Modelling and validation of synthesis of poly lactic acid using an alternative energy source through a continuous reactive extrusion process

PLA is one of the most promising bio-compostable and bio-degradable thermoplastic polymers made from renewable sources. PLA is generally produced by ring opening polymerization (ROP) of lactide using the metallic/bimetallic catalyst (Sn, Zn, and Al) or other organic catalysts in a suitable solvent. In this work, reactive extrusion experiments using stannous octoate Sn(Oct)2 and tri-phenyl phosphine (PPh)3 were considered to perform ROP of lactide. Ultrasound energy source was used for activating and/or boosting the polymerization as an alternative energy (AE) source. Ludovic® software, designed for simulation of the extrusion process, had to be modified in order to simulate the reactive extrusion of lactide and for the application of an AE source in an extruder. A mathematical model for the ROP of lactide reaction was developed to estimate the kinetics of the polymerization process. The isothermal curves generated through this model were then used by Ludovic software to simulate the “reactive” extrusion process of ROP of lactide. Results from the experiments and simulations were compared to validate the simulation methodology. It was observed that the application of an AE source boosts the polymerization of lactide monomers. However, it was also observed that the predicted residence time was shorter than the experimental one. There is potentially a case for reducing the residence time distribution (RTD) in Ludovic® due to the ‘liquid’ monomer flow in the extruder. Although this change in parameters resulted in validation of the simulation, it was concluded that further research is needed to validate this assumption

Farmers’ ethno-ecological knowledge of vegetable pests and pesticidal plant use in Malawi and Zambia

While pests are a major constraint in vegetable production in many parts of Southern Africa, little is known about farmers’ knowledge and management practices. A survey was conducted among 168 and 91 vegetable farmers in Northern Malawi and Eastern Zambia, respectively, to evaluate their knowledge, attitudes and traditional management practices in tomato and crucifers (brassica). All respondents in Malawi and Zambia reported pest damage on tomato and crucifers, and 75% had used synthetic pesticides. The use of pesticidal plants, cultural practices and resistant varieties constituted a smaller portion of the pest control options in both crucifers and tomato. Over 70% of the respondents were aware of pesticidal plants, and more female (75%) than male (55%) respondents reported using them. While over 20 different plant species were mentioned by respondents, Tephrosia vogelii accounted for 61 and 53% of the pesticidal species known to respondents in Malawi and Zambia, respectively. Farmers with small landholdings were more inclined to use pesticidal plants than those with medium and large landholding highlighting the importance of this management alternative for poor farmers. Most respondents were willing to cultivate pesticidal plants, which indicate that farmers understand the potential value of these plants in pest management

Neurodevelopmental Outcomes at 2 and 3.5 Years for Very Preterm Babies Enrolled in a Randomized Trial of Milking the Umbilical Cord versus Delayed Cord Clamping

Background: Guidelines published by the International Liaison Committee for Resuscitation and by the World Health Organization recommend delaying cord clamping at birth as part of routine care for infants. Objective: To study the use of milking of the cord 4 times as an alternative to enhance the redistribution of placental blood into the baby. Methods: This is a prospective cohort study of neurodevelopmental assessment by the Bayley III method of very preterm infants who had participated in a trial of delayed cord clamping versus cord milking at birth that was conducted in a neonatal tertiary care hospital. The primary outcomes were differences in cognitive, motor and language development at 2 and 3.5 years. Two-tailed analyses were performed with the χ2 test, Fisher's exact test, t test, Mann-Whitney U test and ANCOVA. Results: Out of the 58 infants enrolled in the original study, 39 infants (67%) were assessed at 2 years and 29 (50%) at 3.5 years of age. Neurodevelopmental outcomes at 2 and 3.5 years did not significantly differ between the two groups for the three Bayley III composite scores. At 3.5 years there was a trend towards higher scores for girls in the language composite scores (girls: mean = 121.6, SD = 15.22; boys: mean = 101.07, SD = 19.84) and on the motor scale (girls: mean = 124.60, SD = 18.15; boys: mean = 97.86, SD = 17.23). Conclusions: In this small number of participants followed up at 2 and 3.5 years of age, milking of the cord 4 times did not have any long-term adverse effect on neurodevelopmental outcome, suggesting that cord milking could be used as an alternative to delayed cord clamping

Progress in environmental-friendly polymer nanocomposite material from PLA: synthesis, processing and applications

The disposal of large amounts of waste from daily use polymers is among one of the foremost concerns in the current era. Effective utilization of bio-renewable materials procured from natural sources has been proposed as a potential solution to this problem. Among such different polymers, Poly lactic acid (PLA) which is a bio-degradable polymer, resembles quite promotable features, which can be polymerized from sustainable sources as chips sugarcane, starch and corn. Ring-opening polymerization (ROP) of Lactide (LA) monomer considering catalysts such as Al, Sn or Zn is one of the efficient methods for the PLA synthesis. However, the PLA polymerized through this type of catalysts may contain trace elements of the catalyst. Due to their carcinogenic nature, the traces of such catalysts should be (ideally) removed from the synthesis process. The use of alternative energy (AE- UV, Microwave) sources could be a potential route. Alternative development of non-metal catalysts is best alternatives for the processing of PLA through ROP. PLA layer based composite materials are gaining huge interest due to their multiple application (food, medical etc.) as eco-friendly material. In this article, we review on the implementation of AE sources for PLA processing and to populate the current state-of-the-art associated with the PLA research, especially application in nanocomposite materials field

