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Phase System (phase + system)
Selected AbstractsAn Investigation of the Nd2O3,MoO3 Phase System: Thermal Decomposition of Nd2Mo4O15 and Formation of Nd6Mo10O39.CHEMINFORM, Issue 39 2006Rosemary S. Barker Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Preferential Interface Nucleation: An Expansion of the VLS Growth Mechanism for NanowiresADVANCED MATERIALS, Issue 2 2009Brent A. Wacaser Abstract A review and expansion of the fundamental processes of the vapor,liquid,solid (VLS) growth mechanism for nanowires is presented. Although the focus is on nanowires, most of the concepts may be applicable to whiskers, nanotubes, and other unidirectional growth. Important concepts in the VLS mechanism such as preferred deposition, supersaturation, and nucleation are examined. Nanowire growth is feasible using a wide range of apparatuses, material systems, and growth conditions. For nanowire growth the unidirectional growth rate must be much higher than growth rates of other surfaces and interfaces. It is concluded that a general, system independent mechanism should describe why nanowires grow faster than the surrounding surfaces. This mechanism is based on preferential nucleation at the interface between a mediating material called the collector and a crystalline solid. The growth conditions used mean the probability of nucleation is low on most of the surfaces and interfaces. Nucleation at the collector-crystal interface is however different and of special significance is the edge of the collector-crystal interface where all three phases meet. Differences in nucleation due to different crystallographic interfaces can occur even in two phase systems. We briefly describe how these differences in nucleation may account for nanowire growth without a collector. Identifying the mechanism of nanowire growth by naming the three phases involved began with the naming of the VLS mechanism. Unfortunately this trend does not emphasize the important concepts of the mechanism and is only relevant to one three phase system. We therefore suggest the generally applicable term preferential interface nucleation as a replacement for these different names focusing on a unifying mechanism in nanowire growth. [source] Forensic Age-at-Death Estimation from the Human Sacrum,JOURNAL OF FORENSIC SCIENCES, Issue 2 2009Nicholas V. Passalacqua M.S. Abstract:, A new method is described here that incorporates seven developmental and degenerative changes for estimating chronological age from morphological features of the human sacrum. The construction of this method involved multiple stages of trait identification, character-state definition and age correlation, rank-order phase development, and percent-correct sample testing with phase and sample aggregation, all of which resulted in a six-phase component system for application on modern individuals. This phase system was first developed on European American male and female samples from the Hamann-Todd collection; then tested on African American male and female Hamann-Todd samples as well as European American male and females from the WM Bass collection to examine possible sex and/or ancestry differences. Variation in age estimates due to sex and ancestry was negligible; thus, the multiple samples were all pooled creating a robust method with a large sample size. Overall age ranges increase in width at two standard deviations as is expected from degenerative age-related processes but retain utility in forensic situations. [source] Kinetic and dynamic study of liquid,liquid extraction of copper in a HFMC: Experimentation, modeling, and simulationAICHE JOURNAL, Issue 6 2010M. Younas Abstract In this work, we present the dispersion-free liquid,liquid extraction of copper from aqueous streams in a hollow fiber membrane contactor (HFMC). Copper has been transferred from aqueous solutions to heptane using LIX 84-I (2-hydroxy-5-nonylacetephenone oxime) as extracting agent. In a first step, batch experiments have been performed to identify the extraction kinetics and to measure the partition coefficient of copper aqueous-organic phase system. Then, the continuous recycled-base extraction process has been performed in a HFMC Liqui-Cel® module. The module has been modeled from resistance in series concept to gain the exit concentrations, which are used to develop a dynamic model to calculate the exit concentration of copper from the output of storage tanks. The model has been validated with experimental data at various operating conditions. The integrated process model algorithm was scripted in MATLAB® 7.4 R (a). Simulations have been made for a range of different operating parameters to determine the optimum criterion conditions. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Molecular dynamics simulations of hydrotropic solubilization and self-aggregation of nicotinamideJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 7 2010Yong Cui Abstract Hydrotropy is a phenomenon where the presence of a large quantity of one solute enhances the solubility of another solute. The mechanism of this phenomenon remains elusive and a topic of debate. This study employed molecular dynamics simulation to investigate the hydrotropic mechanism of a model system consisting of a hydrotropic agent, nicotinamide (NA), a poorly water-soluble solute, PG-300995 (PG), and water. Our study demonstrates that NA and PG undergo significant aggregation in the aqueous solution, a result correlating closely to the self-aggregation of NA under the same conditions. The correlations are found both structurally and dynamically, suggesting that the self-aggregation of NA may be a prerequisite, or at least a major contributor, to its hydrotropic effects. The self-aggregation of NA allows the segregation of the hydrophobic solute from water, a key step to ease the energy increase to the system. Energetic evidences directly show that the hydrotropic solubilization is favored in the presence of NA aggregation. These results are in strong support of the molecular aggregation hypothesis for hydrotropic solubilization. Additionally, it is found that the restoration of water,water HBs from the interference of the NA and PG molecules plays an important role for the aggregation. The HBs between the solute and the hydrotrope may contribute, but is not vital, to the aggregation and hence the hydrotropic effects. The dynamic data confirm that the aggregates, while remain in liquid state, are much more active dynamically than a pure NA amorphous/liquid phase under the same temperature and pressure. By equilibrating an NA amorphous agglomerate with water, it is found that the aggregation state, rather than an NA,water two phase system, is the equilibrium state of the NA,+,water system. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:3048,3059, 2010 [source] Combining state estimator and disturbance observer in discrete-time sliding mode controller design,ASIAN JOURNAL OF CONTROL, Issue 5 2008Jeang-Lin Chang Abstract In response to a multiple input/multiple output discrete-time linear system with mismatched disturbances, an algorithm capable of performing estimated system states and unknown disturbances is proposed first, and then followed with the design of the controller. Attributed to the fact that both system states and disturbances can be estimated simultaneously with our proposed method, the estimation error is constrained at less than O(T) as the disturbance between the two sampling points is insignificant. In addition, the estimated system states and disturbances are then to be used in the controller when implementing our algorithm in a non-minimum phase system (with respect to the relation between the output and the disturbance). The tracking error is constrained in a small bounded region and the system stability is guaranteed. Finally, a numerical example is presented to demonstrate the applicability of the proposed control scheme. Copyright © 2008 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source] COMMENTS ON «TUNING RULES FOR THE PID CONTROLLER USING A DMC STRATEGY»ASIAN JOURNAL OF CONTROL, Issue 4 2004Jing-Chung Shen ABSTRACT It is pointed out that the tuning rules for under damped system and non-minimum phase system that given by Haeri is incorrect. [source] Improved reactor performance and operability in the biotransformation of carveol to carvone using a solid,liquid two-phase partitioning bioreactorBIOTECHNOLOGY & BIOENGINEERING, Issue 5 2008Jenna L.E. Morrish Abstract In an effort to improve reactor performance and process operability, the microbial biotransformation of (,)- trans -carveol to (R)-(,)-carvone by hydrophobic Rhodococcus erythropolis DCL14 was carried out in a two phase partitioning bioreactor (TPPB) with solid polymer beads acting as the partitioning phase. Previous work had demonstrated that the substrate and product become inhibitory to the organism at elevated aqueous concentrations and the use of an immiscible second phase in the bioreactor was intended to provide a reservoir for substrates to be delivered to the aqueous phase based on the metabolic rate of the cells, while also acting as a sink to uptake the product as it is produced. The biotransformation was previously undertaken in a two liquid phase TPPB with 1-dodecene and with silicone oil as the immiscible second phase and, although improvement in the reactor performance was obtained relative to a single phase system, the hydrophobic nature of the organism caused the formation of severe emulsions leading to significant operational challenges. In the present work, eight types of polymer beads were screened for their suitability for use in a solid,liquid TPPB for this biotransformation. The use of selected solid polymer beads as the second phase completely