17,689 research outputs found

    A Marxian Analysis of Inter-Industry Linkages and the Time Structure of Production

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    In this paper we analyze and model the flows of capital in an interlinked economy exhibiting complete simple reproduction. Drawing heavily on Marx\u27s description of circulation in volume 2 of Capital, we graphically and symbolically model the transfer of value between money, productive, and commodity capital. In addition, we allow for the creation of surplus value through production. Combining this with Marx\u27s discussion of simple reproduction and the MELT (Monetary Expression of Labor Time), our model illustrates a capitalist economy in a state of general equilibrium. As a powerful descriptive tool, this mathematical and Maple-coded model combines the insights of volumes 1 and 2 of Capital to enable a more complete understanding of Marxian theory. This model will be usable both as a descriptive and teaching tool, as well as potentially being used to analyze the equalization of profit rates, and the related transformation problem

    Electronic libraries and electronic librarians: Who does what in a national electronic community

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    This talk will have two parts: First, I'm going to describe very briefly what this new kind of library technology is like through a discussion of the Worm Community System (WCS), why it is going to be very important, and why it will involve a lot of money. What I want to emphasize at the start is that while WCS may seem like an esoteric research project, in fact it is one of the flagship information projects funded by the National Science Foundation. In addition, the National Information Infrastructure Act looms in the immediate future, authorizing an enormous amount of money to be spent in the development of digital libraries in specialized areas. Digital libraries will require information systems like WCS. This project has become a national model of this new kind of information system, but its primary content is really just a special collection, in the same sense you already know. It is an important national effort, but there will be lots of other efforts like this in many different subject areas. Second, I'm going to discuss in more detail what kinds of people are required to do this kind of activity. The roles range from traditional librarians all the way to systems architects. Similarly, the roles range from those that involve no computer knowledge at all to those that involve very intensive computing. My expectation is that people who call themselves "librarians" in the foreseeable future will actually span this entire range, even though now they are significantly skewed towards the traditional end.published or submitted for publicatio

    Optimization of a satellite project

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    Improvement in technological performance by project optimizatio

    The importance of nuclear masses in the astrophysical rp-process

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    The importance of mass measurements for astrophysical capture processes in general, and for the rp-process in X-ray bursts in particular is discussed. A review of the current uncertainties in the effective lifetimes of the major waiting points 64Ge, 68Se, and 72Kr demonstrates that despite of recent measurements uncertainties are still significant. It is found that mass measurements with an accuracy of the order of 10 keV or better are desirable, and that reaction rate uncertainties play a critical role as well.Comment: 14 pages, 4 figures, to appear in International Journal of Mass Spectroscop

    How proteins are transported into mitochondria

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    Most mitochondrial polypeptides are synthesized outside the organelle as precursors which are usually larger than the ‘mature’ polypeptides found within mitochondria. The precursors are imported into the mitochondria by a process which is independent of protein synthesis but dependent on high-energy phosphate bonds inside the mitochondria. This mechanism is basically different from that which governs the movement of secretory polypeptides across the membrane of the endoplasmic reticulum

    Quantum mechanical reactive scattering for three-dimensional atom plus diatom systems. II. Accurate cross sections for H+H_2

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    Accurate three‐dimensional reactive and nonreactive quantum mechanical cross sections for the H+H_2 exchange reaction on the Porter–Karplus potential energy surface are presented. Tests of convergence in the calculations indicate an accuracy of better than 5% for most of the results in the energy range considered (0.3 to 0.7 eV total energy). The reactive differential cross sections are exclusively backward peaked, with peak widths increasing monotonically from about 32° at 0.4 eV to 51° at 0.7 eV. Nonreactive inelastic differential cross sections show backwards to sidewards peaking, while elastic ones are strongly forward peaked with a nearly monotonic decrease with increasing scattering angle. Some oscillations due to interferences between the direct and exchange amplitudes are obtained in the para‐to‐para and ortho‐to‐ortho antisymmetrized cross sections above the effective threshold for reaction. Nonreactive collisions do not show a tendency to satisfy a "j_z‐conserving" selection rule. The reactive cross sections show significant rotational angular momentum polarization with the m_j=m′_j=0 transition dominating for low reagent rotational quantum number j. In constrast, the degeneracy averaged rotational distributions can be fitted to statistical temperaturelike expressions to a high degree of accuracy. The integral cross sections have an effective threshold total energy of about 0.55 eV, and differences between this quantity and the corresponding 1D and 2D results can largely be interpreted as resulting from bending motions in the transition state. In comparing these results with those of previous approximate dynamical calculations, we find best overall agreement between our reactive integral and differential cross sections and the quasiclassical ones of Karplus, Porter, and Sharma [J. Chem. Phys. 43, 3259 (1965)], at energies above the quasiclassical effective thresholds. This results in the near equality of the quantum and quasiclassical thermal rate constants at 600 K. At lower temperatures, however, the effects of tunneling become very important with the quantum rate constant achieving a value larger than the quasiclassical one by a factor of 3.2 at 300 K and 18 at 200 K

    Vibrational deactivation on chemically reactive potential surfaces: An exact quantum study of a low barrier collinear model of H + FH, D + FD, H + FD and D + FH

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    We study vibrational deactivation processes on chemically reactive potential energy surfaces by examining accurate quantum mechanical transition probabilities and rate constants for the collinear H + FH(v), D + FD(v), H + FD(v), and D + FH(v) reactions. A low barrier (1.7 kcal/mole) potential surface is used in these calculations, and we find that for all four reactions, the reactive inelastic rate constants are larger than the nonreactive ones for the same initial and final vibrational states. However, the ratios of these reactive and nonreactive rate constants depend strongly on the vibrational quantum number v and the isotopic composition of the reagents. Nonreactive and reactive transition probabilities for multiquantum jump transitions are generally comparable to those for single quantum transitions. This vibrationally nonadiabatic behavior is a direct consequence of the severe distortion of the diatomic that occurs in a collision on a low barrier reactive surface, and can make chemically reactive atoms like H or D more efficient deactivators of HF or DF than nonreactive collision partners. Many conclusions are in at least qualitative agreement with those of Wilkin’s three dimensional quasiclassical trajectory study on the same systems using a similar surface. We also present results for H + HF(v) collisions which show that for a higher barrier potential surface (33 rather than 1.7 kcal/mole), the deactivation process becomes similar in character to that for nonreactive partners, with v→v−1 processes dominating
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