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Many biochemical processes, such as charge hopping or protein folding, can be described by an average timescale to reach a final state, starting from an initial state. Here, we provide a pedagogical treatment of the mean first-passage time (MFPT) of a physical process, which depends on the number of intervening states between the initial state and the target state. Our aim in this tutorial review is to provide a clear development of the mean first-passage time formalism and to show some of its practical utility. The MFPT treatment can provide a useful link between microscopic rates and the average timescales often probed by experiment. [ABSTRACT FROM AUTHOR]

Single-walled carbon nanotube (SWNT)-based nanohybrid compositions based on (6,5) chirality-enriched SWNTs ([(6,5) SWNTs]) and a chiral n-type polymer (SPBN( b)-Ph4PDI) that exploits a perylenediimide (PDI)-containing repeat unit are reported; S-PBN(b)-Ph4PDI-[(6,5) SWNT] superstructures feature a PDI electron acceptor unit positioned at 3 nm intervals along the nanotube surface, thus controlling rigorously SWNT-electron acceptor stoichiometry and organization. Potentiometric studies and redox-titration experiments determine driving forces for photoinduced charge separation (CS) and thermal charge recombination (CR) reactions, as well as spectroscopic signatures of SWNT hole polaron and PDI radical anion (PDI-•) states. Time-resolved pump-probe spectroscopic studies demonstrate that SPBN( b)-Ph4PDI-[(6,5) SWNT] electronic excitation generates PDI-• via a photoinduced CS reaction (ΤCS.0.4 ps, ΦCS ≈0.97). These experiments highlight the concomitant rise and decay of transient absorption spectroscopic signatures characteristic of the SWNT hole polaron and PDI-• states. Multiwavelength global analysis of these data provide two charge-recombination time constants (ΤCR≈31.8 and 250 ps) that likely reflect CR dynamics involving both an intimately associated SWNT hole polaron and PDI-• charge-separated state, and a related charge-separated state involving PDI-• and a hole polaron site produced via hole migration along the SWNT backbone that occurs over this timescale. [ABSTRACT FROM AUTHOR]

Purpose: Here, the authors describe a dosimetry measurement technique for microbeam radiation therapy using a nanoparticle-terminated fiber-optic dosimeter (nano-FOD). Methods: The nano-FOD was placed in the center of a 2 cm diameter mouse phantom to measure the deep tissue dose and lateral beam profile of a planar x-ray microbeam. Results: The continuous dose rate at the x-ray microbeam peak measured with the nano-FOD was 1.91 ± 0.06 cGy s-1, a value 2.7% higher than that determined via radiochromic film measurements (1.86 ± 0.15 cGy s-1). The nano-FOD-determined lateral beam full-width half max value of 420 μm exceeded that measured using radiochromic film (320 µm). Due to the 8° angle of the collimated microbeam and resulting volumetric effects within the scintillator, the profile measurements reported here are estimated to achieve a resolution of ~0.1 mm; however, for a beam angle of 0°, the theoretical resolution would approach the thickness of the scintillator (~0.01 mm). Conclusions: This work provides proof-of-concept data and demonstrates that the novel nano-FOD device can be used to perform real-time dosimetry in microbeam radiation therapy to measure the continuous dose rate at the x-ray microbeam peak as well as the lateral beam shape. [ABSTRACT FROM AUTHOR]

Umgarnt und abgelegt: Polyanionische [Arylen]ethinylen ‐ Polymere, die sich helixförmig um einwandige Kohlenstoffnanoröhren (SWNTs) wickeln, ermöglichen die Herstellung von SWNTs mit Löslichkeit in organischen Solventien. Die SWNTs organisieren sich zu Strukturen aus ausgerichteten Nanoröhren, wobei die optoelektronischen Eigenschaften der einzelnen SWNTs erhalten bleiben. [ABSTRACT FROM AUTHOR]

In vivo fluorescence imaging with near-infrared (NIR) light holds enormous potential for a wide variety of molecular diagnostic and therapeutic applications. Because of its quantitative sensitivity, inherent biological safety, and relative ease of use (i.e., with respect to cost, time, mobility, and its familiarity to a diverse population of investigators), fluorescence-based imaging techniques are being increasingly utilized in small-animal research. Moreover, there is substantial interest in the translation of novel optical techniques into the clinic, where they will prospectively aid in noninvasive and quantitative screening, disease diagnosis, and post-treatment monitoring of patients. Effective deep-tissue fluorescence imaging requires the application of exogenous NIR-emissive contrast agents. Currently, available probes fall into two major categories: organic and inorganic NIR fluorophores (NIRFs). In the studies reviewed herein, we utilized polymersomes (50 nm to 50 µm diameter polymer vesicles) for the incorporation and delivery of large numbers of highly emissive oligo (porphyrin)-based, organic NIRFs Copyright © 2009 John Wiley & Sons, Inc. For further resources related to this article, please visit the . [ABSTRACT FROM AUTHOR]