Enhanced H2O2 Upcycling into Hydroxyl Radicals with GO/Ni:FeOOH-Coated Silicon Nanowire Photocatalysts for Wastewater Treatment.

There remains continued interest in improving the advanced water oxidation process [e.g., ultraviolet (UV)/hydrogen peroxide (H2O2)] for more efficient and environmentally friendly wastewater treatment. Here, we report the design, fabrication, and performance of graphene oxide (GO, on top)/nickel-doped iron oxyhydroxide (Ni:FeOOH, shell)/silicon nanowires (SiNWs, core) as a new multifunctional photocatalyst for the degradation of common pollutants like polystyrene and methylene blue through enhancing the hydroxyl radical (•OH) production rate of the UV/H2O2 system. The photocatalyst combines the advantages of a large surface area and light absorption characteristics of SiNWs with heterogeneous photo-Fenton active Ni:FeOOH and photocatalytically active/charge separator GO. In addition, the built-in electric field of GO/Ni:FeOOH/SiNWs facilitates the charge separation of electrons to GO and holes to Ni:FeOOH, thus boosting the photocatalytic performance. Our photocatalyst increases the •OH yield by 5.7 times compared with that of a blank H2O2 solution sample and also extends the light absorption spectrum to include visible light irradiation.

Transcutaneous Recharge: A Comparison of Numerical Simulation to In Vivo Experiments.

OBJECTIVE: Numerical simulation and animal experiments quantified tissue temperatures during the transcutaneous recharge of neuromodulation implants. The temperature results were used to determine the likelihood of tissue injury in humans. MATERIALS AND METHODS: Experiments were completed using sheep with implants at different depths ranging from 0.7 to 2.15 cm. The calculations were replicates of the experiments. Additional calculations were completed for laterally offset implants (up to 2 cm). Benchtop tests were performed to determine the power dissipation in the components. These power dissipation rates were inputs to the simulation. The now-verified model was next applied to a human situation with a core temperature of 37°C. RESULTS: There was excellent agreement between the simulations and the animal-model for all depths; the experimental and simulated temperatures near the implant were almost identical. The results were negligibly affected by a misalignment of the implant. The maximum experimental temperatures in the sheep were 41.8, 43.2, and 41.8°C while the calculated maxima were 41.9, 43.3, and 41.2°C for the shallow, medium, and deep cases, respectively. The experimental values are 3.1, 4.5, and 3.1°C above the body core temperature. The simulation results are 3.2, 4.6, and 2.5°C above the core temperature. The model was then applied to a human situation with a body core temperature of 37°C. The maximum values of the simulated temperatures are 39.9, 41.2, and 39.1°C. The cumulative equivalent exposure at 43°C (CEM43) for these three implant depths are 0.30, 0.88, and 0.12 min. These thermal exposures are below those known to cause thermal injury in human skin tissue. CONCLUSIONS: The numerical simulation predicts tissue temperatures during transcutaneous recharge of implants. Results show that the implant depth does not have a large impact on the tissue temperatures and thermal exposures are sufficiently low so that they are unlikely to have any physiologic consequence.

Using cadaver temperatures to estimate time of death: A case-specific numerical approach.

A new approach is taken to estimating the time of death based on cadaver temperatures. The predictions are obtained by using numerical simulation that can be performed in a case-by-case scenario. Such a method enables time-of-death predictions for persons of any size and weight and in any thermal environment. An added advantage of the method is that it is not dependent upon an identification of the individual tissue layers and regions. Rather, a homogeneous tissue model is used, and the results that are obtained agree closely with the results of prior estimation methods and also with a prior published case study. Among the results presented in this study are various convective environments in both air and water (or a combination for a partially submerged body). The orientation of the body (face down vs face up) is investigated. It is found that when a body is face up, its body core temperature is more responsive to the ambient conditions, compared with a face-down orientation, at least for some partial-submergence depths. The method disclosed here can also be used to handle situations, where the environmental conditions are changing (such as diurnal temperature variations, variation in cloudy or sunny skies, etc.). Current nomogram methods are not able to handle such timewise variations.

Effect of Fluoroalkylsilane Surface Functionalization on Boron Combustion.

Boron has been regarded as a promising high-energy fuel due to its high volumetric and gravimetric heating values. However, it remains challenging for boron to attain its theoretical heat of combustion because of the existence of its native boron oxide layer and its high melting and boiling temperatures that delay ignition and inhibit complete combustion. Boron combustion is known to be enhanced by physically adding fluorine-containing chemicals, such as fluoropolymer or metal fluorides, to remove surface boron oxides. Herein, we chemically functionalize the surface of boron particles with three different fluoroalkylsilanes: FPTS-B (F3-B), FOTS-B (F13-B), and FDTS-B (F17-B). We evaluated the ignition and combustion properties of those three functionalized boron particles as well as pristine ones. The boron particles functionalized with the longest fluorocarbon chain (F17) exhibit the most powerful energetic performance, the highest heat of combustion, and the strongest BO2 emission among all samples. These results suggest that the surface functionalization with fluoroalkylsilanes is an efficient strategy to enhance boron ignition and combustion.

