A steering law is proposed for a roof type configuration Single Gimbal Control Moment Gyro (SGCMG) system for attitude control of the Large Space Telescope, a payload of the Space Shuttle. Although various steering laws have been developed for SGCMG systems, they have some drawbacks because of singular states of the system. The proposed steering law minimizes the effect of singular states by using a new momentum distribution scheme that makes all the singular states unstable. This scheme is formulated by treating the system as a sampled-data system. 相似文献
In this paper, the controllability under decentralized information structure is studied for linear continuous-time systems. It is defined as follows. A system is controllable under the decentralized information structure if there exists a decentralized control law which transfers any unknown initial state to the origin in a finite time interval Necessary and sufficient conditions of the controllability under the decentralized information structure are given. It is also shown that the controllability under the decentralized information structure is a necessary condition of the pole-assignability with a local dynamic feedback control law. 相似文献
Molecular architectures built of inorganic cyanometalate building blocks provide variegated host structures with several organic guest molecules. The strategies to derive novel structures are presented briefly. The formation of a charge-transfer (CT) complex as the guest inside the cavity and the photochemistry of the CT complexes are discussed. The chemical pressure that the guest experiences inside the cavity is also discussed based on the vibrational spectroscopic results. 相似文献
The 50% aqueous methanolic extract from the bark of Betula platyphylla SUKATCHEV var. japonica (MIQ). HARA was found to show potent inhibitory activity on the liver-injury induced by CCl4 or D-galactosamine (D-GalN)/lipopolysaccharide as well as O2- scavenging and antioxidative activities. From the 50% aqueous methanolic extract, two new diarylheptanoids named betulaplatosides Ia (1) and Ib (2) and a new arylbutanoid named betulaplatoside II (3) were isolated together with seventeen known aromatic constituents. 1, 2, and two known diarylheptanoids [(5S)-5-hydroxy-1,7-bis-(4-hydroxyphenyl)-3-heptanone 5-O-beta-D-apiofurano-syl-(1-->6)-beta-D-glucopyranoside (6) and aceroside VIII (7)] showed protective activity against D-GalN-induced cytotoxicity in primary cultured rat hepatocytes. Furthermore, several aromatic constituents exhibited potent O2- scavenging and antioxidative activities. 相似文献
OBJECTIVE: External irradiation is an accepted curative treatment modality for patients with localized prostatic tumor. The 15-year results in patients treated by radical irradiation alone are presented. The determinant prognostic factors for local tumor control and disease free survival are analyzed. METHODS: 135 patients with a histologically confirmed localized carcinoma of the prostate were treated at our department from May 1972 to January 1998. Fifty patients received Co-60 therapy; the linear accelerator and high energy photons were utilized in the remaining 80 patients. By tumor stage, 53 patients were B1, 49 B2 and 33 C. The mean follow-up was 61 months (range 1-180). Most patients were exposed to localized fields of irradiation; dose ranged from 50-74 Gy, fractionated at a dose of 180-200 cGy/day. RESULTS: Overall local tumor control was 77% at 5 years and 73% at 15 years, with a disease free survival of 63% and 45% at 5 and 15 years, respectively. Local tumor control at 13 years was 71% for stage B1, 82% for B2 and 70% for C. The disease free survival at 13 years for stages B1, B2 and C were 46%, 49% and 36%, respectively. The BD and MD tumors had a 15-year disease free survival of 48% vs 32% for the PD tumors (p = 0.005). Patients with PSA < or = 20 ng/ml before treatment showed a disease free survival of 87% vs 48% for those with PSA > 20 ng/ml ((p = 0.011). Multivariate analysis showed dose to be a determinant prognostic factor for local tumor control (0.0432); dose and histological grade were determinants for disease free survival (p = 0.029 and 0.033). CONCLUSIONS: This retrospective study found dose to be a determinant prognostic factor for local tumor control and both dose and histological grade were determinants for disease free survival. Radiotherapy is a therapeutic option for these patients. The results can be enhanced if the dose delivered to the prostate can be increased while maintaining the complication rate within the same ranges. 相似文献
