3,028 research outputs found
The pi -> pi pi process in nuclei and the restoration of chiral symmetry
The results of an extensive campaign of measurements of the pi -> pi pi
process in the nucleon and nuclei at intermediate energies are presented. The
measurements were motivated by the study of strong pi pi correlations in
nuclei. The analysis relies on the composite ratio C_{pi pi}^A, which accounts
for the clear effect of the nuclear medium on the (pi pi) system. The
comparison of the C_{pi pi}^A distributions for the (pi pi)_{I=J=0} and (pi
pi)_{I=0,J=2} systems to the model predictions indicates that the C_{pi pi}^A
behavior in proximity of the 2m_pi threshold is explainable through the partial
restoration of chiral symmetry in nuclei.Comment: accepted for publication in Nucl. Phys.
Deoxynivalenol content in italian organic durum wheat: Results of a six-year survey
Deoxynivalenol (DON) contamination was investigated of Italian durum wheat from organic agriculture. A number of 661 samples from 13 genotypes were collected within the national organic durum wheat network variety trials during the six-year period between 2007–2012 in five different growing areas across Italy (Northern Italy, Marches, Central Apennines, West-Central Italy, Apulia). Mean temperatures and total rainfalls in April, May and June were collected nearby the study sites. Average DON contamination value along the whole study period was 67 μg/kg, and DON was detected only in 36% of the samples. Noteworthy, 95% of the analyzed grain revealed a DON contamination lower than 334 μg/kg. Maximum allowed DON level for unprocessed durum wheat set by European Union (1750 μg/kg) was exceeded only in four samples (0.6%). The highest mean DON values were detected in Northern Italy (175 μg/kg) and Marches (131 μg/kg). The same was for the percentage of positive samples (80% and 58%, respectively). Lower mean values and percentages of contaminated samples were found in West-Central Italy (22 μg/kg and 29%, respectively), Apennines (3 μg/kg and 8%, respectively) and Apulia (2 μg/kg and 7%, respectively). Statistical analysis (Generalized Linear Model, GLZ) was carried out to highlight the effect of factors like cultivation year, growing area and genotype. It revealed a huge effect of year, growing areas and their interaction, while the effect of genotype resulted significantly but quite less than the other main factors. The effect of the year could be explained by climatic data, which suggested an influence of rainfall and temperature at heading on both DON concentration values and percentage of contaminated samples. Results of this study put in evidence a low DON contamination in Italian organic durum wheat
Nef does not contribute to replication differences between R5 pre-AIDS and AIDS HIV-1 clones from patient ACH142
AIDS-associated, CCR5-tropic (R5) HIV-1 clones, isolated from a patient that never developed CXCR4-tropic HIV-1, replicate to a greater extent and cause greater cytopathic effects than R5 HIV-1 clones isolated before the onset of AIDS. Previously, we showed that HIV-1 Env substantially contributed to the enhanced replication of an AIDS clone. In order to determine if Nef makes a similar contribution, we cloned and phenotypically analyzed nef genes from a series of patient ACH142 derived R5 HIV-1 clones. The AIDS-associated Nef contains a series of residues found in Nef proteins from progressors [1]. In contrast to other reports [1-3], this AIDS-associated Nef downmodulated MHC-I to a greater extent and CD4 less than pre-AIDS Nef proteins. Additionally, all Nef proteins enhanced infectivity similarly in a single round of replication. Combined with our previous study, these data show that evolution of the HIV-1 env gene, but not the nef gene, within patient ACH142 significantly contributed to the enhanced replication and cytopathic effects of the AIDS-associated R5 HIV-1 clone
The interaction in nuclear matter from a study of the reactions
The pion-production reactions were studied on
, , , and nuclei at an incident pion energy
of =283 MeV. Pions were detected in coincidence using the CHAOS
spectrometer. The experimental results are reduced to differential cross
sections and compared to both theoretical predictions and the reaction phase
space. The composite ratio between the
invariant masses on nuclei and on the nucleon is also presented. Near the
threshold pion pairs couple to when produced in
the reaction channel. There is a marked near-threshold
enhancement of which is consistent with theoretical
predictions addressing the partial restoration of chiral symmetry in nuclear
matter. Furthermore, the behaviour of is well
described when the restoration of chiral symmetry is combined with standard
P-wave renormalization of pions in nuclear matter. On the other hand, nuclear
matter only weakly influences , which displays a flat
behaviour throughout the energy range regardless of .Comment: 30 pages, 16 figures, PS format, accepted for publication in Nucl.
