A comparison between the chemical behaviour of lead-gold and lead-bismuth eutectics towards 316L stainless steel

Lead-gold eutectic (LGE) has been recently proposed as an alternative target material for high power spallation sources. In order to compare the corrosive properties of LGE to the better-studied eutectic of lead-bismuth (LBE), an isothermal twin-loop made of SS 316L was built and operated at the Institute of Physics of the University of Latvia. We have measured the concentration of steel alloying elements dissolved in both alloys at the end of two test campaigns via ICP-OES. In case of LGE, a pronounced concentration increase of Fe, Ni, Mn and Cr is found in the liquid metal, which is significantly higher compared to LBE. Similar results were obtained during complementary investigations on material samples exposed to both alloys in this twin-loop at 400 ◦C and 450 ◦C. These findings indicate that in contact with LGE, SS 316L steel suffers from substantial chemical attack. Detailed investigations using structure materials other than SS 316L have to be undertaken before qualifying LGE as a serious alternative to LBE.

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.

Stress free configuration of the human eye

Numerical simulations of eye globes often rely on topographies that have been measured in vivo using devices such as the Pentacam or OCT. The topographies, which represent the form of the already stressed eye under the existing intraocular pressure, introduce approximations in the analysis. The accuracy of the simulations could be improved if either the stress state of the eye under the effect of intraocular pressure is determined, or the stress-free form of the eye estimated prior to conducting the analysis. This study reviews earlier attempts to address this problem and assesses the performance of an iterative technique proposed by Pandolfi and Holzapfel [1], which is both simple to implement and promises high accuracy in estimating the eye's stress-free form. A parametric study has been conducted and demonstrated reliance of the error level on the level of flexibility of the eye model, especially in the cornea region. However, in all cases considered 3-4 analysis iterations were sufficient to produce a stress-free form with average errors in node location <10(-6)mm and a maximal error <10(-4)mm. This error level, which is similar to what has been achieved with other methods and orders of magnitude lower than the accuracy of current clinical topography systems, justifies the use of the technique as a pre-processing step in ocular numerical simulations.

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.

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.

Virtual Cilicia Project. How to use Google Earth as a visualization environment in an archaeological context

Over the past few years, archaeology has experienced a rapid development in geophysical prospection and remote sensing techniques. At the same time, the focus of archaeological research has shifted to landscape evelopment and human interaction. To impart the results, new methods and techniques are necessary. Virtual globes such as Google Earth offer fascinating methods of giving interested amateurs the possibility to interactively explore ancient cities and landscapes. Thanks to the increasing usage of GIS in cultural heritage, the implementation of interactive three dimensional learning opportunities becomes less and less tedious, but the non-linear narrative story telling medium demands for a special adaption of the content. This paper summarizes the experience gained during the realization of the “Virtual Cilicia Project” and outlines the future potential of virtual globes in the field of cultural heritage.

Electrodes for Long-Term Esophageal Electrocardiography

The emerging application of long-term and high-quality ECG recording requires alternative electrodes to improve the signal quality and recording capability of surface skin electrodes. The esophageal ECG has the potential to overcome these limitations but necessitates novel recorder and lead designs. The electrode material is of particular interest, since the material has to ensure conflicting requirements like excellent biopotential recording properties and inertness. To this end, novel electrode materials like PEDOT and silver-PDMS as well as established electrode materials such as stainless steel, platinum, gold, iridium oxide, titanium nitride, and glassy carbon were investigated by long-term electrochemical impedance spectroscopy and model-based signal analysis using the derived in vitro interfacial properties in conjunction with a dedicated ECG amplifier. The results of this novel approach show that titanium nitride and iridium oxide featuring microstructured surfaces did not degrade when exposed to artificial acidic saliva. These materials provide low electrode potential drifts and insignificant signal distortion superior to surface skin electrodes making them compatible with accepted standards for ambulatory ECG. They are superior to the noble and polarizable metals such as platinum, silver, and gold that induced more signal distortions and are superior to esophageal stainless steel electrodes that corrode in artificial saliva. The study provides rigorous criteria for the selection of electrode materials for prolonged ECG recording by combining long-term in vitro electrode material properties with ECG signal quality assessment.

Randomized controlled trial: lip piercing: the impact of material on microbiological findings

PURPOSE The purpose of this study was to investigate whether there are microbiological differences in bacterial samples collected from labial piercings made of different materials. METHODS Sterile piercings of 4 materials were randomly allocated to 80 pierced subjects. After 2 weeks, microbiologic samples were collected and processed by checkerboard DNA-DNA hybridization methods. Wilcoxon signed ranks and Mann-Whitney tests were used for statistical analysis (adjustment for multiple comparisons). RESULTS There were no statistically significant differences between material groups in relation to baseline data. In samples from stainless steel piercings, the total microbial load was significantly higher than the other materials (P<.05). Ten (mainly periopathogenic) species were found at significantly higher levels (P<.001) on steel than on polypropylene and/or polytetrafluoroethylene piercings. CONCLUSIONS Labial piercings made of stainless steel could promote the development of a pathogenic biofilm.

Torque efficiency of different archwires in 0.018- and 0.022-inch conventional brackets.

OBJECTIVE To compare the archwires inserted during the final stages of the orthodontic treatment with the generated moments at 0.018- and 0.022-inch brackets. MATERIALS AND METHODS The same bracket type, in terms of prescription, was evaluated in both slot dimensions. The brackets were bonded on two identical maxillary acrylic resin models, and each model was mounted on the orthodontic measurement and simulation system. Ten 0.017 × 0.025-inch TMA and ten 0.017 × 0.025-inch stainless steel archwires were evaluated in the 0.018-inch brackets. In the 0.022-inch brackets, ten 0.019 × 0.025-inch TMA and ten 0.019 × 0.025-inch stainless steel archwires were measured. A 15° buccal root torque (+15°) and then a 15° palatal root torque (-15°) were gradually applied to the right central incisor bracket, and the moments were recorded at these positions. A t-test was conducted to compare the generated moments between wires within the 0.018- and 0.022-inch bracket groups separately. RESULTS The 0.017 × 0.025-inch archwire in the 0.018-inch brackets generated mean moments of 9.25 Nmm and 14.2 Nmm for the TMA and stainless steel archwires, respectively. The measured moments in the 0.022-inch brackets with the 0.019 × 0.025-inch TMA and stainless steel archwires were 6.6 Nmm and 9.3 Nmm, respectively. CONCLUSION The 0.017 × 0.025-inch stainless steel and β-Ti archwires in the 0.018-inch slot generated higher moments than the 0.019 × 0.025-inch archwires because of lower torque play. This difference is exaggerated in steel archwires, in comparison with the β-Ti, because of differences in stiffness. The differences of maximum moments between the archwires of the same cross-section but different alloys were statistically significant at both slot dimensions.