Modelling of water vapour adsorption on foods products by a statistical physics treatment using the grand canonical ensemble

Knowledge of water adsorption isotherms is very important with regard to concentration, dehydration and drying of food products as well as determining the quality, stability and the shelf life of foods. A new analytical isotherm equation that can be applicable to water vapour–food systems similar to BET equation but modified is developed using the grand canonical ensemble in statistical physics. The establishment of the expression model is based on a statistical physics treatment and some working hypothesises.     

Essential oils of Origanum vulgare L. subsp. glandulosum (Desf.) Ietswaart from Tunisia: chemical composition and antioxidant activity

BACKGROUND: Characterisation of the essential oils from O. glandulosum collected in three locations of Tunisia, chemical composition and the evaluation of their antioxidant activities were carried out. RESULTS: The essential oils from Origanum vulgare L. subsp. glandulosum (Desf.) Ietswaart collected from three localities of north Tunisia—Krib, Bargou and Nefza—were obtained in yields of 2.5, 3.0 and 4.6% (v/w), respectively. The essential oils were analysed by GC and GC/MS and assayed for their total phenolics content, by the Folin–Ciocalteu method, and antioxidant effectiveness, using the 2,2‐diphenyl‐1‐picrylhydrazil (DPPH) radical scavenging assay. The main components of these essential oils, from Nefza, Bargou and Krib, were p‐cymene (36%, 40% and 46%), thymol (32%, 39% and 18%), γ‐terpinene (24%, 12% and 16%) and carvacrol (2%, 2% and 15%), respectively). The ability to scavenge the DPPH radicals, expressed by IC₅₀, ranged from 59 to 80 mg L^?1. The total phenolic content, expressed in gallic acid equivalent (GAE) g kg^?1 dry weight, varied from 9.37 to 17.70 g kg^?1 dw. CONCLUSIONS: A correlation was identified between the total phenolic content of the essential oils and DPPH radical scavenger capacity. The occurrence of a p‐cymene chemotype of O. glandulosum in the northern region of Tunisia is demonstrated. Copyright © 2010 Society of Chemical Industry     

Potential hypoglycaemic effects of insoluble fibres isolated from foxtail millets [Setaria italica (L.) P. Beauvois]

Insoluble fibres were isolated from the two varieties of foxtail millet (white and yellow) grains and evaluated for their hypoglycaemic effects by in vitro studies. The hypoglycaemic effects of these fibres were compared with those of commercial soy insoluble fibre. The results revealed that minimum and maximum amounts of glucose were adsorbed on each sample at 10 and 200 μmol g^?1 glucose concentrations respectively, indicating that the glucose adsorption capacity (GAC) of the fibre materials was proportional to glucose concentration for all samples. There was significant (P < 0.05) difference among all the fibre materials in relation to their GAC values. In the case of the effects of the fibres on glucose diffusion, the millets' insoluble fibres performed better than that of the commercial soy insoluble fibres. The glucose dialysis retardation indexes at the end of the maximum dialysis time were 1.1%, 27.4% and 22.6% for soy bean insoluble fibre, white foxtail millet insoluble fibre and yellow foxtail millet insoluble fibre in that order. The study showed that hypoglycaemic effects of yellow and white foxtail millet fibres were comparable to the commercial soy insoluble fibre.     

Mathematical modeling in genetic networks: relationships between the genetic expression and both chromosomic breakage and positive circuits

The human genome with its 23 pairs of chromosomes, is the result of evolution. This evolution has been ruled by the mutation process and also by the physiological and pathological reorganization of the genomic material inside or between the chromosomes, which are conditioning the genomic variability. This reorganization is starting at singular points on the short or long chromosomic arms, called crossing-over, or translocations, insertions, break points. In this paper, we will show that these points, also called weak points or hot spots of the genome are correlated, independently of their origin. In addition, we will give some properties of the genetic interaction matrices in terms of attractors of the genetic expression dynamics.     

Some characteristics of polyphenol oxidase purified from edible yam (Dioscorea cayenensis-rotundata cv. Longbô) cultivated in Côte d'Ivoire

Polyphenol oxidase (PPO_Y) of edible yam ( Dioscorea cayenensis-rotundata cv. Longbô ) cultivated in Côte d'Ivoire was purified to homogeneity by a procedure that included ion exchange chromatography, ammonium sulphate fractionation, gel filtration and hydrophobic chromatography using dopamine as a substrate. The relative molecular weight of the PPO_Y was estimated to be 94.75 ± 0.63 and 151.56 ± 2.75 kDa by SDS–PAGE and gel filtration on Sephacryl S100 HR, respectively, indicating this PPO_Y as a multimer. Maximal PPO_Y activity occurred at 30 °C and pH 6.6. The enzyme was stable at 25 °C and its pH stability was in the range of 6.0–7.0. The values V _max/ K _m showed that the enzyme had the greatest reactivity towards dopamine among the substrates used. PPO_Y showed no activity toward the monophenols and was completely inhibited by beta-mercaptoethanol, sodium thiosulphate, l -ascorbic acid, sodium bisulphite and l -cysteine. Data generated by this study might help to better prevent edible yam browning.     

Impact of stray load losses on vector control accuracy in current-fed induction motor drives

Vector control accuracy of induction motor drives is affected by variations of motor parameters that are treated in the control algorithm as constant values, and by the phenomena that are not modeled at all and are therefore unaccounted for in the controller. Detuning sources of the first type include variations of rotor and stator resistance, mutual inductance, and leakage inductances, while the second category includes stator iron (core) losses. All these sources of detuned operation have been studied in a considerable depth in the past. It appears that the only potential source of detuned operation, which has never been studied before, is the stray load loss (SLL), which belongs to the category of unmodeled phenomena. This paper develops an analytical model that characterizes detuning due to SLLs in indirect rotor-flux-oriented (RFO) current-fed induction motor drives in steady-state operation by means of the orientation angle error, actual to reference rotor-flux ratio, and actual to reference-torque ratio. A quantitative assessment of the impact of SLL on accuracy of rotor-flux-oriented control is performed, with the necessary motor parameters obtained from IEEE 112-B standard measurements and subsequent equivalent circuit parameter fitting. Detuning is also examined in transient operation. It is shown that, although SLLs are comparable to the iron losses in the studied machine (of approximately the same value in the rated operating point), their impact on accuracy of vector control is much smaller when compared to the iron loss induced detuning.     

Design of cable-driven parallel manipulators for a specific workspace using interval analysis

In this paper, we present a method, based on interval analysis, to solve the problem of designing cable-driven parallel manipulators (CDPMs) for a desired workspace. The constraint of having positive cable tensions ensuring the equilibrium of the platform has to be satisfied within the given workspace. The proposed algorithm is based on interval analysis, which covers the entire workspace and hence guarantees a singularity-free workspace. Furthermore, the algorithm is capable of finding all possible solutions for this problem and an optimal one is selected according to the user-defined criterion. Two examples are selected to show the efficiency of the developed algorithm in solving this complex problem. The first one deals with the design of a planar CDPM and the second one considers a spatial CDPM. In both cases, the algorithm succeeded to find all possible designs from which the designer can select a solution that fits best his application.