bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diffusion tensor fiber tracking of human brain connectivity: aquisition methods, reliability analysis and biological results
Authors: Lori N. F. , Akbudak E. , Shimony J. S. , Cull T. S. , Snyder A. Z. , Guillory R. K. , Conturo T. E. 
Published: December 2002

AbstractWe present a description, biological results and a reliability analysis for the method of diffusion tensor tracking (DTT) of white matter fiber pathways. In DTT, diffusion‐tensor MRI (DT‐MRI) data are collected and processed to visualize the line trajectories of fiber bundles within white matter (WM) pathways of living humans. A detailed description of the data acquisition is given. Technical aspects and experimental results are illustrated for the geniculo‐calcarine tract with broad projections to visual cortex, occipital and parietal U‐fibers, and the temporo‐calcarine ventral pathway. To better understand sources of error and to optimize the method, accuracy and precision were analyzed by computer simulations. In the simulations, noisy DT‐MRI data were computed that would be obtained for a WM pathway having a helical trajectory passing through gray matter. The error vector between the real and ideal track was computed, and random errors accumulated with the square root of track length consistent with a random‐walk process. Random error was most dependent on signal‐to‐noise ratio, followed by number of averages, pathway anisotropy and voxel size, in decreasing order. Systematic error only occurred for a few conditions, and was most dependent on the stepping algorithm, anisotropy of the surrounding tissue, and non‐equal voxel dimensions. Both random and systematic errors were typically below the voxel dimension. Other effects such as track rebound and track recovery also depended on experimental conditions. The methods, biological results and error analysis herein may improve the understanding and optimization of DTT for use in various applications in neuroscience and medicine. Copyright © 2002 John Wiley & Sons, Ltd.
A framework based on spin glass models for the inference of anatomical connectivity from diffusion‐weighted MR data – a technical review
Authors: Mangin J.‐F. , Poupon C. , Cointepas Y. , Rivière D. , Papadopoulos‐Orfanos D. , Clark C. A. , Régis J. , Le Bihan D. 
Published: December 2002

AbstractA family of methods aiming at the reconstruction of a putative fascicle map from any diffusion‐weighted dataset is proposed. This fascicle map is defined as a trade‐off between local information on voxel microstructure provided by diffusion data and a priori information on the low curvature of plausible fascicles. The optimal fascicle map is the minimum energy configuration of a simulated spin glass in which each spin represents a fascicle piece. This spin glass is embedded into a simulated magnetic external field that tends to align the spins along the more probable fiber orientations according to diffusion models. A model of spin interactions related to the curvature of the underlying fascicles introduces a low bending potential constraint. Hence, the optimal configuration is a trade‐off between these two kind of forces acting on the spins. Experimental results are presented for the simplest spin glass model made up of compass needles located in the center of each voxel of a tensor based acquisition. Copyright © 2002 John Wiley & Sons, Ltd.
Fiber tracking: principles and strategies – a technical review
Authors: Mori Susumu , van Zijl Peter C. M. 
Published: December 2002

AbstractThe state of the art of reconstruction of the axonal tracts in the central nervous system (CNS) using diffusion tensor imaging (DTI) is reviewed. This relatively new technique has generated much enthusiasm and high expectations because it presently is the only approach available to non‐invasively study the three‐dimensional architecture of white matter tracts. While there is no doubt that DTI fiber tracking is providing exciting new opportunities to study CNS anatomy, it is very important to understand its limitations. In this review we therefore assess the basic principles and the assumptions that need to be made for each step of the study, including both data acquisition and the elaborate fiber reconstruction algorithms. Special attention is paid to situations where complications may arise, and possible solutions are reviewed. Validation issues and potential future directions and improvements are also discussed. Copyright © 2002 John Wiley & Sons, Ltd.
The basis of anisotropic water diffusion in the nervous system – a technical review
Authors: Beaulieu Christian 
Published: December 2002

