bluuebunny/crossref_metadata_2025 huggingface dataset:
Mars pathfinder: New data and new model simulations
Authors: Savijärvi Hannu , Määttänen Anni , Kauhanen Janne , Harri Ari‐matti
Published: March 2004

The diurnal cycle in the temperature and wind speed of the Mars Pathfinder lander (MPF) is compared with the results from a one‐dimensional high‐solution boundary‐layer model. The radiation scheme of the model has been validated against line‐by‐line calculations in an average Martian case. The agreement with MPF observations is good. Strong daytime turbulent variability and steep vertical temperature gradients characterize the observations. A detailed look at the model physics reveals that the thin atmosphere responds strongly to thermal radiation. During the daytime, absorption of surface‐emitted thermal radiation by CO2, water vapour and dust is the main heating agent below 200 m despite the fact that the surface layer is strongly convective and dust absorbs solar radiation. The night‐time inversion is also transferred to the air mainly by long‐wave processes, although turbulent cooling dominates very near the surface (below 40 m). The near‐surface net heating/cooling displays a sensitive balance between several large and opposite physical processes, wherefore accurate algorithms and high resolution are needed for detailed model results. The modelled hydrologic cycle reveals a well‐mixed layer of up to 5 km with thin icy fog and frost forming in the night‐time. These sublimate back to the air soon after sunrise. Copyright © 2004 Royal Meteorological Society
The accuracy of stratospheric analyses in the northern hemisphere inferred from long‐duration balloon flights
Authors: Hertzog A. , Basdevant C. , Vial F. , Mechoso C. R.
Published: March 2004

In January and February 2002, six superpressure balloons (SPBs) were launched from Kiruna, Sweden (69°N,21°E). The balloons drifted in the polar lower stratosphere for up to 45 days. Temperature, wind and altitude observations were collected every 15 minutes during the flights. This dataset serves as a reference to assess the accuracy of the European Centre for Medium‐Range Weather Forecasts (ECMWF) analyses and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalyses in the lower stratosphere during the 2002 winter. In particular, it is found that both models succeeded in simulating the large temperature fluctuations observed during the SPB flights, which were induced by a geographical shift between the stratospheric vortex and the low temperature area. Furthermore, the model biases are found to be small for all variables (temperature, wind, height). Nevertheless, it is found that NCEP/NCAR reanalyses tend to be slightly warmer (0.8 K) than the observations, while the converse is true for ECMWF analyses (−0.3 K). The observations also exhibit small‐scale fluctuations that are presumably produced by (inertia‐)gravity waves and which induce some scatter in the analysis/observation comparisons. Finally, trajectory comparisons are performed. It is found that trajectories built with ECMWF winds are more accurate than those built with NCEP/NCAR winds. With both models, the trajectory errors increase with time upto about 15 days and then tend to fluctuate. Typical errors after 15 days are 1000 ± 1200 km for ECMWF and 2300 ± 1300 km for NCEP trajectories. Copyright © 2004 Royal Meteorological Society
Organizing New Product Development Projects in Strategic Alliances
Authors: Gerwin Donald , Ferris J. Stephen
Published: March 2004

We utilize research on alliance governance structures and on new product development to study how partners working under an existing alliance governance structure will organize a new product development project. Initially, we consider a contractual alliance doing multiple projects and argue that the critical organization decisions for any project are whether one or both partners should be involved, whether the partners should work with little or considerable interaction, and whether decision-making authority should reside in a project manager or be consensual. Based on the answers to these questions, we identify at least four viable project organization options. We next examine the option that would be selected under conditions involving the alliance's newness, whether a cooperative history exists, and the distribution of skills for the project. Under each condition, we compare the costs and benefits of the options with respect to the underlying transaction costs, potential for learning, and the ability to contribute to developing a social relations network. By allowing variations in time-to-market pressures, the tacit knowledge that a partner can obtain from the project, and the partners' need to work closely together on future projects, we can determine the points at which costs and benefits indicate a switch from one organization option to another. Finally, we indicate how to adjust the theory for it to apply to a contractual alliance doing only one project and to an institutional alliance such as a joint venture.
Interteam Coordination, Project Commitment, and Teamwork in Multiteam R&D Projects: A Longitudinal Study
Authors: Hoegl Martin , Weinkauf Katharina , Gemuenden Hans Georg
Published: March 2004

Organizations increasingly set up multiteam projects for the development of highly complex products. While team research has emphasized the importance of team-internal processes for smaller scale projects, we know little about collaborative processes (especially between teams) in such large-scale projects. This study utilizes a multi-informant longitudinal research design on a product development project (39 teams, 36 months) in the European automotive industry investigating collaboration between and within teams. The results of the study demonstrate that interteam coordination, project commitment, and teamwork quality as rated by the team members at Time 1 (Month 12; end of concept phase) are significantly correlated to project managers’ ratings of overall team performance at Time 3 (Month 36; end of project). The process variables measured at Time 2 (Month 24; end of design phase) display generally weaker correlations with team performance at Time 3. Multiple regression analyses further detail the effects of collaborative processes within and between teams on different measures of team performance (i.e., overall performance, quality, budget, schedule). The results show that collaborative processes during the project have predictive properties in regard to later team performance and can serve as early warning indicators. Furthermore, the results of this study provide support for our hypotheses predicting positive relationships between interteam coordination, project commitment, and teamwork quality. Theoretical and practical implications of this study are discussed.
Creating and Disseminating Knowledge Among Organizational Scholars: The Role of Special Issues
Authors: Olk Paul , Griffith Terri L.
Published: March 2004

