Candidate Tidal Disruption Event AT2019fdr Coincident with a High-Energy Neutrino.

The origins of the high-energy cosmic neutrino flux remain largely unknown. Recently, one high-energy neutrino was associated with a tidal disruption event (TDE). Here we present AT2019fdr, an exceptionally luminous TDE candidate, coincident with another high-energy neutrino. Our observations, including a bright dust echo and soft late-time x-ray emission, further support a TDE origin of this flare. The probability of finding two such bright events by chance is just 0.034%. We evaluate several models for neutrino production and show that AT2019fdr is capable of producing the observed high-energy neutrino, reinforcing the case for TDEs as neutrino sources.

Soft gamma rays from low accreting supermassive black holes and connection to energetic neutrinos.

The Universe is filled with a diffuse background of MeV gamma-rays and PeV neutrinos, whose origins are unknown. Here, we propose a scenario that can account for both backgrounds simultaneously. Low-luminosity active galactic nuclei have hot accretion flows where thermal electrons naturally emit soft gamma rays via Comptonization of their synchrotron photons. Protons there can be accelerated via turbulence or reconnection, producing high-energy neutrinos via hadronic interactions. We demonstrate that our model can reproduce the gamma-ray and neutrino data. Combined with a contribution by hot coronae in luminous active galactic nuclei, these accretion flows can explain the keV - MeV photon and TeV - PeV neutrino backgrounds. This scenario can account for the MeV background without non-thermal electrons, suggesting a higher transition energy from the thermal to nonthermal Universe than expected. Our model is consistent with X-ray data of nearby objects, and testable by future MeV gamma-ray and high-energy neutrino detectors.

Hidden Cores of Active Galactic Nuclei as the Origin of Medium-Energy Neutrinos: Critical Tests with the MeV Gamma-Ray Connection.

Mysteries about the origin of high-energy cosmic neutrinos have deepened by the recent IceCube measurement of a large diffuse flux in the 10-100 TeV range. Based on the standard disk-corona picture of active galactic nuclei (AGN), we present a phenomenological model enabling us to systematically calculate the spectral sequence of multimessenger emission from the AGN coronae. We show that protons in the coronal plasma can be stochastically accelerated up to PeV energies by plasma turbulence, and find that the model explains the large diffuse flux of medium-energy neutrinos if the cosmic rays carry only a few percent of the thermal energy. We find that the Bethe-Heitler process plays a crucial role in connecting these neutrinos and cascaded MeV gamma rays, and point out that the gamma-ray flux can even be enhanced by the reacceleration of secondary pairs. Critical tests of the model are given by its prediction that a significant fraction of the MeV gamma-ray background correlates with ∼10 TeV neutrinos, and nearby Seyfert galaxies including NGC 1068 are promising targets for IceCube, KM3Net, IceCube-Gen2, and future MeV gamma-ray telescopes.

Novel Superhydrophobic Surface with Solar-Absorptive Material for Improved De-Icing Performance.

Ice accretion is detrimental to numerous industries, including infrastructure, power generation, and aviation applications. Currently, some of the leading de-icing technologies utilize a heating source coupled with a superhydrophobic surface. This superhydrophobic surface reduces the power consumption by the heating element. Further power consumption reduction in these systems can be achieved through an increase in passive heat generation through absorption of solar radiation. In this work, a superhydrophobic surface with increased solar radiation absorption is proposed and characterized. An existing icephobic surface based on a polytetrafluoroethylene (PTFE) microstructure was modified through the addition of graphite microparticles. The proposed surface maintains hydrophobic performance nearly identical to the original superhydrophobic coating as demonstrated by contact and roll-off angles within 2.5% of the original. The proposed graphite coating also has an absorptivity coefficient under exposure to solar radiation 35% greater than typical PTFE-based coatings. The proposed coating was subsequently tested in an icing wind tunnel, and showed an 8.5% and 50% decrease in melting time for rime and glaze ice conditions, respectively.

Transition of velocity distributions in collapsing self-gravitating N-body systems.

