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Excellent resistance to CMAS is one of the key parameters for environmental barrier coating (EBC) operated in gas turbine engines. The interaction between CMAS and EBC was usually investigated by the characterization of reaction products after corrosion. The lack of direct observation of the high-temperature CMAS corrosion processes hinders the understanding of CMAS-induced degradation of EBC. In this work, the interaction between CMAS and an EBC candidate (Lu 2 SiO 5) was investigated by an in-situ observation method, where the melting of CMAS and the growth of reaction products were first observed. It was found that the reaction product Ca 2 Lu 8 (SiO 4) 6 O 2 tends to precipitate vertically to form a textured structure. In addition, Lu 2 SiO 5 tends to decompose into Lu 2 Si 2 O 7 and Lu 2 O 3 at 1500 °C, which induces an intergranular infiltration of CMAS and leads to the formation of Ca 2 Lu 8 (SiO 4) 6 O 2 fringes. Compared with the corrosion behavior at 1300 °C, Lu 2 SiO 5 exhibits fast interaction with CMAS and poor CMAS resistance at 1500 °C. The results provide important guidelines on the design of rare earth silicate EBC. [Display omitted] • High temperature promotes the main reaction product (Ca 2 Lu 8 (SiO 4) 6 O 2) to grow fast along [0 0 1] direction with preferential (100) facet exposed. • High temperature elevates the chemical reaction rate and induces the decomposition of Lu 2 SiO 5 leading to weak resistance to CMAS of Lu 2 SiO 5 at 1500 °C. [ABSTRACT FROM AUTHOR]

Upconversion nanoparticles are popular as imaging probes due to their advantages in photostability and controllable emission dimensions. However, upconversion polarization remains largely uncharted with previous reports limited to microstructures. In this work, we report the observation of polarized upconversion emissions from β-NaYF 4 single nanostructures below 100 nm. At the sub-100 nm scale, nanorods, nanodiscs, and nanoplates exhibit distinctive polarization degrees despite the same doping concentrations of lanthanides. We find this varied polarization degree results from the crystallographic orientation of nanostructure in relation to the light field and can be linked to the distinctive emission spectrum profile with varied Stark splitting transition ratios from Er 3+ . Our findings provide a comprehensive understanding of the polarization properties of upconversion nanoparticles, revealing a previously unexplored aspect of light emission. This discovery expands our knowledge of upconversion nanoparticles and also opens new possibilities for their use in future imaging and sensing applications, where polarization sensitivity is crucial.

During lung development, epithelial branches expand preferentially in a longitudinal direction. This bias in outgrowth has been linked to a bias in cell shape and in the cell division plane. How this bias arises is unknown. Here, we show that biased epithelial outgrowth occurs independent of the surrounding mesenchyme, of preferential turnover of the extracellular matrix at the bud tips and of FGF signalling. There is also no evidence for actin-rich filopodia at the bud tips. Rather, we find epithelial tubes to be collapsed during early lung and kidney development, and we observe fluid flow in the narrow tubes. By simulating the measured fluid flow inside segmented narrowepithelial tubes, we show that the shear stress levels on the apical surface are sufficient to explain the reported bias in cell shape and outgrowth. We use a cell-based vertex model to confirm that apical shear forces, unlike constricting forces, can give rise to both the observed bias in cell shapes and tube elongation. We conclude that shear stress may be a more general driver of biased tube elongation beyond its established role in angiogenesis. [ABSTRACT FROM AUTHOR]

Root tropisms are important responses of plants, allowing them to adapt their growth direction. Research on plant tropisms is indispensable for future space programs that envisage plant-based life support systems for long-term missions and planet colonization. Root tropisms encompass responses toward or away from different environmental stimuli, with an underexplored level of mechanistic divergence. Research into signaling events that coordinate tropistic responses is complicated by the consistent coincidence of various environmental stimuli, often interacting via shared signaling mechanisms. On Earth the major determinant of root growth direction is the gravitational vector, acting through gravitropism and overruling most other tropistic responses to environmental stimuli. Critical advancements in the understanding of root tropisms have been achieved nullifying the gravitropic dominance with experiments performed in the microgravity environment. In this review, we summarize current knowledge on root tropisms to different environmental stimuli. We highlight that the term tropism must be used with care, because it can be easily confused with a change in root growth direction due to asymmetrical damage to the root, as can occur in apparent chemotropism, electrotropism, and magnetotropism. Clearly, the use of Arabidopsis thaliana as a model for tropism research contributed much to our understanding of the underlying regulatory processes and signaling events. However, pronounced differences in tropisms exist among species, and we argue that these should be further investigated to get a more comprehensive view of the signaling pathways and sensors. Finally, we point out that the Cholodny-Went theory of asymmetric auxin distribution remains to be the central and unifying tropistic mechanism after 100 years. Nevertheless, it becomes increasingly clear that the theory is not applicable to all root tropistic responses, and we propose further research to unravel commonalities and differences in the molecular and physiological processes orchestrating root tropisms.

