The population of high-energy and very high-energy γ-ray sources, detected with EGRET and the new generation of ground-based Cherenkov telescopes, forms a reduced but physically important sample. ...Most of these sources are extragalactic (e.g. blazars), while among the galactic ones there are pulsars and supernova remnants. The microquasar LS 5039, previously proposed to be associated with an EGRET source by Paredes et al., has recently been detected at TeV energies, confirming that microquasars should be regarded as a class of high-energy γ-ray sources. To model and understand how the energetic photons are produced and escape from LS 5039, it is crucial to unveil the nature of the compact object, which remains unknown. Here, we present new intermediate-dispersion spectroscopy of this source, which, combined with values reported in the literature, provides an orbital period of Porb= 3.906 03 ± 0.000 17 d, a mass function f(M) = 0.0053 ± 0.0009 M⊙ and an eccentricity e= 0.35 ± 0.04. Atmosphere model fitting to the spectrum of the optical companion, together with our new distance estimate of d= 2.5 ± 0.1 kpc, yields RO= 9.3+0.7−0.6 R⊙, log (LO/ L⊙) = 5.26 ± 0.06 and MO= 22.9+3.4−2.9 M⊙. These, combined with our dynamical solution and the assumption of pseudo-synchronization, yield an inclination and a compact object mass MX= 3.7+1.3−1.0 M⊙. This is above neutron star masses for most of the standard equations of state and, therefore, we propose that the compact object in LS 5039 is a black hole. We finally discuss the implications of our orbital solution and new parameters of the binary system on the CNO products, the accretion/ejection energetic balance, the supernova explosion scenario and the behaviour of the very high-energy γ-ray emission with the new orbital period.
The Molecular Cloud Lifecycle Chevance, Mélanie; Kruijssen, J. M. Diederik; Vazquez-Semadeni, Enrique ...
Space science reviews,
2020, Letnik:
216, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Giant molecular clouds (GMCs) and their stellar offspring are the building blocks of galaxies. The physical characteristics of GMCs and their evolution are tightly connected to galaxy evolution. The ...macroscopic properties of the interstellar medium propagate into the properties of GMCs condensing out of it, with correlations between e.g. the galactic and GMC scale gas pressures, surface densities and volume densities. That way, the galactic environment sets the initial conditions for star formation within GMCs. After the onset of massive star formation, stellar feedback from e.g. photoionisation, stellar winds, and supernovae eventually contributes to dispersing the parent cloud, depositing energy, momentum and metals into the surrounding medium, thereby changing the properties of galaxies. This cycling of matter between gas and stars, governed by star formation and feedback, is therefore a major driver of galaxy evolution. Much of the recent debate has focused on the durations of the various evolutionary phases that constitute this cycle in galaxies, and what these can teach us about the physical mechanisms driving the cycle. We review results from observational, theoretical, and numerical work to build a dynamical picture of the evolutionary lifecycle of GMC evolution, star formation, and feedback in galaxies.
ABSTRACT We describe the motivation, design, and implementation of the CORNISH survey, an arcsecond-resolution radio continuum survey of the inner galactic plane at 5 GHz using the Very Large Array ...(VLA). It is a blind survey coordinated with the northern Spitzer GLIMPSE I region covering 10° < l < 65° and |b| < 1° at similar resolution. We discuss in detail the strategy that we employed to control the shape of the synthesised beam across this survey, which covers a wide range of fairly low declinations. Two snapshots separated by 4h kept the beam elongation to less that 1.5 over 75% of the survey area and less than 2 over 98% of the survey. The prime scientific motivation is to provide an unbiased survey for ultra-compact H II regions to study this key phase in massive star formation. A sensitivity around 2 mJy will allow the automatic distinction between radio-loud and radio-quiet mid-IR sources found in the Spitzer surveys. This survey has many legacy applications beyond star formation, including evolved stars, active stars and binaries, and extragalactic sources. The CORNISH survey for compact ionized sources complements other Galactic plane surveys that target diffuse and nonthermal sources, as well as atomic and molecular phases to build up a complete picture of the interstellar medium in the Galaxy.
