Atomic simulation of adsorption of SO2 pollutant by metal (Zn, Be)-oxide and Ni-decorated graphene: a first-principles study.

Due to the impact of toxic gases on human health, considerable interest has been shown in detecting noxious air pollutants, particularly sulfur dioxide (SO2), both experimentally and theoretically. This work provides new insights into the adsorbing (SO2) molecules on the surface of metal-oxide graphitic structures, i.e., Beryllium-Oxide (BeO), Zinc-Oxide (ZnO), and Ni-decorated graphene applying a first-principles study. Computational analyses suggest that the type of binding of SO2 molecule on BeO and ZnO sheets is physisorption so that binding energies of -0.405 and -0.154 eV were assigned to ZnO and BeO nanosheets in that order. The adsorption energy of SO2 on metal oxide sheets was much higher than the pristine graphene. Taking pristine graphene as an adsorbent for SO2 molecule, it was found that such nanomaterial is not an efficient adsorbent due to the weak interactions (-0.157 eV) and low electron charge transfer (0.042 e) present in SO2/graphene complex. To overcome this issue, graphene nanosheets decorated with nickel atoms were studied for interaction with SO2 molecules; the results indicate that the SO2 molecules were chemisorbed on Ni-decorated graphene sheets with an adsorption energy of -2.297 eV. Chemisorption of SO2 molecules on Ni-decorated graphene sheets was proven by the strong orbital hybridization between Ni 3d and sulfur 3p orbitals in the Projected Density of States (PDOS) plot. This work provides useful information about SO2 adsorption on Ni-decorated graphene sheets in order to develop a new class of gas sensing devices. Superior chemisorption of SO2 on Ni-decorated graphene sheets compared to the physical adsorption on BeO and ZnO sheets makes Ni-decorated graphene a potential candidate for detecting SO2 molecules.

Mechanical Properties of C3N Nanotubes from Molecular Dynamics Simulation Studies.

Although the properties of carbon nanotubes (CNTs) are very well-known and are still extensively studied, a thorough understanding of other carbon-based nanomaterials such as C3N nanotubes (C3NNTs) is still missing. In this article, we used molecular dynamics simulation to investigate the effects of parameters such as chirality, diameter, number of walls, and temperature on the mechanical properties of C3N nanotubes, C3N nanobuds, and C3NNTs with various kinds of defects. We also modeled and tested the corresponding CNTs to validate the results and understand how replacing one C atom of CNT by one N atom affects the properties. Our results demonstrate that the Young's modulus of single-walled C3NNTs (SWC3NNTs) increased with diameter, irrespective of the chirality, and was higher in armchair SWC3NNTs than in zigzag ones, unlike double-walled C3NNTs. Besides, adding a second and then a third wall to SWC3NNTs significantly improved their properties. In contrast, the properties of C3N nanobuds produced by attaching an increasing number of C60 fullerenes gradually decreased. Moreover, considering C3NNTs with different types of defects revealed that two-atom vacancies resulted in the greatest reduction of all the properties studied, while Stone-Wales defects had the lowest effect on them.

Kinetics of Cross-Linking Reaction of Epoxy Resin with Hydroxyapatite-Functionalized Layered Double Hydroxides.

