Equivalent dose in quartz from young samples using the SAR protocol and the effect of preheat temperature

Abstract Major concerns in the dating of samples younger than a few hundred years by the optically stimulated luminescence (OSL) technique are thermal transfer and partial bleaching. Thermal transfer during preheating enhances the OSL signal due to the charge transfer from thermally sensitive, but light-insensitive, traps to optical centres of quartz and results in an overestimate in equivalent dose, especially for very young samples. In this study, the single-aliquot regenerative-dose protocol is used to obtain values of equivalent dose (D e ) from young samples taken from various environments around Istanbul. Within this framework, we aim to investigate the effect of preheat temperature on equivalent dose from 150 to 300 • C, the reproducibility of D e measurements for young deposits and the contribution from thermal transfer of charge to the equivalent dose estimation. It was observed that the measured dose is influenced significantly by preheat temperature and the increase in the D e is clearly due to thermal transfer of charge from deep thermally sensitive traps to OSL trap during preheating of the samples prior to the main OSL measurements

Effects of crack tip geometry on dislocation emission and cleavage: A possible path to enhanced ductility

We present a systematic study of the effect of crack blunting on subsequent crack propagation and dislocation emission. We show that the stress intensity factor required to propagate the crack is increased as the crack is blunted by up to thirteen atomic layers, but only by a relatively modest amount for a crack with a sharp 60$^\circ$ corner. The effect of the blunting is far less than would be expected from a smoothly blunted crack; the sharp corners preserve the stress concentration, reducing the effect of the blunting. However, for some material parameters blunting changes the preferred deformation mode from brittle cleavage to dislocation emission. In such materials, the absorption of preexisting dislocations by the crack tip can cause the crack tip to be locally arrested, causing a significant increase in the microscopic toughness of the crack tip. Continuum plasticity models have shown that even a moderate increase in the microscopic toughness can lead to an increase in the macroscopic fracture toughness of the material by several orders of magnitude. We thus propose an atomic-scale mechanism at the crack tip, that ultimately may lead to a high fracture toughness in some materials where a sharp crack would seem to be able to propagate in a brittle manner. Results for blunt cracks loaded in mode II are also presented.Comment: 12 pages, REVTeX using epsfig.sty. 13 PostScript figures. Final version to appear in Phys. Rev. B. Main changes: Discussion slightly shortened, one figure remove

Effect of crotamine, a cell-penetrating peptide, on blastocyst production and gene expression of in vitro fertilized bovine embryos.

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Local density of states in the vortex lattice in a type II superconductor

Local density of states (LDOS) in the triangular vortex lattice is investigated based on the quasi-classical Eilenberger theory. We consider the case of an isotropic s-wave superconductor with the material parameter appropriate to NbSe_2. At a weak magnetic field, the spatial variation of the LDOS shows cylindrical structure around a vortex core. On the other hand, at a high field where the core regions substantially overlap each other, the LDOS is sixfold star-shaped structure due to the vortex lattice effect. The orientation of the star coincides with the experimental data of the scanning tunneling microscopy. That is, the ray of the star extends toward the nearest-neighbor (next nearest-neighbor) vortex direction at higher (lower) energy.Comment: 10 pages, RevTex, 32 figure

Molecular Characterization of a Strawberry FaASR Gene in Relation to Fruit Ripening

BACKGROUND: ABA-, stress- and ripening-induced (ASR) proteins have been reported to act as a downstream component involved in ABA signal transduction. Although much attention has been paid to the roles of ASR in plant development and stress responses, the mechanisms by which ABA regulate fruit ripening at the molecular level are not fully understood. In the present work, a strawberry ASR gene was isolated and characterized (FaASR), and a polyclonal antibody against FaASR protein was prepared. Furthermore, the effects of ABA, applied to two different developmental stages of strawberry, on fruit ripening and the expression of FaASR at transcriptional and translational levels were investigated. METHODOLOGY/PRINCIPAL FINDINGS: FaASR, localized in the cytoplasm and nucleus, contained 193 amino acids and shared common features with other plant ASRs. It also functioned as a transcriptional activator in yeast with trans-activation activity in the N-terminus. During strawberry fruit development, endogenous ABA content, levels of FaASR mRNA and protein increased significantly at the initiation of ripening at a white (W) fruit developmental stage. More importantly, application of exogenous ABA to large green (LG) fruit and W fruit markedly increased endogenous ABA content, accelerated fruit ripening, and greatly enhanced the expression of FaASR transcripts and the accumulation of FaASR protein simultaneously. CONCLUSIONS: These results indicate that FaASR may be involved in strawberry fruit ripening. The observed increase in endogenous ABA content, and enhanced FaASR expression at transcriptional and translational levels in response to ABA treatment might partially contribute to the acceleration of strawberry fruit ripening

Identification of epidemic “flavescence dorée” molecular variants in Emilia-Romagna and Veneto regions

The study of the genetic variability of phytoplasmas is a fundamental tool to clarify their epidemiology and to implement an effective monitoring and management of their associated diseases. “Flavescence dorée” (FD), a threatening disease of grapevine associated to phytoplasmas, is distributed within the most important European wine-producing areas, and has severe effects on both vineyard productivity and landscape management. FD is a quarantine disease in Europe, mainly transmitted by the ampelophagous leafhopper Scaphoideus titanus and, despite the efforts to contain the pathogen dissemination, the disease is still epidemic in several viticultural areas of Northern Italy. Based on sequence and restriction fragment length polymorphism (RFLP) analysis of the 16S rRNA gene two FD ribosomal groups were described as present in Italy during the last century: 16SrV-C and 16SrV-D. However, the sequencing of non-ribosomal loci, such as secY, map and rpsC, allowed the identification over the years of several variants within the FD phytoplasma populations. A multilocus analysis approach was carried out on symptomatic FD-infected samples collected in Emilia-Romagna and Veneto regions, in different areas where the disease is spreading in the last 2-3 years. The geographic distribution of the two strains was confirmed to be different, with areas (Treviso province) with the prevalence of FD-C and others (Verona and Modena provinces) with only FD-D strains presence. Interestingly, FD-D phytoplasmas were identified for the first time also in a vineyard located in Modigliana (Forlì-Cesena province) and surrounded by forests. The molecular analyses allowed the identification of genetic variants among FD-D populations in both regions, that is quite a novel finding for these phytoplasmas that showed since their first identification in 1996 very little variability. In particular, the sequencing of secY amplicons highlighted the presence of the same SNP variation in samples of cultivars Teroldego and Trebbiano collected in Verona province and in grapevines cv Sangiovese located in Modigliana (Forlì-Cesena province). On the other hand, among FD-C phytoplasma strains, the highest variability was shown on rpsC gene, that highlighted 5 restriction profiles after RFLP analyses on samples cv Glera collected in Treviso and Belluno provinces. These findings suggest that the epidemiology of the disease is still to be monitored and is now involving different vectors/plant hosts species that are very likely responsible for the emergence of these FD variants. Therefore, a continuous and capillary monitoring of the FD strains associated with disease on the areas where it is present is necessary for application of the most appropriate and stringent controlling measures aimed to avoid the epidemic spreading of these emerging pathogenic variant strains