A theoretical model of a wake of a body towed in a stratified fluid at large Reynolds and Froude numbers

International audienceThe objective of the present paper is to develop a theoretical model describing the evolution of a turbulent wake behind a towed sphere in a stably stratified fluid at large Froude and Reynolds numbers. The wake flow is considered as a quasi two-dimensional (2-D) turbulent jet flow whose dynamics is governed by the momentum transfer from the mean flow to a quasi-2-D sinuous mode growing due to hydrodynamic instability. The model employs a quasi-linear approximation to describe this momentum transfer. The model scaling coefficients are defined with the use of available experimental data, and the performance of the model is verified by comparison with the results of a direct numerical simulation of a 2-D turbulent jet flow. The model prediction for the temporal development of the wake axis mean velocity is found to be in good agreement with the experimental data obtained by Spedding (1997)

Behaviour of the Blazar CTA 102 during two giant outbursts

Blazar CTA 102 underwent exceptional optical and high-energy outbursts in 2012 and 2016-2017. We analyze its behaviour during these events, focusing on polarimetry as a tool that allows us to trace changes in the physical conditions and geometric configuration of the emission source close to the central black hole. We also use Fermi gamma-ray data in conjunction with optical photometry in an effort to localize the origin of the outbursts.AST-1615796 - Boston Universit

On the S-wave piD-scattering length in the relativistic field theory model of the deuteron

The S-wave scattering length of the strong pion-deuteron (pi D) scattering is calculated in the relativistic field theory model of the deuteron suggested in [1,2].The theoretical result agrees well with the experimental data. The important role of the Delta-resonance contribution to the elastic pi D-scattering is confirmed.Comment: 7 pages, no figures, accepted for publication in Z. Phys.

Dissipation rate of turbulent kinetic energy in stably stratified sheared flows

Over the years, the problem of dissipation rate of turbulent kinetic energy (TKE) in stable stratification remained unclear because of the practical impossibility to directly measure the process of dissipation that takes place at the smallest scales of turbulent motion. Poor representation of dissipation causes intolerable uncertainties in turbulence-closure theory and thus in modelling stably stratified turbulent flows. We obtain a theoretical solution to this problem for the whole range of stratifications from neutral to limiting stable; and validate it via (i) direct numerical simulation (DNS) immediately detecting the dissipation rate and (ii) indirect estimates of dissipation rate retrieved via the TKE budget equation from atmospheric measurements of other components of the TKE budget. The proposed formulation of dissipation rate will be of use in any turbulence-closure models employing the TKE budget equation and in problems requiring precise knowledge of the high-frequency part of turbulence spectra in atmospheric chemistry, aerosol science, and microphysics of clouds.</p

Multiwavelength temporal and spectral variability of the blazar OJ 287 during and after the 2015 December flare: A major accretion disc contribution

© 2018 The Author(s). We present a multiwavelength spectral and temporal analysis of the blazar OJ 287 during its recent activity between 2015 December and 2016 May, showing strong variability in the nearinfrared (NIR) to X-ray energies with detection at γ -ray energies as well. Most of the optical flux variations exhibit strong changes in polarization angle and degree. All the interband time lags are consistent with simultaneous emissions. Interestingly, on days with excellent data coverage in the NIR-UV bands, the spectral energy distributions (SEDs) show signatures of bumps in the visible-UV bands, never seen before in this source. The optical bump can be explained as accretion-disc emission associated with the primary black hole of mass ~1.8 × 1010M⊙ while the little bump feature in the optical-UV appears consistent with line emission. Further, the broad-band SEDs extracted during the first flare and during a quiescent period during this span show very different γ -ray spectra compared to previously observed flare or quiescent spectra. The probable thermal bump in the visible seems to have been clearly present since 2013 May, as found by examining all available NIR-optical observations, and favours the binary supermassive black hole model. The simultaneous multiwavelength variability and relatively weak γ -ray emission that shows a shift in the SED peak is consistent with γ -ray emission originating from inverse Compton scattering of photons from the line emission that apparently contributes to the little blue bump

Diagnostics and treatment challenges of Ph-like acute lymphoblastic leukemia: a description of 3 clinical cases

