Cosmic-Ray Positrons: Are There Primary Sources?

Cosmic rays at the Earth include a secondary component originating in collisions of primary particles with the diffuse interstellar gas. The secondary cosmic rays are relatively rare but carry important information on the Galactic propagation of the primary particles. The secondary component includes a small fraction of antimatter particles, positrons and antiprotons. In addition, positrons and antiprotons may also come from unusual sources and possibly provide insight into new physics. For instance, the annihilation of heavy supersymmetric dark matter particles within the Galactic halo could lead to positrons or antiprotons with distinctive energy signatures. With the High-Energy Antimatter Telescope (HEAT) balloon-borne instrument, we have measured the abundances of positrons and electrons at energies between 1 and 50 GeV. The data suggest that indeed a small additional antimatter component may be present that cannot be explained by a purely secondary production mechanism. Here we describe the signature of the effect and discuss its possible origin.Comment: 15 pages, Latex, epsfig and aasms4 macros required, to appear in Astroparticle Physics (1999

A study of the ultrahigh-energy cosmic ray mass composition with the MACRO and EAS-TOP experiments

Two components of cosmic-ray-induced air showers are measured simultaneously at the Gran Sasso Laboratory: the electromagnetic shower at the ground surface by the EAS-TOP extensive air shower array, and the deep-underground muons by the MACRO experiment. The two independent data sets collected during 96.3 days of simultaneous running are combined, and underground muon multiplicity distributions are obtained for anticoincident events (no surface trigger) and high-energy, coincident events. These categories correspond to ranges in primary energy from about 2 x 10^3 GeV to a few times 10^5 GeV, and from about 1.5 x 10^5 GeV to about 10^7 GeV, respectively. The experimental shower size and muon multiplicity distributions, as well as the distribution of mean muon multiplicity as a function of shower size (N_µ - log(N_e) relation), are compared to the ones obtained with detailed Monte Carlo calculations (with a generator based on recent hadronic accelerator data) using various trial compositions as input. This is done in an effort to discriminate between these models of primary cosmic-ray mass composition at and above the "knee" in the all-particle spectrum, where contradictory experimental evidence exists and where a knowledge of the composition would bear upon possible mechanisms for cosmic-ray acceleration and propagation. Detailed studies of simulated anticoincident event rates (which arise from a region of primary energy where the composition has been measured directly by satellite and balloon experiments) uncover problems with the generator used, with between 25 and 40% too few high-energy muons created. This, combined with the dependence of absolute event rates on the assumed differential primary energy spectra, hampers the interpretation in terms of composition of underground muon or surface air shower data taken separately. However, the (N_µ - log(N_e)relation is independent of the spectra or overall Monte Carlo normalization problems. The simulated (N_µ - log(N_e) relation for coincident events is found to be inconsistent with the possibility that the cosmic ray flux becomes proton-dominated at and above the knee.</p

Overview of Numerical Simulation of Solid-State Anaerobic Digestion Considering Hydrodynamic Behaviors, Phenomena of Transfer, Biochemical Kinetics and Statistical Approaches

Anaerobic digestion (AD) is a promising way to produce renewable energy. The solid-state anaerobic digestion (SSAD) with a dry matter content more than 15% in the reactors is seeing its increasing potential in biogas plant deployment. The relevant processes involve multiple of evolving chemical and physical phenomena that are not crucial to conventional liquid-state anaerobic digestion processes (LSAD). A good simulation of SSAD is of great importance to better control and operate the reactors. The modeling of SSAD reactors could be realized either by theoretical or statistical approaches. Both have been studied to a certain extent but are still not sound. This paper introduces the existing mathematical tools for SSAD simulation using theoretical, empirical and advanced statistical approaches and gives a critical review on each type of model. The issues of parameter identifiability, preference of modeling approaches, multiscale simulations, sensibility analysis, particularity of SSAD operations and global lack of knowledge in SSAD media evolution were discussed. The authors call for a stronger collaboration of multidisciplinary research in order to further developing the numeric simulation tools for SSAD

