Chiral pumping effect induced by rotating electric fields

We propose an experimental setup using 3D Dirac semimetals to access a novel phenomenon induced by the chiral anomaly. We show that the combination of a magnetic field and a circularly polarized laser induces a finite charge density with an accompanying axial current. This is because the circularly polarized laser breaks time-reversal symmetry and the Dirac point splits into two Weyl points, which results in an axial-vector field. We elucidate the appearance of the axial-vector field with the help of the Floquet theory by deriving an effective Hamiltonian for high-frequency electric fields. This anomalous charge density, i.e. the chiral pumping effect, is a phenomenon reminiscent of the chiral magnetic effect with a chiral chemical potential. We explicitly compute the pumped density and the axial-current expectation value. We also take account of coupling to the chiral magnetic effect to calculate a balanced distribution of charge and chirality in a material that behaves as a chiral battery.Comment: 6 pages, 3 figures; a new section added to discuss coupling of the CPE and the CME, a wrong sign corrected, typos fixed, elaborated for better readabilit

Giant Impact Events for Protoplanets: Energetics of Atmospheric Erosion by Head-on Collision

Numerous exoplanets with masses ranging from Earth to Neptune and radii larger than Earth have been found through observations. These planets possess atmospheres that range in mass fractions from 1% to 30%, reflecting the diversity of atmospheric mass fractions. Such diversities are supposed to be caused by differences in the formation processes or evolution. Here we consider head-on giant impacts onto planets causing atmosphere losses in the later stage of their formation. We perform smoothed particle hydrodynamic simulations to study the impact-induced atmosphere loss of young super-Earths with 10%-30% initial atmospheric mass fractions. We find that the kinetic energy of the escaping atmosphere is almost proportional to the sum of the kinetic impact energy and self-gravitational energy released from the merged core. We derive the relationship between the kinetic impact energy and the escaping atmosphere mass. The giant impact events for planets of comparable masses are required in the final stage of the popular scenario of rocky planet formation. We show it results in a significant loss of the atmosphere, if the impact is a head-on collision with comparable masses. This latter fact provides a constraint on the formation scenario of rocky planets with substantial atmospheres.Comment: 29 pages, 27 figures, accepted for publication in Ap

100ps time resolution with thin silicon pixel detectors and a SiGe HBT amplifier

A 100um thick silicon detector with 1mm2 pad readout optimized for sub-nanosecond time resolution has been developed and tested. Coupled to a purposely developed amplifier based on SiGe HBT technology, this detector was characterized at the H8 beam line at the CERN SPS. An excellent time resolution of (106+-1)ps for silicon detectors was measured with minimum ionizing particles

Multi-scale analysis on cavitation damage and its mitigation for the spallation neutron source

Impact of injecting microbubbles on the thermal expansion due to the nuclear spallation reaction were examined numerically. Since the mercury density is higher than the density of solid wall, the interaction between mercury and solid wall must be taken into account. Our approach is to solve the momentum and energy conservation equations and the time development of elastic stress for both bubbly fluid and elastic solid. The Keller equation is employed to reproduce the nonlinear oscillation of bubble with considering the thermal dumping effect by the reduced order model. The continuum phase of liquid mercury is coupled with the discrete phase of microbubbles using the Euler-Lagrange method. As the results, the bubble cloud develops around the center of inertia of motion induced by the thermal expansion. The elasticity of the wall affects on the migration of the center of inertia away from the wall. The injection of microbubbles is effective to decrease the pressure rise due to thermal expansion for both rigid and elastic wall conditions when the void fraction of microbubbles is higher than the volume rate of thermal expansion of liquid mercury

Assessment of cardiovascular function by combining clinical data with a computational model of the cardiovascular system

ObjectiveA sufficient understanding of patients’ cardiovascular status is necessary for doctors to make the best decisions with regard to the treatment of cardiovascular disease; however, it is often not available because of the limitation of clinical measurements. The objective of this study was to examine whether cardiovascular function can be assessed quantitatively and for specific patients by combining clinical data with a computational model of the cardiovascular system.MethodsSeven consecutive patients undergoing off-pump coronary artery bypass grafting were enrolled in this study. The clinical data were collected both during the preoperative diagnosis and during the operation. Sensitivity analysis was performed to select the major model parameters most relevant to the measured data. The major model parameters were then estimated through a data-fitting procedure, enabling a patient-specific quantitative assessment of various aspects of cardiovascular function.ResultsThe results revealed the prevalence of left ventricular diastolic dysfunction in the patients, although the severity of dysfunction exhibits significant interpatient variability (the estimated left ventricular passive elastance varies from 194% to 540% of its reference value). Moreover, 4 of the 7 patients studied had impaired left ventricular systolic function.ConclusionsThe current study demonstrates the feasibility of assessing cardiovascular function quantitatively by combining clinical data with a cardiovascular model. In particular, the assessment utilizes the measurements already in use or available in clinical settings, enhancing the clinical potential of the proposed method