Bi2AE2Co2Ox (AE = Ca, Sr, and Ba) thermoelectric compounds were grown from the melt by the laser floating zone technique. Microstructural analysis of as-grown samples has shown the formation of well-aligned thermoelectric grains together with a relative high amount of secondary phases. On the other hand, a short (24 h) thermal treatment (810 °C for Sr, 800 °C for Ca, and 750 °C for Ba) under air, raises of thermoelectric phase content through the recombination of the secondary ones. These microstructural modifications led to a large decrease of electrical resistivity, improving the power factor. These results have been compared with samples prepared by the conventional solid state method and with the best values reported in the literature. From these data, it is possible to deduce that the high thermoelectric characteristics obtained in these samples make them very attractive for practical applications.

The rational design of hierarchical nanostructured electrode materials is critical for achieving high electrochemical property for supercapacitor (SC) applications. Herein, we report a facile method for fabricating hierarchical NiCoO@NiCo–OH core-shell nanowire array (NiCoO@NiCo–OH NWA) on flexible carbon fiber clothes by using a cobalt-based metal organic framework (Co-MOF) as an intermediate. The growth mechanism study shows the formation process is completed by a localized dissolution of Co-MOF followed by a directional growth of NiCo–OH nanosheets on NiCo 2 O 4 nanowires. The unique hierarchical nanostructure endows the material a high surface area, rich active sites, fast electron transport, and efficient electrolyte ion diffusion. Consequently, the as-prepared material exhibited an over 3 times' higher specific capacity than the pristine NiCo 2 O 4 nanowire arrays and an excellent rate capability at 40 A g−1 for SCs. Moreover, the NiCoO@NiCo–OH NWA based hybrid supercapacitor (HSC) exhibited a considerably high energy density of 57.2 Wh kg−1, a high power density of 17.6 kW kg−1, and ultralong cycling stability of over 10 000 cycles (retention rate of 91.8%), outperforming most of the current state-of-the-art SCs. The directional growth strategy using MOFs as intermediates reported here provides a simple but effective way to fabricate hierarchical nanostructured electrode materials for advanced energy storage applications. [ABSTRACT FROM AUTHOR]

The rapid growth of KDP-type crystals mainly adopts the point seed rapid growth method. The three-dimensional point seed will inevitably lead to the pyramid-prism boundary, which affects the performance and quality of the crystals. In this paper, the traditional rapid growth of point seed method was improved by the designed platform, and the 70% DKDP crystal was successfully grown by the directional growth of point seed. Avoiding the pyramid-prism boundary of the growing crystals, slices were taken, of which the deuterium content, transmittance, laser damage resistance and optical homogeneity were tested. The results show that the deuterium content of the crystals meets the design requirements, the transmittance and laser damage resistance of the crystals are consistent with those of the crystals grown by the traditional rapid growth of point seed. The results of optical homogeneity show that there is no pyramid-prism boundary in the slices, which will guide the growth of large diameter 70% DKDP crystal. [ABSTRACT FROM AUTHOR]

Fifty years ago, Lewis Wolpert introduced the concept of "positional information" to explain how patterns form in a multicellular embryonic field. Using morphogen gradients, whose continuous distributions of positional values are discretized via thresholds into distinct cellular states, he provided, at the theoretical level, an elegant solution to the "French Flag problem." In the intervening years, many experimental studies have lent support to Wolpert's ideas. However, the embryonic patterning of highly repetitive morphological structures, as often occurring in nature, can reveal limitations in the strict implementation of his initial theory, given the number of distinct threshold values that would have to be specified. Here, we review how positional information is complemented to circumvent these inadequacies, to accommodate tissue growth and pattern periodicity. In particular, we focus on functional anatomical assemblies composed of such structures, like the vertebrate spine or tetrapod digits, where the resulting segmented architecture is intrinsically linked to periodic pattern formation and unidirectional growth. These systems integrate positional information and growth with additional patterning cues that, we suggest, increase robustness and evolvability. We discuss different experimental and theoretical models to study such patterning systems, and how the underlying processes are modulated over evolutionary timescales to enable morphological diversification. Key Findings: Through a combination of positional information, directed growth and additional periodic patterning modules, repetitive morphological structures can be specified during development, in a robust, yet flexible manner. [ABSTRACT FROM AUTHOR]

