Aims.
Our goal is to explore the chemical pattern of early-type stars with planets, searching for a possible signature of planet formation. In particular, we study a likely relation between the
λ
...Boötis chemical pattern and the presence of giant planets.
Methods.
We performed a detailed abundance determination in a sample of early-type stars with and without planets via spectral synthesis. Fundamental parameters were initially estimated using Strömgren photometry or literature values and then refined by requiring excitation and ionization balances of Fe lines. We derived chemical abundances for 23 different species by fitting observed spectra with an iterative process. Synthetic spectra were calculated using the program SYNTHE together with local thermodynamic equilibrium ATLAS12 model atmospheres. We used specific opacities calculated for each star, depending on the individual composition and microturbulence velocity
v
micro
through the opacity sampling method. The complete chemical pattern of the stars were then compared to those of
λ
Boötis stars and other chemically peculiar stars.
Results.
We compared the chemical pattern of the stars in our sample (13 stars with planets and 24 stars without detected planets) with those of
λ
Boötis and other chemically peculiar stars. We have found four
λ
Boötis stars in our sample, two of which present planets and circumstellar disks (HR 8799 and HD 169142) and one without planets detected (HD 110058). We have also identified the first
λ
Boötis star orbited by a brown dwarf (
ζ
Del). This interesting pair, the
λ
Boötis star and brown dwarf, could help to test stellar formation scenarios. We found no unique chemical pattern for the group of early-type stars bearing giant planets. However, our results support, in principle, a suggested scenario in which giant planets orbiting pre-main-sequence stars possibly block the dust of the disk and result in a
λ
Boötis-like pattern. On the other hand, we do not find a
λ
Boötis pattern in different hot-Jupiter planet host stars, which does not support the idea of possible accretion from the winds of hot-Jupiters, recently proposed in the literature. As a result, other mechanisms should account for the presence of the
λ
Boötis pattern between main-sequence stars. Finally, we suggest that the formation of planets around
λ
Boötis stars, such as HR 8799 and HD 169142, is also possible through the core accretion process and not only gravitational instability.
•Novel design of a useful platform for immobilizing molecules.•Urease immobilization using harmless and safe methods for the consumer.•Magnetic biocatalyst with enhanced surface area and reusable ...urease activity.
The presence of urea in wines and other alcoholic beverages represents a critical problem since it can chemically react with ethanol, which leads to the formation of ethyl carbamate, a carcinogenic agent according to the World Health Organization. Here we report the creation of a biocatalyst for the hydrolysis of urea, which could potentially be used before bottling alcoholic drinks. For this, the effective surface area of streptavidin-labeled magnetic microparticles was amplified by functionalization with biotin-labeled hen egg lysozyme amyloid fibers. Subsequently, by using copper and hydrogen peroxide induced cross-linking of unmodified proteins (CHICUP), soybean urease was immobilized to the fibers. This gave rise to a magnetic biocatalyst with remarkable urease activity, which was maintained even after 10 reuses. We propose that this strategy could be used as a platform for immobilizing other molecules to design and develop a myriad of biocatalysts for the food industry.
Background
Patients with familial hypercholesterolemia (FH) display high levels of low‐density lipoprotein cholesterol (LDL‐c), endothelial dysfunction, and increased risk of premature ...atherosclerosis. We have previously shown that red blood cells (RBCs) from patients with type 2 diabetes induce endothelial dysfunction through increased arginase 1 and reactive oxygen species (ROS).
Objective
To test the hypothesis that RBCs from patients with FH (FH‐RBCs) and elevated LDL‐c induce endothelial dysfunction.
Methods and results
FH‐RBCs and LDL‐c >5.0 mM induced endothelial dysfunction following 18‐h incubation with isolated aortic rings from healthy rats compared to FH‐RBCs and LDL‐c <2.5 mM or RBCs from healthy subjects (H‐RBCs). Inhibition of vascular but not RBC arginase attenuated the degree of endothelial dysfunction induced by FH‐RBCs and LDL‐c >5.0 mM. Furthermore, arginase 1 but not arginase 2 was elevated in the vasculature of aortic segments after incubation with FH‐RBCs and LDL‐c >5.0 mM. A superoxide scavenger, present throughout the 18‐h incubation, attenuated the degree of endothelial dysfunction induced by FH‐RBCs and LDL‐c >5.0 mM. ROS production was elevated in these RBCs in comparison with H‐RBCs. Scavenging of vascular ROS through various antioxidants also attenuated the degree of endothelial dysfunction induced by FH‐RBCs and LDL‐c >5.0 mM. This was corroborated by an increase in the lipid peroxidation product 4‐hydroxynonenal. Lipidomic analysis of RBC lysates did not reveal any significant changes across the groups.
