bluuebunny/crossref_metadata_2025 huggingface dataset:
Na
+
/Ca
2+
Exchanger Maintains Ionic Homeostasis in the Peri-Infarct Area
Authors: Tortiglione Anna , Picconi Barbara , Barone Ilaria , Centonze Diego , Rossi Silvia , Costa Cinzia , Di Filippo Massimiliano , Tozzi Alessandro , Tantucci Michela , Bernardi Giorgio , Annunziato Lucio , Calabresi Paolo
Published: March 2007

Background and Purpose—

A prominent feature of cerebral ischemia is the excessive intracellular accumulation of both Na
+
and Ca
2+
ions, which results in subsequent cell death. The plasma membrane Na
+
/Ca
2+
exchanger (NCX), regulates the distribution of these ions acting either in the forward mode or in its reverse mode and it can play a critical role in brain ischemia. However, it is unclear whether the activity of NCX leads to detrimental or beneficial effects.

Methods—

Extracellular field potentials and whole-cell patch clamp recordings were obtained from rat corticostriatal brain-slice preparations in the peri-infarct area 24 hours after the permanent middle cerebral artery occlusion. Ischemia was induced in rats by permanents middle cerebral artery occlusion.

Results—

Bepridil, an inhibitor of NCX, reduced in a concentration-dependent manner (IC
50
=68 μmol/L) the field potential amplitude recorded from the peri-infarct area of corticostriatal slices. Conversely, no change was observed in sham-operated animals. The effect of bepridil was mimicked by 5-(
N
-4-chlorobenzyl)-2′,4′-dimethylbenzamil (CB-DMB) (IC
50
=6 μmol/L), a more selective inhibitor of NCX. In whole-cell patch clamp experiments, bepridil and CB-DMB caused an inward current in spiny neurons recorded from the peri-infarct area but not in the same cells recorded from controls. Interestingly, cholinergic interneurons recorded from the striatal peri-infarct area did not develop an inward current after the application of NCX inhibitors, suggesting that the electrophysiological alterations induced by NCX inhibition are cell-type specific. Bepridil and CB-DMB also induced a suppression of excitatory synaptic currents in most of spiny neurons recorded from the peri-infarct area. This effect was not coupled to a significant change of paired-pulse facilitation suggesting a postsynaptic site of action.

Conclusions—

Our data indicate that NCX plays a critical role in the maintenance of ionic homeostasis in the peri-infarct area.
Dual-Doppler and Single-Doppler Analysis of a Tornadic Storm Undergoing Mergers and Repeated Tornadogenesis
Authors: Wurman Joshua , Richardson Yvette , Alexander Curtis , Weygandt Stephen , Zhang Peng Fei
Published: March 2007

Dual-Doppler observations with unprecedented finescale spatial and temporal resolution are used to characterize the vector wind field in and near a tornado occurring near Kiefer, Oklahoma, on 26 May 1997. Analyses of the dual-Doppler vector wind fields document in detail, for the first time, several structures associated with the tornado: a proximate updraft region, a rear-flank downdraft wrapping around the tornado, a double gust front structure occluding near the tornado, and a region of enhanced vorticity separated from the tornado that may have been associated with cyclic tornadogenesis. The analyses are compared to conceptual and computer models of tornadic storms.

A subsequent tornadogenesis was observed with radar every 18 s, providing a finescale temporal view of the genesis process. The genesis process was complex and the evolution of tornado intensity parameters was not monotonic in time. Low-level rotation contracted and intensified, then broadened, then contracted and intensified a second time to form the tornado.

The initial tornadogenesis was coincident with the merger of the main supercell and a much smaller convective storm. This tornado, which was always surrounded by substantial precipitation originating from both storms, began to dissipate just a few minutes after genesis, and the rotation both aloft and near the surface weakened substantially. A second storm merger, with a much larger and supercellular storm, was coincident with a reintensification of the mesocyclone aloft, a new hook echo development, and the genesis of a short-lived tornado. After the dissipation of this second tornado, the merger disrupted the structure of the supercell storm, the hook echo was absorbed, and the mesocyclone dissipated. The current analysis suggests a process in which storm mergers may, in sequence, aid tornadogenesis by enhancing surface convergence, or through another mechanism, but subsequently disrupt the tornado’s parent supercell perhaps by cooling the inflow air, with the result being short-lived tornadoes.
A Method for Imposing Surface Stress and Heat Flux Conditions in Finite-Difference Models with Steep Terrain
Authors: Epifanio C. C.
Published: March 2007

