Small satellite systems appear to be antithetical to human spaceflight systems and flagship robotic satellite systems: Small satellite missions have more focused scientific objectives, lower cost, ...far less complexity, and shorter development and deployment schedules. The shorter schedules offer an opportunity for injecting new technology into their design as a means for keeping costs and schedule under control, for enabling cost-effective operations, and for taking advantage of innovative ideas.
It is often the case that small satellite missions benefit from technologies specifically targeted for their application, but benefits may also be realized by adopting or injecting technologies originally developed for human spaceflight systems, especially if these technologies were conceived using multi-use and multi-disciplinary development principles. In this paper, the authors discuss the precedent of injecting new technology developed for human spaceflight systems into small satellite missions. More importantly, the authors will present five new technologies recently proposed for making the NASA Space Shuttle safer to fly, all of which are directly applicable to small satellite mission design and operations. The technologies, when matured, will provide a means to create new generations of ultra-reliable flight hardware and software. The technologies are all currently at the developmental phase and require modest investment to achieve operational status.
ABSTRACTDeficiency of 21‐hydroxylase (21‐OH), one of the most common genetic defects in humans, causes low glucocorticoid and mineralocorticoid production by the adrenal cortex, but the effect of ...this disorder on the adrenomedullary system is unknown. Therefore, we analyzed the development, structure, and function of the adrenal medulla in 21‐OH‐deficient mice, an animal model resembling human congenital adrenal hyperplasia. Chromaffin cells of 21‐OH‐deficient mice exhibited ultrastructural features of neuronal transdifferentiation with reduced granules, increased rough endoplasmic reticulum and small neurite outgrowth. Migration of chromaffin cells in the adrenal to form a central medulla was impaired. Expression of phenylethanolamine‐N‐methyltransferase (PNMT) was reduced to 27 ± 9% (P<0.05), as determined by quantitative TaqMan polymerase chain reaction, and there was a significant reduction of cells staining positive for PNMT in the adrenal medulla of the 21‐OH‐deficient mice. Adrenal contents of epinephrine were decreased to 30 ± 2% (P<0.01) whereas norepinephrine and dopamine levels were reduced to 57 ± 4% (P<0.01) and 50 ± 9% (P<0.05), respectively. 21‐OH‐deficient mice demonstrate severe adrenomedullary dysfunction, with alterations in chromaffin cell migration, development, structure, and catecholamine synthesis. This hitherto unrecognized mechanism may contribute to the frequent clinical, mental, and therapeutic problems encountered in humans with this genetic disease.—Bornstein, S. R., Tajima, T., Eisenhofer, G., Haidan, A., Aguilera, G. Adrenomedullary function is severely impaired in 21‐hydroxylase‐deficient mice. FASEB J. 13, 1185–1194 (1999)
Time Synchronization in the Eurobalise Subsystem Kurz, T.; Hornstein, R.; Schweinzer, H. ...
2007 IEEE International Symposium on Precision Clock Synchronization for Measurement, Control and Communication,
2007-Oct.
Conference Proceeding
The ETCS standard was released by the European Union to reach interoperability in European railway signaling systems. This standard uses so called Eurobalises to send locally stored information to ...the passing train. Eurobalises are track mounted devices that operate on transponder technology. In order to support the standard for the European train control system (ETCS), a subsystem on the train called balise transmission module (BTM) was developed. The duty of the BTM is to tele-power an Eurobalise as the train passes and to receive the information sent by the Eurobalise. This data has to be demodulated and passed to the European vital computer (EVC), which is the control unit of the locomotive ensuring safe operation. To be able to locate a Eurobalise independent of received telegrams, a Balise Detect signal has to be additionally created by the BTM and sent to the EVC as demanded by ETCS standard. This signal is generated if the received field strength exceeds a given reference level. All components within the ETCS are operating in different time domains. In order to be able to calculate correct timing and odometric data, different time domains have to be synchronized. This has even effect on the safety critical operations within the system. ETCS requires the whole system fulfilling the SIL4 criteria. Considering modularity, it was decided that the BTM has to fulfill SIL4 criteria on its own, too. The crucial aspect is combining safety demands and time synchronization. It affects the communication between the BTM and the EVC. This paper focuses on the synchronization mechanisms within the components of the BTM and the synchronization between BTM and EVC.
