Reconciling solar and stellar magnetic cycles with nonlinear dynamo simulations.

The magnetic fields of solar-type stars are observed to cycle over decadal periods-11 years in the case of the Sun. The fields originate in the turbulent convective layers of stars and have a complex dependency upon stellar rotation rate. We have performed a set of turbulent global simulations that exhibit magnetic cycles varying systematically with stellar rotation and luminosity. We find that the magnetic cycle period is inversely proportional to the Rossby number, which quantifies the influence of rotation on turbulent convection. The trend relies on a fundamentally nonlinear dynamo process and is compatible with the Sun's cycle and those of other solar-type stars.

[Epidemiology of maternal mortality by infectious cause in France, 2007-2009, using data from confidential maternal mortality report]. / Épidémiologie de la mortalité maternelle de cause infectieuse en France, période 2007-2009, à partir des données du rapport confidentiel de mortalité maternelle.

Although deaths caused by infection during pregnancy and the postpartum period are rare in France, mortality rates have increased in several countries of the European community. In France, the rate of maternal mortality by infectious cause has decreased over the last 12 years. Infectious causes are currently in fifth place of maternal deaths. Over the period 2007-2009, 18 deaths occurred, eight by direct infectious causes and 10 by indirect infectious causes. Among the 18 deaths, 17 were examined by the National Expert Committee on Maternal Mortality (CNEMM) with the objectives to determine the direct or indirect link with pregnancy, the adequacy of care and the preventability of death. Among 8 deaths from direct infectious causes, four deaths were deemed "preventable" or "possibly preventable" because of inadequate care. Among nine deaths from indirect infectious causes, preventability could not be established in two deaths, five were non-preventable and two were preventable due to non-optimal care. These cases of puerperal septicemia show that when sepsis is clinically manifest, infection is already well established and widespread deterioration is therefore often irreversible. Maternal mortality is preventable in most cases if several points are observed: early diagnosis, probabilistic antibiotics targeting most frequently involved bacteria including Escherichia coli and Streptococcus A, early transfer to ICU, control septic portal entry, simple preventive measures, influenza vaccination. A "microbiological clinical diagnosis" approach must be initiated at the first clinical signs.

Hospital-wide modification of fluoroquinolone policy and meticillin-resistant Staphylococcus aureus rates: a 10-year interrupted time-series analysis.

In our tertiary university hospital, fluoroquinolones were prohibited during 2001 leading to a 90% reduction in their use. Our objective was to examine the trends in meticillin-resistant Staphylococcus aureus (MRSA) following the reintroduction of fluoroquinolones. We conducted a 10-year time-series analysis of monthly MRSA according to: (i) period of fluoroquinolone restriction (January 2001 to January 2002); (ii) period of fluoroquinolone increase up to pre-restriction levels (January 2002 to December 2004); and (iii) an observational period including the implementation of a hand hygiene campaign with alcohol-based hand rub (January 2005 to June 2009). We used segmented linear autoregression analysis to assess trends between adjacent periods. Fluoroquinolone use increased from 5.2 defined daily doses (DDD) per 1000 patient-days in 2001 to 56.6 DDD per 1000 patient-days in 2005 reaching pre-restriction fluoroquinolone levels (P<0.001) and remained stable during 2005-2010 (P=0.65). The monthly proportion of MRSA decreased during the period of FQ restriction (-0.49 per month, P<0.05). The reintroduction of fluoroquinolones was associated with a significant increase in MRSA (+0.68 per month, P<0.02) compared to the previous period. During period 3, we observed a significant change in MRSA (-5.9, P<0.002) compared to the previous period (-0.32 per month, P<0.001). During the latter period, hand hygiene was promoted and alcohol-based hand-rub consumption increased from 3411 L in 2005 to 14,599 L in 2009. This study reinforces the rationale for a hospital-wide fluoroquinolone formulary policy to control MRSA and suggests that it has an additive effect with a hand hygiene promotion.

Numerical and theoretical study of a monodisperse hard-sphere glass former.

