Abstract
We present structural parameters from a wide-field homogeneous imaging survey of Milky Way satellites carried out with the MegaCam imagers on the 3.6 m Canada–France–Hawaii Telescope and 6.5 ...m Magellan-Clay telescope. Our survey targets an unbiased sample of “outer halo” satellites (i.e., substructures having galactocentric distances greater than 25 kpc) and includes classical dSph galaxies, ultra-faint dwarfs, and remote globular clusters. We combine deep, panoramic
gr
imaging for 44 satellites and archival
gr
imaging for 14 additional objects (primarily obtained with the DECam instrument as part of the Dark Energy Survey) to measure photometric and structural parameters for 58 outer halo satellites. This is the largest and most uniform analysis of Milky Way satellites undertaken to date and represents roughly three-quarters (58/81 ≃ 72%) of all known outer halo satellites. We use a maximum-likelihood method to fit four density laws to each object in our survey: exponential, Plummer, King, and Sérsic models. We systematically examine the isodensity contour maps and color–magnitude diagrams for each of our program objects, present a comparison with previous results, and tabulate our best-fit photometric and structural parameters, including ellipticities, position angles, effective radii, Sérsic indices, absolute magnitudes, and surface brightness measurements. We investigate the distribution of outer halo satellites in the size–magnitude diagram and show that the current sample of outer halo substructures spans a wide range in effective radius, luminosity, and surface brightness, with little evidence for a clean separation into star cluster and galaxy populations at the faintest luminosities and surface brightnesses.
Abstract
The Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) is a dual-hemisphere, near-infrared (NIR), spectroscopic survey with the goal of producing a chemodynamical mapping of ...the Milky Way. The targeting for APOGEE-2 is complex and has evolved with time. In this paper, we present the updates and additions to the initial targeting strategy for APOGEE-2N presented in Zasowski et al. (2017). These modifications come in two implementation modes: (i) “Ancillary Science Programs” competitively awarded to Sloan Digital Sky Survey IV PIs through proposal calls in 2015 and 2017 for the pursuit of new scientific avenues outside the main survey, and (ii) an effective 1.5 yr expansion of the survey, known as the Bright Time Extension (BTX), made possible through accrued efficiency gains over the first years of the APOGEE-2N project. For the 23 distinct ancillary programs, we provide descriptions of the scientific aims, target selection, and how to identify these targets within the APOGEE-2 sample. The BTX permitted changes to the main survey strategy, the inclusion of new programs in response to scientific discoveries or to exploit major new data sets not available at the outset of the survey design, and expansions of existing programs to enhance their scientific success and reach. After describing the motivations, implementation, and assessment of these programs, we also leave a summary of lessons learned from nearly a decade of APOGEE-1 and APOGEE-2 survey operations. A companion paper, F. Santana et al. (submitted; AAS29036), provides a complementary presentation of targeting modifications relevant to APOGEE-2 operations in the Southern Hemisphere.
The Hercules stream as seen by APOGEE-2 South Hunt, Jason A. S; Bovy, Jo; Pérez-Villegas, Angeles ...
Monthly Notices of the Royal Astronomical Society,
02/2018, Letnik:
474, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
The Hercules stream is a group of comoving stars in the solar neighbourhood, which can potentially be explained as a signature of either the outer Lindblad resonance (OLR) of a fast Galactic ...bar or the corotation resonance (CR) of a slower bar. In either case, the feature should be present over a large area of the disc. With the recent commissioning of the APOGEE-2 Southern spectrograph we can search for the Hercules stream at (l, b) = (270°, 0), a direction in which the Hercules stream, if caused by the bar's OLR, would be strong enough to be detected using only the line-of-sight velocities. We clearly detect a narrow, Hercules-like feature in the data that can be traced from the solar neighbourhood to a distance of about 4 kpc. The detected feature matches well the line-of-sight velocity distribution from the fast-bar (OLR) model. Confronting the data with a model where the Hercules stream is caused by the CR of a slower bar leads to a poorer match, as the corotation model does not predict clearly separated modes, possibly because the slow-bar model is too hot.