A numerical implementation of the surface stress boundary condition is presented for finite-difference models in which the terrain slope and curvature cannot necessarily be considered small. The method involves reducing the discretized stress condition in terrain-following coordinates to a pair of coupled linear systems for the two horizontal velocity components at the boundary. The linear systems are then solved iteratively at each model time step to provide the unique boundary values of velocity consistent with the specified values of the stress. Similar methods are used to prescribe the normal flux of heat across the boundary. A related method for imposing stress conditions in two-dimensional vorticity–streamfunction models is also discussed. The effectiveness of the boundary conditions is demonstrated through a series of test problems involving topographic wake flows and thermally driven flows on steep slopes. It is shown that the use of the conventional flat-boundary approximation can lead to substantial errors when the resolved topography is sufficiently steep.
The Nature of a Heat Wave in Eastern Argentina Occurring during SALLJEX
Authors: Cerne S. Bibiana , Vera Carolina S. , Liebmann Brant
Published: March 2007

This note describes the physical processes associated with the occurrence of a heat wave over central Argentina during the austral summer of 2002/03, during which the South American Low-Level Jet Experiment (SALLJEX) was carried out. The SALLJEX heat wave that lasted between 25 January and 2 February 2003 was punctuated by extreme conditions during its last 3 days, with the highest temperature recorded over the last 35 yr at several stations of the region. It was found that not only the activity of synoptic-scale waves, but also the intraseasonal oscillation variability, had a strong impact on the temperature evolution during this summer. During the weeks previous to the heat wave development, an intensified South Atlantic convergence zone (SACZ) dominated the atmospheric conditions over tropical South America. Temperatures started to increase in the subtropics due to the subsidence and diabatic warming associated with the SACZ, as depicted by SALLJEX upper-air observations. An extratropical anticyclone that evolved along southern South America further intensified subsidence conditions. By the end of January the warming processes associated with SACZ activity weakened, while horizontal temperature advection began to dominate over central Argentina due to the intensification of the South American low-level jet. This mechanism led to temperature extremes by 2 February with temperature anomalies at least two standard deviations larger than the climatological mean values. Intense solar heating favored by strong subsidence was responsible for the heat wave until 31 January, after which horizontal temperature advection was the primary process associated with the temperature peak.
A Comparison of Hybrid Ensemble Transform Kalman Filter–Optimum Interpolation and Ensemble Square Root Filter Analysis Schemes
Authors: Wang Xuguang , Hamill Thomas M. , Whitaker Jeffrey S. , Bishop Craig H.
Published: March 2007

A hybrid ensemble transform Kalman filter (ETKF)–optimum interpolation (OI) analysis scheme is described and compared with an ensemble square root filter (EnSRF) analysis scheme. A two-layer primitive equation model was used under perfect-model assumptions. A simplified observation network was used, and the OI method utilized a static background error covariance constructed from a large inventory of historical forecast errors. The hybrid scheme updated the ensemble mean using a hybridized ensemble and static background-error covariance. The ensemble perturbations in the hybrid scheme were updated by the ETKF scheme. The EnSRF ran parallel data assimilation cycles for each member and serially assimilated the observations. The EnSRF background-error covariance was estimated fully from the ensemble.

For 50-member ensembles, the analyses from the hybrid scheme were as accurate or nearly as accurate as those from the EnSRF, depending on the norm. For 20-member ensembles, the analyses from the hybrid scheme were more accurate than analyses from the EnSRF under certain norms. Both hybrid and EnSRF analyses were more accurate than the analyses from the OI. Further reducing the ensemble size to five members, the EnSRF exhibited filter divergence, whereas the analyses from the hybrid scheme were still better than those updated by the OI. Additionally, the hybrid scheme was less prone to spurious gravity wave activity than the EnSRF, especially when the ensemble size was small. Maximal growth in the ETKF ensemble perturbation space exceeded that in the EnSRF ensemble perturbation space. The relationship of the ETKF ensemble variance to the analysis error variance, a measure of a spread–skill relationship, was similar to that of the EnSRF ensemble. The hybrid scheme can be implemented in a reasonably straightforward manner in the operational variational frameworks, and the computational cost of the hybrid is expected to be much less than the EnSRF in the operational settings.
A Numerical Model Study of an Intense Cutoff Low Pressure System over South Africa
Authors: Singleton A. T. , Reason C. J. C.
Published: March 2007

Investigations of extreme rainfall events in the southern African region are limited by the paucity of the observational network. Furthermore, the lack of full radar coverage for South Africa makes quantitative precipitation estimation difficult. Therefore, numerical modeling represents the most effective method for improving the understanding of the mechanisms that contribute to extreme rainfall events in this region with the caveat that accurate validation of model simulations is hampered by the limited observations in the region. This paper describes an intense cutoff low event over South Africa that led to record rainfall and flash flooding along the south coast of the country and adjoining hinterland. Analyses from the Global Forecast System model showed that the cutoff aloft was accompanied by a strong low-level jet (LLJ) impinging onto the south coast where rainfall was heaviest, and that lapse rates were steep in the lower troposphere. Simulations of the event were carried out using a numerical model [i.e., the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5)], which showed that severe convection occurred over the ocean on the right-hand side of the LLJ, and at its leading edge where it impinged on the coastal topography. This topography was also very important in providing additional forcing for the ascent of moist air. A factor separation technique was used to show that surface heat fluxes from the warm sea surface temperature (SST) of the Agulhas Current were important in enhancing low-level cyclogenesis, and that topography was important in maintaining the position of the low-level coastal depression, which led to favorable conditions for rainfall remaining in the same area for an extended period of time. It is suggested that improved representation of the tight topographic and SST gradients of the southern African region in NWP models or postprocessing systems would help to provide more accurate forecasts of the amount and location of heavy precipitation during cutoff low events where surface forcing is important.
Properties of Tropical Convection Observed by Millimeter-Wave Radar Systems
Authors: Stephens Graeme L. , Wood Norman B.
Published: March 2007

