2,286 research outputs found
Energy Levels of "Hydrogen Atom" in Discrete Time Dynamics
We analyze dynamical consequences of a conjecture that there exists a
fundamental (indivisible) quant of time. In particular we study the problem of
discrete energy levels of hydrogen atom. We are able to reconstruct potential
which in discrete time formalism leads to energy levels of unperturbed hydrogen
atom. We also consider linear energy levels of quantum harmonic oscillator and
show how they are produced in the discrete time formalism. More generally, we
show that in discrete time formalism finite motion in central potential leads
to discrete energy spectrum, the property which is common for quantum
mechanical theory. Thus deterministic (but discrete time!) dynamics is
compatible with discrete energy levels.Comment: accepted for publication in Open Systems & Information Dynamic
The Rainbow Scale for the Assessment of the Cervicomental Angle:A Validated Scale
Background: Aging of the neck results in an increased cervicomental angle, which can be treated by various surgical and nonsurgical procedures. To measure the success of these procedures, standardized validated objective photographic measurement tools are needed. However, no online standardized photographic measurement tools exist for the assessment of the cervicomental angle. Objectives: The purpose of this study was to establish a validated and reliable measurement tool for the assessment of the cervicomental angle based on the Rainbow Scale. Methods: A 5-point photographic rating scale was developed and created from 1 photograph with Adobe Photoshop. Fifteen reference photographs of women, 3 photographs per grade, were included for validation. Seven panelists (ie, plastic and maxillofacial surgeons) assessed the reference photographs 3 times with a minimal interval of 3 days in an online survey. Intra- and inter-observer agreements were calculated utilizing the weighted kappa coefficient. Results: Mean intra-observer agreement was 0.93 (0.78-1.00). Mean interobserver agreement was 0.796 (0.574-0.961) for survey 1, 0.868 (0.690-0.960) for survey 2, and 0.820 (0.676-0.959) for survey 3. Conclusions: The Rainbow Scale for the assessment of the cervicomental angle has been validated in an online fashion. The scale is reproducible and reliable and requires no learning curve. Potential applications include objective assessment of neck treatment planning and surgical outcome
New Constraints on Neutrino Oscillations in Vacuum as a Possible Solution of the Solar Neutrino Problem
Two-neutrino oscillations in vacuum are studied as a possible solution of the
solar neutrino problem. New constraints on the parameter sn2, characterizing
the mixing of the electron neutrino with another active or sterile neutrino, as
well as on the mass--squared difference, dm2, of their massive neutrino
components, are derived using the latest results from the four solar neutrino
experiments. Oscillations into a sterile neutrino are ruled out at 99 % C.L. by
the observed mean event rates even if one includes the uncertainties of the
standard solar model predictions in the analysis.Comment: 10 pages + 3 figures attached as postscript files, IFP-480-UNC and
Ref. SISSA 177/93/EP (Updated Version which takes into account the latest
GALLEX results from 30 runs
A simple mathematical model of gradual Darwinian evolution: Emergence of a Gaussian trait distribution in adaptation along a fitness gradient
We consider a simple mathematical model of gradual Darwinian evolution in
continuous time and continuous trait space, due to intraspecific competition
for common resource in an asexually reproducing population in constant
environment, while far from evolutionary stable equilibrium. The model admits
exact analytical solution. In particular, Gaussian distribution of the trait
emerges from generic initial conditions.Comment: 21 pages, 2 figures, as accepted to J Math Biol 2013/03/1
Self-organized criticality in deterministic systems with disorder
Using the Bak-Sneppen model of biological evolution as our paradigm, we
investigate in which cases noise can be substituted with a deterministic signal
without destroying Self-Organized Criticality (SOC). If the deterministic
signal is chaotic the universality class is preserved; some non-universal
features, such as the threshold, depend on the time correlation of the signal.
