A plug-in minielectrode for measurements in stirred photometric cuvettes

A device is described to perform potentiometric measurements with ion-sensitive electrodes in stirred photometric cuvettes. Its design allows to make additions to the reaction medium with microliter syringes during measurements. Originally, this plug-in electrode was designed to register the free Ca2+ concentrations in the incubation medium of mitochondrial suspensions during measurements of the free matrix Ca2+ concentration with a permeant fluorescent Ca2+ indicator. However, numerous other applications can be easily realized, such as the combination of mitochondrial light-scattering measurements and ion-transport measurements, the combination of the permeabilized cell technique with fluorescence measurements of intracellular organelles or simply the calibration of the fluorescence of Ca2+ indicators with a Ca2+ ion-sensitive minielectrode. Compared with the use of a second fluorescent indicator the use of an electrode has the advantage that the signal can be transformed into ion concentrations already during the measurements.     

Activities in dilute solutions of chromium and iron in nickel at 1600° by mass spectrometry

Binary and ternary alloys of chromium and iron with nickel were studied. The total solute content ranged from 1 to 10 at. pct. The first-order interaction coefficients for chromium are ε_Cr ^(Cr)= 1.8 ±2.0, and ε_Cr ^(Fe) = 0.6 ± 5.0 (twice standard deviation). The relative partial molar enthalpy of liquid chromium in nickel at 1550° and at 5 pct chromium is −2200 cal per g-atom. An unusual result was obtained for iron in the form of a minimum in the experimental ln(I_Fe ^N _Ni/I_Ni ^N _Fe)-curve. Formerly Postdoctoral Fellow, Department of Metallurgical Engineering, Ohio State University, Columbus, Ohio. Formerly N. S. F. Trainee at Ohio State University.     

Biomedical Engineering in Health Care?Potential Versus Reality

Although we have heard a great deal about the potential of biomedical engineering in health care, utilization of engineering and technology in the health care field has not progressed as expected. Reasons for this situation are presented and they include the points of view in industry, engineering and the medical community. Expanded and successful use of clinical engineers in health care institutions, the development of relevant educational curricula and a continuum of medical engineering education, as well as early involvement of biomedical engineering in the planning of health care delivery at Federal, State and district levels, could expedite the engineering medical interaction.     

Optimal operation of Petlyuk distillation: steady-state behavior

The “Petlyuk” or “dividing-wall” or “fully thermally coupled” distillation column is an interesting alternative to the conventional cascaded binary columns for separation of multi-component mixtures. However, the industrial use has been limited, and difficulties in operation have been reported as one reason. With three product compositions controlled, the system has two degrees of freedom left for on-line optimization. We show that the steady-state optimal solution surface is quite narrow, and depends strongly on disturbances and design parameters. Thus it seems difficult to achieve the potential energy savings compared to conventional approaches without a good control strategy. We discuss candidate variables which may be used as feedback variables in order to keep the column operation close to optimal in a “self-optimizing” control scheme.     

Optimizing 100%‐renewable grids through shifting residential water‐heater load

A low‐carbon electricity supply for Australia was simulated, and the installed capacity of the electrical grid was optimized by shifting the electricity demand of residential electric water heaters (EWHs). The load‐shifting potential of Australia was estimated for each hour of the simulation period using a nationwide aggregate EWH load model on a 90 × 110 raster grid. The electricity demand of water heaters was shifted from periods of low renewable resource and high demand to periods of high renewable resource and low demand, enabling us to effectively reduce the installed capacity requirements of a 100%‐renewable electricity grid. It was found that by shifting the EWH load by just 1 hour, the electricity demand of Australia could be met using purely renewable electricity at an installed capacity of 145 GW with a capacity factor of 30%, an electricity spillage of 20%, and a generation cost of 15.2 ¢/kWh. A breakdown of the primary energy sources used in our scenario is as follows: 43% wind, 29% concentrated solar thermal power, and 20% utility photovoltaic. Sensitivity analysis suggested that further reduction in installed capacity is possible by increasing the load‐shifting duration as well as the volume and insulation level of the EWH tank.     

Exploiting latent functional capabilities for resilience in design of engineering systems

In this paper, we address latent functional capabilities, capabilities that were neither intended nor recognized in the design process. We propose that latent capabilities can improve the resilience of engineering systems, enabling recovery of performance after disruptive events. Engineering systems are designed to meet their functional requirements, and have a limited ability to avoid critical failures. Normally, redundancies are put in place to reduce the impact of potential disruptions, adding to cost and complexity. An alternative is to uncover latent capabilities that can be used to recover from disruption by altering the function-form mapping. Existing design methods focus on intended, manifest functionality, and do not consider latent capabilities. With basis in design theory, we show that latent capabilities can enhance resilience, and demonstrate this using two illustrative cases. Further, we propose approaches to uncover latent capabilities in systems design, and discuss implications of using latent capabilities to enhance resilience.     

The influence of antioxidants on the oxidation stability of biodiesel

Oxidation stability of bodiesel is an important issue because FA derivatives are more sensitive to oxidative degradation than mineral fuel. Therefore, in the most recent European Specifications for biodiesel, a minimum value of 6 h for the induction period at 110°C, measured with a Rancimat instrument, is specified. To guarantee this value at the filling station, the use of additional antioxidants will be necessary. In this paper we show the influence of different synthetic and natural antioxidants on the oxidation stability, using the specified test method. Biodiesel produced from rapeseed oil, sunflower oil, used frying oil, and beef tallow, both undistilled and distilled, was investigated. The four synthetic antioxidants pyrogallol (PY), propylgallate (PG), TBHQ, and BHA produced the greatest enhancement of the induction period. These four compounds and the widely used BHT were selected for further studies at concentrations from 100 to 1000 mg/kg. The induction periods of methyl esters from rapeseed, oil, used frying oil, and tallow could be improved significantly with PY, PG, and TBHQ, whereas BHT was not very effective. A good correlation was found between the improvement of the oxidation stability and the FA composition.     

Bias and Imprecision in the Determination of Free Glycerin in Biodiesel: The Unexpected Role of Limitations in Solubility

Residual free glycerin (FG) is a critical marker of fatty acid methyl ester (biodiesel) fuel quality. Yet, routine determinations by standard methods display excessive imprecision, and the uncertainties undermine confidence in the data. Various degrees of agitation are used here to evaluate the possibility of heterophase formation as a contributor to imprecision and potential bias. Statistical markers from the analysis of 13 biodiesel samples reveal that seven contain unexpected heterophases, which, due to settling, cause underestimates of 15–68%. Agitation alone re‐suspends heterophases for brief periods, easing potential biases, but also increases imprecision. A promising new sample pretreatment is presented, which reduces the deleterious effects of heterophases. Solubility limitations are explored as possible contributing factors, and measurements made at 23 °C in purified soy FAME reveal an equilibrium solubility which is more than 80% below previously published estimates. Strong interactions of liquid FG with small amounts of moisture reduce solubility to below international quality limits, while interactions of initially dissolved forms of moisture and FG produce bias‐inducing heterophases at 0.02% FG. The unexpected low solubility of FG, exacerbated by interactions with impurities, is seen as an important contributor to underestimates and imprecision, and a strong influencing factor on the fate of residual FG in commercial biodiesel fuels.