ABSTRACT
The nuclear two-photon or double-gamma (2γ) decay is a second-order electromagnetic process whereby a nucleus in an excited state emits two gamma rays simultaneously. To be able to directly measure the 2γ decay rate in the low-energy regime below the electron-positron pair-creation threshold, we combined the isochronous mode of a storage ring with Schottky resonant cavities. The newly developed technique can be applied to isomers with excitation energies down to â¼100 keV and half-lives as short as â¼10 ms. The half-life for the 2γ decay of the first-excited 0^{+} state in bare ^{72}Ge ions was determined to be 23.9(6) ms, which strongly deviates from expectations.
ABSTRACT
Quantum electrodynamics (QED), the quantum field theory that describes the interaction between light and matter, is commonly regarded as the best-tested quantum theory in modern physics. However, this claim is mostly based on extremely precise studies performed in the domain of relatively low field strengths and light atoms and ions1-6. In the realm of very strong electromagnetic fields such as in the heaviest highly charged ions (with nuclear charge Z â« 1), QED calculations enter a qualitatively different, non-perturbative regime. Yet, the corresponding experimental studies are very challenging, and theoretical predictions are only partially tested. Here we present an experiment sensitive to higher-order QED effects and electron-electron interactions in the high-Z regime. This is achieved by using a multi-reference method based on Doppler-tuned X-ray emission from stored relativistic uranium ions with different charge states. The energy of the 1s1/22p3/2 J = 2 â 1s1/22s1/2 J = 1 intrashell transition in the heaviest two-electron ion (U90+) is obtained with an accuracy of 37 ppm. Furthermore, a comparison of uranium ions with different numbers of bound electrons enables us to disentangle and to test separately the one-electron higher-order QED effects and the bound electron-electron interaction terms without the uncertainty related to the nuclear radius. Moreover, our experimental result can discriminate between several state-of-the-art theoretical approaches and provides an important benchmark for calculations in the strong-field domain.
ABSTRACT
Using a novel method of isochronous mass spectrometry, the masses of ^{62}Ge, ^{64}As, ^{66}Se, and ^{70}Kr are measured for the first time, and the masses of ^{58}Zn, ^{61}Ga, ^{63}Ge, ^{65}As, ^{67}Se, ^{71}Kr, and ^{75}Sr are redetermined with improved accuracy. The new masses allow us to derive residual proton-neutron interactions (δV_{pn}) in the N=Z nuclei, which are found to decrease (increase) with increasing mass A for even-even (odd-odd) nuclei beyond Z=28. This bifurcation of δV_{pn} cannot be reproduced by the available mass models, nor is it consistent with expectations of a pseudo-SU(4) symmetry restoration in the fp shell. We performed ab initio calculations with a chiral three-nucleon force (3NF) included, which indicate the enhancement of the T=1 pn pairing over the T=0 pn pairing in this mass region, leading to the opposite evolving trends of δV_{pn} in even-even and odd-odd nuclei.
ABSTRACT
An improved design of a longitudinally sensitive resonant Schottky cavity pickup for the heavy ion storage rings of the Facility for Antiproton and Ion Research in Europe (FAIR) project is reported. The new detector has a higher measured Q value of â¼3000 and a higher simulated shunt impedance of 473.3 kΩ. It is possible to vary the sensitivity of the cavity with a motorized mechanism by inserting a dissipative blade during the operation based on experimental needs. Apart from a lower price tag, the new design features a more robust and production-friendly mechanical structure suitable for a series production in the future FAIR project. The manufactured cavity was built temporarily into the experimental storage ring and had delivered its first results using stored heavy ion beams. The structure, simulation results, and performance of this cavity are presented in this work.