AbstractAnisotropic water diffusion in neural fibres such as nerve, white matter in spinal cord, or white matter in brain forms the basis for the utilization of diffusion tensor imaging (DTI) to track fibre pathways. The fact that water diffusion is sensitive to the underlying tissue microstructure provides a unique method of assessing the orientation and integrity of these neural fibres, which may be useful in assessing a number of neurological disorders. The purpose of this review is to characterize the relationship of nuclear magnetic resonance measurements of water diffusion and its anisotropy (i.e. directional dependence) with the underlying microstructure of neural fibres. The emphasis of the review will be on model neurological systems both in vitro and in vivo. A systematic discussion of the possible sources of anisotropy and their evaluation will be presented followed by an overview of various studies of restricted diffusion and compartmentation as they relate to anisotropy. Pertinent pathological models, developmental studies and theoretical analyses provide further insight into the basis of anisotropic diffusion and its potential utility in the nervous system. Copyright © 2002 John Wiley & Sons, Ltd.
Diffusion‐tensor MRI: theory, experimental design and data analysis – a technical review
Authors: Basser Peter J. , Jones Derek K. 
Published: December 2002

AbstractThis article treats the theoretical underpinnings of diffusion‐tensor magnetic resonance imaging (DT‐MRI), as well as experimental design and data analysis issues. We review the mathematical model underlying DT‐MRI, discuss the quantitative parameters that are derived from the measured effective diffusion tensor, and describe artifacts thet arise in typical DT‐MRI acquisitions. We also discuss difficulties in identifying appropriate models to describe water diffusion in heterogeneous tissues, as well as in interpreting experimental data obtained in such issues. Finally, we describe new statistical methods that have been developed to analyse DT‐MRI data, and their potential uses in clinical and multi‐site studies. Copyright © 2002 John Wiley & Sons, Ltd.
Diffusion tensor imaging of normal and injured developing human brain ‐ a technical review
Authors: Neil J. , Miller J. , Mukherjee P. , Hüppi P. S. 
Published: December 2002

AbstractThe application of diffusion tensor imaging (DTI) to the evaluation of developing brain remains an area of active investigation. This review focuses on the changes in DTI parameters which accompany both brain maturation and injury. The two primary pieces of information available from DTI studies—water apparent diffusion coefficient and diffusion anisotropy measures—change dramatically during development, reflecting underlying changes in tissue water content and cytoarchitecture. DTI parameters also change in response to brain injury. In this context, not only does DTI offer the possibility of detecting injury earlier than conventional imaging methods, but also appears more sensitive to disruption of white matter than any other imaging method. DTI offers unique insight into brain injury and maturation, and does so in a fashion that can be readily applied in a clinical setting. Copyright ­© 2002 John Wiley & Sons, Ltd.
Diffusion tensor imaging and aging – a review
Authors: Moseley Michael 
Published: December 2002

AbstractDiffusion‐tensor imaging (DTI) non‐invasively provides maps of microscopic structural information of oriented tissue in vivo, which is finding utility in studies of the aging population. In contrast to the white matter maturation process, investigators have observed significant declines in the white matter ordering in normal as well as in abnormal aging. These studies suggest that water proton non‐random, anisotropic diffusion measured by DTI is highly sensitive to otherwise subtle disease processes not normally seen with conventional MRI tissue contrast mechanisms. Copyright © 2002 John Wiley & Sons, Ltd.
Applications of diffusion‐weighted and diffusion tensor MRI to white matter diseases – a review
Authors: Horsfield Mark A. , Jones Derek K. 
Published: December 2002

AbstractThis paper reviews the current applications of diffusion‐weighted and diffusion tensor MRI in diseases of the brain white matter. The contribution that diffusion‐weighted imaging has made to our understanding of white matter diseases is critically appraised. The quantitative nature of diffusion MRI is one of its major attractions; however, this is offset by the more advanced hardware required to collect diffusion‐weighted images reliably, and the more complex processing to produce quantitative parametric diffusion images. With the now common availability of scanners equipped to perform echo‐planar imaging, the acquisition of diffusion tensor images is sure to become more widespread and routine. Copyright © 2002 John Wiley & Sons, Ltd.
Diffusion tensor imaging in spinal cord: methods and applications – a review
Authors: Clark Chris A. , Werring David J. 
Published: December 2002

