ALBERT

Notes: We present a diffuse-interface treatment of the internal gravity waves which have been observed experimentally by Berg et al. in xenon near its thermodynamic critical point. The results are compared with theoretical predictions by Berg et al. that were obtained using separate models above and below the critical temperature Tc. The diffuse-interface model applies both above and below Tc, and is formulated by using the density as an order parameter. The diffuse interface is represented as a transition zone of rapid but smooth density variation in the model, and density gradients appear in a capillary tensor, or Korteweg stress term, in the momentum equation. We obtain static density profiles, compute internal wave frequencies and compare with the experimental data and theoretical results of Berg et al. both above and below the critical temperature. The results reveal a singularity in the diffuse-interface model in the limit of incompressible perturbations.

Notes: A two-dimensional volatile liquid droplet on a uniformly heated horizontal surface is considered. Lubrication theory is used to describe the effects of capillarity, thermocapillarity, vapor recoil, viscous spreading, contact-angle hysteresis, and mass loss on the behavior of the droplet. A new contact-line condition based on mass balance is formulated and used, which represents a leading-order superposition of spreading and evaporative effects. Evolution equations for steady and unsteady droplet profiles are found and solved for small and large capillary numbers. In the steady evaporation case, the steady contact angle, which represents a balance between viscous spreading effects and evaporative effects, is larger than the advancing contact angle. This new angle is also observed over much of the droplet lifetime during unsteady evaporation. Further, in the unsteady case, effects which tend to decrease (increase) the contact angle promote (delay) evaporation. In the "large'' capillary number limit, matched asymptotics are used to describe the droplet profile; away from the contact line the shape is determined by initial conditions and bulk mass loss, while near the contact-line surface curvature and slip are important. © 1995 American Institute of Physics.

