Chemical composition and bioactivities of the polyphenolic-rich extract of Ormenis africana Jord. and Fourr

Ormenis africana is an endemic North African species used in folk medicine because of its hypoglycemic property. In this study, the α-amylase and α-glucosidase inhibition and antioxidant activities of the polyphenolic-rich extract from O. africana were determined. The chemical composition was made using liquid chromatography with photodiode array and electrospray ionization mass spectrometry method and the identification of phenolics was assessed by comparing their retention times and ultraviolet and mass spectra with those of the standards and/or reported in the literature. The total phenolic content was estimated by the Folin–Ciocalteu method. The antidiabetic potential was estimated by the determination of α-amylase and α-glucosidase inhibition in vitro. Four assays were used for the evaluation of antioxidant activity of the extracts. Seventeen phenolic compounds were detected. The major peaks are chlorogenic acid, 5-O-di-caffeoylquinic acid, and apigenin and luteolin derivatives. The polyphenolic-rich extract showed remarkable α-amylase and α-glucosidase inhibition activity in a concentration dependent manner. Furthermore, the extract also demonstrated high antioxidant activities. O. africana can serve as a potential natural source for the development of a novel α-amylase and α-glucosidase inhibitory agents against diabetic complications.     

New class of liquid crystalline epoxy resins: Synthesis and properties

A new class of liquid crystalline epoxy resins has been developed by reacting the diglycidyl ether of bisphenol A (DGEBA) with two new mesogenic diols, 3,3′-dimethoxy-4,4′-di(hydroxyhexoxy)-N-benzylidene-o-tolidine and 4,4′-di(6-hydroxyhexoxy)-N-benzylidene-o-tolidine, containing azomethine groups. Fourier transformed infra-red (FT-IR), nuclear magnetic resonance (NMR) spectroscopy and CHN elemental analysis were used to confirm the chemical structures of these azomethine mesogenic diols. Cure reaction between DGEBA and the mesogenic diols were carried out with different ratios 1:1, 1:2 and 2:1. The mesogenic phase transitions for azomethine mesogenic diols and cured polymers were examined by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). Thermal, mechanical and adhesion properties were then investigated for the cured polymers based on new azomethine mesogenic diols. The cured polymers were found to exhibit high thermal stability, flexibility and good adhesion properties compared to conventional resins.     

Nicotine, cotinine, and myosmine determination using polymer films of tailor-designed zinc porphyrins as recognition units for piezoelectric microgravimetry chemosensors

Two electropolymerizable zinc porphyrins with receptor sites tailor-designed for selective recognition of the nicotine, cotinine, or myosmine alkaloids were synthesized. These were 5-(2-phenoxyacetamide)-10,15,20-tris(triphenylamino)porphyrinato zinc(II) 1 and 5-(2,5-phenylene-bis(oxy)diacetamide)-10,15,20-tris(triphenylamino)porphyrinato zinc(II) 2 featuring one and two pendant amide side "pincers", respectively, and three triphenylamine substituents at the meso positions of the porphyrin macrocycles capable of electrochemical polymerization. Thin polymerfilms of these porphyrins served for recognition and the piezoelectric microgravimetry (PM) for analytical signal transduction of a new chemical sensor devised for determination of these alkaloids. The films were deposited by potentiodynamic electropolymerization on the 10 MHz quartz resonators of the electrochemical quartz crystal microbalance (EQCM) without affecting the electronic structure of the porphyrin macrocycles. Under favorable flow injection analysis (FIA) conditions, the alkaloid analytes were determined at the concentration level of 0.1 mM with high sensitivity and selectivity. Affinity toward the analytes of the polymer of 2 was higher than that of 1 due to the higher binding ability offered by two pendant pincers of the former. Because of the selective receptors and PM applied under FIA conditions, the developed procedure offered an alternative to the time-consuming and relatively expensive high-performance liquid chromatography (HPLC), capillary electrophoresis (CE), and gas chromatography mass spectrometry (GC-MS) methods of detection and quantification of these alkaloids.     

