Plant oil bioconversion into increase biological activity through lipases derived from wastes

The aim of this study was to show that abundant and inexpensive plant oils can be biotransformed to increase biological activity (antioxidant, antimicrobial and cytotoxicity) through hydrolysis reaction catalysed by lipases. We tested homemade and commercial lipases through the biotransformation of nine different plant oils in forty different combinations. First, the chemical composition of the samples was investigated. Thereafter, biological tests were conducted to assess the antioxidant and antimicrobial activity of the sampled biotransformation products, as well as analyzed their influence on the viability of healthy and cancer cells. Summarising, sunflower, corn and olive oils modified by orange waste-obtained lipases presented the most promising results, reaching up to 90% of antioxidant activity increase and significant growth inhibition of bacteria colonies belonging to genera Escherichia, Listeria, Staphylococcus, Pseudomonas and Salmonella. In addition, those compounds affected human oral squamous carcinoma cells. The bioconversion of plant oils through lipases improves their biological properties and might be an option for biotechnological application.     

Photochromic Polymers Based on the Photoinduced Opening and Thermal Closing of [1,3]Oxazine Rings

Two macromolecular constructs incorporating a single polymer backbone with multiple photochromic side chains are developed. Both systems are prepared from preformed photochromic [1,3]oxazines after the ring‐opening polymerization of their norbornene appendages. In solution, UV illumination of these polymers opens the [1,3]oxazine rings in their side chains in less than 6 ns and with a quantum yield of 0.09 in both instances. The photogenerated species incorporate a 4‐nitrophenolate chromophore, and hence, their formation is accompanied by the appearance of an intense band in the visible region of the absorption spectrum. The photoproducts revert spontaneously to the original state with first‐order kinetics in microseconds. Furthermore, both photochromic polymers tolerate hundreds of switching cycles with no sign of degradation, even in the presence of molecular oxygen. Thus, this design logic and choice of functional building blocks can translate into the realization of innovative photoresponsive materials with excellent photochromic performance.     

A go-back-N protocol for mobile communications

The author describes a go-back-N (GBN) protocol, which is a type of automatic repeat request (ARQ) technique. The protocol has a buffer and memory at the receiver side and offers low implementation complexity and a structure especially suited to mobile communications. The optimization of the protocol parameters is determined through numerical analysis. Performance is evaluated by computer simulation using a channel model suitable for mobile communications. The results show that the proposed ARQ scheme achieves a higher performance than that of other ARQ protocols and that at high error rates its efficiency compares favorably with selective repeat protocols having an infinite buffer     

Error recovery for ATM transmission over wireless channels

The authors present a technique for efficient recovery from transmission errors to be used when transmitting ATM-like data packets in a wireless channel affected by bursty errors (jamming). Issues related to packet format error protection code structure and retransmission protocol are discussed and simulation results are shown that prove the effectiveness of the proposed approach     

Efficient ARQ technique using soft demodulation

In the letter a new technique for increasing the efficiency of an automatic-repeat-request communication system is described. This technique uses all the received versions of a codeword, and also those versions containing errors. Such a strategy, together with a soft demodulation of each received symbol, is particularly efficient when applied to ARQ schemes in which each block erroneously received is retransmitted many times.     

An ARQ Scheme with Memory and Integrated Modulation

In this paper, the integration of the modulation operation in an automatic-repeat-request scheme, using error-detecting codes, is analyzed. A new protocol is described, in which the modulation operation facilitates the recovery of the transmitted code word. The results show a net improvement in the throughput of the automatic-repeat-request scheme, particularly for mean and high error-rate conditions. Continuous-phase-frequency shift keying modulations, which present a low bandwidth occupancy, are particularly considered.     

Bioactive extracts of orange (Citrus sinensis L. Osbeck) pomace obtained by SFE and low pressure techniques: Mathematical modeling and extract composition

The objective of this study was to obtain orange (Citrus sinensis L. Osbeck) pomace extract using supercritical fluid extraction (SFE) with CO₂ and with CO₂ and co-solvent. In order to evaluate the high pressure method in terms of process yield, extract composition and biological activity, low pressure methods were also applied to obtain orange extracts, such as ultrasound (UE) and soxhlet (SOX), with different organic solvents, and hydrodistillation (HD). The SFE conditions were temperatures of 313.15 K and 323.15 K and pressures from 100 to 300 bar. The SFE kinetics and mathematical modeling of the overall extraction curves (OEC) were also investigated. The antioxidant potential of the extracts was evaluated by the DPPH method, by the Folin-Ciocalteau method and by the β-carotene/linoleic acid bleaching method. The antimicrobial activity of the extracts was also studied. The main compounds identified were l-limonene, palmitic and oleic acids, n-butyl benzenesulfonamide and β-sitosterol.     

Relevant chiroptical and thermal properties in optically active methacrylic copolymers containing carbazole and azoaromatic chromophores in the side-chain

Novel optically active methacrylic copolymers, bearing carbazole and azoaromatic moieties linked to the main chain with a rigid (S)-hydroxysuccinimide residue of one prevailing absolute configuration, have been prepared and characterized with the aim to establish the effects of the chiral group and of the dipolar interactions between the two side-chain chromophores on their properties.In particular, the observed chiroptical properties suggest the presence of ordered chiral conformations at least for chain segments of the macromolecules. Spectroscopic, thermal and chiroptical characterizations of these copolymers demonstrate the occurrence of significant electronic interactions between carbazole chromophores and azobenzene moieties. These interactions are related to the unusual partially alternating structure of the investigated copolymers and the relevant chiroptical and thermal properties. In fact, the polymeric derivates show high glass transition temperatures and good thermal stability, thus opening the way to a variety of potential applications based on photoconductive and optoelectronic properties.