bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of Glass Nanofibers Using Femtosecond Laser Radiation Under Ambient Condition
Authors: Sivakumar M , Venkatakrishnan K , Tan B
Published: July 2009

We report the unique growth of nanofibers in silica and borosilicate glass using femtosecond laser radiation at 8 MHz repetition rate and a pulse width of 214 fs in air at atmospheric pressure. The nanofibers are grown perpendicular to the substrate surface from the molten material in laser-drilled microvias where they intertwine and bundle up above the surface. The fibers are few tens of nanometers in thickness and up to several millimeters in length. Further, it is found that at some places nanoparticles are attached to the fiber surface along its length. Nanofiber growth is explained by the process of nanojets formed in the molten liquid due to pressure gradient induced from the laser pulses and subsequently drawn into fibers by the intense plasma pressure. The attachment of nanoparticles is due to the condensation of vapor in the plasma.
Characterization of Scale Formed on the Surfaces of Toilet Bowls
Authors: Ohki Tohru , Nishikawa Naoki , Hasegawa Takayuki , Okano Tomomichi , Tanizawa Yoshiaki
Published: July 2009

Repeated use of a toilet results in the build‐up of a deposit derived from urine and hard water on the surface of the toilet bowl. The hardened mineral scale is difficult to clean completely, especially in the case of deposits under the rim. A number of studies have focused on kidney stones, which are also caused by urine in the urinary tract; little attention, however, has been paid to the detailed composition and structure of the toilet scale. To develop powerful products for removing the toilet scale effectively instead of relying on acid‐cleaning and scrubbing, the composition and the accumulation mechanism of the scale must be clarified. Scale samples collected from the bowl surface were characterized by IR, XRF, XRD, ICP–AES, SEM–EDS and HPLC techniques and found to consist mainly of calcium phosphates, struvite, calcium carbonate, uric acid and proteins. After acid treatment of the scale, a film‐like structure of protein, produced as a result of the metabolism of bacteria and mold, was left behind. The scale had composite structures that were composed of the inorganic minerals and the organic materials listed above. This structure might be critical to making the scale resistant to removal by acid‐containing cleaners.
Anti‐apoptotic action of hydrogen sulfide is associated with early JNK inhibition
Authors: Shi Sa , Li Qing‐song , Li Hong , Zhang Li , Xu Man , Cheng Jia‐li , Peng Cheng‐hai , Xu Chang‐qing , Tian Ye
Published: July 2009

The mechanism of action of Hydrogen sulfide (H2S) as a novel endogenous gaseous messenger and potential cardioprotectant is not fully understood. We therefore investigated the prevention of cardiomyocyte apoptosis by exogenous H2S and the signaling pathways leading to cardioprotection. Using a simulated ischemia–reperfusion (I/Re) model with primary cultured rat neonatal cardiomyocytes, I/Re induced a rapid, time‐dependent phosphorylation of c‐Jun N‐terminal kinase (JNK), with significant elevation at 0.25 h and a peak at 0.5 h during reperfusion. NaHS (H2S donor) significantly inhibited the early phosphorylation of JNK, especially at 0.5 h. Both NaHS and SP600125 (specific JNK inhibitor) decreased the number of apoptotic cells, lowered cytochrome C release and enhanced Bcl‐2 expression. When NaHS application was delayed 1 h after reperfusion, the inhibition of apoptosis by H2S was negated. In conclusion, this is novel evidence that early JNK inhibition during reperfusion is associated with H2S‐mediated protection against cardiomyocyte apoptosis.
Attentional modulation fails to attenuate the subjective pain experience in chronic, unexplained pain
Authors: Snijders T.J. , Ramsey N.F. , Koerselman F. , Van Gijn J.
Published: July 2009

Background: Chronic, unexplained pain is a common, ill‐understood clinical problem. Increased sensitivity for pain and other stimuli is often implied as an underlying mechanism. Attentional processes influence central pain processing and might mediate hypersensitivity at a cerebral level.

Aims: To study patients with chronic, unexplained pain with respect to (a) subjective pain experience; (b) effects of attentional manipulation; (c) level at which alterations in pain processing occur: locally (symptomatic body region), or generalised.

Methods: We compared 16 patients with chronic, unexplained limb pain with 16 matched healthy controls. Pain thresholds to electrical stimuli were recorded. Subjects then received individually thresholded painful and non‐painful stimuli, with manipulation of attention towards or away from pain. The intensity of pain perception was recorded by means of visual analogue scales (VAS). Pain thresholds and effects of Attention and Laterality on VAS scores were compared between groups by means of general linear modelling (restricted to 12 patients with unilateral pain and 12 controls).

Results: Distraction increased thresholds for pain in healthy volunteers, but this effect was significantly attenuated in patients. Significant interactions between attention‐effects, stimulus laterality and stimulus intensity indicated that VAS scores for painful stimuli were attenuated during distraction in healthy controls, but not in pain patients.

