Complete quantitative online analysis of methanol electrooxidation products via electron impact and electrospray ionization mass spectrometry

We report on a novel approach for complete quantitative online product analysis in electrocatalytic reactions, combining electron impact ionization mass spectrometry (EI-MS) and electrospray ionization mass spectrometry (ESI-MS) for simultaneous detection of both volatile and nonvolatile reaction products. The potential of this method is demonstrated using continuous methanol oxidation in a flow cell. The overall reaction rate was followed via the Faradaic current; CO(2) formation was monitored mass spectrometrically via a membrane inlet system, and formaldehyde and formic acid were detected by ESI-MS after a derivatization-extraction-separation procedure introduced recently (Zhao, W.; Jusys, Z.; Behm, R. J. Anal. Chem.2010, 82, 2472-2479) providing quantitative data on the product distribution. In a more general sense, this approach is applicable for a wide range of reactions at the solid-liquid interface or in liquid phase.     

Short-term time series forecasting based on the identification of skeleton algebraic sequences

A new short-term time series forecasting method based on the identification of skeleton algebraic sequences is proposed in this paper. The concept of the rank of the Hankel matrix is exploited to detect a base fragment of the time series. Particle swarm optimization and evolutionary algorithms are then used to remove the noise and identify the skeleton algebraic sequence. Numerical experiments with an artificially generated and a real-world time series are used to illustrate the functionality of the proposed method.     

Mobile spectroscopic system for trace gas detection using a tunable mid-IR laser

We describe a mobile spectroscopic system for trace gas analysis based on the open path differential absorption spectrometer and the photoacoustic spectrometer. The first method allows long distance measurements (up to a few kilometers) while the second one provides local in situ detection of pollutants. The open path system is based on the nanosecond (f = 10 Hz, tau = 5 ns) lamp pumped Nd:YAG laser and a tunable two cascade optical parametric generator operating in the 5-12 microm spectral region. This source was mounted into the lidar setup based on the coaxial transmitter/receiver. The photoacoustic system was constructed using the same laser as well as a nonresonant photoacoustic cell.     

The effect of ammonium ions on oxygen reduction and hydrogen peroxide formation on polycrystalline Pt electrodes

The influence of ammonium ions on the activity and selectivity of the electrocatalytic oxygen reduction reaction (ORR) on polycrystalline Pt was investigated in model studies under continuous mass transport, both in sulfuric and perchloric acid solutions. Ammonium was found to increase the yield of hydrogen peroxide, particularly in sulfuric acid, but also in perchloric acid solutions, and also at higher potentials (0.80–0.90 V_RHE) typical for fuel cell cathode operation, which may severely impair the long-term stability of membranes and electrodes in fuel cells exposed to fuel gases and/or air containing ammonia. Adsorbed species, assigned to ammonia and nitric oxide, were identified on a Pt film electrode using in situ FTIR spectroscopy. Adsorbed nitric oxide could only be observed in perchloric acid solutions. The higher coverage of adsorbed ammonia in sulfuric acid solution is attributed to a stabilization by coadsorbed (bi-)sulfate species; the higher total coverage in this electrolyte can explain the larger effect of ammonium ions on the ORR activity and selectivity in sulfuric compared to perchloric acid solution.     

Multicriteria Evaluation of Building Foundation Alternatives

In real conditions, decision makers usually deal with multiple objectives and should make a decision in a state of certainty or uncertainty. The selection of the best constructions for a building from a number of alternatives is of great importance for owners, contractors, and stakeholders. Dozens of multicriteria/multi‐attribute decision‐making (MCDM/MADM) models developed for evaluating the performance of the available alternatives can be used for selecting the most suitable alternative from a given finite set of options based on a set of attributes. A guide to systematic selection among the available alternatives of building structures is the integrated methodology, thoroughly analyzed in the article. The article presents a MCDM model for selecting the type of foundation for a single‐storey dwelling house based on the WASPAS‐G (Weighted Aggregated Sum Product Assessment) method and Analytic Hierarchy Process (AHP) approach. The aggregate criteria weights are determined by using the AHP and experts’ judgement methods.     

Risk assessment of Fusarium mycotoxins in Lithuanian small cereal grains

A total of 125 small grain samples, including 60 of winter crop and 65 of spring crop collected during 2006–2007 at harvesting in Lithuanian fields, were involved in the current study on co-occurrence of three Fusarium mycotoxins. All grain samples tested were found to be contaminated with mycotoxins. In 2006, winter cereal grain samples contaminated with one mycotoxin accounted for 16%, and those contaminated with three mycotoxins for 25%. No spring cereal grain samples containing only one toxin were found, while those contaminated with three toxins accounted for 91% of the total samples tested. In the year 2007 winter cereal grain samples contaminated with one toxin accounted for as little as 4%, and all spring cereal grain samples tested were found to be 100% contaminated with deoxynivalenol, zearalenone, and T-2 toxin. Mycotoxin concentrations in grain samples, in most cases, were within the permissible range. A trend was revealed that spring barley grain samples tested contained higher T-2 concentrations irrespective of the test year.     

The solitary solution of the Liouville equation produced by the Exp-function method does not hold for all initial conditions

In this paper we argue that the solitary solution of the Liouville equation produced by the Exp-function method does not satisfy the original differential equation for all initial conditions. Moreover, the region where the solution is correct is located entirely on a curve in the parameter plane of initial conditions. We derive the explicit equation for this curve and argue that classical Exp-function type methods cannot identify such constraints related to initial conditions.     

Oil spill fluorosensing lidar for inclined onshore or shipboard operation

An oil spill detection fluorosensing lidar for onshore or shipboard operation is described. Some difficulties for its operation arise from the inclined path of rays. This is due to the increased reflection of the laser beam at the air-water interface, the decreased fluorescence signal, and the increased background light when compared with other instruments having a close-to-nadir measuring geometry. The analysis of these problems shows that they significantly reduce the detection distance in the presence of a flat water surface. However, waves on the water surface weaken the influence of the laser beam reflections but at the same time cause a variable fluorescence signal, which makes specific signal processing necessary for increased detection ranges. A fluorescence data processing method is proposed that efficiently eliminates the background water column fluorescence from signals such as yellow substance. This enables oil fluorescence to be distinguished from variable natural water fluorescence.