Moving and staying together without a leader

A microscopic, stochastic, minimal model for collective and cohesive motion of identical self-propelled particles is introduced. Even though the particles interact strictly locally in a very noisy manner, we show that cohesion can be maintained, even in the zero-density limit of an arbitrarily large flock in an infinite space. The phase diagram spanned by the two main parameters of our model, which encode the tendencies for particles to align and to stay together, contains non-moving "gas", "liquid"' and "solid" phases separated from their moving counterparts by the onset of collective motion. The "gas/liquid" and "liquid/solid" are shown to be first-order phase transitions in all cases. In the cohesive phases, we study also the diffusive properties of individuals and their relation to the macroscopic motion and to the shape of the flock

Viral Causes of Respiratory Diseases in Swine

Respiratory disease is one of the most frequently encountered pathological conditions in swine. The history of respiratory conditions in swine is indeed mystifying. At one time it was presumed that the majority of chronic pneumonias were associated with a virus causing enzootic pneumonia or with lung worms. it now seems probable that there are many primary causal agents

Testing the Delivery of an Interactive Second Grade Nutrition Education Curriculum

Childhood obesity rates in the United States are alarming. Interventions incorporating nutrition education and physical activity are important for initiating behavior changes that may reduce the risk of childhood obesity and future health complications. The availability of nutrition curriculum for use in a second grade audience is limited. For this project, a nutrition education curriculum for second grade students was developed and tested over a two-week period in the fall of 2013. Six second grade classrooms (N=118) received four 20-minute interactive nutrition lessons. Lesson topics included: My Plate, Handy Portions, Sugar Shockers, and MyTray. Pre and post assessments of nutrition knowledge were used to determine the effectiveness of the nutrition education. Overall, there was an increase in the number of correct survey responses recorded following the nutrition education. By category, there were increases in the students’ ability to identify healthy snacks, grains, dairy products, and protein sources, but not fruits and vegetables. Further development and testing of innovative nutrition education curriculum for the second grade audience is an important step in establishing the knowledge to influence lifelong behavior changes that could reduce future risk of obesity

Identification and instruction of visual and auditory learners

Children have modality strengths through which they learn more efficiently. Certain characteristics and observations have been identified which allow instructors to distinguish between children whose modality strength is visual and those whose strength is auditory. Once a child is recognized as either a visual or auditory learner, appropriate instructional methods can be applied to improve learning

The Convertible Bond Announcement Effect - An Event Study on the Nordic Markets

The announcement effect of convertible bonds is a well-researched topic. However, there is no clear consensus whether the announcements of convertible bond issuance affect the stock price positively or negatively. Previous research shows that this effect differs between markets. As no previous research has been examining the Nordic markets, we find this to be of interest. The aim of this thesis is to examine if there is an announcement effect of convertible bond issues on the Nordic markets. To find if there is an announcement effect, we conduct an event study on 53 observations to obtain abnormal returns for several different event windows. Furthermore, we examine if the firm-specific variables; size of the issuing firm, leverage, market-to-book and the relative issue size are significantly affecting the abnormal returns. Based on the findings of the abnormal returns we find a negative significant announcement effect. The result is also in line with what the majority of studies finds in other European markets. Furthermore, we find leverage to have a positive effect and the relative issue size to have a negative effect on the abnormal returns

