Constellations of driftsonde systems gondolas floating in the stratosphere and able to release dropsondes upon command have so far been used in three major field experiments from 2006 through 2010. With them, high-quality, high-resolution, in situ atmospheric profiles were made over extended periods in regions that are otherwise very difficult to observe. The measurements have unique value for verifying and evaluating numerical weather prediction models and global data assimilation systems; they can be a valuable resource to validate data from remote sensing instruments, especially on satellites, but also airborne or ground-based remote sensors. These applications for models and remote sensors result in a powerful combination for improving data assimilation systems. Driftsondes also can support process studies in otherwise difficult locationsfor example, to study factors that control the development or decay of a tropical disturbance, or to investigate the lower boundary layer over the interior Antarctic continent. The driftsonde system is now a mature and robust observing system that can be combined with flight-level data to conduct multidisciplinary research at heights well above that reached by current research aircraft. In this article we describe the development and capabilities of the driftsonde system, the exemplary science resulting from its use to date, and some future applications.

During the THORPEX (The Observing System Research and Predictability Experiment) Pacific Asian Regional Campaign (T‐PARC), from 1 August to 30 September 2008, ∼1900 high‐quality, high vertical resolution soundings were collected over the Pacific Ocean. These include dropsondes deployed from four aircrafts and zero‐pressure balloons in the stratosphere (NCAR's Driftsonde system). The water vapor probability distribution and spatial variability in the northern subtropical Pacific (14°–20°N, 140°E–155°W) are studied using Driftsonde and COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) data and four global reanalysis products. Driftsonde data analysis shows distinct differences of relative humidity (RH) distributions in the free troposphere between the Eastern and Western Pacific (EP and WP, defined as east and west of 180°, respectively), very dry with a single peak of ∼1% RH in the EP and bi‐modal distributions in the WP with one peak near ice saturation and one varying with altitude. The frequent occurrences of extreme dry air are found in the driftsonde data with 59% and 19% of RHs less than or equal to 5% and at 1% at 500 hPa in the EP, respectively. RH with respect to ice in the free troposphere exhibits considerable longitudinal variations, very low (<20%) in the EP, but varying from 20% to 100% in the WP. Inter‐comparisons of Driftsonde, COSMIC and reanalysis data show generally good agreement among the Driftsonde, COSMIC, ECMWF Reanalysis‐Interim (ERA‐Interim) and Japanese Reanalysis (JRA) below 200 hPa. The ERA‐Interim and JRA are approved to be successful on describing RH frequency distributions and spatial variations in the region. The comparisons also reveal problems in Driftsonde, two National Center for Environmental Prediction (NCEP) reanalyses and COSMIC data. The moist layer at 200–100 hPa in the WP shown in the ERA‐Interim, JRA and COSMIC is missing in Driftsonde data. Major problems are found in the RH means and variability over the study region for both NCEP reanalyses. Although the higher‐moisture layer at 200–100 hPa in the WP in the COSMIC data agrees well with the ERA‐Interim and JRA, it is primarily attributed to the first guess of the 1‐Dimensional (1D) variational analysis used in the COSMIC retrieval rather than the refractivity measurements. The limited soundings (total 268) of Driftsonde data are capable of portraying RH probability distributions and longitudinal variability. This implies that Driftsonde system has the potential to become a valuable operational system for upper air observations over the ocean.

The Concordiasi project is making innovative observations of the atmosphere above Antarctica. The most important goals of the Concordiasi are as follows: To enhance the accuracy of weather prediction and climate records in Antarctica through the assimilation of in situ and satellite data, with an emphasis on data provided by hyperspectral infrared sounders. The focus is on clouds, precipitation, and the mass budget of the ice sheets. The improvements in dynamical model analyses and forecasts will be used in chemical-transport models that describe the links between the polar vortex dynamics and ozone depletion, and to advance the under understanding of the Earth system by examining the interactions between Antarctica and lower latitudes. To improve our understanding of microphysical and dynamical processes controlling the polar ozone, by providing the first quasi-Lagrangian observations of stratospheric ozone and particles, in addition to an improved characterization of the 3D polar vortex dynamics. Techni...

In an effort to improve the accuracy of airborne aerosol studies, we compared a new porous-diffuser low-turbulence inlet (LTI) with three other inlets on the NSF/NCAR C-130, using both dust and sea salt as test aerosols. Analysis of bulk filters behind the LTI and an external reference total aerosol sampler (TAS) found no significant differences, while both the NASA shrouded solid diffuser inlet (SD) and NCAR community aerosol inlet (CAI) passed smaller amounts. However, scanning electron microscopic analyses of particles behind the LTI and TAS confirmed the model prediction that the LTI porous diffuser (PD) enhanced 7 μm particle concentrations by about 60%. Aerodynamic particle size distributions behind the other inlets began to diverge from enhancement-corrected LTI values above 2 μm, with mass concentrations of larger particles lower by as much as a factor of ten behind the CAI and a factor of 2 behind the SD. We conclude that the corrected LTI distributions were closer to ambient values than those from either the CAI or the SD. Since tubing losses contributed the most uncertainty when deducing ambient supermicron size distributions from LTI data, minimizing them should be a high priority for future experiments. Measured transfer tubing losses were larger than model estimates, in part because of some complex pieces for which no suitable model exists. The LTI represents a significant advance in our ability to sample populations of large particles from aircraft. A necessary part of using an LTI is the calculation of and correction for large-particle enhancement using a computational fluid dynamics (CFD) program. Although the solid diffuser inlet performed well under some conditions, its large-particle efficiency cannot be modeled, varies with humidity and particle morphology, and involves wall contact that has the potential to modify some particles.

