Self-separated hydrothermal lead zirconate titanate thick films for high frequency transducer applications

Using a simple rapid heating process, Pb(Zr(0.52)Ti(0.48))O(3) (PZT) thick films prepared by hydrothermal method were separated from a Ti substrate. Scanning electron microscopy (SEM) revealed that the self-separated films were crack-free. After solution infiltration and high temperature annealing, the PZT thick films were shown to possess good electric properties. At 1 kHz, the dielectric constant and the loss were 593 and 0.05, respectively. The remnant polarization was 30.0 muCcm(2) at room temperature. A high frequency single element ultrasound transducer fabricated with these films showed a bandwidth at -6 dB of 73% at a center frequency of 67 MHz.

Piezoelectric PZT thick films on LaNiO(3) buffered stainless steel foils for flexible device applications

In this paper, we report on 4.5µm piezoelectric Pb(Zr(0.52)Ti(0.48))O(3) (PZT) thick films deposited on flexible stainless steel (SS) foils with LaNiO(3) (LNO) buffer layers using a ceramic powder/sol-gel solution modified composite method. The polycrystalline thick films show a hysteresis loop at an applied electric field of 900 kV cm(-1) with remanent polarization and coercive electric field values of 27µC cm(-2) and 85 kV cm(-1), respectively. At 1 kHz, the dielectric constant is 653 and the dielectric loss is 0.052. The leakage current density of the film is lower than 1.55 × 10(-5) Acm(-2) over the range of 0 to ±150V. The conduction current shows ohmic behaviour at a low electric field and space-charge-limited current characteristics at a high electric field.

Structural modulation in the orbitally induced Peierls state of MgTi(2)O(4)

The structural properties associated with the orbitally induced Peierls transition in MgTi(2)O(4) are characterized by in situ cooling TEM observations. A distinctive structural modulation with the wavevector of q(1) = 1/4 (0, 0, 4) has been well demonstrated below a critical temperature of about 260 K for MgTi(2)O(4). Systematic analysis demonstrates that this structural modulation can be well explained by an orbital order existing in the low-temperature insulating phase. It is also noted that the nonstoichiometric feature commonly appearing in the present system could yield visible changes in both physical and structural properties. A low-temperature study of the microstructure of Mg[Ti(1.9)Mg(0.1)]O(4) reveals that a little substitution of Mg(2+) for Ti(3+) ions on the octahedral sites can disrupt the long-range order of the t(2g) orbitals, resulting in complex tweed structures in the superstructure phase.

Low-temperature synthesis and photocatalytic properties of ZnO nanotubes by thermal oxidation of Zn nanowires

A low-cost and catalyst-free two-step approach has been developed to produce ZnO nanotubes (ZNTs) by simple thermal oxidation of Zn nanowires under 20 Pa at a low temperature of 400 °C. The growth mechanism of ZNTs is discussed in detail. The formation of these tubular structures is closely linked to the oxidation pressure and temperature, which involves a process consisting of the deposition of Zn nanowires, cracking of the Zn nanowires and sublimation of the Zn cores, and subsequent oxidation to ZNTs. The optical properties were studied by using Raman and photoluminescence spectra, where a strong green emission related to the single ionized oxygen vacancy appears. The photocatalytic activity measurement indicates an enhanced photocatalytic activity of the prepared ZNTs due to their high surface-to-volume ratios and abundant oxygen vacancies near the surfaces of the ZNTs. This type of high surface area structural ZNTs could find promising potential for optoelectronic and environmental applications.

Effect of the interval between pregnancies on perinatal outcomes among white and black women

OBJECTIVE

We evaluated interpregnancy interval in relation to adverse perinatal outcomes and whether the relationship differed by race.

STUDY DESIGN

We analyzed the vital statistics data for multiparous white and black women in Michigan who delivered a singleton live birth during the period 1993 through 1998, using stratified and logistic regression techniques.

RESULTS

Among women of both races, the risk for delivering low birth weight, premature, and small-for-gestational-age birth was lowest if the interpregnancy interval was 18 to 23 months. In comparison, among white women, the odds ratios for the 3 outcomes were 1.5, 1.3, and 1.3, respectively, if the interval was <6 months, and 1.9, 1.4, and 1.7, respectively, if the interval was > or =120 months, controlling for other factors. Similarly, among black women, the odds ratios were 1.5, 1.2, and 1.3, respectively, if the interval was <6 months, and 1.6, 1.3, and 1.4, respectively, if the interval was > or =120 months.

CONCLUSION

An interpregnancy interval of 18 to 23 months is associated with the lowest risk for adverse perinatal outcomes among both white and black women.

Effect of the interval between pregnancies on perinatal outcomes

BACKGROUND

A short interval between pregnancies has been associated with adverse perinatal outcomes. Whether that association is due to confounding by other risk factors, such as maternal age, socioeconomic status, and reproductive history, is unknown.

