34 research outputs found
Extravehicular tunnel suit system Patent
Design and development of flexible tunnel for use by spacecrews in performing extravehicular activitie
Improving Orbit Estimates for Incomplete Orbits with a New Approach to Priors -- with Applications from Black Holes to Planets
We propose a new approach to Bayesian prior probability distributions
(priors) that can improve orbital solutions for low-phase-coverage orbits,
where data cover less than approximately 40% of an orbit. In instances of low
phase coverage such as with stellar orbits in the Galactic center or with
directly-imaged exoplanets, data have low constraining power and thus priors
can bias parameter estimates and produce under-estimated confidence intervals.
Uniform priors, which are commonly assumed in orbit fitting, are notorious for
this. We propose a new observable-based prior paradigm that is based on
uniformity in observables. We compare performance of this observable-based
prior and of commonly assumed uniform priors using Galactic center and
directly-imaged exoplanet (HR 8799) data. The observable-based prior can reduce
biases in model parameters by a factor of two and helps avoid under-estimation
of confidence intervals for simulations with less than about 40% phase
coverage. Above this threshold, orbital solutions for objects with sufficient
phase coverage such as S0-2, a short-period star at the Galactic center with
full phase coverage, are consistent with previously published results. Below
this threshold, the observable-based prior limits prior influence in regions of
prior dominance and increases data influence. Using the observable-based prior,
HR 8799 orbital analyses favor lower eccentricity orbits and provide stronger
evidence that the four planets have a consistent inclination around 30 degrees
to within 1-sigma. This analysis also allows for the possibility of
coplanarity. We present metrics to quantify improvements in orbital estimates
with different priors so that observable-based prior frameworks can be tested
and implemented for other low-phase-coverage orbits.Comment: Published in AJ. 23 pages, 14 figures. Monte Carlo chains are
available in the published article, or are available upon reques
Phase 1 Trial of Fruquintinib in Patients with Advanced Solid Tumors: Results of the Dose Escalation Phase.
Background: Fruquintinib (Fruq) is a potent, highly selective, novel vascular endothelial growth factor receptor (VEGFR) -1, -2, and -3 tyrosine kinase inhibitor. In the Phase III FRESCO trial1 that led to the drug approval in China, Fruq improved the median overall survival in patients with metastatic colorectal cancer (mCRC) in the third line or later setting when compared to placebo (9.3 vs 6.6 months); hazard ratio 0.65 (95% CI, 0.51-0.83; P \u3c .001),
Methods: This is a Phase 1 open-label, dose escalation/dose expansion study conducted in the US (NCT03251378). The primary objectives are to evaluate the safety and tolerability of Fruq in pts with advanced solid tumors and to determine the recommended phase 2 dose (RP2D). A secondary objective is to evaluate anticancer activity. There were 2 dose cohorts: 3mg and 5 mg qd, each on a 3 weeks on, 1 week (3/1) off schedule.
Results: Fourteen pts were enrolled: 7 (6 evaluable) pts in each dose cohort. Fruq was generally well-tolerated. There was 1 dose-limiting toxicity (DLT) of grade 4 hypertension in the 3 mg cohort, and no DLTs in the 5 mg cohort. The RP2D was 5 mg qd (3/1), which is also the approved dose in China. Two other serious adverse events were reported: colon obstruction and left breast cellulitis; neither was suspected to be drug-related. All 14 pts reported AEs; the most common were vomiting (57%), nausea (50%), constipation (50%, proteinuria (50%), hypertension (50%), dysphonia (43%), anorexia (36%), and dyspepsia (36%). Ten pts were evaluable for best objective response; results were partial response 3, stable disease 6, and disease progression 1. Objective response rate was 3/14 (21.4%) and disease control rate was 9/14 (64.3%). Mean duration on study drug was 5.3 months.
Conclusion: Fruq is generally well-tolerated in heavily pretreated patients. The RP2D in US pts is 5 mg qd (3/1). The safety profile is consistent with that of other anti-angiogenic tyrosine kinase inhibitors. There is preliminary evidence of anticancer activity in pts with advanced solid tumors. The dose expansion phase of the study is ongoing. Further investigation of Fruq in pts with mCRC is planned. 1. JAMA 2018; 319:2486
Testing the gravitational theory with short-period stars around our Galactic Center
Motion of short-period stars orbiting the supermassive black hole in our
Galactic Center has been monitored for more than 20 years. These observations
are currently offering a new way to test the gravitational theory in an
unexplored regime: in a strong gravitational field, around a supermassive black
hole. In this proceeding, we present three results: (i) a constraint on a
hypothetical fifth force obtained by using 19 years of observations of the two
best measured short-period stars S0-2 and S0-38 ; (ii) an upper limit on the
secular advance of the argument of the periastron for the star S0-2 ; (iii) a
sensitivity analysis showing that the relativistic redshift of S0-2 will be
measured after its closest approach to the black hole in 2018.Comment: 4 pages, 2 figures, proceedings of the 52nd Rencontres de Moriond,
Gravitation Sessio
Stellar Populations in the Central 0.5 pc of Our Galaxy III: The Dynamical Sub-structures
We measure the 3D kinematic structures of the young stars within the central
0.5 parsec of our Galactic Center using the 10 m telescopes of the W.~M.~Keck
Observatory over a time span of 25 years. Using high-precision measurements of
positions on the sky, and proper motions and radial velocities from new
observations and the literature, we constrain the orbital parameters for each
young star. Our results show two statistically significant sub-structures: a
clockwise stellar disk with 18 candidate stars, as has been proposed before,
but with an improved disk membership; a second, almost edge-on plane of 10
candidate stars oriented East-West on the sky that includes at least one IRS 13
star. We estimate the eccentricity distribution of each sub-structure and find
that the clockwise disk has = 0.39 and the edge-on plane has =
0.68. We also perform simulations of each disk/plane with incompleteness and
spatially-variable extinction to search for asymmetry. Our results show that
the clockwise stellar disk is consistent with a uniform azimuthal distribution
within the disk. The edge-on plane has an asymmetry that cannot be explained by
variable extinction or incompleteness in the field. The orientation, asymmetric
stellar distribution, and high eccentricity of the edge-on plane members
suggest that this structure may be a stream associated with the IRS 13 group.
