923 research outputs found
The accessibility rank of weak equivalences
We study the accessibility properties of trivial cofibrations and weak
equivalences in a combinatorial model category and prove an estimate for the
accessibility rank of weak equivalences. In particular, we show that the class
of weak equivalences between simplicial sets is finitely accessible.Comment: The main result is improved and its proof is simplified. To appear in
Theory and Applications of Categories. 15 page
Combinatorial Topology Of Multipartite Entangled States
With any state of a multipartite quantum system its separability polytope is
associated. This is an algebro-topological object (non-trivial only for mixed
states) which captures the localisation of entanglement of the state.
Particular examples of separability polytopes for 3-partite systems are
explicitly provided. It turns out that this characterisation of entanglement is
associated with simulation of arbitrary unitary operations by 1- and 2-qubit
gates. A topological description of how entanglement changes in course of such
simulation is provided.Comment: 14 pages, LaTeX2e. Slightly revised version of the poster resented on
the International Conference on Quantum Information, Oviedo, Spain, 13-18
July, 2002. To appear in the special issue of Journal of Modern Optic
An Evaluated Certification Services System for the German National Root CA - Legally Binding and Trustworthy Transactions in E-Business and E-Government
National Root CAs enable legally binding E-Business and E-Government
transactions. This is a report about the development, the evaluation and the
certification of the new certification services system for the German National
Root CA. We illustrate why a new certification services system was necessary,
and which requirements to the new system existed. Then we derive the tasks to
be done from the mentioned requirements. After that we introduce the initial
situation at the beginning of the project. We report about the very process and
talk about some unfamiliar situations, special approaches and remarkable
experiences. Finally we present the ready IT system and its impact to
E-Business and E-Government.Comment: 6 pages; 1 figure; IEEE style; final versio
Exploring atmospheric radon with airborne gamma-ray spectroscopy
Rn is a noble radioactive gas produced along the U decay
chain, which is present in the majority of soils and rocks. As Rn is
the most relevant source of natural background radiation, understanding its
distribution in the environment is of great concern for investigating the
health impacts of low-level radioactivity and for supporting regulation of
human exposure to ionizing radiation in modern society. At the same time,
Rn is a widespread atmospheric tracer whose spatial distribution is
generally used as a proxy for climate and pollution studies. Airborne gamma-ray
spectroscopy (AGRS) always treated Rn as a source of background since
it affects the indirect estimate of equivalent U concentration. In this
work the AGRS method is used for the first time for quantifying the presence of
Rn in the atmosphere and assessing its vertical profile. High
statistics radiometric data acquired during an offshore survey are fitted as a
superposition of a constant component due to the experimental setup background
radioactivity plus a height dependent contribution due to cosmic radiation and
atmospheric Rn. The refined statistical analysis provides not only a
conclusive evidence of AGRS Rn detection but also a (0.96 0.07)
Bq/m Rn concentration and a (1318 22) m atmospheric layer
depth fully compatible with literature data.Comment: 17 pages, 8 figures, 2 table
Chemistry of Organophosphonate Scale Growth lnhibitors: 2. Structural Aspects of 2-Phosphonobutane-1,2,4-Tricarboxylic Acid Monohydrate (PBTC.H2O)
Industrial water systems often suffer from undesirable inorganic deposits, such as calcium carbonate,
calcium phosphate(s), magnesium silicate, and others. Synthetic water additives such as phosphonates and
phosphonocarboxylates are the most important and widely utilized scale inhibitors in a plethora of industrial
applications. The design of efficient and cost-effective inhibitors, as well as the study of their structure and
function at the molecular level are important areas of research. This study reports the crystal and molecular
structure of PBTC (PBTC = 2-phosphonobutane-1,2,4-tricarboxylic acid), one of the most widely used scale
inhibitors in the cooling water treatment industry. Triclinic PBTC monohydrate crystallizes in the P 1 space
group with cell dimesions, a =7.671(1) Å, b = 8.680(1) Å, c = 9.886(1) Å, α = 65.518(2) deg, β = 71.683(2)
deg, γ = 76.173(2) deg, V = 564.20(11) Å3, and Z = 2. Bond distances in the -PO3 moiety are 1.4928(10) Å
for the P=O double bond and 1.5294(10) Ã… and 1.5578(10) Ã… for the two -P-O(H) groups. P-C and C-O
bond lengths fall in the normal range. A network of hydrogen bonds are formed between the water molecule
of crystallization, the -P-OH and the -COOH groups
