Effect of nanostructuring and Al alloying on friction and wear behaviour of thermal sprayed WC–Co coatings

Nanostructured WC–Co and WC–Co–Al coatings, with about 300-μm as-deposited coating thickness, were deposited by high velocity oxy-fuel (HVOF) spraying. Agglomerated nanostructured cermet powders produced by the Mechanomade® process was used for HVOF spraying. Dense and well-adherent coatings with crystal sizes below 30 nm were deposited on stainless steel 304 substrate. Porosity was less than 5% and the bond strength with the substrate was around 60 MPa. Experimental data on friction, wear, and abrasion resistance revealed that nanostructured WC–Co based coatings containing some Al as alloying element, exhibit improved tribological characteristics in comparison to nanostructured and micron-sized WC–Co coatings. This was attributed to a carbide particle distribution within the coating revealed by SEM, the absence of brittle W₂C-like phases revealed by XRD, and the presence of Al at particle/matrix boundaries revealed by TEM.     

Effect of the solubility of antibiotics on their release from degradable polyurethane

Application of biodegradable polyester urethane, as a drug loading matrix in the form of a coating on implant devices was investigated. Polyester urethane films were loaded with model antibiotics, like rifampicin, gentamicin and ciprofloxacin and their release characteristics were evaluated in simulated body fluid. Effect of solubility of antibiotics and degradation of matrix on the drug release behavior of biodegradable polyester urethane coating was also studied. It was observed that antibiotics having hydrophilicity or lipophilicity same as that of polymer matrix provide an extended release with relatively less initial burst release. Effect of degradation of polymer matrix has a dual significance in this case and the drug release rate increases with the increase in degradation rate. A high initial burst release was observed for antibiotics having hydrophilicity or lipophilicity opposite to that of polyurethane matrix and hence in this case antibiotic release was not significantly controlled by degradation of matrix.     

Analysis of distributed thermal management policy for energy-efficient processing of materials by natural convection

Natural convection is the governing phenomena in many material processing applications. The conventional method of uniform heating at the bottom wall of an enclosure may result in inadequate thermal mixing and poor temperature distribution leading energy wastage. In this work, an alternative, energy-efficient method of distributed heating of the cavity is studied and compared with the isothermal bottom wall heating case in enhancing the thermal mixing and improving the temperature distribution in the cavity. Steady laminar natural convection of various fluids of industrial importance (Pr = 0.015, 07, 10, 1000) in the range of Ra = 10³–10⁵ is studied in a differentially heated cavity and in two cases of discretely heated square cavities. Detailed analysis is carried out by visualizing the heat flow by heatlines. The thermal mixing and temperature uniformity in each case are quantified in terms of cup-mixing temperature and root-mean square deviation (RMSD), respectively. It is found that thermal management policy of distributed heating significantly influences the thermal mixing and temperature uniformity in the enclosures. In a case with multiple discrete heat sources, a remarkable uniformity in temperature across the cavity is achieved with moderate thermal mixing.     

Applying global cost-benefit analysis methods to indoor air pollution mitigation interventions in Nepal,Kenya and Sudan: Insights and challenges

Indoor air pollution from burning solid fuels for cooking is a major environmental health problem in developing countries, predominantly affecting children and women. Traditional household energy practices also contribute to substantial time loss and drudgery among households. While effective interventions exist, levels of investment to date have been very low, in part due to lack of evidence on economic viability. Between 2004 and 2007, different combinations of interventions – improved stoves, smoke hoods and a switch to liquefied petroleum gas – were implemented in poor communities in Nepal, Sudan and Kenya. The impacts were extensively evaluated and provided the basis for a household-level cost-benefit analysis, which essentially followed the methodology proposed by the World Health Organization. The results suggest that interventions are justified on economic grounds with estimated internal rates of return of 19%, 429% and 62% in Nepal, Kenya and Sudan, respectively. Time savings constituted by far the most important benefit followed by fuel cost savings; direct health improvements were a small component of the overall benefit. This paper describes the methodology applied, discusses the findings and highlights the methodological challenges that arise when a global approach is applied to a local programme.     

