Impact of short-term heat pre-treatment at 50 °C on the toxicity of contact insecticides to adults of three Sitophilus granarius (L.) populations

The effect of short-term heat pre-treatment on the toxicity of contact insecticides was tested on Sitophilus granarius adults from three populations in order to examine possible interactions. In the laboratory: (a) weevil paralysis time (PT) after start of direct exposure to 50 °C; (b) the impact of three short-term heat pre-treatments at 50 °C (PT₂₀, PT₅₀ and PT₈₀) on the 24 and 72 h recovery rates of laboratory (Lab) strain adults exposed to one of five insecticides on filter papers; and (c) deltamethrin and dichlorvos toxicity to weevils of two populations with altered insecticide susceptibility after exposure to 50 °C over the PT₈₀ interval, were determined.The PT₉₉ values for weevils after exposure to 50 °C showed that the population selected with pirimiphos-methyl had the longest paralysis time. Previous heat treatments of the Lab strain for the PT₂₀ and PT₅₀ intervals had little impact on the toxicity of the insecticides, chlorpyrifos-methyl being the most toxic with the first interval, deltamethrin with the second, while malathion was the least toxic. However, after heat treatment of the Lab strain over the PT₈₀ and after a 72-h recovery period, deltamethrin and dichlorvos showed reduced toxicity, while chlorpyrifos-methyl was the most toxic insecticide and malathion again the least toxic.For field and selected weevils, heat pre-treatment at 50 °C over the PT₈₀ increased deltamethrin and dichlorvos toxicity to selected populations, but not to field populations when compared to their toxicity without pre-heating. Deltamethrin and dichlorvos toxicity after a 72-h recovery period from heat treatment over the PT₈₀ was higher to the selected population than to the resistant field population. Compared to the Lab strain, deltamethrin demonstrated lower toxicity to selected weevils and especially to a field population, while dichlorvos was considerably more toxic to both populations.     

Residual effects of deltamethrin and malathion on different populations of Sitophilus granarius (L.) on treated wheat grains

The impact of 2-, 7-, 14-, 30-, 90-, 150- and 720-day-old deposits of deltamethrin, applied with or without the synergist piperonyl butoxide (PBO), and of malathion, on adults of different populations of granary weevil Sitophilus granarius on wheat was investigated in the laboratory. The insecticides used were commercial formulations and their application rates were as recommended: deltamethrin (dustable powder) 0.5 mg a.i./kg, deltamethrin + PBO (1:10) (emulsifiable concentrate) 0.25 mg a.i./kg, and malathion (dustable powder) 10 mg a.i./kg. The weevil populations examined were: (a) a laboratory population, (b) field populations with different susceptibility to some insecticides as established previously, and (c) populations selected in the laboratory with deltamethrin or pirimiphos-methyl.The 2-day-old deposit of malathion caused complete mortality of all weevil populations after 7 and 14 days. The corresponding deposit of deltamethrin was 100% effective only against the laboratory weevils after 7-14 days, while deltamethrin at the lower level formulated with PBO caused about 90% mortality of laboratory weevils and much lower levels of kill among field and selected weevils.Deposits of deltamethrin and malathion up to 90 days old killed all field weevils after 14 days of exposure. The 150-day-old deposit of deltamethrin was also 100% effective against field weevils exposed for 14 days, while the effectiveness against selected populations was around 50%. Malathion deposits of the same age gave 40-50% mortality of field weevils, and 4-68% mortality of selected weevils. The 720-day-old deposits of malathion were ineffective against all weevil populations, while the mortality of laboratory weevils after 14 days contact with deltamethrin deposits of the same age was 76%, and that of field and selected weevils about 50%.     

Experimental study of density segregation at end walls in a horizontal rotating cylinder saturated with fluid: friction to lubrication transition

What is the effect of interstitial fluid viscosity on granular density segregation in a horizontal rotating cylinder? We conducted experiments in the rolling regime with equal amounts of equal sized high and low density, nearly spherical granular particles saturated with air, water, and water-glycerin mixtures. We held particle density, rotation rate and characteristic length scale constant to highlight differences due purely to the interstitial fluid. Images of the granular flow at an end wall were used to determine radial and axial density segregation rates and patterns. Over a four decade change in viscosity, segregation rates varied by only a factor of two. However, for ratios of lubrication to frictional stresses above one, segregation rates decreased by about 30%, and we observed several notable phenomena in the segregation pattern formation. These were a creeping mode of radial density segregation, a change in shape of the granular bed to kidney shaped from flat, and for cylinders more than half full the typically reported unsheared central portion of the granular bed (often referred to in the literature as a core region) was disrupted by a wavy instability where the rate of disappearance of the core region decreased as the fill level increased.     

Scanning tunnelling microscopy imaging of symmetry-breaking structural distortion in the bismuth-based cuprate superconductors

A complicating factor in unravelling the theory of high-temperature (high-T(c)) superconductivity is the presence of a 'pseudogap' in the density of states, the origin of which has been debated since its discovery. Some believe the pseudogap is a broken symmetry state distinct from superconductivity, whereas others believe it arises from short-range correlations without symmetry breaking. A number of broken symmetries have been imaged and identified with the pseudogap state, but it remains crucial to disentangle any electronic symmetry breaking from the pre-existing structural symmetry of the crystal. We use scanning tunnelling microscopy to observe an orthorhombic structural distortion across the cuprate superconducting Bi(2)Sr(2)Ca(n-1)Cu(n)O(2n+4+x) (BSCCO) family tree, which breaks two-dimensional inversion symmetry in the surface BiO layer. Although this inversion-symmetry-breaking structure can impact electronic measurements, we show from its insensitivity to temperature, magnetic field and doping, that it cannot be the long-sought pseudogap state. To detect this picometre-scale variation in lattice structure, we have implemented a new algorithm that will serve as a powerful tool in the search for broken symmetry electronic states in cuprates, as well as in other materials.     

