In the present study, the influence of the volume fraction of blocky austenite on the microstructure and mechanical properties of novel bainitic steel was investigated. The rolled homogenized sheets ...were austenitized at 950 °C and austempered at 250 °C for 18h (B15VA-1) and 50 h(B15VA-2). X-ray diffraction study of B15VA-1 & B15VA-2 confirmed the presence of carbide-free nanostructured bainitic ferrite (BF) and retained austenite (RA). Optical, scanning and transmission electron microscopic studies delineate the morphology of retained austenite to filmy and blocky forms. On the tensile deformation, majority of blocky austenite in B15VA-1 transformed to strain-induced martensite of ε type. Hardness and yield strength (YS) were increased with an increasing amount of bainitic ferrite, however, ultimate tensile strength (UTS) was found to be a strong function of the extent of strain-induced martensitic (SIM) transformation. As a result of the high amount of SIM, UTS of B15VA-1 increased to 1889 MPa. Ductility is mainly controlled by the transformation-induced plasticity of blocky austenite. Uniform plastic elongation and total plastic elongation were found to be 25% and 28%, respectively. The work hardening behavior can be described by the Swift model. Deformation under tensile load takes place in three stages which are homogeneous deformation, strain-induced martensitic transformation and multiphase deformation-led interaction of dislocations and their recovery. The alloy with nanostructured bainitic ferrite fails by mixed mode of ductile-brittle fracture.
•Carbide free nanostructured bainitic steel was investigated.•Higher vol% of blocky austenite showed excellent hardness and tensile strengths.•Transformation of blocky austenite into strain-induced martensite (SIM).•SIM leads to enhanced elongation due to transformation induced plasticity.•Report highest product of strength and elongation (PSE) value of 55.16 GPa%.
Accurate and consistent constitutive model is required to characterize the material behavior in a variety of thermo-mechanical problems. Herein, widely used Johnson–Cook (J–C) model parameters are ...evaluated for Fe–30Mn–9Al–0.8C low-density steel to predict the flow stress in various forming applications. For this low-density steel prepared in our laboratory, the material compositions are optimally chosen to yield the best ductility (> 70%) with good tensile strength. Tensile tests have been performed at strain rates varying from 10
–4
to 10
–1
s
−1
and at various temperatures such as 150 °C, 300 °C and 450 °C to determine the J–C parameters. Thereafter, genetic algorithm (GA) technique has been used to obtain optimum values of J–C parameters that best fit the experimental stress–strain data. The improved values of the J–C parameter are implemented in ABAQUS explicit software to replicate the experimentally observed tensile test data. It has been observed that the developed constitutive model can produce a fairly accurate and precise estimation of flow stress with a good correlation to experimental data under various strain rates and temperature conditions.
•Skin as a sensory organ with neuroendocrine activities.•Skin and subcutis demonstrate steroidogenic activities.•Cutaneous steroidogenic machinery is involved in production of novel ...secosteroids.•Cutaneous and systemic steroidogenesis are regulated by skin factors and UVR.
