Empirical modelling and scale-up of a semi-batch polyestrification process

A semi-empirical kinetic model that fits laboratory data and predicts pilot plant data was developed. The model is a modified version of a recently reported third-order kinetic equation for the reaction of nonstoichiometric amounts of hydroxyl and carboxylic groups. The model can be used to quantify the effects of reaction temperature and inert gas flow rate on the reaction rate. The Arrhenius temperature dependence of the rate constant permitted the calculation of the reaction activation energy (53.6 kJ/mol). The gas flow rate dependence is an empirical function of the molar ratio of reactants to inert gas. The same function is simultaneously used as the process scale-up rule. The mathematical model can be potentially used for commercial-sized reactors.     

Nanostructured Guidance for Peripheral Nerve Injuries: A Review with a Perspective in the Oral and Maxillofacial Area

Injury to peripheral nerves can occur as a result of various surgical procedures, including oral and maxillofacial surgery. In the case of nerve transaction, the gold standard treatment is the end-to-end reconnection of the two nerve stumps. When it cannot be performed, the actual strategies consist of the positioning of a nerve graft between the two stumps. Guided nerve regeneration using nano-structured scaffolds is a promising strategy to promote axon regeneration. Biodegradable electrospun conduits composed of aligned nanofibers is a new class of devices used to improve neurite extension and axon outgrowth. Self assembled peptide nanofibrous scaffolds (SAPNSs) demonstrated promising results in animal models for central nervous system injuries, and, more recently, for peripheral nerve injury. Aims of this work are (1) to review electrospun and self-assembled nanofibrous scaffolds use in vitro and in vivo for peripheral nerve regeneration; and (2) its application in peripheral nerve injuries treatment. The review focused on nanofibrous scaffolds with a diameter of less than approximately 250 nm. The conjugation in a nano scale of a natural bioactive factor with a resorbable synthetic or natural material may represent the best compromise providing both biological and mechanical cues for guided nerve regeneration. Injured peripheral nerves, such as trigeminal and facial, may benefit from these treatments.     

Analysis of Acceleration Effect in Data Dissemination in Vehicular Networks Using Rateless Codes

Mobility models of nodes have an important role in the evaluation of data dissemination protocols in vehicular ad hoc networks (VANETs). Many recent researches have used the constant velocity mobility models while vehicles have acceleration and their speeds change as they move. Because of the dynamic nature of VANETs, the network changes from a densely connected to the sparsely connected environment in a short time. In sparsely connected networks, it is said that vehicles move in clusters. In this paper, the constant acceleration mobility calculations for the sparsely connected network and its characteristics have been presented. These characteristics are usable for the evaluation of the data dissemination protocols in VANETs. The results show that acceleration affects the number of viewed clusters during the trip and the number of vehicles within a cluster. In fact, acceleration has a significant impact on the network sparsely connection. This matter shows that the appropriate data dissemination protocol should be used to study the acceleration effect which is applicable in sparse networks. The analysis in this research provides the necessary background for better understanding and accurate calculations for the evaluation of data dissemination in VANETs.     

Overheating caused by passive solar elements in Tunis. Effectiveness of some ways to prevent it

Although Tunisian winters are mild compared with northern regions, there are heating requirements; their limited level suggests that passive solar energy would probably be able to meet them. However, the summer is hot enough, and one may wonder whether a solar design oriented toward the cold season would not induce severe overheating. Numerous studies have dealt with the heating performance of passive solar elements, but very little has been done to analyze their behavior in hot climatic conditions. The National School for Engineers of Tunis has built a passive solar pavilion which has been carefully instrumented. Special care has been devoted to the summer behavior of the pavilion. In this paper we describe some of the actions taken to prevent overheating, and we investigate their efficacy both by analysis of recorded measurements and by simulation. It is found that night ventilation is the most responsible action in decreasing room temperature, and that Trombe wall screening is more efficient than operating the walls as a solar chimney; overhangs are of valuable aid, and shuttering of the direct gain element also helps against overheating. The high thermal capacity results in a very stable room temperature, and plays an essential role for cooling when coupled with night ventilation. Finally, it is found that if appropriate action is taken in the hot season, a house equipped with passive solar heating elements can reach a very acceptable level of comfort in summer time.     

Identification and chemical characterization of specific organic indicators in the effluents from chemical production sites

The structural diversity of the wastewater composition was described by the use of detailed non-target screening analyses of industrial effluents from chemical production sites. Determination of the indicative organic compounds acting as potential molecular indicators for industrial emissions from chemical production industries has been possible due to (i) detailed characterisation of industrial contaminants and identification of compounds with high source specificity, (ii) quantitative determination of the organic constituents in the industrial effluents and (iii) the review of their industrial applications. The determination of potential site-specific markers and industrial molecular indicators corresponding to certain production processes (production of starting materials for manufacturing paper and printing inks, powder coatings as well as epichlorohydrin production) was performed in this work.The results of this study allowed significant contributions to the chemical characterisation of industrial contaminants and isolation of indicators that can act as representatives of industrial effluents in the aquatic environment.     

Interpersonal and Print Nutrition Communication for a Spanish-Dominant Latino Population: Secretos de la Buena Vida.

Participants (N = 357) were randomly assigned to 1 of 3 conditions: lay health advisor (promotora) plus tailored print materials, tailored print materials only (tailored), or off-the-shelf print materials (control). The primary outcomes were calories from fat and daily grams of fiber. Secondary outcomes included total energy intake, total and saturated fat intake, and total carbohydrates. Adjusted for baseline values, calories from fat were 29%, 30%, and 30% for the promotora, tailored, and control conditions, respectively, and grams of fiber consumed were 16 g, 17 g, and 16 g. Significant Condition X Time interactions were not observed between baseline and 12-weeks postintervention. The LHA condition achieved significantly lower levels of energy intake, total fat and saturated fat, and total carbohydrates. The relative superiority of the promotora condition may derive from the personal touch achieved in the face-to-face interactions or from the women's use of print materials under the promotora's guidance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

L approximation of a parabolic system regarded as a delay system

We present an approach to the problem of finding an L^∞ approximant of the infinite-dimensional system describing the diffusion of heat in a wall. We show that this system can be regarded as a delay system with Laplace variable √s. We are able to get results, established in Zwart et al. (1988), about partial fraction expansion for delay systems, achieved by some adjustment to the specificities of our particular case. The determination of an L^∞ approximant is realised in two steps, using the optimal Hankel-norm approximation.