No abstract available

No abstract available

[en] The most serious complication of neurovascular interventions is distal cerebral embolism. Diffusion-weighted MR imaging (DWI) appears to be the most sensitive technique for detecting early and small ischemic lesions. To evaluate the incidence and radiological features of embolic events associated with neuro-intervention, we applied DWI to screening for procedure-related ischemiclesions including silent embolisms. One hundred and thirty-seven patients who have received 154 neuro-interventional procedures were studied with DWI before and within 5 days after treatment. Imaging was performed, using single-shot echo-planar imaging with b value of 1000-1100 sec/mm². DWI findings were classified into 5 groups by size and location of lesions: type 0 (n=71), no lesions; I (n=33), lesions in border-zone regions only; II (n=9), lesions at perforator territories mainly; III (n=29), small territorial lesions (<5 mm); IV (n=12), large territorial lesions (≥5 mm). DWI detected procedure-related lesions in 83 of 154 procedures (53.9%), 36 of which demonstrated new neurological symptoms during and/or after procedures. The parent artery occlusion for cerebral aneurysms had a higher incidence of symptomatic embolisms than other procedures. In 71 of 154 procedures (46.1%), DWI detected no lesions (type 0). Although type I was the most frequent pattern presented, it included few neurological symptoms. Type III often resulted in transient symptoms, and type II and IV tended to induce strokes. Because ischemic lesions detected by DWI were likely to arise in border-zone territories by parent artery occlusions, we considered that hypoperfusion as well as emboli were involved in the evolution of cerebral infarctions. Thus, DWI is a useful method to detect silent embolisms, and to determine the safety of neurointervention and the mechanism of embolic ischemia. (author)

[en] Radioactivity from a spherical ion exchange resin containing radioisotopes homogeneously was calculated. For the calculations a mean distance defined by the length from an arbitrary point in the sphere to the spherical surface was used. The radioactivity to be radiated from the point in the mean distance and observed at the surface of the sphere was estimated in the form of integrals, considering a relative intensity obtained from the use of the mean distance. The integral was performed from the center of the sphere to the radius using a numerical method. Homogeneous adsorption of ³²P in a spherical ion exchange resin (Amberlite IRA-425) was carried out as H₂PO₄^- labeled with ³²P. β-rays of ³²P transmitting through the resin were measured. The numbers of ³²P adsorbed in the sphere were calculated from the concentration decrease of a H₂PO₄^- solution in an adsorption flask. The estimated radioactivity was in good agreement with the observed one. (auth.)

[en] We study the cosmic microwave background (CMB) anisotropy due to spherically symmetric nonlinear structures in flat universes with dust and a cosmological constant. By modeling a time-evolving spherical compensated void/lump by Lemaitre-Tolman-Bondi spacetimes, we numerically solve the null geodesic equations with the Einstein equations. We find that a nonlinear void redshifts the CMB photons that pass through it regardless of the distance to it. In contrast, a nonlinear lump blueshifts (or redshifts) the CMB photons if it is located near (or sufficiently far from) us. The present analysis comprehensively covers previous works based on a thin-shell approximation and a linear/second-order perturbation method and the effects of shell thickness and full nonlinearity. Our results indicate that, if quasilinear and large (> or approx.100 Mpc) voids/lumps would exist, they could be observed as cold or hot spots with temperature variance > or approx. 10^-5 K in the CMB sky.

[en] We explore equilibrium solutions of nontopological solitons in a general class of scalar field theories which include global U(1) symmetry. We find new types of solutions, tube-shaped and crust-shaped objects, and investigate their stability. Like Q-balls, the new solitons can exist in supersymmetric extensions of the standard model, which may be responsible for baryon asymmetry and dark matter. Therefore, observational signals of the new solitons would give us more information on the early Universe and supersymmetric theories.

[en] We consider the model of a false-vacuum bubble with a thin wall where the surface energy density is composed of two different components, 'domain-wall' type and 'dust' type, with opposite signs. We find stably oscillating solutions, which we call 'breathing bubbles'. By decay to a lower mass state, such a breathing bubble could become either (i) a child universe or ii) a bubble that 'eats up' the original universe, depending on the sign of the surface energy of the domain-wall component. We also discuss the effect of the finite-thickness corrections to the thin-wall approximation and possible origins of the energy contents of our model

[en] We propose a practical method for analyzing stability of Q-balls for the whole parameter space, which includes the intermediate region between the thin-wall limit and thick-wall limit as well as Q-bubbles (Q-balls in false vacuum), using catastrophe theory. We apply our method to the two concrete models, V₃=m²φ²/2-μφ³ + λφ⁴ and V₄=m²φ²/2-λφ⁴+φ⁶/M². We find that V₃ and V₄ Models fall into fold catastrophe and cusp catastrophe, respectively, and their stability structures are quite different from each other. (author)

[en] We make an analysis of Q-balls and boson stars using catastrophe theory, as an extension of the previous work on Q-balls in flat spacetime. We adopt the potential V₃(φ)=(m²/2)φ²-μφ³+λφ⁴ for Q-balls and that with μ=0 for boson stars. For solutions with |g^rr-1|∼1 at its peak, stability of Q-balls has been lost regardless of the potential parameters. As a result, phase relations, such as a Q-ball charge versus a total Hamiltonian energy, approach those of boson stars, which gives us a unified picture of Q-balls and boson stars.

[en] We explore stability of gravitating Q-balls with potential V₄(φ)=(m²/2)φ²-λφ⁴+(φ⁶/M²) via catastrophe theory, as an extension of our previous work on Q-balls with potential V₃(φ)=(m²/2)φ²-μφ³+λφ⁴. In flat spacetime Q-balls with V₄ in the thick-wall limit are unstable and there is a minimum charge Q_min, where Q-balls with Q< Q_min are nonexistent. If we take self-gravity into account, on the other hand, there exist stable Q-balls with arbitrarily small charge, no matter how weak gravity is. That is, gravity saves Q-balls with small charge. We also show how stability of Q-balls changes as gravity becomes strong.