Anisotropy, disorder, and superconductivity in CeCu2Si2 under high pressure

Resistivity measurements were carried out up to 8 GPa on single crystal and polycrystalline samples of CeCu2Si2 from differing sources in the homogeneity range. The anisotropic response to current direction and small uniaxial stresses was explored, taking advantage of the quasi-hydrostatic environment of the Bridgman anvil cell. It was found that both the superconducting transition temperature Tc and the normal state properties are very sensitive to uniaxial stress, which leads to a shift of the valence instability pressure Pv and a small but significant change in Tc for different orientations with respect to the tetragonal c-axis. Coexistence of superconductivity and residual resistivity close to the Ioffe-Regel limit around 5 GPa provides a compelling argument for the existence of a valence-fluctuation mediated pairing interaction at high pressure in CeCu2Si2.Comment: 12 pages, 7 figure

Performance Evaluation of Reactive Routing Protocols in MANETs in Association with TCP Newreno

We inspect the performance of TCP NewReno protocol for data transfer in Mobile Ad hoc networks (MANETs). Dynamic Source Routing (DSR) protocols and AdHoc On-demand Distance Vector (AODV) are standard reactive routing protocols widely used in MANETs. In addition we also have to consider Transmission Control Protocol (TCP) as essential for MANETs since it is one of the widely used internet protocol for dependable data transmission. TCP has its variants namely TCP Reno, TCP NewReno , TCP Vegas and TCP SACK. In this paper we are evaluating the performance of DSR and AODV in association with TCP Newreno with respect to various parameters such as Average throughput, instant throughput, residual energy, packet delivery ratio. The ns-2 network simulator was used for simulation

Far-infrared optical conductivity of CeCu2Si2

Journal ref.: J. Phys.: Condens. Matter 25, 065602 (2013): We investigated the optical reflectivity of the heavy-fermion metal CeCu2Si2 in the energy range 3 meV - 30 eV for temperatures between 4K - 300K. The results for the charge dynamics indicate a behavior that is expected for the formation of a coherent heavy quasiparticle state: Upon cooling the spectra of the optical conductivity indicate a narrowing of the coherent response. Below temperatures of 30 K a considerable suppression of conductivity evolves below a peak structure at 13 meV. We assign this gap-like feature to strong electron correlations due to the 4f-conduction electron hybridization.Comment: 7 pages, 3 figure

Magnetic fluctuations and superconductivity in Fe pnictides probed by electron spin resonance

The electron spin resonance absorption spectrum of Eu^{2+} ions serves as a probe of the normal and superconducting state in Eu_{0.5}K_{0.5}Fe_2As_2. The spin-lattice relaxation rate 1/T_1^{\rm ESR} obtained from the ESR linewidth exhibits a Korringa-like linear increase with temperature above T_C evidencing a normal Fermi-liquid behavior. Below 45 K deviations from the Korringa-law occur which are ascribed to enhanced magnetic fluctuations within the FeAs layers upon approaching the superconducting transition. Below T_C the spin-lattice relaxation rate 1/T_1^{\rm ESR} follows a T^{1.5}-behavior without the appearance of a coherence peak.Comment: 5 pages, 5 figure

Towards a Characterisation of Emotional Intent During Scripted Scenes Using In-ear Movement Sensors

Theatre provides a unique environment in which to obtain detailed data on social interactions in a controlled and repeatable manner.This work introduces a method for capturing and characterising the underlying emotional intent of performers in a scripted sceneusing in-ear accelerometers. Each scene is acted with different underlying emotional intentions using the theatrical technique ofActioning. The goal of the work is to uncover characteristics in the joint movement patterns that reveal information on the positive ornegative valence of these intentions. Preliminary findings over 3x12 (Covid-19 restricted) non-actor trials suggests people are moreenergetic and more in-sync when using positive versus negative intentions

