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MG Pellegrini I Grappasonni F Petrelli M Cocchioni 《Canadian Metallurgical Quarterly》1997,9(1):81-87
One of the forces generated during skeletal loading is hydrostatic pressure. In the work presented here, the ability of increased pressure to influence recruitment of osteoclasts was evaluated. Murine marrow cultures, with pO2 and pCO2 kept constant, were subjected to either control (1.0 atm) or elevated (1.37 or 2.0 atm) hydrostatic pressure. As compared to control, cultures pressurized for 6 days at 1.37 atm formed less osteoclast-like cells (OCLC) (71 +/- 6% of control, P < 0.0001). A similar degree of inhibition occurred in cultures exposed to pressure during days 2-4 only (62 +/- 6%), while treatment during days 5-7 failed to inhibit the OCLC number relative to control (99 +/- 5%). Delivery of 2.0 atm pressure on days 2-4 generated 52 +/- 4% OCLC compared to control. Since macrophage colony stimulating factor (MCSF)-dependent proliferation of osteoclast precursors occurs during the pressure-sensitive period, semiquantitative RT-PCR for MCSF mRNA was performed after 3 days in 1.37 atm (days 2-4). As compared to controls, pressure caused a decrease in mRNA coding for the membrane bound form of MCSF (71.2 +/- 4% (n = 25, P < or = 0.05), while the MCSF RT-PCR product representing the secreted form showed no consistent change. This lack of response of the soluble MCSF RT-PCR product was expected, as levels of bioassayable MCSF were not altered by pressure. Extrapolating these data to in vivo conditions suggests that load-bearing will inhibit the formation of osteoclasts. 相似文献
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CW Warren JS Santelli SA Everett L Kann JL Collins C Cassell L Morris LJ Kolbe 《Canadian Metallurgical Quarterly》1998,30(4):170-2, 200
CONTEXT: High rates of unintended pregnancy and sexually transmitted diseases (STDs), including HIV infection, among adolescents are major public health concerns that have created interest in trends in teenage sexual activity. METHODS: Nationally representative data from Youth Risk Behavior Surveys conducted in 1990, 1991, 1993 and 1995 are used to examine levels of sexual experience, age at first intercourse, current sexual activity and condom use at last intercourse among students in grades 9-12. RESULTS: The proportion of students who reported being sexually experienced remained at 53-54% from 1990 through 1995, while the percentage of sexually active students who used condoms at last intercourse rose from 46% to 54% between 1991 and 1995. Black students were more likely than white students to report being sexually experienced, being currently sexually active and having had four or more lifetime sexual partners; black students also reported a significantly younger age at first intercourse. Gender differences in sexual behavior were found more frequently among black students than among white or Hispanic students. CONCLUSIONS: Although levels of sexual experience for high school students in the United States have not risen during the 1990s, a very high percentage of students continue to be at risk for unintended pregnancy and STDs, including HIV infection. 相似文献
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C Hughes 《Canadian Metallurgical Quarterly》1999,23(1):41-60
This article describes an investigative process used to identify critical behaviors that relate to social interaction among high school students with and without disabilities. A series of studies resulted in the identification of six empirically and socially validated conversational behaviors that could serve as targets of interventions designed to increase social interaction. Findings also indicated that little social interaction occurred among high school students with and without mental retardation in the absence of programming or supports. Implications of the findings are discussed as well as suggestions for future research. Finally, a model for social skills interventions is proposed that may result in increased social interaction among students with and without disabilities. 相似文献
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CW Warren L Kann ML Small JS Santelli JL Collins LJ Kolbe 《Canadian Metallurgical Quarterly》1997,21(4):225-231
The XYL1 and XYL2 genes from Pichia stipitis encoding xylose reductase (XR) and xylilitol dehydrogenase (XDH), respectively, were transformed into Saccharomyces cerevisiae. These two genes were placed in different directions under the control of the alcohol dehydrogenase I (ADHI) and phosphoglycerate kinase (PGK) promoters and inserted into the E. coli-yeast shuttle plasmid YEp24. Different recombinant S. cerevisiae strains were constructed with different specific activities of XR and XDH. The highest XR or XDH activities were obtained when the expressed gene was controlled by the PGK promoter and located downstream after the ADHI promoter-gene-terminator sequence. The XR/XDH ratio (ratio of specific enzyme activities of XR and XDH) in these recombinant S. cerevisiae strains varied from 17.5 to 0.06. In order to enhance xylose utilization, in the XYL1, XYL2 containing S. cerevisiae strains, the native TKL1 gene encoding transketolase and the TALI gene encoding transaldolase were also overexpressed, which showed considerably good growth on the xylose plate. Fermentation of the recombinant S. cerevisiae strains containing XYL1, XYL2, TKL1, and TAL1 were studied with mixtures of glucose and xylose. The strain with XR/XDH ratio of 0.06 consumed 3.25 g/L xylose and formed no xylitol and less glycerol and acetic acid, but more ethanol compared with the strains with a higher XR/XDH ratio. 相似文献
