1
|
Warda K, Amari S, Boureddane M, Elkamouni Y, Arsalane L, Zouhair S, Bouskraoui M. Changes in pneumococcal serotypes distribution and penicillin resistance in healthy children five years after generalization of PCV10. Heliyon 2024; 10:e25741. [PMID: 38380016 PMCID: PMC10877248 DOI: 10.1016/j.heliyon.2024.e25741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 01/11/2024] [Accepted: 02/01/2024] [Indexed: 02/22/2024] Open
Abstract
Objective Streptococcus pneumoniae (S. pneumoniae) nasopharyngeal carriage has significantly decreased after the generalization of pneumococcal vaccination worldwide. This study sought to investigate changes in S. pneumoniae carriage rates, serotype distribution and penicillin non-susceptibility following the generalization of 10-valent pneumococcal conjugate vaccine. Methods A prospective study was conducted in Marrakesh, Morocco, between 2017 and 2018, among healthy children attending vaccination centers. We collected nasopharyngeal swabs and questionnaire data for each child. Using univariate logistic regression, we analyzed the association between S. pneumoniae carriage and various risk factors. Comparisons of serotype diversity and penicillin resistance between 2017 and 2018 and the period before introduction of vaccination (2008-2009, n = 660) were performed using Simpson index and the chi-squared test, respectively. Results During 2017-2018, 515 children aged between 6 and 36 months participated. The S. pneumoniae carriage rate was 43.3%. Looking at the distribution serotypes, the rate of PCV10 serotypes rate was only 9.6%. Among non-vaccine serotypes, an increase in serotypes 6C/6D (22; 14%), 19B/19C (17; 10.8%), and 15B/15C (11; 7%) was observed. A particular increase in serotype diversity was also observed after the generalization of PCV10 (p < 0.001). S. pneumoniae non-susceptible to penicillin decreased, reaching a rate of 26.6% in 2017-2018. Conclusion The significant change in S. pneumoniae carriage, serotype distribution, and penicillin resistance highlights the effectiveness of the pneumococcal conjugate vaccine among children in Marrakesh, Morocco.
Collapse
Affiliation(s)
- Karima Warda
- Laboratory of Microbiology and Virology, Cadi Ayad University, Marrakesh, Morocco
| | - Sara Amari
- Laboratory of Microbiology and Virology, Cadi Ayad University, Marrakesh, Morocco
| | - Majda Boureddane
- Laboratory of Microbiology and Virology, Cadi Ayad University, Marrakesh, Morocco
| | - Youssef Elkamouni
- Laboratory of Microbiology and Virology, Cadi Ayad University, Marrakesh, Morocco
- Laboratory of Microbiology-Virology and Molecular Biology, Avicenna Military Hospital, Marrakesh, Morocco
| | - Lamiae Arsalane
- Laboratory of Microbiology and Virology, Cadi Ayad University, Marrakesh, Morocco
- Laboratory of Microbiology-Virology and Molecular Biology, Avicenna Military Hospital, Marrakesh, Morocco
| | - Said Zouhair
- Laboratory of Microbiology and Virology, Cadi Ayad University, Marrakesh, Morocco
- Laboratory of Microbiology-Virology and Molecular Biology, Avicenna Military Hospital, Marrakesh, Morocco
| | - Mohammed Bouskraoui
- Laboratory of Microbiology and Virology, Cadi Ayad University, Marrakesh, Morocco
- Department of Pediatrics, Mohamed VI University Hospital Center, Marrakesh, Morocco
| |
Collapse
|
2
|
Amari S, Warda K, Bouraddane M, Katfy M, Elkamouni Y, Arsalane L, Zerouali K, Zouhair S, Bouskraoui M. Antibiotic Resistance of Streptococcus pneumoniae in the Nasopharynx of Healthy Children Less than Five Years Old after the Generalization of Pneumococcal Vaccination in Marrakesh, Morocco. Antibiotics (Basel) 2023; 12:antibiotics12030442. [PMID: 36978307 PMCID: PMC10044557 DOI: 10.3390/antibiotics12030442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Revised: 02/13/2023] [Accepted: 02/16/2023] [Indexed: 02/25/2023] Open
Abstract
Streptococcus pneumoniae (S. pneumoniae) remains one of the most important pathogens causing childhood infections. The spread of antibiotic-resistant bacteria is a leading cause of treatment failure in children. The purpose of this investigation is to report the antibiotic and multidrug resistance (MDR) of S. pneumoniae strains isolated from healthy children throughout the years 2020–2022. Antimicrobial susceptibility testing of S. pneumoniae strains in selected antimicrobials was performed using disk diffusion and E-test methods on bloodMueller–Hinton agar. The antimicrobials tested included oxacillin, amoxicillin, ceftriaxone, norfloxacin, gentamicin, vancomycin, erythromycin, clindamycin, pristinamycin, tetracycline, chloramphenicol, and trimethoprim-sulfamethoxazole. A total of 201 S. pneumoniae strains were isolated from the nasopharynx of healthy children in Marrakesh, Morocco. The highest rate of resistance of S. pneumoniae was found in penicillin (57.2%), followed by tetracycline (20.9%), and erythromycin (17.9%). The rates of resistance to clindamycin, trimethoprim-sulfamethoxazole, and chloramphenicol were 14.9%, 4%, and 1.5%, respectively. All isolates were susceptible to norfloxacin, gentamicin, vancomycin, and pristinamycin. Approximately 17% of all S. pneumoniae strains were resistant to at least three different antibiotic families. This study showed a low rate of antibiotics resistance among nasopharyngeal S. pneumoniae strains, and it is thus essential to monitor S. pneumoniae susceptibility in healthy children.
Collapse
Affiliation(s)
- Sara Amari
- Laboratoire de Lutte Contre les Maladies Infectieuses, Faculté de Médecine et de Pharmacie, Université Cadi Ayyad, Marrakech 40000, Morocco
| | - Karima Warda
- Laboratoire de Lutte Contre les Maladies Infectieuses, Faculté de Médecine et de Pharmacie, Université Cadi Ayyad, Marrakech 40000, Morocco
- Correspondence: ; Tel.:+212-670602083
| | - Majda Bouraddane
- Laboratoire de Lutte Contre les Maladies Infectieuses, Faculté de Médecine et de Pharmacie, Université Cadi Ayyad, Marrakech 40000, Morocco
| | - Mostafa Katfy
- Service de Microbiologie, CHU Ibn Rochd, Casablanca 20000, Morocco
| | - Youssef Elkamouni
- Laboratoire de Lutte Contre les Maladies Infectieuses, Faculté de Médecine et de Pharmacie, Université Cadi Ayyad, Marrakech 40000, Morocco
- Laboratoire de Bactériologie, Virologie, et Biologie Moléculaire, Hôpital Militaire Avicenne, Marrakech 40000, Morocco
| | - Lamiae Arsalane
- Laboratoire de Lutte Contre les Maladies Infectieuses, Faculté de Médecine et de Pharmacie, Université Cadi Ayyad, Marrakech 40000, Morocco
- Laboratoire de Bactériologie, Virologie, et Biologie Moléculaire, Hôpital Militaire Avicenne, Marrakech 40000, Morocco
| | - Khalid Zerouali
- Service de Microbiologie, CHU Ibn Rochd, Casablanca 20000, Morocco
| | - Said Zouhair
- Laboratoire de Lutte Contre les Maladies Infectieuses, Faculté de Médecine et de Pharmacie, Université Cadi Ayyad, Marrakech 40000, Morocco
- Laboratoire de Bactériologie, Virologie, et Biologie Moléculaire, Hôpital Militaire Avicenne, Marrakech 40000, Morocco
| | - Mohamed Bouskraoui
- Laboratoire de Lutte Contre les Maladies Infectieuses, Faculté de Médecine et de Pharmacie, Université Cadi Ayyad, Marrakech 40000, Morocco
- Service de Pédiatrie, Hôpital Universitaire Mohammed VI, Marrakech 40000, Morocco
| |
Collapse
|
3
|
Bellioua S, Amari S, Warda K, Aghraz A, Dilagui I, Ouhaddou S, Sissi S, Bekkouche K, Larhsini M, Markouk M. Chemical profile, antioxidant and antimicrobial effects of essential oil from the Moroccan endemic plant cladanthus scariosus (L.). Journal of Essential Oil Research 2022. [DOI: 10.1080/10412905.2022.2074556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- S. Bellioua
- Biotechnologies and Valorization of Plant Bioresources (AGROBIOVAL), Team of Protection and Valorization of Plant Resources, Faculty of Sciences Semlalia, Cadi Ayyad UniversityLaboratory of Agri-Food, Marrakesh, Morocco
- 05), Cadi Ayyad UniversityCenter of Agrobiotechnology and Bioengineering, CNRST Labelled Research Unit (Centre AgroBiotech, URL-CNRST, Marrakesh, Morocco
| | - S. Amari
- Laboratory of Microbiology and virology, department of medical biology, Faculty of medicine and pharmacy, Cadi Ayyad University, Marrakesh, Morocco
| | - K. Warda
- Laboratory of Microbiology and virology, department of medical biology, Faculty of medicine and pharmacy, Cadi Ayyad University, Marrakesh, Morocco
| | - A. Aghraz
- Biotechnologies and Valorization of Plant Bioresources (AGROBIOVAL), Team of Protection and Valorization of Plant Resources, Faculty of Sciences Semlalia, Cadi Ayyad UniversityLaboratory of Agri-Food, Marrakesh, Morocco
- 05), Cadi Ayyad UniversityCenter of Agrobiotechnology and Bioengineering, CNRST Labelled Research Unit (Centre AgroBiotech, URL-CNRST, Marrakesh, Morocco
| | - I. Dilagui
- Laboratory of Microbiology and virology, department of medical biology, Faculty of medicine and pharmacy, Cadi Ayyad University, Marrakesh, Morocco
| | - S. Ouhaddou
- Biotechnologies and Valorization of Plant Bioresources (AGROBIOVAL), Team of Protection and Valorization of Plant Resources, Faculty of Sciences Semlalia, Cadi Ayyad UniversityLaboratory of Agri-Food, Marrakesh, Morocco
- 05), Cadi Ayyad UniversityCenter of Agrobiotechnology and Bioengineering, CNRST Labelled Research Unit (Centre AgroBiotech, URL-CNRST, Marrakesh, Morocco
| | - S. Sissi
- Biotechnologies and Valorization of Plant Bioresources (AGROBIOVAL), Team of Protection and Valorization of Plant Resources, Faculty of Sciences Semlalia, Cadi Ayyad UniversityLaboratory of Agri-Food, Marrakesh, Morocco
- 05), Cadi Ayyad UniversityCenter of Agrobiotechnology and Bioengineering, CNRST Labelled Research Unit (Centre AgroBiotech, URL-CNRST, Marrakesh, Morocco
| | - K. Bekkouche
- Biotechnologies and Valorization of Plant Bioresources (AGROBIOVAL), Team of Protection and Valorization of Plant Resources, Faculty of Sciences Semlalia, Cadi Ayyad UniversityLaboratory of Agri-Food, Marrakesh, Morocco
- 05), Cadi Ayyad UniversityCenter of Agrobiotechnology and Bioengineering, CNRST Labelled Research Unit (Centre AgroBiotech, URL-CNRST, Marrakesh, Morocco
| | - M. Larhsini
- Biotechnologies and Valorization of Plant Bioresources (AGROBIOVAL), Team of Protection and Valorization of Plant Resources, Faculty of Sciences Semlalia, Cadi Ayyad UniversityLaboratory of Agri-Food, Marrakesh, Morocco
- 05), Cadi Ayyad UniversityCenter of Agrobiotechnology and Bioengineering, CNRST Labelled Research Unit (Centre AgroBiotech, URL-CNRST, Marrakesh, Morocco
| | - M. Markouk
- Biotechnologies and Valorization of Plant Bioresources (AGROBIOVAL), Team of Protection and Valorization of Plant Resources, Faculty of Sciences Semlalia, Cadi Ayyad UniversityLaboratory of Agri-Food, Marrakesh, Morocco
