3,697 research outputs found
Analytical solution of a generalized Penna model
In 1995 T.J.Penna introduced a simple model of biological aging. A modified
Penna model has been demonstrated to exhibit behaviour of real-life systems
including catastrophic senescence in salmon and a mortality plateau at advanced
ages. We present a general steady-state, analytic solution to the Penna model,
able to deal with arbitrary birth and survivability functions. This solution is
employed to solve standard variant Penna models studied by simulation.
Different Verhulst factors regulating both the birth rate and external death
rate are considered.Comment: 6 figure
Uniform approximations for non-generic bifurcation scenatios including bifurcations of ghost orbits
Gutzwiller's trace formula allows interpreting the density of states of a
classically chaotic quantum system in terms of classical periodic orbits. It
diverges when periodic orbits undergo bifurcations, and must be replaced with a
uniform approximation in the vicinity of the bifurcations. As a characteristic
feature, these approximations require the inclusion of complex ``ghost
orbits''. By studying an example taken from the Diamagnetic Kepler Problem,
viz. the period-quadrupling of the balloon-orbit, we demonstrate that these
ghost orbits themselves can undergo bifurcations, giving rise to non-generic
complicated bifurcation scenarios. We extend classical normal form theory so as
to yield analytic descriptions of both bifurcations of real orbits and ghost
orbit bifurcations. We then show how the normal form serves to obtain a uniform
approximation taking the ghost orbit bifurcation into account. We find that the
ghost bifurcation produces signatures in the semiclassical spectrum in much the
same way as a bifurcation of real orbits does.Comment: 56 pages, 21 figure, LaTeX2e using amsmath, amssymb, epsfig, and
rotating packages. To be published in Annals of Physic
Asymmetric c-fos expression in the ventral orbital cortex is associated with impaired reversal learning in a right-sided neuropathy
BACKGROUND:
Recently we showed that unilateral peripheral neuropathic lesions impacted differentially on rat's emotional/cognitive behavior depending on its left/right location; importantly, this observation recapitulates clinical reports. The prefrontal cortex (PFC), a brain region morphofunctionally affected in chronic pain conditions, is involved in the modulation of both emotion and executive function and displays functional lateralization. To test whether the PFC is involved in the lateralization bias associated with left/right pain, c-fos expression in medial and orbital areas was analyzed in rats with an unilateral spared nerve injury neuropathy installed in the left or in the right side after performing an attentional set-shifting, a strongly PFC-dependent task.
RESULTS:
SNI-R animals required more trials to successfully terminate the reversal steps of the attentional set-shifting task. A generalized increase of c-fos density in medial and orbital PFC (mPFC/OFC), irrespectively of the hemisphere, was observed in both SNI-L and SNI-R. However, individual laterality indexes revealed that contrary to controls and SNI-L, SNI-R animals presented a leftward shift in c-fos density in the ventral OFC (VO). None of these effects were observed in the neighboring primary motor area.
CONCLUSIONS:
Our results demonstrate that chronic neuropathic pain is associated with a bilateral mPFC and OFC hyperactivation. We hypothesize that the impaired performance of SNI-R animals is associated with a left/right activity inversion in the VO, whose functional integrity is critical for reversal learning.This work was granted by the Portuguese Science Foundation (FCT) project PTDC/SAU-NEU/108557/2008 and grant SFRH/BPD/80118/2011
An Earth-Mass Planet In A Time Of Covid-19: Kmt-2020-Blg-0414Lb
