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All sourcesNASA NTRSDOE OSTI
NASA NTRS2022

Progress in InAs/InAsSb Superlattice Barrier Infrared Detectors

The InAs/InAsSb (Gallium-free) type-II strained-layer superlattice (T2SLS) has emerged in recent years as a viable infrared detector material. In particular, mid-wavelength InAs/InAsSb T2SLS focal plane array (FPA) based on the nBn detector architecture exhibits good operating characteristics at 160 K, demonstrating a considerably operating temperature advantage over InSb FPAs. In the long and very long cutoff wavelengths, InAs/InAsSb T2SLS detectors with n-type absorbers are limited in their attainable quantum efficiency (QE) due to shorter hole diffusion lengths and relatively modest absorption coefficients. We have explored long and very long wavelength InAs/InAsSb T2SLS complementary barrier infrared detectors (CBIRDs) that contain p-type absorber layers in order to take advantage of the longer electron diffusion length for QE enhancement. We also discuss recent development of the InAs/InAsSb T2SLS infrared detectors at the Jet Propulsion Laboratory for NASA Earth Science applications, including long-wavelength infrared FPAs for land imaging, and mid-wavelength infrared FPAs for CubeSat hyperspectral imaging.

Pagano, Thomas S.↗
NASA NTRS2022

Arctic Biogeochemical and Optical Properties of Dissolved Organic Matter Across River to Sea Gradients

Arctic landscapes are warming and becoming wetter due to changes in precipitation and the timing of snowmelt which consequently alters seasonal runoff and river discharge patterns. These changes in hydrology lead to increased mobilization and transport of terrestrial dissolved organic matter (DOM) to Arctic coastal seas where significant impacts on biogeochemical cycling can occur. Here, we present measurements of dissolved organic carbon (DOC) and chromophoric DOM (CDOM) in the Yukon River-to-Bering Sea system and two river plumes on the Alaska North Slope which flow into the Beaufort Sea. Our sampling characterized optical and biogeochemical properties of DOM during high and low river discharge periods for the Yukon River-Bering Sea system. The average DOC concentration at the multiple Yukon River mouths ranged from a high of 10.36 mg C L-1 during the ascending limb of the 2019 freshet (late May), 6.4 mg C L-1 during the descending limb of the 2019 freshet (late June), and a low of 3.86 mg C L-1 during low river discharge in August 2018. CDOM absorption coefficient at 412 nm (aCDOM(412)) averaged 8.23 m-1, 5.07 m-1, and 1.9 m-1, respectively. Several approaches to model DOC concentration based on its relationship with CDOM properties demonstrated cross-system seasonal and spatial robustness for these Arctic coastal systems despite spanning an order of magnitude decrease in DOC concentration from the lower Yukon River to the Northern Bering Sea as well as the North Slope systems. “Snapshot” fluxes of DOC and CDOM across the Yukon River Delta to Norton Sound were calculated from our measurements and modeled water fluxes forced with upstream USGS river gauge data. Our findings suggest that during high river flow, DOM reaches the delta largely unaltered by inputs or physical and biogeochemical processing and that the transformations of Yukon River DOM largely occur in the plume. However, during low summer discharge, multiple processes including local precipitation events, microbial decomposition, photochemistry, and likely others can alter the DOM properties within the lower Yukon River and Delta prior to flowing into Norton Sound.

Arctic↗
NASA NTRS2024

Foam With Direction: Unraveling the Anisotropic Radiation Shielding Properties of 2D Boron Nitride Nanoplatelet Foams

Neutron radiation exposure is one of the main challenges faced during space missions. There is a critical need for advanced lightweight radiation shielding materials. Two-dimensional (2D) boron nitride nanoplatelets (BNNP) are excellent candidates for polymer matrix nanofillers due to their superior neutron shielding and thermal and mechanical properties. Furthermore, the 2D material anisotropic behavior unlocks the potential for composite property tailoring. This study fabricated ultra- lightweight lamellar BNNP foams (density 0.05 g cm –3 and 97.5% porous) via freeze-drying processing. The neutron shielding effectiveness or mass absorption coefficient of the BNNP foams with walls perpendicular to the direction of the radiation source was 14.47 cm 2 g –1 , while that of the foam with parallel configuration was only 8.51 cm 2 g –1 . The orientation-dependent neutron radiation shielding properties were modeled using the Beer-Lambert law for porous composite materials. The BNNP foam in this study has the potential to benefit advanced tailorable radiation shielding technologies for future aerospace missions.

