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Estudo linguístico no Vale do Jequitinhonha: o léxico de Minas Novas

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varied quite markedly with height, and that air masses aloft (∼200 m above the ground) could have an aerosol loading quite different to that measured on the ground (Rankin and Wolff, 2002). However, for the event described here, at least, it appears that the 4139 ACPD 7, 4127–4163, 2007 Multi-seasonal NOy budget in coastal Antarctica A. E. Jones et al. Title Page Abstract Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion EGU source of surface snow nitrate was wet deposition and scrubbing, and the data are consistent with the nitrate source being p-NO−3 within the boundary layer. 4 Boundary layer trace gas versus snowpack sources of NOx A key question among polar atmospheric chemists concerns the role of polar snow5 packs as a source of trace gases to the overlying boundary layer. For those studying nitrogen chemistry, the interest lies in understanding the budget of NOx; we know that NOx is photochemically produced (Honrath et al., 1999; Jones et al, 2000) and then released (Jones et al., 2001; Wolff et al., 2002) from the snowpack, but the relative contribution compare to NOx production from trace gases in the background atmo10 sphere has not yet been assessed. The data gathered during CHABLIS allow us to constrain the dominant NOx production mechanisms, and by comparing these calculated production rates, to assess the relative importance of sources of boundary layer NOx, both in the air and from the snowpack. This approach also provides insight into which gas-phase species are dominating NOx production within the boundary layer. 15 4.1 Methodology We selected two 24-h periods, one in summer and one in spring, within which to calculate diurnally-averaged NOx (as either NO or NO2) production. The periods selected were 18 January 2005 and from noon of 28 September 2004 through to noon of 29 September 2004. The former period was the first day in the summer season when 20 high-resolution alkyl nitrate data were available to compliment the other high-resolution datasets. This was also a time when an NOy intensive was carried out, so that daily HNO3 measurements are available. During the latter period, an NOy measurement intensive was also conducted, giving, in addition, alkyl nitrate measurements every 6 h – the highest resolution alkyl nitrate data available for the spring period. 4140 ACPD 7, 4127–4163, 2007 Multi-seasonal NOy budget in coastal Antarctica A. E. Jones et al. Title Page Abstract Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion EGU 4.1.1 Deriving gas-phase data NOx production rates were calculated every 3 h during these diurnal periods, giving 8 data points from which daily means could be calculated. Where possible (e.g. for HONO, PAN, summertime methyl and ethyl nitrates), input data were taken from an 5 hourly data merger carried out for all the CHABLIS data and the few missing data points were derived by linear interpolation. For the 6-hourly springtime methyl and ethyl nitrate mixing ratios, it was by default necessary to interpolate to achieve data at a 3-h frequency. These data were thus point-averages rather than hourly-averages, but as mixing ratios did not vary rapidly over the day, the uncertainty introduced by this 10 approach is limited. For HNO3, sampled over a longer timeframe, it was necessary to reconstruct higher resolution data. Summertime HNO3 was measured as a 24-hmean centred around 23:59 on both 17 January and 18 January. These two data points were averaged to derive a daily mean for 18 January. The diurnal variation was reconstructed by comparing with 6-hourly resolution HNO3 data measured previously 15 at Neumayer station (Jones et al., 1999). There, a diurnal cycle with amplitude 7.5 pptv was measured, centred around noon. This amplitude was applied to the 18 January mean to give a reasonable diurnal cycle. For the 28/29 September HNO3, the 6-hourlyresolution data were below the detection limit, so the daily mean for 27 September and 29 September were averaged to give a mean for the calculation period. This mean was 20 only 0.96 pptv, and, being so low, it was taken to be constant over the 24-h period of interest. Finally, several measured NOy species did not exceed 2 pptv throughout the year (e.g. NO3 and the higher alkyl