Face-centered cubic (fcc) HEAs, particularly the typical FeCoNiCrMn HEA, are promising for cryogenic applications but generally exhibit relatively low strength at ambient temperature, which limits ...their widespread uses. In this work, we present a systematic study of enhancing simultaneously the strength and ductility of FeCoNiCrMn HEAs via tailoring the phase stability and stacking fault energy (SFE). It was found that in Fe20CoxNi40-xCr20Mn20 (x = 20–30 at.%) HEAs, with the increase of Co, the SFE was gradually decreased and another hcp (hexagonal close-packed) phase was eventually formed in the alloy containing 28 at.% Co. As a result, the deformation mode changes from dislocation glide to mechanical twinning, then to γfcc → εhcp martensitic transformation. Our analysis indicates that the small critical shear stress for twinning resulted from the reduced SFE provides a steady strain hardening rate in a wide strain regime and postpones the plastic instability, eventually leading to the concurrent enhancement in the tensile strength and ductility. Our results not only shed lights on understanding of the effects of SFE on the mechanical properties, but also have important implications on the development of HEAs with a unique combination of high strength and large ductility.
•Increase of the Co content decreases the SFE and phase stability of FeCoNiCrMn alloy.•TRIP effects were achieved with the increase of Co content.•Increase of Co enhances the strength and ductility simultaneously.•Effects of the SFE on deformation mechanism were explored.
We design, fabricate, and demonstrate a silicon nitride (Si(3)N(4)) multilayer platform optimized for low-loss and compact multilayer photonic integrated circuits. The designed platform, with 200 nm ...thick waveguide core and 700 nm interlayer gap, is compatible for active thermal tuning and applicable to realizing compact photonic devices such as arrayed waveguide gratings (AWGs). We achieve ultra-low loss vertical couplers with 0.01 dB coupling loss, multilayer crossing loss of 0.167 dB at 90° crossing angle, 50 μm bending radius, 100 × 2 μm(2) footprint, lateral misalignment tolerance up to 400 nm, and less than -52 dB interlayer crosstalk at 1550 nm wavelength. Based on the designed platform, we demonstrate a 27 × 32 × 2 multilayer star coupler.
Abstract
We present the discovery and timing results of four pulsars discovered in a pilot survey at intermediate Galactic latitudes with the Five-hundred Aperture Spherical Telescope (FAST). Among ...these pulsars, two belong to the category of millisecond pulsars (MSPs) with spin periods of less than 20 ms. The other two fall under the classification of “mildly recycled” pulsars, with massive white dwarfs as companions. Remarkably, this small survey, covering an area of 4.7 deg
2
, led to the discovery of four recycled pulsars. Such success underscores the immense potential of future surveys at intermediate Galactic latitudes. In order to assess the potential yield of MSPs, we conducted population simulations and found that both FAST and Parkes new phased array feed surveys, focusing on intermediate Galactic latitudes, have the capacity to uncover several hundred new MSPs.
Photocatalytic selective organic transformations provide an efficient synthetic alternative for several industrially relevant chemicals, using solar rather than thermal energy. However, in most ...cases, photocatalytic organic reaction systems involve only reductive or oxidative pathways with the aid of sacrificial reagents as efficient electron acceptors or donors, thus limiting the economic added value. Recently, merging selective organic reductions and oxidations in a dual-functional photocatalytic reaction system has been presented to address this limitation. In this coupled reaction system, both the photogenerated electrons and holes can be simultaneously utilized to produce value-added products, make the overall process more valuable from the economic perspective. In this review, the development of dual-functional photocatalytic organic synthesis is systemically summarized. Particular emphasis is paid to merging selective organic oxidation and reduction reactions and coupling selective organic transformations with chemical fuel generation (e.g., H2, CO). Also, a personal perspective on future developments in this field is provided. Although still in its infancy, it is expected that this dual-functional technology offers opportunities to develop the next-generation selective organic transformation processes that meet the stringent economic, societal, and ecological expectations.