Radiation shielding↗
NASA NTRS2023

Tribological and Radiation Shielding Response of Novel Titanium-Boron Nitride Coatings for Lunar Structural Components

Aluminum (Al) and titanium (Ti) lightweight alloys play a crucial role in space systems due to their exceptional strength-to-weight ratio. However, their premature failure in the presence of lunar regolith and their lack of neutron shielding ability are significant challenges. To address these issues, we have developed air and vacuum plasma-sprayed hBN (hexagonal Boron Nitride) -reinforced titanium coatings with 2 and 10 vol% of hBN. Tribological studies conducted with JSC-1 A lunar regolith simulant revealed a 90 % reduction in wear volume for the Ti/2 vol% hBN coatings compared to conventional materials due to the synergistic action of harder secondary phases and solid lubrication effect of hBN. Additionally, a 27 % enhancement in radiation shielding is obtained based on the mass absorption coefficient (radiation absorbed per sample density and thickness) for VPS Ti/2 vol% hBN coatings.

Wear↗
DOE OSTI2016

Analysis-Software for Hyperspectral Algal Reflectance Probes v. 1.0

This software provides onsite analysis of the hyperspectral reflectance data acquired on an outdoor algal pond by a multichannel, fiber-coupled spectroradiometer. The analysis algorithm is based on numerical inversion of a reflectance model, in which the above-water reflectance is expressed as a function of the single backscattering albedo, which is dependent on the backscatter and absorption coefficients of the algal culture, which are in turn related to the algal biomass and pigment optical activity, respectively. Prior to the development of this software, while raw multichannel data were displayed in real time, analysis required a post-processing procedure to extract the relevant parameters. This software provides the capability to track the temporal variation of such culture parameters in real time, as raw data are being acquired, or can be run in a post processing mode. The software allows the user to select between different algal species, incorporate the appropriate calibration data, and observe the quality of the resulting model inversions.

Timlin, Jerilyn A.↗
DOE OSTI2017

Turbulence radiation coupling in boundary layers of heavy-duty diesel engines

The lack of accurate submodels for in-cylinder radiation and heat transfer has been identified as a key shortcoming in developing truly predictive, physics-based computational fluid dynamics (CFD) models that can be used to develop combustion systems for advanced high-efficiency, low-emissions engines. Recent measurements of wall layers in engines show discrepancies of up to 100% with respect to standard CFD boundary-layer models. And recent analysis of in-cylinder radiation based on the most recent spectral property databases and high-fidelity radiative transfer equation (RTE) solvers has shown that at operating pressures and exhaust-gas recirculation levels typical of modern heavy-duty compression-ignition engines, radiative emission can be as high as 40% of the wall heat losses, that molecular gas radiation (mainly CO2 and H2O) can be more important than soot radiation, and that a significant fraction of the emitted radiation can be reabsorbed before reaching the walls. That is, radiation not only contributes to heat losses, but also changes the in-cylinder temperature distribution, which in turn affects combustion and emissions. The goal of this research is to develop models that explicitly account for the potentially strong coupling between radiative and turbulent boundary layer heat transfer. For example, for optically thick conditions, a simple diffusion model might be formulated in terms of an absorption-coefficient-dependent turbulent Prandtl number.

Sircar, Arpan↗
DOE OSTI2021

Radiative Heat Transport and Optical Characterization of High Temperature Molten Salts

