1,721,018 research outputs found
A COMPACT ALGORITHM FOR THE IMPLEMENTATION OF MONTE CARLO KINEMATICS IN COMPUTER SIMULATIONS OF D-DIMENSIONAL LATTICE GAUGE THEORIES
No full textWe describe a compact, optimized algorithm for analyzing the mutual geometric relations between links and elementary squares in a d-dimensional lattice. The algorithm is used to compute plaquettes in Monte Carlo simulations of gauge field dynamics. In such kind of applications our algorithm, due to its recursive nature, allows one to compute all the plaquettes in a model by means of a technique which is the same for any number of dimensions d. Finally, we indicate how the actual Fortran implementation would be made
A global model study of sulphate and black carbon aerosol perturbations due to aviation emissions and impact on ozone: a EC-REACT4C study,
No full textThe University of L’Aquila climate-chemistry model (ULAQ-CCM) is a global
coupled model including troposphere and stratosphere and a rather comprehensive aerosol module.
The validation of aerosol products from the ULAQ model has focused on surface aerosol mass
density on remote sites, total optical depth on a regional basis, aerosol extinction profiles using
SAGE-II and HALOE data and black carbon (BC) vertical profiles using recent aircraft campaign
data. Three numerical experiments were performed with the ULAQ model using emission
inventories from the collaborative European project EC-REACT4C: no aircraft emissions (EXP1),
NOx and H2O emissions only (EXP2), and including all gas and particle emissions (EXP3). These
experiments have the purpose to study the direct radiative forcing (RF) of sulphate and BC aerosols
and to study the indirect impact on the NOx-HNO3 balance (and hence on O3) via heterogeneneous
chemistry on the surface of sulphate particles. The ULAQ-CCM calculated changes of sulphuric
acid aerosol surface area density reach maximum values of 1.5 μm2/cm3 at about 10 km altitude in
the NH mid-latitudes. Aircraft emissions of BC particles may significantly affect the mass density
of carbonaceous aerosols (0.3 ng/m3 at the same location). One conclusion is that the impact of
aviation SO2 and freshly emitted ultrafine sulphuric acid aerosols is to reduce the net RF
associated to aviation emissions of NOx (i.e. O3 and CH4), H2O and sulphur from 4.5 mW/m2 to 3.1
mW/m2, via changes of heterogeneous chemistry and cooling due to additional or larger sulphate
particles
Immunological characterization of Respiratory Syncytial Virus N protein epitopes recognized by human cytotoxic T lymphocytes
No full textVirus-specific cytotoxic T lymphocytes (CTLs) are crucial for the control of respiratory syncytial virus (RSV) infection. This study has identified CTL epitopes of the RSV N protein in healthy subjects. We screened the primary structure of the N protein for HLA-A(*)0201-binding amino acid consensus motifs, identifying three peptides designated as N-RSV1, N-RSV2, and N-RSV3. These peptides were used to generate CTL lines by stimulating human HLA-A(*)02.01 peripheral blood mononuclear cells (PBMCs) in vitro. These CTL lines were then characterized by performing CTL chromium release assays and IFN-γ secretion detection by intracellular cytokine staining. N-RSV1 and N-RSV3 peptides elicited the strongest cytolytic activity against RSV-infected cells and they could be useful epitopes for the analysis of CTL responses to RSV and for understanding immune-induced disease pathogenesis. © 2007 Mary Ann Liebert, Inc
Humoral immunity to Respiratory Syncytial Virus in young and elderly adults
No full textRespiratory syncytial virus (RSV) has been demonstrated to cause substantial disease in elderly and immunocompromised subjects. The relationship of serum antibody to RSV infection and the risk of infection in elderly subjects is controversial, thus we evaluated the presence of neutralizing antibodies to RSV in healthy people of different age groups and the correlation with viral protection. Baseline blood samples from 197 subjects aged 20-80 years were analysed for the presence of anti-RSV antibodies either by indirect immunofluorescence and microneutralization test. The percentage of people who had neutralizing antibodies to RSV was significantly higher (P=0.001) in the youngest group (92.51%) compared to the frail group (36.21%). The RSV antibody level tends to wane in some older people; this factor could determine proneness to RSV re-infections in the elderly who are at a greater risk of developing severe respiratory disease
Stratospheric circulation changes due to major volcanic eruptions: impact on long-lived species transport and age of air
No full textLarge explosive volcanic eruptions are capable of injecting considerable amounts of particles and sulphur gases above the tropopause, causing increases in stratospheric aerosol optical depth even larger than one order of magnitude. Perturbations of stratospheric tracer species transport result from dynamical changes due to both local stratospheric heating and climate changes associated to the increasing scattering of incoming solar radiation by the volcanic aerosols. Summarizing, the dynamical perturbation of the volcanic aerosols is twofold: (a) the stratospheric mean meridional circulation is affected by local aerosol radiative heating and photo-chemically induced ozone changes; (b) the planetary wave propagation in the mid- to high-latitude lower stratosphere is altered as a consequence of perturbed atmospheric stability due to the climate perturbation. The additional heating rates produce a local temperature increase in the lower stratosphere and upset the stratospheric dynamics, since no radiative equilibrium is achieved. For tropical eruptions an additional residual upwelling motion is produced in the tropical stratosphere as a result of a stronger pole-to-equator gradient of net heating rates.
