Context. The GRAVITY beam-combiner at the Very Large Telescope Interferometer has recently made important contributions to many different fields of astronomy, from observations of the Galactic centre ...to the study of massive stars, young stellar objects, exoplanet atmospheres, and active galactic nuclei. These achievements were only made possible by the development of several key technologies, including the development of reliable and high-performance fringe trackers. These systems compensate for disturbances ranging from atmospheric turbulence to vibrations in the optical system, enabling long exposures and ensuring the stability of interferometric measurements. Aims. As part of the ongoing GRAVITY+ upgrade of the Very Large Telescope Interferometer infrastructure, we aim to improve the performance of the GRAVITY fringe tracker, and to enable its use by other instruments. Methods. We modified the group-delay controller to consistently maintain tracking in the white-light fringe, which is characterised by a minimum group delay. Additionally, we introduced a novel approach in which fringe-tracking is performed in the non-observable optical path length state-space using a covariance-weighted Kalman filter and an auto-regressive model of the disturbance. We outline this new state-space representation and the formalism we used to propagate the state vector and generate the control signal. While our approach is presented specifically in the context of GRAVITY/GRAVITY+, it can easily be adapted to other instruments or interfero-metric facilities. Results. We successfully demonstrate phase-delay tracking within a single fringe, with any spurious phase jumps detected and corrected in less than 100 ms. We also report a significant performance improvement, as shown by a reduction of ~30 to 40% in phase residuals, and a much better behaviour under sub-optimal atmospheric conditions. Compared to what was observed in 2019, the median residuals have decreased from 150 nm to 100 nm on the Auxiliary Telescopes and from 250 nm to 150 nm on the Unit Telescopes. Conclusions. The improved phase-delay tracking combined with white-light fringe tracking means that from now on, the GRAVITY fringe tracker can be used by other instruments operating in different wavebands. The only limitation remains the need for an adjustment of the optical path dispersion.
ABSTRACT The dark compact object at the centre of the Milky Way is well established to be a supermassive black hole with mass $M_{\bullet } \sim 4.3 \times 10^6 \, {\rm M}_{\odot }$, but the nature ...of its environment is still under debate. In this work, we used astrometric and spectroscopic measurements of the motion of the star S2, one of the closest stars to the massive black hole, to determine an upper limit on an extended mass composed of a massive vector field around Sagittarius A*. For a vector with effective mass $10^{-19} \lesssim m_\mathrm{ s} \lesssim 10^{-18} \, \rm eV$, our Markov chain Monte Carlo analysis shows no evidence for such a cloud, placing an upper bound $M_{\rm cloud} \lesssim 0.1 \% \, M_{\bullet }$ at 3σ confidence level. We show that dynamical friction exerted by the medium on S2 motion plays no role in the analysis performed in this and previous works, and can be neglected thus.
This is the first meta-study to analyze the effect size of remittances on the real exchange rate (RER). Using 426 estimates from 67 studies, we found that remittances appreciate RER; however, the ...effect size differs across countries. Compared to global estimates, the mean effect of remittances on RER is significantly larger for East Asia and the Pacific, whereas the same nexus is found to be significantly smaller for Latin America and the Caribbean. Furthermore, the synthesized effect of remittances on RER is found to be significantly positive for lower-middle-income countries. Our empirical examination shows that publication selection bias is less likely in the literature. We found a genuine effect of remittances on RER appreciation. This study also provides policy recommendations and presents suggestions for future research in the field.
This article provides a comprehensive meta‐analysis that addresses an important gap in the literature by examining the relationship between remittances and inequality in recipient countries. While ...numerous empirical studies have explored this relationship, there has been no prior attempt to systematically and rigorously synthesise the evidence. This study employs advanced meta‐analysis techniques, such as Bayesian model averaging, to analyse 578 estimates reported in 45 studies. The overall finding is that the effect of remittances on inequality is negative but economically small. However, significant regional variations exist, with remittances contributing to increased inequality in South Asia, while having a substantial inequality‐reducing effect in East Asia, Eastern Europe and Latin America. In the Middle East and North Africa and Sub‐Saharan Africa, only marginal economic impact is found. We recommend that future studies should control for educational attainment, income level and institutional quality to improve the accuracy of their estimates.
