Automatic rendezvous and capture system development in a manned environment

This paper presents the development of a 'Phase One' AR&C system capability as a logical outgrowth of Rendezvous and Proximity Operations (R&PO) system development for manned space programs. The continuity of the approach to R&PO across the Apollo, Skylab, Apollo-Soyuz, and Shuttle programs is traced and lessons learned which are applicable to AR&C discussed. Use of the Shuttle as a test bed for Automatic Rendezvous and Capture capabilities and technology demonstrations is discussed. A status of the current Phase One System design and brief overview of its capabilities is presented

Predicting On-axis Rotorcraft Dynamic Responses Using Machine Learning Techniques

Physical-law-based models are widely utilized in the aerospace industry. One such use is to provide flight dynamics models for use in flight simulators. For human-in-the-loop use, such simulators must run in real-time. Owing to the complex physics of rotorcraft flight, to meet this real-time requirement, simplifications to the underlying physics sometimes have to be applied to the model, leading to errors in the model's predictions of the real vehicle's response. This study investigated whether a machine-learning technique could be employed to provide rotorcraft dynamic response predictions. Machine learning was facilitated using a Gaussian process (GP) nonlinear autoregressive model, which predicted the on-axis pitch rate, roll rate, yaw rate, and heave responses of a Bo105 rotorcraft. A variational sparse GP model was then developed to reduce the computational cost of implementing the approach on large datasets. It was found that both of the GP models were able to provide accurate on-axis response predictions, particularly when the model input contained all four control inceptors and one lagged on-axis response term. The predictions made showed improvement compared to a corresponding physics-based model. The reduction of training data to one-third (rotational axes) or one-half (heave axis) resulted in only minor degradation of the sparse GP model predictions. response predictions. Machine learning was facilitated using a Gaussian process (GP) nonlinear autoregressive model, which predicted the on-axis pitch rate, roll rate, yaw rate, and heave responses of a Bo105 rotorcraft. A variational sparse GP model was then developed to reduce the computational cost of implementing the approach on large datasets. It was found that both of the GP models were able to provide accurate on-axis response predictions, particularly when the model input contained all four control inceptors and one lagged on-axis response term. The predictions made showed improvement compared to a corresponding physics-based model. The reduction of training data to one-third (rotational axes) or one-half (heave axis) resulted in only minor degradation of the sparse GP model predictions.</jats:p

Scrotal Swelling and Testicular Atrophy due to Schistosomiasis in a 9-Year-Old Boy: A Case Report

Schistosomiasis is a communicable disease which commonly involves urinary bladder causing hematuria, or large bowel causing bloody stool. The common species encountered in this lake region surrounding Lake Victoria in Tanzania are Schistosoma haematobium and Schistosoma mansoni. Complications can lead to portal hypertension due portal fibrosis in liver, and fibrosis in lung can lead to pulmonary hypertension; this commonly seen with S. mansoni. Major complications of S. maeametobium are chronic cystitis with squamous metaplasia with subsequent development of squamous cell carcinoma. Involvement of spinal cord causing paraplegia has been observed in S. haematobium. Other unusual pathology of schistosomiasis has been described, such as involvement of the appendix, ovary, prostate, and cervix. Here, we present a case of schistosomiasis in a 9-year-old boy who presented with left scrotal pain for one year which was accompanied by scrotal swelling; surgical exploration was done, and the finding was hydrocele and atrophic testes with nodules on the surface. Histological examination reveals atrophic testis and heavy active granulomatous inflammation with schistosoma eggs consistent with Schistosoma haematobium in the tunica vaginalis

The ELAV RNA-stability factor HuR binds the 5′-untranslated region of the human IGF-IR transcript and differentially represses cap-dependent and IRES-mediated translation

