Two-dimensional anisotropic Heisenberg antiferromagnet in a field

The classical, square lattice, uniaxially anisotropic Heisenberg antiferromagnet in a magnetic field parallel to the easy axis is studied using Monte Carlo techniques. The model displays a long-range ordered antiferromagnetic, an algebraically ordered spin-flop, and a paramagnetic phase. The simulations indicate that a narrow disordered phase intervenes between the ordered phases down to quite low temperatures. Results are compared to previous, partially conflicting findings on related classical models as well as the quantum variant with spin S=1/2.Comment: 8 pages, 9 figure

Ising antiferromagnet with mobile, pinned and quenched defects

Motivated by recent experiments on (Sr,Ca,La)_14 Cu_24 O_41, a two-dimensional Ising antiferromagnet with mobile, locally pinned and quenched defects is introduced and analysed using mainly Monte Carlo techniques. The interplay between the arrangement of the defects and the magnetic ordering as well as the effect of an external field are studied.Comment: 10 pages, 6 figures. Condensed Matter Physics (Festschrift in honour of R. Folk

Phase diagrams of a classical two-dimensional Heisenberg antiferromagnet with single-ion anisotropy

A classical variant of the two-dimensional anisotropic Heisenberg model reproducing inelastic neutron scattering experiments on La_5 Ca_9 Cu_24 O_41 [M. Matsuda et al., Phys.Rev. B 68, 060406(R) (2003)] is analysed using mostly Monte Carlo techniques. Phase diagrams with external fields parallel and perpendicular to the easy axis of the anisotropic interactions are determined, including antiferromagnetic and spin-flop phases. Mobile spinless defects, or holes, are found to form stripes which bunch, debunch and break up at a phase transition. A parallel field can lead to a spin-flop phase.Comment: 9 pages, 9 figures; final version as accepted by Phys. Rev. B (Fig. 5 replaced, added remarks in Secs. I, III, and V

Auswirkungen der demographischen Entwicklung auf die Zahl der Pflegefälle : Vorausschätzungen bis 2020 mit Ausblick auf 2050

Von der demographischen Entwicklung wird allgemein eine Zunahme der Zahl Pflegebedürftiger erwartet. Um die mögliche Dynamik in diesem Bereich aufzuzeigen, wird mit Hilfe des DIW-Bevölkerungsmodells, das u.a. die weiterhin steigende Lebenserwartung modelliert, die Zahl der Pflegefälle differenziert nach Geschlecht, Altersgruppen und Schweregrad der Pflegebedürftigkeit vorausberechnet. Die Zahl der Pflegefälle umfasst hier sowohl die Leistungsempfänger aus der sozialen als auch aus der privaten Pflegeversicherung. Nach den hier vorgelegten Berechnungen dürfte die Zahl Pflegebedürftiger bis 2020 um 52% oder rund 1 Million steigen. Im Jahre 2050 wird die Zahl der Pflegebedürftigen mit 4,7 Millionen das 2,5fache des heutigen Niveaus erreichen. Da die Zahl der Schwer- und Schwerstpflegebedürftigen stärker steigt als die der "Erheblich Pflegebedürftigen", wird sich der Grad der durchschnittlichen Pflegebedürftigkeit erhöhen. Der Versorgungs- und Betreuungsbedarf weist damit ein dynamischeres Wachstum auf als die Zahl der Pflegefälle. Bereits rein demographisch bedingt wird die Nachfrage nach stationären Pflegediensten stärker steigen als nach ambulanter Betreuung. Diese Tendenz wird durch die veränderten Familien- und Haushaltsstrukturen, die weiterhin steigende Erwerbsbeteiligung der Frauen sowie die Alterung der familiären Pflegekräfte verstärkt. Die Zunahme der Zahl Pflegebedürftiger stellt nicht nur für die soziale Sicherung eine Herausforderung dar, die Nachfragesteigerung nach ambulanten, teilstationären und vollstationären Pflegediensten eröffnet auch merkliche Beschäftigungspotentiale. Diese gilt es durch entsprechende Rahmenbedingungen zu erschließen. Auch wenn es einen politischen Konsens für eine stärkere private Absicherung des Pflegerisikos geben sollte, wird der heute auf 1,7 % festgeschriebene Beitragssatz keinesfalls ausreichen. Erforderlich ist zudem eine Aufwertung der Pflegediensttätigkeiten, um qualifiziertes Personal für die entsprechenden Berufsfelder gewinnen zu können.In general, demographic development is expected to increase the number of cases needing nursing care. In order to explore the possible dynamics in this area, this papers employs a demographic model of the DIW which integrates among others a steadily increasing life expectancy. Grouping by sex, age and intensity of nursing care, the model calculates in advance the number of nursing cases. Calculations include patients both from the statutory and from the private nursing care insurance. According to the calculations presented, the number of patients needing nursing care is expected to increase by 52 % or by one million cases by 2020. By the year 2050, the number of patients needing nursing care will reach 4.7 million cases which increases the current level by a factor of 2.5. As the number of cases needing intensive or most intensive nursing care will increase more than the number of cases just needing significant nursing care, the average intensity in care needed will grow. Need for care and assistance will thus grow more dynamically than the number of cases. Demographic factors alone make the need for inpatient nursing care increase more strongly than that for outpatient assistance. This trend is further pushed forward by the changing structure of families and households, by the increasing participation of women in the labour market and by increasing age of those family members who render nursing care. The increase in the number of cases needing nursing care does not only challenge social security. More than that, the increase in demand for outpatient care as well as for partly or full inpatient nursing care makes up a significant potential for new employment. This potential can be realised by setting the respective framework conditions. Even if there is political consensus for an increase in private insurance of the risk of nursing care, the contribution rate currently fixed at 1.7 % will definitely be insufficient. Additionally, it is necessary to increase the valuation of employment in nursing care; only then qualified personnel may be recruited for the respective positions