The complex dynamical structure of the young nuclear cluster indicates that the
star formation process involved complex gas structures and dynamics and is
inconsistent with a single massive gaseous disk.Comment: 41 pages, 26 figures, 13 tables, 2 appendices. Accepted for
publication in Ap
A population of dust-enshrouded objects orbiting the Galactic black hole
The central 0.1 parsecs of the Milky Way host a supermassive black hole
identified with the position of the radio and infrared source Sagittarius A*, a
cluster of young, massive stars (the S stars) and various gaseous features.
Recently, two unusual objects have been found to be closely orbiting
Sagittarius A*: the so-called G sources, G1 and G2. These objects are
unresolved (having a size of the order of 100 astronomical units, except at
periapse, where the tidal interaction with the black hole stretches them along
the orbit) and they show both thermal dust emission and line emission from
ionized gas. G1 and G2 have generated attention because they appear to be
tidally interacting with the supermassive Galactic black hole, possibly
enhancing its accretion activity. No broad consensus has yet been reached
concerning their nature: the G objects show the characteristics of gas and dust
clouds but display the dynamical properties of stellar-mass objects. Here we
report observations of four additional G objects, all lying within 0.04 parsecs
of the black hole and forming a class that is probably unique to this
environment. The widely varying orbits derived for the six G objects
demonstrate that they were commonly but separately formed
Burkitt lymphoma masquerading as cardiac tamponade
A 61 year old man presented with diffuse large B cell lymphoma of the skin of the back of the shoulder which was excised and treated with chemotherapy (CHOP regime) in 1998. He was in complete remission till he presented in 2002 with extranodal marginal zone lymphoma of the parotid gland for which he underwent superficial parotidectomy and radiotherapy. He continued in remission till 2006 when he presented with recurrent pericardial effusion and tamponade. At median sternotomy, pericardial effusion was drained, an anterior pericardiectomy was done and a left posterior pericardial window made, and an enlarged hard paraaortic lymph node excised. Histology, immunocytochemistry and chromosome analysis revealed Burkitt lymphoma. Patient underwent chemotherapy with CODOX-M regime and continues in remission. This report is unusual on account of the highly atypical presentation of Burkitt lymphoma as cardiac tamponade, only a few cases having been reported previously, the occurrence of three lymphomas of different pathological and genomic profiles in one patient over a period of eight years and the relatively slow rate of growth of an otherwise fulminant tumour with high tumour doubling time. A review of literature with special emphasis on chromosomal diagnosis, transformation of other lymphomas into Burkitt lymphoma and mediastinal and cardiac involvement with Burkitt lymphoma is presented
Improving Orbit Estimates for Incomplete Orbits with a New Approach to Priors: with Applications from Black Holes to Planets
We propose a new approach to Bayesian prior probability distributions (priors) that can improve orbital solutions for low-phase-coverage orbits, where data cover less than ~40% of an orbit. In instances of low phase coverage—such as with stellar orbits in the Galactic center or with directly imaged exoplanets—data have low constraining power and thus priors can bias parameter estimates and produce underestimated confidence intervals. Uniform priors, which are commonly assumed in orbit fitting, are notorious for this. We propose a new observable-based prior paradigm that is based on uniformity in observables. We compare performance of this observable-based prior and of commonly assumed uniform priors using Galactic center and directly imaged exoplanet (HR 8799) data. The observable-based prior can reduce biases in model parameters by a factor of two and helps avoid underestimation of confidence intervals for simulations with less than ~40% phase coverage. Above this threshold, orbital solutions for objects with sufficient phase coverage—such as S0-2, a short-period star at the Galactic center with full phase coverage—are consistent with previously published results. Below this threshold, the observable-based prior limits prior influence in regions of prior dominance and increases data influence. Using the observable-based prior, HR 8799 orbital analyses favor low-eccentricity orbits and provide stronger evidence that the four planets have a consistent inclination of ~30° to within 1σ. This analysis also allows for the possibility of coplanarity. We present metrics to quantify improvements in orbital estimates with different priors so that observable-based prior frameworks can be tested and implemented for other low-phase-coverage orbits
Testing General Relativity with Stellar Orbits around the Supermassive Black Hole in Our Galactic Center
We demonstrate that short-period stars orbiting around the supermassive black hole in our Galactic center can successfully be used to probe the gravitational theory in a strong regime. We use 19 years of observations of the two best measured short-period stars orbiting our Galactic center to constrain a hypothetical fifth force that arises in various scenarios motivated by the development of a unification theory or in some models of dark matter and dark energy. No deviation from general relativity is reported and the fifth force strength is restricted to an upper 95% confidence limit of |α|<0.016 at a length scale of λ=150 astronomical units. We also derive a 95% confidence upper limit on a linear drift of the argument of periastron of the short-period star S0-2 of |ω_(S0-2)|<1.6×10^(-3)  rad/yr, which can be used to constrain various gravitational and astrophysical theories. This analysis provides the first fully self-consistent test of the gravitational theory using orbital dynamic in a strong gravitational regime, that of a supermassive black hole. A sensitivity analysis for future measurements is also presented