A novel method for measuring the evaporation of contaminant liquids from sands

A novel experimental system, electrodynamic levitation, is used to measure the evaporation of liquids from microparticles of sand. The levitator is used to measure the evaporation rate of diethylphthalate (DEP) from microparticles of Saudi Arabian sand at 1 atm pressure and 25 degrees C. Evaporation experiments were conducted for both inland- and coastal-sand microparticles, the diameter of which is 50 microm. The DEP-evaporation rate is determined from gravimetric changes in the DEP-sand-mixture particle, the weight of which is directly proportional to the levitating electric-field intensity. From telemicroscopical observations, it is found that, when the sand particle is enclosed in DEP liquid, the sand-DEP-mixture particle evaporates like a pure DEP droplet. However, when sufficient DEP liquid has evaporated and the DEP is adsorbed into the sand microparticle, the DEP evaporation rate is reduced by a factor of 3-5 as compared with a pure DP droplet.     

ENGINEERING A TRANSITION TO COAL

As nations seek alternatives to oil, coal promises to become one of the principal replacement fuels in the world energy system. Engineering a transition to coal and other energy sources from the current reliance on petroleum will be a difficult task requiring a significant commitment of capital, labour, materials, equipment, land and water resources. Engineering this transition to coal will be further complicated by the long lead times that are required. This paper presents an analysis of the timing and magnitude of national resources required to implement several alternative coal development programmes in the United States. Preliminary experience aimed at extending the analysis to international energy and resource relationships is also discussed. Tandis que les nations cherchent à remplacer le pétrole, le charbon est en passe de devenir un des principaux combustibles de remplacement du système énergétique mondial. Assurer une transition à partir de la dépendance actuelle du pétrole vers le charbon et d'autres sources d'énergie s'avérera être difficile et exigera des investissements importants en capitaux, main-d'oeuvre, matériaux, équipement et ressources en terrains et en eau. Effectuer cette transition vers le charbon sera de plus compliqué par les longs délais d'éxécution qui sont requis. Cet article fait l'analyse du calendrier et de l'ampleur des ressources nationales nécessaires à la mise en valeur de plusieurs programmes de rechange en matière de développement du charbon aux Etats-Unis. On y discute également une expérience préliminaire visant à intégrer l'analyse des rapports internationaux en matière d'énergie et de ressources. En la búsqueda de combustibles alternativos al petróleo, el carbón parece ser la principal alternativa dentro del sistema energético mundial. La adaptación tecnológica al carbón y otros recursos energéticos, partiendo de la dependencia actual en el petróleo, va a ser una tarea difícil que requerirá comprometer importances cantidades de capital, trabajo, equipo, terrenos y recursos de ague. Esta transición al carbón será complicada aún mas por el prolongado lapso necesario para su ejecución. Este artículo presenta un análisis de la programación en el tiempo y la magnitud de los recursos nacionales necesarios para implementar los programas alternatives de desarrollo del carbón en los Estados Unidos. Se discute también experiencias preliminares orientadas a la extensión de este análisis a las relaciones internationales en energía y recursos.     

Altitudinal and horizontal shifts of the upper boundaries of open and closed forests in the Polar Urals in the 20th century

In the Polar Urals (the Rai-Iz massif and Mounts Tchernaya and Malaya Tchernaya), altitudinal and horizontal shifts of the upper boundary of open and closed larch forests in the 20th century have been studied. Spatiotemporal parameters of these shifts have been assessed with the aid of the ARC/INFO geographic information system (ESRI Inc., United States), using our original large-scale geobotanical maps showing the distribution of different types of forest-tundra communities in the early 1910s and 2000s. The results show that tree vegetation has been actively expanding to higher elevations over the past 90 years. On average, the upper boundaries of open and closed forests have ascended 26 and 35 m and shifted horizontally 290 and 520 m, respectively. These shifts have been conditioned by climate warming and increasing humidity observed since the 1920s.     

Dynamic response to danger in a parasitoid wasp

Despite the multitude of work on patch time allocation and the huge number of studies on patch choice in the face of danger, the patch leaving response of foragers perceiving cues of danger has received relatively little attention. We investigated the response of parasitoid insects to cues of danger both theoretically and experimentally. Using stochastic dynamic theory, we demonstrate that patch-leaving responses in response to the detection of danger should be seen as a dynamic decision that depends upon reproductive options on the current host patch and on alternative patches that might be found after leaving the current patch. Our theory predicts a sigmoidal response curve of parasitoids, where they should accept the danger and stay on the patch when patch quality is high and should increasingly avoid the risk and emigrate from the patch with decreasing patch quality and decreasing costs of traveling to an alternative host patch. Experiments with females of the drosophilid parasitoid Asobara tabida that were exposed to a puff of formic acid (a danger cue) at different times through their patch exploitation confirmed the theoretical predictions (i.e., a sigmoid response curve); however, the predicted curve was significantly steeper than observed. We discuss the impact of dynamic patch-exit decisions of individual foragers on population and community dynamics.