1,720,962 research outputs found
Polarization Lidar Calibration Techniques and Sensitivity Analysis
No full textCalibrated lidar measurements of linear depolarization ratio provide highly reliable information to discriminate between spherical and non-spherical particles in the atmosphere and to distinguish between liquid and solid phase clouds. In this paper three different calibration techniques are described. For each technique a sensitivity analysis is performed and the different contributions to the total error are evaluated. The stability of atmosphere, the laser source polarization degree, the accuracy of polarization alignment and the background radiation are taken into account in the simulated depolarization measurements. The influence of these parameters and the choice of calibration range and calibration height are studied also. Two calibration techniques were experimentally validated by more than 28 calibration measurements in nearly 5 months. Furthermore aerosol depolarization measurements taken after the calibration are presented
Retrieval of aerosol extinction-to-backscatter ratios by combining ground-based and space-borne lidar elastic scattering
No full textDevelopment of a Multiparametric Lidar with the depolarization sensor
No full textThe topic of this work was the design, the realization and the calibration of the depolarization sensor added in the Napoli Lidar (Light Detection and Ranging) system. In addition a complete rebuilding of the receiving system was operated, and a new characterization of all the components of the apparatus was done.
From the advent of Lidar technology in 1970 the study of the composition of the atmosphere gets a speed up. Lidar is an active sensor that sends into the atmosphere a short laser pulse and measures the elastic and Raman shifted optical backscattered power from molecules and aerosols. From the delay of the received pulse, the position of the scattering elements is obtained. Analyzing the backscattered radiation some important optical properties of the atmospheric aerosols can be derived: backscattering and extinction coefficients, position and altitude of the layers, colour index and so on.
In this context, a depolarization-sensitive Lidar can help to characterize the particle’s shape.
The discrimination of the shape of the aerosols is very important, for example to distinguish the phase of the clouds (ice-clouds are strongly asymmetric scatterers while low clouds are made by spherical water’s drops) and the type of aerosols (Saharan dust is constituted by non-spherical particles while urban aerosols by little spherical particles).
The depolarization measurements can be performed by using a linearly polarized laser source and a hardware configuration of the receiving system including two channels detecting simultaneously the backscattered radiation in the parallel and orthogonal direction with respect to the laser beam.
The total depolarization ratio, due both to molecular and aerosol contributions, is simply the calibrated ratio of the orthogonal signal to the parallel one. So, a key question to obtain high quality depolarization measurements is performing a good calibration of the Lidar system.
In this work different calibration techniques were analyzed by simulating lidar signals in different atmospheric conditions. In Napoli the sensor was realized and then calibrated while in Potenza the depolarization sensor was only calibrated. These two systems were calibrated with different techniques, due to different apparatus conditions.
My scientific activity was spent for the most in the Atomic and Laser Applications Laboratory in Physics Department of University Federico II of Napoli.
A period of three months was also spent in C.N.R.-I.S.A.C.(Istituto di Scienze Atmosferiche e Climatiche), in Bologna, where some theoretical models about the atmospheric dynamic were developed. Two months period was also spent in C.N.R.-I.M.A.A. (Istituto di Metodologie per l’Analisi Ambientale- Tito Scalo-Potenza), working under the supervision of Dr. Gelsomina Pappalardo
m-DOPA addition in MAPLE immobilization of lipase for biosensor applications
No full textMatrix Assisted Pulsed Laser Evaporation (MAPLE) is a thin film deposition technique which uses a pulsed laser beam impinging, inside a high vacuum chamber, on a frozen target containing the guest molecules in a volatile matrix to induce fast “evaporation” of the matrix, and ejection of the guest molecules. Lipase, an enzyme acting as a catalyst in hydrolysis of lipids, is widely used in biosensors for detection of triglycerides in blood serum. A key action to this purpose is lipase immobilization on a substrate. In a recent paper, we have shown that MAPLE technique is able to deposit lipase on a substrate in an active form. Here we show that addition to the guest/matrix target of a small amount of m-DOPA (3-(3,4-dihydroxyphenyl)-2-methyl-l-alanine) in order to improve adhesion and protect lipase secondary structure, also allows the lowering the laser pulse energy required for matrix evaporation and therefore the risk of damaging the enzyme. Keywords: MAPLE, Lipase, m-DOPA, Biosensor
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Lipase immobilization for catalytic applications obtained using fumed silica deposited with MAPLE technique
No full texttLipases are enzymes used for catalyzing reactions of acylglycerides in biodiesel production from lipids,where enzyme immobilization on a substrate is required.Silica nanoparticles in different morphologies and configurations are currently used in conjunction withbiological molecules for drug delivery and catalysis applications, but up to date their use for triglycerideshas been limited by the large size of long-chain lipid molecules.Matrix assisted pulsed laser evaporation (MAPLE), a laser deposition technique using a frozen solu-tion/suspension as a target, is widely used for deposition of biomaterials and other delicate molecules.We have carried out a MAPLE deposition starting from a frozen mixture containing fumed silica and lipasein water. Deposition parameters were chosen in order to increase surface roughness and to promote theformation of complex structures. Both the target (a frozen thickened mixture of nanoparticles/catalyst inwater) and the deposition configuration (a small target to substrate distance) are unusual and have beenadopted in order to increase surface contact of catalyst and to facilitate access to long-chain molecules.The resulting innovative film morphology (fumed silica/lipase cluster level aggregation) and the lipasefunctionality (for catalytic biodiesel production) have been studied by FESEM, FTIR and transesterificationtests
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