a substrate can be obtained to maximize the surface electric field while a poorly constructed one can be avoided. The maximization can lead to a high Raman enhancement factor. The method is verified using numerical simulations.
Temperature distributions of radio-frequency plasma in water by spectroscopic analysis
Authors: Mukasa Shinobu , Nomura Shinfuku , Toyota Hiromichi , Maehara Tsunehiro , Abe Fumiaki , Kawashima Ayato
Published: December 2009

Distributions of emission intensity from radicals, electron temperature, and rotational temperature at a radio frequency of 27.12 MHz plasma in water are clarified by detailed spectroscopy measurement. Through this investigation, the following were observed. The points of maximum emission intensity of Hα, Hβ, O (777 nm), and O (845 nm) are almost the same, while that of OH shifts upward. The electron temperature decreases, while the rotational temperature increases with pressure. The distribution of the electron temperature changes at a threshold pressure, which is concerned with a change in the electron discharge mechanism. The self-bias of the electrode changes from a negative to positive at a threshold pressure. The point of the maximum rotational temperature of OH radicals shifts to approximately 1 mm above that for the maximum intensity of OH emission.
Spectroscopic properties of Ho3+/Yb3+ codoped lanthanum aluminum germanate glasses with efficient energy transfer
Authors: Zhang Qiang , Chen Guorong , Zhang Guang , Qiu Jianrong , Chen Danping
Published: December 2009

Ho 3 + / Yb 3 + codoped lanthanum aluminum germanate glasses are prepared simply by melt-quenching method. The 2 μm emission characteristic and energy transfer from Yb3+ to Ho3+ upon excitation of a conventional 980 nm laser diode is investigated and the energy transfer efficiency is as high as 83%. The spectroscopic parameters are calculated based on Judd–Ofelt (J-O) theory, the intensity parameters Ω2, Ω4, and Ω6 are 4.44, 1.92, and 1.11×10−20 cm2, respectively. The transition probabilities and branching ratios are also estimated by using the J-O parameters. Beer–Lambert and Fuchtbauer–Ladenburg theories are applied to calculate the absorption, emission, and gain cross sections of I57→I58 transition.
Space charge effect on the photocurrent of Pt-sandwiched Pb(Zr0.20Ti0.80)O3 film capacitors
Authors: Xu Jie , Cao Dawei , Fang Liang , Zheng Fengang , Shen Mingrong , Wu Xinglong
Published: December 2009

The space charge effect on the photocurrent of the Pt-sandwiched Pb(Zr0.20Ti0.80)O3 (PZT) films was investigated. The films were prepared under different annealing temperatures and atmospheres to control the densities of space charges in the PZT films. By testing the short-circuit photocurrent after the films were poled under different voltages and correlating the loops of the static photocurrent-poling voltage with the dynamic polarization-switching voltage, it was manifested that the space charges, especially the time-dependent trapped charges, affected significantly the photoelectric properties of the PZT films through an indirect way of influencing the Schottky barrier in the Pt/PZT/Pt capacitors.
Conjugation of quantum dots and Fe3O4 on carbon nanotubes for medical diagnosis and treatment
Authors: Shi Donglu , Cho Hoon Sung , Huth Chris , Wang Feng , Dong Zhongyun , Pauletti Giovanni. M. , Lian Jie , Wang Wei , Liu Guokui , Bud'ko Sergey L. , Wang Lumin , Ewing Rodney C.
Published: December 2009

Quantum dots (QDs) and Fe3O4 nanoparticles were conjugated onto the surfaces of carbon nanotubes (CNTs) for medical diagnosis and treatment. The nanoassembly was designed to meet the specific needs in cancer in vivo imaging and simultaneous treatment. The key functionalities needed for clinical applications were integrated, including CNT surface functionalization for attachment of biological molecules in targeting, drug storage capabilities, fluorescent emissions near the infrared range, and magnetic hyperthermia. CNT-QD-Fe3O4 developed exhibited a strong fluorescence near the infrared region for noninvasive optical in vivo imaging. Magnetization measurements showed nearly reversible hysteresis curves from CNT-QD-Fe3O4 nanoassembly. Fe3O4 conjugated CNT was found to experience hyperthermia heating under alternating electromagnetic field.
Ultrathin film, high specific power InP solar cells on flexible plastic substrates
Authors: Shiu Kuen-Ting , Zimmerman Jeramy , Wang Hongyu , Forrest Stephen R.
Published: December 2009

