Development and characterization of thermosensitive hydrogels based on poly(N‐isopropylacrylamide) and calcium alginate

This work refers to the synthesis and characterization of thermosensitive hydrogels based on interpenetrating polymer networks (IPNs) of poly(N‐isopropylacrylamide) (PNIPAAm) and calcium alginate in the form of films. The influence of the crosslinking degree of PNIPAAm and alginate content on thermal, swelling, mechanical, and morphological properties of hydrogels is investigated in detail. Characterization of pure PNIPAAm hydrogels and IPN hydrogels was performed by FTIR, DSC, DMA, and SEM. In addition, the studies of equilibrium swelling behavior as well as swelling, deswelling, and reswelling kinetics are performed. The results obtained imply the benefits of synthesizing IPNs based on PNIPAAm and calcium alginate over pure PNIPAAm hydrogels. The presence of calcium alginate contributes to the improvement of mechanical properties, the deswelling rate of hydrogels, and the network porosity, without altering the thermosensitivity of PNIPAAm significantly. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Non-lithographic fabrication of metallic micromold masters by laser machining and welding

A non-lithographic process of rapidly fabricating metallic micromold masters for the manufacture of disposable polymer microfluidic devices is presented in this paper. The developed technique exploits the precision material removal capabilities of industrial lasers to cut accurate profiles of microfeatures (e.g., liquid flow microchannels, reservoirs, passive micromixers) from thin metallic sheets. The machined micropatterns are then laser welded onto a metal substrate to form the final functional mold master. Multiple versions of the functional device are replicated from the assembled master by either soft molding polydimethylsiloxane or hot embossing polymethyl methacrylate. Several metallic micromold masters and polymer replicas are tested for dimensional accuracy and surface roughness to verify the developed microfabrication process.     

Characterization of microflora in homemade semi-hard white Zlatar cheese

The Zlatar cheese belongs to the group of traditionally homemade cheeses, which are produced from nonpasteurized cow's milk, without adding of any bacterial starter culture. Changes were followed in lactic acid bacteria population and chemical composition during the ripening period of cheese up to 60 days. Results showed that the percentage of lactic acid cocci was higher in raw milk and one day old cheese and their percentage was gradually decreasing, whereas the number of lactobacilli was increasing. After 30 days of cheese ripening the number of cocci increased again, reaching the number of lactobacilli. The results of API 50 CH system and rep-PCR analysis showed that Lactobacillus paracasei subsp. paracasei, Lactobacillus brevis, Lactococcus lactis subsp. lactis, Enterococcuus faecium and Enterococcus faecalis were the main groups present during the ripening of Zlatar cheese. Results revealed that in older cheeses (45 and 60 days old) enterococci were the main group present. It was also demonstrated that 57 isolates showed antimicrobial activity. The number of bacteria showing antimicrobial activity slowly decreased during the ripening period and in samples of 60 days old cheese producers of antimicrobial activities were not detected.     

RPATS – Reliable power aware time synchronization protocol

Many applications of Wireless Sensor Networks (WSNs) need the local clocks of the individual sensor nodes (SN) to be synchronized. Almost any form of sensor data fusion or coordinated actuation requires synchronized physical time for reasoning about events in the physical world. However, while the clock accuracy and precision requirements are often stricter in WSN than in traditional distributed systems, energy and channel constraints limit the resources available to meet these goals. In this paper, we present a power aware time synchronization protocol, of type sender–receiver, suitable for implementation in duty-cycled WSN. By using this proposal most of the non-deterministic time delays during packet transfer (media access, waiting packets in queues, propagation delay) as dominant ones (order of several hundred milliseconds), in respect to data processing (interrupt handling, testing status registers in program loop) as minor (up to hundred microseconds), are bypassed. In addition reliable and unreliable data transfer between SNs is considered. With aim to compensate SN’s oscillator instability, i.e. error in time synchronization, we propose duty cycle time extension. Apart from that, in order to evaluate the low-power capability of the proposed protocol we have involved quantitative performance metric called lifetime efficiency and compared it with equivalent (same) metric of the well known Reference-Broadcast Synchronization, RBS, and Timing-sync Protocol for Sensor Networks, TPSN, protocols, for different error prone environment and different period of time synchronization.     

Electrophysiological analysis of interaction between the neuron populations of pons and medulla participating in inhibition of the motor activity]

Neurons of cuneiform, subcuneiform, medial parabrachial, median raphe nuclei were studied. 26-47% units were found to send monosynaptic inputs to the raphe magnus nucleus, gigantocellular reticular and ventral reticular nuclei. 17-43% responded to stimulation of the inhibitory brain stem areas with excitatory-inhibitory reactions. Reciprocal distribution projections among inhibitory brain stem areas, were found.