Primary Dendrites Research Articles

Complete solute trapping of rapidly growing nickel dendrites within liquid Ni72Mo28 hypoeutectic alloy

The rapid dendrite growth in highly undercooled liquid Ni72Mo28 hypoeutectic alloy was accomplished by containerless processing via electromagnetic levitation and drop tube techniques. The (Ni) dendrites achieved a high growth velocity of 26 m/s at the maximum undercooling of 226 K (0.14 TL) under levitated state. Remarkable dendritic structure refinement and Mo solubility extension were observed with the increase in undercooling. For freely falling alloy droplets, the largest undercooling was enhanced to 246 K (0.15 TL), which resulted in thorough solute trapping and almost segregationless solidification. A microstructure transition from columnar dendrite to equiaxed dendrite took place once alloy undercooling exceeded a threshold about 74–79 K. In addition, the Vickers hardness of primary (Ni) dendrite was significantly improved, which was caused by the extension of Mo solubility and microstructure refinement.

Transient Analysis of Fluid Flow, Solidification, and Inclusion Behavior in Electromagnetically Stirred Bloom Caster Mold Using Bifurcated Submerged Entry Nozzle

Herein, the effect of bifurcated submerged entry nozzle (SEN) port angles on transient flow, solidification, and inclusion behavior in a bloom caster mold with electromagnetic stirring (EMS) is investigated. A 3D numerical model is developed to simulate the process, including time‐varying electromagnetic field and Lagrangian inclusion tracking approach, by varying inclusion density and size. The inclusion is modeled to be entrapped in the solidified shell when primary dendrite arm spacing (PDAS) is greater than inclusion size. As compared to the case without use of EMS, the percentage of shell thickness at the strand outlet is seen to increase by 22.18%, 9.45%, 8.03%, 9.31%, and 13.40% for different port angle values of 0°, 15°, 20°, 25°, and 30°, respectively, with EMS. The results show that EMS significantly influences the flow behavior by generating the swirl flow pattern that hinders the movement of inclusion downward in the domain. The bifurcated SEN with 30° port angle (without EMS) is seen to reduce inclusion entrapment and hence enhance inclusion removal. The outcome of present research may provide useful insights for optimizing the parameters of bloom caster mold to improve product quality, reduce production costs, and increase overall efficiency.

Activity-dependent local protection and lateral inhibition control synaptic competition in developing mitral cells in mice.

In developing brains, activity-dependent remodeling facilitates the formation of precise neuronal connectivity. Synaptic competition is known to facilitate synapse elimination; however, it has remained unknown how different synapses compete with one another within a post-synaptic cell. Here, we investigate how a mitral cell in the mouse olfactory bulb prunes all but one primary dendrite during the developmental remodeling process. We find that spontaneous activity generated within the olfactory bulb is essential. We show that strong glutamatergic inputs to one dendrite trigger branch-specific changes in RhoA activity to facilitate the pruning of the remaining dendrites: NMDAR-dependent local signals suppress RhoA to protect it from pruning; however, the subsequent neuronal depolarization induces neuron-wide activation of RhoA to prune non-protected dendrites. NMDAR-RhoA signals are also essential for the synaptic competition in the mouse barrel cortex. Our results demonstrate a general principle whereby activity-dependent lateral inhibition across synapses establishes a discrete receptive field of a neuron.

Microstructural formation and evolution of near-eutectic Al2O3–ZrO2 powders prepared by a rapid cooling technique: An exploration on coupled eutectic growth range

