bluuebunny/crossref_metadata_2025 huggingface dataset:
Conditions governing the occurrence of supershear ruptures under slip‐weakening friction
Authors: Dunham Eric M.
Published: July 2007

A general theory for transitions between sub‐Rayleigh and intersonic rupture speeds is developed for faults governed by slip‐weakening friction. The transition occurs when stresses moving at intersonic speeds ahead of expanding or accelerating sub‐Rayleigh ruptures exceed the peak strength of the fault, initiating slip within a daughter crack. Upon reaching a critical nucleation length, the daughter crack becomes dynamically unstable, expanding into a self‐sustaining intersonic rupture. This mechanism holds in both two and three dimensions. On faults with uniform properties, the seismicSratio [S= (τp−τ0)/(τ0−τr)], a measure of the initial loading stress,τ0, relative to the peak and residual strengths,τpandτr, respectively, must be smaller than some critical value for the transition to occur. The maximumSvalue for unbounded faults in three dimensions is 1.19, smaller than the value of 1.77 that Andrews (1985) has shown to govern the transition in two dimensions. The supershear transition length (i.e., how far the rupture propagates before reaching intersonic speeds) is proportional to a length scale arising from the friction law governing the nucleation and stability of the daughter crack. A sufficiently narrow fault width suppresses the transition; the critical width is approximately 0.8 times the transition length on an unbounded fault. The transition length is highly sensitive to the form of the slip‐weakening law even when the associated fracture energies are identical. Heterogeneous propagation, in the form of abrupt accelerations or increases in stress‐release rate, induces stress‐wave radiation that can trigger transient bursts of intersonic propagation.
Microseismic investigation of an unstable mountain slope in the Swiss Alps
Authors: Spillmann Thomas , Maurer Hansruedi , Green Alan G. , Heincke Björn , Willenberg Heike , Husen Stephan
Published: July 2007

Risks associated with unstable rocky slopes are growing as a result of climate change and rapid expansions of human habitats and critical infrastructure in mountainous regions. To improve our understanding of mountain slope instability, we developed a microseismic monitoring system that operates autonomously in remote areas afflicted by harsh weather. Our microseismic system comprising 12 three‐component geophones was deployed across ∼60,000 m2 of rugged crystalline terrain above a huge (30 million m3) recent rockfall in the Swiss Alps. During its 31‐month lifetime, signals from 223 microearthquakes with approximate moment magnitudes ranging from −2 to 0 were recorded. Determining the hypocenters was challenging for several reasons: (1) P wave velocities were highly heterogeneous, varying abruptly from <1.5 km/s to >3.8 km/s. (2) First‐break picks were either inaccurate or lacking for some microearthquakes. (3) There were no reliable S wave picks. (4) Numerous microearthquakes occurred just outside the network boundaries. These issues were addressed by using a three‐dimensional (3‐D) P wave velocity model of the mountain slope determined from refraction tomography in a nonlinear inversion for hypocenter parameters and their probability density functions. Recordings from geophones at different altitudes and in boreholes constrained microearthquake depth estimates. Most microearthquakes were concentrated within 50–100 m of the surface in two zones, one that followed the recent rockslide scarp and one that spanned the volume of highest fracture zone/fault density. These two active zones delineated a mass of rock that according to geodetic measurements has moved toward the scarp at 1–2 cm/yr.
Persistent scatterer interferometric synthetic aperture radar for crustal deformation analysis, with application to Volcán Alcedo, Galápagos
Authors: Hooper A. , Segall P. , Zebker H.
Published: July 2007

While conventional interferometric synthetic aperture radar (InSAR) is a very effective technique for measuring crustal deformation, almost any interferogram includes large areas where the signals decorrelate and no measurement is possible. Persistent scatterer (PS) InSAR overcomes the decorrelation problem by identifying resolution elements whose echo is dominated by a single scatterer in a series of interferograms. Existing PS methods have been very successful in analysis of urban areas, where stable angular structures produce efficient reflectors that dominate background scattering. However, man‐made structures are absent from most of the Earth's surface. Furthermore, existing methods identify PS pixels based on the similarity of their phase history to an assumed model for how deformation varies with time, whereas characterizing the temporal pattern of deformation is commonly one of the aims of any deformation study. We describe here a method for PS analysis, StaMPS, that uses spatial correlation of interferogram phase to find pixels with low‐phase variance in all terrains, with or without buildings. Prior knowledge of temporal variations in the deformation rate is not required for their identification. We apply StaMPS to Volcán Alcedo, where conventional InSAR fails because of dense vegetation on the upper volcano flanks that causes most pixels to decorrelate with time. We detect two sources of deformation. The first we model as a contracting pipe‐like body, which we interpret to be a crystallizing magma chamber. The second is downward and lateral motion on the inner slopes of the caldera, which we interpret as landsliding.
Upper ocean T‐S variations in the Greenland Sea and their association to climatic conditions
Authors: Häkkinen Sirpa
Published: July 2007