nitrates), and they were ignored for this calculation. Similarly, output from the GEOS-Chem model suggested that HNO4 also remained well below this threshold throughout the year (M. Evans, personal communication) so 25 no account for HNO4 was taken here. 4141 ACPD 7, 4127–4163, 2007 Multi-seasonal NOy budget in coastal Antarctica A. E. Jones et al. Title Page Abstract Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion EGU 4.1.2 Gas-phase kinetic data Gas-phase reaction rates were taken from Atkinson et al. (2004, 2006) and photolysis rates for each 3-h period were calculated using the on-line version of the radiative transfer model TUV (Madronich and Flocke, 1998). For these calculations, input parameters 5 included the total ozone column measured at Halley for these days, and an albedo of 0.9. Clear sky conditions were assumed, so photolysis rates will be overestimated, but the relative effect on all species will be comparable. In addition, OH concentrations were necessary for some kinetic calculations. On 18 January 2005, OH was measured by the FAGE (Fluorescence Assay by Gas Expansion) instrument (Bloss et al., 2007). 10 These data were included in the CHABLIS data merger, so that mean hourly OH concentrations were available for this period. No OH measurements were available for September, so OH was derived indirectly. Bloss et al. (2007) calculated a mid-month OH throughout the CHABLIS measurement period based on varying jO(1D) (from the TUV model). To derive a daily mean OH for 28/29 September, we averaged the mid15 month values for September and October, and found that (28/29 September)calculated = 0.561 (15 January)calculated. A diurnally-varying OH for 28/29 September was calculated from 0.561 * each 3-hourly measured January OH. Temperature data were taken from measured values. For PAN thermal decomposition, the upper limit was calculated according to –d[PAN]/dt = k[PAN]. 20 4.1.3 Calculating snowpack NOx emissions The rates with which NOx was emitted from the snowpack during the periods of interest were calculated in line with previous work by Wolff et al. (2002). In brief, spectral irradiance at 3-h intervals was calculated using the TUV model. These were converted to actinic flux as a function of depth according to output from a model designed to 25 simulate light propagation through snow (Grenfell, 1991). The actinic fluxes were then convoluted with the absorption cross-sections and the quantum yield to give J values. In this case, temperature-dependent quantum yields were used (Chu and Anastasio, 4142 ACPD 7, 4127–4163, 2007 Multi-seasonal NOy budget in coastal Antarctica A. E. Jones et al. Title Page Abstract Introduction Conclusions References Tables Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion EGU 2003) which were not available at the time of the Wolff et al., 2002 work. A temperature of –4 C was taken for 18 January, and of –20 C for 28/29 September. These were chosen by assuming that the top few cms of snow saw an average of the near surface (1 m) air temperature for the preceding 1–2 days. Finally, the nitrate concentration in snow 5 was derived using the average of the 0 cm, 5 cm and 10 cm snow nitrate concentration from the snowpit dug nearest to the date in question. This gave 73 ng/g for September and 157 ng/g for January. 4.2 Outcome The results for the gas-phase production rates are given in Table 3a. It is immedi10 ately evident that the contribution from HONO photolysis completely dominates NOx production for both periods, with rates of 6.20E+05 and 4.80E+04 molecs cm−3 s−1 for January and September respectively. This is no great surprise, given the very short lifetime of HONO to photolysis, and reflects a recycling of NOx through HONO (via NO + OH → HONO) rather than a pure source of NOx. Indeed, NOx, although generally 15 defined as NO + NO2, is sometimes expanded to include HONO as well. However, as discussed earlier, HONO also has a source from snowpack photochemistry (Zhou et al., 2001; Beine et al., 2002; Dibb et al., 2002) so as well as facilitating recycling, boundary layer HONO that has been released from the snowpack can act as a source of atmospheric NOx. With our data it is not possible to determine how much of the 20 NOx produced by HONO photolysis (or reaction with OH) is conduto radicular. O objetivo deste estudo foi investigar e estabelecer uma relação precisa da quantidade de luz transmitida