Phys
Mass discrimination using double-sided silicon microstrip detectors for pions and protons at intermediate energies
Prototype silicon detector modules for the vertex detector of the FINUDA experiment were tested at TRIUMF using pions and protons at 270 and 408 MeV/c in order to study their use for mass discrimination based on energy deposition. The detector modules were constructed using double-sided silicon detectors based on the ALEPH design, read out by VA1 integrated circuits. The test modules and apparatus are described, details of the data analysis are discussed, and the results are presented together with GEANT simulations. Particular attention is given to the detector response for the various particles, with signals ranging from the minimum-ionising pions at 408 MeV/c up to 20 times minimum-ionising for the protons at 270 MeV/c. ( 1999 Elsevier Science B.V. All rights reserved
Industrial Ceramics: From Waste to New Resources for Eco-Sustainable Building Materials
Today, the need to dispose of a huge amount of ceramic industrial waste represents an important problem for production plants. Contextually, it is increasingly difficult to retrieve new mineral resources for the realization of building materials. Reusing ceramic industrial waste as precursors for building blocks/binders, exploiting their aluminosilicate composition for an alkaline activation process, could solve the problem. This chemical process facilitates the consolidation of new binders/blocks without thermal treatments and with less CO2 emissions if compared with traditional cements/ceramics. The alkali-activated materials (AAMs) are today thought as the materials of the future, eco-sustainable and technically advanced. In this study, six different kind of industrial ceramic waste are compared in their chemical and mineralogical composition, together with their thermal behaviour, reactivity in an alkaline environment and surface area characteristics, with the aim of converting them from waste into new resources. Preliminary tests of AAM synthesis by using 80%–100% of ceramic waste as a precursor show promising results. Workability, porosity and mechanical strengths in particular are measured, showing as, notwithstanding the presence of carbonate components, consolidated materials are obtained, with similar results. The main factors which affect the characteristics of the synthetized AAMs are the precursors’ granulometry, curing temperature and the proportions of the activating solutions
First determination of the one-proton induced Non-Mesonic Weak Decay width of p-shell {\Lambda}-Hypernuclei
Previous studies of proton and neutron spectra from Non-Mesonic Weak Decay of
eight Lambda-Hypernuclei (A = 5-16) have been revisited. New values of the
ratio of the two-nucleon and the one-proton induced decay widths,
Gamma_2N/Gamma_p, are obtained from single proton spectra, Gamma_2N/Gamma_p =
0.50 +/- 0.24, and from neutron and proton coincidence spectra,
Gamma_2N/Gamma_p = 0.36 +/- 0.14stat +0.05sys -0.04sys , in full agreement with
previously published ones. With these values, a method is developed to extract
the one-proton induced decay width in units of the free Lambda decay width,
Gamma_p/Gamma_Lambda, without resorting to Intra Nuclear Cascade models but by
exploiting only experimental data, under the assumption of a linear dependence
on A of the Final State Interaction contribution. This is the first systematic
determination ever done and it agrees within the errors with recent theoretical
calculations.Comment: 16 pages, 3 figures, 2 table
emission rates in absorptions at rest on Li, Li, Be, C and O
An experimental study of the reaction
on Li, Li, Be, C and O -shell nuclei is
presented. The data were collected by the FINUDA spectrometer operating at the
DANE -factory (LNF-INFN, Italy). Emission rates for the reaction in
the mentioned nuclei are measured and compared with the few existing data. The
spectra of several observables are discussed; indications of Quasi-Free
absorptions by a pair embedded in the nucleus can be obtained from
the study of the missing mass distributions.Comment: Version accepted by PR
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