Regulation of eutectic compositions is a difficult challenge due to the limited formation range of this microstructure. Al2O3–ZrO2 powders were successfully prepared through a modified high-temperature melt-assisted air atomization technique. Micron-sized raw powders of α-Al2O3 and m-ZrO2 were used to regulate the temperature of system and the composition of final products. The high-temperature melt of 3500 K (3227 °C) was obtained based on the exothermic reaction between Al and O2, which was subsequently atomized and quenched to form composite powders. The phase composition and microstructure of the as-prepared powders were characterized by X-Ray diffraction and scanning electron microscopy. Eutectic colonies with nanolamellae (62–79 nm) were observed in the as-prepared Al2O3-(28–58 mol%) ZrO2 powders, with growth rates ranging from 1.9 to 2.8 mm s−1. Importantly, the powders with ZrO2 contents of 38 mol% and 42 mol% showed complete eutectic microstructures without primary dendrites, which indicated an extended coupled growth range deviating by ∼4.9 mol% from the eutectic composition (CE). The microstructural formation mechanism was discussed based on solidification behavior analysis. Furthermore, the evolution of the microstructure and phase in Al2O3-42 mol% ZrO2 powders was investigated. This work aims to develop a novel strategy for preparing oxide powders with eutectic structures and provide a reference for the composition regulation of eutectics.

Influence of the cooling rate on the solidification path and microstructure of a AlCoCrFeNi2.1 alloy

The AlCoCrFeNi2.1 alloy is a promising eutectic high entropy alloy which may act as an in-situ composite, showing a trade-off between mechanical properties and ductility. Controlling the microstructure formation is crucial for achieving the best balance since it is closely related to the cooling rates during solidification. Hence, the present study determined the relationship between different cooling rates and the formed microstructures. As such, the AlCoCrFeNi2.1 alloy was subjected to a directional solidification process so that samples solidified at different cooling rates could be generated. The examined samples corresponded to a range from 1 to 6 °C/s, which resulted in microstructures composed of primary dendrites and uncoupled eutectic, with varying secondary dendritic spacings from 18 to 54 μm and eutectic spacings from 4.5 to 10 μm. The use of CALPHAD, XRD, SEM-EDS, and EBSD phase mapping enabled to determine that the primary FCC dendrites formed in all samples enveloped by the FCC + B2 eutectic. Moreover, the solidification cooling rate affected both dendritic (primary phase) and eutectic length-scales. Finally, the solidification sequence path was able to be changed, and the primary FCC dendrites were also able to form, due to the non-equilibrium nature of the solidification process, which imposed particular segregation and growth conditions.

Microstructure, Hardness, and Linear Reciprocating Sliding Wear Response of Directionally Solidified Al–(2.5, 3.5, 4.5)Cu–(0.25, 0.50)Cr Alloys

Aluminum alloys containing transition metal alloying elements have attracted interest from researchers. The effect of Cr additions of 0.25 and 0.50% on the thermal profile, microstructure, hardness, and linear reciprocating sliding wear response of as-cast hypoeutectic Al–Cu alloys with 2.5, 3.5, and 4.5% Cu (wt.%) was investigated. The binary Al–Cu and ternary Al–Cu–Cr alloys were directionally solidified under upward non-steady state heat transfer conditions using a dedicated solidification apparatus. Thermal analysis based on differential thermal analysis (DTA) and cooling curve profiles was performed to determine solidification thermal parameters such as Liquidus temperature (TL), transformation enthalpy (ΔH), and liquid cooling rate (ṪL). Samples extracted from the solidified ingots were submitted to optical microscopy, hardness measurement, and linear reciprocating sliding wear test using a high-frequency reciprocating rig (HFRR). The results showed a decrease at the beginning of solidification (TL) and of the transformation enthalpy (ΔH) when both alloy Cu and Cr contents increased, with a higher influence of Cu. The addition of Cu decreased cooling rates, whereas the increase in the alloy Cr concentration showed an opposite behavior, increasing cooling rates. The refinement of the primary dendrite arm spacing (λ1), as a consequence of the increase in alloying elements and solidification cooling rates, enhanced the hardness of the alloys, with the maximum value of 58 HB achieved in the ternary Al–4.5Cu–0.50Cr alloy. The wear tests indicated a better response to wear associated with microstructure refinement for the alloys with 2.5% Cu, for both Cr contents, an almost constant behavior for the 3.5% Cu alloys, and an opposite performance for the alloys with 4.5% Cu alloys that showed better wear resistance with coarsening of the λ1 and with the increase in the amount of the eutectic microconstituent.

