Aerosol optical hygroscopicity measurements during the 2010 CARES campaign

Measurements of the effect of water uptake on particulate light extinction or scattering made at two locations during the 2010 Carbonaceous Aerosols and Radiative Effects Study (CARES) study around Sacramento, CA are reported. The observed influence of water uptake, characterized through the dimensionless optical hygroscopicity parameter γ, is compared with calculations constrained by observed particle size distributions and size-dependent particle composition. A closure assessment has been carried out that allowed for determination of the average hygroscopic growth factors (GFs) at 85% relative humidity and the dimensionless hygroscopicity parameter κ for oxygenated organic aerosol (OA) and for supermicron particles (defined here as particles with aerodynamic diameters between 1 and 2.5 microns), yielding κ = 0.1–0.15 and 0.9–1.0, respectively. The derived range of oxygenated OA κ values are in line with previous observations. The relatively large values for supermicron particles is consistent with substantial contributions of sea-salt-containing particles in this size range. Analysis of time-dependent variations in the supermicron particle hygroscopicity suggest that atmospheric processing, specifically chloride displacement by nitrate and the accumulation of secondary organics on supermicron particles, can lead to substantial depression of the observed GF

Overview of the 2010 Carbonaceous Aerosols and Radiative Effects Study (CARES)

Substantial uncertainties still exist in the scientific understanding of the possible interactions between urban and natural (biogenic) emissions in the production and transformation of atmospheric aerosol and the resulting impact on climate change. The US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program's Carbonaceous Aerosol and Radiative Effects Study (CARES) carried out in June 2010 in Central Valley, California, was a comprehensive effort designed to improve this understanding. The primary objective of the field study was to investigate the evolution of secondary organic and black carbon aerosols and their climate-related properties in the Sacramento urban plume as it was routinely transported into the forested Sierra Nevada foothills area. Urban aerosols and trace gases experienced significant physical and chemical transformations as they mixed with the reactive biogenic hydrocarbons emitted from the forest. Two heavily-instrumented ground sites – one within the Sacramento urban area and another about 40 km to the northeast in the foothills area – were set up to characterize the evolution of meteorological variables, trace gases, aerosol precursors, aerosol size, composition, and climate-related properties in freshly polluted and "aged" urban air. On selected days, the DOE G-1 aircraft was deployed to make similar measurements upwind and across the evolving Sacramento plume in the morning and again in the afternoon. The NASA B-200 aircraft, carrying remote sensing instruments, was also deployed to characterize the vertical and horizontal distribution of aerosols and aerosol optical properties within and around the plume. This overview provides: (a) the scientific background and motivation for the study, (b) the operational and logistical information pertinent to the execution of the study, (c) an overview of key observations and initial findings from the aircraft and ground-based sampling platforms, and (d) a roadmap of planned data analyses and focused modeling efforts that will facilitate the integration of new knowledge into improved representations of key aerosol processes and properties in climate models.United States. Dept. of Energy. Atmospheric System Research Program (Contract DE-AC06-76RLO 1830)United States. National Oceanic and Atmospheric AdministrationUnited States. National Aeronautics and Space Administration. HQ Science Mission Directorate Radiation Sciences ProgramUnited States. National Aeronautics and Space Administration. CALIPSO ProgramUnited States. Dept. of Energy. Atmospheric Radiation Measurement Program (Interagency Agreement No. DE-AI02-05ER63985

Using spectral methods to obtain particle size information from optical data: applications to measurements from CARES 2010

Multi-wavelength in situ aerosol extinction, absorption and scattering measurements made at two ground sites during the 2010 Carbonaceous Aerosols and Radiative Effects Study (CARES) are analyzed using a spectral deconvolution method that allows extraction of particle-size-related information, including the fraction of extinction produced by the fine-mode particles and the effective radius of the fine mode. The spectral deconvolution method is typically applied to analysis of remote sensing measurements. Here, its application to in situ measurements allows for comparison with more direct measurement methods and validation of the retrieval approach. Overall, the retrieved fine-mode fraction and effective radius compare well with other in situ measurements, including size distribution measurements and scattering and absorption measurements made separately for PM1 and PM10, although there were some periods during which the different methods yielded different results. One key contributor to differences between the results obtained is the alternative, spectrally based definitions of fine and coarse modes from the optical methods, relative to instruments that use a physically defined cut point. These results indicate that for campaigns where size, composition and multi-wavelength optical property measurements are made, comparison of the results can result in closure or can identify unusual circumstances. The comparison here also demonstrates that in situ multi-wavelength optical property measurements can be used to determine information about particle size distributions in situations where direct size distribution measurements are not available.</p

Estabilidade do reposicionamento anterior da maxila através de análise cefalométrica lateral Lateral cephalometric analysis of the stability of maxillary anterior repositioning

Este estudo cefalométrico retrospectivo foi proposto objetivando analisar a estabilidade do reposicionamento anterior da maxila, utilizando-se a osteotomia Le Fort I. A amostra consistiu de 30 telerradiografias de dez pacientes submetidos a um avanço cirúrgico da maxila, sem segmentação desta ou associação com qualquer cirurgia na mandíbula, realizado pela Área de Cirurgia Buco-Maxilo-Facial da Faculdade de Odontologia de Piracicaba - Unicamp. A mesma técnica de fixação interna rígida foi utilizada para todos os pacientes, e nenhum enxerto ou substituto ósseo foi usado. Três radiografias cefalométricas laterais foram realizadas para cada paciente, nos períodos pré e pós-operatórios imediatos, e com, no mínimo, seis meses após a cirurgia. Sobre estas radiografias foram feitas linhas de referência horizontal e vertical. Os pontos cefalométricos utilizados para calcular as mudanças de posição da maxila foram tanto esqueléticos, quanto dentários. A análise estatística (teste t de student pareado) não demonstrou diferença estatística significante entre os intervalos pós-operatórios imediato e com no mínimo seis meses. Concluímos que o reposicionamento anterior da maxila, utilizando-se a osteotomia Le Fort I, com fixação interna rígida e sem o uso de enxertos autógenos ou qualquer substituto ósseo, é um procedimento estável.<br>This is a retrospective cephalometric study designed to investigate the stability after anterior maxilla repositioning, by Le Fort I osteotomy. Thirty cephalometric radiographs were selected, from ten patients submitted to one-piece surgical maxillary advancement, with no concomitant mandibular surgery, performed by the Division of Oral and Maxillofacial Surgery of Piracicaba Dental School - Unicamp. These cases were submitted to the same internal rigid fixation technique, with no use of bone grafts or any bone substitute. Three lateral cephalometric radiographs were obtained for each patient, immediately presurgery and postsurgery, and at least six months after surgery. Lines were draw upon the X-rays to serve as horizontal and vertical reference lines.The landmarks used to measure maxillary positional changes consisted of skeletal and dental features. Statistical analysis (paired t student test) showed no significant differences between the immediately postsurgery and at least six months postsurgery periods. We concluded that the anterior maxillary repositioning by Le Fort I osteotomy, using rigid internal fixation, with no bone grafts or any bone substitute, is a stable procedure