Rapid purification of grapevine RNA by a simple electrophoretic method

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Experimental determination of the 3^3He(α\alpha,γ\gamma)7^7Be reaction cross section above the 7^7Be proton separation threshold

The $^3$He($\alpha$,$\gamma$)$^7$Be reaction plays a major role both in the BBN producing the majority of the primordial $^7$Li, and in the pp-chain, where it is the branching point. As a few-nucleon system, this reaction is often used to validate ab-initio theoretical calculations and/or test R-matrix theory and code implementations. For the latter, experimental data in an extended energy range is of crucial importance to test the fit and extrapolation capabilities of the different codes. The $^3$He($\alpha$,$\gamma$)$^7$Be reaction cross section has been measured by several groups up to the first resonance ($E_{c.m.} \approx 3$ MeV) in the reaction. However, only one dataset exists above the $^7$Be proton separation threshold measured in a narrow energy range ($E_{c.m.} = 4.0-4.4$ MeV). In this work we extend the available experimental capture cross section database to the energy range of known $^7$Be levels. The activation method was used. The experiment was performed using a thin-window gas cell with two high-purity Al foils as entrance and exit windows. The activity of the $^7$Be nuclei implanted in the exit/catcher foil was measured by detecting the yield of the emitted $\gamma$~rays using shielded high-purity germanium detectors. New experimental $^3$He($\alpha$,$\gamma$)$^7$Be reaction cross section data were obtained for the first time in the $E_{c.m.}=4.3-8.3$ MeV energy region. The new dataset with about 0.2 MeV step covers the energy range of known levels and particle separation thresholds. No prominent structures are observer around the $^7$Be levels. The reaction cross section is slowly increasing with increasing energy. Above the $^6$Li$+p_1$ threshold, a decrease starts in the cross section trend. The overall structure of the cross section suggest a broad resonance peaking around $E_x=7.5$ MeV $^7$Be excitation energy, with a width of 8 MeV.Comment: Accepted for publication in PR

Activity of 50 Long-Period Comets Beyond 5.2 AU

Remote investigations of the ancient solar system matter has been traditionally carried out through the observations of long-period (LP) comets that are less affected by solar irradiation than the short-period counterparts orbiting much closer to the Sun. Here we summarize the results of our decade-long survey of the distant activity of LP comets. We found that the most important separation in the dataset is based on the dynamical nature of the objects. Dynamically new comets are characterized by a higher level of activity on average: the most active new comets in our sample can be characterized by afrho values >3--4 higher than that of our most active returning comets. New comets develop more symmetric comae, suggesting a generally isotropic outflow. Contrary to this, the coma of recurrent comets can be less symmetrical, ocassionally exhibiting negative slope parameters, suggesting sudden variations in matter production. The morphological appearance of the observed comets is rather diverse. A surprisingly large fraction of the comets have long, teniouos tails, but the presence of impressive tails does not show a clear correlation with the brightness of the comets.Comment: 21 pages, 4 figures, accepted for publication in A

Cross section of 3He(α, γ)7Be around the 7Be proton separation threshold

Background: The 3He(α, γ )7Be reaction is a widely studied nuclear reaction; however, it is still not understood with the required precision. It has a great importance both in Big Bang nucleosynthesis and in solar hydrogen burning. The low mass number of the reaction partners makes it also suitable for testing microscopic calculations. Purpose: Despite the high number of experimental studies, none of them addresses the 3He(α, γ )7Be reaction cross sections above 3.1-MeV center-of-mass energy. Recently, a previously unobserved resonance in the 6Li(p, γ )7Be reaction suggested a new level in 7Be, which would also have an impact on the 3He(α, γ )7Be reaction in the energy range above 4.0 MeV. The aim of the present experiment is to measure the 3He(α, γ )7Be reaction cross section in the energy range of the proposed level. Method: For this investigation the activation technique was used. A thin window gas-cell target confining 3He gas was irradiated using an α beam. The 7Be produced was implanted into the exit foil. The 7Be activity was determined by counting the γ rays following its decay by a well-shielded high-purity germanium detector. Results: Reaction cross sections have been determined between Ecm = 4.0 and 4.4 MeV with 0.04-MeV steps covering the energy range of the proposed nuclear level. One lower-energy cross-section point was also determined to be able to compare the results with previous studies. Conclusions: A constant cross section of around 10.5 μb was observed around the 7Be proton separation energy. An upper limit of 45 neV for the strength of a 3He(α, γ )7Be resonance is derived

A complex system for the production of pathogen-free grapevine propagating material

The use of pathogen-free planting stock for new vineyard establishment is a key component in the maintenance and expansion ofvine and quality table grape production. The success of the necessary changes in the structure of the grape industry is forced by theglobalization process, the climate change, the rediscovery of autochton varieties as well as breeding of new tolerant and resistant varieties.The renewal of vineyards largely depend on the availability of planting stocks. Serbia and Hungary found a common interest in establishingpathogen-free stock materials from newly breed resistant varieties and clonal selections of varieties which are traditional in the Serbian-Hungarian border area. During a cross-border cooperation program a complex system for the production of pathogen-free grapevinepropagating material was established. Using heat therapy, in vitro shoot tip culture and traditional and molecular diagnostic techniques newpathogen-free stock materials were established from 26 varieties. They have been or will be tested for the presence of most importantgrapevine viruses, phytoplasmas, as well as bacterial and fungal pathogens. The complex system applying green grafting for indexing ongrapevine indicators can shorten the duration of the procedure from 4 years to two-three years