- 05), Cadi Ayyad UniversityCenter of Agrobiotechnology and Bioengineering, CNRST Labelled Research Unit (Centre AgroBiotech, URL-CNRST, Marrakesh, Morocco
| |
Collapse
|
4
|
Amari S, Warda K, Elkamouni Y, Arsalane L, Bouskraoui M, Zouhair S. Serotype distribution and antimicrobial resistance of Streptococcus pneumoniae among children with acute otitis media in Marrakech, Morocco. IJM 2022; 14:47-55. [PMID: 35664713 PMCID: PMC9085554 DOI: 10.18502/ijm.v14i1.8801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Background and Objectives: Streptococcus pneumonia (S. pneumoniae) is one of the most frequent pathogens leading to a variety of clinical manifestations. The effects of S. pneumoniae carriage on acute otitis media (AOM) are poorly studied. The study aimed to assess the serotype’s distribution and antimicrobial susceptibility in children with AOM after the implementation of the pneumococcal conjugate vaccine (PCV) in Morocco. Materials and Methods: We conducted a prospective study of AOM children aged 6 to 36 months who visited pediatric centers in Marrakesh between January to June 2018. Parents were asked to complete a questionnaire and a swab was collected from each child. The S. pneumoniae strains were further identified (Hemolysis, optochin sensitivity, and agglutination test), serogrouped (IMMULEX PNEUMOTEST agglutination test), serotyped (Real time PCR) and tested for antimicrobial susceptibility. Results: The S. pneumoniae carriage rate was 49.7% (87/175). As estimated, non-vaccine serotypes (NVT) were most prevalent (51/63; 81%). The most frequent serotypes were 6C/6D (12.7%), 10 (9.5%), and 19B/19C (9.5%). The S. pneumoniae strains that were isolated showed a diminished susceptibility to penicillin G with a rate of 27.5%. Penicillin non-susceptible pneumococci (PNSP) was mostly associated with NVT. More than 90% of S. pneumoniae isolates were susceptible to chloramphenicol (97.5%), clindamycin (97.5%), erythromycin (97.5%), levofloxacin (97.5%), pristinamycin (97.5%), gentamicin (92.5%), and teicoplanin (92.5%). Conclusion: Important nasopharyngeal carriage prevalence was reported among children with AOM. The study showed that new NVT are emerging, including 6C/6D and 10. Furthermore, susceptibility was significantly higher against all antibiotics tested except for penicillin G and amoxicillin.
Collapse
Affiliation(s)
- Sara Amari
- Department of Medical Biology, Laboratory of Microbiology and Virology, Faculty of Medicine and Pharmacy, Cadi Ayyad University, Marrakesh, Morocco
- Corresponding author: Sara Amari, Ph.D, Department of Medical Biology, Laboratory of Microbiology and Virology, School of Medicine and Pharmacy, Cadi Ayyad University, Marrakesh, Morocco. Tel: +212-653052243, Fax: +21-2524432887,
| | - Karima Warda
- Department of Medical Biology, Laboratory of Microbiology and Virology, Faculty of Medicine and Pharmacy, Cadi Ayyad University, Marrakesh, Morocco
| | - Youssef Elkamouni
- Department of Medical Biology, Laboratory of Microbiology and Virology, Faculty of Medicine and Pharmacy, Cadi Ayyad University, Marrakesh, Morocco
- Laboratory of Bacteriology Virology, Avicenne Hospital Military, Marrakesh, Morocco
| | - Lamiae Arsalane
- Department of Medical Biology, Laboratory of Microbiology and Virology, Faculty of Medicine and Pharmacy, Cadi Ayyad University, Marrakesh, Morocco
- Laboratory of Bacteriology Virology, Avicenne Hospital Military, Marrakesh, Morocco
| | - Mohamed Bouskraoui
- Department of Pediatrics, Mohammed VI University Hospital, Marrakesh, Morocco
| | - Said Zouhair
- Department of Medical Biology, Laboratory of Microbiology and Virology, Faculty of Medicine and Pharmacy, Cadi Ayyad University, Marrakesh, Morocco
- Laboratory of Bacteriology Virology, Avicenne Hospital Military, Marrakesh, Morocco
| |
Collapse
|
5
|
Amari S, Blaison G, Groza M, Hautecloque G, Bouldoires B. Une uvéite postérieure bilatérale associée à un tableau clinique complexe révèlent une encéphalite à GFAP. Rev Med Interne 2020. [DOI: 10.1016/j.revmed.2020.10.255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
|
6
|
Pravdivtseva O, Tissot FLH, Dauphas N, Amari S. Evidence of presolar SiC in the Allende Curious Marie calcium aluminum rich inclusion. Nat Astron 2020; 2020:10.1038/s41550-019-1000-z. [PMID: 32021908 PMCID: PMC6999789 DOI: 10.1038/s41550-019-1000-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Accepted: 12/06/2019] [Indexed: 06/10/2023]
Abstract
Calcium aluminum rich inclusions (CAIs) are one of the first solids to have condensed in the solar nebula, while presolar grains formed in various evolved stellar environments. It is generally accepted that CAIs formed close to the Sun at temperatures above 1500 K, where presolar grains could not survive, and were then transported to other regions of the nebula where the accretion of planetesimals took place. In this context, a commonly held view is that presolar grains are found solely in the fine-grained rims surrounding chondrules and in the low-temperature fine-grained matrix that binds the various meteoritic components together. Here we demonstrate, based on noble gas isotopic signatures, that presolar SiC have been incorporated into fine-grained CAIs in the Allende carbonaceous chondrite at the time of their formation, and have survived parent body processing. This finding provides new clues on the conditions in the nascent solar system at the condensation of first solids.