Root tropisms are important responses of plants, allowing them to adapt their growth direction. Research on plant tropisms is indispensable for future space programs that envisage plant-based life support systems for long-term missions and planet colonization. Root tropisms encompass responses toward or away from different environmental stimuli, with an underexplored level of mechanistic divergence. Research into signaling events that coordinate tropistic responses is complicated by the consistent coincidence of various environmental stimuli, often interacting via shared signaling mechanisms. On Earth the major determinant of root growth direction is the gravitational vector, acting through gravitropism and overruling most other tropistic responses to environmental stimuli. Critical advancements in the understanding of root tropisms have been achieved nullifying the gravitropic dominance with experiments performed in the microgravity environment. In this review, we summarize current knowledge on root tropisms to different environmental stimuli. We highlight that the term tropism must be used with care, because it can be easily confused with a change in root growth direction due to asymmetrical damage to the root, as can occur in apparent chemotropism, electrotropism, and magnetotropism. Clearly, the use of Arabidopsis thaliana as a model for tropism research contributed much to our understanding of the underlying regulatory processes and signaling events. However, pronounced differences in tropisms exist among species, and we argue that these should be further investigated to get a more comprehensive view of the signaling pathways and sensors. Finally, we point out that the Cholodny-Went theory of asymmetric auxin distribution remains to be the central and unifying tropistic mechanism after 100 years. Nevertheless, it becomes increasingly clear that the theory is not applicable to all root tropistic responses, and we propose further research to unravel commonalities and differences in the molecular and physiological processes orchestrating root tropisms. [ABSTRACT FROM AUTHOR]

Morphogenesis in plants depends critically on directional (anisotropic) growth. This occurs principally perpendicular to the net orientation of cellulose microfibrils (CMFs), which is in turn controlled by cortical microtubules (CMTs). In young lateral roots of Arabidopsis thaliana, growth anisotropy also depends on RAB-A5c, a plant-specific small GTPase that specifies a membrane trafficking pathway to the geometric edges of cells. Here we investigate the functional relationship between structural anisotropy at faces and RAB-A5c activity at edges during lateral root development. We show that surprisingly, inhibition of RAB-A5c function is associated with increased CMT/CMF anisotropy. We present genetic, pharmacological, and modelling evidence that this increase in CMT/CMF anisotropy partially compensates for loss of an independent RAB-A5c-mediated mechanism that maintains anisotropic growth in meristematic cells. We show that RAB-A5c associates with CMTs at cell edges, indicating that CMTs act as an integration point for both mechanisms controlling cellular growth anisotropy in lateral roots.

Periodontium is the rally of soft and hard tissues, which will be devastated continuously by the compromise of periodontitis. Current periodontal therapeutic methods cannot effectively reconstruct periodontal ligament (PDL), which is oriented at an angle with tooth root and combined hard tissues to form cementum-PDL-alveolar bone complex. Hence, it is urgent to find new techniques for PDL reconstruction to achieve functional regeneration of periodontium. Herein, we developed a novel method to manipulate the distribution and growth of periodontal ligament stem cells (PDLSCs) by utilizing highly paralleled static magnetic field (SMF) and magnetic nanoparticles (MNPs). PDLSCs were incubated with MNPs in vitro to label with them. Meanwhile, CCK8 and live/dead cell staining assay were used to detect the impact of SMF and MNPs on cell viability. The directional migration and growth of PDLSCs were visualized under microscope. Furthermore, real-time quantitative PCR and western blot were utilized to calculate the expression level of PDL-related genes. The results showed that PDLSCs could rapidly take up MNPs without compromising cell proliferation and viability, consequently endowed with the ability to respond via magnetic force. The cell migration analysis indicated that PDLSCs could move along the magnetic induction line, testifying that SMF exerted forces on PDLSCs that labeled with MNPs. It was demonstrated that collective application of SMF and MNPs not only induced PDLSCs organized and grew directionally, but also initiated elongation of cells and nucleus. Furthermore, the morphological alteration of the nucleus could also effectively enhance the gene and protein expression of Collagen Ⅰα2, Collagen Ⅲ, and Periostin, suggesting the capability of PDLSCs to differentiate into PDL. In conclusion, this study exhibits a new approach for directional reconstruction of PDL to obtain physiological and functional regeneration of periodontium. The Clinical Trial Registration number: WCHSIRB-D-2022-458.

Tropisms are essential responses of plants, orienting growth according to a wide range of stimuli. Recently, considerable attention has been paid to root tropisms, not only to improve cultivation systems, such as those developed for plant-based life support systems for future space programs, but also to increase the efficiency of root apparatus in water and nutrient uptake in crops on Earth. To date, the Cholodny–Went theory of differential auxin distribution remains the principal tropistic mechanism, but recent findings suggest that it is not generally applicable to all root tropisms, and new molecular pathways are under discussion. Therefore, an in-depth understanding of the mechanisms and functions underlying root tropisms is needed. Contributions to this special issue aimed to embrace reviews and research articles that deepen molecular, physiological, and anatomical processes orchestrating root tropisms from perception of the stimulus to bending. The new insights will help in elucidating plant–environment interactions, providing potential applications to improve plant growth on Earth and in space where microgravity diminishes or nullifies the gravitropism dominance.