A low-turbulence, aerosol sampling inlet (LTI) has been developed for use on aircraft. The inlet makes use of boundary layer suction in a porous diffuser to slow the sample flow from aircraft air speeds near 150 m/s to velocities near 5 m/s without generating turbulence. The reduction of turbulence reduces losses of supermicron particles by turbulent deposition and permits the use of laminar flow calculations and well-understood drag formulations to accurately predict particle motion. Large particles are enhanced in the sample flow due to inertia. These enhancements are predicted with numerical analysis of fluid flow and integration of the equations of motion for the particles. The diffuser discussed in this article has been used in a number of field experiments, and the enhancement factors have been provided to the experimenters measuring aerosol downstream of the inlet. Some particles are doubtless lost in transport from the LTI to the aircraft fuselage. Estimates of those losses have also been made and provided to experimenters. The enhancement factors (EF) and losses are a function of particle Stokes number. They should be applied to measurements that segregate the sample into size bins that are narrow enough to assign a well-defined EF to each bin. Uncertainties in EF have been estimated. The uncertainties in EF and in the efficiency of transport to the aircraft are small compared to the uncertainties reported in the literature for sampling supermicron particles through solid conical diffusers. Thus the LTI contributes to our ability to quantitatively characterize supermicron particles from aircraft platforms.

A new enclosed injector system for low temperature kinetic studies is described. This system offers a number of advantages over more conventional designs of moveable inlet injectors. The enclosed injector prevents the introduction of contaminants into the flow reactor. In conventional designs, ambient contaminants adsorbed onto the outside of the injector could be transported into the flow reactor. The enclosed injector exposes the reactant gas to the same length of inlet tubing at a uniform temperature regardless of the injector position. In addition, the enclosed injector minimizes temperature gradients in the flow reactor caused by heat transfer along the injector. This is a particular problem when the flow reactor is operated near atmospheric pressure at reduced temperatures. Finally, this design is significantly more compact than conventional injector designs. This system has been successfully employed in studies of the heterogeneous reaction of N2O5 with sulfuric acid aerosols over the temperature range 225–293 K.

A technique employing pressure modulation is described which minimizes all interference fringing produced in small base length multipass absorption cells in diode laser studies.

Duck cultured hepatocytes from Pekin ducks naturally infected by duck hepatitis B virus can remain functional twice longer if a coculture system with rat liver epithelial cells is used instead of ordinary primary culture. The use of a selective medium in which ornithine and lactate replaced arginine and glucose, respectively, allowed viral replication initiated in vivo to be maintained in the coculture for 2 months. Several antiviral compounds including the pyrophosphate analog (phosphonoformic acid) or nucleoside analogs (9β-arabinofuranosyl AMP, 1-(2′-deoxy-2′-fluoro-β-D-arabinofuranosyl)-5-iodocytosine, 1,2′-deoxy-2′-fluoro-β-D-arabinofuranosyl-5-ethyluracil and 1,2′-deoxy-2′-fluoro-β-D-arabinofuranosyl thymine were studied in both culture systems for their ability to inhibit duck hepatitis B virus replication. Hepatocytes were treated for 7 days with 1,2′-deoxy-2′-fluoro-β-D-arabinofuranosyl-5-ethyluracil (10 μM) and 1,2′-deoxy-2′-fluoro-β-D-arabinofuranosyl thymine (0.5 μM) or for 14 days with 9β-arabinofuranosyl AMP (90 μM), phosphonoformic acid (100 μM) and 1-(2′-deoxy-2′-fluoro-β-D-arabinofuranosyl)-5-iodocytosine (6 μM). The effects of the drugs on viral replication were monitored by testing for duck hepatitis B virus DNA in the culture supernatant and in the cells by molecular hybridization. All the above-mentioned drugs demonstrated an inhibitory activity in both types of cultures which at the quite distinct doses used was greater for phosphonoformic acid and 1-(2′-deoxy-2′-fluoro-β-D-arabinofuranosyl)-5-iodocytosine than for 9β-arabinofuranosyl AMP, 1,2′-deoxy-2′-fluoro-β-D-arabinofuranosyl-5-ethyluracil or 1,2′-deoxy-2′-fluoro-β-D-arabinofuranosyl thymine. Viral replication, however, resumed following discontinuation of treatment. More studies are needed to further confirm the relevance of this tissue culture system for the screening of new potential anti-hepatitis B virus agents.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAdditions and Corrections - Nucleosides. XXIX. 1-β-D-Arabinofuranosyl-5-fluorocytosine and Related Arabino Nucleosides.Jack Fox, Naishun Miller, and Iris WempenCite this: J. Med. Chem. 1966, 9, 6, 986Publication Date (Print):November 1, 1966Publication History Published online22 September 2004Published inissue 1 November 1966https://pubs.acs.org/doi/10.1021/jm00324a602https://doi.org/10.1021/jm00324a602research-articleACS PublicationsRequest reuse permissionsArticle Views29Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts