bluuebunny/crossref_metadata_2025 huggingface dataset:
A Mechanism for Neuronal Gain Control by Descending Pathways
Authors: Nelson Mark E.
Published: April 2008

Many implementations of adaptive signal processing in the nervous system are likely to require a mechanism for gain control at the single neuron level. To properly adjust the gain of an individual neuron, it may be necessary to use information carried by neurons in other parts of the system. The ability to adjust the gain of neurons in one part of the brain, using control signals arising from another, has been observed in the electrosensory system of weakly electric fish, where descending pathways to a first-order sensory nucleus have been shown to influence the gain of its output neurons. Although the neural circuitry associated with this system is well studied, the exact nature of the gain control mechanism is not fully understood. In this paper, we propose a mechanism based on the regulation of total membrane conductance via synaptic activity on descending pathways. Using a simple neural model, we show how the activity levels of paired excitatory and inhibitory control pathways can regulate the gain and baseline excitation of a target neuron.
Smooth On-Line Learning Algorithms for Hidden Markov Models
Authors: Baldi Pierre , Chauvin Yves
Published: April 2008

A simple learning algorithm for Hidden Markov Models (HMMs) is presented together with a number of variations. Unlike other classical algorithms such as the Baum-Welch algorithm, the algorithms described are smooth and can be used on-line (after each example presentation) or in batch mode, with or without the usual Viterbi most likely path approximation. The algorithms have simple expressions that result from using a normalized-exponential representation for the HMM parameters. All the algorithms presented are proved to be exact or approximate gradient optimization algorithms with respect to likelihood, log-likelihood, or cross-entropy functions, and as such are usually convergent. These algorithms can also be casted in the more general EM (Expectation-Maximization) framework where they can be viewed as exact or approximate GEM (Generalized Expectation-Maximization) algorithms. The mathematical properties of the algorithms are derived in the appendix.
On Functional Approximation with Normalized Gaussian Units
Authors: Benaim Michel
Published: April 2008

Feedforward neural networks with a single hidden layer using normalized gaussian units are studied. It is proved that such neural networks are capable of universal approximation in a satisfactory sense. Then, a hybrid learning rule as per Moody and Darken that combines unsupervised learning of hidden units and supervised learning of output units is considered. By using the method of ordinary differential equations for adaptive algorithms (ODE method) it is shown that the asymptotic properties of the learning rule may be studied in terms of an autonomous cascade of dynamical systems. Some recent results from Hirsch about cascades are used to show the asymptotic stability of the learning rule.
Statistical Physics, Mixtures of Distributions, and the EM Algorithm
Authors: Yuille Alan L. , Stolorz Paul , Utans Joachim
Published: April 2008

We show that there are strong relationships between approaches to optmization and learning based on statistical physics or mixtures of experts. In particular, the EM algorithm can be interpreted as converging either to a local maximum of the mixtures model or to a saddle point solution to the statistical physics system. An advantage of the statistical physics approach is that it naturally gives rise to a heuristic continuation method, deterministic annealing, for finding good solutions.
Topology Learning Solved by Extended Objects: A Neural Network Model
Authors: Szepesvári Csaba , Balázs László , Lőrincz András
Published: April 2008

It is shown that local, extended objects of a metrical topological space shape the receptive fields of competitive neurons to local filters. Self-organized topology learning is then solved with the help of Hebbian learning together with extended objects that provide unique information about neighborhood relations. A topographical map is deduced and is used to speed up further adaptation in a changing environment with the help of Kohonen-type learning that teaches the neighbors of winning neurons as well.
Dynamics of Discrete Time, Continuous State Hopfield Networks
Authors: Koiran Pascal
Published: April 2008

The dynamics of discrete time, continuous state Hopfield networks is driven by an energy function. In this paper, we use this tool to prove under mild hypotheses that any trajectory converges to a fixed point for the sequential iteration, and to a cycle of length 2 or a fixed point for the parallel iteration. Perhaps surprisingly, it seems that no rigorous proof of these results was published before.
Duality Between Learning Machines: A Bridge Between Supervised and Unsupervised Learning
Authors: Nadal J.-P. , Parga N.
Published: April 2008

We exhibit a duality between two perceptrons that allows us to compare the theoretical analysis of supervised and unsupervised learning tasks. The first perceptron has one output and is asked to learn a classification of p patterns. The second (dual) perceptron has p outputs and is asked to transmit as much information as possible on a distribution of inputs. We show in particular that the maximum information that can be stored in the couplings for the supervised learning task is equal to the maximum information that can be transmitted by the dual perceptron.
Functionally Equivalent Feedforward Neural Networks
Authors: Kůrková Věra , Kainen Paul C.
Published: April 2008

For a feedforward perceptron type architecture with a single hidden layer but with a quite general activation function, we characterize the relation between pairs of weight vectors determining networks with the same input-output function.
Keratohyalin-like granules in embryonic and regenerating epidermis of lizards and Sphenodon punctatus (Reptilia, Lepidosauria)
Authors: Alibardi Lorenzo
Published: April 2008

