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Book ; Online: Propagation effects at low frequencies seen in the LOFAR long-term monitoring of the periodically active FRB 20180916B

Gopinath, A. / Bassa, C. G. / Pleunis, Z. / Hessels, J. W. T. / Chawla, P. / Keane, E. F. / Kondratiev, V. / Michilli, D. / Nimmo, K.

2023

Abstract: LOFAR (LOw Frequency ARray) has previously detected bursts from the periodically active, repeating fast radio burst (FRB) source FRB 20180916B down to unprecedentedly low radio frequencies of 110 MHz. Here we present 11 new bursts in 223 more hours of ... ...

Abstract	LOFAR (LOw Frequency ARray) has previously detected bursts from the periodically active, repeating fast radio burst (FRB) source FRB 20180916B down to unprecedentedly low radio frequencies of 110 MHz. Here we present 11 new bursts in 223 more hours of continued monitoring of FRB 20180916B in the 110-188 MHz band with LOFAR. We place new constraints on the source's activity window $w = 4.3^{+0.7}_{-0.2}$ day, and phase centre $\phi_{\mathrm{c}}^{\mathrm{LOFAR}} = 0.67^{+0.03}_{-0.02}$ in its 16.33-day activity cycle, strengthening the evidence for its frequency-dependent activity cycle. Propagation effects like Faraday rotation and scattering are especially pronounced at low frequencies and constrain properties of FRB 20180916B's local environment. We track variations in scattering and time-frequency drift rates, and find no evidence for trends in time or activity phase. Faraday rotation measure (RM) variations seen between June 2021 and August 2022 show a fractional change $>$50% with hints of flattening of the gradient of the previously reported secular trend seen at 600 MHz. The frequency-dependent window of activity at LOFAR appears stable despite the significant changes in RM, leading us to deduce that these two effects have different causes. Depolarization of and within individual bursts towards lower radio frequencies is quantified using LOFAR's large fractional bandwidth, with some bursts showing no detectable polarization. However, the degree of depolarization seems uncorrelated to the scattering timescales, allowing us to evaluate different depolarization models. We discuss these results in the context of models that invoke rotation, precession, or binary orbital motion to explain the periodic activity of FRB 20180916B. Comment: 21 pages, 10 figures, Submitted to MNRAS
Keywords	Astrophysics - High Energy Astrophysical Phenomena
Subject code	612
Publishing date	2023-05-10
Publishing country	us
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Disorders of cardiac hemodynamic in attack period of bronchial asthma in children

Kondratiev V.А. / Reznyk А.V.

Medičnì Perspektivi, Vol 21, Iss 2, Pp 57-

2016 Volume 62

Abstract: By dopplerechocardiography method there was studied functional state of cardiac ventricles and character of hemodynamic disorders in 48 patients aged 5-17 years in attack period of moderately-severe and severe bronchial asthma. Group of comparison ... ...

Abstract	By dopplerechocardiography method there was studied functional state of cardiac ventricles and character of hemodynamic disorders in 48 patients aged 5-17 years in attack period of moderately-severe and severe bronchial asthma. Group of comparison included 40 healthy peers. Disorders of central and peripheral hemodynamic in attack period of bronchial asthma in children were accompanied both by systolic and diastolic dysfunction of the left and right heart ventricles, herewith right ventricle was functioning in the mode of hyperdynamic, and left one – in the mode of hypodynamic. Combined systolic-diastolic variant of dysfunction both of right and left ventricles was developing in 58,3% of patients with moderately-severe and in 91,6% of patients with severe bronchial asthma. In the attack period of bronchial asthma in children equal directionality of systolic and diastolic dysfunction of heart ventricles was developing; this was characterized by synchronization of their function. Assessment of functional interaction of the ventricles under conditions of severe asthma attack showed direct and high (r=0,67) correlative interaction between finding of Tei index of the left and right ventricles, which characterize their systolic function; this, under conditions of increased hemodynamic pre-loading testified to compensatory increase of systolic interaction of ventricles. Direct and high (r=0,69) correlative interaction between time indices of isovolumic relaxation of the left and right ventricles, characterizing their diastolic function, testified to compensatory increase of diastolic interaction of ventricles under conditions of increase of hemodynamic post-loading. Imbalance of central and peripheral link of hemodynamic in attack period of bronchial asthma in children testified to development of cardiac insufficiency, which was compensated predominantly at the expense of increase of heart contractions rate.
Keywords	children ; cardiovascular system ; hemodynamic ; bronchial asthma ; Medicine ; R
Subject code	610
Language	English
Publishing date	2016-05-01T00:00:00Z
Publisher	Dnipro State Medical University
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Gender peculiarities of cardiac performance in children with bronchial asthma

Kondratiev V.A. / Reznik A.V.

