Browse
Recent Submissions
Now showing 1 - 10 of 4823
- ItemMicrolensing brown-dwarf companions in binaries detected during the 2022 and 2023 seasons(EDP Sciences for The European Southern Observatory, 2024-11) Han C; Bond IA; Udalski A; Lee C-U; Gould A; Albrow MD; Chung S-J; Hwang K-H; Jung YK; Ryu Y-H; Shvartzvald Y; Shin I-G; Yee JC; Yang H; Zang W; Cha S-M; Kim D; Kim D-J; Kim S-L; Lee D-J; Lee Y; Park B-G; Pogge RW; Abe F; Bando K; Barry R; Bennett DP; Bhattacharya A; Fujii H; Fukui A; Hamada R; Hamada S; Hamasaki N; Hirao Y; Ishitani Silva S; Itow Y; Kirikawa R; Koshimoto N; Matsubara Y; Miyazaki S; Muraki Y; Nagai T; Nunota K; Olmschenk G; Ranc C; Rattenbury NJ; Satoh Y; Sumi T; Suzuki D; Tomoyoshi M; Tristram PJ; Vandorou A; Yama H; Yamashita K; Mróz P; Szymański MK; Skowron J; Poleski R; Soszyński I; Pietrukowicz P; Kozlowski S; Rybicki KA; Iwanek P; Ulaczyk K; Wrona M; Gromadzki M; Mróz MJAims. Building on previous works to construct a homogeneous sample of brown dwarfs in binary systems, we investigate microlensing events detected by the Korea Microlensing Telescope Network (KMTNet) survey during the 2022 and 2023 seasons. Methods. Given the difficulty in distinguishing brown-dwarf events from those produced by binary lenses with nearly equal-mass components, we analyze all lensing events detected during the seasons that exhibit anomalies characteristic of binary-lens systems. Results. Using the same criteria consistently applied in previous studies, we identify six additional brown dwarf candidates through the analysis of lensing events KMT-2022-BLG-0412, KMT-2022-BLG-2286, KMT-2023-BLG-0201, KMT-2023-BLG-0601, KMT-2023-BLG-1684, and KMT-2023-BLG-1743. An examination of the mass posteriors shows that the median mass of the lens companions ranges from 0.02 M⊙ to 0.05 M⊙, indicating that these companions fall within the brown-dwarf mass range. The mass of the primary lenses ranges from 0.11 M⊙ to 0.68 M⊙, indicating that they are low-mass stars with substantially lower masses compared to the Sun.
- ItemKMT-2023-BLG-1866Lb: Microlensing super-Earth around an M dwarf host(EDP Sciences for The European Southern Observatory, 2024-07) Han C; Bond IA; Udalski A; Lee C-U; Gould A; Albrow MD; Chung S-J; Hwang K-H; Jung YK; Ryu Y-H; Shvartzvald Y; Shin I-G; Yee JC; Yang H; Zang W; Cha S-M; Kim D; Kim D-J; Kim S-L; Lee D-J; Lee Y; Park B-G; Pogge RW; Abe F; Bando K; Barry R; Bennett DP; Bhattacharya A; Fujii H; Fukui A; Hamada R; Hamada S; Hamasaki N; Hirao Y; Ishitani Silva S; Itow Y; Kirikawa R; Koshimoto N; Matsubara Y; Miyazaki S; Muraki Y; Nagai T; Nunota K; Olmschenk G; Ranc C; Rattenbury NJ; Satoh Y; Sumi T; Suzuki D; Tomoyoshi M; Tristram PJ; Vandorou A; Yama H; Yamashita K; Mróz P; Szymański MK; Skowron J; Poleski RA; Soszyński I; Pietrukowicz P; Kozłowski S; Rybicki KA; Iwanek P; Ulaczyk K; Wrona M; Gromadzki M; Mróz MJAims. We aim to investigate the nature of the short-term anomaly that appears in the lensing light curve of KMT-2023-BLG-1866. The anomaly was only partly covered due to its short duration of less than a day, coupled with cloudy weather conditions and a restricted nighttime duration. Methods. Considering the intricacy of interpreting partially covered signals, we thoroughly explored all potential degenerate solutions. Through this process, we identified three planetary scenarios that account for the observed anomaly equally well. These scenarios are characterized by the specific planetary parameters: (s, q)inner = [0.9740 ± 0.0083, (2.46 ± 1.07) × 10-5], (s, q)intermediate = [0.9779 ± 