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DOE OSTI2020

Materials Data on Ba12Br3Cl2F19 by Materials Project

Ba12Br3Cl2F19 crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. there are seven inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 7-coordinate geometry to two equivalent Cl1- and seven F1- atoms. Both Ba–Cl bond lengths are 3.48 Å. There are a spread of Ba–F bond distances ranging from 2.69–2.78 Å. In the second Ba2+ site, Ba2+ is bonded in a 7-coordinate geometry to two equivalent Br1- and seven F1- atoms. Both Ba–Br bond lengths are 3.50 Å. There are a spread of Ba–F bond distances ranging from 2.66–2.79 Å. In the third Ba2+ site, Ba2+ is bonded in a 5-coordinate geometry to four equivalent Cl1- and five F1- atoms. All Ba–Cl bond lengths are 3.44 Å. There are a spread of Ba–F bond distances ranging from 2.55–2.75 Å. In the fourth Ba2+ site, Ba2+ is bonded in a 5-coordinate geometry to two equivalent Br1-, two equivalent Cl1-, and five F1- atoms. Both Ba–Br bond lengths are 3.47 Å. Both Ba–Cl bond lengths are 3.43 Å. There are a spread of Ba–F bond distances ranging from 2.56–2.77 Å. In the fifth Ba2+ site, Ba2+ is bonded in a 9-coordinate geometry to two equivalent Br1- and seven F1- atoms. Both Ba–Br bond lengths are 3.42 Å. There are a spread of Ba–F bond distances ranging from 2.61–3.10 Å. In the sixth Ba2+ site, Ba2+ is bonded in a 9-coordinate geometry to two equivalent Br1- and seven F1- atoms. Both Ba–Br bond lengths are 3.42 Å. There are a spread of Ba–F bond distances ranging from 2.62–3.10 Å. In the seventh Ba2+ site, Ba2+ is bonded in a 9-coordinate geometry to two equivalent Br1- and seven F1- atoms. Both Ba–Br bond lengths are 3.42 Å. There are a spread of Ba–F bond distances ranging from 2.61–3.10 Å. There are two inequivalent Br1- sites. In the first Br1- site, Br1- is bonded in a 12-coordinate geometry to six Ba2+ and eight F1- atoms. There are a spread of Br–F bond distances ranging from 3.49–3.53 Å. In the second Br1- site, Br1- is bonded in a 12-coordinate geometry to six Ba2+ and nine F1- atoms. There are a spread of Br–F bond distances ranging from 3.55–3.62 Å. Cl1- is bonded in a 6-coordinate geometry to six Ba2+ and eight F1- atoms. There are a spread of Cl–F bond distances ranging from 3.48–3.53 Å. There are eleven inequivalent F1- sites. In the first F1- site, F1- is bonded to four Ba2+, one Br1-, and two equivalent Cl1- atoms to form FBa4BrCl2 tetrahedra that share corners with eleven FBa4Br3 tetrahedra, edges with four FBa4BrCl2 tetrahedra, and faces with five FBa4BrCl2 tetrahedra. In the second F1- site, F1- is bonded to four Ba2+, one Br1-, and two equivalent Cl1- atoms to form FBa4BrCl2 tetrahedra that share corners with eleven FBa4BrCl2 tetrahedra, edges with four FBa4BrCl2 tetrahedra, and faces with five FBa4Br2 tetrahedra. In the third F1- site, F1- is bonded to four Ba2+ and three Br1- atoms to form distorted FBa4Br3 tetrahedra that share corners with eleven FBa4BrCl2 tetrahedra, edges with four FBa4Br3 tetrahedra, and faces with five FBa4Br2 tetrahedra. In the fourth F1- site, F1- is bonded in a 5-coordinate geometry to five Ba2+ atoms. In the fifth F1- site, F1- is bonded in a 5-coordinate geometry to five Ba2+ atoms. In the sixth F1- site, F1- is bonded in a trigonal planar geometry to three Ba2+, two equivalent Br1-, and four equivalent Cl1- atoms. In the seventh F1- site, F1- is bonded to four Ba2+, one Br1-, and one Cl1- atom to form a mixture of face and corner-sharing FBa4BrCl tetrahedra. In the eighth F1- site, F1- is bonded to four Ba2+ and two equivalent Cl1- atoms to form a mixture of face and corner-sharing FBa4Cl2 tetrahedra. In the ninth F1- site, F1- is bonded to four Ba2+ and two equivalent Br1- atoms to form FBa4Br2 tetrahedra that share corners with twelve FBa4BrCl2 tetrahedra, edges with five FBa4Br3 tetrahedra, and faces with four FBa4Br2 tetrahedra. In the tenth F1- site, F1- is bonded to four Ba2+ and two equivalent Br1- atoms to form FBa4Br2 tetrahedra that share corners with twelve FBa4BrCl2 tetrahedra, edges with five FBa4BrCl2 tetrahedra, and faces with four FBa4Br2 tetrahedra. In the eleventh F1- site, F1- is bonded to four Ba2+ and two equivalent Br1- atoms to form FBa4Br2 tetrahedra that share corners with twelve FBa4BrCl2 tetrahedra, edges with five FBa4BrCl2 tetrahedra, and faces with four FBa4Br2 tetrahedra.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on TmBr2 by Materials Project

