In this work, a 316L stainless steel to Inconel 625 functionally graded material (FGM) was built using different deposition strategies (named as direct and smooth-type interfaces) by Twin-Wire and ...Arc Additive Manufacturing (T-WAAM). This combination of materials is of interest in chemical plants, oil & gas, and nuclear applications, where high corrosion and wear resistance are essential requirements. Although these properties are superior in Inconel 625, replacing Inconel with stainless steel in strategic regions of structural components can reduce the overall costs and parts’ weight. Both direct and smooth transition interfaces were tested and characterized. Microscopic analysis revealed that each interface and the as-built samples had an austenitic matrix, and every sample was well bonded and free of defects. Different types of microstructures evolved at the interfaces due to distinct gradients in composition. Synchrotron X-ray diffraction measurements showed that the smooth-gradient produced secondary phases, such as δ-phase (Ni3Nb) and carbides, that were not present with the direct interface strategy. Overall, the properties were superior in the FGM with a direct interface, which experienced higher strengths and elongations upon failure. Moreover, neutron diffraction measurements revealed that lower residual stresses developed in the direct interface FGM than in the smooth gradient FGM.
Background
Dysregulation of the hypothalamic‐pituitary‐adrenal (HPA) axis is associated with poor physical and mental health. Early‐life adversity may dysregulate cortisol response to subsequent ...stress. This study examines the association between patterns of maternal behavior and infant stress response to a challenge. Specifically, we test whether infant exposure to unpredictable maternal sensory signals is related to the cortisol response to a painful stressor.
Method
Participants were 102 mothers and their children enrolled in a longitudinal study. Patterns of maternal sensory signals were evaluated at 6 and 12 months during a 10‐min mother–infant play episode. Entropy rate was calculated as a quantitative measure of the degree of unpredictability of maternal sensory signals (visual, auditory, and tactile) exhibited during the play episode. Infant saliva samples were collected for cortisol analysis before and after inoculation at 12 months.
Results
Unpredictable patterns of maternal sensory signals were associated with a blunted infant cortisol response to a painful stressor. This relation persisted after evaluation of covariates including maternal sensitivity and maternal psychological distress.
Conclusions
This study provides evidence that unpredictable patterns of maternal sensory signals are one process through which caregiving affects the function of infant stress response systems.
The SERS performance of Ag-ZnO-NR 3D substrates strongly depends on the radius, length, and density of ZnO NRs as well as the thickness of Ag layer. The refractive index of dielectric materials in ...nanocomposited 3D SERS substrates is capable of tuning the LSPR frequency as well.
Display omitted
•LSPR frequency is tunable by changing ZnO-NR radius and Ag-layer thickness.•Optimized length of Ag-ZnO-NR is at μn-scale and the density is 83/μm2.•Refractive index is another parameter of optimizing the 3D SERS substrates.•Diploe LSPR of Ag-ZnO-NRs splits into high- and low-frequency two branches.•Low-frequency LSPR is predominant in enhancing Raman signals.
Surface enhanced Raman spectroscopy (SERS) is becoming an effective method of detecting organic molecules, and three-dimensional (3D) SERS substrates are promising in practical applications. To optimizing 3D SERS substrates, the extinction spectra and local electromagnetic fields of Ag-decorated ZnO nanorods (Ag-ZnO-NR) were studied by a finite-difference time-domain (FDTD) method. The diploe local surface plasmonic resonance (LSPR) was found to split into high- and low-frequency two branches, in which the low-frequency mode is predominant in contributing to the Raman enhancement, while the ZnO-NR radius and Ag-layer thickness play important roles in tuning the LSPR frequencies. Both of high- and low-frequency LSPRs were enhanced with the increase in the Ag-ZnO-NR length while the intensity of local electromagnetic field depends on the Ag-ZnO-NR density. The FDTD results were discussed with a comparison to the experimental data obtained from flower-like Ag-ZnO-NR 3D SERS substrates. In addition, the extinction spectra of Ag nanotube and Ag-decorated TiO2 and SiO2 nanorods were calculated and the refractive index of dielectric materials was found to be capable of tuning the LSPR of 3D SERS substrates as well. The principle revealed in this work is helpful for design and optimization of 3D SERS substrates.
Precipitation of Ni4Ti3 plays a critical role in determining the martensitic transformation path and temperature in Ni-Ti shape memory alloys. In this study, the equilibrium shape of a coherent ...Ni4Ti3 precipitate and the concentration and stress fields around it are determined quantitatively using the phase field method. Most recent experimental data on lattice parameters, elastic constants, precipitate-matrix orientation relationship and thermodynamic database are used as model inputs. The effects of the concentration and stress fields on subsequent martensitic transformations are analyzed through interaction energy between a nucleating martensitic particle and the existing microstructure. Results indicate that R-phase formation prior to B19a super(2) phase could be attributed to both direct elastic interaction and stress-induced spatial variation in concentration near Ni4Ti3 precipitates. The preferred nucleation sites for the R-phase are close to the broad side of the lenticular-shaped Ni4Ti3 precipitates, where tension normal to the habit plane is highest, and Ni concentration is lowest.
