Soft matter dynamics: A versatile microgravity platform to study dynamics in soft matter.

We describe an experiment container with light scattering and imaging diagnostics for experiments on soft matter aboard the International Space Station (ISS). The suite of measurement capabilities can be used to study different materials in exchangeable sample cell units. The currently available sample cell units and future possibilities for foams, granular media, and emulsions are presented in addition to an overview of the design and the diagnostics of the experiment container. First results from measurements performed on ground and during the commissioning aboard the ISS highlight the capabilities of the experiment container to study the different materials.

Reorganisation of Brain Hubs across Altered States of Consciousness.

Patterns of functional interactions across distributed brain regions are suggested to provide a scaffold for the conscious processing of information, with marked topological alterations observed in loss of consciousness. However, establishing a firm link between macro-scale brain network organisation and conscious cognition requires direct investigations into neuropsychologically-relevant architectural modifications across systematic reductions in consciousness. Here we assessed both global and regional disturbances to brain graphs in a group of healthy participants across baseline resting state fMRI as well as two distinct levels of propofol-induced sedation. We found a persistent modular architecture, yet significant reorganisation of brain hubs that formed parts of a wider rich-club collective. Furthermore, the reduction in the strength of rich-club connectivity was significantly associated with the participants' performance in a semantic judgment task, indicating the importance of this higher-order topological feature for conscious cognition. These results highlight a remarkable interplay between global and regional properties of brain functional interactions in supporting conscious cognition that is relevant to our understanding of clinical disorders of consciousness.

Correction: Influence of mineralization and injection flow rate on flow patterns in three-dimensional porous media.

Correction for 'Influence of mineralization and injection flow rate on flow patterns in three-dimensional porous media' by R. Moosavi et al., Phys. Chem. Chem. Phys., 2019, 21, 14605-14611.

Influence of mineralization and injection flow rate on flow patterns in three-dimensional porous media.

Reactive flows inside porous media play an important role in a number of geophysical and industrial processes. Here, we present three-dimensional experimental measurements on how precipitation and flow patterns change with the flow rate inside a model porous medium consisting of monodisperse glass beads. The sample is initially filled with an aqueous solution of sodium carbonate into which a solution of barium chloride is injected at a constant flow rate. Upon contact and reaction, the two reactants produce water-insoluble barium carbonate which precipitates onto the glass beads. This precipitate then modifies the flow morphology which in turn changes the spatial distribution of the precipitate. We discuss the influence of the flow rate on the morphology of the flow pattern and demonstrate that neither viscous fingering nor the Rayleigh-Taylor instability have any significant influence in our model system.

Ectoine protects DNA from damage by ionizing radiation.

Ectoine plays an important role in protecting biomolecules and entire cells against environmental stressors such as salinity, freezing, drying and high temperatures. Recent studies revealed that ectoine also provides effective protection for human skin cells from damage caused by UV-A radiation. These protective properties make ectoine a valuable compound and it is applied as an active ingredient in numerous pharmaceutical devices and cosmetics. Interestingly, the underlying mechanism resulting in protecting cells from radiation is not yet fully understood. Here we present a study on ectoine and its protective influence on DNA during electron irradiation. Applying gel electrophoresis and atomic force microscopy, we demonstrate for the first time that ectoine prevents DNA strand breaks caused by ionizing electron radiation. The results presented here point to future applications of ectoine for instance in cancer radiation therapy.

Ectoine can enhance structural changes in DNA in vitro.

Strand breaks and conformational changes of DNA have consequences for the physiological role of DNA. The natural protecting molecule ectoine is beneficial to entire bacterial cells and biomolecules such as proteins by mitigating detrimental effects of environmental stresses. It was postulated that ectoine-like molecules bind to negatively charged spheres that mimic DNA surfaces. We investigated the effect of ectoine on DNA and whether ectoine is able to protect DNA from damages caused by ultraviolet radiation (UV-A). In order to determine different isoforms of DNA, agarose gel electrophoresis and atomic force microscopy experiments were carried out with plasmid pUC19 DNA. Our quantitative results revealed that a prolonged incubation of DNA with ectoine leads to an increase in transitions from supercoiled (undamaged) to open circular (single-strand break) conformation at pH 6.6. The effect is pH dependent and no significant changes were observed at physiological pH of 7.5. After UV-A irradiation in ectoine solution, changes in DNA conformation were even more pronounced and this effect was pH dependent. We hypothesize that ectoine is attracted to the negatively charge surface of DNA at lower pH and therefore fails to act as a stabilizing agent for DNA in our in vitro experiments.

