526 research outputs found
Influence of iron aggregation on the catalytic performance of desilicated MFI in the DeNO(x) process
[EN] In the present study, an influence of the iron aggregation in conventional and micro-mesoporous MFI on their catalytic activity in the NO reduction with ammonia (DeNO(x) process) was studied. Modification of MFI zeolite properties was done by the desilication in the presence of NaOH and TPAOH (tertapropylammonium hydroxide). In the next step, the samples were modified with iron by ion-exchange with the use of a conventional solution of Fe cations (FeSO4) and a solution of iron triple-metallic aggregates (oligocations) ([Fe-3(OAc)(6)O(H2O)(3)](+)). Both of the applied modification techniques (desilication and modification with Fe-3 oligocations) increased the catalytic activity of the MFI zeolite in the DeNO(x) process. This increased catalytic activity was connected with changes in sample porosity, Si/Al ratio, topology, as well as aggregation and dispersion of iron species on the catalyst surface, which was investigated by N-2-sorption, XRD, ICP, NMR, HRTEM and UV-vis-DRS techniques.This work was carried out in the frame of project No. 0670/IP3/2016/74 from the Polish Ministry of Science and Higher Education in the years 2016-2019 and in the frame of project No. 2012/05/B/ST5/00269 from the National Science Centre (Poland). U. D. acknowledges to the Spanish Government by the funding (MAT2017-82288-C2-1-P).Rutkowska, M.; Borcuch, A.; Marzec, A.; Kowalczyk, A.; Samojeden, B.; Moreno, J.; DĂaz Morales, UM.... (2020). Influence of iron aggregation on the catalytic performance of desilicated MFI in the DeNO(x) process. Microporous and Mesoporous Materials. 304:1-8. https://doi.org/10.1016/j.micromeso.2018.09.015S1830
Constraining the nature of the accreting binary in CXOGBS J174623.5-310550
We report optical and infrared observations of the X-ray source CXOGBS
J174623.5-310550. This Galactic object was identified as a potential quiescent
low-mass X-ray binary accreting from an M-type donor on the basis of optical
spectroscopy and the broad Halpha emission line. The analysis of X-shooter
spectroscopy covering 3 consecutive nights supports an M2/3-type spectral
classification. Neither radial velocity variations nor rotational broadening is
detected in the photospheric lines. No periodic variability is found in I- and
r'-band light curves. We derive r' = 20.8, I = 19.2 and Ks = 16.6 for the
optical and infrared counterparts with the M-type star contributing 90% to the
I-band light. We estimate its distance to be 1.3-1.8 kpc. The lack of radial
velocity variations implies that the M-type star is not the donor star in the
X-ray binary. This could be an interloper or the outer body in a hierarchical
triple. We constrain the accreting binary to be a < 2.2 hr orbital period
eclipsing cataclysmic variable or a low-mass X-ray binary lying in the
foreground of the Galactic Bulge.Comment: (9 pages, 5 figures, accepted for publication in MNRAS
Spectroscopic classification of X-ray sources in the Galactic Bulge Survey
We present the classification of 26 optical counterparts to X-ray sources
discovered in the Galactic Bulge Survey. We use (time-resolved) photometric and
spectroscopic observations to classify the X-ray sources based on their
multi-wavelength properties. We find a variety of source classes, spanning
different phases of stellar/binary evolution. We classify CX21 as a quiescent
cataclysmic variable (CV) below the period gap, and CX118 as a high accretion
rate (nova-like) CV. CXB12 displays excess UV emission, and could contain a
compact object with a giant star companion, making it a candidate symbiotic
binary or quiescent low mass X-ray binary (although other scenarios cannot be
ruled out). CXB34 is a magnetic CV (polar) that shows photometric evidence for
a change in accretion state. The magnetic classification is based on the
detection of X-ray pulsations with a period of 81 2 min. CXB42 is
identified as a young stellar object, namely a weak-lined T Tauri star
exhibiting (to date unexplained) UX Ori-like photometric variability. The
optical spectrum of CXB43 contains two (resolved) unidentified double-peaked
emission lines. No known scenario, such as an AGN or symbiotic binary, can
easily explain its characteristics. We additionally classify 20 objects as
likely active stars based on optical spectroscopy, their X-ray to optical flux
ratios and photometric variability. In 4 cases we identify the sources as
binary stars.Comment: Accepted for publication in MNRA
