| 91. |
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| 92. |
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| 93. |
- González-Rivas, Benigno, et al.
(författare)
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Regeneration of dry forest species Population dynamics and spatial distribution of seedlings and saplings of four dry forest species in Nicaragua
- 2009
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Ingår i: Bois Et Forets Des Tropiques. - 0006-579X. ; 63, s. 21-31
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Tidskriftsartikel (refereegranskat)abstract
- The temporal variation in seedling and sapling densities of four dry forest species, Calycophyllum candidissimum, Cedrela odorata, Haematoxylon brasiletto and Gyroscarpus americanus, and the spatial heterogeneity of regeneration in relationship to terrain slope and crown exposure to direct sunlight were examined in the Chacocente National Wildlife Refuge, Nicaragua. Data on all individuals above 10 cm in height and below 5 cm in diameter at breast height were recorded for three consecutive years from 2001 to 2003. The density of seedlings and saplings varied significantly among species, as well as over time. The mean density of seedlings across the census year was thirty-seven, twenty and four individuals per 2 ha for G. americanus, C candidissimum and H. brasiletto, respectively. C. odorata did not regenerate at all. Similarly, the mean density of saplings in a 2-ha plot was fifty-five, twenty and two for G. americanus, C. candidissimum and H. brasiletto, respectively. The change in population density of seedlings and saplings was positive for C candidissimum, indicating continuous and advanced regeneration of this species. For G. americanus and H. brasiletto the seedling population declined while the sapling population increased. For G. americanus and C. candidissimum, seedling and sapling population densities varied with respect to the slope of the terrain and crown exposure to direct sunlight, resulting in a clumped pattern of regeneration. We concluded that natural regeneration alone may not be sufficient to maintain desired stocks of these species, and immediate restoration measures should be taken to assist the natural regeneration process.
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| 94. |
- Cuadra, Steven, et al.
(författare)
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Persistent organochlorine pollutants in children working at a waste-disposal site and in young females with high fish consumption in Managua, Nicaragua
- 2006
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Ingår i: Ambio. - 0044-7447 .- 1654-7209. ; 35:3, s. 109-116
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to assess persistent organochlorine pollutant (POP) levels in serum collected from children (11-15 years old) working and sometimes also living at the municipal waste-disposal site in Managua, located at the shore of Lake Managua, and in nonworking children living both nearby and also far away from the waste-disposal site. The influence of fish consumption was further evaluated by assessing POPS levels in serum from young women (15-24 years old) with markedly different patterns of fish consumption from Lake Managua. 2,2-bis(4-chlorophenyl)-1,1,1-trichloro-ethane (4,4’-DDT) and 2,2-bis(4-chlorophenyl)-1,1-dichloro-ethene (4,4-DDE), T-hexachlorocyclohexane (gamma-HCH), polychlorinated biphenyls, pentachlorophenol, and polychlorobiphenylols were quantified in all samples. In general, the levels observed were higher than those reported in children from developed countries, such as Germany and United States. Toxaphene, aldrin, dieldrin, and beta-HCH could not be identified in any sample. The children working at the waste-disposal site had higher levels of POPS compared with the nonworking reference groups. In children not working, there were also gradients for several POPs, according to vicinity to the waste-disposal site. Moreover, in children, as well as in young women, there were gradients according to fish consumption. The most abundant component was 4,4-DDE, but at levels still lower than those reported in children from malarious areas with a history of recent or current application of 4,4-DDT for vector control.
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| 95. |
- Somarriba, O., et al.
(författare)
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Robust STDMA scheduling in Multi-hop Wireless Networks for single-node position perturbations
- 2009
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Ingår i: 2009 IEEE 20th Personal, Indoor and Mobile Radio Communications Symposium, PIMRC 2009. ; , s. 566-571
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Konferensbidrag (refereegranskat)abstract
- A major design issue in Multi-hop Wireless Networks is the Medium Access Control (MAC) protocols that determine how nodes share the channel to transmit their packets. One type of MAC protocol with efficient spatial reuse characteristics are the Spatial TDMA (STDMA) protocols. STDMA protocols are a class of conflict-free MAC protocols that enable high spectral utilization by scheduling transmissions on the channel. Its main features are high throughput and the possibility of providing delay guarantees. We studied the sensibility of STDMA networks to disruption caused by slow mobility of one "critical" node (single-user perturbation), that causes problems to the schedule maintenance. We assessed a framework that produces robust STDMA scheduling against these topological changes. To do that, we introduced and analyzed heuristic algorithms that mainly exploit capabilities of the physical layer such as power and rate control, and rerouting. We considered the limited-mobility management in STDMA networks to find the ranges where our heuristics will avoid re-scheduling of the whole STDMA frame. We found that a substantial throughput degradation due to slow mobility in STDMA networks can be compensated by means of power or rate control, and rerouting. Our results showed that rate-controlled (RC) STDMA is the most promising scheme to maintain communication under slow mobility.
