Production and purification of fumonisins from a highly toxigenic Fusarium verticilloides strain

Fumonisins are the major mycotoxins produced by Fusarium verticilloides and F. proliferatum fungi which are widely found as contaminants in corn and corn screenings. These molecules are hepatotoxic and nephrotoxic for several species and carcinogenic in rodents. Moreover their consumption was linked to high prevalence of human oesophageal cancer in certain geographic areas. The aim of this work was to improve FB1 production and purification procedures in laboratory conditions in order to produce large quantities of semi-purified toxin that may be used in experimental intoxications of farm animals. We used a highly toxigenic strain of Fusarium verticilloides (NRRL-3428) isolated from feeds. Influence of substrate, temperature, water content, culture recipient size and screen analysis of the substrate on fumonisin production was tested. Optimal production was obtained when strain was grown on coarsely cracked corn with 50% water content at 21°C during 5 weeks. This allowed the production of 3 to 4 g of fumonisin B1 per kg of culture material. The composition of the extracts was found to be as follow : 54% FB1, 8% FB2, 9% FB3 and 29% of pigments coming from corn. The ratio observed between FB1 and FB2 is comparable to the one reported in naturally contaminated corn. Further purification of these extracts on SAX columns led to the removal of pigments and to obtain of fumonisins extracts pure enough to be used for intra-venous or intra-peritoneal injection

Microstructural Characterization of AA6022-T43 Aluminum Alloy Sheet During Monotonic Loading

Environmental issues and regulations are pushing the automotive industry to produce more efficient and environmentally friendly vehicles. To address these issues, reducing the weight of the vehicles by use of aluminum alloys is increasing. AA6022-T43 is a new sheet aluminum alloy designed specifically for automobile enclosure panels. Because this alloy is new, little data exists on its mechanical properties in the open literature. AA6022-T43 is received by the automotive industry in 1-mm thick sheet stock and subsequently stamped into the desired component. The design and manufacturing processes of the component are guided by the materials mechanical behavior. This study characterizes the mechanical and microstructural properties of uniaxially strained AA6022-T43

Deconvoluting the link between weld tool geometry and process parameters

Advancing the process of friction stir welding (FSW) currently relies on a trial and error approach toward selecting tool geometries and determining process parameters. Before a more formalized design process can be established, a methodology for process parameter selection must be developed. In FSW, various flow paths, as influenced by the tool design, have been proposed to explain the formation of a high quality weld. Central to the discussion is whether the metal is extruded around the tool or whether the metal crosses a shear zone which differentiates the stir zone from the parent material. Probing the interaction between the weld tool and workpiece can shed light on the effectiveness of smooth tapered pins in preventing slippage at the tool interface. Creation of a shear surface a finite distance from the weld tool requires that the metal stick to the tool surface so that it is deformed by shearing in the workpiece. Tool slippage would then be limited by pressure generated from either threads or a critical taper angle. In contrast, if the metal were extruded around the tool, a slipping condition would occur at the interface. These variations in the material flow should be observed in the resulting weld structure and force/torque data acquired during the weld. In the present study, a family of weld tools was designed and used to produce FSW panels for comparison. The tools included smooth surface pins with different taper angles and a standard threaded pin. From each weld, specimens were removed for metallographic analysis and tensile testing. Variations in the tool geometry were observed to affect the mechanical power input and tool heat dissipation. The initial process parameters were selected based on a constant “pseudo heat index (PHI)” taken from FSW literature, but for each corresponding tool, variations were seen in the process parameter window that resulted in defectree welds and in their weld properties. Using a one-dimensional heat transfer model, a method is proposed for calculating process parameters that takes into account the specific tool design

liteITD a MATLAB Graphical User Interface (GUI) program for topology design of continuum structures

Over the past few decades, topology optimization has emerged as a powerful and useful tool for the design of structures, also exploiting the ever growing computational speed and power. The design process has also been affected by computers which changed the concept of form into the concept of formation and the emergence of digital design. Topology optimization can modify existing designs, incorporate explicit features into a design and generate completely new designs. This paper will show how topology optimization can be used as a digital tool. The liteITD (lite version of Isolines Topology Design) software package will be described with the purpose of providing a tool for topology design. The liteITD program solves the topology optimization of two-dimensional continuum structures using von Mises stress isolines under single or multiple loading conditions, with different material properties in tension and compression, and multiple materials. The liteITD program is fully implemented in the MATrix LABoratory (MATLAB) software environment of MathWorks under Windows operating system. GUIDE (Graphical User Interface Development Environment) was used to create a friendly Graphical User Interface (GUI). The usage of this application is directed to students mainly (educational purposes), although also to designers and engineers with experience. The liteITD program can be downloaded and used for free from the website: http://www.upct.es/goe/software/liteITD.php

