Coynegoldstein8554

We apply two sparse reconstruction techniques, the least absolute shrinkage and selection operator (LASSO) and the sparse exponential mode analysis (SEMA), to two-dimensional (2D) spectroscopy. The algorithms are first tested on model data, showing that both are able to reconstruct the spectra using only a fraction of the data required by the traditional Fourier-based estimator. Through the analysis of the sparsely sampled experimental fluorescence-detected 2D spectra of LH2 complexes, we conclude that both SEMA and LASSO can be used to significantly reduce the required data, still allowing one to reconstruct the multidimensional spectra. Of the two techniques, it is shown that SEMA offers preferable performance, providing more accurate estimation of the spectral line widths and their positions. Furthermore, SEMA allows for off-grid components, enabling the use of a much smaller dictionary than that of the LASSO, thereby improving both the performance and the lowering of the computational complexity for reconstructing coherent multidimensional spectra.Plasma-assisted combustion can improve the thermal efficiency and stability of internal combustion engines; based on this, among various types of discharge method, surface dielectric barrier discharge (SDBD) induced partial oxidation of hydrocarbons was investigated in this study. To demonstrate the general mechanisms of SDBD-induced partial oxidation of gasoline, we used a five-component gasoline surrogate (S5R), which consisted of a mixture of alkanes (isooctane, n-heptane, and methylcyclohexane), alkenes (trimethyl pentene isomers), and toluene, as the model. The detailed process of SDBD-induced partial oxidation of hydrocarbon was investigated by Fourier transform infrared spectroscopy, ion attachment mass spectrometry, and density functional theory calculation. SDBD irradiation of the hydrocarbon/air mixture induced dissociation of oxygen molecule through direct electron impact and collision with excited nitrogen molecules, and the resultant oxygen atom then reacted with a hydrocarbon molecule. Alkane and toluene were converted to alkyl hydroperoxide by a reaction with the oxygen atom and subsequent attachment of O2. The resultant alkyl hydroperoxide then provided a ketone and/or aldehyde. In contrast, the alkenes underwent attachment of an oxygen atom and were either converted to fragments containing a carbonyl group or to etoposide. Regarding the analytical method, the partially oxidized products were selectively ionized from the hydrocarbon/air mixture when Na+ was used as the reagent ion for ion attachment mass spectrometry.Sulfuric acid aerosol (SAA) can considerably deteriorate air visibility, which poses a threat to human health. Pretreatment methods that enlarge SAA sizes are crucial to enhanced emission control from industrials. This study provides an insight into SAA growth in terms of aerosol dynamics simulation and growth experiments under simulated flue gas conditions. Results show that SAA growth dynamics are dominated by coagulation and condensation mechanisms for small and large aerosols, respectively. The two mechanisms are coupled mainly in SAA sizes smaller than 0.05 μm. A large amount of time was allotted for the SAA distribution to grow into an approximately log-normal form without the use of any activation methods. Cooling gas and corona discharge can both enhance SAA growth. Cooling gas is in charge of condensation, whereas corona discharge mainly acts on coagulation. They exhibited 14.3% and 12.3% increases in mean diameter and 12.3% and 69.1% decreases in number concentration. In contrast, adding vapor led to a 1.58% decrease in mean diameter and a 9.4% increase in number concentration. read more Findings suggest that combining cooling gas and corona discharge to simultaneously promote coagulation and condensation and reduce SAA emission from humid flue gas is possible.Since greenhouse gas mitigation efforts are mostly being implemented in cities, the ability to quantify emission trends for urban environments is of paramount importance. However, previous aircraft work has indicated large daily variability in the results. Here we use measurements of CO2, CH4, and CO from aircraft over 5 days within an inverse model to estimate emissions from the DC-Baltimore region. Results show good agreement with previous estimates in the area for all three gases. However, aliasing caused by irregular spatiotemporal sampling of emissions is shown to significantly impact both the emissions estimates and their variability. Extensive sensitivity tests allow us to quantify the contributions of different sources of variability and indicate that daily variability in posterior emissions estimates is larger than the uncertainty attributed to the method itself (i.e., 17% for CO2, 24% for CH4, and 13% for CO). Analysis of hourly reported emissions from power plants and traffic counts shows that 97% of the daily variability in posterior emissions estimates is explained by accounting for the sampling in time and space of sources that have large hourly variability and, thus, caution must be taken in properly interpreting variability that is caused by irregular spatiotemporal sampling conditions.High even-order surface/interface specific spectroscopy has the potential to provide more structural and dynamical information about surfaces and interfaces. In this work, we developed a novel fourth-order interface-specific two-dimensional electronic sum frequency generation (2D-ESFG) for structures and dynamics at surfaces and interfaces. A translating wedge-based identical pulses encoding system (TWINs) was introduced to generate phase-locked pulse pairs for coherent pump beams in 2D-ESFG. As a proof-of-principle experiment, fourth-order 2D-ESFG spectroscopy was used to demonstrate couplings of surface states for both n-type and p-type GaAs (100). We found surface dark state within the bandgap of the GaAs in 2D-ESFG spectra, which could not be observed in one-dimensional ESFG spectra. To our best knowledge, this is a first demonstration of interface-specific two-dimensional electronic spectroscopy. The development of the 2D-ESFG spectroscopy will provide new structural probes of spectral diffusion, conformational dynamics, energy transfer, and charge transfer for surfaces and interfaces.