Effect of surface chemisorption on the spin reorientation transition in magnetic ultrathin Fe film on Ag(0 0 1)

We have investigated the effect of surface chemisorption on the spin reorientation transitions in magnetic ultrathin Fe films on Ag(0 0 1) by means of the polar and longitudinal magneto-optical Kerr effect (MOKE) and X-ray magnetic circular dichroism (XMCD) measurements. It is found by the MOKE that adsorption of O₂ and NO induces the shift of the critical thickness for the transitions to a thinner side, together with the suppression of the remanent magnetization and the coercive field of the Fe film. This implies destabilization of the perpendicular magnetic anisotropy. On the other hand, H₂ adsorption is found not to change the magnetic anisotropy, though the enhancement of the coercive field is observed. The XMCD reveals that although both the spin and orbital magnetic moments along the surface normal are noticeably reduced upon O₂ and NO adsorption, the reduction of the orbital magnetic moments are more significant. This indicates that the destabilization of the perpendicular magnetic anisotropy upon chemisorption of O₂ and NO originates from the change of the spin-orbit interaction at the surface.     

The 1969–1985 Pozzuoli event and active volcanisms

Pozzuoli is located at the center of the Campi Flegrei caldera, near Naples and is famous for its anomalous subsidence and upheaval documented since the Roman period. Its secular and gradual subsidence can be interpreted as self-loading compaction of the caldera fills while abrupt upheavals are geologically suspected to be caused by magmagenic movements or steam forces. In order to interpret the origin and the process of the Pozzuoli upheavals, they are compared with active volcanisms represented by the 1977–1982 eruption of Usu volcano in Hokkaido.Usu volcano outburst in 1977 in major pumice eruptions and repeated magmatic and phreatomagmatic eruptions, and manifested remarkable ground deformations accompanying earthquake swarms. In 1969, the ground of Pozzuoli began to upheave with increases in seismicity but finally failed to cause any eruptive phenomena at the surface; nevertheless there are common characteristics of their motives and processes between the two events. The motive of the Usu deformation is clearly due to magma movements while that of the Pozzuoli upheaval has not been completely settled. A quantitative relationship between seismicity and deformation gives a clue for discussing the motive of the Pozzuoli deformations. The discharge rates of seismic energy and the deformation rates are compared between the two events and a certain similarity is found. This suggests that the origin of the Pozzuoli event may be partly magmatic as well as the Usu eruption, but its behavior largely depends on the property of the caldera deposits. When their deformation volumes are taken into consideration, their characteristics become quantitatively conspicuous. The ground at Pozzuoli is much more easily deformed by the upward motive force than Usu volcano. This is due to the rheological property of the caldera deposits of Campi Flegrei, and agrees to the theory that interprets the secular subsidence observed in historical times, as self-loading compaction. It is interesting that there is a point of contact between anomalous movements of the ground along the seashore in Italy and remarkable magmatic movements at the active volcano in Japan.     

Nano-segregated structures of hydrogen-bonded mesogens with perfluorinated moieties: cubic phase formation and first order smectic A to smectic C phase transition

Two series of mesogenic compounds having both a perfluorinated substituent and a hydrogen bonding active site were synthesized and their phase behavior investigated. Due to the chemical architecture of these materials exhibiting amphiphilic character, structures of nano-segregation are expected to form. We found a thermotropic cubic phase with Ia3d symmetry in one of the acid/base hydrogen-bonded complexes, which is a nano-segregated structure. Moreover materials exhibiting a first order smectic A to smectic C phase transition were found, which was ascertained by differential scanning calorimetry measuring a large latent heat, and X-ray diffraction experiments observing abrupt changes of physical properties at the phase transition, i.e. the tilt angle, the intensity and the half-width of the small angle reflection. This first order phase transition occurs due to the frustration of nano-segregated structures of lamellar phases.     

Development of Scanning Near-Field Optical Microscope Working under Cryogenic Temperature and Strong Magnetic Field

We report on the development of a cantilever-based scanning near-field optical microscope (SNOM) working in an extreme environment, at cryogenic temperature around 10 K and under strong magnetic field up to 7 T. We designed a new optical system based on an infinite conjugate microscope, which extracts the near-field signal from a small aperture through a narrow chamber into free space as collimated light. Using this system, we successfully measured near-field and topographical images of a metal-hole sample simultaneously. Combining the local optical accessing technique with the external control of the electronic state, this SNOM system will be a powerful tool to study optical properties of semiconductor nanostructures.     

An ESR-CT imaging of the head of a living rat receiving an administration of a nitroxide radical.

Three-dimensional ESR imaging of a living rat has been performed by an L-band ESR system, which is composed of an L-band ESR spectrometer, a field gradient coil, and a data processor. The imaging was carried out by Lauterbur's method. A nitroxide, 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl (Carbamoyl-PROXYL), was used as an imaging agent in saline solution at a concentration of 0.2 M and administered intraperitoneally to obtain a constant concentration in the head for about an hour. It took about 40 min to obtain one set of ESR-CT images. The cross-sectional images were made, both as coronal and horizontal images. In the images of the rat head the nitroxide-rich region was clearly distinguished from the deficient region. The nitroxide-deficient areas corresponded well to the brain of the rat.     

Dissolution behavior of highly burnt fuel

In order to study the dissolution behavior of a highly burnt LWR fuel, a fuel pin irradiated in the DR3 test reactor in Risoe National Laboratory, has been characterized by microstructural examination and then dissolved under PUREX type conditions. The dissolution behavior was investigated and the residues analyzed by scanning electron microscopy and by ICP-MS and IDMS after dissolution.     

Algorithms for finding a Kth best valued assignment

We consider a new problem, the Kth best valued assignment problem. Given a bipartite graph G and a cost vector w on its edge set, this is the problem of finding a perfect matching M_k in G such that there exist perfect matchings M₁,…,M_K−1 satisfying w(M₁) < < w(M_K−1) < w(M_K), and w(M_K) < w(M) for all perfect matchings M with w(M) ≠ w(M₁),…,w(M_K). Here w(M) denotes the sum of costs of edges in M. In this paper, we propose two algorithms for solving this problem and verify the efficiency of our algorithms by our preliminary computational experiments.     

Direct observation of anisotropic interparticle forces in nematic colloids with optical tweezers

Interparticle forces in a nematic liquid-crystal colloid have been directly observed by the dual beam laser trapping method with pN sensitivity. We introduce two different types of spatial distributions of forces, detected between the particles accompanied by hyperbolic hedgehog defects. These force distributions lead to specific particle arrangements, which are both stabilized by the balance of the orientational stress field of nematics. On the basis of these results, we propose novel artificial construction for multiparticle regular arrangements.