Group precipitation and age hardening of nanostructured Fe-based alloys with ultra-high strengths.

The precipitation of nanoparticles plays a key role in determining the properties of many structural materials, and the understanding of their formation and stabilization mechanisms has been a long standing interest in the material field. However, the critical issues involving the group precipitation of various nanoparticles and their cooperative hardening mechanism remain elusive in the newly discovered Fe-based alloys with nanostructures. Here we quantitatively elucidate the nucleation mechanism, evolution kinetics and hardening effects of the group-precipitated nanoparticles in the Fe-Cu-Ni-Al-based alloys by atom probe tomography together with both first-principles and thermodynamic calculations. Our results provide the compelling evidence for two interesting but complex group precipitation pathways of nanoparticles, i.e., the Cu-rich and NiAl-based precipitations. The co-existence of the two precipitation pathways plays a key role in age hardening kinetics and ultimately enhances the hardening response, as compared to the single particle type of strengthening, therefore providing an effective new approach for strengthening materials for structural applications.

Vacancy-controlled ultrastable nanoclusters in nanostructured ferritic alloys.

A new class of advanced structural materials, based on the Fe-O-vacancy system, has exceptional resistance to high-temperature creep and excellent tolerance to extremely high-dose radiation. Although these remarkable improvements in properties compared to steels are known to be associated with the Y-Ti-O-enriched nanoclusters, the roles of vacancies in facilitating the nucleation of nanoclusters are a long-standing puzzle, due to the experimental difficulties in characterizing vacancies, particularly in-situ while the nanoclusters are forming. Here we report an experiment study that provides the compelling evidence for the presence of significant concentrations of vacancies in Y-Ti-O-enriched nanoclusters in a nanostructured ferritic alloy using a combination of state-of-the-art atom-probe tomography and in situ small angle neutron scattering. The nucleation of nanoclusters starts from the O-enriched solute clustering with vacancy mediation. The nanoclusters grow with an extremely low growth rate through attraction of vacancies and O:vacancy pairs, leading to the unusual stability of the nanoclusters.

Temperature-dependent elastic anisotropy and mesoscale deformation in a nanostructured ferritic alloy.

Nanostructured ferritic alloys are a new class of ultrafine-grained oxide dispersion-strengthened steels that have promising properties for service in extreme environments in future nuclear reactors. This is due to the remarkable stability of their complex microstructures containing numerous Y-Ti-O nanoclusters within grains and along grain boundaries. Although nanoclusters account primarily for the exceptional resistance to irradiation damage and high-temperature creep, little is known about the mechanical roles of the polycrystalline grains that constitute the ferritic matrix. Here we report an in situ mesoscale characterization of anisotropic responses of ultrafine ferrite grains to stresses using state-of-the-art neutron diffraction. We show the experimental determination of single-crystal elastic constants for a 14YWT alloy, and reveal a strong temperature-dependent elastic anisotropy that leads to elastic softening and instability of the ferrite. We also demonstrate, from anisotropy-induced intergranular strains, that a deformation crossover exists from low-temperature lattice hardening to high-temperature lattice softening in response to extensive plastic deformation.

Enhancing glass-forming ability via frustration of nano-clustering in alloys with a high solvent content.

The glass-forming ability (GFA) of alloys with a high-solvent content such as soft magnetic Fe-based and Al-based alloys is usually limited due to strong formation of the solvent-based solid solution phase. Herein, we report that the GFA of soft magnetic Fe-based alloys (with >70 at.% Fe to ensure large saturation magnetization) could be dramatically improved by doping with only 0.3 at.% Cu which has a positive enthalpy of mixing with Fe. It was found that an appropriate Cu addition could enhance the liquid phase stability and crystallization resistance by destabilizing the α-Fe nano-clusters due to the necessity to redistribute the Cu atoms. However, excessive Cu doping would stimulate nucleation of the α-Fe nano-clusters due to the repulsive nature between the Fe and Cu atoms, thus deteriorating the GFA. Our findings provide new insights into understanding of glass formation in general.

Detecting density variations and nanovoids.

A combination of simulated and experimental data has been used to investigate the size range of nanovoids that can be detected in atom probe tomography data. Simulated atom probe tomography data have revealed that nanovoids as small as 1 nm in diameter can be detected in atom probe tomography data with the use of iso-density surfaces. Iso-density surfaces may be used to quantify the size, morphology and number density of nanovoids and other variations in density in atom probe tomography data. Experimental data from an aluminum-yttrium-iron metallic glass ribbon have revealed the effectiveness of this approach. Combining iso-density surfaces with atom maps also permits the segregation of solute to the nanovoids to be investigated. Field ion microscopy and thin section atom maps have also been used to detect pores and larger voids.

Fabrication and characterization of APT specimens from high dose heavy ion irradiated materials.

The next generations of advanced energy systems will require materials that can withstand high doses of irradiation at elevated temperatures. Therefore, a methodology has been developed for the fabrication of high-dose ion-irradiated atom probe tomography specimens at a specific dose with the use of a focused ion beam milling system. The method also enables the precise ion dose of the atom probe tomography specimen to be estimated from the local concentration of the implanted ions. The method has been successfully applied to the characterization of the distribution of nanoclusters in a radiation-tolerant 14YWT nanostructured ferritic steel under ion irradiation to doses up to 400 displacements per atom.

WITHDRAWN: A MVSA approach to mine information from APT data.

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Atom probe specimen preparation with a dual beam SEM/FIB miller.

Dual beam scanning electron microscope/focused ion beam (SEM/FIB) methods complement electropolishing methods and enable specimens to be made from a wider range of materials. Several methods have been developed to fabricate specimens from different forms of materials, including thin ribbons, mechanically ground sheet and fine powders. In addition, FIB-based methods can be used in conjunction with electropolishing methods to improve the shape, surface finish and taper angle of specimens. Several lift-out (LO) methods have been developed for selecting specific microstructural features or other regions of interest such as phases, interfaces, grain boundaries, subsurface or implanted regions and interdendritic regions. These LO methods make use of an in situ nanomanipulator and platinum deposition to transfer and attach the lifted out volume to a post for final annular milling into a needle-shaped specimen. In order to improve the efficiency and to facilitate the LO procedure, some special specimen mounts that hold both the specimen and the support post at the appropriate working distance have been developed.

Performance of local electrodes in the local electrode atom probe.

The use of a local electrode in atom probe tomography has enabled higher rates of data acquisition and increased field of view compared to other variants of three-dimensional atom probes, but specimen fracture can result in damage to the local electrode. Specimens and local electrodes were examined before and after analyses that resulted in specimen failure. Most specimens were found to be melted after failure and as a result, material was found deposited onto the surface of the local electrode. Material transfer from the specimen to the local electrode was verified by energy dispersive spectrometry in a scanning electron microscope. After the fracture of brittle materials, some remnants were found embedded in the local electrode. For either failure mode, it is likely that the primary specimen rupture produced a sharp protrusion on the specimen or local electrode and this triggered an electrical discharge or uncontrolled field emission that melted a portion of the specimen. The lifetime of the local electrode was found to be dependent on the shape and position of the debris from the specimen failure rather than the number of ions collected or the number of specimens characterized. Local electrodes with smaller apertures were found to be more susceptible to failure.

TENOR risk score predicts healthcare in adults with severe or difficult-to-treat asthma.

The aim of the present study was to predict which patients with severe or difficult-to-treat asthma are at highest risk for healthcare utilisation can be predicted so as to optimise clinical management. Data were derived from 2,821 adults with asthma enrolled in The Epidemiology and Natural History of Asthma: Outcomes and Treatment Regimens (TENOR) study. Multiple potential predictors were assessed at baseline using a systematic algorithm employing stepwise logistic regression. Outcomes were asthma-related hospitalisations or emergency department (ED) visits within 6 months following baseline. Overall, 239 subjects (8.5%) reported hospitalisation or ED visits at follow-up. Predictors retained after multivariate analysis were as follows: younger age; female sex; non-white race; body mass index > or =35 kg x m(-2); post-bronchodilator per cent predicted forced vital capacity <70%; history of pneumonia; diabetes; cataracts; intubation for asthma; and three or more steroid bursts in the prior 3 months. A final risk score derived from the logistic regression model ranged from 0-18 and was highly predictive (c-index: 0.78) of hospitalisation or ED visits. This tool was re-tested in a prospective validation using outcomes at 12- to 18-months follow-up among the same cohort (c-index: 0.77). The risk score derived is a clinically useful tool for assessing the likelihood of asthma-related hospitalisation or emergency department visits in adults with severe and difficult-to-treat asthma.

