Study of the long-term evolution of the accretion dynamics of GX 339-4

We study the dynamical behaviour of the galactic black hole source GX 339-4 during 2002-2011 outbursts using RXTE, Swift(XRT), XMM-Newton(PN) archival data. We present the spectral evolution of the source using four outbursts data and discuss their similarities/differences between outbursts. We infer that the second peak in 2002/03 and 2004/05 outbursts can be due to a second instant of triggered instability in the accretion disc due to irradiation from the central X-ray source after peak-I. This propagates in viscous time scale and takes ~80-90 days after peak-I to produce peak-II. This unifies all four outbursts having a long rising time of ~90 days. The dynamical evolution of accretion parameters have been studied by modeling the individual observed spectrum with two-component accretion disc model where a Keplerian accretion disc produces the soft photons and the hard part of the spectrum originates from a hot sub-Keplerian central corona. A generic mathematical model has been proposed to understand the evolution of accretion parameters for sources like GX 339-4 which have longer rising time. Also, the possible differences of physical scenario for outbursts with shorter rising time are also discussed.Comment: Accepted for publication in mnra

Larvicidal and mosquito repellent activities of Pine (Pinus longifolia, Family: Pinaceae) oil

Background & objectives: Various plant-based products are safe and biodegradable alternatives tosynthetic chemicals for use against mosquitoes. Oil of Pinus longifolia is traditionally used forprotection against mosquitoes in some rural areas but there is no documented report of its use againstmosquitoes. The present study was undertaken to scientifically evaluate the activity of Pine oilagainst mosquitoes.Methods: The oil was procured from the market and its contents were chemically analysed. Larvicidalactivity of oil was tested in laboratory bioassays, while repellent action was studied during wholenight bait collections in field by direct application on the skin and after its impregnation on mats.Results: Results showed varying degree of larvicidal activity of Pine oil against mosquitoes with LC50values ranging between 82 and 112 ppm. The Pine oil had strong repellent action against mosquitoesas it provided 100% protection against Anopheles culicifacies for 11 h and 97% protection againstCulex quinquefasciatus for nine hours respectively. Electrically heated mats prepared from Pine oilprovided, 94 and 88% protection against An. culicifacies and Cx. quinquefasciatus for 10 and sevenhours respectively.Interpretaion & conclusion: Pine oil is effective against mosquito larvae at very higher doses whichare not of any practical utility. However, Pine oil showed strong repellent action against An. culicifacies(malaria vector) and Cx. quinquefasciatus (pest mosquito). Thus its use could be popularised asmosquito repellent

Evaluation of the impact of ZeroFly® , an insecticide incorporated plastic sheeting on malaria incidence in two temporary labour shelters in India

Background & objectives: Prevention of malaria is a major technical and operational problem in displaced andmobile populations such as refugee camps and temporary labour settlements. Insecticide incorporated plasticsheeting is a new technology to control mosquitoes in emergency shelters and also temporary habitations atdifferent locations. In view of this, efficacy of ZeroFly®, an insecticide incorporated plastic sheeting (factorytreated with deltamethrin 2.0 g/kg or 265 mg/m2) was evaluated for its efficacy against malaria vectors and itsimpact on malaria incidence in temporary labour settlements in two urban areas in India.Methods: This trial was conducted in two labour settlements in two urban areas, Delhi and Noida (U.P.), Indiawith ~ 250 populations. In an area, two localities were selected for intervention with ZeroFly and untreatedplastic sheets (control). Entomological and epidemiological data were collected using standard methods for one year.Results: Baseline studies on the susceptibility of mosquitoes in Delhi and Noida areas revealed 100% susceptibilityof the malaria vector species Anopheles culicifacies and An. stephensi to deltamethrin. Cone bioassay testsperformed against An. culicifacies and An. stephensi to determine the efficacy of ZeroFly sheets showed 100%mortality against An. culicifacies and An. stephensi with 3 min exposure and after 24 h recovery period. AgainstCulex quinquefasciatus and housefly 100% mortality was obtained after 30 min of exposure period. Interventionwith the ZeroFly plastic sheets resulted in almost complete reduction in the resting density of An. culicifaciesand An. stephensi, the two major malaria vectors and also in the reduction of malaria cases in ZeroFly camps ascompared to control camps. The ZeroFly plastic sheeting was found to be safe for human. Barring some complaintsof skin irritation and itching, which were temporary in nature, no adverse health effects were reported by theusers. The community acceptance was high.Conclusion: Results of the present study revealed that ZeroFly® plastic sheeting is highly effective in reducingthe indoor resting density of mosquitoes, man-vector contact and malaria incidences in labour populations livingin temporary shelters

