Catalytic reduction of N2O with CH4 and C3H6 over Ag–Rh/Al2O3 bimetallic catalyst in the presence of oxygen

A study of nitrous oxide (N₂O) reduction with methane (CH₄) and propene (C₃H₆) in the presence of oxygen (5%) over Ag/Al₂O₃, Rh/Al₂O₃ and Ag–Rh/Al₂O₃ catalysts, with Ag and Rh loadings of 5 wt% and 0.05 wt% respectively, has been performed. From the results, it was observed that the Ag–Rh bimetallic catalyst was the most active for both nitrous oxide removal (more than 95%) and hydrocarbon oxidation. This high activity seems to be connected with a synergistic effect between Ag and Rh. The findings from X‐ray diffraction and X‐ray photoelectron spectroscopy studies showed also, that there were no strong interactions (eg alloying) between Ag and Rh. Copyright © 2005 Society of Chemical Industry     

Mass/heat-exchange network representation of distillation networks

This article introduces the “state space” conceptual framework to process synthesis, which is used to provide a novel representation of a distillation network as a composite heat- and mass-exchange network. This representation suggests that distillation network synthesis may best be viewed as an interacting heat- and mass-exchange network synthesis problem. In that regard, familiar tools (such as pinch diagrams) from both heat-exchange network (HEN) and mass-exchange network (MEN) synthesis are shown to be of use in arriving at energy-efficient distillation network designs. Examples of propylene-propane and solvent-water separations are used to illustrate the proposed conceptual framework.     

A Matrix–Matrix Multiplication methodology for single/multi-core architectures using SIMD

In this paper, a new methodology for speeding up Matrix–Matrix Multiplication using Single Instruction Multiple Data unit, at one and more cores having a shared cache, is presented. This methodology achieves higher execution speed than ATLAS state of the art library (speedup from 1.08 up to 3.5), by decreasing the number of instructions (load/store and arithmetic) and the data cache accesses and misses in the memory hierarchy. This is achieved by fully exploiting the software characteristics (e.g. data reuse) and hardware parameters (e.g. data caches sizes and associativities) as one problem and not separately, giving high quality solutions and a smaller search space.     

On constrained infinite-time nonlinear optimal control

In this work, we consider the infinite-time optimal control of input affine nonlinear systems subject to point-wise in time inequality constraints on both the process inputs and outputs. Fundamental to solving this constrained infinite-time nonlinear optimal control (CITNOC) problem is the ability to calculate the value function of it's unconstrained counterpart, the infinite-time nonlinear optimal control (ITNOC) problem. Unfortunately, the traditional ITNOC solution procedure of specifying an objective function and then solving for the optimal control policy and corresponding value function is computationally intractable in all but the simplest of examples. However, in many cases one can easily identify a stabilizing feedback for near operating point regulation. Building from this local policy, the proposed method is to construct a meaningful optimal control objective function as well as its corresponding value function. These functions are then used to analyze the closed-loop stability of the proposed policy. Upon return to the constrained case the constructed objective and value functions are again used to develop a self-consistent constrained finite-time scheme that will, for the first time, provide an exact solution to the CITNOC problem. The mechanics of the proposed method are then illustrated by an example from chemical reactor control.     

Antivirulence Isoquinolone Mannosides: Optimization of the Biaryl Aglycone for FimH Lectin Binding Affinity and Efficacy in the Treatment of Chronic UTI

Uropathogenic E. coli (UPEC) employ the mannose‐binding adhesin FimH to colonize the bladder epithelium during urinary tract infection (UTI). Previously reported FimH antagonists exhibit good potency and efficacy, but low bioavailability and a short half‐life in vivo. In a rational design strategy, we obtained an X‐ray structure of lead mannosides and then designed mannosides with improved drug‐like properties. We show that cyclizing the carboxamide onto the biphenyl B‐ring aglycone of biphenyl mannosides into a fused heterocyclic ring, generates new biaryl mannosides such as isoquinolone 22 (2‐methyl‐4‐(1‐oxo‐1,2‐dihydroisoquinolin‐7‐yl)phenyl α‐d ‐mannopyranoside) with enhanced potency and in vivo efficacy resulting from increased oral bioavailability. N‐Substitution of the isoquinolone aglycone with various functionalities produced a new potent subseries of FimH antagonists. All analogues of the subseries have higher FimH binding affinity than unsubstituted lead 22 , as determined by thermal shift differential scanning fluorimetry assay. Mannosides with pyridyl substitution on the isoquinolone group inhibit bacteria‐mediated hemagglutination and prevent biofilm formation by UPEC with single‐digit nanomolar potency, which is unprecedented for any FimH antagonists or any other antivirulence compounds reported to date.     

