Signal Conditioning for the Kalman Filter: Application to Satellite Attitude Estimation with Magnetometer and Sun Sensors.

Most satellites use an on-board attitude estimation system, based on available sensors. In the case of low-cost satellites, which are of increasing interest, it is usual to use magnetometers and Sun sensors. A Kalman filter is commonly recommended for the estimation, to simultaneously exploit the information from sensors and from a mathematical model of the satellite motion. It would be also convenient to adhere to a quaternion representation. This article focuses on some problems linked to this context. The state of the system should be represented in observable form. Singularities due to alignment of measured vectors cause estimation problems. Accommodation of the Kalman filter originates convergence difficulties. The article includes a new proposal that solves these problems, not needing changes in the Kalman filter algorithm. In addition, the article includes assessment of different errors, initialization values for the Kalman filter; and considers the influence of the magnetic dipole moment perturbation, showing how to handle it as part of the Kalman filter framework.

Efficacy, safety, and tolerance of two types of intragastric balloons placed in obese subjects: a double-blind comparative study.

The intragastric balloon is a temporary treatment for obese patients. Fluid-filled devices have shown efficacy and safety, and are widely used. Recently, although there are no comparative studies between them, an air-filled balloon, Heliosphere® bag, has been proposed. Prospective, double-blind study in 33 patients with morbid and type 2 obesity: 23 female, 43.9±10 years, 120.3±17 kg, and body mass index (BMI) of 44.2±5 kg/m2, placing 18 gastric balloons filled with 960 cm3 of air (Heliosphere® bag) or 15 balloons filled with 700 ml of saline (Bioenterics-BIB®). Both balloons were placed with conscious sedation and removed under general anesthesia 6 months later. Intravenous drugs were given to control symptoms for 48 h. Patients were sent home on a 1000-kcal diet, multivitamin supplements, and oral proton pump inhibitors, and were followed monthly. Complications, symptoms, weight, and quality of life evaluated by the Gastrointestinal Quality of Life Index (GIQLI) scale were recorded. At 6 months, mean weight loss (12.8±8 vs 14.1±8 kg), BMI loss (4.6±3 vs 5.5±3 kg/m2) and percent excess weight loss (27±16 vs.30.2±17) showed no significant differences between both groups. At removal, two Heliosphere® bags were not found in the stomach, and four patients required extraction of the balloon by rigid esophagoscopy or surgery (p=0.02). Tolerance was good in both groups, but early removal occurred in three BIB® (20%) due to vomits and dehydration. The GIQLI total scores remained unchanged. Both balloons achieve a significant weight loss with good tolerance in obese patients. Nevertheless, Heliosphere® bag has severe technical problems that need to be solved before recommending it.

Internal ribosome entry site drives cap-independent translation of reaper and heat shock protein 70 mRNAs in Drosophila embryos.

Translation is a sensitive regulatory step during cellular stress and the apoptosis response. Under such conditions, cap-dependent translation is reduced and internal ribosome entry site (IRES)-dependent translation plays a major role. However, many aspects of how mRNAs are translated under stress remain to be elucidated. Here we report that reaper mRNA, a pro-apoptotic gene from Drosophila melanogaster, is translated in a cap-independent manner. In Drosophila mutant embryos devoid of the eukaryotic initiation factor 4E (eIF4E), reaper transcription is induced and apoptosis proceeds. In vitro translation experiments using wild-type and eIF4E mutant embryonic extracts show that reporter mRNA bearing reaper 5' untranslated region (UTR) is effectively translated in a cap-independent manner. The 5'UTR of reaper exhibits a high degree of similarity with that of Drosophila heat shock protein 70 mRNA, and both display IRES activity. Studies of mRNA association to polysomes in embryos indicate that both reaper and heat shock protein 70 mRNAs are recruited to polysomes under apoptosis or thermal stress. Our data suggest that heat shock protein 70 and reaper, two antagonizing factors in apoptosis, use a similar mechanism for protein synthesis.

Two functionally redundant isoforms of Drosophila melanogaster eukaryotic initiation factor 4B are involved in cap-dependent translation, cell survival, and proliferation.

Eukaryotic initiation factor (eIF) 4B is part of the protein complex involved in the recognition and binding of mRNA to the ribosome. DrosophilaeIF4B is a single-copy gene that encodes two isoforms, termed eIF4B-L (52.2 kDa) and eIF4B-S (44.2 kDa), generated as a result of the alternative recognition of two polyadeynlation signals during transcription termination and subsequent alternative splicing of the two pre-mRNAs. Both eIF4B mRNAs and proteins are expressed during the entire embryogenesis and life cycle. The proteins are cytoplasmic with polarized distribution. The two isoforms bind RNA with the same affinity. eIF4B-L and eIF4B-S preferentially enhance cap-dependent over IRES-dependent translation initiation in a Drosophila cell-free translation system. RNA interference experiments suggest that eIF4B is required for cell survival, although only a modest reduction in rate of protein synthesis is observed. Overexpression of eIF4B in Drosophila cells in culture and in developing eye imaginal discs promotes cell proliferation.

Identification and characterization of the expression of the translation initiation factor 4A (eIF4A) from Drosophila melanogaster.

We have identified the initiation factor 4A (eIF4A) in a two-dimensional protein database of Drosophila wing imaginal discs. eIF4A, a member of the DEAD-box family of RNA helicases, forms the active eIF4F complex that in the presence of eIF4B and eIF4H unwinds the secondary structure of the 5'-UTR of mRNAs during translational initiation. Two-dimensional gel electrophoresis and microsequencing allowed us to purify eIF4A, and generate specific polyclonal antibodies. A combination of immunoblotting and labelling with [(35)S]methionine + [(35)S]cysteine revealed the existence of a single eIF4A isoform encoded by a previously reported gene that maps to chromosome 2L at 26A7-9. Expression of this gene yields two mRNA species, generated by alternative splicing in the 3'-untranslated region. The two mRNAs contain the same open reading frame and produce the identical eIF4A protein. No expression was detected of the eIF4A-related gene CG7483. We detected eIF4A protein expression in the wing imaginal discs of several Drosophila species, and in haltere, leg 1, leg 2, leg 3, and eye-antenna imaginal discs of D. melanogaster. Examination of eIF4A in tumor suppressor mutants showed significantly increased (> 50%) expression in the wing imaginal discs of these larvae. We observed ubiquitous expression of eIF4A mRNA and protein during Drosophila embryogenesis. Yeast two-hybrid analysis demonstrated the in vivo interaction of Drosophila eIF4G with the N-terminal third of eIF4A.