bluuebunny/crossref_metadata_2025 huggingface dataset:
One-Photon and Two-Photon Pump-Probe Spectroscopy of Photoactive Yellow Protein
Authors: Lyngnes O. , Gibbs H. M. , Li C. F. , Devanathan S. B. , Meyer T. E. , Tollin G. , Cusanovich M. A.
Published: October 2003

We present the results of nonlinear optical pump-probe experiments on photoactive yellow protein (PYP). We are able to completely bleach the 446 nm absorption peak of PYP by one-photon excitation using a cw argon laser. We calculate the corresponding index change and find it to be similar to that of bacteriorhodopsin. We also determine an upper limit to the two photon absorption cross-section of PYP by looking for bleaching of the 446 nm absorption peak under irradiation by femtosecond pulses at 820–910 nm. No TPA signal is observed.
Nonlinear Susceptibilities in a Three-Level Atomic System
Authors: Ansari Nadeem A. , Sammut Rowland A.
Published: October 2003

We have studied the effect of the propagation of two strong fields of different frequencies on the nonlinear susceptibility in a medium composed of identical stationary three-level atoms in V-configuration. In particular, we show that each field influences the steady-state susceptibility, absorption and refractive-index change experienced by the other field. At large field strengths of one field, the second field experiences less absorption and an enhanced refractive index change.
Numerical Studies of Signal Amplification in a BaTiO3:Ce Crystal with an Applied Electric Field
Authors: Xie Ping , Dai Jian-Hua , Wang Peng-Ye , Zhang Hong-Jun
Published: October 2003

The gain and the spatial fidelity of signal amplification in photorefractive BaTiO 3: Ce , with considerations of the effect of the externally applied electric field and the fanning effect (or noise), are numerically studied using a three-dimensional analysis. Although the gain of the signal can be enhanced with the applied field, its spatial fidelity is greatly reduced, especially at a small angle between the two propagation directions of the pump and signal beams. The fanning effect reduces the spatial fidelity, and the smaller the input signal to pump intensity ratio is, the smaller the fidelity becomes. At large magnitudes of the applied field, the applied field plays a critical role in the reduction of the fidelity of the signal and the fanning effect on the fidelity is negligible.
Resonant Nonlinear Optical Studies on Porphyrin Derivatives
Authors: Kandasamy K. , Puntambekar P. N. , Singh Bhanu P. , Shetty Shankar J. , Srivastava T. S.
Published: October 2003

The nonlinear optical properties of three porphyrin derivatives (T3,4 BCEMPP, T4 CEMPP and TPP) doped in boric acid glass were probed using the Z-scan technique at different argon-ion laser wavelengths. The nonlinear transmission characteristics of T3,4 BCEMPP and T4 CEMPP exhibit saturable absorption at 457.9 nm and 476.5 nm while these are dominated by excited state absorption at 488.0 nm. However, in the case of TPP, the excited state absorption dominates the nonlinear characteristics except at 457.9 nm. The experimental observations are explained by using the four-level saturable absorber model. Saturation intensity, excited state absorption cross-section, light-induced changes in the absorption and the refractive index along with its sign were determined at these argon-ion laser wavelengths. Furthermore, optical limiting characteristics of these samples were studied. The observed limiting action is consistent with the Z-scan studies.
Laser-Excited One-Atom Source of Electrons
Authors: Letokhov V. S. , Sekatskii S. K.
Published: October 2003

A finite number of color centers in the region of sharp crystal needle's tip has been recently observed by laser resonance photoelectron projection microscopy technique. Hereby we present a new result in the field: only one single color center was observed on the tip region of lithium fluoride and calcium fluoride needles. Due to the high fluorescence yield of these color centers such needles can be treated as one-atom light sources, and perspectives of their application in Scanning One-Atom Fluorescence Resonance Energy Transfer Microscopy are briefly discussed.
Renormalization Group in Mathematical Physics and Some Problems of Laser Optics
Authors: Kovalev Vladimir F. , Shirkov Dmitrii V.
Published: October 2003

An original approach to constructing special type symmetries for boundary value problems, RENORMGROUP SYMMETRIES, is reviewed here. It is applied to a system of geometric optics equations. New solutions to the laser beam self-focusing problem are presented.
Chirped Simultons and Raman Solitons in Three-Level Media
Authors: Andreev A. V.
Published: October 2003

The new self-similar solutions to the problem of bichromatic field interaction with medium of three-level atoms or molecules have been found. The solutions are explicit and hence very helpful to discover the new properties of soliton-like pulses discovered in different experiments.
From Filamentation in Condensed Media to Filamentation in Gases
Authors: Kosareva O. G. , Kandidov V. P. , Brodeur A. , Chin S. L.
Published: October 2003

We demonstrated how the moving focus model developed for condensed media should be modified for the explanation of experiments on filamentation of high-power femtosecond laser pulses in air. This modification is based on the consideration of gas ionization in high-intensity laser field. Numerical simulations based on this modified model allow for the explanation not only of filamentation itself but also the accompanying phenomena such as refocusing and conical emission.
Inertial Confinement Fusion Program at Lawrence Livermore National Laboratory: The National Ignition Facility, Inertial Fusion Energy, 100–1000 TW Lasers, and the Fast Igniter Concept
Authors: Howard Lowdermilk W.
Published: October 2003

