30 research outputs found
Flying Drones Beyond Visual Line of Sight Using 4G LTE: Issues and Concerns
The purpose of this paper is to address the extent in which 4G LTE can be used for air traffic management of small Unmanned Air Vehicles (sUAVs) and the limitations and enhancements that may be necessary. We provide a brief overview of the communications aspects of the Unmanned Aerial System (UAS) Traffic Management Project followed by the evolving trends in air traffic management including beyond visual line of sight (BVLOS) operations concepts and current BVLOS operational systems. Issues and Concerns are addressed including the rapidly evolving global regulations and the resulting communications requirements as well LTE downlink and uplink interference at altitude and how that interference affects command and control reliability as well as application data capabilities and mobility performance
Space Link Extension (SLE) Emulation for High-Throughput Network Communication
As the data rate requirements for space communications increases, significant stress is placed not only on the wireless satellite communication links, but also on the ground networks which forward data from end-users to remote ground stations. These wide area network (WAN) connections add delay and jitter to the end-to-end satellite communication link, effects which can have significant impacts on the wireless communication link. It is imperative that any ground communication protocol can react to these effects such that the ground network does not become a bottleneck in the communication path to the satellite. In this paper, we present our SCENIC Emulation Lab testbed which was developed to test the CCSDS SLE protocol implementations proposed for use on future NASA communication networks. Our results show that in the presence of realistic levels of network delay, high-throughput SLE communication links can experience significant data rate throttling. Based on our observations, we present some insight into why this data throttling happens, and trace the probable issue back to non-optimal blocking communication which is sup-ported by the CCSDS SLE API recommended practices. These issues were presented as well to the SLE implementation developers which, based on our reports, developed a new release for SLE which we show fixes the SLE blocking issue and greatly improves the protocol throughput. In this paper, we also discuss future developments for our end-to-end emulation lab and how these improvements can be used to develop and test future space communication technologies
Flying Drones Beyond Visual Line of Sight Using 4G LTE: Issues and Concerns
The purpose of this paper is to address the extent in which 4G LTE can be used for air traffic management of small Unmanned Air Vehicles (sUAVs) and the limitations and enhancements that may be necessary. We provide a brief overview of the communications aspects of the Unmanned Aerial System (UAS) Traffic Management Project followed by the evolving trends in air traffic management including beyond visual line of sight (BVLOS) operations concepts and current BVLOS operational systems. Issues and Concerns are addressed including the rapidly evolving global regulations and the resulting communications requirements as well LTE downlink and uplink interference at altitude and how that interference affects command and control reliability as well as application data capabilities and mobility performance
Cellular Based Small Unmanned Aircraft Systems (sUAS) MIMO Communications
The use of remotely piloted unmanned aircraft systems/vehicles (UAS/UAV or drones) increases dramatically in recent years. This paper discusses the use of multiple-input and multiple-output (MIMO) technologies in cellular (i.e., LTE) based small UAS (sUAS) communications. More specifically, we will first provide background information about this work, followed by a review of state-of-the-art. Then, we will discuss the benefits of MIMO technologies and propose practical MIMO configurations (e.g., the type, size and number of antennas) that are suitable for NASA's sUAS research and operations. Finally, the design tradeoff among multiplexing, diversity, and interference/jamming cancellation will also be discussed
Controlled comparison of hemodialysis and peritoneal dialysis: Veterans Administration multicenter study
