Letters of information (LOI) for clinical trials are becoming longer and more complicated. We investigated patients' perspectives of their ability to understand the information presented during a ...clinical trial. Satisfaction with and motivation for participation in clinical trials were also ascertained. Perceptions from various treatment disciplines were compared.
Participants were chosen from 14 clinical trials (departments of rheumatology, ophthalmology, and cardiology) conducted at the same university. Subjects were asked to complete a written questionnaire that assessed demographic information, recall and understanding of information, subjects' decisions to participate, and perceptions/opinions of the study. The response rate was 75% (rheumatology, n = 74; ophthalmology, n = 32; cardiology, n = 84).
The majority of respondents (98%) indicated that they were satisfied with the informed consent process and with their involvement in a trial (97%). Subjects who reported having understood the LOI had better recall of placebo/active drug comparator (p < 0.03), and better understanding of why placebo was used (p < 0.04). No differences were found between those who reported understanding and those who did not on understanding the concept of concealed allocation (blinding). Subjects who felt they had received "the right amount of information" were more likely not to understand concealed allocation. The most frequent reason for trial participation was to help medical science (80%). Subjects with higher education were more likely to understand the reason for placebo use (p < 0.0003), but were not more likely to understand concealed allocation (p < 0.08).
Subjects reported that they were satisfied with the informed consent process and their experience in a clinical trial, and that they understood trial concepts. Subjects may be able to self-assess their own level of understanding for trial concepts that intrinsically make sense within the context of their beliefs about medical care, but other trial concepts may be misunderstood/misinterpreted regardless of self-assessment of understanding or education level (i.e., concealed allocation). Subjects may prefer to believe that investigators know which treatment they are receiving, and have made a good treatment decision specific to their case, despite having being told about concealed allocation and placebo use.
Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings were grown under ambient or elevated ( ambient + 180 µmol·mol-1) CO2 and ambient or elevated (ambient + 3.5°C) temperature in outdoor, ...sunlit chambers with a field soil. After 4 years, seedlings were harvested and measured for leaf area, leaf, fine root (<1 mm diameter), and structural (buds, branches, stems, main root, and lateral roots >1 mm in diameter) dry masses, and leaf and fine root C/N ratio, percent sugar, and percent cellulose. Elevated CO2 did not affect biomass production or allocation for any plant organ but increased specific leaf mass, leaf C/N ratio, and percent sugar and decreased the ratio of leaf area to structural weight and leaf percent cellulose. Elevated temperature tended to reduce biomass allocation to leaves and leaf sugar concentration. Fine root percent sugar tended to increase with elevated temperature but only at elevated CO2. Therefore, for Douglas-fir seedlings growing under naturally limiting soil moisture and nutrition conditions, elevated CO2 and temperature may have little impact on biomass or leaf area except for reduced specific leaf mass with elevated CO2 and reduced biomass allocation to leaves with elevated temperature. However, both elevated CO2 and temperature may alter leaf chemistry.
Elevated CO2 increases root growth and fine (diam. les 2 mm) root growth across a range of species and
experimental conditions. However, there is no clear evidence that elevated CO2 changes the ...proportion of C
allocated to root biomass, measured as either the rootratio shoot ratio or the fine rootratio needle ratio. Elevated CO2 tends
to increase mycorrhizal infection, colonization and the amount of extramatrical hyphae, supporting their key role
in aiding the plant to more intensively exploit soil resources, providing a route for increased C sequestration. Only
two studies have determined the effects of elevated CO2 on conifer fine-root life span, and there is no clear trend.
Elevated CO2 increases the absolute fine-root turnover rates; however, the standing crop root biomass is also
greater, and the effect of elevated CO2 on relative turnover rates (turnoverratio biomass) ranges from an increase to
a decrease. At the ecosystem level these changes could lead to increased C storage in roots. Increased fine-root
production coupled with increased absolute turnover rates could also lead to increases in soil organic C as greater
amounts of fine roots die and decompose. Although CO2 can stimulate fine-root growth, it is not known if this
stimulation persists over time. Modeling studies suggest that a doubling of the atmospheric CO2 concentration
initially increases biomass, but this stimulation declines with the response to elevated CO2 because increases in
assimilation are not matched by increases in nutrient supply.