The ultimate goal of worldwide research in inertial confinement fusion (ICF) is to develop fusion as an inexhaustible, economic, environmentally safe source of electric power. Following nearly thirty years of laboratory and underground fusion experiments, the next step toward this goal is to demonstrate ignition and propagating burn of fusion fuel in the laboratory. The National Ignition Facility (NIF) Project is being constructed at Lawrence Livermore National Laboratory (LLNL) for just this purpose. NIF will use advanced Nd-glass laser technology to deliver 1.8 MJ of 0.35 μm laser light in a shaped pulse, several nanoseconds in duration, achieving a peak power of 500 TW. A national community of U.S. laboratories is participating in this project, now in its final design phase. France and the United Kingdom are collaborating on development of required technology under bilateral agreements with the US. This paper presents key aspects of the laser design, and descriptions of principal laser and optical components. Follow-on development of lasers to meet the demands of an inertial fusion energy (IFE) power plant is reviewed.

In parallel with the NIF Project and IFE developments, work is proceeding on ultrashort pulse lasers with peak power in the range of 100–1000 TW. A beamline on the Nova laser at LLNL recently delivered nearly 600 J of 1 μm light in a 0.5 ps duration pulse, for a peak power in excess of a petawatt (1015 W). This beamline, with advanced adaptive optics, will be capable of focused intensities in excess of 1021 W/cm2. Its primary purpose will be to test technological and scientific aspects of an alternate ignition concept, called the "Fast Igniter", that has the potential to produce higher fusion gain than conventional ICF.
Quasi-Phasematched Nonlinear Interactions and Devices
Authors: Byer Robert L.
Published: October 2003

The field of nonlinear optics began nearly simultaneously in the United States and in Russia in 1962. The early years of discovery led to an understanding of nonlinearity in materials, phasematching, and nonlinear device performance. In the second decade of the 1970s, tunable parametric oscillators driven by high-peak-power Q-switched lasers made the transition to tools useful for spectroscopy and remote sensing. In the late 1980s engineered nonlinear materials were introduced with the successful implementation of quasi-phasematching by periodic inversion of ferroelectric domains in lithium niobate. Lithographic processing techniques enabled the fabrication of quasi-phasematched nonlinear "chips" using electric field poling of lithium niobate at the wafer scale.
The Value Drivers of US Internet Retailers
Authors: Yang Dong-Hoon , Kwon Youngsun , Rho Jae Jeung , Ha Mikyoung
Published: October 2003

This study empirically explores the role of web traffic in explaining the stock prices of e-tailers. In particular, we hypothesize that the actual buy rate is a key value driver of Internet retailers because it represents the direct performance of these firms in the electronic market place. Our empirical analysis indicates that the buy rate is strongly related to the market value of e-tailers in a positive way after controlling for the roles of such financial valuation measures as net income, revenue, sales and marketing expenses, research and development costs, and book value.
An Application of Threshold Cointegration to Taiwan Stock Index Futures and Spot Markets
Authors: Lin Ching-Chung , Chen Shen-Yuan , Hwang Dar-Yeh
Published: October 2003

This paper examines the arbitrage opportunity existing between Taiwan stock index futures and spot markets with the consideration of transaction costs. Index-futures arbitrageurs only enter into the market if the deviation from the equilibrium relationship is sufficiently large to compensate for transaction costs, as well as risk and price premiums. Employing the 5-minute intraday data of Taiwan index futures contracts, this paper uses the threshold cointegration model to estimate the upper and lower thresholds within which arbitrage is not profitable and, hence, the mispricing errors do not adjust back to equilibrium in the central regime. Combining these thresholds with an error correction model (ECM), empirical results show that there exists bi-directional Granger–causality relationship between index futures and spot markets. However, once the long-run cointegrated equilibrium does not hold, re-establishment of the equilibrium situation mostly depends on price adjustment in the futures market.
Fuzzy System and CMAC Network with B-Spline Membership/Basis Functions can Approximate A Smooth Function and its Derivatives
Authors: Wang Shitong , Lu Hongjun
Published: October 2003

In control and other modeling applications, fuzzy system with B-spline membership functions and CMAC neural network with B-spline basis functions are sometimes desired to approximate not only the assigned smooth function as well as its derivatives. In this paper, by designing the fuzzy system and CMAC neural network with B-spline basis functions, we prove that such a fuzzy system and CMAC can universally approximate a smooth function and its derivatives, that is to say, for a given accuracy, we can approximate an arbitrary smooth function by such fuzzy system and CMAC that not only the function is approximated within this accuracy, but its derivatives are approximated as well. The conclusions here provide solid theoretical foundation for their extensive applications.
Hierarchical Rank Density Genetic Algorithm for Radial-Basis Function Neural Network Design
Authors: Yen Gary G. , Lu Haiming
Published: October 2003

