We revisited the microstructure of a commercial Nd-Fe-B sintered magnet using scanning electron microscopy (SEM) and aberration corrected scanning transmission electron microscopy (STEM) in order to ...clarify the microstructure feature that is relevant to the coercivity. Two types of thin Nd-rich grain boundary (GB) phases were found: one is crystalline and the other is amorphous. The crystalline Nd-rich GB phase form at the flat surface of c-plane of the Nd2Fe14B grains, which contains a higher amount of Nd compared to the amorphous GB phase that form on the grain boundaries nearly perpendicular to the c-planes. This indicates that the intergranular exchange coupling in sintered Nd-Fe-B magnets is anisotropic. Correlative SEM and STEM analysis of triple junction Nd-rich phases revealed five types of Nd-rich phases, i.e., fcc-NdO, hcp-Nd2O3, NdFe4B4, metallic Nd-rich phases with the fcc structure and the Ia3¯ structure. The metallic Nd-rich phases form at the sharp edges of Nd-rich oxide and boride grains, from which thin Nd-rich phases is infiltrated along grain boundaries to form the thin GB phase. Misaligned Nd2Fe14B grains are often observed in direct contact with the Nd2O3 grains.
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Abstract
Materials that possess nontrivial topology and magnetism is known to exhibit exotic quantum phenomena such as the quantum anomalous Hall effect. Here, we fabricate a novel magnetic ...topological heterostructure Mn
4
Bi
2
Te
7
/Bi
2
Te
3
where multiple magnetic layers are inserted into the topmost quintuple layer of the original topological insulator Bi
2
Te
3
. A massive Dirac cone (DC) with a gap of 40–75 meV at 16 K is observed. By tracing the temperature evolution, this gap is shown to gradually decrease with increasing temperature and a blunt transition from a massive to a massless DC occurs around 200–250 K. Structural analysis shows that the samples also contain MnBi
2
Te
4
/Bi
2
Te
3
. Magnetic measurements show that there are two distinct Mn components in the system that corresponds to the two heterostructures; MnBi
2
Te
4
/Bi
2
Te
3
is paramagnetic at 6 K while Mn
4
Bi
2
Te
7
/Bi
2
Te
3
is ferromagnetic with a negative hysteresis (critical temperature ~20 K). This novel heterostructure is potentially important for future device applications.
Mg–1.2Al–0.3Ca–0.4Mn–0.3Zn (AXMZ1000) (wt%) alloy was rolled in three different conditions in order to understand the effects of the rolling conditions on the microstructure and mechanical ...properties. The sheet subjected to high temperature reheating at 500 °C for 5 min prior to each 100 °C rolling delivers the highest Index Erichsen (I.E.) value of 7.0 mm. The sheet rolled at 300 °C with 500 °C reheating for 5 min delivers the lowest I.E value of 5.4 mm, while the sheet continuously rolled at the same temperature shows a moderate I.E. value of 6.0 mm. Systematic observations of the microstructures of T4-treated and 3 mm stretched formed samples reveal that the large stretch formability of the sheet rolled at 100 °C with 500 °C reheating is associated the weak basal texture and fine-grained microstructure.
Decremental loss of PTEN results in cancer susceptibility and tumor progression. PTEN elevation might therefore be an attractive option for cancer prevention and therapy. We have generated several ...transgenic mouse lines with PTEN expression elevated to varying levels by taking advantage of bacterial artificial chromosome (BAC)-mediated transgenesis. The “Super-PTEN” mutants are viable and show reduced body size due to decreased cell number, with no effect on cell size. Unexpectedly, PTEN elevation at the organism level results in healthy metabolism characterized by increased energy expenditure and reduced body fat accumulation. Cells derived from these mice show reduced glucose and glutamine uptake and increased mitochondrial oxidative phosphorylation and are resistant to oncogenic transformation. Mechanistically we find that PTEN elevation orchestrates this metabolic switch by regulating PI3K-dependent and -independent pathways and negatively impacting two of the most pronounced metabolic features of tumor cells: glutaminolysis and the Warburg effect.
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► “Super-PTEN” mice are viable and show reduced body size due to decreased cell number ► PTEN elevation shifts cellular metabolism to a tumor-suppressive anti-Warburg state ► PTEN controls key metabolic pathways through PI3K-dependent and -independent functions ► PTEN negatively impacts tumor metabolic pathways: glycolysis and glutaminolysis
Increasing the expression of PTEN protects mice from cancer by suppressing metabolic programs, such as aerobic glycolysis, that fuel tumor growth. The findings indicate that cellular metabolic programs can play an important role in cancer prevention.
