Abstract
Cooperative super-radiant emission from a highly relativistic multi-particle source is modeled and solved for the simple case of two particles. An existing model of a single relativistic ...two-level particle is used to construct a Hamiltonian describing relativistic velocity dependent multi-particle super-radiance. The standard diagrammatic framework is applied to the calculation of time evolution and density operators from this Hamiltonian, demonstrating during the process a departure from standard results and calculation methods. In particular, the so-called vertical photon result of the literature is shown to be modified by the relativistic Lorentz factor of the sample; additionally, a set of coupled differential equations describing certain propagators in the velocity-dependent small sample framework are introduced and solved numerically via a hybrid fourth order Runge–Kutta and convolution approach. The model is applied to the simple case of two highly relativistic particles travelling with slightly differing velocities simulated at varying relativistic mean sample
β
factors, and velocity coherence requirements for a sample to demonstrate enhanced super-radiant emission in the observer frame are evaluated. These coherence requirements are found to become increasingly restrictive at higher
β
factors, even in the context of standard results of relativistic velocity differential transformations.
•A bioanalytical method was developed to analyze pharmaceuticals in fish plasma.•Solid phase extraction of 100μL of fish plasma was performed.•LC–MS/MS analysis was conducted within 14min.•Low to ...undetected levels of selected pharmaceutical residues were found in northern pike plasma.•Bioavailability of drugs in environmentally exposed fish depended on their physico-chemical properties.
Aquatic systems near major urban centers are constantly contaminated with effluent from wastewater treatment plants. Pharmaceuticals are part of the contamination and several classes of drugs have been detected in surface waters in the last decade. To better understand the impact of those pharmaceuticals in ecosystems, the exposure to aquatic species needs to be investigated. This study presents a new simple and rugged quantitative method for the determination of several classes of drugs using 100μL of plasma from fish environmentally exposed to a major but highly diluted urban effluent. Six common drugs (i.e., diclofenac, ibuprofen, naproxen, salbutamol, sulfamethoxazole and trimethoprim) and one major metabolite (2-hydroxy-ibuprofen), present in significant amount in impacted waterways have been selected for the development and validation of the method. First, all drugs were extracted using cation exchange solid phase extraction (SPE) and eluted with two solvent mixtures. Then, the extracts were analyzed using a reverse-phase analytical column Waters® CORTECS C18+ (150×2.1mm, 2.7μm) within 14min. MS/MS was performed with an electrospray (ESI) interface in positive ion mode, with multiple reaction monitoring (MRM) experiment acquiring two product ions per drugs. Quantification has been made with standard curves for each analyte using isotopically labeled internal standards. This method has high sensitivity with limits of quantification of 1ngmL−1 for each drug, except for ibuprofen and its metabolite 2-hydroxy-ibuprofen at 2ngmL−1. The precision of the method was below 11%, the accuracy between 94 and 105% and overall recovery between 94 and 111% for all drugs, with high selectivity. Application of the method to plasma samples from wild northern pike inhabiting the St. Lawrence River collected over a three-year period showed the presence of naproxen, diclofenac, trimethoprim and salbutamol at very low concentrations (around 1ngmL−1).
ABSTRACT
We discuss the existence of elliptical polarization in rotational spectral lines of CO and other molecules within the context of the Anisotropic Resonant Scattering (ARS) model. We show that ...the effect of ARS on the radiation field can lead to not only the previously predicted transformation of background linear polarization into circular polarization (i.e. Faraday conversion) but also the occurrence of Faraday rotation and the generation of elliptically polarized signals in an otherwise initially unpolarized radiation field. This is due to a collective behaviour between the large number of molecules acting as a diffraction ensemble that strongly favours forward scattering over any other mode. Our application to astronomical data demonstrates the dependency of the Stokes parameters on the strength and orientation of the ambient magnetic field, and suggests that ARS will manifest itself for a wide range of molecular species and transitions.
