We report our transport studies in quasi one-dimensional (1D) conductors -helical polyacetylene fibers doped with iodine and the data analysis for other polymer single fibers and tubes. We found that at 30 K < T < 300 K the conductance and the current-voltage

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We report the low temperature current-voltage (I-V) characteristics studies in quasi one-dimensional conducting polymer nanofibers. We find a threshold voltage V t below which little current flows at temperatures below 30 -40 K. For V > V t current scales as (V/V t -1) ζ , where ζ ~ 1.8 -2.1 at high biases. Differential conductance oscillations are observed whose magnitude increases as temperature decreases below 10 K. We attributed the observed low temperature I-V behavior to Coulomb blockade effects with a crossover to Luttinger liquid-like behavior at high temperature. We demonstrate that at low temperatures such a doped conjugated polymer fiber can be considered as an array of small conducting regions separated by nanoscale barriers, where the Coulomb blockade tunneling is the dominant transport mechanism.PACS numbers: 71.30.+h, 72.20.Ee, 72.80.Le Complex structures built of nanosize conducting objects provide model systems for investigation of transport phenomena on the mesoscopic scale, where quantum confinement and Coulomb charging play an important role [1]. Electronic transport through an array of metallic nanocrystals separated by nanobarriers is determined by the interplay between single-electron charging of an individual conducting region and tunneling between adjacent islands. In such systems both the tunneling resistance between neighboring regions is large, R T >> h/e 2 and the charging energy E C = e 2 /2C of an excess electron on a site is larger than k B T (C is the capacitance of the region). In the presence of both charge and structural disorder this interplay leads to highly nonOhmic current-voltage (I-V) characteristics. Coulomb blockade theory predicts that at low temperatures, there is no current below a specific threshold voltage, V t , while above V t the current follows a power law:with ζ ~ 1 in one dimensional (1D) and 5/3 or 2 in twodimensional (2D) systems [2]. V t depends on the nanocrystal number, the capacitance of the conducting regions and the capacitance between the each region and the back gate. Such a behavior with scaling exponents between 1 and 2.3 has been found, for example, in narrow chains of carbon nanoparticles [3], and in 100 nm wide multilayer of gold particles which exhibited ζ ~ 1.6 [4]. Coulomb-blockade effects have also been observed in multiwalled carbon nanotubes [5], organic thin-film transistors based on highly ordered molecular materials [6] as well as in single-molecular transistor structures [7]. It is evident that the nature of the individual regions: metallic, semiconducting, quantum dots -is irrelevant for this phenomenon to be observed [8]. In view of these results the question arises whether Coulomb-blockade effects can also be observed in such inherent quasi-1D systems as conducting polymer nanofibers. In this connection polyacetylene (PA) nanofibers are of particular interest as the model system for nanotransport studies because of the simple chemical structure, well defined polycrystallinity [9], and good ability for doping [10][11][12]. It is...

These results demonstrate that dietary supplementation with (+)-catechin could protect epidermal cells against UVB-induced damage by modulating antioxidant enzyme activities.

Previous studies have demonstrated that the treatment of chronic hepatitis B (CHB) infection with adefovir (ADV) can impair renal function. In contrast, treatment with telbivudine (LdT) improves renal function in CHB patients. The aim of this study was to evaluate the renoprotective effect of LdT in CHB patients receiving ADV-based combination therapy. The effects of treatment with ADV + LdT on renal function were compared to those resulting from treatment with ADV + entecavir (ETV), ADV + lamivudine (LAM), ADV alone and ETV alone. The consecutive cohort analysis included 831 CHB patients who received ADV + LdT, ADV + LAM, ADV + ETV, ADV alone or ETV alone for 96 weeks. Alterations in estimated glomerular filtration rate (eGFR) were compared between the five groups using a linear mixed-effects model. HBV DNA levels were also compared between the five groups during the 96-week period. Among the five treatment groups, significant improvements in eGFR were observed in the ADV + LdT and ADV + LAM groups over time (P < 0.001 for each group compared with baseline eGFR). In patients with a baseline eGFR between 50 and 90 mL/min, the change in eGFR was the most significant in the ADV + LdT group (+0.641 mL/min; P < 0.001). Age, gender, baseline eGFR and treatment option were significant predictive factors for eGFR changes. In conclusion, our results suggest that the combination therapy of LdT and ADV is significantly associated with renoprotective effects in CHB patients when compared with other ADV-based combination or single therapies.