890 resultados para METALLIC FERROMAGNET NIMNSB
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Geometric parameters of binary (1:1) PdZn and PtZn alloys with CuAu-L10 structure were calculated with a density functional method. Based on the total energies, the alloys are predicted to feature equal formation energies. Calculated surface energies of PdZn and PtZn alloys show that (111) and (100) surfaces exposing stoichiometric layers are more stable than (001) and (110) surfaces comprising alternating Pd (Pt) and Zn layers. The surface energy values of alloys lie between the surface energies of the individual components, but they differ from their composition weighted averages. Compared with the pure metals, the valence d-band widths and the Pd or Pt partial densities of states at the Fermi level are dramatically reduced in PdZn and PtZn alloys. The local valence d-band density of states of Pd and Pt in the alloys resemble that of metallic Cu, suggesting that a similar catalytic performance of these systems can be related to this similarity in the local electronic structures.
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The nature of the chemical bond in three titanium oxides of different crystal structure and different formal oxidation state has been studied by means of the ab initio cluster-model approach. The covalent and ionic contributions to the bond have been measured from different theoretical techniques. All the analysis is consistent with an increasing of covalence in the TiO, Ti2O3, and TiO2 series as expected from chemical intuition. Moreover, the use of the ab initio cluster-model approach combined with different theoretical techniques has permitted us to quantify the degree of ionic character, showing that while TiO can approximately be described as an ionic compound, TiO2 is better viewed as a rather covalent oxide.
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AIM: Specific factors responsible for interindividual variability should be identified and their contribution quantified to improve the usefulness of biological monitoring. Among others, age is an easily identifiable determinant, which could play an important impact on biological variability. MATERIALS AND METHODS: A compartmental toxicokinetic model developed in previous studies for a series of metallic and organic compounds was applied to the description of age differences. Young male physiological and metabolic parameters, based on Reference Man information, were taken from preceding studies and were modified to take into account age based on available information about age differences. RESULTS: Numerical simulation using the kinetic model with the modified parameters indicates in some cases important differences due to age. The expected changes are mostly of the order of 10-20%, but differences up to 50% were observed in some cases. CONCLUSION: These differences appear to depend on the chemical and on the biological entity considered. Further work should be done to improve our estimates of these parameters, by considering for example uncertainty and variability in these parameters. [Authors]
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Purpose: Cervical foraminal injection performed with a direct foraminal approach may induce serious neurologic complications. We describe a technique of CT-guided cervical facet joint (CFJ) injection as an indirect foraminal injection, including feasibility and diffusion pathways of the contrast agent. Methods and materials: Retrospective study included 84 punctures in 65 consecutive patients presenting neck pain and/or radiculopathy related to osteoarthritis or soft disc herniation. CT images were obtained from C2 to T1 in supine position, with a metallic landmark on the skin. CFJ punctures were performed by MSK senior radiologists with a lateral approach. CT control of the CFJ opacification was performed after injections of contrast agent (1 ml), followed by slow-acting corticosteroid (25 mg). CFJ opacification was considered as successful when joint space and/or capsular recess opacification occurred. The diffusion of contrast agent in foraminal and epidural spaces was recorded. We assessed the epidural diffusion both on axial and sagittal images, with a classification in two groups (small diffusion or large diffusion). Results: CFJ opacification was successful in 82% (69/84). An epidural and/or foraminal opacification was obtained in 74% (51/69). A foraminal opacification occurred in 92% (47/51) and an epidural opacification in 63% (32/51), with small diffusion in 47% (15/32) and large diffusion in 53% (17/32). No complication occurred. Conclusion: CT- guided CFJ injection is easy to perform and safe. It is most often successful, with a frequent epidural and/or foraminal diffusion of the contrast agent. This technique could be an interesting and safe alternative to foraminal cervical injection.
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The use of non-metallic load transfer and reinforcement devices for concrete highway pavements is a possible alternative to avoid corrosion problems related to the current practice of steel materials. Laboratory and field testing of highway pavement dowel bars, made of both steel and fiber composite materials, and fiber composite tie rods were carried out in this research investigation. Fatigue, static, and dynamic testing was performed on full-scale concrete pavement slabs which were supported by a simulated subgrade and which included a single transverse joint. The bahavior of the full-scale specimens with both steel and fiber composite dowels placed in the test joints was monitored during several million load cycles which simulated truck traffic at a transverse joint. Static bond tests were conducted on fiber composite tie rods to determine the required embedment length. These tests took the form of bending tests which included curvature and shear in the embedment zone and pullout tests which subjected the test specimen to axial tension only. Fiber composite dowel bars were placed at two transverse joints during construction of a new concrete highway pavement in order to evaluate their performance under actual field conditions. Fiber composite tie rods were also placed in the longitudinal joint between the two fiber composite doweled transverse joints.
