Structural Polymorphism Kinetics Promoted by Charged Oxygen Vacancies in HfO_{2}.

Defects such as oxygen vacancy are widely considered to be critical for the performance of ferroelectric HfO_{2}-based devices, and yet atomistic mechanisms underlying various exotic effects such as wake-up and fluid imprint remain elusive. Here, guided by a lattice-mode-matching criterion, we systematically study the phase transitions between different polymorphs of hafnia under the influences of neutral and positively charged oxygen vacancies using a first-principles-based variable-cell nudged elastic band technique. We find that the positively charged oxygen vacancy can promote the transition of various nonpolar phases to the polar phase kinetically, enabled by a transient high-energy tetragonal phase and extreme charge-carrier-inert ferroelectricity of the polar Pca2_{1} phase. The intricate coupling between structural polymorphism kinetics and the charge state of the oxygen vacancy has important implications for the origin of ferroelectricity in HfO_{2}-based thin films as well as wake-up, fluid imprint, and inertial switching.

[Study of dental caries and correlated factors of 12-year-old children in Dongxiang, Baoan and Yugu races].

OBJECTIVE: To investigate the epidemiology of dental caries and its correlated factors of 12-year-old children in Dongxiang, Baoan and Yugu races. METHODS: According to the method of third national oral health epidemiologic investigation, 448 12-year-old children in Dongxiang, Baoan and Yugu races were randomly collected and the epidemiological investigation of dental caries, oral bacteriological detection and oral hygiene behavior were carried out. RESULTS: 1) The caries prevalence rate of Dongxiang, Baoan and Yugu races were 40.52%, 44.29%, 46.45%, respectively. The average caries of Dongxiang, Baoan and Yugu races were 0.92, 0.90, 1.13, respectively. 2) The main ranks of Streptococcus mutans in saliva were class 2 and class 3 in Dongxiang and Baoan races. However, it was class 0 or class 1 in Yugu race. The level of Streptococcus mutans in dental plaque was higher in Dongxiang and Baoan races than in Yugu race. 3) The children's everyday brushing rate was higher in Yugu race than in Dongxiang and Baoan races (P<0.01). But there were no difference between Dongxiang and Baoan races. CONCLUSION: The caries prevalence rates of 12-year-old children in Dongxiang, Baoan and Yugu races are high. The main factors of high caries prevalence rate were low brushing rate and dental plaque couldn't be removed effectively. Oral health education should be strengthened in the three race areas.

[Effects of patient-controlled analgesia with small dose ketamine combined with morphine and the influence thereof on plasma beta-endorphin level in patients after radical operation for esophageal carcinoma].

OBJECTIVE: To evaluate the effects of patient-controlled analgesia (PCA) with small dose ketamine combined with morphine on analgesia and influence thereof on the plasma beta-endorphin (EP) level in the patients after radical operation for esophageal carcinoma. METHODS: Thirty ASAI-II patients, aged 35-65, weighing 42-75 kg, with visual analogue score>or=3, undergoing elective radical operation for esophageal carcinoma under general anesthesia received intravenous morphine 2 - 3 mg were randomly divided into 2 equal groups: group m receiving morphine 0.02 mg.kg(-1).h(-1), and with group mk receiving morphine 0.02 mg.kg(-1).h(-1) combined with ketamine 0.08 mg.kg(-1).h(-1) for 50 h. In the course of treatment the patients received intravenous injection of morphine 2-3 mg when the VAS was >or=3. VAS was recorded 4, 8, 20, 24, and 48 h after operation. The amount of morphine used after operation, PCA button pressing times (effective/active), side effects, and vital signs including pulse, saturation of blood oxygen, respiratory rate, heart rate, and average arterial pressure were recorded. Central venous blood samples were collected when entering the operation room (T0), by the end of operation (T1), and 6 h (T2), 24 h (T3), and 48 h (T4) after operation respectively to examine the beta-endorphin level. RESULTS: During the period 4-48 h after operation the VAS scores of the group mk were significantly lower than those of the group m in activity state (all P<0.05) and were not significantly different those of the group m at resting state (all P>0.05). The total amount of morphine consumed and the actual PCA button pressing times were significantly less in the group mk than in the group m (both P<0.05). The incidence rates of nausea, vomiting, and pruritus of the group mk were all significantly lower than those of the group m (all P<0.05). There were not significant differences in the incidence rates of dreaming and pseudoesthesia between these 2 groups. All the vital signs were stable in the 2 groups. The plasma beta-EP levels at the time point T1 of these 2 groups were both significantly higher than those at T0 (both P<0.05). The plasma beta-endorphin levels at T2-4 of the group mk decreased gradually from the level at T1 to the level at T0, and the plasma beta-endorphin levels of the group m rapidly decreased from the level at T0 to the T0 level and remained at this level to the 48 h after operation. CONCLUSION: The combination of small dose of ketamine with morphine provides optimal analgesia with low side-effect rate and little effect on the plasma beta-EP level.

[Investigation of oral health status in 3 516 undergraduate university students].

OBJECTIVE: To investigate the oral health status of undergraduate university students and to guide their oral hygiene behaviors. METHODS: 3516 college students in Northwest University for Nationalities were investigated in this study according to the criterion issued by World Health Organization (WHO) on the basic methods of oral health investigation in 1997. RESULTS: The caries prevalence rate among the students investigated was 47.87%. The average decayed teeth were 1.29. The obturation rate of caries was 20.42%. The students came from city showed significant higher caries rate than those from countryside, and so did the female students compared with the male students. Dental calculus rate was 79.78%. The dental segments related were 3.75. The worst situation was among male students and students from countryside. The examined rates were 53.30% of crowded incisor, 42.58% of maximum upper-incisor anomaly, 50.60% of the maximum lower-incisor anomaly and 31.09% of molar malposition, respectively. More rates of dentofacial anomalies showed no differences of significance between different area and gender. CONCLUSION: In general, the oral health status of the college students are not ideal. It is necessary to advocate early examination, early prevention and early treatment among the students in university.