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Despite widespread use of branched glycerol dialkyl glycerol tetraethers (brGDGTs) for paleo-temperature reconstruction, no global calibration for their application in lakes has been generated since improved analytical methods have allowed for the separation of the structural isomers. This is a substantial obstacle for the application of this tool as soil calibrations underestimate temperature values when applied to lake sediments. Here, we present a comprehensive dataset ( N = 272 ) of lacustrine brGDGT distributions, consisting of both new and previously reported samples, spanning a wide range of geographical locations, air temperatures, and lakewater pH values. Empirical Orthogonal Function (EOF) analysis on the fractional abundance of brGDGTs indicates that temperature exerts a strong control (explaining 58 % of the variance) on brGDGT distribution. The influence of water chemistry is weaker, with pH and conductivity explaining 24 % of the variance. We use our dataset to generate a new Bayesian calibration to the mean temperature of Months Above Freezing (MAF), which has an R 2 = 0.82 and RMSE = 2.9 ° C. Application of the new temperature calibration to a previously published lake core record spanning the last 900 years demonstrates that it generates values comparable to instrumental observations of MAF. Our new calibration facilitates the use of lacustrine brGDGTs to reconstruct continental temperatures, a vital piece of information for understanding past climates.

International audience; This work describes a silicon tracker system developed for experiments with proton-rich radioactive ion beams at the SAMURAI superconducting spectrometer of RIBF at RIKEN. The system is designed for accurate angular reconstruction and atomic number identification of relativistic heavy ions and protons which are simultaneously produced in reactions motivated by studies of proton capture reactions of interest for nuclear astrophysics. The technical characteristics of the tracking array are described in detail as are its performance in two pilot experiments. The physics justification for such a system is also presented.

Rising summer temperatures are expected to increase tree mortality rates across the western United States. Here, we analyze subfossil wood samples from Colorado dating to the last interglacial to a...

Summary Glycerol Dialkyl Glycerol Tetraethers (GDGTs) are a group of molecules that have been successfully used for paleoclimate reconstructions in a wide range of environments. GDGTs have shown to be useful biomarkers as they are widely available, and their structure is relatively resistant to diagenetic alteration. Specific GDGTs are associated with particular environments, which suggests that they could potentially be used to classify ancient depositional conditions in cases where the exact paleoenvironment is not known. In this work we present a comprehensive branched and iGDGT dataset from published and novel analyses, with more than 1000 modern samples from marine, lake and river sediments as well as soils and peat samples. Unsupervised and supervised machine learning techniques were applied to this dataset to generate GDGT and environmentally based clusters and train a classification algorithm. The trained algorithm has the potential to be applied to samples formed in unclear or transitional depositional environments, allowing us to identify the potential environment in which they were formed. Furthermore, the classification model can help determine which environmental calibration is most appropriate for the setting, thereby improving paleoenvironmental reconstructions.

Rotational structures have been measured using the Jurogam II and GAMMASPHERE arrays at low spin following the Gd155(α,2n)Dy157 and Nd148(C12,5n)Dy155 reactions at 25 and 65 MeV, respectively. We report high-K bands, which are conjectured to be the first candidates of a Kπ=2+γ vibrational band, built on the [505]11/2− neutron orbital, in both odd-ADy155,157 isotopes. The coupling of the first excited K=0+ states or the so-called β vibrational bands at 661 and 676 keV in Dy154 and Dy156 to the [505]11/2− orbital, to produce a Kπ=11/2− band, was not observed in both Dy155 and Dy157, respectively. The implication of these findings on the interpretation of the first excited 0+ states in the core nuclei Dy154 and Dy156 are also discussed.

A Monte Carlo simulation-based optimization of a multilayer 10B-RPC thermal neutron detector is performed targeting an increase in the counting rate capability while maintaining high (>50%) detection efficiency for thermal neutrons. The converter layer thicknesses of individual RPCs are optimized for several configurations of a detector containing a stack of 10 double gap RPCs. The results suggest that it is possible to reach a counting rate which is by a factor of eight higher in comparison to the rate of a detector with only one double-gap RPC. The effect of neutron scattering inside the detector contributing to the background is analyzed and design modifications of the first detector prototype, tested at neutron beam, are suggested.

