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Materials Data on La3B(CBr)2 by Materials Project

La3B(CBr)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are three inequivalent La+2.33+ sites. In the first La+2.33+ site, La+2.33+ is bonded to three C4- and three Br1- atoms to form a mixture of distorted edge and corner-sharing LaC3Br3 octahedra. The corner-sharing octahedra tilt angles range from 40–106°. There are one shorter (2.48 Å) and two longer (2.66 Å) La–C bond lengths. There are two shorter (3.12 Å) and one longer (3.39 Å) La–Br bond lengths. In the second La+2.33+ site, La+2.33+ is bonded to three C4- and three equivalent Br1- atoms to form a mixture of distorted edge and corner-sharing LaC3Br3 octahedra. The corner-sharing octahedra tilt angles range from 40–106°. There are one shorter (2.50 Å) and two longer (2.67 Å) La–C bond lengths. There are two shorter (3.19 Å) and one longer (3.43 Å) La–Br bond lengths. In the third La+2.33+ site, La+2.33+ is bonded in a 8-coordinate geometry to four C4- and four Br1- atoms. There are two shorter (2.81 Å) and two longer (2.85 Å) La–C bond lengths. There are a spread of La–Br bond distances ranging from 3.22–3.42 Å. B3+ is bonded in a bent 150 degrees geometry to two C4- atoms. There is one shorter (1.49 Å) and one longer (1.50 Å) B–C bond length. There are two inequivalent C4- sites. In the first C4- site, C4- is bonded in a 1-coordinate geometry to five La+2.33+ and one B3+ atom. In the second C4- site, C4- is bonded in a 1-coordinate geometry to five La+2.33+ and one B3+ atom. There are two inequivalent Br1- sites. In the first Br1- site, Br1- is bonded in a 5-coordinate geometry to five La+2.33+ atoms. In the second Br1- site, Br1- is bonded in a 5-coordinate geometry to five La+2.33+ atoms.

36 MATERIALS SCIENCE↗

Materials Data on Ce6B2(CBr)3 by Materials Project

Ce6B2(CBr)3 crystallizes in the monoclinic P2/m space group. The structure is three-dimensional. there are three inequivalent Ce+3.17+ sites. In the first Ce+3.17+ site, Ce+3.17+ is bonded to three C+3.33- and three Br1- atoms to form a mixture of distorted corner and edge-sharing CeC3Br3 octahedra. The corner-sharing octahedral tilt angles are 0°. There are one shorter (2.35 Å) and two longer (2.54 Å) Ce–C bond lengths. There are two shorter (3.16 Å) and one longer (3.17 Å) Ce–Br bond lengths. In the second Ce+3.17+ site, Ce+3.17+ is bonded in a 9-coordinate geometry to four equivalent B3-, two equivalent C+3.33-, and three Br1- atoms. There are two shorter (2.69 Å) and two longer (2.82 Å) Ce–B bond lengths. Both Ce–C bond lengths are 2.55 Å. There are two shorter (3.24 Å) and one longer (3.30 Å) Ce–Br bond lengths. In the third Ce+3.17+ site, Ce+3.17+ is bonded in a 7-coordinate geometry to two equivalent B3-, three C+3.33-, and two equivalent Br1- atoms. Both Ce–B bond lengths are 2.86 Å. There are two shorter (2.57 Å) and one longer (2.59 Å) Ce–C bond lengths. Both Ce–Br bond lengths are 3.16 Å. B3- is bonded in a distorted single-bond geometry to six Ce+3.17+ and one C+3.33- atom. The B–C bond length is 1.53 Å. There are two inequivalent C+3.33- sites. In the first C+3.33- site, C+3.33- is bonded to five Ce+3.17+ and one B3- atom to form distorted edge-sharing CCe5B octahedra. In the second C+3.33- site, C+3.33- is bonded to six Ce+3.17+ atoms to form edge-sharing CCe6 octahedra. There are two inequivalent Br1- sites. In the first Br1- site, Br1- is bonded in a 5-coordinate geometry to five Ce+3.17+ atoms. In the second Br1- site, Br1- is bonded in a 6-coordinate geometry to six Ce+3.17+ atoms.