Medičnì Perspektivi, Vol 21, Iss 1, Pp 86-

2016 Volume 90

Abstract: By the data of clinical-instrumental examination there was performed comparative assessment of gender differences in cardiac performance of 54 patients aged 5-15 years with persisting form of partially controlled atopic bronchial asthma in inter-attack ... ...

Abstract	By the data of clinical-instrumental examination there was performed comparative assessment of gender differences in cardiac performance of 54 patients aged 5-15 years with persisting form of partially controlled atopic bronchial asthma in inter-attack period of disease. Children were divided in two groups depending on gender - 28 boys and 26 girls. Group of comparison included 52 healthy children - 26 girls and 26 boys. In the girls in the inter-attack period of asthma reliably more often than in the boys there were revealed ventilation disturbance in the lungs by obstructive type; this promoted rise of pressure in the pulmonary artery. Herewith only in girls in 15,4% of cases there was revealed arterial pulmonary hypertension of a mild form. By the data of echocardiography in girls with bronchial asthma as compared with boys more expressed dilatation both of the right and left ventricles of the heart was observed. Average means of left ventricle contractility both in girls and boys in the inter-attack period of bronchial asthma were reliably decreased (р<0,01) as compared with healthy children, but in girl-patients as compared with boys these deviations were more significant. In the majority of such cases (in girls – 73,9%, in boys – 53,8%) decrease of contractile myocardium function was caused by presence of metabolic disorders in the form of repolarization changes of ventricular complex ob electrocardiogram. Investigations performed showed presence of some gender differences in cardiac performance in bronchial asthma children which should be considered in the course of treatment.
Keywords	children ; cardio-vascular system ; gender differences ; bronchial asthma ; Medicine ; R
Subject code	610
Language	English
Publishing date	2016-03-01T00:00:00Z
Publisher	Dnipro State Medical University
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article: Interfacial engineering by creating Cu-based ternary heterostructures on C₃N₄ tubes towards enhanced photocatalytic oxidative coupling of benzylamines

Fu, Yunqi / Zheng, Mang / Li, Qi / Zhang, Liping / Wang, Shuai / Kondratiev, V. V / Jiang, Baojiang

RSC advances. 2020 July 28, v. 10, no. 47

2020

Abstract: Benzylamine coupling is a very important reaction for the synthesis of imine but still faces many challenges. Herein, we present a highly effective strategy towards the coupling reaction by using environmentally friendly catalysts. These catalysts are ... ...

Abstract	Benzylamine coupling is a very important reaction for the synthesis of imine but still faces many challenges. Herein, we present a highly effective strategy towards the coupling reaction by using environmentally friendly catalysts. These catalysts are composed of Cu/Cu₂O/Cu₃N heterostructures supported by C₃N₄ tubes and the composites were synthesized by one-step hydrothermal treatment followed by calcination. Cu₂O, Cu₃N, and C₃N₄ all are responsive to visible light and the heterojunction formed can greatly enhance the charge separation. When used as photocatalysts for oxidative self-coupling of benzylamine at a low temperature of 323 K in air, Cu/Cu₂O/Cu₃N/C₃N₄ was able to give conversion and selectivity values of up to 99% and 98%, respectively. The high efficiency of the catalysts is attributable to their ability to generate large quantities of free radicals (such as ·OH and ·O₂⁻) under visible-light irradiation.
Keywords	air ; benzylamines ; hot water treatment ; imines ; irradiation ; light ; photocatalysis ; photocatalysts ; temperature
Language	English
Dates of publication	2020-0728
Size	p. 28059-28065.
Publishing place	The Royal Society of Chemistry
Document type	Article
Note	NAL-AP-2-clean
ISSN	2046-2069
DOI	10.1039/d0ra03164j
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Peculiarities of cardiac performance in children with bronchial asthma against chronic tonsillitis

Kondratiev V.А. / Reznik А.V. / Yegoreynko А.V.

