Synthesis, characterization, and biological activities of organosoluble and thermally stable xanthone-based polyamides

A series of polyamides, poly (xanthone-amide)s (PXAs) were prepared by direct polycondensation of 2,7-diaminoxanthone with various available aliphatic and aromatic dicarboxylic acids. The monomer and all the PXAs were characterized by FT-IR, ¹H NMR and ¹³C NMR. The prepared polyamides showed inherent viscosities in the range of 0.41–0.68 dL g^?1 in NMP at 25 °C. The PXAs with low crystallinity were soluble in aprotic polar solvents such as DMF, NMP, DMSO, and DMAc at room temperature. These PXAs showed low glass transition temperatures (T _g) (200–310 °C) and high thermal stability, the 10 % weight loss temperature was up to 432 °C under nitrogen. These polymers exhibited strong UV–Vis absorption maxima at 301–316 nm in NMP solutions. Their photoluminescence showed fluorescence emission maxima around 433–444 and 503–521 nm for aliphatic and aromatic polyamides, respectively. The resulting polymers were analyzed for their antioxidant activities using DPPH assay and the antibacterial activities against some bacterial strains (S. aureus, B. subtilis, E. coli and P. aeruginosa). The results revealed that the antioxidant and antibacterial activities of PXAs were more than xanthone nucleus and used standard, respectively. It showed that these polymers can be used in pharmaceutical and food industries (food packaging).     

Polyimide/organo‐montmorillonite nanocomposites: A comparative study of the organoclays modified with aromatic diamines

Six organophilic clays have been obtained through cation‐exchange between sodium montmorillonite (Na^+‐Mt) and the hydrochloride salts of aromatic diamines (DA1–6). The results obtained by thermogravimetric analysis (TGA) showed that the organophilic clays start to decomposition within 150–340°C, which shows that they are thermally stable compared with conventional montmorillonite modified with aliphatic long‐chain quaternary alkyl ammonium salts. The highest thermal stability and interlayer basal spacing were observed for the organoclay obtained from 3,3′‐sulfonyl dianiline (DA2), and therefore it was chosen for preparing clay/polymer nanocomposite materials (CPN). Polyimide/clay nanocomposite materials consisting of benzophenone‐3,3′,4,4′‐tetracarboxylic dianhydride (BTDA) and 2‐(5‐(3,5‐diaminophenyl)‐1,3,4‐oxadiazole‐2‐yl)pyridine (POBD) were also obtained by an in situ polymerization reaction through a thermal imidization. DA2‐Mt was used as filler at different concentrations. Both the thermal stability and the glass transition temperature (T_g) are increased with respect to pure polyimide (PI) at low clay loadings. At high clay concentrations, the organoclay particles make aggregate and as results of this phenomena T_g and thermal stability are decreased. POLYM. COMPOS., 36:613–622, 2015. © 2014 Society of Plastics Engineers     

Utilizing ultraviolet photooxidation as a pre‐treatment of volatile organic compounds upstream of a biological gas cleaning operation

Laboratory experiments were conducted to evaluate the potential to utilize ultraviolet (UV) photooxidation as a pre‐treatment to render recalcitrant volatile organic compounds into more biodegradable compounds. α‐Pinene was selected due to its low water solubility and low biodegradability. α‐Pinene‐contaminated gaseous streams with inlet loadings between 250 and 2500 g m^?3 h^?1 were passed through an annular reactor equipped with a UV lamp that emitted light at 254 nm and 185 nm wavelengths. The outlet stream containing UV photooxidation intermediates was then sparged through nanopure water that was then analyzed for its total organic carbon (TOC) content and subjected to batch biodegradability tests. UV photooxidation effectively degraded α‐pinene with a maximum removal rate of about 700 g m^?3 h^?1. The removal rate followed first order kinetics at low inlet loadings (less than 1200 g m^?3 h^?1) and approached zero order behavior at higher inlet loadings. The principal oxidizing species in the reactor was ozone. Of the total α‐pinene removed, measured as TOC, 50% was converted to water‐soluble and more biodegradable intermediates. The biodegradability of the resultant intermediates was similar to that of methyl ethyl ketone (MEK), which is 3–30 times more biodegradable than α‐pinene. These results show that the use of UV photooxidation is a promising and effective pre‐treatment technique for enhancing the biodegradability of hydrophobic and recalcitrant organic compounds such as α‐pinene. Copyright © 2004 Society of Chemical Industry     

Age-related and vasomotor stimuli-induced changes in renal vascular resistance detected by Doppler ultrasound

