Stellar scintillation statistics and the impact of aperture averaging on space-to-ground optical communications.

Statistical probability distributions characterizing received optical power fluctuations, or scintillation, enable performance predictions of space-to-ground optical communication systems. In this paper, we present measurements of stellar scintillation over a wide range of elevation angles and turbulence conditions collected simultaneously with a 5 cm and 40 cm telescope aperture, which allows a comparison between minimal and significant aperture averaging conditions. The measured data is compared to a reasonable set of candidate probability distribution functions (PDFs), including lognormal, which is most often cited in the literature for weak to moderate scintillation. For scintillation indices (SIs) less than about 0.2, the Nakagami-m distribution provides the best representation of the collected data for both apertures and imposes a greater lasercom link penalty than a lognormal distribution, which has been inaccurately implemented as the default probability distribution in the literature. For larger values of the SI, the scintillation is best characterized by a Gamma-Gamma distribution. Additionally, the measured temporal covariance for weak to moderate scintillation conditions is found to be in reasonably good agreement with theoretical predictions.

Optical communications downlink from a low-earth orbiting 1.5U CubeSat.

In this article, we present the first demonstration of an optical communications downlink from a low-earth orbiting free-flying CubeSat. Two 1.5U vehicles, AC7-B&C, built under NASA's Optical Communications and Sensors Demonstration (OCSD) program were launched in November 2017 and subsequently placed into a 450-km, 51.6° inc. circular orbit. Pseudorandom data streams using on-off key (OOK) modulation were transmitted from AC-7B to a 40 cm aperture telescope located at sea level in El Segundo, CA. At 200 Mbps, without forward error correction (FEC), we achieved a 115-second link that was ~78% error free, with the remaining portion exhibiting an error rate below 1E-5. At the time of the engagement, the 1064-nm laser transmitter was operating at 2 W (half capacity) with a full width half maximum (FWHM) beam divergence of ~1 mrad, which was approximately double the anticipated pointing accuracy of the vehicle.

A survey of practice of rapid sequence induction for caesarean section in England.

BACKGROUND: In view of newer techniques of preoxygenation and laryngoscopy and recent obstetric guidelines concerning the management of difficult intubation, we aimed to evaluate the current practice of rapid sequence induction for caesarean section in England. METHODS: In 2017, 316 questionnaire surveys were posted to all 158 hospitals with caesarean section capabilities in England. At each hospital, one questionnaire was to be completed by the obstetric anaesthetic consultant lead and one by an anaesthetic trainee. Differences in responses between consultants and trainees, regardless of their place of work, were compared for all data using the chi-square and the Fisher's exact tests. RESULTS: One-hundred-and-eighty complete questionnaires were returned, with an overall response rate of 57%, 98 (54%) from obstetric anaesthetic consultant leads and 82 (45.6%) from trainees). Both head up (57%) and ramped (56%) were the preferred positions for preoxygenation. Less than half of respondents (43%) preoxygenated until the surgeon was scrubbed. Cricoid pressure was used by almost all respondents (98%). Thiopentone (67%) was the most commonly chosen anaesthetic induction agent and most respondents (82%) supported a change to the use of propofol. Suxamethonium (92%) was the neuromuscular blocker of choice but more than half the respondents (52%) supported a change to rocuronium. In the event of a failed intubation, the rescue supraglottic airway device of choice was the i-gel® (65%). CONCLUSIONS: Our survey demonstrated the significant variation in the practice of rapid sequence induction for caesarean section in obstetrics in the United Kingdom.

Proof of concept study: Testing human volatile organic compounds as tools for age classification of films.

Humans emit numerous volatile organic compounds (VOCs) through breath and skin. The nature and rate of these emissions are affected by various factors including emotional state. Previous measurements of VOCs and CO2 in a cinema have shown that certain chemicals are reproducibly emitted by audiences reacting to events in a particular film. Using data from films with various age classifications, we have studied the relationship between the emission of multiple VOCs and CO2 and the age classifier (0, 6, 12, and 16) with a view to developing a new chemically based and objective film classification method. We apply a random forest model built with time independent features extracted from the time series of every measured compound, and test predictive capability on subsets of all data. It was found that most compounds were not able to predict all age classifiers reliably, likely reflecting the fact that current classification is based on perceived sensibilities to many factors (e.g. incidences of violence, sex, antisocial behaviour, drug use, and bad language) rather than the visceral biological responses expressed in the data. However, promising results were found for isoprene which reliably predicted 0, 6 and 12 age classifiers for a variety of film genres and audience age groups. Therefore, isoprene emission per person might in future be a valuable aid to national classification boards, or even offer an alternative, objective, metric for rating films based on the reactions of large groups of people.

