Demonstration of a spaser-based nanolaser.

One of the most rapidly growing areas of physics and nanotechnology focuses on plasmonic effects on the nanometre scale, with possible applications ranging from sensing and biomedicine to imaging and information technology. However, the full development of nanoplasmonics is hindered by the lack of devices that can generate coherent plasmonic fields. It has been proposed that in the same way as a laser generates stimulated emission of coherent photons, a 'spaser' could generate stimulated emission of surface plasmons (oscillations of free electrons in metallic nanostructures) in resonating metallic nanostructures adjacent to a gain medium. But attempts to realize a spaser face the challenge of absorption loss in metal, which is particularly strong at optical frequencies. The suggestion to compensate loss by optical gain in localized and propagating surface plasmons has been implemented recently and even allowed the amplification of propagating surface plasmons in open paths. Still, these experiments and the reported enhancement of the stimulated emission of dye molecules in the presence of metallic nanoparticles lack the feedback mechanism present in a spaser. Here we show that 44-nm-diameter nanoparticles with a gold core and dye-doped silica shell allow us to completely overcome the loss of localized surface plasmons by gain and realize a spaser. And in accord with the notion that only surface plasmon resonances are capable of squeezing optical frequency oscillations into a nanoscopic cavity to enable a true nanolaser, we show that outcoupling of surface plasmon oscillations to photonic modes at a wavelength of 531 nm makes our system the smallest nanolaser reported to date-and to our knowledge the first operating at visible wavelengths. We anticipate that now it has been realized experimentally, the spaser will advance our fundamental understanding of nanoplasmonics and the development of practical applications.

Hybrid epitaxial-colloidal semiconductor nanostructures.

We present a growth technique which combines wet-chemical growth and molecular beam epitaxy (MBE) to create complex semiconductor nanostructures with nanocrystals as active optical material. The obtained results show that wet-chemically prepared semiconductor nanocrystals can be incorporated in an epitaxally grown crystalline cap layer. As an exemplary system we chose CdSe nanorods and CdSe(ZnS) core-shell nanocrystals in ZnSe and discuss the two limits of thin (d approximately 2R) and thick (d>2R) ZnSe cap layers of thickness d for CdSe nanorods and nanodots of radii R between 2 and 4 nm. In contrast to the strain-induced CdSe/ZnSe Stranski-Krastanow growth of a quantum dot layer in a semiconductor heterostructure, the technique proposed here does not rely on strain and thus results in additional degrees of freedom for choosing composition, concentration, shape, and size of the nanocrystals. Transmission electron microscopy and X-ray diffractometry show that the ZnSe cap layer is of high crystalline quality and provides all parameters for a consecutive growth of Bragg structures, waveguides, or diode structures for electrical injection.

Exciton fine structure in single CdSe nanorods.

We study the optical properties of excitons in one-dimensional (1D) nanostructures at low temperatures. In single CdSe/ZnS core-shell nanorods we observe a fine structure splitting and explain it by exchange interaction. Two peaks are observed with different degrees of linear polarization of DLP<0.85 and DLP>0.95. For small nanorod radii R< or =a(B)/2, an increase in the photoluminescence decay time is found when the temperature increases from 10 to 80 K. The observations are explained by a radius-dependent change in the symmetry of the 1D-exciton ground state which transforms from a dark state into bright states below a critical radius of R(crit) approximately 3.7 nm.

[HIV seroprevalence in ophthalmologic patients of Cameroon]. / HIV-Prävalenz bei ophthalmologischen Patienten in Kamerun.