0.0017, (1.56 ± 0.25) × 10-5], and (s, q)outer = [0.9894 ± 0.0107, (2.31 ± 1.29) × 10-5], where s and q denote the projected separation (scaled to the Einstein radius) and mass ratio between the planet and its host, respectively. We identify that the ambiguity between the inner and outer solutions stems from the inner-outer degeneracy, while the similarity between the intermediate solution and the others is due to an accidental degeneracy caused by incomplete anomaly coverage. Results. Through Bayesian analysis utilizing the constraints derived from measured lensing observables and blending flux, our estimation indicates that the lens system comprises a very-low-mass planet orbiting an early M-type star situated approximately (6.2-6.5) kpc from Earth in terms of median posterior values for the different solutions. The median mass of the planet host is in the range of (0.48-0.51) M⊙, and that of the planet's mass spans a range of (2.6-4.0) ME, varying across different solutions. The detection of KMT-2023-BLG-1866Lb signifies the extension of the lensing surveys to very-low-mass planets that have been difficult to detect in earlier surveys.
- ItemActivation of arcuate nucleus GABA neurons promotes luteinizing hormone secretion and reproductive dysfunction: Implications for polycystic ovary syndrome.(Elsevier B.V., 2019-06-06) Silva MSB; Desroziers E; Hessler S; Prescott M; Coyle C; Herbison AE; Campbell REBackground Enhanced GABA activity in the brain and a hyperactive hypothalamic-pituitary-gonadal axis are associated with polycystic ovary syndrome (PCOS), the most common form of anovulatory infertility. Women with PCOS exhibit elevated cerebrospinal fluid GABA levels and preclinical models of PCOS exhibit increased GABAergic input to GnRH neurons, the central regulators of reproduction. The arcuate nucleus (ARN) is postulated as the anatomical origin of elevated GABAergic innervation; however, the functional role of this circuit is undefined. Methods We employed a combination of targeted optogenetic and chemogenetic approaches to assess the impact of acute and chronic ARN GABA neuron activation. Selective acute activation of ARN GABA neurons and their fiber projections was coupled with serial blood sampling for luteinizing hormone secretion in anesthetized male, female and prenatally androgenised (PNA) mice modelling PCOS. In addition, GnRH neuron responses to ARN GABA fiber stimulation were recorded in ex vivo brain slices. Chronic activation of ARN GABA neurons in healthy female mice was coupled with reproductive phenotyping for PCOS-like features. Findings Acute stimulation of ARN GABA fibers adjacent to GnRH neurons resulted in a significant and long-lasting increase in LH secretion in male and female mice. The amplitude of this response was blunted in PNA mice, which also exhibited a blunted LH response to GnRH administration. Infrequent and variable GABAA-dependent changes in GnRH neuron firing were observed in brain slices. Chronic activation of ARN GABA neurons in healthy females impaired estrous cyclicity, decreased corpora lutea number and increased circulating testosterone levels. Interpretation ARN GABA neurons can stimulate the hypothalamic-pituitary axis and chronic activation of ARN GABA neurons can mimic the reproductive deficits of PCOS in healthy females. Unexpectedly blunted HPG axis responses in PNA mice may reflect a history of high frequency GnRH/LH secretion and reduced LH stores, but also raise questions about impaired function within the ARN GABA population and the involvement of other circuits.
