Feasibility study of using brine for carbon dioxide capture and storage from fixed sources.

A laboratory-scale reactor was developed to evaluate the capture of carbon dioxide (CO2) from a gas into a liquid as an approach to control greenhouse gases emitted from fixed sources. CO2 at 5-50% concentrations was passed through a gas-exchange membrane and transferred into liquid media--tap water or simulated brine. When using water, capture efficiencies exceeded 50% and could be enhanced by adding base (e.g., sodium hydroxide) or the combination of base and carbonic anhydrase, a catalyst that speeds the conversion of CO2 to carbonic acid. The transferred CO2 formed ions, such as bicarbonate or carbonate, depending on the amount of base present. Adding precipitating cations, like Ca++, produced insoluble carbonate salts. Simulated brine proved nearly as efficient as water in absorbing CO2, with less than a 6% reduction in CO2 transferred. The CO2 either dissolved into the brine or formed a mixture of gas and ions. If the chemistry was favorable, carbonate precipitate spontaneously formed. Energy expenditure of pumping brine up and down from subterranean depths was modeled. We conclude that using brine in a gas-exchange membrane system for capturing CO2 from a gas stream to liquid is technically feasible and can be accomplished at a reasonable expenditure of energy.

Athens QRS Score as a Predictor of Coronary Artery Disease in Patients With Chest Pain and Normal Exercise Stress Test.

BACKGROUND: The diagnostic value of the Athens QRS score to detect obstructive coronary artery disease CAD in patients with otherwise normal exercise stress test remains unclear. METHODS AND RESULTS: We analyzed 458 patients who underwent exercise stress test with or without myocardial perfusion imaging within 2 months of coronary angiography from 2008 to 2011. Patients (n=173) with abnormal stress test based on ST segment criteria were excluded. The Athens QRS score ≤5 was defined as abnormal. In our study cohort, 285 patients met the inclusion criteria and were divided into 2 groups: low Athens QRS score (LQRS, n=56), with QRS score ≤5 and normal Athens QRS score normal Athens QRS score, n=229), with QRS score >5. The presence of single-vessel and multivessel obstructive CAD was higher in LQRS than in normal Athens QRS score patients (47% versus 7.5% and 30% versus 3.8%, respectively, all P<0.001). Logistic regression analysis showed that the likelihood of CAD was strongly and independently associated with LQRS (odds ratio=36.81, 95% CI: 10.77-120.47), diabetes (odds ratio=6.49, 95% CI: 2.41-17.49), lower maximum heart rate (odds ratio=0.92, 95% CI: 0.88-0.95, all P<0.001), and older age (odds ratio=1.93, CI: 1.88-1.97, P=0.002). CONCLUSIONS: In a clinical cohort of patients with chest pain and normal exercise stress test, LQRS score is a strong independent predictor of presence of CAD. LQRS patients have a 6-fold higher prevalence of CAD and may warrant further evaluation even with reassuring exercise stress test.

Simple techniques to reduce bowel activity in cardiac SPECT imaging.

BACKGROUND AND AIM: Scatter from the bowel degrades image quality in 99mTc sestamibi myocardial perfusion imaging (MPI). Iodinated oral contrast, which has been used to outline bowel in medical imaging, absorbs X-rays as well as gamma rays. The purpose of this study was to test our hypothesis that iodinated oral contrast during MPI would absorb gamma rays emitted from 99mTc sestamibi in the bowel, thereby reducing scatter and improving cardiac SPECT images. METHODS AND RESULTS: Thirty subjects undergoing adenosine stress 99mTc sestamibi cardiac SPECT were randomized to receive either iodinated oral contrast (IOC), water or no intervention (controls). Subjects had 1 day rest-stress MPI using the adenosine stress protocol. Images were analysed using infra-cardiac counts, image variability, image contrast and the ratios of anterior to inferior and septal to lateral walls. The improvement in image contrast and variability between first and second images were significant in both the IOC and water groups. The IOC group had a more significant improvement in variability than did the water group. The reduction in infra-cardiac counts was also more significant in the IOC group. CONCLUSION: The use of oral contrast and water improved the image variability and contrast by decreasing the infra-cardiac scatter. The improvement was even more significant in the oral contrast group.

Measurement of the nuclear polarization of hydrogen and deuterium molecules using a Lamb-shift polarimeter.

Lamb-shift polarimeters are used to measure the nuclear polarization of protons and deuterons at energies of a few keV. In combination with an ionizer, the polarization of hydrogen and deuterium atoms was determined after taking into account the loss of polarization during the ionization process. The present work shows that the nuclear polarization of hydrogen or deuterium molecules can be measured as well, by ionizing the molecules and injecting the H2(+) (or D2(+)) ions into the Lamb-shift polarimeter.

Assessment of left ventricular mass and geometry by cardiac single photon emission computed tomography.

BACKGROUND: Left ventricular (LV) hypertrophy is an independent predictor of increased morbidity and mortality. However, whether assessment of LV mass and geometry by cardiac single photon emission computed tomography (SPECT) is feasible remains unclear. MATERIAL/METHODS: We compared LV mass and geometry measured by cardiac SPECT to standard echocardiography in thirty consecutive patients (female 73%n mean age 22.64+/-17 years) who had both cardiac SPECT and echocardiography done less than 1 week apart. RESULTS: There was good correlation between the LV mass (r=0.73, p <0.001) and relative wall thickness (r=0.50, p<0.01) derived by cardiac SPECT to those of standard echocardiography. Using Bland-Altman method, the 95% confident interval of agreement between cardiac SPECT and standard echocardiography ranged from -52 g (5th percentile) to 124 g (95th percentile, mean difference =36+/-45) for LV mass and from -1 (5th percentile) to -0.6 (95th percentile, mean difference =-0.8+/-0.1) for relative wall thickness. CONCLUSIONS: Assessment of left ventricular mass and geometry using cardiac SPECT is feasible and may provide prognostic information beyond measurement of perfusion and function.