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1

Trypanosomiasis vector control in Africa and Latin America  

PubMed Central

Vectors of trypanosomiasis – tsetse (Glossinidae) in Africa, kissing-bugs (Triatominae) in Latin America – are very different insects but share demographic characteristics that render them highly vulnerable to available control methods. For both, the main operational problems relate to re-invasion of treated areas, and the solution seems to be in very large-scale interventions covering biologically-relevant areas rather than adhering to administrative boundaries. In this review we present the underlying rationale, operational background and progress of the various trypanosomiasis vector control initiatives active in both continents. PMID:18673535

Schofield, Chris J; Kabayo, John P

2008-01-01

2

Trypanosomiasis control.  

PubMed

In July 2000, Heads of State of the 36th Session of the Organisation for African Unity signed a potentially important declaration on African trypanosomiasis, urging member states "to act collectively to rise to the challenge of eliminating the problem through concerted efforts in mobilising the necessary human, financial and material resources required to render Africa tsetse-free within the shortest time possible". To many, such an ambitious dream is received with some scepticism, recalling the doubts that surrounded a similar declaration signed in Brasilia in 1991, which paved the way for the Southern Cone Initiative against American trypanosomiasis (Chagas disease). True, the two diseases are quite different. But the operational challenges are quite similar, and there are sufficient biological parallels to suggest that the Latin American experience in controlling Chagas disease may provide a useful model for the control of African trypanosomiasis. PMID:11334951

Schofield, C J; Maudlin, I

2001-05-01

3

Control and surveillance of human African trypanosomiasis.  

PubMed

In the 1960s, it appeared that human African trypanosomiasis (HAT) could be effectively controlled, but by the beginning of the twenty-first century several decades of neglect had led to alarming numbers of reported new cases, with an estimated 300 000 people infected. The World Health Organization (WHO) responded with a series of initiatives aimed at bringing HAT under control again. Since 2001, the pharmaceutical companies that produce drugs for HAT have committed themselves to providing them free of charge to WHO for distribution for the treatment of patients. In addition, funds have been provided to WHO to support national sleeping sickness control programmes to boost control and surveillance of the disease. That, coupled with bilateral cooperation and the work of nongovernmental organizations, helped reverse the upward trend in HAT prevalence. By 2012, the number of reported cases was fewer than 8000. This success in bringing HAT under control led to its inclusion in the WHO Roadmap for eradication, elimination and control of neglected tropical diseases, with a target set to eliminate the disease as a public health problem by 2020. A further target has been set, by countries in which HAT is endemic, to eliminate gambiense HAT by reducing the incidence of infection to zero in a defined geographical area. This report provides information about new diagnostic approaches, new therapeutic regimens and better understanding of the distribution of the disease with high-quality mapping. The roles of human and animal reservoirs and the tsetse fly vectors that transmit the parasites are emphasized. The new information has formed the basis for an integrated strategy with which it is hoped that elimination of gambiense HAT will be achieved. The report also contains recommendations on the approaches that will lead to elimination of the disease. PMID:24552089

2013-01-01

4

Prospects for Developing Odour Baits To Control Glossina fuscipes spp., the Major Vector of Human African Trypanosomiasis  

PubMed Central

We are attempting to develop cost-effective control methods for the important vector of sleeping sickness, Glossina fuscipes spp. Responses of the tsetse flies Glossina fuscipes fuscipes (in Kenya) and G. f. quanzensis (in Democratic Republic of Congo) to natural host odours are reported. Arrangements of electric nets were used to assess the effect of cattle-, human- and pig-odour on (1) the numbers of tsetse attracted to the odour source and (2) the proportion of flies that landed on a black target (1×1 m). In addition responses to monitor lizard (Varanus niloticus) were assessed in Kenya. The effects of all four odours on the proportion of tsetse that entered a biconical trap were also determined. Sources of natural host odour were produced by placing live hosts in a tent or metal hut (volumes?16 m3) from which the air was exhausted at ?2000 L/min. Odours from cattle, pigs and humans had no significant effect on attraction of G. f. fuscipes but lizard odour doubled the catch (P<0.05). Similarly, mammalian odours had no significant effect on landing or trap entry whereas lizard odour increased these responses significantly: landing responses increased significantly by 22% for males and 10% for females; the increase in trap efficiency was relatively slight (5–10%) and not always significant. For G. f. quanzensis, only pig odour had a consistent effect, doubling the catch of females attracted to the source and increasing the landing response for females by ?15%. Dispensing CO2 at doses equivalent to natural hosts suggested that the response of G. f. fuscipes to lizard odour was not due to CO2. For G. f. quanzensis, pig odour and CO2 attracted similar numbers of tsetse, but CO2 had no material effect on the landing response. The results suggest that identifying kairomones present in lizard odour for G. f. fuscipes and pig odour for G. f. quanzensis may improve the performance of targets for controlling these species. PMID:19434232

Omolo, Maurice O.; Hassanali, Ahmed; Mpiana, Serge; Esterhuizen, Johan; Lindh, Jenny; Lehane, Mike J.; Solano, Philippe; Rayaisse, Jean Baptiste; Vale, Glyn A.; Torr, Steve J.; Tirados, Inaki

2009-01-01

5

American Trypanosomiasis (Also Known as Chagas Disease) Prevention and Control  

MedlinePLUS

... gov . Parasites - American Trypanosomiasis (also known as Chagas Disease) Parasites Home Share Compartir Prevention & Control In endemic areas of Mexico, Central America, and South America improved housing and ...

6

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

7

Genome Sequence of the Tsetse Fly (Glossina morsitans): Vector of African Trypanosomiasis  

PubMed Central

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

2014-01-01

8

A review of recent knowledge of the ecology of the main vectors of trypanosomiasis*  

PubMed Central

In this survey of recent ecological research on the main vectors of trypanosomiasis in those countries of East, Central and West Africa that are not predominantly French-speaking, the authors, after outlining the distribution of tsetse flies and the type of country in which they occur, discuss the direct and indirect effects of climate on these insects—particularly on their physiological water balance and on pupal fat reserves—and their recent advances into new areas. They review the considerable work that has been done on the resting habits and breeding-sites of different Glossina species, knowledge of which is important for effective control, and research on predators of pupae and adult flies and on the feeding activity of tsetse flies. Means of assessing populations and various factors affecting the size and nutritional status of tsetse flies are also discussed, as is the effect on the fly population of artificial changes in the habitat. Finally, a plea is made for a revision of present methods of land use and stock management, if full advantage is to be taken of achievements in fly control. PMID:13928678

Langridge, W. P.; Kernaghan, R. J.; Glover, P. E.

1963-01-01

9

Trypanosomiasis Control, Democratic Republic of Congo, 1993-2003  

PubMed Central

In the Democratic Republic of Congo (DRC), human African trypanosomiasis (HAT) reached unprecedented levels in the 1990s. To assess recent trends and evaluate control efforts, we analyzed epidemiologic and financial data collected by all agencies involved in HAT control in DRC from 1993 to 2003. Funds allocated to control populations, as well as to the population screened, doubled from 1993 to 1997 and from 1998 to 2003. The number of cases detected decreased from 26,000 new cases per year in 1998 to 11,000 in 2003. Our analysis shows that HAT control in DRC is almost completely dependent on international aid and that sudden withdrawal of such aid in 1990 had a long-lasting effect. Since 1998, control efforts intensified because of renewed donor interest, including a public-private partnership, and this effort led to a major reduction in HAT incidence. To avoid reemergence of this disease, such efforts should be sustained. PMID:16229766

Lutumba, Pascal; Robays, Jo; Bilenge, Constantin Miaka mia; Mesu, Victor Kande Betu Ku; Molisho, Didier; Declercq, Johan; Van der Veken, Wim; Meheus, Filip; Jannin, Jean

2005-01-01

10

Control of human African trypanosomiasis in the Qui?ama focus, Angola.  

PubMed Central

OBJECTIVE: To update the epidemiological status of human African trypanosomiasis (HAT), also known as sleeping sickness, in the Quiçama focus, province of Bengo, Angola, and to establish a HAT control programme. METHODS: In 1997, 8796 people (the population of 31 villages) were serologically screened for Trypanosoma brucei gambiense, the causative agent of HAT. In 1998 and 1999, surveys were carried out in villages where HAT cases had been identified in 1997. Individuals were screened using the card agglutination trypanosomiasis test (CATT), and then examined for the presence of the parasite. CATT- positive individuals in whom the presence of the parasite could not be confirmed were further tested with the CATT using serum dilutions, and those with a positive antibody end titre of 1-in-4 or above were followed-up. Patients with < or =10 white cells/micro l and no trypanosomes in their cerebrospinal fluid (CSF) were classified as being in the first stage of the disease. Vector control was not considered necessary or feasible. FINDINGS: The main transmission areas were on the Kwanza riverbanks, where 5042 inhabitants live. In 1997, the HAT prevalence was 1.97%, but this decreased to 0.55% in 1998 and to 0.33% in 1999. The relapse rate was 3% in patients treated with pentamidine and 3.5% in patients treated with melarsoprol. In patients treated with pentamidine, there was no difference in the relapse rate for patients with initial CSF white cell counts of 0-5 cells/ micro l or 6-10 cells/micro l. The overall mortality rate was 0.6% and the rate of reactive arsenical encephalopathy among the melarsoprol-treated patients was 1.7%. CONCLUSION: The epidemiological status of the disease was updated and the transmission areas were defined. The control methods implemented allowed the disease prevalence to be reduced. PMID:12378293

Ruiz, Jose Antonio; Simarro, Pere P.; Josenando, Teofilo

2002-01-01

11

Human African trypanosomiasis.  

PubMed

Human African trypanosomiasis or sleeping sickness is a neglected tropical disease that affects populations in sub-Saharan Africa. The disease is caused by infection with the gambiense and rhodesiense subspecies of the extracellular parasite Trypanosoma brucei, and is transmitted to humans by bites of infected tsetse flies. The disease evolves in two stages, the hemolymphatic and meningoencephalitic stages, the latter being defined by central nervous system infection after trypanosomal traversal of the blood-brain barrier. African trypanosomiasis, which leads to severe neuroinflammation, is fatal without treatment, but the available drugs are toxic and complicated to administer. The choice of medication is determined by the infecting parasite subspecies and disease stage. Clinical features include a constellation of nonspecific symptoms and signs with evolving neurological and psychiatric alterations and characteristic sleep-wake disturbances. Because of the clinical profile variability and insidiously progressive central nervous system involvement, disease staging is currently based on cerebrospinal fluid examination, which is usually performed after the finding of trypanosomes in blood or other body fluids. No vaccine being available, control of human African trypanosomiasis relies on diagnosis and treatment of infected patients, assisted by vector control. Better diagnostic tools and safer, easy to use drugs are needed to facilitate elimination of the disease. PMID:23829907

Lejon, Veerle; Bentivoglio, Marina; Franco, José Ramon

2013-01-01

12

African trypanosomiasis.  

PubMed

Trypanosomiasis remains one of the most serious constraints to economic development in sub-Saharan Africa and, as a consequence, related research has been subject to strong social and political as well as scientific influences. The epidemics of sleeping sickness that occurred at the turn of the 20th Century focussed research efforts on what became known as 'the colonial disease'. This focus is thought to have produced 'vertical' health services aimed at this one disease, while neglecting other important health issues. Given the scale of these epidemics, and the fact that the disease is fatal if left untreated, it is unsurprising that sleeping sickness dominated colonial medicine. Indeed, recent evidence indicates that, if anything, the colonial authorities greatly under-estimated the mortality attributable to sleeping sickness. Differences in approach to disease control between Francophone and Anglophone Africa, which in the past have been considered ideological, on examination prove to be logical, reflecting the underlying epidemiological divergence of East and West Africa. These epidemiological differences are ancient in origin, pre-dating the colonial period, and continue to the present day. Recent research has produced control solutions, for the African trypanosomiases of humans and livestock, that are effective, affordable and sustainable by small-holder farmers. Whether these simple solutions are allowed to fulfil their promise and become fully integrated into agricultural practice remains to be seen. After more than 100 years of effort, trypanosomiasis control remains a controversial topic, subject to the tides of fashion and politics. PMID:17227648

Maudlin, I

2006-12-01

13

[Control of human African trypanosomiasis: back to square one].  

PubMed

The natural history of sleeping sickness is cyclic. The first epidemic outbreak in the 19th century devastated the population and resolved spontaneously for lack of victims. Intensive development during the colonial period and the movement of population that it spawned led to another epidemic in the early 1920s that reached such severe proportions that drastic steps had to be taken. At that time, Jamot was given complete political, administrative, and financial freedom to combat the disease. This program led to the development of the mobile team concept and so-called vertically structured vector control strategy and was so successful that sleeping sickness ceased to be considered as a major public health problem at the beginning of the 1960s. In the ensuing years sleeping sickness was largely neglected. Monitoring the disease required specialized teams that were no longer considered as cost-effective. One by one the measures that had been implemented to control the disease disappeared, thus setting the scene for a new outbreak grew. In 1995, the incidence of sleeping sickness reached the same levels as in the 1920s. The current situation is a classic example of a neglected disease with a paucity of competent specialists, diagnostic tests, effective drugs, and operational facilities. It was not until 2001 that new hope appeared thanks to a combined public- and private-sector initiative allowing restructuring of treatment teams, renovation of facilities, free distribution of drugs, and research to develop new therapeutic agents. Also thanks to the PATTEC initiative, the governments of the African affected nations are showing new in interest in sleeping sickness. However the battle is far from won and much effort will be required. Time is running out and the stakes are high. PMID:11803838

Jannin, J; Louis, F J; Lucas, P; Simarro, P P

2001-01-01

14

Human African Trypanosomiasis Transmission, Kinshasa, Democratic Republic of Congo  

Microsoft Academic Search

To investigate the epidemiology of human African try- panosomiasis (sleeping sickness) in Kinshasa, Democratic Republic of Congo, 2 entomologic surveys were conducted in 2005. Trypanosoma brucei gambiense and human-blood meals were found in tsetse fly midguts, which suggested active disease transmission. Vector control should be used to improve human African trypanosomiasis control efforts.

Gustave Simo; Philemon Mansinsa Diabakana; Victor Kande; Betu Ku; Emile Zola Manzambi; Gaelle Ollivier; Gerard Cuny

15

Modeling the Control of Trypanosomiasis Using Trypanocides or Insecticide-Treated Livestock  

PubMed Central

Background In Uganda, Rhodesian sleeping sickness, caused by Trypanosoma brucei rhodesiense, and animal trypanosomiasis caused by T. vivax and T. congolense, are being controlled by treating cattle with trypanocides and/or insecticides. We used a mathematical model to identify treatment coverages required to break transmission when host populations consisted of various proportions of wild and domestic mammals, and reptiles. Methodology/Principal Findings An Ro model for trypanosomiasis was generalized to allow tsetse to feed off multiple host species. Assuming populations of cattle and humans only, pre-intervention Ro values for T. vivax, T. congolense, and T. brucei were 388, 64 and 3, respectively. Treating cattle with trypanocides reduced R0 for T. brucei to <1 if >65% of cattle were treated, vs 100% coverage necessary for T. vivax and T. congolense. The presence of wild mammalian hosts increased the coverage required and made control of T. vivax and T. congolense impossible. When tsetse fed only on cattle or humans, R0 for T. brucei was <1 if 20% of cattle were treated with insecticide, compared to 55% for T. congolense. If wild mammalian hosts were also present, control of the two species was impossible if proportions of non-human bloodmeals from cattle were <40% or <70%, respectively. R0 was <1 for T. vivax only when insecticide treatment led to reductions in the tsetse population. Under such circumstances R0<1 for T. brucei and T. congolense if cattle make up 30% and 55%, respectively of the non-human tsetse bloodmeals, as long as all cattle are treated with insecticide. Conclusions/Significance In settled areas of Uganda with few wild hosts, control of Rhodesian sleeping sickness is likely to be much more effectively controlled by treating cattle with insecticide than with trypanocides. PMID:22616017

Hargrove, John W.; Ouifki, Rachid; Kajunguri, Damian; Vale, Glyn A.; Torr, Stephen J.

2012-01-01

16

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. PMID:11143188

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

2000-01-01

17

Fluidic thrust vector control  

NASA Astrophysics Data System (ADS)

The design and testing of a fluidic control nozzle for tactical missile thrust vector control (TVC) are discussed. Attention is given to a nozzle with a circular cross section up to the point of flow separation, two control ports that alternately open and close, and a nozzle extension downstream of the control ports being a two-dimensional rectangular slot. Design of the TVC system involved characterizing the flow and the sensitivity parameters, the dynamic response, and the performance of hot-gas firings. The test firings verified the feasibility of a nozzle that could withstand 5000 F, the use of thrust vector angles of over 20 deg. A dynamic model test demonstrated a repeatable performance with pressures up to 2000 psia, driving frequencies up to 50 Hz, and a response of 10-15 msec. Adjustment of the chamber pressures permitted equivalent performance using with different heat ratios during cold dynamic tests with CH4.

Haloulakos, V. E.

18

African Trypanosomiasis Gambiense, Italy  

PubMed Central

African trypanosomiasis caused by Trypanosoma brucei gambiense has not been reported in Italy. We report 2 cases diagnosed in the summer of 2004. Theses cases suggest an increased risk for expatriates working in trypanosomiasis-endemic countries. Travel medicine clinics should be increasingly aware of this potentially fatal disease. PMID:16318728

Beltrame, Anna; Monteiro, Geraldo; Arzese, Alessandra; Marocco, Stefania; Rorato, Giada; Anselmi, Mariella; Viale, Pierluigi

2005-01-01

19

The history of African trypanosomiasis  

Microsoft Academic Search

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

Dietmar Steverding

2008-01-01

20

Thrust-Vector-Control System  

NASA Technical Reports Server (NTRS)

Control gains computed via matrix Riccati equation. Software-based system controlling aim of gimbaled rocket motor on spacecraft adaptive and optimal in sense it adjusts control gains in response to feedback, according to optimizing algorithm based on cost function. Underlying control concept also applicable, with modifications, to thrust-vector control on vertical-takeoff-and-landing airplanes, control of orientations of scientific instruments, and robotic control systems.

Murray, Jonathan

1992-01-01

21

Improvements on Restricted Insecticide Application Protocol for Control of Human and Animal African Trypanosomiasis in Eastern Uganda  

PubMed Central

Background African trypanosomes constrain livestock and human health in Sub-Saharan Africa, and aggravate poverty and hunger of these otherwise largely livestock-keeping communities. To solve this, there is need to develop and use effective and cheap tsetse control methods. To this end, we aimed at determining the smallest proportion of a cattle herd that needs to be sprayed on the legs, bellies and ears (RAP) for effective Human and Animal African Trypanosomiasis (HAT/AAT) control. Methodology/Principal finding Cattle in 20 villages were ear-tagged and injected with two doses of diminazene diaceturate (DA) forty days apart, and randomly allocated to one of five treatment regimens namely; no treatment, 25%, 50%, 75% monthly RAP and every 3 month Albendazole drench. Cattle trypanosome re-infection rate was determined by molecular techniques. ArcMap V10.3 was used to map apparent tsetse density (FTD) from trap catches. The effect of graded RAP on incidence risk ratios and trypanosome prevalence was determined using Poisson and logistic random effect models in R and STATA V12.1 respectively. Incidence was estimated at 9.8/100 years in RAP regimens, significantly lower compared to 25.7/100 years in the non-RAP regimens (incidence rate ratio: 0.37; 95% CI: 0.22–0.65; P<0.001). Likewise, trypanosome prevalence after one year of follow up was significantly lower in RAP animals than in non-RAP animals (4% vs 15%, OR: 0.20, 95% CI: 0.08–0.44; P<0.001). Contrary to our expectation, level of protection did not increase with increasing proportion of animals treated. Conclusions/significance Reduction in RAP coverage did not significantly affect efficacy of treatment. This is envisaged to improve RAP adaptability to low income livestock keepers but needs further evaluation in different tsetse challenge, HAT/AAT transmission rates and management systems before adopting it for routine tsetse control programs. PMID:25356758

Muhanguzi, Dennis; Picozzi, Kim; Hatendorf, Jan; Thrusfield, Michael; Welburn, Susan Christina; Kabasa, John David; Waiswa, Charles

2014-01-01

22

Epidemiology of human African trypanosomiasis.  

PubMed

Human African trypanosomiasis (HAT), or sleeping sickness, is caused by Trypanosoma brucei gambiense, which is a chronic form of the disease present in western and central Africa, and by Trypanosoma brucei rhodesiense, which is an acute disease located in eastern and southern Africa. The rhodesiense form is a zoonosis, with the occasional infection of humans, but in the gambiense form, the human being is regarded as the main reservoir that plays a key role in the transmission cycle of the disease. The gambiense form currently assumes that 98% of the cases are declared; the Democratic Republic of the Congo is the most affected country, with more than 75% of the gambiense cases declared. The epidemiology of the disease is mediated by the interaction of the parasite (trypanosome) with the vectors (tsetse flies), as well as with the human and animal hosts within a particular environment. Related to these interactions, the disease is confined in spatially limited areas called "foci", which are located in Sub-Saharan Africa, mainly in remote rural areas. The risk of contracting HAT is, therefore, determined by the possibility of contact of a human being with an infected tsetse fly. Epidemics of HAT were described at the beginning of the 20th century; intensive activities have been set up to confront the disease, and it was under control in the 1960s, with fewer than 5,000 cases reported in the whole continent. The disease resurged at the end of the 1990s, but renewed efforts from endemic countries, cooperation agencies, and nongovernmental organizations led by the World Health Organization succeeded to raise awareness and resources, while reinforcing national programs, reversing the trend of the cases reported, and bringing the disease under control again. In this context, sustainable elimination of the gambiense HAT, defined as the interruption of the transmission of the disease, was considered as a feasible target for 2030. Since rhodesiense HAT is a zoonosis, where the animal reservoir plays a key role, the interruption of the disease's transmission is not deemed feasible. PMID:25125985

Franco, Jose R; Simarro, Pere P; Diarra, Abdoulaye; Jannin, Jean G

2014-01-01

23

Epidemiology of human African trypanosomiasis  

PubMed Central

Human African trypanosomiasis (HAT), or sleeping sickness, is caused by Trypanosoma brucei gambiense, which is a chronic form of the disease present in western and central Africa, and by Trypanosoma brucei rhodesiense, which is an acute disease located in eastern and southern Africa. The rhodesiense form is a zoonosis, with the occasional infection of humans, but in the gambiense form, the human being is regarded as the main reservoir that plays a key role in the transmission cycle of the disease. The gambiense form currently assumes that 98% of the cases are declared; the Democratic Republic of the Congo is the most affected country, with more than 75% of the gambiense cases declared. The epidemiology of the disease is mediated by the interaction of the parasite (trypanosome) with the vectors (tsetse flies), as well as with the human and animal hosts within a particular environment. Related to these interactions, the disease is confined in spatially limited areas called “foci”, which are located in Sub-Saharan Africa, mainly in remote rural areas. The risk of contracting HAT is, therefore, determined by the possibility of contact of a human being with an infected tsetse fly. Epidemics of HAT were described at the beginning of the 20th century; intensive activities have been set up to confront the disease, and it was under control in the 1960s, with fewer than 5,000 cases reported in the whole continent. The disease resurged at the end of the 1990s, but renewed efforts from endemic countries, cooperation agencies, and nongovernmental organizations led by the World Health Organization succeeded to raise awareness and resources, while reinforcing national programs, reversing the trend of the cases reported, and bringing the disease under control again. In this context, sustainable elimination of the gambiense HAT, defined as the interruption of the transmission of the disease, was considered as a feasible target for 2030. Since rhodesiense HAT is a zoonosis, where the animal reservoir plays a key role, the interruption of the disease’s transmission is not deemed feasible. PMID:25125985

Franco, Jose R; Simarro, Pere P; Diarra, Abdoulaye; Jannin, Jean G

2014-01-01

24

Impact of tsetse and trypanosomiasis control on cattle herd composition and calf growth and mortality at Arbaminch District (Southern Rift Valley, Ethiopia).  

PubMed

The effect of tsetse/trypanosomiasis control on cattle herd composition and growth and mortality of calves in tsetse controlled (by Southern Tsetse Eradication Project (STEP)) and uncontrolled blocks in southern Ethiopia was assessed. Structured questionnaire was used to interview 182 households to estimate cattle herd composition and calf mortality. Calves were bled to examine the presence of trypanosomes by the buffy coat technique. Forty NGU traps were deployed and fly catches determined. A case-control study was performed on 40 calves for 6 months to estimate calve growth parameters. Accordingly, the mean cattle herd size was lower in tsetse-controlled block than in the uncontrolled block, whereas the relative number of calves in a herd tend to be higher in the tsetse-controlled block (P = 0.06). While there was no report of cattle mortality in tsetse-controlled block, 16.48 % of the respondents have lost calves in tsetse-uncontrolled block in 1 year time. The prevalence of trypanosome positive calves was 2.95 % for uncontrolled block but no positive case in tsetse-controlled block. The apparent densities of flies/trap/day in tsetse-uncontrolled block were 30-fold higher than in tsetse-controlled block (P < 0.01). The case-control study revealed that the mean body weight gain of calves in tsetse-controlled block (40.23 ± 0.7 kg) was significantly higher than that of the uncontrolled block (34.74 ± 0.68 kg). The above findings strongly suggest that the intervention by the STEP project has significantly reduced tsetse population and trypanosomiasis consequently contributing to improved calf growth and survival. PMID:22467042

Gechere, Geja; Terefe, Getachew; Belihu, Kelay

2012-10-01

25

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. PMID:22205439

La Greca, Florencia

2011-01-01

26

[Research progress on malaria vector control].  

PubMed

Vector control plays a crucial role in the stages of malaria control and elimination. Currently, it mainly relies on the chemical control methods for adult mosquitoes in malaria endemic areas, however, it is undergoing the serious threat by insecticide resistance. In recent years, the transgenic technologies of malaria vectors have made a great progress in the laboratory. This paper reviews the challenges of the traditional methods and the rapid developed genetic modified technology in the application of vector control. PMID:24024458

Zhu, Guo-Ding; Cao, Jun; Zhou, Hua-Yun; Gao, Qi

2013-06-01

27

Thrust Vector Control System Study for a Large Liquid Booster.  

National Technical Information Service (NTIS)

This effort consisted of evaluating six thrust vector control systems for application on a Large Liquid Booster. The thrust vector control systems evaluated were liquid injection thrust vector control, hot gas secondary injection thrust vector control and...

D. Stump, V. Olivier

1968-01-01

28

Parameter estimation of vector controlled induction machine  

E-print Network

This thesis deals with the modeling and control of induction machine under indirect vector control with parameter estimation in order to get better field oriented performance. Because of its excellent decoupled control, wide flux weakening region...

Rahman, Tahmid Ur

2012-06-07

29

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. PMID:20606968

Claborn, David M

2010-01-01

30

Malaria vector control: from past to future  

Microsoft Academic Search

Malaria is one of the most common vector-borne diseases widespread in the tropical and subtropical regions. Despite considerable\\u000a success of malaria control programs in the past, malaria still continues as a major public health problem in several countries.\\u000a Vector control is an essential part for reducing malaria transmission and became less effective in recent years, due to many\\u000a technical and

Kamaraju Raghavendra; Tapan K. Barik; B. P. Niranjan Reddy; Poonam Sharma; Aditya P. Dash

2011-01-01

31

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

32

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. PMID:19091038

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

2008-01-01

33

Ascent thrust vector control system test  

NASA Technical Reports Server (NTRS)

Testing of the Ascent Thrust Vector Control System in support of the Ares 1-X program at the Marshall Space Flight Center in Huntsville, Alabama. This image is extracted from a high definition video file and is the highest resolution available

2008-01-01

34

Prospects for vector control through sterilization procedures  

PubMed Central

Interest in sterilization as a possible method for controlling insects of public health importance can be said to have arisen first in the mid-fifties, when the screw-worm fly was successfully eradicated from the island of Curaçao by the release over the entire island of large numbers of male flies sterilized by gamma-radiation. Since then, many studies on the sterilization of various insect vectors of disease have been carried out. This paper reviews these studies and discusses the present position regarding vector control by sterilization procedures, with special reference to the use of chemosterilants. These compounds have certain advantages over radiation since they can be used not only as a substitute for X-rays or gamma-rays in the sterilization of insects specially reared for release in large numbers, but also as a means of inducing sterility in natural populations of insects. The author emphasizes that chemosterilants cannot at present be recommended as a practical control or eradication procedure for any vector species of insect, but considers that this extension of the sterilization method holds great promise and merits intensive investigation. PMID:20604181

Smith, Carroll N.

1963-01-01

35

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.

36

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

37

Controlling Vector Bessel Beams with Metasurfaces  

NASA Astrophysics Data System (ADS)

Unprecedented control of an electromagnetic wave front is demonstrated with reflectionless metasurfaces that can manipulate vector Bessel beams: cylindrical vector beams with a Bessel profile. First, two metasurfaces are developed to convert linearly and circularly polarized Gaussian beams into vector Bessel beams. Each unit cell of the metasurfaces provides polarization and phase control with high efficiency. Next, the reciprocal process is demonstrated: an incident radially polarized Bessel beam is transformed into collimated, linearly and circularly polarized beams. In this configuration, a planar Bessel beam launcher is integrated with a collimating metasurface lens to realize a low-profile lens-antenna. The lens-antenna achieves a high directivity (exceeding 20 dB) with a subwavelength overall thickness. Finally, a metasurface providing isotropic polarization rotation is used to transform a radially polarized Bessel beam into an azimuthally polarized Bessel beam. This work demonstrates that metasurfaces can be used to generate arbitrary combinations of radial and azimuthal polarizations for applications such as focus shaping or generating tractor beams.

Pfeiffer, Carl; Grbic, Anthony

2014-10-01

38

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. PMID:24982143

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

39

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

40

Introducing control flow into vectorized code.  

SciTech Connect

Single instruction multiple data (SIMD) functional units are ubiquitous in modern microprocessors. Effective use of these SIMD functional units is essential in achieving the highest possible performance. Automatic generation of SIMD instructions in the presence of control flow is challenging, however, not only because SIMD code is hard to generate in the presence of arbitrarily complex control flow, but also because the SIMD code executing the instructions in all control paths may slow compared to the scalar original, which may bypass a large portion of the code. One promising technique introduced recently involves inserting branches-on-superword-condition-codes (BOSCCs) to bypass vector instructions. In this paper, we describe two techniques that improve on the previous approach. First, BOSCCs are generated in a nested fashion so that even BOSCCs themselves can be bypassed by other BOSCCs. Second, we generate all vec any instructions to bypass even some predicate-defining instructions. We implemented these techniques in a vectorizing compiler. On 14 kernels, the compiler achieves distinct speedups, including 1.99X over the previous technique that generates single-level BOSCCs and vec any ne only.

Shin, J.; Mathematics and Computer Science

2007-01-01

41

Electromechanical actuation for thrust vector control applications  

NASA Astrophysics Data System (ADS)

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

42

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

43

Using Cell Phones for Mosquito Vector Surveillance and Control  

E-print Network

Using Cell Phones for Mosquito Vector Surveillance and Control S. Lozano-Fuentes, S. Ghosh, J. M--Novel, low-cost approaches to improving prevention and control of vector-borne diseases, such as mosquito the use of cell phones for field capture and rapid transfer of mosquito vector surveillance data

Bieman, James M.

44

Immobilization of game animals in trypanosomiasis research  

PubMed Central

The proximity of human populations to communities of large animals in Africa creates suitable conditions for the transmission of zoonotic diseases. Since the indiscriminate destruction of these communities to control zoonoses is highly undesirable, the epidemiological role of the animals must be properly assessed in order that alternative methods of control can be developed. For this purpose, techniques should be available to permit large animals to be examined alive. Immobilization techniques using various drugs were tried but only limited success was achieved with the species most likely to be involved in the transmission cycle of trypanosomiasis. In the study reported here, xylazine was the drug selected, one reason being that an antagonist was not required. The drug was administered from a distance by means of a projectile syringe shot from a special rifle. In seven attempts, two waterbuck (Kobus defassa) and one reedbuck (Redunca redunca) were sufficiently immobilized to be handled. The reactions of all seven animals, whether successfully immobilized or not, are discussed. PMID:4544834

Allsopp, R.

1972-01-01

45

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

46

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. PMID:13986384

Prothero, R. Mansell

1963-01-01

47

Towards a new role for vector systematics in parasite control.  

PubMed

Vector systematics research is being transformed by the recent development of theoretical, experimental and analytical methods, as well as conceptual insights into speciation and reconstruction of evolutionary history. We review this progress using examples from the mosquito genus Anopheles. The conclusion is that recent progress, particularly in the development of better tools for understanding evolutionary history, makes systematics much more informative for vector control purposes, and has increasing potential to inform and improve targeted vector control programmes. PMID:21679487

Zarowiecki, Magdalena; Loaiza, Jose R; Conn, Jan E

2011-11-01

48

Abnormal biochemical and haematological indices in trypanosomiasis as a threat to herd production.  

PubMed

Blood samples were collected from 46 domestic ruminants comprising of 23 trypanosomiasis infected and 23 uninfected control groups to study some biochemical and haematological effects of trypanosomiasis under natural condition. The effect of trypanosome infection in ruminant animals showed that infected animals had significantly lower (P<0.05) packed cell volume, erythrocyte count and higher (P<0.01) mean cell volumes than uninfected animals. Leucocytosis, reticulocytosis and thrombocytopenia were also observed. The infection also produced a decrease in albumin (P<0.001), significant increase in total protein and bilirubin levels. These changes were not seen in the animals that were not infected. The outcome of the work shows that herds are severely affected by the disease, and therefore supports the prospect of routine check as an epidemiologic tool in trypanosomiasis based on its abnormal effects in blood. PMID:21382664

Ohaeri, C C; Eluwa, M C

2011-05-11

49

Vector control in some countries of Southeast Asia: comparing the vectors and the strategies.  

PubMed

The use of information on malaria vector behaviour in vector control is discussed in relation to the area of Southeast Asia comprising Cambodia, Laos, Myanmar, Thailand and Vietnam. The major vectors in the region are Anopheles dirus, An. minimus, An. maculatus and An. sundaicus, of which An. dirus is the most important. Options for vector control and the biological features of mosquitoes, which would make them amenable to control by these measures, are listed. The methods with the greatest potential for controlling each of the four vector species are described. Experiences of vector control by residual spraying, insecticide-treated nets and larva control and of personal protection against the four vectors are outlined, and it is noted that choice of control strategy is often determined by epidemiological, economic and political considerations, whilst entomological observations may help to explain failures of control and to indicate alternative strategies. Future research needs include basic entomological field studies using the most appropriate indicators to detect changes related to rapidly changing environmental conditions, such as loss of forest and climate change. Further studies of the efficacy of insecticide-treated mosquito nets, with greater attention to study design, are needed before it can be assumed that they will work in Southeast Asia. At the same time, research to improve sustainable utilization of nets is important, bearing in mind that nets are not the only means to control malaria and should not drain resources from supervision and training, which improve access to diagnosis and treatment of malaria and other diseases. Research is needed to make decisions on whether vector control is appropriate in different environments, and, if so, how to carry it out in different health systems. Researchers need to play a greater role in making operational research (entomological, epidemiological, social, economic and health systems research) of good quality an integral component of implementation programmes. PMID:7605123

Meek, S R

1995-04-01

50

A longitudinal survey of African animal trypanosomiasis in domestic cattle on the Jos Plateau, Nigeria: prevalence, distribution and risk factors  

PubMed Central

Background Trypanosomiasis is a widespread disease of livestock in Nigeria and a major constraint to the rural economy. The Jos Plateau, Nigeria was free from tsetse flies and the trypanosomes they transmit due to its high altitude and the absence of animal trypanosomiasis attracted large numbers of cattle-keeping pastoralists to inhabit the plateau. The Jos Plateau now plays a significant role in the national cattle industry, accommodating approximately 7% of the national herd and supporting 300,000 pastoralists and over one million cattle. However, during the past two decades tsetse flies have invaded the Jos Plateau and animal trypanosomiasis has become a significant problem for livestock keepers. Methods In 2008 a longitudinal two-stage cluster survey on the Jos Plateau. Cattle were sampled in the dry, early wet and late wet seasons. Parasite identification was undertaken using species-specific polymerase chain reactions to determine the prevalence and distribution bovine trypanosomiasis. Logistic regression was performed to determine risk factors for disease. Results The prevalence of bovine trypanosomiasis (Trypanosoma brucei brucei, Trypanosoma congolense savannah, Trypanosoma vivax) across the Jos Plateau was found to be high at 46.8% (39.0 – 54.5%) and significant, seasonal variation was observed between the dry season and the end of the wet season. T. b. brucei was observed at a prevalence of 3.2% (1% – 5.5%); T. congolense at 27.7% (21.8% - 33.6%) and T. vivax at 26.7% (18.2% - 35.3%). High individual variation was observed in trypanosomiasis prevalence between individual villages on the Plateau, ranging from 8.8% to 95.6%. Altitude was found to be a significant risk factor for trypanosomiasis whilst migration also influenced risk for animal trypanosomiasis. Conclusions Trypanosomiasis is now endemic on the Jos Plateau showing high prevalence in cattle and is influenced by seasonality, altitude and migration practices. Attempts to successfully control animal trypanosomiasis on the Plateau will need to take into account the large variability in trypanosomiasis infection rates between villages, the influence of land use, and husbandry and management practices of the pastoralists, all of which affect the epidemiology of the disease. PMID:23958205

2013-01-01

51

Vector control of induction motor without shaft encoder  

Microsoft Academic Search

A method of introduction motor drive that requires no shaft encoder is presented. This system has both torque and speed controls that are performed by vector control. The vector-control scheme is based on a rotor-flux speed control, which is performed by torque-producing current and rotor flux, derived from the stator voltages and currents. If it is possible to obtain both

Tsugutoshi Ohtani; Noriyuki Takada; Koji Tanaka

1992-01-01

52

Exploiting the potential of vector control for disease prevention.  

PubMed Central

Although vector control has proven highly effective in preventing disease transmission, it is not being used to its full potential, thereby depriving disadvantaged populations of the benefits of well tried and tested methods. Following the discovery of synthetic residual insecticides in the 1940s, large-scale programmes succeeded in bringing many of the important vector-borne diseases under control. By the late 1960s, most vector-borne diseases--with the exception of malaria in Africa--were no longer considered to be of primary public health importance. The result was that control programmes lapsed, resources dwindled, and specialists in vector control disappeared from public health units. Within two decades, many important vector-borne diseases had re-emerged or spread to new areas. The time has come to restore vector control to its key role in the prevention of disease transmission, albeit with an increased emphasis on multiple measures, whether pesticide-based or involving environmental modification, and with a strengthened managerial and operational capacity. Integrated vector management provides a sound conceptual framework for deployment of cost-effective and sustainable methods of vector control. This approach allows for full consideration of the complex determinants of disease transmission, including local disease ecology, the role of human activity in increasing risks of disease transmission, and the socioeconomic conditions of affected communities. PMID:16462987

Townson, H.; Nathan, M. B.; Zaim, M.; Guillet, P.; Manga, L.; Bos, R.; Kindhauser, M.

