Preliminary insights on the development of a continuous-flow solar system for the photocatalytic degradation of contaminants of emerging concern in water.

The ubiquity and impact of pharmaceuticals and pesticides, as well as their residues in environmental compartments, particularly in water, have raised human and environmental health concerns. This emphasizes the need of developing sustainable methods for their removal. Solar-driven photocatalytic degradation has emerged as a promising approach for the chemical decontamination of water, sparking intensive scientific research in this field. Advancements in photocatalytic materials have driven the need for solar reactors that efficiently integrate photocatalysts for real-world water treatment. This study reports preliminary results from the development and evaluation of a solar system for TiO2-based photocatalytic degradation of intermittently flowing water contaminated with doxycycline (DXC), sulfamethoxazole (SMX), dexamethasone (DXM), and carbendazim (CBZ). The system consisted of a Fresnel-type UV solar concentrator that focused on the opening and focal point of a parabolic trough concentrator, within which tubular quartz glass reactors were fixed. Concentric springs coated with TiO2, arranged one inside the other, were fixed inside the quartz reactors. The reactors are connected to a raw water tank at the inlet and a check valve at the outlet. Rotating wheels at the collector base enable solar tracking in two axes. The substances (SMX, DXC, and CBZ) were dissolved in dechlorinated tap water at a concentration of 1.0 mg/L, except DXM (0.8 mg/L). The water underwent sequential batch (~ 3 L each, without recirculation) processing with retention times of 15, 30, 60, 90, and 120 min. After 15 min, the degradation rates were as follows: DXC 87%, SMX 35.5%, DXM 32%, and CBZ 31.8%. The system processed 101 L of water daily, simultaneously removing 870, 355, 256, and 318 µg/L of DXC, SMX, DXM, and CBZ, respectively, showcasing its potential for real-world chemical water decontamination application. Further enhancements that enable continuous-flow operation and integrate highly effective adsorbents and photocatalytic materials can significantly enhance system performance.

Tepuazines A-E: Phenazine Glycosides from a Venezuelan Quartz-Rich (Tepui) Cave Soil-Derived Streptomyces virginiae CMB-CA091.

Investigation of the secondary metabolites of Streptomyces virginiae CMB-CA091 isolated from the quartz-rich (tepui) soil of a cave in Venezuela yielded two new dimeric phenazine glycosides, tepuazines A and B (1 and 2); three new monomeric phenazine glycosides, tepuazines C-E (3-5); and a series of known analogues, baraphenazine G (6), phenazinolin D (7), izumiphenazine C (8), 4-methylaminobenzoyl-l-rhamnopyranoside (9), and 2-acetamidophenol (10). Structures were assigned to 1-10 on the basis of detailed spectroscopic analysis and biosynthetic considerations, with 1 and 2 featuring a rare 2-oxabicyclo[3.3.1]nonane-like ring C/D bridge shared with only a handful of known Streptomyces natural products. We propose a plausible convergent biosynthetic relationship linking all known members of this structure class that provides a rationale for the observed ring C/D configuration.

Acetone Detection and Classification as Biomarker of Diabetes Mellitus Using a Quartz Crystal Microbalance Gas Sensor Array.

A gas sensor array was developed and evaluated using four high-frequency quartz crystal microbalance devices (with a 30 MHz resonant frequency in fundamental mode). The QCM devices were coated with ethyl cellulose (EC), polymethylmethacrylate (PMMA), Apiezon L (ApL), and Apiezon T (ApT) sensing films, and deposited by the ultrasonic atomization method. The objective of this research was to propose a non-invasive technique for acetone biomarker detection, which is associated with diabetes mellitus disease. The gas sensor array was exposed to methanol, ethanol, isopropanol, and acetone biomarkers in four different concentrations, corresponding to 1, 5, 10, and 15 µL, at temperature of 22 °C and relative humidity of 20%. These samples were used because human breath contains them and they are used for disease detection. Moreover, the gas sensor responses were analyzed using principal component analysis and discriminant analysis, achieving the classification of the acetone biomarker with a 100% membership percentage when its concentration varies from 327 to 4908 ppm, and its identification from methanol, ethanol, and isopropanol.

