46 research outputs found
Kadanoff-Baym approach to the thermal resonant leptogenesis
Using the non-equilibrium Green function method (Kadanoff-Baym equations) in
the expanding universe, we investigate evolution of the lepton number asymmetry
when the right-handed (RH) neutrinos have almost degenerate masses
. The resonantly enhanced -violating parameter
associated with the decay of the RH neutrino is obtained.
It is proportional to an enhancement factor with the regulator . The result is consistent with the previous result obtained by Garny
et al., in a constant background with an out-of-equilibrium initial state. We
discuss the origin of such a regulator, and why it is not like .Comment: 51 pages + appendices (46 pages), 5 figures; typos corrected,
references adde
Gamma rays from a reverse shock with turbulent magnetic fields in GRB 180720B
Gamma-ray bursts (GRBs) are the most electromagnetically luminous cosmic
explosions. They are powered by collimated streams of plasma (jets) ejected by
a newborn stellar-mass black hole or neutron star at relativistic velocities
(near the speed of light). Their short-lived (typically tens of seconds) prompt
-ray emission from within the ejecta is followed by long-lived
multi-wavelength afterglow emission from the ultra-relativistic forward shock.
This shock is driven into the circumburst medium by the GRB ejecta that are in
turn decelerated by a mildly-relativistic reverse shock. Forward shock emission
was recently detected up to teraelectronvolt-energy -rays, and such
very-high-energy emission was also predicted from the reverse shock. Here we
report the detection of optical and gigaelectronvolt-energy -ray
emission from GRB 180720B during the first few hundred seconds, which is
explained by synchrotron and inverse-Compton emission from the reverse shock
propagating into the ejecta, implying a low-magnetization ejecta. Our optical
measurements show a clear transition from the reverse shock to the forward
shock driven into the circumburst medium, accompanied by a 90-degree change in
the mean polarization angle and fluctuations in the polarization degree and
angle. This indicates turbulence with large-scale toroidal and
radially-stretched magnetic field structures in the reverse and forward shocks,
respectively, which tightly couple to the physics of relativistic shocks and
GRB jets -- launching, composition, dissipation and particle acceleration.Comment: 5 pages, 4 figures (main) plus Methods and Supplementary Methods,
accepted for publicatio
Identification and functional analysis of a splice variant of mouse sodium-dependent phosphate transporter Npt2c
Mutations in the SLC34A3 gene, a sodium-dependent inorganic phosphate (Pi) cotransporter, also referred to as NaPi IIc, causes hereditary hypophosphatemic rickets with hypercalciuria (HHRH), an autosomal recessive disorder. In human and rodent, NaPi IIc is mainly localized in the apical membrane of renal proximal tubular cells. In this study, we identified mouse NaPi IIc variant (Npt2c-v1) that lacks the part of the exon 3 sequence that includes the assumed translation initiation site of Npt2c. Microinjection of mouse Npt2c-v1 cRNA into Xenopus oocytes demonstrated that Npt2c-v1 showed sodium-dependent Pi cotransport activity. The characterization of pH dependency showed activation at extracellular alkaline-pH. Furthermore, Npt2c-v1 mediated Pi transport activity was significantly higher at any pH value than those of Npt2c. In an in vitro study, the localization of the Npt2c-v1 protein was detected in the apical membrane in opossum kidney cells. The expression of Npt2c-v1 mRNA was detected in the heart, spleen, testis, uterus, placenta, femur, cerebellum, hippocampus, diencephalon and brain stem of mouse. Using mouse bone primary cultured cells, we showed the expression of Npt2c-v1 mRNA. In addition, the Npt2c protein was detected in the spermatozoa head. Thus, Npt2c-v1 was expressed in extra-renal tissues such as epididymal spermatozoa and may function as a sodium-dependent phosphate transporter