The neutron-deficient mercury isotopes serve as a classical example of shape coexistence, whereby at low energy near-degenerate nuclear states characterized by different shapes appear. The electromagnetic structure of even-mass 182-188 Hg isotopes was studied using safe-energy Coulomb excitation of neutron-deficient mercury beams delivered by the REX-ISOLDE facility at CERN. The population of $ 0^{+}_{1,2}$01,2+, $ 2^{+}_{1,2}$21,2+and $ 4^{+}_{1}$41+states was observed in all nuclei under study. Reduced E2 matrix elements coupling populated yrast and non-yrast states were extracted, including their relative signs. These are a sensitive probe of shape coexistence and may be used to validate nuclear models. The experimental results are discussed in terms of mixing of two different configurations and are compared with three different model calculations: the Beyond Mean Field model, the Interacting Boson Model with configuration mixing and the General Bohr Hamiltonian. Partial agreement with experiment was observed, hinting to missing ingredients in the theoretical descriptions. The neutron-deficient mercury isotopes serve as a classical example of shape coexistence, whereby at low energy near-degenerate nuclear states characterized by different shapes appear. The electromagnetic structure of even-mass 182-188 Hg isotopes was studied using safe-energy Coulomb excitation of neutron-deficient mercury beams delivered by the REX-ISOLDE facility at CERN. The population of $ 0^{+}_{1,2}$01,2+, $ 2^{+}_{1,2}$21,2+and $ 4^{+}_{1}$41+states was observed in all nuclei under study. Reduced E2 matrix elements coupling populated yrast and non-yrast states were extracted, including their relative signs. These are a sensitive probe of shape coexistence and may be used to validate nuclear models. The experimental results are discussed in terms of mixing of two different configurations and are compared with three different model calculations: the Beyond Mean Field model, the Interacting Boson Model with configuration mixing and the General Bohr Hamiltonian. Partial agreement with experiment was observed, hinting to missing ingredients in the theoretical descriptions. ispartof: The European Physical Journal A - Hadrons and Nuclei vol:55 issue:8 pages:130-130 status: published

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) in lake sediments are increasingly being used to reconstruct past temperatures. However, recent studies suggest that brGDGT distributions and concentrations vary with lake size and environmental conditions, such as seasonality and its effects on water column temperature and chemistry. To test their use as a paleothermometer in high-altitude environments of mid-latitude North America, we analyzed brGDGT distributions in lake surface sediments across a range of lake depths and elevations in the Rocky Mountains of Wyoming and Colorado. Our results suggest that brGDGT distributions and the MBT′5Me index correlate with water column temperatures, which are sensitive to both lake water depth and air temperatures. Based on these relationships, we developed a calibration to mean summer air temperatures using a Bayesian regression model that incorporates the MBT′5Me index and lake water depth. We applied our calibration to lake sediments from Lower Paintrock Lake in northern Wyoming to test its use as a paleothermometer. Reconstructed temperature trends are consistent with pollen-inferred temperatures at the same site and with known regional climate history, demonstrating that our calibration can be successfully applied to infer temperatures in high-altitude environments of mid-latitude North America.

A sequence of low-energy levels in _{32}^{78}Ge_{46} has been identified with spins and parity of 2^{+}, 3^{+}, 4^{+}, 5^{+}, and 6^{+}. Decays within this band proceed strictly through ΔJ=1 transitions, unlike similar sequences in neighboring Ge and Se nuclei. Above the 2^{+} level, members of this sequence do not decay into the ground-state band. Moreover, the energy staggering of this sequence has the phase that would be expected for a γ-rigid structure. The energies and branching ratios of many of the levels are described well by shell-model calculations. However, the calculated reduced transition probabilities for the ΔJ=2 in-band transitions imply that they should have been observed, in contradiction with the experiment. Within the calculations of Davydov, Filippov, and Rostovsky for rigid-triaxial rotors with γ=30°, there are sequences of higher-spin levels connected by strong ΔJ=1 transitions which decay in the same manner as those observed experimentally, yet are calculated at too high an excitation energy.

A sequence of low-energy levels in _{32}^{78}Ge_{46} has been identified with spins and parity of 2^{+}, 3^{+}, 4^{+}, 5^{+}, and 6^{+}. Decays within this band proceed strictly through ΔJ=1 transitions, unlike similar sequences in neighboring Ge and Se nuclei. Above the 2^{+} level, members of this sequence do not decay into the ground-state band. Moreover, the energy staggering of this sequence has the phase that would be expected for a γ-rigid structure. The energies and branching ratios of many of the levels are described well by shell-model calculations. However, the calculated reduced transition probabilities for the ΔJ=2 in-band transitions imply that they should have been observed, in contradiction with the experiment. Within the calculations of Davydov, Filippov, and Rostovsky for rigid-triaxial rotors with γ=30°, there are sequences of higher-spin levels connected by strong ΔJ=1 transitions which decay in the same manner as those observed experimentally, yet are calculated at too high an excitation energy.

