British Women Chemists and the First World War

The First World War is sometimes called the 'Chemist's War' as its prosecution demanded ever increasing quantities of explosives, poison gases, optical glass, synthetic dyes, and pharmaceuticals (1). As the war progressed and severe shortages of chemicals occurred, more and more women were pressed into chemical-related work. Very little has been published about the skilled women chemists who were assigned to war duties (2). They were obviously much fewer in number than the hundreds of thousands of unskilled women who worked in the explosive factories (3), though they certainly did exist. Fortunately, the Women's Work Collection of the Imperial War Museum (IWM) has a significant amount of documentary evidence on the wartime women scientists. This useful material was compiled in 1919 by Agnes Ethel Conway of the Women's Work Sub-Committee of the IWM. Conway circulated a questionnaire to universities and industries informing them that the Committee was compiling a historical record of war work performed by women for the National Archives. In particular, Conway adds: "they [the Sub-Committee] are anxious that women's share in scientific research and in routine work should not be overlooked ..." (4). A sufficient number of replies were received to provide a sense of the breadth of employment of scientifically trained women during the War

Effect of a major ice storm on understory light conditions in an old-growth Acer-Fagus forest: Pattern of recovery over seven years

We evaluated the effects of a major ice storm on understory light conditions (%PPFD, photosynthetic photon flux density) in an old-growth Acer-Fagus forest in Quebec, based on pre- and post-disturbance light measurements taken until the seventh growing season after the event (which occurred in January 1998). Before the ice storm, most microsites received between 2 and 4%PPFD. Following the ice storm, the stand-level mean %PPFD increased four- to five-fold, ranging from 13.8 to 20.5%PPFD, from 0.3 to 4 m aboveground. Despite its magnitude, the post-ice storm increase in light transmission was short-lived. By 1999 (2-year+), the mean light levels had decreased by half, and recovery to pre-storm conditions occurred within 3-7 years, depending on height. The decrease in light transmission during the post-disturbance years followed an inverse J-shape trend, indicating more dynamic changes early after disturbance. By 2004 (7-year+), light levels at ≤2 m had become slightly but significantly lower than before the ice storm, with most microsites receiving <2%PPFD. The ice storm led to a synchronized increase of the light levels at almost all understory locations, which might allow a high proportion of the advanced regeneration to experience a release. However, due to the rapid recovery of the light conditions to levels similar or lower than before the ice storm, this disturbance should be more advantageous to shade-tolerant species

Structural Flyby Characterization of Nanoporosity

Recently, Ferreira da Silva et al. [3] have performed a gradient pattern analysis of a canonical sample set (CSS) of scanning force microscopy (SFM) images of p-Si. They applied the so-called Gradient Pattern Analysis to images of three typical p-Si samples distinguished by different absorption energy levels and aspect ratios. Taking into account the measures of spatial asymmetric fluctuations they interpreted the global porosity not only in terms of the amount of roughness, but rather in terms of the structural complexity (e.g., walls and fine structures as slots). This analysis has been adapted in order to operate in a OpenGL flyby environment (the StrFB code), whose application give the numerical characterization of the structure during the flyby real time. Using this analysis we compare the levels of asymmetric fragmentation of active porosity related to different materials as p-Si and "porous diamond-like" carbon. In summary we have shown that the gradient pattern analysis technique in a flyby environment is a reliable sensitive method to investigate, qualitatively and quantitatively, the complex morphology of active nanostructures

Aperture Valve for the Mars Organic Molecule Analyzer (MOMA)

