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The phosphatase complex PPH3 consists of three subunits: catalytic Pph3 and auxiliary Pph2 and Psy4. Pph3 also forms a double complex with subunit Psy2, which binds to kinase Rad53 and dephosphorylates it without recruiting the third subunit. The triple complex dephosphorylates γH2A. We have previously shown that gene HSM6 corresponds to gene PSY4 on the genetic map of Saccharomyces cerevisiae. Mutation hsm6-1 increases the rate of spontaneous and UV-induced mutagenesis. In this work, we have shown that mutations in gene PPH3 increase the rate of spontaneous reparative mutagenesis sevenfold, while mutations pph3Δ and hsm6-1 show an epistatic effect. At high doses, the frequency of UV-induced mutations in mutants pph3Δ, psy4Δ, and hsm6-1 is the same and exceeds the level of mutagenesis in the wild-type strain by approximately twofold. All mutants show a higher (approximately 10-fold) frequency of γ-induced mutations compared to the wild-type strain. The combination of mutations in genes encoding PPH3 subunits and mutations in MMS2 and XRS2, which control an error-free postreplication repair pathway, leads to blocking of PPH3-specific UV-induced mutagenesis. Thus, we have identified the PPH3 complex as a novel factor involved in the regulation of the error-free branch of postreplication repair. The double mutant for genes PTC2 and PTC3, encoding the other two phosphatases that dephosphorylate Rad53, does not differ from the wild-type strain with respect to UV-induced mutagenesis and survival. This means that hyperphosphorylation of only the Pph3-specific sites of protein Rad53 and histone H2A increases the level of UV mutagenesis.

We apply the nuclear model with explicit mesons to photoproduction of neutral pions off protons at the threshold. In this model the nucleons do not interact with each other via a potential but rather emit and absorb mesons that are treated explicitly on equal footing with the nucleons. We calculate the total cross section of the reaction for energies close to threshold and compare the calculations with available experimental data. We show that the model is able to reproduce the experimental data and determine the range of the parameters where the model is compatible with the experiment.

Combining laser spectroscopy in a Versatile Arc Discharge and Laser Ion Source, with Penning-trap mass spectrometry at the CERN-ISOLDE facility, this work reports on mean-square charge radii of neutron-rich mercury isotopes across the $N = 126$ shell closure, the electromagnetic moments of $^{207}$Hg and more precise mass values of $^{206-208}$Hg. The odd-even staggering (OES) of the mean square charge radii and the kink at $N = 126$ are analyzed within the framework of covariant density functional theory (CDFT), with comparisons between different functionals to investigate the dependence of the results on the underlying single-particle structure. The observed features are defined predominantly in the particle-hole channel in CDFT, since both are present in the calculations without pairing. However, the magnitude of the kink is still affected by the occupation of the $1i_{11/2}$ and $2g_{9/2}$ orbitals with a dependence on the relative energies as well as pairing., 20 pages, 12 figures, Phys. Rev. C in press

The changes in the mean-square charge radius (relative to 209Bi), magnetic dipole, and electric quadrupole moments of 187,188,189,191Bi were measured using the in-source resonance-ionization spectroscopy technique at ISOLDE (CERN). A large staggering in radii was found in 187,188,189Big, manifested by a sharp radius increase for the ground state of 188Bi relative to the neighboring 187,189Big. A large isomer shift was also observed for 188Bim. Both effects happen at the same neutron number, N=105, where the shape staggering and a similar isomer shift were observed in the mercury isotopes. Experimental results are reproduced by mean-field calculations where the ground or isomeric states were identified by the blocked quasiparticle configuration compatible with the observed spin, parity, and magnetic moment. ispartof: Physical Review Letters vol:127 issue:9 ispartof: location:United States status: published

A study of the laser-ionized and mass-separated neutron-deficient isotopes Au 176 , 177 , 179 was performed using the Resonance Ionization Laser Ion Source and the Windmill detection setup at ISOLDE, CERN. New and improved data on complex fine-structure α decays of the three isotopes were deduced, providing insight into the low-lying levels in the daughter nuclei Ir 172 , 173 , 175 . New information on the properties of β -decay daughter products Pt 177 , 179 was also obtained. From the first in-source laser spectroscopy measurements of the hyperfine structure in the atomic 267.6-nm transition of Au 176 , the nuclear magnetic moments for both high- and low-spin α -decaying states were deduced. Together with the values determined from the additivity relations, they were used to propose the most probable spins and configurations for both states. The α -decay branching ratios were determined as b α ( Au ls 176 ) = 58 ( 5 ) % and b α ( Au hs 176 ) = 29 ( 5 ) % .