We present new proper motions from the 10 m Keck telescopes for a puzzling population of massive, young stars located within 35 (0.14 pc) of the supermassive black hole at the Galactic center. Our ...proper motion measurements have uncertainties of only 0.07 mas yr-1 (3 km s-1), which is 7 times better than previous proper motion measurements for these stars, and enables us to measure accelerations as low as 0.2 mas yr-2 (7 km s-1 yr-1). Using these measurements, line-of-sight velocities from the literature, and three-dimensional velocities for additional young stars in the central parsec, we constrain the true orbit of each individual star and directly test the hypothesis that the massive stars reside in two stellar disks as has been previously proposed. Analysis of the stellar orbits reveals only one of the previously proposed disks of young stars using a method that is capable of detecting disks containing at least seven stars. The detected disk contains 50% of the young stars, is inclined by ~115° from the plane of the sky, and is oriented at a position angle of ~100° east of north. Additionally, the on-disk and off-disk populations have similar K-band luminosity functions and radial distributions that decrease at larger radii as r -2. The disk has an out-of-the-disk velocity dispersion of 28 ± 6 km s-1, which corresponds to a half-opening angle of 7° ± 2°, and several candidate disk members have eccentricities greater than 0.2. Our findings suggest that the young stars may have formed in situ but in a more complex geometry than a simple, thin circular disk.
We report the short-pulse operation of a 460 GHz gyrotron oscillator both at the fundamental (near 230 GHz) and second harmonic (near 460 GHz) of electron cyclotron resonance. During operation in a ...microsecond pulse length regime with 13-kV beam voltage and 110-mA beam current, the instrument generates several watts of power in two second harmonic modes, the TE/sub 2,6,1/ at 456.15 GHz and the TE/sub 0,6,1/ at 458.56 GHz. Operation in the fundamental modes, including the TE/sub 0,3,1/ mode at 237.91 GHz and the TE/sub 2,3,1/ at 233.15 GHz, is observed at output powers up to 70 W. Further, we demonstrate broadband continuous frequency tuning of the fundamental modes of the oscillator over a range of more than 2 GHz through variation of the magnetic field alone. We interpret these results in terms of smooth transitions between higher order axial modes of the resonator. The 460 GHz gyrotron is currently being processed for continuous duty operation, where it will serve as a microwave source for sensitivity-enhanced nuclear magnetic resonance (dynamic nuclear polarization) studies at 16 T (700 MHz /sup 1/H), a field strength which is two-fold higher than has been accessible with previous technology.
We present new diffraction-limited images of the Galactic center, obtained with the W. M. Keck I 10 m telescope. Within 0".4 of the Galaxy's central dark mass, 17 proper-motion stars, with K ...magnitudes ranging from 14.0 to 16.8, are identified, and 10 of these are new detections (six were also independently discovered by others). In this sample, three newly identified (S0-16, S0-19, and S0-20) and four previously known (S0-1, S0-2, S0-4, and S0-5) sources have measured proper motions that reveal orbital solutions. Orbits are derived simultaneously so that they jointly constrain the central dark object's properties: its mass, its position, and, for the first time using orbits, its motion on the plane of the sky. This analysis pinpoints the Galaxy's central dark mass to within 1.3 mas (10 AU) and limits its proper motion to 1.5 c 0.5 mas yr super(-1) (or equivalently 60 c 20 km s super(-1)) with respect to the central stellar cluster. This localization of the central dark mass is consistent with our derivation of the position of the radio source Sgr A* in the infrared reference frame (c10 mas) but with an uncertainty that is a factor of 8 times smaller, which greatly facilitates searches for near-infrared counterparts to the central black hole. Consequently, one previous claim for such a counterpart can now be ascribed to a close stellar passage in 1996. Furthermore, we can place a conservative upper limit of 15.5 mag on any steady state counterpart emission. The estimated central dark mass from orbital motions is 3.7(c0.2) x 10 super(6) R sub(0)/ (8 kpc) super(3) M sub( ); this is a more direct measure of mass than those obtained from velocity dispersion measurements, which are as much as a factor of 2 smaller. The Galactic center's distance, which adds an additional 19% uncertainty in the estimated mass, is now the limiting source of uncertainty in the absolute mass. For stars in this sample, the closest approach is achieved by S0-16, which came within a mere 45 AU (=0.0002 pc = 600R sub(s)) at a velocity of 12,000 km s super(-1). This increases the inferred dark mass density by 4 orders of magnitude compared to earlier analyses based on velocity and acceleration vectors, making the Milky Way the strongest existing case for a supermassive black hole at the center of a normal-type galaxy. Well-determined orbital parameters for these seven Sgr A* cluster stars also provide new constraints on how these apparently massive, young (<10 Myr) stars formed in a region that seems to be hostile to star formation. Unlike the more distant He I emission line stars--another population of young stars in the Galactic center--that appear to have coplanar orbits, the Sgr A* cluster stars have orbital properties (eccentricities, angular momentum vectors, and apoapse directions) that are consistent with an isotropic distribution. Therefore, many of the mechanisms proposed for the formation of the He I stars, such as formation from a preexisting disk, are unlikely solutions for the Sgr A* cluster stars. Unfortunately, alternative theories for producing young stars, or old stars that look young, in close proximity to a central supermassive black hole are all also somewhat problematic. Understanding the apparent youth of stars in the Sgr A* cluster, as well as the more distant He I emission line stars, has now become one of the major outstanding issues in the study of the Galactic center.