The goal of this project was to advance the field of molten fluoride radiative heat transfer (RHT), through optical property measurements, heat transfer loop construction and operation, and computational fluid dynamics simulations. The following outcomes have been accomplished. A comprehensive review has been conducted to compile all available RHT-relevant optical absorption data for molten fluorides. The various measurement methods have also been compiled and critiqued. Thermal emission measurement methods have been refined and documented. A unique thermal emissivity measurement facility has been constructed and used to measure the emissivity of flowing FLiBe-exposed SS316 samples. A slight increase has been observed in the emissivity compared to unexposed SS316. A dual reflectance-emission setup was partially demonstrated for the purpose of molten fluoride absorption measurement. Preliminary infrared edge data for FLiNaK was obtained. A visible near-infrared (NIR) measurement setup has been constructed and will be used to measure absorption of corrosion products in FLiBe. A new multi-band thermal radiation method using blackbody-weighted spectral bands for the absorption-coefficient was deployed to investigate the thermal performance of the UW Natural Circulation FLiBe Loop under various power levels and operating conditions. The results showed an increasing and decreasing trend in the overall heat transfer with optical thickness with a maximum at optical thickness τ D ≈Ο(1). A forced convection FLiBe loop was constructed for the purpose of studying corrosion and thermal hydraulic phenomena. A vertical cantilever pump is used to achieve up to 5 gpm and 5 m/s flow velocity in hot and cold test sections. A methodology has been established for modeling radiative heat transfer (RHT) in molten salt coolants for the purpose of quantifying the contribution of thermal radiation in conditions relevant to FHR or MSR systems. The comparison between the results obtained for forced and mixed convection showed that in the studied ranges of optical thickness, the maximum effect of RHT on overall heat transfer was 60% improvement observed at z/D = 250 for forced convection; whereas for mixed convection, that value was higher at 170% observed at z/D = 30. The highest effect of RHT on the overall energy distribution was observed at τ D ≈3.4. Negligible effect (<20%) was observed above τ D =18 and below τ D ≈0.002. A CFD code-to-code comparison was conducted using COMSOL Multiphysics at UW-Madison and STAR-CCM at MIT, for a forced and mixed convection laminar flow for a grey medium in a vertical heated using both COMSOL Multiphysics at UW-Madison and STAR-CCM at MIT. The relative error was the largest at τ D =40 for the radiative heat flux, bulk temperature, and Nusselt number. On the other hand, the relative error was the least at τ D =0.002 for the conductive heat flux, bulk temperature, and Nusselt number.

Anderson, Mark↗
DOE OSTI2021

Apparatus and method to measure semiconductor optical absorption using microwave charge sensing

A time-resolved microwave reflectance apparatus comprises a pulsed or modulated optical source that irradiates a semiconductor sample with an excitation pump beam, a microwave oscillator that irradiates the sample with a continuous beam of microwaves, and a microwave detector that detects the microwaves reflected by the sample. Therefore, charge detection, rather than conventional absorption measurements (that detect the loss of photons), can be used to extract the absorption coefficient and band edge of a semiconductor material.

Shaner, Eric A.↗
DOE OSTI2012

Inverse transport problem solvers based on regularized and compressive sensing techniques

According to the direct exposure measurements from flash radiographic image, regularized-based method and compressive sensing (CS)-based method for inverse transport equation are presented. The linear absorption coefficients and interface locations of objects are reconstructed directly at the same time. With a large number of measurements, least-square method is utilized to complete the reconstruction. Owing to the ill-posedness of the inverse problems, regularized algorithm is employed. Tikhonov method is applied with an appropriate posterior regularization parameter to get a meaningful solution. However, it's always very costly to obtain enough measurements. With limited measurements, CS sparse reconstruction technique Orthogonal Matching Pursuit (OMP) is applied to obtain the sparse coefficients by solving an optimization problem. This paper constructs and takes the forward projection matrix rather than Gauss matrix as measurement matrix. In the CS-based algorithm, Fourier expansion and wavelet expansion are adopted to convert an underdetermined system to a well-posed system. Simulations and numerical results of regularized method with appropriate regularization parameter and that of CS-based agree well with the reference value, furthermore, both methods avoid amplifying the noise. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2016

