Use of orthogonal arrays in mechanism synthesis

No single optimization method exists that is best suited to solve all path generation problems effectively [Erdman 1991]. Graphical illustrations of the mechanism design space, given in this paper, attest to the difficulties encountered in the optimization of path generation tasks. An example has also been provided to illustrate the importance of a good initial guess in achieving proper convergence. Use of experimental design techniques that are based on statistically designed orthogonal arrays is suggested in this paper, as an alternate method to solve mechanism design tasks. It will also be benificial to use this method to obtain a good starting point for the traditional optimal synthesis procedures. Also, when a theoretical solution is translated into physical reality, manufacturing tolerances, joint clearances, and elasticity in link members cause variations in mechanism performance. Orthogonal arrays and the related robust design procedures, suggested here, account for such variations as well. Design examples are given to illustrate the use of orthogonal arrays.     

HermesB: a continuous neural recording system for freely behaving primates

Chronically implanted electrode arrays have enabled a broad range of advances in basic electrophysiology and neural prosthetics. Those successes motivate new experiments, particularly, the development of prototype implantable prosthetic processors for continuous use in freely behaving subjects, both monkeys and humans. However, traditional experimental techniques require the subject to be restrained, limiting both the types and duration of experiments. In this paper, we present a dual-channel, battery-powered neural recording system with an integrated three-axis accelerometer for use with chronically implanted electrode arrays in freely behaving primates. The recording system called HermesB, is self-contained, autonomous, programmable, and capable of recording broadband neural (sampled at 30 kS/s) and acceleration data to a removable compact flash card for up to 48 h. We have collected long-duration data sets with HermesB from an adult macaque monkey which provide insight into time scales and free behaviors inaccessible under traditional experiments. Variations in action potential shape and root-mean square (RMS) noise are observed across a range of time scales. The peak-to-peak voltage of action potentials varied by up to 30% over a 24-h period including step changes in waveform amplitude (up to 25%) coincident with high acceleration movements of the head. These initial results suggest that spike-sorting algorithms can no longer assume stable neural signals and will need to transition to adaptive signal processing methodologies to maximize performance. During physically active periods (defined by head-mounted accelerometer), significantly reduced 5-25-Hz local field potential (LFP) power and increased firing rate variability were observed. Using a threshold fit to LFP power, 93% of 403 5-min recording blocks were correctly classified as active or inactive, potentially providing an efficient tool for identifying different behavioral contexts in prosthetic applications. These results demonstrate the utility of the HermesB system and motivate using this type of system to advance neural prosthetics and electrophysiological experiments.     

Pharmaceutical applications of hot-melt extrusion: Part II

The advent of high through-put screening in the drug discovery process has resulted in compounds with high lipophilicity and poor solubility. Increasing the solubility of such compounds poses a major challenge to formulation scientists. Various approaches have been adopted to address this including preparation of solid dispersions and solid solutions. Hot-melt extrusion is an efficient technology for producing solid molecular dispersions with considerable advantages over solvent-based processes such as spray drying and co-precipitation. Hot-melt extrusion has been demonstrated to provide sustained, modified, and targeted drug delivery. Improvements in bioavailability utilizing the hot-melt extrusion technique demonstrate the value of the technology as a potential drug delivery processing tool. The interest in hot-melt extrusion technology for pharmaceutical applications is evident from the increasing number of patents and publications in the scientific literature. Part II of this article reviews the myriad of hot-melt extrusion applications for pharmaceutical dosage forms including granules, pellets, tablets, implants, transmucosal, and transdermal systems.     

