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Detailed Study (detailed + study)
Kinds of Detailed Study Selected AbstractsNumerical Treatment of Seismic Accelerograms and of Inelastic Seismic Structural Responses Using Harmonic WaveletsCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 4 2007Pol D. Spanos The effectiveness of the harmonic wavelets for capturing the temporal evolution of the frequency content of strong ground motions is demonstrated. In this regard, a detailed study of important earthquake accelerograms is undertaken and smooth joint time-frequency spectra are provided for two near-field and two far-field records; inherent in this analysis is the concept of the mean instantaneous frequency. Furthermore, as a paradigm of usefulness for aseismic structural purposes, a similar analysis is conducted for the response of a 20-story steel frame benchmark building considering one of the four accelerograms scaled by appropriate factors as the excitation to simulate undamaged and severely damaged conditions for the structure. The resulting joint time-frequency representation of the response time histories captures the influence of nonlinearity on the variation of the effective natural frequencies of a structural system during the evolution of a seismic event. In this context, the potential of the harmonic wavelet transform as a detection tool for global structural damage is explored in conjunction with the concept of monitoring the mean instantaneous frequency of records of critical structural responses. [source] An analysis of VI Architecture primitives in support of parallel and distributed communicationCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 1 2002Andrew Begel Abstract We present the results of a detailed study of the Virtual Interface (VI) paradigm as a communication foundation for a distributed computing environment. Using Active Messages and the Split-C global memory model, we analyze the inherent costs of using VI primitives to implement these high-level communication abstractions. We demonstrate a minimum mapping cost (i.e. the host processing required to map one abstraction to a lower abstraction) of 5.4 ,s for both Active Messages and Split-C using four-way 550 MHz Pentium III SMPs and the Myrinet network. We break down this cost to the use of individual VI primitives in supporting flow control, buffer management and event processing and identify the completion queue as the source of the highest overhead. Bulk transfer performance plateaus at 44 Mbytes/s for both implementations are due to the addition of fragmentation requirements. Based on this analysis, we present the implications for the VI successor, Infiniband. Copyright © 2002 John Wiley & Sons, Ltd. [source] Refining Biodiversity Conservation PrioritiesCONSERVATION BIOLOGY, Issue 6 2005GRANT M. HARRIS Bosque del Atlántico; percepción remota; priorización; SIG; sitios prioritarios para la conservación Abstract:,Although there is widespread agreement about conservation priorities at large scales (i.e., biodiversity hotspots), their boundaries remain too coarse for setting practical conservation goals. Refining hotspot conservation means identifying specific locations (individual habitat patches) of realistic size and scale for managers to protect and politicians to support. Because hotspots have lost most of their original habitat, species endemic to them rely on what remains. The issue now becomes identifying where this habitat is and these species are. We accomplished this by using straightforward remote sensing and GIS techniques, identifying specific locations in Brazil's Atlantic Forest hotspot important for bird conservation. Our method requires a regional map of current forest cover, so we explored six popular products for mapping and quantifying forest: MODIS continuous fields and a MODIS land cover (preclassified products), AVHRR, SPOT VGT, MODIS (satellite images), and a GeoCover Landsat thematic mapper mosaic (jpg). We compared subsets of these forest covers against a forest map based on a Landsat enhanced thematic mapper. The SPOT VGT forest cover predicted forest area and location well, so we combined it with elevation data to refine coarse distribution maps for forest endemic birds. Stacking these species distribution maps enabled identification of the subregion richest in threatened birds,the lowland forests of Rio de Janeiro State. We highlighted eight priority fragments, focusing on one with finer resolved imagery for detailed study. This method allows prioritization of areas for conservation from a region >1 million km2 to forest fragments of tens of square kilometers. To set priorities for biodiversity conservation, coarse biological information is sufficient. Hence, our method is attractive for tropical and biologically rich locations, where species location information is sparse. Resumen:,Aunque hay acuerdo generalizado sobre las prioridades de conservación a escalas mayores (i. e., sitios prioritarios para la conservación de la biodiversidad), los límites son muy gruesos como para definir metas de conservación prácticas. La refinación de la conservación de sitios prioritarios significa la identificación de localidades específicas (parches de hábitat individuales) de tamańo y escala realistas para ser protegidos por gestores y apoyados por políticos. Debido a que los sitios prioritarios han perdido la mayor parte de su hábitat original, las especies endémicas dependen del que permanece. Ahora el asunto es identificar donde están el hábitat y las especies. Logramos lo anterior mediante técnicas directas de percepción remota y de SIG para identificar localidades específicas importantes para la conservación de aves en el sitio prioritario Bosque del Atlántico en Brasil. Nuestro método requiere de un mapa regional de la cobertura forestal actual, así que exploramos seis productos populares para el mapeo y cuantificación de bosques: campos continuos MODIS y una cobertura de suelo MODIS (productos preclasificados), AVHRR, SPOT VGT, MODIS (imágenes de satélite) y un mosaico GeoCover Landsat thematic mapper (jpg). Comparamos subconjuntos de estas coberturas forestales con las de un mapa basado en un Landsat enhanced thematic mapper. La cobertura forestal SPOT VGT predijo bien la superficie y localización del bosque, así que lo combinamos