Unsteady-State Mass Transfer of Gases between Two Quiescent Phases

It is shown that many gases interact with water by reactions similar to that characteristic of sulfur dioxide. The unsteady-state transfer of such gases from one quiescent phase into another is studied in the cases where these gases are absorbed by a liquid or released from a liquid solution.     

Influence of PP‐g‐MA on morphology,mechanical properties and deformation mechanism of copolypropylene/clay nanocomposite

Copolypropylene/organoclay nanocomposites are prepared by melt intercalation method in this research. Two different routes for addition of compatibilizer are examined, i.e. addition in the twin‐screw extruder along with the polymer and the clay powder simultaneously and premixing the compatibilizer with the reinforcement in a batch mixer before addition to the polypropylene (PP) matrix. Morphology, tensile and impact properties and deformation mechanisms of the samples made via two procedures are studied and compared with those of the noncompatibilized system. To study the structure of nanocomposites, x‐ray diffraction and transmission electron microscopy techniques are utilized. The deformation mechanisms of different samples are examined via reflected and transmitted optical microscopy. The results reveal that introduction of compatibilizer and also the procedure in which the compatibilizer is added to the compound, affect structure and mechanical properties of nanocomposite. The elastic modulus of PP‐clay nanocomposite has increased 11.5% with incorporation of compatibilizer. Also, introduction of organoclay without compatibilizer facilitates crazing at the notch tip of PP in 3PB testing. Incorporation of compatibilizer, however, makes difficulties in initiation and growth of crazes at the notch tip. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Encapsulation of nanoparticles by polymerization compounding in a gas/solid fluidized bed reactor

For the first time, a fluidized bed reactor was used for encapsulating nanoparticles by the polymerization compounding approach using Ziegler–Natta catalysts. The polymerization reaction was carried out using a solvent-free process in a gas-phase reactor. This direct gas–solid reaction greatly simplified collecting the particles of interest after polymerization because none of the extra steps often found in encapsulation processes, such as filtering and drying, were performed in this work. The grafting of the catalyst to the original surface of particles was confirmed by X-ray photoelectron spectroscopy. Micrographs obtained by transmission electron microscopy confirmed the presence of a thin layer of polymer, in the order of a few nanometers, around the particles. The thickness of this coating was affected by the operating conditions of the process. The characterization of the modified particles with electron microscopy also revealed that zirconia nanoparticles tend to be coated in an agglomerated state, whereas aluminum particles were mostly individually encapsulated by the polymer. In addition, the effects of temperature and pressure were studied on the encapsulation process and a kinetic analysis was presented based on the available models in the literature. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

The effect of nanoparticles on wettability alteration for enhanced oil recovery: micromodel experimental studies and CFD simulation

The applications of nanotechnology in oilfields have attracted the attention of researchers to nanofluid injection as a novel approach for enhanced oil recovery. To better understand the prevailing mechanisms in such new displacement scenarios, micromodel experiments provide powerful tools to visually observe the way that nanoparticles may mobilize the trapped oil. In this work, the effect of silicon oxide nanoparticles on the alteration of wettability of glass micromodels was investigated in both experimental and numerical simulation approaches. The displacement experiments were performed on the original water-wet and imposed oil-wet (after aging in stearic acid/n-heptane solution) glass micromodels. The results of injection of nanofluids into the oil-saturated micromodels were then compared with those of the water injection scenarios. The flooding scenarios in the micromodels were also simulated numerically with the computational fluid dynamics (CFD) method. A good agreement between the experimental and simulation results was observed. An increase of 9% and 13% in the oil recovery was obtained by nanofluid flooding in experimental tests and CFD calculations, respectively.     

Developing a Robust Multi-Attribute Decision-Making Framework to Evaluate Performance of Water System Design and Planning under Climate Change

In theory, emergence of robustness concept has pushed decision-makers toward designing alternatives, such as resistant against the potential fluctuations fueled by uncertain surrounding environment. This study promotes an objective-based multi-attributes decision-making framework that takes into account the uncertainties associated with the impacts of the climate change on water resources systems. To capture the uncertainties of climate change, Monte Carlo approach has been used to generate a series of ensembles. These generated ensembles represent the stochastic behavior of the hydro-climatic variables under climate change. This framework represents the inherent uncertainties associated with hydro-climatic simulations. Next, a coupled TOPSIS/Entropy multi-attribute decision-making framework has been formed to prioritize the feasible alternatives using system performance measures. The main objective of this framework is to minimize the risk of deceptive and subjective assessments during decision-making process. Karkheh River basin has been selected as a case study to demonstrate the implication of this framework. Using a set of system performance attributes, the performance of two hydropower systems has been estimated during the baseline period and under the future climate change conditions. According to the conducted frequency analysis, the alternative in which both hydropower projects would go under construction emerged as the robust solution (i.e., there was a 99.9% chance that it outperforms other solutions). The results indicate that the construction of these hydropower systems leads to the increase of Karkheh River basin robustness in the future.

     

Human Cellular Retinol Binding Protein II Forms a Domain-Swapped Trimer Representing a Novel Fold and a New Template for Protein Engineering

Domain-swapping is a mechanism for evolving new protein structure from extant scaffolds, and has been an efficient protein-engineering strategy for tailoring functional diversity. However, domain swapping can only be exploited if it can be controlled, especially in cases where various folds can coexist. Herein, we describe the structure of a domain-swapped trimer of the iLBP family member hCRBPII, and suggest a mechanism for domain-swapped trimerization. It is further shown that domain-swapped trimerization can be favored by strategic installation of a disulfide bond, thus demonstrating a strategy for fold control. We further show the domain-swapped trimer to be a useful protein design template by installing a high-affinity metal binding site through the introduction of a single mutation, taking advantage of its threefold symmetry. Together, these studies show how nature can promote oligomerization, stabilize a specific oligomer, and generate new function with minimal changes to the protein sequence.