Photochemistry of single wall carbon nanotubes embedded in a mesoporous silica matrix

By embedding single wall carbon nanotubes in a mesoporous silica matrix (SWNT@SiO2) the photochemical properties have been measured upon laser excitation at 266 nm; the SWNT@SiO2 exhibits long-lived emission (lambda em = 400 nm, tau = 0.95 microsecond), transient absorption (lambda max = 390 nm, tau = 11 microseconds) and is able to generate singlet oxygen in D2O.     

Continuous solid-phase extraction and preconcentration of bisphenol A in aqueous samples using molecularly imprinted columns

A bisphenol A (BPA) molecularly imprinted polymer, the composition of which was optimised using a chemometric approach, has been applied to the selective preconcentration of the template from aqueous samples. The selectivity of the polymer toward BPA and related compounds was evaluated chromatographically. The BPA-imprinted polymer was packed in a column and used for continuous on-column solid-phase extraction (MISPE) of aqueous samples followed by subsequent analysis by HPLC with fluorescence detection of the eluted fractions. The composition of the washing solvent applied in the MISPE procedure was optimised to favour the specific interactions of the MIP with BPA and to remove the non-selectively bound matrix components. The MISPE method has proven to be effective for selective preconcentration of BPA in aqueous samples (recoveries >84% obtained in the eluate for 10–100 mL sample volumes) enabling detection and quantification limits of 1.0 and 3.3 ng mL^–1, respectively (based on 25 mL sample size). Analytical recoveries were between 92 and 101% for river water samples spiked with known amounts of BPA (30, 60, and 80 ng mL^–1); relative standard deviations (RSD) were lower than 5.0%.     

Ethyl N‐[2‐(hydroxy­acetyl)­phenyl]­carbamate,ethyl N‐[2‐(hydroxy­acetyl)‐4‐iodo­phenyl]­carbamate and ethyl N‐[2‐(hydroxy­acetyl)‐4‐methyl­phenyl]­carbamate

In ethyl N‐[2‐(hydroxy­acetyl)phenyl]carbamate, C₁₁H₁₃NO₄, all of the non‐H atoms lie on a mirror plane in the space group Pnma; the mol­ecules are linked into simple chains by a single C—H⋯O hydrogen bond. The mol­ecules of ethyl N‐[2‐(hydroxy­acetyl)‐4‐iodo­phenyl]carbamate, C₁₁H₁₂INO₄, are linked into sheets by a combination of O—H⋯I and C—H⋯O hydrogen bonds and a dipolar I⋯O contact. Ethyl N‐­[2‐(hydroxy­acetyl)‐4‐methyl­phenyl]carbamate, C₁₂H₁₅NO₄, crystallizes with Z′ = 2 in the space group P; pairs of mol­ecules are weakly linked by an O—H⋯O hydrogen bond and these aggregates are linked into chains by two independent aromatic π–π stacking inter­actions.     

Radionuclides in biota collected near a dicalcium phosphate plant, southern Catalonia, Spain

Industrial waste containing radioactive U-decay series isotopes was released into the Ebro River, Spain, over a period of >20 years from a dicalcium phosphate (DCP) plant. This release raised activities of several natural radionuclides (e.g. ²³⁸U, ²³⁴U, ²³⁰Th, ²³²Th and ²²⁶Ra) in biota taken from the area near the DCP plant. Plants and animals selected for this study included the green algae (Cladophora glomerata), the blue mussel (Mytilus edulis), the zebra mussel (Dreissena polymorpha) and the scavenger catfish (Silurus glanis) because they are all common in the area. Multiple sampling points were chosen for this study: (1) a site in the Riba-Roja Reservoir, above the DCP plant’s area of influence, (2) four sites in the area surrounding the DCP plant, close to the town of Flix, and (3) a location in the Ebro Delta Estuary in Fangar Bay. Significant differences in the activities (in Bq kg^?1 of dry weight) for the radioisotopes included in this study among samples were attributed to sample location and the species evaluated. For instance, relatively high activities for uranium and radium were obtained in algae collected around the DCP plant, compared to results obtained for algae samples taken from the unimpacted Riba-Roja Reservoir. In contrast, for zebra mussels, enhanced activities were observed for all radionuclides and, in particular, for thorium and radium isotopes within the area of influence. Among catfish samples, activity values from different locations were not significantly different, though slightly higher activities were observed at the sampling point just downstream of the DCP factory.     

Optimizing vehicle routes in a bakery company allowing flexibility in delivery dates

The work addressed in this paper is motivated from a real problem proposed to the authors by a bakery company in Northern Spain. The objective is to minimize the total distance travelled for the daily routes over the week. In order to reduce this total distance, some flexibility in the dates of delivery is introduced. A mixed-integer linear model for the problem is formulated. In addition, a two-phase method based in GRASP and path-relinking metaheuristic strategies is proposed. Computational experiments show that the method performs very well, obtaining high-quality solutions in short computational times. Moreover, when it is applied to real-data-based instances, the obtained solutions considerably reduce transportation costs over the planning horizon.