In this paper, we propose a genetic algorithm based design procedure for a radial-basis function neural network. A Hierarchical Rank Density Genetic Algorithm (HRDGA) is used to evolve the neural network's topology and parameters simultaneously. Compared with traditional genetic algorithm based designs for neural networks, the hierarchical approach addresses several deficiencies highlighted in literature. In addition, the rank-density based fitness assignment technique is used to optimize the performance and topology of the evolved neural network to deal with the confliction between the training performance and network complexity. Instead of producing a single optimal solution, HRDGA provides a set of near-optimal neural networks to the designers so that they can have more flexibility for the final decision-making based on certain preferences. In terms of searching for a near-complete set of candidate networks with high performances, the networks designed by the proposed algorithm prove to be competitive, or even superior, to three other traditional radial-basis function networks for predicting Mackey–Glass chaotic time series.
Optimization of Production Systems Using Genetic Algorithms
Authors: Mustafa Wael
Published: October 2003

This paper presents a Genetic Algorithm for Production Systems Optimization (GAPSO). The GAPSO finds an ordering of Condition Elements (CEs) in the rules of a Production System (PS) that results in a (near) optimal PS with respect to execution time. Finding such an ordering can be difficult since there is often a large number of ways to order CEs in the rules of a PS. Additionally, existing heuristics to order CEs in many cases conflict with each other. The GAPSO is applicable to PSs in general and no assumptions are made about the matching algorithm or the interpreter that executes the PS. The results of applying the GAPSO to some example PSs are presented. In all examples, the GAPSO found an optimal ordering of CEs in a small number of iterations.
Distributed Neural Networks for Quality of Service Estimation in Communication Networks
Authors: Mahul Antoine , Aussem Alex
Published: October 2003

We study an original scheme based on distributed feedforward neural networks, aimed at modelling several queueing systems in cascade fed with bursty traffic. For each queueing system, a neural network is trained to anticipate the average number of waiting packets, the packet loss rate and the coefficient of variation of the packet inter-departure time, given the mean rate, the peak rate and the coefficient of variation of the packet inter-arrival time. The latter serves for the calculation of the coefficient of variation of the cell inter-arrival time of the aggregated traffic which is fed as input to the next neural network along the path. The potential of this method is successfully illustrated on several single server FIFO (First In, First Out) queues and on small queueing networks made up from a combination of queues in tandem and in parallel fed by a superposition of ideal sources. Our long-term goal is the design of preventive control strategy in a multiservice communication network.
An Extension of ε-Insensitive Hebbian Learning to Form a Non-Interfering Basis.
Authors: Corchado Emilio , Fyfe Colin
Published: October 2003

We review an extension of Hebbian learning which has been called ε-Insensitive Hebbian Learning (Fyfe and MacDonald, 2001) and derive lateral connections from a probability density function. We use these lateral connections to move outputs towards the mode of the pdf and use the resulting outputs to train the feedforward connections. We show that the resulting network is able to identify a single orientation of bars from a mixture of horizontal and vertical bars.
Fuzzy Moves Using Compensatory Granular Reasoning
Authors: Zhang Yan-Qing , Kandel Abraham
Published: October 2003

In this paper, compensatory granular reasoning methods are proposed based on fuzzy logic, neural networks, genetic algorithms, compensatory computing and granular computing. The compensatory operation can be reduced to the relevant general compensatory AND operations which replace the traditional AND operations in the compensatory granular reasoning. Different compensatory AND operations such as fuzzy compensatory AND, neural compensatory AND, genetic compensatory AND, linear compensatory AND, and exponential compensatory AND are defined. The compensatory granular reasoning methods can be used to make more reliable decisions. For example, the compensatory granular reasoning methods can make more fault-tolerant fuzzy moves in a fuzzy game if a player carefully chooses a reasonable compensatory operation. In the future, different compensatory granular reasoning methods will be used in different decision-making applications.
Exponentially dissipative nonlinear dynamical systems: a nonlinear extension of strict positive realness
Authors: Chellaboina VijaySekhar , Haddad Wassim M.
Published: October 2003

We extend the notion of dissipative dynamical systems to
formalize the concept of the nonlinear analog of strict positive
realness and strict bounded realness. In particular, using
exponentially weighted system storage functions with appropriate
exponentially weighted supply rates, we introduce the concept of
exponential dissipativity. The proposed results provide a
generalization of the strict positive real lemma and the strict
bounded real lemma to nonlinear systems. We also provide a nonlinear
analog to the classical passivity and small gain stability
theorems for state space nonlinear feedback systems. These
results are used to construct globally stabilizing static and
dynamic output feedback controllers for nonlinear passive systems
that minimize a nonlinear nonquadratic performance criterion.
Peristaltic motion of a Johnson‐Segalman fluid in a planar channel
Authors: Hayat T. , Wang Y. , Siddiqui A. M. , Hutter K.
Published: October 2003

This paper is devoted to the
study of the two‐dimensional flow of a Johnson‐Segalman fluid in
a planar channel having walls that are transversely displaced by
an infinite, harmonic travelling wave of large wavelength. Both
analytical and numerical solutions are presented. The analysis
for the analytical solution is carried
out for small Weissenberg
numbers. (A Weissenberg number is the ratio of the relaxation
time of the fluid to a characteristic time associated with the
flow.) Analytical solutions have been obtained for the stream
function from which the relations of the velocity and
the longitudinal pressure gradient have been derived. The
expression of the pressure rise over a wavelength has
also been determined. Numerical computations are performed and
compared to the perturbation analysis. Several limiting
situations with their implications can be examined from the
presented analysis.
CREDIT, DEBT, AND HONOR IN CASTILE, 1600-1650
Authors: Taylor Scott
Published: October 2003

Based largely on the findings of anthropologists of the Mediterranean in the twentieth century, the traditional understanding of honor in early modern Spain has been defined as a concern for chastity, for women, and a willingness to protect women's sexual purity and avenge affronts, for men. Criminal cases from Castile in the period 1600-1650 demonstrate that creditworthiness was also an important component of honor, both for men and for women. In these cases, early modern Castilians became involved in violent disputes over credit, invoking honor and the rituals of the duel to justify their positions and attack their opponents. Understanding the connection between credit, debt, and honor leads us to update the anthropological models that pre-modern European historians employ, on the one hand, and to a new appreciation for the way seventeenth-century Castilians understood their public reputations and identity, on the other.
UNEASY PEACE: THE PRACTICE OF THE STALLUNG RITUAL IN ZÜRICH, 1400-1525
Authors: Pohl Susanne
Published: October 2003

This article discusses the Stallung or "peace bidding" ritual in the imperial city of Zürich during the fifteenth and early sixteenth centuries. According to city law, every Zürcher had to ask quarrelling citizens to make peace, and the contestants were then obligated to end their fight. The discussion of Stallung in this article is informed by practice theory as developed by Pierre Bourdieu and Sherry Ortner. While habitus or structure constrains and produces the goals of social actors, those social actors also enact and transform structure. The meaning of the Stallung ritual was not stable, but subject to constant situational adjustment. The Stallung ritual may have prevented outbreaks of violence in many instances, yet the evidence demonstrates that the ritual was often absorbed into the ongoing dynamic of challenge and riposte that shaped contests over honor between male citizens.
BOURDIEU IN BED: THE SEDUCTION OF INNOCENTIA (ROME, 1570)
Authors: Cohen Thomas
Published: October 2003

Early modern tales of seduction and abandonment, and of legal proceedings to redress the moral and social balance, are not that rare. But this case, with its pathos and wry twists, is rich and interesting, both for the abundant detail, and for the picture it offers of female agency; both the girl and her governess are active players in the courtship and the marriage negotiations. The tale also illustrates uses of literacy, central to both the seduction and the legal prosecution, where the suitor's home-grown poetry, in the girl's mouth, helps crack his resistance to a match. The paper argues that a reading through Bourdieu's notion of "sense of play" helps explicate the blend of impulse and calculation that led the players through the several intrigues: the seduction, the marriage negotiations, the shambling betrayal, the court-brokered settlement. The essay contends that, when, as here, fields of play join awkwardly, ironies and odd twists abound. Such circumstances invite microhistories such as this, that explore the boundaries of routine behavior and the stresses that arise when scripts and roles collide.
WESTERN TRAVELERS, EASTERN ANTIQUITIES, AND THE IMAGE OF THE TURK IN EARLY MODERN EUROPE
Authors: Wunder Amanda
Published: October 2003

Educated elite Europeans who visited Constantinople on diplomatic, scholarly, and commercial enterprises in the sixteenth century shared a common culture of antiquarianism, and their passion for the antiquities of the East shaped their accounts of the Turk and Ottoman Constantinople. The traveling antiquarians Augier Ghislain de Busbecq, Pierre Gilles, Melchior Lorck, Pieter Coecke van Aelst, and Nicholas de Nicolay produced a diverse range of printed works based on their firsthand experiences in the Ottoman Empire, in which they used traditional Renaissance genres (such as the urban encomium, the city view, the historia painting, and the costume book) to depict the Turk either as the enemy of antiquities or, alternatively, as an eternal, exotic object like the relics of the past. While some antiquarian travelers, most notably Lorck, Coecke, and Nicolay, demonstrated the variety that existed amongst the Turks, the ultimate impact of sixteenth-century antiquarian accounts of the Ottoman Empire was to deepen the Western perception of Oriental difference.
WAR FINANCE AND ABSOLUTIST STATE DEVELOPMENT IN EARLY MODERN EUROPE: AN EXAMINATION OF FRENCH VENALITY IN THE SEVENTEENTH CENTURY
Authors: Potter Mark
Published: October 2003