Abstract: Chiral nematic liquid crystals are stimuli‐responsive soft materials that can self‐organize into complex chiral superstructures. Control and manipulation of the chiral ordering is essential in the development of functional electro‐optic devices. Here, the effect of surface topography is combined with an applied electric field to steer the directional growth of cholesteric fingers in a cell with thickness larger than the chiral pitch. The periodic e‐beam resist grating gives rise to micrometer‐scale periodic variations of the surface anchoring. By applying a voltage to the cell, controlled growth of cholesteric fingers along the surface grating is observed. The 2D liquid crystal director configuration at different voltages is identified by numerical simulations based on finite element Q‐tensor theory. The results demonstrate that samples with modulated surface chemistry lead to enhanced control over the formation of chiral structures. This can stimulate the development of electro‐optic devices (diffraction gratings, lasers, displays, etc.) with improved characteristics. [ABSTRACT FROM AUTHOR]

Eudicot leaves have astoundingly diverse shapes. The central problem addressed in this paper is the developmental origin of this diversity., To investigate this problem, we propose a computational model of leaf development that generalizes the largely conserved molecular program for the reference plants Arabidopsis thaliana, Cardamine hirsuta and Solanum lycopersicum. The model characterizes leaf development as a product of three interwoven processes: the patterning of serrations, lobes and/or leaflets on the leaf margin; the patterning of the vascular system; and the growth of the leaf blade spanning the main veins. The veins play a significant morphogenetic role as a local determinant of growth directions., We show that small variations of this model can produce diverse leaf shapes, from simple to lobed to compound., It is thus plausible that diverse shapes of eudicot leaves result from small variations of a common developmental program. [ABSTRACT FROM AUTHOR]

Here, we demonstrate the synthesis of monolayer molybdenum disulfide (MoS 2 ) ribbons and their branched structures by chemical vapor deposition (CVD) in sulfur-enriched environment. The growth of the MoS 2 ribbons, triangular and other crystals significantly depends on the exposure of sulfur and concentration of molybdenum oxide (MoO 3 ) vapor on the substrate surface. The width and length of the synthesized ribbons is around 5–10 and 50–100 μm, respectively, where the width reduces from the nucleation point toward the end of the ribbon. Unidirectional, bi and tri-directional growth of ribbons from the nucleation point with an angle of 60° and 120° were obtained attributing to crystallographic growth orientation of MoS 2 crystals. The directional growth of dichalcogenides ribbons is a significant challenge, our process shows that such unidirectional and other branched structures can be achieved by controlling the stoichiometric composition of MoO 3 and sulfur exposure on the substrate surface. Interestingly, all the individual and branched ribbons possess uneven abundant edge structures, where the edges are formed with angles of 60° and 120°, indicating variation in molybdenum and sulfur edge terminations. The directional growth of MoS 2 ribbons with defined edge structures in particular CVD condition can open up new possibilities for electronic and electrochemical applications. [ABSTRACT FROM AUTHOR]

Tricalcium silicate (CS) mineral was prepared by sol-gel method, using tetraethyl orthosilicate as silicon source, Ca(NO)·4HO as calcium source, EtOH as cosolvent and saltpeter solution as catalyst. The percentage of f-CaO of CS is less than 0.18 %. CS samples were hydrated with a w/ b ratio 20 at room temperature. SEM results show calcium silicate hydrate (C-S-H) is a tightly coupled laminated structure within hydration 12 h and grew acicular fiber at later ages. The mean C/S ratios of C-S-H remain around 1.55 at 28 days. Calcium hydroxide (CH) occurs the directional growth toward the (001) crystal plane. XRD results show the width of CH diffraction peak got broadened with the increase in hydration ages and the crystallinity of CS has dropped. Bound water in C-S-H at different ages of hydration supports the assumption that the hydration rate of CS at early stage is much faster than that at late ages. [ABSTRACT FROM AUTHOR]

Hypereutectic Al-Co alloys of various Co contents (7-20 weight % (wt.%) Co) were prepared by vacuum arc melting, aiming at investigating the influence of the cobalt content on the microstructure and corrosion behavior. Quite uniform and directional microstructures were attained. The obtained microstructures depended on the Co content, ranging from fully eutectic growth (7 wt.% and 10 wt.% Co) to coarse primary Al9Co2 predominance (20 wt.% Co). Co dissolution in Al far exceeded the negligible equilibrium solubility of Co in Al; however, it was hardly uniform. By increasing the cobalt content, the fraction and coarseness of Al9Co2, the content of Co dissolved in the Al matrix, and the hardness and porosity of the alloy increased. All alloys exhibited similar corrosion behavior in 3.5 wt.% NaCl with high resistance to localized corrosion. Al-7 wt.% Co showed slightly superior corrosion resistance than the other compositions in terms of relatively low corrosion rate, relatively low passivation current density and scarcity of stress corrosion cracking indications. All Al-Co compositions demonstrated substantially higher resistance to localized corrosion than commercially pure Al produced by casting, cold rolling and arc melting. A corrosion mechanism was formulated. Surface films were identified. [ABSTRACT FROM AUTHOR]

