Effect of sodium bicarbonate on the properties of metronidazole floating matrix tablets

The effect of sodium bicarbonate (SB) on the swelling behavior and the sustained release of floating systems was studied with varied proportions of this excipient and metronidazole. Two polymers with different hydration characteristics, Methocel K4M and Carbopol 971P NF, were used to formulate the matrices. Under in vitro dissolution conditions, the addition of SB to metronidazole sustained-release tablets modifies the matrix hydration volume, increasing at the beginning, reaching a maximum, and then declining. Pure Carbopol matrices show a rapid hydration with a limited further effect of the SB and metronidazole loads. Methocel show a significant increase of the apparent hydration volume due to SB addition with no further notable change due to metronidazole load. Increasing the metronidazole load reduces the floating time of Carbopol matrices while no effect on Methocel matrices could be observed within 8 hours dissolution. Matrices show increasing release constant values (k) as the metronidazole load increases. Methocel matrices release the drug 10% to 15% faster than Carbopol matrices. SB increases the cumulative amount of drug released from Methocel but not that releasing from Carbopol. These results are attributed to the intrinsic polymer properties, the barrier effect of CO₂ bubbles, and the matrix volume expansion produced after addition of SB.     

Distribution of volatile organic compounds in Sicilian groundwaters analysed by head space-solid phase micro extraction coupled with gas chromatography mass spectrometry (SPME/GC/MS)

This work presents the results of an assessment of the existence and concentration of 13 volatile organic compounds (VOCs) in groundwaters from 14 hydrological basins in Sicily (25,710km(2)). On the basis of hydrological, hydrogeochemical and geological studies, 324 sampling points were selected. All groundwater sampled were collected twice, from October to December 2004 and from February to May 2005, and were analysed to determine the concentration and spatial distribution of the VOCs in the aquifers. The need to analyze a large number of samples in a short space of time so as to obtain quantitative analyses in trace concentration levels spurred us to create a new analytical method, both simple and sensitive, based on HS-SPME/GC/MS. The concentrations of VOCs measured in industrial and intensive agricultural unconfined aquifers were greater than those found in other aquifers. Tetrachloroethylene, chloroform, trichloroethylene and 1,2-dichloropropane were the most frequently detected VOCs. However, they exceeded the guideline values proposed by the EU in only three aquifers located near to industrial and intense agricultural areas.     

Residual-free bubbles for the Helmholtz equation

The Galerkin method enriched with residual-free bubbles is considered for approximating the solution of the Helmholtz equation. Two-dimensional tests demonstrate the improvement over the standard Galerkin method and the Galerkin-least-squares method using piecewise bilinear interpolations. © 1997 John Wiley & Sons, Ltd.     

Methyl Ethyl Ketone Production through an Intensified Process

Methyl ethyl ketone (MEK) is widely used in the industry and is mainly produced from petroleum. Some works have projected MEK as a possible fuel since its performance in spark engines has overcome the performance of gasoline in certain indexes. Two intensified alternatives to produce MEK are introduced here, consisting of a reactive distillation column, an extractive distillation column, and three conventional distillation columns. The direct alternative resulted as the most promising when it was evaluated based on energy consumption, greenhouse gas emissions, and an environmental index. The obtained energy consumption for MEK production was 11.62 MJ kg_MEK⁻¹ for the entire process. Moreover, those intensified alternatives showed better performance indexes in comparison with a conventional process.     

The effect of advance payment with discount facility on supply decisions of deteriorating products whose demand is both price and stock dependent

Generally, in the business world, it is observed that suppliers give different kinds of benefits to retailers due to advance payment. One of the popular benefits is instant cash discount due to advance payment. If a retailer pays off his total purchase cost before receiving the products, then he receives a certain percentage of cash discount instantly. However, if the retailer pays off a certain fraction of the total purchasing cost, then price discount is given only at the time of receiving the products while paying the remaining amount of the total purchasing cost. Using this concept, this paper formulates, under both cases of advance payment (full or partial), an inventory model for deteriorating products where shortages are allowed and demand function is considered as price and stock dependent. The closed‐form solutions for each case are presented and two numerical examples are solved. In addition, a sensitivity analysis is also performed to show the effects of advance payment with discount facility.     

