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In this study, films of graphene oxide and chemically or thermally reduced graphene oxide were produced by a simple vacuum filtration method and submitted to a thorough characterization by X-ray diffraction (XRD), Raman and infrared spectroscopies, field-emission scanning electron microscopy, transmission electron microscopy, atomic force microscopy, confocal microscopy, and contact angle measurements. Graphene oxide (GO) was produced from graphite by the modified Hummers method and thereafter reduced with NaBH4 or by heating under argon in a tubular furnace. The films were produced from aqueous solutions by vacuum filtration on a cellulose membrane. Graphite presents two characteristic XRD peaks corresponding to d=0.34 nm and d=0.17 nm. After oxidation, only a peak at d=0.84 nm is found for powder GO, confirming the insertion of oxygen groups with an increase in the interplanar distance of graphene nanoplatelets. However, for GO films, other unexpected peaks are observed at d=0.63 nm, d=0.52 nm, and d=0.48 nm. After reduction, both chemical and thermal, the peak at 0.84 nm disappears, while those corresponding to interplanar distances of 0.63 nm, 0.52 nm, and 0.48 nm are still present. The other characterizations confirm the production and chemical composition of GO and reduced GO films. The results indicate the combination of crystalline regions with different interplanar distances, suggesting the ordering of graphene/graphene oxide intercalated sheets.

Background: Brain network dynamics are responsive to task induced fluctuations, but such responsivity may not hold in schizophrenia (SCZ). We introduce and implement Centrality Dynamics (CD), a method developed specifically to capture task-driven dynamic changes in graph theoretic measures of centrality. We applied CD to functional MRI (fMRI) data in SCZ and Healthy Controls (HC) acquired during associative learning. Methods: fMRI (3T Siemens Verio) was acquired in 88 participants (49 SCZ). Time series were extracted from 246 functionally defined cerebral nodes. We applied a dynamic windowing technique to estimate 280 partially overlapping connectomes (with 30,135 unique region-pairs per connectome). In each connectome we calculated every node’s Betweenness Centrality (BC) following which we built 246 unique time series from a node’s BC in successive connectomes (where each such time series represents a node’s CD). Next, in each group similarities in CD were used to cluster nodes. Results: Clustering revealed fewer sub-networks in SCZ, and these sub-networks were formed by nodes with greater functional heterogeneity. The averaged CD of nodes in these sub-networks also showed greater Approximate Entropy (ApEn) (indicating greater stochasticity) but lower amplitude variability (suggesting less adaptability to task-induced dynamics). Finally, higher ApEn was associated with worse clinical symptoms and poorer task performance. Limitations: Centrality Dynamics is a new method for network discovery in health and schizophrenia. Further extensions to other task-driven and resting data in other psychiatric conditions will provide fuller understanding of its promise. Conclusion: The brain’s functional connectome under task-driven conditions is not static. Characterizing these task-driven dynamics will provide new insight on the dysconnection syndrome that is schizophrenia. Centrality Dynamics provides novel characterization of task-induced changes in the brain’s connectome and shows that in the schizophrenia brain, learning-evoked sub-network dynamics were a) less responsive to learning evoked changes and b) showed greater stochasticity.

The classic monitoring methods for detecting faults in automotive vehicles based on on-board diagnostics (OBD) are insufficient when diagnosing several mechanical failures. Other sensing techniques present drawbacks such as high invasiveness and limited physical range. The present work presents a fully noninvasive system for fault detection and isolation in internal combustion engines through sound signals processing. An acquisition system was developed, whose data are transmitted to a smartphone in which the signal is processed, and the user has access to the information. A study of the chaotic behavior of the vehicle was carried out, and the feasibility of using fractal dimensions as a tool to diagnose engine misfire and problems in the alternator belt was verified. An artificial neural network was used for fault classification using the fractal dimension data extracted from the sound of the engine. For comparison purposes, a strategy based on wavelet multiresolution analysis was also implemented. The proposed solution allows a diagnosis without having any contact with the vehicle, with low computational cost, without the need for installing sensors, and in real time. The system and method were validated through experimental tests, with a success rate of 99% for the faults under consideration.

