Chemical and physical properties of bulk aerosols within four sectors observed during TRACE-P

Chemical and physical aerosol data collected on the DC-8 during TRACE-P were grouped into four sectors based on back trajectories. The four sectors represent long-range transport from the west (WSW), regional circulation over the western Pacific and Southeast Asia (SE Asia), polluted transport from northern Asia with substantial sea salt at low altitudes (NNW) and a substantial amount of dust (Channel). WSW has generally low mixing ratios at both middle and high altitudes, with the bulk of the aerosol mass due to non-sea-salt water-soluble inorganic species. Low altitude SE Asia also has low mean mixing ratios in general, with the majority of the aerosol mass comprised of non-sea-salts, however, soot is also relatively important in this region. NNW had the highest mean sea salt mixing ratios, with the aerosol mass at low altitudes (\u3c2 km) evenly divided between sea salts, non-sea-salts, and dust. The highest mean mixing ratios of water-soluble ions and soot were observed at the lowest altitudes (\u3c2 km) in the Channel sector. The bulk of the aerosol mass exported from Asia emanates from Channel at both low and midaltitudes, due to the prevalence of dust compared to other sectors. Number densities show enhanced fine particles for Channel and NNW, while their volume distributions are enhanced due to sea salt and dust. Low-altitude Channel exhibits the highest condensation nuclei (CN) number densities along with enhanced scattering coefficients, compared to the other sectors. At midaltitudes (2–7 km), low mean CN number densities coupled with a high proportion of nonvolatile particles (≥65%) observed in polluted sectors (Channel and NNW) are attributed to wet scavenging which removes hygroscopic CN particles. Low single scatter albedo in SE Asia reflects enhanced soot

Noise-aided gradient descent bit-flipping decoders approaching maximum likelihood decoding

International audienceIn the recent literature, the study of iterative LDPC decoders implemented on faulty-hardware has led to the counter-intuitive conclusion that noisy decoders could perform better than their noiseless version. This peculiar behavior has been observed in the finite codeword length regime, where the noise perturbating the decoder dynamics help to escape the attraction of fixed points such as trapping sets. In this paper, we will study two recently introduced LDPC decoders derived from noisy versions of the gradient descent bit-flipping decoder (GDBF). Although the GDBF is known to be a simple decoder with limited error correction capability compared to more powerful soft-decision decoders, it has been shown that the introduction of a random perturbation in the decoder could greatly improve the performance results, approaching and even surpassing belief propagation or min-sum based decoders. For both decoders, we evaluate the probability of escaping from a Trapping set, and relate this probability to the parameters of the injected noise distribution, using a Markovian model of the decoder transitions in the state space of errors localized on isolated trapping sets. In a second part of the paper, we present a modified scheduling of our algorithms for the binary symmetric channel, which allows to approach maximum likelihood decoding (MLD) at the cost of a very large number of iterations

Muller C-element based Decoder (MCD): A Decoder Against Transient Faults

This work extends the analysis and application of a digital error correction method called Muller C-element Decoding (MCD), which has been proposed for fault masking in logic circuits comprised of unreliable elements. The proposed technique employs cascaded Muller C-elements and XOR gates to achieve efficient error-correction in the presence of internal upsets. The error-correction analysis of MCD architecture and the investigation of C-element’s robustness are first introduced. We demonstrate that the MCD is able to produce error-correction benefit in a high error-rate of internal faults. Significantly, for a (3,6) short-length LDPC code, when the decoding process is internally error-free the MCD achieves also a gain in terms of decoding performance by comparison to the well-known Gallager Bit-Flipping method. We further consider application of MCD to a general-purpose fault-tolerant model, coded Dual Modular Redundancy (cDMR), which offers low-redundancy error-resilience for contemporary logic systems as well as future nanoeletronic architectures

Prayer as Interpersonal Coping in the Lives of Mothers with HIV

The spirituality of 22 mothers diagnosed with HIV was explored through face-to-face interviews and revealed that 95% of the mothers pray. Active prayers (e.g., talking to God by adoring, thanking, confessing, and supplicating) were more frequently reported than receptive prayers (e.g., quietly listening to God, being open, surrendering). Supplicatory or petitionary prayers for help and health were the most frequent type of prayer, and adoration was the least frequent. The majority of mothers in the sample perceived prayer as a positive coping mechanism associated with outcomes such as: support, positive attitude/affect, and peace. Overall, results supported expanding the boundary conditions of the interpersonal coping component of the Social Interaction Model (Derlega & Barbee, 1998) to include the spiritual dimension of prayer

Spectral aerosol extinction (SpEx): a new instrument for in situ ambient aerosol extinction measurements across the UV/visible wavelength range

We introduce a new instrument for the measurement of in situ ambient aerosol extinction over the 300– 700 nm wavelength range, the spectral aerosol extinction (SpEx) instrument. This measurement capability is envisioned to complement existing in situ instrumentation, allowing for simultaneous measurement of the evolution of aerosol optical, chemical, and physical characteristics in the ambient environment. In this work, a detailed description of the instrument is provided along with characterization tests performed in the laboratory. Measured spectra of NO2 and polystyrene latex spheres (PSLs) agreed well with theoretical calculations. Good agreement was also found with simultaneous aerosol extinction measurements at 450, 530, and 630 nm using CAPS PMex instruments in a series of 22 tests including nonabsorbing compounds, dusts, soot, and black and brown carbon analogs. SpEx measurements are expected to help identify the presence of ambient brown carbon due to its 300 nm lower wavelength limit compared to measurements limited to longer UV and visible wavelengths. Extinction spectra obtained with SpEx contain more information than can be conveyed by a simple power law fit (typically represented by Ångström exponents). Planned future improvements aim to lower detection limits and ruggedize the instrument for mobile operation