Notes: Laboratory experiments were conducted to determine the effects of soil moisture, simulated rainfall and time of day of spray application on the efficacy of glufosinate-ammonium in barley (Hordeum vulgare L. cv. ‘Samson’) and green foxtail (Setaria viridis (L.) Beauv.) plants. Environmental variables examined were three soil moisture levels (18% moisture, 50% moisture and saturated), three intensities of simulated rainfall following spray application [drizzle (4 mm), moderate (9 mm) and heavy (22 mm)] and two times of spray application (begin ning and end of a 16-h photoperiod). The efficacy of 100 g ha−1 glufosinate-ammonium on barley was greatest at 18% soil moisture when measured by both ammonia and dry weight accumulation in the shoots. At the same dose green foxtail showed less ammonia accumula tion at 18% soil moisture than under other soil moisture levels, but showed no significant differences in dry weight accumulation 14 days after treatment (DAT). Simulated rainfall shortly after spraying reduced the efficacy of glufosinate-ammonium on both species. At the field dose of 800 g ha−1, a rain-free period of 1–8 h was necessary for barley, while a period of less than 20 min was necessary for green foxtail to obtain herbicidal activity comparable with that of treated plants which received no rain. Based on dry weight accumulation, barley plants were equally sensitive and green foxtail plants were significantly more susceptible when glufosinate-ammonium was applied at the end compared to the beginning of the photoperiod. Both species accumulated significantly more ammonia in the shoots during the initial 24 h following application if sprayed at the end of the photoperiod. Of the environmental factors examined in this study, rainfall after spray application caused the greatest reduction of glufosinate-ammonium efficacy. Influence de I'humiditt du sol, de la pluie artificielle et de I'époque d'application sur I'effi cacité du glufosinate-ammonium Des essais de laboratoire ont été conduits pour déterminer les effets de Phumidité du sol, de la pluie et de I'époque d'application sur 1'efficacité de glufosinate-ammonium sur 1'orge (Hordeum vulgare L. c.v. ‘Samson’) et la sétaire (Setaria viridis (L.) Beauv.). Les variables environne mentales examinées étaient 3 taux d'humidité du sol (18%, 50% et saturation), 3 intensités de pluie artificielle suivant ('application (faible—4 mm; modéré 9 mm; et forte 22 mm) et 2 époques d'application (début et fin d'une photopériode de 16 h). L'efficacite de 100 g ha−1 de glufosinate-ammonium sur orge était maximale a 18% d'humidité du sol, mesurée à la fois par I'accumulation d'azote et de matiére séche dans les tiges. A la même dose, la sétaire exprime une moins grande accumulation d'azote à 18% d'humidité du sol qu'aux autres taux d'humidité mais ne montre pas de différences dans I'accumulation de matière sèche 14 jours après le traitement (JAT). Une pluie artificielle suivant de près la pulvérisation réduit 1'eficacité du glufosinate-ammonium sur les deux espèces. A la dose d'utilisation de 800 g ha−1, une période sans pluie de 1 à 8 heures est nécessaire pour l'orge, tandis que moins de 20 minutes sont nécessaires pour le sétaire pour obtenir une activité herbicide comparable à celle observée avec des plantes traitées sans pluie. En se fondant sur l'accumulation de matière sèche, les plantes d'orge étaient également sensibles, et les sétaires étaient significativement plus sensibles quand le glufosinate-ammonium était appliquéà la fin plutêt qu'au début de la photopériode. Les 2 espèces accumulent significativement plus d'azote dans les tiges pendant les 24 premières heures suivant l'application quand elle a lieu en fin de photopériode. Des facteurs environnementaux examinés dans cette étude, la pluie après la pulvérisation cause la plus grande réduction d'efficacité glufosinate-ammonium. Einfluβ von Bodenfeuchte, simuliertem Niederschlag und Applikationszeitpunkt auf die Wirksamkeit von Glufosinat-ammonium In Laborversuchen wurde der Einfluß von Bodenfeuchte, simuliertem Niederschlag und Applikationszeitpunkt auf die Wirksamkeit von Glufosinat-ammonium auf die Gersten-Sorte ‘Samson’ (Hordeum vulgäre L.) und Grüne Borstenhirse (Setaria viridis (L.) Beauv.) untersucht. Als Umweltvariablen wurden 3 Bodenfeuchtegrade (18%, 50% und gesättigt), 3 Niederschlagsintensitäten [Niesei (4 mm), mäßig (9 mm) und stark (22 mm)] nach der Behandlung und 2 Applikationszeitpunkte (Beginn und Ende einer 16-h-Photoperiode) eingesetzt. Die Wirkung von 100 g ha−1 Glufosinat-ammonium auf die Gerste war bei 18% Bodenfeuchte sowohl hinsichtlich des Ammoniumgehalts als auch der Trockenmasse des Sprosses am größten. Bei derselben Dosis hatte die Grüne Borstenhirse einen geringeren Ammoniumgehalt bei 18% Bodenfeuchte als bei anderen Feuchtegraden, zeigte jedoch 14 Tage nach der Behandlung keine signifikanten Unterschiede in der Trockenmasse. Niederschlag kurz nach der Behandlung verminderte die Wirksamkeit bei beiden Arten. Bei der Felddosis von 800 g ha−1 war eine niederschlagsfreie Periode von 8 Stunden notwendig, bei der Grünen Borstenhirse jedoch weniger als 20 Minuten, um dieselbe Wirkung zu erreichen wie bei Pflanzen, die ohne Regen geblieben waren. Hinsichtlich der Trockenmassebildung waren Gerstenpflanzen gleich empfindlich und Borstenhirsenpflanzen signifikant empfindlicher, wenn Glufosinat-ammonium am Ende statt am Beginn der Photoperiode appliziert wurde. Beide Arten hatten in den Sprossen während der ersten 24 Stunden nach der Behandlung am Ende der Photoperiode einen signifikant höheren Ammoniumgehalt. Von den hieruntersuchten Umweltfaktoren reduzierte der Niederschlag nach der Behandlung die Wirkung von Glufosinat-ammonium am meisten.