There exists a variety of theories of the glass transition and many more numerical models. But because the models need built-in complexity to prevent crystallization, comparisons with theory can be difficult. We study the dynamics of a deeply supersaturated monodisperse four-dimensional (4D) hard-sphere fluid, which has no such complexity, but whose strong intrinsic geometrical frustration inhibits crystallization, even when deeply supersaturated. As an application, we compare its behavior to the mode-coupling theory (MCT) of glass formation. We find MCT to describe this system better than any other structural glass formers in lower dimensions. The reduction in dynamical heterogeneity in 4D suggested by a milder violation of the Stokes-Einstein relation could explain the agreement. These results are consistent with a mean-field scenario of the glass transition.

Geometrical frustration: a study of four-dimensional hard spheres.

The smallest maximum-kissing-number Voronoi polyhedron of three-dimensional (3D) Euclidean spheres is the icosahedron, and the tetrahedron is the smallest volume that can show up in Delaunay tessellation. No periodic lattice is consistent with either, and hence these dense packings are geometrically frustrated. Because icosahedra can be assembled from almost perfect tetrahedra, the terms "icosahedral" and "polytetrahedral" packing are often used interchangeably, which leaves the true origin of geometric frustration unclear. Here we report a computational study of freezing of 4D Euclidean hard spheres, where the densest Voronoi cluster is compatible with the symmetry of the densest crystal, while polytetrahedral order is not. We observe that, under otherwise comparable conditions, crystal nucleation in four dimensions is less facile than in three dimensions, which is consistent with earlier observations [M. Skoge, Phys. Rev. E 74, 041127 (2006)]. We conclude that it is the geometrical frustration of polytetrahedral structures that inhibits crystallization.

Hard-sphere crystallization gets rarer with increasing dimension.

We recently found that crystallization of monodisperse hard spheres from the bulk fluid faces a much higher free-energy barrier in four than in three dimensions at equivalent supersaturation, due to the increased geometrical frustration between the simplex-based fluid order and the crystal [J. A. van Meel, D. Frenkel, and P. Charbonneau, Phys. Rev. E 79, 030201(R) (2009)]. Here, we analyze the microscopic contributions to the fluid-crystal interfacial free energy to understand how the barrier to crystallization changes with dimension. We find the barrier to grow with dimension and we identify the role of polydispersity in preventing crystal formation. The increased fluid stability allows us to study the jamming behavior in four, five, and six dimensions and to compare our observations with two recent theories [C. Song, P. Wang, and H. A. Makse, Nature (London) 453, 629 (2008); G. Parisi and F. Zamponi, Rev. Mod. Phys. (to be published)].

Dynamical heterogeneity and nonlinear susceptibility in supercooled liquids with short-range attraction.

Recent work has demonstrated the strong qualitative differences between the dynamics near a glass transition driven by short-ranged repulsion and one governed by short-ranged attraction. Here we study in detail the behavior of nonlinear, higher-order correlation functions that measure the growth of length scales associated with dynamical heterogeneity in both types of systems. We find that this measure is qualitatively different in the repulsive and attractive cases with regards to the wave vector dependence as well as the time dependence of the standard nonlinear four-point dynamical susceptibility. We discuss the implications of these results for the general understanding of dynamical heterogeneity in glass-forming liquids.

Phase behavior and far-from-equilibrium gelation in charged attractive colloids.

In this Rapid Communication we demonstrate the applicability of an augmented Gibbs ensemble Monte Carlo approach for the phase behavior determination of model colloidal systems with short-ranged depletion attraction and long-ranged repulsion. This technique allows for a quantitative determination of the phase boundaries and ground states in such systems. We demonstrate that gelation may occur in systems of this type as the result of arrested microphase separation, even when the equilibrium state of the system is characterized by compact microphase structures.

Systematic characterization of thermodynamic and dynamical phase behavior in systems with short-ranged attraction.

In this paper we demonstrate the feasibility and utility of an augmented version of the Gibbs ensemble Monte Carlo method for computing the phase behavior of systems with strong, extremely short-ranged attractions. For generic potential shapes, this approach allows for the investigation of narrower attractive widths than those previously reported. Direct comparison to previous self-consistent Ornstein-Zernike approximation calculations is made. A preliminary investigation of out-of-equilibrium behavior is also performed. Our results suggest that the recent observations of stable cluster phases in systems without long-ranged repulsions are intimately related to gas-crystal and metastable gas-liquid phase separation.