B-cell acute lymphoblastic leukemia (B-ALL) is a diverse group of malignant blood disorders both with regard to the biological properties of the tumor and to therapeutic approaches. Immunophenotyping, molecular genetic techniques, whole-genome sequencing characterize B-ALL as a very diverse group for sensitivity to chemotherapy and prognosis. We present three clinical cases of patients with B-ALL and expected good response to standard therapy, in whom standard protocol treatment failured: refractoriness, persistence of minimal residual disease (MRD), and progression (MRD increase). The remission in these patients was achieved after chemotherapy change to immunological targeted therapy. Nowadays a unified therapeutic approach to all primary patients of the B-ALL is considered generally outdated. Great efforts are carrying out to develop molecular genetic classifications. The molecular dissection of subtypes of B-ALL goes on, and new protocols for selective treatment with targeting are clearly outlined for each subtype of B-ALL

Pan-Eurasian Experiment (PEEX): Towards a holistic understanding of the feedbacks and interactions in the land-Atmosphere-ocean-society continuum in the northern Eurasian region

The northern Eurasian regions and Arctic Ocean will very likely undergo substantial changes during the next decades. The Arctic-boreal natural environments play a crucial role in the global climate via albedo change, carbon sources and sinks as well as atmospheric aerosol production from biogenic volatile organic compounds. Furthermore, it is expected that global trade activities, demographic movement, and use of natural resources will be increasing in the Arctic regions. There is a need for a novel research approach, which not only identifies and tackles the relevant multi-disciplinary research questions, but also is able to make a holistic system analysis of the expected feedbacks. In this paper, we introduce the research agenda of the Pan-Eurasian Experiment (PEEX), a multi-scale, multi-disciplinary and international program started in 2012 (https://www.atm.helsinki.fi/peex/). PEEX sets a research approach by which large-scale research topics are investigated from a system perspective and which aims to fill the key gaps in our understanding of the feedbacks and interactions between the land-Atmosphere-Aquatic-society continuum in the northern Eurasian region. We introduce here the state of the art for the key topics in the PEEX research agenda and present the future prospects of the research, which we see relevant in this context

Results of program acute myeloid leukemia therapy use in National Medical Research Center for Hematology of the Ministry of Health of Russian Federation

Objective. To analyze treatment results of 172 patients with acute myeloid leukemia (AML) aged 18-60 years in National Medical Research Center for Hematology of MHRF. Materials and methods. Inductive and consolidation program for 139 (80%) patients was based on a standardized protocol: 4 courses “7+3” with different anthracycline use (2 courses of daunorubicin, idarubicin, mitoxantrone) and continuous use of cytarabine on the second inductive course. In 20% of patients cytarabine courses at the dose of 1 g/m2 2 times a day for 1-3 days combined with idarubicin and mitoxantrone were used as two consolidation courses. Allogenic bone marrow transplantation was performed in the first complete remission (CR) period in 40% of patients. Results. The frequency of CR achievement in all patients was 78.6%, refractory forms were observed in 13.9% of patients, early mortality - in 7.5% of patients. Seven-year overall survival (OS) rate was 40.7%, relapse free survival (RFS) - 43.2%. When estimating effectiveness depending on cytogenetic risk group it was demonstrated that 5-year OS and RFS in patients with translocation (8; 21) cannot be considered as satisfying, it accounted for 50 and 34%, respectively. At the same time in patients with 16th chromosome inversion (inv16) these characteristics accounted for 68.6 and 63.5%. Acquired results forced reconsidering of the consolidation program in AML patients of this subgroup. The median time to allogenic blood stem cells transplantation (allo-BSCT) in patients with first CR was 6.5 months that was taken as a reference point in landmark analysis of patients in whom allo-BSCT was not performed. Landmark analysis showed that in AML patients of favorable prognosis group allo-BSCT does not significantly reduce the probability of relapse (0 and 36%) and does not influence RFS (33 and 64%). In patients of border-line and poor prognosis allo-BSCT significantly reduces relapse probability (26 and 66%; 20 and 100%) and significantly increases a 7-year RFS (68.7 and 30%; 45.6 and 0%). Allo-BSCT also results in significant RFS increase and reduces the probability of relapse (25 and 78%) in patients in whom CR was achieved only after the second induction course. At the same time allo-BSCT does not influence patients who achieved CR after the first treatment course: 55 and 50%. Conclusion. Multivariate analysis showed that cytogenetic risk group (HR=2.3), time of CR achievement (HR=2.9), and allo-BSCT transplantation (HR=0.16) are independent factors for disease relapse prognosis after achieving CR