Mercury distribution and speciation in two lagoons with different pollution and eutrophication conditions in Taiwan.

This study explored biogeochemical processes controlling the distribution of mercury (Hg) species in two lagoons with different pollution and eutrophication conditions in southwestern Taiwan. The eutrophication and pollution levels were higher in the Dapeng Bay than in the Chiku Lagoon, engendering a higher particulate Hg concentration and enrichment factor in the Dapeng Bay. The concentration range of total dissolved Hg (HgTD) and reactive Hg (HgR) was comparable between the lagoons, but the concentration of particulate Hg (HgP) was higher in the Dapeng Bay. HgR and HgTD abundance was primarily controlled by the availability of dissolved oxygen (DO) and biological absorption. In addition to pollution (which elevated HgP concentration), biological absorption and/or adsorption rather than lithogenic processes more likely regulated the HgP concentration. The effect of Hg pollution may superimpose on that of DO on the distributions of HgR and HgTD and may enhance HgP formation in the Dapeng Bay.

Determination of free electron density in sequentially doped InxGa1-xAs by Raman spectroscopy.

The advent and exponential growth of mobile computing has spurred greater emphasis on the adoption of III-V compound semiconductors in device architectures. The introduction of high charge carrier densities within InxGa1-xAs and the development of metrologies to quantitate the extent of doping have thus emerged as an urgent imperative. As an amphoteric dopant, Si begins to occupy anionic sites at high concentrations, thereby limiting the maximum carrier density that can be obtained upon Si doping of III-V semiconductors. Here, we present Raman results on sequentially doped In0.53Ga0.47As wherein sulfur monolayer doping is used to introduce additional carrier density to Si-doped samples. The sequential doping of Si and S allows for high carrier concentrations of up to 1.3 × 10(19) cm(-3) to be achieved without damaging the III-V lattice. The coupling of the plasmon in the doped samples to the longitudinal optic phonons allows Raman spectroscopy to serve as an excellent probe of the extent of dopant activation, charge carrier density, and the surface depletion region. In particular, the energy position of a high-frequency coupled mode (HFCM) that is detected above 400 cm(-1) is used to extract the free electron density in these samples. The extracted free electron densities are well correlated with measured sheet resistance values and the carrier densities deduced from Hall measurements.

Chloride molecular doping technique on 2D materials: WS2 and MoS2.

Low-resistivity metal-semiconductor (M-S) contact is one of the urgent challenges in the research of 2D transition metal dichalcogenides (TMDs). Here, we report a chloride molecular doping technique which greatly reduces the contact resistance (Rc) in the few-layer WS2 and MoS2. After doping, the Rc of WS2 and MoS2 have been decreased to 0.7 kΩ·µm and 0.5 kΩ·µm, respectively. The significant reduction of the Rc is attributed to the achieved high electron-doping density, thus a significant reduction of Schottky barrier width. As a proof-of-concept, high-performance few-layer WS2 field-effect transistors (FETs) are demonstrated, exhibiting a high drain current of 380 µA/µm, an on/off ratio of 4 × 10(6), and a peak field-effect mobility of 60 cm(2)/(V·s). This doping technique provides a highly viable route to diminish the Rc in TMDs, paving the way for high-performance 2D nanoelectronic devices.

Raman spectroscopy studies of dopant activation and free electron density of In(0.53)Ga(0.47)As via sulfur monolayer doping.

We present a Raman spectroscopy study of electron-phonon coupling in In0.53Ga0.47As epilayers doped via the sulfur-monolayer doping method. A high-frequency coupled mode (HFCM) detected above 400 cm(-1) shifts with increasing charge carrier density and allows for extraction of the activated dopant concentrations.

Acute hemiplegia associated with herpes zoster infection in children: report of one case.

Herpes zoster infection has been rarely reported to cause angiitis of the central nervous system in children. We describe a 4-year, 8-month-old female with acute hemiplegia and central facial palsy 6 weeks after she had had zoster ophthalmicus. The findings of magnetic resonance angiography, the clinical picture, and a preceding history of herpes zoster ophthalmicus suggested zoster vasculitis. Herpes zoster vasculitis is thus another consideration when examining a child with acute hemiplegia and a recent herpes zoster infection.