2005-01-01

53

A vector control technique for medium-voltage multilevel inverters  

Microsoft Academic Search

This paper presents a switching strategy for multilevel cascade inverters, based on the space-vector theory. The proposed switching strategy generates a voltage vector with very low harmonic distortion and reduced switching frequency. This new control method is an attractive alternative to the classic multilevel pulsewidth modulation techniques considering the following aspects: (1) voltage and current total harmonic distortion; (2) range

José Rodríguez; Luis Morán; Pablo Correa; Cesar Silva

2002-01-01

54

A vector control technique for medium voltage multilevel inverters  

Microsoft Academic Search

This paper presents a switching strategy for multilevel cascade inverters, based on the space vector theory. The proposed switching strategy generates a voltage vector with very low harmonic distortion and reduced switching frequency. This new control method is an attractive alternative to the classic multilevel PWM techniques considering the following aspects: (i) voltage and current THD, (ii) range of linear

J. Rodriguez; P. Correa; L. Moran

2001-01-01

55

Genetics and evolution of triatomines: from phylogeny to vector control  

Microsoft Academic Search

Triatomines are hemipteran bugs acting as vectors of the protozoan parasite Trypanosoma cruzi. This parasite causes Chagas disease, one of the major parasitic diseases in the Americas. Studies of triatomine genetics and evolution have been particularly useful in the design of rational vector control strategies, and are reviewed here. The phylogeography of several triatomine species is now slowly emerging, and

S Gourbière; P Dorn; F Tripet; E Dumonteil

2012-01-01

56

Towards the Atlas of human African trypanosomiasis  

PubMed Central

Background Updated, accurate and comprehensive information on the distribution of human African trypanosomiasis (HAT), also known as sleeping sickness, is critically important to plan and monitor control activities. We describe input data, methodology, preliminary results and future prospects of the HAT Atlas initiative, which will allow major improvements in the understanding of the spatial distribution of the disease. Methods Up-to-date as well as historical data collected by national sleeping sickness control programmes, non-governmental organizations and research institutes have been collated over many years by the HAT Control and Surveillance Programme of the World Health Organization. This body of information, unpublished for the most part, is now being screened, harmonized, and analysed by means of database management systems and geographical information systems (GIS). The number of new HAT cases and the number of people screened within a defined geographical entity were chosen as the key variables to map disease distribution in sub-Saharan Africa. Results At the time of writing, over 600 epidemiological reports and files from seventeen countries were collated and included in the data repository. The reports contain information on approximately 20,000 HAT cases, associated to over 7,000 different geographical entities. The oldest epidemiological records considered so far date back to 1985, the most recent having been gathered in 2008. Data from Cameroon, Central African Republic, Chad, Congo, Equatorial Guinea and Gabon from the year 2000 onwards were fully processed and the preliminary regional map of HAT distribution is presented. Conclusion The use of GIS tools and geo-referenced, village-level epidemiological data allow the production of maps that substantially improve on the spatial quality of previous cartographic products of similar scope. The significant differences between our preliminary outputs and earlier maps of HAT transmission areas demonstrate the strong need for this systematic approach to mapping sleeping sickness and point to the inaccuracy of any calculation of population at risk based on previous maps of HAT transmission areas. The Atlas of HAT will lay the basis for novel, evidence-based methodologies to estimate the population at risk and the burden of disease, ultimately leading to more efficient targeting of interventions. Also, the Atlas will help streamline future field data collection in those parts of Africa that still require it. PMID:19296837

Cecchi, Giuliano; Paone, Massimo; Franco, José R; Fèvre, Eric M; Diarra, Abdoulaye; Ruiz, José A; Mattioli, Raffaele C; Simarro, Pere P

2009-01-01

57

Photonic control of phased arrays using analog vector modulation  

Microsoft Academic Search

A compact free-space\\/solid optics photonic controller for phased array antennas\\/transducers is introduced that uses the principle of in-phase (I) and quadrature (Q) vector modulation via two dimensional (2-D) spatial light modulators (SLMs). The SLMs are used as distributed optical gain control devices to implement the vector modulation operation required to generate the desired radio frequency (RF) signals with the correct

Nabeel A. Riza

1996-01-01

58

[Action duality of nitrogen oxide (NO) in experimental African trypanosomiasis].  

PubMed

Patients with human African trypanosomiasis present a major dysruption of the circadian rhythmicity of the sleep-wake cycle, which was also found in rats infected with Trypanosoma brucei brucei (T.b.b.). The alterations in the immune function and nervous system in African trypsanosomiasis led us to investigate the involvement of nitric oxide (NO), a key molecule in immune and neurophysiological mechanisms, in experimental trypanosomiasis. NO was measured in 35 Sprague Dawley rats using differential impulsional voltammetry with a carbon fiber coated with porphyrin-nickel and nafion, ex vivo in the blood and in vivo in the brain. The rats were anaesthetized with sodium chlorate. Infection was performed intraperitoneally (i.p.) with 0.2 ml of a T.b.b. cryostabilate (clone AnTat 1.1E). Blood was collected by an intracardiac puncture with immediate replacement of blood volume (1 ml) in 7 control rats and 8 rats infected since 15 days, before and after i.p. administration of L-ANA (L-arginine-p-nitro-anilide, 100 mg.kg-1, an inhibitor of NO synthase). Brain measures were done in 20 rats (8 controls, and 12 rats infected since 15 or 21 days), in the cortex (H, -0.5 mm; AP, -0.8 mm; L, 1.2 mm) and the lateral ventricle (H,-3.2 mm). In infected rats, blood NO was at 70% of control values (p < 0.001), and L-ANA suppressed the NO signal in all animals (p < 0.0001), demonstrating that the signal originated from NO. Cortical NO was higher than in the ventricle in both control (p < 0.0001) and infected rats (p < 0.001). NO was more elevated in both structures in 15-day-infected rats than in control rats (p < 0.0001), the difference being enhanced in 21-day-infected rats (p < 0.001). L-ANA suppressed the NO signal in 30 to 60 min. These data suggest that NO intervenes in the development of trypanosomiasis in different manners. It is increased in the brain, which remains unexplained, where it may be involved in blood-brain barrier permeation. Conversely, it is decreased in the blood, may be because of macrophage function impairment, which would explain why trypanosomes can multiply in the host. PMID:8761666

Buguet, A; Burlet, S; Auzelle, F; Montmayeur, A; Jouvet, M; Cespuglio, R

1996-03-01

59

The population structure of Glossina fuscipes fuscipes in the Lake Victoria basin in Uganda: implications for vector control  

PubMed Central

Background Glossina fuscipes fuscipes is the primary vector of trypanosomiasis in humans and livestock in Uganda. The Lake Victoria basin has been targeted for tsetse eradication using a rolling carpet initiative, from west to east, with four operational blocks (3 in Uganda and 1 in Kenya), under a Pan-African Tsetse and Trypanosomiasis Eradication Campaign (PATTEC). We screened tsetse flies from the three Ugandan PATTEC blocks for genetic diversity at 15 microsatellite loci from continental and offshore populations to provide empirical data to support this initiative. Methods We collected tsetse samples from 11 sites across the Lake Victoria basin in Uganda. We performed genetic analyses on 409 of the collected tsetse flies and added data collected for 278 individuals in a previous study. The flies were screened across 15 microsatellite loci and the resulting data were used to assess the temporal stability of populations, to analyze patterns of genetic exchange and structuring, to estimate dispersal rates and evaluate the sex bias in dispersal, as well as to estimate demographic parameters (NE and NC). Results We found that tsetse populations in this region were stable over 4-16 generations and belong to 4 genetic clusters. Two genetic clusters (1 and 2) corresponded approximately to PATTEC blocks 1 and 2, while the other two (3 and 4) fell within PATTEC block 3. Island populations grouped into the same genetic clusters as neighboring mainland sites, suggesting presence of gene flow between these sites. There was no evidence of the stretch of water separating islands from the mainland forming a significant barrier to dispersal. Dispersal rates ranged from 2.5?km per generation in cluster 1 to 14?km per generation in clusters 3 and 4. We found evidence of male-biased dispersal. Few breeders are successfully dispersing over large distances. Effective population size estimates were low (33–310 individuals), while census size estimates ranged from 1200 (cluster 1) to 4100 (clusters 3 and 4). We present here a novel technique that adapts an existing census size estimation method to sampling without replacement, the scheme used in sampling tsetse flies. Conclusion Our study suggests that different control strategies should be implemented for the three PATTEC blocks and that, given the high potential for re-invasion from island sites, mainland and offshore sites in each block should be targeted at the same time. PMID:23036153

2012-01-01

60

Support Vector Machines in Fault Tolerance Control  

NASA Astrophysics Data System (ADS)

This paper presents a new approach for quality monitoring of on-line molded parts in the context of an injection molding problem using Support Vector Machines (SVMs). While the main goal in the industrial framework is to automatically calculate the setpoints, a less important task is to classify plastic molded parts defects efficiently in order to assess multiple quality characteristics. The paper presents a comparison of the performance assessment of SVMs and RBF neural networks as part quality monitoring tools by analyzing complete data patterns. Results show that the classification model using SVMs presents slightly better performance than RBF neural networks mainly due to the superior generalization of the SVMs in high-dimensional spaces. Particularly, when RBF kernels are used, the accuracy of the task increases thus leading to smaller error rates. Besides, the optimization method is a constrained quadratic programming, which is a well studied and understood mathematical programming technique.

Ribeiro, Bernardete

2002-09-01

61

Robust nonlinear control of vectored thrust aircraft  

NASA Technical Reports Server (NTRS)

An interdisciplinary program in robust control for nonlinear systems with applications to a variety of engineering problems is outlined. Major emphasis will be placed on flight control, with both experimental and analytical studies. This program builds on recent new results in control theory for stability, stabilization, robust stability, robust performance, synthesis, and model reduction in a unified framework using Linear Fractional Transformations (LFT's), Linear Matrix Inequalities (LMI's), and the structured singular value micron. Most of these new advances have been accomplished by the Caltech controls group independently or in collaboration with researchers in other institutions. These recent results offer a new and remarkably unified framework for all aspects of robust control, but what is particularly important for this program is that they also have important implications for system identification and control of nonlinear systems. This combines well with Caltech's expertise in nonlinear control theory, both in geometric methods and methods for systems with constraints and saturations.

Doyle, John C.; Murray, Richard; Morris, John

1993-01-01

62

Chemotherapy of human African trypanosomiasis: current and future  

E-print Network

- ment of African trypanosomiasis (sleeping sickness) were developed over 50 years ago. All) has historical roots that date back to the pioneering work by Paul Ehrlich on dyes and arsenicals. Yet]. The disease status African trypanosomiasis causes sleeping sickness in humans and nagana (depressed and low

Schnaufer, Achim

63

A Quasioptical Vector Interferometer for Polarization Control  

NASA Technical Reports Server (NTRS)

We present a mathematical description of a Quasioptical Vector Interferometer (QVI), a device that maps an input polarization state to an output polarization state by introducing a phase delay between two linear orthogonal components of the input polarization. The advantages of such a device over a spinning wave-plate modulator for measuring astronomical polarization in the far-infrared through millimeter are: 1. The use of small, linear motions eliminates the need for cryogenic rotational bearings, 2. The phase flexibility allows measurement of Stokes V as well as Q and U, and 3. The QVI allows for both multi-wavelength and broadband modulation. We suggest two implementations of this device as an astronomical polarization modulator. The first involves two such modulators placed in series. By adjusting the two phase delays, it is possible to use such a modulator to measure Stokes Q, U, and V for passbands that are not too large. Conversely, a single QVI may be used to measure Q and V independent of frequency. In this implementation, Stokes U must be measured by rotating the instrument. We conclude this paper by presenting initial laboratory results.

Chuss, David T.; Wollack, Edward J.; Moseley, Harvey S.; Novak, Giles

2005-01-01

64

Controllable vector bottle-shaped fields generated by focused spatial-variant linearly polarized vector beams  

NASA Astrophysics Data System (ADS)

We demonstrate that the optical bottle-shaped fields can be controllably generated by the focused spatial-variant linearly polarized vector beams. Based on the vectorial Rayleigh-Sommerfeld formulas under the paraxial approximation, we present theoretically the analytical expression for the focused field of the vector beam and predict the evolution of the sate of polarization (SoP) in the focal region. Experimentally, we observe the vector bottle-shaped field that is in agreement with the numerical simulations. In particular, we validate that both the SoP and the size of the optical bottle field are manipulated easily by varying the azimuthal topological charge and the radial mode index.

Gu, Bing; Wu, Jia-Lu; Pan, Yang; Cui, Yiping

2013-11-01

65

Vectors  

NSDL National Science Digital Library

This lesson was created by Larry Friesen and Anne Gillis for Butler Community College. It will help physics and calculus students differentiate between the uses of vectors in mathematics vs. physics. This website provides two PDF documents that give detailed lessons about vectors, including an overview of terminology, sample problems, and an HTML worksheet is also provided. For educators or students, this site offers well laid-out lessons and/or practice with vectors.

Friesen, Larry; Gillis, Anne

2008-04-18

66

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.

67

Methods for control of tick vectors of Lyme Borreliosis  

USGS Publications Warehouse

During the IVth International Conference on Lyme Borreliosis in Stockholm, 1990, a workshop on control of Lyme disease vectors briefly reviewed: basic ecological principles for tick control; biocontrol of ticks; chemical control, including the use of repellents and use of permethrin-treated rodent nest material; tick control by habitat modification; and reduction of tick host availability. It was concluded that, although much research work remains, Lyme borreliosis is to a large extent a preventable infection. Avoidance of heavily tick-infested areas, personal protection using proper clothing, and prompt removal of attached ticks remain the most effective protective measures. Many other prophylactic measures are available and could be efficiently integrated into schemes to reduce the abundance of vectors. However, since the ecology of the infection varies greatly between different localities it may be necessary to apply different combinations of control methods in different endemic regions.

Jaenson, T.G.T.; Fish, D.; Ginsberg, H.S.; Gray, J.S.; Mather, T.N.; Piesman, J.

1991-01-01

68

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. PMID:22438737

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

2012-01-01

69

Solid rocket booster thrust vector control subsystem description  

NASA Technical Reports Server (NTRS)

Major Solid Rocket Booster-Thrust Vector Control (SRB-TVC) subsystem components and subcomponents used in the Space Transportation System (STS) are identified. Simplified schematics, detailed schematics, figures, photographs, and data are included to acquaint the reader with the operation, performance, and physical layout as well as the materials and instrumentation used.

Redmon, J., Jr. (compiler)

1983-01-01

70

Application of Lanczos vectors to control design of flexible structures  

NASA Technical Reports Server (NTRS)

This report covers research conducted during the first year of the two-year grant. The research, entitled 'Application of Lanczos Vectors to Control Design of Flexible Structures' concerns various ways to obtain reduced-order mathematical models for use in dynamic response analyses and in control design studies. This report summarizes research described in several reports and papers that were written under this contract. Extended abstracts are presented for technical papers covering the following topics: controller reduction by preserving impulse response energy; substructuring decomposition and controller synthesis; model reduction methods for structural control design; and recent literature on structural modeling, identification, and analysis.

Craig, Roy R., Jr.; Su, Tzu-Jeng

1990-01-01

71

Human African Trypanosomiasis in South Sudan: How Can We Prevent a New Epidemic?  

Microsoft Academic Search

Human African trypanosomiasis (HAT) has been a major public health problem in South Sudan for the last century. Recurrent outbreaks with a repetitive pattern of responding-scaling down activities have been observed. Control measures for outbreak response were reduced when the prevalence decreased and\\/or socio-political crisis erupted, leading to a new increase in the number of cases. This paper aims to

José A. Ruiz-Postigo; José R. Franco; Mounir Lado; Pere P. Simarro

2012-01-01

72

Seroprevalence Survey of American Trypanosomiasis in Central Valley of Toluca  

PubMed Central

American trypanosomiasis is a growing health issue in the Americas. México is an endemic country, where some locations such as in the State of México are considered highly prevalent. In the valley of Toluca city, the capital of the State of Mexico, there exists an apparent high prevalence in dogs. The absence of triatomine vectors suggests that dogs may not be infected. Therefore, we conducted a directed survey to domiciliated and nondomiciliated dogs to reassess dogs' T. cruzi seroprevalence status. HAI and ELISA serologic tests were applied to 124 and 167 serums of domiciliated and nondomiciliated dogs in the target city. Risk factors were estimated, but the results did not show any evidence to assess them. No domiciliated dogs tested positive to both tests, whereas only one non-domiciliated dog resulted positive. This animal may have acquired the infection in an endemic area and then migrated to Toluca. Research results indicate that T. cruzi infection is not actively transmitted among dogs, and it is pointed out that dogs are the main sentinel animal population to evaluate a possible expansion of the territory affected by Chagas' disease. PMID:22649293

Quijano-Hernandez, Israel A.; Castro-Barcena, Alejandro; Barbabosa-Pliego, Alberto; Ochoa-GarcIa, Laucel; Del Angel-Caraza, Javier; Vazquez-Chagoyan, Juan C.

2012-01-01

73

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

74

Thrust vector control algorithm design for the Cassini spacecraft  

NASA Technical Reports Server (NTRS)

This paper describes a preliminary design of the thrust vector control algorithm for the interplanetary spacecraft, Cassini. Topics of discussion include flight software architecture, modeling of sensors, actuators, and vehicle dynamics, and controller design and analysis via classical methods. Special attention is paid to potential interactions with structural flexibilities and propellant dynamics. Controller performance is evaluated in a simulation environment built around a multi-body dynamics model, which contains nonlinear models of the relevant hardware and preliminary versions of supporting attitude determination and control functions.

Enright, Paul J.

1993-01-01

75

[Monitoring human African trypanosomiasis in Central Africa in 2001 and cartography: results and perspectives].  

PubMed

Cases of human African trypanosomiasis are distributed in changing geographical "outbreak areas" that can be visualized over time and space. Because of these variations in distribution, cartography and spatial analysis provide powerful tools for planning surveillance and control strategies. In 1996, the WHO in collaboration with the 15 most endemic countries in Central Africa undertook a program to develop a standardized inter-regional map of trypanosomiasis. This article provides a brief overview of the value of geomatic tools in public health followed by a description of the WHO program and its preliminary results. Also presented in this article is the Trypinfo site being development on the internet to increase the surveillance response-time and improve the feedback system. PMID:11803827

Lucas, P; Fanchey, G; Mouton, C; Jannin, J

2001-01-01

76

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. PMID:23209860

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

2012-01-01

77

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. PMID:16707042

Goh, Kee-Tai; Gubler, Duane J.

2006-01-01

78

American Trypanosomiasis (Also Known as Chagas Disease) Treatment  

MedlinePLUS

... About CDC.gov . Parasites - American Trypanosomiasis (also known as Chagas Disease) Parasites Home Share Compartir Treatment Treatment ... patients may be referred to a specialist, such as a cardiologist, gastroenterologist, or infectious disease specialist. In ...

79

American Trypanosomiasis (Also Known as Chagas Disease) Diagnosis  

MedlinePLUS

... About CDC.gov . Parasites - American Trypanosomiasis (also known as Chagas Disease) Parasites Home Share Compartir Diagnosis Trypansoma ... made after consideration of the patient's clinical findings, as well as by the likelihood of being infected, ...

80

Attitude Control for an Aero-Vehicle Using Vector Thrusting and Variable Speed Control Moment Gyros  

NASA Technical Reports Server (NTRS)

Stabilization of passively unstable thrust-levitated vehicles can require significant control inputs. Although thrust vectoring is a straightforward choice for realizing these inputs, this may lead to difficulties discussed in the paper. This paper examines supplementing thrust vectoring with Variable-Speed Control Moment Gyroscopes (VSCMGs). The paper describes how to allocate VSCMGs and the vectored thrust mechanism for attitude stabilization in frequency domain and also shows trade-off between vectored thrust and VSCMGs. Using an H2 control synthesis methodology in LMI optimization, a feedback control law is designed for a thrust-levitated research vehicle and is simulated with the full nonlinear model. It is demonstrated that VSCMGs can reduce the use of vectored thrust variation for stabilizing the hovering platform in the presence of strong wind gusts.

Shin, Jong-Yeob; Lim, K. B.; Moerder, D. D.

2005-01-01

81

Fault tolerant vector control of induction motor drive  

NASA Astrophysics Data System (ADS)

For electric composed of technical objects hazardous industries, such as nuclear, military, chemical, etc. an urgent task is to increase their resiliency and survivability. The construction principle of vector control system fault-tolerant asynchronous electric. Displaying recovery efficiency three-phase induction motor drive in emergency mode using two-phase vector control system. The process of formation of a simulation model of the asynchronous electric unbalance in emergency mode. When modeling used coordinate transformation, providing emergency operation electric unbalance work. The results of modeling transient phase loss motor stator. During a power failure phase induction motor cannot save circular rotating field in the air gap of the motor and ensure the restoration of its efficiency at rated torque and speed.

Odnokopylov, G.; Bragin, A.

2014-10-01

82

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.” PMID:24626310

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

2013-01-01

83

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

84

Design and test of electromechanical actuators for thrust vector control  

NASA Astrophysics Data System (ADS)

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

1993-05-01

85

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. PMID:24932861

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

86

Autonomous Control of an Autonomous Underwater Vehicle Towing a Vector Sensor Array  

E-print Network

Autonomous Control of an Autonomous Underwater Vehicle Towing a Vector Sensor Array Michael R), and the particular considerations required to allow proper control while towing a 100-meter vector sensor array on autonomous control and communications with a single AUV fitted with a vector sensor array (Fig. 1) operating

Schmidt, Henrik

87

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

88

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. PMID:23497700

2013-01-01

89

139 Dengue vector control: critical needs and opportunities for helping to control the dengue pandemic  

PubMed Central

Aedes aegypti mosquito control is currently the only option for controlling and preventing epidemic dengue and dengue hemorrhagic fever. However, current approaches for vector control are not stemming the rising tide of dengue disease throughout the tropical world. In the absence of a vaccine, new and effective approaches are needed to improve vector control. Novel approaches to prevent dengue virus transmission will be described and discussed, including (1) the Casa Segura approach to prevent dengue transmission in the home, (2) development of a new generation of molecular mosquitocides to address the rise of resistance to existing insecticides, and (3) engineering dengue virus resistant mosquitoes. There is a public health imperative to increase the armamentarium for vector control.

Beaty, Barry

2014-01-01

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

Challenges and future perspective for dengue vector control in the Western Pacific Region  

PubMed Central

Dengue remains a significant public health issue in the Western Pacific Region. In the absence of a vaccine, vector control is the mainstay for dengue prevention and control. In this paper we describe vector surveillance and vector control in the Western Pacific countries and areas. Vector surveillance and control strategies used by countries and areas of the Western Pacific Region vary. Vector control strategies include chemical, biological and environmental management that mainly target larval breeding sites. The use of insecticides targeting larvae and adult mosquitoes remains the mainstay of vector control programmes. Existing vector control tools have several limitations in terms of cost, delivery and long-term sustainability. However, there are several new innovative tools in the pipeline. These include Release of Insects Carrying a Dominant Lethal system and Wolbachia, an endosymbiotic bacterium, to inhibit dengue virus in the vector. In addition, the use of biological control such as larvivorous fish in combination with community participation has potential to be scaled up. Any vector control strategy should be selected based on evidence and appropriateness for the entomological and epidemiological setting and carried out in both inter-epidemic and epidemic periods. Community participation and interagency collaboration are required for effective and sustainable dengue prevention and control. Countries and areas are now moving towards integrated vector management. PMID:23908883

Christophel, Eva Maria; Gopinath, Deyer; Abdur, Rashid Md.; Vectorborne, Other; Diseases, Parasitic

2011-01-01

92

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

93

A general space vector PWM control algorithm for multilevel inverters  

Microsoft Academic Search

To solve the problem of computational complexity in multilevel inverters due to the large number of space vectors and redundant switching states, a simple and general space vector PWM algorithm is proposed. Based on this algorithm, the location of the reference voltage vector can be easily determined and the calculation of dwell times becomes very simple. More importantly, the proposed

Sanmin Wei; Bin Wu; Fahai Li; Congwei Liu

2003-01-01

94

Emergence and Prevalence of Human Vector-Borne Diseases in Sink Vector Populations  

PubMed Central

Vector-borne diseases represent a major public health concern in most tropical and subtropical areas, and an emerging threat for more developed countries. Our understanding of the ecology, evolution and control of these diseases relies predominantly on theory and data on pathogen transmission in large self-sustaining ‘source’ populations of vectors representative of highly endemic areas. However, there are numerous places where environmental conditions are less favourable to vector populations, but where immigration allows them to persist. We built an epidemiological model to investigate the dynamics of six major human vector borne-diseases in such non self-sustaining ‘sink’ vector populations. The model was parameterized through a review of the literature, and we performed extensive sensitivity analysis to look at the emergence and prevalence of the pathogen that could be encountered in these populations. Despite the low vector abundance in typical sink populations, all six human diseases were able to spread in 15–55% of cases after accidental introduction. The rate of spread was much more strongly influenced by vector longevity, immigration and feeding rates, than by transmission and virulence of the pathogen. Prevalence in humans remained lower than 5% for dengue, leishmaniasis and Japanese encephalitis, but substantially higher for diseases with longer duration of infection; malaria and the American and African trypanosomiasis. Vector-related parameters were again the key factors, although their influence was lower than on pathogen emergence. Our results emphasize the need for ecology and evolution to be thought in the context of metapopulations made of a mosaic of sink and source habitats, and to design vector control program not only targeting areas of high vector density, but working at a larger spatial scale. PMID:22629337

Rascalou, Guilhem; Pontier, Dominique; Menu, Frederic; Gourbiere, Sebastien

2012-01-01

95

Community involvement in dengue vector control: cluster randomised trial  

PubMed Central

Objective To assess the effectiveness of an integrated community based environmental management strategy to control Aedes aegypti, the vector of dengue, compared with a routine strategy. Design Cluster randomised trial. Setting Guantanamo, Cuba. Participants 32 circumscriptions (around 2000 inhabitants each). Interventions The circumscriptions were randomly allocated to control clusters (n=16) comprising routine Aedes control programme (entomological surveillance, source reduction, selective adulticiding, and health education) and to intervention clusters (n=16) comprising the routine Aedes control programme combined with a community based environmental management approach. Main outcome measures The primary outcome was levels of Aedes infestation: house index (number of houses positive for at least one container with immature stages of Ae aegypti per 100 inspected houses), Breteau index (number of containers positive for immature stages of Ae aegypti per 100 inspected houses), and the pupae per inhabitant statistic (number of Ae aegypti pupae per inhabitant). Results All clusters were subjected to the intended intervention; all completed the study protocol up to February 2006 and all were included in the analysis. At baseline the Aedes infestation levels were comparable between intervention and control clusters: house index 0.25% v 0.20%, pupae per inhabitant 0.44×10?3 v 0.29×10?3. At the end of the intervention these indices were significantly lower in the intervention clusters: rate ratio for house indices 0.49 (95% confidence interval 0.27 to 0.88) and rate ratio for pupae per inhabitant 0.27 (0.09 to 0.76). Conclusion A community based environmental management embedded in a routine control programme was effective at reducing levels of Aedes infestation. Trial registration Current Controlled Trials ISRCTN88405796. PMID:19509031

2009-01-01

96

Leakage current control of nano-scale full adder cells using input vectors  

Microsoft Academic Search

As CMOS technology scaling continues into the nanoscale domain, static or leakage power consumption becomes a vital design parameter. This paper proposes methods for reducing leakage currents by controlling the input vector in nano-scale full adder cells operating in either active mode or standby mode. With proper input vector control, it is possible to obtain over 40% leakage power savings

Savithra Eratne; Pradeep Nair; Eugene John

2007-01-01

97

A Review of Ecological Factors Associated with the Epidemiology of Wildlife Trypanosomiasis in the Luangwa and Zambezi Valley Ecosystems of Zambia  

PubMed Central

Trypanosomiasis has been endemic in wildlife in Zambia for more than a century. The disease has been associated with neurological disorders in humans. Current conservation strategies by the Zambian government of turning all game reserves into state-protected National Parks (NPs) and game management areas (GMAs) have led to the expansion of the wildlife and tsetse population in the Luangwa and Zambezi valley ecosystem. This ecological niche lies in the common tsetse fly belt that harbors the highest tsetse population density in Southern Africa. Ecological factors such as climate, vegetation and rainfall found in this niche allow for a favorable interplay between wild reservoir hosts and vector tsetse flies. These ecological factors that influence the survival of a wide range of wildlife species provide adequate habitat for tsetse flies thereby supporting the coexistence of disease reservoir hosts and vector tsetse flies leading to prolonged persistence of trypanosomiasis in the area. On the other hand, increase in anthropogenic activities poses a significant threat of reducing the tsetse and wildlife habitat in the area. Herein, we demonstrate that while conservation of wildlife and biodiversity is an important preservation strategy of natural resources, it could serve as a long-term reservoir of wildlife trypanosomiasis. PMID:22693499

Munang'andu, Hetron Mweemba; Siamudaala, Victor; Munyeme, Musso; Nalubamba, King Shimumbo

2012-01-01

98

40 CFR 258.22 - Disease vector control.  

...of human health and the environment. (b) For purposes of this section, disease vectors means any rodents, flies, mosquitoes, or other animals, including insects, capable of transmitting disease to...

2014-07-01

99

Treatment options for second-stage gambiense human African trypanosomiasis.  

PubMed

Treatment of second-stage gambiense human African trypanosomiasis relied on toxic arsenic-based derivatives for over 50 years. The availability and subsequent use of eflornithine, initially in monotherapy and more recently in combination with nifurtimox (NECT), has drastically improved the prognosis of treated patients. However, NECT logistic and nursing requirements remain obstacles to its deployment and use in peripheral health structures in rural sub-Saharan Africa. Two oral compounds, fexinidazole and SCYX-7158, are currently in clinical development. The main scope of this article is to discuss the potential impact of new oral therapies to improve diagnosis-treatment algorithms and patients' access to treatment, and to contribute to reach the objectives of the recently launched gambiense human African trypanosomiasis elimination program. PMID:25204360

Eperon, Gilles; Balasegaram, Manica; Potet, Julien; Mowbray, Charles; Valverde, Olaf; Chappuis, François

2014-11-01

100

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. PMID:24990155

2014-01-01

101

[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

102

High-Speed Current dq PI Controller for Vector Controlled PMSM Drive  

PubMed Central

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

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

2014-01-01

103

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

104

The Effective Population Size of Malaria Mosquitoes: Large Impact of Vector Control  

PubMed Central

Malaria vectors in sub-Saharan Africa have proven themselves very difficult adversaries in the global struggle against malaria. Decades of anti-vector interventions have yielded mixed results—with successful reductions in transmission in some areas and limited impacts in others. These varying successes can be ascribed to a lack of universally effective vector control tools, as well as the development of insecticide resistance in mosquito populations. Understanding the impact of vector control on mosquito populations is crucial for planning new interventions and evaluating existing ones. However, estimates of population size changes in response to control efforts are often inaccurate because of limitations and biases in collection methods. Attempts to evaluate the impact of vector control on mosquito effective population size (Ne) have produced inconclusive results thus far. Therefore, we obtained data for 13–15 microsatellite markers for more than 1,500 mosquitoes representing multiple time points for seven populations of three important vector species—Anopheles gambiae, An. melas, and An. moucheti—in Equatorial Guinea. These populations were exposed to indoor residual spraying or long-lasting insecticidal nets in recent years. For comparison, we also analyzed data from two populations that have no history of organized vector control. We used Approximate Bayesian Computation to reconstruct their demographic history, allowing us to evaluate the impact of these interventions on the effective population size. In six of the seven study populations, vector control had a dramatic impact on the effective population size, reducing Ne between 55%–87%, the exception being a single An. melas population. In contrast, the two negative control populations did not experience a reduction in effective population size. This study is the first to conclusively link anti-vector intervention programs in Africa to sharply reduced effective population sizes of malaria vectors. PMID:23271973

Athrey, Giridhar; Hodges, Theresa K.; Reddy, Michael R.; Overgaard, Hans J.; Matias, Abrahan; Ridl, Frances C.; Kleinschmidt, Immo; Caccone, Adalgisa; Slotman, Michel A.

2012-01-01

105

[Vector control for armed forces: a historical requirement requiring continual adaptation].  

PubMed

From time immemorial vector-borne diseases have decimated the fighting capacity of armies and caused suspension or cancellation of military operations. For this reason vector control strategies have always been a major requirement in ensuring the operational readiness of armed forces. Using malaria as an example, this article provides an update on vector control methods used by the French army in terms of available tools and of their applications in function of the operational situation. In coming years vector control strategies must be modernized not only by assessing vector-borne disease threats in the field and improving resources available to troops but also by professionalizing this service by creating specialized units. PMID:19545043

Pagès, F

2009-04-01

106

Space Vector PWM Control Synthesis for a H-Bridge Drive in Electric Vehicles  

E-print Network

,245" #12;­ by using multilevel inverters topologies used in a high power traction drive [5 with a synthesis of Space Vector PWM control methods applied for a H-bridge inverter feeding a 3-phase Permanent--Motor drives, Inverters, Space vector pulse width modulation (SVPWM), Permanent magnet machines, Semiconductor

Paris-Sud XI, Université de

107

An Experimental Research on Vector Control of Induction Motor Based on Simple Model  

Microsoft Academic Search

\\u000a Given the heavy computation, easy saturation and cumulate errors of conventional direct vector control, the vector control\\u000a of induction motor based on simple model is studied and the detailed scheme is described on the basis of the decomposing and\\u000a approximating the rotor flux. Because of the direct closed-loop control of the magnetizing current and the torque current\\u000a and the complex

Yinhai Zhang; Jinfa Ge; Weixia Liu; Qin Wang

2009-01-01

108

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

109

Immunosuppression in bovine trypanosomiasis: Field studies using foot-and-mouth disease vaccine and clostridial vaccine  

Microsoft Academic Search

The immunosuppressive effect of naturally acquired trypanosomiasis was investigated in four groups of zebu cattle maintained in an area of high tsetse fly challenge in Western Ethiopia. Two of the groups remained without chemoprophylaxis against trypanosomiasis and became parasitaemic. The animals of one of these two groups received a polyvalent foot-and-mouth disease vaccine and the cattle of the other group

J. M. Scott; R. G. Pegram; P. H. Holmes; T. W. F. Pay; P. A. Knight; F. W. JENurbros; G. M. Urquhart

1977-01-01

110

EXPLICIT MODEL PREDICTIVE CONTROL OF A HYBRID SYSTEM USING SUPPORT VECTOR MACHINES  

Microsoft Academic Search

The objective of this work is to study the capabili ties of support vector machines for approximating the complex control law arising from model predictive control of a hybrid MIMO-system. By approximating the control law, an explicit formulation can be obtained, which is computationally less intensive for on-line use. The explicit model predictive control approach is applied to a simulated

Bernt M. Åkesson; Mats J. Nikus; Hannu T. Toivonen

111

Modeling and Simulation of Matrix Converter Using Space Vector Control Algorithm  

Microsoft Academic Search

In this work, Matlab\\/Simulink modeling and simulation of the three - phase matrix converter feeding a passive RL load have been performed using the space vector control algorithm. The model has been designed to support real time implementation with a simulation supported DSP control board. The algorithm uses a simpler method than the other control algorithms to control the input

Ebubekir Erdem; Yetkin Tatar; S. Stinter

2005-01-01

112

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

E-print Network

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 ...

Bomblies, Arne

113

Development and qualification of a STAR 48 rocket motor with thrust vector control  

NASA Astrophysics Data System (ADS)

A thrust vector control (TVC) nozzle for use on the STAR 48 rocket motor (STAR 48V) has been developed for use on the COMET program aboard the Conestoga launch vehicle. The first stages of qualification testing have been completed. The first STAR 48V has been successfully static-tested. The flexseal TVC nozzle design is based upon the qualified and flight-proven fixed nozzle design used on spin-stabilized spacecraft. The flexseal design and fabrication approach benefit from flight-proven and man-rated Thiokol Corporation flexseal designs. The thrust vector control system provides vectoring capability to 4 deg for use on nonspinning spacecraft. Electromechanical actuators coupled with a closed-loop controller provide thrust vector positioning and spacecraft attitude control.

Hamke, R.; Rade, J.; Weldin, R.

1992-07-01

114

The potential for environmental management to contribute to malaria vector control in western Niger  

E-print Network

This thesis investigated the potential for environmental management techniques to contribute to malaria vector control in Niger, with a case study on Banizoumbou village in western Niger. Numerical modeling was used to ...

Gianotti, Rebecca L. (Rebecca Louise)

2008-01-01

115

Controlling trilevel center-split power quality compensator by 3-dimensional space vector modulation  

Microsoft Academic Search

In the past researches, strategies based on hysteresis control are proposed for controlling trilevel 3-leg center-split inverter, which can be used as a shunt power quality compensator for three-phase four-wire system. In this paper, results indicate that the complicated 3-dimensional (3D) space vector allocation of the trilevel center-split inverter can be simplified into six space vector regions of two-level center-split

Ning-Yi Dai; Man-Chung Wong; Ying-Duo Han

2003-01-01

116

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. PMID:21610862

Barbu, Corentin; Dumonteil, Eric; Gourbière, Sébastien

2011-01-01

117

Expansion of operating limits for permanent magnet motor by current vector control considering inverter capacity  

Microsoft Academic Search

The current vector control method of PM (permanent magnet) motors is examined to expand the operating limits associated with inverter capacity. This control method is optimum in the sense of deriving maximum output torque within the voltage and current constraints. The effects of motor parameters are examined by computer simulation. The operating limits are greatly expanded by controlling the d-

S. Morimoto; Y. Takeda; T. Hirasa; K. Taniguchi

1990-01-01

118

Design and test of a high power electromechanical actuator for thrust vector control  

NASA Astrophysics Data System (ADS)

NASA-Marshall is involved in the development of electromechanical actuators (EMA) for thrust-vector control (TVC) system testing and implementation in spacecraft control/gimballing systems, with a view to the replacement of hydraulic hardware. TVC system control is furnished by solid state controllers and power supplies; a pair of resolvers supply position feedback to the controller for precise positioning. Performance comparisons between EMA and hydraulic TVC systems are performed.

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

1992-07-01

119

A restructurable VLSI robotics vector processor architecture for real-time control  

Microsoft Academic Search

The authors propose a restructurable architecture based on a VLSI robotics vector processor (RVP) chip. It is specially tailored to exploit parallelism in the low-level matrix\\/vector operations characteristic of the kinematics and dynamics computations required for real-time control. The RVP is composed of three tightly synchronized 32-bit floating-point processors to provide adequate computational power. Besides adder and multiplier units in

PONNUSWAMY SADAYAPPAN; YONG-LONG CALVIN LING; KARL W. OLSON; DAVID E. ORIN

1989-01-01

120

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

121

Direct torque control of induction machines using space vector modulation  

Microsoft Academic Search

A direct induction machine torque control method based on predictive, deadbeat control of the torque and flux is presented. By estimating the synchronous speed and the voltage behind the transient reactance, the change in torque and flux over the switching period is calculated. The stator voltage required to cause the torque and flux to be equal to their respective reference

Thomas G. Habetler; Francesco Profumo; Michele Pastorelli; Leon M. Tolbert

1992-01-01

122

Adaptive speed identification for vector control of induction motors without rotational transducers  

Microsoft Academic Search

A model-reference adaptive system (MRAS) for the estimation of induction motor speed from measured terminal voltages and currents is described. The estimated speed is used as feedback in a vector control system, thus achieving moderate bandwidth speed control without the use of shaft-mounted transducers. This technique is less complex and more stable than previous MRAS tacholess drives. It has been

C. Schauder

1992-01-01

123

Adaptive speed identification for vector control of induction motors without rotational transducers  

Microsoft Academic Search

A model-reference adaptive system (MRAS) for the estimation of induction motor speed from measured terminal voltages and currents is described. The estimated speed is used as feedback in a vector control system, thus achieving moderate bandwidth speed control without the use of shaft-mounted transducers. This technique is less complex and more stable than previous MRAS tacholess drives. It was implemented

Colin Schauder

1989-01-01

124

A Rotor Parameter Identification Scheme for Vector-Controlled Induction Motor Drives  

Microsoft Academic Search

A rotor parameter identification technique for the purpose of updating the control gains of an induction motor vector controller is described. The approach utilizes the current source nature of a current-regulated PWM inverter by injecting a prescribed negative sequence current perturbation signal. The corresponding negative sequence voltage is sensed and decomposed into its d and q components. By injecting the

Takayoshi Matsuo; Thomas A. Lipo

1985-01-01

125

Adaptive Inverse Control System Based on Least Squares Support Vector Machines  

Microsoft Academic Search

\\u000a Adaptive inverse control (AIC) uses three adaptive filters: plant model, controller and disturbance canceller. A kind of hybrid\\u000a AIC system based on Least Squares Support Vector Machines (LS-SVMs) is proposed in this paper. It has a PID controller to\\u000a compensate the control signal error. A kind of adaptive disturbance canceller based on LS-SVM is also proposed. It can optimally\\u000a eliminate

Xiaojing Liu; Jianqiang Yi; Dongbin Zhao

2005-01-01

126

[The epidemiology of human African trypanosomiasis: a complex multifactorial history].  

