Highly efficient cryogenically-cooled Yb:YAG laser

A MOPA laser system for high pulse energy and high average power has been developed by using a cryogenic Yb:YAG. In the regenerative amplifier with our original TRAM architecture, the high pulse energies of 6.5 and 1.5 mJ were obtained at the repetition rate of 200 Hz and 1 kHz, respectively. An optical efficiency was as high as η_o-o = 9.3% with an excellent beam quality of M ² < 1.1, which ensured that a cryogenic Yb:YAG TRAM had a high thermal strength. The following four pass power amplifier with a cryogenic Yb:YAG rod showed 140 mJ at 100 Hz. Both a high optical efficiency of η_o-o = 30% and a high slope efficiency of η_s = 44% showed that an efficient laser operation could be realized for a power amplification with both a high pulse energy and a high average power by using a cryogenic Yb:YAG.     

Total synthesis of ecteinascidin 743

The total synthesis of ecteinascidin 743 (1), an extremely potent antitumor agent, has been accomplished. The synthesis features Ugi's 4CC reaction, intramolecular Heck reaction, phenol-aldehyde cyclization, and acid-induced intramolecular sulfide formation.     

Total synthesis of polyamine toxin HO-416b and Agel-489 using a 2-nitrobenzenesulfonamide strategy

Total synthesis of spider toxins HO-416b (1) and Agel-489 (2) was accomplished using the 2-nitrobenzenesulfonamide (Ns) group as both a protecting and activating group. In this strategy, the C-N bonds were constructed by alkylation of sulfonamides with alkyl halides or Mitsunobu reaction with the corresponding alcohol. Beginning with monoprotection of the symmetrical diamine, the construction of the backbone from diamine 3 was efficiently accomplished in 7 steps for 14 and 9 steps for 29. Removal of the Ns group while the substrate was attached to a novel solid support enabled the efficient isolation of this highly polar compound.     

Local chemical state change in Co–O resistance random access memory

Kelvin probe force microscopy (KFM) and conductive atomic force microscopy (C‐AFM) together with micro X‐ray photoelectron spectroscopy (XPS) were performed for the stacking structure comprising of the transition metal oxide Co–O and metal electrode, which exhibits large reproducible resistance switching. The application of the external voltage by the C‐AFM cantilever decreases the resistance of Co–O, which well accords with the non‐polar forming process observed in the Pt/Co–O/Pt trilayer, known as the candidate of resistance random access memory (ReRAM). Furthermore, the KFM and micro XPS experimentally revealed that the local reductive reaction of Co–O possibly nucleates the defect related energy levels which dominates the current conduction in the low resistance state. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Dissociation between lactate accumulation and acidosis in middle cerebral artery-occluded rats assessed by P and H NMR metabolic images under A 2-T magnetic field

The relationships among tissue edema, lactate accumulation, and intracellular pH in middle cerebral artery (MCA)-occluded rats were investigated with multiecho ¹H magnetic resonance imaging and spatially resolved metabolic images constructed by ¹H and ³¹P nuclear magnetic resonance (NMR) chemical shift imaging (CSI). For the effective and sensitive detection of NMR signals from the brain, outer volume suppression (OVS), reduced k-space sampling and proton irradiation were incorporated into the CSI sequences. The consecutive three measurements of calculated T₂ image, lactate image, and pH image which were required for 3.75 h were repeated for four cycles of 1–16 h after MCA occlusion. Tissue edema and lactate accumulation in the infarcted region were gradually and consistently increased during the 15-h observation period. In contrast, severe acidosis was already detected on the first pH image (2–4.7 h after MCA occlusion); thereafter, the degree of acidosis became milder and showed no further progression. The dissociation between the time courses of the lactate accumulation and pH decrease was clearly demonstrated by the NMR metabolic images. Acid-base balance in cerebral infarction might be affected not only by lactate production but also by complicated interactions with tissue edema and some other factors.     

On convection in a fluid filling the cavity of a moving solid body

The problem of simultaneous motion about a fixed point O of a solid body and unevenly heated viscous incompressible fluid completely filling a finite cavity of the body is considered in linear formulation. The center of mass of the system body plus fluid in the state of mechanical equilibrium is assumed to coincide with point O. The theorem on solvability of the Cauchy problem for small unsteady equilibrium perturbations is proved, and normal perturbations and the spectrum of the problem arising in the analysis of such perturbations are investigated. It is shown that the whole spectrum consists of normal eigenvalues and lies in some half-band containing the real axis. It is shown that the respective system of root vectors is complete. Properties of the spectrum and the dependence on Rayleigh numbers are investigated. Rayleigh numbers for which the real parts of eigenvalues are positive,i.e. when the generated oscillating normal perturbations are damped in time, are evaluated in the case of the fluid being heated from below and above.     

Magneto-volume effect and invar phenomena in ferromagnetic metals

The magneto-volume effect is discussed in terms of the recent unified theory of ferromagnetic metals based on general spin fluctuations. Explanations are given for the large negative thermal expansion observed in weakly ferromagnetic metals and for the invar effect in some f.c.c. alloys. Large thermal expansion in nearly ferromagnetic metals is also pointed out.     

A thermobalance for high pressure process studies

A DuPont 950 TG has been modified to permit operation at up to 30 atm, 1100°C, with corrosive atmospheres, and steam partial pressures up to 20 atm.The major areas of instrument development included: weight and temperature measurement at high pressures in a dynamic flow system; modification of a TG to accept corrosive gas atmospheres containing high partial pressures of steam; design of a pressure balanced flow system for safe introduction of corrosive gas atmospheres; design of a working steam generation system for low flows.Process studies illustrating the utility of the high presure thermobalance include the cyclic CO₂-acceptor reaction for half-calcined dolomite

and the cyclic H₂S absorption and regeneration reaction for half-calcined dolomite