1,689 research outputs found

    Three degree of freedom translational axis hand controller mechanism

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    A hand controller which includes a hand grip having therein a mechanism for allowing truly linear motion along at least two axes by modifying a four-bar linkage with a second four-bar linkage to counteract any rotational motion that would otherwise occur

    Distribution and Abundance of Molluscs in a Fresh Water Environment

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    The molluscs of o northwestern Minnesota lake were sampled using transects, a sampling frame, and SCUBA. The species sampled were: Amnicola limosa, Valvata tricarinata, Gyraulus parvus, Physa cf. P. gyrina, Helisoma anceps, H. campanulata, Promenetus exacuous, Ferrissia parallela, Anodonta marginata, Lampsilis siliquoidea, and Sphaerium cf. S. striatum. The unionid clams, the adult Helisoma spp. and the Physa adults were associated with the absence of aquatic vegetation. Distinct associations of snail species were found with each plant association: G. parvus and V. tricarinata with the deep water Nitella opaca association, A. limosa and V. tricarinata with the mid-depth mixed macrophyte association, and H. anceps and Physa adults with the shallow water, rocky bottom macrophyte association. Two estimates of snail abundance were made for each depth. Neither proved very satisfactory, but they did indicate that snail abundance was related to the type and abundance of aquatic plants

    1861-10-04 James H. Bacon of Company A solicits a promotion

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    https://digitalmaine.com/cw_me_2nd_regiment_corr/1164/thumbnail.jp

    The M 31 double nucleus probed with OASIS and HST. A natural m=1 mode?

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    We present observations with the adaptive optics assisted integral field spectrograph OASIS of the M 31 double nucleus at a spatial resolution better than 0.5 arcsec FWHM. These data are used to derive the two-dimensional stellar kinematics within the central 2 arcsec. Archival WFPC2/HST images are revisited to perform a photometric decomposition of the nuclear region. We also present STIS/HST kinematics obtained from the archive. The luminosity distribution of the central region is well separated into the respective contributions of the bulge, the nucleus including P1 and P2, and the so-called UV peak. We then show that the axis joining P1 and P2, the two local surface brightness maxima, does not coincide with the kinematic major-axis, which is also the major-axis of the nuclear isophotes (excluding P1). We also confirm that the velocity dispersion peak is offset by ~ 0.2 arcsec from the UV peak, assumed to mark the location of the supermassive black hole. The newly reduced STIS/HST velocity and dispersion profiles are then compared to OASIS and other published kinematics. We find significant offsets with previously published data. Simple parametric models are then built to successfully reconcile all the available kinematics. We finally interpret the observations using new N-body simulations. The nearly keplerian nuclear disk of M31 is subject to a natural m=1 mode, with a very slow pattern speed (3 km/s/pc for M_BH = 7 10^7~\Msun), that can be maintained during more than a thousand dynamical times. The resulting morphology and kinematics of the mode can reproduce the M~31 nuclear-disk photometry and mean stellar velocity, including the observed asymmetries. It requires a central mass concentration and a cold disk system representing between 20 and 40% of its mass. Abridged..Comment: 21 pages. accepted for publication in A&

    Break up of silica nanoparticle clusters using ultrasonication

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    This study is concerned with the deagglomeration of hydrophilic silica nanoparticle clusters (Aerosil® 200V) in water using an ultrasonicator operated in batch mode. An impeller was also present in the tank to ensure homogeneity. The effect of power input was studied in the range of 18 to 77 W (9 to 39 kW m-3) on the kinetics and mechanisms of deagglomeration and the dispersion fineness. The effect of particle concentration was also studied in the range of 1 to 15% wt. The process was monitored through the evolution of particle size distribution (PSD), which indicated erosion as the dominant mechanism of breakup. The smallest attainable particle size was found to be independent of power input and solid concentration. Faster break up kinetics were noted as the power input was increased whereas increasing the solids concentration to 15% wt. slowed the process. It could also be shown that processing concentrated dispersions can be beneficial as the break up rate assessed on the basis of energy per unit mass of solids was faster for increased particle concentration

    T'hat's the way we happen to do things around here': Richard Rorty and political liberalism.

