Driving risk assessment using driving behavior data under continuous tunnel environment.

Objective: Driving behavior is the key feature for determining the nature of traffic stream qualities and reflecting the risk of operating environments. However, evaluating the driving risk accurately and practically in continuous tunnels (tunnels with a space more than 250 m and less than 1000 m) still faces severe challenges due to the complex driving conditions. The objective of this study is to predict the driving risk indicators and determine different risk levels.Methods: The naturalistic driving system equipped with a road environment and driving behavior data acquisition system combined with the fixed-point test method was used for data collection in 130 tunnels on four highways. A traditional AASHTO braking model and convex hull algorithm were adopted to predict the critical safety speed and the critical time headway of each risk feature point in tunnels. According to the risk constraints under free-flow, car-following and lane-changing conditions, the average traffic flow risk index (TFRI) representing six risk levels and the safety threshold of the corresponding risk indicators were determined.Results: The findings of this study revealed that the critical safety speed at nighttime is slower than in other daytime conditions in continuous tunnels. The time headway slightly changes under 90 km/h. As the speed continues to increase, speed has a significant influence on the critical time headway. The only reliable interaction involved the different adverse weather conditions on the mean critical safety speed in the continuous tunnels (short plus long) (F = 9.730, p＜0.05) and single long tunnels (F = 12.365, p＜0.05).Conclusions: It can be concluded that driving behaviors significantly vary in different tunnel risk feature points and the combined effect of high speed and luminance variation may result in high driving risk. The performance validation indicted that the risk assessment level determined by the proposed approach is consistent with the real safety situations. The study provides an effective and generally acceptable method for identifying driving risk criteria that can also be applied for traffic management and safety countermeasures with a view to possible implementation in continuous tunnels.

[Effect of transcutaneous neuromuscular electrical stimulation on prevention of intensive care unit-acquired weakness in chronic obstructive pulmonary disease patients with mechanical ventilation].

OBJECTIVE: To evaluate the effect of transcutaneous neuromuscular electrical stimulation on prevention of intensive care unit-acquired weakness (ICU-AW) in chronic obstructive pulmonary disease (COPD) patients with mechanical ventilation. METHODS: A prospective randomized controlled study was conducted. Sixty COPD patients aged 18-85 years old who were accepted mechanical ventilation therapy admitted to general intensive care unit (ICU) of the First Affiliated Hospital of Hunan University of Medicine from October 2017 to October 2018 were enrolled. Patients were divided into control group (n = 30) and intervention group (n = 30) by random number table method. All patients were accepted routine treatment, and on this basis, the intervention group was applied transcutaneous neuromuscular electrical stimulation on the extremities (twice a day, 30 minutes each time) after 24 hours of admission until ICU discharge. The Medical Research Council muscle strength score (MRC-Score), grip strength, incidence of ICU-AW on the 7th day after admission and on the day of ICU discharge; modified Barthel index score on the day of ICU discharge; and duration of mechanical ventilation, the length of ICU stay, and the length of hospital stay were compared between the two groups. RESULTS: Twenty-nine and 27 patients in the control group and the intervention group respectively finally completed the study in dividually. There was no significant difference in gender, age, Barthel index score before 2 weeks of ICU admission, body mass index or acute physiology and chronic health evaluation (APACHE) in ICU between the two groups. There was no significant difference in the MRC-Score, grip strength or incidence of ICU-AW on the 7th day after ICU admission between the two groups. Compared to the control group, the MRC-Score, grip strength and Barthel index score in the intervention group were significantly increased [MRC-Score: 55.97±8.43 vs. 46.32±7.36, grip strength (kg): 33.46±11.62 vs. 27.42±9.64, Barthel index score: 46.04±5.46 vs. 42.13±3.32, all P < 0.05], the incidence rate of ICU-AW was significantly decreased [7.4% (2/27) vs. 31.0% (9/29), P < 0.05], and duration of mechanical ventilation, the length of ICU stay, the length of hospital stay were significantly shortened [duration of mechanical ventilation (days): 5.12±2.01 vs. 7.24±4.35, the length of ICU stay (days): 8.34±2.36 vs. 10.45±2.62, the length of hospital stay (days): 13.21±2.21 vs. 15.38±3.67, all P < 0.05]. CONCLUSIONS: Transcutaneous neuromuscular electrical stimulation can effectively improve the muscle strength of COPD patients with mechanical ventilation and reduce the incidence of ICU-AW.

α-Tocopherol protects keratinocytes against ultraviolet A irradiation by suppressing glutathione depletion, lipid peroxidation and reactive oxygen species generation.

This study aimed to investigate whether α-tocopherol is able to protect keratinocytes against ultraviolet A (UVA) radiation by increasing glutathione (γ-glutamylcysteinylglycine; GSH) levels or decreasing lipid peroxidation and reactive oxygen species (ROS) generation. The cell survival fraction was 43.6% when keratinocytes were irradiated with UVA at a dose of 8 J/cm2. α-Tocopherol was added prior to UVA irradiation and the cell viability was assayed. The cell survival fractions were 60.2, 77.1, 89.0, 92.9 and 96.2% when α-tocopherol was added at concentrations of 2.9, 5.9, 8.8, 11.8 and 14.7 IU/ml, respectively. These results suggested that α-tocopherol is capable of protecting keratinocytes against UVA irradiation. Furthermore, the levels of GSH, lipid peroxidation and ROS were measured. The levels of GSH were 0.354 and 0.600 mmol/g protein in keratinocytes irradiated with UVA (8 J/cm2) and in non-irradiated cells, respectively, whereas they were 0.364, 0.420, 0.525, 0.540 and 0.545 mmol/g protein when α-tocopherol was added at concentrations of 2.9, 5.9, 8.8, 11.8 and 14.7 IU/ml, respectively. The levels of lipid peroxidation were 20.401 or 5.328 µmol/g [malondialdehyde (MDA)/protein] in keratinocytes irradiated with UVA (8 J/cm2) and in non-irradiated cells, respectively, whereas they were 11.685, 6.544, 5.847, 4.390 and 2.164 µmol/g (MDA/protein) when α-tocopherol was added at concentrations of 2.9, 5.9, 8.8, 11.8 and 14.7 IU/ml, respectively. The levels of ROS were 3,952.17 or 111.87 1/mg protein in keratinocytes irradiated with UVA (8 J/cm2) and in non-irradiated cells, respectively, whereas they were 742.48, 579.36, 358.16, 285.63 and 199.82 1/mg protein when α-tocopherol was added at concentrations of 2.9, 5.9, 8.8, 11.8 and 14.7 IU/ml, respectively. These findings suggested that α-tocopherol protects keratinocytes against UVA irradiation, possibly through increasing the levels of GSH or decreasing the levels of lipid peroxidation and ROS generation.