Effects of thermal history of in-situ thermal management on as-built property heterogeneity of plasma arc additively manufactured Inconel 625

In-situ thermal management (ISTM) is one of the most prospective approaches to alleviating heat accumulation and achieving progressive forming for arc-based additive manufacturing. The aim of this study was to investigate the influences of thermal history, i.e., the cooling rate and the intrinsic heat treatment (IHT), of ISTM on as-built property heterogeneity of plasma arc additively manufactured Inconel 625 thin-wall deposit. The thermal history is obtained from numerical simulation. Results show that the variation of the thermal history of ISTM results in the bottom-up varied cooling rate and IHT, which together lead to the location-heterogeneous primary dendrite arm spacing, interdendritic phases and grain size. IHT of each layer is quantified by temperature-time integration (TTI), and Gaussian distributed TTI (above 600 °C) indicates the middle region of the deposit with ISTM is subjected to the most intense IHT. Compared with the counterpart of the conventional interlayer cooling strategy, the intensified high-temperature IHT of ISTM contributes to significant mitigation of micro-segregation, i.e., the brittle-hard interdendritic phases reduce 61.9%. Furthermore, a weighted value of cooling rate and TTI is innovatively introduced to depict the heterogeneity of mechanical property, which presents an exponential growth of ultimate tensile strength with the weighted value. Moreover, the layer-by-layer decreased heat input and the high-temperature preheating between layers of ISTM contribute to a certain residual stress release effect along the building direction.

Структура и свойства низкоуглеродистой стали после плазменной наплавки борсодержащей обмазки

Introduction. One of the effective thermochemical methods for increasing the hardness of steel is boronizing by diffusion of boron atoms into the steel surface at high temperatures. As a result of boronizing, coatings are formed on the steel surface, consisting of columnar crystals of FeB and Fe2B. The volume fraction of phases and the thickness of the coatings depend on the heating temperature and the chemical composition of the base material and the saturating medium. The main disadvantage of these boronized layers is its high brittleness. Boronizing by plasma heating is one of the alternatives to the diffusion boronizing process to minimize the brittleness of the boronized layer. The purpose of the work: to form boride coatings on low-carbon steel using plasma-jet hard-facing. The research methods are: determination of the content of chemical elements using an electron probe micro-analyzer, metallographic studies, analysis of the phase composition of the boronized layer, as well as measurement of the microhardness of the coating after plasma-jet hard-facing. In this work boronized layers obtained on low-carbon steel 20 by plasma-jet hard-facing of a boron-containing coating are studied. Powdered amorphous boron was used as an alloying element. The parameter varied during plasma-jet hard-facing process is the current strength (120 A, 140 A and 160 A). Results and discussions. Based on the studies performed, it is found that it is possible to form boronized layers on the steel surface using plasma-jet hard-facing method. It is noted that the surface layer of the coating of the 1st and 2nd specimens after plasma-jet hard-facing has a heterogeneous structure, consisting of rows of different zones. The first zone has a hypereutectic structure, which consists of primary borides FeB and Fe2B, located in the eutectic, consisting of Fe2B and α-Fe. The second zone above the boundary with the base metal is represented by eutectic colonies composed of Fe2B and α-Fe. The third specimen is characterized by a hypoeutectic structure consisting of boride eutectic and primary dendrites of the α-solid solution of boron in iron. The maximum hardness is fixed on the surface of the first specimen and is 1,575 HV. The depth of the hardened layer increases with increasing current, but the hardness value and boron content decrease after treatment. The slight hardness gradient observed over the depth of the coating, as well as the gradual decrease in hardness due to the presence of the transition zone, are considered favorable for good adhesion of the boronized layer to the surface of the base material.