Special issues of scholarly journals have become more common during the last decade of management research. We review this trend and assess the effectiveness of special issues for knowledge dissemination. Methods include interviews with journal editors, compiling data on time to publication and on impact and quality of special issues for five mainstream management journals, and a case study chronicling the creation of the Organization Science special issue on “Knowledge, Knowing, and Organizations.” The findings show that journal special issue articles appear to be published more quickly than regular issue articles (time to publication), and for three of the five journals there is a significant difference in impact (measured as citation counts per article) when special and regular issue articles are compared. Further, we find evidence of greater variation in the quality of special issue articles compared to regular issue articles, although this reflects special issues publishing exceptional articles rather than the inclusion of substandard ones. The case analysis suggests that a series of preconferences on a common topic prior to a special issue did not appear to impact the type of papers submitted to or published in the special issue. We discuss the role of special issues and preconferences in knowledge development in organization science.
Experiential Learning Processes of Exploitation and Exploration Within and Between Organizations: An Empirical Study of Product Development
Authors: Holmqvist Mikael
Published: March 2004

This article examines a fundamental characteristic of modern organizations: the dynamics of exploitation and exploration in intra- and interorganizational learning processes. Exploitation is about creating reliability in experience, and thrives on productivity and refinement. Exploration is concerned with creating variety in experience, and thrives on experimentation and free association. The findings of a case study on product development within a leading Scandinavian software producer and its interorganizational collaborations with business partners suggest how experiential learning processes of exploitation and exploration within the organizations concerned generate interorganizational exploitation and exploration. Conversely, the data suggest how exploitation and exploration between the organizations generate intraorganizational exploitation and exploration. A conceptual framework describing the nature of such learning dynamics is proposed. This framework emphasizes that experiential learning is a driving force behind much intra- and interorganizational change in the form of transformations between exploitation and exploration.
How Organizations Change: The Role of Institutional Support Mechanisms in the Incorporation of Higher Education Visibility Strategies, 1874–1995
Authors: Washington Marvin , Ventresca Marc J.
Published: March 2004

This paper develops the argument that institutional mechanisms support changes in organizational strategies in ways that contrast with the standard interpretation of institutional “iron cages” that pressure organizations to conform. We specify three institutional process mechanisms that support organizational change” dominant logic-consistent activity, external charters, and peer emulation” and we test these claims with longitudinal data on the emerging strategies in early U.S. intercollegiate athletics. We argue that the supporting institutional mechanisms affect the incorporation patterns of intercollegiate programs in basketball, ice hockey, and lacrosse over the period from the late nineteenth century to the present. The research strategy of examining the spread of three different sports programs, each a proxy for different strategies of resources and visibility, provides evidence on the comparative pattern of effects of the three institutional mechanisms. Results indicate that all three institutional support mechanisms affect the incorporation of the intercollegiate programs. Differences in the pattern of incorporation across the three strategies provide robust evidence for alternatives to a prevailing “iron cage” view of institutional pressures and constraints. These findings also reinforce the importance of specifying field-level mechanisms to supplement a focus on organization-level mechanisms.
On the Relationship Between Organizational Complexity and Organizational Structuration
Authors: Moldoveanu Mihnea C. , Bauer Robert M.
Published: March 2004

This article represents a contribution to the conceptualization of organizational complexity. The first part of the article relates the concept of complexity to the production tasks of the organization by deriving measures of the complexity of production and planning tasks within the organization. This move allows us to analyze organizational activities in terms of the computational complexity of the tasks that the organization carries out. Drawing on concepts from theoretical computer science, the article introduces a taxonomy of production tasks based on their computational complexity and shows how to use the notion of computational complexity to analyze organizational phenomena such as vertical integration disintegration, the choice between markets and organizations as performers of particular production tasks, and the internal partitioning of organizational tasks and activities. The article then relates the complexity of the production function of the organization to the ways in which organizations structure themselves. It attempts to bring theorizing about organizational behavior based on complexity theory closer to the conceptual realm of "mainstream" organization theory and to make the concepts of complexity theory more useful to empirical examinations of firm dynamics and organizational behavior.
Welcome to the New Editorial Team at Organization Science
Authors: Schoonhoven Claudia Bird
Published: March 2004

Professor Linda Argote of Carnegie Mellon University has been named the Editor-in-Chief of Organization Science, effective January 1, 2004. Until further notice, all new submissions should be sent to Professor Argote at CMU. See the below website at CMU for submission instructions: http://web.gsia.cmu.edu/orgsci/submission.htm
From the Editor
Authors: Argote Linda
Published: March 2004

