Effect of Hydrostatic Pressure on Aggregation and Viscoelastic Properties of Tilapia (Orechromis niloticus) Myosin

ABSTRACT: Hydrostatic pressures from 500 to 2000 atmospheres (atm) were applied at 0°C to determine the aggregation and viscoelastic properties of tilapia ( Orechromis niloticus ) myosin. Native myosins were present as long, linear, and single filaments. After a 500-atm treatment, these filaments unfolded and their volume decreased. Upon 1000-atm and 1500-atm treatments, myosins aggregated and formed inseparable network structures. Further, they transformed from viscous sol to elastic gels with a pressure of 500 to 1000 atm. At 2000 atm, the myosin formed irregular aggregates. This study reveals that at 500 atm, myosins unfolded; at 1000 atm, they aggregated, and beyond 1500 atm, they formed both a precipitate and gel.     

The possible role of arterial radial vibration in heart rate and blood pressure matching

MOTIVATION: This study tests if the 'oscillating spring' analogy for the radial vibration of the arterial wall can help to describe the relationship between the heart rate (HR), the blood pressure (BP), and properties of the arterial wall when different types of stimulation are applied on the cardiovascular system. It may help to suggest a possible role for arterial radial vibration in the association between the arterial stiffening and hypertension. METHODS: Either mechanical stimulation was applied (0.5-mmHg pressure variation) to Wistar rats by at near-HR frequency (group A) or administered Propranolol (2mg/kg i.p.; group B), and measured HR and BP simultaneously. RESULTS: In both groups, HR and BP were noted to change in the same direction (r2 = 0.72 and 0.62, respectively; p both < 0.05 by F-test). ANCOVA was performed on these two regression lines, and it was found that there was no significant difference between them (p > 0.3). CONCLUSION: In both groups, changes in haemodynamic parameters can be explained by the 'oscillating spring' analogy for the radial vibration of the arterial wall. This illustrates that, when facing various stimulations, it may be an important regulatory mechanism for the heart and the arteries to restore their frequency-matching condition in order to improve the arterial transmission efficiency. Paying more attention to the radial movement of the wall may therefore help to suggest a novel explanation of the mechanism that underlies the bidirectional relation between hypertension and arterial stiffening.     

Chemical evolution of CO2 by electrocatalytic oxidation of vanadium-impregnated coke anode material

Baked carbon containing impregnated vanadium may be electrochemically oxidized to CO₂ in 1 M H₂SO₄ at 80–90% current efficiency during prolonged electrolysis (>20 h) at 70°C under an applied potential of 1.0 V versus saturated calomel electrode (SCE). The vanadium is electrocatalytically maintained in the highest oxidation state with an activation energy of 44–80 kJ mol^–1 at temperatures up to 80°C.     

Atmosphere-ocean dynamics in the Western Indian Ocean recorded in corals

We present a set of Porites coral oxygen isotope records from the tropical and subtropical Western Indian Ocean covering the past 120-336 years. All records were thoroughly validated for proxy response to regional climate factors and their relation to large-scale climate modes. The records show markedly different imprints of regional climate factors. At the same time, all coral records show clear teleconnections between the Western Indian Ocean and the El Nino-Southern Oscillation (ENSO). The multi-proxy site analysis enables the detection of the covariance structure between individual records and climate modes such as ENSO. This method unravels shifts in ENSO teleconnectivity of the Western and Central Indian Ocean on multi-decadal time-scales (after 1976). The Seychelles record shows a stationary correlation with ENSO, Chagos corals show evidence for non-stationary delta18O/ENSO relationships and the Southwestern Indian Ocean corals show a strong relationship with ENSO when the forcing is strong (1880-1920, 1970 to present). Our results indicate that the coral delta18O, in combination with other proxies, can be used to monitor temporal and spatial variations in the sea-surface temperature and the fresh water balance within the Indian Ocean on interannual to interdecadal time-scales.     

Rotational positioning system adapted to atomic force microscope for measuring anisotropic surface properties

The diverse atomic configurations induce the anisotropic surface properties. For investigating anisotropic phenomena, we developed a rotational positioning system adapted to atomic force microscope (AFM). This rotational positioning system is applied to revolve the measured sample to defined angular direction, and it composed of an inertial rotational stepper and a visual angular measurement. The inertial rotational stepper with diameter 30 mm and height 7.6 mm can be easily attached to the AFM-system built in any general optical microscope. Based on a clearance less bearing and the inertial driving method, its bidirectional angular resolution reaches 0.005° per step. For realizing a close-loop controlled angular positioning function, the visual measurement method is utilized. Through the feedback control, the angular positioning error is less than 0.01°. For verifying the system performance, we used it to investigate the anisotropic surface properties of graphite. Through a modified cantilever tip, the atomic-scale stick-slip, and the anisotropic friction phenomena can be distinctly detected.     

In situ paired electrooxidative degradation of formaldehyde with electrogenerated hydrogen peroxide and hypochlorite ion

Formaldehyde was degraded with hydrogen peroxide and hypochlorite ion electrogenerated by paired electrolysis of dissolved oxygen and chloride ion in aqueous solution. Degradation of formaldehyde in the cathodic compartment was significantly affected by the ratio of electrolyte volume to cathodic surface area, oxygen sparging rate and stirring rate. The model calculations correlated sufficiently well with the experimental results. The average current efficiency and degradation fraction of the in situ paired electrooxidative degradation of formaldehyde were experimentally found to be 62.0% and 93.2%, respectively.     

Single molecule tracking on supported membranes with arrays of optical nanoantennas

Coupling of the localized surface plasmons between two closely apposed gold nanoparticles (nanoantenna) can cause strong enhancements of fluorescence or Raman signal intensity from molecules in the plasmonic "hot-spot". Harnessing these properties for practical applications is challenging due to the need to fabricate gold particle arrays with well-defined nanometer spacing and a means of delivering functional molecules to the hot-spot. We report fabrication of billions of plasmon-coupled nanostructures on a single substrate by a combination of colloid lithography and plasma processing. Controlled spacing of the nanoantenna gaps is achieved by taking advantage of the fact that polystyrene particles melt together at their contact point during plasma processing. The resulting polymer thread shadows a gap of well-defined spacing between each pair of gold triangles in the final array. Confocal surface-enhanced Raman spectroscopy imaging confirms the array is functionally uniform. Furthermore, a fully intact supported membrane can be formed on the intervening substrate by vesicle fusion. Trajectories of freely diffusing individual proteins are traced as they sequentially pass through, and are enhanced by, multiple gaps. The nanoantenna array thus enables enhanced observation of a fluid membrane system without static entrapment of the molecules.     

Mechanism of copper electrodeposition by pulse current and its relation to current efficiency

The effects of pulse periods and duty cycles on the current efficiency of acid copper plating in a wide range of pulse periods from 200 to 0.02 ms were studied. It was found the current efficiency decreased with shortening pulses in the millisecond range but increased with shortening pulses in the microsecond range. A mathematical model based on the concept of equivalent circuit was employed to simulate the potential responses. Shortening the pulse period was found to change the rate-determining step from charge transfer and surface diffusion to the first step charge transfer. In the millisecond range, the current efficiency decreases with shortening pulse period due to the disproportionation of cuprous ions and the dissolution of copper adatom. However, in the microsecond range, the current efficiency was found to increase with decreasing pulse period because the adatoms are directly incorporated into steps and kink sites, and the disproportionation of cuprous ions or the dissolution of copper adatoms has less chance to occur.