Impact Of Water Content Research Articles

A HS–SPME–GC–MS analysis of IR heated wood: Impact of the water content on the depth profile of oak wood aromas extractability

Controlled and reproducible IR heat treatments were applied to oak wood surfaces in order to establish a depth-profiled picture of the extractability of volatile compounds, with particular emphasis on the impact of the initial water content. Headspace–solid phase microextraction–gas chromatography coupled to mass spectrometry (HS–SPME–GC–MS) has been used to compare the concentrations of six aroma compounds (vanillin, furfural, eugenol; guaiacol and cis- and trans-whisky lactones) in hydroalcoholic extracts of series of slices representative of the first 8mm of the wood facing the IR source. Results have shown that although water is supposed to have a delaying effect with respect to the thermal degradation of wood macromolecules, it can favor heat transfers and thus promote higher-than-expected transient local temperatures in a soaked wood. Yet, distinct behaviors could be observed between thermally-generated compounds (vanillin and guaiacol), where adsorbed water seemed to prevent the thermal degradation of the parent macromolecule, and thermally-degraded compounds such as eugenol where the presence of water would balance the compound degradation through a more efficient extraction process of this biogenesis molecule. Furfural exhibited a more complex behavior since its production as a result of hemicellulose degradation was thermally-favored in the presence of adsorbed water. Finally, whatever the applied heat flux and regardless of the initial water content, temperatures experienced by the wood deeper than 4mm, were lower than 160°C, which meant that beyond that depth, the initial wood composition was unaffected.

On the potential of ethanol fuel stratification to extend the high load limit in stratified-charge compression-ignition engines

A multi-zone model is applied to investigate the potential of ethanol fuel stratification to reduce the problematic high rates of pressure-rise that can occur in homogeneous-charge compression-ignition (HCCI) engines. The model is first validated against published experimental data. Novel techniques for inducing in-cylinder stratification are then identified, that involve exploiting the high latent heat of vaporisation of ethanol to induce thermal stratification. This stratification introduces a range of induction times into the cylinder, leading to a staged combustion event. The impact of water content in the fuel is also investigated.This study finds that ethanol fuel stratification has the potential to provide significant improvements relative to the nominally homogeneous operating condition. Significant reductions in pressure-rise rates are attainable, providing the potential for extending the possible operating regime to higher loads. The trade-off between reduced pressure-rise rate and increased NO emissions is discussed. Mixing the fuel with quantities of water, which has cost and overall energy efficiency advantages, is found to significantly reduce the NO production and slightly accentuate the reductions of pressure-rise rate.

Experimental Study of Loess Structural Strength and Resistance Coefficient

The paper proposes a calculation method of soil particles framework structural strength, and provides a new parameter, defined as resistance coefficient, which can quantitatively describe the relationship between active stress and passive stress on soil particles framework. The research of the impact of water content, binding materials content and dry density on structural strength and resistance coefficient is conducted under confined compression test with undisturbed and man-made cement structural loess from Yangling. The research shows that structural strength of loess particles framework increases with the increasing of deformation, and with the same deformation, the structural strength of loess particles framework increases with the increasing of water content ; loess particles framework is sensitive to the weakening role of water. The resistance coefficient is smaller and more instability with the increasing of deformation under high water content conditions. The binding material has significant effect on structural strength and resistance coefficient. Moderate cement mixed with loess particles framework cannot only improve the structural strength but also decrease the sensitivity of loess particles framework to the weakening role of water. By controlling the binding material content, water content and dry density, the structural strength and resistance coefficient of man-made cement structural loess will be the same as the undisturbed loess. Increasing dry density can make the structural strength of loess particles framework higher, but the value and the stability of resistance coefficient of loess particles framework structure with high dry density is lower than that in the initial dry density.

Effect of water content in a canned food on voluntary food intake and body weight in cats

To determine whether water content in a canned food diet induces decreases in voluntary energy intake (EI) or body weight (BW) in cats fed ad libitum. 16 sexually intact male domestic shorthair cats. Maintenance EI was determined for 2 months in 10 weight-stable cats consuming a control diet (typical colony diet). Cats were allocated into 2 groups of equal BW and fed a canned diet (with-water [WW] diet) or a freeze-dried version of the canned diet (low-water [LW] diet) twice daily. Diets were identical in nutrient profile on a dry-matter basis. Each dietary treatment period of the crossover experiment lasted 3 weeks, with a 3-week washout period between diets. Body composition measurements were determined by use of deuterium oxide at the end of each dietary treatment. Daily food intake was measured for determination of dry-matter intake and EI. Six other cats were used in preference tests for the 3 diets. EI was significantly decreased for the WW diet (mean ± SD, 1,053.0 ± 274.9 kJ/d), compared with EI for the LW diet (1,413.8 ± 345.8 kJ/d). Cats had a significant decrease in BW during consumption of the WW diet. Body composition was unaltered by diet. In short-term preference tests, cats ate significantly more of the WW than the LW diet. Bulk water in the WW diet stimulated decreases in EI and BW in cats. The impact of water content on energy density and food consumption may help promote weight loss in cats.