This editorial describes the objectives of Organization Science and the kind of manuscripts that we hope to attract to the journal. Previous Editors-in-Chief are acknowledged and thanked for the excellent jobs they have done and for the superb reputation that the journal developed under their leadership. Incoming Senior Editors and members of the Editorial Review Board are introduced and welcomed. Ideas for continuing the traditions of innovation and excellence at Organization Science are discussed.
Adenovirally Expressed Noggin and Brain-Derived Neurotrophic Factor Cooperate to Induce New Medium Spiny Neurons from Resident Progenitor Cells in the Adult Striatal Ventricular Zone
Authors: Chmielnicki Eva , Benraiss Abdellatif , Economides Aris N. , Goldman Steven A.
Published: March 2004

Neurogenesis from endogenous progenitor cells in the adult forebrain ventricular wall may be induced by the local viral overexpression of cognate neuronal differentiation agents, in particular BDNF. Here, we show that the overexpression of noggin, by acting to inhibit glial differentiation by subependymal progenitor cells, can potentiate adenoviral BDNF-mediated recruitment of new neurons to the adult rat neostriatum. The new neurons survive at least 2 months after their genesis in the subependymal zone and are recruited primarily as GABAergic DARPP-32+medium spiny neurons in the caudate-putamen. The new medium spiny neurons successfully project to the globus pallidus, their usual developmental target, extending processes over several millimeters of the normal adult striatum. Thus, concurrent suppression of subependymal glial differentiation and promotion of neuronal differentiation can mobilize endogenous subependymal progenitor cells to achieve substantial neuronal addition to otherwise non-neurogenic regions of the adult brain.
Analysis of Cerebellar Development inmath1Null Embryos and Chimeras
Authors: Jensen Patricia , Smeyne Richard , Goldowitz Dan
Published: March 2004

The cerebellar granule cell is the most numerous neuron in the nervous system and likely the source of the most common childhood brain tumor, medulloblastoma. The earliest known gene to be expressed in the development of these cells ismath1. In themath1null mouse, neuroblasts never populate the external germinal layer (EGL) that gives rise to granule cells. In this study, we examined the embryonic development of themath1null cerebellum and analyzed experimental mouse chimeras made frommath1null embryos. We find that the anterior rhombic lip gives rise to more than one cell type, indicating that the rhombic lip does not consist of a homogeneous population of cells. Furthermore, we demonstrate thatmath1null granule cells are absent in themath1null chimeric cerebellum, from the onset of their genesis in the mouse anterior rhombic lip. This finding indicates a vital cell intrinsic role for Math1 in the granule cell lineage. In addition, we show that wild-type cells are unable to compensate for the loss of mutant cells. Finally, the colonization of the EGL by wild-type cells and the presence of acellular gaps provides evidence that EGL neuroblasts undergo active migration and likely have a predetermined spatial address in the rhombic lip.
Reactive Astrocytes Protect Tissue and Preserve Function after Spinal Cord Injury
Authors: Faulkner Jill R. , Herrmann Julia E. , Woo Michael J. , Tansey Keith E. , Doan Ngan B. , Sofroniew Michael V.
Published: March 2004

Reactive astrocytes are prominent in the cellular response to spinal cord injury (SCI), but their roles are not well understood. We used a transgenic mouse model to study the consequences of selective and conditional ablation of reactive astrocytes after stab or crush SCI. Mice expressing a glial fibrillary acid protein-herpes simplex virus-thymidine kinase transgene were given mild or moderate SCI and treated with the antiviral agent ganciclovir (GCV) to ablate dividing, reactive, transgene-expressing astrocytes in the immediate vicinity of the SCI. Small stab injuries in control mice caused little tissue disruption, little demyelination, no obvious neuronal death, and mild, reversible functional impairments. Equivalent small stab injuries in transgenic mice given GCV to ablate reactive astrocytes caused failure of blood-brain barrier repair, leukocyte infiltration, local tissue disruption, severe demyelination, neuronal and oligodendrocyte death, and pronounced motor deficits. Moderate crush injuries in control mice caused focal tissue disruption and cellular degeneration, with moderate, primarily reversible motor impairments. Equivalent moderate crush injuries combined with ablation of reactive astrocytes caused widespread tissue disruption, pronounced cellular degeneration, and failure of wound contraction, with severe persisting motor deficits. These findings show that reactive astrocytes provide essential activities that protect tissue and preserve function after mild or moderate SCI. In nontransgenic animals, crush or contusion SCIs routinely exhibit regions of degenerated tissue that are devoid of astrocytes. Our findings suggest that identifying ways to preserve reactive astrocytes, to augment their protective functions, or both, may lead to novel approaches to reducing secondary tissue degeneration and improving functional outcome after SCI.
Different Behavior toward Bovine Spongiform Encephalopathy Infection of Bovine Prion Protein Transgenic Mice with One Extra Repeat Octapeptide Insert Mutation
Authors: Castilla J. , Gutiérrez-Adán A. , Brun A. , Pintado B. , Parra B. , Ramírez M. A. , Salguero F. J. , Díaz San Segundo F. , Rábano A. , Cano M. J. , Torres J. M.
Published: March 2004