By means of N-body simulations, we study the evolution of gravity-dominated systems from an early relaxation to a collapse, focusing on the velocity distributions and thermodynamic properties. To simulate the dynamical evolution, we consider self-gravitating small N-body systems enclosed in a spherical container with adiabatic or semipermeable walls. It is demonstrated that in the early relaxation process, the velocity distribution is non-Gaussian and q-Gaussian, since the system is in quasiequilibrium states (here q is the Tsallis entropic parameter). Thereafter, the velocity distribution undergoes higher non-Gaussian distributions, especially when the core forms rapidly in the collapse process; i.e., q tends to be larger than that for the quasiequilibrium state, since the velocity distribution further deviates from Gaussian. However, after the core forms sufficiently, the velocity distribution gradually relaxes toward a Gaussian-like distribution. Accordingly, the velocity distribution evolves from a non-Gaussian distribution through a higher non-Gaussian distribution to a Gaussian-like distribution; i.e., the velocity distribution does not monotonically relax toward a Gaussian-like distribution in our collapse simulations. We clearly show such a transition of the velocity distribution, based not only on the Tsallis entropic parameter but also on the ratio of velocity moments. We also find that a negative specific heat occurs in a collapse process with mass and energy loss (such as the escape of stars from globular clusters), even if the velocity distribution is Gaussian-like.

Thermodynamic properties of an evaporation process in self-gravitating N -body systems.

By means of N -body simulations, we consider self-gravitating open systems enclosed in a spherical container with semipermeable reflecting walls, in order to investigate the thermodynamics of the evaporation process in self-gravitating N -body systems (such as the escape of stars from globular clusters). To simulate the evaporation process, when the energy of a particle exceeds a certain threshold value, the particle passes through the semipermeable reflecting wall freely. We show that the thermodynamic properties of the evaporation process, such as the dependence of the temperature on energy, agree well with those of stellar polytropes, if the system is in an approximate virial equilibrium state. However, in a lower-energy region or for a rapid evaporation process, the thermodynamic properties deviate from those for the stellar polytrope. Nevertheless, we found that a negative specific heat occurs even in the lower-energy region or for a rapid evaporation process.

Negative specific heat in self-gravitating N-body systems enclosed in a spherical container with reflecting walls.

Gravity-dominated systems have a negative specific heat. We investigate the negative specific heat of self-gravitating systems enclosed in a spherical container with reflecting walls by means of N-body simulations. To simulate nonequilibrium processes, a particle reflected at a nonadiabatic wall is cooled to mimic energy loss by reflecting walls, while an adiabatic wall is employed for microcanonical ensembles. We show that a negative specific heat occurs not only in the microcanonical ensemble but also in certain nonequilibrium processes with the nonadiabatic wall. With increasing cooling rates, the dependence of temperature T on energy epsilon , i.e., the epsilon-T curve, gradually deviates from the microcanonical ensemble and approaches a certain common curve at a low-energy region. The common curve agrees with an epsilon-T curve for stellar polytropes, especially for the polytrope index of n approximately 5 . We show that the stellar polytrope should be related to the present nonequilibrium process appearing in the self-gravitating system with the nonadiabatic wall. In the nonequilibrium process, a rapid change in velocity at the nonadiabatic wall significantly affects the velocity and density profiles. In particular, the greater the cooling rate, the greater the local velocity gradient at a low-energy region.

Synthesis, structure, and reactivity of novel 3,4-diphosphacyclobutenes bearing silyl groups.

[reaction: see text] Copper-mediated homocoupling of sterically hindered 2-(2,4,6-tri-tert-butylphenyl)-1-trialkylsilyl-2-phosphaethenyllithiums afforded 1,2-bis(trialkylsilyl)-3,4-diphosphacyclobutenes (1,2-dihydrodiphosphetenes) through a formal electrocyclic [2+2] cyclization in the P=C-C=P skeleton as well as 2-trimethylsilyl-1,4-diphosphabuta-1,3-diene. Reduction of 1,2-bis(trimethylsilyl)-3,4-diphosphacyclobutenes followed by quenching with electrophiles afforded ring-opened products, (E)-1,2-bis(phosphino)-1,2-bis(trimethylsilyl)ethene and (Z)-2,3-bis(trimethylsilyl)-1,4-diphosphabut-1-ene. The structures of the ring-opened products indicated E/Z isomerization around the C=C bond after P-P bond cleavage of 5, and the isomerization of the P-C=C skeleton. Ring opening of 1,2-bis(trimethylsilyl)-3,4-diphosphacyclobutenes affording (E,E)- and (Z,Z)-1,4-diphosphabuta-1,3-dienes was observed upon desilylation.

Experimental and theoretical studies on the conjugation of the phosphorus-carbon double bond with a cyclopropyl group.

