Reservoir formation in shallow granular flows through a contraction

We consider flow of dry granular matter down an inclined chute with a localized contraction. Measurements and analysis show that changes in particle volume fraction are important, especially across granular bores. For fixed upstream conditions and depending on the nozzle width of the contraction, we observe either small oblique jumps, a reservoir with a steady jump, or a reservoir with an upstream traveling bore. Shallow layer theory extended to include porosity changes qualitatively predicts these regimes. Implications for volcanic debris \ud ows are discussed

Mechanical strain influence on functional signaling of neurons in vitro

Neuronal cells are embedded in the soft brain tissue and are protected by the thick meninges, as well as the rigid skull bones. Despite being highly sensitive and vastly protected, neurons are prone to internal and external mechanical forces. Many internal tensile loading scenarios affect neurons during development, growth and blood flow. Moreover, neurons are exposed to be strained externally by regular body movements or to be severely injured as a result of serious falls, accidents or tumor formation. In specific cases neuronal tissue could be dissected where intercellular connections get an entire cut and may cause cell death for some neurons in a network, such as the case of brain surgery to remove a tumor or to implant a neurostimulator device. However, limited experimental data is available for the mechanobiology of brain cells and it remained quite unattended. Beside the chemical and molecular cues, some studies reported the importance of the mechanical input in nervous tissue homeostasis. Latest studies, show the key role of the physical microenvironment, such as topographical cues and stiffness alterations. Moreover, reports on physiological cyclic mechanical strain show the potential to accelerate axonal growth. While strain induced responses on the molecular and structural levels has been identified, much less is known about the consequences of these changes to neuronal functionality. As neurons are the basic functional units in transmitting information in the nervous system, the functional behavior of neurons under mechanical strain is the focus of this dissertation. In the context of this thesis, primary cortical neurons were functionally characterized upon exposure to physiological and traumatic uniaxial stretch conditions within different developing stages. Also, spontaneous signaling events were characterized upon single cellular compartment loss induced by laser ablation. The dynamic changes in cells was determined by recording spatial and temporal changes in Ca2+ concentrations ([Ca2+]) of single-cells and on synchronized network level using the Cal-590 AM Ca2+ indicator. The focus here is on both the immediate cell response and to their long-term adaptation to mechanical strain. This work shows that neurons are robust and can functionally tolerate cyclic stretching of up to 30% strain by keeping active communication between cells no matter if strain is applied at different periods during neuronal network formation. Simulating traumatic brain injuries using rapid stretch pulses identified a threshold for functional impairment of about 60% with a high ability to adapt and restore cellular connectivity with time. In spite of the broad range of assessed strains, cells keep maintained without further effects on cell viability, inflammatory responses or synapse formation. Co-cultures with astrocytes revealed more stable and better communicating networks while functional responses to strain remained unaffected. Laser-induced death of single cellular compartment resulted in an increased intracellular calcium concentration [Ca2+]i in neurons surrounding the ablated point. The [Ca2+]i-increase was distance-dependent as closely connected neurons to the ablated cell were highly affected by Ca2+ inflow compared with other cells. Furthermore, the increased [Ca2+]i caused a temporarily interruption in neuronal spiking activity that recovered gradually with time. In spite of the distance-dependent alterations, the overall network functionality was unaffected and the level of connectivity was maintained in the long-term analysis. Taken together, this research work illustrates the internal dynamic responses of neurons to multiple loading conditions and to single-cell death. These data will be advantageous in developing more effective neuronal tolerance criteria to injury. Understanding and pushing the limits of nerve stretch holds tremendous potential for tissue engineering efforts to prevent nervous system injury and facilitate nerve repair

Paleoseismic History of the Dead Sea Fault Zone

International audienceThe aim of this entry is to describe the DSF as a transform plate boundary pointing out the rate of activedeformation, fault segmentation, and geometrical complexities as a control of earthquake ruptures. Thedistribution of large historical earthquakes from a revisited seismicity catalogue using detailedmacroseismic maps allows the correlation between the location of past earthquakes and fault segments.The recent results of paleoearthquake investigations (paleoseismic and archeoseismic) with a recurrenceinterval of large events and long-term slip rate are presented and discussed along with the identification ofseismic gaps along the fault. Finally, the implications for the seismic hazard assessment are also discussed

Search for Top Squark Pair Production in the Dielectron Channel

This report describes the first search for top squark pair production in the channel stop_1 stopbar_1 -> b bbar chargino_1 chargino_1 -> ee+jets+MEt using 74.9 +- 8.9 pb^-1 of data collected using the D0 detector. A 95% confidence level upper limit on sigma*B is presented. The limit is above the theoretical expectation for sigma*B for this process, but does show the sensitivity of the current D0 data set to a particular topology for new physics.Comment: Five pages, including three figures, submitted to PRD Brief Report

Measurement of the WW Boson Mass

A measurement of the mass of the $W$ boson is presented based on a sample of 5982 $W \rightarrow e \nu$ decays observed in $p\overline{p}$ collisions at $\sqrt{s}$ = 1.8~TeV with the D\O\ detector during the 1992--1993 run. From a fit to the transverse mass spectrum, combined with measurements of the $Z$ boson mass, the $W$ boson mass is measured to be $M_W = 80.350 \pm 0.140 (stat.) \pm 0.165 (syst.) \pm 0.160 (scale) GeV/c^2$.Comment: 12 pages, LaTex, style Revtex, including 3 postscript figures (submitted to PRL

