QuEChERS method combined with GC‒MS for pesticide residues determination in water

A miniaturized, QuEChERS based, liquid–liquid extraction method followed by gas chromatography–mass spectrometry was developed and validated for pesticide residues determination in water. Malathion, chlorpyrifos, profenofos, chlorfenapyr, pyriproxyfen, λ-cyhalothrin, coumaphos and α-cypermethrin were selected for this study. The accuracy, precision, specificity, linearity, limit of detection and limit of quantification were evaluated. The recovery ranged from 85.3 to 107% with RSD ranging from 1.8 to 15.4%. The linearity showed reliable range (0.995–0.999). The limit of detection ranged from 0.3 to 4 μg/L. Matrix effect was evaluated. The obtained results meet the European Commission standard legislations, implying that our method can be considered accurate and reproducible. The validated method was used to analyze river and well water samples. No residues of the investigated pesticides were detected in all collected water samples.     

Theoretical characterisation of highly efficient dye-sensitised solar cells

Molecular electronic structure calculations, employing density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methodologies, have been carried out to improve the performance of the synthesised dye YD2-o-C8 which is characterised by 11.9%–12.7% efficiencies. We aimed to narrow the band gap of YD2-o-C8 to extend the light-harvesting region to near-infrared (NIR). This was done by incorporating Cd instead of Zn onto the porphyrin ring and elongating the length of π-conjugation by adding ethynylene link and anthracene unit, so that the performances of the suggested cells could be expected to exceed the 11.9%–12.7% efficiencies with TiO₂, ZnO₂, and WO₃ oxide electrodes. The effects of modifying the central metal and elongating the length of π-conjugation on cell performance are confirmed in terms of frontier molecular orbital (FMO) energy gaps, density of states (DOS), molecular electrostatic potentials (MEPs), non-linear optical (NLO) properties, ultraviolet–visible (UV–vis) electronic absorption, and ¹H nuclear magnetic resonance chemical shifts. Increasing the length of π-conjugation of the D–π–A dyes leads to increasing the DOS near Fermi levels, more active NLO performance, strong response to the external electric field, delocalisation of the negative charges near the anchoring groups, deep electron injection, suppressing macrocycle aggregation, active dye regeneration, and inhibited dye recombination. The calculated band gap/eV of the present DMP-Zn is correlated with the experimental (E_1/2(oxidation)–E_1/2(reduction)/V) potentials of the identical YD2-o-C8. A co-sensitiser is suggested for NIR sensitisation (550–950 nm) to increase the power-to-conversion efficiency beyond 14%.     

Seasonal variation in essential oil yield and composition from Thymus vulgaris L. during different growth stages in the south of Jordan

The effect of plant space and time of harvesting on yield and quality of Thymus vulgaris was evaluated in Jordan. Thyme was cultivated in rows of 50?cm apart with inter-row spacing of 15, 30 or 45?cm and was grown at various development stages. Plants were harvested during different growth stages including vegetation, beginning of blooming, full blooming and fruit maturation. Results indicated that oil yields of thyme were affected by growth stage and inter-row spacing. The maximum oil yields was obtained by harvesting at the early growth stage, which was found superior to oil yield corresponding to the later stages of collection. With 45?cm inter-row spacing, the maximum oil yield was recorded when the samples were collected at growth stage. Indicated results showed that the chemical composition during various growth stages was characterised by high percentage of carvacrol and its corresponding monoterpenic hydrocarbon precursors ρ-cymene and γ-terpinene, and ether 1,4-cineol.     

Synthesis of new 1,2,4-oxadiazolidin-5-ylthiophenes and thienopyrimidine derivatives by aza-Wittig reaction using a thienyl carbodiimide

Azidation of aminothiophene derivative 1 afforded the corresponding azido derivative 2.The latter reacted with triphenylphosphine to afford iminophosphorane derivatives 3.Reacting 3 with phenylisocyanate gave the highly reactive carbodiimide intermediate 4,which was reacted with different nitrones to afford new l,2,4-oxadiazolidin-5-ylidene-aminothiophenes 5a-c. Treatment of 4 with absolute EtOH at room temperature gave methyleneamino-5-(methylthio)thiophene 7,(methylthio)-3-(3- phenylureidothiophene)-2-carboxylate 8 or thienopyrimidine 9 and 10 at refluxing temperature.Finally reaction of carbodiimide intermediate 4 with different secondary amines gave the new thienopyrimidines 11a-c.     

Full-trapped three-level ion in the lamb–dicke limit: analyzing and comparing quantum entanglement measures of two qudits

Our aim is to investigate the entanglement dynamics and quantum correlations of a full-trapped ion interacting with two time-independent laser beams in view of the Lamb–Dicke parameter. For this purpose, the three probability amplitudes in the trapped ion is taken as ?{1

Ag‐doped TiO2 enhanced photocatalytic oxidation of 1,2‐cyclohexanediol

The superiority of silver‐doped titania for photocatalytic oxidation (PCO) of organic compounds inspired us to investigate PCO of 1,2‐cyclohexanediol. Ag/TiO₂ was prepared, characterized (nanosize 19–24 nm) and used for oxidation of 1,2‐cyclohexanediol (1) in acetonitrile. The photolysate was analyzed using GC and GC/MS techniques. The PCO products are 2‐hydroxylcyclohexanone (2), 1,2‐cyclohexandione (3), 2‐cyclohexenone(4), cyclohexanone (5), and adipic acid (6).The formation of electron–hole pair at the surface of the catalyst followed by oxidation reactions was the suggested mechanism. Kinetic studies revealed first‐order mechanism for PCO of 1 and rate constant (k) = ?0.145 h^–1. Copyright © 2012 John Wiley & Sons, Ltd.     