The luminous transmittance of the quartz-glass fiber posts is superior to glass fiber posts.

Fiber-reinforced prefabricated intraarticular posts have gained popularity due to several favorable characteristics for clinical use compared to metallic intraradicular posts. AIM: To evaluate the light transmission capacity of two types of fiber posts, using two different methods. MATERIALS AND METHOD: The posts were divided into two groups: experimental group - quartz-glass fiber posts (n=10) and control group - glass fiber posts (n=10). The light transmittance of the samples was compared by means of light intensity test by photographs and ultraviolet-visible spectrophotometer. This test was analyzed by thirds: coronal, middle, and apical. The spectophotometer tested the luminous transmittance along the length of the post. The statistical analysis was conducted with a significance level of 0.05. RESULTS: Light transmission was 97% on the coronal third, 68% in the middle third, and 27.66% in the apical third in the posts of the experimental group. In the posts of the control group, the light transmission was 95.33% in the coronal third, 80.66% in the middle third, and 41.33% in the apical third. Light transmission was significantly higher in the middle third of the posts of the experimental group when compared to the control group (p<0.05). The luminous transmittance of the posts of the experimental group was 97.4% with wavelengths of 400 nm, 97% at 450 and 500 nm, and 96.9% at 550 nm. In the posts of the control group, the luminous transmittance was 72.3% with wavelengths of 400 nm, 68.6% at 450 nm; 64.6% at 500 nm and 61.5% at 550 nm. The posts of the experimental group demonstrated significantly higher light transmittance than the control group (p<0.001).

Os pinos intra-articulares pré-fabricados reforçados com fibras têm ganhado popularidade devido a várias características favoráveis ao uso clínico em comparação com os pinos intra-radiculares metálicos). Objetivo: Avaliar a capacidade de transmissão de luz de dois tipos de pinos de fibra, usando dois métodos diferentes. Materiais e Método: Os pinos foram divididos em dois grupos: grupo experimental - pinos de fibra de vidro de quartzo e grupo controle - pinos de fibra de vidro. A transmitância de luz das amostras foi comparada por meio de teste de intensidade de luz por fotografias e espectrofotômetro ultravioleta-visível. Este teste foi analisado por terços: coronal, médio e apical. O espectrofotômetro testou a transmitância luminosa ao longo do comprimento do pino. A análise estatística foi realizada com nível de significância de 0,05. Resultados: A transmissão luminosa foi de 97% no terço coronal, 68% no terço médio e 27,66% no terço apical nos pinos do grupo experimental. Nos pinos do grupo controle, a transmissão de luz foi de 95,33% no terço coronal, 80,66% no terço médio e 41,33% no terço apical. A transmissão luminosa foi significativamente maior no terço médio dos pinos do grupo experimental quando comparado ao grupo controle (p<0,05). A transmitância luminosa dos pinos do grupo experimental foi de 97,4% com comprimento de onda de 400 nm, 97% em 450 e 500 nm e 96,9% em 550 nm. Nos postes do grupo controle, a transmitância luminosa foi de 72,3% com comprimento de onda de 400 nm, 68,6% em 450 nm; 64,6% a 500 nm e 61,5% a 550 nm. Os pinos do grupo experimental demonstraram transmitância de luz significativamente maior do que o grupo controle (p<0,001). Conclusão: a transmitância luminosa dos pinos de fibra de vidro de quartzo é maior do que pinos de fibra de vidro.

Thermoluminescence properties and identification of irradiated cocoa beans during long-term storage.

This work reports on the thermoluminescence (TL) properties and detection of contaminating minerals isolated from Mexican cocoa beans irradiated with gamma radiation and stored for 4 years. Contaminating minerals isolated from cocoa beans consisting of quartz, diopside, plagioclase, albite, and iron oxide with irregular and rectangular grains and average length of 135 µm. Cocoa beans are detected as irradiated even after 4 years of storage using the shape and maximum temperature of the TL glow curve of contaminating minerals. The TL properties of dose-response, and fading of minerals were also analysed. The TL dose-response is linear from 5 to 100 Gy, supra-linear between 250 and 1000 Gy, and sub-linear above 1500 Gy. Based on the TL1/TL2 ratio the minerals are identified as irradiated from 250 Gy to 4500 Gy in the dose-response test and after different storage times in the darkness at room temperature. A continuum trap distribution can be associated with the TL glow curve of minerals using the Tm-Tstop method. First order kinetic peaks were used in the Glow Curve Deconvolution of natural and irradiated (1 and 10 kGy) TL curves.