The impact of warfare on absolutist state development in early modern Europe was more complicated than often thought by historians and theorists of the state. The competitive pressures of warfare did not always lead to linear political developments which would culminate in a centralized bureaucratic state. Instead, rulers' financial strategies along with the political effects of these strategies were conditioned by both structural and historical constraints. Political change in France over the course of the seventeenth century illustrates the impact of these two sets of constraints. Here, I trace in particular the changing property rights of office holding as a measure of political change shaped by war finance within these two sets of constraints.
ATLANTIC SUGAR AND ANTWERP'S TRADE WITH GERMANY IN THE SIXTEENTH CENTURY
Authors: Harreld Donald
Published: October 2003

Once the Portuguese opened new Atlantic trade routes and began producing sugar on their Atlantic islands, Antwerp succeeded Venice as Europe's principal sugar market. Large numbers of Italian and German sugar refiners established themselves in Antwerp by the middle of the sixteenth century. Merchants shipped the bulk of the Atlantic sugar to the German market towns, with Cologne being the most important destination during the first half of the sixteenth century. The demand for sugar in Germany increased as the practice of taking sugar spread east setting the stage for the sugar revolution of the seventeenth century.
EARLY MODERN STATE-BUILDING, THE SCANDINAVIAN MACHTSTAAT, AND THE SHORTCOMINGS OF ANGLO-SAXON SCHOLARSHIP
Authors: Frost Robert
Published: October 2003

This Review Article discusses recent work on the Scandinavian Machtstaat, taking a critical attitude towards recent Anglo-Saxon scholarship on the state and absolute monarchy in the early modern period.
Methods for a Randomized Trial of Weight-Supported Treadmill Training Versus Conventional Training for Walking During Inpatient Rehabilitation after Incomplete Traumatic Spinal Cord Injury
Authors: Dobkin Bruce H. , Apple David , Barbeau Hugues , Basso Michele , Behrman Andrea , Deforge Dan , Ditunno John , Dudley Gary , Elashoff Robert , Fugate Lisa , Harkema Susan , Saulino Michael , Scott Michael ,   Spinal Cord Injury Locomotor Trial (SCILT) Group
Published: October 2003

The authors describe the rationale and methodology for the first prospective, multicenter, randomized clinical trial (RCT) of a task-oriented walking intervention for subjects during early rehabilitation for an acute traumatic spinal cord injury (SCI). The experimental strategy, body weight-supported treadmill training (BWSTT), allows physical therapists to systematically train patients to walk on a treadmill at increasing speeds typical of community ambulation with increasing weight bearing. The therapists provide verbal and tactile cues to facilitate the kinematic, kinetic, and temporal features of walking. Subjects were randomly assigned to a conventional therapy program for mobility versus the same intensity and duration of a combination of BWSTT and over-ground locomotor retraining. Subjects had an incomplete SCI (American Spinal Injury Association grades B, C, and D) from C-4 to T-10 (upper motoneuron group) or from T-11 to L-3 (lower motoneuron group). Within 8 weeks of a SCI, 146 subjects were entered for 12 weeks of intervention. The 2 single-blinded primary outcome measures are the level of independence for ambulation and, for those who are able to walk, the maximal speed for walking 50 feet, tested 6 and 12 months after randomization. The trial's methodology offers a model for the feasibility of translating neuroscientific experiments into a RCT to develop evidence-based rehabilitation practices.
Methods for a Multisite Randomized Trial to Investigate the Effect of Constraint-Induced Movement Therapy in Improving Upper Extremity Function among Adults Recovering from a Cerebrovascular Stroke
Authors: Winstein Carolee J. , Miller J. Philip , Blanton Sarah , Taub Edward , Uswatte Gitendra , Morris David , Nichols Deborah , Wolf Steven
Published: October 2003

This article describes the study design, methodological considerations, and demographic characteristics of a phase III RCT to determine if 1) constraint-induced therapy (CI therapy) can be applied with therapeutic success 3 to 9 months after stroke across different sites, 2) gains that might occur persist over 2 years, 3) initial level of motor ability determines responsiveness to CI therapy, and 4) the treatment effect differs between those treated before 9 months and after 1 year. Six sites will screen and recruit poststroke survivors stratified on initial level of motor ability and after randomization allocate participants to immediate or delayed intervention. Primary outcomes include a laboratory-based measure of function (Wolf Motor Function Test [WMFT]) and a real-world participant-centered functional use measure (Motor Activity Log [MAL]). Secondary outcomes concern function, behavior, and compliance. This is the first multisite, single-blind RCT of a formal training intervention for upper extremity rehabilitation in subacute stroke in the United States.
Functional Gains During Acute Hospitalization for Stroke
Authors: Bohannon Richard W. , Ahlquist Martha , Lee Nora , Maljanian Rose
Published: October 2003