Conclusions: Results support the notion that pain processing is enhanced in chronic, unexplained pain, and that the influence of attentional modulation on pain processing is attenuated. Potential cerebral mechanisms are changes in either attentional allocation or attention‐mediated descending pain modulation. The changes seem to occur at a generalised level.
Global Justice, Freedom of Movement and Democratic Citizenship
Authors: Bauböck Rainer
Published: July 2009

The article discusses three liberal arguments about freedom of movement: immigration as a remedy for global injustice in the distribution of opportunities, freedom of movement as an integral aspect of individual autonomy, and immigration control as implied in democratic self-determination and citizenship. The article shows how these apparently irreconcilable stances can be reconstructed as partially overlapping once we realize that liberal citizenship provides not only reasons for closure but entails a bundle of mobility rights and is open for access by migrant stakeholders.
Altruisme, égoïsme et individualisme dans l’École durkheimienne
Authors: Steiner Philippe
Published: July 2009

This article studies Durkheim's views on altruism and selfishness and, therefore, on modern individualism. In contrast to Comte and Spencer, Durkheim used these concepts in his empirical work on suicide and then as intellectual tools for explaining his view on the professional and political organization required in a modern democracy. Finaly, the article examines how Durkheim's views were modified by the Durkheimian, notably with Marcel Mauss’ emphasis on interested/desinterested behaviors in gift-giving processes which are the empirical and symbolical roots of social solidarity.
The Importance of Protestantism in Max Weber's Theory of Secularisation
Authors: Carroll Anthony J.
Published: July 2009

In this article, I review my recent bookProtestant Modernity. Weber, Secularisation and Protestantism,which reconstructs Weber's theory of secularisation and argues that this is formulated within a liberal Protestant framework. I argue that this theory is a part of his Protestant account of modernity. I also sketch some of the major issues involved in developing a Catholic account of modernity and provide some worked through examples of the sociological implications of this change of confessional presuppositions.
Secularism in Context: The Relations between the Greek State and the Church of Greece in Crisis
Authors: Karagiannis Evangelos
Published: July 2009

The present article addresses the question of secularism in Greece. It discusses the prevalent modernist and civilisationist explanations of the recent crisis in state-church relations in Greece. Based on the idea that there is neither a single route to, nor a single pattern of, modernity and secularism, the article argues that the entanglement between state and church in modern Greece does not necessarily indicate either incomplete modernity or incomplete secularism. The paper emphasises both the structural weakness of the Orthodox Church in the modern Greek state and the secularisation of the church's ideology as core dimensions of the particular pattern of secularism in this country. The recent crisis is interpreted as a result of the twofold challenge of democratisation and globalisation that this historically grown pattern of secularism is facing over the last decades. Further, the article seeks to demonstrate that the nationalist stance of the Church of Greece should not be seen as persistent blind traditionalism and anti-modernism.
SCHEDULING A HETEROGENEOUS SET OF TRAINS OVER A SINGLE LINE TRACK USING LAGRANGIAN RELAXATION
Authors: MACKENZIE SCOTT , MILLS GRAHAM
Published: July 2009

There is increasing interest in the cost of railway infrastructure access as a variety of private companies operate trains with different lengths over a common rail network. It is important to have a method for evaluating the cost of adding an additional train to a railway timetable. This is particularly so for single line track with occasional passing loops. The concept of a fixed loop capacity is extended to one that is dependent on the trains. We develop a model for scheduling a heterogeneous set of trains on single line systems with loops. Our method minimizes the total weighted delay. A Lagrangian relaxation technique is used that relaxes the capacity constraints for track segments and super segments. We measure the delay for each train and the total weighted delay for the heterogeneous set of trains. Our model allows us to investigate the robustness of the weighted delay to variation in the departure time of individual trains. The paper demonstrates that a Lagrangian relaxation heuristic provides optimal train schedules for instances of small heterogeneous train sets. The method is used primarily to check the effectiveness of heuristic algorithms commonly used to find schedules for practical problems.
DELAY-DEPENDENT ROBUST H∞ CONTROL FOR SINGULAR SYSTEMS WITH MULTIPLE DELAYS
Authors: ZHU SHUQIAN , ZHANG CHENGHUI , LIU XINZHI , LI ZHENBO
Published: July 2009

This paper studies the problem of delay-dependent robust H∞ control for singular systems with multiple delays. Based on a Lyapunov–Krasovskii functional approach, an improved delay-dependent bounded real lemma (BRL) for singular time-delay systems is established without using any of the model transformations and bounding techniques on the cross product terms. Then, by applying the obtained BRL, a delay-dependent condition for the existence of a robust state feedback controller, which guarantees that the closed-loop system is regular, impulse free, robustly stable and satisfies a prescribed H∞ performance index, is proposed in terms of a nonlinear matrix inequality. The explicit expression for the H∞ controller is designed by using linear matrix inequalities and the cone complementarity iterative linearization algorithm. Numerical examples are also given to illustrate the effectiveness of the proposed method.
Postseismic deformation due to the Mw 6.0 2004 Parkfield earthquake: Stress‐driven creep on a fault with spatially variable rate‐and‐state friction parameters
Authors: Barbot Sylvain , Fialko Yuri , Bock Yehuda
Published: July 2009

