Laser heating of solid matter by light-pressure-driven shocks at ultrarelativistic intensities.

The heating of solid targets irradiated by 5 x 10(20) W cm(-2), 0.8 ps, 1.05 microm wavelength laser light is studied by x-ray spectroscopy of the K-shell emission from thin layers of Ni, Mo, and V. A surface layer is heated to approximately 5 keV with an axial temperature gradient of 0.6 microm scale length. Images of Ni Ly(alpha) show the hot region has 100 G bar light pressure compresses the preformed plasma and drives a shock into the solid, heating a thin layer.

Socio-demographic features and fluoride technologies contributing to higher fluorosis scores in permanent teeth of Canadian children.

OBJECTIVE: To examine levels of fluorosis among children in two Canadian communities exposed to fluoride. BACKGROUND: One community had discontinued fluoride, the other had maintained it. Water supplies, however, were fluoridated for all the children when their esthetically important teeth were mineralized. METHODS: We examined 8,277 children to assess Thystrup-Fejerskov Index (TFI) scores. Multivariate Poisson regression models were used to identify the relationship between TFI and water fluoride status, age, gender, SES, and dietary and fluoride exposure histories (supplements, rinses, toothpaste amount, tooth brushing frequency, and tooth brushing starting age). Parent(s) completed questionnaires. RESULTS: Overall, levels of fluorosis were low to mild, with residents of the fluoridation-ended communities having marginally higher TFI scores than those of the still-fluoridated community. Females had higher TFI scores than males. Children aged 10 years or more had higher TFI scores than younger children. Consuming bottled water between birth and 6 months of age was protective. Exposure to fluoridation technologies was consistently associated with fluorosis experience. Children who began brushing with fluoride toothpaste between their first and second birthdays had higher TFI scores than those who began between their second and third birthdays, regardless of daily brushing frequency. Children who regularly used supplements had higher TFI scores than those who did not. Children with a college-educated father had higher TFI scores than those whose fathers had less education. CONCLUSIONS: Higher fluoride exposure slightly increased the likelihood that a child had a higher TFI score, especially when more fluoridation technologies were used at home.

Detection of eubacterial 3-hydroxy-3-methylglutaryl coenzyme a reductases from natural populations of actinomycetes.

Three natural populations of actinomycetes were investigated by PCR for the presence of type I 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG CoA), a gene associated with isoprenoid biosynthesis. The populations were obtained from an agricultural site (69 isolates), a coastal salt marsh (220 isolates), and a desert soil (96 isolates). A set (34) of standard actinomycete reference strains were also investigated. The target gene was only detected in 5 of the 419 actinomycetes screened, which represented 4 from the coastal salt marsh and one reference strain. The isolates that contained the gene were taxonomically diverse (4 Streptomyces spp. and 1 Nocardia sp.). These results suggest that type I HMG CoA containing pathways are rare in actinomycetes and their distribution within actinomycetes populations is not random.

Detection of Borrelia lonestari in Amblyomma americanum (Acari: Ixodidae) from Tennessee.

Genetic sequences characteristic of Borrelia lonestari (Barbour et al. 1996) were detected in two pools of adult Amblyomma americanum (L.) from Tennessee, corresponding to an estimated minimum field infection rate of 8.4 infected ticks/1000 adults. DNA amplification was conducted using primers derived from the B. lonestari flagellin gene that would also amplify Borrelia burgdorferi (Johnson, Schmid, Hyde, Steigerwalt, and Brenner). Species-specific, internal probes were then used to differentiate between genetic sequences of the spirochetes. Subsequent nucleotide sequencing confirmed the presence of B. lonestari in A. americanum; B. burgdorferi was not detected. This represents the first report of B. lonestari from Tennessee, and suggests that Lyme-like illness may occur in Tennessee.

Tooth-surface progression and reversal changes in fluoridated and no-longer-fluoridated communities over a 3-year period.

OBJECTIVE: To compare permanent tooth surface-specific progression/reversal changes between fluoridation-ended (F-E) and still-fluoridated (S-F) communities in British Columbia, Canada, over a 3-year period. METHODS: D1D2MFS examinations were contrasted for 2,964 schoolchildren in 1993/94 (grades 2, 3, 8 and 9) and 1996/97 (grades 5, 6, 11 and 12). Generalized Estimating Equation (GEE) models explored the relation between progression/reversal changes and fluoridation status, age, gender, socioeconomic status, and dietary/fluoride histories. RESULTS: Within a scenario of low levels of caries overall, few children had multiple surfaces progressing. At least one smooth surface progressed in 31.4% of subjects; at least one pit-and-fissure (PF) surface progressed in 43.1% of subjects. At least one smooth surface reverted in 89% of subjects who had reversible stages; at least one PF surface reverted in 23.8% of subjects who had reversible stages. GEE (smooth) indicated that odds ratios of progression were twice as large in the F-E site compared to the S-F site, and slightly increased in older participants and in participants exposed to more fluoride technologies. GEE (PF) also indicated that progression was slightly more common in the F-E site; more frequent snacking and lower parental educational attainment had modest associations with increased progression in PF surfaces. For the two types of surfaces, GEE models demonstrated that unerupted surfaces were less likely to progress than sound surfaces. No associations were found between reversals and independent variables. CONCLUSION: Progressions were found to be weakly linked to socio-demographic factors; baseline surface statuses were better predictors of progression. Using the current definitions for disease transitions, F-E communities had more frequent progressions than a S-F community.