Wash durability and optimal drying regimen of four brands of long-lasting insecticide-treated nets after repeated washing under tropical conditions

<p>Abstract</p> <p>Background</p> <p>The current study was undertaken to determine the optimal wash-drying regimen and the effects of different washing procedures on the efficacy, and durability of four brands of newly introduced long-lasting insecticide-treated nets (LLINs) under tropical conditions.</p> <p>Methods</p> <p>In the current study, the following four LLINs were tested: Olyset^®, PermaNet ^®2.0, BASF^®and TNT^®. Nets were divided into three sets; one set was washed by hand rubbing and air-dried either hanging or spread on the ground in direct sunlight or hanging or spread on the ground under the shade. A second set was washed using the WHO protocol (machine) and the third set was washed by beating the nets on rocks. The biological activities of the nets were assessed by a three-minute bioassay cone test and the residual insecticide contents were determined using high performance liquid chromatography (HPLC) procedure.</p> <p>Results</p> <p>Nets that were dried hanging under the shade retained more insecticide, 62.5% and recorded higher mortality compared to nets which were dried lying on the ground in direct sunlight 58.8%, nets dried under the shade spread on the ground 56.3%, and 57.8% for nets dried hanging in direct sunlight. It was also observed that nets washed by the standard WHO protocol, retained more insecticide and were more effective in killing mosquitoes compared to nets washed by local methods of hand rubbing and beating on rocks. There were significant differences between drying regimens (p < 0.0001) and between washing procedures (p < 0.001) respectively. However, the effect of net type was statistically insignificant. The statistical differences on individual nets were also compared, for PermaNet^®and TNT there were no significant differences observed between the four drying regimens (<it>p </it>= 0.7944 and 0.4703) respectively). For BASF and Olyset, the differences were significant (p < 0.001 and p > 0.0001).</p> <p>Conclusion</p> <p>The results of this study suggest that washing and drying regimen influence the insecticidal activity of LLINs. The standard WHOPES washing protocol underestimates the amount of insecticide washed from LLINs compared to the abrasive washing procedures that are used in the field. This suggests that there is need to educate net users to adopt a more gentle washing procedure while handling LLINs. The education should accompany net distribution campaigns.</p

The effect of repeated washing of long-lasting insecticide-treated nets (LLINs) on the feeding success and survival rates of Anopheles gambiae

<p>Abstract</p> <p>Background</p> <p>Insecticide-treated nets protect users from mosquito bites, thereby preventing transmissions of mosquito borne pathogens. Repeated washing of nets removes insecticide on the netting rendering them ineffective within a short period. Long-lasting insecticide-treated nets (LLINs) offer longer time protection against such bites because they are more wash resistant, and are preferred to conventionally treated nets. However, there is limited information on the effect of repeated washing of LLINs on the feeding success and survival of wild malaria vectors.</p> <p>Methods</p> <p>The current study evaluated the effect of repeated washing of four brands of LLINs on the feeding success and survival rates of <it>Anopheles gambiae </it>sl reared from wild strains. In this study, two- to five-day old F1s, reared from gravid mosquitoes collected from an area with a high coverage of LLINs were offered blood meals through protective barriers of the above LLINs. Mosquitoes were exposed for a period of 10 minutes each time. Nets were tested unwashed and subsequently after every 5^ththrough wash 15. After exposure mosquitoes were sorted out according to their feeding status. They were then held under normal laboratory conditions for 24 hours and mortality was scored in both fed and unfed.</p> <p>Results</p> <p>It was observed that mosquitoes did not feed through a barrier of unwashed LLINs. However, the feeding success and survival rates increased with successive number of washes and were also net brand dependant. After 15 washes, 49% of vectors succeeded to feed through a protective barrier of PermaNet 2.0 and 50% of the fed died after 24 hrs while after the same number of washes 60% of vectors succeeded to feed through Olyset brand of LLINs and all of them survived. In general, more mosquitoes survived after feeding through Olyset compared to the other four brands that were evaluated. When efficacy of individual LLINs was compared by a t-test analysis to a conventionally treated net, the results were not significantly different statistically for Olyset (<it>p = </it>0.239) and NetProtect (TNT) (<it>p = </it>0.135). However, the results were highly significant when comparison was made with PermaNet and Interceptor (BASF); <it>p </it>values 0.015 and 0.025 respectively.</p> <p>Conclusion</p> <p>The result of this study shows that repeated washing of LLINs at short time intervals using local washing methods may render them infective within a short time in preventing local vectors from feeding.</p

