Effects of multiple-stage membrane process designs on the achievable performance of automatic control

There is limited information from literature on the dynamic operability of membrane processes with multiple stages or loops. Such information is useful for assessing the performance achievable by an automatic controller proposed for a process design before the actual controller is implemented. Based on dynamic modeling of an industrial whey ultrafiltration process with an increasing number of stages up to a maximum of 12, the dynamic responses of the flowrate and concentration of the retentate were obtained. Features of the dynamic responses were used to determine the performance, in terms of quality and speed, that can be achieved by automatic controllers. In particular, limitations on the performance are indicated by features of dynamic responses such as effective time delay and inverse responses. Changes in effective time delay and inverse responses with the number of stages in the whey ultrafiltration process demonstrate a trade-off between process performance and control performance. This trade-off should be considered during process and controller design to maximize the economic return from the production of whey protein concentrates.     

Sample covariance shrinkage for high dimensional dependent data

For high dimensional data sets the sample covariance matrix is usually unbiased but noisy if the sample is not large enough. Shrinking the sample covariance towards a constrained, low dimensional estimator can be used to mitigate the sample variability. By doing so, we introduce bias, but reduce variance. In this paper, we give details on feasible optimal shrinkage allowing for time series dependent observations.     

An exact approach to sparse principal component analysis

We show a branch and bound approach to exactly find the best sparse dimension reduction of a matrix. We can choose between enforcing orthogonality of the coefficients and uncorrelation of the components, and can explicitly set the degree of sparsity. We suggest methods to choose the number of non-zero loadings for each component; illustrate and compare our approach with existing methods through a benchmark data set.     

Probabilistic approach for break-up and coalescence in bubbly-flow and coupling with CFD codes

In this paper, a CFD model for bubbly-flow including break-up and coalescence is discussed. The probabilistic method, developed according to this model, is tested for an industrial configuration: numerical bubble-size distributions are compared with those derived by experiments.     

Effects of ionizing radiation on bio-active plant extracts useful for preventing oxidative damages

Humans are exposed to ionizing radiations in medical radiodiagnosis and radiotherapy that cause oxidative damages and degenerative diseases. Airplane pilots, and even more astronauts, are exposed to a variety of potentially harmful factors, including cosmic radiations. Among the phytochemicals, phenols are particularly efficient in countering the oxidative stress. In the present study, different extracts obtained from plant food, plant by-products and dietary supplements, have been compared for their antioxidant properties before and after irradiation of 140 cGy, a dose absorbed during a hypothetical stay of three years in the space. All the dry extracts, characterized in terms of vitamin C and phenolic content, remained chemically unaltered and maintained their antioxidant capability after irradiation. Our results suggest the potential use of these extracts as nutraceuticals to protect humans from oxidative damages, even when these extracts must be stored in an environment exposed to cosmic radiations as in a space station.     

Voltage‐Switchable HCl Transport Enabled by Lipid Headgroup–Transporter Interactions

Synthetic anion transporters that facilitate transmembrane H⁺/Cl^? symport (cotransport) have anti‐cancer potential due to their ability to neutralize pH gradients and inhibit autophagy in cells. However, compared to the natural product prodigiosin, synthetic anion transporters have low‐to‐modest H⁺/Cl^? symport activity and their mechanism of action remains less well understood. We report a chloride‐selective tetraurea macrocycle that has a record‐high H⁺/Cl^? symport activity similar to that of prodigiosin and most importantly demonstrates unprecedented voltage‐switchable transport properties that are linked to the lack of uniport activity. By studying the anion binding affinity and transport mechanisms of four other anion transporters, we show that the lack of uniport and voltage‐dependent H⁺/Cl^? symport originate from strong binding to phospholipid headgroups that hampers the diffusion of the free transporters through the membrane, leading to an unusual H⁺/Cl^? symport mechanism that involves only charged species. Our work provides important mechanistic insights into different classes of anion transporters and a new approach to achieve voltage‐switchability in artificial membrane transport systems.