23,784 research outputs found
Advances in oral transmucosal drug delivery
Original article can be found at : http://sciencedirect.com/ Copyright ElsevierThe successful delivery of drugs across the oral mucosa represents a continuing challenge, as well as a great opportunity. Oral transmucosal delivery, especially buccal and sublingual delivery, has progressed far beyond the use of traditional dosage forms with novel approaches emerging continuously. This review highlights the physiological challenges as well as the advances and opportunities for buccal/sublingual drug delivery. Particular attention is given to new approaches which can extend dosage form retention time or can be engineered to deliver complex molecules such as proteins and peptides. The review will also discuss the physiology and local environment of the oral cavity in vivo and how this relates to the performance of transmucosal delivery systems.Peer reviewe
Switchable Speaker Driver for Power-efficient Proximity Sensing and Device Wake-up
This disclosure describes power-efficient ultrasonic techniques for proximity detection and device wake-up from sleep mode. In sleep mode, the host application processor, e.g., the main device processor, is inactive. A low-power embedded controller remains on during sleep mode and generates an ultrasonic waveform that is amplified by a low-power speaker driver that also remains on during sleep mode. In some of the described architectures, a switch is provided that switches between the low-power speaker driver in sleep mode and a high-power speaker amplifier in active mode. A microphone captures echoes of reflected ultrasonic waves. Echoes arising from within a certain distance of the screen of the device are indicative of human presence and trigger the waking up of the device
Friction force on slow charges moving over supported graphene
We provide a theoretical model that describes the dielectric coupling of a 2D
layer of graphene, represented by a polarization function in the Random Phase
Approximation, and a semi-infinite 3D substrate, represented by a surface
response function in a non-local formulation. We concentrate on the role of the
dynamic response of the substrate for low-frequency excitations of the combined
graphene-substrate system, which give rise to the stopping force on slowly
moving charges above graphene. A comparison of the dielectric loss function
with experimental HREELS data for graphene on a SiC substrate is used to
estimate the damping rate in graphene and to reveal the importance of phonon
excitations in an insulating substrate. A signature of the hybridization
between graphene's pi plasmon and the substrate's phonon is found in the
stopping force. A friction coefficient that is calculated for slow charges
moving above graphene on a metallic substrate shows an interplay between the
low-energy single-particle excitations in both systems.Comment: 13 pages, 5 figures, submitted to Nanotechnology for a special issue
related to the NGC 2009 conference (http://asdn.net/ngc2009/index.shtml
Energy Spectrum of the Electrons Accelerated by a Reconnection Electric Field: Exponential or Power Law?
The direct current (DC) electric field near the reconnection region has been
proposed as an effective mechanism to accelerate protons and electrons in solar
flares. A power-law energy spectrum was generally claimed in the simulations of
electron acceleration by the reconnection electric field. However in most of
the literature, the electric and magnetic fields were chosen independently. In
this paper, we perform test-particle simulations of electron acceleration in a
reconnecting magnetic field, where both the electric and magnetic fields are
adopted from numerical simulations of the MHD equations. It is found that the
accelerated electrons present a truncated power-law energy spectrum with an
exponential tail at high energies, which is analogous to the case of diffusive
shock acceleration. The influences of reconnection parameters on the spectral
feature are also investigated, such as the longitudinal and transverse
components of the magnetic field and the size of the current sheet. It is
suggested that the DC electric field alone might not be able to reproduce the
observed single or double power-law distributions.Comment: 18 pages, 6 figures, published in Ap
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