BACKGROUND: It is difficult to estimate the exact HIV infection rates in countries such as Cameroon because of diagnostic and statistical problems. The majority of people seek help from traditional healers outside the health system. PATIENTS AND METHODS: A screening for human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2) was performed on 2452 patients of the western province of Cameroon. All data were evaluated regarding HIV seroprevalence and ophthalmological findings in HIV-seropositive patients. The test covered all patients who came for cataract surgery (group 1), all outpatients with suspicious ophthalmological findings (group 2), and all remarkable patients of the collaborating department of general medicine (group 3) between 20 September 2000 and 20 September 2001. RESULTS: Of the 2452 screened patients, 467 (19.0%) were HIV seropositive. A positive test result was obtained in 29 (5.5%) of the 525 patients in group 1, 154 (35.6%) of the 433 patients in group 2, and 284 (19.0%) of the 1494 patients in group 3. The main ocular manifestations of the 154 HIV-seropositive patients in group 2 were uveitis (17.6%), squamous cell carcinoma of the conjunctiva (14.9%), zoster ophthalmicus (14.9%), and corneal ulcers (11.0%). CONCLUSIONS: This study shows that the seroprevalence of the screened population of Cameroon lies between 5.5% (results of group 1) and 19.0% (results of group 3).

The use of EPSDT and other health care services by children enrolled in Medicaid: the impact of OBRA'89.

To increase the participation of Medicaid children in the Early and Periodic Screening, Diagnosis and Treatment (EPSDT) program and to improve their health, Congress included several provisions in the Omnibus Budget Reconciliation Act of 1989 (OBRA'89) that addressed problematic program features. The impact of these provisions on children's health service use was investigated in a study funded by the Health Care Financing Administration. After conducting site visits to four states, the authors analyzed claims data for the children residing there and found evidence that, in 1992, these states placed a higher priority on improving the effectiveness of EPSDT than they did before 1989. The states' efforts to expand the EPSDT provider base and to enhance outreach and service provision were either directly or indirectly inspired by OBRA'89. The authors also found evidence of a significant impact on provider participation and caseloads and on children's use of both preventive care and diagnostic and treatment services. However, the effects were modest in comparison to the size of the progress that is required.

A comparison of Medicaid and non-Medicaid obstetrical care in California.

The use of prenatal care and rates of low birth weight were examined among four groups of women who delivered in California in October 1983. Medicaid paid for the deliveries of two groups, and two groups were not so covered. The analyses suggest that longer Medicaid enrollment improved the use of prenatal care. The association between prenatal care and birth weight was less clear. For women under Medicaid, measures of infant and maternal morbidity, hospital characteristics, and Medicaid eligibility were all statistically related to charges, payments, and length of stay for the delivery hospitalization.

Access to hospital care for California and Michigan Medicaid recipients.

This article is a comparison of the characteristics of hospitals serving the general population and Medicaid recipients in California and Michigan, using data from Medicaid uniform claims files and the American Hospital Association Annual Survey for 1984. A greater concentration of discharges in a small number of "high Medicaid volume" urban and rural hospitals in each State was observed for Medicaid recipients compared with the general population. In addition, discharge data suggest that Supplemental Security Income crossovers (individuals covered by both Medicaid and Medicare) and other recipients (mostly children not enrolled in the Aid to Families with Dependent Children program) receive inpatient care in different hospitals from the general population as well as from other Medicaid eligibility groups. Medicaid cost-containment policies and differential access to hospital care are discussed.

Spectrin modifications in a heterozygous case of both hereditary elliptocytosis and beta-thalassemia.

The clinical and hematological parameters of a patient described here, who inherited the genes of both hereditary elliptocytosis (HE) and beta-thalassemia, seem to reflect a mutual enhancement of the two diseases. The coexistence of the two pathologies is probably also responsible for the observed changes in spectrin: the appearance of an extra spectrin band between tetramers and dimers on denaturing gel electrophoresis and the metabolic-dependent reduction in spectrin amount. It is assumed that the instability of the skeletal network that results from the HE pathology caused increased exposure of the spectrin molecule to oxidative damage that usually occurs in thalassemic red cells. The products of such oxidation may have led to abnormal spectrin associations which finally resulted in the above changes.

Infertility and bioethical issues of the new reproductive technologies.

