The Effect of He Implantation on the Tensile Properties and Microstructure of Cu/Fe Nano‐Bicrystals

In situ uniaxial tensile experiments on as‐fabricated and helium‐implanted 100 nm‐diameter Cu/Fe bicrystals unearth the effect of individual face‐centred‐cubic/body‐centred‐cubic (fcc‐bcc) interfaces on improving radiation‐damage tolerance and helium absorption. Arrays of nanotensile specimens, each containing a single Cu grain in the bottom half and a single Fe grain on top, were fabricated by templated electron‐beam lithography and electrodeposition. Helium is implanted at 200 keV to a dose of 10¹⁴ ion/cm² nominally into the interface region. High‐resolution, site‐specific transmission electron microscopy (TEM) and through‐focus analysis reveal that the interfaces are nonplanar and contain ≈5 nm‐spaced He bubbles with diameters of 1–2 nm. Nanomechanical experimental results show that the irradiated samples exhibit yield and ultimate tensile strengths more than 60% higher than the as‐fabricated ones, while they retain comparable ductility. Tensile failure always occurs gradually, along the interfaces, with no noticeable shape localization. The absence of brittle failure in He‐irradiated metals might be explained, in part, by the inability of the small He bubbles to serve as sufficient stress concentrators for cracking. In addition, the non‐orthogonal orientation of the interfaces with respect to the loading axes results in the development of both normal‐ and shear‐stress components. Tensile loading along the pillar axes may cause those interfacial regions subjected to normal stresses to detach, while the inclined regions, subjected to shear, to carry plastic deformation until final fracture.     

Phase selection in supercooled Cu–Nb alloys

Electromagnetic levitation was used to determine Cu–Nb phase diagram and to study supercooling effects on solidification characteristics of the alloys containing 5–70 wt% Nb. The Cu–Nb stable phase diagram was found to exhibit near-flat liquidus with a peritectic reaction at 1093 °C. Melt separation was found only for specimens containing approximately 20 wt% Nb. The results indicate that melt separation in the alloy requires supercooling exceeding 230 K combined with high cooling rates during solidification. Some specimens quenched from the solid + liquid zone on a copper chill also show evidence of melt separation which is attributed to minor oxygen impurities. Nb-rich liquid which nucleates below the T ₀ curve solidifies as a metastable Nb-bcc lattice containing only 67 wt% Nb as compared to 96 wt% of the regular Nb dendrites.     

Outcome measures of a chronic pain program: a prospective statistical study

Ion beam enhanced deposition (IBED) was adopted to synthesize biocompatible titanium oxide film. Structure characteristics of titanium oxide film were investigated by RBS, AES, and XRD. The blood compatibility of the titanium oxide film was studied by measurements of blood clotting time and platelet adhesion. The results show that the anticoagulation property of titanium oxide film is improved significantly. The mechanism of anticoagulation of the titanium oxide film was discussed.     

Anterolateral soft-tissue impingement in the ankle: diagnosis using MR imaging

OBJECTIVE: This study was performed to elucidate the MR imaging findings and pitfalls for the diagnosis of anterolateral soft-tissue impingement in the ankle, a cause of chronic ankle pain that can be relieved by arthroscopic resection. MATERIALS AND METHODS: We retrospectively reviewed MR imaging examinations of 18 patients with arthroscopically confirmed anterolateral ankle impingement. The MR images of 18 additional subjects with symptoms that could mimic anterolateral impingement, but who had a surgically confirmed alternate diagnosis (instability, peroneal tendon injury, osteochondral defect, normal arthroscopy) and no evidence of impingement at arthroscopy, served as controls. RESULTS: On the MR imaging studies, nine patients had an ankle effusion, eight of whom showed an abnormal soft-tissue structure in the anterolateral gutter, 2-15 mm in maximal diameter. No soft-tissue mass was seen in the patients without joint fluid. Four control subjects with instability had a similar soft-tissue structure in the anterolateral gutter, but in the control subjects the finding represented a portion of the torn anterior talofibular ligament. CONCLUSION: Anterolateral soft-tissue impingement of the ankle can be suggested by MR imaging when fluid in the lateral gutter outlines an abnormal soft-tissue structure separate from the anterior talofibular ligament.     