36 MATERIALS SCIENCE↗

Materials Data on SiH8(CBr)4 by Materials Project

SiH8(CBr)4 is Silicon tetrafluoride-derived structured and crystallizes in the tetragonal P-42_1c space group. The structure is zero-dimensional and consists of two tetrakis(bromomethyl)silane molecules. Si4+ is bonded in a tetrahedral geometry to four equivalent C2- atoms. All Si–C bond lengths are 1.89 Å. C2- is bonded to one Si4+, two H1+, and one Br1- atom to form distorted corner-sharing CSiH2Br tetrahedra. There is one shorter (1.09 Å) and one longer (1.10 Å) C–H bond length. The C–Br bond length is 1.97 Å. There are two inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C2- atom. Br1- is bonded in a single-bond geometry to one C2- atom.

36 MATERIALS SCIENCE↗

Attosecond Probing of Coherent Vibrational Dynamics in CBr 4

A coherent vibrational wavepacket is launched and manipulated in the symmetric stretch (a1) mode of CBr 4 , by impulsive stimulated Raman scattering (ISRS) from nonresonant 400 nm laser pump pulses with various peak intensities on the order of tens of 10 12 W/cm 2 . Extreme ultraviolet (XUV) attosecond transient absorption spectroscopy (ATAS) records the wavepacket dynamics as temporal oscillations in XUV absorption energy at the bromine M 4,5 3d 3/2,5/2 edges around 70 eV. The results are augmented by nuclear timedependent Schrödinger equation simulations. Slopes of the (Br 3d 3/2,5/2 ) –1 10a 1 * core-excited state potential energy surface (PES) along the a 1 mode are calculated to be –9.4 eV/Å from restricted open-shell Kohn–Sham calculations. Using analytical relations derived for the small-displacement limit and the calculated slopes of the core-excited state PES, a deeper insight into the vibrational dynamics is obtained by retrieving the experimental excursion amplitude of the vibrational wavepacket and the amount of population transferred to the vibrational first-excited state as a function of pump-pulse peak intensity. Experimentally, the results show that XUV ATAS is capable of resolving oscillations in the XUV absorption energy on the order of a few to tens of meV with tens of femtosecond time precision. This corresponds to change in C–Br bond length on the order of 10 –4 to 10 –3 Å. The results and the analytic relationships offer a clear physical picture, on multiple levels of understanding, of how the pump-pulse peak intensity controls the vibrational dynamics launched by nonresonant ISRS in the small-displacement limit.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Materials Data on P2H9(CBr)3 by Materials Project

P(CH3)3PBr3 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of four phosphorus tribromide molecules and four trimethylphosphine molecules.

36 MATERIALS SCIENCE↗

Materials Data on FePH12(CBr)4 by Materials Project

FeBr4(CH3)4P is Silicon tetrafluoride-derived structured and crystallizes in the cubic F-43m space group. The structure is zero-dimensional and consists of four phosphonium, tetramethyl- molecules and four tetrabromoiron molecules.

36 MATERIALS SCIENCE↗

National Campaign (NC)-1 Strategic Conflict Management Simulation (X4) Community Based Rules