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| 96. |
- Benavente, Martha, et al.
(författare)
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Biosorption of Heavy Metals on Chitosan
- 2007
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Ingår i: Hydro Copper 2007. - Santiago, Chile : GECAMIN Ltda.. - 9789568504076 ; , s. 283-290
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Konferensbidrag (refereegranskat)
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| 97. |
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| 98. |
- Pena, R., et al.
(författare)
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Evaluating a peer intervention strategy for the promotion of sexual health-related knowledge and skills in 10- to 14-year-old girls. Findings from the "Entre Amigas" project in Nicaragua
- 2008
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Ingår i: American Journal of Health Promotion. - 0890-1171 .- 2168-6602. ; 22:4, s. 275-281
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Tidskriftsartikel (refereegranskat)abstract
- Purpose. Report effects on knowledge of sexual health and gender from an intervention using peer methodology in Nicaragua. Design. A prepost nonequivalent control group design. Setting. Ciudad Sandino, Managua, Nicaragua. Subjects. A total of 599 girls were surveyed, 60% nonintervened and 40% intervened. Intervention. Peer methodology consisted of (1) meetings in which. girls talked and worked with other girls, (2) mothers taking an active role in the peer groups, and/or (3) girls watching the soap opera "Sexto Sentido." Measures. Indices measuring changes in sexual knowledge and gender vision. Results. Girls participating in the peer groups were twice us likely to have satisfactory sexual health-related self-esteem as those who did not participate. Eleven percent of the girls achieved satisfactory self-esteem as a result of the (peer groups X mothers) interaction and 15% due to the (peer groups X mothers X "Sexto Sentido') interaction. Girls participating in the peer groups were three times as likely to have satisfactory gender visions; if exposed to all three components, they were almost four times as likely to develop satisfactory gender visions. Conclusions. Peer methodology, participation of a female family member, and an educational soap opera seem beneficial in promoting sexual health-related knowledge and gender vision in young girls.
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| 99. |
- Benavente, Martha, et al.
(författare)
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Remoción de Mercurio de Efluentes Mineros por Biosorción
- 2007
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Ingår i: Nexo. - Managua, Nicaragua : National University of Engineering (UNI). - 1818-6742. ; 20:2, s. 47-55
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Tidskriftsartikel (refereegranskat)abstract
- La minería y la extracción de oro en operaciones a pequeña escala han contribuido a la contaminación de los recursos acuáticos de Nicaragua durante décadas. En este trabajo se investigó un proceso de biosorción a bajo costo para la remoción de iones mercurio (II) de soluciones estándar y de aguas naturales usando quitosano como adsorbente. La regeneración del adsorbente también fue estudiada. Los resultados mostraron que la adsorción de iones mercurio fue independiente del pH en el rango de pH 4-10 y que la capacidad se reduce considerablemente a pH 2. Los estudios de la cinética mostraron una fase inicial rápida de adsorción seguida por una fase más lenta. Por otro lado, se comprobó que los datos experimentales se ajustan al modelo de Langmuir, y se determinó, mediante el uso de este modelo, una capacidad de adsorción de 106 mg Hg/g quitosano. Una solución acuosa de NaCl demostró ser una opción barata y eficiente para la regeneración del adsorbente; además, el adsorbente mostró una capacidad de adsorción alta después de la regeneración. Se encontró que la concentración de mercurio en 4 de las 8 muestras recolectadas cerca de la ciudad de la Libertad, excedían ligeramente los niveles permisibles (1.09-2.25 μg Hg L-1) para agua de consumo humano según las normas CAPRE. Además, se determinó que la capacidad de adsorción de mercurio es menor en aguas naturales que en las soluciones estándares.
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| 100. |
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