Improvements in the production of bacterial synthesized biocellulose nanofibres using different culture methods

This review summarizes previous work that was done to improve the production of bacterial cellulose nanofibres. Production of biocellulose nanofibres is a subject of interest owing to the wide range of unique properties that makes this product an attractive material for many applications. Bacterial cellulose is a natural nanomaterial that has a native dimension of less than 50 nm in diameter. It is produced in the form of nanofibres, yielding a very pure cellulose product with unique physical properties that distinguish it from plant‐derived cellulose. Its high surface‐to‐volume ratio combined with its unique properties such as poly‐functionality, hydrophilicity and biocompatibility makes it a potential material for applications in the biomedical field. The purpose of this review is to summarize the methods that might help in delivering microbial cellulose to the market at a competitive cost. Different feedstocks in addition to different bioreactor systems that have been previously used are reviewed. The main challenge that exists is the low yield of the cellulosic nanofibres, which can be produced in static and agitated cultures. The static culture method has been used for many years. However, the production cost of this nanomaterial in bioreactor systems is less expensive than the static culture method. Biosynthesis in bioreactors will also be less labour intensive when scaled up. This would improve developing intermediate fermentation scale‐up so that the conversion to an efficient large‐scale fermentation technology will be an easy task. Copyright © 2009 Society of Chemical Industry     

Combined use of single and double-cross steel wires for closure of midline sternotomy

BACKGROUND: We describe an improved technique for sternal closure which is performed using combined single and double-cross steel wires. We made a mechanical study of these single and double-cross shapes considering the effects of applied transverse and longitudinal shearing forces. METHODS: We used this technique in 80 patients who underwent coronary surgery with the use of bilateral internal mammary arteries. RESULTS: Among them no major wound complications occurred, and in all cases a firm stabilization of the sternum was achieved. CONCLUSIONS: We therefore consider this technique of sternal closure easy, safe and effective, also in patients considered at risk for sternal dehiscence.     

Application of the statistical Taguchi method to optimize TiO2 nanoparticles synthesis by the hydrothermal assisted sol–gel technique

TiO₂ nanoparticles were synthesized by hydrothermal assisted sol–gel technique. The preparation parameters including pH value, the amount of water, titanium tetra isopropoxide content, temperature and time of hydrothermal process were investigated by Taguchi statistical experiments to determine the influence of synthesizing variables on the optimal conditions and to realize the highest degree of crystallinity or smallest crystallite size. X-ray diffraction (XRD) analysis and direct band gap energy (E_g) values, measured via diffuse reflectance spectra (DRS), proved that all the samples consist of anatase as a unique phase. Transmission electron microscopy (TEM) and specific surface area values showed that the sample with the smallest crystallite size could exert more effective photoactivity confirmed by measuring the decomposition rate of methylene blue. The apparent photodegradation rate constant of the sample with the smallest crystallite size was about five times greater than that of commercial TiO₂.     

CR-CEA: A collision- and energy-aware routing method for cognitive radio wireless sensor networks

Currently, working in the overcrowded shared unlicensed spectrum band, leads to a reduction in the quality of communications in wireless networks. This makes a considerable increase in packet loss caused by collisions that necessitates packets retransmissions. In the case of wireless sensor networks (WSN), a large amount of energy of sensor nodes will be wasted by these retransmissions. Cognitive radio technology makes it possible for sensor nodes, to opportunistically use licensed bands with better propagation characteristics and less congestion. In this paper a routing method for cognitive radio wireless sensor networks (CR-CEA) is presented, that is based on a cross-layer design that jointly considers route and spectrum selection. The CR-CEA method has two main phases: next hop selection and channel selection. The routing is performed hop-by-hop with local information and decisions, which are more compatible with sensor networks. Primary user activity and prevention from interference with them, is considered in all spectrum decisions. It uniformly distributes frequency channels between adjacent nodes, which lead to a local reduction in collision probability. This clearly affects energy consumption in all sensor nodes. In CR-CEA, route selection is energy-aware and a learning-based technique is used to reduce the packet delay in terms of hop-count. The simulation results reveal that by applying cognitive radio technology to WSNs and selecting a proper operating channel, we can consciously decrease collision probability. This saves energy of sensor nodes and improves the network lifetime.     

Abdominal aortic aneurysms in heart transplanted patients

BACKGROUND: Protein contact dermatitis is a form of contact dermatitis possibly triggered by proteinaceous allergens. MATERIALS AND METHODS: We report two patients with a history of erythematous and urticarial skin reactions followed by transformation into prolonged papular symptoms upon contact with proteinaceous material. RESULTS: The symptoms reported by the patients were reproducible by skin testing with meat (cow) and fish (salmon). Both patients experienced extracutaneous manifestations after ingestion of meat and fish, as proven by oral challenge. Specific immunoglobulin E (IgE) antibodies were detected in the patients' blood. CONCLUSIONS: Both cases meet all major criteria of protein contact dermatitis, suggesting IgE-mediated immediate-type hypersensitivity with late-phase cutaneous reactions.     

Cuk converter global control via fuzzy logic and scaling factors

A successful implementation of a low-cost PI-fuzzy controller for a Cuk converter is presented in this paper. Properties of the proposed controller are robustness around the operating point, good performance of transient responses in changing load conditions and/or input voltage, and invariant dynamic performance in the face of varying output operating points. Simulations and experimental results have been obtained via a suitable variation of the scaling factors related to the input variables of the fuzzy controller     

Synthesis and study of a new class of red pigments based on perovskite YAlO3 structure

A red pigment has been prepared by substituting chromium ions in aluminum ion sites in YAlO₃ perovskite structure. In a first step, effect of various mineralizers on YAlO₃ formation has been investigated, which resulted in decrease of formation temperature down to 1400 °C. In the next step, a red pigment corresponding to YAl_1−yCr_yO₃ (y = 0.05), has been prepared by heating a mixture containing Y₂O₃, Al₂O₃ and Cr₂O₃ at 1500 °C for 6 h. Later, effect of the doped chromium amount on the pigment redness (a^*) has been studied. The highest redness has been obtained when y was 0.04(YAl_1−yCr_yO₃). Application of the prepared red pigment in low and high temperature glazes, demonstrated its high chemical and thermal stability.     

Anhydroretinol, a retinoid active in preventing mammary cancer induced in rats by N-methyl-N-nitrosourea

As determined by in vitro tests, anhydroretinol, a metabolic product of retinol, was bound specifically by serum retinol-binding protein and by cellular retinol-binding protein but not by cellular retinoic acid-binding protein or the nuclear receptors, RARs and RXRs. For rats dosed with the mammary carcinogen, N-methyl-N-nitrosourea (45 mg/kg body weight) and given diets containing either the retinoid vehicle, anhydroretinol (67, 134, 268, or 536 mg/kg of diet), or retinyl acetate (328 mg/kg of diet), there were, over a 90-day observation period, no significant differences in body weights. The compound did not accumulate in liver tissue or cause an increase in hepatic levels of retinyl palmitate (potential problems observed with other retinoids). The numbers of mammary cancers were as follows: no retinoid, 4.5/rat; retinyl acetate, 2.1/rat; and increasing doses of anhydroretinol, 2.9, 3.3, 3.0, and 1.7/rat, respectively. Thus, anhydroretinol, at non-toxic levels, was effective as a preventive agent in this experimental model of breast cancer.