Oscillating Fracture in Rubber

We have found an oscillating instability of fast-running cracks in thin rubber sheets. A well-defined transition from straight to oscillating cracks occurs as the amount of biaxial strain increases. Measurements of the amplitude and wavelength of the oscillation near the onset of this instability indicate that the instability is a Hopf bifurcation

Effective Programs in Elementary Mathematics: A Meta-Analysis

This article reviews research on the achievement outcomes of elementary mathematics programs. 87 rigorous experimental studies evaluated 66 programs in grades K-5. Programs were organized in 6 categories. Particularly positive outcomes were found for tutoring programs (ES=+0.20, k=22). Positive outcomes were also seen in studies focused on professional development for classroom organization and management (e.g., cooperative learning) (ES=+0.19, k=7). Professional development approaches focused on helping teachers gain in understanding of mathematics content and pedagogy had little impact on student achievement. Professional development intended to help in the adoption of new curricula had a small but significant impact for traditional (non-digital) curricula (ES=+0.12, k=7), but not for digital curricula. Traditional and digital curricula with limited professional development, as well as benchmark assessment programs, found few positive effects

Modifiers of notch transcriptional activity identified by genome-wide RNAi

<p>Abstract</p> <p>Background</p> <p>The Notch signaling pathway regulates a diverse array of developmental processes, and aberrant Notch signaling can lead to diseases, including cancer. To obtain a more comprehensive understanding of the genetic network that integrates into Notch signaling, we performed a genome-wide RNAi screen in <it>Drosophila </it>cell culture to identify genes that modify Notch-dependent transcription.</p> <p>Results</p> <p>Employing complementary data analyses, we found 399 putative modifiers: 189 promoting and 210 antagonizing Notch activated transcription. These modifiers included several known Notch interactors, validating the robustness of the assay. Many novel modifiers were also identified, covering a range of cellular localizations from the extracellular matrix to the nucleus, as well as a large number of proteins with unknown function. Chromatin-modifying proteins represent a major class of genes identified, including histone deacetylase and demethylase complex components and other chromatin modifying, remodeling and replacement factors. A protein-protein interaction map of the Notch-dependent transcription modifiers revealed that a large number of the identified proteins interact physically with these core chromatin components.</p> <p>Conclusions</p> <p>The genome-wide RNAi screen identified many genes that can modulate Notch transcriptional output. A protein interaction map of the identified genes highlighted a network of chromatin-modifying enzymes and remodelers that regulate Notch transcription. Our results open new avenues to explore the mechanisms of Notch signal regulation and the integration of this pathway into diverse cellular processes.</p

Liver and Intestine Transplantation in the United States, 1996–2005

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72937/1/j.1600-6143.2007.01782.x.pd

Plant–pathogen interactions and elevated CO2: morphological changes in favour of pathogens

Crop losses caused by pests and weeds have been estimated at 42% worldwide, with plant pathogens responsible for almost $10 billion worth of damage in the USA in 1994 alone. Elevated carbon dioxide [ECO2] and associated climate change have the potential to accelerate plant pathogen evolution, which may, in turn, affect virulence. Plant–pathogen interactions under increasing CO2 concentrations have the potential to disrupt both agricultural and natural systems severely, yet the lack of experimental data and the subsequent ability to predict future outcomes constitutes a fundamental knowledge gap. Furthermore, nothing is known about the mechanistic bases of increasing pathogen agressiveness. In the absence of information on crop species, it is shown here that plant pathogen (Erysiphe cichoracearum) aggressiveness is increased under ECO2, together with changes in the leaf epidermal characteristics of the model plant Arabidopsis thaliana L. Stomatal density, guard cell length, and trichome numbers on leaves developing post-infection are increased under ECO2 in direct contrast to non-infected responses. As many plant pathogens utilize epidermal features for successful infection, these responses provide a positive feedback mechanism facilitating an enhanced susceptibility of newly developed leaves to further pathogen attack. Furthermore, a screen of resistant and susceptible ecotypes suggest inherent differences in epidermal responses to ECO2

Evolution of FLRW spacetime after the birth of a cosmic string

We consider the evolution of an initially FLRW universe after the formation of a long, straight, cosmic string with arbitrary tension and mass per unit length. The birth of the string sources scalar and tensor-type perturbations in the background metric and both density and velocity perturbations in the background fluid, which compensate for the string mass and maintain energy conservation. The former generate the deficit angle within the light cone of the string and a gravitational shock front at the cosmological horizon, whereas the latter are confined within the sound cone. We study the properties of the metric within each region of the resulting spacetime and give the explicit coordinate transformations which demonstrate non-violation of causality. This paper generalizes the work of previous studies for the Nambu-Goto string.Comment: 16 pages, 2 figures, published versio

