Nonlinear optical properties of polymer dispersed liquid crystals doped with La2CaB10019

Date du colloque : 2012</p

Predominance of deterministic microbial community dynamics in salterns exposed to different light intensities

While the dynamics of microbial community assembly driven by environmental perturbations have been extensively studied, our understanding is far from complete, particularly for light‐induced perturbations. Extremely halophilic communities thriving in coastal solar salterns are mainly influenced by two environmental factors—salt concentrations and high sunlight irradiation. By experimentally manipulating light intensity through the application of shading, we showed that light acts as a deterministic factor that ultimately drives the establishment of recurrent microbial communities under near‐saturation salt concentrations. In particular, the stable and highly change‐resistant communities that established under high‐light intensities were dominated (>90% of metagenomic reads) by Haloquadratum spp. and Salinibacter spp. On the other hand, under 37‐fold lower light intensity, different, less stable and change‐resistant communities were established, mainly dominated by yet unclassified haloarchaea and relatively diverse photosynthetic microorganisms. These communities harboured, in general, much lower carotenoid pigment content than their high‐irradiation counterparts. Both assemblage types appeared to be highly resilient, re‐establishing when favourable conditions returned after perturbation (i.e. high‐irradiation for the former communities and low‐irradiation for the latter ones). Overall, our results revealed that stochastic processes were of limited significance to explain these patterns.This study was funded by the Spanish Ministry of Economy projects CGL2012-39627-C03-03 CLG2015_66686-C3-1-P and PGC2018-096956-B-C41 (to R.R.M.), CGL2015_66686-C3-3-P (to J.A.) and CGL2015_66686-C3-2-P (to J.E.G.P.), which were also supported with European Regional Development Fund (FEDER) funds. R.A. was funded by the Max Planck Society. KTK’s research was supported, in part, by the U.S. National Science Foundation (Award No. 1831582). T.V.P. received a pre-doctoral fellowship (No. BES-2013-064420) from the Spanish Government Ministry for Finance and Competition. R.R.M. acknowledges the financial support of the sabbatical stay at Georgia Tech supported by the Grant PRX18/00048 of the Ministry of Sciences, Innovation and Universities

A neutron diffuse scattering study of PbZrO₃ and Zr-rich PbZr_1-xTi_xO₃

A combined neutron diffuse scattering study and model analysis of the antiferroelectric crystal PbZrO3is described. Following on from earlier X-ray diffuse scattering studies, supporting evidence for disordering of oxygen octahedral tilts and Pb displacements is shown in the high-temperature cubic phase. Excess diffuse scattering intensity is found at theMandRpoints in the Brillouin zone. A shell-model molecular dynamics simulation closely reproduces the neutron diffuse scattering pattern. Both in-phase and antiphase tilts are found in the structural model, with in-phase tilts predominating. The transition between disordered and ordered structure is discussed and compared with that seen in Zr-rich PbZr1−xTixO3.</jats:p

Artificial Intelligence in Metrology - Expert System for Measuring Instruments Selection

Od samego powstania pierwszych komputerów człowiek powierzał im coraz bardziej skomplikowane i wyszukane problemy, z którymi odpowiednio zaprogramowana maszyna radzi sobie lepiej niż człowiek [5]. Z czasem pojawiły się hipotezy stworzenia sztucznych systemów, które potrafiłyby rozumować i pojmować otaczający nas świat w sposób do tej pory dostępny jedynie "Homo sapiens". Jeden z prekursorów "sztucznej inteligencji" Turing [13] zaproponował nawet test sprawdzający czy stworzoną przez człowieka maszynę można uznać za inteligentną: "Maszyna jest nazwana inteligentną, jeśli zewnętrzny obserwator nie jest w stanie odróżnić jej odpowiedzi od odpowiedzi człowieka mogącego zastepować maszynę. Jedną z koncepcji takiego, ale jednocześnie inteligentnego systemu są tzw. "Systemy ekspertowe"".From the moment when the very first computer was created a man his given it tasks with which a properly programmed machine can cope much better than he himself [5]. These tasks gradually became more and more complicated. This is how first hypothensis emerged to create artificial systems, capable of analyze and understand the surrounding world in such a way as so far only a "Homo sapiens" could do it. One of the first inventor of so called "artificial intelligence" Turing [13] proposed even a test verifying whether a machine created by a man can be considered as an intelligent one: "Machine is intelligent if an externally observing person is not able to distinguish a difference between its answer and the answer of a man who could replace the machine. One of the concepts of such an intelligent system is "Expert systems""

