Intrinsic Fluctuations and Driven Response of Insect Swarms

Animals of all sizes form groups, as acting together can convey advantages over acting alone; thus, collective animal behavior has been identified as a promising template for designing engineered systems. However, models and observations have focused predominantly on characterizing the overall group morphology, and often focus on highly ordered groups such as bird flocks. We instead study a disorganized aggregation (an insect mating swarm), and compare its natural fluctuations with the group-level response to an external stimulus. We quantify the swarm’s frequency-dependent linear response and its spectrum of intrinsic fluctuations, and show that the ratio of these two quantities has a simple scaling with frequency. Our results provide a new way of comparing models of collective behavior with experimental data

Carrier-controlled ferromagnetism in SrTiO3

Magnetotransport and superconducting properties are investigated for uniformly La-doped SrTiO3 films and GdTiO3/SrTiO3 heterostructures, respectively. GdTiO3/SrTiO3 interfaces exhibit a high-density two-dimensional electron gas on the SrTiO3-side of the interface, while for the SrTiO3 films carriers are provided by the dopant atoms. Both types of samples exhibit ferromagnetism at low temperatures, as evidenced by a hysteresis in the magnetoresistance. For the uniformly doped SrTiO3 films, the Curie temperature is found to increase with doping and to coexist with superconductivity for carrier concentrations on the high-density side of the superconducting dome. The Curie temperature of the GdTiO3/SrTiO3 heterostructures scales with the thickness of the SrTiO3 quantum well. The results are used to construct a stability diagram for the ferromagnetic and superconducting phases of SrTiO3.Comment: Revised version that is closer to the published version; Fig. 2 correcte

Evidence of the validity and accuracy of the Brazilian social attitude of students scale towards politics

Objetivou-se apresentar as evidências de validade e confiabilidade de uma escala brasileira para medir atitudes políticas de estudantes brasileiros de nível superior ante seus comportamentos políticos. O estudo teve uma amostra de abrangência nacional (N = 445), com estudantes brasileiros oriundos de distintos estados. Os resultados indicaram uma estrutura empírica sustentável (teste de Kaiser-Meyer-Olkin - KMO = 0,81), com indicadores psicométricos considerados adequados à mensuração das atitudes políticas. Três fatores empíricos foram identificados: grau de conhecimento sobre política (15 itens, cargas fatoriais entre 0,31 e 0,82, alfa = 0,82, eigenvalue = 5,07 e variância explicada = 18,78 %), afetos relativos à política (7 itens, cargas fatoriais entre 0,41 e 0,58, alfa = 0,72, eigenvalue = 3,17 e variância explicada = 11,73 %) e intenções de comportamento político (2 itens, cargas fatoriais entre 0,70 e 0,72, alfa = 0,80, eigenvalue = 1,8 e variância explicada = 6,8 %). Conclui-se que os resultados fortalecem a estrutura fatorial original da escala e mostram sua utilidade para a identificação de atitudes sociais ante comportamentos políticos.El objetivo de la presente investigación fue presentar las pruebas de confiabilidad y validez de una escala brasileña para medir las actitudes políticas de los estudiantes universitarios brasileños ante su comportamiento político. El estudio contó con una muestra nacional (N = 445) de estudiantes brasileños de diferentes Estados. Los resultados indicaron una estructura empírica sustentable (KMO = .81), con indicadores psicométricos que se consideran adecuados para la medición de las actitudes políticas. Específicamente, se identificaron tres factores empíricos: nivel de conocimiento sobre la política (15 ítems, cargas factoriales entre .31 y .82, alfa = .82, eigenvalue = 5.07 y varianza explicada = 18.78 %), sentimientos acerca de la política (7 ítems, factoriales de .41 y .58, alfa = .72, eigenvalue = 3.17 y varianza explicada = 11.73 °/o) e intenciones del comportamiento político (2 ítems, factoriales de .70 y .72, alfa = .80, eigenvalue = 1.8 y varianza explicada = 6.8 %). Se llegó a la conclusión de que los resultados apoyan la estructura factorial original de la escala y muestran su utilidad en la identificación de las actitudes sociales ante la conducta política.The objective of this study was to present the validity and reliability evidences of a Brazilian scale to measure the political attitudes of Brazilian higher education students regarding their political behavior. The study had a nationwide sample (N = 445), with Brazilian students from different states. The results indicated a sustainable empirical structure (KMO = 0.81), with psychometric indicators considered adequate to the measurement of political attitudes. Three empirical factors were identified: degree of political knowledge (15 items, factorial loads between 0.31 and 0.82, alpha = 0.82, eigenvalue = 5.07 and explained variance = 18.78%), feelings about politics (7 items, factorial loads between 0.41 and 0.58, alpha = 0.72, eigenvalue = 3.17 and explained variance = 11.73%) and intentions of political behavior (2 items, factorial loads between 0, 70 and 0.72, alpha = 0.80, eigenvalue = 1.8 and explained variance = 6.8%). It is concluded that the results strengthen the original factorial structure of the scale and show its utility for the identification of social attitudes regarding political behaviors

