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Conventional Systems (conventional + system)
Selected AbstractsThe First Teleautomatic Low-Voltage Prosthesis With Multiple Therapeutic Applications: A New Version of the German Artificial Sphincter SystemARTIFICIAL ORGANS, Issue 8 2010Olaf Ruthmann Abstract To date, there are no artificial sphincter prostheses for urinary or fecal incontinence that may be implemented elsewhere instead, for example, in the upper gastrointestinal tract. Conventional systems are conceptually similar but are constructed specifically for distinct applications and are manual in operation. The German Artificial Sphincter System (GASS) II is the evolution of a highly integrative, modular, telemetric sphincter prosthesis with more than one application. Redesigning and integrating multilayer actuators into the pump allows us to reduce the input voltage to ,10 to +20 V (VPP = 30 V). This provides for a flow rate of 2.23 mL/min and a counterpressure stability of 260 mbar. Furthermore, multiple applications have become feasible due to our standardized connection system, therapy-specific compression units, and application-specific software. These innovations allow us to integrate not only severe fecal and urinary incontinence, erectile dysfunction, and therapy-resistant reflux disease, but also morbid adiposity into the gamut of therapeutic GASS applications. [source] Cushioning the pressure vibration of a zeolite concentrator system using a decoupled balancing duct systemENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 2 2007Feng-Tang Chang Abstract A honeycomb Zeolite Rotor Concentrator (HZRC) is the main air pollution control device utilized by many semiconductor and optoelectronics manufacturers. Various plant exhaust streams are collected and then transferred to the HZRC for decontamination. In a conventional HZRC, the exhaust fan movement and the switching between different air ducts can cause significant duct pressure variations resulting in production interruption. The minimization of pressure fluctuations to ensure continuous operation of production lines while maintaining a high volatile organic compounds (VOCs) removal efficiency is essential for exhaust treatment in these high technology manufactures. The article introduces a decoupled balancing duct system (DBDS) for controlling the airflows to achieve a balanced pressure in the HZRC system by adding a flow rate control device to the VOCs loaded stream bypass duct of a conventional system. Performance comparisons of HZRC with DBDS and other air flow control systems used by the wafer manufacturers in Hsinchu Science Park, Taiwan are presented. DBDS system had been proved effectively to stabilize the pressure in the airflow ducts, and thus avoided pressure fluctuations; it helped to achieve a high VOCs removal efficiency while ensuring the stability of the HZRC. © 2007 American Institute of Chemical Engineers Environ Prog, 2007 [source] An early warning system for financial crisis using a stock market instability indexEXPERT SYSTEMS, Issue 3 2009Dong Ha Kim Abstract: This paper proposes to utilize a stock market instability index (SMII) to develop an early warning system for financial crisis. The system focuses on measuring the differences between the current market conditions and the conditions of the past when the market was stable. Technically the system evaluates the current time series against the past stable time series modelled by an asymptotic stationary autoregressive model via artificial neural networks. Advantageously accessible to extensive resources, the system turns out better results than the conventional system which detects similarities between the conditions of the current market and the conditions of previous markets that were in crisis. Therefore, it should be considered as a more advanced tool to prevent financial crises than the conventional one. As an empirical example, an SMII for the Korean stock market is developed in order to demonstrate its potential usefulness as an early warning system. [source] Comparison of conventional and ultrasound-assisted extraction of carvone and limonene from caraway seedsFLAVOUR AND FRAGRANCE JOURNAL, Issue 3 2004Smain Chemat Abstract Extraction experiments with hexane were carried out at atmospheric pressure in Soxhlet, conventional and ultrasound extractions of ,aked caraway seeds, and detailed results are given for two major plant extract components, carvone and limonene. The results indicate that carvone yield and plant extract quality are better in ultrasound extraction compared to those given by conventional methodology. Extraction rates of carvone and limonene reported that ultrasound-assisted extraction was 1.3,2 times more rapid, depending on temperature, than a conventional system, according to the rate constant obtained during the initial 10 minutes of extraction. Moreover, the SEM micrographs provided more evidence for the mechanical effects of ultrasound, mainly appearing on cell walls and shown by the destruction of cells, faulitating the release of their contents, in contrast to conventional maceration or extraction, which involve diffusion of plant extracts across glandular walls and causing cell rupture over longer time periods. Copyright © 2004 John Wiley & Sons, Ltd. [source] Use of low frequencies for sub-basalt imagingGEOPHYSICAL PROSPECTING, Issue 3 2003Anton Ziolkowski ABSTRACT Many prospective passive ocean margins are covered by large areas of basalts. These basalts are often extremely heterogeneous and scatter the seismic energy of the conventional seismic reflection system so that it becomes difficult to obtain information on deeper reflectors. Since high frequencies are scattered more than low frequencies, we argue that the acquisition system for sub-basalt targets should be modified to emphasize the low frequencies, using much larger airguns, and towing the source and receivers at about 20 m depth. In the summer of 2001 we obtained seismic reflection data over basalt in the northeast Atlantic using a system modified to enhance the low-frequency energy. These new data show deep reflections that are not visible on lines shot in the same places with a conventional system. [source] Elevated atmospheric CO2 effects on biomass production and soil carbon in conventional and conservation cropping systemsGLOBAL CHANGE BIOLOGY, Issue 4 2005Stephen A. Prior Abstract Increasing atmospheric CO2 concentration has led to concerns about potential effects on production agriculture as well as agriculture's role in sequestering C. In the fall of 1997, a study was initiated to compare the response of two crop management systems (conventional and conservation) to elevated CO2. The study used a split-plot design replicated three times with two management systems as main plots and two CO2 levels (ambient=375 ,L L,1 and elevated CO2=683 ,L L,1) as split-plots using open-top chambers on a Decatur silt loam (clayey, kaolinitic, thermic Rhodic Paleudults). The conventional system was a grain sorghum (Sorghum bicolor (L.) Moench.) and soybean (Glycine max (L.) Merr.) rotation with winter fallow and spring tillage practices. In the conservation system, sorghum and soybean were rotated and three cover crops were used (crimson clover (Trifolium incarnatum L.), sunn hemp (Crotalaria juncea L.), and wheat (Triticum aestivum L.)) under no-tillage practices. The effect of management on soil C and biomass responses over two cropping cycles (4 years) were evaluated. In the conservation system, cover crop residue (clover, sunn hemp, and wheat) was increased by elevated CO2, but CO2 effects on weed residue were variable in the conventional system. Elevated CO2 had a greater effect on increasing soybean residue as compared with sorghum, and grain yield increases were greater for soybean followed by wheat and sorghum. Differences in sorghum and soybean residue production within the different management systems were small and variable. Cumulative residue inputs were increased by elevated CO2 and conservation management. Greater inputs resulted in a substantial increase in soil C concentration at the 0,5 cm depth increment in the conservation system under CO2 -enriched conditions. Smaller shifts in soil C were noted at greater depths (5,10 and 15,30 cm) because of management or CO2 level. Results suggest that with conservation management in an elevated CO2 environment, greater residue amounts could increase soil C storage as well as increase ground cover. [source] Performance analysis of a modified two-bed solar-adsorption air-conditioning systemINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 7 2009K. Sumathy Abstract This paper presents the description and operation of a solar-powered modified two-bed adsorption air-conditioning system with activated carbon and methanol as the working pair. A simple lumped parameter model is established to investigate the performance of this continuous adsorption cycle consisting of a twin adsorber immersed in water tanks, which is measured in terms of the temperature histories, gross solar coefficient of performance and specific cooling power. In addition, the influence of some important design and operational parameters on the performance of the system has been studied. Compared with the conventional system, it is found that the modified system can operate more cycles and at a higher efficiency. The parametric study also shows that the adsorbent mass and the solar collector area have significant effect on the system performance as well as on the system size. Finally, when the system uses gas heater as an auxiliary heat source, it is found that the system can provide a stable cooling effect for a longer period of operation. Copyright © 2008 John Wiley & Sons, Ltd. [source] A new concept for an osmotic energy converterINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 15 2001A. Seppälä Abstract A new concept for an osmosis power generation system is presented. While the power production of a conventional system is based on continuous, increasing volumetric flow of solution directed to a turbine, the new concept is based on the pressurizing of fluids by osmosis. Two different new concepts were studied. In the first case, the osmotic module consists of the osmotic membranes, fresh water and solution. In the second case, gas is included in the solution part of the module. Consequently, the new system without gas was found to result in more than 2.5 times higher power values than the conventional concept. Copyright © 2001 John Wiley & Sons, Ltd. [source] A Study of Gypsum Scale Formation using Quartz Crystal MicrobalanceASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1-2 2006T. A. Hoang The quartz crystal microbalance (QCM) has been used extensively as a mass sensor due to its extremely high sensitivity to small mass loadings. Conventional measurement of the amount of scale deposited on a surface is restricted by the sensitivity limit of analytical balances. Thefirst attempt to investigate the deposition of gypsum scale on a surface using a rotating electrochemical QCMsystem was carried out to investigate the eflects of many factors at the early stages of scale formation. Results indicated there was almost no induction time for this system, and the long induction time observed in the conventional system was due to the limited sensitivity of the analytical balance. A slow increase in scale amount was observed at the beginning of the scaling process as shown by the plot offrequency or mass change against time. After this period the curve rises steeply and becomes almost linear. The supersaturation level of the solutions and the rotating speed have significant effects on the gypsum scaling. A QCM flow-cell system has also been developed to investigate the scaling of gypsum on the pipe wall. This system is similar to a conventional pipe flow system except that its size is much smaller and the deposition of scales can be monitored with the QCM electrode throughout the scaling process. The mass change is plotted against time and results are compared for the rotating QCM system and the conventional system. It is noticed that the formation of gypsum on the QCM electrode is greatly dependent on both the supersaturation of the solution and the flow rate of the fluid passing through the flow cell. [source] Effects of new adhesive resin root canal filling materials on vertical root fracturesAUSTRALIAN ENDODONTIC JOURNAL, Issue 1 2010Takahiro Hanada dds Abstract The aim of this study was to compare the fracture resistance of roots following root canal therapy using the RC Sealer system, the Epiphany system and the conventional system of gutta-percha and Sealapex. Fifty-six maxillary central incisors were divided into eight groups of seven teeth each, according to master apical file size and obturation systems. Obturation materials in the root canal were vertically loaded using a universal testing machine. Fracture loads were analysed by anova and Tukey comparison, and fracture patterns were analysed with ordinal logistic regression. Master apical file size 80 had a significantly lower fracture load than size 40 (P < 0.05). The groups obturated using the Resilon Cone and the Epiphany Sealer had significantly lower fracture loads than the other groups (P < 0.05). There was no significant improvement in resistance to vertical root fractures using the examined adhesive resin root canal filling systems, compared with conventional gutta-percha and sealer. [source] Self-centering structural systems with combination of hysteretic and viscous energy dissipationsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 10 2010Weng Yuen Kam Abstract This paper presents an innovative set of high-seismic-resistant structural systems termed Advanced Flag-Shaped (AFS) systems, where self-centering elements are used with combinations of various alternative energy dissipation elements (hysteretic, viscous or visco-elasto-plastic) in series and/or in parallel. AFS systems is developed using the rationale of combining velocity-dependent with displacement-dependent energy dissipation for self-centering systems, particularly to counteract near-fault earthquakes. Non-linear time-history analyses (NLTHA) on a set of four single-degree-of-freedom (SDOF) systems under a suite of 20 far-field and 20 near-fault ground motions are used to compare the seismic performance of AFS systems with the conventional systems. It is shown that AFS systems with a combination in parallel of hysteretic and viscous energy dissipations achieved greater performance in terms of the three performance indices. Furthermore, the use of friction slip in series of viscous energy dissipation is shown to limit the peak response acceleration and induced base-shear. An extensive parametric analysis is carried out to investigate the influence of two design parameters, ,1 and ,2 on the response of SDOF AFS systems with initial periods ranging from 0.2 to 3.0,s and with various strength levels when subjected to far-field and near-fault earthquakes. For the design of self-centering systems with combined hysteretic and viscous energy dissipation (AFS) systems, ,1 is recommended to be in the range of 0.8,1.6 while ,2 to be between 0.25 and 0.75 to ensure sufficient self-centering and energy dissipation capacities, respectively. Copyright © 2010 John Wiley & Sons, Ltd. [source] Perforated Sheets Exhibiting Negative Poisson's Ratios,ADVANCED ENGINEERING MATERIALS, Issue 6 2010Joseph N. Grima Abstract Sheets made from readily available conventional materials containing diamond or star shaped perforations are shown to exhibit various Poisson's ratio values which could also be negative (auxetic). This behavior may be exhibited in both tension and compression and can be explained through models based on "rotating rigid units." This provides an easy manner for the manufacture of auxetic or conventional systems at any scale which can be tailor