Investigating the effect of laser cladding parameters on the microstructure, geometry and temperature changes of Inconel 718 superalloy using the numerical and experimental procedures

In this paper, a novel numerical model was used to simulate the laser cladding process using the finite element technique in order to assess the influence of scanning rate and laser power on the microstructure, geometry and temperature changes of Inconel 718. The laser cladding process was also performed experimentally to show the capability of the applied model for prediction of the results. The results showed that a maximum temperature of 2942 °C was obtained at the end of cladding layer for scanning rate of 4 mm/s and laser power of 250 W. With the increase of scanning rate and the decrease of laser power the height and length of cladded sample decreased, because the heat transfer to the sample was faster than its temperature rise. The microstructure analysis demonstrated that a columnar grain structure was formed when the scanning rate and laser power reached to 4 mm/s and 200 W respectively, due to the increase of cooling rate. However, the increase of laser power up to 250 W led to formation of an equiaxed microstructure, which was owing to the reduction of thermal gradient and consequently the reduction of G/R ratio. An elevation of the laser power from 200 to 250 W resulted in a reduction in the cooling rate and thus an increase in the primary and secondary dendrite arm spacings by about 27 % and 31.5 % respectively. Moreover, a rise of scanning rate from 4 to 5 mm/s led to a decrease in the primary and secondary dendrite arm spacings by about 14 % and 17 % respectively.

Effect of Cooling Condition on Microstructure after Unidirectional Solidification of Cu-Ni-Si Alloys

In order to consider the effect of cooling conditions on microstructure formation during casting of Cu-Ni-Si alloy (Corson alloy), the microstructures of unidirectional solidification of the alloy were evaluated. Ingots of Corson alloy with several cooling conditions were prepared by Mizuta method, and microstructural observations and analysis of the distribution of added elements were performed. The primary and secondary dendrite arm spacings (P-DAS and S-DAS) became smaller with increasing cooling rate, and it was found that P-DAS and S-DAS can be accurately approximated by multiplier of cooling rate times temperature gradient, and by that of cooling rate, respectively. Between secondary dendrites, Si was enriched from the initial solidification zone to the final solidification zone, and Ni was almost constant around the initial solidification zone and enriched slightly around the final solidification zone. The Si enrichment was larger under the condition of lower cooling rate, which is expected to be closer to the equilibrium state. In this study, it was found for Corson alloy that DAS became bigger and Si enrichment between secondary dendrites was larger under the condition of lower cooling rate, and Ni enrichment was not affected by cooling rate.

Convection effect on solidification microstructure: dendritic arm spacing and microsegregation

Convection affect primary crystalline structure, particularly, the dendrite crystal velocity and dendrite tip radius. The present work aims on the influence of the convective flow on the primary dendrite spacing between neighbouring crystals within the dendrite ensemble. Solidification of a binary alloy is considered within the model of stagnant boundary layer, under imposed thermal gradient which influence on the crystal microstructure and chemical microsegregation. Chemical composition in the solidifying liquid and crystalline solid is derived from the solution of the solute diffusion transport equation taking into account the convective flow. The model results are consistent with the Scheil-Brody-Flemings model, experimental data and computational results.

Effects of electromagnetic stirring and subsequent homogenization treatment on the microstructure and mechanical properties of Al70Zn10Mg10Cu5Si5 multi-component alloy

Coarse structure and composition segregation inevitably occurred in light-weight multi-component alloys that manufactured by traditional methods due to the high concentration of solute elements. This work proposes a novel idea to address this challenge by using a combination of electromagnetic stirring and homogenization treatment. The optimum ultimate compressive strength and compressive yield strength were 497 MPa and 432 MPa, which were 12.7% and 14.3% higher than those without electromagnetic stirring, respectively. The electromagnetic force increases the number of nuclei and the equiaxed crystal rate by breaking the primary Mg2Si dendrites and shedding the fine grains on the surface of the mold, so as to achieve the purpose of grain refinement. Furthermore, electromagnetic stirring with appropriate frequency can greatly increase the solid solubility, aggravate the lattice distortion, and consequently lead to a noticeable diffusion sluggish effect, resulting in fine and uniform dispersion of the precipitated MgZn2 phase during homogenization. Finally, a strengthening model was established, and the estimated values were highly consistent with the experimental data, with an error ranging within 5%. This study elaborated the microstructure evolution mechanism, offering guidance to fabricate light-weight multi-component alloys with large-size and excellent mechanical properties.

