Search results for " absorption"
showing 10 items of 1056 documents
Sound absorption coefficient of a porous material covered with a low open area perforated plate under high sound excitation
2012
International audience; The sound absorption coefficient of porous materials covered with low open area perforated plate is studied under high sound intensities in the absence of mean flow. The theoretical considerations are based on the equivalent fluid following the Johnson-Champoux-Allard approach and the use of the transfer matrix method. To take into account the high sound levels effects, the air flow resistivity of each layer is modified following the Forchheimer law. Two specimens of perforated plate are built and tested when backed by a polymeric foam and a fibrous material. A specific impedance tube setup is developed for the measurement of the surface acoustic impedance for sound …
Excitons in few-layer hexagonal boron nitride: Davydov splitting and surface localization
2018
Hexagonal boron nitride (hBN) has been attracting great attention because of its strong excitonic effects. Taking into account few-layer systems, we investigate theoretically the effects of the number of layers on quasiparticle energies, absorption spectra, and excitonic states, placing particular focus on the Davydov splitting of the lowest bound excitons. We describe how the inter-layer interaction as well as the variation in electronic screening as a function of layer number $N$ affects the electronic and optical properties. Using both \textit{ab initio} simulations and a tight-binding model for an effective Hamiltonian describing the excitons, we characterize in detail the symmetry of t…
A critical size for emergence of nonbulk electronic and geometric structures in dodecanethiolate-protected Au clusters.
2014
We report on how the transition from the bulk structure to the cluster-specific structure occurs in n-dodecanethiolate-protected gold clusters, Au(n)(SC12)m. To elucidate this transition, we isolated a series of Au(n)(SC12)m in the n range from 38 to ∼520, containing five newly identified or newly isolated clusters, Au104(SC12)45, Au(∼226)(SC12)(∼76), Au(∼253)(SC12)(∼90), Au(∼356)(SC12)(∼112), and Au(∼520)(SC12)(∼130), using reverse-phase high-performance liquid chromatography. Low-temperature optical absorption spectroscopy, powder X-ray diffractometry, and density functional theory (DFT) calculations revealed that the Au cores of Au144(SC12)60 and smaller clusters have molecular-like elec…
The complementary structural studies of the double metal cyanide type catalysts for the ring opening polymerization of the oxiranes
2016
Przeprowadzono badania strukturalne katalizatorów dimetalocyjankowych (DMC) z dwoma rodzajami ligandów organicznych. Zaproponowano wyjaśnienie etapów przebiegu krzywych otrzymanych metodą analizy termograwimetrycznej i różnicowej kalorymetrii skaningowej (TG/DSC) badanych katalizatorów. Wykazano obecność kilku stopni związania ligandów w kompleksach DMC. Na podstawie wyników badań z wykorzystaniem absorpcji rentgenowskiej (XAS) stwierdzono, że centrum aktywne katalizatora stanowi atom cynku. W bezpośrednim sąsiedztwie atomów Zn wykryto obecność atomów Cl, natomiast w najbliższych sferach koordynacyjnych atomu Zn nie wykryto atomów tlenu.
