Towards a fuller, more nuanced narrative of Chalcolithic and Early Bronze Age Britain 2500-1500 BC

This contribution considers some of the many recent advances in our understanding of Chalcolithic and Bronze Age Britain and uses these to highlight the weak points in our current state of knowledge. Focusing mainly on the period 2500–1500 BC, it concentrates on issues of chronology, human movement, the role of metal and monuments as 'drivers' of action, and the potential offered by current studies of artefact manufacture, use and depositio

Two-D results on human operator perception

The application of multidimensional scaling methodology in human factors engineering is presented. The nonorthogonality of internally perceived task variables is exhibited for first and second order plants with both dependent and independent task variables. Directions of operator preference are shown for actual performance, pilot opinion rating, and subjective measures of fatigue, adaptability, and system recognition. Improvement of performance in second order systems is exhibited by the use of bang-bang feedback information. Dissimilarity measures for system comparison are suggested in order to account for human operator rotations and subjective sense of time

The re-dating of some Scottish specimens by the Oxford Radiocarbon Accelerator Unit (ORAU)

The purpose of this note is to alert readers to the fact that some AMS dates determined by ORAU on Scottish material between 2000 and 2002 have had to be deleted and re-determined, because of a problem in the ultrafiltration system used to pretreat bone samples during that period (see C Bronk Ramsey, T Higham, A Bales and R Hedges 2004, Improvements in the pretreatment of bone at Oxford, Radiocarbon 46(1), 155–63, for details). In many cases it has been possible to undertake the re-dating using left over material from the original (unprocessed) samples; in other cases, re-sampling will be necessary. Lists of both sets of material are appended here, and readers are requested to use only the new dates, and to delete the old versions

Rates and equilibria at the acetylcholine receptor of electrophorus electroplaques. A study of neurally evoked postsynaptic currents and of voltage-jump relaxations

Kinetic measurements are employed to reconstruct the steady-state activation of acetylcholine [Ach] receptor channels in electrophorus electroplaques. Neurally evoked postsynaptic currents (PSCs) decay exponentially; at 15°C the rate constant, α, equals 1.2 ms^(-1) at 0 mV and decreases e-fold for every 86 mV as the membrane voltage is made more negative. Voltage-jump relaxations have been measured with bath-applied ACh, decamethonium, carbachol, or suberylcholine. We interpret the reciprocal relaxation time 1/τ as the sum of the rate constant α for channel closing and a first-order rate constant for channel opening. Where measureable, the opening rate increases linearly with [agonist] and does not vary with voltage. The voltage sensitivity of small steady-state conductances (e- fold for 86 mV) equals that of the closing rate α, confirming that the opening rate has little or no additional voltage sensitivity. Exposure to α-bungarotoxin irreversibly decreases the agonist-induced conductance but does not affect the relaxation kinetics. Tubocurarine reversibly reduces both the conductance and the opening rate. In the simultaneous presence of two agonist species, voltage-jump relaxations have at least two exponential components. The data are fit by a model in which (a) the channel opens as the receptor binds the second in a sequence of two agonist molecules, with a forward rate constant to 10^(7) to 2x10^(8) M^(-1)s^(-1); and (b) the channel then closes as either agonist molecule dissociates, with a voltage-dependent rate constant of 10^(2) to 3x10^(3)s^(-1)