Entropy Generation During Natural Convection in a Porous Cavity: Effect of Thermal Boundary Conditions

Entropy generation plays a significant role in the overall efficiency of a given system, and a judicious choice of optimal boundary conditions can be made based on a knowledge of entropy generation. Five different boundary conditions are considered and their effect of the permeability of the porous medium, heat transfer regime (conduction and convection) on entropy generation due to heat transfer, and fluid friction irreversibilities are investigated in detail for molten metals (Pr = 0.026) and aqueous solutions (Pr = 10), with Darcy numbers (Da) between 10^?5–10^?3 and at a representative high Rayleigh number, Ra = 5 × 10⁵. It is observed that the entropy generation rates are reduced in sinusoidal heating (case 2) when compared to that for uniform heating (case 1), with a penalty on thermal mixing. Finally, the analysis of total entropy generation due to variation in Da and thermal mixing and temperature uniformity indicates that, there exists an intermediate Da for optimal values of entropy generation, thermal mixing, and temperature uniformity.     

Insight into the rescue of oxidized soluble guanylate cyclase by the activator cinaciguat

Nitric oxide (NO) signaling mediates many important physiological processes through the receptor soluble guanylate cyclase (sGC). Under disease conditions sGC heme can be oxidized resulting in NO insensitivity. Here, we show that the therapeutic compound cinaciguat (Cin) rescues dysfunctional sGC by direct displacement of the oxidized heme.     

Cobalt(II) Phthalocyanine‐Catalyzed Highly Chemoselective Reductive Amination of Carbonyl Compounds in a Green Solvent

Cobalt phthalocyanine has been employed for the highly chemoselective reductive amination of aldehydes and ketones in ethanol as a green solvent. A large range of functional groups such as nitro, acid, amide, ester, nitrile, halogen, lactone, methoxy, hydroxy, alkene, N‐benzyl, O‐benzyl and heterocyclic rings were well tolerated under the present reaction conditions.     

Development of cardiac prescreening device for rural population using ultralow-power embedded system

The invention is inspired by the desire to understand the opportunities and expectations of developing economies in terms of healthcare. The designed system is a point-of-care (POC) device that can deliver heart-care services to the rural population and bridge the rural-urban divide in healthcare delivery. The product design incorporates several innovations including the effective use of adaptive and multiresolution signal-processing techniques for acquisition, denoising, segmentation, and characterization of the heart sounds (HS) and murmurs using an ultralow-power embedded Mixed Signal Processor. The device is able to provide indicative diagnosis of cardiac conditions and classify a subject into either normal, abnormal, ischemic, or valvular abnormalities category. Preliminary results demonstrated by the prototype confirm the applicability of the device as a prescreening tool that can be used by paramedics in rural outreach programs. Feedback from medical professionals also shows that such a device is helpful in early detection of common congenital heart diseases. This letter aims to determine a framework for utilization of automated HS analysis system for community healthcare and healthcare inclusion.     

Gold-silver alloy nanoshells: a new candidate for nanotherapeutics and diagnostics

We have developed novel gold-silver alloy nanoshells as magnetic resonance imaging (MRI) dual T₁ (positive) and T₂ (negative) contrast agents as an alternative to typical gadolinium (Gd)-based contrast agents. Specifically, we have doped iron oxide nanoparticles with Gd ions and sequestered the ions within the core by coating the nanoparticles with an alloy of gold and silver. Thus, these nanoparticles are very innovative and have the potential to overcome toxicities related to renal clearance of contrast agents such as nephrogenic systemic fibrosis. The morphology of the attained nanoparticles was characterized by XRD which demonstrated the successful incorporation of Gd(III) ions into the structure of the magnetite, with no major alterations of the spinel structure, as well as the growth of the gold-silver alloy shells. This was supported by TEM, ICP-AES, and SEM/EDS data. The nanoshells showed a saturation magnetization of 38 emu/g because of the presence of Gd ions within the crystalline structure with r₁ and r₂ values of 0.0119 and 0.9229 mL mg^-1 s^-1, respectively (Au:Ag alloy = 1:1). T₁- and T₂-weighted images of the nanoshells showed that these agents can both increase the surrounding water proton signals in the T₁-weighted image and reduce the signal in T₂-weighted images. The as-synthesized nanoparticles exhibited strong absorption in the range of 600-800 nm, their optical properties being strongly dependent upon the thickness of the gold-silver alloy shell. Thus, these nanoshells have the potential to be utilized for tumor cell ablation because of their absorption as well as an imaging agent.