Hydrography from the Nordic seas from 1951 to 2003 was analyzed focusing on the upper ocean conditions during known periods of deep mixing. The analysis used data from NOAA National Oceanographic Data Center and from International Council for the Exploration of the Sea Oceanographic Database. Because of the sparseness of the wintertime data, only summertime data are analyzed, primarily at 200 m, which retains memory of previous winter’s effects below summer mixed layer. It is found that the salinity variability in the central Greenland Gyre follows closely the sea level pressure (SLP) fluctuations found along the Greenland Coast, e.g., at Angmagssalik. Corresponding large‐scale SLP field resembles North Atlantic Oscillation (NAO) in its negative index phase. The dissimilarity between the central gyre salinity fluctuations and the incoming Atlantic water salinity fluctuations suggests that mixing with other water masses (Arctic origin waters and recirculating Atlantic waters) present in the central gyre is important in modifying the incoming Atlantic water salinity at interannual timescales. However, the largest freshwater addition to the Atlantic waters takes place in the Norwegian Sea or even further upstream in the North Atlantic. The variability of this freshwater intake resembles the NAO index on multidecadal timescales.
Regional transport and dilution during high‐pollution episodes in southern France: Summary of findings from the Field Experiment to Constraint Models of Atmospheric Pollution and Emissions Transport (ESCOMPTE)
Authors: Drobinski P. , Saïd F. , Ancellet G. , Arteta J. , Augustin P. , Bastin S. , Brut A. , Caccia J. L. , Campistron B. , Cautenet S. , Colette A. , Coll I. , Corsmeier U. , Cros B. , Dabas A. , Delbarre H. , Dufour A. , Durand P. , Guénard V. , Hasel M. , Kalthoff N. , Kottmeier C. , Lasry F. , Lemonsu A. , Lohou F. , Masson V. , Menut L. , Moppert C. , Peuch V. H. , Puygrenier V. , Reitebuch O. , Vautard R.
Published: July 2007

In the French Mediterranean basin the large city of Marseille and its industrialized suburbs (oil plants in the Fos‐Berre area) are major pollutant sources that cause frequent and hazardous pollution episodes, especially in summer when intense solar heating enhances the photochemical activity and when the sea breeze circulation redistributes pollutants farther north in the countryside. This paper summarizes the findings of 5 years of research on the sea breeze in southern France and related mesoscale transport and dilution of pollutants within the Field Experiment to Constraint Models of Atmospheric Pollution and Emissions Transport (ESCOMPTE) program held in June and July 2001. This paper provides an overview of the experimental and numerical challenges identified before the ESCOMPTE field experiment and summarizes the key findings made in observation, simulation, and theory. We specifically address the role of large‐scale atmospheric circulation to local ozone vertical distribution and the mesoscale processes driving horizontal advection of pollutants and vertical transport and mixing via entrainment at the top of the sea breeze or at the front and venting along the sloped terrain. The crucial importance of the interactions between processes of various spatial and temporal scales is thus highlighted. The advances in numerical modeling and forecasting of sea breeze events and ozone pollution episodes in southern France are also underlined. Finally, we conclude and point out some open research questions needing further investigation.
Decadal changes of ENSO persistence barrier in SST and ocean heat content indices: 1958–2001
Authors: Yu Jin‐Yi , Kao Hsun‐Ying
Published: July 2007

Decadal changes of El Niño‐Southern Oscillation (ENSO) persistence barriers in various indices of sea surface temperature (SST) and ocean heat content (OHC) are examined in this study using observations and ocean data assimilation products for the period 1958–2001. It is found that the SST indices in the eastern and central equatorial Pacific exhibit very different decadal barrier variability. The variability is large for the eastern Pacific SST indices (NINO1+2 and NINO3) whose persistence barriers shifted abruptly in 1976/1977 and 1989/1990. In contrast, the central Pacific SST indices (NINO3.4 and NINO4) experienced little decadal barrier variability and have had their persistence barriers fixed in spring in the past four decades. The zonal mean OHC index averaged over the equatorial Pacific shows decadal barrier changes similar to those in the eastern Pacific SST indices and always leads the NINO3 SST barrier by about one season. It is noticed that the SST persistence barrier appeared first in the eastern Pacific before 1976/1977, first in the central Pacific between 1976/1977 and 1989/1990, and almost simultaneous in both the eastern and central Pacific after 1989/1990. These timings coincide with the westward propagating, eastward propagating, and standing pattern of ENSO SST anomalies observed in these three periods. These results suggest that ENSO SST anomalies in the equatorial Pacific can be considered to consist of two different processes: a central Pacific process whose phase transition (such as onset) and barrier always happen in spring, and an eastern Pacific process whose phase transition and barrier change from decade to decade and are influenced by changes in the mean thermocline depth along the equatorial Pacific.
Midlatitude cirrus clouds and multiple tropopauses from a 2002–2006 climatology over the SIRTA observatory
Authors: Noël Vincent , Haeffelin Martial
Published: July 2007

