Observational information on high-energy astrophysical neutrinos is being continuously collected by the IceCube observatory. However, the sources of the neutrinos are still unknown. In this study, we ...use radio very long baseline interferometry (VLBI) data for a complete VLBI flux density-limited sample of active galactic nuclei (AGNs). We address the problem of the origin of astrophysical neutrinos with energies above 200 TeV in a statistical manner. It is found that AGNs positionally associated with IceCube events have typically stronger parsec-scale cores than the rest of the sample. The posttrial probability of a chance coincidence is 0.2%. We select the four strongest AGNs as highly probable associations: 3C 279, NRAO 530, PKS 1741−038, and OR 103. Moreover, we find an increase of radio emission at frequencies above 10 GHz around neutrino arrival times for several other VLBI-selected AGNs on the basis of RATAN-600 monitoring. The most pronounced example of such behavior is PKS 1502+106. We conclude that AGNs with bright Doppler-boosted jets constitute an important population of neutrino sources. High-energy neutrinos are produced in their central parsec-scale regions, probably in proton-photon interactions at or around the accretion disk. Radio-bright AGNs that are likely associated with neutrinos have very diverse γ-ray properties, suggesting that γ-rays and neutrinos may be produced in different regions of AGNs and not directly related. A small viewing angle of the jet-disk axis is, however, required to detect either of them.
Russia's Dead End Kovalev, Andrei A; Levine, Steven I; Reddaway, Peter
08/2017
eBook
Elite-level Soviet politics, privileged access to state secrets, knowledge about machinations inside the Kremlin-such is the environment in which Andrei A. Kovalev lived and worked. In this memoir of ...his time as a successful diplomat serving in various key capacities and as a member of Mikhail Gorbachev's staff, Kovalev reveals hard truths about his country as only a perceptive witness can do. InRussia's Dead EndKovalev shares his intimate knowledge of political activities behind the scenes at the Ministry of Foreign Affairs and the Kremlin before and after the dissolution of the USSR in December 1991, including the Russia of Vladimir Putin.Kovalev analyzes Soviet efforts to comply with international human-rights obligations, the machinations of the KGB, and the link between corrupt oligarchs and state officials. He documents the fall of the USSR, the post-Soviet explosion of state terrorism and propaganda, and offers a nuanced historical explanation of the roots of Russia's contemporary crisis under Vladimir Putin. This insider's memoir provides a penetrating analysis of late-Soviet and post-Soviet Russian politics that is pungent, pointed, witty, and accessible. It assesses the current dangerous status of Russian politics and society while illuminating the path to a more just and democratic future.
Recently we have shown that high-energy neutrinos above 200 TeV detected by IceCube are produced within several parsecs in the central regions of radio-bright blazars, that is active galactic nuclei ...with jets pointing toward us. To independently test this result and extend the analysis to a wider energy range, we use public data for all neutrino energies from seven years of IceCube observations. The IceCube point-source likelihood map is analyzed against the positions of blazars from a statistically complete sample selected according to their compact radio flux density. The latter analysis delivers a 3.0 significance, with the combined post-trial significance of both studies being 4.1 . The correlation is driven by a large number of blazars. Together with fainter but physically similar sources not included in the sample, they may explain the entire IceCube astrophysical neutrino flux as derived from muon-track analyses. The neutrinos can be produced in interactions of relativistic protons with X-ray self-Compton photons in parsec-scale blazar jets.
The activation of direct interspecies electron transfer (DIET) by the supplementation of conductive materials is one of the effective and available methods to enhance anaerobic digestion (AD). ...Microorganisms that colonize the surface of these materials form biofilms, the study of which could provide new insights into the character of the DIET process and its effect on AD. The present study focused on AD performance, microbial community, as well as morphological and topological features of biofilms on various materials used to promote DIET during AD of low-concentration swine manure. The best AD characteristics were observed in stainless steel mesh (SM)/digested cow manure (CM) and polyester felt (PF)/digested sewage sludge (SS) combinations used as material/inoculum, respectively. Thus, potential methane yields in CM-SM and SS-PF were up to 26.4% and 26.2% higher compared to the corresponding controls. Microbial analysis of biofilms revealed the dominance of putatively syntrophic bacteria of the MBA03 group of the Limnochordia class in CM inoculated reactors, and syntrophic proteolytic bacteria of the genus Coprothermobacter and acetogenic Clostridium sensu stricto 1, known for their ability to carry out DIET, in SS inoculated reactors. Biofilms on non-conductive materials contained pili-like structures, which were observed only in SS inoculated reactors. Polyester felt tended to biofoul better than carbon felt, resulting in up to 2.8, 3.2 and 1.8 higher nucleic acid, extracellular polymeric substances, and total biomass content, respectively, depending on the inoculum. These results provide new insights into the different types of DIET that can occur in low-loaded AD systems with attached growth.
