Laboratory Evaluation of Flurox, a Chitin Synthesis Inhibitor, on the Termite, Microcerotermes diversus

Microcerotermes diversus (Silvestri) (Isoptera: Termitidae) is the most economically destructive termite in structures in southwest Iran. One sustainable control strategy that usually helps to reduce subterranean termite damage in buildings, is the use of insect growth regualtors in a suitable bait matrix that are safe to the user and the environment. In the laboratory assays described here, the delayed toxicity of Flurox, a chitin synthesis inhibitor, to M. diversus was evaluated under force-feeding and choice trials. Flurox induced worker and nymph mortality and incomplete ecdysis in nymphs of M. diversus under no-choice and two-choice feeding tests. These adverse effects may cause disruption of the caste balance in M. diversus, leading to the collapse of the colony. These assays determined concentrations of Flurox that can be used in bait formulations

Pathological mucus and impaired mucus clearance in cystic fibrosis patients result from increased concentration, not altered pH

Cystic fibrosis (CF) is a recessive genetic disease that is characterised by airway mucus plugging and reduced mucus clearance. There are currently alternative hypotheses that attempt to describe the abnormally viscous and elastic mucus that is a hallmark of CF airways disease, including: 1) loss of CF transmembrane regulator (CFTR)-dependent airway surface volume (water) secretion, producing mucus hyperconcentration-dependent increased viscosity, and 2) impaired bicarbonate secretion by CFTR, producing acidification of airway surfaces and increased mucus viscosity. A series of experiments was conducted to determine the contributions of mucus concentration versus pH to the rheological properties of airway mucus across length scales from the nanoscopic to macroscopic. For length scales greater than the nanoscopic, i.e. those relevant to mucociliary clearance, the effect of mucus concentration dominated over the effect of airway acidification. Mucus hydration and chemical reduction of disulfide bonds that connect mucin monomers are more promising therapeutic approaches than alkalisation

Experimental demonstration of a transparent graphene millimetre wave absorber with 28% fractional bandwidth at 140 GHz

The development of transparent radio-frequency electronics has been limited, until recently, by the lack of suitable materials. Naturally thin and transparent graphene may lead to disruptive innovations in such applications. Here, we realize optically transparent broadband absorbers operating in the millimetre wave regime achieved by stacking graphene bearing quartz substrates on a ground plate. Broadband absorption is a result of mutually coupled Fabry-Perot resonators represented by each graphene-quartz substrate. An analytical model has been developed to predict the absorption performance and the angular dependence of the absorber. Using a repeated transfer-and-etch process, multilayer graphene was processed to control its surface resistivity. Millimetre wave reflectometer measurements of the stacked graphene-quartz absorbers demonstrated excellent broadband absorption of 90% with a 28% fractional bandwidth from 125-165 GHz. Our data suggests that the absorbers’ operation can also be extended to microwave and low-terahertz bands with negligible loss in performance

Effects of Aqueous and Powder Formulations of N’N-napthaloylhydroxyamine on Feeding and Mortality of Laboratory Groups of Microcerotermes diversus Silvestri (Isoptera: Termitidae)

