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1

Recent advances in research and control of malaria, leishmaniasis, trypanosomiasis and schistosomiasis  

Microsoft Academic Search

SUMMARY In the Eastern Mediterranean Region of the World Health Organization (WHO), malaria, schisto- somiasis, leishmaniasis and trypanosomiasis are the parasitic diseases of major importance. Our review focuses on recent advances in the control and treatment of these diseases with particular reference to diagnosis, chemotherapy, vaccines, vector and environmental control. The Roll Back Malaria Programme, for example, emphasizes the use

S. L. Croft; L. Vivas; S. Brooker

2

Genome sequence of the tsetse fly (Glossina morsitans): vector of African trypanosomiasis.  

PubMed

Tsetse flies are the sole vectors of human African trypanosomiasis throughout sub-Saharan Africa. Both sexes of adult tsetse feed exclusively on blood and contribute to disease transmission. Notable differences between tsetse and other disease vectors include obligate microbial symbioses, viviparous reproduction, and lactation. Here, we describe the sequence and annotation of the 366-megabase Glossina morsitans morsitans genome. Analysis of the genome and the 12,308 predicted protein-encoding genes led to multiple discoveries, including chromosomal integrations of bacterial (Wolbachia) genome sequences, a family of lactation-specific proteins, reduced complement of host pathogen recognition proteins, and reduced olfaction/chemosensory associated genes. These genome data provide a foundation for research into trypanosomiasis prevention and yield important insights with broad implications for multiple aspects of tsetse biology. PMID:24763584

2014-04-25

3

Cryptic Diversity within the Major Trypanosomiasis Vector Glossina fuscipes Revealed by Molecular Markers  

PubMed Central

Background The tsetse fly Glossina fuscipes s.l. is responsible for the transmission of approximately 90% of cases of human African trypanosomiasis (HAT) or sleeping sickness. Three G. fuscipes subspecies have been described, primarily based upon subtle differences in the morphology of their genitalia. Here we describe a study conducted across the range of this important vector to determine whether molecular evidence generated from nuclear DNA (microsatellites and gene sequence information), mitochondrial DNA and symbiont DNA support the existence of these taxa as discrete taxonomic units. Principal Findings The nuclear ribosomal Internal transcribed spacer 1 (ITS1) provided support for the three subspecies. However nuclear and mitochondrial sequence data did not support the monophyly of the morphological subspecies G. f. fuscipes or G. f. quanzensis. Instead, the most strongly supported monophyletic group was comprised of flies sampled from Ethiopia. Maternally inherited loci (mtDNA and symbiont) also suggested monophyly of a group from Lake Victoria basin and Tanzania, but this group was not supported by nuclear loci, suggesting different histories of these markers. Microsatellite data confirmed strong structuring across the range of G. fuscipes s.l., and was useful for deriving the interrelationship of closely related populations. Conclusion/Significance We propose that the morphological classification alone is not used to classify populations of G. fuscipes for control purposes. The Ethiopian population, which is scheduled to be the target of a sterile insect release (SIT) programme, was notably discrete. From a programmatic perspective this may be both positive, given that it may reflect limited migration into the area or negative if the high levels of differentiation are also reflected in reproductive isolation between this population and the flies to be used in the release programme.

Choi, Kwang-Shik; Darby, Alistair C.; Causse, Sandrine; Kapitano, Berisha; Hall, Martin J. R.; Steen, Keith; Lutumba, Pascal; Madinga, Joules; Torr, Steve J.; Okedi, Loyce M.; Lehane, Michael J.; Donnelly, Martin J.

2011-01-01

4

Human/vector relationships during human African trypanosomiasis: initial screening of immunogenic salivary proteins of Glossina species.  

PubMed

The morbidity and mortality of vector-borne diseases is closely linked to exposure of the human host to vectors. Qualitative and quantitative evaluation of individual exposure to arthropod bites by investigation of the specific immune response to vector saliva would make it possible to monitor individuals at risk of vectorial transmission of pathogens. The objective of this study was to evaluate and compare the antibody (IgG) response to saliva from uninfected Glossina species, vectors, or non-vectors of Trypanosoma brucei gambiense by detecting immunogenic proteins in humans residing in an area endemic for human African trypanosomiasis in the Democratic Republic of Congo. Our results suggest that the immunogenic profiles observed seemed specific to the Glossina species (vector or non-vector species) and to the infectious status of exposed individuals (infected or not infected). This preliminary work tends to support the feasibility of development of an epidemiologic tool based on this antibody response to salivary proteins. PMID:17297044

Poinsignon, Anne; Cornelie, Sylvie; Remoue, Franck; Grébaut, Pascal; Courtin, David; Garcia, Andre; Simondon, Francois

2007-02-01

5

Short-course eflornithine in Gambian trypanosomiasis: a multicentre randomized controlled trial  

Microsoft Academic Search

Objective A randomized controlled trial was conducted to determine whether 7 days of intravenous eflornithine (100 mg\\/kg every 6 h) was as effective as the standard 14-day regimen in the treatment of late-stage Trypanosoma brucei gambiense trypanosomiasis. Methods A total of 321 patients (274 new cases, 47 relapsing cases) were randomized at four participating centres in Congo, Cote d'Ivoire, the

Jacques Pepin; Nzambi Khonde; Faustine Maiso; Felix Doua; Shabbar Jaffar; Stephane Ngampo; Bokelo Mpia; Dawson Mbulamberi; Felix Kuzoe

6

American Trypanosomiasis.  

National Technical Information Service (NTIS)

American trypanosomiasis is a zoonosis caused by the flagellate protozoon Trypanosoma cruzi (previously Schizotrypanum cruzi). In humans, T. cruzi can infect parenchymal cells of many different organs, most commonly the heart, brain, esophagus, and colon.

E. M. Andersen M. K. Klassen-Fischer R. C. Neafie

2011-01-01

7

The history of African trypanosomiasis  

PubMed Central

The prehistory of African trypanosomiasis indicates that the disease may have been an important selective factor in the evolution of hominids. Ancient history and medieval history reveal that African trypanosomiasis affected the lives of people living in sub-Saharan African at all times. Modern history of African trypanosomiasis revolves around the identification of the causative agents and the mode of transmission of the infection, and the development of drugs for treatment and methods for control of the disease. From the recent history of sleeping sickness we can learn that the disease can be controlled but probably not be eradicated. Current history of human African trypanosomiasis has shown that the production of anti-sleeping sickness drugs is not always guaranteed, and therefore, new, better and cheaper drugs are urgently required.

Steverding, Dietmar

2008-01-01

8

Short-course eflornithine in Gambian trypanosomiasis: a multicentre randomized controlled trial.  

PubMed Central

OBJECTIVE: A randomized controlled trial was conducted to determine whether 7 days of intravenous eflornithine (100 mg/kg every 6 h) was as effective as the standard 14-day regimen in the treatment of late-stage Trypanosoma brucei gambiense trypanosomiasis. METHODS: A total of 321 patients (274 new cases, 47 relapsing cases) were randomized at four participating centres in Congo, Côte d'Ivoire, the Democratic Republic of the Congo, and Uganda to one of these treatment regimens and followed up for 2 years. RESULTS: Six patients died during treatment, one of whom was on the 7-day regimen, whereas the other five had been on the 14-day regimen (P = 0.2). The response to eflornithine differed markedly between Uganda and other countries. Among new cases in Uganda, the 2-year probability of cure was 73% on the 14-day course compared with 62% on the 7-day regimen (hazard ratio (HR) for treatment failure, 7-day versus 14-day regimen: 1.45, 95% CI: 0.7, 3.1, P = 0.3). Among new cases in Côte d'Ivoire, Congo, and the Democratic Republic of the Congo combined, the 2-year probability of cure was 97% on the 14-day course compared with 86.5% on the 7-day regimen (HR for treatment failure, 7-day vs 14-day: 6.72, 95% confidence interval (CI): 1.5, 31.0, P = 0.003). Among relapsing cases in all four countries, the 2-year probability of cure was 94% with 7 days and 100% with 14 days of treatment. Factors associated with a higher risk of treatment failure were: a positive lymph node aspirate (HR 4.1; 95% CI: 1.8-9.4), a cerebrospinal fluid (CSF) white cell count > or = 100/mm3 (HR 3.5; 95% CI: 1.1-10.9), being treated in Uganda (HR 2.9; 95% CI: 1.4-5.9), and CSF trypanosomes (HR 1.9; 95% CI: 0.9-4.1). Being stuporous on admission was associated with a lower risk of treatment failure (HR 0.18; 95% CI: 0.02-1.4) as was increasing age (HR 0.977; 95% CI: 0.95-1.0, for each additional year of age). DISCUSSION: The 7-day course of eflornithine is an effective treatment of relapsing cases of Gambian trypanosomiasis. For new cases, a 7-day course is inferior to the standard 14-day regimen and cannot be recommended.

Pepin, J.; Khonde, N.; Maiso, F.; Doua, F.; Jaffar, S.; Ngampo, S.; Mpia, B.; Mbulamberi, D.; Kuzoe, F.

2000-01-01

9

The impact of insecticide-resistance on control of vectors and vector-borne diseases  

PubMed Central

A questionnaire inquiring into the nature of schemes for the insecticidal control of disease vectors, the development of resistance in these vectors, and the effect of any such resistance on their control and on the extent of disease was sent to more than 100 health authorities throughout the world. The replies to the questionnaire are summarized in this paper. Until recently, the use of insecticides in public health has been largely based on three organochlorine compounds—DDT, HCH and dieldrin. However, in some countries resistance to these has now severely affected control both of many insect species and of the diseases they transmit (e.g., malaria, yellow fever, filariasis, typhus, plague). Certain other public health problems (onchocerciasis, Chagas' disease, trypanosomiasis, leishmaniasis) have not so far been greatly affected by resistance, but it is difficult to be sure of the continued reliability of the organochlorines. Research in the past 5 years, much of it sponsored by WHO, has shown the value of various organophosphorus and carbamate insecticides as replacements for the organochlorines, although resistance to them, too, can occur. Attention must therefore be focused on all facets of the use of these newer compounds and particular scrutiny made of possible instances of resistance to them.

Busvine, J. R.; Pal, R.

1969-01-01

10

Vector control in developed countries  

PubMed Central

The recent rapid growth of California's population, leading to competition for space between residential, industrial and agricultural interests, the development of its water resources and increasing water pollution provide the basic ingredients of its present vector problems. Within the past half-century, the original mosquito habitats provided by nature have gradually given place to even more numerous and productive habitats of man-made character. At the same time, emphasis in mosquito control has shifted from physical to chemical, with the more recent extension to biological approaches as well. The growing domestic fly problem, continuing despite the virtual disappearance of the horse, is attributable to an increasing amount of organic by-products, stemming from growing communities, expanding industries and changing agriculture. The programme for the control of disease vectors and pest insects and animals directs its major effort to the following broad areas: (1) water management (including land preparation), (2) solid organic wastes management (emphasizing utilization), (3) community management (including design, layout, and storage practices of buildings and grounds), and (4) recreational area management (related to wildlife management). It is apparent that vector control can often employ economics as an ally in securing its objectives. Effective organization of the environment to produce maximum economic benefits to industry, agriculture, and the community results generally in conditions unfavourable to the survival of vector and noxious animal species. Hence, vector prevention or suppression is preferable to control as a programme objective.

Peters, Richard F.

1963-01-01

11

Progress in malaria vector control*  

PubMed Central

Malaria control, except in tropical Africa, will probably continue to be based to a large extent on the use of insecticides for many years. However, the development of resistance to insecticides in the vectors has caused serious difficulties and it is necessary to change the strategy of insecticide use to maximize their efficacy. A thorough knowledge of the ecology and behaviour of each vector species is required before the control strategy can be adapted to different epidemiological situations. The behavioural differences between sibling species have been recognized for several years, but study of this problem has recently been simplified by improved means of identification that involve chromosomal banding patterns and electrophoretic analysis. Behavioural differences have also been associated with certain chromosomal rearrangements. New records of insecticide resistance among anophelines continue to appear and the impact of this on antimalaria operations has been seriously felt in Central America (multi-resistance in Anopheles albimanus), Turkey (A. sacharovi), India and several Asian countries (A. culicifacies and A. stephensi), and some other countries. Work continues on the screening and testing of newer insecticides that can be used as alternatives, but DDT, malathion, temephos, fenitrothion, and propoxur continue to be used as the main insecticides in many malaria control projects. The search for simpler and innovative approaches to insecticide application also continues. Biological control of vectors is receiving increased attention, as it could become an important component of integrated vector control strategies, and most progress has been made with the spore-forming bacterium, serotype H-14 of Bacillus thuringiensis. Larvivorous fish such as Gambusia spp. and Poecilia spp. continue to be used in some programmes. Application of environmental management measures, such as source reduction, source elimination, flushing of drainage and irrigation channels, and intermittent irrigation have been re-examined and currently a great deal of interest is being shown in these approaches. There has been limited interest in the genetic control of mosquitos and the phenomenon of refractoriness in some strains of the disease vectors, with the idea of replacing the vector species with the refractory strain. More research is needed before this approach can become a practical tool. It is apparent that in future a more integrated approach will have to be used for vector control within the context of antimalaria programmes. Training of staff, research, and cooperation at all levels will be an essential requirement for this approach.

Pant, C. P.; Rishikesh, N.; Bang, Y. H.; Smith, A.

1981-01-01

12

Human Trypanosomiasis in Ethiopia.  

National Technical Information Service (NTIS)

Four hundred fifty people living near Gambela Ethiopia were examined by the East African Trypanosomiasis Research Organization, by means of thick blood films, and the collection of blood on filter paper for the determination of IgM content and for indirec...

J. R. Baker E. McConnell

1969-01-01

13

Light-controlled vector polyphotochromism  

NASA Astrophysics Data System (ADS)

Phenomenon of vector polyphotochromism was observed in some high-efficient polarization-sensitive materials dependent on the radiant exposure when material was illuminated with linearly polarized actinic light. The phenomenon has purely vector nature, since under probing by unpolarized light, the transmission spectra of the irradiated and unirradiated area of the material are practically identical. However, an essential change in the transmission spectrum of the material was observed by placing the irradiated area between crossed polarizers when the orientation of the axis of induced anisotropy was of 45 degrees relative to the axes of the polarizers. The dispersion of photoanisotropy was studied at different exposure values. Kinetic curves of the photoanisotropy were obtained for wavelength of 532 nm and 635 nm of probing beam for different values of exposure (30, 60 and 250 J/cm2) with linearly polarized actinic light (457 nm). The dispersion curves of the photoanisotropy were obtained for these values of exposure showing an anomalous behavior for exposures above of 30 J/cm2. This phenomenon was observed in specially synthesized organic materials based on azo dyes introduced in a polymer matrix. The difference between optical densities was obtained for polarized light with a wavelength of 532 nm and 635 nm at different exposures, which makes the prospect the dynamic polarization spectral filters controlled by light and the spectrally selective dynamic polarization holographic gratings to be created.

Chaganava, Irakli; Kakauridze, George; Kilosanidze, Barbara; Mshvenieradze, Yuri

2014-05-01

14

Insecticide Resistance and Vector Control  

Microsoft Academic Search

Insecticide resistance has been a problem in all insect groups that serve as vectors of emerging diseases. Although mechanisms by which insecticides become less effective are similar across all vector taxa, each resistance problem is potentially unique and may involve a complex pattern of resistance foci. The main defense against resistance is close surveillance of the susceptibility of vector populations.

William G. Brogdon; Janet C. McAllister

1998-01-01

15

Vaccination against trypanosomiasis  

PubMed Central

To date, human African trypanosomiasis (HAT) still threatens millions of people throughout sub-Sahara Africa, and new approaches to disease prevention and treatment remain a priority. It is commonly accepted that HAT is fatal unless treatment is provided. However, despite the well-described general symptoms of disease progression during distinct stages of the infection, leading to encephalitic complications, coma and death, a substantial body of evidence has been reported suggesting that natural acquired immunity could occur. Hence, if under favorable conditions natural infections can lead to correct immune activation and immune protection against HAT, the development of an effective anti-HAT vaccine should remain a central goal in the fight against this disease.
In this review, we will (1) discuss the vaccine candidates that have been proposed over the past years, (2) highlight the main obstacles that an efficient anti-trypanosomiasis vaccine needs to overcome and (3) critically reflect on the validity of the widely used murine model for HAT.

La Greca, Florencia

2011-01-01

16

Vector Control Activities. Fiscal Year, 1982.  

National Technical Information Service (NTIS)

The goal of the TVA Vector Control Program is to protect the public from potential vectors of disease by controlling medically-important arthropod pests that are propagated on TVA lands or waters. In addition, freedom from annoying mosquitoes and other bl...

E. Pickard J. C. Cooney B. R. McDuff

1983-01-01

17

Insecticide resistance and vector control.  

PubMed

Insecticide resistance has been a problem in all insect groups that serve as vectors of emerging diseases. Although mechanisms by which insecticides become less effective are similar across all vector taxa, each resistance problem is potentially unique and may involve a complex pattern of resistance foci. The main defense against resistance is close surveillance of the susceptibility of vector populations. We describe the mechanisms of insecticide resistance, as well as specific instances of resistance emergence worldwide, and discuss prospects for resistance management and priorities for detection and surveillance. PMID:19785227

Brogdon, William G; McAllister, Janet C

2004-01-01

18

The Biology and Control of Leishmaniasis Vectors  

PubMed Central

Vector control remains a key component of many anti-leishmaniasis programs and probably will remain so until an effective vaccine becomes available. Technologies similar to those used for control of adult mosquitoes, specifically interior residual sprays and insecticide-treated nets, are currently at the forefront as disease control measures. This article provides a review of literature on the biology and control of sand fly vectors of leishmaniasis in the context of changing disease risks and the realities of modern vector control. The Literature Retrieval System of the Armed Forces Pest Management Board, Washington, DC, was the primary search engine used to review the literature.

Claborn, David M

2010-01-01

19

Malaria vector control in South Africa.  

PubMed

Malaria vector control is primarily insecticide based and relies on indoor residual spraying (IRS) and the distribution of long-lasting insecticide-treated bednets (LLINs). These interventions have generally proved effective where appropriately implemented. However, the increasing incidence of insecticide resistance in target vector populations can, and in several cases already has, undermined the effectiveness of IRS and LLINs. Today there are very few localities on the African continent where populations of vector mosquitoes are still susceptible to the approved classes of insecticides. If elimination is to be achieved, SA needs to invest more resources into malaria control.  PMID:24079634

Brooke, B; Koekemoer, L; Kruger, P; Urbach, J; Misiani, E; Coetzee, M

2013-10-01

20

Vector control activities. Fiscal year, 1982  

SciTech Connect

The goal of the TVA Vector Control Program is to protect the public from potential vectors of disease by controlling medically-important arthropod pests that are propagated on TVA lands or waters. In addition, freedom from annoying mosquitoes and other blood-sucking pests permits the development, use, and full enjoyment of the vast recreational opportunities offered by the many miles of freshwater lakes. To attain this goal the program is divided into operations and support studies. The support studies are designed to improve the operational effectiveness and efficiency of the control program and to identify other vector control problems that require TVA attention and study. Specifically, activities concerning water level management of TVA lakes, dewatering projects, plant growth control, drainage and insect control programs are detailed. Further, report is made of post-impoundment surveys, soil sampling studies of Mosquite larvae and ecological mosquito management studies.

Pickard, E.; Cooney, J.C.; McDuff, B.R.

1983-06-01

21

Problems of diagnosis of trypanosomiasis*  

PubMed Central

Diagnostic problems in trypanosomiasis arise from the inadequacy of current diagnostic procedures. This inadequacy deprives the clinician of essential data, hinders individual therapy and therapeutic control programmes, and makes suspect many conclusions drawn from previous experimental work. In this paper the author examines alternative methods of diagnosis, emphasizing cultivation and immunological procedures. An independent standard for diagnostic evaluation is available with the culture method. Comparison indicates that conventional procedures are frequently in error and that the error is always an underestimation, which may reach 20%-25% or more. The culture method has proved to be sensitive, reliable, usable under African field and hospital conditions, and applicable to isolation of Trypanosoma gambiense and T. rhodesiense from both blood and spinal fluid. Complement-fixation is the most widely used of the immunological reactions available. Procedures and results are reviewed and possibilities both with this method and others are discussed. Continuing research on diagnostic methods is needed, and certain practical difficulties in such a continuing research programme are discussed.

Weinman, David

1963-01-01

22

Integrated vector management for malaria control  

PubMed Central

Integrated vector management (IVM) is defined as "a rational decision-making process for the optimal use of resources for vector control" and includes five key elements: 1) evidence-based decision-making, 2) integrated approaches 3), collaboration within the health sector and with other sectors, 4) advocacy, social mobilization, and legislation, and 5) capacity-building. In 2004, the WHO adopted IVM globally for the control of all vector-borne diseases. Important recent progress has been made in developing and promoting IVM for national malaria control programmes in Africa at a time when successful malaria control programmes are scaling-up with insecticide-treated nets (ITN) and/or indoor residual spraying (IRS) coverage. While interventions using only ITNs and/or IRS successfully reduce transmission intensity and the burden of malaria in many situations, it is not clear if these interventions alone will achieve those critical low levels that result in malaria elimination. Despite the successful employment of comprehensive integrated malaria control programmes, further strengthening of vector control components through IVM is relevant, especially during the "end-game" where control is successful and further efforts are required to go from low transmission situations to sustained local and country-wide malaria elimination. To meet this need and to ensure sustainability of control efforts, malaria control programmes should strengthen their capacity to use data for decision-making with respect to evaluation of current vector control programmes, employment of additional vector control tools in conjunction with ITN/IRS tactics, case-detection and treatment strategies, and determine how much and what types of vector control and interdisciplinary input are required to achieve malaria elimination. Similarly, on a global scale, there is a need for continued research to identify and evaluate new tools for vector control that can be integrated with existing biomedical strategies within national malaria control programmes. This review provides an overview of how IVM programmes are being implemented, and provides recommendations for further development of IVM to meet the goals of national malaria control programmes in Africa.

Beier, John C; Keating, Joseph; Githure, John I; Macdonald, Michael B; Impoinvil, Daniel E; Novak, Robert J

2008-01-01

23

Chemotherapy of Human African Trypanosomiasis  

PubMed Central

Human Africa trypanosomiasis is a centuries-old disease which has disrupted sub-Saharan Africa in both physical suffering and economic loss. This article presents an update of classic chemotherapeutic agents, in use for >50 years and the recent development of promising non-toxic combination chemotherapy suitable for use in rural clinics.

Bacchi, Cyrus J.

2009-01-01

24

Electromechanical actuation for thrust vector control applications  

Microsoft Academic Search

At present, actuation systems for the Thrust Vector Control (TVC) for launch vehicles are hydraulic systems. The Advanced Launch System (ALS), a joint initiative between NASA and the Air Force, is a launch vehicle that is designed to be cost effective, highly reliable and operationally efficient with a goal of reducing the cost per pound to orbit. As part of

Mary Ellen Roth

1990-01-01

25

Chagas disease (American trypanosomiasis) in Mexico: an update.  

PubMed

Chagas disease is a parasitic infection caused by the protozoan Trypanosoma cruzi, a flagellated organism that is transmitted mainly to humans through the infected feces of triatomine kissing bugs (vector transmission in endemic areas) or by transfusion of infected blood, donations of infected organ, or transmission from an infected mother to her child at birth. Chagas disease was first described in 1909 by the Brazilian physician Carlos Chagas, and due to the parasite's distribution throughout North, Central and South America, the disease is commonly known as American trypanosomiasis. However, this disease is now present in non-endemic countries such as Canada, the United States of America, and several countries in Europe (principally Spain). Moreover, Chagas disease was recently designated by the World Health Organization as one of the main neglected tropical diseases. The aim of this review is to summarize the research efforts recently described in studies conducted in Mexico on Chagas disease. In this country, there are no existing vector control programs. In addition, there is no consensus on the diagnostic methods for acute and chronic Chagas disease in maternity wards and blood banks, and trypanocidal therapy is not administered to chronic patients. The actual prevalence of the disease is unknown because no official reporting of cases is performed. Therefore, the number of people infected by different routes of transmission (vector, congenital, blood transfusion, organ transplantation, or oral) is unknown. We believe that by promoting education about Chagas disease in schools starting at the basic elementary level and including reinforcement at higher education levels will ensure that the Mexican population would be aware of this health problem and that the control measures adopted will have more acceptance and success. We hope that this review sensitizes the relevant authorities and that the appropriate measures to reduce the risk of infection by T. cruzi are undertaken to provide the Mexican people a better quality of life. PMID:23643518

Carabarin-Lima, Alejandro; González-Vázquez, María Cristina; Rodríguez-Morales, Olivia; Baylón-Pacheco, Lidia; Rosales-Encina, José Luis; Reyes-López, Pedro Antonio; Arce-Fonseca, Minerva

2013-08-01

26

Space vector PWM control of dual three phase induction machine using vector space decomposition  

Microsoft Academic Search

The technique of vector space decomposition control of voltage source inverter fed dual three phase induction machines is presented in this paper. By vector space decomposition, the analysis and control of the machine are accomplished in three two-dimensional orthogonal subspaces and the dynamics of the electromechanical and nonelectromechanical energy conversion related machine variables are thereby totally decoupled. A space vector

Y. Zhao; T.A. Lipo

1994-01-01

27

High efficiency thrust vector control allocation  

NASA Astrophysics Data System (ADS)

The design of control mixing algorithms for launch vehicles with multiple vectoring engines yields competing objectives for which no straightforward solution approach exists. The designer seeks to optimally allocate the effector degrees of freedom such that maneuvering capability is maximized subject to constraints on available control authority. In the present application, such algorithms are generally restricted to linear transformations so as to minimize adverse control-structure interaction and maintain compatibility with industry-standard methods for control gain design and stability analysis. Based on the application of the theory of ellipsoids, a complete, scalable, and extensible framework is developed to effect rapid analysis of launch vehicle capability. Furthermore, a control allocation scheme is proposed that simultaneously balances attainment of the maximum maneuvering capability with rejection of internal loads and performance losses resulting from thrust vectoring in the null region of the admissible controls. This novel approach leverages an optimal parametrization of the weighted least squares generalized inverse and exploits the analytic properties of the constraint geometry so as to enable recovery of more than ninety percent of the theoretical capability while maintaining linearity over the majority of the attainable set.

Orr, Jeb S.

28

Flexible joints for thrust vector control  

NASA Technical Reports Server (NTRS)

Flexible joints have been used to achieve thrust vector control over a wide range of sizes of nozzles and have been demonstrated successfully in bench tests and static firings, and are operational on two motors. From these many joints the problems of flexible joints have been defined as establishment of the movable nozzle envelope, definition of the actuation power requirements, definition of the mechanical properties of joint materials, adhesive bonding, test methods, and quality control. These data and problem solutions are contained in a large number of reports. Data relating to joint configuration, design requirements, materials selection, joint design, structural analysis, manufacture, and testing are summarized.

Woodberry, R. F. H.

1975-01-01

29

Electromechanical actuation for thrust vector control applications  

NASA Technical Reports Server (NTRS)

The advanced launch system (ALS), is a launch vehicle that is designed to be cost-effective, highly reliable, and operationally efficient with a goal of reducing the cost per pound to orbit. An electromechanical actuation (EMA) system is being developed as an attractive alternative to the hydraulic systems. The controller will integrate 20 kHz resonant link power management and distribution (PMAD) technology and pulse population modulation (PPM) techniques to implement field-oriented vector control (FOVC) of a new advanced induction motor. The driver and the FOVC will be microprocessor controlled. For increased system reliability, a built-in test (BITE) capability will be included. This involves introducing testability into the design of a system such that testing is calibrated and exercised during the design, manufacturing, maintenance, and prelaunch activities. An actuator will be integrated with the motor controller for performance testing of the EMA thrust vector control (TVC) system. The EMA system and work proposed for the future are discussed.

Roth, Mary Ellen

1990-01-01

30

40 CFR 258.22 - Disease vector control.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Disease vector control. 258.22 Section...LANDFILLS Operating Criteria § 258.22 Disease vector control. (a) Owners or operators...prevent or control on-site populations of disease vectors using techniques...

2013-07-01

31

The Biological Control of the Malaria Vector  

PubMed Central

The call for malaria control, over the last century, marked a new epoch in the history of this disease. Many control strategies targeting either the Plasmodium parasite or the Anopheles vector were shown to be effective. Yet, the emergence of drug resistant parasites and insecticide resistant mosquito strains, along with numerous health, environmental, and ecological side effects of many chemical agents, highlighted the need to develop alternative tools that either complement or substitute conventional malaria control approaches. The use of biological means is considered a fundamental part of the recently launched malaria eradication program and has so far shown promising results, although this approach is still in its infancy. This review presents an overview of the most promising biological control tools for malaria eradication, namely fungi, bacteria, larvivorous fish, parasites, viruses and nematodes.

Kamareddine, Layla

2012-01-01

32

Human African trypanosomiasis–neurologicalaspects  

Microsoft Academic Search

Human African Trypanosomiasis\\u000a (HAT),which is also\\u000a known as sleeping sickness, is a\\u000a major cause of death and disability\\u000a in 36 countries in sub-Saharan\\u000a Africa. The disease is caused by the\\u000a protozoan parasite of the Trypanosoma\\u000a genus which is transmitted\\u000a by the bite of the tsetse fly. The\\u000a two types of HAT, the East African\\u000a form due to Trypanosoma b.rhodesiensei (T.

Peter G. E. Kennedy

2006-01-01

33

Electromechanical actuation for thrust vector control applications  

NASA Technical Reports Server (NTRS)

At present, actuation systems for the Thrust Vector Control (TVC) for launch vehicles are hydraulic systems. The Advanced Launch System (ALS), a joint initiative between NASA and the Air Force, is a launch vehicle that is designed to be cost effective, highly reliable and operationally efficient with a goal of reducing the cost per pound to orbit. As part of this initiative, an electromechanical actuation system is being developed as an attractive alternative to the hydraulic systems used today. NASA-Lewis is developing and demonstrating an Induction Motor Controller Actuation System with a 40 hp peak rating. The controller will integrate 20 kHz resonant link Power Management and Distribution (PMAD) technology and Pulse Population Modulation (PPM) techniques to implement Field Oriented Vector Control (FOVC) of a new advanced induction motor. Through PPM, multiphase variable frequency, variable voltage waveforms can be synthesized from the 20 kHz source. FOVC shows that varying both the voltage and frequency and their ratio (V/F), permits independent control of both torque and speed while operating at maximum efficiency at any point on the torque-speed curve. The driver and the FOVC will be microprocessor controlled. For increased system reliability, a Built-in Test (BITE) capability will be included. This involves introducing testability into the design of a system such that testing is calibrated and exercised during the design, manufacturing, maintenance and prelaunch activities. An actuator will be integrated with the motor controller for performance testing of the EMA TVC system. The design and fabrication of the motor controller is being done by General Dynamics Space Systems Division. The University of Wisconsin-Madison will assist in the design of the advanced induction motor and in the implementation of the FOVC theory. A 75 hp electronically controlled dynamometer will be used to test the motor controller in all four quadrants of operation using flight type control algorithms. Integrated testing of the controller and actuator will be conducted at a facility yet to be named. The EMA system described above is discussed in detail.

Roth, Mary Ellen

1990-01-01

34

Using species distribution models to optimize vector control in the framework of the tsetse eradication campaign in Senegal  

PubMed Central

Tsetse flies are vectors of human and animal trypanosomoses in sub-Saharan Africa and are the target of the Pan African Tsetse and Trypanosomiasis Eradication Campaign (PATTEC). Glossina palpalis gambiensis (Diptera: Glossinidae) is a riverine species that is still present as an isolated metapopulation in the Niayes area of Senegal. It is targeted by a national eradication campaign combining a population reduction phase based on insecticide-treated targets (ITTs) and cattle and an eradication phase based on the sterile insect technique. In this study, we used species distribution models to optimize control operations. We compared the probability of the presence of G. p. gambiensis and habitat suitability using a regularized logistic regression and Maxent, respectively. Both models performed well, with an area under the curve of 0.89 and 0.92, respectively. Only the Maxent model predicted an expert-based classification of landscapes correctly. Maxent predictions were therefore used throughout the eradication campaign in the Niayes to make control operations more efficient in terms of deployment of ITTs, release density of sterile males, and location of monitoring traps used to assess program progress. We discuss how the models’ results informed about the particular ecology of tsetse in the target area. Maxent predictions allowed optimizing efficiency and cost within our project, and might be useful for other tsetse control campaigns in the framework of the PATTEC and, more generally, other vector or insect pest control programs.

Dicko, Ahmadou H.; Lancelot, Renaud; Seck, Momar T.; Guerrini, Laure; Sall, Baba; Lo, Mbargou; Vreysen, Marc J. B.; Lefrancois, Thierry; Fonta, William M.; Peck, Steven L.; Bouyer, Jeremy

2014-01-01

35

Using species distribution models to optimize vector control in the framework of the tsetse eradication campaign in Senegal.  

PubMed

Tsetse flies are vectors of human and animal trypanosomoses in sub-Saharan Africa and are the target of the Pan African Tsetse and Trypanosomiasis Eradication Campaign (PATTEC). Glossina palpalis gambiensis (Diptera: Glossinidae) is a riverine species that is still present as an isolated metapopulation in the Niayes area of Senegal. It is targeted by a national eradication campaign combining a population reduction phase based on insecticide-treated targets (ITTs) and cattle and an eradication phase based on the sterile insect technique. In this study, we used species distribution models to optimize control operations. We compared the probability of the presence of G. p. gambiensis and habitat suitability using a regularized logistic regression and Maxent, respectively. Both models performed well, with an area under the curve of 0.89 and 0.92, respectively. Only the Maxent model predicted an expert-based classification of landscapes correctly. Maxent predictions were therefore used throughout the eradication campaign in the Niayes to make control operations more efficient in terms of deployment of ITTs, release density of sterile males, and location of monitoring traps used to assess program progress. We discuss how the models' results informed about the particular ecology of tsetse in the target area. Maxent predictions allowed optimizing efficiency and cost within our project, and might be useful for other tsetse control campaigns in the framework of the PATTEC and, more generally, other vector or insect pest control programs. PMID:24982143

Dicko, Ahmadou H; Lancelot, Renaud; Seck, Momar T; Guerrini, Laure; Sall, Baba; Lo, Mbargou; Vreysen, Marc J B; Lefrançois, Thierry; Fonta, William M; Peck, Steven L; Bouyer, Jérémy

2014-07-15

36

Thrust vector control using electric actuation  

SciTech Connect

Presently, gimbaling of launch vehicle engines for thrust vector control is generally accomplished using a hydraulic system. In the case of the space shuttle solid rocket boosters and main engines, these systems are powered by hydrazine auxiliary power units. Use of electromechanical actuators would provide significant advantages in cost and maintenance. However, present energy source technologies such as batteries are heavy to the point of causing significant weight penalties. Utilizing capacitor technology developed by the Auburn University Space Power Institute in collaboration with the Auburn CCDS, Marshall Space Flight Center (MSFC) and Auburn are developing EMA system components with emphasis on high discharge rate energy sources compatible with space shuttle type thrust vector control requirements. Testing has been done at MSFC as part of EMA system tests with loads up to 66000 newtons for pulse times of several seconds. Results show such an approach to be feasible providing a potential for reduced weight and operations costs for new launch vehicles. {copyright} 1995 {ital American} {ital Institute} {ital of} {ital Physics}

Bechtel, R.T.; Hall, D.K. [Marshall Space Flight Center, Marshall Space Flight Center, Alabama 35812 (United States)

1995-01-25

37

Hot gas thrust vector control motor  

NASA Astrophysics Data System (ADS)

A hot gas thrust vector control (HGTVC) motor developed in the framework of a Foreign Weapon Evaluation program is discussed. Two HGTVC versions were evaluated on the two nozzles of the program, normal injection with a blunt pintle and 10 deg upstream injection with a tapered pintle. The HGTVC system was tested on a modified ORBUS-1 motor which is based on two technologies, namely, a composite chamber polar boss (CPB) and a two-piece C-C nozzle which threads to the CPB and receives two HGVs embedded into its exit cone, 180 deg apart. It is concluded that the composite polar bosses and C-C nozzles performed successfully in both firings.

Berdoyes, Michel; Ellis, Russell A.

1992-07-01

38

Paratransgenic Control of Vector Borne Diseases  

PubMed Central

Conventional methodologies to control vector borne diseases with chemical pesticides are often associated with environmental toxicity, adverse effects on human health and the emergence of insect resistance. In the paratransgenic strategy, symbiotic or commensal microbes of host insects are transformed to express gene products that interfere with pathogen transmission. These genetically altered microbes are re-introduced back to the insect where expression of the engineered molecules decreases the host's ability to transmit the pathogen. We have successfully utilized this strategy to reduce carriage rates of Trypanosoma cruzi, the causative agent of Chagas disease, in the triatomine bug, Rhodnius prolixus, and are currently developing this methodology to control the transmission of Leishmania donovani by the sand fly Phlebotomus argentipes. Several effector molecules, including antimicrobial peptides and highly specific single chain antibodies, are currently being explored for their anti-parasite activities in these two systems. In preparation for eventual field use, we are actively engaged in risk assessment studies addressing the issue of horizontal gene transfer from the modified bacteria to environmental microbes.

Hurwitz, Ivy; Fieck, Annabeth; Read, Amber; Hillesland, Heidi; Klein, Nichole; Kang, Angray; Durvasula, Ravi

2011-01-01

39

Thrust Vector Control for Nuclear Thermal Rockets  

NASA Technical Reports Server (NTRS)

Future space missions may use Nuclear Thermal Rocket (NTR) stages for human and cargo missions to Mars and other destinations. The vehicles are likely to require engine thrust vector control (TVC) to maintain desired flight trajectories. This paper explores requirements and concepts for TVC systems for representative NTR missions. Requirements for TVC systems were derived using 6 degree-of-freedom models of NTR vehicles. Various flight scenarios were evaluated to determine vehicle attitude control needs and to determine the applicability of TVC. Outputs from the models yielded key characteristics including engine gimbal angles, gimbal rates and gimbal actuator power. Additional factors such as engine thrust variability and engine thrust alignment errors were examined for impacts to gimbal requirements. Various technologies are surveyed for TVC systems for the NTR applications. A key factor in technology selection is the unique radiation environment present in NTR stages. Other considerations including mission duration and thermal environments influence the selection of optimal TVC technologies. Candidate technologies are compared to see which technologies, or combinations of technologies best fit the requirements for selected NTR missions. Representative TVC systems are proposed and key properties such as mass and power requirements are defined. The outputs from this effort can be used to refine NTR system sizing models, providing higher fidelity definition for TVC systems for future studies.

Ensworth, Clinton B. F.

2013-01-01

40

Malaria and dengue vector biology and control in Southeast Asia  

Microsoft Academic Search

This chapter reviews the situation of vector biology and control of both malaria and dengue in the Southeast-Asian region as part of the World Health Organization (WHO\\/TDR) working-group meeting on strategic planning to bridge laboratory and field research in disease vector control. Many research studies on malaria were related to the survey of malaria vectors and parasites and their spatial

Pattamaporn Kittayapong

41

Controllable Pairs of Vector Fields on SL(n,R).  

National Technical Information Service (NTIS)

Consider the class C of compact right invariant vectors fields on SL(n,R). We show that for each non zero element (X sub 1) of C there exists an element (X sub 2) of C such that the pair of vectors fields ((X sub 1), (X sub 2)) is controllable.

B. Bonnard

1979-01-01

42

Addressing malaria vector control challenges in South Sudan: proposed recommendations  

PubMed Central

Upon the signing of the Comprehensive Peace Agreement in 2005, the Republic of South Sudan (RSS) has faced a lot of challenges, such as a lack of infrastructure, human resources and an enormous burden of vector borne diseases including malaria. While a national malaria strategic plan 2006-2011 was developed, the vector control component has remained relatively weak. The strategy endorses the distribution of long-lasting insecticidal nets (LLINs) as the frontline intervention with other interventions recommended only when technical and institutional capacity is available. In 2006, a draft integrated vector management (IVM) strategic plan 2007–2012 was developed but never implemented, resulting in minimal coordination, implementation and coverage of malaria vector control tools including their inherent impact. To address this challenge, the vector control team of the National Malaria Control Programme (NMCP) is being strengthened. With the objective of building national capacity and technical collaboration for effective implementation of the IVM strategy, a national malaria vector control conference was held from 15-17th October 2012 in Juba. A range of NMCP partners, state ministries, acadaemia, private sector, national and international non-governmental organizations, including regional and global policymakers attended the meeting. The conference represented a major milestone and made recommendations revolving around the five key elements of the IVM approach. The meeting endorsed that vector control efforts in RSS be augmented with other interventions within the confines of the IVM strategy as a national approach, with strong adherence to its key elements.

2013-01-01

43

Population mobility and trypanosomiasis in Africa*  

PubMed Central

Population mobility has long been established as a feature of life in Africa south of the Sahara. Even though it appears to be a factor in the spread of sleeping-sickness there do not seem to have been serious epidemics until the latter part of the nineteenth century and the early decades of the twentieth century. Various types of population movement of the present day and their possible relevance to trypanosomiasis are discussed. Density of population and settlement patterns are also important. Some of the changes in these which are relevant to trypanosomiasis are outlined and the need for more detailed information on these and on population mobility is emphasized.

Prothero, R. Mansell

1963-01-01

44

From population structure to genetically-engineered vectors: new ways to control vector-borne diseases?  

PubMed

Epidemiological studies on vectors and the pathogens they can carry (such as Borrelia burgdorferi) are showing some correlations between infection rates and biodiversity highlighting the "dilution" effects on potential vectors. Meanwhile other studies comparing sympatric small rodent species demonstrated that rodent species transmitting more pathogens are parasitized by more ectoparasite species. Studies on population structure and size have also proven a difference on the intensity of the parasitic infection. Furthermore, preliminary results in genetic improvement in mosquitoes (genetic markers, sexing, and genetic sterilization) will also increase performance as it has already been shown in field applications in developing countries. Recent results have greatly improved the fitness of genetically-modified insects compared to wild type populations with new approaches such as the post-integration elimination of transposon sequences, stabilising any insertion in genetically-modified insects. Encouraging results using the Sterile Insect Technique highlighted some metabolism manipulation to avoid the viability of offspring from released parent insect in the wild. Recent studies on vector symbionts would also bring a new angle in vector control capabilities, while complete DNA sequencing of some arthropods could point out ways to block the deadly impact on animal and human populations. These new potential approaches will improve the levels of control or even in some cases would eradicate vector species and consequently the vector-borne diseases they can transmit. In this paper we review some of the population biology theories, biological control methods, and the genetic techniques that have been published in the last years that are recommended to control for vector-borne diseases. PMID:17560836

Sparagano, O A E; De Luna, C J

2008-07-01

45

The Burden of Human African Trypanosomiasis  

Microsoft Academic Search

Human African trypanosomiasis (HAT, or sleeping sickness) is a protozoan parasitic infection caused by Trypanosoma brucei rhodesiense or Trypanoso- ma brucei gambiense. These are neglected tropical diseases, and T.b. rhodesiense HAT is a zoonosis. We review current knowledge on the burden of HAT in sub- Saharan Africa, with an emphasis on the disability- adjusted life year (DALY), data sources, and

Eric M. Fèvre; Beatrix v. Wissmann; Susan C. Welburn; Pascal Lutumba

2008-01-01

46

Parallel and vector computation for stochastic optimal control applications  

NASA Technical Reports Server (NTRS)

A general method for parallel and vector numerical solutions of stochastic dynamic programming problems is described for optimal control of general nonlinear, continuous time, multibody dynamical systems, perturbed by Poisson as well as Gaussian random white noise. Possible applications include lumped flight dynamics models for uncertain environments, such as large scale and background random atmospheric fluctuations. The numerical formulation is highly suitable for a vector multiprocessor or vectorizing supercomputer, and results exhibit high processor efficiency and numerical stability. Advanced computing techniques, data structures, and hardware help alleviate Bellman's curse of dimensionality in dynamic programming computations.

Hanson, F. B.

1989-01-01

47

Implementation of a new fuzzy vector control of induction motor.  

PubMed

The aim of this paper is to present a new approach to control an induction motor using type-1 fuzzy logic. The induction motor has a nonlinear model, uncertain and strongly coupled. The vector control technique, which is based on the inverse model of the induction motors, solves the coupling problem. Unfortunately, in practice this is not checked because of model uncertainties. Indeed, the presence of the uncertainties led us to use human expertise such as the fuzzy logic techniques. In order to maintain the decoupling and to overcome the problem of the sensitivity to the parametric variations, the field-oriented control is replaced by a new block control. The simulation results show that the both control schemes provide in their basic configuration, comparable performances regarding the decoupling. However, the fuzzy vector control provides the insensitivity to the parametric variations compared to the classical one. The fuzzy vector control scheme is successfully implemented in real-time using a digital signal processor board dSPACE 1104. The efficiency of this technique is verified as well as experimentally at different dynamic operating conditions such as sudden loads change, parameter variations, speed changes, etc. The fuzzy vector control is found to be a best control for application in an induction motor. PMID:24629620

Rafa, Souad; Larabi, Abdelkader; Barazane, Linda; Manceur, Malik; Essounbouli, Najib; Hamzaoui, Abdelaziz

2014-05-01

48

DSP-based fuzzy logic controller for VSI-fed vector controlled AC motors  

Microsoft Academic Search

The paper deals with the fuzzy logic control(ler) (FLC) application to the vector controlled AC motor drive. The aspects of major importance in the application to vector controlled AC motor drives are pointed out and discussed. The rule base can be easily built using the general dynamics of the process, and than readily updated to contain the delayed information for

D. Fodor; J. Vass; Z. Katona

1995-01-01

49

Control chart pattern recognition using learning vector quantization networks  

Microsoft Academic Search

Pattern recognition systems using neural networks for discriminating between different types of control chart patterns are discussed. A class of pattern recognizers based on the Learning Vector Quantization (LVQ) network is described. A procedure to increase the classification accuracy and decrease the learning time for LVQ networks is presented. The results of control chart pattern recognition experiments using both existing

D. T. PHAM; E. OZTEMEL

1994-01-01

50

State Transitions in Vector Controlled AC Tram Drive  

Microsoft Academic Search

The paper deals with the control strategy for the prototype AC tram drive designed for modernization of existing trams in Poland. The basis of the drive are vector-controlled induction motors sourced from voltage inverters. Motor shaft speed sensing enables torque and rotor flux indirect control in stator-current oriented co-ordinates system. In the paper the block scheme of such a control

Andrzej Debowski; Piotr Chudzik; Grzegorz Lisowski

2006-01-01

51

[Disease vector control strategy in the French army].  

PubMed

Disease vector control is a major priority for the Medical Health Corps of the French Armed Forces which maintains around 23,000 troops in tropical areas and is involved in numerous military and humanitarian missions throughout the world. Control strategy includes both general and personal control measures. Personal control measures include wearing permetherin-impregnated combat uniforms, application of repellents to the skin, and use of deltamethrin-impregnated bednets. General measures are implemented in facilities and in the environment. Measures in facilities include not only physical deterrents such as screens on openings and air-conditioning but also application of chemical insecticides to walls, curtains, and screening. Environmental measures include control of larval deposits and elimination of potential breeding areas. Low-volume wide-area spraying of imagocides is a supplemental option used in case of disease outbreak. For units stationed in tropical areas, command and surveillance of vector control operations is under the responsibility of the mosquito control committee which includes personnel from the affected field unit. Strategies are chosen in function of local climate and operational conditions. The efficacy of vector control programs is assessed annually by reviewing the incidence in armed forces personnel of the main vector-transmitted diseases: malaria, dengue fever, and leishmaniasis. Documentation and training are dispensed to all units stationed in tropical areas. To ensure that knowledge of military physicians remains current, three courses on malaria control are offered each year at the Tropical Medicine Institute of the Armed Forces Health Corps (Le Pharo) in Marseille. Field research conducted in collaboration with military or civilian organizations independent of the Armed Services Health Corps makes it possible to keep chiefs of staff informed of state-of-the art vector control measures adapted to use by personnel on assignment or mission in tropical areas. PMID:11584664

Deparis, X; Boutin, J P; Michel, R; Galoisy-Guibal, L; Meynard, J B; Pages, F; Matton, T; Spiegel, A; Baudon, D

2001-01-01

52

vectors  

NSDL National Science Digital Library

The word vector comes from the Latin term vehere, to carry. In Biology, a vector is an agent which carries disease, such as a mosquito carrying infected blood from one patient to the next. In physics, a vector is a quantity which has both a magnitude and a direction associated with it. The most commonly used example of vectors in everyday life is velocity. When you drive your car, your speedometer tells you the speed of your car, but it doesn't tell you where you are going. The combination of both where you are going and how fast you are going there is your car's velocity.

Joiner, David; The Shodor Education Foundation, Inc.

53

The Burden of Human African Trypanosomiasis  

Microsoft Academic Search

Human African trypanosomiasis (HAT, or sleeping sickness) is a protozoan parasitic infection caused by Trypanosoma brucei rhodesiense or Trypanosoma brucei gambiense. These are neglected tropical diseases, and T.b. rhodesiense HAT is a zoonosis. We review current knowledge on the burden of HAT in sub-Saharan Africa, with an emphasis on the disability-adjusted life year (DALY), data sources, and methodological issues relating

Eric M. Fèvre; Beatrix v. Wissmann; Susan C. Welburn; Pascal Lutumba

2008-01-01

54

A vector oriented control for a magnetically levitated shaft  

SciTech Connect

Considering the nonlinear model of Active Magnetic Bearings, a new means of nonlinear control is presented which treats variables as rotating vectors in the control plane, specially the unbalance. It became easy to cancel out the effect of this perturbation in a rotating reference. Therefore, the rotor can rotate around any desired point, particularly the geometric center or the center of gravity. Simulations illustrate the efficacy of this control law.

De Miras, J.; Charara, A. [UTC, Compiegne (France)] [UTC, Compiegne (France)

1998-07-01

55

The impact of host species and vector control measures on the fitness of African malaria vectors  

PubMed Central

Many malaria vector mosquitoes in Africa have an extreme preference for feeding on humans. This specialization allows them to sustain much higher levels of transmission than elsewhere, but there is little understanding of the evolutionary forces that drive this behaviour. In Tanzania, we used a semi-field system to test whether the well-documented preferences of the vectors, Anopheles arabiensis and Anopheles gambiae sensu stricto (s.s.) for cattle and humans, respectively, are predicted by the fitness they obtain from host-seeking on these species relative to other available hosts. Mosquito fitness was contrasted, when humans were fully exposed and when they were protected by a typical bednet. The fitness of both vectors varied between host species. The predicted relationship between host preference and fitness was confirmed in An. arabiensis, but not in An. gambiae s.s., whose fitness was similar on humans and other mammals. Use of typical, imperfect bednets generated only minor reductions in An. gambiae s.s. feeding success and fitness on humans, but was predicted to generate a significant reduction in the lifetime reproductive success of An. arabiensis on humans relative to cows. This supports the hypothesis that such human-protective measures could additionally benefit malaria control by increasing selection for zoophily in vectors.

Lyimo, Issa N.; Haydon, Daniel T.; Russell, Tanya L.; Mbina, Kasian F.; Daraja, Ally A.; Mbehela, Edgar M.; Reeve, Richard; Ferguson, Heather M.

2013-01-01

56

Modelling and control of PEMFC based on support vector machine  

Microsoft Academic Search

When current is drawn from a proton exchange membrane fuel cell (PEMFC), it is critical that the reacted oxygen is replenished rapidly by the air supply system to avoid oxygen starvation and damage. This paper proposes a support vector machine (SVM) model based model predictive control (MPC) strategy to maintain a necessary level of the oxygen excess ratio during abrupt

Jun Lu; Ahmad Zahedi

2011-01-01

57

Vector Disparity Sensor with Vergence Control for Active Vision Systems  

PubMed Central

This paper presents an architecture for computing vector disparity for active vision systems as used on robotics applications. The control of the vergence angle of a binocular system allows us to efficiently explore dynamic environments, but requires a generalization of the disparity computation with respect to a static camera setup, where the disparity is strictly 1-D after the image rectification. The interaction between vision and motor control allows us to develop an active sensor that achieves high accuracy of the disparity computation around the fixation point, and fast reaction time for the vergence control. In this contribution, we address the development of a real-time architecture for vector disparity computation using an FPGA device. We implement the disparity unit and the control module for vergence, version, and tilt to determine the fixation point. In addition, two on-chip different alternatives for the vector disparity engines are discussed based on the luminance (gradient-based) and phase information of the binocular images. The multiscale versions of these engines are able to estimate the vector disparity up to 32 fps on VGA resolution images with very good accuracy as shown using benchmark sequences with known ground-truth. The performances in terms of frame-rate, resource utilization, and accuracy of the presented approaches are discussed. On the basis of these results, our study indicates that the gradient-based approach leads to the best trade-off choice for the integration with the active vision system.