This study presents a comparison of lidar observations of midlatitude cirrus clouds over the Site Instrumental de Recherche par Télédétection Atmosphérique (SIRTA) observatory between 2002 and 2006 with multiple tropopauses (MT) retrieved from radiosounding temperature profiles. The temporal variability of MT properties (frequency, thickness) are discussed. Results show a marked annual cycle, with MT frequency reaching its lowest point in May (∼18% occurrence of MT) and slowly rising to more than 40% in December, January, and February (DJF). The average thickness of the MT also follows an annual cycle, going from less than 1 km in spring to 1.5 km in late autumn. Comparison with lidar observations show that cirrus clouds show a preference for being located close below the first tropopause. When the cloud top is above the first tropopause (7% of observations), in 20% of cases, the cloud base is above it as well, resulting in a cirrus cloud “sandwiched” between the two tropopauses. Compared with the general distribution of cirrus, cross‐tropopause cirrus clouds show a higher frequency of large optical depths, while intertropopause cirrus clouds show almost exclusively low optical depths (τ < 0.03 in 90% of cases) typical of subvisible clouds. Results suggest that the occurrence of intertropopause cirrus clouds is correlated with the frequency of multiple tropopauses.
Testing sprite initiation theory using lightning measurements and modeled electromagnetic fields
Authors: Hu W. , Cummer S. A. , Lyons W. A.
Published: July 2007

Previous research has shown that the statistical measurements of charge moment changes in sprite‐producing lightning are in general agreement with the predictions based on the conventional breakdown theory for sprite initiation in the mesosphere. Measurements have progressed to the point where a detailed, event‐level quantitative comparison between the measurements and predictions could more rigorously test the existing theories by estimating the electric fields above the thunderstorm clouds responsible for sprite initiation. We selected for this analysis a set of sprite events from the summer of 2004 whose initiation times are well bounded. Then we measured the current moments and charge moment changes of the parent lightning discharges using the radiated electromagnetic fields recorded by our extremely low frequency/ultra low frequency lightning remote sensing systems. The measured current moments were then used as the input of a two‐dimensional cylindrical full‐wave finite‐difference time‐domain model for lightning‐generated electromagnetic field simulations. We compared the simulated mesospheric electric fields to the threshold electric field for conventional breakdown to see whether, according to theory, conventional breakdown (and thus a sprite) would be initiated by that electric field and at what altitude. By analyzing sprites that are both short and long delayed from the source lightning strokes, we compared measurements and theory across a wide range of timescales. The results show that for bright, short‐delayed sprites, the measurement‐inferred mesospheric electric field agrees within 20% with the threshold electric field for conventional breakdown. However, for long delayed sprite events and dimmer sprites, the measurement‐inferred mesospheric electric field for sprite initiation is somewhat below the threshold for conventional breakdown.
Martian corona: Nonthermal sources of hot heavy species
Authors: Cipriani F. , Leblanc F. , Berthelier J. J.
Published: July 2007

We have studied the production of hot O and C atoms, and hot CO2 and CO molecules in the Martian upper atmosphere and exosphere by dissociative recombination (DR) of O2+ and CO+ ions, and sputtering of the atmosphere by incident O+ pick‐up ions. Production and collisional thermalization of the hot particles in the upper atmosphere are described by using a unique Monte Carlo test particle approach to simulate both nonthermal processes. Velocity distributions, atmospheric loss rates, and density profiles are derived for suprathermal O, C, CO, and CO2 at low and high solar activity. At high solar activity the hot oxygen escape rate estimated from DR of O2+ is found to be less than two times the sputtering rate. Sputtering is found to efficiently populate the corona with molecular species such as CO and CO2 at high solar activity and also to produce a carbon escape rate that is comparable to that derived from the major photochemical sources. Dissociation of CO2 molecules by the impacting pick‐up ions flux are found to produce about 50% of the sputtered exospheric oxygen density at high solar activity. Collisions of the background atmospheric gas with hot O atoms produced by DR of O2+ produce densities of hot CO2 and CO molecules larger than 102 cm−3 for altitudes lower than 1000 km, at both high and low solar activity. Interestingly, the hot CO2 density scale height is observed to be process dependent. The hot oxygen energy distributions associated with sputtering and DR near the exobase are also found to follow distinct decreasing energy laws. We suggest that the effects of the solar zenithal angle (SZA), crustal magnetic fields, and atmospheric tides on the ionospheric structure may produce exospheric signatures.
Recursion‐based multiple changepoint detection in multiple linear regression and application to river streamflows
Authors: Seidou O. , Ouarda T. B. M. J.
Published: July 2007

A large number of models in hydrology and climate sciences rely on multiple linear regression to explain the link between key variables. The relationship in the physical world may experiment sudden changes because of climatic, environmental, or anthropogenic perturbations. To deal with this issue, a Bayesian method of multiple changepoint detection in multiple linear regression is proposed in this paper. It is an adaptation of the recursion‐based multiple changepoint method of Fearnhead (2005, 2006) to the classical multiple linear model. A new class of priors for the parameters of the multiple linear model is introduced, and useful formulas are derived that permit straightforward computation of the posterior distribution of the changepoints. The proposed method is numerically efficient and does not involve time consuming Monte‐Carlo Markov Chain simulation as opposed to other Bayesian changepoint methods. It allows fast and straightforward simulation of the probability of each possible number of changepoints as well as the posterior probability distribution of each changepoint conditional on the number of changes. The approach is validated on simulated data sets and then compared to the methodology of Seidou et al. (2006) on two practical problems, as follows: (1) the changepoint detection in the multiple linear relationship between mean basin scale precipitation at different periods of the year and the summer‐autumn flood peaks of the Broadback River located in Northern Quebec, Canada; and (b) the detection of trend variations in the streamflows of the Ogoki River located in the province of Ontario, Canada.
Role of neutral atmospheric dynamics in cusp density and ionospheric patch formation
Authors: Carlson Herbert C.
Published: July 2007

