Subtle variations in the structure of crosslinked epoxy networks and the impact upon mechanical and thermal properties

Presented here is an investigation of the structure–property relationships of crosslinked networks using three bi-functional glycidyl ether aromatic epoxy resins, two bi-aryl and one tri-aryl, cured with bi- and tri-aryl amines. Subtle changes to the monomer chemistry including changing aromatic substitution patterns from meta to para, methylene to isopropyl and isopropyl to ether were explored. Changing an epoxy resin backbone from methylene to isopropyl enhances backbone rigidity thus increasing glass transition temperature (T_g), yield strength, and strain despite reducing modulus. Changing meta-substitution to para increases T_g and yield strain while leaving strength unaffected and reducing modulus. Changing isopropyl linkages to ether reduces modulus, strength, T_g, and yield strain reflecting increased molecular flexibility. Using three instead of two aromatic rings increases the molecular weight between crosslinks thereby decreasing T_g and yield strain while increasing modulus and strength. Despite the complexities of multiple systems for varying epoxy resins and amine hardeners, the effect upon network properties is explained in terms of short- and long-range molecular and segmental mobility, crosslink density, and equilibrium packing density. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48874.     

Magnetoelectric sensor for microtesla magnetic-fields based on (Fe80Co20)78Si12B10/PZT laminates

The magnetoelectric sensor based on (Fe₈₀Co₂₀)₇₈Si₁₂B₁₀/PZT laminates is designed, fabricated and characterized for determining dc and ac magnetic-field strengths as well as field orientations. At low dc magnetic-fields, a ME-voltage response (dV_ME/dH) as high as 2 mV/Oe is achieved. The linear relation V_ME(h_ac) with a slope of dV_ME/dh_ac of 17 mV/Oe shows a great ability to self-powered detecting low ac magnetic-fields. The field orientation can be detected by using the sinusoidal dependence of the magnetoelectric voltage. The sensor is promising not only for microtesla magnetic-field sensing but also for magnetic biosensor applications.     

Synthesis of optical quality ZnO nanowires utilizing ultrasonic spray pyrolysis

ZnO nanowires were grown by an ultrasonic spray pyrolysis technique. The aspect ratio and size of the wire were dependent mainly on the pH value of a precursor solution and the growth temperature. By high-resolution transmission electron microscopic analysis and photoluminescence measurements, it was confirmed that the nanowires are monocrystalline with good optical quality.     

Achievement of 100% Removal of Oil from Feathers Employing Magnetic Particle Technology

Iron powder has previously been demonstrated to be a potential dry cleansing agent for oiled feathers, whereby both the oil ad(b)sorbing particles and the contaminant may be harvested magnetically. Previous studies on feather clusters have only been able to achieve 97.4% removal. While impressive, this is not considered to be entirely satisfactory for wildlife rehabilitation in practice. Reported in this Technical Note is a series of experiments designed to establish whether a grade of iron powder can be identified that is capable of achieving 100% removal and to identify those characteristics responsible for such improvement. To this end, the abilities of nine different grades of iron powder to remove four different contaminants (three crude oils and a crude oil/seawater emulsion) from feather clusters have been compared, as have the relative physical characteristics of the different iron powders. It has been established that the efficiency of remediation is indeed related to certain physical attributes of the particles (the “grade”). Specifically, a spongy superfine iron powder has been identified that is capable of achieving 100% removal (within experimental error) for all four contaminants tested. This represents an important proof of principle that makes the development of a practical field device a real possibility.     

Multiple familiar occurrence of ochronotic arthropathy

Complete papillary muscle rupture is a catastrophic complication of acute myocardial infarction which usually leads to acute severe mitral regurgitation requiring urgent or emergent surgery. A case in which this complication occurred after chordal sparing mitral valve replacement is described. The severed papillary muscle was removed surgically. The incidence and natural history of papillary muscle rupture occurring after chordal sparing mitral valve replacement for ischemic mitral insufficiency is not known.     

Mixed land uses,land-use externalities,and residential property values: A reevaluation

Empirical evidence concerning the impact of neighborhood land-use externalities on residential property value is mixed. That is, no concensus has emerged in the literature as to whether locating non-residential land-use activities in residential neighborhoods can be expected to increase, decrease or leave unaltered surrounding property values. The purpose of this research was two-fold: 1) to construct a theoretical model of consumer behavior in which both the positive and negative effects of neighborhood land-use externalities are taken into account, and 2) to test this generalized model empirically, using hedonic pricing equations. The principal implication of the theoretical model is that the effect of non-residential activity on residential property values isa priori indeterminate, the outcome depending on the relative strength of the associated positive and negative external effects generated. The empirical test of the model was conducted for the city of Tucson, Arizona, where it is shown that over low ranges, increasing the amount of industrial, commercial, multifamily and public land-use activity in a neighborhood tended to increase surrounding residential property values. It is concluded that in locating future economic activity an optimal mix of landuse activities should be sought, not the regional separation of activities.     

Letter: Reliability of transcutaneous PO2 with Roche Oxygen Monitor 5300 at 44 C in newborn infants with RDS

A microtiter cell-culture method was developed and used to titrate virus isolates for characterization. Virus dilutions and chicken kidney cell suspensions were dispensed into the wells of disposable microculture plates, with infectivity endpoints being determined microscopically on the fifth or sixth day, or by reading crystal-violet-stained monolayers on day 6. With this method, 37 candidate avian adenoviruses isolated from diagnostic accessions were characterized as avian adenoviruses (AAV). The criteria used for characterization were production of round-cell cytopathic effect, resistance to chloroform treatment, inhibition by 5-bromodeoxyuridine, and the presence of an antigen showing identity with a known AAV by precipitation in agar gel. Statistical anlaysis of eight replicate titrations of three AAV indicated that the titration method was highly reproducible. Use of the microculture method for titrations gave substantial savings in indicator cells, media, incubator space, culture dishes, and time.     

Anodic oxidation ofp-t-butyltoluene in sulphuric acid solution

The electrochemical oxidation ofp-t-butyltoluene has been investigated. From several anode materials studied, Pb-Sb alloys give the best yields ofp-t-butylbenzaldehyde at 60° C in 1 M H₂SO₄.     

Cloning and heterologous expression of a beta-fructofuranosidase gene from Arthrobacter globiformis IFO 3062, and site-directed mutagenesis of the essential aspartic acid and glutamic acid of the active site

We have cloned the gene encoding a beta-fructofuranosidase from Arthrobacter globiformis IFO 3062, and subsequently, the gene was heterologously expressed in Escherichia coli. This beta-fructofuranosidase gene encodes a protein of 548 amino acid residues with a calculated molecular mass of 60,519 Da. We have examined the roles of three residues of A. globiformis IFO 3062 beta-fructofuranosidase by site-directed mutagenesis, and found that aspartic acid 130 and glutamic acid 392, which are two of the apparent catalytic residues, are essential for hydrolase activity. This study provides the first experimental evidence showing that these two amino acid residues of beta-fructofuranosidase play a critical role in hydrolyzing sucrose.     

An implementation of no-slip boundary conditions in DPD

We report an implementation of the no-slip boundary condition in the modeling of solid boundaries by dissipative particle dynamics (DPD) method. Stimulated by a model for several types of solid boundaries, we develop an implementation that satisfies no-slip boundary condition with practically no-density distortion near the boundaries. The model is implemented to simulate the planar Poiseuille and Couette flows, as well as the flow through a contraction and diffusion channel. Results compare excellently with the previous methods.