Field dependence of the temperature at the peak of the ZFC magnetization

The effect of an applied magnetic field on the temperature at the maximum of the ZFC magnetization, $M_{ZFC}$, is studied using the recently obtained analytic results of Coffey et al. (Phys. Rev. Lett. {\bf 80}(1998) 5655) for the prefactor of the N\'{e}el relaxation time which allow one to precisely calculate the prefactor in the N\'{e}el-Brown model and thus the blocking temperature as a function of the coefficients of the Taylor series expansion of the magnetocrystalline anisotropy. The present calculations indicate that even a precise determination of the prefactor in the N\'{e}el-Brown theory, which always predicts a monotonic decrease of the relaxation time with increasing field, is insufficient to explain the effect of an applied magnetic field on the temperature at the maximum of the ZFC magnetization. On the other hand, we find that the non linear field-dependence of the magnetization along with the magnetocrystalline anisotropy appears to be of crucial importance to the existence of this maximum.Comment: 14 LaTex209 pages, 6 EPS figures. To appear in J. Phys.: Condensed Matte

Striking the right balance and supporting social aspirations: how agency and choice play out in a recovery-oriented mental health service

Introduction There has been an increasing drive for a transformation of the mental health system towards recovery orientation, with research identifying a series of key recovery principles. It has been argued that these principles remain rhetoric rather than routine practice, and it remains unclear how these are operationalised and promoted within inpatient settings. Aim To address the knowledge gap of how staff and service-users enact recovery principles during the daily workings of an inpatient mental health service. Method Twenty-one interviews were conducted with staff and service-users at a recovery-oriented inpatient service in the United Kingdom. Data was analysed using framework analysis. Findings Analysis of research interview data identified three subcategories grouped under the category of choice. These categories were: a delicate balancing act, acceptability of choices, and social issues impacting choice. Discussion Staff were uncertain of their role in promoting choice, resulting in service-users feeling unsupported in their recovery. Staff had to adopt a titrated approach to social inclusion, to protect service-users from discrimination and rejection. Implications Mental health professionals need to take a more proactive role in enabling service-users to realise their social aspirations, as well as managing any adverse impacts of stigma and discrimination

Stochastic dynamics beyond the weak coupling limit: thermalization

We discuss the structure and asymptotic long-time properties of coupled equations for the moments of a Brownian particle's momentum derived microscopically beyond the lowest approximation in the weak coupling parameter. Generalized fluctuation-dissipation relations are derived and shown to ensure convergence to thermal equilibrium at any order of perturbation theory.Comment: 6+ page

Integral Relaxation Time of Single-Domain Ferromagnetic Particles

The integral relaxation time \tau_{int} of thermoactivating noninteracting single-domain ferromagnetic particles is calculated analytically in the geometry with a magnetic field H applied parallel to the easy axis. It is shown that the drastic deviation of \tau_{int}^{-1} from the lowest eigenvalue of the Fokker-Planck equation \Lambda_1 at low temperatures, starting from some critical value of H, is the consequence of the depletion of the upper potential well. In these conditions the integral relaxation time consists of two competing contributions corresponding to the overbarrier and intrawell relaxation processes.Comment: 8 pages, 3 figure

Thermally activated escape rates of uniaxial spin systems with transverse field

Classical escape rates of uniaxial spin systems are characterized by a prefactor differing from and much smaller than that of the particle problem, since the maximum of the spin energy is attained everywhere on the line of constant latitude: theta=const, 0 =< phi =< 2*pi. If a transverse field is applied, a saddle point of the energy is formed, and high, moderate, and low damping regimes (similar to those for particles) appear. Here we present the first analytical and numerical study of crossovers between the uniaxial and other regimes for spin systems. It is shown that there is one HD-Uniaxial crossover, whereas at low damping the uniaxial and LD regimes are separated by two crossovers.Comment: 4 PR pages, 3 figures, final published versio