Geochemistry signatures of mercury in soils of the Amazon rainforest biome.

Mercury (Hg) toxicity in soils depends on Hg species and other physical and chemical attributes, as selenium (Se) hotspots in soils, particularly relevant in Amazonian soils. The study of Hg species and their relations in representative locations of the Amazon rainforest biome is critical for assessing the potential risks of Hg in this environment. This work aimed to determine the concentration of total Hg and its species (Hg0, Hg22+ and Hg2+), and to correlate Hgtotal concentration with total elemental composition, magnetic susceptibility, and physicochemical attributes of Amazon soils. Nine sites in the Amazon rainforest biome, Brazil, were selected and analyzed for their chemical, physical, and mineralogical attributes. The clay fraction of the studied Amazon soils is dominated by kaolinite, goethite, hematite, gibbsite, and quartz. Mica was also found in soils from the States of Acre and Amazonas. Hgtotal ranged from 21.5 to 208 µg kg-1 (median = 104 µg kg-1), and the concentrations did not exceed the threshold value established for Brazilian soils (500 µg kg-1). The Hg2+ was notably the predominant species. Its occurrence and concentration were correlated with the landscape position and soil attributes. Hgtotal was moderately and positively correlated with TiO2, clay, and Se. The findings showed that geographic location, geological formation, and pedological differences influence the heterogeneity and distribution of Hgtotal in the studied soil classes. Thus, a detailed characterization and knowledgment of the soil classes is very important to clarify the complex behavior of this metal in the Amazon rainforest biome.

Mercury background values in soils and saprolites in the gold-rich greenstone belt of Suriname, Guiana Shield: The role of parent rock and residual enrichment.

In order to develop criteria to distinguish polluted from unpolluted materials in areas subjected to artisanal small-scale gold mining, background mercury values were established in 62 natural soil and saprolite profiles on 16 different parent rock types in the greenstone belt of Suriname. Hg values in pristine topsoils often amount to up to 200 µg/kg, about 100 times higher than Hg in common parent rocks. Additional analyses of 40 major and trace elements in two pilot profiles show that Hg values are strongly correlated to Fe, Cr and V values, which suggests that just as those elements Hg is residually enriched in topsoils by laterisation processes. In the deeper pallid zones of the profiles, Hg has often been leached almost completely together with iron by reducing groundwater action. In this way the range of Hg values within a single profile can be greater than between profiles. Maximum and average Hg values of 196 samples from the 16 different parent rock types fall apart into two main groups. Felsic parent rocks with predominance of quartz and feldspar have maximum Hg values around 100 µg/kg and averages around 50 µg/kg, mafic ones with less silica and higher Fe, Mg and Ca have maximum values around 250-300 µg/kg and averages around 150 µg/kg. In general the natural soil and saprolite Hg values are in the same order of magnitude as many published mine tailings and stream sediments, and therefore cannot be used to separate polluted from unpolluted materials.

Pino de quartzo personalizado: descriçâo da técnica e protocolo de cimentação / Personalized quartz pin: description of technique and cementation protocol

O tratamento endodôntico frequentemente leva à perda de parte coronária de um elemento dentário, seja pelo enfraquecimento de sua estrutura, por lesões traumáticas ou por cárie. Desde que em condições favoráveis, esses dentes podem ser restaurados por meio de retenção adequada provida por meio de retentores intrarradiculares. Os pinos de quartzo utilizados como retentor intrarradicular surgiram com os avanços da odontologia adesiva, sendo uma opção relevante com inúmeras vantagens. A literatura odontológica aponta que a adaptação do pino às paredes do conduto radicular, somada a técnica de cimentação adesiva, são fatores essenciais para a longevidade do tratamento, sendo necessário em alguns casos sua personalização, para garantir melhor assentamento e promover prognóstico favorável. Objetivou-se neste artigo apresentar a técnica de preparo, personalização e cimentação do pino de quartzo na reconstrução de um dente tratado endodonticamente ilustrado por meio de caso clínico. Através de um protocolo ordenado e meticuloso da técnica de aplicação, foi possível alcançar o resultado desejado(AU)