made to exhibit particular values of the Poisson's ratio. [source] Sequential detection CDMA multi-user receiverINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 6 2005Mitsuhiro Tomita Abstract This paper proposes a sequential detection technique for a multi-user receiver that is constructed over a CDMA system. In this system, the transmitter transmits a symbol made by spreading the spectrum with an enveloped sequence protected by guard sequences, and a receiver de-modulates the core-sequence part of the received symbol with either a de-correlating detector or an MMSE detector. The advantage is that performance is improved without reducing the number of the active users. This sequential detection system estimates the best user signal from all of the soft outputs, which are obtained by solving a de-correlating system of equations. Once detected, the best user component is removed from the received symbol. The resultant symbol composed of the remaining user signals is then sequentially detected by repeating the method stated above. A computer simulation of this system reveals a remarkable improvement in the bit-error rate performance compared to conventional systems. Copyright © 2005 John Wiley & Sons, Ltd. [source] Sharpless Asymmetric Dihydroxylation of Olefins in WaterSurfactant Media with Recycling of the Catalytic System by Membrane NanofiltrationADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2008Abstract This paper presents a new and more sustainable alternative approach for the Sharpless catalytic asymmetric dihydroxylation (AD) of olefins using a water/surfactant system as reaction media. The AD reaction was performed using several cationic and anionic surfactants allowing yields and enantiomeric excesses higher or comparable with the conventional systems (using organic mixtures). The use of this water/surfactant medium offers the additional advantage of performing the reactions without the need of a slow addition of olefins. Asymmetric dihydroxylation of 1-hexene in a 1.5,mM sodium cholate aqueous solution, using N -methylmorpholine N -oxide (NMO) as co-oxidant was selected as model system to evaluate the feasibility of recycling the Sharpless catalytic system by nanofiltration. The reaction media was processed by nanofiltration, the product was isolated in the permeate, whereas the catalytic system and surfactant were retained by the membrane and recycled through six successive reactions, improving the catalyst turn-over number. The experimental results were compared with the ones calculated on the basis of mass balances, membrane rejections to product and reaction yields. [source] Removing pharmaceuticals and endocrine-disrupting compounds from wastewater by photocatalysisJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2 2007Omatoyo K Dalrymple Abstract Widespread concerns continue to be raised about the increasing presence of emerging contaminants in the environment. Such compounds include a wide range of persistent organic chemicals, including pharmaceuticals and endocrine-disrupting compounds whose effects are poorly known, often because they have only begun to enter the environment and are showing up in wastewater treatment plants. The occurrence and behavior of these compounds in wastewater are key issues with regard to water reclamation and reuse. Treatment plants are now faced with the challenge of removing the compounds from their effluent before they enter natural waterways. In this regard, photocatalysis is a promising technology for wastewater treatment that offers many advantages over conventional and some advanced treatment options. The application of photocatalysis for the removal of pharmaceuticals and endocrine-disrupting compounds for wastewater is comprehensively surveyed in this paper. This treatment technology is not intended to replace conventional systems but to supplement for higher-quality effluent. The assessment places emphasis on the process fundamentals, advantages, and disadvantages of the technology. It also focuses on the current limitations and future research needs. Copyright © 2007 Society of Chemical Industry [source] Biological treatment of saline wastewaters from marine-products processing factories by a fixed-bed reactorJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2002Neji Gharsallah Abstract Wastewaters generated by a factory processing marine products are characterized by high concentrations of organic compounds and salt constituents (>30,g,dm,3). Biological treatment of these saline wastewaters in conventional systems usually results in low chemical oxygen demand (COD) removal efficiency, because of the plasmolysis of the organisms. In order to overcome this problem a specific flora was adapted to the wastewater from the fish-processing industry by a gradual increase in salt concentrations. Biological treatment of this effluent was then studied in a continuous fixed biofilm reactor. Experiments were conducted at different organic loading rates (OLR), varying from 250 to 1000,mg,COD,dm,3 day,1. Under low OLR (250,mg,COD,dm,3 day,1), COD and total organic carbon (TOC) removal efficiencies were 92.5 and 95.4%, respectively. Thereafter, fluctuations in COD and TOC were observed during the experiment, provoked by the progressive increase of OLR and the nature of the wastewater