Evidence of Radiosensitizing Effects of GdPO{sub 4} Nanostructures

Developing new methods to improve the outcome of cancer treatment has been one of the main research areas in medicine. Many approaches that allow for tumor targeting and thus reduction of side effects are currently under investigation. Among those, the combination of radiation therapy with certain chemotherapeutic agents has shown significant advances in cancer treatment. Another option is the use of radiosensitizers along with radiation therapy. Radiosensitizers are materials intended to enhance the radiation dose received in the tumor while maintaining the damage to the normal tissue to a minimum. Hence, the development of radiosensitizers has been of interest in recent years in order to improve the survival rate and the quality of life of the patient while reducing the cost of treatment. In this area, nanoparticles (NPs) have been widely explored as radiosensitizers due to the fact that tumor targeting can be achieved and the concentration of NPs on tumor environments can be greatly enhanced through the modification of NPs' surface by addition of agents such as antibodies. More importantly, the chemical composition of the NPs can be adjusted based on the application of interest. In this context, NPs that contain heavy elements have great potential as radiosensitizers due to their mechanisms of interaction with X-rays. For instance, gold NPs have been recognized as radiosensitizers due to their large photoelectric absorption coefficient. Furthermore, lanthanide based NPs have also shown characteristics as radiosensitizers. Among the various lanthanide containing NPs, gadolinium-based nanomaterials (NMs) have shown great potential for multiple applications in medicine such as contrast agents for magnetic resonance imaging (MRI). Additionally, the combination of gadolinium-based NPs and irradiation has evidenced a significant dose enhancement in in-vivo testing. Moreover, gadolinium-based ultra-small rigid platforms (USRPs) have shown theranostic properties for multimodal detection of lung cancers and radiosensitization effects. Among the various Gd based NPs, GdPO{sub 4} NMs are of increasing interest due to the multiple functions and applications that they may have. To illustrate, GdPO{sub 4} NPs have evidenced relaxitivities that are comparable to the contrast agents commonly used in MRI. Moreover, these NPs can be doped with different lanthanides ions allowing for the implementation of MRI and cellular luminescence for diagnostic purposes. Furthermore, gold-coated gadolinium-lanthanum phosphate NPs have evidenced their ability to encapsulate alpha-emitting radioisotopes of radiotherapeutic interest. This allows for targeted internal radiotherapy by functionalizing the NPs with specific molecules Moreover, low toxicity has been observed on dextran coated GdPO{sub 4} NPs regardless of the potential toxicity of free Gd{sup 3+}. Despite the various applications of GdPO{sub 4}, its response and interaction with X-ray evaluating their potential as radiosensitizers has not been explored. In this work, the radiosensitization of GdPO{sub 4} NMs is evidenced through the decomposition of a dye, methylene blue (MB), after X-ray radiation in the presence of NMs. GdPO{sub 4} was synthesized at moderate temperature following a hydrothermal method based on the precipitation reaction of a salt precursor and a surfactant. The crystalline structure and morphology of these NMs were characterized using Xray diffraction (XRD) and transmission electron microscopy (TEM). Crystalline GdPO{sub 4} was obtained following the hydrothermal synthesis. Besides, it was observed that the addition of GdPO{sub 4} to the MB solution enhances the decomposition of this dye under X-ray radiation. Therefore, GdPO{sub 4} NMs prove to be promising as radiosensitizers in radiation therapy. Nevertheless, the effect of GdPO{sub 4} on MB decomposition under X-ray radiation requires further study to evaluate the effect of the morphology and concentration of GdPO{sub 4} and the dose effect. (authors)

36 MATERIALS SCIENCE↗
DOE OSTI2024

UN-SiC TRISO Post Irradiation Examination Developmental Work

As part of efforts to strengthen INL?s post irradiation analysis capabilities with non-Advanced Gas Reactor (AGR) tristructural isotropic (TRISO) fuels, two developmental activities were conducted. The first activity was to determine how best to analyze uranium nitride TRISO fuel kernels using electron probe microanalysis, while the second activity focused on developing a method to deconsolidate TRISO fuel particles that have been encased in a silicon carbide matrix. Because these two activities were unrelated, they have been presented separately in this report. Initial EPMA analyses showed nitrogen contents that far exceeded the concentration expected for UN--a line compound. Further examination showed that current literature values for the mass absorption coefficient (MAC) for the N ka X-ray absorbed by U ranged from approximately 1600 to 9500, with most values tending toward 9500. Measuring UN with five different progressively increasing accelerating voltages followed by using the modeling program xMAC suggests the actual MAC is approximately 2115. Additional MAC modifications were required to produce reasonable analytical results. Because of the inaccuracies of necessary MAC coefficients, UN analysis via scanning electron microscopy (SEM) is likely to produce inaccurate results. This is because SEM software does not typically allow the user to alter MACs. Tests have been performed to examine the feasibility of an electrochemical technique to liberate irradiated TRISO fuel from a SiC matrix without damaging the outer pyrolytic carbon layer of the fuel particle. The method is performed by electrochemically exposing the SiC to magnesium metal forming Mg2Si and C. Following exposure, the small SiC samples showed slight mass increases with no evidence of conversion to Mg2Si and C nor obvious degradation of the SiC samples.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2024

Utilizing highly scattered light for intelligence through aerosols

A method for modeling light transport through a scattering medium prior to being incident on a detector and a corresponding system is disclosed. The method determines the effects of scattering and absorption caused by particles as a function of the density, size, and refractive index of the particles, as well as the wavelength of the light source. Based on the determined scattering and absorption coefficients, the signal incident on the detector may be calculated. The calculation may also be inverted such that based upon the detected signal, an object may be detected, and its location in the scattering medium may be estimated.

