Legumes seeds protein isolates in the production of ascorbic acid microparticles

This study evaluated the use of pea (Pisum sativum) and cowpea (Vigna unguiculata) protein isolates (PPI and CPI) in the microencapsulation of ascorbic acid (AA), by spray drying. PPI and CPI were used pure or mixed with maltodextrin (M) as wall materials of AA. The process yield was improved from 66% to 86% by the addition of M (CPI/M and PPI/M); also, AA particles yield was 79%. The AA retention from the drying process was higher in PPI/M (69%) than in CPI/M (66%), and this was attributed to PPI proteolysis profile, demonstrated by the SDS–PAGE electrophoresis. Scanning electron microscopy revealed that AA particles were similarly spherical and shriveled. Mean particle sizes of PPI/M/AA and CPI/M/AA were 7 and 8 μm, respectively. This study showed the exploration of protein isolates from legumes in the development of a microparticulate system containing AA with great potential for use in human health.     

Correlation between polyethylene topology and melt flow instabilities by determining in-situ pressure fluctuations and applying advanced data analysis

Using three high sensitive pressure transducers located inside a slit-die of a capillary rheometer and applying a set of advanced mathematical tools to process the acquired time dependent pressure signals, we are able to detect in-situ pressure fluctuations associated with sharkskin instabilities. Other distortions, as spurt and gross melt fracture, can also be in-situ detected. This originates from a factor of 10³ and 10² improvement in terms of time and pressure resolution achieved using the new set-up and data analysis that it will be described in detail in this article. Our approach quantifies the effect of polymer topology and shear rate on the characteristic frequency and amplitude of these pressure fluctuations inside the die. Depending on the polymer structure and the shear rate, different instabilities with large deviation in their main properties at melt-state, can be determined. Based on our results, a polymer-independent power law relationship between the characteristic frequency of the instability and the apparent shear stress has been found. Combining this new technique with the advanced mathematical analysis used, clear evidences concerning the origin and location of these instabilities, could be established. According to our analysis, the spurt instability starts in the entrance of the die and it propagates downstream while increasing its velocity along the die. This was confirmed by non-zero-time-lags in the cross-correlation function between the transducers located inside the slit-die. In case of sharkskin instability, pressure fluctuations inside the die indicate that its origin could also be already inside the die instead of being exclusively located at the die-exit region, as stated in earlier investigations.     

Design of grounding systems in substations using a mixed-integer linear programming formulation

The main purpose of this paper is the development of an optimization model to design grounding grids in electrical substations. The design of a grounding grid in a substation is formulated as a mixed-integer linear programming problem. The developed optimization model incorporates the constructive characteristics, as well as the technical and security requirements inherent to the construction, installation and operation of these grids.     

A Novel Approach to Detect Faults Occurring During Power Swings by Abrupt Change of Impedance Trajectory

The main purpose of power swing blocking is to distinguish faults from power swings. However, faults occurred during a power swing should still be detected and cleared promptly. This paper proposes an index based on detecting abrupt jump of impedance trajectory by utilization of the predicting capability of the Kalman Filter. The proposed index is calculated by assessing the difference between predicted and actual samples of impedance. The predicted impedance samples are obtained using the Kalman filter and Taylor expansion, which are used in this paper to track the phasor precisely. Second order of Taylor expansion is used to decrease the corrugation effect of impedance estimation and increase the reliability of the proposed method. Furthermore, in order to increase the selectivity of the proposed method, the proposed index is armed with phase comparison logic to detect internal faults. The instantaneous estimation and prediction capability of the Kalman filter are two reasons for proposing the use of Kalman filter. Intensive studies have been performed and the merit of the method is demonstrated by test simulations.     

A novel application of mesoporous silica material for extraction of pesticides

The mesoporous silica material MCM-41 was prepared by the sol-gel method and characterized using X-ray diffraction (XRD), N₂ adsorption-desorption and thermogravimetric analysis. The material was tested for extraction of trichlorfon, pyrimethanil, tetraconazole, thiabendazole, imazalil and tebuconazole from mango fruit, with analysis using gas chromatography-mass spectrometry (GC/MS). In experiments carried out in triplicate, at a 1.0 mg/kg concentration level, recoveries using the MCM-41 sorbent were in the range 73-103%. Comparison of MCM-41 with commercially available silica gel showed that MCM-41 was a similar extracting phase for the pesticides investigated with a significant cost advantage over this conventional material.     

