Nanotailoring Stereolithography Resins for Unique Applications using Carbon Nanotubes

Nanostructured materials and exploiting their properties in stereolithography (SL) may open new markets for unique rapidly manufactured functional devices. Controlled amounts of multiwalled carbon nanotubes (MWCNTs) were successfully dispersed in SL epoxy-based resins and complex three-dimensional (3D) parts were successfully fabricated by means of a multi-material SL setup. The effect of the nanosized filler was evaluated using mechanical testing. Small dispersions of MWCNTs resulted in significant effects on the physical properties of the polymerized resin. A MWCNT concentration of .05 wt% (w/v) in DSM Somos® WaterShed™ 11120 resin increased the ultimate tensile stress and fracture stress an average of 17% and 37%, respectively. Electron microscopy was used to examine the morphology of the nanocomposite and results showed affinity between the MWCNTs and SL resin and identified buckled nanotubes that illustrated strong interfacial bonding. These improved physical properties may provide opportunities for using nanocomposite SL resins in end-use applications. Varying types and concentrations of nanomaterials can be used to tailor existing SL resins for particular applications.Mechanical Engineerin

Malignant melanoma arising from a perianal fistula and harbouring a BRAF gene mutation: a case report

<p>Abstract</p> <p>Background</p> <p>Melanoma of the anal region is a very uncommon disease, accounting for only 0.2-0.3% of all melanoma cases. Mutations of the <it>BRAF </it>gene are usually absent in melanomas occurring in this region as well as in other sun-protected regions. The development of a tumour in a longstanding perianal fistula is also extremely rare. More frequent is the case of a tumour presenting as a fistula, that is, the fistula being a consequence of the cancerous process, although we have found only two cases of fistula-generating melanomas reported in the literature.</p> <p>Case Presentation</p> <p>Here we report the case of a 38-year-old male who presented with a perianal fistula of four years of evolution. Histopathological examination of the fistulous tract confirmed the presence of malignant melanoma. Due to the small size and the central location of the melanoma inside the fistulous tract, we believe the melanoma reported here developed in the epithelium of the fistula once the latter was already formed. Resected sentinel lymph nodes were negative and the patient, after going through a wide local excision, remains disease-free nine years after diagnosis. DNA obtained from melanoma tissue was analysed by automated direct sequencing and the <it>V600E </it>(<it>T1799A</it>) mutation was detected in exon 15 of the <it>BRAF </it>gene.</p> <p>Conclusion</p> <p>Since fistulae experience persistent inflammation, the fact that this melanoma harbours a <it>BRAF </it>mutation strengthens the view that oxidative stress caused by inflammatory processes plays an important role in the genesis of <it>BRAF </it>gene mutations.</p

Theotonio dos Santos (1936-2018), the revolutionary intellectual who pioneered dependency theory

This article analyzes the origins and development of the dependency theory through the life and work of Theotonio Dos Santos. His formative years at the academy and his early political activism in Brazil are examined, particularly, his time at the University of Brasilia with Vania Bambirra, Ruy Mauro Marini and André Gunder Frank ("the quartet"). This is followed by a discussion about their years of exile in Chile where the quartet regrouped at the Center for Socio-Economic Studies (ceso) of the University of Chile, and where they wrote their founding texts on dependency theory. Chile provided fertile ground for the development of this theory due to its intellectual climate, institutionality, and the country's political transformations in the late 1960s and early 1970s. The military overthrow of the Allende government on that fateful September 11th, 1973 forced the quartet once again into exile. The article continues with an analysis of Dos Santos' writings during his exile in Mexico and then back in Brazil. During this period he became involved with world system theory which culminated in the publication of his extensive trilogy on the contemporary crisis of capitalism and social theory

Modelling large-scale effects of estuarine and morphodynamic gradients on distribution and abundance of the sandy beach isopod Excirolana armata

7 páginas, 5 figuras, 1 tabla.Understanding the relationships between beach morphodynamics and macrofauna assemblages has been critical in theoretical evolution of sandybeach ecology. However, macroscale studies that consider the concurrent effects of large-scaleestuarine and morphodynamicgradients have been exceptional. The present study evaluates the combined effects of large-scale (>400 km) salinity and morphodynamics on the distribution of Excirolanaarmata. Along a salinity gradient (from 0.10 to 34.30) generated by the Río de la Plata estuary (SW Atlantic Ocean), sixteen Uruguayan sandybeaches were analyzed over a two-year period. A conditional two-step procedure using a General Additive Model (2-step GAM) was performed in order to model occurrence (1st-step) and abundance (2nd-step) of E. armata, in relation to salinity, grain size, sand moisture, compaction and organic matter of the sand, slope, beach and swash width, and water and sediment temperature. The 1st-step GAM retained 6 physical descriptors in the model (decreasing order): mean grain size, organic matter, salinity, beach width, sand moisture and water temperature. The 2nd-step GAM showed that mean grain size, salinity, sand moisture, beach width, sand compaction and organic matter were the most important explanatory variables (in decreasing order) of abundance. Mean grain size was the main predictor in both models, suggesting an important substrate specificity of E. armata towards smallest grain sizes. A meta-analysis concerning large-scale variation in abundance of E. armata in sandybeaches of the Rio Grande ecoregion (28°S–35°S) of the Warm-Temperate Southwestern Atlantic Province gave compelling evidence of this high-substrate specificity of the E. armata. Salinity was also a key factor shaping patterns in occurrence and abundance, which increased from low to intermediate/high salinities (>20), reinforcing the notion of E. armata as a marine species with relatively high tolerance to estuarine conditions. The potential role that internal brooding gives for protection of offspring to osmotic stress is discussed.JPL thanks AECID for the financial support (Mutis PhD Grant) and especially Cate for continuous encouragement. Financial support from CONICYT (project n° 1018 and 4034), PDT (project S/C/OP/07/49) and DINARA (UTF/URU/025/URU) is acknowledged.Peer reviewe

Sermon a las funebres exequias, lugubres memorias de los Antiguos catalanes, que jacen debajo de la lobrega laude de la muerte, y fallecieron siendo asilo de su inuencible patria ... : predicado en la suntuosa Capilla de las casas ...

Sign.: A¡8, B¡6Port. con esc. xi

Sermon a las funebres exequias, lugubres memorias de los antiguos catalanes, que jacen debajo de la lobrega laude de la muerte, y fallecieron siendo asilo de su inuencible patria ... : predicado en la suntuosa Capilla de las casas ...

Sign.: A\p8\s, B\p6\sPort. con esc. xi

A General Modeling Approach for Shock Absorbers: 2 DoF MR Damper Case Study

A methodology is proposed for designing a mathematical model for shock absorbers; the proposal is guided by characteristic diagrams of the shock absorbers. These characteristic diagrams (Force-Displacement, Velocity-Acceleration) are easily constructed from experimental data generated by standard tests. By analyzing the diagrams at different frequencies of interest, they can be classified into one of seven patterns, to guide the design of a model. Finally, the identification of the mathematical model can be obtained using conventional algorithms. This methodology has generated highly non-linear models for 2 degrees of freedom magneto-rheological dampers with high precision (2–10% errors)