Continuous Elastic Phase Transitions in Pure and Disordered Crystals

We review the theory of second--order (ferro--)elastic phase transitions, where the order parameter consists of a certain linear combination of strain tensor components, and the accompanying soft mode is an acoustic phonon. In three--dimensional crystals, the softening can occur in one-- or two--dimensional soft sectors. The ensuing anisotropy reduces the effect of fluctuations, rendering the critical behaviour of these systems classical for a one--dimensional soft sector, and classical with logarithmic corrections in case of a two--dimensional soft sector. The dynamical critical exponent is $z = 2$, and as a consequence the sound velocity vanishes as $c_s \propto | T - T_c |^{1/2}$, while the phonon damping coefficient is essentially temperature--independent. Disorder may lead to a variety of precursor effects and modified critical behaviour. Defects that locally soften the crystal may induce the phenomenon of local order parameter condensation. When the correlation length of the pure system exceeds the average defect separation $n_{\rm D}^{-1/3}$, a disorder--induced phase transition to a state with non--zero average order parameter can occur at a temperature $T_c(n_{\rm D})$ well above the transition temperature $T_c^0$ of the pure crystal. Near $T_c^0$, the order--parameter curve, susceptibility, and specific heat appear rounded. For $T < T_c(n_{\rm D})$ the spatial inhomogeneity induces a static central peak with finite $q$ width in the scattering cross section, accompanied by a dynamical component that is confined to the very vicinity of the disorder--induced phase transition.Comment: 26 pages, Latex (rs.sty now IS included), 11 figures can be obtained from U.C. T\"auber ([email protected]); will appear in Phil. Trans. Roy. Soc. Lond. A (October 1996

Ice dynamics and sediment movement : last glacial cycle, Clyde Basin, Scotland

The nature and behaviour of sediment beneath glaciers influences how they flow and respond to changing environmental conditions. The difficulty of accessing the bed of current glaciers is a key constraint to studying the processes involved. This paper explores an alternative approach by relating sediments under the beds of former mid-latitude ice sheets to changing ice behaviour during a glacial cycle. The paper focuses on the partly marine-based Pleistocene British-Irish ice sheet in the Clyde basin, Scotland. A three-dimensional computation of subsurface glacial sediment distribution is derived from 1260 borehole logs. Sediment distribution is linked to an empirically based reconstruction of ice-sheet evolution, permitting identification of distinctive phases of sedimentation. Maximum sediment mobilization and till deposition (∼0.04 m a-1) occurred during ice advance into the basin from adjacent uplands. Transport distances were generally short. Subglacial processes were influenced locally by the relative stiffness of pre-existing sediments, the permeability of the sub-till lithology, and topography; the resulting mean till thickness is 7.7 m with a high standard deviation of 7.0 m. In places, focused till deposition sealed pre-existing permeable substrates, promoting lower effective pressures. Sediment remobilization by meltwater was a key process as ice margins retreated through the basin

The effect of certain insecticides on the germination and growth of onions, II: Insecticides applied to the seed

n/

The electrokinetic behavior of calcium oxalate monohydrate in macromolecular solutions

Electrophoretic mobilities were measured for calcium oxalate monohydrate (COM) in solutions containing macromolecules. Two mucopolysaccharides (sodium heparin and chrondroitin sulfate) and two proteins (positively charged lysozyme and negatively charged bovine serum albumin) were studied as adsorbates. The effects of pH, calcium oxalate surface charge (varied by calcium or oxalate ion activity), and citrate concentration were investigated. All four macromolecules showed evidence for chemical adsorption. The macromolecule concentrations needed for reversing the surface charge indicated that the mucopopolysacchrides have greater affinity for the COM surface than the proteins. The amount of proteins that can chemically adsorb appears to be limited to approximately one monomolecular layer. When the surface charge is high, an insufficient number of proteins can chemically adsorb to neutralize or reverse the surface charge. The remaining surface charge is balanced by proteins held near the surface by longer range electrostatic forces only. Citrate ions at high concentrations appear to compete effectively with the negative protein for surface sites but show no evidence for competing with the positively charged protein

Effect of BMI and Binge Eating on Food Reward and Energy Intake: Further Evidence for a Binge Eating Subtype of Obesity

Background: The psychological characteristics of binge eating have been proposed as a phenotype to further understanding of overconsumption and susceptibility to obesity. This study examined the influence of trait binge eating in lean and overweight or obese women on appetite, food reward and energy intake. Methods: 25 lean and 25 overweight or obese women were categorised as either ‘binge type' or ‘non-binge type' based on their scores on the Binge Eating Scale. Food reward and food intake were assessed in fasted and fed conditions. Results: Overweight or obese binge types (O-B) consumed more energy than overweight or obese non-binge types (O-NB) and lean binge (L-B) and non-binge types (L-NB). Both L-B and O-B exhibited greater preference for sweet foods. In O-NB, L-B and L-NB, lower liking and wanting for sweet foods was exhibited in the fed condition compared to the fasted condition. However, in O-B wanting for sweet foods was greater when they were fed compared to when they were in a fasted state. Conclusions: These findings provide further support for trait binge eating as a hedonic subtype of obesity. Binge types were characterised by greater intake of high-fat sweet foods and increased wanting for these foods when satiated. Additionally, these findings highlight the potential for separation in liking and wanting for food as a marker of susceptibility to overeat

The efficacy of organocarbamate, organochlorine, and organophosphate insecticides against turnip maggots and resistant cabbage maggots in rutabaga in British Columbia

n/

Carabid and Staphylinid beetles from agricultural land in the lower Fraser Valley, British Columbia

Pit-traps were emptied every two or three days for two seasons in crop, fallow, and grass plots to determine the species and population density of Carabidae and Staphylinidae associated with agricultural land, and their relationship with brassica crops. Half of the plots were enclosed by plastic barriers and the beetles were trapped to extinction: half were not enclosed. Thirty-three carabid and 16 staphylinid species were captured. The dominant species was the small, generalized. European carabid predator, &lt;i&gt;Bembidion lampros&lt;/i&gt;, which had a population on crop and fallow land of about 29000/hectare. It was almost absent in grass. Other numerous carabids were &lt;i&gt;Harpalus aeneus&lt;/i&gt;, &lt;i&gt;Calathus fuscipes&lt;/i&gt;, and &lt;i&gt;Clivina fossor&lt;/i&gt;, all introduced European spp., with populations of almost 2000, 5600, and llOOO/hectare respectively. The first and third of these were scarce in grassland but the second was abundant. In plots of Brussels sprouts &lt;i&gt;Aleochara bilineata&lt;/i&gt;, a staphylinid, was effectively parasitic on root maggots, and averaged more than 6000/hectare. Soil cores taken in October centred on a Brussels sprouts plant averaged 26.4 &lt;i&gt;Hylemya puparia&lt;/i&gt; per core of which 44% were parasitized by &lt;i&gt;A. bilineata&lt;/i&gt;

The effect of dosage of organophosphate insecticides on the emergence of radish seedlings and on damage by cabbage maggots

n/