AbstractThe spinal cord is a clinically eloquent site within the central nervous system, containing important sensorimotor tracts confined within a small cross‐sectional area. Damage to the spinal cord may be caused by a wide range of pathologies, and can result in profound functional disability. Characterization of the structural integrity of the spinal cord can be assessed using diffusion tensor imaging methods. Development and application of this technique may improve our understanding of the nature and evolution of structural damage in spinal cord disease. Possible developments include improved detection of ischaemic lesions, clarification of the relationship between clinical disability and structural damage to the cord and monitoring of anti‐inflammatory or neuroprotective therapies. In this review current technical aspects, clinical applications and the suggested future development of spinal cord diffusion imaging are discussed. Copyright © 2002 John Wiley & Sons, Ltd.
Neuropsychiatric applications of DTI – a review
Authors: Lim K. O. , Helpern J. A. 
Published: December 2002

AbstractPsychiatric disorders are common throughout the world and are a leading cause of disability. There is a growing appreciation of the importance of connectivity to brain function. Disruption of this connectivity can result in brain dysfunction manifested in impaired cognitive functioning and the development of clinical symptoms. White matter forms the basis of anatomical connectivity. Diffusion tensor imaging (DTI) is a useful tool for examining and quantifying white matter microstructure. Clinical research studies in alcoholism, HIV‐1 infection, geriatric depression and schizophrenia using DTI have revealed abnormalities in white matter microstructure. The use of complementary imaging methods may be helpful in further characterizing these abnormalities. Other psychiatric disorders may also have white matter involvement amenable to study with DTI. Advances in acquisition and analysis methods will be necessary to further advance work in this field. The study of animal models and postmortem tissue may be helpful in elucidating the neurobiological underpinnings of abnormalities observed with DTI. Copyright © 2002 John Wiley & Sons, Ltd.
From the diffusion coefficient to the diffusion tensor
Authors: Le Bihan Denis , van Zijl Peter 
Published: December 2002

AbstractWith diffusion tensor MRI one has access to the organization in space of tissue microstructural components. This outstanding potential adds, however, another layer of complexity to the diffusion MRI data acquisition and analysis processes. Over the last few years many articles have been published dealing with those matters. This special issue is thus timely to provide readers with the synthesis and the overall viewpoints from leading contributors to the field. Copyright © 2002 John Wiley & Sons, Ltd.
Metal fingers on grain boundaries in multicrystalline silicon solar cells
Authors: Ebner Rita , Radike Michael , Schlosser Viktor , Summhammer Johann 
Published: December 2002

AbstractWe have developed a method of applying a net‐like finger grid to the front of multicrystalline (mc) silicon solar cells, which lies mainly on the grain boundaries (grain‐boundary‐oriented‐finger GBOF grid). This net has no busbars. It is drawn by a plotter, using screen printing paste dispensed through a fine tube. The power output of cells contacted in this manner has been tested in a statistical study of pairs and triplets of cells of size 100 × 100 mm2 (Bayer) and 103 × 103 mm2 (Eurosolare). In the pairs study, pairs of neighbouring wafers of the original ingot were processed into solar cells. One wafer received a GBOF grid, the other got the same grid rotated by 90°, and so had little coverage of grain boundaries. In the study of triplets the third wafer of each triplet was equipped with a standard H‐pattern of the same shading as the GBOF grid. In the pairs study, we find that under approximately standard conditions there is an 89% chance that the GBOF grid increases power output over cells with an identical, but 90° rotated, grid, the most probable increase being 2.6%. The triplets study shows that there is an 87% chance that the GBOF grid increases power output over cells with the standard H‐pattern, the most probable increase being 2.5%. Copyright © 2002 John Wiley & Sons, Ltd.
Comparative study of maximum power point tracking algorithms
Authors: Hohm D. P. , Ropp M. E. 
Published: December 2002

AbstractMaximum power point trackers (MPPTs) play an important role in photovoltaic (PV) power systems because they maximize the power output from a PV system for a given set of conditions, and therefore maximize the array efficiency. Thus, an MPPT can minimize the overall system cost. MPPTs find and maintain operation at the maximum power point, using an MPPT algorithm. Many such algorithms have been proposed. However, one particular algorithm, the perturb‐and‐observe (P&O) method, claimed by many in the literature to be inferior to others, continues to be by far the most widely used method in commercial PV MPPTs. Part of the reason for this is that the published comparisons between methods do not include an experimental comparison between multiple algorithms with all algorithms optimized and a standardized MPPT hardware. This paper provides such a comparison. MPPT algorithm performance is quantified through the MPPT efficiency. In this work, results are obtained for three optimized algorithms, using a microprocessor‐controlled MPPT operating from a PV array and also a PV array simulator. It is found that the P&O method, when properly optimized, can have MPPT efficiencies well in excess of 97%, and is highly competitive against other MPPT algorithms. Copyright © 2002 John Wiley & Sons, Ltd.
Analysis of light scattering in amorphous Si:H solar cells by a one‐dimensional semi‐coherent optical model
Authors: Krč Janez , Smole Franc , Topič Marko 
Published: December 2002