Inflation, cold dark matter, and the central density problem

A problem with high central densities in dark halos has arisen in the context of LCDM cosmologies with scale-invariant initial power spectra. Although n=1 is often justified by appealing to the inflation scenario, inflationary models with mild deviations from scale-invariance are not uncommon and models with significant running of the spectral index are plausible. Even mild deviations from scale-invariance can be important because halo collapse times and densities depend on the relative amount of small-scale power. We choose several popular models of inflation and work out the ramifications for galaxy central densities. For each model, we calculate its COBE-normalized power spectrum and deduce the implied halo densities using a semi-analytic method calibrated against N-body simulations. We compare our predictions to a sample of dark matter-dominated galaxies using a non-parametric measure of the density. While standard n=1, LCDM halos are overdense by a factor of 6, several of our example inflation+CDM models predict halo densities well within the range preferred by observations. We also show how the presence of massive (0.5 eV) neutrinos may help to alleviate the central density problem even with n=1. We conclude that galaxy central densities may not be as problematic for the CDM paradigm as is sometimes assumed: rather than telling us something about the nature of the dark matter, galaxy rotation curves may be telling us something about inflation and/or neutrinos. An important test of this idea will be an eventual consensus on the value of sigma_8, the rms overdensity on the scale 8 h^-1 Mpc. Our successful models have values of sigma_8 approximately 0.75, which is within the range of recent determinations. Finally, models with n>1 (or sigma_8 > 1) are highly disfavored.Comment: 13 pages, 6 figures. Minor changes made to reflect referee's Comments, error in Eq. (18) corrected, references updated and corrected, conclusions unchanged. Version accepted for publication in Phys. Rev. D, scheduled for 15 August 200

Measurement of the production of a W boson in association with a charm quark in pp collisions at √s = 7 TeV with the ATLAS detector

The production of a W boson in association with a single charm quark is studied using 4.6 fb−1 of pp collision data at s√ = 7 TeV collected with the ATLAS detector at the Large Hadron Collider. In events in which a W boson decays to an electron or muon, the charm quark is tagged either by its semileptonic decay to a muon or by the presence of a charmed meson. The integrated and differential cross sections as a function of the pseudorapidity of the lepton from the W-boson decay are measured. Results are compared to the predictions of next-to-leading-order QCD calculations obtained from various parton distribution function parameterisations. The ratio of the strange-to-down sea-quark distributions is determined to be 0.96+0.26−0.30 at Q 2 = 1.9 GeV2, which supports the hypothesis of an SU(3)-symmetric composition of the light-quark sea. Additionally, the cross-section ratio σ(W + +c¯¯)/σ(W − + c) is compared to the predictions obtained using parton distribution function parameterisations with different assumptions about the s−s¯¯¯ quark asymmetry

The Maintenance of Traditions in Marmosets: Individual Habit, Not Social Conformity? A Field Experiment

Social conformity is a cornerstone of human culture because it accelerates and maintains the spread of behaviour within a group. Few empirical studies have investigated the role of social conformity in the maintenance of traditions despite an increasing body of literature on the formation of behavioural patterns in non-human animals. The current report presents a field experiment with free-ranging marmosets (Callithrix jacchus) which investigated whether social conformity is necessary for the maintenance of behavioural patterns within groups or whether individual effects such as habit formation would suffice.Using a two-action apparatus, we established alternative behavioural patterns in six family groups composed of 36 individuals. These groups experienced only one technique during a training phase and were thereafter tested with two techniques available. The monkeys reliably maintained the trained method over a period of three weeks, despite discovering the alternative technique. Three additional groups were given the same number of sessions, but those 21 individuals could freely choose the method to obtain a reward. In these control groups, an overall bias towards one of the two methods was observed, but animals with a different preference did not adjust towards the group norm. Thirteen of the fifteen animals that discovered both techniques remained with the action with which they were initially successful, independent of the group preference and the type of action (Binomial test: exp. proportion: 0.5, p<0.01).The results indicate that the maintenance of behavioural patterns within groups 1) could be explained by the first rewarded manipulation and subsequent habit formation and 2) do not require social conformity as a mechanism. After an initial spread of a behaviour throughout a group, this mechanism may lead to a superficial appearance of conformity without the involvement of such a socially and cognitively complex mechanism. This is the first time that such an experiment has been conducted with free-ranging primates

A Revision of Malagasy Species of Anochetus Mayr and Odontomachus Latreille (Hymenoptera: Formicidae)

Species inventories are essential for documenting global diversity and generating necessary material for taxonomic study and conservation planning. However, for inventories to be immediately relevant, the taxonomic process must reduce the time to describe and identify specimens. To address these concerns for the inventory of arthropods across the Malagasy region, we present here a collaborative approach to taxonomy where collectors, morphologists and DNA barcoders using cytochrome c oxidase 1 (CO1) participate collectively in a team-driven taxonomic process. We evaluate the role of DNA barcoding as a tool to accelerate species identification and description. This revision is primarily based on arthropod surveys throughout the Malagasy region from 1992 to 2006. The revision is based on morphological and CO1 DNA barcode analysis of 500 individuals. In the region, five species of Anochetus (A