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AM Smith R de Visser A Akande D Rosenthal S Moore 《Canadian Metallurgical Quarterly》1998,27(3):279-294
To understand safe sex behavior in two countries which have been differentially affected by the HIV/AIDS epidemic, the present study compared the AIDS-related knowledge, attitudes, and behaviors of 920 heterosexual undergraduate students in Australia and 228 heterosexual undergraduate students in South Africa. South African students were found to have significantly less knowledge about HIV/AIDS, and significantly less favorable attitudes toward safe sex behavior than their Australian counterparts. They were also more likely to report that they have avoided various groups of people for fear of contracting AIDS. Experience from Australia over the period 1986-1995 suggests that significant improvements in the AIDS-related knowledge, attitudes, and behaviors of South African undergraduates are achievable. 相似文献
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Previous research has shown that bicycle helmet use among older children and adolescents continues to be low. This study determined middle school students' knowledge, attitudes, beliefs, and behaviors related to bicycle helmet use. Six middle schools in Hillsborough County, Fla., served as the research settings. A pretested survey instrument was administered to students. Overall, 3,333 sixth and seventh graders responded. Results showed that most children owned a bicycle, 38.1% owned a helmet, but only 15.8% wore a helmet the last time they rode a bike. Many students (49.7%) did not know or did not believe there was a bicycle helmet law in Florida. Predictors of helmet use were intention to use a helmet the next time one rides a bike, having a helmet, siblings' use of helmets, and friends' use of helmets. 相似文献
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Timlin-Scalera Rebecca M.; Ponterotto Joseph G.; Blumberg Fran C.; Jackson Margo A. 《Canadian Metallurgical Quarterly》2003,50(3):339
This study used grounded theory methodology (B. G. Glaser & A. L. Strauss, 1967; A. Strauss & J. Corbin, 1990) to explore the help-seeking behaviors of a select group of White male adolescents to understand and identify the mental health stressors in their lives and the factors involved with their decisions to seek or not to seek help for those stressors. Semistructured interviews were conducted with 22 males, 4 female adolescent counterparts, 4 male parents, and 5 high school staff members. The substantive grounded theory that emerged was that the communal pressures of wealth, success, and high expectations creates a tremendous amount of stress for males to be successful and "fit in" and contributes to a gender-linked stigma about males' help-seeking behaviors. Specific motivators and barriers to help seeking are identified and discussed, as are common methods and resources used by males to deal with personal problems. Finally, suggestions for making professional helping services more acceptable to this population are presented, and specific research directions are posited. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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The study investigated the behaviors, interactions, and perceptions of junior high school students as they worked in structured or unstructured cooperative learning groups on problem-solving, curriculum-based tasks in mathematics, science, and English. Two hundred twenty students in Grade 8 participated in the study, which was conducted across 3 school terms. The students worked in 4-person, gender-balanced, heterogeneous achievement groups. The results show that the children in the structured groups were more cooperative and provided more relevant verbal help and assistance to each other as they worked together in their groups than their peers in the unstructured groups. Furthermore, they had stronger perceptions of small-group work as being enjoyable and providing them with the opportunity to do quality work together. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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Writing is a very demanding task, requiring the orchestration of a variety of cognitive resources. For developing writers, it can be especially demanding, as they have not yet mastered important writing processes, skills, and knowledge involved in planning, drafting, and revising text. In the present study, middle school students were directly taught strategies that facilitated the execution of each of these processes. They were also taught the knowledge and skills needed to carry out these strategies. In comparison to peers in the control condition, students in the experimental treatment condition produced essays that were longer, contained more mature vocabulary, and were qualitatively better. These gains were evident immediately following instruction and on a short-term maintenance probe administered 1 month later. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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D'Amico Elizabeth J.; Metrik Jane; McCarthy Denis M.; Frissell Kevin C.; Applebaum Mark; Brown Sandra A. 《Canadian Metallurgical Quarterly》2001,15(4):341
