Excitation functions of proton-induced reactions on natural Nd and production of radionuclides relevant for double beta decay: Completing measurement in 5-35 MeV energy range

Cross-sections for the proton-induced reactions on natural neodymium in energy regions 5-10 MeV and 30-35 MeV were measured using the cyclotron U-120M at the Nuclear Physics Institute at Rez near Prague. This measurement completes the investigation previously done in the 10-30 MeV energy range. Results revealed practical production thresholds and secondary maxima and minima in the excitation functions. It allowed for more appropriate calculation of thick target yields and production rates of many longer-lived radionuclides potentially disturbing the search for neutrinoless double beta decay. Measured cross-sections are consistent with our previously published data

Oidium neolycopersici: Intra-specific variability inferred from AFLP analysis and relationship with closely related powdery mildew fungi infecting various plant species

Previous works indicated a considerable variation in the pathogenicity, virulence, and host range of Oidium neolycopersici isolates causing tomato powdery mildew epidemics in many parts of the world. In this study, rDNA internal transcribed spacer (ITS) sequences, and amplified fragment length polymorphism (AFLP) patterns were analyzed in 17 O. neolycopersici samples collected in Europe, North America, and Japan, including those which overcame some of the tomato major resistance genes. The ITS sequences were identical in all 10 samples tested and were also identical to ITS sequences of eight previously studied O. neolycopersici specimens. The AFLP analysis revealed a high genetic diversity in O. neolycopersici and indicated that all 17 samples represented different genotypes. This might suggest the existence of either a yet unrevealed sexual reproduction or other genetic mechanisms that maintain a high genetic variability in O. neolycopersici. No clear correlation was found between the virulence and the AFLP patterns of the O. neolycopersici isolates studied. The relationship between O. neolycopersici and powdery mildew anamorphs infecting Aquilegia vulgaris, Chelidonium majus, Passiflora caerulea, and Sedum alboroseum was also investigated. These anamorphs are morphologically indistinguishable from and phylogenetically closely related to O. neolycopersici. The cross-inoculation tests and the analyses of ITS sequences and AFLP patterns jointly indicated that the powdery mildew anamorphs collected from the above mentioned plant species all represent distinct, but closely related species according to the phylogenetic species recognition. All these species were pathogenic only to their original host plant species, except O. neolycopersici which infected S. alboroseum, tobacco, petunia, and Arabidopsis thaliana, in addition to tomato, in cross-inoculation tests. This is the first genome-wide study that investigates the relationships among powdery mildews that are closely related based on ITS sequences and morphology. The results indicate that morphologically indistinguishable powdery mildews that differed in only one to five single nucleotide positions in their ITS region are to be considered as different taxa with distinct host ranges

Spatially uniform calibration of a liquid xenon detector at low energies using 83m-Kr

A difficult task with many particle detectors focusing on interactions below ~100 keV is to perform a calibration in the appropriate energy range that adequately probes all regions of the detector. Because detector response can vary greatly in various locations within the device, a spatially uniform calibration is important. We present a new method for calibration of liquid xenon (LXe) detectors, using the short-lived 83m-Kr. This source has transitions at 9.4 and 32.1 keV, and as a noble gas like Xe, it disperses uniformly in all regions of the detector. Even for low source activities, the existence of the two transitions provides a method of identifying the decays that is free of background. We find that at decreasing energies, the LXe light yield increases, while the amount of electric field quenching is diminished. Additionally, we show that if any long-lived radioactive backgrounds are introduced by this method, they will present less than 67E-6 events/kg/day in the next generation of LXe dark matter direct detection searchesComment: 9 pages, 9 figures. Accepted to Review of Scientific Instrument

Precise energy of the 9.4 keV gamma transition observed in the 83Rb decay

The energy of the 9.4 keV γ-transition observed in the 83Rb decay was established to be 9405.8(3) eV. This energy value was obtained from photon spectrometry measurements of the differences in the energies of closely spaced lines. The result allows one to determine more precisely the energy of conversion electrons of the 9.4 keV transition, which represent a unique tool for energy calibration of the tritium beta spectrum and systematic measurements in the KATRIN neutrino mass determination experiment