[Current techniques used for the diagnosis of respiratory virus infectious in intensive care units]. / Techniques actuelles de diagnostic des infections virales respiratoires en réanimation.

Hundred viruses can be isolated in patients suffering from respiratory virus infections and hospitalised in intensive care unit (ICU): influenza virus, respiratory syncytial virus, para-influenza virus, adenovirus, coronavirus, rhinovirus, enterovirus, human metapneumovirus, bocavirus… Nasal or tracheobronchial specimens, which contain many epithelial cells will be used to isolate these common viruses. In immunocompromised patients a bronchoalveolar lavage has to be added to these specimens in order to detect cytomegalovirus and some adenovirus. The immunofluorescence or immunoenzymatic assays, which detect viral antigens in the infected cells are the easiest and fastest diagnostic methods, theoretically. As with other techniques, specimen quality is a major determinant of their performance. Unfortunately, the sensitivity of the antigen detection assays is low in respiratory infections in adults. Then the virus recovery by cell culture, which is usually more sensitive than the antigen detection assays, can be helpful. Many studies have reported more respiratory virus detections using nucleic acid testing such as PCR. They detect viruses, which are missed by conventional methods and increase the detection of common respiratory virus. Multiplex PCR assays have been developed, and these can simultaneously detect several viruses directly in clinical specimens. Nucleic acid testing can subtype viruses using subtype-specific primers, and analyse strain variation through genetic. It can be used also to quantify the viral load in clinical specimens. More recently real-time RT-PCR assays have been developed to get more rapidly the results of the nucleic acids assays. Specimen quality, timing and transportation conditions may be less critical for nucleic acid testing than for culture or antigen detection, as viable virus and intact infected cells need not to be preserved. Moreover, viral nucleic acids are detectable for several days longer into the clinical course than is cultivable virus, potentially allowing a diagnosis to be made in late-presenting patients. However, in a clinical virology laboratory, where the speed, low cost, and high sensitivity of the methods are required, the sequential use of antigen detection tests and multiplex PCR could be the best choice, particularly in the clinical setting of respiratory virus infections in adults hospitalised in ICU. In the future, the development of real-time multiplex PCR is likely to be top-priority.

Out-of-equilibrium dynamical fluctuations in glassy systems.

In this paper we extend the earlier treatment of out-of-equilibrium mesoscopic fluctuations in glassy systems in several significant ways. First, via extensive simulations, we demonstrate that models of glassy behavior without quenched disorder display scalings of the probability of local two-time correlators that are qualitatively similar to that of models with short-ranged quenched interactions. The key ingredient for such scaling properties is shown to be the development of a criticallike dynamical correlation length, and not other microscopic details. This robust data collapse may be described in terms of a time-evolving "extreme value" distribution. We develop a theory to describe both the form and evolution of these distributions based on a effective sigma model approach.

[Epidemiology and diagnosis of respiratory syncitial virus in adults]. / Epidémiologie et diagnostic des infections à virus respiratoire syncytial de l'adulte.

INTRODUCTION: Respiratory syncytial virus (RSV) is rarely searched for in respiratory infections in adults. This study assessed its frequency and diagnosis. METHODS: Three separate studies were conducted in adults presenting with (1) a flu-like illness, (2) a lower respiratory tract infection in the community, and (3) a severe pneumonia requiring hospitalisation. The diagnosis of RSV infection was sought by PCR in all cases, and compared to antigen detection and culture in two studies. RESULTS: RSV was identified in 20 (11.7%) of 170 influenza-vaccinated adults suffering from flu-like symptoms. In the 270 cases of non-severe lower respiratory tract illnesses in the community, viruses were identified in 86 (31.8%) cases, with RSV accounting for 13 (4.8%). In the 164 cases of acute bronchitis, a virus was detected in 64 (36.7%) of which 11 (6.3%) were RSV, 37 (21.3%) rhinovirus, 5 influenza viruses A and B, and 12 other viruses. In the 60 cases of infective exacerbations of chronic bronchitis, rhinovirus was detected in 9 (15%) and para-influenza 3 virus in 2 cases. In the 21 acute pneumonia's, 1 RSV, 1 influenza virus A and 2 rhinovirus cases were detected as well as 1 RSV, 1 parainfluenza 3 viruses and 4 rhinovirus cases in the 11 lower respiratory tract illnesses in patients with pre-existing lung disease. There were overall 19 viral and bacterial associated infections. Finally, in the 51 acute pneumonias hospitalised with respiratory distress syndrome, a virus was identified in 17 (33.3%) cases, including 3 (5.5%) RSV, 6 influenza A, 3 rhinovirus, 2 adenovirus, 2 herpes simplex virus and 1 cytomegalovirus. There were 6 bacterial-associated infections, and 4 were hospital-acquired. All RSV-infected patients were old people and had chronic pulmonary or cardiac disease. CONCLUSIONS: In adults, RSV is a frequent cause of flu-like symptoms. It can sometimes cause lower respiratory tract illness, which can be severe, and should be considered in the differential diagnosis in such cases. The PCR method is a particularly effective diagnostic test, but as yet is not routinely available.