con datos de altitud para refinar los mapas generales de distribución de aves endémicas de bosques. La sobreposición de estos mapas de distribución permitió la identificación de la subregión más rica en aves amenazadas,los bosques en bajíos del Estado de Río de Janeiro. Dimos relevancia a ocho fragmentos prioritarios, con atención en uno con imágenes de resolución fina para estudio en detalle. Este método permite la priorización de áreas para conservación de fragmentos de decenas de kilómetros cuadrados en una región >1 millón km2. La información biológica general es suficiente para definir prioridades de conservación de la biodiversidad. Por lo tanto, nuestro método es atractivo para localidades tropicales y biológicamente ricas, para las que la información sobre la ocalización de las especies es escasa. [source] Tropomyosin expression and dynamics in developing avian embryonic musclesCYTOSKELETON, Issue 5 2008Jushuo Wang Abstract The expression of striated muscle proteins occurs early in the developing embryo in the somites and forming heart. A major component of the assembling myofibrils is the actin-binding protein tropomyosin. In vertebrates, there are four genes for tropomyosin (TM), each of which can be alternatively spliced. TPM1 can generate at least 10 different isoforms including the striated muscle-specific TPM1, and TPM1,. We have undertaken a detailed study of the expression of various TM isoforms in 2-day-old (stage HH 10,12; 33 h) heart and somites, the progenitor of future skeletal muscles. Both TPM1, and TPM1, are expressed transiently in embryonic heart while TPM1, is expressed in somites. Both RT-PCR and in situ hybridization data suggest that TPM1, is expressed in embryonic heart whereas TPM1, is expressed in embryonic heart, and also in the branchial arch region of somites, and in the somites. Photobleaching studies of Yellow Fluorescent Protein-TPM1, and -TPM1, expressed in cultured avian cardiomyocytes revealed that the dynamics of the two probes was the same in both premyofibrils and in mature myofibrils. This was in sharp contrast to skeletal muscle cells in which the fluorescent proteins were more dynamic in premyofibrils. We speculate that the differences in the two muscles is due to the appearance of nebulin in the skeletal myocytes premyofibrils transform into mature myofibrils. Cell Motil. Cytoskeleton 2008. © 2008 Wiley-Liss, Inc. [source] Differential growth and multicellular villi direct proepicardial translocation to the developing mouse heartDEVELOPMENTAL DYNAMICS, Issue 1 2008Laurel S. Rodgers Abstract In the mammalian system the proepicardium (PE) arises from mesothelium of the septum transversum before translocation to the heart where it forms the epicardium and progenitor cells of the coronary vessels. Despite its importance, the process in which PE cells translocate to the myocardium in mammals is not well defined. The current paradigm states that cellular cysts of PE float across the pericardial space and contact the outer surface of the myocardium. This mechanism does not provide a satisfactory explanation for the directionality or localization of PE migration. To better define PE migration, we performed a detailed study of mouse PE development. We provide thorough documentation that redefines the size of the PE migratory field and the mechanism of migration. Our new model incorporates differential growth and direct contact between multicellular PE villi and the myocardium as mechanisms in formation of the epicardium. Developmental Dynamics 237:145,152, 2008. © 2007 Wiley-Liss, Inc. [source] Stroke in the developing brain and intractable epilepsy: effect of timing on hippocampal sclerosisDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 9 2003Waney Squier FRCP FRC Path A detailed study was made of the pathology of specimens removed by hemispherectomy for the treatment of intractable epilepsy in children with unilateral middle cerebral artery stroke. Neuropathological criteria were used to differentiate strokes that occurred in early intrauterine development (before 28 weeks gestational age) from those occurring in the last trimester, at birth, or after birth: 19 children had early strokes and 21 late. There was no difference in seizure history or occurrence of febrile convulsions in these two groups. Hippocampal tissue was available in 20 patients; pathology in the hippocampus, remote from the infarcted area, showed a marked difference between early-onset and late-onset groups. Hippocampal sclerosis was uncommon in children with early-onset strokes but developed in most of the children whose strokes were of later origin. However, hippocampal sclerosis was more closely related to a clinical history of a late initial precipitating insult irrespective of infarct timing. These findings demonstrate the changing vulnerability of the developing brain and show that hippocampal pathology is more closely related to the timing of an insult than seizure history or the occurrence of febrile convulsions. [source] A diffusible signal attracts olfactory sensory axons toward their target in the developing brain of the mothDEVELOPMENTAL NEUROBIOLOGY, Issue 1 2003Lynne A. Oland Abstract The signals that olfactory receptor axons use to navigate to their target in the CNS are still not well understood. In the moth Manduca sexta, the primary olfactory pathway develops postembryonically, and the receptor axons navigate from an experimentally accessible sensory epithelium to the brain along a pathway long enough for detailed study of regions in which axon behavior changes. The current experiments ask whether diffusible factors contribute to receptor axon guidance. Explants were made from the antennal receptor epithelium and co-cultured in a collagen gel matrix with slices of various regions of the brain. Receptor axons were attracted toward the central regions of the brain, including the protocerebrum and antennal lobe. Receptor axons growing into a slice of the most proximal region of the antennal nerve, where axon sorting normally occurs, showed no directional preference. When the antennal lobe was included in the slice, the receptor axons entering the sorting region grew directly toward the antennal lobe. Taken together with the previous in vivo experiments, the current results suggest that an attractive diffusible