Long-term carbon and nitrogen dynamics at SPRUCE revealed through stable isotopes in peat profiles

Peatlands encode information about past vegetation dynamics, climate, and microbial processes. Here, we used δ15N and δ13C patterns from 16 peat profiles to deduce how the biogeochemistry of the Marcell S1 forested bog in northern Minnesota responded to environmental and vegetation change over the past  ∼ 10000 years. In multiple regression analyses, δ15N and δ13C correlated strongly with depth, plot location, C∕N, %N, and each other. Correlations with %N, %C, C∕N, and the other isotope accounted for 80% of variance for δ15N and 38% of variance for δ13C, reflecting N and C losses. In contrast, correlations with depth and topography (hummock or hollow) reflected peatland successional history and climate. Higher δ15N in plots closer to uplands may reflect upland-derived DON inputs and accompanying shifts in N dynamics in the lagg drainage area surrounding the bog. The Suess effect (declining δ13CO2 since the Industrial Revolution) lowered δ13C in recent surficial samples. High δ15N from −35 to −55cm probably indicated the depth of ectomycorrhizal activity after tree colonization of the peatland over the last 400 years, as confirmed by the occasional presence of wood down to −35cm depth. High δ13C at  ∼ 4000 years BP (−65 to −105cm) could reflect a transition at that time to slower rates of peat accumulation, when 13C discrimination during peat decomposition may increase in importance. Low δ13C and high δ15N at −213 and −225cm ( ∼ 8500 years BP) corresponded to a warm period during a sedge-dominated rich fen stage. The above processes appear to be the primary drivers of the observed isotopic patterns, whereas there was no clear evidence for methane dynamics influencing δ13C patterns

The level of recognition of physical symptoms in patients with a major depression episode in the outpatient psychiatric practice in Puerto Rico: An observational study

BACKGROUND: This study was designed to evaluate the psychiatrists' level of recognition of somatic symptoms associated to a major depressive episode (MDE) (DSM-IV-TR criteria) and the impact of those somatic symptoms on the treatment effectiveness. METHODS: This non-interventional study was conducted in 25 medical offices in Puerto Rico from February to December 2003. It had 2 visits separated by 8 weeks. The level of recognition was determined by: the correlation between the physician clinical evaluation and their patients' self-evaluations through different validated instruments using kappa statistics. Chi-square test was used to evaluate the impact of somatic symptoms on treatment antidepressants' effectiveness. RESULTS: All the 145 recruited patients reported the presence of at least one somatic symptom associated with their current MDE. In the two visits covered by the study, a fair agreement between the psychiatrists' and the patients' reports was noted for headache, abdominal pain and upper limb pains (0.4003 ≤ κ ≥ 0.6594). For other painful symptoms and painless somatic symptoms, the Kappa values obtained were non-significant. Slight but significant reductions in depression and painful symptoms severity were observed after 8 weeks of treatment. A proportional relationship between the pain and depression severity was observed (p < 0.0001). CONCLUSION: The study results show that somatic symptoms: are very common in depressed Puerto Rican patients; are significant under-reported by psychiatrists; and have a significant impact on the antidepressant effectiveness

Comparison of Carboxyhaemoglobin Concentrations between Low-flow and Minimal-flow Anaesthesia with Desflurane

This was a prospective randomised study comparing carboxyhaemoglobin concentrations between low-flow anaesthesia (fresh gas flow 1.0 L/min) and minimal-flow anaesthesia (0.5 L/min) using desflurane. Sixty (ASA 1 or 2) adult patients undergoing elective surgery under general anaesthesia were randomly allocated to receive either low-flow (Group 1) or minimal flow anaesthesia (Group 2). Venous blood samples for carboxyhaemoglobin levels were taken at baseline and at 10 mins intervals for 40 mins. Both groups showed significant increase in carboxyhaemoglobin concentrations within the first 10 mins when fresh gas flow of 4.0 L/min was used. Reduction in carboxyhemoglobin levels was seen after 20 mins of minimal or low flow anaesthesia. However, there was no significant difference in the magnitude of reduction of carboxyhemoglobin concentrations between the groups. The fractional inspired of oxygen (FiO2) showed no significant changes in either group. In conclusion, desflurane usage in anaesthesia with either low-flow or minimal-flow was not associated with increased carboxyhaemoglobin concentrations

From the Top: Surface-derived Carbon Fuels Greenhouse Gas Production at Depth in a Neotropical Peatland

Tropical peatlands play an important role in global carbon (C) cycling but little is known about factors driving carbon dioxide (CO2) and methane (CH4) emissions from these ecosystems, especially production below the surface. This study aimed to identify source material and processes regulating C emissions from deep in a Neotropical peatland on the Caribbean coast of Panama. We hypothesized that: 1) surface derived organic matter transported down the soil profile is the primary C source for respiration products at depth and 2) high lignin content results in hydrogenotrophic methanogenesis as the dominant CH4 production pathway throughout the profile. We used radiocarbon isotopes to determine whether CO2 and CH4 at depth (measured to 2 m) are produced from modern substrates or ancient deep peat, and we used stable C isotopes to identify the dominant CH4 production pathway. Peat organic chemistry was characterized using 13C solid state nuclear magnetic resonance spectroscopy (13C-NMR). We found that deep peat respiration products had radiocarbon signatures that were more similar to surface dissolved organic C (DOC) than deep solid peat. Radiocarbon ages for deep peat ranged from 1200 &ndash; 1800 yrBP at the sites measured. These results indicate that surface derived C was the dominant source for gas production at depth in this peatland, likely because of vertical transport of DOC from the surface to depth. Carbohydrates did not vary with depth across these sites, whereas lignin, which was the most abundant compound (55&ndash;70 % of C), tended to increase with depth. These results suggest that there is no preferential decomposition of carbohydrates, but preferential retention of lignin. Stable isotope signatures of respiration products indicated that hydrogenotrophic rather than acetoclastic methanogenesis was the dominant production pathway of CH4 throughout the peat profile. These results suggest, even C compounds that are typically considered vulnerable to decomposition (i.e., carbohydrates) are preserved deep in these tropical peats, highlighting the importance of anaerobic, waterlogged conditions for preserving tropical peatland C

Spiritual experiences of women with breast cancer in Singapore: a qualitative study

Objective: Although there has been increasing emphasis on the importance of spirituality in patients with cancer, few studies have examined the spiritual experiences of an ethnically diverse sample of Asian women with breast cancer. The objective of this study was to examine the spiritual experiences of Singaporean women with breast cancer in the first year of diagnosis. Methods: A qualitative exploratory study design was used and data were gathered using individual semi-structured interviews. Purposive sampling selected the participants and data saturation sample size was reached after interviews with 28 participants. Data were analyzed using Braun and Clarke's thematic approach. Results: The participants were aged between 28 and 64 years and included women from the three major ethnic groups. The three themes that emerged from the data included transcendental experiences, meaning and purpose, and changing perspectives. Conclusions: This study informs that while spiritual needs are common, Singaporean women in their first year of the breast cancer diagnosis express spirituality in culturally specific ways. The clinical implications of the study emphasize the importance of addressing women's spiritual concerns, with attention to cultural differences so as to render holistic patient-centered care