Objectives. 1) Confirm clinimetric suitability of 5 Functional Independence Measure TM (FIM) items for characterizing functional independence. 2) Describe functional changes and relationships between selected variables and functional independence at discharge and functional change. Methods. For 451 patients hospitalized for acute stroke, scores were recorded at admission and discharge for 5 FIM items (transfers, eating, walking, expression, and memory). The sum of the 5 FIM items and functional change between admission and discharge were calculated. Results. The FIM scores were internally consistent (alpha = .894 and .918) and reflected 1 factor. Functional independence increased (t = 17.46, P < .001) over a mean 5.5 days. Regression analysis showed the same variables (admission function, NIHSS score, length of stay, age, and total therapy units) to best predict discharge function (R 2 = .804) and function change (R 2 = .184). Conclusions. Together, 5 easily observed FIM items demonstrated that functional independence increased during hospitalization. Discharge function and functional change were predicted significantly (but weakly) by therapy units.
Fitness to Drive with Neurological Disabilities
Authors: Keller M. , Kesselring J. , Hiltbrunner B.
Published: October 2003

To restore the ability to drive is one aim of the rehabilitation of patients with neurological disabilities. In some instances, an evaluation is required to judge a patient's fitness to drive in today's traffic. Forty-three patients of the neurorehabilitation unit of the Valens Clinic were assessed by a standard traffic psychological test protocol and a control drive. In 88%, there was agreement between the judgments based on each procedure. Four patients had failed either the psychological tests or the control drive but not both. Six patients had failed the psychological test and the control drive. Two drove nevertheless, and three patients stopped driving. Nineteen of 32 patients cleared to drive were followed up. Eleven drove without accidents or traffic fines. The traffic psychological tests and control drive yield complementary information on the fitness to drive. However, the assessments need to be improved. New generations of interactive driving simulators may refine the fitness to drive evaluation and become useful tools in driving rehabilitation.
Effectiveness of Sensory and Motor Rehabilitation of the Upper Limb Following the Principles of Neuroplasticity: Patients Stable Poststroke
Authors: Byl Nancy , Roderick Jennifer , Mohamed Olfat , Hanny Monica , Kotler Josh , Smith Amy , Tang Molly , Abrams Gary
Published: October 2003

Based on the principles of neuroplasticity, the purpose of this crossover study was to determine if improvement in upper extremity (UE) function and independence could be achieved in patients 6 months to 7 years poststroke following an outpatient rehabilitation program (supervised 1.5 hours per week for 8 weeks reinforced with home gloving unaffected side and attended, graded, repetitive sensory and motor training activities). Twenty-one subjects (right or left hemiparesis; able to walk 100 feet with or without a cane; partially opened and closed the hand; partially elevated the shoulder and elbow against gravity) were randomly assigned to Group A (sensory training 4 weeks, motor training 4 weeks) or Group B (motor training 4 weeks, sensory training 4 weeks). Greater than 20% (P <0.01) improvement was measured in functional independence and UE function (fine motor, sensory discrimination, and musculoskeletal performance). Gains were hemispheric and training specific and maintained over 3 months. This study provides evidence documenting significant improvement in function in the late poststroke recovery period following 12 hours of supervised learning based sensory motor training.
Testing the Revised Stress-Response Sequence Model in Pediatric Oncology Nurses
Authors: Hinds Pamela S. , Srivastava Deo Kumar , Randall Elizabeth A. , Green Amanda , Stanford Dianne , Pinlac Renee , Tong Xin , Tyc Vida , Davis Jorri , Taylor Kimberly
Published: October 2003

In a series of five studies, the research team tested components of the stress-response sequence (SRS) model to determine the relationships between role-related stress, coping, and work consequences in pediatric oncology nurses. The combined outcomes indicated that the model required revision to include role-related meaning; this study tested the revised model. Eighty-nine pediatric oncology nurses from one setting completed seven study questionnaires. The new scale, the Role-Related Meaning Scale, created for this study achieved a Cronbach's alpha of .83 and significant positive correlations with other study variables. Descriptive findings indicate that the nurses are moderately to highly stressed; use coping strategies frequently and effectively; have high levels of job satisfaction, organizational commitment, and group cohesion; and exhibit low intent to leave the organization. Importantly, the stress and coping components of the model did not predict role consequences. These outcomes suggest that the revised SRS model does not adequately predict role consequences in pediatric oncology nurses. A new model is proposed.
Parental Involvement in Restoring the Health of a Child with Cancer in Hong Kong
Authors: Martinson Ida M. , Yee Kuan Hau
Published: October 2003

The parents of 93 children with cancer in Hong Kong participated in a research study to identify concepts related to the category of restoring health in their child with cancer. These concepts included providing adequate nutrition such as attempting to increase the child's appetite, the preparation of soups, providing food supplements, and restricting the intake of certain foods; using alternative therapy to supplement the Western medicine, using tonics to strengthen the body, using Chinese medicine to regulate the body functions, using Chinese herbs to prevent metastasis or reoccurrence, as well as providing another chance of a cure when Western medicine was not effective; and preventing infections by reducing exposure to crowded places, having a clean home environment, using a face mask to protect the child from infections, and screening visitors.
Gradients of Neurotrophins, Ion Channels, and Tuning in the Cochlea
Authors: Davis Robin L.
Published: October 2003