Binding waste anthracite fines with Si-containing materials as an alternative fuel for foundry cupola furnaces

An alternative fuel to replace foundry coke in cupolas was developed from waste anthracite fines. Waste anthracite fines were briquetted with Si-containing materials and treated in carbothermal (combination of heat and carbon) conditions that simulated the cupola preheat zone to form silicon carbide nanowires (SCNWs). SCNWs can provide hot crushing strengths, which are important in cupola operations. Lab-scale experiments confirmed that the redox level of the Si-source significantly affected the formation of SiC. With zerovalent silicon, SCNWs were formed within the anthracite pellets. Although amorphous Si (+4) plus anthracite formed SiC, these conditions did not transform the SiC into nanowires. Moreover, under the test conditions, SiC was not formed between crystallized Si (+4) and anthracite. In a full-scale demonstration, bricks made from anthracite fines and zerovalent silicon successfully replaced a part of the foundry coke in a full-scale cupola. In addition to saving in fuel cost, replacing coke by waste anthracite fines can reduce energy consumption and CO2 and other pollution associated with conventional coking.     

Analysis of high-pressure hydrogen, methane, and heptane laminar diffusion flames: Thermal diffusion factor modeling

Direct numerical simulations are conducted for one-dimensional laminar diffusion flames over a large range of pressures (1?P₀?200 atm) employing a detailed multicomponent transport model applicable to dense fluids. Reaction kinetics mechanisms including pressure dependencies and prior validations at both low and high pressures were selected and include a detailed 24-step, 12-species hydrogen mechanism (H₂/O₂ and H₂/air), and reduced mechanisms for methane (CH₄/air: 11 steps, 15 species) and heptane (C₇H₁₆/air: 13 steps, 17 species), all including thermal NO_x chemistry. The governing equations are the fully compressible Navier-Stokes equations, coupled with the Peng-Robinson real fluid equation of state. A generalized multicomponent diffusion model derived from nonequilibrium thermodynamics and fluctuation theory is employed and includes both heat and mass transport in the presence of concentration, temperature, and pressure gradients (i.e., Dufour and Soret diffusion). Previously tested high-pressure mixture property models are employed for the viscosity, heat capacity, thermal conductivity, and mass diffusivities. Five models for high-pressure thermal diffusion coefficients related to Soret and Dufour cross-diffusion are first compared with experimental data over a wide range of pressures. Laminar flame simulations are then conducted for each of the four flames over a large range of pressures for all thermal diffusion coefficient models and results are compared with purely Fickian and Fourier diffusion simulations. The results reveal a considerable range in the influence of cross-diffusion predicted by the various models; however, the most plausible models show significant cross-diffusion effects, including reductions in the peak flame temperatures and minor species concentrations for all flames. These effects increase with pressure for both H₂ flames and for the C₇H₁₆ flames indicating the elevated importance of proper cross-diffusion modeling at large pressures. Cross-diffusion effects, while not negligible, were observed to be less significant in the CH₄ flames and to decrease with pressure. Deficiencies in the existing thermal diffusion coefficient models are discussed and future research directions suggested.     

Enhanced oral bioavailability of felodipine by naringenin in Wistar rats and inhibition of P-glycoprotein in everted rat gut sacs in vitro

The aim of this study was to investigate the effect of naringenin on the pharmacokinetics (PK) of felodipine in rats and membrane permeability across rat everted gut sacs in vitro. Rats were simultaneously co-administered with felodipine 10?mg/kg, p.o. and naringenin (25, 50 and 100?mg/kg, p.o.) for 15 consecutive days. Rats of the control groups received the corresponding volume of vehicle. Blood samples were withdrawn from retro-orbital plexus on first day in single dose PK study (SDS) and on 15th day in multiple dosing PK study (MDS). The PK parameters were calculated using Thermo kinetica. The co-administration of naringenin significantly elevated the C_max and increased the AUC_total of felodipine in dose-dependent manner. The C_max of felodipine was increased from 173.25?±?14.65 to 275.61?±?44.62 and 223.26?±?26.35 to 561.32?±?62.53?ng/mL in SDS and MDS, respectively, at the dose of naringenin 100?mg/kg. The AUC_total of felodipine was significantly (p?max and AUC of felodipine is due to P-gp and CYP3A4 inhibition.     