Well-textured BiSrCaCuO/2.9 wt % Ag composite samples have been grown by the laser floating zone at very low rates (1, 3, and 5 mm/h). The as-grown samples present superconducting behavior, as a result of being composed by long and well-textured Bi-2212 grains as major phase. After annealing, the samples do not dramatically increase their J. This effect has been associated with the presence of long cracks along the ab planes of the superconducting grains. Even after annealing, the cracks have not been totally removed and, as a consequence, the critical current of the samples after the thermal treatment has only been improved in around 50 %, compared with the as-grown samples. [ABSTRACT FROM AUTHOR]

Hypereutectic Al-Co alloys of various Co contents (7–20 weight % (wt.%) Co) were prepared by vacuum arc melting, aiming at investigating the influence of the cobalt content on the microstructure and corrosion behavior. Quite uniform and directional microstructures were attained. The obtained microstructures depended on the Co content, ranging from fully eutectic growth (7 wt.% and 10 wt.% Co) to coarse primary Al9Co2 predominance (20 wt.% Co). Co dissolution in Al far exceeded the negligible equilibrium solubility of Co in Al; however, it was hardly uniform. By increasing the cobalt content, the fraction and coarseness of Al9Co2, the content of Co dissolved in the Al matrix, and the hardness and porosity of the alloy increased. All alloys exhibited similar corrosion behavior in 3.5 wt.% NaCl with high resistance to localized corrosion. Al-7 wt.% Co showed slightly superior corrosion resistance than the other compositions in terms of relatively low corrosion rate, relatively low passivation current density and scarcity of stress corrosion cracking indications. All Al-Co compositions demonstrated substantially higher resistance to localized corrosion than commercially pure Al produced by casting, cold rolling and arc melting. A corrosion mechanism was formulated. Surface films were identified.

The thermoelectric conversion efficiency of the thermoelectric material Bi2Te3 is significantly affected by its microstructure because of its anisotropy. In this study, the zone-melting technique is used to grow Bi2Te3 columnar crystals. The zone-melting process directionally solidifies and purifies an ingot by a moving a heater along the ingot. For predicting the temperature variation and distribution in the crystallization process and the microstructures of Bi2Te3, a zone-melting model is developed and numerical simulation techniques are used. The simulation results are compared with experimental measurements to verify the numerical model. The verified numerical model is used to investigate the optimal process parameters. The process parameters, namely the temperature of the heater and the movement speed of the heater and the cooling devices, are adjusted in order to obtain good-quality columnar crystals. The shapes of the solidification interface, which greatly affect the direction of grain growth and the grain size, are compared. [ABSTRACT FROM AUTHOR]

Abstract: Lanthanum modified lead zirconate titanate (PLZT) thick film with molecular formula of Pb0.92La0.08(Zr0.52Ti0.48)0.98O3 was grown preferentially along (111) direction on Pt/SiO2/Si (platinum/silicon oxide/silicon) substrate by spin coating of chemical solution. The directional growth of the film was facilitated by platinum (Pt) (111) template and rapid thermal annealing. X-ray diffraction pattern and atomic force microscopy revealed the preferential growth of the PLZT film. The film was characterized for ferroelectric and detailed piezoelectric properties in a parallel plate capacitor (metal–PLZT–metal) configuration. Ferroelectric characterization of the film showed saturated hysteresis loop with remanent polarization and coercive electric field values of 10.14μC/cm2 and 42kV/cm, respectively, at an applied field of 300kV/cm. Longitudinal piezoelectric coefficient (d33,f) was measured by employing converse piezoelectric effect where electrical charge response and displacement were measured with electrical voltage excitation on the sample electrodes. The effective transverse piezoelectric coefficient (e31,f) was derived from charge measurement with an applied mechanical excitation strain by using the four point bending method. d33,f and e31,f coefficients of PLZT films were found to be 380pm/V and −0.831C/m2 respectively. [Copyright &y& Elsevier]

Abstract: New type Ti-base composite coatings with in-situ synthesized directional growth whiskers were successfully fabricated from a precursor mixture of titanium alloy and B4C powder by laser cladding. The typical microstructures, formation mechanism and properties of the reinforced composite coatings were experimentally studied for the purpose of developing novel hard facing coatings of titanium alloy. The results show that, there are two typical microstructures obtained in the composite coatings, i.e. the equiaxial composite structures and the columnar composite structures. The novel and interesting TiB whiskers, namely the directional growth TiB whiskers, are founded in the columnar composite structure zones. These TiB whiskers show uniform growth directions and display the characteristics of large slenderness ratio. The lengths of the whiskers are in the range of 10–30μm, but the diameters are of extremely fine size in the nanometer range. The microhardness of the coating is in the range of 430–520 HV and is about 150 HV higher than that of the substrate, which implies that these composite coatings are effectively reinforced by in situ synthesized TiB phases. The analysis shows that, solidification velocity R, temperature gradient G and direction of heat flow were the key factors to determine what kind of whiskers can be obtained. [Copyright &y& Elsevier]

