Large Constituent Research Articles

Spherical constituent particles formed by a multistage solution treatment in Al–Zn–Mg–Cu alloys

The corrosion resistance and fracture toughness of Al–Zn–Mg–Cu alloys are greatly affected by the remaining large constituent particles with sharp corners and sharp edges. Here, we show that with a careful high-temperature solution treatment, these constituent particles can be formed into spherical rather than irregular shapes. This results in better corrosion resistance and mechanical properties for the alloys than the conventional solution treatment. The complex microstructures of the formed spherical constituent particles and their formation mechanism were studied using focused ion beam (FIB), scanning transmission electron microscopy (STEM) and selected area electron diffraction (SAED). It was revealed that there are five types of spherical constituent particles formed after the special solution treatment, and each type has its own characteristic microstructural features.

β-Cryptoxanthin Restores Nicotine-Reduced Lung SIRT1 to Normal Levels and Inhibits Nicotine-Promoted Lung Tumorigenesis and Emphysema in A/J Mice

Nicotine, a large constituent of cigarette smoke, is associated with an increased risk of lung cancer, but the data supporting this relationship are inconsistent. Here, we found that nicotine treatment not only induced emphysema but also increased both lung tumor multiplicity and volume in 4-nitrosamino-1-(3-pyridyl)-1-butanone (NNK)-initiated lung cancer in A/J mice. This tumor-promoting effect of nicotine was accompanied by significant reductions in survival probability and lung Sirtuin 1 (SIRT1) expression, which has been proposed as a tumor suppressor. The decreased level of SIRT1 was associated with increased levels of AKT phosphorylation and interleukin (il)-6 mRNA but decreased tumor suppressor p53 and retinoic acid receptor (RAR)-β mRNA levels in the lungs. Using this mouse model, we then determined whether β-cryptoxanthin (BCX), a xanthophyll that is strongly associated with a reduced risk of lung cancer in several cohort studies, can inhibit nicotine-induced emphysema and lung tumorigenesis. We found that BCX supplementation at two different doses was associated with reductions of the nicotine-promoted lung tumor multiplicity and volume, as well as emphysema in mice treated with both NNK and nicotine. Moreover, BCX supplementation restored the nicotine-suppressed expression of lung SIRT1, p53, and RAR-β to that of the control group, increased survival probability, and decreased the levels of lung il-6 mRNA and phosphorylation of AKT. The present study indicates that BCX is a preventive agent against emphysema and lung cancer with SIRT1 as a potential target. In addition, our study establishes a relevant animal lung cancer model for studying tumor growth within emphysematous microenvironments.

Abstract A37: Beta-cryptoxanthin restores nicotine-reduced lung SIRT1 to normal levels and inhibits nicotine-promoted lung tumorigenesis and emphysema in A/J mice

Abstract Nicotine, a large constituent of cigarette smoke, is associated with an increased risk of lung cancer but the data remains inconsistent. Here, we found that nicotine treatment not only induced emphysema, but also increased both lung tumor multiplicity and volume, in 4-nitrosamino-1-(3-pyridyl)-1-butanone (NNK)-initiated lung cancer in A/J mice. This tumor-promoting effect of nicotine was accompanied with significant reductions of survival probability and lung Sirtuin 1 (SIRT1), which has been proposed as a tumor suppressor. The decreased SIRT1 was associated with increased levels of AKT phosphorylation and interleukin (il)-6 mRNA, but decreased tumor suppressor p53 and retinoic acid receptor (rar)-beta mRNA levels in the lungs. Using this mouse model, we then determine whether a xanthophyll beta-cryptoxanthin (BCX), which is associated with a reduced risk of lung cancer from a pooled analysis of seven prospective cohort studies, can inhibit the nicotine-induced emphysema and lung tumorigenesis. We found that BCX supplementation at two different doses reduced the nicotine-promoted lung tumor multiplicity and volume, as well as emphysema in mice treated with both NNK and nicotine. Moreover, BCX supplementation restored the nicotine-suppressed lung SIRT1, p53, and rar-beta to the levels of the control group, increased the survival probability, and decreased the lung il-6 mRNA and AKT phosphorylation levels. The present study indicates that the SIRT1 is a potential target for the action of BCX against emphysema and lung cancer. In addition, our study established a relevant animal lung cancer model for studying tumor growth within emphysemateous microenvironments. Citation Format: Anita Iskandar, Chun Liu, Donald Smith, Kang-Quan Hu, Sang-Woon Choi, Lynne Ausman, Xiang-Dong Wang. Beta-cryptoxanthin restores nicotine-reduced lung SIRT1 to normal levels and inhibits nicotine-promoted lung tumorigenesis and emphysema in A/J mice. [abstract]. In: Proceedings of the Eleventh Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2012 Oct 16-19; Anaheim, CA. Philadelphia (PA): AACR; Cancer Prev Res 2012;5(11 Suppl):Abstract nr A37.

