3,345 research outputs found
Dynamical mass determination and partial eclipses of the heartbeat star HD 181793
Funding: ACC and TGW acknowledge support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1.We identify the bright Am-type star HD 181793 to be a previously-unknown eclipsing, chemically peculiar heartbeat binary, the second of its kind known. The system carries an orbital period of P = 11.47578275 ± 0.00000055 days. We use TESS photometry and LCOGT NRES radial velocity data to build a self-consistent orbital model and determine the fundamental stellar characteristics of the primary. We use a spectral separation method to unveil the secondary and measure the masses of both stars. The radial velocity amplitude of the primary, K1 = 47.41+0.13-0.12 km s-1, gives a mass M1 = 1.57 ± 0.01 Mâ. The secondary radial velocity amplitude K2 = 84.95+0.12-0.09 km s-1 yields a mass ratio and a secondary mass M2 = 0.87 ± 0.01 Mâ. From the spectral energy distribution and Gaia parallax we find a radius R1 = 2.04 ± 0.05 Râ. The grazing transit profile and spectroscopic luminosity ratio indicate R2 = 1.04+0.15-0.10 Râ, suggesting an early-K spectral type. We show that the heartbeat feature in the TESS light curve can be explained by time-varying ellipsoidal variation, driven by the orbital eccentricity of e = 0.3056+0.0024-0.0026, and relativistic beaming of the light of the primary. We find no evidence of tidally-excited oscillations.Peer reviewe
Synthesis, In Silico Studies, Antiprotozoal and Cytotoxic Activities of QuinolineâBiphenyl Hybrids
This is the pre-peer reviewed version of the following article: Synthesis, In Silico Studies, Antiprotozoal and Cytotoxic Activities of QuinolineâBiphenyl Hybrids, which has been published in final form at https://doi.org/10.1002/slct.201903835. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived VersionsThe synthesis, in silico studies, antiprotozoal and cytotoxic activities of eleven quinolineâbiphenyl hybrids are described herein. The structure of the synthesized products was elucidated by a combination of spectrometric analyses. The synthesized compounds were evaluated against Plasmodium falciparum, and amastigotes forms both Leishmania (V) panamensis and Trypanosoma cruzi. Cytotoxicity was evaluated against human Uâ937 macrophages. 8âphenylquinoline (4âa) showed similar activity than meglumine antimoniate and 4â(quinolinâ8âyl)phenol (4âb) exhibited an activity similar to that of benznidazole. 8â(3,4âdimethoxyphenyl) quinoline (4âk) showed the best activity against P. falciparum. Although these compounds were toxic for mammalian Uâ937 cells, however they may still have potential to be considered as candidates for drug development because of their antiparasite activity. Molecular docking was used to determine the in silico inhibition of some of the designed compounds against PfLDH and cruzipain, two important pharmacological targets involved in antiparasitic diseases. All hybrids were docked to the threeâdimensional structures of PfLDH and T. cruzi cruzipain as enzymes using AutoDock Vina. Notably, the docking results showed that the most active compounds 4â(quinolinâ8âyl)phenol (4âb, CE50: 11.33â
ÎŒg/mL for T. cruzi) and 8â(3,4âdimethoxyphenyl) quinoline (4âk, CE50: 8.84â
ÎŒg/mL for P. falciparum) exhibited the highest scoring pose (â7.5 and â7.7â
kcal/mol, respectively). This result shows a good correlation between the predicted scores with the experimental data profile, suggesting that these ligands could act as competitive inhibitors of PfLDH or T. cruzi cruzipain enzymes, respectively. Finally, in silico ADME studies of the quinoline hybrids showed that these novel compounds have suitable drugâlike properties, making them potentially promising agents for antiprotozoal therapy
Synthesis and in-vitro evaluation of s-allyl cysteine ester-caffeic acid amide hybrids as potential anticancer agents
We have synthesized a series of S-allyl cysteine ester-caffeic acid amide hybrids and evaluated them in order to determine their possible anticancer activity and selectivity in colorectal cancer, which is still one of the leading causes of morbidity and mortality worldwide. All compounds were tested against SW480 human colon adenocarcinoma cells and the non-malignant CHO-K1 cell line. Among the tested compounds, hybrids 6e, 9a, 9b, 9c and 9e exhibited the highest effect on viability (IC50 SW480-48h= 0.18, 0.12, 0.12, 0.11 and 0.12 mM, respectively) and selectivity (SI= 10.3, 1.5, >83.33, >90.91 and >83.33, respectively) in a time- and concentration-dependent manner. Besides, our results were even better as regards lead compounds (S-allyl cysteine and caffeic acid) and the standard drug (5-FU). Additionally, these five compounds induced mitochondrial depolarization that could be related with an apoptotic process. Moreover, hybrids 6e, 9a and 9e induced cell cycle arrest in G2/M phase, and compound 9c in S- phase, which suggests that these hybrid compounds could have also a cytostatic effect in SW480 cell line. The SAR analysis showed that hydroxyl groups increased the activity, besides, there was not a clear relationship between the antitumor properties and the length of the alkyl chain. Since hybrid compounds were much more selective than the conventional drug (5-FU), this make them promising candidates for further studies against colorectal cancer
