RESUMEN

The elastic properties of neutron star crusts are relevant for a variety of currently observable or near-future electromagnetic and gravitational wave phenomena. These phenomena may depend on the elastic properties of nuclear pasta found in the inner crust. We present large-scale classical molecular dynamics simulations where we deform nuclear pasta. We simulate idealized samples of nuclear pasta and describe their breaking mechanism. We also deform nuclear pasta that is arranged into many domains, similar to what is known for the ions in neutron star crusts. Our results show that nuclear pasta may be the strongest known material, perhaps with a shear modulus of 10^{30} ergs/cm^{3} and a breaking strain greater than 0.1.

RESUMEN

This single-center study examines the incidence, etiology, and outcomes associated with prolonged mechanical ventilation (PMV), defined as time to definite spontaneous ventilation >21 days after double lung transplantation (LTx). A total of 690 LTx recipients between January 2005 and December 2012 were analyzed. PMV was necessary in 95 (13.8%) patients with decreasing incidence during the observation period (p < 0.001). Independent predictors of PMV were renal replacement therapy (odds ratio [OR] 11.13 [95% CI, 5.82-21.29], p < 0.001), anastomotic dehiscence (OR 8.74 [95% CI 2.42-31.58], p = 0.001), autoimmune comorbidity (OR 5.52 [95% CI 1.86-16.41], p = 0.002), and postoperative neurologic complications (OR 5.03 [95% CI 1.98-12.81], p = 0.001), among others. Overall 1-year survival was 86.0% (90.4% for LTx between 2010 and 2012); it was 60.7% after PMV and 90.0% in controls (p < 0.001). Conditional long-term outcome among hospital survivors, however, did not differ between the groups (p = 0.78). Multivariate analysis identified renal replacement therapy (hazard ratio [HR] 3.55 [95% CI 2.40-5.25], p < 0.001), post-LTx extracorporeal membrane oxygenation (HR 3.47 [95% CI 2.06-5.83], p < 0.001), and prolonged inotropic support (HR 1.95 [95% CI 1.39-2.75], p < 0.001), among others, as independent predictors of mortality. In conclusion, PMV complicated 14% of LTx procedures and, although associated with increased in-hospital mortality, outcomes among patients surviving to hospital discharge were unaffected.

Asunto(s)

RESUMEN

Nuclear pasta, with nonspherical shapes, is expected near the base of the crust in neutron stars. Large-scale molecular dynamics simulations of pasta show long lived topological defects that could increase electron scattering and reduce both the thermal and electrical conductivities. We model a possible low-conductivity pasta layer by increasing an impurity parameter Q_{imp}. Predictions of light curves for the low-mass x-ray binary MXB 1659-29, assuming a large Q_{imp}, find continued late time cooling that is consistent with Chandra observations. The electrical and thermal conductivities are likely related. Therefore, observations of late time crust cooling can provide insight on the electrical conductivity and the possible decay of neutron star magnetic fields (assuming these are supported by currents in the crust).

RESUMEN

OBJECTIVE: Writer's cramp is defined as a task specific focal dystonia generating hypertonic muscle co-contractions during handwriting resulting in impaired writing performance and exaggerated finger force. However, little is known about the generalisation of grip force across tasks others than writing. The aim of the study was to directly compare regulation of grip forces during handwriting with force regulation in other fine-motor tasks in patients and control subjects. METHODS: Handwriting, lifting and cyclic movements of a grasped object were investigated in 21 patients and 14 controls. The applied forces were registered in all three tasks and compared between groups and tasks. In addition, task-specific measures of fine-motor skill were assessed. RESULTS: As expected, patients generated exaggerated forces during handwriting compared to control subjects. However there were no statistically significant group differences during lifting and cyclic movements. The control group revealed a generalisation of grip forces across manual tasks whereas in patients there was no such correlation. CONCLUSION: We conclude that increased finger forces during handwriting are a task-specific phenomenon that does not necessarily generalise to other fine-motor tasks. SIGNIFICANCE: Force control of patients with writer's cramp in handwriting and other fine-motor tasks is characterised by individualised control strategies.