PubMed

Sleeping sickness has long been known from descriptions by Arab merchants and slave traders. However it was not until 1901 that Forbes discovered the offending agent and 1903 that Bruce described the role of the tsetse fly. The basic epidemiological transmission cycle was described less than 10 years later. Although the main outline of the original model can still be considered as sound, subsequent research has greatly expanded our knowledge. Molecular biology has identified different parasites causing clinical forms of varying severity. Understanding of the antigenic variability to the parasite has also improved. While available data is still insufficient on the relationship between the vector and human being and the vector and the animal reservoir, the behavior of glossinae is well-documented. Current geographical information systems have promoted understanding of the distribution of the disease to enhance targeting of screening, treatment, and vector-control activities. To repeat the success achieved in controlling the disease in endemic countries in the 1960s, it will be necessary to develop new strategies based on this new knowledge. PMID:11803821

Cattand, P

2001-01-01

127

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

128

Sustainability of vector control strategies in the Gran Chaco Region: current challenges and possible approaches  

PubMed Central

Sustainability has become a focal point of the international agenda. At the heart of its range of distribution in the Gran Chaco Region, the elimination of Triatoma infestans has failed, even in areas subject to intensive professional vector control efforts. Chagas disease control programs traditionally have been composed of two divorced entities: a vector control program in charge of routine field operations (bug detection and insecticide spraying) and a disease control program in charge of screening blood donors, diagnosis, etiologic treatment and providing medical care to chronic patients. The challenge of sustainable suppression of bug infestation and Trypanosoma cruzi transmission can be met through integrated disease management, in which vector control is combined with active case detection and treatment to increase impact, cost-effectiveness and public acceptance in resource-limited settings. Multi-stakeholder involvement may add sustainability and resilience to the surveillance system. Chagas vector control and disease management must remain a regional effort within the frame of sustainable development rather than being viewed exclusively as a matter of health pertinent to the health sector. Sustained and continuous coordination between governments, agencies, control programs, academia and the affected communities is critical. PMID:19753458

Gurtler, Ricardo E

2011-01-01

129

A community empowerment strategy embedded in a routine dengue vector control programme: a cluster randomised controlled trial.  

PubMed

The non-sustainability of vertically organised dengue vector control programmes led to pleas for changing the emphasis towards community-based strategies. We conducted a cluster randomised controlled trial with 16 intervention and 16 control clusters to test the effectiveness of a community empowerment strategy intertwined with the routine dengue vector control programme in La Lisa, Havana City, Cuba. The intervention included four components on top of routine control: organisation and management; entomological risk surveillance; capacity building; and community work for vector control. In the control clusters, routine activities continued without interference. The community participation score increased from 1.4 to 3.4. Good knowledge of breeding sites increased by 52.8% and 27.5% in the intervention and control clusters, respectively. There were no changes in adequate Aedes aegypti control practices at household level in the control clusters, but in the intervention clusters adequacy increased by 36.2%. At baseline, the Breteau indices (BI) were approximately 0.1 and were comparable; they fluctuated over time but became different with the launch of the community-based dengue control activities in the intervention clusters. Over the intervention period, the BI remained 53% (95% CI 22-92%) lower in these clusters than in the control clusters. The empowerment strategy increased community involvement and added effectiveness to routine A. aegypti control. PMID:22465423

Castro, Marta; Sánchez, Lizet; Pérez, Dennis; Carbonell, Nestor; Lefèvre, Pierre; Vanlerberghe, Veerle; Van der Stuyft, Patrick

2012-05-01

130

A Vector-Controlled Cycloconverter Drive for an Icebreaker  

Microsoft Academic Search

A high-power high-performance variable-speed drive system using a cycloconverter-fed synchronous motor is described. The control uses the field-orientation principle to give the drive system good steady-state and dynamic performance criteria. The accuracy of the field orientation is improved with the use of current regulators operating in the airgap flux reference frame. The system was manufactured to deliver 16 000 hp

Walter A. Hill; Richard A. Turton; Robert J. Dungan; C. Louis Schwalm

1987-01-01

131

Multiple Insecticide Resistance: An Impediment to Insecticide-Based Malaria Vector Control Program  

Microsoft Academic Search

BackgroundIndoor Residual Spraying (IRS), insecticide-treated nets (ITNs) and long-lasting insecticidal nets (LLINs) are key components in malaria prevention and control strategy. However, the development of resistance by mosquitoes to insecticides recommended for IRS and\\/or ITNs\\/LLINs would affect insecticide-based malaria vector control. We assessed the susceptibility levels of Anopheles arabiensis to insecticides used in malaria control, characterized basic mechanisms underlying resistance,

Delenasaw Yewhalaw; Fantahun Wassie; Walter Steurbaut; Pieter Spanoghe; Wim van Bortel; Leen Denis; Dejene A. Tessema; Yehenew Getachew; Marc Coosemans; Luc Duchateau; Niko Speybroeck; Immo A. Hansen

2011-01-01

132

Fast efficiency optimization techniques for the indirect vector-controlled induction motor drives  

Microsoft Academic Search

This paper presents two simple and very useful techniques for the efficiency optimization of the indirect vector-controlled induction motor drives. In the synchronously rotating reference frame the flux-producing current is controlled until the power at the DC link is minimum. Of the two techniques, the first method controls the flux-producing current in a regular and smooth manner. The second technique

Chandan Chakraborty; Yoichi Hori

2003-01-01

133

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. PMID:23318237

Espino, Fe; Marco, Jesusa; Salazar, Nelia P; Salazar, Ferdinand; Mendoza, Ysadora; Velazco, Aldwin

2012-01-01

134

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

135

Blazed vector gratings fabricated using photosensitive polymer liquid crystals and control of polarization diffraction  

NASA Astrophysics Data System (ADS)

The blazed vector grating possessing antisymmetric distributions of the birefringence were fabricated by exposing the line-focused linearly polarized ultraviolet light on the photosensitive polymer liquid crystals. The polarization states of the diffraction beams can be highly and widely controlled by designing the blazed structures, and the diffraction properties were well-explained by Jones calculus.

Ono, Hiroshi; Kuzuwata, Mitsuru; Sasaki, Tomoyuki; Noda, Kohei; Kawatsuki, Nobuhiro

2014-03-01

136

Application of the DRBEM to model ablation characteristics of a thrust vector control vane  

Microsoft Academic Search

A dual reciprocity boundary element method (DRBEM) is implemented to predict ablation in model thrust vector control (TVC) vanes. A moving front algorithm is described. Experimental data are available from tests performed on scaled vanes. Numerical results for recession of quarter-scale and half-scale vanes compare well with experimental data. Future work includes full coupling of the flowfield and conduction solutions.

E. Divo; A. Kassab; R. Cavalleri

1999-01-01

137

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

138

Malaria vector control at a crossroads: public health entomology and the drive to elimination.  

PubMed

Vector control has been at the core of successful malaria control. However, a dearth of field-oriented vector biologists threatens to undermine global reductions in malaria burden. Skilled cadres are needed to manage insecticide resistance, to maintain coverage with current interventions, to develop new paradigms for tackling 'residual' transmission and to target interventions as transmission becomes increasingly heterogeneous. Recognising this human resource crisis, in September 2013, WHO Global Malaria Programme issued guidance for capacity building in entomology and vector control, including recommendations for countries and implementing partners. Ministries were urged to develop long-range strategic plans for building human resources for public health entomology and vector control (including skills in epidemiology, geographic information systems, operational research and programme management) and to set in place the requisite professional posts and career opportunities. Capacity building and national ownership in all partner projects and a clear exit strategy to sustain human and technical resources after project completion were emphasised. Implementing partners were urged to support global and regional efforts to enhance public health entomology capacity. While the challenges inherent in such capacity building are great, so too are the opportunities to establish the next generation of public health entomologists that will enable programmes to continue on the path to malaria elimination. PMID:25009173

Mnzava, Abraham P; Macdonald, Michael B; Knox, Tessa B; Temu, Emmanuel A; Shiff, Clive J

2014-09-01

139

Solid rocket booster thrust vector control subsystem verification test (V-2) report  

NASA Technical Reports Server (NTRS)

The results of the verification testing sequence V-2 performed on the space shuttle solid rocket booster thrust vector control subsystem are presented. A detailed history of the hot firings plus additional discussion of the auxiliary power unit and the hydraulic component performance is presented. The test objectives, data, and conclusions are included.

Pagan, B.

1979-01-01

140

Certifying achievement in the control of Chagas disease native vectors: what is a viable scenario?  

PubMed Central

As an evaluation scheme, we propose certifying for “control”, as alternative to “interruption”, of Chagas disease transmission by native vectors, to project a more achievable and measurable goal and sharing good practices through an “open online platform” rather than “formal certification” to make the key knowledge more accumulable and accessible. PMID:25317713

Hashimoto, Ken; Yoshioka, Kota

2014-01-01

141

Population control of the malaria vector Anopheles pseudopunctipennis by habitat manipulation.  

PubMed Central

Insect vector-borne diseases continue to present a major challenge to human health. Understanding the factors that regulate the size of mosquito populations is considered fundamental to the ability to predict disease transmission rates and for vector population control. The mosquito, Anopheles pseudopunctipennis, a vector of Plasmodium spp., breeds in riverside pools containing filamentous algae in Mesoamerica. Breeding pools along 3 km sections of the River Coatan, Chiapas, Mexico were subjected to algal extraction or left as controls in a cross-over trial extending over 2 years. Initial densities of An. pseudopunctipennis larvae were directly proportional to the prevalence of filamentous algae in each breeding site. The extraction of algae brought about a striking decline in the density of An. pseudopunctipennis larvae sustained for about six weeks, and a concurrent reduction in the adult population in both years of the study. Mark-release experiments indicated that dispersal from adjacent untreated areas was unlikely to exert an important influence on the magnitude of mosquito control that we observed. Habitat manipulation by extraction of filamentous algae offers a unique opportunity for sustainable control of this malaria vector. This technique may represent a valuable intervention, complimenting insecticide spraying of households, to minimize Plasmodium transmission rates in Mesoamerica. PMID:15475337

Bond, J. Guillermo; Rojas, Julio C.; Arredondo-Jiménez, Juan I.; Quiroz-Martínez, Humberto; Valle, Javier; Williams, Trevor

2004-01-01

142

An air-gap-flux-oriented vector controller for stable operation of bearingless induction motors  

Microsoft Academic Search

A bearingless induction machine has combined characteristics of an induction motor and magnetic bearings. It is known that the magnetic suspension of the rotor becomes unstable at overload operation, particularly in transient conditions. A novel air-gap-flux-oriented vector control scheme has been proposed to operate the bearingless induction motor during the high torque acceleration period. It has been found that there

Takahiro Suzuki; Akira Chiba; M. Azizur Rahman; Tadashi Fukao

2000-01-01

143

Hybrid electrical power source for thrust vector control electromechanical actuation  

SciTech Connect

The next generation of launch vehicles propose to use electromechanical actuators (EMA`s) for engine gimbaling and aerosurface control to eliminate hydraulics and its associated systems and problems. The new actuation systems are not without their own challenges. An EMA`s duty cycle has two components: a high power pulse to initiate and perform the actuation, and a nominal load to maintain position. Conventional batteries must be sized to meet the pulse power requirement while maintaining a bus voltage in range to satisfy the needs of the EMA control electronics, and therein lies the problem. Restricting the voltage sag limits the discharge rate of the battery and therefore requires an increase in the Amp-hour rating, which relates directly to an increase in weight. An option to lower power source weight is a hybrid source consisting of a conventional battery and a capacitor bank. A hybrid source of this type would utilize the power density strengths of a capacitor bank to meet the high power pulse demands, and the energy density strengths of a battery to provide average power and capacitor recharging. Testing has been performed at NASA`s Marshall Space Flight Center (MSFC) with support from Auburn University`s Space Power Institute to investigate the validity of the hybrid power source concept. This proof-of-concept testing used chemical double layer (CDL) capacitor technology in the form of a {approx}5 farad-270 volt capacitor bank, standard deep cycle marine lead-acid batteries, and a 25 horse power EMA developed at MSFC. The test data was used to size a flight type Ag-Zn battery to perform the same task in a battery-only configuration, and also size a battery for a hybrid configuration. Test results and analysis show that a >50% weight savings can be realized with this type of hybrid power source with no negative effect on performance. These results support the need for further development in the area of CDL capacitors and hybrid configurations.

Hall, D.K. [NASA, Huntsville, AL (United States). Marshall Space Flight Center; Merryman, S.A. [Auburn Univ., AL (United States). Space Power Inst.

1995-12-31

144

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

145

Revising EPA's guidance for controlling pathogens and vector attraction in biosolids  

SciTech Connect

EPA's guidance document, Environmental Regulations and Technology: Control of Pathogens and Vector Attraction in Sewage Sludge (so called White House Document) is under revision. Planned changes, additions, and clarifications relate to the following topics: additional information on pathogens in the environment, intent and application of time and temperature requirements, intent and application site access restrictions, meeting vector attraction reduction requirements, composting guidelines, testing frequency and methodology, and role of the Pathogen Equivalency Committee (PEC). Comments received in the more than six years since the 40CFR Part 503 Regulation went into effect and from regulatory personnel as well as the regulated community and their consultants are being addressed.

Smith, J.E. Jr.

1999-07-01

146

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. PMID:24799896

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

2014-01-01

147

Dynamic voltage restorer based on voltage-space-vector PWM control  

Microsoft Academic Search

A dynamic voltage restorer (DVR) based on the voltage-space-vector pulsewidth-modulation algorithm is presented. Phase-jump compensation is achieved using a software phase-locked loop and a lead-acid battery energy store. A battery-charging control technique using the DVR itself is also described. To validate the control of the DVR, a three-phase prototype with a power rating of 10 kVA has been successfully developed.

Changjiang Zhan; Vigna Kumaran Ramachandaramurthy; Atputharajah Arulampalam; Chris Fitzer; Stylianos Kromlidis; M. Bames; Nicholas Jenkins

2001-01-01

148

GA-based support vector machines for adaptive power system damping controller of SMES  

Microsoft Academic Search

This paper proposes the application of support vector machines (SVMs) to design of an adaptive power system damping controller for superconducting magnetic energy storage (SMES). A genetic algorithm is used to optimize the SVM parameters based on k-fold cross-validation. The SVMs for SMES controllers are trained by the data obtained from a multi-machine power system, and the optimal SVM parameters.

Jonglak Pahasa; Issarachai Ngamroo

2010-01-01

149

Virus-vectored immunocontraception to control feral cats on islands: a mathematical model  

Microsoft Academic Search

Summary 1. Feral cats Felis catus introduced onto oceanic islands pose a major ecological threat to endemic vertebrates, but their control is diÅcult. Immunocontraception has not been considered previously as a method for their control or eradication, and therefore we used a modelling approach to assess whether virus-vectored immunocontraception (VVIC) might be eÄective. 2. We compared the relative eÅciency of

Franck Courchamp; Stephen J. Cornell

2000-01-01

150

Legal aspects of public health: difficulties in controlling vector-borne and zoonotic diseases in Brazil.  

PubMed

In recent years, vector-borne and zoonotic diseases have become a major challenge for public health. Dengue fever and leptospirosis are the most important communicable diseases in Brazil based on their prevalence and the healthy life years lost from disability. The primary strategy for preventing human exposure to these diseases is effective insect and rodent control in and around the home. However, health authorities have difficulties in controlling vector-borne and zoonotic diseases because residents often refuse access to their homes. This study discusses aspects related to the activities performed by Brazilian health authorities to combat vector-borne and zoonotic diseases, particularly difficulties in relation to the legal aspect, which often impede the quick and effective actions of these professionals. How might it be possible to reconcile the need to preserve public health and the rule on the inviolability of the home, especially in the case of abandoned properties or illegal residents and the refusal of residents to allow the health authority access? Do residents have the right to hinder the performance of health workers even in the face of a significant and visible focus of disease transmission? This paper argues that a comprehensive legal plan aimed at the control of invasive vector-borne and zoonotic diseases including synanthropic animals of public health importance should be considered. In addition, this paper aims to bridge the gap between lawyers and public health professionals and to facilitate communication between them. PMID:25051187

Mendes, Marcílio S; de Moraes, Josué

2014-11-01

151

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

152

Direct torque controlled space vector modulated induction motor fed by a Z-source inverter for electric vehicles  

Microsoft Academic Search

This paper proposes a new closed loop speed control of an induction motor fed by a high performance Z-source inverter (ZSI), the speed control is based on direct torque control space vector modulation (DTC-SVM) control strategy. The modified space vector modulation (MSVM) is used to insert the shoot-through state within the switching signals for the ZSI. A dual loop controller

Omar Ellabban; Joeri Van Mierlo; Philippe Lataire

2011-01-01

153

Aparasitemic serological suspects in Trypanosoma brucei gambiense human African trypanosomiasis: a potential human reservoir of parasites?  

PubMed

The serological and parasitological tests used for Trypanosoma brucei gambiense human African trypanosomiasis (HAT) diagnosis have low specificity and sensitivity, respectively, and in the field, control program teams are faced with subjects with positive serology but negative parasitology who remain untreated. The aim of this work was to explore, using PCR tool, the significance of these aparasitemic serological suspects. Since discordant PCR results have been observed earlier with different extraction methods, two DNA extraction methods were compared (the Chelex 100 resin and the DNeasy Tissue kit). The study was conducted on 604 blood samples: 574 from parasitologically confirmed patients, aparasitemic serological suspects and endemic controls collected in Côte d'Ivoire and 30 from healthy volunteers collected in France. No significant differences were observed between the PCR results obtained with the two extraction methods. Concerning PCR, problems of reproducibility and discordances with both serological and parasitological test results were observed, mainly for the aparasitemic serological suspects. In addition to previous results that pointed to the existence of non-virulent or non-pathogenic trypanosome strains and of individual susceptibility leading to long term seropositivity without detectable parasitaemia but positive PCR, the results of this study support the notion of a long lasting human reservoir that may contribute to the maintenance or periodic resurgences of HAT in endemic foci. PMID:16723098

Koffi, M; Solano, P; Denizot, M; Courtin, D; Garcia, A; Lejon, V; Büscher, P; Cuny, G; Jamonneau, V

2006-05-01

154

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

155

American trypanosomiasis (Chagas' disease) in Central American immigrants.  

PubMed

A survey was conducted to determine the prevalence of infection with Trypanosoma cruzi, the protozoan etiologic agent of American trypanosomiasis (Chagas' disease), among Nicaraguan and Salvadoran immigrants living in the Washington, D.C., area. The serum samples of study subjects were tested for reactivity with T. cruzi antigens in an enzyme-linked immunosorbent assay, and also tested for antibody specific for the 72 and 90 kilodalton (kDa) surface glycoproteins of the parasite in an immunoprecipitation and electrophoresis procedure. Xenodiagnosis using reduviid bugs to detect parasites, and clinical evaluations for cardiac and gastrointestinal disease were performed in patients in whom results of both serologic tests were positive. Of 205 subjects studied, 4.9 percent were infected with T. cruzi, and parasites were isolated from 50 percent of those in whom xenodiagnosis was attempted. No significant cardiac or gastrointestinal abnormalities were detected in the six infected patients who were evaluated clinically. These findings suggest that a sizable proportion of persons in this immigrant group are infected with this organism. Thus, routine serologic testing for antibody to T. cruzi may be warranted in immigrants from these countries, especially in view of the potentially serious consequences of infection with this parasite, and also because of the risk of transmission of T. cruzi by blood transfusion. PMID:3107385

Kirchhoff, L V; Gam, A A; Gilliam, F C

1987-05-01

156

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

NASA Astrophysics Data System (ADS)

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 pool persistence time to less than the time needed for establishment of mosquito breeding, approximately 7 days. Undertaking soil surface plowing can also reduce pool persistence time by increasing the infiltration rate through an existing pool basin. Reduction of the pool persistence time to less than the rainfall interstorm period increases the frequency of pool drying events, removing habitat for subadult mosquitoes. Both management approaches could potentially be considered within a given context. This investigation demonstrates that management methods that modify the hydrologic environment have significant potential to contribute to malaria vector control in water-limited, Sahelian Africa.

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

2009-08-01

157

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. PMID:24069492

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

2013-01-01

158

In silico models for predicting vector control chemicals targeting Aedes aegypti  

PubMed Central

Human arboviral diseases have emerged or re-emerged in numerous countries worldwide due to a number of factors including the lack of progress in vaccine development, lack of drugs, insecticide resistance in mosquitoes, climate changes, societal behaviours, and economical constraints. Thus, Aedes aegypti is the main vector of the yellow fever and dengue fever flaviviruses and is also responsible for several recent outbreaks of the chikungunya alphavirus. As for the other mosquito species, the A. aegypti control relies heavily on the use of insecticides. However, because of increasing resistance to the different families of insecticides, reduction of Aedes populations is becoming increasingly difficult. Despite the unquestionable utility of insecticides in fighting mosquito populations, there are very few new insecticides developed and commercialized for vector control. This is because the high cost of the discovery of an insecticide is not counterbalanced by the ‘low profitability’ of the vector control market. Fortunately, the use of quantitative structure–activity relationship (QSAR) modelling allows the reduction of time and cost in the discovery of new chemical structures potentially active against mosquitoes. In this context, the goal of the present study was to review all the existing QSAR models on A. aegypti. The homology and pharmacophore models were also reviewed. Specific attention was paid to show the variety of targets investigated in Aedes in relation to the physiology and ecology of the mosquito as well as the diversity of the chemical structures which have been proposed, encompassing man-made and natural substances. PMID:25275884

Devillers, J.; Lagneau, C.; Lattes, A.; Garrigues, J.C.; Clemente, M.M.; Yebakima, A.

2014-01-01

159

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; Rasib, Abdul; Darus, Azlan; Ting, Anselm Su

2014-11-01

160

In silico models for predicting vector control chemicals targeting Aedes aegypti.  

PubMed

Human arboviral diseases have emerged or re-emerged in numerous countries worldwide due to a number of factors including the lack of progress in vaccine development, lack of drugs, insecticide resistance in mosquitoes, climate changes, societal behaviours, and economical constraints. Thus, Aedes aegypti is the main vector of the yellow fever and dengue fever flaviviruses and is also responsible for several recent outbreaks of the chikungunya alphavirus. As for the other mosquito species, the A. aegypti control relies heavily on the use of insecticides. However, because of increasing resistance to the different families of insecticides, reduction of Aedes populations is becoming increasingly difficult. Despite the unquestionable utility of insecticides in fighting mosquito populations, there are very few new insecticides developed and commercialized for vector control. This is because the high cost of the discovery of an insecticide is not counterbalanced by the 'low profitability' of the vector control market. Fortunately, the use of quantitative structure-activity relationship (QSAR) modelling allows the reduction of time and cost in the discovery of new chemical structures potentially active against mosquitoes. In this context, the goal of the present study was to review all the existing QSAR models on A. aegypti. The homology and pharmacophore models were also reviewed. Specific attention was paid to show the variety of targets investigated in Aedes in relation to the physiology and ecology of the mosquito as well as the diversity of the chemical structures which have been proposed, encompassing man-made and natural substances. PMID:25275884

Devillers, J; Lagneau, C; Lattes, A; Garrigues, J C; Clémenté, M M; Yébakima, A

2014-01-01

161

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

162

Hepatic microsomal alterations during chronic trypanosomiasis in the field vole, Microtus montanus.  

PubMed

The field vole, Microtus montanus, was used as a model system to evaluate the chronic effects of infection by Trypanosoma brucei gambiense on hepatic mixed-function oxidase activity. At day 28 post inoculation there was a 97% increase in liver wet weight per g body weight. A portion of the increase (21%) was accounted for by tissue edema which occurred after day 14 of infection. Total hepatic cytochrome P-450 content and related total tissue mixed-function oxidase activities were decreased to about 60% of control levels at day 28 post inoculation. The decrease in total tissue mixed-function oxidase activity was partly due to a small decrease in microsomal protein per cell, and partly to a large decrease in cytochrome P-450 concentration in the endoplasmic reticulum. Although the decrease in total liver monooxygenase activity in several substrates roughly paralleled the loss in cytochrome P-450 content, several other microsomal enzyme markers not related to cytochrome P-450 monooxygenation were elevated in proportion to total liver microsomal protein content. The results suggest that in M. montanus during trypanosomiasis, there is proliferation of hepatic cells with normal content of endoplasmic reticulum. Furthermore, there appears to be selective toxicity for hepatic cytochrome P-450 and related monooxygenase activities. This may compromise the animals' ability to metabolize and dispose of other drugs to which the animal may be exposed in the course of infection. PMID:7050701

Shertzer, H G; Hall, J E; Seed, J R

1982-07-01

163

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

164

A Novel Space-Vector Current Control Based on Circular Hysteresis Areas of a Three-Phase Neutral-Point-Clamped Inverter  

Microsoft Academic Search

This paper presents a novel space-vector current-control strategy for three-phase neutral-point (NP)-clamped inverters. The main task of this control technique is to force the actual current vector to reach the reference current vector. This original strategy consists in defining three circular hysteresis bands around the error vector. Then, according to the location of this error vector, a selection process of

Tarak Ghennam; El Madjid Berkouk; Bruno Francois

2010-01-01

165

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. PMID:20049114

van den Berg, Henk

2009-01-01

166

Modest additive effects of integrated vector control measures on malaria prevalence and transmission in western Kenya  

PubMed Central

Background The effect of integrating vector larval intervention on malaria transmission is unknown when insecticide-treated bed-net (ITN) coverage is very high, and the optimal indicator for intervention evaluation needs to be determined when transmission is low. Methods A post hoc assignment of intervention-control cluster design was used to assess the added effect of both indoor residual spraying (IRS) and Bacillus-based larvicides (Bti) in addition to ITN in the western Kenyan highlands in 2010 and 2011. Cross-sectional, mass parasite screenings, adult vector populations, and cohort of active case surveillance (ACS) were conducted before and after the intervention in three study sites with two- to three-paired intervention-control clusters at each site each year. The effect of larviciding, IRS, ITNs and other determinants of malaria risk was assessed by means of mixed estimating methods. Results Average ITN coverage increased from 41% in 2010 to 92% in 2011 in the study sites. IRS intervention had significant added impact on reducing vector density in 2010 but the impact was modest in 2011. The effect of IRS on reducing parasite prevalence was significant in 2011 but was seasonal specific in 2010. ITN was significantly associated with parasite densities in 2010 but IRS application was significantly correlated with reduced gametocyte density in 2011. IRS application reduced about half of the clinical malaria cases in 2010 and about one-third in 2011 compare to non-intervention areas. Conclusion Compared with a similar study conducted in 2005, the efficacy of the current integrated vector control with ITN, IRS, and Bti reduced three- to five-fold despite high ITN coverage, reflecting a modest added impact on malaria transmission. Additional strategies need to be developed to further reduce malaria transmission. PMID:23870708

2013-01-01

167

Silver nanoparticles: a possibility for malarial and filarial vector control technology.  

PubMed

Green synthesis technology is one of the rapid, reliable and best routes for the synthesis of silver nanoparticles (AgNPs). There are bioactive compounds with enormous potential in Azadirachta indica (Neem). The extraordinary mosquitoes warrant nanotechnology to integrate with novel molecules. This will be sustainable technology for future. Here, we synthesized AgNPs using aqueous extracts of leaves and bark of Az. indica (Neem). We tested AgNPs as larvicides, pupicides and adulticides against the malaria vector Anopheles stephensi and filariasis vector Culex quinquefasciatus. The results were obtained using UV-visible spectrophotometer and the images were recorded with a transmission electron microscope (TEM). The efficacy tests were then performed at different concentrations varying many hours by probit analysis. The synthesized AgNPs were spherical in shape and with varied sizes (10.47-nm leaf and 19.22-nm bark). The larvae, pupae and adults of filariasis vector C. quinquefasciatus were found to be more susceptible to our AgNPs than the malaria vector An. stephensi. The first and the second instar larvae of C. quinquefasciatus show a mortality rate of 100 % after 30 min of exposure. The results against the pupa of C. quinquefasciatus were recorded as LC50 4 ppm, LC90 11 ppm and LC99 13 ppm after 3 h of exposure. In the case of adult mosquitoes, LC50 1.06 ?L/cm(2), LC90 2.13 ?L/cm(2) and LC99 2.4 ?L/cm(2) were obtained after 4 h of exposure. These results suggest that our AgNPs are environment-friendly for controlling malarial and filarial vectors. PMID:25132567

Soni, Namita; Prakash, Soam

2014-11-01

168

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

2014-05-01

169

Clinical features, diagnosis, and treatment of human African trypanosomiasis (sleeping sickness).  

PubMed

Human African trypanosomiasis, or sleeping sickness, is caused by infection with parasites of the genus Trypanosoma, transmitted by the tsetse fly. The disease has two forms, Trypanosoma brucei (T b) rhodesiense and T b gambiense; and is almost always fatal if untreated. Despite a recent reduction in the number of reported cases, patients with African trypanosomiasis continue to present major challenges to clinicians. Because treatment for CNS-stage disease can be very toxic, diagnostic staging to distinguish early-stage from late-stage disease when the CNS in invaded is crucial but remains problematic. Melarsoprol is the only available treatment for late-stage T b rhodesiense infection, but can be lethal to 5% of patients owing to post-treatment reactive encephalopathy. Eflornithine combined with nifurtimox is the first-line treatment for late-stage T b gambiense. New drugs are in the pipeline for treatment of CNS human African trypanosomiasis, giving rise to cautious optimism. PMID:23260189

Kennedy, Peter Ge

2013-02-01

170

Application of Lanczos vectors to control design of flexible structures, part 2  

NASA Technical Reports Server (NTRS)

This report covers the period of the grant from January 1991 until its expiration in June 1992. Together with an Interim Report (Ref. 9), it summarizes the research conducted under NASA Grant NAG9-357 on the topic 'Application of Lanczos Vectors to Control Design of Flexible Structures.' The research concerns various ways to obtain reduced-order mathematical models of complex structures for use in dynamics analysis and in the design of control systems for these structures. This report summarizes the research.

Craig, Roy R., Jr.; Su, Tzu-Jeng

1992-01-01

171

Benefit of Insecticide-Treated Nets, Curtains and Screening on Vector Borne Diseases, Excluding Malaria: A Systematic Review and Meta-analysis  

PubMed Central

Introduction Insecticide-treated nets (ITNs) are one of the main interventions used for malaria control. However, these nets may also be effective against other vector borne diseases (VBDs). We conducted a systematic review and meta-analysis to estimate the efficacy of ITNs, insecticide-treated curtains (ITCs) and insecticide-treated house screening (ITS) against Chagas disease, cutaneous and visceral leishmaniasis, dengue, human African trypanosomiasis, Japanese encephalitis, lymphatic filariasis and onchocerciasis. Methods MEDLINE, EMBASE, LILACS and Tropical Disease Bulletin databases were searched using intervention, vector- and disease-specific search terms. Cluster or individually randomised controlled trials, non-randomised trials with pre- and post-intervention data and rotational design studies were included. Analysis assessed the efficacy of ITNs, ITCs or ITS versus no intervention. Meta-analysis of clinical data was performed and percentage reduction in vector density calculated. Results Twenty-one studies were identified which met the inclusion criteria. Meta-analysis of clinical data could only be performed for four cutaneous leishmaniasis studies which together showed a protective efficacy of ITNs of 77% (95%CI: 39%–91%). Studies of ITC and ITS against cutaneous leishmaniasis also reported significant reductions in disease incidence. Single studies reported a high protective efficacy of ITS against dengue and ITNs against Japanese encephalitis. No studies of Chagas disease, human African trypanosomiasis or onchocerciasis were identified. Conclusion There are likely to be considerable collateral benefits of ITN roll out on cutaneous leishmaniasis where this disease is co-endemic with malaria. Due to the low number of studies identified, issues with reporting of entomological outcomes, and few studies reporting clinical outcomes, it is difficult to make strong conclusions on the effect of ITNs, ITCs or ITS on other VBDs and therefore further studies be conducted. Nonetheless, it is clear that insecticide-treated materials such as ITNs have the potential to reduce pathogen transmission and morbidity from VBDs where vectors enter houses. PMID:25299481

Wilson, Anne L.; Dhiman, Ramesh C.; Kitron, Uriel; Scott, Thomas W.; van den Berg, Henk; Lindsay, Steven W.

2014-01-01

172

Multiple Insecticide Resistance: An Impediment to Insecticide-Based Malaria Vector Control Program  

PubMed Central

Background Indoor Residual Spraying (IRS), insecticide-treated nets (ITNs) and long-lasting insecticidal nets (LLINs) are key components in malaria prevention and control strategy. However, the development of resistance by mosquitoes to insecticides recommended for IRS and/or ITNs/LLINs would affect insecticide-based malaria vector control. We assessed the susceptibility levels of Anopheles arabiensis to insecticides used in malaria control, characterized basic mechanisms underlying resistance, and evaluated the role of public health use of insecticides in resistance selection. Methodology/Principal findings Susceptibility status of An. arabiensis was assessed using WHO bioassay tests to DDT, permethrin, deltamethrin, malathion and propoxur in Ethiopia from August to September 2009. Mosquito specimens were screened for knockdown resistance (kdr) and insensitive acetylcholinesterase (ace-1R) mutations using AS-PCR and PCR-RFLP, respectively. DDT residues level in soil from human dwellings and the surrounding environment were determined by Gas Chromatography with Electron Capture Detector. An. arabiensis was resistant to DDT, permethrin, deltamethrin and malathion, but susceptible to propoxur. The West African kdr allele was found in 280 specimens out of 284 with a frequency ranged from 95% to 100%. Ace-1R mutation was not detected in all specimens scored for the allele. Moreover, DDT residues were found in soil samples from human dwellings but not in the surrounding environment. Conclusion The observed multiple-resistance coupled with the occurrence of high kdr frequency in populations of An. arabiensis could profoundly affect the malaria vector control programme in Ethiopia. This needs an urgent call for implementing rational resistance management strategies and integrated vector control intervention. PMID:21264325

Steurbaut, Walter; Spanoghe, Pieter; Van Bortel, Wim; Denis, Leen; Tessema, Dejene A.; Getachew, Yehenew; Coosemans, Marc; Duchateau, Luc; Speybroeck, Niko

2011-01-01

173

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

174

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. PMID:21998654

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

2011-01-01

175

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. PMID:22873707

2012-01-01

176

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

177

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

178

Vector population manipulation for control of arboviruses--a novel prospect for India.  

PubMed

India, the seventh largest country in the world, has diverse geographical and climatic regions with vast rural and peri-urban areas. Many are experiencing an escalation in the spread and intensity of numerous human diseases transmitted by insects. Classically, the management of these vector-borne diseases is underpinned by either chemical insecticides and/or environmental management targeted at the vector. However, these methods or their present implementation do not offer acceptable levels of control, and more effective and sustainable options are now available. Genetic strategies for the prevention of arbovirus transmission are most advanced for dengue and chikungunya, targeting their primary vector, Aedes aegypti. The national burden in terms of morbidity and mortality as a direct consequence of dengue virus in India is considered to be the largest worldwide, over 4 times that of any other country. Presently, new genetic technologies are undergoing field evaluation of their biosafety and efficacy in several countries. This paper discusses the merits of these approaches and argues for fair and transparent appraisal in India as a matter of urgency. Identification of any associated risks and their appropriate mitigation are fundamental to that process. PMID:24254373

Niranjan Reddy, Bp; Gupta, Bhavna; Rao, B Prasad

2014-04-01

179

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

Microsoft Academic Search

BackgroundBetween 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

Karen I. Barnes; David N. Durrheim; Francesca Little; Amanda Jackson; Ushma Mehta; Elizabeth Allen; Sicelo S. Dlamini; Joyce Tsoka; Barry Bredenkamp; D. Jotham Mthembu; Nicholas J. White; Brian L. Sharp

2005-01-01

180

The hormonal effects of long-term DDT exposure on malaria vector-control workers in Limpopo Province, South Africa  

Microsoft Academic Search

DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane] compounds, used in many developing countries, including South Africa, for the control of malaria vectors, have been shown to be endocrine disruptors in vitro and in vivo. The study hypothesis was that male malaria vector-control workers highly exposed to DDT in the past should demonstrate clinically significant exposure-related anti-androgenic and\\/or estrogenic effects that should be reflected in abnormalities

Mohamed A Dalvie; Jonathan E Myers; Mary Lou Thompson; Silke Dyer; Thomas G Robins; Shaheed Omar; John Riebow; Josef Molekwa; Phillip Kruger; R Millar

2004-01-01

181

The development of H-II rocket solid rocket booster thrust vector control system  

NASA Astrophysics Data System (ADS)

The development of the thrust-vector-control (TVC) system for the two solid rocket boosters (SRBs) of the H-II rocket, which was started in 1984 and completed in 1989, is described. Special attention is given to the system's design, the trade-off studies, and the evaluation of the SRB-TVC system performance, as well as to problems that occurred in the course of the system's development and to the countermeasures that were taken. Schematic diagrams are presented for the H-II rocket, the SRB, and the SRB-TVC system configurations.

Nagai, Hirokazu; Fukushima, Yukio; Kazama, Hiroo; Asai, Tatsuro; Okaya, Shunichi; Watanabe, Yasushi; Muramatsu, Shoji

182

[Biological control of vectors of human and tropical diseases. Present means and prospects (author's transl)].  

PubMed

Biological control is "direct or indirect use of natural enemies of the injurious species to increase its mortality" (W.H.O., 1963). The more and more frequent apparition of resistant insects populations, the fears as regards the environment, the increase cost of hydrocarbur products and also some technic and operational difficulties to stop transmission by the use of only insecticide pulvérisation, impose this process. Nevertheless, practic use of natural enemies of vectors is yet unusual in spite of important research. (Identification problems, dynamic of species, insufficiency of ethology knowledge particulary of the host specificity, difficulties of application on the vectors which are the most usually widely scattered). For control of insects of medical importance (mosquitoes, black flies, tse-tse flies) it has been used either pathogen agents such as virus bacteria, microsporida or parasit agents such as fungi, mermithid nematods or at last, predators, essentially larvivorus fish. Actually, no biological agent is able to take the place of chemical and physical "traditional" means. In case of mosquito control which is more advanced, the only biological mean which is operational is the use of larvivorus fish and specially Gambusia. PMID:106214

Chauvet, G

1978-01-01

183

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

184

Experimental therapy of African trypanosomiasis with a nanobody-conjugated human trypanolytic factor  

E-print Network

Experimental therapy of African trypanosomiasis with a nanobody-conjugated human trypanolytic. Here, we conjugated Tr-apoL-I with a single- domain antibody (nanobody) that efficiently targets its efficiency. Nanobodies, the single-domain antigen-binding fragments derived from camel heavy

Arnold, Jonathan

185

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

186

Characterisation of the Wildlife Reservoir Community for Human and Animal Trypanosomiasis in the Luangwa Valley, Zambia  

Microsoft Academic Search

BackgroundAnimal and human trypanosomiasis are constraints to both animal and human health in Sub-Saharan Africa, but there is little recent evidence as to how these parasites circulate in wild hosts in natural ecosystems. The Luangwa Valley in Zambia supports high densities of tsetse flies (Glossina species) and is recognised as an historical sleeping sickness focus. The objective of this study

Neil E. Anderson; Joseph Mubanga; Eric M. Fevre; Kim Picozzi; Mark C. Eisler; Robert Thomas; Susan C. Welburn

2011-01-01

187

Instantaneous power control-an alternative to vector and direct torque control?  

