Analysis and characterization of hydraulic mortars from ancient cisterns and baths in Greece

Structural mortars and plasters from cisterns and baths (thermes) from Roman, Byzantine and Ottoman period in Greece are analyzed in terms of their physico-mechanical, chemical, and microstructural characteristics, in order to find the key factors for their functionality. From the analysis it is found that their coherent and dense structure is due to the action of different mechanisms caused by the selection and combination of raw materials and the interaction with the special environment into which they served. The binding system is mixed, with the combination of hydrated lime and materials with pozzolanic properties. The aggregates are both siliceous and brick fragments of different granulometry, according to the mortar’s type (structural or plaster). The raw materials used as binders and aggregates and the technology practices during mortar application contribute to low porosity mortars with dense structure. Additionally, the environment of the cisterns and baths functioned on the benefit of the materials, as it favored the dilution of the calcite and the secondary phases formed in the mortars’ porous nature assisted towards the cohesiveness of their structure. The technology used for the production of mortars applied in baths and cisterns for a long period of time proves the high knowledge of materials’ behavior in order to produce durable constructions, resistant to highly deteriorating factors.     

Single step fabrication of polymer/silicate porous composite membranes via water-glass induced phase inversion

Water-glass, a low-cost silica precursor solution, is used to produce mostly skinned, polymer–silicate composite membranes with a porous bulk. We explore primarily Nylon 6-10/formic acid dopes where the polymer solvent is an acid, and polysulfone/DMF dope as an example of a polymer dope based on a non-acidic water-miscible solvent. Elemental distribution of silicon in cross sections suggests compositional uniformity of the formed membranes with in some cases 20 wt. % of silicate load. Membranes formed can be used either as separation media or as precursors for compact polymers reinforced with silicate particles.     

Sensory, chemical and microbiological assessment of farm-raised European sea bass (Dicentrarchus labrax) stored in melting ice

Farm raised European sea bass ( Dicentrarchus labrax ) were stored in melting ice for a period up to 22 days from the time of harvest, and sensory, chemical, and microbiological assessments were made at intervals. The storage life of the ungutted fish, determined by sensory evaluation of the cooked flesh, was 19 days. Of the chemical tests, only k ₁ value provided a useful means of monitoring early storage change. Trimethylamine, total volatile bases and pH showed practically no change during the first half of the edible storage life of the fish. Changes in free fatty acid (FFA) content and thiobarbituric acid (TBA) value could not be used to determine loss of acceptability or end of storage life. Sulphide producing bacteria constituted a very low proportion of the total aerobic flora, suggesting that the common sulphide producer Shewanella putrefaciens was not a major spoiler of sea bass in this trial.     

Managing uncertainties in a safety-constrained process system for solvent selection and usage: an optimization approach with technical, economic, and risk factors

This paper addresses the problem of managing uncertainties in a safety-constrained process system for economic performance enhancement. Within such a context, a typical solvent selection problem involves a number of different solvents with nominal property values that are utilized in various process units and requires the minimization of the total operating cost while satisfying certain technical performance criteria and process safety constraints. Practically, in any process system, property values of streams are not exact; they are usually functions of operating variables and market conditions that change over time inevitably introducing irreducible uncertainties in system performance. A key aim of the present study is to systematically explore the effect of volatility in solvent prices on the economic performance of the process. Appropriate sensitivity analysis and Monte Carlo simulation work have been carried out to assist the decision maker in taking into account the continuously changing market conditions, while identifying operationally safe feasibility regions for solvents with different risk characteristics in the underlying optimization problem. The aforementioned uncertain inputs are shown to cause shifts of the associated Pareto front of optimal solutions toward feasibility regions that can be characterized in a more realistic manner. Finally, an illustrative case study that uses the permissible exposure limit as a risk factor is considered to evaluate the proposed method.     

An algebraic approach to targeting waste discharge and impure fresh usage via material recycle/reuse networks

This paper introduces an algebraic procedure that targets material-recycle networks. The problem involves the allocation of process streams and fresh sources to process units (sinks) with the objective of minimizing fresh usage and waste discharge. First, observations from the graphical targeting approach are transformed into algebraic insights. Then, a geometrical transformation is developed to account for the possibility of using impure fresh resources. These insights and geometrical transformations are arranged through a cascade analysis, which identifies and adjusts any recycle infeasibilities so as to maximize the recycle opportunities. A systematic non-iterative algebraic approach is developed to identify rigorous targets for minimum usage of impure fresh resources, maximum recycle of process resources and minimum discharge of waste. These targets are identified a priori and without commitment to the detailed design of the recycle/reuse network. The approach is valid for both pure and impure fresh resources. The devised procedure also identifies the location of the material-recycle pinch point and addresses its significance in managing process sources, fresh usage, and waste discharge. Two case studies are solved to illustrate the ease, rigor, and applicability of the developed targeting technique and its relationship to graphical targeting techniques.     

Side-chain conformations in 4-{{alpha}}-helical bundles

The distribution of the ₁, ₂ dihedral angles in a dataset consistingof 12 unrelated 4--helical bundle proteins was determined andqualitatively compared with that observed in globular proteins.The analysis suggests that the 4--helical bundle motif couldoccasionally impose steric constraints on side chains: (i) theside-chain conformations are limited to only a subset of theconformations observed in globular proteins and for some aminoacids they are sterically more constrained than those in helicalregions of globular proteins; (ii) aspartic acid and asparagineoccasionally adopt rotamers that have not been previously reportedfor globular or helical proteins; (iii) some rotamers of tyrosineand isoleucine are predominantly or exclusively associated withhydrophobic core positions (a, d); (iv) mutations in the hydrophobiccore occur preferentially between residue types which amongother physicochemical properties also share a predominant rotamer.