- ItemIdentifying and Prioritizing Critical Risk Factors in the Context of a High-Voltage Power Transmission Line Construction Project: A Case Study from Sri Lanka(MDPI, Basel, Switzerland, 2024-12) Weerakkody W; Rathnayaka B; Siriwardana C; Luongo A; Giunta MSThis study addresses critical risk factors in high-voltage power transmission line (HVPTL) construction projects, which are vital components of national energy infrastructure. HVPTL projects are essential for meeting energy needs but are often plagued by risks due to their linear construction nature, leading to project underperformance. However, the lack of attention to risk management often leads to project underperformance. This research aims to identify and rank these risks to facilitate effective risk management. Through literature review and preliminary surveys, 63 risk elements were identified under 14 main categories. These risks were ranked using two rounds of Delphi surveys and the analytical hierarchy process (AHP). The study focuses on a Sri Lankan HVPTL project. The most critical risk factors identified include “improper planning by the main contractor”, “delays in decision-making by the client/consultant”, “errors in initial costing”, and “inaccuracies in survey data”, with AHP analysis assigning significant weights of 43.9%, 18%, 16%, and 14.9% to these factors, respectively. Comparative analysis with similar studies reveals consistent findings, underscoring the importance of addressing delays in approvals, material unavailability, and construction-quality challenges. These results emphasize the necessity of adopting systematic risk-management techniques in HVPTL projects to mitigate uncertainties and enhance project outcomes.
- ItemKMT-2021-BLG-0284, KMT-2022-BLG-2480, and KMT-2024-BLG-0412: Three microlensing events involving two lens masses and two source stars(EDP Sciences for The European Southern Observatory, 2024-12) Han C; Udalski A; Bond IA; Lee C-U; Gould A; Albrow MD; Chung S-J; Hwang K-H; Jung YK; Ryu Y-H; Shvartzvald Y; Shin I-G; Yee JC; Yang H; Zang W; Cha S-M; Kim D; Kim D-J; Kim S-L; Lee D-J; Lee Y; Park B-G; Pogge RW; Mróz P; Szymanski MK; Skowron J; Poleski R; Soszynski I; Pietrukowicz P; Kozłowski S; Rybicki KA; Iwanek P; Ulaczyk K; Wrona M; Gromadzki M; Mróz MJ; Abe F; Barry R; Bennett DP; Bhattacharya A; Fujii H; Fukui A; Hamada R; Hirao Y; Ishitani Silva S; Itow Y; Kirikawa R; Koshimoto N; Matsubara Y; Miyazaki S; Muraki Y; Olmschenk G; Ranc C; Rattenbury NJ; Satoh Y; Sumi T; Suzuki D; Tomoyoshi M; Tristram PJ; Vandorou A; Yama H; Yamashita KAims. We carried out a project involving the systematic analysis of microlensing data from the Korea Microlensing Telescope Network survey. The aim of this project is to identify lensing events with complex anomaly features that are difficult to explain using standard binary-lens or binary-source models. Methods. Our investigation reveals that the light curves of microlensing events KMT-2021-BLG-0284, KMT-2022-BLG-2480, and KMT-2024BLG-0412 display highly complex patterns with three or more anomaly features. These features cannot be adequately explained by a binary-lens (2L1S) model alone. However, the 2L1S model can effectively describe certain segments of the light curve. By incorporating an additional source into the modeling, we identified a comprehensive model that accounts for all the observed anomaly features. Results. Bayesian analysis, based on constraints provided by lensing observables, indicates that the lenses of KMT-2021-BLG-0284 and KMT-2024-BLG-0412 are binary systems composed of M dwarfs. For KMT-2022-BLG-2480, the primary lens is an early K-type main-sequence star with an M dwarf companion. The lenses of KMT-2021-BLG-0284 and KMT-2024-BLG-0412 are likely located in the bulge, whereas the lens of KMT-2022-BLG-2480 is more likely situated in the disk. In all events, the binary stars of the sources have similar magnitudes due to a detection bias favoring binary source events with a relatively bright secondary source star, which increases detection efficiency.
- ItemNitrous oxide (N2O) synthesis by the freshwater cyanobacterium Microcystis aeruginosa(Copernicus Publications on behalf of the European Geosciences Union, 2023-02-13) Fabisik F; Guieysse B; Procter J; Plouviez M; Treude T; Bouillon SPure cultures of the freshwater cyanobacterium Microcystis aeruginosa synthesized nitrous oxide (N2O) when supplied with nitrite (NO2-) in darkness (198.9 nmol g-DW-1 h-1 after 24 h) and illumination (163.1 nmol g-DW-1 h-1 after 24 h), whereas N2O production was negligible in abiotic controls supplied with NO2- and in cultures deprived of exogenous nitrogen. N2O production was also positively correlated to the initial NO2- and M. aeruginosa concentrations but was low to negligible when nitrate (NO3-) and ammonium (NH4+) were supplied as the sole exogenous N source instead of NO2-. A protein database search revealed that M. aeruginosa possesses protein homologous to eukaryotic microalgae enzymes known to catalyze the successive reduction of NO2- into nitric oxide (NO) and N2O. Our laboratory study is the first demonstration that M. aeruginosa possesses the ability to synthesize N2O. As M. aeruginosa is a bloom-forming cyanobacterium found globally, further research (including field monitoring) is now needed to establish the significance of N2O synthesis by M. aeruginosa under relevant conditions (especially in terms of N supply). Further work is also needed to confirm the biochemical pathway and potential function of this synthesis.
- ItemOCT-based dynamic mechanical analysis of vitreous humour(Elsevier Ltd, 2024-01) Urbańska MA; Thakur SS; Kolenderska SMThe vitreous humour plays an important role in shock absorption, i.e. the damping of the mechanical movement, to protect the delicate tissues within the eye. However, this damping is different for movements with different frequencies/velocities. While the collective low-frequency (below 100 Hz) damping behaviour of the vitreous humour associated with the saccadic and lens movements is well-studied, to the best of our knowledge, the high-frequency damping behaviour of the vitreous humour, which represents the response of the microstructural components, is not exhaustively documented. Here, we utilise a non-destructive testing method called Optical Coherence Tomography (OCT) to measure the high-frequency (100–350 Hz, waves able to probe approximately 500 µm distances) biomechanical behaviour of the vitreous humour. We parametrise this behaviour by calculating the shear storage modulus, shear loss modulus and phase angle. We compare these parameters to their low-frequency counterparts obtained with a rheometer, providing a comprehensive mechanical spectrum of the vitreous humour behaviour. The processing method developed in this study and the data collected help better understand the vitreous humour shock absorption properties. Consequently, they could allow a development of better vitreous humour substitutes. The local probing of the high-frequency regime and the non-invasive character of the OCT method provide new qualities in mapping the damping behaviour.
- ItemUnderstanding intercalative modulation of G-rich sequence folding: solution structure of a TINA-conjugated antiparallel DNA triplex.(Oxford University Press, 2024-01-28) Garavís M; Edwards PJB; Serrano-Chacón I; Doluca O; Filichev VV; González CWe present here the high-resolution structure of an antiparallel DNA triplex in which a monomer of para-twisted intercalating nucleic acid (para-TINA: (R)-1-O-[4-(1-pyrenylethynyl)phenylmethyl]glycerol) is covalently inserted as a bulge in the third strand of the triplex. TINA is a potent modulator of the hybridization properties of DNA sequences with extremely useful properties when conjugated in G-rich oligonucleotides. The insertion of para-TINA between two guanines of the triplex imparts a high thermal stabilization (ΔTM = 9ºC) to the structure and enhances the quality of NMR spectra by increasing the chemical shift dispersion of proton signals near the TINA location. The structural determination reveals that TINA intercalates between two consecutive triads, causing only local distortions in the structure. The two aromatic moieties of TINA are nearly coplanar, with the phenyl ring intercalating between the flanking guanine bases in the sequence, and the pyrene moiety situated between the Watson-Crick base pair of the two first strands. The precise position of TINA within the triplex structure reveals key TINA-DNA interactions, which explains the high stabilization observed and will aid in the design of new and more efficient binders to DNA.
