Informational Entropy: a Failure Tolerance and Reliability Surrogate for Water Distribution Networks

Evolutionary algorithms are used widely in optimization studies on water distribution networks. The optimization algorithms use simulation models that analyse the networks under various operating conditions. The solution process typically involves cost minimization along with reliability constraints that ensure reasonably satisfactory performance under abnormal operating conditions also. Flow entropy has been employed previously as a surrogate reliability measure. While a body of work exists for a single operating condition under steady state conditions, the effectiveness of flow entropy for systems with multiple operating conditions has received very little attention. This paper describes a multi-objective genetic algorithm that maximizes the flow entropy under multiple operating conditions for any given network. The new methodology proposed is consistent with the maximum entropy formalism that requires active consideration of all the relevant information. Furthermore, an alternative but equivalent flow entropy model that emphasizes the relative uniformity of the nodal demands is described. The flow entropy of water distribution networks under multiple operating conditions is discussed with reference to the joint entropy of multiple probability spaces, which provides the theoretical foundation for the optimization methodology proposed. Besides the rationale, results are included that show that the most robust or failure-tolerant solutions are achieved by maximizing the sum of the entropies.     

Use of cascade reduction potential for selective precipitation of Au,Cu, and Pb in hydrochloric acid solution

Optimization of reduction potential for electroseparation was studied for the recovery of gold, copper, and lead from acidic solution. A linear sweep voltammetric method enabled us to determine characteristic reduction potentials for each metal and the kinetics of the metal deposition indicated by current-voltage curves. In order to precipitate the metal species sequentially, reduction potentials were examined for the individual and mixed solutions of Au(III), Cu(II), and Pb(II). The three metals were reasonably well isolated from the mixed solutions such as Cu(II)/ Pb(II) and Au(III)/Cu(II)/Pb(II) in the order of the corresponding reduction potentials, in particular, the mass transfer controlled reduction potentials, obtained from linear sweep voltammetry (LSV) measurement.     

Hydrodynamic characteristics of a FCC regenerator

The hydrodynamic and gas mixing characteristics have been determined in a FCC regenerator (0.48 m I.D.x3.4 m high) with FCC particles. Solids holdup in the dense bed decreases with increasing gas velocity, but it increases in the freeboard region. The bubble/void fraction increases with an increase along the bed height at a given gas velocity and increases with increasing gas velocity at a constant bed height. Backmixed tracer gas at the wall region is higher than that at the center region of the bed. The gas backmixing coefficient decreases with increasing gas velocity.     

Diffusion coefficient in polymer solutions

Molecular diffusivity of a solute in a solvent may be determined by measuring the extent of dispersion of solute in solvent flowing in a straight circular tube under the conditions of laminar flow. This simple and rapid method for determination of molecular diffusivity in aquous polymer solutions is discussed. Experimental results show a substantial reduction in the solute diffusivity with increase in polymer concentration.     

Formation of Polymeric Lewis Acid–Lewis Base Complexes with Well-defined Organoboron Polymers

The binding of Lewis bases to organoboron polymeric Lewis acids has been studied and the parameters that determine the complexation equilibrium have been investigated, which include (i) the strength of the individual Lewis acids and Lewis bases, (ii) concentration, and (iii) temperature. While the strongly Lewis acidic borane polymers poly(4-bis(pentafluorophenyl)borylstyrene) (PS-BPf) and poly(4-(di-2-thienylboryl)styrene) (PS-BTh) form isolable complexes with strong Lewis bases such as 4-t-butylpyridine (^tPy), a temperature dependent equilibrium is established with weaker bases such as THF. Similarly, the weakly Lewis acidic boronate polymer poly(4-diethoxyborylstyrene) (PS-BOEt) undergoes a temperature dependent equilibrium with the strong Lewis base 4-dimethylaminopyridine (DMAP), while poly(4-pinacolatoborylstyrene) (PS-BPin) does not significantly bind to pyridine bases. Decomplexation of PS-BTh· ^t Py is achieved by treatment with the stronger Lewis acid, B(C₆F₅)₃, thereby confirming the reversible nature of the polymeric Lewis acid–base adducts. This paper is dedicated to Professor Ian Manners in gratitude of his guidance throughout the years and recognition of his scientific accomplishments     

Sterol metabolism in the opportunistic pathogen <Emphasis Type="Italic">Pneumocystis</Emphasis>: Advances and new insights

Pneumocystis can transiently colonize healthy individuals without causing adverse symptoms, and most people test positive for exposure to this organism early in life. However, it can cause Pneumocystis pneumonia (PcP) in people with impaired immune systems and is a major cause of death in HIV/AIDS. Although it has close affinities to the Ascomycetes, Pneumocystis has features unlike those of any single group of fungi. For example, Pneumocystis does not synthesize ergosterol, which is consistent with the inefficacy of amphotericin B and some triazoles in clearing PcP. Pneumocystis sterols include distinct Δ⁷ 24-alkylsterols. Metabolic radiolabeling experiments demonstrated that P. carinii synthesizes sterols de novo. Cholesterol is the most abundant sterol in Pneumocystis; most, if not all, is scavenged from the mammalian host lung by the pathogen. The P. carinii erg7, erg6, and erg11 genes have been cloned, sequenced, and expressed in heterologous systems. The recombinant P. carinii S-adenosyl-l-methionine:C-24 sterol methyl transferase (SAM:SMT) has a preference for lanosterol over zymosterol as substrate, and the enzyme can catalyze the transfer of either one or two methyl groups to the C-24 position of the sterol side chain. Two different sterol compositions were detected among human-derived P. jirovecii; one was dominated by C₂₈ and C₂₉ sterols, and the other had high proportions of higher molecular mass components, notably the C₃₂ sterol pneumocysterol. The latter phenotype apparently represents organisms blocked at 14α-demethylation of the sterol nucleus. These studies suggest that SAM:SMT is an attractive drug target for developing new chemotherapy for PcP.     

