Thermal conductivity of multi-walled carbon nanotube sheets: radiation losses and quenching of phonon modes.

The extremely high thermal conductivity of individual carbon nanotubes, predicted theoretically and observed experimentally, has not yet been achieved for large nanotube assemblies. Resistances at tube-tube interconnections and tube-electrode interfaces have been considered the main obstacles for effective electronic and heat transport. Here we show that, even for infinitely long and perfect nanotubes with well-designed tube-electrode interfaces, excessive radial heat radiation from nanotube surfaces and quenching of phonon modes in large bundles are additional processes that substantially reduce thermal transport along nanotubes. Equivalent circuit simulations and an experimental self-heating 3omega technique were used to determine the peculiarities of anisotropic heat flow and thermal conductivity of single MWNTs, bundled MWNTs and aligned, free-standing MWNT sheets. The thermal conductivity of individual MWNTs grown by chemical vapor deposition and normalized to the density of graphite is much lower (kappa(MWNT) = 600 +/- 100 W m(-1) K(-1)) than theoretically predicted. Coupling within MWNT bundles decreases this thermal conductivity to 150 W m(-1) K(-1). Further decrease of the effective thermal conductivity in MWNT sheets to 50 W m(-1) K(-1) comes from tube-tube interconnections and sheet imperfections like dangling fiber ends, loops and misalignment of nanotubes. Optimal structures for enhancing thermal conductivity are discussed.

Ciprofloxacin and cefazolin as a combination for empirical initial therapy of peritoneal dialysis-related peritonitis: five-year follow-up.

The treatment of peritoneal dialysis (PD)-related peritonitis has been a matter of extensive investigation, frequently generating therapeutic trials. Several combinations of antibiotics have served as newer protocols and tended to be efficacious, comfortable, and cost-effective. According to the more recent recommendations from the International Society for Peritoneal Dialysis, the rationale for empirical initial therapy of clinically detected peritonitis in PD patients has been to follow the bacterial profile derived from cultured specimens of PD effluents. The current study describes 5 year's experience with the use of a new antibiotic regimen for the treatment of peritonitis. We herein analyze the outcome of 95 episodes of peritonitis in 54 patients on either automated PD or continuous ambulatory PD at the dialysis unit of the Federal University of Rio de Janeiro. Peritoneal dialysis-related peritonitis was treated with the combination of oral ciprofloxacin and intraperitoneal cefazolin. The observed cure rate was 85.2% and the sensitivity test was observed to be positive for this combination of antibiotics in 88.9% of positive cultures. Of the 14 unsuccessful episodes, 7 were due to catheter colonization and the rest did not respond to the proposed therapy within 48 hours. These 7 cases were also related to peritoneal fluid cultures that were resistant to both ciprofloxacin and cefazolin. From this study, we propose this combination of oral ciprofloxacin and intraperitoneal cefazolin as a first choice for empirical initial therapy of PD-related peritonitis, given its efficacy and low cost. However, in order to apply the most adequate cost-effective therapy, careful examination of the bacterial profile and sensitivities to antibiotics used in each unit is strongly recommended.