Microsoft Academic Search

This paper presents a new algorithm for the control of AC machines based on the concept of controlling the instantaneous real and imaginary power. This strategy, called instantaneous power control (IPC), allows decoupled control of the torque and flux in the machine. This paper outlines the basic algorithm and then presents simulation results of its performance

R. E. Betzt; B. J. Cook

2000-01-01

188

The Use of Mini-Vector Instructions for Implementing High-Speed Feedback Controllers on General-Purpose  

E-print Network

. Keywords Active magnetic bearing, flywheel, vector instructions, API, multi-threaded execution. 1-spin- rate flywheel. This application is representative of many control environments that require both high application for feedback control is real-time control of active magnetic bearings (AMBs) in a high

Skadron, Kevin

189

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. PMID:24062411

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

190

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. PMID:24086399

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

2013-01-01

191

Chlorfenapyr: a new insecticide with novel mode of action can control pyrethroid resistant malaria vectors  

PubMed Central

Background Malaria vectors have acquired widespread resistance to many of the currently used insecticides, including synthetic pyrethroids. Hence, there is an urgent need to develop alternative insecticides for effective management of insecticide resistance in malaria vectors. In the present study, chlorfenapyr was evaluated against Anopheles culicifacies and Anopheles stephensi for its possible use in vector control. Methods Efficacy of chlorfenapyr against An. culicifacies and An. stephensi was assessed using adult bioassay tests. In the laboratory, determination of diagnostic dose, assessment of residual activity on different substrates, cross-resistance pattern with different insecticides and potentiation studies using piperonyl butoxide were undertaken by following standard procedures. Potential cross-resistance patterns were assessed on field populations of An. culicifacies. Results A dose of 5.0% chlorfenapyr was determined as the diagnostic concentration for assessing susceptibility applying the WHO tube test method in anopheline mosquitoes with 2 h exposure and 48 h holding period. The DDT-resistant/malathion-deltamethrin-susceptible strain of An. culicifacies species C showed higher LD50 and LD99 (0.67 and 2.39% respectively) values than the DDT-malathion-deltamethrin susceptible An. culicifacies species A (0.41 and 2.0% respectively) and An. stephensi strains (0.43 and 2.13% respectively) and there was no statistically significant difference in mortalities among the three mosquito species tested (p > 0.05). Residual activity of chlorfenapyr a.i. of 400 mg/m2 on five fabricated substrates, namely wood, mud, mud+lime, cement and cement + distemper was found to be effective up to 24 weeks against An. culicifacies and up to 34 weeks against An. stephensi. No cross-resistance to DDT, malathion, bendiocarb and deltamethrin was observed with chlorfenapyr in laboratory-reared strains of An. stephensi and field-caught An. culicifacies. Potentiation studies demonstrated the antagonistic effect of PBO. Conclusion Laboratory studies with susceptible and resistant strains of An. culicifacies and An. stephensi, coupled with limited field studies with multiple insecticide-resistant An. culicifacies have shown that chlorfenapyr can be a suitable insecticide for malaria vector control, in multiple-insecticide-resistant mosquitoes especially in areas with pyrethroid resistant mosquitoes. PMID:21266037

2011-01-01

192

Insecticide Resistance and Malaria Vector Control: The Importance of Fitness Cost Mechanisms in Determining Economically Optimal Control Trajectories  

PubMed Central

The evolutionary dynamics of insecticide resistance in harmful arthropods has economic implications, not only for the control of agricultural pests (as has been well studied), but also for the control of disease vectors, such as malaria-transmitting Anopheles mosquitoes. Previous economic work on insecticide resistance illustrates the policy relevance of knowing whether insecticide resistance mutations involve fitness costs. Using a theoretical model, this article investigates economically optimal strategies for controlling malaria-transmitting mosquitoes when there is the potential for mosquitoes to evolve resistance to insecticides. Consistent with previous literature, we find that fitness costs are a key element in the computation of economically optimal resistance management strategies. Additionally, our models indicate that different biological mechanisms underlying these fitness costs (e.g., increased adult mortality and/or decreased fecundity) can significantly alter economically optimal resistance management strategies. PMID:23448053

Brown, Zachary S.; Dickinson, Katherine L.; Kramer, Randall A.

2014-01-01

193

Hyperbranched polysiloxysilane nanoparticles: surface charge control of nonviral gene delivery vectors and nanoprobes.  

PubMed

New hyperbranched polysiloxysilane (HBPS) materials containing terminal carboxylic acid and quaternary ammonium groups were designed and synthesized to obtain fluorescent-dye-encapsulated nanoparticles. These polymers exhibited desirable characteristics, including amphiphilicity for nanoparticle formation, and contained various terminal groups for surface-charge control on the nanoparticles or for further bioconjugation for targeted imaging. Nanoprobes composed of polysiloxysilane nanoparticles encapsulating two-photon dyes were also prepared for optical bioimaging with controlled surface charge density (zeta potential) for modulation of cellular uptake. Intracellular delivery of these structurally similar polysiloxysilane nanoparticles, with substantially different surface charges, was investigated using confocal and two-photon fluorescence microscopy as well as flow cytometry. Finally, the use of these nanoparticles as efficient gene delivery vectors was demonstrated by means of in vitro transfection study using beta-galactosidase plasmid and pEGFP-N1 plasmid and the most efficient combination was obtained using HBPS-CN30:70. PMID:19409467

Kim, Won Jin; Bonoiu, Adela C; Hayakawa, Teruaki; Xia, Cheng; Kakimoto, Masa-Aki; Pudavar, Haridas E; Lee, Kwang-Sup; Prasad, Paras N

2009-07-01

194

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

195

Anti-trypanosome specific immune responses in bovids of differing susceptibility to African trypanosomiasis.  

PubMed Central

A clone of Trypanosoma brucei brucei (DiTat 1.1) was injected into 32 bovids of various breeds, 11 animals being kept as controls. Five animals, Simmental-Ndama F1 crosses, were extremely sensitive. They showed overt symptoms and one died on day 18 of infection despite treatment with a trypanocidal drug. Seven other animals became ill but recovered progressively and cleared the infection. Twenty animals, of breeds generally considered to be trypanosensitive as well as ones from trypanotolerant breeds, did not show symptoms apart from anaemia and cleared the infection. Putative protective antibody, i.e. directed against exposed determinants on the coat variant-specific glycoprotein, was detected by agglutination, complement-mediated lysis and inhibition of infectivity. All animals showed a primary immune response consisting of IgM whose kinetics and amplitude were indistinguishable between animals of differing sensitivity. The response was long-lasting, whether the animals had been treated or not with a trypanocidal drug 3 weeks after infection, and antibody of IgG1 and IgG2 types were detected in certain sensitive as well as resistant animals after 2 months. Some animals were rechallenged with DiTat 1.1 either 1 year after the primary infection or 6 months after inoculation of irradiated trypanosomes. Peak titres of antibody were lower than was the case following primary infection but higher levels of mercaptoenthanol-resistant antibodies were seen. In no case was there any difference in the response of sensitive or tolerant animals. Our results do not support the idea that resistance of certain bovids to African trypanosomiasis is due to a better protective antibody response. PMID:6693134

Pinder, M; Libeau, G; Hirsch, W; Tamboura, I; Hauck-Bauer, R; Roelants, G E

1984-01-01

196

Robust vibration suppression of an adaptive circular composite plate for satellite thrust vector control  

NASA Astrophysics Data System (ADS)

In this paper, a novel application of adaptive composite structures, a University of Hawaii at Manoa (UHM) smart composite platform, is developed for the Thrust Vector Control (TVC) of satellites. The device top plate of the UHM platform is an adaptive circular composite plate (ACCP) that utilizes integrated sensors/actuators and controllers to suppress low frequency vibrations during the thruster firing as well as to potentially isolate dynamic responses from the satellite structure bus. Since the disturbance due to the satellite thruster firing can be estimated, a combined strategy of an adaptive disturbance observer (DOB) and feed-forward control is proposed for vibration suppression of the ACCP with multi-sensors and multi-actuators. Meanwhile, the effects of the DOB cut-off frequency and the relative degree of the low-pass filter on the DOB performance are investigated. Simulations and experimental results show that higher relative degree of the low-pass filter with the required cut-off frequency will enhance the DOB performance for a high-order system control. Further, although the increase of the filter cut-off frequency can guarantee a sufficient stability margin, it may cause an undesirable increase of the control bandwidth. The effectiveness of the proposed adaptive DOB with feed-forward control strategy is verified through simulations and experiments using the ACCP system.

Yan, Su; Ma, Kougen; Ghasemi-Nejhad, Mehrdad N.

2008-03-01

197

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

198

Optimization of Control Strategies for Non-Domiciliated Triatoma dimidiata, Chagas Disease Vector in the Yucat?n Peninsula, Mexico  

PubMed Central

Background Chagas disease is the most important vector-borne disease in Latin America. Regional initiatives based on residual insecticide spraying have successfully controlled domiciliated vectors in many regions. Non-domiciliated vectors remain responsible for a significant transmission risk, and their control is now a key challenge for disease control. Methodology/Principal Findings A mathematical model was developed to predict the temporal variations in abundance of non-domiciliated vectors inside houses. Demographic parameters were estimated by fitting the model to two years of field data from the Yucatan peninsula, Mexico. The predictive value of the model was tested on an independent data set before simulations examined the efficacy of control strategies based on residual insecticide spraying, insect screens, and bednets. The model accurately fitted and predicted field data in the absence and presence of insecticide spraying. Pyrethroid spraying was found effective when 50 mg/m2 were applied yearly within a two-month period matching the immigration season. The >80% reduction in bug abundance was not improved by larger doses or more frequent interventions, and it decreased drastically for different timing and lower frequencies of intervention. Alternatively, the use of insect screens consistently reduced bug abundance proportionally to the reduction of the vector immigration rate. Conclusion/Significance Control of non-domiciliated vectors can hardly be achieved by insecticide spraying, because it would require yearly application and an accurate understanding of the temporal pattern of immigration. Insect screens appear to offer an effective and sustainable alternative, which may be part of multi-disease interventions for the integrated control of neglected vector-borne diseases. PMID:19365542

Barbu, Corentin; Dumonteil, Eric; Gourbiere, Sebastien

2009-01-01

199

Test stand for precise measurement of impulse and thrust vector of small attitude control jets  

NASA Technical Reports Server (NTRS)

A test stand which accurately measures the impulse bit and thrust vector of reaction jet thrusters used in the attitude control system of space vehicles has been developed. It can be used to measure, in a vacuum or ambient environment, both impulse and thrust vector of reaction jet thrusters using hydrazine or inert gas propellants. The ballistic pendulum configuration was selected because of its accuracy, simplicity, and versatility. The pendulum is mounted on flexure pivots rotating about a vertical axis at the center of its mass. The test stand has the following measurement capabilities: impulse of 0.00004 to 4.4 N-sec (0.00001 to 1.0 lb-sec) with a pulse duration of 0.5 msec to 1 sec; static thrust of 0.22 to 22 N (0.05 to 5 lb) with a 5 percent resolution; and thrust angle alinement of 0.22 to 22 N (0.05 to 5 lb) thrusters with 0.01 deg accuracy.

Woodruff, J. R.; Chisel, D. M.

1973-01-01

200

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. PMID:24240781

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

201

Major QTLs control resistance to rice hoja blanca virus and its vector Tagosodes orizicolus.  

PubMed

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. PMID:24240781

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

2014-01-01

202

might, however, be a cheap and effective alternative to conventional pesticides for vector control, and one that  

E-print Network

might, however, be a cheap and effective alternative to conventional pesticides for vector control) Fungal pathogen reduces potential for malaria transmission. Science 308, 1638­1641 2 Scholte, E.J. et al. (2005) An entomopathogenic fungus for control of adult African malaria mosquitoes. Science 308, 1641

deYoung, Brad

203

Different mosquito species host Wickerhamomyces anomalus (Pichia anomala): perspectives on vector-borne diseases symbiotic control.  

PubMed

The genetic manipulation of the microbial community associated with hematophagus insects is particularly relevant for public health applications. Within mosquito populations, this relationship has been overlooked until recently. New advances in molecular biotechnology propose the genetic manipulation of mosquito symbionts to prevent the transmission of pathogens to humans by interfering with the obligatory life cycle stages within the insect through the use of effector molecules. This approach, defined as 'paratransgenesis', has opened the way for the investigation and characterization of microbes residing in the mosquito body, particularly those localised within the gut. Some interesting bacteria have been identified as candidates for genetic modification, however, endosymbiotic yeasts remain largely unexplored with little information on the symbiotic relationships to date. Here we review the recent report of symbiotic relationship between Wickerhamomyces anomalus (Pichia anomala) and several mosquito vector species as promising methods to implement control of mosquito-borne diseases. PMID:21113816

Ricci, Irene; Mosca, Michela; Valzano, Matteo; Damiani, Claudia; Scuppa, Patrizia; Rossi, Paolo; Crotti, Elena; Cappelli, Alessia; Ulissi, Ulisse; Capone, Aida; Esposito, Fulvio; Alma, Alberto; Mandrioli, Mauro; Sacchi, Luciano; Bandi, Claudio; Daffonchio, Daniele; Favia, Guido

2011-01-01

204

Characterization of truck-mounted atomization equipment typically used in vector control.  

PubMed

The control of medically important arthropod vectors of human and animal disease is a high priority for both public health and military officials. Because droplet size of pesticide spray material is a critical factor affecting vector control applications, the droplet-size spectra produced by 11 sprayers and 3 spray formulations were evaluated. Droplet-size spectra were measured by a laser diffraction instrument, a hot-wire system, and rotating slides. There were considerable differences in the droplet-size spectra produced by the different sprayers tested. The volume median diameter (Dv0.5) for the water-based sprays ranged from 4.7 to 211 microm, depending on the sprayer, and the percent of spray volume contained in droplets less than 20 microm (%vol <20 microm) ranged between 0.5% and 98.9%. The Dv0.5 measurements for the oil-based sprays ranged from 9.4 to 125.3 microm and the %vol <20 microm ranged between 2.4% and 97.9%. The correlations between the Dv0.5 measured by the laser system (Dv0.5-laser) and the mass median diameter, Sauter diameter, and Dv0.5 measured by the AIMS probe were all significant. Generally, the slide Dv0.5s were numerically similar to the Dv0.5 from the laser system and the Sauter diameter from the Army Insecticide Measuring System probe. There was less consistent agreement between the % <32 microm values obtained from the slides and those from the other 2 samplers. The information presented can be used by applicators to select the sprayer that produces the droplet-size spectra needed for their particular application situation. PMID:17939514

Hoffmann, W C; Walker, T W; Martin, D E; Barber, J A B; Gwinn, T; Smith, V L; Szumlas, D; Lan, Y; Fritz, B K

2007-09-01

205

Control strategies for power smoothing using a flywheel driven by a sensorless vector-controlled induction machine operating in a wide speed range  

Microsoft Academic Search

This paper presents a novel control strategy for power smoothing. The system is based on a sensorless vector-controlled induction machine driving a flywheel. The problem of regulating the DC-link voltage against input power surges or sudden changes in load demand is addressed. The induction machine is controlled to operate in a wide speed range by using flux weakening above rated

Roberto Cárdenas; Rubén Peña; Greg M. Asher; Jon Clare; Ramón Blasco-Giménez

2004-01-01

206

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

207

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

208

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. PMID:24139513

2013-01-01

209

Human African trypanosomiasis in a rural community, Democratic Republic of Congo  

Microsoft Academic Search

According to the World Health Organization, human African trypanosomiasis (HAT) (sleeping sickness) caused the loss of ?1.5 million disability-adjusted life years (DALYs) in 2002. This article describes the effect of HAT during 2000–2002 in Buma, a rural community near Kinshasa in the Democratic Republic of Congo. Retrospective questionnaire surveys were used to estimate HAT-related household costs and DALYs. The HAT

Pascal Lutumba; Eric Makieya; Alexandra Shaw; Filip Meheus; Marleen Boelaert

2007-01-01

210

Human antibody response to Anopheles saliva for comparing the efficacy of three malaria vector control methods in Balombo, Angola.  

PubMed

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. PMID:23028499

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

2012-01-01

211

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. PMID:23028499

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

212

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

213

Pneumatic motor powered Thrust Vector Control (TVC) for liquid propelled launch vehicles  

NASA Astrophysics Data System (ADS)

Recent studies performed for the Titan 4 launch vehicle indicate significant potential advantages in replacing the current stage 1 and 2 recirculating hydraulic TVC (thrust vector control) system with a PMA (pneumatic mechanical actuation) system. Some of the advantages of a PMA system over the recirculating hydraulic system include reduced part count and weight, reduced maintenance and life-cycle cost, and improved mission reliability. PMA technology, used in aircraft applications since the 1960s, is well suited in launch vehicle TVC applications where an existing pneumatic pressure source is available. A typical pneumatic motor TVC consists of a pneumatic power source, a dual rotor pneumatic motor, a gear box, a ball screw actuator, and the associated closed-loop servo-control elements. One key issue with implementing this mechanical approach is designing a TVC system to withstand large load transient disturbances during liquid engine starting. Hydraulic actuator transient loads have exceeded 60,000 lb(sub f) for a 30,000 lb(sub f) stall design actuator during ground starts of the Titan 3B, Stage 1 engine. A PMA TVC system must also withstand these start transients without imparting excessive reaction loads to the engine nozzle and thrust structure. Work completed to date with Martin Marietta to examine pneumatic motor powered TVC options and technology benefits is presented. The load transient issue is discussed along with potential solutions and the associated trades. General background on PMA technology and experience base is also presented.

Malone, Mark C.; Evans, P. S.

1992-02-01

214

1066 IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 51, NO. 5, OCTOBER 2004 Stator-Flux-Oriented Vector Control of Synchronous  

E-print Network

and per- manent-magnet machines in certain variable-speed drive applications. These machines have torque losses, can make these machines preferable to permanent-magnet machines in applications where the machine-mentioned advantages is a motor/generator for a flywheel energy storage system [4]. Vector control of synchronous

Hofmann, Heath F.

215

Aspects of the use of honeybees and bumblebees as vector of antagonistic micro-organisms in plant disease control  

Microsoft Academic Search

Honeybees (Apis mellifera L.) and bumblebees (Bombus terrestris L.) are used for pollination in agriculture and horticulture. The morphological and behavioural characteristics of bees make them good pollinators. Thanks to this, bees may also be used as vector of antagonistic micro-organisms for plant disease control, both preventive and curative. To determine the practical consequences of this way of plant disease

J. J. M. van der Steen; C. J. Langerak; C. A. M. van Tongeren; A. J. Dik

216

Aspects of the use of honeybees and bumblebees as vector of antagonistic micro-organisms in plant diseas control  

Microsoft Academic Search

Honeybees (Apis mellifera L.) and bumblebees (Bombus terrestris L.) are used for pollination in agriculture and horticulture. The morphological and behavioural characteristics of bees make them good pollinators. Thanks to this, bees may also be used as vector of antagonistic micro-organisms for plant disease control, both preventive and curative. To determine the practical consequences of this way of plant disease

Steen van der J. J. M; C. J. Langerak; Tongeren van C. A. M; A. J. Dik

2003-01-01

217

On-line stator and rotor resistance estimation scheme for vector-controlled induction motor drive using artificial neural networks  

Microsoft Academic Search

This paper presents a new method of on-line estimation for the stator and rotor resistances of the induction motor in the indirect vector controlled drive, using artificial neural networks. The back propagation algorithm is used for training of the neural networks. The error between the desired state variable of an induction motor and the actual state variable of a neural

Baburaj Karanayil; Muhammed Fazlur Rahman; Colin Grantham

2003-01-01

218

Online Stator and Rotor Resistance Estimation Scheme Using Artificial Neural Networks for Vector Controlled Speed Sensorless Induction Motor Drive  

Microsoft Academic Search

This paper presents a new method of online estimation for the stator and rotor resistances of the induction motor for speed sensorless indirect vector controlled drives, using artificial neural networks. The error between the rotor flux linkages based on a neural network model and a voltage model is back propagated to adjust the weights of the neural network model for

Baburaj Karanayil; Muhammed Fazlur Rahman; Colin Grantham

2007-01-01

219

Eefficient switching of three-phase PFC converters based on a sensorless current control neuro-computing space vector modulation  

Microsoft Academic Search

A sensorless current control scheme based on a neuro-computing SVM is proposed in this paper. The neuron indexes in the proposed scheme are used to identify the highest current carrying phase and the switching vectors. In addition, the proposed scheme is simple, accurate, and easy to implement. Moreover, four different switching patterns are introduced, and a novel switching pattern that

D. Yazdani; A. Bakhshai

2005-01-01

220

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

221

Model Reference Adaptive Controller-Based Rotor Resistance and Speed Estimation Techniques for Vector Controlled Induction Motor Drive Utilizing Reactive Power  

Microsoft Academic Search

In this paper, a detailed study on the model reference adaptive controller (MRAC) utilizing the reactive power is presented for the online estimation of rotor resistance to maintain proper flux orientation in an indirect vector controlled induction motor drive. Selection of reactive power as the functional candidate in the MRAC automatically makes the system immune to the variation of stator

Suman Maiti; Chandan Chakraborty; Yoichi Hori; Minh C. Ta

2008-01-01

222

Community mobilization and household level waste management for dengue vector control in Gampaha district of Sri Lanka; an intervention study  

PubMed Central

Introduction Waste management through community mobilization to reduce breeding places at household level could be an effective and sustainable dengue vector control strategy in areas where vector breeding takes place in small discarded water containers. The objective of this study was to assess the validity of this assumption. Methods An intervention study was conducted from February 2009 to February 2010 in the populous Gampaha District of Sri Lanka. Eight neighborhoods (clusters) with roughly 200 houses each were selected randomly from high and low dengue endemic areas; 4 of them were allocated to the intervention arm (2 in the high and 2 in the low endemicity areas) and in the same way 4 clusters to the control arm. A baseline household survey was conducted and entomological and sociological surveys were carried out simultaneously at baseline, at 3 months, at 9 months and at 15 months after the start of the intervention. The intervention programme in the treatment clusters consisted of building partnerships of local stakeholders, waste management at household level, the promotion of composting biodegradable household waste, raising awareness on the importance of solid waste management in dengue control and improving garbage collection with the assistance of local government authorities. Results The intervention and control clusters were very similar and there were no significant differences in pupal and larval indices of Aedes mosquitoes. The establishment of partnerships among local authorities was well accepted and sustainable; the involvement of communities and households was successful. Waste management with the elimination of the most productive water container types (bowls, tins, bottles) led to a significant reduction of pupal indices as a proxy for adult vector densities. Conclusion The coordination of local authorities along with increased household responsibility for targeted vector interventions (in our case solid waste management due to the type of preferred vector breeding places) is vital for effective and sustained dengue control. PMID:23318240

Abeyewickreme, W; Wickremasinghe, A R; Karunatilake, K; Sommerfeld, Johannes; Kroeger, Axel

2012-01-01

223

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

224

The significance of controlled conditions in lentiviral vector titration and in the use of multiplicity of infection (MOI) for predicting gene transfer events  

PubMed Central

Background Although lentiviral vectors have been widely used for in vitro and in vivo gene therapy researches, there have been few studies systematically examining various conditions that may affect the determination of the number of viable vector particles in a vector preparation and the use of Multiplicity of Infection (MOI) as a parameter for the prediction of gene transfer events. Methods Lentiviral vectors encoding a marker gene were packaged and supernatants concentrated. The number of viable vector particles was determined by in vitro transduction and fluorescent microscopy and FACs analyses. Various factors that may affect the transduction process, such as vector inoculum volume, target cell number and type, vector decay, variable vector – target cell contact and adsorption periods were studied. MOI between 0–32 was assessed on commonly used cell lines as well as a new cell line. Results We demonstrated that the resulting values of lentiviral vector titre varied with changes of conditions in the transduction process, including inoculum volume of the vector, the type and number of target cells, vector stability and the length of period of the vector adsorption to target cells. Vector inoculum and the number of target cells determine the frequencies of gene transfer event, although not proportionally. Vector exposure time to target cells also influenced transduction results. Varying these parameters resulted in a greater than 50-fold differences in the vector titre from the same vector stock. Commonly used cell lines in vector titration were less sensitive to lentiviral vector-mediated gene transfer than a new cell line, FRL 19. Within 0–32 of MOI used transducing four different cell lines, the higher the MOI applied, the higher the efficiency of gene transfer obtained. Conclusion Several variables in the transduction process affected in in vitro vector titration and resulted in vastly different values from the same vector stock, thus complicating the use of MOI for predicting gene transfer events. Commonly used target cell lines underestimated vector titre. However, within a certain range of MOI, it is possible that, if strictly controlled conditions are observed in the vector titration process, including the use of a sensitive cell line, such as FRL 19 for vector titration, lentivector-mediated gene transfer events could be predicted. PMID:15291957

Zhang, Bing; Metharom, Pat; Jullie, Howard; Ellem, Kay AO; Cleghorn, Geoff; West, Malcolm J; Wei, Ming Q

2004-01-01

225

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

NASA Astrophysics Data System (ADS)

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; Gong, Jiangbin; Oh, C. H.

2010-06-01

226

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

227

The design of constant frequency hysteresis current controller with voltage space vector in PV grid-connected inverter  

Microsoft Academic Search

A new constant-frequency hysteresis current control algorithm for PV grid-connected inverter is proposed, in which the complex plane is divided into six sectors based on line voltage space vector of electric power grid, and two-phase switches are decoupled respectively in every sector to control corresponding line currents, and the hysteresis band is modified by prediction, so that the output current

Genping Wang; Lingzhi Yi; Xiao Zou; Sufeng He; Ming Li

2008-01-01

228

Exposure and health assessment during application of lambda-cyhalothrin for malaria vector control in Pakistan.  

PubMed Central

Icon 10 WP insecticide, a wettable powder formulation containing 10% lambda-cyhalothrin, was evaluated for possible adverse effects on the health of spraymen and villagers during treatment of dwellings for malaria vector control. Skin sensory effects and occasional coughing and sneezing in confined spaces were the only symptoms noted by the workers resulting from the handling and spraying of the insecticide. Absorption of lambda-cyhalothrin was estimated by determining its metabolites in urine and serum. The average amount of lambda-cyhalothrin absorbed by the workers per day (54 micrograms) represents less than 0.0001% (< 1 micrograms.kg-1.day-1) of the average daily amount of the substance handled. Only a small proportion of villagers showed detectable levels of lambda-cyhalothrin metabolites in their urine. Absorption of lambda-cyhalothrin from the formulation tested was therefore very low and, apart from the nuisance of skin sensory effects, there should be no risk to the health of workers or to the villagers whose dwellings are treated. PMID:1464147

Chester, G.; Sabapathy, N. N.; Woollen, B. H.

1992-01-01

229

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. PMID:24312606

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

2013-01-01

230

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

231

Application of Diagnostic Analysis Tools to the Ares I Thrust Vector Control System  

NASA Technical Reports Server (NTRS)

The NASA Ares I Crew Launch Vehicle is being designed to support missions to the International Space Station (ISS), to the Moon, and beyond. The Ares I is undergoing design and development utilizing commercial-off-the-shelf tools and hardware when applicable, along with cutting edge launch technologies and state-of-the-art design and development. In support of the vehicle s design and development, the Ares Functional Fault Analysis group was tasked to develop an Ares Vehicle Diagnostic Model (AVDM) and to demonstrate the capability of that model to support failure-related analyses and design integration. One important component of the AVDM is the Upper Stage (US) Thrust Vector Control (TVC) diagnostic model-a representation of the failure space of the US TVC subsystem. This paper first presents an overview of the AVDM, its development approach, and the software used to implement the model and conduct diagnostic analysis. It then uses the US TVC diagnostic model to illustrate details of the development, implementation, analysis, and verification processes. Finally, the paper describes how the AVDM model can impact both design and ground operations, and how some of these impacts are being realized during discussions of US TVC diagnostic analyses with US TVC designers.

Maul, William A.; Melcher, Kevin J.; Chicatelli, Amy K.; Johnson, Stephen B.

2010-01-01

232

Inductance and Active Phase Vector Based Torque Control for Switched Reluctance Motor Drives.  

NASA Astrophysics Data System (ADS)

The Switched Reluctance Motor (SRM) drive technology has developed significantly over the last few years. The simplicity in both motor design and power converter requirement along with the availability of high frequency, high power semiconductor switches have made SRMs compete with conventional adjustable speed drive technologies. The subject of winding current control in switched reluctance machines has always been associated with the shaft position information. The use of inductance for direct commutation control is the central subject of this dissertation. In contrast to the conventional methods based on position commutation, new methods of control based on inductance commutation are presented. The object of a commutation algorithm is to switch the currents in the phase coils, in order to provide continuous energy conversion with maximum torque output for a given unit of input current. Since torque production in a SRM is based on the concept of variable reluctance, it makes more sense to observe the instantaneous phase inductance or reluctance instead of estimating the rotor position. The inductance sensors observe the machine parameters and provide sufficient information on the electrical characteristics of the coils. This control strategy avoids the inductance to position transformation blocks conventionally used in SRM control systems. In a typical SRM, the phase coils have a nonlinear behavior of inductance due to effects of current saturation. Also the parameters of one phase coil differ from those of the other due to manufacturing tolerances or due to bearing wear. In such cases, the algorithms written during the stage of manufacturing may not be valid after parameter changes. Optimizing torque production in the event of phase asymmetry and saturation is developed in this research. Indirect sensors connected to the active phase coil of the SRM are based on sensing the flux level in the active coil. New commutation algorithms based on flux sensing concepts are derived and commutation based on observable phase coil parameters are developed. The commutation methods are based on a composite vector of the observable parameters of the active phase coil. These methods work on a tabular approach which is ideal for implementation using digital computers.

Kalpathi, Ramani Raman

233

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. PMID:22581989

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

2011-01-01

234

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

PubMed

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. PMID:22581989

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

2012-05-01

235

Comparison of nucleic acid sequence-based amplification and loop-mediated isothermal amplification for diagnosis of human African trypanosomiasis.  

PubMed

Diagnosis of human African trypanosomiasis (HAT) using molecular tests should ideally achieve high sensitivity without compromising specificity. This study compared 2 simplified tests, nucleic acid sequence-based amplification (NASBA) combined with oligochromatography (OC) and loop-mediated isothermal amplification (LAMP), executed on 181 blood samples from 65 Trypanosoma brucei gambiense HAT patients, 86 controls, and 30 serological suspects from Uganda. Basing on the composite reference standard, the diagnostic sensitivity and specificity of NASBA were 93.9% (95% confidence interval [CI] = 84.9-98.3%) and 100% (95% CI = 94.9-100%), respectively. The same parameters for LAMP were 76.9% (95% CI = 64.8-86.5%) and 100% (95% CI = 91.6-100%), respectively. The level of agreement between LAMP and microscopy was good with a kappa (?) value of 79.2% (95% CI = 69.4-88.9%), while that of NASBA-OC/microscopy was very good (? value 94.6%; 95% CI = 89.3-99.8%). The sensitivity of NASBA-OC was significantly higher than that of LAMP (Z = 2.723; P = 0.007). These tests have potential application to HAT surveillance. PMID:24439269

Mugasa, Claire M; Katiti, Diana; Boobo, Alex; Lubega, George W; Schallig, Henk D F H; Matovu, Enock

2014-02-01

236

Sleep-wake transition in narcolepsy and healthy controls using a support vector machine.  

PubMed

Narcolepsy is characterized by abnormal sleep-wake regulation, causing sleep episodes during the day and nocturnal sleep disruptions. The transitions between sleep and wakefulness can be identified by manual scorings of a polysomnographic recording. The aim of this study was to develop an automatic classifier capable of separating sleep epochs from epochs of wakefulness by using EEG measurements from one channel. Features from frequency bands ? (0-4 Hz), ? (4-8 Hz), ? (8-12 Hz), ? (12-16 Hz), 16 to 24 Hz, 24 to 32 Hz, 32 to 40 Hz, and 40 to 48 Hz were extracted from data by use of a wavelet packet transformation and were given as input to a support vector machine classifier. The classification algorithm was assessed by hold-out validation and 10-fold cross-validation. The data used to validate the classifier were derived from polysomnographic recordings of 47 narcoleptic patients (33 with cataplexy and 14 without cataplexy) and 15 healthy controls. Compared with manual scorings, an accuracy of 90% was achieved in the hold-out validation, and the area under the receiver operating characteristic curve was 95%. Sensitivity and specificity were 90% and 88%, respectively. The 10-fold cross-validation procedure yielded an accuracy of 88%, an area under the receiver operating characteristic curve of 92%, a sensitivity of 87%, and a specificity of 87%. Narcolepsy with cataplexy patients experienced significantly more sleep-wake transitions during night than did narcolepsy without cataplexy patients (P = 0.0199) and healthy subjects (P = 0.0265). In addition, the sleep-wake transitions were elevated in hypocretin-deficient patients. It is concluded that the classifier shows high validity for identifying the sleep-wake transition. Narcolepsy with cataplexy patients have more sleep-wake transitions during night, suggesting instability in the sleep-wake regulatory system. PMID:25271675

Jensen, Julie B; Sorensen, Helge B D; Kempfner, Jacob; Sørensen, Gertrud L; Knudsen, Stine; Jennum, Poul

2014-10-01

237

Unexpected failures to control Chagas Disease vectors with pyrethroid spraying in northern Argentina.  

PubMed

Effectiveness of the elimination efforts against Triatoma infestans (Klug) in South America through residual application of pyrethroid insecticides has been highly variable in the Gran Chaco region. We investigated apparent vector control failures after a standard community-wide spraying with deltamethrin SC in a rural area of northeastern Argentina encompassing 353 houses. Insecticide spraying reduced house infestation less than expected: from 49.5% at baseline to 12.3 and 6.7% at 4 and 8 mo postspraying, respectively. Persistent infestations were detected in 28.4% of houses, and numerous colonies with late-stage bugs were recorded after the interventions. Laboratory bioassays showed reduced susceptibility to pyrethroids in the local bug populations. Eleven of 14 bug populations showed reduced mortality in diagnostic dose assays (range, 35 +/- 5% to 97 +/- 8%) whereas the remainder had 100% mortality. A fully enclosed residual bug population in a large chicken coop survived four pyrethroid sprays, including two double-dose applications, and was finally suppressed with malathion. The estimated resistance ratio of this bug population was 7.17 (range, 4.47-11.50). Our field data combined with laboratory bioassays and a residual foci experiment demonstrate that the initial failure to suppress T. infestans was mainly because of the unexpected occurrence of reduced susceptibility to deltamethrin in an area last treated with pyrethroid insecticides 12 yr earlier. Our results underline the need for close monitoring of the impact of insecticide spraying to provide early warning of possible problems because of enhanced resistance or tolerance and determine appropriate responses. PMID:23270166

Gurevitz, Juan M; Gaspe, María Sol; Enríquez, Gustavo F; Vassena, Claudia V; Alvarado-Otegui, Julián A; Provecho, Yael M; Cueto, Gastón A Mougabure; Picollo, María Inés; Kitron, Uriel; Gürtler, Ricardo E

2012-11-01

238

Unexpected Failures to Control Chagas Disease Vectors With Pyrethroid Spraying in Northern Argentina  

PubMed Central

Effectiveness of the elimination efforts against Triatoma infestans (Klug) in South America through residual application of pyrethroid insecticides has been highly variable in the Gran Chaco region. We investigated apparent vector control failures after a standard community-wide spraying with deltamethrin SC in a rural area of northeastern Argentina encompassing 353 houses. Insecticide spraying reduced house infestation less than expected: from 49.5% at baseline to 12.3 and 6.7% at 4 and 8 mo postspraying, respectively. Persistent infestations were detected in 28.4% of houses, and numerous colonies with late-stage bugs were recorded after the interventions. Laboratory bioassays showed reduced susceptibility to pyrethroids in the local bug populations. Eleven of 14 bug populations showed reduced mortality in diagnostic dose assays (range, 35 ± 5% to 97 ± 8%) whereas the remainder had 100% mortality. A fully enclosed residual bug population in a large chicken coop survived four pyrethroid sprays, including two double-dose applications, and was finally suppressed with malathion. The estimated resistance ratio of this bug population was 7.17 (range, 4.47–11.50). Our field data combined with laboratory bioassays and a residual foci experiment demonstrate that the initial failure to suppress T. infestans was mainly because of the unexpected occurrence of reduced susceptibility to deltamethrin in an area last treated with pyrethroid insecticides 12 yr earlier. Our results underline the need for close monitoring of the impact of insecticide spraying to provide early warning of possible problems due to enhanced resistance or tolerance and determine appropriate responses. PMID:23270166

Gurevitz, J. M.; Gaspe, M. S.; Enriquez, G. F.; Vassena, C. V.; Alvarado-Otegui, J. A.; Provecho, Y. M.; Mougabure Cueto, G. A; Picollo, M. I.; Kitron, U.; Gurtler, R. E.

2013-01-01

239

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. PMID:21897846

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

240

Multiaxis control power from thrust vectoring for a supersonic fighter aircraft model at Mach 0.20 to 2.47  

NASA Technical Reports Server (NTRS)

The aeropropulsive characteristics of an advanced twin-engine fighter aircraft designed for supersonic cruise have been studied in the Langley 16-Foot Tansonic Tunnel and the Lewis 10- by 10-Foot Supersonic Tunnel. The objective was to determine multiaxis control-power characteristics from thrust vectoring. A two-dimensional convergent-divergent nozzle was designed to provide yaw vector angles of 0, -10, and -20 deg combined with geometric pitch vector angles of 0 and 15 deg. Yaw thrust vectoring was provided by yaw flaps located in the nozzle sidewalls. Roll control was obtained from differential pitch vectoring. This investigation was conducted at Mach numbers from 0.20 to 2.47. Angle of attack was varied from 0 to about 19 deg, and nozzle pressure ratio was varied from about 1 (jet off) to 28, depending on Mach number. Increments in force or moment coefficient that result from pitch or yaw thrust vectoring remain essentially constant over the entire angle-of-attack range of all Mach numbers tested. There was no effect of pitch vectoring on the lateral aerodynamic forces and moments and only very small effects of yaw vectoring on the longitudinal aerodynamic forces and moments. This result indicates little cross-coupling of control forces and moments for combined pitch-yaw vectoring.

Capone, Francis J.; Bare, E. Ann

1987-01-01

241

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

242

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. PMID:23046535

2012-01-01

243

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. PMID:24587059

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

2014-01-01

244

A New Power-Factor-Based Vector Control Method for Sensorless Drive of Permanent-Magnet Synchronous Motors  

NASA Astrophysics Data System (ADS)

As a simple vector control method for sensorless drives of permanent-magnet synchronous motors, the so-called “Power-Factor-Based (PFB) Vector Control Method” has been proposed. The conventional PFB method directly estimates the phase of the quasi-optimal stator current through a control of the power factor phase, instead of the estimation of the rotor phase. The stator current is controlled in the current reference frame whose secondary axis phase is the same as the stator current phase. This paper proposes a new PEB method where the stator current is controlled in the voltage reference frame whose secondary axis phase is the same as the voltage phase rather than the current phase. It is shown that the similar quasi-optimal stator current control can be attained through the current control with appropriate current commands taking the power factor phase into account. This paper also shows a practical method for generating the current commands and a practical guideline for the design parameters of the new PFB method.

Shinnaka, Shinji

245

Deployment of Innovative Genetic Vector Control Strategies: Progress on Regulatory and Biosafety Aspects, Capacity Building and Development of Best-Practice Guidance  

Microsoft Academic Search

In the ongoing fight against vectors of human diseases, disease endemic countries (DECs) may soon benefit from innova- tive control strategies involving modified insect vectors. For instance, three promising methods (viz. RIDL® (Release of Insects with a Dominant Lethal), Wolbachia infection, and refractory mosquito technology) are being developed by researchers around the world to combat Aedes aegypti, the primary mosquito

Camilla J. Beech; S. S. Vasan; M. Megan Quinlan; Margareth Lara Capurro; Luke Alphey; Vicente Bayard; Madama Bouaré; Maria Corena McLeod; Pattamaporn Kittayapong; James V. Lavery; Lee Han Lim; Mauro Toledo Marrelli; J. Nagaraju; Kenneth Ombongi; Rofina Yasmin Othman; Vilasini Pillai; Janine Ramsey; Rachel Reuben; Robert I. Rose; Brij Kishore Tyagi; John Mumford

2009-01-01

246

Screening Mosquito House Entry Points as a Potential Method for Integrated Control of Endophagic Filariasis, Arbovirus and Malaria Vectors  

PubMed Central

Background Partial mosquito-proofing of houses with screens and ceilings has the potential to reduce indoor densities of malaria mosquitoes. We wish to measure whether it will also reduce indoor densities of vectors of neglected tropical diseases. Methodology The main house entry points preferred by anopheline and culicine vectors were determined through controlled experiments using specially designed experimental huts and village houses in Lupiro village, southern Tanzania. The benefit of screening different entry points (eaves, windows and doors) using PVC-coated fibre glass netting material in terms of reduced indoor densities of mosquitoes was evaluated compared to the control. Findings 23,027 mosquitoes were caught with CDC light traps; 77.9% (17,929) were Anopheles gambiae sensu lato, of which 66.2% were An. arabiensis and 33.8% An. gambiae sensu stricto. The remainder comprised 0.2% (50) An. funestus, 10.2% (2359) Culex spp. and 11.6% (2664) Mansonia spp. Screening eaves reduced densities of Anopheles gambiae s. l. (Relative ratio (RR) ?=?0.91; 95% CI?=?0.84, 0.98; P?=?0.01); Mansonia africana (RR?=?0.43; 95% CI?=?0.26, 0.76; P<0.001) and Mansonia uniformis (RR?=?0.37; 95% CI?=?0.25, 0.56; P<0.001) but not Culex quinquefasciatus, Cx. univittatus or Cx. theileri. Numbers of these species were reduced by screening windows and doors but this was not significant. Significance This study confirms that across Africa, screening eaves protects households against important mosquito vectors of filariasis, Rift Valley Fever and O'Nyong nyong as well as malaria. While full house screening is required to exclude Culex species mosquitoes, screening of eaves alone or fitting ceilings has considerable potential for integrated control of other vectors of filariasis, arbovirus and malaria. PMID:20689815

Ogoma, Sheila B.; Lweitoijera, Dickson W.; Ngonyani, Hassan; Furer, Benjamin; Russell, Tanya L.; Mukabana, Wolfgang R.; Killeen, Gerry F.; Moore, Sarah J.

