A two-channel microfluidic sensor that uses anodic electrogenerated chemiluminescence as a photonic reporter of cathodic redox reactions

This paper describes a new approach for sensing electrochemically active substrates in microfluidic systems. This two-electrode sensor relies on electrochemical detection at one electrode and electrogenerated chemiluminescent (ECL) reporting at the other. Each microfabricated indium tin oxide electrode is located in a separate microfluidic channel, but the channels are connected downstream of the electrodes to maintain a complete electrical circuit. Because of laminar flow, there is no bulk mixing of the fluids in the detecting and reporting channels. This approach allows the ECL reaction to be physically and chemically decoupled from the sensing channel of the device, which greatly expands the number of analytes that can be detected. However, because the cathode and anode are connected, electron-transfer processes occurring at the sensing electrode are electrically coupled to the ECL reaction. Charge balance permits the ECL light output to be quantitatively correlated to electrochemical reductions at the cathode. The system is used to detect Fe(CN)6(3-), Ru(NH3)6(3+), and benzyl viologen and report their presence via Ru(bpy)3(2+) (bpy = bipyridine) luminescence. Each different redox target initiates ECL at a unique potential bias related to its standard redox potential. The influence of the concentrations of Ru(bpy)3(2+) and the target analytes is discussed.     

Removal of methyl tert-butyl ether from water by pervaporation: bench- and pilot-scale evaluations

The ability of pervaporation to remove methyl tert-butyl ether (MTBE) from water was evaluated at bench and pilot scales. Process parameters studied included flow rate, temperature, MTBE concentration, membrane module type, and permeate pressure. Pervaporation performance was assessed based on the calculated mass transport coefficient of MTBE, the single-pass removal of MTBE (only at the pilot scale), and the fluxes of water and MTBE. The observations for MTBE are compared to results for toluene and 1,1,1-trichloroethane, compounds for which removal by pervaporation has been demonstrated. MTBE removal and mass transfer coefficients were lower than for toluene and trichloroethane. However, MTBE removal efficiency improved significantly with increasing process temperatures from 40 to 80 degrees C. With one of the pilot-scale systems, MTBE removal efficiency approached that of the other VOCs. The observed response of pervaporation performance to temperature was attributed to the strong effect of temperature on the Henry's law constant of MTBE.     

Heavy metal removal with Mexican clinoptilolite: multi-component ionic exchange

This paper describes the interactions of Pb(II), Cd(II), and Cr(VI) competing for ion-exchange sites in naturally occurring clinoptilolite. Dissolved Pb and Cd were effectively removed within 18 h in batch reactors, with higher removal efficiencies (> 95%) in the acidic pH range. The presence of Cr(VI), which can interact with these metals to form anionic complexes, significantly diminished the Pb and Cd removal efficiencies. A decrease in the efficiency of clinoptilolite to remove Pb was also observed in the high (> or = 10) pH range. This was attributed to the formation of anionic hydroxo-complexes with little affinity for cationic ion exchange sites. Pb outcompeted Cd for ion exchange sites in a flow-through column packed with clinoptilolite (contact time = 10 s). The preferential removal of Pb in column, but not in batch reactors, reflects that competitive retention can be affected by contact time because diffusion kinetics may influence the removal efficiency to a greater extent than equilibrium partitioning. Phenol, which was tested as a representative organic co-contaminant, slightly hindered heavy metal removal in batch reactors. This was attributed to the formation of organometallic complexes that cannot penetrate the zeolite exchange channels. Altogether, these results show that natural zeolites hold great potential to remove cationic heavy metal species from industrial wastewater. Nevertheless, process efficiency can be hindered by the presence of ligands that form complexes with reduced accessibility and/or affinity for ion exchange.     

Optical and structural properties of ZnO + Zn<Subscript>2</Subscript>TiO<Subscript>4</Subscript> thin films prepared by the sol–gel method

ZnO + Zn₂TiO₄ thin films were obtained by the sol–gel method using precursor solutions with different Ti/Zn ratios in the 0.18–2.13 range. The films were deposited on glass substrates and annealed in an open atmosphere at 550 °C. The oxide was characterized by X-ray diffraction and photoacoustic (PA) spectroscopy. The films were constituted of polycrystalline ZnO for the lowest Ti/Zn ratio (0.18), polycrystalline Zn₂TiO₄ for the 0.70 and 1.0 ratios, and mixes of both oxides for the intermediate ratios (0.32 and 0.50). For the highest ratios studied (1.44 and 2.13), the films were amorphous. The energy band gap (E_g) values were determined from optical absorption spectra, measured by means of the PA technique spectra. E_g varied in the 3.15 eV (ZnO) to 3.70 eV (Zn₂TiO₄) range.     