Projected demand for transportation services in the urban environment has led to the development of several Concepts of Operation for Urban Air Mobility, or UAM. UAM is a concept for the transportation of people and goods in the metropolitan environment using small, efficient aircraft over short distances as part of an expanding multimodal transportation network. UAM will leverage emerging technologies including electric Vertical Takeoff and Landing (eVTOL) aircraft, increasing levels of automation and a new operational paradigm in dense airspace where a set of agreed-upon rules govern the procedures and interactions defining a cooperative environment in which operators are entrusted with a range of functions typically conducted by Air Traffic Control (ATC). These rules, proposed in the FAA NextGen Office’s UAM Concept of Operations [1], were originally termed Community Based Rules or Community Business Rules (CBRs), and will in the future termed Cooperative Operating Practices (COPs); this document uses the original term, CBR. CBRs are a set of rules, developed by the UAM community and (where necessary) approved by the FAA that govern the interactions between UAM entities and limit the need for ATC services including, but not limited to, separation control by ATC, addressing a fundamental challenge to scaling UAM operations. UAM community development of CBRs is anticipated to accelerate the adoption of new practices while retaining the regulatory authority of the FAA within required domains (e.g., NAS safety, security and equal access). However, there currently exists no agreed industry forum or defined procedures for CBR development. Investigation of best practices for the development of UAM CBRs was identified by NASA and the FAA NextGen Office as a research need. In collaboration with seven industry partners, NASA participated in a series of simulations that investigated elements of the envisioned UAM operations, with a primary focus on Strategic Conflict Management (SCM). The development and conduct of cooperative UAM simulations with seven industry partners provided a unique opportunity to investigate CBR development practices. Development of CBRs for the UAM SCM simulations was conducted in parallel with simulation capability development and was closely related to requirements definition for the simulations. As such, the CBR development effort presented herein had two objectives: explore CBR development practices in collaboration with the industry partners and develop an initial set of UAM CBRs to support simulation requirements definition and development. Consensus was achieved among NASA and the industry partners on 24 CBRs that were developed to support the cooperative simulation operations across five topic areas: General (related to test requirements), Operational Intent, Conformance Monitoring, Demand Capacity Balancing, and Airspace Constraint Management. Additional topic areas and CBRs were discussed but were deemed outside the scope of the simulation; these are included in the appendices. A collaborative, iterative process was employed for developing the CBRs engaging both NASA and Industry; because CBR development is envisioned to be community-driven, opportunities were sought that provided industry partners leadership roles in developing CBRs. The following key observations and recommendations may aid the UAM industry in future CBR development efforts: - The lack of a defined process proved challenging initially. Stakeholder engagement in the early stages of CBR development was intermittent and may have been due to the lack of a clear definition of roles and responsibilities of those involved in the effort. - Industry leadership of CBR topic areas proved successful. Discussions in these topic areas were engaging, with alternate viewpoints freely discussed and detailed CBRs resulting. This points to the importance of identifying the best-suited leadership in technical areas for CBR development. - Discussions within a CBR topic area were typically dominated by only a few participants. Whereas all industry partners contributed to CBR development, within each topic area, technical leadership was evident even when not formally established. This observation may indicate that smaller, focused groups may be more effective in initial CBR development than an open forum or large standards development effort (although both maybe required prior to FAA review and approval for some CBRs). - Identifying suitable forums for initial UAM CBR development and identifying the most effective industry participants and leadership will be crucial for successful CBR development. Although the operational need for UAM CBRs may not be immediate, establishing the forums and leadership to define the processes for CBR development is a prudent early step to UAM realization.

Community Based Rules↗

Measurements of the cosmic background radiation

Measurements of the attributes of the 2.7-K microwave background radiation (CBR) are reviewed, with emphasis on the analytic phase of CBR studies. Methods for the direct measurement of the CBR spectrum are discussed; attention is given to receivers, antennas, absolute receiver calibration, atmospheric emission and absorption, the galactic background contribution, the analysis of LF measurements, and recent HF observations of the CBR spectrum. Measurements of the large-angular-scale intensity distribution of the CBR (the most convincing evidence that the radiation is of cosmological origin) are examined, along with limits on the linear polarization of the CBR. A description is given of the NASA-sponsored Cosmic Background Explorer (COBE) satellite mission. The results of the COBE mission will be a set of sky maps showing, in the wave number range from 1 to 10,000 kaysers, the galactic background radiation due to synchrotron emission from galactic cosmic rays, to diffuse thermal emission from H II regions, and to diffuse thermal emission from interstellar and interplanetary dust, as well as a residue consisting of the CBR and whatever other cosmological background might exist.

Weiss, R.↗

Role of central command in carotid baroreflex resetting in humans during static exercise

The purpose of the experiments was to examine the role of central command in the exercise-induced resetting of the carotid baroreflex. Eight subjects performed 30 % maximal voluntary contraction (MVC) static knee extension and flexion with manipulation of central command (CC) by patellar tendon vibration (PTV). The same subjects also performed static knee extension and flexion exercise without PTV at a force development that elicited the same ratings of perceived exertion (RPE) as those observed during exercise with PTV in order to assess involvement of the exercise pressor reflex. Carotid baroreflex (CBR) function curves were modelled from the heart rate (HR) and mean arterial pressure (MAP) responses to rapid changes in neck pressure and suction during steady state static exercise. Knee extension exercise with PTV (decreased CC activation) reset the CBR-HR and CBR-MAP to a lower operating pressure (P < 0.05) and knee flexion exercise with PTV (increased CC activation) reset the CBR-HR and CBR-MAP to a higher operating pressure (P < 0.05). Comparison between knee extension and flexion exercise at the same RPE with and without PTV found no difference in the resetting of the CBR-HR function curves (P > 0.05) suggesting the response was determined primarily by CC activation. However, the CBR-MAP function curves were reset to operating pressures determined by both exercise pressor reflex (EPR) and central command activation. Thus the physiological response to exercise requires CC activation to reset the carotid-cardiac reflex but requires either CC or EPR to reset the carotid-vasomotor reflex.

Non-NASA Center↗

Antimicrobial Resources for Disinfection of Potable Water Systems for Future Spacecraft

As human exploration adventures beyond low earth orbit, life support systems will require more innovation and research to become self-sustaining and durable. One major concern about future space travel is the ability to store and decontaminate water for consumption and hygiene. This project explores materials and technologies for possible use in future water systems without requiring point-of-use (POU) filtering or chemical additives such as iodine or silver that require multiple doses to remain effective. This experimentation tested the efficacy of a variety of antimicrobial materials against biofilm formation in a high shear CDC Biofilm Reactor (CBR) and some materials in a low shear Drip Flow Reactor (DFR) which(also utilizes ultra violet light emitting diodes (UVLEDs) as an antimicrobial resource. Most materials were tested in the CBR using the ASTM E 2562-07 1method involving the Pseudomonas aeruginosa and coupon samples that vary in their antimicrobial coatings and surface layer topographies. In a controlled environmental chamber (CEC), the CBR underwent a batch phase, continuous flow phase (CFP), and a harvest before analysis. The DFR portion of this experimentation was performed in order to assess the antimicrobial capabilities of ultraviolet-A LEDs (UV-A) in potable water systems. The ASTM E 2647-08 was modified in order to incorporate UV-A LEDs and to operate as a closed, re-circulating system. The modified DFR apparatus that was utilized contains 4 separate channels each of which contain 2 UV-A LEDs (1 chamber is masked off to serve as a control) and each channel is equipped with its own reservoir and peristaltic pump head. The 10 DFR runs discussed in this report include 4 initial experimental runs that contained blank microscope slides to test the UVA LEDs alone, 2 that incorporated solid silver coupons, 2 that utilized titanium dioxide (Ti02) coupons as a photocatalyst, and 2 runs that utilized silver coated acrylic slides. Both the CBR and DFR experiments were analyzed for microbial content via heterotrophic plate counts (HPC) and acridine orange direct counts (AODC). Ofthe materials used in the CBR, only two materials performed as anti~icrobials under high shear conditions (a reduction of 5 or more logs) showing a>7 log reduction in viable microbes.

Morford, Megan A.↗

Chromatin binding by HORMAD proteins regulates meiotic recombination initiation

The meiotic chromosome axis coordinates chromosome organization and interhomolog recombination in meiotic prophase and is essential for fertility. In S. cerevisiae , the HORMAD protein Hop1 mediates the enrichment of axis proteins at nucleosome-rich islands through a central chromatin-binding region (CBR). Here, we use cryoelectron microscopy to show that the Hop1 CBR directly recognizes bent nucleosomal DNA through a composite interface in its PHD and winged helix–turn–helix domains. Targeted disruption of the Hop1 CBR-nucleosome interface causes a localized reduction of axis protein binding and meiotic DNA double-strand breaks (DSBs) in axis islands and leads to defects in chromosome synapsis. Synthetic effects with mutants of the Hop1 regulator Pch2 suggest that nucleosome binding delays a conformational switch in Hop1 from a DSB-promoting, Pch2-inaccessible state to a DSB-inactive, Pch2-accessible state to regulate the extent of meiotic DSB formation. Phylogenetic analyses of meiotic HORMADs reveal an ancient origin of the CBR, suggesting that the mechanisms we uncover are broadly conserved.

59 BASIC BIOLOGICAL SCIENCES↗

Neural blockade during exercise augments central command's contribution to carotid baroreflex resetting

This investigation was designed to determine central command's role on carotid baroreflex (CBR) resetting during exercise. Nine volunteer subjects performed static and rhythmic handgrip exercise at 30 and 40% maximal voluntary contraction (MVC), respectively, before and after partial axillary neural blockade. Stimulus-response curves were developed using the neck pressure-neck suction technique and a rapid pulse train protocol (+40 to -80 Torr). Regional anesthesia resulted in a significant reduction in MVC. Heart rate (HR) and ratings of perceived exertion (RPE) were used as indexes of central command and were elevated during exercise at control force intensity after induced muscle weakness. The CBR function curves were reset vertically with a minimal lateral shift during control exercise and exhibited a further parallel resetting during exercise with neural blockade. The operating point was progressively reset to coincide with the centering point of the CBR curve. These data suggest that central command was a primary mechanism in the resetting of the CBR during exercise. However, it appeared that central command modulated the carotid-cardiac reflex proportionately more than the carotid-vasomotor reflex.

NASA Discipline Cardiopulmonary↗

Carotid baroreflex regulation of sympathetic nerve activity during dynamic exercise in humans

We sought to determine whether carotid baroreflex (CBR) control of muscle sympathetic nerve activity (MSNA) was altered during dynamic exercise. In five men and three women, 23.8 +/- 0.7 (SE) yr of age, CBR function was evaluated at rest and during 20 min of arm cycling at 50% peak O(2) uptake using 5-s periods of neck pressure and neck suction. From rest to steady-state arm cycling, mean arterial pressure (MAP) was significantly increased from 90.0 +/- 2.7 to 118.7 +/- 3.6 mmHg and MSNA burst frequency (microneurography at the peroneal nerve) was elevated by 51 +/- 14% (P < 0.01). However, despite the marked increases in MAP and MSNA during exercise, CBR-Delta%MSNA responses elicited by the application of various levels of neck pressure and neck suction ranging from +45 to -80 Torr were not significantly different from those at rest. Furthermore, estimated baroreflex sensitivity for the control of MSNA at rest was the same as during exercise (P = 0.74) across the range of neck chamber pressures. Thus CBR control of sympathetic nerve activity appears to be preserved during moderate-intensity dynamic exercise.

Non-NASA Center↗

Differential baroreflex control of heart rate in sedentary and aerobically fit individuals

PURPOSE: We compared arterial, aortic, and carotid-cardiac baroreflex sensitivity in eight average fit (maximal oxygen uptake, VO2max = 42.2+/-1.9 mL x kg(-1) x min(-1)) and eight high fit (VO2max = 61.9+/-2.2 mL x kg(-1) x min(-1)) healthy young adults. METHODS: Arterial and aortic (ABR) baroreflex functions were assessed utilizing hypo- and hyper-tensive challenges induced by graded bolus injections of sodium nitroprusside (SN) and phenylephrine (PE), respectively. Carotid baroreflex (CBR) sensitivity was determined using ramped 5-s pulses of both pressure and suction delivered to the carotid sinus via a neck chamber collar, independent of drug administration. RESULTS: During vasoactive drug injection, mean arterial pressure (MAP) was similarly altered in average fit (AF) and high fit (HF) groups. However, the heart rate (HR) response range of the arterial baroreflex was significantly attenuated (P < 0.05) in HF (31+/-4 beats x min(-1)) compared with AF individuals (46+/-4 beats x min(-1)). When sustained neck suction and pressure were applied to counteract altered carotid sinus pressure during SN and PE administration, isolating the ABR response, the response range remained diminished (P < 0.05) in the HF population (24+/-3 beats x min(-1)) compared with the AF group (41+/-4 beats x min(-1)). During CBR perturbation, the HF (14+/-1 beats-min(-1)) and AF (16+/-1 beats-min(-1)) response ranges were similar. The arterial baroreflex response range was significantly less than the simple sum of the CBR and ABR (HF, 38+/-3 beats x min(-1) and AF, 57+/-4 beats x min(-1)) in both fitness groups. CONCLUSIONS: These data confirm that reductions in arterial-cardiac reflex sensitivity are mediated by diminished ABR function. More importantly, these data suggest that the integrative relationship between the ABR and CBR contributing to arterial baroreflex control of HR is inhibitory in nature and not altered by exercise training.

NASA Discipline Cardiopulmonary↗

Advanced Fuel Cycle Cost Basis Report: Supporting Document 6 A Proposed Methodology for Transformation of Reactor Cost Data to the ‘What-It-Takes’ Table

Note: This document represents work undertaken to refine the CBR approach for arriving at recommended cost values for the reactor sub-modules. This information is provided to indicate the possible direction of evolution in future CBR updates and encourage comments from CBR users. Since this document was developed concurrent with many of the following R-modules, the methodology was applied only in the analysis of the fast reactor (Module R2) data. In future revisions an attempt will be made to use this methodology uniformly.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

Investigation of a bearingless helicopter rotor concept having a composite primary structure

Experimental and analytical investigations were conducted to evaluate a bearingless helicopter rotor concept (CBR) made possible through the use of the specialized nonisotropic properties of composite materials. The investigation was focused on four principal areas which were expected to answer important questions regarding the feasibility of this concept. First, an examination of material properties was made to establish moduli, ultimate strength, and fatigue characteristics of unidirectional graphite/epoxy, the composite material selected for this application. The results confirmed the high bending modulus and strengths and low shear modulus expected of this material, and demonstrated fatigue properties in torsion which make this material ideally suited for the CBR application. Second, a dynamically scaled model was fabricated and tested in the low speed wind tunnel to explore the aeroelastic characteristics of the CBR and to explore various concepts relative to the method of blade pitch control. Two basic control configurations were tested, one in which pitch flap coupling could occur and another which eliminated all coupling. It was found that both systems could be operated successfully at simulated speeds of 180 knots; however, the configuration with coupling present revealed a potential for undesirable aeroelastic response. The uncoupled configuration behaved generally as a conventional hingeless rotor and was stable for all conditions tested.

Bielawa, R. L.↗

A search for the Sunyaev-Zel'dovich effect at millimeter wavelengths

It is believed that X-ray emission from clusters of galaxies represents thermal bremsstrahlung from a hot plasma. According to Sunyaev and Zel'dovich (1972), the plasma column density and temperature derived from this model imply a measurable distortion of the cosmic background radiation (CBR) in the cluster direction. This distortion results from the Compton scattering of the CBR photons by the electrons in the plasma, resulting in an average increase of each photon. This process, known as the Sunyaev-Zel'dovich effect, is photon conserving and 'shifts' the CBR spectrum to higher frequencies. The result is a decrease of flux at frequencies below 7.5 per cm (the Rayleigh-Jeans region), and an increase above. The investigation is concerned with measurements of the Sunyaev-Zel'dovich effect at frequencies in the range from 3 to 10 per cm. Attention is given to the employed observing and analysis technique, and an initial null result for the cluster Abell 1795.

Meyer, S. S.↗

Measurements of the anisotropy of the cosmic background radiation and diffuse galactic emission at millimeter and submillimeter wavelengths

The results of a balloon-borne observing program to measure the large angular scale brightness distribution of the 2.7 K cosmic background radiation (CBR) at millimeter and submillimeter wavelengths are reported. A new determination of the dipole anisotropy of the CBR is found with 3.40 + or - 0.42 mK toward alpha = 12.1 + or - 0.24 hr, delta = - 23 + or - 5 deg in a 1.2 to 8/cm band and 4.7 + or - 1.4 mK toward alpha = 9.9 + 1.7 or - 1.1 hr, delta = - 38 + or - 21 deg between 5 and 18/cm, where the amplitudes are listed as thermodynamic temperatures. New estimates of the absolute temperature in these two bands of 2.86 + or - 0.26 K and 3.01 + or - 0.31 are obtained under the assumption that the CBR has a Planck spectrum. The diffuse Galactic emission is fitted by a secant distribution in Galactic latitude, and the resulting Galactic pole antenna temperatures are given. Maps of sky brightness, measurements of zodiacal emission, and measurements of fluctuations of the atmospheric emission which dominates the noise budget are also presented.

Halpern, Mark↗