Bentz, Brian Z.↗
DOE OSTI2024

Establishing robust correction schemes for improved and reliable ARM-AOS aerosol optical data products

Aerosol light absorption and scattering of solar radiation play an important role in the earth’s atmosphere in terms of direct and semi-direct radiative forcing. Optical parameters of importance to the US Department of Energy (DOE) climate models include absorption and scattering coefficients, single scattering albedo (SSA), absorption Angstrom exponents (AAE), and the asymmetry parameter (g). These parameters depend on aerosol size, shape and composition (refractive index), and are spectrally sensitive in the shortwave region. Additionally, these parameters have a complex dependency on the emission source, especially for carbonaceous aerosols. The DOE Atmospheric Radiation Measurement (ARM) user facility has deployed aerosol observing systems (AOS) containing several filter-based instruments to measure and constrain aerosol optical properties and related parameters at multiple sites worldwide. For measurement of aerosol light absorption, the AOS includes filter-based instruments (particle soot absorption photometer and tricolor absorption photometer) that infer particle-phase aerosol absorption coefficients at nominal red, green, and blue wavelength bands from the attenuation (ATN) of light passing through a particulate filter on which aerosols are deposited. Measurement of aerosol scattering is done in situ using nephelometers. By combining inferred absorption coefficients from filter-based ATN measurements and in situ scattering coefficients, value-added products (VAPs) such as SSA, AAE, and g are derived.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1981

A model describing the microwave emission from a multi-layer snowpack at 37 GHz

A multilayer emission model is described and applied to emission measurements obtained at 37 GHz and H polarization using a microwave radiometer attached to a truck-mounted boom in Steamboat Springs, Colorado in 1977. Estimated absorption and scattering coefficients and their dependence on wetness were obtained using calculated values of the dielectric constant at 37 GHz along with the model. It was found that the scattering coefficient is comparable in value to the absorption coefficient for dry snow however, the absorption coefficient increases linearly with increasing snow wetness while the scattering coefficient decreases linearly with increasing wetness. The emission from each layer of the snowpack was also calculated using the estimated coefficients. It is shown that for dry snow, the ground underneath the snowpack contributes about 45% of all measured emission while the rest is due to emission from all the layers within the snowpack. When the wetness of the top 5 cm layer of snowpack increases to about 2% by volume, this top 5 cm snowlayer contributes more than 90% of all the measured emission.

Abdelrazik, M.↗
DOE OSTI2015

SU-D-210-03: Limited-View Multi-Source Quantitative Photoacoustic Tomography

Purpose: This work is to investigate a novel limited-view multi-source acquisition scheme for the direct and simultaneous reconstruction of optical coefficients in quantitative photoacoustic tomography (QPAT), which has potentially improved signal-to-noise ratio and reduced data acquisition time. Methods: Conventional QPAT is often considered in two steps: first to reconstruct the initial acoustic pressure from the full-view ultrasonic data after each optical illumination, and then to quantitatively reconstruct optical coefficients (e.g., absorption and scattering coefficients) from the initial acoustic pressure, using multi-source or multi-wavelength scheme.Based on a novel limited-view multi-source scheme here, We have to consider the direct reconstruction of optical coefficients from the ultrasonic data, since the initial acoustic pressure can no longer be reconstructed as an intermediate variable due to the incomplete acoustic data in the proposed limited-view scheme. In this work, based on a coupled photo-acoustic forward model combining diffusion approximation and wave equation, we develop a limited-memory Quasi-Newton method (LBFGS) for image reconstruction that utilizes the adjoint forward problem for fast computation of gradients. Furthermore, the tensor framelet sparsity is utilized to improve the image reconstruction which is solved by Alternative Direction Method of Multipliers (ADMM). Results: The simulation was performed on a modified Shepp-Logan phantom to validate the feasibility of the proposed limited-view scheme and its corresponding image reconstruction algorithms. Conclusion: A limited-view multi-source QPAT scheme is proposed, i.e., the partial-view acoustic data acquisition accompanying each optical illumination, and then the simultaneous rotations of both optical sources and ultrasonic detectors for next optical illumination. Moreover, LBFGS and ADMM algorithms are developed for the direct reconstruction of optical coefficients from the acoustic data. Jing Feng and Hao Gao were partially supported by the NSFC (#11405105), the 973 Program (#2015CB856000) and the Shanghai Pujiang Talent Program (#14PJ1404500)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Determination of reactive mass transfer coefficients for CO 2 absorption predictions

