Evaluation of nickel-hydrogen battery for space application

Results of electrical space qualification tests of nickel-hydrogen battery type HR 23S are presented. The results obtained for the nickel-cadmium battery type VO 23S are similar except that the voltage level and the charge conservation characteristics vary significantly. The electrical and thermal characteristics permit predictions of the following optimal applications: charge coefficient in the order of 1.3 to 1.4 at 20C; charge current density higher than C/10 at 20C; discharge current density from C/10 to C/3 at 20C; maximum discharge temperature: OC; storage temperature: -20C

Can managed grasslands enhance pollinators in intensively farmed areas?

Wild flower strips is a common agri-environmental scheme used by farmers and land managers in order to improve biodiversity of pollinators. However, managed grasslands may also provide flower resources for flower visiting insects in agricultural landscapes. Botanically diverse grasslands on arable farms may support a range of wild pollinators, enhancing pollination services of crops. Intensively managed leys, on the other hand, typically contain only a few high-yielding, competitively strong species. One of the aims of the Multiplant project (2014-2018) was to test perennial seed mixtures targeted for bio-energy, feed protein and biodiversity, in order to develop multi-functional seed mixtures for grasslands. In the current study, we specifically investigated if yield (biomass production) and floral resources for pollinators could be simultaneously optimized by varying botanical composition of mixtures and cutting frequency. We tested four different perennial seed mixtures (3-, 5-, 11- and 13-species mixtures) at three sites varying in surrounding environment using three cutting strategies (no cutting, two cuts per year, four cuts per year). We measured flower production during the season, composition of flower-visitors (in functional groups), and biomass production of all plant species in the seed mixtures. The 11- and 13-species mixtures, which were designed to enhance pollinators, produced similar or higher yield than the 3- and 5- species mixtures under certain cutting regimes. The 3- and 5- species mixtures had a high accumulated flower abundance due to excessive flowering of lucerne under the two-cut strategy and white clover under the four-cut strategy. However, the 11- and 13 species mixtures presented a higher diversity of flowers during the flowering season. Interestingly, accumulated flower abundance was not significantly reduced under the two-cut strategy compared to no cut. Pollinator profiles (visits by different functional groups of insects) were plant-species specific, i.e. at all sites, plant species attracted similar types of insects. Legume species mainly attracted large bees (honey bees and bumblebees), while herbs attracted other insect groups, in particular syrphids and other flies. Our results suggest that multi-species grassland mixtures can be designed to support a higher diversity of pollinators without compromising herbage yield. In particular, adding forbs to the grass-legume mixtures and using a two-cut strategy rather than four cuts per year, may increase flower resources available for a larger range of wild pollinators

Long-lived quantum memory with nuclear atomic spins

We propose to store non-classical states of light into the macroscopic collective nuclear spin ($10^{18}$ atoms) of a $^3$He vapor, using metastability exchange collisions. These collisions, commonly used to transfer orientation from the metastable state $2^{3}S\_1$ to the ground state state of $^3$He, can also transfer quantum correlations. This gives a possible experimental scheme to map a squeezed vacuum field state onto a nuclear spin state with very long storage times (hours).Comment: 4 page

Optical control of solar sails using distributed reflectivity

The dynamics of solar sails with a variable surface reflectivity distribution are investigated. When changing the reflectivity across the sail film, which can be achieved using electro-chromic coatings, the solar radiation pressure forces and torques across the sail film can be controlled without changing the attitude of the spacecraft relative to the Sun and without using mechanical systems. The paper presents two approaches. First, a continuous reflectivity distribution is presented to control the sail attitude under the influence of, for example, gravity gradient torques in Earth orbit. The second approach assumes discrete on/o reflectivity regions across the surface. Both concepts of `optical reconfiguration' of solar sails enable a more flexible steering of the spacecraft and minimize actuation effort

La restauration des lacs au Québec: un défi face aux problèmes environnementaux actuels

Le Canada possède l'une des plus importantes réserves d'eau douce au monde. La province de Québec n'y fait pas exception puisqu'on y trouve près de 750 000 lacs et une multitude de rivières. Une grande partie de cette ressource est très fragile et exposée à divers problèmes environnementaux. Ces problèmes prennent leur source à l'échelle locale, régionale, continentale ou même planétaire dans certains cas et sont de différentes natures : eutrophisation, contamination par diverses substances polluantes, acidification, changements climatiques, etc. Au Québec, les moyens d'action actuels visent principalement à réduire les pollutions à la source par voie de réglementation, de programmes d'incitation ou de programmes de subvention (actions d'assainissement des eaux), en ne recourant aux interventions directes à court terme que dans des situations d'urgence ou d'extrême nécessité. Le présent texte rend compte des problèmes liés à l'eutrophisation, à l'acidification et à la contamination, ainsi qu'à leur échelle d'occurrence et des solutions disponibles pour amoindrir leur impact. Cette discussion est menée en favorisant une approche globale concertée qui vise à établir les bases d'une réelle politique de gestion de l'eau.Canada has one of the greatest freshwater reserves in the world. The province of Québec is not an exception to this generalization in that there are over 750 000 lakes and a large number of rivers of all sizes within the provincial boundaries. A major portion of this resource is highly vulnerable and is exposed to many contamination and environmental problems such as eutrophication, contamination from various pollutants, acidification, global climate changes, etc. In the province of Québec, actions are presently oriented toward reducing pollution hazards at the source by way of legislation, incentives and grant programs (wastewater cleanup programs), while resorting to short term direct approaches only in cases of emergencies and extreme necessity. The present article summarizes information about the problems encountered in Québec, their incidence, and the range of solutions available to reduce the impacts. This reflection is conducted in a way that favors a concerted global approach, which could act as the basis for a true water management policy

04/11/1931 Letter from J. Arthur Dupont

Letter from the J. Arthur Dupont, Director of C.K.A.C. Radio in Montreal, to Louis-Philippe Gagné.https://digitalcommons.usm.maine.edu/fac-lpg-letters-1920-1939/1009/thumbnail.jp

Observation of metastable hcp solid helium

We have produced and observed metastable solid helium-4 below its melting pressure between 1.1 K and 1.4 K. This is achieved by an intense pressure wave carefully focused inside a crystal of known orientation. An accurate density map of the focal zone is provided by an optical interferometric technique. Depending on the sample, minimum density achieved at focus corresponds to pressures between 2 and 4 bar below the static melting pressure. Beyond, the crystal undergoes an unexpected instability much earlier than the predicted spinodal limit. This opens a novel opportunity to study this quantum crystal in an expanded metastable state and its stability limits.Comment: deuxi\`eme versio