Microstructure of Low C Steel Isothermally Transformed in the M S to M f Temperature Range

An isothermal transformation was observed when a fully austenitized lean-alloyed, low C steel was quenched to a temperature in the MS to Mf temperature range and held at the quenching temperature. The dilatometric analysis revealed that the isothermal transformation was distinct from the bainitic transformation. Internal friction (IF) measurements and X-ray diffraction (XRD) analysis showed that the dislocation density in the isothermal transformation product was larger than in lower bainite, and lower than in athermal martensite. Microstructural analysis by transmission electron microscopy (TEM) revealed that the isothermal transformation product had a specific microstructure consisting of large lath-type constituent units with wavy boundaries, with a Nishiyama–Wassermann orientation relationship (NW OR) with respect to the parent austenite. The isothermal transformation below MS proceeds by the thickening of athermally formed laths.

C/CrN multilayer coating for polymer electrolyte membrane fuel cell metallic bipolar plates

The two most important issues that plague wider use of stainless steel bipolar plates in polymer electrolyte membrane fuel cells (PEMFCs) are insufficient corrosion resistance and surface conductivity. In this study, C/CrN multilayer coatings are deposited on 316L stainless steel samples by close-field unbalanced magnetron sputtering ion plating. SEM shows that the C/CrN coatings are dense, continuous, and composing of carbon granules on the surface. Raman spectroscopy reveals an amorphous structure with a large sp2 constituent. The corrosion resistance and interfacial contact resistance (ICR) are investigated systematically. A superior ICR in the range of 2.6–2.9mΩ-cm2 at a compaction force of 150N/cm2 is achieved and it is even better than that of graphite. The deposited film possesses high chemical inertness thereby significantly enhancing the corrosion resistance of the coated SS316L. A thickness of 800nm is sufficient to protect against corrosion. C/CrN multilayer coatings are beneficial in that it can lead to a faster PVD deposition process and lower material cost, while permitting a superior performance in terms of surface conductivity and corrosion resistance.

Recrystallization Textures in Aluminum Alloys: Experimental Study and Modelling

The changes in crystallographic texture are investigated during recrystallization in 5182 and 6016 aluminum alloys, which were subjected to various cold rolling reductions. In the current study, the texture varieties in the recrystallized materials are conditioned by both the material’s chemistry and the applied rolling strain. The presence of large constituent particles produces strain heterogeneities during cold rolling which causes a specific texture development. The development of recrystallization textures is discussed based on experimental data and results of crystal plasticity simulations. A recrystallization model based on nucleation and growth selection is presented. The driving force for nucleation was accounted for by applying continuum mechanics crystal plasticity models. For the modeling of the strain heterogeneities around hard undeformable particle a FE-code was used.

