Adsorption of H2S on carbonaceous materials of different dimensionality

The effect of the dimension of carbonaceous systems, from two to zero, on the adsorption strength of H₂S is investigated by density functional theory based methods. To this end, a carbon nanocone (CNC), a (3, 3) carbon nanotube ((3, 3)-CNT), and graphene (G) are chosen as models for zero-, one- and two-dimensional systems, respectively. Pristine G and CNC have low tendency to adsorb H₂S but on the (3, 3)-CNT the molecule adsorbs dissociatively and deforms the surface. The effect of doping the surface of these materials with Ti has also been investigated. The presence of Ti modifies H₂S adsorption capability to the point that it is chemically adsorbed on the three decorated surfaces although H₂S adsorption on Ti decorated graphene appears to be different from two other doped surfaces. Only in this case, the H₂S molecule dissociates and releases hydrogen atoms which form H₂ molecule. The resulting H₂ molecule is physisorbed on the Ti-decorated graphene surface and the S atom adsorbs directly on the Ti atom. The density of states of pristine, Ti decorated and H₂S adsorbed nanostructures demonstrate that the systems change their conductivity and magnetic properties.     

Fabrication of interpenetrating polymer network to enhance the biological activity of synthetic hydrogels

A three dimensional porous hydrogel with suitable biological and mechanical properties are required for bone tissue engineering. Hydrogels of poly(lactic-ethylene oxide fumarate) (PLEOF), crosslinked with poly(ethylene glycol)-diacrylate (PEG-da) have desirable mechanical properties, however, their application for bone regeneration is limited due to the lack of cell motif sites within their structure. The aim of this study was to incorporate a naturally derived polymer such as gelatin into PLEOF hydrogels to promote their biological properties. Interpenetrating polymer network (IPN) was used as an efficient technique to acquire uniform mixture of these two polymers. Additionally gas foaming agents were used to create pores with average diameter of 250 μm in these IPN hydrogels. The concentrations of PEG-da and gelatin were optimized to tune the mechanical strength and degradation properties of these hydrogels. A compression modulus of 500 kPa was achieved for hydrogel fabricated with 400 mg/ml PLEOF, 200 mg/ml PEG-da and 150 mg/ml gelatin. The addition of gelatin to PLEOF elevated the compression modulus by two-fold and decreased the energy loss by 40%. The result of protein analysis demonstrated that IPN substantially enhanced the retention of physically crosslinked gelatin in the 3D structure of hydrogel. More than 50% of gelatin was retained in IPN hydrogel after two weeks of incubation in simulated physiological environment. Preserving gelatin in the hydrogel structure provides cell motif sites for a longer period of time, which is desirable for uniform cell proliferation. In vitro studies showed that primary human osteoblast cells adhered and proliferated in PLEOF-gelatin hydrogel. These results demonstrated the potential of using this IPN hydrogel for bone tissue engineering.     

Disinfection effectiveness of organic chloramines, investigating the effect of pH

The disinfection effectiveness of three organic N-chloramines (chlorinated amino acids and peptides) on the bacteria Escherichia coli (E. coli) was investigated, including a more detailed study into the pH dependency of the disinfection effectiveness of N-chloroglycine. The organic N-chloramines were prepared by combining sodium hypochlorite with each amino acid or peptide (glycine, Ala-Ala and Arg-Gly-Asp-Ser), at a N:Cl molar ratio of 1:0.4, and then used to treat E. coli suspensions for 180 min.No evidence of inactivation was observed at pH 8.1 for any of the tested organic N-chloramines. At pH 6.0 and 6.9, E. coli inactivation with N-chloroglycine was characterized by an initial lag phase, during which little or no measurable inactivation occurred, followed by a pseudo-first-order inactivation. This is in accordance with other results in the literature and supports the two step microbial inactivation mechanism proposed by some authors. Inactivation rate coefficients (Chick-Watson and lag coefficients) were calculated by fitting the experimental data with the Rennecker-Mariñas model. pH-dependent inactivation kinetics were observed, with faster inactivation rates occurring at lower pH values, when temperature and chlorine-to-nitrogen ratio where kept constant.N-chloroglycine was determined to be the only contributor to the inactivation process in these experiments. The free chlorine contribution was considered to be negligible in all experiments due to its very low concentration. As well, given that the anionic form of N-chloroglycine is expected to be the single predominant species over the tested pH range, changes in residual N-chloroglycine speciation could not be responsible for the observed pH-dependency of E. coli inactivation. However, while pH stress was considered as a possible synergistic factor, no significant effect of pH stress on E. coli viability was observed at the tested pH levels.     