X-ray structural analysis for (Z)-2-cyclopropyl-1-(2,4,6-tri-tert-butylphenyl)-1-phosphaethene (2) was performed to confirm that the cyclopropyl group largely interacts with the P[double bond]C group compared with its carbon analogue, vinylcyclopropane (1). Absorption spectrum and redox properties of 2 were also studied to prove the conjugation. Theoretical investigation for nonsubstituted derivatives (4) indicated conjugative interaction between the P[double bond]C and cyclopropyl groups and revealed the physicochemical similarities between the P=C and C[double bond]C.

Preparation, structure, and reaction of a sterically encumbered 1-phosphaallene containing a cyclopropylidene moiety.

[reaction: see text] Sterically protected (Z)-1-(2,4,6-tri-tert-butylphenyl)-2,5-dibromo-1-phosphapent-1-ene was allowed to react with potassium tert-butoxide to afford a cyclopropylidenephosphaethene, which was characterized spectroscopically and by X-ray crystallography. Construction of the cycloalkyl groups and isomerization of 1-phosphapenta-1,2,4-trienes to cyclopropylidenephosphaethenes are also described.

Percutaneous cervical cordotomy and subarachnoid phenol block using fluoroscopy in pain control of costopleural syndrome.

We examined the efficacy of percutaneous cervical cordotomy (PCC) and subarachnoid phenol block using fluoroscopy (SAPB-F) for control of chest and/or back pain from costopleural syndrome. The efficacy of each block was evaluated by changes in pain score (PS), analgesic dose and performance status 1 week after the block, as well as by the complications. Between 1980 and 1986, PCC was performed in 10 patients. SAPB-F was performed in 13 patients between 1987 and 1991. Pain was not well controlled by analgesics in any of these patients. For PCC the follow-up period was 94.7 +/- 71.1 days. PS (VAS, 0-10) reduced from 8.5 +/- 0.9 to 3.0 +/- 2.7. No analgesics were needed in 4 patients. Pain recurred in 1 patient. Hemiparesis occurred in 2 patients. General fatigue occurred in 6 patients. In 4 patients with these complications performance status deteriorated and did not recover during the follow-up period. For SAPB-F the follow-up period was 71.8 +/- 44.0 days. SAPB-F was designed to achieve selective phenol deposit at the targeted nerve root. PS decreased from 7.5 +/- 1.9 to 2.7 +/- 2.6. No analgesics were needed in 5 patients. Pain recurred in 3 patients. There were no complications and no changes in performance status. From this study we concluded that PCC is an effective method of pain control for costopleural syndrome, but a risk of serious complications is involved. SAPB-F is an effective and safe method and should be the first choice of nociceptive pathway block.

Reference of pain following percutaneous cervical cordotomy.

In order to clarify the mechanism of reference of pain following cordotomy (ROPC), the authors investigated ROPC in 66 patients undergoing percutaneous cervical cordotomy (PCC) and examined the features of ROPC and the correlation between the occurrence of ROPC and the pre-operative pain states, as well as the results of PCC. ROPC was observed in 7 patients. It occurred immediately after PCC in 6 of 7 patients and 6 h after PCC in 1 patient. The pain was referred horizontally and cranially from the region rendered totally or largely analgesic by PCC to the normally innervated region. The region to which the pain was referred was not fixed. The referred pain disappeared by rendering the region where referred pain was felt analgesic with additional PCC. There was no correlation between the occurrence of ROPC and pre-operative pain states, or the results of PCC. From these results we postulate that: (1) ROPC occurs via a subsidiary pathway consisting of ascending chains of short neurons connecting dorsal horn neurons longitudinally and latitudinally; (2) the subsidiary pathway is inhibited under normal conditions by feedback inhibition from second-order neurons and/or higher central neurons of the nociceptive pathway; and (3) ROPC results from the release of the feedback inhibition by cordotomy.

A mechanism of new pain following cordotomy; reference of sensation.

An antero-lateral cordotomy was performed on a 62-year-old man who had been suffering from intractable right chest pain caused by lung cancer. Six hours after the cordotomy a new pain occurred in an analogous part of the body on the opposite side; the intensity increased gradually and it became as severe as the original within 1 week. Reference of sensation from analgesic area of cordotomy to the opposite side of the body was induced by noxious stimuli. Intrathecal phenol block to the nerves conveying the cancer pain abolished the new pain and the reference of sensation from this blocked area, though it remained unchanged in other analgesic areas of cordotomy. This substantiates that the new pain was a reference of the original cancer pain.