Strujanje uzrokovano vjetrom u stratificiranom fluidu: numeričko istraživanje i primjena na Tršćanski zaljev u uvjetima jake bure

This study investigates the circulation driven by a severe bora wind event in the Gulf of Trieste during the stratification season. A preliminary numerical analysis of the wind driven transport in the surface boundary layer is carried out for an idealized, laterally unbounded, shallow domain. Then, the simulations are focused on the Gulf of Trieste, using a realistic bathymetry and assuming stably stratified initial conditions. First, the model is driven by constant wind forcing, then qualitative and quantitative estimations of the dynamics of the basin are made reproducing the strong Bora event of the 25 June 2002. Numerical results show good agreement with in situ measurements and remotely sensed images. The relevance of coastal upwelling and its persistence are also assessed. The results prove that mixing and coastal upwelling (both wind-driven) govern the circulation of the basin. When bora starts blowing, buoyant surface water is moved by EKMAN transport offshore inducing a bottom onshore current. Simultaneously, wind driven stirring breaks the initial stable stratification. The surface offshore current generates a sea surface level setup on the northern boundary. When bora decreases, this surface tilt is no longer sustained, and a reversal of the circulation is observed in the upper layer. The sensitivity to the wind forcing is also discussed. All of these issues are crucial to environmental problems such as pollutant dispersion or anoxia phenomena in the bottom layers of the Gulf.U ovom se radu analizira strujanje u Tršćanskom zaljevu uzrokovano jakom burom u vertikalno stratificiranom slučaju. Preliminarna numerička analiza strujnog polja uzrokovanog vjetrom urađena je za idealizirani slučaj horizontalno neograničene domene. Zatim su numeričke simulacije primijenjene na Tršćanski zaljev upotrebivši realnu batimetriju i uz pretpostavku vertikalno stabilne stratifikacije. 25. lipnja 2002. godine najprije je primjenijen stacionaran vjetar, a zatim realistična situacija jake bure. Rezultati numeričke integracije pokazuju dobro slaganje s in situ i daljinskim mjerenjima. Posebna je pažnja poklonjena intenzitetu obalnog “upwellinga” i njegovoj postojanosti. Rezultati ukazuju da su vertikalno miješanje i “upwelling” odgovorni za strujanje u bazenu. Bura uzrokuje EKMANOV transport i odnosi slatku vodu prema sredini zaljeva, te uzrokuje formiranje pridnene struje ka obali. Istovremeno vertikalno miješanje slabi vertikalnu stabilnost vodenog stupca. Površinska struja od obale prema sredini zaljeva uzrokuje nagib razine mora od sjeverne obale ka jugu. Kada prestane bura nagib razine mora se više ne može održati i javlja se površinska struja suprotnog smjera. U ovom je radu također istraživana osjetljivost numeričkih rješenja na utjecaj vjetra. Ovi su procesi važni za širenje otpadnih tvari kao i za eventualnu pojavu anoksije u pridnenom sloju zaljeva

A sequential element rejection and admission (SERA) topology optimization code written in Matlab

This paper presents the Matlab implementation of the Sequential Element Rejection and Admission (SERA) method for topology optimization of structures and compliant mechanisms. The lines comprising this code include definition of design domain, finite element analysis, sensitivity analysis, mesh-independency filter, optimization algorithm and display of results. Extensions and changes in the algorithm are also included in order to solve multiple load cases, active and passive elements and compliant mechanisms design. The code is intended for educational purposes and introduces an alternative approach to traditional structural topology optimization algorithms. The complete code is provided in the Appendix

Layout optimization of multi-material continuum structures with the isolines topology design method

A heterogeneous or multi-material object is one made from different materials which are distributed continuously or discontinuously. Its properties can be adjusted by controlling the material composition, microstructure and geometry of the object. The development of manufacturing technologies such as rapid prototyping can eliminate the high cost of tooling and offers the possibility to make multi-material structures. However, designing such technologies is not a trivial task and requires the development or modifications of optimization algorithms to take into consideration the different aspects of these problems. This article presents an enhancement to the isolines topology design (ITD) algorithm that allows it to produce multi-material designs. Four examples of the topology design of two-dimensional continuum structures are presented to demonstrate that the ITD algorithm is an efficient and reliable method to achieve the layout optimization of multi-material continuum structures

Estimation of Actuation System Parameters for Prosthetic Ankle

The loss in mobility following amputation results in a degradation of the quality of life of the amputees as it affects many aspects of their personal and professional lives. Lower limb prostheses are used to replace the lost limbs and assist amputees in restoring their missing mobility functions. Despite the current technological advances in prosthetics, amputees still suffer from gait asymmetry and high metabolic energy costs. The gait asymmetry pattern and high metabolic energy costs occur due to: the inability to deliver the required level of assistance/power at the right time and the inertia and mass distribution asymmetry between the intact and the prosthetic leg