Summary
Dendritic cells (DCs) are the key professional antigen‐presenting cells which bridge innate and adaptive immune responses, inducing the priming and differentiation of naive to effector CD4+ T ...cells, the cross‐priming of CD8+ T cells and the promotion of B cell antibody responses. DCs also play a critical role in the maintenance of immune homeostasis and tolerance. DC–T cell interactions underpin the generation of an autoimmune response in rheumatoid arthritis (RA). Here we describe the function of DCs and review evidence for DC and T cell involvement in RA pathogenesis, in particular through the presentation of self‐peptide by DCs that triggers differentiation and activation of autoreactive T cells. Finally, we discuss the emerging field of targeting the DC–T cell interaction for antigen‐specific immunotherapy of RA.
DC–T cell interactions underpin the generation of an autoimmune response in rheumatoid arthritis (RA). We describe the function of DCs and review evidence for DC and T cell involvement in RA pathogenesis, in particular through the presentation of self‐peptide by DCs that triggers differentiation and activation of autoreactive T cells. We then discuss the emerging field of targeting the DC–T cell interaction for antigen‐specific immunotherapy of RA.
A common approach for determining musical competence is to rely on information about individuals' extent of musical training, but relying on musicianship status fails to identify musically untrained ...individuals with musical skill, as well as those who, despite extensive musical training, may not be as skilled. To counteract this limitation, we developed a new test battery (Profile of Music Perception Skills; PROMS) that measures perceptual musical skills across multiple domains: tonal (melody, pitch), qualitative (timbre, tuning), temporal (rhythm, rhythm-to-melody, accent, tempo), and dynamic (loudness). The PROMS has satisfactory psychometric properties for the composite score (internal consistency and test-retest r>.85) and fair to good coefficients for the individual subtests (.56 to.85). Convergent validity was established with the relevant dimensions of Gordon's Advanced Measures of Music Audiation and Musical Aptitude Profile (melody, rhythm, tempo), the Musical Ear Test (rhythm), and sample instrumental sounds (timbre). Criterion validity was evidenced by consistently sizeable and significant relationships between test performance and external musical proficiency indicators in all three studies (.38 to.62, p<.05 to p<.01). An absence of correlations between test scores and a nonmusical auditory discrimination task supports the battery's discriminant validity (-.05, ns). The interrelationships among the various subtests could be accounted for by two higher order factors, sequential and sensory music processing. A brief version of the full PROMS is introduced as a time-efficient approximation of the full version of the battery.
Various factors affecting the determination of laminar flames speeds from outwardly propagating spherical flames in a constant-pressure combustion chamber were considered, with emphasis on the ...nonlinear variation of the stretched flame speed to the flame stretch rate, and the associated need to nonlinearly extrapolate the stretched flame speed to yield an accurate determination of the laminar flame speed and Markstein length. Experiments were conducted for lean and rich
n-butane/air flames at
1
atm
initial pressure, demonstrating the complex and nonlinear nature of the dynamics of flame evolution, and the strong influences of the ignition transient and chamber confinement during the initial and final periods of the flame propagation, respectively. These experimental data were analyzed using the nonlinear relation between the stretched flame speed and stretch rate, yielding laminar flame speeds that agree well with data determined from alternate flame configurations. It is further suggested that the fidelity in the extraction of the laminar flame speed from expanding spherical flames can be facilitated by using small ignition energy and a large combustion chamber.
The primary objective of the present endeavor is to collect, consolidate, and review the vast amount of experimental data on the laminar flame speeds of hydrocarbon and oxygenated fuels that have ...been reported in recent years, analyze them by using a detailed kinetic mechanism for the pyrolysis and combustion of a large variety of fuels at high temperature conditions, and thereby identify aspects of the mechanism that require further revision. The review and assessment was hierarchically conducted, in the sequence of the foundational C0–C4 species; the reference fuels of alkanes (n-heptane, iso-octane, n-decane, n-dodecane), cyclo-alkanes (cyclohexane and methyl-cyclo-hexane) and the aromatics (benzene, toluene, xylene and ethylbenzene); and the oxygenated fuels of alcohols, C3H6O isomers, ethers (dimethyl ether and ethyl tertiary butyl ether), and methyl esters up to methyl decanoate. Mixtures of some of these fuels, including those with hydrogen, were also considered. The comprehensive nature of the present mechanism and effort is emphasized.