Epidermal shedding in lepidosaurians is determined by the formation of an intraepidermal shedding complex, made of an upper clear layer which interdigitates with a lower oberhautchen layer. The latter produces species-specific microornamentations. The ultrastructure of embryonic and regenerating epidermis in seven species of lizards representing five different squamate families (Gekkonidae, Agamidae, Lacertidae, Iguanidae and Scincidae), and on the regenerating caudal epidermis of the tuatara (Sphenodon punctatus, suborder Sphenodontia), has shown a broad variation in dimension and morphology of keratohyalin-like granules present in the clear layer of the shedding complex. Where the oberhautchen ornamentations are well developed, like in the setae of the climbing pads, keratohyalin-like granules appear more irregular, larger or more numerous. The present study suggests that keratohyalin-like granules might be involved in the formation of a fibrous network around the forming oberhautchen microornamentations.
A new Bolivian species of the genus Telmatobius (Anura: Leptodactylidae) with a humeral spine
Authors: Lavilla E.O. , Ergueta Sandoval Patricia
Published: April 2008

A new species of the genus Telmatobius is described based on two adult males from Chuspipata, Provincia Nor-Yungas, Departamento La Paz, Boliva, at 3050 m asl. This is the second species of the genus known to have an evident, externally projected humeral spine.
Phénologie de la reproduction chez Pelodytes punctatus Daudin, 1802 (Amphibia, Anura)
Authors: Guyétant R. , Temmermans W. , Avrillier J.N.
Published: April 2008

Pelodytes punctatus est une espèce dont les biotopes de reproduction sont localisés en plaine principalement (90% des cas). De nouvelles données sur la phénologie de la reproduction ainsi que sur le type de milieu ont été collectées durant 6 ans sur 4 régions comprenant plus de 35 sites. La période de ponte principale survient au printemps mais on peut en observer une deuxième en automne dans le sud de la France. Les œufs sont fixés en cordons par les femelles sur les tiges de plantes aquatiques. Le succès de l'éclosion dépend de l'oxygénation de l'eau. La croissance larvaire est relativement rapide en conditions contrôlées (19°C ± 1°C) et les têtards se métamorphosent 40 à 60 jours après l'éclosion. Dans le sud, deux catégories de têtards sont observées en automne, les plus petits hivernent et se métamorphosent durant le printemps suivant.
Development of testes and differentiation of germ cells in water frogs of the Rana esculenta - complex (Amphibia, Anura)
Authors: Ogielska Maria , Bartmańska Jolanta
Published: April 2008

The European water frog, Rana esculenta, is a hybrid whose genome is composed of haploid chromosome sets of its parental species R. lessonae and R. ridibunda. Prior to meiosis one of the parental sets is discarded and the other is duplicated (hybridogenesis). In the parental species sex differentiation begins at tadpole stages 28-30 (Gosner, 1960), at stages 30-36 the testes are composed of proliferating pale spermatogonia 1°. At stages 36-39 a new class of spermatogonia I° (dark) appears. Before first hibernation, seminiferous lobules are filled with cysts containing germ cells at various stages of spermatogenesis up to elongating spermatids. In R. esculenta gonad development is affected from the earliest stages: the gonads are smaller and composed of reduced number of spermatogonia I°. The phase of pale spermatogonia I° proliferation is prolonged up to the second year of life. The structure of the gonads, as well as that of germ cells themselves, are often abnormal.
Foraging modes in lacertid lizards from southern Africa
Authors: Cooper William E. , Whiting Martin J.
Published: April 2008

Most lacertids are active foragers, but intrafamilial variation in foraging mode is greater than in most lizard families. We collected data on eight species of African lacertids to assess this variation. Both active and ambush foraging occurred within Pedioplanis and Meroles. Meroles ctenodactylus had a proportion of time moving and proportion of attacked prey detected while moving intermediate to those for actively foraging and ambushing Pedioplanis, but its number of movements per minute was exceptionally high. This species has a unique mixed foraging mode. Like active foragers, it seeks food by tongue-flicking while moving and spends a high percentage of the time moving. Like ambush foragers, it searches visually for prey during pauses between movements. Our findings confirm published data on four Kalahari lacertids. We discuss the history of foraging modes in advanced lacertids.
The Agonistic Behaviour of Juvenile Blennius Pholis L. (Teleostei)
Authors: Gibson R.N.
Published: April 2008

The agonistic behaviour of juvenile Blennius pholis, L. was observed in tanks of 28 x 43 x 30 cm and 75 x 40 x 30 cm, the larger tanks thus having a floor area 2.5 times that of the smaller tanks. The smaller tanks contained two fish, the larger ones either two or five fish. Those containing five fish thus had a population density equivalent to the smaller tanks. Eight main elements of agonistic behaviour were observed. They were; advancing, threatening, charging, snapping, fleeing, chasing, retreating and submitting. It was found that charging, fleeing, and chasing were by far the most common elements performed. Charging, threatening and chasing were performed most frequently by dominant fish, fleeing and retreating by subordinate fish. Advancing was performed more or less equally by both dominant and subordinate fish. It is suggested that submission is a displacement activity. Size difference was the main factor deciding dominance and the intensity of aggression, but the onset of light, food, available space, and the activity of the fish concerned were also of importance. The size of the tank and the number of fish it contained had an effect upon the relationship between size difference and the intensity of aggression. In the smaller tanks the intensity of aggression was directly related to the difference in size between the two fish. This relationship was not as clear in the larger tanks. Territoriality in the normally accepted sense of the word was not observed, because the fish were not seen to defend any particular area of the tank against others. A hypothesis suggesting the existence of 'individual distances' is put forward, in which the fish are considered to defend a particular area of space around themselves. These individual distances fluctuate in size according to the state of the aggressive drive of the individual and the amount of space available to it for movement. An attempt is made to relate the behaviour observed in the laboratory to that occurring in nature.
Preoptic Activation of Frog Mating Behavior
Authors: Schmidt Robert S.
Published: April 2008

