Magnetic structure and dynamics of a strongly one-dimensional cobaltII^{II} metal-organic framework

We investigate the magnetism of the Co$^{II}_4$(OH)$_2$(C$_1$$_0$H$_1$$_6$O$_4$)$_3$ metal-organic framework which displays complex inorganic chains separated from each other by distances of 1 to 2 nm, and which orders at ~5.4 K. The zero-field magnetic structure is determined using neutron powder diffraction: it is mainly antiferromagnetic but posseses a ferromagnetic component along the $\textbf{c}$-axis. This magnetic structure persists in presence of a magnetic field. Ac susceptibility measurements confirm the existence of a single thermally activated regime over 7 decades in frequency ($E/k_B\approx64 K$) whereas time-dependent relaxation of the magnetization after saturation in an external field leads to a two times smaller energy barrier. These experiments probe the slow dynamics of domain walls within the chains: we propose that the ac measurements are sensitive to the motion of existing domain walls within the chains, while the magnetization measurements are governed by the creation of domain walls.Comment: 12 pages, 14 figure

The fractal nature of a diffusion front and the relation to percolation

International audienceUsing a two dimensional simulation, a diffusion front is shown to have a fractal geometry in a range increasing with the diffusion length. The number of particles on the front, and the width measuring its spread, follow power laws as a function of the diffusion length. The associated exponents and the fractal dimension can be expressed as simple functions of the critical exponents of the two dimensional percolation problem

Evaluation of the use of ultrasonography in primary care

Ultrasonography is proposed as a useful diagnostic aid for primary care physicians. This prospective study describes the demand for ultrasound examinations, excluding heart, vessels and pregnancy monitoring, in primary care in Switzerland. Eleven independent physicians requested an average of 2.7 ultrasound examinations per month and 18 residents 1.9 per month, which was similar to the figure of 2.2 obtained in a population-based study of 82 primary care physicians serving a region of 80, 000 inhabitants. Current demand for ultrasound scanning is low and does not indicate systematic training of primary care physicians until the efficacy of ultrasonography in this setting has been show

Mychael Danna: l'atípic

Abstract not availabl

Positive and negative emotion induction through avatars and its impact on reasoning performance: cardiovascular and pupillary correlates

International audienceMany studies have shown the impact of emotion on cognition (Damasio, 1994), however these influences remain ambiguous. The contradictions may be explained by a lack of experimental control (emotional induction, objective clues on emotional states...) but also by the existence of complex cross-influences between the dorsolateral prefrontal cortex, a major substratum of executive functions (EFs) and the ventromedial prefrontal cortex, an area strongly connected to the limbic system. This work aimed at gaining a more precise view of the links between emotion and EFs, utilizing an experimental protocol that used avatars for a well-controlled emotional induction, measurements of the autonomic nervous system activity as evidence of the emotional state (cardiovascular and pupillary responses) and a neuropsychological test battery (dynamic reasoning and deductive reasoning tasks) for the detection of EFs variations in response to emotion. The experimental data showed that positive emotion (joy) led to a performance decrease during both tasks, together with physiological variations. These counterintuitive results showed that positive mood can impair executive functioning in our tasks. In addition, our results highlighted the lack of learning effects on deductive performance

On the crystallization behavior of syndiotactic-b-atactic polystyrene stereodiblock copolymers, atactic/syndiotactic polystyrene blends, and aPS/sPS blends modified with sPS-b-aPS

International audienceCrystallization and morphological features of syndiotactic-b-atactic polystyrene stereodiblock copolymers (sPS-b-aPS), atactic/syndiotactic polystyrene blends (aPS/sPS), and aPS/sPS blends modified with sPS-b-aPS, with different compositions in aPS and sPS, have been investigated using differential scanning calorimetry (DSC), polarized light optical microscopy (POM) and wide angle X-ray diffraction (WAXRD) techniques. For comparative purposes, the properties of parent pristine sPS samples were also studied. WAXRD analyses revealed for all the samples, independently from their composition (aPS/sPS ratio) and structure (blends, block copolymers, blends modified with block copolymers), the same polymorphic β form of sPS. The molecular weight of aPS and sPS showed opposite effects on the crystallization of 50:50 aPS/sPS blends: the lower the molecular weight of aPS, the slower the crystallization while the lower the molecular weight of sPS, the faster the crystallization. DSC studies performed under both isothermal and non-isothermal conditions, independently confirmed by POM studies, led to a clear trend for the crystallization rate at a given sPS/aPS ratio (ca. 50:50 and 20:80): sPS homopolymers > sPS-b-aPS block copolymers ∼sPS/aPS blends modified with sPS-b-aPS copolymers > sPS/aPS blends. Interestingly, sPS-b-aPS block copolymers not only crystallized faster than blends, but also affected positively the crystallization behavior of blends. At 50:50 sPS/aPS ratio, blends (Blend-2), block copolymers (Cop-1) and blends modified with block copolymers (Blend-2-mod) crystallized via spherulitic crystalline growth controlled by an interfacial process. In all cases, an instantaneous nucleation was observed. The density of nuclei in block copolymers (160,000−190,000 nuclei mm−3) was always higher than that in blends and modified blends (30,000−60,000 nuclei mm−3), even for quite different sPS/aPS ratio. At 20:80 sPS/aPS ratio, the block copolymers (Cop-2) preserved the same crystallization mechanism than at 45:55 ratio (Cop-1). On the other hand, the 20:80 sPS/aPS blend (Blend-4) and blend modified with block copolymers (Blend-4-mod) showed a spinodal decomposition

Upper extremity fractures in the elderly: consequences on utilization of rehabilitation care

Background and aims: While hip fractures represent the most dramatic consequence of osteoporosis, fractures of the humerus, forearm and wrist account for one-third of the total incidence of fractures due to osteoporosis in the older population. The aim of this retrospective cohort study was to evaluate rehabilitation care utilization and associated factors in elderly individuals with upper limb fracture. Methods: Over two years, 667 patients 65 years of age or older were studied, who presented to the emergency department either from their private homes or nursing homes with an upper extremity fracture. The following outcome variables were collected: gender; age; residence; location of fracture; treatment; discharge destination; length of hospitalization; length of stay in a rehabilitation facility; and ultimate place of habitation after the event. Results: The most frequent sites of fracture were distal radius (37.2%) and proximal humerus (29.1%). Two-thirds of the patients were treated non-operatively. Inpatient rehabilitation care was necessary for 248 patients (37.2%; length of stay, 46 days). Factors associated with increased care included older age (≥80 years), coming from private home, sustaining two fractures, fractures of the humerus, and operative treatment. Six percent of the patients required permanent nursing home care. Conclusions: Upper extremity fractures in older people often require prolonged hospitalization and therefore account for considerable health care costs. Reasons are more related to advanced age and living conditions than to particular injury or treatmen

Ophioglossum polyphyllum A. Braun in Seub. (Ophioglossaceae, Pteridophyta), a rare potherb in south central Tibet (T.A.R., P.R.China)

peer reviewe