Collapse
Affiliation(s)
- O Pravdivtseva
- Physics Department and McDonnell Center for the Space Sciences, Washington University, Saint Louis, MO 63130, USA
| | - F L H Tissot
- The Isotoparium, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
| | - N Dauphas
- Origins Laboratory, Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, Chicago, Il 60637, USA
| | - S Amari
- Physics Department and McDonnell Center for the Space Sciences, Washington University, Saint Louis, MO 63130, USA
| |
Collapse
|
7
|
Tadjer G, Liani N, Akif N, Khoudour Z, Amari S, Lamara-Mahamed A. Altération de l’audition chez les téléconseillers. ARCH MAL PROF ENVIRO 2014. [DOI: 10.1016/j.admp.2014.03.074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
8
|
Cao J, Murata N, Amari S, Cichocki A, Takeda T. A robust approach to independent component analysis of signals with high-level noise measurements. ACTA ACUST UNITED AC 2012; 14:631-45. [PMID: 18238044 DOI: 10.1109/tnn.2002.806648] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We propose a robust approach for independent component analysis (ICA) of signals where observations are contaminated with high-level additive noise and/or outliers. The source signals may contain mixtures of both sub-Gaussian and super-Gaussian components, and the number of sources is unknown. Our robust approach includes two procedures. In the first procedure, a robust prewhitening technique is used to reduce the power of additive noise, the dimensionality and the correlation among sources. A cross-validation technique is introduced to estimate the number of sources in this first procedure. In the second procedure, a nonlinear function is derived using the parameterized t-distribution density model. This nonlinear function is robust against the undue influence of outliers fundamentally. Moreover, the stability of the proposed algorithm and the robust property of misestimating the parameters (kurtosis) have been studied. By combining the t-distribution model with a family of light-tailed distributions (sub-Gaussian) model, we can separate the mixture of sub-Gaussian and super-Gaussian source components. Through the analysis of artificially synthesized data and real-world magnetoencephalographic (MEG) data, we illustrate the efficacy of this robust approach.
Collapse
Affiliation(s)
- Jianting Cao
- Dept. of Electron. Eng., Saitama Inst. of Technol., Japan
| | | | | | | | | |
Collapse
|
9
|
Yonezawa N, Amari S, Takahashi K, Ikeda K, Imai FL, Kanai S, Kikuchi K, Nakano M. Participation of the nonreducing terminal beta-galactosyl residues of the neutral N-linked carbohydrate chains of porcine zona pellucida glycoproteins in sperm-egg binding. Mol Reprod Dev 2005; 70:222-7. [PMID: 15570618 DOI: 10.1002/mrd.20195] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The zona pellucida (ZP) surrounding the mammalian oocyte is composed of three glycoprotein components (ZPA, ZPB, and ZPC). Mammalian sperm bind to carbohydrate chains of a ZP glycoprotein in the initial phase of fertilization. Sperm-ligand carbohydrate chains have been characterized in mouse, cow, and pig. In pigs, triantennary/tetraantennary neutral complex-type chains from ZPB/ZPC mixture possess stronger sperm-binding activity than those of biantennary chains (Kudo et al., 1998: Eur J Biochem 252:492-499). Most of these oligosaccharides have beta-galactosyl residues at the nonreducing ends. This study used two in vitro competition assays to investigate the participation of the nonreducing terminal beta-galactosyl residues of the ligand active chains in porcine sperm binding. The removal of the nonreducing terminal beta-galactosyl residues from either the ligand active carbohydrate chains or endo-beta-galactosidase-digested glycoproteins significantly reduced their inhibition of sperm-egg binding, indicating that the beta-galactosyl residues at the nonreducing ends are involved in porcine sperm-egg binding. A correlation between the sperm-binding activity and in vitro fertilization rate is also presented.
Collapse
Affiliation(s)
- N Yonezawa
- Graduate School of Science and Technology, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba-shi, Chiba 163-8522, Japan
| | | | | | | | | | | | | | | |
Collapse
|
10
|
Kouassi D, Diafouka F, Sawadogo GD, Amari S, Kone M, Monnet D, Sangarre A. [Antiphospholipid antibodies in African women presenting obstetrical complications]. Ann Biol Clin (Paris) 2004; 62:213-5. [PMID: 15047474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Abstract
The presence of antiphospholipid antibodies (APL) has been investigated in 68 African women presenting obstetrical complications versus a control group of 22 pregnant healthy women. Patients inclusion criterias were recurrent foetal loss, pre eclampsia, retroplacental haematoma and chronic foetal suffering. Eight of patients (11.8%) had a positive APL diagnosis, versus 0% in controls, using the combination of diluted thromboplastin test and Staclot LA These results argue for the systematic APL screening in African women with obstetrical complications, and could further improve the management of patients at risk.
Collapse
Affiliation(s)
- D Kouassi
- Laboratoire d'hématologie, UFR, Sciences pharmaceutiques et biologiques d'Abidjan, Côte d'Ivoire
| | | | | | | | | | | | | |
Collapse
|
11
|
Abstract
The inferred crystallographic class of circumstellar silicon carbide based on astronomical infrared spectra is controversial. We have directly determined the polytype distribution of circumstellar SiC from transmission electron microscopy of presolar silicon carbide from the Murchison carbonaceous meteorite. Only two polytypes (of a possible several hundred) were observed: cubic 3C and hexagonal 2H silicon carbide and their intergrowths. We conclude that this structural simplicity is a direct consequence of the low pressures in circumstellar outflows and the corresponding low silicon carbide condensation temperatures.
Collapse
Affiliation(s)
- T L Daulton
- Materials Science Division, Argonne National Laboratory, Argonne IL, 60439-4838, USA.
| | | | | | | | | | | |
Collapse
|
12
|
Burnashev MV, Han TS, Amari S. On Some Estimation Problems with Information Constraints. Theory Probab Appl 2002. [DOI: 10.1137/s0040585x97978889] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
13
|
Abstract
Principal component and minor component extractions provide powerful techniques in many information processing fields. There have been proposed a number of algorithms for principal and minor component (or subspace) extraction, which have different dynamical behaviors. In this paper, we give rigorous stability analysis of these algorithms, obtaining a unified insight view on the dynamical behaviors of various algorithms.
Collapse
Affiliation(s)
- T Chen
- Department of Mathematics, Fudan University, Shanghai, PR China.
| | | |
Collapse
|
14
|
Abstract
This study investigates the influence of attention modulation on neural tuning functions. It has been shown in experiments that attention modulation alters neural tuning curves. Attention has been considered at least to serve to resolve limiting capacities and to increase the sensitivity to attended stimulus, while the exact functions of attention are still under debate. Inspired by recent experimental results on attention modulation, we investigate the influence of changes in the height and base rate of the tuning curve on the encoding accuracy, using the Fisher information. Under an assumption of stimulus-conditional independence of neural responses, we derive explicit conditions that determine when the height and base rate should be increased or decreased to improve encoding accuracy. Notably, a decrease in the tuning height and base rate can improve the encoding accuracy in some cases. Our theoretical results can predict the effective size of attention modulation on the neural population with respect to encoding accuracy. We discuss how our method can be used quantitatively to evaluate different aspects of attention function.