AbstractA one‐dimensional semi‐coherent optical model for thin‐film solar cells is presented. The optical circumstances at flat interfaces are addressed and the situation at rough interfaces in the model is described for the case of direct (coherent) incident and scattered (incoherent) incident light. After the model has been experimentally verified, analysis of the light scattering process in hydrogenated amorphous silicon (a‐Si:H) p–i–n solar cells is carried out. The influence of the interface root‐mean‐square roughness and the effect of different angular distribution functions of diffused light on quantum efficiency and short‐circuit current are investigated by the optical model. Copyright © 2002 John Wiley & Sons, Ltd.
Evaluation of the Algerian photovoltaic market potential
Authors: Labed S. , Lorenzo E. 
Published: December 2002

AbstractThe Algerian energy sector will certainly face a crisis this century with the gradual diminution of oil and gas reserves estimated at 4.2 billion Toe (Tons of oil equivalent), which can last for only a few decades at today's production levels. In the meantime the population and its energy needs will have doubled. This situation is complicated by the fact that the energy sector is Algeria's major source of revenue, and finances the national economy at a level of 66%. Many decision‐makers now agree that time has come to implement a new energy policy, based on energy diversification, and to set up new mechanisms. The Algerian energy sector is still dominated by hydrocarbons, and has promoted a major effort to reach a mean national electrification rate of 96%. Nevertheless, the remaining zones are very isolated and widespread. The conventional electrification solutions or grid extensions are no longer economically viable. The recourse to renewable energies in general and PV solar energy in particular has become a reality. This source represents a good alternative for 85% of Algerian territory, which is composed of arid and semi‐arid zones, characterized by low population density and limited energy needs. These regions represent a strategic alternative in order to reverse the population migration and to encourage a new migration to the south, since northern Algeria is less and less welcoming (high population density, unemployment, shrinkage of agricultural land, inflation). In this paper we try to evaluate the potential of the Algerian PV market in order to inform decision‐makers and future investors. To this end, and after identifying the PV solar energy segments, we attempt to estimate them under different scenarios. Copyright © 2002 John Wiley & Sons, Ltd.
TiO2DLAR coatings for planar silicon solar cells
Authors: Richards B. S. , Rowlands S. F. , Honsberg C. B. , Cotter J. E. 
Published: December 2002

AbstractIn this paper we demonstrate that a double‐layer anti‐reflection (DLAR) coating can be fabricated using only titanium dioxide (TiO2). Two TiO2thin films were deposited onto planar silicon wafers using a simple atmospheric pressure chemical vapour deposition (APCVD) system under different deposition conditions. Weighted average reflectances of 6.5% (measured) and 7.0% (calculated) were achieved for TiO2DLAR coatings in air and under glass, respectively. An increase in the short‐circuit current density of ΔJsc = 2.5 mA/cm2can be expected for an optimised TiO2DLAR coating when compared with a commercial TiO2single‐layer anti‐reflection coating. Copyright © 2003 John Wiley & Sons, Ltd.
Solar cell efficiency tables (version 21)
Authors: Green Martin A. , Emery Keith , King David L. , Igari Sanekazu , Warta Wilhelm 
Published: December 2002

AbstractConsolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined and new entries since July, 2002 are reviewed. Copyright © 2003 John Wiley & Sons, Ltd.
17.6% efficient tricrystalline silicon solar cells with spatially uniform texture
Authors: Schmiga Christian , Schmidt Jan , Metz Axel , Endrös Arthur , Hezel Rudolf 
Published: December 2002

