Theoretical and Experimental Study of the Magnetic Separation of Pollutants from Wastewater

This Thesys reports the study of a HGMS (High GradientMagnetic Separation) process for the treatment of industrialwastewaters that considers an assisted chemical-physical pre-treatment for the removal of heavy metals through the bound by adsorption with added iron-oxide particulate matter (hematite). The considered filter, constituted by ferromagnetic stainless steel wool and permanent magnets, is studied with a new approach based on a statistical analysis that requires the study of the trajectories of the particles. Experimental activity on a laboratory device has been carried out in order to test the model.

Comportamento tribologico di materiali per componenti di interesse industriale: Failure analysis e prove tribologiche in laboratorio

L’attività di ricerca della presente tesi di dottorato ha riguardato sistemi tribologici complessi di interesse industriale per i quali sono stati individuati, mediante failure analysis, i meccanismi di usura dominanti. Per ciascuno di essi sono state studiate soluzioni migliorative sulla base di prove tribologiche di laboratorio. Nella realizzazione di maglie per macchine movimentazione terra sono ampiamente utilizzati i tradizionali acciai da bonifica. La possibilità di utilizzare i nuovi microlegati a medio tenore di carbonio, consentirebbe una notevole semplificazione del ciclo produttivo e benefici in termini di costi. Una parte della tesi ha riguardato lo studio del comportamento tribologico di tali acciai. E’ stato anche affrontato lo studio tribologico di motori idraulici, con l’obiettivo di riuscire a migliorarne la resistenza ad usura e quindi la vita utile. Sono state eseguite prove a banco, per valutare i principali meccanismi di usura, e prove di laboratorio atte a riprodurre le reali condizioni di utilizzo, valutando tecniche di modificazione superficiale che fossero in grado di ridurre l’usura dei componenti. Sono state analizzate diverse tipologie di rivestimenti Thermal Spray in termini di modalità di deposizione (AFS-APS) e di leghe metalliche depositate (Ni,Mo,Cu/Al). Si sono infine caratterizzati contatti tribologici nel settore del packaging, dove l’utilizzo di acciai inox austenitici è in alcuni casi obbligatorio. L’acciaio inossidabile AISI 316L è ampiamente utilizzato in applicazioni in cui siano richieste elevate resistenze alla corrosione, tuttavia la bassa resistenza all’usura, ne limitano l’impiego in campo tribologico. In tale ambito, è stata analizzata una problematica tribologica relativa a macchine automatiche per il dosaggio di polveri farmaceutiche. Sono state studiate soluzioni alternative che hanno previsto sia la completa sostituzione dei materiali della coppia tribologica, sia l’individuazione di tecniche di modificazione superficiale innovative quali la cementazione a bassa temperatura anche seguita dalla deposizione di un rivestimento di carbonio amorfo idrogenato a-C:H

Randomised comparison of titanium-nitride-oxide coated stents with bare metal stents: five year follow-up of the TiNOX trial

Revascularisation with Titanium-Nitride-Oxide (TiNOX) coated stents is safe and effective in patients with de novo native coronary artery lesions. In the TiNOX trial there was a reduction in restenosis and major adverse cardiac events as compared with stainless steel stents of otherwise identical design. The purpose of the present study was to evaluate the long-term outcome of these patients over five years.

