823 research outputs found
Local curvature-dimension condition implies measure-contraction property
No full textAbstractWe prove that for non-branching metric measure spaces the local curvature condition CDloc(K,N) implies the global version of MCP(K,N). The curvature condition CD(K,N) introduced by the second author and also studied by Lott and Villani is the generalization to metric measure space of lower bounds on Ricci curvature together with upper bounds on the dimension. This paper is the following step of Bacher and Sturm (2010) [1] where it is shown that CDloc(K,N) is equivalent to a global condition CD⁎(K,N), slightly weaker than the usual CD(K,N). It is worth pointing out that our result implies sharp Bishop–Gromov volume growth inequality and sharp Poincaré inequality
Dust dynamics in planet-driven spirals
No full textContext. Protoplanetary disks are known to host spiral features that are observed in scattered light, the ALMA continuum, and more recently in CO gas emission and gas dynamics. However, it is unknown whether spirals in gas and dust trace the same morphology.
Aims. We aim to study the morphology and amplitude of dusty spirals as function of the Stokes number and the underlying mechanisms that cause a difference between dusty spirals and gas spirals. We then construct a model to relate the deviation from Keplerian rotation in the gas to a perturbation in surface density of the gas and dust.
Methods. We used FARGO-3
UWB orthogonal pulse design using Sturm–Liouville boundary value problem
No full textThe problem of designing UWB pulses which meet specific spectrum requirements is usually treated by filtering common pulses such as Gaussian doublets, modified Hermite polynomials and wavelets. When there is the need to have a number of orthogonal pulses (e.g., in a multiuser scenario), a naive approach is to filter all the members of an orthogonal set, which is likely to destroy their orthogonality property. In this paper, we study the design of a set of pulses that simultaneously satisfy the orthogonality property and spectrum requirements. Our design is based on the eigenfunctions of Sturm–Liouville boundary value problems. Indeed, we introduce Sturm–Liouville differential equations for which the eigenfunctions meet the FCC mask constraints. Computer simulation results show that all such waveforms occupy almost 55% of the allowed spectrum (utilization efficiency). A comparison of the proposed method with some conventional techniques of orthogonal UWB pulse generation will demonstrate the advantages of the new proposal.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Team Bart De Schutte
Sturm-Picone type theorems for second order nonlinear impulsive differential equations
No full textWe obtain Sturm Picone type comparison theorems for nonlinear impulsive differential equations. Our results cover the previous results existing in the literature and useful in investigating qualitative behaviour of solutions of such equations
A single web-interface to access, visualise and model data from multiple geo- and cosmochemical databases
No full textAnalysis of a Sturm–Liouville Problem Arising in Atmosphere
No full textWe present recent results in study of a mathematical model of the sea-breeze flow, arising from a general model of the ’morning glory’ phenomena. Based on analysis of the Dirichlet spectrum of the corresponding Sturm–Liouville problem and application of the Fredholm alternative, we establish conditions of existence/uniqueness of solutions to the given problem.Mathematical Physic
From IEDs to AIDS? Detection of HIV in human corpses by rapid screening tests after suspected intentional transmission in terrorist attacks
No full textObjectives We evaluated the feasibility of intentional transmission of HIV by means of suicide bombing and rape as a terrorist tactic in asymmetric conflicts by evaluating the recognised optimum conditions for biological warfare. We also estimated the suitability of a fourthgeneration rapid test for HIV detection in the blood of dead terrorists killed in the completion of their mission. Methods The feasibility of deliberate transmission of HIV for terroristic ends was evaluated on the basis of published experience from passive biological warfare research. In addition, blood from four recently deceased HIV-positive patients and four HIV-negative control corpses, stored at 4 degrees C in a mortuary, was analysed at 12, 24, 36 and 48 h postmortem by rapid serological testing. Results The feasibility of HIV infection for terroristic purposes was established. The fourth-generation HIV rapid test we evaluated identified all HIV-positive samples and was negative for all HIV-negative samples. Conclusions Rapid HIV testing from the remains of dead terrorists in the deployed military environment is possible. Samples should be acquired quickly, basic sample preparation is advisable and consequent decisions concerning postexposure prophylaxis should take into account the diagnostic gap in early infections
Overcoming Fragmentation of Geochemical Data Resources: Collaboration between EarthChem, Astromat, GEOROC, and MetBase
No full textGlobal geochemical datasets are increasingly valuable for solving research questions in geochemistry, volcanology and beyond. To support new research, open sharing and access of geochemical data needs to be easy for researchers so they can take full advantage of the rapidly growing volume of data generated in laboratories across the globe, and to comply with the principles of Open Science. Instead, the fragmented landscape of geochemical data systems makes it difficult for researchers to find, access, and contribute their data: Geochemical data are curated and published in a range of thematic, institutional, and programmatic data systems that differ in architecture, metadata schemas, terminology, and data output formats. Researchers have to figure out where to obtain the data they need; learn to use different search applications; retrieve data from multiple databases and painstakingly reformat the datasets they obtained from different systems to integrate them. They need to select an appropriate repository for their data, and potentially work with different submission systems and templates. Collaboration among geochemical data systems is a critical step to overcome this fragmentation and facilitate geochemical data management and access for the research community by coordinating, aligning, and integrating their systems. Through collaboration, data repositories and databases can also leverage each other’s expertise and resources to operate their services more effectively and efficiently.
We here report about new collaborative efforts among four geochemical data systems that aim to harmonize and integrate their data holdings and software ecosystem for the benefit of the research community and to improve their sustainability: EarthChem (https://earthchem.org/), GEOROC (https://georoc.eu/), MetBase (https://metbase.org/), and the Astromaterials Data System (https://www.astromat.org/). Building on the long-term collaboration between EarthChem and GEOROC, this collaboration leverages the new development of the Astromaterials Data System with modern technology and two new projects funded to overhaul the infrastructure of the GEOROC and MetBase databases as an opportunity to jointly develop a more resilient, sustainable platform for data exchange. Results of the collaboration so far include: a) alignment of the Astronaut and MetBase data models b) migration of the MetBase data holdings into the Astromat synthesis database; c) alignment of the EarthChem and GEOROC data models; d) new automated synchronization process of GEOROC data to the ECP; e) harmonized vocabularies for chemical variables, analytical methods (Others are in development in alignment with emerging efforts of the OneGeochemstry initiative); f) design of the future shared architecture of EarthChem and GEOROC that includes plans for a joint data entry tool for curators and a single data submission platform for researchers to contribute their data to the affiliated domain repositories.
The ultimate goal of this harmonization between EarthChem, Astromat, GEOROC and MetBase is to make it easier for researchers to access and contribute data. We hope to integrate further systems in the future, building on ongoing collaborations with the Australian Geochemistry Network, the US Geological Survey, SAMIS (Sample Analysis Microinformation System), the GFZ Data Services, and the Sparrow software
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