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RATIONALE: Induction of oxidative stress and impairment of the antioxidant defense are considered important biological responses following nanoparticle (NP) exposure. The acellular in vitro dithiothreitol (DTT) assay is proposed to measure the oxidative potential of NP. In addition, DTT can be considered as a model compound of sulfur containing antioxidants. The objective of this work is to evaluate the surface reactivity in solution of a NP panel toward DTT. METHOD: The NP panel was composed of four carbonaceous particles, six types of metal oxides and silver with primary size ranged from 7 to 300 nm. Suspensions were prepared in surfactant solution with 30 min sonication. DTT was used as reductant to evaluate the oxidative properties of the different NP. The determination of the NP ability to catalyze electron transfer from DTT to oxygen was carried out as described in Sauvain et al., Nanotoxicology, 2008, 2:3, 121−129. RESULTS: All the carbonaceous NP catalyzed the oxidation of DTT by oxygen following the mass based order: carbon black > diesel exhaust particle > nanotubes > fullerene. A contrasting reactivity was observed for the metallic NP. Except for nickel oxide and metallic silver, which reacted similarly to the carbonaceous NP, all other metal oxides hindered the oxidation of DTT by oxygen, with ZnO being the most effective one. CONCLUSIONS : DTT was stabilized against oxidation in the presence of metal oxide NP in the solution. This suggests that different chemical interactions take place compared with carbonaceous NP. To explain these differences, we hypothesize that DTT could form complexes with the metal oxide surface (or dissolved metal ions), rendering it less susceptible to oxidation. By analogy, such a process could be thought to apply in biological systems with sulfur−containing antioxidants, reducing their buffer capacity. Such NP could thus contribute to oxidative stress by an alternative mechanism.
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The emerald ash borer (EAB) is a very small but very destructive beetle. Metallic green in color, its slender body measures 1/2 inch in length and 1/8 inch wide. The average adult
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Large Dynamic Message Signs (DMSs) have been increasingly used on freeways, expressways and major arterials to better manage the traffic flow by providing accurate and timely information to drivers. Overhead truss structures are typically employed to support those DMSs allowing them to provide wider display to more lanes. In recent years, there is increasing evidence that the truss structures supporting these large and heavy signs are subjected to much more complex loadings than are typically accounted for in the codified design procedures. Consequently, some of these structures have required frequent inspections, retrofitting, and even premature replacement. Two manufacturing processes are primarily utilized on truss structures - welding and bolting. Recently, cracks at welding toes were reported for the structures employed in some states. Extremely large loads (e.g., due to high winds) could cause brittle fractures, and cyclic vibration (e.g., due to diurnal variation in temperature or due to oscillations in the wind force induced by vortex shedding behind the DMS) may lead to fatigue damage, as these are two major failures for the metallic material. Wind and strain resulting from temperature changes are the main loads that affect the structures during their lifetime. The American Association of State Highway and Transportation Officials (AASHTO) Specification defines the limit loads in dead load, wind load, ice load, and fatigue design for natural wind gust and truck-induced gust. The objectives of this study are to investigate wind and thermal effects in the bridge type overhead DMS truss structures and improve the current design specifications (e.g., for thermal design). In order to accomplish the objective, it is necessary to study structural behavior and detailed strain-stress of the truss structures caused by wind load on the DMS cabinet and thermal load on the truss supporting the DMS cabinet. The study is divided into two parts. The Computational Fluid Dynamics (CFD) component and part of the structural analysis component of the study were conducted at the University of Iowa while the field study and related structural analysis computations were conducted at the Iowa State University. The CFD simulations were used to determine the air-induced forces (wind loads) on the DMS cabinets and the finite element analysis was used to determine the response of the supporting trusses to these pressure forces. The field observation portion consisted of short-term monitoring of several DMS Cabinet/Trusses and long-term monitoring of one DMS Cabinet/Truss. The short-term monitoring was a single (or two) day event in which several message sign panel/trusses were tested. The long-term monitoring field study extended over several months. Analysis of the data focused on trying to identify important behaviors under both ambient and