Scaling in Fracture and Refreezing of Sea Ice

Sea ice breaks up and regenerates rapidly during winter conditions in the Arctic. Analyzing satellite data from the Kara Sea, we find that the average ice floe size depends on weather conditions. Nevertheless, the frequency of floes of size $A$ is a power law, $N\sim A^{-\tau}$, where $\tau=1.6\pm 0.2$, for $A$ less than approximately 100 $km^2$. This scale-invariant behaviour suggests a competition between fracture due to strains in the ice field and refreezing of the fractures. A cellular model for this process gives results consistent with observations.Comment: Physica A (in press

The fractal micro mechanics of normal compression

The fundamental fractal micro mechanics of normal compression of granular materials is studied using DEM. This paper examines the emergence of a finite fractal bounded by two particle sizes as stress increases, and the evolution of various definitions of the ‘smallest particles’. It is revealed that if particles are categorised according to their coordination number, then the volume of all particles with 4 contacts or fewer is directly proportional to the void space. These particles are called ‘critical particles’ and are shown, for the first time, to explain quantitatively the voids reduction with increasing vertical stress

Transition from damage to fragmentation in collision of solids

We investigate fracture and fragmentation of solids due to impact at low energies using a two-dimensional dynamical model of granular solids. Simulating collisions of two solid discs we show that, depending on the initial energy, the outcome of a collision process can be classified into two states: a damaged and a fragmented state with a sharp transition in between. We give numerical evidence that the transition point between the two states behaves as a critical point, and we discuss the possible mechanism of the transition.Comment: Revtex, 12 figures included. accepted by Phys. Rev.

Modeling complex word reading : Examining influences at the level of the word and child on mono-and polymorphemic word reading

Purpose The probability of a child reading a word correctly is influenced by both child skills and properties of the word. The purpose of this study was to investigate child-level skills (set for variability and vocabulary), word-level properties (concreteness), word structure (mono- vs polymorphemic), and interactions between these properties and word structure within a comprehensive item-level model of complex word reading. This study is unique in that it purposely sampled both mono- and polymorphemic polysyllabic words. Method A sample of African American (n = 69) and Hispanic (n = 6) students in grades 2–5 (n = 75) read a set of mono- and polymorphemic polysyllabic words (J = 54). Item-level responses were modeled using cross-classified generalized random-effects models allowing variance to be partitioned between child and word while controlling for other important child factors and word features. Results Set for variability and the interaction between concreteness and word structure (i.e., mono- vs polymorphemic) were significant predictors. Higher probabilities of reading poly- over monomorphemic words were identified at lower levels of concreteness with the opposite at higher levels of concreteness. Conclusions Results indicate important predictors at both the child- and word-level and support the importance of morphological structure for reading abstract polysyllabic words

Kingston Allergy Birth Cohort (KABC); Exposome Characteristics and Parentally- Reported Respiratory Outcomes to Age 2

Background: The Kingston Allergy Birth Cohort (KABC) is a prenatally-recruited cohort initiated to study the developmental origins of allergic disease. Kingston General Hospital was chosen for recruitment, as it serves a population with notable diversity in exposures relevant to the emerging concept of the exposome. Objective: Establish a profile of the KABC cohort using the exposome framework, and examine parentally-reported respiratory symptoms to age 2. Methods: Data on phase 1 of the cohort (n=560 deliveries) were compiled and multivariate Cox proportional hazard models were used to determine associations with respiratory symptoms. Results: The KABC exhibits diversity within the three exposome domains; “general external” (SES, rural/urban residency), “specific external” (cigarette smoke, breastfeeding, mold/dampness), and “internal” (respiratory health, gestational age). We demonstrate relationships between exposome domains, as residential locale and SES significantly affected characteristics of the home environment. Significant associations emerged between parental reports of wheeze/cough without a cold and exposures within all three domains, including SES, 70 breastfeeding, gestational age, prenatal cigarette smoke exposure, and mold/dampness. Conclusions: The KABC is a unique cohort with diversity that can be leveraged for exposomics- based studies, and a notably high prevalence of prenatal smoke exposure. This study demonstrated the impacts of all three domains of the exposome on the respiratory health of KABC children. Ongoing studies using phase 1 of the KABC are further exploring the internal exposome through allergy skin testing and epigenetic analyses, and the specific external domain through in-home environmental analyses, air pollution modeling and ultimately the potential convergence of the two.MLN; J.A. Stewart Award, Department of Medicine, Queen’s University, Ontario Ministry of Research & Innovation Award, and AllerGen N.C.E. Canadian Allergy and Immune Diseases Advanced Training Initiative (CAIDATI). The study was supported by an Ontario Thoracic Society & Canadian Lung Association Grant-in aid of Research, an Allergy/Asthma Information Association (AAIA) and Canadian Allergy, Asthma & Immunology Foundation (CAAIF) Award for Ontario Research in Food Allergy, and an American College of Allergy, Asthma & Immunology (ACAAI) Young Faculty Support Award