Síntese de ferritas de cobalto e níquel dopadas com zinco e caracterização de suas propriedades eletromagnéticas

This work shows that the synthesis by combustion is a prominent alternative to obtain ceramic powders of higher oxides, nanostructured and of high purity, as the ferrites of formulas Co(1-x)Zn(x)Fe2O4 e Ni(1-x)Zn(x)Fe2O4 with x ranging from 0.2 mols, in a range from 0.2 ≤ x ≥ 1.0 mol, that presents magnetic properties in coexistence of ferroelectric and ferrimagnetic states, which can be used in antennas of micro tapes and selective surfaces of low frequency in a range of miniaturized microwaves, without performance loss. The obtainment occurred through the combustion process, followed by appropriate physical processes and ordered to the utilization of the substrate sinterization process, it gave us a ceramic material, of high purity degree in a nanometric scale. The Vibrating Sample Magnetometer (VSM) analysis showed that those ferritic materials presents parameters, as materials hysteresis, that have own behavior of magnetic materials of good quality, in which the magnetization states can be suddenly changed with a relatively small variation of the field intensity, having large applications on the electronics field. The X-ray Diffraction (XRD) analysis of the ceramic powders synthesized at 900 °C, characterize its structural and geometrical properties, the crystallite size and the interplanar spacing. Other analysis were developed, as Scanning Electron Microscopy (SEM), X-ray Fluorescence (XRF), electric permittivity and the tangent loss, in high frequencies, through the equipment ZVB - 14 Vector Network Analyzer 10 MHz-14 GHz, of ROHDE & SCHWART.

Desenvolvimento e caracterização de biocompósito de látex (borracha natural) e fibra de carnaúba

The development of composite materials encompasses many different application areas. Among the composites, it is had, especially, the materials of organic origin, which have the greatest potential for biodegradability and so, have been bringing relevance and prominence in the contemporary setting of environmental preservation and sustainable development. Following this perspective of ecological appeal, it was developed a biocomposite material with natural inputs typically brazilian. This composite was made from latex (natural rubber) and carnauba fiber in different mass proportions. Formulations had varied by 5%, 10%, 15% and 20% of fiber in relation the matrix. This material has been designed aiming at application in thermal insulation systems, which requirethermal protection surfaces and/or reduction of thermal energy loss. Therefore, the composite was characterized by thermal conductivity testing, specific heat, thermal diffusivity and thermogravimetry. As has also been characterized for their physical-mechanical, by testing density, moisture content, tensile strength, hardness and scanning electron microscopy (SEM). The characterization of the material revealed that the composite presents a potential of thermal insulation higher than the natural rubber, that was used as reference. And the formulation at 15% fiber in relation the matrix showed the best performance. Thus, the composite material in question presents itself as a viable and effective alternative for new thermal insulation material design.

Desenvolvimento e caracterização de biocompósito de látex (borracha natural) e fibra de carnaúba

The development of composite materials encompasses many different application areas. Among the composites, it is had, especially, the materials of organic origin, which have the greatest potential for biodegradability and so, have been bringing relevance and prominence in the contemporary setting of environmental preservation and sustainable development. Following this perspective of ecological appeal, it was developed a biocomposite material with natural inputs typically brazilian. This composite was made from latex (natural rubber) and carnauba fiber in different mass proportions. Formulations had varied by 5%, 10%, 15% and 20% of fiber in relation the matrix. This material has been designed aiming at application in thermal insulation systems, which requirethermal protection surfaces and/or reduction of thermal energy loss. Therefore, the composite was characterized by thermal conductivity testing, specific heat, thermal diffusivity and thermogravimetry. As has also been characterized for their physical-mechanical, by testing density, moisture content, tensile strength, hardness and scanning electron microscopy (SEM). The characterization of the material revealed that the composite presents a potential of thermal insulation higher than the natural rubber, that was used as reference. And the formulation at 15% fiber in relation the matrix showed the best performance. Thus, the composite material in question presents itself as a viable and effective alternative for new thermal insulation material design.

