Pyrolysis gas chromatography of Streptococcus faecalis: effect of cultural conditions on pyrochromatograms

Streptococcus faecalis 251 was cultured under a variety of different growth conditions, i.e. incubation for 24 or 70 h; at 22 degrees, 37 degrees or 45 degrees C; on blood agar or on MacConkey agar plates; aerobically or anaerobically. Replicate cultures were analysed by pyrolysis-gas liquid chromatography on columns of 7% Carbowax 2 M, TPA on Chromosorb G (AW-DMCS, 80-100 mesh) programmed from 40 degrees C up to 170 degrees C. Culture grown under identical conditions resulted in reproducible pyrochromatograms which were only slightly modified by change in temperature of growth from 37 degrees to 45 degrees C, or length of growth from 24 to 70 h, or growth on MacConkey agar instead of blood agar. Growth under anaerobic conditions resulted in a modified pyrochromatogram; while growth at only 22 degrees C resulted in a major change in pyrochromatogram.     

An automated differential thermal and potentiometric titration apparatus for binding studies

A differential pH-termal titration apparatus is described which can detect pH differences with a sensitivity of ±0.0001 pH units and a thermal sensitivity of ±0.00002°C at a time constant of 0.1 s. With a reaction which yields 1 kcal mol⁻¹, the current system can detect concentrations as low as 4×10⁻⁶ M or, in a 2 ml volume, a total amount of 40 nmol. With a time constant of 0.1 s, the sensitivity is 20±4 μ°C. The experimental protocol is specified by a microprocessor and three modes of operation are possible: titration at constant rate of reagent addition, titration at variable rates of addition so that the contents of both cells are at either constant pH or at a constant temperature and variable rate when a rate of change is specified. Experimental data are collected in files, corrected for heat loss, initial baseline drift, and changes in volume. The final corrected from the standardized run of 0.01338 M HCl in 0.2 M KCl at 25°C calibrate the pH scale yielded the calorimetric conversion constants and pK_w which are calculated and stored for subsequent corrections for the titration of an unknown acid or the measurement of bindin constants and heats.     

The biology of the scaldfish, Arnoglossus laterna (Walbaum) on the west coast of Scotland.

The biology of a Scottish population of the small bothid flatfish, Arnoglossus laterna , was studied from January 1975 until September 1976. The data were taken from monthly samples totalling over 500 fish trawled in 18–36 m on a soft mud bottom. Otoliths were used for age determination and a growth curve was constructed which showed that most growth occurs in the first 2–3 years of life. The maximum age recorded was 8+ years. The fish first mature sexually in their second year at a standard length of 6–7 cm and the short spawning season lasts from the late June to August. Fecundity is length-dependent and the relationship could be described by the regression equation: log fecundity = 3·3472 log standard length (mm) -2·1064. The diet consists mainly of decapod crustaceans (particularly crangonid shrimps), polychaetes, mysids and small fish.     

Detection of Fainters and Epileptics in a Young Adult Population

A screening procedure for the detection of fainters and of epileptics was tested on 212 university student volunteers. No subject in this series gave a history of epilepsy but four definitely abnormal electroencephalograms were recorded. As a supplement to routine electroencephalography various circulatory stresses were applied with the subject sitting upright. The application of needle electrodes to the scalp was itself a potent stimulus to fainting. Under these conditions 16 of the 21 subjects with a history of repeated fainting were detected by their cardiovascular response to electrode placement or ocular compression. The use of painless pad electrodes reduced the total stress and produced inferior results. By careful adjustment of total stress intensity the majority of habitual fainters can be detected.     

Learning and Long-Term Retention of Large-Scale Artificial Languages

Recovering discrete words from continuous speech is one of the first challenges facing language learners. Infants and adults can make use of the statistical structure of utterances to learn the forms of words from unsegmented input, suggesting that this ability may be useful for bootstrapping language-specific cues to segmentation. It is unknown, however, whether performance shown in small-scale laboratory demonstrations of “statistical learning” can scale up to allow learning of the lexicons of natural languages, which are orders of magnitude larger. Artificial language experiments with adults can be used to test whether the mechanisms of statistical learning are in principle scalable to larger lexicons. We report data from a large-scale learning experiment that demonstrates that adults can learn words from unsegmented input in much larger languages than previously documented and that they retain the words they learn for years. These results suggest that statistical word segmentation could be scalable to the challenges of lexical acquisition in natural language learning.