In humans, insert mutations within the repetitive octapeptide region of the prion protein gene (Prnp) are often associated with familial spongiform encephalopathies. In this study, transgenic mice expressing bovine PrP (boTg mice) bearing an additional octapeptide insertion to the wild type (seven octapeptide repeats instead of six) showed an altered course of bovine spongiform encephalopathy (BSE) infection, reflected as reduced incubation times when compared with boTg mice expressing similar levels of the wild-type six-octapeptide protein. In both boTg mouse lines (bo6ORTg and bo7ORTg), incubation times were affected drastically depending on transgene expression levels and the inoculum used. In accordance with the lack of an interspecies barrier to BSE infection, we detected the typical signs of CNS spongiform degeneration by histopathological analysis and the presence of the bovine prion PrPresby Western blot or immunohistochemical analyses. When 7OR-PrPreswas propagated in bo7ORTg mice, a similar earlier onset of clinical signs was observed compared with bo6ORTg mice. Proteins PrPCand PrPrescontaining seven octapeptides (7OR-PrPCand 7OR-PrPres) showed similar protease sensitivity and insolubility in nondenaturing detergents to homologous 6OR-PrPCand 6OR-PrPres. In addition, bo7ORTg mice showed a higher sensitivity than bo6ORTg mice for detecting prion infection in specimens previously diagnosed as negative by conventional biochemical techniques. In the absence of clinical signs of disease, 7OR-PrPrescould be detected as early as 120 d after inoculation by immunohistochemical and Western blot analyses. These findings may help us improve the current mouse bioassays and understand the role of the octapeptide repeat region in susceptibility to disease.
Phosphorylation of Tau by Fyn: Implications for Alzheimer's Disease
Authors: Lee Gloria , Thangavel Ramasamy , Sharma Vandana M. , Litersky Joel M. , Bhaskar Kiran , Fang Sandy M. , Do Lana H. , Andreadis Athena , Van Hoesen Gary , Ksiezak-Reding Hanna
Published: March 2004

The abnormal phosphorylation of tau protein on serines and threonines is a hallmark characteristic of the neurofibrillary tangles of Alzheimer's disease (AD). The discovery that tau could be phosphorylated on tyrosine and evidence that Aβ signal transduction involved tyrosine phosphorylation led us to question whether tyrosine phosphorylation of tau occurred during the neurodegenerative process. In this study we determined that human tau tyr18 was phosphorylated by the src family tyrosine kinase fyn. By developing both polyclonal and monoclonal probes specific for phospho-tyr18, we found that the phosphorylation of tau at tyr18 occurred at early developmental stages in mouse but was absent in the adult. Our phosphospecific probes also revealed that paired helical filament preparations exhibited phospho-tyr18 reactivity that was sensitive to phosphotyrosine-specific protein phosphatase treatment. Moreover, immunocytochemical studies indicated that tyrosine phosphorylated tau was present in the neurofibrillary tangles in AD brain. However, the staining pattern excluded neuropil threads and dystrophic neurites indicating that tyrosine phosphorylated tau was distributed in AD brain in a manner dissimilar from other abnormally phosphorylated tau. We also found evidence suggesting that differentially phosphorylated tau existed within degenerating neurons. Our data add new support for a role for fyn in the neurodegenerative process.
Macrophage-Derived Tumor Necrosis Factor α, an Early Developmental Signal for Motoneuron Death
Authors: Sedel Frédéric , Béchade Catherine , Vyas Sheela , Triller Antoine
Published: March 2004

Mechanisms inducing neuronal death at defined times during embryogenesis remain enigmatic. We show in explants that a developmental switch occurs between embryonic day 12 (E12) and E13 in rats that is 72-48 hr before programmed cell death. Half the motoneurons isolated from peripheral tissues at E12 escape programmed cell death, whereas 90% of motoneurons isolated at E13 enter a death program. The surrounding somite commits E12 motoneurons to death. This effect requires macrophage cells, is mimicked by tumor necrosis factor α (TNFα), and is inhibited by anti-TNFα antibodies.In vivo, TNFα is detected within somite macrophages, and TNF receptor 1 (TNFR1) is detected within motoneurons precisely between E12 and E13. Although motoneuron cell death occurs normally inTNFα-/-mice, this process is significantly reduced in explants fromTNFα-/-andTNFR1-/-mice. Thus, embryonic motoneurons acquire the competence to die, before the onset of programmed cell death, from extrinsic signals such as macrophage-derived TNFα
Two Loci of Expression for Long-Term Depression at Hippocampal Mossy Fiber-Interneuron Synapses
Authors: Lei Saobo , McBain Chris J.
Published: March 2004