Notes: The influence of temperature and relative humidity (r.h.) on the efficacy of glufosinate ammonium was investigated in controlled environment growth chambers using a tolerant species, barley (Hordeum vulgare L. cv. ‘Samson’), and a susceptible species, green foxtail (Setaria viridis (L.) Beauv.). The shoot ammonia concentration and visual injury of plants treated with glufosinate-ammonium doses of 100 and 800 g ha−1 were compared at day/night temperature regimes of 8/5,15/10 and 22/17°C at 60% r.h. The effect of relative humidity levels of 40% and 95% on the shoot ammonia concentration, visual injury and dry weight accumulation of glufosinate-ammonium treated plants was tested at temperature regimes of 15/10 and 22/17°C, with both species treated with 800 g ha−1. In addition, green foxtail treated with 100 g ha−1. was tested at both r.h. levels at 22/17°C. As the temperature de creased, less ammonia was produced in treated green foxtail plants. However, ammonia levels were comparable at all temperature regimes for barley. Lowest temperatures resulted in delayed injury to both species, but only small differences in injury existed among temperature regimes 288 h after spraying. The activity of glufosinate ammonium on both species was significantly de creased by low r.h. For example, when grown at 22/17°C, green foxtail survived the potentially lethal dose of 100 g ha−1 at 40% r.h. and accumulated 70% of the dry weight of control plants, but was killed at 95% r.h. Of the two environmental factors examined, r.h. had the most significant effect on the phytotoxic action of glufosinate-ammonium. L'influence de la température et de I'humidité relative sur I'efficacité du glufosinate-ammonium L'influence de la température et de 1'humidité relative (hr) sur I'efficacité du glufosinate ammonium a étéétudiée en chambre climatique en utilisant une espéce d'orge tolérante (Hor deum vulgare L. cv ‘Samson’) et une espéce sensible la svtaire verte (Setaria viridis L. Beauv).La concentration en ammoniaque des pieds et les dégats visuels des plantes traitérs avec des doses de glufosinate ammonium de 100 et 800 g/ ha−1 ont été comparés pour des régimes de températures jour/nuit de 8/5, 15/10 et 22/17°C à 60% hr. L'effet de taux d'humidité relative de 40 et 95% sur la teneur en ammoniaque des pieds, les dégats visuels et (l'accumulation de matiére séche chez des plantes traitéres au glufosinate ammonium a été testéà des régimes de températures de 15/10 et 22/17°C, pour les 2 espéces traitées à 800 g ha−1. En outre, la sétaire verte traitée à 100 g hr−1 a été testée aux 2 hr à 22/17°C. Quand la température diminue, il y a moins d'ammoniaque produit chez les sétaires vertes trailérs. Cependant les taux d'ammon iaque ont été comparables à toutes les tempéra tures chez 1'orge. Les températures les plus basses ont abouti à un retard de phytotoxicité ches les 2 espéces, mais à peu de différences entre les régimes de températures 288 h après 1'application. L'activité du glufosinate ammon ium chez les deux espèces a été significative ment réduite par des faibles hr. Par exemple cul tivée à 22/17°C, la sétaire verte a survécu à des doses potentiellement léthales de 100 g ha−1à 40% d'hr et a accumulé 70% de la matière sèche des témoins mais a été détruite à 95% d'hr. Sur les 2 facteurs environnementaux étudiés, l'hr a l'effet le plus important sur l'activité phytotoxique du glufosinate ammonium. Einfluβ von Temperatur und relativer Feuchte auf die Wirksamkeit von Glufosinat-ammonium Der Einfluß von Temperatur und relativer Feuchte (rF) auf die Wirksamkeit von Glufosinat-ammonium wurde in Klimakammern anhand einer toleranten Art, der Gersten-Sorte ‘Samson’ (Hordeum vulgare L.), und einer empfindlichen Art, der Grünen Borstenhirse (Setaria viridis (L.) Beauv.), untersucht. Die Ammonium-Konzentration im Sproß und sichtbare Schädigungen der Pflanzen, die mit Dosen von 100 und 800 g ha−1 behandelt worden waren, wurden bei Tag/Nacht-Temperaturen von 8/5, 15/10 und 22/17 °C bei 60% rF verglichen. Die Wirkung von 40 oder 95% rF auf die Ammonium-Konzentrationen im Sproß, sichtbare Pflanzenschädigungen und die Trockenmassebildung wurde bei 15/10 und 22/17°C und bei 800 g ha−1 Glufosinat-ammonium untersucht. Zusätzlich wurde die Grüne Borstenhirse mit 100 g ha−1 behandelt und bei den beiden Feuchtegraden und 22/17 °C untersucht. Mit abnehmender Temperatur bildete die Grüne Borstenhirse weniger Ammonium, dessen Gehalt bei der Gerste jedoch bei allen Temperaturen gleich war. Geringere Temperaturen verzögerten bei beiden Arten die Schädigungen, doch ließen sich 288 h nach der Behandlung nur noch geringe Unterschiede bei den verschiedenen Temperaturen beobachten. Die Wirkung von Glufosinat-ammonium war bei niedriger rF bei beiden Arten signifikant schwächer. Z. B. überlebte die Grüne Borstenhirse die potentiell letale Dosis von 100 g ha−1 bei 22/17 °C und 40% rF und bildete 70% der Trockenmasse von Kontrollpflanzen, wurde jedoch bei 95% rF abgetötet. Die rF war von den beiden untersuchten Umweltfakoren der signkfikantere für die phytotoxische Wirkung des Glufosinat-ammoniums.