The superelasticity and shape memory effect of shape memory alloys originate from martensitic transformations (MT) that produce self-accommodated polydomain structures. In order to understand the ...formation mechanism of various domain patterns, a phase field model of cubic to orthorhombic MT in NiTiPt and NiTiCu is formulated, through which microstructure evolutions dominated by long-range elastic interactions are simulated. A rich variety of morphological patterns are predicted and analyzed. In particular, autocatalytic events leading to multi-variant “pyramidal triangular” and “nested triangular” configurations in NiTiCu are revealed. These morphological patterns are beyond the reach of the classical phenomenological theory of martensitic crystallography (PTMC). The simulation predictions agree well with experimental observations. By distinguishing deformation variant from orientation variant, the theoretical connection and distinction between PTMC and phase field microelasticity theory are discussed, and their predictions are compared with experimental observations.
Abstract Acid-sensing ion channels (ASICs), the members of the epithelial sodium channel/degenerin (ENaC/DEG) superfamily, are proton-gated voltage-insensitive cation channels. Six ASIC subunits have ...been identified and characterized in the mammalian nervous system so far. Of these subunits, ASIC3 has been shown to be predominantly expressed in the peripheral nervous system of rodents and implicated in mechnosensation, chemosensation and pain perception. Little is known on ASIC3 in the brain. We thus employed reverse transcription–polymerase chain reaction (RT-PCR) and Western blot to examine the expression of ASIC3 in various rat brain regions, including hippocampus, amygdala, caudate putamen, prefrontal cortex, and hypothalamus. Specific attention was paid to the distribution of ASIC3 in the hypothalamus of rats by using immunohistochemistry. ASIC3 immunoreactivity showed a widespread pattern throughout the hypothalamus, with the highest density in paraventricular nucleus, supraoptic nucleus, suprachiasmatic nucleus, arcuate nucleus, dorsomedial nucleus, median preoptic nucleus, ventromedial preoptic nucleus, and dorsal tuberomammillary nucleus. This study may contribute to the understanding of ASIC3 functions in the CNS.
Lithium-sulfur batteries discharge via the transformation of solid sulfur to solid lithium sulfide via the formation of several polysulfide species that have only been observed in solution. Reported ...here is the first experimental phase diagram of a S
-Li
S-electrolyte system, which is shown to be a practical tool to determine the solution composition and formation of solid (S
and Li
S) phases in lithium-sulfur batteries. The phase diagram is constructed by the combination of measurements of the total sulfur concentration S
and average oxidation state (S
) of polysulfide solutions prepared by reaction of S
and Li
S. The phase diagram is used to predict the equilibrium discharge/charge profile of lithium-sulfur batteries as a function of the amount of electrolyte and the onset of precipitation and dissolution of solid products. High energy batteries should operate with a minimum amount of electrolyte, where both solid S
and Li
S will be present during most of the charge and discharge of the cell, in which case we predict the observation of only one voltage plateau, instead of the two voltage plateaus commonly reported.
Increased expression of HBEGF in estrogen receptor-negative breast tumors is correlated with enhanced metastasis to distant organ sites and more rapid disease recurrence upon removal of the primary ...tumor. Our previous work has demonstrated a paracrine loop between breast cancer cells and macrophages in which the tumor cells are capable of stimulating macrophages through the secretion of colony-stimulating factor-1 while the tumor-associated macrophages (TAMs), in turn, aid in tumor cell invasion by secreting epidermal growth factor. To determine how the autocrine expression of epidermal growth factor receptor (EGFR) ligands by carcinoma cells would affect this paracrine loop mechanism, and in particular whether tumor cell invasion depends on spatial ligand gradients generated by TAMs, we generated cell lines with increased HBEGF expression. We found that autocrine HBEGF expression enhanced in vivo intravasation and metastasis and resulted in a novel phenomenon in which macrophages were no longer required for in vivo invasion of breast cancer cells. In vitro studies revealed that expression of HBEGF enhanced invadopodium formation, thus providing a mechanism for cell autonomous invasion. The increased invadopodium formation was directly dependent on EGFR signaling, as demonstrated by a rapid decrease in invadopodia upon inhibition of autocrine HBEGF/EGFR signaling as well as inhibition of signaling downstream of EGFR activation. HBEGF expression also resulted in enhanced invadopodium function via upregulation of matrix metalloprotease 2 (MMP2) and MMP9 expression levels. We conclude that high levels of HBEGF expression can short-circuit the tumor cell/macrophage paracrine invasion loop, resulting in enhanced tumor invasion that is independent of macrophage signaling.
One of the most effective ways to improve reactive wetting of dual phase (DP) steels during galvanizing process is annealing under relatively high oxygen partial pressure. This annealing process can ...lead to internal oxide formation rather than external ones. Since these oxides are mostly observed in grain boundaries (GBs), their presence could influence GB-related phenomena such as liquid metal embrittlement (LME) cracking during further manufacturing processes such as resistance spot welding (RSW). The present work has shown that internal oxides located at GBs assisted LME crack formation during RSW of DP steel. Two types of LME cracks were observed in the shoulder and center of the weld. It has been shown that at the initial stages of welding time, LME cracks initiate in the shoulder of the nugget by the Zn diffusion into oxide-bearing GBs. As welding time continues, higher temperatures and tensile stresses are applied to the steel sheets which allow center cracks to be formed more easily due to the presence of oxides which degrade the GBs.
PDF