We demonstrate ultrathin-film, single-crystal InP Schottky-type solar cells mounted on flexible plastic substrates. The lightly p-doped InP cell is grown epitaxially on an InP substrate via gas source molecular beam epitaxy. The InP substrate is removed via selective chemical wet-etching after the epitaxial layers are cold-welded to a 25 μm thick Kapton® sheet, followed by the deposition of an indium tin oxide top contact that forms the Schottky barrier with InP. The power conversion efficiency under 1 sun is 10.2±1.0%, and its specific power is 2.0±0.2 kW/kg. The ultrathin-film solar cells can tolerate both tensile and compressive stress by bending over a <1 cm radius without damage.
Low-voltage pentacene organic field-effect transistors with high-κ HfO2 gate dielectrics and high stability under bias stress
Authors: Zhang Xiao-Hong , Tiwari Shree Prakash , Kim Sung-Jin , Kippelen Bernard
Published: December 2009

Low-voltage pentacene organic field-effect transistors are demonstrated (operating voltage of −3 V) with high-κ hafnium dioxide gate dielectrics grown by atomic layer deposition at 200 °C. A high hole mobility of 0.39 cm2/V s with low threshold voltage (<−0.5 V) and low subthreshold slope of 120 mV/dec is achieved with a HfO2 dielectric layer modified with a phosphonic acid based treatment. A high value of 94.8 nF/V s is obtained for the product of mobility and capacitance density. The devices show excellent bias stress stability with or without the phosphonic acid at the HfO2 gate dielectric surface.
Detection of high-κ and interfacial layer breakdown using the tunneling mechanism in a dual layer dielectric stack
Authors: Raghavan N. , Pey K. L. , Li X.
Published: December 2009

With the advent of high-κ materials as a replacement to silicon oxynitride based gate dielectric, reliability study of high-κ (HK) based devices has become imperative. Processing of HK dielectrics is associated with a thin interfacial layer (IL) of SiOx sandwiched between the high-κ and silicon substrate making it a dual layer dielectric stack. We propose here a simple electrical test algorithm that enables successive separate breakdown and detection of each layer in the bilayer stack during accelerated time dependent dielectric breakdown testing. The algorithm uses the tunneling current mechanism as the yardstick to distinguish between HK and IL breakdown. This technique is useful to decode the Weibull slope of each of these layers in the dielectric stack and decipher their impact on the overall gate stack reliability.
Controlled reversal of coupled Néel walls in flux-closure magnetic trilayer elements
Authors: Huang L. , Zhu Y.
Published: December 2009

We report the detailed field-induced transformation of coupled Néel walls in micron-sized trilayer elliptical elements for novel domain-wall-based device applications. Using in situ Lorentz transmission electron microscopy and micromagnetic simulation, we demonstrate that the magnetostatically coupled composite wall structure can be switched controllably without affecting the overall flux-closure domain configuration via separate translation of vortex cores in the two magnetic layers. The top and bottom Néel walls either trap or expel each other depending on the relative orientation of their magnetization directions, leading to the interesting domain switching behavior observed during magnetization reversal.
Ferrimagnetism in epitaxially grown Mn2VAl Heusler alloy investigated by means of soft x-ray magnetic circular dichroism
Authors: Kubota Takahide , Kodama Kenji , Nakamura Tetsuya , Sakuraba Yuya , Oogane Mikihiko , Takanashi Koki , Ando Yasuo
Published: December 2009

Epitaxially grown Mn2VAl films were fabricated on MgO (001) single crystalline substrates by using a sputtering technique. The resulting Mn2VAl films with substrate temperatures of Ts=500 and 600 °C showed an L21-ordered structure. The saturation magnetization was 150 emu/cm3 at 300 K for a sample with Ts=600 °C. Ferrimagnetic coupling between the Mn and V magnetic moments in the L21-Mn2VAl film was clearly demonstrated by soft x-ray magnetic circular dichroism. In previous studies, this coupling was found only in polycrystalline bulk samples examined by nuclear magnetic resonance.
Buckling resistant graphene nanocomposites
Authors: Rafiee M. A. , Rafiee J. , Yu Z.-Z. , Koratkar N.
Published: December 2009