Among the most widely used medical radionuclides there are isotopes of elements with relatively low ionization potential. The simplest type of a mass-separator ion-source in this case is a hot cavity surface ionizer. However, the ionization efficiency of such a type of ionizer for non-alkalis is low (for example, of about 1% for Tl). To increase the surface ionization efficiency, a new material for the surface ion source (monocrystalline tungsten) was used at the mass separator working on-line with the 1-GeV proton synchrocyclotron of Petersburg Nuclear Physics Institute. The ionization efficiency for certain elements with medium ionization potential (Sr, In, Tl) was measured: 45(5)%, 33(8)%, and 21(8)% respectively.

The mean-square charge radii of $^{207,208}$Hg ($Z=80, N=127,128$) have been studied for the first time and those of $^{202,203,206}$Hg ($N=122,123,126$) remeasured by the application of in-source resonance-ionization laser spectroscopy at ISOLDE (CERN). The characteristic \textit{kink} in the charge radii at the $N=126$ neutron shell closure has been revealed, providing the first information on its behavior below the $Z=82$ proton shell closure. A theoretical analysis has been performed within relativistic Hartree-Bogoliubov and non-relativistic Hartree-Fock-Bogoliubov approaches, considering both the new mercury results and existing lead data. Contrary to previous interpretations, it is demonstrated that both the kink at $N=126$ and the odd-even staggering (OES) in its vicinity can be described predominately at the mean-field level, and that pairing does not need to play a crucial role in their origin. A new OES mechanism is suggested, related to the staggering in the occupation of the different neutron orbitals in odd- and even-$A$ nuclei, facilitated by particle-vibration coupling for odd-$A$ nuclei.

A nuclear model is proposed where the nucleons interact by emitting and absorbing mesons, and where the mesons are treated explicitly. A nucleus in this model finds itself in a quantum superposition of states with different number of mesons. Transitions between these states hold the nucleus together. The model—in its simplest incarnation—is applied to the deuteron, where the latter becomes a superposition of a neutron-proton state and a neutron-proton-meson state. Coupling between these states leads to an effective attraction between the nucleons and results in a bound state with negative energy, the deuteron. The model is able to reproduce the accepted values for the binding energy and the charge radius of the deuteron. The model, should it work in practice, has several potential advantages over the existing non-relativistic few-body nuclear models: the reduced number of model parameters, natural inclusion of few-body forces, and natural inclusion of mesonic physics.

A study of the ground states of the laser-ionized and mass-separated odd-odd isotopes 180,182Au was performed using the Resonance Ionization Laser Ion Source, Windmill detection setup and ISOLTRAP Multi-Reflection Time-of-Flight Mass Spectrometer at ISOLDE, CERN. A complex fine-structure α-decay pattern of 180Au was deduced, providing insight into the low-lying levels in the daughter nucleus 176Ir. An α-decay branching ratio of bα(180Au)=0.58(10)% and a half-life of T1/2=7.2(5) s have also been derived, allowing for the calculation of the reduced α-decay widths and determining the degree of hindrance of respective α-decay branches. From complementary first in-source laser spectroscopy measurements of the hyperfine structure in atomic transitions of 180,182Au, the nuclear magnetic moments of μ(180Au)=−0.83(9)μN and μ(182Au)=1.66(9)μN were extracted with an inclusion of a correction for the hyperfine anomaly. Based on the observed hyperfine structure patterns, and on the comparison of the measured and calculated μ values, a preferred ground-state spin and parity Iπ(180Augs)=(1+) is proposed, and the earlier assignment of Iπ(182Augs)=(2+) is confirmed. For 180Au, the most probable proton-neutron Nilsson configuration of π3/2−[532]⊗ν5/2−[512] suggests the same proton state as in the heavier deformed odd-odd nuclei 182,184Au.

Hyperfine-structure constants for the 6s2S1/2 and 6p2P1/2 atomic states of the Iπ=11/2− gold isomers Aum177,191,193,195 have been measured at CERN-ISOLDE, using the in-source laser resonance-ionization spectroscopy technique. From the measured hyperfine constants the differences between hyperfine anomalies for these atomic states have been deduced. These differential hyperfine anomaly values have been used to determine the 6s-state hyperfine anomaly relative to the stable Au197 with advanced atomic calculations. Magnetic dipole moments for the gold isomers in question have been deduced, taking into account the corresponding relative hyperfine-anomaly values. It has been shown that the commonly used prescription for the extraction of the magnetic moment values for the gold isotopes should be reconsidered. The magnetic moments calculated by this prescription have been reevaluated by properly accounting for the hyperfine anomaly, which is as large as 10% for several gold isotopes.