We investigate the coseismic and postseismic deformation due to the Mw 6.0 2004 Parkfield, California, earthquake. We produce coseismic and postseismic slip models by inverting data from an array of 14 continuous GPS stations from the SCIGN network. Kinematic inversions of postseismic GPS data over a time period of 3 years show that afterslip occurred in areas of low seismicity and low coseismic slip, predominantly at a depth of ∼5 km. Inversions suggest that coseismic stress increases were relaxed by predominantly aseismic afterslip on a fault plane. The kinetics of afterslip is consistent with a velocity‐strengthening friction generalized to include the case of infinitesimal velocities. We performed simulations of stress‐driven creep using a numerical model that evaluates the time‐dependent deformation due to coseismic stress changes in a viscoelastoplastic half‐space. Starting with a coseismic slip distribution, we compute the time‐dependent evolution of afterslip on a fault plane and the associated displacements at the GPS stations. Data are best explained by a rate‐strengthening model with frictional parameter (a − b) = 7 × 10−3, at a high end of values observed in laboratory experiments. We also find that the geodetic moment due to creep is a factor of 100 greater than the cumulative seismic moment of aftershocks. The rate of aftershocks in the top 10 km of the seismogenic zone mirrors the kinetics of afterslip, suggesting that postearthquake seismicity is governed by loading from the nearby aseismic creep. The San Andreas fault around Parkfield is deduced to have large along‐strike variations in rate‐and‐state frictional properties. Velocity strengthening areas may be responsible for the separation of the coseismic slip in two distinct asperities and for the ongoing aseismic creep occurring between the velocity‐weakening patches after the 2004 rupture.
Remote triggering of tremor along the San Andreas Fault in central California
Authors: Peng Zhigang , Vidale John E. , Wech Aaron G. , Nadeau Robert M. , Creager Kenneth C.
Published: July 2009

We perform a systematic survey of triggered tremor along the San Andreas Fault in central California for the 31 teleseismic earthquakes with Mw ≥ 7.5 since 2001. We identify 10 teleseismic events associated with clear triggered tremor. About 52% of the tremor is concentrated south of Parkfield near Cholame, where ambient tremor has been identified previously, and the rest is widely distributed in the creeping section of the San Andreas Fault north of Parkfield. Tremor is generally initiated and is in phase with the Love wave particle velocity. However, the pattern becomes complicated with the arrival of the Rayleigh waves, and sometimes tremor continues after the passage of the surface waves. We identify two cases in which tremor is triggered during the teleseismic PKP phase. These results suggest that while shear stress from the passage of the Love waves plays the most important role in triggering tremor in central California, other factors, such as dilatational stresses from the Rayleigh and P waves, also contribute. We also examine the ambient tremor occurrence rate before and after the teleseismic events and find a transient increase of stacked tremor rate during the passage of the teleseismic surface waves. This observation implies that the occurrence time of tremor is temporally advanced by the dynamic stresses of the teleseismic waves. The amplitude of the teleseismic waves correlates with the occurrence of triggered tremor, and the inferred tremor‐triggering threshold is ∼2–3 kPa. The relatively low triggering threshold indicates that the effective stress at the tremor source region is very low, most likely due to near‐lithostatic fluid pressure.
High‐resolution three‐dimensional simulations of mid‐ocean ridge hydrothermal systems
Authors: Coumou D. , Driesner T. , Geiger S. , Paluszny A. , Heinrich C. A.
Published: July 2009

High‐resolution numerical simulations give clear insights into the three‐dimensional structure of thermal convection associated with black‐smoker hydrothermal systems. We present a series of simulations that show that, at heat fluxes expected at mid‐ocean ridge spreading axes, upflow is focused in circular, pipe‐like regions, with the bulk of the recharge taking place in the near‐axial region. Recharging fluids have relatively warm temperatures. In this configuration, the system maximizes its heat output, which can be shown to be linked to nonlinearity in the fluid properties. Furthermore, we present a series of simulations with different permeability scenarios. These show that when permeability contrasts are moderate, convection maintains this pipe‐like fluid flow structure. The permeability contrast has a dominant effect on flow patters only at early, immature, stages of convection, focussing upflow in high‐permeability regions and downflow in low‐permeability regions. In such early stages of convection, diffusive vent styles can emerge, which look remarkably similar to diffuse vent fields in natural systems. Finally, simulations in which permeability is defined as a function of temperature indicate that the brittle‐ductile condition is likely to occur at temperatures not lower than 650°C. At lower brittle‐ductile transition temperatures, the system cannot remove the heat delivered from the magma chamber and vent temperatures are substantially lower than 400°C. This result is in agreement with estimates of the brittle‐ductile transition temperature from rock‐mechanical studies and the occurrence of earthquakes in the oceanic lithosphere.
A decade of acoustic thermometry in the North Pacific Ocean
Authors: Dushaw B. D. , Worcester P. F. , Munk W. H. , Spindel R. C. , Mercer J. A. , Howe B. M. , Metzger K. , Birdsall T. G. , Andrew R. K. , Dzieciuch M. A. , Cornuelle B. D. , Menemenlis D.
Published: July 2009

