Cyclotron motion and magnetic focusing in semiconductor quantum wells with spin-orbit coupling

We investigate the ballistic motion of electrons in III-V semiconductor quantum wells with Rashba spin-orbit coupling in a perpendicular magnetic field. Taking into account the full quantum dynamics of the problem, we explore the modifications of classical cyclotron orbits due to spin-orbit interaction. As a result, for electron energies comparable with the cyclotron energy the dynamics are particularly rich and not adequately described by semiclassical approximations. Our study is complementary to previous semiclassical approaches concentrating on the regime of weaker fields.Comment: 14 pages, 8 figures included, version to appear in Phys. Rev.

Detection of spin polarized currents in quantum point contacts via transverse electron focusing

It has been predicted recently that an electron beam can be polarized when it flows adiabatically through a quantum point contact in a system with spin-orbit interaction. Here, we show that a simple transverse electron focusing setup can be used to detect such polarized current. It uses the amplitude's asymmetry of the spin-split transverse electron focusing peak to extract information about the electron's spin polarization. On the other hand, and depending on the quantum point contact geometry, including this one-body effect can be important when using the focusing setup to study many-body effects in quantum point contacts.Comment: 5 pages, 5 figure

Patterns of Drug Use and Serum Sodium Concentrations in Older Hospitalized Patients : A Latent Class Analysis Approach

Peer reviewedPublisher PD

Pilot-scale continuous synthesis of a vanadium-doped LiFePO4/C nanocomposite high-rate cathodes for lithium-ion batteries

A high performance vanadium-doped LiFePO4 (LFP) electrode is synthesized using a continuous hydrothermal method at a production rate of 6 kg per day. The supercritical water reagent rapidly generates core/shell nanoparticles with a thin, continuous carbon coating on the surface of LFP, which aids electron transport dynamics across the particle surface. Vanadium dopant concentration has a profound effect on the performance of LFP, where the composition LiFe0.95V0.05PO4, achieves a specific discharge capacity which is among the highest in the comparable literature (119 mA h g−1 at a discharge rate of 1500 mA g−1). Additionally, a combination of X-ray absorption spectroscopy analysis and hybrid-exchange density functional theory, suggest that vanadium ions replace both phosphorous and iron in the structure, thereby facilitating Li+ diffusion due to Li+ vacancy generation and changes in the crystal structure

K‑CLASP: A Tool to Identify Phosphosite Specific Kinases and Interacting Proteins

Few methods are available to discover the cellular kinase that phosphorylates a specific amino acid, or phosphosite, on a protein. In addition, identifying the associated proteins bound near a phosphosite during phosphorylation would provide insights into cell biology and signaling. Here, we report K-CLASP (Kinase Catalyzed CrossLinking And Streptavidin Purification) as a method for both phosphosite-specific kinase identification and the discovery of kinase interacting proteins. K-CLASP offers a powerful tool to discover unanticipated protein–protein interactions in phosphorylation-mediated biological events

Correlative study of microstructure and performance for porous transport layers in polymer electrolyte membrane water electrolysers by X-ray computed tomography and electrochemical characterization

The porous transport layer (PTL) in polymer electrolyte membrane water electrolysers (PEMWEs) has the multiple roles of delivering water to the electro-catalyst, removal of product gas, and acts as a conduit for electronic and thermal transport. They are, thus, a critical component for optimized performance, especially at high current density operation. This study examines the relationship between the microstructure and corresponding electrochemical performance of commonly used titanium sinter PTLs. Four PTLs, with mean pore diameter (MPD) ranging from 16 μm to 90 μm, were characterized ex-situ using scanning electron microscopy and X-ray computed micro-tomography to determine key structural properties. The performance of these PTLs was studied operando using polarization and electrochemical impedance spectroscopy. Results showed that an increase in mean pore size of the PTLs correlates to an increase in the spread and multimodality of the pore size distribution and a reduction in homogeneity of porosity distribution. Electrochemical measurements reveal a strong correlation of mean pore size of the PTLs with performance. Smaller pore PTLs showed lower Ohmic resistance but higher mass transport resistance at high current density of 3.0 A cm−2. A non-monotonic trend of mass transport resistance was observed for different PTLs, which suggests an optimal pore size beyond which the advantageous influence of macroporosity for mass transport is diminished. The results indicate that maximizing contact points between the PTL and the catalyst layer is the overriding factor in determining the overall performance. These results guide PTL design and fabrication of PEMWEs

Operando flow regime diagnosis using acoustic emission in a polymer electrolyte membrane water electrolyser

Polymer electrolyte membrane water electrolysers (PEMWE) are a key technology for producing clean (‘green’) hydrogen for decarbonisation of the transport sector and grid stabilisation utilising increasing levels of renewable energy. In this work, acoustic emission analysis is used as a non-destructive, operando diagnostic tool to provide information about the relative number and size of gas bubbles generated locally within a PEMWE, providing effective characterisation of the local flow conditions. An optically transparent single-channel PEMWE is used to investigate the relationship between the acoustic signals obtained and the two-phase flow conditions inside the cell. The number of acoustic hits, their frequency, and average peak amplitude is reported for several flow rates and current densities. Using high-speed imaging, the average bubble number and size in the flow cannels is compared to the acoustic signal. Results show good correlation between the number of acoustic ‘hits’ and the number of bubbles passing through the flow channel. The size of bubbles is also shown to affect the average frequency of the hits. Consequently, the transition between bubbly and slug flow regime can be identified by acoustic emission analysis, paving the way for a simple, low-cost, non-destructive means of mapping flow inside commercial-scale PEMWEs