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12. Study on Chunking Mechanisms for a 3-layered Associative Memory and Recall Model

Author

Mungai, Peter Kimani

Subjects
Memory models, short term memory, chunking mechanisms, Long term memory, Hopfield model, associative learning
Abstract

Memory models are important components that support AI computational models to learn and remember things. Usually, computers operate using an address-based memory for storage where each memory item resides in a unique location. This study proposes a 3-layered associative memory model based on chunking mechanisms of the brain to store knowledge in form of association between entities. The human brain is a cognitive model that derives information from sensory data like vision, auditory, and touch, associates different patterns to create knowledge and uses chunking mechanisms to package the acquired knowledge into manageable entities. Through Chunking, each item held in the STM is a singular entity (chunk) containing more associations (knowledge) in it. Using chunking mechanisms of the brain, AMR model can store knowledge in manner that enables faster response to stimuli. To represent knowledge and semantic relations effectively, the hyper structure (concept) defined in denotational mathematics is employed. A network of concepts is maintained in a cognitive knowledge base that continually evolves as knowledge accumulates. The chunking mechanisms used in this study are goal-oriented chunking and automatic chunking.

Published
2019

15. Physical condition and maintenance of mosquito bed nets in Kwale County, coastal Kenya

Author

Mutuku Francis M, Khambira Maureen, Bisanzio Donal, Mungai Peter, Mwanzo Isaac, Muchiri Eric M, King Charles H, and Kitron Uriel

Subjects
Arctic medicine. Tropical medicine, RC955-962, Infectious and parasitic diseases, RC109-216
Abstract

Abstract Background Despite the extensive ownership and use of insecticide-treated nets (ITNs) over the last decade, the effective lifespan of these nets, especially their physical integrity, under true operational conditions is not well-understood. Usefulness of nets declines primarily due to physical damage or loss of insecticidal activity. Methods A community based cross-sectional survey was used to determine the physical condition and to identify predictors of poor physical condition for bed nets owned by individuals from communities in Kwale County, coastal Kenya. A proportionate hole index (pHI) was used as a standard measure, and the cut-offs for an ‘effective net’ (offer substantial protection against mosquito bites) and ‘ineffective nets’ (offer little or no protection against mosquito bites) were determined (pHI ≤88 (about ≤500 cm2 of holes surface area) and pHI of >88 (≥500 cm2 of holes surface area), respectively). Results The vast majority (78%) of the surveyed nets had some holes. The median pHI was 92 (range: 1–2,980). Overall, half of the nets were categorized as ‘effective nets’ or ‘serviceable nets’. Physical deterioration of nets was associated with higher use and washing frequency. Young children and older children were found to use ineffective bed nets significantly more often than infants, while the physical integrity of nets owned by pregnant women was similar to those owned by infants. Estuarine environment inhabitants owned nets with the worst physical condition, while nets owned by the coastal slope inhabitants were in fairly good physical condition. The results suggest that bed nets are optimally utilized when they are new and physically intact. Thereafter, bed net utilization decreases gradually with increasing physical deterioration, with most net owners withdrawing physically damaged nets from routine use. This withdrawal commonly happens following 1.5 years of use, making bed net use the most important predictor of physical integrity. On average, the nets were washed twice within six months prior to the survey. Washing frequency was significantly influenced by the bed net colour and bed net age. Lack of knowledge on reasons for net retreatment and the retreatment procedure was evident, while net repair was minimal and did not seem to improve the physical condition of the nets. The “catch-up” bed net distribution strategies are sufficient for ensuring adequate ownership and utilization of ‘effective nets’ in the targeted groups, but bi-annual mass distribution is necessary to provide similar ownership and utilization for the other groups not targeted by “catch-up” strategies. Conclusions Monitoring and maintenance strategies that will deliver locally appropriate education messages on net washing and repair will enhance the effectiveness of malaria control programmes, and further research to assess ineffective nets need is needed.

