Nef vector bundles on a projective space with first Chern class 3 and second Chern class 8

We describe nef vector bundles on a projective space with first Chern class three and second Chern class eight over an algebraically closed field of characteristic zero by giving them a minimal resolution in terms of a full strong exceptional collection of line bundles.Comment: 10 pages. v.2: Corrected typos and an error in the proof. To appear in Le Matematich

Visualization of Stent Lumen in MR Imaging: Relationship with Stent Design and RF Direction

Magnetic resonance imaging (MRI) visualization of metallic stent lumens is possible if the stent structure counteracts eddy currents in the lumen induced by the radio frequency magnetic field, B1. To examine the effectiveness of various stent designs in counteracting eddy currents, we anchored eight copper stent models and 2 commercially available nickel-titanium alloy (Nitinol) stents in a gel phantom, perpendicular or parallel to the direction of B1. A mesh stent lumen showed hypointensity irrespective of its alignment relative to B1. A solenoid stent lumen showed hypointensity with the stent axis parallel to B1, but it had the same signal intensity as outside the lumen when perpendicular to B1. A Moebius stent lumen showed no signal reduction, irrespective of alignment relative to B1. Lumens of the commercially available stents showed hypointensity regardless of alignment relative to B1. Computer simulation revealed that the signal intensities of the stents corresponded to magnetic flux densities of B1 in the stents, which are modified by the structure of the stent. While in vivo MRI viewing of a Moebius stent lumen is likely possible regardless of axis alignment, inherent structural weakness may be problematic. As a more practical choice, the solenoid stent is easier to manufacture and generates no hypointensive signal when the axis is parallel to B0

Rates of Dissolution of Rotating Cobalt Cylinders in Liquid Copper and Cu-Co Alloys

Cobalt cylinders having the top and bottom faces capped with molybdenum were rotated at the speeds of 260, 600, and 860 rpm in liquid copper and Cu-Co alloys maintained at 1200, 1270, and 1340℃ under argon at 1 atm. pressure. The dependence of the dissolution rate of the cylinders on the concentration of cobalt in the bulk liquid was observed. The solution-rate constants defined by a modified form of the Berthoud equation varied from 6.6×10^ to 2.7×10^ cm・sec^. The activation energies for the dissolution processes at the rotational speeds of 260 and 600 rpm were 12.7 and 13.7 kcal. mol^, respectively. The rate constant was found to vary with the 0.76 to the 0.94 power of the Reynolds number in the range 5.7×10^4<Re<2.1×10^4. The dependence of the dissolution rate on the activity of cobalt in the bulk liquid was observed and was discussed on the basis of the thermodynamic expression for diffusion. The results of this investigation suggest that the dissolution process is diffusion controlled. Oxygen increases markedly the dissolution rate

Use of FDG-PET in Radiation Treatment Planning for Thoracic Cancers

Radiotherapy plays an important role in the treatment for thoracic cancers. Accurate diagnosis is essential to correctly perform curative radiotherapy. Tumor delineation is also important to prevent geographic misses in radiotherapy planning. Currently, planning is based on computed tomography (CT) imaging when radiation oncologists manually contour the tumor, and this practice often induces interobserver variability. F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) has been reported to enable accurate staging and detect tumor extension in several thoracic cancers, such as lung cancer and esophageal cancer. FDG-PET imaging has many potential advantages in radiotherapy planning for these cancers, because it can add biological information to conventional anatomical images and decrease the inter-observer variability. FDG-PET improves radiotherapy volume and enables dose escalation without causing severe side effects, especially in lung cancer patients. The main advantage of FDG-PET for esophageal cancer patients is the detection of unrecognized lymph node or distal metastases. However, automatic delineation by FDG-PET is still controversial in these tumors, despite the initial expectations. We will review the role of FDG-PET in radiotherapy for thoracic cancers, including lung cancer and esophageal cancer

Spectral Evolutions in Gamma-Ray Burst Exponential Decays Observed with Suzaku WAM

This paper presents a study on the spectral evolution of gamma-ray burst (GRB) prompt emissions observed with the Suzaku Wide-band All-sky Monitor (WAM). By making use of the WAM data archive, 6 bright GRBs exhibiting 7 well-separated fast-rise-exponential-decay (FRED) shaped light curves are presented and the evaluated exponential decay time constants of the energy-resolved light curves from these FRED peak light curves are shown to indicate significant spectral evolution. The energy dependence of the time constants is well described with a power-law function tau(E) ~ E^gamma, where gamma ~ -(0.34 +/- 0.12) in average, although 5 FRED peaks show consistent value of gamma = -1/2 which is expected in synchrotron or inverse-Compton cooling models. In particular, 2 of the GRBs were located with accuracy sufficient to evaluate the time-resolved spectra with precise energy response matrices. Their behavior in spectral evolution suggests two different origins of emissions. In the case of GRB081224, the derived 1-s time-resolved spectra are well described by a blackbody radiation model with a power-law component. The derived behavior of cooling is consistent with that expected from radiative cooling or expansion of the emission region. On the other hand, the other 1-s time-resolved spectra from GRB100707A is well described by a Band GRB model as well as with the thermal model. Although relative poor statistics prevent us to conclude, the energy dependence in decaying light curve is consistent with that expected in the former emission mechanism model.Comment: 11 pages, 7 figures, 5 tables. PASJ accepte