Only a third of the people living in Sub-Saharan Africa have access to electricity. While the benefits of electricity services for the society continue to increase, solar home system (SHS) provides a long-term rural electrification and development solution. SHS is thought out to be a robust and cost-effective option for supplying basic electrification under Kenya’s metrological conditions. This paper begins with an in-depth justification of the need for SHS in rural areas, and then it presents an overview of SHS financing, benefits and barriers, followed by a crucial component of existing SHSs in Kenya, Pay-As-You-Go (PAYG) technology. It ends with succinct analysis of the payment models highlighting the benefits, challenges and methods adopted in overcoming those challenges. Lessons from this review suggest that solar firms face a myriad of challenges operating in poor rural areas in Kenya; credit risk is a major concern for solar firms as well as financiers which makes payment models notably challenging. Technical performance of SHS is becoming well proven, and end users desire a wide range of component preferences and service levels that are of benefit. The challenges faced by solar firms using different payment models show that there is a dire need for integration of SHS with rural electrification policy in Kenya. The principal conclusion is that PAYG model offers the best option for SHS dissemination, though energy-as-a-service implementation has a great potential of improving the dissemination process in rural communities as it offers a promising mechanisms from a sustainability point of view.

Cardiac morphology and mass have been associated with activity levels for bony fishes and elasmobranchs; however, there is little information on cardiac morphology of deep-sea sharks (living primarily below 200 m) and how that morphology compares to cardiac morphology of shallow coastal species. We examined relative heart mass and relative ventricle dry mass in 10 species of sharks from coastal to bathydemersal habitats (23–870 m) to test our hypothesis that relative heart mass decreases with depth. Relative heart mass and relative ventricle dry mass decreased with increasing depth of capture for sharks. The coastal, obligate ram ventilator Carcharhinus limbatus had the highest relative heart mass (1.17 g/kg) and relative ventricle dry mass (0.18 g/kg), whereas the deep-sea species Centrophorus uyato had the lowest (relative heart mass, 0.34 g/kg; relative ventricle dry mass, 0.057 g/kg). Our findings of decreasing relative heart and ventricle size with increasing depth support the visual interaction hypothesis as an explanation for reduced metabolic capacity in deep-sea sharks.

We present a novel Active Magnetic Shield (AMS), designed and implemented for the n2EDM experiment at the Paul Scherrer Institute. The experiment will perform a high-sensitivity search for the electric dipole moment of the neutron. Magnetic-field stability and control is of key importance for n2EDM. A large, cubic, 5 m side length, magnetically shielded room (MSR) provides a passive, quasi-static shielding-factor of about 10 5 for its inner sensitive volume. The AMS consists of a system of eight complex, feedback-controlled compensation coils constructed on an irregular grid spanned on a volume of less than 1000 m 3 around the MSR. The AMS is designed to provide a stable and uniform magnetic-field environment around the MSR, while being reasonably compact. The system can compensate static and variable magnetic fields up to ± 50 μ T (homogeneous components) and ± 5 μ T/m (first-order gradients), suppressing them to a few μ T in the sub-Hertz frequency range. The presented design concept and implementation of the AMS fulfills the requirements of the n2EDM experiment and can be useful for other applications, where magnetically silent environments are important and spatial constraints inhibit simpler geometrical solutions.

Flavonoids have long been recognized for their general health-promoting properties, of which their antioxidant activity may play an important role. In this work we have studied the properties of two flavonols, quercetin and myricetin, using semi-empirical methods in order to validate the application of the recent Parametric Model 6 and to understand the fundamental difference between the two molecules. Their geometries have been optimized and important molecular properties have been calculated. The energetic of the possible antioxidant mechanisms have also been analyzed. The two studied flavonols do not differ significantly in their molecular properties, but the antioxidant mechanisms by which they may act in solution can be rather different. Moreover, we also show that the Parametric Model 6 can produce reliable information for this type of compounds.