Magnetic properties of substitutional Mn in (110) GaAs surface and subsurface layers

Motivated by recent STM experiments, we present a theoretical study of the electronic and magnetic properties of the Mn-induced acceptor level obtained by substituting a single Ga atom in the (110) surface layer of GaAs or in one of the atoms layers below the surface. We employ a kinetic-exchange tight-binding model in which the relaxation of the (110) surface is taken into account. The acceptor wave function is strongly anisotropic in space and its detailed features depend on the depth of the sublayer in which the Mn atom is located. The local-density-of-states (LDOS) on the (110) surface associated with the acceptor level is more sensitive to the direction of the Mn magnetic moment when the Mn atom is located further below the surface. We show that the total magnetic anisotropy energy of the system is due almost entirely to the dependence of the acceptor level energy on Mn spin orientation, and that this quantity is strongly dependent on the depth of the Mn atom.Comment: 14 pages, 13 figure

Microwave Spectroscopy

Contains research objectives, reports on work completed and one research project.Joint Services Electronics Programs (U. S. Army, U.S. Navy, and U.S. Air Force) under Contract DA 28-043-AMC-02536(E

Microwave Spectroscopy

Contains reports on two research projects.Joint Services Electronics Programs (U.S. Army, U.S. Navy, and U.S. Air Force) under Contract DA 28-043-AMC-02536(E

Microwave Spectroscopy

Contains research objectives and reports on three research projects.Joint Services Electronics Programs (U. S. Army, U.S. Navy, and U.S. Air Force) under Contract DA 36-039-AMC-03200(E

Microwave Spectroscopy

Contains reports on three research projects.Signal Corps Contract DA36-039-sc-7489

Elastic Compton Scattering from 3He and the Role of the Delta

We report observables for elastic Compton scattering from $^3$He in Chiral Effective Field Theory with an explicit $\Delta(1232)$ degree of freedom ($\chi$EFT) for energies between 50 and 120 MeV. The $\gamma\,{}^3$He amplitude is complete at N3LO, $\mathcal{O}(e^2\delta^3)$, and in general converges well order by order. It includes the dominant pion-loop and two-body currents, as well as the Delta excitation in the single-nucleon amplitude. Since the cross section is two to three times that for deuterium and the spin of polarised $^3$He is predominantly carried by its constituent neutron, elastic Compton scattering promises information on both the scalar and spin polarisabilities of the neutron. We study in detail the sensitivities of 4 observables to the neutron polarisabilities: the cross section, the beam asymmetry and two double asymmetries resulting from circularly polarised photons and a longitudinally or transversely polarised target. Including the Delta enhances those asymmetries from which neutron spin polarisabilities could be extracted. We also correct previous, erroneous results at N2LO, i.e.~without an explicit Delta, and compare to the same observables on proton, neutron and deuterium targets. An interactive Mathematica notebook of our results is available from [email protected]: 37 pages LaTeX2e (pdflatex) including 16 figures as .pdf files using includegraphics; minor corrections, triggered by referee comments, plus typographical errors; text-identical to version published as EPJA 54 (2018) 12

Magnetic Anisotropy of Isolated Cobalt Nanoplatelets

Motivated in part by experiments performed by M.H. Pan et al. (nanoletters, v.5, p 83, 2005), we have undertaken a theoretical study of the the magnetic properties of two-monolayer thick Co nanoplatelets with an equilateral triangular shape. The analysis is carried out using a microscopic Slater-Koster tight-binding model with atomic exchange and spin-orbit interactions designed to realistically capture the salient magnetic features of large nanoclusters containing up to 350 atoms. Two different truncations of the FCC lattice are studied, in which the nanoplatelet surface is aligned parallel to the FCC (111) and (001)crystal planes respectively. We find that the higher coordination number in the (111) truncated crystal is more likely to reproduce the perpendicular easy direction found in experiment. Qualitatively, the most important parameter governing the anisotropy of the model is found to be the value of the intra-atomic exchange integral J. If we set the value of J near the bulk value in order to reproduce the experimentally observed magnitude of the magnetic moments, we find both quasi-easy-planes and perpendicular easy directions. At larger values of J we find that the easy-axis of magnetization is perpendicular to the surface, and the value of the magnetic anisotropy energy per atom is larger. The possible role of hybridization with substrate surface states in the experimental systems is discussed.Comment: 15 pages, 13 figure

Do women give the same information on binge drinking during pregnancy when asked repeatedly?

