Mechanisms determining species succession and dominance during an iron-induced phytoplankton bloom in the Southern Ocean (LOHAFEX)

To improve the understanding of population dynamics of organisms, it is necessary to examine organisms under natural conditions. Only at such conditions, knowledge about their in situ use of resources, predator-prey interactions and loss rates can be obtained. It is possible to examine and understand these processes with controlled ocean iron fertilization experiments, which stimulate the growth of unicellular algae. This thesis provides a comprehensive description of the reactions and vertical distribution of the main components of the pelagic ecosystem and highlights the food-web interactions of individual organisms, which characterize this habitat. The response of the plankton community to iron addition was successfully observed during the Indo-German iron fertilisation experiment LOHAFEX (LOHA is hindi and means iron, FEX stands for fertilisation experiment) carried out in the Southern Ocean from January to March in 2009 lasting for 38 days. The iron-induced bloom was achieved in the closed core of a mesoscale eddy. The aim of the experiment was to study the growth and demise of the phytoplankton bloom and to examine whether the biomass is retained in the surface layers through recycling processes or whether biomass sinks out to the deep ocean. The fertilized patch was characterized by low silicic acid concentrations, which is an essential nutrient for diatoms, hence a flagellate-bloom developed with cells < 20 µm in size. The bloom remained stable over the course of the experiment. This was verified by microscopic analysis and molecular methods. The main reason for the lack of large scale biomass increase, was the strong grazing pressure by the large copepod population, consisting primarily of Calanus simillimus and Oithona similis. Incubation experiments proved that copepods increased their grazing rates and fecal pellet production within the patch. Neutrally buoyant PELAGRA traps were deployed to quantify the export fluxes. These contained a few diatoms and fecal pellets and were dominated by unicellular plankton like dinoflagellates, flagellates and coccoid cells. Hence fertilizing this type of plankton community did not increase the vertical flux. This lead to the hypothesis that the system was influenced by recycling processes in surface layers. The protozoan community and its vertical distribution was an important part of this work and was studied by focussing on key heterotrophic organisms. These included thekate dinoflagellates, loricate and aloricate ciliates, foraminifera, radiolarians, and juvenile and adult copepods. Again, the high grazing pressure by the copepods controlled the development of the protozoan community, and the copepod fecal pellets contained large amounts of damaged and empty loricae, but also foraminifera, which are usually not a preferred food item for copepods. This indicated that the copepods were food limited and resorted to large, armoured protozoans which they might have otherwise avoided. Dinoflagellates were mainly abundant at depths below 100 m, possibly this distribution pattern was caused by an escape response in order to avoid predators and to feed on the flux of larger particles which generally peaks at those depths. In conclusion, the plankton community during LOHAFEX was top-down controlled whereby a highly efficient retention type system prevailed, which resulted in low particle export fluxe

ENIGMA-anxiety working group : Rationale for and organization of large-scale neuroimaging studies of anxiety disorders

Altres ajuts: Anxiety Disorders Research Network European College of Neuropsychopharmacology; Claude Leon Postdoctoral Fellowship; Deutsche Forschungsgemeinschaft (DFG, German Research Foundation, 44541416-TRR58); EU7th Frame Work Marie Curie Actions International Staff Exchange Scheme grant 'European and South African Research Network in Anxiety Disorders' (EUSARNAD); Geestkracht programme of the Netherlands Organization for Health Research and Development (ZonMw, 10-000-1002); Intramural Research Training Award (IRTA) program within the National Institute of Mental Health under the Intramural Research Program (NIMH-IRP, MH002781); National Institute of Mental Health under the Intramural Research Program (NIMH-IRP, ZIA-MH-002782); SA Medical Research Council; U.S. National Institutes of Health grants (P01 AG026572, P01 AG055367, P41 EB015922, R01 AG060610, R56 AG058854, RF1 AG051710, U54 EB020403).Anxiety disorders are highly prevalent and disabling but seem particularly tractable to investigation with translational neuroscience methodologies. Neuroimaging has informed our understanding of the neurobiology of anxiety disorders, but research has been limited by small sample sizes and low statistical power, as well as heterogenous imaging methodology. The ENIGMA-Anxiety Working Group has brought together researchers from around the world, in a harmonized and coordinated effort to address these challenges and generate more robust and reproducible findings. This paper elaborates on the concepts and methods informing the work of the working group to date, and describes the initial approach of the four subgroups studying generalized anxiety disorder, panic disorder, social anxiety disorder, and specific phobia. At present, the ENIGMA-Anxiety database contains information about more than 100 unique samples, from 16 countries and 59 institutes. Future directions include examining additional imaging modalities, integrating imaging and genetic data, and collaborating with other ENIGMA working groups. The ENIGMA consortium creates synergy at the intersection of global mental health and clinical neuroscience, and the ENIGMA-Anxiety Working Group extends the promise of this approach to neuroimaging research on anxiety disorders

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an

Risk portfolio on modern finance has become increasingly technical, requiring the use of sophisticated mathematical tools in both research and practice. Since companies cannot insure themselves completely against risk, as human incompetence in predicting the future precisely that written in Al-Quran surah Luqman verse 34, they have to manage it to yield an optimal portfolio. The objective here is to minimize the variance among all portfolios, or alternatively, to maximize expected return among all portfolios that has at least a certain expected return. Furthermore, this study focuses on optimizing risk portfolio so called Markowitz MVO (Mean-Variance Optimization). Some theoretical frameworks for analysis are arithmetic mean, geometric mean, variance, covariance, linear programming, and quadratic programming. Moreover, finding a minimum variance portfolio produces a convex quadratic programming, that is minimizing the objective function ðð¥with constraintsð ð 𥠥 ðandð´ð¥ = ð. The outcome of this research is the solution of optimal risk portofolio in some investments that could be finished smoothly using MATLAB R2007b software together with its graphic analysis

Search for supersymmetry in events with one lepton and multiple jets in proton-proton collisions at root s=13 TeV

Peer reviewe

Measurement of the top quark mass using charged particles in pp collisions at root s=8 TeV

Peer reviewe

Search for anomalous couplings in boosted WW/WZ -> l nu q(q)over-bar production in proton-proton collisions at root s=8TeV

Peer reviewe