Collapse
Affiliation(s)
- H Nakahara
- RIKEN Brain Science Institute, Wako, Saitama, 351-0198, Japan
| | | | | |
Collapse
|
15
|
Amari S, Yonezawa N, Mitsui S, Katsumata T, Hamano S, Kuwayama M, Hashimoto Y, Suzuki A, Takeda Y, Nakano M. Essential role of the nonreducing terminal alpha-mannosyl residues of the N-linked carbohydrate chain of bovine zona pellucida glycoproteins in sperm-egg binding. Mol Reprod Dev 2001; 59:221-6. [PMID: 11389558 DOI: 10.1002/mrd.1026] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
It has been proposed that mammalian sperm bind species-specifically to carbohydrate chains of zona pellucida glycoproteins at fertilization. Although the sperm ligand carbohydrate chains have been characterized in mice and pigs, the existence of the ligands of other mammals remains unclear. In order to explore the bovine sperm ligand, two in vitro competition assay methods were applied. As a result, a high-mannose-type carbohydrate chain, Manalpha1-6(Manalpha1-3)Manalpha1-6(Manalpha1-3)Manbeta1-4GlcNAcbeta1-4GlcNAc, which is the major neutral chain in bovine egg zona glycoproteins, was shown to possess bovine sperm ligand activity. When nonreducing terminal alpha-mannosyl residues were eliminated from the zona glycoproteins by alpha-mannosidase digestion, the ligand activity was reduced, indicating that the alpha-mannosyl residues play an essential role in bovine sperm-egg binding. The number of sperm binding to eggs was reduced to about one-half after fertilization. The ligand-active high-mannose-type chain may be buried after fertilization, since its amount remains unchanged. Pretreatment of bovine sperm with the sperm ligand-carbohydrate chain significantly inhibited penetration of the sperm into oocyte and the male pronucleus formation. Thus, a correlation between the sperm ligand activity and in vitro fertilization rate was observed.
Collapse
Affiliation(s)
- S Amari
- Graduate School of Science and Technology, Chiba University, Chiba, Japan
| | | | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Abstract
We discuss some delayed dynamical systems, investigating their stability and convergence. We prove that under mild conditions, these delayed systems are global exponential convergent.
Collapse
Affiliation(s)
- T Chen
- Department of Mathematics, Fudan University, Shanghai, China
| | | |
Collapse
|
17
|
Abstract
This article studies a general theory of estimating functions of independent component analysis when the independent source signals are temporarily correlated. Estimating functions are used for deriving both batch and on-line learning algorithms, and they are applicable to blind cases where spatial and temporal probability structures of the sources are unknown. Most algorithms proposed so far can be analyzed in the framework of estimating functions. An admissible class of estimating functions is derived, and related efficient on-line learning algorithms are introduced. We analyze dynamical stability and statistical efficiency of these algorithms. Different from the independently and identically distributed case, the algorithms work even when only the second-order moments are used. The method of simultaneous diagonalization of cross-covariance matrices is also studied from the point of view of estimating functions.
Collapse
Affiliation(s)
- S Amari
- RIKEN Brain Science Institute, Japan
| |
Collapse
|
18
|
Kuno M, Yonezawa N, Amari S, Hayashi M, Ono Y, Kiss L, Sonohara K, Nakano M. The presence of a glycosyl phosphatidylinositol-anchored alpha-mannosidase in boar sperm. IUBMB Life 2000; 49:485-9. [PMID: 11032241 DOI: 10.1080/15216540050167016] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
alpha-Mannosidase and beta-galactosidase were released from boar sperm into the medium by treatment with calcium ionophore A23187 or by 0.2% Brij-35/2% acetic acid. About half as much alpha-mannosidase activity as that in the acid extract was recovered by digestion with phosphatidylinositol-specific phospholipase C (PI-PLC), whereas the liberation rate of beta-galactosidase treated with PI-PLC was low. These results suggest that some alpha-mannosidase is anchored in the plasma membrane of the acrosomal region by attachment to the lipid phosphatidylinositol and that beta-galactosidase is localized mainly in the acrosome or integrated in the plasma membrane by a spanning stretch of hydrophobic peptides. beta-Galactosidase, which is present as an oligomers in the acid extract of sperm, dissociated into monomers under weakly alkaline conditions; under acidic conditions, the monomers associated again. No pH-sensitive association-dissociation of alpha-mannosidase was observed.
Collapse
Affiliation(s)
- M Kuno
- Graduate School of Science and Technology, Faculty of Science, Chiba University, Japan.
| | | | | | | | | | | | | | | |
Collapse
|
19
|
Abstract
Independent component analysis or blind source separation extracts independent signals from their linear mixtures without assuming prior knowledge of their mixing coefficients. It is known that the independent signals in the observed mixtures can be successfully extracted except for their order and scales. In order to resolve the indeterminacy of scales, most learning algorithms impose some constraints on the magnitudes of the recovered signals. However, when the source signals are nonstationary and their average magnitudes change rapidly, the constraints force a rapid change in the magnitude of the separating matrix. This is the case with most applications (e.g., speech sounds, electroencephalogram signals). It is known that this causes numerical instability in some cases. In order to resolve this difficulty, this article introduces new nonholonomic constraints in the learning algorithm. This is motivated by the geometrical consideration that the directions of change in the separating matrix should be orthogonal to the equivalence class of separating matrices due to the scaling indeterminacy. These constraints are proved to be nonholonomic, so that the proposed algorithm is able to adapt to rapid or intermittent changes in the magnitudes of the source signals. The proposed algorithm works well even when the number of the sources is overestimated, whereas the existent algorithms do not (assuming the sensor noise is negligibly small), because they amplify the null components not included in the sources. Computer simulations confirm this desirable property.