The precise localization of the repeating fast radio burst (FRB 121102) has provided the first unambiguous association (chance coincidence probability p 3 × 10−4) of an FRB with an optical and ...persistent radio counterpart. We report on optical imaging and spectroscopy of the counterpart and find that it is an extended (0 6-0 8) object displaying prominent Balmer and O iii emission lines. Based on the spectrum and emission line ratios, we classify the counterpart as a low-metallicity, star-forming, mr′ = 25.1 AB mag dwarf galaxy at a redshift of z = 0.19273(8), corresponding to a luminosity distance of 972 Mpc. From the angular size, the redshift, and luminosity, we estimate the host galaxy to have a diameter 4 kpc and a stellar mass of M* ∼ (4-7) × 107 M , assuming a mass-to-light ratio between 2 to 3 M L −1. Based on the H flux, we estimate the star formation rate of the host to be 0.4 M yr−1 and a substantial host dispersion measure (DM) depth 324 pc cm−3. The net DM contribution of the host galaxy to FRB 121102 is likely to be lower than this value depending on geometrical factors. We show that the persistent radio source at FRB 121102's location reported by Marcote et al. is offset from the galaxy's center of light by ∼200 mas and the host galaxy does not show optical signatures for AGN activity. If FRB 121102 is typical of the wider FRB population and if future interferometric localizations preferentially find them in dwarf galaxies with low metallicities and prominent emission lines, they would share such a preference with long gamma-ray bursts and superluminous supernovae.
In order to evaluate the potential of partial hydrocarbon substitution to improve the safety of hydrogen use in general and the performance of internal combustion engines in particular, the outward ...propagation and development of surface cellular instability of spark-ignited spherical premixed flames of mixtures of hydrogen, hydrocarbon, and air were experimentally studied at NTP condition in a constant-pressure combustion chamber. With methane, ethylene, and propane being the substituents, the laminar burning velocities, the Markstein lengths, and the propensity of cell formation were experimentally determined, while the laminar burning velocities and the associated flame thicknesses were computed using recent kinetic mechanisms. Results show substantial reduction of laminar burning velocities with hydrocarbon substitution, and support the potential of propane as a suppressant of both diffusional–thermal and hydrodynamic cellular instabilities in hydrogen–air flames. Such a potential, however, was not found for methane and ethylene as substituents.
The state of the art and the further challenges of combustion chemistry research in laminar flames are reviewed. Laminar flames constitute an essential part of kinetic model development as the rates ...of elementary reactions are studied and/or validated in the presence of temperature and species concentration gradients. The various methods considered in this review are the flat, low-pressure, burner-stabilized premixed flame for chemical speciation studies, and the stagnation, spherically expanding, and burner-stabilized flames for determining the global flame properties. The data derived using these methods are considered at present as the most reliable ones for three decades of pressures ranging from about 50 mbar to over 50 bar. Furthermore, the attendant initial and/or boundary conditions and physics are in principle well characterized, allowing for the isolation of various physical parameters that could affect the flame structure and thus the reported data. The merits of each approach and the advances that have been made are outlined and the uncertainties of the reported data are discussed. At the same time, the potential sources of uncertainties associated with the experimental methods and the hypotheses for data extraction using each method are discussed. These uncertainties include unquantified physical effects, inherent instrument limitations, data processing, and data interpretation. Recommendations to reduce experimental uncertainties and increase data fidelity, essential for accurate kinetic model development, are given.
FRB 121102 is the only known repeating fast radio burst source. Here we analyze a wide-frequency-range (1-8 GHz) sample of high signal-to-noise, coherently dedispersed bursts detected using the ...Arecibo and Green Bank telescopes. These bursts reveal complex time-frequency structures that include subbursts with finite bandwidths. The frequency-dependent burst structure complicates the determination of a dispersion measure (DM); we argue that it is appropriate to use a DM metric that maximizes frequency-averaged pulse structure, as opposed to peak signal-to-noise, and find DM = 560.57 0.07 pc cm−3 at MJD 57,644. After correcting for dispersive delay, we find that the subbursts have characteristic frequencies that typically drift lower at later times in the total burst envelope. In the 1.1-1.7 GHz band, the ∼0.5-1 ms subbursts have typical bandwidths ranging from 100 to 400 MHz, and a characteristic drift rate of ∼200 MHz ms−1 toward lower frequencies. At higher radio frequencies, the subburst bandwidths and drift rate are larger, on average. While these features could be intrinsic to the burst emission mechanism, they could also be imparted by propagation effects in the medium local to the source. Comparison of the burst DMs with previous values in the literature suggests an increase of ΔDM ∼ 1-3 pc cm−3 in 4 yr; though, this could be a stochastic variation as opposed to a secular trend. This implies changes in the local medium or an additional source of frequency-dependent delay. Overall, the results are consistent with previously proposed scenarios in which FRB 121102 is embedded in a dense nebula.
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