We conducted a 4-year study of juvenile Pinus ponderosa fine root (≤ 2 mm) responses to atmospheric CO₂ and N-fertilization. Seedlings were grown in open-top chambers at three CO₂ levels (ambient, ...ambient + 175 μmol/mol, ambient + 350 μmol/mol) and three N-fertilization levels (0, 10, 20 g m⁻² year⁻¹). Length and width of individual roots were measured from minirhizotron video images bimonthly over 4 years starting when the seedlings were 1.5 years old. Neither CO₂ nor N-fertilization treatments affected the seasonal patterns of root production or mortality. Yearly values of fine-root length standing crop (m m⁻²), production (m m⁻² year⁻¹), and mortality (m m⁻² year⁻¹) were consistently higher in elevated CO₂ treatments throughout the study, except for mortality in the first year; however, the only statistically significant CO₂ effects were in the fine-root length standing crop (m m⁻²) in the second and third years, and production and mortality (m m⁻² year⁻¹) in the third year. Higher mortality (m m⁻² year⁻¹) in elevated CO₂ was due to greater standing crop rather than shorter life span, as fine roots lived longer in elevated CO₂. No significant N effects were noted for annual cumulative production, cumulative mortality, or mean standing crop. N availability did not significantly affect responses of fine-root standing crop, production, or mortality to elevated CO₂. Multi-year studies at all life stages of trees are important to characterize belowground responses to factors such as atmospheric CO₂ and N-fertilization. This study showed the potential for juvenile ponderosa pine to increase fine-root C pools and C fluxes through root mortality in response to elevated CO₂.
Monoterpene levels in current year needles of Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings were measured at the end of 4 years of exposure to ambient or elevated CO2 (+179 µmol ...mol−1), and ambient or elevated temperature (+0.3.5^C). Eleven monoterpenes were identified and quantified using gas chromatography/flame ionization detector/mass spectroscopy, with eight of these compounds regularly occurring in all trees examined. Elevated CO2 exposure significantly reduced the levels for four of the eight main compounds in needles. Total monoterpene production was reduced by 52% (P < 0.05). Elevated temperature also reduced monoterpene levels (P < 0.07). The combination of elevated temperature and elevated CO2 resulted in a 64% reduction in total monoterpenes compared with needles on ambient temperature trees. Two‐way anova showed no significant temperature‐CO2 interaction. It is hypothesized that seasonal reductions in needle monoterpene pools under elevated CO2 and temperature conditions may be due to a combination of competing carbon sinks, including increased carbon flux through the roots.
The effects of elevated CO2 and temperature on principal carbon constituents (PCC) and C and N allocation between needle, woody (stem and branches) and root tissue of Pseudotsuga menziesii Mirb. ...Franco seedlings were determined. The seedlings were grown in sun‐lit controlled‐environment chambers that contained a native soil. Chambers were controlled to reproduce ambient or ambient +180 ppm CO2 and either ambient temperature or ambient +3.5 °C for 4 years. There were no significant CO2 × temperature interactions; consequently the data are presented for the CO2 and temperature effects. At the final harvest, elevated CO2 decreased the nonpolar fraction of the PCC and increased the polar fraction and amount of sugars in the needles. In contrast, elevated temperature increased the nonpolar fraction of the PCC and decreased sugars in needles. There were no CO2 or temperature effects on the PCC fractions in the woody tissue or root tissue. Elevated CO2 and temperature had no significant effects on the C content of any of the plant tissues or fractions. In contrast, the foliar N content declined under elevated CO2 and increased under elevated temperature; there were no significant effects in other tissues. The changes in the foliar N concentrations were in the cellulose and lignin fractions, the fractions, which contain protein, and are the consequences of changes in N allocation under the treatments. These results indicate reallocation of N among plant organs to optimize C assimilation, which is mediated via changes in the selectivity of Rubisco and carbohydrate modulation of gene expression.
Evapotranspiration (ET) is driven by evaporative demand, available solar energy and soil moisture (SM) as well as by plant physiological activity which may be substantially affected by elevated CO2 ...and O3. A multi-year study was conducted in outdoor sunlit-controlled environment mesocosm containing ponderosa pine seedlings growing in a reconstructed soil–litter system. The study used a 2 x 2 factorial design with two concentrations of CO2 (ambient and elevated), two levels of O3 (low and high) and three replicates of each treatment. The objective of this study was to assess the effects of chronic exposure to elevated CO2 and O3, alone and in combination, on daily ET. This study evaluated three hypotheses: (i) because elevated CO2 stimulates stomatal closure, O3 effects on ET will be less under elevated CO2 than under ambient CO2; (ii) elevated CO2 will ameliorate the long-term effects of O3 on ET; and (iii) because conductance (g) decreases with decreasing SM, the impacts of elevated CO2 and O3, alone and in combination, on water loss via g will be greater in early summer when SM is not limiting than to other times of the year. A mixed-model covariance analysis was used to adjust the daily ET for seasonality and the effects of SM and photosynthetically active radiation when testing for the effects of CO2 and O3 on ET via the vapor pressure deficit gradient. The empirical results indicated that the interactive stresses of elevated CO2 and O3 resulted in a lesser reduction in ET via reduced canopy conductance than the sum of the individual effects of each gas. CO2-induced reductions in ET were more pronounced when trees were physiologically most active. O3-induced reductions in ET under ambient CO2 were likely transpirational changes via reduced conductance because needle area and root biomass were not affected by exposures to elevated O3 in this study.