Two distinct forms of long-term depression (LTD) exist at mossy fiber synapses between dentate gyrus granule cells and hippocampal CA3 stratum lucidum interneurons. Although induction of each form of LTD requires an elevation of postsynaptic intracellular Ca2+, at Ca2+-impermeable AMPA receptor (CI-AMPAR) synapses, induction is NMDA receptor (NMDAR) dependent, whereas LTD at Ca2+-permeable AMPA receptor (CP-AMPAR) synapses is NMDAR independent. However, the expression locus of either form of LTD is not known. Using a number of criteria, including the coefficient of variation, paired-pulse ratio, AMPA-NMDA receptor activity, and the low-affinity AMPAR antagonist γ-d-glutamyl-glycine, we demonstrate that LTD expression at CP-AMPAR synapses is presynaptic and results from reduced transmitter release, whereas LTD expression at CI-AMPAR synapses is postsynaptic. TheN-ethylmaleimide-sensitive fusion protein-AP2-clathrin adaptor protein 2 inhibitory peptide pep2m occluded LTD expression at CI-AMPAR synapses but not at CP-AMPAR synapses, confirming that CI-AMPAR LTD involves postsynaptic AMPAR trafficking. Thus, mossy fiber innervation of CA3 stratum lucidum interneurons occurs via two parallel systems targeted to either Ca2+-permeable or Ca2+-impermeable AMPA receptors, each with a distinct expression locus for long-term synaptic plasticity.
A Novel Role For Serum Response Factor in Neuronal Survival
Authors: Chang Sandra H. , Poser Steve , Xia Zhengui
Published: March 2004

Recent studies indicate that neuroprotection afforded by brain-derived neurotrophic factor (BDNF) is mediated by extracellular signal-regulated kinase (ERK) and phosphatidylinositol-3 kinase (PI3K). However, the mechanisms by which ERK and PI3K exert neuroprotection are not completely understood. Because ERK1/2 and PI3K both stimulate serum response element (SRE)-mediated gene expression, and serum response factor (SRF) is indispensable for SRE-mediated transcription, we investigated whether SRF contributes to ERK1/2 and PI3K neuroprotection. To accomplish this goal, we used an established experimental paradigm in which BDNF protects postnatal cortical neurons against both trophic deprivation and camptothecin-induced DNA damage. BDNF protection against camptothecin is mediated primarily by ERK1/2 activation, whereas its protection against trophic deprivation is mainly through stimulation of the PI3K pathway (Hetman et al., 1999). Here we demonstrate that expression of a wild-type SRF is sufficient to protect postnatal cortical neurons against camptothecin or trophic deprivation. Expression of a dominant-negative SRF partially reversed BDNF neuroprotection against both apoptotic insults. Moreover, the dominant-negative SRF inhibited neuroprotection against trophic withdrawal afforded by expression of a constitutive active PI3K. In addition, protection against camptothecin by expression of constitutive active mitogen-activated protein kinase kinase 1, an upstream kinase that activates ERK1/2, was also blocked by expression of the dominant-negative SRF. These data suggest that SRF is both necessary and sufficient for BDNF neuroprotection of cortical neurons against trophic deprivation and DNA damage. Our data provide a direct demonstration of a biological function of SRF in neurons and a novel downstream neuroprotective mechanism common to both ERK1/2 and PI3K pathways.
Suppression of Proinflammatory Cytokines Interleukin-1β and Tumor Necrosis Factor-α in Astrocytes by a V1Vasopressin Receptor Agonist: A cAMP Response Element-Binding Protein-Dependent Mechanism
Authors: Zhao Lixia , Brinton Roberta D.
Published: March 2004

Previous research from our laboratory has demonstrated that V1vasopressin receptor agonist (V1agonist) induces a complex intracellular Ca2+-signaling cascade in cortical astrocytes that is initiated by G-protein-coupled V1avasopressin receptor-mediated cytoplasmic and nuclear Ca2+rise and converges during activation of the nuclear transcription factor cAMP response element-binding protein (CREB). In the current study, we pursued the downstream functional consequences of V1agonist-induced Ca2+-signaling cascade for gene expression. Because astrocytes can exert immune effects analogous to immune cells in the periphery, we investigated V1agonist regulation of cytokine gene expression in astrocytes. Results from gene array studies indicated that V1agonist dramatically decreased the mRNA level of five cytokines. Two prominent proinflammatory cytokines, interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α), were selected for detailed analysis, and their expression was also confirmed with reverse transcriptase-PCR. Furthermore, ELISA analyses demonstrated that the peptide level of IL-1β and TNF-α in the astrocyte medium was also decreased in response to V1agonist. Using CREB antisense to determine the causal relationship between V1agonist-induced CREB activation and suppression of IL-1β and TNF-α, we demonstrated that decreased IL-1β and TNF-α gene expression was dependent on upstream CREB activation. V1agonist-induced decrease of cytokine release from cortical astrocytes was also shown to be neuroprotective in cortical neurons. To our knowledge, this is the first documentation of V1agonist modulation of cytokine gene expression in any cell type. Implications for vasopressin as an antipyretic agent and the role of vasopressin in neurodegeneration, autoimmune diseases, stress, and neuropsychiatric behaviors are discussed.
Asymmetry in Visual Cortical Circuits Underlying Motion-Induced Perceptual Mislocalization
Authors: Fu Yu-Xi , Shen Yaosong , Gao Hongfeng , Dan Yang
Published: March 2004

