1,721,056 research outputs found
Sensitivity of a solid Eu(III) complex towards acetonitrile vapor: Structural and spectroscopic characterization
No full textThe Eu(III) nitrate complex of the meso- N,N′-bis(2-pyridylmethylene)-1,2-(R,S)-cyclohexanediamine ligand was synthesized and characterized by single crystal and powder X-ray diffraction. The crystal lattice of the complex is capable of absorbing and desorbing selectively acetonitrile molecules, at 293 K upon an acetonitrile vapor pressure of ∼0.1 × 105 Pa. This process, which is partially reversible, can be easily followed by both powder X-ray diffraction (P-XRD) and Eu(III) luminescence spectroscopy. The acetonitrile molecule, located in the outer coordination sphere of the metal ion, does not affect the radiative transition probability of 5D0 level of Eu(III) and also it does not activate further non-radiative channels from this level. On the other hand, this molecule is capable of affecting the energy position and intensities of the crystal field components of the 5D0→7F2 transition. The complex in solid form can be considered a promising material for the optical sensing of acetonitrile vapors
Studio della sicurezza della prevedibilità e dell'efficacia della LASIK con laser a femtosecondi
No full textScopo: Lo scopo di questo lavoro è riportare la nostra esperienza sulla prevedibilità, l’efficacia e la sicurezza del laser a femtosecondi nella tecnica LASIK per la correzione dei difetti refrattivi.
Materiali e metodi: Sono stati reclutati 33 pazienti (per un totale di 66 occhi) che dovevano essere sottoposti a correzione del difetto refrattivo con LASIK con laser a femtosecondi (VisumaxTM-Zeiss) e laser ad eccimeri(MEL80TM Excimer Laser – Zeiss). Prima e dopo trattamento sono stati valutati sia il visus che la refrazione. Inoltre durante la visiva preoperatoria sono stati eseguiti i calcoli atti a valutare il tessuto corneale da ablare durante l’esecuzione del laser e lo spessore corneale residuo previsto. Sono stati confrontati i dati dello spessore corneale previsto con i valori ottenuti dopo il trattamento ed è stata valutata la precisione del taglio lamellare, misurando le dimensioni dello spessore del flap su tutta la superficie con immagini OCT Visante.
Risultati: L’acuità visiva naturale postoperatoria è risultata in tutti i pazienti superiore o uguale a 9/10.la refrazione media postoperatoria è stata di -0,07 + 0,02 D (range – 1,75/ e 0 D) (Tabella 1 e 2). Lo spesore cornealemedio ottenuto dopo il trattamento è stato di 465,5 + 36.7 micron (range 573 – 380 micron)a fronte di un residuo previsto medio di 446,8 + 46,5 micron (range 553 – 302) con una elevata correlazione fra lo spessore pianificato e quello ottenuto dopo l’intervento (r=0,45). Il flap è risultato di morfologia sempre molto regolare con uno spessore medio all’apice corneale di 111,3 + 3 micron, a 3 mm. e 7 mm. dall’apicecorneale rispettivamente di 111 + 2.7 micron e 110,6 + 2.3 micron. In nessun caso si sono presentate complicanze intra-operatorie e, nel post-operatorio, abbiamo osservato come complicanza post-operatoria solamente in due occhi nel primi 20 giorni un transitorio aumento del tono oculare, ben controllato dalla terapia topica e successivamente regredito.
Conclusioni: I dati in nostro possesso indicano che il trattamento LASIK con laser a femtosecondi VisumaxTM – Zeiss e laser ad eccimeri(MEL80TM Excimer Laser – Zeiss) risulta essere sicuro, efficace e prevedibile e ha costituito un importante miglioramento rispetto alla chirurgia refrattiva con microcheratomo
Surface response-based performance assessment of a virtual-flowmeter based transducer for helium monitoring
No full textThe assessment of the metrological performance of a virtual flowmeter-based transducer for helium under cryogenic conditions is proposed. At this aim, first a model of the transducer, mainly based on a virtual flowmeter exploiting Sereg-Schlumberger method and a valve model exploiting finite-element approach, is presented. The transducer and valve models are validated experimentally on a case study for helium monitoring in cryogenic systems at the European Organization for Nuclear Research (CERN). Then, a fully simulated approach is performed in order to assess the transducer performance. In particular, the analysis effort is optimized by systematically exploring operating conditions by means of 3d-CCRD strategy
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
Site selective luminescence spectroscopy of Eu3+ in the rhombohedral pyrochlores Mg2La3Sb3O14 and Ca(2)La(3)Sb(3)O1(4): Observation of Eu3+ in a strongly distorted site
No full textLow temperature site selective spectroscopy has been used to probe the distribution of the Eu3+ ion on sites available in the ordered and disordered pyrochlores, Mg2La3Sb3O14 and Ca2La3Sb3O14. While the Mg-pyrochlore shows the presence of a single site with inversion symmetry, the emission spectrum of the Ca-pyrochlore is indicative of the presence of several different non-centrosymmetric sites for the dopant ion. These observations are consistent with the structural model that was proposed earlier. The 5D0 -> 7F0 emission transition in the Capyrochlore occurs at very high energy (17,550 cm- 1) and under a very specific excitation wavelength. Possible explanation for this observation is provided
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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