Bi-2212 samples prepared by the classical solid-state method have been grown from the melt using the Laser Floating Zone (LFZ) method. They have shown good grain alignment and transport critical current densities ( J). After postannealing processes designed to produce the Bi-2212 phase controlled decomposition, J values have been increased in an important manner. Maximum values have been achieved when samples were thermally treated at 680 °C for 168 h with improvements around 80 %, compared with the original textured samples. The results clearly indicate that postannealing processes, when adequately controlled, produce the formation of effective pinning centers which are responsible for the increase in the measured J values. [ABSTRACT FROM AUTHOR]

It is well know that HO and CO (both present in the atmosphere) can react chemically with BSCCO superconductors, especially with the alkaline-earth cations, producing chemical degradation and reducing their performances. In this work, Bi-2212 highly textured rods were grown from the melt through a laser floating zone melting technique. In order to determine the influence of HO and CO on these bulk textured samples, they were immersed in distilled water and in CO saturated water. The evolution of the electrical and mechanical properties of these rods was determined as a function of the immersion time in both media and compared with their initial properties. It has been found that performance degradation was higher in distilled water than in CO saturated one. Nevertheless, in any case, the degradation has been found to be not very important. [ABSTRACT FROM AUTHOR]

The contribution of vegetative recruitment by non-tree species to the regeneration of tropical forests in man-made clearings or tree-fall gaps tends to be ignored. In a series of field studies near Amacayacu, Colombian Amazonia, we tested if hemiepiphytic aroids quickly colonize such open habitats through seed dispersal, sprouting plant fragments, or lateral invasion of flagellar aroids from the closed forest nearby. A seed germination experiment applying two soil substrates and three shade levels showed that abundant light reduced the germination success of three Philodendron species. A total of 400 cuttings from five Philodendron species were placed in forest clearings and almost 12% of these sprouted within 14 wk. Monitoring more than 2000 aroid plants over 14 mo in different habitats showed that recruitment was low (0.3 plants per 10 m2) compared with initial densities (3.1 plants per 10 m2). Flagellar aroids grew about 2.5 times faster than non-flagellar aroids. In forest edges they reached a mean apical growth of 98 cm in 14 mo. However, non-flagellar aroids were five to six times more abundant than flagellar individuals everywhere. It was concluded that hemiepiphytic aroids colonize open habitats mostly through a post-disturbance survival of plants or plant fragments. [ABSTRACT FROM PUBLISHER]

Several synthetic methods, solid-state, sol-gel and polymer solution methods, have been used to prepare prereacted precursors, as well as a vitreous material obtained by melt quenching. The influence of the starting powder characteristics on the phase formation, microstructure, T and J of Bi-2212 textured rods prepared by directional crystallization from the melt has been analyzed. In all the cases, high transport critical current values (higher than 3000 A/cm at 77 K) have been obtained, independently of the precursor type. Samples obtained by the polymer route show improved T values, associated to a lower oxygen content. [ABSTRACT FROM AUTHOR]

Liquid-solid interface morphological evolution of SCN-2wt%H2O alloy was investigated in the presence of shear flow. It has been found that shear flow strikingly enhances the stability of planar interface at lower pulling rates. In the intermediate range of pulling rate, the interface experiences periodical oscillating "planar-cellular" and "cellular-dendritic" growth patterns. The formation of oscillating growth modes can be explained by two reasons: (i) The stabilizing effect induced by shear flow competes with the growing destabilizing effect by the increase of pulling rate, which provides the driving force for morphological evolution; and (ii) the establishment of stable solute field at the liquid-solid interface needs a period of time, leading to the result that the interface evolution can not stay stable at the equilibrium state. However, as the puling rate becomes higher, it plays more and more important roles in pattern selection and dendritic growth forms. [ABSTRACT FROM AUTHOR]

This article is focused on gravity and light effects on growth and bending of laminas as well as unfolding and morphology of petioles of garden cress (Lepidium sativum L.) leaves. Experiments were performed in conditions of normal and altered by fast clinorotation (50-rpm) gravity, in red (660 nm) and far-red (735 nm) light or in the dark. Clinorotation retarded unfolding of leaves in the dark, whereas the applied light suppressed disorientation of leaves on the clinostat. We identified sedimenting amyloplasts in endodermic cells which were located in the proximal region of L. sativum petioles. The obtained data imply that red and far-red light, even in altered gravity, is an essential factor for the directional growth of leaves. [ABSTRACT FROM AUTHOR]

