Electromagnetic shielding effectiveness of carbon fibre reinforced composites

This paper reports results on the shielding effectiveness parameter of laminated epoxy composites with carbon fibre reinforcements. Measurements of shielding effectiveness were carried out with a coaxial transmission line testing chamber according to ASTM 4935 standard and epoxy-matrix composites with continuous carbon-fibres were proven to be an excellent electromagnetic interference shielding material, where a composite slab made of 4 layers of prepregs provided more than 99.9% of electromagnetic attenuation. It was found that the reflection mechanism of the shielding material was mainly influenced by the fibre volume ratio, and that an increase in the number of layers of the composite resulted in higher shielding effectiveness due to a greater absorption mechanism. Calculations of the shielding effectiveness parameter of the material used were made by means of commercial electromagnetic simulation tools, having determined experimentally the overall resistivity of the composite. The findings presented in this work suggest that in presence of a greater number of interfaces at different impedance the separate modelling of matrix and fibres at mesoscopic scale must be taken into account

Evaluation of fluoropyruvate as nucleophile in reactions catalysed by N-acetyl neuraminic acid lyase variants: Scope, limitations and stereoselectivity

The catalysis of reactions involving fluoropyruvate as donor by N-acetyl neuraminic acid lyase (NAL) variants was investigated. Under kinetic control, the wild-type enzyme catalysed the reaction between fluoropyruvate and N-acetyl mannosamine to give a 90:10 ratio of the (3R,4R)- and (3S,4R)-configured products; after extended reaction times, equilibration occurred to give a 30:70 mixture of these products. The efficiency and stereoselectivity of reactions of a range of substrates catalysed by the E192N, E192N/T167V/S208V and E192N/T167G NAL variants were also studied. Using fluoropyruvate and (2R,3S)- or (2S,3R)-2,3-dihydroxy-4-oxo-N,N-dipropylbutanamide as substrates, it was possible to obtain three of the four possible diastereomeric products; for each product, the ratio of anomeric and pyranose/furanose forms was determined. The crystal structure of S. aureus NAL in complex with fluoropyruvate was determined, assisting rationalisation of the stereochemical outcome of C-C bond formation

A new economic instrument for financing accelerated landfill aftercare

The key aspects of landfill operation that remain unresolved are the extended timescale and uncertain funding of the post-closure period. This paper reviews the topic and proposes an economic instrument to resolve the unsustainable nature of the current situation. Unsustainability arises from the sluggish degradation of organic material and also the slow flushing of potential pollutants that is exacerbated by low-permeability capping. A landfill tax or aftercare provision rebate is proposed as an economic instrument to encourage operators to actively advance the stabilization of landfilled waste. The rebate could be accommodated within existing regulatory and tax regimes and would be paid for: (i) every tonne of nitrogen (or other agreed leachate marker) whose removal is advanced via the accelerated production and extraction of leachate; (ii) every tonne of non-commercially viable carbon removed via landfill gas collection and treatment. The rebates would be set at a level that would make it financially attractive to operators and would encourage measures such as leachate recirculation, in situ aeration, and enhanced flushing. Illustrative calculations suggest that a maximum rebate of up to ~€50/tonne MSW would provide an adequate incentive

EMI Spectral Aggregation of Modulation Schemes in a lab-based DC Microgrid

DC Microgrid research has developed in the recent years following the increasing integration of power electronic based switching devices at the point of common coupling in DC grids. This has led to electromagnetic interference problems caused by the spectral aggregation of conducted emissions in the low-frequency range (2–150 kHz). To investigate this, a framework for understanding spectral aggregation resulting from the multiple switching harmonics from the interconnected DC grid devices is analysed. In this work, three modulation techniques are applied to identical & parallel connected DC/DC converters forming a lab-based DC grid. The harmonics are then analysed for spectral aggregation using an EMI receiver. This provides insights into the spectral aggregation of conducted emissions in the low-frequency range to promote electromagnetic compatibility and further facilitate a possible framework for standardisation of DC power quality

Latest developments on the shielding effectiveness measurements of materials and gaskets in reverberation chambers

In this study, the authors present the latest developments on the measurements for the shielding effectiveness (SE) of gaskets and materials in reverberation chambers (RCs). A variant method, where the insertion loss of the fixture is achieved from the SE of the fixture with no sample in the aperture is found; it is appropriate for gaskets and for any flat material having a sufficiently high reflectivity at least on one side. A simple and usable condition under which the simplest method for the SE measurements of gaskets and materials in RCs can be used is also given, as well as particular cases where it can be directly applied are shown. This method, whose applicability is enhanced in this study, can be used for gaskets and any flat sample. Such developments simplify measurement setup and associated procedures. Comparisons of results support the methods for the SE measurements of gaskets and material in RCs shown in this study

Rethinking Cuts in Public Higher Education: An American Example

Recent cuts in public higher education spending have often been matched by tuition increases. This may result in a decline in the number of college graduates that a state produces. The secondary effect might be that personal income and personal income tax receipts decline. Utilizing a net present value model, we quantify these results using New York State data. Furthermore, we utilize sensitivity analysis to ensure the robustness of the model. Finding that potential revenue losses quickly dwarf the short-run savings, we advocate a longer-term analysis of budget cuts that are accompanied by tuition increases.

Fumaroylamino-4,5-epoxymorphinans and Related Opioids with Irreversible μ Opioid Receptor Antagonist Effects

We have previously shown that cinnamoyl derivatives of 14β-amino-17-cyclopropylmethyl-7,8-dihydronormorphinone and 7α-aminomethyl-6,14-endoethanonororipavine have pronounced pseudoirreversible μ opioid receptor (MOR) antagonism. The present communication describes the synthesis and evaluation of fumaroylamino analogues of these cinnamoylamino derivatives together with some related fumaroyl derivatives. The predominant activity of the new ligands was MOR antagonism. The fumaroylamino analogues (<b>2a</b>, <b>5a</b>) of the pseudoirreversible antagonist cinnamoylamino morphinones and oripavines (<b>2b</b>, <b>5b</b>) were themselves irreversible antagonists in vivo. However the fumaroylamino derivatives had significantly higher MOR efficacy than the cinnamoylamino derivatives in mouse antinociceptive tests. Comparison of <b>2a</b> and <b>5a</b> with the prototypic fumaroylamino opioid β-FNA (<b>1a</b>) shows that they have similar MOR irreversible antagonist actions but differ in the nature of their opioid receptor agonist effects; <b>2a</b> is a predominant MOR agonist and <b>5a</b> shows no opioid receptor selectivity, whereas the agonist effect of β-FNA is clearly κ opioid receptor (KOR) mediated