We present the 2SXPS (Swift-XRT Point Source) catalog, containing 206,335 point sources detected by the Swift X-ray Telescope (XRT) in the 0.3-10 keV energy range. This catalog represents a ...significant improvement over 1SXPS, with double the sky coverage (now 3790 deg2), and several significant developments in source detection and classification. In particular, we present for the first time techniques to model the effect of stray light-significantly reducing the number of spurious sources detected. These techniques will be very important for future, large effective area X-ray missions, such as the forthcoming Athena X-ray observatory. We also present a new model of the XRT point-spread function and a method for correctly localizing and characterizing piled-up sources. We provide light curves-in four energy bands, two hardness ratios, and two binning timescales-for every source, and from these deduce that over 80,000 of the sources in 2SXPS are variable in at least one band or hardness ratio. The catalog data can be queried or downloaded via a web interface at https://www.swift.ac.uk/2SXPS, via HEASARC, or in Vizier (IX/58).
Students used an Excel spreadsheet and a Jupyter notebook located at https://chemcompute.org/jupyterhub/ to generate data in lieu of face-to-face laboratory instruction during COVID-19. This ...communication discusses strengths and weaknesses of both exercises. First, students generated absorbance data using an Excel spreadsheet, but they were overwhelmingly put off by simulated noise in their absorbance values. Second, students simulated running an HPLC using a Jupyter notebook and designed a method to separate three components of Excedrin. Students reported that the simulation helped them to understand HPLC and suggested that the online activity be used as a supplement when face-to-face laboratory instruction resumes. The main weakness of the online activities was that students did not perform any sample preparation. Therefore, they did not experience the extractions and dilutions required to prepare the analytical sample and had a difficult time working backward to calculate starting amounts from simulated sample concentrations. Concerns that students would extract answers from the equations used in the spreadsheet and Jupyter notebook were not realized.
There is a growing understanding that secondary organic aerosol (SOA) can form through reactions in atmospheric waters (i.e., clouds, fogs, and aerosol water). In clouds and wet aerosols, ...water-soluble organic products of gas-phase photochemistry dissolve into the aqueous phase where they can react further (e.g., with OH radicals) to form low volatility products that are largely retained in the particle phase. Organic acids, oligomers and other products form via radical and non-radical reactions, including hemiacetal formation during droplet evaporation, acid/base catalysis, and reaction of organics with other constituents (e.g., NH4+). This paper provides an overview of SOA formation through aqueous chemistry, including atmospheric evidence for this process and a review of radical and non-radical chemistry, using glyoxal as a model precursor. Previously unreported analyses and new kinetic modeling are reported herein to support the discussion of radical chemistry. Results suggest that reactions with OH radicals tend to be faster and form more SOA than non-radical reactions. In clouds these reactions yield organic acids, whereas in wet aerosols they yield large multifunctional humic-like substances formed via radical-radical reactions and their O/C ratios are near 1.
The 5th edition of the
Roma-BZCAT
Multifrequency Catalogue of Blazars is available in a printed version and online at the ASDC website (
http://www.asdc.asi.it/bzcat
); it is also in the NED ...database. It presents several relevant changes with respect to the past editions which are briefly described in this paper.
Nematic liquid crystals lack positional order of their constituent molecules, which share an average orientational order only. Modulated nematic liquid crystal phases also lack positional order, but ...possess a periodic variation in this direction of average orientation. In the recently discovered splay nematic (N
S
) phase the average orientational order is augmented with a periodic splay deformation of orientation perpendicular to the director. In this communication we report the first example of a splay nematic phase which is chemically induced by mixing two materials, neither of which exhibit the N
S
phase. The splay-nematic phase is identified based on its optical textures, X-ray scattering patterns, and small enthalpy of the associated phase transition. We measure the splay periodicity optically, finding it to be ∼9 μm. This unexpected generation of the splay-nematic phase through binary mixtures offers a new route to materials which exhibit this phase which complements ongoing studies into structure-property relationships and could accelerate the development of technologies utilising this remarkable polar nematic variant.