Strategies for fabricating atom probe specimens with a dual beam FIB.

A FIB-based lift-out method for preparing atom probe specimens at site specific locations such as coarse precipitates, grain boundaries, interphase interfaces, denuded zones, heat affected zones, implanted, near surface and subsurface regions, shear bands, etc. has been developed. FIB-based methods for the fabrication of atom probe specimens from thin ribbons, sheet stock, and powders have been developed.

Atom probe tomography: a technique for nanoscale characterization.

Atom probe tomography is a technique for the nanoscale characterization of microstructural features. Analytical techniques have been developed to estimate the size, composition, and other parameters of features as small as 1 nm from the atom probe tomography data. These methods are outlined and illustrated with examples of yttrium-, titanium-, and oxygen-enriched particles in a mechanically alloyed, oxide-dispersion-strengthened steel.

Some aspects of atom probe specimen preparation and analysis of thin film materials.

Some of the factors in the preparation of atom probe specimens of metallic multilayer thin films have been investigated. A series of Ti/Nb multilayer films were sputtered deposited on n-doped Si [001] substrates with either 5 or 0.05Omega cm resistivity. Each wafer was pre-fabricated into a series of 5 microm x 5 microm x approximately 80 microm island posts by photolithography and reactive ion etching. Once the film was grown on the wafer, a Si post was mounted to either a tungsten or stainless steel fine tip needle that was mechanically crimped to a Cu tube for handling. The specimen was then loaded into a Focus Ion Beam instrument where a sacrificial Pt cap was in situ deposited onto the surface of the film and subsequently annularly ion milled into the appropriate geometry. The Pt cap was found to be an effective method in reducing Ga ion damage and implantation into the film during milling. The multilayers deposited on the high resistivity Si exhibited uncontrolled field evaporation which lead to high mass tails in the mass spectra, a reduction in the mass resolution, high background noise, propensity for "flash-failure", and a variation in the apparent layer thickness as the experiment elapsed in time. The multilayers deposited on lower resistivity Si did not suffer from these artifacts.

Immunohistochemical analysis of prostate specific antigen in breast cancer.

The presence of immunoreactive prostate-specific antigen (IR-PSA) has been reported in breast cancers and has been suggested to confer a positive prognosis. However, recent large, well-controlled studies have found no significant prognostic value when IR-PSA positivity is examined as an independent variable, even when ultrasensitive immunofluorometric techniques are utilized. The present study, using indirect immunohistochemistry on 75 formalin-fixed, paraffin-embedded breast cancers shows PSA immunoreactivity in only seven of 75 cases (9%), suggesting that PSA positivity in breast carcinoma is not useful as a prognostic or tumor marker with hospital-based methods.

Concurrent chronic lymphocytic leukemia cutis and acute myelogenous leukemia cutis in a patient with untreated CLL.

Patients who have chronic lymphocytic leukemia (CLL) are known to have a high frequency of second malignant neoplasms. However, acute myelogenous leukemia (AML) occurring concurrent with or after a diagnosis of CLL is extremely rare. In this article we report a case of AML developing in a 55-year-old male with a 6-year history of untreated CLL. The diagnosis was facilitated by touch preparation of a skin punch biopsy specimen. The patient presented with a two-week history of fever, weakness, anasarca, and a skin rash. Physical examination revealed pink to skin-colored firm papules, which coalesced into indurated plaques on his trunk, upper extremities, and face. The lesions, in combination with generalized edema, produced a leonine facies. Touch prep of the biopsy showed medium to large blasts, large monocytoid cells, and numerous small mature lymphocytes, providing the preliminary diagnosis of a second, previously undiagnosed myelomonocytic malignancy in this patient. The initial diagnosis was subsequently confirmed by histologic, cytochemical, immunohistochemical and flow cytometry studies. This is the first reported case of CLL with concurrent AML in which rapid touch prep of a skin punch biopsy facilitated diagnosis.

