Gender, change and periodisation

No abstract available

Isolation and characterisation of Sri Lankan yeast germplasm and its evaluation for alcohol production

Use of inferior yeast cultures represents one of the reasons for low fermentation efficiencies in Sri Lankan alcohol distilleries that use sugarcane molasses. The present study isolated and characterised yeast strains found in natural environments in Sri Lanka and evaluated their performance under laboratory conditions in an effort to select superior strains for industrial fermentations. Yeasts were characterised based on morphological and physiological features such as sugar fermentation and nitrate assimilation. Ethanol production, alcohol tolerance and growth rate of the most promising strains were monitored following laboratory fermentations of molasses. Over a thousand yeast cultures were collected and screened for fermentative activity and a total of 83 yeast isolates were characterised as higher ethanol producers. Most of these belonged to the genus Saccharomyces. Certain strains produced over 10% (v/v) alcohol in molasses media during 72 h laboratory fermentations. Only two strains, SL-SRI-C-102 and 111, showed an appreciable fermentation efficiency of about 90%. The latter strain produced the highest level of ethanol, 11% (v/v) within a 48 h fermentation and exhibited improved alcohol tolerance when compared with the baker's yeast strains currently used in Sri Lankan alcohol distilleries. This study highlights the benefits of exploiting indigenous yeasts for industrial fermentation processes

Unusual relative strengths of the diffuse interstellar bands in some interstellar dust clouds

Some of the diffuse interstellar features (DIBs) in the spectra of certain stars at high galactic latitudes (1 is greater than 15 degrees) are unusually weak or absent while others have the strength expected for their color excess. In some cases the stars are probably reddened by single interstellar clouds. There appear to be three families of DIBs. The effects of these families are examined. The existance of the three families implies that at least three agents cause the DIBs and that the proportions of the agents or the physical conditions giving rise to the DIBs can vary from cloud to cloud

Method for deducing anisotropic spin-exchange rates

Using measured spin-transfer rates from alkali atoms to He-3, combined with spin-relaxation rates of the alkali atoms due to He-3 and He-4, it should be possible to differentiate between isotropic and anisotropic spin-exchange. This would give a fundamental limit on the He-3 polarization attainable in spin-exchange optical pumping. For K-He, we find the limit to be 0.90+-0.11

Velocity dominated singularities in the cheese slice universe

We investigate the properties of spacetimes resulting from matching together exact solutions using the Darmois matching conditions. In particular we focus on the asymptotically velocity term dominated property (AVTD). We propose a criterion that can be used to test if a spacetime constructed from a matching can be considered AVTD. Using the Cheese Slice universe as an example, we show that a spacetime constructed from a such a matching can inherit the AVTD property from the original spacetimes. Furthermore the singularity resulting from this particular matching is an AVTD singularity.Comment: 11 pages, 3 figures, accepted for publication in the International Journal of Modern Physics

Associating object names with descriptions of shape that distinguish possible from impossible objects.

Five experiments examine the proposal that object names are closely linked torepresentations of global, 3D shape by comparing memory for simple line drawings of structurally possible and impossible novel objects.Objects were rendered impossible through local edge violations to global coherence (cf. Schacter, Cooper, & Delaney, 1990) and supplementary observations confirmed that the sets of possible and impossible objects were matched for their distinctiveness. Employing a test of explicit recognition memory, Experiment 1 confirmed that the possible and impossible objects were equally memorable. Experiments 2–4 demonstrated that adults learn names (single-syllable non-words presented as count nouns, e.g., “This is a dax”) for possible objectsmore easily than for impossible objects, and an item-based analysis showed that this effect was unrelated to either the memorability or the distinctiveness of the individual objects. Experiment 3 indicated that the effects of object possibility on name learning were long term (spanning at least 2months), implying that the cognitive processes being revealed can support the learning of object names in everyday life. Experiment 5 demonstrated that hearing someone else name an object at presentation improves recognition memory for possible objects, but not for impossible objects. Taken together, the results indicate that object names are closely linked to the descriptions of global, 3D shape that can be derived for structurally possible objects but not for structurally impossible objects. In addition, the results challenge the view that object decision and explicit recognition necessarily draw on separate memory systems,with only the former being supported by these descriptions of global object shape. It seems that recognition also can be supported by these descriptions, provided the original encoding conditions encourage their derivation. Hearing an object named at encoding appears to be just such a condition. These observations are discussed in relation to the effects of naming in other visual tasks, and to the role of visual attention in object identification

Multiple and plastic receptors mediate tonic GABAA receptor currents in the hippocampus

Persistent activation of GABAA receptors by extracellular GABA (tonic inhibition) plays a critical role in signal processing and network excitability in the brain. In hippocampal principal cells, tonic inhibition has been reported to be mediated by {alpha}5-subunit-containing GABAA receptors ({alpha}5GABAARs). Pharmacological or genetic disruption of these receptors improves cognitive performance, suggesting that tonic inhibition has an adverse effect on information processing. Here, we show that {alpha}5GABAARs contribute to tonic currents in pyramidal cells only when ambient GABA concentrations increase (as may occur during increased brain activity). At low ambient GABA concentrations, activation of {delta}-subunit-containing GABAA receptors predominates. In epileptic tissue, {alpha}5GABAARs are downregulated and no longer contribute to tonic currents under conditions of raised extracellular GABA concentrations. Under these conditions, however, the tonic current is greater in pyramidal cells from epileptic tissue than in pyramidal cells from nonepileptic tissue, implying substitution of {alpha}5GABAARs by other GABAA receptor subtypes. These results reveal multiple components of tonic GABAA receptor-mediated conductance that are activated by low GABA concentrations. The relative contribution of these components changes after the induction of epilepsy, implying an adaptive plasticity of the tonic current in the presence of spontaneous seizures

Trans-spectral orbital angular momentum transfer via four-wave mixing in Rb vapor

We report the transfer of phase structure and, in particular, of orbital angular momentum from near-infrared pump light to blue light generated in a four-wave-mixing process in Rb-85 vapor. The intensity and phase profile of the two pump lasers at 780 and 776 nm, shaped by a spatial light modulator, influences the phase and intensity profile of light at 420 nm, which is generated in a subsequent coherent cascade. In particular, we observe that the phase profile associated with orbital angular momentum is transferred entirely from the pump light to the blue. Pumping with more complicated light profiles results in the excitation of spatial modes in the blue that depend strongly on phase matching, thus demonstrating the parametric nature of the mode transfer. These results have implications on the inscription and storage of phase information in atomic gases