Subsequent Growth Behavior Research Articles

Achieving fully equiaxed grains with minor Sc addition of a novel Al-Li alloy fabricated by laser direct energy deposition

In this study, a novel Al-Li alloy with minor Sc addition was fabricated by laser directed energy deposition (LDED), resulting in a fully equiaxed grain structure. The precipitation behavior of primary Al3Sc particles was studied based on transient nucleation theory, and the results showed that sufficient heterogeneous nuclei by primary Al3Sc particles could preferentially form at initial solidification stage and induce into equiaxed grains. Besides, a large number of acicular T1 (Al2CuLi) phases and spherical Al3Sc phases, as well as rod-shaped TB (Al7Cu4Li) phases and quasicrystalline T2 (Al6CuLi3) phases, were distributed in as-built alloy that served as primary strengthening phases by thermal cycling. However, the specific nucleation behavior of α-Al grains on primary Al3Sc particles and subsequent growth behavior during rapid solidification need to be further investigated.

Recent Advances in Carbon‐Based Current Collectors/Hosts for Alkali Metal Anodes

The urgent demand for high‐energy‐density storage systems evokes the research upsurge on the alkali metal batteries with high theoretical capacities. However, the utilization of alkali metal anodes, including Li, Na, and K, is significantly hindered by notorious dendrite growth, undesirable corrosion, and unstable solid electrolyte interface. In order to resolve these issues, the carbon materials for the rational design of current collector/host that can regulate the plating/stripping behavior of alkali metal have been exploited. These carbon‐based current collectors/hosts are featured with many pivotal advantages, including mechanical integrity to accommodate the volume change, superior electronic/ionic conductivity, large available surface area, and rich functionalization chemistries to increase the affinity to alkali metal. In this review, the recent progress on various dimensional carbon‐based current collectors/hosts with different chemical components in stabilizing the alkali metal anodes through the regulation of initial deposition and subsequent growth behavior during plating/stripping process is provided. The nanostructured carbon scaffolds with self‐affinity to alkali metals, as well as the carbon frameworks with internal/external affinitive sites to alkali metals, catalogued by various dimensions, are discussed in this review. Therefore, these appealing strategies based on the carbon‐based current collectors/hosts can provide a paradigm for the realization of high‐energy‐density alkali metal batteries.

Penicillium rubens germination on desiccated and nutrient-depleted conditions depends on the water activity during sporogenesis

Fungal growth often appears in a surrounding where water and nutrients are scarce. The impact of this environment during sporogenesis on subsequent growth is often neglected.This study investigates the effect of water availability during sporogenesis on subsequent early growth. Therefore, a carbon-depleted substrate was constructed. Humidity is then the only parameter of interest. The water conditions during sporogenesis, and during subsequent growth, were varied. This is a stressing environment: no carbon source is present, and water provided solely via the vapour.The lag time, tl, and initial growth rate, μfp, of the germ tubes were monitored.The effect of aw history on germination and initial growth depends on the RH of the environment. Only at low RH do spores produced at low aw have a smaller tl and higher μfp compared to those grown at high aw. This result was remarkably pronounced when the substrate was also made hydrophobic: growth only occurred when spores were developed at low aw and placed in high RH.Spores grown on lowered aw attract more water. It is hypothesized that this attraction affects subsequent growth behaviour, and is the reason why growth on hydrophobic glass only prevails in the condition of high RH and lowered aw history.We demonstrate the influence of cultivation conditions on germination, which becomes more pronounced in a more desiccated environment.

Effect of chlorine stress on the subsequent growth behavior of individual Salmonella cells.

The present work investigates the effect of chlorine stress on the subsequent growth behavior of individual Salmonella cells. A time-lapse microscopy method was used which allowed to evaluate the effect of chlorine on the division times of Salmonella individual cells and the percentage of cells able to divide after the treatment. The results showed that the percentage of cells able to divide after the chlorine treatment decreased from 92.7% for untreated cells to 43.12% and 22% for cell exposed to 127 and 150 mg/l chlorine for 3 min, respectively. The first division time of Salmonella cells was not affected by the chlorine stress at the lower tested concentration of 11 mg/l. Exposure at higher chlorine concentrations however, resulted in significantly longer and more variable division times. The mean first division times were 1.46 ± 0.61, 1.41 ± 0.53, 1.69 ± 0.59, 5.34 ± 4.03 and 19.2 ± 8.71 h after 3 min treatments with 0, 11, 61, 127 and 150 mg/l chlorine, respectively. The effect of chlorine on the second division time of the cells was milder compared to the first division. Exposure of cells to chlorine concentrations up to 61 mg/l did not affect the second division. These results indicate that the daughter cells have no "memory" of the chlorine treatment at these concentrations. For cells exposed to the highest tested chlorine concentration of 150 mg/l the mean second division time was almost 3.5 times longer compared to untreated cells indicating that potential damages of the cells caused by the chlorine treatment are not fully repaired in the second generation. The quantitative data provided by this study at the level of individual cell may lead to a better understanding of microbial resistance to chlorine and improve sanitation and decontamination procedures in the food industry.