Tularemia is a zoonosis caused by Francisella tularensis that can be transmitted by several ways to human being and cause different clinical manifestations. We report three clinical cases of tularemia with ulceroglandular presentation in young males acquired during outdoor activities in Southern Belgium. Confirmation of the diagnosis was established by serology. Only three cases of tularemia have been reported in Belgium between 1950 and 2012 by the National Reference Laboratory CODA-CERVA (Ref Lab CODA-CERVA) but re-emergence of tularemia is established in several European countries and F. tularensis is also well known to be present in animal reservoirs and vectors in Belgium. The diagnosis of tularemia has to be considered in case of suggestive clinical presentation associated with epidemiological risk factors.

Fast-rotating N = 151 isotones 245 Pu, 247 Cm and 249 Cf have been studied through inelastic excitation and transfer reactions with radioactive targets. While all have a ground-state band built on a ν j 15 / 2 [ 734 ] 9 / 2 − Nilsson configuration, new excited bands have also been observed in each isotone. These odd- N excited bands allow a comparison of the alignment behavior for two different configurations, where the ν j 15 / 2 alignment is either blocked or allowed. The effect of higher order deformations is explored through cranking calculations, which help clarify the elusive nature of ν j 15 / 2 alignments.

The Multi-Grid detector technology has evolved from the proof-of-principle and characterisation stages. Here we report on the performance of the Multi-Grid detector, the MG.CNCS prototype, which has been installed and tested at the Cold Neutron Chopper Spectrometer, CNCS at SNS. This has allowed a side-by-side comparison to the performance of $^3$He detectors on an operational instrument. The demonstrator has an active area of 0.2 m$^2$. It is specifically tailored to the specifications of CNCS. The detector was installed in June 2016 and has operated since then, collecting neutron scattering data in parallel to the He-3 detectors of CNCS. In this paper, we present a comprehensive analysis of this data, in particular on instrument energy resolution, rate capability, background and relative efficiency. Stability, gamma-ray and fast neutron sensitivity have also been investigated. The effect of scattering in the detector components has been measured and provides input to comparison for Monte Carlo simulations. All data is presented in comparison to that measured by the $^3$He detectors simultaneously, showing that all features recorded by one detector are also recorded by the other. The energy resolution matches closely. We find that the Multi-Grid is able to match the data collected by $^3$He, and see an indication of a considerable advantage in the count rate capability. Based on these results, we are confident that the Multi-Grid detector will be capable of producing high quality scientific data on chopper spectrometers utilising the unprecedented neutron flux of the ESS., submitted to JINST

High-elevation environments above 2500 metres above sea level (m.a.s.l.) were among the planet's last frontiers of human colonization. Research on the speed and tempo of this colonization process is active and holds implications for understanding rates of genetic, physiological and cultural adaptation in our species. Permanent occupation of high-elevation environments in the Andes Mountains of South America tentatively began with hunter–gatherers around 9 ka according to current archaeological estimates, though the timing is currently debated. Recent observations on the archaeological site of Soro Mik'aya Patjxa (8.0–6.5 ka), located at 3800 m.a.s.l. in the Andean Altiplano, offer an opportunity to independently test hypotheses for early permanent use of the region. This study observes low oxygen ( δ 18 O) and high carbon ( δ 13 C) isotope values in human bone, long travel distances to low-elevation zones, variable age and sex structure in the human population and an absence of non-local lithic materials. These independent lines of evidence converge to support a model of permanent occupation of high elevations and refute logistical and seasonal use models. The results constitute the strongest empirical support to date for permanent human occupation of the Andean highlands by hunter–gatherers before 7 ka.

Journal of Instrumentation 14(10), P10020 - P10020 (2019). doi:10.1088/1748-0221/14/10/P10020, HEIMDAL is a thermal powder diffractometer designed to operate at the European Spallation Source, world's most intense neutron source. The detailed design of the instrument, which is expected to enter user operation in 2024/2025, assumes that the neutrons scattered by the powder under investigation will be collected with hundreds of large-area Multi-Wire Proportional Counters employing a 10B4C-solid converter. The gas counters will consist of large active volumes and tapered trapezoidal shapes that allow for close packing into a cylindrical shell with high solid angle coverage. The whole detector will operate in an air environment within the shielding cave and provide signals with sensitivity for locating detection in three dimensions. This paper presents the results of a GEANT4 study of the baseline design for the HEIMDAL powder diffraction detector. The detector model was used to study the spatial resolution, which in the horizontal scattering plane must be below 3 mm in order to enable high-resolution diffraction studies. The contribution of the detector to the resolving power of the instrument, one of the key figures-of-merit for powder diffractometers, was also investigated. Most of the simulation results reported in this work cannot be validated against a sufficiently similar physical reference until the first segment or module are constructed and tested with a neutron beam. However, these results can help to identify possible ways of optimising the detector design and provide the first glimpse into the expected performance of this technological approach., Published by Inst. of Physics, London