Barranco, Francisco; Diaz, Javier; Gibaldi, Agostino; Sabatini, Silvio P.; Ros, Eduardo

2012-01-01

58

Investigations of Thrust Vector Control for High-Alpha Pitchover.  

National Technical Information Service (NTIS)

Historically, thrust vector control (TVC) system investigations at the Naval Weapons Center have touched on a wide variety of technologies. Emphasis in this paper is on two technologies, the movable-nozzle and the jet-vane TVC, whose performance capabilit...

A. O. Danielson R. B. Dillinger

1989-01-01

59

Vector control of filariasis in the Solomon Islands.  

PubMed

In Solomon Islands, filariasis is caused by the nocturnally perodic form of Wuchereria bancrofti and is transmitted by the same vectors of malaria. This study explores the control of this disease as an additional effect of the Malaria Eradication Programme. PMID:3855

Webber, R H

1975-09-01

60

Topographic models for predicting malaria vector breeding habitats: potential tools for vector control managers  

PubMed Central

Background Identification of malaria vector breeding sites can enhance control activities. Although associations between malaria vector breeding sites and topography are well recognized, practical models that predict breeding sites from topographic information are lacking. We used topographic variables derived from remotely sensed Digital Elevation Models (DEMs) to model the breeding sites of malaria vectors. We further compared the predictive strength of two different DEMs and evaluated the predictability of various habitat types inhabited by Anopheles larvae. Methods Using GIS techniques, topographic variables were extracted from two DEMs: 1) Shuttle Radar Topography Mission 3 (SRTM3, 90-m resolution) and 2) the Advanced Spaceborne Thermal Emission Reflection Radiometer Global DEM (ASTER, 30-m resolution). We used data on breeding sites from an extensive field survey conducted on an island in western Kenya in 2006. Topographic variables were extracted for 826 breeding sites and for 4520 negative points that were randomly assigned. Logistic regression modelling was applied to characterize topographic features of the malaria vector breeding sites and predict their locations. Model accuracy was evaluated using the area under the receiver operating characteristics curve (AUC). Results All topographic variables derived from both DEMs were significantly correlated with breeding habitats except for the aspect of SRTM. The magnitude and direction of correlation for each variable were similar in the two DEMs. Multivariate models for SRTM and ASTER showed similar levels of fit indicated by Akaike information criterion (3959.3 and 3972.7, respectively), though the former was slightly better than the latter. The accuracy of prediction indicated by AUC was also similar in SRTM (0.758) and ASTER (0.755) in the training site. In the testing site, both SRTM and ASTER models showed higher AUC in the testing sites than in the training site (0.829 and 0.799, respectively). The predictability of habitat types varied. Drains, foot-prints, puddles and swamp habitat types were most predictable. Conclusions Both SRTM and ASTER models had similar predictive potentials, which were sufficiently accurate to predict vector habitats. The free availability of these DEMs suggests that topographic predictive models could be widely used by vector control managers in Africa to complement malaria control strategies.

2013-01-01

61

Attitude control of a spinning rocket via thrust vectoring  

SciTech Connect

Two controllers are developed to provide attitude control of a spinning rocket that has a thrust vectoring capability. The first controller has a single-input/single-output design that ignores the gyroscopic coupling between the control channels. The second controller has a multi-input/multi-output structure that is specifically intended to account for the gyroscopic coupling effects. A performance comparison between the two approached is conducted for a range of roll rates. Each controller is tested for the ability to track step commands, and for the amount of coupling impurity. Both controllers are developed via a linear-quadratic-regulator synthesis procedure, which is motivated by the multi-input/multi-output nature of second controller. Time responses and a singular value analysis are used to evaluate controller performance. This paper describes the development and comparison of two controllers that are designed to provide attitude control of a spinning rocket that is equipped with thrust vector control. 12 refs., 13 figs., 2 tabs.

White, J.E.

1990-12-19

62

Control of HVDC Light System Using Conventional and Direct Current Vector Control Approaches  

Microsoft Academic Search

With the advance of power electronic technology, the application of HVdc light systems based on voltage-source insulated gate bipolar transistor (IGBT) converters has increased rapidly in renewable, microgrid, and electric power systems. This paper proposes an optimal control strategy for an HVdc light system using a direct current vector control mechanism. The proposed approach is compared with the traditional vector

Shuhui Li; Timothy A. Haskew; Ling Xu

2010-01-01

63

Design of high power electromechanical actuator for thrust vector control  

NASA Technical Reports Server (NTRS)

NASA-Marshall has undertaken the development of electromechanical actuators (EMAs) for thrust vector control (TVC) augmentation system implementation. The TVC EMA presented has as its major components two three-phase brushless dc motors, a two-pass gear-reduction system, and a roller screw for rotary-to-linear motion conversion. System control is furnished by a solid-state electronic controller and power supply; a pair of resolvers deliver position feedback to the controller, such that precise positioning is achieved. Peformance comparisons have been conducted between the EMA and comparable-performance hydraulic systems applicable to TVCs.

Cowan, J. R.; Myers, W. N.

1991-01-01

64

Dengue Prevention and 35 Years of Vector Control in Singapore  

PubMed Central

After a 15-year period of low incidence, dengue has reemerged in Singapore in the past decade. We identify potential causes of this resurgence. A combination of lowered herd immunity, virus transmission outside the home, an increase in the age of infection, and the adoption of a case-reactive approach to vector control contribute to the increased dengue incidence. Singapore's experience with dengue indicates that prevention efforts may not be sustainable. For renewed success, Singapore needs to return to a vector control program that is based on carefully collected entomologic and epidemiologic data. Singapore's taking on a leadership role in strengthening disease surveillance and control in Southeast Asia may also be useful in reducing virus importation.

Goh, Kee-Tai; Gubler, Duane J.

2006-01-01

65

A review of the control of Simulium vectors of onchocerciasis  

PubMed Central

The purpose of this paper is to bring together all the available information concerning the control of Simulium vectors of onchocerciasis in Africa and Central and South America. Some of the larger control schemes are described in detail. Insecticidal formulations, rates of dosage, and methods of application are given when available, and costs per square mile (or square kilometre) are quoted where possible as a guide to future operations. The efficacy of ground application (larviciding) as compared with aerial application (larviciding and adulticiding) is discussed and it is concluded that ground larviciding is likely to achieve the best results, at less cost, in onchocercal foci where the vectors usually breed in small, densely wooded streams. Data in connexion with fly densities, prior and subsequent to control schemes, are quoted when available.

McMahon, J. P.

1967-01-01

66

Insecticide Control of Vector-Borne Diseases: When Is Insecticide Resistance a Problem?  

Microsoft Academic Search

Many of the most dangerous human diseases are transmitted by insect vectors. After decades of repeated insecticide use, all of these vector species have demonstrated the capacity to evolve resistance to insecticides. Insecticide resistance is generally considered to undermine control of vector-transmitted diseases because it increases the number of vectors that survive the insecticide treatment. Disease control failure, however, need

Ana Rivero; Julien Vézilier; Mylène Weill; Andrew F. Read; Sylvain Gandon

2010-01-01

67

Simulation Study of AC Motor Speed Sensorless Vector Control System Based on SVPWM  

Microsoft Academic Search

The paper applies the space vector pulse width modulation (SVPWM) algorithm to speed sensorless vector control system according to the theory of space vector pulse width modulation, so as to enhance the stability and the performance of speed sensorless drives. The vector control strategy of the SVPWM voltage source inverter fed induction motor is studied. To testify the correctness and

Hui Jin; Yue-ling Zhao; Da-zhi Wang

2009-01-01

68

CFD evaluation of an advanced thrust vector control concept  

NASA Technical Reports Server (NTRS)

A potential concept that can offer an alternate method for thrust vector control of the Space Shuttle Solid Rocket Booster is the use of a cylindrical probe that is inserted (on demand) through the wall of the rocket nozzle. This Probe Thrust Vector Control (PTVC) concept is an alternate to that of a gimbaled nozzle or a Liquid Injection Thrust Vector (LITVC) system. The viability of the PTVC concept can be assessed either experimentally and/or with the use of CFD. A purely experimental assessment can be time consuming and expensive, whereas a CFD assessment can be very time- and cost-effective. Two key requirements of the proposed concept are PTVC vectoring performance and the active cooling requirements for the probe to maintain its thermal and structural integrity. An active thermal cooling method is the injection of coolant around the pheriphery of the probe. How much coolant is required and how this coolant distributes itself in the flow field is of major concern. The objective of the work reported here is the use of CFD to answer these question and in the design of test hardware to substantiate the results of the CFD predictions.

Tiarn, Weihnurng; Cavalleri, Robert

1990-01-01

69

Controlling Compressor Vane Flow Vectoring Angles at Transonic Speeds  

NASA Astrophysics Data System (ADS)

The ability to control flow separation angles from compressor inlet guide vanes with a Coanda-type actuator is demonstrated using both wind tunnel experiments and finite element simulations. Vectoring angles up to 40 degrees from the uncontrolled baseline state were measured with helium schlieren visualization at transonic Mach numbers ranging from 0.1 to 0.6, and with airfoil chord Reynolds numbers ranging from 89,000 to 710,000. The magnitude of the vectoring angle is shown to depend upon the geometry of the trailing edge, and actuator slot size, and the momentum flux coefficient. Under certain conditions the blowing has no effect on the vectoring angle indicating that the Coanda effect is not present. DNS simulations with the finite element method investigated the effects of geometry changes and external flow. Continuous control of the vectoring angle is demonstrated, which has important implications for application to rotating machinery. The technique is shown to reduce the stall flow coefficient by 15 percent in an axial flow compressor.

Munson, Matthew; Rempfer, Dietmar; Williams, David; Acharya, Mukund

2003-11-01

70

Optimal control by least squares support vector machines.  

PubMed

Support vector machines have been very successful in pattern recognition and function estimation problems. In this paper we introduce the use of least squares support vector machines (LS-SVM's) for the optimal control of nonlinear systems. Linear and neural full static state feedback controllers are considered. The problem is formulated in such a way that it incorporates the N-stage optimal control problem as well as a least squares support vector machine approach for mapping the state space into the action space. The solution is characterized by a set of nonlinear equations. An alternative formulation as a constrained nonlinear optimization problem in less unknowns is given, together with a method for imposing local stability in the LS-SVM control scheme. The results are discussed for support vector machines with radial basis function kernel. Advantages of LS-SVM control are that no number of hidden units has to be determined for the controller and that no centers have to be specified for the Gaussian kernels when applying Mercer's condition. The curse of dimensionality is avoided in comparison with defining a regular grid for the centers in classical radial basis function networks. This is at the expense of taking the trajectory of state variables as additional unknowns in the optimization problem, while classical neural network approaches typically lead to parametric optimization problems. In the SVM methodology the number of unknowns equals the number of training data, while in the primal space the number of unknowns can be infinite dimensional. The method is illustrated both on stabilization and tracking problems including examples on swinging up an inverted pendulum with local stabilization at the endpoint and a tracking problem for a ball and beam system. PMID:11213211

Suykens, J A; Vandewalle, J; De Moor, B

2001-01-01

71

Genetically Distinct Glossina fuscipes fuscipes Populations in the Lake Kyoga Region of Uganda and Its Relevance for Human African Trypanosomiasis  

PubMed Central

Tsetse flies (Glossina spp.) are the sole vectors of Trypanosoma brucei—the agent of human (HAT) and animal (AAT) trypanosomiasis. Glossina fuscipes fuscipes (Gff) is the main vector species in Uganda—the only country where the two forms of HAT disease (rhodesiense and gambiense) occur, with gambiense limited to the northwest. Gff populations cluster in three genetically distinct groups in northern, southern, and western Uganda, respectively, with a contact zone present in central Uganda. Understanding the dynamics of this contact zone is epidemiologically important as the merger of the two diseases is a major health concern. We used mitochondrial and microsatellite DNA data from Gff samples in the contact zone to understand its spatial extent and temporal stability. We show that this zone is relatively narrow, extending through central Uganda along major rivers with south to north introgression but displaying no sex-biased dispersal. Lack of obvious vicariant barriers suggests that either environmental conditions or reciprocal competitive exclusion could explain the patterns of genetic differentiation observed. Lack of admixture between northern and southern populations may prevent the sympatry of the two forms of HAT disease, although continued control efforts are needed to prevent the recolonization of tsetse-free regions by neighboring populations.

Echodu, Richard; Sistrom, Mark; Hyseni, Chaz; Enyaru, John; Okedi, Loyce; Aksoy, Serap; Caccone, Adalgisa

2013-01-01

72

Adaptive support vector regression for UAV flight control.  

PubMed

This paper explores an application of support vector regression for adaptive control of an unmanned aerial vehicle (UAV). Unlike neural networks, support vector regression (SVR) generates global solutions, because SVR basically solves quadratic programming (QP) problems. With this advantage, the input-output feedback-linearized inverse dynamic model and the compensation term for the inversion error are identified off-line, which we call I-SVR (inversion SVR) and C-SVR (compensation SVR), respectively. In order to compensate for the inversion error and the unexpected uncertainty, an online adaptation algorithm for the C-SVR is proposed. Then, the stability of the overall error dynamics is analyzed by the uniformly ultimately bounded property in the nonlinear system theory. In order to validate the effectiveness of the proposed adaptive controller, numerical simulations are performed on the UAV model. PMID:20970303

Shin, Jongho; Jin Kim, H; Kim, Youdan

2011-01-01

73

Design and test of electromechanical actuators for thrust vector control  

NASA Technical Reports Server (NTRS)

New control mechanisms technologies are currently being explored to provide alternatives to hydraulic thrust vector control (TVC) actuation systems. For many years engineers have been encouraging the investigation of electromechanical actuators (EMA) to take the place of hydraulics for spacecraft control/gimballing systems. The rationale is to deliver a lighter, cleaner, safer, more easily maintained, as well as energy efficient space vehicle. In light of this continued concern to improve the TVC system, the Propulsion Laboratory at the NASA George C. Marshall Space Flight Center (MSFC) is involved in a program to develop electromechanical actuators for the purpose of testing and TVC system implementation. Through this effort, an electromechanical thrust vector control actuator has been designed and assembled. The design consists of the following major components: Two three-phase brushless dc motors, a two pass gear reduction system, and a roller screw, which converts rotational input into linear output. System control is provided by a solid-state electronic controller and power supply. A pair of resolvers and associated electronics deliver position feedback to the controller such that precise positioning is achieved. Testing and evaluation is currently in progress. Goals focus on performance comparisons between EMA's and similar hydraulic systems.

Cowan, J. R.; Weir, Rae Ann

1993-01-01

74

The FAO/IAEA DGIS Coordinated research programmes on trypanosomiasis diagnosis and animal production in Africa.  

PubMed

During the period 1987-1992, Professor Dick Zwart played a key role in guiding the work of two African research networks established by the Joint FAO/IAEA Division and supported financially by the Netherlands Directorate General of Development Co-operation. These networks brought together staff from African institutes involved in the diagnosis and control of trypanosomiasis and in animal production, with scientists from International Agricultural Research Centres and other advanced research institutions in the Netherlands and elsewhere. Through this approach, the value of recently-developed immunoassay methods was assessed for diagnosing trypanosomiasis and monitoring control programmes, and similar methods were used to monitor animal productivity and ways of improving this on small-holder farms. Furthermore it strengthened the portion together with the functioning of the national agriculture research institutions. This paper outlines the main technical and other accomplishments of these networks. PMID:8372426

Dargie, J D; Ooijen, C J; Plaizier, J C

1993-06-01

75

Drug Resistance in African Trypanosomiasis  

Microsoft Academic Search

\\u000a African trypanosomes include the causative agents of sleeping sickness in humans and those affecting live stock. Vaccination\\u000a being jeopardized by the ever-changing surface coats of bloodstream-form trypanosomes, chemotherapy is the mainstay in the\\u000a control of infections. However, the drugs in use are old, cause severe side effects, and their efficacy is undermined by the\\u000a emergence of drug-resistant trypanosomes. Reliable supply

Enock Matovu; Pascal Mäser

76

Interruption of vector transmission by native vectors and "the art of the possible"  

PubMed Central

In a recent article in the Reader’s Opinion, advantages and disadvantages of the certification processes of interrupted Chagas disease transmission (American trypanosomiasis) by native vector were discussed. Such concept, accepted by those authors for the case of endemic situations with introduced vectors, has been built on a long and laborious process by endemic countries and Subregional Initiatives for Prevention, Control and Treatment of Chagas, with Technical Secretariat of the Pan American Health Organization/World Health Organization, to create a horizon target and goal to concentrate priorities and resource allocation and actions. With varying degrees of sucess, which are not replaceable for a certificate of good practice, has allowed during 23 years to safeguard the effective control of transmission of Trypanosoma cruzi not to hundreds of thousands, but millions of people at risk conditions, truly “the art of the possible.”

Salvatella, Roberto; Irabedra, Pilar; Castellanos, Luis G

2013-01-01

77

Interruption of vector transmission by native vectors and "the art of the possible".  

PubMed

In a recent article in the Reader's Opinion, advantages and disadvantages of the certification processes of interrupted Chagas disease transmission (American trypanosomiasis) by native vector were discussed. Such concept, accepted by those authors for the case of endemic situations with introduced vectors, has been built on a long and laborious process by endemic countries and Subregional Initiatives for Prevention, Control and Treatment of Chagas, with Technical Secretariat of the Pan American Health Organization/World Health Organization, to create a horizon target and goal to concentrate priorities and resource allocation and actions. With varying degrees of sucess, which are not replaceable for a certificate of good practice, has allowed during 23 years to safeguard the effective control of transmission of Trypanosoma cruzi not to hundreds of thousands, but millions of people at risk conditions, truly "the art of the possible." PMID:24626310

Salvatella, Roberto; Irabedra, Pilar; Castellanos, Luis G

2014-02-01

78

Impulsive formation control using orbital energy and angular momentum vector  

NASA Astrophysics Data System (ADS)

This paper presents a multi-impulsive formation control strategy using orbit energy-matching and relative angular momentum vector between leader and follower satellites. These conservative parameters (energy and angular momentum) provide analytical and global solutions for orbital maneuver design without relying on Gauss variational equations. The relationship with orbit element differences is discussed in the simplifying assumptions. The proposed approach is free from small variation assumptions, so that it is suitable for handling even the case of large error corrections. General limitations of impulse control and associated compensation maneuvers are also addressed.

Choi, Yoonhyuk; Mok, Sunghoon; Bang, Hyochoong

2010-09-01

79

Underpinning Sustainable Vector Control through Informed Insecticide Resistance Management  

PubMed Central

Background There has been rapid scale-up of malaria vector control in the last ten years. Both of the primary control strategies, long-lasting pyrethroid treated nets and indoor residual spraying, rely on the use of a limited number of insecticides. Insecticide resistance, as measured by bioassay, has rapidly increased in prevalence and has come to the forefront as an issue that needs to be addressed to maintain the sustainability of malaria control and the drive to elimination. Zambia's programme reported high levels of resistance to the insecticides it used in 2010, and, as a result, increased its investment in resistance monitoring to support informed resistance management decisions. Methodology/Principal Findings A country-wide survey on insecticide resistance in Zambian malaria vectors was performed using WHO bioassays to detect resistant phenotypes. Molecular techniques were used to detect target-site mutations and microarray to detect metabolic resistance mechanisms. Anopheles gambiae s.s. was resistant to pyrethroids, DDT and carbamates, with potential organophosphate resistance in one population. The resistant phenotypes were conferred by both target-site and metabolic mechanisms. Anopheles funestus s.s. was largely resistant to pyrethroids and carbamates, with potential resistance to DDT in two locations. The resistant phenotypes were conferred by elevated levels of cytochrome p450s. Conclusions/Significance Currently, the Zambia National Malaria Control Centre is using these results to inform their vector control strategy. The methods employed here can serve as a template to all malaria-endemic countries striving to create a sustainable insecticide resistance management plan.

Hemmings, Kay; Hughes, Angela J.; Chanda, Emmanuel; Musapa, Mulenga; Kamuliwo, Mulakwa; Phiri, Faustina N.; Muzia, Lucy; Chanda, Javan; Kandyata, Alister; Chirwa, Brian; Poer, Kathleen; Hemingway, Janet; Wondji, Charles S.; Ranson, Hilary; Coleman, Michael

2014-01-01

80

Harnessing mosquito-Wolbachia symbiosis for vector and disease control.  

PubMed

Mosquito species, members of the genera Aedes, Anopheles and Culex, are the major vectors of human pathogens including protozoa (Plasmodium sp.), filariae and of a variety of viruses (causing dengue, chikungunya, yellow fever, West Nile). There is lack of efficient methods and tools to treat many of the diseases caused by these major human pathogens, since no efficient vaccines or drugs are available; even in malaria where insecticide use and drug therapies have reduced incidence, 219 million cases still occurred in 2010. Therefore efforts are currently focused on the control of vector populations. Insecticides alone are insufficient to control mosquito populations since reduced susceptibility and even resistance is being observed more and more frequently. There is also increased concern about the toxic effects of insecticides on non-target (even beneficial) insect populations, on humans and the environment. During recent years, the role of symbionts in the biology, ecology and evolution of insect species has been well-documented and has led to suggestions that they could potentially be used as tools to control pests and therefore diseases. Wolbachia is perhaps the most renowned insect symbiont, mainly due to its ability to manipulate insect reproduction and to interfere with major human pathogens thus providing new avenues for pest control. We herein present recent achievements in the field of mosquito-Wolbachia symbiosis with an emphasis on Aedes albopictus. We also discuss how Wolbachia symbiosis can be harnessed for vector control as well as the potential to combine the sterile insect technique and Wolbachia-based approaches for the enhancement of population suppression programs. PMID:24252486

Bourtzis, Kostas; Dobson, Stephen L; Xi, Zhiyong; Rasgon, Jason L; Calvitti, Maurizio; Moreira, Luciano A; Bossin, Hervé C; Moretti, Riccardo; Baton, Luke Anthony; Hughes, Grant L; Mavingui, Patrick; Gilles, Jeremie R L

2014-04-01

81

DSP-based vector and current controllers for a permanent magnet synchronous motor drive  

Microsoft Academic Search

The design of DSP-based vector and current controllers for a permanent magnet synchronous motor (PMSM) drive is presented. Several different implementations of the vector controller are evaluated, and the consequent effect on the maximum motor speed is examined. A careful choice of the cosine look-up table which is used in the vector controller is presented. The possibility of implementing a

P. Pillay; C. R. Allen; R. Budhabhathi

1990-01-01

82

Decoupling control of thrust and attractive force of a LIM using a space vector control inverter  

Microsoft Academic Search

A control method for magnetic levitation vehicles using linear induction motors which can generate both thrust and attractive force, is described. By selecting voltage vectors of PWM inverters appropriately, control with decoupling of the thrust and attractive force is achieved. Levitation control is accomplished by detecting the gap length and controlling the attractive force of each linear induction motor. Ultrasonic

Isao Takahashi; Yuji Ide

1993-01-01

83

On fuzzy logic speed control for vector controlled AC motors  

Microsoft Academic Search

The paper deals with the fuzzy logic control(ler) (FLC) application to the field-oriented AC motor drive. Some fundamentals of the FLC are illustrated. The aspects of major importance in the application to field-oriented AC motor drives are pointed out and discussed. A FLC field-oriented drive is designed, simulated and experimented in a speed control loop. The results are compared with

D. Fodor; Z. Katona; J. Vass

1996-01-01

84

Dengue vector control: present status and future prospects.  

PubMed

Dengue Fever (DF) and Dengue Haemorrhagic Fever (DHF) have been the most common urban diseases in Southeast Asia since the 1950s. More recently, the diseases have spread to Central and South America and are now considered as worldwide diseases. Both Aedes aegypti and Aedes albopictus are involved in the transmission of DF/DHF in Southeast Asian region. The paper discusses the present status and future prospects of Aedes control with reference to the Malaysian experience. Vector control approaches which include source reduction and environmental management, larviciding with the use of chemicals (synthetic insecticides and insect growth regulators and microbial insecticide), and adulticiding which include personal protection measures (household insecticide products and repellents) for long-term control and space spray (both thermal fogging and ultra low volume sprays) as short-term epidemic measures are discussed. The potential incorporation of IGRs and Bacillus thuringiensis-14 (Bti) as larvicides in addition to insecticides (temephos) is discussed. The advantages of using water-based spray over the oil-based (diesel) spray and the use of spray formulation which provide both larvicidal and adulticidal effects that would consequently have greater impact on the overall vector and disease control in DF/DHF are highlighted. PMID:7844836

Yap, H H; Chong, N L; Foo, A E; Lee, C Y

1994-12-01

85

Human African Trypanosomiasis Diagnosis in First-Line Health Services of Endemic Countries, a Systematic Review  

PubMed Central

While the incidence of Human African Trypanosomiasis (HAT) is decreasing, the control approach is shifting from active population screening by mobile teams to passive case detection in primary care centers. We conducted a systematic review of the literature between 1970 and 2011 to assess which diagnostic tools are most suitable for use in first-line health facilities in endemic countries. Our search retrieved 16 different screening and confirmation tests for HAT. The thermostable format of the Card Agglutination Test for Trypanosomiasis (CATT test) was the most appropriate screening test. Lateral flow antibody detection tests could become alternative screening tests in the near future. Confirmation of HAT diagnosis still depends on visualizing the parasite in direct microscopy. All other currently available confirmation tests are either technically too demanding and/or lack sensitivity and thus rather inappropriate for use at health center level. Novel applications of molecular tests may have potential for use at district hospital level.

Mitashi, Patrick; Hasker, Epco; Lejon, Veerle; Kande, Victor; Muyembe, Jean-Jacques; Lutumba, Pascal; Boelaert, Marleen

2012-01-01

86

Modelling the risk of being bitten by malaria vectors in a vector control area in southern Benin, west Africa  

PubMed Central

Background The diversity of malaria vector populations, expressing various resistance and/or behavioural patterns could explain the reduced effectiveness of vector control interventions reported in some African countries. A better understanding of the ecology and distribution of malaria vectors is essential to design more effective and sustainable strategies for malaria control and elimination. Here, we analyzed the spatio-temporal risk of the contact between humans and the sympatric An. funestus and both M and S molecular forms of An. gambiae s.s. in an area of Benin with high coverage of vector control measures with an unprecedented level of resolution. Methods Presence-absence data for the three vectors from 1-year human-landing collections in 19 villages were assessed using binomial mixed-effects models according to vector control measures and environmental covariates derived from field and remote sensing data. After 8-fold cross-validations of the models, predictive maps of the risk of the contact between humans and the sympatric An. funestus and both molecular M and S forms of An. gambiae s.s. were computed. Results Model validations showed that the An. funestus, An. gambiae M form, and S form models provided an excellent (Area Under Curve>0.9), a good (AUC>0.8), and an acceptable (AUC>0.7) level of prediction, respectively. The distribution area of the probability of contact between human and An. funestus largely overlaps that of An. gambiae M form but this latter showed important seasonal variation. An. gambiae S form also showed seasonal variation but with different ecological preferences. Landscape data were useful to discriminate between the species’ distributions. Conclusions These results showed that available remote sensing data could help in predicting the human-vector contact for several species of malaria vectors at a village level scale. The predictive maps showed seasonal and spatial variations in the risk of human-vector contact for all three vectors. Such maps could help Malaria Control Programmes to implement more effective vector control strategy by taking into account to the dynamics of malaria vector species.

2013-01-01

87

Vector control of induction machines using wavenet based controller for traction applications  

Microsoft Academic Search

In this paper induction motor and its vector control are simulated and a novel artificial neural network based on wavelets is used as controller in order to make the system more robust. The data for training the NN is extracted from the process with several PID set controller to achieve the best operation for all regions of the system operations.

H. Moghbelli; A. Rahideh; A. A. Safavi

2003-01-01

88

Multichannel vector field control module for LLRF control of superconducting cavities  

Microsoft Academic Search

The field control of multiple superconducting RF cavities with a single Klystron, such as the proposed RF scheme for the ILC, requires high density (number of RF channels) signal processing hardware so that vector control may be implemented with minimum group delay. The MFC (Multichannel Field Control) module is a 33- channel, FPGA based down-conversion and signal processing board in

P. Varghese; B. Chase; B. Barnes; J. Branlard; P. W. Joireman; D. Klepec; U. Mavric; V. Tupikov

2007-01-01

89

The Burden of Human African Trypanosomiasis  

PubMed Central

Human African trypanosomiasis (HAT, or sleeping sickness) is a protozoan parasitic infection caused by Trypanosoma brucei rhodesiense or Trypanosoma brucei gambiense. These are neglected tropical diseases, and T.b. rhodesiense HAT is a zoonosis. We review current knowledge on the burden of HAT in sub-Saharan Africa, with an emphasis on the disability-adjusted life year (DALY), data sources, and methodological issues relating to the use of this metric for assessing the burden of this disease. We highlight areas where data are lacking to properly quantify the impact of these diseases, mainly relating to quantifying under-reporting and disability associated with infection, and challenge the HAT research community to tackle the neglect in data gathering to enable better evidence-based assessments of burden using DALYs or other appropriate measures.

Fevre, Eric M.; Wissmann, Beatrix v.; Welburn, Susan C.; Lutumba, Pascal

2008-01-01

90

Silica nanoparticle: a potential new insecticide for mosquito vector control.  

PubMed

Presently, there is a need for increased efforts to develop newer and effective methods to control mosquito vectors as the existing chemical and biological methods are not as effective as in earlier period owing to different technical and operational reasons. The use of nanomaterial products in various sectors of science including health increased during the last decade. We tested three types of nanosilica, namely lipophilic, hydrophilic and hydrophobic, to assess their larvicidal, pupicidal and growth inhibitor properties and also their influence on oviposition behaviour (attraction/deterrence) of mosquito species that transmit human diseases, namely malaria (Anopheles), yellow fever, chickungunya and dengue (Aedes), lymphatic filariasis and encephalitis (Culex and Aedes). Application of hydrophobic nanosilica at 112.5 ppm was found effective against mosquito species tested. The larvicidal effect of hydrophobic nanosilica on mosquito species tested was in the order of Anopheles stephensi > Aedes aegypti > Culex quinquefasciatus, and the pupicidal effect was in the order of A. stephensi > C. quinquefasciatus > Ae. aegypti. Results of combined treatment of hydrophobic nanosilica with temephos in larvicidal test indicated independent toxic action without any additive effect. This is probably the first report that demonstrated that nanoparticles particularly nanosilica could be used in mosquito vector control. PMID:22565400

Barik, Tapan K; Kamaraju, Raghavendra; Gowswami, Arunava

2012-09-01

91

Mixture for controlling insecticide-resistant malaria vectors.  

PubMed

The spread of resistance to pyrethroids in the major Afrotropical malaria vectors Anopheles gambiae s.s. necessitates the development of new strategies to control resistant mosquito populations. To test the efficacy of nets treated with repellent and insecticide against susceptible and insecticide-resistant An. gambiae mosquito populations, we impregnated mosquito bed nets with an insect repellent mixed with a low dose of organophosphorous insecticide and tested them in a rice-growing area near Bobo-Dioulasso, Burkina Faso. During the first 2 weeks posttreatment, the mixture was as effective as deltamethrin alone and was more effective at killing An. gambiae that carried knockdown resistance (kdr) or insensitive acetylcholinesterase resistance (Ace1R) genes. The mixture seemed to not kill more susceptible genotypes for the kdr or Ace1R alleles. Mixing repellents and organophosphates on bed nets could be used to control insecticide-resistant malaria vectors if residual activity of the mixture is extended and safety is verified. PMID:18976553

Pennetier, Cédric; Costantini, Carlo; Corbel, Vincent; Licciardi, Séverine; Dabiré, Roch K; Lapied, Bruno; Chandre, Fabrice; Hougard, Jean-Marc

2008-11-01

92

Modeling and simulation of induction machine vector control with rotor resistance identification  

Microsoft Academic Search

This paper shows that it is possible to use available commercial software to model and simulate a vector-controlled induction machine system. The components of a typical vector control system are introduced and methods given for incorporating these in the MATLAB\\/SIMULINK software package. The identification of rotor resistance is important in vector control, if high-performance torque control is needed, and modeling

Scott Wade; Matthew W. Dunnigan; Barry W. Williams

1997-01-01

93

Static Compaction Techniques to Control Scan Vector Power Dissipation  

Microsoft Academic Search

Excessive switching activity during scan testing can cause average power dissipation and peak power during test to be much higher than during normal operation. This can cause problems both with heat dissipation and with current spikes. Compacting scan vectors greatly increases the power dissipation for the vectors (generally the power becomes several times greater). The compacted scan vectors often can

Ranganathan Sankaralingam; Rama Rao Oruganti; Nur A. Touba

2000-01-01

94

Space transportation system solid rocket booster thrust vector control system  

NASA Technical Reports Server (NTRS)

The Solid Rocket Booster, Thrust Vector Control (TVC) system was designed in accordance with the following requirements: self-contained power supply, fail-safe operation, 20 flight uses after exposure to seawater landings, optimized cost, and component interchangeability. Trade studies were performed which led to the selection of a recirculating hydraulic system powered by Auxiliary Power Units (APU) which drive the hydraulic actuators and gimbal the solid rocket motor nozzle. Other approaches for the system design were studied in arriving at the recirculating hydraulic system powered by an APU. These systems must withstand the imposed environment and be usable for a minimum of 20 Space Transportation System flights with a minimum of refurbishment. The TVC system has completed the major portion of qualification and verification tests and is prepared to be cleared for the first Shuttle flight (STS-1). Substantiation data will include analytical and test data.

Verble, A. J., Jr.; Mccool, A. A.; Potter, J. H.

1979-01-01

95

Trapping volume control in optical tweezers using cylindrical vector beams.  

PubMed

We present the result of an investigation into the optical trapping of spherical microparticles using laser beams with a spatially inhomogeneous polarization direction [cylindrical vector beams (CVBs)]. We perform three-dimensional tracking of the Brownian fluctuations in the position of a trapped particle and extract the trap spring constants. We characterize the trap geometry by the aspect ratio of spring constants in the directions transverse and parallel to the beam propagation direction and evaluate this figure of merit as a function of polarization angle. We show that the additional degree of freedom present in CVBs allows us to control the optical trap strength and geometry by adjusting only the polarization of the trapping beam. Experimental results are compared with a theoretical model of optical trapping using CVBs derived from electromagnetic scattering theory in the T-matrix framework. PMID:23282827

Skelton, S E; Sergides, M; Saija, R; Iatì, M A; Maragó, O M; Jones, P H

2013-01-01

96

FPGA implementation of space vector PWM for speed control of 3-phase induction motor  

Microsoft Academic Search

Advancements in solid state and Programmable Logic Devices have given a tremendous support to digital control techniques for speed control of motors. Space Vector PWM (SVPWM) is a sophisticated technique for generating a sine wave that provides a higher source voltage utilization and lower total harmonic distortion. Also, it is inherently suitable for digital implementation of vector control (Field Oriented

Aishanou Osha Rait; Praveen Bhosale

2011-01-01

97

Efficacy of local neem extracts for sustainable malaria vector control in an African village  

Microsoft Academic Search

BACKGROUND: Larval control of malaria vectors has been historically successful in reducing malaria transmission, but largely fell out of favour with the introduction of synthetic insecticides and bed nets. However, an integrated approach to malaria control, including larval control methods, continues to be the best chance for success, in view of insecticide resistance, the behavioural adaptation of the vectors to

Rebecca L Gianotti; Arne Bomblies; Mustafa Dafalla; Ibrahim Issa-Arzika; Jean-Bernard Duchemin; Elfatih AB Eltahir

2008-01-01

98

Design Three-phase Asynchronous Motor's Vector Control System Based on DSP  

Microsoft Academic Search

Better to meet the high performance AC speed adjustable speed control strategies and advanced control algorithms in the application of asynchronous motor, Introduced the hardware and software design of asynchronous motor control system development platform based on TMS320F2812.Discussed the vector control system for three-phase Asynchronous motor which use this platform as the control core, described the vector control principle and

Junyi Shen; Wenguang Luo; Chengwu Yang; Deliang Meng

2011-01-01

99

Trypanosomiasis, cardiomyopathy and the risk of ischemic stroke.  

PubMed

American (Chagas disease) and African (sleeping sickness) trypanosomiasis are neglected tropical diseases and are a heavy burden in Latin America and Africa, respectively. Chagas disease is an independent risk factor for stroke. Apical aneurysm, heart failure and cardiac arrhythmias are associated with ischemic stroke in chagasic cardiomyopathy. Not all chagasic patients who suffer an ischemic stroke have a severe cardiomyopathy, and stroke may be the first manifestation of Chagas disease. Cardioembolism affecting the middle cerebral artery is the most common stroke subtype. Risk of recurrence is high and careful evaluation of recurrence risk should be addressed. Repolarization changes, low voltage and prolonged QT interval are common electrocardiography alterations in human African trypanosomiasis, and can be found in more than 70% of patients. Epidemiological studies are needed to asses the risk of stroke in African trypanosomiasis perimyocarditis. PMID:20450304

Carod-Artal, Francisco Javier

2010-05-01

100

Importance of L-tryptophan metabolism in trypanosomiasis.  

PubMed

African trypanosomiasis or sleeping sickness is caused by extracellular trypanosomes. The presence of seric antibodies directed to a tryptophan-like epitope in trypanosome infected patients and animals led us to investigate the roles of tryptophan in trypanosomiasis. These antibodies are directed against a tryptophan-rich conserved sequence inside the major parasite surface glycoprotein. In vitro, a rapid uptake of tryptophan by trypanosomes is measured. Seric tryptophan levels are decreased during trypanosomiasis. This decrease may be linked with an increase in indoleamine 2,3-dioxygenase (IDO) induced by Interferon-gamma. In vivo inhibition of IDO by norharman provokes a dramatic increase in circulating parasite number. All these data show the essential role of tryptophan in parasite growth. Moreover, antibodies against tryptophan, the decreased concentration of the neurotransmitter serotonin in the brain following infection and the tryptophan metabolites (tryptophol) produced by trypanosomes may participate to the pathophysiological mechanisms provoking sleeping sickness. PMID:10721096

Vincendeau, P; Lesthelle, S; Bertazzo, A; Okomo-Assoumou, M C; Allegri, G; Costa, C V

1999-01-01

101

Using a Geographical-Information-System-Based Decision Support to Enhance Malaria Vector Control in Zambia  

PubMed Central

Geographic information systems (GISs) with emerging technologies are being harnessed for studying spatial patterns in vector-borne diseases to reduce transmission. To implement effective vector control, increased knowledge on interactions of epidemiological and entomological malaria transmission determinants in the assessment of impact of interventions is critical. This requires availability of relevant spatial and attribute data to support malaria surveillance, monitoring, and evaluation. Monitoring the impact of vector control through a GIS-based decision support (DSS) has revealed spatial relative change in prevalence of infection and vector susceptibility to insecticides and has enabled measurement of spatial heterogeneity of trend or impact. The revealed trends and interrelationships have allowed the identification of areas with reduced parasitaemia and increased insecticide resistance thus demonstrating the impact of resistance on vector control. The GIS-based DSS provides opportunity for rational policy formulation and cost-effective utilization of limited resources for enhanced malaria vector control.

Chanda, Emmanuel; Mukonka, Victor Munyongwe; Mthembu, David; Kamuliwo, Mulakwa; Coetzer, Sarel; Shinondo, Cecilia Jill

2012-01-01

102

Prevalence of trypanosomiasis in cattle in south-west Zambia.  

PubMed

A trypanosomiasis survey was conducted in South-West Zambia. From a total of 3,346 cattle sampled 342 cattle showed a positive trypanosomiasis parasitaemia. During the survey trypanosome species and PCV values were also recorded. With simple statistical analysis populations with higher and lower prevalence rates were differentiated. The results indicated that the Kwando River Basin Tsetse Fly Belt and the Kafue River Basin Tsetse Fly Belt infested a larger area than originally assumed and that a link-up between both belts occurred or will occur in the near future. PMID:3400114

Corten, J J; ter Huurne, A A; Moorhouse, P D; de Rooij, R C

1988-05-01

103

The use of attractants and repellents in vector control.  

PubMed

A great many stimuli-auditory, visual and chemical-attract or repel insects and some of these play an essential role in maintaining the life of the individual or perpetuating the species. The author examines the modes of action of attractants in nature, particularly in relation to blood feeding. The predominant mechanism of attraction to an odour source (e.g., in host finding) appears to be positive anemotaxis. Success in locating the source is influenced by wind conditions and by the visual acuity and field of view of the insect. The author considers the physical and chemical properties of materials that have been widely used as attractants and repellents and indicates the unsatisfactory nature of present theories to explain their action. Possible applications of attractants in vector control include their use in traps, baits and sprays, while repellents are mainly of value for personal protection. Increased understanding of the mechanism of action is likely to lead to the development of much more effective materials and to their wider application. PMID:20604160

Hocking, B

1963-01-01

104

Spray Characterization of Ultra-Low-Volume Sprayers Typically Used in Vector Control.  

National Technical Information Service (NTIS)

Numerous spray machines are used to apply pesticides for the control of human disease vectors, such as mosquitoes and flies, and the selection and setup of these machines significantly affects the level of control achieved during an application. The dropl...

B. K. Fritz M. Farooq T. W. Walker V. L. Smith W. C. Hoffmann

2009-01-01

105

GA-Based Optimization of PI Speed Controller Coefficients for ANN-Modelled Vector Controlled Induction Motor  

NASA Astrophysics Data System (ADS)

This study proposes a new approach to indirect vector controlled induction motor drives. Induction motor drives for variable speed have many common industrial applications. An application of Artificial Neural Network (ANN) and genetic algorithms on vector control are carried out using space vector pulse width modulation in this study. Proportional plus derivative (PI) controller is used to control speed of induction motor. In this study, optimization of PI coefficients in vector control is carried out by ANN-Genetic. These controllers are applied to drive system with 0.55 kW induction motor. A Digital Signal Processor Controller (dsPIC30F6010) was used to carry out control applications. It is suitable to control induction motor as a soft starter and speed adjustment in compressors, blowers, fans, pumps and many other applications.

Vakkas Ustun, Seydi

106

High-speed current dq PI controller for vector controlled PMSM drive.  

PubMed

High-speed current controller for vector controlled permanent magnet synchronous motor (PMSM) is presented. The controller is developed based on modular design for faster calculation and uses fixed-point proportional-integral (PI) method for improved accuracy. Current dq controller is usually implemented in digital signal processor (DSP) based computer. However, DSP based solutions are reaching their physical limits, which are few microseconds. Besides, digital solutions suffer from high implementation cost. In this research, the overall controller is realizing in field programmable gate array (FPGA). FPGA implementation of the overall controlling algorithm will certainly trim down the execution time significantly to guarantee the steadiness of the motor. Agilent 16821A Logic Analyzer is employed to validate the result of the implemented design in FPGA. Experimental results indicate that the proposed current dq PI controller needs only 50 ns of execution time in 40 MHz clock, which is the lowest computational cycle for the era. PMID:24574913

Marufuzzaman, Mohammad; Reaz, Mamun Bin Ibne; Rahman, Labonnah Farzana; Chang, Tae Gyu

2014-01-01

107

Vector control programs in Saint Johns County, Florida and Guayas, Ecuador: successes and barriers to integrated vector management  

PubMed Central

Background Vector-borne diseases (VBDs) and mosquito control programs (MCPs) diverge in settings and countries, and lead control specialists need to be aware of the most effective control strategies. Integrated Vector Management (IVM) strategies, once implemented in MCPs, aim to reduce cost and optimize protection of the populations against VBDs. This study presents a strengths, weaknesses, opportunities, and threats (SWOT) analysis to compare IVM strategies used by MCPs in Saint Johns County, Florida and Guayas, Ecuador. This research evaluates MCPs strategies to improve vector control activities. Methods Methods included descriptive findings of the MCP operations. Information was obtained from vector control specialists, directors, and residents through field trips, surveys, and questionnaires. Evaluations of the strategies and assets of the control programs where obtained through SWOT analysis and within an IVM approach. Results Organizationally, the Floridian MCP is a tax-based District able to make decisions independently from county government officials, with the oversight of an elected board of commissioners. The Guayas program is directed by the country government and assessed by non-governmental organizations like the World health Organization. Operationally, the Floridian MCP conducts entomological surveillance and the Ecuadorian MCP focuses on epidemiological monitoring of human disease cases. Strengths of both MCPs were their community participation and educational programs. Weaknesses for both MCPs included limitations in budgets and technical capabilities. Opportunities, for both MCPs, are additional funding and partnerships with private, non-governmental, and governmental organizations. Threats experienced by both MCPs included political constraints and changes in the social and ecological environment that affect mosquito densities and control efforts. IVM pillars for policy making were used to compare the information among the programs. Differences included how the Ecuadorian MCP relies heavily on the community for vector control while the American MCP relies on technologies and research. Conclusion IVM based recommendations direct health policy leaders toward improving surveillance systems both entomologically and epidemiologically, improving community risk perceptions by integrating components of community participation, maximizing resources though the use of applied research, and protecting the environment by selecting low-risk pesticides. Outcomes of the research revealed that inter-sectorial and multidisciplinary interventions are critical to improve public health.

2014-01-01

108

Double Inverted Pendulum Control Based on Support Vector Machines and Fuzzy Inference  

Microsoft Academic Search

\\u000a In this paper, a fuzzy inference system based on support vector machi- nes is proposed for nonlinear system control. Support\\u000a vector machines provides a mechanism to extract support vectors for generating fuzzy if-then rules from the training data\\u000a set, and a method to describe the fuzzy inference system in terms of kernel functions. Thus it has the inherent advantages\\u000a that

Han Liu; Haiyan Wu; Fucai Qian

2006-01-01

109

Vector transmission regulates immune control of Plasmodium virulence  

PubMed Central

Defining mechanisms by which Plasmodium virulence is regulated is central to understanding the pathogenesis of human malaria. Serial blood passage of Plasmodium through rodents1-3, primates4 or humans5 increases parasite virulence, suggesting that vector transmission regulates Plasmodium virulence within the mammalian host. In agreement, disease severity can be modified by vector transmission6-8, which is assumed to ‘reset’ Plasmodium to its original character3. However, direct evidence that vector transmission regulates Plasmodium virulence is lacking. Here we utilise mosquito transmission of serially blood passaged (SBP) Plasmodium chabaudi chabaudi9 to interrogate regulation of parasite virulence. Analysis of SBP P.c. chabaudi before and after mosquito transmission demonstrates that vector transmission intrinsically modifies the asexual blood-stage parasite, which in turn, modifies the elicited mammalian immune response, which in turn, attenuates parasite growth and associated pathology. Attenuated parasite virulence associates with modified expression of the pir multi-gene family. Vector transmission of Plasmodium therefore regulates gene expression of probable variant antigens in the erythrocytic cycle, modifies the elicited mammalian immune response, and thus regulates parasite virulence. These results place the mosquito at the centre of our efforts to dissect mechanisms of protective immunity to malaria for the development of an effective vaccine.

Spence, Philip J.; Jarra, William; Levy, Prisca; Reid, Adam J.; Chappell, Lia; Brugat, Thibaut; Sanders, Mandy; Berriman, Matthew; Langhorne, Jean

2013-01-01

110

Vector transmission regulates immune control of Plasmodium virulence.  

PubMed

Defining mechanisms by which Plasmodium virulence is regulated is central to understanding the pathogenesis of human malaria. Serial blood passage of Plasmodium through rodents, primates or humans increases parasite virulence, suggesting that vector transmission regulates Plasmodium virulence within the mammalian host. In agreement, disease severity can be modified by vector transmission, which is assumed to 'reset' Plasmodium to its original character. However, direct evidence that vector transmission regulates Plasmodium virulence is lacking. Here we use mosquito transmission of serially blood passaged (SBP) Plasmodium chabaudi chabaudi to interrogate regulation of parasite virulence. Analysis of SBP P.?c.?chabaudi before and after mosquito transmission demonstrates that vector transmission intrinsically modifies the asexual blood-stage parasite, which in turn modifies the elicited mammalian immune response, which in turn attenuates parasite growth and associated pathology. Attenuated parasite virulence associates with modified expression of the pir multi-gene family. Vector transmission of Plasmodium therefore regulates gene expression of probable variant antigens in the erythrocytic cycle, modifies the elicited mammalian immune response, and thus regulates parasite virulence. These results place the mosquito at the centre of our efforts to dissect mechanisms of protective immunity to malaria for the development of an effective vaccine. PMID:23719378

Spence, Philip J; Jarra, William; Lévy, Prisca; Reid, Adam J; Chappell, Lia; Brugat, Thibaut; Sanders, Mandy; Berriman, Matthew; Langhorne, Jean

2013-06-13

111

Determining the spatial autocorrelation of dengue vector populations: influences of mosquito sampling method, covariables, and vector control.  

PubMed

We investigated spatial autocorrelation of female Aedes aegypti L. mosquito abundance from BG-Sentinel trap and sticky ovitrap collections in Cairns, north Queensland, Australia. BG-Sentinel trap collections in 2010 show a significant spatial autocorrelation across the study site and over a smaller spatial extent, while sticky ovitrap collections only indicate a non-significant, weak spatial autocorrelation. The BG-Sentinel trap collections were suitable for spatial interpolation using ordinary kriging and cokriging techniques. The uses of Premise Condition Index and potential breeding container data have helped improve our prediction of vector abundance. Semiovariograms and prediction maps indicate that the spatial autocorrelation of mosquito abundance determined by BG-Sentinel traps extends farther compared to sticky ovitrap collections. Based on our data, fewer BG-Sentinel traps are required to represent vector abundance at a series of houses compared to sticky ovitraps. A lack of spatial structure was observed following vector control treatment in the area. This finding has implications for the design and costs of dengue vector surveillance programs. PMID:24820568

Azil, Aishah H; Bruce, David; Williams, Craig R

2014-06-01

112

Adaptative Variable Structure Control for an Online Tuning Direct Vector Controlled Induction Motor Drives  

NASA Astrophysics Data System (ADS)

This study demonstrates that high performance speed control can be obtained by using an adaptative sliding mode control method for a direct vector controlled Squirrel Cage Induction Motor (SCIM). In this study a new method of designing a simple and effective adaptative sliding mode rotational speed control law is developed. The design includes an accurate sliding mode flux observation from the measured stator terminals and rotor speed. The performance of the Direct Field-Orientation Control (DFOC) is ensured by online tuning based on a Model Reference Adaptative System (MRAS) rotor time constant estimator. The control strategy is derived in the sense of Lyapunov stability theory so that the stable tracking performance can be guaranteed under the occurrence of system uncertainties and external disturbances. The proposed scheme is a solution for a robust and high performance induction motor servo drives. Simulation results are provided to validate the effectiveness and robustness of the developed methodology.

