Quantum Effect and Curvature Strength of Naked Singularities

There are many solutions to the Einstein field equations that demonstrate naked singularity (NS) formation after regular evolution. It is possible, however, that such a quantum effect as particle creation prevents NSs from forming. We investigate the relation between the curvature strength and the quantum effects of NSs in a very wide class of spherical dust collapse. Through a perturbative calculation, we find that if the NS is very strong, the quantum particle creation diverges as the Cauchy horizon is approached, while if the NS is very weak, the creation should be finite. In the context of cosmic censorship, strong NSs will be subjected to the backreaction of quantum effects and may disappear or be hidden behind horizons, while weak NSs will not.Comment: 21 pages, 1 table, 3 figures. Final version to appear in Progress of Theoretical Physic

Uniqueness of static spherically symmetric vacuum solutions in the IR limit of Ho\v{r}ava-Lifshitz gravity

We investigate static spherically symmetric vacuum solutions in the IR limit of projectable nonrelativistic quantum gravity, including the renormalisable quantum gravity recently proposed by Ho\v{r}ava. It is found that the projectability condition plays an important role. Without the cosmological constant, the spacetime is uniquely given by the Schwarzschild solution. With the cosmological constant, the spacetime is uniquely given by the Kottler (Schwarzschild-(anti) de Sitter) solution for the entirely vacuum spacetime. However, in addition to the Kottler solution, the static spherical and hyperbolic universes are uniquely admissible for the locally empty region, for the positive and negative cosmological constants, respectively, if its nonvanishing contribution to the global Hamiltonian constraint can be compensated by that from the nonempty or nonstatic region. This implies that static spherically symmetric entirely vacuum solutions would not admit the freedom to reproduce the observed flat rotation curves of galaxies. On the other hand, the result for locally empty regions implies that the IR limit of nonrelativistic quantum gravity theories does not simply recover general relativity but includes it.Comment: 10 pages, accepted for publication in International Journal of Modern Physics

Upper limits of particle emission from high-energy collision and reaction near a maximally rotating Kerr black hole

The center-of-mass energy of two particles colliding near the horizon of a maximally rotating black hole can be arbitrarily high if the angular momentum of either of the incident particles is fine-tuned, which we call a critical particle. We study particle emission from such high-energy collision and reaction in the equatorial plane fully analytically. We show that the unconditional upper limit of the energy of the emitted particle is given by 218.6% of that of the injected critical particle, irrespective of the details of the reaction and this upper limit can be realized for massless particle emission. The upper limit of the energy extraction efficiency for this emission as a collisional Penrose process is given by 146.6%, which can be realized in the collision of two massive particles with optimized mass ratio. Moreover, we analyze perfectly elastic collision, Compton scattering, and pair annihilation and show that net positive energy extraction is really possible for these three reactions. The Compton scattering is most efficient among them and the efficiency can reach 137.2%. On the other hand, our result is qualitatively consistent with the earlier claim that the mass and energy of the emitted particle are at most of order the total energy of the injected particles and hence we can observe neither super-heavy nor super-energetic particles.Comment: 22 pages, 3 figures, typos corrected, reference updated, accepted for publication in Physical Review D, typos correcte

Video-Assisted Thoracoscopic Surgery Using Extracorporeal Membrane Oxygenation for Intractable Pneumothorax

Intractable pneumothorax with poor lung function that has received multiple conservative treatments may occur. Case 1 was a 70-year-old woman with aspergilloma who was admitted for pneumothorax. Case 2 was a 68-year-old man with acute exacerbation of interstitial pneumonia who developed pneumothorax. In both cases, multiple conservative therapies were administered, but the leak continued; thus, operations using veno-venous extracorporeal membrane oxygenation (ECMO) were planned. By video-assisted thoracoscopic surgery (VATS), we obtained the optimal surgical field by lung collapse. We removed many blood clots that were used for pleurodesis, ligated the bulla in case 1, and covered the leak point with strengthening agents in case 2. For cases of intractable pneumothorax, lung collapse by ECMO is advantageous because we can check details and leak points even in blood clots or in poor condition of the lung, and we can maneuver the lung in poor condition with a clear surgical field

アキレス腱付着部症に対しアキレス腱モーメントアーム長が及ぼす影響

Insertional Achilles tendinopathy (IAT) is caused by traction force of the tendon. The effectiveness of the suture bridge technique in correcting it is unknown. We examined the moment arm in patients with IAT before and after surgery using the suture bridge technique, in comparison to that of healthy individuals. We hypothesized that the suture bridge method influences the moment arm length. An IAT group comprising 10 feet belonging to 8 patients requiring surgical treatment for IAT were followed up postoperatively and compared with a control group comprising 15 feet of 15 healthy individuals with no ankle complaints or history of trauma or surgery. The ratio of the moment arm (MA) length/foot length was found to be statistically significant between the control group, the IAT group preoperatively and the IAT group postoperatively (p < 0.01). Despite no significant difference in the force between the control and preoperative IAT groups, a significantly higher force to the Achilles tendon was observed in the IAT group postoperatively compared to the other groups (p < 0.05). This study demonstrates that a long moment arm may be one of the causes of IAT, and the suture bridge technique may reduce the Achilles tendon moment arm.博士（医学）・甲第845号・令和4年9月28日© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)

エジプト紅海沿岸のマングローブ林の林分構造

Established mangrove forests along the coastal area of the Arabian Peninsula and African side of the Red Sea are uniquely different from mangrove forests in other parts of the world because of their low biodiversity and harsh habitat of arid and highly saline conditions. Therefore mangrove forests in this area appear in patchy and scattered patterns at mouths of wadi or in sheltered lagoons with rare and irregular flooding. Most of them are pure forests of Avicennia marina, occasionally mixed with Rhizophora mucronata in the southern part of the Red Sea. In this study, we analyze the forest structure of A. marina and discuss the regeneration strategy and the forest dynamics of this unique mangrove species. Three experimental plots of 1000 to 2000 trees/ha were selected from north to south along the Red Sea coast. The highest tree size (6.8m) suggested severe effects of the high salinity of the Red Sea (3.2 to 4.9%) on tree growth. Dense mantle vegetation had developed at the forest edge facing the open sea to protect the forest interior against strong waves and wind. Tree growth was also prevented by severe drought on the landside edge of the forest. All the forests had a dense seedling bank throughout the forest floor, with a very high rate of turnover and regeneration, which seldom occurred in other forests

Hydrogen-bond-assisted isotactic-specific radical polymerization of N-vinyl-2-pyrrolidone with tartrate additives in toluene at low temperatures : high-resolution 1H NMR analysis

A diethyl L-tartrate (L-EtTar)-assisted radical polymerization of N-vinyl-2-pyrrolidone has been developed as the first reported example of the synthesis of isotactic-rich poly(N-vinyl-2-pyrrolidone) (PVP). The addition of L-EtTar in toluene at temperatures of –40°C and lower led to a significant increase in the polymer yield by one order of magnitude compared with the reaction in the absence of L-EtTar. Decreasing the polymerization temperature led to increases in the isotacticity of the PVP, with the mm triad reaching 66.4% at −93 °C. 1H NMR measurement at 920 MHz was conducted to establish a reliable strategy for quantifying the triad tacticities. High-temperature NMR measurements at 250 °C were performed using a specially-designed NMR probe, which led to dramatic narrowing of the 1H line width