Absorption of carbon dioxide (CO 2 ) by solvents is an important process in many practical applications such as capture of greenhouse gases from flue gas, gas processing in the chemical and petroleum industries, capture of radioactive isotopes in the nuclear cycle, etc. High pH alkaline solutions were used in this research project to capture CO 2 . The chemical reaction between CO 2 and the hydroxyl ion is known to significantly increase the absorption rate compared to the same process without chemical reaction. The aim of this report is to study the influence of the chemical reaction on the absorption rate. Because of this, the gas-liquid mass transfer coefficient was measured under reactive and nonreactive conditions. Reactive mass transfer coefficient values were higher than similar ones without chemical reaction. Under the operating conditions used in this work, the mass transfer process was found to be controlled by the liquid phase resistance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2001

Time-dependent oral absorption models

The plasma concentration-time profiles following oral administration of drugs are often irregular and cannot be interpreted easily with conventional models based on first- or zero-order absorption kinetics and lag time. Six new models were developed using a time-dependent absorption rate coefficient, ka(t), wherein the time dependency was varied to account for the dynamic processes such as changes in fluid absorption or secretion, in absorption surface area, and in motility with time, in the gastrointestinal tract. In the present study, the plasma concentration profiles of propranolol obtained in human subjects following oral dosing were analyzed using the newly derived models based on mass balance and compared with the conventional models. Nonlinear regression analysis indicated that the conventional compartment model including lag time (CLAG model) could not predict the rapid initial increase in plasma concentration after dosing and the predicted Cmax values were much lower than that observed. On the other hand, all models with the time-dependent absorption rate coefficient, ka(t), were superior to the CLAG model in predicting plasma concentration profiles. Based on Akaike's Information Criterion (AIC), the fluid absorption model without lag time (FA model) exhibited the best overall fit to the data. The two-phase model including lag time, TPLAG model was also found to be a good model judging from the values of sum of squares. This model also described the irregular profiles of plasma concentration with time and frequently predicted Cmax values satisfactorily. A comparison of the absorption rate profiles also suggested that the TPLAG model is better at prediction of irregular absorption kinetics than the FA model. In conclusion, the incorporation of a time-dependent absorption rate coefficient ka(t) allows the prediction of nonlinear absorption characteristics in a more reliable manner.

Non-NASA Center↗
NASA NTRSDate not supplied

The Tables of Aerosol Optics (TAO) Project

The Table of Aerosol Optics (TAO) project is a community repository of optics computations (extinction, absorption, single-scatter albedo, lidar ratio, etc) that are useful for global models and remote sensing applications. TAO expands upon historical efforts (e.g., Hess et al., 1998) by building an open database that uses recent measurements and new computational techniques for non-spherical particles. The ‘open’ aspect of TAO is important, since the size distributions, hygroscopicities, refractive indices, and morphological recommendations of today will undoubtedly yield to different values in the future; the open framework of TAO allows scientists to keep adding new computations to the database as the science evolves. TAO is meant to be a community repository where specialists can put their computations for other scientists to use. So for instance, some groups are advancing new techniques that can accommodate complex fractal aggregates of black carbon, other groups are working on realistic irregular shapes for mineral dust, and different groups are updating the hygroscopicity of various aerosol types using new techniques. The TAO database gives these scientists a place to distribute their products. As TAO grows, modelers and remote sensing specialists will look to TAO as a place to find a wide variety of choices for testing. Meanwhile, global modelers can also use TAO to lobby for new tables that accommodate their needs. Eventually, TAO will provide mass extinction coefficients, mass absorption coefficients, lidar ratios, etc., at popular remote sensing and global modeling wavelengths (0.25-40 µm) for all pertinent species (sulfate, sea salt, BC, OC, BrC, dust, etc.). TAO will also accept computations for aerosol ‘type’ (e.g., biomass burning, urban, background, etc.) that may include regional and seasonal variability. Multiple tables may be created for each species or type to account for the multiple valid size distributions, hygroscopicities, complex refractive indices, and shapes that can be found in the literature.

Greg Schuster↗