factor can serve as one cue to direct misrouted olfactory receptor axons toward the medial regions of the brain, where local cues guide them to the antennal lobe. They also suggest that under normal circumstances, in which the receptor axons follow a pre-existing pupal nerve to the antennal lobe, the diffusible factor emanating from the lobe acts in parallel and at short range to maintain the fidelity of the path into the antennal lobe. © 2003 Wiley Periodicals, Inc. J Neurobiol 56: 24,40, 2003 [source] Spermatogenesis in Boccardiella hamata (Polychaeta: Spionidae) from the Sea of Japan: sperm formation mechanisms as characteristics for future taxonomic revisionACTA ZOOLOGICA, Issue 4 2010Arkadiy A. Reunov Abstract Reunov, A.A., Yurchenko, O.V., Alexandrova, Y.N. and Radashevsky, V.I. 2009. Spermatogenesis in Boccardiella hamata (Polychaeta: Spionidae) from the Sea of Japan: sperm formation mechanisms as characteristics for future taxonomic revision. ,Acta Zoologica (Stockholm) 91: 477,456. To characterize novel features that will be useful in the discussion and validation of the spionid polychaete Boccardiella hamata from the Sea of Japan, the successive stages of spermatogenesis were described and illustrated. Spermatogonia, spermatocytes and early spermatids are aflagellar cells that develop synchronously in clusters united by a cytophore. At the middle spermatid stage, the clusters undergo disintegration and spermatids produce flagella and float separately in coelomic fluid as they transform into sperm. Spermatozoa are filiform. The ring-shaped storage platelets are located along the anterior nuclear area. The nucleus is cupped by a conical acrosome. A nuclear plate is present between the acrosome and nucleus. The nucleus is a cylinder with the implantation fossa throughout its length and with the anterior part of the flagellum inside the fossa. There is only one centriole, serving as a basal body of the flagellum, situated in close vicinity of the acrosomal area. A collar of four mitochondria is located under the nuclear base. The ultrastructure of B. hamata spermatozoa from the Sea of Japan appears to be close to that of B. hamata from Florida described by Rice (Microscopic Anatomy of Invertebrates, Wiley-Liss, Inc., New York, 1992), suggesting species identity of the samples from the two regions. However, more detailed study of Florida's B. hamata sperm is required for a reliable conclusion concerning the similarity of these two polychaetes. In addition to sperm structure, features such as the cytophore-assigned pattern of spermatogenic cell development, the synchronous pattern of cell divisions, the non-flagellate early spermatogenic stages, and the vesicle amalgamation that drives meiotic cell cytokinesis and spermatid diorthosis will likely be useful in future testing of the validity of B. hamata and sibling species throughout the world. [source] Osteoderm morphology in recent and fossil euphractine xenarthransACTA ZOOLOGICA, Issue 4 2009C. M. Krmpotic Abstract The presence of osteoderms within the integument, forming a carapace, is one of the most distinctive features of armadillos with the external morphology of these elements forming the basis of most systematic schemes. This is especially true for fossil taxa, where these elements are most frequent in the palaeontological record. A detailed study of osteoderms from the cephalic shield and different regions of the dorsal armour of Chaetophractus villosus (Euphractinae, Xenarthra) was made and compared to those of the extant genus Dasypus (Dasypodinae, Xenarthra), and the extinct genus ,Eutatus. Three distinct histological zones were recognized: outer and inner zones are thin, formed by regular compact bone, the middle zone is thicker, with large cavities that contain mainly adipose tissue, hair follicles, and sweat and sebaceous glands. The internal structure of ,Eutatus (also a member of Euphractinae) osteoderms is close to that of C. villosus, consistent with the notion that these taxa are phylogenetically closely related. In contrast, Dasypus shows marked differences. Dasypus shows hair follicles associated with both gland types (sweat and sebaceous) and connected to foramina on the external surface. Although not observed in adult C. villosus, it has been documented during embryonic development, only to atrophy later in ontogeny. Furthermore, the presence of red bone marrow is rare in C. villosus, but widespread in Dasypus novemcinctus osteoderms. These results suggest an early split of both subfamilies and support the hypothesis that the Euphractinae are more derived than the Dasypodinae. [source] On the tail of Errivaspis and the condition of the caudal fin in heterostracansACTA ZOOLOGICA, Issue 2009Elga Mark-Kurik Abstract Articulated caudal fins of heterostracans are preserved in very rare cases. Their morphology and internal structure are completely unknown for the majority of species. One of the few preserved caudal fins belongs to the Early Devonian pteraspidid Errivaspis waynensis from the Welsh Borderland, UK. There are two different reconstructions of the tail: (1) strongly asymmetric, with a considerably longer ventral lobe, and a rather concave posterior margin (e.g. White 1935); and (2) almost symmetrical with an only slightly longer ventral lobe and a small notch in the posterior margin (e.g. Blieck 1984). A new reconstruction of the Errivaspis caudal fin, based on a detailed study of White's specimens is presented here. The ventral lobe is longer than the dorsal one but not so much as in White's reconstruction, and the notch in the posterior margin of the fin is less deep. The comparatively massive ventral lobe and ,en echelon' arrangement of three digitations, supporting the fin web and branching off from this lobe, indicate the hypocercal condition of the asymmetrical tail. The same internal structure is present in other heterostracans with nearly symmetrical caudal fins (e.g. Doryaspis, Nahanniaspis, Dinaspidella and Athenaegis) where all, or most, of the intermediate digitations branch off from the ventral lobe. [source] An "Omics" view of drug developmentDRUG DEVELOPMENT RESEARCH, Issue 2 2004Russ B. Altman Abstract The pharmaceutical industry cannot be blamed for having a love/hate relationship with the fields of pharmacogenetics and pharmacogenomics. At