Green Synthesis of Silver Nanoparticles Induced by the Fungus Penicillium citrinum

Purpose: To evaluate a green process for the extracellular production of silver (Ag) nanoparticles synthesized and stabilized using Penicillium citrinum isolated from soil.Methods: The pure colonies of Penicillium citrinum were cultured in Czapek dox broth. The supernatant of the broth was examined for the ability to produce silver nanoparticles. The reactions were performed in a dark compartment at 28 oC. After 24 h, the synthesized silver nanoparticles were filtered through a membrane filter (0.45 ƒÊ) and characterized by UV-visible spectroscopy, fluorescence spectroscopy, photon correlation spectroscopy (PCS), scanning electron microscopy (SEM) and Fourier transformed infrared spectroscopy (FTIR) for particle size, shape and the presence of different functional groups in the nanoparticles.Results: The silver nanoparticles formed were fairly uniform in size with a spherical shape and a Zaverage diameter of 109 nm. FTIR spectra revealed the presence of amide linkage groups which were also found in the fungal extract itself.Conclusion: The current approach suggests that rapid synthesis of nanoparticles of silver nitrate would be suitable for developing a biological process for mass scale production of formulations.Keywords: Green synthesis, Penicillium citrinum, silver nanoparticles

Design and Modeling of Membrane-Based Evaporative Cooling Devices for Thermal Management of High Heat Fluxes

We present a high-heat-flux cooling device for advanced thermal management of electronics. The device incorporates nanoporous membranes supported on microchannels to enable thin-film evaporation. The underlying concept takes advantage of the capillary pressure generated by small pores in the membrane, and minimizes the viscous loss by reducing the membrane thickness. The heat transfer and fluid flow in the device were modeled to determine the effect of different geometric parameters. With the optimization of various parameters, the device can achieve a heat transfer coefficient in excess of 0.05 kW/cm²-K, while dissipating a heat flux of 1 kW/cm². When applied to power electronics, such as GaN high-electron-mobility transistors, this membrane-based evaporative cooling device can lower the near-junction temperature by more than 40 K compared with contemporary single-phase microchannel coolers

To Protect and to Preserve: Novel Preservation Strategies for Extracellular Vesicles

Extracellular vesicles (EVs)-based therapeutics are based on the premise that EVs shed by stem cells exert similar therapeutic effects and these have been proposed as an alternative to cell therapies. EV-mediated delivery is an effective and efficient system of cell-to-cell communication which can confer therapeutic benefits to their target cells. EVs have been shown to promote tissue repair and regeneration in various animal models such as, wound healing, cardiac ischemia, diabetes, lung fibrosis, kidney injury, and many others. Given the unique attributes of EVs, considerable thought must be given to the preservation, formulation and cold chain strategies in order to effectively translate exciting preclinical observations to clinical and commercial success. This review summarizes current understanding around EV preservation, challenges in maintaining EV quality, and also bioengineering advances aimed at enhancing the long-term stability of EVs

PLGA-Coated Drug-Loaded Nanotubes Anodically Grown on Nitinol

This study evaluates the use of nanotubes (NTs) as a matrix for local drug delivery modified by a biodegradable polymeric coating on medical-grade nitinol (NiTi alloy) surfaces. For this purpose, NiTi was anodized within parameters that promote the formation of NTs, ultrasonicated, annealed and impregnated with vancomycin hydrochloride. To improve bioperformance, poly(lactic-co-glycolic acid) (PLGA) was also deposited on the drug-loaded NTs. The samples were characterized in terms of structure, wettability, drug delivery, corrosion and cytocompatibility. Scanning electron microscopy and water contact angle measurements signify the formation of open-top homogeneous NTs of 600– 700 nm in length and ~30 nm in diameter with improved hydrophilicity. The bare antibiotic-impregnated NTs exhibit a burst release of about 49% of the loaded drug in the first 6 h of soaking in a physiological medium, followed by the entire drug diffusing out before 96 h. The PLGA coating effectively controls the burst release of vancomycin to 26% and retains almost 50% of the loaded drug beyond 7 days. The kinetics of the different vancomycin-release stages is also correlated to several well-established models. As a comparative criterion of metallic ions leaching kinetics, the corrosion resistance of nitinol is found to be reduced by the formation of the NTs, while the PLGA coating enhances this electrochemical feature. Due to the alteration of the drug delivery and corrosion protection, the PLGA-coated vancomycin-impregnated sample presents a higher dental pulp stem cell viability in comparison to both the bare drug-loaded and non-loaded NTs. In conclusion, PLGA-coated vancomycin-loaded NT-covered NiTi can be effectively used as a controlled drug-delivery device, while having a drug-release dosage within the therapeutic window and a minimal negative effect on biocompatibility

Probabilistic metric of infrastructure resilience considering time-dependent and time-independent covariates

The lifetime estimation for power semiconductors individually is a mature technology, and many empirical lifetime estimation models have been develo-ped based on abundant test data by several projects, such as LESIT project (Held et al., 1997) and the German project, RAPSDRA (Bayerer et al., 2008). These approaches analytically estimate the lifetime of a device module in terms of the number of cycles to failure Nf considering variable factors such as cyclic junction temperature variations ∆Tj, medium junction temperature, frequency and wire-bond current. These descriptive models are purely statistical analyses and have proven to be unsatisfactory since the aging effects due to the amplitude of junction temperature variations ∆Tj are not well considered (Lai et al., 2015), thus these approaches are not yet suitable in power fluctuation condition

To Protect and to Preserve:Novel Preservation Strategies for Extracellular Vesicles

Extracellular vesicles (EVs)-based therapeutics are based on the premise that EVs shed by stem cells exert similar therapeutic effects and these have been proposed as an alternative to cell therapies. EV-mediated delivery is an effective and efficient system of cell-to-cell communication which can confer therapeutic benefits to their target cells. EVs have been shown to promote tissue repair and regeneration in various animal models such as, wound healing, cardiac ischemia, diabetes, lung fibrosis, kidney injury, and many others. Given the unique attributes of EVs, considerable thought must be given to the preservation, formulation and cold chain strategies in order to effectively translate exciting preclinical observations to clinical and commercial success. This review summarizes current understanding around EV preservation, challenges in maintaining EV quality, and also bioengineering advances aimed at enhancing the long-term stability of EVs

An expert-based approach to production performance analysis of oil and gas facilities considering time-independent Arctic operating conditions

The availability and throughput of offshore oil and gas plants operating in the Arctic are adversely influenced by the harsh environmental conditions. One of the major challenges in quantifying such effects is lack of adequate life data. The data collected in normal-climate regions cannot effectively reflect the negative effects of harsh Arctic operating conditions on the reliability, availability, and maintainability (RAM) performance of the facilities. Expert opinions, however, can modify such data. In an analogy with proportional hazard models, this paper develops an expert-based availability model to analyse the performance of the plants operating in the Arctic, while accounting for the uncertainties associated with expert judgements. The presented model takes into account waiting downtimes and those related to extended active repair times, as well as the impacts of operating conditions on components’ reliability. The model is illustrated by analysing the availability and throughput of the power generation unit of an offshore platform operating in the Western Barents Sea