Endodontic treatment often leads to loss of the coronary part of a tooth, either by weakening its structure, by traumatic lesions or by caries. Since under faborable conditions, these teetn can be restored by means of the biomechanical reinforcement promoted by the intraradicular retainers. The quartz posts have appeared with the advances of restorative dentistry, being a relevant option with numerous advantages. The dental literature indicates that the adaptation of the post to the root canal walls, together with the adhesive cementation technique, are essential factors for the longevity of the treatmet, being necessary in some cases its personalization, which guarantees its better settlement, avoiding the impression of undesirable forces to the tooth anf promoting better prognosis. The objective was to present the technique of preparation, personalization and cementation of the quartz post in the reconstruction of an endodontically treated tooth. Through an orderly and meticulous protocol of the application technique, it was possible to achieve the desired result(AU)

Biomolecules from Fossilized Hot Spring Sinters: Implications for the Search for Life on Mars.

Hot spring environments are commonly dominated by silica sinters that precipitate by the rapid cooling of silica-saturated fluids and the activity of microbial communities. However, the potential for preservation of organic traces of life in silica sinters back through time is not well understood. This is important for the exploration of early life on Earth and possibly Mars. Most previous studies have focused on physical preservation in samples <900 years old, with only a few focused on organic biomarkers. In this study, we investigate the organic geochemistry of hot spring samples from El Tatio, Chile and the Taupo Volcanic Zone, with ages varying from modern to ∼9.4 ka. Results show that all samples contain opaline silica and contain hydrocarbons that are indicative of a cyanobacterial origin. A ∼3 ka recrystallized, quartz-bearing sample also contains traces of cyanobacterial biomarkers. No aromatic compounds were detected in a ∼9.4 ka opal-A sample or in a modern sinter breccia sample. All other samples contain naphthalene, with one sample also containing other polyaromatic hydrocarbons. These aromatic hydrocarbons have a thermally mature distribution that is perhaps reflective of geothermal fluids migrating from deep, rather than surface, reservoirs. These data show that hot spring sinters can preserve biomolecules from the local microbial community, and that crystallinity rather than age may be the determining factor in their preservation. This research provides support for the exploration for biomolecules in opaline silica deposits on Mars.

Microtensile bond strength of root canal dentin treated with adhesive and fiber-reinforced post systems.

Nowadays, demand for esthetic restorations has risen considerably; thus, nonmetal esthetic posts made of either high-strength ceramics or reinforced resins, such as fiber-reinforced resin posts, have become more and more popular. Important characteristics of fiber-reinforced posts involve a modulus of elasticity similar to dentin and their ability to be cemented by an adhesive technique. A total of 36 maxillary incisors were divided into four groups. In this study, four adhesively luted fiber-reinforced (glass fiber, quartz glass fiber, zirconia glass fiber and woven polyethylene fiber ribbon) post systems were used. Post spaces were prepared by employing drills according to the protocol established for each group, and each post was adhesively luted with one of three adhesive systems. Three segments per root apical to the cementoenamel junction (CEJ) were obtained by sectioning the root under distilled water with a carbon spare saw. The samples (total of 108 sections) were 2.0±0.1 mm in thickness and they were stored individually in black film canisters with sterile distilled water. In order to determine the bond strength, the bonding area of each specimen was measured, and specimens were attached to a device to test microtensile strength at a speed of 1 mm/min. The analyses revealed no statistically significant differences between the adhesive systems and fiber-reinforced posts. (P> 0.05). However, the coronal portion of the root dentin had the highest bond strength. Adhesive systems used along with fiber-reinforced resin posts demonstrated reliable bonding.

