Multi-criteria design optimization study of solvent extraction in mixer–settler units

Solvent extraction is considered as a multi-criteria optimization problem, since several chemical species with similar extraction kinetic properties are frequently present in the aqueous phase and the selective extraction is not practicable. This optimization, applied to mixer–settler units, considers the best parameters and operating conditions, as well as the best structure or process flow-sheet. Global process optimization is performed for a specific flow-sheet and a comparison of Pareto curves for different flow-sheets is made. The positive weight sum approach linked to the sequential quadratic programming method is used to obtain the Pareto set.In all investigated structures, recovery increases with hold-up, residence time and agitation speed, while the purity has an opposite behaviour. For the same treatment capacity, counter-current arrangements are shown to promote recovery without significant impairment in purity. Recycling the aqueous phase is shown to be irrelevant, but organic recycling with as many stages as economically feasible clearly improves the design criteria and reduces the most efficient organic flow-rate.     

Characterization of peptide and amino acid profile in casein hydrolysates

The nutritional quality of protein hydrolysates has been related in several reports to their di- and tripeptide contents. In the present work different hydrolytic conditions were tested using papain in order to prepare casein hydrolysates with a suitable peptide profile for being used in special diets. The hydrolysates were fractionated by size-exclusion HPLC and the rapid Correct Fraction Area method was used for quantifying the peptides. Among the five hydrolytic conditions studied, three of them gave rise to preparations having nutritionally similar peptide profiles. However, the use of the temperature of 37 degrees C and enzyme:substrate ratio (E:S) of 2% may probably be the most economical condition for industrial production.     

射频等离子体聚合SiOx薄膜的研究

在射频等离子体放电条件下，以六甲基二硅氧烷（Hexamethyldisilone，HMDSO）为单体，氧气为反应气体，在PET薄膜及载玻片上聚合SiOx薄膜。通过红外光谱（FTIR）分析了工作压强、功率、单体氧气比、聚合时间等对聚合薄膜的结构和沉积速度的影响；通过扫描电子显微镜（SEM）观察了薄膜的表面形貌；通过表面轮廓仪测试了薄膜厚度，计算了沉积速率并对薄膜的均匀性做了研究。在38％恒温水浴箱中进行的水蒸汽阻隔实验表明，PET薄膜的阻隔性能得到有效的提高。     

Encoding Linear Logic with Interaction Combinators

The purpose of this paper is to demonstrate how Lafont's interaction combinators, a system of three symbols and six interaction rules, can be used to encode linear logic. Specifically, we give a translation of the multiplicative, exponential, and additive fragments of linear logic together with a strategy for cut-elimination which can be faithfully simulated. Finally, we show briefly how this encoding can be used for evaluating λ-terms. In addition to offering a very simple, perhaps the simplest, system of rewriting for linear logic and the λ-calculus, the interaction net implementation that we present has been shown by experimental testing to offer a good level of sharing in terms of the number of cut-elimination steps (resp. β-reduction steps). In particular it performs better than all extant finite systems of interaction nets.     

A neural-network-based space-vector PWM controller for athree-level voltage-fed inverter induction motor drive

A neural-network-based implementation of space-vector modulation (SVM) of a three-level voltage-fed inverter is proposed in this paper that fully covers the linear undermodulation region. A neural network has the advantage of very fast implementation of an SVM algorithm, particularly when a dedicated application-specific IC chip is used instead of a digital signal processor (DSP). A three-level inverter has a large number of switching states compared to a two-level inverter and, therefore, the SVM algorithm to be implemented in a neural network is considerably more complex. In the proposed scheme, a three-layer feedforward neural network receives the command voltage and angle information at the input and generates symmetrical pulsewidth modulation waves for the three phases with the help of a single timer and simple logic circuits. The artificial-neural-network (ANN)-based modulator distributes switching states such that neutral-point voltage is balanced in an open-loop manner. The frequency and voltage can be varied from zero to full value in the whole undermodulation range. A simulated DSP-based modulator generates the data which are used to train the network by a backpropagation algorithm in the MATLAB Neural Network Toolbox. The performance of an open-loop volts/Hz speed-controlled induction motor drive has been evaluated with the ANN-based modulator and compared with that of a conventional DSP-based modulator, and shows excellent performance. The modulator can be easily applied to a vector-controlled drive, and its performance can be extended to the overmodulation region     

Classes of Timed Automata and the Undecidability of Universality

Universality for deterministic Timed Automata (TA) is PSPACE-complete but becomes highly undecidable when unrestricted nondeterminism is allowed. More precisely, universality for nondeterministic TA is Π₁¹-hard and it is still open whether it is π₁¹-complete. It is interesting to note that the entire arithmetical hierarchy is contained in this computability gap between determinism and nondeterminism. In this paper we consider three types of syntactical restrictions to nondeterministic TA, which may contribute to a better understanding of the universality problem for TA. For the first two types, which are of independent interest, the universality problem is shown to be Π₁¹-complete. For the third one, universality is Π₁⁰-complete, which is the same as saying that the complementary problem is complete in the recursively enumerable class. We also show that all the restrictions define proper subclasses of the class of timed languages defined by nondeterministic TA; and establish the relationships between the classes.     