Conclusion
FH‐RBCs induce endothelial dysfunction dependent on LDL‐c levels via arginase 1 and ROS‐dependent mechanisms.
ABSTRACT
The origin of mercury–manganese (HgMn) stars is still poorly understood and the statistical analysis of an extensive sample of well characterized objects would be very valuable. ...Nevertheless, the compilation of a clean and reliable list of all known HgMn stars, and complete characterization of those objects, is still a pending issue. We report the identification of 13 new HgMn stars from our own spectroscopic observations and from publicly available spectral libraries. In addition, we perform a thorough literature search to give a list of 46 confirmed HgMn stars (plus a further nine suspected HgMn stars) discovered over the last years or neglected by other compilations. When required, we performed specific observations to confirm doubtful cases. For the 13 newly identified HgMn stars we derived photospheric chemical abundances by spectral synthesis. Besides Hg and Mn, which are overabundant in the whole sample, P, Ga, and Xe are overabundant in the hottest stars of the sample, and Sr, Zr, and Pt among the coolest; Y is present in most stars of the sample. Three of these new HgMn stars are members of open clusters: HD 93549 in IC 2602, HD 96473 in NGC 3532, and HD 322659 in NGC 6281. Furthermore, our sample includes HD 145842, an object remarkable for its high rotation. In fact, its projected rotational velocity of ve sin i = 124 km s−1 is the highest measured in any HgMn star and is more than 30 per cent above the theoretical limit predicted by the diffusion theory, which makes HD 145842 a challenging test case for the current models.
Abstract
In this work, chemical vapor deposition (CVD) coated carbide inserts with different hardness of P types entitled as hard, semi-hard and tough are utilized for turning of AISI 1050 steel. ...Flank wear, surface roughness, cutting force, acoustic emissions and chips morphology were considered under dry turning conditions for the comparison of the effect of cutting speed, feed rate and cutting tool hardness. The novelty of the study is to investigate comprehensively the effect of tool hardness along with cutting parameters on the the machinability characteristics. This approach provides to understand the underlying mechanism of tool wear and its influence on the surface properties of the workpiece which is useful in practice for upgraded machinability. The results indicated that the tool hardness affects flank wear dramatically followed by surface roughness and acoustic emissions values and ideal values of cutting conditions are attained with semi-hard tool. Scanning electron microscope (SEM), energy dispersive spectrum (EDX) and mapping analysis also demonstrated the wear developments are distinctive with using different types of tool hardness values. The findings depicted that tool hardness has significant impact on machining characteristics which need to be dealed under particular cutting conditions. 65 HRC of cutting tool provides better machinability in terms of surface roughness, tool wear, acoustic emissions and cutting forces followed by 60 HRC and 70 HRC respectively.
Evaporitic ecosystems of the Atacama Desert contain a rich endemic fauna, including mollusk species. A recent study performed in the freshwater snail
, endemic to the Atacama Saltpan, revealed a ...strong interdependence of genetic patterns with climatic fluctuations and landscape physiography. The species is currently listed as Critically Endangered at regional scale and as Data Deficient on the International Union for Conservation of Nature (IUCN) Red List. Here, we studied genetic diversity and demographic history of several populations of the species occurring on a connectivity gradient, including snails from new peripherical localities (Peine and Tilomonte), which were compared with topotype specimens. In addition, we reassessed the conservation status using the IUCN Red List categories and criteria considering species-specific idiosyncrasy. Phylogenetic and phylogeographical analyses indicated that snails from Peine and Tilomonte belong to
. We discovered significant differentiation in shell morphology, which was generally greater in geographically isolated populations. We also inferred six genetic clusters and a demographic expansion congruent with the wet periods that occurred at the end of the Pleistocene. Considering the highest risk category obtained,
was reassessed as Endangered at regional scale. Future conservation plans should consider the genetic assemblages as conservation units.
