23,593 research outputs found
An inquiry into the effect of the intellectual revolution of the sixteenth and seventeenth centuries on the coming of the French Revolution
Since the late seventeenth century a lively debate has been in progress concerning the worth of history. Although professional historians no longer abuse their credit with the public, which as ceased seriously to question their veracity, the debate goes on. This historical Pyrrhonism of the seventeenth century was no based upon irresponsible skepticism; the fables, folk legends, and pure inventions preserved in the histories of the period had reduced history to a mere art form. The subsequent attempt to correct this situation, through it produced a reliable body of information, has tened to reduce history to a narrow objectivity that scarcely dares think for itself. Thus Voltaire remarked, with more moderation than he usually addressed to the subject, The qualification in which historians are commonly defective is a true philosophical spirit... For Voltaire, true philosophy begins with Bacon and Locke; hence the true philosophy begins with Bacon and Locke; hence the truce philosophical spirit\u27 of which he wrote is the scientific spirit
Force Dynamics in Weakly Vibrated Granular Packings
The oscillatory force F_b^ac on the bottom of a rigid, vertically vibrated,
grain filled column, reveals rich granular dynamics, even when the peak
acceleration of the vibrations is signicantly less than the gravitational
acceleration at the earth's surface. For loose packings or high frequencies,
F_b^ac 's dynamics are dominated by grain motion. For moderate driving
conditions in more compact samples, grain motion is virtually absent, but
F_b^ac nevertheless exhibits strongly nonlinear and hysteretic behavior,
evidencing a granular regime dominated by nontrivial force-network dynamics.Comment: 4 pages, 5 figure
The quantitative soil pit method for measuring belowground carbon and nitrogen stocks
Many important questions in ecosystem science require estimates of stocks of soil C and nutrients. Quantitative soil pits provide direct measurements of total soil mass and elemental content in depth-based samples representative of large volumes, bypassing potential errors associated with independently measuring soil bulk density, rock volume, and elemental concentrations. The method also allows relatively unbiased sampling of other belowground C and nutrient stocks, including roots, coarse organic fragments, and rocks. We present a comprehensive methodology for sampling these pools with quantitative pits and assess their accuracy, precision, effort, and sampling intensity as compared to other methods. At 14 forested sites in New Hampshire, nonsoil belowground pools (which other methods may omit, double-count, or undercount) accounted for upward of 25% of total belowground C and N stocks: coarse material accounted for 4 and 1% of C and N in the O horizon; roots were 11 and 4% of C and N in the O horizon and 10 and 3% of C and N in the B horizon; and soil adhering to rocks represented 5% of total B-horizon C and N. The top 50 cm of the C horizon contained the equivalent of 17% of B-horizon carbon and N. Sampling procedures should be carefully designed to avoid treating these important pools inconsistently. Quantitative soil pits have fewer sources of systematic error than coring methods; the main disadvantage is that because they are time-consuming and create a larger zone of disturbance, fewer observations can be made than with cores
Static and Dry Friction due to Multiscale Surface Roughness
It is shown on the basis of scaling arguments that a disordered interface
between two elastic solids will quite generally exhibit static and "dry
friction" (i.e., kinetic friction which does not vanish as the sliding velocity
approaches zero), because of Tomlinson model instabilities that occur for small
length scale asperities. This provides a possible explanation for why static
and "dry" friction are virtually always observed, and superlubricity almost
never occurs
Detecting Star Formation in Brightest Cluster Galaxies with GALEX
We present the results of GALEX observations of 17 cool core (CC) clusters of
galaxies. We show that GALEX is easily capable of detecting star formation in
brightest cluster galaxies (BCGs) out to and 50-100 kpc. In most of
the CC clusters studied, we find significant UV luminosity excesses and colors
that strongly suggest recent and/or current star formation. The BCGs are found
to have blue UV colors in the center that become increasingly redder with
radius, indicating that the UV signature of star formation is most easily
detected in the central regions. Our findings show good agreement between UV
star formation rates and estimates based on H observations. IR
observations coupled with our data indicate moderate-to-high dust attenuation.
Comparisons between our UV results and the X-ray properties of our sample
suggest clear correlations between UV excess, cluster entropy, and central
cooling time, confirming that the star formation is directly and
incontrovertibly related to the cooling gas.Comment: 39 pages, 11 figures; accepted for publication in The Astrophysical
Journal. Figure quality reduced to comply with arXiv file size requirement
Corpus Refactoring: a Feasibility Study
© 2007 Johnson et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens
Electric-octupole and pure-electric-quadrupole effects in soft-x-ray photoemission
Second-order [O(k^2), k=omega/c] nondipole effects in soft-x-ray
photoemission are demonstrated via an experimental and theoretical study of
angular distributions of neon valence photoelectrons in the 100--1200 eV
photon-energy range. A newly derived theoretical expression for nondipolar
angular distributions characterizes the second-order effects using four new
parameters with primary contributions from pure-quadrupole and octupole-dipole
interference terms. Independent-particle calculations of these parameters
account for a significant portion of the existing discrepancy between
experiment and theory for Ne 2p first-order nondipole parameters.Comment: 4 pages, 3 figure
Adoption of Conservation-Tillage Practices in Cotton Production
Replaced with revised version of paper 10/23/07.conservation tillage, cotton, genetically modified seed, herbicide-resistant cotton, stacked-gene cotton, simultaneous logit model, single-equation logit model, technology adoption, Crop Production/Industries,
The Star Formation and Extinction Co-Evolution of UV-Selected Galaxies over 0.05<z<1.2
We use a new stacking technique to obtain mean mid IR and far IR to far UV
flux ratios over the rest near-UV/near-IR color-magnitude diagram. We employ
COMBO-17 redshifts and COMBO-17 optical, GALEX far and near UV, Spitzer IRAC
and MIPS Mid IR photometry. This technique permits us to probe infrared excess
(IRX), the ratio of far IR to far UV luminosity, and specific star formation
rate (SSFR) and their co-evolution over two orders of magnitude of stellar mass
and redshift 0.1<z<1.2. We find that the SSFR and the characteristic mass (M_0)
above which the SSFR drops increase with redshift (downsizing). At any given
epoch, IRX is an increasing function of mass up to M_0. Above this mass IRX
falls, suggesting gas exhaustion. In a given mass bin below M_0 IRX increases
with time in a fashion consistent with enrichment. We interpret these trends
using a simple model with a Schmidt-Kennicutt law and extinction that tracks
gas density and enrichment. We find that the average IRX and SSFR follows a
galaxy age parameter which is determined mainly by the galaxy mass and time
since formation. We conclude that blue sequence galaxies have properties which
show simple, systematic trends with mass and time such as the steady build-up
of heavy elements in the interstellar media of evolving galaxies and the
exhaustion of gas in galaxies that are evolving off the blue sequence. The IRX
represents a tool for selecting galaxies at various stages of evolution.Comment: Accepted for publication in GALEX Special Ap.J.Suppl., December, 200
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