► ZnO/multiwalled carbon nanotube composite was synthesized via reactive magnetron sputtering in Ar/O2 environment. ► The electrochemical tests were carried out with a wide potential range from −2V ...to 1V using non aqueous electrolyte. ► ZnO/multiwalled carbon nanotube composite exhibits high energy density of 13.1Whkg−1 with good cycle stability.
A facile, green and highly efficient method for the decoration of carbon nanotubes with ZnO was developed for the fabrication of binder-free composite electrode for supercapacitor applications. The nano composite was prepared by using reactive magnetron sputtering in Ar/O2 environment. This approach leads to more uniform coating with tuneable thickness, which alters the electrochemical performance of the nano composite electrodes. The structure and surface morphology of the composite film have been studied by means of X-ray diffraction (XRD) analysis, scanning electron microscopy and field emission scanning electron microscopy (FESEM). The XRD study reveals the formation of Wurtzite ZnO structure. The electrochemical performance of nano composite electrode was investigated using cyclic voltammetry, chronopotentiometry and electrochemical impedance measurements in non-aqueous electrolyte. The nano composite electrode shows significant increase in the specific capacitance up to 48Fg−1 with an energy density 13.1Whkg−1 in the potential range −2V to 1V.
Electrochemical supercapacitors are vital for the advancement of energy storage devices. Herein, we report the synthesis of molybdenum selenide (MoSe2), tungsten-doped molybdenum selenide (WMoSe2) ...and their graphene (G) composites (WMoSe2/G) via a facile hydrothermal method. Physiochemical properties of the as-synthesized samples are examined using X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller measurements, scanning electron microscopy, high resolution transmission electron microscopy and energy dispersive X-ray spectroscopy measurements. Used as working electrodes for supercapacitors, MoSe2 nanostructures could deliver the specific capacitance of 106 F g−1 at 2 mV s−1 scan rate. Further, doping with tungsten (W) demonstrates the variation of specific capacitances with 2 M % of tungsten as the optimum doping amount, delivering the maximum specific capacitance of 147 F g−1. Furthermore, graphene composites of these nanostructures deliver the enhanced specific capacitances of 248 F g−1 and complimented with excellent capacitance retention capability of 102% for 20000 cycles.
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•Molybdenum selenides (MoSe2) were prepared employing hydrothermal method.•Tungsten (W) doping enhanced the specific capacitances of electrodes.•Specific capacitance depends on W-doping concentration.•Graphene composites display enhanced specific capacitance and cyclic retention.
► New frontiers in environmentally friendly cellulose nanofiber technologies. ► Extraction techniques and modifications of cellulose nanofibers have been highlighted. ► Sustainability, perspectives ...and applications of cellulose research in chronological order. ► Nanocomposite materials based on biopolymers reinforced cellulose nanofibrils.
Green composites are materials having ecofriendly attributes that are technically and economically feasible while minimizing the generation of pollution. In this context it refers to the combination of fully degradable fibers mostly cellulosic materials and natural resins to develop green composite materials. In the past decade, overdependence on petroleum products (synthetic polymers, resins, etc.) has consistently increased and on account of this, the researchers are now focusing more on green materials specially cellulosics. Cellulosic fibers in micro and nano scale are attractive to replace man-made fibers as reinforcement to make environmentally friendly green products. In this study, we will discuss the processing, extraction, properties, chronological events and applications of cellulose and cellulosic-based nanocomposite materials. Cellulosic nanocomposites are currently considered one of the most promising areas of scientific and technological development in the field of plant products. The aim of this review is to demonstrate the current state of development in the field of cellulose nanofibril based green composites research and application through examples.
During an earthquake, part of the released elastic strain energy is dissipated within the slip zone by frictional and fracturing processes, the rest being radiated away via elastic waves. While ...frictional heating plays a key role in the energy budget of earthquakes, it could not be resolved by seismological data up to now. Here we investigate the dynamics of laboratory earthquakes by measuring frictional heat dissipated during the propagation of shear instabilities at stress conditions typical of seismogenic depths. We estimate the complete energy budget of earthquake rupture and demonstrate that the radiation efficiency increases with thermal‐frictional weakening. Using carbon properties and Raman spectroscopy, we map spatial heat heterogeneities on the fault surface. We show that an increase in fault strength corresponds to a transition from a weak fault with multiple strong asperities and little overall radiation, to a highly radiative fault behaving as a single strong asperity.
Plain Language Summary
In nature, earthquakes occur when the stress accumulated in a medium is released by frictional sliding on faults. The stress released is dissipated into fracture and heat energy or radiated through seismic waves. The seismic efficiency of an earthquake is a measure of the fraction of the energy that is radiated away into the host medium. Because faults are at inaccessible depths, we reproduce earthquakes in the laboratory under natural in situ conditions to understand the physical processes leading to dynamic rupture. We estimate the first complete energy budget of an earthquake and show that increasing heat dissipation on the fault increases the radiation efficiency. We develop a novel method to illuminate areas of the fault that get excessively heated up. We finally introduce the concept of spontaneously developing heat asperities, playing a major role in the radiation of seismic waves during an earthquake.
Key Points
Spatial heat heterogeneities are imaged on a frictional interface using carbon properties and Raman spectroscopy
Rupture processes become more efficient with increasing slip on fault
Heating efficiency depends on time‐dependent memory effect of the fault surface
Large earthquakes are the product of elastic stress that has accumulated over decades to centuries along segments of active faults. Assuming an elastic crust, one can roughly estimate the location ...and rate of accumulation of elastic stress. However, this general framework does not account for inelastic, irrecoverable deformation, which results in large‐scale topography. We do not know over which part of the earthquake cycle such deformation occurs. Using InSAR and GNSS measurements, we report on a potential correlation between long‐term, inelastic vertical rate and short‐term, interseismic vertical rate in northern Chile. Approximately 4% to 8% of the geodetically derived interseismic vertical rates translate into permanent deformation, suggesting that topography of the forearc builds up during the interseismic period. This observation provides a quantitative basis for an improved understanding of the interplay between short‐term and long‐term dynamics along convergent plate boundaries.
Key Points
We propose an approach to quantify the ratio between elastic and inelastic deformation in subduction forearcs
Two distinct correlations can be observed between interseismic and Quaternary uplift rates
We propose that 4% to 8% of interseismic uplift rates translate into persistent deformation in northern Chile
We monitor dynamic rupture propagation during laboratory stick‐slip experiments performed on saw‐cut Westerly granite under upper crustal conditions (10–90 MPa). Spectral analysis of high‐frequency ...acoustic waveforms provided evidence that energy radiation is enhanced with stress conditions and rupture velocity. Using acoustic recordings band‐pass filtered to 400–800 kHz (7–14 mm wavelength) and high‐pass filtered above 800 kHz, we back projected high‐frequency energy generated during rupture propagation. Our results show that the high‐frequency radiation originates behind the rupture front during propagation and propagates at a speed close to that obtained by our rupture velocity inversion. From scaling arguments, we suggest that the origin of high‐frequency radiation lies in the fast dynamic stress‐drop in the breakdown zone together with off‐fault coseismic damage propagating behind the rupture tip. The application of the back‐projection method at the laboratory scale provides new ways to locally investigate physical mechanisms that control high‐frequency radiation.
Plain Language Summary
Over geological time scales, partially or fully locked tectonic plates accumulate stress and strain. The stress and the strain build up on discontinuities that we call “faults.” Natural faults exist either inside a tectonic plate or at the boundary between two distinct tectonic plates. When the stress accumulated on a fault exceeds the strength of the fault, the accumulated stress and strain, which can be interpreted in term of accumulated energy, are suddenly released. This natural phenomenon is called an “earthquake.” During an earthquake, part of the energy is released in the form of seismic waves. Those seismic waves are responsible for the ground shaking. High‐frequency waves usually cause most of the damage. To better understand the physical parameters that influence the generation of high‐frequency waves, we experimentally reproduced microearthquakes and used them as a proxy to study real earthquakes. Our results showed that the higher the pressure acting on the fault when an earthquake is generated, the higher the amount of high‐frequency radiations. Moreover, our observations underlined that, during an earthquake, high‐frequency waves are released in specific areas on the fault. Thus, these results might be of relevance to improve seismic hazard assessment.
Key Points
High‐frequency radiation is enhanced with both confining pressure and rupture velocity
Acoustic sensors can be used as an array to track high‐frequency sources during rupture propagation
High‐frequency radiation sources propagate consistently with the rupture front and are located behind it
The long‐term erosion of steep landscapes is punctuated by dramatic erosional events that can remove significant amount of sediments within a timescale shorter than a seismic cycle. However, the role ...of such large erosional events on seismicity is poorly understood. We use QDYN, a quasi‐dynamic numerical model of earthquake cycles to investigate the effect of a large erosional event on seismicity. The progressive evacuation of landslide sediments is modeled by a transient normal stress decrease. We show that erosional events with a shorter duration compared with the duration of a seismic cycle can significantly increase the seismicity rate, even for small stress changes. Moreover, large erosional events with a shorter period compared with the earthquake nucleation timescale can change earthquake size distribution by triggering more small events. Those results suggest that large erosional events can significantly affect seismicity, illustrating in turn the short‐term impact of surface processes on tectonics.
