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Manuel Almeida

University Salvador - UNIFACS, Design, Post-Doc

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ICMAB-CSIC

Instituto Superior Técnico

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Instituto Superior Técnico

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Papers by Manuel Almeida

Gold Complexes with Dithiothiophene Ligands: A Metal Based on a Neutral Molecule

Chemistry-a European Journal, 2001

The gold complexes n-Bu 4 N-[Au(a-tpdt) 2 ] (5), n-Bu 4 N[Au(dtpdt) 2 ] (4) and n-Bu 4 N[Au(tpdt)... more The gold complexes n-Bu 4 N-[Au(a-tpdt) 2 ] (5), n-Bu 4 N[Au(dtpdt) 2 ] (4) and n-Bu 4 N[Au(tpdt) 2 ] (6) based on new dithiothiophene ligands (a-tpdt 2,3-thiophenedithiolate, dtpdt 2,3dihydro-5,6-thiophenedithiolate and tpdt 3,4-thiophenedithiolate) have been prepared and characterised. These gold(iii) complexes are diamagnetic, but they can be oxidised with iodine to the paramagnetic compounds [Au(a-tpdt) 2 ] (8), [Au(dtpdt) 2 ] (7) and n-Bu 4 N-[{Au(tpdt) 2 } n$2 ] (9), which were isolated as fine powders and which exhibit paramagnetic susceptibilities that are almost temperature independent with room temperature values of 2.5 Â 10 À4 , 2.0 Â 10 À4 and 5 Â 10 À4 emu mol À1 , respectively. Interestingly, the neutral complex [Au(a-tpdt) 2 ] (8) as a polycrystalline sample displays the properties of a metallic system with a room temperature electrical conductivity of 6 S cm À1 and a thermoelectric power of 5.5 mV K À1 ; this is the first time that this metallic property has been observed in a molecular system based on a neutral species.

Gold Complexes with Dithiothiophene Ligands: A Metal Based on a Neutral Molecule

Chemistry-a European Journal, 2001

The gold complexes n-Bu 4 N-[Au(a-tpdt) 2 ] (5), n-Bu 4 N[Au(dtpdt) 2 ] (4) and n-Bu 4 N[Au(tpdt)... more The gold complexes n-Bu 4 N-[Au(a-tpdt) 2 ] (5), n-Bu 4 N[Au(dtpdt) 2 ] (4) and n-Bu 4 N[Au(tpdt) 2 ] (6) based on new dithiothiophene ligands (a-tpdt 2,3-thiophenedithiolate, dtpdt 2,3dihydro-5,6-thiophenedithiolate and tpdt 3,4-thiophenedithiolate) have been prepared and characterised. These gold(iii) complexes are diamagnetic, but they can be oxidised with iodine to the paramagnetic compounds [Au(a-tpdt) 2 ] (8), [Au(dtpdt) 2 ] (7) and n-Bu 4 N-[{Au(tpdt) 2 } n$2 ] (9), which were isolated as fine powders and which exhibit paramagnetic susceptibilities that are almost temperature independent with room temperature values of 2.5 Â 10 À4 , 2.0 Â 10 À4 and 5 Â 10 À4 emu mol À1 , respectively. Interestingly, the neutral complex [Au(a-tpdt) 2 ] (8) as a polycrystalline sample displays the properties of a metallic system with a room temperature electrical conductivity of 6 S cm À1 and a thermoelectric power of 5.5 mV K À1 ; this is the first time that this metallic property has been observed in a molecular system based on a neutral species.

An Organic Spin-Ladder Molecular Material

Angewandte Chemie-international Edition, 1997

Design Tools and Reusable Libraries for FPGA-Based Digital Circuits

This paper suggests tools that provide significant improvements in the design and verification of... more This paper suggests tools that provide significant improvements in the design and verification of FPGAbased digital circuits. These tools include reusable specifications of hardware components (modules) that have been proposed for two types of CAD environments; Xilinx ISE 5.x and Celoxica DK1. The components can be employed to implement both application-specific blocks from the selected area (mainly from the scope of combinatorial computations) and a number of interfaces that are very useful for interaction and data exchange with devices attached to a FPGA, such as LCD and touch panels, bus controllers, etc. The designed modules can be easily integrated into any application-specific digital system and used for visualizing the results, fast data transfer, debugging of internal sub-circuits, etc. They were constructed in such a way that their functionality can be either fixed or modifiable (both statically and dynamically). The latter capability was provided with the aid of re-loadable RAM-based blocks. To illustrate the capabilities of the tools suggested, four design examples are discussed. Additional materials for this paper are available in the form of a number of tutorials and projects for FPGAs that can be accessed through the Internet.

Design tools for reconfigurable embedded systems

This paper describes the developed hardware/software tools, libraries and design methods for FPGA... more This paper describes the developed hardware/software tools, libraries and design methods for FPGA-based embedded systems which include: a kernel prototyping board with the Xilinx Spartan 3 FPGA; a set of projects for reusable FPGA-based circuits; utilities for FPGA programming; software/hardware tools that provide support for reconfiguration; and programs enabling the designers to partition the functionality of the developed system between software, running on a PC computer, and hardware, implemented in FPGA. A special attention has been paid to data exchange between a host computer and the kernel prototyping board based on compression/decompression techniques. Examples of practical applications are also presented.

Design Tools for Rapid Prototyping of Embedded Controllers

Electronic devices used in the scope of robotics and embedded systems have to be adapted to numer... more Electronic devices used in the scope of robotics and embedded systems have to be adapted to numerous external events and many of them might be unknown in advance. This application-specific particularity requires environment-specific adaptation and frequent changes in the predefined behaviour. In general, all feasible functionality cannot be incorporated in the device during the design phase, i.e. some eventual modifications are postponed until physical tests in real working conditions. Even after executing physical tests, some unexpected events (requiring the appropriate device reaction) might appear. Thus, either sophisticated adaptable electronics has to be implemented or the device has to be able to communicate with another more intelligent host computer, which would assist to cope with emerging problems. The paper suggests tools that provide support for dealing with the considered situations. This is achieved through the following: 1) FPGA-based prototyping core board (reconfigurable platform) establishing both wired and wireless interactions with host computers; 2) Design templates and libraries for interacting with standard peripheral equipment and widely used components for different types of control and computations; 3) Software providing support for interactions with the core board; 4) Intellectual property cores for solving a number of optimization problems common to many engineering applications.

Mixtures of Vegetable Oils and Animal Fat for Biodiesel Production: Influence on Product Composition and Quality

Energy & Fuels, 2008

Studying alternative raw materials for biodiesel production is of major importance. The use of mi... more

Waste materials for activated carbon preparation and its use in aqueous-phase treatment: A review

Journal of Environmental Management, 2007

Commercial activated carbon is a preferred adsorbent for the removal of micropollutants from the ... more Commercial activated carbon is a preferred adsorbent for the removal of micropollutants from the aqueous phase; however, its widespread use is restricted due to high associated costs. To decrease treatment costs, attempts have been made to find inexpensive alternative activated carbon (AC) precursors, such as waste materials. Some reviews report the use of waste materials for the preparation of AC; however, these studies are restricted to either type of wastes, preparation procedures, or specific aqueous-phase applications. The present work reviews and evaluates literature dedicated both to the preparation of AC by recycling different types of waste materials and also to its application in various aqueous-phase treatments. It is clear that conventional (from agriculture and wood industry) and nonconventional (from municipal and industrial activities) wastes can be used to prepare AC, that can be applied in various aqueous treatment processes, namely to remove organic pollutants, dyes, volatile organic compounds, and heavy metals. Moreover, high surface areas can be obtained using either physical or chemical activation; however, combined treatments might enhance the surface properties of the adsorbent, therefore increasing its adsorption capacity. It is evident from the revision made that AC prepared from both conventional and non-conventional wastes might effectively compete with the commercial ones. This happens mostly when the activation procedures are optimized considering both the raw material used to produce the carbons and the contaminants to be removed. r