Durability associated efficacy of long-lasting insecticidal nets after five years of household use

<p>Abstract</p> <p>Background</p> <p>Long-lasting insecticidal nets (LLINs) have been strongly advocated for use to prevent malaria in sub-Saharan Africa and have significantly reduced human-vector contact. PermaNet^®2.0 is among the five LLINs brands which have been given full approval by the WHO Pesticide Evaluation Scheme (WHOPES). The LLINs are expected to protect the malaria endemic communities, but a number of factors within the community can affect their durability and efficacy. This study evaluated the durability, efficacy and retention of PermaNet^®2.0 after five years of use in a Tanzanian community.</p> <p>Method</p> <p>Two to three day- old non blood-fed female mosquitoes from an insectary susceptible colony (<it>An. gambiae </it>s.s, this colony was established at TPRI from Kisumu, Kenya in 1992) and wild mosquito populations (<it>An. arabiensis </it>and <it>Culex quinquefasciatus</it>) were used in cone bioassay tests to assess the efficacy of mosquito nets.</p> <p>Findings</p> <p>The knockdown effect was recorded after three minutes of exposure, and mortality was recorded after 24 hours post-exposure. Mortality of <it>An. gambiae </it>s.s from insectary colony was 100% while <it>An. arabiensis </it>and <it>Cx.quinquefasciatus </it>wild populations had reduced mortality. Insecticide content of the new (the bed net of the same brand but never used before) and used PermaNet^®2.0 was determined using High Performance Liquid Chromatography (HPLC).</p> <p>Conclusion</p> <p>The results of this study suggest that, in order to achieve maximum protection against malaria, public health education focusing on bed net use and maintenance should be incorporated into the mass distribution of nets in communities.</p

Comparison of the efficacy of long-lasting insecticidal nets PermaNet® 2.0 and Olyset® against Anopheles albimanus under laboratory conditions

Insecticide-treated nets provide a reduction in human-vector contact through physical barrier, mortality and/or repellent effects that protect both users and non-users, thereby protecting the wider community from vector-borne diseases like malaria. Long-lasting insecticide-treated nets (LLINs) are the best alternative. This study evaluated the bioefficacy of LLINs PermaNet® 2.0 and Olyset® under laboratory conditions with Anopheles albimanus. The laboratory strain was evaluated for insecticide susceptibility with selected insecticides used for malarial control. Regeneration time and wash resistance were evaluated with the standard bioassay cone technique following WHO guidelines. Heat assistance was used for Olyset® nets; the nets were exposed to four different temperatures to speed the regeneration process. The regeneration study of PermaNet® 2.0 showed that efficacy was fully recovered by 24 h after one and three washes and wash resistance persisted for 15 washes. Regeneration of Olyset® nets was not observed for nets washed three times, even with the different temperature exposures for up to seven days. Thus, for Olyset® the wash resistance evaluation could not proceed. Differences in response between the two LLINs may be associated with differences in manufacturing procedures and species response to the evaluated LLINs. PermaNet® 2.0 showed higher and continuous efficacy against An. albimanus