In the paper, we focus on atom diffusion behavior in Ni-based superalloys, which have important applications in the aero-industry. Specifically, the expressions of the key physical parameter – transition rate (jump rate) in the diffusion can be given from the diffusion theory in solids and the kinetic Monte Carlo (KMC) method, respectively. The transition rate controls the diffusion process and is directly related to the energy of vacancy formation and the energy of migration of atom from density functional theory (DFT). Moreover, from the KMC calculations, the diffusion coefficients for Ni and Al atoms in the γ phase (Ni matrix) and the γʹ phase (intermetallic compound Ni3Al) of the superalloy have been obtained. We propose a strategy of time stepping to deal with the multi-time scale issues. In addition, the influence of temperature and Al concentration on diffusion in dilute alloys is also reported.

Materials synthesis and the functioning of devices often involve liquid media. However, direct visualization of dynamic processes in liquids, especially with high spatial and temporal resolution, has been challenging. For solid materials, advances in aberration-corrected electron microscopy have made observations of atomic-level features a routine practice. Here, we discuss the extent to which one can take advantage of the resolution of modern electron microscopes to image phenomena occurring in liquids. We describe the fundamentals of two different experimental approaches that use closed and open liquid cells. We illustrate the capabilities of each approach by considering processes in batteries and nucleation and growth of nanoparticles from solution. Liquid-cell electron microscopy appears to be duly fulfilling its role and promise for in situ studies of nanoscale processes in liquids, revealing physical and chemical processes that are otherwise difficult to observe.

Since the advent of the transmission electron microscope (TEM), continuing efforts have been made to image material under native and reaction environments that typically involve liquids, gases, and external stimuli. With the advances of aberration-corrected TEM for improving the imaging resolution, steady progress has been made on developing methodologies that allow imaging under dynamic operating conditions, or in situ TEM imaging. The success of in situ TEM imaging is closely associated with advances in microfabrication techniques that enable manipulation of nanoscale objects around the objective lens of the TEM. This study summarizes and highlights recent progress involving in situ TEM studies of energy storage materials, especially rechargeable batteries. The study is organized to cover both the in situ TEM techniques and the scientific discoveries made possible by in situ TEM imaging.

The recent development of in-situ liquid stages for (scanning) transmission electron microscopes now makes it possible for us to study the details of electrochemical processes under operando conditions. As electrochemical processes are complex, care must be taken to calibrate the system before any in-situ/operando observations. In addition, as the electron beam can cause effects that look similar to electrochemical processes at the electrolyte/electrode interface, an understanding of the role of the electron beam in modifying the operando observations must also be understood. In this paper we describe the design, assembly, and operation of an in-situ electrochemical cell, paying particular attention to the method for controlling and quantifying the experimental parameters. The use of this system is then demonstrated for the lithiation/delithiation of silicon nanowires.

Objective: To study when and how an urgent public health message about a boil-water order reached an urban population after the Massachusetts water main break.

Methods: In-person surveys were conducted in waiting areas of clinics and emergency departments at a large urban safety net hospital within 1 week of the event.

Results: Of 533 respondents, 97% were aware of the order; 34% of those who lived in affected cities or towns were potentially exposed to contaminated water. Among those who were aware, 98% took action. Respondents first received the message through word of mouth (33%), television (25%), cellular telephone calls (20%), landline calls (10%), and other modes of communication (12%). In multivariate analyses, foreign-born respondents and those who lived outside the city of Boston had a higher risk of exposure to contaminated water. New modes (eg, cellular telephones) were used more commonly by females and younger individuals (ages 18 to 34). Individuals who did not speak English at home were more likely to receive the message through their personal networks.

Conclusions: Given the increasing prevalence of cellular telephone use, public officials should encourage residents to register landline and cellular telephone for emergency alerts and must develop creative ways to reach immigrants and non–English-speaking groups quickly via personal networks.

(Disaster Med Public Health Preparedness. 2011;5:235–241)