Comparison of the performance of different homogeneous alkali catalysts during transesterification of waste and virgin oils and evaluation of biodiesel quality

Fuel, 2008

A large amount of studies might be found regarding the improvement of biodiesel production; howev... more A large amount of studies might be found regarding the improvement of biodiesel production; however, there is a lack of information concerning both, the simultaneous comparison of the catalyst performance for different raw materials, and the final product quality. Therefore, the objective of the present study was to evaluate: (i) the biodiesel synthesis from waste frying oil, sunflower and soybean refined oil using KOH, NaOH and CH 3 ONa as catalysts; and (ii) the final product quality according to European biodiesel standard EN 14214. The results obtained showed that the use of virgin oils resulted in higher yields (reaching 97%) as compared to waste frying oils (reaching 92%). From the quality parameters, the ones that mostly depended on the reaction conditions were the kinematic viscosity and the methyl ester content (purity). Overall, KOH was less effective than the sodium based catalysts because, using KOH, purity was lower than the minimum required according to standard EN 14214 for all samples. Considering the studied feedstock, the optimum conditions which ensured that the final product was in agreement with the European biodiesel standard were: (i) 0.6 (wt%) CH 3 ONa for both virgin oils; (ii) 0.6 (wt%) NaOH for sunflower oil and 0.8 (wt%) for soybean oil and; (iii) 0.8 (wt%) using both sodium based catalysts for waste frying oils. Under optimum conditions, a purity of 99.4 (wt%) could be obtained.

Experimental Design of 2,4Dichlorophenol Oxidation by Fenton's Reaction

Industrial & Engineering Chemistry Research, 2006

An experimental design methodology has been drawn regarding the model contaminant 2, 4-dichloroph... more

Gold Complexes with Dithiothiophene Ligands: A Metal Based on a Neutral Molecule

Chemistry-a European Journal, 2001

The gold complexes n-Bu 4 N-[Au(a-tpdt) 2 ] (5), n-Bu 4 N[Au(dtpdt) 2 ] (4) and n-Bu 4 N[Au(tpdt)... more The gold complexes n-Bu 4 N-[Au(a-tpdt) 2 ] (5), n-Bu 4 N[Au(dtpdt) 2 ] (4) and n-Bu 4 N[Au(tpdt) 2 ] (6) based on new dithiothiophene ligands (a-tpdt 2,3-thiophenedithiolate, dtpdt 2,3dihydro-5,6-thiophenedithiolate and tpdt 3,4-thiophenedithiolate) have been prepared and characterised. These gold(iii) complexes are diamagnetic, but they can be oxidised with iodine to the paramagnetic compounds [Au(a-tpdt) 2 ] (8), [Au(dtpdt) 2 ] (7) and n-Bu 4 N-[{Au(tpdt) 2 } n$2 ] (9), which were isolated as fine powders and which exhibit paramagnetic susceptibilities that are almost temperature independent with room temperature values of 2.5 Â 10 À4 , 2.0 Â 10 À4 and 5 Â 10 À4 emu mol À1 , respectively. Interestingly, the neutral complex [Au(a-tpdt) 2 ] (8) as a polycrystalline sample displays the properties of a metallic system with a room temperature electrical conductivity of 6 S cm À1 and a thermoelectric power of 5.5 mV K À1 ; this is the first time that this metallic property has been observed in a molecular system based on a neutral species.