the same time that pharmacogenetics and pharmacogenomics promise to save pipeline drugs by identifying subsets of the population for which they work best, they also threaten to increase the complexity of new drug applications, fragment markets, and create uncertainty for prescribers who simply do not understand or have time to master "personalized medicine." Most importantly, the logical case for genetics-specific drug selection and dosing is much more mature than the practical list of drugs for which outcomes are demonstrably improved. Understandably, pharmaceutical developers and regulators have been careful in creating strategies for using genetics in drug development, and only recently has the FDA begun to establish preliminary rules for pharmacogenetic testing. A growing public academic effort in pharmacogenetics and pharmacogenomics is helping flesh out the basic science underpinnings of the field, and this should combine with extensive efforts of industry to create a solid foundation for future use of genetics in drug development. Two grand challenges to accelerate our capabilities include the characterization of all human genes involved in the basic pharmacokinetics of drugs, and the detailed study of the genes and pathways associated with G-protein-coupled receptors and how they are affected by genetic variation. Drug Dev. Res. 62:81,85, 2004. © 2004 Wiley-Liss, Inc. [source] Flow energy and channel adjustments in rills developed in loamy sand and sandy loam soilsEARTH SURFACE PROCESSES AND LANDFORMS, Issue 1 2009Jovan R. Stefanovic Abstract The storms usually associated with rill development in nature are seldom prolonged, so development is often interrupted by interstorm disturbances, e.g. weathering or tillage. In laboratory simulated rainfall experiments, active rill development can be prolonged, and under these conditions typically passes through a period of intense incision, channel extension and bifurcation before reaching quasi-stable conditions in which little form change occurs. This paper presents laboratory experiments with coarse textured soils under simulated rainfall which show how channel adjustment processes contribute to the evolution of quasi-stability. Newly incised rills were stabilized for detailed study of links between rill configuration and flow energy. On a loamy sand, adjustment towards equilibrium occurred due to channel widening and meandering, whereas on a sandy loam, mobile knickpoints and chutes, pulsations in flow width and flow depth and changes in stream power and sediment discharge occurred as the channel adjusted towards equilibrium. The tendency of rill systems towards quasi-stability is shown by changes in stream power values which show short-lived minima. Differences in energy dissipation in stabilized rills indicate that minimization of energy dissipation was reached locally between knickpoints and at the downstream ends of rills. In the absence of energy gradients in knickpoints and chutes, stabilized rill sections tended toward equilibrium by establishing uniform energy expenditure. The study confirmed that energy dissipation increased with flow aspect ratio. In stabilized rills, flow acceleration reduced energy dissipation on the loamy sand but not on the sandy loam. On both soils flow deceleration tended to increase energy dissipation. Understanding how rill systems evolve towards stability is essential in order to predict how interruptions between storms may affect long-term rill dynamics. This is essential if event-based physical models are to become effective in predicting sediment transport on rilled hillslopes under changing weather and climatic conditions. Copyright © 2008 John Wiley and Sons, Ltd. [source] Prevalence of various radiographic manifestations of osteochondrosis and their correlations between and within joints in Dutch Warmblood horsesEQUINE VETERINARY JOURNAL, Issue 1 2009E. M. Van Grevenhof Summary Reasons for performing study: Osteochondrosis (OC) is the most important orthopaedic developmental disorder in horses and may manifest in several different forms. No detailed study on the prevalence and/or interrelation of these forms is available, even though these data are a prerequisite for conclusive genetic studies. Objectives: To assess the prevalence of the various manifestations of OC as detected radiographically and to evaluate possible relationships between their occurrence within the same joint and between different joints. Methods: The FP (femoropatellar), TC (tarsocrural) and MCP/MTP (metacarpophalangeal/metatarsophalangeal) joints of 811 yearlings selected randomly, descending from 32 representative stallions, were radiographed and scored for the presence and grade of osteochondrotic lesions. Results were compared at the sire, animal, joint and predilection site levels. Results: In the FP joint, the percentage of animals showing normal joint contours in all sites was 60.7%. For the TC joint and the combined MCP/MTP joints, these figures were 68.6 and 64.6%, respectively. For all joints combined, the percentage dropped to 30.5%. Sedation improved detection of OC lesions in the FP joint. There was a high correlation between the right and left joints. The correlation between flattened bone contours and fragments was considerably less. Conclusions: Scoring on a detailed scale is necessary to achieve good insight into the prevalence of OC. Observations on the right and left joints can be combined in further analyses, whereas flattened bone contours and fragments should be evaluated as statistically different disorders. Potential relevance: This study provides insight into the prevalences of various manifestations of OC and their relationships, within and between joints. These results form the basis for detailed quantitative and/or molecular genetic studies that should lead to the establishment of breeding indices and/or genetic marker sets for OC. [source] Highly avid, oligoclonal, early-differentiated antigen-specific CD8+ T cells in chronic HIV-2 infectionEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 7 2010Aleksandra Leligdowicz Abstract HIV-1-specific CD8+ T cells are present in most HIV-1-infected people and play an important role in controlling viral replication, but the characteristics of an effective HIV-specific T-cell response are largely unknown. The