Fabrication and characterization of bioactive glass (45S5)/titania biocomposites

Bioactive glass (BG) (45S5) has been used successfully as bone-filling material in orthopedic and dental surgery but its lean mechanical strength limits its applications in load-bearing positions. Approaches to strengthen these materials decreased their bioactivity. In order to realize the optimal matching between mechanical and bioactivity properties, bioactive glass (45S5) was reinforced by introducing titania (TiO₂) in anatase form and treated at 1000 °C to form new bioactive glass/titania biocomposites. The prepared biocomposites were assessed by XRD, FT-IR, mechanical properties and SEM. The results verified that the increase of titania percentage to BG powder enhanced gradually the mechanical data of the prepared biocomposites. SEM and FT-IRRS confirmed the presence of a rich bone-like apatite layer post-immersion on the composite surface. It has been found that the new BG/titania biocomposite materials especially those containing high content of titania have high bioactivity properties and compressive strength values comparable to cortical bone. Therefore, these biocomposite materials are promising for medical applications such as bone substitutes especially in load-bearing sites.     

Functionalization of polymethylhydrosiloxane gels with an allyl ureido benzocrown ether derivative: Complexation properties

Crosslinked polymethylhydrosiloxane (PMHS) thin films prepared by sol–gel polycondensation have been functionalized by Pt‐catalyzed hydrosilylation of SiH groups with an allyl ureido crown ether precursor. To this purpose, both 4′‐allylurea‐benzo‐15‐crown‐5 ( 1 ) and 1‐allyl‐3‐propyl‐urea ( 2 ) were synthesized and characterized. We have shown that competitive side‐reactions occurred following hydrosilylation due to the hydrolysis of part of the SiH groups resulting in the formation of new crosslinks Si(CH₃)O_3/2 as shown by solid‐state ²⁹Si‐NMR. This is explained by the deactivation of the Pt catalyst toward hydrosilylation by amide groups. For thin films (～ 1 μm) prepared on silicon wafers, a quantitative method based on FT‐IR transmission spectroscopy was used to measure the crosslinking density of the network, and the percentage of functionalization (SiC %) following hydrosilylation. The results are discussed in relation to the mesh size of the network, and the diffusion of alkenes and water molecules within lightly crosslinked PMHS gels obtained by varying the amount of triethoxysilane crosslinker (mol %) from 15 to 1%. The self‐organization properties of ureido groups by H‐bonding were studied by FT‐IR for the functionalized thin films. The complexation properties of the crown ether 1 ‐functionalized thin films were evidenced by using FT‐IR following diffusion‐reactions of NaSCN and KSCN salts in CHCl₃ : MeOH solvent mixtures within thin films. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Nanoparticles as tool for enhanced ophthalmic delivery of vancomycin: a multidistrict-based microbiological study,solid lipid nanoparticles formulation and evaluation

Context: A microbiological multidistrict-based survey from different Egyptian governorates was conducted to determine the most prevalent causative agents of ocular infections in the Egyptian population. Antibiotic sensitivity testing was then performed to identify the most potent antimicrobial agent. Vancomycin (VCM) proved the highest activity against gram-positive Staphylococcus bacteria, which are the most commonly isolated causative agents of ocular infection. However, topically applied VCM suffers from poor ocular bioavailability because of its high molecular weight and hydrophilicity. Objective: The aim of the present study was to develop VCM-loaded solid lipid nanoparticles (SLNs) using water-in-oil-in-water (W/O/W) double emulsion, solvent evaporation technique to enhance ocular penetration and prolong ophthalmic residence of VCM. Method: Two consecutive full factorial designs (2⁴ followed by 3²) were adopted to study the effect of different formulation and process parameters on SLN formulation. The lipid type and structure, polyvinyl alcohol (PVA) molecular weight and concentration, sonication time, as well as lipid:drug ratio were studied as independent variables. The formulated SLN formulae were evaluated for encapsulation efficiency (EE%), particle size (PS), and zeta potential as dependent variables. Results: The statistically-optimized SLN formula (1:1 ratio of glyceryltripalmitate:VCM with 1% low molecular weight PVA and 1?min sonication time) had average PS of 277.25?nm, zeta potential of ?20.45, and 19.99% drug encapsulation. Scanning and transmission electron micrographs showed well-defined, spherical, homogenously distributed particles. Conclusion: The present study suggests that VCM incorporation into SLNs is successfully achievable; however, further studies with different nanoencapsulation materials and techniques would be valuable for improving VCM encapsulation.     

Optimization of biodegradable sponges as controlled release drug matrices. I. Effect of moisture level on chitosan sponge mechanical properties

Cross-linked chitosan sponges as controlled release drug carrier systems were developed. Tramadol hydrochloride, a centrally acting analgesic, was used as a model drug. The sponges were prepared by freeze-drying 1.25% and 2.5% (w/w) high and low M.wt. chitosan solutions, respectively, using glutaraldehyde as a cross-linking agent. The hardness of the prepared sponges was a function of glutaraldehyde concentration and volume where the optimum concentration that offered accepted sponge consistency was 5%. Below or above 5%, very soft or very hard and brittle sponges were obtained, respectively. The determined drug content in the prepared sponges was uniform and did not deviate markedly from the calculated amount. Scanning electron microscopy (SEM) was used to characterize the internal structures of the sponges. The SEM photos revealed that cross-linked high M.wt. chitosan sponges have larger size surface pores that form connections (channels) with the interior of the sponge than cross-linked low M.wt. ones. Moreover, crystals of the incorporated Tramadol hydrochloride were detected on the lamellae and within pores in both chitosan sponges. Differences in pore size and dissolution medium uptake capacity were crucial factors for the more delayed drug release from cross-linked low M.wt. chitosan sponges over high M.wt. ones at pH 7.4. Kinetic analysis of the release data using linear regression followed the Higuchi diffusion model over 12 hours. Setting storage conditions at room temperature under 80-92% relative humidity resulted in soft, elastic, and compressible sponges.     