Asunto(s)

RESUMEN

BACKGROUND AND STUDY AIM: Placement of covered self-expanding metal or plastic stents (SEMS or SEPS) is an established method for managing intrathoracic leaks. Recently, endoscopic vacuum-assisted closure (EVAC) has been described as a new effective treatment option. Our aim was to compare stent placement with EVAC for nonsurgical closure of intrathoracic anastomotic leaks. PATIENTS AND METHODS: In a retrospective analysis we were able to identify 39 patients who were treated with SEMS or SEPS and 32 patients who were treated with EVAC for intrathoracic leakage. In addition to successful fistula closure, we analyzed hospital mortality, number of endoscopic interventions, incidence of stenoses, and duration of hospitalization. RESULTS: In a multivariate analysis, successful wound closure was independently associated with EVAC therapy (hazard ratio 2.997, 95 % confidence interval [95 %CI] 1.568 - 5.729; P = 0.001). The overall closure rate was significantly higher in the EVAC group (84.4 %) compared with the SEMS/SEPS group (53.8 %). No difference was found for hospitalization and hospital mortality. We found significantly more strictures in the stent group (28.2 % vs. 9.4 % with EVAC, P < 0,05). CONCLUSIONS: EVAC is an effective endoscopic treatment option for intrathoracic leaks and showed higher effectiveness than stent placement in our cohort.

Asunto(s)

RESUMEN

This study addresses the epidemiology of injuries in adolescent male and female soccer players in Germany. Therefore, the purpose of the study was to analyse the injuries in male and female youth soccer players in Germany. This study was designed as a cross-sectional web-based survey. From March until December 2011 we investigated 1110 soccer players (male n = 841; female n = 269) aged 12 - 19 years (15.0 ± 2.0 years) from 60 clubs in Southern Germany. A total of 664 (79 %) of the 841 boys and 67 (25 %) of the 269 girls reported being injured due to soccer. The total number of injuries was 2373. Respectively the frequency of injury was 2.85 in boys and 7.10 in girls. The lower extremities were affected in 70 % of all reported cases. Strains were the most common injuries in the lower and upper extremities (35 %). The boys reported in 51.5 % of all injuries that the injury was non-contact in nature. In contrast, 52.1 % of the injuries in girls were reported as contact injuries. Similar amounts of injuries were observed in training versus games for both genders. Prevention procedures, such as a thorough warm-up, should be implemented before every game and training to reduce the risk of injury.

Asunto(s)

RESUMEN

Secondary sclerosing cholangitis in critically ill patients (SSC - CIP) is an underdiagnosed emerging disease. The aim of this study was to characterize clinical features and prognostic factors for mortality in SSC - CIP. This retrospective study included 54 patients who were diagnosed via endoscopic retrograde cholangiopancreatography (ERCP) after cardiothoracic surgery (n = 21), sepsis (n = 13), polytrauma (n = 11), and others (n = 9). In total, 33 patients who either died (n = 27) or needed liver transplantation (n = 6) were compared with surviving patients (n = 21). The model for end-stage liver disease (MELD) score and need for renal replacement therapy were independent risk factors for mortality. Compared with ERCP, accuracy was 30% for ultrasound and 36 % for liver biopsies. As a result of microbiological bile analysis, 28 % of patients required a change in antibiotic treatment. SSC - CIP is frequently a fatal disease. ERCP should be considered in selected patients to establish the diagnosis and hence provide useful clinical information.

Asunto(s)

RESUMEN

We determine the liquid-solid phase diagram for carbon-oxygen and oxygen-selenium plasma mixtures using two-phase molecular dynamics simulations. We identify liquid, solid, and interface regions using a bond angle metric. To study finite-size effects, we perform 27,648- and 55,296-ion simulations. To help monitor nonequilibrium effects, we calculate diffusion constants D(i). For the carbon-oxygen system we find that D(O) for oxygen ions in the solid is much smaller than D(C) for carbon ions and that both diffusion constants are 80 or more times smaller than diffusion constants in the liquid phase. There is excellent agreement between our carbon-oxygen phase diagram and that predicted by Medin and Cumming. This suggests that errors from finite-size and nonequilibrium effects are small and that the carbon-oxygen phase diagram is now accurately known. The oxygen-selenium system is a simple two-component model for more complex rapid proton capture nucleosynthesis ash compositions for an accreting neutron star. Diffusion of oxygen, in a predominantly selenium crystal, is remarkably fast, comparable to diffusion in the liquid phase. We find a somewhat lower melting temperature for the oxygen-selenium system than that predicted by Medin and Cumming. This is probably because of electron screening effects.

