Preparation of quaternary boro-phosphate multifunctional glasses and their structural,optical, switching and antibacterial properties

In this paper, the glass composition of (50-x)P₂O₅-xB₂O₃-30CuO-20Li₂O (x?=?0, 5, 10, 15, and 20?mol%) was prepared and the effect of P₂O₅ substitution by B₂O₃ on their structural, optical, switching, and antibacterial characteristics was studied. FT-IR spectra showed that an increase in the B₂O₃ content leads to gradual erosion of the phosphate characteristic bonds, and the emergence of borate-related ones by creating new linkages between phosphate chains through P–O–B bonds and formation of highly cross-linked P³-O-B⁴ linkages. The incorporation of boron up to 20?mol%, also leads to an overall increase in glass transition temperature together with a decrease in the molar volume which both, implied improvement of glass stability. Optical studies revealed that all glasses are almost transparent in the UV–Vis region with high band gap energy about 3.83?eV, which experiences a red-shift with increase in the B₂O₃ concentration to 15?mol%. By calculating the wavelength-dependent optical parameters, however, it was found that the present glass composition with highest concentration of B₂O₃ shows refractive index near one and very negligible extinction coefficient (and imaginary optical dielectric function) at the visible region. These results support the great potential of the mentioned glass composition as a window layer. The analysis of the high electric field measurements demonstrated a wide range reduction in switching threshold voltage as the B₂O₃ content increases. This hints at their potential application as electrical-induced sensors. The antibacterial activity of x?=?0 and x?=?5 glass compositions has been examined by zone of inhibition measurements and it was found that they have potential applications as antibacterial agent.     

Nonlocal and surface effects on the buckling behavior of flexoelectric sandwich nanobeams

In this article, an analytical approach is presented to study the surface and flexoelectric effects on the buckling characteristics of an embedded piezoelectric sandwich nanobeam. According to the nonlocal elasticity theory, the flexoelectricity is believed to be authentic for size-dependent properties in nanostructures. The boundary conditions and the governing equations are derived by Hamilton's principle and are solved by Navier method. The results obtained from the present work show that the nonlocal term has an important reduction on the critical load and also the flexoelectricity shows an increasing influence on the buckling loads of the sandwich nanobeam, especially at lower thicknesses.     

Investigation of chemical keys for relationship between plants and their unifloral honeys by hydrodistillation and SPME and biological activities of honeys

Volatile compounds of unifloral honeys and their plants essential oils obtained by hydrodistillation (EOH) and solid phase micro extraction (EOS) methods were investigated and compared with each other for the first time. The results exhibited presence of volatile compounds of plant such as o-cymene and carvacrol in Thymus, cis-linalool oxide in Citrus, aliphatic hydrocarbons in Citrus and Astragalus and hexadecanoic acid (palmitic acid) in Astragalus and Medicago honeys. The amounts of terpenes were decreased by increasing molecular weight in EOS, while this pattern does not occur in EOH. Total phenols and antioxidant activities were increased from Citrus to Thymus honey (Citrus < Medicago < Astragalus < Thymus). In antibacterial assay, Thymus honey showed the most potential inhibition to all the experimented strains of bacteria. Increase in phenol content may be an effective factor for antibacterial activity of honey against Escherichia coli, Staphylococcus aureus and Bacillus subtilis. It seems that active compounds with antioxidant properties were responsible for growth inhibition effect on E. coli and S. aureus.     

Optimizing nanoencapsulation of Heracleum lasiopetalum by response surface methodology

This study was carried out to optimize formulation for Heracleum lasiopetalum (golpar) extract nanoencapsulation by response surface methodology (RSM). The primary water-in-oil emulsion was fabricated by (5%–10%) golpar extract (GE), (40%–35%) emulsifier span 80 (EM), and (50%–60%) sunflower oil (SO). The coating materials were the mixture of Lepidium sativum seed gum (LSG) and whey protein concentrate (WPC) at different ratios (1:0, 1:1, and 0:1). The yield of nanoencapsulation of GE, particle size, and zeta potential was investigated as responses of RSM. The optimal formulation for water-in-oil-in-water emulsion of GE were SO: 50.46%, GE 9.52%, and EM: 36.30% in LSG, SO: 57.07%, GE: 7.12%, and EM: 30.85% in LSG:WPC, and SO: 54.98%, GE: 9.05%, and EM: 39.87% in WPC coating. In conclusion, the nanoencapsulation of GE prepared with the optimized formulation by RSM ensures the gradual release and higher stability to sedimentation during storage with nanometric size and high yield of encapsulation. The nanocapsules of GE can be used as a natural antioxidant in food systems.     