Lasaad, Sbita; Dalila, Zaltni; Naceurq, Abdelkrim Mohamed

113

African trypanosomiasis: Sensitive and rapid detection of the sub-genus Trypanozoon by loop-mediated isothermal amplification (LAMP) of parasite DNA  

Microsoft Academic Search

Control of human African trypanosomiasis (HAT) is dependent on accurate diagnosis and treatment of infected patients. However, sen- sitivities of tests in routine use are unsatisfactory, due to the characteristically low parasitaemias in naturally infected individuals. We have identified a conserved sequence in the repetitive insertion mobile element (RIME) of the sub-genus Trypanozoon and used it to design prim- ers

Z. K. Njiru; A. S. J. Mikosza; E. Matovu; J. C. K. Enyaru; J. O. Ouma; S. N. Kibona; R. C. A. Thompson

2007-01-01

114

Accuracy of Five Algorithms to Diagnose Gambiense Human African Trypanosomiasis  

PubMed Central

Background Algorithms to diagnose gambiense human African trypanosomiasis (HAT, sleeping sickness) are often complex due to the unsatisfactory sensitivity and/or specificity of available tests, and typically include a screening (serological), confirmation (parasitological) and staging component. There is insufficient evidence on the relative accuracy of these algorithms. This paper presents estimates of the accuracy of five algorithms used by past Médecins Sans Frontières programmes in the Republic of Congo, Southern Sudan and Uganda. Methodology and Principal Findings The sequence of tests in each algorithm was programmed into a probabilistic model, informed by distributions of the sensitivity, specificity and staging accuracy of each test, constructed based on a literature review. The accuracy of algorithms was estimated in a baseline scenario and in a worst-case scenario introducing various near worst-case assumptions. In the baseline scenario, sensitivity was estimated as 85–90% in all but one algorithm, with specificity above 99.9% except for the Republic of Congo, where CATT serology was used as independent confirmation test: here, positive predictive value (PPV) was estimated at <50% in realistic active screening prevalence scenarios. Furthermore, most algorithms misclassified about one third of true stage 1 cases as stage 2, and about 10% of true stage 2 cases as stage 1. In the worst-case scenario, sensitivity was 75–90% and PPV no more than 75% at 1% prevalence, with about half of stage 1 cases misclassified as stage 2. Conclusions Published evidence on the accuracy of widely used tests is scanty. Algorithms should carefully weigh the use of serology alone for confirmation, and could enhance sensitivity through serological suspect follow-up and repeat parasitology. Better evidence on the frequency of low-parasitaemia infections is needed. Simulation studies should guide the tailoring of algorithms to specific scenarios of HAT prevalence and availability of control tools.

Checchi, Francesco; Chappuis, Francois; Karunakara, Unni; Priotto, Gerardo; Chandramohan, Daniel

2011-01-01

115

Ethical, legal and social issues in the use of genetically modified vectors for disease control  

Microsoft Academic Search

Genetic control of vectors may have an important role to play in the interruption of vector-borne disease transmission if the main biotechnological and implementation challenges are adequately addressed. Following the demonstration, in the laboratory, of the technical feasibility to develop transgenic mosquitoes unable to transmit malaria and dengue pathogens, the following actions will need to be taken in order to

Yeya T. Touré; Lucien Manga

116

Framework for Computer Numerical Control Machine Code Generation from Vector Data  

Microsoft Academic Search

This Paper presents the framework for Computer Numerical Control (CNC) Machine code generation from the vector data. Two standard vector data formats are Drawing Exchange Format (DXF) and Initial Graphics Exchange Specification (IGES). Data exchange between these formats has been implemented as first phase in this project; when parameter of an entity in one format is different to other then

Yasir Nawazish Ali; Syed M. Jafar Rizvi; Ghulam Mustafa; Muhammad Imran

117

A combined gate replacement and input vector control approach for leakage current reduction  

Microsoft Academic Search

Due to the increasing role of leakage power in CMOS circuit's total power dissipation, leakage reduction has attracted a lot of attention recently. Input vector control (IVC) takes advantage of the transistor stack effect to apply the minimum leakage vector (MLV) to the primary inputs of the circuit during the standby mode. However, IVC techniques become less effective for circuits

Lin Yuan; Gang Qu

2006-01-01

118

Switching-based fault-tolerant control for an F-16 aircraft with thrust vectoring  

Microsoft Academic Search

Thrust vectoring technique enables aircraft to perform various maneuvers not available to conventional-engined planes. This paper presents an application of switching control concepts to fault-tolerant control design for an F-16 aircraft model augmented with thrust vectoring. Two controllers are synthesized using a switching logic, and they are switched on a fault parameter. During normal flight conditions, the F-16 aircraft relies

Bei Lu; Fen Wu

2009-01-01

119

Subolesin/Akirin vaccines for the control of arthropod vectors and vectorborne pathogens.  

PubMed

Diseases transmitted by arthropod vectors such as mosquitoes, ticks and sand flies greatly impact human and animal health, and therefore, their control is important for the eradication of vectorborne diseases (VBD). Vaccination is an environmentally friendly alternative for vector control that allows control of several VBD by targeting their common vector. Recent results have suggested that subolesin (SUB) and its orthologue in insects, akirin (AKR) are good candidate antigens for the control of arthropod vector infestations and pathogen infection. SUB was discovered as a tick-protective antigen in Ixodes scapularis. Vaccination trials with recombinant SUB/AKR demonstrated effective control of arthropod vector infestations in various hard and soft tick species, mosquitoes, sand flies, poultry red mites and sea lice by reducing their numbers, weight, oviposition, fertility and/or moulting. SUB/AKR vaccination also reduced tick infection with tickborne pathogens, Anaplasma phagocytophilum, A. marginale, Babesia bigemina and Borrelia burgdorferi. The effect of vaccination on different hosts, vector species, developmental stages and vectorborne pathogen infections demonstrated the feasibility of SUB/AKR universal vaccines for the control of multiple vector infestations and for reduction in VBD. PMID:24589118

de la Fuente, J; Moreno-Cid, J A; Galindo, R C; Almazan, C; Kocan, K M; Merino, O; Perez de la Lastra, J M; Estrada-Peña, A; Blouin, E F

2013-11-01

120

Is the Even Distribution of Insecticide-Treated Cattle Essential for Tsetse Control? Modelling the Impact of Baits in Heterogeneous Environments  

Microsoft Academic Search

BackgroundEliminating Rhodesian sleeping sickness, the zoonotic form of Human African Trypanosomiasis, can be achieved only through interventions against the vectors, species of tsetse (Glossina). The use of insecticide-treated cattle is the most cost-effective method of controlling tsetse but its impact might be compromised by the patchy distribution of livestock. A deterministic simulation model was used to analyse the effects of

Steve J. Torr; Glyn A. Vale

2011-01-01

121

Multichannel vector field control module for LLRF control of superconducting cavities  

SciTech Connect

The field control of multiple superconducting RF cavities with a single Klystron, such as the proposed RF scheme for the ILC, requires high density (number of RF channels) signal processing hardware so that vector control may be implemented with minimum group delay. The MFC (Multichannel Field Control) module is a 33-channel, FPGA based down-conversion and signal processing board in a single VXI slot, with 4 channels of high speed DAC outputs. A 32-bit, 400MHz floating point DSP provides additional computational and control capability for calibration and implementation of more complex control algorithms. Multiple high speed serial transceivers on the front panel and the backplane bus allow a flexible architecture for inter-module real time data exchanges. An interface CPLD supports the VXI bus protocol for communication to a Slot0 CPU, with Ethernet connections for remote in system programming of the FPGA and DSP as well as data acquisition.

Varghese, P; Chase, B.; Barnes, B.; Branlard, J.; Joireman, P.W.; Klepec, D.; Mavric, U.; Tupikov, V.; /Fermilab

2007-06-01

122

Insecticide Control of Vector-Borne Diseases: When Is Insecticide Resistance a Problem?  

PubMed Central

Many of the most dangerous human diseases are transmitted by insect vectors. After decades of repeated insecticide use, all of these vector species have demonstrated the capacity to evolve resistance to insecticides. Insecticide resistance is generally considered to undermine control of vector-transmitted diseases because it increases the number of vectors that survive the insecticide treatment. Disease control failure, however, need not follow from vector control failure. Here, we review evidence that insecticide resistance may have an impact on the quality of vectors and, specifically, on three key determinants of parasite transmission: vector longevity, competence, and behaviour. We argue that, in some instances, insecticide resistance is likely to result in a decrease in vector longevity, a decrease in infectiousness, or in a change in behaviour, all of which will reduce the vectorial capacity of the insect. If this effect is sufficiently large, the impact of insecticide resistance on disease management may not be as detrimental as previously thought. In other instances, however, insecticide resistance may have the opposite effect, increasing the insect's vectorial capacity, which may lead to a dramatic increase in the transmission of the disease and even to a higher prevalence than in the absence of insecticides. Either way—and there may be no simple generality—the consequence of the evolution of insecticide resistance for disease ecology deserves additional attention.

Rivero, Ana; Vezilier, Julien; Weill, Mylene; Read, Andrew F.; Gandon, Sylvain

2010-01-01

123

Vector control of permanent magnet synchronous motor based on matrix converter  

Microsoft Academic Search

A matrix converter (MC) based vector control of permanent magnet synchronous motor (PMSM) with current hysteresis control is designed. Signals of current hysteresis controller and selection of input voltages are analyzed in detail. How to decide on or off of power switch of matrix converter under current hysteresis control is also deduced in this paper. Finally, simulating model of the

Weijie Lin; Qiuxuan Wu

2011-01-01

124

Control of arbovirus diseases: is the vector the weak link?  

Microsoft Academic Search

Arthropod-borne virus (arbovirus) diseases (ABVDs) remain major threats to human health and well-being and, as an epidemiologic\\u000a group, inflict an unacceptable health and economic burden on humans and animals, including livestock. The developed world\\u000a has been fortunate to have escaped much of the burden that arboviruses and their arthropod vectors inflict on humans in disease\\u000a endemic countries, but the introduction

B. J. Beaty

125

A V2G vector control model of electric car charging and discharging machine  

Microsoft Academic Search

circuit topology structure of electric vehicle charging and discharging inverter based on space vector is presented. The control strategy uses rotation vector of the directional three-phase active tide reversible PWM converter, and the circuit topology is two-way control DC\\/DC converter with double buck reversible structure. In order to improve the efficiency of the charging and discharging machine, the main circuit

Xiaolei Wang; Pan Yan; Liang Yang; Wendao Yao; Guangwen Shi

2011-01-01

126

Evaluation and modelling of cross saturation due to leakage flux in vector controlled induction machines  

Microsoft Academic Search

A detailed magnetic, reluctance based, computational model of an induction machine into which a traditional, rotor-flux-orientated, vector, control-scheme has been grafted, is used to examine the influence of saturation of both main and leakage flux paths upon vector controlled drive performance. Individual machine teeth, windings and conductors are incorporated, as is pseudo 3 dimensional modelling of skew. The cross saturation

Chris Gerada; Keith Bradley; Mark Sumner; Phil Sewell

2003-01-01

127

Evaluation and Modeling of Cross Saturation Due to Leakage Flux in Vector-Controlled Induction Machines  

Microsoft Academic Search

A detailed magnetic reluctance-based computational model of an induction machine, into which a traditional rotor-flux-orientated vector control scheme has been grafted, is used to examine the influence of saturation of both main and leakage flux paths upon vector-controlled drive performance. Individual machine teeth, windings, and conductors are incorporated, as is pseudo-3-D modeling of skew. The cross-saturation effect is therefore determined

Chris Gerada; Keith J. Bradley; Mark Sumner; Phillip Sewell

2007-01-01

128

Microprocessor-Based Vector Control System for Induction Motor Drives with Rotor Time Constant Identification Function  

Microsoft Academic Search

A microprocessor-based high-performance vector control system for induction motor drives is discussed. In this system the high-performance current control method is employed, which can operate stably even when the saturation of a supplied voltage occurs. To estimate the rotor flux vector accurately, the powerful identification method of the rotor time constant is investigated, which does not require additional sensors for

Masato Koyama; Masao Yano; Isao Kamiyama; Sadanari Yano

1986-01-01

129

Progress of partial integration of malaria control with other vector borne diseases control in northern Thailand.  

PubMed

Thailand partially integrated the malaria program into the provincial and local Public Health system starting in 2003 by adding it to the control of other vector borne diseases and by transferring some activities to the Public Health Department. This study evaluates the results of this transfer on 8 high malaria incidence districts of Mae Hong Son and Chiang Mai Provinces. Indicators were measured for all community hospitals, Vector Borne Disease Control Units, (VBDU), health centers (HC), malaria clinics, and malaria posts in 2003 and 2004 during the first two years of partial integration. The number of Vector Borne Disease Control staff decreased 1.8 - 3%, and their operational budgets decreased 25%. The VBDU staff did all the indoor residual spraying (IRS), insecticide treated net (ITN) work and entomology surveys, they took 80.6% of the blood films, and treated 72% of the patients, while Public Health system did the remainder. The Annual Parasite Incidence (API) (1 - 10/1,000) and IRS coverage (88 - 100%) remained adequate in most areas during the first years after partial integration, but the API increased (to 31.6 - 57.6/1,000) in some populations. The percentage of insecticide treated bed net coverage was adequate in Mae Hong Son (95.4%), but inadequate in Chiang Mai (52.2%). Early diagnosis and prompt treatment (4 - 23 days), hospitals reporting disruption of anti-malarial drugs (3 of 7), and health centers having all needed equipment, training, and drugs for malaria diagnosis (9%) remain inadequate. If the program is allowed to diminish, malaria could spread again among the population. Integration of antimalarial activities into the general Public Health system has only been partially successful. We recommend the integration process and results should be monitored and evaluated to find and mitigate problems as they occur, and modify the integration process if needed. PMID:21329301

Suwonkerd, Wannapa; Vryheid, Robert; Suwannachote, Nantawan

2010-11-01

130

Developmental Testing of Electric Thrust Vector Control Systems for Manned Launch Vehicle Applications  

NASA Technical Reports Server (NTRS)

This paper describes recent developmental testing to verify the integration of a developmental electromechanical actuator (EMA) with high rate lithium ion batteries and a cross platform extensible controller. Testing was performed at the Thrust Vector Control Research, Development and Qualification Laboratory at the NASA George C. Marshall Space Flight Center. Electric Thrust Vector Control (ETVC) systems like the EMA may significantly reduce recurring launch costs and complexity compared to heritage systems. Electric actuator mechanisms and control requirements across dissimilar platforms are also discussed with a focus on the similarities leveraged and differences overcome by the cross platform extensible common controller architecture.

Bates, Lisa B.; Young, David T.

2012-01-01

131

Status of pesticide management in the practice of vector control: a global survey in countries at risk of malaria or other major vector-borne diseases  

PubMed Central

Background It is critical that vector control pesticides are used for their acceptable purpose without causing adverse effects on health and the environment. This paper provides a global overview of the current status of pesticides management in the practice of vector control. Methods A questionnaire was distributed to WHO member states and completed either by the director of the vector-borne disease control programme or by the national manager for vector control. In all, 113 countries responded to the questionnaire (80% response rate), representing 94% of the total population of the countries targeted. Results Major gaps were evident in countries in pesticide procurement practices, training on vector control decision making, certification and quality control of pesticide application, monitoring of worker safety, public awareness programmes, and safe disposal of pesticide-related waste. Nevertheless, basic conditions of policy and coordination have been established in many countries through which the management of vector control pesticides could potentially be improved. Most countries responded that they have adopted relevant recommendations by the WHO. Conclusions Given the deficiencies identified in this first global survey on public health pesticide management and the recent rise in pesticide use for malaria control, the effectiveness and safety of pesticide use are being compromised. This highlights the urgent need for countries to strengthen their capacity on pesticide management and evidence-based decision making within the context of an integrated vector management approach.

2011-01-01

132

Evaluation of Spatially Targeted Strategies to Control Non-Domiciliated Triatoma dimidiata Vector of Chagas Disease  

PubMed Central

Background Chagas disease is a major neglected tropical disease with deep socio-economical effects throughout Central and South America. Vector control programs have consistently reduced domestic populations of triatomine vectors, but non-domiciliated vectors still have to be controlled efficiently. Designing control strategies targeting these vectors is challenging, as it requires a quantitative description of the spatio-temporal dynamics of village infestation, which can only be gained from combinations of extensive field studies and spatial population dynamic modelling. Methodology/Principal Findings A spatially explicit population dynamic model was combined with a two-year field study of T. dimidiata infestation dynamics in the village of Teya, Mexico. The parameterized model fitted and predicted accurately both intra-annual variation and the spatial gradient in vector abundance. Five different control strategies were then applied in concentric rings to mimic spatial design targeting the periphery of the village, where vectors were most abundant. Indoor insecticide spraying and insect screens reduced vector abundance by up to 80% (when applied to the whole village), and half of this effect was obtained when control was applied only to the 33% of households closest to the village periphery. Peri-domicile cleaning was able to eliminate up to 60% of the vectors, but at the periphery of the village it has a low effect, as it is ineffective against sylvatic insects. The use of lethal traps and the management of house attractiveness provided similar levels of control. However this required either house attractiveness to be null, or ?5 lethal traps, at least as attractive as houses, to be installed in each household. Conclusion/Significance Insecticide and insect screens used in houses at the periphery of the village can contribute to reduce house infestation in more central untreated zones. However, this beneficial effect remains insufficient to allow for a unique spatially targeted strategy to offer protection to all households. Most efficiently, control should combine the use of insect screens in outer zones to reduce infestation by both sylvatic and peri-domiciliated vectors, and cleaning of peri-domicile in the centre of the village where sylvatic vectors are absent. The design of such spatially mixed strategies of control offers a promising avenue to reduce the economic cost associated with the control of non-domiciliated vectors.

Barbu, Corentin; Dumonteil, Eric; Gourbiere, Sebastien

2011-01-01

133

The risk and dynamics of onchocerciasis recrudescence after cessation of vector control.  

PubMed Central

Using a computer simulation study, we have investigated the risk and dynamics of onchocerciasis recrudescence after stopping vector control, in order to provide guidelines for operational decision-making in the Onchocerciasis Control Programme in West Africa (OCP). For this purpose, we used the microsimulation model ONCHOSIM to predict for periods of 9-15 years of vector control the ensuing risk and dynamics of recrudescence in an onchocerciasis focus. The model was quantified and validated using OCP evaluation and field research data. A range of plausible values was determined for important confounding parameters, i.e., vector biting rate, variation in exposure between individuals, parasite life span, and the relation between skin microfilarial load and vector infection. Different model quantifications were used in order to take account of the possible confounding effect of these parameters on the prediction of recrudescence. In the absence of immigration of infected humans or invasion by infected flies, the model predicts that 14 years of full-scale vector control are required to reduce the risk of recrudescence to less than 1%. The risk depends, in particular, on the vector biting rate, and this has implications for the planning of post-larviciding surveillance. Recrudescence will be a relatively slow process, and its rate will depend on the duration of vector control. Even if vector control were stopped too early, i.e., after 12-13 years in a highly endemic area, it would take more than 20 years before the intensity of infection in the community would reach levels of public health importance.

Plaisier, A. P.; van Oortmarssen, G. J.; Remme, J.; Alley, E. S.; Habbema, J. D.

1991-01-01

134

[Human African trypanosomiasis in an urban area: an emerging problem?].  

PubMed

The human African trypanosomiasis is essentially a rural disease. The notification of cases in urban area has always been incidental; either a diagnosis made in town revealed a disease contracted in rural environment or it meant the preservation of a complete epidemiological cycle in a remaining urban micro-focus. In Kinshasa, in Democratic Republic of Congo, about forty cases have been notified each year. All of them came from the nearby foci of Bandundu, Lower Congo and Kasaï. In 1996 the number of cases reached suddenly 254 and today the average annual number comes up to 500 in spite of all the efforts undertaken to fight the disease. A study of cases in 1998 and 1999 shows that patients are essentially distributed in suburbs and that the most affected by the disease are the 15-49 year old ones whose job is related with agricultural or fishing activities. Two phenomena seem to explain this sudden increase: the massive inflow of refugees in outskirts of town coming from provinces where trypanosomiasis is endemic and a major economic crisis throwing out urban population in suburbs living on a subsistence micro-agriculture. These concomitant factors have contributed to the setting up of a trypanosomiasis belt around the capital. Today a strategy has to be reconsidered in order to fight against the disease in the capital itself and to make the medical staff aware of the diagnosis of a disease still unknown in their sanitary district. PMID:14582296

Louis, F J; Bilenge, C M; Simarro, P P; Meso, V Kande; Lucas, P; Jannin, J

2003-08-01

135

A Novel Sliding Mode Observer with Adaptive Feedback Gain for PMSM Sensorless Vector Control  

Microsoft Academic Search

A novel sliding mode observer (SMO) with adaptive feedback gain is presented for sensorless vector control of permanent magnet synchronous machines (PMSM). The rotor position angle is estimated based on the equivalent control in the sliding mode observer. By selecting adaptive feedback gain, the equivalent control has the same constant magnitude as rotor flux over full speed range. Compared to

S. Chi; Z. Zhang; L. Xu

2007-01-01

136

Precision control of piezoelectric actuator using support vector regression nonlinear model and neural networks  

Microsoft Academic Search

Due to the inherent hysteresis nonlinearity, the piezoelectric actuator always causes positioning error in the opening system and instability in the closed system. In order to improve the positioning accuracy and response speed, a hybrid controller is proposed. The proposed hybrid controller consists of a feed-forward controller based on support vector machine for regression nonlinear model of piezoelectric actuator and

Hua-Wei Ji; Shi-Xi Yang; Zhao-Tong Wu; Gong-Biao Yan

2005-01-01

137

Feasibility of Controlling Ixodes scapularis Ticks (Acari: Ixodidae), the Vector of Lyme Disease, by Parasitoid Augmentation  

Microsoft Academic Search

A theoretical analysis of the feasibility of controlling tick populations (Ixodidae) by the release of reared Ixodiphagus parasitoids in tick ecosystems yielded promising results. The analysis suggested that if reasonable progress could be made in mass-rearing the parasitoids, it would be possible to control the blacklegged tick, Ixodes scapularis (Say), the vector of Lyme disease, by this biological control procedure.

E. F. Knipling; C. D. Steelman

2000-01-01

138

Vector controlled induction machines for stand-alone wind energy applications  

Microsoft Academic Search

This paper describes the system and control structures for vector controlled induction generators used for variable speed, wind energy conversion (WEC) systems. The paper focuses on WEC systems feeding an isolated load or weak grid since for such systems the generated voltage and power flow must be regulated by the WEC system itself and the control structures are not trivial.

R. S. Pena; R. J. Cardenas; G. M. Asher; J. C. Clare

2000-01-01

139

Dual-Plane Vector Control of a Five-Phase Induction Machine for an Improved Flux Pattern  

Microsoft Academic Search

A technique to improve the flux pattern within a five-phase induction machine is presented. The technique is developed through dual-plane vector control, with synchronized fluxes. By vector space decomposition, an analytical model and vector control of the machine are accomplished in two orthogonal vector planes,d1-q1 and ds-qs . The magnitude and rotating speed of the associated fluxes (fundamental and third

Libo Zheng; John E. Fletcher; Barry W. Williams; Xiangning He

2008-01-01

140

Simulation Research of Fuzzy-PID Synthesis Yaw Vector Control System of Wind Turbine  

Microsoft Academic Search

Enhancing the stability and robust of yawing system effectively, carrying out the simulation research of fuzzy-PID synthesis control. Designing the yawing vector control system with the synthesis controller of fuzzy-PID, modeling the system with Matlab simulation software, and taking simulation test. Comparing the simulation curves with common PID control and fuzzy PID subsection control, the result indicate that the fuzzy-PID

PIAO HAIGUO; WANG ZHIXIN

141

Vector control strategy for small-scale grid-connected PMSG wind turbine converter  

Microsoft Academic Search

The purpose of this paper is to find an innovative, high efficiency, practical and low cost control system structure with an optimized control strategy for small-scale grid-connected wind turbine with direct-driven permanent magnet synchronous generator (PMSG). This research adopts the sensorless vector control strategy based on phase-locked loop (PLL) for PMSG control, and the grid-side inverter control strategy is based

Chunxue Wen; Guojie Lu; Peng Wang; Zhengxi Li; Xiongwei Liu; Zaiming Fan

2011-01-01

142

Global Trends in the Use of Insecticides to Control Vector-Borne Diseases  

PubMed Central

Background: Data on insecticide use for vector control are essential for guiding pesticide management systems on judicious and appropriate use, resistance management, and reduction of risks to human health and the environment. Objective: We studied the global use and trends of insecticide use for control of vector-borne diseases for the period 2000 through 2009. Methods: A survey was distributed to countries with vector control programs to request national data on vector control insecticide use, excluding the use of long-lasting insecticidal nets (LNs). Data were received from 125 countries, representing 97% of the human populations of 143 targeted countries. Results: The main disease targeted with insecticides was malaria, followed by dengue, leishmaniasis, and Chagas disease. The use of vector control insecticides was dominated by organochlorines [i.e., DDT (dichlorodiphenyltrichloroethane)] in terms of quantity applied (71% of total) and by pyrethroids in terms of the surface or area covered (81% of total). Global use of DDT for vector control, most of which was in India alone, was fairly constant during 2000 through 2009. In Africa, pyrethroid use increased in countries that also achieved high coverage for LNs, and DDT increased sharply until 2008 but dropped in 2009. Conclusions: The global use of DDT has not changed substantially since the Stockholm Convention went into effect. The dominance of pyrethroid use has major implications because of the spread of insecticide resistance with the potential to reduce the efficacy of LNs. Managing insecticide resistance should be coordinated between disease-specific programs and sectors of public health and agriculture within the context of an integrated vector management approach.

van den Berg, Henk; Zaim, Morteza; Soares, Agnes; Ameneshewa, Birkinesh; Mnzava, Abraham; Hii, Jeffrey; Dash, Aditya Prasad; Ejov, Mikhail

2012-01-01

143

Control of Ducted Fan Flying Object Using Thrust Vectoring  

NASA Astrophysics Data System (ADS)

Recently, R/C helicopter is used in fields of aerial photography and aerial investigation. But helicopter rotor blades are not covered, and the thrust is generated by high rotational speed. Thus R/C helicopter has a high risk of damage. In this study, we developed a new flying object using ducted fans instead of rotor blades. At first, PD control was employed for pitch and roll attitude control, but it caused steady state error. Moreover, PI-D control was used instead of PD control, and it reduced the steady state error. We succeeded to achieve stable hovering by 3-axes (roll, pitch and yaw axis) attitude control.

Miwa, Masafumi; Shigematsu, Yuki; Yamashita, Takashi

144

Vector control interventions for visceral leishmaniasis elimination initiative in South Asia, 2005-2010  

PubMed Central

The Visceral Leishmaniasis (VL) Elimination Initiative in the Indian subcontinent was launched in 2005 as a joint effort between the governments in the Region (India, Nepal and Bangladesh) and the World Health Organization (WHO). The objective is to reduce the annual VL incidence below 1/10,000 inhabitants by 2015 based on detection and treatment of VL cases and vector control. We present here a review of studies published in the period 2005-2010 on the efficacy of different tools to control Phlebotomus argentipes. The review indicates that the current indoor residual spraying (IRS) and novel vector control methods mainly insecticide treated nets (ITN) have low effectiveness for several reasons. Efforts to improve quality of IRS operations and further research on alternative and integrated vector control methods need to be promoted to reach the VL elimination target by 2015.

Picado, Albert; Dash, Aditya P.; Bhattacharya, Sujit; Boelaert, Marleen

2012-01-01

145

Omni-axis secondary injection thrust vector control system  

NASA Technical Reports Server (NTRS)

The concept, development, design study and preliminary analysis and layout of the required digital logic scheme to be used for injection valve control are presented. An application and optimization study of an Omni-Axis Secondary Injection Control System applicable to the proposed Space Shuttle Pressure Fed Engine is reported. Technical definition and analysis control procedures and test routines, as well as a supporting set of drawing sketches and reference manual, are enclosed.

Kirkley, D. J.

1973-01-01

146

PORCINE TRYPANOSOMIASIS IN SOUTHEASTERN UGANDA: PREVALENCE AND ASSESSMENT OF THERAPEUTIC EFFECTIVENESS  

Microsoft Academic Search

Summary Waiswa, C., 2005. Porcine trypanosomiasis in Southeastern Uganda: Prevalence and assessment of therapeutic effectiveness. Bulg. J. Vet. Med., 8, No 1, 59?68. This study aimed at investigating the prevalence of trypanosomiasis and the usefulness of diminazene aceturate and isometamidium chloride in the treatment of pigs infected with Trypanosoma brucei sub- group. Whole blood was collected from pigs kept in

C. WAISWA

2005-01-01

147

Space vector alpha-beta sliding mode current controllers for three-phase multilevel inverters  

Microsoft Academic Search

Robust sliding mode on-line space vector controllers, designed for output current control in multilevel three-phase power inverters are described. Capacitor voltage divider equalisation is included using the same approach. Using two four-level comparators, simulation and experimental results show no steady state-errors, very fast dynamics and robustness against power supply variations and load unbalances

J. Fernando Silva; N. Rodrigues; J. Costan

2000-01-01

148

Sensorless vector control of induction machines for variable-speed wind energy applications  

Microsoft Academic Search

A sensorless vector-control strategy for an induction generator in a grid-connected wind energy conversion system is presented. The sensorless control system is based on a model reference adaptive system (MRAS) observer to estimate the rotational speed. In order to tune the MRAS observer and compensate for the parameter variation and uncertainties, a separate estimation of the speed is obtained from

Roberto Cárdenas; Rubén Peña

2004-01-01

149

Vector-controlled induction motor drive with a self-commissioning scheme  

Microsoft Academic Search

Different vector-controlled structures are discussed, and their suitability for an economical and reliable industrial drive system is explored. From this, the design of a compact control hardware is derived, composed of an 80196 microcontroller and an ASIC (application-specific integrated circuit) for the generation of the pulsewidth modulation (PWM) signals. The drive system can be configured from a host computer or

Ashwin M. Khambadkone; Joachim Holtz

1991-01-01

150

High-Performance Vector-Controlled AC Motor Drives: Applications and New Technologies  

Microsoft Academic Search

A high-performance ac motor control has been developed by employing the vector control concept. Its versatility has been proven through the six years of experience in applications to pinch roll drives of continuous casting plants, machine tool spindle drives, and other drive systems in industry. Equivalent torque characteristics are achieved with ac motors compared to dc motors without direct detection

Tsuneo Kume; Takanobu Iwakane

1987-01-01

151

Loss minimization in vector-controlled interior permanent-magnet synchronous motor drives  

Microsoft Academic Search

An efficiency optimization method for vector-controlled interior permanent-magnet synchronous motor drives is presented. Based on theoretical analysis, a loss minimization condition that determines the optimal d-axis component of the armature current is derived. Selected experimental results are presented to validate the effectiveness of the proposed control method.

Christos Mademlis; Nikos Margaris

2002-01-01

152

Dengue vector control strategies in an urban setting: an economic modelling assessment  

PubMed Central

Summary Background An estimated 2·5 billion people are at risk of dengue. Incidence of dengue is especially high in resource-constrained countries, where control relies mainly on insecticides targeted at larval or adult mosquitoes. We did epidemiological and economic assessments of different vector control strategies. Methods We developed a dynamic model of dengue transmission that assesses the evolution of insecticide resistance and immunity in the human population, thus allowing for long-term evolutionary and immunological effects of decreased dengue transmission. We measured the dengue health burden in terms of disability-adjusted life-years (DALYs) lost. We did a cost-effectiveness analysis of 43 insecticide-based vector control strategies, including strategies targeted at adult and larval stages, at varying efficacies (high-efficacy [90% mortality], medium-efficacy [60% mortality], and low-efficacy [30% mortality]) and yearly application frequencies (one to six applications). To assess the effect of parameter uncertainty on the results, we did a probabilistic sensitivity analysis and a threshold analysis. Findings All interventions caused the emergence of insecticide resistance, which, with the loss of herd immunity, will increase the magnitude of future dengue epidemics. In our model, one or more applications of high-efficacy larval control reduced dengue burden for up to 2 years, whereas three or more applications of adult vector control reduced dengue burden for up to 4 years. The incremental cost-effectiveness ratios of the strategies for two high-efficacy adult vector control applications per year was US$615 per DALY saved and for six high-efficacy adult vector control applications per year was $1267 per DALY saved. Sensitivity analysis showed that if the cost of adult control was more than 8·2 times the cost of larval control then all strategies based on adult control became dominated. Interpretation Six high-efficacy adult vector control applications per year has a cost-effectiveness ratio that will probably meet WHO's standard for a cost-effective or very cost-effective intervention. Year-round larval control can be counterproductive, exacerbating epidemics in later years because of evolution of insecticide resistance and loss of herd immunity. We suggest the reassessment of vector control policies that are based on larval control only. Funding The Fulbright Programme, CAPES (Brazilian federal agency for post-graduate education), the Miriam Burnett trust, and the Notsew Orm Sands Foundation.

Luz, Paula Mendes; Vanni, Tazio; Medlock, Jan; Paltiel, A David; Galvani, Alison P

2012-01-01

153

Model Predictive Control of a switched reluctance machine using discrete Space Vector Modulation  

Microsoft Academic Search

This work proposes an algorithm to control the torque of a switched reluctance machine (SRM). A 6\\/4 three phases SRM drive is controlled and simulated on PSCAD\\/EMTDC software. The machine is modeled using an analytical model that takes into consideration the non-linearity of the machine. The control is designed as a Model Predictive Control (MPC) using Discrete Space Vector Modulation

J. Villegas; S. Vazquez; J. M. Carrasco; I. Gil

2010-01-01

154

Fluidic scale model multi-plane thrust vector control test results  

NASA Technical Reports Server (NTRS)

An experimental investigation has been conducted at the NASA Langley 16-Foot Transonic Tunnel Static Test Facility to determine the concept feasibility of using fluidics to achieve multiplane thrust vector control in a 2D convergent-divergent (2D-CD) fixed aperture nozzle. Pitch thrust vector control is achieved by injection of flow through a slot in the divergent flap into the primary nozzle flow stream. Yaw vector control results from secondary air delivered tangentially to vertical Coanda flaps. These flaps are offset laterally and aligned parallel to the primary nozzle side walls. All tests were conducted at static (no external flow) conditions. Flow visualization was conducted using a paint flow technique and Focus Schlieren. Significant levels of pitch deflection angles (19 deg) were achieved at low pressure ratios and practical levels (14 deg) resulted at typical intermediate power settings. The ability of the Coanda surface blowing concept to produce yaw deflection was limited to NPR not greater than 4.

Chiarelli, Charles; Johnsen, Raymond K.; Shieh, Chih F.; Wing, David J.

1993-01-01

155

CONTROL OF PATHOGENS AND VECTORS IN SEWAGE SLUDGE  

EPA Science Inventory

This document describes the federal requirements concerning pathogens in sewage sludge and septage destined for land application or surface disposal. t also provides guidance for meeting those requirements. he chapters of this document discuss why pathogen control is necessary, t...

156

A small-molecule-controlled system for efficient pseudotyping of prototype foamy virus vectors.  

PubMed

Foamy virus (FV) vector systems have recently demonstrated their power as efficient gene transfer tools for different target tissues. Unfortunately, FVs cannot be naturally pseudotyped by heterologous viral glycoproteins due to an unusual particle morphogenesis involving a FV Env-dependent particle release process. Therefore, current FV vector systems are constrained to the broad host cell range provided by the cognate viral glycoprotein. We evaluated different approaches for pseudotyping of FV vectors, in which the specific FV Gag-Env interaction, essential for particle egress, is substituted by a small-molecule controlled heterodimerization (HD) system. In one system developed, one HD-domain (HDD) is fused to a membrane-targeting domain (MTD), such as the human immunodeficiency virus (HIV) Gag matrix (MA) subunit, with a second fused to the FV capsid protein. Coexpression of both components with different heterologous viral glycoproteins allowed an efficient, dimerizer-dependent pseudotyping of FV capsids. With this system FV vesicular stomatitis virus glycoprotein (VSV-G) pseudotype titers greater than 1 × 10(6) IU/ml were obtained, at levels comparable to authentic FV vector particles. As a proof-of-principle we demonstrate that Pac2 cells, naturally resistant to FV vectors, become permissive to FV VSV-G pseudotypes. Similar to other retroviral vectors, this FV pseudotyping system now enables adaptation of cell-specific targeting approaches for FVs. PMID:22472951

Ho, Yu-Ping; Schnabel, Viktor; Swiersy, Anka; Stirnnagel, Kristin; Lindemann, Dirk

2012-06-01

157

Controlling brain tumor growth via intraventricular administration of an AAV vector encoding IFN-?  

PubMed Central

Glioblastoma multiforme (GBM) is the most aggressive type of all primary brain tumors, with an overall median survival < 1 year after diagnosis. Despite introduction of multimodal treatment approaches, the prognosis has not improved significantly over the last 50 years. In this study we investigated the effect of intracerebroventricular injection of an AAV vector encoding human interferon-beta (hIFN-?) on glioblastoma growth. Recently, we found that peri-tumoral parenchymal transduction with an AAV vector encoding hIFN-? was exceptionally efficient in eradicating GBM brain tumors. However the extensive infiltration and migration displayed by glioblastoma cells in patients may leave a significant number of tumor cells outside a local therapeutic zone created by intraparenchymal delivery of AAV vectors. Here we show that pretreatment of mice via intracerebroventricular (ICV) infusion of an AAV vector encoding hIFN-? (AAV-IFN-?) completely prevents tumor growth in an orthotopic model of GBM. Furthermore, ICV infusion of AAV-IFN-? into mice bearing pre-established U87 intracranial tumors improved their survival compared to mice infused via the same route with a control AAV vector. These data suggest that ICV injection of AAV vectors encoding anti-tumor proteins is a promising approach deserving further consideration for the treatment of GBM.

Meijer, Dimphna H.; Maguire, Casey A.; LeRoy, Stanley G.; Sena-Esteves, Miguel

2010-01-01

158

Improvement in vehicle agility and stability by G-Vectoring control  

Microsoft Academic Search

We extracted a trade-off strategy between longitudinal traction\\/braking force and cornering force by using jerk information through observing an expert driver's voluntary braking and turning action. Using the expert driver's strategy, we developed a new control concept, called ‘G-Vectoring control’, which is an automatic longitudinal acceleration control (No DYC) in accordance with the vehicle's lateral jerk caused by the driver's

Makoto Yamakado; Jyunya Takahashi; Shinjiro Saito; Atsushi Yokoyama; Masato Abe

2010-01-01

159

Why and how to use vector autoregressive models for quality control: the guideline and procedures  

Microsoft Academic Search

While quality control on multivariate and serially correlated processes has attracted research attentions, a number of very\\u000a detailed problems need to be overcome in order to construct practical control charts. We suggest guidelines for construction\\u000a of control charts based on vector autoregressive (VAR) residuals. We discuss why VAR model is reasonable for real processes\\u000a in nature, the use of VAR

Xia Pan; Jeffrey E. Jarrett

2012-01-01

160

Heritable strategies for controlling insect vectors of disease  

PubMed Central

Mosquito-borne diseases are causing a substantial burden of mortality, morbidity and economic loss in many parts of the world, despite current control efforts, and new complementary approaches to controlling these diseases are needed. One promising class of new interventions under development involves the heritable modification of the mosquito by insertion of novel genes into the nucleus or of Wolbachia endosymbionts into the cytoplasm. Once released into a target population, these modifications can act to reduce one or more components of the mosquito population's vectorial capacity (e.g. the number of female mosquitoes, their longevity or their ability to support development and transmission of the pathogen). Some of the modifications under development are designed to be self-limiting, in that they will tend to disappear over time in the absence of recurrent releases (and hence are similar to the sterile insect technique, SIT), whereas other modifications are designed to be self-sustaining, spreading through populations even after releases stop (and hence are similar to traditional biological control). Several successful field trials have now been performed with Aedes mosquitoes, and such trials are helping to define the appropriate developmental pathway for this new class of intervention.

Burt, Austin

2014-01-01

161

Heritable strategies for controlling insect vectors of disease.  

PubMed

Mosquito-borne diseases are causing a substantial burden of mortality, morbidity and economic loss in many parts of the world, despite current control efforts, and new complementary approaches to controlling these diseases are needed. One promising class of new interventions under development involves the heritable modification of the mosquito by insertion of novel genes into the nucleus or of Wolbachia endosymbionts into the cytoplasm. Once released into a target population, these modifications can act to reduce one or more components of the mosquito population's vectorial capacity (e.g. the number of female mosquitoes, their longevity or their ability to support development and transmission of the pathogen). Some of the modifications under development are designed to be self-limiting, in that they will tend to disappear over time in the absence of recurrent releases (and hence are similar to the sterile insect technique, SIT), whereas other modifications are designed to be self-sustaining, spreading through populations even after releases stop (and hence are similar to traditional biological control). Several successful field trials have now been performed with Aedes mosquitoes, and such trials are helping to define the appropriate developmental pathway for this new class of intervention. PMID:24821918

Burt, Austin

2014-01-01

162

Low-magnetic-field control of electric polarization vector in a helimagnet.  

PubMed

The mutual control of the electric and magnetic properties of a solid is currently of great interest because of the possible application for novel electronic devices. We report on the low-magnetic-field (for example, B values of +/-30 milliteslas) control of the polarization (P) vector in a hexaferrite, Ba2Mg2Fe12O22, which shows the helimagnetic spin structure with the propagation vector k0 parallel to [001]. The B-induced transverse conical spin structure carries the P vector directing perpendicular to both B and k0, in accord with the recently proposed spin-current model. Then, the oscillating or multidirectionally rotating B produces the cyclic displacement current via the flexible handling of the magnetic cone axis. PMID:18356519

Ishiwata, Shintaro; Taguchi, Yasujiro; Murakawa, Hiroshi; Onose, Yoshinori; Tokura, Yoshinori

2008-03-21

163

Low-Magnetic-Field Control of Electric Polarization Vector in a Helimagnet  

NASA Astrophysics Data System (ADS)

The mutual control of the electric and magnetic properties of a solid is currently of great interest because of the possible application for novel electronic devices. We report on the low-magnetic-field (for example, B values of ±30 milliteslas) control of the polarization (P) vector in a hexaferrite, Ba2Mg2Fe12O22, which shows the helimagnetic spin structure with the propagation vector k0 parallel to [001]. The B-induced transverse conical spin structure carries the P vector directing perpendicular to both B and k0, in accord with the recently proposed spin-current model. Then, the oscillating or multidirectionally rotating B produces the cyclic displacement current via the flexible handling of the magnetic cone axis.

Ishiwata, Shintaro; Taguchi, Yasujiro; Murakawa, Hiroshi; Onose, Yoshinori; Tokura, Yoshinori

2008-03-01

164

A Vector Control for Grid-connected Wind Power Generation with Doubly Fed Induction Generator  

NASA Astrophysics Data System (ADS)

Recently, doubly fed induction generator (DFIG) and synchronous generator are mostly applied for wind power generation due to high efficiently for wind energy capture. An inverter system is required to control wind turbine speed and power factor in those generators. The inverter rating of the synchronous generator equals to generator rating. However, DFIG has the advantage that the inverter rating is about 25% to the generator rating. The paper describes a vector control of DFIG inter-connected to power line. The performance of proposed vector control is examined using power system simulation software PSCAD/EMTDC for the DFIG inter-connected to 6.6kv distribution line. The results show good dynamic responses and high accuracy to the stator active power control and the stator reactive power control.

Kai, Takaaki; Tanaka, Yuji; Kaneda, Hirotoshi; Kobayashi, Daichi; Tanaka, Akio

165

Analysis of Power Converter Losses in Vector Control System of a Self-Excited Induction Generator  

NASA Astrophysics Data System (ADS)

This paper provides analysis of losses in the hysteresis-driven three-phase power converter with IGBTs and free-wheeling diodes. The converter under consideration is part of the self-excited induction generator (SEIG) vector control system. For the analysis, the SEIG vector control system is used in which the induction generator iron losses are taken into account. The power converter losses are determined by using a suitable loss estimation algorithm reported in literature. The chosen algorithm allows the power converter losses to be determined both by type (switching/conduction losses) and by converter component (IGBT/diode losses). The overall power converter losses are determined over wide ranges of rotor speed, dc-link voltage and load resistance, and subsequently used for offline correction of the overall control system's losses (efficiency) obtained through control system simulations with an ideal power converter. The control system's efficiency values obtained after the correction are compared with the measured values.

Baši?, Mateo; Vukadinovi?, Dinko; Poli?, Miljenko

2014-03-01

166

Community-based dengue vector control: experiences in behavior change in Metropolitan Manila, Philippines  

PubMed Central

Dengue is the most important mosquito-borne disease in the Philippines, especially in Metropolitan Manila where communities are socially and economically diverse, and city governments struggle to provide basic services such as continuously available, piped water supply to residents. We examined responses to introducing water container management to control dengue vectors in two diverse communities in Masagana City: Village A (gated community) and Village B (informal settlers community). The roll out of the intervention was carried out by the study team, dengue control personnel and local health workers (BHWs). A behavioural change framework was used to describe the community responses to the introduction of a new vector control intervention - household water container management. Although, the desired outcome was not achieved during the study's timeline, observation on processes of behaviour change underscored the importance of understanding the social nature of the urban communities, often overlooked structures when dengue control program and researchers introduce new dengue control interventions.

Espino, Fe

2012-01-01

167

Investigations on the control of bilharziasis vectors in Israel*  

PubMed Central

In spite of the arrival in Israel over the past decade of large numbers of immigrants infected with bilharziasis and although during that period there have been two sporadic outbreaks of the disease, there seems little immediate danger of bilharziasis spreading in the country. However, hydrographical, agricultural and economic conditions are subject to rapid changes in Israel and the present favourable situation may not be lasting. In anticipation, therefore, of possible outbreaks, laboratory experiments have been conducted to evaluate the efficacy in the control of Bulinus ova and adult snails and schistosome cercariae of a number of known molluscides and other substances. Although similar studies have been made in several other countries, it was felt advisable to repeat them under local hydrological conditions, particularly in view of the high carbonate content of the local waters. While most of the substances tested exert some molluscicidal action, only copper sulfate, sodium pentachlorophenate and common salt were found to be of practical value.

Saliternik, Z.; Witenberg, G.

1959-01-01

168

Fluidic Thrust Vector Control for the Stabilization of Man/Ejection Seat Systems.  

National Technical Information Service (NTIS)

A 2-axis, hydrofluidic thrust vector control (TVC) system was designed to improve the total trajectory of an ejection seat system during adverse conditions from 0 to 600 knots air speed. A nonlinear model of the seat was derived and linearized to determin...

R. B. Beale

1975-01-01

169

A speed estimator for sensorless vector control of induction machines in the field weakening region  

Microsoft Academic Search

A number of speed estimation schemes for sensorless vector control of induction machines utilise a mathematical model of the machine in the estimation process. Operation of a sensorless indirect rotor flux oriented machine in the field weakening region requires that the variable degree of main flux saturation is recognised and compensated in the speed estimator. The paper describes implementation of

Emil Levi; Mingyu Wang

2000-01-01

170

a novel states feedback control of unknown dynamics systems by using support vector machines  

Microsoft Academic Search

This paper proposes a very novel method which makes it possible that state feedback controller can be designed for unknown dynamic system with measurable states. This novel method uses the support vector machines (SVM) with its function approximation property. It works together with RLS (recursive least-squares) algorithm. The RLS algorithm is used for the identification of input-output relationship. A virtual

Fa-Guang Wang; Seung-Kyu Park; Tae-Sung Yoorr

2007-01-01

171

Speed sensorless vector control of induction motor using extended Kalman filter  

Microsoft Academic Search

A vector control of an induction motor by an estimated speed using an extended Kalman filter is proposed. With this method, the states are composed of stator current and rotor flux. The rotor speed is regarded as a parameter, and the composite states consist of the original states and the rotor speed. The extended Kalman filter is employed to identify

Young-Real Kim; Seung-Ki Sul; Min-Ho Park

1994-01-01

172

Hydrologic modeling to screen potential environmental management methods for malaria vector control in Niger  

Microsoft Academic Search

This paper describes the first use of Hydrology-Entomology and Malaria Transmission Simulator (HYDREMATS), a physically based distributed hydrology model, to investigate environmental management methods for malaria vector control in the Sahelian village of Banizoumbou, Niger. The investigation showed that leveling of topographic depressions where temporary breeding habitats form during the rainy season, by altering pool basin microtopography, could reduce the

Rebecca L. Gianotti; Arne Bomblies; Elfatih A. B. Eltahir

2009-01-01

173

An effective method for rotor resistance identification for high-performance induction motor vector control  

Microsoft Academic Search

An effective method for rotor resistance identification is presented for the purpose of improving the performance of vector control of induction motor drives. The method is mathematically derived from proper selection of coordinate axes and utilization of the steady-state model of the induction motor. The major advantages of the method lie in its simplicity and accuracy. A series of computer

C. C. Chan; HUAQIAN WANG

1990-01-01

174

Ecologists can enable communities to implement malaria vector control in Africa  

Microsoft Academic Search

BACKGROUND: Integrated vector management (IVM) for malaria control requires ecological skills that are very scarce and rarely applied in Africa today. Partnerships between communities and academic ecologists can address this capacity deficit, modernize the evidence base for such approaches and enable future scale up. METHODS: Community-based IVM programmes were initiated in two contrasting settings. On Rusinga Island, Western Kenya, community

W Richard Mukabana; Khadija Kannady; G Michael Kiama; Jasper N Ijumba; Evan M Mathenge; Ibrahim Kiche; Gamba Nkwengulila; Leonard Mboera; Deo Mtasiwa; Yoichi Yamagata; Ingeborg van Schayk; Bart GJ Knols; Steven W Lindsay; Marcia Caldas de Castro; Hassan Mshinda; Marcel Tanner; Ulrike Fillinger; Gerry F Killeen

2006-01-01

175

Transition from slip-frequency control to vector control for induction motor drives of traction applications in Japan  

Microsoft Academic Search

AC motor drive systems for electric rolling stocks with variable-voltage, variable-frequency inverters have many features such as high performance, maintenance free, smaller size and light weight. This paper describes brief history on control methods for induction motor drives of railway traction applications in Japan. That is the transition from the slip-frequency control to the vector control. Furthermore the superiority of

M. Yano; Michio Iwahori

2003-01-01

176

Chagas disease vector control in Tupiza, southern Bolivia.  

PubMed

Heavy domestic and peridomestic infestations of Triatoma infestans were controlled in two villages in southern Bolivia by the application of deltamethrin SC25 (2.5% suspension concentrate) at a target dose of 25 mg a.i./m2. Actual applied dose was monitored by HPLC analysis of filter papers placed at various heights on the house walls, and was shown to range from 0 to 59.6 about a mean of 28.5 mg a.i./m2. Wall bioassays showed high mortality of T. infestans during the first month after the application of deltamethrin. Mortality declined to zero as summer temperatures increased, but reappeared with the onset of the following winter. In contrast, knockdown was apparent throughout the trial, showing no discernible temperature dependence. House infestation rates, measured by manual sampling and use of paper sheets to collect bug faeces, declined from 79% at the beginning of the trial to zero at the 6 month evaluation. All but one of the houses were still free of T. infestans at the final evaluation 12 months after spraying, although a small number of bugs were found at this time in 5 of 355 peridomestic dependencies. Comparative cost studies endorse the recommendation of large-scale application of deltamethrin, or pyrethroid of similar cost-effectiveness, as a means to eliminate domestic T. infestans populations in order to interrupt transmission of Chagas disease. PMID:9302405

Guillen, G; Diaz, R; Jemio, A; Cassab, J A; Pinto, C T; Schofield, C J

1997-01-01

177

Clustering of Vector Control Interventions Has Important Consequences for Their Effectiveness: A Modelling Study  

PubMed Central

Vector control interventions have resulted in considerable reductions in malaria morbidity and mortality. When universal coverage cannot be achieved for financial or logistical reasons, the spatial arrangement of vector control is potentially important for optimizing benefits. This study investigated the effect of spatial clustering of vector control interventions on reducing the population of biting mosquitoes. A discrete-space continuous-time mathematical model of mosquito population dynamics and dispersal was extended to incorporate vector control interventions of insecticide treated bednets (ITNs), Indoor residual Spraying (IRS), and larviciding. Simulations were run at varying levels of coverage and degree of spatial clustering. At medium to high coverage levels of each of the interventions or in combination was more effective to spatially spread these interventions than to cluster them. Suggesting that when financial resources are limited, unclustered distribution of these interventions is more effective. Although it is often stated that locally high coverage is needed to achieve a community effect of ITNs or IRS, our results suggest that if the coverage of ITNs or IRS are insufficient to achieve universal coverage, and there is no targeting of high risk areas, the overall effects on mosquito densities are much greater if they are distributed in an unclustered way, rather than clustered in specific localities. Also, given that interventions are often delivered preferentially to accessible areas, and are therefore clustered, our model results show this may be inefficient. This study provides evidence that the effectiveness of an intervention can be highly dependent on its spatial distribution. Vector control plans should consider the spatial arrangement of any intervention package to ensure effectiveness is maximized.

Lutambi, Angelina Mageni; Chitnis, Nakul; Briet, Olivier J. T.; Smith, Thomas A.; Penny, Melissa A.

