Magnetism in tetragonal manganese-rich Heusler compounds

A comprehensive study of the total energy of manganese-rich Heusler compounds using density functional theory is presented. Starting from a large set of cubic parent systems, the response to tetragonal distortions is studied in detail. We single out the systems that remain cubic from those that most likely become tetragonal. The driving force of the tetragonal distortion and its effect on the magnetic properties, especially where they deviate from the Slater--Pauling rule, as well as the trends in the Curie temperatures, are highlighted. By means of partial densities of states, the electronic structural changes reveal the microscopic origin of the observed trends. We focus our attention on the magnetocrystalline anisotropy and find astonishingly high values for tetragonal Heusler compounds containing heavy transition metals accompanied by low magnetic moments, which indicates that these materials are promising candidates for spin-transfer torque magnetization-switching applications

Heusler 4.0: Tunable Materials

Heusler compounds are a large family of binary, ternary and quaternary compounds that exhibit a wide range of properties of both fundamental and potential technological interest. The extensive tunability of the Heusler compounds through chemical substitutions and structural motifs makes the family especially interesting. In this article we highlight recent major developments in the field of Heusler compounds and put these in the historical context. The evolution of the Heusler compounds can be described by four major periods of research. In the latest period, Heusler 4.0 has led to the observation of a variety of properties derived from topology that includes: topological metals with Weyl and Dirac points; a variety of non-collinear spin textures including the very recent observation of skyrmions at room temperature; and giant anomalous Hall effects in antiferromagnetic Heuslers with triangular magnetic structures. Here we give a comprehensive overview of these major achievements and set research into Heusler materials within the context of recent emerging trends in condensed matter physics

PITX1 is a regulator of TERT expression in prostate cancer with prognostic power

Simple Summary Most prostate cancer is of an indolent form and is curable. However, some prostate cancer belongs to rather aggressive subtypes leading to metastasis and death, and immediate therapy is mandatory. However, for these, the therapeutic options are highly invasive, such as radical prostatectomy, radiation or brachytherapy. Hence, a precise diagnosis of these tumor subtypes is needed, and the thus far applied diagnostic means are insufficient for this. Besides this, for their endless cell divisions, prostate cancer cells need the enzyme telomerase to elongate their telomeres (chromatin endings). In this study, we developed a gene regulatory model based on large data from transcription profiles from prostate cancer and chromatin-immuno-precipitation studies. We identified the developmental regulator PITX1 regulating telomerase. Besides observing experimental evidence of PITX1′s functional role in telomerase regulation, we also found PITX1 serving as a prognostic marker, as concluded from an analysis of more than 15,000 prostate cancer samples. Abstract The current risk stratification in prostate cancer (PCa) is frequently insufficient to adequately predict disease development and outcome. One hallmark of cancer is telomere maintenance. For telomere maintenance, PCa cells exclusively employ telomerase, making it essential for this cancer entity. However, TERT, the catalytic protein component of the reverse transcriptase telomerase, itself does not suit as a prognostic marker for prostate cancer as it is rather low expressed. We investigated if, instead of TERT , transcription factors regulating TERT may suit as prognostic markers. To identify transcription factors regulating TERT , we developed and applied a new gene regulatory modeling strategy to a comprehensive transcriptome dataset of 445 primary PCa. Six transcription factors were predicted as TERT regulators, and most prominently, the developmental morphogenic factor PITX1. PITX1 expression positively correlated with telomere staining intensity in PCa tumor samples. Functional assays and chromatin immune-precipitation showed that PITX1 activates TERT expression in PCa cells. Clinically, we observed that PITX1 is an excellent prognostic marker, as concluded from an analysis of more than 15,000 PCa samples. PITX1 expression in tumor samples associated with (i) increased Ki67 expression indicating increased tumor growth, (ii) a worse prognosis, and (iii) correlated with telomere length

Availability Targets Scaled According to Assurance Complexity in the FCC-ee

The Future Circular Collider (FCC) is the leading proposal for the next generation of energy- frontier particle accelerators. Its first stage, the FCC-ee, schedules 185 days to physics each year, of which 80% must be spent at nominal parameters if integrated luminosity goals are to be reached. For comparison, the Large Hadron Collider (LHC) was available for 77% of the physics production in Run 2, 2016-2018. The additional challenges in maintaining the FCC-ee, like its size, complexity and ambitious technical objectives, make availability a significant risk to its physics deliverables. This paper presents a heuristic methodology to break down the global 80% availability requirement into the FCC-ee’s main constituent systems. This quantifies availability targets that scale with the complexity (or “difficulty”) of assuring availability. The contributions are threefold: First, this provides a benchmark against which to assess the severity of the FCC-ee availability challenge and the risk to availability from each system. Second, the presented methodology provides a platform to translate changes in one system’s availability to that of the FCC-ee overall, which is applicable in numerous future studies. Third, the methodology is generally applicable to any future machine for which concrete and detailed designs are unavailable, and may be re-utilized in numerous engineering applications

