Characterization of heat treated eastern redcedar (Juniperus virginiana L.)

The objective of the study is to investigate the influence of heat treatment on shrinkage, density, surface roughness, water absorption, diffusion coefficient, swelling and shear strength of eastern redcedar (Juniperus virginiana L.) samples. The anatomical structures of samples are also observed by scanning electron microscope (SEM). Specimens are exposed to temperature levels of 120 °C, 160 °C and 190 °C for time spans of 2 and 8 h. Based on the results of this study, dimensional stability in the form of shrinkage of the samples is improved by 2.68%, 1.40% and 1.49% for tangential, longitudinal and radial grain orientations as function of heat treatment, respectively. Heat treatment also enhances surface quality of the samples based on numerical values determined from stylus type of equipment. Water absorption, swelling values and diffusion coefficient of the samples are also reduced with heat treatment. Samples exposed to heat treatment have lower shear strength values, ranging from 25.12% to 52.67%, than those of control samples. It appears that all properties evaluated in this work are affected more pronouncedly as temperature and exposure time is increased.     

Characterization and application of propylene grafted hydrogenated dicyclopentadiene hydrocarbon resin

Hydrocarbon resins, which are defined as low molecular weight, amorphous, and thermoplastic polymers, are widely used as tackifiers for various types of adhesives, as processing aids in rubber compounds, and as modifiers for paint and ink products, and for use in plastics polymers such as isotactic polypropylene. Recently, the quantities of the hydrocarbon resin׳ raw materials which are the side products from naphtha cracking process have decreased because of light-feed cracking such as gas cracking, so new raw materials for hydrocarbon resin production are essential. To be satisfied with the previously mentioned factors, the substitution of hydrocarbon resin raw materials with renewable resources is a worthy consideration. Moreover, new hydrocarbon resin having high adhesion performance, low specific gravity, and good compatibility with various polymers has been requested in various adhesives.To meet those requests, in this study, propylene instead of side product from naphtha cracking as main raw material of hydrocarbon resin were partially used. The propylene serves as a new, sustainable raw material and was successfully grafted onto dicyclopentadiene. The reaction of the propylene with dicyclopentadiene was confirmed because, according to NMR and FT-IR analyses, a pendant methyl-propylene group exists in the structure of the propylene-grafted, hydrogenated dicyclopentadiene hydrocarbon resin. To establish an optimal production condition regarding the propylene-grafted, hydrogenated dicyclopentadiene hydrocarbon resin, numerous experiments were conducted according to the mole ratio of the raw materials and the polymerization temperature. The propylene-grafted, hydrogenated dicyclopentadiene hydrocarbon resin that was manufactured according to optimal conditions results in a lower specific gravity and a high molecular weight, whereby the advantages of the adhesion properties of an SIS-based pressure-sensitive-adhesive are exploited. When the propylene-grafted, hydrogenated dicyclopentadiene hydrocarbon resin was formulated with the SIS-based pressure-sensitive-adhesive, both the heat stability and the shear-adhesion strength are sound.     

Flexural buckling of simply-supported thin-walled columns with consideration of membrane shear deformations: Analytical solutions based on shell model

In this paper, flexural buckling of pin-ended thin-walled columns is discussed. The classical formulae for the critical force are based on a beam model. The simplest formulae use the classical Euler–Bernoulli beam theory, but solutions based on the shear-deformable beam theory are also known. In the presented research alternative formulae are derived. The column is modeled as a set of flat plane elements, and the in-plane membrane shear deformations are explicitly considered. The derivations can be carried out in various, slightly different ways, leading to different formulae. The derived critical force formulae are discussed through theoretical considerations and numerical studies.     

Investigation of basic molecular gas structural effects on hydrodynamics and thermal behaviors of rarefied shear driven micro/nano flow using DSMC

In the present work, rarefied gas flow between two parallel moving plates maintained at the same uniform temperature is simulated using the direct simulation Monte Carlo (DSMC) method. Heat transfer and shear stress behavior in the micro/nano-Couette flow is studied and the effects of the important molecular structural parameters such as molecular diameter, mass, degrees of freedom and viscosity–temperature index on the macroscopic behavior of gases are investigated. Velocity, temperature, heat flux and shear stress in the domain are studied in details. Finally, a discussion on the role of the molecular structural parameters in the decrease or increase of amounts of hydrodynamics and thermal properties of the gas is presented.     

A three dimensional exact equation for the turbulent dissipation rate of Generalised Newtonian Fluids

The flow of non-Newtonian fluids is of interest in many biological and industrial applications, including nanofluids. Most of the papers of the literature on turbulent non-Newtonian fluids focused the attention on viscoelastic fluids. In order to make accurate and low cost prediction of turbulent inelastic non-Newtonian fluids, a RANS Generalised Newtonian Fluid (GNF) turbulence model, based on the exact equations for the turbulent variables, is required. In a previous paper of the same authors the exact equations for the turbulent kinetic energy and the dissipation rate have been derived in a two-dimensional (2D) domain, through the introduction of an apparent viscosity equation. The aim of the present paper is to extend the approach to a three-dimensional (3D) domain, giving the full mathematical demonstration of the exact equations.     

Effects of blade tenderization,aging method and aging time on meat quality characteristics of Longissimus lumborum steaks from cull Holstein cows

The effects of blade tenderization (BT), two aging methods (dry (D) and wet (W)), and aging time (2 and 23 d) on tenderness, color, and sensory properties of Longissimus lumborum muscles from 12 cull Holstein cows were evaluated. Dry-aged loins had higher combined trim and aging losses than control (C) for both D- and W-aging, mostly because of excess trim losses. BT steaks had WBSF of 33.13 N while C steaks had WBSF of 41.46 N (P = 0.09). Aging decreased WBSF. Blade tenderized steaks had higher cook loss than C steaks. Aging, W-aging, and BT × W-aging improved myofibrillar (sensory) tenderness scores. Aging and/or BT improves sensory panel tenderness cull cow Longissimus lumborum steaks. Aging and blade tenderization combined can increase tenderness and value of Longissimus steaks from cull Holstein cows.     