We present a novel design for a macrostructured cathode that can be coated with a thin layer of the B-10 solid converter and mounted to replace the Boron-lined flat parallel plates of a proportional counter used for slow neutron detection. The proposed design consists of a 3D regular pattern exhibiting millimeter deep grooves with an opening angle of alpha = 45 degrees, which could be created in the substrate material by milling or forming. When a commonly used coating method like magnetron sputtering is employed to deposit the Boron-layer, due to the line-of-sight distribution of the ions, the thickness of the coating on the side of the grooves will be reduced by a factor similar to sin alpha/2 with respect to the thickness of the layer deposited on a flat surface normal to the ion flux. The effective neutron absorption film thickness is in this case similar for the sidewalls of the grooves and a surface at normal incidence, yielding comparable absorption efficiencies. However, the escape efficiency for the reaction products is higher for the sidewalls, owing to the thinner coating. This leads to a higher overall detection efficiency for the grooved cathode when compared to a flat cathode with the same surface area and coated with a Boron layer with roughly the same thickness. In this paper we present and discuss the GEANT4 simulations performed to optimize the geometry of the cathode, the manufacturing and coating by magnetron sputtering, as well as the proof-of-principle measurements carried out in order to assess the performance of the proposed design. (C) 2013 Elsevier B.V. All rights reserved. (Less)

The structure of neutron-rich 96,98Sr nuclei was investigated by low-energy safe Coulomb excitation of radioactive beams at the REX-ISOLDE facility, CERN, with the MINIBALL spectrometer. A rich set of transitional and diagonal E2 matrix elements, including those for non-yrast structures, has been extracted from the differential Coulomb-excitation cross sections. The results support the scenario of a shape transition at N = 60, giving rise to the coexistence of a highly deformed prolate and a spherical configuration in 98Sr, and are compared to predictions from several theoretical calculations. The experimental data suggest a significant contribution of the triaxal degree of freedom in the ground state of both isotopes. In addition, experimental information on low-lying states in 98Rb has been obtained.

Here, the decay of a Kπ = 8– isomer in 244Pu and the collective band structures populating the isomer were studied using deep inelastic excitations with 47Ti and 208Pb beams, respectively. Precise measurements of M1/E2 branching ratios in the band confirm a 9/2–[734]νⓍ7/2+[624]ν configuration assignment for the isomer, validating the systematics of Kπ = 8–, two-quasineutron isomers observed in even-Z, N = 150 isotones. These isomers around the deformed shell gap at N = 152 provide critical benchmarks for theoretical predictions of single-particle energies in this gateway region to superheavy nuclei.

Neutron-rich {96,98}Sr isotopes have been investigated by safe Coulomb excitation of radioactive beams at the REX-ISOLDE facility. Reduced transition probabilities and spectroscopic quadrupole moments have been extracted from the differential Coulomb excitation cross sections. These results allow, for the first time, the drawing of definite conclusions about the shape coexistence of highly deformed prolate and spherical configurations. In particular, a very small mixing between the coexisting states is observed, contrary to other mass regions where strong mixing is present. Experimental results have been compared to beyond-mean-field calculations using the Gogny D1S interaction in a five-dimensional collective Hamiltonian formalism, which reproduce the shape change at N=60.