2014-01-01

178

Thailand Momentum on Policy and Practice in Local Legislation on Dengue Vector Control  

PubMed Central

Over a past decade, an administrative decentralization model, adopted for local administration development in Thailand, is replacing the prior centralized (top-down) command system. The change offers challenges to local governmental agencies and other public health agencies at all the ministerial, regional, and provincial levels. A public health regulatory and legislative framework for dengue vector control by local governmental agencies is a national topic of interest because dengue control program has been integrated into healthcare services at the provincial level and also has been given priority in health plans of local governmental agencies. The enabling environments of local administrations are unique, so this critical review focuses on the authority of local governmental agencies responsible for disease prevention and control and on the functioning of local legislation with respect to dengue vector control and practices.

Bhumiratana, Adisak; Intarapuk, Apiradee; Chujun, Suriyo; Kaewwaen, Wuthichai; Sorosjinda-Nunthawarasilp, Prapa; Koyadun, Surachart

2014-01-01

179

A direct torque control scheme for permanent magnet synchronous motors based on space vector modulation  

NASA Astrophysics Data System (ADS)

In order to solve the problem of direct torque control (DTC) for permanent magnet synchronous motor (PMSM) related to the flux and the torque ripple and the uncertainty of switching frequency, A novel direct torque control system based on space vector modulation(SVM-DTC) for permanent magnet synchronous motor was proposed. In this method flux and torque are controlled through stator voltage components in stator flux linkage coordinate axes and space vector modulation is used to control inverters. Therefore, the errors of torque and flux linkage could be compensated accurately. The whole system has only one easily adjustable PI adjuster and needs no high for hardware and easy for realize. The simulation results verify the feasibility of this method, reduction of the flux and the torque ripple, and the good performance of DTC.

Su, Xiao-hui; Xu, Shu-Ping

2013-03-01

180

The argument for integrating vector control with multiple drug administration campaigns to ensure elimination of lymphatic filariasis  

PubMed Central

Background There is a danger that mass drug administration campaigns may fail to maintain adequate treatment coverage to achieve lymphatic filariasis elimination. Hence, additional measures to suppress transmission might be needed to ensure the success of the Global Program for the Elimination of Lymphatic Filariasis. Discussion Vector control successfully eliminated lymphatic filariasis when implemented alone or with mass drug administration. Challenges to lymphatic filariasis elimination include uncertainty of the exact level and duration of microfilarial suppression required for elimination, the mobility of infected individuals, consistent non-participation of some infected individuals with mass drug administration, the possible development of anti-filarial drug resistance and treatment strategies in areas co-endemic with loasis. Integration of vector control with mass drug administration can address some of these challenges. The potential benefits of vector control would include: (1) the ability to suppress filariasis transmission without the need to identify all individual 'foci of infection'; (2) minimizing the risk of reestablishment of transmission from imported microfilaria positive individuals; and (3) decreasing the risk of dengue or malaria transmission where, respectively, Aedes or Anopheles are lymphatic filariasis vectors. Summary With adequate sustained treatment coverage, mass drug administration should meet the criteria for elimination of lymphatic filariasis. However, it may be difficult to sustain sufficiently high mass drug administration coverage to achieve lymphatic filariasis elimination in some areas, particularly, where Aedes species are the vectors. Since vector control was effective in controlling and even eliminating lymphatic filariasis transmission, integration of vector control with mass drug administration will ensure the sustainability of transmission suppression and thereby better ensure the success of national filariasis elimination programs. Although trials of some vector control interventions are needed, proven vector control strategies are ready for immediate integration with mass drug administration for many important vectors. Vector control is the only presently available additional lymphatic filariasis control measure with the potential for immediate implementation.

Burkot, TR; Durrheim, DN; Melrose, WD; Speare, R; Ichimori, K

2006-01-01

181

Genetic shifting: a novel approach for controlling vector-borne diseases.  

PubMed

Rendering populations of vectors of diseases incapable of transmitting pathogens through genetic methods has long been a goal of vector geneticists. We outline a method to achieve this goal that does not involve the introduction of any new genetic variants to the target population. Rather we propose that shifting the frequencies of naturally occurring alleles that confer refractoriness to transmission can reduce transmission below a sustainable level. The program employs methods successfully used in plant and animal breeding. Because no artificially constructed genetically modified organisms (GMOs) are introduced into the environment, the method is minimally controversial. We use Aedes aegypti and dengue virus (DENV) for illustrative purposes but point out that the proposed program is generally applicable to vector-borne disease control. PMID:24794113

Powell, Jeffrey R; Tabachnick, Walter J

2014-06-01

182

The natural decline of Wuchereria bancrofti infection in a vector control situation in the Solomon Islands.  

PubMed

In a situation where filariasis and malaria are transmitted by the same vector, as seen here in the Solomon Islands, the Malaria Eradication Programme aimed at controlling the vector, was found to have an effect on both diseases. In an area of Choiseul island first surveyed by the author in 1970, three follow-up surveys were conducted--in 1974, 1975 and 1976. These showed a progressive decrease in persons infected. When the densities, especially the median microfilarial counts, were expressed as percentage values of the pre-spray survey, there was found to be a proportional decrease over eight years. It is possible that the Anopheline vector needs to be reduced less for the cessation of transmission of filariasis than for malaria. A theoretical ratio was calculated and supporting field evidence presented. PMID:595094

Webber, R H

1977-01-01

183

Discovery and Verification of Osteopontin and Beta-2-microglobulin as Promising Markers for Staging Human African Trypanosomiasis*  

PubMed Central

Human African trypanosomiasis, or sleeping sickness, is a parasitic disease endemic in sub-Saharan Africa, transmitted to humans through the bite of a tsetse fly. The first or hemolymphatic stage of the disease is associated with presence of parasites in the bloodstream, lymphatic system, and body tissues. If patients are left untreated, parasites cross the blood-brain barrier and invade the cerebrospinal fluid and the brain parenchyma, giving rise to the second or meningoencephalitic stage. Stage determination is a crucial step in guiding the choice of treatment, as drugs used for S2 are potentially dangerous. Current staging methods, based on counting white blood cells and demonstrating trypanosomes in cerebrospinal fluid, lack specificity and/or sensitivity. In the present study, we used several proteomic strategies to discover new markers with potential for staging human African trypanosomiasis. Cerebrospinal fluid (CSF) samples were collected from patients infected with Trypanosoma brucei gambiense in the Democratic Republic of Congo. The stage was determined following the guidelines of the national control program. The proteome of the samples was analyzed by two-dimensional gel electrophoresis (n = 9), and by sixplex tandem mass tag (TMT) isobaric labeling (n = 6) quantitative mass spectrometry. Overall, 73 proteins were overexpressed in patients presenting the second stage of the disease. Two of these, osteopontin and ?-2-microglobulin, were confirmed to be potential markers for staging human African trypanosomiasis (HAT) by Western blot and ELISA. The two proteins significantly discriminated between S1 and S2 patients with high sensitivity (68% and 78%, respectively) for 100% specificity, and a combination of both improved the sensitivity to 91%. The levels of osteopontin and ?-2-microglobulin in CSF of S2 patients (?g/ml range), as well as the fold increased concentration in S2 compared with S1 (3.8 and 5.5 respectively) make the two markers good candidates for the development of a test for staging HAT patients.

Tiberti, Natalia; Hainard, Alexandre; Lejon, Veerle; Robin, Xavier; Ngoyi, Dieudonne Mumba; Turck, Natacha; Matovu, Enock; Enyaru, John; Ndung'u, Joseph Mathu; Scherl, Alexander; Dayon, Loic; Sanchez, Jean-Charles

2010-01-01

184

Thrust shock vector control of an axisymmetric conical supersonic nozzle via secondary transverse gas injection  

NASA Astrophysics Data System (ADS)

Transverse secondary gas injection into the supersonic flow of an axisymmetric convergent-divergent nozzle is investigated to describe the effects of the fluidic thrust vectoring within the framework of a small satellite launcher. Cold-flow dry-air experiments are performed in a supersonic wind tunnel using two identical supersonic conical nozzles with the different transverse injection port positions. The complex three-dimensional flow field generated by the supersonic cross-flows in these test nozzles was examined. Valuable experimental data were confronted and compared with the results obtained from the numerical simulations. Different nozzle models are numerically simulated under experimental conditions and then further investigated to determine which parameters significantly affect thrust vectoring. Effects which characterize the nozzle and thrust vectoring performances are established. The results indicate that with moderate secondary to primary mass flow rate ratios, ranging around 5 %, it is possible to achieve pertinent vector side forces. It is also revealed that injector positioning and geometry have a strong effect on the shock vector control system and nozzle performances.

Zmijanovic, V.; Lago, V.; Sellam, M.; Chpoun, A.

2014-01-01

185

Drivers, dynamics, and control of emerging vector-borne zoonotic diseases  

PubMed Central

Emerging vector-borne diseases represent an important issue for global health. Many vector-borne pathogens have appeared in new regions in the past two decades, and many endemic diseases have increased in incidence. Although introductions and local emergence are frequently considered distinct processes, many emerging endemic pathogens are in fact invading at a local scale coincident with habitat change. We highlight key differences in the dynamics and disease burden that result from increased pathogen transmission following habitat change compared with the introduction of pathogens to new regions. Truly in situ emergence is commonly driven by changes in human factors as much as by enhanced enzootic cycles whereas pathogen invasion results from anthropogenic trade and travel and suitable conditions for a pathogen, including hosts, vectors, and climate. Once established, ecological factors related to vector characteristics shape the evolutionary selective pressure on pathogens that may result in increased use of humans as transmission hosts. We describe challenges inherent in the control of vector-borne zoonotic diseases and some emerging non-traditional strategies that may be more effective in the long term.

Kilpatrick, A. Marm; Randolph, Sarah E.

2013-01-01

186

Prevention and control of neglected tropical diseases: overview of randomized trials, systematic reviews and meta-analyses  

PubMed Central

Abstract Objective To analyse evidence from randomized controlled trials (RCTs) on the prevention and control of neglected tropical diseases (NTDs) and to identify areas where evidence is lacking. Methods The Cochrane Central Register of Controlled Trials and PubMed were searched for RCTs and the Cochrane Database of Systematic Reviews and PubMed were searched for meta-analyses and systematic reviews, both from inception to 31 December 2012. Findings Overall, 258 RCTs were found on American trypanosomiasis, Buruli ulcer, dengue, geohelminth infection, leishmaniasis, leprosy, lymphatic filariasis, onchocerciasis, rabies, schistosomiasis or trachoma. No RCTs were found on cysticercosis, dracunculiasis, echinococcosis, foodborne trematodes, or human African trypanosomiasis. The most studied diseases were geohelminth infection (51 RCTs) and leishmaniasis (46 RCTs). Vaccines, chemoprophylaxis and interventions targeting insect vectors were evaluated in 113, 99 and 39 RCTs, respectively. Few addressed how best to deliver preventive chemotherapy, such as the choice of dosing interval (10) or target population (4), the population coverage needed to reduce transmission (2) or the method of drug distribution (1). Thirty-one publications containing 32 systematic reviews (16 with and 16 without meta-analyses) were found on American trypanosomiasis, dengue, geohelminths, leishmaniasis, leprosy, lymphatic filariasis, onchocerciasis, schistosomiasis or trachoma. Together, they included only 79 of the 258 published RCTs (30.6%). Of 36 interventions assessed, 8 were judged effective in more than one review. Conclusion Few RCTs on the prevention or control of the principal NTDs were found. Trials on how best to deliver preventive chemotherapy were particularly rare.

Kappagoda, Shanthi

2014-01-01

187

Vector control through environmental management with special reference to India--approach prospectives.  

PubMed

The introduction of different types of pollutants like those from industrial effluence, bye-products from petro-chemical industries, pesticidal application, wastages of nuclear power industries, etc. is viewed seriously by the society. For the control of vectors of disease the adoption of environmental management is, therefore, imperative. The physical methods like drainage of excess and waste water, making water unsuitable for vector breeding by adopting various indigenous methods in vogue, the intra and inter-sectrol coordination and community based activities are identified as the basic approaches for achieving this goal. Minimising the potentiality of vector breeding through source reduction and water management is thought to be the simplest, cheapest and most permanent method. For the society having varying types of habitation and varying degree of habitational facilities like planned housing, water supply and disposal, sanitation and organized anti-vector measures, the adoption of environmental management to exercise check over vector population is a promising proposition. The suitability of such an approach has already been demonstrated by MRC, (ICMR), Delhi and V.C.R.C., Pondicherry. The implementation of these methods is to be initiated right from Primary Health Centre and district level onwards and community is to be motivated to the extent that the various methods of environmental management for vector control are adopted in the routine way of life. In the present article these ideas have been touched upon and various methods of environmental management described in brief. In addition what other Governmental agencies are required to do in order to effectively implement environmental management methods are briefly enlisted. PMID:1940229

Yadava, R L; Rao, C K; Biswas, H; Narasimham, M V

1991-06-01

188

Vista/F-16 Multi-Axis Thrust Vectoring (MATV) control law design and evaluation  

NASA Technical Reports Server (NTRS)

For the Multi-Axis Thrust Vectoring (MATV) program, a new control law was developed using multi-axis thrust vectoring to augment the aircraft's aerodynamic control power to provide maneuverability above the normal F-16 angle of attack limit. The control law architecture was developed using Lockheed Fort Worth's offline and piloted simulation capabilities. The final flight control laws were used in flight test to demonstrate tactical benefits gained by using thrust vectoring in air-to-air combat. Differences between the simulator aerodynamics data base and the actual aircraft aerodynamics led to significantly different lateral-directional flying qualities during the flight test program than those identified during piloted simulation. A 'dial-a-gain' flight test control law update was performed in the middle of the flight test program. This approach allowed for inflight optimization of the aircraft's flying qualities. While this approach is not preferred over updating the simulator aerodynamic data base and then updating the control laws, the final selected gain set did provide adequate lateral-directional flying qualities over the MATV flight envelope. The resulting handling qualities and the departure resistance of the aircraft allowed the 422nd_squadron pilots to focus entirely on evaluating the aircraft's tactical utility.

Zwerneman, W. D.; Eller, B. G.

1994-01-01

189

Analysis of Phase Control Characteristics for Vector Control of Wound-Field Synchronous Motor at a Fixed Modulation Ratio  

NASA Astrophysics Data System (ADS)

This paper presents the phase control characteristics for the vector control of a wound-field synchronous motor at a fixed modulation ratio. In the general vector control method, current control is based on two-axis or three-axis control by estimation of the flux direction. In this case, the amplitude of the current control result is generally neglected. However, because several current controllers are work independently, the synthetic amplitude of the voltage must be less than the maximum value of the inverter voltage. This amplitude of the inverter voltage is due to the error in flux estimation. This implies that the utilization efficiency based on inverter voltage modulation reduces. In this paper, the method of phase control using fixed modulation ratio is proposed. With this method, the rating voltage of the inverter and the margin can be easily set. The phase control method assumes a fixed modulation ratio, and hence, it is more efficient than the conventional M-T axis method, which involves current control. Continuous crossover gain change is applied to this control in order to combine the conventional M-T axis current control and the proposed phase control. The characteristics of this control are confirmed by experimental results.

Tsukakoshi, Masahiko; Matsuse, Kouki

190

Strategies, Effectiveness and Rationale of Vector-borne Disease Control in the Pastoralist System of South-western Uganda  

Microsoft Academic Search

In Uganda, control of vector-borne diseases is mainly in form of vector control, and chemotherapy. There have been reports that acaricides are being misused in the pastoralist systems in Uganda. This is because of the belief by scientists that intensive application of acaricide is uneconomical and unsustainable particularly in the indigenous cattle. The objective of this study was to investigate

A Mugisha; A. McLeod; R. Percy; E. Kyewalabye

2005-01-01

191

Malaria vector control practices in an irrigated rice agro-ecosystem in central Kenya and implications for malaria control  

Microsoft Academic Search

Background  Malaria transmission in most agricultural ecosystems is complex and hence the need for developing a holistic malaria control\\u000a strategy with adequate consideration of socio-economic factors driving transmission at community level. A cross-sectional\\u000a household survey was conducted in an irrigated ecosystem with the aim of investigating vector control practices applied and\\u000a factors affecting their application both at household and community level.

Peter N Ng'ang'a; Josephat Shililu; Gayathri Jayasinghe; Violet Kimani; Charity Kabutha; Lucy Kabuage; Ephantus Kabiru; John Githure; Clifford Mutero

2008-01-01

192

Development and Evaluation of a Pyriproxyfen-Treated Device to Control the Dengue Vector, Aedes Aegypti (L.) (Diptera: Culicidae).  

National Technical Information Service (NTIS)

The resurgence of dengue fever and the chikungunya epidemic make the control of Aedes aegypti mosquitoes, the vectors of these diseases, critically important. We developed and evaluated an Ae. aegypti control device that is visually-attractive to mosquito...

A. Pongsiri A. Ponlawat P. W. McCardle S. Kurusarttra T. Fansiri

2013-01-01

193

Multi-cavity complex controller with vector simulator for TESLA technology linear accelerator  

NASA Astrophysics Data System (ADS)

A digital control, as the main part of the Low Level RF system, for superconducting cavities of a linear accelerator is presented. The FPGA based controller, supported by MATLAB system, was developed to investigate a novel firmware implementation. The complex control algorithm based on the non-linear system identification is the proposal verified by the preliminary experimental results. The general idea is implemented as the Multi-Cavity Complex Controller (MCC) and is still under development. The FPGA based controller executes procedure according to the prearranged control tables: Feed-Forward, Set-Point and Corrector unit, to fulfill the required cavity performance: driving in the resonance during filling and field stabilization for the flattop range. Adaptive control algorithm is applied for the feed-forward and feedback modes. The vector Simulator table has been introduced for an efficient verification of the FPGA controller structure. Experimental results of the internal simulation, are presented for a cavity representative condition.

Czarski, Tomasz; Pozniak, Krzysztof T.; Romaniuk, Ryszard S.; Szewinski, Jaroslaw

2008-01-01

194

[New vector control measures implemented between 2005 and 2011 on Reunion Island: lessons learned from chikungunya epidemic].  

PubMed

A major chikungunya outbreak concerned 38% of people living in Reunion Island in 2005-2006. Chikungunya is an arthropod-born-virus disease conveyed by mosquitoes called Aedes albopictus. The health agency in Indian Ocean is responsible for vector control. Previously, in the early 40s, vector control concerned only malaria prophylaxis in La Réunion. Then, during the chikungunya outbreak, a new vector control team was installed and learned from this epidemic. The lessons drawn from chikungunya outbreak in La Réunion are about global executive management and organization linked the local partners and population. The lessons also concern technical topics such as the need of scientific research about vectors and vector-control methods. Finally, the regional cooperation in Indian Ocean (Réunion, Maurice, Seychelles, Comoros, Madagascar) has to be developed to share epidemiologic and entomologic data in order to prevent new chikungunya or dengue outbreak. PMID:22693927

Bâville, M; Dehecq, J S; Reilhes, O; Margueron, T; Polycarpe, D; Filleul, L

2012-03-01

195

Combining zooprophylaxis and insecticide spraying: a malaria-control strategy limiting the development of insecticide resistance in vector mosquitoes.  

PubMed Central

Strategies to eradicate the vector-borne infectious diseases (e.g. malaria and Japanese encephalitis) are often directed at controlling vectors with insecticides. Spraying insecticide, however, opens the way for the development of insecticide resistance in vectors, which may lead to the failure of disease control. In this paper, we examine whether the combined use of insecticide spray and zooprophylaxis can limit the development of insecticide resistance in mosquitoes. Zooprophylaxis refers to the control of vector-borne diseases by attracting vectors to domestic animals in which the pathogen cannot amplify (a dead-end host). The human malaria parasite Plasmodium spp. has a closed transmission cycle between humans and mosquitoes, and hence cattle can serve as a dead-end host. Our model reveals that, by a suitable choice of insecticide spraying rate and cattle density and location, malaria can, in some situations, be controlled without mosquitoes developing insecticide resistance.

Kawaguchi, Isao; Sasaki, Akira; Mogi, Motoyoshi

2004-01-01

196

Identification of Stage Biomarkers for Human African Trypanosomiasis  

PubMed Central

Human African trypanosomiasis (HAT), caused by infection with sub-species of Trypanosoma brucei (T. b.), manifests as a hemolymphatic stage followed by an encephalitic stage. The distinction of the two stages needs improvement as drugs used for the late stage are highly toxic. Transcripts encoding 16 secreted proteins differentially expressed in the brains of mice at late stage T. b. brucei infection when the early stage drug suramin is no longer effective and different to immunoglobulins, chemokines, and cytokines, were selected by microarray analysis. Lipocalin 2 and secretory leukocyte peptidase inhibitor (SLPI) mRNA showed the highest differential expression in mice. These transcripts were also upregulated in brains from infected rats. Lipocalin 2 was increased in cerebrospinal fluid (CSF) from rats during late stage T. b. brucei infection. Protein levels of lipocalin 2, SLPI, and the chemokine CXCL10 were found increased in CSF from Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense late stage HAT compared to early stage.

Amin, Daniel Ndem; Ngoyi, Dieudonne Mumba; Nhkwachi, Gondwe-Mphepo; Palomba, Maria; Rottenberg, Martin; Buscher, Philippe; Kristensson, Krister; Masocha, Willias

2010-01-01

197

Development of novel drugs for human African trypanosomiasis.  

PubMed

Human African trypanosomiasis (HAT) or 'sleeping sickness' is a neglected tropical disease caused by the parasite Trypanosoma brucei. Novel models for funding pharmaceutical development against HAT are beginning to yield results. The Drugs for Neglected Diseases initiative (DNDi) rediscovered a nitroimidazole, fexinidazole, which is currently in Phase I clinical trials. Novel benzoxaboroles, discovered by Anacor, Scynexis and DNDi, have good pharmacokinetic properties in plasma and in the brain and are curative in a murine model of stage two HAT with brain infection. The Consortium for Parasitic Drug Development (CPDD) has identified a series of dicationic compounds that can cure a monkey model of stage two HAT. With other screening programs yielding hits, the pipeline for new HAT drugs might finally begin to fill. PMID:21707314

Brun, Reto; Don, Robert; Jacobs, Robert T; Wang, Michael Zhuo; Barrett, Michael P

2011-06-01

198

Comparative seroprevalences of bovine trypanosomiasis and anaplasmosis in five states of Malaysia.  

PubMed

A comparative seroprevalence study on bovine trypanosomiasis and anaplasmosis was conducted. Sera of adult cattle and buffaloes of different breeds from farms from five different states in Malaysia were collected and tested for the presence of Trypanosoma evansi antibodies by CATT and Anaplasma marginale antibodies by c-ELISA. Of the 116 samples, 14.7% tested positive for bovine trypanosomiasis and 77.6% for bovine anaplasmosis. PMID:22543604

Rahman, Wahab A; Fong, Samantha; Chandrawathani, P; Nurulaini, R; Zaini, C M; Premalaatha, B

2012-03-01

199

Opportunities for Improved Chagas Disease Vector Control Based on Knowledge, Attitudes and Practices of Communities in the Yucatan Peninsula, Mexico  

PubMed Central

Background Chagas disease is a vector-borne parasitic disease of major public health importance. Current prevention efforts are based on triatomine vector control to reduce transmission to humans. Success of vector control interventions depends on their acceptability and value to affected communities. We aimed to identify opportunities for and barriers to improved vector control strategies in the Yucatan peninsula, Mexico. Methodology/principal findings We employed a sequence of qualitative and quantitative research methods to investigate knowledge, attitudes and practices surrounding Chagas disease, triatomines and vector control in three rural communities. Our combined data show that community members are well aware of triatomines and are knowledgeable about their habits. However, most have a limited understanding of the transmission dynamics and clinical manifestations of Chagas disease. While triatomine control is not a priority for community members, they frequently use domestic insecticide products including insecticide spray, mosquito coils and plug-in repellents. Families spend about $32 US per year on these products. Alternative methods such as yard cleaning and window screens are perceived as desirable and potentially more effective. Screens are nonetheless described as unaffordable, in spite of a cost comparable to the average annual spending on insecticide products. Conclusion/Significance Further education campaigns and possibly financing schemes may lead families to redirect their current vector control spending from insecticide products to window screens. Also, synergism with mosquito control efforts should be further explored to motivate community involvement and ensure sustainability of Chagas disease vector control.

Rosecrans, Kathryn; Cruz-Martin, Gabriela; King, Ashley; Dumonteil, Eric

2014-01-01

200

Using Hydrologic Modeling to Screen Potential Environmental Management Methods for Malaria Vector Control in Niger  

NASA Astrophysics Data System (ADS)

This study describes the use of HYDREMATS, a physically-based distributed hydrology model, to investigate environmental management methods for malaria vector control in the Sahelian village of Banizoumbou, Niger. The model operates at fine spatial and temporal scales to enable explicit simulation of individual pool dynamics and isolation of mosquito breeding habitats. The results showed that leveling of topographic depressions where temporary breeding habitats form during the rainy season could reduce the persistence time of a pool to less than the time needed for establishment of mosquito breeding, approximately 7 days. Increasing the surface soil permeability by ploughing could also reduce the persistence time of a pool but this technique was not as effective as leveling. Therefore it is considered that leveling should be the preferred of the two options where possible. This investigation demonstrates that management methods that modify the hydrologic environment have significant potential to contribute to malaria vector control and human health improvement in Sahelian Africa.

Gianotti, R. L.; Bomblies, A.; Eltahir, E. A.

2008-12-01

201

Temephos Resistance in Aedes aegypti in Colombia Compromises Dengue Vector Control  

PubMed Central

Background Control and prevention of dengue relies heavily on the application of insecticides to control dengue vector mosquitoes. In Colombia, application of the larvicide temephos to the aquatic breeding sites of Aedes aegypti is a key part of the dengue control strategy. Resistance to temephos was recently detected in the dengue-endemic city of Cucuta, leading to questions about its efficacy as a control tool. Here, we characterize the underlying mechanisms and estimate the operational impact of this resistance. Methodology/Principal Findings Larval bioassays of Ae. aegypti larvae from Cucuta determined the temephos LC50 to be 0.066 ppm (95% CI 0.06–0.074), approximately 15× higher than the value obtained from a susceptible laboratory colony. The efficacy of the field dose of temephos at killing this resistant Cucuta population was greatly reduced, with mortality rates <80% two weeks after application and <50% after 4 weeks. Neither biochemical assays nor partial sequencing of the ace-1 gene implicated target site resistance as the primary resistance mechanism. Synergism assays and microarray analysis suggested that metabolic mechanisms were most likely responsible for the temephos resistance. Interestingly, although the greatest synergism was observed with the carboxylesterase inhibitor, DEF, the primary candidate genes from the microarray analysis, and confirmed by quantitative PCR, were cytochrome P450 oxidases, notably CYP6N12, CYP6F3 and CYP6M11. Conclusions/Significance In Colombia, resistance to temephos in Ae. aegypti compromises the duration of its effect as a vector control tool. Several candidate genes potentially responsible for metabolic resistance to temephos were identified. Given the limited number of insecticides that are approved for vector control, future chemical-based control strategies should take into account the mechanisms underlying the resistance to discern which insecticides would likely lead to the greatest control efficacy while minimizing further selection of resistant phenotypes.

Grisales, Nelson; Poupardin, Rodolphe; Gomez, Santiago; Fonseca-Gonzalez, Idalyd; Ranson, Hilary; Lenhart, Audrey

2013-01-01

202

Recombinant Bacterial Larvicides for Control of Important Mosquito Vectors of Disease  

Microsoft Academic Search

\\u000a The development of recombinant DNA techniques has made it possible to significantly improve the efficacy of Bacillus thuringiensis subsp. israelensis (Bti) currently used to control larvae of important mosquito disease vectors. As part of this symposium honoring the career\\u000a of Professor Mir S. Mulla, I briefly review here advances we have made using recombinant DNA technology to combine the most

Brian A. Federici

203

User's guide for vectorized code EQUIL for calculating equilibrium chemistry on Control Data STAR-100 computer  

NASA Technical Reports Server (NTRS)

A vectorized code, EQUIL, was developed for calculating the equilibrium chemistry of a reacting gas mixture on the Control Data STAR-100 computer. The code provides species mole fractions, mass fractions, and thermodynamic and transport properties of the mixture for given temperature, pressure, and elemental mass fractions. The code is set up for the electrons H, He, C, O, N system of elements. In all, 24 chemical species are included.

Kumar, A.; Graves, R. A., Jr.; Weilmuenster, K. J.

1980-01-01

204

Comparison of low-cost-implementation sensorless schemes in vector controlled adjustable speed drives  

Microsoft Academic Search

The paper describes the comparison between different high-performance low-cost-implementation techniques for the estimation of the rotor flux in medium-high speed sinusoidal AC motor drives. In sensorless estimation, rotor flux is estimated from measured terminal voltages and currents, and is used as a feedback in vector control schemes, achieving almost the same high-performance of sensored drives. At high speed, a key

M. Cacciato; G. Scarcella; G. Scelba; S. M. Bille; D. Costanzo; A. Cucuccio

2008-01-01

205

Cost-Effectiveness of Chagas Disease Vector Control Strategies in Northwestern Argentina  

PubMed Central

Background Control and prevention of Chagas disease rely mostly on residual spraying of insecticides. In Argentina, vector control shifted from a vertical to a fully horizontal strategy based on community participation between 1992 and 2004. The effects of such strategy on Triatoma infestans, the main domestic vector, and on disease transmission have not been assessed. Methods and Findings Based on retrospective (1993–2004) records from the Argentinean Ministry of Health for the Moreno Department, Northwestern Argentina, we performed a cost-effectiveness (CE) analysis and compared the observed CE of the fully horizontal vector control strategy with the expected CE for a vertical or a mixed (i.e., vertical attack phase followed by horizontal surveillance) strategy. Total direct costs (in 2004 US$) of the horizontal and mixed strategies were, respectively, 3.3 and 1.7 times lower than the costs of the vertical strategy, due to reductions in personnel costs. The estimated CE ratios for the vertical, mixed and horizontal strategies were US$132, US$82 and US$45 per averted human case, respectively. When per diems were excluded from the costs (i.e., simulating the decentralization of control activities), the CE of vertical, mixed and horizontal strategies was reduced to US$60, US$42 and US$32 per averted case, respectively. Conclusions and Significance The mixed strategy would have averted between 1.6 and 4.0 times more human cases than the fully horizontal strategy, and would have been the most cost-effective option to interrupt parasite transmission in the Department. In rural and dispersed areas where waning vertical vector programs cannot accomplish full insecticide coverage, alternative strategies need to be developed. If properly implemented, community participation represents not only the most appealing but also the most cost-effective alternative to accomplish such objectives.

Vazquez-Prokopec, Gonzalo M.; Spillmann, Cynthia; Zaidenberg, Mario; Kitron, Uriel; Gurtler, Ricardo E.

2009-01-01

206

GFP vectors for controlled expression and dual labelling of protein fusions in Bacillus subtilis  

Microsoft Academic Search

We report the development of a series of plasmid vectors for the construction of fusions to mutants of the intrinsically fluorescent green fluorescent protein, GFPmut1 (Cormack et al., 1996. Gene173, 33–38) and GFPuv (Crameri et al., 1996. Nature Biotechnology14, 315–319). Both N- and C-terminal fusions can be produced, and their expression can be finely controlled from the inducible Pxyl promoter

Peter J. Lewis; Adele L. Marston

1999-01-01

207

ACRR: Ad Hoc On-Demand Distance Vector Routing with Controlled Route Requests  

Microsoft Academic Search

Reactive routing protocols like Ad-hoc On-Demand Distance Vector Routing (AODV) and Dynamic Source Routing in Ad-Hoc Wireless Networks (DSR) which are used in Mobile and Ad-hoc Networks (MANETs) work by flooding the network with control packets. There is generally a limit on the number of these packets that can be generated or forwarded. But a malicious node can disregard this

Jayesh Kataria; P. S. Dhekne; Sugata Sanyal

2010-01-01

208

Noise-Induced Hearing Loss and Associated Factors Among Vector Control Workers in a Malaysian State.  

PubMed

This study aims to determine the prevalence and associated factors of noise-induced hearing loss (NIHL) among vector control workers in the state of Negeri Sembilan, Malaysia. This was an analytical cross-sectional study conducted on 181 vector control workers who were working in district health offices in a state in Malaysia. Data were collected using a self-administered questionnaire and audiometry. Prevalence of NIHL was 26% among this group of workers. NIHL was significantly associated with the age-group of 40 years and older, length of service of 10 or more years, current occupational noise exposure, listening to loud music, history of firearms use, and history of mumps/measles infection. Following logistic regression, age of more than 40 years and noise exposure in current occupation were associated with NIHL with an odds ratio of 3.45 (95% confidence interval = 1.68-7.07) and 6.87 (95% confidence interval = 1.54-30.69), respectively, among this group of vector control workers. PMID:22548779

Masilamani, Retneswari; En, Abdul Rasib; Darus, Azlan; Ting, Anselm Su

2012-05-01

209

Mapping Neglected Swimming Pools from Satellite Data for Urban Vector Control  

NASA Astrophysics Data System (ADS)

Neglected swimming pools provide suitable breeding habit for mosquitoes, can contain thousands of mosquito larvae, and present both a significant nuisance and public health risk due to their inherent proximity to urban and suburban populations. The rapid increase and sustained rate of foreclosures in California associated with the recent recession presents a challenge for vector control districts seeking to identify, treat, and monitor neglected pools. Commercial high resolution satellite imagery offers some promise for mapping potential neglected pools, and for mapping pools for which routine maintenance has been reestablished. We present progress on unsupervised classification techniques for mapping both neglected pools and clean pools using high resolution commercial satellite data and discuss the potential uses and limitations of this data source in support of vector control efforts. An unsupervised classification scheme that utilizes image segmentation, band thresholds, and a change detection approach was implemented for sample regions in Coachella Valley, CA and the greater Los Angeles area. Comparison with field data collected by vector control personal was used to assess the accuracy of the estimates. The results suggest that the current system may provide some utility for early detection, or cost effective and time efficient annual monitoring, but additional work is required to address spectral and spatial limitations of current commercial satellite sensors for this purpose.

Barker, C. M.; Melton, F. S.; Reisen, W. K.

2010-12-01

210

All-in-One inducible lentiviral vector systems based on drug controlled FLP recombinase.  

PubMed

Site specific recombinases are frequently used as gene switches in transgenic animals where recombination is induced by drug treatment or by tissue specific recombinase expression. Alternatively, lentiviral gene transfer can be utilized for the genetic modification of a wide variety of cell types, albeit systems for tight control of transcriptional activity are scarce. Here, we combined lentiviral gene transfer and the development of a tightly drug-controlled FLP recombinase for the construction of "All-in-One" inducible gene expression systems. Tight control of FLP activity was achieved through N-terminal fusion with a FKBP12-derived conditional destruction domain and a C-terminal estrogen receptor binding domain making recombination dependent on the presence of Shield-1 and 4-hydroxytamoxifen. Exploiting the capacity of FLP to mediate excision and inversion, "All-in-One" lentiviral gene switch vector systems were generated where drug-induced recombination resulted in abrogation of FLP expression and subsequent overexpression or knockdown of the prototypical tumor suppressor phosphatase and tensin homolog PTEN. "All-in-One" vectors proved their functionality in a variety of hematopoietic cell lines, and primary murine bone marrow cells. Our new vector system thus combines the ease of lentiviral gene transfer and the power of site specific recombinases for analysis of gene function. PMID:24529624

Maetzig, Tobias; Kuehle, Johannes; Schwarzer, Adrian; Turan, Soeren; Rothe, Michael; Chaturvedi, Anuhar; Morgan, Michael; Ha, Teng Cheong; Heuser, Michael; Hammerschmidt, Wolfgang; Baum, Christopher; Schambach, Axel

2014-05-01

211

An update on the incidence of dengue gaining strength in Saudi Arabia and current control approaches for its vector mosquito  

PubMed Central

Background The cases of dengue reported earlier in the late 1990s from the Kingdom of Saudi Arabia (KSA) occurred in the cities of Jeddah and Makkah. Although the kingdom has ample financial resources to establish effective control measures for the dengue vector, numerous cases of dengue occur and fluctuate in numbers from year to year. This necessitates a serious review of the current vector control strategies being practiced in order to identify the existing shortcomings. This short report provides an update on epidemiology of dengue in KSA (specifically in cities of Jeddah and Makkah) with a critical look at the current vector control strategies. Findings In 2013, 4411 cases of dengue were reported, with 8 cases of mortality. This number of dengue incidence was four times higher compared to 2012. In 2013, the highest number of 1272 dengue cases was reported in May, while the lowest number (37) of cases was reported in September. Conclusions It is evident that the control strategies of the dengue vector presently employed are inadequate. There seems to be serious deficiencies in following proper scientific procedures during field application(s) of control materials against the vector as is evident by the increases in the number of dengue cases as well as frequent outbreaks of the vector mosquito populations. In this review, some specific suggestions are made to draw attention to the relevant KSA authorities of the possible reasons behind unsuccessful control results and as to how to improve the strategy of dengue vector control in the kingdom.

2014-01-01

212

Spatial Predictions of Rhodesian Human African Trypanosomiasis (Sleeping Sickness) Prevalence in Kaberamaido and Dokolo, Two Newly Affected Districts of Uganda  

PubMed Central

The continued northwards spread of Rhodesian sleeping sickness or Human African Trypanosomiasis (HAT) within Uganda is raising concerns of overlap with the Gambian form of the disease. Disease convergence would result in compromised diagnosis and treatment for HAT. Spatial determinants for HAT are poorly understood across small areas. This study examines the relationships between Rhodesian HAT and several environmental, climatic and social factors in two newly affected districts, Kaberamaido and Dokolo. A one-step logistic regression analysis of HAT prevalence and a two-step logistic regression method permitted separate analysis of both HAT occurrence and HAT prevalence. Both the occurrence and prevalence of HAT were negatively correlated with distance to the closest livestock market in all models. The significance of distance to the closest livestock market strongly indicates that HAT may have been introduced to this previously unaffected area via the movement of infected, untreated livestock from endemic areas. This illustrates the importance of the animal reservoir in disease transmission, and highlights the need for trypanosomiasis control in livestock and the stringent implementation of regulations requiring the treatment of cattle prior to sale at livestock markets to prevent any further spread of Rhodesian HAT within Uganda.

Batchelor, Nicola A.; Atkinson, Peter M.; Gething, Peter W.; Picozzi, Kim; Fevre, Eric M.; Kakembo, Abbas S. L.; Welburn, Susan C.

2009-01-01

213

Development of Novel Magnetic Encoder and Vector Control Method for Servo Control of High-Speed Motor  

NASA Astrophysics Data System (ADS)

This paper presents a novel unipolar magnetic encoder and a new Vector control method of AC servo which can enable the feedback of the rotor position with high accuracy in high speed occasion. The signal generator of encoder consists of three pairs of semiconductor hall elements and a rotor of alnico magnet with one pair of poles. This encoder is featured with the operation module and the communication module to transmit an angular data in the form of asynchronous serial transfer protocol. Besides, a delay compensation algorithm is proposed to ensure the accurate estimation of instant angular position and the estimation error is also analyzed. At last, an experimental apparatus was built for a 600W, 4 pairs of pole, at rated speed 20,000min-1, permanent-magnet synchronous motor drive and the proposed vector control scheme has been implemented. The experiment results supported the validity of the proposed magnetic encoder and vector control method for high-speed AC servo control within 0.05 % error of revolving speed.

Hao, Shuanghui; Liu, Jie; Mizugaki, Yoshio

214

Progress in controlling the reinvasion of windborne vectors into the western area of the Onchocerciasis Control Programme in West Africa.  

PubMed

Since vector control began in 1975, waves of Simulium sirbanum and S. damnosum s.str., the principal vectors of severe blinding onchocerciasis in the West African savannas, have reinvaded treated rivers inside the original boundaries of the Onchocerciasis Control Programme in West Africa. Larviciding of potential source breeding sites has shown that these 'savanna' species are capable of travelling and carrying Onchocerca infection for at least 500 km northeastwards with the monsoon winds in the early rainy season. Vector control has, therefore, been extended progressively westwards. In 1984 the Programme embarked on a major western extension into Guinea, Sierra Leone, western Mali, Senegal and Guinea-Bissau. The transmission resulting from the reinvasion of northern Côte d'Ivoire and Burkina Faso has been reduced by over 95%, but eastern Mali has proved more difficult to protect because of sources in both Guinea and Sierra Leone. Rivers in Sierra Leone were treated for the first time in 1989 and biting and transmission rates in Sierra Leone and Guinea fell by over 90%. Because of treatment problems in some complex rapids and mountainous areas, flies still reinvaded Mali, though biting rates were approximately 70% lower than those recorded before anti-reinvasion treatments started. It was concluded that transmission in eastern Mali has now been reduced to the levels required to control onchocerciasis. PMID:1976266

Baker, R H; Guillet, P; Sékétéli, A; Poudiougo, P; Boakye, D; Wilson, M D; Bissan, Y

1990-06-30

215

The journey towards elimination of gambiense human African trypanosomiasis: not far, nor easy.  

PubMed

Considering the epidemic situation of gambiense human African trypanosomiasis (HAT) at the end of the twentieth century, the World Health Organization (WHO) and partners strengthened disease control and surveillance. Over the last 15 years, the activities implemented through the National Control Programmes have brought gambiense HAT under control and now its elimination is deemed as an achievable goal. In 2012, WHO targeted gambiense HAT for elimination as a public health problem by 2020. The final goal will be the sustainable disease elimination by 2030, defined as the interruption of the transmission of gambiense HAT. The elimination is considered feasible, because of the epidemiological vulnerability of the disease, the current state of control, the availability of strategies and tools and international commitment and political will. Integration of activities in the health system is needed to ensure the sustainability of the elimination. The development of user-friendly diagnostic and treatment tools will facilitate the integration process. Adequate funding is needed to implement activities, but also to support research that will make the elimination sustainable. A long-term commitment by donors is needed and ownership of the process by endemic countries is critical. PMID:24709291

Franco, J R; Simarro, P P; Diarra, A; Ruiz-Postigo, J A; Jannin, J G

2014-05-01

216

Pyrethroid Resistance in Anopheles gambiae, in Bomi County, Liberia, Compromises Malaria Vector Control  

PubMed Central

Background Long Lasting Insecticidal Nets (LLIN) and Indoor Residual Spraying (IRS) have both proven to be effective malaria vector control strategies in Africa and the new technology of insecticide treated durable wall lining (DL) is being evaluated. Sustaining these interventions at high coverage levels is logistically challenging and, furthermore, the increase in insecticide resistance in African malaria vectors may reduce the efficacy of these chemical based interventions. Monitoring of vector populations and evaluation of the efficacy of insecticide based control approaches should be integral components of malaria control programmes. This study reports on entomological survey conducted in 2011 in Bomi County, Liberia. Methods Anopheles gambiae larvae were collected from four sites in Bomi, Liberia, and reared in a field insectary. Two to five days old female adult An gambiae s.l. were tested using WHO tube (n?=?2027) and cone (n?=?580) bioassays in houses treated with DL or IRS. A sample of mosquitoes (n?=?169) were identified to species/molecular form and screened for the presence of knock down resistance (kdr) alleles associated with pyrethroid resistance. Results Anopheles gambiae s.l tested were resistant to deltamethrin but fully susceptible to bendiocarb and fenithrothion. The corrected mortality of local mosquitoes exposed to houses treated with deltamethrin either via IRS or DL was 12% and 59% respectively, suggesting that resistance may affect the efficacy of these interventions. The presence of pyrethroid resistance was associated with a high frequency of the 1014F kdr allele (90.5%) although this mutation alone cannot explain the resistance levels observed. Conclusion High prevalence of resistance to deltamethrin in Bomi County may reduce the efficacy of malaria strategies relying on this class of insecticide. The findings highlight the urgent need to expand and sustain monitoring of insecticide resistance in Liberian malaria vectors, evaluate the effectiveness of existing interventions and develop appropriate resistance management strategies.

Temu, Emmanuel A.; Maxwell, Caroline; Munyekenye, Godwil; Howard, Annabel F. V.; Munga, Stephen; Avicor, Silas W.; Poupardin, Rodolphe; Jones, Joel J.; Allan, Richard; Kleinschmidt, Immo; Ranson, Hilary

2012-01-01

217

Global Status of DDT and Its Alternatives for Use in Vector Control to Prevent Disease  

PubMed Central

Objective I review the status of dichlorodiphenyltrichloroethane (DDT), used for disease vector control, along with current evidence on its benefits and risks in relation to the available alternatives. Data sources and extraction Contemporary data on DDT use were largely obtained from questionnaires and reports. I also conducted a Scopus search to retrieve published articles. Data synthesis DDT has been recommended as part of the arsenal of insecticides available for indoor residual spraying until suitable alternatives are available. Approximately 14 countries use DDT for disease control, and several countries are preparing to reintroduce DDT. The effectiveness of DDT depends on local settings and merits close consideration in relation to the alternatives. Concerns about the continued use of DDT are fueled by recent reports of high levels of human exposure associated with indoor spraying amid accumulating evidence on chronic health effects. There are signs that more malaria vectors are becoming resistant to the toxic action of DDT, and that resistance is spreading to new countries. A comprehensive cost assessment of DDT versus its alternatives that takes side effects into account is missing. Effective chemical methods are available as immediate alternatives to DDT, but the choice of insecticide class is limited, and in certain areas the development of resistance is undermining the efficacy of insecticidal tools. New insecticides are not expected in the short term. Nonchemical methods are potentially important, but their effectiveness at program level needs urgent study. Conclusions To reduce reliance on DDT, support is needed for integrated and multipartner strategies of vector control and for the continued development of new technologies. Integrated vector management provides a framework for developing and implementing effective technologies and strategies as sustainable alternatives to reliance on DDT.

van den Berg, Henk

2009-01-01

218

Optical control of retrogradely infected neurons using drug-regulated "TLoop" lentiviral vectors.  

PubMed

Many approaches that use viral vectors to deliver transgenes have limited transduction efficiency yet require high levels of transgene expression. In particular, infection via axon terminals is relatively inefficient but is a powerful means of achieving infection of specific neuron types. Combining this with optogenetic approaches requires high gene expression levels that are not typically achieved with nontoxic retrogradely infecting vectors. We generated rabies glycoprotein-pseudotyped lentiviral vectors that use a positive feedback loop composed of a Tet promoter driving both its own tetracycline-dependent transcription activator (tTA) ("TLoop") and channelrhodopsin-2-YFP (ChR2YFP). We show that TLoop vectors strongly express proteins in a drug-controllable manner in neurons that project to injection sites within the mouse brain. After initial infection, the virus travels retrogradely, stably integrates into the host genome, and expresses gene products. The expression is robust and allows optogenetic studies of neurons projecting to the location of virus injection, as demonstrated by fluorescence-targeted intracellular recordings. ChR2YFP expression did not cause observable signs of toxicity and continued for up to 6 mo after infection. Expression can be reversibly blocked by administration of doxycycline, if necessary, for expression of gene products that might be more toxic. Overall, we present a system that will allow researchers to achieve high levels of gene expression even in the face of inefficient viral transduction. The particular vectors that we demonstrate may enhance efforts to gain a precise understanding of the contributions of specific types of projection neurons to brain function. PMID:24572099

Cetin, Ali; Callaway, Edward M

2014-05-15

219

Circadian entrainment by light and host in the Chagas disease vector, Triatoma infestans.  

PubMed

Triatoma infestans (Reduviidae: Triatominae, "kissing bug") is the main insect vector of Trypanosoma cruzi, the causative agent of Chagas disease, a chronic trypanosomiasis infecting 10 million people world-wide. This hematophagous bug feeds on diurnal and nocturnal species during each host's quiescent time. As the hosts are also its major predators, kissing bugs are subjected to dual selective pressures from a single source. Therefore, synchronization of feeding with the host's behavior is critical to the insects' survival. We show that nonphotic signals linked to the host eclipse the role of light and dark as the primary circadian zeitgeber for these bugs, although light still strongly inhibits locomotor behavior directly. In nature, this combination provides the insect with great flexibility in organizing physiology and behavior: anticipating a quiescent host or avoiding its potential predation while remaining directly responsive to immediate environmental conditions. Manipulation of nonphotic entrainment could be a useful chronobiotic tool in the control of Chagas disease. PMID:24156522

Valentinuzzi, Verónica Sandra; Amelotti, Ivana; Gorla, David Eladio; Catalá, Silvia Susana; Ralph, Martin Roland

2014-03-01

220

Defeasible Deontic Robot Control Based on Extended Vector Annotated Logic Programming  

NASA Astrophysics Data System (ADS)

We have already proposed an annotated logic program called an EVALPSN (Extended Vector Annotated Logic Program with Strong Negation) to deal with defeasible deontic reasoning. In this paper, we propose a defeasible deontic action control system for a virtual robot based on EVALPSN. We suppose a beetle robot who is traveling a maze with three kinds of obstacles and has some different kinds of sensors to detect the obstacles. If some sensor values are input to the robot control, the next action that the robot should do is computed by the EVALPSN programming system.

Nakamatsu, Kazumi; Abe, Jair Minoro; Suzuki, Atsuyuki

2002-09-01

221

Development of fungal applications on netting substrates for malaria vector control.  

PubMed

Mosquito resistance to chemical insecticides is considered a serious threat for the sustainable use of contemporary malaria vector control methods. Fungal entomopathogens show potential as alternative biological control agents against (insecticide-resistant) anophelines. This study was designed to test whether the fungus, Beauveria bassiana, could be delivered to mosquitoes on netting materials that might be used in house screens, such as eave curtains. Tests were conducted to determine effects of formulation, application method, netting material, and nature of mosquito contact. Beauveria had a twice as high impact on Anopheles gambiae s.s. longevity when suspended in Shellsol solvent compared with Ondina oil (HR = 2.12, 95% confidence interval = 1.83-2.60, P < 0.001), and was significantly more infective when applied through spraying than dipping. Polyester and cotton bednets were the most effective substrates for mosquito infections, with highest spore viability on cotton nets. Whereas fungal impact was highest in mosquitoes that had passed through large-meshed impregnated nets, overall efficacy was equal between small- and large-meshed nets, with < or = 30-min spore contact killing >90% of mosquitoes within 10 d. Results indicate that the use of fungal spores dissolved in Shellsol and sprayed on small-meshed cotton eave curtain nets would be the most promising option for field implementation. Biological control with fungus-impregnated eave curtains could provide a means to target host-seeking mosquitoes upon house entry, and has potential for use in integrated vector management strategies, in combination with chemical vector control measures, to supplement malaria control in areas with high levels of insecticide resistance. PMID:21485366

Farenhorst, Marit; Hilhorst, Anne; Thomas, Matthew B; Knols, Bart G J

2011-03-01

222

The role of vector control in stopping the transmission of malaria: threats and opportunities  

PubMed Central

Malaria control, and that of other insect borne diseases such as dengue, is heavily dependent on our ability to control the mosquito populations that transmit these diseases. The major push over the last decade to reduce the global burden of malaria has been driven by the distribution of pyrethroid insecticide-treated bednets and an increase in coverage of indoor residual spraying (IRS). This has reduced malaria deaths by a third. Progress towards the goal of reducing this further is threatened by lack of funding and the selection of drug and insecticide resistance. When malaria control was initially scaled up, there was little pyrethroid resistance in the major vectors, today there is no country in Africa where the vectors remain fully susceptible to pyrethroids. The first pyrethroid resistance mechanisms to be selected produced low-level resistance which had little or no operational significance. More recently, metabolically based resistance has been selected, primarily in West Africa, which in some mosquito populations produces more than 1000-fold resistance. As this spreads the effectiveness of pyrethroid-based bednets and IRS will be compromised. New public health insecticides are not readily available. The pipeline of agrochemical insecticides that can be re-purposed for public health dried up 30 years ago when the target product profile for agricultural insecticides shifted from broad spectrum, stable, contact-acting insecticides to narrow spectrum stomach poisons that could be delivered through the plant. A public–private partnership, the Innovative Vector Control Consortium, was established in 2005 to stimulate the development of new public health pesticides. Nine potential new classes of chemistry are in the pipeline, with the intention of developing three into new insecticides. While this has been successfully achieved, it will still take 6–9 years for new insecticides to reach the market. Careful management of the resistance situation in the interim will be needed if current gains in malaria control are not to be reversed.

Hemingway, Janet

2014-01-01

223

The role of vector control in stopping the transmission of malaria: threats and opportunities.  