majority of HIV-2-infected people behave as long-term non-progressors while those who progress to AIDS do so in a manner indistinguishable from HIV-1. A detailed study of HIV-2 infection may identify protective immune responses. Robust gag p26-specific T-cell responses are elicited during HIV-2 infection and correlate with control of viremia. In this study, we analyzed features of an HLA-B*3501-restricted T-cell response to HIV-2 p26 that may contribute to virus control. In contrast to HIV-1, HIV-2-specific T cells are at an early stage of differentiation (CD27+CD28+), a finding that relates directly to CD4+ T-cell levels and inversely to immune activation. The cells demonstrate IFN-, secretion, oligoclonal T-cell receptor V, gene segment usage, exceptional avidity and secretion of pro-inflammatory cytokines. Despite the potentially strong selection pressure imposed on the virus by these cells, there was no evidence of HIV-2 sequence evolution. We propose that in chronic HIV-2 infection, the maintenance of early-differentiated, highly avid CD8+ T cells could account for the non-progressive course of disease. Such responses may be desirable from an HIV vaccine. [source] Checking the Route to Cluster HelicatesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2008Manuel R. Bermejo Abstract The aim of the work described here was to test the general applicability of our recently reported route to cluster helicates and to carry out a systematic study to relate the structural and coordinative properties of the organic strands with the microarchitectures of the resulting cluster helicates. Nine new ZnII, CuI and AgI complexes were prepared from three Schiff base ligands [H2La: bis(4-methyl-3-thiosemicarbazone)-2,6-diacetylpyridine; H2Lb: bis(4-methyl-3-thiosemicarbazone)-2,6-diacetylbenzene; H2Lc: bis(4-ethyl-3-thiosemicarbazone)-2,6-diacetylbenzene]. The experimental data confirm that AgI and CuI tetranuclear cluster helicates were obtained with a [M4(Lx)2] stoichiometry, and this finding demonstrates the general applicability of the synthetic route. The cluster helicates presented in this work were characterized for the first time in solution by NMR spectroscopy. In addition, six of the nine complexes were characterized by X-ray diffraction studies, and three of them were found to be tetranuclear cluster helicates. A detailed study of these three crystal structures leads us to state that the changes introduced in the organic strands do not prevent the assembly of the tetranuclear cluster dihelicates, but they do affect the microarchitectures. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Non-Covalent Aggregation of Discrete Metallo-Supramolecular Helicates into Higher Assemblies by Aromatic Pathways: Structural and Chemical Studies of New Aniline-Based Neutral Metal(II) DihelicatesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 17 2005Miguel Vázquez Abstract Neutral manganese(II), iron(II), cobalt(II), nickel(II), zinc(II) and cadmium(II) complexes with an N -tosyl-substituted N4 -donor Schiff base containing a 4,4'-methylenedianiline residue as spacer [H2La: N,N' -bis(2-tosylaminobenzylidene)-4,4'-methylenedianiline], and the zinc(II) complex with an analogous ligand [H2Lb: N,N' -bis(2-tosylaminobenzylidene)-4,4'-oxodianiline] have been prepared by an electrochemical procedure. FAB and ESI mass spectra of the complexes show peaks due to species corresponding to a general formula [M2(La,b)2 + H]+, thereby suggesting their dinuclear nature. A detailed study of the crystal packing in the unit cell of the zinc(II) complex with H2La shows that the helicates aggregate to form discrete prismatic moieties containing three molecules held together by ,,, and ,,, interactions. Moreover, the ZnII neutral dihelicate with H2Lb forms a 3D network in the solid state due to intermolecular ,-stacking interactions. 1H NMR studies of the diamagnetic compounds reported herein have been performed. Finally, the ligand H2La and its ZnII and CdII complexes have been studied by spectrophotometric and spectrofluorimetric techniques in order to get a better understanding of the formation mechanisms of the complexes and of the nature of their fluorescence emission. Emission studies show that the ZnII and CdII dihelicates with H2La display a green fluorescence in acetonitrile solution (, = 473 nm, , = 0.03 and , = 476 nm, , = 0.01, respectively). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Differential induction of LTP and LTD is not determined solely by instantaneous calcium concentration: an essential involvement of a temporal factorEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2001Tomoyuki Mizuno Abstract Two opposite types of synaptic plasticity in the CA1 hippocampus, long-term potentiation (LTP) and long-term depression (LTD), require postsynaptic Ca2+ elevation. To explain these apparently contradictory phenomena, the current view assumes that a moderate postsynaptic increase in Ca2+ leads to LTD, whereas a large increase leads to LTP. No detailed study has so far been attempted to investigate whether the instantaneous Ca2+ elevation level differentially induces LTP or LTD. We therefore used low-frequency (1 Hz) stimulation of Schaffer collateral/commissural fibers in rat hippocampal slices, during a Mg2+ -free period, as the conditioning stimulus to investigate this. This allowed low-frequency afferent stimulation to cause a postsynaptic Ca2+ influx because the voltage-dependent block of N -methyl- d -aspartate (NMDA) receptor-channels by Mg2+ was removed. When delivered during the Mg2+ -free period, a single pulse, as well as 2,600 pulses, induced LTP that was occluded with tetanus-induced LTP. To decrease the Ca2+ influx, ,-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors were completely blocked by the addition of 10 µm 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) to the conditioning medium, in which 1 Hz afferent stimuli (1,600 pulses) induced less LTP and never induced LTD. To further reduce the Ca2+ influx, NMDA receptors were partially blocked with d -(,)-2-amino-5-phosphonopentanoic acid (d -AP5). A small number of 1 Hz stimuli, however, never induced LTD. Only when the conditioning stimuli exceeded 200 pulses was LTD induced. The present findings provide definitive evidence that protracted conditioning is a