Infrared Variability of Two Dusty White Dwarfs
The most heavily polluted white dwarfs often show excess infrared radiation
from circumstellar dust disks, which are modeled as a result of tidal
disruption of extrasolar minor planets. Interaction of dust, gas, and
disintegrating objects can all contribute to the dynamical evolution of these
dust disks. Here, we report on two infrared variable dusty white dwarfs, SDSS
J1228+1040 and G29-38. For SDSS J1228+1040, compared to the first measurements
in 2007, the IRAC [3.6] and [4.5] fluxes decreased by 20% by 2014 to a level
also seen in the recent 2018 observations. For G29-38, the infrared flux of the
10 m silicate emission feature became 10% stronger between 2004 and 2007,
We explore several scenarios that could account for these changes, including
tidal disruption events, perturbation from a companion, and runaway accretion.
No satisfactory causes are found for the flux drop in SDSS J1228+1040 due to
the limited time coverage. Continuous tidal disruption of small planetesimals
could increase the mass of small grains and concurrently change the strength of
the 10 m feature of G29-38. Dust disks around white dwarfs are actively
evolving and we speculate that there could be different mechanisms responsible
for the temporal changes of these disks.Comment: ApJ, in pres
Soil pH and organic matter content add explanatory power to Northern Lapwing Vanellus vanellus distribution models and suggest soil amendment as a conservation measure on upland farmland
Habitat associations of farmland birds are well studied, yet few have considered relationships between species distribution and soil properties. Charadriiform waders (shorebirds) depend upon penetrable soils, rich in invertebrate prey. Many species, such as the Northern Lapwing Vanellus vanellus, have undergone severe declines across Europe, despite being targeted by agri-environment measures. This study assessed whether there were additive effects of soil variables (depth, pH and organic matter content) in explaining Lapwing distribution, after controlling for known habitat relationships, at 89 farmland sites across Scotland. The addition of these soil variables and their association with elevation improved model fit by 55\%, in comparison with models containing only previously established habitat relationships. Lapwing density was greatest at sites at higher elevation, but only those with less peaty and less acidic soil. Lapwing distribution is being constrained between intensively managed lowland farmland with favourable soil conditions and upland sites where lower management intensity favours Lapwings but edaphic conditions limit their distribution. Trials of soil amendments such as liming are needed on higher elevation grassland sites to test whether they could contribute to conservation management for breeding Lapwings and other species of conservation concern that depend upon soil-dwelling invertebrates in grassland soils, such as Eurasian Curlew Numenius arquata, Common Starling Sturnus vulgaris and Ring Ouzel Turdus torquatus. Results from such trials could support improvement and targeting of agri-environment schemes and other conservation measures in upland grassland systems
Simulations of imperfect refractive index matching in scanning laser optical tomography and a method for correction
Since additive manufacturing has become increasingly popular in prototyping, printed optics are also beginning to enter the market. Novel characterization methods for printed optics are needed because traditional, destructive methods often do not work on these optics. The scope of investigation is also different for additively manufactured optics. Homogeneity of subtractive manufactured optics such as glass lenses is usually granted but for printed optics the interfaces in-between layers can cause absorption, scattering or refraction. Functionalized optics can also have characteristics such as fluorescence that cannot be tested with traditional methods. The presented work tries to fill the void for this particular challenge by studying two non-destructive methods for optical characterization of such components and expanding their use by clever combination. In Scanning Laser Optical Tomography (SLOT), a needle-like beam is formed and focused into the sample. The sample is scanned to form projection images and rotated to allow for reconstruction, which yields volumetric data about scattering, transmission and fluorescence of sample structures. Simulated SLOT measurements with imperfect Refractive Index (RI) matching of sample and medium are presented. A method to correct distorted measurements is presented and evaluated. The simulations imply that a measurement with a RI mismatch of up to 0.1 can still yield reasonable results.