PubMed

Malaria control, and that of other insect borne diseases such as dengue, is heavily dependent on our ability to control the mosquito populations that transmit these diseases. The major push over the last decade to reduce the global burden of malaria has been driven by the distribution of pyrethroid insecticide-treated bednets and an increase in coverage of indoor residual spraying (IRS). This has reduced malaria deaths by a third. Progress towards the goal of reducing this further is threatened by lack of funding and the selection of drug and insecticide resistance. When malaria control was initially scaled up, there was little pyrethroid resistance in the major vectors, today there is no country in Africa where the vectors remain fully susceptible to pyrethroids. The first pyrethroid resistance mechanisms to be selected produced low-level resistance which had little or no operational significance. More recently, metabolically based resistance has been selected, primarily in West Africa, which in some mosquito populations produces more than 1000-fold resistance. As this spreads the effectiveness of pyrethroid-based bednets and IRS will be compromised. New public health insecticides are not readily available. The pipeline of agrochemical insecticides that can be re-purposed for public health dried up 30 years ago when the target product profile for agricultural insecticides shifted from broad spectrum, stable, contact-acting insecticides to narrow spectrum stomach poisons that could be delivered through the plant. A public-private partnership, the Innovative Vector Control Consortium, was established in 2005 to stimulate the development of new public health pesticides. Nine potential new classes of chemistry are in the pipeline, with the intention of developing three into new insecticides. While this has been successfully achieved, it will still take 6-9 years for new insecticides to reach the market. Careful management of the resistance situation in the interim will be needed if current gains in malaria control are not to be reversed. PMID:24821917

Hemingway, Janet

2014-01-01

224

Universal Parameter Measurement and Sensorless Vector Control of Induction and Permanent Magnet Synchronous Motors  

NASA Astrophysics Data System (ADS)

Recently, induction motors (IMs) and permanent-magnet synchronous motors (PMSMs) have been used in various industrial drive systems. The features of the hardware device used for controlling the adjustable-speed drive in these motors are almost identical. Despite this, different techniques are generally used for parameter measurement and speed-sensorless control of these motors. If the same technique can be used for parameter measurement and sensorless control, a highly versatile adjustable-speed-drive system can be realized. In this paper, the authors describe a new universal sensorless control technique for both IMs and PMSMs (including salient pole and nonsalient pole machines). A mathematical model applicable for IMs and PMSMs is discussed. Using this model, the authors derive the proposed universal sensorless vector control algorithm on the basis of estimation of the stator flux linkage vector. All the electrical motor parameters are determined by a unified test procedure. The proposed method is implemented on three test machines. The actual driving test results demonstrate the validity of the proposed method.

Yamamoto, Shu; Ara, Takahiro

225

Simplified Models of Vector Control Impact upon Malaria Transmission by Zoophagic Mosquitoes  

PubMed Central

Background High coverage of personal protection measures that kill mosquitoes dramatically reduce malaria transmission where vector populations depend upon human blood. However, most primary malaria vectors outside of sub-Saharan Africa can be classified as “very zoophagic,” meaning they feed occasionally (<10% of blood meals) upon humans, so personal protection interventions have negligible impact upon their survival. Methods and Findings We extended a published malaria transmission model to examine the relationship between transmission, control, and the baseline proportion of bloodmeals obtained from humans (human blood index). The lower limit of the human blood index enables derivation of simplified models for zoophagic vectors that (1) Rely on only three field-measurable parameters. (2) Predict immediate and delayed (with and without assuming reduced human infectivity, respectively) impacts of personal protection measures upon transmission. (3) Illustrate how appreciable indirect communal-level protection for non-users can be accrued through direct personal protection of users. (4) Suggest the coverage and efficacy thresholds required to attain epidemiological impact. The findings suggest that immediate, indirect, community-wide protection of users and non-users alike may linearly relate to the efficacy of a user’s direct personal protection, regardless of whether that is achieved by killing or repelling mosquitoes. High protective coverage and efficacy (?80%) are important to achieve epidemiologically meaningful impact. Non-users are indirectly protected because the two most common species of human malaria are strict anthroponoses. Therefore, the small proportion of mosquitoes that are killed or diverted while attacking humans can represent a large proportion of those actually transmitting malaria. Conclusions Simplified models of malaria transmission by very zoophagic vectors may be used by control practitioners to predict intervention impact interventions using three field-measurable parameters; the proportion of human exposure to mosquitoes occurring when an intervention can be practically used, its protective efficacy when used, and the proportion of people using it.

Kiware, Samson S.; Chitnis, Nakul; Moore, Sarah J.; Devine, Gregor J.; Majambere, Silas; Merrill, Stephen; Killeen, Gerry F.

2012-01-01

226

A Model Framework to Estimate Impact and Cost of Genetics-Based Sterile Insect Methods for Dengue Vector Control  

PubMed Central

Vector-borne diseases impose enormous health and economic burdens and additional methods to control vector populations are clearly needed. The Sterile Insect Technique (SIT) has been successful against agricultural pests, but is not in large-scale use for suppressing or eliminating mosquito populations. Genetic RIDL technology (Release of Insects carrying a Dominant Lethal) is a proposed modification that involves releasing insects that are homozygous for a repressible dominant lethal genetic construct rather than being sterilized by irradiation, and could potentially overcome some technical difficulties with the conventional SIT technology. Using the arboviral disease dengue as an example, we combine vector population dynamics and epidemiological models to explore the effect of a program of RIDL releases on disease transmission. We use these to derive a preliminary estimate of the potential cost-effectiveness of vector control by applying estimates of the costs of SIT. We predict that this genetic control strategy could eliminate dengue rapidly from a human community, and at lower expense (approximately US$ 2?30 per case averted) than the direct and indirect costs of disease (mean US$ 86–190 per case of dengue). The theoretical framework has wider potential use; by appropriately adapting or replacing each component of the framework (entomological, epidemiological, vector control bio-economics and health economics), it could be applied to other vector-borne diseases or vector control strategies and extended to include other health interventions.

Alphey, Nina; Alphey, Luke; Bonsall, Michael B.

2011-01-01

227

Operational efficiency and sustainability of vector control of malaria and dengue: descriptive case studies from the Philippines  

PubMed Central

Background Analysis is lacking on the management of vector control systems in disease-endemic countries with respect to the efficiency and sustainability of operations. Methods Three locations were selected, at the scale of province, municipality and barangay (i.e. village). Data on disease incidence, programme activities, and programme management were collected on-site through meetings and focus group discussions. Results Adaptation of disease control strategies to the epidemiological situation per barangay, through micro-stratification, brings gains in efficiency, but should be accompanied by further capacity building on local situational analysis for better selection and targeting of vector control interventions within the barangay. An integrated approach to vector control, aiming to improve the rational use of resources, was evident with a multi-disease strategy for detection and response, and by the use of combinations of vector control methods. Collaboration within the health sector was apparent from the involvement of barangay health workers, re-orientation of job descriptions and the creation of a disease surveillance unit. The engagement of barangay leaders and use of existing community structures helped mobilize local resources and voluntary services for vector control. In one location, local authorities and the community were involved in the planning, implementation and evaluation of malaria control, which triggered local programme ownership. Conclusions Strategies that contributed to an improved efficiency and sustainability of vector control operations were: micro-stratification, integration of vector control within the health sector, a multi-disease approach, involvement of local authorities, and empowerment of communities. Capacity building on situational analysis and vector surveillance should be addressed through national policy and guidelines.

2012-01-01

228

Theory and simulation of vector control based on rotor position orientation of rare-earth permanent magnet motor  

Microsoft Academic Search

Since the rare-earth permanent materials were invented, all kinds of PM motors and their relevant control methods have been booming. Requirements on high efficiency and flexible control systems are the core of its development. Vector control method based on rotor position orientation of rare-earth PM is presented under this case, and it has so many control qualifies that general DC

Yong Zhang; Keran Shao; Lan Li; Xinhua Li

2003-01-01

229

A Gyroless Safehold Control Law Using Angular Momentum as an Inertial Reference Vector  

NASA Technical Reports Server (NTRS)

A novel safehold control law was developed for the nadir-pointing Vegetation Canopy Lidar (VCL) spacecraft, necessitated by a challenging combination of constraints. The instrument optics did not have a recloseable cover to protect them form potentially catastrophic damage if they were exposed to direct sunlight. The baseline safehold control law relied on a single-string inertial reference unit. A gyroless safehold law was developed to give a degree of robustness to gyro failures. Typical safehold solutions were not viable; thermal constraints made spin stabilization unsuitable, and an inertial hold based solely on magnetometer measurements wandered unaceptably during eclipse. The novel approach presented here maintains a momentum bias vector not for gyroscopic stiffness, but to use as an inertial reference direction during eclipse. The control law design is presented. The effect on stability of the rank-deficiency of magnetometer-based rate derivation is assessed. The control law's performance is evaluated by simulation.

Stoneking, Eric; Lebsock, Ken

2008-01-01

230

A Gyroless Safehold Control Law using Angular Momentum as an Inertial Reference Vector  

NASA Technical Reports Server (NTRS)

A novel safehold control law was developed for the nadir-pointing Vegetation Canopy Lidar (VCL) spacecraft, necessitated by a challenging combination of constraints. The instrument optics did not have a reclosable cover to protect them from potentially catastrophic damage if they were exposed to direct sunlight. The baseline safehold control law relied on a single-string inertial reference unit. A gyroless safehold law was developed to give a degree of rebustness to gyro failures. Typical safehold solutions were not viable; thermal constraints made spin stabilization unsuitable, and an inertial hold based solely on magnetometer measurements wandered unacceptably during eclipse. The novel approach presented here maintains a momentum bias vector not for gyroscopic stiffness, but to use as an inertial reference direction during eclipse. The control law design is presented. The effect on stability of the rate-deficiency of magnetometer-based rate derivation is assessed. The control law's performance is evaluated by simulation.

Stoneking, Eric; Lebsock, Ken

2008-01-01

231

Oviposition Site Selection by the Dengue Vector Aedes aegypti and Its Implications for Dengue Control  

PubMed Central

Background Because no dengue vaccine or antiviral therapy is commercially available, controlling the primary mosquito vector, Aedes aegypti, is currently the only means to prevent dengue outbreaks. Traditional models of Ae. aegypti assume that population dynamics are regulated by density-dependent larval competition for food and little affected by oviposition behavior. Due to direct impacts on offspring survival and development, however, mosquito choice in oviposition site can have important consequences for population regulation that should be taken into account when designing vector control programs. Methodology/Principal Findings We examined oviposition patterns by Ae. aegypti among 591 naturally occurring containers and a set of experimental containers in Iquitos, Peru. Using larval starvation bioassays as an indirect measure of container food content, we assessed whether females select containers with the most food for their offspring. Our data indicate that choice of egg-laying site is influenced by conspecific larvae and pupae, container fill method, container size, lid, and sun exposure. Although larval food positively influenced oviposition, our results did not support the hypothesis that females act primarily to maximize food for larvae. Females were most strongly attracted to sites containing immature conspecifics, even when potential competitors for their progeny were present in abundance. Conclusion/Significance Due to strong conspecific attraction, egg-laying behavior may contribute more to regulating Ae. aegypti populations than previously thought. If highly infested containers are targeted for removal or larvicide application, females that would have preferentially oviposited in those sites may instead distribute their eggs among other suitable, previously unoccupied containers. Strategies that kill mosquitoes late in their development (i.e., insect growth regulators that kill pupae rather than larvae) will enhance vector control by creating “egg sinks,” treated sites that exploit conspecific attraction of ovipositing females, but reduce emergence of adult mosquitoes via density-dependent larval competition and late acting insecticide.

Wong, Jacklyn; Stoddard, Steven T.; Astete, Helvio; Morrison, Amy C.; Scott, Thomas W.

2011-01-01

232

Instantaneous switch state fuzzy vector controller for 3-phase switch controlled rectifiers  

Microsoft Academic Search

Conventional feedback control of a switch controlled 3-phase rectifier usually utilises PI control in the forward path. Studies have shown that fuzzy logic control (FLC) can provide advantages when power system and other parameters change in a nonlinear and nonpredictable way. In microprocessor control applications power semiconductor switching speeds are often limited by the microprocessor calculation times. This paper studies

K. Hoffman

1998-01-01

233

Least squares support vector machines for direction of arrival estimation with error control and validation.  

SciTech Connect

The paper presents a multiclass, multilabel implementation of least squares support vector machines (LS-SVM) for direction of arrival (DOA) estimation in a CDMA system. For any estimation or classification system, the algorithm's capabilities and performance must be evaluated. Specifically, for classification algorithms, a high confidence level must exist along with a technique to tag misclassifications automatically. The presented learning algorithm includes error control and validation steps for generating statistics on the multiclass evaluation path and the signal subspace dimension. The error statistics provide a confidence level for the classification accuracy.

Christodoulou, Christos George (University of New Mexico, Albuquerque, NM); Abdallah, Chaouki T. (University of New Mexico, Albuquerque, NM); Rohwer, Judd Andrew

2003-02-01

234

A three-year follow-up of ocular onchocerciasis in an area of vector control*  

PubMed Central

An evaluation of the effects on onchocerciasis of a 3-year period of vector control was undertaken during 1978 in the Onchocerciasis Control Programme area in West Africa. The results revealed that the overall prevalence of ocular onchocerciasis showed only a slight decrease at the follow-up in 1978, but that there was significantly less infection among children in the age group 5-14 years as compared with 1975. There was a total incidence of ocular signs of onchocerciasis of 8.6% over the 3 years, but also a disappearance of those signs in 11.7% of the sample examined. The incidence of severe onchocercal eye manifestations was low, compared with similar areas of uncontrolled transmission. The particularly low incidence of sclerosing keratitis may be associated with the finding of a significantly decreased microfilarial load in the cornea, whereas the number of living microfilariae in the anterior chamber of the eye was apparently unchanged. The incidence of blindness due to onchocerciasis was low and confined to individuals who already presented severe eye manifestations of the disease before the beginning of the vector control campaign.

Thylefors, B.; T?njum, A. M.

1980-01-01

235

Evaluation of novel insecticides for control of dengue vector Aedes aegypti (Diptera: Culicidae).  

PubMed

Insecticides are one of the major tools for controlling vector populations and for reducing the transmission of human pathogens. However, there are few new insecticides being developed and marketed for vector control. Herein, we report on the toxicity of six novel insecticides to both adult and larval Aedes aegypti (L). and the toxicity of three novel insect growth regulators (IGRs) to larvae. Four insecticides were highly or moderately toxic to larvae with LC50 values of 16 (chlorfenapyr), 70 (hydramethylnon), 79 (indoxacarb), and 84 ng/ml (imidacloprid). Diafenthiuron and chlorfenapyr were moderately toxic to adult mosquitoes with LC50 values of 13 and 92 ng/cm2, respectively. Imidacloprid was strongly synergized by piperonyl butoxide (PBO) in Ae. aegypti adults, suggesting that neonicotinoids are intrinsically very toxic to adult mosquitoes (in the absence of detoxification). The effect of PBO on the toxicity in adults and larvae was considerably different, both in terms of the insecticides that were synergized (or antagonized for chlorfenapyr versus adults) and in terms of the degree of synergism. This result implies that the cytochrome P450s involved in metabolism of these insecticides are different between adults and larvae. Pyriproxyfen was confirmed as a potent IGR (EC50 of 0.0017 ng/ml) for mosquitoes, although tebufenozide lacked activity. The potential for use of these materials in mosquito control is discussed. PMID:16506447

Paul, Ayesa; Harrington, Laura C; Scott, Jeffrey G

2006-01-01

236

Advances in biological control in relation to vectors of human diseases  

PubMed Central

In recent years, increased knowledge of insect pathology and ecology and the development of insecticide-resistance have led to a revival of interest in biological methods of controlling insects that carry human diseases. The author of this paper reviews the information at present available with regard to the various pathogens, predators and parasites of insect vectors of human disease—cockroaches, lice, bugs, fleas, mosquitos, flies and ticks—and suggests lines of future research that might prove profitable. In this connexion he stresses that only a world-wide investigation of the diseases of medically important insects will yield data on which a balanced biological research programme can be based—a programme leading to the development of practicable control procedures and their integration with chemical and other methods of control.

Weiser, J.

1963-01-01

237

Dyes, trypanosomiasis and DNA: a historical and critical review.  

PubMed

Trypanosomiasis, a group of diseases including sleeping sickness in humans and Nagana in cattle in Africa, and Chagas' disease in South America, remains a considerable problem in the 21(st) century. The therapies that are available, however, usually have their roots in the "dye therapy" of a century ago, knowledge gained at the microscope from parasite staining procedures and converted to chemotherapy based on compounds closely related to the laboratory reagents. Dyes such as trypan red and trypan blue led to the development of suramin, while cationic nitrogen heterocyclic dyes furnished examples of the phenanthridinium class, such as ethidium (homidium) and isometamidium. Both suramin and isometamidium remain in use. Owing to mutagenicity issues, the presence of ethidium among the phenanthridinium dyes has led to concerns over the clinical use of related derivatives. There are several mechanisms for dye-DNA interaction, however, including possible hydrogen bonding of dye to the polymer, and these are discussed together with structure-activity relations and cellular localization of the phenanthridine and isomeric acridines involved. Better understanding of nucleic acid binding properties has allowed the preparation of more effective phenanthridinium analogues intended for use as anticancer/antiviral therapy. PMID:21080764

Wainwright, M

2010-12-01

238

Options for Field Diagnosis of Human African Trypanosomiasis  

PubMed Central

Human African trypanosomiasis (HAT) due to Trypanosoma brucei gambiense or T. b. rhodesiense remains highly prevalent in several rural areas of sub-Saharan Africa and is lethal if left untreated. Therefore, accurate tools are absolutely required for field diagnosis. For T. b. gambiense HAT, highly sensitive tests are available for serological screening but the sensitivity of parasitological confirmatory tests remains insufficient and needs to be improved. Screening for T. b. rhodesiense infection still relies on clinical features in the absence of serological tests available for field use. Ongoing research is opening perspectives for a new generation of field diagnostics. Also essential for both forms of HAT is accurate determination of the disease stage because of the high toxicity of melarsoprol, the drug most widely used during the neurological stage of the illness. Recent studies have confirmed the high accuracy of raised immunoglobulin M levels in the cerebrospinal fluid for the staging of T. b. gambiense HAT, and a promising simple assay (LATEX/IgM) is being tested in the field. Apart from the urgent need for better tools for the field diagnosis of this neglected disease, improved access to diagnosis and treatment for the population at risk remains the greatest challenge for the coming years.

Chappuis, Francois; Loutan, Louis; Simarro, Pere; Lejon, Veerle; Buscher, Philippe

2005-01-01

239

Modelling the impact of vector control interventions on Anopheles gambiae population dynamics  

PubMed Central

Background Intensive anti-malaria campaigns targeting the Anopheles population have demonstrated substantial reductions in adult mosquito density. Understanding the population dynamics of Anopheles mosquitoes throughout their whole lifecycle is important to assess the likely impact of vector control interventions alone and in combination as well as to aid the design of novel interventions. Methods An ecological model of Anopheles gambiae sensu lato populations incorporating a rainfall-dependent carrying capacity and density-dependent regulation of mosquito larvae in breeding sites is developed. The model is fitted to adult mosquito catch and rainfall data from 8 villages in the Garki District of Nigeria (the 'Garki Project') using Bayesian Markov Chain Monte Carlo methods and prior estimates of parameters derived from the literature. The model is used to compare the impact of vector control interventions directed against adult mosquito stages - long-lasting insecticide treated nets (LLIN), indoor residual spraying (IRS) - and directed against aquatic mosquito stages, alone and in combination on adult mosquito density. Results A model in which density-dependent regulation occurs in the larval stages via a linear association between larval density and larval death rates provided a good fit to seasonal adult mosquito catches. The effective mosquito reproduction number in the presence of density-dependent regulation is dependent on seasonal rainfall patterns and peaks at the start of the rainy season. In addition to killing adult mosquitoes during the extrinsic incubation period, LLINs and IRS also result in less eggs being oviposited in breeding sites leading to further reductions in adult mosquito density. Combining interventions such as the application of larvicidal or pupacidal agents that target the aquatic stages of the mosquito lifecycle with LLINs or IRS can lead to substantial reductions in adult mosquito density. Conclusions Density-dependent regulation of anopheline larvae in breeding sites ensures robust, stable mosquito populations that can persist in the face of intensive vector control interventions. Selecting combinations of interventions that target different stages in the vector's lifecycle will result in maximum reductions in mosquito density.

2011-01-01

240

Modelling of V–Hz and vector controlled ASDs in PSCAD\\/EMTDC for voltage sag studies  

Microsoft Academic Search

This paper deals with modelling and performance of adjustable speed drives (ASDs) subjected to voltage disturbances in electric supply. The aim of this study was to develop appropriate models of typical ASD and investigate their sensitivity to voltage disturbances under various practical modes of operation and control. Accordingly, scalar controlled open and closed loop volts–hertz (V–Hz) and vector controlled closed

S. C. Vegunta; J. V. Milanovi?; S. Ž. Djoki?

2010-01-01

241

Predictive Direct Power Control of Three-Phase Pulsewidth Modulation (PWM) Rectifier Using Space-Vector Modulation (SVM)  

Microsoft Academic Search

In this paper, we present a direct power control (DPC) of three-phase pulsewidth modulation rectifier with constant switching frequency using space-vector modulation (SVM). The developed DPC scheme is based on the predictive control strategy to achieve direct control of instantaneous active and reactive power of the converter. For this purpose, at the beginning of each switching period, the required rectifier

Abdelouahab Bouafia; Jean-Paul Gaubert; Fateh Krim

2010-01-01

242

A sliding mode controller based DTC of 3 level NPC inverter fed induction motor employing space vector modulation technique  

Microsoft Academic Search

This paper presents the space vector modulation (SVM) based direct torque control (DTC) of induction motor fed by a three level neutral point clamped (NPC) inverter. The SVM DTC system avoids the use of the hysteresis controllers and the look up table which are usually used in the classical DTC scheme. A novel sliding mode controller (SMC) is proposed which

Thalakola Vamsee Kiran; Jinka Amarnath

2012-01-01

243

Efficacy of local neem extracts for sustainable malaria vector control in an African village  

PubMed Central

Background Larval control of malaria vectors has been historically successful in reducing malaria transmission, but largely fell out of favour with the introduction of synthetic insecticides and bed nets. However, an integrated approach to malaria control, including larval control methods, continues to be the best chance for success, in view of insecticide resistance, the behavioural adaptation of the vectors to changing environments and the difficulties of reaching the poorest populations most at risk,. Laboratory studies investigating the effects of neem seed (Azadirachta indica) extracts on Anopheles larvae have shown high rates of larval mortality and reductions in adult longevity, as well as low potential for resistance development. Methods This paper describes a method whereby seeds of the neem tree can be used to reduce adult Anopheles gambiae s.l. abundance in a way that is low cost and can be implemented by residents of rural villages in western Niger. The study was conducted in Banizoumbou village, western Niger. Neem seeds were collected from around the village. Dried seeds were ground into a coarse powder, which was then sprinkled onto known Anopheles larvae breeding habitats twice weekly during the rainy season 2007. Adult mosquitoes were captured on a weekly basis in the village and captures compared to those from 2005 and 2006 over the same period. Adult mosquitoes were also captured in a nearby village, Zindarou, as a control data set and compared to those from Banizoumbou. Results It was found that twice-weekly applications of the powder to known breeding habitats of Anopheles larvae in 2007 resulted in 49% fewer adult female Anopheles gambiae s.l. mosquitoes in Banizoumbou, compared with previous captures under similar environmental conditions and with similar habitat characteristics in 2005 and 2006. The productivity of the system in 2007 was found to be suppressed compared to the mean behaviour of 2005 and 2006 in Banizoumbou, whereas no change was found in Zindarou. Conclusion With a high abundance of neem plants in many villages in this area, the results of this study suggest that larval control using neem seed powder offers a sustainable additional tool for malaria vector control in the Sahel region of Niger.

Gianotti, Rebecca L; Bomblies, Arne; Dafalla, Mustafa; Issa-Arzika, Ibrahim; Duchemin, Jean-Bernard; Eltahir, Elfatih AB

2008-01-01

244

Is participation contagious? Evidence from a household vector control campaign in urban Peru  

PubMed Central

Objectives High rates of household participation are critical to the success of door-to-door vector control campaigns. We used the Health Belief Model to assess determinants of participation, including neighbor participation as a cue to action, in a Chagas disease vector control campaign in Peru. Methods We evaluated clustering of participation among neighbors; estimated participation as a function of household infestation status, neighborhood type, and number of participating neighbors; and described reported reasons for refusal to participate in a district of 2911 households. Results We observed significant clustering of participation along city blocks (p< .0001). Participation was significantly higher for households in new vs. established neighborhoods, for infested households, and for households with more participating neighbors. The effect of neighbor participation was greater in new neighborhoods. Conclusions Results support a “contagion” model of participation, highlighting the possibility that one or two participating households can tip a block towards full participation. Future campaigns can leverage these findings by making participation more visible, by addressing stigma associated with spraying, and by employing group incentives to spray.

Buttenheim, Alison M.; Paz-Soldan, Valerie; Barbu, Corentin; Skovira, Christine; Calderon, Javier Quintanilla; Riveros, Lina Margot Mollesaca; Cornejo, Juan Oswaldo; Small, Dylan S.; Bicchieri, Christina; Naquira, Cesar; Levy, Michael Z.

2013-01-01

245

Can vector control play a useful supplementary role against bancroftian filariasis?  

PubMed Central

A single campaign of mass treatment for bancroftian filariasis with diethylcarbamazine (DEC) in Makunduchi, a town in Zanzibar, United Republic of Tanzania, combined with elimination of mosquito breeding in pit latrines with polystyrene beads was followed by a progressive decline over a 5-year period in the microfilarial rate from 49% to 3%. Evidence that vector control had contributed to this long-term decline was obtained by comparison with another town, Moga, where a DEC campaign was used without vector control and where resurgence of microfilariae could be observed 3-6 years after the campaign. In Zanzibar town, treatment of 3844 wet pit latrines and cesspits with polystyrene beads reduced the adult mosquito population in houses by about 65%. Supplementary treatment of open drains and marshes with Bacillus sphaericus produced little or no additional reduction compared to a sector of the town where only pit treatment with polystyrene was carried out. The cost and effort of achieving the 65% reduction in mosquito population could hardly be justified for its impact on filariasis alone, but its noticeable impact on biting nuisance might help to gain community support for an integrated programme.

Maxwell, C. A.; Mohammed, K.; Kisumku, U.; Curtis, C. F.

1999-01-01

246

Evaluation of New Tools for Malaria Vector Control in Cameroon: Focus on Long Lasting Insecticidal Nets  

PubMed Central

Background From 2006 to 2011, biological activity of insecticides for Indoor Residual Spraying (IRS), conventional treatment of nets (CTNs) or long lasting insecticidal nets (LLINs) was evaluated before their approval in Cameroon. The objective of the study was to select the best tools for universal malaria vector control coverage. Methodology Bioassays were performed using WHO cones and the Kisumu susceptible strain of Anopheles gambiae s.s.. Among tested products, residual activity and wash resistance of Alpha-cypermethrin LLINs (Interceptor) and CTNs (Fendona) were assessed during 5 months in the Ntougou neighborhood. Principal Findings All the 14 tested products were found effective (95–100% knockdown and mortality rates), although a significant decrease of efficacy was seen with lambda-cyhalothrinWP IRS, alpha-cypermethrin CTNs and LLINs (p< 0.05). However, the efficacy of Interceptor nets did not decrease during the 5 months evaluation, even after 25 washes (0.07vector control in Cameroon.

Etang, Josiane; Nwane, Philippe; Piameu, Michael; Manga, Blaise; Souop, Daniel; Awono-Ambene, Parfait

2013-01-01

247

Hyperlipidaemia in trypanosomiasis of naturally infected horses: possible cachexia-anorexia syndrome?  

PubMed

Trypanosomiasis caused by Trypanosoma evansi commonly produces wasting disease with signs of emaciation and cachexia mainly at the end stage. The present study was conducted to explore the possible hyperlipaemia or hyperlipidaemia and its association with cachexia-anorexia in equine trypanosomiasis. Out of the fifteen confirmed animals, none of the plasma sample was opaque. There was a significant increase in plasma triglyceride, total cholesterol and blood urea nitrogen and a highly significant increase in low-density lipoprotein (LDL) levels. A mild increase in high-density lipoprotein (HDL) and very low-density lipoprotein levels were observed, while the relative percentage of HDL and LDL was altered with high significance. A moderate increase in triglyceride and highly significant increase in LDL might be the reasons for retention of appetite and lipolysis. Possible protein breakdown and presence of lipolysis might be the reasons for cachexia in equine trypanosomiasis. PMID:22836485

Ranjithkumar, Muthusamy; Malik, Tauseef Ahmed; Saxena, Anju; Dan, Ananya; Sakthivel, Pillanatham Civalingam; Dey, Sahadeb

2013-02-01

248

Vector control and fuzzy logic control of doubly fed variable speed drives with DSP implementation  

SciTech Connect

Field orientation control and fuzzy logic control are designed for variable speed drive systems with a doubly fed machine in slip power recovery configuration. Laboratory implementation with a general purpose DSP (digital signal processing) system is described and experimental results are given. High performance potential of a slip power recovery system is realized with these advanced controls, while flexible reactive power control becomes possible, and compared to the ordinary variable speed drives with singly fed induction machine, power converter rating is reduced.

Tang, Y.; Xu, L. [Ohio State Univ., Columbus, OH (United States). Dept. of Electrical Engineering] [Ohio State Univ., Columbus, OH (United States). Dept. of Electrical Engineering

1995-12-01

249

Framework for rapid assessment and adoption of new vector control tools.  

PubMed

Evidence-informed health policy making is reliant on systematic access to, and appraisal of, the best available research evidence. This review suggests a strategy to improve the speed at which evidence is gathered on new vector control tools (VCTs) using a framework based on measurements of the vectorial capacity of an insect population to transmit disease. We explore links between indicators of VCT efficacy measurable in small-scale experiments that are relevant to entomological and epidemiological parameters measurable only in large-scale proof-of-concept randomised control trials (RCTs). We hypothesise that once RCTs establish links between entomological and epidemiological indicators then rapid evaluation of new products within the same product category may be conducted through smaller scale experiments without repetition of lengthy and expensive RCTs. PMID:24657042

Vontas, John; Moore, Sarah; Kleinschmidt, Immo; Ranson, Hilary; Lindsay, Steve; Lengeler, Christian; Hamon, Nicholas; McLean, Tom; Hemingway, Janet

2014-04-01

250

Space-vector ?? modulator and sliding mode control of the three-phase buck type rectifier with freewheeling diode  

Microsoft Academic Search

This paper presents a vector based sliding mode control method for three-phase buck type three-phase rectifiers with freewheeling diode. This fast and robust technique uses sliding mode to generate ?? space-vector modulation, which forces the input line currents to track a suitable sinusoidal reference. A near unity power factor operation of the rectifier is obtained using a sinusoidal reference in

V. Ferngo Pires; J. Fernando Silva; G. D. Marques

2002-01-01

251

Socio-economic factors influencing control of vector-borne diseases in the pastoralist system of south western Uganda.  

PubMed

Research in control of tick-borne diseases and trypanosomosis, and their vectors, namely, ticks and tsetse flies respectively, has been on going for decades. However, very little attention has been paid to the socio-economic factors that are likely to influence the outcome of the interventions in the control of these diseases. Thus, this study was designed to investigate these factors, mainly the intra-household factors influencing decision-making in the control of Vector-borne diseases in the pastoralist areas of Uganda. These factors included: indigenous technical knowledge, household economic factors, and gender. Both qualitative and quantitative methods were used in the collection and analysis of data. The tools used for data collection included among others, participatory learning and action (PLA), and Case studies. The findings included the following: In pastoralist households, a big proportion of the household budget was allocated to vector-borne diseases control. In the male-headed households, men dominated decision-making on vector-borne diseases control, although the goals and priorities of men and women in these households were not the same. Also, vector-borne disease control was predominantly by use of modern veterinary drugs, and pastoralists treated sick cattle by themselves even in situations where there were veterinary personnel. PMID:18557192

Mugisha, Anthony; McLeod, Anni; Percy, Rachel; Kyewalabye, Elizabeth

2008-05-01

252

Monitoring malaria vector control interventions: effectiveness of five different adult mosquito sampling methods.  

PubMed

Long-term success of ongoing malaria control efforts based on mosquito bed nets (long-lasting insecticidal net) and indoor residual spraying is dependent on continuous monitoring of mosquito vectors, and thus on effective mosquito sampling tools. The objective of our study was to identify the most efficient mosquito sampling tool(s) for routine vector surveillance for malaria and lymphatic filariasis transmission in coastal Kenya. We evaluated relative efficacy of five collection methods--light traps associated with a person sleeping under a net, pyrethrum spray catches, Prokopack aspirator, clay pots, and urine-baited traps--in four villages representing three ecological settings along the south coast of Kenya. Of the five methods, light traps were the most efficient for collecting female Anopheles gambiae s.l. (Giles) (Diptera: Culicidae) and Anopheles funestus (Giles) (Diptera: Culicidae) mosquitoes, whereas the Prokopack aspirator was most efficient in collecting Culex quinquefasciatus (Say) (Diptera: Culicidae) and other culicines. With the low vector densities here, and across much of sub-Saharan Africa, wherever malaria interventions, long-lasting insecticidal nets, and/or indoor residual spraying are in place, the use of a single mosquito collection method will not be sufficient to achieve a representative sample of mosquito population structure. Light traps will remain a relevant tool for host-seeking mosquitoes, especially in the absence of human landing catches. For a fair representation of the indoor mosquito population, light traps will have to be supplemented with aspirator use, which has potential for routine monitoring of indoor resting mosquitoes, and can substitute the more labor-intensive and intrusive pyrethrum spray catches. There are still no sufficiently efficient mosquito collection methods for sampling outdoor mosquitoes, particularly those that are bloodfed. PMID:24180120

Onyango, Shirley A; Kitron, Uriel; Mungai, Peter; Muchiri, Eric M; Kokwaro, Elizabeth; King, Charles H; Mutuku, Francis M

2013-09-01

253

Monitoring Malaria Vector Control Interventions: Effectiveness of Five Different Adult Mosquito Sampling Methods  

PubMed Central

Long-term success of ongoing malaria control efforts based on mosquito bed nets (long-lasting insecticidal net) and indoor residual spraying is dependent on continuous monitoring of mosquito vectors, and thus on effective mosquito sampling tools. The objective of our study was to identify the most efficient mosquito sampling tool(s) for routine vector surveillance for malaria and lymphatic filariasis transmission in coastal Kenya. We evaluated relative efficacy of five collection methods—light traps associated with a person sleeping under a net, pyrethrum spray catches, Prokopack aspirator, clay pots, and urine-baited traps—in four villages representing three ecological settings along the south coast of Kenya. Of the five methods, light traps were the most efficient for collecting female Anopheles gambiae s.l. (Giles) (Diptera: Culicidae) and Anopheles funestus (Giles) (Diptera: Culicidae) mosquitoes, whereas the Prokopack aspirator was most efficient in collecting Culex quinquefasciatus (Say) (Diptera: Culicidae) and other culicines. With the low vector densities here, and across much of sub-Saharan Africa, wherever malaria interventions, long-lasting insecticidal nets, and/or indoor residual spraying are in place, the use of a single mosquito collection method will not be sufficient to achieve a representative sample of mosquito population structure. Light traps will remain a relevant tool for host-seeking mosquitoes, especially in the absence of human landing catches. For a fair representation of the indoor mosquito population, light traps will have to be supplemented with aspirator use, which has potential for routine monitoring of indoor resting mosquitoes, and can substitute the more labor-intensive and intrusive pyrethrum spray catches. There are still no sufficiently efficient mosquito collection methods for sampling outdoor mosquitoes, particularly those that are bloodfed.

Onyango, Shirley A.; Kitron, Uriel; Mungai, Peter; Muchiri, Eric M.; Kokwaro, Elizabeth; King, Charles H.; Mutuku, Francis M.

2014-01-01

254

Vector control in a malaria epidemic occurring within a complex emergency situation in Burundi: a case study  

PubMed Central

Background African highlands often suffer of devastating malaria epidemics, sometimes in conjunction with complex emergencies, making their control even more difficult. In 2000, Burundian highlands experienced a large malaria outbreak at a time of civil unrest, constant insecurity and nutritional emergency. Because of suspected high resistance to the first and second line treatments, the provincial health authority and Médecins Sans Frontières (Belgium) decided to implement vector control activities in an attempt to curtail the epidemic. There are few reported interventions of this type to control malaria epidemics in complex emergency contexts. Here, decisions and actions taken to control this epidemic, their impact and the lessons learned from this experience are reported. Case description Twenty nine hills (administrative areas) were selected in collaboration with the provincial health authorities for the vector control interventions combining indoor residual spraying with deltamethrin and insecticide-treated nets. Impact was evaluated by entomological and parasitological surveys. Almost all houses (99%) were sprayed and nets use varied between 48% and 63%. Anopheles indoor resting density was significantly lower in treated as compared to untreated hills, the latter taken as controls. Despite this impact on the vector, malaria prevalence was not significantly lower in treated hills except for people sleeping under a net. Discussion Indoor spraying was feasible and resulted in high coverage despite being a logistically complex intervention in the Burundian context (scattered houses and emergency situation). However, it had little impact on the prevalence of malaria infection, possibly because it was implemented after the epidemic's peak. Nevertheless, after this outbreak the Ministry of Health improved the surveillance system, changed its policy with introduction of effective drugs and implementation of vector control to prevent new malaria epidemics. Conclusion In the absence of effective drugs and sufficient preparedness, present study failed to demonstrate any impact of vector control activities upon the course of a short-duration malaria epidemic. However, the experience gained lead to increased preparedness and demonstrated the feasibility of vector control measures in this specific context.

Protopopoff, Natacha; Van Herp, Michel; Maes, Peter; Reid, Tony; Baza, Dismas; D'Alessandro, Umberto; Van Bortel, Wim; Coosemans, Marc

2007-01-01

255

Thrust-vector control of a three-axis stabilized upper-stage rocket with fuel slosh dynamics  

NASA Astrophysics Data System (ADS)

This paper studies the thrust vector control problem for an upper-stage rocket with fuel slosh dynamics. The dynamics of a three-axis stabilized spacecraft with a single partially-filled fuel tank are formulated and the sloshing propellant is modeled as a multi-mass–spring system, where the oscillation frequencies of the mass–spring elements represent the prominent sloshing modes. The equations of motion are expressed in terms of the three-dimensional spacecraft translational velocity vector, the attitude, the angular velocity, and the internal coordinates representing the slosh modes. A Lyapunov-based nonlinear feedback control law is proposed to control the translational velocity vector and the attitude of the spacecraft, while attenuating the sloshing modes characterizing the internal dynamics. A simulation example is included to illustrate the effectiveness of the control law.

Rubio Hervas, Jaime; Reyhanoglu, Mahmut

2014-05-01

256

Sensorless Vector Control of the Charging Process for Flywheel Battery with Artificial Neural Network Observer  

NASA Astrophysics Data System (ADS)

The new type of flywheel battery requires control system with compact structure and low manufacturing cost. To meet this requirement, a new method for the sensorless vector control of flywheel battery is proposed in this paper. The advantage of the proposed control system is that it does not need an extra sensor to obtain the flywheel speed and position information. The determination of flywheel position and thereby speed are made by estimating back electromotive force (EMF) using the artificial neural network (ANN) observers. By doing so, the dimensions and cost of the driver system can be reduced. The ANN observers use the instantaneous values of stator voltages and currents and the estimated error of the stator current as their input to output the back EMF components in the ?-? reference frame. A simulation model was established by the use of MATLAB/Simulink software to carry out the numerical experiments. The test results demonstrate that the proposed charging control system for flywheel battery has a good control performance and a good robustness. The speed /position estimation precision is high and the error is acceptable for a wide speed range.

Qin, Honglin; Huang, Meng; Li, Zhixiong; Tang, Shuangqing

257

Chagas disease vector control through different intervention modalities in endemic localities of Paraguay.  

PubMed Central

In a field study carried out in three rural communities in Paraguay in a zone endemic for Chagas disease, we implemented three different vector control interventions--spraying, housing improvement, and a combination of spraying plus housing improvement--which effectively reduced the triatomine infestation. The reduction of triatomine infestation was 100% (47/47) in the combined intervention community, whereas in the community where housing improvement was carried out it was 96.4% (53/55). In the community where fumigation alone was used, the impact was 97.6% (40/41) in terms of domiciliary infestation. In all the houses where an intervention was made, an 18-month follow-up showed reinfestation rates of less than 10%. A serological survey of the population in the pre- and post-intervention periods revealed a shift in positive cases towards older age groups, but no significant differences were observed. The rate of seroconversion was 1.3% (three new cases) in the community with housing improvement only, but none of these cases could have resulted from vector transmission. The most cost-effective intervention was insecticide spraying, which during a 21-month follow-up period had a high impact on triatomine infestation and cost US$ 29 per house as opposed to US$ 700 per house for housing improvement.

Rojas de Arias, A.; Ferro, E. A.; Ferreira, M. E.; Simancas, L. C.

1999-01-01

258

Major QTLs Control Resistance to Rice Hoja Blanca Virus and Its Vector Tagosodes orizicolus  

PubMed Central

Rice hoja blanca (white leaf) disease can cause severe yield losses in rice in the Americas. The disease is caused by the rice hoja blanca virus (RHBV), which is transmitted by the planthopper vector Tagosodes orizicolus. Because classical breeding schemes for this disease rely on expensive, time-consuming screenings, there is a need for alternatives such as marker-aided selection. The varieties Fedearroz 2000 and Fedearroz 50, which are resistant to RHBV and to the feeding damage caused by T. orizicolus, were crossed with the susceptible line WC366 to produce segregating F2:3 populations. The F3 families were scored for their resistance level to RHBV and T. orizicolus. The F2:3 lines of both crosses were genotyped using microsatellite markers. One major QTL on the short arm of chromosome 4 was identified for resistance to RHBV in the two populations. Two major QTL on chromosomes 5 and 7 were identified for resistance to T. orizicolus in the Fd2000 × WC366 and Fd50 × WC366 crosses, respectively. This comparative study using two distinct rice populations allowed for a better understanding of how the resistance to RHBV and its vector are controlled genetically. Simple marker-aided breeding schemes based on QTL information can be designed to improve rice germplasm to reduce losses caused by this important disease.

Romero, Luz E.; Lozano, Ivan; Garavito, Andrea; Carabali, Silvio J.; Triana, Monica; Villareal, Natalia; Reyes, Luis; Duque, Myriam C.; Martinez, Cesar P.; Calvert, Lee; Lorieux, Mathias

2013-01-01

259

Contrasting Population Structures of Two Vectors of African Trypanosomoses in Burkina Faso: Consequences for Control  

PubMed Central

Background African animal trypanosomosis is a major obstacle to the development of more efficient and sustainable livestock production systems in West Africa. Riverine tsetse species such as Glossina palpalis gambiensis Vanderplank and Glossina tachinoides Westwood are the major vectors. A wide variety of control tactics is available to manage these vectors, but their removal will in most cases only be sustainable if the control effort is targeting an entire tsetse population within a circumscribed area. Methodology/Principal Findings In the present study, genetic variation at microsatellite DNA loci was used to examine the population structure of G. p. gambiensis and G. tachinoides inhabiting four adjacent river basins in Burkina Faso, i.e. the Mouhoun, the Comoé, the Niger and the Sissili River Basins. Isolation by distance was significant for both species across river basins, and dispersal of G. tachinoides was ?3 times higher than that of G. p. gambiensis. Thus, the data presented indicate that no strong barriers to gene flow exists between riverine tsetse populations in adjacent river basins, especially so for G. tachinoides. Conclusions/Significance Therefore, potential re-invasion of flies from adjacent river basins will have to be prevented by establishing buffer zones between the Mouhoun and the other river basin(s), in the framework of the PATTEC (Pan African Tsetse and Trypanosomosis Eradication Campaign) eradication project that is presently targeting the northern part of the Mouhoun River Basin. We argue that these genetic analyses should always be part of the baseline data collection before any tsetse control project is initiated.

Ravel, Sophie; Vreysen, Marc J. B.; Domagni, Kouadjo T.; Causse, Sandrine; Solano, Philippe; de Meeus, Thierry

2011-01-01

260

Micro controller based low cost accurate method for measuring 3 dimensional vector quantities  

Microsoft Academic Search

An accurate, simple, low cost on-line 3-dimensional vector quantities measurement method has been developed by employing commonly used electronic components, the vector components are measured and then the proposed instrument calculates the resultant value of the vector. The system displays both the individual components as well as the resultant value on a two line alphanumeric CD display unit. The system

A. A. Mahfou

2003-01-01

261

On the stability and control of nonlinear dynamical systems via vector Lyapunov functions  

Microsoft Academic Search

Vector Lyapunov theory has been developed to weaken the hypothesis of standard Lyapunov theory in order to enlarge the class of Lyapunov functions that can be used for analyzing system stability. In this paper, we extend the theory of vector Lyapunov functions by constructing a generalized comparison system whose vector field can be a function of the comparison system states

Sergey G. Nersesov; Wassim M. Haddad

2006-01-01

262

Plant extracts, isolated phytochemicals, and plant-derived agents which are lethal to arthropod vectors of human tropical diseases--a review.  

PubMed

The recent scientific literature on plant-derived agents with potential or effective use in the control of the arthropod vectors of human tropical diseases is reviewed. Arthropod-borne tropical diseases include: amebiasis, Chagas disease (American trypanosomiasis), cholera, cryptosporidiosis, dengue (hemorrhagic fever), epidemic typhus (Brill-Zinsser disease), filariasis (elephantiasis), giardia (giardiasis), human African trypanosomiasis (sleeping sickness), isosporiasis, leishmaniasis, Lyme disease (lyme borreliosis), malaria, onchocerciasis, plague, recurrent fever, sarcocystosis, scabies (mites as causal agents), spotted fever, toxoplasmosis, West Nile fever, and yellow fever. Thus, coverage was given to work describing plant-derived extracts, essential oils (EOs), and isolated chemicals with toxic or noxious effects on filth bugs (mechanical vectors), such as common houseflies (Musca domestica Linnaeus), American and German cockroaches (Periplaneta americana Linnaeus, Blatella germanica Linnaeus), and oriental latrine/blowflies (Chrysomya megacephala Fabricius) as well as biting, blood-sucking arthropods such as blackflies (Simulium Latreille spp.), fleas (Xenopsylla cheopis Rothschild), kissing bugs (Rhodnius Stål spp., Triatoma infestans Klug), body and head lice (Pediculus humanus humanus Linnaeus, P. humanus capitis De Geer), mosquitoes (Aedes Meigen, Anopheles Meigen, Culex L., and Ochlerotatus Lynch Arribálzaga spp.), sandflies (Lutzomyia longipalpis Lutz & Neiva, Phlebotomus Loew spp.), scabies mites (Sarcoptes scabiei De Geer, S. scabiei var hominis, S. scabiei var canis, S. scabiei var suis), and ticks (Ixodes Latreille, Amblyomma Koch, Dermacentor Koch, and Rhipicephalus Koch spp.). Examples of plant extracts, EOs, and isolated chemicals exhibiting noxious or toxic activity comparable or superior to the synthetic control agents of choice (pyrethroids, organophosphorous compounds, etc.) are provided in the text for many arthropod vectors of tropical diseases. PMID:21432748

Pohlit, Adrian Martin; Rezende, Alex Ribeiro; Lopes Baldin, Edson Luiz; Lopes, Norberto Peporine; Neto, Valter Ferreira de Andrade

2011-04-01

263

A novel simplified space-vector-modulated control scheme for three-phase switch-mode rectifier  

Microsoft Academic Search

A novel simplified control scheme for a three-phase switch-mode rectifier is proposed in this paper. The proposed control scheme is based upon a load-conductance rectifier controller, in which reference current signals are obtained. The goal to follow the reference current is converted to follow a reference voltage. A simplified control scheme utilizing space-vector modulation is developed to calculate the duty

Chern-Lin Chen; Che-Ming Lee; Rong-Jie Tu; Guo-Kiang Horng

1999-01-01

264

Estimating dengue vector abundance in the wet and dry season: implications for targeted vector control in urban and peri-urban Asia  

PubMed Central

Background: Research has shown that the classical Stegomyia indices (or “larval indices”) of the dengue vector Aedes aegypti reflect the absence or presence of the vector but do not provide accurate measures of adult mosquito density. In contrast, pupal indices as collected in pupal productivity surveys are a much better proxy indicator for adult vector abundance. However, it is unknown when it is most optimal to conduct pupal productivity surveys, in the wet or in the dry season or in both, to inform control services about the most productive water container types and if this pattern varies among different ecological settings. Methods: A multi-country study in randomly selected twelve to twenty urban and peri-urban neighborhoods (“clusters”) of six Asian countries, in which all water holding containers were examined for larvae and pupae of Aedes aegypti during the dry season and the wet season and their productivity was characterized by water container types. In addition, meteorological data and information on reported dengue cases were collected. Findings: The study reconfirmed the association between rainfall and dengue cases (“dengue season”) and underlined the importance of determining through pupal productivity surveys the “most productive containers types”, responsible for the majority (>70%) of adult dengue vectors. The variety of productive container types was greater during the wet than during the dry season, but included practically all container types productive in the dry season. Container types producing pupae were usually different from those infested by larvae indicating that containers with larval infestations do not necessarily foster pupal development and thus the production of adult Aedes mosquitoes. Conclusion: Pupal productivity surveys conducted during the wet season will identify almost all of the most productive container types for both the dry and wet seasons and will therefore facilitate cost-effective targeted interventions.

Wai, Khin Thet; Arunachalam, Natarajan; Tana, Susilowati; Espino, Fe; Kittayapong, Pattamaporn; Abeyewickreme, W; Hapangama, Dilini; Tyagi, Brij Kishore; Htun, Pe Than; Koyadun, Surachart; Kroeger, Axel; Sommerfeld, Johannes; Petzold, Max

2012-01-01

265

Stability Analysis Methods for Digital Vector Control System of Induction Motor  

NASA Astrophysics Data System (ADS)

To perform the vector control, relatively complicated control algorythm is required. The digital sampling control system is apt to be unstable dependent on its sampling period. To equip with many functions under the limitation of lower cost, the longer sampling period is inevitable and the performance of the system becomes less stable. Therefore it is important to evaluate the permissible maximum sampling period of each system. To evaluate it, software simulation tools such as PSIM and EMTP can be used. However these tools require a long execution time even for the sole model under each circuit condition. Therefore simpler methods are necessary to investigate the stability rapidly for many cases of the circuit conditions. In this paper, we propose three kinds of stability judging methods using root loci in a z-plane. The first metod is the most practical one based on a simple approximated model. The second and third methods are based on detailed models each having continuously rotating axis and stepwise rotating axis of the motor coordinates. To evaluate the proposed analytical methods, these results are compared with those obtained from detailed simulation taking PWM control into account.

Tsuji, Mineo; Tsuboi, Katsutaka; Yamada, Eiji

266

PAB3D Simulations of a Nozzle with Fluidic Injection for Yaw Thrust-Vector Control  

NASA Technical Reports Server (NTRS)

An experimental and computational study was conducted on an exhaust nozzle with fluidic injection for yaw thrust-vector control. The nozzle concept was tested experimentally in the NASA Langley Jet Exit Test Facility (JETF) at nozzle pressure ratios up to 4 and secondary fluidic injection flow rates up to 15 percent of the primary flow rate. Although many injection-port geometries and two nozzle planforms (symmetric and asymmetric) were tested experimentally, this paper focuses on the computational results of the more successful asymmetric planform with a slot injection port. This nozzle concept was simulated with the Navier-Stokes flow solver, PAB3D, invoking the Shih, Zhu, and Lumley algebraic Reynolds stress turbulence model (ASM) at nozzle pressure ratios (NPRs) of 2,3, and 4 with secondary to primary injection flow rates (w(sub s)/w(sub p)) of 0, 2, 7 and 10 percent.

Deere, Karen A.

1998-01-01

267

Large-scale spraying of bednets to control mosquito vectors and malaria in Sichuan, China.  

PubMed Central

Since 1987, up to 2.42 million bednets owned by rural householders in over 40 counties in seven prefectures of Sichuan Province, China, have been sprayed annually with deltamethrin at a dose of about 10 mg/m2. Data for the years 1987-89 indicate that there were marked reductions in the biting populations and survival of the two vector species Anopheles anthropophagus and A. sinensis. Extensive tests in 1992 in areas where bednet spraying had been carried out for 5 years showed that mortality was 100% with the WHO-recommended discriminating dose of deltamethrin, i.e., there was no indication of resistance. Malaria data obtained by passive surveillance of reported cases, mass blood surveys of schoolchildren, and active surveillance of reported blood slides from fever cases all indicated marked reductions after introduction of the net spraying. In contrast, in the control areas, where the nets were not treated, the situation remained static or deteriorated slightly.