CHIRAL MAGNETIC EFFECT AND QCD PHASE TRANSITIONS WITH EFFECTIVE MODELS

We study the influence of the chiral phase transition on the chiral magnetic effect. The chiral electric current density along the magnetic field, the electric charge difference between on each side of the reaction plane, and the azimuthal charged-particle correlations as functions of the temperature during the QCD phase transitions are calculated. It is found that with the decrease of the temperature, the chiral electric current density, the electric charge difference, and the azimuthal charged-particle correlations all get a sudden suppression at the critical temperature of the chiral phase transition, because the large quark constituent mass in the chiral symmetry broken phase quite suppresses the axial anomaly and the chiral magnetic effect. We suggest that the azimuthal charged-particle correlations (including the correlators divided by the total multiplicity of produced charged particles which are used in current experiments and another kind of correlators not divided by the total multiplicity) can be employed to identify the occurrence of the QCD phase transitions in RHIC energy scan experiments.

Microstructural characteristics and toughness of the simulated coarse grained heat affected zone of high strength low carbon bainitic steel

Abstract The correlation of microstructural characteristics and toughness of the simulated coarse grained heat affected zone (CGHAZ) of low carbon bainitic steel was investigated in this study. The toughness of simulated specimens was examined by using an instrumented Charpy impact tester after the simulation welding test was conducted with different cooling times. Microstructure observation and crystallographic feature analysis were conducted by means of optical microscope and scanning electron microscope equipped with electron back scattered diffraction (EBSD) system, respectively. The main microstructure of simulated specimen changes from lath martensite to coarse bainite with the increase in cooling time. The deterioration of its toughness occurs when the cooling time ranges from 10 to 50 s compared with base metal toughness, and the toughness becomes even worse when the cooling time increases to 90 s or more. The MA (martensite–austenite) constituent is primary responsible for the low toughness of simulated CGHAZ with high values of cooling time because the large MA constituent reduces the crack initiation energy significantly. For crack propagation energy, the small effective grain size of lath martensite plays an important role in improving the crack propagation energy. By contrast, high misorientation packet boundary in coarse bainite seems to have few contributions to the improvement of the toughness because cleavage fracture micromechanism of coarse bainite is mainly controlled by crack initiation.

Modeling the crystallographic texture changes in aluminum alloys during recrystallization

The evolution of crystallographic texture during recrystallization annealing is affected by the hot and cold rolling parameters. A 6016 Al alloy with various hot band textures was subjected to conventional rolling and short time annealing at elevated temperature. Asymmetric rolling with differential circumferential velocities of the top and bottom rolls was applied to the aluminum alloy under investigation to modify the hot rolling texture. The presence of large constituent particles enforces strain heterogeneities during cold rolling. The influence of particles on the development of recrystallization textures is discussed based on the experimental data and the results of crystal plasticity simulations. A recrystallization model based on nucleation and growth selection is presented. The driving force for nucleation was accounted for by applying continuum mechanics crystal plasticity models, which allow calculation of the stored energy of plastic strain for specific orientations of the polycrystalline aggregate and for the strain mode under consideration. Crystal misorientations of type 〈1 1 1〉 40° were attributed to enhanced mobility during the growth stage of recrystallization.

Effect of Concurrent Precipitation on Recrystallization and Evolution of the P-Texture Component in a Commercial Al-Mn Alloy

The recrystallization behavior of a cold-rolled Al-Mn alloy was investigated, focusing on the effect of concurrent precipitation on nucleation and growth of recrystallization and the formation of the P- \( \left( {\left\{ {011} \right\}\left\langle {111} \right\rangle } \right) \) and ND-rotated cube \( \left( {\left\{ {001} \right\}\left\langle {310} \right\rangle } \right) \) texture components. It was observed that if precipitation took place prior to or simultaneously with recovery and recrystallization processes, i.e., by concurrent precipitation, this resulted in a delayed recrystallization, a coarse and elongated grain structure, and an unusually sharp P-texture component. The P-texture component sharpened with increasing initial cold rolling reduction, increasing initial supersaturation of Mn, and decreasing annealing temperature. The P- and ND-rotated cube nucleation sites have an initial growth advantage compared to the particle-stimulated nucleation (PSN) sites due to their 40 deg \( \left\langle {111} \right\rangle \)-rotation relationship to the Cu component of the deformation texture. The boundaries between such sites and the surrounding matrix will be of the Σ7 type, and it is assumed that such highly perfect boundaries will be less affected by solute segregation and precipitation, resulting in early growth advantage. It was further observed that dispersoids present prior to cold rolling and annealing had a weaker effect on the recrystallized grain size and texture compared to concurrent precipitation, even though the average dispersoid density was higher in the pre-precipitation cases. The finer grain size was explained by the wider dispersoid free zones surrounding the large constituent particles compared to the concurrent precipitation cases. Subsequent growth of the nucleated grains, however, was more hindered due to the Zener drag, consistent with the higher dispersoid densities.

