Effect of boron doping on nanostructure and magnetism of rapidly quenched Zr\u3csub\u3e2\u3c/sub\u3eCo\u3csub\u3e11\u3c/sub\u3e-based alloys

The role of B on the microstructure and magnetism of Zr16Co82.5-xMo1.5Bx ribbons prepared by arc melting and melt spinning is investigated. Microstructure analysis show that the ribbons consist of a hard-magnetic rhombohedral Zr2Co11 phase and a minor amount of soft-magnetic Co. We show that the addition of B increases the amount of hard-magnetic phase, reduces the amount of soft-magnetic Co and coarsens the grain size from about 35 nm to 110 nm. There is a monotonic increase in the volume of the rhombohedral Zr2Co11 unit cell with increasing B concentration. This is consistent with a previous theoretical prediction that B may occupy a special type of large interstitial sites, called interruption sites. The optimum magnetic properties, obtained for x = 1, are a saturation magnetization of 7.8 kG, a coercivity of 5.4 kOe, and a maximum energy product of 4.1 MGOe

Experimental Evaluation of Compressive Elastocaloric Cooling System

Elastocaloric cooling, or thermoelastic cooling, has the potential to substitute the state-of-the-art vapor compression cooling systems. The elastocaloric effect refers to the latent heat associated with the stress-induced martensitic phase transformation process in shape memory alloys. In this study, we demonstrated our latest testing results of world’s first of-its-kind prototype based on elastocaloric effect. Two beds with Ni-Ti alloy tubes were implemented in the system to generate cooling and heating. Water was used as the heat transfer fluid to reject heat to an air-cooled heat sink and deliver cooling to an electric heater. The system was driven by a linear actuator under compression mode. Operating under a single stage reverse Brayton cycle, the two beds design also enabled the heat recovery and work recovery feature to enhance the system’s performance. The initial effort led to a successful elastocaloric cooling system prototype with useful cooling capacity of 38 W at a water-to-water temperature lift of 1.5 K. To enhance the system performance, a series of modifications were applied to the system. By better aligning the linear actuator and the two Ni-Ti tube beds, the system temperature lift was increased up to 1.8 K due to increased strain and latent heat. The plastic insulation tube design significantly reduced the heat loss from heat transfer fluid to the metal parts, which successfully increased the system temperature lift to 2.8 K. Furthermore, by modifying the motor layout and making it compress more Ni-Ti tubes per bed the system achieved a 4.2 K temperature lift with 65 W cooling capacity. Plastic insertions to block partial heat transfer fluid inside each Ni-Ti tube reduced the cyclic loss associated with periodic heating and cooling of the heat transfer fluid, which boosted the system temperature lift to 4.7 K.  Unfortunately, the active thermal mass of Ni-Ti tubes was too small when compared to the big losses in the prototype, which indicated that the system mass should be reduced significantly. The system temperature lift of 6.1 K was predicted based on the test results, when assuming no pump parasitic heat generation and no heat conduction loss to the metal supporting frame in each bed. This study built the step stone for elastocaloric cooling technology by successfully achieving an effective cooling for the first time in the world. However, the elastocaloric cooling technology needs a substantial following research to enhance its performance

Mutant p53 drives clonal hematopoiesis through modulating epigenetic pathway

Clonal hematopoiesis of indeterminate potential (CHIP) increases with age and is associated with increased risks of hematological malignancies. While TP53 mutations have been identified in CHIP, the molecular mechanisms by which mutant p53 promotes hematopoietic stem and progenitor cell (HSPC) expansion are largely unknown. Here we discover that mutant p53 confers a competitive advantage to HSPCs following transplantation and promotes HSPC expansion after radiation-induced stress. Mechanistically, mutant p53 interacts with EZH2 and enhances its association with the chromatin, thereby increasing the levels of H3K27me3 in genes regulating HSPC self-renewal and differentiation. Furthermore, genetic and pharmacological inhibition of EZH2 decreases the repopulating potential of p53 mutant HSPCs. Thus, we uncover an epigenetic mechanism by which mutant p53 drives clonal hematopoiesis. Our work will likely establish epigenetic regulator EZH2 as a novel therapeutic target for preventing CHIP progression and treating hematological malignancies with TP53 mutations

Author Correction: Mutant p53 drives clonal hematopoiesis through modulating epigenetic pathway

An amendment to this paper has been published and can be accessed via a link at the top of the paper

Microstructure and Magnetic Behavior Studies of Processing-controlled and Composition-modified Fe-Ni and Mn-Al Alloys