Motion signals in the visual field can cause strong biases in the perceived positions of stationary objects. Local motion signal within an object induces a shift in the perceived object position in the direction of motion, whereas adaptation to motion stimuli causes a perceptual shift in the opposite direction. The neural mechanisms underlying these illusions are poorly understood. Here we report two novel receptive field (RF) properties in cat primary visual cortex that may account for these motion-position illusions. First, motion signal in a stationary test stimulus causes a displacement of the RF in the direction opposite to motion. Second, motion adaptation induces a shift of the RF in the direction of adaptation. Comparison with human psychophysical measurements under similar conditions indicates that these RF properties can primarily account for the motion-position illusions. Importantly, both RF properties indicate a spatial asymmetry in the synaptic connections from direction-selective cells, and this circuit feature can be predicted by spike-timing-dependent synaptic plasticity, a widespread phenomenon in the nervous system. Thus, motion-induced perceptual mislocalization may be mediated by asymmetric cortical circuits, as a natural consequence of experience-dependent synaptic modification during circuit development.
Rapid Deletion of Mossy Cells Does Not Result in a Hyperexcitable Dentate Gyrus: Implications for Epileptogenesis
Authors: Ratzliff Anna d. H. , Howard Allyson L. , Santhakumar Vijayalakshmi , Osapay Imola , Soltesz Ivan
Published: March 2004

Loss of cells from the hilus of the dentate gyrus is a major histological hallmark of human temporal lobe epilepsy. Hilar mossy cells, in particular, are thought to show dramatic numerical reductions in pathological conditions, and one prominent theory of epileptogenesis is based on the assumption that mossy cell loss directly results in granule cell hyperexcitability. However, whether it is the disappearance of hilar mossy cells from the dentate gyrus circuitry after various insults or the subsequent synaptic-cellular alterations (e.g., reactive axonal sprouting) that lead to dentate hyperexcitability has not been rigorously tested, because of the lack of available techniques to rapidly remove specific classes of nonprincipal cells from neuronal networks.

We developed a fast, cell-specific ablation technique that allowed the targeted lesioning of either mossy cells or GABAergic interneurons in horizontal as well as axial (longitudinal) slices of the hippocampus. The results demonstrate that mossy cell deletion consistently decreased the excitability of granule cells to perforant path stimulation both within and outside of the lamella where the mossy cell ablation took place. In contrast, ablation of interneurons caused the expected increase in excitability, and control aspirations of the hilar neuropil or of interneurons in the presence of GABA receptor blockers caused no alteration in granule cell excitability.

These data do not support the hypothesis that loss of mossy cells from the dentate hilus after seizures or traumatic brain injury directly results in hyperexcitability.
Minocycline Treatment Reduces Delayed Oligodendrocyte Death, Attenuates Axonal Dieback, and Improves Functional Outcome after Spinal Cord Injury
Authors: Stirling David P. , Khodarahmi Kourosh , Liu Jie , McPhail Lowell T. , McBride Christopher B. , Steeves John D. , Ramer Matt S. , Tetzlaff Wolfram
Published: March 2004

Minocycline has been demonstrated to be neuroprotective after spinal cord injury (SCI). However, the cellular consequences of minocycline treatment on the secondary injury response are poorly understood. We examined the ability of minocycline to reduce oligodendrocyte apoptosis, microglial/macrophage activation, corticospinal tract (CST) dieback, and lesion size and to improve functional outcome after SCI. Adult rats were subjected to a C7-C8 dorsal column transection, and the presence of apoptotic oligodendrocytes was assessed within the ascending sensory tract (AST) and descending CST in segments (3-7 mm) both proximal and distal to the injury site. Surprisingly, the numbers of dying oligodendrocytes in the proximal and distal segments were comparable, suggesting more than the lack of axon-cell body contiguity played a role in their demise. Minocycline or vehicle control was injected into the intraperitoneal cavity 30 min and 8 hr after SCI and thereafter twice daily for 2 d. We report a reduction of apoptotic oligodendrocytes and microglia within both proximal and distal segments of the AST after minocycline treatment, using immunostaining for active caspase-3 and Hoechst 33258 staining in combination with cell-specific markers. Activated microglial/macrophage density was reduced remote to the lesion as well as at the lesion site. Both CST dieback and lesion size were diminished after minocycline treatment. Footprint analysis revealed improved functional outcome after minocycline treatment. Thus, minocycline ameliorates multiple secondary events after SCI, rendering this clinically used drug an attractive candidate for SCI treatment trials.
Numerous GABAergic Afferents to Locus Ceruleus in the Pericerulear Dendritic Zone: Possible Interneuronal Pool
Authors: Aston-Jones Gary , Zhu Yan , Card J. Patrick
Published: March 2004