Geometric origin of mechanical properties of granular materials

Some remarkable generic properties, related to isostaticity and potential energy minimization, of equilibrium configurations of assemblies of rigid, frictionless grains are studied. Isostaticity -the uniqueness of the forces, once the list of contacts is known- is established in a quite general context, and the important distinction between isostatic problems under given external loads and isostatic (rigid) structures is presented. Complete rigidity is only guaranteed, on stability grounds, in the case of spherical cohesionless grains. Otherwise, the network of contacts might deform elastically in response to load increments, even though grains are rigid. This sets an uuper bound on the contact coordination number. The approximation of small displacements (ASD) allows to draw analogies with other model systems studied in statistical mechanics, such as minimum paths on a lattice. It also entails the uniqueness of the equilibrium state (the list of contacts itself is geometrically determined) for cohesionless grains, and thus the absence of plastic dissipation. Plasticity and hysteresis are due to the lack of such uniqueness and may stem, apart from intergranular friction, from small, but finite, rearrangements, in which the system jumps between two distinct potential energy minima, or from bounded tensile contact forces. The response to load increments is discussed. On the basis of past numerical studies, we argue that, if the ASD is valid, the macroscopic displacement field is the solution to an elliptic boundary value problem (akin to the Stokes problem).Comment: RevTex, 40 pages, 26 figures. Close to published paper. Misprints and minor errors correcte

Self-organized Vortex State in Two-dimensional Dictyostelium Dynamics

We present results of experiments on the dynamics of Dictyostelium discoideum in a novel set-up which constraints cell motion to a plane. After aggregation, the amoebae collect into round ''pancake" structures in which the cells rotate around the center of the pancake. This vortex state persists for many hours and we have explicitly verified that the motion is not due to rotating waves of cAMP. To provide an alternative mechanism for the self-organization of the Dictyostelium cells, we have developed a new model of the dynamics of self-propelled deformable objects. In this model, we show that cohesive energy between the cells, together with a coupling between the self-generated propulsive force and the cell's configuration produces a self-organized vortex state. The angular velocity profiles of the experiment and of the model are qualitatively similar. The mechanism for self-organization reported here can possibly explain similar vortex states in other biological systems.Comment: submitted to PRL; revised version dated 3/8/9

Adolescent Self-Organization and Adult Smoking and Drinking over Fifty Years of Follow-Up:The British 1946 Birth Cohort

Variations in markers of adolescent self-organization predict a range of economic and health-related outcomes in general population studies. Using a population-based birth cohort study we investigated associations between adolescent self-organization and two common factors over adulthood influencing health, smoking and alcohol consumption. The MRC National Survey of Health and Development (the British 1946 birth cohort) was used to test associations between a dimensional measure of adolescent self-organization derived from teacher ratings, and summary longitudinal measures of smoking and alcohol consumption over the ensuing five decades. Multinomial regression models were adjusted for sex, adolescent emotional and conduct problems, occupational social class of origin, childhood cognition, educational attainment and adult occupational social class. With all covariates adjusted, higher adolescent self-organization was associated with fewer smoking pack years, although not with quitting; there was no association with alcohol consumption across adulthood (none or heavy compared with light to moderate). Adolescent self-organization appears to be protective against smoking, but not against heavy alcohol consumption. Interpretation of this differential effect should be embedded in an understanding of the social and sociodemographic context in which these health behaviours occur over time

Effects of sulfate starvation on agar polysaccharides of Gracilaria species (Gracilariaceae, Rhodophyta) from Morib, Malaysia

The effects of sulfate starvation on the agar characteristics of Gracilaria species was investigated by culturing two red algae from Morib, Malaysia, Gracilaria changii and Gracilaria salicornia in sulfate-free artificial seawater for 5 days. The seaweed samples were collected in October 2012 and March 2013, periods which have significant variation in the amount of rainfall. The agar yields were shown to be independent of sulfate availability, with only 0.60–1.20 % increment in treated G. changii and 0.31–1.40 % increment in treated G. salicornia while their gel strengths did not increase significantly (approximately 5–7 %) after sulfate starvation for both species. The gelling and melting temperatures did not vary between control and treated samples from both species, except for the treated G. changii collected in March 2013. The gel syneresis index of G. salicornia collected in March 2013 increased significantly after sulfate deprivation. Sulfate starvation introduced some variations in the content of 3, 6-anhydrogalactose and total sulfate esters, but the changes did not have a pronounced effect on the physical properties of agar