Enrichment Factors of Perfluoroalkyl Oxoanions at the Air/Water Interface

The refractory, water-bound perfluoro-n-alkyl carboxylate F(CF_2)_nCO_2^− and sulfonate F(CF_2)_nSO_3^− surfactant anions reach remote locations by mechanisms that are not well understood. Here we report experiments in which the relative concentrations of these anions on the surface of microdroplets produced by nebulizing their aqueous solutions are measured via electrospray ionization mass spectrometry. Enrichment factors f (relative to Br^−: f(Br^−) ≡ 1) increase with n, asymptotically reaching f[F(CF_2)_nSO_3^−] ~2f[F(CF_2)_nCO_2^−] ~200 f(Br^−) values above n ~ 8. The larger f values for F(CF_2)_nSO_3^− over their F(CF_2)_nCO_2^− congeners are consistent with a closer approach of the bulkier, less hydrated −SO_3^− headgroup to the air/water interface. A hyperbolic, rather than the predicted linear log f[F(CF_2)_nCO_2^−] vs n dependence suggests the onset of conformational restrictions to interfacial enrichment above n ~4. Marine aerosols produced from contaminated ocean surface waters are therefore expected to be highly enriched in F(CF_2)_nCO_2^−/F(CF_2)_nSO_3^− species

Rapid determination of octanol–water partition coefficient using vortex-assisted liquid–liquid microextraction

Vortex-assisted liquid–liquid microextraction (VALLME) coupled with high-performance liquid chromatography (HPLC) is proposed here for the rapid determination of octanol–water partitioning coefficients (Kow). VALLME uses vortex agitation, a mild emulsification procedure, to disperse microvolumes of octanol in the aqueous phase thus increasing the interfacial contact area and ensuring faster partitioning rates. With VALLME, 2 min were enough to achieve equilibrium conditions between the octanolic and aqueous phases. Upon equilibration, separation was achieved using centrifugation and the octanolic microdrop was collected and analyzed in a HPLC system. Six model compounds with log Kow values ranging between ∼0.5 and 3.5 were used during the present investigations. The proposed method produced log Kow values that were consistent with previously published values and the recorded uncertainty was well within the acceptable log unit range. Overall, the key features of the proposed Kow determination procedure comprised speed, reliability, simplicity, low cost and minimal solvent consumption.EP is grateful to the Region of Crete (Perifereia Kritis) for funding. Financial support from the Spanish Government (Project CTQ2011-23968) is also acknowledged. I.P.R. also thanks “Caja de Ahorros del Mediterraneo (CAM)” for his predoctoral grant and financial support

An investigation into the effect of denture adhesives on incisal bite force of complete denture wearers using pressure transducers - a clinical study

PURPOSE: Study was conducted to determine and assess the effect of different type of denture adhesives on the incisal bite force of complete denture wearers until the dislodgement of upper denture, using pressure transducer. MATERIALS AND METHODS: 30 patients out of 100 were included in the study. Based on the Kapur's method of scoring denture retention and stability, these patients were divided into 3 groups- Group A - Clinically good dentures; Group B - Clinically fair dentures; and Group C - Clinically poor dentures. A custom made occlusal force meter was constructed based on the load cell type of pressure transducers. Different adhesives (powder, paste and adhesive strips) were used in the study. Complete denture wearers were asked to bite on the load cell and the readings of incisal bite force were recorded. The readings of incisal bite force were subjected to statistical analysis using Repeated measures ANOVA followed by post-hoc bonferroni test. RESULTS: The result suggests that denture adhesives improved the incisal bite force of complete denture wearers significantly The incisal bite force (in kg) in Group A without using adhesives, with powder adhesive, with paste adhesive and with adhesive strips was found to be 2.48 (± 0.16), 3.43 (± 0.11), 6.01 (± 0.11), 3.22 (± 0.09) respectively. The incisal bite force (in kg) in Group B without using adhesives, with powder adhesive, with paste adhesive and with adhesive strips was found to be 1.87 (± 0.18), 3.35 (± 0.14), 5.34 (± 0.18), 3.21 (± 0.12) respectively. The incisal bite force (in kg) in Group C without using adhesives, with powder adhesive, with paste adhesive and with adhesive strips was found to be 1.00 (± 0.17), 3.07 (± 0.14), 4.37 (± 0.26), 2.99 (± 0.14) respectively. CONCLUSION: Within the limitations of the study, it was concluded that the use of denture adhesive was found to be significantly effective in improving the incisal bite force of complete dentures until the dislodgement of upper denture. Fittydent paste adhesive was found to be more effective than the powder and strips adhesives. The improvement in incisal bite force was found to be higher in Group C in comparison to that of Group A and Group B