Medičnì Perspektivi, Vol 20, Iss 4, Pp 34-

2015 Volume 39

Abstract: A comparative assessment of cardiac performance by the data of clinical-instrumental examination of 50 patients aged 5-15 years with persisting form of partially-controlled atopic bronchial asthma in the period between the attacks of the disease was made. ...

Abstract	A comparative assessment of cardiac performance by the data of clinical-instrumental examination of 50 patients aged 5-15 years with persisting form of partially-controlled atopic bronchial asthma in the period between the attacks of the disease was made. Children were divided into two groups depending on presence of concomitant chronic tonsillitis (18 patients) or absence of the latter (32 patients). In all cases by the data of spirography in children against chronic tonsillitis in the period between the attacks of the disease there were revealed ventillation disorders in the lungs by obstruction type, this promoted elevation of pressure in the pulmonary artery. Only in this group of patients in 27,8% of cases pulmonary arterial hypertension of moderate severity was revealed. By echocardiography data in children with asthma against chronic tonsillitis reliably more often (р<0,01) there was revealed decrease of contractile function of myocardium of the left cardiac ventricle; this was caused by the presence of metabolic disturbances in the myocardium in the majority of cases (83,3%). These changes were registered on the electrocardiogram in the form of repolarisation changes of the ventricular complex. Presence of concomitant chronic tonsillitis in children with bronchial asthma favored formation of pulmonary hypertension on the one side and worsening of contractile ability of myocardium of the left cardiac ventricle on the other side; this required performing therapeutic-preventive measures for sanation of chronic infectious focus in the nasopharynx to prevent formation of chronic cardiac insufficiency during asthma course.
Keywords	children ; cardio-vascular system ; bronchial asthma ; chronic tonsilitis ; Medicine ; R
Subject code	610
Language	English
Publishing date	2015-11-01T00:00:00Z
Publisher	Dnipro State Medical University
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Interfacial engineering by creating Cu-based ternary heterostructures on C

Fu, Yunqi / Zheng, Mang / Li, Qi / Zhang, Liping / Wang, Shuai / Kondratiev, V V / Jiang, Baojiang

RSC advances

2020 Volume 10, Issue 47, Page(s) 28059–28065

Abstract	Benzylamine coupling is a very important reaction for the synthesis of imine but still faces many challenges. Herein, we present a highly effective strategy towards the coupling reaction by using environmentally friendly catalysts. These catalysts are composed of Cu/Cu
Language	English
Publishing date	2020-07-28
Publishing country	England
Document type	Journal Article
ISSN	2046-2069
ISSN (online)	2046-2069
DOI	10.1039/d0ra03164j
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Disturbance of intracardiac hemodynamics in children with chronic rheumatic cardiac disease

Kondratiev V.A. / Porokhnya N.H. / Kunak Ye.V.

Medičnì Perspektivi, Vol 18, Iss 4, Pp 79-

2013 Volume 85

Abstract: By means of Doppler echocardiography there have been studied disturbances of intracardiac hemodynamics in 44 children aged 8-17 years with chronic rheumatic cardiac disease and developed mitral aortal and combined heart defects, as well as in chronic ... ...

Abstract	By means of Doppler echocardiography there have been studied disturbances of intracardiac hemodynamics in 44 children aged 8-17 years with chronic rheumatic cardiac disease and developed mitral aortal and combined heart defects, as well as in chronic rheumatic cardiac disease without developed valvar defect. Differential approach has been defined to administration of inhibitors of angiotensin-converting factor in rheumatic heart defects: developed insufficiency of mitral and/or aortal valves II-III stage leads to remodeling of the left heart portions with developing chronic insufficiency of blood circulation, being an index for prolonged, not less than a year usage of the angiotensin-converting factor. In the presence of isolated mitral regurgitation, I stage in children with chronic rheumatic cardiac disease usage of the angiotensin-converting factor may be cancelled due to insignificant disturbances of valvar hemodynamics and a small risk of developing blood circulation insufficiency. Timely sanation of chronic infection foci in nasopharynx (conservative and surgical treatment of chronic tonsillitis, adenoid vegetations, therapy of hemolytic streptococcus presence) decreases risk of developing rheumatic heart defect in children suffered acute rheumatic fever.
Keywords	children ; chronic rheumatic cardiac disease ; Doppler echocardiography ; hemodynamics ; inhibitors of angiotensin-converting factor ; Medicine ; R
Language	English
Publishing date	2013-12-01T00:00:00Z
Publisher	Dnipro State Medical University
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article: Labour resources and manpower policies in the Byelorussian SSR.