através de pinos de fibra e seu efeito na KHN e na RA de um cimento resinoso de dupla polimerização. Nossos resultados mostram boas evidências de que a quantidade de luz tranamitida é baixa e não tem influência na retenção do pino ao conduto radicular ou na microdureza do cimento resinoso dual auto-adesivo utilizado. Em face aos nossos achados não recomendamos utilizar cimentos fotopolimerizáveis ou de dupla polimerização. Pelas razões discutidas nossa recomendação é de que até o surgimento de novas evidências científicas apenas materiais auto-polimerizáveis sejam utilizados. Importante salientar que não estamos contraindicando os pinos translucentes. Estes pinos tem características mecânicas semelhantes aos outros fibroresinosos. Só não recomendamos seu uso associado a cimentos que dependam da luz no seu processo de polimerização. A utilização de cimentos resinosos auto-adesivos de dupla polimerização deve ser discutida à parte. O uso desses cimentos traz vantagens baseadas na diminuição de passos clínicos, facilidade técnica, diminuição da possibilidade de erros e do tempo clínico gasto nos dos procedimentos de cimentação. Em recente estudo pode-se verificar que em algumas situações clínicas valores de resistência adesiva foram superiores para pinos cimentados com um cimento auto-adesivo comparativamente aos cimentados pela técnica adesiva convencional independente do tipo do cimento quanto à reação química (Mongruel et al., 2012), e a justificativa para tais achados é exatamente pelo fato da simplicidade da técnica. Sendo assim, o uso do cimento auto-adesivo utilizado em nosso trabalho parece ser eficiente na cimentação de pinos intrarradiculares desde que, assim como em qualquer cimentação, os conceitos que regem estes procedimentos sejam fielmente atendidos.     58   Não obstante a toda essa discussão técnico-científica, o fator preponderante na retenção de um pino continua a ser a retenção friccional. Uma boa adaptação do pino continua sendo primordial para o sucesso restaurador. A função do cimento é tão somente preencher os espaços entre o pino e o canal radicular favorecendo a retenção friccional. Lembrando por fim que nenhum cimento tem a capacidade de compensar preparos intrarradiculares em comprimento inadequado ou um pino mal adaptado (Summitt at al., 2001).   59 8 – ANEXOS   Referências   61   1. Akgungor G, Akkayan B. Influence of dentin bonding agents and polymerization modes on the bond strength between translucent fiber posts and three dentin regions within a post space. J Prosthet Dent 2006;95:368-78. 2. Albuquerque RC, Polleto LTA, Fontana RHBTS, Cimini Junior CA. Stress analysis of an upper central incisor restored with different posts. J Oral Rehabil 2003;30:936-43. 3. Anusavice KJ. Phillips, Materiais Dentários. Rio de Janeiro: Elservier, 2005. 4. Asmussen E, Peutzfeldt A, Heitmann T. Stiffness, elastic limit, and strength of newer types of endodontics posts. J Dent 1999;27:275-8. 5. Braga RR, César PF, Gonzaga CC. Mechanical properties of resin cements with different activation modes. J Oral Rehabil 2002;29:257– 66. 6. Carrilho MRO, Tay FR, Pashley DH, Tjaderhane L, Carvalho RM. Mechanical stability of resin-dentin bond components. Dent Mater 2005;21:232-41. 7. Ceballos L, Garrido MA, Fuentes V, Rodrígues Jesús. Mechanical characterization of resin cements used for luting fiber post by nanoindentation. Dent Mater 2007;23:100-5. 20. Chersoni S, Acquaviva GL, Prati C, Ferrari M, Gardini, S; Pashley DH, Tay FR. In vivo fluid movement though dentin adhesives in endodontically treated teeth. J Dent Res 2005;84:223-7. 8. D’Arcangelo C, D’Amario M, Vadini M, Zazzeroni S, De Angelis F, Caputi S. an evaluation of luting agent application technique effect on fibre post retention. J Dent 2008;36:235-40. 9. Dewald JP, Ferracane JL. A comparison of four modes of evaluating depth of cure of lightactivated composites. J dent Res 1987;66:727-30. 25. ESPE M. Rely X Unicem self-adhesive universal resin cement. Germany: 3M ESPE; 2006. 10. Faria-e-Silva AL, Casselli DSM, Lima GS, Ogliari FA, Piva E, Martins LRM. Kinetics of conversion of two dual-cured adhesive systems. J Endod 2008;34:1115-8 11. Fennis WMM, Ray NJ, Creugers NHJ, Kreulen CM. Microhardness of resin composite materials light-cured through fiber reinforced composite. Dent Mater 2009; 25:947-51. 12. Ferrari M, Mannocci F, Vichi A, Cagidiaco MC, Mjor IA. Bonding to root canal: structural characteristics of the substrate. Am J Dent 2000;13:255-60. 