Unusual Surface Latent Heat Flux Variations and Their Critical Dynamics Revealed before Strong Earthquakes.

We focus on the possible thermal channel of the well-known Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) mechanism to identify the behavior of thermal anomalies during and prior to strong seismic events. For this, we investigate the variation of Surface Latent Heat Flux (SLHF) as resulting from satellite observables. We demonstrate a spatio-temporal variation in the SLHF before and after a set of strong seismic events occurred in Kathmandu, Nepal, and Kumamoto, Japan, having magnitudes of 7.8, 7.3, and 7.0, respectively. Before the studied earthquake cases, significant enhancements in the SLHF were identified near the epicenters. Additionally, in order to check whether critical dynamics, as the signature of a complex phenomenon such as earthquake preparation, are reflected in the SLHF data, we performed a criticality analysis using the natural time analysis method. The approach to criticality was detected within one week before each mainshock.

De novo Cu-MOF@CNS nanocomposite coated on a cotton fibrils framework for sustainable solar-driven desalination.

Environmental researchers are extremely concerned about addressing the declining availability of drinking water, which is a critical issue in many nations. Solar-driven desalination is an emerging and pioneering renewable approach to reduce potable water scarcity that is suitable for remote locations, developing countries, and disaster zones as it does not require additional energy supply. However, there are still issues with the scalable preparation of photothermal materials, such as achieving low cost and widening the assortment of useful applications. Conventional carbon- and metal-based absorbers are intricate and fragile, which make them difficult to install and transport in places with minimal infrastructure. Thus, a universal process for creating adaptable solar evaporators is sorely required. Herein, we have come up with a holistic approach using a solar absorber (GJ-01(Cal)) derived from a Cu-MOF (HKUST-1) and carbon nanosheets (CNSs) for generating potable water from saline water using solar radiation. The as-synthesized material provides high-performance photothermal water evaporation when illuminated under solar irradiation at the air-water interface. Moreover, its porous structure, high photothermal conversion efficiency, rapid water flow, and heat insulation make it appropriate for saline water desalination. CNS play a pivotal role in improving the photothermal features of the solar absorber (GJ-01(Cal)) in terms of conjugation to promote Cu(0) species and pyrrolic nitrogen (P-N) amplification and thereby enrich the p-type nature of the absorber's triphasic configuration. With these photothermal factors, the localised surface plasmon resonance (LSPR) of electrons increases and achieves high solar spectrum absorption. The GJ-01(Cal) was further coated on porous cotton fibrils (CF) that regulate photothermal interfacial evaporation (PTIE) by allowing water transportation via capillary action. This assemblage of the nanocomposite on CF efficiently evaporates water at a higher surface temperature of ∼47 °C under one solar illumination, achieving 4.23 kg m-2 h-1 of evaporation flux and 96.5% light-to-heat conversion efficiency. Interestingly, the GJ-01(Cal) coated over CF can be recycled at least 10 times. Additionally, it offers scalable production for higher photothermal efficiency with a flexible substrate as a solar evaporator and is beneficial for society paving new horizons towards a sustainable environment.

Compact living or policy inaction? Effects of urban density and lockdown on the COVID-19 outbreak in the US.

The coronavirus pandemic has reignited the debate over urban density. Popular media has been quick to blame density as a key contributor to rapid disease transmission, questioning whether compact cities are still a desirable planning goal. Past research on the density-pandemic connection have produced mixed results. This article offers a critical perspective on this debate by unpacking the effects of alternative measures of urban density, and examining the impacts of mandatory lockdowns and the stringency of other government restrictions on cumulative Covid-19 infection and mortality rates during the early phase of the pandemic in the US. Our results show a consistent positive effect of density on Covid-19 outcomes across urban areas during the first six months of the outbreak. However, we find modest variations in the density-pandemic relationship depending on how densities are measured. We also find relatively longer duration mandatory lockdowns to be associated with lower infection and mortality rates, and lockdown duration's effect to be relatively more pronounced in high-density urban areas. Moreover, we find that the timing of lockdown imposition and the stringency of the government's response additionally influence Covid-19 outcomes, and that the effects vary by urban density. We argue that the adverse impact of density on pandemics could be mitigated by adopting strict lockdowns and other stringent human mobility and interaction restriction policies in a spatially targeted manner. Our study helps to inform current and future government policies to contain the virus, and to make our cities more resilient against future shocks and threats.