The effects of preoptic lesions on mating calling and mate orientation were studied in Rana pipiens and several species of tree frogs (Hylidae). Mating calling was evoked by electrical stimulation of the preoptic area of Rana pipiens and Bufo americanus. A new chronic electrode holder is described. It is concluded that the region of the dorsal magnocellular preoptic nucleus is needed for mate orientation and that the region of the ventral magnocellular preoptic nucleus is needed for mating calling. It is suggested that these preoptic regions may act mainly as activators of more posterior "centers". Mating calling may have evolved through the origin of connections between pre-existing preoptic activators and a pre-existing release calling "center", rather than through the origin of a new mating calling "center".
A Feasibility Study for a Sans Investigation of a Heat Cured and Laser Machined Organic Resin Microturbine as Used for Airflow Sensing
Authors: Heaton M.E. , Rogante M. , Len A.
Published: April 2008

In this paper, Gamma‐Butyrolactone (GLB) mixed with Triarylsulfonia and Hexafluroantimonate in the substrate of a microturbine is considered for a Small Angle Neutron Scattering (SANS) diagnostic study, paying particular attention to molecular orientations and other micro‐characteristics in connection with the mechanical properties of the substrate. The investigated microturbine is a new MEMS device for the first pioneering study of either gas or airflow sensing using the low pressurehead characteristics of axial‐flow. The substrate material of the microturbine is a negative photoresist composed of an epoxy resin organic solvent. This study wishes to demonstrate the feasibility of the SANS process for examining this substrate on the nano‐scale prior to a full materials investigation, which aims to provide both the information to both improve the characteristics and performance of the microturbine and estimate its maximum lifetime more accurately. The data could also be used to match microturbines to appropriate applications in either flow‐sensing or micro‐power generation in accordance with structural strength limits.
A Combined Multi‐Material Euler/Lagrange Computational Analysis of Blast Loading Resulting from Detonation of Buried Landmines
Authors: Grujicic M. , Pandurangan B. , Mocko G.M. , Hung S.T. , Cheeseman B.A. , Roy W.N. , Skaggs R.R.
Published: April 2008

Detonation of landmines buried to different depths in water‐saturated sand is analyzed computationally using transient non‐linear dynamics simulations in order to quantify impulse loading. The computational results are compared with the corresponding experimental results obtained using the Vertical Impulse Measurement Fixture (VIMF), a structural mechanical device that enables direct experimental determination of the blast‐loading impulse. The structural‐dynamic/ballistic response of the Rolled Homogenized Armor (RHA) used in the construction of the VIMF witness plate and the remainder of the VIMF and the hydrodynamic response of the TNT high‐energy explosive of a mine and of the air surrounding the VIMF are represented using the standard materials models available in literature. The structural‐dynamic/ballistic response of the sand surrounding the mine, on the other hand, is represented using our recent modified compaction model which incorporates the effects of degree of saturation and the rate of deformation, two important effects which are generally neglected in standard material models for sand. The results obtained indicate that the use of the modified compaction model yields a substantially better agreement with the experimentally‐determined impulse loads over the use the original compaction model. Furthermore, the results suggest that, in the case of fully saturated sand, the blast loading is of a bubble type rather than of a shock type, i.e. the detonation‐induced momentum transfer to the witness plate is accomplished primarily through the interaction of the sand‐over‐burden (propelled by the high‐pressure expanding gaseous detonation by‐products) with the witness plate.
60- to 1-Min Rainfall-Rate Conversion: Comparison of Existing Prediction Methods with Data Obtained in the Southeast Asia Region
Authors: Mandeep J. S. , Hassan S. I. S.
Published: April 2008

Rainfall-rate statistics are frequently derived on the basis of rain gauge recordings with effective integration times of 10 min or longer. The conversion of such data to equivalent statistics for an effective integration time of 1 min is very important to predict rainfall attenuation at a location accurately. Because of the limited availability of 1-min rainfall-rate data, conversion of available rainfall-rate distributions with longer integration times to the desired 1-min distributions is needed. Several methods for converting 60-min rainfall rates to 1-min rainfall rates are tested against measured rainfall rates from tropical, high-rainfall-rate regions. Segal’s method was found to perform the best overall when compared with other conversion methods.
Flood Fatalities in the United States
Authors: Ashley Sharon T. , Ashley Walker S.
Published: April 2008