Real-time spectroscopy of solar pp neutrinos using Nd-150

The potential real-time spectroscopy of solar pp neutrinos using Nd-150 as target is investigated. The threshold of 196 keV would be the lowest of all solar neutrino experiments running so far. Experimental rates and parameters are discussed, about 580 SNU can be expected from pp-neutrinos and another 367 SNU from Be-7. Furthermore, it is investigated whether charged current reactions might cause a new background component for future double beta decay experiments based on a large amount of Nd-150.Comment: 9 pages, 1 figur

Positronic lithium, an electronically stable Li-e+^+ ground state

Calculations of the positron-Li system were performed using the Stochastic Variational Method and yielded a minimum energy of -7.53208 Hartree for the L=0 ground state. Unlike previous calculations of this system, the system was found to be stable against dissociation into the Ps + Li$^+$ channel with a binding energy of 0.00217 Hartree and is therefore electronically stable. This is the first instance of a rigorous calculation predicting that it is possible to combine a positron with a neutral atom and form an electronically stable bound state.Comment: 11 pages, 2 tables. To be published in Phys.Rev.Let

Using Repeat Photography to Examine Change in a U.S. National Park Gateway Community: A Case Study of Estes Park, Colorado

Since the creation of the National Park Service in the United States, tourists from around the world visiting America\u27s national parks are served by gateway communities. Gateway communities are the towns and cities that border public lands and protected spaces. The impact of our visits on these gateway communities is considerable, with many gateways and their residents relying on consistent and ever-increasing visitation to national parks to spur economic growth and development. To better understand the impacts that national park designations have had on their gateway communities, it is important to determine what changes have occurred both physically and culturally in these communities. This research is a case study of Estes Park, Colorado, the gateway community of Rocky Mountain National Park, the third most visited national park in the United States in 2018. This project utilized a repeat photography method to analyze the changes in Estes Park since the establishment of Rocky Mountain National Park in 1915. This analysis suggests that Estes Park has grown considerably around tourism, with new development focused mainly on meeting the needs of visitors and a larger resident population spurred by the creation of the park

Possibilities for Modifying the System of Proportional Representation Aimed at Stabilizing the Executive in the CR

As a result of the Czech Republic's experience of a series of unstable minority governments, serious debate has arisen over the need for changes to the electoral system. The aim here is to find a suitable alternative to the representational system, one capable of ushering in a period of government stability, by modeling the results of the 1996 & 1998 elections. It is also necessary to determine which type of proportional electoral system could transform the party system in such a manner so as to render it capable of setting up a two-party majority coalition government. The method of modeling the election results is rooted in an exact calculation of specific election results by applying particular mathematical formulas to examples of various sizes of electoral constituencies. Three possible solutions emerge, one of which appears to be exceptionally effective. A number of options have been worked out whereby the political party system in the Czech Republic could be reconstructed. A description & brief evaluation of the proposal for changing the electoral system made by the two largest political parties in Jan 2000, which is also grounded in making modifications to the representational system, is presented

Isotopic Niche Analysis of Silver Carp and Gizzard Shad

Kentucky Lake is the largest impoundment east of the Mississippi River and is located on the Tennessee River in western Kentucky. The reservoir has a diverse fishery that includes large populations of native planktivorous Gizzard Shad (Dorosoma cepedianum) and Threadfin Shad (D. petenense). Silver Carp (Hypophthalmichthys molitrix) are an invasive planktivorous fish species that invaded Kentucky Lake in 2004 and have successfully established a reproducing population. Silver Carp and Gizzard Shad have been shown to feed on similar food items that include both phytoplankton and zooplankton. Therefore, diet overlap between Silver Carp and Gizzard Shad is a major concern to biologists, commercial fishermen, and recreational fishermen due to the potential for competition with commercial and sportfish populations. We used stable isotope analyses to determine trophic position and potential for competition between Silver Carp and Gizzard Shad in Kentucky Lake. Samples of fish and end members were collected at two embayment sites and one channel site. Preliminary results suggest that Silver Carp and Gizzard Shad are filling similar isotopic niches within Kentucky Lake. As populations of Silver Carp increase, the potential for competition with native fish species may increase and potentially result in ecosystem effects