Fibronectin Synthesis is a Marker for Peritubular Cell Contaminants in Sertoli Cell-Enriched Cultures

With indirect immunofluorescent microscopic techniques, we have shown that fibronectin is distributed primarily in or along the basal lamina of the seminiferous tubule boundary tissue in sections of testes from 20-day-old rats. Purified rat Sertoli cell-enriched aggregates, maintained in culture in the presence or absence of serum, exhibit no detectable immunofluorescence with fibronectin antibody, whereas purified peritubular cells in culture do have a positive reaction to fibronectin antibody. Peritubular cells in culture incorporate [35S] methionine into fibronectin which can be immunoprecipitated with a fibronectin antiserum, but Sertoli cells do not. We have used various criteria to estimate the degree of purity of Sertoli cell-enriched preparations. The presence of peritubular myoid cells in conventional Sertoli cell-enriched aggregates, cultured in the presence or absence of serum, can be detected with transmission electron microscopic examination, by the Feulgen staining procedure, and by the immunocytochemical identification of fibronectin. We describe a technique to purify Sertoli cells in conventional Sertoli cell-enriched preparations by treatment with hyaluronidase, resulting in a lesser number of peritubular cells by the above criteria, even in preparations cultured in the presence of serum. Data presented suggest that some of the products previously attributed exclusively to Sertoli cells in Sertoli cell-enriched preparations, particularly those cultured in the presence of serum, may have been contributed by peritubular cells

The design of a microfabricated air electrode for liquid electrolyte fuel cells

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references.In this dissertation, the microfabricated electrode (MFE) concept was applied to the design of an air electrode for liquid electrolyte fuel cells. The catalyst layer of the electrode is envisioned to be fabricated by using a microfabricated die to apply a three-dimensionally patterned macro-texture upon a microporous carbon matrix. The resulting dual porosity structure consists of an array of cylindrical holes that are formed from the die and micropores present in the carbon matrix. The holes are used for gas transport while the micropores are saturated with a liquid electrolyte for ion transport. The catalyst is loaded into the microfabricated structure by electrodepositing thin catalyst films within the cylindrical holes. In this dissertation, three issues concerning the design of the MFE were investigated: 1) identification of the best material to use for the microporous carbon matrix, 2) the study of electrokinetic parameters of electrodeposited Pt films, and 3) the study of oxygen transport behavior within a Pt film supported on the surface of a microporous carbon matrix. Two types of polymer-bonded carbon materials have been identified as suitable materials for the carbon matrix. They are carbon black particles bonded into a microporous matrix either by polytetrafluoroethylene (PTFE) fibrils or by polyethersulfone (PES), which is a soluble polymer in common solvents. Experiments and modeling have indicated that these materials will allow the microfabricated catalyst layer to have an effective ionic conductivity that is 4 to 5 times greater than the conventional catalyst layer. Rotating disk electrode experiments on electrodeposited Pt films in 0.5 M sulfuric acid show that these films have an oxygen reduction reaction mass activity that is 2.5 times greater than that of Pt particles supported on carbon black.(cont.) Furthermore, oxygen gain experiments on electrodeposited Pt films supported on a microporous membrane indicate that these films experienced no oxygen transport losses in air, up to a current density of 130 mA/cm2. These results strongly support the use of thin catalyst film technology in catalyst layers of fuel cells. The experimental results presented this dissertation were used to develop a half-cell model of the MFE in concentrated phosphoric acid. The results of the model suggest that the MFE is capable of producing a current density 3.5 times greater than that of the conventional electrode. It is believed that such potential improvements in the performance of the air electrode support continued efforts to fabricate and test the MFE design concept presented in this dissertation.by Pierre Fritz, Jr.Ph.D

A New System for Automatic Radiotracking of Small Mammals

We developed a radiotracking system for automatic and continuous data collection, which allows the radiotracking of several animals at the same time. Based on a system controller, 3 fixed antennas, and small-size radiotransmitters (<2 g, 14 by 12 by 4 mm), the system has the capacity to record several individuals continuously at intervals of <5 min. Antennas, positioned at fixed points in the field, forward the signals from tagged animals to the system controller, where data are collected. The coordinates of the individual's locations are calculated through triangulation on the basis of the angles of incidence from the transmitter signal to each antenna. Transmitters are individually identified by the chronological sequence of their signals. Field tests with Microtus arvalis show the utility of the new technique and possibilities for the syste

The Neogene and Quaternary : chronostratigraphic compromise or non-overlapping magisteria?