This study compiles a nationwide database of flood fatalities for the contiguous United States from 1959 to 2005. Assembled data include the location of fatalities, age and gender of victims, activity and/or setting of fatalities, and the type of flood events responsible for each fatality report. Because of uncertainties in the number of flood deaths in Louisiana from Hurricane Katrina, these data are not included in the study. Analysis of these data reveals that a majority of fatalities are caused by flash floods. People between the ages of 10 and 29 and >60 yr of age are found to be more vulnerable to floods. Findings reveal that human behavior contributes to flood fatality occurrences. These results also suggest that future structural modifications of flood control designs (e.g., culverts and bridges) may not reduce the number of fatalities nationwide. Spatially, flood fatalities are distributed across the United States, with high-fatality regions observed along the northeast Interstate-95 corridor, the Ohio River valley, and near the Balcones Escarpment in south-central Texas. The unique distributions found are likely driven by both physical vulnerabilities for flooding as well as the social vulnerabilities.
Cluster Sequencing to Analyze Synoptic Transitions Affecting Regional Ozone
Authors: Beaver Scott , Palazoglu Ahmet , Tanrikulu Saffet
Published: April 2008

Synoptic conditions are known to strongly influence mesoscale flows and hence local ozone levels in the San Francisco Bay Area of California. Sets of individual days sharing certain combinations of synoptic features constitute “static” meteorological patterns (or regimes) that account for much of the variability in regional ozone levels. Upon labeling each day of the core Bay Area ozone season using a small number of synoptic regimes, the resulting daily sequence of static patterns indicates the time evolution of the synoptic system through a series of regimes realized for various durations. Further insight into ozone buildup processes can be gained by examining this sequence of static labels to identify “dynamic” meteorological patterns affecting local ozone levels. Transition probabilities between each pair of synoptic regimes are modeled using binomial statistics to determine transitions that are either energetically favored or disfavored to occur. The persistency of the meteorological regimes is additionally considered to complement the transition probabilities in forming a more complete statistical characterization of the synoptic evolution. The sequencing method allows identification of two scenarios under which exceedance of air quality standards occurs in the Bay Area.
Intercalibrated Passive Microwave Rain Products from the Unified Microwave Ocean Retrieval Algorithm (UMORA)
Authors: Hilburn K. A. , Wentz F. J.
Published: April 2008

The Unified Microwave Ocean Retrieval Algorithm (UMORA) simultaneously retrieves sea surface temperature, surface wind speed, columnar water vapor, columnar cloud water, and surface rain rate from a variety of passive microwave radiometers including the Special Sensor Microwave Imager (SSM/I), the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI), and the Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E). The rain component of UMORA explicitly parameterizes the three physical processes governing passive microwave rain retrievals: the beamfilling effect, cloud and rainwater partitioning, and effective rain layer thickness. Rain retrievals from the previous version of UMORA disagreed among different sensors and were too high in the tropics. These issues have been fixed with more realistic rain column heights and proper modeling of saturation and footprint-resolution effects in the beamfilling correction. The purpose of this paper is to describe the rain algorithm and its recent improvements and to compare UMORA retrievals with Goddard Profiling Algorithm (GPROF) and Global Precipitation Climatology Project (GPCP) rain rates. On average, TMI retrievals from UMORA agree well with GPROF; however, large differences become apparent when the instantaneous retrievals are compared on a pixel-to-pixel basis. The differences are due to fundamental algorithm differences. For example, UMORA generally retrieves higher total liquid water, but GPROF retrieves a higher surface rain rate for a given amount of total liquid water because of differences in microphysical assumptions. Comparison of UMORA SSM/I retrievals with GPCP shows similar spatial patterns, but GPCP has higher global averages because of greater amounts of precipitation in the extratropics. UMORA and GPCP have similar linear trends over the period 1988–2005 with similar spatial patterns.
Simulations of the Urban Planetary Boundary Layer in an Arid Metropolitan Area
Authors: Grossman-Clarke Susanne , Liu Yubao , Zehnder Joseph A. , Fast Jerome D.
Published: April 2008

A modified version of the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5) was applied to the arid Phoenix, Arizona, metropolitan region. The ability of the model to simulate characteristics of the summertime urban planetary boundary layer (PBL) was tested by comparing model results with observations from two field campaigns conducted in May/June 1998 and June 2001. The modified MM5 included a refined land use/cover classification and updated land use data for Phoenix and bulk approaches of characteristics of the urban surface energy balance. PBL processes were simulated by a version of MM5’s Medium-Range Forecast Model (MRF) scheme that was enhanced by new surface flux and nonlocal mixing approaches. Simulated potential temperature profiles were tested against radiosonde data, indicating that the modified MRF scheme was able to simulate vertical mixing and the evolution and height of the PBL with good accuracy and better than the original MRF scheme except in the late afternoon. During both simulation periods, it is demonstrated that the modified MM5 simulated near-surface air temperatures and wind speeds in the urban area consistently and considerably better than the standard MM5 and that wind direction simulations were improved slightly.
Evaluation of Limited-Area Models for the Representation of the Diurnal Cycle and Contrasting Nights in CASES-99
Authors: Steeneveld G. J. , Mauritsen T. , de Bruijn E. I. F. , Vilà-Guerau de Arellano J. , Svensson G. , Holtslag A. A. M.
Published: April 2008

