Amplitude dynamics of charge density wave in LaTe3_3: theoretical description of pump-probe experiments

We formulate a dynamical model to describe a photo-induced charge density wave (CDW) quench transition and apply it to recent multi-probe experiments on LaTe$_3$ [A. Zong et al., Nat. Phys. 15, 27 (2019)]. Our approach relies on coupled time-dependent Ginzburg-Landau equations tracking two order parameters that represent the modulations of the electronic density and the ionic positions. We aim at describing the amplitude of the order parameters under the assumption that they are homogeneous in space. This description is supplemented by a three-temperature model, which treats separately the electronic temperature, temperature of the lattice phonons with stronger couplings to the electronic subsystem, and temperature of all other phonons. The broad scope of available data for LaTe$_3$ and similar materials as well as the synergy between different time-resolved spectroscopies allow us to extract model parameters. The resulting calculations are in good agreement with ultra-fast electron diffraction experiments, reproducing qualitative and quantitative features of the CDW amplitude evolution during the initial few picoseconds after photoexcitation.Comment: 21 pages, 14 figures; this version is almost identical to the published version; comparing to the earlier arXiv submission, current version contains a new figure (Fig.10), and a broader discussion of theoretical results and approximation

Experimental and Numerical Investigation on Laminar Pipe Flow of Magneto-Rheological Fluids under Applied External Magnetic Field

An experimental and numerical study of Magnetorheological (MR) fluids flow in circular pipes under the influence of uniform magnetic field is considered. In the experiments, an electromagnetic device was manufactured to generate the magnetic field. The experiments were performed using magnetic fields B= 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.12 and 0.15 T. Numerical study was performed to show the accuracy of the results obtained from experimental study. In numerical study, Computational Fluid Dynamics (CFD) analysis was used. The ANSYS Fluent 14.0 code based on the finite volume method was used for the CFD analysis. In the experiments, the applied magnetic field decreased the flow rate of the fluids by increasing viscosity. In case of 10 mm pipe diameter, the flow velocity of the A, B and C fluids were obtained as 0.593, 0.749 and 0.938 m/s respectively in situation B=0 T. When magnetic field was applied as B=0.15 T, decreases have occurred in the velocity of A, B and C fluids as 95.27%, 90.24% and 85.6% respectively. Similarly, in case of 15 mm pipe diameter, 96.87%, 95.06% and 90.76% decreases have occurred in the flow velocity of A, B and C fluids having 0.301, 0.363 and 0.445 m/s flow velocity respectively. The results were compared for the magnetic field values B=0, 0.05, 0.10 and 0.15 T. It was found that the differences between experimental and numerical study were found as 6.10% and 1.71% for the B=0 T and B≠0 T situations respectively when the pipe has 10 mm pipe diameter. In case of 15 mm pipe diameter, the differences were found as 2.31% and 0.89%. As a result, it was found that the results obtained from experimental and numerical study were qualitatively and quantitatively in good agreement

Bochdalek hernia with concomitant partial situs inversus in an adult

We report the case of 44-year-old woman with a left-sided Bochdalek hernia (BH) with concomitant partial situs inversus. The patient was presented from the outpatient clinic with lower chest discomfort. She had suffered from abdominal pain for one year, with no history of trauma, previous surgery, or extreme physical exertion. Chest radiograph revealed a large left-sided BH. The patient underwent thoracotomy. Intestinal organs, containing bowel, small intestine, caecum, and appendix were seen in the left hemithorax. Because of the failure to reduce the intestinal organs into the peritoneal cavity, laparotomy was performed. The right side of the abdominal cavity was empty. In conclusion, partial situs inversus was diagnosed. The diaphragmatic defect was repaired with non-absorbable sutures via laparotomy, and with a prolene mesh via thoracotomy. Bochdalek hernia with partial situs inversus is a rare clinical entity with none reported in medical literature. (Folia Morphol 2010; 69, 2: 119-122

A review of Morgagni and Bochdalek hernias in adults

The incidence of Bochdalek and Morgagni hernias among adults is very rare. The purpose of this study was to determine retrospectively the prevalence and characteristics of adult Bochdalek and Morgagni hernias in a decade. Consequently, we demonstrated 12 patients with Bochdalek and 8 patients with Morgagni hernias. We presented plain radiography, operation images, and computed tomography findings of an adult patient with symptoms due to Bochdalek and Morgagni hernias. In surgical repair, the Morgagni hernia is best approached via laparotomy, and the Bochdalek hernia can be treated through thoracotomy or laparotomy. (Folia Morphol 2011; 70, 1: 5-12

Observation of spin Coulomb drag in a two-dimensional electron gas

An electron propagating through a solid carries spin angular momentum in addition to its mass and charge. Of late there has been considerable interest in developing electronic devices based on the transport of spin, which offer potential advantages in dissipation, size, and speed over charge-based devices. However, these advantages bring with them additional complexity. Because each electron carries a single, fixed value (-e) of charge, the electrical current carried by a gas of electrons is simply proportional to its total momentum. A fundamental consequence is that the charge current is not affected by interactions that conserve total momentum, notably collisions among the electrons themselves. In contrast, the electron's spin along a given spatial direction can take on two values, "up" and "down", so that the spin current and momentum need not be proportional. Although the transport of spin polarization is not protected by momentum conservation, it has been widely assumed that, like the charge current, spin current is unaffected by electron-electron (e-e) interactions. Here we demonstrate experimentally not only that this assumption is invalid, but that over a broad range of temperature and electron density, the flow of spin polarization in a two-dimensional gas of electrons is controlled by the rate of e-e collisions

