A Model of the Relationship Between Psychosocial Variables and Diurnal Cortisol Rhythm Under Chronic Stress by Using Structural Equations

By using structural equations, we investigated the effect of chronic stress on salivary cortisol rhythm and proposed a causal model of chronic stress by using psychosocial and physiological data. First, 111 healthy workers (48 males, 63 females) completed questionnaires on chronic stress and lifestyle habits. Then, they provided saliva samples and answered questionnaires that were prepared to assess their psychological states 5 times (on waking up and at 10:00, 11:40, 14:00, and 16:00) on workdays. Structural equation modeling (SEM) revealed that chronic stress and longer commuting time resulted in sleep irregularities and this disrupted the cortisol circadian rhythm. This suggests that chronic stress disrupts the cortisol circadian rhythm even in healthy individuals, and sleep regularity mediates the effect of chronic stress on the cortisol rhythm.

     

Preparation and Aqueous Properties of Starch‐grafted Polyacrylamide Copolymers

In the present work, starch‐grafted polyacrylamide copolymers were prepared and their rheological properties, either in water or in water‐based muds, were investigated. The advantages in using starches as substrates to prepare additives which are suited for improving stability and the rheological properties of water‐based muds, lie in their low cost, and their lower biodegradability than native starches. Thus, various copolymer series were prepared by free‐radically grafting acrylamide (AM) onto starch using ceric ammonium sulphate (CAS) as initiator. It is shown that the intrinsic viscosity and the molecular weight of the grafted starches are controlled by the initiator and monomer concentrations. Furthermore, to predict the behaviour of the samples under oil‐well conditions, the aqueous solution properties of the copolymers such as water solubility, viscosity, shear rate, were determined as function of temperature, salt concentration and type, and aging time. The knowledge of these properties is a prerequisite for the use of the copolymers in drilling fluids. The data indicate that starch‐grafted polyacrylamide copolymers as compared to the non‐modified starch, behave as shear‐thinning, are salt resistant, and their rheological properties are stable with time. The grafted starches as prepared above were also added to water‐based mud and the rheological properties of the resulting muds were determined under oil‐well conditions. Grafted starches, having high AM contents, are more efficient in decreasing the filtrate volume, and increasing the plastic viscosity of the muds, when compared to PAC‐L, a modified cellulosic polymer used in the filtration control of most water‐based muds. Such improvements in the rheological properties of the muds were found to result from the behaviour and/or properties of the grafted starches in water.     

Adsorption and surface properties of silica with transformer insulating oils

The presence of polar species in transformer insulating oil may cause degradation and electric discharges in the power transformer. Such oil polar fraction can originate either from the neat oil and/or from its oxidative degradation in the power transformer. The aim of this study is to examine the relation between the insulating oil and the electrical properties of its polar fraction in order to predict eventual failure in the power transformer.We investigate at ambient temperature the adsorption of the polar fractions of various transformers insulating oils (a new and two used oils) from the neat oils onto silica particles. The adsorbed amount was higher for the used oils as compared to the new one. Infrared spectra of the polar fraction indicate the presence of hydroxyl, aromatic and carboxyl functional groups that are found in the asphaltenes compounds. Microelectrophoresis study of the oil polar fraction covered silica particles gives negatively charged oil polar fraction. Such oil surface charge depends on the pH and results from the ionisation of the oil acidic surface groups. Finally, we obtain a good correlation between the amount of the oil polar fraction and the magnitude of the zeta potential at the water/oil-silica interface.     

Efficient Light‐Emitting Devices Based on Phosphorescent Polyhedral Oligomeric Silsesquioxane Materials

Synthesis, photophysical, and electrochemical characterizations of iridium‐complex anchored polyhedral oligomeric silsesquioxane (POSS) macromolecules are reported. Monochromatic organic light‐emitting devices based on these phosphorescent POSS materials show peak external quantum efficiencies in the range of 5–9%, which can be driven at a voltage less than 10 V for a luminance of 1000 cd m^?2. The white‐emitting devices with POSS emitters show an external quantum efficiency of 8%, a power efficiency of 8.1 lm W^?1, and Commission International de'lÉclairage coordinates of (0.36, 0.39) at 1000 cd m^?2. Encouraging efficiency is achieved in the devices based on hole‐transporting and Ir‐complex moieties dual‐functionalized POSS materials without using host materials, demonstrating that triplet‐dye and carrier‐transporting moieties functionalized POSS material is a viable approach for the development of solution‐processable electrophosphorescent devices.     

