Geometric erogdicity of a bead-spring pair with stochastic Stokes forcing

We consider a simple model for the uctuating hydrodynamics of a exible polymer in dilute solution, demonstrating geometric ergodicity for a pair of particles that interact with each other through a nonlinear spring potential while being advected by a stochastic Stokes uid velocity field. This is a generalization of previous models which have used linear spring forces as well as white-in-time uid velocity fields. We follow previous work combining control theoretic arguments, Lyapunov functions, and hypo-elliptic diffusion theory to prove exponential convergence via a Harris chain argument. To this, we add the possibility of excluding certain "bad" sets in phase space in which the assumptions are violated but from which the systems leaves with a controllable probability. This allows for the treatment of singular drifts, such as those derived from the Lennard-Jones potential, which is an novel feature of this work

Geometric ergodicity of a bead-spring pair with stochastic Stokes forcing

We consider a simple model for the fluctuating hydrodynamics of a flexible polymer in dilute solution, demonstrating geometric ergodicity for a pair of particles that interact with each other through a nonlinear spring potential while being advected by a stochastic Stokes fluid velocity field. This is a generalization of previous models which have used linear spring forces as well as white-in-time fluid velocity fields. We follow previous work combining control theoretic arguments, Lyapunov functions, and hypo-elliptic diffusion theory to prove exponential convergence via a Harris chain argument. In addition we allow the possibility of excluding certain "bad" sets in phase space in which the assumptions are violated but from which the system leaves with a controllable probability. This allows for the treatment of singular drifts, such as those derived from the Lennard-Jones potential, which is a novel feature of this work.Comment: A number of corrections and improvements. We thank the careful referee for useful suggestions and correction

Maximum Likelihood Estimation for Single Particle, Passive Microrheology Data with Drift

Volume limitations and low yield thresholds of biological fluids have led to widespread use of passive microparticle rheology. The mean-squared-displacement (MSD) statistics of bead position time series (bead paths) are either applied directly to determine the creep compliance [Xu et al (1998)] or transformed to determine dynamic storage and loss moduli [Mason & Weitz (1995)]. A prevalent hurdle arises when there is a non-diffusive experimental drift in the data. Commensurate with the magnitude of drift relative to diffusive mobility, quantified by a P\'eclet number, the MSD statistics are distorted, and thus the path data must be "corrected" for drift. The standard approach is to estimate and subtract the drift from particle paths, and then calculate MSD statistics. We present an alternative, parametric approach using maximum likelihood estimation that simultaneously fits drift and diffusive model parameters from the path data; the MSD statistics (and consequently the compliance and dynamic moduli) then follow directly from the best-fit model. We illustrate and compare both methods on simulated path data over a range of P\'eclet numbers, where exact answers are known. We choose fractional Brownian motion as the numerical model because it affords tunable, sub-diffusive MSD statistics consistent with typical 30 second long, experimental observations of microbeads in several biological fluids. Finally, we apply and compare both methods on data from human bronchial epithelial cell culture mucus.Comment: 29 pages, 12 figure

Applications of Fluorescent Quantum Dots for Reproductive Medicine and Disease Detection

Understanding the mechanisms associated with fertility and disease management in animals remains challenging. Continuing advances in nanotechnology provide new tools and alternative approaches for the investigation of these mechanisms. Fluorescent quantum dot nanoparticles, for example, have unique physicochemical properties, which allow for in vivo and in vitro imaging in various areas of life sciences. Traditional quantum dots contain heavy metal semiconductor cores, which have raised concern over their potential for toxicity. The majority of available quantum dots today prevent heavy metal release with additional chemical and polymer layers for safe water solubility. In this chapter, the most widely used quantum dots made of cadmium selenide, which possess great potential for real-time imaging in disease detection and reproductive medicine, are discussed

