Electrostastic control of spontaneous curvature in catanionic reverse micelles

By means of small-angle neutron scattering and conductivity measurements, we study the microstructure of octylammoniumoctanoate/octane/water catanionic reverse microemulsions with an excess of anionic or cationic surfactant. Increasing the surface charge makes the microemulsion able to incorporate much more water than in the neutral case, up to 10 water molecules per surfactant. Even with charges in the surfactant film, wormlike micelles are present in the microemulsion domain. Along water dilution lines, the classical rod-to-sphere transition due to the minimization of the curvature energy of the rigid surfactant film is observed. When temperature is decreased, a re-entrant phase transition associated with the liquid-gas equilibrium of attractive cylinders is observed. Using the framework of the Tlusty-Safran theory, attraction could originate from junctions between wormlike reverse micelles. In any case, the spontaneous curvature of the catanionic surfactant film depends on both the temperature and the net charge, whatever the sign of the latter.     

Mathematical modeling of TE CO2 laser with SF6 as a saturable absorber

A mathematical model describing the dynamic emission of a single mode TE CO₂ laser with saturable absorber has been adapted. A six-temperature model has been used to describe the amplifying medium, while a four-coupled energy level is used to describe the selective absorbing medium. The suggested mathematical model allows the investigation of the effects of the intracavity absorber on the mode characteristics of the TE CO₂ laser and, moreover, the study of the effect of the laser input parameters on the output laser pulse. The model simulates the passive Q-switch in both low- and high-pressure cases in the absorbing medium.

In addition, numerical solutions of a non-linear rate equation system of the suggested model are quantitatively discussed. The solutions describe the photon number density, the population inversion and the energy transfer processes of amplifying and absorbing media.     

The Coagulation Impact of 50% Epoxidised Natural Rubber Chain in Ethylene Carbonate-Plasticized Solid Electrolytes

In this research, thin, soft and flexible free standing films can be obtained from poly (methyl methacrylate) (PMMA)/50% epoxidised natural rubber (ENR 50)/lithium triflate (LiCF₃SO₃) blends. However, phase separation is observed on the surface of the films which indicates that the blending is not homogeneous. The blend became more homogeneous when ethylene carbonate (EC) plasticizer is introduced into the blend system. However, the anti-plasticization effect of EC on ENR 50 occurs at lower concentration of EC at which the rubber became coagulated due to immiscibility of the rubber with EC plasticizer during solution casting. These ENR 50 coagulates can be observed as large solid structures in the Field Emission Scanning Electron Microscope (FESEM) micrographs of the EC-plasticized rubber-based electrolytes. The presence of these coagulates, hinder the migration of lithium ions in the system and also trap the lithium ions within the coil. This in turn reduced the number of free lithium ions that contribute to the ionic conduction. As a result, the conductivity of the un-plasticized PMMA/ENR 50/LiCF₃SO₃ film dropped drastically by two orders of magnitude.     

QuEChERS method combined with GC‒MS for pesticide residues determination in water

A miniaturized, QuEChERS based, liquid–liquid extraction method followed by gas chromatography–mass spectrometry was developed and validated for pesticide residues determination in water. Malathion, chlorpyrifos, profenofos, chlorfenapyr, pyriproxyfen, λ-cyhalothrin, coumaphos and α-cypermethrin were selected for this study. The accuracy, precision, specificity, linearity, limit of detection and limit of quantification were evaluated. The recovery ranged from 85.3 to 107% with RSD ranging from 1.8 to 15.4%. The linearity showed reliable range (0.995–0.999). The limit of detection ranged from 0.3 to 4 μg/L. Matrix effect was evaluated. The obtained results meet the European Commission standard legislations, implying that our method can be considered accurate and reproducible. The validated method was used to analyze river and well water samples. No residues of the investigated pesticides were detected in all collected water samples.     

Cardinality enrichment of flexible cross correlation (FCC) code for SAC-OCDMA system by alleviation interference scheme (AIS)

In this paper, we propose an alleviation interference scheme (AIS) for spectral amplitude coding (SAC) – optical code division multiple access (OCDMA) coding system approaches. The AIS SAC-OCDMA systems is demonstrated by utilizing the new flexible cross correlation (FCC) code. The FCC code has advantages, such as flexibility in-phase cross-correlation at any given number of users and weights, as well as effectively reduces the impacts of phase-induced intensity noise (PIIN) and has the multiple-access interference (MAI) cancelation property. The results indicated good performance whereas the FCC (W = 4, K = 150) AIS SAC-OCDMA coding system offers 66%, 172%, 650% and 900% percentage of cardinality enrichments as a contrast to DCS (W = 4, K = 90), MDW (W = 4, K = 55), MFH (W = 4, K = 20) and Hadamard (W = 8, K = 15) codes, respectively. Finally, the FCC AIS SAC-OCDMA coding system has low effective receive power Psr = −21 dBm which is expected to be more significant for future SAC-OCDMA coding systems without requiring any amplification at the receiving plant.     