Overview of Numerical Simulation of Solid-State Anaerobic Digestion Considering Hydrodynamic Behaviors, Phenomena of Transfer, Biochemical Kinetics and Statistical Approaches

International audienceAnaerobic digestion (AD) is a promising way to produce renewable energy. The solid-state anaerobic digestion (SSAD) with a dry matter content more than 15% in the reactors is seeing its increasing potential in biogas plant deployment. The relevant processes involve multiple of evolving chemical and physical phenomena that are not crucial to conventional liquid-state anaerobic digestion processes (LSAD). A good simulation of SSAD is of great importance to better control and operate the reactors. The modeling of SSAD reactors could be realized either by theoretical or statistical approaches. Both have been studied to a certain extent but are still not sound. This paper introduces the existing mathematical tools for SSAD simulation using theoretical, empirical and advanced statistical approaches and gives a critical review on each type of model. The issues of parameter identifiability, preference of modeling approaches, multiscale simulations, sensibility analysis, particularity of SSAD operations and global lack of knowledge in SSAD media evolution were discussed. The authors call for a stronger collaboration of multidisciplinary research in order to further developing the numeric simulation tools for SSAD

Novel approaches to modeling dry anaerobic digestion by considering water porosity evolution

International audienceOur previous findings revealed the distribution and evolution of three different pore water porosity types (microscopic, mesoscopic and macroscopic porosities) during dry anaerobic digestion (D-AD). Two novel and different models considering this phenomenon were developed. The first one combined the AM2 biochemical model with saturated Mobile-Immobile water model (AM2-MIM). The model considered the interactions of mass transfer between mobile phase (macroporosity) and immobile phase (microporosity + mesoporosity). The second model coupled this new model with a biofilm diffusion model to consider separately microporosity and mesoporosity (AM2-MIM+Biofilm), simulating the diffusion and the transformation of hydrolyzed substrates within the biofilm (mesoporosity). Both models allow a better understanding of the microbiological and hydrodynamic phenomena during D-AD processes

Novel approaches to modeling dry anaerobic digestion by considering water porosity evolution

International audienceOur previous findings revealed the distribution and evolution of three different pore water porosity types (microscopic, mesoscopic and macroscopic porosities) during dry anaerobic digestion (D-AD). Two novel and different models considering this phenomenon were developed. The first one combined the AM2 biochemical model with saturated Mobile-Immobile water model (AM2-MIM). The model considered the interactions of mass transfer between mobile phase (macroporosity) and immobile phase (microporosity + mesoporosity). The second model coupled this new model with a biofilm diffusion model to consider separately microporosity and mesoporosity (AM2-MIM+Biofilm), simulating the diffusion and the transformation of hydrolyzed substrates within the biofilm (mesoporosity). Both models allow a better understanding of the microbiological and hydrodynamic phenomena during D-AD processes

New immobilization method of anti-PepD monoclonal antibodies for the detection of Listeria monocytogenes p60 protein – Part A: Optimization of a crosslinked film support based on chitosan and cellulose nanocrystals (CNC)

International audienceThis paper presents the development of a support membrane based on chitosan, cellulose nanocrystals and glycerol (m-CCG) for the antibody immobilization by a covalent crosslinking using glutaraldehyde. The chemical characterization of the support by FTIR showed that m-CCG formation process was stabilized by the formation of hydrogen bonding between each component of m-CCG and the reactive amine groups allowing the antibody immobilization on m-CCG via glutaraldehyde. Moreover, this immobilization on m-CCG was optimized by mathematics modeling approaches, and it exhibited robustness and predictable detection in presence of 0.6% of cellulose nanocrystals (CNCs), 0.5 g of CCG solution per well, after 2 h of antibody immobilization. Results also showed that CNCs (0.6% w/v) was the most important factor of the optimization. At this concentration, CNCs improve the resistance of m-CCG during the crosslinking treatment by a modification of the surface topography and the reinforcement of the tensile strength of m-CCG at >30%

Interactions between below‐ground traits and rhizosheath fungal and bacterial communities for phosphorus acquisition

International audienc