This paper describes the results of analysis of over 825 000 profiles of millimeter-wave radar (MWR) reflectivities primarily collected by zenith-pointing surface radars observing tropical convection associated with various phases of activity of the large-scale tropical circulation. The data principally analyzed in this paper come from surface observations obtained at the Atmospheric Radiation Measurement Manus site during active and break episodes of the Madden–Julian oscillation (MJO) and from observations collected from a shipborne radar during an active phase of the monsoon over the Indian Ocean during the Joint Air–Sea Monsoon Interaction Experiment. It was shown, for example, in a histogram regime analysis that the MWR data produce statistics on convection regimes similar in most respects to the analogous regime analysis of the Tropical Rainfall Measuring Mission radar–radiometer observations. Attenuation of the surface MWRs by heavy precipitation, however, incorrectly shifts a small fraction of the deeper precipitation modes into the shallow modes of precipitation. The principal findings are the following. (i) The cloud and precipitation structures of the different convective regimes are largely identical regardless of the mode of synoptic forcing, that is, regardless of whether the convection occurred during an active phase of the MJO, a transition phase of the MJO, or in an active monsoon period. What changes between these synoptically forced modes of convection are the relative frequencies of occurrences of the different storm regimes. (ii) The cloud structures associated with the majority of cases of observed precipitation (ranging in occurrence from 45% to 53% of all precipitation profiles) were multilayered structures regardless of the mode of synoptic forcing. The predominant multilayered cloud mode was of higher-level cirrus of varying thickness overlying cumulus congestus–like convection. (iii) The majority of water accumulated (i.e., 53%–63%) over each of the periods assigned to the active monsoon (5 days of data), the active MJO (38 days of data), and the transition MJO (53 days of data) fell from these multiple-layered cloud systems. (iv) Solar transmittances reveal that significantly less sunlight (reductions of about 30%–50%) reaches the surface in the precipitating regimes than reaches the surface under drizzle and cloud-only conditions, suggesting that the optical thicknesses of precipitation-bearing clouds significantly exceeds those of nonprecipitating clouds.
Parameter Estimation Using a Particle Method: Inferring Mixing Coefficients from Sea Level Observations
Authors: Vossepoel Femke C. , Jan van Leeuwen Peter
Published: March 2007

This paper presents a first attempt to estimate mixing parameters from sea level observations using a particle method based on importance sampling. The method is applied to an ensemble of 128 members of model simulations with a global ocean general circulation model of high complexity. Idealized twin experiments demonstrate that the method is able to accurately reconstruct mixing parameters from an observed mean sea level field when mixing is assumed to be spatially homogeneous. An experiment with inhomogeneous eddy coefficients fails because of the limited ensemble size. This is overcome by the introduction of local weighting, which is able to capture spatial variations in mixing qualitatively. As the sensitivity of sea level for variations in mixing is higher for low values of mixing coefficients, the method works relatively well in regions of low eddy activity.
On the Structure of the Lower Troposphere in the Summertime Stratocumulus Regime of the Northeast Pacific
Authors: Stevens Bjorn , Beljaars Anton , Bordoni Simona , Holloway Christopher , Köhler Martin , Krueger Steven , Savic-Jovcic Verica , Zhang Yunyan
Published: March 2007

Data collected in situ as part of the second field study of the Dynamics and Chemistry of Marine Stratocumulus field program are used to evaluate the state of the atmosphere in the region of field operations near 30°N, 120°W during July 2001, as well as its representation by a variety of routinely available data. The routine data include both the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) and NCEP–NCAR reanalyses, forecasts from their respective forecast systems (the Integrated and Global Forecast Systems), the 30-km archive from the International Satellite Cloud Climatology Project (ISCCP), the Quick Scatterometer surface winds, and remotely sensed fields derived from radiances measured by the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI), the Advanced Microwave Sounding Unit, and the Advanced Very High Resolution Radiometer. The analysis shows that outside of the boundary layer the state of the lower troposphere is reasonably represented by the reanalysis and forecast products, with the caveat of a slight warm bias at 850 hPa in the NCEP–NCAR products. Within the planetary boundary layer (PBL) the agreement is not as good: both the boundary layer depth and cloud amount are underpredicted, and the boundary layer temperature correlates poorly with the available data, which may be related to a poor representation of SSTs in this region of persistent cloud cover. ERA-40 also suffers from persistently weak zonal winds within the PBL. Among the satellite records the ISCCP data are found to be especially valuable, evincing skill in both predicting boundary layer depth (from cloud-top temperatures and TMI surface temperatures) and cloud liquid water paths (from cloud optical depths). An analysis of interannual variability (among Julys) based on ERA-40 and the 1983–2001 ISCCP record suggests that thermodynamic quantities show similar interannual and synoptic variability, principally concentrated just above the PBL, while dynamic quantities vary much more on synoptic time scales. Furthermore, the analysis suggests that the correlation between stratocumulus cloud amount and lower-tropospheric stability exhibits considerable spatial structure and is less pronounced than previously thought.
Unmitigated Communion and Health Among Adolescents With and Without Diabetes
Authors: Helgeson Vicki S. , Escobar Oscar , Siminerio Linda , Becker Dorothy
Published: March 2007

