Using a water-soluble melamine-formaldehyde resin to improve the hardness of Norway spruce wood

Samples of Norway spruce wood were impregnated with a water-soluble melamine formaldehyde resin by using short-term vacuum treatment and long-term immersion, respectively. By means of Fourier transform infrared (FTIR) spectroscopy and UV microspectrophotometry, it was shown that only diffusion during long-term immersion leads to sufficient penetration of melamine resin into the wood structure, the flow of liquids in Norway spruce wood during vacuum treatment being greatly hindered by aspirated pits. After an immersion in aqueous melamine resin solution for 3 days, the resin had penetrated to a depth > 4 mm, which, after polymerization of the resin, resulted in an improvement of hardness comparable to the hardwood beech. A finite element model describing the effect of increasing depth of modification on hardness demonstrated that under the test conditions chosen for this study, a minimum impregnation depth of 2 mm is necessary to achieve an optimum increase in hardness. (C) 2004 Wiley Periodicals, Inc.

Composition and cure temperature: The influence on properties of final flexible PU cold cure foam parts

Foams are cellular structures, produced by gas bubbles formed during the polyurethane polymerization mixture. Flexible PU foams meet the following two criteria: have a limited resistance to an applied load, being both permeable to air and reversibly deformable. There are two main types of flexible foams, hot and cold cure foams differing in composition and processing temperatures. The hot cure foams are widely applied and represent the main composition of actual foams, while cold cure foams present several processing and property advantages, e.g, faster demoulding time, better humid aging properties and more versatility, as hardness variation with index changes are greater than with hot cure foams. The processing of cold cure foams also is attractive due to the low energy consumption (mould temperature from 30 degrees to 65 degrees C) comparatively to hot cure foams (mould temperature from 30 degrees to 250 degrees C). Another advantage is the high variety of soft materials for low temperature processing moulds. Cold cure foams are diphenylmethane diisocyanate (MDI) based while hot cure foams are toluene diisocyanate (TDI) based. This study is concerned with Viscoelastic flexible foams MDI based for medical applications. Differential Scanning Calorimetry (DSC) was used to characterize the cure kinetics and Dynamical Mechanical Analisys to collect mechanical data. The data obtained from these two experimental procedures were analyzed and associated to establish processing/properties/operation conditions relationships. These maps for the selection of optimized processing/properties/operation conditions are important to achieve better final part properties at lower costs and lead times.

Quality of medicines stored together in multi-compartment compliance aids

Background and Objective: Dispensing medicines into compliance aids is a common practice in pharmacy contrary to manufacturers’ advice and studies have shown the appearance of light-sensitive tablets is compromised by such storage; we previously found evidence of reduced bioavailability at elevated temperature and humidity. Our objective was to examine the physicochemical stability of two generic atenolol tablets in different compliance aids and with aspirin co-storage at room temperature and at 40 °C/75% relative humidity. Methods: The physicochemical stability of atenolol tablets was evaluated after 28 days of storage and compared with controls by examining visual appearance, weight, disintegration, dissolution, friability and hardness to accepted standards and using a previously validated HPLC method for chemical assay. Results and Discussion: The response to storage was brand-dependent and not straightforward. With one make of atenolol (Alpharma), storage in compliance aids even at room temperature impacted on physical stability, reducing tablet hardness, with storage in Dosett® exerting a greater impact than storage in Medidos® (t-test P < 0·001). Co-storage at elevated temperature and humidity also impacted on the appearance of non-coated aspirin tablets (Angette™). The chemical stability of atenolol was not affected and we did not find evidence of changes to bioavailability with either make. Certainly data for one atenolol make (CP Pharmaceuticals) co-stored with aspirin (Angette™ and Nu-Seals) in both compliance aids at room temperature provided evidence of short-term stability. But medicines are dispensed into compliance aids in multi-factorial ways so our study highlights not only the lack of evidence but also a realization that evidence to support real practice may not be accomplished through research. Conclusion: Reassuring practitioners of the continued stability of medicines in compliance aids under the countless condition in which they are dispensed in practice may requires a different approach involving medical device regulators and more definitive professional guidance.

