The Hard X-ray Detector (HXD) on board Suzaku covers a wide energy range from 10 keV to 600 keV by the combination of silicon PIN diodes and GSO scintillators. The HXD is designed to achieve an extremely low in-orbit background based on a combination of new techniques, including the concept of a well-type active shield counter. With an effective area of $142 \,\mathrm{cm}^{2}$ at 20 keV and $273 \,\mathrm{cm}^{2}$ at 150 keV, the background level at sea level reached $\sim 1 \times 10^{-5} \,\mathrm{cts} \,\mathrm{s}^{-1} \,\mathrm{cm}^{-2} \,\mathrm{keV}^{-1}$ at 30 keV for the PIN diodes, and $\sim 2 \times 10^{-5} \,\mathrm{cts} \,\mathrm{s}^{-1} \,\mathrm{cm}^{-2} \,\mathrm{keV}^{-1}$ at 100 keV, and $\sim 7 \times 10^{-6} \,\mathrm{cts} \,\mathrm{s}^{-1} \,\mathrm{cm}^{-2} \,\mathrm{keV}^{-1}$ at 200 keV for the phoswich counter. Tight active shielding of the HXD results in a large array of guard counters surrounding the main detector parts. These anti-coincidence counters, made of $\sim 4 \,\mathrm{cm}$ thick BGO crystals, have a large effective area for sub-MeV to MeV $\gamma$-rays. They work as an excellent $\gamma$-ray burst monitor with limited angular resolution ($\sim 5^{\circ}$). The on-board signal-processing system and the data transmitted to the ground are also described.

Plant alkaloids, one of the largest groups of natural products, provide many pharmacologically active compounds. Several genes in the biosynthetic pathways for scopolamine, nicotine, and berberine have been cloned, making the metabolic engineering of these alkaloids possible. Expression of two branching-point enzymes was engineered: putrescine N-methyltransferase (PMT) in transgenic plants of Atropa belladonna and Nicotiana sylvestris and (S)-scoulerine 9-Omethyltransferase (SMT) in cultured cells of Coptis japonica and Eschscholzia californica. Overexpression of PMT increased the nicotine content in N. sylvestris, whereas suppression of endogenous PMT activity severely decreased the nicotine content and induced abnormal morphologies. Ectopic expression of SMT caused the accumulation of benzylisoquinoline alkaloids in E. californica. The prospects and limitations of engineering plant alkaloid metabolism are discussed.berberine ͉ nicotine ͉ polyamine ͉ sanguinarine ͉ scopolamine H igher plants constitute one of our most important natural resources. They provide not only foodstuffs, fibers, and woods, but many chemicals, such as oils, flavorings, dyes, and pharmaceuticals. Although plants are renewable resources, some species are becoming more difficult to obtain in sufficient amounts to meet increasing demands. Destruction of natural habitats and technical difficulties in cultivation also are driving the drastic reductions in plant availability. For example, it is claimed that the demand for paclitaxel, a potent anticancer compound, could endanger forests of Taxus brevifolia (Pacific yew) because of the low paclitaxel content (40-100 mg͞kg of bark) in and slow growth of the trees (1).For many natural chemicals it is possible to synthesize alternatives from petroleum, coal, or both. The economic limitations of chemical synthesis and the pollution that accompanies this type of chemical synthesis, however, have led to the development of cell culture and molecular engineering of plants for the production of important and commodity chemicals. Plant cell and organ culture offer promising alternatives for the production of chemicals because totipotency enables plant cells and organs to produce useful secondary metabolites in vitro (2). Cell culture is also advantageous in that useful metabolites are obtained under a controlled environment, independent of climatic changes and soil conditions. In addition, the products are free of microbe and insect contamination. Fermentation technology also can be used to produce desired metabolites and can be optimized to maintain high and stable yields of known quality by cellular and molecular breeding techniques to further improve productivity and quality. After extensive empirical trials, some metabolites are now being produced by large-scale cell culture (e.g., shikonin and berberine; ref. 2), but the numbers of compounds that are producible commercially by cell culture technology are still very few. The main limitations are low productivity and the necessity of the down-stream pr...

The in-orbit performance and calibration of the Hard X-ray Detector (HXD) on board the X-ray astronomy satellite Suzaku are described. Its basic performances, including a wide energy bandpass of 10–600 keV, energy resolutions of $\sim 4 \,\mathrm{keV}$ (FWHM) at 40 keV and $\sim 11\%$ at 511 keV, and a high background rejection efficiency, have been confirmed by extensive in-orbit calibrations. The long-term gains of PIN-Si diodes have been stable within 1% for half a year, and those of scintillators have decreased by 5–20%. The residual non-X-ray background of the HXD is the lowest among past non-imaging hard X-ray instruments in energy ranges of 15–70 and 150–500 keV. We provide accurate calibrations of energy responses, angular responses, timing accuracy of the HXD, and relative normalizations to the X-ray CCD cameras using multiple observations of the Crab Nebula.

Background and Purpose: The purpose of this study was to compare the effects of low-to-high doses of aspirin on platelet aggregability determined by different methods and on the metabolism of thromboxane A 2 and prostacyclin.Methods: We administered increasing doses (40, 320, and 1,280 mg/day) of aspirin to 19 poststroke patients and studied the differences in 1) the changes in platelet aggregability depending on the methods of evaluation and 2) the concentrations of prostaglandin metabolites in the blood and urine.Results: Aggregation of platelet-rich plasma induced by a strong stimulus (10 fiM ADP) was significantly reduced after 40 mg/day aspirin (p<0.005), and this reduction was similar to that after higher aspirin doses. In contrast, aggregation of platelet-rich plasma induced by weaker stimuli (1 and 5 fiM ADP) decreased less significantly after 40 mg/day aspirin compared with that after higher aspirin doses. The serum thromboxane B 2 generated after ex vivo incubation was reduced significantly (by 85%) after 40 mg/day aspirin and decreased further after 320 mg/day (by 96%) and 1,280 mg/day (by >99%) of aspirin. The urinary 11-dehydro-thromboxane B 2 concentration decreased less significantly after 40 mg/day aspirin (by 42%) compared with that after 320 mg/day (by 78%) and 1,280 mg/day (by 91%) aspirin doses. The urinary concentration of 2,3-dinor-6-keto-prostaglandin ¥ la did not decrease after 40 mg/day aspirin but decreased significantly after higher doses of aspirin.Conclusions: These findings suggest that different doses of aspirin may be necessary to prevent thrombogenesis induced by different triggers of different strengths and that 40 mg/day aspirin is able to inhibit a large proportion of maximum thromboxane A 2 release provoked acutely, with the prostaglandin I 2 synthesis being little affected; however, higher doses of aspirin are required to attain further inhibition.