The authors examined the implications of unmitigated communion—a focus on others to the exclusion of the self—for psychological and physical health among adolescents with (n = 132) and without (n = 131) diabetes times / during a 1-year period. Unmitigated communion predicted greater psychological distress and lower levels of competence cross-sectionally and longitudinally, controlling for sex, pubertal status, and communion. Health status moderated some longitudinal relations, such that relations held only for adolescents with diabetes. In addition, unmitigated communion was associated with poor metabolic control and predicted a deterioration in metabolic control over the year for adolescents with diabetes. Unmitigated communion also was associated with disturbed eating behavior cross-sectionally and longitudinally, and disturbed eating behavior explained some of the relations of unmitigated communion to psychological but not physical health outcomes.
The Effectiveness of a Balance Training Intervention in Reducing the Incidence of Noncontact Ankle Sprains in High School Football Players
Authors: McHugh Malachy P. , Tyler Timothy F. , Mirabella Michael R. , Mullaney Michael J. , Nicholas Stephen J.
Published: March 2007

Background

A high body mass index and previous ankle sprains have been shown to increase the risk of sustaining noncontact inversion ankle sprains in high school football players.

Hypothesis

Stability pad balance training reduces the incidence of noncontact inversion ankle sprains in football players with increased risk.

Study Design

Cohort study; Level of evidence, 2.

Methods

Height, body mass, history of previous ankle sprains, and current ankle brace/tape use were documented at the beginning of preseason training in 2 high school varsity football teams for 3 consecutive years (175 player-seasons). Players were categorized as minimal risk, low risk, moderate risk, and high risk based on the history of previous ankle sprain and body mass index. Players in the low-, moderate-, and high-risk groups (ie, any player with a high body mass index and/or a previous ankle sprain) were placed on a balance training intervention on a foam stability pad. Players balanced for 5 minutes on each leg, 5 days per week, for 4 weeks in preseason and twice per week during the season. Postintervention injury incidence was compared with preintervention incidence (107 players-seasons) for players with increased risk.

Results

Injury incidence for players with increased risk was 2.2 injuries per 1000 exposures (95% confidence interval, 1.1-3.8) before the intervention and 0.5 (95% confidence interval, 0.2-1.3) after the intervention (P < .01). This represents a 77% reduction in injury incidence (95% confidence interval, 31%-92%).

Conclusion

The increased risk of a noncontact inversion ankle sprain associated with a high body mass index and a previous ankle sprain was eliminated by the balance training intervention.
Influence of Modern Studded and Bladed Soccer Boots and Sidestep Cutting on Knee Loading during Match Play Conditions
Authors: Kaila Rajiv
Published: March 2007

Background

The influence of modern studded and bladed soccer boots and sidestep cutting on noncontact knee loading during match play conditions is not fully understood.

Hypothesis

Modern soccer boot type and sidestep cutting compared with straight-ahead running do not significantly influence knee internal tibia axial and valgus moments, anterior joint forces, and flexion angles.

Study Design

Controlled laboratory study.

Methods

Fifteen professional male outfield soccer players undertook trials of straight-ahead running and sidestep cutting at 30° and 60° with a controlled approach velocity on a Fédération Internationale de Football Association (FIFA) approved soccer surface. Two bladed and 2 studded soccer boots from 2 manufacturers were investigated. Three-dimensional inverse dynamics analysis determined externally applied internal/external tibia axial and valgus/varus moments, anterior forces, and flexion angles throughout stance.

Results

The soccer boot type imparted no significant difference on knee loading for each maneuver. Internal tibia and valgus moments were significantly greater for sidestep cutting at 30° and 60° compared with straight-ahead running. Sidestep cutting at 60° compared with straight-ahead running significantly increased anterior joint forces.

Conclusion

Varying soccer boot type had no effect on knee loading for each maneuver, but sidestep cutting significantly increased internal tibia and valgus moments and anterior joint forces.

Clinical Relevance

Sidestep cutting, irrespective of the modern soccer boot type worn, may be implicated in the high incidence of noncontact soccer anterior cruciate ligament injuries by significantly altering knee loading.
Failure Strengths in Distal Biceps Tendon Repair
Authors: Kettler Mark , Lunger Josef , Kuhn Volker , Mutschler Wulf , Tingart Markus J.
Published: March 2007

Background

Surgical repair is the most favored treatment for a rupture of the distal biceps tendon. A variety of techniques have been described for distal biceps tendon reattachment, including transosseous sutures, suture anchors, interference screws, and an EndoButton-based technique.

