Simultaneous polarimeter retrievals of microphysical aerosol and ocean color parameters from the "MAPP" algorithm with comparison to high-spectral-resolution lidar aerosol and ocean products.

We present an optimal-estimation-based retrieval framework, the microphysical aerosol properties from polarimetry (MAPP) algorithm, designed for simultaneous retrieval of aerosol microphysical properties and ocean color bio-optical parameters using multi-angular total and polarized radiances. Polarimetric measurements from the airborne NASA Research Scanning Polarimeter (RSP) were inverted by MAPP to produce atmosphere and ocean products. The RSP MAPP results are compared with co-incident lidar measurements made by the NASA High-Spectral-Resolution Lidar HSRL-1 and HSRL-2 instruments. Comparisons are made of the aerosol optical depth (AOD) at 355 and 532 nm, lidar column-averaged measurements of the aerosol lidar ratio and Ångstrøm exponent, and lidar ocean measurements of the particulate hemispherical backscatter coefficient and the diffuse attenuation coefficient. The measurements were collected during the 2012 Two-Column Aerosol Project (TCAP) campaign and the 2014 Ship-Aircraft Bio-Optical Research (SABOR) campaign. For the SABOR campaign, 73% RSP MAPP retrievals fall within ±0.04 AOD at 532 nm as measured by HSRL-1, with an R value of 0.933 and root-mean-square deviation of 0.0372. For the TCAP campaign, 53% of RSP MAPP retrievals are within 0.04 AOD as measured by HSRL-2, with an R value of 0.927 and root-mean-square deviation of 0.0673. Comparisons with HSRL-2 AOD at 355 nm during TCAP result in an R value of 0.959 and a root-mean-square deviation of 0.0694. The RSP retrievals using the MAPP optimal estimation framework represent a key milestone on the path to a combined lidar+polarimeter retrieval using both HSRL and RSP measurements.

Long-term comparisons of UV index values derived from a NILU-UV instrument, NWS, and OMI in the New York area.

A comparison is presented of UV index (UVI) values obtained under different cloud conditions from a Norwegian Institute for Air Research UV (NILU-UV) instrument, the ozone monitoring instrument (OMI) onboard the Aura satellite, and the National Weather Service (NWS) model for the time period of 2010-2014. The NILU-UV irradiance meter is a ground-based, multi-channel, moderate bandwidth filter instrument. UVI values derived from measurements by a NILU-UV instrument deployed in the New York area (40.74°N, -74.03°E) to monitor the erythemal UV radiation from 2010 to present is compared to UVI values derived from OMI measurements and predicted by the NWS model. OMI overestimated the UVI values by 13.06% for all cloud conditions compared with the UVI values derived from measurements by the NILU-UV instrument. The heavier the cloud cover, the higher the overestimation. The mean relative difference between the UVI derived from the NWS model and from NILU-UV measurements was 11.54%. The UVI prediction by NWS was also overestimated under cloudy conditions. Under overcast conditions the NWS predictions of UVI values differ significantly from those derived from NILU-UV measurements, yielding a correlation of only 0.8025 and a mean relative difference of 28.25%.

Comparisons of three NILU-UV instruments deployed at the same site in the New York area.

The Norwegian Institute for Air Research ultraviolet (NILU-UV) irradiance meter is a ground-based, multichannel, moderate bandwidth filter instrument that measures irradiances at ultraviolet (UV) and visible wavelengths with five channels in the UV (302, 312, 320, 340, and 380 nm) and one channel in the visible (400-700 nm) part of the spectrum. Minute-by-minute irradiances recorded in these channels are used to infer the total ozone column (TOC) amount, and a radiation modification factor (RMF) designed to have a value close to 100 under cloud-free conditions. The performance of three NILU-UV instruments deployed side-by-side in the New York area (40.74°N, -74.03°E) is assessed, and derived TOC values are compared with those derived from the ozone monitoring instrument (OMI) deployed on NASA's AURA satellite. Based on about three years of data, it was found that the three instruments yielded similar TOC values that were in close agreement with those derived from the OMI. The relative difference in TOC values derived from the three NILU-UV instruments was generally less than 2.5%. Cloud cover affects the accuracy of the inferred TOC, but reliable values can be obtained in the presence of clouds, although the accuracy deteriorates under heavy overcast conditions with RMF values smaller than 65 (low cloud transmittance).

Comparison of discrete ordinate and Monte Carlo simulations of polarized radiative transfer in two coupled slabs with different refractive indices.