Validation of non-REM sleep stage decoding from resting state fMRI using linear support vector machines.

A growing body of literature suggests that changes in consciousness are reflected in specific connectivity patterns of the brain as obtained from resting state fMRI (rs-fMRI). As simultaneous electroencephalography (EEG) is often unavailable, decoding of potentially confounding sleep patterns from rs-fMRI itself might be useful and improve data interpretation. Linear support vector machine classifiers were trained on combined rs-fMRI/EEG recordings from 25 subjects to separate wakefulness (S0) from non-rapid eye movement (NREM) sleep stages 1 (S1), 2 (S2), slow wave sleep (SW) and all three sleep stages combined (SX). Classifier performance was quantified by a leave-one-subject-out cross-validation (LOSO-CV) and on an independent validation dataset comprising 19 subjects. Results demonstrated excellent performance with areas under the receiver operating characteristics curve (AUCs) close to 1.0 for the discrimination of sleep from wakefulness (S0|SX), S0|S1, S0|S2 and S0|SW, and good to excellent performance for the classification between sleep stages (S1|S2:~0.9; S1|SW:~1.0; S2|SW:~0.8). Application windows of fMRI data from about 70 s were found as minimum to provide reliable classifications. Discrimination patterns pointed to subcortical-cortical connectivity and within-occipital lobe reorganization of connectivity as strongest carriers of discriminative information. In conclusion, we report that functional connectivity analysis allows valid classification of NREM sleep stages.

Interplay between nonadiabatic dynamics and Frenkel exciton transfer in molecular aggregates: formulation and application to a perylene bismide model.

The quantum dynamics of linear molecular aggregates in the presence of S0 → S1 and S0 → S2 transitions is investigated by putting emphasis on the interplay between local nonadiabatic S2 to S1 deactivation and Frenkel exciton transfer. The theoretical approach combines aspects of the linear vibronic coupling and Frenkel exciton models. Dynamics calculations are performed for the absorption spectrum and the electronic state populations using the multiconfiguration time-dependent Hartree approach. As an application, perylene bisimde J-type dimer and trimer aggregates are considered, including four tuning and one coupling mode per monomer. This leads to a dynamical model comprising up to 7 electronic states and 15 vibrational modes. The unknown nonadiabatic coupling strength is treated as a parameter that is chosen in accordance with available absorption spectra. This leaves some flexibility that can be limited by the clearly distinguishable population dynamics.

Phase and amplitude patterns in DySEM mappings of vibrating microstructures.

We use a dynamic scanning electron microscope (DySEM) to analyze the movement of oscillating micromechanical structures. A dynamic secondary electron (SE) signal is recorded and correlated to the oscillatory excitation of scanning force microscope (SFM) cantilever by means of lock-in amplifiers. We show, how the relative phase of the oscillations modulate the resulting real part and phase pictures of the DySEM mapping. This can be used to obtain information about the underlying oscillatory dynamics. We apply the theory to the case of a cantilever in oscillation, driven at different flexural and torsional resonance modes. This is an extension of a recent work (Schröter et al 2012 Nanotechnology 23 435501), where we reported on a general methodology to distinguish nonlinear features caused by the imaging process from those caused by cantilever motion.

Analytical and numerical analysis of imaging mechanism of dynamic scanning electron microscopy.

The direct observation of small oscillating structures with the help of a scanning electron beam is a new approach to study the vibrational dynamics of cantilevers and microelectromechanical systems. In the scanning electron microscope, the conventional signal of secondary electrons (SE, dc part) is separated from the signal response of the SE detector, which is correlated to the respective excitation frequency for vibration by means of a lock-in amplifier. The dynamic response is separated either into images of amplitude and phase shift or into real and imaginary parts. Spatial resolution is limited to the diameter of the electron beam. The sensitivity limit to vibrational motion is estimated to be sub-nanometer for high integration times. Due to complex imaging mechanisms, a theoretical model was developed for the interpretation of the obtained measurements, relating cantilever shapes to interaction processes consisting of incident electron beam, electron-lever interaction, emitted electrons and detector response. Conclusions drawn from this new model are compared with numerical results based on the Euler-Bernoulli equation.

The neural correlates of negative prediction error signaling in human fear conditioning.