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•Better AD characteristics correlated well with the presence of pili-like structures.•Coprothermobacter and Clostridium sensu stricto 1 play a key role in A-type DIET.•MBA03 group of the Limnochordia class dominated in biofilms on conductive mesh.•Polyester felt had denser biofilms than carbon felt regardless of the inoculum used.•DIET could take place and be beneficial to the performance of low-loaded AD systems.
In this paper we discuss lower bounds for convergence of convex optimization methods of high order and attainability of this bounds. We formulate a hypothesis that covers all the cases. It is ...noticeable that we provide this statement without a proof. Newton method is the most famous method that uses gradient and Hessian of optimized function. However, it converges locally even for strongly convex functions. Global convergence can be achieved with cubic regularization of Newton method Nesterov, Polyak, 2006, whose iteration cost is comparable with iteration cost of Newton method and is equivalent to inversion of Hessian of optimized function. Yu.Nesterov proposed accelerated variant of Newton method with cubic regularization in 2008 Nesterov, 2008. R.Monteiro and B. Svaiter managed to improve global convergence of cubic regularized method in 2013 Monteiro, Svaiter, 2013. Y.Arjevani, O. Shamir and R. Shiff showed that convergence bound of Monteiro and Svaiter is optimal (cannot be improved by more than logarithmic factor with any second order method) in 2017 Arjevani et al., 2017. They also managed to find bounds for convex optimization methods of p-th order for $p 2$. However, they got bounds only for first and second order methods for strongly convex functions. In 2018 Yu.Nesterov proposed third order convex optimization methods with rate of convergence that is close to this lower bounds and with similar to Newton method cost of iteration Nesterov, 2018. Consequently, it was showed that high order methods can be practical. In this paper we formulate lower bounds for p-th order methods for $p 3$ for strongly convex unconstrained optimization problems. This paper can be viewed as a little survey of state of the art of high order optimization methods.
The Shatak Formation, comprising a part of the Mashak Suite (RF2), is located on the western slope of the Southern Urals. It consists of various rock types, including sedimentary rocks, such as ...conglomerates, polymictic sandstones, aleurolites, and carbonaceous clayey shales, as well as igneous rocks, including picrites, basalts, dacites, rhyodacites, and rhyolites, and volcanogenic–sedimentary rocks, such as tuffs and tuff breccias. In this article, oxyfluoride (La, Ce) (OnFm)3 mineralization, occurring in the contact zone between the metabasalts and quartz sandstones, is described for the first time in the literature. This is represented by compounds of variable compositions forming an isomorphic series: trifluoride, (La, Ce)F3–oxyfluoride, (La, Ce)OF–oxide, and (La, Ce)2O3. By analyzing several binary phase diagrams, significant coordination between oxygen, fluorine, and cerium in the chemical composition of oxyfluorides has been highlighted. However, the behavior of lanthanum has been shown to exhibit some irregularity. The genesis of oxyfluoride mineralization is attributed to the regional metamorphism of rocks within the Shatak Formation. During the hydrothermal process, the decomposition of fluorapatite, which is unstable during both hydrothermal metamorphism and supergene processes, resulted in the release of fluorine, as well as potentially lanthanum and cerium. Variations in the chemical composition of oxyfluorides, which are formed in the presence of an excess of oxygen resulting from water dissociation, are determined by local differences in the content of the main components within the forming microfractures.
According to the International Energy Agency, only a small part of the full potential of biomass energy is currently used in the world. The annual amount of agricultural waste in the Russian ...Federation is estimated at about 152 million tons, and the energy potential of animal waste is 201 PJ/year. Anaerobic digestion is an efficient method of converting organic waste into renewable energy sources. Previously, the positive effect of pretreatment of various organic feedstocks in vortex layer apparatus (VLA) on the characteristics of anaerobic digestion and energy efficiency was shown. Currently, there is a significant interest in the world in obtaining biohydrogen from organic waste using the dark fermentation (DF) process. During pretreatment in the VLA, the iron working bodies are abraded and iron particles are introduced into the feedstock of the DF reactor. This may have a positive effect on the production rate and yield of hydrogen, which has not been previously studied. This work is aimed at evaluating the possibility of using the VLA as a method for pretreatment of a dark fermentation feedstock for the intensification of biohydrogen production. To achieve this goal, an experimental setup was constructed. It consisted of a 45 L DF reactor, a VLA and a process control system to collect data on the DF process parameters every 5 min. At a hydraulic retention time in the DF reactor of 24 h and in the VLA of 30 s, the hydrogen content in the biogas increased from 51.1% to 52.2%. At the same time, the pH increased from 3.85 to 4.8–4.9, and the hydrogen production rate increased by 16% to 1.941 L/(L day). The hydrogen yield was 80.9 ml/g VS. Thus, pretreatment of the feedstock in VLA can be an effective way to intensify the DF process; however, further study of the VLA operating modes is required in order to optimize the concentrations of iron particles introduced into the feedstock for the most efficient continuous production of dark fermentative biohydrogen.