Hypothesis

EndoButton and suture anchor have initially stronger fixation strengths than do transosseous sutures, allowing early postoperative rehabilitation.

Study Design

Controlled laboratory study.

Methods

Single loads to failure and mode of failure of 13 different fixation techniques were determined using 130 human cadaveric elbows. Quantitative computer tomography was performed to exclude differences in bone mineral density as an affecting factor. Repeated-measures analysis of variance was used to assess differences in failure load between repair techniques.

Results

The EndoButton-based technique showed a significantly higher failure load (259 ± 28 N) than did all other techniques (P < .05). No significant differences were seen between the transosseous suture technique (210 ± 29 N) and most other techniques (P > .05). Failure loads of the TwinFix-QuickT (57 ± 29 N) and Biocuff screw (105 ± 28 N) were significantly lower than those of all other repairs (P < .05).

Conclusion

Significant differences exist in failure loads and modes of failure for the different repair techniques after rupture of the distal biceps tendon.

Clinical Relevance

The transosseous technique is still a sufficient and cost-saving procedure for repair of the distal biceps tendon. TwinFix-QuickT 5.0 mm and Biocuff screw 5.7 mm had significantly lower failure loads, which might affect early rehabilitation, particularly in patients with poor bone quality.
A New Piezoelectric Actuator using a Feed-screw for Quasi-static Motion Accumulation — Part II: Mathematical Modeling and Design Optimization
Authors: Loverich J.J. , Koopmann G.H. , Lesieutre G.A.
Published: March 2007

In recent piezoelectric actuator development, a new feed-screw motion accumulation concept has demonstrated reversible, robust, and high force actuation. However, the feed-screw actuator's complicated structure and frequency-dependent operation necessitate the use of an efficient method to optimize its performance. Consequently, this study presents the formulation of a dynamic mathematical feed-screw actuator model and its integration in an optimization algorithm. To accurately model the feed-screw actuator, nonlinear contact stiffness and micro-slip is considered, as well as rate-dependent friction behavior. Results from numerical model simulations compare well with experimental data for a range of loads corresponding to the actuator's peak power output. A simulated annealing optimization algorithm is used to determine an actuator design that maximizes specific power (W/kg). For an actuation rate and load of 0.26in./s and 1220lb, a factor of 5 increase in specific power over that of the original experimental hardware is predicted. Expanding the optimization to consider a broad range of loads and speeds indicates that the feed-screw actuator could achieve a 195 W/kg specific power — a level approximately double that of similarly sized electromagnetic actuator. The most significant design improvements contributing to the large gains in specific power involve an increase in the screw pitch angle and a reduction of its diameter.
Analysis of Brillouin Scattering Based Fiber Optic Sensor Bonding Effects
Authors: Brown Kellie , Brown Anthony W. , Colpitts Bruce G. , Bremner Theodore W.
Published: March 2007

Brillouin scattering based sensors can measure strain and/or temperature at all points along an optical fiber; first, the fiber must be calibrated. A problem arises because the temperature coefficient of a fiber bonded to a host is changed by the host structure. Using the loose fiber coefficient could lead to large strain and temperature measurement errors. This article studies the change in the Brillouin temperature coefficient due to bonding. The intrinsic Brillouin temperature coefficient of two fibers is also found. This coefficient allows accurate strain and temperature measurements to be made, assuming the coefficient of thermal expansion of the host is known.
Long-term Structural Health Monitoring System for a FRP Composite Highway Bridge Structure
Authors: Guan Hong , Karbhari Vistasp M. , Sikorsky Charles S.
Published: March 2007

This article discusses the implementation of a long-term structural health monitoring system for a FRP highway bridge using vibration-based monitoring techniques. The design and installation of such a system is prompted by the need to present a quantitative assessment of structural response to owners and operators in order to provide early warnings for major changes in response in the case of impending catastrophic failures. The bridge under discussion is instrumented with accelerometers as well as corresponding data acquisition and transmission equipment for automatic data collection. Ambient vibration based techniques are used to extract modal parameters from measured bridge response. Information regarding the change of internal structural characteristics is then obtained through a mode shape curvature based approach. Structural stiffness change is based on the analysis of collected data. A finite element model updating technique is used to provide an improved baseline model. The updated model is then used for simulation of damage effects.
Structural Damage Detection in the Frequency Domain using Neural Networks
Authors: Lee Jungwhee , Kim Sungkon
Published: March 2007

