Expanding the Spectrum of Antibiotics Capable of Killing Multidrug-Resistant Staphylococcus aureus and Pseudomonas aeruginosa

Infections from antibiotic-resistant Staphylococcus aureus and Pseudomonas aeruginosa are a serious threat because reduced antibiotic efficacy complicates treatment decisions and prolongs the disease state in many patients. To expand the arsenal of treatments against antimicrobial-resistant (AMR) pathogens, 600-Da branched polyethylenimine (BPEI) can overcome antibiotic resistance mechanisms and potentiate β-lactam antibiotics against Gram-positive bacteria. BPEI binds cell-wall teichoic acids and disables resistance factors from penicillin binding proteins PBP2a and PBP4. This study describes a new mechanism of action for BPEI potentiation of antibiotics generally regarded as agents effective against Gram-positive pathogens but not Gram-negative bacteria. 600-Da BPEI is able to reduce the barriers to drug influx and facilitate the uptake of a non-β-lactam co-drug, erythromycin, which targets the intracellular machinery. Also, BPEI can suppress production of the cytokine interleukin IL-8 by human epithelial keratinocytes. This enables BPEI to function as a broad-spectrum antibiotic potentiator, and expands the opportunities to improve drug design, antibiotic development, and therapeutic approaches against pathogenic bacteria, especially for wound care.     

Specifics of Quantitation of Exogenous cis Fatty Acids in Biological Objects

Protection of Metals and Physical Chemistry of Surfaces - A method for quantitation of exogenous cis fatty acids in the presence of exogenous cis and trans fatty acids that does not require...     

Melting heat transfer analysis of electrically conducting nanofluid flow over an exponentially shrinking/stretching porous sheet with radiative heat flux under a magnetic field

Modern magnetic nanomaterial processing operations are progressing rapidly and require increasingly sophisticated mathematical models for their optimization. Stimulated by such developments, in this paper, a theoretical and computational study of a steady magnetohydrodynamic nanofluid over an exponentially stretching/shrinking permeable sheet with melting (phase change) and radiative heat transfer is presented. Besides, wall transpiration, that is, suction and blowing (injection), is included. This study deploys Buongiorno's nanofluid model, which simulates the effects of the Brownian motion and thermophoresis. The transport equations and boundary conditions are normalized via similarity transformations and appropriate variables, and the similarity solutions are shown to depend on the transpiration parameter. The emerging dimensionless nonlinear coupled ordinary differential boundary value problem is solved numerically with the Newton-Fehlberg iteration technique. Validation with special cases from the literature is included. The increase in the magnetic field, that is, the Hartmann number, is observed to elevate nanoparticle concentration and temperature, whereas it dampens the velocity. Higher values of the melting parameter consistently decelerate the boundary layer flow and suppress temperature and nanoparticle concentration. A higher radiative parameter strongly increases temperature (and thermal boundary layer thickness) and weakly accelerates the flow. The increase in the Brownian motion reduces nanoparticle concentrations, whereas a greater thermophoretic body force strongly enhances them. The Nusselt number and Sherwood number are observed to be decreased with an increasing Hartmann number, whereas they are elevated with a stronger wall suction and melting parameter.     

Process and joint quality of ultrasonic vibration enhanced friction stir lap welding

In order to improve the process effectiveness and joint quality, ultrasonic vibrations were integrated with friction stir lap welding. Effect of ultrasonic exertion on the process and joint quality of AA 6061-T6 were investigated. Upon ultrasonic exertion, joints owned larger effective lap width, shorter hooks and improved strength. Weld fracture mode changed from a ductile–brittle mixed mode to a more ductile mode while the fracture path shifted from lap interface to beyond the stir zone. Material flow and interface defects were characterised using lap welded dissimilar aluminium alloy joints. Ultrasonic vibration improved the material flow and reduced the interfacial defects. Variations in failure load of joints were found in accordance with the variations in material flow and interfacial defects.     

Microstructure,hardness, toughness and abrasive wear resistance of 16.0 wt. % chromium white iron after continuous and cyclic destabilisation treatment

Destabilisation of as-cast chromium white iron with 16 wt-% chromium are performed by continuous destabilisation treatment for 4 h and short duration (0.66 h) cyclic destabilisation treatment at 900, 950, 1000, 1050, and 1100 °C. Continuous destabilisation causes secondary carbides precipitation from austenite which on slow cooling transforms to pearlite matrix. Cyclic destabilisation treatment causes similar precipitation of finer secondary carbides following shorter period austenitisation and a matrix containing martensite and retained austenite on forced-air cooling. After continuous destabilisation, hardness falls below the as-cast value (HV622); whereas it rises to HV950 after cyclic destabilisation treatment. The as-cast notched impact toughness (4.0 J) increases to 8.5 J or more after both continuous and cyclic destabilisation at 1050 and 1100 °C. Abrasive wear resistance after continuous destabilisation improves only at higher wear load (49.0 N), while after cyclic destabilisation it supersedes the as-cast and Ni-Hard IV performance at both low (19.6 N) and high (49.9 N) wear load.     