Avoiding Litigation: The Benefits of Employment Contracts and Arbitration

This research reviews the current environment in employment disputes. In an ever-increasing litigious era where it is not uncommon to see six-figure settlements, the entrepreneur needs to examine the possible legal options in the event of a lawsuit involving current or former employees. While many employment-oriented lawsuits are settled through litigation, this is a time-consuming and costly process. Indeed, due to its adversarial nature, dispute resolution through litigation can take years  to settle.   In contrast,  one business strategy that  is growing in popularity includes the use of employment contracts specifying arbitration in dispute resolution. Because arbitration is "almost entirely  separate from  the  legal  system " (Siegel, Sect. 586), it offers many advantages to both employers and employees

Managing sleep and wakefulness in a 24 hour world

This article contributes to literature on the sociology of sleep by exploring the sleeping practices and subjective sleep experiences of two social groups: shift workers and students. It draws on data, collected in the UK from 25 semi-structured interviews, to discuss the complex ways in which working patterns and social activities impact upon experiences and expectations of sleep in our wired awake world. The data show that, typically, sleep is valued and considered to be important for health, general wellbeing, appearance and physical and cognitive functioning. However, sleep time is often cut back on in favour of work demands and social activities. While shift workers described their efforts to fit in an adequate amount of sleep per 24-hour period, for students, the adoption of a flexible sleep routine was thought to be favourable for maintaining a work–social life balance. Collectively, respondents reported using a wide range of strategies, techniques, technologies and practices to encourage, overcome or delay sleep(iness) and boost, promote or enhance wakefulness/alertness at socially desirable times. The analysis demonstrates how social context impacts not only on how we come to think about sleep and understand it, but also how we manage or self-regulate our sleeping patterns

Investigating Biological Matter with Theoretical Nuclear Physics Methods

The internal dynamics of strongly interacting systems and that of biomolecules such as proteins display several important analogies, despite the huge difference in their characteristic energy and length scales. For example, in all such systems, collective excitations, cooperative transitions and phase transitions emerge as the result of the interplay of strong correlations with quantum or thermal fluctuations. In view of such an observation, some theoretical methods initially developed in the context of theoretical nuclear physics have been adapted to investigate the dynamics of biomolecules. In this talk, we review some of our recent studies performed along this direction. In particular, we discuss how the path integral formulation of the molecular dynamics allows to overcome some of the long-standing problems and limitations which emerge when simulating the protein folding dynamics at the atomistic level of detail.Comment: Prepared for the proceedings of the "XII Meeting on the Problems of Theoretical Nuclear Physics" (Cortona11

The circumstellar environment of HD50138 revealed by VLTI/AMBER at high angular resolution

HD50138 is a Herbig B[e] star with a circumstellar disc detected at IR and mm wavelength. Its brightness makes it a good candidate for NIR interferometry observations. We aim to resolve, spatially and spectrally, the continuum and hydrogen emission lines in the 2.12-2.47 micron region, to shed light on the immediate circumstellar environment of the star. VLTI/AMBER K-band observations provide spectra, visibilities, differential phases, and closure phases along three long baselines for the continuum, and HI emission in Br$\gamma$ and five high-n Pfund lines. By computing the pure-line visibilities, we derive the angular size of the different line-emitting regions. A simple LTE model was created to constrain the physical conditions of HI emitting region. The continuum region cannot be reproduced by a geometrical 2D elongated Gaussian fitting model. We estimate the size of the region to be 1 au. We find the Br$\gamma$ and Pfund lines come from a more compact region of size 0.4 au. The Br$\gamma$ line exhibits an S-shaped differential phase, indicative of rotation. The continuum and Br$\gamma$ line closure phase show offsets of $\sim$-25$\pm$5 $^o$ and 20$\pm$10$^o$, respectively. This is evidence of an asymmetry in their origin, but with opposing directions. We find that we cannot converge on constraints for the HI physical parameters without a more detailed model. Our analysis reveals that HD50138 hosts a complex circumstellar environment. Its continuum emission cannot be reproduced by a simple disc brightness distribution. Similarly, several components must be evoked to reproduce the interferometric observables within the Br$\gamma$, line. Combining the spectroscopic and interferometric data of the Br$\gamma$ and Pfund lines favours an origin in a wind region with a large opening angle. Finally, our results point to an evolved source.Comment: accepted for publication in A&