Biocompatible polymeric microparticles produced by a simple biomimetic approach

The use of superhydrophobic surfaces to produce polymeric particles proves to be biologically friendly since it entails the pipetting and subsequent cross-linking of polymeric solutions under mild experimental conditions. Moreover, it renders encapsulation efficiencies of ∼100%. However, the obtained particles are 1 to 2 mm in size, hindering to a large extent their application in clinical trials. Improving on this technique, we propose the fabrication of polymeric microparticles by spraying a hydrogel precursor over superhydrophobic surfaces followed by photo-cross-linking. The particles were produced from methacrylamide chitosan (MA-CH) and characterized in terms of their size and morphology. As demonstrated by optical and fluorescence microscopy, spraying followed by photo-cross-linking led, for the first time, to the production of spherical particles with diameters on the order of micrometers, nominal sizes not attainable by pipetting. Particles such as these are suitable for medical applications such as drug delivery and tissue engineering.We thank Ivo Aroso and Ana Isabel Neto for their valuable support with FTIR and compression experiments, respectively. A.M.S.C. thanks FCT for financial support through grant BIM/PTDC/CTM-BPC/112774/2009_02. M.A.-M. thanks CONACyT (Mexico) for financial support through post-doc grant no. 203732. N.M.O. thanks FCT for financial support through Ph.D. scholarship no. SFRH/BD/73172/2010. This work was funded by the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. REGPOT-CT2012-316331-POLARIS, by FEDER through the Competitive Factors Operation Program-COMPETE, and by national funds through FCT - Fundacao para a Ciencia e a Tecnologia in the scope of project PTDC/CTM-BIO/1814/2012

Lean burn natural gas fueled S.I. engine and exhaust emissions

An experimental study was undertaken to study exhaust emission from a lean-burn natural gas spark ignition engine. The possibility that such an engine may help to reduce exhaust emissions substantially by taking advantage of natural gas fuel properties, such as its antiknock properties and extended lean flammability limit compared to gasoline, was the main motivation behind the investigation. A four cylinder, automotive type spark ignition engine was used in the investigation. The engine was converted to operate on natural gas by replacing its fuel system with a gaseous carburetion system. A 3-way metal metrix catalytic converter was used in the engine exhaust system to reduce emission levels. The engine operated satisfactorily at an equivalence ratio as lean as 0.6, at all speeds and loads. As a result NOx emissions were significantly reduced. However, hydrocarbon emissions were high, particularly at very lean conditions and light loads. Most of these hydrocarbons were made up of methane with small concentrations of ethane and propane. Coefficient of variations in hydrocarbons were generally high at very lean operating conditions and light loads, but decreased with increasing equivalence ratio and engine speed. Methane concentrations in the engine exhaust decreased with increasing load and equivalence ratio. At lean air-to-fuel ratios and light loads oxidation of methane in the catalyst was substantially limited and no NOx reduction was achieved. In addition, the proportion of nitric oxide in oxides of nitrogen increased with increasing amount of NOx in the engine exhaust. A major problem encountered in the study was the inability of the fuel system to maintain near constant air-to-fuel ratios at steady operating conditions. © Copyright 1995 Society of Automotive Engineers, Inc

Development of an integrated methodology in support of remaining life assessment of Co-60 based gamma irradiation facilities

An integrated approach has been developed for the remaining life assessment of an irradiation facility. The probabilistic safety assessment (PSA) was performed for the plant to develop the quantified indicators of safety for various situations. PSA results were used to identify and prioritize the systems and components for deterministic assessment. The insight developed from various accidents world over has also been used as an input to investigate the likelihood of such failures and assessment of safety provisions against such failures. This paper discusses development of safety indicator in details and touches upon the other aspects as and when required. The objective is that the extended life of the facility should be predicted in a manner that likelihood of accident is low. As far as Cobalt-60 based Gamma Irradiation Facilities are concerned a survey of available literature shows that this study is unique in three respects; (a) it is for the first time that such a comprehensive re-assessment work has been performed on an irradiation facility. (b) In this study an integrated framework has been developed and applied for safety reassessment of Gamma Irradiation Plant (ISOMED) for Sterilization of Medical Products) one of the oldest, category - II type Cobalt-60 based Gamma Irradiation Facilities in the world and (c) A procedure has been developed in support of regulatory re-licensing and life extension of the Cobalt-60 based Gamma Irradiation plant. Based on this study eleven recommendations dealing with system retrofitting, change in operation and maintenance practices and further testing and qualification to get added confidence as part of life extension programme. Even though this study recommended life extension of ten years the first regulatory clearance of three years was given by the regulatory agency. (C) 2010 Elsevier B.V. All rights reserved

Chemical investigation of some Indian plants

Isolation of several known compounds belonging to the class of steroids, terpenoids, coumarins, etc., from a number of Indian plants is recorded