Mapping and maneuvering long-term natural orbits around Titania, a satellite of Uranus

In this work, we present the results of a set of numerical simulations carried out to obtain long-duration orbits for a probe around Titania, Uranus' largest satellite. We also propose orbital maneuvers to extend the lifetime of some orbits. Titania's $J_2$ and $C_{22}$ gravitational coefficients and Uranus' gravitational perturbation are considered. The analysis of lifetime sensitivity due to possible errors in $J_2$ and $C_{22}$ values is investigated using multiple regression models. Simulations were performed for eccentricity equal 10-4, and lifetime maps were constructed. The results show that low-altitude orbits have longer lifetimes due to the balance between the disturbance of Uranus and the gravitational coefficients of Titania. The results also show that non-zero values of periapsis longitude ($\omega$) and ascending node longitude ($\Omega$) are essential to increase lifespan. Furthermore, the results indicate that the most economical maneuver occurs for final orbits of radius equal to 1050 km, this is observed for all inclination values.Comment: 5 pages, 3 figures, 1 table. arXiv admin note: substantial text overlap with arXiv:2203.1444

TEN-YEAR OUTCOMES OF TIPS FOR BUDD-CHIARI SYNDROME: SYSTEMATIC REVIEW AND META-ANALYSIS

ABSTRACT Background: Budd-Chiari syndrome (BCS) results from the obstruction of the hepatic venous flow, usually at the level of the hepatic vein or inferior vena cava. When left untreated, it can progress with several complications, including liver cirrhosis. Transjugular intrahepatic portosystemic shunt (TIPS) appears to be effective in a subgroup of BCS patients. Objective: To perform a systematic review and meta-analysis of TIPS effectiveness in BCS treatment, considering the survival rate, reduction in portosystemic pressure, need for liver transplantation, technical failure, and shunt dysfunction for up to 10 years of follow-up. Methods: We evaluated 17 studies published in PubMed, Science Direct, Web of Science, and SCOPUS databases, which used TIPS as a treatment for BCS, comprising 618 subjects between 18 and 78 years old. We assessed the bias risk by the NOS, NHI, and JBI scales for cohort studies, before-after studies, and case series, respectively. We conducted the meta-analyses by extracting the number of events and the total patients evaluated to perform the proportion meta-analyses using the R software (“meta” package - version 4.9-6). Results: The pooled results (95%CI) showed a 19% (25.9-12.5%) rate of portosystemic pressure reduction, 6% (1-12%) rate for the need for liver transplants despite the use of TIPS, 2% (1-6%) technical failure rate, 30% (18-46%) shunt dysfunction rate, and 88% (81-93%) for the mean frequency of patients alive between 1 and 10 years after the procedure. We stratified survival rate and found an 86% (74-93%) prevalence of living subjects during less than five years, 92% (83-97%) at five years, and a 77% frequency (68-83%) of patients alive ten years after the TIPS placement. Conclusion: TIPS is an effective treatment for BCS, providing a high 10-year frequency of living patients and a significant decrease in portosystemic pressure. The need for liver transplants after TIPS and the technical failure rate is low

Mapping Long-Term Natural Orbits about Titania, a Satellite of Uranus

Close polar and circular orbits are of great interest for the exploration of natural satellites. There are still no studies in the literature investigating orbits around Titania, the largest satellite of Uranus. In this work, we present results of a set of numerical simulations carried out to obtain long-duration orbits for a probe around Titania. Through an expansion of the gravitational potential up to second order, the asymmetry of the gravitational field due to Titania’s coefficient C22, the zonal coefficient J2, and the gravitational perturbation of Uranus is considered. The analysis of lifetime sensitivity due to possible errors in the values of J2 and C22 is investigated using multiple regression models. Simulations were performed for different eccentricity values, and lifetime maps were constructed. The results show that low-altitude and near-circular orbits have longer lifetimes due to the balance between the disturbance of Uranus and the gravitational coefficients of Titania. The results also show that non-zero values of the longitude of periapsis (ω) and longitude of the ascending node (Ω) are essential to increase the lifetime up to eight times compared to cases where ω=Ω=0∘. We also show that an orbit with eccentricity 10−3 is the most affected by errors in the values of J2 and C22

MODELAGEM FLUVIAL DO RESERVATÓRIO DE JUSANTE DA UHE TUCURUÍ PARA AVALIAÇÃO DE LOCAIS PARA IMPLANTAÇÃO DE TURBINAS HIDROCINÉTICAS

Este estudo considera a modelagem fluvial do reservatório de jusante da UHE Tucuruí para a avaliação de locais onde possam ser instaladas turbinas hidrocinéticas para o aproveitamento do potencial remanescente da hidrelétrica. O escoamento foi simulado através do modelo de Saint-Venant. Para tanto, foram levantados dados de topobatimetria para elaboração do modelo de elevação do terreno; dados de substrato para obtenção do coeficiente de Manning; e dados de vazão e nível d'água para as condições de contorno. As velocidades e profundidades foram simuladas para as vazões máxima e mínima observadas no período entre 2008 e 2013. Foram selecionados 10 pontos no canal do reservatório, onde as maiores velocidades e profundidades foram observadas através das simulações. Nesse caso, as velocidades variaram entre 0,6 e 2,0 m/s; e as profundidades variaram entre 11,93 e 42,60 m, demonstrando que, na área de estudo, há potencial para utilização da energia remanescente através da implantação de turbinas hidrocinéticas

Reliability of one-repetition maximum test in untrained young adult men and women

BACKGROUND: The one repetition maximum (1RM) test is the most widely used method to analyze muscular strength. However, the 1RM reliability may be dependent on gender.OBJECTIVE: The purpose of the study was to investigate the reliability of one-repetition maximum (1RM) test in untrained young adult men and women.METHODS: Thirteen men and eleven women between 18-35 years were recruited. All subjects performed the 1RM tests in the bench press (BP), Smith machine squat (SQ), and arm curl (AC) in four sessions separated by 48 to 72 hours of recovery. At each measurement session, the subjects performed exercise-specific warm-ups and were given three attempts to reach a peak strength level for each exercise.RESULTS: There was a significant session-by-time interaction (P < 0.05) in BP and SQ, while men reached a stabilized load between sessions 2-3, women stabilized their load between sessions 1-2. Significant increases (P < 0.05) in maximal strength occurred between session 1 and 4 in BP (men = + 10.5%, women = + 13.1%), SQ (men = +17.6%, women = +20.7%), and AC (men = +7.5%, women = +11.7%).CONCLUSION: We conclude that the reliability of the 1RM tests in multiple-joint exercises may be gender dependent.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq