A new magnetic field dependence of Landau levels on a graphene like structure

We consider a tight-binding model on the honeycomb lattice in a magnetic field. For special values of the hopping integrals, the dispersion relation is linear in one direction and quadratic in the other. We find that, in this case, the energy of the Landau levels varies with the field B as E_n(B) ~ [(n+\gamma)B]^{2/3}. This result is obtained from the low-field study of the tight-binding spectrum on the honeycomb lattice in a magnetic field (Hofstadter spectrum) as well as from a calculation in the continuum approximation at low field. The latter links the new spectrum to the one of a modified quartic oscillator. The obtained value $\gamma=1/2$ is found to result from the cancellation of a Berry phase.Comment: 4 pages, 4 figure

Magnetoresistance in Disordered Graphene: The Role of Pseudospin and Dimensionality Effects Unraveled

We report a theoretical low-field magnetotransport study unveiling the effect of pseudospin in realistic models of weakly disordered graphene-based materials. Using an efficient Kubo computational method, and simulating the effect of charges trapped in the oxide, different magnetoconductance fingerprints are numerically obtained in system sizes as large as 0.3 micronmeter squared, containing tens of millions of carbon atoms. In two-dimensional graphene, a strong valley mixing is found to irreparably yield a positive magnetoconductance (weak localization), whereas crossovers from positive to a negative magnetoconductance (weak antilocalization) are obtained by reducing disorder strength down to the ballistic limit. In sharp contrast, graphene nanoribbons with lateral size as large as 10nm show no sign of weak antilocalization, even for very small disorder strength. Our results rationalize the emergence of a complex phase diagram of magnetoconductance fingerprints, shedding some new light on the microscopical origin of pseudospin effects.Comment: 8 pages, 5 figure

A unified picture of ferromagnetism, quasi-long range order and criticality in random field models

By applying the recently developed nonperturbative functional renormalization group (FRG) approach, we study the interplay between ferromagnetism, quasi-long range order (QLRO) and criticality in the $d$-dimensional random field O(N) model in the whole ($N$, $d$) diagram. Even though the "dimensional reduction" property breaks down below some critical line, the topology of the phase diagram is found similar to that of the pure O(N) model, with however no equivalent of the Kosterlitz-Thouless transition. In addition, we obtain that QLRO, namely a topologically ordered "Bragg glass" phase, is absent in the 3--dimensional random field XY model. The nonperturbative results are supplemented by a perturbative FRG analysis to two loops around $d=4$.Comment: 4 pages, 4 figure

Two-loop Functional Renormalization Group of the Random Field and Random Anisotropy O(N) Models

We study by the perturbative Functional Renormalization Group (FRG) the Random Field and Random Anisotropy O(N) models near $d=4$, the lower critical dimension of ferromagnetism. The long-distance physics is controlled by zero-temperature fixed points at which the renormalized effective action is nonanalytic. We obtain the beta functions at 2-loop order, showing that despite the nonanalytic character of the renormalized effective action, the theory is perturbatively renormalizable at this order. The physical results obtained at 2-loop level, most notably concerning the breakdown of dimensional reduction at the critical point and the stability of quasi-long range order in $d<4$, are shown to fit into the picture predicted by our recent non-perturbative FRG approach.Comment: 19 pages, 20 figures. Minor correction

The Galactic disk mass function: reconciliation of the HST and nearby determinations

We derive and parametrize the Galactic mass function (MF) below 1 \msol characteristic of both single objects and binary systems. We resolve the long standing discrepancy between the MFs derived from the HST and from the nearby luminosity functions, respectively. We show that this discrepancy stemmed from {\it two} cumulative effects, namely (i) incorrect color-magnitude determined distances, due a substantial fraction of M dwarfs in the HST sample belonging to the metal-depleted, thick-disk population, as corrected recently by Zheng et al. and (ii) unresolved binaries. We show that both the nearby and HST MF for unresolved systems are consistent with a fraction $\sim$50% of M-dwarf binaries, with the mass of both the primaries and the companions originating from the same underlying single MF. This implies that $\sim$30% of M dwarfs should have an M dwarf companion and $\sim$20% should have a brown dwarf companion, in agreement with recent determinations. The present calculations show that the so-called "brown-dwarf desert" should be reinterpreted as a lack of high mass-ratio (m_2/m_1\la 0.1) systems, and does not preclude a substantial fraction of brown dwarfs as companions of M dwarfs or for other brown dwarfs.Comment: 16 pages, Latex file, uses aasms4.sty, to appear in ApJ Letter

Joint analyses of open comments and quantitative data: Added value in a job satisfaction survey of hospital professionals.