A powder of equiatomic CoCrFeNiCu high entropy alloy (HEA) was prepared by short-term (120 min) high energy ball milling (HEBM). Our structural and chemical analysis showed that microsized particles ...of fcc CoCrFeNiCu with a grain size of 8 nm were obtained after 120 min of HEBM at 694/1388 rpm. The structural/phase evolution of CoCrFeNiCu HEA powder and its thermal stability were explored by high-temperature XRD at 600 °C, 800 °C and 1000 °C, by DSC up to 1500 °C, through the consolidation by SPS at 800 °C and 1000 °C, and characterized using XRD, SEM and EDX analyses. In-situ HT XRD analysis during 5.5 h of annealing showed the involvement of transient phases: the bcc phase that appeared in 1 h of annealing at 600 °C and disappeared at higher temperatures; and the fcc1 phase (Cu-rich) arising in 2 h of annealing at 800 °C and disappearing at 1000 °C in 3 h of annealing. SPS consolidation at 1000 °C and annealing at 1000 °C for 5.5 h were found to result in the formation of single-phase fcc2 CoCrFeNiCu alloy with a lean amount of Cu. The melting points for Cu-rich and Cu-depleted HEAs were found as 1118 °C and 1288 °C (Calphad calculations) and 1115 °C and 1365 °C (DSC measurements), respectively. SPS consolidation at 1000 °C under a pressure of 50 MPa yielded the single-phase fcc CoCrFeNiCu0.5 alloy that turned thermodynamically more favorable than the equiatomic one. Thus, we can suppose thereupon, that the equiatomic fcc phase that appears after 120 min of HEBM is metastable because of the excess of Cu atoms. During annealing in the temperature range 800–1000 °C, the Cu-rich fcc1 phase precipitates from the initial single-phase alloy, while the “mother phase” transforms into the more stable Cu-depleted fcc2 phase. The chemical compositions of Cu-depleted and Cu-rich phases for the SPS-consolidated HEA CoCrFeNiCu alloy (at 800 °C) were determined from TEM–EDX analyses. Optimal combination of short-term HEBM and SPS consolidation can be recommended as a facile route to fabrication of single-phase fcc equiatomic CoCrFeNiCu HEA powders and bulk materials with good structural/elemental homogeneity.
•Equiatomic fcc CoCrFeNiCu HEA was synthesized by short-term (120 min) HEBM.•At 800–1000 °C, HEBM-processed fcc phase transforms to Cu-rich and Cu-depleted ones.•In situ HT XRD (5.5 h) and SPS at 1000 °C yield Cu-depleted single fcc phase.•Melting points for Cu-rich and Cu-depleted HEAs were detected by DSC and Calphad.•Cu-depleted fcc HEA showed higher heat resistance than the equiatomic one.
We present the results from a multiwavelength campaign conducted in 2006 August of the powerful unk-ray quasar PKS 1510-089 (z = 0.361). This campaign commenced with a deep Suzaku observation lasting ...3 days for a total exposure time of 120 ks and continued with Swift monitoring over 18 days. Besides Swift observations, the campaign included ground-based optical and radio data and yielded a quasi-simultaneous broadband spectrum from 10 super(9) to 10 super(19) Hz. The Suzaku observation provided a high signal-to-noise ratio X-ray spectrum, which is well represented by an extremely hard power law with a photon index of Gamma unk 1.2, augmented by a soft component apparent below 1 keV, which is well described by a blackbody model with a temperature of kT unk 0.2 keV. Monitoring by Suzaku revealed temporal variability that differs between the low- and high-energy bands, again suggesting the presence of a second, variable component in addition to the primary power-law emission. We model the broadband spectrum, assuming that the high-energy spectral component results from Comptonization of infrared radiation produced by hot dust located in the surrounding molecular torus. The adopted internal shock scenario implies that the power of the jet is dominated by protons, but with a number of electrons and/or positrons that exceeds the number of protons by a factor of similar to 10. We also find that inhomogeneities responsible for the shock formation prior to the collision may produce bulk Compton radiation, which can explain the observed soft X-ray excess and possible excess at similar to 18 keV. We note, however, that the bulk Compton interpretation is not unique, as discussed briefly in the text.
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