Suppressing electron disorder-induced heating of ultracold neutral plasma via optical lattice

Disorder-induced heating (DIH) prevents ultracold neutral plasma into electron strong coupling regime. Here we propose a scheme to suppress electronic DIH via optical lattice. We simulate the evolution dynamics of ultracold neutral plasma constrained by three-dimensional optical lattice using classical molecular dynamics method. The results show that for experimentally achievable condition, electronic DIH is suppressed by a factor of 1.3, and the Coulomb coupling strength can reach to 0.8 which is approaching the strong coupling regime. Suppressing electronic DIH via optical lattice may pave a way for the research of electronic strongly coupled plasma

Formation Damage due to Drilling and Fracturing Fluids and Its Solution for Tight Naturally Fractured Sandstone Reservoirs

Drilling and fracturing fluids can interact with reservoir rock and cause formation damage that impedes hydrocarbon production. Tight sandstone reservoir with well-developed natural fractures has a complex pore structure where pores and pore throats have a wide range of diameters; formation damage in such type of reservoir can be complicated and severe. Reservoir rock samples with a wide range of fracture widths are tested through a multistep coreflood platform, where formation damage caused by the drilling and/or fracturing fluid is quantitatively evaluated and systematically studied. To further mitigate this damage, an acidic treating fluid is screened and evaluated using the same coreflood platform. Experimental results indicate that the drilling fluid causes the major damage, and the chosen treating fluid can enhance rock permeability both effectively and efficiently at least at the room temperature with the overburden pressure

Observation of Colossal Terahertz Magnetoresistance and Magnetocapacitance in a Perovskite Manganite

We have studied the terahertz response of a bulk single crystal of La$_{0.875}$Sr$_{0.125}$MnO$_3$ at around its Curie temperature, observing large changes in the real and imaginary parts of the optical conductivity as a function of magnetic field. The terahertz resistance and capacitance extracted from the optical conductivity rapidly increased with increasing magnetic field and did not show any sign of saturation up to 6 T, reaching 60% and 15%, respectively, at 180 K. The observed terahertz colossal magnetoresistance and magnetocapacitance effects can be qualitatively explained by using a two-component model that assumes the coexistence of two phases with vastly different conductivities. These results demonstrate the potential use of perovskite manganites for developing efficient terahertz devices based on magnetic modulations of the amplitude and phase of terahertz waves.Comment: 7 pages, 6 figure

Right ventricular outflow tract obstruction caused by right ventricular fibroma in a 5-month-old infant: a case report

Abstract Background Cardiac fibroma is rarely encountered in children, and even more rare in neonates. We herein report a case of a 5-month-old female with severe right ventricular outflow tract obstruction caused by a large right ventricle fibroma that was successfully surgically resected. Case presentation This report describes the case of a 5-month-old female infant with a large mass measuring 26 × 22 mm in the right ventricle cured successfully with surgery. Physical examination revealed a harsh S1 sound and a grade IV systolic murmur on the left sternal border. Surgical resection was indicated due to severe right ventricular outflow tract obstruction and further follow-up evaluation was uneventful. Conclusion The surgical procedure to excise such a large cardiac fibroma in a 5-month-old infant is feasible and safe

Microstructure and mechanical properties of a multilayered CoCrNi/Ti coating with varying crystal structure

Medium entropy alloys (MEAs), such as CoCrNi, have been demonstrated to combine high hardness and excellent ductility, thereby outperforming many high entropy alloys reported to date. In this study, a multilayered CoCrNi/Ti coating was deposited onto a M2 steel substrate using a DC magnetron sputtering system. Columnar grains can be observed in both the CoCrNi and Ti layers. A high density of periodic twin boundaries, aligned in a direction normal to the growth direction, was also observed within the columnar CoCrNi grains. Moreover, different crystal structures were identified for different CoCrNi layers. The outermost CoCrNi layer exhibited a FCC structure, whilst in contrast, both the middle and bottom CoCrNi layers exhibited a BCC structure. It was assumed that Shockley partial dislocations were responsible for the FCC to BCC transition occurring in both the bottom and middle CoCrNi layers. A high hardness of ~7.6 GPa and elastic modulus of ~233 GPa were determined for this multilayered coating by nanoindentation testing. Further, extraordinary damage tolerance was found in the multilayered CoCrNi/Ti coating under indentation loading. The steady shear banding behaviour during deformation may benefit energy dissipation and promote structural plasticity

The microstructure and mechanical properties of thin film Ni(Ti) nanocomposite coatings containing both oxygen and nitrogen

Thin film Ni(Ti) nanocomposite coatings, containing both oxygen and nitrogen, were deposited onto tool steel substrates using a reactive DC magnetron sputtering system at room temperature. A NiTi alloy target (Ni/Ti = 80/20 at.%) was used during deposition. The evolution of the microstructure of these coatings under varying N2 gas flow rate was studied by focused ion beam microscopy and transmission electron microscopy. A clear structural change, from columnar grains to very fine equiaxed grains with a considerable level of porosity, was evidenced. X-ray diffraction, together with X-ray photoelectron spectroscopy, was employed to determine the crystal structure and composition of these coatings. Analysis of these data revealed that the nanocomposite coatings were composed of a Ni matrix with nanocrystalline TiN, embedded together with amorphous TiO2. Nanoindentation results demonstrated that Ni dissolved with ~ 15 at.% Ti solid solution possesses higher values of elastic modulus, hardness and better resistance to both elastic and plastic deformation than the Ni(Ti) nanocomposite coatings containing higher concentrations of both nitrogen and oxygen. The presence of porosity in the nanocomposite coatings was expected to worsen the mechanical properties of these coatings, while the amorphous TiO2 phase may help facilitate grain boundary motion. © 2016 Elsevier B.V

Medium entropy alloy CoCrNi coatings: Enhancing hardness and damage-tolerance through a nanotwinned structuring

Medium entropy alloys (MEA) are defined as alloys consisting of three equiatomic elements, such as CoCrNi. MEAs are reported to have superior mechanical properties and high thermodynamic stability, as well as excellent fracture toughness at cryogenic temperatures. Here, we investigate a series of equiatomic medium entropy alloy coatings, containing three elements, Co, Cr, Ni. These coatings were deposited onto M2 steel substrates with a range of coating thicknesses using a DC magnetron sputtering system using a CoCrNi alloy target (1:1:1 at.%). The microstructure and mechanical properties were examined by a number of characterization techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM) and nanoindentation. XRD analysis showed that the coatings were dominated by a fcc CoCrNi phase, with a smaller amount of hcp Co. TEM analysis demonstrated that the elongated grains contained a high density of {111} nanotwins. In addition, the residual stresses in the coatings were analysed using X-ray diffraction by adopting the conventional sin2ψ method. A high hardness value, ~ 10 GPa, was determined by nanoindentation of these coatings. Exceptional damage-tolerance was also found in these coatings under contact loading. It is believed that the nanotwinned structure is responsible for the high hardness and damage tolerance observed in the new coatings