Electron spin relaxation by nuclei in semiconductor quantum dots

We have studied theoretically the electron spin relaxation in semiconductor quantum dots via interaction with nuclear spins. The relaxation is shown to be determined by three processes: (i) -- the precession of the electron spin in the hyperfine field of the frozen fluctuation of the nuclear spins; (ii) -- the precession of the nuclear spins in the hyperfine field of the electron; and (iii) -- the precession of the nuclear spin in the dipole field of its nuclear neighbors. In external magnetic fields the relaxation of electron spins directed along the magnetic field is suppressed. Electron spins directed transverse to the magnetic field relax completely in a time on the order of the precession period of its spin in the field of the frozen fluctuation of the nuclear spins. Comparison with experiment shows that the hyperfine interaction with nuclei may be the dominant mechanism of electron spin relaxation in quantum dots

Codes and standards and other guidance cited in regulatory documents

As part of the U.S. Nuclear Regulatory Commission (NRC) Standard Review Plan Update and Development Program (SRP-UDP), Pacific Northwest National Laboratory developed a listing of industry consensus codes and standards and other government and industry guidance referred to in regulatory documents. The SRP-UDP has been completed and the SRP-Maintenance Program (SRP-MP) is now maintaining this listing. Besides updating previous information, Revision 3 adds approximately 80 citations. This listing identifies the version of the code or standard cited in the regulatory document, the regulatory document, and the current version of the code or standard. It also provides a summary characterization of the nature of the citation. This listing was developed from electronic searches of the Code of Federal Regulations and the NRC`s Bulletins, Information Notices, Circulars, Enforcement Manual, Generic Letters, Inspection Manual, Policy Statements, Regulatory Guides, Standard Technical Specifications and the Standard Review Plan (NUREG-0800)

Glassy phonon heralds a strain glass state in a shape memory alloy

Shape memory strain glasses are frustrated ferroelastic materials with glasslike slow relaxation an

Inhibition by interleukin-4 of constitutive beta interferon synthesis in mouse macrophages

We have found that interleukin-4 (IL-4) abrogated constitutive beta interferon (IFN-beta) synthesis in mouse macrophages. Analysis of endogenous IFN mRNA by reverse transcription-PCR clearly documented the presence of IFN-beta but not of IFN-alpha transcripts in RNA from bone marrow-derived macrophages (BMM). Culture of bone marrow cells for 7 days in the presence of macrophage colony-stimulating factor plus IL-4 or treatment of mature BMM with IL-4 for 3 to 4 days resulted in pronounced inhibition of IFN-beta transcript levels. As a consequence, BMM became highly permissive to viral infection and induction of the IFN-responsive 2',5'-oligoadenylate synthetase was inhibited. In view of the evidence for low-level constitutive secretion of IFN in vivo, it is possible that IL-4 influences the host's antiviral defense system.</jats:p

An Analytical Approach for Computing the Coefficient of Refrigeration Performance in Giant Inverse Magnetocaloric Materials

An analytical approach for computing the coefficient of refrigeration performance (CRP) was described for materials that exhibited a giant inverse magnetocaloric effect (MCE), and their governing thermodynamics were reviewed. The approach defines the magnetic work input using thermodynamic relationships rather than isothermal magnetization data discretized from the literature. The CRP was computed for only cyclically reversible temperature and entropy changes in materials that exhibited thermal hysteresis by placing a limit on their operating temperature in a thermodynamic cycle. The analytical CRP serves to link meaningful material properties in first-order MCE refrigerants to their potential work and efficiency and can be employed as a metric to compare the behaviors of dissimilar alloy compositions or for materials design. We found that an optimum in the CRP may exist that depends on the applied field level and Clausius–Clapeyron (CC) slope. Moreover, through a large literature review of NiMn-based materials, we note that NiMn(In/Sn) alloys offer the most promising materials properties for applications within the bounds of the developed framework.</jats:p