Sedimentary characteristics and origin of the Late Pleistocene Ice Complex on north-east Siberian Arctic coastal lowlands and islands – A review

The origin of Late Pleistocene ice-rich, fine-grained permafrost sequences (Ice Complex deposits) in arctic and subarctic Siberia has been in dispute for a long time. Corresponding permafrost sequences are frequently exposed along seacoasts and river banks in Yedoma hills, which are considered to be erosional remnants of Late Pleistocene accumulation plains. Detailed cryolithological, sedimentological, geochronological, and stratigraphical results from 14 study sites along the Laptev and East Siberian seacoasts were summarized for the first time in order to compare and correlate the local datasets on a large regional scale. The sediments of the Ice Complex are characterized by poorly-sorted silt to fine-sand, buried cryosols, TOC contents of 1.2–4.8 wt%, and very high ground ice content (40–60 wt% absolute). A second large constituent of the Ice Complex are large syngenetic ice wedges, resulting in a total ice content of the Ice Complex of up to 80 vol%. Ice Complex deposits were mostly formed during the Middle Weichselian interstadial and/or during the Late Weichselian stadial periods. A conceptual model of nival lithogenesis of Ice Complex deposits was developed that integrates various other formation hypotheses. A combination of various local and regional paleogeographical, geological, and paleoclimate conditions controlled the formation of Ice Complex sequences during the Late Pleistocene in northern East Siberia. They are chronologically and stratigraphically, but not genetically equivalent to Eurasian and Alaskan loess deposits.

Validity criteria of the discrete dipole approximation

There are two widely accepted restrictions on the application of the discrete dipole approximation (DDA) in the study of light scattering by particles comparable to the wavelength: (1) when considering dielectric particles, the size of the cells must satisfy the condition kd|m|<0.5, where k is the wavenumber, d is the size of the cells, and m is the complex refractive index of the constituent material and (2) when considering conductive particles, the size of the cells must be small enough to reproduce sufficiently the evolution of the electromagnetic field in the skin layer. We examine both restrictions when the DDA is applied to irregularly shaped particles and show that its restrictions are not as strong as is widely accepted. For instance, when studying irregularly shaped particles averaged over orientations, even at kd|m|=1, the DDA provides highly accurate numerical results. Moreover, we show that the impact of using large constituent cells is similar to that produced by surface roughness; therefore, the replacement of the target particle by an array of large constituent cells has the same effect, qualitatively, as incorporating additional small-scale surface roughness on the particle. Such a modification of the target particle can be desirable in many practical applications of DDA when irregularly shaped particles are considered. When applying DDA to conductive, nonspherical particles, the insufficient description of the electromagnetic field in the skin layer does not lead to a violation of the Maxwell equations, although it has a visible but nonmajor influence on the light-scattering properties of the target.

Three-phonon phase space and lattice thermal conductivity in semiconductors

We present calculations of the phase space for three-phonon scattering events in severalgroup IV, III–V and II–VI semiconductors employing an adiabatic bond charge model toaccurately represent the phonon dispersions. We demonstrate that this phase space variesinversely with the measured lattice thermal conductivities of these materials overa wide range of temperatures where three-phonon scattering is the dominantmechanism for scattering phonons. We find that this qualitative relationship isrobust in spite of variations in material parameters between the semiconductors.Anomalous behavior occurs in three III–V materials that have large mass differencesbetween constituent elements, which we explain in terms of the severely restrictedthree-phonon phase space arising from the large gap between acoustic and optic phononbranches.

