Experimental investigation of laser beam welding of explosion-welded steel/aluminum structural transition joints

The steel/aluminum structural transition joints are widely used in shipbuilding industry due to the advantages of joining these two materials with important weight savings while exploiting their best properties. The use of laser welding to strongly connect components made of Fe and Al alloys as base materials with Fe/Al structural transition joints is very attractive. The authors report results achieved during the laser welding of these particular joints with the scope to evaluate effects of the laser-induced thermal loads on the integrity of the Fe/Al bond interface, from metallurgical and mechanical points of view. The increase of both inter-metallic film thickness and extension were detected as a result of the laser beam induced heat on the Fe/Al bond interface. These increases did not cause severe reductions of the mechanical resistance of the investigated structural transition joint.     

Chemical fingerprinting and bioactivity of Amazonian Ecuador Croton lechleri Müll. Arg. (Euphorbiaceae) stem bark essential oil: A new functional food ingredient?

Croton lechleri essential oil has been obtained by steam distillation of fresh stem bark from Amazonian Ecuador adult plants (yield: 0.61 ml/kg [0.061%]; density: 1.01 g/ml), and then chemically characterised by GC (Gas Chromatography) and GC–MS (gas chromatography–mass spectrometry). Seventy-four chemicals were detected and identified; the most abundant in descending order, were the sesquiterpenes sesquicineole (17.29%), α-calacorene (11.29%), 1,10-di-epi-cubenol (4.75%), β-calacorene (4.34%) and epi-cedrol (4.09%). Monoterpenes checked with a relative peak area higher than 2.0% were α-pinene (2.01%), p-cymene (2.61%), limonene (4.20%) and borneol (2.67%). The structure of the main chemicals were confirmed by GC–MS and ¹H NMR analyses. Spectrophotometric 1,1-diphenyl-2-picrylhydrazyl (DPPH) and DPPH-(high performance) thin layer chromatography (DPPH-(HP)TLC) bioautographic assays showed a lower radical scavenging capacity (IC₅₀) with respect to commercial thyme essential oil and BHA (butylated hydroxyl anisole), pointing out, however, that the C. lechleri essential oil fraction, characterised by α-calacorene, β-calacorene and δ-cadalene, was the most involved in the bioactivity. Similar results were obtained with β-carotene bleaching assay, where the IC₅₀ values were 0.291 ± 0.024 mg/ml for C. lechleri essential oil, 0.164 ± 0.013 and 1.34 × 10⁻⁴ ± 10⁻⁵ mg/ml for thyme essential oil and BHA, respectively. (HP)TLC-bioautographic assay performed with Gram positive and Gram negative bacteria revealed a minimum inhibitory concentration (MIC) values comprised between 0.10 mg/ml (Escherichia coli) and 10.10 mg/ml (for e.g. Pseudomonas aeruginosa), and the fraction mainly characterised by sesquicineole (97.38%) as the most involved in antibacterial capacity. Ames test employing Salmonella typhimurium TA98 and TA100 with and without a metabolic activation mixture (S9 mix) demonstrated the absence of mutagenicity of the C. lechleri essential oil between a concentration range of 10⁻² and 100 mg/plate. The same results were achieved by Saccharomyces cerevisiae D7 strain assay. An interesting mutagen-protective efficacy was evidenced by a 30% and 33% revertants reduction of TA98 strain treated with 2-aminoanthracene and nitrofluorene (2 μg/plate), suggesting, above all, the possibility to employ C. lechleri essential oil as a new flavouring protective ingredient for foods or dietary supplements against potential mutagens formed during cooking and/or processing in general.     

Second-order sliding-mode control of DC drives

One of the most recent topics in variable-structure systems theory is represented by the second-order sliding-mode control (2-SMC) methodology. This approach guarantees the same robustness and dynamic performance of traditional first-order SMC algorithms, and, at the same time, attenuates the chattering phenomenon, which is the main drawback in the actual implementation of this technique. In the present paper, a recently-proposed 2-SMC algorithm is used to synthesize a robust dc-drive control system which does not require current feedback and demands only rough information about the actual motor parameters. Stability and performance are analyzed, and an experimental comparison with a proportional-integral-based control scheme is reported.     

A follow-up study in individuals subjected to ileo-cecal resection in infancy and childhood

It is stated that the ileocecal valve delays the passage of ileal contents into the cecum and acts as a barrier against reflux and ascension of colonic bacterial flora into the small bowel: its resection may lead to bacterial colonization of the ileum and to abnormalities of intestinal motility, transit and absorption. In this study twenty individuals subjected in pediatric age (1 day to 11 years) to ileocecal resection have been evaluated from 2 to 19 years after surgery. Three patients underwent limited ileocecal resection, in four this was associated with a significant ileal resection, in five with extensive right colon resection and in eight with extensive ileal and right colon resection. Growth, stool habit, hematology and serum biochemistry were examined; all patients also underwent abdominal ultrasonography. In all body weight and height were within normal limits; seven had moderate diarrhea up to 18 months after surgery and two who required extensive intestinal resection (40 and 30 cm of small bowel left) had diarrhea until about 36 months after surgery: now all of them have daily fecal evacuation. Hematological, biochemical, urinary and fecal studies proved normal except in one treated with TPN who presented transaminases slightly increased and in three suffering from mucoviscidosis in whom steatorrhea with moderate alterations of fats and elevation of alkaline phosphatase and transaminases were present. Urinary and gall stones were not seen in anyone. In conclusion from this study it can be postulated that removal of ileocecal valve can be done safely in children.     

Studying and designing emotions in live interactions with the audience

Multimedia Tools and Applications - In the last decade, a number of projects have investigated the use of digital technologies to increase the engagement of the audience in live interactive...