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991.
992.
The diploid-like chromosome pairing in polyploid wheat is controlled by the Ph1 (pairing homoeologous) gene that is located on chromosome arm 5BL. By using a combination of cytogenetic and molecular techniques, we report the physical location of the Ph1 gene to a submicroscopic chromosome region (Ph1 gene region) that is flanked by the breakpoints of two deletions (5BL-1 and ph1c) and is marked by a DNA probe (XksuS1). The Ph1 gene region is present distal to the breakpoint of deletion 5BL-1 but proximal to the C-band 5BL2.1. Two other DNA probes (Xpsr128 and Xksu75) flank the region-Xpsr128 being proximal and Xksu75 being distal. The estimated size of the region is less than 3 Mb. The chromosome region around the Ph1 gene is high in recombination as the genetic distance of the region between 5BL-1 breakpoint and C-band 5BL2.1 (not resolved by the microscope) is at least 9.3 cM. 相似文献
993.
Molecular cloning of a novel melanocortin receptor 总被引:2,自引:0,他引:2
I Gantz Y Konda T Tashiro Y Shimoto H Miwa G Munzert SJ Watson J DelValle T Yamada 《Canadian Metallurgical Quarterly》1993,268(11):8246-8250
Using the technique of the polymerase chain reaction primed with oligonucleotides based on the homologous transmembrane regions of seven transmembrane G protein-linked receptors, we isolated three full-length human genes that encode a novel subgroup of this receptor family. Recently, two of these receptors were identified as specific for alpha-melanocyte-stimulating hormone (alpha-MSH) and adrenocorticotropic hormone. We report the molecular cloning and pharmacologic characterization of a third member of this subgroup. The gene for this receptor encodes a protein of 361 amino acids in length. Its pharmacology characterizes it as an MSH receptor specific to the heptapeptide core common to adrenocorticotropic hormone and alpha-, beta-, and gamma-MSH. By Northern blot hybridization and polymerase chain reaction, it is expressed in brain, placental, and gut tissues but not in melanoma cells or in the adrenal gland. These findings may yield insight into the physiology of peptides derived from pro-opiomelanocortin post-translational processing. 相似文献
994.
MIMO-OFDM for wireless communications: signal detection with enhanced channel estimation 总被引:4,自引:0,他引:4
Multiple transmit and receive antennas can be used to form multiple-input multiple-output (MIMO) channels to increase the capacity by a factor of the minimum number of transmit and receive antennas. In this paper, orthogonal frequency division multiplexing (OFDM) for MIMO channels (MIMO-OFDM) is considered for wideband transmission to mitigate intersymbol interference and enhance system capacity. The MIMO-OFDM system uses two independent space-time codes for two sets of two transmit antennas. At the receiver, the independent space-time codes are decoded using prewhitening, followed by minimum-Euclidean-distance decoding based on successive interference cancellation. Computer simulation shows that for four-input and four-output systems transmitting data at 4 Mb/s over a 1.25 MHz channel, the required signal-to-noise ratios (SNRs) for 10% and 1% word error rates (WER) are 10.5 dB and 13.8 dB, respectively, when each codeword contains 500 information bits and the channel's Doppler frequency is 40 Hz (corresponding normalized frequency: 0.9%). Increasing the number of the receive antennas improves the system performance. When the number or receive antennas is increased from four to eight, the required SNRs for 10% and 1% WER are reduced to 4 dB and 6 dB, respectively. Therefore, MIMO-OFDM is a promising technique for highly spectrally efficient wideband transmission. 相似文献
995.
996.
A numerical simulation model for random large amplitude vibration control of composite plate using piezoelectric material is presented. The H∞ control design is employed to suppress the large amplitude vibrations of composites plates under random loading. The numerical simulation model is developed and based on the finite element method. The finite element governing equation includes fully coupled structural and electrical nodal degrees of freedom, and consider the von Karman large amplitude vibration. The modal reduction method using the structural modes is adopted to reduce the finite element equations into a set of modal equations with fewer degrees of freedom. The modal equations are then employed for controller design and time domain simulation. In the simulations without control, the value of the linear mode to the nonlinear deflection is quantified; and the minimum number of linear modes needed for accurate model is obtained. In the simulations with control, it is shown that the truncated modes, which are neglected in the control design, deteriorate the controller performance. Generally, the vibration reduction level is not monotonically increasing with the size of the piezoelectric actuator. The optimal piezoelectric actuator size depends on the excitation level. For higher excitation level, optimal actuator size is larger. The H∞ controller based on the linear finite element formulation gives better vibration reduction for small amplitude vibration, but it still gives reasonable performance for large amplitude vibration provided that the piezoelectric actuator is big and powerful enough. 相似文献
997.
