Class I Gap-formation in Highly-viscous Glass-ionomer Restorations: Delayed vs Immediate Polishing

This in vitro study evaluated the effects of delayed versus immediate polishing to permit maturation of interfacial gap-formation around highly viscous conventional glass-ionomer cement (HV-GIC) in Class I restorations, together with determining the associated mechanical properties. Cavity preparations were made on the occlusal surfaces of premolars. Three HV-GICs (Fuji IX GP, GlasIonomer FX-II and Ketac Molar) and one conventional glass-ionomer cement (C-GIC, Fuji II, as a control) were studied, with specimen subgroups (n=10) for each property measured. After polishing, either immediately (six minutes) after setting or after 24 hours storage, the restored teeth were sectioned in a mesiodistal direction through the center of the model Class I restorations. The presence or absence of interfacial-gaps was measured at 1000× magnification at 14 points (each 0.5-mm apart) along the cavity restoration interface (n=10; total points measured per group = 140). Marginal gaps were similarly measured in Teflon molds as swelling data, together with shear-bond-strength to enamel and dentin, flexural strength and moduli. For three HV-GICs and one C-GIC, significant differences (p<0.05) in gap-incidence were observed between polishing immediately and after one-day storage. In the former case, 80–100 gaps were found. In the latter case, only 9–21 gaps were observed. For all materials, their shear-bond-strengths, flexural strength and moduli increased significantly after 24-hour storage.</p

Periodic billiard trajectories and Morse theory on loop spaces

We study periodic billiard trajectories on a compact Riemannian manifold with boundary, by applying Morse theory to Lagrangian action functionals on the loop space of the manifold. Based on the approximation method due to Benci-Giannoni, we prove that nonvanishing of relative homology of a certain pair of loop spaces implies the existence of a periodic billiard trajectory. We also prove a parallel result for path spaces. We apply those results to show the existence of short billiard trajectories and short geodesic loops. We also recover two known results on the length of a shortest periodic billiard trajectory on a convex body: Ghomi's inequality, and Brunn-Minkowski type inequality due to Artstein-Ostrover.Comment: 26 page

Handle attaching in wrapped Floer homology and brake orbits in classical Hamiltonian systems

The objective of this note is to prove an existence result for brake orbits in classical Hamiltonian systems (which was first proved by S.V.Bolotin) by using Floer theory. To this end, we compute an open string analogue of symplectic homology (so called wrapped Floer homology) of some domains in cotangent bundles, which appear naturally in the study of classical Hamiltonian systems. The main part of the computations is to show invariance of wrapped Floer homology under certain handle attaching to domains.Comment: 31 pages, close to the published versio

Symplectic homology of disc cotangent bundles of domains in Euclidean space

Let $V$ be a bounded domain with smooth boundary in $\R^n$, and $D^*V$ denote its disc cotangent bundle. We compute symplectic homology of $D^*V$, in terms of relative homology of loop spaces on the closure of $V$. We use this result to show that Floer-Hofer capacity of $D^*V$ is between $2r(V)$ and $2(n+1)r(V)$, where $r(V)$ denotes inradius of $V$. As an application, we study periodic billiard trajectories on $V$.Comment: minor changes reflecting referee comment

Class I Gap-formation in Highly-viscous Glass-ionomer Restorations: Delayed vs Immediate Polishing

This in vitro study evaluated the effects of delayed versus immediate polishing to permit maturation of interfacial gap-formation around highly viscous conventional glass-ionomer cement (HV-GIC) in Class I restorations, together with determining the associated mechanical properties. Cavity preparations were made on the occlusal surfaces of premolars. Three HV-GICs (Fuji IX GP, GlasIonomer FX-II and Ketac Molar) and one conventional glass-ionomer cement (C-GIC, Fuji II, as a control) were studied, with specimen subgroups (n=10) for each property measured. After polishing, either immediately (six minutes) after setting or after 24 hours storage, the restored teeth were sectioned in a mesiodistal direction through the center of the model Class I restorations. The presence or absence of interfacial-gaps was measured at 1000× magnification at 14 points (each 0.5-mm apart) along the cavity restoration interface (n=10; total points measured per group = 140). Marginal gaps were similarly measured in Teflon molds as swelling data, together with shear-bond-strength to enamel and dentin, flexural strength and moduli. For three HV-GICs and one C-GIC, significant differences (p<0.05) in gap-incidence were observed between polishing immediately and after one-day storage. In the former case, 80–100 gaps were found. In the latter case, only 9–21 gaps were observed. For all materials, their shear-bond-strengths, flexural strength and moduli increased significantly after 24-hour storage.</p

Enhancing Jewish Learning & Engagement in Preschool Life: Documenting the JRS Model

The Jewish Resource Specialist (JRS) Initiative, designed in 2008 by the Early Childhood Education Initiative (ECEI) of the Jewish Community Federation of San Francisco, the Peninsula, Marin and Sonoma Counties (the Federation), in partnership with the Jim Joseph Foundation, positions the early childhood years as a gateway into Jewish life for children and their families. It is a response to several catalyzing factors. First, preschool is a critical time for young families. Children are eager to learn and are developing socially, emotionally, cognitively and spiritually. For parents, at no other moment will they be so involved in their children's schooling. They are also choosing how they spend their time and with whom they spend it. The JRS Initiative came about to leverage this unique time for families.Second, the JRS Initiative also addresses the dearth of leaders working to build the field of Jewish early childhood education (ECE). Those who want to focus on Jewish ECE and build communities of engaged Jewish families with preschool-aged children are challenged to find the support, mentors and professional development opportunities they need to craft a career path. The JRS Initiative seeks to meet these field-wide demands by developing the skills and Jewish knowledge of the JRS educators who then bring ideas and guidance to their schools