A comparison is presented of two different methods for polarized radiative transfer in coupled media consisting of two adjacent slabs with different refractive indices, each slab being a stratified medium with no change in optical properties except in the direction of stratification. One of the methods is based on solving the integro-differential radiative transfer equation for the two coupled slabs using the discrete ordinate approximation. The other method is based on probabilistic and statistical concepts and simulates the propagation of polarized light using the Monte Carlo approach. The emphasis is on non-Rayleigh scattering for particles in the Mie regime. Comparisons with benchmark results available for a slab with constant refractive index show that both methods reproduce these benchmark results when the refractive index is set to be the same in the two slabs. Computed results for test cases with coupling (different refractive indices in the two slabs) show that the two methods produce essentially identical results for identical input in terms of absorption and scattering coefficients and scattering phase matrices.

Protease-dependent T cell activation: ligation of effector cell protease receptor-1 (EPR-1) stimulates lymphocyte proliferation.

Blood proteases regulate cellular growth through the recognition and signaling properties of specialized membrane receptors. Previous studies have identified a novel lymphocyte activation-dependent antigen, denominated effector cell protease receptor-1 (EPR-1), which binds the coagulation protease factor Xa on various leukocyte subsets. Here we show that occupancy of EPR-1 with physiologic concentrations of factor Xa (15-75 nM), or with "surrogate" monoclonal antibody ligands, stimulates proliferation of both T and B lymphocyte subsets and augments CD3-dependent lymphocyte proliferation. At suboptimal responder cell concentrations, ligation of EPR-1 costimulates lymphocyte proliferation in the presence of accessory signals, i.e., phorbol ester, IL-2. At higher responder cell concentrations, occupancy of EPR-1 per se is sufficient to initiate lymphocyte proliferation. EPR-1-dependent T cell activation is associated with early surface expression of IL-2 receptor on target cells, thus increasing by five- to eightfold their mitogenic responsiveness to very low doses of IL-2 (0.2 U/ml). Consistent with a postulated role in transmembrane signal transduction, cross-linking of EPR-1 transiently increases cytosolic free [Ca2+]i in single adherent T cells. These findings suggest that proteases ubiquitously generated in vivo might contribute a regulatory mechanism of cytokine- or antigen receptor-dependent T cell activation and identify EPR-1 as a novel signal-transducing molecule of lymphocyte stimulation.

Regulated Ca2+ signalling through leukocyte CD11b/CD18 integrin.

General mechanisms of adhesion in the immune response are coordinated by the leukocyte integrins CD11/CD18. The possible participation of these differentiation molecules in early events of transmembrane signalling was investigated. Monoclonal antibody (mAb) cross-linking of CD18, the integrin beta subunit ubiquitously expressed by all leukocytes, increased the cytosolic free Ca2+ concentration ([Ca2+]i) by 2-3-fold in monocyte THP-1 cells. Digitalized imaging in single adherent cells showed that this Ca2+ response is temporally biphasic, involves both release of Ca2+ from the intracellular stores as well as Ca2+ influx from the external compartment, and is dramatically down-modulated by terminal differentiation of THP-1 cells to a mature monocyte phenotype. Similarly, only a minor subset of 20-30% of peripheral blood monocytes heterogeneously maintain the CD18-mediated Ca(2+)-signalling properties. Cross-linking of CD18 also increased cytosolic free [Ca2+]i in a subset of approx. 15-20% of resting T lymphocytes, in a Ca2+ response that was completely abrogated during T-cell mitogenic activation with lectins or alloreactive antigen. While cross-linking of CD11a or CD11c was without effect, occupancy of CD11b increased cytosolic free [Ca2+]i in monocytic cells. This response was functionally coupled with a transient activation state of CD11b/CD18, which was reflected in its increased avidity to bind the complementary ligand fibrinogen. These results suggest that occupancy of CD18 transduces a stimulatory Ca2+ signal that is critically regulated by the state of cell activation/differentiation and by the association with the unique alpha-subunit CD11b. These intrinsic signalling properties may directly participate in regulating the oligospecific ligand recognition of leukocyte integrins.

Enumeration of cytokine-secreting cells at the single-cell level.

A sensitive assay utilizing enzyme-linked immunosorbent assay methodology has been developed for the quantitation of single cells secreting interferon (IFN)-gamma or tumor necrosis factor (TNF). Cloned T cells or cells from lymphoid organs were stimulated with antigen, concanavalin A, or phorbol myristate acetate and ionomycin in microwells coated with antibodies specific for IFN-gamma. Discrete "spots" overlying areas where cells secrete IFN-gamma were then developed by incubation with a second antibody to IFN-gamma, followed by an enzyme-labeled antibody conjugate and substrate. Similarly, using TNF-specific antibody reagents, TNF-secreting cells were detected and quantitated in cell populations obtained from normal lymphoid tissues, bone marrow and peripheral blood, following activation with phorbol myristate acetate and ionomycin. Provided specific antibodies are available, this method has the potential to measure the frequency of cells secreting any cytokine.