Collapse
Affiliation(s)
- S Amari
- RIKEN Brain Science Institute, Brain-Style Information Systems Group, Japan
| | | | | |
Collapse
|
20
|
Abstract
The natural gradient learning method is known to have ideal performances for on-line training of multilayer perceptrons. It avoids plateaus, which give rise to slow convergence of the backpropagation method. It is Fisher efficient, whereas the conventional method is not. However, for implementing the method, it is necessary to calculate the Fisher information matrix and its inverse, which is practically very difficult. This article proposes an adaptive method of directly obtaining the inverse of the Fisher information matrix. It generalizes the adaptive Gauss-Newton algorithms and provides a solid theoretical justification of them. Simulations show that the proposed adaptive method works very well for realizing natural gradient learning.
Collapse
Affiliation(s)
- S Amari
- RIKEN Brain Science Institute, Hirosawa, Saitama, Japan
| | | | | |
Collapse
|
21
|
|
22
|
Abstract
The influence of a macroscopic time-dependent threshold on the retrieval dynamics of attractor associative memory models with ternary neurons ¿-1, 0, +1¿ is examined. If the threshold is chosen appropriately as a function of the cross-talk noise and of the activity of the memorized patterns in the model, adapting itself in the course of the time evolution, it guarantees an autonomous functioning of the model. Especially in the limit of sparse coding, it is found that this self-control mechanism considerably improves the quality of the fixed-point retrieval dynamics, in particular the storage capacity, the basins of attraction and the information content. The mutual information is shown to be the relevant parameter to study the retrieval quality of such sparsely coded models. Numerical results confirm these observations.
Collapse
Affiliation(s)
- D Bollé
- Instituut voor Theoretische Fysica, Katholieke Universiteit Leuven, Belgium.
| | | | | |
Collapse
|
23
|
Abstract
Local minima and plateaus pose a serious problem in learning of neural networks. We investigate the hierarchical geometric structure of the parameter space of three-layer perceptrons in order to show the existence of local minima and plateaus. It is proved that a critical point of the model with H - 1 hidden units always gives many critical points of the model with H hidden units. These critical points consist of many lines in the parameter space, which can cause plateaus in learning of neural networks. Based on this result, we prove that a point in the critical lines corresponding to the global minimum of the smaller model can be a local minimum or a saddle point of the larger model. We give a necessary and sufficient condition for this, and show that this kind of local minima exist as a line segment if any. The results are universal in the sense that they do not require special properties of the target, loss functions and activation functions, but only use the hierarchical structure of the model.
Collapse
Affiliation(s)
- K Fukumizu
- Laboratory for Information Synthesis, RIKEN Brain Science Institute, Wako, Saitama, Japan.
| | | |
Collapse
|
24
|
Abstract
Independent component analysis or blind source separation is a new technique of extracting independent signals from mixtures. It is applicable even when the number of independent sources is unknown and is larger or smaller than the number of observed mixture signals. This article extends the natural gradient learning algorithm to be applicable to these overcomplete and undercomplete cases. Here, the observed signals are assumed to be whitened by preprocessing, so that we use the natural Riemannian gradient in Stiefel manifolds.
Collapse
Affiliation(s)
- S Amari
- RIKEN Brain Science Institute, Wako-shi, Hirosawa, Saitama 351-01, Japan
| |
Collapse
|
25
|
Abstract
We propose a method of modifying a kernel function to improve the performance of a support vector machine classifier. This is based on the structure of the Riemannian geometry induced by the kernel function. The idea is to enlarge the spatial resolution around the separating boundary surface, by a conformal mapping, such that the separability between classes is increased. Examples are given specifically for modifying Gaussian Radial Basis Function kernels. Simulation results for both artificial and real data show remarkable improvement of generalization errors, supporting our idea.
Collapse
Affiliation(s)
- S Amari
- RIKEN Brain Science Institute, The Institute for Physical and Chemical Research, Hirosawa 2-1, Wako-shi, Saitama, Japan
| | | |
Collapse
|
26
|
Abstract
A new, efficient algorithm for blind separation of uniformly distributed sources is proposed. The mixing matrix is assumed to be orthogonal by prewhitening the observed signals. The learning rule adaptively estimates the mixing matrix by conceptually rotating a unit hypercube so that all output signal components are contained within or on the hypercube. Under some ideal constraints, it has been theoretically shown that the algorithm is very similar to an ideal O(1/T2) convergent algorithm, which is much faster than the existing O(1/T) convergent algorithms. The algorithm has been generalized to take care of the noisy signals by adaptively dilating the hypercube in conjunction with its rotation.
Collapse
Affiliation(s)
- J Basak
- RIKEN Frontier Research Program, Hirosawa 2-1 Wako-shi, Saitama 351-01, Japan.
| | | |
Collapse
|
27
|
Abstract
Counter-selections for the loss of introduced plasmid sequences are useful for gene manipulations in yeast. We have used GAL10 promoter-mediated overexpression of GIN sequences, which inhibit the growth of cells, to develop a novel counter-selection system. Yeast cells carrying a GIN sequence grow normally on glucose medium but are unable to grow on galactose medium, whereas derivatives that have lost the GIN sequence are able to grow in the presence of galactose. We constructed autonomously replicating, integrating, and disruption plasmids carrying GIN sequences and tested their use to select for loss of the plasmid. The results showed that the GIN sequences provide a selection for efficient loss of plasmids or integrated constructs from yeast during growth on galactose medium, indicating that this system can be used for plasmid shuffling, gene replacements and marker gene recycling. This counter-selection system has wide application, because any Gal+ strain and a wide variety of marker genes can be used. In addition, counter-selection systems using growth-inhibitory sequences should be applicable to other yeasts and possibly to other organisms.
Collapse
Affiliation(s)
- M Kawahata
- Department of Applied Chemistry and Chemical Engineering, Faculty of Engineering, Yamaguchi University, Ube, Japan
| | | | | | | |
Collapse
|
28
|
Basak J, Amari S. Blind separation of uniformly distributed signals: a general approach. IEEE Trans Neural Netw 1999; 10:1173-1185. [PMID: 18252618 DOI: 10.1109/72.788656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
A general algorithm for blind separation of uniformly distributed signals is presented. First maximum likelihood equations are obtained for dealing with this task. It is difficult to obtain a closed form maximum likelihood solution for arbitrary mixing matrix. The learning rules are obtained based on the geometric interpretation of the maximum likelihood estimator. The algorithm, under special constraint of orthogonal mixing matrix, is the same as the O(1/T2) convergent algorithm. Special noise correction mechanisms are incorporated in the algorithm, and it has been found that the algorithm exhibits stable performance even in the presence of large amount of noise.