Gold Complexes with Dithiothiophene Ligands: A Metal Based on a Neutral Molecule

Chemistry-a European Journal, 2001

The gold complexes n-Bu 4 N-[Au(a-tpdt) 2 ] (5), n-Bu 4 N[Au(dtpdt) 2 ] (4) and n-Bu 4 N[Au(tpdt)... more The gold complexes n-Bu 4 N-[Au(a-tpdt) 2 ] (5), n-Bu 4 N[Au(dtpdt) 2 ] (4) and n-Bu 4 N[Au(tpdt) 2 ] (6) based on new dithiothiophene ligands (a-tpdt 2,3-thiophenedithiolate, dtpdt 2,3dihydro-5,6-thiophenedithiolate and tpdt 3,4-thiophenedithiolate) have been prepared and characterised. These gold(iii) complexes are diamagnetic, but they can be oxidised with iodine to the paramagnetic compounds [Au(a-tpdt) 2 ] (8), [Au(dtpdt) 2 ] (7) and n-Bu 4 N-[{Au(tpdt) 2 } n$2 ] (9), which were isolated as fine powders and which exhibit paramagnetic susceptibilities that are almost temperature independent with room temperature values of 2.5 Â 10 À4 , 2.0 Â 10 À4 and 5 Â 10 À4 emu mol À1 , respectively. Interestingly, the neutral complex [Au(a-tpdt) 2 ] (8) as a polycrystalline sample displays the properties of a metallic system with a room temperature electrical conductivity of 6 S cm À1 and a thermoelectric power of 5.5 mV K À1 ; this is the first time that this metallic property has been observed in a molecular system based on a neutral species.

An Organic Spin-Ladder Molecular Material

Angewandte Chemie-international Edition, 1997

Design Tools and Reusable Libraries for FPGA-Based Digital Circuits

This paper suggests tools that provide significant improvements in the design and verification of... more This paper suggests tools that provide significant improvements in the design and verification of FPGAbased digital circuits. These tools include reusable specifications of hardware components (modules) that have been proposed for two types of CAD environments; Xilinx ISE 5.x and Celoxica DK1. The components can be employed to implement both application-specific blocks from the selected area (mainly from the scope of combinatorial computations) and a number of interfaces that are very useful for interaction and data exchange with devices attached to a FPGA, such as LCD and touch panels, bus controllers, etc. The designed modules can be easily integrated into any application-specific digital system and used for visualizing the results, fast data transfer, debugging of internal sub-circuits, etc. They were constructed in such a way that their functionality can be either fixed or modifiable (both statically and dynamically). The latter capability was provided with the aid of re-loadable RAM-based blocks. To illustrate the capabilities of the tools suggested, four design examples are discussed. Additional materials for this paper are available in the form of a number of tutorials and projects for FPGAs that can be accessed through the Internet.

Design tools for reconfigurable embedded systems

This paper describes the developed hardware/software tools, libraries and design methods for FPGA... more This paper describes the developed hardware/software tools, libraries and design methods for FPGA-based embedded systems which include: a kernel prototyping board with the Xilinx Spartan 3 FPGA; a set of projects for reusable FPGA-based circuits; utilities for FPGA programming; software/hardware tools that provide support for reconfiguration; and programs enabling the designers to partition the functionality of the developed system between software, running on a PC computer, and hardware, implemented in FPGA. A special attention has been paid to data exchange between a host computer and the kernel prototyping board based on compression/decompression techniques. Examples of practical applications are also presented.

Design Tools for Rapid Prototyping of Embedded Controllers

Electronic devices used in the scope of robotics and embedded systems have to be adapted to numer... more Electronic devices used in the scope of robotics and embedded systems have to be adapted to numerous external events and many of them might be unknown in advance. This application-specific particularity requires environment-specific adaptation and frequent changes in the predefined behaviour. In general, all feasible functionality cannot be incorporated in the device during the design phase, i.e. some eventual modifications are postponed until physical tests in real working conditions. Even after executing physical tests, some unexpected events (requiring the appropriate device reaction) might appear. Thus, either sophisticated adaptable electronics has to be implemented or the device has to be able to communicate with another more intelligent host computer, which would assist to cope with emerging problems. The paper suggests tools that provide support for dealing with the considered situations. This is achieved through the following: 1) FPGA-based prototyping core board (reconfigurable platform) establishing both wired and wireless interactions with host computers; 2) Design templates and libraries for interacting with standard peripheral equipment and widely used components for different types of control and computations; 3) Software providing support for interactions with the core board; 4) Intellectual property cores for solving a number of optimization problems common to many engineering applications.