Kondratiev, V

International labour review

1979 Volume 118, Issue 6, Page(s) 731–745

MeSH term(s)	Developed Countries ; Economics ; Employment ; Health Manpower ; Legislation as Topic ; Public Policy ; Social Class ; Socioeconomic Factors ; USSR
Language	English
Publishing date	1979
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	1498683-8
ISSN	1564-913X ; 0020-7780
ISSN (online)	1564-913X
ISSN	0020-7780
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Dispersion measure variability for 36 millisecond pulsars at 150 MHz with LOFAR

Astronomy and Astrophysics

2020

Abstract: Context. Radio pulses from pulsars are affected by plasma dispersion, which results in a frequency-dependent propagation delay. Variations in the magnitude of this effect lead to an additional source of red noise in pulsar timing experiments, including ... ...

Abstract	Context. Radio pulses from pulsars are affected by plasma dispersion, which results in a frequency-dependent propagation delay. Variations in the magnitude of this effect lead to an additional source of red noise in pulsar timing experiments, including pulsar timing arrays (PTAs) that aim to detect nanohertz gravitational waves. Aims. We aim to quantify the time-variable dispersion with much improved precision and characterise the spectrum of these variations. Methods. We use the pulsar timing technique to obtain highly precise dispersion measure (DM) time series. Our dataset consists of observations of 36 millisecond pulsars, which were observed for up to 7.1 yr with the LOw Frequency ARray (LOFAR) telescope at a centre frequency of ~150 MHz. Seventeen of these sources were observed with a weekly cadence, while the rest were observed at monthly cadence. Results. We achieve a median DM precision of the order of 10−5 cm−3 pc for a significant fraction of our sources. We detect significant variations of the DM in all pulsars with a median DM uncertainty of less than 2 × 10−4 cm−3 pc. The noise contribution to pulsar timing experiments at higher frequencies is calculated to be at a level of 0.1–10 μs at 1.4 GHz over a timespan of a few years, which is in many cases larger than the typical timing precision of 1 μs or better that PTAs aim for. We found no evidence for a dependence of DM on radio frequency for any of the sources in our sample. Conclusions. The DM time series we obtained using LOFAR could in principle be used to correct higher-frequency data for the variations of the dispersive delay. However, there is currently the practical restriction that pulsars tend to provide either highly precise times of arrival (ToAs) at 1.4 GHz or a high DM precision at low frequencies, but not both, due to spectral properties. Combining the higher-frequency ToAs with those from LOFAR to measure the infinite-frequency ToA and DM would improve the result.
Subject code	535
Publishing country	de
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Book: On the completeness of root functions of elliptic boundary problems in a domain with conical points on the boundary

Egorov, Yu.V / Kondratiev, V.A / Schulze, B.-W

(Preprint / Universität Potsdam, Institut für Mathematik, Arbeitsgruppe Partielle Differentialgleichungen und Komplexe Analysis ; 2004,17)

2004

Author's details	Yu.V. Egorov ; V.A. Kondratiev ; B.-W. Schulze. Hrsg.: Arbeitsgruppe "Partielle Differentialgleichungen und Komplexe Analysis" am Institut für Mathematik der Universität Potsdam
Series title	Preprint / Universität Potsdam, Institut für Mathematik, Arbeitsgruppe Partielle Differentialgleichungen und Komplexe Analysis ; 2004,17
Language	English
Size	21 S., 30 cm
Publisher	Inst. für Mathematik, Arbeitsgruppe Partielle Differentialgleichungen und Komplexe Analysis
Publishing place	Potsdam
Document type	Book
Database	Library catalogue of the German National Library of Science and Technology (TIB), Hannover

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