Comment on "Frustrating interactions and broadened magnetic interactions in the edge-sharing CuO_2 chains in La_5 Ca_9 Cu_24 O_41"

Using Monte Carlo techniques, we show that the two--dimensional anisotropic Heisenberg model reproducing nicely inelastic neutron scattering measurements on La_5 Ca_9 Cu_24 O_41 (Matsuda et al. [Phys. Rev. B 68, 060406(R) (2003)]) seems to be insufficient to describe correctly measurements on thermodynamic quantities like the magnetization or the susceptibility. Possible reasons for the discrepancy are suggested.Comment: 3 pages, 2 EPS figures; part (ii) rewritten, some typos corrected; final version that has been accepted for publication in Phys. Rev.

Incorporating interactive 3-dimensional graphics in astronomy research papers

Most research data collections created or used by astronomers are intrinsically multi-dimensional. In contrast, all visual representations of data presented within research papers are exclusively 2-dimensional. We present a resolution of this dichotomy that uses a novel technique for embedding 3-dimensional (3-d) visualisations of astronomy data sets in electronic-format research papers. Our technique uses the latest Adobe Portable Document Format extensions together with a new version of the S2PLOT programming library. The 3-d models can be easily rotated and explored by the reader and, in some cases, modified. We demonstrate example applications of this technique including: 3-d figures exhibiting subtle structure in redshift catalogues, colour-magnitude diagrams and halo merger trees; 3-d isosurface and volume renderings of cosmological simulations; and 3-d models of instructional diagrams and instrument designs.Comment: 18 pages, 7 figures, submitted to New Astronomy. For paper with 3-dimensional embedded figures, see http://astronomy.swin.edu.au/s2plot/3dpd

Информационная система оценки результативности внедрения облачных технологий

Motivated by experiments on (Sr,Ca,La)_14 Cu_24 O_41, a two-dimensional Ising model with mobile defects and a two-dimensional anisotropic Heisenberg antiferromagnet have been proposed and studied recently. We extend previous investigations by analysing phase diagrams of both models in external fields using mainly Monte Carlo techniques. In the Ising case, the phase transition is due to the thermal instability of defect stripes, in the Heisenberg case additional spin-flop structures play an essential role.Comment: 3 pages, 4 figures. Submitted to JEMS'0

Quenched charge disorder in CuO2 spin chains: Experimental and numerical studies

We report on measurements of the magnetic response of the anisotropic CuO_2 spin chains in lightly hole-doped La_x (Ca,Sr)_14-x Cu_24 O_41, x>=5. The experimental data suggest that in magnetic fields B >~ 4T (applied along the easy axis) the system is characterized by short-range spin order and quasi-static (quenched) charge disorder. The magnetic susceptibility chi(B) shows a broad anomaly, which we interpret as the remnant of a spin-flop transition. To corroborate this idea, we present Monte Carlo simulations of a classical, anisotropic Heisenberg model with randomly distributed, static holes. Our numerical results clearly show that the spin-flop transition of the pure model (without holes) is destroyed and smeared out due to the disorder introduced by the quasi-static holes. Both the numerically calculated susceptibility curves chi(B) and the temperature dependence of the position of the anomaly are in qualitative agreement with the experimental data.Comment: 10 pages, REVTeX4. 11 figures; v2: Fig.2 replaced, small changes in Figs.1 and 11; minor revisons in Sec. III.C; accepted by Phys. Rev.