Microtensile bond strength of root canal dentin treated with adhesive and fiber-reinforced post systems

Abstract Nowadays, demand for esthetic restorations has risen considerably; thus, nonmetal esthetic posts made of either high-strength ceramics or reinforced resins, such as fiber-reinforced resin posts, have become more and more popular. Important characteristics of fiber-reinforced posts involve a modulus of elasticity similar to dentin and their ability to be cemented by an adhesive technique. A total of 36 maxillary incisors were divided into four groups. In this study, four adhesively luted fiber-reinforced (glass fiber, quartz glass fiber, zirconia glass fiber and woven polyethylene fiber ribbon) post systems were used. Post spaces were prepared by employing drills according to the protocol established for each group, and each post was adhesively luted with one of three adhesive systems. Three segments per root apical to the cementoenamel junction (CEJ) were obtained by sectioning the root under distilled water with a carbon spare saw. The samples (total of 108 sections) were 2.0±0.1 mm in thickness and they were stored individually in black film canisters with sterile distilled water. In order to determine the bond strength, the bonding area of each specimen was measured, and specimens were attached to a device to test microtensile strength at a speed of 1 mm/min. The analyses revealed no statistically significant differences between the adhesive systems and fiber-reinforced posts. (P> 0.05). However, the coronal portion of the root dentin had the highest bond strength. Adhesive systems used along with fiber-reinforced resin posts demonstrated reliable bonding.

Late Pleistocene to early Holocene high-quality quartz crystal procurement from the Valiente quarry workshop site (32°S, Chile, South America).

The procurement of high-quality lithic resources is amongst the most indicative processes of decision-making in the archaeology of early human groups peopling the Americas. Directly dated deposits from quarry workshops have been absent of the late Pleistocene record of South America. We present the results of the excavations of a high-quality translucent quartz crystal workshop that yielded radiocarbon-dated coherently layered stratigraphic deposits that shed light into the behavior of the initial stages of lithic procurement. Based on a detailed analysis of the context of the Valiente site (32° S, Chile, South America), we discuss the stages of bifacial production of point technology. The deposit produced evidence of cumulative occupations over the period between 12,630 and 11,320 calibrated years before present. This ~1,300-year span is coincidental with a major environmental step-wise drying trend as indicated by the local and regional pollen records. Furthermore, it is synchronous to the process in which natural landscapes became the earliest taskscapes in the region, thereby encompassing major cultural changes related to the organization of the land use. These results are discussed in the frame of contemporaneous archaeological data to discuss specific aspects of technology and decision-making of the earliest settlers of South America.

Resolución integral de una fractura coronorradicular complicada por traumatismo dentoalveolar: informe de un caso / Integral resolution of a complicated crown-root fracture by dentoalveolar traumatism: report of a case

Objetivo: Mostrar una alternativa de tratamiento para las fracturas coronorradiculares complicadas, que restablece la función y la estética de las piezas traumatizadas. Caso clínico: Una paciente de 16 años se presentó en la guardia del Centro Odontológico OSEP tras haber sufrido un accidente vial que le produjo un traumatismo dentoalveolar. El diagnóstico fue fractura coronaria sin exposición pulpar de la pieza dentaria 12 y fractura coronorradicular complicada de la pieza 11. El tratamiento incluyó restauración con resina compuesta de la pieza 12 y endodoncia, extrusión ortodóntica, alargamiento coronario y rehabilitación con perno de fibra de cuarzo y corona de resina compuesta de la pieza 11. Conclusiones: El tratamiento de las fracturas coronorradiculares representa un desafío para el odontólogo. Los resultados del tratamiento, en este paciente, fueron excelentes, ya que lograron devolver estética y función (AU)

Aim: To show an alternative treatment for complicated crown-root fractures, which restores function and aesthetics of the traumatized teeth. Case report: This paper reports the case of a 16-yearold girl who attends the OSEP Dental Center, stating that she had suffered a traffic accident resulting in a dentoalveolar trauma. The diagnosis was a coronary fracture without pulp exposure of tooth 12, and complicated crown-root fracture of tooth 11. Treatment included composite resin restoration of tooth 12 and endodontic, orthodontic extrusion, crown lengthening and rehabilitation with quartz fiber post and composite resin crown of tooth 11. Conclusions: The treatment of crown-root fractures poses a challenge for the dentist. The results of the treatment in this patient were excellent, and aesthetics and function were restored (AU)

Pedogenetic processes in anthrosols with pretic horizon (Amazonian Dark Earth) in Central Amazon, Brazil.

