A Method for the Rapid Cultivation of Desulfovibrio aestuarii on Filter Membranes

The cultivation of sulfate-reducing bacteria on agar plates is a somewhat involved and time-consuming process. This is partly due to the requirement for fairly strict anaerobic conditions but mainly because of the length of the incubation period which may vary from 6 days to weeks with the resulting delay of the required information. The work reported herein was undertaken in an attempt to apply the advantageous features of the membrane filter method to the detection of anaerobic organisms. As originally developed, the membrane filter (Goetz and Tsuneishi, 1951; Clark et al., 1951) permits the recovery of small numbers of organisms from large volumes of water and the rapid cultivation of many aerobic bacteria. The ultimate purpose was to develop a method which would not require more complex manipulation than the membrane procedure according to Standard Methods for the Examination of Water, Sewage, and Industrial Wastes (A.P.H.A. 1955) and to reduce the incubation period for anaerobic bacteria

Psychological and physiological adaptations to sperm competition in humans

Postcopulatory competition between males, in the form of sperm competition, is a widespread phenomenon in many animal species. The extent to which sperm competition has been an important selective pressure during human evolution remains controversial, however. The authors review critically the evidence that human males and females have psychological, behavioral, and physiological adaptations that evolved in response to selection pressures associated with sperm competition. The authors consider, using evidence from contemporary societies, whether sperm competition is likely to have been a significant adaptive problem for ancestral humans and examine the evidence suggesting that human males have physiological and psychological mechanisms that allow for “prudent” sperm allocation in response to variations in the risk of sperm competition

Ernst Troeltsch\u27s Quest for Certainty

This paper examines the thought of Ernst Troeltsch, specifically in regards to his attempt to show that Christ­ianity is a superior religion among other world religions . The key to understanding Troeltsch\u27s thinking in this re­gard is to consider his methodological foundation which was historicist. The problem which Troeltsch sought to address throughout his works but especially in The Absolute­ness, i. e., how to find universal values within relative historical phenomena, was generated out of his desire for religious certainty while at the same time being consistent with historicist methodology. Although, in his early career, Troeltsch did find a satisfactory balance between these two desires, he ultimate­ly came to a skeptical conclusion concerning religious cer­tainty because of his deepening commitment to consider histor­ical variety, which is an overriding historicist principle. The paper proposes to examine Troeltsch\u27s quest for certainty focusing on three phases of his life represented by three of his most important works. The first phase is epitomized by his work The Absolute­ness of and the of Here Troeltsch worked out an apologetic based on a comparison of Christianity with other world religions and concluded that, although not absolute, Christianity was normative among other religions because it brought to flower all the latent potentialities of other faiths and combined them into one. The second phase of Troeltsch\u27s life is epitomized by his work, The Social of the Christian Churches.In the course of researching and writing this work, Troeltsch became increasingly impressed with the uniqueness and indivi­duality of Christianity in particular and all religions in general. Consequently , he began to doubt whether religions could be compared in the manner he had employed in The Absoluteness. The extreme diversity and variety of all his­torical phenomena , Troeltsch felt , precluded such a method­ology, and, finally, at the end of his life, he reversed his belief in the normativeness of Christianity. This was spelled out in his work Der Historismus und seine Probleme , which epitomizes the third phase of his life. His search for some kind of religious certainty and universal value was terminated by his desire to be true to the facts wie sie eigentlich gewesen sind . His search for validity in History was overcome by his recognition of the overwhelming individual character of all historical/phenomena. The foundation of this defeat can be located in Troeltsch\u27s specifically historicist methodology

The influence of defects of the fatigue resistance of butt and girth welds in A106B steel

This three-phase study was directed at developing a fitness for service defect acceptance criteria for welds with defect indications. The study focussed on A106 Gr. B steel pipe. The first phase involved a literature search and critical review to develop the preliminary acceptance criteria to the extent permitted by the data. The second phase developed data for flat plate, wall segment, and vessel specimens containing artificial or natural planar or volumetric defects. The final phase developed acceptance criteria from the test data

Deconstructing and reconstructing the mouse and human early embryo.