Puroindoline-b mutations control the lipid binding interactions in mixed puroindoline-a: puroindoline-b systems

The interactions have been investigated of puroindoline-a (Pin-a) and mixed protein systems of Pin-a and wild-type puroindoline-b (Pin-b+) or puroindoline-b mutants (G46S mutation (Pin bH) or W44R mutation (Pin-bS)) with condensed phase monolayers of an anionic phospholipid (L-α-dipalmitoylphosphatidyl-dl-glycerol (DPPG)) at the air/water interface. The interactions of the mixed systems were studied at three different concentration ratios of Pin-a:Pin-b, namely 3:1, 1:1 and 1:3 in order to establish any synergism in relation to lipid binding properties. Surface pressure measurements revealed that Pin-a interaction with DPPG monolayers led to an equilibrium surface pressure increase of 8.7 ± 0.6 mN m-1. This was less than was measured for Pin-a:Pin-b+ (9.6 to 13.4 mN m-1), but was significantly more than was measured for Pin-a:Pin-bH (4.0 to 6.2 mN m-1) or Pin-a:Pin-bS (3.8 to 6.3 mN m-1) over the complete range of concentration ratio. Consequently, surface pressure increases were shown to correlate to endosperm hardness phenotype, with puroindolines present in hard-textured wheat varieties yielding lower equilibrium surface pressure changes. Integrated amide I peak areas from corresponding external reflectance Fourier-transform infrared (ER-FTIR) spectra, used to indicate levels of protein adsorption to the lipid monolayers, showed that differences in adsorbed amount were less significant. The data therefore suggest that Pin-b mutants having single residue substitutions within their tryptophan-rich loop that are expressed in some hard-textured wheat varieties influence the degree of penetration of Pin-a and Pin-b into anionic phospholipid films. These findings highlight the key role of the tryptophan-rich loop in puroindoline-lipid interactions.

Single amino acid substitutions in puroindoline-b mutants influence lipid binding properties

External reflectance Fourier transform infrared (ER-FTIR) spectroscopy and surface pressure measurements have been used to characterize the interaction of wild-type puroindoline-b (Pin-b) and two mutant forms featuring single residue substitutions-namely, Gly-46 to Ser-46 (Pin-bH) and Trp-44 to Arg-44 (Pin-bS)-with condensed-phase monolayers of zwitterionic (L-alpha-dipalmitoylphosphatidylcholine, DPPC) and anionic (L-alpha-dipalmitoylphosphatidyl-dl-glycerol, DPPG) phospholipids. The interaction with anionic DPPG monolayers, monitored by surface pressure isotherms, was influenced significantly by mutations in Pin-b (p < 0.05); wild-type Pin-b showed the highest surface pressure change of 10.6 +/- 1.0 mN m(-1), followed by Pin-bH (7.9 +/- 1.6 mN m(-1)) and Pin-bS (6.3 +/- 1.0 mN m(-1)), and the surface pressure isotherm kinetics were also different in each case. Integrated Amide I peak areas from corresponding ER-FTIR spectra confirmed the differences in adsorption kinetics, but also showed that differences in adsorbed amount were less significant, suggesting that mutations influence the degree of penetration into DPPG films. All Pin-b types showed evidence of interaction with DPPC films, detected as changes in surface pressure (5.6 +/- 1.1 mN m(-1)); however, no protein peaks were detected in the ER-FTIR spectra, which indicated that the interaction was via penetration with limited adsorption at the lipid/water interface. The expression of Pin-b mutants is linked to wheat endosperm hardness; therefore, the data presented here suggest that the lipid binding properties may be pivotal within the mechanism for this quality trait. In addition, the data suggest antimicrobial activities of Pin-b mutants would be lower than those of the wild-type Pin-b, because of decreased selectivity toward anionic phospholipids.

Effect of combined heat and high-pressure treatments on the texture of chicken breast muscle (Pectoralis fundus)

Commercially supplied chicken breast muscle was subjected to simultaneous heat and pressure treatments. Treatment conditions ranged from ambient temperature to 70 °C and from 0.1 to 800 MPa, respectively, in various combinations. Texture profile analysis (TPA) of the treated samples was performed to determine changes in muscle hardness. At treatment temperatures up to and including 50 °C, heat and pressure acted synergistically to increase muscle hardness. However, at 60 and 70 °C, hardness decreased following treatments in excess of 200 MPa. TPA was performed on extracted myofibrillar protein gels that after treatment under similar conditions revealed similar effects of heat and pressure. Differential scanning calorimetry analysis of whole muscle samples revealed that at ambient pressure the unfolding of myosin was completed at 60 °C, unlike actin, which completely denatured only above 70 °C. With simultaneous pressure treatment at >200 MPa, myosin and actin unfolded at 20 °C. Unfolding of myosin and actin could be induced in extracted myofibrillar protein with simultaneous treatment at 200 MPa and 40 °C. Electrophoretic analysis indicated high pressure/temperature regimens induced disulfide bonding between myosin chains.

