Mass Transfer from Wooden Surfaces and Internal Moisture Non-Equilibrium

ABSTRACT

The transfer of moisture from a wooden surface and the corresponding mass transfer coefficient in relation to the heat transfer coefficient are considered. Experimental data are reviewed that show that the mass transfer coefficient often is one order of magnitude smaller than what could be expected from the analogy between heat and mass transfer. The nature of this deviation and its influence on wood drying models is discussed. It has been suggested by Wadsö.that moisture flow inside the wood exhibits non–Fickian behaviour and that this may be due to a slow desorptiodabsorption by the wood fibre. A model is thus developed where the normal assumption of internal local equilibrium between the vapour and bound phases is replaced by a mass transfer resistance. The model is applied to one–dimensional moisture flow in a body of finite thickness and solved analytically. Numerical values calculated with the model are analysed in order to establish whether “apparent” non–Fickian behaviour of the kind observed could be explained by such a model. It is also analysed whether the model could explain an apparent decreased mass transfer coefficient at the surface.     

Brittle tensosensitive coatings for determining the stress-strain state of parts and structures

Brittle new tensosensitive coatings of E-23 epoxy resin are investigated. The influence of the method of application and the layer thickness on the properties of such coatings is established. The accuracy with which the stress-strain state of samples may be determined by means of these coatings is estimated.     

Effects of abomasal infusion of tallow or camelina oil on responses to glucose and insulin in dairy cows during late pregnancy

Late pregnancy is associated with moderate insulin resistance in ruminants. Reduced suppression of lipolysis by insulin facilitates mobilization of nonesterified fatty acids (NEFA) from adipose tissue, resulting in elevated plasma NEFA concentrations. Decrease in dry matter intake (DMI) before parturition leads to accelerated lipomobilization and increases plasma NEFA, which may further impair insulin sensitivity. The aim of the study was to evaluate the effects of elevation of plasma NEFA concentration by abomasal infusions tallow (TAL) or camelina oil (CAM) on whole-body responses to exogenous glucose and insulin. We further assessed whether CAM, rich in C18:3n-3, enhances whole-body insulin sensitivity compared with TAL. Six late-pregnant, second-parity, rumen-cannulated dry Ayrshire dairy cows fed grass silage to meet 95% of metabolizable energy requirements were used in a replicated 3 × 3 Latin square with 5-d periods and 5 recovery days between each period. Treatments consisted of abomasal infusion of 500 mL/d (430 g of lipids/d) of water (control), TAL, or CAM administered in 10 equal doses daily. Intravenous glucose tolerance test (IVGTT) and i.v. insulin challenge (IC) were performed on d 5 after 98 and 108 h of treatment infusions, respectively. Infusion of lipids increased basal plasma NEFA concentrations on d 5 (CAM: 0.25; TAL: 0.28; control: 0.17 mmol/L). Following glucose injection, the rate of glucose clearance (CR) was lower in lipid-treated cows (CAM: 1.34; TAL: 1.48; control: 1.74%/min) and time to reach half-maximal glucose concentration (T(1/2)) was longer (CAM: 54; TAL: 47; control: 42 min). Similar responses were observed after insulin injection. Increased plasma NEFA concentration tended to decrease insulin secretion in IVGTT. Infusion of CAM increased plasma C18:3n-3 content (CAM: 26.4; TAL: 16.1; control: 20.9 g/100g of fatty acids). Data suggest that CAM had an insulin-sensitizing effect, because the disposition index and insulin sensitivity index, derived from minimal model analysis, were higher in CAM than in TAL during IVGTT, and lower insulin concentrations during IC led to similar glucose clearance in CAM as in TAL. These results indicate that elevated plasma NEFA concentration per se induces whole-body insulin resistance in late-pregnant dry cows.     

A feasibility study of adaptive Plasma‐Assisted incineration,Part 1: Demonstration on a laboratory model system

The use of a thermal plasma afterburner in hazardous waste incineration could prevent the formation of toxic organochlorine pollutants. The present work demonstrated cost‐optimal adaptive operation of a laboratory model system composed of an induction plasma jet with optical emission diagnostic tools. Input settings (plasma power and oxygen content) were continually adjusted in response to on‐line spectroscopic analysis of the product gas. This adaptive strategy allowed cost‐effective destruction of organic contaminants under a variable feed load. The system was able to reach and maintain a target level of destruction efficiency using optimal combinations of input settings.     