Udgivelsesdato: 2006-NovOBJECTIVE: To study if pregnant women give the same answers to questions on frequency and timing of binge drinking when asked more than once during and after pregnancy. DESIGN: Cohort study.Setting:The Danish National Birth Cohort. SUBJECTS: The study is based on 76 307 pregnant women with repeated information on binge drinking during the early part of pregnancy and 8933 pregnant women with information on binge drinking during pregnancy weeks 30-36, obtained while pregnant and 6 months after delivery. RESULTS: More women reported binge drinking, if the interview took place close to the period in question. As the report of binge drinking was highest in the first of two interviews referring to the same period, as well as women who participated in the first interview in pregnancy week 12 or earlier reported more binge drinking compared to women who participated in the interview later in pregnancy. CONCLUSIONS: Self-reported information on binge drinking is more frequently under-reported when the recall period is long. To improve the validity of data on binge drinking, future birth cohorts should obtain information several times during pregnancy

Microwave Spectroscopy

Contains research objectives, summary of research and reports on two research projects.Joint Services Electronics Programs (U. S. Army, U. S. Navy, and U. S. Air Force) under Contract DAAB07-71-C-030

Muistisairaiden liikunnallisen kuntoutuksen vaikuttavuus : Satunnaistettu vertailutukimus

Tutkimuksen tavoitteena oli selvittää satunnaistetulla,kontrolloidulla asetelmalla liikunnallisen harjoittelun vaikuttavuutta kotona asuvien, Alzheimerin tautia sairastavien toimintakyvyn eri ulottuvuuksiin, heidän omaishoitajiensa elämänlaatuun sekä molempien palveluiden käyttöön ja niiden kustannuksiin vuosina 2008–2011. Tutkimukseen osallistui 210 pariskuntaa, joista toinen puoliso oli muistisairaan omaishoitaja. Pariskunnat randomoitiin kolmeen yhtä suureen ryhmään: 1) ryhmäkuntoutusryhmään (liikuntaharjoittelua neljä tuntia kaksi kertaa viikossa päiväkeskuksessa vuoden ajan), 2) kotikuntoutusryhmään (tunti kaksi kertaa viikossa kotona vuoden ajan fysioterapeutin ohjauksessa) ja 3) vertailuryhmään (tavallinen kunnallinen hoito). Tutkimushoitajan haastattelut tehtiin lähtötilanteessa sekä 3:n, 6:n, 12:n ja 24 kuukauden kohdalla. Päätulosmuuttujat olivat muistisairaan ihmisen toimintakyky (mitattiin FIM-toimintakykymittarilla) sekä liikuntakyky (mitattiin Guralnikin liikuntakyky- ja tasapainotesteillä = SPPB). Kotona annetulla räätälöidyllä kuntoutuksella voidaan hidastaa muistisairaiden fyysisen toimintakyvyn (mitattu FIM-mittarilla) heikkenemistä merkitsevästi. Liikuntatesteissä (SPPB) ei ollut eroja ryhmien välillä. Myös kognitiossa näkyi myönteinen muutos toiminnanohjauksen osalta kellotestillä mitattuna kotikuntoutusryhmässä. Ryhmäkuntoutuksessa palveluiden kokonaiskustannusten säästöt olivat merkittävät, joskaan muutokset toimintakyvyssä eivät saavuttaneet tilastollista merkitsevyyttä. Omaisten elämänlaadussa tai muissa mittareissa ei ollut merkitseviä eroja interventioryhmien ja vertailuryhmien välillä. Kaatumiset vähenivät molemmissa interventioryhmissä. Kuolemanvaara näytti pienentyneen kotikuntoutusryhmässä. Tutkimuksessa luotiin kuntoutusmalli, joka parantaa Alzheimerin tautia sairastavien toimintakykyä lisäämättä sosiaali- ja terveyspalveluiden kokonaiskustannuksia.15,00 euro