NASA's participation in the multi-nation ExoMars 2018 Rover mission includes a critical astrobiology Mass Spectrometer Instrument on the Rover called the Mars Organic Molecule Analyzer (MOMA). The Aperture Valve is a critical electromechanical valve used by the Mass Spectrometer to facilitate the transfer of ions from Martian soil to the Mass Spectrometer for analysis. The MOMA Aperture Valve development program will be discussed in terms of the Initial valve design and subsequent improvements that resulted from prototype testing. The Initial Aperture Valve concept seemed promising, based on calculations and perceived merits. However, performance results of this design were disappointing, due to delamination of TiN and DLC coatings applied to the Titanium base metals, causing debris from the coatings to seize the valve. While peer reviews and design trade studies are important forums to vet a concept design, results from testing should not be underestimated. Despite the lack of development progress to meet requirements, valuable information from weakness discovered in the Initial Valve design was used to develop a second, more robust Aperture valve. Based on a check-ball design, the ETU /flight valve design resulted in significantly less surface area to create the seal. Moreover, PVD coatings were eliminated in favor of hardened, nonmagnetic corrosion resistant alloys. Test results were impressive, with the valve achieving five orders of magnitude better sealing leak rate over end of life requirements. Cycle life was equally impressive, achieving 280,000 cycles without failure

Generalised Reactive Processes in Isabelle/UTP

Hoare and He’s UTP theory of reactive processes provides a unifying foundation for the semantics of process calculi and reactive programming. A reactive process is a form of UTP relation which can refer to both state variables and also a trace history of events. In their original presentation, a trace was modelled solely by a discrete sequence of events. Here, we generalise the trace model using “trace algebra”, which characterises traces abstractly using cancellative monoids, and thus enables application of the theory to a wider family of computational models, including hybrid computation. We recast the reactive healthiness conditions in this setting, and prove all the associated distributivity laws. We tackle parallel composition of reactive processes using the “parallel-by-merge” scheme from UTP. We also identify the associated theory of “reactive relations”, and use it to define generic reactive laws, a Hoare logic, and a weakest precondition calculus

Stereocontrolled enantioselective total synthesis of the [2+2] quadrigemine alkaloids

Abstract A unified strategy for enantioselective total synthesis of all stereoisomers of the [2+2] family of quadrigemine alkaloids is reported. In this approach, two enantioselective intramolecular Heck reactions are carried out at the same time on precursors fashioned in four steps from either meso- or (+)-chimonanthine to form the two critical quaternary carbons of the peripheral cyclotryptamine rings of these products. Useful levels of catalyst control are realized in either desymmetrizing a meso precursor or controlling diastereoselectivity in elaborating C2-symmetric intermediates. None of the synthetic quadrigemines are identical with alkaloids isolated previously and referred to as quadrigemines A and E. In addition, we report improvements in our previous total syntheses of (+)- or (-)-quadrigemine C that shortened the synthetic sequence to 10 steps and provided these products in 2.2% overall yield from tryptamine

Aseptic Operations for Post DHMR Processing of MOMA Mass Spectrometer

Mars Organic Molecule Analyzer - Mass Spectrometer (MOMA-MS) is an instrument in the MOMA instrument suite for the European Space Agency (ESA) ExoMars 2020 Rover. The rover is Planetary Protection Mission Category IVb, the first IVb mission since the Viking missions in the 1970s. Within the sample path of the MOMA instrument suite, the hardware surfaces of the must be sanitized to a level of less than 0.03 spore/m sq. To meet this requirement, the MS sample path was subjected to Dry Heat Microbial Reduction (DHMR) to decrease the number of viable spores by 4 orders of magnitude from a measured 88 spores/m sq to 0.009 spores/m sq. Before DHMR, the hardware is handled using standard cleanroom practices. After DHMR, planetary protection filters protect the sample path for most of integration, but when sample path exposure is required, aseptic operations are instituted and exposure times are kept to an absolute minimum. The surface area of exposure is also taken into account to determine safe exposure times. Before work begins, the ISO class 5 aseptic workspace is cleaned and tested for surface and airborne bioburden, and all tools that will contact or be used near sample path surfaces are sterilized. During the exposure activity, sterile garments are worn, sterile gloves are changed as often as necessary, and the environment is monitored with active and passive fallout for bioburden and real time airborne particle counts. Sterile tools are handled by a two person team so that the operator touches only the tool and not the exterior surfaces of the sterilization pouch, and a sterile operating field is established as a safe place to organize tools or parts during the aseptic operations. In cases where aseptic operations are not feasible, localized DHMR is used after exposure. Any breach in the planetary protection cleanliness can necessitate repeating instrument level DHMR, which not only has significant cost and schedule implications, it also become a risk to hardware that is not rated for repeated long exposures to high temperatures