Patterns of dental caries following the cessation of water fluoridation.

OBJECTIVES: To compare prevalence and incidence of caries between fluoridation-ended and still-fluoridated communities in British Columbia, Canada, from a baseline survey and after three years. METHODS: At the baseline (1993/4 academic year) and follow-up (1996/7) surveys, children were examined at their schools. Data were collected on snacking, oral hygiene, exposure to fluoride technologies, and socio-economic level. These variables were used together with D1D2MFS indices in multiple regression models. RESULTS: The prevalence of caries (assessed in 5,927 children, grades 2, 3, 8, 9) decreased over time in the fluoridation-ended community while remaining unchanged in the fluoridated community. While numbers of filled surfaces did not vary between surveys, sealed surfaces increased at both study sites. Caries incidence (assessed in 2,994 life-long residents, grades 5, 6, 11, 12) expressed in terms of D1D2MFS was not different between the still-fluoridating and fluoridation-ended communities. There were, however, differences in caries experienced when D1D2MFS components and surfaces at risk were investigated in detail. Regression models did not identify specific variables markedly affecting changes in the incidence of dental decay. CONCLUSIONS: Our results suggest a complicated pattern of disease following cessation of fluoridation. Multiple sources of fluoride besides water fluoridation have made it more difficult to detect changes in the epidemiological profile of a population with generally low caries experience, and living in an affluent setting with widely accessible dental services. There are, however, subtle differences in caries and caries treatment experience between children living in fluoridated and fluoridation-ended areas.

Social constructs of curricular change.

The adoption of problem-based approaches to teaching and learning in dental and medical education requires educators to consider a significantly different role and responsibilities as teacher from what they have experienced previously. This qualitative study explored how some educators experienced and interpreted changes in the newly merged dental and medical curriculum at the University of British Columbia. Our findings present how educators explained and dealt with change. In-depth interviews provided considerable insight into factors influencing the resistance or acceptance to change. The educators' beliefs about teaching and learning and their understanding of the development and implementation process of change mediated these factors. Findings from this study should help administrators, faculty developers, and educators themselves to understand better how curricular change is experienced and to plan effective and appropriate faculty development.

The effectiveness of 10% chlorhexidine varnish treatment on dental caries incidence in adults with dry mouth.

OBJECTIVES: This study compared a 10% chlorhexidine varnish treatment with placebo and sham treatments for preventing dental caries in adult patients with xerostomia (dry mouth). DESIGN: The study was a multicentred, randomized, parallel group, double blind, placebo-controlled clinical trial. SETTING: All examinations and procedures were performed at Tuft's University, Boston, MA, the University of British Columbia, Vancouver, BC or the University of Western Ontario, London, ON. SUBJECTS: Subjects were adults with recent or current dental caries experience, high salivary levels of cariogenic microorganisms and low salivary flow rates. RESULTS: 236 subjects completed at least one post-treatment examination. There were 697 new carious lesions diagnosed, 446 (64%) located on coronal surfaces and 251 (36%) located on root surfaces. The mean attack rate was 0.23 surfaces/100 surfaces at risk. A treatment difference observed between the Active and Placebo groups was statistically significant for root caries increment (p = .02) and total caries increment (p = .03). A treatment difference observed between the Active and Sham groups was not statistically significant for coronal, root or total caries increment. Analysis of variance of treatment group differences was performed using mutans streptococci counts, salivary flow rates, age, sex, caries prevalence, medications, time to first event and early withdrawal as co-variables. These factors did not meaningfully alter the findings. CONCLUSIONS: The difference between the 10% chlorhexidine varnish and placebo treatments is considered to be highly clinically significant for root caries increment (41% reduction) and for total caries increment (25% reduction) but only for coronal caries increment (14%).

Project neighborhoods in action: an HIV-related intervention project targeting drug abusers in Washington, DC.