A bi-level damage detection algorithm that utilizes dynamic responses of the structure as input and neural network (NN) as a pattern classifier is presented. The signal anomaly index (SAI) is proposed to express the amount of changes in the shape of frequency response functions (FRFs) or strain frequency response function (SFRF). SAI is calculated by using the acceleration and dynamic strain responses acquired from intact and damaged states of the structure. In a bi-level damage identification algorithm, first the presence of damage is identified from the magnitude of the SAI value. Then the location of the damage is identified using the pattern recognition capability of the NN. The proposed algorithm is applied to an experimental model bridge to demonstrate the feasibility of the algorithm. Numerically simulated signals are used for training the NN, and experimentally acquired signals are used to test the NN. The results of this example application suggest that the SAI based pattern recognition approach may be applied to the structural health monitoring system for a real bridge.
Adaptive Tuned Mass Damper based on Pre-stressable Leaf-springs
Authors: Gsell Daniel , Feltrin Glauco , Motavalli Masoud
Published: March 2007

Lightweight bridges exhibit a high live load to dead load ratio. Thus, their resonance frequencies depend on the current loading state and can vary in quite a broad range. This behavior is a real challenge in vibration mitigation of such structures controlled by tuned mass dampers (TMDs), since the performance of single passive TMDs degrades significantly if the resonance frequency of a structure differs even slightly from design frequency. This study proposes an adaptive TMD, which continuously adapts its natural frequency to the current resonance frequency of the structure. The concept is based on pre-stressable leaf-springs that are controlled by piezoceramic stack actuators. Experiments performed on a first prototype show that the TMD is continuously tunable in a broad frequency range.
A Concept for Airfoil-like Active Bistable Twisting Structures
Authors: Schultz Marc R.
Published: March 2007

A novel type of morphing structure capable of a large change in shape with a small energy input is discussed. The considered structures consist of two curved shells that are joined in a specific manner to form an airfoil-like structure with two stable configurations. These configurations have a difference in axial twist, and the structure can be transformed between the stable shapes by a simple snap-through action. The benefit of a bistable structure of this type is that, if the stable shapes are operational ones, power is needed only to transform the structure from one shape to another. Several composites and one steel device are considered as proof-of-concept models and active control using piezocomposite actuators is demonstrated. Finite-element analysis is used to compare the predicted shapes with the experimental shapes, and to study how changes to the geometric input values affect the shape and operational characteristics of the structures. An interesting method for combining both continuous shape change with the bistable behavior is discussed.
Can We Find It at the Concessions? Understanding Price Elasticity in Professional Sports
Authors: Krautmann Anthony C. , Berri David J.
Published: March 2007

The sports economics literature regularly finds that sports teams price admissions in the inelastic range of demand. Given that marginal revenue is negative in this range, yet marginal cost is always nonnegative, this result suggests an inconsistency in the profit motive of owners. In this article, we attempt to explain inelastic ticket pricing by considering the complementarity between tickets sold and concessions. Depending on marginal revenue and cost parameters, we show that it is entirely possible to find profit-maximizing owners pricing tickets in the inelastic region of demand to sell more concessions.
Sports Leagues and Parity When League Parity Generates Fan Enthusiasm
Authors: Crooker John R. , Fenn Aju J.
Published: March 2007

This article demonstrates theoretically that, given a casual relationship exists from league parity to fan interest, as large-market teams myopically outbid small-market teams for talent there is potential for league parity to be underprovided. In this model, league parity is treated as a public good. With this characterization, this article arrives at the familiar economic result that public goods tend to be underprovided. This article does not discuss the impact of declining league parity intertemporally. Intuition suggests this decline could hamper interest in the league sport and even lead to a smaller fan base. The results suggest that if league parity is an important determinant of fan interest, a league lump-sum payment (transfer) and tax (subsidy) system may result in higher league profits. The article does add as a caveat that the authors are in no way justifying the revenue sharing plan adopted by Major League Baseball or any other league.
Salary Determination in the National Hockey League Is Arbitration Efficient?
Authors: Lambrinos James , Ashman Thomas D.
Published: March 2007

The final-offer arbitration system in baseball has been studied quite extensively, but there has not been an investigation into the effects of the arbitration system used in the National Hockey League (NHL). The goal of this study is to determine if arbitrated salaries in the NHL differ from negotiated salaries. Following the work of Ashenfelter, the objective of arbitrators is to use the same factors in making their arbitration decisions as are used for negotiated salaries. The results show that for forwards and defensemen, arbitrated salaries are not significantly different from negotiated salaries.
Explaining International Soccer Rankings
Authors: Macmillan Peter , Smith Ian
Published: March 2007

Existing research on the determinants of FIFA's international soccer rankings suffers from serious statistical problems, particularly sample selection bias and nonnormal errors. The authors correct for this by extending the data set by an additional 100 countries. Furthermore, they find important roles for new variables in the form of the size of population and a long history of international soccer in explaining world football rankings. The authors also investigate the determinants of an alternative ranking measure to that constructed by FIFA.
"What About People Our Age?" Applying Qualitative and Quantitative Methods to Uncover How Political Ads Alienate College Students
Authors: Parmelee John H. , Perkins Stephynie C. , Sayre Judith J.
Published: March 2007