Anthrosols known as Amazonian Dark Earth (ADE) have borne witness to the intensification of sedentary patterns and the demographic increase in Central Amazon. As a result, a recurring pattern has been observed of mounds with ADE arising from domestic activities and the disposal of waste. The objective of this research was to demonstrate the relationship of these anthropic activities with pedogenetic formation processes of ADE in the municipality of Iranduba, Brazil. Disturbed and undisturbed soil samples were taken from two areas of ADE (pretic horizon) and from a non-anthropic pedon. Physical, chemical, micromorphological and SEM-EDS analyses were performed. The coarse material of the pretic horizons consisted predominantly of quartz, iron nodules, ceramics and charcoal fragments, and the fine material is organo-mineral. There was a direct relationship between the color of pretic horizons and the number of charcoal fragments. The thickness of the ADE results from the redistribution of charcoal at depth through bioturbation, transforming subsurface horizons into anthropic horizons. ADE presents granular microaggregates of geochemical and zoogenetic origin. Degradation of iron nodules is intensified in pretic horizons, promoting a reverse pedogenic process contributing to the xanthization process. Surprisingly the anthropic activities also favor clay dispersion and argilluviation; clay coatings on the ceramic fragments and in the pores demonstrate that this is a current process. Processes identified as contributing to ADE genesis included: i) addition of organic residues and ceramic artifacts (cumulization) with the use of fire; ii) mechanical action of humans, roots and macrofauna (bioturbation); iii) melanization of deeper horizons as a result of bioturbation; iv) argilluviation and degradation of iron nodules. This study offers new support to archaeological research in respect to ADE formation processes in Central Amazon and confirmed the hypothesis that ancient anthropic activities may trigger and/or accelerate pedogenetic processes previously credited only to natural causes.

A crosta laterítica ferro-titanífera da Vila Nova Colina e a lateritização no sul de Roraima / The iron-titaniferous lateritic crust of the Vila Nova Colina and the lateritization in south of Roraima

Lateritic crusts developed upon the Guiana Shield basement rocks (e.g. granites of the Água Branca Intrusive Suite) was recognized in the Vila Nova Colina region, located in south Roraima state. The objectives of this work were to study the mineral and geochemical characteristics of lateritic crusts and to evaluate the relationship between them and the rocks of the region, in order to understand the evolution of laterization and provide information about the economic potential. This study comprises petrography, mineralogy and litogeochemical investigations of the granites, the quartz-hornblende gabbro and the lateritic crusts formed from these rocks. The granites and the quartz-hornblende gabbro has developed, respectively, a specific type of lateritic crust: (i) the ferruginous vermiform one with high amounts of kaolinite, goethite, hematite, magnetite and anatase, higher concentration of Al2O3, Sc, Th e Zr and, (ii) the iron-titaniferous massive one with high amounts of magnetite, hematite, maghemite, goethite, kaolinite, anatase, gibbsite and ilmenite, and consequently in higher amounts of Fe2O3, TiO2, V e Cu. Each crust type indicates the effect of the lateritization in the south portion of Roraima and their topographic position. The higher topographic position of the massive crust (220 m), its mineral and geochemical composition, indicate the maturity (i.e. needed more time to be formed) and may represent a relict of an erosion phase in the region, probably associated with a subsidence of the Tacutu basin in the Miocene. Otherwise, the vermiform crust formed at a lower topographic position (140 m) with no gibbsite, suggests that it is younger than the massive one and represents the immature laterization of the Plio-Pleistocene.