Characterization of patinas by means of microscopic techniques

Many stone-made historic buildings have a yellowish layer called 'patina' on their external surface. In some cases, it is due to the natural ageing of the stone caused by chemical–physical reactions between the surface of the stone and the environment, and in other cases it is the result of biological activity. The origin of these patinas can be also be due to ancient protective treatments. The use of organic additives, such as protein-based compounds, in lime or gypsum-based patinas is a traditional technique, which has been used in past centuries for the conservation and protection of stone materials. The thinness of the patinas ensures that microscopic techniques are irreplaceable for their analysis. Optical Microscopy, Fluorescence Microscopy, Scanning Electron Microscopy together with an Energy Dispersive X-ray Spectrometer, and Electron Microprobe are the microscopic techniques used for the characterization of these coverings, providing very useful information on their composition, texture and structure.     

Understanding barriers to home‐based and self‐care in‐center hemodialysis

Despite superior outcomes and lower associated costs, relatively few patients with end‐stage renal disease undergo self‐care or home hemodialysis. Few studies have examined patient‐ and physician‐specific barriers to self‐care and home hemodialysis in the modern era. The degree to which innovative technology might facilitate the adoption of these modalities is unknown. We surveyed 250 patients receiving in‐center hemodialysis and 51 board‐certified nephrologists to identify key barriers to adoption of self‐care and home hemodialysis. Overall, 172 (69%) patients reported that they were “likely” or “very likely” to consider self‐care hemodialysis if they were properly trained on a new hemodialysis system designed for self‐care or home use. Nephrologists believed that patients were capable of performing many dialysis‐relevant tasks, including: weighing themselves (98%), wiping down the chair and machine (84%), clearing alarms during treatment (53%), taking vital signs (46%), and cannulating vascular access (41%), but thought that patients would be willing to do the same in only 69%, 34%, 31%, 29%, and 16%, respectively. Reasons that nephrologists believe patients are hesitant to pursue self‐care or home hemodialysis do not correspond in parallel or by priority to reasons reported by patients. Self‐care and home hemodialysis offer several advantages to patients and dialysis providers. Overcoming real and perceived barriers with new technology, education and coordinated care will be required for these modalities to gain traction in the coming years.     

Feasibility study for the installation of HVAC for a spa by means of energy recovery from thermal water—Part II: Energy analysis

The use of a low temperature geothermal spring together with the heat energy still contained in waste water from the different therapy systems installed in a spa (shower, jets, bathrooms, jacuzzis, pools, ventilation processes) can significantly reduce the operating and maintenance costs of the installation. This covers part of the air conditioning needs of the building and of the heating of thermal water to the appropriate temperature for therapeutic use.In the first part of the study, an analysis of the spring's situation was made, calculating the thermal water needs and presenting the consumption according to the operation schedule on different types of day. In this way, the contribution the spring was capable of giving was compared and the evolution of the thermal water in the tanks was studied. In the second part, the climatic conditions that the spa should meet are studied, along with the loads that it should support, the energy reclaimed from the different heat focuses and the repercussions on the final solution.     

Effect of hybrid system battery performance on determining CO2 emissions of hybrid electric vehicles in real-world conditions

Hybrid electric vehicles (HEVs) can potentially reduce vehicle CO₂ emissions by using recuperated kinetic vehicle energy stored as electric energy in a hybrid system battery (HSB). HSB performance affects the individual net HEV CO₂ emissions for a given driving pattern, which is considered to be equivalent to unchanged net energy content in the HSB. The present study investigates the influence of HSB performance on the statutory correction procedure used to determine HEV CO₂ emissions in Europe based on chassis dynamometer measurements with three identical in-use examples of a full HEV model featuring different mileages. Statutory and real-world driving cycles and full electric vehicle operation modes have been considered. The main observation is that the selected HEVs can only use 67–80% of the charge provided to the HSB, which distorts the outcomes of the statutory correction procedure that does not consider such irreversibility. CO₂ emissions corrected according to this procedure underestimate the true net CO₂ emissions of one HEV by approximately 13% in real-world urban driving. The correct CO₂ emissions are only reproduced when considering the HSB performance in this driving pattern. The statutory procedure for correcting HEV CO₂ emissions should, therefore, be adapted.     

Computer simulation and SERR detection of cytochrome c dynamics at SAM-coated electrodes

In this paper we present a combined experimental and theoretical study of the heterogeneous electron transfer reaction of cytochrome c electrostatically adsorbed on metal electrodes coated with monolayers of 6-mercaptohexanoic acid. Molecular dynamics simulations and pathways calculations show that adsorption of the protein leads to a broad distribution of orientations and, thus, to a correspondingly broad distribution of electron transfer rate constants due to the orientation-dependence of the electronic coupling parameter. The adsorbed protein exhibits significant mobility and, therefore, the measured reaction rate is predicted to be a convolution of protein dynamics and tunnelling probabilities for each orientation. This prediction is confirmed by time-resolved surface enhanced resonance Raman which allows for the direct monitoring of protein (re-)orientation and electron transfer of the immobilised cytochrome c. The results provide a consistent explanation for the non-exponential distance-independence of electron transfer rates usually observed for proteins immobilized on electrodes.