Time domain impedance modelling and applications

AbstractToday, there is a high, often not fully evolved potential of noise attenuation by passive acoustic treatments. Current numerical methods are able to help developing optimal treatments. Thus, the simulation of acoustic lining in aeroengines is one of the core objectives for the development of modern CAA solvers. Here, the opportunities of the Extended Helmholtz Resonator (EHR) model of Rienstra in the time domain in this design and optimisation process are demonstrated. The optimization of a lining for a specific application as the obvious objective is still out of reach for many cases with current numerical resources. However, the model allows the optimisation towards the dissipation characteristics in an impedance flow tube measurement with a physical liner sample, which provides the numerical parameters of the liner for high fidelity CAA simulations. Moreover, the model parameters are related to the cell geometry and face sheet of the liner panel. An example is provided for the purely numerical prediction of the attenuation in the complex flow of an aeroengine duct. This is demonstrated by considering the resulting parameters in modal axisymmetric and three dimensional simulations of the rearward sound radiation from a lined bypass duct. The example demonstrates, that the optimisation of the liner properties is not achievable in a justifiable time, even if simplified two dimensional conditions are considered. A possible solution to this problem is to use the computational power of a graphics processing unit (GPU). The development of pixel shaders which implement a large number of parallel processors into the GPU, shows a much more agile growth than any CPU based system does. As an outlook, a platform independent implementation of a GPU based CAA solver with impedance boundary condition and the capability to handle axisymmetric duct geometries is presented. It demonstrates a speed up by a factor > 100

Reprint of: Time Domain Impedance Modelling and Applications

AbstractToday, there is a high, often not fully evolved potential of noise attenuation by passive acoustic treatments. Current numerical methods are able to help developing optimal treatments. Thus, the simulation of acoustic lining in aeroengines is one of the core objectives for the development of modern CAA solvers. Here, the opportunities of the Extended Helmholtz Resonator (EHR) model of Rienstra in the time domain in this design and optimisation process are demonstrated. The optimization of a lining for a specific application as the obvious objective is still out of reach for many cases with current numerical resources. However, the model allows the optimisation towards the dissipation characteristics in an impedance flow tube measurement with a physical liner sample, which provides the numerical parameters of the liner for high fidelity CAA simulations. Moreover, the model parameters are related to the cell geometry and face sheet of the liner panel. An example is provided for the purely numerical prediction of the attenuation in the complex flow of an aeroengine duct. This is demonstrated by considering the resulting parameters in modal axisymmetric and three dimensional simulations of the rearward sound radiation from a lined bypass duct. The example demonstrates, that the optimisation of the liner properties is not achievable in a justifiable time, even if simplified two dimensional conditions are considered. A possible solution to this problem is to use the computational power of a graphics processing unit (GPU). The development of pixel shaders which implement a large number of parallel processors into the GPU, shows a much more agile growth than any CPU based system does. As an outlook, a platform independent implementation of a GPU based CAA solver with impedance boundary condition and the capability to handle axisymmetric duct geometries is presented. It demonstrates a speed up by a factor>100

Peptide-Grafted Nontoxic Cyclodextrins and Nanoparticles against Bacteriophage Infections

One of the biggest threats for bacteria-based bioreactors in the biotechnology industry is infections caused by bacterial viruses called bacteriophages. More than 70% of companies admitted to encountering this problem. Despite phage infections being such a dangerous and widespread risk, to date, there are no effective methods to avoid them. Here we present a peptide-grafted compounds that irreversibly deactivate bacteriophages and remain safe for bacteria and mammalian cells. The active compounds consist of a core (cyclodextrin or gold nanoparticle) coated with a hydrophobic chain terminated with a peptide selective for bacteriophages. Such peptides were selected via a phage display technique. This approach enables irreversible deactivation of the wide range of T-like phages (including the most dangerous in phage infections, phage T1) at 37 degrees C in 1 h. We show that our compounds can be used directly inside the environment of the bioreactor, but they are also a safe additive to stocks of antibiotics and expression inducers (such as isopropyl beta-D-1-thiogalactopyranoside, i.e., IPTG) that cannot be autoclaved and are a common source of phage infections