Road Aware Geographical Routing Protocol Coupled with Distance,Direction and Traffic Density Metrics for Urban Vehicular Ad Hoc Networks

The new information and communication technologies have changed the trend of communication in all fields. The transportation sector is one of the emerging field, where vehicles are communicating with each other or with infrastructure for different safety and comfort applications in the network. Vehicular ad hoc networks is one of the emerging multi-hop communication type of intelligent transportation field to deal with high mobility and dynamic vehicular traffic to deliver data packets in the network. The high mobility and dynamic topologies make the communication links unreliable and leads to frequent disconnectivity, delay and packet dropping issues in the network. To address these issues, we proposed a road aware geographical routing protocol for urban vehicular ad hoc networks. The proposed routing protocol uses distance, direction and traffic density routing metrics to forward the data towards the destination. The simulation results explore the better performance of proposed protocol in terms of data delivery, network delay and compared it with existing geographical routing protocols.

     

Multi-Attribute Selection Procedures Based on Regret and Rejoice for the Decision-Maker

Feelings influence human beings’ decision-making; therefore, incorporation of feeling factors in decision-making is very important. Regret and rejoice are very important emotional feelings that can have a great impact on decision-making if they are considered together. While regret has received most of the attention in related research, rejoice has been less considered even though it can greatly influence people’s preferences in decision-making. Furthermore, systematically incorporating regret and rejoice in the multi-criteria decision-making (MCDM) modeling frameworks for decision-making has received little research attention. In this paper, we introduce a new multi-attribute selection procedure that incorporates both regret and rejoice to select the best choice. We utilize the positional advantage operator concept to develop regret and rejoice mathematical equations, and prove them. The proposed MCDM procedure that incorporates these two emotional factors offers a decision-maker the flexibility to trade off some benefits in order to gain a state of psychological satisfaction. More specifically, regret and rejoice are presented mathematically to enable the decision-maker to determine the values of regret and rejoice, and then make the decision in which the rejoice value is higher than the regret value. To test the performance of this new procedure, we apply it to three numerical examples proposed in previous works. The results are matched with those obtained by other methods such as the regret model, VIKOR, PROMETHEE I, and PROMETHEE II, thereby proving the efficacy of the new procedure.     

Effects of THC on driving performance, physiological state and subjective feelings relative to alcohol

BACKGROUND: The effects of marijuana or THC on driving has been tested in several studies, but usually not in conjunction with physiological and subjective responses and not in comparison to alcohol effects on all three types of measures. OBJECTIVE: To assess the effects of two dosages of THC relative to alcohol on driving performance, physiological strain, and subjective feelings. METHOD: We tested the subjective feelings and driving abilities after placebo, smoking two dosages of THC (13 mg and 17 mg), drinking (0.05% BAC) and 24 h after smoking the high dose THC cigarette, while monitoring physiological activity of the drugs by heart rate. Fourteen healthy students, all recreational marijuana users, participated in the study. RESULTS: Both levels of THC cigarettes significantly affected the subjects in a dose-dependent manner. The moderate dose of alcohol and the low THC dose were equally detrimental to some of the driving abilities, with some differences between the two drugs. THC primarily caused elevation in physical effort and physical discomfort during the drive while alcohol tended to affect sleepiness level. After THC administration, subjects drove significantly slower than in the control condition, while after alcohol ingestion, subjects drove significantly faster than in the control condition. No THC effects were observed after 24 h on any of the measures.     

Effect of combining Al,Mg, Ce or La oxides to extracted rice husk nanosilica on the catalytic performance of NiO during COx-free hydrogen production via methane decomposition

Amorphous nanosilica powder was extracted from rice husk and used as a catalyst support as well as a starting material for the preparation of different binary oxides, i.e., SiO₂Al₂O₃, SiO₂MgO, SiO₂CeO₂ and SiO₂La₂O₃. A series of supported nickel catalysts with the metal loading of 50 wt % were prepared by wet impregnation method and evaluated in methane decomposition to “CO_x-free” hydrogen production. The fresh and spent catalysts were extensively characterized by different techniques. Among the evaluated catalysts, both Ni/SiO₂Al₂O₃ and Ni/SiO₂La₂O₃ catalysts were the most active with an over-all H₂ yield of ca. 80% at the initial period of the reaction. This distinguishable higher catalytic activity is mainly referred to the presence of free mobile surface NiO and/or that NiO fraction weakly interacted with the support easily reducible at low temperatures. The Ni/SiO₂CeO₂ catalyst has proven a great potential for application in the hydrogen production in terms of its catalytic stability. The formation of Mg_xNi_(1?x)O solid solution caused the Ni/SiO₂MgO catalyst to lose its activity and stability at a long reaction time. Various types of carbon materials were formed on the catalyst surface depending on the type of support used. TEM images of as-deposited carbon showed that multi-walled carbon nanotubes (MWCNTs) and graphene platelets were formed on Ni/SiO₂, while only MWCNTs were deposited on all binary oxide supported Ni catalysts.