Orographically Modified Ice-Phase Precipitation Processes During the Olympic Mountains Experiment (OLYMPEX)

Over mountainous terrain, windward enhancement of stratiform precipitation results from a combination of warm-rain and ice-phase processes. In this study, ice-phase precipitation processes are investigated within frontal systems during the Olympic Mountains Experiment (OLYMPEX). An enhanced layer of radar reflectivity (ZH) above the melting level bright band (i.e., a secondary ZH maximum) is observed over both the windward slopes of the Olympic Mountains and the upstream ocean, with a higher frequency of occurrence and higher ZH values over the windward slopes indicating an orographic enhancement of ice-phase precipitation processes. Aircraft-based in situ observations are evaluated for the 01-02 and 03 December 2015 orographically-enhanced precipitation events. Above the secondary ZH maximum, the hydrometeors are primarily horizontally oriented dendritic and branched crystals. Within the secondary ZH maximum, there are high concentrations of large (> ~2 mm diameter) dendrites, plates, and aggregates thereof, with a significant degree of riming. In both events, aggregation and riming appear to be enhanced within a turbulent layer near sheared flow at the top of a low-level jet impinging on the terrain and forced to rise above the melting level. Based on windward ground sites at low-, mid-, and high-elevations, secondary ZH maxima periods during all of OLYMPEX are associated with increased rain rates and larger mass-weighted mean drop diameters compared to periods without a secondary ZH maximum. This result suggests that precipitation originating from secondary ZH maxima layers may contribute to enhanced windward precipitation accumulations through the formation of large, dense particles that accelerate fallout.

Electrochemical Immunosensor for the Early Detection of Rheumatoid Arthritis Biomarker: Anti-Cyclic Citrullinated Peptide Antibody in Human Serum Based on Avidin-Biotin System

Rheumatoid arthritis (RA) is a chronic autoimmune disease that produces a progressive inflammatory response that leads to severe pain, swelling, and stiffness in the joints of hands and feet, followed by irreversible damage of the joints. The authors developed a miniaturized, label-free electrochemical impedimetric immunosensor for the sensitive and direct detection of arthritis Anti-CCP-ab biomarker. An interdigitated-chain-shaped microelectrode array (ICE) was fabricated by taking the advantage of microelectromechanical systems. The fabricated ICE was modified with a self-assembled monolayer (SAM) of Mercaptohexanoic acid (MHA) for immobilization of the synthetic peptide bio-receptor (B-CCP). The B-CCP was attached onto the surface of SAM modified ICE through a strong avidin-biotin bio-recognition system. The modified ICE surface with the SAM and bio-molecules (Avidin, B-CCP, Anti-CCP-ab and BSA) was morphologically and electrochemically characterized. The change in the sensor signal upon analyte binding on the electrode surface was probed through the electrochemical impedance spectroscopy (EIS) property of charge-transfer resistance (Rct) of the modified electrodes. EIS measurements were target specific and the sensor response was linearly increased with step wise increase in target analyte (Anti-CCP-ab) concentrations. The developed sensor showed a linear range for the addition of Anti-CCP-ab between 1 IU mL−1 → 800 IU mL−1 in phosphate buffered saline (PBS) and Human serum (HS), respectively. The sensor showed a limit of detection of 0.60 IU mL−1 and 0.82 IU mL−1 in the PBS and HS, respectively. The develop bio-electrode showed a good reproducibility (relative standard deviation (RSD), 1.52%), selectivity and stability (1.5% lost at the end of 20th day) with an acceptable recovery rate (98.0% → 101.18%) and % RSD’s for the detection of Anti-CCP-ab in spiked HS samples.

INFLUENCE OF THE TIME STORAGE OF ICE POWDER ON KINETICS OF FORMATION AND GROWTH OF FREON-12 GAS HYDRATE

The article explores the influence a storage time on the samples of pure ice powder and mod-ified ice powder with polyvinylpyrrolidone on process formation and growth of the gas hydrate by used P-V-T measurements. It has been established that increased storage time of the pure ice powder leads to a decrease the rate of growth of gas hydrate. Fresh modified ice powder has induction time of hydrate formation which increased in a polyvinylpyrrolidone concentration. At long-term storage of modified ice powder with a polyvinylpyrrolidone concentration less 0,3 % the induction time don’t registrate and growth rate of gas hydrate likes zero. In the samples of modified ice powder with a polyvinylpyrrolidone concentration more 0,75 % after 10 days a storage were retained growth rate of gas hydrate likes fresh modified ice powder. There is no induction effect.

KINETICS OF GAS HYDRATES FORMATION AND GROWTH BASED ON MODIFIED ICE

The results of the studies of influence of polyvinylpyrrolidone on the kinetics of formation and the growth of Freon-12 gas hydrate are presented. Based on the P-V-T measurements the degree of conversion of ice into gas hydrate at various concentrations of polyvinylpyrrolidone was calculated. The fact of preservation of inhi-biting properties of polyvinylpyrrolidone in formation of a gas hydrate based on frozen aqueous solutions has been established. The studied polymer shows promoting properties, which leads to an increase in rate of the growth of Freon-12 hydrate based on modified ice.

Spherical Indentation Tests on Confined Ice Specimens at Small Scales

A recent series of small-scale ice indentation tests was conducted as a continuation of previous series, to cover additional strain rates and indentor sizes, and to test the effect of scaling. Tests using indentors 10, 20, 40 and 70 mm in diameter attached to a very stiff structure were carried out at indentation rates over three orders of magnitude, while scaling indentation rate with indentor diameter. Slow rates resulted in creep-like response and deep and wide damage zones. As indentation rate was increased, sawtooth loading and random failure activity were observed, together with a thin layer of microstructurally modified ice beneath the indentor. This latest test series also included indentation tests with a flexible beam apparatus, with the aim of generating locked-in vibrations. It was determined from previous tests that indenting at much faster rates was necessary to produce lock-in with such an apparatus. For this series, two new beam apparatus of differing stiffness and variable natural frequency were fabricated; the beams were designed in a manner that enabled control and testing of the outcome of varying these factors independently. Tests were conducted with either one or two indentors attached. The typical sawtooth behaviour occurred at lower indentation rates, progressing at higher rates into lock-in activity, which occurred over a range of speeds for both beams. The frequency of lock-in vibrations was found to be lower than the structure’s natural frequency, and to increase with indentation speed over the lock-in range. The ice load on the indentor during lock-in activity appears more ‘cusp’ shaped, rather than the assumed sawtooth.

Mechanics of Dynamic Ice Failure Against Vertical Structures

Ice interaction with vertical faces of structures can result in regular vibrations given certain conditions such as temperature and speed of interaction. The mechanism that can provide this regular behaviour is studied. Fracture in general does not offer a solution in compressive failure. An approach based on viscoelastic theory, with softening resulting from microstructural change, is given. The pivotal observation was a layer of microstructurally modified ice adjacent to the structure or indentor, together with high local pressures transmitted into the layer. The microstructural changes include microfracturing and recrystallization. A series of triaxial tests was performed to determine the inputs into the viscoelastic theory. The theory recognizes changes in the microstructure of the ice by means of a state variable, which is a function of prior stress history, and therefore of location within the ice mass. The theory and the calibration thereof are reviewed, and the results of triaxial tests examined. One feature of these tests is the occurrence of “runaway” strains and associated localization of damage. This appears to be sensitive to confining pressure, and is considered to be a key factor in the rapid load drops observed in ice-structure interaction. Temperature effects are also studied. Directions for future research are identified.