Fixed point theorems for multivalued generalized nonlinear contractive maps in partial metric spaces

We prove some fixed-point results for multivalued generalized nonlinear contractive mappings in partial metric spaces, which generalize and improve the corresponding recent fixed-point results due to Ćirić [L. B. Ćirić, “Multivalued nonlinear contraction mappings,” Nonlin. Anal., 71, 2716–2723 (2009)] and Klim and Wardowski [D. Klim and D. Wardowski, “Fixed-point theorems for set-valued contractions in complete metric spaces,” J. Math. Anal. Appl., 334, 132–139 (2007)].Доведено ДЄЯКІ теореми про нерухому точку в частково метричних просторах, що узагальнюють та покращують відповідні нові результати про нерухому точку, отримані Чірічем (CiriC L. B. Multivalued nonlinear contraction mappings // Nonlinear Anal. - 2009. - 71. - P. 2716-2723) та Клімом i Вардовським (Klim D., Wardowski D. Fixed point theorems for set-valued contractions in complete metric spaces // J. Math. Anal. and Appl. - 2007. - 334. - P. 132-139)

Active Galactic Nuclei under the scrutiny of CTA

Active Galactic Nuclei (hereafter AGN) produce powerful outflows which offer excellent conditions for efficient particle acceleration in internal and external shocks, turbulence, and magnetic reconnection events. The jets as well as particle accelerating regions close to the supermassive black holes (hereafter SMBH) at the intersection of plasma inflows and outflows, can produce readily detectable very high energy gamma-ray emission. As of now, more than 45 AGN including 41 blazars and 4 radiogalaxies have been detected by the present ground-based gamma-ray telescopes, which represents more than one third of the cosmic sources detected so far in the VHE gamma-ray regime. The future Cherenkov Telescope Array (CTA) should boost the sample of AGN detected in the VHE range by about one order of magnitude, shedding new light on AGN population studies, and AGN classification and unification schemes. CTA will be a unique tool to scrutinize the extreme high-energy tail of accelerated particles in SMBH environments, to revisit the central engines and their associated relativistic jets, and to study the particle acceleration and emission mechanisms, particularly exploring the missing link between accretion physics, SMBH magnetospheres and jet formation. Monitoring of distant AGN will be an extremely rewarding observing program which will inform us about the inner workings and evolution of AGN. Furthermore these AGN are bright beacons of gamma-rays which will allow us to constrain the extragalactic infrared and optical backgrounds as well as the intergalactic magnetic field, and will enable tests of quantum gravity and other "exotic" phenomena.Comment: 28 pages, 23 figure

A slow gravity compensated Atom Laser

We report on a slow guided atom laser beam outcoupled from a Bose-Einstein condensate of 87Rb atoms in a hybrid trap. The acceleration of the atom laser beam can be controlled by compensating the gravitational acceleration and we reach residual accelerations as low as 0.0027 g. The outcoupling mechanism allows for the production of a constant flux of 4.5x10^6 atoms per second and due to transverse guiding we obtain an upper limit for the mean beam width of 4.6 \mu\m. The transverse velocity spread is only 0.2 mm/s and thus an upper limit for the beam quality parameter is M^2=2.5. We demonstrate the potential of the long interrogation times available with this atom laser beam by measuring the trap frequency in a single measurement. The small beam width together with the long evolution and interrogation time makes this atom laser beam a promising tool for continuous interferometric measurements.Comment: 7 pages, 8 figures, to be published in Applied Physics

Suitability and optimisation of analytical indoor shelter model used for infiltration of carbon dioxide for typical dwellings