Excited states with seniority $\ensuremath{\nu}=3$, 5, and 7 have been investigated in odd neutron-rich $^{119,121,123,125}\text{Sn}$ isotopes produced by fusion-fission of 6.9-MeV/$A\phantom{\rule{4pt}{0ex}}^{48}\text{Ca}$ beams with $^{208}\text{Pb}$ and $^{238}\text{U}$ targets and by fission of a $^{238}\text{U}$ target bombarded with 6.7-MeV/$A\phantom{\rule{4pt}{0ex}}^{64}\text{Ni}$ beams. Level schemes have been established up to high spin and excitation energies in excess of 6 MeV, based on multifold gamma-ray coincidence relationships measured with the Gammasphere array. In the analysis, the presence of isomers was exploited to identify gamma rays and propose transition placements using prompt and delayed coincidence techniques. Gamma decays of the known $27/{2}^{\ensuremath{-}}$ isomers were expanded by identifying new deexcitation paths feeding $23/{2}^{+}$ long-lived states and $21/{2}^{+}$ levels. Competing branches in the decay of $23/{2}^{\ensuremath{-}}$ states toward two $19/{2}^{\ensuremath{-}}$ levels were delineated as well. In $^{119}\text{Sn}$, a new $23/{2}^{+}$ isomer was identified, while a similar $23/{2}^{+}$ long-lived state, proposed earlier in $^{121}\text{Sn}$, has now been confirmed. In both cases, isomeric half-lives were determined with good precision. In the range of $\ensuremath{\nu}=3$ excitations, the observed transitions linking the various states enabled one to propose with confidence spin-parity assignments for all the observed states. Above the $27/{2}^{\ensuremath{-}}$ isomers, an elaborate structure of negative-parity levels was established reaching the ($39/{2}^{\ensuremath{-}}$), $\ensuremath{\nu}=7$ states, with tentative spin-parity assignments based on the observed deexcitation paths as well as on general yrast population arguments. In all the isotopes under investigation, strongly populated sequences of positive-parity ($35/{2}^{+}$), ($31/{2}^{+}$), and ($27/{2}^{+}$) states were established, feeding the $23/{2}^{+}$ isomers via cascades of three transitions. In the $^{121,123}\text{Sn}$ isotopes, these sequences also enabled the delineation of higher-lying levels, up to ($43/{2}^{+}$) states. In $^{123}\text{Sn}$, a short half-life was determined for the ($35/{2}^{+}$) state. Shell-model calculations were carried out for all the odd Sn isotopes, from $^{129}\text{Sn}$ down to $^{119}\text{Sn}$, and the results were found to reproduce the experimental level energies rather well. Nevertheless, some systematic deviations between calculated and experimental energies, especially for positive-parity states, point to the need to improve some of the two-body interactions used in calculations. The computed wave-function amplitudes provide for a fairly transparent interpretation of the observed level structures. The systematics of level energies over the broad $A$ = 117--129 range of Sn isotopes displays a smooth decrease with mass $A$, and the observed regularity confirms most of the proposed spin-parity assignments. The systematics of the $B(E2)$ reduced transition probabilities extracted for the $23/{2}^{+}$ and $19/{2}^{+}$ isomers is discussed with an emphasis on the close similarity of the observed $A$ dependence with that of the $E2$ transition rates established for other $\ensuremath{\nu}=2$, 3, and 4 isomers in the Sn isotopic chain.

The ambitious instrument suite for the future European Spallation Source whose civil construction started recently in Lund, Sweden, demands a set of diverse and challenging requirements for the neutron detectors. For instance, the unprecedented high flux expected on the samples to be investigated in neutron diffraction or reflectometry experiments requires detectors that can handle high counting rates, while the investigation of sub-millimeter protein crystals will only be possible with large-area detectors that can achieve a position resolution as low as 200 {\mu}m. This has motivated an extensive research and development campaign to advance the state-of-the-art detector and to find new technologies that can reach maturity by the time the ESS will operate at full potential. This paper presents the key detector requirements for three of the Time-of-Flight diffraction instrument concepts selected by the Scientific Advisory Committee to advance into the phase of preliminary engineering design. We discuss the available detector technologies suitable for this particular instrument class and their major challenges. The detector technologies selected by the instrument teams to collect the diffraction patterns are briefly discussed. Analytical calculations, Monte-Carlo simulations, and real experimental data are used to develop a generic method to esti- mate the event rate in the diffraction detectors. The proposed approach is based upon conservative assumptions that use information and input parameters that reflect our current level of knowledge and understanding of the ESS project. We apply this method to make predictions for the future diffraction instruments, and thus provide additional information that can help the instrument teams with the optimisation of the detector designs., Comment: 25 pages, 5 figures

This paper reports an analysis of the accuracy and sensitivity of ultimate tensile strength and strain to failure to changes in microstructure constituents in Al–Si alloys ranging from 7 to 18%Si. The influence of amount of constituents, namely dendrites, eutectic, silicon particles and intermetallics as well as their geometrical features, namely secondary dendrite arm spacing, silicon eutectic thickness and intermetallics thickness on both ultimate tensile strength and strain to failure is evaluated. This study provides information that will be useful in the establishment of robust correlations between mechanical properties and metallurgical features, since they are highly dependent on their sensitivity and accuracy.

The light krypton isotopes were studied in a series of Coulomb excitation experiments using radioactive beams at GANIL. The static quadrupole moments found in these experiments give firm experimental evidence for the shape coexistence scenario that is based on theoretical calculations and on the systematics of low-lying excited 0+ states. The experimental results are interpreted within a phenomenological two-band mixing model. Configuration mixing calculations based on triaxial Hartree-Fock-Bogolyubov calculations with the Gogny D1S effective interaction have been performed and compared to experimental data.

