Performance of a cyclone with an aslant shaped inlet

This paper presents an analysis of selected operating parameters of a cyclone with a modified inlet. The modification consisted in an angular arrangement of an inlet channel wall. This can result – in view of previously conducted experiments – in a faster insertion of a dusty gas into a swirl motion, an improvement of particles separation process. The analysis was carried out using numeric CFD simulations. The results were compared to those obtained from simulations and lab-measurements for a cyclone with standard inlet

Monitoring observations of 6.7 GHz methanol masers

We report results of 6.7 GHz methanol maser monitoring of 139 star-forming sites with theTorun 32 m radio telescope from June 2009 to February 2013. The targets were observedat least once a month, with higher cadences of 2-4 measurements per week for circumpolarobjects. Nearly 80 per cent of the sources display variability greater than 10 per cent on atime-scale between a week and a few years but about three quarters of the sample have only1-3 spectral features which vary significantly. Irregular intensity fluctuation is the dominanttype of variability and only nine objects show evidence for cyclic variations with periodsof 120 to 416 d. Synchronised and anti-correlated variations of maser features are detectedin four sources with a disc-like morphology. Rapid and high amplitude bursts of individualfeatures are seen on 3-5 occasions in five sources. Long (>50 d to 20 months) lasting burstsare observed mostly for individual or groups of features in 19 sources and only one sourceexperienced a remarkable global flare. A few flaring features display a strong anti-correlationbetween intensity and line-width that is expected for unsaturated amplification. There is aweak anti-correlation between the maser feature luminosity and variability measure, i.e. maserfeatures with low luminosity tend to be more variable than those with high luminosity. Theanalysis of the spectral energy distribution and continuum radio emission reveals that thevariability of the maser features increases when the bolometric luminosity and Lyman fluxof the exciting object decreases. Our results support the concept of a major role for infraredpumping photons in triggering outburst activity of maser emission

6.7 GHz variability characteristics of new periodic methanol maser sources

Discovery of periodic maser emission was an unexpected result from monitoring observations of methanol transitions in high-mass young stellar objects. We report on the detection of five new periodic sources from a monitoring program with the Torun 32 m telescope. Variability with a period of 149 to 540 d and different patterns from sinusoidal-like to intermittent was displayed. Three-dimensional structure of G59.633−0.192 determined from the time delays of burst peaks of the spectral features and high angular resolution map implies that the emission traces a disc. For this source the 6.7 GHz light curve followed the infrared variability supporting a radiative scheme of pumping. An unusual time delay of ∼80 d occurred in G30.400−0.296 could not be explained by the light travel time and may suggest a strong differentiation of physical conditions and excitation in this deeply embedded source. Our observations suggest the intermittent variability may present a simple response of maser medium to the underlying variability induced by the accretion luminosity while other variability patterns may reflect more complex changes in the physical conditions

Long-term multi-frequency maser observations of the intermediate-mass young stellar object G107.298+5.639

Context: Periodic flares of maser emission are thought to be induced either by variations of the seed photon flux in young binary systems or the pump rate regulated by stellar and accretion luminosities. Aims: We seek to study the variability of four maser transitions of three different species in G107.298+5.639 to constrain the dominant mechanism of periodic flares. Methods: Light curves of the 6.7 GHz methanol and 22.2 GHz water vapour maser were obtained with the Torun 32 m radio telescope over 39 and 34 cycles, respectively. The target was also monitored at the 1.6 GHz hydroxyl transitions with the Nançay radio telescope over 13 cycles. All these maser lines were imaged using VLBI arrays. Results: The study confirms alternating flares of the methanol and water masers with a period of 34.4 d and reveals the synchronised behaviour of the methanol and hydroxyl masers in this source. The observed spatial distribution of the methanol maser cloudlets and the measured time delays of the flares of individual features imply a ring-like structure of radius 240 au and thickness 30 au. Internal proper motions indicate that the velocity of methanol cloudlets is dominated by a disc-wind component of about 5 km s −1 . The methanol emission detected during only one VLBI observation is located in a region about 550 au from a central star, which also exhibits OH maser flares. The erratic appearance of methanol features can be related to a powering object of relatively low luminosity which, during some variability cycles, can excite molecules only in the nearest part of the disc. A careful analysis of the maser and infrared light curves reveal a strong correlation between the 6.7 GHz line and the infrared flux densities supporting a radiative pumping of the maser. Conclusions: The synchronised behaviour of the hydroxyl 1665/1667 MHz and 6.7 GHz methanol transitions indicates a common pumping mechanism for the periodic flares of G107.298+5.639