Determination of fatigue related discontinuity state of 7000 series of aerospace aluminum alloys

The current methods of fatigue life estimation do not model the interaction of stress with microstructural discontinuities. An experimental study of fatigue crack nucleation in 7075-T6 and 7079-T6 aluminum alloy sheet was performed to obtain more information on the role of discontinuities in the microstructure and to determine the relative contributions of each type of discontinuity. Some specimens were machined from recently manufactured material without any coating (cladding or anodizing). Some were fabricated from old clad-anodized material from an aircraft fuselage and old anodized material from a stock of unused wing panels. In the uncoated materials, large constituent particles and the surface roughness were found to be important factors in fatigue crack nucleation. In the coated materials, discontinuities related to the cladding and anodizing appeared to be the controlling factors in crack nucleation and particles did not play any role. The coated specimens showed a low scatter and a relatively low fatigue life. Multiple nucleation sites were observed in the coated materials.

Large constituent families help children parse compounds

The family size of the constituents of compound words, or the number of compounds sharing the constituents, has been shown to affect adults' access to compound words in the mental lexicon. The present study was designed to see if family size would affect children's segmentation of compounds. Twenty-five English-speaking children between 3;7 and 5;9 were asked to explain the meaning of existing compounds with constituents of varying family size to an alien puppet. The results showed that children were more likely to mention the modifier of compounds if they came from large constituent families than if they came from small constituent families. Other variables were also shown to have some, but smaller effects on children's parsing, including the frequency of the constituent words and the compounds, whether the compounds were already known, and age. These results suggest that children's segmentation of compounds might be facilitated by analogy with other compounds already in their vocabularies.

Modeling of Nucleation Spectra for Primary Recrystallization and Application to Through-Process Texture Modeling

Schemes to model deformation inhomogeneities and nuclei distributions based on the grain cluster model for deformation texture simulation GIA are presented. The orientation distributions of nuclei in stable orientations, nuclei in grains with orientation gradients and nuclei due to subgrain growth at grain boundaries are predicted. Additionally, nuclei with a random orientation distribution are considered, reflecting nucleation at shear bands or large constituent particles. Furthermore, models for a quantitative assessment of the participating nucleation mechanisms are proposed. The resulting nucleation texture was input to the static recrystallization texture model StaRT. The through-process texture development during a sequence of several hot rolling, cold rolling and annealing steps in industrial production of the aluminum alloy AA5182 is presented.

Response of a member of the Verrucomicrobia, among the dominating bacteria in a hypolimnion, to increased phosphorus availability

In Lake Siggeforasjon, Sweden, a member of the Verrucomicrobia was found to be a large constituent of the bacteria in the hypolimnion, but not in the epilimnion. In a mesocosm experiment in the epilimnion, this particular Verrucomicrobia was favoured by increased phosphorus availability. The community composition of bacterioplankton was investigated by denaturing gradient gel electrophoresis (DGGE) and sequencing of 16S rDNA.During the last decade, molecular studies of the taxonomic composition of bacterioplankton communities in lakes and oceans have led to the discovery of a large number of ‘new’ bacteria (Giovannoni and Rappe, 2000; Glockner et al., 2000). The occurrence of different bacterial taxa in the plankton community varies in time and space, and thus these taxa are likely to play different roles in the ecosystems. Recent results have indicated that the number of bacterioplankton taxa that still remain to be discovered is limited (Hagstrom et al., 2002; Zwart et al., 2002). However, so far, very little is known about the ecology of individual bacterioplankton species, for instance about which environmental factors can impact their abundance (Zwart et al., 2002).The purpose of this study was to investigate the factors that affect the composition of bacterioplankton at different depths in lakes. We compared the bacterioplankton communities in the epilimnion and the hypolimnion of a lake, and performed a 4 day mesocosm experiment where phosphorus (P) availability was manipulated to test whether it contributed to differences in bacterioplankton community composition between the layers.The community composition of bacterioplankton was investigated by denaturing gradient gel electrophoresis (DGGE) of 16S rDNA, as described previously (Lindstrom, 1998). DGGE is a method that can be used to obtain an overview of the composition of the most dominant bacterioplankton taxa [e.g. (Torsvik et al., 1998)]. The pairwise similarity of the gel patterns of the samples was calculated using Sorensen’s index (Sorensen, 1948).Samples were taken from the temperate dimictic Lake Siggeforasjon, located near Uppsala, in the southern part of central Sweden (59°N, 17°E). This lake is oligo-mesotrophic and moderately humic (Table I). The community composition of the bacterioplankton in the lake has been investigated previously (Lindstrom, 1998, 2000; Lindstrom and Leskinen, 2002).