Current practice of rapid sequence induction of anaesthesia in the UK - a national survey.

BACKGROUND: The 'classical' technique of rapid sequence induction (RSI) of anaesthesia was described in 1970. With the introduction of new drugs and equipment in recent years, a wide variation in this technique has been used. The role of cricoid pressure is controversial because of the lack of scientific evidence. Moreover, gentle mask ventilation has been recommended in situations such as obesity and critically ill patients, to prevent hypoxaemia during the apnoeic period. In identifying multiple techniques, we conducted a national postal survey to establish the current practice of RSI in the UK. METHODS: A survey consisting of 17 questions was created and posted to 255 National Health Service (NHS) hospitals in the UK. We included two copies of the questionnaire in each envelope; one to be completed by the airway lead (consultant anaesthetist with responsibility of overseeing the standard of airway training and implementing national airway guidelines and recommendations within their institution) and the other by a trainee in the same department. The difference in responses from consultants and trainees were assessed using the χ(2) test and the Fisher's exact test. RESULTS: In total we received 272 responses (response rate 53%) of which 266 (58% from consultants and 42% from trainees) were analysed. A majority of the respondents (68%) pre-oxygenated by monitoring end-tidal oxygen concentration and 76% of the respondents use 20-25° head up tilt for all RSIs. Propofol is the most commonly used induction agent (64% of all respondents). Opioid has been used by 80% of respondents and only 18% of respondents use suxamethonium for all patients and others choose rocuronium or suxamethonium based on clinical situation. Although 92% of anaesthetists use cricoid pressure, 83% of them never objectively measure the force used. During the apnoeic period 17% of the respondents use gentle mask ventilation. CONCLUSIONS: Our survey demonstrated a persistent variation in the practice of RSI amongst the anaesthetists in the UK. The 'classical' technique of RSI is now seldom used. Therefore there is a clear need for developing consistent guidelines for the practice of RSI.

Lorneamides A and B: two new aromatic amides from a southern Australian marine actinomycete.

A marine actinomycete (MST-MA190) isolated from a sample of beach sand collected near Lorne on the southwest coast of Victoria, Australia, has yielded two new aromatic amides, lorneamide A (1) and lorneamide B (2). The lorneamides belong to a novel class of tri-alkyl-substituted benzenes, and their structures were determined by spectroscopic methods.

Protection of cattle against Fasciola hepatica infection by vaccination with glutathione S-transferase.

Glutathione S-transferase (GST) from the liver fluke Fasciola hepatica was assessed as a vaccine immunogen in cattle in a number of immunological adjuvants. Significant reductions in fluke burdens (49-69%) were only observed in cattle vaccinated with GST in Quil Alsqualene Montanide (SM) and PLG microspheres in SM but there was no correlation between anti-GST IgG titres and protection. In separate experiments, animals vaccinated with GST in Quil AlSM were still significantly protected (48%, P < 0.05) 6 months after boosting and no significant differences in protection were seen when the metacercarial challenge was given over 1 month instead of as a single bolus. Inhibition of GST enzyme activity in vitro by cattle antisera did not correlate with reduced fluke burdens.

Vaccination of sheep with purified cysteine proteinases of Fasciola hepatica decreases worm fecundity.

There has been some evidence from several parasite systems that proteinases might have potential as protective antigens against parasitic infection. A cysteine proteinase complex identified in the regurgitant of adult F. hepatica was examined in this context. The thiol-cathepsin-related proteinases of M(r) 28,000 were purified and tested in vaccine trials of sheep infected with liver fluke. Ten animals were immunised with the purified proteinases and developed antibodies to the cysteine proteinases prior to challenge with F. hepatica metacercariae. Infection appeared to cause a boost in antibody response by Week 4 into infection, and antibody levels were generally sustained throughout infection. The cysteine proteinases are not novel antigens, since low-level antibody titres were also detected in nonimmunised controls by late infection. On completion of the trial, there was no difference in worm burden between the two groups. However, faecal egg counts and therefore worm fecundity were significantly decreased.