Viscoelastic and photo-actuation studies of composites based on polystyrene-grafted carbon nanotubes and styrene-b-isoprene-b-styrene block copolymer

Photoactuating composites based on the linear triblock copolymer polystyrene-b-polyisoprene-b-polystyrene (SIS) were prepared by incorporation of polystyrene-modified multiwalled carbon nanotubes (MWCNT–PS). Modification of MWCNT was performed by surface-initiated atom transfer radical polymerization (SI ATRP) of styrene. The presence of the polystyrene chains on the MWCNT surface facilitated their dispersion in the SIS matrix. Improved interactions of the modified MWCNT–PS compared to neat MWCNT were confirmed by dynamic mechanical analysis. The activation energy of glass transition of the polystyrene phase in the MWCNT–PS/SIS composite increased significantly compared to the neat SIS matrix, while the incorporation of neat MWCNT to the SIS matrix disturbed the physical cross-linking of the SIS and degraded its elastic properties. The photo-actuation ability of the MWCNT–PS/SIS composite was proved using atomic force microscopy.     

Green synthesis of Ag nanoparticles: Effect of algae life cycle on Ag nanoparticle production and long-term stability

Spherical Ag nanoparticles (AgNPs) were biologically synthesized using four different extracts prepared from Parachlorella kessleri algae cultivated for 1, 2, 3 and 4 weeks. The influence of algae life cycle on AgNPs formation and effect of different storage conditions on AgNPs long-term stability were investigated. The age of algae influenced the rate of AgNPs synthesis and amount of AgNPs in solution. The age of algae did not influence the AgNPs long-term stability. UV–vis and TEM observation revealed that long-term stability of AgNPs can be influenced by storage temperatures, and low temperature positively influences the AgNPs stability. AgNPs stored at dark and at temperature of ～5 °C showed the best long-term stability regardless of the culture age. Such AgNPs remained spherical, fine (5–20 nm) and stable (no agglomeration) even after 6 months.     

Electronically controlled oscillator with linear frequency adjusting for four‐phase or differential quadrature output signal generation

This paper introduces novel four‐phase oscillator employing two Dual‐Output Controlled Gain Current Follower Buffered Amplifiers (DO‐CG‐CFBAs), single Current Amplifier, three resistors, and two grounded capacitors suitable for differential quadrature signal production (floating outputs). To control the frequency of oscillation (FO) and condition of oscillation (CO), only the current gain adjustment of active elements is used. The circuit was designed by well‐known state variable approach. The oscillator employs three active elements for linear control of FO and to adjust CO and provides low‐impedance voltage outputs. Furthermore, two straightforward ways of automatic amplitude gain control were used and compared. Active elements with very good performance are implemented to fulfill required features. Suitable CMOS implementation of introduced DO‐CG‐CFBA was shown. Important characteristics of the designed oscillator were verified experimentally and by PSpice simulations to confirm theoretical and expected presumptions. Copyright © 2013 John Wiley & Sons, Ltd.     

Sensorically and antimicrobially active metabolite production of Lactobacillus strains on Jerusalem artichoke juice

BACKGROUND: In the tubers of Jerusalem artichoke (Helianthus tuberosus L.) the main carbohydrate is the well‐known prebiotic inulin, which is a good growth substrate for gut microorganisms. Jerusalem artichoke tuber is traditionally consumed boiled or pickled rather than in fermented form. Lactic acid bacteria are traditionally used in the production of fermented foods; nevertheless their behavior and metabolite production are considerably influenced by the substrate. The purpose of this study was to investigate the growth and production of the most important sensorically and antimicrobially active metabolites of different Lactobacillus strains on Jerusalem artichoke juice. RESULTS: All investigated strains grew well (in the range 10⁹ cfu mL^?1) in the media. The organic acids (lactic acid, 110–337 mmol L^?1; acetic acid, 0–180 mmol L^?1; and succinic acid, 0–79 mmol L^?1), hydrogen peroxide (0.25–1.77 mg L^?1), mannitol (0.06–3.24 g L^?1), acetoin and diacetyl production of strains varies not only according to the species but also from strain to strain, which will be demonstrated and discussed in the paper. CONCLUSION: Our results showed that lactobacilli can be used for the fermentation of Jerusalem artichoke, which in this form could be used, alone or mixed with other raw food material, as a new synbiotic functional food. Copyright © 2011 Society of Chemical Industry     

Implant Evaluation of a Nuclear Power Source? Betacel? Battery

In order to evaluate nuclear power sources for biomedical applications, a nuclear battery, Betacel?, was used to power two telemetry transmitters designed with a very low power consumption. The transmitters were implanted in a dog to measure the voltage of the battery and the deep body temperature. Special care was given to the glass packaging to prevent possible damage from body fluids. The experiment ran continuously for a 6-month period before termination. At that time, the animal was sacrificed to examine the radiation damage of tissues in the vicinity of the transmitters as well as the effects on vital organs. No measurable abnormality was detected. The experiment suggests that the nuclear power source can be used to extend the working life of implanted medical instruments.