Orbit optimization for ASTROD-GW and its time delay interferometry with two arms using CGC ephemeris

ASTROD-GW (ASTROD [Astrodynamical Space Test of Relativity using Optical Devices] optimized for Gravitation Wave detection) is an optimization of ASTROD to focus on the goal of detection of gravitation waves. The detection sensitivity is shifted 52 times toward larger wavelength compared to that of LISA. The mission orbits of the 3 spacecraft forming a nearly equilateral triangular array are chosen to be near the Sun-Earth Lagrange points L3, L4 and L5. The 3 spacecraft range interferometrically with one another with arm length about 260 million kilometers. In order to attain the requisite sensitivity for ASTROD-GW, laser frequency noise must be suppressed below the secondary noises such as the optical path noise, acceleration noise etc. For suppressing laser frequency noise, we need to use time delay interferometry (TDI) to match the two different optical paths (times of travel). Since planets and other solar-system bodies perturb the orbits of ASTROD-GW spacecraft and affect the (TDI), we simulate the time delay numerically using CGC 2.7 ephemeris framework. To conform to the ASTROD-GW planning, we work out a set of 20-year optimized mission orbits of ASTROD-GW spacecraft starting at June 21, 2028, and calculate the residual optical path differences in the first and second generation TDI for one-detector case. In our optimized mission orbits for 20 years, changes of arm length are less than 0.0003 AU; the relative Doppler velocities are less than 3m/s. All the second generation TDI for one-detector case satisfies the ASTROD-GW requirement.Comment: 17 pages, 7 figures, 1 tabl

Super-ASTROD: Probing primordial gravitational waves and mapping the outer solar system

Super-ASTROD (Super Astrodynamical Space Test of Relativity using Optical Devices or ASTROD III) is a mission concept with 3-5 spacecraft in 5 AU orbits together with an Earth-Sun L1/L2 spacecraft ranging optically with one another to probe primordial gravitational-waves with frequencies 0.1 microHz - 1 mHz, to test fundamental laws of spacetime and to map the outer solar system. In this paper we address to its scientific goals, orbit and payload selection, and sensitivity to gravitational waves.Comment: 7 pages, 1 figure, presented to 7th International LISA Symposium, 16-20 June 2008, Barcelona; submitted to Classical and Quantum Gravity; presentation improve

Numerical simulation of time delay interferometry for eLISA/NGO

eLISA/NGO is a new gravitational wave detection proposal with arm length of 10^6 km and one interferometer down-scaled from LISA. Just like LISA and ASTROD-GW, in order to attain the requisite sensitivity for eLISA/NGO, laser frequency noise must be suppressed to below the secondary noises such as the optical path noise, acceleration noise etc. In previous papers, we have performed the numerical simulation of the time delay interferometry (TDI) for LISA and ASTROD-GW with one arm dysfunctional by using the CGC 2.7 ephemeris. The results are well below their respective limits which the laser frequency noise is required to be suppressed. In this paper, we follow the same procedure to simulate the time delay interferometry numerically. To do this, we work out a set of 1000-day optimized mission orbits of the eLISA/NGO spacecraft starting at January 1st, 2021 using the CGC 2.7 ephemeris framework. We then use the numerical method to calculate the residual optical path differences in the second-generation TDI solutions as in our previous papers. The maximum path length difference, for all configurations calculated, is below 13 mm (43 ps). It is well below the limit which the laser frequency noise is required to be suppressed for eLISA/NGO. We compare and discuss the resulting differences due to the different arm lengths for various mission proposals -- eLISA/NGO, an NGO-LISA-type mission with a nominal arm length of 2 x 10^6 km, LISA and ASTROD-GW.Comment: 17 pages, 13 figures, 3 tables, minor changes in description to match the accepted version of Classical and Quantum Gravity. arXiv admin note: text overlap with arXiv:1102.496

Cost Effectiveness of Protease Inhibitor Monotherapy Versus Standard Triple Therapy in the Long-Term Management of HIV Patients: Analysis Using Evidence from the PIVOT Trial

