123 research outputs found
The effect of dopants on magnetic properties of the ordered FE 65-XAL35-YMX,Y (MX,Y=GA,B,V; X,Y=5,10) alloys
The results of X-ray diffraction, complex in-field (up to 9 T) and temperature (5-300 K) Mössbauer and magnetometric studies of the ordered Fe65Al35-xMx (M=Ga, B; x=0,5,10) and Fe 65-xVxAl35(x=5,10) alloys are presented. Analysis of the magnetometry studies shows that the systems Fe 65Al35 H Fe65Al35-xGax (x=5, 10) are characterized by two different magnetic states with essentially distinguishing hysteresis loops and AC susceptibility values. The temperature and external magnetic field values inducing the transition from one magnetic state to another are higher in the Ga-doped alloys than in the reference Fe 65Al35 alloy. The boron addition transforms the magnetic state of the initial alloy Fe65Al35 into a ferromagnetic one exhibiting high magnetic characteristics. Substitution of V for Fe in the ternary alloys Fe65-xVxAl35 results in reduction of magnetic characteristics and collapsing of 57Fe hyperfine magnetic filed. © (2012) Trans Tech Publications
Ta(n, γ) cross-section measurement and the astrophysical origin of the Ta isotope
Ta is nature\u27s rarest (quasi) stable isotope and its astrophysical origin is an open question. A possible production site of this isotope is the slow neutron capture process in asymptotic giant branch stars, where it can be produced via neutron capture reactions on unstable Ta. We report a new measurement of the Ta(n,γ) Ta cross section at thermal-neutron energies via the activation technique. Our results for the thermal and resonance-integral cross sections are 952±57 and 2013±148 b, respectively. The thermal cross section is in good agreement with the only previous measurement [Phys. Rev. C 60, 025802 (1999)], while the resonance integral is different by a factor of ≈1.7. While neutron energies in this work are smaller than the energies in a stellar environment, our results may lead to improvements in theoretical predictions of the stellar cross section
Coexistence of the spin-density-wave and superconductivity in the (Ba,K)Fe2As2
The relation between the spin-density-wave (SDW) and superconducting order is
a central topic in current research on the FeAs-based high Tc superconductors.
Conflicting results exist in the LaFeAs(O,F)-class of materials, for which
whether the SDW and superconductivity are mutually exclusive or they can
coexist has not been settled. Here we show that for the (Ba,K)Fe2As2 system,
the SDW and superconductivity can coexist in an extended range of compositions.
The availability of single crystalline samples and high value of the energy
gaps would make the materials a model system to investigate the high Tc
ferropnictide superconductivity.Comment: 4 pages, 5 figure
Storage, Accumulation and Deceleration of Secondary Beams for Nuclear Astrophysics
Low-energy investigations on rare ion beams are often limited by the
available intensity and purity of the ion species in focus. Here, we present
the first application of a technique that combines in-flight production at
relativistic energies with subsequent secondary beam storage, accumulation and
finally deceleration to the energy of interest. Using the FRS and ESR
facilities at GSI, this scheme was pioneered to provide a secondary beam of
Te for the measurement of nuclear proton-capture at energies of
6 and 7 MeV/u. The technique provided stored beam intensities of about
ions at high purity and brilliance, representing a major step towards
low-energy nuclear physics studies using rare ion beams
Analysis of arterial intimal hyperplasia: review and hypothesis
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Background: Despite a prodigious investment of funds, we cannot treat or prevent arteriosclerosis and restenosis, particularly its major pathology, arterial intimal hyperplasia. A cornerstone question lies behind all approaches to the disease: what causes the pathology? Hypothesis: I argue that the question itself is misplaced because it implies that intimal hyperplasia is a novel pathological phenomenon caused by new mechanisms. A simple inquiry into arterial morphology shows the opposite is true. The normal multi-layer cellular organization of the tunica intima is identical to that of diseased hyperplasia; it is the standard arterial system design in all placentals at least as large as rabbits, including humans. Formed initially as one-layer endothelium lining, this phenotype can either be maintained or differentiate into a normal multi-layer cellular lining, so striking in its resemblance to diseased hyperplasia that we have to name it "benign intimal hyperplasia". However, normal or "benign " intimal hyperplasia, although microscopically identical to pathology, is a controllable phenotype that rarely compromises blood supply. It is remarkable that each human heart has coronary arteries in which a single-layer endothelium differentiates earl
Advances and new ideas for neutron-capture astrophysics experiments at CERN n_TOF
This article presents a few selected developments and future ideas related to the measurement of (n,γ) data of astrophysical interest at CERN n_TOF. The MC-aided analysis methodology for the use of low-efficiency radiation detectors in time-of-flight neutron-capture measurements is discussed, with particular emphasis on the systematic accuracy. Several recent instrumental advances are also presented, such as the development of total-energy detectors with γ-ray imaging capability for background suppression, and the development of an array of small-volume organic scintillators aimed at exploiting the high instantaneous neutron-flux of EAR2. Finally, astrophysics prospects related to the intermediate i neutron-capture process of nucleosynthesis are discussed in the context of the new NEAR activation area
Advances and new ideas for neutron-capture astrophysics experiments at CERN n_TOF
This article presents a few selected developments and future ideas related to the measurement of (n,γ) data of astrophysical interest at CERN n_TOF. The MC-aided analysis methodology for the use of low-efficiency radiation detectors in time-of-flight neutron-capture measurements is discussed, with particular emphasis on the systematic accuracy. Several recent instrumental advances are also presented, such as the development of total-energy detectors with γ-ray imaging capability for background suppression, and the development of an array of small-volume organic scintillators aimed at exploiting the high instantaneous neutron-flux of EAR2. Finally, astrophysics prospects related to the intermediate i neutron-capture process of nucleosynthesis are discussed in the context of the new NEAR activation area
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