Unique cellular organization in the oldest root meristem

Roots and shoots of plant bodies develop from meristems—cell populations that self-renew and produce cells that undergo differentiation—located at the apices of axes [1].The oldest preserved root apices in which cellular anatomy can be imaged are found in nodules of permineralized fossil soils called coal balls [2], which formed in the Carboniferous coal swamp forests over 300 million years ago [3, 4, 5, 6, 7, 8 and 9]. However, no fossil root apices described to date were actively growing at the time of preservation [3, 4, 5, 6, 7, 8, 9 and 10]. Because the cellular organization of meristems changes when root growth stops, it has been impossible to compare cellular dynamics as stem cells transition to differentiated cells in extinct and extant taxa [11]. We predicted that meristems of actively growing roots would be preserved in coal balls. Here we report the discovery of the first fossilized remains of an actively growing root meristem from permineralized Carboniferous soil with detail of the stem cells and differentiating cells preserved. The cellular organization of the meristem is unique. The position of the Körper-Kappe boundary, discrete root cap, and presence of many anticlinal cell divisions within a broad promeristem distinguish it from all other known root meristems. This discovery is important because it demonstrates that the same general cellular dynamics are conserved between the oldest extinct and extant root meristems. However, its unique cellular organization demonstrates that extant root meristem organization and development represents only a subset of the diversity that has existed since roots first evolved.</p

Pharmacological and combined interventions to reduce vaccine injection pain in children and adults systematic review and meta-analysis

Background: This systematic review assessed the effectiveness and safety of pharmacotherapy and combined interventions for reducing vaccine injection pain in individuals across the lifespan. Design/Methods: Electronic databases were searched for relevant randomized and quasi-randomized controlled trials. Self-reported pain and fear as well as observer-rated distress were critically important outcomes. Data were combined using standardized mean difference (SMD) or relative risk with 95% confidence intervals (CI). Results: Fifty-five studies that examined breastfeeding (which combines sweet-tasting solution, holding, and sucking), topical anesthetics, sweet-tasting solutions (sucrose, glucose), vapocoolants, oral analgesics, and combination of 2 versus 1 intervention were included. The following results report findings of analyses of critical outcomes with the largest number of participants. Compared with control, acute distress was lower for infants breastfed: (1) during vaccination (n=792): SMD -1.78 (CI, -2.35, -1.22) and (2) before vaccination (n=100): SMD -1.43 (CI, -2.14, -0.72). Compared with control/placebo, topical anesthetics showed benefit on acute distress in children (n=1424): SMD -0.91 (CI, -1.36, -0.47) and self-reported pain in adults (n=60): SMD -0.85 (CI, -1.38, -0.32). Acute and recovery distress was lower for children who received sucrose (n=2071): SMD -0.76 (CI, -1.19, -0.34) or glucose (n=818): SMD -0.69 (CI, -1.03, -0.35) compared with placebo/no treatment. Vapocoolants reduced acute pain in adults [(n=185), SMD -0.78 (CI, -1.08, -0.48)] but not children. Evidence from other needle procedures showed no benefit of acetaminophen or ibuprofen. The administration of topical anesthetics before and breastfeeding during vaccine injections showed mixed results when compared with topical anesthetics alone. There were no additive benefits of combining glucose and non-nutritive sucking (pacifier) compared with glucose or non-nutritive sucking (pacifier) alone or breastfeeding and sucrose compared with breastfeeding or sucrose alone. Conclusions: Breastfeeding, topical anesthetics, sweet-tasting solutions, and combination of topical anesthetics and breastfeeding demonstrated evidence of benefit for reducing vaccine injection pain in infants and children. In adults, limited data demonstrate some benefit of topical anesthetics and vapocoolants

COVID-19 and venous thromboembolism: A narrative review

COVID-19 (severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2]) is associated with coagulopathy through numerous mechanisms. The reported incidence of venous thromboembolism (VTE) in hospitalized patients with COVID-19 has varied widely, and several meta-analyses have been performed to assess the overall prevalence of VTE. The novelty of this coronavirus strain along with its unique mechanisms for microvascular and macrovascular thrombosis has led to uncertainty as to how to diagnose, prevent, and treat thrombosis in patients affected by this virus. This review discusses the epidemiology and pathophysiology of thrombosis in the setting of SARS-CoV-2 infection along with an updated review on the preventative and treatment strategies for VTE associated with SARS-CoV-2 infection