Unravelling the kinetics of the formation of acrylamide in the Maillard reaction of fructose and asparagine by multiresponse modelling

A kinetic model for the formation of acrylamide in a fructose–asparagine reaction system at initial pH 5.5 is proposed, based on an approach called multiresponse kinetic modelling. The formation of acetic acid and formic acid from the degradation of fructose and its isomer glucose was included in the proposed kinetic model. The kinetic model suggests that the effect of temperature on acrylamide formation with fructose is more due to the preceding steps with the formation of the Schiff base. The use of fructose and lower pH resulted in a higher yield of acrylamide (3%), suggesting that both can play an important role in acrylamide mitigation. Furthermore, these models have shown that, at high temperatures (120–200 °C), the Maillard reaction rapidly goes into the advanced stages, forming high amounts of organic acids and high molecular weight melanoidins. Overall, these mechanistic models provide more insight of the formation of acrylamide in a quantitative way.     

Molecular insights into human taste perception and umami tastants: A review

Understanding taste is key for optimizing the palatability of seaweeds and other non-animal-based foods rich in protein. The lingual papillae in the mouth hold taste buds with taste receptors for the five gustatory taste qualities. Each taste bud contains three distinct cell types, of which Type II cells carry various G protein-coupled receptors that can detect sweet, bitter, or umami tastants, while type III cells detect sour, and likely salty stimuli. Upon ligand binding, receptor-linked intracellular heterotrimeric G proteins initiate a cascade of downstream events which activate the afferent nerve fibers for taste perception in the brain. The taste of amino acids depends on the hydrophobicity, size, charge, isoelectric point, chirality of the alpha carbon, and the functional groups on their side chains. The principal umami ingredient monosodium l -glutamate, broadly known as MSG, loses umami taste upon acetylation, esterification, or methylation, but is able to form flat configurations that bind well to the umami taste receptor. Ribonucleotides such as guanosine monophosphate and inosine monophosphate strongly enhance umami taste when l -glutamate is present. Ribonucleotides bind to the outer section of the venus flytrap domain of the receptor dimer and stabilize the closed conformation. Concentrations of glutamate, aspartate, arginate, and other compounds in food products may enhance saltiness and overall flavor. Umami ingredients may help to reduce the consumption of salts and fats in the general population and increase food consumption in the elderly.     

The effects of hydraulic and organic shock loads on the robustness of upflow anaerobic sludge blanket reactors treating sewage.

In this investigation, the robustness and stability of UASB reactors was evaluated on the basis of four indicators: (i) COD removal efficiency; (ii) effluent variability; (iii) pH stability; and (iv) recovery time. The experiments were carried out using six pilot-scale UASB reactors fed with domestic sewage and operated under different operational conditions. After establishment of a "steady-state", organic and hydraulic shock loads (six times the loading rate during six hours) were imposed. The results show that the UASB reactors are robust systems with regards to COD removal efficiency and pH stability when exposed to shock loads. However, this reactor cannot attenuate the imposed fluctuation in the influent COD. A secondary treatment unit is needed to retain the expelled sludge occurring as a result of a hydraulic shock load, or prior to the shock, a sufficient amount of sludge needs to be discharged from the reactor.     

Status and Potential of Spate Irrigation in Ethiopia

This article discusses spate irrigation in Ethiopia and aims to take stock of the current status of spate irrigation development. It summarizes experiences so far and formulates a number of recommendations on the development of this upcoming resource management system. It argues that raised weirs are useful mainly in areas where a large head for spate flow diversion is required, but that traditional earthen structures with conical stone/gabion reinforcements are cost-effective and technically adequate for floodwater distribution and management. It contends that the practical successes of sediment settling ponds (gravel traps) are at best mixed. Even where a small basin is justified, it can only ever trap a small proportion of the incoming sediment load. It is better to allow large floods with excessive sediment load (>100,000 ppm) to by-pass upstream intakes to be diverted lower down the system, and provide additional livelihood opportunities in downstream areas in the form of rangeland and agro-forestry development. This is particularly useful in the lowlands of Ethiopia with large pastoral community where spate irrigation is yet to make in-roads. The article further explains that water rights in spate are different from the sharing and allocation of perennial flows—they are dynamic and respond to a situation that differs from year to year as well as within a year and that a certain degree of inequity among users is inevitable. Keeping the command area compact can ensure two or more irrigation turns and this can highly increase productivity as crops are no longer in the ‘stress zone’. To transform spate irrigation in Ethiopia from subsistence to a business-oriented production system, the article proposes the promotion of cash crops including pulses and oil seeds as well as encouraging investors to go for bio-fuel development and agro-forestry in the lowland areas where huge potential exist. To avoid vehement conflicts that may arise among the settled agricultural and pastoral communities due to the implementation of the business-oriented production system, the traditional rights of the pastoral communities must be respected and their rangeland and water resources be safeguarded. For maximum yield, soil moisture conservation measures such as pre-irrigation land preparation, deep ploughing and mulching are essential as is the conjunctive use of spate flow and groundwater. Last, but most important, the article emphasizes that farmers need to be placed at the heart of any spate irrigation development programme as primary beneficiaries, managers and operators as well as part of the decision making institution.     