Electrospinning is a versatile technique for fabricating three-dimensional (3D) nanofibrous scaffolds and the scaffolds have been found to elicit desirable cellular behavior for tissue regeneration because the nanofibrous structures mimic the nanofibrous extracellular matrix (ECM) of biological tissues. From the material point of view, the ECM of bone is a nanofibrous nanocomposite consisting of an organic matrix (mainly collagen) and inorganic bone apatite nanoparticles. Therefore, for bone tissue engineering scaffolds, it is natural to construct nanofibrous nanocomposites having a biodegradable polymer matrix and nanosized bioactive bioceramics. Our previous studies demonstrated: (1) electrospun nanocomposite fiber loaded with calcium phosphate (Ca-P) were osteoconductive and could promote osteoblastic cell proliferation and differentiation better than pure polymer fibers; (2) The controlled release of recombinant human bone morphogenetic protein (rhBMP-2) from scaffolds provided the scaffolds with desired osteoinductivity. In the current investigation, novel bicomponent scaffolds for bone tissue engineering were produced using our established dual-source dual-power electrospinning technique to achieve both osteoconductivity and osteoinductivity. In the bicomponent scaffolds, one fibrous component was electrospun Ca-P/PLGA nanocomposite fibers and the other component was emulsion electrospun PDLLA nanofibers incorporated with rhBMP-2. Through electrospinning optimization, both fibers were evenly distributed in bicomponent scaffolds. The mass ratio of rhBMP-2/PDLLA fibers to Ca-P/PLGA fibers in bicomponent scaffolds could be controlled using multiple syringes. The structure and morphology of mono- and bicomponent scaffolds were examined. The in vitro release of rhBMP-2 from mono- and bicomponent scaffolds showed different release amount but similar release profile, exhibiting an initial burst release. Blending PDLLA with polyethylene glycol (PEG) could reduce the initial burst release of rhBMP-2.

In order to assess the influence of nutrient elements on the accumulation of β-N-oxalyl-L-α, β-diaminopropionic acid (β-ODAP; the probable cause of lathyrism) in Lathyrus sativus L. (grass pea), it was first examined under field conditions during the lifespan of a grass pea plant using high-performance liquid chromatography (HPLC). β-ODAP mainly accumulated in young seedlings, in developing and mature seeds and in young leaves, especially in young seedlings. In contrast, all mature leaves, roots, and stems showed a low level of β-ODAP. The β-ODAP accumulation pattern in seedlings grown in a nutrient-deficient solution was highest (3·57 mg/g) in shoots at 7 d growing in the nitrogen-deficient solution and higher compared to the control (2·31 mg/g) in zinc-, calcium-, phosphorus- and molybdenum-deficient shoots (P<0·05). The contents of β-ODAP in seedlings growing in other element-deficient solutions were similar to controls. When the content of β-ODAP in grass pea seedlings fertilized with different forms of organic nitrogen was assayed the results indicated that amino acids such as glutamine and serine, as well as nucleotide nitrogen, all significantly enhanced the accumulation of β-ODAP in young seedlings relative to controls (P<0·05). Taken together, these data suggest that β-ODAP accumulation in grass pea might be related to the level of total free nitrogenous compounds and that nitrogen and phosphate may be the crucial nutrient factors influencing β-ODAP content under field conditions. Thus, the application of appropriate nitrogen and phosphorus fertilizers to the soil could decrease the content of β-ODAP in the seeds and leaves of grass pea.

We successfully synthesized helical core-shell crystalline SiC/SiO2 nanowires, core-shell crystalline SiC/C nano-crosses and well-aligned core-shell crystalline SiC/C fibers by using a chemical vapor deposition technique. For the helical crystalline SiC/SiO2 nanowires, the SiC core typically has diameters of 10-40 nm with a helical periodicity of 40-80 nm and is covered by a uniform layer of 30-60 nm thick amorphous SiO2. Detailed structural characterizations suggested that the growth of this novel structure was induced by screw dislocations on the nanometer scale. For the core-shell nanocrosses, the crystalline SiC core typically has diameters of 10 to 40 nm and is covered by a uniform layer of 80-110 nm graphitic carbon. The wellaligned SiC/C fibers were shown to be formed by two sequential steps: catalytic SiC growth and graphitic carbon nano-sheets coating. The helical nanowires and core-shell nanocrosses may have potential applications in nano-electronics. The formation mechanism of the carbon fibers suggested that fabrication of field emission filament carbon nano-fibers may be realized by using the aligned crystalline nanowires as templates.

The tensile creep behavior of yttrium- and lanthanum-doped alumina (at dopant levels below the solubility limit) was examined. Both compositions (100 ppm yttrium, 100 ppm lanthanum) exhibited a uniform microstructure consisting of fine, equiaxed grains. The creep resistance of both doped aluminas was enhanced, compared with undoped alumina, by about two orders of magnitude, which was almost the same degree of improvement as for materials with higher dopant levels (in excess of the solubility limit). In addition, measured creep rupture curves exhibited predominantly steady-state creep behavior. Our results, therefore, verified that the creep improvement in these rare-earth doped aluminas was primarily a solid-solution effect.