Oxidative Etching of Pd Decahedral Nanocrystals with a Penta-twinned Structure and Its Impact on Their Growth Behavior

We report a systematic study of the oxidative etching of penta-twinned Pd decahedral nanocrystals by O2/I– under different conditions and its impact on their subsequent growth behavior. Analysis by transmission electron microscopy shows significant rounding of the decahedral structure. More specifically, the etching is found to begin at the equatorial vertices, due to their high surface free energy, and proceed along the adjacent, equatorial edges through the dissolution of low-coordination atoms. Comparison of the etching behaviors under different conditions reveals the critical role of a reductive environment for the initiation of oxidative etching, possibly due to the presence of a protective oxide layer on the surface of Pd decahedra. Overgrowth on the seeds with a rounded profile generates penta-twinned Pd nanorods with an asymmetric, tapered structure as a result of simultaneous axial and radial growth. In comparison, the original decahedral seeds only show axial growth, leading to the formation of ...

Role of Poly(butylene fumarate) on Crystallization Behavior of Poly(butylene succinate)

The details of poly(butylene fumarate) (PBF) as highly effective nucleating agent for poly(butylene succinate) (PBS) were systematically studied via X-ray diffraction, differential scanning calorimeter, polarized optical microscopy, and atom force microscopy. All results show that PBF can significantly improve the melt-crystallization temperature and the degree of crystallinity of PBS during the nonisothermal crystallization process. Both crystallization time span and spherulitic size of PBS decrease drastically with the addition of a small amount of PBF, which shows that PBF not only enhances the primary nucleation of PBS by epitaxial mechanism, but also greatly accelerates the secondary nucleation during spherulite growth. The secondary nucleation parameters of PBS, Kg and G0, are notably improved just with a small amount of PBF. Furthermore, the appearance of wrinkles on PBF-nucleated PBS ultrathin film visually suggests that PBF indeed affects the subsequent growth behavior, besides the primary nuclea...

Two-dimensional growth of lattice matched Nd-doped (Gd,Lu)2O3 films on Y2O3 by pulsed laser deposition

This letter focuses on epitaxial growth of a 1-μm-thick lattice matched Nd-doped monocrystalline (Gd,Lu)2O3 film deposited on a {100} oriented Y2O3 substrate by pulsed laser deposition. Layer-by-layer growth indicated by in situ reflection high energy electron diffraction was observed up to film thicknesses of 100nm. The subsequent growth behavior could be explained by a multilevel growth mode. Thus, the growth mode was two-dimensional and epitaxial. Lattice matching of up to 99.3% was achieved. The evolution of the structural and topographical properties of the films was verified by ex situ x-ray diffraction analysis and atomic force microscopy, respectively.

Water and mixed OH/water adsorption at close packed metal surfaces

Recent experimental and theoretical results have challenged existing models for the wetting layer and the structure of multilayer water films at metal surfaces. The structures formed depend sensitively on the strength of the metal–water interaction, which determines both whether the film wets the surface, the ice registry to the metal and whether water partially dissociates to form mixed OH + H 2O structures. The template formed by the wetting layer also determines the subsequent growth behaviour of the ice multilayer, potentially changing the surface from hydrophilic to hydrophobic depending on the structure adopted.

Deteriogenic micro-organisms in houses as a hazard to respiratory health

Fungal growth often appears in a surrounding where water and nutrients are scarce. The impact of this environment during sporogenesis on subsequent growth is often neglected.This study investigates the effect of water availability during sporogenesis on subsequent early growth. Therefore, a carbon-depleted substrate was constructed. Humidity is then the only parameter of interest. The water conditions during sporogenesis, and during subsequent growth, were varied. This is a stressing environment: no carbon source is present, and water provided solely via the vapour.The lag time, tl, and initial growth rate, μfp, of the germ tubes were monitored.The effect of aw history on germination and initial growth depends on the RH of the environment. Only at low RH do spores produced at low aw have a smaller tl and higher μfp compared to those grown at high aw. This result was remarkably pronounced when the substrate was also made hydrophobic: growth only occurred when spores were developed at low aw and placed in high RH.Spores grown on lowered aw attract more water. It is hypothesized that this attraction affects subsequent growth behaviour, and is the reason why growth on hydrophobic glass only prevails in the condition of high RH and lowered aw history.We demonstrate the influence of cultivation conditions on germination, which becomes more pronounced in a more desiccated environment.