This study evaluates the ability of three limited-area models [the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5), the Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS), and the High-Resolution Limited-Area Model (HIRLAM)] to predict the diurnal cycle of the atmospheric boundary layer (ABL) during the Cooperative Atmosphere–Surface Exchange Study (CASES-99) experimental campaign. Special attention is paid to the stable ABL. Limited-area model results for different ABL parameterizations and different radiation transfer parameterizations are compared with the in situ observations. Model forecasts were found to be sensitive to the choice of the ABL parameterization both during the day and at night. At night, forecasts are particularly sensitive to the radiation scheme. All three models underestimate the amplitude of the diurnal temperature cycle (DTR) and the near-surface wind speed. Furthermore, they overestimate the stable boundary layer height for windy conditions and underestimate the stratification of nighttime surface inversions. Favorable parameterizations for the stable boundary layer enable rapid surface cooling, and they have limited turbulent mixing. It was also found that a relatively large model domain is required to model the Great Plains low-level jet. A new scheme is implemented for the stable boundary layer in the Medium-Range Forecast Model (MRF). This scheme introduces a vegetation layer, a new formulation for the soil heat flux, and turbulent mixing based on the local scaling hypothesis. The new scheme improves the representation of surface temperature (especially for weak winds) and the stable boundary layer structure.
A Basin- to Channel-Scale Unstructured Grid Hurricane Storm Surge Model Applied to Southern Louisiana
Authors: Westerink Joannes J. , Luettich Richard A. , Feyen Jesse C. , Atkinson John H. , Dawson Clint , Roberts Hugh J. , Powell Mark D. , Dunion Jason P. , Kubatko Ethan J. , Pourtaheri Hasan
Published: April 2008

Southern Louisiana is characterized by low-lying topography and an extensive network of sounds, bays, marshes, lakes, rivers, and inlets that permit widespread inundation during hurricanes. A basin- to channel-scale implementation of the Advanced Circulation (ADCIRC) unstructured grid hydrodynamic model has been developed that accurately simulates hurricane storm surge, tides, and river flow in this complex region. This is accomplished by defining a domain and computational resolution appropriate for the relevant processes, specifying realistic boundary conditions, and implementing accurate, robust, and highly parallel unstructured grid numerical algorithms.

The model domain incorporates the western North Atlantic, the Gulf of Mexico, and the Caribbean Sea so that interactions between basins and the shelf are explicitly modeled and the boundary condition specification of tidal and hurricane processes can be readily defined at the deep water open boundary. The unstructured grid enables highly refined resolution of the complex overland region for modeling localized scales of flow while minimizing computational cost. Kinematic data assimilative or validated dynamic-modeled wind fields provide the hurricane wind and pressure field forcing. Wind fields are modified to incorporate directional boundary layer changes due to overland increases in surface roughness, reduction in effective land roughness due to inundation, and sheltering due to forested canopies. Validation of the model is achieved through hindcasts of Hurricanes Betsy and Andrew. A model skill assessment indicates that the computed peak storm surge height has a mean absolute error of 0.30 m.
Cluster Analysis for Object-Oriented Verification of Fields: A Variation
Authors: Marzban Caren , Sandgathe Scott
Published: April 2008

In a recent paper, a statistical method referred to as cluster analysis was employed to identify clusters in forecast and observed fields. Further criteria were also proposed for matching the identified clusters in one field with those in the other. As such, the proposed methodology was designed to perform an automated form of what has been called object-oriented verification. Herein, a variation of that methodology is proposed that effectively avoids (or simplifies) the criteria for matching the objects. The basic idea is to perform cluster analysis on the combined set of observations and forecasts, rather than on the individual fields separately. This method will be referred to as combinative cluster analysis (CCA). CCA naturally lends itself to the computation of false alarms, hits, and misses, and therefore, to the critical success index (CSI). A desirable feature of the previous method—the ability to assess performance on different spatial scales—is maintained. The method is demonstrated on reflectivity data and corresponding forecasts for three dates using three mesoscale numerical weather prediction model formulations—the NCEP/NWS Nonhydrostatic Mesoscale Model (NMM) at 4-km resolution (nmm4), the University of Oklahoma’s Center for Analysis and Prediction of Storms (CAPS) Weather Research and Forecasting Model (WRF) at 2-km resolution (arw2), and the NCAR WRF at 4-km resolution (arw4). In the small demonstration sample herein, model forecast quality is efficiently differentiated when performance is assessed in terms of the CSI. In this sample, arw2 appears to outperform the other two model formulations across all scales when the cluster analysis is performed in the space of spatial coordinates and reflectivity. However, when the analysis is performed only on spatial data (i.e., when only the spatial placement of the reflectivity is assessed), the difference is not significant. This result has been verified both visually and using a standard gridpoint verification, and seems to provide a reasonable assessment of model performance. This demonstration of CCA indicates promise in quickly evaluating mesoscale model performance while avoiding the subjectivity and labor intensiveness of human evaluation or the pitfalls of non-object-oriented automated verification.
Implications of the Form of the Ensemble Transformation in the Ensemble Square Root Filters
Authors: Sakov Pavel , Oke Peter R.
Published: April 2008