Over the decade 1996–2006, acoustic sources located off central California (1996–1999) and north of Kauai (1997–1999, 2002–2006) transmitted to receivers distributed throughout the northeast and north central Pacific. The acoustic travel times are inherently spatially integrating, which suppresses mesoscale variability and provides a precise measure of ray‐averaged temperature. Daily average travel times at 4‐day intervals provide excellent temporal resolution of the large‐scale thermal field. The interannual, seasonal, and shorter‐period variability is large, with substantial changes sometimes occurring in only a few weeks. Linear trends estimated over the decade are small compared to the interannual variability and inconsistent from path to path, with some acoustic paths warming slightly and others cooling slightly. The measured travel times are compared with travel times derived from four independent estimates of the North Pacific: (1) climatology, as represented by the World Ocean Atlas 2005 (WOA05); (2) objective analysis of the upper‐ocean temperature field derived from satellite altimetry and in situ profiles; (3) an analysis provided by the Estimating the Circulation and Climate of the Ocean project, as implemented at the Jet Propulsion Laboratory (JPL‐ECCO); and (4) simulation results from a high‐resolution configuration of the Parallel Ocean Program (POP) model. The acoustic data show that WOA05 is a better estimate of the time mean hydrography than either the JPL‐ECCO or the POP estimates, both of which proved incapable of reproducing the observed acoustic arrival patterns. The comparisons of time series provide a stringent test of the large‐scale temperature variability in the models. The differences are sometimes substantial, indicating that acoustic thermometry data can provide significant additional constraints for numerical ocean models.
Late Cenozoic structural and tectonic development of the western margin of the central Andean Plateau in southwest Peru
Authors: Schildgen Taylor F. , Hodges Kip V. , Whipple Kelin X. , Pringle Malcolm S. , van Soest Matthijs , Cornell Katrina
Published: July 2009

Structural and thermochronologic studies of the western margin of the central Andean Plateau show changing styles of deformation through time that give insights into tectonic evolution. In southwest Peru, uplift of the plateau proceeded in several distinct phases. First, NW striking, NE dipping reverse faults accommodated uplift prior to ∼14–16 Ma. Subsequent uplift of the plateau relative to the piedmont (between the plateau and the Pacific Ocean) occurred between ∼14 and 2.2 Ma and was accommodated by NW striking, SW dipping normal faults and subparallel monoclinal folds. The youngest phase of uplift affected the piedmont region and the plateau margin as a coherent block. Although the uplift magnitude associated with phase 1 is unknown, phases 2 and 3 resulted in at least 2.4–3.0 km of uplift. Up to 1 km of this may have occurred during phase 3. Geodynamic processes occurring in both the continental interior and the subduction zone likely contributed to uplift.
Geostatistical simulation of two‐dimensional fields of raindrop size distributions at the meso‐γ scale
Authors: Schleiss M. A. , Berne A. , Uijlenhoet R.
Published: July 2009

The large variability of the raindrop size distribution (DSD) in space and time must be taken into account to improve remote sensing of precipitation. The ability to simulate a large number of 2‐D fields of DSDs sharing the same statistical properties provides a very useful simulation framework that nicely complements experimental approaches based on DSD ground measurements. These simulations can be used to investigate radar beam propagation through rain and to evaluate different radar retrieval techniques. The proposed approach uses geostatistical methods to provide structural analysis and stochastic simulation of DSD fields. First, the DSD is assumed to follow a Gamma distribution with three parameters. As a consequence, 2‐D fields of DSDs can be described as a multivariate random function. The parameters are normalized using a Gaussian anamorphosis and simulated by taking advantage of fast Gaussian simulation algorithms. Variograms are used to characterize the spatial structure of the DSD fields. The generated fields have identical spatial structure and are consistent with the observations. Because intermittency cannot be simulated using this technique, the size of the simulation domain is limited to the meso‐γ scale (2‐20 km). To assess the proposed approach, the method is applied to data collected during intense Mediterranean rainfall. Taylor's hypothesis is invoked to convert time series into 1‐D range profiles. The anisotropy of the fields is derived from radar measurements. Simulated and measured reflectivity fields are in good agreement with respect to the mean, the standard deviation, and the spatial structure, demonstrating the promising potential of the proposed stochastic model of DSD fields.
Aerosol effects on the inter‐cloud region of a small cumulus cloud field
Authors: Koren Ilan , Feingold Graham , Jiang Hongli , Altaratz Orit
Published: July 2009

In a recent paper, we used observations to show that the inter‐cloud “cloud‐free regime” (or “twilight zone”) is not free of clouds and comprises small fragments of clouds, hydrated aerosol, as well as incipient, hesitant, and decaying clouds. In this paper we characterize the properties of, and investigate the aerosol affect on, the twilight zone using high resolution large eddy simulations of clean and polluted shallow cumulus. We analyze the occurrence of these clouds with weak signature and show that cloud fields forming in polluted environments are characterized by a more rapid decrease in liquid water path with increasing distance from cloud than their cleaner counterparts, and that the inter‐cloud zone contains significantly fewer low liquid water path pockets. This reduction in liquid water content in the area considered cloud‐free in the polluted cases is countered by more aerosol uptake of water vapor.
Wintertime Antarctic coastal polynya area: 1992–2008
Authors: Kern S.
Published: July 2009