In a temporal difference (TD) learning approach to classical conditioning, a prediction error (PE) signal shifts from outcome deliverance to the onset of the conditioned stimulus. Omission of an expected outcome results in a negative PE signal, which is the initial step towards successful extinction. In order to visualize negative PE signaling during fear conditioning, we employed combined functional magnetic resonance (fMRI) and skin conductance response (SCR) measurements in a conditioning task with visual stimuli and mild electrical shocks. Positive PE signaling was associated with increased activation in the bilateral insula, supplementary motor area, brainstem, and visual cortices. Negative PE signaling was associated with increased activation in the ventromedial and dorsolateral prefrontal cortices, the left lateral orbital gyrus, the middle temporal gyri, angular gyri, and visual cortices. The involvement of the ventromedial prefrontal and orbitofrontal cortex in extinction learning has been well documented, and this study provides evidence for the notion that these regions are already involved in negative PE signaling during fear conditioning.

The neural correlates and temporal sequence of the relationship between shock exposure, disturbed sleep and impaired consolidation of fear extinction.

Consolidation of extinction learning is a primary mechanism disrupted in posttraumatic stress disorder (PTSD), associated with hypoactivity of the ventromedial prefrontal cortex and hippocampus. A role for rapid eye movement (REM) sleep disturbances in this failure to consolidate extinction learning has been proposed. We performed functional magnetic resonance imaging (fMRI) with simultaneous skin conductance response (SCR) measurements in 16 healthy participants during conditioning/extinction and later recall of extinction. The visual stimuli were basic geometric forms and electrical shocks functioned as the unconditioned stimulus. Between the conditioning/extinction and recall sessions, participants received a 90-min sleep window in the sleep laboratory. This daytime sleep was polysomnographically recorded and scored by professionals blind to the study design. Only seven out of 16 participants had REM sleep; participants without REM sleep had a significantly slower decline of both SCR and neural activity of the laterodorsal tegmentum in response to electrical shocks during conditioning. At recall of fear extinction, participants with preceding REM sleep had a reduced SCR and stronger activation of the left ventromedial prefrontal cortex and bilateral lingual gyrus in response to the extinguished stimulus than participants lacking REM sleep. This study indicates that trait-like differences in shock reactivity/habituation (mediated by the brainstem) are predictive of REM sleep disruption, which in turn is associated with impaired consolidation of extinction (mediated by the ventromedial prefrontal cortex). These findings help understand the neurobiological basis and the temporal sequence of the relationship between shock exposure, disturbed sleep and impaired consolidation of extinction, as observed in PTSD.

Fluidization of granular media wetted by liquid 4He.

We explore experimentally the fluidization of vertically agitated polymethylmethacrylate spheres wetted by liquid 4He . By controlling the temperature around the lambda point, we change the properties of the wetting liquid from a normal fluid (helium I) to a superfluid (helium II). For wetting by helium I, the critical acceleration for fluidization (Gamma_{c}) shows a steep increase close to the saturation of the vapor pressure in the sample cell. For helium II wetting, Gamma_{c} starts to increase at about 75% saturation, indicating that capillary bridges are enhanced by the superflow of the unsaturated helium film. Above saturation, Gamma_{c} enters a plateau regime where the capillary force between particles is independent of the bridge volume. The plateau value is found to vary with temperature and shows a peak at 2.1K , which we attribute to the influence of the specific heat of liquid helium.

[Ethical discussion on criteria for policy makers in public health authorities for preventative measures against a pandemic caused by a novel influenza A virus]. / Ethische Kriterienberatung für Entscheidungsträger in Institutionen der öffentlichen Gesundheit zur Vorsorge einer Pandemie mit einem neuartigen Influenza A Virus.

Federal and regional authorities are currently preparing for a possible influenza pandemic caused by a new human influenza virus subtype. Ethical discussions in the context of such a pandemic were not systematically held within the Public Health scientific community in Germany as yet. This deficit is being approached by the authors. They plea for a systematic conception of a Public Health Ethics framework. Normative benchmarks can be set within such a framework that are more adequate for the discussion than the traditional ethical principles used within medical ethics. Public Health Ethics is an applied ethics that can be utilised for Public Health scientists and policy makers to give them advice and counsel them for a morally acceptable public health practice. The authors present a concise set of ethical principles that are applied in this article to the challenges of an influenza pandemic.

[3rd Workshop on Epidemiology, Prevention and Treatment of Invasive Meningococcal Disease in Würzburg 2006]. / 3. Würzburger Workshop zur Epidemiologie, Prävention und Therapie der invasiven Meningokokkenerkrankung 2006.