This paper considers implications of different forms of the ensemble transformation in the ensemble square root filters (ESRFs) for the performance of ESRF-based data assimilation systems. It highlights the importance of using mean-preserving solutions for the ensemble transform matrix (ETM). The paper shows that an arbitrary mean-preserving ETM can be represented as a product of the symmetric solution and an orthonormal mean-preserving matrix. The paper also introduces a new flavor of ESRF, referred to as ESRF with mean-preserving random rotations. To investigate the performance of different solutions for the ETM in ESRFs, experiments with two small models are conducted. In these experiments, the performances of two mean-preserving solutions, two non-mean-preserving solutions, and a traditional ensemble Kalman filter with perturbed observations are compared. The experiments show a significantly better performance of the mean-preserving solutions for the ETM in ESRFs compared to non-mean-preserving solutions. They also show that applying the mean-preserving random rotations prevents the buildup of ensemble outliers in ESRF-based data assimilation systems.
An Efficient Dual-Resolution Approach for Ensemble Data Assimilation and Tests with Simulated Doppler Radar Data
Authors: Gao Jidong , Xue Ming
Published: April 2008

A new efficient dual-resolution (DR) data assimilation algorithm is developed based on the ensemble Kalman filter (EnKF) method and tested using simulated radar radial velocity data for a supercell storm. Radar observations are assimilated on both high-resolution and lower-resolution grids using the EnKF algorithm with flow-dependent background error covariances estimated from the lower-resolution ensemble. It is shown that the flow-dependent and dynamically evolved background error covariances thus estimated are effective in producing quality analyses on the high-resolution grid.

The DR method has the advantage of being able to significantly reduce the computational cost of the EnKF analysis. In the system, the lower-resolution ensemble provides the flow-dependent background error covariance, while the single-high-resolution forecast and analysis provides the benefit of higher resolution, which is important for resolving the internal structures of thunderstorms. The relative smoothness of the covariance obtained from the lower 4-km-resolution ensemble does not appear to significantly degrade the quality of analysis. This is because the cross covariance among different variables is of first-order importance for “retrieving” unobserved variables from the radar radial velocity data.

For the DR analysis, an ensemble size of 40 appears to be a reasonable choice with the use of a 4-km horizontal resolution in the ensemble and a 1-km resolution in the high-resolution analysis. Several sensitivity tests show that the DR EnKF system is quite robust to different observation errors. A 4-km thinned data resolution is a compromise that is acceptable under the constraint of real-time applications. A data density of 8 km leads to a significant degradation in the analysis.
Typhoon Initialization in a Mesoscale Model—Combination of the Bogused Vortex and the Dropwindsonde Data in DOTSTAR
Authors: Chou Kun-Hsuan , Wu Chun-Chieh
Published: April 2008

Issues concerning the initialization and simulation of tropical cyclones by integrating both dropwindsonde data and a bogused vortex into a mesoscale model have been studied. A method is proposed to combine dropwindsonde data with a bogused vortex for tropical cyclone initialization and to improve track and intensity prediction. A clear positive impact of this proposed method on both the tropical cyclone track and intensity forecasts in a mesoscale model is demonstrated in three cases of typhoons, including Meari (2004), Conson (2004), and Megi (2004). The effectiveness of the proposed method in improving the track and intensity forecasts is also demonstrated in the evaluation of all 10 cases of Dropwindsonde Observations for Typhoon Surveillance near the Taiwan Region (DOTSTAR) missions in 2004. This method provides a useful and practical means to improve operational tropical cyclone prediction with dropwindsonde observations.
Comparison of Observed 10-m Wind Speeds to Those Based on Monin–Obukhov Similarity Theory Using IHOP_2002 Aircraft and Surface Data
Authors: Strassberg Diane , LeMone Margaret A. , Warner Thomas T. , Alfieri Joseph G.
Published: April 2008

Comparisons of 10-m above ground level (AGL) wind speeds from numerical weather prediction (NWP) models to point observations consistently show that model daytime wind speeds are slow compared to observations, even after improving model physics and going to smaller grid spacing. Previous authors have attributed the discrepancy to differences between the areas represented by model and observations, and the small surface roughness upstream of wind vanes compared with the corresponding model grid value. Using daytime fair-weather data from the May–June 2002 International H2O Experiment (IHOP_2002), the effect of wind-vane exposure is explored by comparing observed 10-m winds from nine surface-flux towers in well-exposed locations to modeled 10-m winds found by applying Monin–Obukhov (MO) similarity for unstable conditions to flight-track-averaged data collected by the University of Wyoming King Air over flat to rolling terrain with occasional trees and buildings. In the calculations, King Air winds and fluxes are supplemented with thermodynamic means and fluxes from the surface-flux towers. After exercising considerable care in characterizing and reducing biases in aircraft winds and fluxes, the authors found that MO-based surface winds averaged 0.5–0.7 ± 0.2 m s−1 less than those measured—about the same as the smaller reported discrepancies between NWP models and observed winds.
Atlantic Hurricane Season of 2006
Authors: Franklin James L. , Brown Daniel P.
Published: April 2008