A comparison of similar aerosol measurements made on the NASA P3-B, DC-8, and NSF C-130 aircraft during TRACE-P and ACE-Asia

Two major aircraft experiments occurred off the Pacific coast of Asia during spring 2001: the NASA sponsored Transport and Chemical Evolution over the Pacific (TRACE-P) and the National Science Foundation (NSF) sponsored Aerosol Characterization Experiment-Asia (ACE-Asia). Both experiments studied emissions from the Asian continent (biomass burning, urban/industrial pollution, and dust). TRACE-P focused on trace gases and aerosol during March/April and was based primarily in Hong Kong and Yokota Air Force Base, Japan, and involved two aircraft: the NASA DC-8 and the NASA P3-B. ACE-Asia focused on aerosol and radiation during April/May and was based in Iwakuni Marine Corps Air Station, Japan, and involved the NSF C-130. This paper compares aerosol measurements from these aircraft including aerosol concentrations, size distributions (and integral properties), chemistry, and optical properties. Best overall agreement (generally within RMS instrumental uncertainty) was for physical properties of the submircron aerosol, including condensation nuclei concentrations, scattering coefficients, and differential mobility analyzer and optical particle counter (OPC) accumulation mode size distributions. Larger differences (typically outside of the RMS uncertainty) were often observed for parameters related to the supermicron aerosols (total scattering and absorption coefficients, coarse mode Forward Scattering Spectrometer Probe and OPC size distributions/integral properties, and soluble chemical species usually associated with the largest particles, e.g., Na+, Cl−, Ca2+, and Mg2+), where aircraft sampling is more demanding. Some of the observed differences reflect different inlets (e.g., low-turbulence inlet enhancement of coarse mode aerosol), differences in sampling lines, and instrument configuration and design. Means and variances of comparable measurements for horizontal legs were calculated, and regression analyses were performed for each platform and allow for an assessment of instrument performance. These results provide a basis for integrating aerosol data from these aircraft platforms for both the TRACE-P and ACE-Asia experiments

Low-energy electron-impact excitation of the ^(3,1)A_2(n→π*) states of formaldehyde

A three-state calculation of electron-impact excitation of formaldehyde to the ã^3A_2 and Ã^1A_2 states is carried out using the Schwinger multichannel variational method. The integral and differential cross sections so obtained agree fairly well with theoretical results obtained using the complex Kohn method. Though agreement between the calculated integral cross section and the single available experimental measurement is qualitative, similar conclusions regarding the excitation mechanism are reached. A generalization of the selection rule for (Σ^+⇆Σ^−) electron-impact excitation of diatomic molecules is used to explain the shape of the differential cross sections for the ã^3A_2 and Ã^1A_2 excitations

The impact of local sources and long-range transport on aerosol properties over the northeast U.S. region during INTEX-NA

We use data collected aboard the NASA DC-8 aircraft during the summer 2004, Intercontinental Transport and Chemical Evolution Experiment over North America (INTEX-NA) field campaign to examine the origin, composition, physical and optical properties of aerosols within air masses sampled over and downwind of the northeastern U.S. We note that aerosol concentrations within the region exhibited steep vertical gradients and significant variability in both time and space. An examination of air mass chemical signatures and backward trajectories indicates that transport from four, significantly different source regions contributed to the variability: the subtropical Atlantic Ocean (AO); the U.S. west coast and eastern Pacific (WCP); the U.S. east coast and Midwestern states (EC); and northwest Canada and Alaska (CA). AO air masses were typically confined to below 2 km altitude, exhibited low pollutant contents, contained enhanced levels of sea salt, and were typically observed when the Bermuda High strengthened. The most common air mass present in the upper troposphere, WCP air often contained weak dust and aged pollution enhances from convective input occurring over the central part of the continent. CA air exhibited enhancements in anthropogenic pollution tracers below 2 km and contained some black-carbon rich haze layers between 3 and 5 km that could be traced to forest fires burning in western Canada and Alaska. EC air was prevalent at lower elevations throughout the study area and exhibited enhanced scattering along with elevated levels of sulfate aerosols and combustion tracers. There is an overall balance between the observed cations and anions for all cases, except EC air mass below 4 km

Observational evidence for the convective transport of dust over the central United States

Bulk aerosol composition and aerosol size distributions measured aboard the DC-8 aircraft during the Deep Convective Clouds and Chemistry Experiment mission in May/June 2012 were used to investigate the transport of mineral dust through nine storms encountered over Colorado and Oklahoma. Measurements made at low altitudes (\u3c5 km mean sea level (MSL)) in the storm inflow region were compared to those made in cirrus anvils (altitude \u3e 9 km MSL). Storm mean outflow Ca2+ mass concentrations and total coarse (1 µm \u3c diameter \u3c 5 µm) aerosol volume (Vc) were comparable to mean inflow values as demonstrated by average outflow/inflow ratios greater than 0.5. A positive relationship between Ca2+, Vc, ice water content, and large (diameter \u3e 50 µm) ice particle number concentrations was not evident; thus, the influence of ice shatter on these measurements was assumed small. Mean inflow aerosol number concentrations calculated over a diameter range (0.5 µm \u3c diameter \u3c 5.0 µm) relevant for proxy ice nuclei (NPIN) were ~15–300 times higher than ice particle concentrations for all storms. Ratios of predicted interstitial NPIN (calculated as the difference between inflow NPIN and ice particle concentrations) and inflow NPIN were consistent with those calculated for Ca2+ and Vc and indicated that on average less than 10% of the ingested NPIN were activated as ice nuclei during anvil formation. Deep convection may therefore represent an efficient transport mechanism for dust to the upper troposphere where these particles can function as ice nuclei cirrus forming in situ