The reduction behavior of sulfurized polyacrylonitrile (SPAN) in lithium-sulfur batteries using a carbonate electrolyte: a computational study.

Lithium-sulfur batteries (LSBs) have attracted attention due to their high theoretical energy density. This and various other advantages, such as the availability and non-toxicity of sulfur, raise interest in LSBs against the background of the energy revolution. However, a polysulfide shuttle mechanism can adversely affect the electrochemical performance of the cell. The sulfur redox properties are influenced, for example, by the electrolyte and the cathode material. Here, a computational study of the discharge process of an LSB with sulfurized poly(acrylonitrile) (SPAN) as the cathode material in combination with a carbonate electrolyte is presented. The nucleation of produced solid Li2S is compared to soluble Li2S. Dominating species are determined by comparing the Gibbs free energy of several species. We found that multiple lithiation steps occur before each Li2S detachment, preventing longer-chain polysulfide cleavage and a polysulfide shuttle. Through nucleating on the nitrogen-rich backbone of SPAN, Li2S units are stabilized by interactions with each other and with the nitrogen atoms. Experimental data show a potential drop and plateau during discharge, which is consistent with the calculated discharge profiles of SPAN with both soluble and nucleated Li2S, and hints at a direct solid-solid transition in the Li-SPAN cell during discharge when using carbonate-based electrolytes.

[Visualization of local cortical defects in Charcot foot using microcomputed tomography]. / Visualisierung lokaler kortikaler Defekte im Charcot-Fuß mittels Mikrocomputertomographie.

BACKGROUND: In the pathogenesis of diabetic neuropathic osteoarthropathy (Charcot's foot) fractures cause chronic destruction of soft tissue and bone structure. To improve an early diagnosis of Charcot foot, modern diagnostic imaging is mainly based on magnetic resonance imaging (MRI), for example in relation to the detection of cortical bone fractures. OBJECTIVES: In this study we investigated the cortical microstructure in cases of Charcot foot with respect to fractures and porosity in order to visualize local cortical defects. This may substantiate recent efforts in a reclassification based on MRI. MATERIAL AND METHODS: Using microcomputed tomography (microCT) we investigated bone parameters, such as cortical thickness and porosity in order to quantify the local metatarsal microstructure in cases of Charcot foot. RESULTS: All bone samples showed a high degree of cortical porosity including pores that perforated the cortical bone. The data suggest that areas with reduced cortical thickness coincide with large cortical pores that may serve as initial points for fractures. Whether the detected microfractures are physiological or artefacts of preparation could not be determined. CONCLUSION: By means of microCT we were able to visualize and quantify the extent of cortical porosity for the first time in high resolution. The data suggest that both cortical fractures and cortical porosity play an important role in the pathogenesis in cases of Charcot foot.

The MARS questionnaire: quality of life survey for acute rhinosinusitis.

PURPOSE: Acute rhinosinusitis (ARS) significantly reduces the quality of life (QoL). While intensive research has focused on the QoL in patients with chronic rhinosinusitis, data regarding the impact of ARS on the QoL are relatively sparse. The aim of this study was to construct and validate a simple, reliable QoL questionnaire for ARS patients, which is also one of the priorities set for EPOS 2012. METHODS: The questionnaire was constructed as follows: a review of literature, collection of symptoms as well as social and emotional consequences by a panel of ENT specialists and general practitioners, interviews with patients experiencing ARS, and a pre-test with another patient group. The questionnaire was validated by determining its internal reliability, discriminant validity, and responsiveness. The survey was given to 50 ARS patients at the time of diagnosis and again 14 days after treatment. The ARS diagnosis was established using the EPOS 12 criteria. The control group consisted of 50 medical students without any sinonasal symptoms. RESULTS: We developed a 13-item questionnaire, called the MARS (Measurement of Acute Rhinosinusitis). Cronbach's alpha was determined to be 0.679. The two-tailed t-test showed a statistically significant difference between the patient group and the control group (p = 0.0000). The SRM coefficient was 1.781. CONCLUSION: The MARS questionnaire is a QoL instrument developed and validated especially for patients with ARS. This survey demonstrated good internal consistency and excellent discriminant validity, responsiveness, and feasibility for use in daily clinical practice and research.