Spectral calibration of hyperspectral imagery using atmospheric absorption features
2006
One of the initial steps in the preprocessing of remote sensing data is the atmospheric correction of the at-sensor radiance images, i.e., radiances recorded at the sensor aperture. Apart from the accuracy in the estimation of the concentrations of the main atmospheric species, the retrieved surface reflectance is also influenced by the spectral calibration of the sensor, especially in those wavelengths mostly affected by gaseous absorptions. In particular, errors in the surface reflectance appear when a systematic shift in the nominal channel positions occurs. A method to assess the spectral calibration of hyperspectral imaging spectrometers from the acquired imagery is presented in this p…
The Use of Bark in Biomonitoring Heavy Metal Pollution of Forest Areas on the Example of Selected Areas in Poland
2020
Abstract In the year 2016, passive biomonitoring studies were conducted in the forest areas of southern and north-eastern Poland: the Karkonosze Mountains (Kark), the Beskidy Mountains (Beskid), Borecka Forest (P. Bor), Knyszynska Forest (P. Kny), and Białowieza Forest (P. Bia). This study used bark from the tree, Betula pendula Roth. Samples were collected in spring (Sp), summer (Su), and autumn (Au). Concentrations of Mn, Fe, Ni, Cu, Zn, Cd, and Pb were determined for the samples using the atomic absorption spectrometry method with flame excitation (F-AAS). Based on the obtained results, the studied areas were ranked according to level of heavy-metal deposition: forests of southern Poland…
Ocena jednorodności zanieczyszczenia kory drzew liściastych metalami ciężkimi
2018
Celem badań była ocena jednorodności zanieczyszczenia metalami ciężkimi (Ni, Cu, Zn, Cd i Pb) kory drzew liściastych pobranej z lasu mieszanego na terenie gminy Ozimek (województwo opolskie). W ramach biomonitoringu pasywnego pobrano próbki kory z trzech gatunków drzew liściastych: z brzozy brodawkowatej (Betula pendula Roth.), buka zwyczajnego (Fagus sylvatica L.) oraz z dębu szypułkowego (Quercus robur L.). Metale ciężkie oznaczono za pomocą absorpcyjnej spektrometrii atomowej (AAS). Na podstawie przeprowadzonych badań można jednoznacznie stwierdzić, że kora drzew wykorzystanych do badań różni się pod względem stężeń metali ciężkich. Największe średnie zawartości Cu, Zn, Cd i Pb występują…
Kora brzozy brodawkowatej jako biomonitor zanieczyszczenia powietrza metalami ciężkimi
2018
Celem przeprowadzonych badań była ocena możliwości wykorzystania kory brzozy brodawkowatej (Betula pendula Roth) w biomonitoringu terenów leśnych. Do badań wykorzystano korę drzew rosnących na obszarze Beskidów i Puszczy Boreckiej. W korze, metodą absorpcyjnej spektrometrii atomowej ze wzbudzeniem w płomieniu (F-AAS), oznaczono stężenia metali ciężkich: Mn, Fe, Ni, Cu, Zn, Cd oraz Pb. Na podstawie przeprowadzonych badań stwierdzono sezonowe zmiany stężenia analitów. Wykazano również, że kora brzozy brodawkowatej może być wykorzystywana jako bioindykator do oceny zanieczyszczenia aerozolu atmosferycznego na tych obszarach np. metalami ciężkimi. Ważne jest jednak, aby dokonać walidacji poszcz…
Dietary polyphenols as antidiabetic agents: Advances and opportunities
2020
Abstract Dietary polyphenols have been widely investigated as antidiabetic agents in cell, animals, human study, and clinical trial. The number of publication (Indexed by Web of Science) on “polyphenols and diabetes” significantly increased since 2010. This review highlights the advances and opportunities of dietary polyphenols as antidiabetic agents. Dietary polyphenols prevent and manage Type 2 diabetes mellitus via the insulin‐dependent approaches, for instance, protection of pancreatic islet β‐cell, reduction of β‐cell apoptosis, promotion of β‐cell proliferation, attenuation of oxidative stress, activation of insulin signaling, and stimulation of pancreas to secrete insulin, as well as…
Characterization of Self-Growing Biomaterials Made of Fungal Mycelium and Various Lignocellulose-Containing Ingredients
2022
In this study, novel blends of mycelium biocomposites (MB) were developed. Various combinations of birch sawdust and hemp shives with birch bark (BB) and wheat bran (WB) additives were inoculated with basidiomycete Trametes versicolor to produce self-growing biomaterials. MB were characterized according to mycelial biomass increment in final samples, changes in chemical composition, elemental (C, H, N) analyses, granulometry of substrates, water-related and mechanical properties, as well as mold resistance and biodegradability. The mycelial biomass in manufactured MB increased by ~100% and ~50% in hemp and sawdust substrates, respectively. The lignocellulose ingredients during fungal growth…