An experimental study on buckling of graphene/epoxy nanocomposite beam structures is presented. Significant increase (up to 52%) in critical buckling load is observed with addition of only 0.1% weight fraction of graphene platelets into the epoxy matrix. Based on the classical Euler-buckling model, the buckling load is predicted to increase by ∼32%. The over 50% increase in buckling load observed in our testing suggests a significant enhancement in load transfer effectiveness between the matrix and the graphene platelets under compressive load. Such nanocomposites with high buckling stability show potential as lightweight and buckling-resistant structural elements in aeronautical and space applications.
An accurate model potential for alkali neon systems
Authors: Zanuttini D. , Jacquet E. , Giglio E. , Douady J. , Gervais B.
Published: December 2009

We present a detailed investigation of the ground and lowest excited states of M-Ne dimers, for M=Li, Na, and K. We show that the potential energy curves of these Van der Waals dimers can be obtained accurately by considering the alkali neon systems as one-electron systems. Following previous authors, the model describes the evolution of the alkali valence electron in the combined potentials of the alkali and neon cores by means of core polarization pseudopotentials. The key parameter for an accurate model is the M+-Ne potential energy curve, which was obtained by means of ab initio CCSD(T) calculation using a large basis set. For each MNe dimer, a systematic comparison with ab initio computation of the potential energy curve for the X, A, and B states shows the remarkable accuracy of the model. The vibrational analysis and the comparison with existing experimental data strengthens this conclusion and allows for a precise assignment of the vibrational levels.
High quality GaInP nonlinear photonic crystals with minimized nonlinear absorption
Authors: Combrié Sylvain , Tran Quynh Vy , De Rossi Alfredo , Husko Chad , Colman Pierre
Published: December 2009

We have established a new material, indium gallium phosphide, lattice matched to gallium arsenide, for two-dimensional photonic crystals at 1.55 μm. We have demonstrated single-mode cavities with intrinsic Q-factor larger than one million and achieved very large self-phase-modulation coefficient 1.1×103 W1 m−1 in line-defect waveguides. Importantly, the material band gap is such that two-photon absorption, Eg>2ℏω, is completely suppressed at this important telecommunications wavelength.
Low-voltage electric-double-layer paper transistors gated by microporous SiO2 processed at room temperature
Authors: Sun Jia , Wan Qing , Lu Aixia , Jiang Jie
Published: December 2009

Battery drivable low-voltage SnO2-based paper thin-film transistors with a near-zero threshold voltage (Vth=0.06 V) gated by microporous SiO2 dielectric with electric-double-layer (EDL) effect are fabricated at room temperature. The operating voltage is found to be as low as 1.5 V due to the huge gate specific capacitance (1.34 μF/cm2 at 40 Hz) related to EDL formation. The subthreshold gate voltage swing and current on/off ratio is found to be 82 mV/decade and 2.0×105, respectively. The electron field-effect mobility is estimated to be 47.3 cm2/V s based on the measured gate specific capacitance at 40 Hz.
New Urbanism and the Barrio
Authors: González Erualdo Romero , Lejano Raul P
Published: December 2009

The last decade has seen a growing turn toward New Urbanism in the redevelopment of urban neighborhoods. In October 2007 the City of Santa Ana released a draft Renaissance Plan to revitalize a transit-oriented district and government center supported by two neighborhoods. The plan exemplifies New Urbanist design principles which promote mixed income residential neighborhoods and respect local culture. Using a case study in two Mexican and working-class immigrant barrios and the adjacent downtown district, we investigate these principles. We describe different community-wide perspectives concerning ‘redevelopment’ and employ a textual analysis of the Renaissance Plan. One salient finding is that local planning codes reflect and support cultural and class beliefs that alienate Latino barrios. Another finding is that it is in the construction of a new science of form that the disciplinary gaze of New Urbanism reshapes places upon cultural-alien and class-alien norms. We conclude by suggesting research on the tensions between ethno-cultural-dominant city councils and ethno-cultural and economically marginalized neighborhoods while exploring how policy and discourse impact urban place.