truck induced winds and the effect of daily temperature changes. Results of the CFD investigation, field experiments and structural analysis of the wind induced forces on the DMS cabinets and their effect on the supporting trusses showed that the passage of trucks cannot be responsible for the problems observed to develop at trusses supporting DMS cabinets. Rather the data pointed toward the important effect of the thermal load induced by cyclic (diurnal) variations of the temperature. Thermal influence is not discussed in the specification, either in limit load or fatigue design. Although the frequency of the thermal load is low, results showed that when temperature range is large the restress range would be significant to the structure, especially near welding areas where stress concentrations may occur. Moreover stress amplitude and range are the primary parameters for brittle fracture and fatigue life estimation. Long-term field monitoring of one of the overhead truss structures in Iowa was used as the research baseline to estimate the effects of diurnal temperature changes to fatigue damage. The evaluation of the collected data is an important approach for understanding the structural behavior and for the advancement of future code provisions. Finite element modeling was developed to estimate the strain and stress magnitudes, which were compared with the field monitoring data. Fatigue life of the truss structures was also estimated based on AASHTO specifications and the numerical modeling. The main conclusion of the study is that thermal induced fatigue damage of the truss structures supporting DMS cabinets is likely a significant contributing cause for the cracks observed to develop at such structures. Other probable causes for fatigue damage not investigated in this study are the cyclic oscillations of the total wind load associated with the vortex shedding behind the DMS cabinet at high wind conditions and fabrication tolerances and induced stresses due to fitting of tube to tube connections.
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Our objective was to evaluate efficacy and patency of metallic stent placement for symptomatic Budd-Chiari syndrome (BCS) due to prothrombotic disorders. Eleven patients with proved BCS due to prothrombotic disorders were referred for endovascular treatment because of refractory ascites (n=9), abdominal pain (n=8), jaundice (n=6), and/or gastrointestinal bleeding (n=4). Stents were inserted for stenosed hepatic vein (n=7), inferior vena cava (n=2), or mesenterico-caval shunt (n=2). Clinical efficacy and stent patency was evaluated by clinical and Doppler follow-up. After a mean follow-up of 21 months, 6 patients had fully patent stents without reintervention (primary stent patency: 55%). Two patients with hepatic vein stenosis had stent thrombosis and died 4 months after procedure. Restenosis occurred in 3 cases (2 hepatic vein and 1 mesenterico-caval shunt stenosis) and were successfully treated by balloon angioplasty (n=2) and addition of new stents (n=1) leading to a 82% secondary stent patency. Of 9 patients with patent stent, 7 were asymptomatic (77%) at the end of the study. Stent placement is a safe and effective procedure to control of symptomatic BCS. Prothrombotic disorder does not seem to jeopardize patency in anticoagulated patients.
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BACKGROUND: Biodegradable polymers for release of antiproliferative drugs from metallic drug-eluting stents aim to improve long-term vascular healing and efficacy. We designed a large scale clinical trial to compare a novel thin strut, cobalt-chromium drug-eluting stent with silicon carbide-coating releasing sirolimus from a biodegradable polymer (O-SES, Orsiro; Biotronik, Bülach, Switzerland) with the durable polymer-based Xience Prime/Xpedition everolimus-eluting stent (EES) (Xience Prime/Xpedition stent, Abbott Vascular, IL) in an all-comers patient population. DESIGN: The multicenter BIOSCIENCE trial (NCT01443104) randomly assigned 2,119 patients to treatment with biodegradable polymer sirolimus-eluting stents (SES) or durable polymer EES at 9 sites in Switzerland. Patients with chronic stable coronary artery disease or acute coronary syndromes, including non-ST-elevation and ST-elevation myocardial infarction, were eligible for the trial if they had at least 1 lesion with a diameter stenosis >50% appropriate for coronary stent implantation. The primary end point target lesion failure (TLF) is a composite of cardiac death, target vessel myocardial infarction, and clinically driven target lesion revascularization within 12 months. Assuming a TLF rate of 8% at 12 months in both treatment arms and accepting 3.5% as a margin for noninferiority, inclusion of 2,060 patients would provide more than 80% power to detect noninferiority of the biodegradable polymer SES compared with the durable polymer EES at a 1-sided type I error of 0.05. Clinical follow-up will be continued through 5 years. CONCLUSION: The BIOSCIENCE trial will determine whether the biodegradable polymer SES is noninferior to the durable polymer EES with respect to TLF.