The 2006 Atlantic hurricane season is summarized and the year’s tropical cyclones are described. A verification of National Hurricane Center official forecasts during 2006 is also presented. Ten cyclones attained tropical storm intensity in 2006. Of these, five became hurricanes and two became “major” hurricanes. Overall activity was near the long-term mean, but below the active levels of recent seasons. For the first time since 2001, no hurricanes made landfall in the United States. Elsewhere in the basin, hurricane-force winds were experienced in Bermuda (from Florence) and in the Azores (from Gordon). Official track forecast errors were smaller in 2006 than during the previous 5-yr period (by roughly 15%–20% out to 72 h), establishing new all-time lows at forecast projections through 72 h. Since 1990, 24–72-h official track forecast errors have been reduced by roughly 50%.
Myocardial Infarction With Distal Embolization Associated With Myocardial Bridging in a Postoperative Patient: A Case Report
Authors: Huang Henry W.
Published: April 2008

Myocardial bridging is associated with myocardial infarction (MI) on rare occasions. The mechanism by which this occurs is unclear; vessel occlusion in this setting may be due to superimposed thrombosis or vasospasm. An unusual case is presented of postoperative MI from thrombosis associated with myocardial bridging and intravascular volume depletion, with subsequent distal embolization. Endothelial injury as a result of myocardial bridging may predispose to thrombus formation. To avoid MI, adequate fluid hydration is recommended during the perioperative period in patients with myocardial bridging.
Transient Left Ventricular Apical Ballooning Syndrome: The First Series in Taiwanese Patients
Authors: Fang Ching-Chang , Yeun Tarl Fresner Ng Jao  , Yi-Chen  , Yu Ching-Lung , Chen Chi-Liang , Wang Shih-Pu
Published: April 2008

Previously thought as exclusive in Japanese patients, cases of transient left ventricular apical ballooning from other countries have also been reported. The cause remains unknown. From January 1997 to December 2005, 25 patients presenting with signs and symptoms of acute myocardial infarction with normal coronary arteries were analyzed. In all, 10 patients fulfilled all the criteria for transient left ventricular apical ballooning. In all, 6 patients had chest pain and diaphoresis, 5 patients had ST segment elevation, 7 had T wave inversions, and 5 had QT prolongation; 6 patients had normal coronary arteries and 4 had insignificant stenosis. In all, 2 patients died of sepsis, whereas the rest recovered. This is the first series in Taiwanese patients. Our series showed male preponderance, and most patients recovered with supportive treatment. Without any delineating preangiographic feature differentiating it from acute myocardial infarction, any patient should be treated as a case of myocardial infarction until proven otherwise.
Intracoronary Autologous Bone Marrow−Derived Mononuclear Cell Transplantation Improves Coronary Collateral Vessel Formation and Recruitment Capacity in Patients With Ischemic Cardiomyopathy: A Combined Hemodynamic and Scintigraphic Approach
Authors: Tayyareci Yelda , Sezer Murat , Umman Berrin , Besisik Sevgi , Mudun Ayse , Sanli Yasemin , Oncul Aytac , Gurses Nuray , Sargin Deniz , Meric Mehmet , Nisanci Yilmaz
Published: April 2008

This study investigated the effects of intracoronary autologous bone marrow−derived mononuclear cell (BMC) transplantation on coronary microcirculation. Fifteen patients with ischemic cardiomyopathy were treated by intracoronary infusion of BMCs via the patent infarct-related artery. The thermodilution-derived coronary flow reserve, index of microvascular resistance, pressure-derived collateral flow index, and coronary wedge pressure were measured at baseline and at 6 months. Successive balloon inflations during BMC transplantation were performed to observe the recruitment in pressure-derived collateral flow index and coronary wedge pressure, and the percentage changes between baseline and 6 months were calculated. The mean (SD) coronary flow reserve increased from 1.3 (0.4) to 2.1 (0.5), and the mean (SD) index of microvascular resistance decreased from 44.9 (24.4) to 21.2 (14.1) ( P = .001 for both). The mean (SD) improvement in pressure-derived collateral flow index (from 0.14 [0.05] to 0.22 [0.08]) was also statistically significant ( P = .001). Similarly, the percentage improvements in pressure-derived collateral flow index and coronary wedge pressure were statistically significant ( P = .01 for both). The percentage improvement in perfusion assessed by single-photon emission computed tomography strongly correlated with the percentage changes in pressure-derived collateral flow index ( r = 0.88, P = .001) and coronary wedge pressure ( r = 0.69, P = .01). These results demonstrate for the first time (to our knowledge) that intracoronary autologous BMC transplantation improves coronary collateral vessel formation and recruitment capacity in human subjects.
Treatment of End-Stage “Trash Feet” With the End-Diastolic Pneumatic Boot
Authors: Filip John R. , Dillon Richard S.
Published: April 2008

