We report that the 3d electron signal for the transition metals (Cr, Co, and Ni) and the NiAl-based alloys (NiAl, Ni
48Al
45Cr
7, and Ni
48Al
45Co
7) can be extracted by a two-detector coincidence ...system from the Doppler broadening of positron annihilation radiation. The experimental results show that the 3d electron signal for the undoped NiAl alloy is relatively low. The additions of Cr and Co to NiAl alloy lead to an increase in the probability of positron annihilation with 3d electrons. The 3d electron signal in the spectrum of Ni
48Al
45Co
7 alloy is higher than that of Ni
48Al
45Cr
7 alloy. The Co addition is more effective in enhancing the d–d interactions in NiAl alloy as compared with the Cr addition.
El metotrexato es un fármaco usado en el tratamiento de muchas enfermedades autoinmunes y autoinflamatorias. Sin embargo, ciertos eventos adversos se relacionaron con su administración, entre ellos ...laafectación mucocutánea.Presentamos el caso de un paciente con manifestaciones de toxicidad dermatológica secundaria a la ingestade metotrexato en forma diaria, sin indicación médica. Las lesiones respondieron a la suspensión de ladroga y al tratamiento sintomático. El paciente no presentó compromiso sistémico severo.
Positronium formation and escaping has been studied in porous silica thin films at temperature ranging from 13 to 300 K by 2-3 gamma ratio of positronium (3gamma-PAS) measurements. Nanoporous silica ...thin films were deposited by spin coating on p-type (1 0 0) Si substrates and thermal treated in air at temperatures of 600 deg C. Two different molar ratios of porogen (polyvinylpyrrolidone) were used in the TEOS-ethanol mixture to obtain samples with close porosity and connected porosity with the surfaces. In both types of sample a reduction of the 2-3 gamma ratio of positronium was observed by decreasing the temperature. This finding, in disagreement with the theoretical expectation, is discussed on the basis of the possible quenching mechanisms.
We compare the recent values of positron total cross sections in benzene, cyclohexane and aniline by Zecca et al. with our previous measurements Karwasz et al. Acta Phys. Pol. A, 107 (2005) 666 on ...the same apparatus. An apparent discrepancy disappears if Zecca's data are shifted by +0.2 eV; then their data can be approximated by the modified effective range theory, as well. This observation induced us to compare recent Trento data with other experiments and theories for polar targets, H2O and HCOOH. The evidence points out towards the need of a careful energy calibration in positron experiments.
Buried nanocavities at about 350 nm depth in Si were produced by thermal treatment of He implanted p-type (100) Si. The internal surfaces of the nanocavities were found free of impurity decorations ...by examining the high-momentum part of the Doppler-broadened positron annihilation spectra. Positron lifetime measurements with a pulsed slow positron beam show neither a short lifetime (125-150 ps) ascribable to parapositronium nor a longer lifetime (2-4 ns) ascribable to pick-off annihilation of orthopositronium. The lifetime of positrons trapped into nanocavities was found to be about 500 ps. The absence of positronium formation could be explained by an insufficient electron density and a lack of electron states in the band gap at the nanocavities internal surfaces produced in the p-type silicon.
Limb girdle muscular dystrophies (LGMD) are genetic heterogeneous disorders characterized by slow but progressive muscular impairment. Despite the recent identification of new genes, about 30% of ...these LGMDs remain without molecular diagnosis. However clinical-genetic correlations are fundamental for genetic counselling, definition of natural history and insight into pathogenesis. We collected detailed clinical, biochemical, histological and molecular data of 467 Italian LGMD patients, belonging to 8 neuromuscular Italian centres. Detailed data about neuromuscular, cardiological, respiratory involvement as far as molecular analysis and muscle biopsy were collected. Molecular analysis identified mutations in LGMD causative genes in 312 patients; 109 patients (23.1%) are still without a molecular diagnosis and 46 subjects (9.8%) carried heterozygous mutations in genes responsible for autosomal recessive forms. The relative frequency was as follows: 5.8% LGMD1B, 11.2% LGMD1C, 24.3% LGMD2A, 25.6% LGMD2B, 9.6% LGMD2I, 9.9% LGMD2D, 6.4% LGMD2E, 4.2% LGMD2C, 1.9% LGMD2L, 0.3% LGMD2F. Interestingly 1 LGMD patient (0.3%) carried mutations in ISPD and one patient in LAMA2 gene. Onset spans from the first decade to adulthood; LGMD2E being the most precocious (6.2 ± 5.3 years) and LGMD2L the latest (36.6 ± 7.1 years). Creatine-kinase values were generally increased, especially in sarcoglycanopathies, LGMD2B, LGMD1C. Cardiomyopathy was more frequent in LGMD1B (100%), LGMD2E (47%) and LGMD2I (50%) and restrictive pulmonary involvement in LGMD2I (53%) and LGMD2E (47%). About 30% of patients were wheelchair bound. The study of undiagnosed patients will potentially lead to identification of new LGMD causative genes. Overall this study defined the relative frequency of Italian LGMD and improved the knowledge about clinical, morphological and molecular spectrum as far as their natural history as far as the parameters that can better define the clinical evolution of these forms.
Grazing incidence X-rays diffraction (GI-XRD), X-rays reflectivity (XRR) and positron annihilation spectroscopy (PAS) analysis on Pd–Mg thin bilayer films deposited by electron-gun on Si wafer and ...glass substrate evidence a two-region structure: (i) a surface region consisting of the Pd capping layer, the Mg–Pd interface and some Mg subinterface layers; because of the interface roughness, in this region the deposited Mg layers are encased in Pd and, upon the metal to deuteride phase transition, they became highly compressed by the Pd capping layer; (ii) a second region consisting of a pure Mg layer, which extends up to the substrate. This two-region structure is stable upon repeated D
2 absorption and desorption cycles. PAS analysis reveals the formation of vacancy-like defects after D
2 desorption at a concentration higher than that of the as-deposited sample. The two-region structure and the defect dynamics observed in the present study can explain the presence of two peaks in the deuterium desorption spectrum and the diminished D
2 storage efficiency after the first D
2 absorption and desorption cycles.
A fiber detector to monitor ortho-Ps formation and decay Rienäcker, B.; Brusa, R.S.; Caravita, R. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2022, Letnik:
1027
Journal Article
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We describe a novel method to use a scintillating fiber detector similar to the Fast Annihilation Cryogenic Tracking (FACT) used at the antimatter experiment AEḡIS to monitor the presence of ...ortho-positronium. A single scintillating fiber was coupled to a photomultiplier tube and irradiated by flashes of about 6 × 106 gamma quanta with 511keV energy, produced by approximately 10ns long positron pulses. The results were used to demonstrate the ability to track the creation and annihilation of ortho-positronium atoms over time in cryogenic and highly magnetic environments by using the FACT detector as a “digital calorimeter”.
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