The energy conversion of nickel-impregnated coconut shells using supercritical water has not yet been explored. The impregnation process was conducted at room temperature and a pH of 5.80 for 72 h. ...Characterization of the prepared sample confirmed the presence of nickel nanoparticles with an average size of 7.15 nm. The gasification of control and impregnated samples was performed at 400–500 °C, biomass loading from 20 to 30 wt% and residence time from 20 to 60 min. The response surface methodology (RSM) approach, with a Box–Behnken method, was used to design the experiments. The optimization model showed that the non-catalytic process at 500 °C, 60 min and 20 wt% of biomass loading could promote an H2 yield of 8.8 mol% and gasification efficiency of 47.6%. The gasification of nickel-impregnated coconut shells showed significantly higher gasification efficiency (58.6%) and hydrogen yield (17.2 mol%) with greater carbon and hydrogen efficiencies (109.4 and 116.9%) when compared to the non-catalytic process. The presence of nickel particles in the biomass matrix as nanocatalysts promoted higher hydrogen production and supercritical water gasification efficiency.
Abstract
In this work, we use structural properties of the Milky Way’s outer halo (
R
G
> 25 kpc) satellites (dwarf spheroidal galaxies, ultra-faint dwarf (UFD) galaxies and globular clusters (GCs)) ...derived from deep, wide-field, and homogeneous data to present evidence of a correlation in the Sérsic index versus effective radius plane followed by a large fraction of outer halo GCs and satellite dwarf galaxies. We show that this correlation can be entirely reproduced by fitting empirical relations in the central surface brightness versus absolute magnitude and Sérsic index versus absolute magnitude parameter spaces, and by assuming the existence of two types of outer halo GCs: one of high surface brightness (HSB group), with properties similar to those of inner halo clusters; and another of low surface brightness (LSB group), which share characteristics with dwarf spheroidal and UFD galaxies. Given the similarities of LSB clusters with dwarf spheroidal and UFD galaxies, we discuss the possibility that outer halo clusters also originated inside dark matter halos and that tidal forces from different host galaxy potentials are responsible for the different properties between HSB and LSB clusters.
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► This work details the efficiency of microwave solvothermal synthesis in obtaining ZnS nanocrystals. ► The structure, surface chemical composition and optical properties were ...investigated as function of the precursor. ► According to the different precursors used, the PL behavior of ZnS causes a red shift which enables the design of LEDs with different colors. ► Photoluminescence is one more interesting property for technological applications this material.
In this article, we report the development of an efficient and rapid microwave assisted solvothermal (MAS) method to prepare wurtzite ZnS nanoparticles at 413K using different precursors. The materials obtained were analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (MET) ultraviolet–visible (UV–vis) and photoluminescence (PL) measurements. The structure, surface chemical composition and optical properties were investigated as a function of the precursor. In addition, effects as well as merits of microwave heating on the processing and characteristics of ZnS nanoparticles obtained are reported. The possible formation mechanism and optical properties of these nanoparticles were also reported.
Impregnation of metal catalysts into biomass before thermochemical conversion may provide benefits of increased selective reactivity to obtain desirable products. In this work, coconut shells ...impregnated with increasing loadings of nickel were successfully prepared using a room-temperature impregnation method using a nickel salt solution at 1 and 2 molar (M) concentrations. The physicochemical characterization of the 2 M impregnated sample revealed the presence of 5.6 wt% of nickel with a particle size of 13.5 nm. The nickel-impregnated samples’ supercritical water gasification (SCWG) was conducted with biomass loading ranging from 20 wt% to 30 wt%, at temperatures between 400 °C and 500 °C, and residence times from 20 to 60 min. Higher nickel loading, higher temperatures and longer reaction times promoted the production of H2 and CO2 up to 15 and 79 mol%. Higher nickel loading also led to an increased Hydrogen Gasification Efficiency value of up to 133%. The analysis of hydrochars suggested that increasing nickel loading enhanced the reduction in nickel ions to the Ni0 nanoparticles, leading to higher H2. Additionally, the chemical composition of the liquid product showed the significant ability of nickel to promote lignin decomposition into phenol, facilitating the phenol hydrogenation reaction and subsequent gas production.