Carbon Capture Utilisation and Storage (CCUS) schemes involve transporting large quantities of carbon dioxide (CO2). A release of CO2 from CCUS transportation infrastructure could cause severe consequences for the surrounding population if the risk is not appropriately managed. Following a release of CO2, people in the surrounding environment could move away and seek shelter. The CO2 plume could drift past buildings causing the concentration of CO2 inside these buildings to build up. How much CO2 accumulates inside the buildings is key to the safety of their occupants. Previously an analytical infiltration model, based on wind and buoyancy driven ventilation, and a CFD infiltration model were created which can be used to predict the effect of CO2 exposure on building occupants following a release from an onshore CO2 pipeline [1]. These models can be used to determine the consequences of failure the dispersion behaviour of CO2 and the infiltration rate of a plume of CO2 into buildings and can form part of a Quantitative Risk Assessment (QRA) process for a CO2 pipeline. The models were validated against an experimental test of CO2 infiltration into a small enclosure. Comparisons were made between the analytical model, CFD model and experimental data for the build-up of CO2 in the enclosure and the changes in internal temperature. This paper investigates the suitability of the analytical model for buildings geometries more closely resembling domestic abodes and against a wider range of conditions by comparing its results to those of the CFD model for a set of representative case studies. It also tunes the parameters used in the model. Thirty test cases were created which explore the key parameters affecting the CO2 ventilation rate: wind speed, the area and height of the openings, internal temperature and building height, width and length. The analytical model’s predictions of the accumulation of CO2 inside a building are shown to be extremely close to the CFD results for all cases except one, where it makes an over prediction of the level of CO2. Furthermore, it is recommended that the analytical infiltration model is used with the tuned set of coefficients identified in this paper

Contributing factors to advanced brain aging in depression and anxiety disorders

Depression and anxiety are common and often comorbid mental health disorders that represent risk factors for aging-related conditions. Brain aging has shown to be more advanced in patients with major depressive disorder (MDD). Here, we extend prior work by investigating multivariate brain aging in patients with MDD, anxiety disorders, or both, and examine which factors contribute to older-appearing brains. Adults aged 18–57 years from the Netherlands Study of Depression and Anxiety underwent structural MRI. A pretrained brain-age prediction model based on >2000 samples from the ENIGMA consortium was applied to obtain brain-predicted age differences (brain PAD, predicted brain age minus chronological age) in 65 controls and 220 patients with current MDD and/or anxiety. Brain-PAD estimates were associated with clinical, somatic, lifestyle, and biological factors. After correcting for antidepressant use, brain PAD was significantly higher in MDD (+2.78 years, Cohen’s d = 0.25, 95% CI −0.10-0.60) and anxiety patients (+2.91 years, Cohen’s d = 0.27, 95% CI −0.08-0.61), compared with controls. There were no significant associations with lifestyle or biological stress systems. A multivariable model indicated unique contributions of higher severity of somatic depression symptoms (b = 4.21 years per unit increase on average sum score) and antidepressant use (−2.53 years) to brain PAD. Advanced brain aging in patients with MDD and anxiety was most strongly associated with somatic depressive symptomatology. We also present clinically relevant evidence for a potential neuroprotective antidepressant effect on the brain-PAD metric that requires follow-up in future research

Analytical and computational indoor shelter models for infiltration of carbon dioxide into buildings : comparison with experimental data

This paper describes two indoor shelter models – an analytical model and a Computational Fluid Dynamics (CFD) model - that can be used to predict the level of infiltration of carbon dioxide (CO2) into a building following a release from an onshore CO2 pipeline. The motivation behind the development of these models was to demonstrate that the effects of shelter should be considered as part of a Quantitative Risk Assessment (QRA) for CO2 pipeline infrastructure and to provide a methodology for considering the impact of a CO2 release on building occupants.A key component in the consequence modelling of a release from a CO2 pipeline is an infiltration model for CO2 into buildings which can describe the impact on people inside buildings during a release event. This paper describes the development of an analytical shelter model and a CFD model which are capable of predicting the change in internal concentration, temperature and toxic load within a single roomed building that is totally engulfed by a transient cloud of gaseous CO2. Application of the models is demonstrated by comparison with experimental measurements of CO2 accumulation in a building placed in the path of a drifting cloud of CO2. The analytical and CFD models are shown to make good predictions of the average change in internal concentration. Furthermore, it is demonstrated that the effects of shelter should be taken into account when conducting QRA assessments on CO2 pipelines. Document type: Articl