introduced. High COD (87%) and TOC (99%) removal efficiencies were obtained at 1000,mg,COD,dm,3 day,1. © 2002 Society of Chemical Industry [source] Thermal machines based on surface energy of wetting: Thermodynamic analysisAICHE JOURNAL, Issue 3 2003A. Laouir This work proposes an original thermodynamic-energetic analysis of the feasibility and ideal performance of thermal machines based on the wetting phenomenon proposed by V. A. Eroshenko. The extension or contraction of a liquid film is taken as a "tutorial" example to introduce the basic thermodynamic relations of this 2-D transformation. It implies both mechanical and thermal effects, and this coupling allows conversion of heat to work (thermal engine) or conversely to pump heat (refrigeration/heat pump effect). A similar approach is then developed for the interface between a liquid and a highly microporous solid, having a large internal surface area. The thermodynamic behavior of this interface involves as state variables the surface tension of the liquid, the contact angle, and their dependence on temperature. Depending on the relative magnitude and sign of these quantities, and, therefore, on the working couple and the temperature range, a variety of machine cycles are feasible, or excluded, and a method is proposed for a comprehensive inventory. Order-of-magnitude calculations of the energy densities are presented based on the existing experimental data for several systems involving water as the fluid. The tentative conclusions are that the energy densities are very small on a mass basis compared to conventional systems based on vaporization, but the contrary is true on a volume basis because the phase transformation (extension of the surface) occurs in a condensed state. There may, therefore, be some niches for thermal machines of this type, but they remain to be identified and validated. [source] Grain mineral concentrations and yield of wheat grown under organic and conventional managementJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 3 2004MH Ryan Abstract On the low-P soils in southeastern Australia, organic crops differ from conventional ones primarily in the use of relatively insoluble, as opposed to soluble, P fertilisers and in the non-use of herbicides. As organic management, particularly elimination of soluble fertilisers, is often claimed to enhance grain mineral concentrations, we examined grain from wheat on paired organic and conventional farms in two sets of experiments: (1) four pairs of commercial crops (1991,1993); and (2) fertiliser experiments on one farm pair where nil fertiliser was compared with 40 kg ha,1 of P as either relatively insoluble reactive phosphate rock or more soluble superphosphate (1991 and 1992). All wheat was grown following a 2,6 year legume-based pasture phase. Both conventional management and the superphosphate treatment greatly increased yields but reduced colonisation by mycorrhizal fungi. While only minor variations occurred in grain N, K, Mg, Ca, S and Fe concentrations, conventional grain had lower Zn and Cu but higher Mn and P than organic grain. These differences were ascribed to: soluble P fertilisers increasing P uptake but reducing mycorrhizal colonisation and thereby reducing Zn uptake and enhancing Mn uptake; dilution of Cu in heavier crops; and past lime applications on the organic farm decreasing Mn availability. These variations in grain minerals had nutritional implications primarily favouring the organic grain; however, organic management and, specifically, elimination of soluble fertilisers did not induce dramatic increases in grain mineral concentrations. In addition, organic management was coupled with yield reductions of 17,84 per cent due to P limitation and weeds. The impact of large regional variations in the characteristics of organic and conventional systems on the general applicability of the results from this study and other similar studies is discussed. Copyright © 2004 Society of Chemical Industry [source] Soil chemical quality changes and implications for fertilizer management after 11 years of no-tillage wheat production systems in semiarid MoroccoLAND DEGRADATION AND DEVELOPMENT, Issue 6 2001R. Mrabet Abstract A long-term experiment comparing no-till with conventional tillage systems across five rotations was evaluated 11 years after initiation. The objectives of the present paper are (1) to report differences in soil chemical properties (namely soil organic matter, total nitrogen, phosphorus, potassium and pH) that have resulted by converting from conventional to no-till under contrasting cropping systems and (2) to draw tentative conclusions and recommendations on fertility status and fertilizer use and management. Soil in the no-till system had increased surface soil organic C levels relative to conventional tillage regardless of rotation. In addition, depending on the rotation, the N and P content of the soil improved with no-till compared with conventional tillage. In other words, no-till has helped to retain soil organic matter (SOM), conserved more N, and resulted in increased extractable P and exchangeable K concentrations in the upper root-zone. Hence, wheat produced in a no-till system may receive more nutrients from decomposition of SOM and acidification of the seed zone. It is possible that