The influence of the thermomagnetic treatment on metallurgical and mechanical properties of the rolling bearing steel was investigated. The heating and/or cooling and tempering processes of the samples occurred in a magnetic field having certain strengths. The X-ray diffraction (XRD) patterns of the rolling bearing (RUL 1) steel samples exhibited a beneficial effect of the magnetic field on the structure, phase transformation, and tension state. An increased fatigue reliability was found for the rolling tribomodel made from thermomagnetically treated steel.

This paper is concerned with the sensitivity of different Al–Si alloys to centrifugal effect of the vertical centrifugal casting technique on castings as compared to the traditional gravity casting technique. A comparison of mechanical properties of specimens obtained by both centrifugal casting technique and gravity casting technique is made on three different Al–Si alloys (from a hypoeutectic to a hypereutectic alloy). A microstructure analysis, in order to quantify the phase/constituent distribution along the gradation axis, is made to understand the relationship between constituents and mechanical properties for both casting techniques. It was verified that the centrifugal effect is very alloy dependent and may be substantially well correlated with the eutectic volume fraction of the alloy. It was also found that the centrifugal effect on mechanical properties is more is more pronounced in alloys with high eutectic contents.

The low-lying states in the odd-odd and unstable isotopes 106, 108In have been Coulomb excited from the ground state and the first excited isomeric state at the REX-ISOLDE facility at CERN. With the additional data provided here the $ \pi$ g 9/2 -1 ⊗ $ \nu$ d 5/2 and $ \pi$ g 9/2 -1 ⊗ $ \nu$ g 7/2 multiplets have been re-analyzed and are modified compared to previous results. The observed $ \gamma$ -ray de-excitation patterns were interpreted within a shell model calculation based on a realistic effective interaction. The agreement between theory and experiment is satisfactory and the calculations reproduce the observed differences in the excitation pattern of the two isotopes. The calculations exclude a 6+ ground state in 106In . This is in agreement with the conclusions drawn using other techniques. Furthermore, based on the experimental results, it is also concluded that the ordering of the isomeric and ground state in 108In is inverted compared to the shell model prediction. Limits on B(E2) values have been extracted where possible. A previously unknown low-lying state at 367keV in 106In is also reported.

The high-spin level schemes of odd–odd 100Nb ( Z = 41 , N = 59 ) and 148La ( Z = 57 , N = 91 ) were identified from γ – γ – γ coincidence studies of prompt γ rays in the spontaneous fission of 252Cf with Gammasphere. Spin/parity assignments for the levels in these two nuclei were made based on the low-lying levels assigned in decay work, on the internal conversion coefficient (ICC) measurements and the level systematics of the neighboring isotopes. A K π = 1 + deformed ground-state band was identified in 100Nb. The onset of ground-state deformation in Nb isotopes is found to take place at N = 59 , in contrast to N = 60 for Sr ( Z = 38 ), Y ( Z = 39 ) and Zr ( Z = 40 ) isotopes. Unlike the observation in 99Nb, the N = 56 subshell closure seems to be no longer dominant in 100Nb. The bands observed in 148La are interpreted as aligned coupling of [ π h 11 / 2 υ h 9 / 2 ] low J to the deformed core rotor.

This paper is concerned with the influence of vibration on the mechanical properties of castings. The main vibration effects include promotion of nucleation and thus reducing as-cast grain size; reduction of shrinkage porosities due to improved metal feeding; and production of a more homogenous metal structure. In this study, mechanical mould vibration was applied to an Al–Si hypereutectic alloy at fixed amplitude and different frequencies. Tensile tests were done on specimens obtained with the different vibrating frequency levels. Experimental results show that mechanical properties were influenced by the level of applied frequency. The tensile strength was improved for low vibration frequencies but decreased for high frequencies, as compared with gravity castings without vibration. A microstructure analysis along with a solidification behavior study was performed in order to understand the mechanism responsible for the previous behavior. A heat-transfer mechanism, that is acceleration dependent, seems to be responsible for the shift in mechanical properties response to the vibration effect.

The yrast and near-yrast level scheme of light neutron-rich 143La ( Z = 57 , N = 86 ) is reinvestigated and expanded and that of 144La ( N = 87 ) is proposed for the first time by measuring prompt γ rays from the spontaneous fission of 252Cf at Gammasphere. Spins/parities are assigned to the lowest-lying levels of 143,144La based on the early studies of β − decay, and the assignments for high-spin levels of 143,144La are made by measuring internal conversion coefficients and following the level systematics of the neighboring heavier La isotopes and even–even Ba and Ce nuclei. The B ( E 1 ) / B ( E 2 ) ratios, energy displacements δ E ( I ) and rotational frequency ratios ω − ( I ) / ω + ( I ) of the new parity-doublets of 143,144La indicate that octupole deformations/correlations also develop in these nuclei. The band-crossings observed in a rotational frequency range of 0.31 to 0.34 MeV for the two even-parity bands in 143La but being absent in 144La are interpreted as due to alignment of a pair of i 13 / 2 neutrons in 143La.

