Susceptibility of different life stages of saw-toothed grain beetle Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae) to modified atmospheres enriched with carbon dioxide

The susceptibility of the different life stages of the saw-toothed grain beetle Oryzaephilus surinamensis to different modified atmospheres (MAs) containing various concentrations of carbon dioxide (CO₂) was studied as an alternative to methyl bromide fumigation at 30 °C and 65 ± 5% relative humidity (r.h.). The tested MAs were 55%, 65%, 75% and 85% CO₂ gas in the air. Mortality (%) was recorded after exposure periods of 3, 6, 12, 24, 48, 72 and 96 h. Larvae and adults were more susceptible while eggs and pupae were more tolerant to CO₂. A two-day exposure period was adequate to completely kill larvae and adults under all tested MAs. All eggs and pupae were killed after four days of exposure to the high-CO₂ atmospheres (75% and 85%).     

Weighted PLS-discriminant analysis with application to conventional sensory profiling

Within the framework of sensory conventional profiling, we propose a general strategy of weight assignment to the various statistical units (products × assessors). This means that for each product, an assessor who does not agree with the other assessors on the evaluation of the product under consideration will be down-weighted thus limiting their impact on the outcome of the analysis. The weights are derived from similarity measures between assessors which reflect the extent to which the assessors agree on the position of each product in the perceptual space. The weights are used to compute the usual statistical parameters such as means and variance-covariance matrices. They are also used to compute the PLS-discriminant components which reflect directions of discrimination among the products. The usefulness of the strategy of weight assignment is demonstrated on the basis of a case study where it is shown that it improves the stability of the representation of the products to small perturbations.     

Synthesis,Characterization and Catalytic Activities of Palladium(II) Nitroaryl Complexes

Two palladium(II) nitroaryl complexes trans-[bromo(p-nitrophenyl)bis(triphenylphosphine)palladium(II)] 1 and trans-[bromo(2,4-dinitrophenyl)bis(triphenylphosphine)palladium(II)] 2 have been synthesized. The complexes were characterized by FTIR and NMR (¹H, ¹³C and ³¹P) spectroscopy and elemental analysis. The molecular structure of complex 2, as confirmed by X-ray crystallography, reveals that the Pd atom and its neighboring groups (two PPh₃, Br and phenylene group) lie in a slightly distorted square plane. In the UV–Vis spectra of the complexes 1 and 2, the palladium to aryl charge transfer bands were observed. The emission peaks from the singlet excited states (S₁ → S₀) were observed in the photoluminescence spectra of the complexes. The thermal stability of the complexes has been studied by thermal gravimetric analysis (TGA). TGA data showed that both complexes are thermally stable up to 200 °C, and complex 1 is more stable than 2. The catalytic efficiency of the new palladium(II) complexes was studied as demonstrated using the Sonogashira coupling reactions with good yields. The experimental results suggest that the Sonogashira coupling reactions can be performed at moderate temperature (50 °C) using these new palladium(II) complexes as catalysts.     

Interrogating the Tailoring Steps of Pactamycin Biosynthesis and Accessing New Pactamycin Analogues

Pactamycin is a bacteria‐derived aminocyclitol antibiotic with a wide‐range of biological activity. Its chemical structure and potent biological activities have made it an interesting lead compound for drug discovery and development. Despite its unusual chemical structure, many aspects of its formation in nature remain elusive. Using a combination of genetic inactivation and metabolic analysis, we investigated the tailoring processes of pactamycin biosynthesis in Streptomyces pactum. The results provide insights into the sequence of events during the tailoring steps of pactamycin biosynthesis and explain the unusual production of various pactamycin analogues by S. pactum mutants. We also identified two new pactamycin analogues that have better selectivity indexes than pactamycin against malarial parasites.     

Sonochemical Synthesis of a Nanocrystalline Tin(IV) Complex based on a Bulky Anthracene Carboxylate Ligand: Spectroscopic and Photophysical Properties