L10-type (Space group P4/mmm) magnetic compounds, including FeNi and MnAl, possess promising technical magnetic properties of both high magnetization and large magnetocrystalline anisotropy energy, and thus offer potential in replacing rare earth permanent magnets in some applications. In equiatomic Fe-Ni, the disorder-order transformation from fcc structure to the L10 structure is a diffusional transformation, but is inhibited by the low ordering temperature. The transformation could be enhanced through the creation of vacancies. Thus, mechanical alloying was employed to generate more open-volume defects. A decrease in grain size and concomitant increase in grain boundary area resulted from the mechanical alloying, while an initial increase in internal strain (manifested through an increase in dislocation density) was followed by a subsequent decrease with further alloying. However, a decrease in the net defect concentration was determined by Doppler broadening positron annihilation spectroscopy, as open volume defects utilized dislocations and grain boundaries as sinks. An alloy, Fe32Ni52Zr3B13, formed an amorphous structure after rapid solidification, with a higher defect concentration than crystalline materials. Mechanical milling was utilized in an attempt to generate even more defects. However, it was observed that Fe32Ni52Zr3B13 underwent crystallization during the milling process, which appears to be related to enhanced vacancy-type defect concentrations allowing growth of pre-existing Fe(Ni) nuclei. The milling and enhanced vacancy concentration also de-stabilizes the glass, leading to decreased crystallization temperatures, and ultimately leading to complete crystallization. In Mn-Al, the L10 structure forms from the parent hcp phase. However, this phase is slightly hyperstoichiometric relative to Mn, and the excess Mn occupies Al sites and couples antiparallel to the other Mn atoms. In this study, the Zr substituted preferentially for the Mn atoms in the Al layer, resulting in an increase in saturation magnetization, from 115 emu/g in the alloys without Zr to 128 emu/g in Mn53Al43C3Zr1. To further improve the coercivity in Mn53Al43C3Zr1, microstructure modification was achieved through the addition of excessive C and through surfactant-assisted mechanical milling. Enhancement in coercivity was accomplished through the microstructure modification, however, the loss of saturation magnetization was observed due to the formation of other equilibrium phases, including ε, β-Mn and ZrO. Adviser: Jeffrey E. Shiel

Phase transformation and magnetic properties of rapidly solidified Mn-Al-C alloys modified with Zr

Mn54-xAl43C3Zrx (x=1, 3) alloys were prepared by rapid solidification followed by heat treatment to produce the ferromagnetic s phase. The substitution of Zr for Mn in the structure resulted in an increase of the saturation magnetization (Ms) compared to that of Mn54-xAl43C3. While the highest Ms (12861 emu/g) was obtained in Mn54-xAl43C3Zr1, the coercivity was also improved to 1.62 kOe, compared to 1.25 kOe for Mn54-xAl43C3. To further improve the coercivity through grain refinement, additional C (1%, 3%, 5%, and 7%) was added to Mn54-xAl43C3Zr1. An increase in the coercivity was observed due to a decrease of grain size and the formation of nonmagnetic phases, which reduced the magnetostatic interactions between the s-phase grains. However, excess C reduced the saturation magnetization due to the formation of the other non-ferromagnetic phases, including e, c2, and b phases

Directivity Analysis of Piezoelectric Micromachined Ultrasonic Transducer Array

A piezoelectric micromachined ultrasonic transducer (pMUT) is proposed. The (Pt/Ti)/Polyimide/PZT/Si3N4/SiO2/Si/SiO2/Si3N4 multimorph structure is designed and fabricated with micromachined process, resonance frequency of which is supposed to locate near 53.6 kHz. To improve the directivity pattern and increase radiation acoustic power, transducer array is adopted. A numerical simulation model was presented to study the influences of design parameters of plane combination array transducer. Interspacing between elements and number of elements are optimized. Subsequently, to verify the optimization results, experiment platform is established, directivity pattern of transducer array is obtained and compared with simulation results, which validated the optimization. The results provide the basis for structural design and fabrication of pMUT, a reliable reference for optimization of transducer array, and a method to test the directivity pattern

Identification of Potential Therapeutic Targets and Molecular Regulatory Mechanisms for Osteoporosis by Bioinformatics Methods

Background. Osteoporosis is characterized by low bone mass, deterioration of bone tissue structure, and susceptibility to fracture. New and more suitable therapeutic targets need to be discovered. Methods. We collected osteoporosis-related datasets (GSE56815, GSE99624, and GSE63446). The methylation markers were obtained by differential analysis. Degree, DMNC, MCC, and MNC plug-ins were used to screen the important methylation markers in PPI network, then enrichment analysis was performed. ROC curve was used to evaluate the diagnostic effect of osteoporosis. In addition, we evaluated the difference in immune cell infiltration between osteoporotic patients and control by ssGSEA. Finally, differential miRNAs in osteoporosis were used to predict the regulators of key methylation markers. Results. A total of 2351 differentially expressed genes and 5246 differentially methylated positions were obtained between osteoporotic patients and controls. We identified 19 methylation markers by PPI network. They were mainly involved in biological functions and signaling pathways such as apoptosis and immune inflammation. HIST1H3G, MAP3K5, NOP2, OXA1L, and ZFPM2 with higher AUC values were considered key methylation markers. There were significant differences in immune cell infiltration between osteoporotic patients and controls, especially dendritic cells and natural killer cells. The correlation between MAP3K5 and immune cells was high, and its differential expression was also validated by other two datasets. In addition, NOP2 was predicted to be regulated by differentially expressed hsa-miR-3130-5p. Conclusion. Our efforts aim to provide new methylation markers as therapeutic targets for osteoporosis to better treat osteoporosis in the future