Adhesion,plasticity and other peculiar properties of solid methane

Adhesion and plasticity of polycrystalline solid methane have been studied in the temperature range 10–90 K. It was shown that adhesion is very strong in the 50–90 K temperature range where the solid methane is soft and sticky. Closer to the melting point (at 90.6 K) the solid methane behaves as extremely viscous non-Newtonian liquid. Below 30 K solid methane loses its stickiness and ductility and acts like ordinary glass. Methane adhesion remains similar for very different materials. We have also made some video observations which reveal unexpected and mostly inexplicable properties of solid methane which could be of some interest for designing new methane moderators for neutron sources and planetary physics particularly the study of the environment of Titan.     

Lake extent changes in Basotu,Tanzania: a mixed-methods approach to understanding the impacts of anthropogenic influence and climate variability

Incompatible land use is a major contributor to ecosystem degradation, and is often exacerbated by climate change impacts. We investigate Lake Basotu, Tanzania as a case study where natural lake variability has been affected by agricultural land use. Comparisons between a satellite-derived history of lake surface area, local precipitation records, and corresponding anthropogenic activity show the impacts of agricultural and historical practices. We argue that insufficient consideration to the wider ecological impacts of large agricultural projects has lasting implications. This is particularly true in semi-arid environments where food production demands need to be continuously met. In the future, major conservation strategies should be investigated to maintain the environmental integrity and sustainability of freshwater resources.     

Effects of Vitamin D3‐Enriched Diet on Egg Yolk Vitamin D3 Content and Yolk Quality

A 40‐wk experiment was conducted using Hy‐Line W‐36 laying hens (19‐wk old) to investigate the impact of feeding cholecalciferol‐enriched diets on egg yolk quality. Feeds were enriched with 4 cholecalciferol levels, 9700 (diet 2), 17200 (diet 3), 24700 (diet 4), and 102200 (diet 5) IU/kg feed. The control (diet 1) contained 2200 IU cholecalciferol/kg feed. Eggs from each replicate group of enriched diets were collected daily and the yolks were pooled into 2‐d period during the first 2 wk. During weeks 3, 4, 6, 8, 12, 16, 20, 24, 28, 32, 36, and 40, pooled samples were generated by daily collection of 3 consecutive days of egg production. The cholecalciferol content of egg yolk from the enriched diets increased rapidly during the first 3 wk. The peak cholecalciferol concentrations in egg yolk that occurred at week 3 were 865, 1641, 2411, and 34815 IU/100 g egg yolk (wet basis) from diet 2 to 5. The average cholecalciferol concentration in yolk during weeks 3 to 40 and the deposition rate of cholecalciferol during the first 3 wk were both linearly increased with the dietary cholecalciferol level when the feed contained no more than 24700 IU/kg cholecalciferol. Egg yolk lipid profile (total lipid content, fatty acid composition, phospholipid composition, and unsaponifiables), physical and functional properties (yolk viscosity and emulsifying property), and sensory quality of hard‐boiled egg yolk were not affected by the cholecalciferol enrichment in the feed. Practical Application: A linear dose‐response relationship between dietary vitamin D₃ level and egg yolk vitamin D₃ content was established at relatively low enrichment levels. Such relationship can be used to formulate feed to achieve a target egg vitamin D level. High vitamin D yolk showed no difference from the conventional yolk in other compositional, functional, and sensory properties.     

Studies of cyclic and linear poly(dimethyl siloxanes): 12. Observation of diffusion behaviour by quasielastic neutron scattering

High resolution neutron scattering experiments have been used to observe the diffusive motion of low molecular weight linear and cyclic poly(dimethyl siloxane) molecules in dilute solution in deuterated benzene. Diffusion coefficients (D) and hydrodynamic radii (R_H) have been compared with values obtained by light scattering for higher molecular weight samples and with radii of gyration (R_g) obtained by small-angle neutron scattering. While the ratio $\text{D}{}_{\mathrm{<mtext>ring</mtext>}}\text{D}{}_{\mathrm{<mtext>chain</mtext>}}$ is close to the predicted value of 0.85, the ratio $\text{R}{}_{\mathrm{g}}\text{R}{}_{\mathrm{<mtext>H</mtext>}}$ falls below the theoretical value for both ring and chain molecules. The scattering curves show effects arising from both centre of mass diffusion and internal molecular motion, and the observed inverse correlation times are compared with calculated behaviour as a function of scattering vector, Q.     

