Stroboscopic image capture: reducing the dose per frame by a factor of 30 does not prevent beam-induced specimen movement in paraffin

Beam-induced specimen movement may be the major factor that limits the quality of high-resolution images of organic specimens. One of the possible measures to improve the situation that was proposed by Henderson and Glaeser [Ultramicroscopy 16 (1985) 139-150], which we refer to here as "stroboscopic image capture", is to divide the normal exposure into many successive frames, thus reducing the amount of electron exposure--and possibly the amount of beam-induced movement--per frame. The frames would then be aligned and summed. We have performed preliminary experiments on stroboscopic imaging using a 200-kV electron microscope that was equipped with a high dynamic range Charge-coupled device (CCD) camera for image recording and a liquid N2-cooled cryoholder. Single-layer paraffin crystals on carbon film were used as a test specimen. The ratio F(g)/F(0) of paraffin reflections, calculated from the images, serves as our criterion for the image quality. In the series that were evaluated, no significant improvement of the F(image)(g)/F(image)(0) ratio was found, even though the electron exposure per frame was reduced by a factor of 30. A frame-to-frame analysis of image distortions showed that considerable beam-induced movement had still occurred during each frame. In addition, the paraffin crystal lattice was observed to move relative to the supporting carbon film, a fact that cannot be explained as being an electron-optical effect caused by specimen charging. We conclude that a significant further reduction of the dose per frame (than was possible with this CCD detector) will be needed in order to test whether the frame-to-frame changes ultimately become small enough for stroboscopic image capture to show its potential.     

Eco-friendly (green) synthesis of magnetically active gold nanoclusters

Abstract

Au–Fe_xO_y composite nanoparticles (NPs) are of great technological interest due to their combined optical and magnetic properties. However, typical syntheses are neither simple nor ecologically friendly, creating a challenging situation for process scale-up. Here we describe conditions for preparing Au–Fe_xO_y NPs in aqueous solutions and at ambient temperatures, without resorting to solvents or amphiphilic surfactants with poor sustainability profiles. These magnetic gold nanoclusters (MGNCs) are prepared in practical yields with average sizes slightly below 100 nm, and surface plasmon resonances that extend to near-infrared wavelengths, and sufficient magnetic moment (up to 6 emu g^–1) to permit collection within minutes by handheld magnets. The MGNCs also produce significant photoluminescence when excited at 488 nm. Energy dispersive X-ray (EDX) analysis indicates a relatively even distribution of Fe within the MGNCs, as opposed to a central magnetic core.     

Was there significant tax evasion after the 1999 50 cent per pack cigarette tax increase in California?

OBJECTIVES: Several states, including California, have implemented large cigarette excise tax increases, which may encourage smokers to purchase their cigarettes in other lower taxed states, or from other lower or non-taxed sources. Such tax evasion thwarts tobacco control objectives and may cost the state substantial tax revenues. Thus, this study investigates the extent of tax evasion in the 6-12 months after the implementation of California's 0.50 dollars/pack excise tax increase. DESIGN AND SETTING: Retrospective data analysis from the 1999 California Tobacco Surveys (CTS), a random digit dialled telephone survey of California households. MAIN OUTCOME MEASURES: Sources of cigarettes, average daily cigarette consumption, and reported price paid. RESULTS: Very few (5.1 (0.7)% (+/-95% confidence limits)) of California smokers avoided the excise tax by usually purchasing cigarettes from non- or lower taxed sources, such as out-of-state outlets, military commissaries, or the internet. The vast majority of smokers purchased their cigarettes from the most convenient and expensive sources: convenience stores/gas (petrol) stations (45.0 (1.9)%), liquor/drug stores (16.4 (1.6)%), and supermarkets (8.8 (1.2)%). CONCLUSIONS: Despite the potential savings, tax evasion by individual smokers does not appear to pose a serious threat to California's excise tax revenues or its tobacco control objectives.     

Modes of ice formation and flow blockage that occur while filling a cold pipe

Pipe blockages caused by dendritic ice formation can occur during the filling of a cold water pipe. For any particular pipe wall material there is a range of temperatures for which such a blockage is probable. A pipe start-up is most likely to be accomplished successfully at very low temperatures. This counterintuitive behavior is due to the fact that supercooling and the resulting dendritic ice growth blockage of a pipe only occurs near the freezing point.     