Most nuclei in the CNS are composed of principal neurons that project to other areas and interneurons that serve to integrate information among afferents. The noradrenergic brain nucleus locus ceruleus (LC) has appeared to be an exception to this general rule, because the LC is composed almost entirely of noradrenergic principal neurons. Here, we report that numerous small neurons in the peri-LC region become retrogradely labeled after focal injections of wheat germ agglutinin-apo (inactivated) horseradish peroxidase conjugated to colloidal gold, or pseudorabies virus (PRV), into the nuclear core of the rat LC. A substantial number of these neurons were routinely found within the dendritic field of the LC, in the area surrounding the compact cell-dense region classically defined as LC. Double labeling revealed that a large percentage of these cells stained for GABA. Ultrastructural analyses revealed axodendritic and axosomatic contacts between PRV-labeled afferents and LC neurons labeled with tyrosine hydroxylase immunohistochemistry. In addition, PRV-labeled neurons or axons were immunopositive for GABA in ultrastructural localizations. Analysis of the synaptology of immunopositive profiles demonstrated that these LC afferents in the peri-LC region receive several non-LC synaptic inputs. These results indicate that a population of small GABAergic neurons in the peri-LC dendritic zone may provide interneuronal integration for LC noradrenergic neurons.
A Conserved Postsynaptic Transmembrane Protein Affecting Neuromuscular Signaling inCaenorhabditis elegans
Authors: Loria Paula M. , Hodgkin Jonathan , Hobert Oliver
Published: March 2004

For a motor unit to function, neurons and muscle cells need to adopt their correct cell fate, form appropriate cellular contacts, and assemble a specific repertoire of signaling proteins into presynaptic and postsynaptic structures. In the nematodeCaenorhabditis elegans, a disruption of any of these steps causes uncoordinated locomotory behavior (uncphenotype). We report here the positional cloning of a newuncgene,unc-122, which we show by mosaic analysis and tissue-specific rescue experiments to act in muscle to affect locomotory behavior.unc-122codes for a phylogenetically conserved type II transmembrane protein with collagen repeats and a cysteine-rich olfactomedin domain. Together with uncharacterized proteins inC. elegans, Drosophila, and vertebrates, UNC-122 defines a novel family of proteins that we term “Colmedins.” UNC-122 protein is expressed exclusively in muscle and coelomocytes and localizes to the postsynaptic surface of GABAergic and cholinergic neuromuscular junctions (NMJs). Presynaptic and postsynaptic structures are present and properly aligned inunc-122mutant animals, yet the animals display neurotransmission defects characterized by an altered sensitivity toward drugs that interfere with cholinergic signaling. Moreover,unc-122mutant animals display anatomical defects in motor axons that are likely a secondary consequence of neurotransmission defects. Both the neuroanatomical and locomotory defects worsen progressively during the life of an animal, consistent with a role ofunc-122in acute signaling at the NMJ. On the basis of motifs in the UNC-122 protein sequence that are characteristic of extracellular matrix proteins, we propose that UNC-122 is involved in maintaining a structural microenvironment that allows efficient neuromuscular signaling.
Real‐time identification of vehicle chassis dynamics using a novel reparameterization based on sensitivity invariance
Authors: Brennan S. , Alleyne A.
Published: March 2004

This work presents a novel methodology to identify model parameters using the concept of sensitivity invariance. Within many classical system representations, relationships between Bode parameter sensitivities may exist that are not explicitly accounted for by the formal system model. These relationships, called sensitivity invariances, will explicitly limit the possible parameter variation of the system model to a small subspace of the possible parameter gradients. By constraining the parameter identification or adaptation to a model structure with uncoupled parameter sensitivities, a more efficient identification can be obtained at a reduced computational and modelling cost. As illustration, an identification method of using sensitivity invariance is demonstrated on an experimental problem to identify, in real time, a time‐varying tire parameter associated with the chassis dynamics of passenger vehicles at highway speeds. The results are validated with simulations as well as an experimental implementation on a research vehicle driven under changing road conditions. Copyright © 2004 John Wiley & Sons, Ltd.
Probing small scale structure in the atmosphere of V471 Tauri
Authors: Walter F. M.
Published: March 2004

The white dwarf in the eclipsing binary system V471 Tau is viewed through the atmosphere of the active K star prior to ingress and after egress. In the far UV the surface brightness of the hot white dwarf far outshines the K star emission. We can use this to probe the structure of the extended K star atmosphere along one line of sight, in absorption, on spatial scales of the radius of the white dwarf (10,000 km). The time series of HST/STIS spectra which show a hot (>250,000 K) extended (>1 K star radius) atmosphere around the K star. We see discrete structures in the velocity‐resolved spectra, on spatial scales of less than 100,000 km. The mean velocity is that expected of gas in co‐rotation with the K star, but the discrete velocity structures have excursions of up to 70 km/s from the mean. The mean temperature seems to increase with height above the K star photosphere. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
What can we learn from accretion disc eclipse mapping experiments?
Authors: Baptista R.
Published: March 2004

The accretion disc eclipse mapping method is an astrotomographic inversion technique that makes use of the information contained in eclipse light curves to probe the structure, the spectrum and the time evolution of accretion discs in cataclysmic variables. This paper presents examples of eclipse mapping results that have been key to improve our understanding of accretion physics. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stokes imaging and Doppler mapping of the magnetic cataclysmic variable V834 Cen
Authors: Potter S. , Romero‐Colmenero E. , Buckley D. A. H.
Published: March 2004

We report on new phase resolved spectroscopic and polarimetric observations of the polar (AM Herculis star) V834 Cen during a high state of accretion. Strong emission lines and high levels of variable circular and linear polarization are observed over the orbital period.

The polarization data is modelled using the Stokes imaging technique of Potter et al. The spectroscopic emission lines are investigated using the Doppler tomography technique of Marsh & Horne.