Experimental study of the turbulent structure of the surface marine Atmospheric Boundary Layer over the Aegean Pelagos under etesian winds
In order to study the physical processes of the turbulent transportation of mass and energy within the surface Marine Atmospheric Boundary Layer over the Aegean Pelagos, field measurements were conducted on the island of Skyros, mainly under the etesian winds, during summer 2011. Α meteorological mast was installed close to the shoreline, instrumented with fast anemometer (sonic) and hydrometer measuring the three components of the wind, the virtual temperature and water vapor at 10m height with a sampling frequency of 20Hz. At the same mast slow response sensors were measuring wind speed and direction, temperature and humidity at three levels (2, 6 and 10 m). Weak stable to near neutral flows were recorded during the experimental period. The eddy correlation analysis re-vealed the momentum and heat fluxes values which are presented and discussed. The estimated values are related both with stability and wind speed variations
In vitro efficacy of fungal endophytes and silver pyrazolate against Raffaelea lauricola, causal agent of laurel wilt of avocado
The South Florida avocado industry is being severely impacted by laurel wilt disease. Laurel wilt disease of avocado is caused by the fungal pathogen, Raffaelea lauricola (RL) and is vectored by ambrosia beetle, Xyleborus glabratus. Treatments options are limited, economically not sustainable, and require reapplication fungicides every couple of years. There is a crucial need for developing multiple modes of control using novel biological and chemical agents. The ambrosia beetle associated pathogenic fungi are known to outcompete other microorganisms by taking advantage of ethanol produced by the pathogen and the stressed tree. Endophytes, which reside inside the host plant tissue are part of the plant microbiome represent source of new potential biological control agents. In this study, three ethanol tolerant endophytic fungal species, isolated from avocado bark, were evaluated using in vitro dual culture assay and colonization tube (packed with bark/sapwood shaving) against RL. The endophytic isolates Tricoderma crissum, Tricoderma simmonsii, Lasiodiplodia theobromae were found to be highly capable of suppressing the mycelial colony growth of RL. The results suggest that combined abilities of ethanol tolerance and competitive colonization can provide useful criteria for identifying potential biocontrol agents. In vitro anti-RL activity of silver pyrazolate compound was assessed in both agar and liquid medium. Silver pyrazolate at levels of 30 and 45 ppm were found to be highly effective against RL. Further in planta research is needed to study the effects of endophytic fungal isolates and silver pyrazolate to assess their potential as additional tools for management of laurel wilt
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Assessment of surface solar irradiance derived from real-time modelling techniques and verification with ground-based measurements
This study focuses on the assessment of surface solar radiation (SSR) based on operational neural network (NN) and multi-regression function (MRF) modelling techniques that produce instantaneous (in less than 1 min) outputs. Using real-time cloud and aerosol optical properties inputs from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on board the Meteosat Second Generation (MSG) satellite and the Copernicus Atmosphere Monitoring Service (CAMS), respectively, these models are capable of calculating SSR in high resolution (1 nm, 0.05 degree, 15 min) that can be used for spectrally integrated irradiance maps, databases and various applications related to energy exploitation. The real-time models are validated against ground-based measurements of the Baseline Surface Radiation Network (BSRN) in a temporal range varying from 15 min to monthly means, while a sensitivity analysis of the cloud and aerosol effects on SSR is performed to ensure reliability under different sky and climatological conditions. The simulated outputs, compared to their common training dataset created by the radiative transfer model (RTM) libRadtran, showed median error values in the range −15 to +15 % for the NN that produces spectral irradiances (NNS), 5–6 % underestimation for the integrated NN and close to zero errors for the MRF technique. The verification against BSRN revealed that the real-time calculation uncertainty ranges from −100 to +40 and −20 to +20 W/m^2, for the 15 min and monthly mean global horizontal irradiance (GHI) averages, respectively, while the accuracy of the input parameters, in terms of aerosol and cloud optical thickness (AOD and COT), and their impact on GHI, was of the order of 10 % as compared to the ground-based measurements. The proposed system aims to be utilized through studies and real-time applications which are related to solar energy production planning and use
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