This study uses a sequential transformative mixed methods research design to explain how political advertising fails to engage college students. Qualitative focus groups examined how college students interpret the value of political advertising to them, and a quantitative manifest content analysis concerning ad framing of more than 100 ads from the 2004 presidential race revealed why focus group participants felt so alienated by political advertising. By not selecting issues and people to which youth can relate, political advertising is framed to decrease the salience of young voters, thereby promoting an interpretation among college students that the messages within candidate ads are not relevant to them. Suggestions are made for building more engaging ads. The utility of this research design is also discussed in terms of its benefits for data analysis and validity.
Reading Mixed Methods Research: Contexts for Criticism
Authors: Freshwater Dawn
Published: March 2007

Health and social care researchers, in their haste to ``belong'' to academia, have adopted the system of mixed methodology research, overestimating its ability to reveal the truth and occasionally imprisoning their thought in one system. In this article, some of the assumptions underpinning mixed methodology research and its discourse are subjected to an interrogative reading. Every reading is an act of criticism and every reader a critic. To read literature is to practice criticism, that is, to read one way and not another. Examples are given of writing regarding mixed methods research in health care from within the critical contexts of author—audience and literature—reality. The aim of the article is to examine the language used to represent mixed methods research within a particular context rather than focus on actual mixed methods research studies.
Enhanced erythro-phagocytosis in polycythemic mice overexpressing erythropoietin
Authors: Bogdanova Anna , Mihov Deyan , Lutz Hans , Saam Bianca , Gassmann Max , Vogel Johannes
Published: March 2007

Adaptive mechanisms to hematocrit levels of 0.9 in our erythropoietin-overexpressing mice (tg6) include increased plasma nitric oxide levels and erythrocyte flexibility. Doubled reticulocyte counts in tg6 suggest an increased erythrocyte turnover. Here we show that compared with wild-type (wt) animals, erythrocyte lifespan in tg6 is 70% lower in tg6 mice. Transgenic mice have a younger erythrocyte population as indicated by higher intercellular water and potassium content, higher flexibility, decreased density, increased surface to volume ratio, and decreased osmotic fragility. Interestingly, despite being younger, the tg6 erythrocyte population also harbors characteristics of accelerated aging such as an increased band 4.1a to 4.1b ratio, signs of oxidative stress, or decreased surface CD47 and sialic acids. In tg6, in vivo tracking of PKH26-labeled erythrocytes revealed dramatically increased erythrocyte incorporation by their liver macrophages. In vitro experiments showed that tg6 macrophages are more active than wt macrophages and that tg6 erythrocytes are more attractive for macrophages than wt ones. In conclusion, in tg6 mice erythrocyte aging is accelerated, which results, together with an increased number and activity of their macrophages, in enhanced erythrocyte clearance. Our data points toward a new mechanism down-regulating red cell mass in excessive erythrocytosis in mice.
Local genetic and environmental factors in asthma disease pathogenesis: chronicity and persistence mechanisms
Authors: Holgate S. T. , Davies D. E. , Powell R. M. , Howarth P. H. , Haitchi H. M. , Holloway J. W.
Published: March 2007

While asthma is an inflammatory disorder of the airways usually associated with atopy, an important additional component is involvement of the epithelium and underlying mesenchyme acting as a trophic unit (EMTU).

In addition to allergens, a wide range of environmental factors interact with the EMTU, such as virus infections, environmental tobacco smoke and pollutants, to initiate tissue damage and aberrant repair responses that are translated into remodelling of the airways. While candidate gene association studies have revealed polymorphic variants that influence asthmatic inflammation, positional cloning of previously unknown genes is identifying a high proportion of novel genes in the EMTU.

Dipeptidyl peptidase (DPP) 10 and disintegrin and metalloproteinase (ADAM)33 are newly identified genes strongly associated with asthma that are preferentially expressed in the airway epithelium and underlying mesenchyme, respectively.

Also of increasing importance is the recognition that genes associated with asthma and atopy have important interactions with the environment through epigenetic mechanisms that influence their expression. This type of research will not only identify biomarkers of different types of asthma across the full range of phenotypic expression, but will also identify novel therapeutic targets that could influence the natural history of the heterogenes lung disease.
Social problem-solving plus psychoeducation for adults with personality disorder
Authors: Huband Nick , McMurran Mary , Evans Chris , Duggan Conor
Published: March 2007

Background

Social problem-solving therapy may be relevant in the treatment of personality disorder, although assessments of its effectiveness are uncommon.

Aims

To determine the effectiveness of a problem-solving intervention for adults with personality disorder in the community under conditions resembling routine clinical practice.

Method

Participants were randomly allocated to brief psychoeducation plus 16 problem-solving group sessions (n=87) or to waiting-list control (n=89). Primary outcome was comparison of scores on the Social Problem Solving Inventory and the Social Functioning Questionnaire between intervention and control arms at the conclusion of treatment, on average at 24 weeks after randomisation.

