2,409 research outputs found

    Relationship Between Partial Carbon Dioxide Pressure and Strong Ions in Humans: A Retrospective Study

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    Little is known about the role of a strong ions in humans with respiratory abnormalities. In this study, we investigated the associations between partial carbon dioxide pressure (pCO2) and each of sodium ion (Na+) concentrations, chloride ion (Cl−) concentrations and their difference (SIDNa-Cl). Blood gas data were obtained from patients in a teaching hospital intensive care unit between August 2013 and January 2017. The association between pCO2 and SIDNa-Cl was defined as the primary outcome. The associations between pCO2 and [Cl−], [Na+] and other strong ions were secondary outcomes. pCO2 was stratified into 10 mmHg-wide bands and treated as a categorical variable for comparison. As a result, we reviewed 115,936 blood gas data points from 3,840 different ICU stays. There were significant differences in SIDNa-Cl, [Cl−], and [Na+] among all categorized pCO2 bands. The respective pCO2 SIDNa-Cl, [Cl−], and [Na+] correlation coefficients were 0.48, −0.31, and 0.08. SIDNa-Cl increased and [Cl−] decreased with pCO2, with little relationship between pCO2 and [Na+] across subsets. In conclusion, we found relatively strong correlations between pCO2 and SIDNa-Cl in the multiple blood gas datasets examined. Correlations between pCO2 and chloride concentrations, but not sodium concentrations, were further found to be moderate in these ICU data

    Secondary instability of salt sheets

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    In the presence of a vertically varying horizontal current (background shear), the salt-fingering instability is supplanted by the salt-sheet instability. Previous direct numerical simulation (DNS) experiments on salt sheets revealed that flow becomes turbulent via secondary instabilities. We call these instabilities zig-zag and tip modes. Here, we investigate the physics of these modes using linear normal mode stability analysis. As the primary instability (salt-sheet instability) grows, the zig-zag mode emerges, which denotes undulation of growing salt sheets at the center of fingering regions. This mode is shown to be an extension of secondary instability of unsheared two-dimensional salt-fingering. The zig-zag mode is amplifed almost uniformly at all horizontal wavelengths exceeding O(1 m). This mechanism may, therefore, account for the tilted laminae seen in shadowgraph images of microstructure in salt fingering regions. Subsequently, the tip mode appears at the tips of undulating salt sheets introducing streamwise dependence that leads the flow into turbulent regime

    Dynamics of coupled vortices in a pair of ferromagnetic disks

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    We here experimentally demonstrate that coupled gyration modes can be resonantly excited primarily by the ac current in a pair of ferromagnetic disks with varied separating distance. The sole gyrotropic mode clearly splits into a higher and a lower frequency modes for different configurations of polarities via dipolar interaction. These experimental results indicate that the magnetostatically coupled pair of vortices behaves similar to a diatomic molecule with bonding and anti-bonding states. These findings lead to the possible extension of designing the magnonic band structure in a chain or an array of vortices.Comment: 4 pages, 4 figures, accepte

    Quantum cascade laser absorption spectroscopy with the amplitude-to-time conversion technique for atmospheric-pressure plasmas

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    Yumii, T., Kimura, N., and Hamaguchi, S., Journal of Applied Physics 113(21), 213101 (2013) http://doi.org/10.1063/1.480826

    Paraoxonase 1 in Chronic Kidney Failure

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    In this review we summarize the findings from the literature and our own laboratory on the decreased PON1 activity in renal failure, the mechanisms proposed and the effect of interventions. In addition to profound alterations in lipoproteins, reduced serum PON1 activity has been clearly established in the past decade and could contribute to accelerated development of atherosclerosis in ESRD and in HD. PON1 lactonase activity is lower in ESRD patients. Hemodialysis partially restores PON1 lactonase and the other activities. PON1 activity recovery after dialysis suggests that uremic toxins may play a mechanistic role in PON1 inactivation. Lower PON1 activity in CRF patients is associated with low thiol concentration, high CRP, and is beneficially enhanced with vitamin C and flavonoids. Changes in HDL subclasses, namely lower HDL3 in these patients may also play a role in PON1 lower activity. Future research should focus on: (1) mechanistic studies on causes for low PON1 activity and mass; (2) prospective studies focusing on whether there is an added predictive value in measuring PON1 activity (and PON1 activity in HDL3) in this patient population; (3) intervention studies attempting to increase PON1 activity

    Estimation of ice shelf melt rate in the presence of a thermohaline staircase

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    Diffusive convection–favorable thermohaline staircases are observed directly beneath George VI Ice Shelf, Antarctica. A thermohaline staircase is one of the most pronounced manifestations of double-diffusive convection. Cooling and freshening of the ocean by melting ice produces cool, freshwater above the warmer, saltier water, the water mass distribution favorable to a type of double-diffusive convection known as diffusive convection. While the vertical distribution of water masses can be susceptible to diffusive convection, none of the observations beneath ice shelves so far have shown signals of this process and its effect on melting ice shelves is uncertain. The melt rate of ice shelves is commonly estimated using a parameterization based on a three-equation model, which assumes a fully developed, unstratified turbulent flow over hydraulically smooth surfaces. These prerequisites are clearly not met in the presence of a thermohaline staircase. The basal melt rate is estimated by applying an existing heat flux parameterization for diffusive convection in conjunction with the measurements of oceanic conditions at one site beneath George VI Ice Shelf. These estimates yield a possible range of melt rates between 0.1 and 1.3 m yr−1, where the observed melt rate of this site is ~1.4 m yr−1. Limitations of the formulation and implications of diffusive convection beneath ice shelves are discussed

    Dehydration of main-chain amides in the final folding step of single-chain monellin revealed by time-resolved infrared spectroscopy

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    Kinetic IR spectroscopy was used to reveal β-sheet formation and water expulsion in the folding of single-chain monellin (SMN) composed of a five-stranded β-sheet and an α-helix. The time-resolved IR spectra between 100 μs and 10 s were analyzed based on two consecutive intermediates, I1 and I2, appearing within 100 μs and with a time constant of ≈100 ms, respectively. The initial unfolded state showed broad amide I′ corresponded to a fluctuating conformation. In contrast, I1 possessed a feature at 1,636 cm−1 for solvated helix and weak features assignable to turns, demonstrating the rapid formation of helix and turns. I2 possessed a line for solvated helix at 1,637 cm−1 and major and minor lines for β-sheet at 1,625 and 1,680 cm−1, respectively. The splitting of the major and minor lines is smaller than that of the native state, implying an incomplete formation of the β-sheet. Furthermore, both major and minor lines demonstrated a low-frequency shift compared to those of the native state, which was interpreted to be caused by hydration of the C=O group in the β-sheet. Together with the identification of solvated helix, the core domain of I2 was interpreted as being hydrated. Finally, slow conversion of the water-penetrated core of I2 to the dehydrated core of the native state was observed. We propose that both the expulsion of water, hydrogen-bonded to main-chain amides, and the completion of the secondary structure formation contribute to the energetic barrier of the rate-limiting step in SMN folding
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