Polymer stent coating for prevention of neointimal hyperplasia

AIMS: Restenosis has been the principal limitation of bare metal stents. Based upon the presumption that platelet and inflammatory cell recruitment initiate neointimal proliferation, we explored a novel polymer coating that reduces cell-stent interactions. The purpose of the present study was to investigate the effect of poly(L-lysine)-graft-poly(ethyleneglycol) (PLL-g-PEG) adsorbed to stent surfaces to reduce neointimal hyperplasia in the porcine restenosis model. METHODS AND RESULTS: Seven animals were instrumented each with 2 stainless steel stents (15 mm length, 2.5-3.5 mm diameter), randomly implanted in 1 major epicardial coronary artery. One stent was dip-coated with PLL-g-PEG, whereas the other stent served as the uncoated control stent. All animals were sacrificed after 6 weeks for histological examination. Neointimal hyperplasia was significantly less (-51%) in the PLL-g-PEG-coated stents (1.15 +/- 0.59 mm2) than in the uncoated control stents (2.33 +/- 1.01 mm2; p < 0.001). Conversely, lumen size was larger in the PLL-g-PEG-coated stents (2.91 +/- 1.17 mm2) than in the uncoated stents (2.04 +/- 0.64 mm2; p < 0.001). High magnification histomorphologic examination revealed no signs of inflammation or thrombus formation in either stent group. CONCLUSIONS: Polymeric steric stabilization of stents with PLL-g-PEG significantly reduces neointimal hyperplasia in the porcine restenosis model. Reduction of cell-stent interactions mediated by PLL-g-PEG appear to improve biocompatibility of stainless steel stents without evidence of adverse inflammatory or prothrombotic effects.

Percutaneous autologous venous valve transplantation: short-term feasibility study in an ovine model

BACKGROUND: Limited experience with bioprosthetic venous valve percutaneously inserted into femoral veins in 15 patients has been promising in short-term results only to show disappointing long-term results. Percutaneous autogenous venous valve (PAVV) transplantation was explored in an ovine model as a possible alternative treatment. METHODS: PAVV consisted of a vein segment containing a valve that was attached to a stent template. The stent templates (n = 9) were designed and hand made in our research laboratory. They consist of two stainless steel square stents 13 or 15 mm in diameter to fit the ovine jugular veins (JV), which ranges from 10 to 15 mm in diameter. A valve-containing segment of JV was harvested and attached with sutures and barbs inside the stent template (n = 9). The valve devices were then manually folded and front loaded inside the 4 cm chamber of the 13F delivery sheath and delivered into the contralateral JV by femoral vein approach. Transplanted PAVVs were studied by immediate and 3 months venograms. Animals were euthanized at 3 months, and jugular veins harvested to perform angioscopic evaluations in vitro. RESULTS: PAVV transplantation was successful in all nine animals. Good valve function with no reflux was observed on immediate and 3 months venograms in eight valves. The transplanted maximal JV diameter ranged from 10.2 mm to 15.4 mm (mean 13.1 +/- 1.5 mm). Venoscopic examination revealed intact, flexible, nonthickened valve leaflets in eight specimens. One PAVV exhibited normal function of one leaflet only; the other cusp was accidentally cut during the transplantation procedure. All transplanted autologous valves were free of thrombus and incorporated into the vein wall of the host vessel. CONCLUSION: This study demonstrated that autogenous valve transplants remained patent and competent without long-term anticoagulation for up to 3 months. The percutaneous autogenous venous valve may provide in future minimally invasive treatment for patients with chronic deep venous insufficiency, but long-term studies need to be done to document its continued patency and function.

Osteoblast responses to different oxide coatings produced by the sol-gel process on titanium substrates

In order to improve the osseointegration of endosseous implants made from titanium, the structure and composition of the surface were modified. Mirror-polished commercially pure (cp) titanium substrates were coated by the sol-gel process with different oxides: TiO(2), SiO(2), Nb(2)O(5) and SiO(2)-TiO(2). The coatings were physically and biologically characterized. Infrared spectroscopy confirmed the absence of organic residues. Ellipsometry determined the thickness of layers to be approximately 100nm. High resolution scanning electron microscopy (SEM) and atomice force microscopy revealed a nanoporous structure in the TiO(2) and Nb(2)O(5) layers, whereas the SiO(2) and SiO(2)-TiO(2) layers appeared almost smooth. The R(a) values, as determined by white-light interferometry, ranged from 20 to 50nm. The surface energy determined by the sessile-drop contact angle method revealed the highest polar component for SiO(2) (30.7mJm(-2)) and the lowest for cp-Ti and 316L stainless steel (6.7mJm(-2)). Cytocompatibility of the oxide layers was investigated with MC3T3-E1 osteoblasts in vitro (proliferation, vitality, morphology and cytochemical/immunolabelling of actin and vinculin). Higher cell proliferation rates were found in SiO(2)-TiO(2) and TiO(2), and lower in Nb(2)O(5) and SiO(2); whereas the vitality rates increased for cp-Ti and Nb(2)O(5). Cytochemical assays showed that all substrates induced a normal cytoskeleton and well-developed focal adhesion contacts. SEM revealed good cell attachment for all coating layers. In conclusion, the sol-gel-derived oxide layers were thin, pure and nanostructured; consequent different osteoblast responses to those coatings are explained by the mutual action and coadjustment of different interrelated surface parameters.