Copyright 2023 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited
Do Students Value On-Campus Field-Based Education? A Case Study of Science Educational Initiatives in the Jock Marshall Reserve
Fieldwork, known for fostering more engaging and authentic learning experiences, is an established tradition in higher education which is changing; increasingly run on-campus for financial and logistical reasons and enhanced through education technologies to reflect industry practices. Here we examine student perceptions of on-campus fieldwork with the aim of understanding if on-campus fieldwork was valued and why, to be able to compare against literature on off-campus fieldwork. We explore student views on activities at the Jock Marshall Reserve, an on-campus nature reserve of Monash University, Australia using mixed-methods approach. An online survey targeted students undertaking four subjects across first to third year and received 116 responses. In alignment with off-campus fieldwork studies, we found that overwhelmingly respondents highly valued fieldwork with dominant reasons being; 1) developed skills relevant to âreal-worldâ science, 2) reinforced theoretical learning, and 3) was more engaging than traditional study, with some benefits to their wellbeing. The novel perceptions related to increased convenience and authenticity. Since a majority of respondents wished to undertake on-campus fieldwork more frequently, this study suggests that the inclusion of on-campus fieldwork should be considered within science curriculum in higher education
Background reionization history from omniscopes
The measurements of the 21-cm brightness temperature fluctuations from the
neutral hydrogen at the Epoch of Reionization (EoR) should inaugurate the next
generation of cosmological observables. In this respect, many works have
concentrated on the disambiguation of the cosmological signals from the
dominant reionization foregrounds. However, even after perfect foregrounds
removal, our ignorance on the background reionization history can significantly
affect the cosmological parameter estimation. In particular, the
interdependence between the hydrogen ionized fraction, the baryon density and
the optical depth to the redshift of observation induce nontrivial degeneracies
between the cosmological parameters that have not been considered so far. Using
a simple, but consistent reionization model, we revisit their expected
constraints for a futuristic giant 21-cm omniscope by using for the first time
Markov Chain Monte Carlo (MCMC) methods on multiredshift full sky simulated
data. Our results agree well with the usual Fisher matrix analysis on the
three-dimensional flat sky power spectrum but only when the above-mentioned
degeneracies are kept under control. In the opposite situation, Fisher results
can be inaccurate. We show that these conditions can be fulfilled by combining
cosmic microwave background measurements with multiple observation redshifts
probing the beginning of EoR. This allows a precise reconstruction of the total
optical depth, reionization duration and maximal spin temperature. Finally, we
discuss the robustness of these results in presence of unresolved ionizing
sources. Although most of the standard cosmological parameters remain weakly
affected, we find a significant degradation of the background reionization
parameter estimation in presence of nuisance ionizing sources.Comment: 22 pages, 18 figures, uses RevTex. References added, matches
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