Stimulating muscarinic receptors in pig bladder urothelium causes the release of a diffusable factor that inhibits contractions of the underlying detrusor muscle. We investigated whether the ...contractions of human detrusor strips elicited by the muscarinic agonist carbachol, electrical field stimulation, KCl or the neurokinin receptor agonist neurokinin A are affected by the urothelium.
Paired intact and urothelium denuded muscle strips were placed in modified gassed Tyrode’s solution at 37C. Cumulative concentration-response curves to carbachol or KCl were constructed. In other tissues the strips were stimulated electrically (1 to 40 Hz) with trains of square wave pulses 20 seconds in duration at 5-minute intervals.
Cholinergic contractions evoked by electrical field stimulation at 10 and 30 Hz or by carbachol were significantly inhibited in the presence of an intact urothelium. Contractions elicited by KCl and by 10 μM neurokinin A were not modified by the urothelium. The urothelium mediated inhibition of contractions induced by carbachol was not affected by 300 μM L-N
G-nitroarginine, 1 μM ODQ (1H-1,2,4oxadiazolo4,3-αquinoxalin-1-one), 1 μM propranolol or 5 μM indomethacin.
Muscarinic agonists stimulate the release of an inhibitory factor from the human urothelium. The factor is distinct from nitric oxide and it persists in the presence β-adrenoceptor blockade or cyclooxygenase inhibition.
The effects of anandamide on 3H‐acetylcholine release and muscle contraction were studied on the myenteric plexus‐longitudinal muscle preparation of the guinea‐pig ileum preincubated with 3H‐choline.
...Anandamide increased both basal 3H‐acetylcholine release (pEC50 6.3) and muscle tone (pEC50 6.3). The concentration‐response curves for anandamide were shifted to the right by 1 μM capsazepine (pKB 7.5 and 7.6), and by the combined blockade of NK1 and NK3 tachykinin receptors with the antagonists CP99994 plus SR142801 (each 0.1 μM). The CB1 and CB2 receptor antagonists, SR141716A (1 μM) and SR144528 (30 nM), did not modify the facilitatory effects of anandamide.
Anandamide inhibited the electrically‐evoked release of 3H‐acetylcholine (pEC50 5.8) and contractions (pEC50 5.2). The contractile response to the muscarinic agonist methacholine was not significantly affected by 10 μM anandamide.
The inhibitory effects of anandamide were not changed by either capsazepine (1 μM), SR144528 (30 nM) or CP99994 plus SR142801 (each 0.1 μM). SR141716A (1 μM) produced rightward shifts in the inhibitory concentration‐response curves for anandamide yielding pKB values of 6.6 and 6.2.
CP55940 inhibited the evoked 3H‐acetylcholine release and contractions, and SR141716A (0.1 μM) shifted the concentration‐response curves of CP55940 to the right with pKB values of 8.4 and 8.9.
The experiments confirm the existence of release‐inhibitory CB1 receptors on cholinergic myenteric neurones. We conclude that anandamide inhibits the evoked acetylcholine release via stimulation of a receptor that is different from the CB1 and CB2 receptor. Furthermore, anandamide increases basal acetylcholine release via stimulation of vanilloid receptors located at primary afferent fibres.
British Journal of Pharmacology (2001) 134, 161–167; doi:10.1038/sj.bjp.0704220
The Incidence of Smartphone Usage among Tourists Mang, Colin F.; Piper, Linda A.; Brown, Natalya R.
The international journal of tourism research,
November/December 2016, Letnik:
18, Številka:
6
Journal Article
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