Depolarization block in olfactory sensory neurons expands the dimensionality of odor encoding.

Upon strong and prolonged excitation, neurons can undergo a silent state called depolarization block that is often associated with disorders such as epileptic seizures. Here, we show that neurons in the peripheral olfactory system undergo depolarization block as part of their normal physiological function. Typically, olfactory sensory neurons enter depolarization block at odor concentrations three orders of magnitude above their detection threshold, thereby defining receptive fields over concentration bands. The silencing of high-affinity olfactory sensory neurons produces sparser peripheral odor representations at high-odor concentrations, which might facilitate perceptual discrimination. Using a conductance-based model of the olfactory transduction cascade paired with spike generation, we provide numerical and experimental evidence that depolarization block arises from the slow inactivation of sodium channels-a process that could affect a variety of sensory neurons. The existence of ethologically relevant depolarization block in olfactory sensory neurons creates an additional dimension that expands the peripheral encoding of odors.

Selective dispersion of high purity semiconducting single-walled carbon nanotubes with regioregular poly(3-alkylthiophene)s.

Conjugated polymers, such as polyfluorene and poly(phenylene vinylene), have been used to selectively disperse semiconducting single-walled carbon nanotubes (sc-SWNTs), but these polymers have limited applications in transistors and solar cells. Regioregular poly(3-alkylthiophene)s (rr-P3ATs) are the most widely used materials for organic electronics and have been observed to wrap around SWNTs. However, no sorting of sc-SWNTs has been achieved before. Here we report the application of rr-P3ATs to sort sc-SWNTs. Through rational selection of polymers, solvent and temperature, we achieved highly selective dispersion of sc-SWNTs. Our approach enables direct film preparation after a simple centrifugation step. Using the sorted sc-SWNTs, we fabricate high-performance SWNT network transistors with observed charge-carrier mobility as high as 12 cm(2) V(-1) s(-1) and on/off ratio of >10(6). Our method offers a facile and a scalable route for separating sc-SWNTs and fabrication of electronic devices.

Stent restenosis in a Chinese population.

BACKGROUND: Stents are now widely used in Hong Kong and China and there is a clinical impression that restenosis is less common because of the lower prevalence of coronary artery disease and associated risk factors in the Chinese. However, there are no published data on angiographic stent restenosis rates in Chinese patients. METHOD: In a prospective study of 114 consecutive Chinese patients who underwent coronary stenting, quantitative coronary analyses were made at the time of stent implantation and subsequently at 6 months post-stenting (n = 97). RESULTS: At 6 months, restenosis (> or = 50% diameter stenosis in the dilated segment) was present in 42 (43.3%) of the 97 patients and 54 (33.5%) of the total 161 lesions stented. Vessel reference diameter (VRD) of < 3 mm and stented length of > or = 18 mm were associated with higher restenosis rates (36% and 38%). Compared to those without, those with restenosis had a greater residual stenosis of 16.53+/-11.54% and smaller final minimal luminal diameter (MLD) of 2.41+/-0.49 mm, (p < 0.01 and p < 0.008 respectively). Standard coronary risk factors were not associated with a higher rate of restenosis. Lesion morphology was significantly associated with restenosis. CONCLUSION: Coronary stenting in Hong Kong Chinese patients is associated with a restenosis rate comparable to that demonstrated in previously published trials from populations in the West.