The influence of leaf water content and isoprenoids on flammability of some Mediterranean woody species

The impact of water content and isoprenoids on leaf flammability was studied. Field and laboratory experiments were carried out on monoterpene-emitting evergreen broad-leaved species (Quercus ilex, Quercus suber); a needle-leaved species (Pinus halepensis) that emits and stores monoterpenes; an evergreen species (Myrtus communis) that emits isoprene but stores monoterpenes; and a deciduous species (Quercus pubescens) that emits isoprene. Photosynthesis, leaf water content (LWC) and isoprenoid emission were measured. Isoprenoid content was calculated. Temperatures of visible smoke, incandescence and flame appearance were recorded. The LWC significantly correlated with both photosynthesis and isoprenoid emissions. Linear correlation and factorial analysis revealed a positive correlation between temperature of flame appearance and LWC and a negative relationship between temperature of flame appearance and isoprenoid emission. Multiple regression analysis indicated that the temperature of flame appearance was reduced in broadleaved monoterpene-emitting species. In monoterpene emitters, the temperature of flame appearance depended for ~65% on LWC, whereas monoterpene emissions explained ~35% of the dependency. P. halepensis and M. communis, storing high levels of isoprenoids, ignited at high humidity. The results may be explained if isoprenoids indeed facilitate leaf ignition but, being dissolved in water, isoprenoids are also an indicator of a high water content that decreases flammability.

Impact of Water Content on the Electrical Behavior of Epoxy Insulators

Polymers are widely used in indoor insulation. We analyze three epoxy samples with varying matrix and filler properties to determine the influence of water on their insulating properties. We observed a strong dependency of the leakage current and the sample temperature, under electrical stress, on the amount of absorbed water. Tri- hydrated alumina filler reduced the leakage current and temperature rise under electrical stress.

Acceleration of bromide mediated benzoylperoxide oxidations of secondary alcohols in aqueous organic solvents

The efficiency of the bromide mediated benzoylperoxide oxidation of 2° alcohols to ketones was greatly improved by the addition of water. The aqueous oxidation protocol allows also the direct use of off-the-shelf benzoylperoxide reagent without an otherwise necessary and potentially dangerous drying procedure. The oxidation of cyclopentanol, cyclohexanol, 1-phenyl-ethanol and three menthol isomers occurred in good to excellent yields. The oxidation reaction tolerated N, N-dimethylacetamide (DMA) as the solvent, which resulted in a slightly lower oxidation rate than acetonitrile. Chemoselective oxidation of vicinal diols to α-hydroxy ketones did not succeed under the aqueous organic conditions employed as over-oxidation and bromination side-reactions were observed. The impact of water content, solvent, oxidant source and type of alcohol substrates employed was investigated.

A laboratory and full-scale study on the fragmentation behavior of rocks

Rock fines produced in rock blasting and crushing processes is a major problem for aggregate producers. Laboratory and full-scale studies were carried out to explore the possible relationship between fines production and water content of rock material. The Brazilian tensile test was selected for the laboratory study while a cone crusher machine was employed for the full-scale trials. Results of the laboratory work showed that the percentage of fines fraction produced was a function of the type of rock tested and the tensile strength of individual specimens. Different rocks produced various amounts of fines, but for the rocks investigated, a correlation between its strength and its fines generation could be attained. The influence of water content on production of fines was also examined and showed that increased water content reduces both tensile strength and fines generation in the laboratory. The impact of water content on aggregate production was also studied in full-scale but the results were not as clear as those of the laboratory tests.

Potato water content impact on soil moisture measurement by neutron meter

A field study was conducted to examine the effect of the water content of potato tubers on the neutron count ratios of a neutron probe in an irrigated potato field. At the 20 cm depth, where tubers are concentrated, the neutron count ratios within the potato row (CW) were significantly higher than the neutron count ratios between the rows (CB). In contrast, the measured soil water contents within the rows (SW) at this depth, tended to be less than those measured between the rows (SB). At 45 cm depth, results were similar in a dry but not a wet year. The SW values, in contrast, were less than SB. Neither (CW-CB) or (SW-SB) were significant at 75 cm depth and values of (CW-CB) and (SW-SB) were similar. This study provides qualitative information regarding the influence of a potato tuber water content on neutron measurements, resulting in an overestimations of soil moisture in a potato field. Further studies should be conducted to develop relationships for corrections.

Beyond water activity: Recent advances based on an alternative approach to the assessment of food quality and safety

Water, the most abundant constituent of natural foods, is a ubiquitous plasticizer of most natural and fabricated food ingredients and products. Many of the new concepts and developments in modern food science and technology revolve around the role of water, and its manipulation, in food manufacturing, processing, and preservation. This article reviews the effects of water, as a near-universal solvent and plasticizer, on the behavior of polymeric (as well as oligomeric and monomeric) food materials and systems, with emphasis on the impact of water content (in terms of increasing system mobility and eventual water "availability") on food quality, safety, stability, and technological performance. This review describes a new perspective on moisture management, an old and established discipline now evolving to a theoretical basis of fundamental structure-property principles from the field of synthetic polymer science, including the innovative concepts of "water dynamics" and "glass dynamics". These integrated concepts focus on the non-equilibrium nature of all "real world" food products and processes, and stress the importance to successful moisture management of the maintenance of food systems in kinetically metastable, dynamically constrained glassy states rather than equilibrium thermodynamic phases. The understanding derived from this "food polymer science" approach to water relationships in foods has led to new insights and advances beyond the limited applicability of traditional concepts involving water activity. This article is neither a conventional nor comprehensive review of water activity, but rather a critical overview that presents and discusses current, usable information on moisture management theory, research, and practice applicable to food systems covering the broadest ranges of moisture content and processing/storage temperature conditions.