[Penetrating laryngotracheal injury during a suicide attempt]. / Penetrierende laryngotracheale Verletzung beim Suizid.

The authors present a case of a 40-year-old man who intentionally stabbed himself several times in the trachea and larynx during a suicide attempt, and also inflicted other penetrating injuries of the stomach and liver upon himself. The preoperative examination using fiber-optic tracheoscopy and CT revealed only transection of the ligamentum cricothyroideum; the remaining two defects were discovered later, during the surgical revision. All three injuries were successfully treated with sutures, in one case using the transtracheal approach.

3D sub-nanometer analysis of glucose in an aqueous solution by cryo-atom probe tomography.

Atom Probe Tomography (APT) is currently a well-established technique to analyse the composition of solid materials including metals, semiconductors and ceramics with up to near-atomic resolution. Using an aqueous glucose solution, we now extended the technique to frozen solutions. While the mass signals of the common glucose fragments CxHy and CxOyHz overlap with (H2O)nH from water, we achieved stoichiometrically correct values via signal deconvolution. Density functional theory (DFT) calculations were performed to investigate the stability of the detected pyranose fragments. This paper demonstrates APT's capabilities to achieve sub-nanometre resolution in tracing whole glucose molecules in a frozen solution by using cryogenic workflows. We use a solution of defined concentration to investigate the chemical resolution capabilities as a step toward the measurement of biological molecules. Due to the evaporation of nearly intact glucose molecules, their position within the measured 3D volume of the solution can be determined with sub-nanometre resolution. Our analyses take analytical techniques to a new level, since chemical characterization methods for cryogenically-frozen solutions or biological materials are limited.

An X-ray outburst from the rapidly accreting young star that illuminates McNeil's nebula.

Young, low-mass stars are luminous X-ray sources whose powerful X-ray flares may exert a profound influence over the process of planet formation. The origin of the X-ray emission is uncertain. Although many (or perhaps most) recently formed, low-mass stars emit X-rays as a consequence of solar-like coronal activity, it has also been suggested that X-ray emission may be a direct result of mass accretion onto the forming star. Here we report X-ray imaging spectroscopy observations which reveal a factor approximately 50 increase in the X-ray flux from a young star that is at present undergoing a spectacular optical/infrared outburst (this star illuminates McNeil's nebula). The outburst seems to be due to the sudden onset of a phase of rapid accretion. The coincidence of a surge in X-ray brightness with the optical/infrared eruption demonstrates that strongly enhanced high-energy emission from young stars can occur as a consequence of high accretion rates. We suggest that such accretion-enhanced X-ray emission from erupting young stars may be short-lived, because intense star-disk magnetospheric interactions are quenched rapidly by the subsequent flood of new material onto the star.

Gaussian Moments as Physically Inspired Molecular Descriptors for Accurate and Scalable Machine Learning Potentials.

Machine learning techniques allow a direct mapping of atomic positions and nuclear charges to the potential energy surface with almost ab initio accuracy and the computational efficiency of empirical potentials. In this work, we propose a machine learning method for constructing high-dimensional potential energy surfaces based on feed-forward neural networks. As input to the neural network, we propose an extendable invariant local molecular descriptor constructed from geometric moments. Their formulation via pairwise distance vectors and tensor contractions allows a very efficient implementation on graphical processing units (GPUs). The atomic species is encoded in the molecular descriptor, which allows the restriction to one neural network for the training of all atomic species in the data set. We demonstrate that the accuracy of the developed approach in representing both chemical and configurational spaces is comparable to the one of several established machine learning models. Due to its high accuracy and efficiency, the proposed machine-learned potentials can be used for any further tasks, for example, the optimization of molecular geometries, the calculation of rate constants, or molecular dynamics.

Field evaporation and atom probe tomography of pure water tips.