Postnatal Inhibition of TrkB Kinase Reduces the Number of Phrenic Motor Neurons

During embryonic development, the number of phrenic motor neurons (PhMNs) declines precipitously during the final trimester and continues into the early postnatal period. When BDNF/TrkB signaling is absent in utero, animals do not survive after birth, most likely due to excessive loss of vital motor neurons (e.g., PhMNs). Far less is known about the early postnatal effect of BDNF/TrkB signaling. We have shown that BDNF/TrkB signaling is important in promoting PhMN neuroplasticity in mature rodents. Taken together, we hypothesized that inhibition of BDNF/TrkB signaling during early postnatal development results in fewer PhMNs. Chemo-genetic TrkBF616A mutant mice were used to induce inhibition of TrkB kinase activity in response to oral administration (via drinking water) of a phosphoprotein phosphatase 1 inhibitor derivative (1NMPP1). 1NMPP1-induced TrkB kinase inhibition was initiated at P0 and continued until P21 and compared to untreated control mice. At P28, PhMNs were retrogradely labeled via rhodamine phrenic nerve dip. One day later, mice were euthanized, perfused with 4% paraformaldehyde, and the cervical spinal cord was excised and processed for longitudinal cryosectioning (70 μm). Labeled PhMNs were imaged by 3D high resolution confocal microscopy. The number of PhMNs were counted. PhMN somal surface area and number of primary dendrites were also determined. 1NMPP1-induced inhibition of TrkB kinase resulted in 24% fewer PhMNs (P=0.01) and 21% more primary dendrites (P=0.0002) than control mice. The distribution of PhMN somal surface areas was not affected. We conclude that BDNF/TrkB signaling is essential in promoting survival of PhMNs in the early postnatal period. BDNF/TrkB signaling during postnatal development also plays a role in paring primary dendrites. While inhibition of TrkB kinase did not significantly alter the distribution of PhMN somal surface areas at P28, it is possible that further growth of PhMNs into maturity might have been altered as larger PhMNs emerge as a result of disproportionate growth beyond this age in mice. Supported by National Institutes of Health grants R01-AG044615 (GCS), R01-HL96750 (GCS). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Thermal and solute diffusion in [formula omitted]-Mg dendrite growth of Mg-5wt.%Zn alloy: A phase-field study

Thermal and solute diffusion plays an important role in α-Mg dendrite growth, the diffusion mechanism of which is still unclear. Here, thermal and solute diffusion in α-Mg dendrite growth of Mg-5wt.%Zn alloy under non-isothermal solidification were studied using the phase-field method. Results show that solidification latent heat will be concentrated at the dendrite intersection, which makes thermal field distribution non-uniform, and it is similar to the profile formed by connecting primary dendrite tips. The increase in temperature will shorten primary dendrite arms, reduce side-branching development, increase dendrite tip temperature, and decrease dendrite tip concentration stability. Moreover, solidification latent heat will first diffuse to undercooled melt, then diffuse to other areas, finally, system temperature tends to be unified. The variation range of concentration difference is very small in the solidification process, and solute field distribution is uniform all the time. The local high-concentration areas will be formed after the superposition of the solute enrichment layer, and solute atoms will first diffuse to undercooled melt through the solid-liquid interface, and then concentrate between side-branching and dendrites.