The mammalian skin is a heterogeneous organ/tissue covering our body, showing regional variations and endowed with neuroendocrine activities. The latter is represented by its ability to produce and respond to neurotransmitters, neuropeptides, hormones and neurohormones, of which expression and phenotypic activities can be modified by ultraviolet radiation, chemical and physical factors, as well as by cytokines. The neuroendocrine contribution to the responses of skin to stress is served, in part, by local synthesis of all elements of the hypothalamo-pituitary–adrenal axis. Skin with subcutis can also be classified as a steroidogenic tissue because it expresses the enzyme, CYP11A1, which initiates steroid synthesis by converting cholesterol to pregnenolone, as in other steroidogenic tissues. Pregnenolone, or steroidal precursors from the circulation, are further transformed in the skin to corticosteroids or sex hormones. Furthermore, in the skin CYP11A1 acts on 7-dehydrocholesterol with production of 7-dehydropregnolone, which can be further metabolized to other Δ7steroids, which after exposure to UVB undergo photochemical transformation to vitamin D like compounds with a short side chain. Vitamin D and lumisterol, produced in the skin after exposure to UVB, are also metabolized by CYP11A1 to several hydroxyderivatives. Vitamin D hydroxyderivatives generated by action of CYP11A1 are biologically active and are subject to further hydroxylations by CYP27B1, CYP27A1 and CP24A. Establishment of which intermediates are produced in the epidermis in vivo and whether they circulate on the systemic level represent a future research challenge. In summary, skin is a neuroendocrine organ endowed with steroid/secosteroidogenic activities
Topological protection offers unprecedented opportunities for wave manipulation and energy transport in various fields of physics, including elasticity, acoustics, quantum mechanics, and ...electromagnetism. Distinct classes of topological waves have been investigated by establishing analogs with the quantum, spin, and valley Hall effects. We here propose and experimentally demonstrate the possibility of supporting multiple classes of topological modes within a single platform. Starting from a patterned elastic plate featuring a double Dirac cone, we create distinct topological interfaces by lifting such degeneracy through selective breaking of symmetries across the thickness and in the plane of the plate. We observe the propagation of a new class of heterogeneous helical-valley edge waves capable of isolating modes on the basis of their distinct polarization, i.e., the specific mode wave field distribution within the unit cell. Our results show the onset of wave splitting resulting from the interaction of multiple topological equal-frequency wave modes, which may have significance in applications involving elastic beam splitters, switches, and filters.
Steroid hormones are synthesized in the adrenal gland, gonads, placenta and brain and are critical for normal reproductive function and bodily homeostasis. The steroidogenic acute regulatory (StAR) ...protein regulates the rate-limiting step in steroid biosynthesis, i.e. the delivery of cholesterol from the outer to the inner mitochondrial membrane. The expression of the StAR protein is predominantly regulated by cAMP-dependent mechanisms in the adrenal and gonads. Whereas StAR plays an indispensable role in the regulation of steroid biosynthesis, a complete understanding of the regulation of its expression and function in steroidogenesis is not available. It has become clear that the regulation of StAR gene expression is a complex process that involves the interaction of a diversity of hormones and multiple signaling pathways that coordinate the cooperation and interaction of transcriptional machinery, as well as a number of post-transcriptional mechanisms that govern mRNA and protein expression. However, information is lacking on how the StAR gene is regulated in vivo such that it is expressed at appropriate times during development and is confined to the steroidogenic cells. Thus, it is not surprising that the precise mechanism involved in the regulation of StAR gene has not yet been established, which is the key to understanding the regulation of steroidogenesis in the context of both male and female development and function.
The effect of tensile straining on the precipitation and dislocation behavior of the over-aged 7075 aluminum alloy at T7352 temper have been investigated. Microstructures depict dissolution of the ...precipitates at low tensile straining but reprecipitation occurs at a higher amount of strain. Such precipitation improves the resistance against stress-corrosion cracking as well as other mechanical properties. Detailed characterization displayed the formation of dislocation loops, forest dislocation along with tangled dislocations at a low amount of straining corresponding to a true strain of ~0.02. In contrast, low-density, high-density Taylor lattices, and dislocation cell structures were seen at higher true straining of 0.06, and 0.1 respectively. Dissolution, reprecipitation of second phases, changes in orientation, and development of dislocation structures are contributing to the two-slope deformation behavior of AA7075T7352 alloy.