13. Galhano GA, Melo RM, Barbosa SH, Zamboni SC, Bottino MA, Scotti R. Evaluation of light transmission through translucent and opaque posts. Oper Dent 2008;33:321-4.   62     14. Giachetti L, Grandini S, Calamai P, Fantini G, Russo DS. Translucent fiber post cementation using light- and dual-curing adhesive techniques and a self-adhesive material: push-out test. J Dent 2009:37:638-42. 15. Goracci C, Fabianelli A, Sadek FT, Papacchini F, Tay FR, Ferrari M. The contribution of friccion to the dislocation resistance of bonded fiber posts. J Endod 2005;31:608-12. 16. Ho Y, Lai Y, Chou I, Yang S, Lee S. Effects of light attenuation by fibre posts on polymerization of a dual-cured resin cement and microleakage of post-restored teeth. J Dent 2011;39:309-15. 18. Janke V, Von Neuhoff N, Schlegelberger B, Leyhausen G, Geurtsen W. TEGDMA causes apoptosis in primary human gingival fibroblasts. J Dent Res 2003;82:814-8. 19. Kalkan M, Usumez A, Ozturk N, Belli S, Eskitascioglu G. Bond strength between root dentin and three glass-fiber post system. J Prosthet Dent 2006;96:41-6. 20. Koulaouzidou EA, Papazisis KT, Yiannaki E, Palaghias G, Helvatjoglu-Antoniades M. Effects of dentin bonding agents on the cell cycle of fibroblasts. J Endod 2009;35:275–9. 21. Kong N, Jiang T, Zhou Z, Fu J. Cytotoxicity of polymerized resin cements on human dental pulp cells in vitro. Dent Mater 2009;25:1371–5. 22. Lui JL. Depth of composite polymerization within simulated root canals using lighttransmitting posts. Oper Dent 1994;19:165-8. 23. Mclean A. Criterial for the predictable restorable endodontically treated tooth. J Can Dent Assoc 1998;64:652-6. 24. Mallmann A, Jacques LB, Valandro LF, Muench A. Microtensile Bond strength of photoactivated and autopolymerized adhesive systems to root dentin using translucent and opaque fiber-reinforced composite posts. J Prosthet Dent;97:165-72. 25. Morgan LFSA , Albuquerque RC, Poletto LTA, Peixoto RTRC, Corrêa MFS, Pinotti MB. Light transmission through translucent fiber posts. J Endod 2008;34:299-302. 26. Naumann M, Sterzenbach G, Rosentritt M, Beuer F, Frankenberger R. Is adhesive cementation of endodontic posts necessary? J Endod 2008;34:1006-10. 27. Papa J, Cain C, Messer H. Moisture of vital vs. endodontically treated teeth. End Dent Traumat 1994;10:91-3. 28. Pedreira APRV, et al. Microhardness of resin cements in the intraradicular environment: Effects of water storage and softening treatment. Dent Mater 2009;25: 868-76.   63     29. Pirani C, Chersoni S, Foschi F, Piana G, Loushine RJ, Tay FR, Prati C. Does Hybridization of intraradicular dentin really improve fiber post retention in endodontically treated teeth? J Endod 2005;31:891-4. 30. Radovic I, Corciolani G, Magni E, Krstanovic G, Pavlovic V, Vulicevic ZR, Ferrari M. Light transmission through fiber post: The effect on adhesion, elastic modulus and hardness of dualcure resin cement. Dent Mater 2009;25:837-44. 31. Roberts HW, Leonard DL, Vandewalle KS, Cohen ME, Charlton DG. The effect of a translucent post on a resin composite depth of cure. Dent Mater 2004;20:617-22. 32. Silva ALF, Arias VG, Soares LES, Martin AA, Martins LRM. Influence of fiber-post translucency on the degree of conversion of a dual-cured resin cement. J Endod 2007;33:303-5. 33. Teixeira CS, Silva-Sousa YT, Sousa-Neto MD. Bond strenght of fiber posts to weakened roots after resin restoration with different light-curing times. J Endod 2009;35:1034-39. 34. Vichi A, Grandini S, Ferrari M. Comparison between two clinical procedures for bonding fiber post into a root canal: a microscopic investigation. J Endod 2002;28:355-60. 35. Wang VJJ, Chen YM, Yip KHK, Smales RJ, Meng QF, Chen L. Effect of two fiber post types and two luting cement systems on regional post retention using the push-out test. Dent Mater 2008;24:372-77. 36. Yoldas O, Alacam T. Microhardness of composite in simulate root canals cured with light transmitting posts and glass fiber reinforced composite posts. J Endod 2005;31:104-6. 37. Zicari F, Coutinho E, Munck JD, Poitevin A, Scotti R, Naert I, Meerbeek BV. Dent Mater 2008;24:967-77. 38.Mongruel 39. Summitt JB, Robbins JW, Schwartz RS. Fundamentals of operative dentistry. Quintessence, 2o.Ed., 2001;.546-66.
Estudo linguístico no Vale do Jequitinhonha: o léxico de Minas Novas
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