Pressure effects on the heavy-fermion antiferromagnet CeAuSb2

The f-electron compound CeAuSb2, which crystallizes in the ZrCuSi2-type tetragonal structure, orders antiferromagnetically between 5 and 6.8 K, where the antiferromagnetic transition temperature T_N depends on the occupancy of the Au site. Here we report the electrical resistivity and heat capacity of a high-quality crystal CeAuSb2 with T_N of 6.8 K, the highest for this compound. The magnetic transition temperature is initially suppressed with pressure, but is intercepted by a new magnetic state above 2.1 GPa. The new phase shows a dome shape with pressure and coexists with another phase at pressures higher than 4.7 GPa. The electrical resistivity shows a T^2 Fermi liquids behavior in the complex magnetic state, and the residual resistivity and the T^2 resistivity coefficient increases with pressure, suggesting the possibility of a magnetic quantum critical point at a higher pressure.Comment: 5 pages, 5 firure

Conjugate field and fluctuation-dissipation relation for the dynamic phase transition in the two-dimensional kinetic Ising model

The two-dimensional kinetic Ising model, when exposed to an oscillating applied magnetic field, has been shown to exhibit a nonequilibrium, second-order dynamic phase transition (DPT), whose order parameter Q is the period-averaged magnetization. It has been established that this DPT falls in the same universality class as the equilibrium phase transition in the two-dimensional Ising model in zero applied field. Here we study for the first time the scaling of the dynamic order parameter with respect to a nonzero, period-averaged, magnetic `bias' field, H_b, for a DPT produced by a square-wave applied field. We find evidence that the scaling exponent, \delta_d, of H_b at the critical period of the DPT is equal to the exponent for the critical isotherm, \delta_e, in the equilibrium Ising model. This implies that H_b is a significant component of the field conjugate to Q. A finite-size scaling analysis of the dynamic order parameter above the critical period provides further support for this result. We also demonstrate numerically that, for a range of periods and values of H_b in the critical region, a fluctuation-dissipation relation (FDR), with an effective temperature T_{eff}(T, P, H_0) depending on the period, and possibly the temperature and field amplitude, holds for the variables Q and H_b. This FDR justifies the use of the scaled variance of Q as a proxy for the nonequilibrium susceptibility, \partial / \partial H_b, in the critical region.Comment: revised version; 31 pages, 12 figures; accepted by Phys. Rev.

Effects of pressure on the ferromagnetic state of the CDW compound SmNiC2

We report the pressure response of charge-density-wave (CDW) and ferromagnetic (FM) phases of the rare-earth intermetallic SmNiC2 up to 5.5 GPa. The CDW transition temperature (T_{CDW}), which is reflected as a sharp inflection in the electrical resistivity, is almost independent of pressure up to 2.18 GPa but is strongly enhanced at higher pressures, increasing from 155.7 K at 2.2 GPa to 279.3 K at 5.5 GPa. Commensurate with the sharp increase in T_{CDW}, the first-order FM phase transition, which decreases with applied pressure, bifurcates into the upper (T_{M1}) and lower (T_c) phase transitions and the lower transition changes its nature to second order above 2.18 GPa. Enhancement both in the residual resistivity and the Fermi-liquid T^2 coefficient A near 3.8 GPa suggests abundant magnetic quantum fluctuations that arise from the possible presence of a FM quantum critical point.Comment: 5 pages, 5 figure

A 0.5GHz 0.35mW LDO-Powered Constant-Slope Phase Interpolator with 0.22% INL

Clock generators are an essential and critical building block of any communication link, whether it be wired or wireless, and they are increasingly critical given the push for lower I/O power and higher bandwidth in Systems-on-Chip (SoCs) for the Internet-of-Things (IoT). One recurrent issue with clock generators is multiple-phase generation, especially for low-power applications; several methods of phase generation have been proposed, one of which is phase interpolation. We propose a phase interpolator (PI) that employs the concept of constant-slope operation. Consequently, a low-power highly-linear operation is coupled with the wide dynamic range (i.e., phase wrapping) capabilities of a PI. Furthermore, the PI is powered by a low-dropout regulator (LDO) supporting fast transient operation. Implemented in 65-nm CMOS technology, it consumes 350μ W at a 1.2-V supply and a 0.5-GHz clock; it achieves energy efficiency 4× -15× lower than state-of-the-art (SoA) digital-to-time converters (DTCs) and an integral non-linearity (INL) of 2.5× -3.1× better than SoA PIs, striking a good balance between linearity and energy efficiency