TmBr2 is Baddeleyite-like structured and crystallizes in the orthorhombic Pbca space group. The structure is three-dimensional. Tm is bonded in a 7-coordinate geometry to seven Br atoms. There are a spread of Tm–Br bond distances ranging from 2.89–3.11 Å. There are two inequivalent Br sites. In the first Br site, Br is bonded in a trigonal planar geometry to three equivalent Tm atoms. In the second Br site, Br is bonded to four equivalent Tm atoms to form a mixture of distorted edge and corner-sharing BrTm4 tetrahedra.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on NaZnBr3O5 by Materials Project

NaZnO5Br3 crystallizes in the trigonal R3 space group. The structure is two-dimensional and consists of three NaZnO5Br3 sheets oriented in the (0, 0, 1) direction. Na is bonded in a 3-coordinate geometry to three equivalent O and three equivalent Br atoms. All Na–O bond lengths are 2.77 Å. All Na–Br bond lengths are 3.31 Å. Zn is bonded in a trigonal planar geometry to three equivalent Br atoms. All Zn–Br bond lengths are 2.35 Å. There are three inequivalent O sites. In the first O site, O is bonded in a bent 120 degrees geometry to one Na and one O atom. The O–O bond length is 1.39 Å. In the second O site, O is bonded in a trigonal non-coplanar geometry to three equivalent O atoms. In the third O site, O is bonded in a distorted T-shaped geometry to three equivalent Br atoms. All O–Br bond lengths are 2.46 Å. Br is bonded in a 3-coordinate geometry to one Na, one Zn, and one O atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Cd(BrO2)2 by Materials Project

Cd(O2Br)2 crystallizes in the orthorhombic Pnnm space group. The structure is three-dimensional. Cd is bonded in a distorted linear geometry to two equivalent O and four equivalent Br atoms. Both Cd–O bond lengths are 2.16 Å. All Cd–Br bond lengths are 2.97 Å. There are two inequivalent O sites. In the first O site, O is bonded in a distorted single-bond geometry to two equivalent O and one Br atom. Both O–O bond lengths are 1.94 Å. The O–Br bond length is 1.97 Å. In the second O site, O is bonded in a 2-coordinate geometry to one Cd, two equivalent O, and one Br atom. The O–Br bond length is 2.13 Å. Br is bonded in a 2-coordinate geometry to two equivalent Cd and two O atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on PrMoBrO4 by Materials Project