On October 5th, 2006, the German Reference Centre for Meningococci (NRZM) held the 3rd Workshop on Epidemiology, Prevention and Treatment of Invasive Meningococcal Disease, in collaboration with the German Society for Hygiene and Microbiology (DGHM). Given the recent recommendation of the German Standing Committee on Vaccination (STIKO) for conjugate meningococcal C vaccination of all children in the second year of life, observations from meningococcal C conjugate vaccination campaigns in other European countries were presented and compared to the German situation. Moreover, the newly implemented cluster detection routines employed at the NRZM and their integration into the interactive geographical information system EpiScanGIS were shown. Based on recent experiences from regional outbreaks in Oberallgäu, Sangerhausen, and Greater Aachen, examples for public health intervention were given at the conference. In addition, current developments in the area of meningococcal research, as well as trends in antimicrobial susceptibility were covered. Finally, the latest evidence concerning the clinical management and chemoprophylaxis of this invasive bacterial disease was discussed.

Tracer test with As(V) under variable redox conditions controlling arsenic transport in the presence of elevated ferrous iron concentrations.

To study transport and reactions of arsenic under field conditions, a small-scale tracer test was performed in an anoxic, iron-reducing zone of a sandy aquifer at the USGS research site on Cape Cod, Massachusetts, USA. For four weeks, a stream of groundwater with added As(V) (6.7 muM) and bromide (1.6 mM), was injected in order to observe the reduction of As(V) to As(III). Breakthrough of bromide (Br(-)), As(V), and As(III) as well as additional parameters characterizing the geochemical conditions was observed at various locations downstream of the injection well over a period of 104 days. After a short lag period, nitrate and dissolved oxygen from the injectate oxidized ferrous iron and As(V) became bound to the freshly formed hydrous iron oxides. Approximately one week after terminating the injection, anoxic conditions had been reestablished and increases in As(III) concentrations were observed within 1 m of the injection. During the observation period, As(III) and As(V) were transported to a distance of 4.5 m downgradient indicating significant retardation by sorption processes for both species. Sediment assays as well as elevated concentrations of hydrogen reflected the presence of As(V) reducing microorganisms. Thus, microbial As(V) reduction was thought to be one major process driving the release of As(III) during the tracer test in the Cape Cod aquifer.

Prevalence, incidence, and clinical relevance of the reverse transcriptase V207I mutation outside the YMDD motif of the hepatitis B virus polymerase during lamivudine therapy.

The reverse transcriptase V207I mutation within the hepatitis B virus (HBV) polymerase is associated with resistance to lamivudine in vitro. The prevalence of this mutation in treatment-naive patients was 1% (1/96). A follow-up of the patient carrying this mutation prior to treatment revealed no loss of sensitivity of HBV to lamivudine in vivo.

Redox chemistry of Cu colloids probed by adsorbed CO: an in situ attenuated total reflection Fourier transform infrared study.

The IR spectroscopic investigation of both the adsorption of carbon monoxide and the interaction of oxygen and CO on the surface of copper colloids is described for the first time. The copper colloids were produced by pyrolysis of [Cu(OCH(Me)CH(2)NMe(2))(2)] in hot n-hexadecylamine. Upon contact to synthetic air Cu/Cu(x)O core-shell particles are formed. The treatment of these particles with CO results in the reestablishment of pure Cu(0) particles. These results demonstrate that small molecules penetrate the ligand shell of the nanoparticles and reversibly adsorb at the surface without affecting the particle morphology and size distribution.

Prevalence of SENV-H viraemia among healthy subjects and individuals at risk for parenterally transmitted diseases in Germany.

The prevalence of a newly described DNA virus (SENV-H) was examined in a population of 599 individuals by polymerase chain reaction (PCR). All individuals were assigned to a nonrisk or a risk group depending on the presence of historical or serological factors indicating an increased risk for parenterally transmitted diseases. In a group of 226 healthy blood donors, 38 (16.8%) were found to be SENV-H viraemic. The highest prevalence of SENV-H viraemia was observed among patients infected by HIV (28 of 63; 44.4%). Contrarily, of 78 individuals on maintenance haemodialysis, only 10 (12.8%) were found positive in the SENV-H PCR. Our results demonstrate that SENV-H viraemia is widespread in the general population. Therefore, it seems to be questionable if parenteral transmission is the main route for spreading SENV-H. The hepatitis-inducing capacity of SENV-H is unclear. However, taking our clinical and epidemiological data into account it seems unlikely that this virus is responsible for hepatitis.