Up to now both techniques have been used separately to investigate the geometry and accretion dynamics in Cataclysmic Variables. For the first time we apply both techniques to phase resolved spectroscopic and polarimetric observations: in this case to the polar V834 Cen. This allows us to compare and test each technique against each other and hence derive a better understanding of the geometry, dynamics and system parameters of V834 Cen.

Both techniques are consistent with the interpretation that the ballistic stream extends for more than approximately 40 degrees in azimuth around the white dwarf before becoming, threaded by the magnetic field lines. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Doppler tomography of accretion in binaries
Authors: Steeghs D.
Published: March 2004

Since its conception, Doppler tomography has matured into a versatile and widely used tool. It exploits the information contained in the highly‐structured spectral line‐profiles typically observed in mass‐transferring binaries. Using inversion techniques akin to medical imaging, it permits the reconstruction of Doppler maps that image the accretion flow on micro‐arcsecond scales. I summarise the basic concepts behind the technique and highlight two recent results; the use of donor star emission as a means to system parameter determination, and the real‐time movies of the evolving accretion flow in the cataclysmic variable WZ Sge during its 2001 outburst. I conclude with future opportunities in Doppler tomography by exploiting the combination of superior data sets, second generation reconstruction codes and simulated theoretical tomograms to delve deeper into the physics of accretion flows. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Doppler tomography of cataclysmic variables
Authors: Morales‐Rueda L.
Published: March 2004

The study of cataclysmic variables (CVs), and in particular of the evolution of their accretion discs throughout their different brightness states, has benefited largely from the use of indirect imaging techniques. I report on the latest results obtained from Doppler tomography of CVs concentrating mainly on results published since the 2000 Astrotomography meeting in Brussels. Emphasis is given to the spiral structures found in the accretion discs of some CVs, to the evolution of these structures throughout quiescence and outburst, and to our search for them in more systems. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Approaching Supramolecular Functionality
Authors: Schalley Christoph A. , Lützen Arne , Albrecht Markus
Published: March 2004

Functional molecules require a high degree of complexity which is difficult to achieve by covalent synthesis. This article discusses supramolecular approaches to the creation of larger architectures through noncovalent bonds, self‐assembly, and template strategies. It highlights selected examples for the structural and conformational control of function and attempts to identify difficulties and challenges which may arise in future.
Selective Generation and Reactivity of 5′‐Adenosinyl and 2′‐Adenosinyl Radicals
Authors: Chatgilialoglu Chryssostomos , Duca Maria , Ferreri Carla , Guerra Maurizio , Ioele Marcella , Mulazzani Quinto G. , Strittmatter Harald , Giese Bernd
Published: March 2004

The reaction of hydrated electrons (e${{- \hfill \atop {\rm aq}\hfill}}$) with 8‐bromoadenosine 7 has been investigated by radiolytic methods coupled with product studies. Pulse radiolysis revealed that one‐electron reductive cleavage of the CBr bond gives the C8 radical 8 followed by a fast radical translocation to the sugar moiety. The reaction is partitioned between C5′ and C2′ positions in a 60:40 ratio leading to 5′‐adenosinyl radical 9 and 2′‐adenosinyl radical 11. This radical translocation from C8 to different sites of the sugar moiety has also been addressed computationally by means of DFT B3LYP calculations. In addition, ketone 21 was prepared and photolyzed providing an independent generation of C2′ radical 11. Both C5′ and C2′ radicals undergo unimolecular reactions. Radical 9 attacks adenine with a rate constant of 1.0×104 s−1 and gives the aromatic aminyl radical 10, whereas C2′ radical 11 liberates adenine with a rate constant of 1.1×105 s−1.
Pd‐Catalyzed Coupling Reactions Involving Propargylic/Allenylic Species
Authors: Ma Shengming
Published: March 2004

In this review, the Pd‐catalyzed coupling reaction involving propargylic/allenylic species is discussed. In these reactions, η1‐ and η3‐propargylic/allenylic species have been proposed as the key intermediates for the selective formation of either allenes or alkynes. It should be noted that, in most cases, allenes are formed as the major products. Electronic, steric, and ligand effects have been observed for the control of the regioselectivity. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Entropy‐Driven Asymmetric Synthesis with Chiral Tethers
Authors: Sugimura Takashi
Published: March 2004

The 2,4‐pentanediol (PD)‐tethered reaction is a stereocontrolled reaction having versatile applicability. When reactant and reagent elements are connected through a PD tether prior to their reaction, stereochemical purity of the product is very high for nine different types of reactions so far studied. Selectivity of one of the reactions shows temperature independency over a wide range from −78 to 150 °C, which indicates that the stereocontrol is driven by the entropy term. The strict stereocontrol of this reaction at high temperatures can be extended to vapor phase reactions performed above 250 °C. To understand how the two methyl groups on the PD tether stereocontrol the reaction, a new parameter, a chiral perturbation factor, is introduced. By this analysis, it is disclosed that the methyl groups promote an activation entropy change for both the diastereomeric processes, and the strict stereocontrol is achieved when the changes have opposite signs. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)