147 research outputs found
INDOOR AIR QUALITY IN SUBMARINES
ABSTRACT The next generation of conventional submarines will be submerged for several weeks, creating a need for regenerative air purification methods and new air monitoring instruments. Submarine air is a complex mixture of compounds, where the most obvious contaminant is metabolically produced carbon dioxide. Normal eight-hour occupational exposure limits are not applicable on a submarine, instead special longtime exposure limits must be set. A number of air purification methods for submarines are either available or under development, e.g. cryogenic plants, biological plants and solid amine plants. For air monitoring compact GC/MS is an interesting option, already in use onboard nuclear submarines
Exploring metabolic responses of potato tissue induced by electric pulses
In this study, we investigated the metabolic
responses of potato tissue induced by pulsed electric field
(PEF). Potato tissue was subjected to field strengths ranging
from 30 to 500 V/cm, with a single rectangular pulse of 10 μs,
100 μs, or 1 ms. Metabolic responses were monitored using
isothermal calorimetry, changes on electrical resistance during
the delivery of the pulse, as well as impedance measurements.
Our results show that the metabolic response involves oxygen
consuming pathways as well as other unidentified events that
are shown to be insensitive to metabolic inhibitors such as
KCN and sodium azide. The metabolic response is strongly
dependent on pulsing conditions and is independent of the
total permeabilization achieved by the pulse. Evidence shows
that calorimetry is a simple and powerful method for
exploring conditions for metabolic stimulation, providing
information on metabolic responses that can not be obtained
from electrical measurements. This study set the basis for
further investigations on defense-related consequences of
PEF-induced stress.Sparbanksstiftelsen Färs & Frosta (Sweden).Fundação para a Ciência e a Tecnologia (FCT).Lund University (Sweden).Department of Cell and Organism Biology; Department of Plant Biochemistry
The effect of microencapsulated phase change materials on the rheology of geopolymer and Portland cement mortars
The effect of microencapsulated phase‐change materials (MPCM) on the rheological properties of pre‐set geopolymer and Portland cement mortars was examined. Microcapsules with hydrophilic and hydrophobic shells were compared. The shear rate dependency of the viscosities fitted well to a double Carreau model. The zero shear viscosities are higher for geopolymer mortar, illustrating poorer workability. The time evolution of the viscosities was explored at shear rates of 1 and 10 s−1. New empirical equations were developed to quantify the time‐dependent viscosity changes. The highest shear rate disrupted the buildup of the mortar structures much more than the lower shear rate. Microcapsules with a hydrophobic shell affect the rheological properties much less than the microcapsules with a hydrophilic shell, due to the higher water adsorption onto the hydrophilic microcapsules. Shear forces was found to break down the initial structures within geopolymer mortars more easily than for Portland cement mortars, while the geopolymer reaction products are able to withstand shear forces better than Portland cement hydration products. Initially, the viscosity of geopolymer mortars increases relatively slowly during due to formation of geopolymer precursors; at longer times, there is a steeper viscosity rise caused by the development of a 3D‐geopolymer network. Disruption of agglomerates causes the viscosities of portland cement mortars to decrease during the first few minutes, after which the hydration process (increasing viscosities) competes with shear‐induced disruption of the structures (decreasing viscosities), resulting in a complex viscosity behavior.publishedVersio
Impact of environmental moisture on C(3)A polymorphs in the absence and presence of CaSO4 center dot 0.5 H2O
The phenomenon of water vapour sorption by anhydrous C3A polymorphs both in the absence and in the presence of CaSO4·0·5 H2O was studied utilising dynamic and static sorption methods. It was found that orthorhombic C3A starts to sorb water at 55% relative humidity (RH) and cubic C3A at 80% RH. Also, C3Ao sorbs a higher amount of water which is predominantly physically bound, whereas C3Ac preferentially interacts with water by chemical reaction. In the presence of calcium sulfate hemihydrate, ettringite was observed as the predominant pre-hydration product for both C3A modifications: that is, ion transport had occurred between C3A and sulfate. Environmental scanning electron microscopic imaging revealed that in a moist atmosphere, a liquid water film condenses on the surface of the phases as a consequence of capillary condensation between the particles. C3A and sulfate can then dissolve and react with each other. Seemingly, pre-hydration is mainly facilitated through capillary condensation and less through surface interaction with gaseous water molecules
Procedure to determine the impact of the surface film resistance on the hygric properties of composite clay/fibre plasters
International audienc
Effect of Torrefaction on Water Vapor Adsorption Properties and Resistance to Microbial Degradation of Corn Stover
The equilibrium moisture content (EMC) of biomass affects transportation, storage, downstream feedstock processing, and the overall economy of biorenewables production. Torrefaction is a thermochemical process conducted in the temperature regime between 200 and 300 °C under an inert atmosphere that, among other benefits, aims to reduce the innate hydrophilicity and susceptibility to microbial degradation of biomass. The objective of this study was to examine water sorption properties of torrefied corn stover. The EMC of raw corn stover, along with corn stover thermally pretreated at three temperatures, was measured using the static gravimetric method at equilibrium relative humidity (ERH) and temperatures ranging from 10 to 98% and from 10 to 40 °C, respectively. Five isotherms were fitted to the experimental data to obtain the prediction equation that best describes the relationship between the ERH and the EMC of lignocellulosic biomass. Microbial degradation of the samples was tested at 97% ERH and 30 °C. Fiber analyses were conducted on all samples. In general, torrefied biomass showed an EMC lower than that of raw biomass, which implied an increase in hydrophobicity. The modified Oswin model performed best in describing the correlation between ERH and EMC. Corn stover torrefied at 250 and 300 °C had negligible dry matter mass loss due to microbial degradation. Fiber analysis showed a significant decrease in hemicellulose content with the increase in pretreatment temperature, which might be the reason for the hydrophobic nature of the torrefied biomass. The outcomes of this work can be used for torrefaction process optimization, and decision-making regarding raw and torrefied biomass storage and downstream processing
Enthalpy of formation of ye’elimite and ternesite
Calcium sulfoaluminate clinkers containing ye’elimite (Ca4Al6O12(SO4)) and ternesite (Ca5(SiO4)2SO4) are being widely investigated as components of calcium sulfoaluminate cement clinkers. These may become low energy replacements for Portland cement. Conditional thermodynamic data for ye’elimite and ternesite (enthalpy of formation) have been determined experimentally using a combination of techniques: isothermal conduction calorimetry, X-ray powder diffraction and thermogravimetric analysis. The enthalpies of formation of ye’elimite and ternesite at 25 °C were determined to be − 8523 and − 5993 kJ mol−1, respectively
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