We find that the splay nematic phase can be chemically induced in binary mixtures of two materials, neither of which exhibits the splay nematic phase in their neat state.
Behavioural weight management interventions consistently produce 8–10% reductions in body weight, yet most participants regain weight after treatment ends. One strategy for extending the effects of ...behavioural interventions has been the provision of extended care. The current study is a systematic review and meta‐analysis of the literature on the effect of extended care on maintenance of weight loss. Through database searches (using PubMED, PsychInfo and Cochrane Reviews) and manual searches through reference lists of related publications, 463 studies were identified. Of these, 11 were included in the meta‐analysis and an additional two were retained for qualitative analysis. The average effect of extended care on weight loss maintenance was g = 0.385 (95% confidence interval: 0.281, 0.489; P < 0.0001). This effect would lead to the maintenance of an additional 3.2 kg weight loss over 17.6 months post‐intervention in participants provided extended care compared with control. There was no significant heterogeneity between studies, Q = 5.63, P = 0.845, and there was minimal evidence for publication bias. These findings suggest that extended care is a viable and efficacious solution to addressing long‐term maintenance of lost weight. Given the chronic disease nature of obesity, extended care may be necessary for long‐term health benefits.
ABSTRACT
Blazars research is one of the hot topics of contemporary extragalactic astrophysics. That is because these sources are the most abundant type of extragalactic γ-ray sources and are ...suspected to play a central role in multimessenger astrophysics. We have used Swift$\_$xrtproc, a tool to carry out an accurate spectral and photometric analysis of the Swift-XRT data of all blazars observed by Swift at least 50 times between December 2004 and the end of 2020. We present a database of X-ray spectra, best-fit parameter values, count rates and flux estimations in several energy bands of over 31 000 X-ray observations and single snapshots of 65 blazars. The results of the X-ray analysis have been combined with other multifrequency archival data to assemble the broad-band Spectral Energy Distributions (SEDs) and the long-term light curves of all sources in the sample. Our study shows that large X-ray luminosity variability on different time-scales is present in all objects. Spectral changes are also frequently observed with a ‘harder-when-brighter’ or ‘softer-when-brighter’ behaviour depending on the SED type of the blazars. The peak energy of the synchrotron component (νpeak) in the SED of HBL blazars, estimated from the log-parabolic shape of their X-ray spectra, also exhibits very large changes in the same source, spanning a range of over two orders of magnitude in Mrk421 and Mrk501, the objects with the best data sets in our sample.
Improving our understanding of the nuclear properties of high-Eddington-ratio (
λ
Edd
) active galactic nuclei (AGN) is necessary since at this regime the radiation pressure is expected to affect the ...structure and efficiency of the accretion disc-corona system. This may cause departures from the typical nuclear properties of low-
λ
Edd
AGN, which have been largely studied so far. We present here the X-ray spectral analysis of 14 radio-quiet,
λ
Edd
≳ 1 AGN at 0.4 ≤
z
≤ 0.75, observed with
XMM-Newton
. Optical/UV data from simultaneous Optical Monitor observations have also been considered. These quasars were selected to have relatively high values of black hole mass (
M
BH
∼ 10
8 − 8.5
M
⊙
) and bolometric luminosity (
L
bol
∼ 10
46
erg s
−1
) in order to complement previous studies of high-
λ
Edd
AGN at lower
M
BH
and
L
bol
. We studied the relation between
λ
Edd
and other key X-ray spectral parameters, such as the photon index (Γ) of the power-law continuum, the X-ray bolometric correction (
k
bol, X
), and the optical/UV-to-X-ray spectral index (
α
ox
). Our analysis reveals that, despite the homogeneous optical and supermassive black hole accretion properties, the X-ray properties of these high-
λ
Edd
AGN are quite heterogeneous. We indeed measured values of Γ between 1.3 and 2.5, at odds with the expectations based on previously reported Γ −
λ
Edd
relations, for which Γ ≥ 2 would be a ubiquitous hallmark of AGN with
λ
Edd
∼ 1. Interestingly, we found that ∼30% of the sources are X-ray weak, with an X-ray emission about a factor of ∼10 − 80 fainter than that of typical AGN at similar UV luminosities. The X-ray weakness seems to be intrinsic and not due to the presence of absorption along the line of sight to the nucleus. This result may indicate that high-
λ
Edd
AGN commonly undergo periods of intrinsic X-ray weakness. Furthermore, results from follow-up monitoring with
Swift
of one of these X-ray weak sources suggest that these periods can last for several years.