We also show that, if the signal introduced is periodic, SOC is preserved but
in a different universality class, as long as the spectrum of frequencies is
broad enough.Comment: RevTex, 8 pages, 8 figure
Evolutionary trajectories in rugged fitness landscapes
We consider the evolutionary trajectories traced out by an infinite
population undergoing mutation-selection dynamics in static, uncorrelated
random fitness landscapes. Starting from the population that consists of a
single genotype, the most populated genotype \textit{jumps} from a local
fitness maximum to another and eventually reaches the global maximum. We use a
strong selection limit, which reduces the dynamics beyond the first time step
to the competition between independent mutant subpopulations, to study the
dynamics of this model and of a simpler one-dimensional model which ignores the
geometry of the sequence space. We find that the fit genotypes that appear
along a trajectory are a subset of suitably defined fitness \textit{records},
and exploit several results from the record theory for non-identically
distributed random variables. The genotypes that contribute to the trajectory
are those records that are not \textit{bypassed} by superior records arising
further away from the initial population. Several conjectures concerning the
statistics of bypassing are extracted from numerical simulations. In
particular, for the one-dimensional model, we propose a simple relation between
the bypassing probability and the dynamic exponent which describes the scaling
of the typical evolution time with genome size. The latter can be determined
exactly in terms of the extremal properties of the fitness distribution.Comment: Figures in color; minor revisions in tex
Reply:The Effects of Facial Lipografting on Skin Quality: A Systematic Review
BACKGROUND: Autologous lipografting for improvement of facial skin quality was first described by Coleman in 2006. The current dogma dictates that adipose tissue-derived stromal cells that reside in the stromal vascular fraction of lipograft contribute to skin rejuvenation (e.g., increased skin elasticity), a more homogenous skin color, and softening of skin texture. Nowadays, many studies have been reported on this "skin rejuvenation" effect of autologous fat grafting. This systematic review was undertaken to assess the efficacy of autologous lipografting on skin quality.METHODS: The MEDLINE, Embase, Cochrane Central, Web of Science, and Google Scholar databases were searched for studies evaluating the effect of autologous lipografting on facial skin quality (May 11, 2018). Outcomes of interest were skin texture, color, and elasticity in addition to histologic outcomes and number of complications.RESULTS: Nine studies were included, with 301 patients treated in total. No meta-analysis could be performed because of heterogeneity of the metrics and outcomes. Eight studies reported increased skin elasticity; improvement in skin texture; and a more homogeneous skin color after treatment with lipografting, cellular stromal vascular fraction, or nanofat. One study reported no increased skin elasticity after lipografting. Histologic improvement was seen after lipografting and adipose tissue-derived stromal cell injections. However, in general, the level of evidence of the included studies was low. No serious complications were reported.CONCLUSION: Autologous facial lipografting and cellular stromal vascular fraction and adipose tissue-derived stromal cell injections hardly seem to improve facial skin quality but can be considered a safe procedure.</p
Common Origin for the Solar and Atmospheric Neutrino Deficits
Some typos corrected, slightly different abstract, same plots, results and
conclusions.Comment: 14 Latex pages, 3 figures attached as postscript files, IFP-472-UNC,
PRL-TH-93/1
Potential economic impacts from improving breastfeeding rates in the UK
This article has been made available through the Brunel Open Access Publishing Fund.RATIONALE: Studies suggest that increased breastfeeding rates can provide substantial financial savings, but the scale of such savings in the UK is not known. OBJECTIVE: To calculate potential cost savings attributable to increases in breastfeeding rates from the National Health Service perspective. DESIGN AND SETTINGS: Cost savings focussed on where evidence of health benefit is strongest: reductions in gastrointestinal and lower respiratory tract infections, acute otitis media in infants, necrotising enterocolitis in preterm babies and breast cancer (BC) in women. Savings were estimated using a seven-step framework in which an incidence-based disease model determined the number of cases that could have been avoided if breastfeeding rates were increased. Point estimates of cost savings were subject to a deterministic sensitivity analysis. RESULTS: Treating the four acute diseases in children costs the UK at least £89 million annually. The 2009-2010 value of lifetime costs of treating maternal BC is estimated at £959 million. Supporting mothers who are exclusively breast feeding at 1 week to continue breast feeding until 4 months can be expected to reduce the incidence of three childhood infectious diseases and save at least £11 million annually. Doubling the proportion of mothers currently breast feeding for 7-18 months in their lifetime is likely to reduce the incidence of maternal BC and save at least £31 million at 2009-2010 value. CONCLUSIONS: The economic impact of low breastfeeding rates is substantial. Investing in services that support women who want to breast feed for longer is potentially cost saving
A Common Explanation for the Atmospheric, Solar-Neutrino and Double Beta Decay Anomalies
We make a number of small changes, including correcting an error in our
heavy-neutrino decay rate. None of our analysis is changed, either in substance
or detail.Comment: 25 pages, 6 Figures, McGill-93/1
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