Notes: An extension of the maximum-entropy (ME) data- restoration method is presented that is sensitive to periodic correlations in data. The method takes advantage of the higher signal-to-noise ratio for periodic information in Fourier space, thus enhancing statistically significant frequencies in a manner which avoids the user bias inherent in conventional Fourier filtering. This procedure incorporates concepts underlying new approaches in quantum mechanics that consider entropies in both position and momentum spaces, although the emphasis here is on data restoration rather than quantum physics. After a fast Fourier transform of the image, the phases are saved and the array of Fourier moduli are restored using the maximum-entropy criterion. A first-order continuation method is introduced that speeds convergence of the ME computation. The restored moduli together with the original phases are then Fourier inverted to yield a new image; traditional real-space ME restoration is applied to this new image completing one stage in the restoration process. In test cases with various types of added noise and in examples of normal and high-resolution electron-microscopy images, dramatic improvement can be obtained from two to four stages of iteration, even in cases where traditional ME restoration provides little improvement. It is shown that in traditional Fourier filtering spurious features can be induced by selection or elimination of Fourier components without regard to their statistical significance. With the present approach there is no such freedom for the user to exert personal bias, so that features present in the final image and power spectrum are those which have survived the tests of statistical significance in both real and Fourier space. However, it is still possible for periodicities to 'bleed' across sharp boundaries. An 'uncertainty' relation is derived describing the inverse relationship between the resolution of these boundaries and the level of noise that can be eliminated.

Notes: Abstract Life cycle changes that allow populations of the toxic dinoflagellate Gonyaulax tamarensis Lebour to inhabit the benthos and the plankton alternately are important factors regulationg the initiation and decline of blooms in restricted embavments. When the dynamics of these estuarine populations were monitored during “bloom” and “non bloom” years, it was shown that: (1) each year, germination of benthie cysts inoculated the overlying waters during the vernal warming period, but a large residual population remained in the sediments throughout the blooms; (2) the resulting planktonic population began growth under suboptimal temperature conditions; (3) the populations developed from this inoculum through asexual reproduction until sexuality (and cyst formation) were induced; (4) encystment was not linked to any obvious environmental cue and occurred under apparently optimal conditions; and (5) an increase in the number of non-mitotic swimming cells (planozygotes, the precursors to dormant cysts) accompanied the rapid decline of the planktonic population. Thus encystment, in combination with hypothesized losses due to advection and grazing, contributed substantiatly to the decline of the vegetative cell population. We conclude that the encystment/excystment cycle temporally restricts the occurrence of the vegetative population and may not be optimized for rapid or sustained vegetative growth and bloom formation in shallow embayments. The factors that distinguish “bloom” from “non-bloom” years thus appear to be operating on the growth of the planktonic population.

Notes: Summary One of the scientific objectives of the Viking Mission to Mars was to accomplish an analysis of water in the Martian regolith. The analytical scheme originally envisioned was severly compromised in the latter stages of the Lander instrument package design. Nevertheless, a crude soil water analysis was accomplished. Samples from each of the two widely separated sites yielded roughly 1 to 3% water by weight when heated successively to several temperatures up to 500°C. A significant portion of this water was released in the 200° to 350°C interval indicating the presence of mineral hydrates of relatively low thermal stability, a finding in keeping with the low temperatures generally prevailing on Mars. The presence of a duricrust at one of the Lander sites is taken as possible evidence for the presence of hygroscopic minerals on Mars. The demonstrated presence of atmospheric water vapor and thermodynamic calculations lead to the belief that adsorbed water could provide a relatively favorable environment for endolithic organisms on Mars similar to types recently discovered in the dry antarctic deserts.