Análise wavelet em curvas de luz estelares de sistemas binários da missão espacial CoRoT

Binary systems are key environments to study the fundamental properties of stars. In this work, we analyze 99 binary systems identified by the CoRoT space mission. From the study of the phase diagrams of these systems, our sample is divided into three groups: those whose systems are characterized by the variability relative to the binary eclipses; those presenting strong modulations probably due to the presence of stellar spots on the surface of star; and those whose systems have variability associated with the expansion and contraction of the surface layers. For eclipsing binary stars, phase diagrams are used to estimate the classification in regard to their morphology, based on the study of equipotential surfaces. In this context, to determine the rotation period, and to identify the presence of active regions, and to investigate if the star exhibits or not differential rotation and study stellar pulsation, we apply the wavelet procedure. The wavelet transform has been used as a powerful tool in the treatment of a large number of problems in astrophysics. Through the wavelet transform, one can perform an analysis in time-frequency light curves rich in details that contribute significantly to the study of phenomena associated with the rotation, the magnetic activity and stellar pulsations. In this work, we apply Morlet wavelet (6th order), which offers high time and frequency resolution and obtain local (energy distribution of the signal) and global (time integration of local map) wavelet power spectra. Using the wavelet analysis, we identify thirteen systems with periodicities related to the rotational modulation, besides the beating pattern signature in the local wavelet map of five pulsating stars over the entire time span.

Análise wavelet em curvas de luz estelares de sistemas binários da missão espacial CoRoT

Binary systems are key environments to study the fundamental properties of stars. In this work, we analyze 99 binary systems identified by the CoRoT space mission. From the study of the phase diagrams of these systems, our sample is divided into three groups: those whose systems are characterized by the variability relative to the binary eclipses; those presenting strong modulations probably due to the presence of stellar spots on the surface of star; and those whose systems have variability associated with the expansion and contraction of the surface layers. For eclipsing binary stars, phase diagrams are used to estimate the classification in regard to their morphology, based on the study of equipotential surfaces. In this context, to determine the rotation period, and to identify the presence of active regions, and to investigate if the star exhibits or not differential rotation and study stellar pulsation, we apply the wavelet procedure. The wavelet transform has been used as a powerful tool in the treatment of a large number of problems in astrophysics. Through the wavelet transform, one can perform an analysis in time-frequency light curves rich in details that contribute significantly to the study of phenomena associated with the rotation, the magnetic activity and stellar pulsations. In this work, we apply Morlet wavelet (6th order), which offers high time and frequency resolution and obtain local (energy distribution of the signal) and global (time integration of local map) wavelet power spectra. Using the wavelet analysis, we identify thirteen systems with periodicities related to the rotational modulation, besides the beating pattern signature in the local wavelet map of five pulsating stars over the entire time span.

Estudo da incorporação de cinza e chamote gerado pela cerâmica vermelha ao próprio processo industrial

The ceramics industry generates waste at various stages of that process, defective products, waste from burning solid fuels, among others. This waste is dumped in landfills, garbage dumps or directly on roads, which has a negative environmental impact. This paper presents a study to incorporate the waste of algaroba wood and chamote (scrap pieces of ceramic already sintered), in to the ceramic material for making sealing blocks. The methodological procedures consist in the characterization of chemical and mineralogical residues, raw materials, and physical-mechanical of the formulations of mixes with clay, silt and waste. By pressing test pieces were produced using a pressure of 200 kgf/cm², varying compositions in the range of 0%, 5%, 10% and 15% by weight of residue. The sintering was performed in a muffle furnace, with the temperature levels of 850 ° C, 900 ° C, 950 ° C, 1000 ° C and 1050 ° C. The evaluated physical and mechanical properties were: Water Absorption, Linear Shrinkage Burning, Apparent Porosity, Apparent Density and Mechanical Resistance to Flexion. Analysis was carried out by Scanning Electron Microscopy on fracture surfaces of the specimens. Evaluation of linear shrinkage property drying and firing , water absorption and mechanical resistance to compression of the sealing blocks 5% wood ash residue, sintered at 900 °C hold temperature in the laboratory the products manufactured on an industrial scale. The main results, it was found on the viability of using the residues of algaroba wood and to confer refractory properties of the ceramic product. The main results, it was concluded feasibility of using the ash residues algaroba wood to impart refractory properties to the ceramic product and the residue of chamote, being derived from the own ceramic product not interfere with the properties, when used in a percentage of up to 5%.Since the residue of chamote being derived from the ceramic product itself had no effect on the properties. Studies in the laboratory have shown that the incorporation of up to 5% of these residues may be adopted as an alternative technology to reduce the environmental impact caused by the industrial sector, without compromising the final properties of the material, since the results on an industrial scale showed absorption values 11.66 and 11.74 of water and waste products respectively, within the parameters of NBR - 15,270, since the mechanical strength was 1.25 MPa and 0.94 MPa respectively for products with and without residue, lower than the minimum required by the technical standard that is 1.5 MPa.