To obtain a comprehensive understanding of the job opinions of hospital professionals by conducting qualitative analyses of the open comments included in a job satisfaction survey and combining these results with the quantitative results. A cross-sectional survey targeting all Lausanne University Hospital professionals was performed in the fall of 2013. The survey considered ten job satisfaction dimensions (e.g. self-fulfilment, workload, management, work-related burnout, organisational commitment, intent to stay) and included an open comment section. Computer-assisted qualitative analyses were conducted on these comments. Satisfaction rates on the included dimensions and professional groups were entered as predictive variables in the qualitative analyses. Of 10 838 hospital professionals, 4978 participated in the survey and 1067 provided open comments. Data from 1045 respondents with usable comments constituted the analytic sample (133 physicians, 393 nurses, 135 laboratory technicians, 247 administrative staff, including researchers, 67 logistic staff, 44 psycho-social workers, and 26 unspecified). Almost a third of the comments addressed scheduling issues, mostly related to problems and exhaustion linked to shifts, work-life balance, and difficulties with colleagues' absences and the consequences for quality of care and patient safety. The other two-thirds related to classic themes included in job satisfaction surveys. Although some comments were provided equally by all professional groups, others were group specific: work and hierarchy pressures for physicians, healthcare quality and patient safety for nurses, skill recognition for administrative staff. Overall, respondents' comments were consistent with their job satisfaction ratings. Open comment analysis provides a comprehensive understanding of hospital professionals' job experiences, allowing better consideration of quality initiatives that match the needs of professionals with reality

Workplace Well-Being and Intent to Stay by Health Care Workers Reassigned during the First COVID-19 Wave: Results of a Swiss Survey.

Our study aimed at investigating the way not having the choice to be reassigned was associated to a poorer experience of reassignment among health care workers (HCWs) during the first wave of the coronavirus disease 2019 (COVID-19), and indirectly to a lower workplace well-being and reduced intent to stay at the hospital. We also investigated the moderating role of the perceived hospital management responsiveness on these associations. A cross sectional survey was sent to all professionals from 11 hospitals and clinics in the French-speaking part of Switzerland, in July 2020. Out of 2811 professionals who completed the survey, 436 were HCWs reassigned to COVID-19 units during the first wave of the pandemic and constituted our analysis sample. Results indicated that hospital management responsiveness moderated the association between lack of choice and reassignment experience, indicating that the more HCWs perceived responsiveness, the less the lack of choice affected their experience of reassignment and thus their intent to stay and workplace well-being. Lack of choice during reassignments can reduce intent to stay and workplace well-being, in particular if hospital management is not perceived to be responsive during the crisis. Attempts by hospital management to find solutions, such as flexibility in working hours or extraordinary leaves, can alleviate the perceived constraints of reassignment and be considered signs of responsiveness from hospital management

Healthcare stakeholders' perspective on barriers to integrated care in Switzerland: Results from the open-ended question of a nationwide survey.

We aimed to identify the main barriers to integrated care (IC) as reported by healthcare stakeholders from various linguistic regions and health system specificities, according to their reality of practice. Information was gathered through an open-ended question from a national survey conducted in Switzerland in 2019. Responses were analysed qualitatively with the IRaMuTeQ software. Answers from 410 respondents were obtained. Respondents reported barriers at two levels: the system and professional level. Threat to financial benefits, concerns for patient data sharing and tensions between quality of care and benefits for patients versus costs were mentioned at the professional level, in their activity and in patient care. At the system level, limitations at the political level due to federalism and the lack of support and training for professionals were important barriers, in addition to the lack of recognition and compensation for professionals and the fragmented functioning of the health care system. Our study underlines the importance of implementing innovative funding strategies and reimbursement schemes, as well as political willingness to move towards IC. The alignment between federal policies and cantonal specificities also appears as necessary to achieve involvement of professionals, promote integration of services and coordination of professionals for continuous and efficient care

Factors Associated With Intent to Leave the Profession for the Allied Health Workforce: A Rapid Review.

Shortages of satisfied and well-trained health care professionals are an urgent threat for health systems worldwide. Although numerous studies have focused on retention issues for nurses and physicians, the situation for the allied health workforce remains understudied. We conducted a rapid review of the literature on allied health workers to investigate the main reasons for leaving their profession. 1,305 original research articles were retrieved from databases MEDLINE, CINAHL, PsycInfo, and Epistemonikos, of which 29 were eligible for data extraction. Reviewed studies featured mainly pharmacists, psychologists, dietitians, physical therapists, emergency medical professionals, and occupational therapists. We categorized 17 typical factors of the intent to leave as organizational, psychological, team and management, and job characteristics. The relative importance of each factor was assessed by measuring its prevalence in the selected literature. By revealing common themes across allied health professions, our work suggests actionable insights to improve retention in these vital services

Why students need to be prepared to cooperate : a cooperative nudge in statistics learning at university

Despite the potential benefits of cooperative learning at university, its implementation is challenging. Here, we propose a theory-based 90-min intervention with 185 first-year psychology students in the challenging domain of statistics, consisting of an exercise phase and an individual learning post-test. We compared three conditions that manipulated the exercise phase: individual work, cooperative dyadic instructions (structuring three basic components of cooperative learning: positive goal interdependence, individual responsibility and promotive interactions) and cooperative dyadic interactions (the three basic components with an additional cooperative nudge, namely explaining why and how to cooperate in this task) in order to test whether a progressive increase in benefits occurs as the cooperative structure is reinforced. Results indicated a linear trend in individual post-test learning and competence perception, from individual work to cooperative instructions to cooperative interactions. Competence perception mediated the effect of experimental conditions on learning. The results highlight the benefits of the cooperative nudge