High-frequency spin valve effect in ferromagnet-semiconductor-ferromagnet structure based on precession of injected spins

New mechanism of magnetoresistance, based on tunneling-emission of spin polarized electrons from ferromagnets (FM) into semiconductors (S) and precession of electron spin in the semiconductor layer under external magnetic field, is described. The FM-S-FM structure is considered, which includes very thin heavily doped (delta-doped) layers at FM-S interfaces. At certain parameters the structure is highly sensitive at room-temperature to variations of the field with frequencies up to 100 GHz. The current oscillates with the field, and its relative amplitude is determined only by the spin polarizations of FM-S junctions at relatively large bias voltage.Comment: 5 pages, 2 figures, (v2) new plot with a dependence of current J on magnetic field H added in Fig.2 (top panel), minor amendments in the text; (v3) minor typos corrected. To appear in Phys. Rev. Letter

An engineering approach to the use of expert systems technology in avionics applications

The concept of using a knowledge compiler to transform the knowledge base and inference mechanism of an expert system into a conventional program is presented. The need to accommodate real-time systems requirements in applications such as embedded avionics is outlined. Expert systems and a brief comparison of expert systems and conventional programs are reviewed. Avionics applications of expert systems are discussed before the discussions of applying the proposed concept to example systems using forward and backward chaining

Tunnelling between non-centrosymmetric superconductors with significant spin-orbit splitting studied theoretically within a two-band treatment

Tunnelling between non-centrosymmetric superconductors with significant spin-orbit splitting is studied theoretically in a two-band treatment of the problem. We find that the critical Josephson current may be modulated by changing the relative angle between the vectors describing absence of inversion symmetry on each side of the junction. The presence of two gaps also results in multiple steps in the quasiparticle current-voltage characteristics. We argue that both these effects may help to determine the pairing states in materials like CePt$_3$Si, UIr and Cd$_2$Re$_2$O$_7$. We propose experimental tests of these ideas, including scanning tunnelling microscopy.Comment: 5 pages, 1 figure. Minor changes. Some new references added. Journal-ref. adde

Streamflow, groundwater and ground response data

CER70-71DBS-EVR-MAS-JHD-VCD-50.August 1971.VIMHEX is an intensive program of tropical meteorological and hydrological observations taken in northeast Venezuela during the summer of 1969 to support a study of tropical atmospheric physics and the resulting effects of rainfall. The objectives of the program are to express the meso-scale weather structure in terms of the synoptic-scale envelope and to formulate the ground response to the rainfall produced by tropical weather disturbances over relatively flat tropical topography. The Volume II Hydrology Report is a compilation of the data obtained on streamflow, groundwater, and ground response in the VIMHEX study area during the summer of 1969. The report includes 2-hourly stream flow and mean daily discharge records at 25 river discharge gaging stations; measured suspended sediment at 4 river locations; river bed material size analyses at 30 locations; river bank material descriptions; groundwater table levels in 38 wells; chemical quality analysis and specific conductance for various discharges at selected river stations; soil moisture content at 4 locations; infiltration test results and soil descriptions for various areas in the drainage basins; and soil temperature data at 1 station.VIMHEX was sponsored by the Department of Defense through its THEMIS program

Report of the Terrestrial Bodies Science Working Group. Volume 4: The moon

A rationale for furture exploration of the moon is given. Topics discussed include the objectives of the lunar polar orbiter mission, the mission profile, and general characteristics of the spacraft to be used

Precipitation data and analysis

CER70-71DBS-EJR-MAS-JHD-VCD-HR50.May 1971.VIMHEX is an intensive program of tropical meteorological and hydrological observations taken in northeast Venezuela during the summer of 1969 to support a study of tropical atmospheric physics and the resulting effects of rainfall. The objectives of the program are to express the meso-scale weather structure in terms of the synoptic-scale envelope and to formulate the ground response to the rainfall produced by tropical weather disturbances over relatively flat tropical topography. The Volume I Hydrology Report lists all the precipitation data collected during the summer of 1969 in the study area of northeast Venezuela. Most of the precipitation data is in the form of hourly rainfall. In addition, weekly and other longer period isohyetal maps are presented for the study area. The weekly and monthly average precipitations over the drainage basins have been determined. For the summer months of July, August, and September an average of 4.8 mm of precipitation per day fell on the drainage basins. In subsequent reports, these data will be related to the hydrology and stream response of the area.VIMHEX was sponsored by the Department of Defense through its THEMIS program

