Analysis of the new ternary phase with C_(6)Cr_(23) structure in Mg-Co-B system by Rietveld method and physical properties of its Ni-substituting effect

A new ternary Mg_(1.4)Co_(21.6)B_(6) compound in the Mg-Co-B system was synthesized via a conventional solid-state reaction method and the effect of Ni-substitution on its crystal structure,thermal stability,solid solubility and physical properties were systematically investigated.The crystal structure of the Mg_(1.4)Co_(21.6)B_(6) compound was fully determined by the X-ray diffraction technique with Rietveld refinement method.It is found that Mg_(1.4)Co_(21.6)B_(6) crystallizes in the form of C_(6)Cr_(23) structure type(space group:Fm-3m(No.225),a=10.5617(2)A,Z=4).The results showed that the 4a sites have been occupied completely by Co atoms in present compound which with M_(2-x)Ni_(21+x)B_(6) form belonging to the W_(2)Cr_(21)C_(6)-type.When Mg_(1.4)Co_(21.6)B_(6) is repeatedly sintered at elevated temperatures,it becomes unstable and decomposes into Co3B and Mg.The lattice parameters of the Mg_(1.4)Co_(21.6)B_(6) solid solution alters dramtically with increasing Ni substitution,with no regular trend being observed.The electrical and magnetic performances of the 3.6Mg:3Co:17Ni:6B and 3.6Mg:3Co:18Ni:6B(nominal compositions)samples suggest that both samples are typical ferromagnetic materials.The temperature in the maximum drop of theρ(T)curve decreases as a function of the Ni content.Base on the correlation between the critical temperature and Ni content,a linear fitting equation is obtained and the critical temperature of Mg_(1.4)Co_(21.6)B_(6) calculated utilizing the linear fitting equation.The findings in this work may provide certain reference values for material science on electrical magnetic properties and other references for researching the material further.

Preleukemic stem cells:leave it or not?

Acute myeloid leukemia(AML)has been shown to undergo multiple acquired mutations in hematopoietic cell lineages over years before becoming clinically apparent.The early stage of AML(before it becomes clinically recognizable)may be characterized by acquisition of some,but not all,leukemia-related somatic mutations in hematopoietic stem cells(HSCs).The physiological roles of these mutations remain puzzling.These HSCs have been termed as preleukemic HSCs.However,those frequent acquired somatic mutations are also found in healthy aging adults,namely,“age-related clonal hematopoiesis.”Multiple studies have demonstrated that the preleukemic HSCs survive through chemotherapy and then contribute to the relapse and the development of de novo AML.Whether preleukemic HSCs should be targeted or whether a preventive therapy should be considered for those individuals remains to be determined.This article aims to shed light on this special subject and to discuss the roles of preleukemic HSCs in leukemogenesis.