Optical band gap and conductivity measurements of polypyrrole-chitosan composite thin films

Electrical conductivity and optical properties of polypyrrole-chitosan（PPy-CHI） conducting polymer composites have been investigated to determine the optical transition characteristics and energy band gap of composite films.The two electrode method and I-V characteristic technique were used to measure the conductivity of the PPy-CHI thin films,and the optical band gap was obtained from their ultraviolet absorption edges.Depending upon experimental parameter,the optical band gap（E_g） was found within 1.30-2.32 eV as estimated from optical absorption data.The band gap of the composite films decreased as the CHI content increased.The room temperature electrical conductivity of PPy-CHI thin films was found in the range of 5.84×10^-7-15.25×10^-7 S·cm^-1 depending on the chitosan content.The thermogravimetry analysis（TGA） showed that the CHI can improve the thermal stability of PPy-CHI composite films.     

Investigation of the intracavity frequency doubling of a gain-switched InGaAs/GaAs pulsed diode laser

A mathematical model describing the dynamic emission of the intracavity frequency doubling (IFD) of a gain-switched two-section InGaAs/GaAs diode laser has been presented. One section is electrically pumped to provide gain, while the second section is unpumped (reverse biased) to provide a saturable absorber. The three-dimensional physical problem is reduced to one-dimensional model using adiabatic approximation, which allows the separation of the wavefunction. The suggested model in this paper allows studying the impact of the variations of the input InGaAs/GaAs/KTP diode laser parameters on the output pulsation characteristics. The proposed mathematical model is solved numerically using fourth-order Runge-Kutta method. The numerical calculations reflect the influence of the variation of the applied gain current and saturable bias current on the output laser pulse characteristics. The numerical results show good consistency with the available experimental data in references.     

Honey: a novel antioxidant

The global prevalence of chronic diseases such as diabetes mellitus, hypertension, atherosclerosis, cancer and Alzheimer's disease is on the rise. These diseases, which constitute the major causes of death globally, are associated with oxidative stress. Oxidative stress is defined as an "imbalance between oxidants and antioxidants in favor of the oxidants, potentially leading to damage". Individuals with chronic diseases are more susceptible to oxidative stress and damage because they have elevated levels of oxidants and/or reduced antioxidants. This, therefore, necessitates supplementation with antioxidants so as to delay, prevent or remove oxidative damage. Honey is a natural substance with many medicinal effects such as antibacterial, hepatoprotective, hypoglycemic, reproductive, antihypertensive and antioxidant effects. This review presents findings that indicate honey may ameliorate oxidative stress in the gastrointestinal tract (GIT), liver, pancreas, kidney, reproductive organs and plasma/serum. Besides, the review highlights data that demonstrate the synergistic antioxidant effect of honey and antidiabetic drugs in the pancreas, kidney and serum of diabetic rats. These data suggest that honey, administered alone or in combination with conventional therapy, might be a novel antioxidant in the management of chronic diseases commonly associated with oxidative stress. In view of the fact that the majority of these data emanate from animal studies, there is an urgent need to investigate this antioxidant effect of honey in human subjects with chronic or degenerative diseases.     

Fructose might contribute to the hypoglycemic effect of honey

Honey is a natural substance with many medicinal properties, including antibacterial, hepatoprotective, hypoglycemic, antioxidant and antihypertensive effects. It reduces hyperglycemia in diabetic rats and humans. However, the mechanism(s) of its hypoglycemic effect remain(s) unknown. Honey comprises many constituents, making it difficult to ascertain which component(s) contribute(s) to its hypoglycemic effect. Nevertheless, available evidence indicates that honey consists of predominantly fructose and glucose. The objective of this review is to summarize findings which indicate that fructose exerts a hypoglycemic effect. The data show that glucose and fructose exert a synergistic effect in the gastrointestinal tract and pancreas. This synergistic effect might enhance intestinal fructose absorption and/or stimulate insulin secretion. The results indicate that fructose enhances hepatic glucose uptake and glycogen synthesis and storage via activation of hepatic glucokinase and glycogen synthase, respectively. The data also demonstrate the beneficial effects of fructose on glycemic control, glucose- and appetite-regulating hormones, body weight, food intake, oxidation of carbohydrate and energy expenditure. In view of the similarities of these effects of fructose with those of honey, the evidence may support the role of fructose in honey in mediating the hypoglycemic effect of honey.     

Applications of supercritical fluid extraction (SFE) of palm oil and oil from natural sources

Supercritical fluid extraction (SFE), which has received much interest in its use and further development for industrial applications, is a method that offers some advantages over conventional methods, especially for the palm oil industry. SC-CO? refers to supercritical fluid extraction (SFE) that uses carbon dioxide (CO?) as a solvent which is a nontoxic, inexpensive, nonflammable, and nonpolluting supercritical fluid solvent for the extraction of natural products. Almost 100% oil can be extracted and it is regarded as safe, with organic solvent-free extracts having superior organoleptic profiles. The palm oil industry is one of the major industries in Malaysia that provides a major contribution to the national income. Malaysia is the second largest palm oil and palm kernel oil producer in the World. This paper reviews advances in applications of supercritical carbon dioxide (SC-CO?) extraction of oils from natural sources, in particular palm oil, minor constituents in palm oil, producing fractionated, refined, bleached, and deodorized palm oil, palm kernel oil and purified fatty acid fractions commendable for downstream uses as in toiletries and confectionaries.