Our goal was to explore self‐care practices among men who have sex with men in the context of Mpox in Brazil. This study used qualitative research methods, including interviews and thematic analysis, ...to collect and analyze data from male participants across the Brazilian territory. The narratives unveil men's perspectives on self‐care, risk reduction, and health beliefs during the Mpox pandemic. Our findings highlight a multifaceted approach to self‐care among men, encompassing hygiene, physical contact management, mask usage, skin lesion vigilance, and adherence to official guidelines. Men's attitudes toward sexual behaviors emphasize the importance of reducing sexual partners, practicing safe sex, and combating misinformation through accurate information dissemination. The development of these behaviors and self‐care practices can be facilitated by nurses guided by Dorothea Orem's Self‐Care Theory, supported by patient‐centered care, with strategies to address and confront the stigma associated with the disease and provide emotional support. Thus, the study underscores the pivotal role of self‐care in mitigating infection risks, especially in the context of emerging infectious diseases. It acknowledges the impact of socio‐cultural factors and healthcare policies on men's preventive measures. However, it also recognizes limitations, such as potential bias due to stigma concerns and a nonrepresentative sample. Ultimately, the research advocates for tailored education, promotion of gender equity, and healthcare empowerment to effectively manage health risks in such contexts.
Abstract
We describe a deep, systematic imaging study of satellites in the outer halo of the Milky Way. Our sample consists of 58 stellar overdensities—i.e., substructures classified as either ...globular clusters, classical dwarf galaxies, or ultra-faint dwarf galaxies—that are located at Galactocentric distances of
R
GC
≥ 25 kpc (outer halo) and out to ∼400 kpc. This includes 44 objects for which we have acquired deep, wide-field,
g
- and
r
-band imaging with the MegaCam mosaic cameras on the 3.6 m Canada–France–Hawaii Telescope and the 6.5 m Magellan-Clay telescope. These data are supplemented by archival imaging, or published
gr
photometry, for an additional 14 objects, most of which were discovered recently in the Dark Energy Survey (DES). We describe the scientific motivation for our survey, including sample selection, observing strategy, data reduction pipeline, calibration procedures, and the depth and precision of the photometry. The typical 5
σ
point-source limiting magnitudes for our MegaCam imaging—which collectively covers an area of ≈52 deg
2
—are
g
lim
≃ 25.6 and
r
lim
≃ 25.3 AB mag. These limits are comparable to those from the coadded DES images and are roughly a half-magnitude deeper than will be reached in a single visit with the Large Synoptic Survey Telescope. Our photometric catalog thus provides the deepest and most uniform photometric database of Milky Way satellites available for the foreseeable future. In other papers in this series, we have used these data to explore the blue straggler populations in these objects, their density distributions, star formation histories, scaling relations, and possible foreground structures.
Poincianella pyramidalis (Tul.) LP Queiroz (Fabaceae) is an endemic tree of northeastern Brazil, occurring mainly in the Caatinga. Its medicinal use is widespread and is an important therapeutic ...option against diarrhea, dysentery, and respiratory and urinary infections, among other diseases. In this study we determined the chemical marker and evaluated the interaction between P. pyramidalis extract and a commercial antimicrobial through the use of biological and analytical models. To obtain the extract, an ethanol-water mixture (50:50 v/v) was used as solvent. It was nebulized in a spray dryer using colloidal silicon dioxide as a drying adjuvant. The extract (ENPp) was subjected to HPLC analysis to verify the presence of certain secondary metabolites. The Minimum Inhibitory Concentration (MIC) of the extract against Gram-negative bacteria was determined by broth microdilution and the MIC of synthetic antimicrobial drugs in the presence and absence of the extract. The antioxidant activity of ENPp was evaluated by the DPPH method. The compatibility between the antimicrobial and the extract was evaluated by thermal analysis (TG/DTA). The acute toxicity of the extract was evaluated in vivo in rodents. The results indicate significant additive action of the extract on synthetic antibiotics, considerable antioxidant activity and absence of toxicity. This extract shows high potential for the development of formulations for antimicrobial therapy when used with a vegetable-active ingredient.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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