Analytical calculations of four-neutrino oscillations in matter

We analytically derive the transition probabilities for four-neutrino oscillations in matter. The time-evolution operator giving the neutrino oscillations is expressed by a finite sum of terms up to the third power of the Hamiltonian in a matrix form, using the Cayley-Hamilton theorem. The result of the computation for the probabilities in some mass patterns tells us that it is actually difficult to observe the resonance between one of the three active neutrinos and the fourth (sterile) neutrino near the earth, even if the fourth neutrino exists. Received: 9 October 2002 / Revised version: 27 December 2002 / Published online: 14 March 2003 RID="a" ID="a" e-mail: kamo@sci.kumamoto-u.ac.jp     

Logic of Simultaneity

A logical model of spatiotemporal structures is pictured as a succession of processes in time. One usual way to formalize time structure is to assume the global existence of time points and then collect some of them to form time intervals of processes. Under this set-theoretic approach, the logic that governs the processes acquires a Boolean structure. However, in a distributed computer system or a relativistic universe where the message-passing time between different locations is not negligible, the logic has no choice but to accept time interval instead of time point as a primitive concept. The resulting logico-algebraic structure matches that of orthologic, which is known as the most simplified version of quantum logic, and the conventionality of simultaneity claim is reduced to the non-distributivity of the logic.     

Simple and selective sensing of cysteine using gold nanoparticles conjugated with a thermoresponsive copolymer having carboxyl groups.

We describe a simple, yet selective cysteine sensor based on gold nanoparticles (AuNPs) conjugated with thermoresponsive copolymers, the carboxyl groups of which are incorporated. Copolymer-conjugated AuNPs, used as the cysteine sensor, in a solution form sediment when cysteine is added. Heating followed by cooling the solution induces phase transitions of the thermoresponsive copolymers, resulting in an acceleration of sedimentation of the copolymer-conjugated AuNPs. The absorbance of supernatants at 520 nm, which are ascribed to a surface plasmon band of discrete AuNPs, decays with increasing concentration of cysteine. Sedimentation of the copolymer-conjugated AuNPs is specific to cysteine. The addition of other popular amino acids, or ascorbic acid, causes no sedimentation of the AuNPs. The relationship between the absorbance of the supernatant at 520 nm and the cysteine concentration provides a sigmoidal profile at a concentration range between 1 x 10(-6) to 6 x 10(-6) mol dm(-3). The determination of cysteine in a supplement is achieved using an inflection point on the sigmoidal profiles.     

Extraction of Quasi-Straightforward-Propagating Photons Through a Scattering Medium by Up-Conversion Method as a Coherent Light Detection Technique

Aiming at the realization of optical CT (computed tomography), the extraction of quasi-straightforward-propagating photons from optical pulses transmitting through a standard scattering medium of Intralipid-10% aqueous solution has been demonstrated by an up-conversion method (second harmonic generation). We have found that this operates as a coherent light detection method rather than a time-gate one and extends the dynamic range where the Lambert-Beer’s law holds to − 86 dB. We have also proposed improvements to obtain the largest possible dynamic range by such an up-conversion technique.     

Core excitations in (d,p) reactions including transitions to continuum levels

Effects of core excitations in (d, p) reactions are investigated for ¹²C(d, p)¹³C¹ reactions in the CCBA framework, where couplings of channels are considered for the ground and first-excited levels of ¹²C in the initial state and for the bound $\text{1}\text{2}{}^{\mathrm{+}}\text{and}\text{5}\text{2}{}^{\mathrm{+}}$ levels and low-lying continuum levels of ¹³C in the final state, where a discretization is introduced for the continuum region. In the transitions to the continuum levels, matrix elements are calculated by the use of scattering-state wave functions for the final neutron. Theoretical cross sections and vector analyzing powers are compared with experimental data, where significant contributions of core-excitation processes are identified, particularly in the transition to the $\text{5}\text{2}{}^{\mathrm{+}}{}_{\mathrm{II}}$ level of ¹³C. Spectra of emitted protons are calculated and compared with the measured ones. Adequate agreement between theory and experiment is found throughout the present investigation.     

Synthesis and electrode performance of carbon coated Na2FePO4F for rechargeable Na batteries

Carbon-coated Na₂FePO₄F is synthesized by a simple solid-state method with ascorbic acid as carbon source. Structural characterization of Na₂FePO₄F by synchrotron X-ray diffraction, scanning/transmission electron microscopy, and Raman spectroscopy reveals that ascorbic acid effectively suppresses the particle growth of Na₂FePO₄F, forming the nano-sized carbon coated materials. Electrode performance of Na₂FePO₄F for rechargeable sodium batteries is also examined. The carbon-coated Na₂FePO₄F sample (1.3 wt% carbon) delivers initial discharge capacity of 110 mAh g^-1 at a rate of 1/20 C (6.2 mA g^-1) with well-defined voltage plateaus at 3.06 and 2.91 V vs. Na metal. The sample also shows acceptable capacity retention and rate capability as the positive electrode materials for rechargeable Na batteries, which is operable at room temperature.