1,440,467 research outputs found
The bionomics of the malaria mosquito Anopheles gambiae sensu lato in Southeast Tanzania : adult size variation and its effect on female fecundity, survival and malaria transmission
No full textSize of adult mosquitoes is known to affect both population dynamics as well as disease transmission. Studies devoted to this topic have given different results for different species. For example in some mosquito species, large size was found to be associated with high fecundity and longer survival (Steinwascher, 1982; Nasci, 1986a; 1986b; 1987) but in others large size did not result in longer survival (Walker et al ., 1987; Landry et al ., 1988; Pumpuni & Walker, 1989). Similar data were found for disease transmission. Some results indicated that smaller mosquitoes transmit Japanese Encephalitis, West Nile and La Cross viruses more efficiently than larger mosquitoes (Takahashi, 1976; Baqar et al ., 1980; Grimstad & Haramis, 1984), while other results did not show any difference between small and larger mosquitoes in their ability to transmit viral diseases (Kay et al ., 1989). With Plasmodium parasites, Ichimori (1989) did not find any relationship between Anopheles stephensi Liston female size and the number of P.yoelii nigeriensis oocysts developed, whereas Kitthawee et. al. (1990) showed that large An. dirus Peyton and Harrison developed more P.falciparum oocysts than small ones.Variation in mosquito adult size is associated with the type of breeding sites used by a species. Several studies have shown that temporary habitat breeders are more variable in size than permanent habitat breeders (Haramis, 1983; 1985; Fish, 1985; Nasci, 1987). An. gambiae Giles, the subject of this study, breeds preferably in temporary water bodies and is one of the most size variable anophelines in the sub-Saharan region. No work has previously been undertaken to study the effect of adult size on the bionomics of this mosquito, information which could elucidate our understanding of the biology of this important mosquito.The present research study was initiated in order to answer the following general questions: (1) what causes adult size variation in An. gambiae and (2) how does adult size affect important female characteristics such as reproduction, survival duration and malaria transmission. The specific aims of the study were:- to investigate the effects of temperature and larval density on development and survival of immature An. gambiae and on the size of adults.- to investigate the effects of adult size on blood feeding and on fecundity.- to investigate the effects of adult size on survival.- and to find out the relationship between adult size and malaria parasite infections.In the course of this research, a total of 50,321 female An. gambiae s. 1. were caught using various sampling methods, and 11,097 wings were measured, wing length being an accepted measurement of body size (Christophers, 1960; Haramis, 1983).Factors affecting larval development and adult size were studied in the laboratory as well as in the field. Mosquitoes were reared in the laboratory under various constant temperatures and densities (chapter 2). In the field, larvae were reared at constant densities under natural fluctuating temperatures (chapter 3). Developmental times and survival rates of immatures under different conditions were monitored and the wing length of emerged females compared. Rate of larval development and immature survival as well as size of adults were determined by the interaction between density and temperature.Natural breeding sites were monitored to determine relative densities and survival of immature stages, and the size of emerging adults. Mortality of immatures was very high (on average 95%), caused mainly by pathogens and by predators, as well as weather conditions. Large, semi-permanent breeding sites produced larger sized females than the small temporary puddles (chapter 4). Spatial and temporal differences in adult size were investigated in field populations of An. gambiae s. 1. There was a significant variation in adult size of populations from different localities, and also a seasonal variation in size of mosquitoes collected from the same locality over a two year period, with larger females being caught during the cooler months of the year (chapter 5). Density of female An. gambiae inside houses peaked towards the end of the rainy season in May, which was accompanied by an increase in entomological inoculation rates (the number of infective bites per person per night). Thus, the intensity of malaria transmission was higher towards the end of the rainy season (chapter 6).Effect of adult size on pre-gravidity and on fecundity was examined for blood fed indoor resting mosquitoes and for newly emerged wild females fed in the laboratory. Females which developed eggs after a single blood meal were larger than those which required more than one meal to produce one batch of eggs, and produced more eggs per batch (chapter 7). Survival of adults was investigated by comparing the size of newly emerged females from field collected pupae with that of nulliparous and parous host seeking females (chapter 8). Newly emerged females were significantly smaller than the host seeking females. There was no difference in mean size between nulliparous and parous host seeking mosquitoes. Small- sized females were equally likely to be infected during blood feeding as were large-sized females, but large females produced more oocysts. The proportion of mosquitoes with sporozoites, however, was highest in intermediate sized females (chapter 9). Finally, the effect of adult mosquito size on the overall malaria transmission was examined using a malaria transmission model described by Koella (1991), (chapter 10). The model predicts that mosquito size has little effect on malaria transmission. Possible reasons for this are discussed.The conclusions from these studies are:(1) Environmental factors, notably the temperature of breeding water, and the density of larvae directly affect the amount of food available to larvae and influence the development and survival of immatures and the size of adult An. gambiae s. 1.(2) Adult size affects time of first reproduction and fecundity of An. gambiae s. I. , hence fitness of individual females.(3) Small sized mosquitoes die early in adult life and do not contribute much to the bionomics, of the species.(4) Large-sized mosquitoes produced many oocysts, but they did not survive well enough to transmit the parasites (probably due to their heavy oocyst infections).(5) The effect of adult size on the overall malaria transmission is negligible due to the effects of co-variation in the transmission parameters