prevented emulsion formation and therefore improved overall operability of the reactor. Three modes of solid,liquid TPPB operation were considered: the use of a single polymer bead type (styrene/butadiene copolymer) in the reactor, the use of a mixture of polymer beads in the reactor (styrene/butadiene copolymer plus Hytrel® 8206), and the use of one type of polymer beads in the reactor (styrene/butadiene copolymer), and another bead type (Hytrel® 8206) in an external column through which fermentation medium was recirculated. This last configuration achieved the best reactor performance with 7 times more substrate being added throughout the biotransformation relative to a single aqueous phase benchmark reactor and 2.7 times more substrate being added relative to the best two liquid TPPB case. Carvone was quantitatively recovered from the polymer beads via single stage extraction into methanol, allowing for bead re-use. Biotechnol. Bioeng. © 2008 Wiley Periodicals, Inc. [source] Carbon metabolism and product inhibition determine the epoxidation efficiency of solvent-tolerant Pseudomonas sp. strain VLB120,CBIOTECHNOLOGY & BIOENGINEERING, Issue 6 2007Jin-Byung Park Abstract Utilization of solvent tolerant bacteria as biocatalysts has been suggested to enable or improve bioprocesses for the production of toxic compounds. Here, we studied the relevance of solvent (product) tolerance and inhibition, carbon metabolism, and the stability of biocatalytic activity in such a bioprocess. Styrene degrading Pseudomonas sp. strain VLB120 is shown to be solvent tolerant and was engineered to produce enantiopure (S)-styrene oxide from styrene. Whereas glucose as sole source for carbon and energy allowed efficient styrene epoxidation at rates up to 97 µmol/min/(g cell dry weight), citrate was found to repress epoxidation by the engineered Pseudomonas sp. strain VLB120,C emphasizing that carbon source selection and control is critical. In comparison to recombinant Escherichia coli, the VLB120,C-strain tolerated higher toxic product levels but showed less stable activities during fed-batch cultivation in a two-liquid phase system. Epoxidation activities of the VLB120,C-strain decreased at product concentrations above 130 mM in the organic phase. During continuous two-liquid phase cultivations at organic-phase product concentrations of up to 85 mM, the VLB120,C-strain showed stable activities and, as compared to recombinant E. coli, a more efficient glucose metabolism resulting in a 22% higher volumetric productivity. Kinetic analyses indicated that activities were limited by the styrene concentration and not by other factors such as NADH availability or catabolite repression. In conclusion, the stability of activity of the solvent tolerant VLB120,C-strain can be considered critical at elevated toxic product levels, whereas the efficient carbon and energy metabolism of this Pseudomonas strain augurs well for productive continuous processing. Biotechnol. Bioeng. 2007;98: 1219,1229. © 2007 Wiley Periodicals, Inc. [source] Preferential Interface Nucleation: An Expansion of the VLS Growth Mechanism for NanowiresADVANCED MATERIALS, Issue 2 2009Brent A. Wacaser Abstract A review and expansion of the fundamental processes of the vapor,liquid,solid (VLS) growth mechanism for nanowires is presented. Although the focus is on nanowires, most of the concepts may be applicable to whiskers, nanotubes, and other unidirectional growth. Important concepts in the VLS mechanism such as preferred deposition, supersaturation, and nucleation are examined. Nanowire growth is feasible using a wide range of apparatuses, material systems, and growth conditions. For nanowire growth the unidirectional growth rate must be much higher than growth rates of other surfaces and interfaces. It is concluded that a general, system independent mechanism should describe why nanowires grow faster than the surrounding surfaces. This mechanism is based on preferential nucleation at the interface between a mediating material called the collector and a crystalline solid. The growth conditions used mean the probability of nucleation is low on most of the surfaces and interfaces. Nucleation at the collector-crystal interface is however different and of special significance is the edge of the collector-crystal interface where all three phases meet. Differences in nucleation due to different crystallographic interfaces can occur even in two phase systems. We briefly describe how these differences in nucleation may account for nanowire growth without a collector. Identifying the mechanism of nanowire growth by naming the three phases involved began with the naming of the VLS mechanism. Unfortunately this trend does not emphasize the important concepts of the mechanism and is only relevant to one three phase system. We therefore suggest the generally applicable term preferential interface nucleation as a