PrMoO4Br crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent Pr3+ sites. In the first Pr3+ site, Pr3+ is bonded in a 8-coordinate geometry to five O2- and three Br1- atoms. There are a spread of Pr–O bond distances ranging from 2.43–2.69 Å. There are two shorter (3.02 Å) and one longer (3.03 Å) Pr–Br bond lengths. In the second Pr3+ site, Pr3+ is bonded in a 8-coordinate geometry to seven O2- and one Br1- atom. There are a spread of Pr–O bond distances ranging from 2.42–2.88 Å. The Pr–Br bond length is 3.08 Å. There are two inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.78–1.83 Å. In the second Mo6+ site, Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.77–1.83 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Pr3+, one Mo6+, and three equivalent Br1- atoms. There are a spread of O–Br bond distances ranging from 3.47–3.69 Å. In the second O2- site, O2- is bonded in a distorted linear geometry to one Pr3+, one Mo6+, and one Br1- atom. The O–Br bond length is 3.25 Å. In the third O2- site, O2- is bonded in a 3-coordinate geometry to two Pr3+, one Mo6+, and two equivalent Br1- atoms. There are one shorter (3.45 Å) and one longer (3.54 Å) O–Br bond lengths. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to two Pr3+, one Mo6+, and two equivalent Br1- atoms. There are one shorter (3.43 Å) and one longer (3.56 Å) O–Br bond lengths. In the fifth O2- site, O2- is bonded in a distorted linear geometry to one Pr3+, one Mo6+, and one Br1- atom. The O–Br bond length is 3.19 Å. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Pr3+ and one Mo6+ atom. In the seventh O2- site, O2- is bonded in a distorted linear geometry to one Pr3+ and one Mo6+ atom. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to two Pr3+ and one Mo6+ atom. There are two inequivalent Br1- sites. In the first Br1- site, Br1- is bonded in a distorted water-like geometry to two equivalent Pr3+ atoms. In the second Br1- site, Br1- is bonded in a 2-coordinate geometry to two Pr3+ and nine O2- atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on GdWBrO4 by Materials Project

GdWO4Br crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent Gd3+ sites. In the first Gd3+ site, Gd3+ is bonded in a 8-coordinate geometry to five O2- and three Br1- atoms. There are a spread of Gd–O bond distances ranging from 2.32–2.79 Å. There are a spread of Gd–Br bond distances ranging from 2.94–2.96 Å. In the second Gd3+ site, Gd3+ is bonded in a 6-coordinate geometry to six O2- and one Br1- atom. There are a spread of Gd–O bond distances ranging from 2.32–2.52 Å. The Gd–Br bond length is 3.03 Å. There are two inequivalent W6+ sites. In the first W6+ site, W6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of W–O bond distances ranging from 1.80–1.84 Å. In the second W6+ site, W6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of W–O bond distances ranging from 1.79–1.86 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one Gd3+, one W6+, and three equivalent Br1- atoms. There are a spread of O–Br bond distances ranging from 3.39–3.67 Å. In the second O2- site, O2- is bonded in a distorted linear geometry to one Gd3+, one W6+, and one Br1- atom. The O–Br bond length is 3.20 Å. In the third O2- site, O2- is bonded in a 2-coordinate geometry to two Gd3+, one W6+, and two equivalent Br1- atoms. There are one shorter (3.43 Å) and one longer (3.46 Å) O–Br bond lengths. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to two Gd3+, one W6+, and two equivalent Br1- atoms. There are one shorter (3.35 Å) and one longer (3.50 Å) O–Br bond lengths. In the fifth O2- site, O2- is bonded in a distorted linear geometry to one Gd3+, one W6+, and one Br1- atom. The O–Br bond length is 3.17 Å. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Gd3+ and one W6+ atom. In the seventh O2- site, O2- is bonded in a distorted linear geometry to one Gd3+ and one W6+ atom. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to two Gd3+ and one W6+ atom. There are two inequivalent Br1- sites. In the first Br1- site, Br1- is bonded in a distorted water-like geometry to two equivalent Gd3+ atoms. In the second Br1- site, Br1- is bonded in a 2-coordinate geometry to two Gd3+ and nine O2- atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2023

CO 2 Activation with Manganese Tricarbonyl Complexes through an H–Atom Responsive Benzimidazole Ligand

Herein, we report the synthesis and characterization of two manganese tricarbonyl complexes, Mn I (HL)(CO) 3 Br (1 a-Br) and Mn I (MeL)(CO) 3 Br (1 b-Br) (where HL=2-(2’-pyridyl)benzimidazole; MeL=1-methyl-2-(2’-pyridy)benzimidazole) and assayed their electrocatalytic properties for CO 2 reduction. A redox-active pyridine benzimidazole ancillary ligand in complex 1 a-Br displayed unique hydrogen atom transfer ability to facilitate electrocatalytic CO 2 conversion at a markedly lower reduction potential than that observed for 1 b-Br. Notably, a one-electron reduction of 1 a-Br yields a structurally characterized H-bonded binuclear Mn(I) adduct (2 a’) rather than the typically observed Mn(0)-Mn(0) dimer, suggesting a novel method for CO 2 activation. Furthermore, combining advanced electrochemical, spectroscopic, and single crystal X-ray diffraction techniques, we demonstrate the use of an H-atom responsive ligand may reveal an alternative, low-energy pathway for CO 2 activation by an earth-abundant metal complex catalyst.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2023