The evaluation of 3D parameters appointed using the spiral sampling method

W Zakładzie Metrologii i Systemów Pomiarowych Politechniki Poznańskiej opracowano nową metodę pomiaru trójwymiarowej geometrii powierzchni bazującą na próbkowaniu spiralnym. Jest to nowe podejście do zagadnienia zbierania punktów z powierzchni za pomocą niekartezjańskiej siatki próbkowania. Pomiar wykonuje się na siatce utworzonej ze zbioru punktów tworzących spiralę Archimedesa. Główną zaletą tej metody jest mniejsza czasochłonność pomiaru w porównaniu z innymi siatkami próbkowania. Stosując siatkę prostokątną, po każdym przejściu końcówki pomiarowej należy wycofać ją w położenie początkowe. Należy także poprzecznie przesunąć stolik pomiarowy o wartość odpowiadającą odległości między kolejnymi przejściami. Jeśli przy próbkowaniu spiralnym może być mowa o odcinkach wejściowym i wyjściowym, to tylko przy rozpoczęciu i przy zakończeniu pomiaru, ponieważ końcówka przez cały czas pomiaru jest w ruchu. Jest to oczywisty zysk czasu, który może wynosić od 30 % do 70 % w porównaniu z czasem przy użyciu siatki prostokątnej. Próbkowanie spiralne rozwiązuje problem czasochłonności pomiarów przestrzennych powierzchni. Jednakże, jak pokazały badania, istnieją różnice w wartościach parametrów 3D, uzyskanych metodą próbkowania spiralnego i metodą siatki prostokątnej. Nie była również znana zależność opisująca wpływ parametrów siatki spiralnej (skok spirali) na wartości parametrów przestrzennych. W artykule przedstawiono analizę wpływu próbkowania spiralnego na parametry topografii powierzchni. Podczas badań korzystano z programów MATLAB, AWK, Statistica. Do pomiarów powierzchni wykorzystano profilometry Perthen, TOPO, Wyko. Za pomocą wymienionych narzędzi opracowano program do analizy i symulacji metody próbkowania spiralnego. Przeprowadzono badania symulacyjne strategii próbkowania spiralnego dla wytypowanych powierzchni.In the world around us, all the surfaces are rough. Most of surfaces in mechanics are very complicated, and in order to describe it with certain values, the measurement and analysis of some parameters should be performed. Before 1980th, roughness analysis consisted of 2D measurement, which gave twodimensional characteristics of the surface. During the last decades, many scientists and constructors became convinced that the third dimension should be added to the analysis. At present, 3D analysis of the surface geometry is widely accepted, though some disorder in terminology and in 3D parameters classification is still present. One of important problems is also the way of measurement (points collection) for further analysis. Most of known measuring systems collect a number of parallel profiles. Are known also efforts to collect radial profiles from one point. Anyway, the stereometrical surface measurement requires far more time than typical 2D measurement. In the Division of Metrology of Poznan University of Technology the new method of measurement has been worked out, based on spiral sampling. One of the most important merits of this kind of measurement is much shorter time, when the surface of same dimensions is to be measured. When the parallel profiles are being collected, after each movement forward, the useless move back would come, and also the movement in perpendicular direction (step between profiles) would take additional time. Moreover, in each profile, beside the evaluation length, there are allowances for run-up and for overtravel. In spiral sampling, those allowances appear only once, at the beginning and at the end of measuring process, and the stylus collects the point during all the time of movement. Comparing to parallel profiles, the spiral sampling takes 30 % to 70 % less time of measurement

Mathematical description of vertical algal accessory pigment distributions in oceans – a brief presentation

A straightforward mathematical expression for describing the vertical distributions of algal accessory pigments in oceans is presented. To this end ca 1500 empirical datasets of accessory pigment depth profiles gathered during some 200 research cruises in different oceanic regions were analysed. These data were retrieved from the bio-optical databases of SeaBASS and U.S. JGOFS published on the Internet. The statistical relationships were analysed between the concentrations of accessory pigments and the trophic indices of waters, as measured by the surface concentrations of chlorophyll a and the optical depths in different oceanic regions. A mathematical expression was established and formulas based on it were found, approximating the relations between the vertical distributions of accessory pigments and the chlorophyll a concentration. These formulas can be used to model the species composition of algae in different parts of the ocean and in remote sensing algorithms

The Design Concept of the Laboratory Heater for Studying the Effect of Surface Topography to Emissivity

Remote temperature sensing and thermal imaging systems [1, 2] are invaluable tools in various fields of science and technology. The fact that radiation is a function of object surface temperature makes it possible for remote temperature measurement systems to calculate this temperature. However, to measure temperature accurately with IR system, it is necessary to know emissivity. Emissivity is one of the major sources of error in radiometric measurements. Generally, emissivity is not constant as it depends on several parameters: temperature, viewing angle, wavelength, contamination or roughness. The article presents a laboratory heater which can be used to measure the thermal emissivity ε depending on the sample surface topography