ABSTRACT
We report the first measurement of low-energy proton-capture cross sections of ^{124}Xe in a heavy-ion storage ring. ^{124}Xe^{54+} ions of five different beam energies between 5.5 and 8 AMeV were stored to collide with a windowless hydrogen target. The ^{125}Cs reaction products were directly detected. The interaction energies are located on the high energy tail of the Gamow window for hot, explosive scenarios such as supernovae and x-ray binaries. The results serve as an important test of predicted astrophysical reaction rates in this mass range. Good agreement in the prediction of the astrophysically important proton width at low energy is found, with only a 30% difference between measurement and theory. Larger deviations are found above the neutron emission threshold, where also neutron and γ widths significantly impact the cross sections. The newly established experimental method is a very powerful tool to investigate nuclear reactions on rare ion beams at low center-of-mass energies.
ABSTRACT
Masses of ^{52g,52m}Co were measured for the first time with an accuracy of â¼10 keV, an unprecedented precision reached for short-lived nuclei in the isochronous mass spectrometry. Combining our results with the previous ß-γ measurements of ^{52}Ni, the T=2, J^{π}=0^{+} isobaric analog state (IAS) in ^{52}Co was newly assigned, questioning the conventional identification of IASs from the ß-delayed proton emissions. Using our energy of the IAS in ^{52}Co, the masses of the T=2 multiplet fit well into the isobaric multiplet mass equation. We find that the IAS in ^{52}Co decays predominantly via γ transitions while the proton emission is negligibly small. According to our large-scale shell model calculations, this phenomenon has been interpreted to be due to very low isospin mixing in the IAS.
ABSTRACT
A short review of the current state in ethnogenomics was carried out. The main breakthroughs in the field are described, and small-scale historical overview is presented. The methods and approaches currently used in Y-chromosome, mitochondrial DNA and genome-wide studies are listed.
Subject(s)
Chromosomes, Human, Y/genetics , DNA, Mitochondrial/genetics , Genetics, Medical/methods , Genome-Wide Association Study/methods , Genetic Markers , HumansABSTRACT
An analysis of genetic diversity in nine ethnic groups of the Volga-Ural region was carried out using 15 biallelic loci in the nonrecombining region of the Y-chromosome. The major Y-chromosome haplogroups in the region are R1a-M198, R1b-M269, and N-M231. It was found that Bashkirs show the greatest difference from other populations of the Volga-Ural region according both to F(st) and to the principal component analysis. In addition, analysis of the frequency distribution of Y-chromosome haplogroups was carried out in the Besermyan population, which was not studied previously from the Y-chromosome perspective. The results of this study revealed the predominance of haplogroup N-M231 (54.7%) in this ethnic group, which may indicate the prevalence of the Finno-Ugric component in the formation of the patrilineal component in the gene pool of the Besermyan ethnic group.
Subject(s)
Chromosomes, Human, Y/genetics , Gene Pool , Genetic Variation , Haplotypes , Humans , Male , Russia/ethnologyABSTRACT
Global efforts to eradicate dracunculiasis have continued to progress with only 542 cases reported in 2012 versus almost 1 million cases in the 1980s when the initiative was launched. The disease is still endemic, but in only four countries: South Sudan (541 cases), Chad (10 cases), Mali (4 cases), and Ethiopia (4 cases). The International Commission for the Certification of Dracunculiasis Eradication declared that 180 countries were free of the disease by 2013. Dracunculiasis was first eradicated in the former USSR in 1931 when its last case was registered due to the successful implementation of a package of appropriate measures (case detection and management, vector control, and health education, including water filtration from open water sources and behavioral changes). These approaches were actively taken into account when developing the global strategy for dracunculiasis. The World Health Organization has set a goal to eradicate the disease by 2015. However, despite the fact that the global situation looks very optimistic, the time for completing the program will be most likely postponed due to a few operational challenges remaining in the still endemic countries, in South Sudan in particular.
