9,165 research outputs found
Multiple phase transitions in an agent-based evolutionary model with neutral fitness
Null models are crucial for understanding evolutionary processes such as speciation and adaptive radiation. We analyse an agent-based null model, considering a case without selection—neutral evolution—in which organisms are defined only by phenotype. Universal dynamics has previously been demonstrated in a related model on a neutral fitness landscape, showing that this system belongs to the directed percolation (DP) universality class. The traditional null condition of neutral fitness (where fitness is defined as the number of offspring each organism produces) is extended here to include equal probability of death among organisms. We identify two types of phase transition: (i) a non-equilibrium DP transition through generational time (i.e. survival), and (ii) an equilibrium ordinary percolation transition through the phenotype space (based on links between mating organisms). Owing to the dynamical rules of the DP reaction–diffusion process, organisms can only sparsely fill the phenotype space, resulting in significant phenotypic diversity within a cluster of mating organisms. This highlights the necessity of understanding hierarchical evolutionary relationships, rather than merely developing taxonomies based on phenotypic similarity, in order to develop models that can explain phylogenetic patterns found in the fossil record or to make hypotheses for the incomplete fossil record of deep time
Precision cosmology defeats void models for acceleration
The suggestion that we occupy a privileged position near the centre of a
large, nonlinear, and nearly spherical void has recently attracted much
attention as an alternative to dark energy. Putting aside the philosophical
problems with this scenario, we perform the most complete and up-to-date
comparison with cosmological data. We use supernovae and the full cosmic
microwave background spectrum as the basis of our analysis. We also include
constraints from radial baryonic acoustic oscillations, the local Hubble rate,
age, big bang nucleosynthesis, the Compton y-distortion, and for the first time
include the local amplitude of matter fluctuations, \sigma_8. These all paint a
consistent picture in which voids are in severe tension with the data. In
particular, void models predict a very low local Hubble rate, suffer from an
"old age problem", and predict much less local structure than is observed.Comment: 22 pages, 12 figures; v2 adds models in closed backgrounds;
conclusions strengthened; version accepted to Phys. Rev.
Spitzer Phase Curves of KELT-1b and the Signatures of Nightside Clouds in Thermal Phase Observations
We observed two full orbital phase curves of the transiting brown dwarf
KELT-1b, at 3.6um and 4.5um, using the Spitzer Space Telescope. Combined with
previous eclipse data from Beatty et al. (2014), we strongly detect KELT-1b's
phase variation as a single sinusoid in both bands, with amplitudes of
ppm at 3.6um and ppm at 4.5um, and confirm the secondary
eclipse depths measured by Beatty et al. (2014). We also measure noticeable
Eastward hotspot offsets of degrees at 3.6um and
degrees at 4.5um. Both the day-night temperature contrasts and the hotspot
offsets we measure are in line with the trends seen in hot Jupiters (e.g.,
Crossfield 2015), though we disagree with the recent suggestion of an offset
trend by Zhang et al. (2018). Using an ensemble analysis of Spitzer phase
curves, we argue that nightside clouds are playing a noticeable role in
modulating the thermal emission from these objects, based on: 1) the lack of a
clear trend in phase offsets with equilibrium temperature, 2) the sharp
day-night transitions required to have non-negative intensity maps, which also
resolves the inversion issues raised by Keating & Cowan (2017), 3) the fact
that all the nightsides of these objects appear to be at roughly the same
temperature of 1000K, while the dayside temperatures increase linearly with
equilibrium temperature, and 4) the trajectories of these objects on a Spitzer
color-magnitude diagram, which suggest colors only explainable via nightside
clouds.Comment: AJ in press. Updated to reflect the accepted versio
A Public Health Emergency of International Concern? Response to a Proposal to Apply the International Health Regulations to Antimicrobial Resistance
Adam Kamradt-Scott critiques a proposal to apply the International Health Regulations
(IHR) to the global health threat of antimicrobial resistance
Comprehensive behavioral characterization of an APP/PS-1 double knock-in mouse model of Alzheimer\u27s disease
INTRODUCTION: Despite the extensive mechanistic and pathological characterization of the amyloid precursor protein (APP)/presenilin-1 (PS-1) knock-in mouse model of Alzheimer\u27s disease (AD), very little is known about the AD-relevant behavioral deficits in this model. Characterization of the baseline behavioral performance in a variety of functional tasks and identification of the temporal onset of behavioral impairments are important to provide a foundation for future preclinical testing of AD therapeutics. Here we perform a comprehensive behavioral characterization of this model, discuss how the observed behavior correlates with the mechanistic and pathological observations of others, and compare this model with other commonly used AD mouse models.
