6,437 research outputs found
Lifting classes for the fixed point theory of -valued maps
The theory of lifting classes and the Reidemeister number of single-valued
maps of a finite polyhedron is extended to -valued maps by replacing
liftings to universal covering spaces by liftings with codomain an orbit
configuration space, a structure recently introduced by Xicot\'encatl. The
liftings of an -valued map split into self-maps of the universal
covering space of that we call lift-factors. An equivalence relation is
defined on the lift-factors of and the number of equivalence classes is the
Reidemeister number of . The fixed point classes of are the projections
of the fixed point sets of the lift-factors and are the same as those of
Schirmer. An equivalence relation is defined on the fundamental group of
such that the number of equivalence classes equals the Reidemeister number. We
prove that if is a manifold of dimension at least three, then algebraically
the orbit configuration space approach is the same as one utilizing the
universal covering space. The Jiang subgroup is extended to -valued maps as
a subgroup of the group of covering transformations of the orbit configuration
space and used to find conditions under which the Nielsen number of an
-valued map equals its Reidemeister number. If an -valued map splits into
single-valued maps, then its -valued Reidemeister number is the sum of
their Reidemeister numbers.Comment: near complete rewrite from previous versio
Modules for Experiments in Stellar Astrophysics (MESA): Giant Planets, Oscillations, Rotation, and Massive Stars
We substantially update the capabilities of the open source software package
Modules for Experiments in Stellar Astrophysics (MESA), and its one-dimensional
stellar evolution module, MESA Star. Improvements in MESA Star's ability to
model the evolution of giant planets now extends its applicability down to
masses as low as one-tenth that of Jupiter. The dramatic improvement in
asteroseismology enabled by the space-based Kepler and CoRoT missions motivates
our full coupling of the ADIPLS adiabatic pulsation code with MESA Star. This
also motivates a numerical recasting of the Ledoux criterion that is more
easily implemented when many nuclei are present at non-negligible abundances.
This impacts the way in which MESA Star calculates semi-convective and
thermohaline mixing. We exhibit the evolution of 3-8 Msun stars through the end
of core He burning, the onset of He thermal pulses, and arrival on the white
dwarf cooling sequence. We implement diffusion of angular momentum and chemical
abundances that enable calculations of rotating-star models, which we compare
thoroughly with earlier work. We introduce a new treatment of
radiation-dominated envelopes that allows the uninterrupted evolution of
massive stars to core collapse. This enables the generation of new sets of
supernovae, long gamma-ray burst, and pair-instability progenitor models. We
substantially modify the way in which MESA Star solves the fully coupled
stellar structure and composition equations, and we show how this has improved
MESA's performance scaling on multi-core processors. Updates to the modules for
equation of state, opacity, nuclear reaction rates, and atmospheric boundary
conditions are also provided. We describe the MESA Software Development Kit
(SDK) that packages all the required components needed to form a unified and
maintained build environment for MESA. [Abridged]Comment: Accepted for publication in The ApJ Supplement Series. Extra
informations required to reproduce the calculations in this paper are
available at http://mesastar.org/results/mesa
Tall Buildings and Their Foundations: Three Examples
The influence of foundations on the design and behavior of tall buildings is explored by examining two built towers: Burj Khalifa, Trump International Hotel and Tower, and the partially built Plaza Rakyat, a 77 story tower in Malaysia. The paper reviews how foundation conditions were considered in the design of the buildings, and how the foundations were anticipated to influence the behavior of the towers
Geochemical Implications of CO2 Leakage Associated with Geologic Storage: A Review
Leakage from deep storage reservoirs is a major risk factor associated with geologic sequestration of carbon dioxide (CO2). Different scientific theories exist concerning the potential implications of such leakage for near-surface environments. The authors of this report reviewed the current literature on how CO2 leakage (from storage reservoirs) would likely impact the geochemistry of near surface environments such as potable water aquifers and the vadose zone. Experimental and modeling studies highlighted the potential for both beneficial (e.g., CO2 re sequestration or contaminant immobilization) and deleterious (e.g., contaminant mobilization) consequences of CO2 intrusion in these systems. Current knowledge gaps, including the role of CO2-induced changes in redox conditions, the influence of CO2 influx rate, gas composition, organic matter content and microorganisms are discussed in terms of their potential influence on pertinent geochemical processes and the potential for beneficial or deleterious outcomes. Geochemical modeling was used to systematically highlight why closing these knowledge gaps are pivotal. A framework for studying and assessing consequences associated with each factor is also presented in Section 5.6
Combined analysis of microbial metagenomic and metatranscriptomic sequencing data to assess in situ physiological conditions in the premature infant gut.