The spatial distribution of nucleation sites and its effect on recrystallization kinetics in commercial aluminum alloys

Particle distributions play a major role in the processing response of aluminum alloys. While large constituent particles play an important role in the nucleation of recrystallization, small particles may heavily restrict the growth of recrystallized grains. In the present investigation, a two-dimensional (2-D) tesselation procedure has been used to characterize the particle distribution in commercial aluminum alloys and its relevance to nucleation of recrystallization. This procedure enabled the quantification of the degree of particle clustering in samples rolled to different strain levels. A characteristic aspect seems to be a transition from a rather nonuniform spatial distribution at low rolling strains, toward a more or less random distribution at high strains. Nucleation kinetics has been found to be site saturated, indicating that all nucleation events effectively occur at the start of recrystallization. A simple model is proposed, which explains the development of the spatial particle distribution as a function of rolling strain.

Characterization of the Low Molecular Weight Human Serum Proteome

Serum potentially carries an archive of important histological information whose determination could serve to improve early disease detection. The analysis of serum, however, is analytically challenging due to the high dynamic concentration range of constituent protein/peptide species, necessitating extensive fractionation prior to mass spectrometric analyses. The low molecular weight (LMW) serum proteome is that protein/peptide fraction from which high molecular weight proteins, such as albumin, immunoglobulins, transferrin, and lipoproteins, have been removed. This LMW fraction is made up of several classes of physiologically important proteins such as cytokines, chemokines, peptide hormones, as well as proteolytic fragments of larger proteins. Centrifugal ultrafiltration of serum was used to remove the large constituent proteins resulting in the enrichment of the LMW proteins/peptides. Because albumin is known to bind and transport small molecules and peptides within the circulatory system, the centrifugal ultrafiltration was conducted under solvent conditions effecting the disruption of protein-protein interactions. The LMW serum proteome sample was digested with trypsin, fractionated by strong cation exchange chromatography, and analyzed by microcapillary reversed-phase liquid chromatography coupled on-line with electrospray ionization tandem mass spectrometry. Analysis of the tandem mass spectra resulted in the identification of over 340 human serum proteins; however, not a single peptide from serum albumin was observed. The large number of proteins identified demonstrates the efficacy of this method for the removal of large abundant proteins and the enrichment of the LMW serum proteome.

Trends and Variations in South Pacific Island and Ocean Surface Temperatures

An analysis of temperature variability and trends in the South Pacific, mainly in the twentieth century, using data from 40 island stations and optimally interpolated sea surface and night marine air temperature data is presented. The last-named dataset is new and contains improved corrections for changes in the height of thermometer screens as ships have become larger. It is shown that the South Pacific convergence zone plays a pivotal role in both variability and trends in all three datasets. Island, collocated sea surface temperature, and night marine air temperature time series for four large constituent regions are created and analyzed. These have been corrected for artificial changes in variance due to changes in the availability of constituent island stations whose intrinsic variance varies from station to station. The method is described in detail. Objective estimates of uncertainty in the sea surface temperature data are also provided. The results extend previous work, showing that annual and seasonal surface ocean and island air temperatures have increased throughout the South Pacific. Variations in trends in the island and marine data show reasonable consistency, with distinctly different patterns of multidecadal change in the four regions. However, a notable inconsistency is the recent lack of warming in night marine air temperature in one of the tropical regions relative to sea surface temperature, with signs of this effect in a second tropical region. Another tropical region near the South Pacific convergence zone shows recent strong warming in the island data but not in the marine data.