The current study examined binge drinking among high school students over an academic year. Adolescent drinkers (N?=?621; 58% female) were grouped into 4 trajectories: drinkers (35%), increasers (14%), decreasers (16%), and persistent binge drinkers (35%). Prospective analyses indicated several factors that predicted escalation and de-escalation of binge drinking. Increasers were more likely to regularly use alcohol and cigarettes at a younger age than drinkers. Compared with decreasers, persistent binge drinkers reported regular alcohol and marijuana use at younger ages. Lower levels of perceived student drinking appeared to be a protective factor for onset of binge drinking. The results highlight the need to study precursors to the naturally occurring fluctuations in binge drinking and suggest factors that may accentuate the risk of binge drinking. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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Examined the relationship between D. W. Reid and E. E. Ware's multidimensional measure of internal–external (I–E) locus of control and licit and illicit drug use among 920 high school students over a 2-yr period. Results based on 1-way ANOVAs indicate that dimensions of I–E control are differentially related to drug use. Greater externality on the dimension of fatalism was significantly related to the use of a number of drugs, while externality on the dimensions of self-control and sociopolitical control was not consistently related to drug use. Certain interpretations regarding the relationship between fatalism and drug use were tested. Since the I–E subscales appear to have a different validity, it is concluded that older unidimensional scales may obscure the relationship between I–E and drug use. The use of multidimensional measures is suggested since these offer more precise measurement of particular expectancy domains. (French summary) (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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RS Carman 《Canadian Metallurgical Quarterly》1977,12(1):53-64
Internal-external (I-E) control and current drug use were assessed among rural junior high school students. As expected, a negative relationship was found between internal control and drug use quantity-frequency. Correlations involving I-E control and drug use outcomes, while in the expected direction, were not significant. Data from the junior high sample were compared with previously collected high school data, and it was found that while overall patterns of use were similar for the two groups, the junior high students report lower quantity-frequency and more social complications. 相似文献
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A range of health behaviors was related to beliefs concerning health practices and health knowledge. A questionnaire dealing with health-related practices, health beliefs and knowledge of health risk factors was answered by 166 male and 179 female students aged 18-30 years at Stockholm University. Female students reported engaging in better health behavior than males. Beliefs about the importance of health behaviors were closely related to their frequency of occurrence. There was only a weak relationship between health behaviors and knowledge of specific health matters. It is concluded that health attitudes rather than health knowledge determine health behavior. 相似文献
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While academic performance and achievement motivation among elementary school students have received considerable attention, far less is known with respect to adolescents. The primary purpose of this project was to examine the ability of measures of perceived competence, control, and autonomy support to predict self-worth and academic performance with a group of regular education, learning disabled, and continuation high school students. Stepwise regression analyses indicated that indices of perceived competence, control, and autonomy support were significant predictors of self-worth and grade point average. Additionally, school status (i.e., regular education and continuation) and a depression variable were significant predictors in the regression model for academic performance. The results highlight the need for continued empirical investigation into issues surrounding the academic performance and achievement motivation of adolescents. 相似文献