Effect of Shear Rate Distribution on Particle Aggregation in a Stirred Vessel

The modeling of particle aggregation under a simple shear flow and the extension of the model to a stirred vessel is described. The model quantitatively demonstrates the change of the number of aggregates with time for each shear rate. This number increased with higher shear rate and, conversely, the aggregate size became small when raising the shear rate. This was because aggregates were broken by the stronger shear force. The number of aggregates for different impellers was determined. The shear rate was back‐calculated from the experimentally obtained aggregate size and the model equation. This shear rate was different from that estimated from the Metzner‐Otto method, consequently, some revisions of the Metzner‐Otto equation might be necessary for its application to particle aggregation.     

Stress and strain analysis in tar-containing antiskid runways using finite element models

Tar-containing antiskid surface layers are widely used for runways in airfields. Antiskid mixtures with tar-containing binders show apart from a high skid resistance, excellent adhesion of the antiskid layer to the underlying layer, and a extremely high fuel resistance, which make them more suitable for airfields than other materials. However, tar-containing antiskid has a high Polycyclic Aromatic Hydrocarbons (or PAHs) content, which makes them toxic to humans. Because of these environmental concerns, tar-containing antiskid runways are not allowed anymore after 2010 in the Netherlands. Therefore alternatives need to be developed.In order to be able to develop alternatives, the stress and strain distributions in a tar-containing antiskid surface layer should be evaluated. Structural characteristics and rheology properties of tar-containing antiskid surface layers were studied by means of nano CT scanning and Dynamic Shear Rheometer measurements, respectively. Using these results, two finite element models were developed. Stress and strain distributions in the antiskid layer under taking off and landing aircrafts were determined by means of these models. The results indicate that the stiffness of the binder has a slightly influence on the principal stress and strain. Finite element modeling (FEM) models can be developed for alternatives to tar-containing binder.     

Fluorescent Probe DCVJ Shows High Sensitivity for Characterization of Amyloid β-Peptide Early in the Lag Phase

The aggregation of intrinsically disordered and misfolded proteins in the form of oligomers and fibrils plays a crucial role in a number of neurological and neurodegenerative diseases. Currently, most probes and biophysical techniques that detect and characterize fibrils at high resolution fail to show sensitivity and binding for oligomers. Here, we show that 9-(dicyano-vinyl)julolidine (DCVJ), a class of molecular rotor, binds amyloid beta (Aβ) early aggregates, and we report the kinetics as well as packing of the oligomer formation. The binding of DCVJ to Aβ40 increased its emission intensity with time at 510 nm and produced a second excimer peak at 575 nm. However, DCVJ did not bind to the prefibrillar aggregates of Aβ42, which indicated that the oligomers formed by Aβ40 and Aβ42 were not the same. The F4C F19W mutant of Aβ40, which did not form fibrils, also bound DCVJ, but the emission spectral profile varied from that of the wild-type (WT). Atomic force microscopy images of WT Aβ40, the F4C F19W mutant, and Aβ42 oligomers displayed differences in size and shape, confirming the difference in their DCVJ spectra. The effect of epigallocatechin-3-gallate (EGCG) on the reduction of Aβ42 fibrils was also observed with finer detail than with other techniques. The results of this study show that DCVJ detects early aggregates and provides valuable information regarding the oligomer kinetics, packing, and mechanism of formation.     

Aspects of enamel bonding using experimental silanes for orthodontic adhesion

This in vitro study investigates bonding to enamel using experimental silane-based primers with and without 2-hydroxyethylmethacrylate (HEMA) under various artificial ageing methods. One hundred and fifty sound extracted human premolars were used and randomly assigned to three experimental study groups. They were first acid-etched for 15 s, rinsed with water spray, air dried, and applied 0.3 ml of artificial saliva on the enamel surfaces. Two groups of enamel surfaces were primed using silane-based experimental primers (1.0 vol% of 3-isocyanatopropyltrimethoxysilane and 0.5 vol% of bis-1,2-(triethoxysilylethane) with and without 25% HEMA) while one group was served as control. Then, stainless steel premolar orthodontic brackets were fixed onto teeth with orthodontic resin composite. The specimens from each group (n=10) were stored under different ageing conditions: thermo-cycling (500, 2000, and 6000 cycles), storage in artificial saliva for 24 h, and for one year. The shear adhesion (bond) strength (SBS) was tested by using a universal testing machine at a crosshead speed of 1.0 mm/min. Surface morphology and failure modes at the debonded interfaces were examined using SEM. Two-way ANOVA and post hoc tests were used to compare the SBS (α=0.05). The results suggested that an experimental primer with 25% HEMA, after 24 h storage in artificial saliva, produced the highest mean SBS (22.1 MPa, SD 2.2 MPa). The lowest mean value (5.8 MPa, SD 1.1 MPa) was obtained with the control group thermo-cycled (6000 cycles). There was a significant difference between the experimental primers (p<0.001) and artificial ageing (p<0.001). We conclude that 25% HEMA inclusion in silane primer could provide satisfactory adhesion strength, and 500 cycles of thermo-cycling (ISO TR 11450) does not correlate with 1-year artificial saliva storage for enamel bonding test.