Collapse
Affiliation(s)
- J Basak
- Machine Intelligence Unit, Indian Statistical Institute, Calcutta-700 035, India
| | | |
Collapse
|
29
|
Abstract
The natural gradient descent method is applied to train an n-m-1 multilayer perceptron. Based on an efficient scheme to represent the Fisher information matrix for an n-m-1 stochastic multilayer perceptron, a new algorithm is proposed to calculate the natural gradient without inverting the Fisher information matrix explicitly. When the input dimension n is much larger than the number of hidden neurons m, the time complexity of computing the natural gradient is O(n).
Collapse
Affiliation(s)
- H H Yang
- Oregon Graduate Institute, Computer Science Dept, Box 91000, Portland OR 97291, USA.
| | | |
Collapse
|
30
|
|
31
|
|
32
|
Amari S, Murata N, Muller KR, Finke M, Yang H. Asymptotic statistical theory of overtraining and cross-validation. ACTA ACUST UNITED AC 1997; 8:985-96. [DOI: 10.1109/72.623200] [Citation(s) in RCA: 220] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
33
|
Nicolussi GK, Pellin MJ, Calaway WF, Lewis RS, Davis AM, Amari S, Clayton RN. Isotopic Analysis of Ca from Extraterrestrial Micrometer-Sized SiC by Laser Desorption and Resonant Ionization Mass Spectroscopy. Anal Chem 1997. [DOI: 10.1021/ac960871k] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- G. K. Nicolussi
- Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637, Materials Science and Chemistry Divisions, Argonne National Laboratory, Argonne, Illinois 60439, Department of Chemistry, University of Chicago, Chicago, Illinois 60637, Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois 60637, and McDonnell Center for the Space Sciences, Washington University, St. Louis, Missouri 63130
| | - M. J. Pellin
- Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637, Materials Science and Chemistry Divisions, Argonne National Laboratory, Argonne, Illinois 60439, Department of Chemistry, University of Chicago, Chicago, Illinois 60637, Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois 60637, and McDonnell Center for the Space Sciences, Washington University, St. Louis, Missouri 63130
| | - W. F. Calaway
- Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637, Materials Science and Chemistry Divisions, Argonne National Laboratory, Argonne, Illinois 60439, Department of Chemistry, University of Chicago, Chicago, Illinois 60637, Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois 60637, and McDonnell Center for the Space Sciences, Washington University, St. Louis, Missouri 63130
| | - R. S. Lewis
- Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637, Materials Science and Chemistry Divisions, Argonne National Laboratory, Argonne, Illinois 60439, Department of Chemistry, University of Chicago, Chicago, Illinois 60637, Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois 60637, and McDonnell Center for the Space Sciences, Washington University, St. Louis, Missouri 63130
| | - A. M. Davis
- Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637, Materials Science and Chemistry Divisions, Argonne National Laboratory, Argonne, Illinois 60439, Department of Chemistry, University of Chicago, Chicago, Illinois 60637, Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois 60637, and McDonnell Center for the Space Sciences, Washington University, St. Louis, Missouri 63130
| | - S. Amari
- Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637, Materials Science and Chemistry Divisions, Argonne National Laboratory, Argonne, Illinois 60439, Department of Chemistry, University of Chicago, Chicago, Illinois 60637, Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois 60637, and McDonnell Center for the Space Sciences, Washington University, St. Louis, Missouri 63130
| | - R. N. Clayton
- Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637, Materials Science and Chemistry Divisions, Argonne National Laboratory, Argonne, Illinois 60439, Department of Chemistry, University of Chicago, Chicago, Illinois 60637, Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois 60637, and McDonnell Center for the Space Sciences, Washington University, St. Louis, Missouri 63130
| |
Collapse
|
34
|
Abstract
A theoretical framework is presented for designing birdcage resonators for MRI and MR spectroscopy. The analogy between the birdcage problem and the phonon problem in solid-state physics is used to achieve multiple tuning. Allowing that the capacitances in the columns of the cage assume unequal values, it is possible to achieve multiple tuning and simultaneously preserve the sinusoidal current distribution necessary to set a homogeneous magnetic field. Given the physical dimensions of the columns and branches of the cage as well as the desired resonant frequencies, the corresponding values of the capacitances can be calculated exactly. Closed-form expressions for the capacitances are given in terms of the mutual inductances and the desired resonant frequencies. A detailed analysis for a symmetrical low-pass birdcage is presented. The expressions for the resonant frequencies reduce to those given by other authors when only nearest-neighbor mutual inductances are included.
Collapse
Affiliation(s)
- S Amari
- Centre for Advanced Materials and Related Technology, University of Victoria, British Columbia, Canada
| | | | | | | | | |
Collapse
|
35
|
Abstract
The universal asymptotic scaling laws proposed by Amari et al. are studied in large scale simulations using a CM5. Small stochastic multilayer feedforward networks trained with backpropagation are investigated. In the range of a large number of training patterns t, the asymptotic generalization error scales as 1/t as predicted. For a medium range t a faster 1/t2 scaling is observed. This effect is explained by using higher order corrections of the likelihood expansion. It is shown for small t that the scaling law changes drastically, when the network undergoes a transition from strong overfitting to effective learning.
Collapse
Affiliation(s)
- K R Müller
- Department of Mathematical Engineering and Inf. Physics, University of Tokyo, Japan
| | | | | | | | | |
Collapse
|
36
|
Abstract
The circumstellar silicon carbide (SiC) grain X57 from the Murchison meteorite contains large amounts of radiogenic calcium-44 (20 times its solar system abundance) and has an anomalous silicon isotopic composition, different from other circumstellar SiC grains. Its inferred initial 44Ti/Si and 44Ti/48Ti ratios are 1.6 x 10(-4) and 0.37. In addition, it contains radiogenic magnesium-26; the inferred initial 26Al/27Al ratio is 0.11. The isotopic and elemental data of X57 can be explained by selective mixing of matter from different zones of a typical type II supernova of 25 solar masses during its explosion. The high 44Ti/Si ratio requires contributions from the innermost nickel zone of the supernova to the SiC condensation site, as similarly suggested by astronomical observations.