2010-01-01

247

Area-wide biological control of disease vectors and agents affecting wildlife  

Microsoft Academic Search

Summary Two examples of area-wide programmes, employing the sterile insect technique (SIT), which have eradicated a parasite and a disease vector common to domestic and wild animals are described. New World screwworm (NWS), Cochliomyia hominivorax, caused significant morbidity and mortality of livestock and wild mammals in tropical and subtropical areas of America before eradication was achieved in North America using

R. E. Reichard

2002-01-01

248

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. ...

249

Use of polymerase chain reaction in human African trypanosomiasis stage determination and follow-up.  

PubMed Central

Stage determination of human African trypanosomiasis is based on the detection of parasites and measurements of biological changes in the cerebrospinal fluid (CSF) (concentration of white blood cells > 5 cells per mm3 and increased total protein levels). The patient is treated accordingly. Demonstration of the absence or presence of trypanosomes by the double centrifugation technique is still the only test available to clinicians for assessing treatment success. In this study, however, we evaluate the polymerase chain reaction (PCR) as a tool for assessing the disease stage of trypanosomiasis and for determining whether treatment has been successful. All 15 study patients considered to be in the advanced stage of the disease were PCR positive; however, trypanosomes were demonstrated by double centrifugation in only 11 patients. Of the five remaining patients, who were considered to be in the early stage, PCR and double centrifugation were negative. Following treatment, 13 of the 15 second-stage patients were found to be negative for the disease in at least two samples by PCR and double centrifugation. Two others were still positive by PCR immediately and one month after the treatment. Trypanosome DNA detection using PCR suggested that the two positive patients were not cured but that their possible relapse could not be identified by a search for parasites using the double centrifugation technique. Further evaluation of the PCR method is required, in particular to determine whether PCR assays could be used in studies on patients who fail to respond to melarsoprol, as observed in several foci. PMID:10534898

Truc, P.; Jamonneau, V.; Cuny, G.; Frezil, J. L.

1999-01-01

250

A review of the vector management methods to prevent and control outbreaks of West Nile virus infection and the challenge for Europe  

PubMed Central

West Nile virus infection is a growing concern in Europe. Vector management is often the primary option to prevent and control outbreaks of the disease. Its implementation is, however, complex and needs to be supported by integrated multidisciplinary surveillance systems and to be organized within the framework of predefined response plans. The impact of the vector control measures depends on multiple factors and the identification of the best combination of vector control methods is therefore not always straightforward. Therefore, this contribution aims at critically reviewing the existing vector control methods to prevent and control outbreaks of West Nile virus infection and to present the challenges for Europe. Most West Nile virus vector control experiences have been recently developed in the US, where ecological conditions are different from the EU and vector control is organized under a different regulatory frame. The extrapolation of information produced in North America to Europe might be limited because of the seemingly different epidemiology in the European region. Therefore, there is an urgent need to analyse the European experiences of the prevention and control of outbreaks of West Nile virus infection and to perform robust cost-benefit analysis that can guide the implementation of the appropriate control measures. Furthermore, to be effective, vector control programs require a strong organisational backbone relying on a previously defined plan, skilled technicians and operators, appropriate equipment, and sufficient financial resources. A decision making guide scheme is proposed which may assist in the process of implementation of vector control measures tailored on specific areas and considering the available information and possible scenarios. PMID:25015004

2014-01-01

251

A review of the vector management methods to prevent and control outbreaks of West Nile virus infection and the challenge for Europe.  

PubMed

West Nile virus infection is a growing concern in Europe. Vector management is often the primary option to prevent and control outbreaks of the disease. Its implementation is, however, complex and needs to be supported by integrated multidisciplinary surveillance systems and to be organized within the framework of predefined response plans. The impact of the vector control measures depends on multiple factors and the identification of the best combination of vector control methods is therefore not always straightforward. Therefore, this contribution aims at critically reviewing the existing vector control methods to prevent and control outbreaks of West Nile virus infection and to present the challenges for Europe.Most West Nile virus vector control experiences have been recently developed in the US, where ecological conditions are different from the EU and vector control is organized under a different regulatory frame. The extrapolation of information produced in North America to Europe might be limited because of the seemingly different epidemiology in the European region. Therefore, there is an urgent need to analyse the European experiences of the prevention and control of outbreaks of West Nile virus infection and to perform robust cost-benefit analysis that can guide the implementation of the appropriate control measures. Furthermore, to be effective, vector control programs require a strong organisational backbone relying on a previously defined plan, skilled technicians and operators, appropriate equipment, and sufficient financial resources. A decision making guide scheme is proposed which may assist in the process of implementation of vector control measures tailored on specific areas and considering the available information and possible scenarios. PMID:25015004

Bellini, Romeo; Zeller, Herve; Van Bortel, Wim

2014-01-01

252

An agent–vector–host–environment model for controlling small arms and light weapons  

Microsoft Academic Search

Armed violence is a significant public health problem. It results in fatal and non-fatal injuries and disrupts social and economic processes that are essential to the health of individuals and communities. We argue that an agent–vector–host–environment model can be helpful in understanding and describing the availability and misuse of small arms and light weapons. Moreover, such a model can assist

Andrew D. Pinto; Malika Sharma; Robert Muggah

2011-01-01

253

Stoking the drug target pipeline for human African trypanosomiasis.  

PubMed

Trypanosoma brucei is the causative agent of African sleeping sickness, putting at risk up to 50 million people in sub-Saharan Africa. Current drug therapies are limited by toxicity and difficult treatment regimes and as the development of vaccines remains unlikely, the identification of better drugs to control this deadly disease is needed. Strategies for the identification of new lead compounds include phenotypic screening or target-based approaches. Implementation of the latter has been hampered by the lack of defined targets that are both essential and druggable. In this issue of Molecular Microbiology, Jones et?al. (2012) report on the characterization of T.?brucei pyridoxal kinase (PdxK), an enzyme required for the salvage of vitamin B6, an essential enzymatic cofactor. Genetic knock-down and small molecule inhibitor studies were used to demonstrate that PdxK is essential for parasite growth both in vitro and in a mouse model, providing both genetic and chemical validation of the target. An enzyme assay compatible with high-throughput screening (HTS) was developed and the X-ray crystal structure solved, showing the potential for species selective inhibition. These studies add a greatly needed additional target into the drug discovery pipeline for this deadly parasitic infection. PMID:22925123

Phillips, Margaret A

2012-10-01

254

Magnetic resonance imaging findings in human African trypanosomiasis: a four-year follow-up study in a patient and review of the literature.  

PubMed

Serial magnetic resonance imaging (MRI) was performed up to 4 years after treatment in a patient with Trypanosoma brucei gambiense infection. Four years after treatment and cure abnormalities were still present, although the patient led a normal social life, without physical and mental impairments. The literature on MRI in human African trypanosomiasis is reviewed. The MRI is useful to discriminate between encephalitis induced by trypanosomiasis and post-treatment reactive encephalopathy, a severe and often fatal complication of treatment, in particular of treatment with arsenicals. The MRI is not useful for diagnosis of human African trypanosomiasis (HAT). PMID:19478256

Kager, Piet A; Schipper, Hans G; Stam, Jan; Majoie, Charles B L M

2009-06-01

255

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

256

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

257

Outcome of acute East African trypanosomiasis in a Polish traveller treated with pentamidine  

PubMed Central

Background African trypanosomiasis is a parasitic infection sporadically imported to Europe by tourists or immigrants returning from endemic areas. We present the first and an unusual case of East African trypanosomiasis imported to Poland by a patient returning from a tourist trip to Uganda and Rwanda, which was successfully treated with pentamidine. Case presentation A 61-year-old Polish man was admitted to the Department because of high-grade fever and multi-organ dysfunction after a tourist trip to East Africa. He experienced a single tsetse fly bite during a safari trip to the Queen Elizabeth National Park in Uganda. On admission, his clinical status was severe, with high fever of 41ºC, preceded by chills, bleeding from the gums and oral mucosa, haemorrhages at the sites of venipuncture, numerous ecchymoses, fine-spotted skin rash, tachycardia, hepatosplenomegaly, dehydration, jaundice, dyspnoea, hypoxaemia, generalised oedema and oliguria. There was a typical non-painful trypanosomal chancre with central necrosis and peripheral erythema on his left arm. Laboratory investigations showed leucopenia, thrombocytopenia, haemolytic anaemia, hyperbilirubinaemia, hypoglycaemia, elevated creatinine and urea, high activity of aminotransferases, elevated levels of inflammatory markers, hypoproteinaemia, proteinuria, abnormal clotting and bleeding times, low fibrinogen level, metabolic acidosis, and electrolyte disturbances. A peripheral blood smear showed numerous Trypanosoma brucei trypomastigotes with a massive parasitaemia of 100,000/?l. T. brucei rhodesiense subspecies was finally identified on the basis of the characteristic serum resistance-associated gene using a polymerase chain reaction, and a seroconversion of specific immunoglobulin M and G antibodies in the peripheral blood by enzyme-linked immunosorbent assay. Serological tests for T. brucei gambiense subspecies were negative. A severe clinical course of acute rhodesiense trypanosomiasis with renal failure, respiratory distress, disseminated intravascular coagulation syndrome, haemolysis, liver insufficiency and myocarditis was confirmed. Intensive anti-parasitic and symptomatic treatment was immediately instituted, including intravenous pentamidine, plasmaphereses, oxygen therapy, blood transfusion, catecholamine administration, and fluid infusions, as well as haemostatic, hepatoprotective, anti-inflammatory, antipyretic and diuretic drugs. The final outcome was a full recovery with no late sequelae. Conclusion Sleeping sickness should always be considered in the differential diagnosis of fever in people returning from safari trips to the national parks or nature reserves of sub-Saharan Africa. PMID:24571399

2014-01-01

258

Mapping the capacities of fixed health facilities to cover people at risk of gambiense human African trypanosomiasis  

PubMed Central

Background The emphasis placed on the activities of mobile teams in the detection of gambiense human African trypanosomiasis (HAT) can at times obscure the major role played by fixed health facilities in HAT control and surveillance. The lack of consistent and detailed data on the coverage of passive case-finding and treatment further constrains our ability to appreciate the full contribution of the health system to the control of HAT. Methods A survey was made of all fixed health facilities that are active in the control and surveillance of gambiense HAT. Information on their diagnostic and treatment capabilities was collected, reviewed and harmonized. Health facilities were geo-referenced. Time-cost distance analysis was conducted to estimate physical accessibility and the potential coverage of the population at-risk of gambiense HAT. Results Information provided by the National Sleeping Sickness Control Programmes revealed the existence of 632 fixed health facilities that are active in the control and surveillance of gambiense HAT in endemic countries having reported cases or having conducted active screening activities during the period 2000-2012. Different types of diagnosis (clinical, serological, parasitological and disease staging) are available from 622 facilities. Treatment with pentamidine for first-stage disease is provided by 495 health facilities, while for second-stage disease various types of treatment are available in 206 health facilities only. Over 80% of the population at-risk for gambiense HAT lives within 5-hour travel of a fixed health facility offering diagnosis and treatment for the disease. Conclusions Fixed health facilities have played a crucial role in the diagnosis, treatment and coverage of at-risk-population for gambiense HAT. As the number of reported cases continues to dwindle, their role will become increasingly important for the prospects of disease elimination. Future updates of the database here presented will regularly provide evidence to inform and monitor a rational deployment of control and surveillance efforts. Support to the development and, if successful, the implementation of new control tools (e.g. new diagnostics and new drugs) is crucial, both for strengthening and expanding the existing network of fixed health facilities by improving access to diagnosis and treatment and for securing a sustainable control and surveillance of gambiense HAT. PMID:24517513

2014-01-01

259

Seroprevalence of canine leishmaniasis and American trypanosomiasis in dogs from Grenada, West Indies.  

PubMed

Canine leishmaniasis and American trypanosomiasis (AT) are caused by related hemoflagellated parasites, Leishmania spp. and Trypanosoma cruzi, which share several common host species. Dogs are reservoirs for human infections by both pathogens. We determined the prevalence of antibodies to Leishmania spp. and T. cruzi in dogs from Grenada, West Indies. We examined 70 dog sera using the qualitative immunochromatographic dipstick tests (ICTs) based on recombinant antigens specific for visceral leishmaniasis and AT. Antibodies to visceral Leishmania were not detected in Grenadian dogs by ICT. Using the canine dipsticks for AT, antibodies to T. cruzi were determined in 3 (4.3%) of the 70 dogs. Results from this study indicate that dogs in Grenada are exposed in low levels to T. cruzi , but not to visceral Leishmania spp. at all. PMID:19712013

Rosypal, Alexa C; Tripp, Shanesha; Kinlaw, Christopher; Sharma, R N; Stone, D; Dubey, J P

2010-02-01

260

[Seroprevalence of American trypanosomiasis in adults in an area of the western Brazilian Amazon region].  

PubMed

From January to March 2001 a seroepidemiological survey for American trypanosomiasis (Chagas disease) was carried out among urban and rural human populations in areas of the Upper Purus basin, in the western Brazilian Amazon region, using serial testing with three different serological techniques. The sample was composed of 1,055 individuals: 844 from urban and 211 from rural areas. Autochthonous infection was identified in nine individuals aged 16 to 72 years: five from urban and four from rural areas. The estimated prevalences of Chagas infection for the urban and rural areas were 0.6% (95% CI: 0.2-1.4) and 1.9% (95% CI: 0.6-4.5) respectively. An apparent clustering trend was noted: seven were born along the Purus river: three lived at the same locality and two of them in the same dwelling. PMID:17876467

Dantas-Maia, Thor Oliveira; Castro, Cleudson; Ostermayer, Alejandro Luquetti; Macêdo, Vanize

2007-01-01

261

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. PMID:22206031

Lucantoni, Leonardo; Magaraggia, Michela; Lupidi, Giulio; Ouedraogo, Robert Kossivi; Coppellotti, Olimpia; Esposito, Fulvio; Fabris, Clara; Jori, Giulio; Habluetzel, Annette

2011-01-01

262

Domestic pigs as potential reservoirs of human and animal trypanosomiasis in Northern Tanzania  

PubMed Central

Background Pig keeping is becoming increasingly common across sub-Saharan Africa. Domestic pigs from the Arusha region of northern Tanzania were screened for trypanosomes using PCR-based methods to examine the role of pigs as a reservoir of human and animal trypanosomiasis. Methods A total of 168 blood samples were obtained from domestic pigs opportunistically sampled across four districts in Tanzania (Babati, Mbulu, Arumeru and Dodoma) during December 2004. A suite of PCR-based methods was used to identify the species and sub-species of trypanosomes including: Internally Transcribed Sequence to identify multiple species; species specific PCR to identify T. brucei s. l. and T. godfreyi and a multiplex PCR reaction to distinguish T. b. rhodesiense from T. brucei s. l. Results Of the 168 domestic pigs screened for animal and human infective trypanosome DNA, 28 (16.7%) were infected with one or more species of trypanosome; these included: six pigs infected with Trypanosoma vivax (3.6%); three with Trypanosoma simiae (1.8%); two with Trypanosoma congolense (Forest) (1%) and four with Trypanosoma godfreyi (2.4%). Nineteen pigs were infected with Trypanosoma brucei s. l. (10.1%) of which eight were identified as carrying the human infective sub-species Trypanosoma brucei rhodesiense (4.8%). Conclusion These results show that in Tanzania domestic pigs may act as a significant reservoir for animal trypanosomiasis including the cattle pathogens T. vivax and T. congolense, the pig pathogen T. simiae, and provide a significant reservoir for T. b. rhodesiense, the causative agent of acute Rhodesian sleeping sickness. PMID:24499540

2013-01-01

263

Vector control measures failed to affect genetic structure of Aedes aegypti in a sentinel metropolitan area of Brazil.  

PubMed

In order to evaluate subpopulation differentiation, effective population size (Ne) and evidence for population bottlenecks at various geographic levels, Aedes aegypti larvae were collected longitudinally from 2007 to 2009 from four areas in the city of Salvador, Brazil. The DNA from each larva was isolated and genotyped with five independent microsatellite markers. FST and Jost's D revealed significant population structuring (P<0.05) at the municipal and regional levels, while only RST was able to detect genetic differentiation at the level of strata within these areas. Ne analysis from longitudinal data did not show any evidence of significant change in population structure. The census population measured by the house index, however, showed a significant trend toward decrease in these areas. Active vector control measures did contribute to vector reduction, but this was not enough to decrease A. aegypti population genetic diversity in Salvador. The understanding of A. aegypti population dynamics may be helpful for planning and evaluation of control measures to make them more effective. PMID:24028791

Souza, Kathleen R; Ribeiro, Gilmar; Silva dos Santos, Carlos Gustavo; de Lima, Eliaci Couto; Melo, Paulo R S; Reis, Mitermayer G; Blanton, Ronald E; Silva, Luciano K

2013-12-01

264

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

265

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

266

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

267

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

268

Optimal control of a universal rotating magnetic vector for petal-shaped capsule robot in curve environment  

NASA Astrophysics Data System (ADS)

Steering control of a capsule robot in curve environment by magnetic navigation is not yet solved completely. A petal-shaped capsule robot with less steering resistance based on multiple wedge effects is presented, and an optimization method with two processes for determining the orientation of a pre-applied universal magnetic spin vector is proposed. To realize quick and non-contact steering swimming, a fuzzy comprehensive evaluation method for optimizing the steering driving angle is presented based on two evaluation indexes including the average steering speed and the average steering trajectory deviation, achieving the initial optimal orientation of a universal magnetic spin vector. To further reduce robotic magnetic vibration, a main target method for optimizing its final orientation, which is used for fine adjustment, is employed under the constrains of the magnetic moments. Swimming experimental results in curve pipe verified the effectiveness of the optimization method, which can be effectively used to realize non-contact steering swimming of the petal-shaped robot and reduce its vibration.

Zhang, Yongshun; Bai, Jianwei; Chi, Minglu; Cheng, Cunxin; Wang, Dianlong

2014-08-01

269

Key Source Habitats and Potential Dispersal of Triatoma infestans Populations in Northwestern Argentina: Implications for Vector Control  

PubMed Central

Background Triatoma infestans —the principal vector of the infection that causes Chagas disease— defies elimination efforts in the Gran Chaco region. This study identifies the types of human-made or -used structures that are key sources of these bugs in the initial stages of house reinfestation after an insecticide spraying campaign. Methodology and Principal Findings We measured demographic and blood-feeding parameters at two geographic scales in 11 rural communities in Figueroa, northwest Argentina. Of 1,297 sites searched in spring, 279 (21.5%) were infested. Bug abundance per site and female fecundity differed significantly among habitat types (ecotopes) and were highly aggregated. Domiciles (human sleeping quarters) had maximum infestation prevalence (38.7%), human-feeding bugs and total egg production, with submaximal values for other demographic and blood-feeding attributes. Taken collectively peridomestic sites were three times more often infested than domiciles. Chicken coops had greater bug abundance, blood-feeding rates, engorgement status, and female fecundity than pig and goat corrals. The host-feeding patterns were spatially structured yet there was strong evidence of active dispersal of late-stage bugs between ecotopes. Two flight indices predicted that female fliers were more likely to originate from kitchens and domiciles, rejecting our initial hypothesis that goat and pig corrals would dominate. Conclusions and Significance Chicken coops and domiciles were key source habitats fueling rapid house reinfestation. Focusing control efforts on ecotopes with human-fed bugs (domiciles, storerooms, goat corrals) would neither eliminate the substantial contributions to bug population growth from kitchens, chicken coops, and pig corrals nor stop dispersal of adult female bugs from kitchens. Rather, comprehensive control of the linked network of ecotopes is required to prevent feeding on humans, bug population growth, and bug dispersal simultaneously. Our study illustrates a demographic approach that may be applied to other regions and triatomine species for the design of innovative, improved vector control strategies. PMID:25299653

Gurtler, Ricardo E.; Cecere, Maria C.; Fernandez, Maria del Pilar; Vazquez-Prokopec, Gonzalo M.; Ceballos, Leonardo A.; Gurevitz, Juan M.; Kitron, Uriel; Cohen, Joel E.

2014-01-01

270

Turning cigarette butt waste into an alternative control tool against an insecticide-resistant mosquito vector.  

PubMed

Annually, 4.5 trillion cigarette butts (CBs) are flicked into our environment. Evidence exists that CB waste is deadly to aquatic life, but their lethality to the aquatic life of the main dengue vector is unknown. CBs are full of toxicants that occur naturally, during planting and manufacturing, which may act as larvicidal agents. We assessed Aedes aegypti vulnerability to Marlboro butts during its development. Overall, CBs showed insecticidal activities against larvae. At early phases of development, mortality rates were much higher in two CBs solution (2CBSol) and 3CBSol microcosms (MICRs). Larval survival gradually decreased with development in 1CBSol-MICRs. However, in great presence of CBs, mortality was high even for the late developmental stages. These results suggest that A. aegypti larvae are vulnerable to CB presence in their habitats, but this effect was seen most during the early developmental phases and in the presence of increased amounts of cigarette remnants. CB filters are being used as raw material in many sectors, i.e., brick, art, fashion, plastic industries, as a practical solution to the pollution problem, the observed butt waste toxicity to mosquito larvae open new avenues for the identification of novel insecticide products. PMID:23999373

Dieng, Hamady; Rajasaygar, Sudha; Ahmad, Abu Hassan; Ahmad, Hamdan; Rawi, Che Salmah Md; Zuharah, Wan Fatma; Satho, Tomomitsu; Miake, Fumio; Fukumitsu, Yuki; Saad, Ahmad Ramli; Ghani, Idris Abd; Vargas, Ronald Enrique Morales; Majid, Abdul Hafiz Ab; Abubakar, Sazaly

2013-12-01

271

Trypanosoma brucei gambiense African trypanosomiasis: differences between men and women in severity of disease and response to treatment  

Microsoft Academic Search

To compare the characteristics of women and men with Trypanosoma brucei gambiense trypanosomiasis, all 3231 cases treated in Nioki hospital, Democratic Republic of Congo, from 1982 to 2000 were reviewed for demographic information, date and mode of diagnosis, pre-treatment cerebrospinal fluid (CSF) examination, treatment given and its adverse effects, and whether a diagnosis of relapse was made during post-treatment follow-up.

Jacques Pépin; Bokelo Mpia; Masasa Iloasebe

2002-01-01

272

IDENTIFICATION OF OPTIMUM SITES FOR A POWER SYSTEM CONTROLLER USING NORMAL FORMS OF VECTOR FIELD  

Microsoft Academic Search

In stressed power system, due to the pres- ence of increased nonlinearity and the existence of nonlin- ear modal interactions, there exist some limitations to the use of conventional linear system theory to identify the optimum sites for a controller. This paper suggests an approach based on the method of normal forms to identify suitable sites for controllers with incorporating

Gilsoo Jang; Insoo Lee; Sae-Hyuk Kwon

2002-01-01

273

Vector control method applied to a traveling wave in a finite beam.  

PubMed

This paper presents the closed-loop control of exciters to produce a traveling wave in a finite beam. This control is based on a dynamical modeling of the system established in a rotating reference frame. This method allows dynamic and independent control of the phase and amplitude of two vibration modes. The condition to obtain the traveling wave is written in this rotating frame, and requires having two vibration modes with the same amplitude, and imposing a phase shift of 90° between them. The advantage of the method is that it allows easy implementation of a closed loop control that can handle parameter drift of the system, after a temperature rise, for example. The modeling is compared with measurement on an experimental test bench which also implements real-time control. We managed to experimentally obtain a settling time of 250 ms for the traveling wave, and a standing wave ratio (SWR) of 1.3. PMID:24402901

Giraud, Frédéric; Giraud-Audine, Christophe; Amberg, Michel; Lemaire-Semail, Betty

2014-01-01

274

Symbolic computer vector analysis  

NASA Technical Reports Server (NTRS)

A MACSYMA program is described which performs symbolic vector algebra and vector calculus. The program can combine and simplify symbolic expressions including dot products and cross products, together with the gradient, divergence, curl, and Laplacian operators. The distribution of these operators over sums or products is under user control, as are various other expansions, including expansion into components in any specific orthogonal coordinate system. There is also a capability for deriving the scalar or vector potential of a vector field. Examples include derivation of the partial differential equations describing fluid flow and magnetohydrodynamics, for 12 different classic orthogonal curvilinear coordinate systems.

Stoutemyer, D. R.

1977-01-01

275

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

276

Configuration management and automatic control of an augmentor wing aircraft with vectored thrust  

NASA Technical Reports Server (NTRS)

An advanced structure for automatic flight control logic for powered-lift aircraft operating in terminal areas is under investigation at Ames Research Center. This structure is based on acceleration control; acceleration commands are constructed as the sum of acceleration on the reference trajectory and a corrective feedback acceleration to regulate path tracking errors. The central element of the structure, termed a Trimmap, uses a model of the aircraft aerodynamic and engine forces to calculate the control settings required to generate the acceleration commands. This report describes the design criteria for the Trimmap and derives a Trimmap for Ames experimental augmentor wing jet STOL research aircraft.

Cicolani, L. S.; Sridhar, B.; Meyer, G.

1979-01-01

277

Harmonic domain modelling of three phase thyristor-controlled reactors by means of switching vectors and discrete convolutions  

SciTech Connect

The main objective of this paper is to report on a newly developed three phase Thyristor Controlled Reactor (TCR) model which is based on the use of harmonic switching vectors and discrete convolutions. This model is amenable to direct frequency domain operations and provides a fast and reliable means for assessing 6- and 12-pulse TCR plant performance at harmonic frequencies. The use of alternate time domain and frequency domain representations is avoided as well as the use of FFTs. In this approach, each single phase unit of the TCR is modelled as a voltage-dependent harmonic Norton equivalent where all the harmonics and cross-couplings between harmonics are explicitly shown. This model is suitable for direct incorporation into the harmonic domain frame of reference where all the busbars, phases, harmonics and cross-couplings between harmonics are combined together for a unified iterative solution through a Newton-Raphson technique exhibiting quadratic convergence.

Rico, J.J.; Acha, E.; Miller, T.J.E. [Univ. of Glasgow (United Kingdom). Dept. of Electronics and Electrical Engineering] [Univ. of Glasgow (United Kingdom). Dept. of Electronics and Electrical Engineering

1996-07-01

278

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

279

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

280

Insecticide resistance in Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) and Anopheles gambiae Giles (Diptera: Culicidae) could compromise the sustainability of malaria vector control strategies in West Africa.  

PubMed

Insecticides from the organophosphate (OP) and pyrethroid (PY) chemical families, have respectively, been in use for 50 and 30 years in West Africa, mainly against agricultural pests, but also against vectors of human disease. The selection pressure, with practically the same molecules year after year (mainly on cotton), has caused insecticide resistance in pest populations such as Bemisia tabaci, vector of harmful phytoviruses on vegetables. The evolution toward insecticide resistance in malaria vectors such as Anopheles gambiae sensus lato (s.l.) is probably related to the current use of these insecticides in agriculture. Thus, successful pest and vector control in West Africa requires an investigation of insect susceptibility, in relation to the identification of species and sub species, such as molecular forms or biotypes. Identification of knock down resistance (kdr) and acetylcholinesterase gene (Ace1) mutations modifying insecticide targets in individual insects and measure of enzymes activity typically involved in insecticide metabolism (oxidase, esterase and glutathion-S-transferase) are indispensable in understanding the mechanisms of resistance. Insecticide resistance is a good example in which genotype-phenotype links have been made successfully. Insecticides used in agriculture continue to select new resistant populations of B. tabaci that could be from different biotype vectors of plant viruses. As well, the evolution of insecticide resistance in An. gambiae threatens the management of malaria vectors in West Africa. It raises the question of priority in the use of insecticides in health and/or agriculture, and more generally, the question of sustainability of crop protection and vector control strategies in the region. Here, we review the susceptibility tests, biochemical and molecular assays data for B. tabaci, a major pest in cotton and vegetable crops, and An. gambiae, main vector of malaria. The data reviewed was collected in Benin and Burkina Faso between 2008 and 2010 under the Corus 6015 research program. This review aims to show: (i) the insecticide resistance in B. tabaci as well as in An. gambiae; and (ii) due to this, the impact of selection of resistant populations on malaria vector control strategies. Some measures that could be beneficial for crop protection and vector control strategies in West Africa are proposed. PMID:23792227

Gnankiné, Olivier; Bassolé, Imael H N; Chandre, Fabrice; Glitho, Isabelle; Akogbeto, Martin; Dabiré, Roch K; Martin, Thibaud

2013-10-01

281

Vector Voyage!  

NSDL National Science Digital Library

In this activity, students will use vector analysis to understand the concept of dead reckoning. Students will use vectors to plot their course based on a time and speed. They will then correct the positions with vectors representing winds and currents.

Integrated Teaching And Learning Program

282

Efficacy of Aquatain, a Monomolecular Film, for the Control of Malaria Vectors in Rice Paddies  

PubMed Central

Background Rice paddies harbour a large variety of organisms including larvae of malaria mosquitoes. These paddies are challenging for mosquito control because their large size, slurry and vegetation make it difficult to effectively apply a control agent. Aquatain, a monomolecular surface film, can be considered a suitable mosquito control agent for such breeding habitats due to its physical properties. The properties allow Aquatain to self-spread over a water surface and affect multiple stages of the mosquito life cycle. Methodology/Principal Findings A trial based on a pre-test/post-test control group design evaluated the potential of Aquatain as a mosquito control agent at Ahero rice irrigation scheme in Kenya. After Aquatain application at a dose of 2 ml/m2 on rice paddies, early stage anopheline larvae were reduced by 36%, and late stage anopheline larvae by 16%. However, even at a lower dose of 1 ml/m2 there was a 93.2% reduction in emergence of anopheline adults and 69.5% reduction in emergence of culicine adults. No pupation was observed in treated buckets that were part of a field bio-assay carried out parallel to the trial. Aquatain application saved nearly 1.7 L of water in six days from a water surface of 0.2 m2 under field conditions. Aquatain had no negative effect on rice plants as well as on a variety of non-target organisms, except backswimmers. Conclusions/Significance We demonstrated that Aquatain is an effective agent for the control of anopheline and culicine mosquitoes in irrigated rice paddies. The agent reduced densities of aquatic larval stages and, more importantly, strongly impacted the emergence of adult mosquitoes. Aquatain also reduced water loss due to evaporation. No negative impacts were found on either abundance of non-target organisms, or growth and development of rice plants. Aquatain, therefore, appears a suitable mosquito control tool for use in rice agro-ecosystems. PMID:21738774

Bukhari, Tullu; Takken, Willem; Githeko, Andrew K.; Koenraadt, Constantianus J. M.

2011-01-01

283

Standardizing Visual Control Devices for Tsetse Flies: East African Species Glossina fuscipes fuscipes and Glossina tachinoides  

PubMed Central

Background Riverine species of tsetse are responsible for most human African trypanosomiasis (HAT) transmission and are also important vectors of animal trypanosomiasis. This study concerns the development of visual control devices for two such species, Glossina fuscipes fuscipes and Glossina tachinoides, at the eastern limits of their continental range. The goal was to determine the most long-lasting, practical and cost-effective visually attractive device that induces the strongest landing responses in these species for use as insecticide-impregnated tools in vector population suppression. Methods and Findings Field trials were conducted in different seasons on G. f. fuscipes in Kenya, Ethiopia and the Sudan and on G. tachinoides in Ethiopia to measure the performance of traps and 2D targets of different sizes and colours, with and without chemical baits, at different population densities and under different environmental conditions. Adhesive film was used to enumerate flies at these remote locations to compare trapping efficiencies. The findings show that targets made from black and blue fabrics (either phthalogen or turquoise) covered with adhesive film render them equal to or more efficient than traps at capturing G. f. fuscipes and G. tachinoides. Biconical trap efficiency varied between 25% and 33% for the two species. Smaller 0.25 m×0.25 m phthalogen blue-black targets proved more efficient than the regular 1 m2 target for both species, by over six times for Glossina f. fuscipes and two times for G. tachinoides based on catches per m2. Overall, targets with a higher edge/surface area ratio were more efficient at capturing flies. Conclusions/Significance Taking into account practical considerations and fly preferences for edges and colours, we propose a 0.5×0.75 m blue-black target as a simple cost-effective device for management of G. f. fuscipes and G. tachinoides, impregnated with insecticide for control and covered with adhesive film for population sampling. PMID:25411931

Oloo, Francis; Sciarretta, Andrea; Kröber, Thomas; McMullin, Andrew; Mihok, Steve; Guerin, Patrick M.

2014-01-01

284

Macro level control of an activity switch in a scientific vector processor which processor requires an external executive control program  

SciTech Connect

This patent describes a scientific data processor requiring an external executive control program, the scientific data processor having an activity switch which includes an instruction cache buffer to receive the temporarily store data from a main storage, an instruction address selection logic means connected to the instruction cache buffer and an instruction decode and sequencing control means coupled to the instruction cache buffer, apparatus for controlling the activity switch of the scientific processor at the macro instruction level comprising: (a) macro code storage means to store a plurality of macro coded instructions and to provide a source thereof; (b) macro code control means responsive to a plurality of interrupt signals from various sources and to provide a plurality of control signals; (c) a source of data from a main storage means; and (d) an instruction buffer writer data selector means commonly connected to (a), (b) and (c) to selectively receive information from either the (a) or (c) under the control of (b) such that in response to any one of a plurality of interrupt signals to the macro code control means, the macro code control means causes the instruction buffer write data selector means to selectively shift from the receipt of data from the main storage to the receipt of data from the macro code store means thereby providing macro level control of the activity switch in the scientific processor.

Lahti, A.E.; James, R.L.; Byers, L.L.

1988-12-13

285

Made-to-measure malaria vector control strategies: rational design based on insecticide properties and coverage of blood resources for mosquitoes  

PubMed Central

Eliminating malaria from highly endemic settings will require unprecedented levels of vector control. To suppress mosquito populations, vector control products targeting their blood hosts must attain high biological coverage of all available sources, rather than merely high demographic coverage of a targeted resource subset, such as humans while asleep indoors. Beyond defining biological coverage in a measurable way, the proportion of blood meals obtained from humans and the proportion of bites upon unprotected humans occurring indoors also suggest optimal target product profiles for delivering insecticides to humans or livestock. For vectors that feed only occasionally upon humans, preferred animal hosts may be optimal targets for mosquito-toxic insecticides, and vapour-phase insecticides optimized to maximize repellency, rather than toxicity, may be ideal for directly protecting people against indoor and outdoor exposure. However, for vectors that primarily feed upon people, repellent vapour-phase insecticides may be inferior to toxic ones and may undermine the impact of contact insecticides applied to human sleeping spaces, houses or clothing if combined in the same time and place. These concepts are also applicable to other mosquito-borne anthroponoses so that diverse target species could be simultaneously controlled with integrated vector management programmes. Measurements of these two crucial mosquito behavioural parameters should now be integrated into programmatically funded, longitudinal, national-scale entomological monitoring systems to inform selection of available technologies and investment in developing new ones. PMID:24739261

2014-01-01

286

VECTOR CONTROL, PEST MANAGEMENT, RESISTANCE, REPELLENTS Impact of Inorganic Pollutants Perchlorate and Hexavalent Chromium  

E-print Network

and Hexavalent Chromium on Efficacy of Bacillus sphaericus and Bacillus thuringiensis subsp. israelensis Against) ABSTRACT The effects of two widespread environmental pollutants, perchlorate and hexavalent chromium, were, did not affect the control provided by either larvicide, presence of 1.04 mg/liter hexavalent chromium

Trumble, John T.

287

Design Specification for a Thrust-Vectoring, Actuated-Nose-Strake Flight Control Law for the High-Alpha Research Vehicle  

NASA Technical Reports Server (NTRS)

Specifications for a flight control law are delineated in sufficient detail to support coding the control law in flight software. This control law was designed for implementation and flight test on the High-Alpha Research Vehicle (HARV), which is an F/A-18 aircraft modified to include an experimental multi-axis thrust-vectoring system and actuated nose strakes for enhanced rolling (ANSER). The control law, known as the HARV ANSER Control Law, was designed to utilize a blend of conventional aerodynamic control effectors, thrust vectoring, and actuated nose strakes to provide increased agility and good handling qualities throughout the HARV flight envelope, including angles of attack up to 70 degrees.

Bacon, Barton J.; Carzoo, Susan W.; Davidson, John B.; Hoffler, Keith D.; Lallman, Frederick J.; Messina, Michael D.; Murphy, Patrick C.; Ostroff, Aaron J.; Proffitt, Melissa S.; Yeager, Jessie C.; Foster, John V.; Bundick, W. Thomas; Connelly, Patrick J.; Kelly, John W.; Pahle, Joseph W.; Thomas, Michael; Wichman, Keith D.; Wilson, R. Joseph

1996-01-01

288

The Importance of Veterinary Policy in Preventing the Emergence and Re-Emergence of Zoonotic Disease: Examining the Case of Human African Trypanosomiasis in Uganda  

PubMed Central

Rapid changes in human behavior, resource utilization, and other extrinsic environmental factors continue to threaten the current distribution of several endemic and historically neglected zoonoses in many developing regions worldwide. There are numerous examples of zoonotic diseases which have circulated within relatively localized geographical areas for some time, before emerging into new regions as a result of changing human, environmental, or behavioral dynamics. While the world’s focus is currently on the Ebola virus gaining momentum in western Africa, another pertinent example of this phenomenon is zoonotic human African trypanosomiasis (HAT), endemic to south and eastern Africa, and spread via infected cattle. In recent years, the ongoing northwards spread of this disease in the country has posed a serious public health threat to the human population of Uganda, increasing the pressure on both individual families and government services to control the disease. Moreover, the emergence of HAT into new areas of Uganda in recent years exemplifies the important role of veterinary policy in mitigating the severe human health and economic impacts of zoonotic disease. The systemic challenges surrounding the development and enforcement of veterinary policy described here are similar across sub-Saharan Africa, highlighting the necessity to consider and support zoonotic disease control in broader human and animal health systems strengthening and associated development programs on the continent.

Okello, Anna L.; Welburn, Susan C.

2014-01-01

289

A new space vector PWM control strategy for high performance converters  

E-print Network

38 41 41 42 vu CHAPTER Page 3. Simulation result B. Summary V IMPLEMENTATION OF THE PROPOSED SPACE VEC- TOR PWM WITH DSP TECHNOLOGY. . . . . . . . . . . A. Digital signal processing and control B. Selection of the DSP processor 1. System... described situations in real time and guarantee high performance characteristics in pulse width modulated rectifier and inverter systems. The computational procedure of the switching states is simple and is adaptable to implementation in modern DSP...