Indirect measurement of renal vascular resistance by duplex Doppler waveform analysis was evaluated in relation to aging and some pathophysiological conditions. Baseline renal resistive index (RRI) (peak systolic frequency shift - lowest diastolic frequency shift/peak systolic frequency shift) was measured in healthy controls aged 20 to 85 years by analyzing the blood flow velocity waveform of interlobar arteries. RRI changes induced by sympathetic activation (cold pressor test and handgrip test) or by fluid load were evaluated. Both repeatability and reproducibility were very good, as the intra and interoperator variations were all less than their reproducibility coefficients. RRI showed a significant increase with aging (ANOVA P < .001), particularly evident in subjects older than 50 years. Both the cold pressor test and handgrip test induced in all the subjects (n = 16) a significant increase in RRI (P < .001), from 0.59 +/- 0.04 to 0.69 +/- 0.04 (12 +/- 6%) for the cold pressor test and from 0.57 +/- 0.03 to 0.66 +/- 0.03 (15 +/- 2%) for the handgrip test. In eight subjects intravenous fluid load (0.25 mL/kg/min of 0.9% NaCl for 120 min) caused a significant decrease in RRI (P < .001), from 0.62 +/- 0.02 to 0.53 +/- 0.01 (17 +/- 2%), which was inversely related to mean blood pressure rise (r = 0.71, P < .001). These data show that pulsed wave Doppler analysis is an accurate method for an indirect evaluation of changes in renal vascular resistance induced by common vasomotor stimuli.     

An investigation of water-flow pressure distribution on bridge piers under flood loading

This study simulates the flood effect on piers using a finite volume method in the ANSYS-FLUENT package. The pier is modelled as a non-structural column with a rectangular and a circular cross-section. To simplify the methodology, the pier, as well as the bed and side walls, is assumed to have non-slip boundaries for the fluid domain. A crucial feature of this investigation is the consideration of the effect of water while it is flowing around an object like a bridge pier and the distribution of pressure along the pier height. A numerical model is proposed to explore the influence of variation of velocity on the hydrodynamic force and pressure distribution exerted on piers. A significant finding is that the shape of the pier cross-section has a significant effect on the fluid pressure exerted on bridge piers under flood loading. It is noted that the AS5100 method is appropriate for a conservative estimation of the pressure on rectangular piers, whereas the technique will have a risky safety margin for bridge piers with a circular cross-section and need to be used with caution.     

New strategies in model order reduction of trajectory piecewise‐linear models

Model order reduction based on trajectory piecewise linearization (TPWL) is a beneficial technique for approximating nonlinear models. One efficient method for building projection matrix in TPWL reduction is by aggregation of projection matrices of linearization points (LPs). However, in this method, the size of projection matrix will also grow up by increasing the number of LPs, which yield the increment of the size of reduced model. In other words, the size of reduced model will depend on the number of LPs. In this paper, we will address this issue and propose two new strategies for obviating this problem. Contrarily to former works in TPWL modeling, we established a model via TWPL based on output weighting of parallel linear models. Then, we proposed two reduction strategies for suggested TPWL model. The first algorithm inspires from former works in this field but in a parallel structure that enable segregation of projection matrices whereas the second algorithm remedies the problem by considering the high‐order TPWL model as a unit linear model and reduces this model like a linear model but uses back projection method for constructing different outputs. The efficiency of methods is shown by comparison with former TPWL methods through vast simulations. Copyright © 2015 John Wiley & Sons, Ltd.     

Behaviour of a Moving Droplet under Electrowetting Actuation: Numerical Simulation

Numerical simulation of droplet transport in microchannels under electrostatic actuation is investigated. Volume‐of‐Fluid (VOF) technique is employed, in which electrowetting effects are implemented through Lippmann's relation in the form of modified contact angles at the boundary. A velocity of about 35 mm/s is achieved with the actuation of 40 V. The droplet flow under electrowetting actuation is characterized for the majority of the process parameters such as actuation voltage, channel dimension, electrode size, and resultant velocity.     

Compounding fibre grade polyethylene terephthalate with a hyperbranched additive and studying its dyeability with a disperse dye

A hyperbranched polymer which comprised a polyesteramide structure was used to study improvements in dyeability of fibre grade polyethylene terephthalate films. The optical measurements of the dyed samples showed that, by increasing the percentages of the dendritic additive, K/S as a dye uptake parameter changed in the presence or absence of a carrier. The amount of chroma increased while the hue did not change significantly. The dyeability of the prepared samples was attributed to the decrease in glass transition temperature and the lower crystallinity of the polymer, as studied by differential scanning calorimetry. Thus, a new fibre grade polyethylene terephthalate, which is dyeable, could be obtained, with less need to use a toxic carrier compound.