An iterative classification technique based on Special Sensor Microwave/Imager data is used to estimate the total daily circum‐Antarctic coastal polynya area for 1992–2008. The average wintertime (June to September) area is estimated at 245,000 ± 10,000 km2, and varies between 210,000 km2 (1997) and 281,000 km2 (2007). The polynyas along East‐Antarctica (60 to 160°E) contribute about 40% to this area. The most persistent polynyas are located along East Antarctica: Lars‐Christensen Coast (LCC), Prydz Bay, Western Davis Sea, Mertz Glacier, and in the Ross Sea: Ross Ice Shelf and Terra Nova Bay. The polynya at the LCC is observed on 110 ± 5 days during winter for 1992–2008. It is the most persistent of the observed polynyas, covering an average area of 2400 km2 on more than 90 days. Trends in the average wintertime area of the major coastal polynyas during 1992–2008 are small and not significant.
Enhanced aerosol backscatter adjacent to tropical trade wind clouds revealed by satellite‐based lidar
Authors: Tackett Jason Lucas , Di Girolamo Larry
Published: July 2009

There have been many proposed processes by which clouds modify aerosol properties, suggesting that aerosol properties near clouds are different than far from clouds. We provide the first satellite‐based lidar observations of backscatter and color ratio, quantities directly related to aerosol properties, as a function of distance to cloud edge for boundary layer clouds over the western tropical Atlantic. We show backscatter and color ratio are enhanced adjacent to cloud edge, particularly near cloud top and cloud base. Specifically, layer integrated median backscatter increases by 31 ± 3% and 42 ± 2%, at wavelengths of 532 nm, and 1,064 nm, respectively, and layer averaged color ratio increases by 15 ± 5%. Backscatter calculations suggest our observations adjacent to cloud are best explained by an aerosol size distribution with reduced number concentration, increased median radius, and decreased width compared to far from cloud.
Nonlinear mechanisms of lower‐band and upper‐band VLF chorus emissions in the magnetosphere
Authors: Omura Yoshiharu , Hikishima Mitsuru , Katoh Yuto , Summers Danny , Yagitani Satoshi
Published: July 2009

We develop a nonlinear wave growth theory of magnetospheric chorus emissions, taking into account the spatial inhomogeneity of the static magnetic field and the plasma density variation along the magnetic field line. We derive theoretical expressions for the nonlinear growth rate and the amplitude threshold for the generation of self‐sustaining chorus emissions. We assume that nonlinear growth of a whistler mode wave is initiated at the magnetic equator where the linear growth rate maximizes. Self‐sustaining emissions become possible when the wave propagates away from the equator during which process the increasing gradients of the static magnetic field and electron density provide the conditions for nonlinear growth. The amplitude threshold is tested against both observational data and self‐consistent particle simulations of the chorus emissions. The self‐sustaining mechanism can result in a rising tone emission covering the frequency range of 0.1–0.7 Ωe0, where Ωe0 is the equatorial electron gyrofrequency. During propagation, higher frequencies are subject to stronger dispersion effects that can destroy the self‐sustaining mechanism. We obtain a pair of coupled differential equations for the wave amplitude and frequency. Solving the equations numerically, we reproduce a rising tone of VLF whistler mode emissions that is continuous in frequency. Chorus emissions, however, characteristically occur in two distinct frequency ranges, a lower band and an upper band, separated at half the electron gyrofrequency. We explain the gap by means of the nonlinear damping of the longitudinal component of a slightly oblique whistler mode wave packet propagating along the inhomogeneous static magnetic field.
A homogeneous database of sunspot areas covering more than 130 years
Authors: Balmaceda L. A. , Solanki S. K. , Krivova N. A. , Foster S.
Published: July 2009

The historical record of sunspot areas is a valuable and widely used proxy of solar activity and variability. The Royal Greenwich Observatory regularly measured this and other parameters between 1874 and 1976. After that time records from a number of different observatories are available. These, however, show systematic differences and often have significant gaps. Our goal is to obtain a uniform and complete sunspot area time series by combining different data sets. A homogeneous composite of sunspot areas is essential for different applications in solar physics, among others for irradiance reconstructions. Data recorded simultaneously at different observatories are statistically compared in order to determine the intercalibration factors. Using these data we compile a complete and cross‐calibrated time series. The Greenwich data set is used as a basis until 1976, the Russian data (a compilation of observations made at stations in the former USSR) are used between 1977 and 1985, and data compiled by the USAF network are used since 1986. Other data sets (Rome, Yunnan, and Catania) are used to fill up the remaining gaps. Using the final sunspot areas record the Photometric Sunspot Index is calculated. We also show that the use of uncalibrated sunspot areas data sets can seriously affect the estimate of irradiance variations. Our analysis implies that there is no basis for the claim that UV irradiance variations have a much smaller influence on climate than total solar irradiance variations.
Manipulation of the microbiota of mass-reared Mediterranean fruit flies Ceratitis capitata (Diptera: Tephritidae) improves sterile male sexual performance
Authors: Ami Eyal Ben , Yuval Boaz , Jurkevitch Edouard
Published: July 2009