Ionospheric patches are islands of plasma transiting the polar cap, with density at least double the surrounding background plasma. Since their discovery 25 years ago, many mechanisms for their production have been proposed and examined. However all of these mechanisms consider only electric fields and charged particles as candidate mechanisms for patch formation, particularly transient changes in these electrodynamic terms. Here for the first time, we call attention to the role of thermospheric dynamics in Patch formation. We show that the thermospheric response to transient heating events near the cusp must significantly increase exospheric densities over the cusp, and also that a plausible doubling of these densities near and above 400 km altitude leads to a new patch production mechanism. The underlying processes must drive a solar cycle variation of how many hours UT experience strong polar patches and scintillation. These processes must be added to present thinking and modeling.
Models of the distribution and abundance of hydrogen at the lunar south pole
Authors: Elphic R. C. , Eke V. R. , Teodoro L. F. A. , Lawrence D. J. , Bussey D. B. J.
Published: July 2007

Permanently shadowed locations at the lunar poles are potential sites for significant concentrations of cold‐trapped volatiles, including water ice. Hydrogen enhancements are seen at the poles, but the physical form, abundance and distribution of this hydrogen remains controversial. Using a pixon‐based image reconstruction algorithm to effectively improve spatial resolution, we derive maps of the lunar south polar water‐equivalent hydrogen concentration that are fully consistent with the orbital neutron measurements, with abundances greater than 0.5 wt% in some permanently shadowed locations. This is much greater than the highest solar wind hydrogen abundance in returned lunar samples, and may indicate ice between regolith grains. If the hydrogen distribution is inhomogeneous within a permanently shadowed crater, then even higher abundances are implied. In Shackleton crater, for example, the derived count rates are consistent with 10% of the crater floor area having 20‐wt% water‐equivalent hydrogen, and the remainder at 0.25 wt%.
On the seasonal variation of electric and magnetic turbulence at high latitudes
Authors: Golovchanskaya I. V.
Published: July 2007

High‐pass filtered field measurements from the low‐altitude polar‐orbiting Dynamic Explorer 2 (DE2) spacecraft are used to investigate seasonal variation in the high‐latitude electric and magnetic fields on the scales from 3.8 km to 100 km. It is shown that the seasonal asymmetry has an opposite sense for the electric and magnetic components. The electric fields are by factor 3 enhanced and the magnetic fields are by factor 1.5 reduced under winter conditions as compared to summer conditions. The effect persists at very high polar latitudes, where the magnetic field lines are strongly stretched or open, so that the time required for the Alfvén‐wave communication between the ionosphere of summer and winter hemispheres is very large (>1 hour) or infinite. In this case, the earlier interpretations of the seasonal effect, which suggest that the magnetospheric generator of the turbulent fields is linked by the field‐aligned currents (FACs) to the high‐latitude ionosphere of both hemispheres, may be not applicable. A new explanation is proposed, in which it is assumed that the FACs from the generator region close through the Pedersen current in the ionosphere of only one hemisphere, either wintertime or summertime, and through the inertial current in the front of an outgoing Alfvén wave. It is demonstrated that the values of conductances derived within such an assumption are in a reasonable agreement with observations.
Balance of drag between the middle and lower atmospheres in a global atmospheric forecast model
Authors: Kim Young‐Joon
Published: July 2007

A global atmospheric forecast model that includes the middle atmosphere is used to investigate systematic model biases. As in many other global atmospheric models, Northern Hemispheric winter simulations from the vertically extended Navy Operational Global Atmospheric Prediction System reveal an unrealistic vertical tilt of the polar‐night jet associated with a temperature bias in the northern polar middle atmosphere. This bias has important implication for satellite data assimilation in that inaccurate model background field associated with the bias can cause a data assimilation system to reject useful observation data. Efforts are made to alleviate this bias using improved radiation and orographic gravity wave drag parameterizations, the latter of which can provide adequate amount of drag to greatly reduce the bias, but at the cost of overestimated surface polar pressure. To understand and fix this secondary bias, this study addresses the cause and effect of the bias in terms of the balance of model drag mechanisms between the middle and lower atmospheres as well as within the lower atmosphere. Disruption of these balances in the model is argued to lead to degradation of surface simulation by reasonable middle atmospheric gravity wave drag despite an improvement in the middle atmospheric circulation. An experimental treatment of limiting the parameterized gravity wave drag to the middle atmosphere, as similarly done with a spectral gravity wave drag parameterization, is shown to largely alleviate the bias. This study discusses results from a series of winter and multiyear simulations, schematically illustrates the drag balance in the model, and investigates conservation of atmospheric angular momentum.
Good statistical practice in pharmacology Problem 2
Authors: Lew M
Published: July 2007

Background and purpose:

This paper is intended to assist pharmacologists to make the most of statistical analysis and in avoid common errors.

Approach:

A scenario is presented where an experimenter performed an experiment to test the effects of two drugs on cultured cells. Analysis of the results, expressed as percentage of control, by a one‐way ANOVA yielded P=0.058 and the experimenter concluded that neither drug was effective. The data were expressed as percentage of control because of pairing of the data within each experimental run, a common feature in cell culture experiments. Such data can be analysed with potentially more powerful ANOVA methods equivalent to the paired t‐test. Monte Carlo simulations are presented to compare the power of relevant analyses.