Isotopes with an odd number of neutrons are usually slightly smaller in size than their even-neutron neighbours. In charge radii of short-lived copper isotopes, a reduction of this effect is observed when the neutron number approaches fifty. The mesoscopic nature of the atomic nucleus gives rise to a wide array of macroscopic and microscopic phenomena. The size of the nucleus is a window into this duality: while the charge radii globally scale as $A^{1/3}$, their evolution across isotopic chains reveals unanticipated structural phenomena [1-3]. The most ubiquitous of these is perhaps the Odd-Even Staggering (OES) [4]: isotopes with an odd number of neutrons are usually smaller in size than the trend of their even-neutron neighbours suggests. This OES effect varies with the number of protons and neutrons and poses a significant challenge for nuclear theory [5-7]. Here, we examine this problem with new measurements of the charge radii of short-lived copper isotopes up to the very exotic $^{78}$Cu $(Z=29, N=49)$, produced at only 20 ions/s, using the highly-sensitive Collinear Resonance Ionisation Spectroscopy (CRIS) method at ISOLDE-CERN. Due to the presence of a single proton outside of the closed Z=28 shell, these measurements provide crucial insights into the single-particle proton structure and how this affects the charge radii. We observe an unexpected reduction in the OES for isotopes approaching the $N=50$ shell gap. To describe the data, we applied models based on nuclear Density Functional Theory [2,8] (DFT) and ab-initio Valence-Space In-Medium Similarity Renormalization Group (VS-IMSRG) theory [9,10]. Through these comparisons, we demonstrate a relation between the global behavior of charge radii and the saturation density of nuclear matter, and show that the local charge radii variations, which reflect the many-body polarization effects due to the odd neutron, naturally emerge from the VS-IMSRG calculations.

A comprehensive study of the isotope 178Au has been made at the CERN-ISOLDE facility, using resonance laser ionization. Two long-lived states in 178Au were identified—a low-spin ground state and a high-spin isomer—each of which were produced as pure beams. Using the ISOLTRAP precision Penning trap, the excitation energy of the isomeric state in 178Au was determined to be E∗=189(14)keV. The α-decay fine structure patterns of the two states were studied using the Windmill decay station, providing information on the low-lying states in the daughter nucleus 174Ir. Nuclear spin assignments of I(178Aug)=(2,3) and I(178Aum)=(7,8) are made based on the observed β-decay feeding and hyperfine structure intensity patterns. These spin assignments are used for fitting the hyperfine structures of the two states from which values for the magnetic dipole moments are extracted. The extracted moments are compared with calculations using additivity relations to establish the most probable configurations for 178Aug,m.

A cyclotron (C-80) designed to produce protons with an energy of 40–80 MeV and beam intensity of 100–200 μA has been launched at the Petersburg Nuclear Physics Institute, National Research Center Kurchatov Institute. The main task of C-80 is the production of a wide range of medical radionuclides for diagnosis and therapy. A complex named Radioactive Isotopes on the C-80 Cyclotron (RIC-80) and intended to function on the C-80 beam was developed for this purpose. A brief description of the RIC-80 complex is given, and the results of the use of new methods and studies of target devices for the production of the generator radioisotope 82Sr; 223Ra, 224Ra, and 225Ac radioisotopes that undergo alpha-decay; 67Cu; and other medical radionuclides are presented. The use of a mass separator in the “on-line” mode to obtain ion beams of high-purity radioisotopes is a distinctive feature of the complex used in the project, and it is especially important for medical applications.

The concept of deterministic chaos at the initial development stage was considered as an unusual phenomenon that never arose in the solution of practical problems and was of interest only for a narrow circle of scientists. However, later chaotic dynamics was discovered in a large number of different systems. Further development revealed a number of practical problems, when there were chaotic regimes, sometimes harmful, and sometimes useful. Practically important classes of problems have appeared, when a non-linear system must be controlled, reduced, or, on the contrary, increased in degree of randomness.

This paper presents the results of an investigation into autoionizing states of atomic chromium, in the service of the resonance ionization laser ion source (RILIS): the principal ion source of the ISOLDE radioactive ion beam facility based at CERN. The multi-step resonance photo-ionization process enables element selective ionization which, in combination with mass separation, allows isotope specific selectivity in the production of radioactive ion beams at ISOLDE. The element selective nature of the process requires a multi-step “ionization scheme” to be developed for each element. Using the method of in-source resonance ionization spectroscopy, an optimal three-step, three-resonance photo-ionization scheme originating from the 3d 5 ( 6 S)4s a 7 S 3 atomic ground state has been developed for chromium. The scheme uses an ionizing transition to one of the 15 newly observed autoionizing states reported here. Details of the spectroscopic studies are described and the new ionization scheme is summarized.

