Mirror-symmetry violation in bound nuclear ground states.

Conservation laws are deeply related to any symmetry present in a physical system1,2. Analogously to electrons in atoms exhibiting spin symmetries3, it is possible to consider neutrons and protons in the atomic nucleus as projections of a single fermion with an isobaric spin (isospin) of t = 1/2 (ref. 4). Every nuclear state is thus characterized by a total isobaric spin T and a projection Tz-two quantities that are largely conserved in nuclear reactions and decays5,6. A mirror symmetry emerges from this isobaric-spin formalism: nuclei with exchanged numbers of neutrons and protons, known as mirror nuclei, should have an identical set of states7, including their ground state, labelled by their total angular momentum J and parity π. Here we report evidence of mirror-symmetry violation in bound nuclear ground states within the mirror partners strontium-73 and bromine-73. We find that a J π = 5/2- spin assignment is needed to explain the proton-emission pattern observed from the T = 3/2 isobaric-analogue state in rubidium-73, which is identical to the ground state of strontium-73. Therefore the ground state of strontium-73 must differ from its J π = 1/2- mirror bromine-73. This observation offers insights into charge-symmetry-breaking forces acting in atomic nuclei.

ß Decay of

The interpretation of observations of cooling neutron star crusts in quasipersistent x-ray transients is affected by predictions of the strength of neutrino cooling via crust Urca processes. The strength of crust Urca neutrino cooling depends sensitively on the electron-capture and ß-decay ground-state-to-ground-state transition strengths of neutron-rich rare isotopes. Nuclei with a mass number of A=61 are predicted to be among the most abundant in accreted crusts, and the last remaining experimentally undetermined ground-state-to-ground-state transition strength was the ß decay of ^{61}V. This Letter reports the first experimental determination of this transition strength, a ground-state branching of 8.1_{-3.1}^{+4.0}%, corresponding to a log ft value of 5.5_{-0.2}^{+0.2}. This result was achieved through the measurement of the ß-delayed γ rays using the total absorption spectrometer SuN and the measurement of the ß-delayed neutron branch using the neutron long counter system NERO at the National Superconducting Cyclotron Laboratory at Michigan State University. This method helps to mitigate the impact of the pandemonium effect in extremely neutron-rich nuclei on experimental results. The result implies that A=61 nuclei do not provide the strongest cooling in accreted neutron star crusts as expected by some predictions, but that their cooling is still larger compared to most other mass numbers. Only nuclei with mass numbers 31, 33, and 55 are predicted to be cooling more strongly. However, the theoretical predictions for the transition strengths of these nuclei are not consistently accurate enough to draw conclusions on crust cooling. With the experimental approach developed in this work, all relevant transitions are within reach to be studied in the future.

Adolescents' risky behavior and mass media use.

OBJECTIVE: To understand better the relationship between adolescents' use of the mass media (including television, radio, and magazines) and their risky or unhealthy behaviors. DESIGN: Secondary data analysis of a 1987 in-home survey of 2760 randomly selected 14- to 16-year-old adolescents in 10 urban areas in the southeastern United States. MEASUREMENT: The extent of participation in eight potentially risky behaviors (sexual intercourse, drinking, smoking cigarettes, smoking marijuana, cheating, stealing, cutting class, and driving a car without permission) and the use of a variety of mass media. RESULTS: Adolescents who had engaged in more risky behaviors listened to radio and watched music videos and movies on television more frequently than those who had engaged in fewer risky behaviors, regardless of race, gender, or parents' education. White male adolescents who reported engaging in five or more risky behaviors were most likely to name a heavy metal music group as their favorite. Adolescents reported reading a wide diversity of magazines, and most reported reading at least one of a few selected magazines. Sports and music magazines were most likely to be read by adolescents who had engaged in many risky behaviors. CONCLUSIONS: Mass media health promotion efforts could more specifically target adolescents who are engaging in multiple risky behaviors.

Comparison of blood-culture contamination rates in a pediatric emergency room: newly inserted intravenous catheters versus venipuncture.

We compared contamination rates of blood cultures obtained either from newly inserted intravenous catheters or via venipuncture. Of 2,431 blood cultures, the overall contamination rate was 2.7% (intravenous catheter, 3.4%; venipuncture, 2.0%; P=.043). The site of lowest contamination was the antecubital fossa, making this the optimal choice for blood-culture sampling.

Finding health and AIDS information in the mass media: an exploratory study among Chinese college students.

Western health officials believe the incidence of HIV infection in the People's Republic of China is much higher than has been reported, but knowledge about the disease remains low. This paper describes a preliminary study of Chinese college students' AIDS knowledge and beliefs and of the acceptability of mass media for AIDS education. Focus group interviews of 73 Xiamen University students showed that the students used radio more consistently than any other media and viewed magazines as the best media source of health information. However, they expressed a general distrust of the health information media offer. They possessed quite a bit of accurate information about AIDS but also harbored many inaccurate beliefs. Most felt that their personal risk from AIDS was very low because they felt distanced--either geographically or morally--from those at risk. Disturbing numbers felt that fate, not individual behavior, determines whether or not a person contracts HIV. The paper discusses the study's implications for future research.