The $ \beta^{{+}}_{}$ /EC decay of 189m, gPb has been studied at the ISOLDE facility using nuclear spectroscopy and in-source laser spectroscopy. A level scheme of 189Tl has been built from $ \gamma$ - $ \gamma$ coincidence relationships and information on the feeding of some excited levels of 189Tl provided by the hyperfine spectra obtained from laser ionization. The half-lives of both the 13/2+ and 3/2- 189Pb isomers have been estimated to be T 1/2 = 50±3 s and T 1/2 = 39±8 s, respectively. Calculations have been performed for different oblate and prolate nuclear deformations using an axial-rotor coupled to one-quasiparticle model, a structure has been suggested for the low-lying levels of the 189Tl nucleus.

Rotational bands in 108,110,112Ru have been investigated by means of γ – γ – γ and γ – γ ( θ ) coincidences of prompt γ rays emitted in the spontaneous fission of 252Cf. The positive parity bands are described by different versions of IBA, where 108Ru is best described as a γ-soft nucleus whereas 110,112Ru are more like rigid triaxial rotors. New Δ I = 1 negative parity doublet bands are found. In case of 110,112Ru, these are interpreted as soft chiral vibrations. Many of the experimental findings can be explained by microscopic calculations that combine the TAC mean-field with random phase approximation but a simple geometrical explanation is not apparent.

The upgraded LISOL beta-decay detection setup, which was used for the measurement of the mass A=67 Fe–Co–Ni decay chain, is presented. A new decay correlation technique has been developed in order to characterize an isomeric 492 keV transition, observed in this decay chain. Correlating single b and c events and b-coincident c events with each other in the seconds range, allowed for the placement of this isomeric transition in 67Co. A new half-life for the 67Co ground state was determined. The technique and its possibilities and limitations are discussed. ispartof: Nuclear Instruments & Methods in Physics Research B vol:266 issue:19 pages:4600-4605 ispartof: location:FRANCE, Deauville status: published

In this paper we present a methodology for determination of tritium inventory in a tritium removal facility. The method proposed is based on the developing of computing models for accountancy of the mobile tritium inventory in the separation processes, of the stored tritium and of the trapped tritium inventory in the structure of the process system components. The configuration of the detritiation process is a combination of isotope catalytic exchange between water and hydrogen (LPCE) and the cryogenic distillation of hydrogen isotopes (CD). The computing model for tritium inventory in the LPCE process and the CD process will be developed basing on mass transfer coefficients in catalytic isotope exchange reactions and in dual-phase system (liquid-vapour) of hydrogen isotopes distillation process. Accounting of tritium inventory stored in metallic hydride will be based on in-bed calorimetry. Estimation of the trapped tritium inventory can be made by subtraction of the mobile and stored tritium inventories from the global tritium inventory of the plant area. Determinations of the global tritium inventory of the plant area will be made on a regular basis by measuring any tritium quantity entering or leaving the plant area. This methodology is intended to be applied to the Heavy Watermore » Detritiation Pilot Plant from ICIT Rm. Valcea (Romania) and to the Cernavoda Tritium Removal Facility (which will be built in the next 5-7 years). (authors)« less

On this paper, a study that evaluates the influence of some variables on the mechanical properties of the vertical centrifugal casting is made. It is emphasized the fact that the centrifugal effect from vertical centrifugal casting brings special features on mechanical properties. It has been observed that the centrifugal effect may substantially increase, in some alloys, the rupture strength, rupture strain, and Young modulus, as compared to the gravity casting technique. When compared to gravity casting, the centrifugal casting process, besides the centrifugal force (pressure effect), always has an inherent associated vibration during the casting. In this study, as an attempt to isolate the vibration effect from the overall centrifugal effect, tests on castings obtained by vibrating gravity casting process are made. A comparison between castings obtained by centrifugal casting technique, vibrating casting technique and gravity casting technique is made in order to fully understand the features that allow the improvement on mechanical properties during the vertical centrifugal casting technique. An analysis of the most important effects, on both mechanical properties and on some metallurgical features is made.

