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NASA NTRS2005

Regression Analysis of Long-Term Profile Ozone Data Set from BUV Instruments

We have produced a profile merged ozone data set (MOD) based on the SBUV/SBUV2 series of nadir-viewing satellite backscatter instruments, covering the period from November 1978 - December 2003. In 2004, data from the Nimbus 7 SBUV and NOAA 9, ll, and 16 SBUV/2 instruments were reprocessed using the Version 8 (V8) algorithm and most recent calibrations. More recently, data from the Nimbus 4 BUT instrument, which was operational from 1970 - 1977, were also reprocessed using the V8 algorithm. As part of the V8 profile calibration, the Nimbus 7 and NOAA 9 (1993-1997 only) instrument calibrations have been adjusted to match the NOAA 11 calibration, which was established based on comparisons with SSBUV shuttle flight data. Differences between NOAA 11, Nimbus 7 and NOAA 9 profile zonal means are within plus or minus 5% at all levels when averaged over the respective periods of data overlap. NOAA 16 SBUV/2 data have insufficient overlap with NOAA 11, so its calibration is based on pre-flight information. Mean differences over 4 months of overlap are within plus or minus 7%. Given the level of agreement between the data sets, we simply average the ozone values during periods of instrument overlap to produce the MOD profile data set. Initial comparisons of coincident matches of N4 BUV and Arosa Umkehr data show mean differences of 0.5 (0.5)% at 30km; 7.5 (0.5)% at 35 km; and 11 (0.7)% at 40 km, where the number in parentheses is the standard error of the mean. In this study, we use the MOD profile data set (1978-2003) to estimate the change in profile ozone due to changing stratospheric chlorine levels. We use a standard linear regression model with proxies for the seasonal cycle, solar cycle, QBO, and ozone trend. To account for the non-linearity of stratospheric chlorine levels since the late 1990s, we use a time series of Effective Chlorine, defined as the global average of Chlorine + 50 * Bromine at 1 hPa, as the trend proxy. The Effective Chlorine data are taken from the 3-D Goddard CTM. We will show the latest trend results using this statistical model. In addition, the Nimbus 4 BUV data offer an opportunity to test the physical properties of our statistical model. From ground-based comparisons we will establish an uncertainty range for the Nimbus 4 data. We then extrapolate our statistical model fit backwards in time and compare to the Nimbus 4 data. We compare the characteristics of the residual, defined as the difference between the data and statistical regression fit, during the Nimbus 4 time period and the 1978-2003 period over which the statistical model coefficients were estimated, and present these results.

Stolarski, Richard S.↗

DOE OSTI2019

Nuclear Data Sheets for A=50

The experimental nuclear structure and decay data are evaluated for all the known nuclides of mass 50 (Cl, Ar, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni). Here, detailed evaluated nuclear structure information are presented in individual decay and reaction datasets and the best values are recommended in the Adopted dataset for level properties, γ and β radiations, and other spectroscopic information. No excited states are known in 50Cl and 50Ni, and limited information is available for 50 Ar, 50 K, 50 Fe and 50 Co. This work supersedes earlier evaluations of A=50 by 2011El01, 1995Bu09, 1990Bu18, 1984Al29, and 1976Au07.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2011

Nuclear Data Sheets for A = 50

The experimental nuclear spectroscopic data for known nuclides of mass number 50 (Cl,Ar,K,Ca,Sc,Ti,V, Cr,Mn,Fe,Co,Ni) have been evaluated and presented together with Adopted properties for levels and {gamma} rays. This evaluation has been carried out about 15 years after the previous one by Thomas Burrows (1995Bu29). Except for {sup 50}Sc and {sup 50}V, extensive new data have become available for all the other nuclides in the intervening years. The data for {sup 50}Sc and {sup 50}V have also been checked again in detail and several changes made. No data are yet available for excited states in {sup 50}Cl, {sup 50}Ar and {sup 50}Ni. This work supersedes earlier evaluations (1995Bu29, 1990Bu18, 1984Al29, 1976Au07) of A=50 nuclides.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

NASA NTRS1987

Infrared spectroscopic measurements of halogenated sink and reservoir gases in the stratosphere with the ATMOS instrument

The Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument recorded 19 sets of interferograms during solar occultations in both the Northern and Southern Hemispheres over the course of the Spacelab 3 mission. The resulting IR spectra furnish concentration profiles for over 25 atmospheric species. Attention is presently given to the volume mixing ratio profiles for HCl and HF in the 15-60-km altitude region, retrieved from northern sunsets and southern sunrises. The HF/HCl ratios deduced are in good agreement with model predictions. The total atmospheric chlorine at 50 km is nearly all in the form of HCl.