Mixtures of Vegetable Oils and Animal Fat for Biodiesel Production: Influence on Product Composition and Quality

Energy & Fuels, 2008

Studying alternative raw materials for biodiesel production is of major importance. The use of mi... more

Waste materials for activated carbon preparation and its use in aqueous-phase treatment: A review

Journal of Environmental Management, 2007

Commercial activated carbon is a preferred adsorbent for the removal of micropollutants from the ... more Commercial activated carbon is a preferred adsorbent for the removal of micropollutants from the aqueous phase; however, its widespread use is restricted due to high associated costs. To decrease treatment costs, attempts have been made to find inexpensive alternative activated carbon (AC) precursors, such as waste materials. Some reviews report the use of waste materials for the preparation of AC; however, these studies are restricted to either type of wastes, preparation procedures, or specific aqueous-phase applications. The present work reviews and evaluates literature dedicated both to the preparation of AC by recycling different types of waste materials and also to its application in various aqueous-phase treatments. It is clear that conventional (from agriculture and wood industry) and nonconventional (from municipal and industrial activities) wastes can be used to prepare AC, that can be applied in various aqueous treatment processes, namely to remove organic pollutants, dyes, volatile organic compounds, and heavy metals. Moreover, high surface areas can be obtained using either physical or chemical activation; however, combined treatments might enhance the surface properties of the adsorbent, therefore increasing its adsorption capacity. It is evident from the revision made that AC prepared from both conventional and non-conventional wastes might effectively compete with the commercial ones. This happens mostly when the activation procedures are optimized considering both the raw material used to produce the carbons and the contaminants to be removed. r

Comparison of the performance of different homogeneous alkali catalysts during transesterification of waste and virgin oils and evaluation of biodiesel quality

Fuel, 2008

A large amount of studies might be found regarding the improvement of biodiesel production; howev... more A large amount of studies might be found regarding the improvement of biodiesel production; however, there is a lack of information concerning both, the simultaneous comparison of the catalyst performance for different raw materials, and the final product quality. Therefore, the objective of the present study was to evaluate: (i) the biodiesel synthesis from waste frying oil, sunflower and soybean refined oil using KOH, NaOH and CH 3 ONa as catalysts; and (ii) the final product quality according to European biodiesel standard EN 14214. The results obtained showed that the use of virgin oils resulted in higher yields (reaching 97%) as compared to waste frying oils (reaching 92%). From the quality parameters, the ones that mostly depended on the reaction conditions were the kinematic viscosity and the methyl ester content (purity). Overall, KOH was less effective than the sodium based catalysts because, using KOH, purity was lower than the minimum required according to standard EN 14214 for all samples. Considering the studied feedstock, the optimum conditions which ensured that the final product was in agreement with the European biodiesel standard were: (i) 0.6 (wt%) CH 3 ONa for both virgin oils; (ii) 0.6 (wt%) NaOH for sunflower oil and 0.8 (wt%) for soybean oil and; (iii) 0.8 (wt%) using both sodium based catalysts for waste frying oils. Under optimum conditions, a purity of 99.4 (wt%) could be obtained.

Experimental Design of 2,4Dichlorophenol Oxidation by Fenton's Reaction

Industrial & Engineering Chemistry Research, 2006

An experimental design methodology has been drawn regarding the model contaminant 2, 4-dichloroph... more