The microstructure of sediment-hosted hydrates: evidence from effective medium modelling of laboratory and borehole seismic data

Much of our knowledge of hydrate distribution in the subsurface comes frominterpretations of remote seismic measurements. A key step in such interpretations isan effective medium theory that relates the seismic properties of a given sediment toits hydrate content. A variety of such theories have been developed; these theoriesgenerally give similar results if the same assumptions are made about the extent towhich hydrate contributes to the load-bearing sediment frame. We have furtherdeveloped and modified one such theory, the self-consistentapproximation/differential effective medium approach, to incorporate additionalempirical parameters describing the extent to which both the sediment matrix material(clay or quartz) and the hydrate are load-bearing. We find that a single choice ofthese parameters allows us to match well both P and S wave velocity measurementsfrom both laboratory and in situ datasets, and that the inferred proportion of hydratethat is load-bearing varies approximately linearly with hydrate saturation. Thisproportion appears to decrease with increasing hydrate saturation for gas-richlaboratory environments, but increase with hydrate saturation when hydrate is formedfrom solution and for an in situ example

Charge pumping in monolayer graphene driven by a series of time-periodic potentials

We applied the Floquet scattering-matrix formalism to studying the electronic transport properties in a mesoscopic Dirac system. Using the method, we investigate theoretically quantum pumping driven by a series of time-periodic potentials in graphene monolayer both in the adiabatic and non-adiabatic regimes. Our numerical results demonstrate that adding harmonic modulated potentials can break the time reversal symmetry when no voltage bias is applied to the graphene monolayer. Thus, when the system is pumped with proper dynamic parameters, these scatterers can produce a nonzero dc pumped current. We also find that the transmission is anisotropic as the incident angle is changed.Comment: 8 pages, 6 figure

Pulmonary Toxicity and the Pathophysiology of Electronic Cigarette, or Vaping Product, Use Associated Lung Injury

New emerging tobacco products, especially electronic cigarettes (E-Cig) or electronic nicotine delivery systems (ENDS), have gained a huge popularity, particularly in younger populations. The lack of sufficient evidence-based health effect studies has promoted widespread use/abuse with the assumption that E-Cig or ENDS and/or vaping products are safer and less toxic than conventional tobacco smoking. However, the recent escalation in acute lung injuries and their associated fatalities among ENDS or vaping product users has now brought attention to this silent epidemic via investigation into the constituents of ENDS/vaping products and their toxic effects on pulmonary health. Accordingly, CDC has declared an “outbreak” of the e-cigarette or vaping product use associated lung injury (EVALI). EVALI is characterized by sterile exogenous pneumonitis like reaction with substantial involvement of innate immune mechanisms. Vitamin-E acetate (VEA) is found in counterfeit cartridges and bronchoalveolar lavage fluid of EVALI patients. Other reports implicated the presence of aromatic/volatile hydrocarbons and oils consisting of medium-chain triglycerides (MCT oil), including terpenes and mineral oil in tetrahydrocannabinol (THC) containing counterfeit vaping products. These compounds are involved in oxidative stress and inflammatory responses in the lung. Here, we provide the perspectives on the recent case reports on EVALI, etiology, and discuss pulmonary toxicity as well as the mechanisms underlying EVALI susceptibility and lung pathophysiology