Asunto(s)

RESUMEN

The neutron-rich isotope ²²Ne may be a significant impurity in carbon and oxygen white dwarfs and could impact how the stars freeze. We perform molecular dynamics simulations to determine the influence of ²²Ne in carbon-oxygen-neon systems on liquid-solid phase equilibria. Both liquid and solid phases are present simultaneously in our simulation volumes. We identify liquid, solid, and interface regions in our simulations using a bond angle metric. In general we find good agreement for the composition of liquid and solid phases between our MD simulations and the semianalytic model of Medin and Cumming. The trace presence of a third component, neon, does not appear to strongly impact the chemical separation found previously for two-component carbon and oxygen systems. This suggests that small amounts of ²²Ne may not qualitatively change how the material in white dwarf stars freezes. However, we do find systematically lower melting temperatures (higher Γ) in our MD simulations compared to the semianalytic model. This difference seems to grow with impurity parameter Q_{imp} and suggests a problem with simple corrections to the linear mixing rule for the free energy of multicomponent solid mixtures that is used in the semianalytic model.

RESUMEN

Diffusion in Coulomb crystals can be important for the structure of neutron star crusts. We determine diffusion constants D from molecular dynamics simulations. We find that D for Coulomb crystals with relatively soft-core 1/r interactions may be larger than D for Lennard-Jones or other solids with harder-core interactions. Diffusion, for simulations of nearly perfect body-centered-cubic lattices, involves the exchange of ions in ringlike configurations. Here ions "hop" in unison without the formation of long lived vacancies. Diffusion, for imperfect crystals, involves the motion of defects. Finally, we find that diffusion, for an amorphous system rapidly quenched from Coulomb parameter Γ=175 to Coulomb parameters up to Γ=1750, is fast enough that the system starts to crystalize during long simulation runs. These results strongly suggest that Coulomb solids in cold white dwarf stars, and the crust of neutron stars, will be crystalline and not amorphous.

RESUMEN

Acute liver failure is a multisystem disease with predominantly sudden and severe hepatic injury and hepatic encephalopathy caused by apoptotic or necrotic hepatocyte damage. The clinical challenge in patients with acute liver failure is to promptly identify those with poor prognosis and refer them for emergency liver transplantation. This review article highlights the main aspects of decision making in the setting of acute liver failure, summarizes new aspects of its critical care management and gives an overview of sclerosing cholangitis in the critically ill patient, an under-recognized disease entity that can progress to acute liver failure.

Asunto(s)

RESUMEN

We determine the phase diagram for dense carbon-oxygen mixtures in white dwarf (WD) star interiors using molecular dynamics simulations involving liquid and solid phases. Our phase diagram agrees well with predictions from Ogata et al. and from Medin and Cumming and gives lower melting temperatures than Segretain et al. Observations of WD crystallization in the globular cluster NGC 6397 by Winget et al. suggest that the melting temperature of WD cores is close to that for pure carbon. If this is true, our phase diagram implies that the central oxygen abundance in these stars is less than about 60%. This constraint, along with assumptions about convection in stellar evolution models, limits the effective S factor for the 12C(α,γ)16O reaction to S(300)≤170 keV b.

RESUMEN

OBJECTIVE: Writer's Cramp (WC) is defined as a task-specific form of focal-hand-dystonia generating hypertonic muscle co-contractions resulting in impaired handwriting. Little is known about kinematic and dynamic characteristics in handwriting in the different subtypes of WC. METHODS: In this study, kinematic and force analyses were used to compare handwriting capacity of 14 simple, 13 dystonic WC-patients and 14 healthy subjects. The effect of task-complexity was investigated using a simple repetitive writing-task, writing pairs of letters, a sentence and copying a text. RESULTS: In general, patients showed significant deficits in kinematic and force parameters during writing, but no consistent differences between the two subtypes of WC were found. The complexity of writing material modulated writing parameters in all groups, but less complex material did not ameliorate the patients' deficits relative to control subjects. CONCLUSIONS: The similarity of deficits in patients with simple and dystonic WC does not support the concept of a unitary progression of deficits causing a switch from simple to dystonic WC. Dystonic WC seems to be characterized by a spread of symptoms independent of severity. Obviously, the deficits concern elementary aspects of writing and are not modulated by more complex aspects. SIGNIFICANCE: Quantification of writing deficits by simple and short phrases with kinematic and force parameters can substantially improve the characterization of WC.