Equidistribution of Heegner Points and Ternary Quadratic Forms

We prove new equidistribution results for Galois orbits of Heegner points with respect to reduction maps at inert primes. The arguments are based on two different techniques: primitive representations of integers by quadratic forms and distribution relations for Heegner points. Our results generalize one of the equidistribution theorems established by Cornut and Vatsal in the sense that we allow both the fundamental discriminant and the conductor to grow. Moreover, for fixed fundamental discriminant and variable conductor, we deduce an effective surjectivity theorem for the reduction map from Heegner points to supersingular points at a fixed inert prime. Our results are applicable to the setting considered by Kolyvagin in the construction of the Heegner points Euler system

Efficient nonlinear room-temperature spin injection from ferromagnets into semiconductors through a modified Schottky barrier

We suggest a consistent microscopic theory of spin injection from a ferromagnet (FM) into a semiconductor (S). It describes tunneling and emission of electrons through modified FM-S Schottky barrier with an ultrathin heavily doped interfacial S layer . We calculate nonlinear spin-selective properties of such a reverse-biased FM-S junction, its nonlinear I-V characteristic, current saturation, and spin accumulation in S. We show that the spin polarization of current, spin density, and penetration length increase with the total current until saturation. We find conditions for most efficient spin injection, which are opposite to the results of previous works, since the present theory suggests using a lightly doped resistive semiconductor. It is shown that the maximal spin polarizations of current and electrons (spin accumulation) can approach 100% at room temperatures and low current density in a nondegenerate high-resistance semiconductor.Comment: 7 pages, 2 figures; provides detailed comparison with earlier works on spin injectio

Editorial DEPP: drug experienced young people in contact with the criminal justice system. Understanding the challenges and working towards solutions

The focus of this collection of papers is on young people (age 14–25) who are drug experienced and are in contact with the Criminal Justice System (CJS). In general, research tends to focus on either young people’s drug use or offending; equally, we see a tendency within policy and service responses to focus on interventions aimed either at drug use or at offending but rarely addressing complex problems that may include drug use and offending (Herold et al., 2019). By drawing on young peoples’ own perspectives and experiences and focusing on multiple problem areas at the same time, this collection presents findings that complement and augment the existing literature, and are highly relevant to policy development and service provision by: providing an account of young people’s own perspectives and experiences of their drug use and offending trajectories and the experienced relationship between these trajectories; describing young people’s own perspectives and experiences of different kinds of drug and/or offending reducing initiatives they have participated in and what they appreciate and/or find difficult in these institutional arrangements; showing how professionals engage with this group of young people, and how young people themselves consider engagement in services offered to them; and finally, highlighting the unintended consequences for and experienced by young people of the application of prohibitive drug policies and of involvement in the criminal justice system

A Matrix Approach to Numerical Solution of the DGLAP Evolution Equations

A matrix-based approach to numerical integration of the DGLAP evolution equations is presented. The method arises naturally on discretisation of the Bjorken x variable, a necessary procedure for numerical integration. Owing to peculiar properties of the matrices involved, the resulting equations take on a particularly simple form and may be solved in closed analytical form in the variable t=ln(alpha_0/alpha). Such an approach affords parametrisation via data x bins, rather than fixed functional forms. Thus, with the aid of the full correlation matrix, appraisal of the behaviour in different x regions is rendered more transparent and free of pollution from unphysical cross-correlations inherent to functional parametrisations. Computationally, the entire programme results in greater speed and stability; the matrix representation developed is extremely compact. Moreover, since the parameter dependence is linear, fitting is very stable and may be performed analytically in a single pass over the data values.Comment: 13 pages, no figures, typeset with revtex4 and uses packages: acromake, amssym