3,348 research outputs found
Single site observations of \textit{TESS} single transit detections
Context: TESS has been successfully launched and has begin data acquisition.
To expedite the science that may be performed with the resulting data it is
necessary to gain a good understanding of planetary yields. Given the observing
strategy employed by TESS the probability of detecting single transits in long
period systems is increased. These systems require careful consideration.
Aims: To simulate the number of TESS transit detections during its 2 year
mission with a particular emphasis on single transits. Additionally, to
determine the feasibility of ground-based follow-up observations from a single
site.
Methods: A distribution of planets is simulated around the 4 million
stars in the TESS Candidate Target List. These planets are tested for
detectable transits and characterised. Based on simulated parameters the single
transit detections are further analysed to determine which are amenable to
ground-based follow-up.
Results: TESS will discover an approximate lower bound of 4700 planets with
around 460 being single transits. A large fraction of these will be observable
from a single ground-based site. This paper finds that, in a single year,
approximately 1000 transit events of around 320 unique TESS single transit
detections are theoretically observable.
Conclusions: As we consider longer period exoplanets the need for exploring
single transit detections increases. For periods days the number of
single transit detections outnumber multitransits by a factor of 3 (8218
and 257 respectively) a factor which only grows as longer period
detections are considered. Therefore, it is worth expending the extra effort
required to follow-up these more challenging, but potentially very rewarding,
discoveries. Additionally, we conclude that a large fraction of these targets
can be theoretically observed from just a single ground-based site.Comment: 12 pages, 19 figures. To be published in Astronomy and Astrophysic
mTORC1 Controls Synthesis of Its Activator GTP
In this issue of Cell Reports, Emmanuel et al. (2017) report that mTORC1 activity is regulated by purine availability. This increases the number of mTORC1 regulators to include metabolites whose synthesis mTORC1 controls
Combining metformin with lactate transport inhibitors as a treatment modality for cancer-recommendation proposal
Highly glycolytic cancer cells excrete lactate to maintain cellular homeostasis. Inhibiting lactate export by pharmacological targeting of plasma membrane lactate transporters is being pursued as an anti-cancer therapy. Work from many laboratories show that the simultaneous inhibition of lactate export and mitochondrial respiration elicits strong synthetic lethality. The mitochondrial inhibitor, metformin, has been the subject of numerous clinical trials as an anti-cancer agent. We propose that, in future clinical trials, metformin be combined with lactate transport inhibitors to exploit this synergistic interaction
Lactate jump-starts mTORC1 in cancer cells
The kinase mammalian target of rapamycin ( mTOR ) is a major regulatory hub that senses and integrates nutrient, energy, and growth factor inputs to promote cell growth. In this issue of EMBO Reports , Byun et al [1] report that high intracellular levels of lactate activate mTORC 1 in KRAS transformed cells independently of a growth factor input. This suggests a mechanism for how mTORC 1 can be co‐opted to support oncogenic growth and proliferation
A GFP-based assay for rapid screening of compounds affecting ARE-dependent mRNA turnover
A reporter transcript containing the green fluorescent protein (GFP) gene upstream of the destabilizing 3′-untranslated region (3′-UTR) of the murine IL-3 gene was inserted in mouse PB-3c-15 mast cells. The GFP-IL-3 transcript was inherently unstable due to the presence of an adenosine-uridine (AU)-rich element (ARE) in the 3′-UTR and was subject to rapid decay giving a low baseline of GFP fluorescence. Transcript stabilization with ionomycin resulted in an increase of fluorescence that is quantitated by FACS analysis of responding cells. Using this system we have identified okadaic acid as a novel stabilizing compound, and investigated the upstream signaling pathways leading to stabilization. This reporter system has the advantage of speed and simplicity over standard methods currently in use and in addition to serving as a research tool it can be easily automated to increase throughput for drug discover
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Biased Beliefs About Random Samples: Evidence from Two Integrated Experiments
Classifying post-traumatic stress disorder using the magnetoencephalographic connectome and machine learning
Given the subjective nature of conventional diagnostic methods for post-traumatic stress disorder (PTSD), an objectively measurable biomarker is highly desirable; especially to clinicians and researchers. Macroscopic neural circuits measured using magnetoencephalography (MEG) has previously been shown to be indicative of the PTSD phenotype and severity. In the present study, we employed a machine learning-based classification framework using MEG neural synchrony to distinguish combat-related PTSD from trauma-exposed controls. Support vector machine (SVM) was used as the core classification algorithm. A recursive random forest feature selection step was directly incorporated in the nested SVM cross validation process (CV-SVM-rRF-FS) for identifying the most important features for PTSD classification. For the five frequency bands tested, the CV-SVM-rRF-FS analysis selected the minimum numbers of edges per frequency that could serve as a PTSD signature and be used as the basis for SVM modelling. Many of the selected edges have been reported previously to be core in PTSD pathophysiology, with frequency-specific patterns also observed. Furthermore, the independent partial least squares discriminant analysis suggested low bias in the machine learning process. The final SVM models built with selected features showed excellent PTSD classification performance (area-under-curve value up to 0.9). Testament to its robustness when distinguishing individuals from a heavily traumatised control group, these developments for a classification model for PTSD also provide a comprehensive machine learning-based computational framework for classifying other mental health challenges using MEG connectome profiles
An examination of the effect of the TESS extended mission on southern hemisphere monotransits
Context: NASA recently announced an extended mission for TESS. As a result it
is expected that the southern ecliptic hemisphere will be re-observed
approximately two years after the initial survey. Aims: We aim to explore how
TESS re-observing the southern ecliptic hemisphere will impact the number and
distribution of mono-transits discovered during the first year of observations.
This simulation will be able to be scaled to any future TESS re-observations.
Methods: We carry out an updated simulation of TESS detections in the southern
ecliptic hemisphere. This simulation includes realistic Sector window-functions
based on the first 11 sectors of SPOC 2 min SAP lightcurves. We then extend
this simulation to cover the expected Year 4 of the mission when TESS will
re-observed the southern ecliptic fields. For recovered monotransits we also
look at the possibility of predicting the period based on the coverage in the
TESS data. Results: We find an updated prediction of 339 monotransits from the
TESS Year 1 southern ecliptic hemisphere, and that approximately 80% of these
systems (266/339) will transit again in the Year 4 observations. The Year 4
observations will also contribute new monotransits not seen in Year 1,
resulting in a total of 149 monotransits from the combined Year 1 and Year 4
data sets. We find that 75% (189/266) of recovered Year 1 monotransits will
only transit once in the Year 4 data set. For these systems we will be able to
constrain possible periods, but period aliasing due to the large time gap
between Year 1 and Year 4 observations means that the true period will remain
unknown with further spectroscopic or photometric follow-up.Comment: 6 pages, 6 figures. Version to be published Astronomy and
Astrophysic
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