Carbon nanosheets to unravel the production of bioactive compounds from microalgae: A robust approach in drug discovery.

The conglomeration of active pharmaceutical ingredients (APIs) has influenced the development of life-saving drugs. These APIs are customarily synthetic products, albeit with adverse side effects. Thus, to overcome the bottlenecks associated with synthetically derived APIs, the approach of photocatalytically obtaining bioactive compounds from natural ingredients has emerged. Amid the pool of photoactive nanomaterials, this short review emphasizes the intelligent strategy of exploiting photoactive carbon nanosheets to photocatalytically derive bioactive compounds from natural algal biomass to treat many acute or chronic medical conditions. Carbon nanosheets result in phototrophic harvesting of bioactive compounds from microalgae as a result of their being an effective biocatalyst that increases the rate of photosynthesis. To understand the clinical translation of bioactive compounds, the pharmacodynamics of algal bioactive compounds are highlighted to determine the practicality and feasibility of using this green approach for pharmaceutical drug discovery.

Metal organic framework-derived recyclable magnetic coral Co@Co3O4/C for adsorptive removal of antibiotics from wastewater.

The menace posed by antibiotic contamination to humanity has increased due to the absence of efficient antibiotic removal processes in the conventional waste water treatment methods from the hospitals, households, animal husbandry, and pharma industry. Importantly, only a few commercially available adsorbents are magnetic, porous, and have the ability to selectively bind and separate various classes of antibiotics from the slurries. Herein, we report the synthesis of a coral-like Co@Co3O4/C nanohybrid for the remediation of three different classes of antibiotics - quinolone, tetracycline, and sulphonamide. The coral like Co@Co3O4/C materials are synthesized via a facile room temperature wet chemical method followed by annealing in a controlled atmosphere. The materials demonstrate an attractive porous structure with an excellent surface-to-mass ratio of 554.8 m2 g-1 alongside superior magnetic responses. A time-varying adsorption study of aqueous nalidixic acid solution on Co@Co3O4/C nanohybrids indicates that these coral-like Co@Co3O4/C nanohybrids could achieve a high removal efficiency of 99.98% at pH 6 in 120 min. The adsorption kinetics data of Co@Co3O4/C nanohybrids follow a pseudo-second-order reaction kinetics suggesting a chemisorption effect. The adsorbent has also shown its merit in reusability for four adsorption-desorption cycles without showing significant change in the removal efficiency. More in-depth studies validate that the excellent adsorption capability of Co@Co3O4/C adsorbent attributing to the electrostatic and π-π interaction between adsorbent and various antibiotics. Concisely, the adsorbent manifests the potential for the removal of a wide range of antibiotics from the water alongside showing their utility in the hassle-free magnetic separation.

Emergence of the Janus-MOF (J-MOF) Boat as a Nascent Amalgamation in the Arena of Photothermal Desalination.

The diminution of potable water is a pressing issue in several countries and is the most prioritized obligation of environmental scientists. Thence, the ardent emergence of photothermal interfacial evaporation (PTIE) is seen as a neoteric horizon in the avenue of water remediation. Consequently, for the first time, the decoration of metal-organic frameworks (MOFs) over a Janus architecture as an avant-garde marriage was explored in the domain of photothermal desalination. In this study, a solar absorber was developed by inducing phase change to Ni-doped HKUST-1 (Cu-MOF) via high-temperature calcination to create biphasic CuO/Cu2O caged in N-doped graphene oxide (NGO) sheets. The doping of Ni in the framework demonstrated to enhance the pyrrolic nitrogen (PN) of NGO sheets, which improved the photothermal feature of the solar absorber in union with promoting Cu2+ species as well as enriching the p-type nature of the biphasic configuration for augmented nonradiative relaxation of electrons. In order to take advantage of the robust potential of the designed solar absorber, it was coated over a Janus membrane prepared via the facile approach, composed of poly(methyl methacrylate) (PMMA) and agarose gel having opposing wettability, referred to as the J-MOF boat. This nascent amalgamation recorded a maximum evaporation rate of 1.5 kg/m2 h with pure water and 1.3 kg/m2 h with simulated seawater under 1 sun irradiation. This phenomenon was ascribed to the highly porous agarose layer to facilitate extraordinary water pumping, while concomitantly rejecting salts via capillary action in a nature-mimicking fashion as seen in mangrove trees. The boat-like feature arises from the PMMA layer to conduct PTIE at the water/air interface by uniformly dispersing the localized heat from the solar absorber owing to its low thermal conductivity and three-dimensional (3D) porous structure. Thus, it is believed that this nascent strategy could push the boundaries of solar-driven desalination.

