Abstract. Photochemical pollution control strategies require an understanding of photochemical oxidation precursors, making it important to distinguish between primary and secondary sources of HCHO. Estimates for the relative strengths of primary and secondary sources of formaldehyde (HCHO) were obtained using a statistical regression analysis with time series data of carbon monoxide (CO) and glyoxal (CHOCHO) measured in the Mexico City Metropolitan Area (MCMA) during the spring of 2003. Differences between Easter week and more typical weeks are evaluated. The use of CO-CHOCHO as HCHO tracers is more suitable for differentiating primary and secondary sources than CO-O 3 . The application of the CO-O 3 tracer pair to mobile laboratory data suggests a potential in-city source of background HCHO. A significant amount of HCHO observed in the MCMA is associated with primary emissions.
We prove an extension of Ekeland's variational principle to locally complete spaces which uses subadditive, strictly increasing continuous functions as perturbations.Since its appearance in 1972, Ekeland's variational principle has found many applications in several areas of analysis. In addition to these applications, a great deal of effort has gone into looking for, either equivalent formulations of the principle, or extensions of Ekeland's principle to the non-Banach space setting (see, for instance, [1-3]).In this paper we continue this effort by giving a generalization of the principle to locally complete spaces. Although there are extensions of the variational principle to locally complete spaces (see, for instance, [2]), our approach uses a different form of perturbations, those introduced by J. Qiu in [3], where he discusses Ekeland's principle for Fréchet spaces. Our proof is inspired by A. Hamel's argument in [1, Theorem 2] where he extends a version of R. Phelps of
While the structure
of a multitude of viral particles has been
resolved to atomistic detail, their assembly pathways remain largely
elusive. Key unresolved issues are particle nucleation, particle growth,
and the mode of genome compaction. These issues are difficult to address
in bulk approaches and are effectively only accessible by the real-time
tracking of assembly dynamics of individual particles. This we do
here by studying the assembly into rod-shaped viruslike particles
(VLPs) of artificial capsid polypeptides. Using fluorescence optical
tweezers, we establish that small oligomers perform one-dimensional
diffusion along the DNA. Larger oligomers are immobile and nucleate
VLP growth. A multiplexed acoustic force spectroscopy approach reveals
that DNA is compacted in regular steps, suggesting packaging via helical
wrapping into a nucleocapsid. By reporting how real-time assembly
tracking elucidates viral nucleation and growth principles, our work
opens the door to a fundamental understanding of the complex assembly
pathways of both VLPs and naturally evolved viruses.
Abstract. We present a new numerical code, Mexican MAX-DOAS Fit (MMF),
developed to retrieve profiles of different trace gases from the network of
MAX-DOAS instruments operated in Mexico City. MMF uses differential slant
column densities (dSCDs) retrieved with the QDOAS (Danckaert et al., 2013) software. The
retrieval is comprised of two steps, an aerosol retrieval and a trace gas
retrieval that uses the retrieved aerosol profile in the forward model for
the trace gas. For forward model simulations, VLIDORT is used
(e.g., Spurr et al., 2001; Spurr, 2006, 2013). Both steps use
constrained least-square fitting, but the aerosol retrieval uses Tikhonov
regularization and the trace gas retrieval optimal estimation. Aerosol
optical depth and scattering properties from the AERONET database, averaged
ceilometer data, WRF-Chem model data, and temperature and pressure
sounding data are used for different steps in the retrieval chain. The MMF code was applied to retrieve NO2 profiles with 2 degrees of
freedom (DOF = 2) from spectra of the MAX-DOAS instrument located at the Universidad Nacional Autónoma de
México (UNAM)
campus. We describe the full error analysis of the retrievals and include a
sensitivity exercise to quantify the contribution of the uncertainties in the
aerosol extinction profiles to the total error. A data set comprised of
measurements from January 2015 to July 2016 was processed and the results
compared to independent surface measurements. We concentrate on the analysis
of four single days and additionally present diurnal and annual variabilities
from averaging the 1.5 years of data. The total error, depending on the exact
counting, is 14 %–20 % and this work provides new and relevant information
about NO2 in the boundary layer of Mexico City.
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