prerequisite for the induction of LTD. Thus, not only the amplitude but also the duration of postsynaptic Ca2+ elevation could be essential factors for differentially inducing LTP or LTD. [source] A critical path method for the estimation of service restoration time in power distribution systemsEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 4 2008C. Lakshminarayana Abstract Distribution systems (DSs) are invariably subjected to various types of faults, causing power blackouts to occur. Distribution Engineers have the main responsibility to minimizing the duration of these power blackouts. This minimization can be achieved by the detailed study of pre-fault load condition of the DS, isolating the faulted section, and restoring the supply to healthy sections of the DS. Hence the estimation of service restoration time (SRT) is very important in electrical distribution systems (EDS). The estimation of SRT requires detailed knowledge of the commencement time of the emergency diesel generator (EDG) in EDS and also the operating time of the various relays in EDS. This paper introduces a new concept of optimistic time (OT), pessimistic time (PT), and most likely time (MT) of starting of the EDGs in addition to the OT, PT, and MT of the operation of the relays. The proposed concept is tested on 14-bus, 17-bus, and 29-bus distribution networks. The results reveal that it is highly suitable technique for the estimation of SRT under abnormal conditions. Hence this technique can easily be improved in distribution automation/service restoration algorithms. Copyright © 2007 John Wiley & Sons, Ltd. [source] Controlling Photoactivity in Ultrathin Hematite Films for Solar Water-SplittingADVANCED FUNCTIONAL MATERIALS, Issue 7 2010Florian Le Formal Abstract A promising route to increase the performance of hematite (,-Fe2O3) photoelectrodes for solar hydrogen production through water-splitting is to use an extremely thin layer of this visible light absorber on a nanostructured scaffold. However, the typically poor performance of ultrathin (ca. 20,nm) films of hematite has been the limiting factor in implementing this approach. Here, the surprising effect of a substrate pretreatment using tetraethoxysilicate (TEOS) is reported; it results in drastic improvements in the photoperformance of 12.5,nm thick films of hematite. These films exhibit a water oxidation photocurrent onset potential at 1.1,V versus the reversible hydrogen electrode (vs. RHE) and a plateau current of 0.63,mA cm,2 at 1.5,V vs. RHE under standard illumination conditions, representing the highest reported performance for ultrathin hematite films. In contrast, almost no photoactivity is observed for the photoanode with the same amount of hematite on an untreated substrate. A detailed study of the effects of the TEOS treatment shows that a monolayer of SiOx is formed, which acts to change the hematite nucleation and growth mechanism, increases its crystallinity, reduces the concentration of carrier trapping states of the ultrathin films, and suggests its further application to quantum-dot and extremely-thin-absorber (ETA)-type solar cells. [source] The potential role of waterbirds in dispersing invertebrates and plants in arid AustraliaFRESHWATER BIOLOGY, Issue 2 2008A. J. GREEN Summary 1. The role of waterbirds as vectors of plants and invertebrates within and between arid-zone wetlands is poorly understood. We present the first detailed study of passive dispersal by nomadic birds in Australasia. We investigated the numbers and types of invertebrate and plant propagules within freshly collected faecal samples as well as their viability. We compared dispersal among Grey Teal (Anas gracilis), Eurasian Coot (Fulica atra) and Black Swan (Cygnus atratus) in the Macquarie Marshes, a complex of temporary to semi-permanent wetlands in New South Wales. 2. When faecal samples (n = 60) were inundated in the laboratory and monitored over 3 weeks, ciliates (75% of samples), nematodes (22%), ostracods (13%) and rotifers (5%) were recorded, with higher taxon richness in coot samples. Faecal samples (n = 71) were also sieved to quantify intact propagules, and ostracod eggs (70% of samples), large branchiopod eggs (31%) and bryozoan statoblasts (31%) were the most abundant invertebrates. Diaspores of 19 plant taxa were recorded, 14 of which were germinated in the laboratory or shown to be viable at the end of germination trials. The abundance and diversity of invertebrate propagules was highest in coot samples, whereas the abundance and diversity of diaspores was highest in teal samples. 3. One Australian Pelican (Pelecanus conspicillatus) sample was obtained and found to contain more taxa and far more propagules than any sample from other waterbirds, suggesting that piscivorous birds might have an important role in the indirect dispersal of propagules ingested by fish. 4. Our results support a role for birds in explaining the distributions of cosmopolitan plant genera such as Lemna, Typha, Myriophyllum and Nitella. The alien plants Ranunculus sceleratus, Medicago polymorpha and Polygonum arenastrum were recorded, demonstrating the potential role of waterfowl in the spread of exotic species. As the frequency and duration of flooding of arid-zone wetlands decreases owing to human activities, the importance of waterbirds in facilitating recolonisation of temporary wetlands is likely to increase. [source] Towards Thermoconductive, Electrically Insulating Polymeric Composites with Boron Nitride Nanotubes as FillersADVANCED FUNCTIONAL MATERIALS, Issue 12 2009Chunyi Zhi Abstract Ultilizing boron nitride nanotubes (BNNTs) as fillers, composites are fabricated with poly(methyl methacrylate), polystyrene, poly(vinyl butyral), or poly(ethylene vinyl alcohol) as the matrix and their thermal, electrical, and mechanical properties are evaluated. More than 20-fold thermal conductivity improvement in BNNT-containing polymers is obtained, and such composites maintain good electrical insulation. The coefficient of thermal expansion (CTE) of the BNNT-loaded polymers is dramatically reduced because of interactions between the polymer chains and the nanotubes. Moreover, the composites possess good mechanical properties, as revealed by Vickers microhardness tests. This detailed study indicates that BNNTs are very promising