AbstractUp to now solar cells fabricated on tricrystalline Czochralski‐grown silicon (tri‐Si) have shown relatively low short‐circuit current densities of about 31–33 mA/cm2because the three {110}‐oriented grains cannot effectively be textured by commonly used anisotropic etching solutions. In this work, we have optimised a novel chemical texturing step for tri‐Si and integrated it successfully into our solar cell process. Metal/insulator/semiconductor‐contacted phosphorus‐diffused n+p junction silicon solar cells with a silicon‐dioxide‐passivated rear surface and evaporated aluminium contacts were manufactured, featuring a spatially uniform surface texture over all three grains on both cell sides. Despite the simple processing sequence and cell structure, an independently confirmed record efficiency of 17.6% has been achieved. This excellent efficiency is mainly due to an increased short‐circuit current density of 37 mA/cm2obtained by substantially reduced reflection and enhanced light trapping. Copyright © 2003 John Wiley & Sons, Ltd.
Synthesis, spectroscopic, theoretical and structural studies of new trihalomethyl sulphenyl derivatives of 5‐methyl‐1,3,4‐thiadiazole‐2‐thiol
Authors: Coyanis E. M. , Boese R. , Autino J. C. , Romano R. M. , Della Védova C. O. 
Published: December 2002

AbstractAlthough 2‐mercapto‐5‐methyl‐1,3,4‐thiadiazole (mmtd) is commonly thought of as a thione tautomer, electrophilic substitution occurs on the thiol moiety. The tautomeric ability of mmtd allows a substitution reaction to take place at the sulphur; this is shown by reaction with Cl3−nF
nCSCI compounds (n = 0–2) to give perhalomethyldithio thiadiazole derivatives. Three novel perhalomethylsulphenyl compounds, which exhibit a wide range of potentially interesting applications, were obtained and characterized by x‐ray crystal diffraction, mass spectrometry, IR and Raman spectroscopy and density functional theory calculations. Copyright © 2002 John Wiley & Sons, Ltd.
Information theory description of synthetic strategies. A new similarity index
Authors: Barone R. , Petitjean M. , Baralotto C. , Piras P. , Chanon M. 
Published: December 2002

AbstractInformation theory was used to analyse and compare organic syntheses leading to the targets, daucene, longifolene and estrone. This paper expands the work of Bertz, who analysed syntheses from the complexity of molecular structures. Herein, a more complete model involving similarity was evaluated. We published previously a study in this direction limited to a skeletal level. In order to improve on this initial approach, we attempted to analyse some syntheses not only limited to the skeleton by including different definitions of similarity. Copyright © 2002 John Wiley & Sons, Ltd.
Thermal transformation of monoterpenes within thionin‐supported zeolite Na‐Y. Acid‐catalyzed or electron transfer‐induced?
Authors: Stratakis Manolis , Stavroulakis Manolis , Sofikiti Nikoletta 
Published: December 2002

AbstractSeveral monoterpenes (monocyclic, bicyclic or acyclic) isomerize and finally transform to p‐cymene in the dark upon loading within thionin‐supported zeolite Na‐Y. The same reactions occur in Na‐Y dried under the same conditions as thionin/Na‐Y. It is postulated that the thermal treatment of Na‐Y generates ‘electron holes’ (probably acidic sites). The transformation of monoterpenes occurs more likely via an electron transfer‐induced reaction subordinated to the occurrence of the acidic sites. The radical cation of the more thermodynamically stable monoterpene, α‐terpinene, eventually dehydrogenates to p‐cymene. For comparison, the same reactions were performed within methyl viologen‐supported Na‐Y. Copyright © 2002 John Wiley & Sons, Ltd.
Cyclic hydrogen bond arrays: vibrational spectroscopic study of aminomethyl‐substituted resorcinarene‐based cavitands and their clathrates with THF
Authors: Dormann Jörg , Ruoff Andreas , Schatz Jürgen , Middel Oskar , Verboom Willem , Reinhoudt David N. 
Published: December 2002

AbstractMono‐ and tetrakis(aminomethyl)‐substituted resorcinarene‐based cavitands 1 and 2 and their clathrates 1
2·THF and 2·(THF)2 were investigated by FTIR spectroscopy and thermogravimetric analysis. Both hosts form stable clathrates with THF both in solution and in the solid state. Major intra‐ and intermolecular interactions could be identified and located by the use of vibrational spectroscopy. In all cases, dynamic cyclic intramolecular hydrogen bonds between the amino groups and neighbouring ether bridges are observable. Copyright © 2002 John Wiley & Sons, Ltd.