Raper, O. F.↗

NASA NTRS1992

Effects of culture conditions and biofilm formation on the iodine susceptibility of Legionella pneumophila

The susceptibility of Legionella pneumophila to iodination was studied with cultures grown in well water, on rich agar media, and attached to stainless-steel surfaces. Legionella pneumophila grown in water cultures in association with other microorganisms were less sensitive to disinfection by chlorine and iodine than were agar-passaged cultures. Differences in sensitivity to disinfection between water-cultured and agar-grown legionellae were determined by comparing C x T values (concentration in milligrams per litre multiplied by time in minutes to achieve 99% decrease in viability) and CM x T values (concentration in molarity). Iodine (1500x) gave a greater difference in CM x T values than did chlorine (68x). Iodine was 50 times more effective than chlorine when used with agar-grown cultures but was only twice as effective when tested against water-grown Legionella cultures. C x T x S values (C x T multiplied by percent survivors), which take into consideration the percent surviving bacteria, were used to compare sensitivities in very resistant populations, such as those in biofilms. Water cultures of legionellae associated with stainless-steel surfaces were 135 times more resistant to iodination than were unattached legionellae, and they were 210,000 times more resistant than were agar-grown cultures. These results indicate that the conditions under which legionellae are grown can dramatically affect their susceptibility to some disinfectants and must be considered when evaluating the efficacy of a disinfecting agent.

Non-NASA Center↗

DOE OSTI2024

Octupole moment driven free charge generation in partially chlorinated subphthalocyanine for planar heterojunction organic photodetectors

In this study, high-performance organic photodetectors are presented which utilize a pristine chlorinated subphthalocyanine photoactive layer. Optical and optoelectronic analyses indicate that the device photocurrent is primarily generated through direct charge generation within the chlorinated subphthalocyanine layer, rather than exciton separation at layer interfaces. Molecular modelling suggests that this direct charge generation is facilitated by chlorinated subphthalocyanine high octupole moment (-80 DÅ 2 ), which generates a 200 meV shift in molecular energetics. Increasing the thickness of chlorinated subphthalocyanine leads to faster response time, correlated with a decrease in trap density. Notably, photodetectors with a 50 nm thick chlorinated subphthalocyanine photoactive layer exhibit detectivities approaching 10 13 Jones, with a dark current below 10 -7 A cm -2 up to -5 V. Based on these findings, we conclude that high octupole moment molecular semiconductors are promising materials for high-performance organic photodetectors employing single-component photoactive layer.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1995

HCl absorption toward Sagittarius B2

We have detected the 626 GHz J = 1 approaches 0 transition of hydrogen chloride (H(sup 35)Cl) in absorption against the blending of the three hyperfine components of this transition by the velocity profile of Sgr B2 observed in other species. The apparent optical depth of the line is tau approximately equal to 1, and the minimum HCl column density is 1.6 x 10(exp 14)/sq cm. A detailed radiative transfer model was constructed which includes collisional and radiative excitation, absorption and emission by dust, and the radial variation of temperature and density. Good agreement between the model and the data is obtained for HCl/H2 approximately 1.1 x 10(exp -9). Comparison of this result to chemical models indicates that the depletion factor of gas-phase chlorine is between 50-180 in the molecular envelope surrounding the SgrB2(N) and (M) dust cores.

Zmuidzinas, J.↗

DOE OSTI2016

Synthetic Chlorins, Possible Surrogates for Chlorophylls, Prepared by Derivatization of Porphyrins

Chlorophylls make Earth green, are the central constituents in the engine of photosynthesis, and not surprisingly have garnered extensive attention. A chlorin, the core chromophore of a chlorophyll, is a dihydroporphyrin macrocycle that contains one pyrroline ring and three pyrrole rings. The dominant method for the synthesis of chlorins has entailed the derivatization of porphyrins. The present review covers the ostensibly simple conversion of porphyrins, regardless of synthetic or biological origin, to chlorins. The period covered encompasses the entire history since the beginnings of chlorin synthetic chemistry in the early 20th century through 2015. Representative transformations include hydrogenation, cycloaddition, annulation, and diverse “breaking and mending” approaches. Altogether, the synthesis of >1000 chlorins or chlorin-like compounds (containing >50 distinct pyrroline motifs) is described. Such diversity animates the question “what structural features are essential for a chlorin to resemble chlorophyll?” To begin to address the structure–spectrum relationship, > 250 absorption spectra are provided for representative structures. The synthesis and spectral properties of the vast collection of compounds described herein are expected to illuminate the scope to which synthetic chlorins can serve as surrogates for chlorophylls and be exploited in diverse ways.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1996

Balloon observations of organic and inorganic chlorine in the stratosphere: the role of HClO4 production on sulfate aerosols

Simultaneous observations of stratospheric organic and inorganic chlorine were made in September 1993 out of Fort Sumner, New Mexico, using JPL balloon-borne MkIV interferometer. Between 15 and 20 km, a significant fraction (20-60%) of the inorganic chlorine could not be accounted for by the sum of measured HCl, ClONO2, and HOCl. Laboratory measurements of the reaction of ClO radicals on sulfuric acid solutions have indicated that, along with HCl, small amounts of perchloric acid, HClO4, were formed. Very little is known about the fate of HClO4 in the stratosphere and we use a photochemical box model to determine the impact of this new species on the partitioning of inorganic chlorine in the stratosphere. Assuming that HClO4 is photochemically stable, it is shown that in the enhanced aerosol loading conditions resulting from Mt. Pinatubo's eruption, HClO4 could represent a significant reservoir of chlorine in the lower stratosphere, sequestering up to 0.2 ppbv (or 50%) of the total inorganic chlorine at 16 km. The occurrence of this new species could bring to closure the inorganic chlorine budget deficiency made apparent by recent ER-2 aircraft in situ measurements of HCl.

unmanned↗

NASA NTRS1994

Increase in Levels of Stratospheric Chlorine and Fluorine Loading between 1985 and 1992

Mixing ratios of 3.44 ppbv (parts per billion by volume) and 1.23 ppbv for HCl and HF above 50 km, surrogates for total chlorine and fluorine, have been measured by the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment on a March 1992 flight of the Space Shuttle. Compared to the measured values obtained on a 1985 flight, these correspond to a 37% and 62% increase for HCl and HF, respectively. The derived trend in HCl (approx. 0.13 ppbv per year) is in good agreement with the model-predicted increase in chlorine loading of 0.13 ppbv per year, and with the measured trends in HCl total column abundance from reported ground-based observations. The main source of this change can be attributed to the release of man-made chlorofluorocarbons (CFC's) and hydro-chloro-fluoro-carbons (HCFC's). This new value for HCl represents an upper limit to the inorganic chlorine concentration in the stratosphere available for participation in photochemical processes which destroy ozone.

Gunson, M. R.↗

DOE OSTI2024

Macroscale properties and atomic-scale mechanisms of ash removal in low-temperature hydrothermal carbonization

Biogenic ash is a significant impediment to the utilization of agricultural residues in biofuel production. Such challenge can be addressed by various treatments, as demonstrated in this study on the experimental and computational mechanisms involved in the hydrothermal treatment (HT) of wheat straw. A combination of classical (all-atom) molecular dynamics simulations of cellulose carrying silica and calcium species, along with first principles quantum chemical calculations, indicates the dissociation of inorganics from the cellulose with increased HT temperature. Here, this observation is confirmed by experimental evidence of effective ash removal by HT, showing at least 50% removal of sulfur, chlorine, potassium, and calcium, and 12.5% of silica, leading to a reduced total ash content (from 6.7% to 4.2%).Changes in structural features upon HT, such as surface cellular structure and porosity, were revealed, accompanied by an increased specific surface area (from 1.17 to 6.34 m 2 /g). Our simulations suggest that silica binds tightly to the hydrophobic face of cellulose at room temperature, but HT significantly reduces the binding free energy of association with both hydrophobic and hydrophilic surfaces. Most significantly, ash removal leads to an increased calorific value, rising from approximately 16 MJ/kg to about 19 MJ/kg, along with improved thermal behavior. The improved integration combustion index parameter S indicates that the combustion properties improve with ash removal efficiency. The proposed atomic-level mechanism for the observed removal of inorganics during mild HT underscores the potential of such treatment in producing energy-dense wheat straw, a widely available agricultural residue.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1991

The potential for ozone depletion in the Arctic polar stratosphere

The nature of the Arctic polar stratosphere is observed to be similar in many respects to that of the Antarctic polar stratosphere, where an ozone hole has been identified. Most of the available chlorine (CHl and ClONO2) was converted by reactions on polar stratospheric clouds to reactive ClO and Cl2O2 thoroughout the Arctic polar vortex before midwinter. Reactive nitrogen was converted to HNO3, and some, with spatial inhomogeneity, fell out of the stratosphere. These chemical changes ensured characteristic ozone losses of 10 to 15 percent at altitudes inside the polar vortex where polar stratospheric clouds had occurred. These local losses can translate into 5 to 8 percent losses in the vertical column abundance of ozone. As the amount of stratospheric chlorine inevitably increases by 50 percent over the next two decades, ozone losses recognizable as an ozone hole may well appear.