Toxicity testing of groundwater quality

Groundwater is an important resource in the UK, with 45% of public water supplies in the Thames Water region derived from subterranean sources. In urban areas, groundwater has been affected by onthropogenic activities over 0 long period of time and from a multitude of sources, At present, groundwater quality is assessed using a range of chemical species to determine the extent of contamination. However, analysing a complex mixture of chemicals is time-consuming and expensive, whereas the use of an ecotoxicity test provides information on (a) the degree of pollution present in the groundwater and (b) the potential effect of that pollution. Microtox (TM), Eclox (TM) and Daphnia magna microtests were used in conjunction with standard chemical protocols to assess the contamination of groundwaters from sites throughout the London Borough of Hounslow and nearby Heathrow Airport. Because of their precision, range of responses and ease of use, Daphnia magna and Microfox (TM) tests are the bioassays that appear to be most effective for assessing groundwater toxicity However, neither test is ideal because it is also essential to monitor water hardness. Eclox (TM) does not appear to be suitable for use in groundwater-quality assessment in this area, because it is adversely affected by high total dissolved solids and electrical conductivity.

Modelling metal cutting using modern ductile fracture mechanics: Quantitative explanations for some longstanding problems

The assumption that negligible work is involved in the formation of new surfaces in the machining of ductile metals, is re-examined in the light of both current Finite Element Method (FEM) simulations of cutting and modern ductile fracture mechanics. The work associated with separation criteria in FEM models is shown to be in the kJ/m2 range rather than the few J/m2 of the surface energy (surface tension) employed by Shaw in his pioneering study of 1954 following which consideration of surface work has been omitted from analyses of metal cutting. The much greater values of surface specific work are not surprising in terms of ductile fracture mechanics where kJ/m2 values of fracture toughness are typical of the ductile metals involved in machining studies. This paper shows that when even the simple Ernst–Merchant analysis is generalised to include significant surface work, many of the experimental observations for which traditional ‘plasticity and friction only’ analyses seem to have no quantitative explanation, are now given meaning. In particular, the primary shear plane angle φ becomes material-dependent. The experimental increase of φ up to a saturated level, as the uncut chip thickness is increased, is predicted. The positive intercepts found in plots of cutting force vs. depth of cut, and in plots of force resolved along the primary shear plane vs. area of shear plane, are shown to be measures of the specific surface work. It is demonstrated that neglect of these intercepts in cutting analyses is the reason why anomalously high values of shear yield stress are derived at those very small uncut chip thicknesses at which the so-called size effect becomes evident. The material toughness/strength ratio, combined with the depth of cut to form a non-dimensional parameter, is shown to control ductile cutting mechanics. The toughness/strength ratio of a given material will change with rate, temperature, and thermomechanical treatment and the influence of such changes, together with changes in depth of cut, on the character of machining is discussed. Strength or hardness alone is insufficient to describe machining. The failure of the Ernst–Merchant theory seems less to do with problems of uniqueness and the validity of minimum work, and more to do with the problem not being properly posed. The new analysis compares favourably and consistently with the wide body of experimental results available in the literature. Why considerable progress in the understanding of metal cutting has been achieved without reference to significant surface work is also discussed.

Recent advances in biomimetic sensing technologies

The importance of biological materials has long been recognized from the molecular level to higher levels of organization. Whereas, in traditional engineering, hardness and stiffness are considered desirable properties in a material, biology makes considerable and advantageous use of softer, more pliable resources. The development, structure and mechanics of these materials are well documented and will not be covered here. The purpose of this paper is, however, to demonstrate the importance of such materials and, in particular, the functional structures they form. Using only a few simple building blocks, nature is able to develop a plethora of diverse materials, each with a very different set of mechanical properties and from which a seemingly impossibly large number of assorted structures are formed. There is little doubt that this is made possible by the fact that the majority of biological ‘materials’ or ‘structures’ are based on fibres and that these fibres provide opportunities for functional hierarchies. We show how these structures have inspired a new generation of innovative technologies in the science and engineering community. Particular attention is given to the use of insects as models for biomimetically inspired innovations.

Stress relaxation behaviour of frozen sucrose solutions

The stress relaxation behaviour of two frozen sucrose solutions (7% and 19%) during indentation in the temperature range of -20C to -40C were investigated. The stress relaxation is similar to that of pure polycrystalline ice, which is controlled by steady-state creep. The steady state creep rate exponent, m, of 7% and 19% sucrose solutions lies between 2.3 and 3.6. The steady state creep rate constant, B, of 19% sucrose solution is greater than that of 7% sucrose solution. It is suggested that the steady-state creep rate exponent m depends on contributions from the proportions of favourably oriented grains, unfavourably oriented grains and grain boundaries to creep and that these components depend on the value of internal stress which is related to the hardness of samples at the different testing temperatures. The steady-state creep rate constant B depends on the mobility of dislocations in sucrose solutions which, in turn, depends on the temperature and the concentration of sucrose.

Effects of fat on the properties of halloumi cheese

Halloumi cheese was produced from 11 bovine milks with fat contents of 1.61-4.04%, giving a range of 32-53% fat in dry matter (FDM) in the cheeses. Starter culture and/or microparticulated whey protein (Simplesse((R)) 100(E)) was also added to selected batches of milk. Hardness decreased with increasing FDM, with increase in moisture and with lower pH. On sensory evaluation, there was an increase in preference score with FDM (R-2 = 0.8). Inclusion of microparticulated whey protein may have had a fat mimetic effect, as preference scores otherwise decreased with increasing protein levels (R-2 = 0.75).

High pressure/thermal treatment effects on the texture of beef muscle

The effects of high pressure (to 800 MPa) applied at different temperatures (20-70 degreesC) for 20 min on beef post-rigor longissimus dorsi texture were studied. Texture profile analysis showed that when heated at ambient pressure there was the expected increase in hardness with increasing temperature and when pressure was applied at room temperature there was again the expected increase in hardness with increasing pressure. Similar results to those found at ambient temperature were found when pressure was applied at 40 degreesC. However, at higher temperatures, 60 and 70 degreesC it was found that pressures of 200 MPa caused large and significant decreases in hardness. The results found for hardness were mirrored by those for gumminess and chewiness. To further understand the changes in texture observed, intact beef longissimus dorsi samples and extracted myofibrils were both subjected to differential scanning calorimetry after being subjected to the same pressure/temperature regimes. As expected collagen was reasonably inert to pressure and only at temperatures of 60-70 degreesC was it denatured/unfolded. However, myosin was relatively easily unfolded by both pressure and temperature and when pressure denatured a new and modified structure was formed of low thermal stability. Although this new structure had low thermal stability at ambient pressure it still formed in both the meat and myofibrils when pressure was applied at 60 degreesC. It seems unlikely that structurally induced changes can be a major cause of the significant loss of hardness observed when beef is treated at high temperature (60-70 degreesC) and 200 MPa and it is suggested that accelerated proteolysis under these conditions is the major cause. (C) 2004 Elsevier Ltd. All rights reserved.

Effect of chymosin reduction and salt substitution on the properties of white salted cheese

A whey salts mixture was used as a partial substitute for sodium chloride to provide a modified Na:K ratio (1:3.4) in the manufacture of white salted cheese using ultrafiltration. Reduction of chymosin addition from 20 to 8 mu L kg(-1) of cheese was also investigated. Variation of salt and chymosin levels did not result in any significant differences in composition and physicochemical properties. The rates of proteolysis in terms of water-soluble nitrogen (WSN) and nitrogen soluble in 12% trichloroacetic acid (TCA-SN) were affected by chymosin levels but not by salt treatment. Urea-PAGE electrophoretic analysis of caseins from the cheeses manufactured using three levels of chymosin and two salt types showed that the hydrolysis of alpha(s1)-casein was higher than for beta-caseins but the differences between the cheeses were not significant (P > 0.05). The chymosin level did not have a significant effect (P > 0.05) on hardness and fracturability, suggesting that any variation in hardness due to the initial hydrolysis was being confounded by other variables. Cheeses including the whey salts product were harder and more fracturable (P < 0.01) than the cheese treated with NaCl only. Both hardness and fracturability values decreased (P < 0.05) over the maturation period. The scores for bitterness were low; neither the effects of salt nor chymosin levels were significant (P > 0.05). (c) 2005 Elsevier Ltd. All rights reserved.