Global optimality properties of total annualized and operating cost problems for compressor sequences

The minimum total annualized cost problem for a series of nonisentropic compressors and coolers that brings a gas with constant compressibility factor from a specified initial pressure and temperature to a specified final pressure and the same temperature is studied in this work. It is established analytically that at the global optimum, the cooler outlet temperatures are equal to the minimum allowable temperature. For constant heat capacity, constant compressibility factor gases, additional properties of the globally optimal compressor sequence are analytically established for the minimum operating cost case. The aforementioned properties permit development of a solution strategy that identifies the globally minimum operating cost. Several case studies are presented to illustrate the developed theorems and solution strategies. © 2014 American Institute of Chemical Engineers AIChE J 60: 4134–4149, 2014     

Evaluation of polyesters from renewable resources as alternatives to the current fossil-based polymers. Phase transitions of poly(butylene 2,5-furan-dicarboxylate)

Poly(butylene 2,5-furan dicarboxylate) (PBF) is an alipharomatic polyester that can be prepared using monomers derived from renewable resources such as 2,5-furan dicarboxylic acid and 1,4-butanediol. In the present work the thermal behavior of PBF was studied. Multiple melting was observed during heating traces of samples isothermally crystallized from the melt using differential scanning calorimetry (DSC). The wide angle X-ray diffraction (WAXD) patterns did not reveal the presence of a second crystal population, or a crystal transition upon heating. DSC study showed that the phenomena are closely related to recrystallization. Temperature modulated DSC (TMDSC) tests indeed evidenced enhanced recrystallization. The equilibrium melting point was estimated to be 184.5 °C using the linear Hoffman–Weeks extrapolation. The heat of fusion of the pure crystalline polymer was found equal to 129 J/g or (27.35 kJ/mol), a little lower than that of PBT. The Lauritzen–Hoffman secondary nucleation theory was used and the surface energy values and the work of chain folding were found to be comparable to those of PBT, but quite lower than those of poly(ethylene terephthalate) (PET). The non-isothermal crystallization on cooling and the cold-crystallization of quenched samples were also studied. Condensed spherulites were observed on isothermal crystallization under large supercoolings by using polarized optical microscopy (POM), while the spherulites turned to ring-banded morphology at higher temperatures. In every case the nucleation density was high.     

Role of cation demixing and quasicrystal formation and breakup on the stability of smectitic colloids

The Derjaguin–Landau–Verwey–Overbeek (DLVO) theory has been extensively used to explain colloid stability. This study investigated the effect of demixing of monovalent and divalent cations and crystalline swelling on the breakup and formation of smectite quasicrystals (QCs) and how these processes affect flocculation and dispersion of natural soil clay–humic complexes. The results indicated that in a Ca-dominated system the formation of large QCs enhanced flocculation and that increasing the concentration of Na⁺, K⁺, or NH₄⁺ resulted in the breakup of large Ca-QCs, which enhanced dispersion. In low ionic strength systems, dispersion was caused by expanded double layers (DLVO) and the formation of small QCs. X-ray diffraction analyses showed that as large Ca-QCs breakup, monovalent cations resided primarily on the external surfaces and Ca²⁺ was preferentially retained in the interlayers. In high ionic strength systems increasing concentrations of monovalent cations also decreased the size of QCs but the effect was partially counteracted by compression of double layers between QCs. X-ray diffraction analyses indicated that monovalent cations were sorbed on both the external surfaces and in the interlayers in high ionic strength systems.     

Self-organization of quantum wire-like morphology on InxGa1 − xAs single quantum wells grown on (100)InP vicinal surfaces depending on the substrate misorientation, buffer mismatch and growth temperature

The appearance of a quantum wire-like morphology on the In_xGa_{1 − x}As single quantum well of High Electron Mobility Transistor structures grown by Molecular Beam Epitaxy (MBE) on (100)InP vicinal surfaces is reported. This quantum wire morphology in the InGaAs well is driven by the lateral modulation existing in the In_yAl_{1 − y} As tensile buffer of the heterostructure. The development of the lateral modulation in the buffer, related to In-rich or Alrich regions oriented along {133} or {122} planes, has been found to be favoured by the presence of steps at the interface of 4° off (100) towards (111)A misoriented InP substrates and also attributed to a thermally activated phenomenon. Furthermore, the results of Transmission Electron Microscopy (TEM) and X-Ray Diffraction (XRD) reveal that the lateral composition modulation acts as a strain relieving mechanism that accommodates the tensile mismatch between the InAlAs buffer and the substrate.