Key Points
We investigate seismicity response to an erosional event by modeling the effects of transient normal stress changes on a frictional fault
Erosional events with a duration shorter than a seismic cycle can increase the seismicity rate and the proportion of small earthquakes
Large erosional events have the potential to contribute significantly to the deformation of the first kilometers of the Earth's crust
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•Hydrothermal method is employed to synthesize Co(OH)2 hexagonal nanosheets.•Co(OH)2 nanosheets are transformed to CoTe2 and CoSe2via anion-exchange reaction.•Nanoporous CoTe2 and ...CoSe2 are fabricated as pseudo-capacitor electrodes.•Specific capacitance at 5mVs−1 scan rate for CoTe2=360Fg−1 and CoSe2=951Fg−1.•Excellent capacitance of CoSe2 is complimented by its good retention capability.
Electrochemical supercapacitor is an essential technology that is pivotal for the development of reliable energy storage devices. Herein, we report the fabrication of supercapacitor electrodes using nanostructured porous cobalt chalcogenide (CoTe2 and CoSe2) electrodes, anticipating an enhanced performance owing to their higher contact area with electrolyte and large pore volume enabling shorter diffusion paths for ion exchange. In this regard, we synthesized CoTe2 and CoSe2 nanostructures via an anion-exchange-reaction between pre-synthesized Co(OH)2 hexagonal nanosheets and chalcogen (tellurium and selenium) ions under hydrothermal conditions. Structural, morphological and compositional properties of the as-synthesized materials are examined using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, high resolution transmission electron microscopy and energy dispersive X-ray spectroscopy. Pseudo-capacitive properties of CoTe2 and CoSe2 nanostructures as working electrodes are studied through cyclic voltammetry and galvanostatic charge-discharge methods using an electrochemical workstation. CoSe2 electrode delivered a specific capacitance of 951Fg−1 at a scan rate of 5mVs−1, which surprisingly is almost three times higher in comparison to CoTe2 electrode (360Fg−1). Both CoTe2 and CoSe2 electrodes exhibited good capacitance retention capability for 2500 CV cycles. The superior electrochemical performance of the nanoporous CoSe2 electrode indicate their applicability for high-performance energy storage device applications.
Slow earthquakes are important constituents of the seismic cycle and are involved in the stress transfer between the viscously slipping portion of the plate interface and the seismogenic zone. Their ...occurrence is likely associated with the near-lithostatic pore pressure in the slow earthquake source region, where fluids might modify fault friction and whose presence is indicated by high ratios of compressional (P)–wave velocity to shear (S)–wave velocity observed at the interface between the subducting plate and the overlying crust. Here we compare two slow earthquake phenomena observed in the Guerrero region of the Mexican subduction zone: low-frequency earthquakes (LFEs) and a slow-slip event (SSE) recorded by GPS. We observe variations of the LFE occurrence rates over month-long time scales during a large SSE that we interpret as a manifestation of transient changes in the fault shear strength. We argue that these transient changes are caused by a pore pressure fluctuation that migrates updip along the subduction interface. This mechanism suggests that fluids do not only passively weaken the plate interface but also play an active role in slow earthquake source regions.
•Subduction interface seen through a dense low-frequency earthquake catalog.•Response of the plate interface to a large Mw 7.5 slow-slip event.•Evidence of the dynamic role of pore-pressure in the slow earthquake source region.
Purpose
Polycystic ovarian syndrome (PCOS) is a multi-faceted endocrinopathy frequently observed in reproductive-aged females, causing infertility. Cumulative evidence revealed that genetic and ...epigenetic variations, along with environmental factors, were linked with PCOS. Deciphering the molecular pathways of PCOS is quite complicated due to the availability of limited molecular information. Hence, to explore the influence of genetic variations in PCOS, we mapped the GWAS genes and performed a computational analysis to identify the SNPs and their impact on the coding and non-coding sequences.
Methods
The causative genes of PCOS were searched using the GWAS catalog, and pathway analysis was performed using ClueGO. SNPs were extracted using an Ensembl genome browser, and missense variants were shortlisted. Further, the native and mutant forms of the deleterious SNPs were modeled using I-TASSER, Swiss-PdbViewer, and PyMOL. MirSNP, PolymiRTS, miRNASNP3, and SNP2TFBS, SNPInspector databases were used to find SNPs in the miRNA binding site and transcription factor binding site (TFBS), respectively. EnhancerDB and HaploReg were used to characterize enhancer SNPs. Linkage Disequilibrium (LD) analysis was performed using LDlink.
Results
25 PCOS genes showed interaction with 18 pathways. 7 SNPs were predicted to be deleterious using different pathogenicity predictions. 4 SNPs were found in the miRNA target site, TFBS, and enhancer sites and were in LD with reported PCOS GWAS SNPs.
Conclusion
Computational analysis of SNPs residing in PCOS genes may provide insight into complex molecular interactions among genes involved in PCOS pathophysiology. It may also aid in determining the causal variants and consequently contributing to predicting disease strategies.
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