The scientific breakthroughs resulting in the delivery of Louise Brown in 1978 have opened the floodgates for an ongoing bioethical discussion about medically assisted reproduction. The majority in our society has accepted in vitro fertilization as an ethically justifiable procedure for infertile couples. The concern persists, however, that new reproductive technology has started us on the course of a slippery slope with potentially dire consequences for the so-created children, the traditional family, and, indeed, for society as a whole. The moral status of the embryo is the central issue in debates about such reproductive developments as the "spare" embryo, embryo freezing, embryo donation, embryo research and micromanipulation. Conflicts of interests between the adult's desire to become a parent and the welfare of the offspring are at the root of moral objections raised against manipulation of human reproduction. Extracorporal conception with the possibility for various gamete donors has also brought the long-practiced procedure of artificial insemination by donor and the potential consequences for the child into the discussion. Surrogate mothering and surrogate gestational mothering force us to redefine the age old dictum mater certa est and can render the child a helpless pawn in parental, emotional, and legal strife. Over the ages, society has through firmly established values exerted control over reproduction and acceptance of the new member in the community. Sex without reproduction was a severe blow to the highly regarded societal belief in parenting as the epitomy of life goals. Reproduction without sex through various technically feasible collaborative means further jolts fundamental traditional values and mandates their re-evaluation. Ethical belief systems are by nature highly charged and fiercely defended. Thus, in a pluralistic society, a consensus on the question "What ought to be done of all that can be done with new reproductive technologies?" is probably unachievable. Heated controversies between interest groups constitute an additional psychological burden complicating the ethical ambiguities for some infertile couples who have to decide about using noncoital conception. The interdisciplinary group report by the ethics committee of the American Fertility Society published in the "Ethical Considerations of the New Reproductive Technologies" constitutes a wide framework of guidelines for rational consideration. It will, one hopes, help to formulate needed regulations because some segments of our society as well as many scientists and physicians in the field believe that not all that potentially can be done ought to be done.(ABSTRACT TRUNCATED AT 400 WORDS)

Family planning for teens: strategies for improving outreach and service delivery in public health settings.

The persistent underuse of family planning services by inner-city, low-income, sexually active youth underscores the importance of testing innovative programs that maximize participation. Presented in this paper is an analysis of a Chicago public health clinic's special program for adolescents that originated from the staff's observations of the scheduling, educational, and support needs of teens seeking family planning services from a traditionally managed public health facility. Between December 1982, when the special program--the Teen Clinic--was implemented, and March 1985, more than 600 adolescents sought social support and contraceptive services--an 82 percent increase in new-patient registration compared with the enrollment before the program began. In contrast, two neighboring public health department facilities without special family planning programs for teens experienced either a small increase, 4 percent, or a modest decrease, 17 percent, in utilization by teenagers during the same period. The increased use of the study facility by teens, coupled with patients' self-reported nonuse of alternative sources of care and referral patterns, suggests that the new program was successful in recruiting sexually active teens who had previously been inadequately protected against pregnancy. The perceived institutional and interpersonal factors influencing 153 teens' initial and repeated use of the Teen Clinic, as measured by a structured survey, echo the findings of previous research. Strategies suggested by the study's findings for improving outreach and service delivery are described.

A survey of referral activities of agencies serving adolescents.

The referral activities of 373 agencies (38.4% of the sample originally polled) are presented with regard to health care, educational, and social services for teenagers residing in a midwestern metropolitan area. Approximately 66% of the responding agencies receive referrals from without and 87% make referrals to other organizations, with counseling and psychiatry, family planning, and general medical care being the most commonly sought services. Social service agencies had the highest volume of referrals and hospitals the lowest. The results of the survey are discussed in terms of the official recommendations made for coordinated services for teenagers, predicted cutbacks in preventive services, and the special needs of adolescents.

Family life education for young inner-city teens: identifying needs.

PIP: Sexual decision making, perceptions of responsibility for birth control and pregnancy, and knowledge of contraception and the consequences of teenage pregnancy were assessed among 251 high-risk 7th and 8th grade black, US inner-city adolescents to determine their need for information. Survey results indicate that these adolescents are aware of contraceptive methods, but lack practical information about requirements for obtaining them or method effectiveness. Many students are uniformed about the circumstances under which pregnancy can occur. Males indicate a willingness to have intercourse regardless of the contraceptives used, if any, and believe responsibility for the use of a birth control method belonges to females. Females believe themselves to be responsible for contraceptive utilization and prefer intercourse with adequate protection. Both genders endorse the notion of mutual responsibility for unplanned pregnancies and related decisions. More systematic research assessing the effectiveness of a variety of curricula for enhancing skills in decision-making and moral reasoning in young teens is needed.^ieng

Correlates of adolescent parenting.

