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91.
Gap junctions are collections of intercellular membrane channels that allow adjacent cells to share small molecules (< 1 kDa). Gap junction channels are composed of connexins, a homologous family of more than 20 proteins. In developing follicles, gap junctions couple the growing oocyte and its surrounding follicle cells into a functional syncytium. This review summarizes evidence on the expression of various connexins in developing follicles and the likely roles that some of the connexins play, on the basis of findings from gene targeting experiments in mice. Gap junctions between cumulus cells contain predominantly connexin43, and this connexin has also been detected using immunoelectron microscopy in a small minority of gap junctions at the oocyte surface. The importance of connexin43 for granulosa cell function is demonstrated by the fact that follicles lacking this connexin arrest in early preantral stages and produce incompetent oocytes. Connexin37 appears to be the only connexin contributed by oocytes to the gap junctions coupling them with granulosa cells, and loss of this connexin interferes with the development of antral follicles. The expression of multiple connexins in developing follicles is thus likely to reflect the multiple functions served by gap junctional communication in folliculogenesis. 相似文献
92.
Prasad D Polur Gerald E Miller 《IEEE transactions on neural systems and rehabilitation engineering》2005,13(4):558-561
In this study, a hidden Markov Model was constructed and conditions were investigated that would provide improved performance for a dysarthric speech (isolated word) recognition system. The speaker dependant system was intended to act as an assistive/control tool. A small size vocabulary spoken by three cerebral palsy subjects was chosen. Fast Fourier transform, linear predictive, and Mel frequency cepstral coefficients extracted from data provided training input to several whole-word hidden Markov model configurations. The effect of model structure, number of states, and frame rates were also investigated. It was noted that a 10-state ergodic model using 15 msec frames was better than other configurations. Furthermore, it was found that a Mel cepstrum based model outperformed a fast Fourier transform and linear prediction based model. The system offers effective and robust application as a rehabilitation and/or control tool to assist dysarthric motor impaired individuals. 相似文献
93.
Xin Miao Peng Gong Sarah Swope Ruiliang Pu Raymond Carruthers Gerald L. Anderson Jill S. Heaton C.R. Tracy 《Remote sensing of environment》2006,101(3):329-341
The invasive weed yellow starthistle (Centaurea solstitialis) has infested between 4 and 6 million hectares in California. It often forms dense infestations and rapidly depletes soil moisture, preventing the establishment of other species. Precise assessment of its canopy cover, especially low-density abundance in the earlier growing season, is the key to effective management. Compact Airborne Spectrographic Imager 2 (CASI-2) hyperspectral imagery was acquired at the western edge of California's Central Valley grasslands on July 15, 2003. Four linear spectral mixture models (LSMM) were investigated from the original CASI-2 data. Band selections based upon residual analysis and feature extraction (PCA) were further explored to reduce the data dimension. All approaches, except four band-selection unconstrained LSMMs, provide consistent results. The uncertainty of the PCA-based LSMM was estimated through a Monte-Carlo simulation. The maximum standard deviation was approximately 11%. The results suggest that unmixing CASI-2 imagery could be used for estimating and mapping yellow starthistle for larger regional areas. 相似文献
94.
Logic simulation is used extensively in the design of digital systems for the purpose of studying the behaviour of circuits under various conditions and for verifying the required performance of circuits. There is considerable interest in methods which reduce the simulation time during the design process. In this paper, we investigate how this can be achieved by simulating the action of logic circuits using a network of loosely coupled processors. Circuits modelled as directed graphs comprising clocked sequential components and (unclocked) arbitrary combinational logic gates can be partitioned into separate tasks each consisting of a sequential component with an associated network of combinational components. We present cost functions for evaluating a task subject to probabilistic assumptions about the functioning of the circuits. The circuit evaluation method used in the simulation process is significant. We apply lazy evaluation, a demand-driven evaluation strategy in which signals in the circuit are evaluated on a ‘need to do' basis, resulting in a considerable saving in circuit simulation time. We achieve distributed logic simulation using a network of workstations and show from experimental results that by using such a configuration, we essentially obtain a single computation engine which can be used to obtain speedups in circuit simulation when compared with uniprocessor simulation systems. Interprocess communications between tasks on different workstations proceed via remote procedure calls while local communications between tasks take place via shared memory. The method of partitioning used in the circuit model ensures that communications between tasks take place only at defined times in the simulation sequence. 相似文献
95.