Results:

For data correlated within experimental run (i.e. paired values), transformation to percentage of control improved the power of a one‐way ANOVA to detect a real effect, but a randomized block ANOVA (equivalent to a 2‐way ANOVA with experiment and treatment as factors) using the raw values was substantially more powerful. The randomized block ANOVA performed well even with uncorrelated data, being only marginally less powerful than the one‐way ANOVA.

Conclusions and implications:

A randomized block ANOVA is far superior to the one‐way ANOVA with correlated data, and with uncorrelated data it is only marginally less powerful. Thus where there is, or might reasonably be, such a correlation (e.g. relatedness among the data within a single experimental run, or within a multi‐well culture plate, or within an animal, et cetera), use the more powerful randomized block ANOVA rather than one‐way ANOVA.

British Journal of Pharmacology (2007) 152, 299–303; doi:10.1038/sj.bjp.0707372; published online 9 July 2007
Nocistatin inhibits 5‐hydroxytryptamine release in the mouse neocortex via presynaptic Gi/oprotein linked pathways
Authors: Fantin M , Fischetti C , Trapella C , Morari M
Published: July 2007

Background and purpose:

Nocistatin (NST) is a neuropeptide generated from cleavage of the nociceptin/orphanin FQ (N/OFQ) precursor. Evidence has been presented that NST acts as a functional antagonist of N/OFQ, although NST receptor and transduction pathways have not yet been identified. We previously showed that N/OFQ inhibited [3H]5‐hydroxytryptamine ([3H]5‐HT) release from mouse cortical synaptosomes via activation of NOP receptors. We now investigate whether NST regulates [3H]5‐HT release in the same preparation.

Experimental approach:

Mouse and rat cerebrocortical synaptosomes in superfusion, preloaded with [3H]5‐HT and stimulated with 1 min pulses of 10 mM KCl, were used.

Key results:

Bovine NST (b‐NST) inhibited the K+‐induced [3H]5‐HT release, displaying similar efficacy but lower potency than N/OFQ. b‐NST action underwent concentration‐dependent and time‐dependent desensitization, and was not prevented either by the NOP receptor antagonist [Nphe1Arg14,Lys15]N/OFQ(1‐13)‐NH2(UFP‐101) or by the non‐selective opioid receptor antagonist, naloxone. Contrary to N/OFQ, b‐NST reduced [3H]5‐HT release from synaptosomes obtained from NOP receptor knockout mice. However, both N/OFQ and NST were ineffective in synaptosomes pre‐treated with the Gi/oprotein inhibitor,Pertussistoxin. NST‐N/OFQ interactions were also investigated. Co‐application of maximal concentrations of both peptides did not result in additive effects, whereas pre‐application of maximal b‐NST concentrations partially attenuated N/OFQ inhibition.

Conclusions and implications:

We conclude that b‐NST inhibits [3H]5‐HT release via activation of Gi/oprotein linked pathways, not involving classical opioid receptors and the NOP receptor. The present data strengthen the view that b‐NST is,per se, a biologically active peptide endowed with agonist activity.

British Journal of Pharmacology(2007)152, 549–555; doi:10.1038/sj.bjp.0707377; published online 9 July 2007
Role of α2C‐adrenoceptors in the reduction of skin blood flow induced by local cooling in mice
Authors: Honda M , Suzuki M , Nakayama K , Ishikawa T
Published: July 2007

Background and purpose:

The reduction of skin blood flow induced by local cooling results from a reflex increase in sympathetic output and an enhanced vasoconstrictor activity of cutaneous vessels. The present study investigated the latter local response in vivo in tetrodotoxin‐treated mice, in which the sympathetic nerve tone was abolished.

Experimental approach:

Male ddY mice, anaesthetized with pentobarbitone, were treated with tetrodotoxin and artificially ventilated. The plantar skin blood flow (PSBF) was measured by laser Doppler flowmetry.

Key results:

Cooling the air temperature around the left foot from 25 to 10°C decreased the PSBF of the left foot. Bunazosin, an α1‐adrenoceptor antagonist, RS79948, an α2‐adrenoceptor antagonist, and MK‐912, an α2C‐adrenoceptor antagonist, all significantly inhibited the cooling‐induced reduction of PSBF; the inhibition by bunazosin was relatively small compared with that by RS79948 and MK‐912. The response was not affected by guanethidine or bretylium, but was diminished in adrenalectomized mice. An intra‐arterial injection of clonidine, an α2‐adrenoceptor agonist, to the left iliac artery of adrenalectomized mice caused a transient decrease in PSBF, which was significantly augmented at 10°C. MK‐912 suppressed only the augmented portion at 10°C. Y‐27632, H‐1152 and fasudil, Rho kinase inhibitors, also inhibited the cooling‐induced reduction of PSBF. RS79948 caused no further reduction of the cooling‐induced response after the inhibition by Y‐27632.

Conclusions and implications:

Local cooling‐induced reduction of skin blood flow in mice primarily results from increased reactivity of α2C‐adrenoceptors to circulating catecholamines, in which the Rho/Rho kinase pathway is involved.