A simple-structured benzo[1,2-b:4,5-b’]dithiophene-based molecule as a third component enables organic solar cells with over 18.2% efficiency

In this study, research has shown that ternary strategy is an effective tool for improving the performance of organic solar cells (OSCs) and simple-structured small molecules with low-cost and wide bandgap which broadens the scope of the choice in third components recently attracted the attention of researchers. Herein, a small molecule with benzo[1,2-b:4,5-b’]dithiophene (BDT) core named BR-C12 which mixed well with PM6 has been designed and synthesized. Incorporating BR-C12 as third component into PM6:Y6, BR-C12 exhibits a complementary absorption with PM6 and Y6, promoted exciton dissociation and charge collection, reduced bimolecular recombination, resulting in more ordered molecular packing. The PM6:Y6:BR-C12 (1:1.2:0.1, weight ratio) OSC shows an improved power conversion efficiency (PCE) of 17.02% in comparison to host binary devises (16.42%). In addition, by employing BR-C12 as third component into PM6:L8-BO, the ternary device based on PM6:L8-BO:BR-C12 also achieves significant enhancement in device photovoltaic performance with a PCE of 18.26%. In addition, BR-C12-added ternary devices exhibit improved stability than binary ones. This work presents a method for constructing high-performance ternary OSCs and enriches the abundance of materials for the third components.

14 SOLAR ENERGY↗

DOE OSTI2021

Halide Ion Migration in Perovskite Nanocrystals and Nanostructures

The optical and electronic properties of metal halide perovskites provide insight into the operation of solar cells as well as their long-term operational stability. Halide mobility in perovskite films is an important factor influencing solar cell performance. One can visualize halide ion migration through halide exchange between two nanocrystal suspensions or between physically paired films of two different metal halide perovskites. The ability to tune band gap by varying halide ratios (Cl:Br or Br:I) allows the synthesis of mixed halide perovskites with tailored absorption and emission across the entire visible spectrum. Interestingly, mixed halide (e.g., MAPb(Br 0.5 I 0.5 ) 3 ) films undergo phase segregation to form Br-rich and I-rich sites under steady state illumination. Upon halting illumination, segregated phases mix to restore original mixed halide compositions. Introducing multiple cations (Cs, formamidinium) at the A site or alloying with Cl greatly suppresses halide mobilities. Long-term irradiation of MAPb(Br 0.5 I 0.5 ) 3 films also cause expulsion of iodide leaving behind Br-rich phases. Hole trapping at I-rich sites in MAPb(Br 0.5 I 0.5 ) 3 is considered to be an important step in inducing halide mobility in photoirradiated films. Finally, this Account focuses on halide ion migration in nanocrystals and nanostructured films driven by entropy of mixing in dark and phase segregation under light irradiation.

14 SOLAR ENERGY↗

DOE OSTI2024

Ramifications of X-Site Ion Modification in a Zero-Dimensional Piezoelectric Tetrahalozincate

Using mixtures of A, B, or X site ions in piezoelectric hybrid organic inorganic materials has been shown to be an effective strategy to improve piezoelectric properties. Here, we investigated the effect of increasing Br content within histammonium tetrachlorozincate [HistNH3Zn(Cl x Br 1–x )4] by varying the relative amounts of Cl and Br from x = 0% to 100% on nonlinear optical and piezoelectric properties. We found that the crystal structures were unchanged with Br percentages up to 100%, but the melting point of the materials changed substantially with increasing Br content. On the other hand, the nonlinear optical properties were only moderately affected with increasing Br content. The piezoelectric response of each material was measured and compared with DFT calculated values, both of which agreed that the overall the materials had relatively similar d 33 coefficients. The x = 75% Br compound had the largest magnitude d 33 value at maximum strain at both 29 °C (−97.56 pm/V) and 40 °C (−92.00 pm/V). The observed negative piezoelectric response is a rare trait that was ascribed to the large number of intermolecular interactions between lattice elements, as described by others.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