Ergonomics, gerontechnology, and design for the home-environment

An ergonomic approach could improve the quality of life and activities in daily living. Gerontechnology reduces the effects of age-related impairments with technological devices and particular design for the home-environment. Physiological decline with increasing age renders the daily activities at home more difficult. This paper highlights some "common sense" and specific design suggestions in the entrance and kitchen, aimed to increase the self-sufficiency of elderly people. We suggest that gerontechnology may have a particular role in the improvement of comfort and safety for aged people.     

Reduced inward rectifying and increased E-4031-sensitive K+ current density in arrhythmogenic subendocardial purkinje myocytes from the infarcted heart

Astrocytes in primary culture from rat cerebral cortex were probed concerning the expression of delta-opioid receptors and their coupling to changes in intracellular free calcium concentrations ([Ca2+]i). Fluo-3 or fura-2 based microspectrofluorometry was used for [Ca2+]i measurements on single astrocytes in a mixed astroglial-neuronal culture. Application of the selective delta-opioid receptor agonist, [D-Pen2, D-Pen5]-enkephalin (DPDPE), at concentrations ranging from 10 nM to 100 microM, induced concentration-dependent increases in [Ca2+]i (EC50 = 114 nM). The responses could be divided into two phases, with an initial spike in [Ca2+]i followed by either oscillations or a sustained elevation of [Ca2+]i. These effects were blocked by the selective delta-opioid receptor antagonist ICI 174864 (10 microM). The expression of delta-opioid receptors on astroglial cells was further verified immunohistochemically, using specific antibodies, and by Western blot analyses. Pre-treatment of the cells with pertussis toxin (100 ng/ml, 24 h) blocked the effects of delta-opioid receptor activation, consistent with a Gi- or Go-mediated response. The sustained elevation of [Ca2+]i was not observed in low extracellular Ca2+ and was partly blocked by nifedipine (1 microM), indicating the involvement of L-type Ca2+ channels. Stimulating neurons with DPDPE resulted in a decrease in [Ca2+]i, which may be consistent with the closure of the plasma membrane Ca2+ channels on these cells. The current results suggest a role for astrocytes in the response of the brain to delta-opioid peptides and that these opioid effects in part involve altered astrocytic intracellular Ca2+ homeostasis.     

High- versus low-dose ACE inhibition in chronic heart failure: a double-blind, placebo-controlled study of imidapril

OBJECTIVES: To determine dose-related clinical and neurohumoral effects of angiotensin-converting enzyme (ACE) inhibitors in patients with chronic heart failure (CHF), we conducted a double-blind, placebo-controlled, randomized study of three doses (2.5 mg, 5 mg and 10 mg) of the long-acting ACE inhibitor imidapril. BACKGROUND: The ACE inhibitors have become a cornerstone in the treatment of CHF, but whether high doses are more effective than low doses has not been fully elucidated, nor have the mechanisms involved in such a dose-related effect. METHODS: In a parallel group comparison, the effects of three doses of imidapril were examined. We studied 244 patients with mild to moderate CHF (New York Heart Association class II-III: +/-80%/20%), who were stable on digoxin and diuretics. Patients were treated for 12 weeks, and the main end points were exercise capacity and plasma neurohormones. RESULTS: At baseline, the four treatment groups were well-matched for demographic variables. Of the 244 patients, 25 dropped out: 3 patients died, and 9 developed progressive CHF (3/182 patients on imidapril vs. 6/62 patients on placebo, p < 0.05). Exercise time increased 45 s in the 10-mg group (p = 0.02 vs. placebo), but it did not significantly change in the 5-mg (+16 s), and 2.5-mg (+11 s) imidapril group, compared to placebo (+3 s). Physical working capacity also increased in a dose-related manner. Plasma brain and atrial natriuretic peptide decreased (p < 0.05 for linear trend), while (nor)epinephrine, aldosterone and endothelin were not significantly affected. Renin increased in a dose-related manner, but plasma ACE activity was suppressed similarly (+/-60%) on all three doses. CONCLUSIONS: Already within 3 months after treatment initiation, high-dose ACE inhibition (with imidapril) is superior to low-dose. This is reflected by a more pronounced effect on exercise capacity and some of the neurohormones, but it does not appear to be related to the extent of suppression of plasma ACE.