METHODS

We evaluated the interpregnancy interval in relation to low birth weight, preterm birth, and small size for gestational age by analyzing data from the birth certificates of 173,205 singleton infants born alive to multiparous mothers in Utah from 1989 to 1996.

RESULTS

Infants conceived 18 to 23 months after a previous live birth had the lowest risks of adverse perinatal outcomes; shorter and longer interpregnancy intervals were associated with higher risks. These associations persisted when the data were stratified according to and controlled for 16 biologic, sociodemographic, and behavioral risk factors. As compared with infants conceived 18 to 23 months after a live birth, infants conceived less than 6 months after a live birth had odds ratios of 1.4 (95 percent confidence interval, 1.3 to 1.6) for low birth weight, 1.4 (95 percent confidence interval, 1.3 to 1.5) for preterm birth, and 1.3 (95 percent confidence interval, 1.2 to 1.4) for small size for gestational age; infants conceived 120 months or more after a live birth had odds ratios of 2.0 (95 percent confidence interval, 1.7 to 2.4);1.5 (95 percent confidence interval, 1.3 to 1.7), and 1.8 (95 percent confidence interval, 1.6 to 2.0) for these three adverse outcomes, respectively, when we controlled for all 16 risk factors with logistic regression.

CONCLUSIONS

The optimal interpregnancy interval for preventing adverse perinatal outcomes is 18 to 23 months.

The relationship between cigarette smoking and education revisited: implications for categorizing persons' educational status

OBJECTIVE

This study sought to reassess the relationship between cigarette smoking and education.

METHODS

Data from the 1983 to 1991 National Health Interview Survey for participants aged 25 years and older were used to plot the prevalence of current smoking, ever smoking, heavy smoking, and smoking cessation, as well as the adjusted log odds ratios, by years of education.

RESULTS

The "less than high school graduate" category consisted of two groups with distinct smoking patterns: persons with 0 to 8 years and persons with 9 to 11 years of education. The latter were the most likely to be current, ever, and heavy smokers and the least likely to have quit smoking, whereas the former were similar to persons having 12 years of education. After 11 years of education, the likelihood of smoking decreased and that of smoking cessation increased with each successive year of education. These results persisted after the statistical adjustment for age, sex, ethnicity, poverty status, employment status, marital status, geographic region, and year of survey.

CONCLUSIONS

The relationship between smoking and education is not monotonic. Thus, when evaluating smoking in relation to education, researchers should categorize years of education as follows: 0 to 8, 9 to 11, 12, 13 to 15, and 16 or more years.

Cigarette smoking and its risk factors among elementary school students in Beijing

OBJECTIVES

This study investigated patterns of and risk factors for smoking among elementary school children in Beijing, China.

METHODS

In 1988, anonymous questionnaires were administered to a multistage stratified cluster sample of 16996 students, aged mostly 10 to 12, in 479 fourth- to sixth-grade classes from 122 Beijing elementary schools.

RESULTS

Approximately 28% of boys and 3% of girls had smoked cigarettes. The most frequently cited reasons for smoking initiation were "to imitate others' behavior" and "to see what it was like." Girls were more likely to get cigarettes from home than to purchase their own. Having close friends who smoked and being encouraged by close friends to smoke were strong risk factors for smoking. Smoking was also associated with lower parental socioeconomic status; having parents, siblings, or teachers who smoked; buying cigarettes for parents; performing poorly in school; and not believing that smoking is harmful to health.

CONCLUSIONS

Gender differences in smoking prevalence among adolescents in China are larger than those among US teenagers, whereas the proximal risk factors for smoking are similar. Major efforts are needed to monitor and prevent smoking initiation among Chinese adolescents, particularly girls.

Factors affecting the performance of the models in the Mortality Probability Model II system and strategies of customization: a simulation study

OBJECTIVES

To examine the impact of hospital mortality and intensive care unit (ICU) size on the performance of the Mortality Probability Model II system for use in quality assessment, and to examine the ability of model customization to produce accurate estimates of hospital mortality to characterize patients by severity of illness for clinical trials.

DESIGN

Prospective evaluation of model performance, using retrospective data.

SETTING

Data for the simulation were assembled from six adult medical and surgical ICUs in Massachusetts and New York.

PATIENTS

Consecutive admissions (n = 4,224) to the Massachusetts and New York ICUs were studied. The mortality rate in the database was 18.7%.

INTERVENTIONS

A computer simulation of several different hospital mortality rates and ICU sample sizes, using a multicenter database of consecutive ICU admissions, was utilized. We simulated 20 different mortality rates by randomly changing the outcomes at hospital discharge from "survived" to "deceased" and from "deceased" to "survived". Four sample size simulations used 75%, 50%, 25%, and 10% of the database. Ten replications of each mortality rate and samples size were constructed, and model calibration and discrimination were assessed for each replication. Model coefficients were customized, using logistic regression.