UV-254 degradation of nicotine in natural waters and leachates produced from cigarette butts and heat-not-burn tobacco products.

Summarization: Nicotine is an important emerging contaminant widely detected in water resources. The main nicotine sources are human excretions from users and leaching from discarded tobacco product waste, which represents the most commonly littered item in urban areas and coasts. In this study, the UV254 photolytical fate of nicotine in natural water and leachates produced from conventional cigarettes (CCs) and the new generation heat-not-burn (HnBs) tobacco products is examined for the first time. The effect of UV254 irradiation on nicotine depletion in ultrapure water was initially studied. The reaction was pseudo first-order with respect to nicotine concentration at low concentrations and shifted to lower order at higher concentrations, an effect associated to absorption saturation. Although nicotine removal was fast, only 9.5% of the total organic carbon was removed after irradiation due to the formation of by-products. The chemical structures of six photo-products were derived by means of liquid and gas chromatography coupled to mass spectrometry. The photodegradation kinetics was found to depend on pH and faster kinetics were recorded when the monoprotonated form of nicotine was dominant (pH = 5–8). The presence of humic acids was found to slightly delay kinetics as they competed with nicotine for lamp irradiance, whereas the presence of salt had no effect on the direct photolysis of nicotine. Direct photolysis studies were also performed using natural waters. Compared to ultra-pure water, photodegradation was found to proceed slightly slower in river water, in similar kinetics in seawater, and relatively faster in rain water. The later was assumed to be due to the lower pH compared to the rest of the natural water tested. Leachates from used HnBs and smoked CCs were also submitted to UV254 irradiation and direct photolysis was found to proceed fast despite the high complexity of these matrices. Nonetheless, the total organic carbon in the system remained the same after irradiation due to the abundance of organics and photo-products formed. We take advantage of the present investigations and report the leaching behavior of nicotine from HnBs and CCs. Among others, we found that in HnBs ~70% of the total and bioavailable nicotine content remains in the tobacco sticks after operation and this percentage drops to 15% in CCs due to the reduction in mass after smoking. This finding demonstrated the importance of properly disposing tobacco product waste to prevent nicotine leaching in water bodies. Presented on: Environmental Researc

Low Cost Inferential Forecasting and Tourism Demand in Accommodation Industry

This paper establishes a low cost inferential model that allows reliable time series forecasts. The model provides a naive unique computationally straightforward approach based on widely-used additive models. It refers to the decomposition of every time series value in “random” components, which are compounded to constitute a “Fibonacci type” predictor random variable. The expected value of this predictor gives a forecast of a future time series value. The standard deviation of the predictor serves to construct a prediction interval at a predefined confidence level. The major features of our model are: forecasting accuracy, simplicity of the implementation technique, generic usefulness, and extremely low cost effort. These features enable our model to be adopted by tourism practitioners on various types of forecasting demands. In this paper, we present an application study to forecast tourism demand that exists in the Greek accommodation industry (i.e. in Greece and in the broad region of Athens). In the application study, two independent approaches have been adopted. In the first approach we implemented our model, and in the second approach we implemented the well-known Box-Jenkins method