Abstract
The diffuse Galactic gamma-ray flux between 0.1 and 1 PeV has recently been measured by the Tibet AS
γ
Collaboration. The flux and spectrum are consistent with the decay of neutral pions ...from hadronuclear interactions between Galactic cosmic rays and the interstellar medium (ISM). We derive the flux of the Galactic diffuse neutrino emission from the same interaction process that produces the gamma rays. Our calculation accounts for the effect of gamma-ray attenuation inside the Milky Way and uncertainties due to the spectrum and distribution of cosmic rays, gas density, and infrared emission of the ISM. We find that the contribution from the Galactic plane (GP) to the all-sky neutrino flux is ≲5%–10% around 100 TeV. The Galactic and extragalactic neutrino intensities are comparable in the GP region. Our results are consistent with the upper limit reported by the IceCube and ANTARES Collaborations, and predict that next-generation neutrino experiments may observe the Galactic component. We also show that the Tibet AS
γ
data imply either an additional component in the cosmic-ray nucleon spectrum or contribution from discrete sources, including PeVatrons such as superbubbles and hypernova remnants, and PeV electron accelerators. Future multimessenger observations between 1 TeV and 1 PeV are crucial to decomposing the origin of sub-PeV gamma-rays.
Abstract
Powerful jets and outflows generated in tidal disruption events (TDEs) around supermassive black holes have been suggested as possible sites producing high-energy neutrinos, but it is ...unclear whether such an environment can provide the bulk of the neutrinos detected by the IceCube Observatory. In this work, by considering realistic limits on the non-thermal emission power of a TDE jet and the birth rate of the TDEs with jets pointing towards us, we show that it is hard to use the jetted TDE population to explain the large flux and isotropic arrival directions of the observed TeV–PeV neutrinos. Therefore, TDEs cannot be the dominant sources, unless those without aligned jets can produce wide-angle emission of high-energy neutrinos. Supposing that is the case, we list a few recent jetted and non-jetted TDEs that have the best chance to be detected by IceCube, based on their energetics, distances and directions. A spatial and temporal association of these predicted events with the IceCube data should provide a decisive test on TDEs as origin of the IceCube neutrinos.
Recent measurements of the Geminga and B0656+14 pulsars by the gamma-ray telescope HAWC (along with earlier measurements by Milagro) indicate that these objects generate significant fluxes of very ...high-energy electrons. In this paper, we use the very high-energy gamma-ray intensity and spectrum of these pulsars to calculate and constrain their expected contributions to the local cosmic-ray positron spectrum. Among models that are capable of reproducing the observed characteristics of the gamma-ray emission, we find that pulsars invariably produce a flux of high-energy positrons that is similar in spectrum and magnitude to the positron fraction measured by PAMELA and AMS-02. In light of this result, we conclude that it is very likely that pulsars provide the dominant contribution to the long perplexing cosmic-ray positron excess.
A palladium‐catalyzed enantioselective sequential ring‐opening/cross‐coupling of cyclobutanones is disclosed that provides chiral indanones bearing C3‐quaternary stereocenters. The reaction process ...involves palladium‐catalyzed nucleophilic addition of cyclobutanones and aryl halides, enantioselective β‐carbon elimination, and intermolecular trapping of a transient σ‐alkylpalladium complex with boronic acids. Alternatively, an intramolecular cyclopropanation is realized through C−H bond functionalization in the absence of external coupling reagents, affording chiral cyclopropane‐fused‐indanones in good yields and enantioselectivity.
Enantioselective desymmetrization of prochiral cyclobutanones was realized through tandem palladium‐catalyzed ring‐opening/cyclopropanation to provide chiral cyclopropane‐fused indanones. With external coupling reagents, the transient σ‐alkylpalladium intermediate can be captured to afford an array of chiral indanones bearing C3‐quaternary stereocenters.
The merger of a neutron star (NS) binary may result in the formation of a long-lived, or indefinitely stable, millisecond magnetar remnant surrounded by a low-mass ejecta shell. A portion of the ...magnetar's prodigious rotational energy is deposited behind the ejecta in a pulsar wind nebula, powering luminous optical/X-ray emission for hours to days following the merger. Ions in the pulsar wind may also be accelerated to ultra-high energies, providing a coincident source of high-energy cosmic rays and neutrinos. At early times, the cosmic rays experience strong synchrotron losses; however, after a day or so, pion production through photomeson interaction with thermal photons in the nebula comes to dominate, leading to efficient production of high-energy neutrinos. After roughly a week, the density of background photons decreases sufficiently for cosmic rays to escape the source without secondary production. These competing effects result in a neutrino light curve that peaks on a few day timescale near an energy of ∼1018eV. This signal may be detectable for individual mergers out to ∼10 (100) Mpc by current (next generation) neutrino telescopes, providing clear evidence for a long-lived NS remnant, the presence of which may otherwise be challenging to identify from the gravitational waves alone. Under the optimistic assumption that a sizable fraction of NS mergers produce long-lived magnetars, the cumulative cosmological neutrino background is estimated to be for an NS merger rate of , overlapping with IceCube's current sensitivity and within the reach of next-generation neutrino telescopes.