Since the mid-1990s, the decline of the yellow perch population of Lake Saint-Pierre (hereinafter LSP) in Quebec, Canada has been the subject of several research programs. The combined effect of ...habitat deterioration, the presence of invasive species, and poor water quality negatively affected the yellow perch population in this lake. In 2013, we sampled yellow perch (larvae, juveniles and adults) at six sites along the St. Lawrence River representing a gradient of increasing human influences from upstream to downstream and measured several biomarkers including retinoid compounds (vitamin A). In the most contaminated sites (LSP, north and south shores), we found that retinoid stores were decreased in all three stages of development. To corroborate these results and to test other biomarkers, we once again sampled yellow perch (adults only) from the same sites. Results from our 2014 and 2015 samplings confirmed that LSP yellow perch appeared to be at a disadvantage compared to fish from upstream populations. Individuals from LSP have lower acetylcholinesterase (AChE) activity as well as lower retinoid levels in liver and plasma. These fish were also marked by lower levels of antioxidants such as lycopene and vitamin E. A discriminant analysis of this set of results confirmed that the yellow perch of the LSP could be easily discriminated from those of the other sites (2014 and 2015) on the basis of liver retinoid and, to a lesser extent, of the liver tocopherol and protein concentration of the muscle, as well as AChE activity and DROH (all-trans-3,4-dehydroretinol) measured in plasma.
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•Multiple biomarkers tested in adult yellow perch in St. Lawrence River, Québec, Canada.•Fish from contaminated sites had lower AChE activity and antioxidants lycopene and tocopherol.•For 2 consecutive years, retinoid compounds were depleted in yellow perch from the most contaminated sites.•Retinoid-based biomarkers were relevant to distinguish fish from the most contaminated sites.
ABSTRACT
We investigate the application of the conventional quasi-steady state maser modelling algorithm of Menegozzi & Lamb (ML) to the high field transient regime of the one-dimensional ...Maxwell-Bloch (MB) equations for a velocity distribution of atoms or molecules. We quantify the performance of a first order perturbation approximation available within the ML framework when modelling regions of increasing electric field strength, and we show that the ML algorithm is unable to accurately describe the key transient features of R. H. Dicke’s superradiance (SR). We extend the existing approximation to one of variable fidelity, and we derive a generalization of the ML algorithm convergent in the transient SR regime by performing an integration on the MB equations prior to their Fourier representation. We obtain a manifestly unique integral Fourier representation of the MB equations which is $\mathcal {O}\left(N\right)$ complex in the number of velocity channels N and which is capable of simulating transient SR processes at varying degrees of fidelity. As a proof of operation, we demonstrate our algorithm’s accuracy against reference time domain simulations of the MB equations for transient SR responses to the sudden inversion of a sample possessing a velocity distribution of moderate width. We investigate the performance of our algorithm at varying degrees of approximation fidelity, and we prescribe fidelity requirements for future work simulating SR processes across wider velocity distributions.
ABSTRACT
The source G9.62+0.20E surprises yet again! Analysis of the associated methanol maser feature at vlsr = +8.8 km s−1 revealed a second period of P = 52.1 ± 0.3 d, along with the previously ...reported period P = 243 d for this source. Various explanations, harmonic flaring, Dicke’s superradiance, a secondary pulsation, or two different periodically varying radio sources in the field of view with associated methanol masers are presented. The latter two hypotheses appear more plausible but it is not clear which, if any, best describe these observations.
Context.
Supernova remnants (SNRs) represent a major feedback source from stars in the interstellar medium of galaxies. During the latest stage of supernova explosions, shock waves produced by the ...initial blast modify the chemistry of gas and dust, inject kinetic energy into the surroundings, and may alter star formation characteristics. Simultaneously,
γ
-ray emission is generated by the interaction between the ambient medium and cosmic rays (CRs), including those accelerated in the early stages of the explosion.
Aims.
We study the stellar and interstellar contents of IC443, an evolved shell-type SNR at a distance of 1.9 kpc with an estimated age of 30 kyr. We aim to measure the mass of the gas and characterize the nature of infrared point sources within the extended G region, which corresponds to the peak of
γ
-ray emission detected by VERITAS and
Fermi
.
