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341.
Samia Kaddour Fernando Lpez-Gallego Tahar Sadoun Roberto Fernandez-Lafuente Jose M. Guisan 《Journal of Molecular Catalysis .B, Enzymatic》2008,55(3-4):142-145
Multimeric catalase from Aspergillus niger was immobilized on CNBr activated agarose, increasing the enzyme stability. However, it was found that some enzyme subunits could be desorbed to the supernatant after boiling the enzyme preparation in the presence of SDS or during thermal inactivation. Moreover, a positive enzyme concentration-enzyme stability correlation was detected in the immobilized preparation. This suggested the existence of some dissociation mechanism as a first step in the enzyme inactivation. The treatment of the immobilized enzyme with aldehyde–dextran permitted to fully stabilize its multimeric structure, but even this preparation exhibited an enzyme concentration-stability correlation. The presence of EDTA reduced the enzyme stability, suggesting that some cation could be involved in enzyme stability. It was found that 10 mM Zn2+ increased the enzyme stability of this immobilized–stabilized preparation. Now, the dilution of the biocatalyst did not produce a reduction in the enzyme stability.Thus, we have prepared an immobilized enzyme that does not release any subunit to the medium even after inactivation, and found that Zn2+ has a very positive effect on the stability of this immobilized–stabilized enzyme. 相似文献
342.
Bacterial classification with convolutional neural networks based on different data reduction layers
Samia M. Abd –Alhalem Naglaa F. Soliman S. E. Abd Elrahman Nabil A. Ismail El-Sayed M. El-Rabaie 《Nucleosides, nucleotides & nucleic acids》2020,39(4):493-503
AbstractFor high accuracy classification of DNA sequences through Convolutional Neural Networks (CNNs), it is essential to use an efficient sequence representation that can accelerate similarity comparison between DNA sequences. In addition, CNN networks can be improved by avoiding the dimensionality problem associated with multi-layer CNN features. This paper presents a new approach for classification of bacterial DNA sequences based on a custom layer. A CNN is used with Frequency Chaos Game Representation (FCGR) of DNA. The FCGR is adopted as a sequence representation method with a suitable choice of the frequency k-lengthen words occurrence in DNA sequences. The DNA sequence is mapped using FCGR that produces an image of a gene sequence. This sequence displays both local and global patterns. A pre-trained CNN is built for image classification. First, the image is converted to feature maps through convolutional layers. This is sometimes followed by a down-sampling operation that reduces the spatial size of the feature map and removes redundant spatial information using the pooling layers. The Random Projection (RP) with an activation function, which carries data with a decent variety with some randomness, is suggested instead of the pooling layers. The feature reduction is achieved while keeping the high accuracy for classifying bacteria into taxonomic levels. The simulation results show that the proposed CNN based on RP has a trade-off between accuracy score and processing time. 相似文献
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Mohamed A. El-Farrash Mohamed F. Badr Samia A. Hawas Nariman M. El-Nashar Joko Imai Haruko Komoda Yorio Hinuma 《Microbiology and immunology》1988,32(9):981-984
Sera from 3,158 individuals living in northern Egypt were tested for the presence of antibodies against human T-lymphotropic virus type I (HTLV-I) by the newly developed particle agglutination (PA) test. Ten sera gave a positive reaction in the PA test. Eight of these sera were examined further by Western blotting and all of them gave several bands corresponding to HTLV-I structural proteins. Two of the 8 sera gave positive results in the indirect immunofluorescence test. The results indicate the presence of HTLV-I carriers in this area, although at very low incidence (0.063%). 相似文献
345.
Rossana de Aguiar Cordeiro Kharla Rabelo Nobre Patoilo Silviane Bandeira Praciano Delia Jessica Astete Medrano Francisca Jakelyne de Farias Marques Liline Maria Soares Martins Kelsen Dantas Eulalio Antônio de Deus Filho Maria do Amparo Salmito Cavalvanti Maria Auxiliadora Bezerra Fechine Raimunda Samia Nogueira Brilhante Zoilo Pires de Camargo Marcos Fábio Gadelha Rocha José Júlio Costa Sidrim 《Mycopathologia》2013,175(1-2):25-32
Serologic diagnosis has been presented as a safe alternative for coccidioidomycosis. However, commercial kits based on coccidioidal antibodies available in the USA are considered too expensive for laboratories outside that country. In this study, we describe the preparation of antigens for detection of human coccidioidal antibodies by the immunodiffusion test (ID) and enzyme immunoassay (EIA). Antigens were tested against serum samples from patients with coccidioidomycosis, histoplasmosis and paracoccidioidomycosis, as well as healthy individuals. The highest reactivity in the ID tests was seen in the F0-90 antigen. In the EIAs, the best results were obtained with the F60-90 antigen. None of the serum samples from healthy individuals were recognized by any of the antigen extracts tested by ID or EIA. In conclusion, the F0-90 and F60-90 antigens have the potential to be commercially employed in presumptive diagnosis of coccidioidomycosis by ID or EIA, respectively. The tests could improve serological diagnosis of coccidioidomycosis in South America. 相似文献
346.
Xisca Timoner Miriam Colls Samia M. Salomón Francesc Oliva Vicenç Acuña Sergi Sabater 《Freshwater Biology》2020,65(3):514-523
- In some regions, climate change is increasing the variability of rainfall and the frequency of extreme events such as drought. Consequently, non-flow periods have grown in length and frequency, both in temporary and in formerly permanent streams. Water abstraction for human use may further prolong these dry periods.
- We analysed the resistance and resilience of biofilms from permanent and temporary streams to non-flow conditions. This was achieved by exposing cobbles (collected from permanent and temporary streams) with intact biofilm to 31 days of non-flow, followed by 20 days of stream flow in artificial stream channels. Biofilm resistance and resilience were assessed at a structural (algal biomass, pigment composition, and algae and cyanobacteria composition) and functional level (photosynthetic efficiency and community metabolism).
- Algal taxa in biofilms from permanent and temporary streams differed throughout the experiment. Biofilms from permanent streams were less resistant to non-flow than those from temporary streams at structural level. Permanent stream biofilms also presented lower resilience at a structural level, but responded similarly to temporary stream biofilms at a functional level.
- Our investigation shows how the non-flow period disturbed permanent stream biofilms, and suggests that temporary stream biofilms will have greater adaptive capacity as hydroperiod becomes shorter due to climate change.
347.
A generalized threshold mixed model for analyzing nonnormal nonlinear time series, with application to plague in Kazakhstan 总被引:1,自引:0,他引:1
We introduce the generalized threshold mixed model for piecewise-linearstochastic regression with possibly nonnormal time-series data.It is assumed that the conditional probability distributionof the response variable belongs to the exponential family,and the conditional mean response is linked to some piecewise-linearstochastic regression function. We study the particular casewhere the response variable equals zero in the lower regime.Some large-sample properties of a likelihood-based estimationscheme are derived. Our approach is motivated by the need formodelling nonlinearity in serially correlated epizootic events.Data coming from monitoring conducted in a natural plague focusin Kazakhstan are used to illustrate this model by obtainingbiologically meaningful conclusions regarding the thresholdrelationship between prevalence of plague and some covariatesincluding past abundance of great gerbils and other climaticvariables. 相似文献
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