Mangrove forests as a nature-based solution for coastal flood protection: Biophysical and ecological considerations

Nature-based coastal protection is increasingly recognised as a potentially sustainable and cost-effective solution to reduce coastal flood risk. It uses coastal ecosystems such as mangrove forests to create resilient designs for coastal flood protection. However, to use mangroves effectively as a nature-based measure for flood risk reduction, we must understand the biophysical processes that govern risk reduction capacity through mangrove ecosystem size and structure. In this perspective, we evaluate the current state of knowledge on local physical drivers and ecological processes that determine mangrove functioning as part of a nature-based flood defence. We show that the forest properties that comprise coastal flood protection are well-known, but models cannot yet pinpoint how spatial heterogeneity of the forest structure affects the capacity for wave or surge attenuation. Overall, there is relatively good understanding of the ecological processes that drive forest structure and size, but there is a lack of knowledge on how daily bed-level dynamics link to long-term biogeomorphic forest dynamics, and on the role of combined stressors influencing forest retreat. Integrating simulation models of forest structure under changing physical (e.g. due to sea-level change) and ecological drivers with hydrodynamic attenuation models will allow for better projections of long-term natural coastal protection.     

Experimental evaluation of losses in magnetic components for powerconverters

A very versatile experimental method for measuring losses in magnetic components is presented. This is not subject to the bandwidth constraints associated with the direct wattmeter method. The proposed method features accurate measurement of conduction losses, separation of core and conduction losses, measurement at high frequencies, and scale modeling of magnetic components. The experimental measurements are compared with theoretical predictions of components as applicable to certain power electronic converters     

Optimum nonlinear turn-off snubbers: design and application

The optimization of the general turn-off snubber, consisting of a nonlinear saturable snubber capacitor with an energy recovery circuit, is done in terms of minimum total energy loss in the power electronic turn-off circuit. To analyze this nonlinear circuit without a computer simulation, a two-step piecewise-linear approximation of the capacitor's capacitance-voltage curve is presented. Results regarding the total energy loss in the circuit during the switch turn-off indicate that the nonlinear capacitor as a snubber element is superior to the normal linear capacitor even if the ceramic capacitor is used only up to its specified voltage value     

Analysis and implications of aircraft disinsectants

Aircraft disinsection is required by various countries. In-flight spraying with a 2% phenothrin aerosol exposes passengers and crew directly. Residual spaying uses a permethrin emulsions in the absence of passengers and crew and results in dermal and oral exposures. Exposed passengers and crew often complain of, skin rashes, respiratory problems, tingling and numbness in fingertips and lips and burning eyes. A number of formulations were analyzed for their constituents using GLC-Mass. spec. Volatile organic compounds (VOCs) were found in all aerosol preparations including, ethyl benzene and xylene isomers along with phenothrin. Residual sprays contained, cis-, and trans-, permethrins, palmidrol, and occasionally naphthalene. Headspace analysis found methylene chloride and hexene derivatives but not the active ingredients. The known synergistic effects between organophosphates and pyrethrins, based on carboxyesterases inhibition, can be expected in the presence of Tricresylphosphates (TCPs), constituents found in jet engine oils and in some hydraulic fluids. During oil seal failure, the presence of TCP in the ventilation air could explain the increased sensitivity of some crew members and passengers to disinsectants.     

Benchmarking international scientific excellence: Are highly cited research papers an appropriate frame of reference?

This paper introduces a citation-based "systems approach" for analyzing the various institutional and cognitive dimensions of scientific excellence within national research systems. The methodology, covering several aggregate levels, focuses on the most highly cited research papers in the international journal literature. The distribution of these papers across institutions and disciplines enables objective comparisons their (possible) international-level scientific excellence. By way of example, we present key results from a recent series of analyses of the research system in the Netherlands in the mid 1990s, focussing on the performance of the universities across the various major scientific disciplines within the context of the entire system"s scientific performance. Special attention is paid to the contribution in the world"s top 1% and top 10% most highly cited research papers. The findings indicate that these high performance papers provide a useful analytical framework - both in terms of transparency, cognitive and institutional differentiation, as well as its scope for domestic and international comparisons - providing new indicators for identifying "world class" scientific excellence at the aggregate level. The average citation scores of these academic "Centres of Scientific Excellence" appear to be an inadequate predictor of their production of highly cited papers. However, further critical reflection and in-depth validation studies are needed to establish the true potential of this approach for science policy analyses and evaluation of research performance. This revised version was published online in August 2006 with corrections to the Cover Date.