No abstract

No abstract

BackgroundCurrent efforts are underway to quantify the chemical concentration in a treated air space that elicits a spatial repellent (deterrent) response in a vector population. Such information will facilitate identifying the optimum active ingredient (AI) dosage and intervention coverage important for the development of spatial repellent tools – one of several novel strategies being evaluated for vector-borne disease control. This study reports initial findings from air sampling experiments conducted under field conditions to describe the relationship between air concentrations of repellent AIs and deterrent behavior in the dengue vector, Aedes aegypti.MethodsAir samples were taken inside and outdoors of experimental huts located in Pu Tuey Village, Kanchanaburi Province, Thailand in conjunction with mosquito behavioral evaluations. A mark-release-recapture study design using interception traps was used to measure deterrency of Ae. aegypti against 0.00625% metofluthrin coils and DDT-treated fabric (2g/m2) within separate experimental trials. Sentinel mosquito cohorts were positioned adjacent to air sampling locations to monitor knock down responses to AI within the treated air space. Air samples were analyzed using two techniques: the U.S. Environmental Protection Agency (USEPA) Compendium Method TO-10A and thermal desorption (TD).ResultsBoth the USEPA TO-10A and TD air sampling methods were able to detect and quantify volatized AIs under field conditions. Air samples indicated concentrations of both repellent chemicals below thresholds required for toxic responses (mortality) in mosquitoes. These concentrations elicited up to a 58% and 70% reduction in Ae. aegypti entry (i.e., deterrency) into treated experimental huts using metofluthrin coils and DDT-treated fabric, respectively. Minimal knock down was observed in sentinel mosquito cohorts positioned adjacent to air sampling locations during both chemical evaluations.ConclusionsThis study is the first to describe two air sampling methodologies that are appropriate for detecting and quantifying repellent chemicals within a treated air space during mosquito behavior evaluations. Results demonstrate that the quantity of AI detected by the mosquito vector, Ae. aegypti, that elicits repellency is far lower than that needed for toxicity. These findings have important implications for evaluation and optimization of new vector control tools that function through mosquito behavior modification as opposed to mortality.

No abstract

A series of novel terbium tetracyanoplatinate compounds all incorporating tridentate 2,2':6'2″-terpyridine (terpy) or 4'-chloro-2,2':6'2″-terpyridine (terpy-Cl) were synthesized and used to investigate the phenomenon of dual-donor sensitization of Tb(3+). Judicious choice of the Tb(3+) salt and reaction conditions results in the isolation of {Tb(terpy)(H2O)2(NO3)Pt(CN)4}·CH3CN (1A), {Tb(terpy)(H2O)2(NO3)Pt(CN)4}·3.5H2O (1B), {Tb(terpy-Cl)(H2O)2(NO3)Pt(CN)4}·2.5H2O (2), [Tb(terpy)(H2O)2(CH3COO)2]2Pt(CN)4·4H2O (3), or [Tb2(terpy)2(H2O)2(CH3COO)5]2Pt(CN)4·7H2O (4). The compounds 1A, 1B, and 2 contain one-dimensional polymeric structures with bridging of [Tb(L)(NO3)(H2O)2](2+) (L = terpy or terpy-Cl) moieties by cis-bridging tetracyanoplatinate (TCP) anions as determined via single-crystal X-ray diffraction studies. Both 3 and 4, however, contain Tb(3+) coordinated by multiple acetate ligands and terpy, but not TCP, and are classified as zero-dimensional complex salts. Platinophilic interactions that dominate tetracyanoplatinate structural chemistry are present in the form of dimeric units in the polymeric compounds, but are totally absent in 3 and 4. The structural differences result in markedly different luminescence properties for the two classes of compounds. All of the polymeric compounds display efficient donor-acceptor intramolecular energy transfer (IET) from the terpy unit to the Tb(3+) ion. Although the TCP units are also directly coordinated to the Tb(3+) ion in the three polymers, only in 1B and 2 are the Pt···Pt interactions strong enough to provide MMLCT bands of appropriate energy to result in a dual-donor effect to the Tb(3+) sensitization. Even in these cases, TCP does not efficiently sensitize the Tb(3+), rather a broad band TCP emission results. However, terpy and acetate ligands are bonded directly to the Tb(3+) ion in 3 and 4 and provide a strong dual-donor sensitization effect as evidenced by the large QY for Tb(3+).