Cryogenic electron tomography to determine thermodynamic quantities for nanoparticle dispersions

Here we present a method to extract thermodynamic quantities for nanoparticle dispersions in solvents. The method is based on the study of tomograms obtained from cryogenic electron tomography (cryoET). The approach is demonstrated for gold nanoparticles (diameter < 5 nm). Tomograms are reconstructed from tilt-series 2D images. Once the three-dimensional (3D) coordinates for the centres of mass of all of the particles in the sample are determined, we calculate the pair distribution function g(r) and the potential of mean force U(r) without any assumption. Importantly, we show that further quantitative information from 3D tomograms is readily available as the spatial fluctuation in the particles’ position can be efficiently determined. This in turn allows for the prompt derivation of the Kirkwood-Buff integrals with all their associated quantities such as the second virial coefficient. Finally, the structure factor and the agglomeration states of the particles are evaluated directly. These thermodynamic quantities provide key insights into the dispersion properties of the particles. The method works well both for dispersed systems containing isolated particles and for systems with varying degrees of agglomerations

Cryoconite – from minerals and organic matter to bioengineeredsediments on glacier's surfaces

Cryoconite is a mixture of mineral and organic material covering glacial ice, playing important roles in biogeochemical cycles and lowering the albedo of a glacier surface. Understanding the differences in structure of cryoconite across the globe can be important in recognizing past and future changes in supraglacial environments and ice-organisms-minerals interactions. Despite the worldwide distribution and over a century of studies, the basic characteristics of cryoconite, including its forms and geochemistry, remain poorly studied. The major purpose of our study is the presentation and description of morphological diversity, chemical and photoautotrophs composition, and organic matter content of cryoconite sampled from 33 polar and mountain glaciers around the globe. Observations revealed that cryoconite is represented by various morphologies including loose and granular forms. Granular cryoconite includes smooth, rounded, or irregularly shaped forms; with some having their surfaces covered by cyanobacteria filaments. The occurrence of granules increased with the organic matter content in cryoconite.Moreover, amajor driver of cryoconite colouringwas the concentration of organicmatter and its interplay with minerals. The structure of cyanobacteria and algae communities in cryoconite differs between glaciers, but representatives of cyanobacteria families Pseudanabaenaceae and Phormidiaceae, and algae families Mesotaeniaceae and Ulotrichaceaewere themost common. Themost of detected cyanobacterial taxa are known to produce polymeric substances (EPS) that may cement granules. Organic matter content in cryoconite varied between glaciers, ranging from 1% to 38%. The geochemistry of all the investigated samples reflected local sediment sources, except of highly concentrated Pb andHg in cryoconite collected fromEuropean glaciers near industrialized regions, corroborating cryoconite as element-specific collector and potential environmental indicator of anthropogenic activity. Our work supports a notion that cryoconite may bemore than just simple sediment and instead exhibits complex structure with relevance for biodiversity and the functioning of glacial ecosystem

Pielęgniarstwo na rzecz milenijnych celów rozwoju. Cz. 2

Praca recenzowana / Peer-reviewed paperZ przyjemnością oddajemy w Państwa ręce drugi tom monografii wydanej z okazji XII Kongresu Pielęgniarek Polskich w Krakowie, w którym udział wzięło blisko 500 pielęgniarek, zaprezentowano 160 prac w 9 sesjach. Ta kolejna już publikacja świadczy o dynamicznym rozwoju badań naukowych w pielęgniarstwie. Dowodzi, że pielęgniarstwo to nie tylko zawód, ale i interdyscyplinarna nauka

Centrality evolution of the charged-particle pseudorapidity density over a broad pseudorapidity range in Pb-Pb collisions at root s(NN)=2.76TeV

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