Fracture characteristics of a burst tested maraging steel rocket motor case

A 0.3 m diameter, 2 m long and 0.0015 m thick, 18 nickel 1800 MNm^–2 grade maraging steel motor case was designed, fabricated and burst tested to gain experience for using the steel as booster case material in satellite launch vehicles. The bursting occurred at 15.2 MPa for which the effective hoop stress worked out to be 1754 MNm^–2 almost equal to the ultimate tensile strength (1764 MNm^–2) of the material in the solution treated and aged condition. The failure analysis revealed that the material failed due to normal tensile overload fracture. The burst test data was used to arrive at fracture mechanics parameters like crack size, gross section area stress and the stress for leak before bursting.     

Optimization of barium titanate nanopowder slip for tape casting

Dispersion of barium titanate nano powder of average particle size ∼30 nm in different solvent systems of tape casting (toluene–ethanol, methyl ethyl ketone–ethanol, xylene–ethanol) along with Triton x-100 or phosphate ester as dispersants has been studied using sedimentation experiments. The influence of different parameters such as type of solvent system, dispersant and concentration of dispersant on BaTiO₃ slip dispersion, viscosity and the properties of green tape were studied. The optimal concentration of dispersant was determined from the minimum slip viscosity. Xylene–ethanol with phosphate ester was found to be the best solvent and dispersant system for tape casting. Defect free, denser and smooth green tapes are formed with this system.     

Region based coronary artery segmentation using modified Frangi's vesselness measure

Recent research suggests that the cardiovascular diseases (CVDs), seem to be the foremost cause of mortality among the world populace. Three dimensional (3D) imaging modality such as computed tomography angiography(CTA) is a standard noninvasive imaging modality which has great potentials for the visualization of heart and coronary arteries. This article presents a fully automated method for coronary artery extraction using modified Frangi's vesselness measure and region based segmentation. In this article, grayness and gradient based measures are used while computing Frangi's vesselness measure to improve the extraction of coronary arteries. The obtained vesselness measures are utilized for automatically computing the location of ostia. The locations of ostia are then used as starting seed points in region growing segmentation to extract coronary arteries. Three major coronary arteries, namely the left anterior descending artery (LAD), left circumflex artery (LCX) and right coronary artery (RCA) are segmented using the proposed method and the centerlines are extracted for the main coronary branches. The performance of the proposed method is evaluated using 12 3D CCTA data set. The experimental results reveal that during the calculation of modified Frangi's vesselness measure the proposed method gives improved results. The qualitative results obtained during the segmentation stage are also convincing. The average segmentation accuracy and overlap measure of the proposed method are 97.4% and 77.86%, respectively. Hence, the proposed automated approach can detect and extract coronary arteries in CCTA images with high performance.     

Membranes,minerals, and proteins of developing vertebrate enamel

Developing tooth enamel is formed as organized mineral in a specialized protein matrix. In order to analyze patterns of enamel mineralization and enamel protein expression in species representative of the main extant vertebrate lineages, we investigated developing teeth in a chondrichthyan, the horn shark, a teleost, the guppy, a urodele amphibian, the Mexican axolotl, an anuran amphibian, the leopard frog, two lepidosauria, a gecko and an iguana, and two mammals, a marsupial, the South American short-tailed gray opossum, and the house mouse. Electron microscopic analysis documented the presence of a distinct basal lamina in all species investigated. Subsequent stages of enamel biomineralization featured highly organized long and parallel enamel crystals in mammals, lepidosaurians, the frog, and the shark, while amorphous mineral deposits and/or randomly oriented crystals were observed in the guppy and the axolotl. In situ hybridization using a full-length mouse probe for amelogenin mRNA resulted in amelogenin specific signals in mouse, opossum, gecko, frog, axolotl, and shark. Using immunohistochemistry, amelogenin and tuftelin enamel proteins were detected in the enamel organ of many species investigated, but tuftelin epitopes were also found in other tissues. The anti-M179 antibody, however, did not react with the guppy and axolotl enameloid matrix. We conclude that basic features of vertebrate enamel/enameloid formation such as the presence of enamel proteins or the mineral deposition along the dentin-enamel junction were highly conserved in vertebrates. There were also differences in terms of enamel protein distribution and mineral organization between the vertebrates lineages. Our findings indicated a correlation between the presence of amelogenins and the presence of long and parallel hydroxyapatite crystals in tetrapods and shark.     

Nanoscale Surface Characterization of Ceramic/Ceramic Coated Metallic Biomaterials Using Chromatic Length Aberration Technique

With the chromatic length aberration (CLA) technique, imaging of surfaces with complex three dimensional geometry is possible. Analysis of sample sizes in micro or nanometer scale is an added advantage available with CLA system. This article describes the methodology adopted for establishing the CLA technique for characterizing selected ceramic/ceramic coated substrates used in cardiovascular and orthopedic applications. The measurement of surface finish and coating thickness were validated against benchmarked technologies based on atomic force microscopy (AFM), stylus profilometry and standard ball cratering methods. Results of measurements were statistically analyzed by Student t test and reported the two tail p values to compare the results from different measurements techniques.     

Robust Reliable H∞ Control for Discrete‐Time Systems with Actuator Delays

This article focuses on the robust state feedback reliable H_∞ control problem for discrete‐time systems. Discrete‐time systems with time‐varying delayed control input are formulated. Based on the Lyapunov–Krasovskii method and linear matrix inequality (LMI) approach, delay‐dependent sufficient conditions are developed for synthesizing the state feedback controller for an uncertain discrete‐time system. The parameter uncertainty is assumed to be norm bounded. A design scheme for the state feedback reliable H_∞ controller is proposed in terms of LMIs, which can guarantee the global asymptotic stability and the minimum disturbance attenuation level. Finally, numerical examples are provided to illustrate the effectiveness and reduced conservatism of the proposed methods.     