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Adolescence brings with it displays of false self-behavior, including the suppression of opinions. C. Gilligan (1993) argued that lack of "voice" is problematic for girls when they enter adolescence. In the present study, the authors examined level of self-reported voice with parents, teachers, male classmates, female classmates, and close friends among both female and male high school students. Findings revealed no gender differences nor evidence that voice declines in female adolescents. For both genders, perceived support for voice was predictive of level of voice. Moreover, feminine girls reported lower levels of voice than did androgynous girls in public (but not private) relational contexts. Lower levels of voice were associated with more negative evaluations of self-worth. Discussion focused on the need to understand the causes of individual differences in voice within each gender, cautioning against generalizations about either gender as a group. 相似文献
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The preliminary development of a measure of self-efficacy to participate in vigorous physical activity when confronted with specific perceived barriers to physical activity is described. Measures used in previous research ([Hofstetter, C.R., Hovell, M.F., Sallis, J.F., 1990a. Social learning correlates of exercise self-efficacy: Early experiences with physical activity, Social Science and Medicine, 31, 1169-1176.]; [Hofstetter, C.R., Sallis, J.F., Hovell, M.F., 1990b. Some health dimensions of self-efficacy: Analysis of theoretical specificity, Social Science and Medicine, 31, 1051-1056.]; [Reynolds, K.D., Killen, J.D., Bryson, M.S., Maron, D.J., Taylor, C.B., Maccoby, N., Farquhar, J.W., 1990. Psychosocial predictors of physical activity in adolescents, Preventive Medicine, 19, 541-551.]; [Sallis, J.F., Pinski, R.B., Grossman, R.M., Patterson, T.L., Nader, P.R., 1988. The development of self-efficacy scales for health-related diet and exercise behaviors, Health Education Research, 3, 283-292.]) were adapted and original items were developed. The 20-item measure has a 5-point Likert format ranging from not at all confident (1) to very confident (5). An earlier pilot study of 200 secondary school students showed that the measure was free of social desirability. The data were derived from a survey of 1041 secondary school students from a Metropolitan Toronto board of education. Principal component analysis (PCA) with oblique rotation of the data yielded two factors: self-efficacy to overcome external barriers and self-efficacy to overcome internal barriers. The 12-item external barriers subscale had a coefficient alpha of 0.88 and the 8-item internal barriers subscale had a coefficient alpha of 0.87. The subscales significantly correlated with the frequency of participation in vigorous physical activity. In summary, the results provide some support for the internal consistency reliability, construct validity, criterion validity, and discriminant validity of the measure. Though further psychometric research is warranted, the self-efficacy measure shows promise for physical activity research. 相似文献
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P Sachdev 《Canadian Metallurgical Quarterly》1998,26(4):37-57
Eight hundred eighty-seven students in social work, nursing, and humanities from two major universities in Delhi were compared regarding their knowledge about AIDS/HIV and attitudes toward PWAs and homosexuals. Their scores on the 20-item knowledge test indicate fair degree of knowledge; however, they lacked information in crucial areas of AIDS prevention and human sexual anatomy. Unmarried, female and older students and those in social work and nursing disciplines scored significantly higher on correct answers. Social work students were likely to be more positive in their attitudes toward AIDS victims than those in nursing or humanities. Knowledge was positively related to attitudes and perception of risk. Despite their awareness of personal risks only four in ten used condoms sometimes during intercourse. Educational strategies to increase cognitive and affective understanding of AIDS and its victims are discussed. 相似文献
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In the High School and Beyond study (National Center for Educational Statistics, 1986), students were asked in their sophomore year and again in their senior year whether they lived with their mother, a stepmother, their father, or a stepfather. Comparisons were made among 3 family configurations (2-parent, stepparent, and single-parent families) when they were stable during the last 2 years of high school and when the family configuration changed. 22 senior-year and postsecondary outcomes were related to different family configurations. After controlling for background variables (sex, race, SES, etc.) and comparable sophomore-year outcomes, differences in family configurations had little effect on the senior-year and postsecondary outcomes. This lack of effect was consistent across subgroups based on sex, race, religion, SES, and other background variables. Results suggest that for a wide variety of outcome variables, growth and change during the last 2 years of high school are relatively unrelated to different family configurations. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献