Search for the standard model Higgs boson in the diphoton decay channel with 4.9 fb(-1) of pp collision data at √s=7 TeV with ATLAS

A search for the standard model Higgs boson is performed in the diphoton decay channel. The data used correspond to an integrated luminosity of 4.9 fb(-1) collected with the ATLAS detector at the Large Hadron Collider in proton-proton collisions at a center-of-mass energy of √s=7 TeV. In the diphoton mass range 110-150 GeV, the largest excess with respect to the background-only hypothesis is observed at 126.5 GeV, with a local significance of 2.8 standard deviations. Taking the look-elsewhere effect into account in the range 110-150 GeV, this significance becomes 1.5 standard deviations. The standard model Higgs boson is excluded at 95% confidence level in the mass ranges of 113-115 GeV and 134.5-136 GeV.     

Artificial pozzolanic cement pastes containing burnt clay with and without silica fume

Pozzolanic cement blends were prepared by the partial substitution of ordinary Portland cement (OPC) with different percentages of burnt clay (BC), Libyan clay fired at 700 °C, of 10, 20, and 30%. The pastes were made using an initial water/solid ratio of 0.30 by mass of each cement blend and hydrated for 1, 3, 7, 28, and 90 days. The pozzolanic OPC–BC blend containing 30% BC was also admixed with 2.5 and 5% silica fume (SF) to improve the physicomechanical characteristics. The hardened pozzolanic cement pastes were subjected to compressive strength and hydration kinetics tests. The results of compressive strength indicated slightly higher values for the paste made of OPC–BC blend containing 10% BC The results of DSC and XRD studies indicated the formation and later the stabilization of calcium silicates hydrates (CSH) and calcium aluminosilicate hydrates (C₃ASH₄ and C₂ASH₈) as the main hydration products in addition to free calcium hydroxide (CH). Scanning electron microscopic (SEM) examination revealed that the pozzolanic cement pastes made of OPC–BC mixes possesses a denser structure than that of the neat OPC paste. Furthermore, the addition of SF resulted in a further densification of the microstructure of the hardened OPC–BC–SF pastes; this was reflected on the observed improvement in the compressive strength values at all ages of hydration.     

Excess Molar Volumes of Oligo(Oxyethylene Glycol) Monodecyl Ethers in n-Dodecane, and Apparent Dipole Moments of {(Oligo(Oxyethylene Glycol) Monodecyl Ethers?+?n-Heptane, n-Decane or n-Dodecane} at T?=?298.15?K

Excess molar volumes and relative permittivities at a frequency of 30?kHz of oligo(oxyethylene glycol) monodecyl ethers (C₁₀E _m ) for m?=?1?C8 in n-heptane, n-decane or n-dodecane solutions were determined for the mole fraction range 0?<?x?<?0.04 at the temperature of 298.15?K. By using Frohlich??s equation the apparent dipole moments, ??, of C₁₀E _m were calculated, and the limiting values, ?? ₀, were determined by extrapolating to infinite dilution. The values of ?? ₀ increase linearly with increasing number of oxyethylene units (m) of oligo(oxyethylene glycol) monodecyl ethers in the range m?=?2?C8, while ?? ₀ of C₁₀E₁ is less than its extrapolated value. By comparing the present results with our previous ones measured in n-heptane and decane, a solvent effect on ?? ₀ was found. The excess partial molar volumes of oligo(oxyethylene glycol) monodecyl ethers at infinite dilution increase with increasing m. Those results are discussed from the viewpoint of the interactions between oligo(oxyethylene glycol) monodecyl ethers and solvent molecules.     

Synthesis of new transition metal complexes of 1H-perimidine derivatives having antimicrobial and anti-inflammatory activities

New series of 1H-perimidine-2-thiol derivatives and (2-substituted-1H-perimidin-1-yl)ethane-1,2-dione derivatives and their ligands (C₂₄H₁₄N₄S₂O₂) H₂L¹ and (C₂₆H₁₈N₄S₂O₂) H₂L² have been synthesized with transition metal ions, e.g., Copper (II), Silver (I), Cobalt (II) and Ruthenium (III) were prepared and evaluated for their antimicrobial, analgesic and anti-inflammatory activities. The synthesized compounds and their complexes were characterized by elemental analysis, ¹H NMR, IR, MS, molar conductance, thermal gravimetric analysis and electronic spectra. All results revealed that compounds 3 and 13 exhibited high inhibitory effects against some bacterial strains by the disc diffusion method. On the other hand, compounds 2, 3, 7 and 12 displayed potent anti-inflammatory activity.