High-pressure resonance Raman experiments were performed on linear carbon chains Cn confined in double-wall carbon nanotubes (Cn@DWCNT). Our results indicate that the frequency of the chain mode ...undergoes a non-linear decreasing as pressure increases, in agreement with previous studies of the behavior of carbon chains into multi-wall carbon nanotubes. After the pressure cycle, the Cn modes present an irreversible frequency downshift together with an irreversible upshift (downshift) of the RBM modes (G+ band) of the inner tube. These spectral changes are interpreted as evidence of cross-linking between the carbon chain and the wall of the inner tube. Density functional theory (DFT) calculations were performed in order to shed light on the interpretation of the experimental data. The theoretical calculations show a pressure-induced charge transfer from the nanotube to the carbon chain, thus resulting in an increasing of the C≡C bond length, and consequently, a softening frequency of the Cn Raman mode. Furthermore, an irreversible cross-linking between the tube and Cn is observed when the maximum applied pressure is higher than the pressure of radial tube collapse is predicted by modelling, thus supporting the experimental results.
We study the pressure induced collapse of single-, double- and triple-wall carbon nanotubes. Theoretical simulations were performed using density-functional tight-binding theory. For tube walls ...separated by the graphitic distance, we show that the radial collapse pressure, Pc, is mainly determined by the diameter of the innermost tube, din and that its value significantly deviates from the usual Pc∝din−3 Lévy-Carrier law. A modified expression, Pcdin−3=α(1−β2∕din2) with α and β numerical parameters, which reduces the collapse pressure for low diameters is proposed. For din ≳ 1.5 nm an enhanced stability is found which may be assigned as due to the bundle intertube geometry-induced interactions. If the inner and outer tubes are separated by larger distances, the collapse process is found to be more complex. High-pressure resonant Raman experiments were performed in double-wall carbon nanotubes having inner and outer diameters averaging 1.5 nm and 2.0 nm, respectively. A modification in the response of the G-band and the disappearance of the radial breathing modes between 2 GPa and 5 GPa indicate the beginning and the end of the radial collapse process. Experimental results are in good agreement with our theoretical predictions, but do not allow to discriminate from those corresponding to a continuum mechanics model.
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Patients with chronic obstructive pulmonary disease (COPD) exhibit aerobic function, autonomic nervous system, and mucociliary clearance alterations. These parameters can be attenuated by aerobic ...training, which can be applied with continuous or interval efforts. However, the possible effects of aerobic training, using progressively both continuous and interval sessions (ie, linear periodization), require further investigation.
To analyze the effects of 12-week aerobic training using continuous and interval sessions on autonomic modulation, mucociliary clearance, and aerobic function in patients with COPD.
Sixteen patients with COPD were divided into an aerobic (continuous and interval) training group (AT) (n=10) and a control group (CG) (n=6). An incremental test (initial speed of 2.0 km·h(-1), constant slope of 3%, and increments of 0.5 km·h(-1) every 2 minutes) was performed. The training group underwent training for 4 weeks at 60% of the peak velocity reached in the incremental test (vVO2peak) (50 minutes of continuous effort), followed by 4 weeks of sessions at 75% of vVO2peak (30 minutes of continuous effort), and 4 weeks of interval training (5×3-minute effort at vVO2peak, separated by 1 minute of passive recovery). Intensities were adjusted through an incremental test performed at the end of each period.
The AT presented an increase in the high frequency index (ms(2)) (P=0.04), peak oxygen uptake (VO2peak) (P=0.01), vVO2peak (P=0.04), and anaerobic threshold (P=0.02). No significant changes were observed in the CG (P>0.21) group. Neither of the groups presented changes in mucociliary clearance after 12 weeks (AT: P=0.94 and CG: P=0.69).
Twelve weeks of aerobic training (continuous and interval sessions) positively influenced the autonomic modulation and aerobic parameters in patients with COPD. However, mucociliary clearance was not affected by aerobic training.
Background: Elective treatment of the neck in oral squamous cell carcinoma has changed over the last 20 years. The main object of this report is to present the results of a multi-institutional ...prospective study designed to compare standard treatment with modified radical classical neck dissection (MRND) to supraomohyoid neck dissection (SOH) in the management of the clinically negative neck in oral cancer patients.
Patients and methods: A total of 148 patients were included in the trial. All patients had previously untreated T2 to T4 N0 squamous cell carcinoma of the oral tongue (62 cases), floor of the mouth (49 cases), inferior gingiva (12 cases), or retromolar trigone (25 cases). Tumor stages were T2, 91; T3, 27; and T4, 30. There were no significant imbalances between groups.
Results: The false-negative rate was 28%, and most positive nodes were sited at level II and III. Complications were seen in 41% of MRND patients and in 25% of SOH patients (
P = 0.043). Median total duration of hospitalization was 9 days in MRND patients and 7 days in the SOH group. To date, 19 and 16 patients presented with local and neck recurrences, respectively. The 60-month actuarial survival rates were 63% in the MRND group and 67% in the SOH group (
P = 0.7150).
Conclusions: This study demonstrates that the recurrence and survival rates were similar in both groups. SOH neck dissection can be recommended as standard elective treatment for patients with T2–T4 oral squamous cell carcinomas.
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