Relative periodic orbits in point vortex systems

We give a method to determine relative periodic orbits in point vortex systems: it consists mainly into perform a symplectic reduction on a fixed point submanifold in order to obtain a two-dimensional reduced phase space. The method is applied to point vortices systems on a sphere and on the plane, but works for other surfaces with isotropy (cylinder, ellipsoid, ...). The method permits also to determine some relative equilibria and heteroclinic cycles connecting these relative equilibria.Comment: 27 pages, 17 figure

Microbial taxonomy in the post-genomic era: Rebuilding from scratch?

Microbial taxonomy should provide adequate descriptions of bacterial, archaeal, and eukaryotic microbial diversity in ecological, clinical, and industrial environments. Its cornerstone, the prokaryote species has been re-evaluated twice. It is time to revisit polyphasic taxonomy, its principles, and its practice, including its underlying pragmatic species concept. Ultimately, we will be able to realize an old dream of our predecessor taxonomists and build a genomic-based microbial taxonomy, using standardized and automated curation of high-quality complete genome sequences as the new gold standard.National Science Foundation (U.S.) (NSF Grant DEB-1046413)National Science Foundation (U.S.) (NSF Grant CNS-1305112)National Science Foundation (U.S.) (NSF Grant DEB 0918333)National Science Foundation (U.S.) (NSF grant OCE 1441943)Gordon and Betty Moore FoundationUnited States. Dept. of Energy. Office of ScienceUnited States. Dept. of Energy. Office of Biological and Environmental ResearchOak Ridge National LaboratoryCarlos Chagas Filho Foundation for Research Support of the State of Rio de JaneiroBrazil. Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (grant)Conselho Nacional de Pesquisas (Brazil

Direct single-cell biomass estimates for marine bacteria via Archimedes’ principle

Microbes are an essential component of marine food webs and biogeochemical cycles, and therefore precise estimates of their biomass are of significant value. Here, we measured single-cell biomass distributions of isolates from several numerically abundant marine bacterial groups, including Pelagibacter (SAR11), Prochlorococcus and Vibrio using a microfluidic mass sensor known as a suspended microchannel resonator (SMR). We show that the SMR can provide biomass (dry mass) measurements for cells spanning more than two orders of magnitude and that these estimates are consistent with other independent measures. We find that Pelagibacterales strain HTCC1062 has a median biomass of 11.9±0.7 fg per cell, which is five- to twelve-fold smaller than the median Prochlorococcus cell’s biomass (depending upon strain) and nearly 100-fold lower than that of rapidly growing V. splendidus strain 13B01. Knowing the biomass contributions from various taxonomic groups will provide more precise estimates of total marine biomass, aiding models of nutrient flux in the ocean.National Science Foundation (U.S.) (OCE-1129359)Simons Foundation (337262)United States. Army Research Office (W911NF-09-D-0001

Near-realtime quantitative precipitation estimation and prediction (RealPEP)

Flash floods in small- to medium-sized catchments and intense precipitation over cities caused by severe local storms pose increasing threats to our society. For the timely prediction of such events, the value of high-resolution and high-quality QPE and corresponding forecasts cannot be overrated. Seamless predictions harmonizing nowcasting and numerical weather prediction (NWP) across forecast lead times from minutes to days would greatly help to improve the value and efficiency of warnings. Organized by the Research Unit on Near-Realtime Precipitation Estimation and Prediction (RealPEP, www2.meteo.uni-bonn.de/realpep) and supported by the Project on Seamless Integrated Forecasting System (SINFONY, www.dwd .de/DE/forschung/forschungsprogramme/sinfony_iafe/sinfony_node.html) of the German Meteorological Service (DWD), an international 3-day online conference was held from 5 to 7 October 2020, dedicated to Precipitation and Flash-Flood Predictions from Minutes to Days (https://indico .scc.kit.edu/event/883/). Most speakers agreed to have their presentations recorded, which we uploaded to YouTube for further distribution (see, e.g., on the conference homepage, https:// indico.scc.kit.edu/event/883/page/588-recorded-talks). The speakers were both invited experts in the respective research fields and researchers from the RealPEP and SINFONY projects. Talks and discussions could be followed on video stream. Interaction between the about 250 participants was enabled by entering written questions and comments via a dedicated tool, which allowed for voting and thus also ranking questions. Registered participants could enter chat rooms from where they could be moved to the speaker room for posing the questions directly to the speakers and the auditorium. On the last day of the conference podium discussions with selected speakers summarized talks and discussions and elaborated on overarching problems, ideas, and developments in the fields of quantitative precipitation estimation (QPE), quantitative precipitation nowcasting (QPN), quantitative precipitation forecasting (QPF), flash-flood prediction (FFP), and their organization into seamless prediction systems, which also constituted the topics of the five sessions during the conference. We report here in particular on the outcomes of the panel discussions

Compact Cryogenic Source of Periodic Hydrogen and Argon Droplet Beams for Relativistic Laser-Plasma Generation