British Journal of Pharmacology (2007) 152, 91–100; doi:10.1038/sj.bjp.0707380
Mesoporous Gold Sponge
Authors: Cortie Michael B. , Maaroof Abbas I. , Stokes Nicholas , Mortari Alessia
Published: July 2007

Mesoporous gold sponge may be prepared by the removal of aluminium from AuAl2 by an alkaline leach. The resulting material has nanoscale pores and channels, with a high specific surface area that can be exploited in electrochemical applications. For example, the material may serve as the basis of a more sensitive capacitive sensor or biosensor, as an electrode material for a high efficiency ultracapacitor, as the semi-transparent current collector in a dye sensitized photovoltaic cell, or as the lithium storage electrode in a lithium ion cell. The properties of the sponge may be controlled by varying its density, pore size, and pore size distribution, factors which are in turn controlled by the microstructure of the precursor compound and the conditions of deposition.
On the Development of Fluidized Bed Chemical Vapour Deposition for Large-Scale Carbon Nanotube Synthesis: Influence of Synthesis Temperature
Authors: See Chee Howe , Harris Andrew T.
Published: July 2007

The absence of large-scale carbon nanotube synthesis technology (which we define as being of the order of 10 000 tonnes per plant per year) is limiting research and development activities across the sector. We contend that fluidized bed chemical vapour deposition (FBCVD) is the most promising technology for large-scale, low-cost, carbon nanotube synthesis. In this work, multi-walled carbon nanotubes were synthesized on alumina-supported iron, cobalt, or nickel catalysts by catalytic chemical vapour deposition in a 0.5 kg h–1 FBCVD reactor, using ethylene as a carbon source. The carbon nanotube yield was shown to increase with an increase in synthesis temperature from 3.3% at 550°C to 87.6% at 900°C. At higher synthesis temperatures the quality of the nanotubes appeared to improve, although further experiments are required to quantify this within statistically significant limits.
Carbon Nanotube Free-Standing Membrane of Pt/SWNTs as Catalyst Layer in Hydrogen Fuel Cells
Authors: Tang Jason M. , Jensen Kurt , Li Wenzhen , Waje Mahesh , Larsen Paul , Ramesh Palanisamy , Itkis Mikhail E. , Yan Yushan , Haddon Robert C.
Published: July 2007

A simple and promising fuel-cell architecture is demonstrated using a carbon nanotube free-standing membrane (CNTFSM) made from Pt supported on purified single-walled carbon nanotubes (Pt/SWNT), which act as the catalyst layer in a hydrogen proton exchange membrane fuel cell without the need for Nafion in the catalyst layer. The CNTFSM made from Pt/SWNT at a loading of 0.082 mg Pt cm–2 exhibits higher performance with a peak power density of 0.675 W cm–2 in comparison with a commercially available E-TEK electrocatalyst made of Pt supported on XC-72 carbon black, which had a peak power density of 0.395 W cm–2 at a loading of 0.084 mg Pt cm–2 also without Nafion in the catalyst layer.
Toughening, Thermal Stability, Flame Retardancy, and Scratch–Wear Resistance of Polymer–Clay Nanocomposites
Authors: Dasari Aravind , Lim Szu-Hui , Yu Zhong-Zhen , Mai Yiu-Wing
Published: July 2007

Addition of a small percent of clay to polymers improves their stiffness, strength, dimensional stability, and thermal, optical, and barrier properties. Improvements are often attributed to the availability of large numbers of clay nanolayers with tremendous interfacial area. Despite the positive effects from the addition of clay, there are unresolved issues, such as embrittlement, thermal stability, flame retardancy, scratch–wear response of the resultant nanocomposites, and/or achieving a balance between different mechanical and physical properties. In this review, we discuss these issues and the approaches that have been adopted in the expectation of resolving and understanding them, with particular emphasis on our recent and current research.
Review of the Synthetic Chemistry Involved in the Production of Core/Shell Semiconductor Nanocrystals
Authors: van Embden Joel , Jasieniak Jacek , Gómez Daniel E. , Mulvaney Paul , Giersig Michael
Published: July 2007

Passivation of CdSe semiconductor nanocrystals can be achieved by overcoating the particles with a homogeneous shell of a second semiconductor. Shell layers are grown in monolayer steps to ensure homogeneous growth of the shell. The relative band edges of the two materials determine the photoreactiveity of the resultant core-shell nanocrystals. The critical role of ligands in minimizing nucleation of the shell material during the growth of the passivating layer is emphasized. The delocalization of charge carriers into the shell layers can be followed spectroscopically during the growth processes. The relative spectral shifts are directly correlated to the relative energies of the band edges.
Inventing Canada in the Mulroney Years
Authors: Feaver George
Published: July 2007