We report the discovery of KMT-2020-BLG-0414Lb, with a planet-to-host mass ratio q (2) = 0.9-1.2 x 10(-5) = 3-4 circle plus at 1 sigma, which is the lowest mass-ratio microlensing planet to date. Together with two other recent discoveries (4 less than or similar to q/q (circle plus) less than or similar to 6), it fills out the previous empty sector at the bottom of the triangular (log s, log q) diagram, where s is the planet-host separation in units of the angular Einstein radius theta E. Hence, these discoveries call into question the existence, or at least the strength, of the break in the mass-ratio function that was previously suggested to account for the paucity of very low-q planets. Due to the extreme magnification of the event, A (max) similar to 1450 for the underlying single-lens event, its light curve revealed a second companion with q (3) similar to 0.05 and |log s (3)| similar to 1, i.e., a factor similar to 10 closer to or farther from the host in projection. The measurements of the microlens parallax pi (E) and the angular Einstein radius theta E allow estimates of the host, planet and second companion masses, (M (1), M (2), M (3)) similar to (0.3 M (circle dot), 1.0 M (circle plus), 17 M-J ), the planet and second companion projected separations, (a (perpendicular to,2), a (perpendicular to,3)) similar to (1.5, 0.15 or 15) au, and system distance D (L) similar to 1 kpc. The lens could account for most or all of the blended light (I similar to 19.3) and so can be studied immediately with high-resolution photometric and spectroscopic observations that can further clarify the nature of the system. The planet was found as part of a new program of high-cadence follow-up observations of high-magnification events. The detection of this planet, despite the considerable difficulties imposed by COVID-19 (two KMT sites and OGLE were shut down), illustrates the potential utility of this program
Self-healing and injectable hydrogel for matching skin flap regeneration
The fabrication of highly biocompatible hydrogels with multiple unique healing abilities for the whole healing process, for example, multifunctional hydrogels with injectable, degradation, antibacterial, antihypoxic, and wound healingâpromoting properties that match the dynamic healing process of skin flap regeneration, is currently a research challenge. Here, a multifunctional and dynamic coordinative polyethylene glycol (PEG) hydrogel with mangiferin liposomes (MFâLip@PEG) is developed for clinical applications through AgâS coordination of fourâarmâPEGâSH and Ag+. Compared to MFâPEG, MFâLip@PEG exhibits selfâhealing properties, lower swelling percentages, and a longer endurance period. Moreover, the hydrogel exhibits excellent drug dispersibility and release characteristics for slow and persistent drug delivery. In vitro studies show that the hydrogel is biocompatible and nontoxic to cells, and exerts an outstanding neovascularizationâpromoting effect. The MFâLip@PEG also exhibits a strong cytoprotective effect against hypoxiaâinduced apoptosis through regulation of the Bax/Bclâ2/caspaseâ3 pathway. In a random skin flap animal model, the MFâLip@PEG is injectable and convenient to deliver into the skin flap, providing excellent antiâinflammation, antiâinfection, and proneovascularization effects and significantly reducing the skin flap necrosis rate. In general, the MFâLip@PEG possesses outstanding multifunctionality for the dynamic healing process of skin flap regeneration.Peer reviewe
Correction Self-Healing and Injectable Hydrogel for Matching Skin Flap Regeneration
Several images in Figure 3, Figure 4, and Figure S7, Supporting Information, accidentally presented duplicate samples in the original article. The correct figures are presented below. The authors apologize for any inconvenience this may have caused.Peer reviewe
Gene-by-Environment Interaction in Non-Alcoholic Fatty Liver Disease and Depression: The Role of Hepatic Transaminases
Non-alcoholic fatty liver disease (NAFLD) encompasses a range of liver conditions, from benign fatty accumulation to severe fibrosis. The global prevalence of NAFLD has risen to 25-30%, with variations across ethnic groups. NAFLD may advance to hepatocellular carcinoma, increases cardiovascular risk, is associated with chronic kidney disease, and is an independent metabolic disease risk factor. Assessment methods for liver health include liver biopsy, magnetic resonance imaging, ultrasound, and vibration-controlled transient elastography (VCTE by FibroScan). Hepatic transaminases are cost-effective and minimally invasive liver health assessment methods options.
