STUDYING THE EFFECT OF DIFFERENT ADDITIVES ON THE THERMAL CONDUCTIVITY AND MECHANICAL CHARACTERISTICS OF EPOXY-BASED COMPOSITE MATERIALS

The current paper deals with investigating the effect of two different fillers on the thermal and mechanical characteristics of epoxy-based composite. The filler used throughout the study are: charcoal and Pyrex, both of them are different in nature and have not been investigated thoroughly or even compared fairly in terms of their effect on polymer matrix. Further, they can be considered as a cheap filler, charcoal can be obtained from a simple pyrolysis process of plants (charcoal) and Pyrex waste can be collected easily. Both types are added to the selected matrix with volume percent ranged from 10 to 60 with increments of 10. To ensure a fair comparison, the particle size is fixed (is about 1.7 micrometer). The results showed that the epoxy thermal conductivity has enhanced by about two orders of magnitudes over the studied range of filler. In terms of mechanical properties, the charcoal improves the tensile strength about 84% at 60% volume fraction while the Pyrex effect is about 40% at the same filler level. On the contrast, the results of compressive strength do not show an appreciable improvement overall. It decreases by about 12% at 60% volume fraction of charcoal while increases about the same percent with Pyrex at the same filler level.

Central airway and peripheral lung structures in airway disease dominant COPD

The concept that the small airway is a primary pathological site for all COPD phenotypes has been challenged by recent findings that the disease starts from the central airways in COPD subgroups and that a smaller central airway tree increases COPD risk. This study aimed to examine whether the computed tomography (CT)-based airway disease-dominant (AD) subtype, defined using the central airway dimension, was less associated with small airway dysfunction (SAD) on CT, compared to the emphysema-dominant (ED) subtype.COPD patients were categorised into mild, AD, ED, and mixed groups based on wall area percent (WA%) of the segmental airways and low attenuation volume percent in the Kyoto-Himeji (n=189) and Hokkaido COPD cohorts (n=93). The volume percent of SAD regions (SAD%) was obtained by nonrigidly registering inspiratory and expiratory CT.The AD group had a lower SAD% than the ED group and similar SAD% to the mild group. The AD group had a smaller lumen size of airways proximal to the segmental airways and more frequent asthma history before age 40 years than the ED group. In multivariable analyses, while the AD and ED groups were similarly associated with greater airflow limitation, the ED, but not the AD group, was associated with greater SAD%, whereas the AD, but not the ED group, was associated with a smaller central airway size.The CT-based AD COPD subtype might be associated with a smaller central airway tree and asthma history, but not with peripheral lung pathologies including small airway disease, unlike the ED subtype.

Spermatogenesis, gonadal sperm reserves and fertility of rabbits fed micro doses of fumonisin

The effects of micro doses of dietary fumonisin, a metabolite of Fusarium verticillioides, on spermatogenesis, gonadal sperm reserves and fertility of rabbits were studied. Relative paired testis weight; sperm production rate and sperm storage potential were not adversely affected in rabbits which were exposed to varied minute levels of dietary fumonisin of about 153-161 µg/kg body weight/day over a period of 8 weeks. The toxin also failed to exert any influence (P>0.05) on seminiferous tubular diameter and volume percent of testicular elements. Male fertility as evidenced by conception rate, litter size and embryo survival and normalcy was also not affected (P>0.05). However, the frequency of occurrence of stages II and VIII of the cycle of the seminiferous epithelium were significantly (P<0.05) influenced with increased dietary fumonisin levels. The results suggest that the ingestion of Fusarium-infected feed that would result in the liberation of about 153 µg of fumonisin/kg of body weight per day for a short time may not influence spermatogenesis, fertility in the male or the normalcy of the resulting foetuses.

Dynamic Stability Analysis in Hybrid Nanocomposite Polymer Beams Reinforced by Carbon Fibers and Carbon Nanotubes

The objective of this innovative research is assessment of dynamic stability for a hybrid nanocomposite polymer beam. The considered beam formed by multiphase nanocomposite, including polymer–carbon nanotubes (CNTs)–carbon fibers (CFs). Hence, as to compute the effective material characteristics related to multiphase nanocomposite layers, the Halpin–Tsai model, as well as micromechanics equations are employed. To model the structure realistically, exponential shear deformation beam theory (ESDBT) is applied and using energy methods, governing equations are achieved. Moreover, differential quadrature method (DQM) as well as Bolotin procedures are used for solving the obtained governing equations and the dynamic instability region (DIR) relative to the beam is determined. To extend this novel research, various parameters pinpointing the influences of CNT volume fraction, CFs volume percent, boundary edges as well as the structure’s geometric variables on the dynamic behavior of the beam are presented. The results were validated with the theoretical and experimental results of other published papers. The outcomes reveal that increment of volume fraction of CNT is able to shift DIR to more amounts of frequency. Further, rise of carbon fibers volume percent leads to increase the excitation frequency of this structure.