UV-Induced Reaction Pathways in Bromoform Probed with Ultrafast Electron Diffraction

For many chemical reactions, it remains notoriously difficult to predict and experimentally determine the rates and branching ratios between different reaction channels. This is particularly the case for reactions involving short-lived intermediates, whose observation requires ultrafast methods. The UV photochemistry of bromoform (CHBr 3 ) is among the most intensely studied photoreactions. Yet, a detailed understanding of the chemical pathways leading to the production of atomic Br and molecular Br 2 fragments has proven challenging. In particular, the role of isomerization and/or roaming and their competition with direct C–Br bond scission has been a matter of continued debate. Here, in this work, gas-phase ultrafast megaelectronvolt electron diffraction (MeV-UED) is used to directly study structural dynamics in bromoform after single 267 nm photon excitation with femtosecond temporal resolution. The results show unambiguously that isomerization contributes significantly to the early stages of the UV photochemistry of bromoform. In addition to direct C–Br bond breaking within <200 fs, formation of iso-CHBr 3 (Br-CH-Br-Br) is observed on the same time scale and with an isomer lifetime of >1.1 ps. The branching ratio between direct dissociation and isomerization is determined to be 0.4 ± 0.2:0.6 ± 0.2, i.e., approximately 60% of molecules undergo isomerization within the first few hundred femtoseconds after UV excitation. The structure and time of formation of iso-CHBr 3 compare favorably with the results of an ab initio molecular dynamics simulation. The lifetime and interatomic distances of the isomer are consistent with the involvement of a roaming reaction mechanism.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Two- and three-body fragmentation of multiply charged tribromomethane by ultrafast laser pulses

We investigate the two- and three-body fragmentation of tribromomethane (bromoform, CHBr 3 ) resulting from multiple ionization by 28-femtosecond near-infrared laser pulses with a peak intensity of 6 × 10 14 W cm -2 . The analysis focuses on channels consisting exclusively of ionic fragments, which are measured by coincidence momentum imaging. The dominant two-body fragmentation channel is found to be Br + + CHBr 2 +. Weaker HBr + + CBr 2 +, CHBr + + Br 2 +, CHBr 2+ + Br 2 +, and Br + + CHBr 2 2+ channels, some of which require bond rearrangement prior to or during the fragmentation, are also observed. The dominant three-body fragmentation channel is found to be Br + + Br + + CHBr + . This channel includes both concerted and sequential fragmentation pathways, which we identify using the native frames analysis method. We compare the measured kinetic energy release and momentum correlations with the results of classical Coulomb explosion simulations and discuss the possible isomerization of CHBr 3 to BrCHBr–Br (iso-CHBr 3 ) prior to the fragmentation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1983

Handgrip and general muscular strength and endurance during prolonged bedrest with isometric and isotonic leg exercise training

Measurements of maximal grip strength and endurance at 40 percent max strength were obtained for 7 men 19-21 years of age, 1-2 days before and on the first recovery day during three 2-week bedrest (BR) periods, each separated by a 3-week ambulatory recovery period. The subjects performed isometric exercise (IME) for 1 hr/day, isotonic exercise (ITE) for 1 hr/day, and no exercise (NOE) in the three BR periods. It was found that the mean maximal grip strength was unchanged after all three BR periods. Mean grip endurance was found to be unchanged after IME and ITE training, but was significantly reduced after NOE. These results indicate that IME and ITE training during BR do not increase or decrease maximal grip strength, alghough they prevent loss of grip endurance, while the maximal strength of all other major muscle groups decreases in proportion to the length of BR to 70 days. The maximal strength reduction of the large muscle groups was found to be about twice that of the small muscle groups during BR. In addition, it is shown that changes in maximal strength after spaceflight, BR, or water immersion deconditioning cannot be predicted from changes in submaximal or maximal oxygen uptake values.

