245 research outputs found
Exploring the multi-humped fission barrier of 238U via sub-barrier photofission
The photofission cross-section of 238U was measured at sub-barrier energies
as a function of the gamma-ray energy using, for the first time, a
monochromatic, high-brilliance, Compton-backscattered gamma-ray beam. The
experiment was performed at the High Intensity gamma-ray Source (HIgS) facility
at beam energies between E=4.7 MeV and 6.0 MeV and with ~3% energy resolution.
Indications of transmission resonances have been observed at gamma-ray beam
energies of E=5.1 MeV and 5.6 MeV with moderate amplitudes. The triple-humped
fission barrier parameters of 238U have been determined by fitting EMPIRE-3.1
nuclear reaction code calculations to the experimental photofission cross
section.Comment: 5 pages, 3 figure
Nuclear photonics at ultra-high counting rates and higher multipole excitations
Next-generation gamma beams beams from laser Compton-backscattering
facilities like ELI-NP (Bucharest)] or MEGa-Ray (Livermore) will drastically
exceed the photon flux presently available at existing facilities, reaching or
even exceeding 10^13 gamma/sec. The beam structure as presently foreseen for
MEGa-Ray and ELI-NP builds upon a structure of macro-pulses (~120 Hz) for the
electron beam, accelerated with X-band technology at 11.5 GHz, resulting in a
micro structure of 87 ps distance between the electron pulses acting as mirrors
for a counterpropagating intense laser. In total each 8.3 ms a gamma pulse
series with a duration of about 100 ns will impinge on the target, resulting in
an instantaneous photon flux of about 10^18 gamma/s, thus introducing major
challenges in view of pile-up. Novel gamma optics will be applied to
monochromatize the gamma beam to ultimately Delta E/E~10^-6. Thus
level-selective spectroscopy of higher multipole excitations will become
accessible with good contrast for the first time. Fast responding gamma
detectors, e.g. based on advanced scintillator technology (e.g. LaBr3(Ce))
allow for measurements with count rates as high as 10^6-10^7 gamma/s without
significant drop of performance. Data handling adapted to the beam conditions
could be performed by fast digitizing electronics, able to sample data traces
during the micro-pulse duration, while the subsequent macro-pulse gap of ca. 8
ms leaves ample time for data readout. A ball of LaBr3 detectors with digital
readout appears to best suited for this novel type of nuclear photonics at
ultra-high counting rates.Comment: 4 pages, 1 figure, 1 tabl
Effects of Goji berries supplementation on the productive performance of rabbit
Abstract
Recognized by the traditional medicine and recent scientific research studies, Lycium barbarum berries (Goji berries) have beneficial effects on human and animal health. The aim of our study was to evaluate the effects of Goji berries on the productive performance of rabbits. One month before insemination, 60 New Zealand White does were randomly assigned to one of the following 3 dietary treatments: commercial standard diet (C); C supplemented with 1% Goji berries (LG); and C supplemented with 3% Goji berries (HG). After weaning up to 91 days of age, 15 randomly selected rabbits/group were fed the same diet as the mothers (C, LG, and HG). Non-pregnant and lactating does of C group showed the highest feed intake (P < 0.01), although no significant differences in body weight (BW) were observed between groups. Nutritional treatment did not affect the offspring's feed intake. However, the rabbits fed with Goji supplementation showed not only higher mean BW both during growth (P < 0.001) and at slaughter (P < 0.01), but also better feed conversion ratio (FCR; P < 0.01) than the control group. Rabbits of LG group showed the best performances in the pre-weaning period which was probably related to the highest milk production of the LG does (P < 0.001). Indeed, LG group showed lower pre-weaning mortality (P < 0.05), higher litter size (P < 0.05), and higher litter weight (P < 0.05) at day 18 as well as higher litter size at weaning (P = 0.05) compared to C group. In conclusion, the present study demonstrates that a low percentage of dietary supplementation with Goji berry improves both reproductive and productive traits of rabbits. Although further studies are needed, our study paves the way for the use of Goji berries in the rabbit nutrition
In-beam fast-timing measurements in 103,105,107Cd
Fast-timing measurements were performed recently in the region of the
medium-mass 103,105,107Cd isotopes, produced in fusion evaporation reactions.
Emitted gamma-rays were detected by eight HPGe and five LaBr3:Ce detectors
working in coincidence. Results on new and re-evaluated half-lives are
discussed within a systematic of transition rates. The states in
103,105,107Cd are interpreted as arising from a single-particle excitation. The
half-life analysis of the states in 103,105,107Cd shows no change in
the single-particle transition strength as a function of the neutron number
Ethical procedures and patient consent differ in Europe
BACKGROUND: Research ethics approvals, procedures and requirements for institutional research ethics committees vary considerably by country and by type of organisation. OBJECTIVE: To evaluate the requirements and procedures of research ethics committees, details of patient information and informed consent based on a multicentre European trial. DESIGN: Survey of European hospitals participating in the prospective observational study on chronic postsurgical pain (euCPSP) using electronic questionnaires. SETTING: Twenty-four hospitals in 11 European countries. PARTICIPANTS: From the 24 hospitals, 23 local investigators responded; 23 answers were analysed. OUTCOME MEASURES: Comparison of research ethics procedures and committee requirements from the perspective of clinical researchers. Comparison of the institutions' procedures regarding patient information and consent. Description of further details such as costs and the duration of the approval process. RESULTS: The approval process lasted from less than 2 weeks up to more than 2 months with financial fees varying between 0 and 575 €. In 20 hospitals, a patient information sheet of variable length (half page up to two pages) was provided. Requirements for patients' informed consent differed. Written informed consent was mandatory at 12, oral at 10 and no form of consent at one hospital. Details such as enough time for consideration, possibility for withdrawal and risks/benefits of participation were provided in 25 to 30% of the institutions. CONCLUSION: There is a considerable variation in the administrative requirements for approval procedures by research ethics committees in Europe. This results in variation of the extent of information and consent procedures for the patients involved
Fast-timing measurements in 95,96Mo
Half-lives of the 19/2+ and 21/2+ states in 95Mo and of the 8+ and 10+ states
in 96Mo were measured. Matrix elements for yrast transitions in 95Mo and 96Mo
are discussed.Comment: Proceedings of XIX International School on Nuclear Physics, Neutron
Physics and Applications, Varna, Bulgaria, 2011, 5 pages, 6 figure
Energy separation of the 1⁺/1⁻ parity doublet in ²⁰Ne
The parity doublet of 1⁺/1⁻ states of Ne⁻²⁰ at 11.26 MeV excitation energy is one of the best known test cases to study the weak part of the nuclear Hamiltonian. The feasibility of parity violation experiments depend on the effective nuclear enhancement factor (RN/|E(1⁺) − E(l⁻)|) which amplifies the impact of the matrix element of the weak interaction on observables indicating parity mixing. An extreme large value of Rn/|E(1⁺) − E(l⁻)| = (670 ± 7000) MeV⁻¹ was reported for the doublet in ²⁰Ne. The large uncertainty depends amongst others on the large uncertainty of |E(1⁺) − E(l⁻)| = 7.7±5.5 keV of the parity doublet. Nuclear resonance fluorescence (NRF) experiments with linearly and circularly polarized photon beams were performed at the High Intensity Gamma-Ray Source at Duke University, Durham, NC, USA, to determine the energy difference of the parity doublet with higher precision. The different angular distributions for 0⁺ → 1⁻ → 0⁺ and 0⁺ → 1⁺ → 0⁺ NRF cascades in polarized γ-ray beams were used to determine the energy difference of the parity doublet to 2.9(13) keV
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