Rapid microbial methanogenesis during CO2 storage in hydrocarbon reservoirs.

Carbon capture and storage (CCS) is a key technology to mitigate the environmental impact of carbon dioxide (CO2) emissions. An understanding of the potential trapping and storage mechanisms is required to provide confidence in safe and secure CO2 geological sequestration1,2. Depleted hydrocarbon reservoirs have substantial CO2 storage potential1,3, and numerous hydrocarbon reservoirs have undergone CO2 injection as a means of enhanced oil recovery (CO2-EOR), providing an opportunity to evaluate the (bio)geochemical behaviour of injected carbon. Here we present noble gas, stable isotope, clumped isotope and gene-sequencing analyses from a CO2-EOR project in the Olla Field (Louisiana, USA). We show that microbial methanogenesis converted as much as 13-19% of the injected CO2 to methane (CH4) and up to an additional 74% of CO2 was dissolved in the groundwater. We calculate an in situ microbial methanogenesis rate from within a natural system of 73-109 millimoles of CH4 per cubic metre (standard temperature and pressure) per year for the Olla Field. Similar geochemical trends in both injected and natural CO2 fields suggest that microbial methanogenesis may be an important subsurface sink of CO2 globally. For CO2 sequestration sites within the environmental window for microbial methanogenesis, conversion to CH4 should be considered in site selection.

Methoxyl stable isotopic constraints on the origins and limits of coal-bed methane.

Microbial coal-bed methane is an important economic resource and source of a potent greenhouse gas, but controls on its formation are poorly understood. To test whether the microbial degradability of coal limits microbial methane, we monitored methoxyl group demethylation­a reaction that feeds methanogenesis­in a global sample suite ranging in maturity from wood to bituminous coal. Carbon isotopic compositions of residual methoxyl groups were inconsistent with a thermal reaction, instead implying a substrate-limited biologic process. This suggests that deep biosphere communities participated in transforming plant matter to coal on geologic time scales and that methoxyl abundance influences coal-bed methane yield. Carbon isotopic enrichments resulting from microbial methylotrophy also explain an enigmatic offset in the carbon-13 content of microbial methane from coals and conventional hydrocarbon deposits.

InterCarb: A Community Effort to Improve Interlaboratory Standardization of the Carbonate Clumped Isotope Thermometer Using Carbonate Standards.

Increased use and improved methodology of carbonate clumped isotope thermometry has greatly enhanced our ability to interrogate a suite of Earth-system processes. However, interlaboratory discrepancies in quantifying carbonate clumped isotope (Δ47) measurements persist, and their specific sources remain unclear. To address interlaboratory differences, we first provide consensus values from the clumped isotope community for four carbonate standards relative to heated and equilibrated gases with 1,819 individual analyses from 10 laboratories. Then we analyzed the four carbonate standards along with three additional standards, spanning a broad range of δ47 and Δ47 values, for a total of 5,329 analyses on 25 individual mass spectrometers from 22 different laboratories. Treating three of the materials as known standards and the other four as unknowns, we find that the use of carbonate reference materials is a robust method for standardization that yields interlaboratory discrepancies entirely consistent with intralaboratory analytical uncertainties. Carbonate reference materials, along with measurement and data processing practices described herein, provide the carbonate clumped isotope community with a robust approach to achieve interlaboratory agreement as we continue to use and improve this powerful geochemical tool. We propose that carbonate clumped isotope data normalized to the carbonate reference materials described in this publication should be reported as Δ47 (I-CDES) values for Intercarb-Carbon Dioxide Equilibrium Scale.

Gas formation. Formation temperatures of thermogenic and biogenic methane.

Methane is an important greenhouse gas and energy resource generated dominantly by methanogens at low temperatures and through the breakdown of organic molecules at high temperatures. However, methane-formation temperatures in nature are often poorly constrained. We measured formation temperatures of thermogenic and biogenic methane using a "clumped isotope" technique. Thermogenic gases yield formation temperatures between 157° and 221°C, within the nominal gas window, and biogenic gases yield formation temperatures consistent with their comparatively lower-temperature formational environments (<50°C). In systems where gases have migrated and other proxies for gas-generation temperature yield ambiguous results, methane clumped-isotope temperatures distinguish among and allow for independent tests of possible gas-formation models.