The European Spallation Source (ESS), currently under construction in Lund, Sweden, will house a suite of 16 user instruments for neutron scattering experiments. The spallation source of the ESS will emit relatively long, 2.8 ms, neutron pulses with an integrated flux that will greatly exceed that of current facilities. This leads to both large advancements in instrument performance as well as to increased length and complexity of the beam delivery systems. The instruments will each be equipped with neutron beam monitors used for data normalisation and analysis, as well as commissioning and diagnostics. In this paper we present the requirements for beam monitors for the ESS and the strategy to meet these in a standardised approach. A large range of specifications in efficiency, dynamic range, time and position resolution, compatible materials are needed. A new feature for neutron beam monitors for some locations, is the ability to measure time profile of each source pulse individually. In general, event mode readout will be used for monitors, similarly to other neutron detectors at the facility. A selection of detectors based on different technologies will be available. Monitors will be integrated with beam lines and choppers in a way that allows to freely choose the type of monitor based on final requirements of an instrument. For this end, space for a standardised module, housing a monitor will be provided in conjunction with chopper assemblies and elsewhere on each beam line.

The Multi-Grid (MG) detector has been introduced at ILL and developed by a collaboration between ILL, ESS and Linkoping University. This detector design addresses the severely decreased availability of He3, in particular for neutron scattering instruments with large-area detectors, such as time-of-flight neutron spectrometers at ESS and other facilities. The MG detector is based on thin converter films of boron-10 carbide arranged in layers orthogonal to the incoming neutrons. The design of the detector provides position resolution, efficiency competitive with He3 and a strong gamma rejection capability. This paper presents the MG large-area (2.4m2) demonstrator and the progress made in order to meet the needs of production of B4C-coated layers, mechanical parts and assembly on a scale similar to that of the final detectors for ESS. A particular effort was made to produce aluminium detector parts with a low alpha background, successfully reducing the background rate to acceptable levels. Following the IN5 demonstrator, a compact prototype has been designed in order to finalise the electronic readout to be used at the ESS instruments equipped with the MG.

The exact nature of the lowest Kπ=2+ rotational bands in all deformed nuclei remains obscure. Traditionally they are assumed to be collective vibrations of the nuclear shape in the γ degree of freedom perpendicular to the nuclear symmetry axis. Very few such γ bands have been traced past the usual backbending rotational alignments of high-j nucleons. We have investigated the structure of positive-parity bands in the N=90 nucleus Dy156, using the Nd148(C12,4n)Dy156 reaction at 65 MeV, observing the resulting γ-ray transitions with the Gammasphere array. The even- and odd-spin members of the Kπ=2+γ band are observed up to 32+ and 31+, respectively. This rotational band faithfully tracks the ground-state configuration to the highest spins. The members of a possible γ vibration built on the aligned yrast S band are observed up to spins 28+ and 27+. An even-spin positive-parity band, observed up to spin 24+, is a candidate for an aligned S band built on the seniority-zero configuration of the 0+2 state at 676 keV. The crossing of this band with the 0+2 band is at ℏωc=0.28(1)MeV and is consistent with the configuration of the 0+2 band not producing any blocking of the monopole pairing.

New level schemes of odd-Z 99,101Y (Z = 39) and 101,105Nb (Z = 41) are established based on the measurement of prompt gamma rays from the fission of 252Cf at Gammasphere. Bands of π5/2+[422], π5/2−[303] and π3/2−[301] are observed and extended to provide spectroscopic information concerning nuclear shapes in this important odd-Z region. In combination with the level structure of the odd-Z Tc (Z = 43), Rh (Z = 45) and the neighbouring even-Z isotopes the level systematics, signature splittings and kinematic and dynamic moments of inertia of the bands in the Y and Nb isotopes are discussed in terms of shape transition and triaxiality. The pronounced difference observed in the signature splittings between Y and Tc, Rh isotopes is interpreted as evidence of the axially symmetric deformed shape in the Y isotopes, and, as previously reported, large and near maximum triaxiality in Tc–Rh isotopes. The likely lowering of crossing frequencies of the ground-state bands in Tc and Rh isotones in comparison with those in Y isotones also implies a shape transition from axially symmetric deformed shapes in Y nuclei to triaxiality in Tc and Rh isotones. Triaxial-rotor-plus-particle model calculations strongly support a pure axially symmetric shape with large quadrupole deformation in Y isotopes. The model calculations yielded γ values ranging from −19° to −13° for the 5/2+[422] ground-state bands of 101,103,105Nb and of −5° for the two negative-parity bands in 101Nb. The fact that Nb isotopes have intermediate values of signature splitting and band crossing frequencies between those of Y and Tc, Rh isotopes is interpreted as that the Nb isotopes are transitional nuclei with regard to triaxial deformation. A correlation of quadrupole deformations and of triaxiality is seen in the neutron-rich nuclei with Z = 39–45.