Project Neighborhoods in Action was a human immunodeficiency virus (HIV) outreach and intervention program that was conducted with injection drug users and crack users in several inner-city neighborhoods in the District of Columbia. Study participants were placed randomly in either a standard intervention or an enhanced intervention condition, with more than 800 persons being assigned to each group. Drug use frequency dropped from 15.2 days to 12.4 for alcohol (P<.0001), 2.1 days to 1.6 for marijuana (P<.003), 13.0 days to 8.8 days for crack (P<.0001), 2.4 days to 1.5 days for cocaine (P<.0001), 19.7 days to 15.6 for heroin (P<.0001), and 5.2 days to 3.4 for speedball (P<.0001). Drug injecting decreased from an average of 90.8 times to 66.9 (P<.0001), with both direct sharing and indirect sharing rates decreasing significantly as well (from 2.4 to 1.1 times for the former [P<.002] and from 12.0 to 8.1 times for the latter [P<.0004]). The number of sexual partners dropped from a mean of 1.6 to 1.1 (P<.0001). The number of drug-injecting sexual partners went from 0.3 to 0.2 (P<.01). Having sex while high decreased from 11.2 times to 7.9 (P<.0001). Trading sex for drugs and/or money declined from 1.9 times to 1.3 (P<.001). Protected sex increased from 29.5% to 63.7% (P<.0001), and the number of unprotected sexual acts dropped from 9.6 to 7.2 (P<.0001). Only a few differences were observed for standard versus enhanced intervention respondents, with no particular pattern formed. We were left with the impression that the standard intervention and enhanced intervention used in this program were about equally effective at reducing the involvement of drug abusers in HIV-related risky behaviors.

Studies of suicide in later life: methodologic considerations and research directions.

Later-life suicide is a tragedy that occurs worldwide. Often it is preventable. Here, the authors summarize an international workshop where they review four research approaches to studying putative risk factors: epidemiologic studies of suicidal behaviors, clinic-based follow-up studies, studies of suicide attempters, and psychological autopsy studies. They provide brief descriptions of the approaches, examples of questions best addressed by each approach, and their weaknesses and limitations; they also recommend promising areas for future research and propose opportunities for research that could be conducted cross-nationally.

Esophageal atresia and tracheoesophageal fistula.

Esophageal atresia, with or without tracheoesophageal fistula, is a fairly common congenital disorder that family physicians should consider in the differential diagnosis of a neonate who develops feeding difficulties and respiratory distress in the first few days of life. Esophageal atresia is often associated with other congenital anomalies, most commonly cardiac abnormalities such as ventricular septal defect, patent ductus arteriosus or tetralogy of Fallot. Prompt recognition, appropriate clinical management to prevent aspiration, and swift referral to an appropriate tertiary care center have resulted in a significant improvement in the rates of morbidity and mortality in these infants over the past 50 years.

Effects of dietary fish oil supplementation on the phospholipid composition and fluidity of cell membranes from human volunteers.

BACKGROUND: Membrane fluidity is an important aspect of cellular physiology which may be manipulated by diet. METHODS: We studied the effect of dietary fish oil on the membrane composition of erythrocytes and cheek cells, and on membrane fluidity of erythrocytes as assessed by fluorescence recovery after photobleaching (FRAP). Healthy volunteers received a daily supplement of fish oil (930 mg EPA, 630 mg DHA) for 42 days. RESULTS: The intervention reduced the ratio of n-6 to total fatty acid in the phospholipid fraction of erythrocyte membranes but the n-3 fraction remained stable and the ratio of cholesterol to phospholipid increased. The level of EPA and DHA in cheek cells increased significantly during the intervention period. The mean diffusion coefficient of the fluorescent probe in erythrocyte membranes increased from 7.2 +/- 0.7 x 10-9 cm2/s at the start to 9.8 +/- 0.5 x 10-9 cm2/s after 21 days. Membrane fluidity remained higher than the initial value 42 days after withdrawal of the supplement. Fish oil also reduced platelet aggregation in response to ADP but there was no effect on plasma lipid profiles. CONCLUSION: We conclude that n-3 fatty acids influence erythrocyte membrane composition at relatively low levels of supplementation by a mechanism which does not necessarily involve an increase in the level of EPA or DHA present in the membrane.

The effect of entering drug treatment on involvement in HIV-related risk behaviors.

The research described here is based on a sample of 8,241 out-of-drug-treatment users of injected drugs and/or crack, aged 18 or older, recruited from 22 sites across the United States and Puerto Rico. The study divided respondents into three groups-(a) cocaine or crack users who did not also use heroin or speedball (cocaine-only users), (b) heroin injectors who did not also use cocaine or crack or speedball (heroin injectors), and (c) users of cocaine or crack and injected heroin or speedball (dual users)--and compared the efficacy of entering drug treatment for these groups' involvement in HIV-related risk behaviors. The study found that entry into treatment corresponded to greater reductions in substance abusers' frequency of drug use and involvement in risky injection practices compared to those observed in people who did not enter treatment between their baseline and 6-month follow-up interviews. Entry into drug treatment was also associated with reductions in the practice of risky sexual behaviors, but these reductions were less substantial and less consistent than those noted for drug use and injection risk behaviors.

Adolescent suicide.

This article reviews the origin of youth suicide. Theoretic suicide risk factors and empirically observed suicide risk factors are discussed along with proposed resiliency factors that prevent suicide. Finally, suicide prevention and intervention strategies are covered, and a call for better studies on suicide prevention is heralded.