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(I): Hexaaquacobalt(II) aqua[ethylenediaminetetraacetato(3-)]cobaltate(II) dihydrate, [Co(H2O)6][Co(C10H13N2O8)(H2O)]2.2H2O (Ibis): Hexaaquamagnesium(II) aqua[ethylenediaminetetraacetato(3-)]magnesiate(II) dihydrate, [Mg(H2O)6][Mg(C10H13N2O8)(H2O)]2.2H2O (II):Tetraaquabis{aqua[ethylenediaminetetraacetato(3-)]cadmium(II)-O-O'}Cadmium(II) tetrahydrate
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(I): Hexaaquacobalt(II) aqua[ethylenediaminetetraacetato(3-)]cobaltate(II) dihydrate, [Co(H2O)6][Co(C10H13N2O8)(H2O)]2.2H2O (Ibis): Hexaaquamagnesium(II) aqua[ethylenediaminetetraacetato(3-)]magnesiate(II) dihydrate, [Mg(H2O)6][Mg(C10H13N2O8)(H2O)]2.2H2O (II):Tetraaquabis{aqua[ethylenediaminetetraacetato(3-)]cadmium(II)-O-O'}Cadmium(II) tetrahydrate
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(I): Hexaaquacobalt(II) aqua[ethylenediaminetetraacetato(3-)]cobaltate(II) dihydrate, [Co(H2O)6][Co(C10H13N2O8)(H2O)]2.2H2O (Ibis): Hexaaquamagnesium(II) aqua[ethylenediaminetetraacetato(3-)]magnesiate(II) dihydrate, [Mg(H2O)6][Mg(C10H13N2O8)(H2O)]2.2H2O (II):Tetraaquabis{aqua[ethylenediaminetetraacetato(3-)]cadmium(II)-O-O'}Cadmium(II) tetrahydrate
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In cases of transjugular liver biopsies, the venous angle formed between the chosen hepatic vein and the vena cava main axis in a frontal plane can be large, leading to technical difficulties. In a prospective study including 139 consecutive patients who underwent transjugular liver biopsy using the Quick-Core biopsy set, the mean venous angle was equal to 49.6 degrees. For 21.1% of the patients, two attempts at hepatic venous catheterization failed because the venous angle was too large, with a mean of 69.7 degrees. In all of these patients, manual reshaping of the distal curvature of the stiffening metallic cannula, by forming a new mean angle equal to 48 degrees , allowed successful completion of the procedure in less than 10 min.
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Background, aim, and scope A coupled Life Cycle Costing and life cycle assessment has been performed for car-bodies of the Korean Tilting Train eXpress (TTX) project using European and Korean databases, with the objective of assessing environmental and cost performance to aid materials and process selection. More specifically, the potential of polymer composite car-body structures for the Korean Tilting Train eXpress (TTX) has been investigated. Materials and methods This assessment includes the cost of both carriage manufacturing and use phases, coupled with the life cycle environmental impacts of all stages from raw material production, through carriage manufacture and use, to end-of-life scenarios. Metallic carriages were compared with two composite options: hybrid steel-composite and full-composite carriages. The total planned production for this regional Korean train was 440 cars, with an annual production volume of 80 cars. Results and discussion The coupled analyses were used to generate plots of cost versus energy consumption and environmental impacts. The results show that the raw material and manufacturing phase costs are approximately half of the total life cycle costs, whilst their environmental impact is relatively insignificant (3-8%). The use phase of the car-body has the largest environmental impact for all scenarios, with near negligible contributions from the other phases. Since steel rail carriages weigh more (27-51%), the use phase cost is correspondingly higher, resulting in both the greatest environmental impact and the highest life cycle cost. Compared to the steel scenario, the hybrid composite variant has a lower life cycle cost (16%) and a lower environmental impact (26%). Though the full composite rail carriage may have the highest manufacturing cost, it results in the lowest total life cycle costs and lowest environmental impacts. Conclusions and recommendations This coupled cost and life cycle assessment showed that the full composite variant was the optimum solution. This case study showed that coupling of technical cost models with life cycle assessment offers an efficient route to accurately evaluate economic and environmental performance in a consistent way.