In Japan, the incidence of heat illness in older people has rapidly increased during midsummer in the last decade, and we suggested that whey-protein+carbohydrate supplementation during aerobic training would increased plasma volume (PV) to enhance thermoregulatory adaptation in older men ( J Appl Physiol 107: 725-733, 2009); however, >60% of people age 65 and older suffer from hypertension, and the symptoms may be worsened by hypervolemia. To examine this, we randomly divided 21 older men (∼69 yr) with ∼160 mmHg for systolic and ∼90 mmHg for diastolic blood pressure at rest into two groups: Glc ( n = 11) consuming glucose alone (25 g) and Pro-Glc ( n = 10) consuming whey protein (10 g) + glucose (15 g), immediately after cycling exercise at 60–75% of peak aerobic capacity (V̇o2 peak) for 60 min/day, 3 days/wk, for 8 wk. Before and after training, we measured PV (dye dilution), baroreflex sensitivity (BRS) of heart rate (Valsalva maneuver), and carotid arterial compliance (CAC) from carotid arterial diameter (ultrasound imaging) responses to pulsatile arterial pressure change (photoplethysmography) at rest. Additionally, we measured esophageal temperature (Tes) and forearm skin blood flow (plethysmography) during exercise at 60% pretraining V̇o2 peak for 20 min in a warm environment. We found that the forearm skin vascular conductance response to increased Tes was enhanced in Pro-Glc with increased PV, but this was not found in Glc; however, despite the increased PV, arterial blood pressures rather decreased with increased CAC and BRS in Pro-Glc. Thus, the prescription was applicable to older men with hypertension to prevent heat illness during exercise.
A detailed structural analysis and dielectric property measurements of silicon nitride films fabricated using atmospheric pressure (AP) plasma were carried out, and the results were compared to those of nitride films fabricated using a radio frequency plasma. Using AP plasma, 1.8-nm-thick silicon nitride films composed of Si3N3.5O0.7 were obtained at nitridation temperatures ranging from 25to500°C. X-ray photoelectron spectroscopy using a monochromatic AlKα source at 1486.6eV and high-resolution Rutherford backscattering spectrometry revealed approximately 10% more nitrogen atoms corresponding to the N–Si3 bond in the film using AP plasma than those using rf plasma. In the range of 25–500°C, the nitridation temperature did not affect the leakage current densities of the films fabricated using AP plasma. Films fabricated at 25°C showed leakage current density of as low as 7×10−2A∕cm2 at 5MV∕cm. This value was one order of magnitude lower than that using rf plasma. The direct-tunneling current simulation analysis with the Wentzel-Kramers-Brillouin approximation revealed that the effective tunneling mass of holes increased due to the nitrogen atoms incorporated in the films. From deep-level transient spectroscopy, signals attributed to defects generated by plasma irradiation in the silicon substrate were not observed.
The reaction process model during initial nitridation of Si (111) using atmospheric pressure plasma source was constructed and it was compared to that using a radio frequency plasma source. In atmospheric pressure plasma, emission lines from the N2 second positive system were dominantly observed. By exposing the atmospheric pressure plasma to Si substrate at the temperature ranging from 25to500°C, silicon nitride films with a thickness below 1.8nm were formed. In order to study the nitridation process, the changes in the film thickness against the substrate temperature and nitridation time were systematically studied at a pressure ranging from 50to700Torr. The film thickness increases with increasing the nitridation pressure below 400Torr and it saturates above 500Torr. It was completely regardless of the substrate temperature. From the time dependence of the film thickness at various nitridation pressures, it was revealed that these experimental results were well fitted to a Langmuir-type adsorption model. In the case of nitridation using atmospheric pressure (AP) plasma, molecular species play an important role for nitridation without thermal diffusion. The difference of silicon nitride films fabricated using AP plasma and rf plasma originates from the difference in the active species.
We report that ultrathin silicon nitride films can be fabricated using N2 plasma near atmospheric pressure. In this paper, we describe the effect of additional oxygen on the formation of oxynitride films. Silicon oxynitride films were formed at an oxygen flow rate as low as 2.5 mL/min with a nitrogen flow rate of 10 L/min, in which the introduction of such a small amount of additional oxygen into the nitrogen plasma generated near atmospheric pressure enhances the oxidation reaction. X-ray photoemission spectroscopy analysis revealed that with increasing oxygen flow rate, the composition of the oxynitride films changed from Si3N3.5O0.7 to Si3N0.8O4.6. Optical emission spectroscopy showed emission peaks attributed to NO-γ transition as well as to the N2 second-positive system in the plasma discharge space. Emissions from the NO-γ transition show the dissociation of additional oxygen molecules, and active species such as oxygen atoms as well as NO and N2O molecules were generated by collisions between the N2(A3Σu +) and the O2(X3Σg -) states, resulting in the enhancement of Si oxidation near atmospheric pressure. Leakage current density decreases with increasing in the oxygen concentration. The 2.1-nm-thick silicon oxynitride film composed of Si3N0.8O4.6 showed a leakage current density as low as 3.5×10-4 A/cm2 at 5 MV/cm.
Stable discharging of pure nitrogen can be maintained even at atmospheric pressure when alternative pulsed voltage is applied between two parallel plate electrodes. From optical emission spectroscopy, strong emissions from the N2 2nd positive system, weak emissions from N2 Herman's infrared system and N2 1st positive system were observed. The emission intensities from the N2 2nd positive system and the N2 Herman's infrared system increase with increasing the nitrogen gas pressure, whereas the emission intensities from the N2+ 1st negative system and N2 1st positive system decrease. The thickness of the silicon nitride film fabricated at 500 Torr was 1.6 nm at a nitridation temperature as low as 25°C, regardless of the nitridation temperature and nitridation time. From these results, we conclude that N2(C3IIu) plays an important role for the excellent reactivity of the nitrogen plasma generated near atmospheric pressure.
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