A self-selected sample of 177 teenage parents participated in a study of the correlates of teenage parenting. An ecological model of the predictors of parenting behavior was used to define factors which potentially influence teenage parents' parenting skills as measured by the Home Observation for Measurement of the Environment (HOME). The factors tested include level of punitiveness toward child rearing, knowledge of developmental milestones, level of depression, perceived social support, parental age, and parental race. The results of a stepwise hierarchical regression analysis found that parental race, punitive attitudes toward child rearing, and parental age were statistically significant predictors of total HOME scores. The older, white adolescent mother with less punitive attitudes toward child rearing and child discipline scored the highest on parenting skills. The relevance of these findings to program planners and service providers involved in teenage parent support and education programs is discussed.

PIP: This study of correlates of teenage parenting involving 177 US teenage parents identified parental race, punitive attitudes toward child rearing, and age as significantly related to parenting behavior. An ecological model of the predictors of parenting behavior was used to define factors which potentially influence teenage parents' skills as measured by the Home Observation for Measurement of the Environment (HOME). The factors tested include level of punitiveness toward child rearing, knowledge of developmental milestones, level of depression, perceived social support, parental age, and parental race. The results of a stepwise hierachical regressions analysis found that punitive attitudes, parental race, and age were significant predictors of total HOME scores. The older, white adolescent parent with less punitive attitudes toward child rearing and discipline scored the highest on the parenting skills. The average total HOME score for the white teenage mothers is comparable to the standing of other groups of parents. The mean HOME score for the black parents participating is lower than that reported for other samples. The prominent role of race needs further study and may be of special interest to program planners.

Family planning for inner-city adolescent males: pilot study.

The results of a pilot family planning program (FPP) in a pediatric practice are reported for 66 inner-city male adolescents. The FPP was designed to eliminate registration barriers to the procurement of contraceptives by adolescent males, and to prompt the community neighborhood health center (CNHC) providers to initiate discussion of birth control with their male adolescent patients. Utilization data show that males were more likely to receive contraceptives if the provider first raised the topic of birth control to them. Unstructured follow-up interviews with 27 adolescent male FPP users identified a desire for anonymity/confidentiality and embarrassment or discomfort as the key reasons for not seeking contraceptives from the CNHC. If health care providers are sensitive to male adolescents' feelings about birth control, community health centers potentially could serve as a cost-effective source of contraceptives for sexually active male adolescents.

PIP: The results of a pilot family planning program (FPP) in a pediatric practice are reported for 66 inner-city US male adolescents. The FPP was designed to eliminate registration barriers to the procurement of contraceptives by adolescent males, and to prompt the community neighborhood health center (CNHC) providers to initiate discussion of birth control with their male adolescent patients. Utilization data show that males were more likely to receive contraceptives if the provider first raised the topic of birth control to them. Unstructured follow-up interviews with 27 adolescent male FPP users identified a desire for anonymity and confidentiality, and embarrassment or discomfort as the key reasons for not seeking contraceptives from the CNHC. If health care providers are sensitive to male adolescents' feelings about birth control, community health centers potentially could serve as a cost-effective source of contraceptives for sexually active male adolescents.

Factorial and discriminant validity of the Center for Epidemiological Studies Depression (CES-D) scale.

The factorial and discriminant validity of the Center for Epidemiological Studies Depression (CES-D) scale was examined for a sample of 116 parents who were participating in family support programs designed to prevent child abuse and neglect. Participants' self-reports of depressive symptoms as measured by the CES-D were analyzed in relation to their self-esteem (measured with the Rosenberg Self-Esteem scale) and state and trait anxiety (measured with Spielberger's State-Trait Anxiety Inventory). Factorial validity was adequate, and results indicated a moderate correlation between the CES-D and self-esteem and state anxiety. However, a high correlation was obtained between the CES-D and trait anxiety, which suggests that the CES-D measures in large part the related conceptual psychological domain of predisposition for anxiousness.

Family life education for young teens: an assessment of three interventions.