Evolution of morphological and rheological properties along the extruder length for blends of a commercial liquid crystalline polymer and polypropylene

The main aim of this work is to study the morphological and rheological evolution during extrusion of blends of polypropylene and a commercial liquid crystalline polymer, Rodrun LC3000. This study was performed for blends with 10, 20 and 40 wt% LCP, processed at 220 and 240 °C. For this purpose, a special collecting device was used that allows the removal of samples at different locations along the extruder length. The results of the morphological study revealed that the mean diameter of the LCP structures decrease as they proceed along the extruder axis. The rheological properties were also studied ex situ both in the linear and in the non-linear regime. From the results obtained in oscillatory shear it was observed that the elastic modulus and the complex viscosity decreases from the beginning to the end of the extrusion process, reaching a minimum for the final extrudate. FT rheology was used to study the non-linear viscoelastic behavior and the results also show marked difference between samples collected at various stages of the process, the ratio I(3ω₁)/I(ω₁) decreasing along the extruder.     

Evolution of Chemistry,Morphology and Rheology of Various Polymer Systems along a Twin‐Screw Extruder

Intermeshing twin‐screw extruders have been recently identified as useful in special application niches such as the extrusion of PVC dry blends (counter‐rotating machines) and compounding operations (co‐rotating machines). Thus, it is of interest to study the mechanical and/or chemical effects that occur along the screw axis of the extruders, since they will dictate the characteristics and performance of the final material. This work aims at illustrating the usefulness of a simple experimental tool recently developed for the study of the physical, chemical and morphological evolution along the extruder of polymer based systems, data being presented and discussed for a number of composites and blends.     

Intercontinental spread of a multidrug-resistant methicillin-resistant Staphylococcus aureus clone

Two hundred ten methicillin-resistant Staphylococcus aureus (MRSA) isolates recovered between 1990 and 1997 from three Portuguese hospitals located in Lisbon and Oporto were analyzed by molecular fingerprinting techniques. The hybridization of ClaI restriction digests with the mecA- and Tn554-specific DNA probes combined with pulsed-field gel electrophoresis documented the abrupt appearance and extensive intrahospital spread of the Brazilian epidemic MRSA clone in the 1995 samples of each one of the three hospitals analyzed-suggesting the intercontinental transfer of this strain from Brazil to Portugal. The appearance of this clone may challenge the dominance of another highly epidemic imported clone-the Iberian MRSA, currently the most widely spread MRSA clone in Portuguese hospitals.     

Expression of the c-erbB-3 gene product in gastric cancer

The pattern of c-erbB-3 gene product was studied in 91 advanced gastric carcinomas, adjacent hyperplastic mucosa, intestinal metaplasia and dysplasia and in normal controls, using immunohistochemistry in archival material. All tumours showed positive c-erbB-3 staining in both cytoplasm and membrane. No significant differences of expression were observed between intestinal and diffuse-type carcinomas or any other clinical parameters. Of interest is the expression in the adjacent mucosa, which is extensive, cytoplasmic, and of lower intensity than in the tumours. Further studies are currently being carried out to clarify the role of this protein in tumour behaviour and gastric carcinogenesis.     

Radiopharmaceuticals for targeted radiotherapy

This work intends to find specific radiopharmaceuticals for cancer therapy based on beta (153Sm and 166Ho) or Auger (99Tc(m)) emitter radionuclides, using cyclic and acyclic polyamines as bifunctional chelators. These chelators are designed to allow the binding of a tumour seeking biomolecule and/or a DNA intercalator. The cyclic amines, such as 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid, 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetic acid and 1,4,7,10-tetraazacyclotridecane-1,4,7,10-tetraacetic acid, were radiolabelled with 153Sm and 166Ho. The radiochemical and biological behaviour of the resulting complexes were evaluated in order to assess their potential as building blocks for the attachment of selected biomolecules, with the aim of further applying them for the development of specific therapeutic radiopharmaceuticals. Novel pyrazolyldiamines, bearing a DNA intercalating anthracenyl fragment, were also explored to synthesize radioactive complexes with the fac-[99Tc(m)(CO)]3]+ moiety. The identity of these 99Tc(m) tricarbonyl complexes was confirmed by high-performance liquid chromatography comparison with rhenium congeners fully characterized. By including a DNA intercalator into the chelator framework, we expect to induce more efficient and selective damage to the DNA of cancer cells by the action of the short-range Auger electrons emitted by 99Tc(m).