The mammalian cochlea is exquisitely designed to decompose complex sounds into their component frequencies, accounting in part for the superb auditory discrimination displayed by many species. To perform this task, numerous mechanical and electrical specializations are graded along the length of the cochlea that create a tonotopic map in which sounds of different frequencies produce maximal responses at different cochlear locations. Graded mechanical features include structural changes in the vibratory basilar membrane, on which the hair cell sensory receptors sit, to systematic changes in receptor cell size and stereociliary length. Furthermore, there is growing evidence that frequency specificity does not stop at mechanical and morphological elements in the cochlea, but also extends to the intrinsic electrical profile of the hair cell sensory receptors and the first neural element in the auditory system—the spiral ganglion neurons.
Prefrontal DA Transmission at D1 Receptors and the Pathology of Schizophrenia
Authors: Abi-Dargham Anissa , Moore Holly
Published: October 2003

The current view on the dopamine (DA) hypothesis of schizophrenia postulates a cortical/subcortical imbalance: subcortical mesolimbic DA projections might be hyperactive, resulting in hyperstimulation of D2receptors and positive symptoms, whereas mesocortical DA projections to the prefrontal cortex might be hypoactive, resulting in hypostimulation of D1 receptors, negative symptoms, and cognitive impairment. Although the subcortical abnormalities are relatively well established now, the evidence for cortical hypodopaminergia is just emerging. This article will review current evidence for prefrontal hypodopaminergia in schizophrenia, with special emphasis on positron emission tomography (PET) studies measuring cortical D1 receptors in schizophrenia. The presentation of the clinical data will be introduced by a brief overview of the function of prefrontal DA systems, both at the cellular and cognitive level. The impact of antipsychotic drugs on prefrontal DA function will also be reviewed. We will conclude with the formulation of several models of altered prefrontal DA transmission at D1 receptors in schizophrenia.
Axon Guidance by Growth Cones and Branches: Common Cytoskeletal and Signaling Mechanisms
Authors: Dent Erik W. , Tang Fangjun , Kalil Katherine
Published: October 2003

Growing axons are guided to appropriate targets by responses of their motile growth cones to environmental cues. Interstitial axon branching is also an important form of axon guidance in the mammalian CNS. Visualization of growing axons in cortical slices and in dissociated cortical cultures showed that growth cone pausing behaviors demarcate sites of future axon branching. Studies of vertebrate and invertebrate growth cones suggest common mechanisms that regulate growth cone behaviors and axon branching. These include reorganization of the actin and microtubule cytoskeleton, dynamic interactions between microtubules and actin filaments, effects of axon guidance molecules, actions of actin regulatory proteins, and dynamic changes in intracellular calcium signaling. Future challenges will be to extend high-resolution imaging of single neurons to studies of intracellular events in the intact nervous system and to apply knowledge of developmental mechanisms to the promotion of axon sprouting after injury in the adult CNS.
Complex Receptive Fields in Primary Visual Cortex
Authors: Martinez Luis M. , Alonso Jose-Manuel
Published: October 2003

In the early 1960s, Hubel and Wiesel reported the first physiological description of cells in cat primary visual cortex. They distinguished two main cell types: simple cells and complex cells. Based on their distinct response properties, they suggested that the two cell types could represent two consecutive stages in receptive-field construction. Since the 1960s, new experimental and computational evidence provided serious alternatives to this hierarchical model. Parallel models put forward the idea that both simple and complex receptive fields could be built in parallel by direct geniculate inputs. Recurrent models suggested that simple cells and complex cells may not be different cell types after all. To this day, a consensus among hierarchical, parallel, and recurrent models has been difficult to attain; however, the circuitry used by all models is becoming increasingly similar. The authors review theoretical and experimental evidence for each line of models emphasizing their strengths and weaknesses.
P2X Receptor-Mediated Modulation of Sensory Transmission to the Spinal Cord Dorsal Horn
Authors: Gu Jianguo G.
Published: October 2003

In the somatosensory system, P2X receptors are expressed on both peripheral and central terminals of primary afferent neurons. Those expressed on peripheral terminals are activated in response to both nociceptive and innocuous stimuli, whereas those at central terminals (“central terminal P2X receptors”) play an important role in modulating sensory transmission to the spinal cord dorsal horn. The author reviews recent studies on the central terminal P2X receptors. It is proposed that central terminal P2X receptors, once activated, may be involved in both central sensitization and initiation of pain. Thus, these receptors may repesent a promising target for therapeutic management of pathological pain.
Functional Imaging and Pain: Behavior, Perception, and Modulation
Authors: Porro Carlo A.
Published: October 2003