We present extensive photometry at ultraviolet (UV), optical, and near-infrared (NIR) wavelengths, as well as dense sampling of optical spectra, for the normal Type Ia supernova (SN Ia) 2005cf. The ...optical photometry, performed at eight different telescopes, shows a 1σ scatter of lsim0.03 mag after proper corrections for the instrument responses. From the well-sampled light curves, we find that SN 2005cf reached a B-band maximum at 13.63 ± 0.02 mag, with an observed luminosity decline rate Δm 15(B) = 1.05 ± 0.03 mag. The correlations between the decline rate and various color indexes, recalibrated on the basis of an expanded SN Ia sample, yield a consistent estimate for the host-galaxy reddening of SN 2005cf, E(B – V)host = 0.10 ± 0.03 mag. The UV photometry was obtained with the Hubble Space Telescope and the Swift Ultraviolet/Optical Telescope, and the results match each other to within 0.1-0.2 mag. The UV light curves show similar evolution to the broadband U, with an exception in the 2000-2500 Å spectral range (corresponding to the F220W/uvm2 filters), where the light curve appears broader and much fainter than that on either side (likely owing to the intrinsic spectral evolution). Combining the UV data with the ground-based optical and NIR data, we establish the generic UV-optical-NIR bolometric light curve for SN 2005cf and derive the bolometric corrections in the absence of UV and/or NIR data. The overall spectral evolution of SN 2005cf is similar to that of a normal SN Ia, but with variety in the strength and profile of the main feature lines. The spectra at early times displayed strong, high-velocity (HV) features in the Ca II H&K doublet and NIR triplet, which were distinctly detached from the photosphere (v ≈ 10,000 km s–1) at a velocity ranging from 20,000 to 25,000 km s–1. One interesting feature is the flat-bottomed absorption observed near 6000 Å in the earliest spectrum, which rapidly evolved into a triangular shape and then became a normal Si II λ6355 absorption profile at about one week before maximum brightness. This premaximum spectral evolution is perhaps due to the blending of the Si IIλ6355 at photospheric velocity and another HV absorption component (e.g., an Si II shell at a velocity ~18,000 km s–1) in the outer ejecta, and may be common in other normal SNe Ia. The possible origin of the HV absorption features is briefly discussed.
ABSTRACT
We present the first measurement of pulse scattering close to the eclipse region of PSR B1957+20, which is in a compact binary system with a low-mass star. We measured pulse scattering ...time-scales up to 0.2 ms close to the eclipse and showed that it scales with the dispersion measure (DM) excess roughly as τ ∝ ΔDM2. Our observations provide the first evidence of strong scattering due to multipath propagation effects in the eclipsing material. We show that Kolmogorov turbulence in the eclipsing material with an inner scale of ∼100 m and an outer scale of the size of the eclipse region can naturally explain the observation. Our results show that the eclipsing material in such systems can be highly turbulent and suggest that scattering is one of the main eclipsing mechanisms at around 1.4 GHz.
Is reproductive aging in granulosa cells associated with markers of ovarian reserve?
Age acceleration was associated with anti-Mullerian hormone (AMH) levels, antral follicle count (AFC), oocyte ...yield and maturity, and the number of successfully fertilized embryos.
The rate of reproductive aging varies among women of the same age. DNA methylation can be used to predict epigenetic age in a variety of tissues.
This was a cross-sectional study of 70 women at the time of oocyte retrieval.
The 70 participants were recruited for this study at an academic medical center and they provided follicular fluid samples at the time of oocyte retrieval. Granulosa cells were isolated and assessed on the MethylationEPIC array. Linear regression was used to evaluate the associations between DNA methylation-based age predictions from granulosa cells and chronological age. Age acceleration was calculated as the residual of regressing DNA methylation-based age on chronological age. Linear regressions were used to determine the associations between age acceleration and markers of ovarian reserve and IVF cycle outcomes.
Participants were a mean of 36.7 ± 3.9 years old. In regards to race, 54% were white, 19% were African American and 27% were of another background. Age acceleration was normally distributed and not associated with chronological age. Age acceleration was negatively associated with AMH levels (t = -3.1, P = 0.003) and AFC (t = -4.0, P = 0.0001), such that women with a higher age acceleration had a lower ovarian reserve. Age acceleration was also negatively correlated with the total number of oocytes retrieved (t = -3.9, P = 0.0002), the number of mature oocytes (t = -3.8, P = 0.0003) and the number of fertilized oocytes or two-pronuclear oocytes (t = -2.8, P = 0.008) in the main analysis.