Search for First Generation Scalar Leptoquark Pairs in ppbar Collisions at sqrt(s)=1.8 TeV

We have searched for first generation scalar leptoquark (LQ) pairs in the enu+jets channel using ppbar collider data (integrated luminosity= 115 pb^-1) collected by the DZero experiment at the Fermilab Tevatron during 1992-96. The analysis yields no candidate events. We combine the results with those from the ee+jets and nunu+jets channels to obtain 95% confidence level (CL) upper limits on the LQ pair production cross section as a function of mass and of beta, the branching fraction to a charged lepton. Comparing with the next-to-leading order theory, we set 95% CL lower limits on the LQ mass of 225, 204, and 79 GeV/c^2 for beta=1, 1/2, and 0, respectively.Comment: 14 pages, 4 figures, submitted to Physical Review Letters Replaced to correct visitor addresse

Effects of asenapine, olanzapine, and risperidone on psychotomimetic-induced reversal-learning deficits in the rat

YesBackground: Asenapine is a new pharmacological agent for the acute treatment of schizophrenia and bipolar disorder. It has relatively higher affinity for serotonergic and α2-adrenergic than dopaminergic D2 receptors. We evaluated the effects of asenapine, risperidone, and olanzapine on acute and subchronic psychotomimetic-induced disruption of cued reversal learning in rats. Methods: After operant training, rats were treated acutely with D-amphetamine (0.75 mg/kg intraperitoneally [i.p.]) or phencyclidine (PCP; 1.5 mg/kg i.p.) or sub-chronically with PCP (2 mg/kg i.p. for 7 days). We assessed the effects of acute coadministration of asenapine, risperidone, or olanzapine on acute D-amphetamine– and PCP-induced deficits and the effects of long-term coadministration of these agents (for 28 additional days) on the deficits induced by subchronic PCP. Results: Deficits in reversal learning induced by acute D-amphetamine were attenuated by risperidone (0.2 mg/kg i.p.). Acute PCP-induced impairment of reversal learning was attenuated by acute asenapine (0.025 mg/kg subcutaneously [s.c.]), risperidone (0.2 mg/kg i.p.), and olanzapine (1.0 mg/kg i.p.). Subchronic PCP administration induced an enduring deficit that was attenuated by acute asenapine (0.075 mg/kg s.c.) and by olanzapine (1.5 mg/kg i.p.). Asenapine (0.075 mg/kg s.c.), risperidone (0.2 mg/kg i.p.), and olanzapine (1.0 mg/kg i.p.) all showed sustained efficacy with chronic (29 d) treatment to improve subchronic PCP-induced impairments. Conclusion: These data suggest that asenapine may have beneficial effects in the treatment of cognitive symptoms in schizophrenia. However, this remains to be validated by further clinical evaluation.This research was supported by Schering-Plough Corporation, now Merck & Co., Inc. and Pfizer Inc

Limits on Anomalous WWgamma and WWZ Couplings

Limits on the anomalous WWgamma and WWZ couplings are presented from a simultaneous fit to the data samples of three gauge boson pair final states in pbar-p collisions at sqrt(s)=1.8 TeV: Wgamma production with the W boson decaying to enu or munu, W boson pair production with both of the W bosons decaying to enu or munu, and WW or WZ production with one W boson decaying to enu and the other W boson or the Z boson decaying to two jets. Assuming identical WWgamma and WWZ couplings, 95 % C.L. limits on the anomalous couplings of -0.30<Delta kappa<0.43 (lambda = 0) and -0.20<lambda<0.20 (Delta kappa = 0) are obtained using a form factor scale Lambda = 2.0 TeV. Limits found under other assumptions on the relationship between the WWgamma and WWZ couplings are also presented.Comment: 13 pages, 3 figures, submitted to Physical Review

Measurement of Dijet Angular Distributions and Search for Quark Compositeness

We have measured the dijet angular distribution in $\sqrt{s}$=1.8 TeV $p\bar{p}$ collisions using the D0 detector. Order $\alpha^{3}_{s}$ QCD predictions are in good agreement with the data. At 95% confidence the data exclude models of quark compositeness in which the contact interaction scale is below 2 TeV.Comment: 11 pages, Latex, 3 postscript figure

Second Generation Leptoquark Search in p\bar{p} Collisions at s\sqrt{s} = 1.8 TeV

We report on a search for second generation leptoquarks with the D\O\ detector at the Fermilab Tevatron $p\bar{p}$ collider at $\sqrt{s}$ = 1.8 TeV. This search is based on 12.7 pb$^{-1}$ of data. Second generation leptoquarks are assumed to be produced in pairs and to decay into a muon and quark with branching ratio $\beta$ or to neutrino and quark with branching ratio $(1-\beta)$. We obtain cross section times branching ratio limits as a function of leptoquark mass and set a lower limit on the leptoquark mass of 111 GeV/c$^{2}$ for $\beta = 1$ and 89 GeV/c$^{2}$ for $\beta = 0.5$ at the 95%\ confidence level.Comment: 18 pages, FERMILAB-PUB-95/185-