Evidence for the First Excited State of

The ^{7}H system was populated in the ^{2}H(^{8}He,^{3}He)^{7}H reaction with a 26 AMeV ^{8}He beam. The ^{7}H missing mass energy spectrum, the ^{3}H energy and angular distributions in the ^{7}H decay frame were reconstructed. The ^{7}H missing mass spectrum shows a peak, which can be interpreted either as unresolved 5/2^{+} and 3/2^{+} doublet or one of these states at 6.5(5) MeV. The data also provide indications of the 1/2^{+} ground state of ^{7}H located at 1.8(5) MeV with quite a low population cross section of ∼25 µb/sr within angular range θ_{c.m.}≃(17°-27°).

Towards the Limits of Existence of Nuclear Structure: Observation and First Spectroscopy of the Isotope

The most remote isotope from the proton dripline (by 4 atomic mass units) has been observed: ^{31}K. It is unbound with respect to three-proton (3p) emission, and its decays have been detected in flight by measuring the trajectories of all decay products using microstrip detectors. The 3p emission processes have been studied by the means of angular correlations of ^{28}S+3p and the respective decay vertices. The energies of the previously unknown ground and excited states of ^{31}K have been determined. This provides its 3p separation energy value S_{3p} of -4.6(2) MeV. Upper half-life limits of 10 ps of the observed ^{31}K states have been derived from distributions of the measured decay vertices.

[Hygienic assessment of the impact of diesel fuel on the ordinary black soil microbiocenosis].

The main sources of soil contamination by oil products in the Dnepropetrovsk region are oil depots, gas stations and all types of transport that use and transport oil. The diesel fuel was found to be the one of the priority multicomponent components of the petroleum products, so it there was occurred the necessity for the hygienic regulation of the oil component in order to monitor a multicomponent composition ofpetroleum products in the study of complex influence of environmental factors on health population. In the study of the effect of various concentrations of diesel fuel on the number of total bacterial count (TBC) as the threshold for general sanitary indicator of hazard, there was recommended the concentration of4000 mg/kg, which oppressed the vital activity of soil microorganisms by 50-27.3% for the first 2 weeks of the laboratory experiment.

Observation and Spectroscopy of New Proton-Unbound Isotopes ³°Ar and ²9Cl: An Interplay of Prompt Two-Proton and Sequential Decay.

Previously unknown isotopes (30)Ar and (29)Cl have been identified by measurement of the trajectories of their in-flight decay products (28)S+p+p and (28)S+p, respectively. The analysis of angular correlations of the fragments provided information on decay energies and the structure of the parent states. The ground states of (30)Ar and (29)Cl were found at 2.25(-0.10)(+0.15) and 1.8±0.1 MeV above the two- and one-proton thresholds, respectively. The lowest states in (30)Ar and (29)Cl point to a violation of isobaric symmetry in the structure of these unbound nuclei. The two-proton decay has been identified in a transition region between simultaneous two-proton and sequential proton emissions from the (30)Ar ground state, which is characterized by an interplay of three-body and two-body decay mechanisms. The first hint of a fine structure of the two-proton decay of (30)Ar*(2(+)) has been obtained by detecting two decay branches into the ground and first-excited states of the (28)S fragment.

Observation of long-range three-body coulomb effects in the decay of (16)Ne.

The interaction of an E/A=57.6-MeV ^{17}Ne beam with a Be target is used to populate levels in ^{16}Ne following neutron knockout reactions. The decay of ^{16}Ne states into the three-body ^{14}O+p+p continuum is observed in the High Resolution Array (HiRA). For the first time for a 2p emitter, correlations between the momenta of the three decay products are measured with sufficient resolution and statistics to allow for an unambiguous demonstration of their dependence on the long-range nature of the Coulomb interaction. Contrary to previous measurements, our measured limit Γ<80 keV for the intrinsic decay width of the ground state is not in contradiction to the small values (of the order of keV) predicted theoretically.

[VNTR-genotyping of Vibrio cholerae strains isolated from objects in the territory of Russian Federation in 2012].

AIM: VNTR-typing of Vibrio cholerae strains isolated in the territory of Russian Federation in 2012. MATERIALS AND METHODS: 71 Vibrio cholerae O3 and 3 V cholerae O1/O139 strains were used in the study. Genotyping was performed by using PCR for 5 VNTR-loci. RESULTS: Multilocus VNTR-typing allowed to group the strains into 31 VNTR-genotypes. Genotypes were divided among 10 discrete clusters by results of a cluster analysis. The presence of tcpA gene is clearly linked with the presence of VcB locus. Each geographic region was characterized by their own VNTR-genotypes. CONCLUSION: In the course of the carried out VNTR-genotyping of V. cholerae isolated in 2012, 2 types of vibrio population formation were detected. A geographic attachment to specific regions was characteristic for most of the genotypes.

Lifetime and fragment correlations for the two-neutron decay of 26O ground state.

The structure and decay of 26O are investigated in a three-body 24O+n+n model suitable for studies of the long-lived (including radioactivity time scale) states. We have found extremely strong effects of the subbarrier configuration mixing on the decay width of true 2n emitters due to core recoil and neutron-neutron final state interaction. This effect far exceeds the analogous effect in the true 2p emitters. Our calculations provide reasonably narrow boundaries for the lifetime vs decay energy dependence for the true 2n emission. An upper limit of ∼1 keV for the decay energy of the unbound 26O is inferred based on the recent experimental lifetime value.

Democratic decay of 6Be exposed by correlations.