We investigate the evolutionary connection between local infrared (IR)-bright galaxies (...) and quasars. We use high-angular resolution (~0.3-0.4 arcsec ~ few hundred parsecs) 8-13 mu m ground-based ...spectroscopy to disentangle the active galactic nuclei (AGN) mid-IR properties from those of star formation. The comparison between the nuclear 11.3 mu m polycyclic aromatic hydrocarbon feature emission and that measured with Spitzer/Spitzer Infrared Spectrograph indicates that the star formation is extended over a few kpc in the IR-bright galaxies. The AGN contribution to the total IR luminosity of IR-bright galaxies is lower than in quasars. Although the dust distribution is predicted to change as IR-bright galaxies evolve to IR-bright quasars and then to optical quasars, we show that the AGN mid-IR emission of all the quasars in our sample is not significantly different. In contrast, the nuclear emission of IR-bright galaxies with low AGN contributions appears more heavily embedded in dust although there is no clear trend with the interaction stage or projected nuclear separation. This suggests that the changes in the distribution of the nuclear obscuring material may be taking place rapidly and at different interaction stages washing out the evidence of an evolutionary path. When compared to normal AGN, the nuclear star formation activity of quasars appears to be dimming, whereas it is enhanced in some IR-bright nuclei, suggesting that the latter are in an earlier star formation-dominated phase. (ProQuest: ... denotes formulae/symbols omitted.)
The implementation of green approaches towards the preparation of graphene and graphene-based materials with enhanced functionality from graphite oxide has been relatively little explored. ...Particularly, the use of bioreductants and the testing of their relative efficacies is an incipient area of research. Here, a pool of 20 environmentally friendly, natural antioxidants have been tested for their ability to reduce graphene oxide. These antioxidants were mostly vitamins, amino acids and organic acids. By establishing a protocol to systematically compare and optimize their performance, several new efficient bioreductants of graphene oxide have been identified, namely, pyridoxine and pyridoxamine (vitamin B6), riboflavin (vitamin B2), as well as the amino acids arginine, histidine and tryptophan. These biomolecules were used to prepare reduced graphene oxide–silver nanoparticle hybrids that displayed colloidal stability in water in the absence of additional dispersants. Particularly, hybrids prepared with pyridoxamine exhibited a combination of long-term colloidal stability and exceptionally high catalytic activity among silver nanoparticle-based catalysts in the reduction of p-nitrophenol with NaBH4. Thus, in addition to expanding substantially the number of green reductants available for graphene oxide reduction, the present results underline the idea that proper selection of bioreductant can be relevant to achieve graphene-based materials with improved performance.
We report the preparation of micro-/mesoporous carbon monolithic xerogels by means of a two-step approach that comprises (1) hydrothermal carbonization of glucose in the presence of graphene oxide ...(GO) sheets as morphology-directing agents and (2) chemical activation of the resulting hydrothermal carbon (HTC) xerogels with KOH. The as-prepared HTC xerogels were made up of a random assembly of thin (<30nm) carbon platelets, which were interpreted to arise via dehydration and condensation reactions of glucose at catalytically active (acidic) sites present on the surface of GO. The chemical activation afforded xerogels with large surface areas and pore volumes (up to ∼2000m2g−1 and 1.15cm3g−1, respectively) and a cellular morphology, which could be attributed to the combined effect of the activating agent and the unusual, compliant nature of the HTC xerogel. Additionally, the use of different activation conditions allowed fine-tuning the porous texture of the activated xerogels. Finally, the activated carbon xerogels displayed CO2 uptake capacities up to 4.9mmolg−1 at 0°C and 1bar, as well as an efficient performance (between 600 and 700mgg−1) in the adsorption of bulky dyes, thus demonstrating their application potential.
Background
Crohn’s disease (CD) and ulcerative colitis (UC) are inflammatory bowel diseases (IBD) that contributes in part to irreversible bowel damage and long-term complications, reduced quality of ...life, invalidity, and economic burden. Suboptimal control of IBD is associated with higher healthcare resource utilization (HCRU), impaired quality of life (QoL), and reduced work productivity.
Aims
The IBD-PODCAST study aimed to assess the proportion of IBD patients with suboptimal control and its associated impact.
Methods
IBD-PODCAST is a cross-sectional, multicenter study that aimed to characterize the CD and UC population with optimal or suboptimal control according to the STRIDE-II criteria and patient- and physician-reported measures. Here we present the results of the Spanish cohort (
n
= 396).
