4,789 research outputs found
On the Change in Archivability of Websites Over Time
As web technologies evolve, web archivists work to keep up so that our
digital history is preserved. Recent advances in web technologies have
introduced client-side executed scripts that load data without a referential
identifier or that require user interaction (e.g., content loading when the
page has scrolled). These advances have made automating methods for capturing
web pages more difficult. Because of the evolving schemes of publishing web
pages along with the progressive capability of web preservation tools, the
archivability of pages on the web has varied over time. In this paper we show
that the archivability of a web page can be deduced from the type of page being
archived, which aligns with that page's accessibility in respect to dynamic
content. We show concrete examples of when these technologies were introduced
by referencing mementos of pages that have persisted through a long evolution
of available technologies. Identifying these reasons for the inability of these
web pages to be archived in the past in respect to accessibility serves as a
guide for ensuring that content that has longevity is published using good
practice methods that make it available for preservation.Comment: 12 pages, 8 figures, Theory and Practice of Digital Libraries (TPDL)
2013, Valletta, Malt
Computational core and fixed-point organisation in Boolean networks
In this paper, we analyse large random Boolean networks in terms of a
constraint satisfaction problem. We first develop an algorithmic scheme which
allows to prune simple logical cascades and under-determined variables,
returning thereby the computational core of the network. Second we apply the
cavity method to analyse number and organisation of fixed points. We find in
particular a phase transition between an easy and a complex regulatory phase,
the latter one being characterised by the existence of an exponential number of
macroscopically separated fixed-point clusters. The different techniques
developed are reinterpreted as algorithms for the analysis of single Boolean
networks, and they are applied to analysis and in silico experiments on the
gene-regulatory networks of baker's yeast (saccaromices cerevisiae) and the
segment-polarity genes of the fruit-fly drosophila melanogaster.Comment: 29 pages, 18 figures, version accepted for publication in JSTA
Stellar-Mass Black Holes in the Solar Neighborhood
We search for nearby, isolated, accreting, ``stellar-mass'' (3 to
) black holes. Models suggest a synchrotron spectrum in visible
wavelengths and some emission in X-ray wavelengths. Of 3.7 million objects in
the Sloan Digital Sky Survey Early Data Release, about 150,000 objects have
colors and properties consistent with such a spectrum, and 87 of these objects
are X-ray sources from the ROSAT All Sky Survey. Thirty-two of these have been
confirmed not to be black-holes using optical spectra. We give the positions
and colors of these 55 black-hole candidates, and quantitatively rank them on
their likelihood to be black holes. We discuss uncertainties the expected
number of sources, and the contribution of blackholes to local dark matter.Comment: Replaced with version accepted by ApJ. 40 pages, 8 figure
In-medium meson properties and field transformations
Since the existing calculations of the effective meson mass in nuclear medium
involve approximations, it is important to examine whether they satisfy the
general requirement of the equivalence theorem that the physical observables
should be independent of the choice of field variables. We study here
consequences of nucleon field transformations. As an illustrative case we
consider the in-medium effective pion mass calculated for the s-wave
pion-nucleon interaction in the linear density approximation. We demonstrate
that it is necessary to include the Born term explicitly in order that the
effective pion mass should obey the equivalence theorem.Comment: 10 pages, using RevTeX4. More detailed discussion, references added.
To be published in Phys. Rev.
Once again on the equivalence theorem
We present the proof of the equivalence theorem in quantum field theory which
is based on a formulation of this problem in the field-antifield formalism. As
an example, we consider a model in which a different choices of natural finite
counterterms is possible, leading to physically non-equivalent quantum theories
while the equivalent theorem remains valid.Comment: 12 pages, LATEX, report number was correcte
Normative Alethic Pluralism
Some philosophers have argued that truth is a norm of judgement and have provided a variety of formulations of this general thesis. In this paper, I shall side with these philosophers and assume that truth is a norm of judgement. What I am primarily interested in here are two core questions concerning the judgement-truth norm: (i) what are the normative relationships between truth and judgement? And (ii) do these relationships vary or are they constant? I argue for a pluralist picture—what I call Normative Alethic Pluralism (NAP)—according to which (i) there is more than one correct judgement-truth norm and (ii) the normative relationships between truth and judgement vary in relation to the subject matter of the judgement. By means of a comparative analysis of disagreement in three areas of the evaluative domain—refined aesthetics, basic taste and morality—I show that there is an important variability in the normative significance of disagreement—I call this the variability conjecture. By presenting a variation of Lynch’s scope problem for alethic monism, I argue that a monistic approach to the normative function of truth is unable to vindicate the conjecture. I then argue that normative alethic pluralism provides us with a promising model to account for it
Closely related phytoplankton species produce similar suites of dissolved organic matter
© The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Frontiers in Microbiology 5 (2014): 111, doi:10.3389/fmicb.2014.00111.Production of dissolved organic matter (DOM) by marine phytoplankton supplies the majority of organic substrate consumed by heterotrophic bacterioplankton in the sea. This production and subsequent consumption converts a vast quantity of carbon, nitrogen, and phosphorus between organic and inorganic forms, directly impacting global cycles of these biologically important elements. Details regarding the chemical composition of DOM produced by marine phytoplankton are sparse, and while often assumed, it is not currently known if phylogenetically distinct groups of marine phytoplankton release characteristic suites of DOM. To investigate the relationship between specific phytoplankton groups and the DOM they release, hydrophobic phytoplankton-derived dissolved organic matter (DOMP) from eight axenic strains was analyzed using high-performance liquid chromatography coupled to mass spectrometry (HPLC-MS). Identification of DOM features derived from Prochlorococcus, Synechococcus, Thalassiosira, and Phaeodactylum revealed DOMP to be complex and highly strain dependent. Connections between DOMP features and the phylogenetic relatedness of these strains were identified on multiple levels of phylogenetic distance, suggesting that marine phytoplankton produce DOM that in part reflects its phylogenetic origin. Chemical information regarding the size and polarity ranges of features from defined biological sources was also obtained. Our findings reveal DOMP composition to be partially conserved among related phytoplankton species, and implicate marine DOM as a potential factor influencing microbial diversity in the sea by acting as a link between autotrophic and heterotrophic microbial community structures.This research was supported by grants to Daniel J. Repeta and Sallie W. Chisholm from the Gordon and Betty Moore Foundation and funding to Daniel J. Repeta, Edward F. DeLong, and Sallie W. Chisholm from the National Science Foundation Science and Technology Center Award 0424599
The correction-to-scaling exponent in dilute systems
The leading correction-to-scaling exponent for the three-dimensional
dilute Ising model is calculated in the framework of the field theoretic
renormalization group approach. Both in the minimal subtraction scheme as well
as in the massive field theory (resummed four loop expansion) excellent
agreement with recent Monte Carlo calculations [Ballesteros H G, et al Phys.
Rev. B 58, 2740 (1998)] is achieved. The expression of as series in a
-expansion up to does not allow a
reliable estimate for .Comment: 4 pages, latex, 1 eps-figure include
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