The image segmentation is a process of segregating image into manageable partitions or segments. Image segmentation involves segmentation of foreground from background, based on similarities in ...features, color or shape. Segmentation is the foremost step in the scrutiny of the printed circuit boards. The segmentation technique basically partitions the PCB into small chunks containing primeval PCB sub-patterns. The conventional threshold segmentation technique considers the effect of image noise and grayscale in the threshold segmentation operation of the PCB (printed circuit board). In this paper, we have tried to overcome the problem of conventional segmentation for PCB such as grayscale overlapping and noise related issues in the segmented images. The basic formula of the optimal threshold operation is given to the threshold segmentation algorithm, the triangular image grid model is designed, the finite difference discrete method is exploited, the optimal threshold calculation formula is devised, and an attempt is made to get the best threshold for segmentation of PCB. Through experimental analysis for the PCB circuit image, two-dimensional OSTU threshold segmentation method, two-dimensional Fisher threshold segmentation method and the proposed research method are used to perform image grid threshold segmentation and to evaluate the performance of the proposed and the existing methods. The experimental results show that the threshold segmentation values obtained by the finite difference based threshold method has low image-noise effect, the gray scale overlap is also minimized, and segmentation accuracy is more as compare to other benchmarked threshold methods.
Aim
To explore the status of quality of life and psychological capital and analyse the different effects of psychological capital on the quality of life of cancer patients with different preferences ...for nurse spiritual therapeutics.
Design
A cross‐sectional survey was used.
Methods
Two hundred and eight cancer patients were recruited using convenience sampling from a tertiary Chinese hospital, between March and July 2019. Data on preferences for nurse spiritual therapeutics (PNST), psychological capital (PsyCap) and quality of life (QoL) were collected using paper questionnaires. Hierarchical multiple regression was employed to investigate the different influences of PsyCap on QoL of cancer patients with various levels of PNST.
Results
Compared with patients having high PNST, patients with mild‐moderate PNST experienced lower self‐efficacy, hope, optimism, PsyCap and social/family well‐being. PsyCap significantly explained the variance on QoL of patients with various levels of PNST. Age, gender, presence of caregiver were significant factors influencing physical, social/family and emotional well‐being of patients with high PNST.
Conclusion
The present study demonstrates disparities in PsyCap and QoL between cancer patients with mild‐moderate and high PNST. It is essential to be aware of the positive influences of PsyCap on QoL and develop effective interventions for patients to improve their QoL, especially for those with mild‐moderate PNST.
Impact
It is necessary to realize the benefits of PsyCap on QoL of cancer patients with various levels of PNST. Appropriate training for nurses needs to be developed to promote their spiritual care competencies. Moreover, supportive interventions should be developed for cancer patients to improve their PsyCap and QoL.
Newly born pulsars offer favorable sites for the injection of heavy nuclei, and for their further acceleration to ultrahigh energies. Once accelerated in the pulsar wind, nuclei have to escape from ...the surrounding supernova envelope. We examine this escape analytically and numerically and discuss the pulsar source scenario in light of the latest ultrahigh energy cosmic ray (UHECR) data. Our calculations show that, at early times, when protons can be accelerated to energies E > 10 super(20) eV, the young supernova shell tends to prevent their escape. In contrast, because of their higher charge, iron-peaked nuclei are still accelerated to the highest observed energies at later times, when the envelope has become thin enough to allow their escape. Ultrahigh energy iron nuclei escape newly born pulsars with millisecond periods and dipole magnetic fields of ~10 super(12)-10 super(13) G, embedded in core-collapse supernovae. Due to the production of secondary nucleons, the envelope crossing leads to a transition of composition from light to heavy elements at a few EeV, as observed by the Auger Observatory. The escape also results in a softer spectral slope than that initially injected via unipolar induction, which allows for a good fit to the observed UHECR spectrum. We conclude that the acceleration of iron-peaked elements in a reasonably small fraction (<, ~0.01%) of extragalactic rotation-powered young pulsars would reproduce satisfactorily the current UHECR data. Possible signatures of this scenario are also discussed.
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Construction of high-efficiency, low cost and stable non-noble metal catalyst on air cathode is of great importance for design and assembly of rechargeable Zn-air battery. Eriochrome ...black T (EBT) has phenolic hydroxyl and -N=Ν- groups, which provides multiple coordination sites for metal ions. Herein, Co9S8 nanoclusters implanted in Co/Mn-S,N multi-doped porous carbon (Co9S8@Co/Mn-S,N-PC) are fabricated with the mixture (i.e. EBT, metal precursors and dicyandiamide) by a coordination regulated pyrolysis strategy. Specifically, EBT effectively chelates with the Co and Mn ions, resulting in multiple incorporation and fine modulation of the carbon electronic structures. Meanwhile, its sulfonic acid groups are reduced at such high temperature, accompanied by simultaneously embedding S element in the carbon, ultimately in situ forming Co9S8 nanoclusters. The Co9S8@Co/Mn-S,N-PC performs as an effective bifunctional oxygen catalyst, displaying a positive half-wave potential of 0.85 V and a large limiting current density of 5.89 mA cm−2 for oxygen reduction reaction (ORR) in alkaline media, coupled with a small overpotential of 320 mV at 10 mA cm−2 towards oxygen evolution reaction (OER), outperforming commercial Pt/C and RuO2 catalysts, respectively. Furthermore, the assembled rechargeable Zn-air battery with Co9S8@Co/Mn-S,N-PC exhibits the much better charge/discharge performance and long-term durability (210 h, 630 cycles). This research opens an instructive avenue to develop high-efficient and stable bifunctional oxygen electrocatalysts in energy transformation and storage devices.
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