Refractive Index Border Associated with Nonlinear Optical Properties in Superhybrid Transparent TiO2 Nanoparticles-Polymer: Great Potential for Ultrafast Optical Waveguide in Optical Communication

The excellency of a superhybrid material based TiO2 nanoparticles (NPs) has been improved by the surface modification of the TiO2 with a coupling agent of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane to render them highly compatible with organic monomer mixtures avoiding aggregation. Such TiO2 NPs are then attached with a polymer. The border of linear refractive index of hybrid TiO2 NPs-polymer is enhanced in comparison with that of pure epoxy resin or polymer. Nonlinear refractive index and nonlinear absorption coefficient of hybrid TiO2 NPs-polymer are measured by femtosecond Z-scan technique at 800 nm. This hybrid material has been fabricated and studied to have a great potential for ultrafast optical waveguide in optical communication quantified by the propagation loss of the hybrid TiO2 NPs-polymer optical waveguide in the range of 4.79 to 11.90 dB/cm, which is depending on the volume percent of TiO2 NPs

Amorphous Mixtures of Ice and C60 Fullerene

Carbon and ice make up a substantial proportion of our Universe. Recent space exploration has shown that these two chemical species often coexist including on comets, asteroids and in the interstellar medium. Here we prepare mixtures of C₆₀ fullerene and H₂O by vapor co-deposition at 90 K with molar C₆₀:H₂O ratios ranging from 1:1254 to 1:5. The C₆₀ percolation threshold is found between the 1:132 and 1:48 samples, corresponding to a transition from matrix-isolated C₆₀ molecules to percolating C₆₀ domains that confine the H₂O. Below this threshold, the crystallization and thermal desorption properties of H₂O are not significantly affected by the C₆₀, whereas the crystallization temperature of H₂O is shifted towards higher temperatures for the C₆₀-rich samples. These C₆₀-rich samples also display exotherms corresponding to the crystallization of C₆₀ as the two components undergo phase separation. More than 60 volume percent C₆₀ is required to significantly affect the desorption properties of H₂O. A thick blanket of C₆₀ on top of pure amorphous ice is found to display large cracks due to water desorption. These findings may help understand the recently observed unusual surface features and the H₂O weather cycle on the 67P/Churyumov–Gerasimenko comet.

Amorphous Mixtures of Ice and C60 Fullerene

Carbon and ice make up a substantial proportion of our Universe. Recent space exploration has shown that these two chemical species often coexist including on comets, asteroids and in the interstellar medium. Here we prepare mixtures of C₆₀ fullerene and H₂O by vapor co-deposition at 90 K with molar C₆₀:H₂O ratios ranging from 1:1254 to 1:5. The C₆₀ percolation threshold is found between the 1:132 and 1:48 samples, corresponding to a transition from matrix-isolated C₆₀ molecules to percolating C₆₀ domains that confine the H₂O. Below this threshold, the crystallization and thermal desorption properties of H₂O are not significantly affected by the C₆₀, whereas the crystallization temperature of H₂O is shifted towards higher temperatures for the C₆₀-rich samples. These C₆₀-rich samples also display exotherms corresponding to the crystallization of C₆₀ as the two components undergo phase separation. More than 60 volume percent C₆₀ is required to significantly affect the desorption properties of H₂O. A thick blanket of C₆₀ on top of pure amorphous ice is found to display large cracks due to water desorption. These findings may help understand the recently observed unusual surface features and the H₂O weather cycle on the 67P/Churyumov–Gerasimenko comet.

The effect of garnet and muscovite on the recrystallized grain size of quartz from general shear experiments