Pricing and ordering decisions in a supply chain with imperfect quality items and inspection under buyback of defective items

In this article, the economic production and inventory model in a three-layer supply chain including one distributor, one manufacturer and one retailer for a single-product and general demand functions under three scenarios is developed. We assume that during the production process, both healthy and defective items are generated. As the first scenario, we develop the first model, in which the defective items are not reworked and all considered as scrape, while in the second model, we assume that the defective items are reworked and are sold as perfect item. In the second scenario, we assume that defective item can be sold with lower price than the selling price. Moreover, raw materials with imperfect quality are sent back from a distributor to outside supplier under a lower price. Determining the order quantity of the distributor and the selling prices of the distributor and the manufacturer as well as the retailer was the goal of this article such that the total profit of each member is maximised. In order to solve the models, the Stackelberg approach is employed between the members, and the concavity of the profit functions is proved using several theorems. Then, closed form solutions are derived for the decision variables and a solution algorithm is proposed to determine the optimal solutions. Finally, a numerical example is presented to illustrate the applicability of the model.     

Preparation of SnO2 Nanoparticles from a New Tin(IV) Complex: Spectroscopic and Photoluminescence Studies

A new dimethyltin(IV) complex, {[Me₂Sn(O₂CNC₉H₆)]₂O}₂ (1), was prepared by reaction of dimethyltin(IV) dichloride with the quinoline-2-carboxylic acid and characterized by elemental analysis, IR, ¹H-, ¹³C-, ¹¹⁹Sn-NMR spectroscopes. The structure of 1 was determined by single-crystal X-ray diffraction. The results showed that 1 is a tetranuclear, centrosymmetric dimeric, and contains two endo-cyclic five-coordinated and two exo-cyclic six-coordinated tin atoms and a N-atom of the 2-quinaldic carboxylate ligand coordinated to exo-cyclic tin. Complex 1 was utilized as a precursor for SnO₂ nanoparticles by direct thermal decomposition at 500 °C in air. The nano-structure of SnO₂ was characterized by scanning electron microscopy and X-ray powder diffraction. The SnO₂ core showed a band gap of ~4 eV determined from the UV/visible absorption spectrum. The SnO₂ nanoparticles show stable photoluminescence (PL) with an emission centered at 557 nm.     

Fabrication and characterization of a new MRI contrast agent based on a magnetic dextran–spermine nanoparticle system

This study aims to fabricate and formulate a new magnetic resonance imaging (MRI) contrast agent based on a dextran?Cspermine nanoparticulate system loaded with super paramagnetic iron oxide nanoparticles (SPION). SPION-loaded spermine?Cdextran nanoparticles were prepared according to a procedure based on the ionic gelation of dextran?Cspermine with sodium tripolyphosphate (TPP) anions. The effects of process parameters such as pH, concentration of spermine dextran, TPP to dextran?Cspermine and SPION to dextran?Cspermine weight ratios, and TPP addition rate were fully investigated to find the optimized formulation through the response surface methodology. At the optimum condition, 75% of the magnetic iron oxide nanoparticles added to the polymeric solution were entrapped in dextran?Cspermine nanoparticles. Samples were investigated by transmission electron microscopy. The mean particle size of the nanoparticles determined by particle size analyzer was found to be 65?nm at the optimum condition with zeta potential of +90?mV. The SPION-loaded dextran?Cspermine nanoparticle formulation has the same superparamagnetic properties as SPIONs and at same iron concentration the saturation magnetization (Ms) of the SPION-loaded dextran?Cspermine nanoparticles was larger than SPIONs. In vitro MRI was performed with gradient echo and spin-echo sequences at 1.5?T. By increasing of iron concentration, the T ₂ relaxation times were reduced. Thus, indicating that the saturation magnetization and r ₂ and $ r_{2}^{*} $ relaxivities were enhanced, and the contrast effects were improved in comparison to commercial SPIONs.     

Symbol Timing Acquisition for Collaborative OFDM WLAN-Based A-GPS

Wide deployment of the 802.11g/n protocols for implementing next generation WLAN has encouraged research on the integration of these networks and GPS as a promising approach to enhance GPS for indoor positioning. WLAN, or WiFi, using the 802.11 standards, can be employed in several different ways as a complementary positioning technology for GPS navigation and the two can be used in an integrated framework to provide a continuous and robust positioning service. This paper presents receiver-level integration of 802.11g OFDM signals and GPS for a WiFi-based assisted-GPS acquisition in a multipath NLOS environment. Although previous research has been conducted to accomplish A-GPS systems using assistance information from other wireless networks (such as cellular networks), a lack of research exists to exploit 802.11 WLAN signals in order to provide complete assistance information including frequency, approximate user position and fine time assistance. Several practical time-domain OFDM timing techniques are evaluated under multipath conditions and an algorithm for relative time estimation is developed that is sufficient to enable an effective and complete WiFi-based A-GPS service. The proposed system can be deployed in places where WiFi coverage is available and where there is no or limited access to other synchronized systems. Examples include WiFi enabled mobile devices deployed on university campuses, hospitals and shopping malls, or tablet computers being used on public WiFi networks.