Activity of comets: Gas Transport in the Near-Surface Porous Layers of a Cometary Nucleus

The gas transport through non-volatile random porous media is investigated numerically. We extend our previous research of the transport of molecules inside the uppermost layer of a cometary surface (Skorov and Rickmann, 1995; Skorov et al. 2001). We assess the validity of the simplified capillary model and its assumptions to simulate the gas flux trough the porous dust mantle as it has been applied in cometary physics. A new microphysical computational model for molecular transport in random porous media formed by packed spheres is presented. The main transport characteristics such as the mean free path distribution and the permeability are calculated for a wide range of model parameters and compared with those obtained by more idealized models. The focus in this comparison is on limitations inherent in the capillary model. Finally a practical way is suggested to adjust the algebraic Clausing formula taking into consideration the nonlinear dependence of permeability on layer porosity. The retrieved dependence allows us to accurately calculate the permeability of layers whose thickness and porosity vary in the range of values expected for the near-surface regions of a cometary nucleus.Comment: 25 pages, 9 figure

Search for supersymmetry in events with one lepton and multiple jets in proton-proton collisions at root s=13 TeV

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Search for heavy resonances decaying to two Higgs bosons in final states containing four b quarks

A search is presented for narrow heavy resonances X decaying into pairs of Higgs bosons (H) in proton-proton collisions collected by the CMS experiment at the LHC at root s = 8 TeV. The data correspond to an integrated luminosity of 19.7 fb(-1). The search considers HH resonances with masses between 1 and 3 TeV, having final states of two b quark pairs. Each Higgs boson is produced with large momentum, and the hadronization products of the pair of b quarks can usually be reconstructed as single large jets. The background from multijet and t (t) over bar events is significantly reduced by applying requirements related to the flavor of the jet, its mass, and its substructure. The signal would be identified as a peak on top of the dijet invariant mass spectrum of the remaining background events. No evidence is observed for such a signal. Upper limits obtained at 95 confidence level for the product of the production cross section and branching fraction sigma(gg -> X) B(X -> HH -> b (b) over barb (b) over bar) range from 10 to 1.5 fb for the mass of X from 1.15 to 2.0 TeV, significantly extending previous searches. For a warped extra dimension theory with amass scale Lambda(R) = 1 TeV, the data exclude radion scalar masses between 1.15 and 1.55 TeV

Measurement of the Splitting Function in &ITpp &ITand Pb-Pb Collisions at root&ITsNN&IT=5.02 TeV

Data from heavy ion collisions suggest that the evolution of a parton shower is modified by interactions with the color charges in the dense partonic medium created in these collisions, but it is not known where in the shower evolution the modifications occur. The momentum ratio of the two leading partons, resolved as subjets, provides information about the parton shower evolution. This substructure observable, known as the splitting function, reflects the process of a parton splitting into two other partons and has been measured for jets with transverse momentum between 140 and 500 GeV, in pp and PbPb collisions at a center-of-mass energy of 5.02 TeV per nucleon pair. In central PbPb collisions, the splitting function indicates a more unbalanced momentum ratio, compared to peripheral PbPb and pp collisions.. The measurements are compared to various predictions from event generators and analytical calculations.Peer reviewe

Measurement of nuclear modification factors of gamma(1S)), gamma(2S), and gamma(3S) mesons in PbPb collisions at root s(NN)=5.02 TeV

The cross sections for ϒ(1S), ϒ(2S), and ϒ(3S) production in lead-lead (PbPb) and proton-proton (pp) collisions at √sNN = 5.02 TeV have been measured using the CMS detector at the LHC. The nuclear modification factors, RAA, derived from the PbPb-to-pp ratio of yields for each state, are studied as functions of meson rapidity and transverse momentum, as well as PbPb collision centrality. The yields of all three states are found to be significantly suppressed, and compatible with a sequential ordering of the suppression, RAA(ϒ(1S)) > RAA(ϒ(2S)) > RAA(ϒ(3S)). The suppression of ϒ(1S) is larger than that seen at √sNN = 2.76 TeV, although the two are compatible within uncertainties. The upper limit on the RAA of ϒ(3S) integrated over pT, rapidity and centrality is 0.096 at 95% confidence level, which is the strongest suppression observed for a quarkonium state in heavy ion collisions to date. © 2019 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP3.Peer reviewe

Search for anomalous couplings in boosted WW/WZ -> l nu q(q)over-bar production in proton-proton collisions at root s=8TeV

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Measurement of the top quark mass using charged particles in pp collisions at root s=8 TeV

