Charge carrier mobility in an organic-inorganic hybrid nanocomposite

Organic-inorganic hybrid materials are media for electronic and optoelectronic applications. We present a study of the electronic transport in such a modelnanoparticle-sensitizedhybridorganic-inorganic photorefractive host system, consisting of poly(N-vinylcarbazole) doped with quantum dots of cadmium sulfide, using standard time-of-flight techniques. The photocurrent transients exhibit features typical of dispersive transport in an amorphous semiconductor. The hole mobility depends strongly on the electric field and temperature indicating Poole–Frenkel-like activated hopping transport; a thickness dependence of the mobility is observed. The presence of nanoparticles does not lead to increased trapping of holes. Conversely, a surprising result is observed: the mobility actually increases with the increase of nanoparticle concentration even though it is well below the percolation limit.This study was supported by a NSF, DMR Solid State and Polymer Chemistry Grant No. DMR0075867. Partial support by a Defense Research Initiative on Nanotechnology (DURINT), Contract No. F496200110358, through the Directorate of Chemistry and Life Sciences of the Air Force Office of Scientific Research is also acknowledged

Cavity-enhanced simultaneous dressing of quantum dot exciton and biexciton states

The authors acknowledge financial support of the Deutsche Forschungsgemeinschaft (DFG) within the SFB/TRR21 and the projects MI500/23-1 and Ka2318/4-1, and the Natural Sciences and Engineering Research Council of Canada.We demonstrate the simultaneous dressing of both vacuum-to-exciton and exciton-to-biexciton transitions of a single semiconductor quantum dot in a high-Q micropillar cavity, using photoluminescence spectroscopy. Resonant two-photon excitation of the biexciton is achieved by spectrally tuning the quantum dot emission with respect to the cavity mode. The cavity couples to both transitions and amplifies the Rabi-frequency of the likewise resonant cw laser, driving the transitions. We observe strong-field splitting of the emission lines, which depend on the driving Rabi field amplitude and the cavity-laser detuning. A dressed state theory of a driven 4-level atom correctly predicts the distinct spectral transitions observed in the emission spectrum, and a detailed description of the emission spectra is further provided through a polaron master equation approach which accounts for cavity coupling and acoustic phonon interactions of the semiconductor medium.PostprintPeer reviewe

Successful Endovascular Treatment of Cerebral Venous Thrombosis with a Novel, Larger Aspiration Catheter (REACT): A Case Report

Cerebral venous thrombosis (CVT) is a rare clinical entity, with clinical presentations extending from headache and seizures to coma and death. For adults developing progressive neurological worsening despite adequate medical management, endovascular thrombolysis and/or mechanical thrombectomy may be considered as treatment options. We present one such patient with CVT who developed seizures and slipped into a coma, despite best medical management. A large-bore aspiration catheter was used as a standalone system for the endovascular procedure. The venous sinuses were successfully re-canalized. The patient was discharged a week later with a modified Rankin scale of 2. Studies show that endovascular thrombolysis used alone or in conjunction with thrombectomy for CVT has a higher risk of hemorrhagic complications. If we were to use mechanical thrombectomy devices (that are specifically designed for intracranial clot retrieval) as a stand-alone system, we would probably have better clinical outcomes with a lower risk of hemorrhagic complications

A Rab5 endosomal pathway mediates Parkin-dependent mitochondrial clearance

Damaged mitochondria pose a lethal threat to cells that necessitates their prompt removal. The currently recognized mechanism for disposal of mitochondria is autophagy, where damaged organelles are marked for disposal via ubiquitylation by Parkin. Here we report a novel pathway for mitochondrial elimination, in which these organelles undergo Parkin-dependent sequestration into Rab5-positive early endosomes via the ESCRT machinery. Following maturation, these endosomes deliver mitochondria to lysosomes for degradation. Although this endosomal pathway is activated by stressors that also activate mitochondrial autophagy, endosomal-mediated mitochondrial clearance is initiated before autophagy. The autophagy protein Beclin1 regulates activation of Rab5 and endosomal-mediated degradation of mitochondria, suggesting cross-talk between these two pathways. Abrogation of Rab5 function and the endosomal pathway results in the accumulation of stressed mitochondria and increases susceptibility to cell death in embryonic fibroblasts and cardiac myocytes. These data reveal a new mechanism for mitochondrial quality control mediated by Rab5 and early endosomes