A latent class analysis of adolescents’ technology and interactive social media use: Associations with academics and substance use

Latent class analysis was used to identify patterns of technology and social media use among adolescents in a national study (n = 26,348). Multinomial logistic regression was used to examine associations between latent classes and academics and substance use. Results demonstrated four classes: Infrequent Users (55%), Interactive Users (21%), Television Watchers (14%), and Constant Users (10%). Compared to Infrequent Users, Interactive, and Constant Users had lower grades and higher alcohol and marijuana use. Television Watchers had lower grades and participated in fewer extracurricular activities compared to Infrequent Users, but there were no differences on substance use. Results show that adolescents with the most media‐intensive profiles were also at greater risk for poor academic outcomes and substance use.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153199/1/hbe2154.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153199/2/hbe2154_am.pd

Daily Associations Between Drinking and Sex Among College Students: A Longitudinal Measurement Burst Design

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111762/1/jora12135.pd

Experimentally induced root mortality increased nitrous oxide emission from tropical forest soils

We conducted an experiment on sand and clay tropical forest soils to test the short‐term effect of root mortality on the soil‐atmosphere flux of nitrous oxide, nitric oxide, methane, and carbon dioxide. We induced root mortality by isolating blocks of land to 1 m using trenching and root exclusion screening. Gas fluxes were measured weekly for ten weeks following the trenching treatment. For nitrous oxide there was a highly significant increase in soil‐atmosphere flux over the ten weeks following treatment for trenched plots compared to control plots. N2O flux averaged 37.5 and 18.5 ng N cm−2 h−1 from clay trenched and control plots and 4.7 and 1.5 ng N cm−2 h−1 from sand trenched and control plots. In contrast, there was no effect for soil‐atmosphere flux of nitric oxide, carbon dioxide, or methane

Fine root dynamics and trace gas fluxes in two lowland tropical forest soils

Fine root dynamics have the potential to contribute significantly to ecosystem-scale biogeochemical cycling, including the production and emission of greenhouse gases. This is particularly true in tropical forests which are often characterized as having large fine root biomass and rapid rates of root production and decomposition. We examined patterns in fine root dynamics on two soil types in a lowland moist Amazonian forest, and determined the effect of root decay on rates of C and N trace gas fluxes. Root production averaged 229 ( 35) and 153 ( 27) gm 2 yr 1 for years 1 and 2 of the study, respectively, and did not vary significantly with soil texture. Root decay was sensitive to soil texture with faster rates in the clay soil (k5 0.96 year 1) than in the sandy loam soil (k5 0.61 year 1),leading to greater standing stocks of dead roots in the sandy loam. Rates of nitrous oxide (N2O) emissions were significantly greater in the clay soil (13 1ngNcm 2 h 1) than in the sandy loam (1.4 0.2 ngNcm 2 h 1). Root mortality and decay following trenching doubled rates of N2O emissions in the clay and tripled them in sandy loam over a 1-year period. Trenching also increased nitric oxide fluxes, which were greater in the sandy loam than in the clay. We used trenching (clay only) and a mass balance approach to estimate the root contribution to soil respiration. In clay soil root respiration was 264–380 gCm 2 yr 1, accounting for 24% to 35% of the total soil CO2 efflux. Estimates were similar using both approaches. In sandy loam, root respiration rates were slightly higher and more variable (521 206 gCm2 yr 1) and contributed 35% of the total soil respiration. Our results show that soil heterotrophs strongly dominate soil respiration in this forest, regardless of soil texture. Our results also suggest that fine root mortality and decomposition associated with disturbance and land-use change can contribute significantly to increased rates of nitrogen trace gas emissions

Age, period and cohort effects in frequent cannabis use among US students: 1991–2018

Background and AimsAs the legal status of cannabis changes across the United States and modes of administration expand, it is important to examine the potential impact on adolescent cannabis use. This study aimed to assess changes in prevalence of frequent cannabis use in adolescents in the United States and how far this varies by age and cohort.DesignAnalysis of Monitoring the Future, a nationally representative annual survey of 8th‐, 10th‐ and 12th‐grade students in the United States conducted from 1991 to 2018.SettingIn‐school surveys completed by US adolescents.ParticipantsA total of 1 236 159 8th‐, 10th‐ and 12th‐graders; 51.5% female, 59.6% non‐Hispanic white, 12.3% non‐Hispanic black, 13.4% Hispanic and 14.7% other race/ethnicity.MeasurementsFrequent cannabis use (FCU), defined as six or more occasions in the past 30 days, stratified by sex, race/ethnicity and parental education.FindingsFCU among US adolescents increased over the study period; the peak in 2010–18 was 11.4% among 18‐year‐old students. This increase was best explained by both period and cohort effects. Compared with respondents in 2005, adolescents surveyed in 2018 had period effects in FCU that were 1.6 times greater. Adolescents in younger birth cohorts (those born > 1988) had a lower increase in FCU than those born prior to 1988. Results were consistent across sex, parent education and race/ethnicity, with period effects indicating increasing FCU after 2005 and cohort effects indicating a lower magnitude of increase in more recent birth cohorts. Age and parental education disparities in FCU have increased over time, whereas race/ethnicity differences have converged over time; black students were 0.67 [95% confidence interval (CI) = 0.64–0.70] times as likely to use cannabis frequently as white students from 1991 to 2000, and 1.03 (95% CI = 0.98–1.09) times as likely from 2011 to 2018 (P‐value for time interaction < 0.001).ConclusionsThe prevalence of frequent cannabis use (FCU) increased from 1991 to 2018 among older adolescents in the United States. Racial/ethnic differences in FCU converged, whereas parental education differences have diverged.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151314/1/add14665_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151314/2/add14665.pd