Published
2013
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19. Impact of insecticide-treated bed nets on malaria transmission indices on the south coast of Kenya

Author

Mutuku Francis M, King Charles H, Mungai Peter, Mbogo Charles, Mwangangi Joseph, Muchiri Eric M, Walker Edward D, and Kitron Uriel

Subjects
Arctic medicine. Tropical medicine, RC955-962, Infectious and parasitic diseases, RC109-216
Abstract

Abstract Background Besides significantly reducing malaria vector densities, prolonged usage of bed nets has been linked to decline of Anopheles gambiae s.s. relative to Anopheles arabiensis, changes in host feeding preference of malaria vectors, and behavioural shifts to exophagy (outdoor biting) for the two important malaria vectors in Africa, An. gambiae s.l. and Anopheles funestus. In southern coastal Kenya, bed net use was negligible in 1997-1998 when Anopheles funestus and An. gambiae s.s. were the primary malaria vectors, with An. arabiensis and Anopheles merus playing a secondary role. Since 2001, bed net use has increased progressively and reached high levels by 2009-2010 with corresponding decline in malaria transmission. Methods To evaluate the impact of the substantial increase in household bed net use within this area on vector density, vector composition, and human-vector contact, indoor and outdoor resting mosquitoes were collected in the same region during 2009-2010 using pyrethrum spray catches and clay pots for indoor and outdoor collections respectively. Information on bed net use per sleeping spaces and factors influencing mosquito density were determined in the same houses using Poisson regression analysis. Species distribution was determined, and number of mosquitoes per house, human-biting rates (HBR), and entomological inoculation rate (EIR) were compared to those reported for the same area during 1997-1998, when bed net coverage had been minimal. Results Compared to 1997-1998, a significant decline in the relative proportion of An. gambiae s.s. among collected mosquitoes was noted, coupled with a proportionate increase of An. arabiensis. Following > 5 years of 60-86% coverage with bed nets, the density, human biting rate and EIR of indoor resting mosquitoes were reduced by more than 92% for An. funestus and by 75% for An. gambiae s.l. In addition, the host feeding choice of both vectors shifted more toward non-human vertebrates. Besides bed net use, malaria vector abundance was also influenced by type of house construction and according to whether one sleeps on a bed or a mat (both of these are associated with household wealth). Mosquito density was positively associated with presence of domestic animals. Conclusions These entomological indices indicate a much reduced human biting rate and a diminishing role of An. gambiae s.s. in malaria transmission following high bed net coverage. While increasing bed net coverage beyond the current levels may not significantly reduce the transmission potential of An. arabiensis, it is anticipated that increasing or at least sustaining high bed net coverage will result in a diminished role for An. funestus in malaria transmission.

Published
2011
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25. Rift Valley Fever Seroprevalence in Coastal Kenya

Author

Grossi-Soyster, Elysse N., primary, Banda, Tamara, additional, Teng, Crystal Y., additional, Muchiri, Eric M., additional, Mungai, Peter L., additional, Mutuku, Francis M., additional, Gildengorin, Ginny, additional, Kitron, Uriel, additional, King, Charles H., additional, and Desiree Labeaud, A., additional

Published
2017
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28. Dengue and West Nile Virus Transmission in Children and Adults in Coastal Kenya

Author

Vu, David M., primary, Banda, Tamara, additional, Teng, Crystal Y., additional, Heimbaugh, Chelsea, additional, Muchiri, Eric M., additional, Mungai, Peter L., additional, Mutuku, Francis M., additional, Brichard, Julie, additional, Gildengorin, Ginny, additional, Borland, Erin M., additional, Powers, Ann M., additional, Kitron, Uriel, additional, King, Charles H., additional, and LaBeaud, A. Desiree, additional

Published
2016
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29. Age-Stratified Profiles of Serum IL-6, IL-10, and TNF-alpha Cytokines among Kenyan Children with Schistosoma haematobium, Plasmodium falciparum, and Other Chronic Parasitic Co-infections

Author

Bustinduy, Amaya L, Sutherland, Laura J, Chang-Cojulun, Alicia, Malhotra, Indu, DuVall, Adam S, Fairley, Jessica K, Mungai, Peter L, Muchiri, Eric M, Mutuku, Francis M, Kitron, Uriel, and King, Charles H

