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NASA NTRS1979

EUV continua of solar flares 1420-1960 A

Measurements of absolute continuum intensities in the wavelength range 1420-1960 A are presented for the SN subflare of 1973 August 9 and the 2B flare of 1973 September 7, observed from the NRL spectrograph aboard Skylab. Continuum measurements are also given for two active-region plages, which are used for background nonflaring levels. Major enhancement of the flare continuum intensity above the plage backgrounds occurs in the Si I 3P and 1D continua. The observed brightness-temperature minimum of the plages is approximately 310 K above the quiet-sun minimum, and occurs at longer wavelength. The earliest flare brightness-temperature minima are approximately 200 K above the plage minimum, and also at longer wavelength. The observed decay time of the flare brightness temperature, which is comparable to the Solrad 9 X-ray decay time, is much longer than the Ulmschneider radiative relaxation time for the 1973 September 7 flare and marginally longer for the 1973 August 9 flare, suggesting continuous excess heating of the plage temperature minimum region throughout the period of our flare observations.

Cook, J. W.↗
NASA NTRS1998

Design, Evaluation and GCM-Performance of a New Parameterization for Microphysics of Clouds with Relaxed Arakawa-Schubert Scheme (McRas)

A prognostic cloud scheme named McRAS (Microphysics of clouds with Relaxed Arakawa-Schubert Scheme) was developed with the aim of improving cloud-microphysics, and cloud-radiation interactions in GCMs. McRAS distinguishes convective, stratiform, and boundary-layer clouds. The convective clouds merge into stratiform clouds on an hourly time-scale, while the boundary-layer clouds do so instantly. The cloud condensate transforms into precipitation following the auto-conversion relations of Sundqvist that contain a parametric adaptation for the Bergeron-Findeisen process of ice crystal growth and collection of cloud condensate by precipitation. All clouds convect, advect, and diffuse both horizontally and vertically with a fully active cloud-microphysics throughout its life-cycle, while the optical properties of clouds are derived from the statistical distribution of hydrometeors and idealized cloud geometry. An evaluation of McRAS in a single column model (SCM) with the GATE Phase III data has shown that McRAS can simulate the observed temperature, humidity, and precipitation without discernible systematic errors. An evaluation with the ARM-CART SCM data in a cloud model intercomparison exercise shows reasonable but not an outstanding accurate simulation. Such a discrepancy is common to almost all models and is related, in part, to the input data quality. McRAS was implemented in the GEOS II GCM. A 50 month integration that was initialized with the ECMWF analysis of observations for January 1, 1987 and forced with the observed sea-surface temperatures and sea-ice distribution and vegetation properties (biomes, and soils), with prognostic soil moisture, snow-cover, and hydrology showed a very realistic simulation of cloud process, incloud water and ice, and cloud-radiative forcing (CRF). The simulated ITCZ showed a realistic time-mean structure and seasonal cycle, while the simulated CRF showed sensitivity to vertical distribution of cloud water which can be easily altered by the choice of time constant and incloud critical cloud water amount regulators for auto-conversion. The CRF and its feedbacks also have a profound effect on the ITCZ. Even though somewhat weaker than observed, the McRAS-GCM simulation produces robust 30-60 day oscillations in the 200 hPa velocity potential. Two ensembles of 4-summer (July, August, September) simulations, one each for 1987 and 1988 show that the McRAS-GCM simulates realistic and statistically significant precipitation differences over India, Central America, and tropical Africa. Several seasonal simulations were performed with McRAS-GEOS II GCM for the summer (June-July- August) and winter (December-January-February) periods to determine how the simulated clouds and CRFs would be affected by: i) advection of clouds; ii) cloud top entrainment instability, iii) cloud water inhomogeneity correction, and (iv) cloud production and dissipation in different cloud-processes. The results show that each of these processes contributes to the simulated cloud-fraction and CRF.