The sterile insect technique (SIT) is a method of biological control whereby millions of factory reared sterile male insects are released into the field. This technique is commonly used to combat the Mediterranean fruit fly (Ceratitis capitata, Diptera: Tephritidae). Sterile medfly males are less competent in attracting and mating with wild females, a property commonly linked to the irradiation process responsible for the sterilization. As bacteria are important partners in the fly's life cycle, we used molecular analytical methods to study the community structure of the gut microbiota in irradiated male medflies. We find that the sterilizing irradiation procedure affects the gut bacterial community structure of the Mediterranean fruit fly. Although the Enterobacteriaceae family remains the dominant bacterial group present in the gut, the levels of Klebsiella species decreases significantly in the days after sterilization. In addition, we detected substantial differences in some bacterial species between the mass rearing strain Vienna 8 and the wild strain. Most notable among these are the increased levels of the potentially pathogenic species Pseudomonas in the industrial strain. Testing the hypothesis that regenerating the original microbiota community could result in enhanced competitiveness of the sterile flies, we found that the addition of the bacterial species Klebsiella oxytoca to the postirradiation diet enables colonization of these bacteria in the gut while resulting in decreased levels of the Pseudomonas sp. Feeding on diets containing bacteria significantly improved sterile male performance in copulatory tests. Further studies will determine the feasibility of bacterial amelioration in SIT operations.
Diversity of aerobic and anaerobic ammonia-oxidizing bacteria in marine sponges
Authors: Mohamed Naglaa M , Saito Keiko , Tal Yossi , Hill Russell T
Published: July 2009

Aerobic ammonia-oxidizing bacteria (AAOB) are known to have an important function in the marine nitrogen cycle. Anaerobic ammonium oxidation (anammox) carried out by some members of Planctomycetales is also an important process in marine ecosystems. Ammonia-monooxygenase gene (amoA) fragments were amplified to investigate the potential for nitrification and the diversity of the AAOB in two marine sponges Ircinia strobilina and Mycale laxissima. All of the AmoA sequences obtained from the two sponges clustered with the AmoA sequences of the Betaproteobacteria Nitrosospira spp. To investigate the anaerobic ammonia-oxidizing bacteria (AnAOB) in sponges, 16S rRNA gene fragments of Planctomycetales and anammox bacteria were also amplified with specific primers, and clone libraries were constructed. The Planctomycetales diversity detected in the two sponges was different. The Planctomycetales community in M. laxissima was affiliated with Pirellula, Planctomyces and anammox bacteria, while all of the I. strobilina Planctomycetales clones were solely affiliated with the candidate phylum ‘Poribacteria’. Interestingly, sequences related to anammox genera were recovered only from M. laxissima. This is the first report of anammox bacteria in marine sponges. It is intriguing to find AAOB and AnAOB in M. laxissima, but the nature of their interaction with the sponge host and with each other remains unclear. This work further supports the potential of sponge-associated microorganisms for nitrification and sheds light on anammox as a new aspect of the nitrogen cycle in marine sponges.
Direct observations of three dimensional growth of hydrates hosted in porous media
Authors: Kerkar Prasad , Jones Keith W. , Kleinberg Robert , Lindquist W. Brent , Tomov Stan , Feng Huan , Mahajan Devinder
Published: July 2009

The visualization of time-resolved three-dimensional growth of tetrahydrofuran hydrates with glass spheres of uniform size as porous media using synchrotron x-ray computed microtomography is presented. The images of hydrate patches, formed from excess tetrahydrofuran in aqueous solution, show random nucleation and growth concomitant with grain movement but independent of container-wall effect. Away from grain surfaces, hydrate surface curvature was convex showing that liquid, not hydrate, was the wetting phase, similar to ice growth in porous media. The extension of the observed behavior to methane hydrates could have implications in understanding their role in seafloor stability and climate change.
Physical degradation of gate dielectrics induced by local electrical stress using conductive atomic force microscopy
Authors: Polspoel W. , Favia P. , Mody J. , Bender H. , Vandervorst W.
Published: July 2009

Local electrical stress in gate dielectrics using conductive atomic force microscopy (C-AFM) induces structural damage in these layers. To allow C-AFM to become a mature technique to study oxide degradation, the impact of this structural damage, i.e., protrusions and holes, on the electrical behavior must be well understood. The physical nature and growth mechanism of protrusions due to a negative substrate voltage (Vs<0) is, however, debated in literature. In this work, we have studied the chemical composition of the surface protrusions using various analysis techniques (atomic force microscopy, transmission electron microscopy, and electron energy loss spectroscopy) showing that it consists of oxidized Si. A mechanism is proposed to explain the correlation between the observed surface damage and the measured current during constant voltage stress.
The effect of local environment on photoluminescence: A time-dependent density functional theory study of silanone groups on the surface of silica nanostructures
Authors: Zwijnenburg M. A. , Sokol A. A. , Sousa C. , Bromley S. T.
Published: July 2009