This study used pooled follicular fluid, which does not allow for the investigation of individual follicles. Infertility patients may also be different from the general population, but, as we used granulosa cells, the participants had to be from an IVF population.
This study demonstrated that epigenetic age and age acceleration can be calculated from granulosa cells collected at the time of oocyte retrieval. GrimAge most strongly predicted chronological age, and GrimAge acceleration was associated with baseline and cycle characteristics as well as cycle outcomes, which indicates its potential clinical relevance in evaluating both oocyte quantity and quality.
This study was supported by the National Institutes of Health (UL1TR002378) and the Building Interdisciplinary Research Careers in Women's Health Program (K12HD085850) to A.K.K. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. The funding source had no role in any aspect of this study. J.B.S. serves as Vice Chair for the American Society for Reproductive Medicine Education Committee, is a Medical Committee Advisor for the Jewish Fertility Foundation and works with Jscreen. J.B.S. has received funding from Georgia Clinical Translational Research Alliance. H.S.H., J.B.S. and A.K.S. have received NIH funding for other projects. A.K.K., S.A.G., S.G., Q.S.K., L.J.M. and W.S. have no conflicts of interest.
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Experimental investigations on atmospheric steam-water two-phase flow regimes and transitions in two transparent narrow rectangular channels with cross-section areas of 1 mm × 20 mm and 2 mm × 20 mm ...were carried out under conditions of 0.007 ≤ Jf ≤ 0.27 m s−1, 0.05 ≤ Jg ≤ 65.2 m s−1, 0 < q ≤ 18 kW m−2. Four flow patterns were observed in narrow rectangular horizontal channels under heated condition, i.e., bubbly flow, slug flow, churn flow and annular flow. New dryout phenomenon of annular flow was observed under high wall heat flux conditions. The liquid phase occupies half of the middle of narrow channel above the bottom rectangular plate. Below the top plate, liquid phase is concentrated to a slender streamline in the middle of upper half narrow channel by high speed steam flow. For the flow regime transitions, the critical values of void fraction for transitions from bubbly flow to slug flow, slug flow to churn flow, and churn flow to annular flow in narrow rectangular horizontal channels under heated condition are 0.7, 0.8 and 0.9, respectively. The heat flux decays flow regime transitions because the generated bubbles from heated wall surfaces promote the separation of bubbles in the upstream and downstream. Flow regime transitions under larger surface tension condition need greater vapor phase velocities to disturb the mainflow. In a general, new flow regime transition criteria were developed and can present excellent predictions for the present data of flow regimes and transitions in narrow rectangular horizontal channels under heated condition.
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•Flow pattern data of steam-water two-phase in narrow rectangular channels are obtained.•The effect of heat flux on flow pattern transition is analyzed.•New flow regime transition criterias in narrow rectangular horizontal channels are developed.
We report on uniform emission intensity profile, uniform propagation constant silicon gratings for beam steering application with ultra-sharp instantaneous field-of-view (IFOV). To achieve uniform ...emission intensity across relatively long emission length, we designed a custom grating with varying Si
N
width and duty cycle while maintaining a uniform propagation constant for relatively narrow divergence emission pattern. We designed and fabricated the custom Si
N
/Si grating with the varying Si
N
width/duty cycle together with the reference Si
N
/Si grating with a constant 50:50 duty cycle. The custom grating demonstrated the beam steering angle value of 6.6° by sweeping wavelength between 1530 nm and 1575 nm with the emission length over 1 mm. The measured IFOV based on the 3-dB beamwidth values of the far field patterns for the TE polarization are 0.10° and 0.75° for the custom grating and for the reference grating, respectively. The custom grating also indicates mode-selective behavior due to the perturbation of propagation constant for input modes other than TE polarization. The measured TE-mode to TM-mode suppression ratio for the custom grating is approximately 8.2 dB peak-to-peak measured at far field.
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