Structural characterization and electrical properties of carbon nanotubes/epoxy polymer composites

The purpose of this study is to identify the relationship between the electrical and structural characteristics of multiwalled carbon nanotubes dispersed into the polymer matrix of a resin. In a first step, the composites were characterized by small‐angle neutron scattering, which provide information about the bulk dispersion of nanotubes in the matrix and form three‐dimensional networks with a surface fractal behavior. In the second step, a dielectric and electrical study was carried out in the frequency range between 1 Hz and 10 MHz at room temperature. We have found that the electric and dielectric behavior of these composites can be described by Jonscher's universal dielectric response. We show that the critical exponents describing the concentration dependence of the conductivity and the dielectric constant, obtained in the vicinity of the percolation threshold, are in good agreement with the theoretical values. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44514.     

New positive-type photosensitive polyimide: poly(hydroxyimide) with diazonaphthoquinone

A positive working photosensitive polyimide based on polyhydroxyimide (PHI) and 2,3,4-tris[1-oxo-2-diazonaphthoquinone-4-sulfonyloxy] benzophenone (D4SB) as a photoreactive compound has been developed. The PHI was prepared by the ring-opening polyaddition of 4,4′-hexafluoroisopropylidenebis(phthalic anhydride) (6FDA), 4,4′-diamino-4″-hydroxytriphenylmethane (DHTM), and 4,4′-oxydianiline (ODA), followed by thermal cyclization in refluxing xylene. The PHI film showed excellent transparency to UV light. The photosensitive polyimide containing 30 wt% of D4SB showed a sensitivity of 250 mJ/cm² and a contrast of 5.2 when it was exposed to 436 nm light followed by developing with a 1% aqueous tetramethylammonium hydroxide (TMAH) solution at 35°C.     

Simultaneous measurement of harmonics by a new measuring method

A harmonic measuring instrument using PICmicro® Microcontroller (PIC) and Phase Locked Loop (PLL), which was discussed in an earlier paper, has been improved. The developed instrument enables a continuous measurement for several days by an additional PIC for power management. A postprocessing program running on a Personal Computer (PC) has also been developed to rearrange the enormous data obtained by multipoint measurements. The developed instrument and the program make the observation of harmonic distribution easier. Harmonic measurements were carried out in buildings of a university campus with the developed instruments. The results shows that rectifier circuits within a building are sources of the harmonic voltages, while a distortion at another building is caused by a harmonic expansion due to a resonance between a line inductance and capacitances for power compensation. The measured characteristics are also confirmed by numerical simulations using Electro‐Magnetic Transient Program (EMTP). © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Polyaniline coated hematite sand supported on graphene oxide (HS@PANI-GO) as a new magnetic material for advanced catalytic oxidation based on sulfate radicals: optimization using response surface methodology

The cover image is based on the Research Article Polyaniline coated hematite sand supported on graphene oxide (HS@PANI-GO) as a new magnetic material for advanced catalytic oxidation based on sulfate radicals: optimization using response surface methodology by Abdellah Ait El Fakir et al., DOI: 10.1002/jctb.6070 .

     

Sized controlled synthesis, purification, and cell studies with silicon quantum dots

This article describes the size control synthesis of silicon quantum dots with simple microemulsion techniques. The silicon nanocrystals are small enough to be in the strong confinement regime and photoluminesce in the blue region of the visible spectrum and the emission can be tuned by changing the nanocrystal size. The silicon quantum dots were capped with allylamine either a platinum catalyst or UV-radiation. An extensive purification protocol is reported and assessed using (1)H NMR to produce ultra pure silicon quantum dots suitable for biological studies. The highly pure quantum dots were used in cellular uptake experiments and monitored using confocal microscopy. The results showed that the amine terminated silicon nanocrystals accumulated in lysosome but not in nuclei and could be used as bio-markers to monitor cancer cells over long timescales.