Collagen and bone morphogenetic protein-2 functionalized hydroxyapatite scaffolds induce osteogenic differentiation in human adipose-derived stem cells

Surface modification is one important way to fabricate successful biocompatible materials in bone tissue engineering. Hydroxyapatite (HAp) materials have received considerable attention as suitable bioceramics for manufacturing osseous implants because of their similarity to bone mineral in terms of chemical composition. In this study, the surface of porous HAp scaffold was modified by collagen treatment and bone morphogenetic protein‐2 (BMP‐2) conjugation. The surface modification did not affect the HAp scaffold's bulk properties. No significant difference in compressive strength was found among different scaffolds, with HAp, collagen modified HAp, and collagen–BMP‐2‐functionalized HAp having compressive strengths of 45.8 ± 3.12, 51.2 ± 4.09, and 50.7 ± 3.98 MPa, respectively. In vitro studies were performed to compare adhesion and osteogenic differentiation between human adipose‐derived stem cells (hADSCs) with modified surfaces and those unmodified HAp surfaces. Collagen or BMP‐2 alone was insufficient and that both collagen and BMP‐2 are necessary to get the desired results. The findings suggest the possibility of using three‐dimensional HAp scaffold treated with gold‐standard collagen coating and highly researched BMP‐2 growth factor as a platform to deliver hADSCs. Results of this study could be used to develop treatment strategy for regenerating completely transected models using more synergistic approaches

Type I Migration in a Non-Isothermal Protoplanetary Disk

We calculate rates of Type I migration of protoplanets in a non-isothermal three-dimensional protoplanetary disk, building upon planet-disk models developed in previous work. We find that including the vertical thickness of the disk results in a decrease in the Type I migration rate by a factor of ~2 from a two-dimensional disk. The vertical temperature variation has only a modest effect on migration rates since the torques at the midplane are weighted heavily both because the density and the perturbing potential are maximized at the midplane. However, temperature perturbations resulting from shadowing and illumination at the disk's surface can decrease the migration rate by up to another factor of 2 for planets at the gap-opening threshold at distances where viscous heating is minimal. This would help to resolve the timescale mismatch between the standard core-accretion scenario for planet formation and the survival of planets, and could help explain some of the rich diversity of planetary systems already observed.Comment: 9 pages, 8 figures. Accepted to the Astrophysical Journa

Superconducting energy gap in MgCNi3 single crystals: Point-contact spectroscopy and specific-heat measurements

Specific heat has been measured down to 600 mK and up to 8 Tesla by the highly sensitive AC microcalorimetry on the MgCNi3 single crystals with Tc ~ 7 K. Exponential decay of the electronic specific heat at low temperatures proved that a superconducting energy gap is fully open on the whole Fermi surface, in agreement with our previous magnetic penetration depth measurements on the same crystals. The specific-heat data analysis shows consistently the strong coupling strength 2D/kTc ~ 4. This scenario is supported by the direct gap measurements via the point-contact spectroscopy. Moreover, the spectroscopy measurements show a decrease in the critical temperature at the sample surface accounting for the observed differences of the superfluid density deduced from the measurements by different techniques

A Case Study of Assessing Button Bits Failure through Wavelet Transform Using Rock Drilling Induced Noise Signals

Finding the precise moment of button breakage of bits during drilling, with the experience of drill rig operators is a serious concern for modern vibrant mining industry. This research proposed a new methodology to find the failure of button using the sound generated by rock-bit interactions. The experiment is conducted by the video and sound data recorded during a drilling process in an underground mine, that uses a Sandvik AXERA7 twin boom jumbo drill rig and Polycrystalline diamond (PCD) tapered button bits. Signal analysis techniques such as Fourier transform and Wavelet transform are utilised to analyse the hectic noise signal recorded. The analysed results are shown that Wavelet Transform is much more effective in finding singularity points such as chipping or breakage of a button in compared to the Fourier Transform. The outcome of this analysis, which is the peak intensity at the breakage point, was correlated to the average intensity of the sound wave using moving average method. The results suggest that the noise generated during the drilling process can be used to detect the condition of the drill bit