Universal Single-Mode Lasing in Fully Chaotic Billiard Lasers

By numerical simulations and experiments of fully chaotic billiard lasers, we show that single-mode lasing states are stable, whereas multi-mode lasing states are unstable when the size of the billiard is much larger than the wavelength and the external pumping power is sufficiently large. On the other hand, for integrable billiard lasers, it is shown that multi-mode lasing states are stable, whereas single-mode lasing states are unstable. These phenomena arise from the combination of two different nonlinear effects of mode-interaction due to the active lasing medium and deformation of the billiard shape. Investigations of billiard lasers with various shapes revealed that single-mode lasing is a universal phenomenon for fully chaotic billiard lasers.     

Relation of gas permeability with structure of aromatic polyimides II

We investigated relations between diffusivities on polyimides and physical parameters with mobilities of segments and examined viscoelasticity of polyimides on introducing the parameter as an index of mobilities of polymer chains.     

Communication: Double Bond Migration of a 1,5-Anhydro-3-C-p-Tolylsulfonyl-D-Hex-2-Enitol Derivative and the Corresponding 5a-Carba-Dl-Sulfonyl Sugar

Although the rate of proton abstraction (kinetic acidity) frequently plays an essential role in determination of reaction pathways and is of theoretical interest,¹ it is still controversial whether an oxygen atom activates or deactivates the abstraction of an α-hydrogen atom of an ether. For example, it is well known that oxidative elimination of a seleno group gives an allyl ether as the major product, indicating the oxygen atom deactivates the kinetic acidity.² Abstraction of the equatorial hydrogen atom at C-2 of 6-methyl-1,3-oxathiane-3,3-dioxide 1 is slower than that at C-4.³ On the other hand, the bridgehead hydrogen atom (H_b) adjacent to the oxygen atom of piperazinedione (2) is abstracted more readily than that of the alternative one (H_a).⁴     

Unconventional anomalous Hall effect enhanced by a noncoplanar spin texture in the frustrated Kondo lattice Pr2Ir2O7

We have investigated the Hall effect in the geometrically frustrated Kondo lattice Pr2Ir2O7. In its spin-liquid-like paramagnetic regime, the Hall resistivity rho(xy) is found to increase logarithmically on cooling. Moreover, in this low temperature region, the field dependence of the Hall conductivity sigma(xy) shows a large enhancement up to 30 Omega(-1) cm(-1) as well as a nonmonotonic change with the magnetization. Our results are far different from the anomalous Hall effect due to the spin-orbit coupling observed in ordinary magnetic conductors. We discuss the possible spin-chirality effect in the Ir 5d conduction band due to the noncoplanar texture of Pr<111> Ising-like moments.     

Metallic spin-liquid behavior of the geometrically frustrated Kondo lattice

Strongly frustrated magnetism of the metallic pyrochlore oxide Pr2Ir2O7 has been revealed by single crystal study. While Pr 4f moments have an antiferromagnetic RKKY interaction energy scale of /T*/ = 20 K mediated by Ir 5d-conduction electrons, no magnetic long-range order is found except for partial spin freezing at 120 mK. Instead, the Kondo effect, including a lnT dependence in the resistivity, emerges and leads to a partial screening of the moments below /T*/. Our results indicate that the underscreened moments show spin-liquid behavior below a renormalized correlation scale of 1.7 K.     

Localized pits and peaks in forbush decrease, associated with stratified structure of disturbed and undisturbed magnetic fields