Hydrographic observations from the US/PRC Cooperative Program in the Western Equatorial Pacific Ocean, cruises 5-8

In support of the Tropical Ocean and Global Atmosphere (TOGA) program, investigators from the Woods Hole Oceanographic Institution (WHOI), NOAA Pacific Marine Environmental Laboratory (PMEL), and the State Oceanic Administration (SOA) from both Qingdao (First Institute) and Guangzhou (South China Sea Branch) conducted hydrographic observations aboard the Chinese R/V Xiang Yang Hong 14 in the western equatorial Pacific Ocean. The objective of this component of the TOGA program was to document the water mass property distributions of the western equatorial Pacific and describe the oceanic velocity field. The four cruises summarized here were conducted during the period November 1988 to July 1990 and are the final half of an eight cruise repeated survey of the region begun in 1985. Conductivity-Temperature-Depth-Oxygen (CTD/O2) stations were collected to a minimum cast depth of 2500m or the bottom when shallower. The cruises reoccupied the same stations to provide temporal information. Summarized listings of CTD/02 data together with selected physical properties of sea water for these cruises are provided here, as well as a description of the hardware used and an explanation of the data reduction techniques employed.Funding was provided by the National Oceanic and Atmospheric Administration under Grant No. NA85AA-D-AC117

Molecular Structure and Dimeric Organization of the Notch Extracellular Domain as Revealed by Electron Microscopy

Background: The Notch receptor links cell fate decisions of one cell to that of the immediate cellular neighbor. In humans, malfunction of Notch signaling results in diseases and congenital disorders. Structural information is essential for gaining insight into the mechanism of the receptor as well as for potentially interfering with its function for therapeutic purposes. Methodology/Principal Findings: We used the Affinity Grid approach to prepare specimens of the Notch extracellular domain (NECD) of the Drosophila Notch and human Notch1 receptors suitable for analysis by electron microscopy and three-dimensional (3D) image reconstruction. The resulting 3D density maps reveal that the NECD structure is conserved across species. We show that the NECD forms a dimer and adopts different yet defined conformations, and we identify the membrane-proximal region of the receptor and its ligand-binding site. Conclusions/Significance: Our results provide direct and unambiguous evidence that the NECD forms a dimer. Our studies further show that the NECD adopts at least three distinct conformations that are likely related to different functional states of the receptor. These findings open the way to now correlate mutations in the NECD with its oligomeric state and conformation

Medical Students and Pandemic Influenza

To assess knowledge of pandemic influenza, we administered a questionnaire to all medical students at the University of Alberta; 354 (69%) of 510 students responded. Data from questionnaires such as this could help determine the role of medical students during a public health emergency

Polygenic mechanisms underpinning the response to exercise-induced muscle damage in humans:In vivo and in vitro evidence

We investigated whether 20 candidate single nucleotide polymorphisms (SNPs) were associated with in vivo exercise-induced muscle damage (EIMD), and with an in vitro skeletal muscle stem cell wound healing assay. Sixty-five young, untrained Caucasian adults performed 120 maximal eccentric knee-extensions on an isokinetic dynamometer to induce EIMD. Maximal voluntary isometric/isokinetic knee-extensor torque, knee joint range of motion (ROM), muscle soreness, serum creatine kinase activity and interleukin-6 concentration were assessed before, directly after and 48 h after EIMD. Muscle stem cells were cultured from vastus lateralis biopsies from a separate cohort (n = 12), and markers of repair were measured in vitro. Participants were genotyped for all 20 SNPs using real-time PCR. Seven SNPs were associated with the response to EIMD, and these were used to calculate a total genotype score, which enabled participants to be segregated into three polygenic groups: ‘preferential’ (more ‘protective’ alleles), ‘moderate’, and ‘non-preferential’. The non-preferential group was consistently weaker than the preferential group (1.93 ± 0.81 vs. 2.73 ± 0.59 N ∙ m/kg; P = 9.51 × 10−4) and demonstrated more muscle soreness (p = 0.011) and a larger decrease in knee joint ROM (p = 0.006) following EIMD. Two TTN-AS1 SNPs in linkage disequilibrium were associated with in vivo EIMD (rs3731749, p ≤ 0.005) and accelerated muscle stem cell migration into the artificial wound in vitro (rs1001238, p ≤ 0.006). Thus, we have identified a polygenic profile, linked with both muscle weakness and poorer recovery following EIMD. Moreover, we provide evidence for a novel TTN gene-cell-skeletal muscle mechanism that may help explain some of the interindividual variability in the response to EIMD.</p