Xie, Bin

2012-06-07

290

Sustained Reduction of the Dengue Vector Population Resulting from an Integrated Control Strategy Applied in Two Brazilian Cities  

PubMed Central

Aedes aegypti has developed evolution-driven adaptations for surviving in the domestic human habitat. Several trap models have been designed considering these strategies and tested for monitoring this efficient vector of Dengue. Here, we report a real-scale evaluation of a system for monitoring and controlling mosquito populations based on egg sampling coupled with geographic information systems technology. The SMCP-Aedes, a system based on open technology and open data standards, was set up from March/2008 to October/2011 as a pilot trial in two sites of Pernambuco -Brazil: Ipojuca (10,000 residents) and Santa Cruz (83,000), in a joint effort of health authorities and staff, and a network of scientists providing scientific support. A widespread infestation by Aedes was found in both sites in 2008–2009, with 96.8%–100% trap positivity. Egg densities were markedly higher in SCC than in Ipojuca. A 90% decrease in egg density was recorded in SCC after two years of sustained control pressure imposed by suppression of >7,500,000 eggs and >3,200 adults, plus larval control by adding fishes to cisterns. In Ipojuca, 1.1 million mosquito eggs were suppressed and a 77% reduction in egg density was achieved. This study aimed at assessing the applicability of a system using GIS and spatial statistic analysis tools for quantitative assessment of mosquito populations. It also provided useful information on the requirements for reducing well-established mosquito populations. Results from two cities led us to conclude that the success in markedly reducing an Aedes population required the appropriate choice of control measures for sustained mass elimination guided by a user-friendly mosquito surveillance system. The system was able to support interventional decisions and to assess the program’s success. Additionally, it created a stimulating environment for health staff and residents, which had a positive impact on their commitment to the dengue control program. PMID:23844059

Regis, Leda N.; Acioli, Ridelane Veiga; Silveira, Jose Constantino; Melo-Santos, Maria Alice Varjal; Souza, Wayner Vieira; Ribeiro, Candida M. Nogueira.; da Silva, Juliana C. Serafim.; Monteiro, Antonio Miguel Vieira; Oliveira, Claudia M. F.; Barbosa, Rosangela M. R.; Braga, Cynthia; Rodrigues, Marco Aurelio Benedetti; Silva, Marilu Gomes N. M.; Ribeiro Jr., Paulo Justiniano; Bonat, Wagner Hugo; de Castro Medeiros, Liliam Cesar; Carvalho, Marilia Sa; Furtado, Andre Freire

2013-01-01

291

Community-centred eco-bio-social approach to control dengue vectors: an intervention study from Myanmar  

PubMed Central

Objectives To build up and analyse the feasibility, process, and effectiveness of a partnership-driven ecosystem management intervention in reducing dengue vector breeding and constructing sustainable partnerships among multiple stakeholders. Methods A community-based intervention study was conducted from May 2009 to January 2010 in Yangon city. Six high-risk and six low-risk clusters were randomized and allocated as intervention and routine service areas, respectively. For each cluster, 100 households were covered. Bi-monthly entomological evaluations (i.e. larval and pupal surveys) and household acceptability surveys at the end of 6-month intervention period were conducted, supplemented by qualitative evaluations. Intervention description The strategies included eco-friendly multi-stakeholder partner groups (Thingaha) and ward-based volunteers, informed decision-making of householders, followed by integrated vector management approach. Findings Pupae per person index (PPI) decreased at the last evaluation by 5.7% (0.35–0.33) in high-risk clusters. But in low-risk clusters, PPI remarkably decreased by 63.6% (0.33–0.12). In routine service area, PPI also decreased due to availability of Temephos after Cyclone Nargis. As for total number of pupae in all containers, when compared to evaluation 1, there was a reduction of 18.6% in evaluation 2 and 44.1% in evaluation 3 in intervention area. However, in routine service area, more reduction was observed. All intervention tools were found as acceptable, being feasible to implement by multi-stakeholder partner groups. Conclusions The efficacy of community-controlled partnership-driven interventions was found to be superior to the vertical approach in terms of sustainability and community empowerment. PMID:23318238

Wai, Khin Thet; Htun, Pe Than; Oo, Tin; Myint, Hla; Lin, Zaw; Kroeger, Axel; Sommerfeld, Johannes; Petzold, Max

2012-01-01

292

Outdoor host seeking behaviour of Anopheles gambiae mosquitoes following initiation of malaria vector control on Bioko Island, Equatorial Guinea  

Microsoft Academic Search

Background  Indoor-based anti-vector interventions remain the preferred means of reducing risk of malaria transmission in malaria endemic\\u000a areas around the world. Despite demonstrated success in reducing human-mosquito interactions, these methods are effective\\u000a solely against endophilic vectors. It may be that outdoor locations serve as an important venue of host seeking by Anopheles gambiae sensu lato (s.l.) mosquitoes where indoor vector suppression

Michael R Reddy; Hans J Overgaard; Simon Abaga; Vamsi P Reddy; Adalgisa Caccone; Anthony E Kiszewski; Michel A Slotman

2011-01-01

293

Structure-activity relationships of synthetic cordycepin analogues as experimental therapeutics for African trypanosomiasis.  

PubMed

Novel methods for treatment of African trypanosomiasis, caused by infection with Trypanosoma brucei are needed. Cordycepin (3'-deoxyadenosine, 1a) is a powerful trypanocidal compound in vitro but is ineffective in vivo because of rapid metabolic degradation by adenosine deaminase (ADA). We elucidated the structural moieties of cordycepin required for trypanocidal activity and designed analogues that retained trypanotoxicity while gaining resistance to ADA-mediated metabolism. 2-Fluorocordycepin (2-fluoro-3'-deoxyadenosine, 1b) was identified as a selective, potent, and ADA-resistant trypanocidal compound that cured T. brucei infection in mice. Compound 1b is transported through the high affinity TbAT1/P2 adenosine transporter and is a substrate of T. b. brucei adenosine kinase. 1b has good preclinical properties suitable for an oral drug, albeit a relatively short plasma half-life. We present a rapid and efficient synthesis of 2-halogenated cordycepins, also useful synthons for the development of additional novel C2-substituted 3'-deoxyadenosine analogues to be evaluated in development of experimental therapeutics. PMID:24283924

Vodnala, Suman K; Lundbäck, Thomas; Yeheskieli, Esther; Sjöberg, Birger; Gustavsson, Anna-Lena; Svensson, Richard; Olivera, Gabriela C; Eze, Anthonius A; de Koning, Harry P; Hammarström, Lars G J; Rottenberg, Martin E

2013-12-27

294

Congenital and oral transmission of American trypanosomiasis: an overview of physiopathogenic aspects.  

PubMed

Chagas disease or American trypanosomiasis is a pathology affecting about 8-11 million people in Mexico, Central America, and South America, more than 300 000 persons in the United States as well as an indeterminate number of people in other non-endemic countries such as USA, Spain, Canada and Switzerland. The aetiological agent is Trypanosoma cruzi, a protozoan transmitted by multiple routes; among them, congenital route emerges as one of the most important mechanisms of spreading Chagas disease worldwide even in non-endemic countries and the oral route as the responsible of multiple outbreaks of acute Chagas disease in regions where the vectorial route has been interrupted. The aim of this review is to illustrate the recent research and advances in host-pathogen interaction making a model of how the virulence factors of the parasite would interact with the physiology and immune system components of the placental barrier and gastrointestinal tract in order to establish a response against T. cruzi infection. This review also presents the epidemiological, clinical and diagnostic features of congenital and oral Chagas disease in order to update the reader about the emerging scenarios of Chagas disease transmission. PMID:23010131

Sánchez, Laura Viviana; Ramírez, Juan David

2013-02-01

295

Human African trypanosomiasis: a review of non-endemic cases in the past 20 years.  

PubMed

Human African trypanosomiasis (HAT) is caused by sub-species of the parasitic protozoan Trypanosoma brucei and is transmitted by tsetse flies, both of which are endemic only to sub-Saharan Africa. Several cases have been reported in non-endemic areas, such as North America and Europe, due to travelers, ex-patriots or military personnel returning from abroad or due to immigrants from endemic areas. In this paper, non-endemic cases reported over the past 20 years are reviewed; a total of 68 cases are reported, 19 cases of Trypanosoma brucei gambiense HAT and 49 cases of Trypanosoma brucei rhodesiense HAT. Patients ranged in age from 19 months to 72 years and all but two patients survived. Physicians in non-endemic areas should be aware of the signs and symptoms of this disease, as well as methods of diagnosis and treatment, especially as travel to HAT endemic areas increases. We recommend extension of the current surveillance systems such as TropNetEurop and maintaining and promotion of existing reference centers of diagnostics and expertise. Important contact information is also included, should physicians require assistance in diagnosing or treating HAT. PMID:21683638

Migchelsen, Stephanie J; Büscher, Philippe; Hoepelman, Andy I M; Schallig, Henk D F H; Adams, Emily R

2011-08-01

296

Metabolic signatures of triatomine vectors of Trypanosoma cruzi unveiled by metabolomics.  

PubMed

Chagas disease is a trypanosomiasis whose causative agent is the protozoan parasite Trypanosoma cruzi, which is transmitted to humans by hematophagous insects known as triatomines and affects a large proportion of South America. The digestive tract of the insect vectors in which T. cruzi develops constitutes a dynamic environment that affects the development of the parasite. Thus, we set out to investigate the chemical composition of the triatomine intestinal tract through a metabolomics approach. We performed Direct Infusion Fourier Transform Ion Cyclotron Resonance Mass Spectrometry on fecal samples of three triatomine species (Rhodnius prolixus, Triatoma infestans, Panstrongylus megistus) fed with rabbit blood. We then identified groups of metabolites whose frequencies were either uniform in all species or enriched in each of them. By querying the Human Metabolome Database, we obtained putative identities of the metabolites of interest. We found that a core group of metabolites with uniform frequencies in all species represented approximately 80% of the molecules detected, whereas the other 20% varied among triatomine species. The uniform core was composed of metabolites of various categories, including fatty acids, steroids, glycerolipids, nucleotides, sugars, and others. Nevertheless, the metabolic fingerprint of triatomine feces differs depending on the species considered. The variable core was mainly composed of prenol lipids, amino acids, glycerolipids, steroids, phenols, fatty acids and derivatives, benzoic acid and derivatives, flavonoids, glycerophospholipids, benzopyrans, and quinolines. Triatomine feces constitute a rich and varied chemical medium whose constituents are likely to affect T. cruzi development and infectivity. The complexity of the fecal metabolome of triatomines suggests that it may affect triatomine vector competence for specific T. cruzi strains. Knowledge of the chemical environment of T. cruzi in its invertebrate host is likely to generate new ways to understand the factors influencing parasite proliferation as well as methods to control Chagas disease. PMID:24204787

Antunes, Luis Caetano M; Han, Jun; Pan, Jingxi; Moreira, Carlos J C; Azambuja, Patrícia; Borchers, Christoph H; Carels, Nicolas

2013-01-01

297

Metabolic Signatures of Triatomine Vectors of Trypanosoma cruzi Unveiled by Metabolomics  

PubMed Central

Chagas disease is a trypanosomiasis whose causative agent is the protozoan parasite Trypanosoma cruzi, which is transmitted to humans by hematophagous insects known as triatomines and affects a large proportion of South America. The digestive tract of the insect vectors in which T. cruzi develops constitutes a dynamic environment that affects the development of the parasite. Thus, we set out to investigate the chemical composition of the triatomine intestinal tract through a metabolomics approach. We performed Direct Infusion Fourier Transform Ion Cyclotron Resonance Mass Spectrometry on fecal samples of three triatomine species (Rhodnius prolixus, Triatoma infestans, Panstrongylus megistus) fed with rabbit blood. We then identified groups of metabolites whose frequencies were either uniform in all species or enriched in each of them. By querying the Human Metabolome Database, we obtained putative identities of the metabolites of interest. We found that a core group of metabolites with uniform frequencies in all species represented approximately 80% of the molecules detected, whereas the other 20% varied among triatomine species. The uniform core was composed of metabolites of various categories, including fatty acids, steroids, glycerolipids, nucleotides, sugars, and others. Nevertheless, the metabolic fingerprint of triatomine feces differs depending on the species considered. The variable core was mainly composed of prenol lipids, amino acids, glycerolipids, steroids, phenols, fatty acids and derivatives, benzoic acid and derivatives, flavonoids, glycerophospholipids, benzopyrans, and quinolines. Triatomine feces constitute a rich and varied chemical medium whose constituents are likely to affect T. cruzi development and infectivity. The complexity of the fecal metabolome of triatomines suggests that it may affect triatomine vector competence for specific T. cruzi strains. Knowledge of the chemical environment of T. cruzi in its invertebrate host is likely to generate new ways to understand the factors influencing parasite proliferation as well as methods to control Chagas disease. PMID:24204787

Antunes, Luis Caetano M.; Han, Jun; Pan, Jingxi; Moreira, Carlos J. C.; Azambuja, Patricia; Borchers, Christoph H.; Carels, Nicolas

2013-01-01

298

A Kalman filtering technique for spacecraft attitude determination and control using Gibbs vector  

E-print Network

presented here is fundamental to spacecraft attitude determination and control. Alternative descriptions can be found in many of the standard 10, 19-21, 33 texts. ' In Section 1, the kinematic equations of motion are developed in terms of the Gibbs... of the spacecraft in the EKF. The filter algorithm can then be used in a closed loop simulation to maneuver the spacecraft. For the open loop attitude determination, the motion is assumed to be uncontrolled, so that Eqs. (60) reduce to e = e Q (61a) w = ? Gl w...

Tallant, Gregory Stephen

2012-06-07

299

Control of health hazards likely to arise from the use of organo-phosphorus insecticides in vector control  

PubMed Central

The widespread use of DDT and the chlorinated hydrocarbon group of insecticides for the control of mosquitos and flies has led to the emergence of resistant strains of flies. Where the DDT group of insecticides is ineffective for the control of resistant insects, it appears that the use of the organo-phosphorus group of insecticides may be an alternative. However, it seems probable that their introduction and application under the same conditions in which DDT has been safely used might carry serious risks to the health of the men who apply them. In this paper, the authors indicate what these dangers are, how they manifest themselves, and how they might be controlled. Four methods of blood-cholinesterase determinations, carried out in the laboratory and in the field, are described in an annex. PMID:13413646

Barnes, J. M.; Hayes, W. J.; Kay, Kingsley

1957-01-01

300

Control of Pyrethroid-Resistant Chagas Disease Vectors with Entomopathogenic Fungi  

PubMed Central

Background Triatoma infestans-mediated transmission of Tripanosoma cruzi, the causative agent of Chagas disease, remains as a major health issue in southern South America. Key factors of T. infestans prevalence in specific areas of the geographic Gran Chaco region—which extends through northern Argentina, Bolivia, and Paraguay—are both recurrent reinfestations after insecticide spraying and emerging pyrethroid-resistance over the past ten years. Among alternative control tools, the pathogenicity of entomopathogenic fungi against triatomines is already known; furthermore, these fungi have the ability to fully degrade hydrocarbons from T. infestans cuticle and to utilize them as fuel and for incorporation into cellular components. Methodology and Findings Here we provide evidence of resistance-related cuticle differences; capillary gas chromatography coupled to mass spectrometry analyses revealed that pyrethroid-resistant bugs have significantly larger amounts of surface hydrocarbons, peaking 56.2±6.4% higher than susceptible specimens. Also, a thicker cuticle was detected by scanning electron microscopy (32.1±5.9 µm and 17.8±5.4 µm for pyrethroid-resistant and pyrethroid-susceptible, respectively). In laboratory bioassays, we showed that the virulence of the entomopathogenic fungi Beauveria bassiana against T. infestans was significantly enhanced after fungal adaptation to grow on a medium containing insect-like hydrocarbons as the carbon source, regardless of bug susceptibility to pyrethroids. We designed an attraction-infection trap based on manipulating T. infestans behavior in order to facilitate close contact with B. bassiana. Field assays performed in rural village houses infested with pyrethroid-resistant insects showed 52.4% bug mortality. Using available mathematical models, we predicted that further fungal applications could eventually halt infection transmission. Conclusions This low cost, low tech, ecologically friendly methodology could help in controlling the spread of pyrethroid-resistant bugs. PMID:19434231

Pedrini, Nicolas; Mijailovsky, Sergio J.; Girotti, Juan R.; Stariolo, Raul; Cardozo, Ruben M.; Gentile, Alberto; Juarez, M. Patricia

2009-01-01

301

Impact of Education Campaign on Community-Based Vector Control in Hastening the Process of Elimination of Lymphatic Filariasis in Tamil Nadu, South India  

ERIC Educational Resources Information Center

Globally mosquito-borne lymphatic filariasis (LF) is targeted for elimination by 2020. Towards this goal, the scope of community-based vector control as a supplementary strategy to mass drug administration (MDA) was assessed through an intensive education campaign and evaluated using pre- and post-educational surveys in an intervention and…

Nandha, B.; Krishnamoorthy, K.

2012-01-01

302

Exploring new thermal fog and ultra-low volume technologies to improve indoor control of the dengue vector, Aedes aegypti (Diptera: Culicidae).  

PubMed

Control of the mosquito vector, Aedes aegypti (L.), inside human habitations must be performed quickly and efficiently to reduce the risk of transmission during dengue outbreaks. As part of abroad study to assess the efficacy of dengue vector control tools for the U.S. Military, two pesticide delivery systems (ultra-low volume [ULV] and thermal fog) were evaluated for their ability to provide immediate control of Ae. aegypti mosquitoes with a contact insecticide inside simulated urban structures. An insect growth regulator was also applied to determine how well each sprayer delivered lethal doses of active ingredient to indoor water containers for pupal control. Mortality of caged Ae. aegypti, pesticide droplet size, and droplet deposition were recorded after applications. In addition, larval and pupal mortality was measured from treated water samples for 4 wk after the applications. The ULV and the thermal fogger performed equally well in delivering lethal doses of adulticide throughout the structures. The ULV resulted in greater larval mortality and adult emergence inhibition in the water containers for a longer period than the thermal fogger. Therefore, the ULV technology is expected to be a better tool for sustained vector suppression when combined with an effective insect growth regulator. However, during a dengue outbreak, either delivery system should provide an immediate knockdown of vector populations that may lower the risk of infection and allow other suppression strategies to be implemented. PMID:25118418

Harwood, James F; Farooq, Muhammad; Richardson, Alec G; Doud, Carl W; Putnam, John L; Szumlas, Daniel E; Richardson, Jason H

2014-07-01

303

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. PMID:24699034

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

304

Depression and the Sense of Control: Aging Vectors, Trajectories and Trends*  

PubMed Central

Adulthood trajectories of outcomes such as depression and the sense of control measure aspects of the human condition that Americans may view as objects of change. Social science should provide information on that progress, or its absence. Whether these trajectories change their shape, and how and why if they do, is important theoretically too. A range of birth cohorts coexist in time, place, and social relationship. Each cohort, as it goes through adulthood, follows in aggregate a path left by older ones, reshaping that path as it goes. The shapes of the trajectories, and the trends reshaping them, represent two inseparable aspects of the same phenomenon. This report describes methods for mapping aging trajectories and inter-cohort trends, using linear latent-growth models of relatively brief followup data (six years in the examples). It reviews shared research ideals that led to the model: put theory into modeling, go where the data lead, use what you have, go beyond where you have been, and risk being precisely wrong. PMID:24311752

Mirowsky, John

2013-01-01

305

Use of larvivorous fish for vector control in the Malvides Republic.  

PubMed

The paper reports on the use of three larvivorous fishes in the Maldives Republic: Poecilia reticulata (Poeciliidae), Mollienesia sphenops (Cyprinodontidae) and for the first time Kuhlia taeniurus (Kuhliidae), a sea fish adapted to life in wells, which are the only sources of water supply (with the exception of a few rain-water cisterns). The approximately 20 000 wells are the main and all-year-round breeding places for both Anophelines and Culicines. Due to this type of breeding places, Maldives are in a unique situation, that the fish can theoretically be used as the main control measure for filariasis. This requires an absolute minimum of work and no cost at all. There has been a reduction of the filariasis overall endemicity rates over the last 10 years although no specific measures have been carried out (except in the capital city of Male) nor have any ecological changes taken place, which could explain this decrease. With this decrease however there has been lately a marked reduction in the percentage of wells with fish in some atolls. PMID:1216337

Velimirovic, B; Clarke, J L

1975-12-01

306

Human antibody response to Aedes albopictus salivary proteins: a potential biomarker to evaluate the efficacy of vector control in an area of chikungunya and dengue virus transmission.  

PubMed

Aedes borne viruses represent public health problems in southern countries and threat to emerge in the developed world. Their control is currently based on vector population control. Much effort is being devoted to develop new tools to control such arbovirus. Recent findings suggest that the evaluation of human antibody (Ab) response to arthropod salivary proteins is relevant to measuring the level of human exposure to mosquito bites. Using an immunoepidemiological approach, the present study aimed to assess the usefulness of the salivary biomarker for measuring the efficacy of Ae. albopictus control strategies in La Reunion urban area. The antisaliva Ab response of adult humans exposed to Ae. albopictus was evaluated before and after vector control measures. Our results showed a significant correlation between antisaliva Ab response and the level of exposure to vectors bites. The decrease of Ae. albopictus density has been detected by this biomarker two weeks after the implementation of control measures, suggesting its potential usefulness for evaluating control strategies in a short time period. The identification of species specific salivary proteins/peptides should improve the use of this biomarker. PMID:24822216

Doucoure, Souleymane; Mouchet, François; Cornelie, Sylvie; Drame, Papa Makhtar; D'Ortenzio, Eric; DeHecq, Jean Sébastien; Remoue, Franck

2014-01-01

307

Human Antibody Response to Aedes albopictus Salivary Proteins: A Potential Biomarker to Evaluate the Efficacy of Vector Control in an Area of Chikungunya and Dengue Virus Transmission  

PubMed Central

Aedes borne viruses represent public health problems in southern countries and threat to emerge in the developed world. Their control is currently based on vector population control. Much effort is being devoted to develop new tools to control such arbovirus. Recent findings suggest that the evaluation of human antibody (Ab) response to arthropod salivary proteins is relevant to measuring the level of human exposure to mosquito bites. Using an immunoepidemiological approach, the present study aimed to assess the usefulness of the salivary biomarker for measuring the efficacy of Ae. albopictus control strategies in La Reunion urban area. The antisaliva Ab response of adult humans exposed to Ae. albopictus was evaluatedbefore and after vector control measures. Our results showed a significant correlation between antisaliva Ab response and the level of exposure to vectors bites. The decrease of Ae. albopictus density has been detected by this biomarker two weeks after the implementation of control measures, suggesting its potential usefulness for evaluating control strategies in a short time period. The identification of species specific salivary proteins/peptides should improve the use of this biomarker. PMID:24822216

Doucoure, Souleymane; Mouchet, Francois; Cornelie, Sylvie; Drame, Papa Makhtar; D'Ortenzio, Eric; DeHecq, Jean Sebastien; Remoue, Franck

2014-01-01

308

Closed-Loop Control of a Three-Phase Neutral-Point-Clamped Inverter Using an Optimized Virtual-Vector-Based Pulsewidth Modulation  

Microsoft Academic Search

This paper presents a closed-loop control scheme for the three-level three-phase neutral-point-clamped dc-ac converter using the optimized nearest three virtual-space-vector pulsewidth modulation, which is a modulation that produces low output-voltage distortion with a significant reduction of the dc-link capacitance. A new specific loop modifying the modulating waveforms is proposed to rapidly control possible perturbations in the neutral-point voltage balance. An

Sergio Busquets-Monge; JosÉ Daniel Ortega; Josep Bordonau; JosÉ Antonio Beristain; Joan Rocabert

2008-01-01

309

Evaluation of a vector-control strategy of haemorrhagic thelohanellosis in carp, caused by Thelohanellus hovorkai (Myxozoa).  

PubMed

The life cycle of Thelohanellus hovorkai (Myxozoa), the causative agent of haemorrhagic thelohanellosis of carp Cyprinus carpio, involves the alternate oligochaete host Branchiura sowerbyi, which plays the role of vector in the parasite's transmission. Field investigations in carp farms suggested that oligochaete fauna were closely associated with the substrate type of the pond. The pond bottom in the enzootic farm consisted of clay soil and soft sediments comprised of organic mud, in which B. sowerbyi dominated in high densities, with a maximum of 5.6 ind. kg(-1) soil. In another case, in a carp farm with no previous history of the disease, the pond bottom was sandy soil, in which small-sized oligochaetes, composed mainly of Limnodrilus socialis, dominated. Laboratory studies on the substrate preference of oligochaetes proved that B. sowerbyi prefers mud to sand, whereas L. socialis has no tendency to substrate tropism. The delicate body surface of B. sowerbyi was subject to damage by rugged-edged sand particles, which inflicted severe injuries to the worms. Transmission experiments showed that L. socialis, which are non-susceptible to T. hovorkai, suppressed the production of T. hovorkai actinospores in B. sowerbyi in a mixed assemblage of oligochaetes. Field and experimental evidence in this study imply that substrate replacement in culture ponds might regulate the benthic oligochaete communities, resulting in minimization of the impact of haemorrhagic thelohanellosis. We propose that ecological control of oligochaete fauna by environmental management is a promising strategy against myxozoan diseases. PMID:12887252

Liyanage, Yasoja S; Yokoyama, Hiroshi; Wakabayashi, Hisatsugu

2003-06-20

310

Large fluctuations in the effective population size of the malaria mosquito Anopheles gambiae s.s. during vector control cycle.  

PubMed

On Bioko Island, Equatorial Guinea, indoor residual spraying (IRS) has been part of the Bioko Island Malaria Control Project since early 2004. Despite success in reducing childhood infections, areas of high transmission remain on the island. We therefore examined fluctuations in the effective population size (N e ) of the malaria vector Anopheles gambiae in an area of persistent high transmission over two spray rounds. We analyzed data for 13 microsatellite loci from 791 An. gambiae specimens collected at six time points in 2009 and 2010 and reconstructed the demographic history of the population during this period using approximate Bayesian computation (ABC). Our analysis shows that IRS rounds have a large impact on N e , reducing it by 65%-92% from prespray round N e . More importantly, our analysis shows that after 3-5 months, the An. gambiae population rebounded by 2818% compared shortly following the spray round. Our study underscores the importance of adequate spray round frequency to provide continuous suppression of mosquito populations and that increased spray round frequency should substantially improve the efficacy of IRS campaigns. It also demonstrates the ability of ABC to reconstruct a detailed demographic history across only a few tens of generations in a large population. PMID:24478799

Hodges, Theresa K; Athrey, Giridhar; Deitz, Kevin C; Overgaard, Hans J; Matias, Abrahan; Caccone, Adalgisa; Slotman, Michel A

2013-12-01

311

Melarsoprol cyclodextrin inclusion complexes as promising oral candidates for the treatment of human African trypanosomiasis.  

PubMed

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 where they enter the central nervous system (CNS) to cause serious neurological disease. The trivalent arsenical drug melarsoprol (Arsobal) is the only currently available treatment for CNS-stage T. b. rhodesiense infection. However, it must be administered intravenously due to the presence of propylene glycol solvent and is associated with numerous adverse reactions. A severe post-treatment reactive encephalopathy occurs in about 10% of treated patients, half of whom die. Thus melarsoprol kills 5% of all patients receiving it. Cyclodextrins have been used to improve the solubility and reduce the toxicity of a wide variety of drugs. We therefore investigated two melarsoprol cyclodextrin inclusion complexes; melarsoprol hydroxypropyl-?-cyclodextrin and melarsoprol randomly-methylated-?-cyclodextrin. We found that these compounds retain trypanocidal properties in vitro and cure CNS-stage murine infections when delivered orally, once per day for 7-days, at a dosage of 0.05 mmol/kg. No overt signs of toxicity were detected. Parasite load within the brain was rapidly reduced following treatment onset and magnetic resonance imaging showed restoration of normal blood-brain barrier integrity on completion of chemotherapy. These findings strongly suggest that complexed melarsoprol could be employed as an oral treatment for CNS-stage HAT, delivering considerable improvements over current parenteral chemotherapy. PMID:21909447

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

2011-09-01

312

Preclinical Assessment of the Treatment of Second-Stage African Trypanosomiasis with Cordycepin and Deoxycoformycin  

PubMed Central

Background There is an urgent need to substitute the highly toxic compounds still in use for treatment of the encephalitic stage of human African trypanosomiasis (HAT). We here assessed the treatment with the doublet cordycepin and the deaminase inhibitor deoxycoformycin for this stage of infection with Trypanosoma brucei (T.b.). Methodology/Principal Findings Cordycepin was selected as the most efficient drug from a direct parasite viability screening of a compound library of nucleoside analogues. The minimal number of doses and concentrations of the drugs effective for treatment of T.b. brucei infections in mice were determined. Oral, intraperitoneal or subcutaneous administrations of the compounds were successful for treatment. The doublet was effective for treatment of late stage experimental infections with human pathogenic T.b. rhodesiense and T.b. gambiense isolates. Late stage infection treatment diminished the levels of inflammatory cytokines in brains of infected mice. Incubation with cordycepin resulted in programmed cell death followed by secondary necrosis of the parasites. T.b. brucei strains developed resistance to cordycepin after culture with increasing concentrations of the compound. However, cordycepin-resistant parasites showed diminished virulence and were not cross-resistant to other drugs used for treatment of HAT, i.e. pentamidine, suramin and melarsoprol. Although resistant parasites were mutated in the gene coding for P2 nucleoside adenosine transporter, P2 knockout trypanosomes showed no altered resistance to cordycepin, indicating that absence of the P2 transporter is not sufficient to render the trypanosomes resistant to the drug. Conclusions/Significance Altogether, our data strongly support testing of treatment with a combination of cordycepin and deoxycoformycin as an alternative for treatment of second-stage and/or melarsoprol-resistant HAT. PMID:19652702

Vodnala, Suman K.; Ferella, Marcela; Lunden-Miguel, Hilda; Betha, Evans; van Reet, Nick; Amin, Daniel Ndem; Oberg, Bo; Andersson, Bjorn; Kristensson, Krister; Wigzell, Hans; Rottenberg, Martin E.

2009-01-01

313

How Much Does Malaria Vector Control Quality Matter: The Epidemiological Impact of Holed Nets and Inadequate Indoor Residual Spraying  

PubMed Central

Background Insecticide treated nets (ITN) and indoor residual spraying (IRS) are the two pillars of malaria vector control in Africa, but both interventions are beset by quality and coverage concerns. Data from three control programs were used to investigate the impact of: 1) the physical deterioration of ITNs, and 2) inadequate IRS spray coverage, on their respective protective effectiveness. Methods Malaria indicator surveys were carried out in 2009 and 2010 in Bioko Island, mainland Equatorial Guinea and Malawi to monitor infection with P.falciparum in children, mosquito net use, net condition and spray status of houses. Nets were classified by their condition. The association between infection and quality and coverage of interventions was investigated. Results There was reduced odds of infection with P.falciparum in children sleeping under ITNs that were intact (Odds ratio (OR): 0.65, 95% CI: 0.55–0.77 and OR: 0.81, 95% CI: 0.56–1.18 in Equatorial Guinea and in Malawi respectively), but the protective effect became less with increasingly worse condition of the net. There was evidence for a linear trend in infection per category increase in deterioration of nets. In Equatorial Guinea IRS offered protection to those in sprayed and unsprayed houses alike when neighbourhood spray coverage was high (?80%) compared to those living in areas of low IRS coverage (<20%), regardless of whether the house they lived in was sprayed or not (adjusted OR?=?0.54, 95% CI 0.33–0.89). ITNs provided only personal protection, offering no protection to non users. Although similar effects were seen in Malawi, the evidence was much weaker than in Equatorial Guinea. Conclusions Universal coverage strategies should consider policies for repair and replacement of holed nets and promote the care of nets by their owners. IRS programs should ensure high spray coverage since inadequate coverage gives little or no protection at all. PMID:21559436

Rehman, Andrea M.; Coleman, Mike; Schwabe, Christopher; Baltazar, Giovanna; Matias, Abrahan; Roncon Gomes, Irina; Yellott, Lee; Aragon, Cynthia; Nseng Nchama, Gloria; Mzilahowa, Themba; Rowland, Mark; Kleinschmidt, Immo

2011-01-01

314

The reliability of virus-induced gene silencing experiments using tobacco rattle virus in tomato is influenced by the size of the vector control.  

PubMed

The tobacco rattle virus (TRV)-based vector pYL156 is the most widely used vector for virus-induced gene silencing (VIGS) in solanaceous plants. We show here that vacuum agroinfiltration of the pYL156 empty vector causes extensive stem lesions, foliar necrosis, stunted growth and delayed flowering in tomato, whereas plants infiltrated with pYL156-based silencing constructs that carry inserts of ?250 bp or more show few symptoms of virus infection. This difference in plant health influences plant susceptibility to insects, a trait measured in many VIGS experiments, and could potentially bias the results of other bioassays designed to assess the phenotypic consequences of VIGS. When plants were infiltrated with the pYL156:GUS construct, which carries a 396-bp fragment of the ?-glucuronidase gene that has no significant homology with any endogenous gene in tomato, they showed similar growth and development as buffer-infiltrated controls, and exhibited significantly fewer viral symptoms than the empty vector. Furthermore, pYL156:GUS did not influence plant susceptibility to aphids. Reverse transcription-polymerase chain reaction (RT-PCR) results indicated that the GUS insert may cause a modest delay in virus movement within the plant, but does not limit TRV replication in infected tissue. Therefore, the pYL156:GUS construct represents an improved negative control for TRV-induced gene silencing. PMID:21356001

Wu, Chengjun; Jia, Lingling; Goggin, Fiona

2011-04-01

315

Vector Fields  

NSDL National Science Digital Library

Vector fields are vectors which change from point to point. A standard example is the velocity of moving air, in other words, wind. For instance, the current wind pattern in the San Francisco area can be found at . This site has a 2-dimensional representation; careful reading of the webpage will tell you at what elevation the wind is shown. How would you represent a vector field in 3 dimensions? What features are important? Some simple examples are shown. Each can be rotated by clicking and dragging with the mouse. Explore!

Ay, Tevian

2006-01-01

316

Potential of contact insecticides to control Xyleborus glabratus (Coleoptera: Curculionidae), a vector of laurel wilt disease in avocados.  

PubMed

Xyleborus glabratus Eichhoff (Coleoptera: Curculionidae: Scolytinae) is an invasive ambrosia beetle that vectors laurel wilt, a new disease that threatens avocado and other species in the Lauraceae Family. The lethal concentrations (LC50 & 90) of nine commercial insecticides to X. glabratus were determined by using a bolt-dip bioassay. Different formulations of bifenthrin, permethrin, fenpropathrin, z-cypermethrin + bifenthrin, 1-cyhalothrin + thiamethoxam, malathion, chlorpyrifos, carbaryl, and methomyl were tested. Four concentrations of each insecticide were tested (0.5, 0.1, 0.03, and 0.01 of the label rate) and with water as a control. Beetles were exposed to treated bolts and mortality registered 48 h later. After 2 wk, bolts were destructively sampled to determine the number of beetles that constructed galleries and were alive inside the wood. Probit analysis was used to determine the LC50 & 90. Six pesticides were applied directly to the trunk and limbs of avocado trees in a commercial grove. Limbs of treated trees were cut weekly after the application and exposed to X. glabratus to determine the number of beetles boring into the logs. The toxicity of pesticides to X. glabratus was greatly reduced 2 wk after application. Among the tested pesticides, malathion and z-cypermethrin + bifenthrin provided the best suppression of X. glabratus. Among the insecticides registered for use in avocado, fenpropathrin and malathion were the most effective in protecting trees from attack by X. glabratus. Other pesticides that are currently not registered for use in avocados could be useful for managing this ambrosia beetle. PMID:24498726

Carrillo, Daniel; Crane, Jonathan H; Peña, Jorge E

2013-12-01

317

Susceptibility of Culicoides biting midge larvae to the insect-pathogenic fungus, Metarhizium anisopliae: prospects for bluetongue vector control.  

PubMed

Culicoides biting midges (Diptera: Ceratopogonidae) are responsible for the spread of several arboviruses of livestock and humans that are of international importance. This study assesses the virulence of 18 insect-pathogenic fungal strains from the genera Metarhizium, Beauveria, Isaria and Lecanicillium to larval stages of Culicoides nubeculous Meigen as a means of examining their potential as biocontrol agents. In initial screening, six strains of M. anisopliae (ERL700, CA1, V275, LRC181A, ARSEF 3291 and ARSEF 4556) outperformed the other tested genera and were found to cause between 90% and 100% larval mortality in all larval instars of this species at 72 h post inoculation. The virulence of the most effective strain, M. anisopliae V275, was then further tested by exposing larvae to doses which ranged from 10(4)-10(8) conidia/ml and recording mortality at 24, 48 and 72 h in a 24-multi-well plate with each well containing 600 microl of water and at 24 and 48 h in 250 ml plastic cups containing 50 ml of water. Sensitivity of larvae was extremely high in the multi-well plates, with LC(50) values of 4.3-4.5 x 10(3)conidia/ml and no significant differences between larval instars. In the 250 ml cups, M. anisopliae V275 caused mortalities of between 70% and 100% to larvae and later instars exhibited higher mortality rates. The results are discussed in relation to incorporation of M. anisopliae into biocontrol programmes to control arboviruses vectored by Culicoides. PMID:19703405

Ansari, M A; Carpenter, S; Butt, T M

2010-01-01

318

Equivalent Vectors  

ERIC Educational Resources Information Center

The cross-product is a mathematical operation that is performed between two 3-dimensional vectors. The result is a vector that is orthogonal or perpendicular to both of them. Learning about this for the first time while taking Calculus-III, the class was taught that if AxB = AxC, it does not necessarily follow that B = C. This seemed baffling. The…

Levine, Robert

2004-01-01

319

Vector quantization  

NASA Technical Reports Server (NTRS)

During the past ten years Vector Quantization (VQ) has developed from a theoretical possibility promised by Shannon's source coding theorems into a powerful and competitive technique for speech and image coding and compression at medium to low bit rates. In this survey, the basic ideas behind the design of vector quantizers are sketched and some comments made on the state-of-the-art and current research efforts.

Gray, Robert M.

1989-01-01

320

Impact of community-based vector control on house infestation and Trypanosoma cruzi infection in Triatoma infestans, dogs and cats in the Argentine Chaco  

PubMed Central

The relative impact of two community-based vector control strategies on house infestation by Triatoma infestans and Trypanosoma cruzi infection in bugs, domestic dogs and cats was assessed in two neighboring rural areas comprising 40 small villages and 323 houses in one of the regions most endemic for Chagas disease in northern Argentina. The prevalence and abundance of domestic infestation were 1.5- and 6.5-fold higher, respectively, in the area under pulsed, non-supervised control actions operating under the guidelines of the National Vector Control Program (NCVP) than in the area under sustained, supervised surveillance carried out jointly by the UBA research team and NCVP. The prevalence of infestation and infection varied widely among village groups within each area. In the pulsed control area, the prevalence of infection in bugs, dogs and cats was two- to three-fold higher than in the area under sustained surveillance, most of the infected animals qualified as autochthonous cases, and evidence of recent transmission was observed. Infection was highly aggregated at the household level and fell close to the 80/20 rule. Using multiple logistic regression analysis clustered by household, infection in dogs was associated positively and significantly with variables reflecting local exposure to infected T. infestans, thus demonstrating weak performance of the vector surveillance system. For high-risk areas in the Gran Chaco region, interruption of vector-mediated domestic transmission of T. cruzi requires residual insecticide spraying that is more intense, of a higher quality and sustained in time, combined with community participation and environmental management measures. PMID:17686448

CARDINAL, M.V.; LAURICELLA, M.A.; MARCET, P.L.; OROZCO, M.M.; KITRON, U.; GURTLER, R.E.