Microbes alter their transcriptomic profiles in response to the environment. The physiological conditions experienced by a microbial community can thus be inferred using meta-transcriptomic sequencing by comparing transcription levels of specifically chosen genes. However, this analysis requires accurate reference genomes to identify the specific genes from which RNA reads originate. In addition, such an analysis should avoid biases in transcript counts related to differences in organism abundance. In this study we describe an approach to address these difficulties. Sample-specific meta-genomic assembled genomes (MAGs) were used as reference genomes to accurately identify the origin of RNA reads, and transcript ratios of genes with opposite transcription responses were compared to eliminate biases related to differences in organismal abundance, an approach hereafter named the "diametric ratio" method. We used this approach to probe the environmental conditions experienced by Escherichia spp. in the gut of 4 premature infants, 2 of whom developed necrotizing enterocolitis (NEC), a severe inflammatory intestinal disease. We analyzed twenty fecal samples taken from four premature infants (4-6 time points from each infant), and found significantly higher diametric ratios of genes associated with low oxygen levels in samples of infants later diagnosed with NEC than in samples without NEC. We also show this method can be used for examining other physiological conditions, such as exposure to nitric oxide and osmotic pressure. These study results should be treated with caution, due to the presence of confounding factors that might also distinguish between NEC and control infants. Nevertheless, together with benchmarking analyses, we show here that the diametric ratio approach can be applied for evaluating the physiological conditions experienced by microbes in situ. Results from similar studies can be further applied for designing diagnostic methods to detect NEC in its early developmental stages
Verbal Compliments As a Differential Source of Mate Poaching Threat For Men and Women
Two studies tested whether people feel threatened by another individual verbally complimenting their romantic partner. Such compliments may indicate that the other person is a potential rival who will try to poach their mate. Across two studies, women were more threatened than men when imagining another person complimenting their partner\u27s physical appearance. There were no sex differences in response to imagining another person complimenting their partner\u27s sense of humor. When another person compliments one\u27s partner\u27s physical appearance, this indicates that they may be sexually attracted to the partner. Mediation analyses revealed that the sex difference occurs because women believe men are more open to casual sex, and therefore more vulnerable to mate poaching when another person expresses sexual interest in them
Semi-Teleparallel Theories of Gravitation
A class of theories of gravitation that naturally incorporates preferred
frames of reference is presented. The underlying space-time geometry consists
of a partial parallelization of space-time and has properties of Riemann-Cartan
as well as teleparallel geometry. Within this geometry, the kinematic
quantities of preferred frames are associated with torsion fields. Using a
variational method, it is shown in which way action functionals for this
geometry can be constructed. For a special action the field equations are
derived and the coupling to spinor fields is discussed.Comment: 14 pages, LaTe
Intraoperative electrocochleographic characteristics of auditory neuropathy spectrum disorder in cochlear implant subjects
Auditory neuropathy spectrum disorder (ANSD) is characterized by an apparent discrepancy between measures of cochlear and neural function based on auditory brainstem response (ABR) testing. Clinical indicators of ANSD are a present cochlear microphonic (CM) with small or absent wave V. Many identified ANSD patients have speech impairment severe enough that cochlear implantation (CI) is indicated. To better understand the cochleae identified with ANSD that lead to a CI, we performed intraoperative round window electrocochleography (ECochG) to tone bursts in children (n = 167) and adults (n = 163). Magnitudes of the responses to tones of different frequencies were summed to measure the “total response” (ECochG-TR), a metric often dominated by hair cell activity, and auditory nerve activity was