Self-similar dynamics of order parameter fluctuations in pump-probe experiments

Upon excitation by a laser pulse, broken-symmetry phases of a wide variety of solids demonstrate similar order parameter dynamics characterized by a dramatic slowing down of relaxation for stronger pump fluences. Motivated by this recurrent phenomenology, we develop a simple non-perturbative effective model of dynamics of collective bosonic excitations in pump-probe experiments. We find that as the system recovers after photoexcitation, it shows universal prethermalized dynamics manifesting a power-law, as opposed to exponential, relaxation, explaining the slowing down of the recovery process. For strong quenches, long-wavelength over-populated transverse modes dominate the long-time dynamics; their distribution function exhibits universal scaling in time and space, whose universal exponents can be computed analytically. Our model offers a unifying description of order parameter fluctuations in a regime far from equilibrium, and our predictions can be tested with available time-resolved techniques

Amplitude dynamics of the charge density wave in LaTe3: Theoretical description of pump-probe experiments

We formulate a dynamical model to describe a photo-induced charge density wave (CDW) quench transition and apply it to recent multi-probe experiments on LaTe$_3$ [A. Zong et al., Nat. Phys. 15, 27 (2019)]. Our approach relies on coupled time-dependent Ginzburg-Landau equations tracking two order parameters that represent the modulations of the electronic density and the ionic positions. We aim at describing the amplitude of the order parameters under the assumption that they are homogeneous in space. This description is supplemented by a three-temperature model, which treats separately the electronic temperature, temperature of the lattice phonons with stronger couplings to the electronic subsystem, and temperature of all other phonons. The broad scope of available data for LaTe$_3$ and similar materials as well as the synergy between different time-resolved spectroscopies allow us to extract model parameters. The resulting calculations are in good agreement with ultra-fast electron diffraction experiments, reproducing qualitative and quantitative features of the CDW amplitude evolution during the initial few picoseconds after photoexcitation

Phonoritons as Hybridized Exciton-Photon-Phonon Excitations in a Monolayer h -BN Optical Cavity

A phonoriton is an elementary excitation that is predicted to emerge from hybridization between exciton, phonon, and photon. Besides the intriguing many-particle structure, phonoritons are of interest as they could serve as functional nodes in devices that utilize electronic, phononic, and photonic elements for energy conversion and thermal transport applications. Although phonoritons are predicted to emerge in an excitonic medium under intense electromagnetic wave irradiation, the stringent condition for their existence has eluded direct observation in solids. In particular, on-resonance, intense pumping schemes have been proposed, but excessive photoexcitation of carriers prevents optical detection. Here, we theoretically predict the appearance of phonoritonic features in monolayer hexagonal boron nitride (h-BN) embedded in an optical cavity. The coherent superposition nature of phonoriton states is evidenced by the hybridization of exciton-polariton branches with phonon replicas that is tunable by the cavity-matter coupling strength. This finding simultaneously provides an experimental pathway for observing the predicted phonoritons and opens a new avenue for tuning materials properties

A Numerical Analysis of Laminar Forced Convection and Entropy Generation of a Diamond-Fe3O4/Water Hybrid Nanofluid in a Rectangular Minichannel

The convective heat transfer and entropy generation of diamond-Fe3O4/water hybrid nanofluid through a rectangular minichannel is numerically investigated under laminar flow conditions. Nanoparticle volume fractions for diamond-Fe3O4/water hybrid nanofluid are in the range 0.05-0.20% and Reynolds number varies from 100 to 1000. The finite volume method is used in the numerical computation. The results obtained for diamond-Fe3O4/water hybrid nanofluid are compared with those of diamond/water and Fe3O4/water conventional nanofluids. It is found that 0.2% diamond-Fe3O4 hybrid nanoparticle addition to pure water provides convective heat transfer coefficient enhancement of 29.96%, at Re=1000. The results show that diamond-Fe3O4/water hybrid nanofluid has higher convective heat transfer coefficient and Nusselt number when compared with diamond/water and Fe3O4/water conventional nanofluids. For diamond-Fe3O4/water hybrid nanofluid, until Re=600, the lowest total entropy generation rate values are obtained for 0.20% nanoparticle volume fraction. However, after Re=800, diamond-Fe3O4/water hybrid nanofluid with 0.20% nanoparticle volume fraction has the highest total entropy generation rate compared to other nanoparticle volume fractions. A similar pattern emerges from the comparison with diamond/water and Fe3O4/water conventional nanofluids. For 0.2% nanoparticle volume fraction, diamond-Fe3O4/water hybrid nanofluid and diamond/water nanofluid have their minimum entropy generation rate at Re=500 and at Re=900, respectively. Moreover, this minimum entropy generation rate point changes with nanoparticle volume fraction values of nanofluids