Results

In intention-to-treat analysis, those allocated to intervention showed significantly better problem-solving skills (P < 0.001), higher overall social functioning (P=0.031) and lower anger expression (P=0.039) compared with controls. No significant differences were found on use of services during the intervention period.

Conclusions

Problem-solving plus psychoeducation has potential as a preliminary intervention for adults with personality disorder.
Psychiatric disorder among British children looked after by local authorities: Comparison with children living in private households
Authors: Ford Tamsin , Vostanis Panos , Meltzer Howard , Goodman Robert
Published: March 2007

Background

Children looked after by local authorities are at higher risk of poor psychosocial outcomes than children living in private households, but nationally representative and random samples of the two groups of children have not previously been compared.

Aims

To find explanations for the increased prevalence of psychiatric disorder in children looked after by local authorities.

Method

We examined socio-demographic characteristics and psychopathology by type of placement among children looked after in Britain by local authorities (n = 1453), and compared these children with deprived and non-deprived children living in private households (n = 10 428).

Results

Children looked after by local authorities had higher levels of psychopathology, educational difficulties and neurodevelopmental disorders, and ‘looked after’ status was independently associated with nearly all types of psychiatric disorder after adjusting for these educational and physical factors. The prevalence of psychiatric disorder was particularly high among those living in residential care and with many recent changes of placement.

Conclusions

Our findings indicate a need for greater support of this vulnerable group of children.
Association between trauma exposure and delusional experiences in a large community-based sample
Authors: Scott James , Chant David , Andrews Gavin , Martin Graham , McGrath John
Published: March 2007

Background

Surveys have found that otherwise well individuals report delusional experiences. Previous studies have shown an association between psychotic symptoms and exposure to trauma.

Aims

To explore the association between trauma and delusional experiences in a community sample.

Method

Respondents (n = 10 641) were assessed for delusional experiences, exposure to various types of traumatic experiences and the presence of post-traumatic stress disorder (PTSD). The endorsement of delusional items was examined in people exposed to traumatic events who did or did not have PTSD.

Results

Exposure to any traumatic event but without the development of PTSD was associated with increased endorsement of delusional experiences (relative risk 2.68, 95% CI 2.18–3.30) and there was a significant dose–response relationship between the number of types of traumatic events and endorsement of such experiences (χ2 =26.74, d.f. =2, P < 0.001). A diagnosis of PTSD further increased endorsement of delusional experiences (RR = 9.24, 95% CI 6.95–12.27). The association between PTSD and delusional experiences remained significant after adjusting for factors associated with psychotic symptoms.

Conclusions

Further investigation into the pathways between trauma, delusions and psychosis may provide insights into shared aetiological mechanisms underpinning these conditions.
Effect of comorbid anxiety on treatment response and relapse risk in late-life depression: controlled study
Authors: Andreescu Carmen , Lenze Eric J. , Dew Mary Amanda , Begley Amy E. , Mulsant Benoit H. , Dombrovski Alexandre Y. , Pollock Bruce G. , Stack Jacqueline , Miller Mark D. , Reynolds Charles F.
Published: March 2007

Background

Comorbid anxiety is common in depressive disorders in both middle and late life, and it affects response to antidepressant treatment.

Aims

To examine whether anxiety symptoms predict acute and maintenance (2 years) treatment response in late-life depression.

Method

Data were drawn from a randomised double-blind study of pharmacotherapy and interpersonal psychotherapy for patients age 70 years and over with major depression. Anxiety symptoms were measured using the Brief Symptom Inventory. Survival analysis tested the effect of pre-treatment anxiety on response and recurrence.

Results

Patients with greater pre-treatment anxiety took longer to respond to treatment and had higher rates of recurrence. Actuarial recurrence rates were 29% (pharmacotherapy, lower anxiety), 58% (pharmacotherapy, higher anxiety), 54% (placebo, lower anxiety) and 81% (placebo, higher anxiety).

Conclusions

Improved identification and management of anxiety in late-life depression are needed to achieve response and stabilise recovery.
Enduring consequences of terrorism: 7-month follow-up survey of reactions to the bombings in London on 7 July 2005
Authors: Rubin G. James , Brewin Chris R. , Greenberg Neil , Hughes Jamie Hacker , Simpson John , Wessely Simon
Published: March 2007

Background

Terrorist attacks can have psychological effects on the general public.

Aims

To assess the medium-term effects of the July 2005 London bombings on the general population in London and to identify risk factors for persistent effects.

Method

We telephoned 1010 Londoners 11–13 days after the bombings to assess stress levels, perceived threat and travel intentions. Seven months later, 574 respondents were contacted again and asked similar questions, and questions concerning altered perceptions of self and the world.

Results

‘Substantial stress' (11%), perceived threat to self (43%) and reductions in travel because of the bombings (19%) persisted at a reduced level; other perceived threats remained unchanged. A more negative world view was common. Other than degree of exposure to the bombings, there were no consistent predictors of which people with short-term reactions would develop persistent reactions.

Conclusions

A longer-term impact of terrorism on the perceptions and behaviour of Londoners was documented.