Summary Forbush decrease (FD) is generally interpreted as a result of diffusion-convection of cosmic rays in a disturbed interplanetary magnetic field associated with the magnetohydrodynamic shock wave caused by solar flare. In this paper, we point out that a large number of FDs contain an isolated region or regions with pit-type time profile, in which cosmic rays are not in a diffusion-convection state but in a trapped state in undisturbed, uniform and strong magnetic field perpendicular to the solar wind. The trapped state is also characterized with a large ratio of the magnetic to ion thermal energy. The median duration time of the state is about 8 hours. About half of these states are associated with the northward (or southward) magnetic field, while the other half with the eastward (or westward) magnetic field. Flares responsible for the former state seem to be concentrated in an eastward region from about 30°W on the solar disk, while those for the latter state seem rather symmetric with respect to the centre of the solar disk. It is suggested that the trapped state is produced inside a magnetic tube of force which is not of a small scale such as that of the magnetic bubble pointed out by Klein and Burlaga, but of a large scale, having a horseshoe structure with its ends supposed to be connected to somewhere in an inner region near the Sun and with its cross-section supposed to be of a thin filament with radial and transverse dimensions of ≈0.1 a.u. and ≈1.1 a.u. at the Earth’s orbit. This belt-like tube of force is supposed to be produced on the solar surface or near the Sun and to be carried out by solar wind in a frozen state, trapping in itself low-density cosmic rays near the Sun. In addition to the pits, we point out also the existence of some peaks which are observed not only in the trapped region but also in a region of extremely disturbed magnetic field neighbouring in between two trapped regions. It is suggested that cosmic rays in the region of the latter type are supposed to be guided freely (or easily) from outer space through a path with similarly disturbed magnetic state, and therefore, they could maintain their density in the region always higher than in the neighbouring regions. Two kinds of cosmic-ray-guiding mechanism in the above can be regarded as being at opposite poles.     

Experimental results of DPIS with a new RFQ

We have developed a new heavy ion production system which uses a combination of an RFQ and a laser ion source. Induced plasma by a laser shot is delivered to the RFQ without an extraction electrode. We named this new idea ‘direct plasma injection scheme (DPIS)’. In 2004, a new RFQ was built for demonstrating the capability of the DPIS. After a few months of commissioning period, we could obtain more than 60 mA of carbon beam from the RFQ. This new scheme could be applied to cancer therapy facilities and high energy nuclear physics accelerator complexes.     

Observation of long-distance radial correlation in toroidal plasma turbulence

This Letter presents the discovery of macroscale electron temperature fluctuations with a long radial correlation length comparable to the plasma minor radius in a toroidal plasma. Their spatiotemporal structure is characterized by a low frequency of ～1-3 kHz, ballistic radial propagation, a poloidal or toroidal mode number of m/n=1/1 (or 2/1), and an amplitude of ～2% at maximum. Nonlinear coupling between the long-range fluctuations and the microscopic fluctuations is identified. A change of the amplitude of the long-range fluctuation is transmitted across the plasma radius at the velocity which is of the order of the drift velocity.     

A new development of dyestuffs degradation system using ultrasound

Dyestuffs are often present in industrial wastewaters and can consist of hazardous substances which have a serious impact on the environment and personal health. This report describes a system developed to degrade these substances using sonochemical reactions. Ultrasonic frequencies of 118, 224, 404 and 651 kHz and power input values of 11.4, 29.0 and 41.5 W were tested on Rhodamine B and Orange II dyestuff solutions in order to find the best degradation conditions. The ultrasonic irradiation of air-saturated solutions produces free radicals that combine and generates hydrogen peroxide, and compared to the production of hydrogen peroxide when irradiating water, a decrease was found during the irradiation to dyestuff solutions, indicating that some of the free radicals were consumed in the dyestuffs degradation process. The effects of the ultrasonic irradiation conditions on the pH, nitric and nitrous acid formations as well as the total organic carbon value (TOC) were also investigated. For the ultrasonic frequencies of 224, 404 and 651 kHz, the degradation rates were very similar, however, the 118 kHz system presented a degradation rate of about one-third that of the higher frequencies for both dyestuffs. The Rhodamine B solutions were decolorized within 2 h of ultrasonic irradiation for all systems with the exception of the 118 kHz one. For Orange II, except for the 118 kHz system, all solutions were decolorized within 4 h of ultrasonic irradiation. All reactions were carried out at 25 degrees C and the total ultrasonic irradiation time was 10 h.     

How to compare the SU(5) value of sin2θw with experiments?

We establish the relation between κsin²θ_w to be found from neutral-current experiments and sin²θ_w(Q) for Q=M_W predicted by grand unified theories. We then calculate sin²θ_W(M_W) in the minimal SU(5) model taking the M_W as well as M_x threshold effects into account. We find that these two threshold effects on sin²θ_W(M_W) cancel with each other and sin²θ_W(M_W)=0.211± 0.005.