Estudo da incorporação de cinza e chamote gerado pela cerâmica vermelha ao próprio processo industrial

The ceramics industry generates waste at various stages of that process, defective products, waste from burning solid fuels, among others. This waste is dumped in landfills, garbage dumps or directly on roads, which has a negative environmental impact. This paper presents a study to incorporate the waste of algaroba wood and chamote (scrap pieces of ceramic already sintered), in to the ceramic material for making sealing blocks. The methodological procedures consist in the characterization of chemical and mineralogical residues, raw materials, and physical-mechanical of the formulations of mixes with clay, silt and waste. By pressing test pieces were produced using a pressure of 200 kgf/cm², varying compositions in the range of 0%, 5%, 10% and 15% by weight of residue. The sintering was performed in a muffle furnace, with the temperature levels of 850 ° C, 900 ° C, 950 ° C, 1000 ° C and 1050 ° C. The evaluated physical and mechanical properties were: Water Absorption, Linear Shrinkage Burning, Apparent Porosity, Apparent Density and Mechanical Resistance to Flexion. Analysis was carried out by Scanning Electron Microscopy on fracture surfaces of the specimens. Evaluation of linear shrinkage property drying and firing , water absorption and mechanical resistance to compression of the sealing blocks 5% wood ash residue, sintered at 900 °C hold temperature in the laboratory the products manufactured on an industrial scale. The main results, it was found on the viability of using the residues of algaroba wood and to confer refractory properties of the ceramic product. The main results, it was concluded feasibility of using the ash residues algaroba wood to impart refractory properties to the ceramic product and the residue of chamote, being derived from the own ceramic product not interfere with the properties, when used in a percentage of up to 5%.Since the residue of chamote being derived from the ceramic product itself had no effect on the properties. Studies in the laboratory have shown that the incorporation of up to 5% of these residues may be adopted as an alternative technology to reduce the environmental impact caused by the industrial sector, without compromising the final properties of the material, since the results on an industrial scale showed absorption values 11.66 and 11.74 of water and waste products respectively, within the parameters of NBR - 15,270, since the mechanical strength was 1.25 MPa and 0.94 MPa respectively for products with and without residue, lower than the minimum required by the technical standard that is 1.5 MPa.

Expressão geofísica-estrutural do lineamento transbrasiliano na porção central da Bacia do Parnaíba (Maranhão-Piauí)