The radiatively forced changes of the stratospheric circulation during the first two years after the eruption of Mt. Pinatubo (June 1991) may help explain the observed trend decline of long-lived greenhouse gases (CH4 in particular), as a result of the increased mid- to high-latitude downward flux at the tropopause. Since the stratosphere contains lower methane mixing ratios, a decline in the observed trends could result from a higher degree of exchange between the stratosphere and the troposphere. Results from the ULAQ-CCM model, using an updated version with respect to the one that has participated to the CCMVal-1 and CCMVal-2 inter-comparison campaigns, are shown for long-lived species perturbations due to volcanic eruptions and also for the stratospheric age-of-air. This type of analysis is made by comparing the results of two model simulations of the ULAQ-CCM: a reference case (1960-2010) with no volcanic heating perturbations and a sensitivity experiment where Agung, El Chichon and Pinatubo eruptions have been included
Multi-model estimate of direct and indirect radiative impact of aviation aerosols
No full textAircraft emissions may perturb the global amount and the size distribution of atmospheric aerosols in two ways: (a) direct emission of ultrafine black carbon (BC) soot and sulphuric acid particles in aircraft plumes and (b) release of gas phase SO2, later dispersed on large atmospheric scales and oxidized in H2SO4 by the OH radical. Direct particle emissions are estimated to account for 4–15% of the overall aircraft emitted sulphur. These direct particle emissions do not significantly change aerosol mass and extinction but may substantially increase surface area density (SAD) in the Northern Hemisphere UTLS. Release of gas phase SO2, on the other hand, may increase the net production of H2SO4, thus enhancing the sulphate mass in the accumulation mode and consequently, the direct RF. It also may increase the gas phase contribution to SAD, in the range of 25% of the change produced by direct plume particle emission. The University of L’Aquila climate-chemistry coupled model (ULAQ-CCM) has calculated the accumulation of sulphate aerosols and BC and their globally averaged direct radiative forcing (RF) at the NCEP tropopause with temperature adjustment and in total sky conditions, i.e. -3.3 W/m2 and +1.1 W/m2, respectively (with forcing efficiencies of -140 W/g-SO4 and +2300 W/g-BC, respectively).
The increase of BC in the upper troposphere due to aviation emissions may trigger formation of ice cloud particles (i.e. aviation ‘soot-cirrus’). The formation of background upper tropospheric ice particles is produced by homogeneous and heterogeneous freezing of supercooled aerosols. The ULAQ-CCM considers the basic physical processes that eventually determine the number of ice crystals Ni forming during an adiabatic ascent, including the link of Ni on temperature and updraft speed. In normal conditions the homogeneous freezing mechanisms dominates, but under significant local emissions of BC from aircraft the competition of heterogeneous and homogeneous freezing mechanisms becomes important. In the parameterization used for the formation of aviation soot-cirrus particles in a model grid-box, the change of ice crystals number concentration ∆Ni-HET is calculated as a function of ∆NBC and PHET, where ∆NBC is the change of soot particles due to aviation emissions, assuming a 1% non-hydrophobic fraction of the particles that may act as ice nuclei. PHET, in turn, is the probability that heterogeneous freezing may occur at given grid-box in the model, calculated as the probability to have ice super-saturation for a given temperature (RHICE › 100%) and taking into account water vapour transport due to subgrid vertical updraft velocity. The ULAQ-CCM calculates a +4.9 W/m2 indirect RF of BC, through formation of soot-cirrus (with forcing efficiency of +5 W/g-ice). Uncertainties in this model calculation of soot cirrus RF are however rather large.