Asunto(s)

RESUMEN

Sedimentation of the neutron rich isotope 22Ne may be an important source of gravitational energy during the cooling of white dwarf stars. This depends on the diffusion constant for 22Ne in strongly coupled plasma mixtures. We calculate self-diffusion constants D(i) from molecular dynamics simulations of carbon, oxygen, and neon mixtures. We find that D(i) in a mixture does not differ greatly from earlier one component plasma results. For strong coupling (coulomb parameter Γ> few), D(i) has a modest dependence on the charge Z(i) of the ion species, D(i)∝Z(i)(-2/3). However, D(i) depends more strongly on Z(i) for weak coupling (smaller Γ). We conclude that the self-diffusion constant D(Ne) for 22Ne in carbon, oxygen, and neon plasma mixtures is accurately known so that uncertainties in D(Ne) should be unimportant for simulations of white dwarf cooling.

RESUMEN

Microcompression tests were performed on focused-ion-beam-machined micropillars of several body-centered-cubic metals (W, Mo, Ta, and Nb) at room temperature. The relationship between yield strength and pillar diameter as well as the deformation morphologies were found to correlate with a parameter specific for bcc metals, i.e., the critical temperature T(c). This finding sheds new light on the phenomenon of small-scale plasticity in largely unexplored non-fcc metals.

Asunto(s)

RESUMEN

Although the adult brain contains nicotinic acetylcholine (ACh) receptors vital to cortical function, little is known about the assembly of embryonic receptor subunits into functional receptors or their role in fetal brain development. We now report the first evidence of functional nicotinic ACh receptors on stem and progenitor cells of fetal mouse cerebral cortex as early as embryonic day 10.

Asunto(s)

RESUMEN

We have found that Na-Ca exchange influences Ca(2+) efflux, signal decay, and the rate of secretion in chromaffin cells. We now report the presence of two distinct splicing variant isoforms of Na-Ca exchange proteins in bovine chromaffin cells and their transport properties in chromaffin granules and plasma membrane vesicles.

Asunto(s)

RESUMEN

The adult cerebral cortex contains nicotinic acetylcholine (ACh) receptors vital to cortical function. However, little is known about the assembly of embryonic nicotinic receptor subunits into functional receptors or whether they play an active role in cortical development. We now report evidence of functional nicotinic acetylcholine receptor channels in fetal mouse cerebral cortex as early as embryonic day 10 (E10), when the cortex consists of dividing stem and progenitor cells. Patch-clamp electrophysiological measurements indicate that nicotine and ACh evoke sizable inward currents characteristic of nicotinic receptors, that are strongly rectifying with a reversal potential near 0 mV. Three different nicotinic agonists, ACh, nicotine, and dimethylphenylpiperazinium, evoked cytosolic Ca(2+) signals. Agonist-evoked Ca(2+) signals and electrophysiological responses were found in greater than 70% of all E10-E11 cells tested and were blocked by nicotinic receptor antagonists. The Ca(2+) response to nicotinic agonists was markedly prolonged in cells from early embryonic stages relative to later stages of development. alpha3, alpha4, and alpha7 receptor subunit proteins were detected immunocytochemically in cortical cells from E10 to birth. The incidence of each subunit declined with embryonic age, suggesting a role in early development. We discuss the possible function of nicotinic receptors in early cortical development and their role as a target for nicotine in the developmental pathologies associated with the fetal tobacco syndrome.

Asunto(s)

RESUMEN

In this chapter, the original descriptions and pre-molecular studies of triosephosphate isomerase (TPI) deficiency are summarized, and the molecular aspects of the disease presented. The gene is well characterized, and several mutations have been described. Structure-function studies have led to an increased understanding of impaired catalysis. All kindreds that have been studied with the predominant Glu104Asp mutation are linked by a common haplotype, indicating descent from a common ancestor. Variant upstream substitutions occur in high frequency in persons of African and East Asian lineage and in lower frequency in other groups, but the possible role, if any, of these variants in clinical TPI deficiency requires further investigation. The possible contribution of deviant lipid metabolism to the pathogenesis of the disorder has been extensively investigated, and an intriguing new area of inquiry is the apparent cell-to-cell transfer of enzyme in cell culture systems, raising the question of the feasibility of enzyme or gene replacement therapy.

Asunto(s)