We present a cryogenic source of periodic streams of micrometer-sized hydrogen and argon droplets as ideal mass-limited target systems for fundamental intense laser-driven plasma applications. The highly compact design combined with a high temporal and spatial droplet stability makes our injector ideally suited for experiments using state-of-the-art high-power lasers in which a precise synchronization between the laser pulses and the droplets is mandatory. We show this by irradiating argon droplets with multi-Terawatt pulses.Comment: To be published in Review of Scientific Instrument

Point vortices on the sphere: a case with opposite vorticities

We study systems formed of 2N point vortices on a sphere with N vortices of strength +1 and N vortices of strength -1. In this case, the Hamiltonian is conserved by the symmetry which exchanges the positive vortices with the negative vortices. We prove the existence of some fixed and relative equilibria, and then study their stability with the ``Energy Momentum Method''. Most of the results obtained are nonlinear stability results. To end, some bifurcations are described.Comment: 35 pages, 9 figure

Социальная ответственность бизнеса: опыт внедрения, характерные черты и особенности

Целью написания данной статьи является изучения опыта украинских предприятий (компаний) с наилучшими показателями в сфере социальной политики, выявление и анализ особенностей их реализации для разработки концептуального подхода к формированию модели внедрения принципов социальной ответственности в других компаниях (на предприятиях).Изучен опыт лучших компаний Украины в сфере корпоративной социальной ответственности; выявлены характерные черты и особенности разработки социальной политики в компании. Предложен концептуальный подход к формированию модели внедрения принципов социальной ответственности бизнеса.Вивчений досвід кращих компаній України в сфері соціальної відповідальності; виявлені характерні риси та особливості розробки соціальної політики в компанії. Запропонований концептуальний підхід до формування моделі впровадження принципів соціальної відповідальності бізнесу.The experience of the best Ukrainian companies in the sphere of the corporate social responsibility is studied; the personal traits and features of the development of social policy in a company are exposed. The conceptual approach is proposed to the formation of model of business social responsibility principles introduction

Genotypic diversity within a natural coastal bacterioplankton population

Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of American Association for the Advancement of Science for personal use, not for redistribution. The definitive version was published in Science 307 (2005): 1311-1313, doi:10.1126/science.1106028.The genomic diversity and relative importance of unique genotypes within natural bacterial populations has remained largely unknown. Here, we analyze the diversity and annual dynamics of a group of coastal bacterioplankton (>99% 16S rRNA identity to Vibrio splendidus). We show that this group consists of at least a thousand distinct genotypes, each occurring at extremely low environmental concentrations (on average <1 cell/ml). Overall, the genomes show extensive allelic diversity and size variation. Individual genotypes rarely recurred in samples and allelic distribution did not show spatial or temporal substructure. Ecological considerations suggest that much genotypic and possibly phenotypic variation within natural populations should be considered neutral.This work was supported by grants from the Department of Energy Genomes to Life program and the National Science Foundation. Sequences have been submitted to Genbank under accession numbers AY836800-AY837464

Ocular involvement of sars-cov-2 in a polish cohort of covid-19-positive patients

The coronavirus SARS-CoV-2 responsible for the current human COVID-19 pandemic has shown tropism toward different organs with variable efficiency, eyes included. The purpose of this study has been to investigate the presence of detectable SARS-CoV-2 infection in ocular swabs in patients affected by COVID-19. A consecutive series of 74 COVID-19-positive patients (age 21–89) were enrolled at two Polish COVID-19 hospitals for 4 months and were characterized by PCR for the presence of the SARS-CoV-2 genetic material in nasopharyngeal (NP) and ocular swabs, while their respiratory and ocular symptoms were noted. Almost 50% of them presented with severe/crit-ical respiratory involvement, and some degree of eye disease. No tight correlation was observed between the presence of ocular and respiratory symptoms. Three male patients presenting with severe/critical lung disease tested positive in ocular swab, however with mild/moderate ocular symptoms. In conclusion, our study lends further support to the view that overt ocular infection by the SARS-CoV-2 virus is not such a frequent occurrence

Spectral shaping of laser generated proton beams

The rapid progress in the field of laser particle acceleration has stimulated a debate about the promising perspectives of laser based ion beam sources. For a long time, the beams produced exhibited quasi-thermal spectra. Recent proof-of-principle experiments demonstrated that ion beams with narrow energy distribution can be generated from special target geometries. However, the achieved spectra were strongly limited in terms of monochromacity and reproducibility. We show that microstructured targets can be used to reliably produce protons with monoenergetic spectra above 2 MeV with less than 10% energy spread. Detailed investigations of the effects of laser ablation on the target resulted in a significant improvement of the reproducibility. Based on statistical analysis, we derive a scaling law between proton peak position and laser energy, underlining the suitability of this method for future applications. Both the quality of the spectra and the scaling law are well reproduced by numerical simulations