Operando Study of Thermal Oxidation of Monolayer MoS2.

Monolayer MoS2 is a promising semiconductor to overcome the physical dimension limits of microelectronic devices. Understanding the thermochemical stability of MoS2 is essential since these devices generate heat and are susceptible to oxidative environments. Herein, the promoting effect of molybdenum oxides (MoO x ) particles on the thermal oxidation of MoS2 monolayers is shown by employing operando X-ray absorption spectroscopy, ex situ scanning electron microscopy and X-ray photoelectron spectroscopy. The study demonstrates that chemical vapor deposition-grown MoS2 monolayers contain intrinsic MoO x and are quickly oxidized at 100 °C (3 vol% O2/He), in contrast to previously reported oxidation thresholds (e.g., 250 °C, t ≤ 1 h in the air). Otherwise, removing MoO x increases the thermal oxidation onset temperature of monolayer MoS2 to 300 °C. These results indicate that MoO x promote oxidation. An oxide-free lattice is critical to the long-term stability of monolayer MoS2 in state-of-the-art 2D electronic, optical, and catalytic applications.

Effect of Adventitious Carbon on Pit Formation of Monolayer MoS2.

Forming pits on molybdenum disulfide (MoS2 ) monolayers is desirable for (opto)electrical, catalytic, and biological applications. Thermal oxidation is a potentially scalable method to generate pits on monolayer MoS2 , and pits are assumed to preferentially form around undercoordinated sites, such as sulfur vacancies. However, studies on thermal oxidation of MoS2 monolayers have not considered the effect of adventitious carbon (C) that is ubiquitous and interacts with oxygen at elevated temperatures. Herein, the effect of adventitious C on the pit formation on MoS2 monolayers during thermal oxidation is studied. The in situ environmental transmission electron microscopy measurements herein show that pit formation is preferentially initiated at the interface between adventitious C nanoparticles and MoS2 , rather than only sulfur vacancies. Density functional theory (DFT) calculations reveal that the C/MoS2 interface favors the sequential adsorption of oxygen atoms with facile kinetics. These results illustrate the important role of adventitious C on pit formation on monolayer MoS2 .

Alterations of Blood Flow Through Arteries Following Atherectomy and the Impact on Pressure Variation and Velocity.

Simulations were made of the pressure and velocity fields throughout an artery before and after removal of plaque using orbital atherectomy plus adjunctive balloon angioplasty or stenting. The calculations were carried out with an unsteady computational fluid dynamic solver that allows the fluid to naturally transition to turbulence. The results of the atherectomy procedure leads to an increased flow through the stenotic zone with a coincident decrease in pressure drop across the stenosis. The measured effect of atherectomy and adjunctive treatment showed decrease the systolic pressure drop by a factor of 2.3. Waveforms obtained from a measurements were input into a numerical simulation of blood flow through geometry obtained from medical imaging. From the numerical simulations, a detailed investigation of the sources of pressure loss was obtained. It is found that the major sources of pressure drop are related to the acceleration of blood through heavily occluded cross sections and the imperfect flow recovery downstream. This finding suggests that targeting only the most occluded parts of a stenosis would benefit the hemodynamics. The calculated change in systolic pressure drop through the lesion was a factor of 2.4, in excellent agreement with the measured improvement. The systolic and cardiac-cycle-average pressure results were compared with measurements made in a multi-patient study treated with orbital atherectomy and adjunctive treatment. The agreements between the measured and calculated systolic pressure drop before and after the treatment were within 3%. This excellent agreement adds further confidence to the results. This research demonstrates the use of orbital atherectomy to facilitate balloon expansion to restore blood flow and how pressure measurements can be utilized to optimize revascularization of occluded peripheral vessels.

Estimating the time and temperature relationship for causation of deep-partial thickness skin burns.

The objective of this study is to develop and present a simple procedure for evaluating the temperature and exposure-time conditions that lead to causation of a deep-partial thickness burn and the effect that the immediate post-burn thermal environment can have on the process. A computational model has been designed and applied to predict the time required for skin burns to reach a deep-partial thickness level of injury. The model includes multiple tissue layers including the epidermis, dermis, hypodermis, and subcutaneous tissue. Simulated exposure temperatures ranged from 62.8 to 87.8°C (145-190°F). Two scenarios were investigated. The first and worst case scenario was a direct exposure to water (characterized by a large convection coefficient) with the clothing left on the skin following the exposure. A second case consisted of a scald insult followed immediately by the skin being washed with cool water (20°C). For both cases, an Arrhenius injury model was applied whereby the extent and depth of injury were calculated and compared for the different post-burn treatments. In addition, injury values were compared with experiment data from the literature to assess verification of the numerical methodology. It was found that the clinical observations of injury extent agreed with the calculated values. Furthermore, inundation with cool water decreased skin temperatures more quickly than the clothing insulating case and led to a modest decrease in the burn extent.