Visual function and long-term chloroquine treatment

Ophthalmic examinations and selected tests of visual function were perfonned on 64 patients with rheumatoid arthritis who had received daily doses of 200 mg chloroquine sulphate for periods ranging from 3 to 11 months. Visual fields were determined by Humphrey automated perimetry and Amsler grids and a further battery of four tests of macular function (visual evoked potentials, critical flicker fusion threshold, Cambridge contrast sensitivity and the macular dazzle test) were administered. No case of retinal pigmentary abnormalities plus visual loss was found, but 2 patients were advised to cease chloroquine therapy on the basis of funduscopic findings. A small group of patients with relatively poor scores on one or more tests had normal visual fields and ophthalmic findings. There were no significant partial correlations between test results and the cumulative dose of chloroquine. These results support the opinion that currently recommended doses of chloroquine pose a minimal risk of retinal toxicity

An investigation into the design of precision weeding mechanisms for inter and intra-row weed control

There is an increasing interest in the use of mechanical intra-row weeders because of concern over environmental degradation and a growing demand for organically produced food. The aim of this study was to investigate the factors that influence the design of precision weeding mechanisms for inter-and intra-row weed control. The purpose is to increase the understanding of the dynamics of the soil-machine interactions and to develop a system for either organic farming or to reduce the environmental loading of agrochemicals in conventional agriculture. Both the graphical computer simulation studies and the use of a mathematical model (O’Dogherty et al., 2007) for the kinematics of discs were used as tools to aid the disc design to determine the optimum geometric characteristics for a rotating disc that will be able to treat the intra-row area between the crop plants undisturbed circle. The model has wide applicability for the interactive design of discs for a range of crops. A force prediction model for shallow asymmetric static and rotating discs (about a vertical axis) developed to predict the forces on rotating discs. The model takes into account the geometric parameters of the discs, the speed of operation, the working depth and the physical properties of the soil based upon those required for the general soil mechanics equation which obeys the Mohr-Coulomb failure criterion. A comparison of all experimental work encompassing the laboratory experiments with non-rotating and rotating discs, incorporating the deflection effect of the shaft when working at 0o inclination angle showed that the model is able to predict the draught force with good accuracy. The predicted forces were 3.5% more than the measured forces overall for a linear regression line (with a coefficient of determination of 0.7) and 61% of the data were within bounds of ± 25% a line of equal magnitude. The effect of working depth, inclination angle and disc geometry on draught and penetration force requirements for flat and convex discs were assessed under controlled laboratory conditions. Because of its simplicity a flat disc was an obvious one to study as it is a circular blade with incorporating a cut-out sector, whilst the convex disc has the advantage of underside clearance. The effect of the concavity on soil failure proved to be of interest by providing smaller aggregates. Four inclination angles (0o - 15o) were examined at 0.5 m s-1 (1.8 km h-1) driving speed and 1 rev s-1 rotational speed at 10 mm deep. Four depths (10 mm - 25 mm) were examined at 0.5 m s-1 driving speed and 1 rev s-1 rotational speed at 10 mm deep and 0o inclination angle were tested under controlled conditions. Inclination angle and disc geometry had a significant effect on disc forces and soil failure. A small increase in inclination angle to the direction of travel reduces the magnitude of draught and vertical force by 70% and 80% respectively on average for both flat and convex disc geometries. The convex disc requires 15% less draught force than an equivalent flat disc. This allowed the optimum working parameters for a disc to be selected to eliminate the weeds with the minimum force requirements. The results of a field experiment after 16; 23; and 33 days transplanting with a working speed of 0.5 m s-1 (1.8 km h-1) showed that the proposed novel mechanical weed control system can achieve a weed reduction within the crop row up to 87%. The disc-hoe has a lower cost for an area of 125 ha of £81 ha-1,in comparison to £139 ha-1 for the inter-row and hand weeding combination and £690 ha-1 for a six man gang manual intra-row weeding, for two passes. It is also less expensive than the cost of the 24 m tractor mounted sprayer of £100 ha-1 The use of the rotating disc-hoe for mechanical weed control would have the benefits of lower mechanical weeding cost, increased potential for organic production and reduction in the number of weeding operations through better targeting to minimise problems caused by frequent soil disturbance and reduced herbicide use having the benefits of environmental advantage.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

THSim v3.2: The Talking Heads simulation tool

The field of language evolution and computation may benefit from using efficient and robust simulation tools that are based on widely exploited principles within the field. The tool presented in this paper is one that could fulfil such needs. The paper presents an overview of the tool -- THSim v3.2 -- and discusses some research questions that can be investigated with it

Turning round the telescope. Centre-right parties and immigration and integration policy in Europe

This is an Author's Original Manuscript of 'Turning round the telescope. Centre-right parties and immigration and integration policy in Europe', whose final and definitive form, the Version of Record, has been published in the Journal of European Public Policy 15(3):315-330, 2008 [copyright Taylor & Francis], available online at: http://www.tandfonline.com/doi.org/10.1080/13501760701847341