Standard value of ultrasound elastography using acoustic radiation force impulse imaging (ARFI) in healthy liver tissue of children and adolescents.

PURPOSE: Ultrasound elastography by acoustic radiation force impulse imaging (ARFI) is used in adults for non invasive measurement of liver stiffness, indicating liver diseases like fibrosis. To establish ARFI in children and adolescents we determined standard values of healthy liver tissue and analysed potentially influencing factors. MATERIALS AND METHODS: 132 patients between 0 and 17 years old were measured using ARFI. None of them had any liver disease or any other disease that could affect the liver secondarily. All patients had a normal ultrasound scan, a normal BMI and normal liver function tests. The mean value of all ARFI measurements was calculated and potentially influencing factors were analysed. RESULTS: The mean value of all ARFI elastography measurements was 1.16 m/sec (SD ±â€Š0.14 m/sec). Neither age (p = 0.533) nor depth of measurement (p = 0.066) had no significant influence on ARFI values, whereas a significant effect of gender was found with lower ARFI values in females (p = 0.025), however, there was no significant interaction between age groups (before or after puberty) and gender (p = 0.276). There was an interlobar difference with lower values in the right liver lobe compared to the left (p = 0.036) and with a significantly lower variance (p < 0.001). Consistend values were measured by different examiners (p = 0.108), however, the inter examiner variance deviated significantly (p < 0.001). CONCLUSION: ARFI elastography is a reliable method to measure liver stiffness in children and adolescents. In relation to studies which analyse liver diseases, the standard value of 1.16 m/sec (±â€Š0.14 m/sec) allows a differentiation of healthy versus pathological liver tissue.

Methods and limitations of 'clumped' CO2 isotope (Delta47) analysis by gas-source isotope ratio mass spectrometry.

The geochemistry of multiply substituted isotopologues ('clumped-isotope' geochemistry) examines the abundances in natural materials of molecules, formula units or moieties that contain more than one rare isotope (e.g. (13)C(18)O(16)O, (18)O(18)O, (15)N(2), (13)C(18)O(16)O(2) (2-)). Such species form the basis of carbonate clumped-isotope thermometry and undergo distinctive fractionations during a variety of natural processes, but initial reports have provided few details of their analysis. In this study, we present detailed data and arguments regarding the theoretical and practical limits of precision, methods of standardization, instrument linearity and related issues for clumped-isotope analysis by dual-inlet gas-source isotope ratio mass spectrometry (IRMS). We demonstrate long-term stability and subtenth per mil precision in 47/44 ratios for counting systems consisting of a Faraday cup registered through a 10(12) ohm resistor on three Thermo-Finnigan 253 IRMS systems. Based on the analyses of heated CO(2) gases, which have a stochastic distribution of isotopes among possible isotopologues, we document and correct for (1) isotopic exchange among analyte CO(2) molecules and (2) subtle nonlinearity in the relationship between actual and measured 47/44 ratios. External precisions of approximately 0.01 per thousand are routinely achieved for measurements of the mass-47 anomaly (a measure mostly of the abundance anomaly of (13)C-(18)O bonds) and follow counting statistics. The present technical limit to precision intrinsic to our methods and instrumentation is approximately 5 parts per million (ppm), whereas precisions of measurements of heterogeneous natural materials are more typically approximately 10 ppm (both 1 s.e.). These correspond to errors in carbonate clumped-isotope thermometry of +/-1.2 degrees C and +/-2.4 degrees C, respectively.

Immediate breast reconstruction after mastectomy increases wound complications: however, initiation of adjuvant chemotherapy is not delayed.