Measuring biological samples by atom probe tomography (APT) in their natural environment, i.e. aqueous solution, would take this analytical method, which is currently well established for metals, semi-conductive materials and non-metals, to a new level. It would give information about the 3D chemical structure of biological systems, which could enable unprecedented insights into biological systems and processes, such as virus protein interactions. For this future aim, we present as a first essential step the APT analysis of pure water (Milli-Q) which is the main component of biological systems. After Cryo-preparation, nanometric water tips are field evaporated with assistance by short laser pulses. The obtained data sets of several tens of millions of atoms reveal a complex evaporation behavior. Understanding the field evaporation process of water is fundamental for the measurement of more complex biological systems. For the identification of the individual signals in the mass spectrum, DFT calculations were performed to prove the stability of the detected molecules.

A cryogenic ice setup to simulate carbon atom reactions in interstellar ices.

The design, implementation, and performance of a customized carbon atom beam source for the purpose of investigating solid-state reaction routes in interstellar ices in molecular clouds are discussed. The source is integrated into an existing ultrahigh vacuum setup, SURFace REaction SImulation DEvice (SURFRESIDE2), which extends this double atom (H/D, O, and N) beamline apparatus with a third atom (C) beamline to a unique system that is fully suited to explore complex organic molecule solid-state formation under representative interstellar cloud conditions. The parameter space for this system is discussed, which includes the flux of the carbon atoms hitting the ice sample, their temperature, and the potential impact of temperature on ice reactions. Much effort has been put into constraining the beam size to within the limits of the sample size with the aim of reducing carbon pollution inside the setup. How the C-atom beam performs is quantitatively studied through the example experiment, C + 18O2, and supported by computationally derived activation barriers. The potential for this source to study the solid-state formation of interstellar complex organic molecules through C-atom reactions is discussed.

X-ray and molecular emission from the nearest region of recent star formation.

The isolated, young, sunlike star TW Hya and four other young stars in its vicinity are strong x-ray sources. Their similar x-ray and optical properties indicate that the stars make up a physical association that is on the order of 20 million years old and that lies between about 40 and 60 parsecs (between about 130 and 200 light years) from Earth. TW Hya itself displays circumstellar CO, HCN, CN, and HCO+ emission. These molecules probably orbit the star in a solar-system-sized disk viewed more or less face-on, whereas the star is likely viewed pole-on. Being at least three times closer to Earth than any well-studied region of star formation, the TW Hya Association serves as a test-bed for the study of x-ray emission from young stars and the formation of planetary systems around sunlike stars.

Ecological dosimetry: radiation levels influenced by plant growth.

The feasibility of using lithium-7-fluoride thermoluminescent dosimeters under field conditions for natural radiation at levels of 5 milliroentgens is demonstrated. Radiation dosages in tree trunks increased threefold from winter to spring and summer. This increase is attributed to the gamma radiation field resulting from relatively high levels of potassium-40 and other radionuclides present in the foliage and branches during the growing season.

Phase I/II trial of dexverapamil, epirubicin and granulocyte/macrophage-colony-stimulating factor in patients with advanced pancreatic adenocarcinoma.

A group of 28 previously untreated patients with locally advanced or metastatic adenocarcinoma of the pancreas were entered in this phase I/II study. Treatment consisted of oral dexverapamil 1000-1200 mg/day for 3 days, epirubicin given as an intravenous bolus injection on day 2 with a starting dose of 90 mg/m2, and 400 micrograms granulocyte/macrophage-colony-stimulating factor (GM-CSF) administered subcutaneously from day 5 through 14. Epirubicin dose escalation levels were 90, 105, 120 and 135 mg/m2. Consecutive cohorts of 4-8 patients were planned at each dose level. Treatment cycles were repeated every 3 weeks. Haematological toxicity, specifically granulocytopenia constituted the dose-limiting toxicity with a maximum tolerated dose of 120 mg/m2 for epirubicin. Despite routine supportive therapy with GM-CSF, 4, 2, and 5 patients experienced grade 4 granulocytopenia during their first two treatment courses at levels of 105, 120, and 135 mg/m2 respectively. Non-haematological toxicity was uncommon, generally modest, and did not demonstrate a clear relationship with the anthracycline dose. Dexverapamil-related cardiovascular symptoms occurred frequently, but they never resulted in serious toxicity requiring active medical intervention or permanent discontinuation of therapy. Of the 28 patients, 9 achieved partial reponses to this therapy. The recommended dose of epirubicin for this regimen with dexverapamil and GM-CSF is 120 mg/m2 every 3 weeks. Therapeutic results suggest this regimen to be an effective and tolerable treatment strategy in pancreatic cancer, which should be evaluated further.