Characterization of unsaturated flow in dual-porosity granular media

A geological medium made up of uncemented coarse porous rock fragments may be described as a “dual-porosity granular medium” due to the presence of two types of pores; small pores within individual fragments and large pores between the fragments. Crushed stone found in heap leach piles, mine waste, backfills, rock drains, and engineered capillary barrier systems fit this description. Unsaturated flow in a dualporosity granular medium will occur both through the fragments (matrix flow), and on the fragment surfaces (film flow). The relative influence of gravity and capillary forces on these two flow regimes will be largely different. Therefore, unsaturated flow in this type of media is expected to differ from the conventional concepts developed for application to single porosity systems. A test column (30 cm diameter, 100 cm tall) was filled with crushed sandstone (~1.5 - 3 cm diameter) as a dual-porosity granular media. Water entered the column from the top through a point source at a steady rate (8.0 ml/minute) and exited through nine equalarea sections at the bottom of the column. Inflow, outflow from each of the nine sections, weight of the column, temperature (ambient and inside the column), humidity (ambient and inside the column) and barometric pressure were measured at 2 minute intervals in four trials (2-40 days long) under variable conditions. It was found that unsaturated flow in dual-porosity granular media is spatially nonuniform, and likely occurs in the form of narrowly focused discrete pathways. The resulting flow structure limits the matrix saturation of the rock fragments to well below 100%. The distribution of flow was observed to change spontaneously, without any apparent external perturbation. Furthermore, the flow distribution was observed to change in response to external perturbations (inflow interruption, relocation of the inlet, and reducing evaporative loss); however, the occurrence and magnitude of redistribution were not predictable

Characterization of unsaturated flow in dual-porosity granular media

A geological medium made up of uncemented coarse porous rock fragments may be described as a “dual-porosity granular medium” due to the presence of two types of pores; small pores within individual fragments and large pores between the fragments. Crushed stone found in heap leach piles, mine waste, backfills, rock drains, and engineered capillary barrier systems fit this description. Unsaturated flow in a dualporosity granular medium will occur both through the fragments (matrix flow), and on the fragment surfaces (film flow). The relative influence of gravity and capillary forces on these two flow regimes will be largely different. Therefore, unsaturated flow in this type of media is expected to differ from the conventional concepts developed for application to single porosity systems. A test column (30 cm diameter, 100 cm tall) was filled with crushed sandstone (~1.5 - 3 cm diameter) as a dual-porosity granular media. Water entered the column from the top through a point source at a steady rate (8.0 ml/minute) and exited through nine equalarea sections at the bottom of the column. Inflow, outflow from each of the nine sections, weight of the column, temperature (ambient and inside the column), humidity (ambient and inside the column) and barometric pressure were measured at 2 minute intervals in four trials (2-40 days long) under variable conditions. It was found that unsaturated flow in dual-porosity granular media is spatially nonuniform, and likely occurs in the form of narrowly focused discrete pathways. The resulting flow structure limits the matrix saturation of the rock fragments to well below 100%. The distribution of flow was observed to change spontaneously, without any apparent external perturbation. Furthermore, the flow distribution was observed to change in response to external perturbations (inflow interruption, relocation of the inlet, and reducing evaporative loss); however, the occurrence and magnitude of redistribution were not predictable

Electronic Scattering Effects in Europium-Based Iron Pnictides

In a comprehensive study, we investigate the electronic scattering effects in EuFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$ by using Fourier-transform infrared spectroscopy. In spite of the fact that Eu$^{2+}$ local moments order around $T_\text{Eu} \approx 20$\,K, the overall optical response is strikingly similar to the one of the well-known Ba-122 pnictides. The main difference lies within the suppression of the lower spin-density-wave gap feature. By analysing our spectra with a multi-component model, we find that the high-energy feature around 0.7\,eV -- often associated with Hund's rule coupling -- is highly sensitive to the spin-density-wave ordering, this further confirms its direct relationship to the dynamics of itinerant carriers. The same model is also used to investigate the in-plane anisotropy of magnetically detwinned EuFe$_{2}$As$_{2}$ in the antiferromagnetically ordered state, yielding a higher Drude weight and lower scattering rate along the crystallographic $a$-axis. Finally, we analyse the development of the room temperature spectra with isovalent phosphor substitution and highlight changes in the scattering rate of hole-like carriers induced by a Lifshitz transition