The contribution of electron microscopic cytochemistry to an understanding of the biogenesis of the endoplasmic reticulum of rat hepatocytes

The endoplasmic reticulum has the enzymic machinery for the synthesis of both protein and phospholipid and hence plays a central role in its own biogenesis and that of other cellular membranes. The evidence available concerning the biogenesis of the phospholipid bilayer of the endoplasmic reticulum, particularly from the application of fine structural cytochemical methods for the localization of acyltransferases, is reviewed. The observations are consistent with a model in which phospholipid is synthesized in situ at the site of membrane growth. Synthesis is asymmetric, with most enzymes located at the cytoplasmic side of the membrane, and controlled transmembrane movement of phospholipid results in an asymmetric bilayer.     

Influence of Biodopants on PEDOT Biomaterial Polymers: Using QCM‐D to Characterize Polymer Interactions with Proteins and Living Cells

Organic conducting polymers (OCPs) are currently the subject of intense research in the area of biomaterials and bioelectronics. Of the OCPs, poly(3,4‐ethylenedioxythiophene) (PEDOT) has attracted significant interest, however there has been little work on investigating the incorporation of biological compounds as the dopant species in the polymer which are aimed at enhancing the biocompatibility and biofunctionality of the material. Here, we incorporate the biological dopants dextran sulphate, chondroitin sulphate, and alginate, into PEDOT polymers and investigate their influence on a suite of physicochemical and electrochemical properties. We employ QCM‐D to study the mass of adsorption and the viscoelastic properties of the important extracellular matrix proteins fibronectin and collagen. Furthermore, we use QCM‐D to study the adhesion of PC12 neural cells to the PEDOT‐biodopant polymers with and without an adsorbed protein conditioning layer. QCM‐D was found to be an excellent tool with which to study conducting polymer–biological interactions, with this report the first time that QCM‐D has been used to study cell interactions with conducting polymer biomaterials.     

Chemometrics can be applied to mechanical testing data to characterise stem toughness and stiffness in crop plants

Mechanical tests have been used to assess the engineering properties of pea (Pisum sativum L) stems. Measurements were made on plants of three different genotypes at four different stages of development and at five defined locations along the stem. The force–displacement curves obtained were used to estimate values of the engineering properties of toughness and flexural modulus, from cutting and flexure mechanical tests respectively. Specimens of all genotypes showed an increase in toughness with age and generally also with stem height. However, there were marked differences in flexural modulus between genotypes. One genotype, known to exhibit a ‘stiff straw’ characteristic, showed a consistent increase in modulus with age and stem height, and at and beyond fruiting had substantially the greatest flexural modulus. The remaining genotypes showed decreasing flexural modulus with age. Chemometric methods were used to analyse sets of complete force–displacement curves, following suitable pre‐processing to allow the application of linear algebra methods. Whereas univariate consideration of the engineering quantities allowed trends to be observed, multivariate analysis of force–distance curves was able to model empirically the genotype differences so that individual specimens could be largely correctly classified. Examination of some of the model coefficients suggested that the ability to discriminate between genotypes is related to structural features of the specimens and that cutting tests in particular are sensitive to the anatomy of the specimen. This is the first time that chemometric methods have been applied to such data and suggests the potential of mechanical tests combined with multivariate analysis to form the basis of a screening system for phenotypic properties of new lines and varieties. Copyright © 2004 Society of Chemical Industry     

Beta 1 integrin ligation stimulates tyrosine phosphorylation of phospholipase C gamma 1 and elevates intracellular Ca2+ in pancreatic acinar cells

We have recently reported increased tyrosine (TYR) phosphorylation of a number of pancreatic acinar cell proteins following antibody ligation of beta 1 integrins (Wrenn and Herman, Biochem, Biophys. Res. Commun. 208, 1995, 978-984). Concurrent with this TYR phosphorylation was a marked activation of protein kinase C (PKC). This led us to investigate phospholipase C gamma 1 (PLC gamma 1), a key enzyme responsible for diacylglycerol generation, as a target for integrin-mediated TYR phosphorylation. Staining with antiphosphotyrosine antibodies revealed increased TYR phosphorylation of immunoprecipitated PLC gamma 1 prepared from beta 1 integrin-ligated acinar cells. Subsequent stripping and reprobing of Western blots with polyclonal anti-PLC gamma 1 was confirmatory. Over this same time period, intracellular [Ca2+] increased from < 100 nM to 600 nM, further suggesting a functional relevance of integrin-linked phosphorylation as a regulatory mechanism in exocrine pancreas.