On the occurrence of buoyancy-induced oscillatory growth instability in directional solidification of alloys

Recent solidification experiments identified an oscillatory growth instability during directional solidification of Ni-based superalloy CMSX4 under a given range of cooling rates. From a modeling perspective, the quantitative simulation of dendritic growth under convective conditions remains challenging, due to the multiple length scales involved. Using the dendritic needle network (DNN) model, coupled with an efficient Navier-Stokes solver, we reproduced the buoyancy-induced growth oscillations observed in CMSX4 directional solidification. These previous results have shown that, for a given alloy and temperature gradient, oscillations occur in a narrow range of cooling rates (or pulling velocity, V p ) and that the selected primary dendrite arm spacing (Λ) plays a crucial role in the activation of the flow leading to oscillations. Here, we show that the oscillatory behavior may be generalized to other binary alloys within an appropriate range of (V p ,Λ) by reproducing it for an Al-4at.%Cu alloy. We perform a mapping of oscillatory states as a function of V p and Λ, and identify the regions of occurrence of different behaviors (e.g., sustained or damped oscillations) and their effect on the oscillation characteristics. Our results suggest a minimum of V p for the occurrence of oscillations and confirm the correlation between the oscillation type (namely: damped, sustained, or noisy) with the ratio of average fluid velocity over V p . We describe the different observed growth regimes and highlight similarities and contrasts with our previous results for a CMSX4 alloy.

Microstructure and mechanical properties of hypoeutectic Al–6Ce–3Ni-0.7Fe (wt.%) alloy

A hypoeutectic, Fe-modified Al–Ce–Ni alloy (Al–6Ce–3Ni-0.7Fe, wt.%) is studied in terms of microstructure, thermal stability, ambient temperature strengthening, and creep resistance. The as-cast microstructure consists of primary Al dendrites and interdendritic binary eutectic regions (Al–Al11Ce3 and/or Al–Al9(Fe,Ni)2), with micron/submicron lamellar spacing, depending on the location along the height of the ingot. The cast alloy exhibits excellent coarsening resistance at 400 °C, with mostly unchanged microstructure and microhardness after 6 weeks of aging, indicating good thermal stability of Al11Ce3 and Al9(Fe,Ni)2. Orowan strengthening and load transfer are identified as strengthening mechanisms at ambient and elevated temperature. A high volume fraction of the intermetallic phases (providing load transfer) and relatively coarse eutectic spacing (for modest Orowan strengthening) result in a moderate as-cast microhardness of 566 ± 32 MPa. Creep resistance at 300 and 350 °C is similar to a binary Al-12.5Ce eutectic alloy (with twice the Ce content) because of two countering effects: Al–6Ce–3Ni-0.7Fe shows a higher volume fraction of strengthening intermetallic phases, but it also exhibits a large fraction of primary Al dendrites which weaken the alloy. By contrast, the alloy, when laser-remelted at the surface, has a fully eutectic microstructure without primary aluminum dendrites achieved by high undercooling on solidification, with a refined network of eutectic phases that doubles the microhardness as compared to the cast alloy. Whereas coarsening is faster due to the shorter diffusion distances between the eutectic phases, hardness remains ∼30% higher than the as-cast alloy after ∼6 weeks aging at 400 °C.

Prediction of Primary Dendrite Arm Spacing of the Inconel 718 Deposition Layer by Laser Cladding Based on a Multi-Scale Simulation.

Primary dendrite arm spacing (PDAS) is a crucial microstructural feature in nickel-based superalloys produced by laser cladding. In order to investigate the effects of process parameters on PDAS, a multi-scale model that integrates a 3D transient heat and mass transfer model with a quantitative phase-field model was proposed to simulate the dendritic growth behavior in the molten pool for laser cladding Inconel 718. The values of temperature gradient (G) and solidification rate (R) at the S/L interface of the molten pool under different process conditions were obtained by multi-scale simulation and used as input for the quantitative phase field model. The influence of process parameters on microstructure morphology in the deposition layer was analyzed. The result shows that the dendrite morphology is in good agreement with the experimental result under varying laser power (P) and scanning velocity (V). PDAS was found to be more sensitive to changes in laser scanning velocity, and as the scanning velocity decreased from 12 mm/s to 4 mm/s, the PDAS increased by 197% when the laser power was 1500 W. Furthermore, smaller PDAS can be achieved by combining higher scanning velocity with lower laser power.