Subject(s)
Disease Eradication/trends , Dracunculiasis/prevention & control , Health Knowledge, Attitudes, Practice , Africa/epidemiology , Dracunculiasis/epidemiology , Global Health , Humans , Neglected Diseases , Water Purification , World Health OrganizationSubject(s)
Neglected Diseases/prevention & control , World Health Organization/organization & administration , Humans , Neglected Diseases/drug therapy , Neglected Diseases/epidemiology , Tropical Medicine/economics , Tropical Medicine/organization & administration , Tropical Medicine/trends , World Health Organization/economicsABSTRACT
Double-strand DNA breaks (DSBs) resulting from cellular metabolic processes and external factors are a serious threat to the stability of the genome. Therefore, the cells have different molecular mechanisms for the efficient repair of this type of dá-mage. In this review we consider two main biochemical pathways of double-strand DNA breaks repair in eukaryotic cells--DNA strands nonhomologous end joining and homologous recombination between sister chromatids or chromatids of homologous chromosomes. Numerous data obtained recently for various eukaryotic cells suggest that complex interplay between the major DSB repair pathways normally facilitate the efficient repair and maintenance of the structural and functional genome integrity, but at the same time, under conditions ofgenotoxic factors exposure may induce increased genomic instability.
Subject(s)
DNA Breaks, Double-Stranded , DNA Repair , DNA/genetics , Recombination, Genetic , Animals , Arabidopsis/genetics , DNA, Plant/genetics , Eukaryotic Cells , Genomic Instability , Homologous RecombinationABSTRACT
An analysis of the frequency of H63D (c. 187C>G) mutations in the HFEgene in 19 populations from Central Eurasia demonstrated that the distribution of the mutation in the region of interest was not uniform and that there were the areas of H63D accumulation. The investigation of three polymorphic variants, c.340+4T>C (rs2071303, IVS2(+4)T>C), c.893-44T>C (rs1800708, IVS4(-44)T>C), and c.1007-47G>A (rs1572982, IVS5(-47)A>G), in the HFE gene in individuals homozygous for H63D mutations in the HFE gene revealed the linkage of H63D with three haplotypes, *CTA, *TG, and *TTA. These findings indicated the partial spread of the mutation in Central Eurasia from Western Europe, as well as the possible repeated appearance of the mutation on the territory on interest.
Subject(s)
Gene Frequency , Histocompatibility Antigens Class I/genetics , Membrane Proteins/genetics , Mutation , Asia, Central , Haplotypes/genetics , Hemochromatosis Protein , Homozygote , Humans , Polymorphism, Genetic , RussiaABSTRACT
Long-lived isomers in (212)Bi have been studied following (238)U projectile fragmentation at 670 MeV per nucleon. The fragmentation products were injected as highly charged ions into a storage ring, giving access to masses and half-lives. While the excitation energy of the first isomer of (212)Bi was confirmed, the second isomer was observed at 1478(30) keV, in contrast to the previously accepted value of >1910 keV. It was also found to have an extended Lorentz-corrected in-ring half-life >30 min, compared to 7.0(3) min for the neutral atom. Both the energy and half-life differences can be understood as being due a substantial, though previously unrecognized, internal decay branch for neutral atoms. Earlier shell-model calculations are now found to give good agreement with the isomer excitation energy. Furthermore, these and new calculations predict the existence of states at slightly higher energy that could facilitate isomer deexcitation studies.
Subject(s)
Arachnid Vectors/physiology , Encephalitis, Tick-Borne/epidemiology , Focal Infection , Ixodidae/physiology , Lyme Disease/epidemiology , Tick Infestations/epidemiology , Altitude , Animals , Arachnid Vectors/microbiology , Arachnid Vectors/virology , Borrelia burgdorferi/physiology , Climate Change , Encephalitis Viruses, Tick-Borne/physiology , Encephalitis, Tick-Borne/parasitology , Encephalitis, Tick-Borne/virology , Humans , Ixodidae/microbiology , Ixodidae/virology , Lyme Disease/microbiology , Lyme Disease/parasitology , Rodentia/microbiology , Rodentia/parasitology , Rodentia/virology , Ruminants/microbiology , Ruminants/parasitology , Ruminants/virology , Russia/epidemiology , Temperature , Tick Infestations/parasitologyABSTRACT
Genetic diversity has been analyzed in 22 ethnic groups of the Caucasus on the basis of data on Y-chromosome and mitochondrial DNA (mtDNA) markers, as well as genome-wide data on autosomal single-nucleotide polymorphisms (SNPs). It has been found that the West Asian component is prevailing in all ethnic groups studied except for Nogays. This Near Eastern ancestral component has proved to be characteristic of Caucasian populations and almost entirely absent in their northern neighbors inhabiting the Eastern European Plain. Turkic-speaking populations, except Nogays, did not exhibit an increased proportion of Eastern Eurasian mtDNA or Y-chromosome haplogroups compared to some Abkhaz-Adyghe populations (Adygs and Kabardians). Genome-wide SNP analysis has also shown substantial differences of Nogays from all other Caucasian populations studied. However, the characteristic difference of Nogays from other populations of the Caucasus seems somewhat ambiguous in terms of the R1a1a-M17(M198) and R1b1b1-M73 haplogroups of the Y chromosome. The state of these haplogroups in Turkic-speaking populations of the Caucasus requires further study.