Analysis of anesthesia practice and needs in Louisiana.

The Louisiana State University Health Sciences Center Department of Anesthesiology performed an analysis of anesthesia practice and needs within the State of Louisiana. The State of Louisiana currently has approximately 300 practicing anesthesiologists (physicians), 700 certified registered nurse anesthetists (CRNAs), and does not currently utilize anesthesiologist assistants (AAs). Approximately 500,000 anesthesia encounters occur annually in Louisiana. Although there is a recognized critical shortage of anesthesiologists nationally, this document will focus mainly on the issue of mid-level providers of anesthesia services. The overwhelming majority of surgical and obstetric procedures is performed using the anesthesia care team approach both nationally and in the State of Louisiana. Within the anesthesia care team model, the practice of certified registered nurse anesthetists and anesthesiologist assistants are interchangeable, and both would meet the need for mid-level anesthesia providers in the State of Louisiana.

Hydroxyurea therapy for pediatric patients with hemoglobin SC disease.

PURPOSE: Hydroxyurea (HU) has laboratory and clinical efficacy in hemoglobin SS (HbSS) disease, but its benefits in hemoglobin SC (HbSC) disease are unknown. A recent adult HbSC disease pilot trial with HU therapy documented a modest laboratory benefit. Our goal was to evaluate the laboratory and clinical responses of selected pediatric patients with severe HbSC disease to HU therapy. PATIENTS AND METHODS: As part of a retrospective case series, patients were selected from the Duke Pediatric Sickle Cell Program based on the frequency and severity of their vasoocclusive events or an episode of acute chest syndrome. Oral HU therapy was started as a single daily dose and increased to the maximally tolerated dose based on myelosuppression. Laboratory evaluation was performed at baseline and monthly thereafter. Once the maximum tolerated dose was reached, laboratory data were monitored bimonthly. RESULTS: We treated six severely affected pediatric HbSC patients with HU for a median of 27 months. Mean corpuscular volume increased significantly (+26 fL) without change in hemoglobin concentration (-0.1 g/dL); neutrophils decreased significantly. Percentage of fetal hemoglobin (+8.5%) and percentage of F cells (+35.7%) increased significantly. Two experienced only mild and reversible toxicity. CONCLUSION: The laboratory responses in our pediatric patients with HbSC disease were striking, with increases in percentage of fetal hemoglobin and percentage of F-cells approaching responses observed in adult and pediatric patients with HbSS disease. All patients improved clinically. Our findings demonstrate that HU therapy benefits pediatric patients with severe HbSC disease, although larger clinical trials of HU therapy in HbSC disease are warranted.

Do learning style and learning environment affect learning outcome?

This study compared learning outcomes of students with different learning styles, as identified by the Kolb Learning Style Inventory indicators, in a traditional in-class environment with those taking the same course via distance education. The above-average scores were evenly distributed, 47% of the in-class group and 43% of the distance group. For three of the four learning styles, there was no relationship to learning outcome or environment. The Diverger group did show a relationship with above-average scores in the distance group (83%). The findings support that the classroom or distance environment did not influence learning outcome. Learning style did not appear to affect learning outcome in either group, except that the Diverger learning style may have a positive relationship to learning in the distance environment.

Ultrasound-guided internal jugular venous cannulation: an introduction for non-radiologists to a technique that is here to stay.

The availability of relatively low-cost, portable ultrasound units has increased interest among non-radiologists in performing image-guided central venous cannulation, especially in high-risk patients. The essential elements of this relatively simple method of increasing the success and safety of internal jugular cannulation are presented.