Subjects
parasitic diseases
Abstract

In a study of children having polyparasitic infections in a Schistosoma haematobium-endemic area, we examined the hypothesis that S. haematobium-positive children, compared with S. haematobium-negative children (anti-soluble worm antigen preparation [SWAP] negative and egg negative) have increased systemic production of pro-inflammatory cytokines (interleukin [IL]-6, tumor necrosis factor [TNF]-a) and decreased down-regulatory IL-10. A total of 804 children, 2-19 years of age, were surveyed between July and December 2009 and tested for S. haematobium, Plasmodium falciparum, filariasis, and soil-transmitted helminth infections. Plasma levels of IL-6, TNF-a, and IL-10 were compared for S. haematobium-positive and S. haematobium-negative children, adjusting for malaria, filaria, and hookworm co-infections, and for nutritional status, age group, sex, and geographic location. IL-10 was significantly elevated among children infected with S. haematobium, showing bimodal peaks in 7-8 and 13-14 years age groups. IL-10 was also higher among children who were acutely malnourished, whereas IL-10 levels were lower in the presence of S. haematobium-filaria co-infection. After adjustment for co-factors, IL-6 was significantly elevated among children of 5-6 years and among those with P. falciparum infection. Lower levels of IL-6 were found in malaria-hookworm co-infection. High levels of TNF-α were found in children aged 11-12 years regardless of infection status. In addition, village of residence was a strong predictor of IL-6 and IL-10 plasma levels. In adolescent children infected with S. haematobium, there is an associated elevation in circulating IL-10 that may reduce the risk of later morbidity. Although we did not find a direct link between S. haematobium infection and circulating pro-inflammatory IL-6 and TNF-α levels, future T-cell stimulation studies may provide more conclusive linkages between infection and cytokine responses in settings that are endemic for multiple parasites and multiple co-infections.

Published
2015

30. Contrasting Patterns of Serologic and Functional Antibody Dynamics to Plasmodium falciparum Antigens in a Kenyan Birth Cohort

Author

Dent, Arlene E., primary, Malhotra, Indu, additional, Wang, Xuelie, additional, Babineau, Denise, additional, Yeo, Kee Thai, additional, Anderson, Timothy, additional, Kimmel, Rhonda J., additional, Angov, Evelina, additional, Lanar, David E., additional, Narum, David, additional, Dutta, Sheetij, additional, Richards, Jack, additional, Beeson, James G., additional, Crabb, Brendan S., additional, Cowman, Alan F., additional, Horii, Toshihiro, additional, Muchiri, Eric, additional, Mungai, Peter L., additional, King, Christopher L., additional, and Kazura, James W., additional

Published
2016
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34. Parasitism in Children Aged Three Years and Under: Relationship between Infection and Growth in Rural Coastal Kenya

Author

LaBeaud, A. Desiree, primary, Nayakwadi Singer, Monica, additional, McKibben, Maxim, additional, Mungai, Peter, additional, Muchiri, Eric M., additional, McKibben, Elisabeth, additional, Gildengorin, Ginny, additional, Sutherland, Laura J., additional, King, Charles H., additional, King, Christopher L., additional, and Malhotra, Indu, additional

Published
2015
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35. Age-Stratified Profiles of Serum IL-6, IL-10, and TNF-α Cytokines Among Kenyan Children with Schistosoma haematobium, Plasmodium falciparum, and Other Chronic Parasitic Co-Infections

Author

Bustinduy, Amaya L., primary, Muchiri, Eric M., additional, Chang-Cojulun, Alicia, additional, Mutuku, Francis M., additional, Sutherland, Laura J., additional, Kitron, Uriel, additional, DuVall, Adam S., additional, Malhotra, Indu, additional, Mungai, Peter L., additional, King, Charles H., additional, and Fairley, Jessica K., additional

Published
2015
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36. High Rates of O’Nyong Nyong and Chikungunya Virus Transmission in Coastal Kenya

Author

LaBeaud, A. Desiree, primary, Banda, Tamara, additional, Brichard, Julie, additional, Muchiri, Eric M., additional, Mungai, Peter L., additional, Mutuku, Francis M., additional, Borland, Erin, additional, Gildengorin, Ginny, additional, Pfeil, Sarah, additional, Teng, Crystal Y., additional, Long, Kristin, additional, Heise, Mark, additional, Powers, Ann M., additional, Kitron, Uriel, additional, and King, Charles H., additional

Published
2015
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