Greenleaf, J. E.↗

NASA NTRS1992

Comparison of saline and fludrocortisone as fluid-loading countermeasures following exposure to simulated microgravity

Saline loading (SL) within hours of reentry is currently used as a countermeasure against postflight orthostatic hypotension in astronauts. However, its effects on blood volume expansion is not quantified and its effectiveness has proved marginal at best. The purposes of the present study were: (1) to quantify the effects of SL on plasma volume and orthostatic tolerance following exposure to simulated microgravity and (2) to compare these effects with the use of a pharacological fluid expander, fludrcortisone (F). Method: Eleven men (30-45 yr.) underwent a 15-minute stand test before and immediately after 7 days of head-down bedrest (BR). Five subjects ingested SL (8 g salt tablets with 1 liter of water) 2 hours before standing at the end of BR while the other 6 subjects received 0.2 mg oral doses of F at 0800 and 2200 hours the day before and 0800 hours the day the subjects got out of bed (i.e., 2 hours before standing). Plasma volume (PV) was measured before BR on day 7 of BR and after the final SL and F treatments just before the post-BR stand test. Blood pressure and heart rate were measured continuously during the stand tests. Results: BR decreased PV from 40.7 plus or minus 1.9 mml/kg to 35.9 plus or minus 1.1 ml/kg (minus 11.8 percent P less than 0.05). Following SL, PV remained at 36.4 plus or minus 1.5 ml/kg while F returned PV to 39.1 plus or minus 1.8 ml/kg. The post BR stand test was completed without syncopal symptoms by 5 of 6 F subjects but only 2 of 5 SL subjects. Conclusions: SL may be ineffective in restoring PV to preflight levels and may provide inadequate protection against postflight orthostatic hypotension. In contrast, F may provide a promising countermeasure since it restored PV and reduced the incidence of syncope following exposure to simulated microgravity in the present study.

Vernikos, J.↗

NASA NTRS1994

Knee-Joint Proprioception During 30-Day 6 deg Head-Down Bed Rest with Isotonic and Isokinetic Exercise Training

To determine if daily isotonic exercise or isokinetic exercise training coupled with daily log proprioceptive training, would influence log proprioceptive tracking responses during Bed Rest (BR), 19 men (36 +/- SD 4 years, 178 +/- 7 cm, 76.8 +/- 7.8 kg) were allocated into a NO-Exercise (NOE) training control group (n = 5), and IsoTanic Exercise (ITE, n = 7) and IsoKinetic Exercise (IKE, n = 7) training groups. Exercise training was conducted during BR for two 30-min period / d, 5 d /week. Only the IKE group performed proprioceptive training using a now isokinetic procedure with each lower extremity for 2.5 min before and after the daily exercise training sessions; proprioceptive testing occurred weekly for all groups. There were no significant differences in proprioceptive tracking scores, expressed as a percentage of the perfect score of 100, in the pro-BR ambulatory control period between the three groups. Knee extension and flexion tracking responses were unchanged with NOE during BR, but were significantly greater (*p less than 0.05) at the end of BR in both exercise groups when compared with NOE responses (extension: NOE 80.7 +/- 0.7%, ITE 82.9 +/- 0.6%, IKE 86.5* +/- 0.7%; flexion: NOE 77.6 +/- 1.50, ITE 80.0 +/- 0.8% (NS), IKE 83.6* +/- 0.8%). Although proprioceptive tracking was unchanged during BR with NOE, both lsotonic exercise training (without additional propriaceptive training) and especially isokinetic exercise training when combined with daily proprioceptive training, significantly improved knee proprioceptive tracking responses after 30 d of BR.