Nucleosome is a fundamental structural unit of chromatin, and the exposure from or occlusion into chromatin of genomic DNA is closely related to the regulation of gene expression. In this study, we analyzed the molecular dynamics of poly-nucleosomal arrays in solution by fast-scanning atomic force microscopy (AFM) to obtain a visual glimpse of nucleosome dynamics on chromatin fiber at single molecule level. The influence of the high-speed scanning probe on nucleosome dynamics can be neglected since bending elastic energy of DNA molecule showed similar probability distributions at different scan rates. In the sequential images of poly-nucleosomal arrays, the sliding of the nucleosome core particle and the dissociation of histone particle were visualized. The sliding showed limited fluctuation within ∼50 nm along the DNA strand. The histone dissociation occurs by at least two distinct ways: a dissociation of histone octamer or sequential dissociations of tetramers. These observations help us to develop the molecular mechanisms of nucleosome dynamics and also demonstrate the ability of fast-scanning AFM for the analysis of dynamic protein–DNA interaction in sub-seconds time scale. 相似文献
The effects of CoCl(2) on retinoic acid (RA)-treated embryoid bodies (EBs) were investigated. Four-day EBs were treated with 5x10(-6) M of RA for 4 d, then subjected to attached culturing for 7 d in the presence of CoCl(2) at 0, 20, and 100 microM. Differentiation into MAP2- and GFAP-immunopositive cells was inhibited by CoCl(2) in a dose-dependent manner. Next, RA-treated EBs were dissociated into single cells and cultured for 7 d at an initial cell density of 1x10(3)/cm(2). The number of cells increased in a CoCl(2)-dose dependent fashion. In cultures with 100 microM of CoCl(2), more than 90% of the cells were immunopositive for nestin and nestin-immunopositive cells formed clusters, while there were few cells immunopositive for MAP2 or GFAP. These results suggest that CoCl(2) inhibits neural differentiation of RA-treated EB cells and promotes the proliferation of nestin-immunopositive cells, i.e., embryonic stem (ES)-derived neural stem-like cells. 相似文献
A high-speed wireline interfaces, e.g. LVDS (Low Voltage Differential Signaling), are widely used in the aerospace field for powerful computing in artificial satellites and aircraft [19]. This paper describes Bit Error Rate (BER) prediction methodology for wireline data transmission under irradiation environment at the design stage of data transmitter, which is useful in proactively determining if the design circuit meets the BER criteria of the target system. Using a custom-designed LVDS transmitter (TX) to enhance latch-up immunity [42], the relationship between transistor size and BER has been analyzed with focusing on Single Event Effect (SEE) as a cause of the bit error. The measurement was executed under 84Kr17+ exposure of 322.0 MeV at various flux condition from 1?×?103 to 5?×?105 count/cm2/sec using cyclotron facility. For the analysis of the bit error, circuit simulation by SPICE was utilized with expressing the irradiation environment by a current source model. The current source model represents a single event strike into the circuit at drain and substrate junctions in bulk MOSFETs. For the construction of the current source model, a charge collection was simulated at the single particle strike with the creation of 3D Technology CAD (TCAD) models for the MOS devices of bulk transistor process technology. The simulation result of the charge correction was converted to a simple time-domain equation, and the single-event current source model was produced using the equation. The single-event current source was applied to SPICE simulation at bias current related circuits in the LVDS transmitter, then simulation results are carefully verified whether the output data is disturbed enough to cause bit errors on wireline data transmission. By the simulation, sensitive MOSFETs have been specified and a sum of the gate area for these MOSFETs has 29% better correlation than the normal evaluation index (sum of the drain area) by comparison to the actual BER measurement. Through the precise revelation of the sensitive area by SPICE simulation using the current model, it became possible to estimate BER under irradiation environment at the pre-fabrication design stage.