This study focuses on the interaction between genetic factors underlying the traits (hepatic transaminases and the FibroScan results) on the one hand and the environment (depression) on the other. We examined 525 individuals at risk for metabolic disorders. We utilized variance components models and likelihood-based statistical inference to examine potential GxE interactions in markers of NAFLD, including aspartate aminotransferase (AST), alanine aminotransferase (ALT), and the AST/ALT ratio, and Vibration-Controlled Transient Elastography (VCTE by FibroScan). We calculated the Fibroscan-AST (FAST) score (a score that identifies the risk of progressive non-alcoholic steatohepatitis (NASH) and screened for depression using the Beck Depression Inventory-II (BDI-II). We identified significant G x E interactions for AST/ALT ratio x BDI-II, but not AST, ALT, or the FAST score. Our findings support that genetic factors play a role in hepatic transaminases, especially the AST/ALT ratio, with depression influencing this relationship. These insights contribute to understanding the complex interplay of genetics, environment, and liver health, potentially guiding future personalized interventions
Symmetry breaking in crossed magnetic and electric fields
We present the first observations of cylindrical symmetry breaking in highly
excited diamagnetic hydrogen with a small crossed electric field, and we give a
semiclassical interpretation of this effect. As the small perpendicular
electric field is added, the recurrence strengths of closed orbits decrease
smoothly to a minimum, and revive again. This phenomenon, caused by
interference among the electron waves that return to the nucleus, can be
computed from the azimuthal dependence of the classical closed orbits.Comment: 4 page REVTeX file including 5 postscript files (using psfig)
Accepted for publication in Physical Review Letters. Difference from earlier
preprint: we have discovered the cause of the earlier apparent discrepancy
between experiment and theory and now achieve excellent agreemen
Genotype-by-socioeconomic status interaction influences heart disease risk scores and carotid artery thickness in Mexican Americans: the predominant role of education in comparison to household income and socioeconomic index
Background: Socioeconomic status (SES) is a potent environmental determinant of health. To our knowledge, no assessment of genotype-environment interaction has been conducted to consider the joint effects of socioeconomic status and genetics on risk for cardiovascular disease (CVD). We analyzed Mexican American Family Studies (MAFS) data to evaluate the hypothesis that genotype-by-environment interaction (GxE) is an important determinant of variation in CVD risk factors.
Methods: We employed a linear mixed model to investigate GxE in Mexican American extended families. We studied two proxies for CVD [Pooled Cohort Equation Risk Scores/Framingham Risk Scores (FRS/PCRS) and carotid artery intima-media thickness (CA-IMT)] in relation to socioeconomic status as determined by Duncanâs Socioeconomic Index (SEI), years of education, and household income.
Results: We calculated heritability for FRS/PCRS and carotid artery intima-media thickness. There was evidence of GxE due to additive genetic variance heterogeneity and genetic correlation for FRS, PCRS, and CA-IMT measures for education (environment) but not for household income or SEI.
Conclusion: The genetic effects underlying CVD are dynamically modulated at the lower end of the SES spectrum. There is a significant change in the genetic architecture underlying the major components of CVD in response to changes in education
Galaxy evolution from strong lensing statistics: the differential evolution of the velocity dispersion function in concord with the LambdaCDM paradigm
We study galaxy evolution from z=1 to z=0 as a function of velocity
dispersion sigma for galaxies with sigma > 95 km/s based on the measured and
Monte Carlo realised local velocity dispersion functions (VDFs) of galaxies and
the revised statistical properties of 30 strongly-lensed sources. We assume
that the total (luminous plus dark) mass profile of a galaxy is isothermal in
the optical region for 0 < z < 1 as suggested by mass modelling of lensing
galaxies. For the evolutionary behaviours of the VDFs we find that: (1) the
number density of massive (mostly early-type) galaxies with sigma > 200 km/s
evolves differentially in the way that the number density evolution is greater
at a higher velocity dispersion; (2) the number density of intermediate and low
mass early-type galaxies (95 km/s < sigma < 200 km/s) is nearly constant; (3)
the late-type VDF transformed from the Monte Carlo realised circular velocity
function is consistent with no evolution in its shape or integrated number
density consistent with galaxy survey results. These evolutionary behaviours of
the VDFs are strikingly similar to those of the dark halo mass function (DMF)
from N-body simulations and the stellar mass function (SMF) predicted by recent
semi-analytic models of galaxy formation under the current LambdaCDM
hierarchical structure formation paradigm. Interestingly, the VDF evolutions
appear to be qualitatively different from ``stellar mass-downsizing''
evolutions obtained by many galaxy surveys. The coevolution of the DMF, the VDF
and the SMF is investigated in quantitative detail in a following paper. We
consider several possible systematic errors for the lensing analysis and find
that they are not likely to alter the conclusions.(abridged)Comment: MNRAS, accepted (20 pages, 12 figures), parts of section 6 of v2
moved to a following wor
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