Surface tension and contact angle of herbicide solutions affected by surfactants

Contact angle and surface tension were measured for distilled and hard water solutions of adjuvants, Ortho X-77, Span-20, Sterox-NJ. Surfactant-WK, Triton B-1956, Triton X-114, Tween-20, and Sun Oil 11E. The same parameters were measured for suspensions of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] and ametryne [2-(ethylamino)-4-(isopropylamino)-6-(methylthio)-s-triazine] with and without each adjuvant. All adjuvants reduced surface tension and contact angle of distilled water; Surfactant-WK was most effective and Tween-20 was least effective. Increasing concentration of surfactants from 0 to 0.1% (v/v) gave progressive reduction in surface tension and contact angle while higher concentrations, 0.1 to 2.0% (v/v), had no further effect. Surfactant-WK at 0.1% (v/v) in distilled water reduced the surfact tension from 72.8 dynes/cm to 27 dynes/cm and contact angle from 110° to 41°. An additional increase in Surfactant-WK concentration from 0.1% (v/v) to 2% (v/v) did not further reduce surface tension and contact angle. Sun Oil 11E was identical in behavior except that it was less effective than the surfactants. Water hardness up to 1,000 ppm as Ca ions did not affect surface tension and contact angle in surfactant solutions. An aqueous solution of atrazine had a higher surface tension and contact angle than ametryne in the absence of surfactants. However, these differences were not observed when surfactants were added to either herbicide.     

Formation of Nanocrystalline Calcia by the Decomposition of Calcite

Formation of nanocrystalline calcia from calcite has been studied in situ via transmission electron microscopy. The crystallographic transformation occurred via two mechanisms: the first is by distortion of the cleaved rhombohedron of calcite, formed by {104} planes in hexagonal coordinates, into a cube. This produced a microstructure of oriented, elongated nanocrystals of calcia with planar boundaries. In the second mechanism, the micrometer-sized parent calcite particles broke up into nano-sized grains as the decomposition began, leading to irregularly shaped, randomly oriented nanocrystals of calcia.     

Thermal stability of PVC/chlororubber-20-graft polyblend–styrene–acrylonitrile blends. I

Thermal stability of PVC blends with chlororubber-20-graft polyblend-styrene-acrylonitrile [CR-20gp-SAN (2:1)] was studied by HCI evolution techniques and thermogravimetry under isothermal condition. The thermal stability of PVC/CR-20gp-SAN (2:1) blends has been compared with those of PVC/CR-20 and PVC/KM-365B blends. It has been observed that the thermal stability of modified PVC is less than that of unmodified PVC. The CR-20gp-SAN (2:1) modified PVC blends were found to be more stable than PVC/CR-20 blends but less stable than PVC/KM-365B blends. The rate of degradation in PVC blends were observed to be unaffected by the concentration of the modifiers, but the PVC/KM-365B blends were found to be degrading slower in comparison with PVC/CR-20 and PVC/CR-20gp-SAN (2:1) blends. The rate of degradation for PVC/CR-20 blends at lower concentrations (<10%) of modifiers is almost equal to that of PVC/CR-20-gp-SAN (2:1) blends, but more at higher concentrations of modifiers (>10%). The experimental results have been explained on the basis of the chemical nature of the modifiers and their miscibility with PVC.     

Note: The Use of Triallyl Cyanurate in Bonding PVC Plastisols to Steel

The use of diallyl phthalate as the basis for a non-extractable plasticizer for poly(vinylchloride) (PVC) is well-known. Used in conjunction with a primary plasticizer and a polymerization initiator, a plastisol coating for steel can be formulated which is oil or grease tolerant and can also be used for bonding some structural steel parts if the area is relatively large compared with the load to be applied. Defrayne and Twiss¹ describe the bonding of automobile hood assemblies by vinyl plastisol adhesives and Schneberger² emphasizes their use in the automobile industry though neither article gives the formulations employed. Commercial formulations giving pull-off strengths of the order of 1 to 4 MN. m^-2 always incorporate a proportion of a phenolformaldehyde resin or even an epoxy, but sound-deadening and other coatings of steel do not necessarily need this reinforcement. Phillips and Longworth³ particularly studied the use of diallylphthalate (DAP) as a polymerizable plasticizer and the consequent improvement in adhesion to mild steel. Sherlock⁴ used a simple formulation without additives when investigating the effect of surface cleaning and conversion coatings (oxides and phosphates). It was suggested that, as outlined below, improved adhesion would be expected if a small proportion of triallyl cyanurate (TAC) were added to the polymerizable plasticizer. This paper shows this expectation to be achieved although the proportion of the more expensive TAC needed for substantial increase in bond strength is greater than was hoped.