BACKGROUND: Immediate breast reconstruction is being increasingly used after mastectomy, although it may increase the incidence of wound complications. The indications for chemotherapy in breast cancer are expanding and wound complications following mastectomy may delay the initiation of adjuvant chemotherapy. HYPOTHESIS: Immediate breast reconstruction after mastectomy for breast cancer does not lead to an increased incidence of wound complications nor delay the initiation of systemic chemotherapy. DESIGN AND SETTING: Retrospective medical record review at a tertiary care center. PATIENTS: One hundred twenty-eight women treated with a mastectomy for breast cancer over an 8-year period (January 1, 1995, through December 31, 2002). MAIN OUTCOME MEASURES: Surgical site complications (infectious and noninfectious) and time to initiation of postoperative chemotherapy. RESULTS: One hundred forty-eight mastectomy procedures in 128 women with breast cancer were evaluated. We analyzed 4 subgroups according to whether or not immediate breast reconstruction was part of the surgical procedure (76 or 72 procedures, respectively) and whether or not postoperative adjuvant chemotherapy was administered (81 or 47 patients, respectively). There was an increased incidence of wound complications in patients who underwent immediate breast reconstruction compared with those who did not (6/72 [8.3%] vs 17/76 [22.3%]; P = .02). However, these complications did not delay initiation of postoperative chemotherapy. CONCLUSIONS: Although we observed an increased incidence of wound complications when immediate breast reconstruction was combined with mastectomy, there was no delay in the initiation of adjuvant therapy. Immediate breast reconstruction should remain an important treatment option after mastectomy even when postoperative chemotherapy is anticipated.

Low-temperature carbonate concretions in the Martian meteorite ALH84001: evidence from stable isotopes and mineralogy.

The martian meteorite ALH84001 contains small, disk-shaped concretions of carbonate with concentric chemical and mineralogical zonation. Oxygen isotope compositions of these concretions, measured by ion microprobe, range from delta18O = +9.5 to +20.5 per thousand. Most of the core of one concretion is homogeneous (16.7 +/- 1.2 per thousand) and over 5 per thousand higher in delta18O than a second concretion. Orthopyroxene that hosts the secondary carbonates is isotopically homogeneous (delta18O = 4.6 +/- 1.2 per thousand). Secondary SiO2 has delta18O = 20.4 per thousand. Carbon isotope ratios measured from the core of one concretion average delta13C = 46 +/- 8 per thousand, consistent with formation on Mars. The isotopic variations and mineral compositions offer no evidence for high temperature (>650 degrees C) carbonate precipitation and suggest non-equilibrium processes at low temperatures (< approximately 300 degrees C).

Factor analysis of the Wechsler Memory Scale: is the associate learning subtest an unclear measure?

A factor analysis of the Wechsler Memory Scale (WMS) with 30-minute delayed recall scores (percent retained) for the Logical Memory, Visual Reproduction, and Associate Learning subtests indicated that this variant of the WMS taps different types of learning and memory for new material. With regard to the verbal learning/recall subtests, Logical Memory appears to be related to attention/ concentration ability, while Associate Learning is relatively independent. The results also showed that both the easy and hard items from Associate Learning tap the same ability, providing evidence that this subtest is a measure of rote verbal learning. These results support the clinical utility of the WMS with delayed recalls in neuropsychiatric populations.

Stimulus persistence and age.

Stimulus persistence theory states that the effects of stimulation are longer lasting in the nervous system of the old person than the younger one. This concept and its relation to perceptual functioning and age was examined via two perceptual aftereffect tasks, the Spiral and the Waterfall. Twenty-four elderly adults (mean age = 65.5) and twenty-four young adults (mean age = 24.8) were each exposed to both stimulus displays, at four exposure durations: 45, 60, 90, and 120 seconds. Following the offset of each display, the duration of any apparent motion aftereffect was recorded. Although on the basis of stimulus persistence theory it was expected that the elderly would exhibit longer mean aftereffects than the young, no support for this hypothesis was noted. Possible explanations of these results and their relation to previous findings, in terms of fatigue effects and sample characteristics, are discussed.