Microfluidic mixing using pulsating flows

Mixing of biological species in microfluidic channels is challenging since the mixing process is limited by the small mass diffusion coefficient of the species and by the dominance of viscous effects, captured by the low value of Reynolds number characteristic of laminar liquid flow in microchannels. This paper investigates the use of pulsating flows to enhance mixing in microflows. The dependence of the degree of mixing on various dimensionless groups is investigated. These dimensionless numbers are Strouhal number, pulse amplitude divided by base velocity, Reynolds number, location along the mixing channel normalized by the channel width, channel cross section aspect ratio, and phase difference between the inlet streams. The degree of mixing, observed to experience both spatial fluctuations down the mixing channel and temporal fluctuations over a pulsation cycle at the quasi-stationary state, is shown to be most sensitive to changes in pulsation amplitude and frequency. For a fixed pulsation amplitude and Reynolds number, the degree of mixing has a peak value for a certain Strouhal number above and below which the degree of mixing decreases. Increasing the pulsation amplitude improves mixing with the behavior becoming asymptotic at large pulsation amplitudes. The temporal fluctuations in the degree of mixing over a cycle at the quasi-stationary state decrease and the average degree of mixing increases downstream the mixing channel. The fluctuations are also smaller at higher values of the Strouhal number and are generally larger for larger pulsation amplitudes. This study also takes into account the rate of work input required to overcome viscous effects. While this power input is independent of the pulsation frequency, it exhibits a parabolic dependence on the pulsation amplitude. Finally, considering the dependence of the degree of mixing (mean and standard deviation), mixing length, and energy consumption on these dimensionless groups, examples of the trade-off that has to be made in choosing the operating conditions based on different constraints are presented.     

Natural-Convection Heat Transfer in Channels With Isoflux Convex Surfaces

Numerical solutions are presented for laminar natural convection heat transfer in channels with convex surfaces that are subjected to a uniform heat flux. Simulations are conducted for several values of Grashof number (10 to 10⁴) and radius of curvature (1 to ∞). The governing elliptic conservation equations are solved in a boundary-fitted coordinate system using a collocated control-volume-based numerical procedure. The results are presented in terms of streamline and isotherm plots, inlet mass flow rates, curved wall temperature profiles, maximum hot wall temperature estimates, and average Nusselt number values. At the lowest radius of curvature, computations reveal the formation of recirculation zones in the exit section for all values of Grashof number considered. For a radius of curvature equal to or greater than 2, recirculation does not occur at any Grashof number. For values of radius of curvature between 1 and 2, the value of Grashof number at which recirculation occurs decreases with increasing values of the former. The variation in the buoyancy-induced volume flow rate is highly nonlinear with respect to the radius of curvature, and the value of the radius of curvature at which the volume flow rate is maximum increases with increasing Grashof number. The value of radius of curvature at which the maximum hot wall temperature is minimized increases with Grashof number. For all configurations studied, the average Nusselt number increases with increasing Grashof number values. Correlations for maximum wall temperature and average Nusselt number are provided.     

Bacterial indicators of faecal pollution in the waters of the El-Kabir River and Akkar watershed in Syria and Lebanon

Water samples for bacterial analyses were taken, when possible, at 41 sites in Lebanon and Syria in the El‐Kabir River watershed. Samples were analysed for total coliform (TC), faecal coliform (FC) and faecal streptococcus. The Lebanese samples also were analysed for the presence of sulphate‐reducing bacteria. The TC and FC concentrations were extremely high throughout the watershed, rendering the water unfit for any human uses. The origin of the bacteria is the untreated sewage waste from the numerous settlements situated throughout the watershed. This primary origin is supported by high ratios of FC/faecal streptococcus, although impacts from animal wastes also were observed. The bacterial levels were higher in summer than in winter, indicating a high winter river flow that dilutes a relatively constant source of human sewage discharged to the system. Spring waters also exhibited elevated levels of bacteria, implicating surface land use and waste disposal practices upstream of the springs. The data clearly shows that human health is at a high risk and that strategies for improving water quality and protecting spring water must be expeditiously implemented.     