Cheng, H.; Yang, W.; Kang, W.; Liu, C.

1995-01-01

268

Beauveria bassiana (Hyphomycetes) as a possible agent for biological control of Chagas disease vectors.  

PubMed

Beauveria bassiana (Balsamo) Vuillemin (isolate CG306) was tested on 3rd instars of 9 Triatoma spp., 4 Rhodnius spp., 2 Panstrongylus spp. and Dipetalogaster maxima (Uhler) at 25 degrees C and 50% RH. Quantitative sporulation of the fungus on cadavers was studied at 25 degrees C and 97% RH. Mortality, estimates of survival time, and conidial production on cadavers differed significantly among the genera and species tested. Panstrongylus herreri Wygodzinsky, Dipetalogaster maxima, Triatoma picturata Usinger, Rhodnius robustus Larrousse, Rhodnius prolixus Stål, Triatoma infestans (Klug), and Triatoma brasiliensis Neiva were most susceptible to fungal infection. Most conidia per cadaver were produced on Triatoma williami Galvão, Souza & Lima and Triatoma lecticularia (Stål). Results indicate that B. bassiana (CG306) might be a candidate for control of important or potential vectors of Trypanosoma cruzi using the fungus as a bioinsecticide. PMID:9835689

Luz, C; Silva, I G; Cordeiro, C M; Tigano, M S

1998-11-01

269

Target product profile choices for intra-domiciliary malaria vector control pesticide products: repel or kill?  

PubMed Central

Background The most common pesticide products for controlling malaria-transmitting mosquitoes combine two distinct modes of action: 1) conventional insecticidal activity which kills mosquitoes exposed to the pesticide and 2) deterrence of mosquitoes away from protected humans. While deterrence enhances personal or household protection of long-lasting insecticidal nets and indoor residual sprays, it may also attenuate or even reverse communal protection if it diverts mosquitoes to non-users rather than killing them outright. Methods A process-explicit model of malaria transmission is described which captures the sequential interaction between deterrent and toxic actions of vector control pesticides and accounts for the distinctive impacts of toxic activities which kill mosquitoes before or after they have fed upon the occupant of a covered house or sleeping space. Results Increasing deterrency increases personal protection but consistently reduces communal protection because deterrent sub-lethal exposure inevitably reduces the proportion subsequently exposed to higher lethal doses. If the high coverage targets of the World Health Organization are achieved, purely toxic products with no deterrence are predicted to generally provide superior protection to non-users and even users, especially where vectors feed exclusively on humans and a substantial amount of transmission occurs outdoors. Remarkably, this is even the case if that product confers no personal protection and only kills mosquitoes after they have fed. Conclusions Products with purely mosquito-toxic profiles may, therefore, be preferable for programmes with universal coverage targets, rather than those with equivalent toxicity but which also have higher deterrence. However, if purely mosquito-toxic products confer little personal protection because they do not deter mosquitoes and only kill them after they have fed, then they will require aggressive "catch up" campaigns, with behaviour change communication strategies that emphasize the communal nature of protection, to achieve high coverage rapidly.

2011-01-01

270

Vector-Borne Diseases  

NSDL National Science Digital Library

This online encyclopedia article discusses vector-borne diseases. It defines vectors as the transmitters of disease-causing organisms that carry the pathogens from one host to another. The article reviews the biological range of vectors, the transmission and types of vector-borne diseases, patterns of occurrence and existing control measures.

Artsob, Harvey; Health, Encyclopedia O.

271

High effective coverage of vector control interventions in children after achieving low malaria transmission in Zanzibar, Tanzania  

PubMed Central

Background Formerly a high malaria transmission area, Zanzibar is now targeting malaria elimination. A major challenge is to avoid resurgence of malaria, the success of which includes maintaining high effective coverage of vector control interventions such as bed nets and indoor residual spraying (IRS). In this study, caretakers' continued use of preventive measures for their children is evaluated, following a sharp reduction in malaria transmission. Methods A cross-sectional community-based survey was conducted in June 2009 in North A and Micheweni districts in Zanzibar. Households were randomly selected using two-stage cluster sampling. Interviews were conducted with 560 caretakers of under-five-year old children, who were asked about perceptions on the malaria situation, vector control, household assets, and intention for continued use of vector control as malaria burden further decreases. Results Effective coverage of vector control interventions for under-five children remains high, although most caretakers (65%; 363/560) did not perceive malaria as presently being a major health issue. Seventy percent (447/643) of the under-five children slept under a long-lasting insecticidal net (LLIN) and 94% (607/643) were living in houses targeted with IRS. In total, 98% (628/643) of the children were covered by at least one of the vector control interventions. Seasonal bed-net use for children was reported by 25% (125/508) of caretakers of children who used bed nets. A high proportion of caretakers (95%; 500/524) stated that they intended to continue using preventive measures for their under-five children as malaria burden further reduces. Malaria risk perceptions and different perceptions of vector control were not found to be significantly associated with LLIN effective coverage. Conclusions While the majority of caretakers felt that malaria had been reduced in Zanzibar, effective coverage of vector control interventions remained high. Caretakers appreciated the interventions and recognized the value of sustaining their use. Thus, sustaining high effective coverage of vector control interventions, which is crucial for reaching malaria elimination in Zanzibar, can be achieved by maintaining effective delivery of these interventions.

2013-01-01

272

Glycogen Synthase Kinase 3 Is a Potential Drug Target for African Trypanosomiasis Therapy  

Microsoft Academic Search

Development of a safe, effective, and inexpensive therapy for African trypanosomiasis is an urgent priority. In this study, we evaluated the validity of Trypanosoma brucei glycogen synthase kinase 3 (GSK-3) as a potential drug target. Interference with the RNA of either of two GSK-3 homologues in bloodstream-form T. brucei parasites led to growth arrest and altered parasite morphology, demonstrating their

Kayode K. Ojo; J. Robert Gillespie; Aaron J. Riechers; Alberto J. Napuli; Christophe L. M. J. Verlinde; Frederick S. Buckner; Michael H. Gelb; Mathias M. Domostoj; Susan J. Wells; Alexander Scheer; Timothy N. C. Wells; Wesley C. Van Voorhis

2008-01-01

273

Indigenous knowledge system for treatment of trypanosomiasis in Kaduna state of Nigeria  

Microsoft Academic Search

A survey was carried out in Kaduna State of Nigeria to establish the indigenous knowledge system for treating trypanosomiasis in domestic animals. Questionnaire and interviews were, respectively, administered to, or conducted with about 200 livestock farmers and traders spread around the state. Data obtained revealed the use of several plants either alone or in combination, for the treatment and management

S. E Atawodi; D. A Ameh; S Ibrahim; J. N Andrew; H. C Nzelibe; E. O Onyike; K. M Anigo; E. A Abu; D. B James; G. C Njoku; A. B Sallau

2002-01-01

274

Development of a nanoparticulate formulation of diminazene to treat African trypanosomiasis  

Microsoft Academic Search

There is a real need to develop new therapeutic strategies for African trypanosomiasis infections. In our study, we developed a new drug delivery system of diminazene (DMZ), a trypanocidal drug registered for veterinary use. This drug candidate presents a limited efficacy, a poor affinity for brain tissue and instability. The development of colloidal formulations based on a porous cationic nanoparticle

Maya Kroubi; Sylvie Daulouede; Hamadi Karembe; Youssef Jallouli; Mike Howsam; Djavad Mossalayi; Philippe Vincendeau; Didier Betbeder

2010-01-01

275

Association between human African trypanosomiasis and the IL6 gene in a Congolese population  

Microsoft Academic Search

Despite the importance of behavioural and environmental risk factors, there are arguments consistent with the existence of a genetic susceptibility to human African trypanosomiasis (HAT). A candidate gene association study was conducted in the Democratic Republic of Congo using a family-based sample which included a total of 353 subjects (86 trios; one case and parents (n=258) and 23 families with

David Courtin; Jacqueline Milet; Vincent Jamonneau; Claude Sese Yeminanga; Victor Kande Betu Kumeso; Constantin Miaka Mia Bilengue; Christine Betard; André Garcia

2007-01-01

276

Dot Enzyme-Linked Immunosorbent Assay for More Reliable Staging of Patients with Human African Trypanosomiasis  

Microsoft Academic Search

Human African trypanosomiasis (HAT) or sleeping sickness is a disease characterized by a hemolymphatic stage 1 followed by a meningoencephalitic stage 2 which is fatal without specific treatment. Furthermore, due to the toxicity of drugs used to treat stage 2 (mainly melarsoprol) accurate staging is required. Actual criteria employed during field surveys are not sensitive enough for precise staging. Antineurofilament

Bertrand Courtioux; Sylvie Bisser; Pascal M'Belesso; Edgard Ngoungou; Murielle Girard; Auguste Nangouma; Theophile Josenando; Marie-Odile Jauberteau-Marchan; Bernard Bouteille

2005-01-01

277

Human Trypanosomiasis in Ethiopia - Ecology of Illubabor Province and Epidemiology in the Baro Region Area.  

National Technical Information Service (NTIS)

African human trypanosomiasis was first seen in Ethiopia in March 1967. Between March 1967 and March 1968, 4 cases were recorded; in the following 12 months the total had risen to 95. The disease occurs mainly in an area of southwestern Ethiopia bounded t...

J. R. Baker E. McConnell D. C. Kent J. Hady

1970-01-01

278

Retaking sleeping sickness control in Angola.  

PubMed

Africa is severely affected by a resurgence of human African trypanosomiasis (HAT) at epidemic proportions. We report the results of the first 5 years of a HAT control programme in northern Angola run by the non-governmental organization (NGO) ANGOTRIP. In the period between 1996 and 2001, 13 426 patients were screened for HAT. The mortality rate of patients in stage II who were treated with melarsoprol fell from 7.5% to 2.9%, possibly as a result of training and the standardization of treatment protocols. A total of 191,578 people in three provinces of Angola were screened for HAT. Vector control activities were initiated using Lancien traps. Our experiences reflect the connection between war and the increasing incidence of disease, but also demonstrate that HAT control is possible by dedicated NGOs in close cooperation with national institutions even under extremely difficult circumstances. PMID:14728618

Abel, Paulo M; Kiala, Godi; Lôa, Vanda; Behrend, Markus; Musolf, Jens; Fleischmann, Hanne; Théophile, Josénando; Krishna, Sanjeev; Stich, August

2004-01-01

279

Results of solar electric thrust vector control system design, development and tests  

NASA Technical Reports Server (NTRS)

Efforts to develop and test a thrust vector control system TVCS for a solar-energy-powered ion engine array are described. The results of solar electric propulsion system technology (SEPST) III real-time tests of present versions of TVCS hardware in combination with computer-simulated attitude dynamics of a solar electric multi-mission spacecraft (SEMMS) Phase A-type spacecraft configuration are summarized. Work on an improved solar electric TVCS, based on the use of a state estimator, is described. SEPST III tests of TVCS hardware have generally proved successful and dynamic response of the system is close to predictions. It appears that, if TVCS electronic hardware can be effectively replaced by control computer software, a significant advantage in control capability and flexibility can be gained in future developmental testing, with practical implications for flight systems as well. Finally, it is concluded from computer simulations that TVCS stabilization using rate estimation promises a substantial performance improvement over the present design.

Fleischer, G. E.

1973-01-01

280

Iterative reconstruction of volumetric modulated arc radiotherapy plans using control point basis vectors  

NASA Astrophysics Data System (ADS)

Volumetric Modulated Arc Radiotherapy is an innovative technique currently utilized to efficiently deliver complex treatments. Dose rate, speed of rotation, and field shape are continuously varied as the radiation source rotates about the patient. Patient specific quality assurance is performed to verify that the delivered dose distribution is consistent with the plan formulated in a treatment planning system. The purpose of this work is to present novel methodology using a Gafchromic EBT3 film image of a patient plan in a cylindrical phantom and calculating the delivered MU per control point. Images of two dimensional plan dose matrices and film scans are analyzed using MATLAB with the imaging toolbox. Dose profiles in a ring corresponding to the film position are extracted from the plan matrices for comparison with the corresponding measured film dose. The plan is made up of a series of individual static Control Points. If we consider these Control Points a set of basis vectors, then variations in the plan can be represented as the weighted sum of the basis. The weighing coefficients representing the actual delivered MU can be determined by any available optimization tool, such as downhill simplex or non-linear programming. In essence we reconstruct an image of the delivered dose. Clinical quality assurance is performed with this technique by computing a patient plan with the measured monitor units and standard plan evaluation tools such as Dose Volume Histograms. Testing of the algorithm with known changes in the reference images indicated a correlation coefficient greater than 0.99.

Barbiere, Joseph C.; Kapulsky, Alexander; Ndlovu, Alois

2014-03-01

281

Proposed use of spatial mortality assessments as part of the pesticide evaluation scheme for vector control  

PubMed Central

Background The WHO Pesticide Evaluation Scheme to evaluate the efficacy of insecticides does not include the testing of a lethal effect at a distance. A tool was developed to evaluate the spatial mortality of an insecticide product against adult mosquitoes at a distance under laboratory and field conditions. Operational implications are discussed. Methods Insecticide paint, Inesfly 5A IGR™, containing two organophosphates (OPs): chlorpyrifos and diazinon, and one insect growth regulator (IGR): pyriproxyfen, was the product tested. Laboratory tests were performed using “distance boxes” with surfaces treated with one layer of control or insecticide paint at a dose of 1 kg/6 sq m. Field tests were conducted up to 12 months in six experimental huts randomly allocated to control or one or two layers of insecticide paint at 1 kg/6 sq m. All distance tests were performed using reference-susceptible strains of Anopheles gambiae and Culex quinquefasciatus left overnight at a distance of 1 m from control or treated surfaces. Results After an overnight exposition at distances of 1 m, field and laboratory evaluations at 0 months after treatment (T0) yielded 100% mortality rates on surfaces treated with one layer at 1 kg/6 sq m against susceptible strains of An. gambiae and Cx. quinquefasciatus. Testing for long-term efficacy in the field gave mortality rates of 96-100% after an overnight exposition at a distance of 1 m for up to 12 months in huts where a larger volume was treated (walls and ceilings) with one or two layers of insecticide paint. Conclusion A comprehensive evaluation of the full profile of insecticide products, both upon contact and spatially, may help rationalize vector control efforts more efficiently. Treating a large enough volume may extend a product’s mortality efficacy in the long-term, which contact tests would fail to assess. It is hereby proposed to explore the development of cost effective methods to assess spatial mortality and to include them as one additional measurement of insecticide efficacy against mosquitoes and other arthropod vectors in WHOPES Phase I and Phase II studies.

2013-01-01

282

Space-vector modulated PWM converters for photo-voltaic interface applications: analysis, power management and control issues  

Microsoft Academic Search

This paper presents new power management and control concepts for power converters that interface a photovoltaic (PV) system to an electric utility power system. The interface circuit is a space-vector modulated (SVM), high-frequency, 3?, PWM buck-type inverter. Decoupled control of DC voltage for peak power tracking, and the quadrature component of AC output current for reactive power flow control is

J. Rajagopalan; B. H. Cho

1995-01-01

283

Digitally controlled high-performance dc SQUID readout electronics for a 304-channel vector magnetometer  

NASA Astrophysics Data System (ADS)

Recently, we have developed a family of dc superconducting quantum interference device (SQUID) readout electronics for several applications. These electronics comprise a low-noise preamplifier followed by an integrator, and an analog SQUID bias circuit. A highly-compact low-power version with a flux-locked loop bandwidth of 0.3 MHz and a white noise level of 1 nV/?Hz was specially designed for a 304-channel low-Tc dc SQUID vector magnetometer, intended to operate in the new Berlin Magnetically Shielded Room (BMSR-2). In order to minimize the space needed to mount the electronics on top of the dewar and to minimize the power consumption, we have integrated four electronics channels on one 3 cm × 10 cm sized board. Furthermore we embedded the analog components of these four channels into a digitally controlled system including an in-system programmable microcontroller. Four of these integrated boards were combined to one module with a size of 4 cm × 4 cm × 16 cm. 19 of these modules were implemented, resulting in a total power consumption of about 61 W. To initialize the 304 channels and to service the system we have developed software tools running on a laptop computer. By means of these software tools the microcontrollers are fed with all required data such as the working points, the characteristic parameters of the sensors (noise, voltage swing), or the sensor position inside of the vector magnetometer system. In this paper, the developed electronics including the software tools are described, and first results are presented.

Bechstein, S.; Petsche, F.; Scheiner, M.; Drung, D.; Thiel, F.; Schnabel, A.; Schurig, Th

2006-06-01

284

Human Antibody Response to Anopheles Saliva for Comparing the Efficacy of Three Malaria Vector Control Methods in Balombo, Angola  

PubMed Central

Human antibody (Ab) response to Anopheles whole saliva, used as biomarker of Anopheles exposure, was investigated over a period of two years (2008–2009), in children between 2 to 9 years old, before and after the introduction of three different malaria vector control methods; deltamethrin treated long lasting impregnated nets (LLIN) and insecticide treated plastic sheeting (ITPS) - Zero Fly®) (ITPS-ZF), deltamethrin impregnated Durable (Wall) Lining (ITPS-DL – Zerovector®) alone, and indoor residual spraying (IRS) with lambdacyhalothrin alone. These different vector control methods resulted in considerable decreases in all three entomological (82.4%), parasitological (54.8%) and immunological criteria analyzed. The highest reductions in the number of Anopheles collected and number of positive blood smears, respectively 82.1% and 58.3%, were found in Capango and Canjala where LLIN and ITPS-ZF were implemented. The immunological data based on the level of anti-saliva IgG Ab in children of all villages dropped significantly from 2008 to 2009, except in Chissequele. These results indicated that these three vector control methods significantly reduced malaria infections amongst the children studied and IRS significantly reduced the human-Anopheles contact. The number of Anopheles, positive blood smears, and the levels of anti-saliva IgG Ab were most reduced when LLIN and ITPS-ZF were used in combination, compared to the use of one vector control method alone, either ITPS-DL or IRS. Therefore, as a combination of two vector control methods is significantly more effective than one control method only, this control strategy should be further developed at a more global scale.

Brosseau, Laura; Drame, Papa Makhtar; Besnard, Patrick; Toto, Jean-Claude; Foumane, Vincent; Le Mire, Jacques; Mouchet, Francois; Remoue, Franck; Allan, Richard; Fortes, Filomeno; Carnevale, Pierre; Manguin, Sylvie

2012-01-01

285

Therapy of vector-borne protozoan infections in nonendemic settings.  

PubMed

Vector-borne protozoan infections are responsible for a wide variety of illnesses (mainly malaria, trypanosomiasis and leishmaniasis) affecting tropical and subtropical areas, but increasingly diagnosed in nonendemic settings. This article summarizes the therapeutic developments for these conditions during the past decade and focuses specifically on treatment recommendations for returning travelers and migrants. The treatment of malaria has known the most spectacular improvements. Progress in the management of leishmaniasis and trypanosomiasis has also been substantial and includes introduction of new drugs into clinical practice, combinations of existing drugs, or new laboratory tools for treatment monitoring as well as extension of treatment indications to new groups of patients. Serious gaps still exist in terms of effectiveness and tolerance. Since the research pipeline is very limited for the coming 5-10 years, optimized combinations of existing drugs need to be urgently explored. PMID:21609269

Bottieau, Emmanuel; Vekemans, Marc; Van Gompel, Alfons

2011-05-01

286

Spray characterization of ultra-low-volume sprayers typically used in vector control.  

PubMed

Numerous spray machines are used to apply pesticides for the control of human disease vectors, such as mosquitoes and flies, and the selection and setup of these machines significantly affects the level of control achieved during an application. The droplet spectra produced by 9 different ultra-low-volume sprayers with oil- and water-based spray solutions were evaluated along with 2 thermal foggers with the use of diesel-based spray solutions. The droplet spectra from the sprayers were measured with the use of laser diffraction droplet sizing equipment. The volume median diameter from the sprayers ranged from 14.8 to 61.9 microm for the oil-based spray solutions and 15.5 to 87.5 microm for the water-based spray solutions. The 2 thermal foggers generated sprays with a volume median diameter of 3.5 microm. The data presented will allow spray applicators to select the spray solution and sprayer that generate the droplet-size spectra that meet the desired specific spray application scenarios. PMID:19852224

Hoffmann, W Clint; Walker, Todd W; Fritz, Bradley K; Farooq, Muhammad; Smith, Vincent L; Robinson, Cathy A; Szumlas, Dan; Lan, Yubin

2009-09-01

287

Influence of stimuli colour in SSVEP-based BCI wheelchair control using support vector machines.  

PubMed

This study aims to develop a Steady State Visual Evoked Potential (SSVEP)-based Brain Computer Interface (BCI) system to control a wheelchair, with improving accuracy as the major goal. The developed wheelchair can move in forward, backward, left, right and stop positions. Four different flickering frequencies in the low frequency region were used to elicit the SSVEPs and were displayed on a Liquid Crystal Display (LCD) monitor using LabVIEW. Four colours (green, red, blue and violet) were included in the study to investigate the colour influence in SSVEPs. The Electroencephalogram (EEG) signals recorded from the occipital region were first segmented into 1?s windows and features were extracted by using Fast Fourier Transform (FFT). Three different classifiers, two based on Artificial Neural Network (ANN) and one based on Support Vector Machine (SVM), were compared to yield better accuracy. Twenty subjects participated in the experiment and the accuracy was calculated by considering the number of correct detections produced while performing a pre-defined movement sequence. SSVEP with violet colour showed higher performance than green and red. The One-Against-All (OAA) based multi-class SVM classifier showed better accuracy than the ANN classifiers. The classification accuracy over 20 subjects varies between 75-100%, while information transfer rates (ITR) varies from 12.13-27 bpm for BCI wheelchair control with SSVEPs elicited by violet colour stimuli and classified using OAA-SVM. PMID:24533888

Singla, Rajesh; Khosla, Arun; Jha, Rameshwar

2014-04-01

288

Novel S-Adenosylmethionine Decarboxylase Inhibitors for the Treatment of Human African Trypanosomiasis? †  

PubMed Central

Trypanosomiasis remains a significant disease across the sub-Saharan African continent, with 50,000 to 70,000 individuals infected. The utility of current therapies is limited by issues of toxicity and the need to administer compounds intravenously. We have begun a program to pursue lead optimization around MDL 73811, an irreversible inhibitor of S-adenosylmethionine decarboxylase (AdoMetDC). This compound is potent but in previous studies cleared rapidly from the blood of rats (T. L. Byers, T. L. Bush, P. P. McCann, and A. J. Bitonti, Biochem. J. 274:527-533). One of the analogs synthesized (Genz-644131) was shown to be highly active against Trypanosoma brucei rhodesiense in vitro (50% inhibitory concentration, 400 pg/ml). Enzyme kinetic studies showed Genz-644131 to be approximately fivefold more potent than MDL 73811 against the T. brucei brucei AdoMetDC-prozyme complex. This compound was stable in vitro in rat and human liver microsomal and hepatocyte assays, was stable in rat whole-blood assays, did not significantly inhibit human cytochrome P450 enzymes, had no measurable efflux in CaCo-2 cells, and was only 41% bound by serum proteins. Pharmacokinetic studies of mice following intraperitoneal dosing showed that the half-life of Genz-644131 was threefold greater than that of MDL 73811 (7.4 h versus 2.5 h). Furthermore, brain penetration of Genz-644131 was 4.3-fold higher than that of MDL 73811. Finally, in vivo efficacy studies of T. b. brucei strain STIB 795-infected mice showed that Genz-644131 significantly extended survival (from 6.75 days for controls to >30 days for treated animals) and cured animals infected with T. b. brucei strain LAB 110 EATRO. Taken together, the data strengthen validation of AdoMetDC as an important parasite target, and these studies have shown that analogs of MDL 73811 can be synthesized with improved potency and brain penetration.

Barker, Robert H.; Liu, Hanlan; Hirth, Bradford; Celatka, Cassandra A.; Fitzpatrick, Richard; Xiang, Yibin; Willert, Erin K.; Phillips, Margaret A.; Kaiser, Marcel; Bacchi, Cyrus J.; Rodriguez, Aixa; Yarlett, Nigel; Klinger, Jeffrey D.; Sybertz, Edmund

2009-01-01

289

Monitoring the aquatic toxicity of mosquito vector control spray pesticides to freshwater receiving waters.  

PubMed

Pesticides are applied to state and local waterways in California to control insects such as mosquitoes, which are known to serve as a vector for West Nile Virus infection of humans. The California State Water Resources Control Board adopted a National Pollutant Discharge Elimination System General Permit to address the discharge to waters of the United States of pesticides resulting from adult and larval mosquito control. Because pesticides used in spray activities have the potential to cause toxicity to nontarget organisms in receiving waters, the current study was designed to determine whether toxicity testing provides additional, useful environmental risk information beyond chemical analysis in monitoring spray pesticide applications. Monitoring included a combination of aquatic toxicity tests and chemical analyses of receiving waters from agricultural, urban, and wetland habitats. The active ingredients monitored included the organophosphate pesticides malathion and naled, the pyrethroid pesticides etofenprox, permethrin, and sumithrin, pyrethrins, and piperonyl butoxide (PBO). Approximately 15% of the postapplication water samples were significantly toxic. Toxicity of half of these samples was attributed to the naled breakdown product dichlorvos. Toxicity of 2 other water samples likely occurred when PBO synergized the effects of pyrethroid pesticides that were likely present in the receiving system. Four of 43 postapplication sediment samples were significantly more toxic than their corresponding pre-application samples, but none of the observed toxicity was attributed to the application events. These results indicate that many of the spray pesticides used for adult mosquito control do not pose significant acute toxicity risk to invertebrates in receiving systems. In the case of naled in water, analysis of only the active ingredient underestimated potential impacts to the receiving system, because toxicity was attributed to the breakdown product, dichlorvos. Toxicity testing can provide useful risk information about unidentified, unmeasured toxicants or mixtures of toxicants. In this case, toxicity testing provided information that could lead to the inclusion of dichlorvos monitoring as a permit requirement. Integr Environ Assess Manag 2014;10:449-455. © 2014 SETAC. PMID:24659580

Phillips, Bryn M; Anderson, Brian S; Voorhees, Jennifer P; Siegler, Katie; Denton, Debra; TenBrook, Patti; Larsen, Karen; Isorena, Philip; Tjeerdema, Ron S

2014-07-01

290

Integration of space vector pulse width modulation controlled STATCOM with wind farm connected to multimachine power system  

Microsoft Academic Search

In this work, dynamic and transient characteristics of a multimachine power system connected with two wind farms composed of fixed speed wind turbine generator systems (WTGS) are analyzed. At each wind farm the terminal one space vector pulse width modulation controlled voltage source converter based static synchronous compensator (STATCOM) is considered to be connected. The capacitor bank capacity of fixed

S. M. Muyeen; Hany. M. Hasanien; Rion Takahashi; Toshiaki Murata; Junji Tamura

2009-01-01

291

Honey Bees (Hymenoptera: Apidae) as Vectors of Bacillus thuringiensis for Control of Banded Sunflower Moth (Lepidoptera: Tortricidae)  

Microsoft Academic Search

A study was conducted in 1996 and 1997 to determine if honey bees, Apis mellifera L., could vector Bacillus thuringiensis Berliner variety kurstaki from hives equipped with a pathogen applicator to sunflower capitula and if the amount of B. thuringiensis deposited on the capitula would be sufficient to control the banded sunflower moth, Cochylis hospes Walsingham. The study dem- onstrated

JAWAHAR L. JYOTI; GARY J. BREWER

1999-01-01

292

Design and development of the quad redundant servoactuator for the space shuttle solid rocket booster thrust vector control  

NASA Technical Reports Server (NTRS)

The design and theory of operation of the servoactuator used for thrust vector control of the space shuttle solid rocket booster is described accompanied by highlights from the development and qualification test programs. Specific details are presented concerning major anomalies that occurred during the test programs and the corrective courses of action pursued.

Lominick, J. M.

1980-01-01

293

Geostatistical evaluation of integrated marsh management impact on mosquito vectors using before-after-control-impact (BACI) design  

Microsoft Academic Search

BACKGROUND: In many parts of the world, salt marshes play a key ecological role as the interface between the marine and the terrestrial environments. Salt marshes are also exceedingly important for public health as larval habitat for mosquitoes that are vectors of disease and significant biting pests. Although grid ditching and pesticides have been effective in salt marsh mosquito control,

Ilia Rochlin; Tom Iwanejko; Mary E Dempsey; Dominick V Ninivaggi

2009-01-01

294

Sensorless vector control of induction motors at very low speed using a nonlinear inverter model and parameter identification  

Microsoft Academic Search

The performance of vector-controlled induction motor drives without a speed sensor is generally poor at very low speed. The reasons are offset and drift components in the acquired feedback signals, voltage distortions caused by the nonlinear behavior of the switching converter, and the increased sensitivity against model parameter mismatch. New modeling and identification techniques are proposed to overcome these problems.

Joachim Holtz; Juntao Quan

2002-01-01

295

A PWM CSI-based vector controlled medium voltage AC drive with sinusoidal input and output waveforms  

Microsoft Academic Search

A vector controlled medium voltage AC motor drive is proposed in this paper which is based on a current source topology consisting of a PWM GTO current source inverter (CSI) as the output connected to the motor and a two-module PWM GTO current source rectifier (CSR) as the front end. The output inverter is operated with selective harmonic elimination (SHE)

Navid Zargari; Yuan Xiao; Bin Wu

1997-01-01

296

Antislip Readhesion Control Based on Speed-Sensorless Vector Control and Disturbance Observer for Electric Commuter Train—Series 205-5000 of the East Japan Railway Company  

Microsoft Academic Search

The improvement of adhesion characteristics is important in electric commuter train. The electric commuter train has both a slip phenomenon and a slide phenomenon. Slip-and-slide phenomena degrade the comfortable riding performance of electric commuter train. We have already proposed an antislip\\/ antislide readhesion control system based on disturbance observer and sensorless vector control. The effectiveness of the proposed method has

Satoshi Kadowaki; Kiyoshi Ohishi; Tadashi Hata; Norifumi Iida; Masashi Takagi; Takashi Sano; Shinobu Yasukawa

2007-01-01

297

The 3 phase PWM voltage source reversible rectifier based on a novel space vector control method  

Microsoft Academic Search

In this paper, a novel voltage space vector (NVSV) method used for 3-phase pulse width modulation voltage source reversible rectifier (PWM VSR) is described in detail. Based on the conventional voltage space vector (CVSV) method and its geometry topology, the actual switching time has a very simple form. With the ??-coordinate transformation, the NVSV can be easily realized. Its effect

Zhan Changjiang; Han Yingduo; Wong Manchung

1998-01-01

298

Retroviral vectors encoding ADA regulatory locus control region provide enhanced T-cell-specific transgene expression  

Microsoft Academic Search

BACKGROUND: Murine retroviral vectors have been used in several hundred gene therapy clinical trials, but have fallen out of favor for a number of reasons. One issue is that gene expression from viral or internal promoters is highly variable and essentially unregulated. Moreover, with retroviral vectors, gene expression is usually silenced over time. Mammalian genes, in contrast, are characterized by

Alice T Trinh; Bret G Ball; Erin Weber; Timothy K Gallaher; Zoya Gluzman-Poltorak; French Anderson; Lena A Basile

2009-01-01

299

Fate of trypanocidal drugs in cattle (chemotherapy of trypanosomiasis). Kenya. Terminal report. Report prepared for the Government of Kenya.  

National Technical Information Service (NTIS)

This document is the final report of a project to determine the fate of tryponocidal drugs in cattle. Drugs are still the primary agent in the struggle against trypanosomiasis although there is little data on their pharmacokinetics, residue levels, bioava...

1992-01-01

300

Strategies, effectiveness and rationale of vector-borne disease control in the pastoralist system of south-western Uganda.  

PubMed

In Uganda, control of vector-borne diseases is mainly in form of vector control, and chemotherapy. There have been reports that acaricides are being misused in the pastoralist systems in Uganda. This is because of the belief by scientists that intensive application of acaricide is uneconomical and unsustainable particularly in the indigenous cattle. The objective of this study was to investigate the strategies, rationale and effectiveness of vector-borne disease control by pastoralists. To systematically carry out these investigations, a combination of qualitative and quantitative research methods was used, in both the collection and the analysis of data. Cattle keepers were found to control tick-borne diseases (TBDs) mainly through spraying, in contrast with the control of trypanosomosis for which the main method of control was by chemotherapy. The majority of herders applied acaricides weekly and used an acaricide of lower strength than recommended by the manufacturers. They used very little acaricide wash, and spraying was preferred to dipping. Furthermore, pastoralists either treated sick animals themselves or did nothing at all, rather than using veterinary personnel. Oxytetracycline (OTC) was the drug commonly used in the treatment of TBDs. Nevertheless, although pastoralists may not have been following recommended practices in their control of ticks and tick-borne diseases, they were neither wasteful nor uneconomical and their methods appeared to be effective. Trypanosomosis was not a problem either in Sembabule or Mbarara district. Those who used trypanocides were found to use more drugs than were necessary. PMID:16248219

Mugisha, A; McLeod, A; Percy, R; Kyewalabye, E

2005-08-01

301

Linear Test Bed. Volume 2: Test Bed No. 2. [linear aerospike test bed for thrust vector control  

NASA Technical Reports Server (NTRS)

Test bed No. 2 consists of 10 combustors welded in banks of 5 to 2 symmetrical tubular nozzle assemblies, an upper stationary thrust frame, a lower thrust frame which can be hinged, a power package, a triaxial combustion wave ignition system, a pneumatic control system, pneumatically actuated propellant valves, a purge and drain system, and an electrical control system. The power package consists of the Mark 29-F fuel turbopump, the Mark 29-0 oxidizer turbopump, a gas generator assembly, and propellant ducting. The system, designated as a linear aerospike system, was designed to demonstrate the feasibility of the concept and to explore technology related to thrust vector control, thrust vector optimization, improved sequencing and control, and advanced ignition systems. The propellants are liquid oxygen/liquid hydrogen. The system was designed to operate at 1200-psia chamber pressure at an engine mixture ratio of 5.5. With 10 combustors, the sea level thrust is 95,000 pounds.

1974-01-01

302

Control of tripod-scheme cold-atom wavepackets by manipulating a non-Abelian vector potential  

SciTech Connect

Tripod-scheme cold atoms interacting with laser beams have attracted considerable interest for their role in synthesizing effective non-Abelian vector potentials. Such effective vector potentials can be exploited to realize an all-optical imprinting of geometric phases onto matter waves. By working on carefully designed extensions of our previous work, we show that coherent lattice structure of cold-atom sub-wavepackets can be formed and that the non-Abelian Aharonov-Bohm effect can be easily manifested via the translational motion of cold atoms. We also show that by changing the frame of reference, effects due to a non-Abelian vector potential may be connected with a simple dynamical phase effect, and that under certain conditions it can be understood as an Abelian geometric phase in a different frame of reference. Results should help design better schemes for the control of cold-atom matter waves.

Zhang Qi, E-mail: cqtzq@nus.edu.s [Centre of Quantum Technologies and Department of Physics, National University of Singapore, 117543 (Singapore); Gong Jiangbin, E-mail: phygj@nus.edu.s [Department of Physics and Centre for Computational Science and Engineering, National University of Singapore, 117542 (Singapore); NUS Graduate School for Integrative Sciences and Engineering, Singapore 117597 (Singapore); Oh, C.H., E-mail: phyohch@nus.edu.s [Centre of Quantum Technologies and Department of Physics, National University of Singapore, 117543 (Singapore); Institute of Advanced Studies, Nanyang Technological University, Singapore 639798 (Singapore)

2010-06-15

303

Implementation and Sensorless Vector-Control Design and Tuning Strategy for SMPM Machines in Fan-Type Applications  

Microsoft Academic Search

This paper presents a complete design methodology for the sensorless vector control of permanent magnet synchronous machine (PMSM) motor drives in fan-type applications. The proposed strategy is built over a linear asymptotic state observer used to estimate the PMSM back-EMF, and a novel tracking controller based on a phase-locked loop (PLL) system, which by synchronizing the estimated and actual d-q

Parag Kshirsagar; R. P. Burgos; A. Lidozzi; Jihoon Jang; F. Wang; D. Boroyevich; Seung-Ki Sul

2006-01-01

304

Evaluation of the Effectiveness of Malaria Vector Control Measures in Urban Settings of Dakar by a Specific Anopheles Salivary Biomarker  

PubMed Central

Standard entomological methods for evaluating the impact of vector control lack sensitivity in low-malaria-risk areas. The detection of human IgG specific to Anopheles gSG6-P1 salivary antigen reflects a direct measure of human–vector contact. This study aimed to assess the effectiveness of a range of vector control measures (VCMs) in urban settings by using this biomarker approach. The study was conducted from October to December 2008 on 2,774 residents of 45 districts of urban Dakar. IgG responses to gSG6-P1 and the use of malaria VCMs highly varied between districts. At the district level, specific IgG levels significantly increased with age and decreased with season and with VCM use. The use of insecticide-treated nets, by drastically reducing specific IgG levels, was by far the most efficient VCM regardless of age, season or exposure level to mosquito bites. The use of spray bombs was also associated with a significant reduction of specific IgG levels, whereas the use of mosquito coils or electric fans/air conditioning did not show a significant effect. Human IgG response to gSG6-P1 as biomarker of vector exposure represents a reliable alternative for accurately assessing the effectiveness of malaria VCM in low-malaria-risk areas. This biomarker tool could be especially relevant for malaria control monitoring and surveillance programmes in low-exposure/low-transmission settings.

Drame, Papa Makhtar; Diallo, Abdoulaye; Poinsignon, Anne; Boussari, Olayide; Dos Santos, Stephanie; Machault, Vanessa; Lalou, Richard; Cornelie, Sylvie; LeHesran, Jean-Yves; Remoue, Franck

2013-01-01

305

Adenoviral and Adeno-Associated Viral Vectors-Mediated Neuronal Gene Transfer to Cardiovascular Control Regions of the Rat Brain  

PubMed Central

Viral vectors have been utilized extensively to introduce genetic material into the central nervous system. In order to investigate gene functions in cardiovascular control regions of rat brain, we applied WPRE (woodchuck hepatitis virus post-transcriptional regulatory element) enhanced-adenoviral (Ad) and adeno-assoicated virus (AAV) type 2 vectors to mediate neuronal gene delivery to the paraventricular nucleus of the hypothalamus, the nucleus tractus solitarius and the rostral ventrolateral medulla, three important cardiovascular control regions known to express renin-angiotensin system (RAS) genes. Ad or AAV2 harboring an enhanced green fluorescent protein (EGFP) reporter gene or the angiotensin type 2 receptor gene were microinjected into these brain regions in adult rats. Our results demonstrated that both AAV2 and Ad vectors elicited long-term neuronal transduction in these regions. Interestingly, we found that the WPRE caused expression of GFP driven by the synapsin1 promoter in pure glial cultures or co-cultures of neurons and glia derived from rat hypothalamus and brainstem. However, in rat paraventricular nucleus WPRE did not cause expression of GFP in glia. This demonstrates the potential use of these vectors in studies of physiological functions of certain genes in the cardiovascular control regions of the brain.

Zhang, Yanling; Gao, Yongxin; Speth, Robert C.; Jiang, Nan; Mao, Yingying; Sumners, Colin; Li, Hongwei

2013-01-01

306

Habitat Hydrology and Geomorphology Control the Distribution of Malaria Vector Larvae in Rural Africa  

PubMed Central

Background Larval source management is a promising component of integrated malaria control and elimination. This requires development of a framework to target productive locations through process-based understanding of habitat hydrology and geomorphology. Methods We conducted the first catchment scale study of fine resolution spatial and temporal variation in Anopheles habitat and productivity in relation to rainfall, hydrology and geomorphology for a high malaria transmission area of Tanzania. Results Monthly aggregates of rainfall, river stage and water table were not significantly related to the abundance of vector larvae. However, these metrics showed strong explanatory power to predict mosquito larval abundances after stratification by water body type, with a clear seasonal trend for each, defined on the basis of its geomorphological setting and origin. Conclusion Hydrological and geomorphological processes governing the availability and productivity of Anopheles breeding habitat need to be understood at the local scale for which larval source management is implemented in order to effectively target larval source interventions. Mapping and monitoring these processes is a well-established practice providing a tractable way forward for developing important malaria management tools.

Hardy, Andrew J.; Gamarra, Javier G. P.; Cross, Donall E.; Macklin, Mark G.; Smith, Mark W.; Kihonda, Japhet; Killeen, Gerry F.; Ling'ala, George N.; Thomas, Chris J.

2013-01-01

307

Independent Orbiter Assessment (IOA): Assessment of the ascent thrust vector control actuator subsystem FMEA/CIL  

NASA Technical Reports Server (NTRS)

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA effort first completed an analysis of the Ascent Thrust Vector Control Actuator (ATVD) hardware, generating draft failure modes and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. The IOA results were then compared to the NASA FMEA/CIL baseline with proposed Post 51-L updates included. A resolution of each discrepancy from the comparison is provided through additional analysis as required. This report documents the results of that comparison for the Orbiter ATVC hardware. The IOA product for the ATVC actuator analysis consisted of 25 failure mode worksheets that resulted in 16 potential critical items being identified. Comparison was made to the NASA baseline which consisted of 21 FMEAs and 13 CIL items. This comparison produced agreement on all CIL items. Based on the Pre 51-L baseline, all non-CIL FMEAs were also in agreement.

Wilson, R. E.

1988-01-01

308

STUDY OF THE ANGLE OF DEPHASING BETWEEN THE VECTORS OF ROTOR AND STATOR MAGNETIC FLOW IN A SYSTEM OF CONTROL THROUGH ORIENTATION OF A MAGNETIC FIELD  

Microsoft Academic Search

This article presents results received from the study of a system of control of three-phase asynchronous motor through an orientation of a magnetic field. The controller does stabilization of the vector of rotor magnetic flow. The purpose of this study is to find how the angle of dephasing between the vectors of magnetic flows in the rotor and stator changes.

Pencho Georgiev; Dinko Gospodinov

309

Diagnostic Accuracy and Feasibility of Serological Tests on Filter Paper Samples for Outbreak Detection of T.b. gambiense Human African Trypanosomiasis  

PubMed Central

Control of human African trypanosomiasis (HAT) in the Democratic Republic of Congo is based on mass population screening by mobile teams; a costly and labor-intensive approach. We hypothesized that blood samples collected on filter paper by village health workers and processed in a central laboratory might be a cost-effective alternative. We estimated sensitivity and specificity of micro-card agglutination test for trypanosomiasis (micro-CATT) and enzyme-linked immunosorbent assay (ELISA)/T.b. gambiense on filter paper samples compared with parasitology-based case classification and used the results in a Monte Carlo simulation of a lot quality assurance sampling (LQAS) approach. Micro-CATT and ELISA/T.b. gambiense showed acceptable sensitivity (92.7% [95% CI 87.4–98.0%] and 82.2% [95% CI 75.3–90.4%]) and very high specificity (99.4% [95% CI 99.0–99.9%] and 99.8% [95% CI 99.5–100%]), respectively. Conditional on high sample size per lot (? 60%), both tests could reliably distinguish a 2% from a zero prevalence at village level. Alternatively, these tests could be used to identify individual HAT suspects for subsequent confirmation.

Hasker, Epco; Lutumba, Pascal; Mumba, Dieudonne; Lejon, Veerle; Buscher, Phillipe; Kande, Victor; Muyembe, Jean Jacques; Menten, Joris; Robays, Jo; Boelaert, Marleen

2010-01-01

310

Computational Study of Fluidic Thrust Vectoring using Separation Control in a Nozzle  

NASA Technical Reports Server (NTRS)

A computational investigation of a two- dimensional nozzle was completed to assess the use of fluidic injection to manipulate flow separation and cause thrust vectoring of the primary jet thrust. The nozzle was designed with a recessed cavity to enhance the throat shifting method of fluidic thrust vectoring. The structured-grid, computational fluid dynamics code PAB3D was used to guide the design and analyze over 60 configurations. Nozzle design variables included cavity convergence angle, cavity length, fluidic injection angle, upstream minimum height, aft deck angle, and aft deck shape. All simulations were computed with a static freestream Mach number of 0.05. a nozzle pressure ratio of 3.858, and a fluidic injection flow rate equal to 6 percent of the primary flow rate. Results indicate that the recessed cavity enhances the throat shifting method of fluidic thrust vectoring and allows for greater thrust-vector angles without compromising thrust efficiency.

Deere, Karen; Berrier, Bobby L.; Flamm, Jeffrey D.; Johnson, Stuart K.

2003-01-01

311

Ecology and control of the sand fly vectors of Leishmania donovani in East Africa, with special emphasis on Phlebotomus orientalis.  

PubMed

A literature review is provided on the state of knowledge of the ecology and control of the sand fly vectors of Leishmania donovani in East Africa, with a special emphasis on Phlebotomus orientalis. Visceral leishmaniasis caused by L. donovani is a major health problem in several areas in East Africa. Studies conducted in the past 70 years identified P. orientalis Parrot and P. martini Parrot as the principal vectors of L. donovani in Sudan, Ethiopia and Kenya and P. celiae Minter as the secondary vector of the parasite in one focus in Ethiopia. Findings on sand fly fauna and other circumstantial evidence indicate that P. martini is also responsible for transmission of L. donovani in VL endemic foci of Somalia and Uganda. Several studies showed that P. orientalis occupy distinct habitat characterized by black cotton soil and Acacia seyal-Balanites aegyptiaca vegetation, whereas P. martini and P. celiae are associated with termite mounds. Little knowledge exists on effective control measures of sand fly vectors of L. donovani in East Africa. However, recent evidence showed that use of insecticide impregnated bednets and insect repellents may reduce exposure to the bites of P. orientalis. PMID:21366778

Elnaiem, Dia-Eldin A

2011-03-01

312

A versatile vector for controlled expression of genes in Escherichia coli and Salmonella typhimurium  

Microsoft Academic Search

We have constructed two expression vectors based on the pJF118HE vector developed for Escherichia coli by Fürste et al. [Gene 48 (1986) 119–131]. The tac promoter (ptac) was exchanged for the trc promoter (ptrc) and an NdeI site was created at the appropriate distance from the ribosome-binding site. The NdeI site permits cloning of a gene at its translation start

Joyce S. Velterop; Marjoleine A. Dijkhuizen; Rechien van't Hof; Pieter W. Postma

1995-01-01

313

Application of eco-friendly tools and eco-bio-social strategies to control dengue vectors in urban and peri-urban settings in Thailand  

PubMed Central

Background: Dengue is considered one of the most important vector-borne diseases in Thailand. Its incidence is increasing despite routine implementation of national dengue control programmes. This study, conducted during 2010, aimed to demonstrate an application of integrated, community-based, eco-bio-social strategies in combination with locally-produced eco-friendly vector control tools in the dengue control programme, emphasizing urban and peri-urban settings in eastern Thailand. Methodology: Three different community settings were selected and were randomly assigned to intervention and control clusters. Key community leaders and relevant governmental authorities were approached to participate in this intervention programme. Ecohealth volunteers were identified and trained in each study community. They were selected among active community health volunteers and were trained by public health experts to conduct vector control activities in their own communities using environmental management in combination with eco-friendly vector control tools. These trained ecohealth volunteers carried out outreach health education and vector control during household visits. Management of public spaces and public properties, especially solid waste management, was efficiently carried out by local municipalities. Significant reduction in the pupae per person index in the intervention clusters when compared to the control ones was used as a proxy to determine the impact of this programme. Results: Our community-based dengue vector control programme demonstrated a significant reduction in the pupae per person index during entomological surveys which were conducted at two-month intervals from May 2010 for the total of six months in the intervention and control clusters. The programme also raised awareness in applying eco-friendly vector control approaches and increased intersectoral and household participation in dengue control activities. Conclusion: An eco-friendly dengue vector control programme was successfully implemented in urban and peri-urban settings in Thailand, through intersectoral collaboration and practical action at household level, with a significant reduction in vector densities.

Kittayapong, Pattamaporn; Thongyuan, Suporn; Olanratmanee, Phanthip; Aumchareoun, Worawit; Koyadun, Surachart; Kittayapong, Rungrith; Butraporn, Piyarat

2012-01-01

314

Influence of source and quantity of protein on the development of immunity and resistance to African trypanosomiasis.  

PubMed Central

Although it is well documented that severe protein deprivation inhibits the development of the immune response and exacerbates certain infections, little has been done to study the effects of native diets on endemic diseases or immunity. Therefore, protein-restricted diets were formulated for mice to mimic the sources and amounts measured in human diets of the Batouri region of Cameroon, endemic for African trypanosomiasis. Weanling C57BL/6 female mice were fed a diet that contained 73% of the recommended daily allowance (RDA) of protein. The sources of protein were all plant (cornmeal), all animal (casein), or a ratio that reflected the native diet (2.2 parts plant to 1 part animal protein). Diets were isocaloric on a weight basis, equal in lipids, and adequate in vitamins and minerals. Control mice were fed laboratory chow or two times the RDA of animal protein (casein). Mice fed only cornmeal or the native diets consumed as much food but did not gain as much weight as mice fed only animal protein, indicating the poorer quality of protein in their diets. Upon infection with Trypanosoma brucei gambiense, however, significantly higher numbers of these mice controlled the first peak of parasitemia and survived the infection as compared with mice fed the other three diets. Since all mice developed patent infections and the parasite growth rate was unaffected by diet, innate immune factors were ruled out as the cause for the higher level of resistance to the parasite. To determine whether diet affected the development of the immune system, weanling mice were maintained on diets for 30 days before immunization with sheep erythrocytes or trinitrophenylated Ficoll. Mice fed only plant protein or native diets elicited higher direct plaque-forming-cell responses to both the T-cell-dependent and T-cell-independent antigens. Since variant-specific immunity which controls levels of African trypanosomes in the blood is a T-cell-independent humoral immunoglobulin M response, this suggests that cornmeal, a protein of poor quality, was adequate for the development of humoral immunity and resistance to African trypanosomiasis while casein, an animal protein of high quality, was not. This provides more evidence that diet plays an important role in infection and immunity.

Norton, J D; Yang, S P; Diffley, P

1986-01-01

315

Indigenous knowledge system for treatment of trypanosomiasis in Kaduna state of Nigeria.  

PubMed

A survey was carried out in Kaduna State of Nigeria to establish the indigenous knowledge system for treating trypanosomiasis in domestic animals. Questionnaire and interviews were, respectively, administered to, or conducted with about 200 livestock farmers and traders spread around the state. Data obtained revealed the use of several plants either alone or in combination, for the treatment and management of trypasonomiasis. The most common plants encountered were Adansonia digitata, Terminalia avicennoides, Khaya senegalensis, Cissus populnea, Tamarindus indica, Lawsonia inermis, Boswellia dalzielli, Pseudocedrela kotschi, Syzyium quinensis, Sterculia setigera, Afzelia africana, Prosopis africana, Lancea kerstingii. The method of preparation and mode of administration of some of these plants in the treatment of trypanosomiasis are reviewed and discussed. PMID:11801393

Atawodi, S E; Ameh, D A; Ibrahim, S; Andrew, J N; Nzelibe, H C; Onyike, E O; Anigo, K M; Abu, E A; James, D B; Njoku, G C; Sallau, A B

2002-02-01

316

Substituted 2-phenylimidazopyridines: a new class of drug leads for human African trypanosomiasis.  