Boundary element method volume conductor models for EEG source reconstruction.

OBJECTIVES: The boundary element method (BEM) approximates the different compartments of volume conductor models by closed triangle meshes with a limited number of nodes. The shielding effect of the weakly conducting skull layer of the human head leads to decreasing potential gradients from the inside to the outside. Thus, there may be an optimum distribution of nodes to the compartments for a given number of nodes corresponding to a fixed computational effort, resulting in improved accuracy as compared to standard uniform distributions. METHODS: Spherical and realistically shaped surfaces are approximated by 500, 1000, 2000, and 3000 nodes, each leading to BEM models with 1500-9000 nodes in total. Electrodes are placed on extended 10/20-system positions. Potential distributions of test-dipoles at 4000 random positions within the innermost compartment are calculated. Dipoles are then fitted using 192 different models to find the optimum node distribution. RESULTS: Fitted dipole positions for all BEM models are evaluated to show the dependency of the averaged and maximum localization errors on their node distributions. Dipoles close to the innermost boundary exhibit the largest localization errors, which mainly depend on the refinement of this compartment's triangle mesh. CONCLUSIONS: More than 500 nodes per compartment are needed for reliable BEM models. For a state-of-the-art model consisting of 6000 nodes overall, the best model consists of 3000, 2000, and 1000 nodes from the inside to the outside.

Effects of nitroglycerin and sodium nitroprusside on endexpiratory concentrations of nitric oxide in healthy humans.

The cellular origin of nitric oxide (NO) in exhaled air of healthy humans is unknown. It is currently not known, whether changes in NO concentrations that originate from pulmonary vessels, can be detected as changes in exhaled NO. Thus, we have studied the effects of increased intravascular NO generation on endexpiratory NO-levels. Twenty-four young healthy volunteers received nitroglycerin (GTN), sodium nitroprusside (SNP) or placebo i.v. in a randomized, double blind cross-over trial. Diastolic blood pressure decreased from 59 mmHg (95% confidence interval: 56-62) during placebo to 48 mmHg (CI: 45-51) and to 48 mmHg (CI: 45-50) after infusions of GTN and SNP, respectively. Heart rate increased from 69 (CI: 65-73) during placebo to 78 (CI: 72-84) and to 84 (CI: 77-92) after infusions of GTN and SNP, respectively (p<0.01 for all comparisons). However, no increase in exhaled NO was detected: endexpiratory NO-concentrations averaged 6.1 ppb (CI: 4.9-7.4), 5.7 ppb (CI: 4.4-7.0) and 6.4 ppb (CI: 5.3-7.6) under placebo, GTN and SNP infusions, respectively (Friedman ANOVA p=0.328). NO release from within the pulmonary vasculature does not significantly contribute to endexpiratory NO concentrations in non-intubated healthy humans suggesting that such NO measurements quantify NO production mainly from non-vascular pulmonary cells.

Sex differences in concentrations of exhaled nitric oxide and plasma nitrate.

Nitric oxide (NO) is generally considered as an endogenous vasoprotective agent. Various studies indicate that the female sex hormone estradiol, that contributes to the well known gender differences in cardiovascular disease, may enhance NO-production. Thus we studied sex differences in NO-generation by measuring single breath NO-exhalation and plasma levels of nitrate (NO3), the stable endmetabolite of NO. In this observational trial 22 male and 21 female volunteers, 19 to 38 years of age, were studied on 3 days at weekly intervals. Median concentrations of NO were 20 parts per billion (95% CI: 16 to 32 ppb) in women and 34 ppb (95% CI: 31 to 58 ppb) in men. The median plasma concentrations of NO3 were 14 microM/L (95% CI: 11 to 23 microM/L) in women and 27 microM/L (95% CI: 24 to 47 microM/L) in men. Thus, men exhaled 59% more NO (p < 0.001) and had 99% higher NO3 levels than women (p < 0.0001). Even when exhaled NO concentrations were corrected for body weight, men exhaled 50% more NO than women (p = 0.024). No significant changes in measured endpoints were seen during the menstrual cycle (p > 0.05) in women. In view of the diversity of NO-actions, the finding of marked sex differences in NO-production is basic to the elucidation of gender differences in a number of (patho)-physiologic conditions.