‘IF THE STATE DID NOT EXIST, WE WOULD HAVE TO INVENT IT. Comment.’ Few of the responses to this examination question qualified its suggestion that the state might be amenable to instantaneous contrivance or conscious design. The oversight on the part of my undergraduate charges pointed to the still potent legacy of a generation of Canadian political artificers whose projects of inventing the Canadian state had abetted the rise of a species of ‘constitutional politics’ given to the ever more elaborate concoction of comprehensive solutions to Canada's vexing constitutional shortcomings. These projects tended to politicize historically embedded elements in the constitutional order, serviceable if imperfect, which had been conventionally regarded as resistant beyond redemption to improved reformulation. This new-style politics was at centre stage in the long and eventful prime ministerial years of the Liberal Party's Pierre Trudeau, the great Cartesian inventor par excellence of the contemporary Canadian state. It would remain a central feature of the nine-year incumbency of Trudeau's Conservative Party successor, Brian Mulroney. Trudeau's vision of a reinvented Canada had proceeded from his background preparation for public life as an academic constitutional lawyer. Mulroney, aiming to finesse what the more cerebral Trudeau could not, would bring to bear on the affairs of the Canadian state the skills of a labour lawyer with the know-how to get Canada's perennially fractious provinces and interest groups to the political bargaining table, there to resolve once and for all any constitutional differences still outstanding.
Rights theory in a specific healthcare context: “Speaking ill of the dead”
Authors: Wildfire Adrian , Stebbing Justin , Gazzard Brian
Published: July 2007

Generally physicians have a legal and ethical obligation of keeping confidentiality regarding their communication with patients and it is clear that we all have rights. The application of rights theorem, which usually refers to the recognition of individual human rights, to the deceased offers possible answers to the problematic question of patient confidentiality after death. Philosophical considerations broadly support utilitarian ideals concerning the ‘common good’. However, it may be possible to rank rights according to a hierarchy of need and thus preserve individual rights where they do not impinge upon the publics' right to protection from harm and the physician's right to tell the truth. This has broad implications for confidentiality, anonymity and health care information in general for patients, their families and healthcare workers. We discuss these issues, with specific reference to an individual case.
Management of overactive bladder syndrome
Authors: Srikrishna Sushma , Robinson Dudley , Cardozo Linda , Vella Maria
Published: July 2007

Overactive bladder (OAB) syndrome is the term used to describe the symptom complex of urinary urgency with or without urge incontinence, usually with frequency and nocturia. Drug treatment continues to have an important role in the management of women with OAB. Other treatment options include conservative management with lifestyle interventions, modification of fluid intake, and physiotherapy including bladder retraining. Surgery remains the last resort in the treatment and is usually reserved for intractable detrusor overactivity, as it is associated with significant morbidity. This article reviews the management of the overactive bladder with specific focus on newer developments in the medical treatment of OAB in women.
Critical Review of Service Life Concepts of Reinforced Concrete Structures
Authors: Mendoza-Rangel José Manuel , Castro-Borges Pedro
Published: July 2007

Service life definitions involve more considerations today than thirty years ago. This is because only mechanical parameters were taken into account then. Other parameters like durability were introduced a few years ago but it is difficult to use these parameters to predict service life and validate future behavior. This is due mainly to a mixture of variables, methods, materials and environments whose behavior is hard to predict. A critical review of service life concepts of reinforced concrete structures is presented in this paper and the main conclusion is that valid predictions of service life must be based on specific stages of service life of concrete structures that include, not only data from the project, but also data from specific stages at the end of the life of the structure.
Service Life of Reinforced Concrete Structures. New Approach
Authors: Castro-Borges Pedro , Helene Paulo
Published: July 2007

The existing concepts about service life may be incomplete regarding those that must take into account the whole life cycle of a concrete structure. One of the reasons for this is the lack of certainty of the service life predictions which are based on models that take into account a mixture of stages. The life cycle of a structure has many similarities with that of a human being. In fact, it is no coincidence that engineering has adopted some terms from the medical sciences like pathology to refer to structures with problems of health . The objective of this paper is to discuss a new approach that takes into account the similarities among the several stages of service life of a human being and the concrete structures. The paper discusses the overlapping of the different life cycle stages as well as the reasons why the prediction models can fail.
Corrosion Propagation Behavior of New Metallic Rebar Materials in Simulated Concrete Environments and Engineering Implications
Authors: Hurley Michael F. , Scully John
Published: July 2007

The radial (depth) and lateral (length) corrosion propagation behavior of 316LN stainless steel, 2101 LDX duplex stainless steel, and MMFX-2 compared to plain carbon steel were characterized in saturated Ca(OH)2 with NaCl additions. Radial pit growth was ohmically controlled for all materials but repassivated more readily at high potentials in the case of 316LN and 2101 LDX stainless steels. Conversely, pit growth on carbon steel propagated at all applied anodic potentials and did not repassivate until deactivation by cathodic polarization. Stainless steel showed the highest resistance to lateral corrosion propagation from an active site during microelectrode array testing. In contrast, carbon steel was found to easily undergo widespread depassivation along the surface compared to stainless steel. 2101 LDX duplex stainless and MMFX-2 showed similar radial propagation behavior and corrosion morphology, which was intermediate between carbon steel and 300 series type stainless steel.
Cathodic Protection in Reinforced Concrete Elements, using Carbon Fibers Base Composites
Authors: Lee-Orantes Francisco , Torres-Acosta A. A. , Martínez-Madrid Miguel , López-Cajún Carlos
Published: July 2007