lesser amounts of fertilizer nutrients will be needed because of the greater efficiency of nutrient cycling in no-till systems relative to conventional systems. Copyright © 2001 John Wiley & Sons, Ltd. [source] Microsystems for Optical Cell Detection: Near versus Far FieldPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 1 2008Stefan Kostner Abstract Optical flow cytometry is a process where physical and (bio-) chemical parameters of single biological cells can be obtained in a flow-through setup by optical measurement techniques. Unlike conventional systems, where measurements are conducted in the optical far field, the proposed system senses the cell's optical projection in the near field by using integrated photodiodes. This allows for the attainment of additional parameters, e.g., size and shape, which are usually hidden in the far field. In addition, parameters such as refractive index and absorption of the cell influence the sensor signal. Additionally, with another setup, a different approach is followed to measure similar parameters with external detection using a DVD laser pickup head and a microchannel equipped with a mirror. This low-cost setup does not measure in the near field, and therefore, is dedicated to different parameters. In this contribution, results from measurements with polystyrene particles and biological cells (yeast and Chinese hamster ovary) are presented and the advantages and limitations of both systems are outlined. [source] Reformer and membrane modules plant to optimize natural gas conversion to hydrogenASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2009M. De Falco Abstract Membrane technology may play a crucial role in the efficient production of hydrogen from natural gas and heavy hydrocarbons. The present work assesses the performance of a hydrogen production plant utilizing by reformer and membrane modules (RMM), by which the hydrogen produced in reaction units is separated by Pd-based membranes. A major advantage of RMM architecture is the shift of chemical equilibria favoring hydrogen production due to the removal of hydrogen through membranes at each reaction step, thus improving hydrogen yield while simultaneously allowing methane conversion at temperatures below 650 °C. Lower operating temperatures allow location of the modules downstream of a gas turbine, achieving an efficient hybrid system producing electric power and hydrogen with a significant reduction in energy consumption of approximately 10% relative to conventional systems. Fundamental concepts are analyzed and integrated into a process scheme. Effects of variables including reactor temperature outlet, steam-to-carbon ratio and recycle ratio throughout pinch and sensitivity analysis are described. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Oligothiophenes Nano-organized on a Cyclotetrasiloxane Scaffold as a Model of a Silica-Bound Monolayer: Evidence for Intramolecular Excimer FormationCHEMISTRY - A EUROPEAN JOURNAL, Issue 46 2009Wojciech Mróz Abstract Excimer formation in a new class of terthiophene-based fluorophores covalently bonded to a cyclotetrasiloxane scaffold has been demonstrated and the photophysical process ruling it has been investigated in detail and modeled theoretically. In contrast to the conventional systems in which long-living fluorophores such as pyrene are linked in the same molecule, an excimer is formed only when two terthiophene-based branches nano-organized on the same cyclotetrasiloxane scaffold are close enough together when excitation takes place. In such a case, excimer formation is extremely efficient, and the new bound excited states are quite stable. [source] Embedded Phases: A Way to Active and Stable CatalystsCHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 1 2010Loredana De, Rogatis Dr. Abstract Industrial catalysts are typically made of nanosized metal particles, carried by a solid support. The extremely small size of the particles maximizes the surface area exposed to the reactant, leading to higher reactivity. Moreover, the higher the number of metal atoms in contact with the support, the better the catalyst performance. In addition, peculiar properties have been observed for some metal/metal oxide particles of critical sizes. However, thermal stability of these nanostructures is limited by their size; smaller the particle size, the lower the thermal stability. The ability to fabricate and control the structure of nanoparticles allows to influence the resulting properties and, ultimately, to design stable catalysts with the desired characteristics. Tuning particle sizes provides the possibility to modulate the catalytic activity. Unique and unexpected properties have been observed by confining/embedding metal nanoparticles in inorganic channels or cavities, which indeed offers new opportunities for the design of advanced catalytic sytems. Innovation in catalyst design is a powerful tool in realizing the goals of more green, efficient and sustainable industrial processes. The present Review focuses on the catalytic performance of noble metal- and non precious metal-based embedded catalysts with respect to traditional impregnated systems. Emphasis is dedicated to the improved thermal stability of these nanostructures compared to conventional systems. [source] | ||||||||||||||||||||||