In order systematically investigate the effect of ligand with a large conjugated π-system on the structure and optical properties of tin complex, anthracene-9-carboxylic acid (L¹) is selected as a primary ligand, and quinoline-2-carboxylic acid (L²) used as second ligand to incorporate with anthracene-9-carboxylic acid to construct a new tin(IV)-carboxylate coordination complex under thermal gradient condition. Prepared complex was fully characterized based on its ¹H and ¹³C NMR, IR and UV spectra and elemental analysis. The molecular structure of complex was determined by single-crystal X-ray analysis. The nanocrystalline complexes of the prepared complex were successfully obtained at 30, 50 and 60 °C by a facile sonochemical route. The new nanocrystalline complexes were characterized by scanning electron microscopy, X-ray powder diffraction, IR spectroscopy and elemental analysis. The photoluminescence properties of the nanocrystalline complexes and crystalline bulk complex in the solid-state indicated that the size of the complex particles has a remarkable effect on the optical properties of it. Absorption and emission peaks of the nanocrystalline complexes blue shifted significantly in comparison with those of in the single-crystal form. Application of the prepared complex in fabrication of an organic light-emitting diode has been demonstrated. The current–voltage (I–V) characteristics and the electroluminescence (EL) properties of the complex have been investigated. The EL of the compound exhibits green emission at 552 nm.     

Study on morphology,thermal, mechanical and Cd(II) adsorption properties of PVC/α-MnO<Subscript>2</Subscript>-stearic acid nanocomposites: production and application

Alpha manganese dioxide nanorods (α-MnO₂) were successfully functionalized with stearic acid (SA) by solvothermal method to prevent agglomeration. The α-MnO₂-SA nanorods were employed as a filler for the preparation of poly(vinyl chloride) (PVC) nanocomposite (NC) films with different percentages (1, 3 and 5 wt%). The morphology, mechanical and thermal properties of the obtained NCs were investigated. The results showed that α-MnO₂-SA can effectively improve the properties of PVC. The enhancement in properties of the NCs was attributed to the improved interfacial bonding by modification. Also, these NCs were used as adsorbent for removal of cadmium ions. Our finding suggests that the PVC/α-MnO₂-SA NCs are good candidates for efficient Cd(??) removal from the wastewater.     

Structural and Gas Sensing Properties of Annealed ZnO Thin Film

Annealed ZnO thin film at 400 °C for two hours was deposited on a glass substrate by using pulsed laser deposition (PLD). The structural properties of the annealed ZnO thin film were studied by XRD, TEM and SEM. Gas sensing properties for different gases such as H₂ and LPG were investigated. Applying XRD the size of the nanocrystals is found to be 10.61 nm. SEM of the thin film consisted of many grains distributed uniformly throughout the surface. An annealed ZnO thin film sensor showed the typical n-type semiconducting behavior in the case of H₂ and LGP gases at low and high operating temperature range, respectively. When working at 50 and 140 °C the sensor exhibits very good dynamic response–recovery characteristics to H₂ and LGP, respectively. These results along with a simple fabrication process demonstrate that the annealed ZnO thin film at 400 °C for two hours is promising for developing low cost and high performance H₂ and LPG sensors. The low cost of the sensor element fabrication, high H₂ and LPG sensitivity, fast response and quick recovery make the entire fabrication process a front-runner and cost-effective for the production of annealed ZnO thin film H₂ and LPG sensors.     

Bromination of some aromatic compounds by means of bromine in chlorosulphonic acid medium

Bromination of a series of aromatic compounds is carried out by means of bromine in chlorosulphonic acid medium in the presence of iodine as a halogen carrier. Some compounds are brominated and oxidised, the others are brominated only with brominolysis of the groups present, e.g. -CHO, -COOH, -NO₂ and -CN groups.     

Arsenic stability in arsenopyrite-rich cemented paste backfills: a leaching test-based assessment

Arsenic (As) is a toxicant in tailings from sulphur deposits. It represents an environmental risk because of its high solubility. Tailings can be mixed with water (typically 25%) and a low proportion of hydraulic binder (3-7%) to produce a cemented paste backfill (CPB), stored in underground mine openings. CPB is a tailings storage technique, but it could also provide environmental advantages by stabilization of polluting elements such as As. Tailings from Casa Berardi mine (QC, Canada) contain As (3800 ppm), mainly in arsenopyrite form. For this study, three different CPBs were synthesized in laboratory using Casa Berardi tailings and three different binders. These pastes were submitted to various leaching tests after 28 days of curing. The results indicate that As is released at higher concentration for a fly ash-based CPB than for slag- and Portland cement-based CPB. However, at lower pH, As is better stabilized in fly ash-based samples. These differences can be explained by a variation of solubility of As-compounds in each CPB. Several mechanisms of As release occur, as diffusion and/or dissolution/precipitation. The accelerated weathering test results show that sulphide reactivity is buffered by the neutralizing minerals contained in CPB, and influence the As release behaviour by decreasing the oxidation of As-bearing sulphides.