A New Tool for Studying the in Situ Growth Processes for Self-Assembled Monolayers under Ambient Conditions

A new tool for studying self-assembled monolayer (SAM) nucleation and growth processes on faceted inorganic substrates under ambient conditions is reported herein. The methodology involves coating an atomic force microscope tip with molecules of interest and raster scanning across a substrate of interest with the modified tip. Large scale images of the deposition process provide kinetic information about the nucleation and growth of SAMs. The water meniscus, which is the transport medium in these experiments, is proposed to strongly influence the growth process for 1-octadecanethiol and 16-mercaptohexadecanoic acid. The former involves an island formation and subsequent growth behavior while the latter shows evidence of more random growth. Lattice-resolved images of both SAM structures have been obtained at the end of film growth, and in the case of the 1-octadecanethiol SAM, lattice-resolved images were obtained for the SAM islands. The virtues of this novel technique are its simplicity, adsorbate genera...

Transmission electron microscopy study of zirconia–alumina nanolaminates grown by reactive sputter deposition. Part I: zirconia nanocrystallite growth morphology

Pure zirconia films and zirconia–alumina nanolaminate films grown by reactive sputter deposition are studied by high resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS). The phase composition and morphology associated with zirconia crystallite growth are investigated by examining films containing zirconia layers of varying thickness. These studies, performed at room temperature, suggest that the zirconia crystallites initially grow in the tetragonal phase to a critical size of 6.0±0.2 nm, in agreement with a value of 6.2 nm predicted by end-point thermodynamics. Past the critical size, incorporation of additional zirconia molecules into the zirconia layers is accomplished predominantly by transformation of the growing crystallites to the monoclinic phase, and less frequently by deposition of amorphous zirconia. Transformation to the monoclinic phase is accompanied by a highly faulted intermediary phase. The subsequent growth behavior of monoclinic crystallites is consistent with a three-dimensional interface-controlled, diffusion-limited growth process with a growth exponent between 3 and 4. Nanoindentation measurements of nanolaminates with 5-nm thick zirconia layers give a hardness of ~8 GPa for the upper strata where the morphology of the tetragonal zirconia layers contains an intrinsic roughness. The hardness increases to ~10 GPa closer to the substrate where the laminar morphology is more pronounced. Young's modulus is between 156 and 195 GPa for these same nanolaminates.

Adsorbed serum protein mediated adhesion and growth behavior of bovine aortic endothelial cells on polyamine graft copolymer surfaces

Polyamine-brushed substrata for cell culture were designed by solvent casting of polystyrene-graft-polyamine copolymer (SA) on hydrophobically modified glass surface, and adhesion, spreading, and proliferation of bovine aortic endothelial cells (BAEC) on these substrata were evaluated. Adhesion and spreading of BAEC increased with increasing polyamine content in the copolymer. Close correlation was found between cellular spreading and subsequent cell growth; the surface inducing better spreading of adhered cells showed higher endothelial cell growth. Adhesion and spreading of BAEC were significantly influenced by fetal calf serum (FCS)-pretreatment of the SA copolymer surfaces, being increased with increasing polyamine content, whereas on bovine serum albumin (BSA)-preadsorbed surfaces, BAEC adhesion was considerably prevented and eventually no cell spreading was observed. Then, adsorption of cell-adhesion proteins, fibronectin (FN), and vitronectin (VN), out of FCS onto SA copolymer surfaces were evaluated using enzyme immunoassay. Both FN and VN adsorption on SA copolymer surfaces were increased with increasing polyamine content in the copolymer, suggesting a crucial role of these cell-adhesion proteins in BAEC adhesion and subsequent growth behavior on SA copolymer surfaces.

The roles of oriented nucleation and oriented growth on recrystallization textures in commercial purity aluminium

The development of the recrystallization texture in commercial purity Al (AA1145) containing large Al 3Fe precipitates was investigated to determine the dependence on the degree of deformation and recrystallization temperature by means of X-ray macrotexture analysis. The amount of Fe in solid solution was varied by applying different heat treatments. The recrystallization textures develop from the competition between the Cube-orientation, the R-orientation (similar to the rolling texture S-orientation) and randomly oriented grains due to particle stimulated nucleation (PSN). The formation of these orientations is discussed in terms of their nucleation and subsequent growth behaviour. Particular attention is focused on the influence of the process parameters, i.e. strain, temperature and heating rate, on the ratio between the individual orientations in the recrystallization textures.