The objective of this study was to characterize the structural-geophysical expression of the Transbrasiliano Lineament (TBL) in the east-central portion of the Parnaíba Basin. The TBL corresponds to a major Neoproterozoic NE-trending shear zone related to the Brasiliano orogenic cycle, with dextral strike-slip kinematics, underlying (but also laterally exposed in the NE and SW basin edges) the sedimentary section of the Parnaíba Basin. In this study, the interpretation of gravity and magnetic anomaly maps is consistent with the TBL kinematics, the signature of the geophysical anomalies corresponding to the high (plastic behaviour) and subsequent declining temperature (ductile to brittle behaviour) stages during Brasiliano and late Brasiliano times. The pattern of residual gravity anomalies is compatible with an S-C dextral pair shaping the geological bodies of an heterogeneous basement, such as slices of gneisses and granulites (positive anomalies), granitic and low-medium grade metasedimentary rocks (negative anomalies). Such anomalies curvilinear trends, ranging from NNE (interpreted as S surfaces) to NE (C surfaces), correspond to flattening surfaces (S), while the NE rectilinear trend must represent a C band. The narrower magnetic anomalies also display NNE to NE (S surfaces) trends and should correspond to similar (although narrower and more discontinuous) sources in the equivalent anomaly patterns. Pre-Silurian pull-apart style grabens may contribute to the NE negative gravimetric anomalies, although this interpretation demands control by seismic data analysis. On the other hand, the curvilinear anomalies associated to contractional trends are incompatible with their interpretation as pre-Silurian graben, in both maps. In the (reduced to the pole) magnetic anomalies map, most of these are again associated to low-temperature shear zones (C planes) and faults, juxtaposing distinct blocks in terms of magnetic properties, or eventually filled with basic bodies. It is also possible that some isolated magnetic anomalies correspond to igneous bodies of late-Brasiliano or Mesozoic age. The basement late discontinuities pattern can be interpreted in analogy to the Riedel fractures model, with steep dipping surfaces and a sub-horizontal movement section. This study also explored 2D gravity modeling controlled by the interpretation of a dip seismic line as regards to the Transbrasiliano Lineament. The rock section equivalent to the Jaibaras Group occupying a graben structure (as identified in the seismic line) corresponds to a discrete negative anomaly superimposed to a gravimetric high, once again indicating a stronger influence of older crystalline basement rocks as gravimetric sources, mainly reflecting the heterogeneities and anisotropies generated at high temperature conditions and their subsequent cooling along the TBL, during the Brasiliano cycle.

Expressão geofísica-estrutural do lineamento transbrasiliano na porção central da Bacia do Parnaíba (Maranhão-Piauí)

The objective of this study was to characterize the structural-geophysical expression of the Transbrasiliano Lineament (TBL) in the east-central portion of the Parnaíba Basin. The TBL corresponds to a major Neoproterozoic NE-trending shear zone related to the Brasiliano orogenic cycle, with dextral strike-slip kinematics, underlying (but also laterally exposed in the NE and SW basin edges) the sedimentary section of the Parnaíba Basin. In this study, the interpretation of gravity and magnetic anomaly maps is consistent with the TBL kinematics, the signature of the geophysical anomalies corresponding to the high (plastic behaviour) and subsequent declining temperature (ductile to brittle behaviour) stages during Brasiliano and late Brasiliano times. The pattern of residual gravity anomalies is compatible with an S-C dextral pair shaping the geological bodies of an heterogeneous basement, such as slices of gneisses and granulites (positive anomalies), granitic and low-medium grade metasedimentary rocks (negative anomalies). Such anomalies curvilinear trends, ranging from NNE (interpreted as S surfaces) to NE (C surfaces), correspond to flattening surfaces (S), while the NE rectilinear trend must represent a C band. The narrower magnetic anomalies also display NNE to NE (S surfaces) trends and should correspond to similar (although narrower and more discontinuous) sources in the equivalent anomaly patterns. Pre-Silurian pull-apart style grabens may contribute to the NE negative gravimetric anomalies, although this interpretation demands control by seismic data analysis. On the other hand, the curvilinear anomalies associated to contractional trends are incompatible with their interpretation as pre-Silurian graben, in both maps. In the (reduced to the pole) magnetic anomalies map, most of these are again associated to low-temperature shear zones (C planes) and faults, juxtaposing distinct blocks in terms of magnetic properties, or eventually filled with basic bodies. It is also possible that some isolated magnetic anomalies correspond to igneous bodies of late-Brasiliano or Mesozoic age. The basement late discontinuities pattern can be interpreted in analogy to the Riedel fractures model, with steep dipping surfaces and a sub-horizontal movement section. This study also explored 2D gravity modeling controlled by the interpretation of a dip seismic line as regards to the Transbrasiliano Lineament. The rock section equivalent to the Jaibaras Group occupying a graben structure (as identified in the seismic line) corresponds to a discrete negative anomaly superimposed to a gravimetric high, once again indicating a stronger influence of older crystalline basement rocks as gravimetric sources, mainly reflecting the heterogeneities and anisotropies generated at high temperature conditions and their subsequent cooling along the TBL, during the Brasiliano cycle.

Evolução estratigráfica da sequência neocarbonífera-eotriássica da Bacia do Parnaíba, NE do Brasil

The Parnaíba Basin consists in an intracratonic basin whose sucession of rocks is arranged in five supersequences. The Upper Carboniferous-Lower Triassic Sequence represents the third major sedimentary cycle and corresponds to Balsas Group, which is divided into four units: Piauí Formation, Pedra de Fogo Formation, Motuca Formation and Sambaíba Formation, from base to top. Different interpretations have been made by several authors in recent decades to interpreted the depositional system and environments related to each unit that belongs to this sequence. In general way, it is described as a thick pack of siliciclastic sediments deposited under complex conditions, varying from clastic/evaporitic shallow marine to lacustrine and desert environment. Aiming to clarify the sedimentary sequence evolution, this work underwent a stratigraphic analysis of the Upper Carboniferous-Lower Triassic deposits by applying modern concepts of the sequence stratigraphy based on well and seismic database. Three main depositional sequences of higher frequency were identified in each well analyzed. The sequence 1 corresponds to rocks initially deposited by a fluvial system with braided channel characteristics which evolved to shallow marine with coastal sabkha conditions related to a transgressive stage, that later evolved to a deltaic system. The Sequence 2 corresponds to rocks deposited in a lacustrine/desert environment associated with sabkha generated during a period of increased aridity in which the area occupied by the Parnaíba Basin had been suffering. The registration of a major regressive phase is shown in Sequence 2 which evolved to a dominantly desert environment recorded in Sequence 3. Seismic stratigraphy analyses allow to define a series of stratigraphic surfaces and related genetic units, as well as to infer its lateral expression. Seismic facies associated with such sequences are dominantly parallel and sub-parallel, with good lateral continuity, suggesting the sedimentary rate was relatively constant during deposition.

Evolução estratigráfica da sequência neocarbonífera-eotriássica da Bacia do Parnaíba, NE do Brasil

The Parnaíba Basin consists in an intracratonic basin whose sucession of rocks is arranged in five supersequences. The Upper Carboniferous-Lower Triassic Sequence represents the third major sedimentary cycle and corresponds to Balsas Group, which is divided into four units: Piauí Formation, Pedra de Fogo Formation, Motuca Formation and Sambaíba Formation, from base to top. Different interpretations have been made by several authors in recent decades to interpreted the depositional system and environments related to each unit that belongs to this sequence. In general way, it is described as a thick pack of siliciclastic sediments deposited under complex conditions, varying from clastic/evaporitic shallow marine to lacustrine and desert environment. Aiming to clarify the sedimentary sequence evolution, this work underwent a stratigraphic analysis of the Upper Carboniferous-Lower Triassic deposits by applying modern concepts of the sequence stratigraphy based on well and seismic database. Three main depositional sequences of higher frequency were identified in each well analyzed. The sequence 1 corresponds to rocks initially deposited by a fluvial system with braided channel characteristics which evolved to shallow marine with coastal sabkha conditions related to a transgressive stage, that later evolved to a deltaic system. The Sequence 2 corresponds to rocks deposited in a lacustrine/desert environment associated with sabkha generated during a period of increased aridity in which the area occupied by the Parnaíba Basin had been suffering. The registration of a major regressive phase is shown in Sequence 2 which evolved to a dominantly desert environment recorded in Sequence 3. Seismic stratigraphy analyses allow to define a series of stratigraphic surfaces and related genetic units, as well as to infer its lateral expression. Seismic facies associated with such sequences are dominantly parallel and sub-parallel, with good lateral continuity, suggesting the sedimentary rate was relatively constant during deposition.