This study reassessed the clinical effect of Circulator Boot (CB) therapy in patients with cholesterol embolization syndrome (CES) of the lower extremities. The medical records were reviewed of 27 patients consecutively referred to the Bryn Mawr Wound Care and Vascular Center with CES who had not responded to previous therapies. All patients with CES referred from January 1, 1997, to September 19, 2005, were followed up and included in the study. The alternate therapy offered for most patients at the time of referral was limb amputation. The median age of the patients was 65 years (age range, 46-84 years) at the time of diagnosis. Healing of CES was observed after a median interval of 11 months (range, 3-32 months) following the initiation of CB therapy. The total number of legs treated was 41. Of 41 legs, 33 (81%) were totally healed, 6 (15%) improved, and 2 (5%) were amputated. After an initial period of improvement, one patient died a month later of causes unrelated to CES or CB therapy. Another patient improved and discontinued treatment before he was totally healed. Cholesterol embolization syndrome is seen predominantly in patients following cardiac or vascular procedures but may occur spontaneously. The CB seems to be the only effective noninvasive therapy for CES. Early initiation of therapy is essential to minimize tissue loss and patient discomfort.
Exposure to Passive Smoking: A Test to Predict Endothelial Dysfunction and Atherosclerotic Lesions
Authors: Leone Aurelio , Balbarini Alberto
Published: April 2008

Acute exposure to environmental tobacco smoke (ETS) is considered to adversely influence atherogenesis. The aim of this article was to assess whether brachial ultrasonography in subjects with endothelial dysfunction after ETS exposure is associated with atherosclerotic lesions. Never smoker healthy volunteers (n = 18) and subjects with a previous myocardial infarction (MI; n = 10) were studied. Healthy volunteers were 12 men (66%) and 6 women (34%) with a mean age of 34 ± 9 years. Post-MI subjects were men with a mean age of 53.8 ± 4.8 years. After assessing endothelial function (by brachial ultrasonography) at rest, study subjects underwent brachial ultrasonography twice: in a smoke-free environment and then in the same environment polluted by cigarette combustion (35 ppm carbon monoxide concentration). Carboxyhemoglobin concentration was measured before and after ETS exposure. Baseline brachial-artery diameter, diameter during reactive hyperemia, and diameter after sublingual nitroglycerin (GTN) administration (endothelium-independent vasodilator) were measured at rest and in both smoke-free and smoking environments. Each study subject acted as their own control. No comparison was made between the two groups. A strong correlation between ETS exposure and endothelial dysfunction was observed in both groups. Post-MI subjects also showed endothelium-independent vasodilation worsening, which is usually due to arterial wall alterations. After ETS exposure, mean flow-mediated vasodilation after GTN was significantly ( P < .01) reduced only in post-MI subjects ( P < .01). Carboxyhemoglobin concentration increased in both groups ( P < .01). ETS exposure may be an effective test to identify endothelial dysfunction and arterial wall alterations by using brachial ultrasonography.
Speaking `Truth' to All Forms of Power
Authors: Habib Adam
Published: April 2008

The political and socioeconomic transformations across the globe in the last two decades make it necessary for public sociologists to bring their collective accumulated knowledge and methodological skills to an engagement with subalterns on the political strategy appropriate to this historical epoch. They must recognize that subaltern groups have insights into their subjugation, and solutions to transcend it. Public sociologists must deploy their skills in an inclusive way to engage the issue of political strategy: how to subvert power in favour of the agendas of subaltern groups.
Strong and Weak Intervention
Authors: Shen Yuan
Published: April 2008

The most important mission of sociology is perhaps to push forward the production of society. Sociologists should not only in its theory, but also in its practice, help resist the pressure from the state and the market, on the one hand, and assist society to emerge and grow, on the other. In facing the problem of the production of society, sociologists must strive for a transition from a sociology of structure to a sociology of action. Faced with a society in which development is unbalanced, we might divide sociological intervention into two types: strong and weak strategies. By incorporating the notions of `public sociology' and `liberation sociology', we have gone beyond Touraine's school in several aspects. Our most important task from now on is to combine social practice and social knowledge effectively.
`Make Way for Professional Sociology!'
Authors: Zdravomyslova Elena
Published: April 2008

This article presents the context of the current debate on the status of sociology in Russia, maps the controversy between professional and public sociology and locates the public sociology agenda in the context of a fight for professional sociology using the case of sociological education. To test the thesis of sociological internationalism, it is necessary to take into account local contexts, especially three aspects: the political opportunities for the public sociology manifesto; the situation with respect to civil society (as `a natural location of sociology'); and the level of institutionalization of sociology. All three contexts frame the cultural translation of the public sociology manifesto to the Russian sociological scene.
Public Sociology and Social Engagement
Authors: Braga Ruy , Gemignani Garcia Sylvia , e Silva Leonardo Mello
Published: April 2008

The debate on public sociology is spreading in Brazil, a country potentially responsive to Burawoy's proposals for two reasons: as one of the most unequal countries on the planet, Brazil offers much historical material for reflexive and socially engaged sociology to bring to the non-academic public; and Brazil has a critical and militant sociology that strongly interacts with public sociology. This article provides a `different' reading, through the lens of public sociology of the intellectual and political course of two representatives of this critical and militant sociology: Florestan Fernandes and Francisco de Oliveira.