PIP: The feasibility of mass media channels for AIDS educational campaigns was investigated through focus group discussions involving 73 journalism and communications students from Xiamen University in Xiamen, China, in 1993. Although students rarely watched television, primarily because of lack of access, radio ownership was widespread. Magazines were identified as the best source of health information, but were infrequently purchased because of their expense. Notable among students were a lack of concern with health issues, a preference for receiving health information from interpersonal sources such as friends, and a general mistrust of health information found in the mass media. In terms of AIDS, students were most interested in articles about foreign celebrities infected with the AIDS virus. Although students' knowledge of AIDS was generally very good, virtually all insisted they were at negligible personal risk as a result of their geographic, cultural, and moral distance from those infected. Despite alarming increases in both prostitution and intravenous drug use in Fuijian province, students did not believe AIDS represents a growing social problem in their area. Also widespread was the belief that AIDS prevention is largely a matter of fate or luck rather than of personal action. These findings indicate a need for a mass media campaign aimed at increasing awareness of the potential AIDS threat to China. Broader comprehension of AIDS on the part of Chinese health care workers and campus leaders, through mediated or interpersonal channels, also could have a beneficial impact.

Evaluation of a single-pass intestinal-perfusion method in rat for the prediction of absorption in man.

Prediction of the fraction of dose absorbed from the intestine (Fa) in man is essential in the early drug discovery stage. In-vitro assays in Caco-2 and MDCK cells are routinely used for that purpose, and their predictive value has been reported. However, in-situ techniques might provide a more accurate estimation of Fa. In this study, we evaluated a single-pass intestinal-perfusion (SPIP) method in the rat for its use in the prediction of absorption in man and compared it with a previous report using cell-based assays. Effective permeability coefficients (Peff) were determined in rats for 14 compounds, and ranged from 0.043x 10(-4) cm s(-1) to 1.67 x 10(-4) cm s(-1). These values strongly correlated (r2 = 0.88) with reported Peff values for man. In addition, the Spearman rank correlation coefficient calculated for in-situ-derived Peff and absorption in man was 0.92 while for the previously tested in-vitro Caco-2 and MDCK systems vs absorption in man, the correlation coefficients were 0.61 and 0.59, respectively. SPIP provided a better prediction of human absorption than the cell-based assays. This method, although time consuming, could be used as a secondary test for studying the mechanisms governing the absorption of new compounds, and for predicting more accurately the fraction absorbed in man.

Effects of acidulated and neutral NaF solutions on bond strengths.

The application of topical fluoride after acid-etching substantially reduces the risk of enamel opacities and caries, but fluoride treatment can reduce strength of the enamel-adhesive interface to a measurable extent. In this in vitro study there was a slight reduction (statistically inconsequential) in bond strength with the use of 2.0% aqueous NaF. In contrast, two acidulated solutions tested here both showed marked reductions (ca. 25%) in bond strengths.

Television and adolescent sexuality.

Existing studies of the sexual content of television programming and advertising and the effects of this content on adolescent viewers are reviewed. Content studies show that the frequency of sexual references have increased in the past decade and are increasingly explicit. Studies of the effects of this content, while scarce, suggest that adolescents who rely heavily on television for information about sexuality will have high standards of female beauty and will believe that premarital and extramarital intercourse with multiple partners is acceptable. They are unlikely to learn about the need for contraceptives as a form of protection against pregnancy or disease. Suggestions for future research and trends in television programming policies are explored.

PIP: US television's effects on 2 broad areas of sexuality: 1)sexual beauty standards; and 2) sexual activity, including sexual intercourse are focused on. Physical attractiveness and thinness are often emphasized in television advertising and programming. The current attractiveness standard on television and in magazines is the slimmest since the 1920s. Commercials often use sexual attractiveness to sell products. Advertising has become much more explicit. References to and depictions of sex activity have gone up in the last 10 years. An average adolescent television viewer watched between 1900 and 2400 sexual references on television in 1985. The average rate of the frequency of sexual acts and references of R-rated movies is 7 times higher than prime-time commercial television. Television can have a powerful effect on adolescents' sex beliefs, especially beliefs about marital fidelity, marital stability, and female sexuality. The few studies done indicate that teenagers who get most of their information about sexuality from television will have higher criteria for female beauty and will accept the idea of premarital sex and extramarital intercourse with one or more partners. Content analyses should be continued to see how models of sexual attractiveness are used by students. Research needs to be done on the idea that women are often shown as sex objects available for men's pleasure. How sexual encounters are initiated should be researched. Content analyses should consider the consequences and context of sexuality that is televised. All adolescents do not interpret what they see in the same way. Subsequent behavior is based on the adolescents' content perception. Experimental studies are needed to set up causal sequence. Longitudinal studies are needed to set up to what extent these effects last and are "generalizable." Each of the 3 television networks had a "censor" board. But, they would not let condoms or other contraceptives be advertised. However, the networks now have a lot of competition. Some think this will loosen network standards and encourage more explicitness. However, portrayals of sexuality on television are now also becoming more responsible, with public service messages on safe sex.

AIDS knowledge, attitudes and beliefs among Chinese college students: implications for PSA development.

With growing numbers of reported HIV cases in The People's Republic of China, PRC health officials face the same information dissemination problems that have plagued other nations for a decade. The purpose of this study was to begin to understand Chinese college students' knowledge, attitudes and beliefs about HIV/AIDS as well as the cultural barriers which may prevent the acceptance of AIDS public service efforts. Focus group interviews were conducted with 76 college students at Xiamen University, PRC. Interviews revealed that many inaccurate beliefs exist regarding the AIDS disease and its modes of transmission. While many of the respondents reported that fate was the determining factor in trans mission of HIV, most felt distanced--physically, morally and culturally--from those at risk.