Nanorheology : an Investigation of the Boundary Condition at Hydrophobic and Hydrophilic Interfaces

t has been shown that the flow of a simple liquid over a solid surface can violate the so-called no-slip boundary condition. We investigate the flow of polar liquids, water and glycerol, on a hydrophilic Pyrex surface and a hydrophobic surface made of a Self-Assembled Monolayer of OTS (octadecyltrichlorosilane) on Pyrex. We use a Dynamic Surface Force Apparatus (DSFA) which allows one to study the flow of a liquid film confined between two surfaces with a nanometer resolution. No-slip boundary conditions are found for both fluids on hydrophilic surfaces only. Significant slip is found on the hydrophobic surfaces, with a typical length of one hundred nanometers.Comment: 8 pages, 7 figures, 2 tables. Accepted for European Physical Journal E - Sofr Mate

Research Priorities for the International Space Station and Beyond

Advanced technology and the desire to explore space have resulted in increasingly longer manned space missions. Long Duration Space Flights (LDSF) have provided a considerable amount of scientific research on the ability of humans to adapt and function in microgravity environments. In addition, studies conducted in analogous environments, such as winter-over expeditions in Antarctica, have complemented the scientific understanding of human performance in LDSF. These findings indicate long duration missions may take a toll on the individual, both physiologically and psychologically, with potential impacts on performance. Significant factors in any manned LDSF are habitability, workload and performance. They are interrelated and influence one another, and therefore necessitate an integrated research approach. An integral part of this approach will be identifying and developing tools not only for assessment of habitability, workload, and performance, but also for prediction of these factors as well. In addition, these tools will be used to identify and provide countermeasures to minimize decrements and maximize mission success. The purpose of this paper is to identify research goals and methods for the International Space Station (ISS) in order to identify critical factors and level of impact on habitability, workload, and performance, and to develop and validate countermeasures. Overall, this approach will provide the groundwork for creating an optimal environment in which to live and work onboard ISS as well as preparing for longer planetary missions

Thin oceanic crust and flood basalts: India-Seychelles breakup

Recent seismic experiments showed that separation of India from the Seychelles occurred in two phases of rifting. The first brief phase of rifting between India and the Laxmi Ridge formed the Gop Rift, which is characterized by thick oceanic crust and underplating of the adjacent continental margins. The age of the Gop Rift is uncertain, initiation of seafloor spreading being some time between 71 and 66 Ma. This was then followed by rifting and seafloor spreading between the Laxmi Ridge and the Seychelles, the onset of which is well dated by magnetic anomalies at 63.4 Ma and characterized by thin oceanic crust. Both of these rift events occurred within 1000 km of the center of the Deccan flood basalts, which formed at 65 ± 1 Ma. To constrain the age of the Gop Rift and to explore the reasons for the change in crustal structure between the Gop Rift and Seychelles-Laxmi Ridge margins, we employ a geodynamic model of rift evolution in which melt volumes, seismic velocity, and rare earth element (REE) chemistry of the melt are estimated. We explore the consequences of different thermal structures, hydration, and depletion on the melt production during the India-Seychelles breakup to understand the reasons behind the thin oceanic crust observed. Magmatism at the Gop Rift is consistent with a model in which the seafloor spreading began at 71 Ma, ca. 6 Myr prior to the Deccan. The opening occurred above a hot mantle layer (temperature of 200°C, thickness of 50 km) that we interpret as incubated Deccan material, which had spread laterally beneath the lithosphere. This scenario is consistent with observed lower crustal seismic velocities of 7.4 km s?1 and 12 km igneous crustal thickness. The model indicates that when the seafloor spreading migrated to the Seychelles-Laxmi Ridge at 63 Ma, the thermal anomaly was reduced significantly but not sufficient to explain the observed reduction in breakup magmatism. From observations here of 5.2 km oceanic crust, lower crustal seismic velocities of 6.9 km s?1 and a flat REE profile, we infer that breakup occurred in a region of mantle that became depleted by prior extension related to the Gop Rift

A re-evaluation of the <i>Macrothrix rosea-triserialis</i> group, with the description of two new species (Crustacea Anomopoda: Macrothricidae)

We redescribe Macrothrix rosea (females and males) based on material collected in Belgium. We also compare seven populations of Macrothrix `triserialis' from different parts of the world, including a topotypical population of M. triserialis s. str. from Sri Lanka, and males from South India (here first described), relying heavily on the structure of the trunk limbs, beside classical features of morphology. M. rosea and M. triserialis are extremely closely related: males are easily separated, but the identification of females requires micro-characters such as the relative length of the apical segment of the setae natatoriae and the adornment of the first antenna and of the longest swimming seta of the antenna. M. rosea and triserialis together constitute a sub-group of the rosea-group. Macrothrix triserialis-like animals occur in the tropical–subtropical belts of four continents. We compare populations from Asia, South America and Africa, and find differences in microcharacters of the trunk limbs, but cannot decide whether these represent random variation or sound taxonomical differences.One of the basic characters of the Macrothrix rosea-triserialis subgroup is that the setae natatoriae of the postabdomen are implanted on a prominence, the `heel'. Other characters include the fact that the Fryer' forks are adorned with one or two big teeth only, and that the scrapers of trunk limb two form a row of eight without any doublings. Possibly, scraper five, and scraper four to a lesser degree has an enlarged subapical tooth. The exopodite of trunk limb three has four plumose setae, the back and front row of the endopodite six setae and/or receptors, the exopodite of trunk limb four has two setae, and the back row of the endopodite six setae, plus one on the gnathobase. The pre-epipodite of trunk limb five consists of three lobes, the `endopodite' is small, and the `exopodite' is reduced to a single seta. The male postabdomen has a tubular ending, without true end-claws, although a rudiment of an end-claw is seen in M. triserialis.Two new species are described: M. tabrizensis and M. agsensis. A comparison, including the males of Macrothrix triserialis, M. rosea, M. smirnovi and M. tabrizensis confirms the relationship of all these taxa, but also reveals a morphological series in the shape of the postabdomen, from a complete absence of end-claws, over rudiments of a pair of end-claws, to complete endclaws. Absence of end-claws is here considered to represent an evolved character state. Macrothrix smirnovi Ciros & Elías (1987) is less closely related to the rosea-triserialis group, and is considered to form a sub-group in its own right. It shows a short `heel' on the postabdomen, but carries a supplementary seta behind scraper 4 of the endopodite of trunk limb two, and has a male with a postabdomen that closely resembles that of the female. These are primitive characters, which are also found in Wlassicsia, Bunops and Onchobunops and provide a possible phylogenetic link between Macrothrix and these three genera, although the genetic distance between them is considered to be quite large