Giant burst of methanol maser in S255IR-NIRS3

Context.High-mass young stellar objects (HMYSOs) can undergo accretion episodes that strongly affect the star evolution, the dynamics of the disk, and its chemical evolution. Recently reported extraordinary bursts in the methanol maser emission may be the observational signature of accretion events in deeply embedded HMYSOs. Aims.We analyze the light curve of 6.7GHz methanol masers in S255IR-NIRS3 during the 2015-2016 burst. Methods.8.5-yr monitoring data with an average sampling interval of 5 days were obtained with the Torun 32 m radio telescope. Archival data were added, extending the time series to ~27 yr. Results.The maser emission showed moderate (25-30%) variability on timescales of months to years over ~23 yr since its discovery.The main burst was preceded by a 1 yr increase of the total flux density by a factor of 2.5, then it grew by a factor of 10 over ~0.4 yr and declined by a factor of 8 during the consecutive 2.4 yr. The peak maser luminosity was a factor of 24.5 higher than the pre-burst quiescent value. The light curves of individual features showed considerable diversity but indicated a general trend of suppression of the maser emission at blueshifted (5.8km/s. This new emission provided a contribution of about 80% to the maser luminosity around the peak of the burst. The duration of the burst at the extreme redshifted velocities of 7.1–-8.7km/s was from 0.9 to 1.9 yr, and its lower limit for the other features was ~3.9 yr. Conclusions.The onset of the maser burst exactly coincides with that of the infrared burst estimated from the motion of the light echo. This strongly supports the radiative pumping scheme of the maser transition. The growth of the maser luminosity is the result of an increasing volume of gas where the maser inversion is achieved

A search for the OH 6035 MHz line in high-mass star-forming regions

Context. The excited states of OH masers detected in the environment of high-mass young stellar objects (HMYSOs) are important for improving our understanding of the physical conditions of these objects and also provide information about their magnetic fields. Aims. We aim to search for excited-state OH 6035 MHz maser emission in HMYSOs which might have escaped detection in previous surveys or were never searched for. Methods. A sample of HMYSOs derived from untargeted surveys of the 6668 MHz methanol maser line was observed at 6035 MHz OH transition with the Torun 32 m radio telescope. The 6035 MHz detections were observed in the OH 6031 MHz line. Two-thirds of the detections were observed at least three times over a two-year period. Results. Out of 445 targets, 37 were detected at 6035 MHz, including seven new discoveries. The 6031 MHz line was detected towards ten 6035 MHz sources, one of which was not previously reported. All the newly detected sources are faint with the peak flux density lower than 4 Jy and show significant or high variability on timescales of 4 to 20 months. Zeeman pair candidates identified in three new sources imply a magnetic field intensity of 2-11 mG. Comparison of our spectra with those obtained ~10 yr ago indicates different degrees of variability but there is a general increase in the variability index on an ~25 yr timescale, usually accompanied by significant changes in the profile shape

New evidence for Dicke's superradiance in the 6.7 GHz methanol spectral line in the interstellar medium

We present new evidence for superradiance (SR) in the methanol 6.7 GHz spectral line for three different star-forming regions: S255IR-NIRS3, G24.329+0.144, and Cepheus A. Our analysis shows that some of the flux–density flares exhibiting fast rise times and asymmetric light curves reported in these sources can naturally be explained within the context of SR. When a threshold for the inverted population column density is exceeded in a maser-hosting region, the radiation mode switches from one regulated by stimulated emission (maser) to SR. Superradiance, as a more efficient energy release mechanism, manifests itself through strong bursts of radiation emanating from spatially compact regions. Elevated inverted population densities and the initiation of SR can be due to a change in radiative pumping. Here, we show that an increase in the pump rate and the inverted population density of only a factor of a few results in a significant increase in radiation. While the changes in the pump rate can take place over a few hundred days, the rise in radiation flux density when SR is initiated is drastic and happens over a much shorter time-scale

Altered functional brain imaging in migraine patients: BOLD preliminary study in migraine with and without aura