2009-01-01

321

SCYX-7158, an Orally-Active Benzoxaborole for the Treatment of Stage 2 Human African Trypanosomiasis  

PubMed Central

Background Human African trypanosomiasis (HAT) is an important public health problem in sub-Saharan Africa, affecting hundreds of thousands of individuals. An urgent need exists for the discovery and development of new, safe, and effective drugs to treat HAT, as existing therapies suffer from poor safety profiles, difficult treatment regimens, limited effectiveness, and a high cost of goods. We have discovered and optimized a novel class of small-molecule boron-containing compounds, benzoxaboroles, to identify SCYX-7158 as an effective, safe and orally active treatment for HAT. Methodology/Principal Findings A drug discovery project employing integrated biological screening, medicinal chemistry and pharmacokinetic characterization identified SCYX-7158 as an optimized analog, as it is active in vitro against relevant strains of Trypanosoma brucei, including T. b. rhodesiense and T. b. gambiense, is efficacious in both stage 1 and stage 2 murine HAT models and has physicochemical and in vitro absorption, distribution, metabolism, elimination and toxicology (ADMET) properties consistent with the compound being orally available, metabolically stable and CNS permeable. In a murine stage 2 study, SCYX-7158 is effective orally at doses as low as 12.5 mg/kg (QD×7 days). In vivo pharmacokinetic characterization of SCYX-7158 demonstrates that the compound is highly bioavailable in rodents and non-human primates, has low intravenous plasma clearance and has a 24-h elimination half-life and a volume of distribution that indicate good tissue distribution. Most importantly, in rodents brain exposure of SCYX-7158 is high, with Cmax >10 µg/mL and AUC0–24 hr >100 µg*h/mL following a 25 mg/kg oral dose. Furthermore, SCYX-7158 readily distributes into cerebrospinal fluid to achieve therapeutically relevant concentrations in this compartment. Conclusions/Significance The biological and pharmacokinetic properties of SCYX-7158 suggest that this compound will be efficacious and safe to treat stage 2 HAT. SCYX-7158 has been selected to enter preclinical studies, with expected progression to phase 1 clinical trials in 2011. PMID:21738803

Jacobs, Robert T.; Nare, Bakela; Wring, Stephen A.; Orr, Matthew D.; Chen, Daitao; Sligar, Jessica M.; Jenks, Matthew X.; Noe, Robert A.; Bowling, Tana S.; Mercer, Luke T.; Rewerts, Cindy; Gaukel, Eric; Owens, Jennifer; Parham, Robin; Randolph, Ryan; Beaudet, Beth; Bacchi, Cyrus J.; Yarlett, Nigel; Plattner, Jacob J.; Freund, Yvonne; Ding, Charles; Akama, Tsutomu; Zhang, Y.-K.; Brun, Reto; Kaiser, Marcel; Scandale, Ivan; Don, Robert

2011-01-01

322

Noise generated by a flight weight, air flow control valve in a vertical takeoff and landing aircraft thrust vectoring system  

Microsoft Academic Search

Tests were conducted in the NASA Lewis Research Center's Powered Lift Facility to experimentally evaluate the noise generated by a flight weight, 12 in. butterfly valve installed in a proposed vertical takeoff and landing thrust vectoring system. Fluctuating pressure measurements were made in the circular duct upstream and downstream of the valve. This data report presents the results of these

Ronald G. Huff

1989-01-01

323

Global Change and Human Vulnerability to Vector-Borne Diseases  

PubMed Central

Global change includes climate change and climate variability, land use, water storage and irrigation, human population growth and urbanization, trade and travel, and chemical pollution. Impacts on vector-borne diseases, including malaria, dengue fever, infections by other arboviruses, schistosomiasis, trypanosomiasis, onchocerciasis, and leishmaniasis are reviewed. While climate change is global in nature and poses unknown future risks to humans and natural ecosystems, other local changes are occurring more rapidly on a global scale and are having significant effects on vector-borne diseases. History is invaluable as a pointer to future risks, but direct extrapolation is no longer possible because the climate is changing. Researchers are therefore embracing computer simulation models and global change scenarios to explore the risks. Credible ranking of the extent to which different vector-borne diseases will be affected awaits a rigorous analysis. Adaptation to the changes is threatened by the ongoing loss of drugs and pesticides due to the selection of resistant strains of pathogens and vectors. The vulnerability of communities to the changes in impacts depends on their adaptive capacity, which requires both appropriate technology and responsive public health systems. The availability of resources in turn depends on social stability, economic wealth, and priority allocation of resources to public health. PMID:14726459

Sutherst, Robert W.

2004-01-01

324

Vector-control personnel’s knowledge, perceptions and practices towards insecticides used for indoor residual spraying in Limpopo Province, South Africa  

PubMed Central

Background Contradictory arguments regarding the benefits and harm of insecticides, especially DDT, have caused concerns in different societal circles, threatening to undermine the achievements of the indoor residual spraying (IRS) programme in South Africa. These concerns were exacerbated by the screening of a documentary on South African Broadcasting Corporation (SABC) Television with anti-DDT sentiments. Consequently, Limpopo Malaria Control Programme (LMCP) Management advocated for an investigation to determine the potential effect of such campaigns on vector-control personnel’s knowledge and perceived effects of insecticides on human health, with a view to improving the educational materials designed for use in training vector-control personnel. Methods The study was a cross-sectional descriptive survey using a structured field-piloted questionnaire, administered to 233 randomly selected vector-control personnel. Ethical clearance was granted by the University of KwaZulu-Natal. Approval for the study was granted by the Department of Health, Limpopo. Participation in the study was voluntary and all respondents signed informed consent. Descriptive statistics were used to analyse the collected data. Results Most respondents (96.6%) had a positive perception of IRS as a method to control malaria. Despite their positive perception, 93.6% viewed IRS insecticides to be potentially harmful to the users. DDT was perceived to cause long-term reproductive and respiratory effects, whereas alpha-cypermethrin and deltamethrin were largely associated with skin irritation/itchiness and skin burn. Study participants were more worried about DDT’s potential effects on their reproductive system, including poor sexual performance, decline in libido, miscarriage and bearing children with genetic defects. However, none reported personal experience of bearing a child with genetic defects or miscarriage. Most anti-insecticide messages, especially relating to DDT, emanated from sources external to the LMCP, mainly through radio (62%) and television (33.9%) and about 70% believed such messages. While most respondents preferred to work with a moderately itchy deltamethrin, DDT was admittedly the most effective insecticide. Conclusion Vector-control personnel faced health and ethical dilemmas, in that, while they perceived insecticides used for IRS in Limpopo to be potentially harmful to the health of users, as purported through media, they also viewed IRS using insecticides to be effective in controlling malaria. PMID:23618516

2013-01-01

325

Community based interventions for the prevention and control of Non-Helmintic NTD.  

PubMed

In this paper, we aim to systematically analyze the effectiveness of community based interventions (CBI) for the prevention and control of non-helminthic diseases including dengue, trypanosomiasis, chagas, leishmaniasis, buruli ulcer, leprosy and trachoma. We systematically reviewed literature published up to May 2013 and included 62 studies in this review. Findings from our review suggest that CBI including insecticide spraying; insecticide treated bednets and curtains; community education and cleanliness campaigns; chemoprophylaxis through mass drug administration; and treatment have the potential to reduce the incidence and burden of non-helminthic diseases. Lack of data limited the subgroup analysis for integrated and non-integrated delivery strategies however, qualitative synthesis suggest that integrated delivery is more effective when compared to vertical interventions; however, such integration was possible only because of the existing vertical vector control programs. Community delivered interventions have the potential to achieve wider coverage and sustained community acceptance. Eradicating these diseases will require a multipronged approach including drug administration, health education, vector control and clean water and sanitation facilities. This would require high level governmental commitment along with strong partnerships among major stakeholders. PMID:25114794

Das, Jai K; Salam, Rehana A; Arshad, Ahmed; Maredia, Hasina; Bhutta, Zulfiqar A

2014-01-01

326

Robotic application of a dynamic resultant force vector using real-time load-control: simulation of an ideal follower load on Cadaveric L4-L5 segments.  

PubMed

Standard in-vitro spine testing methods have focused on application of isolated and/or constant load components while the in-vivo spine is subject to multiple components that can be resolved into resultant dynamic load vectors. To advance towards more in-vivo like simulations the objective of the current study was to develop a methodology to apply robotically-controlled, non-zero, real-time dynamic resultant forces during flexion-extension on human lumbar motion segment units (MSU) with initial application towards simulation of an ideal follower load (FL) force vector. A proportional-integral-derivative (PID) controller with custom algorithms coordinated the motion of a Cartesian serial manipulator comprised of six axes each capable of position- or load-control. Six lumbar MSUs (L4-L5) were tested with continuously increasing sagittal plane bending to 8 Nm while force components were dynamically programmed to deliver a resultant 400 N FL that remained normal to the moving midline of the intervertebral disc. Mean absolute load-control tracking errors between commanded and experimental loads were computed. Global spinal ranges of motion and sagittal plane inter-body translations were compared to previously published values for non-robotic applications. Mean TEs for zero-commanded force and moment axes were 0.7 ± 0.4N and 0.03 ± 0.02 Nm, respectively. For non-zero force axes mean TEs were 0.8 ± 0.8 N, 1.3 ± 1.6 Nm, and 1.3 ± 1.6N for Fx, Fz, and the resolved ideal follower load vector FL(R), respectively. Mean extension and flexion ranges of motion were 2.6° ± 1.2° and 5.0° ± 1.7°, respectively. Relative vertebral body translations and rotations were very comparable to data collected with non-robotic systems in the literature. The robotically coordinated Cartesian load controlled testing system demonstrated robust real-time load-control that permitted application of a real-time dynamic non-zero load vector during flexion-extension. For single MSU investigations the methodology has potential to overcome conventional follower load limitations, most notably via application outside the sagittal plane. This methodology holds promise for future work aimed at reducing the gap between current in-vitro testing and in-vivo circumstances. PMID:23809771

Bennett, Charles R; Kelly, Brian P

2013-08-01

327

Kinase scaffold repurposing for neglected disease drug discovery: Discovery of an efficacious, lapatanib-derived lead compound for trypanosomiasis  

PubMed Central

Human African trypanosomiasis (HAT) is a neglected tropical disease caused by the protozoan parasite Trypanosoma brucei. Since drugs in use against HAT are toxic and require intravenous dosing, new drugs are needed. Initiating lead discovery campaigns by using chemical scaffolds from drugs approved for other indications can speed up drug discovery for neglected diseases. We demonstrated recently that the 4-anilinoquinazolines lapatinib (GW572016, 1) and canertinib (CI-1033) kill T. brucei with low micromolar EC50 values. We now report promising activity of analogs of 1, which provided an excellent starting point for optimization of the chemotype. We report our compound optimization that has led to synthesis of several potent 4-anilinoquinazolines, including NEU621, 23a, a highly potent, orally bioavailable inhibitor of trypanosome replication. At the cellular level, 23a blocks duplication of the kinetoplast and arrests cytokinesis, making it a new tool for studying regulation of the trypanosome cell cycle. PMID:23597080

Patel, Gautam; Karver, Caitlin E.; Behera, Ranjan; Guyett, Paul; Sullenberger, Catherine; Edwards, Peter; Roncal, Norma E.; Mensa-Wilmot, Kojo; Pollastri, Michael P.

2013-01-01

328

Embracing the Open-Source Movement for the Management of Spatial Data: A Case Study of African Trypanosomiasis in Kenya  

PubMed Central

The past decade has seen an explosion in the availability of spatial data not only for researchers, but the public alike. As the quantity of data increases, the ability to effectively navigate and understand the data becomes more challenging. Here we detail a conceptual model for a spatially explicit database management system that addresses the issues raised with the growing data management problem. We demonstrate utility with a case study in disease ecology: to develop a multi-scale predictive model of African Trypanosomiasis in Kenya. International collaborations and varying technical expertise necessitate a modular open-source software solution. Finally, we address three recurring problems with data management: scalability, reliability, and security. PMID:21686072

Langley, Shaun A.; Messina, Joseph P.

2011-01-01

329

Differential control of Yersinia pestis biofilm formation in vitro and in the flea vector by two c-di-GMP diguanylate cyclases.  

PubMed

Yersinia pestis forms a biofilm in the foregut of its flea vector that promotes transmission by flea bite. As in many bacteria, biofilm formation in Y. pestis is controlled by intracellular levels of the bacterial second messenger c-di-GMP. Two Y. pestis diguanylate cyclase (DGC) enzymes, encoded by hmsT and y3730, and one phosphodiesterase (PDE), encoded by hmsP, have been shown to control biofilm production in vitro via their opposing c-di-GMP synthesis and degradation activities, respectively. In this study, we provide further evidence that hmsT, hmsP, and y3730 are the only three genes involved in c-di-GMP metabolism in Y. pestis and evaluated the two DGCs for their comparative roles in biofilm formation in vitro and in the flea vector. As with HmsT, the DGC activity of Y3730 depended on a catalytic GGDEF domain, but the relative contribution of the two enzymes to the biofilm phenotype was influenced strongly by the environmental niche. Deletion of y3730 had a very minor effect on in vitro biofilm formation, but resulted in greatly reduced biofilm formation in the flea. In contrast, the predominant effect of hmsT was on in vitro biofilm formation. DGC activity was also required for the Hms-independent autoaggregation phenotype of Y. pestis, but was not required for virulence in a mouse model of bubonic plague. Our results confirm that only one PDE (HmsP) and two DGCs (HmsT and Y3730) control c-di-GMP levels in Y. pestis, indicate that hmsT and y3730 are regulated post-transcriptionally to differentially control biofilm formation in vitro and in the flea vector, and identify a second c-di-GMP-regulated phenotype in Y. pestis. PMID:21559445

Sun, Yi-Cheng; Koumoutsi, Alexandra; Jarrett, Clayton; Lawrence, Kevin; Gherardini, Frank C; Darby, Creg; Hinnebusch, B Joseph

2011-01-01

330

An exploratory GIS-based method to identify and characterise landscapes with an elevated epidemiological risk of Rhodesian human African trypanosomiasis  

PubMed Central

Background Specific land cover types and activities have been correlated with Trypanosoma brucei rhodesiense distributions, indicating the importance of landscape for epidemiological risk. However, methods proposed to identify specific areas with elevated epidemiological risk (i.e. where transmission is more likely to occur) tend to be costly and time consuming. This paper proposes an exploratory spatial analysis using geo-referenced human African trypanosomiasis (HAT) cases and matched controls from Serere hospital, Uganda (December 1998 to November 2002) to identify areas with an elevated epidemiological risk of HAT. Methods Buffers 3 km from each case and control were used to represent areas in which village inhabitants would carry out their daily activities. It was hypothesised that the selection of areas where several case village buffers overlapped would enable the identification of locations with increased risk of HAT transmission, as these areas were more likely to be frequented by HAT cases in several surrounding villages. The landscape within these overlap areas should more closely relate to the environment in which transmission occurs as opposed to using the full buffer areas. The analysis was carried out for each of four annual periods, for both cases and controls, using a series of threshold values (number of overlapping buffers), including a threshold of one, which represented the benchmark (e.g. use of the full buffer area as opposed to the overlap areas). Results A greater proportion of the overlap areas for cases consisted of seasonally flooding grassland and lake fringe swamp, than the control overlap areas, correlating well with the preferred habitat of the predominant tsetse species within the study area (Glossina fuscipes fuscipes). The use of overlap areas also resulted in a greater difference between case and control landscapes, when compared with the benchmark (using the full buffer area). Conclusions These results indicate that the overlap analysis has enabled the selection of areas more likely to represent epidemiological risk zones than similar analyses using full buffer areas. The identification of potential epidemiological risk zones using this method requires fewer data than other proposed methods and further development may provide vital information for the targeting of control measures. PMID:23171150

2012-01-01

331

Determining areas that require indoor insecticide spraying using Multi Criteria Evaluation, a decision-support tool for malaria vector control programmes in the Central Highlands of Madagascar  

PubMed Central

Background The highlands of Madagascar present an unstable transmission pattern of malaria. The population has no immunity, and the central highlands have been the sites of epidemics with particularly high fatality. The most recent epidemic occurred in the 1980s, and caused about 30,000 deaths. The fight against malaria epidemics in the highlands has been based on indoor insecticide spraying to control malaria vectors. Any preventive programme involving generalised cover in the highlands will require very substantial logistical support. We used multicriteria evaluation, by the method of weighted linear combination, as basis for improved targeting of actions by determining priority zones for intervention. Results Image analysis and field validation showed the accuracy of mapping rice fields to be between 82.3% and 100%, and the Kappa coefficient was 0.86 to 0.99. A significant positive correlation was observed between the abundance of the vector Anopheles funestus and temperature; the correlation coefficient was 0.599 (p < 0.001). A significant negative correlation was observed between vector abundance and human population density: the correlation coefficient was -0.551 (p < 0.003). Factor weights were determined by pair-wise comparison and the consistency ratio was 0.04. Risk maps of the six study zones were obtained according to a gradient of risk. Nine of thirteen results of alert confirmed by the Epidemiological Surveillance Post were in concordance with the risk map. Conclusion This study is particularly valuable for the management of vector control programmes, and particularly the reduction of the vector population with a view to preventing disease. The risk map obtained can be used to identify priority zones for the management of resources, and also help avoid systematic and generalised spraying throughout the highlands: such spraying is particularly difficult and expensive. The accuracy of the mapping, both as concerns time and space, is dependent on the availability of data. Continuous monitoring of malaria transmission factors must be undertaken to detect any changes. A regular case notification allows risk map to be verified. These actions should therefore be implemented so that risk maps can be satisfactorily assessed. PMID:17261177

Rakotomanana, Fanjasoa; Randremanana, Rindra V; Rabarijaona, Léon P; Duchemin, Jean Bernard; Ratovonjato, Jocelyn; Ariey, Frédéric; Rudant, Jean Paul; Jeanne, Isabelle

2007-01-01

332

Selective Vectorization for Short-Vector Instructions  

E-print Network

Multimedia extensions are nearly ubiquitous in today's general-purpose processors. These extensions consist primarily of a set of short-vector instructions that apply the same opcode to a vector of operands. Vector ...

Amarasinghe, Saman

2009-12-18

333

Common-Mode Circulating Current Control of Paralleled Interleaved Three-Phase Two-Level Voltage-Source Converters With Discontinuous Space-Vector Modulation  

SciTech Connect

This paper presents a control method to limit the common-mode (CM) circulating current between paralleled three-phase two-level voltage-source converters (VSCs) with discontinuous space-vector pulsewidth modulation (DPWM) and interleaved switching cycles. This CM circulating current can be separated into two separate components based on their frequency; the high-frequency component, close to the switching frequency, can be effectively limited by means of passive components; the low-frequency component, close to the fundamental frequency, embodies the jumping CM circulating current observed in parallel VSCs. This is the main reason why it is usually recommended not to implement discontinuous and interleaving PWM together. The origin of this low-frequency circulating current is analyzed in detail, and based on this, a method to eliminate its presence is proposed by impeding the simultaneous use of different zero vectors between the converters. This control method only requires six additional switching actions per line cycle, presenting a minimum impact on the converter thermal design. The analysis and the feasibility of the control method are verified by simulation and experimental results.

Zhang, Di [ORNL; Wang, Fei [ORNL; Burgos, Rolando [ABB; Boroyevich, Dushan [Virginia Polytechnic Institute and State University (Virginia Tech)

2011-01-01

334

Pool screen polymerase chain reaction for estimating the prevalence of Onchocerca volvulus infection in Simulium damnosum sensu lato: results of a field trial in an area subject to successful vector control.  

PubMed

Detection of infective parasites in the vector population can be an early indicator of recrudescence in areas freed of new cases of onchocerciasis. However, dissection of vector black flies is inefficient in areas subject to effective control. Recently, a polymerase chain reaction (PCR)-based assay has been used to detect a single Onchocerca volvulus-infected black fly in pools containing large numbers of uninfected flies. This method had not been validated on wild-caught black flies in an area subject to effective vector control. Here, we report a method of restricting the pool screen PCR assay to infectious parasites and the results of a field test in an area subject to long-term vector control. The prevalence of infection determined by dissection did not differ from that determined by pool screen PCR. The results suggest that the PCR assay may be a useful tool for epidemiologic surveillance for 0. volvulus infection. PMID:9988335

Yamèogo, L; Toè, L; Hougard, J M; Boatin, B A; Unnasch, T R

1999-01-01

335

From Tucson to Genomics and Transgenics: The Vector Biology Network and the Emergence of Modern Vector Biology  

E-print Network

renaissance in vector biology/medical entomology. A Casepositions in vector biology or medical entomology; and (vii)Biology and Control of Vectors program at TDR; and (iii) foundations such as the Wellcome Trust and the Howard Hughes Medical

2009-01-01

336

Use of Bacillus thuringiensis var israelensis as a viable option in an Integrated Malaria Vector Control Programme in the Kumasi Metropolis, Ghana  

PubMed Central

Background Integrated Vector Control (IVC) remains the approach for managing the malaria-causing vector. The study investigated the contribution of Bacillus thuringiensis israelensis (Bti) in the control of malaria by targeting the larvae and also mapped and documented major breeding sites in the Kumasi metropolis, Ghana. Methods Using a hand held GPS receiver unit, major breeding sites within the metropolis were mapped out during the larval survey. Mosquito larvae were then collected from the breeding sites and reared in an insectary to obtain an F1 generation for laboratory bioassays. The minimum effective dosage of Bti Water Dispersible Granular (WDG) formulation was determined by a series of bioassays. Based on the results obtained in the laboratory, the optimum effective dosage of Bti formulations against naturally occurring larvae of the indigenous mosquito species was determined through open field trials. Results A total of 33 breeding sites were identified and geo-referenced during the larval surveys with the majority of the breeding sites located in the Asokwa sub-metropolis, Kumasi, Ghana. A Bti (3,000 International Toxic Unit (ITU)/mg) concentration of 0.026 mg/l resulted in 50% mortality whilst a concentration of 0.136 mg/l resulted in 95% mortality. Results from the open field trials with Bti showed that a dosage of 0.2 kg/ha is as effective as 0.4 kg/ha in suppressing late instars and resulting pupae. Conclusion This study reveals that Bti at a very low dosage of 0.2 kg/ha is highly effective against Anopheles larvae and therefore offers viable options for the management of vector mosquitoes. Further research is needed to extend this to the field in order to determine its ability to reduce malaria incidence. PMID:23607376

2013-01-01

337

A new vector for controllable expression of an anti-HER2/neu mini-antibody-barnase fusion protein in HEK 293T cells.  

PubMed

Tumor-targeted vectors with controllable expression of therapeutic genes and specific antitumor antibodies are promising tools for the reduction of malignant tumors. Here we describe a new plasmid for the eukaryotic expression of an anti-HER2/neu mini-antibody-barnase fusion protein (4D5 scFv-barnase-His(5)) with an NH(2)-terminal leader peptide. The 4D5 scFv-barnase-His(5) gene was placed downstream of the tetracycline responsive-element minimal promoter in the vector using the Tet-Off gene-expression system. The Bacillus amyloliquefaciens ribonuclease barnase is toxic for the host cells. To overcome this problem, barstar gene under its own minimal cytomegalovirus promoter was used in designed vector. Barstar inhibits the background level of barnase in the cells in the presence of tetracycline in culture medium. The HEK 293T cells were transfected with the designed vector, and the 4D5 scFv-barnase-His(5) fusion protein was identified by anti-barnase antibodies in cell culture medium and after purification from cell lysates using metal-affinity chromatography. The overexpression of the anti-HER2/neu mini-antibody-barnase fusion protein decreased the intensity of fluorescence of HEK 293T cells co-transfected with the generated plasmid and a plasmid containing the gene of enhanced green fluorescent protein (pEGFP-N1), in comparison with the intensity of fluorescence of HEK 293T cells transfected with pEGFP-N1, in the absence of tetracycline in the medium. The effect of the 4D5 scFv-barnase-His(5) on EGFP fluorescence indicates that the introduced barnase functions as a ribonuclease inside the cells. The anti-HER2/neu mini-antibody could be used to deliver barnase to HER2/neu-positive cells and provide its penetration into the target cells, as HER2/neu is a ligand-internalizing receptor. This expression vector has potential applications to both gene and antibody therapies of cancer. PMID:16300908

Glinka, Elena M; Edelweiss, Eweline F; Sapozhnikov, Alexander M; Deyev, Sergey M

2006-01-17

338

Noise generated by a flight weight, air flow control valve in a vertical takeoff and landing aircraft thrust vectoring system  

NASA Technical Reports Server (NTRS)

Tests were conducted in the NASA Lewis Research Center's Powered Lift Facility to experimentally evaluate the noise generated by a flight weight, 12 in. butterfly valve installed in a proposed vertical takeoff and landing thrust vectoring system. Fluctuating pressure measurements were made in the circular duct upstream and downstream of the valve. This data report presents the results of these tests. The maximum overall sound pressure level is generated in the duct downstream of the valve and reached a value of 180 dB at a valve pressure ratio of 2.8. At the higher valve pressure ratios the spectra downstream of the valve is broad banded with its maximum at 1000 Hz.

Huff, Ronald G.

1989-01-01

339

Space treatments of insecticide for control of dengue virus vector Aedes aegypti in southern Mexico. I. Baseline penetration trials in open field and houses.  

PubMed

We studied the efficacy of space ultra-low volume treatments of 3 insecticides for the control of the dengue virus vector Aedes aegypti in southern Mexico. Insecticides tested were permethrin (Aqua-Reslin Super), d-phenothrin (Anvil), and cyfluthrin (Solfac), applied at rates of 10.87, 7.68, and 2 g/ha, respectively, by using London Fog, HP910-PHXL, or Micro-Gen pumps mounted on vehicles. Studies included 1) open field penetration tests and 2) house penetration tests. Open field tests indicated that Anvil and Solfac were more effective than Aqua-Reslin Super. In house tests, Anvil yielded the highest mosquito mortalities (>/=88%) of the three insecticides in the front porch, living room, bedroom, and backyard. Therefore, Anvil proved to be better than other insecticides evaluated to control Ae. aegypti in Chiapas, Mexico. PMID:17019777

Arrendondo-Jimenez, Juan I; Rivero, Norma E

2006-06-01

340

Chemical and environmental vector control as a contribution to the elimination of visceral leishmaniasis on the Indian subcontinent: cluster randomized controlled trials in Bangladesh, India and Nepal  

Microsoft Academic Search

BACKGROUND: Bangladesh, India and Nepal are working towards the elimination of visceral leishmaniasis (VL) by 2015. In 2005 the World Health Organization\\/Training in Tropical Diseases launched an implementation research programme to support integrated vector management for the elimination of VL from Bangladesh, India and Nepal. The programme is conducted in different phases, from proof-of-concept to scaling up intervention. This study

Anand B Joshi; Murari L Das; Shireen Akhter; Rajib Chowdhury; Dinesh Mondal; Vijay Kumar; Pradeep Das; Axel Kroeger; Marleen Boelaert; Max Petzold

2009-01-01

341

Intratumoral gene therapy versus intravenous gene therapy for distant metastasis control with 2-diethylaminoethyl-dextran methyl methacrylate copolymer non-viral vector-p53.  

PubMed

Lung cancer still remains to be challenged by novel treatment modalities. Novel locally targeted routes of administration are a methodology to enhance treatment and reduce side effects. Intratumoral gene therapy is a method for local treatment and could be used either in early-stage lung cancer before surgery or at advanced stages as palliative care. Novel non-viral vectors are also in demand for efficient gene transfection to target local cancer tissue and at the same time protect the normal tissue. In the current study, C57BL/6 mice were divided into three groups: (a) control, (b) intravenous and (c) intatumoral gene therapy. The novel 2-Diethylaminoethyl-Dextran Methyl Methacrylate Copolymer Non-Viral Vector (Ryujyu Science Corporation) was conjugated with plasmid pSicop53 from the company Addgene for the first time. The aim of the study was to evaluate the safety and efficacy of targeted gene therapy in a Lewis lung cancer model. Indeed, although the pharmacokinetics of the different administration modalities differs, the intratumoral administration presented increased survival and decreased distant metastasis. Intratumoral gene therapy could be considered as an efficient local therapy for lung cancer. PMID:24285215

Baliaka, A; Zarogoulidis, P; Domvri, K; Hohenforst-Schmidt, W; Sakkas, A; Huang, H; Le Pivert, P; Koliakos, G; Koliakou, E; Kouzi-Koliakos, K; Tsakiridis, K; Chioti, A; Siotou, E; Cheva, A; Zarogoulidis, K; Sakkas, L

2014-02-01

342

Comparison of insecticide-treated nets and indoor residual spraying to control the vector of visceral leishmaniasis in Mymensingh District, Bangladesh.  

PubMed

Integrated vector management is a pillar of the South Asian visceral leishmaniasis (VL) elimination program, but the best approach remains a matter of debate. Sand fly seasonality was determined in 40 houses sampled monthly. The impact of interventions on Phlebotomus argentipes density was tested from 2006-2007 in a cluster-randomized trial with four arms: indoor residual spraying (IRS), insecticide-treated nets (ITNs), environmental management (EVM), and no intervention. Phlebotomus argentipes density peaked in March with the highest proportion of gravid females in May. The EVM (mud plastering of wall and floor cracks) showed no impact. The IRS and ITNs were associated with a 70-80% decrease in male and female P. argentipes density up to 5 months post intervention. Vector density rebounded by 11 months post-IRS, whereas ITN-treated households continued to show significantly lower density compared with households without intervention. Our data suggest that both IRS and ITNs may help to improve VL control in Bangladesh. PMID:21540372

Chowdhury, Rajib; Dotson, Ellen; Blackstock, Anna J; McClintock, Shannon; Maheswary, Narayan P; Faria, Shyla; Islam, Saiful; Akter, Tangin; Kroeger, Axel; Akhter, Shireen; Bern, Caryn

2011-05-01

343

The significance of controlled conditions in lentiviral vector titration and in the use of multiplicity of infection (MOI) for predicting gene transfer events  

Microsoft Academic Search

BACKGROUND: Although lentiviral vectors have been widely used for in vitro and in vivo gene therapy researches, there have been few studies systematically examining various conditions that may affect the determination of the number of viable vector particles in a vector preparation and the use of Multiplicity of Infection (MOI) as a parameter for the prediction of gene transfer events.

Bing Zhang; Pat Metharom; Howard Jullie; Kay AO Ellem; Geoff Cleghorn; Malcolm J West; Ming Q Wei

2004-01-01

344

[The beginning of Chagas disease control (homage to Dr. Emmanuel Dias, the pioneer of Chagas disease control, in the year of his birth centenary)].  

PubMed

Very soon Carlos Chagas took into account the need of trypanosomiasis control, considering its great social impact and geographical dispersion The vector was considered the more vulnerable target and housing improvement the basic strategy to face the disease. In parallel, it was required a more clinical visibility for the disease, as an argument for its control. The first concrete tentative occurred in 1918 when Souza Araújo dedicating his efforts in Paraná, trying housing improvement. He was followed by Ezequiel Dias et al, in 1921, employing chemical compounds against the vector, The chemical fight will be retaken by Emmanuel Dias in 1944, assaying several old compounds, fire thrower and cyanidric gas. In 1946, DDT showed to be ineffective, but one year later Dias & Pellegrino described the insecticide gammexane, highly effective against domestic triatomines. Working with Mario Pinotti, expanded trials occurred in Minas Gerais (Triangle Region), justifying the expansion of the campaign to other endemic regions, with the rationale of continuous work in contiguous areas. In 1957 Pedreira de Freitas proposed the selective spraying, which was the model for the future strategy of program evaluation, by SUVEN and SUCAN organizations. In 1975 the national program is reorganized, launching two national surveys (entomology and serology). In 1979 the new pyrethroid compounds are tried and im 1983 the national program is expanded. Transfusion transmitted Chagas Disease was studied since the 1950 by the Nussenzweig group in S. Paulo, showing to be vulnerable to chemoprophylaxis and blood donor pre transfusional serologic screening. Nevertheless, these preventive measures only were implemented in the 1980 decade, following the emergence of HIV/AIDS pandemic. Practically, since the pioneer essays, the control of Chagas Disease transmission showed to be efficient against vector and blood bank mechanisms, depending on continuity, educative support and political will. PMID:21584352

Dias, João Carlos Pinto

2011-01-01

345

Linking Oviposition Site Choice to Offspring Fitness in Aedes aegypti: Consequences for Targeted Larval Control of Dengue Vectors  

Microsoft Academic Search

BackgroundCurrent Aedes aegypti larval control methods are often insufficient for preventing dengue epidemics. To improve control efficiency and cost-effectiveness, some advocate eliminating or treating only highly productive containers. The population-level outcome of this strategy, however, will depend on details of Ae. aegypti oviposition behavior.Methodology\\/Principal FindingsWe simultaneously monitored female oviposition and juvenile development in 80 experimental containers located across 20 houses

Jacklyn Wong; Amy C. Morrison; Steven T. Stoddard; Helvio Astete; Yui Yin Chu; Imaan Baseer; Thomas W. Scott

2012-01-01

346

Natural product of wild Zingiberaceae Elettariopsis slahmong: biopesticide to control the vector of banana blood disease bacterium in West Sumatera, Indonesia.  

PubMed

Banana is one of the most important food crops in Indonesia. Its production is greater than any other agricultural commodity. With the population of 230 million in 2010, banana was consumed up to three million tons in this country. However, Banana Blood Disease Bacterium (BDB), one of the most devastating banana pathogens in the world, which is only found in Indonesia, threatens not only the growth of this plant but also the lives and the livelihoods for most of the Indonesian society. BDB is caused by a lethal bacteria, Ralstonia solanacearum Phylotype-4, which infects a wide range of bananas, from bananas used for consumption to wild bananas. In West Sumatera, the disease killed 1.40% of bananas in 1998, and then increased dramatically to 37.9% in 2003. The total banana production dropped to 62% in this province. The search for controlling the vector has led to the pre-investigation of Wild Zingiberaceae Elettariopsis slahmong C.K. Lim which has a stink bug odour similar to a methidathion insecticide. The plant was collected around the conservation area of Lembah Anal in West Sumatra. The goal of this study was to investigate the effectiveness of natural insecticides compound contained in E. slahmong against D. melanogaster. This study tested the effect of E. slahmong on the mortality, anti-feedant and repellent levels against Drosophila melanogaster, the vector of BDB. The essential oil of E. slahmong was obtained by steam distillation of fresh rhizomes, pseudo stems and leaves. We found that the extract of E. slahmong significantly affected the mortality of D. melanogaster of 30-40% and also acted as an antifeedant (with success rate of 73-93%) and repellent (with success rate of 99-99.6%). The long- term objective of this study is to develop green biopesticide to control BDB in Indonesia, based on an environmentally friendly pest management. PMID:25151825

Nasir, N; Dharma, A; Efdi, M; Yuhendra; Eliesti, F

2013-01-01

347

Application Results and Evaluation of Anti-slip Re-adhesion Control Based on Speed Sensor-less Vector Control and Disturbance Observer for Electric Multiple Units, Series 205-5000  

NASA Astrophysics Data System (ADS)

The improvement of adhesion characteristics is important in electric motor coach. We have already proposed the anti-slip/skid re-adhesion control system based on disturbance observer and sensor-less vector control. The effectiveness of the proposed method has been confirmed by the experiment and the numerical simulation using the tested bogie system of electric motor coach. Then, we apply the proposed method to the actual electric multiple units, which is Series 205-5000. In the experimental results of Series 205-5000, this paper discusses that the proposed anti-slip/skid re-adhesion control system has the desired driving wheel torque response. Moreover, this paper proposes the evaluation method of re-adhesion control test results.

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

348

Vector Addition Calculator  

NSDL National Science Digital Library

The Vector Addition Calculator lets students add vectors graphically in 2 dimensions by dragging the tips of the vectors. The results of a component method of addition for the same problem are also displayed.

Joiner, David; The Shodor Education Foundation, Inc.

349

Does Cattle Milieu Provide a Potential Point to Target Wild Exophilic Anopheles arabiensis (Diptera: Culicidae) with Entomopathogenic Fungus? A Bioinsecticide Zooprophylaxis Strategy for Vector Control  

PubMed Central

Background. Anopheles arabiensis is increasingly dominating malaria transmission in Africa. The exophagy in mosquitoes threatens the effectiveness of indoor vector control strategies. This study aimed to evaluate the effectiveness of fungus against An. arabiensis when applied on cattle and their environments. Methods. Experiments were conducted under semi-field and small-scale field conditions within Kilombero valley. The semi-field reared females of 5–7 days old An. arabiensis were exposed to fungus-treated and untreated calf. Further, wild An. arabiensis were exposed to fungus-treated calves, mud-huts, and their controls. Mosquitoes were recaptured the next morning and proportion fed, infected, and survived were evaluated. Experiments were replicated three times using different individuals of calves. Results. A high proportion of An. arabiensis was fed on calves (>0.90) and become infected (0.94) while resting on fungus-treated mud walls than on other surfaces. However, fungus treatments reduced fecundity and survival of mosquitoes. Conclusion. This study demonstrates for the first time the potential of cattle and their milieu for controlling An. arabiensis. Most of An. arabiensis were fed and infected while resting on fungus-treated mud walls than on other surfaces. Fungus treatments reduced fecundity and survival of mosquitoes. These results suggest deployment of bioinsecticide zooprophylaxis against exophilic An. arabiensis. PMID:22934152

Lyimo, Issa N.; Ng'habi, Kija R.; Mpingwa, Monica W.; Daraja, Ally A.; Mwasheshe, Dickson D.; Nchimbi, Nuru S.; Lwetoijera, Dickson W.; Mnyone, Ladslaus L.

2012-01-01

350

Power balancing in variable speed wind-energy systems using vector control of front-end converters  

Microsoft Academic Search

This paper presents a novel power balance control method for wind energy systems feeding an isolated grid. The system is based on a variable-speed wind energy conversion system (WECS) connected to an AC load using a power converter. An energy storage system, connected to the AC load using an additional converter, is used to balance the power generated by the

Roberto Cárdenas; Rubén Peña; Marcelo Pérez; Fernando Vargas; Greg Asher; Jon Clare

2005-01-01

351

Control of Current-Source Active Power Filter using Unit Vector Template in Three Phase Four Wire Unbalnced System  

Microsoft Academic Search

In recent years there has been considerable interest in the development and application of active power filters using current source active power filters for harmonic filtering. The unbalanced load resulting zero sequence current can affect the performance of shunt active filter adversely. In this paper a novel active, filter control for a three-phase four-wire unbalance system has been designed. This

K. Vadirajacharya; P. Agarwal; H. O. Gupta

2007-01-01

352

Sylvatic focus of American Trypanosomiasis in the State of Morelos, Mexico.  

PubMed

Wild vectors and reservoir hosts of Trypanosoma cruzi were surveyed from February 1993 to June 1994 in Ticumán (18 degrees 46'N, 99 degrees 07'W), Mexico (Deciduous Tropical Forest). Direct faeces examination showed that 87% of Triatoma pallidipennis hosted the parasite; T. cruzi forms were present in cultures inoculated with faeces of fifty 67% triatomine bugs and thirty CD-1 strain mice (10 d old) inoculated (peritoneum) with faeces of positive insects T. cruzi amastigotes were found in heart 67%, kidneys 47%, liver 80%, lungs 50%, oesophagus 60%, skin 23%, spleen 73% and stomach 60%. T. cruzi was isolated by direct blood examination from seven 21% chiropterans and five 38% rodents and T. cruzi forms were present in cultures inoculated with blood of twenty-three 68% chiropterans and seven 54% rodents and T. cruzi amastigotes were seen in the kidneys of one 3% chiropterans and four 31% rodents and only in one Pteronotus parnellii mexicanus, organisms were seen in skin 2%. There was no association between organs and T. cruzi infection (p > 0.05). PMID:11935921

Villegas-García, J C; Santillán-Alarcón, S

2001-06-01

353

Chikungunya Virus–Vector Interactions  

PubMed Central

Chikungunya virus (CHIKV) is a mosquito-borne alphavirus that causes chikungunya fever, a severe, debilitating disease that often produces chronic arthralgia. Since 2004, CHIKV has emerged in Africa, Indian Ocean islands, Asia, Europe, and the Americas, causing millions of human infections. Central to understanding CHIKV emergence is knowledge of the natural ecology of transmission and vector infection dynamics. This review presents current understanding of CHIKV infection dynamics in mosquito vectors and its relationship to human disease emergence. The following topics are reviewed: CHIKV infection and vector life history traits including transmission cycles, genetic origins, distribution, emergence and spread, dispersal, vector competence, vector immunity and microbial interactions, and co-infection by CHIKV and other arboviruses. The genetics of vector susceptibility and host range changes, population heterogeneity and selection for the fittest viral genomes, dual host cycling and its impact on CHIKV adaptation, viral bottlenecks and intrahost diversity, and adaptive constraints on CHIKV evolution are also discussed. The potential for CHIKV re-emergence and expansion into new areas and prospects for prevention via vector control are also briefly reviewed. PMID:25421891

Coffey, Lark L.; Failloux, Anna-Bella; Weaver, Scott C.