Effect of dendrite arrays near grain boundary on the competitive growth of converging Ni-based bi-crystal superalloys

The relationship between the arrangement of dendrite array near grain boundary (GB) and the competitive converging dendrites growth in Ni-based superalloys was characterized by the minimum spanning tree method. The results show that the primary dendrite arm spacing near and far away from GB region is different. The dendrite spacing near GB affects the interlacing of convergent dendrites, thus affecting the competitive growth. At the early solidification stage when the spacing is small, the increasing spacing near GB allows the interlacing of convergent dendrites, which leads to the continuous overgrowth of unfavorably oriented (UO) dendrites to favorably oriented (FO) dendrites. However, at the later stage of solidification when the dendrite spacing become larger, the concomitant growth of developed side-branches will hinder the interlacing of convergent dendrites. Consequently, FO-dendrites with superior growth blocks UO-dendrites with directional growth, and even overgrows UO-dendrites.

Lactoferrin/sialic acid prevents adverse effects of intrauterine growth restriction on neurite length: investigations in an in vitro rabbit neurosphere model.

Intrauterine growth restriction (IUGR) is a well-known cause of impaired neurodevelopment during life. In this study, we aimed to characterize alterations in neuronal development underlying IUGR and discover strategies to ameliorate adverse neurodevelopment effects by using a recently established rabbit in vitro neurosphere culture. IUGR was surgically induced in pregnant rabbits by ligation of placental vessels in one uterine horn, while the contralateral horn remained unaffected for normal growth (control). At this time point, rabbits were randomly assigned to receive either no treatment, docosahexaenoic acid (DHA), melatonin (MEL), or lactoferrin (LF) until c-section. Neurospheres consisting of neural progenitor cells were obtained from control and IUGR pup's whole brain and comparatively analyzed for the ability to differentiate into neurons, extend neurite length, and form dendritic branching or pre-synapses. We established for the very first time a protocol to cultivate control and IUGR rabbit neurospheres not only for 5 days but under long-term conditions up to 14 days under differentiation conditions. Additionally, an in vitro evaluation of these therapies was evaluated by exposing neurospheres from non-treated rabbits to DHA, MEL, and SA (sialic acid, which is the major lactoferrin compound) and by assessing the ability to differentiate neurons, extend neurite length, and form dendritic branching or pre-synapses. We revealed that IUGR significantly increased the neurite length after 5 days of cultivation in vitro, a result in good agreement with previous in vivo findings in IUGR rabbits presenting more complex dendritic arborization of neurons in the frontal cortex. MEL, DHA, and SA decreased the IUGR-induced length of primary dendrites in vitro, however, only SA was able to reduce the total neurite length to control level in IUGR neurospheres. After prenatal in vivo administration of SAs parent compound LF with subsequent evaluation in vitro, LF was able to prevent abnormal neurite extension. We established for the first time the maintenance of the rabbit neurosphere culture for 14 days under differentiation conditions with increasing complexity of neuronal length and branching up to pre-synaptic formation. From the therapies tested, LF or its major compound, SA, prevents abnormal neurite extension and was therefore identified as the most promising therapy against IUGR-induced changes in neuronal development.

Rapid solidification structure refinement mechanism in highly undercooled Cu based ternary alloys

Applying cycle superheating and molten glass purification technologies, Cu60Ni35Co5 alloys were deeply undercooled to maximum undercoolings of 284 K. The microstructure characteristics and its evolution varying with bulk undercooling during the rapidly solidified process were analyzed. It was found that, after minor addition of element Co, crystal refinement mechanisms of the undercooled Cu60Ni35Co5 system was similar to those of the Cu–Ni sytem. Crystal refined microstructure appearing at the low undercoolings was result of dendrite remelting mechanism; the dominant factor of grain refinement microstructure appearing at high undercooling regime was resultant from the recrystallization process. Driving force of stress induced strain energy for recrystallization could be divided into two parts, one was the thermal stress generated by the solidification latent releasing in the recalescence process, and the other was accumulated stress and plastic strain resultant from interaction between primary dendrite and liquid flow driven by rapid solidification.