- ItemDark lens candidates from Gaia Data Release 3(EDP Sciences, France, for The European Southern Observatory, 2024-12) Kruszyńska K; Wyrzykowski L; Rybicki KA; Howil K; Jablońska M; Kaczmarek Z; Ihanec N; Maskoliūnas M; Bronikowski M; Pylypenko U; Udalski A; Mróz P; Poleski R; Skowron J; Szymański MK; Soszyński I; Pietrukowicz P; Kozlowski S; Ulaczyk K; Iwanek P; Wrona M; Gromadzki M; Mróz MJ; Abe F; Bando K; Barry R; Bennett DP; Bhattacharya A; Bond IA; Fukui A; Hamada R; Hamada S; Hamasaki N; Hirao Y; Ishitani Silva S; Itow Y; Koshimoto N; Matsubara Y; Miyazaki S; Muraki Y; Nagai T; Nunota K; Olmschenk G; Ranc C; Rattenbury NJ; Satoh Y; Sumi T; Suzuki D; Tristram PJ; Vandorou A; Yama HGravitational microlensing is a phenomenon that allows us to observe the dark remnants of stellar evolution, even if these bodies are no longer emitting electromagnetic radiation. In particular, it can be useful to observe solitary neutron stars or stellar-mass black holes, providing a unique window through which to understand stellar evolution. Obtaining direct mass measurements with this technique requires precise observations of both the change in brightness and the position of the microlensed star. The European Space Agency's Gaia satellite can provide both. Using publicly available data from different surveys, we analysed events published in the Gaia Data Release 3 (Gaia DR3) microlensing catalogue. Here, we describe our selection of candidate dark lenses, where we suspect the lens is a white dwarf (WD), a neutron star (NS), a black hole (BH), or a mass-gap object, with a mass in the range between the heaviest NS and the least massive BH. We estimated the mass of the lenses using information obtained from the best-fitting microlensing models, source star, Galactic model, and the expected parameter distributions. We found eleven candidates for dark remnants: one WDs, three NSs, three mass-gap objects, and four BHs.
- ItemImpact of the COVID-19 pandemic on cannabis cultivation and use in 18 countries.(Elsevier B.V., 2024-11-22) Werse B; Kamphausen G; Søgaard TF; Bear D; Audran M; Wilkins C; Potter G; Fortin D; Hakkarainen P; Faria R; Quintas J; Grigg J; Jauffret-Roustide M; Barratt MJBackground The COVID-19 pandemic and the accompanying measures to mitigate infection affected many areas of society, including the supply and use of cannabis. This paper explored how patterns of behaviour among people who cultivate cannabis were affected by the COVID-19 pandemic and restrictions. Methods An anonymous web survey of people who cultivated cannabis was conducted from Aug 2020 to Sep 2021, spanning 18 countries and 11 languages (N = 11,479). Descriptive statistics and mean comparison tests were conducted. Results Most cannabis growers reported that their practices were relatively unaffected by the COVID-related restrictions. While 35.2 % reported difficulties buying cannabis from their usual dealer, <10 % stated that access to materials needed for growing was impaired during the pandemic. Over one-quarter (28.2 %) of respondents increased their cannabis use and 21.4 % also increased cannabis cultivation (more than twice as many as those who said they were growing less or not anymore) while COVID restrictions were in place. People who lost their job or were casually employed were more likely to increase use and cultivation. Overall, the pandemic had little impact on reasons for growing, however, difficulties obtaining cannabis were mentioned as the most prevalent COVID-19-related growing motive. A small number (16 %) reported starting their growing activity during the pandemic. Italian and Portuguese growers were more likely to report shortages in supply and increases in their growing activity. Conclusions This study is the first to document an increase in cannabis cultivation activity following COVID restrictions. Increased home cultivation was not only driven by higher use as a result of home isolation, but also by disruptions of wider illegal cannabis supply. Limitations of this study include the non-representativeness of the sample as well as differences in approaches and duration of restrictions in different countries.