Susceptibility to contact insecticides of granary weevil Sitophilus granarius (L.) (Coleoptera: Curculionidae) originating from different locations in the former Yugoslavia

The insecticides dichlorvos, malathion, chlorpyrifos-methyl, pirimiphos-methyl, deltamethrin and cypermethrin were applied to filter paper to assess their toxicity to granary weevil Sitophilus granarius adults. Based on discriminating doses obtained from tests on a susceptible laboratory population, the susceptibility of 12 populations originating from different storage facilities (11 in Serbia and 1 in Bosnia-Herzegovina) was tested. The facilities included silos, floor stockpiles and attic stockpiles. Weevils originating from Apatin, Belgrade Port, Bijeljina and Kikinda were submitted to toxicity testing, and determination of ld-p lines, LD values and levels of susceptibility/resistance. Chlorpyrifos-methyl proved the most toxic and cypermethrin the least toxic insecticides against all populations. Dichlorvos, malathion and pirimiphos-methyl had the least toxic effect on weevils originating from Belgrade Port and Kikinda, While deltamethrin was most toxic to weevils from Belgrade Port, and least toxic to weevils from Kikinda. The resistance ratios (RR) for deltamethrin at the LD₅₀ and LD₉₅ levels 48 h after exposure to treated filter paper were 11.2 and 14.5 for Bijeljina weevils, and 20.9 and 25.5 for Kikinda weevils.     

Physical‐chemical characteristics and oxidative stability of oil obtained from lyophilized raspberry seed

Fresh raspberry (Rubus idaeus), cultivar Willamette, was freeze‐dried (lyophilization). A byproduct of lyophilization is “fine dust” of raspberry consisting of finely ground raspberry fruit body and seed. The seeds were separated. The seed oil was isolated and its physical and chemical characteristics were determined. Parameters that characterize the seed and quality of the oil were examined, including fatty acid composition, oxidative stability under different storage conditions, and radical‐scavenging activity. The fatty acid composition was determined by GC/FID and the contents of the dominant fatty acids were found as: oleic 16.92%, linoleic 54.95%, and α‐linolenic acid 23.97%. The oxidative stability of the oil was poor. The induction period by Rancimat test at 100 °C was 5.2 h. The radical‐scavenging activity is similar to that of resveratrol [1,3‐benzenediol 5‐(1^E‐2‐4‐hydroxy‐phenyl‐ethyl)]. Although this product is used in the candy industry, it would be far more useful if raspberry oil of satisfactory quality could be extracted. This paper demonstrates that sifted lyophilized seeds can be used for the extraction of oils. This process allows for maximal usage of the byproducts, reduces losses and it increases the development of new products.     

Corrosion behaviour of thixoformed and heat-treated ZA27 alloys in NaCl solution

The influence of corrosion on the microstructure of thixoformed and heat-treated ZA27 alloys was investigated. The microstructure of ZA27 alloy was affected by heat treatment. The process of electrochemical corrosion occurs in both ZA27 alloys through the area of η phase. According to the results of immersion test and electrochemical measurements, the corrosion rate of the thixoformed ZA27 alloy is at least 50% lower than that of the thixoformed and thermally processed alloy. This indicates the unfavourable influence of applied heat treatment (T4 regime) on the corrosion resistance of the thixoformed ZA27 alloy.     

Insights from simulations into mechanisms for density segregation of granular mixtures in rotating cylinders

The Discrete Element Method (DEM) is used to study the segregation of a binary mixture of differing density (but same size) granular material in an axially rotating cylinder. The rotation rates used produce a flow that is on the borderline between the avalanching and rolling regimes. The simulations replicate the experimental data well at both qualitative and quantitative levels. Both wall-induced and radial segregation are observed. The simulations show segregation is delineated into two main time regimes. At early times segregation is rapid (when the dense core is being established) and slows down appreciably thereafter. The final asymptotic state is found to be independent of the initial segregation state of the particles. We compare these results with previous theoretical models and relate these two distinct time regimes to the underlying segregation mechanisms. These comparisons suggest segregation varies as a function of two fundamental quantities (a) density ratio of particles and (b) angular speed of the rotating cylinder. It is shown that maximal segregation occurs for specific ranges of these quantities.     

Exposure assessment and risk characterization of aflatoxins intake through consumption of maize products in the adult populations of Serbia,Croatia and Greece

The main objective of this research was to perform an exposure assessment of aflatoxins intake through consumption of maize products in Serbia, Croatia, and Greece. Food consumption survey of maize-based products has been performed during 2017 in the three countries with at least 1,000 interviewees per country covering their dietary habits and body weight. Values for the concentration of aflatoxins were extracted from available research published in the last ten years. Finally, a Monte Carlo analysis of 100,000 iterations was performed to estimate the intake of aflatoxins from consumption of maize-based products. Results revealed that the estimated average exposure of adults to aflatoxins, from maize consumption, in each of the three countries was between 0.44 ng kg^?1 bw day^?1 and 5.59 ng kg^?1 bw day^?1. Margin of exposure values for the mean exposure levels, in all three countries, were between 30 and 389. Estimations for hepatocellular carcinoma cases/year/10⁵ individuals, depending on the HBsAg+ prevalence, were 0.075–0.098, 0.006–0.008 and 0.020–0.026 for Serbia, Croatia and Greece, respectively.