BACKGROUND Endometriosis is a prevalent but enigmatic gynecologic disorder for which few modifiable risk factors have been identified. Fish oil consumption has been associated with symptom ...improvement in studies of women with primary dysmenorrhea and with decreased endometriosis risk in autotransplantation animal studies. METHODS To investigate the relation between dietary fat intake and the risk of endometriosis, we analyzed 12 years of prospective data from the Nurses' Health Study II that began in 1989. Dietary fat was assessed via food frequency questionnaire in 1991, 1995 and 1999. We used Cox proportional hazards models adjusted for total energy intake, parity, race and body mass index at age 18, and assessed cumulatively averaged fat intake across the three diet questionnaires. RESULTS During the 586 153 person-years of follow-up, 1199 cases of laparoscopically confirmed endometriosis were reported. Although total fat consumption was not associated with endometriosis risk, those women in the highest fifth of long-chain omega-3 fatty acid consumption were 22% less likely to be diagnosed with endometriosis compared with those with the lowest fifth of intake 95% confidence interval (CI) = 0.62–0.99; P-value, test for linear trend (Pt) = 0.03. In addition, those in the highest quintile of trans-unsaturated fat intake were 48% more likely to be diagnosed with endometriosis (95% CI = 1.17–1.88; Pt = 0.001). CONCLUSION These data suggest that specific types of dietary fat are associated with the incidence of laparoscopically confirmed endometriosis, and that these relations may indicate modifiable risk. This evidence additionally provides another disease association that supports efforts to remove trans fat from hydrogenated oils from the food supply.
We present the first laser guide star adaptive optics (LGSAO) observations of the Galactic center. LGSAO has dramatically improved the quality and robustness with which high angular resolution ...infrared images of the Galactic center can be obtained with the Keck II 10 m telescope. Specifically, Strehl ratios of 0.7 and 0.3 at L' (3.8 km) and K' (2.1 km), respectively, are achieved in these LGSAO images; these are at least a factor of 2 higher and a factor of 4-5 more stable against atmospheric fluctuations than the Strehl ratios delivered thus far with the Keck natural guide star AO system on the Galactic center. Furthermore, these observations are the first that cover a large area (76 x 76) surrounding the central black hole at diffraction-limited resolution for an 8-10 m class telescope. During our observations, the infrared counterpart to the central supermassive black hole, Sgr A*-IR, showed significant infrared intensity variations, with observed L' magnitudes ranging from 12.6 to 14.5 mag and a decrease in flux density of a factor of 2 over an 8 minute interval. The faintest end of our L' detections, 1.3 mJy (dereddened), is the lowest level of emission yet observed for this source by a factor of 3. No significant variation in the location of Sgr A*-IR is detected as a function of either wavelength or intensity. Previous claims of such positional variations are easily attributable to a nearby (0.09 or 720 AU, projected), extended, very red source, which we suggest arises from a locally heated dust feature. Near a peak in its intensity, we obtained the first measurement of Sgr A*-IR's K'- L' color; its K' - L' of 3.0 c 0.2 mag (observed) or 1.4 c 0.2 (dereddened) corresponds to an intrinsic spectral index of a = -0.5 c 0.3 for F sub( )8 super(a). This is significantly bluer than other recent infrared measurements from the literature, which suggest a = -4 c 1. Because our measurement was taken at a time when Sgr A* was 66 times brighter in the infrared than the other measurements, we posit that the spectral index of the emission arising from the vicinity of our Galaxy's central black hole may depend on the strength of the flare, with stronger flares giving rise to a higher fraction of high-energy electrons in the emitting region.
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