# Feed aggregator

### Senior Geotechnical Engineer - Syracuse NY | ENG-Staff

### Technical Lead | CitiusTech

### Information Technology (IT) Manager | Ada County Highway District (ACHD)

### Neutron holography makes its debut

### Product Engineer | Interface Performance Materials

### Structural Engineer | Cromwell Architects Engineers

### Software Engineer | Google Inc.

### Assistant/ Associate Professor of Polymer Engineering (Polymer Rheology) | The University of Akron

### Multiple earthquakes strike central Italy

BBC: On 26 October two earthquakes, one magnitude 5.5 and the other magnitude 6.1, struck two hours apart near the town of Visso, Italy. In August a magnitude 6.2 earthquake killed nearly 300 people in Amatrice, just 70 km away. Damage and injury reports from yesterday's quakes suggest that the damage was not as severe. The first quake occurred at a relatively shallow depth of 9 km, with an epicenter 7 km southwest of Visso. The second quake struck 2 km north of the town at a depth of 10 km. Mario Tozzi of Italy's National Institute of Geophysics says it's likely the two earthquakes were aftershocks of the August quake.

### Junior Tenure-Track Faculty Position | The Institute of Optics, University of Rochester

### Imagining humans on Mars

### US fourth and eighth graders show improvement in science

### Enhanced efficiency and stability in organic light-emitting diodes by employing a p-i-n-p structure

Organic light-emitting diodes (OLEDs) with a p-i-n-p structure were developed by inserting a p-doped layer, MoO3 doped N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)-benzidine (NPB), between an n-doped electron injection layer and the cathode. The device showed a 33.5% improvement in the power efficiency and 70.7% improvement in the half operational lifetime compared with the conventional p-i-n structure based device. The improved device performance is mainly ascribed to an improved conductivity, an enhanced thermal stability, and the protection of the electron injection layer by the NPB:MoO3 p-doped layer. The finding indicates that the p-i-n-p structure is beneficial for improving the efficiency and the stability of OLEDs.

### Consistency in experiments on multistable driven delay systems

We investigate the consistency properties in the responses of a nonlinear delay optoelectronic intensity oscillator subject to different drives, in particular, harmonic and self-generated waveforms. This system, an implementation of the Ikeda oscillator, is operating in a closed-loop configuration, exhibiting its autonomous dynamics while the drive signals are additionally introduced. Applying the same drive multiple times, we compare the dynamical responses of the optoelectronic oscillator and quantify the degree of consistency among them via their correlation. Our results show that consistency is not restricted to conditions close to the first Hopf bifurcation but can be found in a broad range of dynamical regimes, even in the presence of multistability. Finally, we discuss the dependence of consistency on the nature of the drive signal.

### Performance of Lagrangian descriptors and their variants in incompressible flows

The method of Lagrangian Descriptors has been applied in many different contexts, specially in geophysical flows. In this paper, we analyze their performance in incompressible flows. We construct broad families of systems where this diagnostic fails in the detection of barriers to transport. Another aim of this manuscript is to illustrate the same deficiencies in the recent diagnostic proposed by Craven and Hernández.

### Exact periodic cross-kink wave solutions for the new (2+1)-dimensional KdV equation in fluid flows and plasma physics

The Korteweg-de Vries (KdV)-type models have been shown to describe many important physical situations such as fluid flows, plasma physics, and solid state physics. In this paper, a new (2 + 1)-dimensional KdV equation is discussed. Based on the Hirota's bilinear form and a generalized three-wave approach, we obtain new exact solutions for the new (2 + 1)-dimensional KdV equation. With the help of symbolic computation, the properties for some new solutions are presented with some figures.

### Dynamics of boundary layer electrons around a laser wakefield bubble

The dynamics of electrons forming the boundary layer of a highly nonlinear laser wakefield driven in the so called bubble or blowout regime is investigated using particle-in-cell simulations. It is shown that when the driver pulse intensity increases or the focal spot size decreases, a significant amount of electrons initially pushed by the laser pulse can detach from the bubble structure at its tail, middle, or front and form particular classes of waves locally with high densities, referred to as the tail wave, lateral wave, and bow wave. The tail wave and bow wave correspond to real electron trajectories, while the lateral wave does not. The detached electrons can be ejected transversely, containing considerable energy, and reducing the efficiency of the laser wakefield accelerator. Some of the transversely emitted electrons may obtain MeV level energy. These electrons can be used for wake evolution diagnosis and producing high frequency radiation.

### The photon kinetic approach toward terahertz radiation

A one dimensional spatiotemporal model for the femtosecond laser pulse interaction with air is developed in which the laser pulse propagation as well as the plasma formation and evolution accompanied with the THz radiation are investigated numerically. The photon kinetic approach based on the Klimontovich kinetic equation for the photons is used to describe the ultrashort laser pulse propagation while the Ammosov–Delone–Krainov approach accompanied with the plasma fluid equations is used to investigate the plasma formation and evolution, respectively. It is noteworthy that the model main focus was on the investigation of the long standing disagreement on the mechanisms of air-plasma THz radiation. Therefore, the three mechanisms of plasma current radiation, four-wave mixing by third order nonlinear susceptibility, and the interaction with the self exited plasma wave were inserted into the model, and their contributions to the THz emission were computed and compared. Our obtained results show that the interaction with the plasma wave plays no role in THz generation, while the nonlinear polarization and the plasma current are the two competing mechanisms, which both have significant roles in air plasma THz radiation.

### Effects of filamentation instability on the divergence of relativistic electrons driven by ultraintense laser pulses

Generation of relativistic electron (RE) beams during ultraintense laser pulse interaction with plasma targets is studied by collisional particle-in-cell simulations. A strong magnetic field with a transverse scale length of several local plasma skin depths, associated with RE current propagation in the target, is generated by filamentation instability in collisional plasmas, inducing a great enhancement of the divergence of REs compared to that of collisionless cases. Such an effect is increased with laser intensity and target charge state, suggesting that the RE divergence might be improved by using low-Z materials under appropriate laser intensities in future fast ignition experiments and in other applications of laser-driven electron beams.

### Nonlinear effects associated with oblique whistler waves in space plasmas

In the present work, we have examined the nonlinear interaction of pump whistler wave and low frequency kinetic Alfvén wave (KAW) in three regions viz., solar wind, earth's radiation belt, and magnetopause. The modification in the background density leads to the introduction of nonlinearity. The nonlinear ponderomotive force is responsible for this change in density. Low frequency kinetic Alfvén wave is excited by the nonlinear ponderomotive force of pump whistler wave. A set of dimensionless equations characterizing the dynamics of whistler wave and low frequency KAW perturbed by whistler wave were developed. The coupled equations were then simulated numerically. The nonlinear effects related with the whistler wave were studied. The resulting localized structures and the magnetic turbulent spectra in various regions have been investigated.