PubMed

A phenotypic screen of a compound library for antiparasitic activity on Trypanosoma brucei, the causative agent of human African trypanosomiasis, led to the identification of substituted 2-(3-aminophenyl)oxazolopyridines as a starting point for hit-to-lead medicinal chemistry. A total of 110 analogues were prepared, which led to the identification of 64, a substituted 2-(3-aminophenyl)imidazopyridine. This compound showed antiparasitic activity in vitro with an EC50 of 2 nM and displayed reasonable druglike properties when tested in a number of in vitro assays. The compound was orally bioavailable and displayed good plasma and brain exposure in mice. Compound 64 cured mice infected with Trypanosoma brucei when dosed orally down to 2.5 mg/kg. Given its potent antiparasitic properties and its ease of synthesis, compound 64 represents a new lead for the development of drugs to treat human African trypanosomiasis. PMID:24354316

Tatipaka, Hari Babu; Gillespie, J Robert; Chatterjee, Arnab K; Norcross, Neil R; Hulverson, Matthew A; Ranade, Ranae M; Nagendar, Pendem; Creason, Sharon A; McQueen, Joshua; Duster, Nicole A; Nagle, Advait; Supek, Frantisek; Molteni, Valentina; Wenzler, Tanja; Brun, Reto; Glynne, Richard; Buckner, Frederick S; Gelb, Michael H

2014-02-13

317

Tsetse Fly Control in Kenya's Spatially and Temporally Dynamic Control Reservoirs: A Cost Analysis  

PubMed Central

Human African trypanosomiasis (HAT) and animal African trypanosomiasis (AAT) are significant health concerns throughout much of sub-Saharan Africa. Funding for tsetse fly control operations has decreased since the 1970s, which has in turn limited the success of campaigns to control the disease vector. To maximize the effectiveness of the limited financial resources available for tsetse control, this study develops and analyzes spatially and temporally dynamic tsetse distribution maps of Glossina subgenus Morsitans populations in Kenya from January 2002 to December 2010, produced using the Tsetse Ecological Distribution Model. These species distribution maps reveal seasonal variations in fly distributions. Such variations allow for the identification of “control reservoirs” where fly distributions are spatially constrained by fluctuations in suitable habitat and tsetse population characteristics. Following identification of the control reservoirs, a tsetse management operation is simulated in the control reservoirs using capital and labor control inputs from previous studies. Finally, a cost analysis, following specific economic guidelines from existing tsetse control analyses, is conducted to calculate the total cost of a nationwide control campaign of the reservoirs compared to the cost of a nationwide campaign conducted at the maximum spatial extent of the fly distributions from January 2002 to December 2010. The total cost of tsetse management within the reservoirs sums to $14,212,647, while the nationwide campaign at the maximum spatial extent amounts to $33,721,516. This savings of $19,508,869 represents the importance of identifying seasonally dynamic control reservoirs when conducting a tsetse management campaign, and, in the process, offers an economical means of fly control and disease management for future program planning.

McCord, Paul F.; Messina, Joseph P.; Campbell, David J.; Grady, Sue C.

2011-01-01

318

The Atlas of human African trypanosomiasis: a contribution to global mapping of neglected tropical diseases  

PubMed Central

Background Following World Health Assembly resolutions 50.36 in 1997 and 56.7 in 2003, the World Health Organization (WHO) committed itself to supporting human African trypanosomiasis (HAT)-endemic countries in their efforts to remove the disease as a public health problem. Mapping the distribution of HAT in time and space has a pivotal role to play if this objective is to be met. For this reason WHO launched the HAT Atlas initiative, jointly implemented with the Food and Agriculture Organization of the United Nations, in the framework of the Programme Against African Trypanosomosis. Results The distribution of HAT is presented for 23 out of 25 sub-Saharan countries having reported on the status of sleeping sickness in the period 2000 - 2009. For the two remaining countries, i.e. Angola and the Democratic Republic of the Congo, data processing is ongoing. Reports by National Sleeping Sickness Control Programmes (NSSCPs), Non-Governmental Organizations (NGOs) and Research Institutes were collated and the relevant epidemiological data were entered in a database, thus incorporating (i) the results of active screening of over 2.2 million people, and (ii) cases detected in health care facilities engaged in passive surveillance. A total of over 42 000 cases of HAT and 6 000 different localities were included in the database. Various sources of geographic coordinates were used to locate the villages of epidemiological interest. The resulting average mapping accuracy is estimated at 900 m. Conclusions Full involvement of NSSCPs, NGOs and Research Institutes in building the Atlas of HAT contributes to the efficiency of the mapping process and it assures both the quality of the collated information and the accuracy of the outputs. Although efforts are still needed to reduce the number of undetected and unreported cases, the comprehensive, village-level mapping of HAT control activities over a ten-year period ensures a detailed and reliable representation of the known geographic distribution of the disease. Not only does the Atlas serve research and advocacy, but, more importantly, it provides crucial evidence and a valuable tool for making informed decisions to plan and monitor the control of sleeping sickness.

2010-01-01

319

Focus–Specific Clinical Profiles in Human African Trypanosomiasis Caused by Trypanosoma brucei rhodesiense  

Microsoft Academic Search

BackgroundDiverse clinical features have been reported in human African trypanosomiasis (HAT) foci caused by Trypanosoma brucei rhodesiense (T.b.rhodesiense) giving rise to the hypothesis that HAT manifests as a chronic disease in South-East African countries and increased in virulence towards the North. Such variation in disease severity suggests there are differences in host susceptibility to trypanosome infection and\\/or genetic variation in

Lorna M. MacLean; Martin Odiit; John E. Chisi; Peter G. E. Kennedy; Jeremy M. Sternberg

2010-01-01

320

Melarsoprol Cyclodextrin Inclusion Complexes as Promising Oral Candidates for the Treatment of Human African Trypanosomiasis  

Microsoft Academic Search

Human African trypanosomiasis (HAT), or sleeping sickness, results from infection with the protozoan parasites Trypanosoma brucei (T.b.) gambiense or T.b.rhodesiense and is invariably fatal if untreated. There are 60 million people at risk from the disease throughout sub-Saharan Africa. The infection progresses from the haemolymphatic stage where parasites invade the blood, lymphatics and peripheral organs, to the late encephalitic stage

Jean Rodgers; Amy Jones; Stephane Gibaud; Barbara Bradley; Christopher McCabe; Michael P. Barrett; George Gettinby; Peter G. E. Kennedy

2011-01-01

321

The Atlas of human African trypanosomiasis: a contribution to global mapping of neglected tropical diseases  

Microsoft Academic Search

BACKGROUND: Following World Health Assembly resolutions 50.36 in 1997 and 56.7 in 2003, the World Health Organization (WHO) committed itself to supporting human African trypanosomiasis (HAT)-endemic countries in their efforts to remove the disease as a public health problem. Mapping the distribution of HAT in time and space has a pivotal role to play if this objective is to be

Pere P Simarro; Giuliano Cecchi; Massimo Paone; José R Franco; Abdoulaye Diarra; José A Ruiz; Eric M Fèvre; Fabrice Courtin; Raffaele C Mattioli; Jean G Jannin

2010-01-01

322

Human African trypanosomiasis in a Belgian traveller returning from the Masai Mara area, Kenya, February 2012.  

PubMed

A Belgian traveller was diagnosed with human African trypanosomiasis (HAT) due to Trypanosoma brucei rhodesiense nine days after visiting the Masai Mara area in Kenya. He presented with an inoculation chancre and was treated with suramin within four days of fever onset. Two weeks earlier, HAT was also reported in a German traveller who had visited the Masai Mara area. Because no cases have occurred in the area for over 12 years, this may indicate a focal cluster of HAT. PMID:22433595

Clerinx, J; Vlieghe, E; Asselman, V; Van de Casteele, S; Maes, M B; Lejon, V

2012-01-01

323

Lethal and Pre-Lethal Effects of a Fungal Biopesticide Contribute to Substantial and Rapid Control of Malaria Vectors  

PubMed Central

Rapidly emerging insecticide resistance is creating an urgent need for new active ingredients to control the adult mosquitoes that vector malaria. Biopesticides based on the spores of entomopathogenic fungi have shown considerable promise by causing very substantial mortality within 7–14 days of exposure. This mortality will generate excellent malaria control if there is a high likelihood that mosquitoes contact fungi early in their adult lives. However, where contact rates are lower, as might result from poor pesticide coverage, some mosquitoes will contact fungi one or more feeding cycles after they acquire malaria, and so risk transmitting malaria before the fungus kills them. Critics have argued that ‘slow acting’ fungal biopesticides are, therefore, incapable of delivering malaria control in real-world contexts. Here, utilizing standard WHO laboratory protocols, we demonstrate effective action of a biopesticide much faster than previously reported. Specifically, we show that transient exposure to clay tiles sprayed with a candidate biopesticide comprising spores of a natural isolate of Beauveria bassiana, could reduce malaria transmission potential to zero within a feeding cycle. The effect resulted from a combination of high mortality and rapid fungal-induced reduction in feeding and flight capacity. Additionally, multiple insecticide-resistant lines from three key African malaria vector species were completely susceptible to fungus. Thus, fungal biopesticides can block transmission on a par with chemical insecticides, and can achieve this where chemical insecticides have little impact. These results support broadening the current vector control paradigm beyond fast-acting chemical toxins.

Blanford, Simon; Shi, Wangpeng; Christian, Riann; Marden, James H.; Koekemoer, Lizette L.; Brooke, Basil D.; Coetzee, Maureen; Read, Andrew F.; Thomas, Matthew B.

2011-01-01

324

A current analysis of chemotherapy strategies for the treatment of human African trypanosomiasis  

PubMed Central

Despite the recent advances in drug research, finding a safe, effective, and easy to use chemotherapy for human African trypanosomiasis (HAT) remains a challenging task. The four current anti-trypanosomiasis drugs have major disadvantages that limit more widespread use of these drugs in the endemic regions of sub-Saharan Africa. Pentamidine and suramin are limited by their effectiveness against the only first stage of Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense, respectively. In addition, melarsoprol and eflornithine (two second stage drugs) each have disadvantages of their own. The former is toxic and has increasing treatment failures while the latter is expensive, laborious to administer, and lacks efficacy against T. b. rhodesiense. Furthermore, melarsoprol’s toxicity and decreasing efficacy are glaring problems and phasing out the drug as a frontline treatment against T. b. gambiense is now possible with the emergence of competent, safe combination chemotherapies such as nifurtimox–eflornithine combination treatment (NECT). The future of eflornithine, on the other hand, is more promising. The drug is useful in the context of combination chemotherapy and potential orally administered analogues. Due to the limits of monotherapies, greater emphasis should be placed on the research and development of combination chemotherapies, based on the successful clinical tests with NECT and its current use as a frontline anti-trypanosomiasis treatment. This review discussed the current and future chemotherapy strategies for the treatment of HAT.

Babokhov, Peter; Sanyaolu, Adekunle O; Oyibo, Wellington A; Fagbenro-Beyioku, Adetayo F; Iriemenam, Nnaemeka C

2013-01-01

325

Human African trypanosomiasis with 7-year incubation period: Clinical, laboratory and neuroimaging findings.  

PubMed

Human African trypanosomiasis (HAT), also referred to as "sleeping sickness", is caused by the parasite Trypanosoma brucei. Diagnosing imported HAT outside endemic areas is difficult and diagnosis is often delayed. We report a case of imported human African trypanosomiasis caused by Trypanosoma brucei gambiense with an unusually long incubation period of at least 7years. A 33year old male African patient, a former resident of Cameroon, presented with a 4-month history of progressive personality changes. A few weeks before presentation the patient had first been admitted to a psychiatric ward and received antidepressant treatment, until a lumbar puncture showed pleocytosis and then antibiotic treatment for suspected neuroborreliosis was initiated. The patient continued to deteriorate during antibiotic treatment and became increasingly lethargic. Under antiparasitic and anti-inflammatory treatment, the condition of the patient gradually improved over the following months and he recovered completely after 24months of follow-up. This well-documented case illustrates typical difficulties in establishing the correct diagnosis outside endemic areas and provides an overview of typical clinical, neuropathological and neuroimaging findings in T. b. gambiense trypanosomiasis, guiding the clinician in establishing the correct diagnosis in this rare disease. PMID:24613272

Wengert, Oliver; Kopp, Marcel; Siebert, Eberhard; Stenzel, Werner; Hegasy, Guido; Suttorp, Norbert; Stich, August; Zoller, Thomas

2014-06-01

326

Lack of galectin-3 alleviates trypanosomiasis-associated anemia of inflammation.  

PubMed

A typical pathological feature associated with experimental African trypanosomiasis (Trypanosoma brucei infection in mice) is anemia of chronic disease (ACD), which is due to a sustained type 1 cytokine-mediated inflammation and hyperactivation of M1 macrophages. Galectin-3 (Gal-3) was amply documented to contribute to the onset and persistence of type 1 inflammatory responses and we herein document that this protein is strongly upregulated during T. brucei infection. We evaluated the involvement of Gal-3 in trypanosomiasis-associated anemia using galectin-3 deficient (Gal3(-/-)) mice. T. brucei infected Gal3(-/-) mice manifested significant lower levels of anemia during infection and survived twice as long as wild type mice. Moreover, such mice showed increased levels of serum IL-10 and reduced liver pathology (as evidenced by lower AST/ALT levels). In addition, there was also an increase in gene expression of iron export genes and a reduced expression of genes, which are associated with accumulation of cellular iron. Our data indicate that Gal-3 is involved in the development of inflammation-associated anemia during African trypanosomiasis, possibly due to a disturbed iron metabolism that in turn may also lead to liver malfunction. PMID:20605052

Vankrunkelsven, Ann; De Ceulaer, Kris; Hsu, Daniel; Liu, Fu-Tong; De Baetselier, Patrick; Stijlemans, Benoît

2010-01-01

327

Fully digital, vector-controlled PWM VSI-fed AC drives with an inverter dead-time compensation strategy  

Microsoft Academic Search

A dead-time compensation method in vector-controlled pulse width modulator (PWM) voltage source inverters (VSIs) is proposed. The method is based on a feedforward approach that produces compensating signals obtained from the Id-Iq current and inverter output angular frequency references in the rotating reference (d-q) frame. It provides excellent inverter output voltage distortion correction for both fundamental and harmonic components. The

Takashi Sukegawa; Keno Kamiyama; Katsuhiro Mizuno; Takayuki Matsui; Toshiaki Okuyama

1991-01-01

328

An 18Pulse AC-DC Converter for Power Quality Improvement in Vector Controlled Induction Motor Drives  

Microsoft Academic Search

This paper deals with a novel autotransformer based improved power quality eighteen-pulse ac-dc converter feeding vector controlled induction motor drives (VCIMD's). The design of the proposed autotransformer is presented along with the necessary modifications required for making it suitable for retrofit applications, where presently a 6-pulse diode bridge rectifier is used. The proposed ac-dc converter is found capable of improving

Bhim Singh; G. Bhuvaneswari; Vipin Garg

2006-01-01

329

Power-quality improvements in vector-controlled induction motor drive employing pulse multiplication in AC-DC converters  

Microsoft Academic Search

This paper deals with the pulse doubling in a 12-pulse ac-dc converter for improving power quality in vector-controlled induction motor drives (VCIMDs). The design of proposed magnetics shows the flexibility in varying the voltage ratio of the autotransformer for making it suitable for retrofit applications, where presently a six-pulse diode bridge rectifier is being used. The proposed ac-dc converter is

Bhim Singh; G. Bhuvaneswari; Vipin Garg

2006-01-01

330

Polygon-Connected Autotransformer-Based 24Pulse AC–DC Converter for Vector-Controlled Induction-Motor Drives  

Microsoft Academic Search

This paper presents a novel autotransformer-based 24-pulse AC-DC converter feeding vector-controlled induction motor drives (VCIMDs) for improving power quality at the point of common coupling. The DC-ripple-reinjection technique is used in achieving the pulse multiplication in a 12-pulse AC-DC converter. The design of the proposed autotransformer is given, and necessary modifications are made in it to provide the same output

Bhim Singh; Vipin Garg; G. Bhuvaneswari

2008-01-01

331

Pulse multiplication in AC-DC converters for harmonic mitigation in vector-controlled induction motor drives  

Microsoft Academic Search

In this paper, an autotransformer with reduced kilovoltampere rating for 24-pulse ac-dc converter fed vector controlled induction motor drives (VCIMDs) is presented for harmonic current reduction. The 24-pulse operation is achieved using dc ripple reinjection technique in 12-pulse ac-dc converters. The proposed novel harmonic mitigator is found capable of suppressing up to 21st harmonic in the supply current. The procedure

Bhim Singh; G. Bhuvaneswari; Vipin Garg; Sanjay Gairola

2006-01-01

332

Feasibility and acceptability of insecticide-treated plastic sheeting (ITPS) for vector control in Papua New Guinea  

PubMed Central

Background This study assessed the feasibility and acceptability of utilizing insecticide-treated plastic sheeting (ITPS) as a malaria control intervention in Papua New Guinea (PNG). Methods ZeroVector® ITPS was installed in 40 homes across four study sites representing a cross section of malaria transmission risk and housing style. Structured questionnaires were completed at the time of ITPS installation (n=40) and at four weeks post installation (n=40) with the household head. Similarly, group interviews with the male and/or female household heads were completed at installation (n=5) and four-week follow-up (n=4). Results ZeroVector® ITPS was successfully installed in a range of homes employing traditional and/or modern building materials in PNG. The ITPS installations remained intact over the course of the four-week trial period and were highly acceptable to both male and female household heads. No dissatisfaction with the ITPS product was reported at four-week follow-up; however, the installation process was time consuming, participants reported a reduction in mosquito net use following ITPS installation and many participants expressed concern about the longevity of ITPS over the longer term. Conclusion ZeroVector® ITPS installation is feasible and highly acceptable in a diverse range of PNG contexts and is likely to be favourably received as a vector control intervention if accessible en masse. A longer-term evaluation is required before firm policy or public health decisions can be made regarding the potential application of ITPS in the national malaria control programme. The positive study findings suggest a longer-term evaluation of this promising malaria control intervention warrants consideration.

2012-01-01

333

Effect of Artemether-Lumefantrine Policy and Improved Vector Control on Malaria Burden in KwaZulu-Natal, South Africa  

PubMed Central

Background Between 1995 and 2000, KwaZulu–Natal province, South Africa, experienced a marked increase in Plasmodium falciparum malaria, fuelled by pyrethroid and sulfadoxine-pyrimethamine resistance. In response, vector control was strengthened and artemether-lumefantrine (AL) was deployed in the first Ministry of Health artemisinin-based combination treatment policy in Africa. In South Africa, effective vector and parasite control had historically ensured low-intensity malaria transmission. Malaria is diagnosed definitively and treatment is provided free of charge in reasonably accessible public-sector health-care facilities. Methods and Findings We reviewed four years of malaria morbidity and mortality data at four sentinel health-care facilities within KwaZulu–Natal's malaria-endemic area. In the year following improved vector control and implementation of AL treatment, malaria-related admissions and deaths both declined by 89%, and outpatient visits decreased by 85% at the sentinel facilities. By 2003, malaria-related outpatient cases and admissions had fallen by 99%, and malaria-related deaths had decreased by 97%. There was a concomitant marked and sustained decline in notified malaria throughout the province. No serious adverse events were associated causally with AL treatment in an active sentinel pharmacovigilance survey. In a prospective study with 42 d follow up, AL cured 97/98 (99%) and prevented gametocyte developing in all patients. Consistent with the findings of focus group discussions, a household survey found self-reported adherence to the six-dose AL regimen was 96%. Conclusion Together with concurrent strengthening of vector control measures, the antimalarial treatment policy change to AL in KwaZulu–Natal contributed to a marked and sustained decrease in malaria cases, admissions, and deaths, by greatly improving clinical and parasitological cure rates and reducing gametocyte carriage.

2005-01-01

334

Preliminary Investigation on Battery Sizing Investigation for Thrust Vector Control on Ares I and Ares V Launch Vehicles  

NASA Technical Reports Server (NTRS)

An investigation into the merits of battery powered Electro Hydrostatic Actuation (EHA) for Thrust Vector Control (TVC) of the Ares I and Ares V launch vehicles is described. A top level trade study was conducted to ascertain the technical merits of lithium-ion (Li-ion) and thermal battery performance to determine the preferred choice of an energy storage system chemistry that provides high power discharge capability for a relatively short duration.

Miller, Thomas B.

2011-01-01

335

Intensified Surveillance and Insecticide-based Control of the Chagas Disease Vector Triatoma infestans in the Argentinean Chaco  

PubMed Central

Background The elimination of Triatoma infestans, the main Chagas disease vector in the Gran Chaco region, remains elusive. We implemented an intensified control strategy based on full-coverage pyrethroid spraying, followed by frequent vector surveillance and immediate selective insecticide treatment of detected foci in a well-defined rural area in northeastern Argentina with moderate pyrethroid resistance. We assessed long-term impacts, and identified factors and procedures affecting spray effectiveness. Methods and Findings After initial control interventions, timed-manual searches were performed by skilled personnel in 4,053 sites of 353–411 houses inspected every 4–7 months over a 35-month period. Residual insecticide spraying was less effective than expected throughout the three-year period, mainly because of the occurrence of moderate pyrethroid resistance and the limited effectiveness of selective treatment of infested sites only. After initial interventions, peridomestic infestation prevalence always exceeded domestic infestation, and timed-manual searches consistently outperformed householders' bug detection, except in domiciles. Most of the infestations occurred in houses infested at baseline, and were restricted to four main ecotopes. Houses with an early persistent infestation were spatially aggregated up to a distance of 2.5 km. An Akaike-based multi-model inference approach showed that new site-level infestations increased substantially with the local availability of appropriate refugia for triatomine bugs, and with proximity to the nearest site found infested at one or two preceding surveys. Conclusions and Significance Current vector control procedures have limited effectiveness in the Gran Chaco. Selective insecticide sprays must include all sites within the infested house compound. The suppression of T. infestans in rural areas with moderate pyrethroid resistance requires increased efforts and appropriate management actions. In addition to careful, systematic insecticide applications, housing improvement and development policies that improve material conditions of rural villagers and reduce habitat suitability for bugs will contribute substantially to sustainable vector and disease control in the Gran Chaco.

Gurevitz, Juan M.; Gaspe, Maria Sol; Enriquez, Gustavo F.; Provecho, Yael M.; Kitron, Uriel; Gurtler, Ricardo E.

2013-01-01

336

Development and Assessment of Plant-Based Synthetic Odor Baits for Surveillance and Control of Malaria Vectors  

PubMed Central

Background Recent malaria vector control measures have considerably reduced indoor biting mosquito populations. However, reducing the outdoor biting populations remains a challenge because of the unavailability of appropriate lures to achieve this. This study sought to test the efficacy of plant-based synthetic odor baits in trapping outdoor populations of malaria vectors. Methodology and Principal Finding Three plant-based lures ((E)-linalool oxide [LO], (E)-linalool oxide and (E)-?-ocimene [LO + OC], and a six-component blend comprising (E)-linalool oxide, (E)-?-ocimene, hexanal, ?-pinene, limonene, and (E)-?-farnesene [Blend C]), were tested alongside an animal/human-based synthetic lure (comprising heptanal, octanal, nonanal, and decanal [Blend F]) and worn socks in a malaria endemic zone in the western part of Kenya. Mosquito Magnet-X (MM-X) and lightless Centre for Disease Control (CDC) light traps were used. Odor-baited traps were compared with traps baited with either solvent alone or solvent + carbon dioxide (controls) for 18 days in a series of randomized incomplete-block designs of days × sites × treatments. The interactive effect of plant and animal/human odor was also tested by combining LO with either Blend F or worn socks. Our results show that irrespective of trap type, traps baited with synthetic plant odors compared favorably to the same traps baited with synthetic animal odors and worn socks in trapping malaria vectors, relative to the controls. Combining LO and worn socks enhanced trap captures of Anopheles species while LO + Blend F recorded reduced trap capture. Carbon dioxide enhanced total trap capture of both plant- and animal/human-derived odors. However, significantly higher proportions of male and engorged female Anopheles gambiae s.l. were caught when the odor treatments did not include carbon dioxide. Conclusion and Significance The results highlight the potential of plant-based odors and specifically linalool oxide, with or without carbon dioxide, for surveillance and mass trapping of malaria vectors.

Nyasembe, Vincent O.; Tchouassi, David P.; Kirwa, Hillary K.; Foster, Woodbridge A.; Teal, Peter E. A.; Borgemeister, Christian; Torto, Baldwyn

2014-01-01

338

Impact of combined large-scale ivermectin distribution and vector control on transmission of Onchocerca volvulus in the Niger basin, Guinea.  

PubMed Central

As part of the WHO Onchocerciasis Control Programme in West Africa (OCP), the attack phase of operations in the Niger basin in Guinea began in 1989 with the simultaneous use of ivermectin and vector control. Larvicide applications coupled with annual large-scale ivermectin distribution have greatly reduced blackfly infectivity (by 78.8% for the number of infective larvae per 1000 parous flies). The combination of vector control and ivermectin has permitted excellent control of transmission. In the original OCP area, it took 6-8 years of vector control alone to obtain an equivalent decrease in blackfly infectivity. For the same number of flies caught, transmission was much higher in areas where ivermectin had not been distributed. The combined use of ivermectin and vector control has opened up new prospects for carrying out OCP operations with, notably, the possibility of reducing larviciding operations.

Guillet, P.; Seketeli, A.; Alley, E. S.; Agoua, H.; Boatin, B. A.; Bissan, Y.; Akpoboua, L. K.; Quillevere, D.; Samba, E. M.

1995-01-01

339

The Changing Epidemiology of Human African Trypanosomiasis among Patients from Nonendemic Countries -1902-2012  

PubMed Central

Background Although human African trypanosomiasis (HAT) is uncommon among patients from non-endemic countries (NEC), there has been an increase in the number of cases reported in recent years. Methods A systematic review of the literature was performed. The number of incoming tourists to HAT endemic countries was obtained from the United Nations World Tourism Organization. All HAT cases diagnosed in patients from NEC were included. Immigrants and refugees were excluded. We compared patients during and after the colonial period, and analyzed the relationship between the number of incoming travellers and the number of HAT cases. Results Between 1902 and 2012, HAT was reported in 244 patients. Most HAT cases were reported before 1920, and after the year 2000. In the colonial era the average age of patients was lower (32.5±7.8 vs. 43.0±16.1 years, P<0.001), the proportion of females was lower (10.0% vs. 23.9%, P<0.01], most cases were diagnosed in expatriates, missionaries and soldiers (74.3%), and Gambian trypanosomiasis accounted for 86/110, (78%) of cases. In the post-colonial era most patients 91/125 (72.8%) were short-term tourists to game parks in Eastern and South-Eastern Africa (mainly in Tanzania); Rhodesian trypanosomiasis accounted for 94/123 (76.4%) of cases. Between 1995 and 2010 there has been a constant linear increase in the number of incoming tourists to Tanzania, and HAT cases occurred in small outbreaks rather than following a similar linear pattern. Conclusions In recent decades HAT patients from NEC are older, and more likely to be tourists who acquired the disease while visiting game-parks in Eastern and South-Eastern Africa. While Rhodesian trypanosomiasis is relatively uncommon among Africans, it now accounts for most cases reported among patients from NEC. Returning febrile travellers without an alternative diagnosis should be evaluated for HAT. Cases among travellers may serve as sentinels for Rhodesian trypanosomiasis “hot spots” in Africa.

Neuberger, Ami; Meltzer, Eyal; Leshem, Eyal; Dickstein, Yaakov; Stienlauf, Shmuel; Schwartz, Eli

2014-01-01

340

IMPROVEMENT OF SMVGEAR II ON VECTOR AND SCALAR MACHINES THROUGH ABSOLUTE ERROR TOLERANCE CONTROL (R823186)  

EPA Science Inventory

The computer speed of SMVGEAR II was improved markedly on scalar and vector machines with relatively little loss in accuracy. The improvement was due to a method of frequently recalculating the absolute error tolerance instead of keeping it constant for a given set of chemistry. ...

341

Malaria and dengue vector biology and control in West and Central Africa  

Microsoft Academic Search

In West and Central Africa endemic malaria and epidemic yellow fever are still main causes of morbidity and mortality. From Dakar in Senegal to Kinshasa in the Democratic Republic of Congo the pattern of malaria transmission shows a huge variability, in term of dynamics (rhythm and intensity) of transmission, as well as in terms of the vector species involved. The

Didier Fontenilleand; Pierre Carnevale

342

Quantifying the mosquito's sweet tooth: modelling the effectiveness of attractive toxic sugar baits (ATSB) for malaria vector control  

PubMed Central

Background Current vector control strategies focus largely on indoor measures, such as long-lasting insecticide treated nets (LLINs) and indoor residual spraying (IRS); however mosquitoes frequently feed on sugar sources outdoors, inviting the possibility of novel control strategies. Attractive toxic sugar baits (ATSB), either sprayed on vegetation or provided in outdoor bait stations, have been shown to significantly reduce mosquito densities in these settings. Methods Simple models of mosquito sugar-feeding behaviour were fitted to data from an ATSB field trial in Mali and used to estimate sugar-feeding rates and the potential of ATSB to control mosquito populations. The model and fitted parameters were then incorporated into a larger integrated vector management (IVM) model to assess the potential contribution of ATSB to future IVM programmes. Results In the Mali experimental setting, the model suggests that about half of female mosquitoes fed on ATSB solution per day, dying within several hours of ingesting the toxin. Using a model incorporating the number of gonotrophic cycles completed by female mosquitoes, a higher sugar-feeding rate was estimated for younger mosquitoes than for older mosquitoes. Extending this model to incorporate other vector control interventions suggests that an IVM programme based on both ATSB and LLINs may substantially reduce mosquito density and survival rates in this setting, thereby substantially reducing parasite transmission. This is predicted to exceed the impact of LLINs in combination with IRS provided ATSB feeding rates are 50% or more of Mali experimental levels. In addition, ATSB is predicted to be particularly effective against Anopheles arabiensis, which is relatively exophilic and therefore less affected by IRS and LLINs. Conclusions These results suggest that high coverage with a combination of LLINs and ATSB could result in substantial reductions in malaria transmission in this setting. Further field studies of ATSB in other settings are needed to assess the potential of ATSB as a component in future IVM malaria control strategies.

2013-01-01

343

Efficient generation of double heterologous promoter controlled oncolytic adenovirus vectors by a single homologous recombination step in Escherichia coli  

PubMed Central

Background Oncolytic adenoviruses are promising agents for the multimodal treatment of cancer. However, tumor-selectivity is crucial for their applicability in patients. Recent studies by several groups demonstrated that oncolytic adenoviruses with tumor-/tissue-specific expression of the E1 and E4 genes, which are pivotal for adenoviral replication, have a specificity profile that is superior to viruses that solely target the expression of E1 or E4 genes. Presently the E1 and E4 regions are modified in a time consuming sequential fashion. Results Based on the widely used adenoviral cloning system AdEasy we generated a novel transfer vector that allows efficient and rapid generation of conditionally replication-competent adenovirus type 5 based vectors with the viral E1 and E4 genes under the transcriptional control of heterologous promoters. For insertion of the promoters of interest our transfer vector has two unique multiple cloning sites. Additionally, our shuttle plasmid allows encoding of a transgene within the E1A transcription unit. The modifications, including E1 mutations, are introduced into the adenoviral genome by a single homologous recombination step in Escherichia coli. Subsequently infectious viruses are rescued from plasmids. As a proof-of-concept we generated two conditionally replication-competent adenoviruses Ad.Ki•COX and Ad.COX•Ki with the promoters of the Ki-67 protein and the cyclooxygenase-2 (COX-2) driving E1 and E4 and vice versa. Conclusion We demonstrated with our cloning system efficient generation of double heterologous promoter controlled oncolytic adenoviral vectors by a single homologous recombination step in bacteria. The generated viruses showed preferential replication in tumor cells and in a subcutaneous HT-29 colon cancer xenograft model the viruses demonstrated significant oncolytic activity comparable with dl327.

Hoffmann, Dennis; Wildner, Oliver

2006-01-01

344

Boundaries of the Origin of Replication: Creation of a pET-28a-Derived Vector with p15A Copy Control Allowing Compatible Coexistence with pET Vectors  

PubMed Central

During our studies involving protein-DNA interactions, we constructed plasmid pSAM to fulfill two requirements: 1) to facilitate transfer of cloned sequences from widely used expression vector pET-28a(+), and 2) to provide a vector compatible with pBR322-derived plasmids for use in cells harboring two different plasmids. Vector pSAM is a pET-28a(+)-derived plasmid with the p15A origin of replication (ori); pET-28a(+) contains the pBR322 replicon that is incompatible with other pBR322-derived plasmids. By replacing the original pET-28a(+) replicon–comprising the ori, RNAI, RNAII, and Rom–with the p15A replicon, we generated pSAM, which contains the pET-28a(+) multiple cloning site and is now compatible with pBR322-derived vectors. Plasmid copy number was assessed using quantitative PCR: pSAM copy number was maintained at 18±4 copies per cell, consistent with that of other p15A-type vectors. Compatibility with pBR322-derived vectors was tested with pGEX-6p-1 and pSAM, which maintained their copy numbers of 49±10 and 14±4, respectively, when both were present within the same cell. Swapping of the ori is a common practice; however, it is vital that all regions of the original replicon be removed. Additional vector pSAMRNAI illustrated that incompatibility remains when portions of the replicon, such as RNAI and/or Rom, are retained; pSAMRNAI, which contains the intact RNAI but not ROM, lowered the copy number of pGEX-6p-1 to 18±2 in doubly transformed cells due to retention of the pET-28a(+)-derived RNAI. Thus, pSAMRNAI is incompatible with vectors controlled by the pBR322 replicon and further demonstrates the need to remove all portions of the original replicon and to quantitatively assess copy number, both individually and in combination, to ensure vector compatibility. To our knowledge, this is the first instance where the nascent vector has been quantitatively assessed for both plasmid copy number and compatibility. New vector pSAM provides ease of transferring sequences from commonly used pET-28a(+) into a vector compatible with the pBR322 family of plasmids. This essential need is currently not filled.

Sathiamoorthy, Sarmitha; Shin, Jumi A.

2012-01-01

345

Physclips: Vectors  

NSDL National Science Digital Library

This website provides an introduction to vectors. It includes topics such as magnitude and direction, components, unit vectors, vectors in three dimensions, vector addition and subtraction, and scalar and vector products. Animations, still images, graphs, and diagrams are used to illustrate important concepts. This tutorial is part of the PhysClips collection of web-based resources on introductory mechanics, electricity, and magnetism.

Wolfe, Joe

2009-01-20

346

Establishment of a large semi-field system for experimental study of African malaria vector ecology and control in Tanzania  

PubMed Central

Background Medical entomologists increasingly recognize that the ability to make inferences between laboratory experiments of vector biology and epidemiological trends observed in the field is hindered by a conceptual and methodological gap occurring between these approaches which prevents hypothesis-driven empirical research from being conducted on relatively large and environmentally realistic scales. The development of Semi-Field Systems (SFS) has been proposed as the best mechanism for bridging this gap. Semi-field systems are defined as enclosed environments, ideally situated within the natural ecosystem of a target disease vector and exposed to ambient environmental conditions, in which all features necessary for its life cycle completion are present. Although the value of SFS as a research tool for malaria vector biology is gaining recognition, only a few such facilities exist worldwide and are relatively small in size (< 100 m2). Methods The establishment of a 625 m2 state-of-the-art SFS for large-scale experimentation on anopheline mosquito ecology and control within a rural area of southern Tanzania, where malaria transmission intensities are amongst the highest ever recorded, is described. Results A greenhouse frame with walls of mosquito netting and a polyethylene roof was mounted on a raised concrete platform at the Ifakara Health Institute. The interior of the SFS was divided into four separate work areas that have been set up for a variety of research activities including mass-rearing for African malaria vectors under natural conditions, high throughput evaluation of novel mosquito control and trapping techniques, short-term assays of host-seeking behaviour and olfaction, and longer-term experimental investigation of anopheline population dynamics and gene flow within a contained environment that simulates a local village domestic setting. Conclusion The SFS at Ifakara was completed and ready for use in under two years. Preliminary observations indicate that realistic and repeatable observations of anopheline behaviour are obtainable within the SFS, and that habitat and climatic features representative of field conditions can be simulated within it. As work begins in the SFS in Ifakara and others around the world, the major opportunities and challenges to the successful application of this tool for malaria vector research and control are discussed.

Ferguson, Heather M; Ng'habi, Kija R; Walder, Thomas; Kadungula, Demetrius; Moore, Sarah J; Lyimo, Issa; Russell, Tanya L; Urassa, Honorathy; Mshinda, Hassan; Killeen, Gerry F; Knols, Bart GJ

2008-01-01

347

Advanced solid rocket motor nozzle thrust vector control flexseal development status  

NASA Astrophysics Data System (ADS)

The advanced solid rocket motor (ASRM) flexseal development status is reviewed focusing on design goals and requirements, design configuration, analysis activities, and verification tests. It is concluded that the ASRM flexseal incorporates flight-proven materials in an innovative design configuration. Variable thickness shims and efficient packaging of the flexseal make it possible to achieve a significant weight reduction. A flexseal insulator design derived from strategic solid rocket motor experience will provide the necessary bearing thermal protection while minimizing vectoring torque variability.

Prins, William S.; Meyer, Scott A.; Cox, Paul D.

1992-07-01

348

Progress in directed energy control of vectors for microbes and other cells  

Microsoft Academic Search

Biosynthetic semiconductor, diazoluminomelanin (DALM), is a polymer of tyrosine, luminol, and nitrite. DALM has a very large cross section of absorption for light from ultraviolet to radio frequencies. This polymer can be made efficiently in a genetically engineered E.coli, JM109\\/pIC2ORNR1.1 (ATCC# 69905). We have been pursuing ways to couple electromagnetic radiation to vectors using this polymer. DNA capture elements (DCEs;

Johnathan L. Kiel; Jill E. Parker; Eric A. Holwitt; Jeeva Vivekananda; Mark A. Sloan; Lucille J. V. Stribling

2004-01-01

349

Progress in directed energy control of vectors for microbes and other cells  

NASA Astrophysics Data System (ADS)

Biosynthetic semiconductor, diazoluminomelanin (DALM), is a polymer of tyrosine, luminol, and nitrite. DALM has a very large cross section of absorption for light from ultraviolet to radio frequencies. This polymer can be made efficiently in a genetically engineered E.coli, JM109/pIC2ORNR1.1 (ATCC# 69905). We have been pursuing ways to couple electromagnetic radiation to vectors using this polymer. DNA capture elements (DCEs; formerly aptamers) have made this possible. We incorporated DCEs into the plasmid of this E. coli to direct binding to whatever microbe or cell desired and to produce DALM attached to the plasmid DNA. Using two other vectors pSV2neoNR101 or pSV2neoNR8005 (ATCC # 69617 and 69618, respectively), both propagated in the E. coli host HB101, we have also inserted genes necessary for DALM production into animal and human cell lines (mouse monocytic leukemia: ATCC # CRL- 11771, -11772, -1173, mouse mammary adenocarcinoma: ATCC# CRL-12184, -12185; and human carcinoma of the cervix: ATCC # CRL-12510). The DCE/DALM vectors can be used to tag target cells, detectable by broad-spectrum light absorbance, luminescence, or fluorescence. DCE/DALM can further be activated with light, microwave energy, or by oxidative chemistry to kill the targeted microbes or other cells.

Kiel, Johnathan L.; Parker, Jill E.; Holwitt, Eric A.; Vivekananda, Jeeva; Sloan, Mark A.; Stribling, Lucille J. V.

2004-07-01

350

An alternative to killing? Treatment of reservoir hosts to control a vector and pathogen in a susceptible species.  

PubMed

Parasite-mediated apparent competition occurs when one species affects another through the action of a shared parasite. One way of controlling the parasite in the more susceptible host is to manage the reservoir host. Culling can cause issues in terms of ethics and biodiversity impacts, therefore we ask: can treating, as compared to culling, a wildlife host protect a target species from the shared parasite? We used Susceptible Infected Recovered (SIR) models parameterized for the tick-borne louping ill virus (LIV) system. Deer are the key hosts of the vector (Ixodes ricinus) that transmits LIV to red grouse Lagopus lagopus scoticus, causing high mortality. The model was run under scenarios of varying acaricide efficacy and deer densities. The model predicted that treating deer can increase grouse density through controlling ticks and LIV, if acaricide efficacies are high and deer densities low. Comparing deer treated with 70% acaricide efficacy with a 70% cull rate suggested that treatment may be more effective than culling if initial deer densities are high. Our results will help inform tick control policies, optimize the targeting of control methods and identify conditions where host management is most likely to succeed. Our approach is applicable to other host-vector-pathogen systems. PMID:22939093

Porter, R; Norman, R A; Gilbert, L

2013-02-01

351

Human Antibody Responses to the Anopheles Salivary gSG6-P1 Peptide: A Novel Tool for Evaluating the Efficacy of ITNs in Malaria Vector Control  

Microsoft Academic Search

To optimize malaria control, WHO has prioritised the need for new indicators to evaluate the efficacy of malaria vector control strategies. The gSG6-P1 peptide from gSG6 protein of Anopheles gambiae salivary glands was previously designed as a specific salivary sequence of malaria vector species. It was shown that the quantification of human antibody (Ab) responses to Anopheles salivary proteins in

Papa Makhtar Drame; Anne Poinsignon; Patrick Besnard; Sylvie Cornelie; Jacques Le Mire; Jean-Claude Toto; Vincent Foumane; Maria Adelaide Dos-Santos; Mbacké Sembène; Filomeno Fortes; Francois Simondon; Pierre Carnevale; Franck Remoue; Etienne Joly

2010-01-01

352

A Space Vector Modulation Scheme for Matrix Converter that Gives Top Priority to the Improvement of the Output Control Performance  

NASA Astrophysics Data System (ADS)

This Paper proposes a novel conversion scheme of switching patterns for three-phase to three-phase matrix converters. The conventional virtual indirect conversion method is equivalent to PWM technique via an ordinary PWM rectifier/inverter, offering the advantage that no complicated specialized control is required. On the other hand, 6 of 27 switching patterns cannot be used in this method, because the inputs and outputs are always connected by way of the virtual DC link that is composed of 2 lines. This paper therefore defines the direct space vectors that can express the all 27 switching patterns and utilizes the geometric relationship of direct space vectors so that all switching patterns can be converted from other arbitrary vectors. This conversion scheme also allows the duty factor conversion with simple calculation by utilizing the duties of the virtual indirect conversion approach. In particular, the above-mentioned 6 switching patterns that have been restricted can be fully utilized for reducing output voltage harmonics, switching losses and common-mode voltages. The validity of the proposed conversion method is proven from the experimental results compared with a conventional virtual indirect method.

Tadano, Yugo; Hamada, Shizunori; Urushibata, Shota; Nomura, Masakatsu; Sato, Yukihiko; Ishida, Muneaki

353

The US Air Force Aerial Spray Unit: a history of large area disease vector control operations, WWII through Katrina.  

PubMed

The US Air Force has had a long history of aerial applications of pesticides to fulfill a variety of missions, the most important being the protection of troops through the minimization of arthropod vectors capable of disease transmission. Beginning in World War II, aerial application of pesticides by the military has effectively controlled vector and nuisance pest populations in a variety of environments. Currently, the military aerial spray capability resides in the US Air Force Reserve (USAFR), which operates and maintains C-130 airplanes capable of a variety of missions, including ultra low volume applications for vector and nuisance pests, as well as higher volume aerial applications of herbicides and oil-spill dispersants. The USAFR aerial spray assets are the only such fixed-wing aerial spray assets within the Department of Defense. In addition to troop protection, the USAFR Aerial Spray Unit has participated in a number of humanitarian/relief missions, most recently in the response to the 2005 Hurricanes Katrina and Rita, which heavily damaged the Gulf Coasts of Louisiana, Mississippi, and Texas. This article provides historical background on the Air Force Aerial Spray Unit and describes the operations in Louisiana in the aftermath of Hurricane Katrina. PMID:20088030

Breidenbaugh, Mark; Haagsma, Karl

2008-01-01

354

Can malaria vector control accelerate the interruption of lymphatic filariasis transmission in Africa; capturing a window of opportunity?  

PubMed Central

Background The Global Programme to Eliminate Lymphatic Filariasis (GPELF) was launched in 2000, and nearly all endemic countries in the Americas, Eastern Mediterranean and Asia-Pacific regions have now initiated the WHO recommended mass drug administration (MDA) campaign to interrupt transmission of the parasite. However, nearly 50% of the LF endemic countries in Africa are yet to implement the GPELF MDA strategy, which does not include vector control. Nevertheless, the recent scale up in insecticide treated /long lasting nets (ITNs/LLINs) and indoor residual spraying (IRS) for malaria control in Africa may significantly impact LF transmission because the parasite is transmitted mainly by Anopheles mosquitoes. This study examined the magnitude, geographical extent and potential impact of vector control in the 17 African countries that are yet to or have only recently started MDA. Methods National data on mosquito bed nets, ITNs/LLINs and IRS were obtained from published literature, national reports, surveys and datasets from public sources such as Demographic Health Surveys, Malaria Indicator Surveys, Multiple Indicator Cluster Surveys, Malaria Report, Roll Back Malaria and President’s Malaria Initiative websites. The type, number and distribution of interventions were summarised and mapped at sub-national level. and compared with known or potential LF distributions, and those which may be co-endemic with Loa loa and MDA is contraindicated. Results Analyses found that vector control activities had increased significantly since 2005, with a three-fold increase in ITN ownership and IRS coverage. However, coverage varied dramatically across the 17 countries; some regions reported >70% ITNs ownership and regular IRS activity, while others had no coverage in remote rural populations where the risk of LF was potentially high and co-endemic with high risk L.loa. Conclusions Despite many African countries being slow to initiate MDA for LF, the continued commitment and global financial support for NTDs, and the concurrent expansion of vector control activities for malaria, is promising. It is not beyond the capacity of GPELF to reach its target of global LF elimination by 2020, but monitoring and evaluating the impact of these activities over the next decade will be critical to its success.

2013-01-01

355

The significance of migrant Fulani and human trypanosomiasis in Kainji Lake area of Nigeria.  

PubMed

The transhumance-route followed by the Fulani around Lake Kainji area of Nigeria is presented. Between January and February 1977 130 Fulanis were interviewed at different locations. Most respondents were between 20-60 years of age. In addition to cattle rearing, farming is practised among the Fulanis interviewed at Kaiama and Olli. Those interviewed at Faku practised pastoral transhumance. Less than 15% of the respondents had previous knowledge of human sleeping sickness. Although examination of blood films (thin and thick) did not reveal any blood trypanosome, the transhumance pastoral mobility will be an important factor in any outbreak of human trypanosomiasis around Kainji Lake area in future. PMID:734753

Adekolu-John, E O

1978-09-01

356

False Positivity of Non-Targeted Infections in Malaria Rapid Diagnostic Tests: The Case of Human African Trypanosomiasis  

PubMed Central

Background In endemic settings, diagnosis of malaria increasingly relies on the use of rapid diagnostic tests (RDTs). False positivity of such RDTs is poorly documented, although it is especially relevant in those infections that resemble malaria, such as human African trypanosomiasis (HAT). We therefore examined specificity of malaria RDT products among patients infected with Trypanosoma brucei gambiense. Methodology/Principal Findings Blood samples of 117 HAT patients and 117 matched non-HAT controls were prospectively collected in the Democratic Republic of the Congo. Reference malaria diagnosis was based on real-time PCR. Ten commonly used malaria RDT products were assessed including three two-band and seven three-band products, targeting HRP-2, Pf-pLDH and/or pan-pLDH antigens. Rheumatoid factor was determined in PCR negative subjects. Specificity of the 10 malaria RDT products varied between 79.5 and 100% in HAT-negative controls and between 11.3 and 98.8% in HAT patients. For seven RDT products, specificity was significantly lower in HAT patients compared to controls. False positive reactions in HAT were mainly observed for pan-pLDH test lines (specificities between 13.8 and 97.5%), but also occurred frequently for the HRP-2 test line (specificities between 67.9 and 98.8%). The Pf-pLDH test line was not affected by false-positive lines in HAT patients (specificities between 97.5 and 100%). False positivity was not associated to rheumatoid factor, detected in 7.6% of controls and 1.2% of HAT patients. Conclusions/Significance Specificity of some malaria RDT products in HAT was surprisingly low, and constitutes a risk for misdiagnosis of a fatal but treatable infection. Our results show the importance to assess RDT specificity in non-targeted infections when evaluating diagnostic tests.

Gillet, Philippe; Mumba Ngoyi, Dieudonne; Lukuka, Albert; Kande, Viktor; Atua, Benjamin; van Griensven, Johan; Muyembe, Jean-Jacques; Jacobs, Jan; Lejon, Veerle

2013-01-01

357

Bacterial symbiosis and paratransgenic control of vector-borne Chagas disease.  

PubMed

The triatomine vectors of Chagas disease are obligate haematophagous insects, feeding on vertebrate blood throughout their entire developmental cycle. As a result of obtaining their nutrition from a single food source, their diet is devoid of certain vitamins and nutrients. Consequently, these insects harbour populations of bacterial symbionts within their intestinal tract, which provide the required nutrients that are lacking from their diet. We have isolated and characterised symbiont cultures from various triatomine species and developed a method for genetically transforming them. We can then reintroduce them into their original host species, thereby producing stable paratransgenic insects in which we are able to express heterologous gene products. Using this methodology, we have generated paratransgenic Rhodnius prolixus that are refractory for infection with Trypanosoma cruzi. Two examples of potentially refractory genes are currently being expressed in paratransgenic insects. These include the insect immune peptide cecropin A and active single chain antibody fragments. We have also developed an approach that would allow introduction of genetically modified bacterial symbionts into natural populations of Chagas disease vectors. This approach utilises the coprophagic behaviour of these insects, which is the way in which the symbionts are transmitted among bug populations in nature. The production and ultimate release of transgenic or paratransgenic insects for public health applications is potentially very promising but also worthy of much careful consideration with respect to environmental, political, and human safety concerns. PMID:11334952

Beard, C B; Dotson, E M; Pennington, P M; Eichler, S; Cordon-Rosales, C; Durvasula, R V

2001-05-01

358

Dengue Vector Dynamics (Aedes aegypti) Influenced by Climate and Social Factors in Ecuador: Implications for Targeted Control  

PubMed Central

Background Dengue fever, a mosquito-borne viral disease, is now the fastest spreading tropical disease globally. Previous studies indicate that climate and human behavior interact to influence dengue virus and vector (Aedes aegypti) population dynamics; however, the relative effects of these variables depends on local ecology and social context. We investigated the roles of climate and socio-ecological factors on Ae. aegypti population dynamics in Machala, a city in southern coastal Ecuador where dengue is hyper-endemic. Methods/Principal findings We studied two proximate urban localities where we monitored weekly Ae. aegypti oviposition activity (Nov. 2010-June 2011), conducted seasonal pupal surveys, and surveyed household to identify dengue risk factors. The results of this study provide evidence that Ae. aegypti population dynamics are influenced by social risk factors that vary by season and lagged climate variables that vary by locality. Best-fit models to predict the presence of Ae. aegypti pupae included parameters for household water storage practices, access to piped water, the number of households per property, condition of the house and patio, and knowledge and perceptions of dengue. Rainfall and minimum temperature were significant predictors of oviposition activity, although the effect of rainfall varied by locality due to differences in types of water storage containers. Conclusions These results indicate the potential to reduce the burden of dengue in this region by conducting focused vector control interventions that target high-risk households and containers in each season and by developing predictive models using climate and non-climate information. These findings provide the region's public health sector with key information for conducting time and location-specific vector control campaigns, and highlight the importance of local socio-ecological studies to understand dengue dynamics. See Text S1 for an executive summary in Spanish.

Stewart Ibarra, Anna M.; Ryan, Sadie J.; Beltran, Efrain; Mejia, Raul; Silva, Mercy; Munoz, Angel

2013-01-01

359

Novel, Meso-Substituted Cationic Porphyrin Molecule for Photo-Mediated Larval Control of the Dengue Vector Aedes aegypti  

PubMed Central

Background Control of the mosquito vector population is the most effective strategy currently available for the prevention of dengue fever and the containment of outbreaks. Photo-activated oxidants may represent promising tools for developing effective, safe and ecofriendly novel larvicides. The purpose of this study was to evaluate the potential of the synthetic meso-substituted porphyrin meso-tri(N-methylpyridyl), meso-mono(N-tetradecylpyridyl)porphine (C14) as a photoactivatable larvicide against the dengue vector Aedes (Stegomyia) aegypti. Methodology The photophysical and photochemical properties of the C14 molecule were assessed spectrophotometrically. Photomediated larvicidal efficacy, route of intake and site of action were determined on Ae. aegypti larvae by laboratory bioassays and fluorescence microscopy. Using powdered food pellet for laboratory rodents (a common larval food used in the laboratory) as a carrier for C14, loading-release dynamics, larvicidal efficacy and residual activity of the C14-carrier complex were investigated. Main Findings The C14 molecule was found to exert a potent photosensitizing activity on Ae. aegypti larvae. At irradiation intervals of 12 h and 1 h, at a light intensity of 4.0 mW/cm2, which is 50–100 times lower than that of natural sunlight, LC50 values of 0.1 µM (0.15 mg/l) and 0.5 µM (0.77 mg/l) were obtained, respectively. The molecule was active after ingestion by the larvae and caused irreversible, lethal damage to the midgut and caecal epithelia. The amphiphilic nature of C14 allowed a formulate to be produced that not only was as active against the larvae as C14 in solution, but also possessed a residual activity of at least two weeks, in laboratory conditions. Conclusions The meso-substituted synthetic porphyrin C14, thanks to its photo-sensitizing properties represents an attractive candidate for the development of novel photolarvicides for dengue vector control.