Corticosteroids as adjunctive treatment in Austrian's syndrome (pneumococcal endocarditis, meningitis, and pneumonia): report of two cases and review of the literature.

This report describes two cases of Osler's triad of pneumonia, meningitis, and endocarditis, as a result of Streptococcus pneumoniae infection, also called Austrian's syndrome. In the first patient, a 51 year old non-alcoholic man, the aortic valve was affected and needed to be replaced in an emergency operation. The mitral valve was affected in a 70 year old woman without underlying disease, who only benefited from medical treatment. Both patients received corticosteroids, either dexamethasone followed by low doses of hydrocortisone and fludrocortisone, or only hydrocortisone and fludrocortisone, at the onset of the illness, and their outcome was favourable. These case reports focus on the presentation, prognosis, and therapeutic options for this severe syndrome.

Hyperreninemic hypoaldosteronism: a possible etiological factor of septic shock-induced acute renal failure.

OBJECTIVE: Hyperreninemic hypoaldosteronism has been described in critically ill patients. The present study investigated the plasma aldosterone concentration (PAC) in septic shock patients and its relationship with clinical course. DESIGN AND SETTING: Prospective descriptive study in a medical intensive care unit (ICU) of a university hospital. PATIENTS: Forty-six consecutive patients with septic shock as defined by the ACCP/SCCM criteria. INTERVENTION: A corticotropin stimulation test, followed by treatment with low doses of hydrocortisone and fludrocortisone. MEASUREMENTS AND RESULTS: Plasma renin activity, PAC, and cortisol levels were measured before and after the test. PAC measurements were repeated for 1 week. Relevant clinical and laboratory variables were recorded for ICU stay. Patients were divided into two groups according to PAC/renin activity ratio: above 2 (n=24 patients) and below 2 n=22). Patients with PAC/renin activity less than 2 had higher total volume of infused fluid, serum creatinine level, and fractional excretion of sodium values; aldosterone and serum creatinine were negatively correlated. Hypoaldosteronism was reversible within 1 week. Duration of ICU stay (p=0.0026) and the need for renal replacement therapy (p=0.0021) were greater in the group with PAC/renin less than 2. CONCLUSIONS: Transient hyperreninemic hypoaldosteronism is common in patients with septic shock. These abnormal aldosterone levels are associated with greater sodium and fluid depletion and are followed by enhanced incidence of acute renal failure requiring renal replacement therapy and prolonged length of stay in ICU.

Energy barriers to rotation in axially chiral analogues of 4-(dimethylamino)pyridine.

The barriers to enantiomerization of a series of axially chiral biaryl analogues of 4-(dimethylamino)pyridine (DMAP) 1-10 were determined experimentally by means of dynamic HPLC measurements and racemization studies. The barriers to rotation in derivatives 1-6 (based on the bicyclic 5-azaindoline core) were lower than those in the corresponding derivatives 7-10 (based on the monocyclic DMAP core). Semiempirical (PM3), ab initio Hartree-Fock (HF/STO-3G), and density functional theory (DFT/B3LYP/6-31G*) calculations reveal that these differences in barriers to rotation are the result of differing degrees of hybridization of the non-pyridyl nitrogen in the enantiomerization transition states (TSs). The importance of heteroatom hybridization as a factor in determining nonsteric contributions to barriers to rotation in azabiaryls of this type is discussed.