MEASUREMENTS AND MAIN RESULTS

Vital status at hospital discharge was the outcome measure among the ICU patient population. Model performance was assessed using the Hosmer-Lemeshow C statistic for calibration, and the area under the receiver operating characteristic curve for discrimination. Goodness-of-fit tests and receiver operating characteristic curve areas demonstrated that the models were sensitive to differences in hospital mortality, indicating that they are useful quality assurance tools. Goodness-of-fit tests were more sensitive than the receiver operating characteristic curve areas. The further the hospital mortality rate diverged from the original rate, the worse the performance of the model. Sample size had an impact on these results. The smaller the sample size, the less likely the model was to perform poorly. Model coefficients were successfully customized to demonstrate that improved model performance can be achieved when necessary for clinical trial stratification.

CONCLUSION

Mortality Probability Model II models can be used to assess quality of care in ICUs, but the size of the sample should be considered when assessing calibration and discrimination.

Surveillance for selected tobacco-use behaviors--United States, 1900-1994

PROBLEM/CONDITION

Surveillance of tobacco use is an essential component of any tobacco-control program. The information gathered can be used to guide research initiatives, intervention programs, and policy decisions. REPORTING PERIODS: This report covers the period 1900-1994 for per capita cigarette consumption; 1965-1991 for trends in cigarette smoking prevalence and cessation; 1974-1991 for trends in the number of cigarettes smoked daily by current smokers; 1987-1991 for recent patterns of tobacco use; 1970, 1987, and 1991 for trends in cigar/pipe smoking and snuff/chewing tobacco use; 1984-1992 for trends in state-specific prevalences of regular cigarette smoking; 1987-1992 for state-specific estimates of smokeless-tobacco use; and 1976-1993 for trends in cigarette smoking among U.S. high school seniors.

DESCRIPTION OF SYSTEMS

Estimates of cigarette consumption are reported by the U.S. Department of Agriculture, which uses data from the U.S. Department of the Treasury, the U.S. Department of Commerce, the Tobacco Institute, and other sources. The National Health Interview Survey uses household interviews to provide nationally representative estimates (for the civilian, noninstitutionalized population) of cigarette smoking and other behaviors related to tobacco use. The Behavioral Risk Factor surveillance System uses telephone surveys of civilian, noninstitutionalized adults (> or = 18 years of age) to provide state-specific estimates of current cigarette smoking and use of smokeless tobacco. The University of Michigan's Institute for Social Research uses school-based, self-administered questionnaires to gather data on cigarette smoking from a representative sample of U.S. high school seniors.

RESULTS

During the period 1900-1963, per capita cigarette consumption increased; after 1964, consumption declined. During the years 1965-1991, current cigarette smoking prevalence among persons ages > or = 18 years declined overall and in every sociodemographic category examined. Decrease in current smoking prevalence was slow in some groups (e.g., among persons with fewer years of formal education). Both the prevalence of never smoking and the prevalence of cessation increased from 1965 through 1991. The prevalence of current cigarette smoking, any tobacco smoking, and any tobacco use was highest among American Indians/Alaska Natives and non-Hispanic blacks and lowest among Asians/Pacific Islanders. The prevalence of cigar smoking and pipe smoking has declined substantially since 1970. The prevalence of smokeless-tobacco use among white males ages 18-34 years was higher in 1987 and 1991 than in 1970; among persons > or = 45 years of age, the use of smokeless tobacco was more common among blacks than whites in 1970 and 1987. Cigarette smoking prevalence has decreased in most states. The prevalence of smokeless tobacco use was especially high among men in West Virginia, Montana, and several southern states. From 1984-1993, prevalence of cigarette smoking remained constant among U.S. high school seniors. However, prevalence increased slightly for male seniors and white seniors, decreased slightly for female high school seniors, and decreased sharply for black high school seniors.

INTERPRETATION

With the exceptions of increases in cigarette smoking among white and male high school seniors and in the use of smokeless tobacco among white males ages 18-34 years, reductions in tobacco use occurred in every subgroup examined. This decrease must continue if the national health objectives for the year 2000 are to be reached.

ACTIONS TAKEN

Surveillance of tobacco use is ongoing. Effective interventions that discourage initiation and encourage cessation are being disseminated throughout the United States.

Cigarette smoking among junior high school students in Beijing, China, 1988

Prevalence, behavioural patterns and risk factors of cigarette smoking were studied in a sample of 8437 junior high school students in Beijing in 1988. Smoking at least occasionally was reported by 34.4% of boys and 3.9% of girls, though the intensity tended to be low. Smoking prevalence increased with age among boys. Inhaling smoke into the lungs was practised by 68.2% of the boys who smoked and 37.3% of the girls. 'Believing that one looks elegant when smoking', 'trying to be fashionable' and 'seeking stimulation' were the most important reasons for smoking. Of the boys 83.5% and of the girls 86.5% usually smoked with friends or schoolmates. Many more boys (19.2%) than girls (1.7%) smoked at home. Examinations of risk factors for teenage smoking showed that it was associated with a combination of familial, psychological and socio-school factors, with peer group pressure being the most important one.