A carbon fiber reinforced polymer (CFRP) composite was used as external reinforcement and as a cathodic protection (CP) system of steel in concrete elements. Different epoxy resins were tested by varying the amount and length of the carbon fibers used. The CFRP composites were glued to the concrete prisms using such selected conductive resins, then electrically connected with one of the rebars and used as impressed current anodes. A electrical current was applied between the CFRP composite (anode) and the rebar (cathode) at different current densities (50, 100, and 1000 mA/m2). The results obtained have demonstrated that the CFRP external reinforcement used in this investigation can also work as an anode in a cathodic protection system (CP). No mechanical adverse effect was found on the composite and the epoxy resin selected, although the current densities applied were greater than those used in real structures.
Modeling the Polarization Behavior of a Galvanic Point Anode - Reinforcing Steel in Concrete System
Authors: Dugarte Margareth J. , Sagüés Alberto A. , Powers Rodney
Published: July 2007

This paper addresses the first phase in developing a numerical model for polarization distribution prediction of the rebar- anode system in concrete reinforced slabs with residual chloride contamination, where sacrificial point anodes were embedded in the concrete patch repair area. The modeling approach was developed to characterize the performance of this system under two application scenarios: one with part of the rebar assembly in the active condition and the other with an all-passive assembly. The model results and experimental finding in > 1 year old concrete slabs are compared. Results could be used for determine the anode operating potentials that may be achieved with a specific anode placement spacing for highway applications.
Galvanic Behavior of Type 2 Aluminized Steel in Simulated Natural Waters
Authors: Caseres Leonardo , Sagüés Alberto A.
Published: July 2007

Type 2 aluminized steel has a carbon steel substrate with a layered aluminum/Al-Fe coating that acts as a barrier but does not always provide galvanic protection. This system is being used for very long service life applications (e.g. 75 years) in drainage culvert pipe but relatively little corrosion mechanistic information exist to date. The galvanic coupling between exposed steel and surrounding aluminized coating of specimens with surface distress was studied for ~2,700 hr in nearly neutral pH waters of controlled varying scaling tendencies at room temperature and a moderate (~370 ppm) chloride content. There was rust formation at the bare steel in both solutions early in the test indicated of poor galvanic protection by the coating. At longer exposure times however electrochemical impedance measurements suggested that some uniform corrosion of the aluminized coating was in progress in both solutions that resulted in larger galvanic currents delivered by the coating.
Electrochemical Characterization of X80 Steel under Sour Environments and Addition of Imidazoline Based Compounds Under Linear Flow Conditions
Authors: Hernandez Roberto , Galicia Mónica , Castaneda Homero
Published: July 2007

High strength steels like API X-80 shows excellent mechanical properties for transmission pipeline applications in oil industry, however when exposed to sour gas and aggressive species in solution the mechanical strength decreases. Low pH values in solution consider hydrogen ion concentration in the electrolyte, like in H2S(aq) brine at pH=4 typically used to simulate sour ambient existed in produced water in oil platforms. The hydrogen ion and H2S(aq) decomposition reaction result in sulfur based corrosion products formed at the interface of the steel-solution in the form of film layers. Sulfur corrosion products have semiconductor properties that decrease the current flow distribution through the electrode- electrolyte interface; but the dissolution process may be favored due to the poor adherence and porous number and distribution of the films. Imidazoline used as corrosion inhibitor in acidic environments is characterized for different concentrations. EIS and Cyclic Voltammetry were used to follow the interfacial reactions that permit to understand the mechanism associated to the formation and chemical properties of the steel-sour electrolyte interface under linear flow conditions.
Biocomplexity and Bioelectrochemical Influence of Anaerobic Biofilms in Gasoline Distribution Pipelines
Authors: Dominguez Benetton Xochitl , Ramírez Espinosa Dalinda
Published: July 2007

The present work is based on the biocomplexity analysis and the electrochemical influence of anaerobic biofilms obtained from gasoline distribution pipelines. Microbial populations were grown in anaerobic media using either of the following carbon sources: lactate, acetate, benzene, toluene, xilene, pentane, TBA or MTBE. The cultured microorganisms developed complex biofilms either in pure cultures or in consortia. An analysis of some possible microbial interactions in which the cultured biofilms might impact corrosion is presented as a biocomplexity analysis. The electrochemical activity of the biofilms is monitored using electrochemical impedance spectroscopy, from which it is determined that diffusion is a strong limiting factor under biofilm presence and active sites influence under abiotic conditions, for corrosion control. A simplified 2-dimensional transmission line approach is used to describe the current distribution along a biofilm growing over a carbon steel surface and its influence in corrosion, according to the EIS results obtained.
Effect of Copper Additions on the Interrupted Isothermal Oxidation Behavior of Gamma Titanium Aluminide Alloys
Authors: Fergus J. , Long Christopher , Callender Chad , Gale William
Published: July 2007

The implementation of titanium aluminide alloys requires the development of joining techniques that can be used to fabricate and repair structures without degrading the material properties. One of the critical properties for high- temperature applications is oxidation resistance, which can be significantly affected by small alloying additions. Transient liquid phase (TLP) bonding has recently been used to join titanium aluminide alloys. The successful TLP process introduces small amounts of copper into the alloy. The results presented in this paper show that the amounts of copper introduced during joining are not detrimental to the oxidation resistance of two gamma titanium alloys: Ti-48Al-2Cr- 2Nb and Gamma Met PX.