Increased percentage of T cells with the expression of CD127 and CD132 in hypertrophic adenoid in children with otitis media with effusion
The hypertrophic adenoid may promote chronic suppurative otitis media in children as it fulfills its immune function. The number of lymphocytes in the adenoid and their cooperation in the immune response depend of on their proliferation and migration to the effector sites. Interleukin 7 (IL-7) is essential for the normal development and function lymphocytes. IL-7 plays pivotal role for activation and proliferation of T and B cells. The heterodimeric interleukin-7 receptor (IL-7R) is composed of the IL-7Rι (127) and the common cytokine receptor γc (CD132). The aim of this study was to evaluate the percentage of lymphocytes T (CD4+ and CD8+) with IL-7R (CD127 and CD132) expression in hypertrophic adenoid in children suffering with otitis media with effusion for a duration of 3 months. Adenoid excised due to hypertrophy with or without chronic otitis media with effusion was used as study material. CD4+ CD127+, CD4+132+, CD8+CD127+ and CD8+CD132+ cell subpopulations were identified using monoclonal antibodies and flow cytometry. The percentage of CD4+ and CD8+ T cells with CD127 receptor expression in hypertrophic adenoid of children with otitis media with effusion was statistically significantly higher than in hypertrophic adenoid group. The percentage of CD4+ T cells with CD132 expression in the study group was statistically significantly higher than in the reference group. The percentage of CD8+ T cells with CD132+ expression was not statistically different in both groups. The increased percentage of T lymphocytes with IL-7R expression (CD127 and CD132) in hypertrophic adenoid seems to influence the quantity of lymphocytes and upset the immunological function of tonsils which can influence the course of otitis media with effusion
Astrocytic Ion Dynamics: Implications for Potassium Buffering and Liquid Flow
We review modeling of astrocyte ion dynamics with a specific focus on the
implications of so-called spatial potassium buffering, where excess potassium
in the extracellular space (ECS) is transported away to prevent pathological
neural spiking. The recently introduced Kirchoff-Nernst-Planck (KNP) scheme for
modeling ion dynamics in astrocytes (and brain tissue in general) is outlined
and used to study such spatial buffering. We next describe how the ion dynamics
of astrocytes may regulate microscopic liquid flow by osmotic effects and how
such microscopic flow can be linked to whole-brain macroscopic flow. We thus
include the key elements in a putative multiscale theory with astrocytes
linking neural activity on a microscopic scale to macroscopic fluid flow.Comment: 27 pages, 7 figure
The Galactic Nova Rate: Estimates from the ASAS-SN and Gaia Surveys
We present the first estimate of the Galactic nova rate based on optical
transient surveys covering the entire sky. Using data from the All-Sky
Automated Survey for Supernovae (ASAS-SN) and \textit{Gaia} -- the only two
all-sky surveys to report classical nova candidates -- we find 39 confirmed
Galactic novae and 7 additional unconfirmed candidates discovered from
2019--2021, yielding a nova discovery rate of yr. Using
accurate Galactic stellar mass models, three-dimensional dust maps, and
incorporating realistic nova light curves, we have built a sophisticated
Galactic nova model that allows an estimate of the recovery fraction of
Galactic novae from these surveys over this time period. The observing
capabilities of each survey are distinct: the high cadence of ASAS-SN makes it
sensitive to fast novae, while the broad observing filter and high spatial
resolution of \textit{Gaia} make it more sensitive to highly reddened novae
across the entire Galactic plane and bulge. Despite these differences, we find
that ASAS-SN and \textit{Gaia} give consistent Galactic nova rates, with a
final joint nova rate of yr. This inferred nova rate is
substantially lower than found by many other recent studies. Critically
assessing the systematic uncertainties in the Galactic nova rate, we argue that
the role of faint fast-fading novae has likely been overestimated, but that
subtle details in the operation of transient alert pipelines can have large,
sometimes unappreciated effects on transient recovery efficiency. Our predicted
nova rate can be directly tested with forthcoming red/near-infrared transient
surveys in the southern hemisphere.Comment: 24 pages, 9 figure
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