Author Posting. © Micropaleontology Press, 2009. This article is posted here by permission of Micropaleontology Press for personal use, not for redistribution. The definitive version was published in Stratigraphy 6 (2009): 1-16.The International Commission on Stratigraphy (ICS) together with its subcommissions on Neogene Stratigraphy (SNS) and Quaternary Stratigraphy (SQS) are facing a persistent conundrum regarding the status of the Quaternary, and the implications for the Neogene System/Period and the Pleistocene Series/Epoch. The SQS, in seeking a formal role for the Quaternary in the standard time scale, has put forward reasons not only to truncate and redefine the Neogene in order to accommodate this unit as a third System/Period in the Cenozoic, but furthermore to shift the base of the Pleistocene to c. 2.6 Ma to conform to a new appreciation of when “Quaternary climates” began. The present authors, as members of SNS, support the well-established concept of a Neogene extending to the Recent, as well as the integrity of the Pleistocene according to its classical meaning, and have published arguments for workable options that avoid this conflict. In this paper, we return to the basic principles involved in the conversion of the essentially marine biostratigraphic/ biochronologic units of Lyell and other 19th-century stratigraphers into the modern hierarchical arrangement of chronostratigraphic units, embodied in the Global Standard Stratotype-section and Point (GSSP) formulation for boundary definitions. Seen in this light, an immediate problem arises from the fact that the Quaternary, either in its original sense as a state of consolidation or in the more common sense as a paleoclimatic entity, is conceptually different from a Lyellian unit, and that a Neogene/Quaternary boundary may therefore be a non sequitur. Secondly, as to retaining the base of the Pleistocene at 1.8 Ma, the basic hierarchical principles dictate that changing the boundary of any non-fundamental or “higher” chronostratigraphic unit is not possible without moving the boundary of its constituent fundamental unit. Therefore, to move the base of the Pleistocene, which is presently defined by the Calabrian GSSP at 1.8 Ma, to be identified with the Gelasian GSSP at 2.6 Ma, requires action to formally redefine the Gelasian as part of the Pleistocene. Finally, it is important to keep in mind that the subject under discussion is chronostratigraphy, not biostratigraphy. Both systems are based on the fossil record, but biostratigraphic units are created to subdivide and correlate stratigraphic sequences. The higher-level units of chronostratigraphy, however, were initially selected to reflect the history of life through geological time. The persistence of a characteristic biota in the face of environmental pressures during the last 23 my argues strongly for the concept of an undivided Neogene that extends to the present. Several ways to accommodate the Quaternary in the standard time scale can be envisaged that preserve the original concepts of the Neogene and Pleistocene. The option presently recommended by SNS, and most compatible with the SQS position, is to denominate the Quaternary as a subperiod/subsystem of the Neogene, decoupled from the Pleistocene so that its base can be identified with the Gelasian GSSP at c. 2.6 Ma. A second option is to retain strict hierarchy by restricting a Quaternary subperiod to the limits of the Pleistocene at 1.8 Ma. As a third option, the Quaternary could be a subera/suberathem or a supersystem/ superperiod, decoupled from the Neogene and thus with its base free to coincide with a convenient marker such as the base of the Pleistocene at 1.8 Ma, or to the Gelasian at 2.6 Ma, as opinions about paleoclimatology dictate. If no compromise can be reached within hierarchical chronostratigraphy, however, an alternative might be to consider Quaternary and Neogene as mutually exclusive categories (climatostratigraphic vs. chronostratigraphic) in historical geology. In this case, we would recommend the application of the principle of NOMA, or Non-Overlapping Magisteria, in the sense of the elegant essay by the late Stephen J. Gould (1999) on the mutually exclusive categories of Religion and Science. In this case the Quaternary would have its own independent status as a climatostratigraphic unit with its own subdivisions based on climatic criteria

Last Glacial Maximum in an Andean cloud forest environment (Eastern Cordillera, Bolivia): Comment and Reply

Whether the climate of tropical South America during the Last Glacial Maximum (LGM) was colder and drier or colder and wetter than present day has been widely debated. It is accepted, however, that the LGM in tropical South America was 2–9 °C colder than today (e.g., Betts and Ridgway, 1992; Bush et al., 2001). Without debating the merits of the following choices, if we assume a lapse rate in the LGM similar to the modern one of ~0.6 °C·100 m−1, then an intermediate cooling of 5 °C would lower the boundary between montane cloud forest and the overlying puna grasslands by ~800 or 900 m. Palynologists on both sides of the wet/dry debate have come to similar conclusions about forest-boundary lowering due to temperature decrease (reviewed by Flenley, 1998). In the Eastern Cordillera of Bolivia the modern puna–cloud forest boundary lies ~3400 m above sea level (masl). Ignoring any other environmental changes, LGM cooling would have lowered this boundary to 2500 or 2600 masl

Shape Optimization Using the Adjoint Lattice Boltzmann Method for Aerodynamic Applications

International audienceThe present work focuses on shape optimization using the lattice Boltzmann method applied to aerodynamic cases. The adjoint method is used to calculate the sensitivities of the drag force with respect to the shape of an object. The main advantage of the adjoint method is its cost, because it is independent from the number of optimization parameters. The approach used consists in developing a continuous adjoint of the primal problem discretized in space, time, and velocities. An adjoint lattice Boltzmann equation is thus found, which is solved using the same algorithms as in the primal problem. The test cases investigate new features compared to what exists in the literature, such as the derivation of the grid refinement models in the primal problem to obtain their adjoint counterparts, but also the derivation of a double-relaxation-time algorithm and the Ginzburg et al. interpolation at the wall ("Two-Relaxation-Time Lattice Boltzmann Scheme: About Parametrization, Velocity, Pressure and Mixed Boundary Conditions," Communications in Computational Physics, Vol. 3, No. 2, 2008, pp. 427-478). Regarding the unsteadiness of the primal problem, two methods differing in accuracy and computational effort are compared using a two-dimensional unsteady case. Finally, this first-of-a-kind adjoint solver is applied to a large-scale threedimensional turbulent case (the flow of air around a car at a speed of 130 km/h), which shows its usefulness in the industry