Modelling of selection and mating decisions in tree breeding programs

Hardwood trees from the temperate forests of southern Australia are an important source of timber for high quality paper. Two species in particular, Eucalyptus globulus and Eucalyptus nitens are well suited to this purpose and are now widely grown in commercial plantations. These plantations have been established by professional tree breeders using seedlings derived originally from broadly based collection of seed in natural forests. To increase productivity it is desirable to select trees that grow quickly and give high yields of top quality timber. Nevertheless it is important to maintain genetic diversity in the breeding population and thereby retain a robust capacity to adapt to changing environmental factors. In this article we formulate a number of related mathematical models for the selection and mating processes and discuss the consequences of these models. We recommend a relatively simple scheme which can be implemented on an IBM compatible PC using standard algorithms

Parents' beliefs and knowledge about the management of acute otitis media: A qualitative study

BACKGROUND: Acute otitis media is a common reason for antibiotic prescribing, despite strong evidence that antibiotics provide minimal benefit. Studies have demonstrated that patients’ (or parents’) expectations of antibiotics often influence general practitioners’ (GPs) decision to prescribe antibiotics, but few have explored parents’ expectations of the management of infections in children, or which factors influence the development of these expectations. This study aimed to explore parents’ knowledge and beliefs about the management of acute otitis media in children. METHODS: Individual semi-structured interviews were conducted with 15 parents of children who had recently presented to their GP with acute otitis media. Parents were recruited at childcare centres or playgroups in Brisbane, Australia. RESULTS: Many parents did not have an accurate understanding of what causes acute otitis media. GPs were primarily consulted for the management of symptoms such as pain and fever. Others specifically wanted reassurance or were concerned about hearing loss. Most parents assumed that antibiotics were the best treatment option. Parents’ perceptions about the best treatment were mainly based on their previous experience and the advice of the GP. Pain relief medications, such as paracetamol and non-steroidal anti-inflammatory drugs, were not considered by parents to be sufficient treatment on their own. CONCLUSION: There is discrepancy between parents’ beliefs and expectations of management of acute otitis media and the evidence-based recommendations. This study provides insights into parents’ expectations of management of acute otitis media, which may help inform clinicians about perceptions and misperceptions that may be valuable to elicit and discuss

A PI3K-mediated negative feedback regulates Drosophila motor neuron excitability

Negative feedback can act as a homeostatic mechanism to maintain neuronal activity at a particular specified value. At the Drosophila neuromuscular junction, a mutation in the type II metabotropic glutamate receptor gene (mGluRA) increased motor neuron excitability by disrupting an autocrine, glutamate-mediated negative feedback. We show that mGluRA mutations increase neuronal excitability by preventing PI3 kinase (PI3K) activation and consequently hyperactivating the transcription factor Foxo. Furthermore, glutamate application increases levels of phospho-Akt, a product of PI3K signaling, within motor nerve terminals in an mGluRA-dependent manner. In humans, PI3K and type II mGluRs are implicated in epilepsy, neurofibromatosis, autism, schizophrenia and other neurological disorders; however, neither the link between type II mGluRs and PI3K, nor the role of Foxo in the control of neuronal excitability, had been previously reported. Our work suggests that some of the deficits in these neurological disorders might result from disruption of glutamate-mediated homeostasis of neuronal excitability

Best causal mathematical models for a nonlinear system

©2005 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.We provide new causal mathematical models of a nonlinear system S which are specifications of a nonlinear operator P/sub p/ of degree p=1,2,.... The operator P/sub p/ is determined from a special orthogonalization procedure and minimization of the mean squared difference between outputs of S and P/sub p/. As a result, these models have smallest possible associated errors in the class of such operators P/sub p/. The causality condition is implemented through the use of specific matrices called lower trapezoidal. The associated computational work is reduced by the use of the orthogonalization procedure. We provide a strict justification of the proposed approach including theorems on an explicit representatoin of the models' parameters, and theorems on the associated error representation. The possible extensions of the proposed approach and its potential applications are outlined.Anatoli Torokhti, Phil Howlett, and Charles Pearc

A philosophy for the modelling of realistic nonlinear systems

First published in Proceedings of the American Mathematical Society in volume 132, number 2, by the American Mathematical Society Copyright © 2003 American Mathematical SocietyA nonlinear dynamical system is modelled as a nonlinear mapping from a set of input signals into a corresponding set of output signals. Each signal is specified by a set of real number parameters, but such sets may be uncountably infinite. For numerical simulation of the system each signal must be represented by a finite parameter set and the mapping must be defined by a finite arithmetical process. Nevertheless the numerical simulation should be a good approximation to the mathematical model. We discuss the representation of realistic dynamical systems and establish a stable approximation theorem for numerical simulation of such systems.Phil Howlett, Anatoli Torokhti, Charles Pearc

Cannabinoid receptor interacting protein suppresses agonist-driven CB1 receptor internalization and regulates receptor replenishment in an agonist-biased manner

Cannabinoid receptor interacting protein 1a (CRIP1a) is a CB1 receptor (CB1R) distal C-terminus-associated protein that modulates CB1R signaling via G proteins, and CB1R down-regulation but not desensitization (Blume et al. [2015] Cell Signal., 27, 716-726; Smith et al. [2015] Mol. Pharmacol., 87, 747-765). In this study, we determined the involvement of CRIP1a in CB1R plasma membrane trafficking. To follow the effects of agonists and antagonists on cell surface CB(1)Rs, we utilized the genetically homogeneous cloned neuronal cell line N18TG2, which endogenously expresses both CB1R and CRIP1a, and exhibits a well-characterized endocannabinoid signaling system. We developed stable CRIP1a-over-expressing and CRIP1a-siRNA-silenced knockdown clones to investigate gene dose effects of CRIP1a on CB1R plasma membrane expression. Results indicate that CP55940 or WIN55212-2 (10 nM, 5 min) reduced cell surface CB1R by a dynamin-and clathrin-dependent process, and this was attenuated by CRIP1a over-expression. CP55940-mediated cell surface CB1R loss was followed by a cycloheximide-sensitive recovery of surface receptors (30120 min), suggesting the requirement for new protein synthesis. In contrast, WIN55212-2-mediated cell surface CB(1)Rs recovered only in CRIP1a knockdown cells. Changes in CRIP1a expression levels did not affect a transient rimonabant (10 nM)mediated increase in cell surface CB(1)Rs, which is postulated to be as a result of rimonabant effects on \u27non-agonist-driven\u27 internalization. These studies demonstrate a novel role for CRIP1a in agonist-driven CB1R cell surface regulation postulated to occur by two mechanisms: 1) attenuating internalization that is agonist-mediated, but not that in the absence of exogenous agonists, and 2) biased agonist-dependent trafficking of de novo synthesized receptor to the cell surface

Fall speed measurement and high-resolution multi-angle photography of hydrometeors in free fall

We describe here a new instrument for imaging hydrometeors in free fall. The Multi-Angle Snowflake Camera (MASC) captures high-resolution photographs of hydrometeors from three angles while simultaneously measuring their fall speed. Based on the stereoscopic photographs captured over the two months of continuous measurements obtained at a high altitude location within the Wasatch Front in Utah, we derive statistics for fall speed, hydrometeor size, shape, orientation and aspect ratio. From a selection of the photographed hydrometeors, an illustration is provided for how the instrument might be used for making improved microwave scattering calculations. Complex, aggregated snowflake shapes appear to be more strongly forward scattering, at the expense of reduced back-scatter, than heavily rimed graupel particles of similar size