BaGa 4 Se 7 is a new promising infrared nonlinear optical crystal. Recently, efforts are focused on the growth of high-quality single crystals. Single crystal with size of ϕ25 (diameter) × 35(length) mm3 was grown using vertical gradient freeze technique (VGF) for the first time. The yield of crack free crystals was greatly improved by selecting seed orientation for directional growth. Especially, the absorption coefficient of the BaGa 4 Se 7 crystal is as low as 0.02 cm−1 at 2.05 µm, which means that the as-grown crystal can be used to fabricate optical elements directly and does not need post-thermal annealing like other growth methods. The as-grown crystals were also characterized by X-ray diffraction (XRD), transmission spectra, and optical homogeneity etc. The BGSe-OPO elements were fabricated for infrared nonlinear optical experiments. [ABSTRACT FROM AUTHOR]

• There is pyramid-prism boundary in DKDP grown by "point-seed" rapid growth method. • A new crystal carrier with no shielding was used to grow DKDP crystal. • Z-plate crystal was used as the seed. • DKDP with 90% deuterium concentration was grown by directional rapid growth method. • The crystal of the sample taken has no pyramid-prism boundary. Due to the obvious pyramid-prism boundary in the deuterated potassium dihydrogen phosphate (DKDP) crystal grown by "point-seed" rapid growth method, the crystal uniformity and utilization rate were poor. In this paper, a DKDP crystal with deuterium concentration of about 90% has been grown using a new crystal carrier, and its deuterium concentration, extinction ratio and transmission spectrum have been measured. At the same time, the optical uniformity of this crystal was compared with that grown by the "point-seed" crystal rapid growth method, and the influence of these two methods on the pyramid-prism boundary of the crystal was studied. The result showed that the average deuterium concentration of the directionally grown DKDP crystal was 90.27%, which met the requirements of the experimental plan. Meanwhile, it was shown that the extinction ratio was up to 4623:1, and both the pyramidal sector and the prismatic sector of the crystal had good transmission performance. The optical uniformity test chart indicated that there was obvious pyramid-prism boundary in the crystal samples obtained by "point-seed" rapid growth method, while there was no pyramid-prism boundary in those by directional rapid growth method. [ABSTRACT FROM AUTHOR]

Intermetallic matrix composites (IMCs) are considered candidate materials for high-temperature applications provided that the proper combination of properties can be developed. Among a large number of intermetallics, a particular interest has been shown in the NiAl-based composites. Attractive properties of this compound include higher melting temperature, better oxidation resistance, and lower density when compared to conventional superalloys. However, insufficient low-temperature fracture resistance is a major drawback. Stringent requirements for chemical and mechanical compatibility between the matrix and the reinforcing phase have recently renewed interest in directional solidification of the eutectic alloys. Microcomposite structures generated by directional solidification of eutectics offer many unique microstructural advantages, including thermodynamic stability up to the melting temperature, directional alignment and fine dispersion of component phases. Although a large number of directionally solidified eutectic systems have been investigated so far, little information on the eutectics in NiAl–V system has been reported. The present paper is concerned with the growth morphology of the NiAl–V in situ composites. Samples prepared by arc melting were processed in a directional solidification furnace with induction heating. The main objective was to analyze the solidification microstructure and morphology regarding the growth conditions and composition. Sample characterization, beside the optical and scanning electron microscopy (SEM), included the use of differential thermal analysis (DTA), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) technique. [Copyright &y& Elsevier]

This paper reports the investigation results on directional growth of Al−Mg2Si eutectic alloy in the SZ2 unmanned spaceship. The analysis shows that microgravity has influence on the directional growth of Al−Mg2Si eutectic alloy. The eutectic colony in space-grown sample is larger than that in ground-grown sample, and the directional effect is not so good as that of terrestrial sample. But there is no obvious difference in the lamellar thickness between these samples, and lamellar interspacing in space sample is smaller than that grown on the ground. A simple discussion is done on the gravity effect on the directional growth of Al−Mg2Si eutectic alloy. [ABSTRACT FROM AUTHOR]

Liquid–liquid phase transition is occurring in many chemical engineering processes either as a desired phenomenon or as an undesired side effect. Typically, the phase split is modeled by neglecting all non-equilibrium effects. Here, a simple non-equilibrium situation is considered. Convective flow of a liquid along a decreasing temperature profile in a cooled channel is studied analytically. Three different scenarios for the transition process with two typical phase diagrams for binary mixtures are examined. For a phase diagram with critical concentration, phase segregation occurs via spinodal decomposition as a convective instability. For a cigar-shaped phase diagram the phase transformation is shown to evolve in analogy to directional solidification. Finger-like structures may be established under certain circumstances. [Copyright &y& Elsevier]