The optical absorption spectrum and lowest photoluminescence (PL) signal for silanone terminated silica nanostructures are studied using time-dependent density functional theory calculations on a range of realistic low energy silica nanocluster models. We show that the broad experimental absorption spectrum for silanone centers [V. A. Radtsig and I. M. Senchenya Russ. Chem. Bull. 45, 1849 (1996)] is most likely the result of a synergetic combination of inhomogeneous broadening, thermal broadening and the small energy differences between different excitations. We further demonstrate that upon relaxation of the excited state the excited electron and hole localize on only one silanone center, and that there is a clear and distinct link between the local environment of a silanone center and its absorption and PL spectra. Finally, we provide strong evidence that the silanone center does not have a double bond between the constituent silicon and oxygen atoms but rather can be probably more aptly described as the =Si+–O− charge-transfer species.
Time and space-correlated plasma potential measurements in the near field of a coaxial Hall plasma discharge
Authors: Smith A. W. , Cappelli M. A.
Published: July 2009

Space- and time-correlated measurements of floating and plasma potential are made in the near field, external flow cathode region of a coaxial Hall plasma discharge using an emissive probe synchronized to quasicoherent fluctuations in discharge current. The luminous axial feature frequently observed in the near field of operating plasma accelerators is found to be concomitant with a spike in the plasma potential (and electron temperature). The structure of the plasma potential allows for multiple avenues for back-streaming ions to accelerate toward the discharge front pole and may pull some classes of ions toward the central axis. The fluctuations in plasma properties exhibit a complex structure at frequencies on the order of the so-called “breathing mode” ionization instability often seen in these types of discharges. Most notably, the plasma potential appears to fluctuate in a helical fashion, resembling tilted drift waves rotating about the central axis. A simple analysis of these waves draws attention to the possible role that they may play in driving anomalous cross-field electron transport in the near field region.
Optical fiber-based single-shot picosecond transient absorption spectroscopy
Authors: Cook Andrew R. , Shen Yuzhen
Published: July 2009

A new type of single-shot transient absorption apparatus is described based on a bundle of optical fibers. The bundle contains 100 fibers of different lengths, each successively giving ∼15 ps longer optical delay. Data are collected by imaging light from the exit of the bundle into a sample where it is overlapped with an electron pulse or laser excitation pulse, followed by imaging onto a charge coupled device (CCD) detector where the intensity of light from each fiber is measured simultaneously. Application to both ultrafast pump-probe spectroscopy and pulse radiolysis is demonstrated. For pulse radiolysis, the prototype bundle provides the ability to collect data with a time resolution limited only by the electron pulse width of 7–10 ps, over a total single-shot time window of ∼1.5 ns. Tunable probe light is obtained from a titanium-sapphire laser and an optical parametric amplifier. Corrections are made to remove the fiber-to-fiber variations in signal magnitude due to the spatial overlap of the electron beam and probe image. High quality data can be collected over most of the sensitivity range of the CCD camera detectors. The single-shot instrument is valuable for measurement of samples that are only available in very limited quantities, are too viscous to flow, or are rigid. It is therefore excellent in applications, such as picosecond pulse radiolysis, where the thousands of pulses per kinetic trace typical in classical pump-probe experiments can damage the sample before useful results could be obtained.
Effects and thermal stability of hydrogen microwave plasma treatment on tetrahedral amorphous carbon films by in situ ultraviolet photoelectron spectroscopy
Authors: Chua Daniel H. C. , Hsieh Jovan , Gao Xingyu , Qi Dongchen , Chen Shi , Varghese Binni , Sow Chorng Haur , Wee A. T. S. , Lu Jiong , Loh Kian Ping , Yu Xiaojiang , Moser Herbert O.
Published: July 2009

This paper reports a comprehensive experimental study on the effects of hydrogen microwave plasma treatment on nonhydrogenated high sp3 content tetrahedral amorphous carbon (ta-C) film. In this study, a surface C–H dipole layer was first observed by high resolution electron energy loss spectroscopy, showing the presence of C–H bonding states. This resulted in the enhancement of electron field emission of the plasma treated films by largely lowering the turn-on field. Thermal stability tests using in situ ultraviolet photoelectron spectroscopy confirm that the C–H dipole layer not only reduces the work function of the films, it is extremely stable in both ambient and vacuum conditions and can sustain up to 600 °C annealing in vacuum. Atomic force microscopy studies also show minimal modifications to the surface morphology, leading to the conclusion that the C–H dipole layer is responsible for lowering the work function. This has improved the electron emission properties which can lead to potential applications such as electron emission displays.
In situ measurement of electromigration-induced transient stress in Pb-free Sn–Cu solder joints by synchrotron radiation based x-ray polychromatic microdiffraction
Authors: Chen Kai , Tamura N. , Kunz M. , Tu K. N. , Lai Yi-Shao
Published: July 2009

Electromigration-induced hydrostatic elastic stress in Pb-free SnCu solder joints was studied by in situ synchrotron x-ray white beam microdiffraction. The elastic stresses in two different grains with similar crystallographic orientation, one located at the anode end and the other at the cathode end, were analyzed based on the elastic anisotropy of the β-Sn crystal structure. The stress in the grain at the cathode end remained constant except for temperature fluctuations, while the compressive stress in the grain at the anode end was builtup as a function of time during electromigration until a steady state was reached. The measured compressive stress gradient between the cathode and the anode is much larger than what is needed to initiate Sn whisker growth. The effective charge number of β-Sn derived from the electromigration data is in good agreement with the calculated value.
On the estimation of thermal strains developed during oxide growth
Authors: Sabau Adrian S. , Wright Ian G.
Published: July 2009