Collapse
Affiliation(s)
- P Hoppe
- P. Hoppe, R. Strebel, P. Eberhardt, Physikalisches Institut, Universitat Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland. S. Amari and R. S. Lewis, Enrico Fermi Institute, University of Chicago, Chicago, IL 60637, USA
| | | | | | | | | |
Collapse
|
37
|
Hoppe P, Strebel R, Eberhardt P, Amari S, Lewis RS. Small SiC grains and a nitride grain of circumstellar origin from the Murchison meteorite: implications for stellar evolution and nucleosynthesis. Geochim Cosmochim Acta 1996; 60:883-907. [PMID: 11539147 DOI: 10.1016/0016-7037(95)00435-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We report the results of SIMS isotopic analyses of carbon, nitrogen, oxygen, and silicon made on 849 small (approximately 1 micrometer) individual silicon carbide grains from the Murchison meteorite. The isotopic compositions of the major elements carbon and silicon of most grains (mainstream) are similar to those observed in larger grain studies suggesting an AGB star origin of these grains. In contrast, the trace element nitrogen shows a clear dependency on grain size. 14N/15N ratios increase with decreasing grain size, suggesting different stellar sources for grains of different size. Typically observed 14N/15N ratios in the small grains of this study are approximately 2700, clearly larger than the values expected from model calculations of AGB stars. In addition to the three dredge-up episodes characteristic for the evolution of AGB stars, extra-mixing of CNO-processed matter in low mass AGB stars appears to be a promising possibility in order to explain the high 14N/15N ratios of the small circumstellar SiC grains. A small fraction of grains shows a silicon isotopic signature not observed in larger circumstellar SiC grains from Murchison. Their stellar origin is still uncertain. The minor type A, B, Y, and X grains were found to be present at a level of a percent, which is similar to their abundance in the larger-grain SiC separates from Murchison. Oxygen isotopic compositions are normal within the experimental uncertainties of several 10%, indicating that oxygen of stellar origin is rare or even absent in the SiC grains. We conclude that most of the oxygen is a contaminant which was introduced into the SiC grains after their formation, e.g., during sample processing in the laboratory. We identified a nitride grain, most likely Si3N4 with little carbon, with highly anomalous isotopic compositions (12C/13C = 157 +/- 33, 14N/15N = 18 +/- 1, delta 29 Si = -43 +/- 56%, delta 30 Si = -271 +/- 50%). The isotopic patterns of carbon, nitrogen, and silicon resemble those of the rare SiC X grains suggesting that these two rare constituents of circumstellar matter formed in the same type of stellar source, namely, Type II supernovae.
Collapse
Affiliation(s)
- P Hoppe
- Physikalisches Institut, Unversitat Bern, Switzerland
| | | | | | | | | |
Collapse
|
38
|
Polls A, Ramos A, Ventura J, Amari S, Dickhoff WH. Energy weighted sum rules for spectral functions in nuclear matter. Phys Rev C Nucl Phys 1994; 49:3050-3054. [PMID: 9969583 DOI: 10.1103/physrevc.49.3050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
|
39
|
|
40
|
Murata N, Yoshizawa S, Amari S. Network information criterion-determining the number of hidden units for an artificial neural network model. ACTA ACUST UNITED AC 1994; 5:865-72. [DOI: 10.1109/72.329683] [Citation(s) in RCA: 406] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
41
|
|
42
|
Abstract
The present paper proposes a mathematical theory and a method of recognition of both the 3D structure and the motion of a moving object from its monocular image. Initially, characteristic features are extracted from the 2D perspective image of the object. Because motion of the object induces a change in its 2D perspective image, it also induces a change in the features which depends on the 3D structure and the velocity of the object. This suggests the possibility of detecting the 3D structure and the motion directly from the features and their changing rate, without the need for calculating optical flows. An analysis is made of the relation between the 3D rigid motion of a surface element and the change in local linear features. From this relation, a method is proposed for calculating the velocity of and the normal to the surface element without considering any correspondence of points. An optical flow can also be calculated by this method. Two simple computer simulations are provided.
Collapse
Affiliation(s)
- S Amari
- Department of Mathematical Engineering and Instrumentation Physics, Faculty of Engineering, University of Tokyo, Japan
| | | |
Collapse
|
43
|
Amari S. [Memory--8. Mathematical model of neural pathways and memory]. Nihon Rinsho 1985; 43:1350-3. [PMID: 4057598] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
|
44
|
Abstract
Section 1 lists 12 points which must be addressed by neural models of sensorimotor coordination. Section 2 addresses the problem of extrapolating motor output from noisy data or from sensory input. The Pellionisz-Llinas cerebellar lookahead module addresses this problem for the noise-free case, and we suggest theoretical and experimental tests of the model; we then suggest the investigation of neural analogs of the Kalman-Bucy filter. Section 3 offers a brief exposition of mechanics in a tensor framework to provide the irreducible minimum of mathematical machinery to evaluate the Pellionisz-Llinás tensor theory of brain function and to suggest fruitful new hypotheses. Our critique of this theory in section 4 leads us to conclude that what they offer is based on metaphorical use of terminology from Euclidean tensors, not on rigorous application of the mathematics of tensor analysis. The central claim of their theory--that the input is a covariant intention vector transformed by a metric tensor encoded in the cerebellum to a contravariant execution vector--has not been substantiated and probably cannot be substantiated. However, we do point the way to further use of tensor analysis in the study of neural control of movement. The concluding section then returns to the points raised in section 1 with a highly selective survey of models of cerebellum and tectum.
Collapse
|
45
|
|
46
|
Abstract
Dynamics of excitation patterns is studied in one-dimensional homogeneous lateral-inhibition type neural fields. The existence of a local excitation pattern solution as well as its waveform stability is proved by the use of the Schauder fixed-point theorem and a generalized version of the Perron-Frobenius theorem of positive matrices to the fuction space. The dynamcis of the field is in general multi-stable so that the field can keep short-term memory.
Collapse
|
47
|
|
48
|
|