Retrofitting boreholes contaminated with iron in rural Uganda

During my Peace Corps service as a community health liaison in rural Uganda I noticed that many improved water wells in our area had been abandoned. The communities described the water in these wells as being reddish in color, having a foul taste and odor, discoloring clothes and food, and not able to produce lather for washing. Personal investigations and an initial literature search suggested that the primary contaminant was iron. The water in these wells had a low pH and a rusty metallic smell. The water produced early in the morning appeared very red but the water became more transparent as pumping continued. The iron components of many of these wells experienced accelerated corrosion resulting in frequent pump failure. This rapid corrosion coupled with the timing of the onset of iron contamination (months to years after these wells were completed) suggests that the most likely cause of the poor quality water was iron related bacteria and/or sulphate reducing bacteria. This report describes a remedy for iron contamination employed at 5 wells. The remedy involved disinfecting the wells with chlorine and replacing iron pump components with plastic and stainless steel. Iron concentrations in the wells were less than 1 mg/L when the wells were drilled but ranged from 2.5 to 40 mg/L prior to the remedy. After the remedy was applied, the total iron concentrations returned to levels below 1 mg/L. The presence of iron related bacteria was measured in all of these wells using Biological Activity Reaction Tests. Although IRB are still present in all the wells, the dissolved iron concentrations remain less than 1 mg/L. This remedy is practical for rural areas because the work can be performed with only hand tools and costs less than US $850. Because the source of iron contamination is removed in this approach, substantial follow-up maintenance is not necessary.

The Anodic Polishing of Copper in Solutions of Orthophosphoric Acid

The electrolytic cleaning of metals by anodic methods has been known for many years. It was recognized long ago that when the temperature and concentration of the electro­lyte were properly regulated, bright clean surfaces were obtained.

The Continuous Electrodeposition of Manganese

The object of this research was to produce a workable electrolytic cell for the continuous deposition of manganese from aqueous sulphate solutions and determine the critical factors in its oper­ation.

Construction and Operation of a Laboaratory Size Thum Cell

Electrolytic silver refining was not perfected until the end of the nineteenth century. During the process of development, two systems of silver refining have come into prominence: the Moebius and the Thum types.

Chromizing of Steels

In recent years, considerable thought and study have been given to the use of chromized articles in place of chromium stainless steel articles. The present extensive application of chromizing, indeed, helps greatly to conserve this valuable metal.

Stability after bilateral sagittal split osteotomy advancement surgery with rigid internal fixation: a systematic review

PURPOSE: The purpose of this systematic review was to evaluate horizontal relapse and its causes in bilateral sagittal split advancement osteotomy (BSSO) with rigid internal fixation of different types. MATERIALS AND METHODS: A search of the literature was performed in the databases PubMed, Ovid, Cochrane Library, and Google Scholar Beta. From 488 articles identified, 24 articles were finally included. Six studies were prospective, and 18 were retrospective. The range of postoperative study records was 6 months to 12.7 years. RESULTS: The short-term relapse for bicortical screws was between 1.5% and 32.7%, for miniplates between 1.5% and 18.0%, and for bioresorbable bicortical screws between 10.4% and 17.4%, at point B. The long-term relapse for bicortical screws was between 2.0% and 50.3%, and for miniplates between 1.5% and 8.9%, at point B. CONCLUSIONS: BSSO for mandibular advancement is a good treatment option for skeletal Class II, but seems less stable than BSSO setback in the short and long terms. Bicortical screws of titanium, stainless steel, or bioresorbable material show little difference regarding skeletal stability compared with miniplates in the short term. A greater number of studies with larger skeletal long-term relapse rates were evident in patients treated with bicortical screws instead of miniplates. The etiology of relapse is multifactorial, involving the proper seating of the condyles, the amount of advancement, the soft tissue and muscles, the mandibular plane angle, the remaining growth and remodeling, the skill of the surgeon, and preoperative age. Patients with a low mandibular plane angle have increased vertical relapse, whereas patients with a high mandibular plane angle have more horizontal relapse. Advancements in the range of 6 to 7 mm or more predispose to horizontal relapse. To obtain reliable scientific evidence, further short-term and long-term research into BSSO advancement with rigid internal fixation should exclude additional surgery, ie, genioplasty or maxillary surgery, and include a prospective study or randomized clinical trial design with correlation statistics.