BACKGROUND: Protease inhibitor (PI) monotherapy can maintain virological suppression in the majority of patients once it has been established on triple therapy and may also have the potential for substantial cost savings arising from the use of fewer drugs. However, the cost effectiveness of PI monotherapy has yet to be demonstrated. OBJECTIVES: In this study we examine the cost effectiveness of PI monotherapy with prompt return to combination therapy in the event of viral load rebound compared with ongoing triple therapy (OT) in patients with suppressed viral load on combination antiretroviral therapy (ART) in the UK. METHODS: The analysis used data from the PIVOT trial in which HIV-positive adults with suppressed viral load for ≥24 weeks on combination ART were randomised to maintain OT or to a strategy of PI monotherapy with prompt return to combination therapy if viral load rebounded. A cost-effectiveness analysis including long-term modelling was conducted. Main outcomes included UK National Health Service (NHS) costs and quality-adjusted life-years (QALYs) with comparative results presented as incremental cost-effectiveness ratios. RESULTS: PI monotherapy was cost saving as a result of large savings in ART drug costs while being no less effective in terms of QALYs in the within-trial analysis and marginally less effective with lifetime modelling. In the base-case analysis over 3 years, the incremental total cost per patient was -£6424.11 (95 % confidence interval -7418.84 to -5429.38) and incremental QALYs were 0.0051 (95 % CI -0.0479 to 0.0582), resulting in PI monotherapy 'dominating' OT. Multiple scenario analyses found that PI monotherapy was cost saving with no marked differences in QALYs. Modelling of lifetime costs and QALYs showed that PI monotherapy was associated with significant cost savings and was marginally less effective; PI monotherapy was cost effective at accepted cost-effectiveness thresholds in all but one scenario analysis. CONCLUSIONS: Under most assumptions, PI monotherapy appears to be a cost-effective treatment strategy compared with OT for HIV-infected patients who have achieved sustained virological suppression

MEMINTA CHATBASE UNTUK MEMPELAJARI TENTANG RETRAKSI AKADEMIK

Pada percobaan kedua ini, kami memperbarui data untuk chatbot yang disediakan di [1] dengan mengunggah artikel baru [2] ke server Chatbase untuk pembelajaran. Kami masih ingin mengeksplorasi keterampilan pemahaman bacaan Chatbase serta kemampuannya dalam menyampaikan konten yang diringkas atau diekstraksi secara khusus dari artikel yang disediakan [2]. Selain itu, dalam perintah yang kami berikan kepada Chatbase mengenai konten [2], kami mencoba mempelajari apakah kecerdasan buatan dapat menghubungkan konten yang dibaca dengan prinsip-prinsip yang tecantum di [3-4]. Kami menyediakan percakapan rinci dengan Chatbase sebagai berikut. Perintah 1: Apa pembelajaran utama dari artikel ini? Chatbase: Artikel ini membahas pentingnya retraksi dalam penelitian ilmiah dan menyarankan cara untuk meningkatkan proses retraksi. Penulis berpendapat bahwa retraksi pada dasarnya tidak buruk, melainkan merupakan cara praktis untuk memperbaiki kesalahan dan memperkuat upaya ilmiah. Artikel tersebut menyarankan bahwa mewajibkan pengungkapan kekurangan dapat mencegah pernyataan yang berlebihan dalam sebuah penelitian dan bahwa menguraikan empat jenis informasi jika ada retraksi informasi dapat mendorong peneliti dan institusi untuk mendukung retraksi jika diperlukan. Artikel tersebut juga menyebutkan ceklis integritas publikasi yang dapat membantu menunjukkan masalah atau kekeliruan tanpa memerlukan pernyataan resmi atas pelanggaran atau kesalahan yang dilakukan

Gravitational Waves in Viable f(R) Models

We study gravitational waves in viable $f(R)$ theories under a non-zero background curvature. In general, an $f(R)$ theory contains an extra scalar degree of freedom corresponding to a massive scalar mode of gravitational wave. For viable $f(R)$ models, since there always exits a de-Sitter point where the background curvature in vacuum is non-zero, the mass squared of the scalar mode of gravitational wave is about the de-Sitter point curvature $R_{d}\sim10^{-66}eV^{2}$. We illustrate our results in two types of viable $f(R)$ models: the exponential gravity and Starobinsky models. In both cases, the mass will be in the order of $10^{-33}eV$ when it propagates in vacuum. However, in the presence of matter density in galaxy, the scalar mode can be heavy. Explicitly, in the exponential gravity model, the mass becomes almost infinity, implying the disappearance of the scalar mode of gravitational wave, while the Starobinsky model gives the lowest mass around $10^{-24}eV$, corresponding to the lowest frequency of $10^{-9}$ Hz, which may be detected by the current and future gravitational wave probes, such as LISA and ASTROD-GW.Comment: 18 pages, 6 figures, several statements and references adde

Long-term efficacy and safety of a treatment strategy for HIV infection using protease inhibitor monotherapy: 8-year routine clinical care follow-up from a randomised, controlled, open-label pragmatic trial (PIVOT).