Estudo de tensoativos na organofilização de argila bentonítica para uso em fluido de perfuração à base de óleo

Due to the great challenges encountered in drilling wells, there is a need to develop fluids with appropriated properties and able to meet all the requirements of drilling operations. The physicochemical and rheological properties must be carefully controlled so that a fluid can exercise all its functions. In perforations sensitive to contact with water and "offshore", it becomes necessary the use of oil based drilling fluids, but the bentonite clay cannot be used without a previous surface modification so that their surfaces become hydrophobic. Lately, the oil companies in Brazil use imported organoclays in the preparation of oil-based drilling fluids. The study aimed to modify a calcium clay to increase the affinity of the same organic phase of oil-based drilling fluids, applying three surfactants (OCS, CTAB and UTM 150) at different concentrations. The results indicated that the surfactants UTM 150 and CTAB showed better results compared to OCS. Considering the type of surfactant and concentration as variables used in the statistical analysis, the results indicated that only the surface tension and concentration of calcium oxide in response to organophilization process showed statistically significant effects. The organophilizated clay has potential for application in oil-based drilling fluids.

Rugosidade superficial e adesão bacteriana em compósitos com nanopartículas após acabamento e polimento

Objective: To evaluate in vitro the surface roughness and bacterial adhesion of nanoparticle composites, after being subjected to different finishing and polishing systems. Materials and Methods: 66 specimens were prepared, and 30 with Filtek Z350 XT (3M ESPE, USA) and 30 with the resin IPS Empress Direct (Ivoclar Vivadent, USA), divided into 6 groups (n = 10 ). Six specimens were prepared for analysis in scanning electron microscopy (SEM) .Each kind of resin was subjected to finishing and polishing systems: Sof-Lex Pop-On discs (3M ESPE, USA) and AstropolTM system (Ivoclar Vivadent , USA), featuring the experimental group. The control group did not undergo any kind of finishing and polishing technique. The average roughness (Ra) in both groups was measured using a roughness in the setting of 0.25 mm (cut off) and surface images obtained with photomicrographs taken with a scanning electron microscope (SEM) magnified 500 times. Bacterial adherence was evaluated by determining the absorbance (OD) of the suspension of adhered cells by spectrophotometer at 570 nm. The results were submitted for analyzed with 2-way ANOVA at α=.05 and Tukey multiple comparison tests. Results: Statistically significant differences were found between the groups in terms of roughness and bacterial adhesion. Filtek Z350 XT for resin were no differences between the tested finishing and polishing systems, where the system of lowest surface roughness was the Sof-Lex Pop-On. To the resin IPS Empress Direct, the finishing and polishing system Astropol, had lower results of surface roughness. As for bacterial adhesion, the lowest optical density value for Filtek Z350 XT was for the group that used the finishing and polishing system Sof-Lex Pop-On and the resin IPS Empress Direct the group that used the Astropol system. In addition, there was a positive correlation between surface roughness and bacterial adhesion on polished surfaces (r = 0.612) Conclusions: surface roughness and bacterial adhesion are closely related. The finishing and polishing Sof-Lex Pop-On system is more suitable for nanoparticulate Filtek Z350 XT and the finishing and polishing system Astropol for resin nanohíbrida IPS Empress Direct.

Retificação plana tangencial dos ferros fundidos nodular, vermicular e cinzento em várias condições de corte

In a scenario of increasing competitiveness of the global industrial sector and with a consumer market increasingly demanding, there is an increased demand for new materials and, consequently, possibilities to explore new research and technological advances towards the development of new manufacturing methods or the improvement of existing technologies. In the case of cast irons, new grades of them have been developed so that their mechanical properties have been improved, making them more competitive with steel, expanding the applications and thus represents great economic gain for metallurgy and manufacturing sectors. This increases the interest and creates new opportunities to study these materials and identify how they respond in terms of the surface integrity, tool wear, cutting forces, among others, when machined by grinding operation. In this context, due to the lack of results from grinding of cast irons and studies comparing grindability among several grades of cast irons found in the literature, this work aims to generate scientific and technological contribution to the metallurgical and metal working sector through roughness results (Ra and Rz parameters) and evaluation and analysis of the subsurface integrity of three cast iron grades (gray, compacted graphite and nodular). The machining trials were performed on a surface grinding machine with silicon carbide grinding wheel at different cutting conditions. The input variables were the radial depth of cut (15 and 30 μm), worktable speed, vw (5 and 10 m/min) and the abrasive grain size of the grinding wheel. The results showed that surface roughness increased with the radial depth of cut for all materials tested; and the lowest values were obtained for gray cast iron. Also, roughness was sensitive to variation of worktable speed and the lowest values were obtained after machining with vw = 5 m/min. With respect to the abrasive grain size, as it decreased the roughness values increased to gray and nodular cast iron grades. Furthermore, grinding burns marks were observed on the surfaces of nodular cast iron and compacted graphite iron grades after grinding the smallest grain size, contrary to what is usually reported in literature. However, no evidence of severe thermal damages below the machined surfaces of all cast iron grades was observed after analyzing the results of hardness and the SEM micrograph images.