The cure kinetics analysis of thermoset polymer composites gives useful information about their properties. In this work, two types of layered double hydroxide (LDH) consisting of Mg2+ and Zn2+ as divalent metal ions and CO32- as an anion intercalating agent were synthesized and functionalized with hydroxyapatite (HA) to make a potential thermal resistant nanocomposite. The curing potential of the synthesized nanoplatelets in the epoxy resin was then studied, both qualitatively and quantitatively, in terms of the Cure Index as well as using isoconversional methods, working on the basis of nonisothermal differential scanning calorimetry (DSC) data. Fourier transform infrared spectroscopy (FTIR) was used along with X-ray diffraction (XRD) and thermogravimetric analysis (TGA) to characterize the obtained LDH structures. The FTIR band at 3542 cm-1 corresponded to the O-H stretching vibration of the interlayer water molecules, while the weak band observed at 1640 cm-1 was attributed to the bending vibration of the H-O of the interlayer water. The characteristic band of carbonated hydroxyapatite was observed at 1456 cm-1. In the XRD patterns, the well-defined (00l) reflections, i.e., (003), (006), and (110), supported LDH basal reflections. Nanocomposites prepared at 0.1 wt % were examined for curing potential by the Cure Index as a qualitative criterion that elucidated a Poor cure state for epoxy/LDH nanocomposites. Moreover, the curing kinetics parameters including the activation energy (Eα), reaction order, and the frequency factor were computed using the Friedman and Kissinger-Akahira-Sunose (KAS) isoconversional methods. The evolution of Eα confirmed the inhibitory role of the LDH in the crosslinking reactions. The average value of Eα for the neat epoxy was 54.37 kJ/mol based on the KAS method, whereas the average values were 59.94 and 59.05 kJ/mol for the epoxy containing Zn-Al-CO3-HA and Mg Zn-Al-CO3-HA, respectively. Overall, it was concluded that the developed LDH structures hindered the epoxy curing reactions.

Effect of Daylight on Melatonin and Subjective General Health Factors in Elderly People.

BACKGROUND: This paper investigated the effect of daylight on morning and night melatonin, subjective general health using GHQ questionnaire, sleepiness and alertness on elderly who lived in nursing houses. METHODS: Nineteen nursing home residents participated voluntarily. They exposed to daylight from 9 to 10 a.m. and from 4 to 5 p.m. for 6 wk. The level of melatonin in the morning and at night was measured. General health of all participants was evaluated using General Health Questionnaire (GHQ) as well. RESULTS: Daylight exposure significantly affected morning melatonin from 25.39 pg/ml to 59.77 pg/ml (P=0.001) and night melatonin were changed from 40.30pg/ml to 34.41pg/ml (P=0.081). Mean score of general health changed 36.31 to 29.89 (P=0.003). Karolinska Sleepiness Scale (KSS) and Visual Analogue Scale (VAS) showed increase sleepiness and decrease alertness from 3:00 to 7:00 a.m. Sleepiness decreased and alertness increased during 1:00 p.m. and 20:00 p.m. CONCLUSIONS: Daylight exposure could delay sleep phase and correction of circadian rhythm in elderly. Anxiety and insomnia could be improved with daylight exposure. It suggests that elders should be exposed to scheduled daylight in morning and evening for prevention and improvement of mental disorders. Adequate light should be provided for elder's homes and nursing house.

Spinal 5-HT3 receptor mediates nociceptive effect on central neuropathic pain; possible therapeutic role for tropisetron.

OBJECTIVES: To test the analgesic effect of 5-HT-3 receptor antagonist, tropisetron, in a clip compression injury model of spinal cord pain in rats. METHODS: Four weeks post compression of the spinal cord at lumbar level, tropisetron was administered intrathecally at 100 µg and 150 µg dosages. Behavioral tests were assessed before administration. Fifteen minutes after injection, behavioral tests were repeated. Randall-Sellitto and plantar test was used for mechanical and thermal hyperalgesia, respectively. Mechanical and cold allodynia were evaluated by Von Frey filament and acetone droplets, respectively. The analgesic effect of tropisetron was compared with intrathecal administration of salicylate. Locomotor score was evaluated by Basso, Beattie and Bresnahan (BBB) test every week after spinal cord injury. RESULTS: Intrathecal administration of tropisetron, decreased hyperalgesia and mechanical allodynia, but not cold allodynia were observed after compression of the spinal cord. CONCLUSION: Blockade of 5-HT-3 receptors by tropisetron at the spinal level induces an antinociceptive effect on chronic central neuropathic pain and suggests that this compound may have potential clinical utility for the management of central neuropathic pain, particularly in patients with hyperalgesia and tactile allodynia.