Hydroponics with wastewater: a review of trends and opportunities

Hydroponics is a method of crop production that has been successfully used for the growth of vegetables and flowers. It uses a nutrient solution and generally controlled environmental conditions which makes it more energy intensive, yet more productive than conventional agriculture. Hydroponic systems can be used as a treatment process for partially treated wastewater or reclaimed water (RW) before its release to the environment, as plants have the ability to uptake nutrients, toxic metals and emerging contaminants. The present review has the aim to look into the advantages of hydroponics and evaluate the success of using RW as a nutrient solution. It was found that many examples exist of successful experiments; however, full‐scale examples are still limited. With the recent interest in vertical farming and the production of legal cannabis, interest in hydroponics has increased and the use of RW as a nutrient solution may finally be economically viable.     

Dynamic optimization of the methylmethacrylate cell‐cast process for plastic sheet production

Traditionally, the methylmethacrylate (MMA) polymerization reaction process for plastic sheet production has been carried out using warming baths. However, it has been observed that the manufactured polymer tends to feature poor homogeneity characteristics measured in terms of properties like molecular weight distribution. Nonhomogeneous polymer properties should be avoided because they give rise to a product with undesired wide quality characteristics. To improve homogeneity properties force‐circulated warm air reactors have been proposed, such reactors are normally operated under isothermal air temperature conditions. However, we demonstrate that dynamic optimal warming temperature profiles lead to a polymer sheet with better homogeneity characteristics, especially when compared against simple isothermal operating policies. In this work, the dynamic optimization of a heating and polymerization reaction process for plastic sheet production in a force‐circulated warm air reactor is addressed. The optimization formulation is based on the dynamic representation of the two‐directional heating and reaction process taking place within the system, and includes kinetic equations for the bulk free radical polymerization reactions of MMA. The mathematical model is cast as a time dependent partial differential equation (PDE) system, the optimal heating profile calculation turns out to be a dynamic optimization problem embedded in a distributed parameter system. A simultaneous optimization approach is selected to solve the dynamic optimization problem. Trough full discretization of all decision variables, a nonlinear programming (NLP) model is obtained and solved by using the IPOPT optimization solver. The results are presented about the dynamic optimization for two plastic sheets of different thickness and compared them against simple operating policies. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

SCDBR: An Automated Reasoner for Specifications of Database Updates

In this paper we describe SCDBR, a system that is able to reason automatically from specifications of database updates written in the situation calculus, a first–order language originally proposed by John McCarthy for reasoning about actions and change. The specifications handledby the system are written in the formalism proposed by Ray Reiter for solving the frame problem that appears when one expresses the effects on the database predicates of the execution of atomic transactions.SCDBR is written in PROLOG, and can solve several reasoning tasks, among others,it is able to derive the final specification from effect axioms, to answerqueries to virtually updated databases, to check legality of transactions,to prove integrity constraints from the specification, to modify thespecification in order to embed a desired integrity constraint, and to answer historical queries. For some of these tasks SCDBR can call othersystems, like relational database systems, automated theorem provers, andconstraint solvers.     

Synthesis of ZSM‐5 from diatomite: a case of zeolite synthesis from a natural material

A highly crystalline ZSM‐5 product was obtained from diatomite, a natural raw material, both with and without the presence of diethanolamine. The synthesis process took 40 h, and was carried out under hydrothermal conditions, at autogenic pressure, and at a temperature of 180 °C. The resulting crystals were identified as ZSM‐5 by X‐ray diffraction and characterized by scanning electron microscopy, infrared spectroscopy, thermal gravimetry and differential thermal analysis. Copyright © 2004 Society of Chemical Industry