1,722,241 research outputs found
Importanza e possibilità di utilizzo dei fanghi rivenienti dalla depurazione di acque reflue per l’ottenimento di compost impiegabili nell’agricoltura tradizionale e nei sistemi agricoli sostenibili
No full textP44-A104 Logistics and results with precut and preloaded graft for DMEK
No full textPURPOSE: Descemet membrane endothelial keratoplasty (DMEK) preparation is technically demanding and is a limiting factor for uptake of this kind of surgery. Supply methods that simplify the procedure for surgeons are key to increasing uptake. In this talk logistics and outcomes of Eye bank prepared DMEK tissue will be presented. METHODS: Laboratory studies of two different shipping protocols for DMEK (endothelium trifolded inwards and endothelium rolled outwards) will be presented. Clinical outcomes and complications of patients underwent to DMEK surgery with Eye bank prepared or surgeon prepared tissue will be presented. A Cost analysis of eye bank versus surgeon prepared endothelial grafts will be also part of the presentation. RESULTS: There was no difference in endothelial cell viability between surgeon or eye bank prepared tissue. Surgeon-stripped DMEK grafts in the laboratory investigation showed significantly higher elastic modulus and adhesion force compared to prestripped and preloaded tissues (p<0.0001). In the clinical data, rebubbling rates of 48%, 40% and 15% were observed in preloaded, prestripped and surgeon-stripped DMEK grafts, respectively. The cost analysis showed that eye bank prepared tissues had higher surgical expenses compared to those prepared by the surgeon, while the post-operative care expenses were similar between the two groups CONCLUSION: The Eye bank prepared tissues are a valid alternative to Surgeon prepared tissue, however need to be highlighted that with current method there is a decreased adhesion forces and elastic modulus in eye bank prepared tissues that may contribute to increased rebubbling rates
Il potenziale formale della coppia Ti(IV,III) a 25°C nel mezzo HCl 1 M NaCl 2 M
No full textNell’ambito delle diverse coppie ossidoriduttive di un elemento in soluzione acquosa, vengono indicate come ipoossidate le specie appartenenti a quelle coppie il cui potenziale standard è inferiore a quello di riduzione dell’acqua ad idrogeno, e come iperossidate le specie che fanno parte di coppie con valore del potenziale di riduzione superiore a quello dell’ossigeno ad acqua. Si tratta in entrambi i casi di specie termodinamicamente poco stabili che si trasformano rispettivamente nella forma ossidata con evoluzione di idrogeno e nella forma ridotta con evoluzione di ossigeno. Tali processi sono modulati dall’attività idrogenionica della soluzione (Figura 1).
Figura 1. Intervallo di stabilità termodinamica dell’acqua
La decomposizione di queste specie da parte dell’acqua, spesso catalizzata dagli stessi elettrodi metallici delle celle utilizzate per la misura dei potenziali redox, introduce una rilevante fonte di incertezza sulla composizione delle soluzioni; a questa si aggiunge l’incertezza dovuta alla presenza di giunzioni liquide, di impurezze nei mezzi ionici, alla mancanza di controllo dei coefficienti di attività. Tutto ciò ha come effetto le rilevanti differenze riscontrabili in letteratura tra i pochi valori riportati per i potenziali redox di tali sistemi.
Alcune di queste coppie con specie ipo o iperossidate (Ag2+, Co3+ , Ce4+ , Cr2+ , V2+, U3+ , Yb2+) sono state studiate nel nostro laboratorio e, i relativi valori dei potenziali redox in cui sono coinvolte, misurati [1-7]. Funzionale in questi studi è stata la diminuzione in alcuni casi della temperatura delle soluzioni (-5°C) così da ottenere una significativa attenuazione dell’azione di decomposizione esercitata dall’acqua.
Con riferimento a quanto appena detto, si è intrapreso lo studio della coppia redox (IV,III) del titanio, che nella forma di ione titanoso, Ti3+, in particolare sotto forma di cloruro o solfato, presenta numerose applicazioni analitiche [8]. D’altra parte, per le sue proprietà di elevata resistenza, il titanio metallico trova applicazioni tecnologiche che spaziano dalle leghe speciali, ai pigmenti bianchi, alla realizzazione di protesi ortopediche. Sulla base dell’esperienza acquisita, ci siamo proposti di determinare il potenziale redox della coppia Ti(IV, III), anche perché i valori riportati in soluzione acquosa per tale grandezza risultano notevolmente differenti [9-11].