Genetic localization of the type I trimethoprim resistance gene and its dissemination in urinary tract isolates in Taiwan

In a total of 425 urinary isolates of E. coli, Enterobacter spp., and Klebsiella spp. selected, there were 169 (45.4%) isolates harbouring type I dihydrofolate reductase (DHFR) gene among 374 trimethoprim-resistant isolates. In these 169 isolates, only 17.2% hybridized with the Tn7 probe. According to another probe specific for the integrase gene of integron, 87.6% showed a positive reaction. Further analysis by restriction mapping proved that the type I DHFR gene was inserted into a integron-like structure. These results indicate that the type I DHFR gene that was initially observed in association with transposable element Tn7 is becoming associated with an integrase function similar to integrons in most instances. Further analysis of the distribution of Tn21-like integrase gene in clinical isolates indicated that the prevalence rates were 86.4%, 84.8%, and 76.7% respectively in E. coli, Enterobacter spp., and Klebsiella spp.. Furthermore, the integrase gene found in our clinical isolates proved to be mediated by a plasmid, demonstrated by Southern hybridization. Thus, the trimethoprim-resistant gene that developed under selective pressure from the double drug trimethoprim and sulphonamide was transmitted by insertion into integron-like structure and then mediated by plasmid transfer for dissemination.     

Differentiating thrombus from pannus formation in obstructed mechanical prosthetic valves: an evaluation of clinical, transthoracic and transesophageal echocardiographic parameters

OBJECTIVES: We sought to determine the clinical and echocardiographic parameters that differentiate thrombus from pannus formation as the etiology of obstructed mechanical prosthetic valves. BACKGROUND: Distinction of thrombus from pannus on obstructed prosthetic valves is essential because thrombolytic therapy has emerged as an alternative to reoperation. METHODS: We analyzed clinical, transthoracic and transesophageal echocardiography (TEE) data in 23 patients presenting with 24 obstructed prosthetic valves and compared the findings to pathology at surgery. RESULTS: Fourteen valves had thrombus and 10 had pannus formation. Patients with thrombus had a shorter duration from time of valve insertion to malfunction, shorter duration of symptoms, but similar New York Heart Association functional class at the time of operation. Patients with thrombus had a lower rate of adequate anticoagulation (21% vs. 89%; p=0.0028). Pannus formation was more common in the aortic position (70% vs. 21%; p=0.035). Abnormal prosthetic valve motion was detected by TEE in all cases with thrombus formation but in 60% with pannus (p=0.0198). Thrombi were larger than pannuses (total length 2.8+/-2.47 cm vs. 1.17+/-0.43 cm; p=0.038). This was mostly due to extension of thrombi into the left atrium in prosthetic mitral valves. Thrombi appeared as a soft mass on the valve in 92% of cases, whereas 29% of pannuses had a soft echo density (p= 0.007). Ultrasound video intensity ratio, derived as the videointensity of the mass to that of the prosthetic valve, was lower in the thrombus group (0.46+/-0.14 vs. 0.71+/-0.17, p=0.006). A videointensity ratio of <0.70 had a positive predictive value of 87% and a negative predictive value of 89% for thrombus. Duration from onset of symptoms to reoperation of <1 month separated thrombus from pannus formation. The best objective clinical parameter for prediction of thrombus was inadequate anticoagulation, whereas the best TEE parameters were qualitative and quantitative ultrasound intensity of the mass. The presence of either inadequate anticoagulation or a soft mass by TEE improved the predictive power of either parameter alone and was similar to that of ultrasound videointensity ratio. CONCLUSIONS: Duration of symptoms, anticoagulation status and qualitative and quantitative ultrasound intensity of the mass obstructing a mechanical prosthetic valve can help differentiate pannus formation from thrombus and may therefore be of value in refining the selection of patients for thrombolytic therapy of prosthetic valve obstruction.