Fabrication of morphologically modified strong supramolecular nanocomposite antibacterial hydrogels based on sodium deoxycholate with inverted optical activity and sustained release.

Low Molecular Weight (LMWG) gelators are small molecules that form supramolecular self-assembly involving physical forces and are highly biocompatible. However, fragility of these physical gels restricts their applicability where gels of higher mechanical strength are required. Herein, we have developed two different types of 2-D carbon nanomaterials viz. graphene oxide (GO) and carbon nanosheet (CNS) embedded sodium deoxycholate (NaDC) hydrogels. XRD, scanning electron microscopy (SEM), rheology and CD studies suggest significant modification of morphological, mechanical, viscoelastic and optical properties of the nanocomposite gels which is ascribed to the presence of the 2D nanotemplates and participation of different surface functionalities of GO and CNS in the gelation process. The overall shear resistance of both the nanocomposite hydrogels upto a shear rate of 300 shears/s-1 and above reveals tremendously improved mechanical stability with respect to the pure gels. The increased shear strength of the GO/NaDC and CNS/NaDC hydrogels is attributed to their 3-4 times broader and longer ribbon like structures in comparison to the fibrous structure of pure gels. The intact ribbon like morphology and greater entanglement impart 10 folds greater viscosity to GO-NaDC hydrogels as compared to better elasticity of CNS-NaDC hydrogels possessing broken ribbon edges. Most interestingly both GO and CNS influence the optical activity of the gels and presence of GO results in inversion of optical activity. The GO-NaDC gels are also found to demonstrate antibacterial activity against E. coli, and S. aureus. Thus, these extraordinarily modified mechanically strong gels have enhanced potential for use in tissue engineering, enantioselective and sustained drug delivery, topical antibiotics and other biomedical applications.

Graphene Quantum Dots in the Game of Directing Polymer Self-Assembly to Exotic Kagome Lattice and Janus Nanostructures.

Graphene quantum dots (GQDs) are the harbingers of a paradigm shift that revitalize self-assembly of the colloidal puzzle by adding shape and size to the material-design palette. Although self-assembly is ubiquitous in nature, the extent to which these molecular legos can be engineered reminds us that we are still apprenticing polymer carpenters. In this quest to unlock exotic nanostructures ascending from eventual anisotropy, we have utilized different concentrations of GQDs as a filler in free-radical-mediated aqueous copolymerization. Extensive polymer grafting over the geometrically confined landscape of GQDs (0.05%) bolsters crystallization instilling a loom which steers interaction of polymeric cilia into interlaced equilateral triangles with high sophistication. Such two-dimensional (2D) assemblies epitomizing the planar tiling of "Star of David" forming a molecular kagome lattice (KL) without metal templation evoke petrichor. Interestingly, a higher percentage (0.3%) of GQDs allow selective tuning of the interfacial property of copolymers breaking symmetry due to surface energy incongruity, producing exotic Janus nanomicelles (JNMs). Herein, with the help of a suite of characterizations, we delineate the mechanism behind the formation of the KL and JNMs which forms a depot of heightened drug accretion with targeted delivery of 5-fluorouracil in the colon as validated by gamma scintigraphy studies.

Electrochemically synthesized highly crystalline nitrogen doped graphene nanosheets with exceptional biocompatibility.