BACKGROUND: Treatment-simplification strategies are important tools for patient-centred management. We evaluated long-term outcomes from a PI monotherapy switch strategy. METHODS: Eligible participants attending 43 UK treatment centres had a viral load (VL) below 50 copies/ml for at least 24 weeks on combination ART. Participants were randomised to maintain ongoing triple therapy (OT) or switch to a strategy of physician-selected PI monotherapy (PI-mono) with prompt return to combination therapy if VL rebounded. The primary outcome, previously reported, was loss of future drug options after 3 years, defined as new intermediate/high level resistance to at least one drug to which the participant's virus was considered sensitive at trial entry. Here we report resistance and disease outcomes after further extended follow-up in routine care. The study was registered as ISRCTN04857074. FINDINGS: We randomised 587 participants to OT (291) or PI-mono (296) between Nov 4, 2008, and July 28, 2010 and followed them for a median of more than 8 years (100 months) until 2018. At the end of this follow-up time, one or more future drug options had been lost in 7 participants in the OT group and 6 in the PI-mono group; estimated cumulative risk by 8 years of 2.7% and 2.1% respectively (difference -0.6%, 95% CI -3.2% to 2.0%). Only one PI-mono participant developed resistance to the protease inhibitor they were taking (atazanavir). Serious clinical events (death, serious AIDS, and serious non-AIDS) were infrequent; reported in a total of 12 (4.1%) participants in the OT group and 23 (7.8%) in the PI-mono group (P = 0.08) over the entire follow-up period. INTERPRETATION: A strategy of PI monotherapy, with regular VL monitoring and prompt reintroduction of combination treatment following rebound, preserved future treatment options. Findings confirm the high genetic barrier to resistance of the PI drug class that makes them well suited for creative, patient-centred, treatment-simplification approaches. The possibility of a small excess risk of serious clinical events with the PI monotherapy strategy cannot be excluded. FUNDING: The National Institute for Health Research Health Technology Assessment programme

Alkaline rains on the Tibetan Plateau and their implication for the original pH of natural rainfall

Natural rains are generally considered as weakly acidic. Long-term measurement in the Tibetan capital city, Lhasa, reveals that alkaline rain is also natural. For the last 3 years the volume-weighted mean pH of rainwater is 7.5. Earlier observation shows even higher average pH values, such as 8.36 in the 1987-1988 period. The major cause of alkaline rain is the alkaline and soil-borne continental dusts in this semiarid area. Bicarbonate is the dominant anion in the water samples. The analysis also shows that the rainwater in this city contains few pollutants, compared with other places in the world. Measurements carried out in two additional industrial cities on the northern and northeastern Tibetan Plateau, Xining and Germu, demonstrate how fast human activities such as industrial development may increase rainwater acidity. In a period of 13 years the rainfall pH value of Germu has dropped from 8.03 to 6.8, representing a manyfold increase of the H+ concentration. Such an increase was caused by rising contents of NO3 - and SO4 -2 in the atmosphere. On the basis of the measurements on the Tibetan Plateau, evidence from other places around the world, and the experiments and calculation, the authors believe that the original pH of natural rainwater in arid and semiarid areas on this planet should be weakly alkaline because of the influence of alkaline dusts. Copyright 2002 by the American Geophysical Union.published_or_final_versio

The Laser Astrometric Test of Relativity Mission

This paper discusses new fundamental physics experiment to test relativistic gravity at the accuracy better than the effects of the 2nd order in the gravitational field strength. The Laser Astrometric Test Of Relativity (LATOR) mission uses laser interferometry between two micro-spacecraft whose lines of sight pass close by the Sun to accurately measure deflection of light in the solar gravity. The key element of the experimental design is a redundant geometry optical truss provided by a long-baseline (100 m) multi-channel stellar optical interferometer placed on the International Space Station. The geometric redundancy enables LATOR to measure the departure from Euclidean geometry caused by the solar gravity field to a very high accuracy. LATOR will not only improve the value of the parameterized post-Newtonian (PPN) parameter gamma to unprecedented levels of accuracy of 1 part in 1e8, it will also reach ability to measure effects of the next post-Newtonian order (1/c^4) of light deflection resulting from gravity's intrinsic non-linearity. The solar quadrupole moment parameter, J2, will be measured with high precision, as well as a variety of other relativistic. LATOR will lead to very robust advances in the tests of fundamental physics: this mission could discover a violation or extension of general relativity, or reveal the presence of an additional long range interaction in the physical law. There are no analogs to the LATOR experiment; it is unique and is a natural culmination of solar system gravity experiments.Comment: 8 pages, 2 figures, invited talk given at the Second International Conference on Particle and Fundamental Physics in Space (SpacePart'03), 10-12 December 2003, Washington, D