The feedback of aviation-produced sulphate aerosol SAD on heterogeneous NOx chemistry represents another significant indirect radiative impact of aviation aerosols, via O3 and CH4 changes produced by the aerosol induced NOx perturbation. Here the physical and chemical approaches and the final calculations are much more robust than for upper tropospheric ice. In this case the results of the University of Oslo models (i.e. UiO-CTM2 and UiO-CTM3) have been used together with those from the ULAQ-CCM used in CTM mode, with the following results: -0.8 ± 0.2 W/m2 and +0.5 ± 0.1 W/m2, for O3 and CH4, respectively, where the error bar is obtained from the three models dispersion. The net aviation-aerosol RF calculated in this study accounts to -2.2 W/m2 (direct) and +4.6 W/m2 (indirect, including soot-cirrus) or -0.3 W/m2 (indirect, not including soot-cirrus), that is (in total) +2.4 W/m2 (including soot-cirrus) or -2.5 W/m2 (not including soot-cirrus). Taking into account that the non-CO2 aviation RF of gas species as calculated in the ULAQ-CCM (i.e. O3 and CH4 from aviation NOx changes and stratospheric H2O) accounts to +9.0 W/m2, the net aerosol impact represents a relative correction of the radiative forcing equal to +27% (including soot-cirrus) and -28% (not including soot-cirrus)
Sensitivity of the Methane Lifetime to Sulfate Geoengineering: Results from the Geoengineering Model Intercomparison Project (GeoMIP)
No full textSulfate geoengineering, made by sustained injection of SO2 in the tropical lower stratosphere, may impact the abundance of tropospheric methane through several photochemical mechanisms affecting the tropospheric OH abundance and hence the methane lifetime. Geoengineered sulfate aerosols in the stratosphere are responsible of important radiative and chemical effects: (a) solar radiation scattering increases the planetary albedo and cools the surface, with a tropospheric water vapor decrease as a response to this cooling: less OH. (b) The tropospheric UV budget is upset by the additional aerosol scattering and stratospheric ozone changes: the net effect is meridionally not uniform, with a net decrease in the tropics, thus producing less tropospheric O(1D): less OH. (c) The extratropical downwelling motion from the lower stratosphere tends to increase the sulfate aerosol surface area density available for heterogeneous chemical reactions in the mid-upper troposphere, thus reducing the amount of NOx and tropospheric O3 production: less OH. (d) The tropical lower stratosphere is warmed by solar and planetary radiation absorption by the aerosols. The heating rates perturbation are strongly latitude dependent, producing a significant change of the pole-to-equator temperature gradient and mean zonal wind distribution, with a net increase of tropical upwelling. A stronger meridional component of the Brewer-Dobson circulation may affect the abundance of mid-upper tropospheric sulfate aerosols, NOy, and O3 (all possibly affecting the budget of tropospheric OH), as well as CH4 transport directly. Three climate-chemistry coupled models are used here to explore the above radiative, chemical and dynamical mechanisms affecting the methane lifetime (ULAQ-CCM, CCSM4, GEOSCCM). First results show that the CH4 lifetime may become significantly longer (Fig.1) with a sustained injection of 2.5 Tg-S/yr started in year 2020 (exp. G4), which implies an increase of tropospheric CH4 (Fig. 2) and a positive indirect RF of sulfate geoengineering due to CH4 changes, of the order of 10% the aerosols direct forcing, but with opposite sign
Efficient delivery of DNA to dendritic cells mediated by influenza virosomes
No full textIn an attempt to enhance the immunological efficacy of DNA-based vaccines, we have investigated a new biological means for delivering target gene DNA directly to professional antigen presenting cells (APC), such as the dendritic cells (DC), which are ultimately responsible for the antigen presentation and the primary activation of the immune system. For this purpose we investigated influenza virosomes (IRIV) with assembled DNA as a possible biological carrier for targeting the APC in vivo and in vitro. By cytofluorimetric analysis of the draining lymph nodes of Balb/c mice which had received (by intranasal (in.) administration) FITC-labeled DNA assembled with IRIV, we detected a significant labeled DNA uptake in a subset of lymph node deriving cells expressing DC surface markers. Subsequent mRNA analysis of these lymph nodes showed that the trans-gene delivered by the virosomes was effectively expressed as mRNA. Finally, a further cytofluorimetric analysis performed on human DC-enriched-PMBC, infected in vitro with labeled DNA/IRIV lead to the conclusion that the majority of APC (DC, B lymphocytes and CD16+ cells) are able to incorporate the labeled DNA transported by the construct. These findings suggest that the virosome is an efficient delivery system for testing infectious, as well as anti-cancer, DNA-based vaccine research. © 2003 Elsevier Ltd. All rights reserved
Sulfate aerosols from non-explosive volcanoes: chemical-radiative effects in the troposphere and lower stratosphere
Full text linkImmunosuppressive monoclonal antibody to CD64 from patients with long-term stable multiple sclerosis
No full textHigh intrathecal levels of anti-myelin basic protein (MBP) IgM were previously found to be significantly associated with early favorable course in a cohort of patients with multiple sclerosis (MS). A mAb to MBP 105-120 recognizing the 222-228 epitope of the extracellular domain of high affinity immunoglobulin gamma Fc-receptor I (CD64) was isolated from EBV(+) B cell clones of long-term stable RRMS patients. This mAb exerted immunosuppressive activity on MS-derived T cell lines through induction and release of high amounts of interleukin-10 and decreased levels of interleukin-12 from activated monocytes providing the biological basis for a potential new treatment for MS and other immune-mediated neurological disorders
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