Torque expression of 0.018 and 0.022 inch conventional brackets

The aim of this study was to assess the effect of the moments generated with low- and high-torque brackets. Four different bracket prescription-slot combinations of the same bracket type (Mini Diamond® Twin) were evaluated: high-torque 0.018 and 0.022 inch and low-torque 0.018 and 0.022 inch. These brackets were bonded on identical maxillary acrylic resin models with levelled and aligned teeth and each model was mounted on the orthodontic measurement and simulation system (OMSS). Ten specimens of 0.017 × 0.025 inch and ten 0.019 × 0.025 inch stainless steel archwires (ORMCO) were evaluated in the low- and high-torque 0.018 inch and 0.022 inch brackets, respectively. The wires were ligated with elastomerics into the brackets and each measurement was repeated once after religation. Two-way analysis of variance and t-test were conducted to compare the generated moments between wires at low- and high-torque brackets separately. The maximum moment generated by the 0.017 × 0.025 inch stainless steel archwire in the 0.018 inch brackets at +15 degrees ranged from 14.33 and 12.95 Nmm for the high- and low-torque brackets, respectively. The measured torque in the 0.022 inch brackets with the 0.019 × 0.025 inch stainless steel archwire was 9.32 and 6.48 Nmm, respectively. The recorded differences of maximum moments between the high- and low-torque series were statistically significant. High-torque brackets produced higher moments compared with low-torque brackets. Additionally, in both high- and low-torque configurations, the thicker 0.019 × 0.025 inch steel archwire in the 0.022 inch slot system generated lower moments in comparison with the 0.017 × 0.025 inch steel archwire in the 0.018 inch slot system.

Brain Neuropeptides That Control Prolactin Secretion in Cattle

The objective was to test the hypothesis that dopamine regulates prolactin (PRL) secretion by determining acute changes in catecholamine concentrations in hypophyseal portal blood of cattle and their relation to peripheral blood concentration of PRL in hypophyseal stalk-transected (HST) and sham-operated control (SOC). Holstein heifers were subjected to neurosurgery to collect hypophyseal portal blood with a stainless steel cannula designed with a cuff placed under the pituitary stalk and peripheral blood via a jugular vein catheter. PRL plasma concentration was measured by radioimmunoassay, and dopamine and norepinephrine in portal plasma by radioenzymatic assay. During anesthesia before HST or SOC, PRL plasma concentration ranged from 20–40 ng/ml throughout 255 minutes. PRL abruptly increased and remained above 90 ng/ml after HST, compared with a steady decrease to <20 ng/ml in SOC heifers throughout 440 minutes. Within 5 minutes after severing of the hypophyseal stalk, dopamine in portal blood (>8 ng/ml) was significantly increased (P<0.05) compared with peripheral blood (<2 ng/ml). Norepinephrine concentration in portal blood was significantly greater (P<0.05) than in peripheral blood during the first 60 minutes. The sustained high PRL level in peripheral plasma after severing the hypophyseal stalk stimulated hypothalamic dopamine secretion from hypophyseal portal vessels during the prolonged period of blood collection. Norepinephrine concentration in these cattle was greater in hypophyseal portal blood than in peripheral blood, implicating both an important hypothalamic source of the catecholamine as well as an adrenal gland contribution during anesthesia.