Aims. We present the results of a deep spectral analysis of all Swift observations of Mrk 421 between April 2006 and July 2006, when it reached its highest X-ray flux recorded until the end of ...2006. The peak flux was about 85 milli-Crab in the 2.0–10.0 keV band, and the peak energy (Ep) of the spectral energy distribution (SED) was often at energies higher than 10 keV. We study trends between the spectral parameters, and the physical insights the parameters provide into the underlying acceleration and emission mechanisms. Methods. We performed a spectral analysis of Swift observations to investigate trends between the spectral parameters. We searched for acceleration and energetic features phenomenologically linked to the SSC model parameters, by predicting their effects in the γ-ray band, and in particular, the spectral shape expected in the Fermi Gamma-ray Space Telescope-LAT band. Results. We confirm that the X-ray spectrum is described well by a log-parabolic distribution close to Ep, that the peak flux of the SED (Sp) is correlated with Ep, and that Ep is anti-correlated with the curvature parameter (b). The spectral evolution in the Hardness-ratio-flux plane shows both clockwise and counter-clockwise patterns. During the most energetic flares, the UV-to-soft-X-ray spectral shape requires an electron distribution spectral index of $s\simeq 2.3$. Conclusions. We demonstrate that the UV-to-X-ray emission from Mrk 421 is probably generated by a population of electrons that is actually curved, and has a low energy power-law tail. The observed spectral curvature is consistent with both stochastic acceleration or energy-dependent acceleration probability mechanisms, whereas the power-law slope of XRT-UVOT data is close to that inferred from the GRBs X-ray afterglow and in agreement with the universal first-order relativistic shock acceleration models. This scenario implies that magnetic turbulence may play a twofold role: spatial diffusion relevant to the first order process and momentum diffusion relevant to the second order process.
Physical activity is essential for chronic disease prevention, yet <40% of overweight/obese adults meet the national activity recommendations. For time-efficient counseling, clinicians need a brief, ...easy-to-use tool that reliably and validly assesses a full range of activity levels, and, most importantly, is sensitive to clinically meaningful changes in activity. The Stanford Leisure-Time Activity Categorical Item (L-Cat) is a single item comprising six descriptive categories ranging from inactive to very active. This novel methodological approach assesses national activity recommendations as well as multiple clinically relevant categories below and above the recommendations, and incorporates critical methodological principles that enhance psychometrics (reliability, validity and sensitivity to change).
We evaluated the L-Cat's psychometrics among 267 overweight/obese women who were asked to meet the national activity recommendations in a randomized behavioral weight-loss trial.
The L-Cat had excellent test-retest reliability (κ=0.64, P<0.001) and adequate concurrent criterion validity; each L-Cat category at 6 months was associated with 1059 more daily pedometer steps (95% CI 712-1407, β=0.38, P<0.001) and 1.9% greater initial weight loss at 6 months (95% CI -2.4 to -1.3, β=-0.38, P<0.001). Of interest, L-Cat categories differentiated from each other in a dose-response gradient for steps and weight loss (Ps<0.05) with excellent face validity. The L-Cat was sensitive to change in response to the trial's activity component. Women increased one L-Cat category at 6 months (M=1.0±1.4, P<0.001); 55.8% met the recommendations at 6 months whereas 20.6% did at baseline (P<0.001). Even among women not meeting the recommendations at both baseline and 6 months (n=106), women who moved 1 L-Cat categories at 6 months lost more weight than those who did not (M=-4.6%, 95% CI -6.7 to -2.5, P<0.001).
Given strong psychometrics, the L-Cat has timely potential for clinical use such as tracking activity changes via electronic medical records, especially among overweight/obese populations who are unable or unlikely to reach national recommendations.
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