News media coverage of smoking and health is associated with changes in population rates of smoking cessation but not initiation

OBJECTIVE: To determine whether changes in news media coverage of smoking and health issues are associated with changes in smoking behaviour in the USA. DESIGN AND MAIN OUTCOME MEASURES: Issue importance in the US news media is assessed by the number of articles published annually in major magazines indexed in The Reader's Guide to Periodical Literature. Annual incidence rates for cessation and initiation in the USA were computed from the large, representative National Health Interview Surveys (1965-1992). Patterns in cessation incidence were considered for ages 20-34 years and 35-50 years. Initiation incidence was examined for adolescents (14-17 years) and young adults (18-21 years) of both sexes. RESULTS: From 1950 to the early 1980s, the annual incidence of cessation in the USA mirrored the pattern of news media coverage of smoking and health, particularly for middle aged smokers. Cessation rates in younger adults increased considerably when second hand smoke concerns started to increase in the US population. Incidence of initiation in young adults did not start to decline until the beginning of the public health campaign against smoking in the 1960s. Among adolescents, incidence rates did not start to decline until the 1970s, after the broadcast ban on cigarette advertising. CONCLUSIONS: The level of coverage of smoking and health in the news media may play an important role in determining the rate of population smoking cessation, but not initiation. In countries where cessation has lagged, advocates should work to increase the newsworthiness of smoking and health issues.     

The steady state ice layer profile on a constant temperature plate in a forced convection flow—II. The transition and turbulent regimesCтaциoнapныи пpoфиля cлoя лядa нa oбтeкaeмoи плacтинe пocтoяннoи тeмпepaтypы. чacтя II пepeчoдныи и тypбyлeнтныи peзимы

The process of transition from laminar to turbulent flow on an ice surface was found to be very significantly different from that on a flat plate. The influence of the ice surface occurs because the shape of ice layer responds to the changes in heat-transfer coefficient that occur in the transition regime. As a result of this interaction two modes of transition were observed. Each mode was associated with a distinctive ice profile shape and Reynolds number for the onset of turbulent heat transfer. For both modes the onset Reynolds number was substantially lower than that for a flat plate. For some experimental parameters an interesting hysteresis phenomenon occurred in which the steady state ice layer could take either one of the two characteristic shapes depending on how equilibrium was approached. The decrease in the ice layer thickness that occurs in the transition region was also observed to have a major effect on the heat-transfer rates in the turbulent regime for some distance downstream of transition.     

What fraction of young adults are at risk for future smoking, and who are they?

Recent evidence indicates that higher smoking rates among young adults in the United States may be related in part to increased initiation during young adulthood. The tobacco industry, restricted from overtly targeting adolescents, appears to be focusing on young adults. Thus it is important to estimate the percentage and identify the characteristics of the young adult population (aged 18-29 years) at risk for future smoking. This group would include all current established smokers (smoked at least 100 cigarettes in their lifetime), current experimenters, former established smokers, and former experimenters at risk for smoking again, as well as never-smokers who do not rule out future smoking. Using data from the population-based 2002 California Tobacco Survey (N = 9,364 young adults aged 18-29 years), we designated groups of young adults at risk and identified factors associated with risk. Altogether, 86.7+/-1.5% of current and former established smokers were at risk for future smoking, and 59.6+/-4.3% of former established smokers were at risk. Over half (52.2+/-2.0%) of all experimenters but only 9.0+/-1.2% of never-smokers were at risk. Overall, 43.0+/-1.2% of the young adult population was at risk. Although different demographic and other factors were associated with risk among former established smokers, experimenters, and never-smokers, three factors were consistently associated in each group: Younger age, not having a smoke-free home, and going to bars and clubs. We conclude that the group of young adults at risk for future smoking is sizable and presents a fertile target for tobacco industry efforts to promote smoking. Counter-efforts might include promotion of smoke-free environments.     

Responsiveness of homocysteine concentrations to food and supplemental folate intakes in smokers and never-smokers enrolled in a diet intervention trial.

We investigated circulating homocysteine concentrations in relation to smoking, folate intake (from food and supplements), serum folate concentrations, and other dietary variables. The present study is part of a parent trial assessing the effects of increasing vegetable, fruit, and fiber intakes and reducing the percentage of energy obtained from fat on breast cancer recurrence in 3,088 women previously diagnosed with breast cancer. Of the 121 smokers enrolled in the parent trial, 85 were available at baseline for the present study and were randomly matched to 85 never-smokers on baseline folate intake, age, and intervention status. Follow-up data were available on 53 smokers (22 intervention and 31 comparison) and 56 never-smokers (24 intervention and 32 comparison). No significant differences in circulating homocysteine and folate concentrations were observed between smokers and never-smokers at baseline. For smokers, significant decreases in circulating homocysteine and significant increases in folate concentrations (p < .05) from baseline to 12 months were observed in the comparison group. For never-smokers, significant decreases in circulating homocysteine and significant increases in folate concentrations were observed in the intervention and comparison groups (p < .05). In the multivariate analysis, changes in serum folate concentration and supplemental folic acid were significantly associated with change in plasma homocysteine concentrations (p < .05). These findings show that increasing supplemental folic acid can reduce homocysteine concentrations, which may have implications for lowering cardiovascular disease risk for smokers and never-smokers.