Chromatin remodulators are special multiprotein machines capable of transforming the structure, constitution, and positioning of nucleosomes on DNA. Biochemical activities of remodeling complexes CHD1 and ISWI from the SWI2/SNF2 family are well established. They ensure correct positioning of nucleosomes along the genome, which is probably critical for genome stability, in particular, after action of polymerases, repair enzymes, and transcription. In this paper, we show that single mutations in genes ISW1, ISW2, and CHD1 weakly affect repair and mutagenic processes in yeast cells. At the same time, there are differences in the effect of these mutations on spontaneous mutation levels, which indicates certain specificity of action of protein complexes ISW1, ISW2, and CHD1 on expression of different genes that control repair and mutation processes in yeast.

Within the Correlated Gaussian Method the parameters of the Gaussian basis functions are often chosen stochastically using pseudo-random sequences. We show that alternative low-discrepancy sequences, also known as quasi-random sequences, provide bases of better quality.

Hyperfine-structure parameters and isotope shifts for the 795-nm atomic transitions in $^{217,218,219}$At have been measured at CERN-ISOLDE, using the in-source resonance-ionization spectroscopy technique. Magnetic dipole and electric quadrupole moments, and changes in the nuclear mean-square charge radii, have been deduced. A large inverse odd-even staggering in radii, which may be associated with the presence of octupole collectivity, has been observed. Namely, the radius of the odd-odd isotope $^{218}$At has been found to be larger than the average of its even-$N$ neighbors, $^{217,219}$At. The discrepancy between the additivity-rule prediction and experimental data for the magnetic moment of $^{218}$At also supports the possible presence of octupole collectivity in the considered nuclei.

Excited states in Sn-133 were investigated through the beta decay of In-133 at the ISOLDE facility. The ISOLDE Resonance Ionization Laser Ion Source (RILIS) provided isomer-selective ionization for In-133, allowing us to study separately, and in detail, the beta-decay branch of In-133 J(pi)= (9/2(+)) ground state and its J(pi) = (1/2(-)) isomer.Thanks to the large spin difference of the two beta-decaying states of In-133, it is possible to investigate separately the lower and higher spin states in the daughter, Sn-133, and thus to probe independently different single-particle and single-hole levels. We report here new gamma transitions observed in the decay of In-133, including those assigned to the deexcitation of the neutron-unbound states.

The Be7(n,p) cross section was measured with an ion-implanted Be7 target at a thermal neutron beam of the research reactor LVR-15 in Řež. The cross section to the ground state of Li7 is σ(n,p0)=43800±1400b and the cross section to the first excited state of Li7 is σ(n,p1)=520±260b.

Neutron-deficient Hg177-185 isotopes were studied using in-source laser resonance-ionization spectroscopy at the CERN-ISOLDE radioactive ion-beam facility in an experiment combining different detection methods tailored to the studied isotopes. These include either α-decay tagging or multireflection time-of-flight gating for isotope identification. The endpoint of the odd-even nuclear shape staggering in mercury was observed directly by measuring for the first time the isotope shifts and hyperfine structures of Hg177-180. Changes in the mean-square charge radii for all mentioned isotopes, magnetic dipole, and electric quadrupole moments of the odd-A isotopes and arguments in favor of I=7/2 spin assignment for Hg177,179 were deduced. Experimental results are compared with density functional theory (DFT) and Monte Carlo shell model (MCSM) calculations. DFT calculations using Skyrme parametrizations predict a jump in the charge radius around the neutron N=104 midshell, with an odd-even staggering pattern related to the coexistence of nearly degenerate oblate and prolate minima. This near-degeneracy is highly sensitive to many aspects of the effective interaction, a fact that renders perfect agreement with experiments out of reach for current functionals. Despite this inherent difficulty, the SLy5s1 and a modified UNEDF1SO parametrization predict a qualitatively correct staggering that is off by two neutron numbers. MCSM calculations of states with the experimental spins and parities show good agreement for both electromagnetic moments and the observed charge radii. A clear mechanism for the origin of shape staggering within this context is identified: A substantial change in occupancy of the proton πh9/2 and neutron νi13/2 orbitals., SCOPUS: ar.j, info:eu-repo/semantics/published

A new approach to observe the radiative decay of the $^{229}$Th nuclear isomer, and to determine its energy and radiative lifetime, is presented. Situated at a uniquely low excitation energy, this nuclear state might be a key ingredient for the development of a nuclear clock, a nuclear laser and the search for time variations of the fundamental constants. The isomer's $\gamma$ decay towards the ground state will be studied with a high-resolution VUV spectrometer after its production by the $\beta$ decay of $^{229}$Ac. The novel production method presents a number of advantages asserting its competitive nature with respect to the commonly used $^{233}$U $\alpha$-decay recoil source. In this paper, a feasibility analysis of this new concept, and an experimental investigation of its key ingredients, using a pure $^{229}$Ac ion beam produced at the ISOLDE radioactive beam facility, is reported., Comment: 11 pages, 5 figures, 2 tables