Avaliação da Qualidade e Segurança Microbiológica de Hortofrutícolas

Frutas e vegetais frescos, embora sejam essenciais para uma dieta equilibrada e nutritiva, estão frequentemente associados a surtos de origem alimentar, pois este tipo de produto é muitas vezes consumidos cru, sem qualquer processamento térmico que elimine ou reduza para níveis aceitáveis a carga microbiana patogénica. Desta forma, e para que o consumo deste tipo de produtos continue a aumentar, torna-se importante aumentar o controlo em termos de segurança alimentar em todas as fases de produção. O presente trabalho de investigação teve por objetivos estudar a ocorrência de cinco microrganismos patogénicos: Salmonella sp.; Escherichia coli; Staplylococcus aureus; Listeria monocytogenes; HAV (vírus da Hepatite A), em framboesas e alface à venda no mercado português, otimizando uma técnica simples e rápida para deteção desses microrganismos nesses produtos. Também neste trabalho foi feito um estudo sobre os hábitos de consumo de produtos minimamente processados, framboesas e alface através de um inquérito por questionário. A escolha dos produtos e microrganismos a pesquisar teve por base um levantamento de quais as contaminações e os hortofrutícolas mais afetados nos últimos anos. A investigação iniciou-se com a pesquisa do HAV em framboesas e alface, onde após uma revisão bibliográfica, foram testados quatro protocolos distintos. No entanto devido à complexidade das técnicas para pesquisa de vírus em alimentos, à falta de meios e controlos para o desenvolvimento das respetivas técnicas, este objetivo foi abandonado. Numa segunda fase foi otimizado um método de deteção (PCR) para pesquisa das bactérias patogénicas, igualmente em framboesas e alface. Após otimização das condições de PCR, foram testados dois métodos de preparação da amostra: um com um passo de rebentamento de células baseado na fervura; e outro onde apenas se recolheu algum volume de cultura de pré-enriquecimento, tendo-se usado a mesma diretamente para a reação de PCR. Concluiu-se que apenas o primeiro método é eficiente, mas apenas para bactérias Gram-negativas (Salmonella sp. e E. coli) uma vez que estas possuem uma parede celular fina, capaz de ser destruída pela fervura, ao contrário das Gram-positivas (S. aureus e L. monocytogenes). Das amostras de framboesas e alface à venda no mercado português analisadas, concluiu-se que, apesar do método ainda necessitar de alguns ajustes, apenas a amostra de alface fresca parece não apresentar qualquer contaminação com Salmonella sp. e E. coli. Para S. aureus e L. monocytogenes não foi possível obter conclusões definitivas quanto à sua presença nas amostras analisadas, já que vários testes de confirmação deverão ser repetidos. Relativamente aos resultados obtidos acerca do inquérito de consumo, tem-se que dos 186 inquiridos, a grande maioria consome produtos hortofrutícolas minimamente processados 1-3 vezes/semana, tendo, a grande maioria, o hábito de os lavar com água antes do seu consumo, prática esta que é aconselhada. Quanto ao consumo de alface, a frequência aumenta para 3-5 vezes/semana, sendo esta adquirida maioritariamente inteira fresca e em superfícies comerciais. Por fim o consumo de framboesas ainda é escasso, pois a grande maioria dos inquiridos alega consumir este produto esporadicamente, sendo estas adquiridas embaladas inteiras frescas em superfícies comerciais.