Unusual monotonous intermediate ignimbrites consist of phenocryst-rich dacite that occurs as very large volume (>1000 km
3) deposits that lack systematic compositional zonation, comagmatic rhyolite ...precursors, and underlying plinian beds. They are distinct from countless, usually smaller volume, zoned rhyolite–dacite–andesite deposits that are conventionally believed to have erupted from magma chambers in which thermal and compositional gradients were established because of sidewall crystallization and associated convective fractionation. Despite their great volume, or because of it, monotonous intermediates have received little attention. Documentation of the stratigraphy, composition, and geologic setting of the Lund Tuff – one of four monotonous intermediate tuffs in the middle-Tertiary Great Basin ignimbrite province – provides insight into its unusual origin and, by implication, the origin of other similar monotonous intermediates.
The Lund Tuff is a single cooling unit with normal magnetic polarity whose volume likely exceeded 3000 km
3. It was emplaced 29.02±0.04 Ma in and around the coeval White Rock caldera which has an unextended north–south diameter of about 50 km. The tuff is monotonous in that its phenocryst assemblage is virtually uniform throughout the deposit: plagioclase>quartz≈hornblende>biotite>Fe–Ti oxides≈sanidine>titanite, zircon, and apatite. However, ratios of phenocrysts vary by as much as an order of magnitude in a manner consistent with progressive crystallization in the pre-eruption chamber. A significant range in whole-rock chemical composition (e.g., 63–71 wt% SiO
2) is poorly correlated with phenocryst abundance.
These compositional attributes cannot have been caused wholly by winnowing of glass from phenocrysts during eruption, as has been suggested for the monotonous intermediate Fish Canyon Tuff. Pumice fragments are also crystal-rich, and chemically and mineralogically indistinguishable from bulk tuff. We postulate that convective mixing in a sill-like magma chamber precluded development of a zoned chamber with a rhyolitic top or of a zoned pyroclastic deposit. Chemical variations in the Lund Tuff are consistent with equilibrium crystallization of a parental dacitic magma followed by eruptive mixing of compositionally diverse crystals and high-silica rhyolite vitroclasts during evacuation and emplacement. This model contrasts with the more systematic withdrawal from a bottle-shaped chamber in which sidewall crystallization creates a marked vertical compositional gradient and a substantial volume of capping-evolved rhyolite magma. Eruption at exceptionally high discharge rates precluded development of an underlying plinian deposit.
The generation of the monotonous intermediate Lund magma and others like it in the middle Tertiary of the western USA reflects an unusually high flux of mantle-derived mafic magma into unusually thick and warm crust above a subducting slab of oceanic lithosphere.
We previously used dual stable isotope techniques to partition soil CO₂ efflux into three source components (rhizosphere respiration, litter decomposition, and soil organic matter (SOM) oxidation) ...using experimental chambers planted with Douglas-fir Pseudotsuga menziesii (Mirb.) Franco seedlings. The components responded differently to elevated CO₂ (ambient + 200 μmol mol⁻¹) and elevated temperature (ambient + 4 °C) treatments during the first year. Rhizosphere respiration increased most under elevated CO₂, and SOM oxidation increased most under elevated temperature. However, many studies show that plants and soil processes can respond to altered climates in a transient way. Herein, we extend our analysis to 2 years to evaluate the stability of the responses of the source components. Total soil CO₂ efflux increased significantly under elevated CO₂ and elevated temperature in both years (1994 and 1995), but the enhancement was much less in 1995. Rhizosphere respiration increased less under elevated temperature in 1995 compared with 1994. Litter decomposition also tended to increase comparatively less in 1995 under elevated CO₂, but was unresponsive to elevated temperature between years. In contrast, SOM oxidation was similar under elevated CO₂ in the 2 years. Less SOM oxidation occurred under elevated temperature in 1995 compared with 1994. Our results indicate that temporal variations can occur in CO₂ production by the sources. The variations likely involve responses to antecedent physical disruption of the soil and physiological processes.
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