Development of a high stability pointing mechanism for wide application

A recurrent requirement of spaceborne instruments and communications equipment is that of accurate pointing. This need is recognizable in such diverse applications as Star Sensor trimming, Momentum Wheel gimballing, in-orbit adjustment or alignment of equipment, inter-satellite communication and Antenna Pointing. A pointing mechanism of novel design having several advantages over the more conventional gimbal, centre-pivoted, or cross axis pointing concepts is described

ATP release via anion channels

ATP serves not only as an energy source for all cell types but as an ‘extracellular messenger-for autocrine and paracrine signalling. It is released from the cell via several different purinergic signal efflux pathways. ATP and its Mg2+ and/or H+ salts exist in anionic forms at physiological pH and may exit cells via some anion channel if the pore physically permits this. In this review we survey experimental data providing evidence for and against the release of ATP through anion channels. CFTR has long been considered a probable pathway for ATP release in airway epithelium and other types of cells expressing this protein, although non-CFTR ATP currents have also been observed. Volume-sensitive outwardly rectifying (VSOR) chloride channels are found in virtually all cell types and can physically accommodate or even permeate ATP4- in certain experimental conditions. However, pharmacological studies are controversial and argue against the actual involvement of the VSOR channel in significant release of ATP. A large-conductance anion channel whose open probability exhibits a bell-shaped voltage dependence is also ubiquitously expressed and represents a putative pathway for ATP release. This channel, called a maxi-anion channel, has a wide nanoscopic pore suitable for nucleotide transport and possesses an ATP-binding site in the middle of the pore lumen to facilitate the passage of the nucleotide. The maxi-anion channel conducts ATP and displays a pharmacological profile similar to that of ATP release in response to osmotic, ischemic, hypoxic and salt stresses. The relation of some other channels and transporters to the regulated release of ATP is also discussed

General anaesthetic and airway management practice for obstetric surgery in England: a prospective, multi-centre observational study

There are no current descriptions of general anaesthesia characteristics for obstetric surgery, despite recent changes to patient baseline characteristics and airway management guidelines. This analysis of data from the direct reporting of awareness in maternity patients' (DREAMY) study of accidental awareness during obstetric anaesthesia aimed to describe practice for obstetric general anaesthesia in England and compare with earlier surveys and best-practice recommendations. Consenting patients who received general anaesthesia for obstetric surgery in 72 hospitals from May 2017 to August 2018 were included. Baseline characteristics, airway management, anaesthetic techniques and major complications were collected. Descriptive analysis, binary logistic regression modelling and comparisons with earlier data were conducted. Data were collected from 3117 procedures, including 2554 (81.9%) caesarean deliveries. Thiopental was the induction drug in 1649 (52.9%) patients, compared with propofol in 1419 (45.5%). Suxamethonium was the neuromuscular blocking drug for tracheal intubation in 2631 (86.1%), compared with rocuronium in 367 (11.8%). Difficult tracheal intubation was reported in 1 in 19 (95%CI 1 in 16-22) and failed intubation in 1 in 312 (95%CI 1 in 169-667). Obese patients were over-represented compared with national baselines and associated with difficult, but not failed intubation. There was more evidence of change in practice for induction drugs (increased use of propofol) than neuromuscular blocking drugs (suxamethonium remains the most popular). There was evidence of improvement in practice, with increased monitoring and reversal of neuromuscular blockade (although this remains suboptimal). Despite a high risk of difficult intubation in this population, videolaryngoscopy was rarely used (1.9%)

Factors influencing the gross energy content of grass silage

The gross energy (GE) of a feed represents its total energy content and is measured by burning the material in an atmosphere of oxygen in a bomb calorimeter. The GE of many feeds is often taken to be 18.4 MJ/kg dry matter (DM) (MAFF et al, 1984). This assumption is likely to be doubtful for feeds which are for example high in lipid or which contain products of fermentation. The gross energy content of grass silages in particular has recently been reviewed by Edwards (1986).The GE content of grass silage can account for some 50% of the variability in metabolisable energy (ME). It is however ignored in present laboratory methods used for the prediction of ME which largely depend on using fibre fractions (Givens, 1986) which are more closely related to digestibility. This paper presents the results of GE determinations made on 109 grass silages made in clamps and since GE cannot be measured routinely, examines a number of factors which may be helpful in its prediction.</jats:p

The effect of molasses intake on rumen pH and degradability of hay dry matter in sheep

Cane molasses (CM) a by-product of sugar production, provides a relatively cheap means of increasing the energy content of ruminant diets. It is commonly thought that dietary concentrations of CM above about 200g/kg of the dry matter (DM) intake will lead to a reduction in rumen pH and hence have a depressant effect on forage digestibility. Recent work in vivo at the FEU and in vitro (ref 1) has suggested that there is an interaction between forage and CM, and indeed the in vitro experiment found evidence that increasing the proportion of CM actually enhanced the digestibility of the mixture. A further experiment was therefore conducted to monitor rumen pH and measure the degradability of hay DM in sheep fed increasing levels of molasses.</jats:p

Fermentation characteristics in clamp and big bale silages

In recent years big bale silage (BBS) made in large plastic bags has become an increasingly popular method of grass conservation with one estimate (Catt, 1986) suggesting that 30% of all grass silage in the UK was conserved in this way in 1985.In general BBS is drier than clamp silage (CS) (Butler, 1983) primarily for economic reasons related to contracters.charges for baling the reduced number of bales compared to wet silage. There are however few comparative data on concentrations of fermentation acids and it is not clear whether the fermentation characteristics of BBS are different from CS or merely a function of differences in dry matter content.</jats:p