Novel orbits of Mercury and Venus enabled using low-thrust propulsion

Exploration of the inner planets of the Solar System is vital to significantly enhance the understanding of the formulation of Earth and other planets. This paper therefore considers the development of novel orbits of both Mercury and Venus to enhance the opportunities for remote sensing. Continuous low-thrust propulsion is used to extend the critical inclination of highly elliptical orbits at each planet, which are shown to require very small acceleration magnitudes. Unlike other bodies in the Solar System, natural sun-synchronous orbits do not exist at Mercury or Venus. This research therefore also uses continuous acceleration to enable both circular and elliptical sun-synchronous orbits, which could significantly simplify the spacecraft thermal environment. Considerably high thrust levels are however required to enable these orbits, which could not be provided by current propulsion systems

Extension of Martian orbits using continuous low-thrust propulsion

There has recently been significant interest in exploration of the Martian surface and atmosphere with a view to future human exploration. Thus missions must be developed which are responsive to these scientific goals. This work therefore develops novel orbits around Mars using continuous low-thrust propulsion to enable new and unique investigations of the red planet. This paper considers the use of continuous acceleration, using Solar Electric Propulsion, to alter the critical inclination of Highly Elliptical Orbits away from the conventional values, to any inclination required to optimally fulfill the mission objectives. This allows the spacecraft to spend a large amount of time over a region of interest as a result of apoareion dwell, thus allowing enhanced opportunities for remote sensing. In addition to this, the extension of existing circular Sun-synchronous orbits is considered as well as the development of Sun-synchronous Highly Elliptical Orbits, which force the ascending node angle to rotate at the same rate as the mean rotation of the Sun, whilst maintaining a constant argument of perihelion over the orbit. Thus, allowing simplification of the spacecraft thermal environment. Notably, we can enable these orbits using existing Electric Propulsion technology

Short- and Long-Term Propagation of Spacecraft Orbits

The Planetary Observer Planning Software (POPS) comprises four computer programs for use in designing orbits of spacecraft about planets. These programs are the Planetary Observer High Precision Orbit Propagator (POHOP), the Planetary Observer Long-Term Orbit Predictor (POLOP), the Planetary Observer Post Processor (POPP), and the Planetary Observer Plotting (POPLOT) program. POHOP and POLOP integrate the equations of motion to propagate an initial set of classical orbit elements to a future epoch. POHOP models shortterm (one revolution) orbital motion; POLOP averages out the short-term behavior but requires far less processing time than do older programs that perform long-term orbit propagations. POPP postprocesses the spacecraft ephemeris created by POHOP or POLOP (or optionally can use a less accurate internal ephemeris) to search for trajectory-related geometric events including, for example, rising or setting of a spacecraft as observed from a ground site. For each such event, POPP puts out such user-specified data as the time, elevation, and azimuth. POPLOT is a graphics program that plots data generated by POPP. POPLOT can plot orbit ground tracks on a world map and can produce a variety of summaries and generic ordinate-vs.-abscissa plots of any POPP data

Drug susceptibility profile and pathogenicity of H7N9 influenza virus (Anhui1 lineage) with R292K substitution

Neuraminidase inhibitors (NAIs) are the only available licensed therapeutics against human H7N9 influenza virus infections. The emergence of NAI-resistant variants of H7N9viruses with an NA R292K mutation poses a therapeutic challenge. A comprehensive understanding of the susceptibility of these viruses to clinically available NAIs, non-NAIs and their combinations is crucial for effective treatment. In this study, by using limited serial passage and plaque purification, an R292K variant of the Anhui1 lineage was isolated from a patient with clinical evidence of resistance to oseltamivir. In vitro and cell-based assays confirmed a high level of resistance conferred by the R292K mutation to oseltamivir carboxylate and a moderate level of resistance to zanamivir and peramivir. Non-NAI antivirals, such as T-705, ribavirin and NT-300, efficiently inhibited both the variant and the wild-type in cell-based assays. A combination of NAIs and non-NAIs did not exhibit a marked synergistic effect against the R292K variant. However, the combination of two non-NAIs (T-705 and ribavirin) exhibited significant synergism against the mutant virus. In experimentally infected mice, the variant showed delayed onset of symptoms, a reduced viral load and attenuated lethality compared with the wild-type. Our study suggested non-NAIs should be tested clinically for H7N9 patients with a sustained high viral load. Possible drug combination regimens, such as T-705 plus ribavirin, should be further tested in animal models. The pathogenicity and transmissibility of the R292K H7N9 variant should be further assessed with genetically well-characterized pairs of viruses and, most-desirably, with competitive fitness experiments.published_or_final_versio

High versus standard doses interferon-alpha in the treatment of naïve chronic hepatitis C patients in Taiwan: a 10-year cohort study

