1,642 research outputs found
Intermittency and scaling laws for wall bounded turbulence
Well defined scaling laws clearly appear in wall bounded turbulence, even
very close to the wall, where a distinct violation of the refined Kolmogorov
similarity hypothesis (RKSH) occurs together with the simultaneous persistence
of scaling laws. A new form of RKSH for the wall region is here proposed in
terms of the structure functions of order two which, in physical terms,
confirms the prevailing role of the momentum transfer towards the wall in the
near wall dynamics.Comment: 10 pages, 5 figure
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Development of a portable leaf photosynthesis and volatile organic compounds emission system.
Understanding how plant carbon metabolism responds to environmental variables such as light is central to understanding ecosystem carbon cycling and the production of food, biofuels, and biomaterials. Here, we couple a portable leaf photosynthesis system to an autosampler for volatile organic compounds (VOCs) to enable field observations of net photosynthesis simultaneously with emissions of VOCs as a function of light. Following sample collection, VOCs are analyzed using automated thermal desorption-gas chromatograph-mass spectrometry (TD-GC-MS). An example is presented from a banana plant in the central Amazon with a focus on the response of photosynthesis and the emissions of eight individual monoterpenes to light intensity. Our observations reveal that banana leaf emissions represent a 1.1 +/- 0.1% loss of photosynthesis by carbon. Monoterpene emissions from banana are dominated by trans-β-ocimene, which accounts for up to 57% of total monoterpene emissions at high light. We conclude that the developed system is ideal for the identification and quantification of VOC emissions from leaves in parallel with CO2 and water fluxes.The system therefore permits the analysis of biological and environmental sensitivities of carbon metabolism in leaves in remote field locations, resulting in the emission of hydrocarbons to the atmosphere.•A field-portable system is developed for the identification and quantification of VOCs from leaves in parallel with leaf physiological measurements including photosynthesis and transpiration.•The system will enable the characterization of carbon and energy allocation to the biosynthesis and emission of VOCs linked with photosynthesis (e.g. isoprene and monoterpenes) and their biological and environmental sensitivities (e.g. light, temperature, CO2).•Allow the development of more accurate mechanistic global VOC emission models linked with photosynthesis, improving our ability to predict how forests will respond to climate change. It is our hope that the presented system will contribute with critical data towards these goals across Earth's diverse tropical forests
On the Solved Turbulent Scales in Turbulent Plume Fires
Plume fires are characterized by a turbulent nature with a large number of different
scales. LES is often used to solve the largest structures and to model the smallest ones. Grid size
and time steps become decisive to place the limit between resolved and modelled turbulence.
Significant information on this limit and its placement can be obtained with spectral analyses of
the specific turbulent kinetic energy. While frequency analysis is relatively easy, an analysis in
the wavenumber domain is more challenging. The IWC method, typically used in structures and
acoustics, is used here for this purpose. IWC method allows to obtain wavenumber spectra with
a better resolution than those obtained with a direct approach. Furthermore, in this paper the IWC
method is also used in its reverse form to obtain frequency spectra. Although rather dense grids
have been chosen, the number of nodes along the plume and their spacing is not such as to
guarantee detailed wavenumber spectra with the direct approach and consequently with the
reverse IWC. On the contrary, the IWC method provides wavenumber spectra in agreement with
those obtained directly, but of much higher quality
Knee stability, athletic performance and sport-specific tasks in non-professional soccer players after ACL reconstruction: comparing trans-tibial and antero-medial portal techniques.
Background: a wrong position of bone tunnels, in particular on the femur, is one of the most frequent causes of a failed anterior cruciate ligament (ACL) reconstruct ion. Several studies demonstrated that drilling the femoral tunnel through the antero-medial portal (AMP) allows a more anatomical placement on the lateral femoral condyle and higher knee stability, compared to trans-tibial (TT) technique. The aim of this study was to retrospectively evaluate two groups of soccer players operated on for ACL reconstruction according to either one of these two techniques. Methods: two groups of non-professional soccer players operated on for a single bundle ACL reconstruction with hamstrings autograft using either a TT (20 patients) or an AMP (23 patients) technique were retrospectively evaluated with KT- 1000 arthrometer, manual pivot shift test, isokinetic test, the incremental treadmill-running test, athletic and sport specific tasks, and knee scores (IKDC, Lysholm and KOOS). Results: the AMP group showed better results at pivot shift test and KOOS, but lower flexion angles at single leg squat test. There were no differences in all the other considered outcomes. Conclusions: the better rotational stability of the knee achieved in AMP group did not lead to significantly better clinical and functional results in our patients. Level of evidence III. Treatment study: Case-control study
The allometric partition of whole body protein in lean fraction of growing pigs using information from three different datasets
The hypothesis that a single allometric relationship relating carcass lean protein (CLP) to whole body protein (WBP) can allow accurate estimates of CLP on pigs of different populations, sex and nutritional history, was tested. Three datasets of different origins were used. Data were representative of 548 pigs, castrated males and females, of 8 pig populations, serially slaughtered over ample empty body weight (EBW) ranges (from 22 to 217 kg). WBP and CLP ranged, respectively, from 2 to 28 and from 1 to 16 kg. The pooled data were run and the following relationship was found: CLP=0.497*WBP1.021 (CV=0.062; rsd=0.501 kg). The residuals were subjected to ANOVA to test the effects due to dataset, pig population within dataset and sex; significant differences between datasets mean residuals (+0.095, SE=0.041; -0.258, SE=0.094; -0.116, SE=0.055 kg, P<0.001) were observed. No differences due to sex and pig populations were found. The average residuals were low and only in few cases they differed from zero. Conclusions: CLP can be accurately predicted from WBP; the coefficients of this function are mainly influenced by the procedures of slaughtering, dissection, sampling and analysis
A vision-based fully automated approach to robust image cropping detection
The definition of valid and robust methodologies for assessing the authenticity of digital information is nowadays critical to contrast social manipulation through the media. A key research topic in multimedia forensics is the development of methods for detecting tampered content in large image collections without any human intervention. This paper introduces AMARCORD (Automatic Manhattan-scene AsymmetRically CrOpped imageRy Detector), a fully automated detector for exposing evidences of asymmetrical image cropping on Manhattan-World scenes. The proposed solution estimates and exploits the camera principal point, i.e., a physical feature extracted directly from the image content that is quite insensitive to image processing operations, such as compression and resizing, typical of social media platforms. Robust computer vision techniques are employed throughout, so as to cope with large sources of noise in the data and improve detection performance. The method leverages a novel metric based on robust statistics, and is also capable to decide autonomously whether the image at hand is tractable or not. The results of an extensive experimental evaluation covering several cropping scenarios demonstrate the effectiveness and robustness of our approac
Pre-packaged food products business to consumer (B2C) distance selling and information obligations in Italian mass market retailers
The supply and sale of food online are on the rise. The value of e-commerce in Europe has been estimated in 602 billion euros in 2017, 324 million people in the old continent purchase online. In the European area, the Netherlands and Italy are the countries where the e-commerce market grew faster in the last five years. Nevertheless, in Italy the spread of online shopping has reached the 89.9% of the population between 11 and 74 years old. The access to the Internet, as declared by 43 million Italians, it is carried out from fixed or mobile locations. In terms of revenues the food sector recorded a +24% among the different sectors facing one of the higher grows in terms of percentages. The regulatory framework that disciplines the food products distance selling can be traced back to two fundamental pillars: the European legislation on e-commerce on the one side and the food information to consumers on the other side. Under article 14 of the Regulation (EU) No. 1169/2011, the European legislator states that the mandatory information, as indicated in article 9, shall be available to the consumer before the purchase is concluded and when the product is delivered. The study aims at verifying: the level of compliance by Italians MMR with the information regulation about food products distance selling in relation to (a) the fulfillment of the obligation concerning mandatory provisions and (b) the fulfillment of the obligations concerning availability and readability of the information provided. The research has been conducted analyzing the websites of the ten largest Italian MMR and in particular: if the mandatory information were provided, the availability of the information according to the Regulation (EU) 1169/2011; the number of clicks needed to identify the food product in the website and the number of clicks Non required to obtain all the information. The observation testified a substantial compliance with the information obligations according to the European regulation. Differently, when considering the availability and readability of the information, from the analysis emerged that consumers have to follow a path that is not immediate and intuitive. Conclusions are provided in relation to the presented research
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