Context.
There is very little information to be found in the literature regarding the detection of planets orbiting chemically peculiar stars.
Aims.
Our aim is to determine the detailed chemical ...composition of the remarkable planet host star KELT-17. This object hosts a hot-Jupiter planet with 1.31
M
Jup
detected by transits, and it is one of the more massive and rapidly rotating planet hosts seen to date. We set out to derive a complete chemical pattern for this star, in order to compare it with those of chemically peculiar stars.
Methods.
We carried out a detailed abundance determination in the planet host star KELT-17 via spectral synthesis. Stellar parameters were estimated iteratively by fitting Balmer line profiles and imposing the Fe ionization balance using the SYNTHE program together with plane-parallel ATLAS12 model atmospheres. Specific opacities for an arbitrary composition and microturbulence velocity
v
micro
were calculated through the opacity sampling (OS) method. The abundances were determined iteratively by fitting synthetic spectra to metallic lines of 16 different chemical species using SYNTHE. The complete chemical pattern of KELT-17 was compared to the recently published average pattern of Am stars. We estimated the stellar radius using two methods: a) comparing the synthetic spectral energy distribution with the available photometric data and the
Gaia
parallax, and b) using a Bayesian estimation of stellar parameters using stellar isochrones.
Results.
We found over-abundances of Ti, Cr, Mn, Fe, Ni, Zn, Sr, Y, Zr, and Ba, together with subsolar values of Ca and Sc. Notably, the chemical pattern agrees with those recently published for Am stars, making KELT-17 the first exoplanet host whose complete chemical pattern is unambiguously identified with this class. The stellar radius derived by two different methods agrees to each other and with those previously obtained in the literature.
The New Zealand mudsnail
Potamopyrgus antipodarum
(Gray, 1843) has been considered as one of the most invasive mollusks worldwide and recently was listed among the 50 most damaging species in Europe. ...In the present paper, we report for the first time the presence of
P. antipodarum
in the Maule river basin, Chile. The identity of the species was based on anatomical microdissections, scanning electron microscopy comparisons, and DNA barcode analysis. This finding constitutes the southernmost record of the species until now in this country and South America.
The capability to produce pearls is widespread in the phylum Mollusca, including bivalves of the superfamily Unionoidea. Here, we identified and characterized natural pearls formed by
, a freshwater ...clam native to southern South America, using samples obtained from two lakes located in the Chilean Patagonia. Pearls were studied using light and scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. Naturally formed pearls were found in both male and female
specimens. Pearls are produced in different shapes, including spherical, ellipsoidal, buttoned, and bumpy, ranging in size from 200 µm to 1.9 mm. The internal microstructure is composed of irregular polygonal tablets, about 0.40 to 0.55 μm in thickness. EDX analysis showed that pearls are composed of calcium carbonate. FTIR and Raman spectra recorded several peaks attributable to the aragonite in pearls of this species, as has been shown in other mollusks. In addition to these results, pearls of different colors are illustrated.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
•First time that CZM is used to analyze the Plasticity Induced Crack Closure.•The method avoids the ratcheting effect in the first node after crack tip.•The parameters that governs the ...Traction-Separation law of the CZM and the influence on the PICC are discussed.•Excellent correlation with experimental results.
During the last years different numerical models based on node to node crack growth scheme have been employed to study the effect of plasticity induced crack closure (PICC). This paper presents a numerical analysis of PICC based on a cohesive zone model (CZM) ith with irreversible damage that employs a crack growth method coupled with cyclic plasticity at crack tip and phenomenological fracture. The CZM produces a plastic wake from volumetric plastic strain that is different than that generated in uncoupled methods. Thus, the proposed model generates a high deviatoric plastic strain, allowing the closure study without strain ratcheting at first node behind the crack tip. Results obtained from the proposed numerical analysis are compared with those obtained from experimental fatigue tests conducted on a 2024-T3 aluminum alloy compact-tension specimens (CT). Numerical results show an excellent correlation with those obtained experimentally highlighting the ability of the proposed CZM to capture the influence of crack tip plasticity in the evaluation of crack closure phenomenon.
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