Hongzhou Zhang Jun Yu Ying Chen John Fitz Gerald 《Journal of the American Ceramic Society》2006,89(2):675-679
A boron nitride (BN) nanostructure, conical BN nanorod, has been synthesized in a large quantity on Si substrates for the first time via the ball-milling and annealing method. Nitridation of milled boron carbide (B4 C) powders was performed in nitrogen gas at 1300°C on the surface of the substrates to form the BN nanorods. The highly crystallized nanorods consist of conical BN basal layers stacked along the nanorod axis. Ball milling of the B4 C powders can significantly enhance the nitridation of the powders and thus facilitate the formation of nanorods during the annealing process. 相似文献
96.
I Orlow A Iavarone SJ Crider-Miller F Bonilla E Latres MH Lee WL Gerald J Massagué BE Weissman C Cordón-Cardó 《Canadian Metallurgical Quarterly》1996,56(6):1219-1221
Mammalian cyclin-dependent kinase inhibitors fall into two families, the INK4 and the CIP/KIP. The CIP/KIP family comprises three structurally related members, including p21CiP1/WAF1, p27KIP1, and p57KIP2. These proteins are all capable of inhibiting the progression of the cell cycle by binding and inhibiting G(1) cyclin/cyclin-dependent kinase complexes. In humans, p57KIP2 is expressed specifically in skeletal muscle, heart, brain, kidney, and lung. Human KIP2 resides in 11p15.5, a chromosomal region that is a common site for loss of heterozygosity in certain sarcomas, Wilms' tumors, and tumors associated with the Beckwith-Wiedemann syndrome. Because of the function, selective expression, and chromosomal location of p57KIP2, we undertook the present study to search for potential mutations of KIP2 in a cohort of 126 tumors composed of 75 soft tissue sarcomas and 51 Wilms' tumors. The KIP2 gene was characterized by Southern blot, comparative multiplex PCR, PCR -single-strand conformational polymorphism, and DNA sequencing assays in these neoplasms. Deletions of the KIP2 gene or point mutations at the region encoding the cyclin-dependent kinase inhibitory domain were not found in the tumors analyzed. The absence of KIP2 mutations might indicate that these tumors arise due to defects at a closely linked but separate locus. Alternatively, similarly to the mouse homologue, inactivation of KIP2 could occur via genomic imprinting. 相似文献
97.
C++ uses inheritance as a substitute for subtype polymorphism. We give examples where this makes the type system too inflexible. We then describe a conservative language extension that allows a programmer to define an abstract type hierarchy independent of any implementation hierarchies, to retroactively abstract over an implementation, and to decouple subtyping from inheritance. This extension gives the user more of the flexibility of dynamic typing while retaining the efficiency and security of static typing. With default implementations and views flexible mechanisms are provided for implementing an abstract type by different concrete class types. We first show how the language extension can be implemented in a preprocessor to a C++ compiler, and then detail and analyse the efficiency of an implementation we directly incorporated in the GNU C++ compiler. 相似文献
98.
99.
Gerald J. Fleming 《应用聚合物科学杂志》1969,13(5):989-997
The thermal properties of polymers derived from resorcinol diglycidyl ether cured with several bicyclo Diels-Alder anhydride adducts have been investigated. Increased char yields and decreased rates of weight loss were observed for these systems as compared to polymers cured by Diels–Alder adducts from acyclic dienes. This is explained on the basis of a reverse Diels-Alder reaction which these bicyclo adducts undergo at lower temperatures than do adducts from acyclic dienes. 相似文献
100.
Presents information about the 1968 Convention of the American Psychological Association, held in San Francisco, California. Information includes the names of committee chairmen, committee members, and volunteers who assisted at the Convention. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献