The interaction of an E/A=70-MeV (7)Be beam with a Be target was used to populate levels in (6)Be following neutron knockout reactions. The three-body decay of the ground and first excited states into the α+p+p exit channel were detected in the High Resolution Array. Precise three-body correlations extracted from the experimental data allowed us to obtain insight into the mechanism of the three-body democratic decay. The correlation data are in good agreement with a three-cluster-model calculation and thus validate this theoretical approach over a broad energy range.

Structure of 10He low-lying states uncovered by correlations.

The 0+ ground state of the 10He nucleus produced in the 3H(8He,p)10He reaction was found at about 2.1±0.2 MeV (Γ∼2 MeV) above the three-body ^{8}He+n+n breakup threshold. Angular correlations observed for ^{10}He decay products show prominent interference patterns allowing us to draw conclusions about the structure of low-energy excited states. We interpret the observed correlations as a coherent superposition of a broad 1- state having a maximum at energy 4-6 MeV and a 2+ state above 6 MeV, setting both on top of the 0+ state "tail." This anomalous level ordering indicates that the breakdown of the N=8 shell known in 12Be thus extends also to the ^{10}He system.

Direct observation of two protons in the decay of 54Zn.

The two protons emitted in the decay of 54Zn have been individually observed for the first time in a time projection chamber. The total decay energy and the half-life measured in this work agree with the results obtained in a previous experiment. Angular and energy correlations between the two protons are determined and compared to theoretical distributions of a three-body model. Within the shell model framework, the relative decay probabilities show a strong contribution of the p2 configuration for the two-proton emission. After 45Fe, the present result on 54Zn constitutes only the second case of a direct observation of the ground state two-proton decay of a long-lived isotope.

[Serotyping and genotypic characteristic of Vibrio cholerae non-O1/non-O139 serogroups isolated from water of surface basins and sewages of Rostov-on-Don city in 2003 - 2008].

AIM: Determination of serogroup and PCR-genotyping of Vibrio cholerae non-O1/non-O139 strains isolated from surface basins and sewages of Rostov-on-Don city in 2003 - 2008. MATERIALS AND METHODS: Seven hundred strains of V. cholerae non-O1/non-O139 serogroups were studied in reaction of slide-agglutination with array of 80 diagnostic sera for non-O1/non-O139 serogroups. Selective screening of strains representing dominating serogroups was performed for extended number of genetic determinants of pathogenicity factors. RESULTS: It was established that V. cholerae belonging to serogroups O53, O67, O75, and O76 are dominating in water ecosystems of Rostov-on-Don city at this time. All studied strains were characterized by lack of cholera toxin genes and toxin-coregulated pili but had different combinations of genes of additional virulence factors. There was no correlation between genotypic characteristics and serogroup. CONCLUSION: The study showed that change of serologic landscape of V. cholerae non-O1/non-O139 occurred in water objects in studied area during last decades. Necessity of dynamic surveillance for circulation of V. cholerae non-O1/non-O139 in aquatic environment with widening of studied spectrum of their biological features was demonstrated.

Two-proton correlations in the decay of 45Fe.

The decay of extremely neutron-deficient 45Fe has been studied in detail by means of a novel type of a gaseous detector employing digital imaging to record tracks of charged particles. The two-proton radioactivity channel was clearly identified. For the first time, the angular and energy correlations between two protons emitted from the nuclear ground state were determined, indicating the genuine three-body character of this decay. The half-life of 45Fe was found to be 2.6+/-0.2 ms and the observed 2p decay branching ratio is 70+/-4%.

Observation of two-proton radioactivity of 19Mg by tracking the decay products.

We have observed the two-proton radioactivity of the previously unknown (19)Mg ground state by tracking the decay products in-flight. For the first time, the trajectories of the 2p-decay products, (17)Ne+p+p, have been measured by using tracking microstrip detectors which allowed us to reconstruct the 2p-decay vertices and fragment correlations. The half-life of (19)Mg deduced from the measured vertex distribution is 4.0(15) ps in the system of (19)Mg. The Q value of the 2p decay of the (19)Mg ground state inferred from the measured p-p-(17)Ne correlations is 0.75(5) MeV.

Measurement of the beta+ and orbital electron-capture decay rates in fully ionized, hydrogenlike, and heliumlike 140Pr ions.

We report on the first measurement of the beta+ and orbital electron-capture decay rates of 140Pr nuclei with the simplest electron configurations: bare nuclei, hydrogenlike, and heliumlike ions. The measured electron-capture decay constant of hydrogenlike 140Pr58+ ions is about 50% larger than that of heliumlike 140Pr57+ ions. Moreover, 140Pr ions with one bound electron decay faster than neutral 140Pr0+ atoms with 59 electrons. To explain this peculiar observation one has to take into account the conservation of the total angular momentum, since only particular spin orientations of the nucleus and of the captured electron can contribute to the allowed decay.

Two-proton widths of 12O, 16Ne, and three-body mechanism of Thomas-Ehrman shift.

Two-proton decays of 12O and 16Ne ground states are studied in a three-body model. We have found that the two-proton widths for the states should be much less than the existing experimental values (about 10 times for 12O and about 100 times for 16Ne). We also have found that the structure of these states differs significantly from the mirror isobaric analog states (IAS): breaking of isobaric symmetry is at the level of tens of percents. Together with a corresponding decrease of the Coulomb energy, this effect can be considered as a three-body mechanism of the Thomas-Ehrman shift.

Observation of excited states in 5H.

The 5H system was produced in the 3H(t,p)5H reaction studied with a 58 MeV tritium beam at small c.m. angles. High statistics data were used to reconstruct the energy and angular correlations between the 5H decay fragments. A broad structure in the 5H missing mass spectrum showing up above 2.5 MeV was identified as a mixture of the 3/2+ and 5/2+ states. The data also present evidence that the 1/2+ ground state of 5H is located at about 2 MeV.