estimated visually from the compound action potential (CAP) and auditory nerve neurophonic (ANN) as a ranked “Nerve Score”. Subjects identified as ANSD (45 ears in children, 3 in adults) had higher values of ECochG-TR than adult and pediatric subjects also receiving CIs not identified as ANSD. However, nerve scores of the ANSD group were similar to the other cohorts, although dominated by the ANN to low frequencies more than in the non-ANSD groups. To high frequencies, the common morphology of ANSD cases was a large CM and summating potential, and small or absent CAP. Common morphologies in other groups were either only a CM, or a combination of CM and CAP. These results indicate that responses to high frequencies, derived primarily from hair cells, are the main source of the CM used to evaluate ANSD in the clinical setting. However, the clinical tests do not capture the wide range of neural activity seen to low frequency sounds
New Constraints on the Lyman Continuum Escape Fraction at z~1.3
We examine deep far-ultraviolet (1600 Angstrom) imaging of the Hubble Deep
Field-North (HDFN) and the Hubble Ultra Deep Field (HUDF) to search for leaking
Lyman continuum radiation from starburst galaxies at z~1.3. There are 21
(primarily sub-L*) galaxies with spectroscopic redshifts between 1.1<z<1.5 and
none are detected in the far-UV. We fit stellar population templates to the
galaxies' optical/near-infrared SEDs to determine the starburst age and level
of dust attenuation, giving an accurate estimate of the intrinsic Lyman
continuum ratio, f_1500/f_700, and allowing a conversion from f_700 limits to
relative escape fractions. We show that previous high-redshift studies may have
underestimated the amplitude of the Lyman Break, and thus the relative escape
fraction, by a factor of ~2. Once the starburst age and intergalactic HI
absorption are accounted for, 18 galaxies in our sample have limits to the
relative escape fraction, f_esc,rel < 1.0 with some limits as low as f_esc,rel
< 0.10 and a stacked limit of f_esc,rel < 0.08. This demonstrates, for the
first time, that most sub-L* galaxies at high redshift do not have large escape
fractions. When combined with a similar study of more luminous galaxies at the
same redshift we show that, if all star-forming galaxies at z~1 have similar
relative escape fractions, the value must be less than 0.14 (3 sigma). We also
show that less than 20% (3 sigma) of star-forming galaxies at z~1 have relative
escape fractions near unity. These limits contrast with the large escape
fractions found at z~3 and suggest that the average escape fraction has
decreased between z~3 and z~1. (Abridged)Comment: Accepted for publication in ApJ. aastex format. 39 pages, 11 figure
White Matter Microstructure Contributes to Age-Related Declines in Task-Induced Deactivation of the Default Mode Network
Task-induced deactivations within the brain’s default mode network (DMN) are thought to reflect suppression of endogenous thought processes to support exogenous goal-directed task processes. Older adults are known to show reductions in deactivation of the DMN compared to younger adults. However, little is understood about the mechanisms contributing to functional dysregulation of the DMN in aging. Here, we explored the relationships between functional modulation of the DMN and age, task performance and white matter (WM) microstructure. Participants were 117 adults ranging from 25 to 83 years old who completed an fMRI task switching paradigm, including easy (single) and difficult (mixed) conditions, and underwent diffusion tensor imaging (DTI). The fMRI results revealed an age by condition interaction (β = −0.13, t = −3.16, p = 0.002) such that increasing age affected deactivation magnitude during the mixed condition (β = −0.29, t = −3.24 p = 0.002) but not the single condition (p = 0.58). Additionally, there was a WM by condition interaction (β = 0.10, t = 2.33, p = 0.02) such that decreasing WM microstructure affected deactivation magnitude during the mixed condition (β = 0.30, t = 3.42 p = 0.001) but not the single condition (p = 0.17). Critically, mediation analyses indicated that age-related reductions in WM microstructure accounted for the relationship between age and DMN deactivation in the more difficult mixed condition. These findings suggest that age-related declines in anatomical connectivity between DMN regions contribute to functional dysregulation within the DMN in older adults
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