The impact of three variations of a family life education (FLE) program for 172 inner-city, junior-high-level students was investigated. Variations in exposure time, instructional methods, and teacher quality led to the classification of each intervention on a general intensity dimension. Separate pretest-posttest nonequivalent comparison group designs were utilized to assess program impact along seven knowledge and attitudinal dimensions. Survey results revealed that, in comparison to no-treatment groups, the more intensive the program (a) the greater the gains in knowledge about reproductive physiology, contraception, and the consequences of teen pregnancy and parenthood (especially among experimental group females); and (b) the more birth control methods participants became familiar with over time. Changes in personal acceptance of premarital intercourse and perceived responsibility for contraception were observed only in the study examining the most intensive treatment. The results of the evaluations point to the combined importance of instructional methods, teacher quality, and in-class exposure time for producing change in young adolescents' knowledge of and attitudes toward sexuality. Further potential for the impact of school-based sex education programs on knowledge and attitudes is discussed within the broader context of the young adolescent's social environment.

Family life education in Chicago schools: a study of programs implemented by nonschool agencies.

Although nonschool agencies provide important complementary courses on family life education (FLE) in public and private schools, little is known about the scope and content of such curricula. This paper describes a study documenting the types of school-based family life education programs implemented by nonschool agencies in Chicago. Semistructured telephone interviews were conducted with professionals from 26 health care and social service agencies, identified as offering FLE courses in the metropolitan area. The surveyed organizations provided FLE programs in almost 100 public and private schools in Chicago during the 1982-83 and 1983-84 school years. Most programs were relatively short, utilized few interactive teaching techniques (e.g., role-playing, exercises), covered a wide variety of topics, and were integrated into other curricula units rather than implemented as separate courses. Agency personnel covered topics viewed as important by school administrators and teachers, most notably information on contraception and sexual decision making.

PIP: Although nonschool agencies in the US provide important complementary courses on family life education (FLE) in public and private schools, little is known about the scope and content of such curricula. This paper describes a study documenting the types of school-based FLE programs implemented by nonschool agencies in Chicago. Semistructured telephone interviews were conducted with professionals from 26 health care and social service agencies identified as offering FLE courses in the metropolitan area. The surveyed organizations provided FLE programs in almost 100 public and private schools in Chicago during the 1982-83 and 1983-84 school years. Most programs were relatively short, utilized few interactive teaching technics (e.g., role-playing, exercises), covered a wide variety of topics, and were integrated into other curricula units rather than implemented as separate courses. Agency personnel covered topics viewed as important by school administrators and teachers, most notably information on contraception and sexual decision making.

A baseline evaluation of family support programs.

This paper presents a baseline evaluation of four demonstration family support programs located in communities identified as having a disproportionate number of families at risk for malfunctioning. In this baseline evaluation, a one year cohort of 422 family support participants were assessed along key dimensions of parenting known to contribute to child well-being and potentially to the incidence of child abuse or child neglect. These dimensions include parents' attitudes toward child rearing, knowledge of child development, level of perceived social support, and level of depression. Black participants and teenage parents had more punitive attitudes toward child rearing, less knowledge of child development, and less perceived social support than white or older parents. Overall, attitudes, knowledge, level of perceived social support and depression are interrelated in accordance with previous clinical observations and developmental theory, e.g., depressed parents are less knowledgeable, more punitive and have less support than nondepressed parents. The results of the baseline evaluation suggest that the demonstration projects are successful in reaching some subgroups of families at risk for parenting problems.

Family life education for young adolescents: a quasi-experiment.

The impact of a family life education program for inner-city, minority elementary-school students was investigated. 2 randomly assigned groups of 7th and 8th graders (balanced for gender) completed a self administered survey, both before and after program implementation. In comaprison to the control group, program participants displayed (a) improved knowledge about contraception, reproductive physiology, an adolescent pregnancy outcomes; (b) increased awareness of the existence of specific birth control methods; (c) among 7th gradres, more conservative attitudes toward circumstances under which sexual intercourse was viewed as personally acceptable, and among8th graders, a shift toward more liberal attitudes; and (d) a greater tendency to acknowledge mutual responsibility for contraception. The impact of this intervention and school-based sex education programs in general is discussed within the broader context of the young adolescent's social environment.