Sud, Y. C.↗
NASA NTRS2011

Analysis of Separation Corridors for Visiting Vehicles from the International Space Station

The International Space Station (ISS) is a very dynamic vehicle with many operational constraints that affect its performance, operations, and vehicle lifetime. Most constraints are designed to alleviate various safety concerns that are a result of dynamic activities between the ISS and various Visiting Vehicles (VVs). One such constraint that has been in place for Russian Vehicle (RV) operations is the limitation placed on Solar Array (SA) positioning in order to prevent collisions during separation and subsequent relative motion of VVs. An unintended consequence of the SA constraint has been the impacts to the operational flexibility of the ISS resulting from the reduced power generation capability as well as from a reduction in the operational lifetime of various SA components. The purpose of this paper is to discuss the technique and the analysis that were applied in order to relax the SA constraints for RV undockings, thereby improving both the ISS operational flexibility and extending its lifetime for many years to come. This analysis focused on the effects of the dynamic motion that occur both prior to and following RV separations. The analysis involved a parametric approach in the conservative application of various initial conditions and assumptions. These included the use of the worst case minimum and maximum vehicle configurations, worst case initial attitudes and attitude rates, and the worst case docking port separation dynamics. Separations were calculated for multiple ISS docking ports, at varied deviations from the nominal undocking attitudes and included the use of two separate attitude control schemes: continuous free-drift and a post separation attitude hold. The analysis required numerical propagation of both the separation motion and the vehicle attitudes using 3-degree-of-freedom (DOF) relative motion equations coupled with rigid body rotational dynamics to generate a large set of separation trajectories.

Zaczek, Mariusz P.↗
NASA NTRS2011

A Simple Postflight Measure of Postural Atania in Astronauts

Astronauts returning from space flight universally present with postural ataxia. Throughout the Space Shuttle Program, measurement of ataxia has concentrated on sway in the anterior-posterior (AP) plane. The current investigation, as a part of a larger functional study, concentrated on characterizing postural instability using dynamic stabilographic sway patterns in both the AP and medial-lateral (ML) planes. To accomplish this goal, six astronauts from short-duration (Shuttle) and three from long-duration (ISS) flights were required to recover from a simulated fall. Subjects with eyes open, wearing running shoes lay prone on the floor for 2 minutes and then quickly stood up, maintained a quiet stance for 3 minutes, arms relaxed along the side of the body, and feet comfortably placed on the force plate. Crewmembers were tested twice before flight, on landing day (Shuttle only), and 1, 6, and 30 days after flight. Anterior-posterior and ML center-of-pressure (COP) coordinates were calculated from the ground reaction forces collected at 500 Hz. The 3-minute quiet stance trial was broken into three 1-minute segments for stabilogram diffusion analysis. A mean sway speed (rate of change of COP displacement) was also calculated as an additional postural stability parameter. While there was considerable variation, most of crewmembers tested exhibited increased stochastic activity evidenced by larger short-term COP diffusion coefficients postflight in both the AP and ML planes, suggesting significant changes in postural control mechanisms, particularly control of lower limb muscle function. As expected, postural instability of ISS astronauts on the first day postflight was similar to that of Shuttle crewmembers on landing day. Recoveries of stochastic activity and mean sway speed to baseline levels were typically observed by the 30th day postflight for both long-duration and short-duration crewmembers. Dynamic postural stability characteristics obtained in this low-impact study complement the data measured with computerized dynamic posturography.

Reschke, M. F.↗
NASA NTRS1996

Hybrid Grid Techniques for Propulsion Applications

During the past decade, computational simulation of fluid flow for propulsion activities has progressed significantly, and many notable successes have been reported in the literature. However, the generation of a high quality mesh for such problems has often been reported as a pacing item. Hence, much effort has been expended to speed this portion of the simulation process. Several approaches have evolved for grid generation. Two of the most common are structured multi-block, and unstructured based procedures. Structured grids tend to be computationally efficient, and have high aspect ratio cells necessary for efficently resolving viscous layers. Structured multi-block grids may or may not exhibit grid line continuity across the block interface. This relaxation of the continuity constraint at the interface is intended to ease the grid generation process, which is still time consuming. Flow solvers supporting non-contiguous interfaces require specialized interpolation procedures which may not ensure conservation at the interface. Unstructured or generalized indexing data structures offer greater flexibility, but require explicit connectivity information and are not easy to generate for three dimensional configurations. In addition, unstructured mesh based schemes tend to be less efficient and it is difficult to resolve viscous layers. Recently hybrid or generalized element solution and grid generation techniques have been developed with the objective of combining the attractive features of both structured and unstructured techniques. In the present work, recently developed procedures for hybrid grid generation and flow simulation are critically evaluated, and compared to existing structured and unstructured procedures in terms of accuracy and computational requirements.

Koomullil, Roy P.↗
NASA NTRS1991

Surface activation of air oxidation of hydrazine on kaolinite. 2. Consideration of oxidizing/reducing entities in relationship to other compositional, structural, and energetic factors

The rates (previously reported) for the air oxidation of hydrazine on kaolinite and substituent oxides of kaolinite showed a complex dependence on the relative amounts of several structural oxidizing/reducing entities within the reaction-promoting solids. The rates indicated an important role of the clay but no dominant role of any one of the oxidizing/reducing entities. In this paper we review (a) the reaction-promoting activity of these centers as studied in other systems, (b) various spectroscopic results showing interaction between these entities in clays, and (c) reported spectroscopic studies of the complexation between hydrazine and aluminosilicate surfaces as a whole, in an effort to propose a mechanism for the reaction. Whereas some uncertainties remain, the present synthesis concludes that a mechanism operating through single electron/hole transfers and hydrogen atom transfers by discrete centers is adequate to explain the observed rate behaviors including the observed second order dependence of the oxidation rate on catalyst amount. The effects of these operations on the catalyst can result in no alteration of, or complete or partial electronic relaxation of its contingent of trapped separated charge pairs. The degree to which surface complexation as a whole, intercalation, or luminescent processes may also be associated with the reaction cannot be adequately assessed with the information in hand.

NASA Program Exobiology↗
NASA NTRS2010

Postflight Quiet Stance Stability of Astronauts Following Recovery From a Simulated Fall

INTRODUCTION: Astronauts returning from space flight universally present with postural ataxia. Throughout the Space Shuttle Program, measurement of ataxia has concentrated on sway in the anterior-posterior plane. Implementation of an interdisciplinary pre- and postflight study (Functional Task Test, FTT) designed to evaluate both astronaut postflight functional performance and related physiological changes has allowed the investigation of postural instability by characterizing dynamic stabilographic sway patterns. METHODS: Six astronauts from short-duration (Shuttle) and three from long-duration (ISS) flights were required to recover from a simulated fall. Subjects with eyes open, wearing running shoes lay prone on the floor for 2 minutes and then quickly stood up, maintained a quiet stance for 3 minutes, arms relaxed along the side of the body, and feet comfortably placed on the force plate. Crewmembers were tested twice before flight, on landing day (Shuttle only), and 1, 6, and 30 days after flight. Anterior-posterior (AP) and medial-lateral (ML) center-of-pressure (COP) coordinates were calculated from the ground reaction forces collected at 500 Hz. The 3-minute quiet stance trial was broken into three 1-minute segments for stabilogram diffusion analysis. A mean sway speed (rate of change of COP displacement) was also calculated as an additional postural stability parameter. RESULTS/CONCLUSION: While there was considerable variation, most of crewmembers tested exhibited increased stochastic activity evidenced by larger short-term COP diffusion coefficients postflight in both the AP and ML planes, suggesting significant changes in postural control mechanisms, particularly control of lower limb muscle function. As expected, postural instability of ISS astronauts on the first day postflight was similar to that of Shuttle crewmembers on landing day. Recoveries of stochastic activity and mean sway speed to baseline levels were typically observed by the 30th day postflight for both long-duration and short-duration crewmembers. Dynamic postural stability characteristics obtained in this low-impact study complement the data measured with computerized dynamic posturography.

Reschke, M. F.↗
NASA NTRS1993

Lower hybrid turbulence at cometary bow wave and acceleration of cometary protons

The wave measurements at the spacecraft encounters with Comet Halley have shown intense wave activity at the lower hybrid frequency. The excitation of the lower hybrid instability by the pickup cometary ions (protons and water group) in the bow wave region and the quasi-linear diffusion of the ions in these fluctuations are discussed. The quasi-linear diffusion of the pickup protons takes place over a scale length shorter than that of the heavier water group ions. This enhances damping of the waves by protons, and when the pickup proton density is large enough, it can result in the saturation of the instability as this damping balances the heavy ion driven growth. The observed electric field amplitude and the scale length of proton relaxation are in agreement with the theory. For small pickup proton density the instability can saturate due to the wave energy cascade arising from the modulation instability of the large-amplitude lower hybrid waves. This saturation mechanism leads to electron acceleration and suprathermal tail formation.

Shapiro, V. D.↗
NASA NTRS1994

Particle kinetic simulation of high altitude hypervelocity flight

Rarefied flows about hypersonic vehicles entering the upper atmosphere or through nozzles expanding into a near vacuum may only be simulated accurately with a direct simulation Monte Carlo (DSMC) method. Under this grant, researchers enhanced the models employed in the DSMC method and performed simulations in support of existing NASA projects or missions. DSMC models were developed and validated for simulating rotational, vibrational, and chemical relaxation in high-temperature flows, including effects of quantized anharmonic oscillators and temperature-dependent relaxation rates. State-of-the-art advancements were made in simulating coupled vibration - dissociation - recombination for post-shock flows. Models were also developed to compute vehicle surface temperatures directly in the code rather than requiring isothermal estimates. These codes were instrumental in simulating aerobraking of NASA's Magellan spacecraft during orbital maneuvers to assess heat transfer and aerodynamic properties of the delicate satellite. NASA also depended upon simulations of entry of the Galileo probe into the atmosphere of Jupiter to provide drag and flow field information essential for accurate interpretation of an onboard experiment. Finally, the codes have been used extensively to simulate expanding nozzle flows in low-power thrusters in support of propulsion activities at NASA-Lewis. Detailed comparisons between continuum calculations and DSMC results helped to quantify the limitations of continuum CFD codes in rarefied applications.

Boyd, Iain↗
NASA NTRS1994

Particle kinetic simulation of high altitude hypervelocity flight

Rarefied flows about hypersonic vehicles entering the upper atmosphere or through nozzles expanding into a near vacuum may only be simulated accurately with a direct simulation Monte Carlo (DSMC) method. Under this grant, researchers enhanced the models employed in the DSMC method and performed simulations in support of existing NASA projects or missions. DSMC models were developed and validated for simulating rotational, vibrational, and chemical relaxation in high-temperature flows, including effects of quantized anharmonic oscillators and temperature-dependent relaxation rates. State-of-the-art advancements were made in simulating coupled vibration-dissociation recombination for post-shock flows. Models were also developed to compute vehicle surface temperatures directly in the code rather than requiring isothermal estimates. These codes were instrumental in simulating aerobraking of NASA's Magellan spacecraft during orbital maneuvers to assess heat transfer and aerodynamic properties of the delicate satellite. NASA also depended upon simulations of entry of the Galileo probe into the atmosphere of Jupiter to provide drag and flow field information essential for accurate interpretation of an onboard experiment. Finally, the codes have been used extensively to simulate expanding nozzle flows in low-power thrusters in support of propulsion activities at NASA-Lewis. Detailed comparisons between continuum calculations and DSMC results helped to quantify the limitations of continuum CFD codes in rarefied applications.

Boyd, Iain↗
NASA NTRS1994

Crew factors in flight operations 2: Psychophysiological responses to short-haul air transport operations

Seventy-four pilots were monitored before, during, and after 3- or 4-day commercial short-haul trip patterns. The trips studied averaged 10.6 hr of duty per day with 4.5 hr of flight time and 5.5 flight segments. The mean rest period lasted 12.5 hr and occurred progressively earlier across successive days. On trip nights, subjects took longer to fall asleep, slept less, woke earlier, and reported lighter, poorer sleep with more awakenings than on pretrip nights. During layovers, subjective fatigue and negative affect were higher, and positive affect and activation lower, than during pretrip, in-flight, or posttrip. Pilots consumed more caffeine, alcohol, and snacks on trip days than either pretrip or posttrip. Increases in heart rate over mid-cruise were observed during descent and landing, and were greater for the pilot flying. Heart-rate increases were greater during takeoff and descent under instrument meteorological conditions (IMC) than under visual meteorological conditions (VMC). The following would be expected to reduce fatigue in short-haul operations: regulating duty hours, as well as flight hours; scheduling rest periods to begin at the same time of day, or progressively later, across the days of a trip; and educating pilots about alternatives to alcohol as a means of relaxing before sleep.

Gander, Philippa H.↗
NASA NTRS1996

Vulnerability to dysfunction and muscle injury after unloading

OBJECTIVE: To test whether unloading increases vulnerability to eccentric exercise-induced dysfunction and muscle injury. DESIGN: Before-after trial. SETTING: General community. PATIENTS OR OTHER PARTICIPANTS: Two women and 5 men (73 +/- 3kg [mean +/- SE]) who were active college students but were not trained in lower body resistance exercise volunteered. INTERVENTION: Five weeks of unilateral lower limb suspension (ULLS), which has been shown to decrease strength and size of the unloaded, left, but not load-bearing, right quadriceps femoris muscle group (QF) by 20% and 14%, respectively; performance of 10 sets of ten eccentric actions with each QF immediately after the ULLS strength tests with a load equivalent to 65% of the post-ULLS eccentric 1-repetition maximum. MAIN OUTCOME MEASURE(S): Concentric and eccentric 1-repetition maximum for the left, unloaded and the right, load-bearing QF measured immediately after ULLS and 1,4,7,9, and 11 days later; cross-sectional area and spin-spin relaxation time (T2) of each QF as determined by magnetic resonance imaging and measured the last day of ULLS and 3 days later. RESULTS: The mean load used for eccentric exercise was 23 +/- 2 and 30 +/- 3kg for the left, unloaded and right, load-bearing QF, respectively. The concentric and eccentric 1-repetition maximum for the unloaded and already weakened left QF was further decreased by 18% (p = .000) and 27% (p = .000), respectively, 1 day after eccentric exercise. Strength did not return to post-ULLS levels until 7 days of recovery. The right, load-bearing QF showed a 4% decrease (p = .002) in the eccentric 1-repetition maximum 1 day after eccentric exercise. The left, unloaded QF showed an increase in T2 (p = .002) in 18% of its cross-sectional area 3 days after the eccentric exercise, thus indicating muscle injury. The right, load-bearing QF showed no elevation in T2 (p = .280). CONCLUSION: Unloading increases vulnerability to eccentric exercise-induced dysfunction and muscle injury, even at relatively light loads.

NASA Program Space Physiology and Countermeasures↗
NASA NTRS2011

Low Frequency Turbulence as the Source of High Frequency Waves in Multi-Component Space Plasmas

Space plasmas support a wide variety of waves, and wave-particle interactions as well as wavewave interactions are of crucial importance to magnetospheric and ionospheric plasma behavior. High frequency wave turbulence generation by the low frequency (LF) turbulence is restricted by two interconnected requirements: the turbulence should be strong enough and/or the coherent wave trains should have the appropriate length. These requirements are strongly relaxed in the multi-component plasmas, due to the heavy ions large drift velocity in the field of LF wave. The excitation of lower hybrid waves (LHWs), in particular, is a widely discussed mechanism of interaction between plasma species in space and is one of the unresolved questions of magnetospheric multi-ion plasmas. It is demonstrated that large-amplitude Alfven waves, in particular those associated with LF turbulence, may generate LHW s in the auroral zone and ring current region and in some cases (particularly in the inner magnetosphere) this serves as the Alfven wave saturation mechanism. We also argue that the described scenario can playa vital role in various parts of the outer magnetosphere featuring strong LF turbulence accompanied by LHW activity. Using the data from THEMIS spacecraft, we validate the conditions for such cross-scale coupling in the near-Earth "flow-braking" magnetotail region during the passage of sharp injection/dipolarization fronts, as well as in the turbulent outflow region of the midtail reconnection site.

Khazanov, George V.↗
NASA NTRS1994

Effect of resistance training on muscle use during exercise

This study examined the effect of resistance training on exercise-induced contrast shift in magnetic resonance (MR) images. It was hypothesized that a given load could be lifted after training with less muscle showing contrast shift, thereby suggesting less muscle was used to perform the exercise. Nine males trained the left quadriceps femoris (QF) muscle 2 days/wk for 9 wk using 3-6 sets of 12 knee extensions each day. The right QF served as a control. Exercise-induced contrast shifts in MR images evoked by each of three bouts of exercise (5 sets of 10 knee extensions with a load equal to 50, 75, and 100% of the maximum pretraining load that could be lifted for 5 sets of 10 repetitions) were quantified pre- and posttraining. MR image contrast shift was quantified by determining QF cross-sectional area (CSA) showing increased spin-spin relaxation time. One repetition maximum increased 14% in the left trained QF and 7% in the right untrained QF. Left QF CSA increased 5%, with no change in right QSF CSA. Left QF CSA showing contrast shift was less after each bout of the exercise test posttraining. This was also true, to a lesser extent, for the right QF at the higher two loads. The results suggest that short-term resistance training reduces MR image contrast shift evoked by a given effort, thereby reflecting the use of less muscle to lift the load. Because this response was evident in both trained and contralateral untrained muscle, neural factors are suggested to be responsible. The consequence of this adaptation could be to increase 'stress' per unit area of active muscle during the course of training and thereby evoke hypertrophy.

Ploutz, Lori L.↗
NASA NTRS2011

Lessons Learned from the Space Shuttle Engine Cutoff System (ECO) Anomalies

The Space Shuttle Orbiter's main engine cutoff (ECO) system first failed ground checkout in April, 2005 during a first tanking test prior to Return-to-Flight. Despite significant troubleshooting and investigative efforts that followed, the root cause could not be found and intermittent anomalies continued to plague the Program. By implementing hardware upgrades, enhancing monitoring capability, and relaxing the launch rules, the Shuttle fleet was allowed to continue flying in spite of these unexplained failures. Root cause was finally determined following the launch attempts of STS-122 in December, 2007 when the anomalies repeated, which allowed drag-on instrumentation to pinpoint the fault (the ET feedthrough connector). The suspect hardware was removed and provided additional evidence towards root cause determination. Corrective action was implemented and the system has performed successfully since then. This white paper presents the lessons learned from the entire experience, beginning with the anomalies since Return-to-Flight through discovery and correction of the problem. To put these lessons in better perspective for the reader, an overview of the ECO system is presented first. Next, a chronological account of the failures and associated investigation activities is discussed. Root cause and corrective action are summarized, followed by the lessons learned.

Martinez, Hugo E.↗
NASA NTRS1996

Robust, Brillouin Active Embedded Fiber-Is-The-Sensor System in Smart Composite Structures

Extensive review of our proposed sensing scheme, based mainly on the forward Guided Acoustic Wave Brillouin Scattering (GAWBS) with backward stimulated Brillouin scattering (sBs) as an auxiliary scheme for system fault tolerance has been completed during this project period. This preliminary study is conducted for a number of reasons. The most significant reasons lie in the essential capability of the system to measure temperature and pressure. These two measurands have been proposed to be sensed by sBs in our proposal. Temperature and pressure/strain are important measurands in structural monitoring, so that the effectiveness of sensing by sBs needs to be further examined. It has been pointed out initially that sBs shift will be dependent on temperature and pressure/strain simultaneously. The shift versus temperature or strain is linear. Now, the question is how can these two measurands be separated when sBs is used to sense an environment, in which both temperature and strain are changing simultaneously. Typical sBs shift plotted versus strain and varying temperature is shown in Fig. 1. As is clear, a fiber initially stressed will relax with rising temperature. This is verified by a displacement to the right with rising temperature of the sBs shift vs strain curves in the figure. A way to circumvent this ambiguity is by employing two fibers, one pre-stressed and the other is a free fiber. The latter will measure temperature and subtracting data in the latter fiber from those of the former will give us net strain readings. This is a laborious approach, since it involves the use of two identical fibers, and this is hard to accomplish, especially when many sensors are needed. Additional multiplexing of the data stream for data subtraction becomes a necessity.

Yu, Chung↗
NASA NTRS1993

Mechanical stimulation of skeletal muscle mitigates glucocorticoid induced decreases in prostaglandin synthesis

The glucocorticoid dexamethasone (Dex) induces a decline in protein synthesis and protein content of tissue cultured, avian skeletal muscle cells, and this atrophy is attenuated by repetitive mechanical stretch. Since the prostaglandin synthesis inhibitor indomethacin mitigated this stretch attenuation of muscle atrophy, the role of prostaglandins as growth modulators in these processes was examined. Dex at 10(exp -8) M reduced PGF(sub 2(alpha)) production 55 percent - 65 percent and PGE(sub 2) production 84 - 90 percent after 24 - 72 h of incubation in static cultures. Repetitive 10 percent stretch-relaxations of the non-Dex treated cultures increased PGF(sub 2(alpha)) efflux 41 percent at 24 h and 276 percent at 72 h and increased PGE(sub 2) production 51 percent at 24 h and 236 percent at 72 h. Mechanical stimulation of Dex treated cultures increased PGF(sub 2(alpha)) production 162 percent after 24 h, thus returning PGF(sub 2(alpha)) efflux to the level of non-Dex treated cultures. At 72 h, stretch increased PGF(sub 2(alpha)) efflux 65 percent in Dex treated cultures, but PGF(sub 2(alpha)) production was 45-84 percent less than non-Dex treated cultures. Mechanical stimulation of Dex treated cultures increased PGE(sub 2) production at 24 h, but not at 72 h. Dex reduced prostaglandin H synthase (PGHS) activity in the muscle cultures by 70 percent after 8 - 24 h of incubation, and mechanical stimulation increased PGHS activity of the Dex treated cultures by 98 percent. It is concluded that repetitive mechanical stimulation attenuates the catabolic effects of Dex on cultured skeletal muscle cells in part by reversing the Dex-induced declines in PGHS activity and prostaglandin production.

Chromiak, Joseph A.↗
NASA NTRS2019

Inter-annual variation of tropical cyclones simulated by GEOS-5 AGCM with modified convection scheme

The Goddard Earth Observing System version 5 (GEOS-5) global climate model with a 50-km horizontal resolution is forced by observed sea surface temperature (SST) to examine the fidelity of the seasonal-mean and inter-annual variation of tropical cyclones (TCs) in the western North Pacific (WNP) and the North Atlantic (NATL). The standard Relaxed Arakawa Schubert (RAS) deep convection scheme is modified to improve the representation of TCs, where the scheme implements a stochastic limit of the cumulus entrainment rate. The modification drives mid- and upper-tropospheric cooling and low- to mid-tropospheric drying in the background state, which tends to increase atmospheric instability. This enables the model to increase convective variability on an intra-seasonal timescale and improve the simulation of intense storms. Five-member ensemble runs with the modified RAS scheme for 12 years (1998–2009) exhibit realistic spatial distributions in the climatological-mean TC development area and their pathways over WNP and NATL. The GCM is able to reproduce the inter-annual variation of accumulated cyclone energy (ACE) by prescribing yearly varying observed SST even though the individual TC intensity is still underpredicted. A sensitivity of TC activity to El Niño–Southern Oscillation (ENSO) phase is also reproduced realistically over WNP in terms of the spatial pattern changes in the main development region and TC pathways. However, the model exhibits a notable deficiency in NATL in reproducing the observed inter-annual variation of TC activity and the sensitivity to the ENSO.

accumulated cyclone energy↗