Utsunomiya University

About: Utsunomiya University is a education organization based out in Utsunomiya, Japan. It is known for research contribution in the topics: Laser & Holography. The organization has 4139 authors who have published 6812 publications receiving 91975 citations. The organization is also known as: Utsunomiya daigaku.

Disturbance of Plasma Melatonin Profile by High Dose Melatonin Administration Inhibits Testicular Maturation of Precocious Male Masu Salmon

Abstract: We have previously shown that the testicular development of underyearling male masu salmon Oncorhynchus masou reared under a long photoperiod was accelerated by oral melatonin treatment (0.5 mg melatonin/kg body weight/day), suggesting that melatonin mediates photoperiodic signaling. In this study, we further examined the effects of a disturbance in the plasma melatonin profile on gonadal development in underyearling male masu salmon by administering a higher dose of melatonin. Fish randomly selected in June were divided into two groups. They were reared under a light:dark (LD) cycle of 16:8 (lights on 04:00-20:00 hr) and fed with pellets sprayed with melatonin or vehicle twice a day at 08:30 and at 15:30 hr (7.5 mg melatonin/kg body weight/day) until October. Fish were sampled on Day 0, 25, 60, 90 and 120. The plasma melatonin levels were high in the dark phase and low in the light phase in the control group, while they were constantly high with no significant change in the melatonin-treated group. Melatonin treatment had inhibitory effects on the gonadosomatic index and plasma testosterone levels. Pituitary salmon gonadotropin-releasing hormone content and luteinizing hormone content were significantly lower in the melatonin-treated group on Day 60 and 90, respectively. These results indicate that the plasma melatonin profile is important for mediating photoperiodic signals that regulate brain-pituitary-gonadal axis in underyearling precocious male masu salmon.

The impact of nuclear shape on the emergence of the neutron dripline.

Abstract: Atomic nuclei are composed of a certain number of protons Z and neutrons N. A natural question is how large Z and N can be. The study of superheavy elements explores the large Z limit1,2, and we are still looking for a comprehensive theoretical explanation of the largest possible N for a given Z—the existence limit for the neutron-rich isotopes of a given atomic species, known as the neutron dripline3. The neutron dripline of oxygen (Z = 8) can be understood theoretically as the result of single nucleons filling single-particle orbits confined by a mean potential, and experiments confirm this interpretation. However, recent experiments on heavier elements are at odds with this description. Here we show that the neutron dripline from fluorine (Z = 9) to magnesium (Z = 12) can be predicted using a mechanism that goes beyond the single-particle picture: as the number of neutrons increases, the nuclear shape assumes an increasingly ellipsoidal deformation, leading to a higher binding energy. The saturation of this effect (when the nucleus cannot be further deformed) yields the neutron dripline: beyond this maximum N, the isotope is unbound and further neutrons ‘drip’ out when added. Our calculations are based on a recently developed effective nucleon–nucleon interaction4, for which large-scale eigenvalue problems are solved using configuration-interaction simulations. The results obtained show good agreement with experiments, even for excitation energies of low-lying states, up to the nucleus of magnesium-40 (which has 28 neutrons). The proposed mechanism for the formation of the neutron dripline has the potential to stimulate further thinking in the field towards explaining nucleosynthesis with neutron-rich nuclei. A mechanistic explanation for the origin of the neutron dripline shows that nuclei accommodate the addition of neutrons by becoming increasingly ellipsoidal, up to a maximum number of neutrons, reconciling theory and experiments.

Diffeomorphisms satisfying the specification property

Abstract: Let f be a diffeomorphism of a closed C ∞ manifold M. In this paper, we introduce the notion of the C 1 -stable specification property for a closed f-invariant set Λof M, and we prove that f/ Λ satisfies a C 1 -stable specification property if and only if Λ is a hyperbolic elementary set. As a corollary, the C 1 -interior of the set of diffeomorphisms of M satisfying the specification property is characterized as the set of transitive Anosov diffeomorphisms.

Vector fields with topological stability

Abstract: In this paper, we give a characterization of the structurally stable vector fields by making use of the notion of topological stability More precisely, it is proved that the C1 interior of the set of all topologically stable C1 vector fields coincides with the set of all vector fields satisfying Axiom A and the strong transversality condition