METHODS: Four different groups of mice ranging across the lifespan of this model (test groups: 7, 11, 15, and 24 months old) were run in a behavioral test battery consisting of tasks to assess motor function (grip strength, rotor rod, beam walk, open field ambulatory movement), anxiety-related behavior (open field time spent in peripheral zone vs. center zone, elevated plus maze), and cognitive function (novel object recognition, radial arm water maze).
RESULTS: There were no differences in motor function or anxiety-related behavior between APP/PS-1 knock-in mice and wild-type counterpart mice for any age group. Cognitive deficits in both recognition memory (novel object recognition) and spatial reference memory (radial arm water maze) became apparent for the knock-in animals as the disease progressed.
CONCLUSION: This is the first reported comprehensive behavioral analysis of the APP/PS1 knock-in mouse model of AD. The lack of motor/coordination deficits or abnormal anxiety levels, coupled with the age/disease-related cognitive decline and high physiological relevance of this model, make it well suited for utilization in preclinical testing of AD-relevant therapeutics
Musical Hallucinations Treated with Atypical Antipsychotics in a Geriatric Population – A Case Series
Musical hallucinations have been likened to the auditory equivalent of Charles Bonnet Syndrome, which involves complex visual hallucinations, most often in the context of visual impairment. Musical hallucination frequently take the form of hymns, carols, and show-tunes and are strongly associated with hearing loss, with some studies suggesting a prevalence of 2.5–3.6% in the hearing impaired. Musical hallucinations are typically treated with anticonvulsant and anticholinesterase medications, with some studies having evaluated the efficacy of sedative hypnotics, antipsychotics and antidepressants in various psychiatric and medical subpopulations suggesting a heterogeneous spectrum of causes for this disorder.
We present two cases of musical hallucinations in both a 70-year-old African American female with past psychiatric history of major depressive disorder who developed hymnal auditory hallucinations during an acute medical and psychiatric admission and an 86-year-old Caucasian female, who complained of hearing gospel music with eventual onset of visual hallucinations after a fall at age 80. Our patients were successfully treated in both the inpatient and outpatient settings with atypical antipsychotics.
The presented cases add to the paucity of literature regarding utilization of atypical antipsychotics for treatment of musical hallucinations and demonstrate efficacy to this effect. This study lends further validity to the use of psychopharmacologic agents for novel purposes that have yet to be fully explored
Comprehensive behavioral characterization of an APP/PS-1 double knock-in mouse model of Alzheimer\u27s disease
INTRODUCTION: Despite the extensive mechanistic and pathological characterization of the amyloid precursor protein (APP)/presenilin-1 (PS-1) knock-in mouse model of Alzheimer\u27s disease (AD), very little is known about the AD-relevant behavioral deficits in this model. Characterization of the baseline behavioral performance in a variety of functional tasks and identification of the temporal onset of behavioral impairments are important to provide a foundation for future preclinical testing of AD therapeutics. Here we perform a comprehensive behavioral characterization of this model, discuss how the observed behavior correlates with the mechanistic and pathological observations of others, and compare this model with other commonly used AD mouse models.
METHODS: Four different groups of mice ranging across the lifespan of this model (test groups: 7, 11, 15, and 24 months old) were run in a behavioral test battery consisting of tasks to assess motor function (grip strength, rotor rod, beam walk, open field ambulatory movement), anxiety-related behavior (open field time spent in peripheral zone vs. center zone, elevated plus maze), and cognitive function (novel object recognition, radial arm water maze).
RESULTS: There were no differences in motor function or anxiety-related behavior between APP/PS-1 knock-in mice and wild-type counterpart mice for any age group. Cognitive deficits in both recognition memory (novel object recognition) and spatial reference memory (radial arm water maze) became apparent for the knock-in animals as the disease progressed.
