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排序方式: 共有600条查询结果,搜索用时 31 毫秒
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The semiconducting lanthanide cuprates Pr2CuO4, Nd2CuO4, and Gd2CuO4 have been investigated using X-ray diffraction, magnetic susceptibility, and electron paramagnetic resonance techniques. The susceptibility and resonance studies indicate that the Cu2+ ions are ordered antiferromagnetically and that the exchange interactions involving the Ln3+ ions are relatively weak. The deviations from the Curie-Weiss law in Pr2CuO4 and Nd2CuO4 are in qualitative agreement with the predicted behavior for isolated Ln3+ ions under the influence of a crystal field. Hence these compounds provide interesting examples of planar Cu2+-ion antiferromagnets. 相似文献
53.
Adrian Hernandez-Becerril Mariko Nakano-Miyatake Marco Ramirez-Tachiquin Hector Perez-Meana 《通讯和计算机》2013,(5):649-660
Recently, a multisecret sharing scheme for secret color images among a set of users was proposed, which allows that each participant to share secret color images with the rest of participants in such way that all of them can recover all secret color images only if all participants pool their shares. In this work a parallel implementation of the cellular automata-based multisecret sharing scheme is proposed, in which the technology of CUDA (Compute Unified Device Architecture) is used in parallelization, taking advantage that each cell of cellular automata can be processed independently. The processing time of the proposed scheme is analyzed and it is proved that the proposed parallel algorithm using the CUDA structure is more than 12 times faster than the conventional sequential algorithm. This reduction of temporal complexity allows the practical use of the secret sharing scheme in many information security fields. 相似文献
54.
The discovery of the superantigens (SAgs) offered new insights on the interaction between microorganisms and the host immune system. Associated to Major Histocompatibility Complex (MHC) class II molecules, SAgs bind to the variable domain of the beta chain (V beta) of the TCR alpha beta engaged in the family specificity of lymphocytes. Therefore, these molecules are able to activate a high number of T lymphocytes as well as surface MHC class II bearing cells, leading to an overriding release of cytokines and inflammatory mediators, which have been related to their toxic effects. Endogenous SAgs are encoded by murine tumor proviruses (Mtv) which are integrated in the genome of mice. Bacteria and viruses produce exogenous SAgs and those related to food poisoning have been widely studied. The presence of parasite SAgs is still unclear and further studies are required to establish their existence and effects on the corresponding infections. 相似文献
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F. Xavier Malcata Hector R. Reyes Hugo S. Garcia Charles G. Hill Jr. Clyde H. Amundson 《Journal of the American Oil Chemists' Society》1990,67(12):890-910
This review focuses on the use of immobilized lipase technology to effect hydrolysis, ester synthesis, and interesterification
reactions. The various immobilization procedures, reactor configurations, and process considerations are all reviewed and
discussed. 相似文献
57.
Leonel Pekarek Basilio De la Torre-Escuredo Oscar Fraile-Martinez Cielo García-Montero Miguel A. Saez David Cobo-Prieto Luis G. Guijarro Jose V. Saz Patricia De Castro-Martinez Diego Torres-Carranza Tatiana Pekarek Ana Clara Carrera Melchor Alvarez-Mon Miguel A. Ortega 《International journal of molecular sciences》2022,23(23)
Osteosarcoma represents a rare cause of cancer in the general population, accounting for <1% of malignant neoplasms globally. Nonetheless, it represents the main cause of malignant bone neoplasm in children, adolescents and young adults under 20 years of age. It also presents another peak of incidence in people over 50 years of age and is associated with rheumatic diseases. Numerous environmental risk factors, such as bone diseases, genetics and a history of previous neoplasms, have been widely described in the literature, which allows monitoring a certain group of patients. Diagnosis requires numerous imaging tests that make it possible to stratify both the local involvement of the disease and its distant spread, which ominously determines the prognosis. Thanks to various clinical trials, the usefulness of different chemotherapy regimens, radiotherapy and surgical techniques with radical intent has now been demonstrated; these represent improvements in both prognosis and therapeutic approaches. Osteosarcoma patients should be evaluated in reference centres by multidisciplinary committees with extensive experience in proper management. Although numerous genetic and rheumatological diseases and risk factors have been described, the use of serological, genetic or other biomarkers has been limited in clinical practice compared to other neoplasms. This limits both the initial follow-up of these patients and screening in populations at risk. In addition, we cannot forget that the diagnosis is mainly based on the direct biopsy of the lesion and imaging tests, which illustrates the need to study new diagnostic alternatives. Therefore, the purpose of this study is to review the natural history of the disease and describe the main biomarkers, explaining their clinical uses, prognosis and limitations. 相似文献
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Hector J. Levesque 《Artificial Intelligence》1984,23(2):155-212
We present a new approach to knowledge representation where knowledge bases are characterized not in terms of the structures they use to represent knowledge, but functionally, in terms of what they can be asked or told about some domain. Starting with a representation system that can be asked questions and told facts in a full first-order logical language, we then define ask- and tell-operations over an extended language that can refer not only to the domain but to what the knowledge base knows about that domain. The major technical result is that the resulting knowledge, which now includes auto-epistemic aspects, can still be represented symbolically in first-order terms. We also consider extensions to the framework such as defaults and definitional facilities. The overall result is a formal foundation for knowledge representation which, in accordance with current principles of software design, cleanly separates functionality from implementation structure. 相似文献