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Rural Cooperation : In The Cooperative Movement in Tanzania
No full textFrom an exploration of the cooperative movement's various international iterations to a perspicacious survey of the history of cooperatives in Tanzania, Dr. Lyimo highlights the issues facing farmers and business people and illustrates the way in which cooperative effort- enterprises that put people, and not capital, at the center of their business- can not only improve members' economic power in bargaining for better marketing conditions and prices, but also to increase employment opportunities, thereby improving the standard of living for a large number of people
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Mapping the Discipline of the Olympic Games An Author-Cocitation Analysis
No full textThe authors conducted an author cocitation analysis on prominent authors writing about the Olympics during the 1990s. Author cocitation is an established bibliometric technique that can be used to measure the relative similarities of topics written about by the cited authors. This enables a visual representation of the “intellectual space” of the discipline, in this case the Olympics, to be created for the period under review. So core and peripheral research areas are identified, along with their major contributors. The representation appears as a two-dimensional cluster-enhanced map. Subject expertise was then applied to the results to place labels on the generated clusters of authors and their topics
The Impact of the Financial Crisis on the Tourism industry : The case study of Tanzania.
No full textTitle: The Impact of the Financial Crisis on the Tourism industry: The case study of Tanzania. Author: Beda Fabian Lyimo Supervisor: Anders Hederstierna Department: School of Management, Blekinge Institute of Technology Course: Master’s thesis in business administration, 15credits (ECTS) Background and Problem Discussion: The tourism industry has been considered to be an important sector in Tanzania for many years whereby it has strong positive effects on the economic development of the country. The positive impact of tourism on the host country is in areas such as foreign exchange earnings, employment opportunities, poverty elimination, provision of social services and improvement of the infrastructure. However the current worldwide top agenda of the financial crisis has weakened the above efforts of the tourism industry towards the economic development of Tanzania. Therefore it is the researcher’s belief that there is a need to conduct an in depth study to scrutinize the impact of the financial crisis on the tourism industry in Tanzania. Purpose: This study will provide an insight into the tourism industry on how the current recession affects this sector. This might help to create sufficient and sustainable measures on how to hedge against the crisis within the sector so as to boost the economic development of Tanzania. Method: The researcher conducted an empirical study by using both secondary and primary source of data from the tourism authorities as well as stakeholders in general. For the primary data the main instrument used was telephone interviews with the tourism officials in Tanzania while questionnaires were added to explore both domestic and international tourists’ views on the financial crisis on the tourism industry. Both interview questions and questionnaires were designed using a semi-structured approach. Theory: The researcher explored theories which link tourism and economic development as there were no direct specific theories on tourism. Analysis: The analysis of the research findings was undertaken by using a qualitative approach to the data analysis whereby the impacts of the financial crisis on the tourism industry in Tanzania were discussed in depth. Conclusion: The analysis showed that there are impacts of the financial crisis on the tourism industry in Tanzania. The analysis also showed that there are measures suggested to mitigate the situation however there is still a problem as most of these measures are not yet effectively implemented which could delay its significance, therefore the tourism sector could lose its potential to boost the economic development of Tanzania. Due to these reasons the researcher provided recommendations and suggested areas for further research to enable an in depth study in the future.Beda Fabian Lyimo 59 Putney Road Handsworth Birmingham UK land:+44 121 5152 305 cell :+44 781 3192 13
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Dynamics of Network Formation Processes in the Co-Author Model
No full textThis article studies the dynamics in the formation processes of a mutual consent network in game theory setting: the Co-Author Model. In this article, a limited observation is applied and analytical results are derived. Then, 2 parameters are varied: the number of individuals in the network and the initial probability of the links in the network in its initial state. A simulation result shows a finding that is consistent with an analytical result for a state of equilibrium while it also shows different possible equilibria.Dynamics, Network, Game Theory, Model,Simulation, Equilibrium, Complexity
Measuring industry-science links through inventor-author relations: A profiling method
No full textIn this pilot study we examine the performance of text-based profiling in recovering a set of validated inventor-author links. In a first step we match patents and publications solely based on their similarity in content. Next, we compare inventor and author names on the highest ranked matches for the occurrence of name matches. Finally, we compare these candidate matches with the names listed in a validated set of inventor-author names. Our text-based profile methodology performs significantly better than a random matching of patents and publications, suggesting that text-based profiling is a valuable complementary tool to the name searches used in previous studies.innovation; industry-science links; text-based profiling;
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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