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Facility for the preparation of primary gas mixtures by gravimetry
No full textPresso l’ I.N.RI.M. – Sezione Massa è stato progettato e realizzato un sistema per la preparazione, mediante il metodo gravimetrico, di miscele gassose campione primarie dato che la realizzazione di tali miscele rappresenta un obiettivo importante per l’Istituto.
Il presente prodotto descrive le caratteristiche della stazione per il riempimento e lo svuotamento di bombole le cui parti principali sono le linee di distribuzione per il gas, un sistema per il vuoto e una bilancia per la pesata preliminare delle bombole. Vi è inoltre un comparatore di massa per la pesata di precisione corredato di uno scambiatore meccanico per la movimentazione automatica delle bombole. Sono quindi riportati i risultati ottenuti nel primo Confronto Chiave Internazionale CCQM-K52 effettuato dall'INRIM (M. Sega: persona di riferimento per l'INRIM)utilizzando come campioni le miscele di CO2 in aria preparate mediante la suddetta stazione.A system for the gravimetrical preparation of primary reference gas mixtures was projected and set up at I.N.RI.M.. The realisation of such mixtures is an important goal for a national metrology institute. The features of the apparatus to fill and evacuate the cylinders station are described: its main parts are the lines for distributing the gases, a vacuum system and a balance for the preliminary weighing of the cylinders. The facility has, in addition, a mass comparator for high accuracy weighing and a system for exchanging the cylinder during the weighing process. The results obtained in the International Key Comparison "CCQM-K52" (INRIM contact: M. Sega)are presented. This is the first Key Comparoison carried out by INRIM in the chemical field using as measurement standards a set of primary mixtures of CO2 in air prepared at INRIM with the described facility
Ab-initio study of the electromagnetic response and polarizability properties of carbon chains
No full textWe present the most complete set of calculations to date of the ground state electronic properties and of the optical/UV response function of linear carbon chains CN, using ab-initio methods based on local density and on time-dependent local density approximations (LDA and TDLDA). Making use of the associated transition densities and wavefunctions we are able to provide microscopic insight into the collectivity of the corresponding plasmon spectrum in terms of correlated particle-hole excitations. From this analysis it is found that the (one-dimensional 1-D) delocalization of π (valence) electrons is responsible for the conspicuous values of the static dipole polarizability and of the high value of the exponent describing its dependence with the number of carbon atoms. Within this framework the electronic structure and linear response function of a carbon ring is also calculated. Although many properties of this function are similar to that associated with linear chains of the same number of atoms, the corresponding polarizabilities differ appreciably, providing a reliable method to distinguish between linear and close structures. The first principle results of the properties of linear carbon chains are compared with both theoretical and experimental results available in the literature, and constitute the basis for a systematic study of these 1-D s p-bonded systems, which have been found to be involved in such seemingly disparate phenomena as fullerene growth mechanism and diffuse interstellar bands
Metodi di risonanza elettromeccanica per misure elettriche assolute: prototipo di studio
No full textMultilayer control of an optical reference cavity for space applications
No full textThe paper is concerned with multilayer and fine thermal control of an optical reference cavity for space applications, under development at National Metrology Institute, Turin, Italy. The cavity, made by ultra low expansion glass (Corning ULE), must be kept close to the zero-expansion temperature (close to 25 °C) of the glass. The target can only be met by active control, while leaving the cavity free of sensor and actuators. This is obtained by two concepts: thermal bath and reference thermal sink, the latter allowing zero-expansion temperature to be reached by heaters in a wide environment range. Preliminary experiments of the two concepts leading to cavity design are detailed
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
Mass to planck constant relation via electro-mechanical resonance: feasibility study with a voltage balance
No full text
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
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