2014-01-01

354

Fast Fourier and discrete wavelet transforms applied to sensorless vector control induction motor for rotor bar faults diagnosis.  

PubMed

This paper presents new techniques to evaluate faults in case of broken rotor bars of induction motors. Procedures are applied with closed-loop control. Electrical and mechanical variables are treated using fast Fourier transform (FFT), and discrete wavelet transform (DWT) at start-up and steady state. The wavelet transform has proven to be an excellent mathematical tool for the detection of the faults particularly broken rotor bars type. As a performance, DWT can provide a local representation of the non-stationary current signals for the healthy machine and with fault. For sensorless control, a Luenberger observer is applied; the estimation rotor speed is analyzed; the effect of the faults in the speed pulsation is compensated; a quadratic current appears and used for fault detection. PMID:25004798

Talhaoui, Hicham; Menacer, Arezki; Kessal, Abdelhalim; Kechida, Ridha

2014-09-01

355

Data-mining-based dynamic dispatching rule selection mechanism for shop floor control systems using a support vector machine approach  

Microsoft Academic Search

The purpose of this paper is to develop a data-mining-based dynamic dispatching rule selection mechanism for a shop floor control system to make real-time scheduling decisions. In data mining processes, data transformations (including data normalisation and feature selection) and data mining algorithms greatly influence the predictive accuracy of data mining tasks. Here, the z-scores data normalisation mechanism and genetic-algorithm-based feature

Yeou-Ren Shiue

2009-01-01

356

Use of a gene replacement cosmid vector for cloning alginate conversion genes from mucoid and nonmucoid Pseudomonas aeruginosa strains: algS controls expression of algT.  

PubMed Central

Pseudomonas aeruginosa can convert to a mucoid colony morphology by a genetic mechanism called alginate conversion; this results in the production of copious amounts of the exopolysaccharide alginate. The mucoid phenotype of P. aeruginosa is commonly associated with its ability to cause chronic pulmonary tract infections in patients with cystic fibrosis. In this study we isolated the cis-acting locus involved in alginate conversion, called algS, from both mucoid and nonmucoid isogenic strains. We then examined the role of algS in the control of algT, a trans-active gene required for alginate production in P. aeruginosa. We used a new cosmid cloning vector, called pEMR2, that permitted both the cloning of large DNA fragments and their subsequent gene replacement in P. aeruginosa. To verify the predicted properties of this vector, we isolated and tested a pEMR2 hisI+ clone. Using cloned algS-containing DNA and a method for gene replacement, we constructed isogenic strains of P. aeruginosa that had Tn501 adjacent to algS on the chromosome. Two pEMR2 clone banks containing genomic fragments from isogenic algS(On) (exhibiting the alginate production phenotype) and algS(Off) (exhibiting the non-alginate production phenotype) strains were constructed, and Tn501 served as an adjacent marker to select for clones containing the respective algS allele. The pEMR2 algS(On) and pEMR2 algS(Off) clones were shown to contain the indicated algS allele by gene replacement with the chromosome of strains that carried the opposite allele. To test whether algS controls the expression of the adjacent algT gene, we constructed a pLAFR1 algS(Off)T clone and showed it to be unable to complement an algT::Tn501 mutation in trans. In contrast, a pLAFR1 algS(On)T clone did complement algT::Tn501 in trans. Thus, algS appears to control the activation of algT expression, bringing about alginate conversion. PMID:2838462

Flynn, J L; Ohman, D E

1988-01-01

357

New Chemical Scaffolds for Human African Trypanosomiasis Lead Discovery from a Screen of Tyrosine Kinase Inhibitor Drugs  

PubMed Central

Human African trypanosomiasis (HAT) is caused by the protozoan Trypanosoma brucei. New drugs are needed to treat HAT because of undesirable side effects and difficulties in the administration of the antiquated drugs that are currently used. In human proliferative diseases, protein tyrosine kinase (PTK) inhibitors (PTKIs) have been developed into drugs (e.g., lapatinib and erlotinib) by optimization of a 4-anilinoquinazoline scaffold. Two sets of facts raise a possibility that drugs targeted against human PTKs could be “hits” for antitrypanosomal lead discoveries. First, trypanosome protein kinases bind some drugs, namely, lapatinib, CI-1033, and AEE788. Second, the pan-PTK inhibitor tyrphostin A47 blocks the endocytosis of transferrin and inhibits trypanosome replication. Following up on these concepts, we performed a focused screen of various PTKI drugs as possible antitrypanosomal hits. Lapatinib, CI-1033, erlotinib, axitinib, sunitinib, PKI-166, and AEE788 inhibited the replication of bloodstream T. brucei, with a 50% growth inhibitory concentration (GI50) between 1.3 ?M and 2.5 ?M. Imatinib had no effect (i.e., GI50 > 10 ?M). To discover leads among the drugs, a mouse model of HAT was used in a proof-of-concept study. Orally administered lapatinib reduced parasitemia, extended the survival of all treated mice, and cured the trypanosomal infection in 25% of the mice. CI-1033 and AEE788 reduced parasitemia and extended the survival of the infected mice. On the strength of these data and noting their oral bioavailabilities, we propose that the 4-anilinoquinazoline and pyrrolopyrimidine scaffolds of lapatinib, CI-1033, and AEE788 are worth optimizing against T. brucei in medicinal chemistry campaigns (i.e., scaffold repurposing) to discover new drugs against HAT. PMID:24468788

Behera, Ranjan; Thomas, Sarah M.

2014-01-01

358

Amazonian malaria: Asymptomatic human reservoirs, diagnostic challenges, environmentally-driven changes in mosquito vector populations, and the mandate for sustainable control strategies  

PubMed Central

Across the Americas and the Caribbean, nearly 561,000 slide-confirmed malaria infections were reported officially in 2008. The nine Amazonian countries accounted for 89% of these infections; Brazil and Peru alone contributed 56% and 7% of them, respectively. Local populations of the relatively neglected parasite P. vivax, which currently accounts for 77% of the regional malaria burden, are extremely diverse genetically and geographically structured. At a time when malaria elimination is placed on the public health agenda of several endemic countries, it remains unclear why malaria proved so difficult to control in areas of relatively low levels of transmission such as the Amazon Basin. We hypothesize that asymptomatic parasite carriage and massive environmental changes that affect vector abundance and behavior are major contributors to malaria transmission in epidemiologically diverse areas across the Amazon Basin. Here we review available data supporting this hypothesis and discuss their implications for current and future malaria intervention policies in the region. Given that locally generated scientific evidence is urgently required to support malaria control interventions in Amazonia, we briefly describe the aims of our current field-oriented malaria research in rural villages and gold-mining enclaves in Peru and a recently opened agricultural settlement in Brazil. PMID:22015425

da Silva-Nunes, Monica; Moreno, Marta; Conn, Jan E.; Gamboa, Dionicia; Abeles, Shira; Vinetz, Joseph M.; Ferreira, Marcelo U.

2012-01-01

359

The Design and Synthesis of Potent and Selective Inhibitors of Trypanosoma brucei Glycogen Synthase Kinase 3 for the Treatment of Human African Trypanosomiasis  

PubMed Central

Glycogen synthase kinase 3 (GSK3) is a genetically validated drug target for human African trypanosomiasis (HAT), also called African sleeping sickness. We report the synthesis and biological evaluation of aminopyrazole derivatives as Trypanosoma brucei GSK3 short inhibitors. Low nanomolar inhibitors, which had high selectivity over the off-target human CDK2 and good selectivity over human GSK3? enzyme, have been prepared. These potent kinase inhibitors demonstrated low micromolar levels of inhibition of the Trypanosoma brucei brucei parasite grown in culture. PMID:25198388

2014-01-01

360

Entomopathogenic Fungus as a Biological Control for an Important Vector of Livestock Disease: The Culicoides Biting Midge  

PubMed Central

Background The recent outbreak of bluetongue virus in northern Europe has led to an urgent need to identify control measures for the Culicoides (Diptera: Ceratopogonidae) biting midges that transmit it. Following successful use of the entomopathogenic fungus Metarhizium anisopliae against larval stages of biting midge Culicoides nubeculosus Meigen, we investigated the efficacy of this strain and other fungi (Beauveria bassiana, Isaria fumosorosea and Lecanicillium longisporum) as biocontrol agents against adult C. nubeculosus in laboratory and greenhouse studies. Methodology/Findings Exposure of midges to ‘dry’ conidia of all fungal isolates caused significant reductions in survival compared to untreated controls. Metarhizium anisopliae strain V275 was the most virulent, causing a significantly decrease in midge survival compared to all other fungal strains tested. The LT50 value for strain V275 was 1.42 days compared to 2.21–3.22 days for the other isolates. The virulence of this strain was then further evaluated by exposing C. nubeculosus to varying doses (108–1011 conidia m?2) using different substrates (horse manure, damp peat, leaf litter) as a resting site. All exposed adults were found to be infected with the strain V275 four days after exposure. A further study exposed C. nubeculosus adults to ‘dry’ conidia and ‘wet’ conidia (conidia suspended in 0.03% aq. Tween 80) of strain V275 applied to damp peat and leaf litter in cages within a greenhouse. ‘Dry’ conidia were more effective than ‘wet’ conidia, causing 100% mortality after 5 days. Conclusion/Significance This is the first study to demonstrate that entomopathogenic fungi are potential biocontrol agents against adult Culicoides, through the application of ‘dry’ conidia on surfaces (e.g., manure, leaf litter, livestock) where the midges tend to rest. Subsequent conidial transmission between males and females may cause an increased level of fungi-induced mortality in midges thus reducing the incidence of disease. PMID:21264343

Ansari, Minshad Ali; Pope, Edward C.; Carpenter, Simon; Scholte, Ernst-Jan; Butt, Tariq M.

2011-01-01

361

Plant Based Insect Repellent and Insecticide Treated Bed Nets to Protect against Malaria in Areas of Early Evening Biting Vectors: Double Blind Randomised Placebo Controlled Clinical Trial in the Bolivian Amazon  

Microsoft Academic Search

Objective: To determine the effectiveness in reducing malaria of combining an insect repellent with insecticide treated bed nets compared with the nets alone in an area where vector mosquitoes feed in the early evening. Design: A double blind, placebo controlled cluster-randomised clinical study. Setting: Rural villages and peri-urban districts in the Bolivian Amazon. Participants: 4008 individuals in 860 households. Interventions:

N. Hill; A. Lenglet; A. M. Arnéz; I. Carneiro

2007-01-01

362

Vectoring: Steering a Plane  

NSDL National Science Digital Library

In this two part activity, learners work in pairs or individually to discover how vectoring the thrust from a jet engine affects movement of an airplane. In part one, learners construct an F-15 ACTIVE model with a balloon engine. In part two, learners conduct a series of experiments by changing the angle of the straw to control the direction of the thrust. This activity emphasizes the scientific method including prediction, observation, data collection, and analysis. This lesson plan includes background information, an extension and a sample worksheet.

Nasa

2011-08-20

363

Motion filter vector quantization  

Microsoft Academic Search

Motion-compensated prediction of video is formulated as a novel vector quantization scheme called motion filter vector quantiza- tion (MFVQ). In MFVQ, the motion vector and the pixel-intensity interpolation filter are combined into a motion filter and the en- tire filter is vector quantized. A codebook design algorithm is proposed for designing unit gain and entropy constrained MFVQ codebooks. The algorithm

Dariusz Blasiak; Wai-yip Chan

2002-01-01

364

Rotations with Rodrigues' Vector  

ERIC Educational Resources Information Center

The rotational dynamics was studied from the point of view of Rodrigues' vector. This vector is defined here by its connection with other forms of parametrization of the rotation matrix. The rotation matrix was expressed in terms of this vector. The angular velocity was computed using the components of Rodrigues' vector as coordinates. It appears…

Pina, E.

2011-01-01

365

The promoter of T L DNA gene 5 controls the tissue-specific expression of chimaeric genes carried by a novel type of Agrobacterium binary vector  

Microsoft Academic Search

A “plant gene vector cassette” to be used in combination with various Escherichia coli gene-cloning vectors was constructed. This cassette contains a replication and mobilization unit which allows it to be maintained and to be transferred back and forth between E. coli and Agrobacterium tumefaciens hosts provided these hosts contain plasmid RK2 replication and mobilization helper functions. The cassette also

Csaba Koncz; Jeff Schell

1986-01-01

366

In vitro PHYTOTHERAPY OF VECTOR SNAILS BY BINARY COMBINATIONS OF LARVICIDAL ACTIVE COMPONENTS IN EFFECTIVE CONTROL OF FASCIOLIASIS  

PubMed Central

SUMMARY A food-borne trematode infection fascioliasis is one among common public health problems worldwide. It caused a great economic loss for the human race. Control of snail population below a certain threshold level is one of the important methods in the campaign to reduce the incidence of fascioliasis. The life cycle of the parasite can be interrupted by killing the snail or Fasciola larva redia and cercaria inside of the snail Lymnaea acuminata. In vitro toxicity of different binary combinations (1:1 ratio) of plant-derived larvicidal active components such as citral, ferulic acid, umbelliferone, azadirachtin and allicin against Fasciola redia and cercaria were tested. The mortality of larvae was observed at 2h, 4h, 6h and 8h of treatment. In in vitro condition azadirachtin + allicin (1:1 ratio) was highly toxic against redia and cercaria (8h LC50 0.006 and 0.005 mg/L). Toxicity of citral + ferulic acid was lowest against redia and cercaria larvae. PMID:24037283

Sunita, Kumari; Kumar, Pradeep; Singh, Vinay Kumar; Singh, Dinesh Kumar

2013-01-01

367

In vitro phytotherapy of vector snails by binary combinations of larvicidal active components in effective control of fascioliasis.  

PubMed

A food-borne trematode infection fascioliasis is one among common public health problems worldwide. It caused a great economic loss for the human race. Control of snail population below a certain threshold level is one of the important methods in the campaign to reduce the incidence of fascioliasis. The life cycle of the parasite can be interrupted by killing the snail or Fasciola larva redia and cercaria inside of the snail Lymnaea acuminata. In vitro toxicity of different binary combinations (1:1 ratio) of plant-derived larvicidal active components such as citral, ferulic acid, umbelliferone, azadirachtin and allicin against Fasciola redia and cercaria were tested. The mortality of larvae was observed at 2h, 4h, 6h and 8h of treatment. In in vitro condition azadirachtin + allicin (1:1 ratio) was highly toxic against redia and cercaria (8h LC50 0.006 and 0.005 mg/L). Toxicity of citral + ferulic acid was lowest against redia and cercaria larvae. PMID:24037283

Sunita, Kumari; Kumar, Pradeep; Singh, Vinay Kumar; Singh, Dinesh Kumar

2013-01-01

368

UNDERSTANDING THE VECTOR IN ORDER TO PLAN EFFECTIVE TOBACCO CONTROL POLICIES: AN ANALYSIS OF CONTEMPORARY TOBACCO INDUSTRY MATERIALS  

PubMed Central

Background This paper builds on tobacco document research by analysing contemporary materials to explore how the global tobacco market has changed, how transnational tobacco companies (TTCs) are responding and identify the implications for tobacco control. Methods Analysis of a variety of materials including tobacco company annual reports, investor relations materials, financial analyst reports, market research reports and data. Findings Once China, where TTCs have little market share, is excluded, global cigarette volumes are already declining. Nevertheless, industry profits continue to increase. This pattern is explained by TTCs’ pricing power - their ability to increase prices faster than volumes fall; a consequence of market failure. Pricing power is now fundamental to the TTCs’ long-term future. Consequently, and in light of growing regulations, the TTCs’ business model is changing. Product innovation is now a key marketing technique used to drive consumers to buy more expensive (ie profitable) premium cigarettes. Contrary to established wisdom, high tobacco excise rates, particularly where increases in excise are gradual, can benefit TTCs by enabling price (profit) increases to be disguised. Large intermittent tax increases likely have a greater public health benefit. TTC investments in smokeless appear designed to eliminate competition between smokeless and cigarettes, thereby increasing TTCs’ pricing power while enabling them to harness the rhetoric of harm reduction. Conclusions Monitoring TTCs can inform effective policy development. The TTC’s value maximising approach suggests that a ban on product innovation and more informed tobacco excise policies are needed. PMID:22345234

Gilmore, Anna B

2013-01-01

369

The effectiveness of active population screening and treatment for sleeping sickness control in the Democratic Republic of Congo  

Microsoft Academic Search

Summary background The human African trypanosomiasis (HAT) control programme of the Democratic Republic of Congo (DRC) uses mass screening with the card agglutination test for trypanosomes (CATT). We looked at the contribution of CATT and improved parasitological confirmation to the effectiveness of screening and treatment. method The effectiveness of the screening and treatment process is measured by the percentage of

Jo Robays; Miaka Mia C. Bilengue; Patrick Van der Stuyft; Marleen Boelaert

2004-01-01

370

Modelling american trypanosomiasis in an endemic zone: application to the initial spread of household infection in the argentine chaco.  

PubMed

The complex dynamics of Trypanosoma cruzi infection (Chagas disease) involves different actors and multiple transmission routes. Based on the information currently available, here, we propose a new and more comprehensive model to better understand the dynamics of the infection. This mathematical deterministic model was formulated considering: (i) the three clinical forms in humans: acute, chronic indeterminate and chronic with determinate pathology, (ii) the three main modes of transmission in the human population: vector-borne, congenital and transfusional, (iii) populations of triatomines and dogs as the main domestic reservoirs of T. cruzi and (iv) open populations. A numerical simulation was also performed to estimate the initial spread of the infection in a typical rural household in the endemic zone of the Argentine Gran Chaco. We also analysed the incidence of infected individuals corresponding to each of the three species (humans/triatomines/dogs) over times until the appearance of the first case in the other species. The model predicts that, in the absence of control measures, a few infected individuals are sufficient for the establishment and dispersion of the infection in all the inhabitants of the household. The model proposed and the results obtained allow describing the consequences of the presence of infected individuals in any of the three species considered in the dynamics and the output of the infection. PMID:24528489

Fabrizio, M C; Schweigmann, N J; Bartoloni, N J

2014-12-01

371

Do malaria vector control measures impact disease-related behaviour and knowledge? Evidence from a large-scale larviciding intervention in Tanzania  

PubMed Central

Background Recent efforts of accelerated malaria control towards the long-term goal of elimination had significant impacts in reducing malaria transmission. While these efforts need to be sustained over time, a scenario of low transmission could bring about changes in individual disease risk perception, hindering adherence to protective measures, and affecting disease-related knowledge. The goal of this study was to investigate the potential impact of a successful malaria vector control intervention on bed net usage and malaria-related knowledge. Methods Dar es Salaam’s Urban Malaria Control Program was launched in 2004 with the aim of developing a sustainable larviciding intervention. Larviciding was scaled-up using a stepped-wedge design. Cross-sectional and longitudinal data were collected using a randomized cluster sampling design (2004–2008). Prevalence ratios (PR) for the effect of the larviciding intervention on bed net usage (N?=?64,537) and household heads’ knowledge of malaria symptoms and transmission (N?=?11,254) were obtained from random effects regression models. Results The probability that individuals targeted by larviciding had used a bed net was reduced by 5% as compared to those in non-intervention areas (PR?=?0.95; 95% credible intervals (CrI): 0.94-0.97) and the magnitude of this effect increased with time. Larviciding also led to a decline in household heads’ knowledge of malaria symptoms (PR?=?0.88; 95% CrI: 0.83-0.92) but no evidence of effect on knowledge of malaria transmission was found. Conclusion Successful control interventions could bring about further challenges to sustaining gains in reducing malaria transmission if not accompanied by strategies to avoid changes in individual knowledge and behaviour. This study points to two major research gaps. First, there is an urgent need to gather more evidence on the extent to which countries that have achieved significant decline in malaria transmission are also observing changes in individual behaviour and knowledge. Second, multidisciplinary assessments that combine quantitative and qualitative data, utilizing theories of health behaviour and theories of knowledge, are needed to optimize efforts of national malaria control programmes, and ultimately contribute to sustained reduction in malaria transmission. PMID:24237682

2013-01-01

372

The changing burden of malaria and association with vector control interventions in Zambia using district-level surveillance data, 2006-2011  

PubMed Central

Background Malaria control was strengthened in Zambia over the past decade. The two primary interventions for vector control are indoor residual spraying (IRS) and long-lasting insecticide-treated nets (LLINs). Using passive malaria surveillance data collected from 2006 to 2011 through the Zambian District Health Information System, the associations between increased coverage with LLINs and IRS and the burden of malaria in Zambia were evaluated. Methods National passive malaria surveillance data from 2006 to 2011 were analysed. A district-level, random-effects model with Poisson regression was used to explore the association between malaria cases and coverage with LLINs and IRS. Malaria cases and LLINs and IRS coverage were mapped to visualize spatiotemporal variation in malaria for each year. Results From 2006–2011, 24.6 million LLINs were distributed and 6.4 million houses were sprayed with insecticide. Coverage with LLINs was not uniformly distributed over the study period and IRS was targeted to central and southern districts where malaria transmission was low. LLIN coverage was associated with a reduction in malaria cases, although an increase in the number of malaria cases was reported in some districts over the study period. A high burden of malaria persisted in north-eastern Zambia, whereas a reduction in the number of reported malaria cases was observed in western and southern Zambia. Conclusion Enhanced and targeted interventions in north-eastern Zambia where the burden of malaria remains high, as well as efforts to sustain low malaria transmission in the south-west, will be necessary for Zambia to achieve the national goal of being malaria free by 2030. PMID:24289177

2013-01-01

373

Reduced Vector Preisach Model  

NASA Technical Reports Server (NTRS)

A new vector Preisach model, called the Reduced Vector Preisach model (RVPM), was developed for fast computations. This model, derived from the Simplified Vector Preisach model (SVPM), has individual components that like the SVPM are calculated independently using coupled selection rules for the state vector computation. However, the RVPM does not require the rotational correction. Therefore, it provides a practical alternative for computing the magnetic susceptibility using a differential approach. A vector version, using the framework of the DOK model, is implemented. Simulation results for the reduced vector Preisach model are also presented.

Patel, Umesh D.; Torre, Edward Della; Day, John H. (Technical Monitor)

2002-01-01

374

Anti-mosquito plants as an alternative or incremental method for malaria vector control among rural communities of Bagamoyo District, Tanzania  

PubMed Central

Background Plants represent one of the most accessible resources available for mosquito control by communities in Tanzania. However, no documented statistics exist for their contribution in the management of mosquitoes and other insects except through verbal and some publications. This study aimed at assessing communities’ knowledge, attitudes and practices of using plants as an alternative method for mosquito control among selected communities in a malaria-prone area in Tanzania. Methods Questionnaires were administered to 202 respondents from four villages of Bagamoyo District, Pwani Region, in Tanzania followed by participatory rural appraisal with village health workers. Secondary data collection for plants mentioned by the communities was undertaken using different search engines such as googlescholar, PubMED and NAPRALERT. Results Results showed about 40.3% of respondents used plants to manage insects, including mosquitoes. A broad profile of plants are used, including “mwarobaini” (Azadirachta indica) (22.5%), “mtopetope” (Annona spp) (20.8%), “mchungwa/mlimau” (Citrus spp) (8.3%), “mvumbashi/uvumbati” (Ocimum spp) (7.4%), “mkorosho” (Anacadium occidentale) (7.1%), “mwembe” (5.4%) (Mangifera indica), “mpera” (4.1%) (Psidium spp) and “maganda ya nazi” (4.1%) (Cocos nucifera). Majority of respondents collected these plants from the wild (54.2%), farms (28.9%) and/or home gardens (6%). The roles played by these plants in fighting mosquitoes is reflected by the majority that deploy them with or without bed-nets (p > 0.55) or insecticidal sprays (p >0.22). Most respondents were aware that mosquitoes transmit malaria (90.6%) while few respondents associated elephantiasis/hydrocele (46.5%) and yellow fever (24.3%) with mosquitoes. Most of the ethnobotanical uses mentioned by the communities were consistent with scientific information gathered from the literature, except for Psidium guajava, which is reported for the first time in insect control. Conclusion This survey has indicated some knowledge gap among community members in managing mosquito vectors using plant. The communities need a basic health education and sensitization for effective exploitation of this valuable tool for reducing mosquitoes and associated disease burdens. On the other hand, the government of Tanzania should strengthen advocacy of botanical pesticides development, registration and regulation for public health benefits because they are source of pest control tools people rely on them. PMID:25015092

2014-01-01

375

Eco-bio-social research on dengue in Asia: a multicountry study on ecosystem and community-based approaches for the control of dengue vectors in urban and peri-urban Asia  

PubMed Central

This article provides an overview of methods and cross-site insights of a 5-year research and capacity building initiative conducted between 2006 and 2011 in six countries of South Asia (India, Sri Lanka) and South-East Asia (Indonesia, Myanmar, Philippines, Thailand).The initiative managed an interdisciplinary investigation of ecological, biological, and social (i.e., eco-bio-social) dimensions of dengue in urban and peri-urban areas, and developed community-based interventions aimed at reducing dengue vector breeding and viral transmission. The multicountry study comprised interdisciplinary research groups from six leading Asian research institutions. The groups conducted a detailed situation analysis to identify and characterize local eco-bio-social conditions, and formed a community-of-practice for EcoHealth research where group partners disseminated results and collaboratively developed site-specific intervention tools for vector-borne diseases. In sites where water containers produced more than 70% of Aedes pupae, interventions ranged from mechanical lid covers for containers to biological control. Where small discarded containers presented the main problem, groups experimented with solid waste management, composting and recycling schemes. Many intervention tools were locally produced and all tools were implemented through community partnership strategies. All sites developed socially and culturally appropriate health education materials. The study also mobilised and empowered women’s, students’ and community groups and at several sites organized new volunteer groups for environmental health. The initiative’s programmes showed significant impact on vector densities in some sites. Other sites showed varying effect — partially attributable to the ‘contamination’ of control groups — yet led to significant outcomes at the community level where local groups united around broad interests in environmental hygiene and sanitation. The programme’s findings are relevant for defining efficient, effective and ecologically sound vector control interventions based on local evidence and in accordance with WHO’s strategy for integrated vector management. PMID:23318234

Sommerfeld, Johannes; Kroeger, Axel

2012-01-01

376

Dose-response tests and semi-field evaluation of lethal and sub-lethal effects of slow release pyriproxyfen granules (Sumilarv®0.5G) for the control of the malaria vectors Anopheles gambiae sensu lato  

PubMed Central

Background Recently research has shown that larviciding can be an effective tool for integrated malaria vector control. Nevertheless, the uptake of this intervention has been hampered by the need to re-apply larvicides frequently. There is a need to explore persistent, environmentally friendly larvicides for malaria vector control to reduce intervention efforts and costs by reducing the frequency of application. In this study, the efficacy of a 0.5% pyriproxyfen granule (Surmilarv®0.5G, Sumitomo Chemicals) was assessed for the control of Anopheles gambiae sensu stricto and Anopheles arabiensis, the major malaria vectors in sub-Saharan Africa. Methods Dose–response and standardized field tests were implemented following standard procedures of the World Health Organization’s Pesticide Evaluation Scheme to determine: (i) the susceptibility of vectors to this formulation; (ii) the residual activity and appropriate retreatment schedule for field application; and, (iii) sub-lethal impacts on the number and viability of eggs laid by adults after exposure to Sumilarv®0.5G during larval development. Results Anopheles gambiae s.s. and An. arabiensis were highly susceptible to Sumilarv®0.5G. Estimated emergence inhibition (EI) values were very low and similar for both species. The minimum dosage that completely inhibited adult emergence was between 0.01-0.03 parts per million (ppm) active ingredient (ai). Compared to the untreated control, an application of 0.018?ppm ai prevented 85% (95% confidence interval (CI) 82%-88%) of adult emergence over six weeks under standardized field conditions. A fivefold increase in dosage of 0.09?ppm ai prevented 97% (95% CI 94%-98%) emergence. Significant sub-lethal effects were observed in the standardized field tests. Female An. gambiae s.s. that were exposed to 0.018?ppm ai as larvae laid 47% less eggs, and females exposed to 0.09?ppm ai laid 74% less eggs than females that were unexposed to the treatment. Furthermore, 77% of eggs laid by females exposed to 0.018?ppm ai failed to hatch, whilst 98% of eggs laid by females exposed to 0.09?ppm ai did not hatch. Conclusion Anopheles gambiae s.s. and An. arabiensis are highly susceptible to Sumilarv®0.5G at very low dosages. The persistence of this granule formulation in treated habitats under standardized field conditions and its sub-lethal impact, reducing the number of viable eggs from adults emerging from treated ponds, enhances its potential as malaria vector control tool. These unique properties warrant further field testing to determine its suitability for inclusion in malaria vector control programmes. PMID:23497149

2013-01-01

377

Adding Two Vectors  

NSDL National Science Digital Library

This website from David M. Harrison of the University of Toronto's physics department provides an animation of the addition of two vectors. Instructors may use this animation in explaining the concept of adding vectors and demonstrating the steps involved.

Harrison, David M.

2010-08-13

378

Bacteriological larvicides of dipteran disease vectors.  

PubMed

The apparent success in vector control observed between 1950 and 1970 was followed by worldwide resistance to organosynthetic insecticides wherever they were used intensively. Insect resistance to one or more categories of insecticides has limited the effectiveness of these compounds, and their non-selective mode of action adversely affects non-target organisms. This scenario highlights the need for selective agents in integrated vector control programs. This article gives an overview of the main fundamental and applied research topics on entomopathogenic bacteria in relation to their role in vector control. PMID:11685898

Regis, L; Silva-Filha, M H; Nielsen-LeRoux, C; Charles, J F

2001-08-01

379

Support vector domain description  

Microsoft Academic Search

This paper shows the use of a data domain description method, inspired by the support vector machine by Vapnik, called the support vector domain description (SVDD). This data description can be used for novelty or outlier de- tection. A spherically shaped decision boundary around a set of objects is constructed by a set of support vectors describing the sphere boundary.

David M. J. Tax; Robert P. W. Duin

1999-01-01

380

Rhotrix Vector Spaces  

ERIC Educational Resources Information Center

By rhotrix we understand an object that lies in some way between (n x n)-dimensional matrices and (2n - 1) x (2n - 1)-dimensional matrices. Representation of vectors in rhotrices is different from the representation of vectors in matrices. A number of vector spaces in matrices and their properties are known. On the other hand, little seems to be…

Aminu, Abdulhadi

2010-01-01

381

ContentsContents2828vector 1. Background to Vector Calculus  

E-print Network

ContentsContents2828vector calculus 1 1. Background to Vector Calculus 2. Differential Vector;Background to Vector Calculus 28.1 Introduction Vector Calculus is the study of the various derivatives (VERSION 1: April 14, 2004): Workbook Level 1 28.1: Background to Vector Calculus #12;Solution In the first

Vickers, James

382

Hemolymphatic components in vectors of Trypanosoma cruzi: study in several species of the subfamily Triatominae (Hemiptera: Reduviidae).  

PubMed

The members of the subfamily Triatominae (Hemiptera: Reduviidae) comprise a great number of species of medical importance in the transmission of the T. cruzi (American trypanosomiasis). The aim of this study was to contribute to the knowledge about the chemical composition in proteins, lipids, lipoproteins, and carbohydrates of vectors of Chagas' disease corresponding to twelve members of the subfamily Triatominae. This study was carried out in ninphs of the fifth instar and adult males of the species: T. delpontei, T. dimidiata, T. guasayana, T. infestans, T. mazzotti, T. pallidipennis, T. patagonica, T. platensis, T. rubrovaria, T. sordida of the Triatoma genus, and D. maximus and P. megistus of the Dipatalogaster and Panstrongylus genera respectively. The results show on one hand, qualitative differences in the protein composition, and on the other hand, similarity in the lipoprotein profiles. Lipids, proteins, and carbohydrates did not show significant differences between species or/and stages. PMID:8284596

Canavoso, L E; Rubiolo, E R

1993-01-01

383

Combating tropical infectious diseases: report of the Disease Control Priorities in Developing Countries Project.  

PubMed

Infectious diseases are responsible for >25% of the global disease toll. The new Disease Control Priorities in Developing Countries Project (DCPP) aims to decrease the burden of these diseases by producing science-based analyses from demographic, epidemiologic, disease intervention, and economic evidence for the purpose of defining disease priorities and implementing control measures. The DCPP recently reviewed selected tropical infectious diseases, examined successful control experiences, and defined unsettled patient treatment, prevention, and research issues. Disease elimination programs against American trypanosomiasis (Chagas disease), onchocerciasis, lymphatic filariasis, leprosy, trachoma, and measles are succeeding. Dengue, leishmaniasis, African trypanosomiasis, malaria, diarrheal diseases, helminthic infections, and tuberculosis have reemerged because of inadequate interventions and control strategies and the breakdown of health delivery systems. Application of technologies must be cost-effective and intensified research is essential if these and other scourges are to be controlled or eliminated in the 21st century. PMID:14999633

Hotez, Peter J; Remme, Jan H F; Buss, Paulo; Alleyne, George; Morel, Carlos; Breman, Joel G

2004-03-15

384

Aging partially restores the efficacy of malaria vector control in insecticide-resistant populations of Anopheles gambiae s.l. from Burkina Faso  

PubMed Central

Background The operational impact of insecticide resistance on the effectiveness of long-lasting insecticide nets (LLINs) and indoor residual spraying (IRS) is poorly understood. One factor which may prolong the effectiveness of these tools in the field is the increase in insecticide susceptibility with mosquito age. In this study, LLINs and IRS were tested against young (three to five days) and old (17-19 days) pyrethroid resistant Anopheles gambiae s.l. from Burkina Faso. Methods Blood-fed adult Anopheles gambiae s.l. were collected from south-west Burkina Faso and identified to species/form level. Cohorts of the F1 progeny of An. gambiae s.s. S-forms were exposed to deltamethrin (0.05%) at three to five or 17-19 days post-emergence and tested for the frequency of the resistance allele 1014F. Isofemale lines of the M, S- form of An. gambiae s.s. and Anopheles arabiensis were exposed in WHO cone tests to either a) LLINs deployed in households for two years or (b) bendiocarb sprayed walls. Results Mortality rates in response to deltamethrin (0.05%) increased from levels indicative of strong resistance in three to five day old F1 mosquitoes, to near full susceptibility in the 17-19 day old cohort. On exposure to LLINs sampled from the field, the mortality rate in isofemale lines was higher in older mosquitoes than young (OR = 5.28, CI 95% = 2.81-9.92), although the mortality estimates were affected by the LLIN tested. In general, the LLINs sampled from the field performed poorly in WHO cone bioassays using either laboratory susceptible or field caught mosquito populations. Finally, there was a clear relationship between mortality and age on exposure to bendiocarb-sprayed walls, with older mosquitoes again proving more susceptible (OR = 3.39, CI 95% = 2.35-4.90). Conclusions Age is a key factor determining the susceptibility of mosquitoes to insecticides, not only in laboratory studies, but in response to field-based vector control interventions. This has important implications for understanding the epidemiological impact of resistance. If mosquitoes old enough to transmit malaria are still being suppressed with available insecticides, is resistance potentially having less of an impact than often assumed? However, the poor performance of LLINs used in this study in Burkina Faso, is a cause for concern and requires urgent investigation. PMID:22269002

2012-01-01

385

Conjoint Control of Hippocampal Place Cell Firing by Two Visual Stimuli: II. A Vector-field Theory that Predicts Modifications of the Representation of the Environment  

Microsoft Academic Search

Changing the angular separation between two visual stimuli attached to the wall of a recording cylin- der causes the firing fields of place cells to move relative to each other, as though the representation of the floor undergoes a topological distortion. The displacement of the firing field center of each cell is a vector whose length is equal to the

André A. Fenton; Gyorgy Csizmadia; Robert U. Muller

2000-01-01

386

An extra-domiciliary method of delivering entomopathogenic fungus, Metharizium anisopliae IP 46 for controlling adult populations of the malaria vector, Anopheles arabiensis  

Microsoft Academic Search

Fungal biopesticides have the potential to significantly reduce densities of malaria vectors as well as associated malaria transmission. In previous field trials, entomopathogenic fungus was delivered from within human dwellings, where its efficacy was limited by low infection rates of target mosquitoes, high costs of spraying fungus inside houses, and potential public health concerns associated with introducing fungal conidia inside

Dickson W Lwetoijera; Robert D Sumaye; Edith P Madumla; Deogratius R Kavishe; Ladslaus L Mnyone; Tanya L Russell; Fredros O Okumu

2010-01-01

387

Mapping the magnetic field vector in a fountain clock  

NASA Astrophysics Data System (ADS)

We show how the mapping of the magnetic field vector components can be achieved in a fountain clock by measuring the Larmor transition frequency in atoms that are used as a spatial probe. We control two vector components of the magnetic field and apply audio frequency magnetic pulses to localize and measure the field vector through Zeeman spectroscopy.

Gertsvolf, Marina; Marmet, Louis

2011-12-01

388

MAC3: Vectors  

NSDL National Science Digital Library

This resource is a set of instructional materials developed to help beginning physics students build a solid understanding of vector algebra. It contains two lecture presentations in PDF format and a companion assessment. It gives an overview of terminology, vector notation, and a variety of methods for solving problems relating to vectors. One of the authors' goals is to help students differentiate between the uses of vectors in mathematics vs. physics. This resource is part of a collection developed by the NSF-funded Mathematics Across the Community College Curriculum (MAC 3).

Friesen, Larry; Gillis, Anne

2008-12-22

389

Vector Acoustics, Vector Sensors, and 3D Underwater Imaging  

NASA Astrophysics Data System (ADS)

Vector acoustic data has two more dimensions of information than pressure data and may allow for 3D underwater imaging with much less data than with hydrophone data. The vector acoustic sensors measures the particle motions due to passing sound waves and, in conjunction with a collocated hydrophone, the direction of travel of the sound waves. When using a controlled source with known source and sensor locations, the reflection points of the sound field can be determined with a simple trigonometric calculation. I demonstrate this concept with an experiment that used an accelerometer based vector acoustic sensor in a water tank with a short-pulse source and passive scattering targets. The sensor consists of a three-axis accelerometer and a matched hydrophone. The sound source was a standard transducer driven by a short 7 kHz pulse. The sensor was suspended in a fixed location and the hydrophone was moved about the tank by a robotic arm to insonify the tank from many locations. Several floats were placed in the tank as acoustic targets at diagonal ranges of approximately one meter. The accelerometer data show the direct source wave as well as the target scattered waves and reflections from the nearby water surface, tank bottom and sides. Without resorting to the usual methods of seismic imaging, which in this case is only two dimensional and relied entirely on the use of a synthetic source aperture, the two targets, the tank walls, the tank bottom, and the water surface were imaged. A directional ambiguity inherent to vector sensors is removed by using collocated hydrophone data. Although this experiment was in a very simple environment, it suggests that 3-D seismic surveys may be achieved with vector sensors using the same logistics as a 2-D survey that uses conventional hydrophones. This work was supported by the Office of Naval Research, program element 61153N.

Lindwall, D.

2007-12-01

390

Assessment of Bacillus thuringiensis serotype 14 and Steinernema feltiae [Nematoda: Steinernematidae] for control of the Simulium vectors of onchocerciasis in Mexico  

Microsoft Academic Search

Field evaluations ofBacillus thuringiensis Berliner serotype 14 and the nematodeSteinernema feltiae Filipjev 1934 (=Neoaplectana carpocapsae) were conducted againstSimulium ocharaceum Walker and other simuliid vectors of onchocerciasis in Mexico.B. thuringiensis was highly toxic, causing up to 100 % larval mortality, but only for short distances downstream. Increased dosage did not\\u000a enhance downstream carry ofB. thuringiensis. Highest rates of mortality were recorded

R. Gaugler; B. Kaplan; C. Alvarado; J. Montoya; M. Ortega

1983-01-01

391

Vector Calculus Spring 1997  

E-print Network

Vector Calculus Math 241 Spring 1997 Instructor Information: Professor: Bob Sharpley Office: 313D­ tor calculus including vector fields, line integrals, and Green's theorem in the plane. Exams in Math 142 or an equivalent course. Text: Calculus with Analytic Geometry, by D. Varberg and E.J