1,230 research outputs found
An environmental analysis of the fast transient AT2018cow and implications for its progenitor and late-time brightness
The nature of the newly discovered fast blue optical transients (FBOTs) is
still puzzling astronomers. In this paper we carry out a comprehensive analysis
of the molecular gas, ionized gas and stellar populations in the environment of
the nearby FBOT AT2018cow based on ALMA, VLT/MUSE and HST/WFC3 observations. A
prominent molecular concentration of 6 ( 1) 10 is
found in the vicinity of AT2018cow, which has given rise to two active
star-forming complexes with ages of 4 1 Myr and 2.5 Myr,
respectively. Each star-forming complex has a stellar mass of 3 10
and has photoionized a giant H II region with H luminosity
even comparable to that of the 30 Dor mini-starburst region. AT2018cow is
spatially coincident with one of the star-forming complexes; however, it is
most likely to reside in its foreground since it has a much smaller extinction
than the complex. Its progenitor could have been formed at an earlier epoch in
this area; if it were from a major star-forming event, the non-detection of the
associated stellar population constrains the progenitor's age to be 10
Myr and initial mass to be 20 . We further find the
late-time brightness of AT2018cow is unlikely to be a stellar object. Its
brightness has slightly declined from 2 yr to 4 yr after explosion and is most
likely to originate from AT2018cow itself due to some powering mechanism still
working at such late times.Comment: 13 pages, 10 figures, submitted to MNRA
Thermodynamic study of benzocaine insertion into different lipid bilayers
Despite the general consensus concerning the role played by sodium channels in the molecular mechanism of local anesthetics, the potency of anaesthetic drugs also seems to be related with their solubility in lipid bilayers. In this respect, this work represents a thermodynamic study of benzocaine insertion into lipid bilayers of different compositions by means of molecular dynamics simulation. Thus, the free energy profiles associated with benzocaine insertion into symmetric lipid bilayers composed of different proportions of dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylserine were studied. From the simulation results, a maximum in the free energy (ÎG) profile was measured in the region of the lipid/solution interface. This free energy barrier appears to be very much dependent on the lipid composition of the membrane. On the other hand, the minimum free energy (ÎG) within the bilayer remained almost independent of the lipid composition of the bilayer. By repeating the study at different temperatures, it was seen how the spontaneity of benzocaine insertion into the lipid bilayer is due to an increase in the entropy associated with the process.Fil: LĂłpez Cascales, JosĂ© Javier. Universidad Politecnica de Cartagena; EspañaFil: Oliveira Costa, Sara D.. Universidad Politecnica de Cartagena; EspañaFil: Porasso, Rodolfo Daniel. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico San Luis. Instituto de MatemĂĄtica Aplicada de San Luis; Argentina. Universidad Nacional de San Luis. Facultad de Ciencias FĂsico MatemĂĄticas y Naturales. Departamento de FĂsica; Argentin
Antioxidant potential of kvasses
This study was aimed at determination of antioxidant capacity of commercial kvasses. Four different beverages (âObolonâ, âWileĆskiâ, âGubernijaâ, and Eko-Naturaâ) were purchased in local shops in Poland, one beverage (âBrottrunk Bioveganâ) originated from the German market. Antioxidan capacity of the beverages was investigated using ABTS, FRAP, and DPPH assays. The content of total phenolic compounds was determined using a FolinCiocalteuâs phenol reagent. The profile of phenolic compounds were determined using an HPLC method. The content of total phenolics ranged from 0.083 to 0.372 mg/ml; the TEAC values from 0.133 to 1.001 ÎŒmol Trolox/ml; the FRAP values from 0.893 to 3.079 ÎŒmol Fe2+/ml. The antiradical activity against DPPH radical ranged from 0.097 to 0.463 ÎŒmol Trolox/ml. A strong correlation was noted between the contents of total phenolics and results of antioxidant assays. The presence of benzoic acid in one beverage was confirmed using the HPLC method
Fast divide-and-conquer algorithms for preemptive scheduling problems with controllable processing times â A polymatroid optimization approach
We consider a variety of preemptive scheduling problems with controllable processing times on a single machine and on identical/uniform parallel machines, where the objective
is to minimize the total compression cost. In this paper, we propose fast divide-and-conquer algorithms for these scheduling problems. Our approach is based on the observation that each scheduling problem we discuss can be formulated as a polymatroid optimization problem.