Pharmacokinetics of oral and intravenous dolasetron mesylate in patients with renal impairment

In an open-label, randomized, two-way complete crossover study, the influence of renal impairment on the pharmacokinetics of dolasetron and its primary active metabolite, hydrodolasetron, were evaluated. Patients with renal impairment were stratified into three groups of 12 based on their 24-hour creatinine clearance (Cl(cr)): group 1, mild impairment (Cl(cr) between 41 and 80 mL/min); group 2, moderate impairment (Cl(cr) between 11 and 40 mL/min); and group 3, endstage renal impairment (Cl(cr) < or = 10 mL/min). Twenty-four healthy volunteers from a previous study served as the control group. Each participant received a single intravenous or oral 200-mg dose of dolasetron mesylate on separate occasions. Serial blood samples were collected up to 60 hours after dose for determination of dolasetron and hydrodolasetron, and urine samples were collected in intervals up to 72 hours for determination of dolasetron, hydrodolasetron, and the 5' and 6'-hydroxy metabolites of hydrodolasetron. Because plasma concentrations were low and sporadic, pharmacokinetic parameters of dolasetron were not calculated after oral administration. Although some significant differences in area under the concentration-time curve (AUC0-infinity), volume of distribution (Vd), systemic clearance (Cl), and elimination half-life (t1/2) of the parent drug were observed between control subjects and patients with renal impairment, there were no systematic findings related to degree of renal dysfunction. The elimination pathways of hydrodolasetron include both hepatic metabolism and renal excretion. Consistent increases in mean Cmax, AUC0-infinity, and t1/2 and decreases in renal and total apparent clearance of hydrodolasetron were seen with diminishing renal function after intravenous administration of dolasetron mesylate. No consistent changes were found after oral administration. Urinary excretion of hydrodolasetron and its metabolites decreased with decreasing renal function, but the profile of metabolites remained constant. Dolasetron was well tolerated in all three groups of patients. Based on these findings, no dosage adjustment for dolasetron is recommended in patients with renal impairment.     

Development of new hybrid ultrafiltration membranes by entanglement of macromolecular PPSU‐SO3H chains: Preparation,morphologies, mechanical strength,and fouling resistant properties

The present work focuses on the preparation of Polyphenylsulfone (PPSU) membranes with enhanced antifouling surfaces through an incorporation of sulfonated Polyphenylsulfone (PPSU‐SO₃H), which acts as both, surface modifying agent and macromolecular additive. Initially, Sulfonated polyphenylsulfone (PPSU‐SO₃H) was synthesized by using chlosulfonic acid via bulk modification method. The degree of sulfonation (DS, %) of PPSU‐SO₃H was calculated by using NMR (nuclear magnetic resonance).The phase inversion technique was used to prepare all asymmetric membranes by allowing the PPSU‐SO₃H (different wt %) to entangle with the PPSU membrane matrix. All prepared membranes were characterized by using scanning electron microscope (SEM), X‐ray diffraction analysis (XRD), contact angle analysis (CA), mechanical strength analysis, molecular weight cut off (MWCO), porosity (%), mean pore size, and BSA adsorption studies. The performance efficiency of the membranes was evaluated by using BSA protein as a model foulant in terms of permeability, rejection (SR %), R_m (hydraulic resistance), R_c (cake layer resistance), R_p (pore plugging resistance), R_r (reversible fouling), R_ir (irreversible fouling), and FRR (flux recovery ratio). © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41986.     

Reference biomaterials for biological evaluation

The variability associated with most of the biological evaluation studies is relatively large and hence experimental controls are frequently employed to ensure that the results are reliable. These experimental controls, either positive or negative controls, could be considered as reference materials in the context of biological evaluation. Currently, reference biomaterial needs across the world are not addressed satisfactorily. Affordability and lack of availability of certified reference materials necessitates the development and the use of laboratory developed RMs. A well defined characterization strategy is essential for the successful development of in house reference materials. This article provides an overview of the current international status in the area of reference biomaterials and enumerates the steps involved in the development of an in house reference material. The production and characterization of commercially pure titanium pins for use as negative controls during muscle implantation studies is presented as a case study.     

Separation of oil/water emulsions using nano MgO anchored hybrid ultrafiltration membranes for environmental abatement

This work focuses on utilizing the dual role of sulfonated polyphenyl sulfone (SPPSU) as both an anchoring agent and an interlayer modifying agent in the preparation of nano MgO/SPPSU/PPSU membranes for oil removal from water. These asymmetric membranes were prepared using the phase inversion technique. The dispersed nano MgO was observed in the membrane matrix as seen by scanning electron microscope and energy dispersive X‐ray analysis. The reduction in contact angle value establishes the increases in hydrophilicity. An increase in SPPSU (wt %) loosens the nano MgO/SPPSU/PPSU membrane packing as exhibited by the increase of d‐spacing by X‐ray diffraction analysis. The antifouling properties were tested using humic acid, as a model foulant. Further, in castor oil/water emulsion separation, it was found that the membrane with 25 wt % anchored moiety SPPSU/nano MgO produced a greater flux recovery ratio of 94.9% (±0.3) without compromising the oil rejection of 99% (±0.4) and better oleophobic surfaces for oil. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 132, 42848.