Recurrent cardiac tamponade as first manifestation of gastric cancer.

Malignant pericardial effusion is an uncommon disorder and is usually caused by far advanced lung cancer, breast cancer, lymphoma and leukaemia. Pericardial effusion in recurrent gastric cancer has been reported in only three patients. We report the case of a 53-year-old male with sudden onset of dyspnoea, pericardial effusion and cardiac tamponade and the unexpected and the asymptomatic concurrence of gastric cancer. Recurrent haemorrhagic pericardial effusion with physical signs of cardiac tamponade as the initial and only clinical manifestation of gastric cancer has not been described previously.

Parameters influencing the accuracy of the point of force application determined with piezoelectric force plates.

Errors up to +/- 30 mm in determining the point of force application with piezoelectric force plates have been reported in the literature (Kistler, 1984. Multicomponent Measuring Force Plate for Biomechanics and Industry. Kistler, Switzerland; Bobbert and Schamhardt, 1990. Journal of Biomechanics 23, 705-710; Sommer et al., 1997. Proceedings of the XVI th I.S.B. Congress). To explain the main factors influencing the systematic errors the force plate system is modeled as a two-dimensional beam structure. By this model it is strongly indicated that the cause for the errors in determining the point of force application are bending moments in the measurement posts. The main parameters influencing the shape and magnitude of the error function are the ratios between the bending stiffness of the plate and the bending and compressive stiffnesses of the measurement posts. In the current design it is therefore not possible to eliminate the cause for the errors by changing the constructive parameters. By comparing the error functions derived with the beam model to the correction formulas given in the literature an improved algorithm is proposed. This paper shall help biomechanists in understanding the basic concepts of determining the point of force application with force plates and in constructing custom-made force plates for specific applications.

Mental retardation and adult women's perceptions of adolescent sexual abuse.

This study examined the effect of mental retardation and an adolescent girl's behavior on adult women's perceptions of sexual abuse and the girl's responsibility. Subjects were 288 women, age 18 to 33, who were randomly assigned a vignette describing a sexual encounter between an adolescent girl and boy. Girl's diagnosis (mentally retarded or nonretarded), boy's diagnosis (mentally retarded or nonretarded) and girl's behavior (encouraging, passive, or resisting) were experimentally manipulated. Factor analysis of responses yielded three factors: girl's responsibility, boy's abusiveness, and parents' responsibility. Results indicate that subjects perceive the girl's responsibility differently among girls with and without mental retardation. Regardless of her behavior, subjects perceive the girl as bearing little responsibility when she is retarded. However, when she is nonretarded, she bears more responsibility when she is encouraging than when she is passive or resisting, and she bears greater responsibility when she is passive than when she is resisting. Also, when the girl is encouraging, the boy's perceived sexual abusiveness is less when he is mentally retarded than when he is nonretarded. Finally, parents are assigned greatest responsibility when the girl is passive, regardless of her diagnosis.

[Nonlinear dynamics, chaos theory and wavelet analysis of the heart]. / Nichtlineare Dynamik, Chaostheorie und Waveletanalyse des Herzens.

Over the past years, techniques of nonlinear dynamics have gained increasing attention in cardiology. This kind of partly interdisciplinary research is supposed to provide a better understanding of cardiac disease, especially in the field of tachyarrhythmia. This article intends to introduce the principles of diagnostic procedures in terms of nonlinear dynamics, chaos theory and stochastic processes related to cardiology. An introduction to a new technique of wavelet analysis is given, and possible applications in the quantitative classification of high-risk patients for sudden cardiac death are discussed.