Distribution of striatin, a newly identified calmodulin-binding protein in the rat brain: an in situ hybridization and immunocytochemical study

The worm-like chain model has often been employed to describe the average conformation of long, intrinsically straight polymer molecules, including DNA. The present study extends the applicability of the worm-like chain model to polymers containing bends or sections of different flexibility. Several cases have been explicitly considered: (i) polymers with a single bend; (ii) polymers with multiple coplanar bends; (iii) polymers with two non-coplanar bends; and (iv) polymers comprised of sections with different persistence lengths. Expressions describing the average conformation of such polymers in terms of the mean-square end-to-end distance have been derived for each case. For cases (i) and (iv), expressions for the projection of the end-to-end vector onto the initial orientation of the chain are presented. The expressions derived here have been used to investigate DNA molecules with sequence-induced bending (A-tracts). Mean-square end-to-end distance values determined from a large number of A-tract containing DNA molecules visualized by scanning force microscopy resulted in an average bend angle of 13.5 degrees per A-tract. A similar study was performed to characterize the flexibility of double-strandedDNA molecules containing a single-stranded region. Analysis of their mean-square end-to-end distance yielded a persistence length of 1.3 nm for single-stranded DNA.     

Cellular automata studies of mixing in chaotic flows

Results of cellular automata based studies of mixing in a square cavity are presented. Two periodic models are considered: one in which two walls move in opposite directions one at a time and the other in which they act simultaneously but alternate the directions of motion. Both flows are found to be chaotic and the Poincare sections and Lyapunov exponents are determined. The morphology of mixing is different in the two cases.     

MULTIPLE SCISSIONS OF IONIC FERROFLUID DROPS

A drop of ionic ferrofluid, strongly magnetic (μ ∼ 40), exhibits an instability when it is confined between two parallel boundaries perpendicular to the magnetic field direction. Increasing the magnetic field, the drop successively undergoes a deformation, develops pointed feet and splits into two smaller droplets. We present a model of ellipsoidal shapes to account for the magnetic thresholds of deformation and scissions. It is possible to observe eight successive scissions of a single initial drop leading to 256 smaller droplets which arrange themselves in a regular hexagonal array similar to a two dimensional crystal the long-range order of which is optically tested.     

Novel diode-pumped infrared tunable laser system for multi-photon microscopy

We report on a novel laser source, emitting high energy (20 nanoJoule) femtosecond pulses, in a broad spectrum (250 nm). This source is easily tuned from 950 to 1200 nm, without any laser adjustment, and delivers sub-300 femtosecond pulses with a 10-nm spectral width.     

Online standard additions calibration of transient signals for inductively coupled plasma mass spectrometry

An online standard additions calibration method for transient signals in ICPMS is demonstrated in which a small volume of standard is injected as a spike into the sample/carrier stream, overlaying the analyte peak. This technique provides the advantages of conventional standard additions but requires only a single sample run. The method corrects for matrix effects and is suitable for transient signals in which the severity of the matrix effect changes over the analyte peak. The method uses a peak-fitting program to determine the area of the underlying peak and is shown to be effective for the determination of trace metal concentrations in both a high ionic strength matrix and in a biological matrix (urine). Eight analytes with concentrations in the range of 0.82-233.2 mug L-1 in urine were simultaneously determined using a standard spiking solution of 75 mug L-1 injected through a 100-muL loop. The measured concentrations for analytes free of spectral interferences agreed with the certified values, and the precision achieved was comparable to that achieved by the certifying agency. Using a conventional cross-flow nebulizer and Scott-type spray chamber, the accuracy obtained for online standard additions calibration was within 2%, and the precision was within 5%.     

Numerical prediction of checking during timber drying and a new mechano-sorptive creep model

The dependence of the amount of checking on shrinkage induced stress level during timber drying is considered. This relationship is investigated by comparing theoretically calculated maximal stress with observed amount of checking in a set of drying tests. Different ways of modelling wood creep behaviour are included. It is found that a correlation exists in all the cases studied, except when creep is described with the traditional equation for mechano-sorptive creep. It is shown that this exception is due to a special mathematical property of the equation. A new mechano-sorptive creep model is thus proposed and briefly investigated. Using this model, a method for predicting the amount of checking in timber drying is developed.