Effects of 4-n-nonylphenol on aquatic hyphomycetes

We measured the removal of 4-n-nonylphenol (between 50 and 500 μg L⁻¹) from an aqueous solution with or without linden and oak leaf disks. More 4-n-NP was removed when the leaves were first exposed for 3 weeks in a stream, which allowed colonization by aquatic hyphomycetes. The response of fungal sporulation rates from beech, linden, maple and oak leaves to increasing levels of 4-n-NP was complex. Linear regressions were non-significant, arguing against a no-threshold model. The response at the lowest concentration (50 μg L⁻¹) was between 7% (beech) and 67% (maple) higher than in the absence of 4-n-NP, however, the difference was not significant. The number of sporulating species of aquatic hyphomycetes was significantly higher at the lowest concentration than in the control treatment without 4-n-NP. The composition of the fungal community was affected by leaf species but not by 4-n-NP concentration. The results suggest the presence of a weak hormeotic effect. The known ability of aquatic hyphomycetes and other fungi to degrade nonylphenols and related substances, combined with fungal resilience in their presence, makes decaying leaves potential candidates for bioremediation.     

Conversion of Fly Ash to Swelling Mica: A New Approach for Recycling Fly Ash

Swelling mica exhibits unique characteristics for purification of drinking water contaminated by heavy metals and for selective removal of Sr²⁺ and Ba²⁺ ions from nuclear waste solution. As a new approach to recycle fly ash, conversion of fly ash to swelling mica has been attempted and ion-exchange properties of fly ash-derived swelling mica (referred to hereinafter as FA-swelling mica) were examined in this study. Thermal treatment of fly ash with MgO in the presence of excess NaF led to the formation of swelling mica along with trace quantities of impurities. A swelling mica of good quality was obtained from the reactant ratio of fly ash 1 g : MgO 0.75 g : NaF 1.75 g. Unlike gel or kaolinite-derived synthetic Na-4-micas, FA-swelling mica exhibited heterogeneity in its framework. Its uptake capacity for Sr²⁺ ions was estimated to be 17.4 meq/100 g from 0.1 mM SrCl₂ aqueous solution and 5.0 meq/100 g from 0.5 N NaCl solution containing the same Sr²⁺ concentration. These capacities are less than that of metakaolin-derived Na-4-mica. However, its ion exchange capacity for divalent transitional metal ions was estimated to be 284 meq/100 g from their inaqueous solutions and 206 meq/100 g from the 0.5 N NaCl solution containing the mixed metal ions of Cd²⁺, Co²⁺, Mn²⁺, Ni²⁺ and Zn²⁺ each at 1 mN concentration. These capacities are comparable to that of metakaolin-derived Na-4-mica. Its selectivity for transition metal ions is as follows: Zn²⁺ > Ni²⁺ Co²⁺ Cd²⁺ > Mn²⁺ and this is consistent with the G° values from Gibbs-Duhem equation. These results clearly showed that fly ash could be converted to swelling mica with high uptake capacity for divalent transitional metal ions. Therefore, conversion of fly ash to highly pure swelling mica will lead to a resource from waste.     

MHD radiative Casson—Nanofluid stream above a nonlinear extending surface including chemical reaction through Darcy-Forchiemer medium

The current study aims to study the magnetohydrodynamics (MHD) Casson kind nanofluid stream through a permeable medium above a nonlinear extending surface considered along with Darcy-Forchimer relation and chemical reaction. Thermophoresis and Brownian diffusion effects are considered. The MHD effect is used to highlight the physical and thermal properties of the nanofluid. The Keller Box scheme is used to solve the guiding equations numerically. Graphs are plotted for various nondimensional parameters. To justify the method, the used local parameters are calculated and compared with the existing literature. The results specify that a decreasing tendency is observed in the velocity profile for Forchiemer, magnetic, and stretching rate parameters, whereas the opposite tendency is noted for the Casson parameter. On observing temperature profiles, declination is noticed for Casson, thermal slip parameters and raising nature is detected for increasing values of Brownian diffusion, and thermophoresis, radiation parameters. From the results, it is observed that the momentum boundary layer diminishes for a higher inertial influence and the opposing force offered by the porous media to the fluid flow.