Results
A total of 104/196 (53.1%) CD and 83/200 (41.5%) UC patients were found to have suboptimal disease control. Long-term treatment targets according to STRIDE-II were applied in 172 (87.8%) CD and 181 (90.5%) UC patients. 125 of 172 (72.7%) CD and 74 of 181 (40.9%) UC patients were currently treated with targeted immunomodulators. Patients with CD and UC and suboptimal disease control showed impaired QoL, higher HCRU and direct costs, and also loss of work productivity compared to those with optimal control.
Conclusion
Despite a high rate of targeted immunomodulator therapy, a substantial proportion of IBD patients show suboptimal disease control according to the STRIDE II criteria. Those patients with suboptimal disease control exhibit impaired QoL, less work productivity, and higher HCRU, suggesting that there is considerable need for better treatment approaches in IBD.
Summary
Background
The malignant mechanisms that control the development of cutaneous T‐cell lymphoma (CTCL) are beginning to be identified. Recent evidence suggests that disturbances in specific ...intracellular signalling pathways, such as RAS–mitogen‐activated protein kinase, T‐cell receptor (TCR)–phospholipase C gamma 1 (PLCG1)–nuclear factor of activated T cells (NFAT) and Janus kinase (JAK)–signal transducer and activator of transcription (STAT), may play an essential role in the pathogenesis of CTCL.
Objectives
To investigate the mechanisms controlling disease development and progression in mycosis fungoides (MF), the most common form of CTCL.
Methods
We collected 100 samples that were submitted for diagnosis of, or a second opinion regarding, MF between 2001 and 2018, 80% of which were in the early clinical stages of the disease. Formalin‐fixed paraffin‐embedded tissues were used for histological review and to measure the expression by immunohistochemistry of surrogate markers of activation of the TCR–PLCG1–NFAT, JAK–STAT and NF‐κB pathways. Folliculotropism and large‐cell transformation were also examined.
Results
NFAT and nuclear factor kappa B (NF‐κB) markers showed a comparable activation status in early and advanced stages, while STAT3 activation was more frequent in advanced stages and was associated with large‐cell transformation. Consistently with this observation, STAT3 activation occurred in parallel with MF progression in two initially MF‐negative cases. A significant association of NFAT with NF‐κB markers was also found, reflecting a common mechanism of activation in the two pathways. Genomic studies identified nine mutations in seven genes known to play a potential role in tumorigenesis in T‐cell leukaemia/lymphoma, including PLCG1, JAK3 and STAT3, which underlies the activation of these key cell‐survival pathways. A higher mutational allele frequency was detected in advanced stages.
Conclusions
Our results show that STAT3 is activated in advanced cases and is associated with large‐cell transformation, while the activation of NFAT and NF‐κB is maintained throughout the disease. These findings could have important diagnostic and therapeutic implications.
What's already known about this topic?
Mycosis fungoides is characterized by a clonal expansion of T cells in the skin.
The mechanisms controlling disease development and progression are not fully understood.
What does this study add?
An association of the nuclear factor of activated T cells and nuclear factor kappa B pathways was found, which could reflect a common mechanism of activation. These pathways were activated in early and advanced stages at the same level.
Signal transducer and activator of transcription 3 activation was associated with large‐cell transformation and was more frequent in advanced stages.
A genomic analysis of cutaneous T‐cell lymphoma‐associated genes was performed. Nine mutations were detected.
What is the translational message?
These results could have important implications for the treatment of MF in the near future.
Linked Comment: Ødum. Br J Dermatol 2020; 182:16–17.
The stabilization of reduced graphene oxide (RGO) sheets in aqueous dispersion using a wide range of surfactants of anionic, non-ionic and zwitterionic type has been investigated and compared under ...different conditions of pH, surfactant and RGO concentration, or sheet size. The observed differences in the performance of the surfactants were rationalized on the basis of their chemical structure (e.g., alkylic vs. aromatic hydrophobic tail or sulfonic vs. carboxylic polar head), thus providing a reference framework in the selection of appropriate surfactants for the processing of RGO suspensions towards particular purposes. RGO-surfactant composite paper-like films were also prepared through vacuum filtration of the corresponding mixed dispersions and their main characteristics were investigated. The composite paper-like films were also electrochemically characterized. Those prepared with two specific surfactants exhibited a high capacitance in relation to their surfactant-free counterpart.
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