Imaging of self-generated multifilamentary current patterns in GaAs

Two-dimensional imaging of current filament patterns generated in homogeneousn-type GaAs during avalanche breakdown at low temperatures is reported. The self-generated formation and subsequent growth behavior of distinct single- and multifilament configurations could globally be visualized by means of a scanning electron microscope equipped with a liquid-helium stage. From local conductivity measurements in the smallest possible filaments (typical diameter of about 10 μm) carrier mobilities as high as about 4·106 cm2/Vs at 4.2 K were estimated. Such high-mobility filament channels may become interesting for applications in ultrafast electronic circuits.

Drought hardening of the potato plant as an after-effect of soil drought conditions at planting

A field trial with the potato varietyWhite Rose was carried out in order to investigate the influence of soil drought conditions at planting time on the subsequent growth behaviour and on the tuber yield, Drought at planting time delays tuber set, shortens the tuber formation period, increases tuber number, promotes their active bulking and produces a significant increase in yield. When soil drought conditions are permitted to develop at the beginning of the tuberization stage, the tuber formation period is lengthened to the detriment of their number, growth and yield. These detrimental effects almost disappear if planting is carried out under high soil moisture stress. Thus, drought hardening at the critical stage of water requirement would arise as an after-effect of drought at planting time.

Early Growth in Rice varieties in relation to their Duration and response to growth-substances

A good deal of attention has been devoted in recent years to the inter-relations that exist in a number of crop plants between differences in the early growth and the subsequent growth behaviour of these plants. (Thimann and Lone, 1938; Sinnott, 1939; Van Overbeek, 1935; Kaiser and Albaum 1938). The last two workers were able to find a close relation in the case of oats, between the early growth and the-subsequent flowering behaviour. An early-flowering variety (Fulghum) was found to have in the early stages of growth a slower rate of root growth than a late-flowering type Black Norway. The two varieties differed also in their response to different concentrations of the growth-promoting substance B-indole acetic acid. The late-flowering type Black Norway showed a more rapid shoot growth when treated with concentrations of 002 mg./litre to 2-0 mg./ litre, while the early-flowering type Fulghum remained unaffected. A similar relation was observed in two other varieties of oats as well and the authors.concluded that if such a relation was found to be general, it could be made to serve as a valuable index of flowering time.

EFFECTS OF PERIODS OF WARM WEATHER UPON THE WINTER HARDENED CONDITION OF A PLANT

The influence of alternating periods of high and low temperatures upon the hardening process of plants has been described at various times in the literature (1, 2, 7). The rate at which plants lose this hardened condition when exposed to warm temperatures has been investigated (3, 10, 11). There appears to be relatively little in the literature, however, concerning the ability of a plant to become hardy a second time, following the dehardening process. Most of the work that relates to this subject is intimately connected with the process of vernalization. The implication from the general theory of vernalization, as stated by Lysenko, is that, since every plant passes through a sequence of phases, which replace one another consecutively and in strict rotation,'' a winter-annual plant, such as winterwheat, would pass into the hardened condition once, and that, having passed out, it could scarcely reenter that condition. Since this investigation was begun, a number of papers have appeared that deal with this topic indirectly. Among these are Kostjucenko and Zarubailo (8, 9), who have reviewed literature dealing with the subject of the dependence of winterhardiness on the conditions of seed ripening. If the seeds of rye or wheat were vernalized upon the mother plant during a cold season of ripening, plants grown from them were found lacking in hardiness. Thus, wheat grown in north Russia was found to produce seed that was not suited for planting in that region, since it had been vernalized upon the mother plant, whereas seed produced on plants from the same lot of seed, but grown further south, produced winter hardy plants. Gregory and Purvis (5, 16) have presented further evidence along the same line. Rudorf (12) subjected winter cereals that had been vernalized to \rarying degrees, to a temperature of 10? C, with various day lengths for various periods of time, and determined the rate of loss of winterhardiness and the degree to which these plants could be rehardened. He concluded that loss of the ability to retain hardiness or to reharden was directly correlated with the degree of vernalization and with the development of the growing point. Voss (14, 15) has presented extensive evidence along the same lines, showing that the degree of vernalization, measured both by microscopic examination of the development of the growing point, and by subsequent growth behavior, is intimately related to the response of the plant to temperatures that ordinarily produce the hardened condition. The length of