A TITO Control Strategy to Increase Productivity in Uncertain Exothermic Continuous Chemical Reactors

In this manuscript, a two-input two-output (TITO) control strategy for an exothermic continuous chemical reactor is presented. The control tasks of the continuous chemical reactor are related to temperature regulation by a standard proportional-integral (PI) controller. The selected set point increases reactor productivity due to the temperature effect and prevents potential thermal runaway, and the temperature increases until it reaches isothermal operating conditions. Then, an optimal controller is activated to increase the mass reactor productivity. The optimal control strategy is based on a Euler-Lagrange framework, in which the corresponding Lagrangian is based on the model equations of the reactor, and the optimal controller is coupled with an uncertainty estimator to infer the unknown terms required by the proposed controller. As a benchmark, a continuous stirred tank reactor (CSTR) with a Van de Vusse chemical reaction is considered as an application case study. Notably, the proposed methodology is generally applicable to any continuous stirred tank reactor. The results of numerical experiments verify the satisfactory performance of the proposed control strategy.

Improved Synthesis of Ag/SiO2 Colloidal Nanocomposites and Their Antibacterial Activity Against Ralstonia solanacearum 15

Ag/SiO2 colloidal nanocomposites (NCs) were prepared through the semi-continuous chemical reduction of silver ions on a silica surface; NaBH4 was used as a primary reducing agent, while carboxymethyl cellulose (CMC) served as a secondary reductant and a stabilizer at low temperature. Silver nanoparticles (AgNPs) of an average diameter of 3.89±0.18 nm were uniformly and densely dispersed on the SiO2 surface, forming 218.6-nm-sized Ag/SiO2 NCs. The zeta potential of the Ag/SiO2 NCs (−92.6 mV) was more negative than that of silica (−24 mV), indicating their high long-term stability. Furthermore, their proposed formation mechanism was confirmed via Fourier transform infrared spectroscopy. Then, the bactericidal effect of the Ag/SiO2 was evaluated based on their minimal inhibitory concentration (MIC) against Ralstonia solanacearum 15 (R. solanacearum 15); it was 62.5 ppm, much lower than that of conventional AgNPs (500 ppm). Therefore, these highly stable Ag/SiO2 colloidal NCs with more effective antibacterial activity than conventional AgNPs are a promising nanopesticide in agriculture.

Effects of exogenous addition of cadmium on cadmium speciation in hyperaccumulator of Sedum alfredii Hance

Continuous chemical extraction is considered to be one of the most common methods for the extraction of heavy metals speciations in plants. However, the basis for the extraction order of this method is not explained and has been rarely studied. In this paper, we analyzed the speciations of cadmium in plants by a four-step continuous extraction method. The extraction sequence of ethanol and water was studied to study the effect of extraction sequence on the extraction rate of extraction agent. The results showed that cadmium exists mostly in NaCl extraction state and the extraction rate of the two kinds of extraction agents decreased when the order of ethanol and water was changed.

Chemical composition of organically and conventionally grown fruits of raspberry (Rubus idaeus L.) cv. Willamette

The paper presents two-year results of chemical tests of raspberry fruits in organic and conventional cultivation systems. Raspberry plantations were established on the slopes of Jelica Mountain, on soil having very acidic reaction (pH/KCl 3.67-3.76) and optimal contents of humus and total N. In the conventional cultivation system, the soil had a high supply of readily available P2O5 and K2O and microelements, with excessive levels of Ni, and Cr. In the organic system, the content of Ni and Zn increased. The biochemical properties of organic and conventional fruits showed no significant differences, while the influence of the research year and the interaction of the cultivation system showed significant differences in the content of TA and IS. However, higher values of the levels of soluble solids, total acids and sugars contributed to the more appealing taste and aroma of organic raspberry fruits. The contents of microelements and heavy metals in the fruits of both cultivation systems were measured in the following order Mn>Fe>Zn>Cu>Ni>Cr>Co. No significant difference was found in the contents of the examined elements between organic and conventional fruits, except for the statistically higher content of Fe in organic raspberries. The high share of individual elements (especially Ni) in both cultivation systems indicates the need for continuous chemical testing of soil and fruits. Based on the results, it is important to consider the daily intake of each element in relation to body weight and/or maximum daily intake.

The effect of A-dec ICX TM on microbiological water quality in self-contained dental units' water systems

The contamination of dental unit waterlines (DUWLs) as a result of biofilms that adhere to the inner surfaces of the lines continues to generate concern. The biofilm serves as a reservoir that can increase the number of free-floating microorganisms in the water used for dental treatment.Recent studies found that it presents a confirmed but limited risk to immunocompetent individuals, but may pose a significant hazard for immunocompromised patients and dental professionals. DUWLs are prone to biofilm formation because of their small diameter and water stagnation. Untreated or unfiltered dental unit water is likely to contain high numbers of microorganisms and is unlikely to meet standards for water used as a cool-ant/irrigant for nonsurgical dental procedures.Common approaches to improve water quality include self-contained water systems combined with periodic or continuous chemical treatment protocols, daily draining, air purging regimens, anti-retraction valves, point of use micro-filters, as well as flushing waterlines for several minutes in the morning and after every patient. Centralized systems designed for single chair or entire practice waterlines that purify or treat incoming water to remove or inactivate microorganisms are becoming more popular.In most dental settings, treatment water comes from the municipal water supply directly into the dental unit.