BACKGROUND: Interferon-alpha monotherapy is effective in less than one-third patients with chronic hepatitis C. The dose-effect, tolerability and durability of interferon-alpha treatment and its long-term effect on the prevention of cirrhosis and hepatocellular carcinoma in naïve Taiwanese patients with chronic hepatitis C have not been well investigated. We conducted the present cohort study treated with high and standard interferon-alpha to illustrate the issues. METHODS: We performed a long-term virologic and histological follow-up of 214 chronic hepatitis C patients treated with interferon-alpha, 3 million units (3-MU, n = 80) or 6-MU (n = 134) thrice weekly for 24 weeks, in Taiwan between 1992 and 2001. RESULTS: There was no difference in the incidence of discontinuation between 3-MU and 6-MU groups (4/80, 5.0% versus 10/134. 7.5%). The 6-MU group had similar incidence of adverse events with the 3-MU group, except that 6-MU group had significantly higher incidence of psychological manifestations, mainly presented as irritability. The rates of sustained virological response (SVR) were significantly higher in 6-MU regimen (37.1%) than in 3-MU regimen (23.7%, p < 0.05) in per protocol analysis. Based on multivariate analysis, baseline viral load was strongly associated with SVR, followed by hepatitis C virus genotype, interferon-alpha regimen, and liver fibrosis. A histological improvement in necroinflammatory activity, but not in fibrosis was observed in the follow-up biopsy performed 0.5–5.5 years (mean: 1.9 years, n = 51) after end-of-treatment. Among patients without SVR, there was more activity improvement in 6-MU group. The durability of SVR was 100% (18/18) and 97.8% (45/46) for 3-MU and 6-MU group, respectively, in a mean follow-up period of 6.81 years (5.25–9.18 years). For 163 baseline non-cirrhotic patients, 9 of 84 (10.7%) non-responders and 3 of 79 (3.8%) sustained responders progressed to cirrhosis during a mean follow-up period of 5.52 and 5.74 years, respectively (p = 0.067, Kaplan-Meier survival analysis, log-rank test). For all 200 patients, hepatocellular carcinoma was detected in 12 of 113 (10.6%) non-responders and one of 87 (1.1%) sustained responders during a mean follow-up period of 5.67 and 5.73 years, respectively (p < 0.01, Kaplan-Meier survival analysis, log-rank test). CONCLUSION: We confirm the dose effect of interferon-alpha in chronic hepatitis C. Six-MU regimen had better efficacy than 3-MU regimen in virologic and histological responses. Both regimens had good tolerability and durability in Taiwan. Sustained response could reduce the incidence of cirrhotic change and hepatocarcinogenesis

A study assessing the association of glycated hemoglobin a1C (HbA1C) associated variants with HbA1C, chronic kidney disease and diabetic retinopathy in populations of asian ancestry

10.1371/journal.pone.0079767PLoS ONE811-POLN

Determinants of consumers’ intentions to share knowledge and intentions to purchase on s-commerce sites: incorporating attitudes toward persuasion attempts into a social exchange model

This research explores s-commerce users’ intentions to purchase and to share knowledge by incorporating ‘attitudes toward persuasion attempts,’ ‘ease of use,’ and ‘perceived usefulness’ into a social exchange theory model. A survey using an on-site purposive sampling technique was used to recruit the respondents, and an interception technique was used to approach the consumers. A total of 471 Korean consumers participated in this research. Based on 471 Korean social-commerce users, our results reveal that social exchange belief factors and a site’s usability affect user satisfaction, which subsequently affects users’ intentions to purchase and to share knowledge. In addition, attitudes toward persuasion attempts moderate the effect of satisfaction on users’ purchase intentions. Keywords: social exchange theory, attitudes toward persuasion attempts, intention to share knowledge, social exchange belief

Avian Influenza Virus Glycoproteins Restrict Virus Replication and Spread through Human Airway Epithelium at Temperatures of the Proximal Airways

Transmission of avian influenza viruses from bird to human is a rare event even though avian influenza viruses infect the ciliated epithelium of human airways in vitro and ex vivo. Using an in vitro model of human ciliated airway epithelium (HAE), we demonstrate that while human and avian influenza viruses efficiently infect at temperatures of the human distal airways (37°C), avian, but not human, influenza viruses are restricted for infection at the cooler temperatures of the human proximal airways (32°C). These data support the hypothesis that avian influenza viruses, ordinarily adapted to the temperature of the avian enteric tract (40°C), rarely infect humans, in part due to differences in host airway regional temperatures. Previously, a critical residue at position 627 in the avian influenza virus polymerase subunit, PB2, was identified as conferring temperature-dependency in mammalian cells. Here, we use reverse genetics to show that avianization of residue 627 attenuates a human virus, but does not account for the different infection between 32°C and 37°C. To determine the mechanism of temperature restriction of avian influenza viruses in HAE at 32°C, we generated recombinant human influenza viruses in either the A/Victoria/3/75 (H3N2) or A/PR/8/34 (H1N1) genetic background that contained avian or avian-like glycoproteins. Two of these viruses, A/Victoria/3/75 with L226Q and S228G mutations in hemagglutinin (HA) and neuraminidase (NA) from A/Chick/Italy/1347/99 and A/PR/8/34 containing the H7 and N1 from A/Chick/Italy/1347/99, exhibited temperature restriction approaching that of wholly avian influenza viruses. These data suggest that influenza viruses bearing avian or avian-like surface glycoproteins have a reduced capacity to establish productive infection at the temperature of the human proximal airways. This temperature restriction may limit zoonotic transmission of avian influenza viruses and suggests that adaptation of avian influenza viruses to efficient infection at 32°C may represent a critical evolutionary step enabling human-to-human transmission