Brune, W. H.↗

DOE OSTI2015

Self-Assembled Light-Harvesting System from Chromophores in Lipid Vesicles

Lipid vesicles are used as the organizational structure of self-assembled light-harvesting systems. Following analysis of 17 chromophores, six were selected for inclusion in vesicle-based antennas. The complementary absorption features of the chromophores span the near-ultraviolet, visible, and near-infrared region. Although the overall concentration of the pigments is low (~1 μ M for quantitative spectroscopic studies) in a cuvette, the lipid-vesicle system affords high concentration (≥10 mM) in the bilayer for efficient energy flow from donor to acceptor. Energy transfer was characterized in 13 representative binary mixtures using static techniques (fluorescence–excitation versus absorptance spectra, quenching of donor fluorescence, modeling emission spectra of a mixture versus components) and time-resolved spectroscopy (fluorescence, ultrafast absorption). Binary donor–acceptor systems that employ a boron-dipyrrin donor (S 0 ↔ S 1 absorption/emission in the blue-green) and a chlorin or bacteriochlorin acceptor (S 0 ↔ S 1 absorption/emission in the red or near-infrared) have an average excitation-energy-transfer efficiency (Φ EET ) of ~50%. Binary systems with a chlorin donor and a chlorin or bacteriochlorin acceptor have Φ EET ~ 85%. The differences in Φ EET generally track the donor-fluorescence/acceptor-absorption spectral overlap within a dipole–dipole coupling (Förster) mechanism. Substantial deviation from single-exponential decay of the excited donor (due to the dispersion of donor–acceptor distances) is expected and observed. The time profiles and resulting Φ EET are modeled on the basis of (Förster) energy transfer between chromophores relatively densely packed in a two-dimensional compartment. Initial studies of two ternary and one quaternary combination of chromophores show the enhanced spectral coverage and energy-transfer efficacy expected on the basis of the binary systems. Collectively, this approach may provide one of the simplest designs for self-assembled light-harvesting systems that afford broad solar collection and efficient energy transfer.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2015

Synthesis and characterization of nano crystalline nickel zinc ferrite for chlorine gas sensor at room temperature

Nano crystalline Nickel Zinc ferrite (Ni{sub 0.25}Zn{sub 0.75}Fe{sub 2}O{sub 4}) thin films were synthesized by Sol Gel method for gas response. The phase and microstructure of the obtained Ni{sub 0.25}Zn{sub 0.75}Fe{sub 2}O{sub 4} thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). The nanostructured Ni{sub 0.25}Zn{sub 0.75}Fe{sub 2}O{sub 4} thin film shows single spinel phase. Magnetic study was obtained with the help of VSM. The effects of working temperature on the gas response were studied. The results reveal that the Ni{sub 0.25}Zn{sub 0.75}Fe{sub 2}O{sub 4} thin film gas sensor shows good selectivity to chlorine gas at room temperature. The sensor shows highest sensitivity (∼50%) at room temperature, indicating its application in detecting chlorine gas at room temperature in the future.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

NASA NTRS1993

Chemical loss of ozone in the Arctic polar vortex in the winter of 1991- 1992

In situ measurements of chlorine monoxide, bromine monoxide, and ozone are extrapolated globally, with the use of meteorological tracers, to infer the loss rates for ozone in the Arctic lower stratosphere during the Airborne Arctic Stratospheric Expedition II (AASE II) in the winter of 1991-1992. The analysis indicates removal of 15 to 20 percent of ambient ozone because of elevated concentrations of chlorine monoxide and bromine monoxide. Observations during AASE II define rates of removal of chlorine monoxide attributable to reaction with nitrogen dioxide (produced by photolysis of nitric acid) and to production of hydrochloric acid. Ozone loss ceased in March as concentrations of chlorine monoxide declined. Ozone losses could approach 50 percent if regeneration of nitrogen dioxide were inhibited by irreversible removal of nitrogen oxides (denitrification), as presently observed in the Antarctic, or without denitrification if inorganic chlorine concentrations were to double.

Salawitch, R. J.↗

NASA NTRS1993

Chemical Loss of Ozone in the Arctic Polar Vortex in the Winter of 1991-1992

Salawitch, R. J.↗

NASA NTRS2004

Halogens and the Chemistry of the Free Troposphere

The role of halogens in both the marine boundary layer and the stratosphere has long been recognized, while their role in the free troposphere is often not considered in global chemical models. However, a careful examination of free-tropospheric chemistry constrained by observations using a full chemical data assimilation system shows that halogens do play a significant role in the free troposphere. In particular, the chlorine initiation of methane oxidation in the free troposphere can contribute more than 10%, and in some regions up to 50%, of the total rate of initiation. The initiation of methane oxidation by chlorine is particularly important below the polar vortex and in northern mid-latitudes. Likewise, the hydrolysis of BrONO2 alone can contribute more than 35% of the HNO3 production rate in the free-troposphere.

Lary, David John↗

NASA NTRS1975

Fluorine photochemistry in the stratosphere

The photochemistry of fluorine in the stratosphere is surveyed in order to estimate the effect on ozone of fluorine atoms released by the breakdown of chlorofluoromethanes. The catalytic efficiency for ozone destruction by fluorine is found to be less than .0001 that of chlorine in the altitude range from 25 to 50 km.

Stolarski, R. S.↗