The effect of citric acid on the phenolic contents of olive oil

Response surface methodology was used to optimise the combined effects of malaxation time (t) and aqueous citric acid solution (C_A) added at the beginning of the malaxation step on total polyphenols (TP) and o-diphenols (OD) content and the antiradical power (ARP) of the olive oil extracted from the Italian olive fruits of Coratina cultivar. Different tests were performed according to a 3² full factorial design, varying t from 30 to 90 min and the C_A from 5 to 15 ml/kg_paste. Overall optimal conditions identified by a numerical optimisation for the three responses were found to be at t = 30 min and C_A = 13.79 ml/kg_paste under which the model predicted TP = 604.52 μgCAE/g_oil, OD = 80.44 μgCAE/g_oil and ARP = 28.73 μgDPPH/μlextract. There were also linear correlations between TP (R² = 0.8176) and OD (R² = 0.8633) values of olive oil and waste water. The results of this study demonstrate that considerably short malaxation time and relatively small amounts of citric acid were required to enhance the quality of olive oil. The outcome of our study will therefore be of great value for the commercial production of olive oil with high level of polyphenols and o-diphenols.     

Prevalence of overweight and obesity among indigenous populations in Canada: A systematic review and meta-analysis

Previous studies on overweight and obesity among indigenous peoples in Canada have been inconclusive. A systematic review was conducted on the prevalence of overweight and obesity among Canadian indigenous populations. Major bibliographic databases were searched for relevant studies published between January 1990 and June 2013. We reviewed 594 abstracts and included 41 studies in the meta-analyses. Using the heterogeneity test (Cochrane Q) results, the overall prevalence was estimated using fixed- or random-effects model. Nonadults (<18 years) had a pooled prevalence of overweight and obesity at 29.8% (95% CI: 25.2–34.4) and 26.5% (95% CI: 21.8–31.3), respectively. The pooled prevalence of overweight and obesity among adults were 29.7% (95% CI: 28.2–31.2) and 36.6% (95% CI: 32.9–40.2), respectively. Adult males had higher overweight prevalence than females (34.6% vs. 26.6%), but lower obesity prevalence (31.6% vs. 40.6%). Nonadult girls had higher prevalence than boys [overweight: 27.6%; 95% CI: 22.6–32.7 vs. 24.7%; 95% CI: 19.0–30.5; obesity: 28.6%; 95% CI: 20.3–36.9 vs. 25.1%; 95% CI: 13.8–36.4]. Nonadult Inuit had the highest overweight and lowest obesity prevalence. Although Inuit adult had the lowest prevalence of overweight (28.7%; 95% CI: 27.3–30.2) and obesity (32.3%; 95% CI: 25.5–39.1), it was relatively high. This study highlights the need for nutritional intervention programs for obesity prevention among indigenous populations in Canada.     

Estimating density of supercritical carbon dioxide and methane using modified thermodynamic models

Since the density is an important thermodynamic property of the fluid in the wide field of experimental and theoretical studies, in this work, the density of CO₂ and CH₄, as prominent supercritical fluids in industrial processes was investigated. To that end, five equation of state (EOS) models were used to estimate density of aforementioned. Deviation of each EOS models is validated and then they were modified to achieve lower errors in density prediction. Accordingly, their adjusted correlations reduced the average absolute errors to lower than 5.6%.     

Bifurcation analysis of the Poincaré map function of intracranial EEG signals in temporal lobe epilepsy patients

In this paper, the Poincaré map function as a one-dimensional first-return map is obtained by approximating the scatter plots of inter-peak interval (IPI) during preictal and postictal periods from invasive EEG recordings of nine patients suffering from medically intractable focal epilepsy. Evolutionary Algorithm (EA) is utilized for parameter estimation of the Poincaré map. Bifurcation analyses of the iterated map reveal that as the neuronal activity progresses from preictal state toward the ictal event, the parameter values of the Poincaré map move toward the bifurcation points. However, following the seizure occurrence and in the postictal period, these parameter values move away from the bifurcation points. Both flip and fold bifurcations are analyzed and it is demonstrated that in some cases the flip bifurcation and in other cases the fold bifurcation are the dynamical regime underlying epileptiform events. This information can offer insights into the dynamical nature and variability of the brain signals and consequently could help to predict and control seizure events.     

Fluorescein isothiocyanate‐dyed mesoporous silica nanoparticles for tracking antioxidant delivery

This study investigated the cellular uptake of fluorescein isothiocyanate‐labelled mesoporous silica nanoparticles (FITC‐MSNs), amine‐functionalised FITC‐MSNs (AP‐FITC‐MSNs) and their gallic acid (GA)‐loaded counterparts. Mesoporous silica nanoparticles were labelled with fluorescein isothiocyanate, functionalised by 3‐aminopropyltriethoxysilane (APTES) (AP‐FITC‐MSNs) and then loaded by GA. All nanoparticles were characterised by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy, and X‐ray diffraction. The cytotoxicity of different concentrations of dyed nanoparticles was investigated using (3‐(4,5‐trihydroxybenzoic acid, dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide) assay and flow cytometry. TEM images showed that the average particle sizes of FITC‐MSNs and AP‐FITC‐MSNs were about 100 and 110 nm, respectively. These nanoparticles were internalised by Caco‐2 cells, accumulated and dispersed into the cytoplasm, nucleus, and subcellular organelles. Nanoparticles containing GA clearly decreased the viability of cells. FITC‐MSNs showed no toxicity on Caco‐2 cells at concentrations of ≤50 µg/ml. Functionalisation of FITC‐MSNs using APTES decreased toxicity effects on the cells. It was found that FITC‐MSNs can be applied at low concentrations as a marker in the cells. In addition, AP‐FITC‐MSNs showed better biocompatibility with Caco‐2 cells than FITC‐MSNs, because of their positive surface charges.Inspec keywords: mesoporous materials, porosity, nanoparticles, dyes, silicon compounds, nanocomposites, nanofabrication, nanomedicine, cellular biophysics, molecular biophysics, biochemistry, transmission electron microscopy, Fourier transform infrared spectra, X‐ray diffraction, toxicology, particle size, biomedical materials, surface charging, cancerOther keywords: fluorescein isothiocyanate‐dyed mesoporous silica nanoparticles, antioxidant delivery tracking, cellular uptake, amine‐functionalised FITC‐MSNs, gallic acid‐loaded counterparts, 3‐aminopropyltriethoxysilane, transmission electron microscopy, TEM, Fourier transform infrared spectroscopy, X‐ray diffraction, cytotoxicity, dyed nanoparticles, (3‐(4,5‐trihydroxybenzoic acid‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide) assay, flow cytometry, particle sizes, AP‐FITC‐MSNs, Caco‐2 cells, cytoplasm, subcellular organelles, cell viability, biocompatibility, positive surface charges, SiO₂      

Cloud-point preconcentration and spectrophotometric determination of trace amounts of molybdenum(VI) in steels and water samples

A cloud-point extraction process using micelle of the cationic surfactant CTAB to extract Mo(VI) from aqueous solutions was investigated. The method is based on the color reaction of molybdenum with bromopyrogallol red in the presence of potassium iodide at pH 1.0 glycine/HCl buffer media and micelle-mediated extraction of complex. The optimal extraction and reaction conditions (e.g., surfactant concentration, reagent concentration and effect of time) were studied and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration and improvement factors) were obtained. Linearity was obeyed in the range of 0.3-320.0 ng mL(-1) of molybdenum(VI) ion and the detection limit of the method was 0.1 ng mL(-1). The relative standard deviation (R.S.D.) and relative error for five replicate measurements of 65.0 ng mL(-1) Mo(VI) were 1.1% and 1.9%, respectively. The interference effect of some anions and cations was also tested. The method was applied to the determination of molybdenum(VI) in steels and tap water and well water samples.