replacement for these different names focusing on a unifying mechanism in nanowire growth. [source] Direct adaptive command following and disturbance rejection for minimum phase systems with unknown relative degreeINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 1 2007Jesse B. Hoagg Abstract This paper considers parameter-monotonic direct adaptive command following and disturbance rejection for single-input single-output minimum-phase linear time-invariant systems with knowledge of the sign of the high-frequency gain (first non-zero Markov parameter) and an upper bound on the magnitude of the high-frequency gain. We assume that the command and disturbance signals are generated by a linear system with known characteristic polynomial. Furthermore, we assume that the command signal is measured, but the disturbance signal is unmeasured. The first part of the paper is devoted to a fixed-gain analysis of a high-gain-stabilizing dynamic compensator for command following and disturbance rejection. The compensator utilizes a Fibonacci series construction to control systems with unknown-but-bounded relative degree. We then introduce a parameter-monotonic adaptive law and guarantee asymptotic command following and disturbance rejection. Copyright © 2006 John Wiley & Sons, Ltd. [source] A new tracking controller for discrete-time SISO non minimum phase systems,ASIAN JOURNAL OF CONTROL, Issue 1 2010Mohsen Ruzbehani Abstract A new tracking controller for discrete-time Single Input Single Output (SISO) non-minimum phase (NMP) systems is presented. In the proposed method, after cancelation of poles and cancelable zeros of the system, the controller adds some NMP zeros to compensate the effect of NMP zero (zeros) of the system. As a result, the phase of the overall transfer function will be almost linear and its magnitude approaches unity for all frequencies. The method can be applied even to the systems with complex conjugate NMP zeros. As well, it is applicable to the systems for which the conventional methods cannot properly be used. Furthermore, a generalization of method to continuous-time systems is another given result. Several examples are provided to illustrate the effectiveness of the method. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source] Adaptive Dynamic Output Feedback Stabilisation of Nonlinear SystemsASIAN JOURNAL OF CONTROL, Issue 3 2002A. Ilchmann ABSTRACT An adaptive dynamical output feedback controller is introduced for a class of nonlinear non-minimum phase systems. This adaptive controller achieves practical stabilisation, that means the output will asymptotically tend to a pre-specified neighbourhood of the origin. In case of linear systems, we can even prove adaptive stabilisation. [source] Bioproduction of the aroma compound 2-Phenylethanol in a solid,liquid two-phase partitioning bioreactor system by Kluyveromyces marxianusBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2009Fang Gao Abstract The rose-like aroma compound 2-phenylethanol (2-PE) is an important fragrance and flavor ingredient. Several yeast strains are able to convert l -phenylalanine (l -phe) to 2-PE among which Kluyveromyces marxianus has shown promising results. The limitation of this process is the low product concentration and productivity primarily due to end product inhibition. This study explored the possibility and benefits of using a solid,liquid Two-Phase Partition Bioreactor (TPPB) system as an in situ product removal technique. The system applies polymer beads as the sequestering immiscible phase to partition 2-PE and reduce the aqueous 2-PE concentration to non-inhibitory levels. Among six polymers screened for extracting 2-PE, Hytrel® 8206 performed best with a partition coefficient of 79. The desired product stored in the polymer was ultimately extracted using methanol. A 3,L working volume solid,liquid batch mode TPPB using 500,g Hytrel® as the sequestering phase generated a final overall 2-PE concentration of 13.7,g/L, the highest reported in the current literature. This was based on a polymer phase concentration of 88.74,g/L and aqueous phase concentration of 1.2,g/L. Even better results were achieved via contact with more polymers (approximately 900,g) with the aqueous phase applying a semi-continuous reactor configuration. In this system, a final 2-PE concentration (overall) of 20.4,g/L was achieved with 1.4,g/L in the aqueous and 97,g/L in the polymer phase. The overall productivities of these two reactor systems were 0.38 and 0.43,g/L,h, respectively. This is the first report in the literature of the use of a polymer sequestering phase to enhance the bioproduction of 2-PE, and exceeds the performance of two-liquid phase systems in terms of productivity as well as ease of operation (no emulsions) and ultimate product recovery. Biotechnol. Bioeng. 2009; 104: 332,339 © 2009 Wiley Periodicals, Inc. [source] | |||||||||||||