Machine Protection and Availability in the FCC-ee

The FCC-ee will combine high stored beam energy with small vertical emittance. The loss of only a small part of the beam into accelerator equipment, collimators or passive absorbers could be extremely destructive. Therefore, a highly reliable machine protection system is required for the entire accelerator chain. Further, the FCC-ee schedule has 185 days allocated to physics each year, of which a minimum percent must be spent at nominal parameters if integrated luminosity goals are to be reached. Machine protection and availability are vital considerations from the outset of the design stage. This paper presents the current status and outlook for both topics relating to analysis, research and development (R&D). First, relevant topics in machine protection are discussed. Fault mechanisms are treated as well as key considerations such as minimum reaction time, beam loss detection, dust interaction, fast failures and quench protection. Next, availability assurance is considered. Three steps are proposed: (I) Coarsely define system availability targets scaled to the complexity of delivery. (II) Establish the projected availability based on existing designs and similar systems. (III) If the latter is insufficient, study how this can be improved

Hydrogenous Zintl Phase Ba3Si4HxBa_{3}Si_{4}H_{x} (x = 1 - 2): Transforming Si4Si_{4} "Butterfly" Anions into Tetrahedral Moieties

The hydride Ba3Si4Hx (x = 1–2) was prepared by sintering the Zintl phase Ba3Si4, which contains Si46– butterfly-shaped polyanions, in a hydrogen atmosphere at pressures of 10–20 bar and temperatures of around 300 °C. Initial structural analysis using powder neutron and X-ray diffraction data suggested that Ba3Si4Hx adopts the Ba3Ge4C2 type [space group I4/mcm (No. 140), a ≈ 8.44 Å, c ≈ 11.95 Å, Z = 8] where Ba atoms form a three-dimensional array of corner-condensed octahedra, which are centered by H atoms. Tetrahedron-shaped Si4 polyanions complete a perovskite-like arrangement. Thus, hydride formation is accompanied by oxidation of the butterfly polyanion, but the model with the composition Ba3Si4H is not charge-balanced. First-principles computations revealed an alternative structural scenario for Ba3Si4Hx, which is based on filling pyramidal Ba5 interstices in Ba3Si4. The limiting composition is x = 2 [space group P42/mmm (No. 136), a ≈ 8.4066 Å, c ≈ 12.9186 Å, Z = 8], and for x > 1, Si atoms also adopt tetrahedron-shaped polyanions. Transmission electron microscopy investigations showed that Ba3Si4Hx is heavily disordered in the c direction. Most plausible is to assume that Ba3Si4Hx has a variable H content (x = 1–2) and corresponds to a random intergrowth of P- and I-type structure blocks. In either form, Ba3Si4Hx is classified as an interstitial hydride. Polyanionic hydrides in which H is covalently attached to Si remain elusive

Hydrogenous Zintl Phase Ba₃Si₄H_<i>x</i> (<i>x</i> = 1–2): Transforming Si₄ “Butterfly” Anions into Tetrahedral Moieties

The hydride Ba₃Si₄H_<i>x</i> (<i>x</i> = 1–2) was prepared by sintering the Zintl phase Ba₃Si₄, which contains Si₄^6– butterfly-shaped polyanions, in a hydrogen atmosphere at pressures of 10–20 bar and temperatures of around 300 °C. Initial structural analysis using powder neutron and X-ray diffraction data suggested that Ba₃Si₄H_<i>x</i> adopts the Ba₃Ge₄C₂ type [space group <i>I</i>4/<i>mcm</i> (No. 140), <i>a</i> ≈ 8.44 Å, <i>c</i> ≈ 11.95 Å, <i>Z</i> = 8] where Ba atoms form a three-dimensional array of corner-condensed octahedra, which are centered by H atoms. Tetrahedron-shaped Si₄ polyanions complete a perovskite-like arrangement. Thus, hydride formation is accompanied by oxidation of the butterfly polyanion, but the model with the composition Ba₃Si₄H is not charge-balanced. First-principles computations revealed an alternative structural scenario for Ba₃Si₄H_<i>x</i>, which is based on filling pyramidal Ba₅ interstices in Ba₃Si₄. The limiting composition is <i>x</i> = 2 [space group <i>P</i>4₂/<i>mmm</i> (No. 136), <i>a</i> ≈ 8.4066 Å, <i>c</i> ≈ 12.9186 Å, <i>Z</i> = 8], and for <i>x</i> > 1, Si atoms also adopt tetrahedron-shaped polyanions. Transmission electron microscopy investigations showed that Ba₃Si₄H_<i>x</i> is heavily disordered in the <i>c</i> direction. Most plausible is to assume that Ba₃Si₄H_<i>x</i> has a variable H content (<i>x</i> = 1–2) and corresponds to a random intergrowth of <i>P</i>- and <i>I</i>-type structure blocks. In either form, Ba₃Si₄H_<i>x</i> is classified as an interstitial hydride. Polyanionic hydrides in which H is covalently attached to Si remain elusive