Design. Migraine is regarded as a complex brain dysfunction of sensory and modulatory networks with the secondary sensitisation of the trigeminal system as well as the affected brain area’s activities. The particular role of the hippocampus and the brainstem in the first phase of the attack, the disrupted cognitive network, and the activation of the limbic and visual systems, are the main discoveries in the field of migraine imaging that have been achieved using functional techniques. Thus advanced neuroimaging has been widely employed to study the pathogenesis of migraine. Objective. The evaluation of fMRI BOLD images of migraine patients with or without aura, with particular attention to the interictal phase. Subjects and Methods. The aim of this study was to compare brain activity during visual stimuli by fMRI BOLD in the interictal phase (black and white checkerboard tests, static or flickering) of 16 migraine patients, eight with aura and eight without. Results. We demonstrated differences in the right part of the brainstem, the left part of the cerebellum, and in the right middle temporal gyrus. However, the bilateral brain activation in the occipital and frontal lobe remained similar. Conclusions. Results of our preliminary study suggest that migraine with aura and migraine without aura might be separate disorders, and this requires further investigation

The nature of the methanol maser ring G23.657–00.127 II. Expansion of the maser structure

To protect the copyright in your article, the following copyright notice should be included in the credit: “Reproduced with permission from Astronomy & Astrophysics, © ESO”. https://www.aanda.org/for-authors/author-information/copyrightContext. Ring-like distributions of the 6.7 GHz methanol maser spots at milliarcsecond scales represent a family of molecular structures of unknown origin associated with high-mass young stellar objects. Aims: We aim to study G23.657-00.127, which has a nearly circular ring of the 6.7 GHz methanol masers, and is the most suitable target to test hypotheses on the origin of the maser rings. Methods: The European Very Long Baseline Interferometry Network was used at three epochs spanning 10.3 yr to derive the spatio-kinematical structure of the 6.7 GHz methanol maser emission in the target. Results: The maser cloudlets, lying in a nearly symmetric ring, expand mainly in the radial direction with a mean velocity of 3.2 km s-1. There is an indication that the radial component of the velocity increases with cloudlet's distance from the ring centre. The tangential component does not show any clear evidence for rotation of the cloudlets or any relationship with distance from the ring centre. The blue-shifted masers may hint at an anticlockwise rotation of cloudlets in the southern part of the ring. The nearly circular structure of the ring clearly persisted for more than 10 yr. Interferometric data demonstrated that about one quarter of cloudlets show significant variability in their brightness, although the overall spectrum was non-variable in single-dish studies. Conclusions: Taking into account the three-dimensional motion of the maser cloudlets and their spatial distribution along a small ring, we speculate about two possible scenarios where the methanol masers trace either a spherical outflow arising from an (almost) edge-on disc, or a wide angle wind at the base of a protostellar jet. The latter is associated with near- and mid-infrared emission detected towards the ring. High angular resolution images of complementary (thermal) tracers are needed to interpret the environment of methanol masers

Diagnosis and treatment of post-traumatic hypothermia in hospitals : a pilot study

Background: An unintentional drop in core body temperature of trauma victims is associated with increased mortality. Thermoregulation is impaired in these patients, especially when treated with opioids or anesthetics. Careful thermal insulation and active warming are necessary to maintain normothermia. The aim of the study was to assess the equipment and procedures for diagnosing and managing post-traumatic hypothermia in Polish hospitals. Methods: Survey forms regarding equipment and procedures on monitoring of core temperature (Tc) and active warming were distributed to every hospital that admits trauma victims in the Holy Cross Province. Questionnaires were addressed to surgery departments, intensive care units (ICUs), and operating rooms (ORs). Results: 92% of surgery departments did not have equipment to measure core body temperature and 85% did not have equipment to rewarm patients. Every ICU had equipment to measure Tc and 83% had active warming devices. In 50% of ICUs, there were no rewarming protocols based on Tc and the initiation of rewarming was left to the physician’s discretion. In 58% of ORs, Tc was not monitored and in 33% the patients were not actively warmed. Conclusions: The majority of surveyed ICUs and ORs are adequately equipped to identify and treat hypothermia, however the criteria for initiating Tc monitoring and rewarming remain unstandardized. Surgery departments are not prepared to manage post-traumatic hypothermia