3,114 research outputs found
Political theory and history: The case of anarchism
This essay critically examines one of the dominant tendencies in recent theoretical discussions of anarchism, postanarchism, and argues that this tradition fails to engage sufficiently with anarchism’s history. Through an examination of late 19th-century anarchist political thought—as represented by one of its foremost exponents, Peter Kropotkin—we demonstrate the extent to which postanarchism has tended to oversimplify and misrepresent the historical tradition of anarchism. The article concludes by arguing that all political-theoretical discussions of anarchism going forward should begin with a fresh appraisal of the actual content of anarchist political thought, based on a rigorous analysis of its political, social, and cultural history
Constraints on the Intergalactic Transport of Cosmic Rays
Motivated by recent experimental proposals to search for extragalactic cosmic
rays (including anti-matter from distant galaxies), we study particle
propagation through the intergalactic medium (IGM). We first use estimates of
the magnetic field strength between galaxies to constrain the mean free path
for diffusion of particles through the IGM. We then develop a simple analytic
model to describe the diffusion of cosmic rays. Given the current age of
galaxies, our results indicate that, in reasonable models, a completely
negligible number of particles can enter our Galaxy from distances greater than
Mpc for relatively low energies ( GeV/n). We also find
that particle destruction in galaxies along the diffusion path produces an
exponential suppression of the possible flux of extragalactic cosmic rays.
Finally, we use gamma ray constraints to argue that the distance to any
hypothetical domains of anti-matter must be roughly comparable to the horizon
scale.Comment: 24 pages, AAS LaTex, 1 figure, accepted to Ap
Associations Between Subjective Tinnitus and Cognitive Performance: Systematic Review and Meta-Analyses
Tinnitus is the perception of sound in the absence of a corresponding external sound source, and bothersome tinnitus has been linked to poorer cognitive performance. This review comprehensively quantifies the association between tinnitus and different domains of cognitive performance. The review protocol was preregistered and published in a peer-reviewed journal. The review and analyses were reported according to Preferred Reporting Items for Systematic Review and Meta-analysis guidelines. Peer-reviewed literature was searched using electronic databases to find studies featuring participants with tinnitus who had undertaken measures of cognitive performance. Studies were assessed for quality and categorized according to an established cognitive framework. Random-effects meta-analyses were performed on various cognitive domains with potential moderator variables assessed where possible. Thirty-eight records were included in the analysis from a total of 1,863 participants. Analyses showed that tinnitus is associated with poorer executive function, processing speed, general short-term memory, and general learning and retrieval. Narrow cognitive domains of Inhibition and Shifting (within executive function) and learning and retrieval (within general learning and retrieval) were also associated with tinnitus
Controlling the properties of the micellar and gel phase by varying the counterion in functionalised-dipeptide systems
The micellar aggregates formed at high pH for dipeptide-based gelators can be varied by using different alkali metal salts to prepare the solutions. The nature of the micellar aggregates directly affects the properties of the resulting gels
Maxillomandibular Advancement in the Management of Obstructive Sleep Apnea
Maxillomandibular advancement (MMA) is a surgical option for obstructive sleep apnea (OSA). MMA involves forward-fixing the maxilla and mandible approximately 10
mm via Le Fort I maxillary and sagittal split mandibular osteotomies. We retrospectively reviewed outcomes from 24 consecutive OSA patients who underwent MMA at our institution. MMA resulted in an 83% reduction in the group mean apnea-hypopnea index (AHI) per polysomnography an average of 6.7 months after surgery. Forty-two percent of patients achieved a post-MMA AHI of less than 5 events/hour sleep and 71% achieved an AHI less than or equal to 10 events/hour sleep. The Epworth Sleepiness Scale score decreased by an average of 5 post-surgery. No parameters predictive of cure for OSA by MMA were identified
Adding Value to JWST Spectra and Photometry: Stellar Population and Star Formation Properties of Spectroscopically Confirmed JADES and CEERS Galaxies at
In this paper, we discuss measurements of the stellar population and star
forming properties for 43 spectroscopically confirmed publicly available
high-redshift JWST galaxies in the JADES and CEERS observational
programs. We carry out a thorough study investigating the relationship between
spectroscopic features and photometrically derived ones, including from
spectral energy distribution (SED) fitting of models, as well as morphological
and structural properties. We find that the star formation rates (SFRs)
measured from H line emission are higher than those estimated from
Bayesian SED fitting and UV luminosity, with ratios SFR/ SFR
ranging from 2~13. This is a sign that the star formation history is
consistently rising given the timescales of H vs UV star formation
probes. In addition, we investigate how well equivalent widths (EWs) of
H 4861, [O III] 4959, and [O III] 5007 can be
measured from photometry, finding that on average the EW derived from
photometric excesses in filters is 30% smaller than the direct spectroscopic
measurement. We also discover that a stack of the line emitting galaxies shows
a distinct morphology after subtracting imaging that contains only the
continuum. This gives us a first view of the line or ionized gas emission from
galaxies, demonstrating that this material has a similar distribution,
statistically, as the continuum. We also compare the derived SFRs and stellar
masses for both parametric and non-parametric star formation histories, where
we find that 35% of our sample formed at least 30% of their stellar mass in
recent (< 10 Myr) starburst events.Comment: 17 Pages, 13 Figures, 4 Tables, submitted to MNRA
Dust Extinction Measures for Galaxies using Machine Learning on JWST Imaging
We present the results of a machine learning study to measure the dust
content of galaxies observed with JWST at z > 6 through the use of trained
neural networks based on high-resolution IllustrisTNG simulations. Dust is an
important unknown in the evolution and observability of distant galaxies and is
degenerate with other stellar population features through spectral energy
fitting. As such, we develop and test a new SED-independent machine learning
method to predict dust attenuation and sSFR of high redshift (z > 6) galaxies.
Simulated galaxies were constructed using the IllustrisTNG model, with a
variety of dust contents parameterized by E(B-V) and A(V) values, then used to
train Convolutional Neural Network (CNN) models using supervised learning
through a regression model. We demonstrate that within the context of these
simulations, our single and multi-band models are able to predict dust content
of distant galaxies to within a 1 dispersion of A(V) .
Applied to spectroscopically confirmed z > 6 galaxies from the JADES and CEERS
programs, our models predicted attenuation values of A(V) < 0.7 for all
systems, with a low average (A(V) = 0.28). Our CNN predictions show larger dust
attenuation but lower amounts of star formation compared to SED fitted values.
Both results show that distant galaxies with confirmed spectroscopy are not
extremely dusty, although this sample is potentially significantly biased. We
discuss these issues and present ideas on how to accurately measure dust
features at the highest redshifts using a combination of machine learning and
SED fitting.Comment: submitted to MNRA
WZW-like Action for Heterotic String Field Theory
We complete the construction of the Neveu-Schwarz sector of heterotic string
field theory begun in hep-th/0406212 by giving a closed-form expression for the
action and gauge transformations. Just as the Wess-Zumino-Witten (WZW) action
for open superstring field theory can be constructed from pure-gauge fields in
bosonic open string field theory, our heterotic string field theory action is
constructed from pure-gauge fields in bosonic closed string field theory. The
construction involves a simple alternative form of the WZW action which is
consistent with the algebraic structures of closed string field theory.Comment: 22 pages, no figures, LaTeX2
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