This work reports first electrochemical preparation of exceptionally biocompatible, highly crystalline, and well exfoliated nitrogen doped graphene nanosheets (eNGS) from carbon nanosheets for the development of mighty platforms in the field of modern biosensing and other biological applications for human welfare. eNGS displayed exceptional biocompatibility. Administration of the as-synthesized eNGS to rat models did not lead to any significant deviation or inimical consequences in its functional observation battery (FOB) tests, GSH levels or the histology of the vital organs of the rat models. The pictomicrographs of myocytes nuclei and myofibrillar for heart, hippocampus (CA1) section for brain, central vein, and hepatocytes for liver and parenchyma, tubules and glomeruli for kidney also remained unaffected. Moreover, the resultant nanoelectrocatalyst displayed enhanced electrochemical performance towards real-time sensing of dopamine (DA) from human urine sample in the presence of interferences, such as ascorbic acid (AA) and uric acid (UA).

Hydrothermally functionalized biocompatible nitrogen doped graphene nanosheet based biomimetic platforms for nitric oxide detection.

Hydrothermal synthesis of nanocomposites is of significant importance, as it affords facile, biocompatible, nontoxic, and economic fabrication. Herein, we report a hitherto unexplored cytocompatible and reusable biomimetic electrochemical sensor based on pyridyl porphyrin functionalized nitrogen doped graphene nanosheets. The porphyrin functionalized nitrogen doped graphene nanosheets (PFNGS) were prepared by a low temperature hydrothermal method via non-covalent strategies with a minimal impact on their physicochemical properties. Owing to their exceptional attributes like operational ease, low cost, portability, and sensitivity, the as-synthesized PFNGS, formed by π-π interactions, were employed for sensing nitric oxide (NO), which is a key regulator of diverse biological processes. Compared to porphyrin and nitrogen doped graphene nanosheets alone, PFNGS exhibited exceptional sensitivity (3.6191 µA µM-1) and remarkable electrocatalytic properties (0.61 V). This clearly outperforms the previously reported modified electrode materials for the electrochemical detection of NO. Cyclic voltammetry (CV) data also suggested that the PFNGS modified electrode possessed an increased reactive surface area, which results in an increase in the number of reactive sites and low charge transfer resistance. These results also demonstrated that the PFNGS modified electrode showed high stability and reproducibility, the limit of detection (LOD) (S/N = 3) of which was estimated to be 1 nM. Our PFNGS were found to be highly biocompatible and could also detect NO released from macrophage cells. This blend of biocompatibility, electrode stability, electrocatalytic activity along with enhanced sensitivity and selectivity makes PFNGS a powerful and reliable nanomaterial for various biomedical applications in complex biological systems.

Amine-templated open-framework zinc arsenates of varying dimensionalities: synthesis, structure, polymorphism, and transformation reactions.

Eight new open-framework zinc arsenates, encompassing the entire hierarchy of open-framework structures, have been prepared hydrothermally. The structures include zero-dimensional, one-dimensional chains, two-dimensional layers, and three-dimensional structures formed through the transformation of the molecular zinc arsenates. The structure of [C6N4H21][Zn(HAsO4)2(H2AsO4)], I, is composed of ZnO4 and H2AsO4 units connected through the vertices forming four-membered rings with HAsO4 units hanging from the Zn center. The four-membered rings are connected through the corners forming the one-dimensional chain structures in [C4N2H12][Zn(HAsO4)2] x H2O, II, and [C5N2H14][Zn(HAsO4)2] x H2O, III. ZnO4 and AsO4 units form a fully four-connected two-dimensional structure in [C4N2H12][Zn(AsO4)]2, IV. One-dimensional zigzag ladders are connected through HAsO4 units forming two-dimensional layers in [C4N2H12]1.5[Zn2(AsO4)(HAsO4)2] x H2O, V, while the similar building units form a layer with hanging HAsO4 units in the layered arsenate [C6N4H21]6[Zn12(HAsO4)21], VI. Hanging HAsO4 units are also observed in the polymorphic structures of [C6N3H20][Zn2(AsO4)(HAsO4)2] x 2H2O, VII and VIII. Formation of zero-dimensional monomer, I, a fully four-connected layer, IV, and the polymorphic structures, VII and VIII, are important and noteworthy. The transformation reactions of I indicate that the monomer is reactive and gives rise to structures of higher dimensionalities, indicating a possible Aufbau-type building-up process in these structures.