Methods.
We performed 10′ × 10′ mapped observations of
12
CO,
13
CO
J
= 1–0,
J
= 2–1, and
J
= 3–2 pure rotational lines, as well as C
18
O
J
= 1–0 and
J
= 2–1 obtained with the IRAM 30 m and APEX telescopes over the extent of the
γ
-ray peak to reveal the molecular structure of the region. We first compared our data with local thermodynamic equilibrium models. We estimated the optical depth of each line from the emission of the isotopologs
13
CO and C
18
O. We used the population diagram and large velocity gradient assumption to measure the column density, mass, and kinetic temperature of the gas using
12
CO and
13
CO lines. We used complementary data (stars, gas, and dust at multiple wavelengths) and infrared point source catalogs to search for protostar candidates.
Results.
Our observations reveal four molecular structures: a shocked molecular clump associated with emission lines extending between −31 and 16 km s
−1
, a quiescent, dark cloudlet associated with a line width of ~2 km s
−1
, a narrow ring-like structure associated with a line width of ~1.5 km s
−1
, and a shocked knot. We measured a total mass of ~230, ~90, ~210, and ~4
M
⊙
, respectively, for the cloudlet, ring-like structure, shocked clump, and shocked knot. We measured a mass of ~1100
M
⊙
throughout the rest of the field of observations where an ambient cloud is detected. We found 144 protostar candidates in the region.
Conclusions.
Our results emphasize how the mass associated with the ring-like structure and the cloudlet cannot be overlooked when quantifying the interaction of CRs with the dense local medium. Additionally, the presence of numerous possible protostars in the region might represent a fresh source of CRs, which must also be taken into account in the interpretation of
γ
-ray observationsin this region.
Music practice is a multisensory training that is of great interest to neuroscientists because of its implications for neural plasticity. Music-related modulation of sensory systems has been observed ...in neuroimaging data, and has been supported by results in behavioral tasks. Some studies have shown that musicians react faster than non-musicians to visual, tactile and auditory stimuli. Behavioral enhancement in more complex tasks has received considerably less attention in musicians. This study aims to investigate unisensory and multisensory discrimination capabilities in musicians. More specifically, the goal of this study is to examine auditory, tactile and auditory-tactile discrimination in musicians. The literature suggesting better auditory and auditory-tactile discrimination in musicians is scarce, and no study to date has examined pure tactile discrimination capabilities in musicians. A two-alternative forced-choice frequency discrimination task was used in this experiment. The task was inspired by musical production, and participants were asked to identify whether a frequency was the same as or different than a standard stimulus of 160 Hz in three conditions: auditory only, auditory-tactile only and tactile only. Three waveforms were used to replicate the variability of pitch that can be found in music. Stimuli were presented through headphones for auditory stimulation and a glove with haptic audio exciters for tactile stimulation. Results suggest that musicians have lower discrimination thresholds than non-musicians for auditory-only and auditory-tactile conditions for all waveforms. The results also revealed that musicians have lower discrimination thresholds than non-musicians in the tactile condition for sine and square waveforms. Taken together, these results support the hypothesis that musical training can lead to better unisensory tactile discrimination which is in itself a new and major finding.
ABSTRACT
We report the detection of new 12.178, 12.229, 20.347, and 23.121 GHz methanol masers in the massive star-forming region G358.93−0.03, which are flaring on similarly short time-scales (days) ...as the 6.668 GHz methanol masers also associated with this source. The brightest 12.178 GHz channel increased by a factor of over 700 in just 50 d. The masers found in the 12.229 and 20.347 GHz methanol transitions are the first ever reported and this is only the fourth object to exhibit associated 23.121 GHz methanol masers. The 12.178 GHz methanol maser emission appears to have a higher flux density than that of the 6.668 GHz emission, which is unusual. No associated near-infrared flare counterpart was found, suggesting that the energy source of the flare is deeply embedded.
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