Breast cancer (BC) is a heterogeneous condition and comprises molecularly distinct subtypes. An imbalance in the levels of epigenetic histone deacetylases (HDACs), modulating estrogen accumulation, ...especially 17β-estradiol (E2), promotes breast tumorigenesis. In the present study, analyses of The Cancer Genome Atlas (TCGA) pan-cancer normalized RNA-Seq datasets revealed the dysregulation of 16 epigenetic enzymes (among a total of 18 members) in luminal BC subtypes, in comparison to their non-cancerous counterparts. Explicitly, genomic profiling of these epigenetic enzymes displayed increases in HDAC1, 2, 8, 10, 11, and Sirtuins (SIRTs) 6 and 7, and decreases in HDAC4-7, -9, and SIRT1-4 levels, respectively, in TCGA breast tumors. Kaplan-Meier plot analyses showed that these HDACs, with the exception of HDAC2 and SIRT2, were not correlated with the overall survival of BC patients. Additionally, disruption of the epigenetic signaling in TCGA BC subtypes, as assessed using both heatmaps and boxplots, was associated with the genomic expression of factors that are instrumental for cholesterol trafficking/utilization for accelerating estrogen/E2 levels, in which steroidogenic acute regulatory protein (STAR) mediates the rate-limiting step in steroid biosynthesis. TCGA breast samples showed diverse expression patterns of a variety of key steroidogenic markers and hormone receptors, including
and
. Moreover, regulation of STAR-governed steroidogenic machinery was found to be influenced by various transcription factors, i.e.,
and
. Along these lines, ingenuity pathway analysis (IPA) recognized a number of new targets and downstream effectors influencing BCs. Of note, genomic, epigenomic, transcriptional, and hormonal anomalies observed in human primary breast tumors were qualitatively similar in pertinent BC cell lines. These findings identify the functional correlation between dysregulated epigenetic enzymes and estrogen/E2 accumulation in human breast tumors, providing the molecular insights into more targeted therapeutic approaches involving the inhibition of HDACs for combating this life-threatening disease.
Temperature-pressure phase diagram of the Kitaev hyperhoneycomb iridate β−Li2IrO3 is explored using magnetization, thermal expansion, magnetostriction, and muon spin rotation measurements, as well as ...single-crystal x-ray diffraction under pressure and ab initio calculations. The Néel temperature of β−Li2IrO3 increases with the slope of 0.9 K/GPa upon initial compression, but the reduction in the polarization field Hc reflects a growing instability of the incommensurate order. At 1.4 GPa, the ordered state breaks down upon a first-order transition, giving way to a new ground state marked by the coexistence of dynamically correlated and frozen spins. This partial freezing in the absence of any conspicuous structural defects may indicate the classical nature of the resulting pressure-induced spin liquid, an observation paralleled to the increase in the nearest-neighbor off-diagonal exchange Γ under pressure.
Steroid hormone biosynthesis in steroidogenic cells is regulated through trophic hormone activation of protein kinase A (PKA) signaling pathways. However, many examples of the regulation of steroid ...synthesis via pathways other than the PKA pathway have been documented. In some cases these pathways act independently of PKA activation whereas in other cases, they act synergistically with it. The current understanding of additional signaling pathways and factors, such as the protein kinase C pathway, arachidonic acid metabolites, growth factors, chloride ion, the calcium messenger system, and others capable of regulating/modulating steroid hormone biosynthesis, and in many cases steroidogenic acute regulatory protein expression, are discussed in this review.
A newly designed composition of non-equiatomic Fe
40
Cr
25
Ni
15
Al
15
Co
5
medium-entropy alloy (MEA) was produced by induction melting (IM). The as-cast alloy was found to consist of a two-phase ...microstructure of BCC (2.87 ± 0.01 Å) and ordered B2 (2.88 ± 0.02 Å) type phases. The structures of these phases were confirmed through X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. It was observed that the Ni-Al-enriched ordered B2 phase of cuboidal shapes (~ 100 to 200 nm) is homogeneously distributed in Fe-Cr-rich BCC matrix with a cube-on-cube orientation relationship. The formation of the columnar dendrites (width 50 to 100
μ
m) was identified through optical microscopy (OM). The structural and microstructural stability of the alloy was investigated by heat-treating the alloy through different schedules. Heat-treated samples at different temperatures (< 1273 K) exhibit a similar type of two-phase microstructure with columnar dendrites. However, compositional rearrangement takes place during long time exposure to develop polymorphically related phases. The alloy was observed to possess a high compressive yield strength and hardness,
i.e.
, ~ 1047 MPa and 391 ± 9 HV, respectively, at room temperature. Heat-treated samples at 600 °C and 900 °C (873 K and 1173 K) showed an increase in yield strength and ultimate strength with a significant increase in plasticity due to the increase in volume fraction of B2 phase and softening of the BCC matrix phase. The thermal stability and high strength of this alloy may open new avenues for high-temperature applications.
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