Crostas lateríticas desenvolvidas sobre as rochas do embasamento do Escudo das Guianas (p.e. granitos da Suíte Intrusiva Água Branca) são reconhecidas na região de Vila Nova Colina, localizada ao sul do estado de Roraima. Os objetivos deste trabalho foram estudar as características minerais e geoquímicas dessas crostas lateríticas e avaliar a relação entre elas e as rochas da região, a fim de entender a evolução da lateritização e fornecer informações sobre seu potencial econômico. Este estudo compreende dados de petrografia, mineralogia e litogeoquímica de granitos, quartzo-hornblenda gabro e crostas lateríticas formadas a partir dessas rochas. Os granitos e o quartzo-hornblenda gabro desenvolveram, respectivamente, um tipo específico de crosta laterítica: (i) vermiforme ferruginosa com elevados teores de caulinita, goethita, hematita, magnetita e anatásio e maior concentração de Al2O3, Sc, Th, e Zr e, (ii) maciça ferro-titanífera com altos teores de magnetita, hematita, maghemita, goethita, caulinita, anatásio, gibbsita e ilmenita e de Fe2O3, TiO2, V e Cu. Cada tipo de crosta indica o efeito da lateritização na porção sul de Roraima e sua posição topográfica. O posicionamento topográfico mais elevado da crosta maciça (220 m) e sua composição mineralógica e geoquímica, indicam sua maturidade (isto é, precisou de mais tempo para ser formada) e, portanto relicto de uma fase erosiva na região, provavelmente associada a subsidência da bacia do Tacutu no Mioceno. Enquanto a crosta vermiforme em uma posição mais rebaixada (140 m) sem gibbsita, sugere que ela é mais jovem que a maciça e representa a lateritização imatura do Plio-Pleistoceno.

A crosta laterítica ferro-titanífera da Vila Nova Colina e a lateritização no sul de Roraima / The iron-titaniferous lateritic crust of the Vila Nova Colina and the lateritization in south of Roraima

Lateritic crusts developed upon the Guiana Shield basement rocks (e.g. granites of the Água Branca Intrusive Suite) was recognized in the Vila Nova Colina region, located in south Roraima state. The objectives of this work were to study the mineral and geochemical characteristics of lateritic crusts and to evaluate the relationship between them and the rocks of the region, in order to understand the evolution of laterization and provide information about the economic potential. This study comprises petrography, mineralogy and litogeochemical investigations of the granites, the quartz-hornblende gabbro and the lateritic crusts formed from these rocks. The granites and the quartz-hornblende gabbro has developed, respectively, a specific type of lateritic crust: (i) the ferruginous vermiform one with high amounts of kaolinite, goethite, hematite, magnetite and anatase, higher concentration of Al2O3, Sc, Th e Zr and, (ii) the iron-titaniferous massive one with high amounts of magnetite, hematite, maghemite, goethite, kaolinite, anatase, gibbsite and ilmenite, and consequently in higher amounts of Fe2O3, TiO2, V e Cu. Each crust type indicates the effect of the lateritization in the south portion of Roraima and their topographic position. The higher topographic position of the massive crust (220 m), its mineral and geochemical composition, indicate the maturity (i.e. needed more time to be formed) and may represent a relict of an erosion phase in the region, probably associated with a subsidence of the Tacutu basin in the Miocene. Otherwise, the vermiform crust formed at a lower topographic position (140 m) with no gibbsite, suggests that it is younger than the massive one and represents the immature laterization of the Plio-Pleistocene.(AU)

Crostas lateríticas desenvolvidas sobre as rochas do embasamento do Escudo das Guianas (p.e. granitos da Suíte Intrusiva Água Branca) são reconhecidas na região de Vila Nova Colina, localizada ao sul do estado de Roraima. Os objetivos deste trabalho foram estudar as características minerais e geoquímicas dessas crostas lateríticas e avaliar a relação entre elas e as rochas da região, a fim de entender a evolução da lateritização e fornecer informações sobre seu potencial econômico. Este estudo compreende dados de petrografia, mineralogia e litogeoquímica de granitos, quartzo-hornblenda gabro e crostas lateríticas formadas a partir dessas rochas. Os granitos e o quartzo-hornblenda gabro desenvolveram, respectivamente, um tipo específico de crosta laterítica: (i) vermiforme ferruginosa com elevados teores de caulinita, goethita, hematita, magnetita e anatásio e maior concentração de Al2O3, Sc, Th, e Zr e, (ii) maciça ferro-titanífera com altos teores de magnetita, hematita, maghemita, goethita, caulinita, anatásio, gibbsita e ilmenita e de Fe2O3, TiO2, V e Cu. Cada tipo de crosta indica o efeito da lateritização na porção sul de Roraima e sua posição topográfica. O posicionamento topográfico mais elevado da crosta maciça (220 m) e sua composição mineralógica e geoquímica, indicam sua maturidade (isto é, precisou de mais tempo para ser formada) e, portanto relicto de uma fase erosiva na região, provavelmente associada a subsidência da bacia do Tacutu no Mioceno. Enquanto a crosta vermiforme em uma posição mais rebaixada (140 m) sem gibbsita, sugere que ela é mais jovem que a maciça e representa a lateritização imatura do Plio-Pleistoceno.(AU)