Introduction: Microcerotermes diversus Silvestri is considered the most economically destructive pest of wood products in Khuzestan, Iran. This species lives in subterranean nests and gains access to buildings and vegetation by constructing underground galleries. Therefore, control or management of this termite is of serious public concern. Generally, design and implementation of effective management methods for subterranean termites have faced some limitations due to their cryptic life habits. Millions of dollars have been spent for controlling termites worldwide, and 80% of these expenses relate to structural damage repair and costs expended for termite management. In recent years, the use of new non-repellent and slow-acting termiticides has become an important approach for subterranean termite control and has been gaining popularity. In recent years, an extensive survey on the foraging behavior of the most damaging subterranean termites of Khuzestan province (Iran) has been undertaken with a view to the development of appropriate strategies for control of M. diversus as an extremely destructive structural wood pest, was considered to be the major species with a wide distribution throughout Iran. This species tends to form secondary nests (with reproductive and brood).When the water table is high, secondary nests are usually built in above-ground sites such as tree trunks (adjacent to houses) and wall voids. Termite management has primarily focused on the use of chemical methods such as insecticide applications to soil around and beneath wooden structures. Soil treatments with organophosphates such as Chlorpyrifos (Dursban) did not persist in the environment for long time and proved ineffective against aerial colonies. Therefore, it is important to evaluate new compounds that have potential application for termite management. The main purpose of this study was to evaluate possible delayed toxicity effects of N’N napthaloylhydroxyamine (NHA; A. Johnson Metthey Company, USA) on feeding and mortality on M. diversus. Materials and Methods: Termites (M. diversus), which were collected from infested wooden blocks previously buried in soil, transferred to the laboratory and placed in plastic boxes in a dark incubator at 28±2˚C and 90±5% relative humidity. Only active and healthy termites were used for tests. Feeding inhibition and mortality of workers treated with NHA were evaluated using both ‘choice’ and ‘no-choice’ test. In no-choice tests, termites were provided by only NHA-treated soil, or NHA-treated filter paper alone. Therefore, they could not escape the treated soil, or had only treated filter paper for food. In choice tests, termites were provided both treated and non-treated soil or filter paper, and could escape or avoid the treated substractes concentration. Technical NHA (99% wt:wt) was used. Two formulations, which were powdery and aqueous, were evaluated to envistigate their efficacy for management of M. diversus. Termites were exposed to NHA at concentrations which included ranging from 0.5 to 4.0% (wt:wt) in aqueous formulation, and from 0.5 to 8.0% (wt:wt) in powdered formulation. Termites were exposed to sterilized soil or filter paper treated with mentioned concentrations of NHA. Termites’ behaviors monitored daily and their mortality recorded. Mortality data were corrected using Abbott’s formula. ANOVA was performed in conjunction with a least significant difference (LSD) test, and Duncan’s Multiple Range Test at the 5% level using SAS software (ver. 9.1). A probit analysis was also conducted. The related diagrams were drawn using Microsoft Excel 2007. Noted that the tests were carried out with regard to the standards E1-06 (2006) of the USA and prEN117(2003) of the Europe. Results and Discussion: NHA-treated-soil indicated that over 21 days, mortality rate gradually increased with increasing concentration levels. Trials with filter paper impregnated with the aqueous formulation showed that within 14 days mortality also gradually increased with increasing concentration. Probit analysis indicated that the level of mortality was dependent on concentration. There was an inverse relationship between time to 90% mortality (LT90) and concentration. LC50 and LC90 values when for compared between different tests showed that in no-choice tests where termites were forced to contact NHA, these values are lower compared with the choice tests. This indicates greater lethality in no-choice tests. Overall, at doses of 0.5, 1.0, 2.0, and 4.0% aqueous formulation (treated-filter paper), within 7 to 14-days mortality was 63%. Powdered formulation at doses of 0.5, 1.0, 2.0, 4.0, 6.0 and 8.0% (treated-soil) caused 67% mortality within 14 to 21 days, indicating that NHA is a slow-acting toxin once ingested. Conclusion: With regard to our results, we suggest NHA as an effective non-repellent termiticide for controlling M. diversus, and perhaps other subterranean termites in soil. We suggest that application of NHA may be an effective strategyfor the control of M. diversus. Further, field testing is warranted to determine NHA efficacy in natural conditions

High-Gain Graphene Transistors with a Thin AlOx Top-Gate Oxide

The high-frequency performance of transistors is usually assessed by speed and gain figures of merit, such as the maximum oscillation frequency f(max), cutoff frequency f(T), ratio f(max)/f(T), forward transmission coefficient S-21, and open-circuit voltage gain A(v). All these figures of merit must be as large as possible for transistors to be useful in practical electronics applications. Here we demonstrate high-performance graphene field-effect transistors (GFETs) with a thin AlOx gate dielectric which outperform previous state-of-the-art GFETs: we obtained f(max)/f(T) > 3, A(v) > 30 dB, and S-21 = 12.5 dB (at 10 MHz and depending on the transistor geometry) from S-parameter measurements. A dc characterization of GFETs in ambient conditions reveals good current saturation and relatively large transconductance similar to 600 S/m. The realized GFETs offer the prospect of using graphene in a much wider range of electronic applications which require substantial gain

Novel Powder-Supported Size-Selected Clusters for Heterogeneous Catalysis under Realistic Reaction Conditions

Well-defined nanoparticles show promise as model catalysts in the quest for new/improved practical catalysts with tunable chemical properties. Here we demonstrate the production, chemical performance, and stability of a new class of model catalyst systems, consisting of size-selected (Pd_N) nanoclusters supported on (graphite) powders suitable for realistic, test tube reaction conditions. The catalyst powders were synthesized by cluster beam deposition onto planar surface followed by microdicing. Cluster size-dependent (<i>N</i> = 55 to 400) catalytic activity/selectivity was observed in the vapor phase hydrogenation of 1-pentyne. Aberration-corrected scanning transmission electron microscopy of the nanocluster catalysts before and after catalytic measurements revealed the stability of the cluster catalysts against sintering. Larger nanoclusters, e.g., Pd₄₀₀, showed superior activity, thermal stability, and (very high) selectivity over a period of hours in the reactor