The type I insulin-like growth factor receptor (IGF-IR) is an integral component in the control of cell proliferation, differentiation and apoptosis. The IGF-IR mRNA contains an extraordinarily long (1038 nt) 5′-untranslated region (5′-UTR), and we have characterized a diverse series of proteins interacting with this RNA sequence which may provide for intricate regulation of IGF-IR gene expression at the translational level. Here, we report the purification and identification of one of these IGF-IR 5′-UTR-binding proteins as HuR, using a novel RNA crosslinking/RNase elution strategy. Because HuR has been predominantly characterized as a 3′-UTR-binding protein, enhancing mRNA stability and generally increasing gene expression, we sought to determine whether HuR might serve a different function in the context of its binding the IGF-IR 5′-UTR. We found that HuR consistently repressed translation initiation through the IGF-IR 5′-UTR. The inhibition of translation by HuR was concentration dependent, and could be reversed in trans by addition of a fragment of the IGF-IR 5′-UTR containing the HuR binding sites as a specific competitor, or abrogated by deletion of the third RNA recognition motif of HuR. We determined that HuR repressed translation initiation through the IGF-IR 5′-UTR in cells as well, and that siRNA knockdown of HuR markedly increased IGF-IR protein levels. Interestingly, we also found that HuR potently inhibited IGF-IR translation mediated through internal ribosome entry. Kinetic assays were performed to investigate the mechanism of translation repression by HuR and the dynamic interplay between HuR and the translation apparatus. We found that HuR, occupying a cap-distal position, significantly delayed translation initiation mediated by cap-dependent scanning, but was eventually displaced from its binding site, directly or indirectly, as a consequence of ribosomal scanning. However, HuR perpetually blocked the activity of the IGF-IR IRES, apparently arresting the IRES-associated translation pre-initiation complex in an inactive state. This function of HuR as a 5′-UTR-binding protein and dual-purpose translation repressor may be critical for the precise regulation of IGF-IR expression essential to normal cellular homeostasis

SPIFI: a Direct-Detection Imaging Spectrometer for Submillimeter Wavelengths

The South Pole Imaging Fabry-Perot Interferometer (SPIFI) is the first instrument of its kind -a direct-detection imaging spectrometer for astronomy in the submillimeter band. SPIFI ’s focal plane is a square array of 25 silicon bolometers cooled to 60 mK; the spectrometer consists of two cryogenic scanning Fabry-Perot interferometers in series with a 60-mK bandpass filter. The instrument operates in the short submillimeter windows (350 and 450 μm) available from the ground, with spectral resolving power selectable between 500 and 10,000. At present, SPIFI’s sensitivity is within a factor of 1.5-3 of the photon background limit, comparable with the best heterodyne spectrometers. The instrument ’s large bandwidth and mapping capability provide substantial advantages for specific astrophysical projects, including deep extragalactic observations. We present the motivation for and design of SPIFI and its operational characteristics on the telescope

The Gamma-Ray Blazar Content of the Northern Sky

Using survey data, we have re-evaluated the correlation of flat spectrum radio sources with EGRET sources in the Northern sky. A likelihood analysis incorporating the radio and X-ray properties and the Gamma-ray source localization is used to gauge the reliability of associations and to search for counterparts of previously unidentified EGRET sources. Above |b|=10deg, where the classification is complete, we find that 70% of the Northern EGRET sources have counterparts similar to the bright EGRET blazars. For several of these we identify known blazar counterparts more likely than the earlier proposed 3EG association; for ~20 we have new identifications. Spectroscopic confirmation of these candidates is in progress and we have found flat spectrum radio quasars and BL Lac counterparts with redshifts as high as 4. We also find strong evidence for a set of 28 objects with no plausible counterpart like the known EGRET Blazars. These thus represent either a new extragalactic population or a population of Galactic objects with a large scale height. The survey has been extended into the plane, where we find several new blazar candidates; the bulk of the sources are, however, Galactic. Looking ahead to the GLAST era we predict that several of the present 3EG sources are composite and that higher resolution data will break these into multiple Blazar IDs.Comment: 13 pages, 6 figures, submitted to Ap

Theory of a magnetic microscope with nanometer resolution

We propose a theory for a type of apertureless scanning near field microscopy that is intended to allow the measurement of magnetism on a nanometer length scale. A scanning probe, for example a scanning tunneling microscope (STM) tip, is used to scan a magnetic substrate while a laser is focused on it. The electric field between the tip and substrate is enhanced in such a way that the circular polarization due to the Kerr effect, which is normally of order 0.1% is increased by up to two orders of magnitude for the case of a Ag or W tip and an Fe sample. Apart from this there is a large background of circular polarization which is non-magnetic in origin. This circular polarization is produced by light scattered from the STM tip and substrate. A detailed retarded calculation for this light-in-light-out experiment is presented.Comment: 17 pages, 8 figure

Classical 5D fields generated by a uniformly accelerated point source

Gauge fields associated with the manifestly covariant dynamics of particles in $(3,1)$ spacetime are five-dimensional. In this paper we explore the old problem of fields generated by a source undergoing hyperbolic motion in this framework. The 5D fields are computed numerically using absolute time $\tau$-retarded Green-functions, and qualitatively compared with Maxwell fields generated by the same motion. We find that although the zero mode of all fields coincides with the corresponding Maxwell problem, the non-zero mode should affect, through the Lorentz force, the observed motion of test particles.Comment: 36 pages, 8 figure