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BACKGROUND This study aimed to determine the relative effect of Internet and Internet plus telephone treatment for smoking cessation on smoking abstinence among US adults. A priori hypotheses were that Internet enhanced with tailored content and social support would outperform basic Internet (BI) and that enhanced Internet (EI) plus proactive telephone counseling would outperform the other conditions. METHODS The Quit Using Internet and Telephone Treatment (iQUITT) study used a 3-group randomized controlled design comparing BI, EI, and EI and telephone combined (EI+P). The trial was conducted from March 8, 2005, through November 30, 2008. Current adult smokers in the United States who smoked 5 or more cigarettes per day were recruited via search engines. Characteristics of the 2005 participants include mean (SD) age of 35.9 (10.8) years, 51.1% women, and 86.5% white. The follow-up assessment rate at 18 months was 68.2%. The main outcome measure was 30-day point prevalence abstinence measured at 3, 6, 12, and 18 months after randomization using intent-to-treat analysis. RESULTS At 18 months, the 30-day multiple point prevalence abstinence rate across all follow-up intervals was 3.5% (BI), 4.5% (EI), and 7.7% (EI+P), with EI+P significantly outperforming BI and EI. At 18 months, 30-day single point prevalence abstinence rates were 19.0% (BI), 17.4% (EI), and 19.6% (EI+P) and did not differ among the groups. CONCLUSIONS Combined internet and telephone treatment outperforms static and dynamic Internet interventions. TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT00282009

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Identifying the global drivers of soil priming is essential to understanding C cycling in terrestrial ecosystems. We conducted a survey of soils across 86 globally-distributed locations, spanning a wide range of climates, biotic communities, and soil conditions, and evaluated the apparent soil priming effect using 13 C-glucose labeling. Here we show that the magnitude of the positive apparent priming effect (increase in CO 2 release through accelerated microbial biomass turnover) was negatively associated with SOC content and microbial respiration rates. Our statistical modeling suggests that apparent priming effects tend to be negative in more mesic sites associated with higher SOC contents. In contrast, a single-input of labile C causes positive apparent priming effects in more arid locations with low SOC contents. Our results provide solid evidence that SOC content plays a critical role in regulating apparent priming effects, with important implications for the improvement of C cycling models under global change scenarios.