CONCLUSION: This is the first reported comprehensive behavioral analysis of the APP/PS1 knock-in mouse model of AD. The lack of motor/coordination deficits or abnormal anxiety levels, coupled with the age/disease-related cognitive decline and high physiological relevance of this model, make it well suited for utilization in preclinical testing of AD-relevant therapeutics
Seasonal and Interspecific Variation in Frugivory by a Mixed Resident-Migrant Overwintering Songbird Community
Many temperate passerine bird species switch from diets of mostly invertebrates in the spring and summer to diets that include fruit and seeds in the fall and winter. However, relatively few studies have quantified diet composition or the extent of seasonal shifts during the non-breeding period, particularly among species and across communities with both residents and migrants. We measured carbon and nitrogen stable isotope values in food items (fruits, C3 and C4seeds, and insects from various trophic levels and plant communities) and in multiple tissues (feathers and plasma/whole blood) from 11 species of songbirds wintering in the southeastern U.S. We combined these diet and tissue values with empirically derived discrimination factors and used concentration-dependent mixing models to quantify seasonal diet shifts. We also validated mixing model results with data from fecal samples. Diets in this bird community, as delineated N and C isotopic space, diverged in the fall and winter relative to the summer as consumption of fruits and seeds increased. Across this songbird community, estimated contributions of fruit to plasma/whole blood increased from 16.2 ± 7.5% in the fall (mean ± SD; range: 4–26%) to 21.7 ± 10.3% (range: 9–37%) in the winter, while contributions of seeds increased from 29.4 ± 2.6% (range: 28–32%) in the fall to 36.6 ± 4.8% (range: 32–42%) in the winter. Fecal data showed qualitatively similar trends to mixing models, but consistently estimated higher contributions of fruit. Our work indicates that fruits and seeds constitute substantial sources of sustenance for non-breeding songbirds, there is considerable separation of resource use among species in the fall and winter, and fecal estimates of contributions to songbird tissues should be interpreted cautiously
Closed Head Injury in an Age-Related Alzheimer Mouse Model Leads to an Altered Neuroinflammatory Response and Persistent Cognitive Impairment
Epidemiological studies have associated increased risk of Alzheimer\u27s disease (AD)-related clinical symptoms with a medical history of head injury. Currently, little is known about pathophysiology mechanisms linked to this association. Persistent neuroinflammation is one outcome observed in patients after a single head injury. Neuroinflammation is also present early in relevant brain regions during AD pathology progression. In addition, previous mechanistic studies in animal models link neuroinflammation as a contributor to neuropathology and cognitive impairment in traumatic brain injury (TBI) or AD-related models. Therefore, we explored the potential interplay of neuroinflammatory responses in TBI and AD by analysis of the temporal neuroinflammatory changes after TBI in an AD model, the APP/PS1 knock-in (KI) mouse. Discrete temporal aspects of astrocyte, cytokine, and chemokine responses in the injured KI mice were delayed compared with the injured wild-type mice, with a peak neuroinflammatory response in the injured KI mice occurring at 7 d after injury. The neuroinflammatory responses were more persistent in the injured KI mice, leading to a chronic neuroinflammation. At late time points after injury, KI mice exhibited a significant impairment in radial arm water maze performance compared with sham KI mice or injured wild-type mice. Intervention with a small-molecule experimental therapeutic (MW151) that selectively attenuates proinflammatory cytokine production yielded improved cognitive behavior outcomes, consistent with a link between neuroinflammatory responses and altered risk for AD-associated pathology changes with head injury
A Uniform Analysis of the Ly-alpha forest at z = 0 - 5: I. The sample and distribution of clouds at z > 1.7
We present moderate resolution data for 39 QSOs at z 2 obtained at
the Multiple Mirror Telescope. These data are combined with spectra of
comparable resolution of 60 QSOs with redshifts greater than 1.7 found in the
literature to investigate the distribution of Ly-alpha forest lines in redshift
and equivalent width. We find a value for , the parameter describing
the number distribution of Ly-alpha forest lines in redshift, of
for lines stronger than a rest equivalent width of 0.32 , in good
agreement with some previous studies. The Kolmogorov-Smirnov test was applied
to the data and it is found that this single power law is a good fit over the
relevant redshift ranges. Simulations of the Lyman alpha forest were performed
to determine the completeness of the line lists and to test how well the
analysis the underlying line statistics, given this level of completeness.Comment: minor corrections to text, 37 Latex pages, 11 encapsulated Postscript
figures, uses emulateapj.sty, To appear in the Sept. 2000 ApJS, line lists
and spectra available at http://qso.as.arizona.edu/~jscott/Spectra/index.htm
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