Abstract Staphylococcus (S.) aureus silently stays as our natural flora, and yet sometimes threatens our life as a tenacious pathogen. In addition to its ability to outwit our immune system, its ...multi-drug resistance phenotype makes it one of the most intractable pathogenic bacteria in the history of antibiotic chemotherapy. It conquered practically all the antibiotics that have been developed since 1940s. In 1961, the first MRSA was found among S. aureus clinical isolates. Then MRSA prevailed throughout the world as a multi-resistant hospital pathogen. In 1997, MRSA strain Mu50 with reduced susceptibility to vancomycin was isolated. Vancomycin-intermediate S. aureus (VISA), so named according to the CLSI criteria, was the product of adaptive mutation of S. aureus against vancomycin that had long been the last resort to MRSA infection. Here, we describe the genetic basis for the remarkable ability of S. aureus to acquire multi-antibiotic resistance, and propose a novel paradigm for future chemotherapy against the multi-resistant pathogens.
► Age hardening response of Mg–Sn–Zn alloy is enhanced by double aging. ► Polygonal shaped Mg
2Sn phase heterogeneously nucleates at the tip of MgZn
2 phase. ► Alloying with Al, Cu, Ca
+ Ag
+ Zr ...further increases the peak hardness of Mg–Sn–Zn alloy.
We have investigated the effect of double aging and microalloying on the age hardening behavior of a Mg–2.2Sn–0.5Zn alloy. The double aging at 473
K after pre-aging at 343
K lead to an increased peak hardness to more than 80
HV as a result of the refinement of the polygonal Mg
2Sn precipitates by the heterogeneous nucleation at densely dispersed MgZn
2 precipitates. The age hardening response of the Mg–2.2Sn–0.5Zn alloy was further enhanced by microalloying with 0.2Cu (at.%), 0.2Ca–0.2Ag–0.2Zr or 1.0Al. In particular, the peak hardness of the Mg–2.2Sn–0.5Zn–1.0Al alloy was 95
HV at 433
K, which was attributed to the synergy effect of the dispersion of the fine rod and polygonal Mg
2Sn precipitates and solution hardening with Al.
Abstract
Growing cells increase multiple biosynthetic processes in response to the high metabolic demands needed to sustain proliferation. The even higher metabolic requirements in the setting of ...cancer provoke proportionately greater biosynthesis. Underappreciated key aspects of this increased metabolic demand are guanine nucleotides and adaptive mechanisms to regulate their concentration. Using the malignant brain tumour, glioblastoma, as a model, we have demonstrated that one of the rate-limiting enzymes for guanosine triphosphate (GTP) synthesis, inosine monophosphate dehydrogenase-2 (IMPDH2), is increased and IMPDH2 expression is necessary for the activation of de novo GTP biosynthesis. Moreover, increased IMPDH2 enhances RNA polymerase I and III transcription directly linking GTP metabolism to both anabolic capacity as well as nucleolar enlargement historically observed as associated with cancer. In this review, we will review in detail the basis of these new discoveries and, more generally, summarize the current knowledge on the role of GTP metabolism in cancer.
Nanocrystalline Al–5
at.% Fe alloy powders produced by mechanical alloying were consolidated by spark plasma sintering. The sintered sample showed high strength >1000
MPa with a large plastic strain ...of 15% at room temperature and 500
MPa at 350
°C. Microstructure characterizations by transmission electron microscopy and atom probe tomography revealed that the sintered samples are composed of α-Al and Al
6Fe nanocrystalline regions with 90
nm in diameter and a minor fraction of Al
13Fe
4 phase and coarsened 0.5–1
μm α-Al grains. This bimodally grained feature is attributed to the relatively large plastic strain for the strength level of 1000
MPa at room temperature.
The magnetism of a thin grain-boundary (GB) phase that envelopes the Nd2Fe14B grains in optimally annealed Nd–Fe–B sintered magnets was investigated by electron holography. The phase shift measured ...from a thin-foil specimen containing a tilted amorphous GB phase (∼3nm in width) was −0.34rad, which is substantially smaller than that expected for the nonferromagnetic GB phase of −1.2rad. Simulations of the phase shift with various magnetization values suggest that the magnetic flux density of the GB phase is ∼1.0T. The observations imply significant exchange coupling between Nd2Fe14B grains, which can explain the avalanche propagation of magnetization reversal observed in sintered magnets.
We have characterized the microstructures of as-sintered and optimally post-sinter annealed Nd-rich Ga-doped Nd–Fe–B magnets by scanning electron microscopy (SEM) and aberration-corrected scanning ...transmission electron microscopy (STEM). While the Nd2Fe14B grains in the as-sintered sample with a coercivity of 0.99T are in direct contact with each other, those in the optimally annealed sample with a coercivity of 1.8T are completely enveloped by typically 10-nm-thick Nd-rich phase that contains little Fe. This strongly suggests that the Nd2Fe14B grains in the optimally annealed Nd-rich Ga-doped Nd–Fe–B magnets are exchange decoupled in contrast to those in the commercial sintered magnets.
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