The emergence of form and function during mammalian embryogenesis is a complex process that involves multiple regulatory levels. The foundations of the body plan are laid throughout the first days of post-implantation development as embryonic stem cells undergo symmetry breaking and initiate lineage specification, in a process that coincides with a global morphological reorganization of the embryo. Here, we review experimental models and how they have shaped our current understanding of the post-implantation mammalian embryo.European Research Council (669198) Wellcome Trust (098287/Z/12/Z) Early Career Leverhulme Trust fellowship

Functionality, Parsimony, Discovery, Avoiding Hamartia: How Evolutionary Perspectives are Changing Psychology

Evolutionary psychology offers an important perspective to scientific psychology. Evolutionary psychology, in its short existence, has added an abundance of knowledge to the social sciences, let alone psychology. The study of human cognition and behavior remains incomplete without an evolutionary perspective. Here, we argue that evolutionary psychology uniquely provides a complete understanding of scientific psychology because it explains the functions of our psychological traits, provides us with the most parsimonious explanation of many psychological phenomena, predicts undocumented phenomena, and possibly allows us to avoid the downfalls of some of our contemptible evolved psychological mechanisms

Geothermal Energy from the Main Karoo Basin (South Africa): An Outcrop Analogue Study of Permian Sandstone Reservoir Formations

The geothermal potential of the Main Karoo Basin has not been addressed in the past. A first assessment of Permian sandstone formations in the Eastern Cape Province, including down-hole temperature data from deep boreholes, and evaluation of groundwater temperature and heat flow values from literature leads to 3130 TWh (11.3 EJ) of power generation potential within the central and southern parts of the basin. The low permeability lithotypes may be operated as enhanced geothermal systems (EGS), depending on the fracture porosity in the deeper subsurface. In some areas auto-convective thermal water circulation might be expected and direct heat use becomes reasonable

Modular Multilevel Converter with Sensorless Diode-Clamped Balancing through Level-Adjusted Phase-Shifted Modulation

Cascaded H-bridge and modular multilevel converters (MMC) are on the rise with emerging applications in renewable energy generation, energy storage, and electric motor drives. However, their well-known advantages come at the price of complicated balancing, high-bandwidth isolated monitoring, and numerous sensors that can prevent MMCs from expanding into highly cost driven markets. Therefore, an obvious trend in research is developing control and topologies that depend less on measurements and benefit from simpler control. Diode-clamped topologies are considered among the more applicable solutions. The main problem with a diode-clamped topology is that it can only balance the module voltages of a string in one direction; therefore, it cannot provide a completely balanced operation. This paper proposes an effective balancing technique for the diode-clamped topology. The proposed solution exploits the dc component of the arm current by introducing a symmetrically level-adjusted phase-shifted modulation scheme, and ensures the balancing current flow is always in the correct direction. The main advantages of this method are sensorless operation, no added computation and control effort, and low overall cost. Analysis and detailed simulations provide insight into the operation of the system as well as the new balancing technique and the experimental results confirm the provided discussions

Self-organization of stem cells into embryos: A window on early mammalian development.

Embryonic development is orchestrated by robust and complex regulatory mechanisms acting at different scales of organization. In vivo studies are particularly challenging for mammals after implantation, owing to the small size and inaccessibility of the embryo. The generation of stem cell models of the embryo represents a powerful system with which to dissect this complexity. Control of geometry, modulation of the physical environment, and priming with chemical signals reveal the intrinsic capacity of embryonic stem cells to make patterns. Adding the stem cells for the extraembryonic lineages generates three-dimensional models that are more autonomous from the environment and recapitulate many features of the pre- and postimplantation mouse embryo, including gastrulation. Here, we review the principles of self-organization and how they set cells in motion to create an embryo.M.N.S received funding from an Early Career Leverhulme Trust fellowship and an Advanced EMBO fellowship. Work in the laboratory of M.Z-G. is funded by the Wellcome Trust (207415/Z/17/Z) and the European Research Council (ERC grant 669198). Work of E.D.S. is funded by NIH grant GM101653

Superconductors with Magnetic Impurities: Instantons and Sub-gap States

When subject to a weak magnetic impurity potential, the order parameter and quasi-particle energy gap of a bulk singlet superconductor are suppressed. According to the conventional mean-field theory of Abrikosov and Gor'kov, the integrity of the energy gap is maintained up to a critical concentration of magnetic impurities. In this paper, a field theoretic approach is developed to critically analyze the validity of the mean field theory. Using the supersymmetry technique we find a spatially homogeneous saddle-point that reproduces the Abrikosov-Gor'kov theory, and identify instanton contributions to the density of states that render the quasi-particle energy gap soft at any non-zero magnetic impurity concentration. The sub-gap states are associated with supersymmetry broken field configurations of the action. An analysis of fluctuations around these configurations shows how the underlying supersymmetry of the action is restored by zero modes. An estimate of the density of states is given for all dimensionalities. To illustrate the universality of the present scheme we apply the same method to study `gap fluctuations' in a normal quantum dot coupled to a superconducting terminal. Using the same instanton approach, we recover the universal result recently proposed by Vavilov et al. Finally, we emphasize the universality of the present scheme for the description of gap fluctuations in d-dimensional superconducting/normal structures.Comment: 18 pages, 9 eps figure