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    This thesis advances a defence of Richard Rorty's political liberalism. It is widely held that what Rorty calls anti-foundationalism either consciously proposes, or logically entails, the denial both of ethical commitment and the possibility of moral justification. Others argue that Rorty reduces commitment to a parochial concern, and that justification is relative to the standards of a narrowly conceived community. Commitment and justification, it is said, reduce to pointing out whatever it is that constitutes 'the way we happen to do things around here'. In turn, anti-foundationalism is said to render obsolete any normative project in political theory. The thesis rejects these claims, arguing that Rorty does not reduce commitment and justification in this way. Anti-foundationalism is shown not to reduce reason-giving to 'what we happen to think around here', and it is also cleansed of claims that it is relativistic, irrational and nihilistic. Justification as the response for reasonable requests for explanation of our beliefs and practices remains important for Rorty, centrally in his account of justification through 'wide reflective equilibrium'. The thesis shows how Rorty's view of liberal ironism is the completion, not the negation, of liberalism. It demonstrates that he is able both to justify and defend liberal principles and institutions, and to do so in a way that undercuts many of the criticisms of liberalism that have been levelled by communitarian critics and others. It examines his view of liberal political thought not as providing a philosophical justification of liberalism, but as offering an articulation of it. It closes by considering the scope of liberal claims, suggesting that Rorty is, in the only meaningful sense of the term, a liberal universalist

    Stellar Collisions and the Interior Structure of Blue Stragglers

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    Collisions of main sequence stars occur frequently in dense star clusters. In open and globular clusters, these collisions produce merger remnants that may be observed as blue stragglers. Detailed theoretical models of this process require lengthy hydrodynamic computations in three dimensions. However, a less computationally expensive approach, which we present here, is to approximate the merger process (including shock heating, hydrodynamic mixing, mass ejection, and angular momentum transfer) with simple algorithms based on conservation laws and a basic qualitative understanding of the hydrodynamics. These algorithms have been fine tuned through comparisons with the results of our previous hydrodynamic simulations. We find that the thermodynamic and chemical composition profiles of our simple models agree very well with those from recent SPH (smoothed particle hydrodynamics) calculations of stellar collisions, and the subsequent stellar evolution of our simple models also matches closely that of the more accurate hydrodynamic models. Our algorithms have been implemented in an easy to use software package, which we are making publicly available (see http://vassun.vassar.edu/~lombardi/mmas/). This software could be used in combination with realistic dynamical simulations of star clusters that must take into account stellar collisions.Comment: This revised version has 37 pages, 13 figures, 4 tables; submitted to ApJ; for associated software package, see http://vassun.vassar.edu/~lombardi/mmas/ This revised version presents additional comparisons with SPH results and slightly improved merger recipe

    An Upper Palaeolithic Proto-writing System and Phenological Calendar

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    In at least 400 European caves such as Lascaux, Chauvet and Altamira, Upper Palaeolithic Homo sapiens groups drew, painted and engraved non-figurative signs from at least ~42,000 BP and figurative images (notably animals) from at least 37,000 BP. Since their discovery ~150 years ago, the purpose or meaning of European Upper Palaeolithic non-figurative signs has eluded researchers. Despite this, specialists assume that they were notational in some way. Using a database of images spanning the European Upper Palaeolithic, we suggest how three of the most frequently occurring signs—the line , the dot , and the —functioned as units of communication. We demonstrate that when found in close association with images of animals the line and dot constitute numbers denoting months, and form constituent parts of a local phenological/meteorological calendar beginning in spring and recording time from this point in lunar months. We also demonstrate that the sign, one of the most frequently occurring signs in Palaeolithic non-figurative art, has the meaning . The position of the within a sequence of marks denotes month of parturition, an ordinal representation of number in contrast to the cardinal representation used in tallies. Our data indicate that the purpose of this system of associating animals with calendar information was to record and convey seasonal behavioural information about specific prey taxa in the geographical regions of concern. We suggest a specific way in which the pairing of numbers with animal subjects constituted a complete unit of meaning—a notational system combined with its subject—that provides us with a specific insight into what one set of notational marks means. It gives us our first specific reading of European Upper Palaeolithic communication, the first known writing in the history of Homo sapiens

    Confronting an augmented reality

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    How can educators make use of augmented reality technologies and practices to enhance learning and why would we want to embrace such technologies anyway? How can an augmented reality help a learner confront, interpret and ultimately comprehend reality itself? In this article, we seek to initiate a discussion that focuses on these questions, and suggest that they be used as drivers for research into effective educational applications of augmented reality. We discuss how multi-modal, sensorial augmentation of reality links to existing theories of education and learning, focusing on ideas of cognitive dissonance and the confrontation of new realities implied by exposure to new and varied perspectives. We also discuss connections with broader debates brought on by the social and cultural changes wrought by the increased digitalisation of our lives, especially the concept of the extended mind. Rather than offer a prescription for augmentation, our intention is to throw open debate and to provoke deep thinking about what interacting with and creating an augmented reality might mean for both teacher and learner
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