Why Do High School Seniors Drink? Implications for a Targeted Approach to Intervention

The transition from high school to college provides a potentially critical window to intervene and reduce risky behavior among adolescents. Understanding the motivations (e.g., social, coping, enhancement) behind high school seniors’ alcohol use could provide one important avenue to reducing risky drinking behaviors. In the present study, latent class analysis was used to examine the relationship between different patterns of drinking motivations and behaviors in a sample of 12th graders (N = 1,877) from the 2004 Monitoring the Future survey. Unlike previous variable-centered analyses, this person-centered approach identifies types of motivations that cluster together within individuals and relates membership in these profiles to drinking behaviors. Results suggest four profiles of drinking motivations for both boys and girls, including Experimenters, Thrill-seekers, Multi-reasoners, and Relaxers. Early initiation of alcohol use, past year drunkenness, and drinking before 4 p.m. were associated with greater odds of membership in the Multi-reasoners class as compared to the Experimenters class. Although the strength of these relationships varied for boys and girls, findings were similar across gender suggesting that the riskiest drinking behavior was related to membership in the Multi-reasoners class. These findings can be used to inform prevention programming. Specifically, targeted interventions that tailor program content to the distinct drinking motivation profiles described above may prove to be effective in reducing risky drinking behavior among high school seniors

Adolescent substance use: a prospective longitudinal model of substance use onset among South African adolescents

Substance use onset among Colored adolescents between eighth and ninth grades in an urban area of Cape Town, South Africa was examined using latent transition analysis. Longitudinal self-report data regarding substance use (N = 1118, 50.9% female) were collected in 2004 and 2005. Results indicated that the pattern of onset was similar across genders; adolescents first tried either alcohol or cigarettes, followed by both, then dagga (cannabis), and then inhalants. The prevalence of lifetime cigarette use was slightly greater for females; dagga (cannabis) and inhalant use were greater for males. The similarity of developmental onset in the current sample to previous international work supports the promise of adapting prevention programs across contexts. The study’s limitations are noted.Web of Scienc

Oxidized and reduced [2Fe-2S] clusters from an iron(I) synthon

© 2015 SBIC. Abstract Synthetic [2Fe-2S] clusters are often used to elucidate ligand effects on the reduction potentials and spectroscopy of natural electron-transfer sites, which can have anionic Cys ligands or neutral His ligands. Current synthetic routes to [2Fe-2S] clusters are limited in their feasibility with a range of supporting ligands. Here, we report a new synthetic route to synthetic [2Fe-2S] clusters, through oxidation of an iron(I) source with elemental sulfur. This method yields a neutral diketiminate-supported [2Fe-2S] cluster in the diiron(III)-oxidized form. The oxidized [2Fe-2S] cluster can be reduced to a mixed valent iron(II)-iron(III) compound. Both the diferric and reduced mixed valent clusters are characterized using X-ray crystallography, Mössbauer spectroscopy, EPR spectroscopy and cyclic voltammetry. The reduced compound is particularly interesting because its X-ray crystal structure shows a difference in Fe-S bond lengths to one of the iron atoms, consistent with valence localization. The valence localization is also evident from Mössbauer spectroscopy

Infrared Emission from the Nearby Cool Core Cluster Abell 2597

We observed the brightest central galaxy (BCG) in the nearby (z=0.0821) cool core galaxy cluster Abell 2597 with the IRAC and MIPS instruments on board the Spitzer Space Telescope. The BCG was clearly detected in all Spitzer bandpasses, including the 70 and 160 micron wavebands. We report aperture photometry of the BCG. The spectral energy distribution exhibits a clear excess in the FIR over a Rayleigh-Jeans stellar tail, indicating a star formation rate of ~4-5 solar masses per year, consistent with the estimates from the UV and its H-alpha luminosity. This large FIR luminosity is consistent with that of a starburst or a Luminous Infrared Galaxy (LIRG), but together with a very massive and old population of stars that dominate the energy output of the galaxy. If the dust is at one temperature, the ratio of 70 to 160 micron fluxes indicate that the dust emitting mid-IR in this source is somewhat hotter than the dust emitting mid-IR in two BCGs at higher-redshift (z~0.2-0.3) and higher FIR luminosities observed earlier by Spitzer, in clusters Abell 1835 and Zwicky 3146.Comment: Accepted at Ap