We develop a novel divide-and-conquer technique for the polymatroid optimization problem and then apply it to each scheduling problem. We show that each scheduling problem can
be solved in O(Tfeas(n) log n) time by using our divide-and-conquer technique, where n is the number of jobs and Tfeas(n) denotes the time complexity of the corresponding feasible scheduling problem with n jobs. This approach yields faster algorithms for most of the scheduling problems discussed in this paper
M\"ossbauer, nuclear inelastic scattering and density functional studies on the second metastable state of Na2[Fe(CN)5NO]2H2O
The structure of the light-induced metastable state SII of
Na2[Fe(CN)5NO]2H2O 14 was investigated by transmission M\"ossbauer
spectroscopy (TMS) in the temperature range 15 between 85 and 135 K, nuclear
inelastic scattering (NIS) at 98 K using synchrotron 16 radiation and density
functional theory (DFT) calculations. The DFT and TMS results 17 strongly
support the view that the NO group in SII takes a side-on molecular orientation
18 and, further, is dynamically displaced from one eclipsed, via a staggered,
to a second 19 eclipsed orientation. The population conditions for generating
SII are optimal for 20 measurements by TMS, yet they are modest for
accumulating NIS spectra. Optimization 21 of population conditions for NIS
measurements is discussed and new NIS experiments on 22 SII are proposed
Incorporation by coordination and release of the iron chelator drug deferiprone from zinc-based metalâorganic frameworks
A series of new zinc-based metalâorganic framework materials has been prepared in which deferiprone is incorporated as a chelating ligand on infinite or tri-zinc secondary building units following deprotonation. Deferiprone is immediately released from the MOFs on treatments with 1 N hydrochloric acid or buffer, but slow release is observed in ethanoic acid
COMMENTARY: ETHICAL ISSUES OF CURRENT HEALTH-PROTECTION POLICIES ON LOW-DOSE IONIZING RADIATION
The linear no-threshold (LNT) model of ionizing-radiation-induced cancer is based on the assumption that every radiation dose increment constitutes increased cancer risk for humans. The risk is hypothesized to increase linearly as the total dose increases. While this model is the basis for radiation safety regulations, its scientific validity has been questioned and debated for many decades. The recent memorandum of the International Commission on Radiological Protection admits that the LNT-model predictions at low doses are âspeculative, unproven, undetectable and âphantomâ.â Moreover, numerous experimental, ecological, and epidemiological studies show that low doses of sparsely-ionizing or sparsely-ionizing plus highly-ionizing radiation may be beneficial to human health (hormesis/adaptive response). The present LNT-model-based regulations impose excessive costs on the society. For example, the median-cost medical program is 5000 times more cost-efficient in saving lives than controlling radiation emissions. There are also lives lost: e.g., following Fukushima accident, more than 1000 disaster-related yet non-radiogenic premature deaths were officially registered among the population evacuated due to radiation concerns. Additional negative impacts of LNT-model-inspired radiophobia include: refusal of some patients to undergo potentially life-saving medical imaging; discouragement of the study of low-dose radiation therapies; motivation for radiological terrorism and promotion of nuclear proliferation
Control Software for the SST-1M Small-Size Telescope prototype for the Cherenkov Telescope Array
The SST-1M is a 4-m Davies--Cotton atmospheric Cherenkov telescope optimized
to provide gamma-ray sensitivity above a few TeV. The SST-1M is proposed as
part of the Small-Size Telescope array for the Cherenkov Telescope Array (CTA),
the first prototype has already been deployed. The SST-1M control software of
all subsystems (active mirror control, drive system, safety system,
photo-detection plane, DigiCam, CCD cameras) and the whole telescope itself
(master controller) uses the standard software design proposed for all CTA
telescopes based on the ALMA Common Software (ACS) developed to control the
Atacama Large Millimeter Array (ALMA). Each subsystem is represented by a
separate ACS component, which handles the communication to and the operation of
the subsystem. Interfacing with the actual hardware is performed via the OPC UA
communication protocol, supported either natively by dedicated industrial
standard servers (PLCs) or separate service applications developed to wrap
lower level protocols (e.g. CAN bus, camera slow control) into OPC UA. Early
operations of the telescope without the camera were already carried out. The
camera is fully assembled and is capable to perform data acquisition using
artificial light source.Comment: In Proceedings of the 35th International Cosmic Ray Conference
(ICRC2017), Busan, Korea. All CTA contributions at arXiv:1709.0348
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