K. Yasuda Y. Tomita Y. Masuda T. Ishiguro Y. Kawauchi H. Morishita Y. Agata 《Journal of Electronic Materials》2002,31(7):785-790
Iodine doping of CdTe layers grown on (100) GaAs by metal-organic vapor phase epitaxy (MOVPE) was studied using diethyltelluride
(DETe) and diisopropyltelluride (DiPTe) as tellurium precursors and ethyliodine (EI) as a dopant. Electron densities of doped
layers increased gradually with decreasing the growth temperature from 425°C to 325°C. Doped layers grown with DETe had higher
electron densities than those grown with DiPTe. When the hot-wall temperature was increased from 200°C to 250°C at the growth
temperature of 325°C, doped layers grown with DETe showed an increase of the electron density from 3.7×1016 cm−3 to 2.6×1018 cm−3. On the other hand, such an increase of the electron density was not observed for layers grown with DiPTe. The mechanisms
for different doping properties for DETe and DiPTe were studied on the basis of the growth characteristics for these precursors.
Higher thermal stability of DETe than that of DiPTe was considered to cause the difference of doping properties. With increasing
the hot-wall temperature from 200°C to 250°C, the effective ratio of Cd to Te species on the growth surface became larger
for layers grown with DETe than those grown with DiPTe. This was considered to decrease the compensation of doped iodine and
to increase the electron density of layers grown with DETe. The effective ratio of Cd to Te species on the growth surface
also increased with decreasing growth temperature. This was considered to increase the electron density with decreasing growth
temperature. 相似文献
998.
999.
An integral method is investigated and developed in the current work. The effects of the parameters of inlet distortions
on the trend of downstream flow feature in compressor are simulated. Other than the drag-to-lift ratio of the blade and the
inlet incidence angle, it is found that the distorted inlet velocity is another essential parameter to control the distortion
in propagation. Based on this study, a novel critical distortion line and corresponding critical distortion factor are proposed
to express the effect of the two essential inlet parameters on the propagation of distortion, namely, the inlet incidence
angle and the distorted inlet velocity. From the viewpoint of compressor efficiency, the propagation of inlet flow distortion
is further described by a compressor critical performance and its critical characteristic. The results present a useful physical
insight to an axial flow compressor behavior and asymptotic behavior of the propagation of inlet distortion, and confirm the
active role of compressor in determining the velocity distribution when compressor responds to an inlet flow distortion.
Received: 20 December 2001 / Accepted: 21 August 2002
The authors would like to thank HQ RSAF for permission to publish this work, their financial support and encouragement. The
first author wants to acknowledge Prof. Frank Marble of California Institute of Technology, for bringing the problem to the
author's attention and for his helpful discussion. 相似文献
1000.
R. Gnanamoorthy N. Rajiv K. Gopinath Y. Miyahsita Y. Mutoh 《Journal of Failure Analysis and Prevention》2002,2(4):71-75
Powder-metal-processed bearings and gears are finding increasing application because of their economical and technical advantages.
The residual pores from the sintering operatives act as lubricant pockets and dampen sound and vibration. However, porosity
also decreases the mechanical strength and reduces the life of components fabricated by powder processing relative to similar
wrought components. The rolling contact fatigue behavior of sintered and heat treated steel rollers was investigated using
a fatigue test machine designed and fabricated for that purpose. The powder-metal-processed and the wrought steel rollers
that were tested had similar composition and hardness and were mated against wrought steel rollers of high hardness. The contact
stress versus number of cycles to failure data showed that the wrought steel had a very high endurance limit under rolling
contact fatigue compared to the sintered steels investigated. Rolling contact fatigue behavior was found to depend on the
porosity present in the material. Large surface peeling failures and pitting type fatigue failures were observed in the sintered
and hardened steels, while only pitting type failures were observed in the wrought steels 相似文献