802 research outputs found

    Central and tensor components of three-nucleon forces in low-energy proton-deuteron scattering

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    Contributions of three-nucleon forces (3NF) to proton-deuteron scattering observables at energies below the deuteron breakup threshold are studied by solving the Faddeev equation that includes the Coulomb interaction. At E_p=3.0 MeV, we find that the central part of a two-pion exchange 3NF removes the discrepancy between measured cross sections and the calculated ones by two-nucleon forces, and improves the agreement with T_{22} experimental data. However, the tensor part of the 3NF fails in reproducing data of the analyzing power T_{21} by giving worse agreement between the measured and the calculated. Detailed examinations of scattering amplitudes suggest that a P-wave contribution in spin quartet tensor amplitudes has unsuitable sign for reproducing the T_{21} data.Comment: 6 pages, 6 figure

    Multi-timescale Solar Cycles and the Possible Implications

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    Based on analysis of the annual averaged relative sunspot number (ASN) during 1700 -- 2009, 3 kinds of solar cycles are confirmed: the well-known 11-yr cycle (Schwabe cycle), 103-yr secular cycle (numbered as G1, G2, G3, and G4, respectively since 1700); and 51.5-yr Cycle. From similarities, an extrapolation of forthcoming solar cycles is made, and found that the solar cycle 24 will be a relative long and weak Schwabe cycle, which may reach to its apex around 2012-2014 in the vale between G3 and G4. Additionally, most Schwabe cycles are asymmetric with rapidly rising-phases and slowly decay-phases. The comparisons between ASN and the annual flare numbers with different GOES classes (C-class, M-class, X-class, and super-flare, here super-flare is defined as \geq X10.0) and the annal averaged radio flux at frequency of 2.84 GHz indicate that solar flares have a tendency: the more powerful of the flare, the later it takes place after the onset of the Schwabe cycle, and most powerful flares take place in the decay phase of Schwabe cycle. Some discussions on the origin of solar cycles are presented.Comment: 8 pages, 4 figure

    Back in Time? A Temporal Autobiographical Approach to Afghan Return Migration

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    Repatriation programmes for refugees and asylum seekers are based on the assumption that going ‘home’ is the most desirable thing to do to restore the social order that was disrupted by conflict. Yet the often-limited success of these programmes as migration management solutions, shown in poor reintegration results and re-emigration, shows that there is a need for a better understanding of the lived experiences of (return) migrants. This article studies Afghan managed and “spontaneous” return migrants from Europe through an innovative temporal autobiographical approach, using both verbal and creative participatory narrative methods. I find that some migration movements were experienced as disruptive, while others were not, and that return sometimes meant a return to a previous life, sometimes a continuation, and sometimes the start of something new. I conclude that migration management programmes aimed towards “durable solutions” and the wellbeing of returnees should enable rather than constrain post-return mobility

    Reevaluation of the role of nuclear uncertainties in experiments on atomic parity violation with isotopic chains

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    In light of new data on neutron distributions from experiments with antiprotonic atoms [ Trzcinska {\it et al.}, Phys. Rev. Lett. 87, 082501 (2001)], we reexamine the role of nuclear-structure uncertainties in the interpretation of measurements of parity violation in atoms using chains of isotopes of the same element. With these new nuclear data, we find an improvement in the sensitivity of isotopic chain measurements to ``new physics'' beyond the standard model. We compare possible constraints on ``new physics'' with the most accurate to date single-isotope probe of parity violation in the Cs atom. We conclude that presently isotopic chain experiments employing atoms with nuclear charges Z < 50 may result in more accurate tests of the weak interaction.Comment: 6 pages, 1 fig., submitted to Phys. Rev.

    Low-energy p-d Scattering: High Precision Data, Comparisons with Theory, and Phase-Shift Analyses

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    Angular distributions of sigma(theta), A_y, iT_11, T_20, T_21, and T_22 have been measured for d-p scattering at E_c.m.=667 keV. This set of high-precision data is compared to variational calculations with the nucleon-nucleon potential alone and also to calculations including a three-nucleon (3N) potential. Agreement with cross-section and tensor analyzing power data is excellent when a 3N potential is used. However, a comparison between the vector analyzing powers reveals differences of approximately 40% in the maxima of the angular distributions which is larger than reported at higher energies for both p-d and n-d scattering. Single-energy phase-shift analyses were performed on this data set and a similar data set at E_c.m.=431.3 keV. The role of the different phase-shift parameters in fitting these data is discussed.Comment: 18 pages, 6 figure

    Industrial Field Trials of Oregon Graduate Institute-Developed Electroslag Welding Technology

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    DTFH61-86-X-00119The primary objective of this program was to demonstrate that the Oregon Graduate Institute (OGI)-developed electroslag welding (ESW) technology cay be successfully implemented in commercial fabrication shops. Consequently, opportunity was provided to evaluate the transferability of ESW technology and to develop additional ESW mechanical property data from commercially fabricated weldments

    Repair of Process-Related Defects in Electroslag Welding

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    DTFH61-86-X-00119The primary objectives of this program were to develop a welding procedure for repair of electroslag weldments and to determine if repair welding influenced the fatigue strength of electroslag weldments. Integral to this effort was the identification of the most likely types of defects, their causes, and the potential for effective repair. The electroslag welding (ESW) process is capable of producing a higher volume of defect-free weld deposit than other processes used for joining structural steel. When defects do occur, however, ESW is not well-suited for use as a repair process since it is limited to vertical position, single-pass, full-thickness welding

    Diamond like carbon coatings for potential application in biological implants—a review

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    Production of wear debris has been linked to the failure of numerous hip implants. With the current focus on increasing the implant longevity, thus wear and corrosion resistance is important. Hard coatings have the potential to reduce the wear and corrosion. Diamond like Carbon (DLC) coatings exhibit properties that could make them viable for implants. This paper critically reviews previously published research into usage of DLC coatings for implants. Overall DLCs seem to be an effective coating for implants but with the variance in results, further testing is required for clarification of us

    Recent Advances in Understanding Particle Acceleration Processes in Solar Flares

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    We review basic theoretical concepts in particle acceleration, with particular emphasis on processes likely to occur in regions of magnetic reconnection. Several new developments are discussed, including detailed studies of reconnection in three-dimensional magnetic field configurations (e.g., current sheets, collapsing traps, separatrix regions) and stochastic acceleration in a turbulent environment. Fluid, test-particle, and particle-in-cell approaches are used and results compared. While these studies show considerable promise in accounting for the various observational manifestations of solar flares, they are limited by a number of factors, mostly relating to available computational power. Not the least of these issues is the need to explicitly incorporate the electrodynamic feedback of the accelerated particles themselves on the environment in which they are accelerated. A brief prognosis for future advancement is offered.Comment: This is a chapter in a monograph on the physics of solar flares, inspired by RHESSI observations. The individual articles are to appear in Space Science Reviews (2011
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