Lucantoni, Leonardo; Magaraggia, Michela; Lupidi, Giulio; Ouedraogo, Robert Kossivi; Coppellotti, Olimpia; Esposito, Fulvio; Fabris, Clara; Jori, Giulio; Habluetzel, Annette

2011-01-01

360

A Method for Integrating Thrust-Vectoring and Actuated Forebody Strakes with Conventional Aerodynamic Controls on a High-Performance Fighter Airplane  

NASA Technical Reports Server (NTRS)

A method, called pseudo controls, of integrating several airplane controls to achieve cooperative operation is presented. The method eliminates conflicting control motions, minimizes the number of feedback control gains, and reduces the complication of feedback gain schedules. The method is applied to the lateral/directional controls of a modified high-performance airplane. The airplane has a conventional set of aerodynamic controls, an experimental set of thrust-vectoring controls, and an experimental set of actuated forebody strakes. The experimental controls give the airplane additional control power for enhanced stability and maneuvering capabilities while flying over an expanded envelope, especially at high angles of attack. The flight controls are scheduled to generate independent body-axis control moments. These control moments are coordinated to produce stability-axis angular accelerations. Inertial coupling moments are compensated. Thrust-vectoring controls are engaged according to their effectiveness relative to that of the aerodynamic controls. Vane-relief logic removes steady and slowly varying commands from the thrust-vectoring controls to alleviate heating of the thrust turning devices. The actuated forebody strakes are engaged at high angles of attack. This report presents the forward-loop elements of a flight control system that positions the flight controls according to the desired stability-axis accelerations. This report does not include the generation of the required angular acceleration commands by means of pilot controls or the feedback of sensed airplane motions.

Lallman, Frederick J.; Davidson, John B.; Murphy, Patrick C.

1998-01-01

361

Interpreting the mean shift signals in multivariate control charts using support vector machine-based classifier  

Microsoft Academic Search

As one of the primary Statistical Process Control (SPC) tools, control chart plays a very important role in attaining process stability. There are many cases in which the simultaneous monitoring or control of two or more related quality characteristics is required. Out-of-control signals in multivariate charts may be caused by one or more variables or a set of variables. One

C. S. Cheng; H. P. Cheng; K. K. Huang

2009-01-01

362

Diagnostic Accuracy of Loopamp Trypanosoma brucei Detection Kit for Diagnosis of Human African Trypanosomiasis in Clinical Samples  

PubMed Central

Background Molecular methods have great potential for sensitive parasite detection in the diagnosis of human African trypanosomiasis (HAT), but the requirements in terms of laboratory infrastructure limit their use to reference centres. A recently developed assay detects the Trypanozoon repetitive insertion mobile element (RIME) DNA under isothermal amplification conditions and has been transformed into a ready-to-use kit format, the Loopamp Trypanosoma brucei. In this study, we have evaluated the diagnostic performance of the Loopamp Trypanosoma brucei assay (hereafter called LAMP) in confirmed T.b. gambiense HAT patients, HAT suspects and healthy endemic controls from the Democratic Republic of the Congo (DRC). Methodology/Principal findings 142 T.b. gambiense HAT patients, 111 healthy endemic controls and 97 HAT suspects with unconfirmed status were included in this retrospective evaluation. Reference standard tests were parasite detection in blood, lymph or cerebrospinal fluid. Archived DNA from blood of all study participants was analysed in duplicate with LAMP. Sensitivity of LAMP in parasitologically confirmed cases was 87.3% (95% CI 80.9–91.8%) in the first run and 93.0% (95% CI 87.5–96.1%) in the second run. Specificity in healthy controls was 92.8% (95% CI 86.4–96.3%) in the first run and 96.4% (95% CI 91.1–98.6%) in the second run. Reproducibility was excellent with a kappa value of 0.81. Conclusions/Significance In this laboratory-based study, the Loopamp Trypanosoma brucei Detection Kit showed good diagnostic accuracy and excellent reproducibility. Further studies are needed to assess the feasibility of its routine use for diagnosis of HAT under field conditions.

Mitashi, Patrick; Hasker, Epco; Ngoyi, Dieudonne Mumba; Pyana, Pati Patient; Lejon, Veerle; Van der Veken, Wim; Lutumba, Pascal; Buscher, Philippe; Boelaert, Marleen; Deborggraeve, Stijn

2013-01-01

363

Microbial symbiosis and the control of vector-borne pathogens in tsetse flies, human lice, and triatomine bugs.  

PubMed

Symbiosis is a widespread biological phenomenon, and is particularly common in arthropods. Bloodsucking insects are among the organisms that rely on beneficial bacterial symbionts to complement their unbalanced diet. This review is focused on describing symbiosis, and possible strategies for the symbiont-based control of insects and insect-borne diseases, in three bloodsucking insects of medical importance: the flies of the genus Glossina, the lice of the genus Pediculus, and triatomine bugs of the subfamily Triatominae. Glossina flies are vector of Trypanosoma brucei, the causative agent of sleeping sickness and other pathologies. They are also associated with two distinct bacterial symbionts, the primary symbiont Wigglesworthia spp., and the secondary, culturable symbiont Sodalis glossinidius. The primary symbiont of human lice, Riesia pediculicola, has been shown to be fundamental for the host, due to its capacity to synthesize B-group vitamins. An antisymbiotic approach, with antibiotic treatment targeted on the lice symbionts, could represent an alternative strategy to control these ectoparasites. In the case of triatominae bugs, the genetic modification of their symbiotic Rhodococcus bacteria, for production of anti-Trypanosoma molecules, is an example of paratransgenesis, i.e. the use of symbiotic microorganism engineered in order to reduce the vector competence of the insect host. PMID:24188239

Sassera, Davide; Epis, Sara; Pajoro, Massimo; Bandi, Claudio

2013-09-01

364

The role of the United States military in the development of vector control products, including insect repellents, insecticides, and bed nets.  

PubMed

Arthropod-borne diseases such as malaria, dengue, scrub typhus, and leishmaniasis continue to pose a significant threat to U.S. military forces deployed in support of operational and humanitarian missions. These diseases are transmitted by a variety of arthropods, including mosquitoes, ticks, chiggers, sand flies, and biting midges. In addition to disease threats, biting arthropods can cause dermatitis, allergic reactions, and sleep loss; therefore, monitoring of vector impact and integrated use of personal protective measures (PPM) and methods to reduce the vector populations are needed to protect service members. The U.S. military has played a vital role in vector identification tools and the development and testing of many of the most effective PPM and vector control products available today, including the topical repellent DEET and the repellent/insecticide permethrin, which is applied to clothing and bed nets. Efforts to develop superior products are ongoing. Although the U.S. military often needs vector control products with rather specific properties (e.g., undetectable, long-lasting in multiple climates) in order to protect its service members, many Department of Defense vector control products have had global impacts on endemic disease control. PMID:20836805

Kitchen, Lynn W; Lawrence, Kendra L; Coleman, Russell E

2009-06-01

365

Can Timely Vector Control Interventions Triggered by Atypical Environmental Conditions Prevent Malaria Epidemics? A Case-Study from Wajir County, Kenya  

PubMed Central

Background Atypical environmental conditions with drought followed by heavy rainfall and flooding in arid areas in sub-Saharan Africa can lead to explosive epidemics of malaria, which might be prevented through timely vector-control interventions. Objectives Wajir County in Northeast Kenya is classified as having seasonal malaria transmission. The aim of this study was to describe in Wajir town the environmental conditions, the scope and timing of vector-control interventions and the associated resulting burden of malaria at two time periods (1996–1998 and 2005–2007). Methods This is a cross-sectional descriptive and ecological study using data collected for routine program monitoring and evaluation. Results In both time periods, there were atypical environmental conditions with drought and malnutrition followed by massive monthly rainfall resulting in flooding and animal/human Rift Valley Fever. In 1998, this was associated with a large and explosive malaria epidemic (weekly incidence rates peaking at 54/1,000 population/week) with vector-control interventions starting over six months after the massive rainfall and when the malaria epidemic was abating. In 2007, vector-control interventions started sooner within about three months after the massive rainfall and no malaria epidemic was recorded with weekly malaria incidence rates never exceeding 0.5 per 1,000 population per week. Discussion and Conclusion Did timely vector-control interventions in Wajir town prevent a malaria epidemic? In 2007, the neighboring county of Garissa experienced similar climatic events as Wajir, but vector-control interventions started six months after the heavy un-seasonal rainfall and large scale flooding resulted in a malaria epidemic with monthly incidence rates peaking at 40/1,000 population. In conclusion, this study suggests that atypical environmental conditions can herald a malaria outbreak in certain settings. In turn, this should alert responsible stakeholders about the need to act rapidly and preemptively with appropriate and wide-scale vector-control interventions to mitigate the risk.

Maes, Peter; Harries, Anthony D.; Van den Bergh, Rafael; Noor, Abdisalan; Snow, Robert W.; Tayler-Smith, Katherine; Hinderaker, Sven Gudmund; Zachariah, Rony; Allan, Richard

2014-01-01

366

PCR based diagnosis of trypanosomiasis exploring invariant surface glycoprotein (ISG) 75 gene.  

PubMed

The invariant surface glycoprotein (ISG-75) gene of Trypanosoma evansi buffalo isolate from Karnataka state in India was sequenced and analyzed to elucidate its relationship with other isolates/species. The sequenced ISG-75 gene was also explored to device a polymerase chain reaction (PCR) strategy for the diagnosis of trypanosomiasis in carrier animals. The six cloned ISG gene sequences revealed the open reading frame (ORF) of 1572 and 1527 nucleotide (nt) encoding a polypeptide of 523 and 508 amino acids (aa) respectively and belongs ISG-75 gene family. Sequence analysis revealed 91-100% and 65-99% similarity at nt and aa levels, respectively with other isolates/species and belongs to the RoTat 1.2 strain. The diagnostic PCR based on ISG-75 sequence amplifies a 407 bp product specifically from the different T. evansi isolates and could detect 0.04 pg and 1.2 ng of DNA from purified trypanosomes and T. evansi infected rat blood samples respectively. Subsequently the PCR detected 0.02 and 0.27 trypanosomes ml(-1) respectively, from purified trypanosomes and T. evansi (buffalo isolate) infected rat blood. By the developed PCR assay trypanosomal nucleic acid was detected in experimental rats and buffalo on 24 h post infection (p.i.) and 3rd day post infection (d.p.i.), respectively. The developed ISG-75 gene based PCR assay could be useful in detection of carrier status of trypanosomiasis in animals. PMID:23305969

Rudramurthy, G R; Sengupta, P P; Balamurugan, V; Prabhudas, K; Rahman, H

2013-03-31

367

A CATT Negative Result after Treatment for Human African Trypanosomiasis Is No Indication for Cure  

PubMed Central

Background Cure after treatment for human African trypanosomiasis (HAT) is assessed by examination of the cerebrospinal fluid every 6 months, for a total period of 2 years. So far, no markers for cure or treatment failure have been identified in blood. Trypanosome-specific antibodies are detectable in blood by the Card Agglutination Test for Trypanosomiasis (CATT). We studied the value of a normalising, negative post-treatment CATT result in treated Trypanosoma brucei (T.b.) gambiense sleeping sickness patients as a marker of cure. Methodology/Principal Findings The CATT/T.b. gambiense was performed on serum of a cohort of 360 T.b. gambiense patients, consisting of 242 primary and 118 retreatment cases. The CATT results during 2 years of post-treatment follow-up were studied in function of cure or treatment failure. At inclusion, sensitivity of CATT was 98% (234/238) in primary cases and only 78% (91/117) in retreatment cases. After treatment, the CATT titre decreased both in cured patients and in patients experiencing treatment failure. Conclusions/Significance Though CATT is a good test to detect HAT in primary cases, a normalising or negative CATT result after treatment for HAT does not indicate cure, therefore CATT cannot be used to monitor treatment outcome.

Lejon, Veerle; Ngoyi, Dieudonne Mumba; Boelaert, Marleen; Buscher, Philippe

2010-01-01

368

The role of the polyamine inhibitor eflornithine in the neuropathogenesis of experimental murine African trypanosomiasis.  

PubMed

The treatment of late-stage human African trypanosomiasis is complicated by a post-treatment reactive encephalopathy, also referred to as a 'reactive arsenical encephalopathy', that may be fatal. This study used a well established experimental mouse system to assess the use of the trypanostatic drug, eflornithine, in the management of this post-treatment reaction. Female CD-1 mice infected with an eflornithine-resistant trypanosome stabilate and treated with the trypanocidal compound diminazene aceturate on or after day 21 post-infection develop a reactive encephalopathy and relapsing parasitaemia. If these animals are re-treated with diminazene aceturate, a severe encephalopathy develops histologically comparable with that of human cases and characterized by a severe meningoencephalitis and astrogliosis. Histopathological and immunocytochemical examination shows that administration of eflornithine before or after the development of this reactive encephalopathy prevented or ameliorated the inflammatory reaction. Since an eflornithine resistant stabilate was used, this effect appears to be independent of the drug's trypanostatic action and illustrates an important, previously unrecognized, pharmacological property of eflornithine. Consideration can now be given to the use of eflornithine for the management of human trypanosomiasis cases, even where trypanosome resistance to eflornithine exists. PMID:9223132

Jennings, F W; Gichuki, C W; Kennedy, P G; Rodgers, J; Hunter, C A; Murray, M; Burke, J M

1997-06-01

369

Parasite prolyl oligopeptidases and the challenge of designing chemotherapeuticals for Chagas disease, leishmaniasis and African trypanosomiasis.  

PubMed

The trypanosomatids Trypanosoma cruzi, Leishmania spp. and Trypanosoma brucei spp. cause Chagas disease, leishmaniasis and human African trypanosomiasis, respectively. It is estimated that over 10 million people worldwide suffer from these neglected diseases, posing enormous social and economic problems in endemic areas. There are no vaccines to prevent these infections and chemotherapies are not adequate. This picture indicates that new chemotherapeutic agents must be developed to treat these illnesses. For this purpose, understanding the biology of the pathogenic trypanosomatid- host cell interface is fundamental for molecular and functional characterization of virulence factors that may be used as targets for the development of inhibitors to be used for effective chemotherapy. In this context, it is well known that proteases have crucial functions for both metabolism and infectivity of pathogens and are thus potential drug targets. In this regard, prolyl oligopeptidase and oligopeptidase B, both members of the S9 serine protease family, have been shown to play important roles in the interactions of pathogenic protozoa with their mammalian hosts and may thus be considered targets for drug design. This review aims to discuss structural and functional properties of these intriguing enzymes and their potential as targets for the development of drugs against Chagas disease, leishmaniasis and African trypanosomiasis. PMID:23514419

Bastos, I M D; Motta, F N; Grellier, P; Santana, J M

2013-01-01

370

Haematological changes in experimental trypanosomiasis in Barbari goats  

Microsoft Academic Search

Haematological changes due to Trypanosoma evansi infection were studied in 12 Barbari male goats of 6–9 months of age. These were divided in two groups, A and B, consisting of eight infected and four control animals, respectively. The animals were kept in strict hygienic conditions and on a zero grazing schedule. Animals of group A were exposed to 1×106T. evansi

D. K. Sharma; Chauhan; V. K. Saxena; R. D. Agrawal

2000-01-01

371

Design of smart composite platforms for adaptive trust vector control and adaptive laser telescope for satellite applications  

NASA Astrophysics Data System (ADS)

This paper presents design of smart composite platforms for adaptive trust vector control (TVC) and adaptive laser telescope for satellite applications. To eliminate disturbances, the proposed adaptive TVC and telescope systems will be mounted on two analogous smart composite platform with simultaneous precision positioning (pointing) and vibration suppression (stabilizing), SPPVS, with micro-radian pointing resolution, and then mounted on a satellite in two different locations. The adaptive TVC system provides SPPVS with large tip-tilt to potentially eliminate the gimbals systems. The smart composite telescope will be mounted on a smart composite platform with SPPVS and then mounted on a satellite. The laser communication is intended for the Geosynchronous orbit. The high degree of directionality increases the security of the laser communication signal (as opposed to a diffused RF signal), but also requires sophisticated subsystems for transmission and acquisition. The shorter wavelength of the optical spectrum increases the data transmission rates, but laser systems require large amounts of power, which increases the mass and complexity of the supporting systems. In addition, the laser communication on the Geosynchronous orbit requires an accurate platform with SPPVS capabilities. Therefore, this work also addresses the design of an active composite platform to be used to simultaneously point and stabilize an intersatellite laser communication telescope with micro-radian pointing resolution. The telescope is a Cassegrain receiver that employs two mirrors, one convex (primary) and the other concave (secondary). The distance, as well as the horizontal and axial alignment of the mirrors, must be precisely maintained or else the optical properties of the system will be severely degraded. The alignment will also have to be maintained during thruster firings, which will require vibration suppression capabilities of the system as well. The innovative platform has been designed to have tip-tilt pointing and simultaneous multi-degree-of-freedom vibration isolation capability for pointing stabilization. Analytical approaches have been employed for determining the loads in the components as well as optimizing the design of the system. The different critical components such as telescope tube struts, flexure joints, and the secondary mirror mount have been designed and analyzed using finite element technique. The Simultaneous Precision Positioning and Vibration Suppression (SPPVS) smart composites platforms for the adaptive TVC and adaptive composite telescope are analogous (e.g., see work by Ghasemi-Nejhad and co-workers [1, 2]), where innovative concepts and control strategies are introduced, and experimental verifications of simultaneous thrust vector control and vibration isolation of satellites were performed. The smart composite platforms function as an active structural interface between the main thruster of a satellite and the satellite structure for the adaptive TVC application and as an active structural interface between the main smart composite telescope and the satellite structure for the adaptive laser communication application. The cascaded multiple feedback loops compensate the hysteresis (for piezoelectric stacks inside the three linear actuators that individually have simultaneous precision positioning and vibration suppression), dead-zone, back-lash, and friction nonlinearities very well, and provide precision and quick smart platform control and satisfactory thrust vector control capability. In addition, for example for the adaptive TVC, the experimental results show that the smart composite platform satisfactorily provided precision and fast smart platform control as well as the satisfactory thrust vector control capability. The vibration controller isolated 97% of the vibration energy due to the thruster firing.

Ghasemi-Nejhad, Mehrdad N.

2013-04-01

372

Construction and evaluation of pMycoFos, a fosmid shuttle vector for Mycobacterium spp. with inducible gene expression and copy number control  

Microsoft Academic Search

Molecular tools for Gram-positive bacteria such as Mycobacterium are less well-developed than those for Gram-negatives such as Escherichiacoli. This has slowed the molecular-genetic characterisation of Mycobacterium spp, which is unfortunate, since this genus has high medical, environmental and industrial significance. Here, we developed a new Mycobacterium shuttle vector (pMycoFos, 12.5kb, KmR) which combines desirable features of several previous vectors (controllable

Mai Anh Ly; Elissa F. Liew; Nga B. Le; Nicholas V. Coleman

2011-01-01

373

Identification and Expression of the CCAP Receptor in the Chagas' Disease Vector, Rhodnius prolixus, and Its Involvement in Cardiac Control  

PubMed Central

Rhodnius prolixus is the vector of Chagas’ disease, by virtue of transmitting the parasite Trypanosoma cruzi. There is no cure for Chagas’ disease and therefore controlling R. prolixus is currently the only method of prevention. Understanding the physiology of the disease vector is an important step in developing control measures. Crustacean cardioactive peptide (CCAP) is an important neuropeptide in insects because it has multiple physiological roles such as controlling heart rate and modulating ecdysis behaviour. In this study, we have cloned the cDNA sequence of the CCAP receptor (RhoprCCAPR) from 5th instar R. prolixus and found it to be a G-protein coupled receptor (GPCR). The spatial expression pattern in 5th instars reveals that the RhoprCCAPR transcript levels are high in the central nervous system, hindgut and female reproductive systems, and lower in the salivary glands, male reproductive tissues and a pool of tissues including the dorsal vessel, trachea, and fat body. Interestingly, the RhoprCCAPR expression is increased prior to ecdysis and decreased post-ecdysis. A functional receptor expression assay confirms that the RhoprCCAPR is activated by CCAP (EC50?=?12 nM) but not by adipokinetic hormone, corazonin or an extended FMRFamide. The involvement of CCAP in controlling heartbeat frequency was studied in vivo and in vitro by utilizing RNA interference. In vivo, the basal heartbeat frequency is decreased by 31% in bugs treated with dsCCAPR. Knocking down the receptor in dsCCAPR-treated bugs also resulted in loss of function of applied CCAP in vitro. This is the first report of a GPCR knock-down in R. prolixus and the first report showing that a reduction in CCAPR transcript levels leads to a reduction in cardiac output in any insect.

Lee, Dohee; Vanden Broeck, Jozef; Lange, Angela B.

2013-01-01

374

Identification and expression of the CCAP receptor in the Chagas' disease vector, Rhodnius prolixus, and its involvement in cardiac control.  

PubMed

Rhodnius prolixus is the vector of Chagas' disease, by virtue of transmitting the parasite Trypanosoma cruzi. There is no cure for Chagas' disease and therefore controlling R. prolixus is currently the only method of prevention. Understanding the physiology of the disease vector is an important step in developing control measures. Crustacean cardioactive peptide (CCAP) is an important neuropeptide in insects because it has multiple physiological roles such as controlling heart rate and modulating ecdysis behaviour. In this study, we have cloned the cDNA sequence of the CCAP receptor (RhoprCCAPR) from 5(th) instar R. prolixus and found it to be a G-protein coupled receptor (GPCR). The spatial expression pattern in 5(th) instars reveals that the RhoprCCAPR transcript levels are high in the central nervous system, hindgut and female reproductive systems, and lower in the salivary glands, male reproductive tissues and a pool of tissues including the dorsal vessel, trachea, and fat body. Interestingly, the RhoprCCAPR expression is increased prior to ecdysis and decreased post-ecdysis. A functional receptor expression assay confirms that the RhoprCCAPR is activated by CCAP (EC50?=?12 nM) but not by adipokinetic hormone, corazonin or an extended FMRFamide. The involvement of CCAP in controlling heartbeat frequency was studied in vivo and in vitro by utilizing RNA interference. In vivo, the basal heartbeat frequency is decreased by 31% in bugs treated with dsCCAPR. Knocking down the receptor in dsCCAPR-treated bugs also resulted in loss of function of applied CCAP in vitro. This is the first report of a GPCR knock-down in R. prolixus and the first report showing that a reduction in CCAPR transcript levels leads to a reduction in cardiac output in any insect. PMID:23874803

Lee, Dohee; Vanden Broeck, Jozef; Lange, Angela B

2013-01-01

375

Trypanosomiasis by Trypanosoma vivax in cattle in the Brazilian semiarid: Description of an outbreak and lesions in the nervous system  

Microsoft Academic Search

An outbreak of trypanosomiasis by Trypanosoma vivax is reported in the semiarid of Paraíba, Northeastern Brazil from May to August 2002. Sixty-four cows out of 130 were affected; 11 died and the other recovered after treatment with diminazene aceturate. Affected animals had fever, anemia, weight loss, hypoglycemia, increased serum levels of aspartate aminotransferase and, in nine cows, nervous signs. All

J. S. Batista; F. Riet-Correa; M. M. G. Teixeira; C. R. Madruga; S. D. V. Simões; T. F. Maia

2007-01-01

376

Neurological trypanosomiasis in quinapyramine sulfate-treated horses--a breach of the blood-brain barrier?  

PubMed

Trypanosoma evansi infection typically produces wasting disease, but it can also develop into a neurological or meningoencephalitis form in equids. Trypanosomiasis in horses was treated with quinapyramine sulfate, and all the 14 infected animals were recovered clinically. After clinical recovery, four animals developed a neurological form of the disease at various intervals. Two of these animals treated with diminazene aceturate recovered temporarily. Repeated attempts failed to find the parasite in the blood or the cerebrospinal fluid (CSF), but all of the animals were positive in enzyme-linked immunosorbent assay. The calculation of the antibody index (AI) in the serum and the CSF and polymerase chain reaction (PCR) analysis of the CSF and brain tissue were carried out to confirm the neuro-infection. We found PCR and AI analyses of the CSF to be useful tools in the diagnosis of the neurological form of trypanosomiasis when the organism cannot be found in the blood or CSF. The increased albumin quotient is indicative of barrier leakage due to neuroinflammation. The biochemical changes in the CSF due to nervous system trypanosomiasis include increases in the albumin quotient, total protein, and urea nitrogen. It seems to be the first report on relapse of the nervous form of trypanosomiasis in equids even after quinapyramine treatment in endemic areas. PMID:24197687

Ranjithkumar, Muthusamy; Saravanan, Buddhi Chandrasekaran; Yadav, Suresh Chandra; Kumar, Rajender; Singh, Rajendra; Dey, Sahadeb

2014-02-01

377

Combination chemotherapy with a substance P receptor antagonist (aprepitant) and melarsoprol in a mouse model of human African trypanosomiasis  

Microsoft Academic Search

Drug therapy for late-stage (encephalitic) human African trypanosomiasis (HAT) is currently very unsatisfactory with the most commonly used drug, melarsoprol, having a 5% overall mortality. There is evidence in a mouse model of HAT that Substance P (SP) receptor antagonism reduces the neuroinflammatory reaction to CNS trypanosome infection. In this study we investigated the effects of combination chemotherapy with melarsoprol

Jean Rodgers; Barbara Bradley; Peter GE Kennedy

2007-01-01

378

A Combined CXCL10, CXCL8 and H-FABP Panel for the Staging of Human African Trypanosomiasis Patients  

Microsoft Academic Search

Background: Human African trypanosomiasis (HAT), also known as sleeping sickness, is a parasitic tropical disease. It progresses from the first, haemolymphatic stage to a neurological second stage due to invasion of parasites into the central nervous system (CNS). As treatment depends on the stage of disease, there is a critical need for tools that efficiently discriminate the two stages of

Alexandre Hainard; Natalia Tiberti; Xavier Robin; Veerle Lejon; Dieudonné Mumba Ngoyi; Enock Matovu; John Charles Enyaru; Catherine Fouda; Joseph Mathu Ndung'u; Frédérique Lisacek; Markus Müller; Natacha Turck; Jean-Charles Sanchez

2009-01-01

379

Cardiac Alterations in Human African Trypanosomiasis (T.b. gambiense) with Respect to the Disease Stage and Antiparasitic Treatment  

Microsoft Academic Search

BackgroundIn Human African Trypanosomiasis, neurological symptoms dominate and cardiac involvement has been suggested. Because of increasing resistance to the available drugs for HAT, new compounds are desperately needed. Evaluation of cardiotoxicity is one parameter of drug safety, but without knowledge of the baseline heart involvement in HAT, cardiologic findings and drug-induced alterations will be difficult to interpret. The aims of

Johannes A. Blum; Caecilia Schmid; Christian Burri; Christoph Hatz; Carol Olson; Blaise Fungula; Leon Kazumba; Patrick Mangoni; Florent Mbo; Kambau Deo; Alain Mpanya; Amadeo Dala; Jose R. Franco; Gabriele Pohlig; Michael J. Zellweger

2009-01-01

380

The pathogenesis and modulation of the post-treatment reactive encephalopathy in a mouse model of Human African Trypanosomiasis  

Microsoft Academic Search

Drug treatment of late-stage human African Trypanosomiasis (HAT) in which the central nervous system (CNS) is involved may be complicated by a severe post-treatment reactive encephalopathy (PTRE) which can be fatal in up to 10% of cases. In order to understand the immunopathogenesis of this complication, an experimental mouse model has been developed that mirrors many of the pathological features

Peter G. E Kennedy

1999-01-01

381

A Combined CXCL10, CXCL8 and H-FABP Panel for the Staging of Human African Trypanosomiasis Patients  

Microsoft Academic Search

BackgroundHuman African trypanosomiasis (HAT), also known as sleeping sickness, is a parasitic tropical disease. It progresses from the first, haemolymphatic stage to a neurological second stage due to invasion of parasites into the central nervous system (CNS). As treatment depends on the stage of disease, there is a critical need for tools that efficiently discriminate the two stages of HAT.

Alexandre Hainard; Natalia Tiberti; Xavier Robin; Veerle Lejon; Dieudonné Mumba Ngoyi; Enock Matovu; John Charles Enyaru; Catherine Fouda; Joseph Mathu Ndungu; Frédérique Lisacek; Markus Müller; Natacha Turck; Jean-Charles Sanchez

2009-01-01

382

SHORT REPORT: HUMAN TRYPANOSOMIASIS CAUSED BY TRYPANOSOMA EVANSI IN A VILLAGE IN INDIA: PRELIMINARY SEROLOGIC SURVEY OF THE LOCAL POPULATION  

Microsoft Academic Search

After discovery of the first recorded case of human infection with Trypanosoma evansi, serologic screening of 1,806 persons from the village of origin of the patient in India was performed using the card agglutination test for trypanosomiasis and T. evansi. A total of 410 (22.7%) people were positive by whole blood, but only 81 were confirmed positive by serum. However,

VIJAY R. SHEGOKAR; RAJARAM M. POWAR; PRASHANT P. JOSHI; ARADHANA BHARGAVA

383

Control algorithm for the inverter fed induction motor drive with DC current feedback loop based on principles of the vector control  

SciTech Connect

This paper brings out a control algorithm for VSI fed induction motor drives based on the converter DC link current feedback. It is shown that the speed and flux can be controlled over the wide speed and load range quite satisfactorily for simpler drives. The base commands of both the inverter voltage and frequency are proportional to the reference speed, but each of them is further modified by the signals derived from the DC current sensor. The algorithm is based on the equations well known from the vector control theory, and is aimed to obtain the constant rotor flux and proportionality between the electrical torque, the slip frequency and the active component of the stator current. In this way, the problems of slip compensation, Ri compensation and correction of U/f characteristics are solved in the same time. Analytical considerations and computer simulations of the proposed control structure are in close agreement with the experimental results measured on a prototype drive.

Vuckovic, V.; Vukosavic, S. (Electrical Engineering Inst. Nikola Tesla, Viktora Igoa 3, Belgrade, 11000 (Yugoslavia))

1992-01-01

384

Population size and migration of Anopheles gambiae in the Bancoumana Region of Mali and their significance for efficient vector control.  

PubMed

We present results of two intensive mark-release-recapture surveys conducted during the wet and dry seasons of 2008 in the villages of Fourda and Kenieroba, Mali. The former is a small fishing village by the Niger River with a moderate to high densities of Anopheles gambiae Giles s.s. (Diptera: Culicidae) throughout the year, while the latter is a large agricultural community 2 km inland that experiences strong seasonal fluctuation in An. gambiae densities. We estimate the population size of female An. gambiae in Fourda to be in less than 3,000 during the dry season. We found evidence of large population size and migration from Fourda in Kenieroba during the wet season, but very low numbers and no sign of migrants during the dry season. We suggest that malaria vector control measures aimed at adult mosquitoes might be made more efficient in this region and other seasonal riparian habitats by targeting disruption of mosquito populations by the river during the dry season. This would decrease the size of an already small population, and would be likely to delay the explosive growth in vector numbers in the larger inland villages as rainfall increases. PMID:20422013

Baber, Ibrahima; Keita, Moussa; Sogoba, Nafomon; Konate, Mamadou; Diallo, M'Bouye; Doumbia, Seydou; Traoré, Sékou F; Ribeiro, José M C; Manoukis, Nicholas C

2010-01-01

385

Population Size and Migration of Anopheles gambiae in the Bancoumana Region of Mali and Their Significance for Efficient Vector Control  

PubMed Central

We present results of two intensive mark-release-recapture surveys conducted during the wet and dry seasons of 2008 in the villages of Fourda and Kenieroba, Mali. The former is a small fishing village by the Niger River with a moderate to high densities of Anopheles gambiae Giles s.s. (Diptera: Culicidae) throughout the year, while the latter is a large agricultural community 2 km inland that experiences strong seasonal fluctuation in An. gambiae densities. We estimate the population size of female An. gambiae in Fourda to be in less than 3,000 during the dry season. We found evidence of large population size and migration from Fourda in Kenieroba during the wet season, but very low numbers and no sign of migrants during the dry season. We suggest that malaria vector control measures aimed at adult mosquitoes might be made more efficient in this region and other seasonal riparian habitats by targeting disruption of mosquito populations by the river during the dry season. This would decrease the size of an already small population, and would be likely to delay the explosive growth in vector numbers in the larger inland villages as rainfall increases.

Baber, Ibrahima; Keita, Moussa; Sogoba, Nafomon; Konate, Mamadou; Diallo, M'Bouye; Doumbia, Seydou; Traore, Sekou F.; Ribeiro, Jose M. C.; Manoukis, Nicholas C.

2010-01-01

386

Effectiveness and acceptance of total release insecticidal aerosol cans as a control measure in reducing dengue vectors.  

PubMed

The effectiveness of regular application of insecticidal fogging in reducing dengue is questionable, since delays occur between peak time of outbreak and insecticide administrations. Moreover, many residents do not accept indoor application because of concern about insecticide contamination of household items. The study described in this article was designed to evaluate the effectiveness and acceptance of insecticidal aerosol cans to reduce dengue vectors inside and outside of homes. Residents in Kaohsiung City of South Taiwan were provided with two formulations of aerosol cans (permethrin 3.75% weight/weight [w/w] and cypermethrin 1.716% w/w) and were requested to use these aerosol cans. Although the indoor ovitrap index of the permethrin group returned to the original level in week 3, the index of the cypermethrin group decreased 60% to 20%. The residents accepted the insecticidal aerosol cans but complained of unfavorable effects caused by traditional insecticidal fogging. Results indicate that the insecticidal aerosol cans may serve as a supplementary household control measure for dengue vectors during the time period between the peak of outbreak and the administration of government-organized insecticide fogging. PMID:24645416

Pai, Hsiu-Hua; Hsu, Err-Lieh

2014-01-01

387

Effective control of dengue vectors with curtains and water container covers treated with insecticide in Mexico and Venezuela: cluster randomised trials  

Microsoft Academic Search

Objectives To measure the impact on the dengue vector population (Aedes aegypti) and disease transmission of window curtains and water container covers treated with insecticide. Design Cluster randomised controlled trial based on entomological surveys and, for Trujillo only, serological survey. In addition, each site had a non-randomised external control. Setting 18 urban sectors in Veracruz (Mexico) and 18 in Trujillo

Axel Kroeger; Audrey Lenhart; Manuel Ochoa; Elci Villegas; Michael Levy; Neal Alexander; P J McCall

2006-01-01

388

A kernel-distance-based multivariate control chart using support vector methods  

Microsoft Academic Search

This paper focuses on the monitoring techniques applied in multivariate processes when the underlying distribution of the quality characteristics departs from normality. For most conventional control charts, such as Hotelling's T 2 charts, the design of the control limits is commonly based on the assumption that the quality characteristics follow a multivariate normal distribution. However, this may not be reasonable

Ruixiang Sun; Fugee Tsung

2003-01-01

389

Study on an Application of Induction Motor Speed Sensorless Vector Control to Railway Vehicle Traction  

NASA Astrophysics Data System (ADS)

The Pulse Generators or PGs are equipped to detect the rotor frequency of induction traction motors for the torque control in railway vehicle traction field. Eliminating PGs are preferable from the view points of increasing the reliability of the traction system, reduction of the both initial and maintenance cost and down-sizing induction traction motors. Expecting those merits, we have been studying to apply a sensor less control method to induction traction motor control. Prior to some reports of studies and tests to apply speed sensor-less strategy to railway vehicle traction, we lunched the ideas to apply the speed sensor-less control strategy and results of the studies and the tests. In this paper, we present the novel control method for railway vehicle traction and some results of theoretical study and tests.

Kondo, Keiichiro; Yuki, Kazuaki

390

Construction and evaluation of pMycoFos, a fosmid shuttle vector for Mycobacterium spp. with inducible gene expression and copy number control.  

PubMed

Molecular tools for Gram-positive bacteria such as Mycobacterium are less well-developed than those for Gram-negatives such as Escherichiacoli. This has slowed the molecular-genetic characterisation of Mycobacterium spp, which is unfortunate, since this genus has high medical, environmental and industrial significance. Here, we developed a new Mycobacterium shuttle vector (pMycoFos, 12.5kb, Km(R)) which combines desirable features of several previous vectors (controllable copy number in E. coli, inducible gene expression in Mycobacterium) and provides a new multiple cloning site compatible with large inserts of high-GC content DNA. Copy number control in E. coli was confirmed by the increased Km(R) of cultures after arabinose induction and the greater DNA yield of vector from arabinose-induced cultures. Measurement of beta-galactosidase activity in pMycoFos clones carrying the lacZ gene showed that in Mycobacterium smegmatis mc(2)-155, expression was inducible by acetamide, but in E. coli EPI300, the expression level was primarily determined by the vector copy number. Examination of protein profiles on SDS-PAGE gels confirmed the beta-galactosidase assay results. Construction of a fosmid library with the new vector confirmed that it could carry large DNA inserts. The new vector enabled the stable cloning and expression of an ethene monooxygenase gene cluster, which had eluded previous attempts at heterologous expression. PMID:21689690

Ly, Mai Anh; Liew, Elissa F; Le, Nga B; Coleman, Nicholas V

2011-09-01

391

Prevalence and under-detection of gambiense human African trypanosomiasis during mass screening sessions in Uganda and Sudan  

PubMed Central

Background Active case detection through mass community screening is a major control strategy against human African trypanosomiasis (HAT, sleeping sickness) caused by T. brucei gambiense. However, its impact can be limited by incomplete attendance at screening sessions (screening coverage) and diagnostic inaccuracy. Methods We developed a model-based approach to estimate the true prevalence and the fraction of cases detected during mass screening, based on observed prevalence, and adjusting for incomplete screening coverage and inaccuracy of diagnostic algorithms for screening, confirmation and HAT stage classification. We applied the model to data from three Médecins Sans Frontières projects in Uganda (Adjumani, Arua-Yumbe) and Southern Sudan (Kiri). Results We analysed 604 screening sessions, targeting about 710 000 people. Cases were about twice as likely to attend screening as non-cases, with no apparent difference by stage. Past incidence, population size and repeat screening rounds were strongly associated with observed prevalence. The estimated true prevalence was 0.46% to 0.90% in Kiri depending on the analysis approach, compared to an observed prevalence of 0.45%; 0.59% to 0.87% in Adjumani, compared to 0.92%; and 0.18% to 0.24% in Arua-Yumbe, compared to 0.21%. The true ratio of stage 1 to stage 2 cases was around two-three times higher than that observed, due to stage misclassification. The estimated detected fraction was between 42.2% and 84.0% in Kiri, 52.5% to 79.9% in Adjumani and 59.3% to 88.0% in Arua-Yumbe. Conclusions In these well-resourced projects, a moderate to high fraction of cases appeared to be detected through mass screening. True prevalence differed little from observed prevalence for monitoring purposes. We discuss some limitations to our model that illustrate several difficulties of estimating the unseen burden of neglected tropical diseases.

2012-01-01

392

Society for Vector Ecology  

NSDL National Science Digital Library

Formed in 1968, the Society for Vector Ecology (SOVE) is dedicated to studying "all aspects of the biology, ecology, and control of arthropod vectors and the interrelationships between the vectors and the disease agents they transmit." Comprised of researchers and operational and extension personnel around the globe, SOVE tracks and studies the biological organisms that transmit diseases. The SOVE Website contains information related to the Society (e.g., mission, history), its publications (journal, newsletter -- both .pdf format), and professional opportunities (conferences, employment). Several dozen links to additional vector ecology resources are provided.

2008-09-12

393

Spatial Orientation and Balance Control Changes Induced by Altered Gravito-Inertial Force Vectors  

NASA Technical Reports Server (NTRS)

Seventeen healthy and eight vestibular deficient subjects were exposed to an interaural centripetal acceleration of 1 G (resultant 45 deg roll tilt of 1.4 G) on a 0.8 meter radius centrifuge for a period of 90 minutes in the dark. The subjects sat with head fixed upright, except every 4 of 10 minutes when instructed to rotate their head so that their nose and eyes pointed towards a visual point switched on every 3 to 5 seconds at random places (within +/- 30 deg) in the Earth horizontal plane. Motion sickness caused some subjects to limit their head movements during significant portions of the 90 minute period, and led three normal subjects to stop the test earlier. Eye movements, including directed saccades for subjective Earth- and head-referenced planes, were recorded before, during, and immediately after centrifugation using electro-oculography. Postural stability measurements were made before and within ten minutes after centrifugation. In normal subjects, postural sway and multisegment body kinematics were gathered during an eyes-closed head movement cadence (sway-referenced support platform), and in response to translational/rotational platform perturbations. A significant increase in postural sway, segmental motion amplitude and hip frequency was observed after centrifugation. This effect was short-lived, with a recovery time of several postural test trials. There were also asymmetries in the direction of post-centrifugation center of sway and head tilt which depended on the subject's orientation during the centrifugation adaptation period (left ear or right ear out). To delineate the effect of the magnitude of the gravito-inertial vector versus its direction during the adaptive centrifugation period, we tilted eight normal subjects in the roll axis at a 45 deg angle in the dark for 90 minutes without rotational motion. Their postural responses did not change following the period of tilt. Based on verbal reports, normal subjects overestimated roll-tilt during 90 minutes of both tilt and centrifugation stimuli. Subjective estimates of head-horizontal, provided by directed saccades, revealed significant errors after approximately 30 minutes that tended to increase only in the group who underwent centrifugation. Immediately after centrifugation, subjects reported feeling tilted on average 10 degrees in the opposite direction, which was in agreement with the direction of their earth-directed saccades. In vestibular deficient (VD) subjects, postural sway was measured using a sway-referenced or earth-fixed support surface, and with or without a head movement sequence. 'Me protocol was selected for each patient during baseline testing, and corresponded to the most challenging condition in which the patient was able to maintain balance with eyes closed. Bilaterally VD subjects showed no postural decrement after centrifugation, while unilateral VD subjects had varying degrees of decrement. Unilateral VD subjects were tested twice; they underwent centrifugation both with right ear out and left ear out. Their post-centrifuation center of sway shifted at right angles depending on the centrifuge GIF orientation. Bilateral VD subjects bad shifts as well, but no consistent directional trend. VD subjects underestimated roll-tilt during centrifugation, These results suggest that orientation of the gravito-inertial vector and its magnitude arc both used by the central nervous system for calibration of multiple orientation systems. A change in the background gravito-inertial force (otolith input) can rapidly initiate postural and perceptual adaptation in several sensorimotor systems, independent of a structured visual surround.

Kaufman, Galen D.; Wood, Scott J.; Gianna, Claire C.; Black, F. Owen; Paloski, William H.; Dawson, David L. (Technical Monitor)

1999-01-01

394

A Randomized Longitudinal Factorial Design to Assess Malaria Vector Control and Disease Management Interventions in Rural Tanzania  

PubMed Central

The optimization of malaria control strategies is complicated by constraints posed by local health systems, infrastructure, limited resources, and the complex interactions between infection, disease, and treatment. The purpose of this paper is to describe the protocol of a randomized factorial study designed to address this research gap. This project will evaluate two malaria control interventions in Mvomero District, Tanzania: (1) a disease management strategy involving early detection and treatment by community health workers using rapid diagnostic technology; and (2) vector control through community-supported larviciding. Six study villages were assigned to each of four groups (control, early detection and treatment, larviciding, and early detection and treatment plus larviciding). The primary endpoint of interest was change in malaria infection prevalence across the intervention groups measured during annual longitudinal cross-sectional surveys. Recurring entomological surveying, household surveying, and focus group discussions will provide additional valuable insights. At baseline, 962 households across all 24 villages participated in a household survey; 2,884 members from 720 of these households participated in subsequent malariometric surveying. The study design will allow us to estimate the effect sizes of different intervention mixtures. Careful documentation of our study protocol may also serve other researchers designing field-based intervention trials.

Kramer, Randall A.; Mboera, Leonard E. G.; Senkoro, Kesheni; Lesser, Adriane; Shayo, Elizabeth H.; Paul, Christopher J.; Miranda, Marie Lynn

2014-01-01

395

A randomized longitudinal factorial design to assess malaria vector control and disease management interventions in rural Tanzania.  

PubMed

The optimization of malaria control strategies is complicated by constraints posed by local health systems, infrastructure, limited resources, and the complex interactions between infection, disease, and treatment. The purpose of this paper is to describe the protocol of a randomized factorial study designed to address this research gap. This project will evaluate two malaria control interventions in Mvomero District, Tanzania: (1) a disease management strategy involving early detection and treatment by community health workers using rapid diagnostic technology; and (2) vector control through community-supported larviciding. Six study villages were assigned to each of four groups (control, early detection and treatment, larviciding, and early detection and treatment plus larviciding). The primary endpoint of interest was change in malaria infection prevalence across the intervention groups measured during annual longitudinal cross-sectional surveys. Recurring entomological surveying, household surveying, and focus group discussions will provide additional valuable insights. At baseline, 962 households across all 24 villages participated in a household survey; 2,884 members from 720 of these households participated in subsequent malariometric surveying. The study design will allow us to estimate the effect sizes of different intervention mixtures. Careful documentation of our study protocol may also serve other researchers designing field-based intervention trials. PMID:24840349

Kramer, Randall A; Mboera, Leonard E G; Senkoro, Kesheni; Lesser, Adriane; Shayo, Elizabeth H; Paul, Christopher J; Miranda, Marie Lynn

2014-01-01

396

Monitoring of larval habitats and mosquito densities in the Sudan savanna of Mali: implications for malaria vector control.  

PubMed

In Mali, anopheline mosquito populations increase sharply during the rainy season, but are barely detectable in the dry season. This study attempted to identify the dry season mosquito breeding population in and near the village of Bancoumana, Mali, and in a fishing hamlet 5 km from this village and adjacent to the Niger River. In Bancoumana, most larval habitats were human made, and dried out in January-February. In contrast, in the fishing hamlet, productive larval habitats were numerous and found mainly during the dry season (January-May) as the natural result of drying riverbeds. Adult mosquitoes were abundant during the dry season in the fishermen hamlet and rare in Bancoumana. To the extent that the fishermen hamlet mosquito population seeds Bancoumana with the advent of the rainy season, vector control in this small hamlet may be a cost-effective way to ameliorate malaria transmission in the 40-times larger village. PMID:17620634

Sogoba, Nafomon; Doumbia, Seydou; Vounatsou, Penelope; Baber, Ibrahima; Keita, Moussa; Maiga, Mamoudou; Traoré, Sékou F; Touré, Abdoulaye; Dolo, Guimogo; Smith, Thomas; Ribeiro, José M C

2007-07-01

397

Flight-Determined Subsonic Longitudinal Stability and Control Derivatives of the F-18 High Angle of Attack Research Vehicle (HARV) with Thrust Vectoring  

NASA Technical Reports Server (NTRS)

The subsonic longitudinal stability and control derivatives of the F-18 High Angle of Attack Research Vehicle (HARV) are extracted from dynamic flight data using a maximum likelihood parameter identification technique. The technique uses the linearized aircraft equations of motion in their continuous/discrete form and accounts for state and measurement noise as well as thrust-vectoring effects. State noise is used to model the uncommanded forcing function caused by unsteady aerodynamics over the aircraft, particularly at high angles of attack. Thrust vectoring was implemented using electrohydraulically-actuated nozzle postexit vanes and a specialized research flight control system. During maneuvers, a control system feature provided independent aerodynamic control surface inputs and independent thrust-vectoring vane inputs, thereby eliminating correlations between the aircraft states and controls. Substantial variations in control excitation and dynamic response were exhibited for maneuvers conducted at different angles of attack. Opposing vane interactions caused most thrust-vectoring inputs to experience some exhaust plume interference and thus reduced effectiveness. The estimated stability and control derivatives are plotted, and a discussion relates them to predicted values and maneuver quality.

Iliff, Kenneth W.; Wang, Kon-Sheng Charles

1997-01-01

398

Stator-flux-based vector control of induction machines in magnetic saturation  

Microsoft Academic Search

In many variable-torque applications of induction machines, it is desirable to operate the machine at high flux levels, thus allowing the machine to produce higher torques. This can lead to saturation of the main flux path, introducing cross-coupling effects which can severely disrupt the performance of controllers dependent on knowledge of the machine's magnetic parameters. Stator flux-oriented torque-control schemes need

Heath Hofmann; Seth R. Sanders; Charles R. Sullivan

1997-01-01

399

A vector controlled current-source PWM rectifier with a novel current damping method  

Microsoft Academic Search

Three-phase current-type pulse width modulation (PWM) rectifiers are becoming increasingly popular as the front-end converter unit in power electronic systems due to tighter electromagnetic compatibility (EMC) regulations. In this paper the control of the current source PWM rectifier in the synchronously rotating reference frame is discussed. A control system is presented in which the active and reactive power are independently

Mika Salo; Heikki Tuusa

2000-01-01

400

Phylogeography and Population Structure of Glossina fuscipes fuscipes in Uganda: Implications for Control of Tsetse  

PubMed Central

Background Glossina fuscipes fuscipes, a riverine species of tsetse, is the main vector of both human and animal trypanosomiasis in Uganda. Successful implementation of vector control will require establishing an appropriate geographical scale for these activities. Population genetics can help to resolve this issue by characterizing the extent of linkage among apparently isolated groups of tsetse. Methodology/Principal Findings We conducted genetic analyses on mitochondrial and microsatellite data accumulated from approximately 1000 individual tsetse captured in Uganda and neighboring regions of Kenya and Sudan. Phylogeographic analyses suggested that the largest scale genetic structure in G. f. fuscipes arose from an historical event that divided two divergent mitochondrial lineages. These lineages are currently partitioned to northern and southern Uganda and co-occur only in a narrow zone of contact extending across central Uganda. Bayesian assignment tests, which provided evidence for admixture between northern and southern flies at the zone of contact and evidence for northerly gene flow across the zone of contact, indicated that this structure may be impermanent. On the other hand, microsatellite structure within the southern lineage indicated that gene flow is currently limited between populations in western and southeastern Uganda. Within regions, the average FST between populations separated by less than 100 km was less than ?0.1. Significant tests of isolation by distance suggested that gene flow is ongoing between neighboring populations and that island populations are not uniformly more isolated than mainland populations. Conclusions/Significance Despite the presence of population structure arising from historical colonization events, our results have revealed strong signals of current gene flow within regions that should be accounted for when planning tsetse control in Uganda. Populations in southeastern Uganda appeared to receive little gene flow from populations in western or northern Uganda, supporting the feasibility of area wide control in the Lake Victoria region by the Pan African Tsetse and Trypanosomiasis Eradication Campaign.

Beadell, Jon S.; Hyseni, Chaz; Abila, Patrick P.; Azabo, Rogers; Enyaru, John C. K.; Ouma, Johnson O.; Mohammed, Yassir O.; Okedi, Loyce M.; Aksoy, Serap; Caccone, Adalgisa

2010-01-01

401

Massively parallel vector processing computer  

SciTech Connect

This patent describes a vector processing node for a computer of the type having a network of simultaneously operating vector processing nodes interconnected by bidirectional external busses for conveying parallel data words between the vector processing nodes. The vector processing node comprising: a bi-directional first bus for conveying parallel data words; a bi-directional second bus for conveying parallel data words; vector memory means connected for read and write access through the second bus for storing vectors comprising sequences of parallel data words conveyed on the second bus; vector processing means connected to the second bus for transmitting parallel data words to and receiving parallel data words from the vector memory means for generating output vectors comprising functions of input vectors stored in the vector memory means and for storing the output vectors in the vector memory means; and control means including a computer processor connected to the first bus, external port means controlled by the computer processor and connected between the first bus and the external busses, and local port means controlled by the computer processor connected between the first and second busses, for transmitting parallel data words to and receiving parallel data words from the first bus, the second bus, the external busses, and the vector memory.

Call, D.B.; Mudrow, A.; Johnson, R.C.; Bennion