Mouse ascites tumor cells (MAT-cells) were co-cultured with mesothelial cells of the mouse. During early stages of coexistence (30-60 min) the mesothelial cells show finger-like protrusions formed mostly at their flanks pointing towards MAT-cells in the neighbourhood. Obviously there is a directional response of the mesothelial cells to the existence of MAT-cells. The mesothelial cells are the more active partner at the beginning of coexistence. Later on MAT-cells also develop fingerlike protrusions which grow towards the mesothelial cells. A network of fingerlike protrusions is formed in the region between MAT-cells and mesothelial cells when they come near to each other. The advantages of the system serving as a model for investigations on intercellular communication are discussed. [ABSTRACT FROM AUTHOR]

Whole skin organ cultures of vitiliginous, skin show that the marginal melanocytes are highly sensitive to a pulse of UV exposure (210-380 nm) during the G phase of the cell cycle, as seen by prominent dendricity. Melanocytes are highly dendritic in the epidermis overlying rapidly growing tumors, as well as within proliferative lesions such as basal cell carcinomas and aggressive seborrheic keratosis. In the organ cultures the dendrites extend towards the source of UV, i.e. the surface, while the main body lies along the basement membrane. The epidermal melanocytes overlying tumors lie, almost vertically, dendrites aligned towards the underlying tumor on one side and the surface on the other. Within tumors dendritic elongation is guided by mitotic and PCNA positive (S-phase) tumor cells, which are a source of ultraweak UV emissions in the range of 210-330 nm. These observations indicate that ultraweak biophoton emissions from neighbouring cells can simulate environmental cues and contribute to the plasticity of networks such as the melanocytes or the visual pathways. [ABSTRACT FROM AUTHOR]

• Directional growth behavior of Sn whiskers is associated with the interfacial γ-Ag 2 Al IMCs. • A transitional area forms between the whisker and underneath grain. • A mathematical model is proposed to calculate the distribution of Ag atoms. • Diffusion mode for whisker growth is pipe diffusion. In this paper, the directional growth behavior of Sn whiskers was found to be associated with the interfacial γ-Ag 2 Al IMCs at Sn-3.5Ag/Al interface. A 100 μm thick columnar structured Sn-3.5Ag coating consisted of β-Sn phases and γ-Ag 2 Al phases was fabricated on Al substrate. The as-formed interfacial IMCs between Sn-3.5Ag and Al were confirmed as γ-Ag 2 Al and μ-Ag 3 Al. After aging treatment, the growth direction of Sn whiskers was found to be consistent. μ-Ag 3 Al phases transformed into γ-Ag 2 Al. The newly formed hexagonal γ-Ag 2 Al grew out of the IMCs layer and provided the out-of-plane stress for whisker growth. Ag atoms diffused into Sn sub-grain boundaries and formed γ-Ag 2 Al IMCs leading to the formation of in-plane stress. The c -axis of the β-Sn and γ-Ag 2 Al is parallel, leading to the similar growth direction of the whiskers. The misorientation between the whisker and the underneath grain was lower than 2°. A transitional area formed between the whisker and underneath grain, which consists of extra half-planes of atoms. A mathematical model was proposed to calculate the heterogeneous distribution of Ag atoms. By comparing the calculated growth rate with the measured growth rate of whisker, the Sn atomic transport mode was pipe diffusion. [ABSTRACT FROM AUTHOR]

Tropisms are essential responses of plants, orienting growth according to a wide range of stimuli. Recently, considerable attention has been paid to root tropisms, not only to improve cultivation systems, such as those developed for plant-based life support systems for future space programs, but also to increase the efficiency of root apparatus in water and nutrient uptake in crops on Earth. To date, the Cholodny–Went theory of differential auxin distribution remains the principal tropistic mechanism, but recent findings suggest that it is not generally applicable to all root tropisms, and new molecular pathways are under discussion. Therefore, an in-depth understanding of the mechanisms and functions underlying root tropisms is needed. Contributions to this special issue aimed to embrace reviews and research articles that deepen molecular, physiological, and anatomical processes orchestrating root tropisms from perception of the stimulus to bending. The new insights will help in elucidating plant–environment interactions, providing potential applications to improve plant growth on Earth and in space where microgravity diminishes or nullifies the gravitropism dominance. [ABSTRACT FROM AUTHOR]

Branching morphogenesis generates epithelial trees which facilitate gas exchange, filtering, as well as secretion processes with their large surface to volume ratio. In this review, we focus on the developmental mechanisms that control the early stages of lung branching morphogenesis. Lung branching morphogenesis involves the stereotypic, recurrent definition of new branch points, subsequent epithelial budding, and lung tube elongation. We discuss current models and experimental evidence for each of these steps. Finally, we discuss the role of the mesenchyme in determining the organ-specific shape., (Copyright © 2021 Elsevier Inc. All rights reserved.)