Sequence and function of the two P domain potassium channels: implications of an emerging superfamily.

A new superfamily of K+ channels has emerged in the past 2 years. Notable for possessing two pore-forming P domains in each subunit, members of the superfamily have been recognized through phylogeny from micro-organisms to humans. Four subfamilies of two P domain channels have been isolated thus far; among these are the first cloned examples of outward rectifier and open rectifier (or leak) K+ channels. The two P domain K+ channels offer a new perspective from which to glimpse the molecular basis for function and dysfunction of K+-selective ion channels

A Novel Biphasic-Current-Pulse Calibration Technique for Electrical Neural Stimulation

One of the major challenge in neural prosthetic device design is to ensure charge-balanced stimulation. This paper presents a new calibration technique to minimize the mismatch between anodic and cathodic current amplitudes. The proposed circuit mainly consists of a digital and an analog calibration, where a successive approximation register (SAR) logic and a comparator are used in digital calibration while a source follower is adopted in analog calibration. With a 0. 18 μm high voltage CMOS process, the simulation shows that the maximum current mismatch is 45 nA (<0.05%).published_or_final_versio

Maximum power point tracking (MPPT) of a scale-up pressure retarded osmosis (PRO) osmotic power plant

This paper presents a maximum power point tracking (MPPT) of a scale-up pressure retarded osmosis (PRO) based osmotic power generator. Inspired by the well-known MPPT in photovoltaic (PV) array, two algorithms, perturb & observe (P&O) and incremental mass-resistance (IMR) method, are investigated. Using a series of simulations, both the algorithms are demonstrated to be capable of tracking the maximum power point (MPP) and capturing the transitions between varied MPPs due to the fluctuations of operating temperature. However, in both cases the trade-off between the rise time and the oscillation is found requiring further consideration on the selection of the step-size for perturbation pressure or incremental pressure. In order to improve the performance of the MPPT, furthermore, an optimum model-based controller (OMC) is used to estimate the initial optimum pressure for the MPPT in a scale-up PRO process. It is found that with OMC, the performance of the MPPT is improved significantly. Finally, a strategy to operate and coordinate the MPPT and OMC to deal with the rapid variations of the salinities are proposed and evaluated in terms of individual variation of the concentration or flow rate and co-variation of the both. The simulations demonstrate the preferred performance of the proposed strategy to adjust the operation subject to the rapid changes of the salinities

A Gauge Invariant Theory for Time Dependent Heat Current

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Sufu defines the balance of hindbrain progenitor cells maintenance and differentiation

Suppressor of fused (Sufu) was identified as a regulator in Hedgehog signalling. Study shown that Sufu knockout mice were embryonic lethal at E9.5, exhibiting cephalic deformities, open neural tube and ventralized spinal cord resulting from ectopic Shh signalling, implying indispensable role of Sufu during development of central nervous system. Aiming to investigate the functions of Sufu in hindbrain neurogenesis, we used B2‐r4‐Cre to knock‐out Sufu in rhombomere4 (r4). We observed significant enlargement of mutant r4 size from E10.5, exhibiting more profound expansion in the dorsal region at E12.5. Accordingly, BrdU pulse labelling and sox2 staining showed region specific increased accumulation of proliferative progenitor cells, indicating differential maintenance of progenitor pools along the dorsoventral axis of r4. Tuj1 staining also showed impaired differentiation of the ectopic progenitor cells. Further analysis revealed dramatic dorsal expansion of pMN and p2 progenitor domains in mutant r4. Surprisingly, the FoxA2 positive floor plate, and the dorsal p0 domain were not severely affected, suggesting a novel domain specific regulation of neural progenitor pools by Sufu. Intriguingly, we observed spatial upregulation Gli1 and Gli2 transcription factors, selectively at the region that resides highly proliferative cells, implying that the increased cell proliferation could be caused by the changes of Gli transcription factors. Indeed, concomitant deletion of Gli2 in the Sufu mutant largely rescued the aberrant phenotypes. These findings clearly showed the requirement of Sufu to suppress Gli2 to conduct a domain specific regulation of hindbrain progenitor maintenance and differentiation. Our study demonstrates novel function of Sufu to ensure a tightly controlled progenitor pools maintenance and differentiation, mainly achieve by suppressing Gli2 activation.postprin

A study of Al1-xInxN growth by reflection high-energy electron diffraction-incorporation of cation atoms during molecular-beam epitaxy

Molecular-beam epitaxy of Al1-x Inx N alloys with different indium (In) contents, x, were studied by in situ reflection high-energy electron diffraction (RHEED). Growth rates of the alloys were measured by the RHEED intensity oscillations for different source flux conditions, while the lattice parameters were derived from the diffraction patterns. It was found that under the excess nitrogen growth regime, incorporation of aluminum was complete whereas incorporation of In atoms was incomplete even at temperatures below 400 °C. © 2008 American Institute of Physics.published_or_final_versio

Reprogramming of Dermal Fibroblasts into Osteo-Chondrogenic Cells with Elevated Osteogenic Potency by Defined Transcription Factors

Recent studies using defined transcription factors to convert skin fibroblasts into chondrocytes have raised the question of whether osteo-chondroprogenitors expressing SOX9 and RUNX2 could also be generated during the course of the reprogramming process. Here, we demonstrated that doxycycline-inducible expression of reprogramming factors (KLF4 [K] and c-MYC [M]) for 6 days were sufficient to convert murine fibroblasts into SOX9+/RUNX2+ cellular aggregates and together with SOX9 (S) promoted the conversion efficiency when cultured in a defined stem cell medium, mTeSR. KMS-reprogrammed cells possess gene expression profiles akin to those of native osteo-chondroprogenitors with elevated osteogenic properties and can differentiate into osteoblasts and chondrocytes in vitro, but form bone tissue upon transplantation under the skin and in the fracture site of mouse tibia. Altogether, we provide a reprogramming strategy to enable efficient derivation of osteo-chondrogenic cells that may hold promise for cell replacement therapy not limited to cartilage but also for bone tissues.published_or_final_versio