This paper presents results for the strains and stresses in oxide scales under the conditions of temperature and pressure expected in typical steam boiler operation. These conditions are radically different from those typically encountered in laboratory testing and include features such as a thermal gradient across the tube wall, significant internal (steam) pressure, and cycling of both steam temperature and pressure. Critical examination of the assumptions of flat-plate geometry, which is usually made in calculating stresses and strains in oxide scales, indicated that only the component of the hoop strain that generates stress must be reported for the cylindrical case, and that the use of simple plane-strain is adequate for the system studied. Calculations were made for alloy T22 with a hypothetical, single-layered oxide with appropriate properties. Typical conditions associated with transition of the boiler from full to partial load involve a decrease in both steam temperature and pressure, and these two sources of stress generation were found to exert opposite effects. The relative magnitudes of the resulting strains were used to explain the trends in strain levels calculated when the effects of thermal expansion, temperature loading, and pressure loading were superimposed.
Effect of Mn substitution on electrical and magnetic properties of Bi0.9La0.1FeO3
Authors: Pradhan Dillip K. , Choudhary R. N. P. , Rinaldi C. , Katiyar R. S.
Published: July 2009

Polycrystalline samples of Bi0.90La0.10(Fe1−xMnx)O3 (x=0, 0.05, 0.10, 0.15, and 0.20) were prepared using a novel mechanical activation followed by a conventional solid-state reaction technique. The formation of the desired materials was confirmed using x-ray diffraction. The electrical and magnetic properties of the materials were investigated at different Mn concentrations as a function of temperature. Both dielectric constant and loss tangent increased with the increase in Mn content in the system. The grain and grain boundary contributions have been estimated using impedance spectroscopy analysis. Both grain and grain boundary conductivity increased with a rise in temperature for all Mn concentrations. The value of activation energy for both grain and grain boundary is nearly the same, and decreased with an increase in Mn concentration. There is a systematic increase in the value of magnetization on increasing Mn concentration.
Explicitly correlated intermolecular distances and interaction energies of hydrogen bonded complexes
Authors: Lane Joseph R. , Kjaergaard Henrik G.
Published: July 2009

We have optimized the lowest energy structures and calculated interaction energies for the H2O–H2O, H2O–H2S, H2O–NH3, and H2O–PH3 dimers with the recently developed explicitly correlated CCSD(T)-F12 methods and the associated VXZ-F12 (where X=D,T,Q) basis sets. For a given cardinal number, we find that the results obtained with the CCSD(T)-F12 methods are much closer to the CCSD(T) complete basis set limit than the conventional CCSD(T) results. In general we find that CCSD(T)-F12 results obtained with the VTZ-F12 basis set are better than the conventional CCSD(T) results obtained with an aug-cc-pV5Z basis set. We also investigate two ways to reduce the effects of basis set superposition error with conventional CCSD(T), namely, the popular counterpoise correction and limiting diffuse basis functions to the heavy atoms only. We find that for a given cardinal number, these selectively augmented correlation consistent basis sets yield results that are closer to the complete basis set limit than the corresponding fully augmented basis sets. Furthermore, we find that the difference between standard and counterpoise corrected interaction energies and intermolecular distances is reduced with the selectively augmented basis sets.
Microelectrophoresis in a laser trap: A platform for measuring electrokinetic interactions and flow properties within microstructures
Authors: Kahl V. , Gansen A. , Galneder R. , Rädler J. O.
Published: July 2009

We describe a combination of microelectrophoresis and laser-trap methodology to accurately measure the electric force acting on a charged microsphere which is trapped in an optical tweezer. This field/trap apparatus allows measuring of the zeta potential with submillivolt accuracy and high temporal resolution. The combination with stop-flow techniques in principle provides a mean to observe adsorption or enzyme kinetics with single molecule sensitivity. We show that it is possible to accurately profile the position and frequency dependent hydrodynamic and electro-osmotic flow inside a microchannel structure of dimensions typically used in microfluidic applications without the need of fluorescent markers. We found good agreement to the theory of electrophoretic flow when retardation effects for rapidly alternating electric fields are included.
A calibration procedure for sonic infrared nondestructive evaluation
Authors: Morbidini M. , Cawley P.
Published: July 2009

Sonic infrared is potentially a very attractive nondestructive evaluation technique offering the possibility of rapid testing of complex components. However, at present it is difficult to be sure that sufficient excitation has been applied so that a null (no defect present) result can be trusted. This paper presents a calibration method to improve the reliability of the technique. The method uses a measurement of the vibration of the component during the test, the vibration signal being processed to give a “heating index” which is a measure of the ability of the vibration field to generate heat at any defects of interest that are present. The calculation of the heating index and the rationale for its formulation are described. The method is then applied on two sets of beamlike specimens with cracks of different sizes. The maximum temperature rise in successive tests on a given specimen is shown to correlate well with the maximum heating index, so validating the method. The threshold heating index required to reliably detect cracks as a function of crack size is discussed and practical calibration and test procedures are proposed.