nanofillers for polymeric composites, allowing the simultaneous achievement of high thermal conductivity, low CTE, and high electrical resistance, as required for novel and efficient heat-releasing materials. [source] From the intra-desert ridges to the marine carbonate island chain: middle to late Permian (Upper Rotliegend,Lower Zechstein) of the Wolsztyn,Pogorzela high, west PolandGEOLOGICAL JOURNAL, Issue 2-3 2010Hubert Kiersnowski Abstract The tectonic Wolsztyn,Pogorzela palaeo-High (WPH) is the south-eastern termination of the Brandenburg,Wolsztyn High (western Poland), which during Late Permian times was an intra-basin ridge surrounded by Upper Rotliegend sedimentary basins within the Southern Permian Basin. The geological history and structural framework of the WPH are complex. The High belongs to the Variscan Externides, consisting at present of strongly folded, faulted and eroded Viséan to Namurian flysch deposits capped by a thick cover of Upper Carboniferous,Lower Permian volcanic rocks. This sedimentary-volcanic complex was strongly fragmented and vertically differentiated by tectonic movements and subsequently eroded, resulting in the deposition of coarse clastics surrounding uplifted tectonic blocks. During late Rotliegend time, arid climatic conditions significantly influenced occurrences of specific facies assemblages: alluvial, fluvial, aeolian and playa. Sedimentological study helped to recognize the interplay of tectonic and palaeoclimatic factors and to understand the phenomenon of aeolian sandstones interbedded with coarse deposits of alluvial cones close to fault scarps. Subsequent tectonic and possible thermal subsidence of the studied area was synchronous with inundation by the Zechstein Sea. The rapid inundation process allowed for the preservation of an almost perfectly protected Uppermost Rotliegend landscape. Based on 3D seismic data from the base Zechstein reflector, a reconstruction of Rotliegend palaeogeomorphology was carried out, which shows examples of tectonic rejuvenation of particular tectonic blocks within the WPH area before inundation by the Zechstein Sea. The inundation led to the deposition of the marine Kupferschiefer Shale followed by the Zechstein Limestone. In the deeper parts of the basin the latter is developed in thin basinal facies: in shallow parts (e.g. uplifted tectonic blocks forming in some cases islands), carbonate buildups were formed. The remarkable thickness of those buildups (bryozoan reefs) is interpreted as due to stable tectonic subsidence together with a rise of sea level. A detailed study of carbonate buildups has showed that their internal structure reflects changes in shallow marine environments and even emersion events, caused by sea-level oscillations and tectonic movements of the reef substrate. Copyright © 2010 John Wiley & Sons, Ltd. [source] Synthesis and Structure,Property Correlation in Shape-Controlled ZnO Nanoparticles Prepared by Chemical Vapor Synthesis and their Application in Dye-Sensitized Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 6 2009Revathi R. Bacsa Abstract Here, the large scale synthesis of nanocrystalline ZnO spheres and tetrapods in the size range of 8,40,nm by chemical vapor synthesis using zinc metal as precursor is described. A detailed study of the effect of experimental parameters on the morphology and yield is presented. High-resolution transmission electron microscopy images of the tetrapods show that they are formed by the self assembly of four nanorods in the vapor phase. The tetrapods have optical absorption coefficients that are one order of magnitude greater than the spheres and show intense UV luminescence whereas the spheres show only the green emission. The observed differences in the optical properties are related to the presence of surface defects present in the nanospheres. The tetrapods have increased efficiencies for application in dye sensitized solar cells when compared to spheres. [source] Balancing Intermolecular and Molecule,Substrate Interactions in Supramolecular AssembliesADVANCED FUNCTIONAL MATERIALS, Issue 2 2009Dimas G. de Oteyza Abstract Self-assembly of functional supra-molecular nanostructures is among the most promising strategies for further development of organic electronics. However, a poor control of the interactions driving the assembling phenomena still hampers the tailored growth of designed structures. Here exploration of how non-covalent molecule-substrate interactions can be modified on a molecular level is described. For that, mixtures of DIP and F16CuPc, two molecules with donor and acceptor character, respectively are investigated. A detailed study of their structural and electronic properties is performed. In reference to the associated single-component layers, the growth of binary layers results in films with strongly enhanced intermolecular interactions and consequently reduced molecule-substrate interactions. This new insight into the interplay among the aforementioned interactions provides a novel strategy to balance the critical interactions in the assembly processes by the appropriate choice of molecular species in binary supra-molecular assemblies, and thereby control the self-assembly of functional organic nanostructures. [source] High-Conductivity Polymer Nanocomposites Obtained by Tailoring the Characteristics of Carbon Nanotube Fillers,ADVANCED FUNCTIONAL MATERIALS, Issue 20 2008Nadia Grossiord Abstract We present a detailed study of the influence of carbon nanotube (CNT) characteristics on the electrical conductivity of polystyrene nanocomposites produced using a latex-based approach. We processed both industrially-produced multi-wall CNT (MWCNT) powders and MWCNTs from vertically-aligned films made in-house, and demonstrate that while the raw CNTs are individualized and dispersed comparably within the polymer matrix, the electrical conductivity of the final nanocomposites differs significantly due to the intrinsic characteristics of the CNTs. Owing to their longer length after dispersion, the percolation threshold observed using MWCNTs from vertically-aligned films is five times lower than the value for industrially-produced MWCNT powders. Further, owing to the high structural quality of the CNTs from vertically-aligned films, the resulting composite films exhibit electrical conductivity