L’indagine è stata effettuata con due metodi differenti: nel primo, per ottenere la miscela dei due stati di ossidazione, si è utilizzata l’ossidazione del Ti(III) a Ti(IV) per elettrolisi controllata (titolazioni coulombometriche) seguita dalla misura in situ della fem della cella senza giunzione
+ GE | Soluzione S | Hg - GE = Elettrodo a vetro
Nel secondo metodo, la specie ipoossidata Ti(III) è stata ottenuta per riduzione del Ti(IV) con amalgama di zinco (batch) seguita da determinazione potenziometrica, analoga alla precedente. Le due metodiche indipendenti hanno fornito valori del potenziale cercato in ottimo accordo, precisamente:
Metodo coulombometrico Ef = 9 + 1 mV
Metodo batch Ef = 9 + 2 mV
Riferimenti bibliografici
1. Biedermann G, Maggio F, Romano V, Zingales R. Acta Chem. Scand. 1981; A35: 287.
2. Biedermann G, Orecchio S, Romano V, Zingales R. Acta Chem. Scand. 1986; A40:161
3. Zingales R. J. Chem. Soc. Dalton Trans 1990; 229
4. Biedermann G, Romano V. Acta Chem. Scand. 1975; A35: 615
5. Fiore M, Orecchio S, Romano V, Zingales R. J. Chem. Soc. Dalton Trans 1993; 799
6. Orecchio S, Piazzese D, Romano V, Zingales R. Ann. Chim. 1988; 88: 129
7. Amorello D, Romano V, Zingales R. Ann. Chim. 2004; 94 :113
8. Vogel A I Textbook of Quantitative Inorganic Analysis, Longmans 1961; 329
9. Kolthoff I M, Rec. Trav. Chim. Pays-Bas, 1924; 43 , 768
10. Boch R and Greiner G, Z. Anorg. Chem., 1958; 295 ,61
11. Lingane J J Anal. Chem. 1958 20 79
Simulation of electron-phonon coupling and heating dynamics in suspended monolayer graphene including all the phonon branches
No full textThermal effects in monolayer graphene due to an electron flow are investigated with a direct simulation Monte Carlo (DSMC) analysis. The crystal heating is described by simulating the phonon dynamics of the several relevant branches, acoustic, optical, K and Z phonons. The contribution of each type of phonon is highlighted. In particular, it is shown that the Z phonons, although they do not enter the scattering with electrons, play a non-negligible role in the determination of the crystal temperature. The phonon distributions are evaluated by counting the emission and absorption processes during the MC simulation. The crystal temperature raise is obtained for several applied electric fields and for several positive Fermi energies. The latter produces the effect of a kind of n-doping in the graphene layer. Critical temperatures can be reached in a few tens of picoseconds posing remarkable issues regarding the cooling system in view of a possible application of graphene in semiconductor devices. Moreover, a significant influence of the lattice temperature on the characteristic curves is observed only for long times, confirming graphene rather robust as regards the electrical performance
Assessment of the Constant Phonon Relaxation Time Approximation in Electron–Phonon Coupling in Graphene
No full textThe importance of the correct determination of the relaxation times, entering the electron–phonon coupling, is crucial for a proper evaluation of the rise of the crystal lattice temperature induced by a flow of electrons that undergo an external electric field. We describe the crystal heating by simulating the dynamics of all the phonon branches, i.e. acoustic, optical, K and Z phonons in a suspended monolayer graphene. At each time step the charge transport is determined by means of a direct simulation Monte Carlo procedure while the evolution of the phonon distributions is evaluated by counting the emission and absorption processes in the electron–phonon scatterings. For several applied electric fields and for several positive Fermi energies, the behaviors of the crystal lattice temperature, obtained with different models of the relaxation times, are compared and discussed. The contribution of each type of phonon is highlighted as well
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
How endothelial keratoplasty has revolutionized current treatment of endothelial disease
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