Intersublevel infrared photodetector with strain-free GaAs quantum dot pairs grown by high-temperature droplet epitaxy.

Normal incident photodetection at mid infrared spectral region is achieved using the intersublevel transitions from strain-free GaAs quantum dot pairs in Al(0.3)Ga(0.7)As matrix. The GaAs quantum dot pairs are fabricated by high temperature droplet epitaxy, through which zero strain quantum dot pairs are obtained from lattice matched materials. Photoluminescence, photoluminescence excitation optical spectroscopy, and visible-near-infrared photoconductivity measurement are carried out to study the electronic structure of the photodetector. Due to the intersublevel transitions from GaAs quantum dot pairs, a broadband photoresponse spectrum is observed from 3 to 8 microm with a full width at half-maximum of approximately 2.0 microm.

Keratinocytes produce IL-17c to protect peripheral nervous systems during human HSV-2 reactivation.

Despite frequent herpes simplex virus (HSV) reactivation, peripheral nerve destruction and sensory anesthesia are rare. We discovered that skin biopsies obtained during asymptomatic human HSV-2 reactivation exhibit a higher density of nerve fibers relative to biopsies during virological and clinical quiescence. We evaluated the effects of HSV infection on keratinocytes, the initial target of HSV replication, to better understand this observation. Keratinocytes produced IL-17c during HSV-2 reactivation, and IL-17RE, an IL-17c-specific receptor, was expressed on nerve fibers in human skin and sensory neurons in dorsal root ganglia. In ex vivo experiments, exogenous human IL-17c provided directional guidance and promoted neurite growth and branching in microfluidic devices. Exogenous murine IL-17c pretreatment reduced apoptosis in HSV-2-infected primary neurons. These results suggest that IL-17c is a neurotrophic cytokine that protects peripheral nerve systems during HSV reactivation. This mechanism could explain the lack of nerve damage from recurrent HSV infection and may provide insight to understanding and treating sensory peripheral neuropathies.

On the secondary droplets of self-running gallium droplets on GaAs surface.

Self-running droplets by thermal evaporation GaAs (001) surface are studied and analyzed using a scanning electron microscope. The sample is prepared under high-temperature annealing in an ultrahigh vacuum molecular beam epitaxy system. Particularly, secondary droplets which formed along primary droplet running trails are investigated. The secondary droplets are found to initially move along the [1 ̅10] instead of [110] direction, but these droplets tend to turn into [110] direction as they grow bigger. The scanning electron microscope also captures nanoscale footprints of secondary droplets different from the main droplets.

Nanoscale footprints of self-running gallium droplets on GaAs surface.

In this work, the nanoscale footprints of self-driven liquid gallium droplet movement on a GaAs (001) surface will be presented and analyzed. The nanoscale footprints of a primary droplet trail and ordered secondary droplets along primary droplet trails are observed on the GaAs surface. A well ordered nanoterrace from the trail is left behind by a running droplet. In addition, collision events between two running droplets are investigated. The exposed fresh surface after a collision demonstrates a superior evaporation property. Based on the observation of droplet evolution at different stages as well as nanoscale footprints, a schematic diagram of droplet evolution is outlined in an attempt to understand the phenomenon of stick-slip droplet motion on the GaAs surface. The present study adds another piece of work to obtain the physical picture of a stick-slip self-driven mechanism in nanoscale, bridging nano and micro systems.