of 103,S m,1 at 2,wt% CNTs. On the contrary, composites made using the industrially-produced CNTs exhibit conductivity of only tens of S m,1. To our knowledge, the measured electrical conductivity for CNT/PS composites using CNTs from vertically-aligned films is by far the highest value yet reported for CNT/PS nanocomposites at this loading. [source] Fabrication of radial ZnO nanowire clusters and radial ZnO/PVDF composites with enhanced dielectric properties,ADVANCED FUNCTIONAL MATERIALS, Issue 17 2008Guangsheng Wang Abstract Using an improved microemulsion process novel ZnO nanostructures can be prepared on a large scale. These radial ZnO nanowires grow on hexagonal prism tips and form nanowire clusters. A detailed study of variations in dielectric properties dependent on frequency and temperature shows that composites of radial ZnO and PVDF have significantly higher dielectric constants and exhibit better thermal stability than bulk ZnO/PVDF composites as well as showing a low percolation threshold. Already a low content of radial ZnO increases the dielectric constant of the polymer matrix significantly to a value above 100. [source] Human disease resulting from gene mutations that interfere with appropriate nuclear factor-,B activationIMMUNOLOGICAL REVIEWS, Issue 1 2005Jordan S. Orange Summary:, The nuclear factor (NF)-,B family of transcription factors serves vital roles in a wide array of cell functions. An increasing number of human genetic lesions that result in defined disease entities are linked to inappropriate activation of NF-,B. The resulting aberrant NF-,B function can lead to cellular defects that ultimately impair normal developmental processes, host immune defenses, or both. Molecular defects that lie upstream in cell-signaling pathways and rely upon NF-,B activation tend to give a more specific phenotype, whereas those closer to the actual NF-,B proteins have broader defects. A detailed study of these diseases can provide insight into the biochemistry of NF-,B activation as well as the role of NF-,B in human health. [source] Molecular mechanisms of heavy metal tolerance and evolution in invertebratesINSECT SCIENCE, Issue 1 2009Thierry K. S. Janssens Abstract Following the genomics revolution, our knowledge of the molecular mechanisms underlying defenses against stress has been greatly expanded. Under strong selective pressure many animals may evolve an enhanced stress tolerance. This can be achieved by altering the structure of proteins (through mutations in the coding regions of genes) or by altering the amount of protein (through changes in transcriptional regulation). The latter type of evolution can be achieved by substitutions in the promoter of the gene of interest (cis -regulatory change) or by altering the structure or amount of transcriptional regulator proteins (trans -regulatory change). The metallothionein system is one of the best studied stress response systems in the context of heavy metals. Metallothionein expression is assumed to be regulated by metal transcription factor 1 (MTF-1); however, up to now the involvement of MTF-1 has only been proven for some vertebrates and Drosophila. Data on invertebrates such as nematodes and earthworms suggest that other mechanisms of metallothionein induction may be present. A detailed study of Cd tolerance was done for a species of soil-living springtail, Orchesella cincta. The metallothionein gene of this species is overexpressed in metal-exposed field populations. Analysis of the metallothionein promoter has demonstrated extensive polymorphisms that have a functional significance, as shown in bioreporter assays. In a study comparing 20 different populations, the frequency of a high-expresser promoter allele was positively correlated with the concentration of metals in soil, especially Cd. The springtail study shows that cis -regulatory change of genes involved in the cellular stress response may contribute to evolution of metal tolerance. [source] Voronoi cell finite difference method for the diffusion operator on arbitrary unstructured gridsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2003N. SukumarArticle first published online: 11 MAR 200 Abstract Voronoi cells and the notion of natural neighbours are used to develop a finite difference method for the diffusion operator on arbitrary unstructured grids. Natural neighbours are based on the Voronoi diagram, which partitions space into closest-point regions. The Sibson and the Laplace (non-Sibsonian) interpolants which are based on natural neighbours have shown promise within a Galerkin framework for the solution of partial differential equations. In this paper, we focus on the Laplace interpolant with a two-fold objective: first, to unify the previous developments related to the Laplace interpolant and to indicate its ties to some well-known numerical methods; and secondly to propose a Voronoi cell finite difference scheme for the diffusion operator on arbitrary unstructured grids. A conservation law in integral form is discretized on Voronoi cells to derive a finite difference scheme for the diffusion operator on irregular grids. The proposed scheme can also be viewed as a point collocation technique. A detailed study on consistency is conducted, and the satisfaction of the discrete maximum principle (stability) is established. Owing to symmetry of the Laplace weight, a symmetric positive-definite stiffness matrix is realized which permits the use of efficient linear solvers. On a regular (rectangular or hexagonal) grid, the difference scheme reduces to the classical finite difference method. Numerical examples for the Poisson equation with Dirichlet boundary conditions are presented to demonstrate the accuracy and convergence of the finite difference scheme. Copyright © 2003 John Wiley & Sons, Ltd. [source] Ferromagnetism in ZnO Nanowires Derived from Electro-deposition on AAO Template and Subsequent Oxidation,ADVANCED MATERIALS, Issue 6 2008J. B. Yi ZnO wires are prepared from the oxidation of Zn wires, which are electrodeposited into AAO template. The ZnO wires show ferromagnetism at room temperature. A detailed study indicates that, owing to incomplete oxidation, Zn clusters embedded in the ZnO matrix may attribute to the room-temperature ferromagnetism. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||