THz Stimulated Emission from Simple Superlattice in Positive Differential Conductivity Region

Narrow band emissions at 2.6–2.8 THz are observed out of liquid helium cooled 1 mm disk chips prepared of a wafer with the very low n type doped weak barrier GaAs–GaAlAs superlattice of 1000 periods. The emissions are at about 8.0–18.0 V pulsed voltage applied to the chips in region of the chips positive DC differential conductivity that guaranties absence of inhomogeneous electric field domains in the chips. The emission frequency bands are estimated with a cyclotron resonance filter; the measurements show that the band width is of about that of the THz quantum cascade laser. By using long voltage pulses the chip heating above 100 K is achieved without substantial change in emission power. We speculate that the emission is super luminescence (amplification) of whispering gallery modes in the chips as a result of inverted Wannier-Stark level transitions under bias. The results are the first world demonstration of THz stimulated emission in a simple superlattice within region of positive DC differential conductivity; they give strong impetus for development of THz and higher frequency sources based on such simple superlattices; the sources should well compete with the THz quantum cascade lasers in particular at elevated temperatures.     

High-temperature behavior of oxide dispersion strengthening CoNiCrAlY

To fabricate oxide dispersion strengthened bond coatings, commercial Co–30wt-%Ni–20Cr–8Al–0?4Y powder was milled with 2% additions of Al₂O₃, Y₂O₃ or Y₂O₃ + HfO₂. Low-pressure plasma sprayed, free-standing specimens were oxidised in air + 10%H2O at 1100 °C both isothermally (100 h) and in 500, 1?h cycles. Dry air cyclic testing conducted at both ORNL and FZJ showed remarkably similar results. In general, the water vapour addition caused more scale spallation. Two LPPS specimens without oxide additions were tested for comparison. The specimens with 2%Al₂O₃ addition exhibited the best behaviour as the powder already contained 0?4%Y. Additions of 2%Y₂O₃ and especially 1%Y₂O₃ + 1%HfO₂ resulted in over-doping as evidenced by high mass gains and the formation of Y- and Hf-rich pegs. Scanning transmission electron microscopy of the isothermal specimens showed no Hf and/or Y segregation to the alumina scale grain boundaries in the over-doped specimens.     

Delineation of mineral potential zone using high resolution aeromagnetic data over part of Nasarawa State,North Central,Nigeria

Qualitative analysis of aeromagnetic data of part of Nasarawa State had been carried out with the aim of delineating mineral potential zone. The study area is bounded by Longitude 8.0°E – 9.0°E and Latitude 8.0°N – 9.5°N with an estimated total area of 18,150?km². Different filters were used to enhance the short wavelength anomalies which could give preliminary information about the magnetic minerals present in the study area. The total magnetic intensity map shows variation of both highs and lows magnetic signature ranges from ?51.2?nT to 110.4?nT after the removal of IGRF value of 33,000?nT; the highs which is basement dominates the north-eastern and north-western part of the study area which corresponds to Akwanga, Wamba and Nasarawa Eggon; these are areas with promising solid minerals of economic potentials like, gold at Wamba; Tin, Columbite and Tantalite at Akwanga while Granite rocks with possible radioactive elements are in abundance at Nasarawa Eggon. The low magnetic values on the other hand, which is made up of sediment deposition also dominates the southern part of the study area, this area corresponds to Lafia, Doma and Keana; Lafia and Doma host some industrial minerals like Clay, glass Sands and the Salt Brines at Keana. The major high magnetic signature trends east-west. The greenish part of the study area indicates alluvium deposition. The filters used are vertical derivatives, downward continuation and analytic signal. The first and second vertical derivatives; shows structures like lineament that could be the host to minerals present in the study area and it trends NE-SW. The downward continued at the depth of 50?m and 100?m shows the veins where magnetic minerals most especially gold are known to settle along igneous and metamorphic rocks. The analytic signal map shows that magnetic amplitude highs could be found at the northern end with most lineaments delineated also conform to other filter used. The tilt derivative map enhances short wavelength anomalies which could be used to mapped shallow basement structures and mineral exploration targets. The results of these filters agreed largely and since most magnetic minerals are structural controls, it is expected that those lineaments identified, most especially at the northern part, could play host to those minerals aforementioned.     

Erosion Characteristics of Copper-Based Composite Electrodes in an Electric Arc of Variable Length with Transverse Gas Blowing

We present experimental data on the erosion of electrodes made of copper-based pseudoalloys during contact breaking at current amplitudes up to 150 kA in nitrogen at a pressure of ~2 MPa with transverse gas blowing. The electric-erosion characteristics of copper–iron pseudoalloy CuFe (85/15%) electrodes obtained by laser layer melting, as well as CuFe (70/30%) and CuW (25/75%) pseudoalloy electrodes fabricated by traditional powder technology (sintering of pressed powder compacts) are reported. The specific erosion of electrodes in variable-length arc amounts to ~1 mg/C, which somewhat exceeds the value observed for a fixed-length arc discharge gap.