&lt;p&gt;To investigate the role of strong and weak secondary phases on the recrystallized grain size of quartz, we performed grain size analyses on quenched samples from general shear experiments on quartz-garnet and quartz-muscovite mixtures. Six general shear experiments were conducted in the Griggs apparatus; three with mixtures of quartz-garnet (vol.% garnet 5, 15, 30) and three with mixtures of quartz-muscovite (vol.% muscovite 5, 10, 25). The starting powders for both set of experiments were synthetic mixtures of quartz-muscovite or quartz-garnet with 0.1 wt.% water added. The quartz-garnet experiments were conducted at 900&amp;#176;C, a pressure of 1.2 GPa, and a shear strain rate of ~10&lt;sup&gt;-5&lt;/sup&gt; s&lt;sup&gt;-1&lt;/sup&gt;, while the quartz-muscovite experiments were conducted at 800&amp;#176;C, a pressure of 1.5 GPa, and a shear strain rate of ~10&lt;sup&gt;-5&lt;/sup&gt; s&lt;sup&gt;-1&lt;/sup&gt;. At these deformation conditions quartz is stronger than muscovite and weaker than garnet. We observed that the bulk strength of the aggregate decreases with a greater volume percent of muscovite and increases with a greater volume percent of garnet. Garnet at these conditions does not deform plastically. The presence of secondary phases within the deforming aggregate causes stress concentrations and partitioning of strain rate between the different phases relative to the measured bulk stress and strain rate. The degree of partitioning is primarily related to the rheology and volume percent of the phases. Due to the piezometric relationship between recrystallized grain size and stress, we can use the quartz recrystallized grain size to determine the local stress of quartz in the experiments and compare it to the measured bulk stress. The results from these analyses will provide new insight into the effect of strain partitioning in general and of strong and weak secondary phases on quartz rheology.&lt;/p&gt;

INFRARED THERMOCHEMICAL GAS AND VAPOR DETECTOR STUDY

The results of experimental study of the thermochemical gas and vapor detector (ITCGVD) are given. Functional principle of this detector is based on the measurement of infrared radiation intensity formed during catalytic combustion of flammable gases and vapors on the pellistor surface. The ITCGVD scheme is described. It contains the measuring and the comparing cells equipped with pellistors and infrared diodes working in photogalvanic mode and a counter connected ensuring their signal difference formation, which is registered after amplification by a potentiometer. The dependences of ITCGVD signal on most important parameters were determined as a result of experimental study with use of impulse method of analyzing gases input. These parameters are as follows: analyzing gas concentration in carrier gas (air) flow, a pellistor supply voltage, a distance of a pellistor from infrared photodiode window, carrier gas flow rate. The possibility of ITCGVD use in alerters and analyzers of flammable gasses and vapors micro concentration in air was determined. Experimental correlation of detector signal to hydrogen, methane and propane volume concentration in air was developed. Possibility of ITCGVD application in gas chromatography by using the analysis of calibration gas-air mixture is shown. Basic metrological characteristics of ITCGVD were determined. They are as follows: sensitivity threshold 4 . 10–5 volume percent, maximum concentration within a linear statistical characteristic – 0.4 volume percent; linear dynamic range 1 . 104; the drift of apparent zero signal – 0.6 mV/h; time constant 0.3…1 s (depends on carrier gas flow). Measuring and comparing cell volume was 0.3 ml.

Investigation of Micellization and Viscometric Behaviour of Organo-copper Soap-urea Complexes Derived from Various Edible Oils

Background: Of-late researches in colloid chemistry are becoming increasingly important in various branches of chemistry, industry, medicine and allied fields. Copper surfactants derived from various edible oils provide an interesting area of investigation pertaining to its fundamental information regarding their colloid-chemical behaviour. Copper (II) soaps and their urea complexes in polar and non-polar solvents have gained considerable popularity due to their immense use and widespread applications such as wood preservation, foaming, wetting, biocidal, pesticidal activities, fungicidal, detergency, emulsification, paints, lubrication etc. Objective: Present work has been initiated with a view to obtain a profile due to the nature and structure of copper soap and their urea complexes with long chain fatty acids in polar and non-polar solvent, which have great significance in explaining their characteristics under different conditions. The objective of the present work is study of micellar characterizations of copper soap and their urea complexes in polar (methanol) and non-polar (benzene) solvents of varying composition and subsequent determinations of CMC using physical properties such as, viscosity. This will provide fundamental information regarding their colloid chemical behavior. Methods: The density, molar volume, viscosity, specific viscosity, and fluidity of Cu (II) soap- urea complexes derived from various edible oils in a benzene-methanol solvent system have been determined at a constant temperature of 303.15 K. Results: Results: The results were used to determine the critical micelle concentration (CMC), soap complex-solvent interactions and the effect of chain length of the surfactant molecules on various parameters. The values of the CMC in the higher volume percent of methanol are higher than those of the lower volume percent of methanol. The values of CMC for these complexes are following the order: CSoU>CSeU> CGU > CMU : This shows that there is a decrease in the CMC values with an increase of the average molecular weight of the complex. The conclusions with regard to solute-solute and solutesolvent interactions have been discussed in terms of the well-known Moulik’s and Jones- Dole equations. The effect of surfactant concentration on the viscosity of the solution in the solvent mixtures has been discussed. The observations suggested that the solvent structure breaking effect by the solute on the solvent molecules is more prominent above the CMC as compared to below the CMC. Conclusion: The vital information about the micellar behavior of synthesized molecules as a solute and their interactions with different solvents will plays an important role in various industrial and biological applications.