Bernauer, E. M.↗

NASA NTRS2000

A Simulation of Bromoform's Contribution to Stratospheric Bromine

Many chlorinated and brominated compounds that are inert in the troposphere are destroyed in the stratosphere and act as an in-situ source of stratospheric reactive chlorine and bromine. Other halogenated compounds that are reactive in the troposphere might contribute to the stratosphere's halogen budget in two ways. First, like their unreactive companions, rapid convective transport might carry them to the upper troposphere and make them available for subsequent advection by the mean circulation into the stratosphere before they are oxidized or photolyzed. Second, it is more likely that they are destroyed in the troposphere, and the chlorine and bromine that is released might then be transported to the stratosphere. We evaluate the relative influence of these processes on stratospheric bromine in a three-dimensional chemistry and transport model which simulates the distribution of bromoform (CHBr3). CHBr3 is parameterized as a short-lived, ocean-surface source gas whose destruction by photolysis and reaction with hydroxyl (OH) in the troposphere and stratosphere yields inorganic bromine (Br(sub y)). Many of the observed features of CHBr3 are simulated well, and comparisons with observations are used to show that the model represents aspects of transport in the upper troposphere and lower stratosphere that are critical to the evaluation. In particular, the model maintains the observed troposphere-stratosphere distinctness in transport pathways and reproduces the observed seasonal dependence of the mixture of air in the middle- and high-latitude lowermost stratosphere. We estimate that adding CHBr3 to models which already include the long-lived organic brominated compounds (halons and methyl bromide) will increase the simulated stratospheric mass of Br(sub y) by about 15 percent. In-situ stratospheric destruction of CHBr3 produces Br(sub y) in amounts which are comparable to that transported into the stratosphere after photolysis and oxidation of CHBr3 in the troposphere. In our simulations the mass of Br(sub y) produced from the destruction of CHBr3 does not exceed the mass of Br(sub y) produced from the destruction of the long-lived compounds at any level in the stratosphere. However, Br(sub y) from the loss of CHBr3 accounts for approximately one-third of the total Br(sub y) in the lowest kilometer of the stratosphere.

Nielsen, J. Eric↗

NASA NTRS2003

Recovery After Prolonged Bed-Rest Deconditioning

Recovery data were analyzed from normal healthy test subjects maintained in the horizontal or head-down body position in well-controlled bed rest (BR) studies in which adherence to the well-designed protocol was monitored. Because recovery data were almost always of secondary importance to the data collected during the BR period, there was little consistency in the recovery experimental designs regarding control factors (e.g., diet or exercise), duration, or timing of data collection. Thus, only about half of the BR studies that provided appropriate data were analyzed here. These recovery data were sorted into two groups: those from BR protocols of less than 37 days, and those from protocols greater than 36 days. There was great disparity in the unchanged responses at the end of BR in these two groups. Likewise with the variables that required more than 40 days for recovery; for example, some immune variables required more than 180 days. Knowledge of the recovery process after BR in healthy people should assist rehabilitation workers in differentiating "healthy" BR recovery responses from those of the infirmity of sick or injured patients; this should result in more appropriate and efficient health care.

Greenleaf, John E.↗

NASA NTRS1994

Knee-joint proprioception during 30-day 6 degrees head-down bed rest with isotonic and isokinetic exercise training

To determine if daily isotonic exercise or isokinetic exercise training coupled with daily leg proprioceptive training, would influence leg proprioceptive tracking responses during bed rest (BR), 19 men (36 +/- SD 4 years, 178 +/- 7 cm, 76.8 +/- 7.8 kg) were allocated into a no-exercise (NOE) training control group (n = 5), and isotonic exercise (ITE, n = 7) and isokinetic exercise (IKE, n = 7) training groups. Exercise training was conducted during BR for two 30-min periods.d-1, 5 d.week-1. Only the IKE group performed proprioceptive training using a new isokinetic procedure with each lower extremity for 2.5 min before and after the daily exercise training sessions; proprioceptive testing occurred weekly for all groups. There were no significant differences in proprioceptive tracking scores, expressed as a percentage of the perfect score of 100, in the pre-BR ambulatory control period between the three groups. Knee extension and flexion tracking responses were unchanged with NOE during BR, but were significantly greater (*p < 0.05) at the end of BR in both exercise groups when compared with NOE responses (extension: NOE 80.7 +/- 0.7%, ITE 82.9* +/- 0.6%, IKE 86.5* +/- 0.7%; flexion: NOE 77.6 +/- 1.5%, ITE 80.0 +/- 0.8% (NS), IKE 83.6* +/- 0.8%). Although proprioceptive tracking was unchanged during BR with NOE, both isotonic exercise training (without additional proprioceptive training) and especially isokinetic exercise training when combined with daily proprioceptive training, significantly improved knee proprioceptive tracking responses after 30 d of BR.

Controlled Clinical Trial↗