Controlled comparison of hemodialysis and peritoneal dialysis: Veterans Administration multicenter study. We measured mortality and morbidity among 114 patients assigned randomly to home hemodialysis (HD) and home intermittent peritoneal dialysis (IPD). Data were collected during the time of home training and for 12 months after initiation of home dialysis. Training time was shorter for the IPD than for the HD patients (P < 0.001) with median time 1.8 months for IPD and 3.9 months for HD. Switching to the alternative mode of treatment was more frequent for the IPD group (29/59 vs. 5/55, P < 0.001). Survival time was not different, perhaps because of the modality change. More IPD patients were hospitalized in the first 6 months (20 for IPD vs. 9 for HD, P = 0.02), but they had fewer troublesome cardiovascular events in the first year (0 vs. 12, P < 0.001). The HD patients maintained better nutritional status as reflected in body weight and arm muscle circumference and possibly in urea appearance rate. Thus, these data suggest that for most patients, IPD is a less satisfactory form of therapy than HD, but certain advantages of IPD did emerge. Applications of this information to the currently more popular mode of CAPD await further study.Comparaison contrΓ΄lΓ©e entre l'hΓ©modialyse et la dialyse pΓ©ritonΓ©ale: Γtude multicentrique de l'Administration des Veterans. Nous avons mesurΓ© la mortalitΓ© et la morbiditΓ© chez 114 malades, pris au hasard, en hΓ©modialyse Γ domicile (HD) ou en dialyse pΓ©ritonΓ©ale intermittente Γ domicile (IPD). Les donnΓ©es ont Γ©tΓ© recueillies pendant l'entrainement Γ domicile et pendant les 12 mois suivant le dΓ©but de la dialyse Γ domicile. La durΓ©e d'entrainement Γ©tait plus brΓ¨ve pour les malades en IPD que pour ceux en HD (P < 0,001), avec un temps mΓ©dian de 1,8 mois pour l'IPD et de 3,9 mois pour l'HD. Le changement pour l'autre mode de traitement Γ©tait plus frΓ©quent pour le groupe IPD (29/59 contre 5/55, P < 0,001). La durΓ©e de suivi n'Γ©tait pas diffΓ©rente, peut-Γͺtre Γ cause du changement de modalitΓ©. Plus de malades en IPD ont Γ©tΓ© hospitalisΓ©s dans les 6 premiers mois (20 en IPD, contre 9 en HD, P = 0,02), mais ils ont eu moins d'ennuis cardiovasculaires gΓͺnants au cours de la premiΓ¨re annΓ©e (0 contre 12, P < 0,001). Les malades HD conservaient un meilleur Γ©tat nutritionnel, reflΓ©tΓ© par le poids corporel, la circonfΓ©rence musculaire du bras, et probablement la vitesse d'apparition de l'urΓ©e. Ainsi ces donnΓ©es suggΓ¨rent que pour la plupart des malades, l'IPD est une forme de traitement moins satisfaisante que l'HD, mais certains avantages de l'IPD sont apparus. Les applications de cette information au mode actuellement le plus rΓ©pandu de CAPD requiΓ¨rent d'autres Γ©tudes
Vesicoureteral Reflux and Other Urinary Tract Malformations in Mice Compound Heterozygous for Pax2 and Emx2
Congenital anomalies of the kidney and urinary tract (CAKUT) are the most common cause of chronic kidney disease in children. This disease group includes a spectrum of urinary tract defects including vesicoureteral reflux, duplex kidneys and other developmental defects that can be found alone or in combination. To identify new regulators of CAKUT, we tested the genetic cooperativity between several key regulators of urogenital system development in mice. We found a high incidence of urinary tract anomalies in Pax2;Emx2 compound heterozygous mice that are not found in single heterozygous mice. Pax2+/β;Emx2+/β mice harbor duplex systems associated with urinary tract obstruction, bifid ureter and a high penetrance of vesicoureteral reflux. Remarkably, most compound heterozygous mice refluxed at low intravesical pressure. Early analysis of Pax2+/β;Emx2+/β embryos point to ureter budding defects as the primary cause of urinary tract anomalies. We additionally establish Pax2 as a direct regulator of Emx2 expression in the Wolffian duct. Together, these results identify a haploinsufficient genetic combination resulting in CAKUT-like phenotype, including a high sensitivity to vesicoureteral reflux. As both genes are located on human chromosome 10q, which is lost in a proportion of VUR patients, these findings may help understand VUR and CAKUT in humans
KELT-23Ab: A Hot Jupiter Transiting a Near-solar Twin Close to the TESS and JWST Continuous Viewing Zones
We announce the discovery of KELT-23Ab, a hot Jupiter transiting the relatively bright (V = 10.3) star BD+66 911 (TYC 4187-996-1), and characterize the system using follow-up photometry and spectroscopy. A global fit to the system yields host-star properties of K, , , , (cgs), and . KELT-23Ab is a hot Jupiter with a mass of , radius of , and density of g cm-3. Intense insolation flux from the star has likely caused KELT-23Ab to become inflated. The time of inferior conjunction is and the orbital period is days. There is strong evidence that KELT-23A is a member of a long-period binary star system with a less luminous companion, and due to tidal interactions, the planet is likely to spiral into its host within roughly a gigayear. This system has one of the highest positive ecliptic latitudes of all transiting planet hosts known to date, placing it near the Transiting Planet Survey Satellite and James Webb Space Telescope continuous viewing zones. Thus we expect it to be an excellent candidate for long-term monitoring and follow up with these facilities
TESS hunt for young and maturing exoplanets (THYME). III. A two-planet system in the 400 Myr Ursa major group
A.W.M. was supported through NASA's Astrophysics Data Analysis Program (80NSSC19K0583). M.L.W. was supported by a grant through NASA's K2 GO program (80NSSC19K0097). This material is based on work supported by the National Science Foundation Graduate Research Fellowship Program under grant No. DGE-1650116 to P.C.T. A.V.'s work was performed under contract with the California Institute of Technology/Jet Propulsion Laboratory funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. D.D. acknowledges support from NASA through Caltech/JPL grant RSA-1006130 and through the TESS Guest Investigator Program grant 80NSSC19K1727.Exoplanets can evolve significantly between birth and maturity, as their atmospheres, orbits, and structures are shaped by their environment. Young planets (<1 Gyr) offer an opportunity to probe the critical early stages of this evolution, where planets evolve the fastest. However, most of the known young planets orbit prohibitively faint stars. We present the discovery of two planets transiting HD 63433 (TOI 1726, TIC 130181866), a young Sun-like (Mβ=0.99Β±0.03) star. Through kinematics, lithium abundance, and rotation, we confirm that HD 63433 is a member of the Ursa Major moving group (Ο=414Β±23 Myr). Based on the TESS light curve and updated stellar parameters, we estimate the planet radii are 2.15Β±0.10Rβ and 2.67Β±0.12Rβ, the orbital periods are 7.11 and 20.55 days, and the orbital eccentricities are lower than about 0.2. Using HARPS-N velocities, we measure the Rossiter-McLaughlin signal of the inner planet, demonstrating that the orbit is prograde. Since the host star is bright (V=6.9), both planets are amenable to transmission spectroscopy, radial velocity measurements of their masses, and more precise determination of the stellar obliquity. This system is therefore poised to play an important role in our understanding of planetary system evolution in the first billion years after formation.PostprintPeer reviewe
KELT-24b: A 5M_J Planet on a 5.6 day Well-Aligned Orbit around the Young V=8.3 F-star HD 93148
We present the discovery of KELT-24 b, a massive hot Jupiter orbiting a bright (V=8.3 mag, K=7.2 mag) young F-star with a period of 5.6 days. The host star, KELT-24 (HD 93148), has a T_(eff) =6508Β±49 K, a mass of Mβ = 1.461^(+0.056)_(β0.060) M_β, radius of Rβ = 1.506Β±0.022 R_β, and an age of 0.77^(+0.61)_(β0.42) Gyr. Its planetary companion (KELT-24 b) has a radius of R_P = 1.272^(+0.021)_(β0.022) R_J, a mass of MP = 5.18^(+0.21)_(β0.22) M_J, and from Doppler tomographic observations, we find that the planet's orbit is well-aligned to its host star's projected spin axis (Ξ» = 2.6^(+5.1)_(β3.6)). The young age estimated for KELT-24 suggests that it only recently started to evolve from the zero-age main sequence. KELT-24 is the brightest star known to host a transiting giant planet with a period between 5 and 10 days. Although the circularization timescale is much longer than the age of the system, we do not detect a large eccentricity or significant misalignment that is expected from dynamical migration. The brightness of its host star and its moderate surface gravity make KELT-24b an intriguing target for detailed atmospheric characterization through spectroscopic emission measurements since it would bridge the current literature results that have primarily focused on lower mass hot Jupiters and a few brown dwarfs
CD14 Deficiency Impacts Glucose Homeostasis in Mice through Altered Adrenal Tone
The toll-like receptors comprise one of the most conserved components of the innate immune system, signaling the presence of molecules of microbial origin. It has been proposed that signaling through TLR4, which requires CD14 to recognize bacterial lipopolysaccharide (LPS), may generate low-grade inflammation and thereby affect insulin sensitivity and glucose metabolism. To examine the long-term influence of partial innate immune signaling disruption on glucose homeostasis, we analyzed knockout mice deficient in CD14 backcrossed into the diabetes-prone C57BL6 background at 6 or 12 months of age. CD14-ko mice, fed either normal or high-fat diets, displayed significant glucose intolerance compared to wild type controls. They also displayed elevated norepinephrine urinary excretion and increased adrenal medullary volume, as well as an enhanced norepinephrine secretory response to insulin-induced hypoglycemia. These results point out a previously unappreciated crosstalk between innate immune- and sympathoadrenal- systems, which exerts a major long-term effect on glucose homeostasis