Subject(s)
Chromosomes, Human, Y/genetics , DNA, Mitochondrial/genetics , Ethnicity/genetics , White People/genetics , Genetic Variation , Genome, Human , Haplotypes/genetics , Humans , Polymorphism, Single NucleotideABSTRACT
The behavior of tethered DNA in shear flow is investigated numerically by the smoothed dissipative particle dynamics (SDPD) method. Unlike numerical methods used in previous studies, SDPD models the solvent explicitly, takes into account the fully coupled hydrodynamic interactions and is free of the numerical artifact of wall sticking. Based on numerical simulations the static and dynamic properties of a tethered DNA is studied both qualitatively and quantitatively. The observed properties are in general agreement with previous experimental, numerical and theoretical work. Furthermore, the cyclic-motion phenomenon is studied by power spectrum density and cross-correlation function analysis, which suggest that there is only a very weak coherent motion of tethered DNA for a characteristic timescale larger than the relaxation time. Cyclic motion is more likely relevant as an isolated event than a typical mode of DNA motion.
Subject(s)
Biophysics/methods , DNA/chemistry , Computer Simulation , Models, Statistical , Models, Theoretical , Motion , Nucleic Acid Conformation , Particle Size , Polymers/chemistry , Probability , Solvents/chemistry , Stress, Mechanical , Time FactorsABSTRACT
A study of cooled ¹97Au projectile-fragmentation products has been performed with a storage ring. This has enabled metastable nuclear excitations with energies up to 3 MeV, and half-lives extending to minutes or longer, to be identified in the neutron-rich nuclides ¹8³(,)¹84(,)¹86Hf and ¹86(,)¹87Ta. The results support the prediction of a strongly favored isomer region near neutron number 116.
ABSTRACT
It is a historical review of the development of international health cooperation and participation of Russia at its early stages. Detailed information is presented concerning joint work for control of malaria and other parasitic infections with WHO, CMEA countries, developed and developing states. The important role of E.I. Martsinovsky Institute of Medical Parasitology and Tropical Medicine in combating infections and in health protection at large is emphasized. Current collaboration and its prospects are briefly discussed.
Subject(s)
International Cooperation , Parasitic Diseases/prevention & control , Parasitology/organization & administration , Tropical Medicine/organization & administration , Humans , Parasitic Diseases/epidemiology , RussiaSubject(s)
Academies and Institutes/history , International Cooperation/history , Parasitology/history , Tropical Medicine/history , Animals , Government Programs/economics , Government Programs/education , History, 20th Century , History, 21st Century , Humans , Malaria/prevention & control , RussiaABSTRACT
Time-resolved Schottky mass spectrometry has been applied to uranium projectile fragments which yielded the mass value for the 208Hg (Z=80, N=128) isotope. The mass excess value of ME=-13 265(31) keV has been obtained, which has been used to determine the proton-neutron interaction strength in 210Pb, as a double difference of atomic masses. The results show a dramatic variation of the strength for lead isotopes when crossing the N=126 neutron shell closure, thus confirming the empirical predictions that this interaction strength is sensitive to the overlap of the wave functions of the last valence neutrons and protons.