Guilherme Frederico Bernardo Lenz e Silva

Evidence for a network transcriptional control of promiscuous gene expression in medullary thymic epithelial cells

The expression of peripheral tissue antigens (PTAs) in the thymus by medullary thymic epithelial cells (mTECs) is essential for the central self-tolerance in the generation of the T cell repertoire. Due to heterogeneity of autoantigen representation, this phenomenon has been termed promiscuous gene expression (PGE), in which the autoimmune regulator (Aire) gene plays a key role as a transcription factor in part of these genes. Here we used a microarray strategy to access PGE in cultured murine CD80(+) 3.10 mTEC line. Hierarchical clustering of the data allowed observation that PTA genes were differentially expressed being possible to found their respective induced or repressed mRNAs. To further investigate the control of PGE, we tested the hypothesis that genes involved in this phenomenon might also be modulated by transcriptional network. We then reconstructed such network based on the microarray expression data, featuring the guanylate cyclase 2d (Gucy2d) gene as a main node. In such condition, we established 167 positive and negative interactions with downstream PTA genes. Silencing Aire by RNA interference, Gucy2d while down regulated established a larger number (355) of interactions with PTA genes. T- and G-boxes corresponding to AIRE protein binding sites located upstream to ATG codon of Gucy2d supports this effect. These findings provide evidence that Aire plays a role in association with Gucy2d, which is connected to several PTA genes and establishes a cascade-like transcriptional control of promiscuous gene expression in mTEC cells.

Evaluation of Industrial Rejects of Mineral and Metallurgical Processing as Ceramic Synthetic Proppants

Hydraulic fracturing is a very important technique to increase the productivity and recovery of oil reservoirs with low pressure or high depth. The hydraulic fracturing technique is a method of well stimulation in which liquid under high pressure is pumped down a well to fracture the reservoir rock adjacent to the wellbore. Propping agents are used to keep the fractures/cracks open. They can be made from the reject of mineral extraction processes when they present specifics characteristic. The aim of this paper is the evaluation of the use of industrial rejects to the development of ceramic synthetic proppants that are resistant to chemical corrosion and high mechanical strength in aqueous acid and salt water environment. In this study, industrial rejects from nickel sulfide ore flotation (grey mud - GM), red mud (RM) from Bayer process and black mud (BM) from Caron processing of nickel was used as raw material for the production of ceramic synthetic proppants. The material processing was performed through drying, milling, pressing, sintering and characterizing raw material. Several characterization techniques such as X-ray powder diffraction (XRD), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), high temperature dilatometry and compression strength test were performed after sintering to evaluate the technological potential of recycling these metallurgical and mineral rejects. Mechanical properties were improved after sample sintering. The results show that it is possible to manufacture ceramics of high strength and resistance to acidic/salt water environment as a result of processing minerals reject.

Proppants Development and the Shale Oil and Gas Market Perspective

Unconventional shale gas reservoirs have driven the growth of the oil and gas market to a new reality: till 2035 a 26% increase in US fuel production is predicted. Thus, the hydraulic fracturing technique has been increasingly used as a resource for shale gas extraction and the consequent use of proppants. Several studies have now evaluated the use of nanostructures to produce special proppants, such as nanosensors, coatings, membranes and special fluids. This work presents the perspective of the market for oil, gas, shale, hydraulic fracturing and proppants in addition to a current development of proppants. Proppants were characterized through API RP 19C, DTA and DRX analysis. The morphology of carbon nanostructures (carbon nanotubes, carbon black and few layers’ graphite from reduced graphene oxide synthesis) produced and introduced on AM (alkali-activated metakaolin) matrix composites were evaluated using scanning transmission electron microscopy (STEM).

Development of Sodium Hydroxide-Activated Metakaolin with Nanocarbon Materials as Synthetic Ceramic Proppants

The use of proppants in hydraulic fracturing has significantly grown worldwide in recent years. Discoveries of large unconventional reservoirs in the north of Brazil have collaborated to give it the 10th position among countries with the worlds largest shale reserves. Nowadays, studies on nanomaterials that are used as additives in proppants are the focus of North Americas companies and universities in order to develop either proppants that can suffer mechanical and chemical changes inside the reservoir or that enable their traceability and direction. This paper presents a study on synthesis and characterization of metakaolin’s based ceramic proppants incorporating different types of nanocarbon materials. The method adopted was based on use of high intensive mixing of raw material (metakaolin) granulated with alkaline water solution of dispersed carbon nanomaterials. The SEM analysis testify the carbon nanomaterials dispersion on proppant bulk structure. Mechanical tests (crush resistance or K-value) indicated that metakaolin based proppants reached similar characteristics of white sand natural proppants.