Time-dependent increases of local metabolic or blood flow rates have been described in spinal cord and brain during acute and chronic pain states in experimental animals, in parallel with changes of different behavioral endpoints of pain and hyperalgesia. In healthy human volunteers, pain intensity-related hemo-dynamic changes have been identified in a widespread, bilateral brain system including parietal, insular, cingulate, and frontal cortical areas, as well as thalamus, amygdala, and midbrain. Specific patterns of activity may characterize hyperalgesic states and some chronic pain conditions. Forebrain nociceptive systems are under inhibitory control by endogenous opioids and can be affected by acute administration of [.proportional]-opioid receptor agonists. Anticipation of pain may in itself induce changes in brain nociceptive networks. Moreover, pain-related cortical activity can be modulated by hypnotic suggestions, focusing or diverting attention, and placebo. These findings begin to disclose the spatio-temporal dynamics of brain networks underlying pain perception and modulation.
Compartmentation of Glutamine, Glutamate, and GABA Metabolism in Neurons and Astrocytes: Functional Implications
Authors: Waagepetersen Helle S. , Sonnewald Ursula , Schousboe Arne
Published: October 2003

The classical concept regarding compartmentation of brain metabolism pertinent to the two neurotrans-mitter amino acids, glutamate and GABA (γ-aminobutyrate), operates with different pools of glutamate and glutamine in different cell types, that is, pools that have different sizes and turnover rates. As a result of more sophisticated technology (e.g., nuclear magnetic resonance spectroscopy and mass spectrometry used in relation to cultured neurons and astrocytes), a more complex scenario is emerging. Hence, both neurons and astrocytes exhibit a compartmentalized metabolism that very likely relates to individual cells containing mitochondrial populations having different metabolic roles. Models for this in neurons and astro-cytes, respectively, are presented. The functional implications of this for the homeostatic mechanisms regulating the levels of neurotransmitter glutamate and GABA are discussed in relation to development of therapeutic strategies for neurological disorders in which these transmitters are believed to play important roles.
Why do Seizures Cause Loss of Consciousness?
Authors: Blumenfeld Hal , Taylor Jacob
Published: October 2003

Model systems are needed for the scientific investigation of consciousness. A good model system should include variable states of consciousness, allowing the relationship between brain activity and consciousness to be investigated. Examples include sleep, anesthesia, focal brain lesions, development, evolution, and epilepsy. One advantage of epilepsy is that changes are dynamic and rapidly reversible. The authors review previous investigations of impaired consciousness in epilepsy and describe new findings that may shed light on both normal and abnormal mechanisms of consciousness. Abnormal increased activity in fronto-parietal association cortex and related subcortical structures is associated with loss of consciousness in generalized seizures. Abnormal decreased activity in these same networks may cause loss of conscious-ness in complex partial seizures. Thus, abnormally increased or decreased activity in the same networks can cause loss of consciousness. Information flow during normal conscious processing may require a dynamic balance between these two extremes of excitation and inhibition.
Twitches Versus Movements: A Story of Motor Cortex
Authors: Taylor Charlotte S. R. , Gross Charles G.
Published: October 2003

Modern study of the neurophysiology of the cerebral cortex began with Fritsch and Hitzig's discovery that electrical stimulation of the cortex produces movements. The importance of this discovery was threefold: it was the first demonstration of cortex devoted to motor function, the first indication that the cortex was electrically excitable, and the first evidence of a topographically organized representation in the brain. Fritsch and Hitzig's basic findings were soon replicated by Ferrier, but there were differences between the two studies in both method and interpretation. These different approaches have continued to reverberate in research on the function of motor cortex from the late 19th century to the present day.
Glial Cells Generate Neurons—Master Control within CNS Regions: Developmental Perspectives on Neural Stem Cells
Authors: Götz Magdalena
Published: October 2003

A common problem in neural stem cell research is the poor generation of neuronal or oligodendroglial descendants. The author takes a developmental perspective to propose solutions to this problem. After a general overview of the recent progress in developmental neurobiology, she highlights the necessity of the sequential and hierarchical specification of CNS precursors toward the generation of specific cell types, for example, neurons. In the developing as well as the adult CNS, multipotent stem cells do not directly generate neurons but give rise to precursors that are specified and restricted toward the generation of neurons. Some molecular determinants of this fate restriction have been identified during recent years and reveal that progression via this fate-restricted state is a necessary step of neurogenesis. These discoveries also demonstrate that neuronal fate specification is inseparably linked at the molecular level to regionalization of the developing CNS. These fate determinants and their specific action in distinct region-specific con-texts are essential to direct the progeny of stem cells more efficiently toward the generation of the desired cell types. Recent data are discussed that demonstrate the common identity of precursors and stem cells in the developing and adult nervous system as radial glia, astroglia, or non-myelinating glia. A novel line-age model is proposed that incorporates these new views and explains why the default pathway of stem cells is astroglia. These new insights into the cellular and molecular mechanisms of neurogenesis help to design novel approaches for reconstitutive therapy of neurodegenerative diseases.
‘Deep learning’
Authors: Rosie Anthony
Published: October 2003

The advantages of deep learning over surface learning are well known. This article suggests that students can achieve deep learning effectively by using a dialectical approach. The Web provides a means of developing resources that will enable this goal to be achieved in a variety of ways. For part-time students lack of access and lack of tutor involvement in their work are common problems. The discussion in this article illustrates how a group of part-time postgraduate students achieved such goals in a social theory course. The article shows how dialectical thinking can operate and suggests ways by which larger groups of undergraduate students can benefit from such developments.