Involvement of Acidic Amino Acid Residues in Zn2+ Binding to Respiratory Complex I

Proton transfer across membranes and membrane proteins is a central process in biological systems. Zn²⁺ ions are capable of binding to acidic residues, often found within such specific pathways, thereby leading to a blockage. Here we probed Zn²⁺inhibition of the proton‐pumping NADH:ubiquinone oxidoreductase from Escherichia coli by means of electrochemically induced FTIR difference spectroscopy. Numerous conformational changes were identified including those that arise from the reorganization of the membrane arm upon electron transfer in the peripheral arm of the protein. Signals at very high wavenumbers (1781 and 1756 cm^?1) point to the perturbation of acidic residues in a highly hydrophobic environment upon Zn²⁺ binding. In variant D563N^L, which lacks part of the proton pumping activity (residue located on the horizontal amphipathic helix), the spectral signature of Zn²⁺ binding is changed. Our data support a role for this residue in proton translocation.     

Towards Sustainable Water Quality: Management of Rainwater Harvesting Cisterns in Southern Palestine

Environmental management of rainwater harvesting in southern Palestine is required to reduce the continuously increasing demand for fresh water from limited water aquifers and to reduce the adverse health impact on the people drinking harvested rainwater. This continuously increasing demand for fresh water requires the enhancement of environmental conditions surrounding the cistern owners’ awareness to tackle the mismanagement that contributed to rainwater contamination. In this study, 100 cisterns were sampled and tested for physiochemical and microbiological parameters. Most of the tested physiochemical parameters were within the acceptable limits of WHO and Palestinian standards except turbidity, calcium and magnesium where 24%, 47% and 32% of the samples were non-conforming, respectively. The pH values of the collected rainwater ranged from 7.32 to 8.97 with a mean value of 8.16. The nitrate analysis results range from 1.5 to 7.0 mg/L, with a mean value of 4.2 mg/L. High percentage of cisterns were found to be contaminated with total Coliforms (TC) and faecal Coliforms (FC) with percentages of 95% and 57%, respectively, rendering the cistern water unacceptable for drinking purposes. 78% of samples had a severe degree of contamination for which water needs flocculation, sedimentation then chlorination to become suitable for drinking. On the other hand, based on FC data, none of the tested samples for FC was a “high risk”, but 57% of them were categorized with “simple” to “moderate risk” and 43% were “no risk” cisterns. A cistern owner’s survey was utilized to reveal the roots behind this contamination. Different remediation measures, such as cleaning cisterns and rainwater collection surfaces and discarding water from the first season storm, were recommended to enhance and protect the cistern water quality.     

Effect of weathering on physical,mechanical and morphological properties of chemically modified wood materials

Physical, mechanical and morphological properties of chemically modified Acaciamangium and Acacia hybrid woods were investigated after weathering. The wood blocks prepared from Acaciamangium and Acacia hybrid, were treated with both propionic anhydride and succinic anhydride. Outdoor (natural) weathering was carried out for 1 year, by exposing the samples to external environmental conditions. Chemical modification enhanced the weathering resistance of Acacia spp. to discoloration, weight loss and mechanical properties. Also, succinic anhydride was better in protecting wood than propionic anhydride modification. Fast growing Acaciamangium and Acacia hybrid may be promising for the use of outdoors following propionic anhydride and succinic anhydride chemical treatments.     

Bubble hydrodynamic influence on oxygen transfer rate at presence of cationic and anionic surfactants in electroflotation process

In this work, the effects of the presence of surfactants in the liquid phase and the hydrodynamic regime of the bubble flow on the oxygen transfer rate were investigated in an electroflotation process ...