Peer reviewe

25th annual computational neuroscience meeting: CNS-2016

The same neuron may play different functional roles in the neural circuits to which it belongs. For example, neurons in the Tritonia pedal ganglia may participate in variable phases of the swim motor rhythms [1]. While such neuronal functional variability is likely to play a major role the delivery of the functionality of neural systems, it is difficult to study it in most nervous systems. We work on the pyloric rhythm network of the crustacean stomatogastric ganglion (STG) [2]. Typically network models of the STG treat neurons of the same functional type as a single model neuron (e.g. PD neurons), assuming the same conductance parameters for these neurons and implying their synchronous firing [3, 4]. However, simultaneous recording of PD neurons shows differences between the timings of spikes of these neurons. This may indicate functional variability of these neurons. Here we modelled separately the two PD neurons of the STG in a multi-neuron model of the pyloric network. Our neuron models comply with known correlations between conductance parameters of ionic currents. Our results reproduce the experimental finding of increasing spike time distance between spikes originating from the two model PD neurons during their synchronised burst phase. The PD neuron with the larger calcium conductance generates its spikes before the other PD neuron. Larger potassium conductance values in the follower neuron imply longer delays between spikes, see Fig. 17.Neuromodulators change the conductance parameters of neurons and maintain the ratios of these parameters [5]. Our results show that such changes may shift the individual contribution of two PD neurons to the PD-phase of the pyloric rhythm altering their functionality within this rhythm. Our work paves the way towards an accessible experimental and computational framework for the analysis of the mechanisms and impact of functional variability of neurons within the neural circuits to which they belong

SATELLITE TELEMETRY REVEALS WINTER HOME OF EURASIAN CRANE FROM NORTHWESTERN SIBERIA

Satellite telemetry is a developing technology for the study of crane migration. A greater sandhill crane (Grus canadensis tabida) was tracked by satellite from Florida to Michigan in March 1989 (Nagendran 1992). This note reports the second attempt to use satellite telemetry to follow crane migration. In 1989 -90, tests of various harness and backpack designs for satellite telemetry transmitters (PTT\u27s) with free-flying and confined sandhill cranes led to a 4-strap design (see Olsen et al. 1992) that was accepted for field testing. Through a cooperative effort between the Patuxent Wildlife Research Center (USFWS) , International Crane Foundation, Soviet Nature Conservation and Reserves (USSR), aka State Reserve (Russia), and the National Aeronautics and Space Administration (USA), 3 battery-powered PTT\u27s (weight 161-163 g plus 15 g for harness) manufactured by Telonics (mention does not constitute U.S. Government endorsement) were placed on 1 adult female and 2 adult male Eurasian cranes (G. grus) in the Kunovat Basin in northwestern Siberia in June 1990. The 2 males were captured by using alpha-chloralose-laced sandpiper (Tringa sp.) eggs; the female, then in full wing molt, was captured on foot after helicopter pursuit (see Ellis and Markin 1991 for capture details). Data from System Argos revealed that all 3 birds remained on their territories through the summer. In mid- to late-August. all 3 moved west or southwest to the marshes immediately adjacent to the Ob River. They remained there about 1 month, then proc~eded south parallel to the Ob. One of the 2 males was still mobile when his transmitter went off the air in the Tyumen region 1,038 km from his summer home. The second male traveled 778 lan, but after 20 September his PTT remained stationary (backpack removed or crane dead) until 25 December when the last signal was received. During the last half of October, the female continued south-southwest through Kazakhstan, Uzbekistan, and Turkmenistan. Between 11 and 14 November, she arrived at her wintering area along the Hari River on the Afghan-Iranian border, 3,370 km from her summer home. She and her PTT remained active until the last reception on 23 February 1991. Because the PIT\u27s were programmed to transmit intermittently (to extend battery life), rates of travel are normally known only over periods of days or weeks. However, 1 male, monitored in flight over a 5-hour period, traveled 164 kID (33 kmlhr). The other male traveled 748 kID over a 4-d.ay period. Over a very long stage (1,900 km in 16 days) across Central Asia, the female averaged 116 km/day

Diluted Magnetic Semiconductors InFeSb Prepared by Laser Ablation: Spectroscopic and Microscopic Investigations

We report optical and magneto-optical results as well as atomic force microscopy (AFM) and magnetic force microscopy (MFM) results for InFeSb samples prepared by laser ablation. AFM and MFM studies have revealed the presence of magnetic particles on the samples surface, whose sizes depend on the Fe content and substrate temperature. It has found that both optical and magneto-optical spectra are superposition of spectra from the doped InFeSb layers and particles on their surface