Fijación simplificada de pernos de fibra con cementos de resina autograbante y de ionómero de vidrio modificado con resina: reporte de caso y revisión de la literatura / Simplified placement of fiber posts with self-etching resin cements and resin-modified glass ionomer cement: report of a case and review of the literature

Los pernos de fibra pueden ser fijados con técnicas simplificadas empleando cementos de ionómero de vidrio modificados con resina o de resina autograbante. De esta manera se evitan las técnicas de adhesión y sus variables complejas que comprometen muchas veces el resultado final del tratamiento.Los resultados son promisorios en cuanto a valores de retención, simplificación de la técnica y agilidaddel proceso clínico. En el artículo, se presenta un caso clínico de fijaciónsimplificada de un perno de fibra con un cemento de resina autograbante y se revisa la literatura científica...

Degradation of oil by fungi isolated from Gulf of Mexico beaches.

Fungi of the Ascomycota phylum were isolated from oil-soaked sand patties collected from beaches following the Deepwater Horizon oil spill. To examine their ability to degrade oil, fungal isolates were grown on oiled quartz at 20°C, 30°C and 40°C. Consistent trends in oil degradation were not related to fungal species or temperature and all isolates degraded variable quantities of oil (32-65%). Fungal isolates preferentially degraded short (

Novel method for determination of zinc traces in beverages and water samples by solid surface fluorescence using a conventional quartz cuvette.

A new method for zinc pre-concentration/separation and determination by molecular fluorescence is proposed. The metal was complexed with o-phenanthroline and eosin at pH 7.5 in Tris; a piece of filter paper was used as a solid support and solid fluorescent emission measured using a conventional quartz cuvette. Under optimal conditions, the limits of detection and quantification were 0.36 × 10(-3) and 1.29 × 10(-3) µg L(-1), respectively, and the linear range from 1.29 × 10(-3) to 4.50 µg L(-1). This method showed good sensitivity and selectivity, and it was applied to the determination of zinc in foods and tap water. The absence of filtration reduced the consumption of water and electricity. Additionally, the use of common filter papers makes it a simpler and more rapid alternative to conventional methods, with sensitivity and accuracy similar to atomic spectroscopies using a typical laboratory instrument.

Influence of silicate on the transport of bacteria in quartz sand and iron mineral-coated sand.

The influence of silicate on the transport and deposition of bacteria (Escherichia coli) in packed porous media were examined at a constant 20 mM ionic strength with different silicate concentrations (from 0 to 1 mM) at pH 7. Transport experiments were performed in two types of representative porous media, both bare quartz sand and iron mineral-coated quartz sand. In bare quartz sand, the breakthrough plateaus in the presence of silicate in suspensions were lower and the corresponding retained profiles were higher than those without silicate ions, indicating that the presence of silicate in suspensions decreased cell transport in bare quartz sand. Moreover, the decrease of bacteria transport in quartz sand induced by silicate was more pronounced with increasing silicate concentrations from 0 to 1 mM. However, when EPS was removed from cell surfaces, the presence of silicate in cell suspensions (with different concentrations) did not affect the transport behavior of bacteria in quartz sand. The interaction of silicate with EPS on cell surfaces negatively decreased the zeta potentials of bacteria, resulting in the decreased cell transport in bare quartz sand when silicate was copresent in bacteria suspensions. In contrast, the presence of silicate in suspensions increased cell transport in iron mineral-coated sand. Silicate ions competed with bacteria for the adsorption sites on mineral-coated sand, contributing to the increased cell transport in mineral-coated sand with silicate present in cell suspensions.